158 this issue is dedicated to  professor alexander petrov, whose 75th birthday we have celebrated this year. during all his life alexander petrov was deeply involved into teaching and research in the chemical faculty of  the ural state university. his research interests included wide range of  topics concerning thermodynamics and stability of oxide systems, crystal and defect structure, charge and mass transfer, technical applications of oxide materials, and many others. professor petrov is a co-author of many publications, patents, and text-books. together with his teacher, professor vladimir zhukovsky, alexander petrov became a founder of outstanding research group for solid state chemistry in the ural state university, which raised many talented young scientists. he was one of the first scientists of the ural state university who managed to go on an internship abroad, to professor p. kofstad. as a result, since mid-70th, oslo university remains our good partner for collaboration in different forms. later, professor petrov took part in  research in  well-known research centers in  italy, denmark, usa, and many others, and delivered lectures at international conferences as an invited speaker. for 22 years (1986–2008) professor petrov headed the department of physical chemistry in the ural state university. during that time, he made a lot of effort to maintain close collaboration with institutes of ural branch of the russian academy of science and its predecessor — the academy of science of the ussr. in 1987, he organized a  joint laboratory with the institute of electrophysics. a branch of the department of physical chemistry was established in 1995 in the institute of hightemperature electrochemistry. a scientific laboratory “neutron-diffraction studies of complex oxides” was organized jointly with the institute for metal physics in 1997. it can be said that professor petrov anticipated the trends that the ministry of science and higher education of  russia is currently implementing. alexander petrov repeatedly won high awards. for example, in 1989 together with others he was awarded by the prize of the council of ministers of the ussr for the development of  novel ceramic cathodes for co2-lasers, in 2000 he was awarded the state scholarship for outstanding scholars of the russian federation, in 2001 he was awarded the honored scientist of the russian federation title. in addition to his merits and titles, the most important traits of alexander petrov were his outstanding humanity and decency. he was always ready to fight for justice and come to the rescue. more than 10 years have passed since he is not with us, but we still keep bright memories and warm feelings towards him in our hearts. 127 d o i: 1 0. 15 82 6/ ch im te ch .2 01 5. 2. 2. 01 3 k. v. savateev, s. s. borisov, e. k. voinkov, e. n. ulomsky, v. l. rusinov, o. n. chupakhin institute of organic synthesis ural division of ras, 19 mira street, ekaterinburg 6-aminotriazolo[1,5-a]pyrimidines as precursors of 1,2,4-triazolo[5,1-b]purines* triazolo[5,1-b]purines are rare structural analogues of natural nucleosides and nucleobases purine series. at the same time, prominent representatives of azolopurines exhibit a broad spectrum of antiviral effect, activity against of rheumatoid arthritis, psoriasis, alzheimer’s, parkinson’s and etc. despite the practical value azolo[5,1-b]purines extremely sparingly represented in the chemical literature, due to the complexity of their synthesis. we suggest a convenient way to synthesize triazolopurines with aminotriazolo[1,5-a]pyrimidines (2) as available starting compounds obtained in good yield by reduction of nitro derivatives (1). © savateev k. v., borisov s. s., voinkov e. k., ulomsky e. n., rusinov v. l., chupakhin o. n., 2015 * the work was supported by rfbr grant 13-03-0086 traditionally one of the most widespread way to turn azinons in aminazines is chorine deoxygenization of heterocycles followed by amination of chlorinated derivatives1,2. the need for blocking already existing amino group, for example with acyl moiety, is the peculiarity of this method. we have used several acyl protecting groups using corresponding anhydrides or acids, among which the most convenient one was trifluoracetyl protection, providing good solubility in organic solures of corresponding trifluoroacetyl derivative. as a model compound for chlorine deoxygenization, compound 3a was used. use of phosphoryl chloride and thionyl chloride in presence of tertiary amines or dmf gave no satisfactory results. pyridine usage as tertiary amine proved to be effective. the resulting chlorine derivative (4) was exposed to butylamine for 128 № 2 | 2015 chimica techno acta savateev k. v., borisov s. s., voinkov e. k., ulomsky e. n., rusinov v. l., chupakhin o. n. the purpose of obtaining of pyrimidine 7 aminotriazol straight away (5). however, spectroscopic data and elemental analysis showed the formation of triazolopurine (6). thus, we have shown that the use of cis-6-aminotriazole (2) is a promising way of synthesizing azolo [5,1-b] purines. 1. zhang n., ayral-kaloustian s., nguyen th., afragola j., hernandez r., lucas j., gibbons j., beyer c. synthesis and sar of [1,2,4]triazolo[1,5-a]pyrimidines, a class of anticancer agents with a unique mechanism of tubulin inhibition. j. med. chem. 2007;50(2):319-327. doi: 10.1021/jm060717i. 2. zhao x. l., zhao y. f., guo s. c., song h. s., wang d., gong p. synthesis and anti-tumor activities of novel [1,2,4]triazolo[1,5-a] pyrimidines. molecules 2007;12(5):1136–1146. doi: 10.3390/12051136. 129 у д к 5 47 .8 36 .3 к. в. саватеев, с. с. борисов, е. к. воинков, е. н. уломский, в. л. русинов, о. н. чупахин институт органического синтеза им. и. я. постовского уро ран 620002, екатеринбург, ул. мира, 19 6-аминотриазоло[1,5-a]пиримидины как предшественники 1,2,4-триазоло [5,1-b] пуринов* триазоло[5,1-b]пурины являются малораспространенными структурными аналогами природных нуклеозидов и нуклеиновых оснований пуринового ряда. в то же время известные представители азолопуринов проявляют широкий спектр противовирусного действия, активность в отношении ревматоидного артрита, псориаза, болезней альцгеймера, паркинсона и проч. несмотря на практическую ценность, азоло[5,1-b]пурины чрезвычайно скупо представлены в химической литературе, что обусловлено сложностью их синтеза. нами предложен удобный путь к синтезу триазолопуринов с участием аминотриазоло[1,5-a]пиримидинов (2) в качестве доступных исходных соединений, получаемых с хорошими выходами восстановлением нитропроизводных (1). © саватеев к. в., борисов с. с., воинков е. к., уломский е. н., русинов в. л., чупахин о. н., 2015 * работа была выполнена при поддержке гранта рффи 13-03-0086. традиционно одним из наи более распространенных способов превращения азинонов в аминоазины является хлордезоксигенирование гетероциклов с последующим аминированием хлорпроизводных [1,2]. особенностью синтеза диаминоазинов таким методом является необходимость защиты уже имеющейся аминогруппы, например, а цильным фрагментом. нами было использовано несколько ацильных защитных групп, с помощью соответствующих ангидридов или кислот, из которых наиболее удобной оказалась трифторацетильная защита, обеспечивающая хорошую растворимость в органических растворителях 130 № 2 | 2015 chimica techno acta саватеев к. в., борисов с. с., воинков е. к., уломский е. н., русинов в. л., чупахин о. н. соответс твующего трифторацетильного производного. в качестве модельного соединения для хлордезоксигенирования нами было использовано соединение 3а. использование фосфорилхлорида и тионилхлорида в присутствии третичных аминов или дмфа не дали удовлетворительного результата. эффективным оказалось использование в качестве третичного амина пиридина. полученное хлорпроизводное (4) сразу по выделении обработали бутиламином с целью получения 7-аминотриазолопиримидина (5). однако данные спектроскопии и элементного анализа показали образование триазолопурина (6). таким образом, нами показано, что использование 6-аминотриазолопиримидинонов (2) является перспективным путем синтеза азоло[5,1-b]пуринов. 1. zhang n., ayral-kaloustian s., nguyen th., afragola j., hernandez r., lucas j., gibbons j., beyer c. synthesis and sar of [1,2,4]triazolo[1,5-a]pyrimidines, a class of anticancer agents with a unique mechanism of tubulin inhibition. j. med. chem 2007;50(2):319-327. doi: 10.1021/jm060717i. 2. zhao x. l., zhao y. f., guo s. c., song h. s., wang d., gong p. synthesis and anti-tumor activities of novel [1,2,4]triazolo[1,5-a] pyrimidines. molecules 2007;12(5):1136–1146. doi: 10.3390/12051136. рекомендуем при цитировании данно статьи следующую ссылку: savateev k. v., borisov s. s., voinkov e. k., ulomsky e. n., rusinov v. l., chupakhin o. n. 6-aminotriazolo[1,5-a]pyrimidines as precursors of 1,2,4-triazolo[5,1-b]purines // chimica techno acta. 2015. vol. 2. № 2. p. 127–130. cta_v4_№1.cdr 25 zshevnikov d. n., zshevnikov v. n. chimica techno acta. 2017. vol. 4, no. 1. p. 25–28. issn 2409-5613 d o i: 1 0. 15 82 6/ ch im te ch .2 01 7. 4. 1. 02 1 5 47 .8 7 memory yu. yu. morzherin d. n. коzshevnikov1, v. n. коzshevnikov2 1zao nph vmp, 105, amundsen str., ekaterinburg, russia e-mail: dnk@fmp.ru 2 northumbria university, newcastle, uk, e-mail: valery.kozhevnikov@northumbria.ac.uk combinatorial approach to the synthesis of substituted 1,2,4-triazines this article describes a convenient and easy method of substitution of the nitrile group in 5-cyano-1,2,4-triazines with the aim of obtaining of libraries of substituted 1,2,4-triazines (about 500 compounds. key words: nucleophiles; nitrile group; 1,2,4-triazines. received: 02.03.2017; accepted: 10.03.2017; published: 14.04.2017. памяти ю. ю. моржерина д. н. кожевников1, в. н. кожевников2 1зао нпх вмп, екатеринбург, ул. амундсена, 105, e-mail: dnk@fmp.ru 2 университет нортумбрии, ньюкасл, великобритания, e-mail: valery.kozhevnikov@northumbria.ac.uk 1,2,4 5-1,2,4 1,2,4 ( 500 ). : ; ; 1,2,4. : 02.03.2017; : 10.03.2017; : 14.04.2017. © zshevnikov d.n., zshevnikov v.n., 2017 th e reaction of substitution of the nitrile group in 5-cyano-1,2,4-triazines on the residues of the various nucleophiles occurs very easily both from the point of view of reaction conditions (requires neither an inert atmosphere, no pure solvents, no special reagents, no long heating) and allocation method (in most cases it is suffi cient to dilute with water and fi lter the precipitate). amines [1–4], alcohols [3] and ch-active compounds [5] can act as nucleophiles. in principle, anilines also enter into this reac26 tion, but do so very reluctantly only aft er prolonged heating [6]. to obtain a librar y of substituted 1,2,4-triazines was proposed a strategy involving the synthesis of 1,2,4-triazine-4-oxides 1, their direct cyanation and subsequent substitution of cyano group in 5-cyano-1,2,4-triazines 2. th e simple synthetic procedures and available starting compounds (acetophenones, aldehydes and acetocyanohydrines) allowed to obtain in a 5-stages to 10 to 100 gram quantities of series of cyanotriazines 2 carrying diff erent aliphatic, aromatic and heteroaromatic substituents in positions 3 and 6. despite the originality of the leaving group (cyanide anion) its substitution allows to enter in triazine cycle the residues of ammonia, primary and secondary aliphatic amines (including, esters of amino acids, tryptamine, etc.), as well as aliphatic alcohols with the formation of 5-amino-1,2,4-triazines 3 and 5-alkoxy-1,2,4-triazines 4. th e ease of the reaction passing allowed to realize parallel synthesis of triazines 3 and 4. th e standard procedure involved the addition of excess amine or alcohol (with the addition of base) to samples of 10–30 cyanotriazines 2 in the tubes or bottles. a short heating is necessary to accelerate dissolution of starting materials. th e subsequent (a few hours) addition of water resulted in precipitation of the residues of desired products 3 and 4, which were only fi ltered. if desired, the products can be recrystallize from ethanol, but even without this the substituted triazines don’t contain impurities (according to nmr spectroscopy). th e reactions were with high yields close to quantitative. as a result the unique reaction of substitution of cyano group was turned into a powerful tool that has been successfully used in the parallel synthesis to obtain a library of about 500 compounds 1,2,4-triazine series. in russian реакция замещения нитрильной группы в 5-циано-1,2,4-триазинах на остатки различных нуклеофилов протекает чрезвычайно легко как с точки зрения реакционных условий (не требует ни инертной атмосферы, ни чистых растворителей, ни особых реагентов, ни длительного нагрева), так и способа выделения (в большинстве случаев достаточно разбавить водой и отфильтровать осадок). нуклеофилами могут выступать амины [1–4], спирты [3] и сн-активные 27 соединения [5]. в принципе, анилины также вступают в данную реакцию, но делают это весьма неохотно, лишь после длительного нагрева [6]. для получения библиотеки замещенных 1,2,4-триазинов была предложена стратегия, включающая синтез 1,2,4-триазин-4-оксидов 1, их прямое цианирование и последующее замещение цианогруппы в 5-циано-1,2,4триазинах 2. простые синтетические процедуры и доступные исходные соединения (ацетофеноны, альдегиды и ацетонциангидрин) позволили в 5 стадий получить в 10–100-граммовых количествах серию цианотриазинов 2, несущих различные алифатические, ароматические и гетероароматические заместители в положении 3 и 6. несмотря на своеобразность уходящей группы (цианид анион), ее замещение позволяет вводить в триазиновое ядро остатки аммиака, первичных и вторичных алифатических аминов (в том числе эфиров аминокислот, триптаминов и т. д.), а также алифатических спиртов с образованием 5-амино-1,2,4-триазинов 3 и 5-алкокси-1,2,4-триазинов 4. легкость протекания реакции позволила реализовать параллельный синтез триазинов 3 и 4. стандартная процедура включала добавление избытка амина или спирта (с добавкой основания) к навескам 10–30 цианотриазинов 2 в пробирках или бутыльках. непродолжительное нагревание необходимо для ускорения растворения исходных веществ. последующее (через несколько часов) добавление воды приводило к выпадению осадков желаемых продуктов 3 и 4, которые оставалось только отфильтровать. при желании продукты можно было перекристаллизовать из этанола, но и без этого замещенные триазины не содержали примесей (по данным ямр спектроскопии). реакции с высокими выходами, близкими к количественным. в результате уникальная реакция замещения цианогруппы была превращена в мощный инструмент, который был с успехом использован в условиях параллельного синтеза для получения библиотек – около 500 соединений 1,2,4-триазинового ряда. references 1. huang j. j. j. org. chem. 1985;50:2293–2298. 2. rykowski a., branowska d., makosza m., van ly p.  j. heterocycl. chem. 1996;33:1567– 1571. 28 3. kozhevnikov v.  n., kozhevnikov d. n., shabunina o. v., kataeva n. n., yushchuk s. a., rusinov v. l., chupakhin o. n. russ. chem. bull. 2005;54:2187–2196. 4. kozhevnikov d. n., kozhevnikov v. n., kovalev i. s., rusinov v. l., chupakhin o. n., aleksandrov g. g. russ. j. org. chem. 2002;38:744–750. 5. prokhorov a. m., kozhevnikov d. n., rusinov v. l., matern a. i., nikitin m. m., chupakhin o. n., eremenko i. l., aleksandrov g. g. russ. j. org. chem. 2005;41:1702–1705. 6. kopchuk d. s., chepchugov n. v., kovalev i. s., santra s., rahman m., giri k., zyryanov g. v., majee a., charushin v. n., chupakhin o. n. rsc adv. 2017;7:9610–9619. cite this article as (как цитировать эту статью): коzshevnikov d. n., коzshevnikov v. n. combinatorial approach to the synthesis of substituted 1,2,4-triazines. chimica techno acta. 2016;4(1): 25–28. two mutually complementary synthetic approaches towards 3-substituted 3,4-disubstituted and 1-(2-pyridyl)-substituted isoquinolines 150 i. l. nikonov1,2, d. s. kopchuk1,2, a. f. khasanov1,2, a. p. krinochkin1,2, e. s. starnovskaya1, ya. k. shtaiz1, m. i savchuk1, o. s. tanya1, g. v. zyryanov1,2, v. l. rusinov1,2, o. n. chupakhin1,2 1ural federal university, 19 mira st., ekaterinburg 620002, russian federation 2i. ya. postovskii institute of organic synthesis, ural branch of russian academy of sciences, 22 kovalevskaya st. / 20 akademicheskaya st., ekaterinburg 620990, russian federation e-mail: dkopchuk@mail.ru two mutually complementary synthetic approaches towards 3‑substituted 3,4‑disubstituted and 1‑(2‑pyridyl)‑substituted isoquinolines two mutually complementary synthetic approaches towards 3and 3,4-disubstituted 1-(2-pyridyl) isoquinolines were studied. the aryne-based method was successfully used for the obtaining of the corresponding the 3-cyano-1-(2-pyridyl)isoquinolines in one step / pot reaction, while it is unacceptable for the obtaining of other 1-(2-pyridyl)isoquinolines. the enamine-based approach was successfully applied for the synthesis of other 1-(2-pyridyl)isoquinolines, while it was unacceptable for the obtaining of 3-cyano-1-(2-pyridyl)isoquinolines. keywords: 1,2,4-triazines; arynes; enamines; isoqunolines; aza-diels-alder reaction; dominotransfrormation. received: 08.09.2018. accepted: 19.10.2018. published: 31.10.2018. © nikonov i. l., kopchuk d. s., khasanov a. f., krinochkin a. p., starnovskaya e. s., shtaiz ya. k., savchuk m. i, tanya o. s., zyryanov g. v., rusinov v. l., chupakhin o. n., 2018 d o i: 1 0. 15 82 6/ ch im te ch .2 01 8. 5. 3. 04 results and discussion aryne intermediates, generated in situ, are currently attracting more and more attention from the point of  view of  their use in  organic synthesis, since practically useful products of various purposes can be obtained [1–3]. recently, we have demonstrated the possibilities of their successful use in reactions with substituted 1,2,4-triazines for obtaining both the expected aza-diels-alder reaction products, namely the corresponding isoquinolines, and the domino transformations, for example, 10-(1h1,2,3-triazol-1-yl) pyrido [1,2-a] indoles. the direction of the reaction depends on the nature of the 1,2,4-triazines (or aryns) introduced into the composition of the substituents [4]. this article analyzes the two synthetic approaches we have developed for the synthesis of 1(2-pyridyl) isoquinolines with different substituents in the c3 and c4 positions, which are of interest, in particular, as ligands for transition metal cations [5], as well as from the point of view of creating oled [6]. nikonov i. l., kopchuk d. s., khasanov a. f., krinochkin a. p., starnovskaya e. s., shtaiz ya. k., savchuk m. i, tanya o. s., zyryanov g. v., rusinov v. l., chupakhin o. n. chimica techno acta. 2018. vol. 5, no. 3. p. 150–152. issn 2409–5613 151 thus, the reaction of  3-(2-pyridyl)  -1,2,4-triazines 1a, having an aromatic substituent or a hydrogen atom at the c5 position, with aryne results in  the corresponding pyrido [1,2-a] indoles 2 [7] (scheme 1), while the synthesis of target 1-(2-pyridyl) isoquinolines 3a in  this way is impossible. to solve this problem, we developed an alternative synthetic approach, which was based on  the use of 3-(2-pyridyl)-1,2,4-triazines 1 as starting compounds. the approach involves the preparation of 5,6,7,8-tetrahydroisoquinolines 4a as  a  result of  the reaction of aza-diels-alder (boger) with enamine followed by oxidative aromatization of the isoquinoline system [8]. 1-morpholinocyclohexene was used as a dienophile for the first stage. subsequent aromatization using ddq as an oxidizing agent made it possible to successfully synthesize isoquinolines 3a. it should be noted that in the reaction of  3-(2-pyridyl)-1,2,4-triazine-5-carbonitriles 1b with arynes, the corresponding isoquinolines 3b were also obtained as main products, whereas the products of domino transformation were the minor products (the yield is not more than 3 %) [9]. we also investigated the possibility of obtaining isoquinolines 3b as a result of two-stage synthesis through the preparation of tetrahydroisoquinolines 4b. the first step was performed by the same procedure as in the case of synthesis 4a, and afforded the compound 4b. however, subsequent aromatization of tetrahydrocyanoisoquinoline under various conditions, such as  boiling in  o-xylene or  4-chlorotoluene with oxidants, such as  ddq or chloranil, as well as prolonged boiling in  the same high-boiling solvents in  the pre sence of pd / c did not lead to the formation of the desired isoquinolines 3b. in all cases the initial tetrahydroisoquinoline 4b was isolated. thus, the application of this method is not acceptable for the obtaining the target 3-cyanoisoquinolines 3b. thus, it was demonstrated that two mutually complementary synthetic methodologies can be used to synthesize 3-aryl, 3,4-diaryl-, as well as 3-cyano-1-(2-pyridyl)isoquinolines. thus, in the case of r = cn (scheme 1), the synthesis using aryne intermediates makes it possible to efficiently obtain the corresponding isoquinolines 3b, while the method based of the preparation tetrahydroisoquinolines 4b does not allow this because of the impossibility of subsequent aromatization by using the common methods. at the same time, in the scheme 1. reagents and conditions: i) anthranilic acid, isoamylnitrile, toluene — 1,4-dioxane (4: 1), boiling, 1.5 h; ii) 1-morpholinocyclohexene, without solvent, 200 °c, 4 h; iii) ddq, o-xylene, 143 °c, 10 h n n nar r n n ar r n n ar r n r = h, ph r = cn r = h, ph r = cn i ii iii n n n n ar r r = h, ph i ar = ph, tol, 4-brc6h4 1a,b 2 3a,b 4a,b (a) r = h, ph (b) r = cn 152 case of r = h or ar, the opposite situation is observed: the synthesis of isoquinolines 3a is possible with the use of a two-step pathway by using the corresponding enamine, and in the case of using aryl intermediates, the reaction leads mainly to rearrangement products 2. experimental nmr 1h and 13c spectra were recorded on the spectrometer “bruker-avance-400” (400 mhz), internal standard is sime4. the melting points were measured on the “boetius” device. mass spectra (type of ionization is electrospray) were recorded on the device of series “microtof-q ii” of “bruker daltonics” (bremen, germany). elemental analyses were performed on chn analyzer pe 2400, series ii by perkin elmer. acknowledgements this work was supported by the russian science foundation (reference # 18-13-00365). references 1. yoshida s, hosoya  t.  the renaissance and bright future of  synthetic aryne chemistry. chem lett. 2015;44(11):1450–60. doi: 10.1246 / cl.150839. 2. wu d, ge h, liu sh, yin j. arynes in the synthesis of polycyclic aromatic hydrocarbons. rsc advances. 2013;3(45):22727–38. doi:10.1039 / c3ra43804j. 3. miyabe h. synthesis of oxygen heterocycles via aromatic c-o bond formation using arynes. molecules. 2015;20(7):12558. 4. kopchuk ds, nikonov il, khasanov af, giri k, santra s, kovalev is, et al. studies on the interactions of 5-r-3-(2-pyridyl)-1,2,4-triazines with arynes: inverse demand aza-diels — alder reaction versus aryne-mediated domino process. org biomol chem. 2018;16(28):5119–35. doi: 10.1039 / c8ob00847g. 5. mikata y, yamanaka a, yamashita a, yano s. isoquinoline-based tqen family as tpen-derived fluorescent zinc sensors. inorganic chemistry. 2008;47(16):7295– 301. doi: 10.1021 / ic8002614. 6. tsuboyama a, iwawaki h, furugori m, mukaide t, kamatani j, igawa s, et al. homoleptic cyclometalated iridium complexes with highly efficient red phosphorescence and application to organic light-emitting diode. j am chem soc. 2003;125(42):12971–9. doi: 10.1021 / ja034732d. 7. nikonov il, kopchuk ds, kovalev is, zyryanov gv, khasanov af, slepukhin pa, et al. benzyne-mediated rearrangement of  3-(2-pyridyl)-1,2,4-triazines into 10-(1h1,2,3-triazol-1-yl)pyrido[1,2-a]indoles. tetrahedron lett. 2013;54(48):6427–9. doi: https://doi.org / 10.1016 / j.tetlet.2013.09.042. 8. kopchuk ds, kovalev is, khasanov af, zyryanov gv, slepukhin pa, rusinov vl, et al. a rational protocol for the synthesis of 1-(2-pyridyl)isoquinolines. mendeleev commun. 2013;23(3):142–4. doi: 10.1016 / j.mencom.2013.05.007. 9. kopchuk ds, nikonov il, zyryanov gv, kovalev is, rusinov vl, chupakhin on. preparation of 3-cyano-1-(2-pyridyl)isoquinolines by using aryne intermediates. chem heterocycl compd. 2014;50(6):907–10. doi: 10.1007 / s10593-014-1545-9. 60 kaymieva o. s., morozova m. v., buaynova e. s. ural federal university, 51lenin street, 620083 ekaterinburg fax: +7(343) 261-59-78; phone: +7(343) 261-59-78; e-mail:kaimi-olga@mail.ru synthesis and investigation of la 1–x bi x mn 1–y fe y o 3–δ structure* doped lanthanum manganites la 1–x bi x mn 1-y fe y o 3–δ (x=0.0–0.3; у=0.0–0.5, δх, у=0.1) with perovskite-like structure were synthesized by solid state reaction and solution method. it was determined by x-ray diffraction that sintered samples have rhombohedral symmetry (s.g. r-3c). the parameters of unit cell were calculated. the morphology of briket was investigated by scanning electron microscopy. it was found that sintered sample is homogeneous, porous and grains are formed by different size. elemental composition was checked by atomic emission spectroscopy. additional studies were performed by tg/dsc and laser diffraction (analysis of particle size distribution). *this work was done under financial support rfbr grant № 12-03-00953-a introduction currently a lot of interest is paid to perovskite materials based on lanthanum manganite due to their compatibility with the components of electrochemical cells. these materials can be used as electrodes. the introduction of various elements of replacement in the a and b sublattices can improve properties such as mechanical, thermal and chemical stability with respect to electrolyte material. it is assumed that bismuth doping may improve the chemical stability towards bismuth ceramics. the experimental part samples of la1–xbixmn1–yfeyo3–δ (x = 0.0–0.3; y = 0.0–0.5, δx, y = 0.1) were prepared by two methods: standard ceramic technology and citrate-nitrate method. following components were used as the basis: la2o3, bi2o3, mn2o3, fe2o3, bi (no3) 3 × 5h2o, mn (no3) 2 × 4h2o, fe (no3) 3 × 9h2o. the required amount of reagents was calculated according to the reaction equations. the final processing of the samples, compressed into briquettes, was carried out at a temperature of 1000 °c. for citrate-nitrate synthesis method oxides and nitrates of corresponding metals were dissolved separately in the distillated-water with nitric acid. then these solutions were mixed, citric acid was adddo i: 1 0. 15 82 6/ ch im te ch .2 01 5. 2. 1. 00 6 © kaymieva o. s., morozova m. v., buaynova e. s., 2015 62 № 1 | 2015 chimica techno acta synthesis and investigation of la 1-x bi x mn 1-y fe y o 3-δ structure ed in the ratio of 1:2 (the number of metal atoms: citric acid), and evaporated until the formation of dry intermediates. powder annealing was carried out at of 600 °c and 900–1000 °c. certification of obtained compounds was completed by powder x-ray diffraction by diffractometers dron-3 (monochromator from pyrolytic graphite on the reflected beam) and equinox 3000 enel (position-sensitive detector). radiographs were filmed in cukα-radiation in the angular range 2 = 10–90° at a rate of 2° per minute. finding of the parameters of the unit cells was carried out on a computer using special programs, “fpeak”, “celref”. the phase identification was performed using catalogs icdd. determination of particle size of obtained-powders was performed using a laser dispersion analyzer sald-7101 shimadzu. differential scanning calorimetry and thermal gravimetric analysis were performed using thermal analysis equipment: sta 409 luxx (netzsch, germany). the chemical composition of the samples was determined by atomic emission spectrometer with inductively-coupled plasma – icap 6500 duo thermo scientific. for analysis we took samples weighing 0.02–0.05 g that were dissolved in concentrated hydrochloric acid, adjusted to the mark by deioniized water in a volumetric flask (capacity 100 or 50 cm3). the resulting solution was analyzed. based on the results, the ratio of the metal components in the mix was calculated. for further investigation, the powders were pressed into briquettes and sintered. the bulk density of the samples was determined by hydrostatic weighing. microscopic studies and localized energy-dispersive microanalysis was executed by scanning (raster) electron microscope (sem) jeol jsm 6390la and energy-dispersive analyzer jeol jed 2300 (jeol; japan). results and discussion samples la1–xbixmn1–yfeyo3–δ (x = 0.0–0.3; y = 0.0–0.5, δx, y = 0.1) were obtained using solid-phase method and citrate-nitrate method. according to x-ray diffraction analysis, the compounds were found to have a rhombohedral structure. typical powder x-ray diffractions are shown in fig. 1. it was found that with increasing of bismuth, the final temperature of the synthesis is reducing. the parameters of the elementary cells and the concentration dependence were calculated. radiographical density of the powders was calculated. dsc/tga studies showed small mass loss in ~1% above 750 °c (fig. 2). laser diffraction method shows that the average particle size of the powders obtained by solid-phase method is in the range of 15–20 microns, and in the case of citrate-nitrate method shifts to an area of smaller numbers – 3–5 microns. fig.2. tga/dsc study la0.8bi0.2mn0.9fe0.1o3–δ 64 № 1 | 2015 chimica techno acta kaymieva o. s., morozova m. v., buaynova e. s. sem microimages of the surface of the sintered briquette of la0.9bi0.1mn0.8fe0.2o3±δ, obtained by citrate-nitrate method, showed that the sample is homogeneous; there is a uniform distribution of metal atoms in the cast (fig. 3). a local chemical compostion of the sample la: bi: (mn: fe) = 0.9: 0.08: (0.96) was established using the help of energy-dispersive analysis. the exact content of mn and fe could not be determined due to the overlap of pre-energy lines of 6.4 kev. for the determination of mn and fe in the samples using icp-aes characteristic lines of these elements mn (257.6; 259.3; 279.4 nm) and fe (218.7; 239.5; 259.8; 274.9; 371.9 nm) were taken. according to table 1, it is seen that in the synthesis of compounds elemental composition is preserved, and corresponds to the values shown in the formula. thus, these results support the formation of solid solutions based on lamno3 with the substitution of lanthanum and manganese sublattices. when citrate-nitrate method of synthesis is used, the final annealing temperature is less than when the solid state reaction is performed. fig.1. powder diffraction patterns la1–xbixmn1–yfeyo3–δ fig.3. microimages la0.9bi0.1mn0.8fe0.2o3±δ: a) the surface of the tablet; b) cleavage of the tablet in secondary (left) and reflected (right) electrons table 1 determination of metal elements in the samples by icp-aes compound ratio of la: bi: mn: fe theoretical experimental la 0,8 bi 0,2 mn 0,6 fe 0,4 o 3-δ 0,8:0,2:0,6:0,4 0,80:0,11:0,61:0,43 la 0,9 bi 0,1 mn 0,9 fe 0,1 o 3-δ 0,9:0,1:0,9:0,1 0,80:0,09:0,92:0,11 la 0,7 bi 0,3 mn 0,7 fe 0,3 o 3-δ 0,7:0,3:0,7:0,3 0,60:0,28:0,75:0,28 la 0,9 bi 0,1 mn 0,8 fe 0,2 o 3-δ 0,9:0,1:0,8:0,2 0,82:0,10:0,82:0,20 61 о. с. каймиева, м. в. морозова, е. с. буянова уральский федеральный университет, пр. ленина, 51, екатеринбург. факс: (343) 261-59-78; тел.: (343) 261-59-78; e-mail: kaimi-olga@mail.ru синтез и исследование структуры la 1–x bi x mn 1–y fe y o 3–δ * проведен синтез перовскитоподобных соединений на основе манганита лантана la 1-x bi x mn 1-y fe y o 3-δ (x = 0,0–0,3; у = 0,0–0,5, δх, у = 0,1). методом рентгенофазового анализа определено, что образцы обладают ромбоэдрической структурой (пр. гр. r-3c). рассчитаны параметры элементарных ячеек, построены их концентрационные зависимости. проведено исследование размера частиц по размерам. изучена морфология поверхности и выполнен энергодисперсионный микроанализ. химический состав образцов определен с помощью атомно-эмиссионной спектроскопии с индуктивно-связанной плазмой (аэс-исп). найденный элементный состав соответствует значениям, заявленным в формуле. тг/дск исследования показали убыль массы (~1 %) при температурах выше 750 °с. *работа выполнена при поддержке гранта рффи № 12-03-00953-a. у д к 5 41 .1 22 :5 36 .1 23 :5 46 .5 4 введение в настоящее время большой интерес представляют перовскитоподобные материалы на основе манганита лантана благодаря их совместимости с компонентами электрохимических ячеек. так данные материалы могут применяться в качестве электродов. введение различных замещающих элементов в аи в-подрешетки может улучшить свойства, такие как механическую, термическую и химическую стабильность по отношению к электролитному материалу. так предполагается, что допирование висмутом может повысить химическую стабильность по отношению к висмутсодержащей керамике. экспериментальная часть образцы la1-xbixmn1-yfeyo3-δ (x = 0,0–0,3; у = 0,0–0,5, δх,у = 0,1) были приготовлены по двум методикам: по стандартной керамической технологии и цитратно-нитратным методом. в качестве исходных компонентов были использованы: la2o3, bi2o3, mn2o3, fe2o3, bi(no3)3×5h2o, mn(no3)2×4h2o, fe(no3)3×9h2o. необходимое количество реагентов рассчитывали в со© каймиева о. с., морозова м. в., буянова е. с., 2015 63 № 1 | 2015 chimica techno acta ответствии с уравнениями реакций. окончательную обработку образцов, спрессованных в брикеты, проводили при температуре 1000 °с. для цитратно-нитратного метода синтеза оксиды и нитраты соответствующих металлов растворяли по отдельности в дистиллированной воде с добавлением азотной кислоты. затем полученные растворы смешивали, добавляли лимонную кислоту в соотношении 1:2 (число металлических атомов: лимонная кислота) и выпаривали до образования сухих полупродуктов. отжиг порошков проводили при температуре 600 °с и 900–1000 °с. аттестация полученных соединений выполнена методом порошковой рентгеновской дифракции на дифрактометрах dron-3 (монохроматор из пиролитического графита на отраженном пучке) и equinox 3000 enel (позиционно-чувствительный детектор). рентгенограммы были сняты в cuкα-излучении в интервале углов 2 = 10–90° со скоростью 2 град/мин. нахождение параметров элементарных ячеек проводили на компьютере с помощью специальных программ fpeaк, celref. идентификация фаз проведена с использованием картотеки icdd. определение размеров частиц полученных порошков проводили с помощью лазерного анализатора дисперсности sald-7101 shimadzu. дифференциальная сканирующая калориметрия и термогравиметрический анализ выполнены с использованием прибора термического анализа sta 409 luxx (netzsch, германия). химический состав образцов определяли на атомно-эмиссионном спектрометре с индуктивно-связанной плазмой icap 6500 duo thermo scientific. для проведения анализа брали навески образцов массой 0,02– 0,05 г, растворяли в концентрированной соляной кислоте (ос. ч.), доводили до метки деионизованной водой в мерной колбе (вместимостью 100 или 50 см3). полученный раствор анализировали. по результатам рассчитывали соотношение по металлическим компонентам в соединении. для дальнейшего исследования порошки были спрессованы и спечены в брикеты. объемную плотность образцов определяли методом гидростатического взвешивания. микроскопические исследования и локальный энергодисперсионный микроанализ выполнены с помощью сканирующего (растрового) электронного микроскопа (рэм) jeol jsm 6390la и энергодисперсионного анализатора jeol jed 2300 (jeol, япония). результаты и обсуждение образцы la1-xbixmn1-yfeyo3-δ (x = 0,0–0,3; у = 0,0–0,5, δх,у = 0,1) были получены с помощью твердофазного метода и цитратно-нитратного метода. по данным рентгенофазового анализа найдено, что соединения обладают ромбоэдрической структурой (пр.гр. r-3c). типичные порошковые рентгено граммы представлены на рис. 1. обнаружено, что с повышением содержания висмута конечная температура синтеза снижается. рассчитаны параметры элементарных ячеек, построены концентрационные зависимости. рассчитана рентгенографическая плотность порошков. синтез и исследование структуры la 1-x bi x mn 1-y fe y o 3-δ 65 № 1 | 2015 chimica techno acta дск/тг исследования показали небольшую убыль массы ~1 % выше 750 °с (рис. 2). методом лазерной дифракции обнаружено, что средний размер частиц порошков, полученных твердофазным методом, находится в интервале 15– 20 мкм, а в случае цитратно-нитратного метода смещается в область меньших значений – 3–5 мкм. рэм микроизображения поверхности спеченного брикета состава la0,9bi0,1mn0,8fe0,2o3±δ, полученного цитратно-нитратным методом, показали, что образец гомогенный, наблюдается равномерное распределение атомов металлов в брикете (рис. 3). с помощью энергодисперсионного анализа установлен локальный химический состав образца la:bi:(mn:fe) = 0,9:0,08:(0,96). точное содержание mn и fe определить не удалось из-за наложения линий приэнергии 6,4 кэв. для определения содержания mn и fe в образцах с помощью аэс-исп были выбраны характеристические линии этих элементов mn (257,6; 259,3; 279,4 нм) и fe (218,7; 239,5; 259,8; 274,9; 371,9 нм). по данным таблицы 1, видно, что в ходе синтеза элементный состав соединений сохраняется и соответствует значениям, указанным в формуле. таким образом, полученные результаты свидетельствуют в пользу образования твердых растворов на основе lamno3 при замещении подрешеток лантана и марганца. при цитратнонитратном методе синтеза конечная температура отжига меньше, чем при твердофазной реакции. рис. 1. порошковые дифрактограммы la1-xbixmn1-yfeyo3-δ рис. 2. тг/дск исследование la0,8bi0,2mn0,9fe0,1o3–δ таблица 1 определение содержания металлических элементов в образцах методом аэс-исп соединение соотношение la:bi:mn:fe теоретическое экспериментальное la0,8bi0,2mn0,6fe0,4o3–δ 0,8:0,2:0,6:0,4 0,80:0,11:0,61:0,43 la0,9bi0,1mn0,9fe0,1o3–δ 0,9:0,1:0,9:0,1 0,80:0,09:0,92:0,11 la0,7bi0,3mn0,7fe0,3o3–δ 0,7:0,3:0,7:0,3 0,60:0,28:0,75:0,28 la0,9bi0,1mn0,8fe0,2o3–δ 0,9:0,1:0,8:0,2 0,82:0,10:0,82:0,20 каймиева о. с. , морозова м. в., буянова е. с рис. 3. микроизображения la0,9bi0,1mn0,8fe0,2o3±δ: а – поверхности таблетки; б – скола таблетки во вторичных (слева) и отраженных (справа) электронах 1098-2580-1-pb 1098-2581-1-pb 131 d o i: 1 0. 15 82 6/ ch im te ch .2 01 5. 2. 2. 01 4 v. v. karpov, a. v. bazhenov, a. v. abramov, i. b. polovov, o. i. rebrin institute of physics and technology, 21 mira street, 620002 ekaterinburg fax: +7(343)374-54-91, phone: +7(343)375-41-51; e-mail: polovov@dpt.ustu.ru corrosion resistance of alloys of hastelloy in chloroaluminate melts the corrosion of hastelloy s, hastelloy x, haynes 230, hastelloy n, hastelloy g35 and hastelloy c2000 alloys was studied in kcl–alcl 3 melts at 550°с. the rates and the mechanisms of corrosion of the studied materials were determined. the processes taking place during the interaction between alloys and chloroaluminate melts were investigated. © karpov v. v., bazhenov a. v., abramov a. v., polovov i. b., rebrin o. i., 2015 introduction fast neutron energy reactors with molten salt coolant are related to a whole new generation of safe nuclear reactors where both uranium and thorium nuclear fuel can be used. however, the introduction of nuclear power plants based on molten salts is constrained by a number of problems; the most important of which is the need to develop new or improve existing structural materials, preserving stability in very aggressive conditions of high molten media. the experimental part this work is aimed at a comprehensive study of the interaction of high-temperature alloys hastelloy s, hastelloy x, haynes 230, and corrosion-resistant alloys hastelloy n, hastelloy g35 and hastelloy c2000 with chloroaluminate melts. application of the latter is considered to be promising for the organization of the second coolant circuit of molten nuclear power plants. the corrosion behavior of the materials was studied at a temperature of 550°c in electrolytes kcl-alcl3, molar ratio al: k equals 1:1. in this paper we used a set of independent research methods: gravimetric, metallographic analysis (olympus gx-71f), electron microscopy and x-ray microanalysis (jsm 6490, zeiss crossbeam auriga). in addition to studying the structure of the test materials, chemical analysis of quenched samples after corrosion tests of electrolytes by atomic emission spectroscopy with inductively coupled plasma (optima 2100dv) was carried out. 132 № 2 | 2015 chimica techno acta karpov v. v., bazhenov a. v., abramov a. v., polovov i. b., rebrin o. i. results and discussion the corrosion rates of the materials in molten kcl-alcl3 at a ratio of al/k = 1.1 after 100 hours at 550 °c are given in table 1. we found that heat-resistant alloys hastelloy x, hastelloy s and haynes 230 after exposure to chloaluminates melts are subject to intergranular corrosion (icc). under metallographic corrosion (1) of corroded samples, on their surface continuous chains of secondary excess phases at the grain boundaries are clearly observed (figure 1). the results of x-ray microanalysis demonstrated that along the chromium grain boundary, chromium concentration decreases by 20%, but directly at the grain boundaries increases dramatically. in heat-resistant melts the process of carbides formation on grain boundaries occurs primarily as a result of ‘rebirth’ of carbides due to heat powert (2): 6me6c + ncr = me23–ncrnc6 + (13 + n) me, this leads to the formation and subsequent dissolution of microgalvanopars and their anodic areas. these processes cause the development of these alloys, such as “hastelloy” processes icc. thus, despite the relatively low integral corrosion rate superalloy hastelloy x, table 1 the rate of corrosion of alloys such as “hastelloy” in kcl-alcl3 melt at 550°c. brand corrosion speed depth of corrosion penetration, μmg / (m2×h) mm / year x 0.8±0.2 0.9±0.2 55–65 s 0.8±0.1 0.8±0.1 18–24 230 0.8±0.2 0.8±0.2 27–32 n 0.6±0.1 0.6±0.1 – g35 1.4±0.3 1.4±0.3 – c2000 1.6±0.3 1.7±0.3 – fig. 1. the formation of excessive phase in the alloy hastelloy x after contact with a melt kcl-alcl3 for 100 hours at 550°c. (a – delivery status, b – after exposure to molten electrolyte) 133 № 2 | 2015 chimica techno acta corrosion resistance of alloys of hastelloy in chloroaluminate melts hastelloy s and haynes 230 chloraluminated electrolytes at 550°c, their use as structural materials in these conditions is not recommended due to the propensity to the icc. character of surfaces fracture of corrosion-resistant nickel-chromium-molybdenum alloys (hastelloy n, hastelloy g35, hastelloy c2000) after exposure to kcl-alcl3 at 550°c is solid, uneven (fig. 2). the existing local areas of increased corrosion are associated with structural unevenness of materials and presence of defective zones. metallografic analysis and etching to detect intergranular segregation show that after 100 hours exposure of the samples, secondary phases at grain boundaries are small and fragmented (figure 3). increasing the concentration of existing inclusions in the bulk samples is also not revealed. corrosion rate of alloys hastelloy n, g35 and c2000 is defined by redox processes, as a result of which the ions of sal medium oxidize the most electronegative alloy components such as chromium, manganese and iron. conclusions on the preferential dissolution during exposure in the melt kclalcl3 of the most electronegative component of alloys hastelloy n, hastelloy g35 and hastelloy c2000 (chromium, manganese and iron) are confirmed by the data of chemical analysis of frozen electrolyte melts obtained after corrosion tests. longer contacts with the chloraluminated electrolytes to 500–1000 hours result in a significant reduction of the corrosion rate of studied corrosion resistant alloys “hastelloy”. on the one hand this is due to slow diffusion of electronegative alloy components of the grains of the boundary electrolyte – melt, and low rate of removal of the corrosion products from a melt saturated by these elements. furthermore, we recorded the alloy surface fig. 2. the microstructure of the alloy specimens after 100 hours exposure in the kcl-alcl3 at 550°c (a – hastelloy n, b – hastelloy g35, in – hastelloy c2000) fig. 3. formation of excess phases in corrosion-resistant nickel alloys after 100 hours exposure in kcl-alcl3 at 550°c (a – hastelloy n, b – hastelloy g35, in – hastelloy c2000) 134 № 2 | 2015 chimica techno acta karpov v. v., bazhenov a. v., abramov a. v., polovov i. b., rebrin o. i. layer formation of non-corrosive components molybdenum and nickel. it can be reasonably assumed that the image in the corrosion coating may have a protective effect and protect the structural material from further destruction. thus, using of corrosion-resistant nickel-chromium-molybdenum alloys (hastelloy n, hastelloy g35, hastelloy c2000), it is possible to predict quantitatively the corrosion processes. it is without doubt that the interest to study the possibility of organizing the protection of materials due to the “self-passivation” electropositive surface of the alloy components will exist. 1. bekkert m., klemm h. reference book on metallografic etching. moscow: metallurgy: 1979, 336 p. 2. sims ch. t., stoloff n. s., hagel’ u. k. superalloy ii. refractory materials for aerospace and industrial installations. moscow: metallurgy: 1985, 384 p. 135 у д к 6 20 .1 68 .1 :6 69 .0 18 .8 в. в. карпов, а. в. баженов, а. в. абрамов, и. б. половов, о. и. ребрин физико-технологический институт, 620002, екатеринбург, ул. мира, 21. факс: (343) 374-54-91, тел.: (343) 375-41-51; e-mail: polovov@dpt.ustu.ru коррозионная стойкость сплавов семейства «hastelloy хастеллой» в хлоралюминатных расплавах изучена коррозия сплавов hastelloy s, hastelloy x, haynes 230, hastelloy n, hastelloy g35 и hastelloy c2000 в расплавах kcl–alcl 3 при 550 °с. определены скорости и механизмы коррозии исследуемых материалов в данных условиях. исследованы процессы, протекающие в ходе контакта сплавов с хлоралюминатными электролитами. © карпов в. в., баженов а. в., абрамов а. в., половов и. б., ребрин о. и., 2015 введение энергетические реакторы на быстрых нейтронах с жидкосолевым теплоносителем относятся к совершенно новому поколению безопасных ядерных реакторов, в которых может быть использовано как урановое, так и ториевое ядерное топливо. однако внедрение ядерно-энергетических установок на основе расплавленных солей сдерживается рядом проблем, наиболее важной из которых является необходимость разработки новых, либо совершенствование существующих конструкционных материалов, сохраняющих стойкость в крайне агрессивных условиях высокотемпературных расплавленных сред. экспериментальная часть данная работа нацелена на комплексное исследование процессов взаимодействия жаропрочных сплавов hastelloy s, hastelloy x, haynes 230 и коррозионностойких сплавов hastelloy n, hastelloy g35 и hastelloy c2000 с хлоралюминатными расплавами. применение последних считается перспективным для организации второго контура теплоносителя жидкосолевых ядерно-энергетических установок. коррозионное поведение материалов изучено при температуре 550 °c в электролитах kcl–alcl3 с мольным отношением al : k, равным 1:1. в работе использован комплекс 136 № 2 | 2015 chimica techno acta карпов в. в., баженов а. в., абрамов а. в., половов и. б., ребрин о. и. независимых способов исследования: гравиметрический метод, металлографический анализ (olympus gx-71f), электронная микроскопия и рентгеновский микроанализ (jsm 6490, zeiss crossbeam auriga). в дополнение к изучению структуры тестируемых материалов осуществляли химический анализ закаленных после коррозионных испытаний проб электролитов методом атомно-эмиссионной спектроскопии с индуктивно-связанной плазмой (optima 2100dv). результаты и их обсуждение скорости коррозии исследуемых материалов в расплаве kcl–alcl3 при соотношении al/k = 1,1 после 100 ч. выдержки при 550 °с приведены в таблице 1. нами установлено, что жаропрочные сплавы hastelloy x, hastelloy s и haynes 230 после выдержки в хлоалюминатных расплавах подвержены межкристаллитной коррозии (мкк). при металлографическом травлении [1] прокорродировавших образцов на их поверхности отчетливо наблюдаются сплошные цепочки вторичных избытаблица 1 скорости коррозии сплавов типа «хастеллой» в расплаве kcl–alcl3 при 550 °с марка сплава скорость коррозии глубина проникновения коррозии, мкмг/(м2·ч) мм/год x 0,8 ± 0,2 0,9 ± 0,2 55–65 s 0,8 ± 0,1 0,8 ± 0,1 18–24 230 0,8 ± 0,2 0,8 ± 0,2 27–32 n 0,6 ± 0,1 0,6 ± 0,1 – g35 1,4 ± 0,3 1,4 ± 0,3 – c2000 1,6 ± 0,3 1,7 ± 0,3 – рис. 1. образование избыточных фаз в сплаве hastelloy x после контакта с расплавом kcl–alcl3 в течение 100 ч при 550 °с: a – состояние поставки; б – после выдержки в расплавленном электролите 137 № 2 | 2015 chimica techno acta коррозионная стойкость сплавов семейства «hastelloy хастеллой» в хлоралюминатных расплавах точных фаз по границам зерен (рис. 1). результаты рентгеновского микроанализа показали, что вдоль границ зерен концентрация хрома падает на 20 %, а непосредственно на границах зерен резко возрастает. это указывает на образование по границам зерен цепочек избыточных карбидов хрома. в жаропрочных сплавах образование карбидных фаз по границам зерен протекает преимущественно в результате «перерождения» первичных карбидов вследствие термовлияния [2]: 6me6c + ncr = me23–ncrnc6 + (13+n)me, это приводит к образованию микрогальванопар и последующему растворению их анодных зон. протекание данных процессов обусловливает развитие в жарапрочных сплавах типа «хастеллой» процессов мкк. таким образом, несмотря на относительно низкие интегральные скорости коррозии жаропрочных сплавов hastelloy x, hastelloy s и haynes 230 в хлоалюминатных электролитах при 550 °c, их использование в качестве конструкционных материалов в данных условиях не рекомендуется в силу склонности к мкк. характер разрушения поверхности коррозионностойких никель-хроммолибденовых сплавов (hastelloy n, hastelloy g35, hastelloy с2000) после выдержки в kcl–alcl3 при 550 ос – сплошной, неравномерный (рис. 2). имеющие место локальные зоны повышенной коррозии связаны со структурной неравномерностью материалов и наличием в них дефектных зон. металлографический анализ и травление с целью выявления межкристаллитных сегрегаций показали, что после 100 ч выдержки образцов вторичные фазы на границах зерен имеют малые размеры и разобщены (рис. 3). увеличение концентрации существующих включений в объеме образцов также не выявлено. скорость коррорис. 2. микроструктура образцов сплавов после 100 ч выдержки в kcl–alcl3 при 550 °с: а – hastelloy n, б – hastelloy g35, в – hastelloy с2000 рис. 3. образование избыточных фаз в коррозионно-стойких никелевых сплавах после 100 ч выдержки в kcl–alcl3 при 550 °с: а – hastelloy n; б – hastelloy g35; в – hastelloy с2000 138 № 2 | 2015 chimica techno acta карпов в. в., баженов а. в., абрамов а. в., половов и. б., ребрин о. и. зии сплавов hastelloy n, g35 и с2000 определяется окислительно-восстановительными процессами, в результате которых ионы солевой среды окисляют наиболее электроотрицательные компоненты сплава, такие как хром, марганец и железо. вывод о преимущественном растворении в ходе выдежке в расплаве kcl–alcl3 наиболее электро отрицательных компонентов сплавов hastelloy n, hastelloy g35 и hastelloy с2000 (хрома, марганца и железа) подтвержден данными химического анализа замороженных cплавов элект ролитов, полученных после коррозионных испытаний. увеличение продолжительности контакта с хлоралюминатными электролитами до 500–1000 ч приводит к значительному уменьшению скорости коррозии исследуемых коррозионностойких сплавов семейства «хастеллой». с одной стороны, это вызвано замедленной диффузией электроотрицательных компонентов сплавов из объема зерен к границе электролит – сплав и низкой скоростью отвода продуктов коррозии через расплав, насыщенный по этим элементам. кроме того, на поверхности сплавов нами зафиксировано образование слоя из некорродирующих компонентов – молибдена и никеля. можно обоснованно предположить, что образующееся в ходе коррозии покрытие может оказывать защитное действие и предохранять конструкционный материал от дальнейшего разрушения. таким образом, при использовании коррозионностойких никель-хроммолибденовых сплавов (hastelloy n, hastelloy g35, hastelloy с2000) возможно количественное прогнозирование процессов коррозии. представляет несомненный интерес изучение возможности организации защиты материалов за счет «самопассивации» их поверхности электроположительными компонентами сплавов. 1. беккерт м., клемм х. справочник по металлографическому травлению. м.: металлургия, 1979. 336 с. 2. симс ч. т., столофф н. с., хагель у. к. суперсплавы ii. жаропрочные материалы для аэрокосмических и промышленных энергоустановок. м.: металлургия, 1985. кн. 1. 384 с. рекомендуем при цитировании данно статьи следующую ссылку: karpov v. v., bazhenov a. v., abramov a. v., polovov i. b., rebrin o. i. corrosion resistance of alloys of hastelloy in chloroaluminate melts // chimica techno acta. 2015. vol. 2. № 2. p. 131–138. 164 d o i: 1 0. 15 82 6/ ch im te ch .2 01 5. 2. 2. 01 8 v. m. bakanov, l. n. maskaeva, v. f. markov ural institute of state fire service of emercom of russia, 22 mira street, ekaterinburg phone: +7(343)360-81-68; e-mail: mln@ural.ru thermosensitization of nanostructured pbse films the mode and conditions of thermal sensitization in the temperature range 648–698k lead selenide films deposited from ethylendiamine acetate system were determined. the effect of heat treatment on the morphology and properties of photosensitive chemically deposited films of pbse was showed. it is concluded that the results obtained by hydrochemical synthesis of nanostructed highly sensitive to infrared range radiation layer of lead selenide provide performance on the level of best foreign analogues. © bakanov v. m., maskaeva l. n., markov v. f., 2015 introduction lead selenide is a semiconductor material most in demand for the creation of ir detectors for spectral range of 2–5 mkm1,2. one of the promising methods of forming of pbse thin layers with high functional properties is hydrochemical deposition. this method is simple to implement, has a wide range of technological capabilities helping, by having in its base a colloid-chemical stage, to create nanostructured semiconductor layers3,4. the present study is devoted to the study of the process of thermosensitization of hydrochemically deposited pbse films for providing high sensitivity for ir radiation. one of the key questions in obtaining highly-functional pbse films is the question of formulating of the reactionary bath tank. from the point of view of producing films of a certain thickness and structure, the choice of complexing agents for lead ions is important; this role was performed by ethylendiamine c2h4n2h4 and ammonium acetate nh4ch3coo. as an antioxidant for unstable in air aqueous solutions of selen carbamide csen2h4, sodium sulfite na2so3 was used. for increasing of the sensitivity of the lead selenide films to infrared radiation, ammonium iodide nh4i was additionally introduced into the reaction mixture. the experimental part hydrochemical synthesis of lead selenide layers was carried out in a fixed-type reactor at temperature range of 308–343 k at the process time of 40–60 minutes. degreased pyroceramics plates st-150 were used as substrates. preparation of highly sensitive to ir radiation pbse films requires a manda165 № 2 | 2015 chimica techno acta thermosensitization of nanostructured pbse films tory operation of sensitization, for which annealing in air is used. heating leads to the recrystallization of layers and oxygen phased additions, in particular, to the formation of oxygen-containing impurity phases such as pbo, pbseo3. their presence in the layer helps to optimize the carrier density and increase the value of photo response. for this work, annealing of the deposited films was carried out at temperature range 648–698 k. the crystal structure of the deposited lead selenide films was investigated in details using x-ray diffraction. radiographs were obtained on a diffractometer "dron4" in the angular range 2ϑ = 20–90° in step-scan mode, δθ = 0.03 degrees. copper radiation using pyrolytic graphite as a monochromator for distinguishing cukα doublet from the continuous spectrum was used. electron microscopic images of pbse layers are made with a scanning electron microscope jsm-6390. the measurement of photoresponse of synthesized films was carried out on measuring stand k.54.410 after the electrochemical deposition of paired nickel contacts. the blackbody 573 k was used as a radiation source, providing the irradiated samples at 9×10–5 vt.sm–2 and at a modulation frequency of radiation in the optical flow 1200hz. the bias voltage is set at 6 v/mm. results and discussion using x-ray diffraction, it was found that annealing leads to some increase in constant of the pbse crystal-lattice (structure b1) from a = 0.61185 nm for the freshly precipitated layers to a = 0.61606 nm for the heat-treated at 678 k. this may be due to the process of film recrystallization and the ordering of their structure. the results of electron microscopy studies of pbse layers are shown in fig. 1. it draws attention that freshly precipitated pbse layer (fig. 1a) is formed of spherical particles with prevailing globule sizes of 80–200 nm, which, in turn, are composed of spherical units of ~ 25–40 nm in diameter. thus, obtained hydrochemical pbse deposited layers are nanostructured in their architecture. it can be concluded that formation and growth of films of lead selenide from aqueous solutions proceeds according to cluster-cluster aggregation, involving colloid chemical processes happening not fig. 1. electron microscopic images of freshly precipitated (a) and annealed at a temperature of 678 k (b) pbse films. annealing time is 10 minutes a b 166 № 2 | 2015 chimica techno acta bakanov v. m., maskaeva l. n., markov v. f. only on the substrate surface but also in volume of the reaction mixture. heat treatment significantly alters films morphology. as a result of recrystallization, an increase in pri-mary nanoscale aggregates up to 300–600 nm with changing their crystallographic form occurs (see fig. 1b). we shall note that the size of the films microcrystals from the results of electron microscopy studies are in good agreement with the estimate of the average size of the coherent scattering films regions, calculated according to the debye-sherrer formula from x-ray data from the studies. fig. 2 shows the dependence of the photo-response of pbse films from the time they were annealed at temperatures of 648, 673 and 698 k. dependencies have pronounced maximum of response, which with increasing temperature shifts toward shorter annealing. annealing at 698 k leads apparently to a sharp increase in the rate of oxidation of lead selenide and characterized by narrow time ranges of rated maximum photoresponse. on the other hand, it is clear that at an annealing temperature of 648 k, the process of sensitization is significantly lengthened, not allowing achieving a high volt-watt sensitivity of the films. it can be concluded that the magnitude of photoresponse of layers is the result of interconnected timetemperature effects on the structure and composition of impurity. to ensure high values of photoresponse, it is necessary to select conditions to achieve a certain degree of recrystallization and the level of oxygenation of the layer. it is found that the decrease in crystallite sizes, which form pbse films, contributes to a significant increase in the level of its photoresponse. thus, the heat treatment of hydrochemically in air deposited nanostructured pbse films by choosing of mode and process parameters, provides the possibility of obtaining layers with high values of the photoresponse to ir radiation, including to the level typical of the best foreign models. 1. butkevich v. g., bochkov v. d., globus e. r., appliead physics. 2001; 6:66. 2. bode d. e. detectors on basic ph-salts. 1968; 3:299–327. 3. markov v. f., maskaeva l. n., ivanov p. n. hydrochemical precipitation of film sulfide metals: modelling and experiment. ekaterinburg: uro ran:2006, 216. 4. markov v. f., maskaeva l. n., loshrareva l. d., uimin s. i., kitaev g. a., pb1– xsnxse substitutional solid solution prepared by coprecipitation from aqueos solution.inoranic materials. 1997; 33(6) : 665. fig. 2. dependence of the current-watt sensitivity of the pbse films on duration of annealing at 648 k (1), 673 (2), 698 k (3) 167 у д к 5 49 .3 28 :5 48 .7 64 :5 42 .4 64 в. м. баканов, л. н. маскаева, в. ф. марков кафедра химии и процессов горения. уральский институт гпс мчс россии, ул. мира, 22, 620002, екатеринбург. тел.: (343) 360-81-68; e-mail: mln@ural.ru термосенсибилизация наноструктурированных пленок pbse определены режимы и условия термосенсибилизации в температурном диапазоне 648–698 k пленок селенида свинца, осажденных из этилендиамин-ацетатной системы. показано влияние термообработки на морфологию и фоточувствительные свойства химически осажденных пленок pbse. сделан вывод о том, что гидрохимический синтез обеспечивает получение наноструктурированных высокочувствительных к ик-излучению слоев селенида свинца на уровне лучших зарубежных аналогов. © баканов в. м., маскаева л. н., марков в. ф., 2015 введение селенид свинца является полупроводниковым материалом, наиболее востребованным для создания ик-детекторов для спектрального диапазона 2–5 мкм [1, 2]. одним из перспективных методов формирования тонких слоев pbse с высокими функциональными свойствами является гидрохимическое осаждение. этот метод достаточно прост в реализации, обладает широкими технологическими возможностями, позволяющими за счет находящейся в его основе коллоидно-химической стадии создавать наноструктурированные полупроводниковые слои [3, 4]. настоящее исследование посвящено исследованию процесса термосенсибилизации гидрохимически осажденных пленок pbse с целью обеспечения высокой чувствительности к ик-излучению. одним из ключевых для получения высокофункциональных пленок pbse является вопрос формирования рецептуры реакционной ванны. с точки зрения получения пленок определенной толщины и структурированности важен выбор комплексообразующих агентов для ионов свинца, роль которых выполняли этилендиамин с2н4n2h4 и ацетат аммония nh4 сн3соо. в качестве антиоксиданта для неустойчивых на воздухе водных растворов селенокарбамида csen2h4 использовали сульфит натрия na2so3. для повышения чувствительности пленок селенида свинца к ик-излучению в реакционную смесь дополнительно вводили соль йодида аммония nh4i. 168 № 2 | 2015 chimica techno acta баканов в. м., маскаева л. н., марков в. ф. экспериментальная часть гидрохимический синтез слоев селенида свинца осуществляли в реакторе стационарного типа в диапазоне температур 308–343 k при продолжительности процесса 40−60 мин. в качестве подложек использовались предварительно обезжиренные ситалловые пластины марки ст-150. получение высокочувствительных к ик-излучению пленок pbse требует применения обязательной операции сенсибилизации, в качестве которой используется отжиг в воздушной атмосфере. нагрев приводит к рекристаллизации слоев и дозированному введению кислорода, в частности, к образованию кислородсодержащих примесных фаз таких, как pbo, pbseo3. их присутствие в слое способствует оптимизации концентрации носителей и повышению величины фотоответа. в работе отжиг осажденных пленок проводили в температурном диапазоне 648–698 k. кристаллическая структура осажденных пленок селенида свинца детально исследовали с помощью дифракции рентгеновских лучей. рент генограммы были получены на дифракто-метре «дрон-4» в интервале углов 2ϑ = 20–90° в режиме пошагового сканирования δθ = 0,03°. использовали медное излучение с применением пиролитического графита в качестве монохроматора для выделения cukα − дублета из сплошного спектра. элект ронно-микро скопиче ские изображения слоев pbse выполнены с помощью растрового электронного микроскопа jsm-6390. измерение фотоотклика синтезированных пленок осуществляли на измерительном стенде к.54.410 после электрохимического нанесения парных никелевых контактов. в качестве источника излучения использовали ачт 573 k, обеспечивающего облученность образца на уровне 9×10–5 вт·см–2 при частоте модуляции излучения оптического потока 1200 гц. напряжение смещения устанавливали 6 в/мм. результаты и их обсуждение методом рентгеновской дифракции было установлено, что отжиг приводит к некоторому увеличению постоянной кристаллической решетки pbse (структура b1) с а = 0,61185 нм для свежеосажденных слоев до а = 0,61606 нм, для термообработанных при 678 k. это может быть обусловлено протеканием процесса рекристаллизации пленок и упорядочением их структуры. результаты электронно-микроскопических исследований изображений слоев pbse представлены на рис. 1. обращает на себя внимание то, что свежеосажденный слой pbse (рис. 1, а) сформирован из частиц сферической формы с преобладающими размерами глобул 80−200 нм, которые, в свою очередь, состоят из сферических агрегатов диаметром 25−40 нм. таким образом, полученные в работе гидрохимически осажденные слои pbse по своей архитектуре являются наноструктурированными. отсюда можно сделать вывод, что образование и рост пленок селенида свинца из водных растворов протекает по механизму кластер-кластерной 169 № 2 | 2015 chimica techno acta термосенсибилизация наноструктурированных пленок pbse агрегации с участием коллоидно-химических процессов, протекающих не только на поверхности подложки, но и в объеме реакционной смеси. термообработка существенно изменяет морфологию пленок. в результате рекристаллизации происходит увеличение первичных наноразмерных агрегатов до 300−600 нм с изменением их кристаллографической формы (рис. 1, б). отметим, что размеры микрокристаллитов пленок из результатов электронно-микроскопических исследований хорошо согласуются с оценкой средних размеров областей когерентного рассеяния пленок, рассчитанных по формуле дебая – шеррера из данных рентгеновских исследований. на рис. 2 приведены зависимости фотоотклика пленок pbse от времени их отжига при температурах 648, 673 и 698 k. зависимости имеют выраженный максимум отклика, который с ростом температуры сдвигается в сторону меньшей продолжительности отжига. отжиг при температуре 698 k приводит, по-видимому, к резкому возрастанию скорости окисления селенида свинца и характеризуется узким временным диапазоном максимума фотоответа. с другой стороны, видно, что при температуре отжига 648 k значительно удлиняется процесс сенсибилизации, не обеспечивая достижения высокой вольт-ваттной чувствительности пленок. можно сделать вывод о том, что величина фотоотклика слоев является результатом взаимосвязанного температурно-временного воздействия на их структуру и примесный состав. для обеспечения высоких значений фототклика необходим подбор условий для достижения определенной степени рекристаллизации и уровня оксигенизации слоя. установлено, что уменьшение размеров кристаллирис. 2. зависимость вольт-ваттной чувствительности пленок pbse от продолжительности отжига при 648 k (1), 673 k (2), 698 k (3) рис. 1. электронно-микроскопические изображения свежеосажденных (а) и отожженных при температуре 678 k (б) пленок pbse. время отжига – 10 минут а б 170 № 2 | 2015 chimica techno acta баканов в. м., маскаева л. н., марков в. ф. тов, формирующих пленку pbse, способствует существенному повышению уровня ее фотоответа. таким образом, термообработка на воздухе гидрохимически осажденных наноструктурированных пленок pbse путем подбора режима и параметров процесса обеспечивает возможность получения слоев с высокими значениями фотоотклика к ик-излучению, в том числе до уровня, свойственного лучшим зарубежным образцам. 1. буткевич в. г., бочков в. д., глобус е. р. фотоприемники и фотоприемные устройства на основе поликристаллических и эпитаксиальных слоев халькогенидов свинца. прикладная физика. 2001; 6: 66. 2. боде д. е. детекторы на основе солей свинца / пер. с англ. 1968. т. 3. с. 299– 327. 3. марков в. ф., маскаева л. н., иванов п. н. гидрохимическое осаждение пленок сульфидов металлов: моделирование и эксперимент. екатеринбург: уро ран. 2006. 216 с. 4. марков в. ф., маскаева л. н., лошкарева л. д., уймин с. н., китаев г. а. получение твердых растворов замещения в системе свинец-олово-селен соосаждением из водных растворов. неорганические материалы. 1997: 33; 665. рекомендуем при цитировании данно статьи следующую ссылку: bakanov v. m., maskaeva l. n., markov v. f. thermosensitization of nanostructured pbse films // chimica techno acta. 2015. vol. 2. № 2. p. 164–170. 86 m. v. rotermela, t. i. krasnenkoa, s. a. petrovab, s. g. titovab a institute of solid state chemistry, ural branch of the russian academy of sciences, 91 pervomayskaya st., ekaterinburg, 620990, russian federation b institute of metallurgy, ural branch of the russian academy of sciences, 101amundsena st., ekaterinburg, 620016, russian federation rotermel@ihim.uran.ru conditions for the formation of a non-autonomous phase at the structural deformation of complex vanadium oxides a new previously unknown effect of a reversible transition from a singlephase system to a heterophase system containing a non-autonomous phase was observed during thermal and chemical deformations of the zn 2–2x cd 2x v 2 o 7 structure.the role of local symmetry in the formation of the non-autonomous phase is shown on the basis of x-ray diffraction studies in situ and a comparative crystal-chemical analysis of the structural deformations of isoform monoclinic solid solutions of zinc and copper pyrovanadates with zero volumetric thermal expansion. keywords: non-autonomous phase, volume thermal expansion, m 2 v 2 o 7 received: 02.03.2018. accepted: 10.04.2018. published: 10.05.2018. © rotermel m. v., krasnenko t. i., petrova s. a., titova s. g., 2018 d o i: 1 0. 15 82 6/ ch im te ch .2 01 8. 5. 1. 06 introduction the non-autonomous phase is a phase whose existence under a certain thermodynamic conditions is possible only in an ensemble with one or more compounds. since the introduction of r. defay in 1961 [1, 2], the term of “non-autonomous phase” was used, primarily, in connection with the assumption of a special role of the surface where the concentration of defects is higher than in the volume. to date, non-autonomous phases have been detected as components of various heterophase systems. thus, considerable attention has been paid in recent years to non-autonomous surface phases in the geological and mineralogical literature, where their roles in the adsorption and segregation of impurities on the surface, or in interphase and intergranular borders, and also in the transfer of matter from high pressure to normal conditions have been established [3–7]. stabilization of such phase associations is provided by an increase in the total free energy due to the energy of coherent inter-phase boundaries. changes in the elemental composition of the surface of synthetic single crystals and ceramics due to thermally activated heterosegregation were shown earlier [8]. a supramolecular concept of eutectics that takes into account the interaction of disproportionate substructures and reveals mechanisms of formation of supramorotermel m. v., krasnenko t. i., petrova s. a., titova s. g. chimica techno acta. 2018. vol. 5, no. 1. p. 86–91. issn 2409–5613 87 lecular ensembles in boundary layers, i.e. non-autonomous phases, was suggested in a number of works, which studied eutectic alloys in inorganic systems [9]. a “compo site effect” resulting in high ionic conducti vity was found in several binary systems, and has been used for preparation of electrode materials for the chemical power sources because of the high ionic conductivity of the particles of the nonautonomous phase. the participation of non-autonomous phases in the solid-phase synthesis and sintering of ceramic samples at tammann temperature due to the melting of the non-autonomous phase on the matrix surface were assumed and thermodynamically justified, as well as participation of the non-autonomous phase in the charge and mass transfer processes was shown [10–16]. we discovered a new, previously unknown effect of a reversible transition from a single-phase system to a heterophase system; the latter, together with the main phase, contains also the non-autonomous phase (np). monoclinic β-zn2–2xcd2xv2o7 solid solutions (space group c2/m) contain the non-autonomous phase within the temperature range 20– 735 °c with the compositional range varied from 2.5 to 50 mol.% of cd2v2o7 in amount of several percent (fig. 1). the increase of temperature narrows the region of the heterophase system. high-temperature x-ray diffraction method showed that negative or close to zero volume thermal expansion was observed inside the region where β-zn2–2xcd2xv2o7 and the non-autonomous phase coexisted. a precise high-temperature and low-temperature in situ x-ray diffraction studies of thermal expansion for a number of monoclinic β-cu2–2xzn2xv2o7 (x  = 0.15, 0.3, 0.4, 0.6) solid solution samples (space group c2/c) were performed in order to set the conditions for appearance and stabilization of the non-autonomous phase. although the negative volume thermal expansion over a wide temperatures range was observed, the presence of the nonautonomous phase in the entire region of cu2–2xzn2xv2o7 existence was not confirmed (fig. 1). a comparative analysis of two vanadate systems that contain the solid solutions with identical chemical formula and monoclinic crystal structure, both with the wide range of close to zero and negative volume thermal expansion, allows to propose the structural model for the appearance and stabilization of the non-autonomous phase for the low-symmetric pyrovanadates of divalent metals. experimental solid solutions in the zn2v2o7– cd2v2o7 and zn2v2o7– cu2v2o7 systems were obtained by the ceramic synthesis method. x-ray in situ studies were carried out using a diffractometer shimadzu xdr7000 (cu kα radiation) in the range of angles 2θ from 5° to 120° with steps 0.02°, with silicon as an external standard. high-temperature measurements were performed with an anton paar ttk-450 attachment. the crystal structure refinement of the powder diffraction data was made using the gsas software. results and discussion the changes of unit cell parameters for the solid solutions within the temperature range from the room temperature up to 800 °c were analyzed (fig. 2) in order to 88 establish the relations between the appearance of non-autonomous phase in the zn2v2o7 – cd2v2o7 system and the transformations of the matrix phase. maximum thermal deformations, accompanied by the close to zero volume thermal expansion (for β-zn1.6cd0.4v2o7 αv = –0.08×10 –5 deg-1), were observed within the region of β-zn2–2xcd2xv2o7 and the non-autonomous phase coexistence. noticeable expansion of monoclinic solid solution was observed out of the range of stabilization for the nonautonomous phase. significant changes of the unit cell parameters a and b take place inside the region of heterophase system. the maximal transformation of the monoclinic plane (ac) happens due to the change in the β angle, which causes shear deformation at a fixed rotation angle of [vo4]-tetrahedron; v – obridge–v = 180°, c2/m (fig. 3). analysis of the changes in the unit cell parameters for the β-zn2–2xcd2xv2o7 solid solutions indicates the existence of a correlation between the appearance and disappearance of the non-autonomous phase and the shear strain intensity with a change fig. 1. phase equilibria in the cd2v2o7– zn2v2o7 and zn2v2o7– cu2v2o7 systems:  – solid solution cd2–2xzn2xv2o7;  – solid solution of β-zn2–2xcd2xv2o7;  – solid solution β-zn2–2xcd2xv2o7+ np;  – solid solution of α-zn2–2xcd2xv2o7;  – solid solution α-zn2–2xcu2xv2o7;  – solid solution of β-zn2–2xcu2xv2o7;  – solid solution β-cu2–2xzn2xv2o7; – solid solution of β’-cu2–2xzn2xv2o7;  – solid solution α-cu2–2xzn2xv2o7; – solidus line fig. 2. the unit cells parameters for the β-zn2–2xcd2xv2o7 solid solutions versus temperature β-zn2–2xcd2xv2o7 cd2v2o7 т, °c zn2v2o7 100 200 300 400 500 600 700 800 900 1000 cu2v2o7 0 200 400 600 800 285 288 291 107,2 108,0 108,8 109,6 9,99 10,02 10,05 10,08 8,46 8,52 8,58 8,64 7,00 7,04 7,08 7,12 v , å 3 t , o c β, o c, å b, å zn 1 , 75 cd 0, 2 5 v 2 o 7 zn 1 , 63 cd 0, 3 7 v 2 o 7 zn 1 , 6 cd 0 ,4 v 2 o 7 zn 1 , 2 cd 0 ,6 v 2 o 7 a , å 89 in the monoclinic angle. significant shear deformations were detected exactly in the region where β-zn2–2xcd2xv2o7 and nonautonomous phase coexisted; therefore, it can be assumed that the monoclinic plane in this case serves as a substrate generating the non-autonomous phase. an increase in temperature or concentration of dopant cation leads to the disappearance of the shear deformation, and at the same time – to the disappearance of the non-autonomous phase, as shown in fig. 1. thermal behavior of two representative solid solution samples in the zn2v2o7 – cu2v2o7 system, cu1.6zn0.4v2o7 and cu0.8zn1.2v2o7, were studied in a wide temperature range (–180–400 °c) in order to determine the dependence of the non-autonomous phase appearance on the nature of thermal deformations of crystal lattice. the temperature dependencies of the unit cell parameters for cu1.6zn0.4v2o7 and cu0.8zn1.2v2o7 are shown in fig. 4. one can see that the values of unit cell parameters change monotonously within the studied temperature range. the a parameter decreases significantly with temperature. the values of negative volume thermal expansion of the lattice for the both solid solutions correlate well with changes in the parameter a (for cu1.6zn0.4v2o7 αv = –3.14×10–5 deg-1). the parameter c and the monoclinic angle β remain practically unchanged. it should be noted that the rotation angle of vanadium-oxygen tetrahedron v – obridge – v for the samples cu1.6zn0.4v2o7 and cu0.8zn1.2v2o7 at temperature –180 °c was equal to 131.6(8)° and 129.9(7)°, respectively, and slightly decreased to 130.5(4)° and 129.3(4)°, respectively, when temperature was raised to 400 °c, since the structure belongs to the space group c2/c. based on the obtained data, one can conclude that the absence of the non-autonomous phase in the zn2v2o7 – cu2v2o7 system is due to the combined effect of two factors: insignificant shear deformations of the crystal lattice, governed by the change of the monoclinic angle β, and the mobility of vanadium-oxygen subsystem (fig. 5) due to additional turn of vanadium-oxygen bi-ortogroups, fig. 3. the monoclinic angle and the rotation angle of [vo4]-tetrahedron in β-zn2–2xcd2xv2o7 vs temperature 0 100 200 300 400 500 600 165 170 175 180 185 190 195 -zn1 ,6cd0 ,4v2o 7, v -o-v v o v , o t, oc 107,7 108,0 108,3 108,6 108,9 -zn 1,6 cd 0 ,4 v 2 o 7 , = -1.82 10 -5 1/deg , o β β β αβ fig. 4. the unit cells parameters for the cu1,6zn0,4v2o7 and cu0,8zn1,2v2o7 solid solutions vs temperature -200 -100 0 100 200 300 400 576 580 584 588 109,6 110,4 111,2 10,02 10,08 10,14 8,04 8,10 8,16 8,22 7,44 7,52 7,60 7,68 t, o c v , å 3 , o c, å b, å 80% cu 2 v 2 o 7 20% z n 2 v 2 o 7 40% cu 2 v 2 o 7 60% z n 2 v 2 o 7 a, å β 90 since the angle of the v – obridge – v is not fixed by the symmetry rules. a comparative cr ystal-chemical analysis of monoclinic solid solutions β-zn2–2xcd2xv2o7 and β-cu2–2xzn2xv2o7 showed that the shear deformations are more intensive for β-zn2–2xcd2xv2o7 in the temperature range from the room temperature up to 600  °c (–1.2×10–5 deg–1), which correlates with the appearance of the non-autonomous phase. in the case of β-cu2–2xzn2xv2o7 (0.42×10 –5 deg–1), where shear deformations are absent, no non-autonomous phase was detected. thus, the assumption that non-autonomous phase is generated by the shear deformations of the matrix phase due to a change in the monoclinic angle was confirmed. conclusion the set of in situ x-ray diffraction data and a comparative crystal-chemical analysis of zinc and copper pyrovanadates solid solutions that take into account thermal and chemical deformations of the structure allowed to established that the nonautonomous phase is formed when the following conditions are achieved: (1) the volume thermal expansion is close to zero; (2) shear deformations due to a change in the monoclinic angle appear (the degree of freedom that is not fixed by the symmetry rules in the monoclinic crystals); (3) compounds belong to the space group c2/m (mirror symmetry, the angle of v – obridge – v chain is 180°). the appearance of the non-autonomous phase under these conditions is a result of the matrix phase adaptation to the increase of inner-crystalline pressure that arises, while the unit cell volume remain unchanged, because of the shear deformation and a symmetry prohibition for the polyhedron architecture changes. acknowledgements the work was supported by ub ras (project 18-10-3-32). references 1. rossini fd, prigogine i. chemical thermodynamics. wiley; 1961. 514 p. 2. defay r, prigogine i, bellemans a. surface tension and absorption. london: longmans, green; 1966. 431 p. 3. urusov vs, tauson vl, akimov vv. geokhimiya tverdogo tela [geochemistry of solid state]. мoscow: geos, 1997. 500 p. russian. 4. schegol’kov yuv, tauson vl, medvedev vya, pochekunina mv, ivanova la, lipko sv. vzaimodeystvie poverkhnosti elementnogo zolota s flyuidami – klyuch k ponimaniyu mekhanizmov perekondensatsii i mobilizatsii zolota v endogennykh i ekzogennykh usloviyakh. doklady ran. 2007;412(6):810–3. russian. fig. 5. the monoclinic angle and the rotation angle of [vo4]-tetrahedron in cu2–2xzn2xv2o7 versus temperature 200 -1 00 0 100 2 00 30 0 40 0 1 29,3 1 29,6 1 29,9 1 30,2 1 30,5 1 30,8 1 31,1 1 31,4 1 31,7 -cu1, 6zn0 ,4v2o 7, v -o-v = -1 .57 10 -5 1 /de g -cu0, 8zn1 ,2v2o 7, v -o-v = -0 .79 10 -5 1 /de g v -o -v , o t , o c 10 9 ,8 11 0 ,1 11 0 ,4 11 0 ,7 11 1 ,0 11 1 ,3 11 1 ,6 11 1 ,9 cu 1,6 zn 0, 4 v 2 o 7 , = 0 .44 1 05 1/deg cu 0,8 zn 1, 2 v 2 o 7 , = 0 .34 1 05 1/deg , o β β β β β αβ αβ α α 91 5. lipko sv, tauson vl, akimov vv, zel’berg bi, knizhnik av. povedenie elementovprimesey v poroshkovom alyuminii [behavior of elements-admixtures in powdered aluminium]. tsvetnaya metallurgiya [non-ferrous metallurgy]. 2006;4:13–9. russian. 6. tauson vl, kravtsova rg, smagunov nv, spiridonov am, grebenschikova vi, budyak ae. strukturnoe i poverkhnostno-svyazannoe zoloto v piritakh mestorozhdeniy raznykh geneticheskikh tipov. doklady ran. 2006 ;406(6):806–9. russian. 7. tauson vl, kravtsova rg, smagunov nv, spiridonov am, grebenshchikova vi, budyak ae. structurally and superficially bound gold in pyrite from deposits of different genetic types. russian geology and geophysics. 2014;55(2):273–89. doi:10.1016/j.rgg.2014.01.011 8. tomashpolskiy yuya. poverkhnostnaya avtosegregatsiya v khimicheskikh soedineniyakh [superficial auto-segregation in chemical compounds]. moscow: nauchnyy mir, 2013. 208 p. russian. 9. pervov vs, makhonina ev, dobrokhotova zhv, dubasova vs, zarvazhnov ayu. supramolecular model of eutectics: functional materials based on nonautonomous phases. inorg mater. 2009;45(12):1478–83. doi:10.1134/s0020168509120140 10. gusarov vv, malkov aa, malygin aa, suvorov sa. termicheski stimulirovannye transformatsii 2-mernykh neavtonomnykh faz i uplotnenie oksidnykh polikristallicheskikh materialov. neorganicheskie materialy [russ j inorg chem]. 1995;31(3):346–50. russian. 11. gusarov vv, suvorov sa. temperatura plavleniya lokal’no-ravnovesnykh poverkhnostnykh faz v polikristallicheskikh sistemakh na osnove odnoy ob’emnoy fazy [melting temperatures of locally equilibrated surficial phases in polycrystallic systems based on the single phase]. zhurnal prikladnoy khimii [russ j applied chem]. 1990;63(8):1689–94. russian. 12. gusarov vv, suvorov sa. tolschina 2-mernykh neavtonomnykh faz v lokal’noravnovesnykh polikristallicheskikh sistemakh na osnove odnoy ob’emnoy fazy [thickness of 2d non-autonomous phases in locally equilibrated polycrystallic systems based on the single phase]. zhurnal prikladnoy khimii [russ j applied chem]. 1993;66(7):1529–34. russian. 13. gusarov vv. the thermal effect of melting in polycrystalline systems. thermochim acta. 1995;256(2):467–72. doi:10.1016/0040-6031(94)01993-q 14. gusarov vv. statika i dinamika polikristallicheskikh system na osnove tugoplavkikh oksidov [dissertation]. [st. petersburg]: 1996. russian. 15. uvarov nf, boldyrev vv. size effects in chemistry of heterogeneous systems. russ chem rev. 2001;70(4):307–29. doi:10.1070/rc2001v070n04abeh000638 16. pestereva nn, neiman aya. reversibility of electrosurface transfer through eutectic interfaces of mewo4|wo3 (me − ca, sr, ba). russ j electrochem. 2012;48(11):1070–8. doi:10.1134/s1023193512110134 108 d o i: 1 0. 15 82 6/ ch im te ch .2 01 5. 2. 2. 01 1 p. s. pershin1, а. а. burich1, yu. r. khalimullina1, p. a. arkhipov1, yu. p. zaikov1,2 1institute of high-temperature electrochemistry ub ras, 20 akademicheskaya street, 620990 ekaterinburg fax: +7(343) 3623462; phone: +7(343)3623350; e-mail: paffka19@yandex.ru 2ural federal university, 19 mira street, 620002 ekaterinburg fax: +7(343) 3754676; phone: +7(343) 375 4676; e-mail: aleksei_byrich@mail.ru eelectrode processes during the electrorefiniment of lead in the kcl-pbcl 2 -pbo melt the influence of pbo addition on current efficiency during the electrorefinement of lead in the kcl-pbcl 2 -pbo melt was investigated. it was shown that with pbo concentration in the kcl-pbcl 2 eqiumolar mixture increasing, the current efficiency of lead decreases. electrode processes mechanism is proposed. © pershin p.s., burich а. а., khalimullina yu. r., arkhipov p. a., zaikov yu. p., 2015 introduction studying of the process of electrochemical recovery of lead from blurred salts in the literature is given considerable attention. significant contribution to the electrolysis of molten salts in the production of heavy light-fusible metals was made by the scientists of the ukrainian school of electrochemistry1–4. however, the object of the exploration was chloride melts containing no oxygen ions. electrolytic behavior of oxide of lead (ii) in chloride melts was studied in works by delimarsky y.k., panchenko i.d., and markov b.f.5. the authors conducted electrolysis of the system pbcl2-pbo at temperatures of 500–530 °c and a concentration of pbo to 20 wt%., and showed that there is a possibility of extracting metallic lead from its oxide by electrolysis of molten lead chloride with a current yield of 96–99%. the aim of this work was to measure cathode current output on lead during the electrorefining of lead in melt kcl-pbcl2pbo at a temperature of 500 °c depending on the concentration of pbo in the electrolyte. the experimental part schema of the experimental laboratory system is shown in figure 1. the lead mark c1 was used as an anode. the cathode was a molybdenum rod 109 № 2 | 2015 chimica techno acta eelectrode processes during the electrorefiniment of lead in the kcl-pbcl 2 -pbo melt with a diameter of 1 mm and working height of 10 mm (3), shielded with alundum tube (4). to collect the cathode lead to the alundum tube by nichrome wire a cut corundum crucible with a diameter of 20 mm was attached. for the experiments 4 electrolyte compositions kcl-pbcl2pbo with fixed concentration of pbo 1, 3, 5, and 8 wt. %. were prepared the temperature of the molten salt was checked with the help of platinumplatinum-rhodium (gd) thermocouple. system of temperature stabilization got its fluctuations during the experiments to within ±2 °c. for the supply of electric current, sources of dc gwinstekpsw7 30–72 was used; the difference of potentials between the electrodes was measured with multimeter appa-109 n. electrolysis was carried out at 500 °c for 60 minutes in a potentiostatic mode at a potential difference between the cathode and the reference electrode of 0.6 v. at the end of each experiment, the melt was dissolved in drain-mold. from the change in mass of cathodic and anodic lead, cathode and anode current output was determined, based on faraday's law. results and discussion during electrolysis, the primary reactions at the cathode are the recovery of lead ions by the reaction: pb2+ + 2e → pb0 (1) the main reaction on the anode lead is dissolution by the reaction: pb0 – 2e → pb2+ (2) the theoretical value of the mass of dissolved at the anode and obtained at the cathode lead mteor was determined according to faraday's law: m a z f iтеор = ⋅ ⋅ ⋅τ (3) where a is atomic weight of the metal, g/mole; i is current intensity, a; τ is time, s; z is valence of lead in the electrolyte (based on 2 electrone electrode reaction); f is faraday constant, 96500 c/mol. the output of lead current was calculated by the formula: вт = пр теор m m ⋅100% (4) where mпр is metal mass obtained in the course of the experiment, g. the values of the cathode output current depending on the concentration of fig.1. schema of the experimental laboratory setup: 1 – anode current feeder (mo); 2 – current source to the reference electrode (mo); 3 – the cathode of mo; 4 – corundum tube; 5 – corundum cover the reference electrode; 6 – corundum crucible ø = 45 mm; 7 – the electrolyte kcl-pbcl2-pbo; 8 – thermocouple in a case of beo; 9 – corundum crucible ø = 25 mm; 10 – cathode pb; 11 – the reference electrode (pb); 12 – an anode (pb) 110 № 2 | 2015 chimica techno acta pershin p.s., burich а. а., khalimullina yu. r., arkhipov p. a., zaikov yu. p. pbo in the melt and a current density are shown in table 1. table 1 anode current output in depending on the concentration of pbo in the melt cpbo,% wt. 1 3 5 8 bтk 96.74 92.87 90.37 86.31 bтa 98.38 96.74 94.19 91.11 the values of the cathode and the anode output current in all cases is less than 100% based on the two-electron reaction of the electrode. this indicates that even in dilute kcl-pbcl2 on pbo on the surface of the electrodes other electrochemical reactions occur, and the proportion rises with increasing concentration of pbo. it is worth noting that there was a decrease in the mass of the electrolyte after electrolys that says about the expense of substance. x-ray results show in the electrolyte melt congealed presence of oxychloride lead compounds pb2ocl2, which in melt may be present in the form of ions pb2o2 +6. on the cathode surface after electrolys pbo was found. from the above stated facts we can assume the following mechanism of electron-electrode processes. part of pbo oxidized to pbo2 and shields the anode surface, and a part is deposited at the cathode in conjunction with the lead according to the reaction: pb2o 2+ + 2e → pb0 + pbo (5) fig. 2 shows a photograph of crucible for collection of the cathode lead immediately after the dc disconnect. the photograph shows that the recovered lead dropping from molybdenum cathode surface does not form a "puddle", in a substance with a homogeneous surface, but rolled into balls that are not collected in a single body, even with stirring. this suggests that an oxide film is present on the surface of metallic lead formed together with the metal. with its high strength and surface tension, it pulls together the resulting drop in the metal bowl and stirring does not merge into a single body. part of pbo is the formation of films for metal lead and some remains on the surface of the cathode. depending on the concentration of pbo in a chloride melt deposited oxide can again dissolve in the melt with a low concentration of pbo, and saturated monoxide melt will lead to the cathode surface, or be present in the sheath of the cathode space. conclusions 1. experimentally determined values of the cathode and anode output current lead in the electrorefining of lead oxidechloride melt kcl-pbcl2-pbo. fig. 2 photo of the crucible to collect the cathode lead after the dc disconnected. melt kcl-pbcl2-pbo (8% wt.) 111 № 2 | 2015 chimica techno acta eelectrode processes during the electrorefiniment of lead in the kcl-pbcl 2 -pbo melt 2. it is shown that the cathode and the anode output current are not equal 100% in all experiments. 3. with an increase in concentration of pbo in melt kcl-pbcl2-pbo cathodic current efficiency decreases from 96.7% to 86.31%, and the anode current efficiency declines from 98.38 % to 91.11%. 4. x-ray analysis shows the presence of an electrolyte oxychloride pb2ocl2. 5. metallic lead obtained on molybdenum cathode drops and takes a spherical shape that signifies the presence of a solid oxide film on lead surface formed simultaneously with the metal lead. 1. zarubizsky o.g., penkalo i.i., gorbach v.m. ukranian chemical journal 1972;38:711. 2. omel'chuk a.a., budnik v.g. ukranian chemical journal 1985; 51:1045. 3. zarubizsky o.g. ukranian chemical journal 2000; 66:5. 4. delimarsky yu. k., zarubizsky o.g., budnik v.g. izvestiya vuzov. color metallurgy 1986; 4:27. 5. delimarsky yu.k., panchenko i.d, markov b.f. ukranian chemical journal 1956; 22:574. 6. flengas s., hacetoglu a. canadian journal of chemistry 1990; 68:236. 112 у д к 6 61 .8 52 .2 2: 54 4. 42 1. 03 2. 4 п. с. першин, а. а. бурич, ю. р. халимуллина, п. а. архипов, ю. п. зайков институт высокотемпературной электрохимии уро ран, ул. академическая, 20, 620990, г. екатеринбург. факс: (343) 362-34-62; тел.: (343) 362-33-50; e-mail: paffka19@yandex.ru электродные процессы при электрорафинировании свинца в расплаве kcl-pbcl 2 -pbo исследовано влияние добавки оксида свинца (ii) на выход по току в процессе электрорафинирования свинца в оксихлоридном расплаве kcl-pbcl 2 pbo. показано, что с увеличением концентрации pbo в эквимольной смеси kcl-pbcl 2 выход по току свинца снижается. предложен механизм электродных процессов. © першин п. с., бурич а. а., халимуллина ю. р., архипов п. а., зайков ю. п., 2015 введение исследованию процесса электрохимического восстановления свинца из расплавов солей в литературе уделено значительное внимание. значительный вклад в развитие электролиза солевых расплавов в производстве тяжелых легкоплавких металлов внесли ученые украинской школы электрохимии [1–4]. однако объектом исследования являлись хлоридные расплавы, не содержащие кислородных ионов. электролитическое поведение оксида свинца (ii) в хлоридных расплавах изучено в работе ю. к. делимарского, и. д. панченко и б. ф. маркова [5]. авторы провели электролиз системы pbcl2-pbo в области температур 500–530 °с и концентрации pbo до 20 мас.% и показали, что установлена возможность получения металлического свинца из его оксида электролизом в расплавленном хлориде свинца с выходом по току 96–99 %. целью данной работы являлось измерение катодного выхода по току свинца в процессе электрорафинирования свинца в расплаве kcl-pbcl2-pbo при температуре 500 °с в зависимости от концентрации pbo в электролите. экспериментальная часть схема экспериментальной лабораторной установки представлена на рис. 1. в качестве анода использовали свинец марки с1. катодом служил мо113 № 2 | 2015 chimica techno acta электродные процессы при электрорафинировании свинца в расплаве kcl-pbcl 2 -pbo либденовый стержень диаметром 1 мм и рабочей высотой 10 мм (3), экранированный алундовой трубкой (4). для сбора катодного свинца к алундовой трубке с помощью нихромовой проволоки был присоединен обрезанный алундовый тигель диаметром 20 мм. для опытов было приготовлено 4 состава электролита kcl-pbcl2-pbo с различной фиксированной концентрацией pbo 1, 3, 5 и 8 мас.%. температуру в солевом расплаве контролировали с помощью платинаплатино-родиевой (ппр) термопары. система стабилизации температуры обеспечивала ее колебания в ходе экспериментов в пределах ± 2 °с. для подачи электрического тока использовали источник постоянного тока gwinstekpsw7 30-72, разность потенциалов между электродами измеряли мультиметром appa-109 n. электролиз проводили при 500 °с в течение 60 мин. в потенциостатическом режиме при разности потенциалов между катодом и электродом сравнения 0,6 в. по окончании каждого опыта расплав сливали в изложницу. по изменению массы катодного и анодного свинца определяли катодный и анодный выход по току на основании закона фарадея. результаты и обсуждение в процессе электролиза основной реакцией на катоде является восстановление ионов свинца по реакции: pb2+ + 2e → pb0 (1) основной реакцией на аноде является растворение свинца по реакции: pb0 – 2e → pb2+ (2) теоретическое значение массы растворенного на аноде и полученного на катоде свинца mtеор определили согласно закону фарадея: m a z f iтеор = ⋅ ⋅ ⋅τ , (3) где а – атомный вес металла, г/моль; i – сила тока, а; τ – время, с; z – валент ность свинца в электролите, (в расчете на 2-электронную электродную реакцию); f – постоянная фарадея, 96 500 кл/моль. выход свинца по току рассчитали по формуле: рис. 1. схема экспериментальной лабораторной установки: 1 – анодный токоподвод (мо); 2 – токоподвод к электроду сравнения (мо); 3 – катод из мо; 4 – алундовые трубки; 5 – алундовый чехол электрода сравнения; 6 – алундовый тигель ø = 45 мм; 7 – электролит kcl-pbcl2-pbo; 8 – термопара в чехле из beo; 9 – алундовый тигель ø = 25 мм; 10 – катодный pb; 11 – электрод сравнения (pb); 12 – анод (pb) 114 № 2 | 2015 chimica techno acta першин п. с., бурич а. а., халимуллина ю. р., архипов п. а., зайков ю. п. вт = пр теор m m ⋅100% , (4) где mпр – масса металла, полученная в ходе эксперимента, г. значения катодного выхода по току в зависимости от концентрации pbo в расплаве и плотности тока представлены в табл. 1. таблица 1 значения анодного выхода по току в зависимости от концентрации pbo в расплаве cpbo, масс.% 1 3 5 8 втк 96,74 92,87 90,37 86,31 вта 98,38 96,74 94,19 91,11 значения катодного и анодного выхода по току во всех случаях меньше 100 % в расчете на двухэлектронную электродную реакцию. это говорит о том, что даже в разбавленных растворах kcl-pbcl2 по pbo на поверхности электродов протекают другие электрохимические реакции, и их доля возрастает с увеличением концентрации pbo. стоит отметить, что произошло уменьшение массы электролита после электролиза, что говорит о расходе вещества, входящего в его состав. результаты рентгенофазового анализа показывают в застывшем плаве электролита при-сутствие оксихлоридного соединения свинца pb2ocl2, который в расплаве может присутствовать в виде ионов pb2o2 + [6]. на поверхности катода после электролиза обнаружен pbo. из выше изложенных фактов можно предположить следующий механизм электродных процессов. часть pbo окисляется до pbo2 и экранирует поверхность анода, а часть осаждается на катоде совместно со свинцом по реакции: pb2o 2+ + 2e → pb0 + pbo (5) на рис. 2 представлена фотография тигля для сбора катодного свинца сразу после отключения постоянного тока. на фотографии видно, что восстановившийся свинец, скапывая с поверхности молибденового катода, не образует «лужу», то есть вещество с однородной поверхностью, а скатывается в шарики, которые не собираются в единое тело даже при перемешивании. это говорит о том, что на поверх ности восстановившегося металлического свинца присутствует оксидная пленка, образовавшаяся совместно с металлом. обладая высокой прочностью и поверхностным натяжением, она стягивает образовавшуюся каплю металла в шар и при перемешивании не дает слиться в единое тело. часть pbo рис. 2. фотография тигля для сбора катодного свинца после отключения постоянного тока. расплав kcl-pbcl2-pbo (8 % масс.) 115 № 2 | 2015 chimica techno acta электродные процессы при электрорафинировании свинца в расплаве kcl-pbcl 2 -pbo идет на образование пленки для металлического свинца, а часть остается на поверхности катода. в зависимости от концентрации pbo в хлоридном расплаве, осажденный оксид может снова раствориться в расплаве с низкой концентрацией pbo, а в насыщенном по оксиду свинца расплаве останется на поверхности катода или будет присутствовать в приэлектродном катодном пространстве. выводы 1. экспериментально определены значения катодного и анодного выходов по току свинца в процессе электрорафинирования свинца в оксидно-хлоридном расплаве kcl-pbcl2-pbo. 2. показано, что катодный и анодный выход по току не равны 100 % во всех опытах. 3. с увеличением концентрации pbo в расплаве kcl-pbcl2-pbo катодный выход по току снижается с 96,7 % до 86,31 %, а анодный выход по току снижается с 98,38 % до 91,11 %. 4. рентгенофазовый анализ показывает присутствие в электролите окси хлорида pb2ocl2. 5. полученный на молибденовом катоде металлический свинец скапывает и принимает шарообразную форму, что означает присутствие на поверхности свинца прочной оксидной пленки, полученной одновременно с металлическим свинцом. 1. зарубицкий о. г., пенкало и. и., горбач в. м. // украинский химический журнал. 1972. т. 38. с. 711. 2. омельчук а. а., будник в. г. // украинский химический журнал. 1985. т. 51. с. 1045. 3. зарубицкий о. г. // украинский химический журнал. 2000. т. 66. с. 5. 4. делимарский ю. к., зарубицкий о. г., будник в. г. // известия вузов. цветная металлургия. 1986. № 4. с. 27. 5. делимарский ю. к., панченко и. д., марков б. ф. // украинский химический журнал. 1956. т. 22. с. 574. 6. flengas s. n., hacetoglu a. // canadian journal of chemistry. 1990. v. 68. p. 236. рекомендуем при цитировании данно статьи следующую ссылку: pershin p. s., burich а. а., khalimullina yu. r., arkhipov p. a., zaikov yu. p. eelectrode processes during the electrorefiniment of lead in the kcl-pbcl2-pbo melt // chimica techno acta. 2015. vol. 2. № 2. p. 108–115. sheelite-related strontium molybdates: synthesis and characterization 189 z. a. mikhaylovskayaa*, e. s. buyanovaa, s. a. petrovab, а. а. nikitinaa a ural federal university, 19 mira st., ekaterinburg, 620002, russia b institute for metallurgy, ural branch of the russian academy of sciences, 101 amundsen st., ekaterinburg, 620016, russia e-mail: zozoikina@mail.ru sheelite‑related strontium molybdates: synthesis and characterization the present research is devoted to the cationic-deficient srmoo4-based sheelite-related complex oxides. the doping with bismuth to a sublattice and codoping with bismuth and vanadium (to a and b sublattices, respectively) were discussed. the x-ray powder diffraction and infrared spectroscopy were used to investigate structural characteristics of the complex oxides. in sr1–1.5xbixmoo4, a superstructural ordering was observed. conductivity and dielectric loss of ceramic samples are measured using alternating current. keywords: sheelite; strontium molybdates; dielectric materials. received: 25.10.2018. accepted: 17.12.2018. published: 31.12.2018. © mikhaylovskaya z. a., buyanova e. s., petrova s. a., nikitina а. а., 2018 d o i: 1 0. 15 82 6/ ch im te ch .2 01 8. 5. 4. 03 introduction scheelite-type complex oxides are quite interesting research objects because flexibility of  substitutions in  these systems leads to variety of their compositions, structure types and properties. ideal scheelite-related oxides have a general formula abo4 and consist of a n+ cations and (bo4) n– anions. a-site ions are coordinated with eight oxygen ions, and b-site ions are coordinated with four oxygen ion. each site can be occupied simultaneously by different ions with various oxidation states; additional interstitial positions and vacancies lead to the deviation from the general formula. a lot of  scheelite-type complex oxides are used as materials for scintillation detectors, lasers [1, 2], ionic conductors [3], phosphors [4], photocatalysts [5], and microwave dielectrics [6]. the regulation of the desired properties of sheelite-related materials can be provided by varying the quantity of the dopant, its nature, the ratios between dopants and the presence of additional vacancies or interstitial positions in the structure. for example, a substitution of a-site ions with me+3 in abo4 complex oxide can be described in  two ways: (1) a formation of a1–xme +3 xbo4+x / 2 phases, where electroneutrality is provided by  the interstitial oxygen ions; (2) a  formation of  a+21−1.5xme +3 xф0.5xmoo4 (or a+21−1.5xme +3 xmoo4) phases containing cationic vacancies ф. the first way of substitution was detected for  pb(mo / w)o4 [7, 8] and ca(mo / w)o4 [9] parent compounds. the second way was described for  rare-earth substituted ca(mo / w)o4, sr(mo / w)o4 and cd(mo / w)o4 [10–12]. mikhaylovskaya z. a., buyanova e. s., petrova s. a., nikitina а. а. chimica techno acta. 2018. vol. 5, no. 4. p. 189–195. issn 2409–5613 190 as a result, cationic vacancies ф and their ordering are additional structural factors influencing physico-chemical properties. another way of  the substitution of a positions is codoping with me+3 and me+1 or me+5 ions, which leads to the formulae a1–x me +1 0.5xme +3 0.5xbo4 [13] and a1–xme +3 xb1–xme +5 xo4, respectively [14]. the present research is devoted to  the bi-doped strontium molybdate srmoo4. the existence of  sr1–1.5xbixmoo4 series was shown by  sleight and coauthors [15], who synthesized the complex oxide sr0.88bi0.08moo4 (tetragonal symmetry, sp. gr. i41 / a) and described its good catalytic properties [15]. sr1–1.5xbixmoo4 family has not been described yet, while bi-doped calcium molybdates have been intensively researched as  microwave dielectric [16] or pigments [14]. the basic characteristic and structure types of  srmoo4 are similar to those of camoo4, so the bi-doped strontium molybdates should possess similarly promising properties. in addition, bi-doping of  strontium molybdates is expected to lead to decrease of the unit cell, resulting from the significant changes in  b-sublattice. therefore, the objects of  the present work are sr1–1.5xbixmoo4, sr1–xbixmo1–xvxo4, sr1–1.5xbixmo1–yvyo4–d solid solutions and their structure and properties. experimental synthesis of sr1–1.5xbixmoo4 (0 ≤ x ≤ 0.45), sr 1–xbi xmo 1–xv xo 4 (0 ≤ x ≤ 0.4), sr1–1.5xbixmo1–yvyo4–d (0 < x ≤ 0.4, 0 < y ≤ 0.2) were synthesised by  conventional solid state methods from srco3 (98.5 %), bi2o3 (99.9 %), v2o5 (98.5 %) and moo3 (99.0 %). stoichiometric amounts of dried precursors were weighed and mixed in an agate mortar as dispersion in ethanol. mixtured powders were pelletized and heated at 550– 650 °c with regrinding and repelletizing. time of each heating was ~10 hours, the total time of heating was ~30 hours. x-ray powder diffraction data were obtained on a dron-3 with cu kα monochromatic radiation in the range of 5–75° of 2θ. ir ft spectrometry measurements were carried out at  nicolet 6700 with attenua ted total reflection attachment. density of powder samples was measured by hydrostatic weighting. for conductivity measurements, the ceramic pellets of 10 mm in diameter and ca. 2.5 mm thickness were covered by  pt. impedance spectra were obtained in two-electrode measurement cell on  lcr-819 and elins z-3000 impedance spectrometers, over the frequency ranges 1 hz and 3 mhz to 10 hz, respectively, at  stabilised temperatures from ca. 25 °c to ca. 625 °c. data presented correspond to the second cooling run. data were modelled using equivalent electrical circuits with the zview software (version 2.6b, scribner associates, inc.). results and discussion synthesis of sr1–1.5xbixmoo4 yielded samples with the structure of sr0.88bi0.08moo4 [15], up to x = 0.2 (sp.gr. i41 / a). at 0.2 < x < 0.4 additional peaks in the small angle range are evident; for  the x > 0.45 composition additional peaks in  the pattern can be identified as bi3moo12. we supposed that 0.2 < x ≤ 0.4 compositions have superstructural ordering caused by ordering of cationic vacancies (fig. 1). as a  result, in  the xrpd data for  0.2 < x ≤ 0.4 compositions all peaks can be successfully indexed using a  tetragonally ordered supercell asup=√5asub, 191 csup= csub (where sup and sub subscripts denote the superand subcell, respectively) in  i41 / a  space group (fig. 2). compositional dependence of the unit cell parameters for sr1–1.5xbixmoo4 compositions are shown in fig. 2, where the linear chemical compression is caused by the substitution of the bigger cation with the smaller one (ionic radii r sr2+ = 1.26  å, r bi3+ = 1.17  å [17]). the measurements of density showed that experimental density is equal to the theoretical (x-ray) one to within the 2–3 % of absolute values. synthesis of sr1–xbixmo1–xvxo4 results in  the two-phase samples that consist of bivo4 (monoclinic) and srmoo4 phases. in contrast, ca1–xbixmo1–xvxo4 solid solutions are observed for 0 ≤ x ≤ 0.9 [14]. one possible reason was that the dopants influence differently the composition and structure of strontium and calcium molybdates. the simultaneous presence of bi and v in ca1–xbixmo1–xvxo4 leads to the expansion of the unit cell of a complex oxide due to the replacement of calcium with bismuth and compression of the unit cell due to the replacement of molybdenum with vanadium; as a result, the unit cell changes slightly [14] (ionic radii r ca2+ = 1.12 å, r v 5+ = 0.54 å, r mo6+ = 0.41 å [17]). in contrast, in sr1–xbixmo1–xvxo4 both of bi and v lead to compression of the unit cell, making it unstable. it can be assumed that such compression of the unit cell leads to the decrease of the distance between [bo4] n– (b = mo, v) clusters and, consequently, to the increase of repulsion between them. as a result, the destruction of sr1–xbixmo1–xvxo4 system is observed. creating an oxygen deficiency in  the crystal lattice provides distortion in bo4 tetrahedra and formation of [bo4]– [bo3] n–-type bonds through common oxygen atoms. this can be realized by changing fig. 1. x-ray diffraction profiles for selected sr1–1.5xbixmoo4 compositions. arrows and asterisks indicate superlattice and bi2mo3o12 reflections, respectively fig. 2. compositional variation of unit cell parameters in sr1–1.5xbixmoo4; super (a’,b’) and sub (a,b) — cells in sr1–1.5xbixmoo4 series (inset) 192 the composition of strontium molybdate to sr1–1.5xbixmo1–yvyo4–d. it was expected that low concentration of  bismuth would not provide a  proper compression of  the unit cell and singlephase samples would not be observed even at small y. but high concentration of bismuth can provide an efficient compression of the unit cell and the possibility of doping with vanadium. in fact, we observed such trend. for x = 0.1 in sr1–1.5xbixmo1–yvyo4–d no single-phase samples was obtained, for  x = 0.2 only y = 0.05 composition is single phase, for x = 0.3 and x = 0.4 singlephase compositions were observed at y = 0.05–0.1 and 0.05–0.2, respectively. in this research, the maximum concentration of vanadium was not determined exactly, but the general trend is clear. in the table 1, the unit cell parameters of  the single-phase samples are shown. when x is fixed and y increases or when y is fixed and x increases, a general compression of the unit cell is observed. the presence of vanadium in the structure leads to  the absence of  cationic ordering, and no additional peaks in  x-ray diffraction profiles of x = 0.3–0.4 are observed. unfortunately, it has proved impossible to accurately refine the oxide ion positions in the unit cell using a  rietveld approach, due to dominance of the x-ray scattering by the cations in this system and only neutron diffraction can refute or confirm the specified theory about the [bo4]–[bo3] n–-type bond formation. powders of  the sr1–1.5xbixmoo4 compositions were characterized by  ir ft spectroscopy (fig. 3). several adsorption bands in the range of 950–500 сm–1 were detected. according to  basiev [18] sheelite-related compound abo4 consists of [moo4] 2– clusters and isolated a2+ ions and, as a result, characteristic absorption bands can be assigned only to the vibrations in [moo4] 2– clusters [19]. strong absorption bands in the range 940–550 cm– 1 are related to  o–mo–o stretches of  the table 1 unit cell parameters of sr1–1.5xbixmo1–yvyo4 (0.1 < x < 0.4, 0.05 < y < 0.2) compositions composition а, å b, å c, å v, å3 sr0.7bi0.2mo0.95v0.05o4 5.367 5.367 11.935 343.78 sr0.7bi0.2mo0.9v0.1o4 5.363 5.363 11.961 344.02 sr0.55bi0.3mo0.95v0.05o4 5.353 5.353 11.896 340.87 sr0.55bi0.3mo0.9v0.1o4 5.348 5.348 11.896 340.24 sr0.55bi03mo0.8v0.2o4 5.335 5.335 11.907 338.90 sr0.4bi0.4mo0.95v0.05o4 5.342 5.342 11.826 337.48 sr0.4bi0.4mo0.9v0.1o4 5.326 5.326 11.885 337.13 sr0.4bi0.4mo0.8v0.2o4 5.318 5.318 11.868 335.64 fig. 3. ir ft spectra of the sr1–1.5xbixmoo4 compositions 193 moo4 tetrahedron. additional absorption band near 425–400 cm–1 can also be assigned to the deformational vibrations of o–mo–o bands. in the ir ft spectra, the general shifting of absorption bands is observed. the same trend was observed for ca1–1.5xbixmoo4 [16]; in both cases it is caused by the deformation of moo4 tetrahedra resulting from the presence of cationic vacancies. c onduc t ivity me asurements of sr1–1.5xbixmoo4 ceramic showed very high resistivity of samples (fig. 4). a slight increase of conductivity is observed for the samples with superstructural ordering (0.2  < x < 0.45) and two-phase samples (x > 0.45). changing of  dielectric loss tangent (tgδ) was measured at the range of 303– 903  k at  cooling at  the fixed frequency of 1 khz using the parallel rp + с model (series connected rs and ls were shown to be negligible). the tgδ vs temperature curves of sr1–1.5xbixmoo4 compositions are shown at fig. 5. the acceptable dielectric losses (tgδ < 0.1) of sr1–1.5xbixmoo4 compositions were observed for temperatures below ~573 k, while tgδ decreases with x values until x = 0.3. then, at x > 0.3, tgδ increases, probably because of structural ordering of the samples. for sr1–1.5xbixmo1–yvyo4–d compositions we observed a  significant growth in  conductivity in  comparison with sr1–1.5xbixmoo4. as a  result, in  the range of  ~303–573  k the tgδ rises by  approximately one order (fig. 6). it is consistent with the increase of oxygen ion conductivity associated with structural changes. the tgδ vs frequency dependences of all compositions of  substituted srmoo4 indicate that effective dielectric properties are observed at frequency above 1 mhz, i.e. in  the microwave range, as  well fig. 4. arrhenius plots for selected sr1–1.5xbixmoo4 compositions fig. 5. the tgδ vs temperature curves of sr1–1.5xbixmoo4 compositions at 1 khz fig. 6. the tgδ vs temperature curves of several sr1–1.5xbixmo1–yvyo4–d compositions at 1 khz 194 as camoo4 — based dielectric materials [16] (the example is given in fig. 7). conclusions thus, the present research demonstrates the existence of cationic-deficient sheeliterelated complex oxides of sr1–1.5xbixmoo4 series and sr1–1.5xbixmo1–yvyo4–d series. in sr1–1.5xbixmoo4, superstructural ordering is observed for  0.2 < x ≤ 0.4. for sr1–1.5xbixmo1–yvyo4–d series a changing in oxygen sublattice is assumed. both of the complex oxide series show dielectric properties at temperatures below 503 k and frequencies above 1 mhz. conductivity and tangent of dielectric loss for sr1–1.5xbixmo1–yvyo4–d compositions is greater than for  sr1– 1.5xbixmoo4. it is consistent with the increase of oxygen ion conductivity associated with mentioned structural changes. acknowledgements this work was financially supported by grant of russian foundation for basic research, project № 16-33-60026. references 1. mikhailik vb, kraus h, miller g, mykhaylyk ms, wahl d. luminescence of cawo4, camoo4, and znwo4 scintillating crystals under different excitations. j. appl. phys. 2005:97(8):083523. doi: 10.1063 / 1.1872198. 2. faure n, borel c, couchaud m, basset g, templier r, and wyon c. optical properties and laser performance of neodymium doped scheelites cawo4 and nagd(wo4)2. appl. phys. b: lasers opt. 1996:63(6):593–98. doi: 10.1007 / bf01830998. 3. sharma n, shaju km, rao gvs, chowdari bvr, dong zl, white tj. carbon-coated nanophase camoo4 as anode material for li ion batteries. chem. mater. 2004:16 (3):504–12. doi: 10.1021 / cm0348287. 4. cavalcante ls, longo vm, sczancoski jc, almeida map, batista aa, varela ja, orlandi mo, longo e, liu ms. electronic structure, growth mechanism and photoluminescence of cawo4 crystal. cryst. eng. comm. 2012:14(3):853–68. doi: 10.1039 / c1ce05977g. 5. yao wf, ye jhj. photophysical and photocatalytic properties of  ca1–xbixvxmo1–xo4 solid solutions. phys. chem. b. 2006:110(23):11188–95. http://dx.doi. org / 10.1021 / jp0608729. fig. 7. the tgδ vs frequency curves of sr0.7bi0.2mo0.9v0.1o4–d 195 6. choi gk., kim jr., yoon sh., hong ks. microwave dielectric properties of scheelite (a = ca, sr, ba) and wolframite (a = mg, zn, mn) amoo4 compounds. j. eur. ceram. soc. 2007:27(8-9):3063–67. doi: 10.1016 / j.jeurceramsoc.2006.11.037. 7. esaka t, mina-ai t, iwahara h. oxide ion conduction in the solid solution based on the scheelite-type oxide pbwo4 // solid state ionics: 1992:57(3-4): 319–25. doi: 0.1016 / 0167–2738(92)90165-l 8. zhang gg., fang qf., wang xp., yi zg. dielectric relaxation study of pb1–xlaxmoo4+δ (x = 0–0.3) oxide-ion conductors. j. phys.: condens. matter. 2003:15(24): 4135–42. doi: 10.1088 / 0953–8984 / 15 / 24 / 307. 9. cheng j, liu c, cao w, qi m, shao g. synthesis and electrical properties of scheelite ca1–xsmxmoo4+d solid electrolyte ceramics. mat. res. bull. 2011:46(2):185–89. doi: 10.1016 / j.materresbull.2010.11.019. 10. md. haque m., kim d-k. luminescent properties of eu activated mla2(moo4)4 based (m=ba, sr and ca) novel red-emitting phosphors. mater. lett. 2009:3(910):793–96. doi: 10.1016 / j.matlet.2009.01.018. 11. jiang p., gao w., cong r., yang t. structural investigation of the a-site vacancy in  scheelites and the luminescence behavior of  two continuous solid solutions a1–1.5xeux☐0.5xwo4 and a0.64–0.5yeu0.24liy☐0.12–0.5ywo4 (a = ca, sr; ☐ = vacancy). dalton trans. 2015:44(13):6175–83. doi: 10.1039 / c5dt00022j. 12. tomaszewicz e, kaczmarek sm, fuks h. new cadmium and rare-earth metal molybdates with scheelite type structure // mater. chem. phys. 2010:122(2-3):595–601. doi: 10.1016 / j.matchemphys.2010.03.052. 13. su y, li l, li g. synthesis and optimum luminescence of cawo4-based red phosphors with codoping of eu3+ and na+ . chem. mater. 2008:20(19):6060–67. doi: 10.1021 / cm8014435. 14. sameera s, prabhakar rao p, divya s, raj kv, aju thara tr. high ir reflecting bivo4-camoo4 based yellow pigments for cool roof applications. energ. buildings. 2017:154:491–98. doi: 10.1016 / j.enbuild.2017.08.089. 15. sleight aw, aykan k, rogers db. new nonstoichiometric molybdate, tungstate, and vanadate catalysts with the scheelite-type structure. j.  solid state chem. 1975:13(3):231–36. doi: 10.1016 / 0022–4596(75)90124–3. 16. guo j, randall ca, zhang g, zhou d, chen y, wang h. synthesis, structure, and characterization of new low-firing microwave dielectric ceramics: ca1−3xbi2xфxmoo4. j. mater. chem. c. 2014:2(35):7364–72. doi: 10.1039 / c4tc00698d. 17. shannon rd. revised effective ionic radii and systematic studies of  interatomic distances in  halides and chalcogenides. acta cryst. 1976;a32:751–67. doi: 10.1107 / s0567739476001551. 18. basiev tt, sobol aa, voronko yk, zverev pg. spontaneous raman spectroscopy of tungstate and molybdate crystals for raman lasers. opt. mater.2000:15(3):205–16. doi: 10.1016 / s0925-3467(00)00037–9. 19. cho y, bull y. fine-tuning the emission color of a transparent suspension of srmoo4: eu 3+,tb3+ nanophosphors. korean chem. soc. 2015:36(1):282–86. doi: 10.1002 / bkcs.10065. 208 v. s. nikitin, т. n. ostanina, v. м. rudoy, а. s. farlenkov ural federal university, 19, mira str., ekaterinburg, russia, e-mail: nikitin-viachieslav@mail.ru dynamics of electrocrystallization of dendritic zinc deposits in galvanostatic and potentiostatic modes in the work the dynamics of growth of zinc dendritic deposits in the galvanostatic and potentiostatic modes from an electrolyte containing 0.3 mol/l of zno, and 4 mol/l of naoh has been studied. it has been shown that in galvanostatic conditions decrease in the elongation rate of dendrites and change in the deposit structure from dendritic to compact accompanied by increasing density and decreasing through-thickness porosity are observed. in potentiostatic conditions dendrites grow at a constant rate and the structure of the deposit varies little. the results have been confirmed by electron microscopic studies of morphology of zinc particles. key words: electrocrystallization; zinc; dendritic, electrochemistry. © nikitin v. s., ostanina т. n., rudoy v. м., farlenkov а. s., 2015 d o i: 1 0. 15 82 6/ ch im te ch .2 01 5. 2. 3. 02 2 introduction the electrolytic zinc deposits possess unique dendritic structure and high purity, and powders derived from them are used in various technical fields (manufacture of batteries and zinc-rich composite materials). the structural properties of these deposits produced by electrolysis of aqueous solutions undergo changes after removal from the electrode, but the morphology of the particles, which is laid at the stage of electrolysis, remains unchanged after processing operations of the future powder [1]. in this connection, to obtain electrolytic powders with desired properties it is necessary to know how the deposition modes affect structural properties (density, porosity, surface area, etc.) of the deposit directly during its formation in situ [2]. by varying the conditions of electrodeposition (mode, preset current or potential, concentration of discharging ions, surfactant additives) it is possible to produce powders of various structure. the aim of the present work is to study the dynamics of the electrocrystallisation process and the properties of dendritic zinc deposits in conditions of setting direct current and constant potential. 209 № 3 | 2015 chimica techno acta experimental technique to study the dynamics of dendritic zinc deposits an installation allowing simultaneous registering the change in potential (or  current), video recording deposit growth and fixing the amount of hydrogen released has been used. a 1 cm high pin cathode made of zinc wire with a diameter of 2 mm has been brought to a center of a cylindrical cell. on the edge of the cell a ring zinc anode has been disposed. polarization measurements were performed using solartron potentiostat 1280c. the potential has been measured in respect to the zinc reference electrode. the deposits have been prepared from zincate electrolyte containing 0.3 mol/l of zno, and 4 mol/l of naoh, when setting direct current and constant potential. polarizing current has exceeded the value of the limiting diffusion current in 6 times. when using potentiostatic conditions a constant overvoltage equal to –0.38 v has been maintained, this corresponded to the level of diffusion limitations galvanostatic electrolysis. analysis of video record of the deposit growth process has allowed to establish the dependence of the thickness of the dendritic deposit layer from time and to calculate the overall deposit volume. according to volumetric measurements current efficiency of zinc and hydrogen has been determined, that has allowed calculating the mass change of the deposit in the electrodeposition process. microstructural studies of deposits have been carried out on mira 3 lmu scanning electron microscope in ihte laboratory of ub of the ras. results and discussions under galvanostatic conditions due to the high current density the rate of ad-atoms formation is high. delivery of discharging ions to surfaces with small radii (irregularities and crystallites) is facilitated due to the realization of mechanism of the spherical diffusion, so the discharge of zinc ions occurs mainly on high points, and then on tops of dendrites branches. there is a lengthening of existing and originating of new branches. due to formation of plurality of branches the surface on which the discharge of metal ions takes place increases, and the current density decreases. at that the rate of dendrites elongation over time (fig.  1) and the absolute value of the overvoltage (fig. 2, curve 1) is gradually reduced. after recession of diffusion limitations mechanism of the process changes, particles on the deposits outer surface thicken. after 35 minutes of electrolysis the rate of dendrite growth falls distinctly, and the absolute value of the overvoltage reaches a constant value (fig. 2, curve 1). fig. 1. change the length of zinc dendrites in time in galvanostatic (1) and potentiostatic (2) modes fig. 2. change the overvoltage and current in time in galvanostatic (1) and potentiostatic (2) modes dynamics of electrocrystallization of dendritic zinc deposits in galvanostatic and potentiostatic modes 210 № 3 | 2015 chimica techno acta when setting a constant overvoltage throughout the electrolysis maintained a high level of difficulties in delivery of discharging ions. the development of the active surface, on which an electrochemical process is realized, leads to an increase in the amperage in the electrolysis process (fig. 2, curve 2). as a result, dendrites elongate at a higher and insufficiently time-varying rate in comparison to the electrodeposition at the constant current (fig. 1). differential current output of zinc, which characterizes the ratio of metal and hydrogen recovery processes rates, grows during the electrolysis process in galvanostatic conditions (fig. 3), that is associated with an increase in the deposit surface and a decrease in the true current density. at the moment of the overvoltage recession and achieving limiting diffusion current density hydrogen ceases to release and the current efficiency tends to unity. under the conditions of setting the permanent potential the current efficiency changes insufficiently over time and does not exceed 93 % (fig. 3). as parameters characterizing the structure of the deposit differential density dρос and differential porosity deposit dβ have been defined, which were calculated from a change in the metal mass and the overall deposit volume for a fixed period of time. differential characteristics allow evaluating a change of relevant structural properties of dendrites during the deposition. as seen in fig. 4, the deposits have a low density. when setting direct current integrated density of the deposit increases as the recession of active growth of dendrites, and in a constant potential mode it slightly decreases in time. however, the integral density value is an averaged characteristic, so it is less informative. differential density allows evaluating change of structural properties of dendrites during the deposition process. according to the thickness of the deposits obtained under potentiostatic conditions, the density changes little (fig. 5, curve 2), that indicates a uniform structure of the particles. while during electrodeposition of dendrites under galvanostatic conditions, the density increases gradually, and then increases dramatically (fig. 5, curve 1), that is associated with the intergrowth of separate dendrites branches and a shell formation. resulting deposits have high porosity (fig. 6), which decreases under galvanostatic conditions with cessation of active growth of dendrites (fig. 6, curve 1) and does not change at a constant potential (fig. 6, curve 2). fig. 3. change the differential current output in galvanostatic (1) and potentiostatic (2) modes fig. 4. change the integral density in time in galvanostatic (1) and potentiostatic (2) modes v. s. nikitin, т.n. ostanina, v.м. rudoy, а.s. farlenkov 211 № 3 | 2015 chimica techno acta the studies of morphology of dendritic deposits particles have been conducted using a scanning electron microscope. it is seen in micrographs with a resolution of 20 microns that at the initial stage of electrolysis (10 minutes) the size of certain particles (top radius) slightly differs in deposits obtained in the studied modes (fig. 7 a, b). the particles are similar both in size and shape resembling fern leaves. conclusion the dynamics of growth of dendritic electrolytic zinc deposits essentially depends on the polarization mode. in galvanostatic conditions there are observed a gradual decrease in the rate of elongation of dendrites and change in the deposit structure from dendritic to compact: density increases and porosity reduces. whereas in potentiostatic mode dendrites grow at a constant rate, and the loose deposit throughout the thickness has a uniform structure. the study results have been confirmed by deposits micrographs. fig. 5. change the density over the thickness of dendritic zinc deposits in galvanostatic (1) and potentiostatic (2) modes fig. 6. change the porosity over the thickness of dendritic zinc deposits in galvanostatic (1) and potentiostatic (2) modes fig. 7. micrographs of dendritic zinc deposits obtained in galvanostatic (a) and potentiostatic (b) modes. dynamics of electrocrystallization of dendritic zinc deposits in galvanostatic and potentiostatic modes 212 № 3 | 2015 chimica techno acta 1. neikov  o. d., nabojchenko  s. s., murashova  i. b., gopienko  v. g., frishberg  i. v., lotsko  d. v.  handbook of non-ferrous metal powders. elsevier ltd. amsterdam, the netherlands, 2009. available from: http://www.sciencedirect.com/science/ book/9781856174220 2. patrushev  a. v., ostanina  t. n., rudoy  v. m.  electrochemical methods for the determination of surface area of dendritic deposits. proceedings of phisycal chemistry and electrochemistry of molten and solid electrolytes: materials of xvi russian conference. ekaterinburg, 2013. v. s. nikitin, т.n. ostanina, v.м. rudoy, а.s. farlenkov 213 в. с. никитин, т. н. останина,   в. м. рудой, а. с. фарленков уральский федеральный университет 620002, екатеринбург, ул. мира, 19. e-mail: nikitin-viachieslav@mail.ru динамика электрокристаллизации дендритных осадков цинка в гальваностатическом и потенциостатическом режимах в работе исследована динамика роста дендритных осадков цинка в гальваностатическом и потенциостатическом режимах из электролита, содержащего 0,3 моль/л zno и 4 моль/л naoh. показано, что в гальваностатических условиях наблюдается снижение скорости удлинения дендритов и изменение структуры осадка с дендритной на компактную, сопровождающееся ростом плотности и уменьшением пористости по толщине. в потенциостатических режимах дендриты растут с постоянной скоростью и структура осадка мало меняется. полученные результаты подтверждены электронно-микроскопическими исследованиями морфологии частиц цинка. ключевые слова: электрокристаллизация, цинк, дендриты, электрохимия. © никитин в. с., останина т. н., рудой в. м., фарленков а. с., 2015 введение электролитические осадки цинка обладают уникальной дендритной структурой и  высокой чистотой, а  порошки, получаемые из них, используют в самых различных отраслях техники (производство аккумуляторов и  цинкнаполненных композиционных материалов). структурные свойства таких осадков, получаемых электролизом водных растворов, претерпевают изменения после снятия с  электрода, но морфология частиц, которая закладывается на стадии электролиза, остается неизменной после операций по обработке будущего порошка [1]. в  связи с  этим для получения электролитических порошков с  заданными свойствами необходимо знать, как влияют режимы осаждения на структурные свойства (плотность, пористость, удельную поверхность и  т. д.) осадка непосредственно в  процессе его формирования in situ [2]. варьируя условия электроосаждения (режим, задаваемый ток или потенциал, концентрацию разряжающихся ионов, добавки пав), можно получать порошки с разнообразной структурой. целью настоящей работы является исследование динамики процесу д к : 5 44 .6 53 .2 2: 5 44 .6 .0 18 .4 214 3 214 № 3 | 2015 chimica techno acta са электрокристаллизации и  свойств дендритных осадков цинка в условиях задания постоянного тока и  постоянного потенциала. методика эксперимента для изучения динамики развития дендритных осадков цинка была использована установка, позволяющая одновременно регистрировать изменение потенциала (или тока), проводить видеозапись роста осадка и  фиксировать объем выделяющегося водорода. в  центр цилиндрической ячейки подводился штырьковый катод высотой 1 см, изготовленный из цинковой проволоки диаметром 2 мм. по краю ячейки располагали кольцевой цинковый анод. поляризационные измерения проводили с  помощью потенциостата solartron 1280 с.  потенциал измеряли относительно цинкового электрода сравнения. осадки получали из цинкатного электролита, содержащего 0,3 моль/л zno и  4 моль/л naoh, при задании постоянного тока и  постоянного потенциала. поляризующий ток в  шесть раз превышал величину предельного диффузионного тока. при использовании потенциостатических условий поддерживали постоянное перенапряжение –0,38 в, которое соответствовало уровню диффузионных ограничений гальваностатического электролиза. анализ видеозаписи процесса роста осадка позволил установить зависимость толщины слоя дендритного осадка от времени и рассчитать габаритный объем осадка. по данным волюмометрических измерений определяли выход по току водорода и  цинка, что позволило рассчитать изменение массы осадка в  процессе электроосаждения. микроструктурные исследования осадков проводили на растровом электронном микроскопе mira 3 lmu в  лаборатории ивтэ уро ран. результаты и обсуждение в гальваностатических условиях вследствие высокой плотности тока скорость образования ад-атомов высока. доставка разряжающихся ионов к  поверхностям малого радиуса (неровностям и  кристаллитам) облегчена вследствие реализации механизма сферической диффузии, поэтому разряд ионов цинка преимущественно протекает на выступах, а затем на вершинах ветвей дендритов. происходит удлинение существующих и  зарождение новых ветвей. вследствие образования множества ветвей поверхность, на которой протекает разряд ионов металла, увеличивается, а  плотность тока снижается. при этом скорость удлинения дендритов во времени (рис. 1) и  абсолютная величина перенапряжения (рис. 2, кривая 1) постепенно уменьшаются. после спада диффузионных ограничений меняется механизм процесса, частицы на внешней поверхности осадка утолщаются. после 35 мин электролиза скорость роста дендритов резко падает, а  абсолютная величина перенапряжения выходит на постоянное значение (рис. 2, кривая 1). при задании постоянного перенапряжения в течение всего электролиза сохраняется высокий уровень затруднений по доставке разряжающихся ионикитин в. с., останина т. н., рудой в. м., фарленков а. с. 215 № 3 | 2015 chimica techno acta нов. развитие активной поверхности, на которой реализуется электрохимический процесс, приводит к  увеличению силы тока в процессе электролиза (рис. 2, кривая 2). в результате дендриты удлиняются с более высокой и мало меняющейся во времени скоростью, по сравнению с электроосаждением на постоянном токе (рис. 1). дифференциальный выход по току цинка, характеризующий соотношение скоростей процессов восстановления металла и  водорода, растет в процессе электролиза в гальваностатических условиях (рис. 3), что связано с  увеличением поверхности осадка и  снижением истинной плотности тока. в момент спада перенапряжения и достижения предельной диффузионной плотности тока водород перестает выделяться, и выход по току стремится к  единице. в  условиях задания постоянного потенциала выход по току мало изменяется во времени и не превышает 93 % (рис. 3). в качестве параметров, характеризующих структуру осадка, определяли дифференциальную плотность dρос и  дифференциальную пористость осадка dβ, которые рассчитывали по изменению массы металла и  габаритного объема осадка за фиксированный промежуток времени. дифференциальные характеристики позволяют оценить изменение соответствующих структурных свойств дендритов в процессе осаждения. как видно на рис. 4, осадки обладают малой плотностью. при задании постоянного тока интегральная плотность осадка растет по мере спада активного роста дендритов, а  в  режиме постоянного потенциала она незначительно уменьшается со временем. однако величина интегральной плотности является усредненной характеристикой, поэтому она малоинформативна. дифференциальная плотность позволяет оценить изменение структурных свойств дендритов в  процессе осаждения. по толщине осадков, полурис. 1. изменение длины дендритов цинка во времени при гальваностатическом (1) и потенциостатическом (2) режимах рис. 2. изменение перенапряжения и силы тока во времени при гальваностатическом (1) и потенциостатическом (2) режимах рис. 3. изменение дифференциального выхода по току при гальваностатическом (1) и потенциостатическом (2) режимах динамика электрокристаллизации дендритных осадков цинка в гальваностатическом и потенциостатическом режимах 216 № 3 | 2015 chimica techno acta ченных в  потенциостатических условиях, плотность мало меняется (рис. 5, кривая 2), что свидетельствует об однородной структуре частиц. тогда как при электроосаждении дендритов в гальваностатических условиях плотность постепенно увеличивается, а затем резко возрастает (рис. 5, кривая 1), что связано со срастанием отдельных ветвей дендритов и  образованием скорлупы. полученные осадки обладают высокой пористостью (рис. 6), которая уменьшается в  гальваностатических условиях по мере прекращения активного роста дендритов (рис. 6, кривая 1) рис. 4. изменение интегральной плотности во времени при гальваностатическом (1) и потенциостатическом (2) режимах рис. 5. изменение плотности по толщине дендритных осадков цинка при гальваностатическом (1) и потенциостатическом (2) режимах рис. 6. изменение пористости по толщине дендритных осадков цинка при гальваностатическом (1) и потенциостатическом (2) режимах рис. 7. микрофотографии цинковых дендритных осадков, полученных в гальваностатическом (а) и потенциостатическом (б) режимах. время получения осадков 10 мин никитин в. с., останина т. н., рудой в. м., фарленков а. с. 217 № 3 | 2015 chimica techno acta и практически не меняется при постоянном потенциале (рис. 6, кривая 2). исследования морфологии частиц дендритных осадков были проведены с  помощью растрового электронного микроскопа. на микрофотографиях с  разрешающей способностью 20 мкм видно, что на начальном этапе электролиза (10 мин.) размер отдельных частиц (радиус вершины) мало отличается у осадков, полученных в исследуемых режимах (рис. 7, а, б). частицы похожи как по размеру, так и по форме, напоминающей листья папоротника. заключение динамика роста дендритных электролитических осадков цинка существенно зависит от режима поляризации. в  гальваностатических условиях наблюдается постепенное снижение скорости удлинения дендритов и  изменение структуры осадка с  дендритной на компактную: возрастает плотность и  снижается пористость. тогда как в  потенциостатическом режиме дендриты растут с  постоянной скоростью, а рыхлый осадок по всей толщине имеет однородную структуру. результаты исследований подтверждены микрофотографиями осадков. 1. neikov  o. d., nabojchenko  s. s., murashova  i. b., gopienko  v. g., frishberg  i. v., lotsko d. v. handbook of non-ferrous metal powders. technologies and applications. elsevier, london, n-y, amsterdam, 2009. 634 pp. 2. patrushev  a. v., ostanina  t. n., rudoy  v. m.  electrochemical methods for the determination of surface area of dendritic deposits, phisycal chemistry and electrochemistry of molten and solid electrolytes: materials of xvi russian conference. publishing house of the ural university, ekaterinburg, 2013. динамика электрокристаллизации дендритных осадков цинка в гальваностатическом и потенциостатическом режимах study and optimization of the synthesis routine of the single phase ybaco2o6-δ double perovskite 183 d o i: 1 0. 15 82 6/ ch im te ch /2 01 7. 4. 3. 03 sednev a. l., tsvetkov d. s. chimica techno acta. 2017. vol. 4, no. 3. p. 183–190. issn 2409–5613 a.l. sednev, d.s. tsvetkov institute of natural sciences and mathematics, ural federal university, 19 mira st., ekaterinburg, 620002, russia e-mail: anton.sednev@urfu.ru study and optimization of the synthesis routine of the single phase ybaco 2 o 6–δ double perovskite the chemical interaction of ycoo 3–δ and bacoo 3-δ with formation of double perovskite was studied depending on temperature and oxygen partial pressure. the stability of ycoo 3 was shown to have а crucial influence on the kinetics and mechanism of ybaco 2 o 6-δ formation. it was found that at 1000 °c in air, i.e. under conditions when ycoo 3 is unstable, the double perovskite ybaco 2 o 6-δ is formed much slower compared to the pure oxygen atmosphere where ycoo 3 is stable at the same temperature. thus controlling ycoo 3 stability was shown to be the factor of key importance for optimal preparation of the ybaco 2 o 6-δ single phase. keywords: ybaco 2 o 6 synthesis, ycoo 3 instability, po 2 acceleration, double perovskite synthesis, ybaco 2 o 5 , ycoo 3 , bacoo 3 . received: 07.09.2017; accepted: 25.09.2017; published: 20.10.2017. © sednev a.l., tsvetkov d.s., 2017 introduction complex oxide ybaco2o6–δ with double perovskite structure has been extensively investigated in recent years as a promising material for oxygen membranes [1, 2] and solid oxide fuel cells (sofcs) [3, 6, 7, 9, 12] due to high mixed ionic-electronic conductivity [12] and moderate thermal expansion comparable to that of the state-of-the art sofc electrolytes [3]. however, ybaco2o6–δ is unstable in air at temperatures between 800 and 850 °c [13] and decomposes to mixture of the simple perovskites ycoo3–δ and bacoo3–δ, which are more thermodynamically stable under these conditions. this significantly impedes obtaining a single phase material. moreover, a synthesis routine, which could be provided the single phase ybaco2o6–δ obtaining, has not been discussed in literature so far. the lack of the appropriate data also inhibits a commercial application of the ybaco2o6–δ based materials. therefore the main aim of the current work was to study a formation of the ybaco2o6–δ double perovskite at 900 and 1000  °c in different gas atmospheres in order to optimize its synthesis routine. experimental taking into account that synthesis of ybaco2o6–δ proceeds through the formation of intermediate phases of ycoo3–δ and bacoo3–δ like other double perovs184 kites lnbaco2o6–δ [14] as well as that a synthesis routine for these intermediate phases has been already described in lite rature [15, 16] we selected ycoo3–δ and bacoo3–δ as starting reagents for preparation of the ybaco2o6–δ double perovskite. powder samples of ycoo3–δ, bacoo3–δ were synthesizes by means of glyserolnitrate technique, using co, y2o3 and baco3 as starting materials. all the materials used had a purity of 99.99 %. metallic co was obtained by reduction of co3o4 (purity 99.99 %) in h2 atmosphere at 600 °c. y2o3 and baco3 were preliminary calcined at 1100  °c and 600  °c, respectively, in air for two hours in order to remove adsorbed h2o and co2. stoichiometric mixture of starting materials was dissolved in concentrated nitric acid. then the required quantity of glycerol as a complexing and reducing agent was ad ded to the obtained solution. afterwards the solution was evaporated to dryness, and resulted dry powder was pyrolyzed. the product of pyrolysis was put in a crucible and calcined in a furnace. the final calcination was carried out at 1100  °c in air for two hours с  for bacoo3–δ and at 900  °c for ycoo3–δ. phase composition of the as-prepared powder samples was confirmed by x-ray diffraction using shimadzu xrd-7000 diffractometer (cukα radiation, 20≤2θ, °≤90). x-ray diffraction patterns of the as-synthesized ycoo3–δ and bacoo3–δ are shown in figs. 1 and 2. the results of the structureless le bail fitting are also shown in fig. 1 and 2. it should be noted that the x-ray diffraction pattern of bacoo3 was interpreted as a mixture of two compounds: bacoo3 and bacoo2.61 (see fig. 2). the refined cell parameters of the prepared compounds given in table 1 are in a good agreement with those reported in literature. synthesis of ybaco2o6-δ was stu died by annealing equimolar mixture of ycoo3–δ and bacoo3–δ for 72h (6 steps with duration of 12 h at each step) at temperatures 900 and 1000  °c in atmospheres with oxygen partial pressure (po2) fig. 2. x-ray diffraction pattern and its matching refinement plot of bacoo3-δ: observed x-ray diffraction intensity points and calculated curve (χ2 = 1.87) – line. the bottom curve is the difference of patterns, yobs − ycal, and the small bars indicate the angular positions of the allowed bragg reflections for bacoo3 (blue lines) and bacoo2.61 (red lines) fig. 1. x-ray diffraction pattern and its matching refinement plot of ycoo3-δ: observed x-ray diffraction intensity – points and calculated curve (χ2 = 1.62) – line. the bottom curve is the difference of patterns, yobs − ycal, and the small bars indicate the angular positions of the allowed bragg reflections 185 0.21 and 1 atm with intermediate mixture regrinding in agate mortar. phase composition of the samples after each step of annealing was controlled by xrd. results and discussion fig. 3 shows xrd patterns of the ycoo3–δ + bacoo3–δ equimolar mixtures annealed at 900 °c in air (po2 = 0.21 atm) and pure oxygen (po2 = 1 atm) for 72 h. as seen annealing neither in air nor in oxy gen atmosphere leads to formation of the single phase ybaco2o6–δ at least for this time of annealing. moreover xrd pattern of the mixture annealed at 900 °с in pure oxygen atmosphere does not show any indication of the chemical interaction between the reagents and formation of ybaco2o6–δ double pe rovskite whereas annealing in air leads to formation of significant amount of this double perovskite (see fig. 3). possible reason of this difference seems to be rela ted to the instability of ybaco2o6–δ oxide under oxidizing conditions at temperatures lower than some threshold value [11–13]. figs. 4 and 5 show xrd patterns of the ycoo3–δ and bacoo3–δ equimolar mixtures annealed at 1000  °c in air (po2 = 0.21 atm) and pure oxygen (po2 = 1 atm) for 72 h. as seen annealing in air also did not lead to the formation of the single phase double perovskite. y2o3, bacoo3 and coo can be identified as impurities in the x-ray diffraction pattern shown in fig. 4. the presence of these impurities is a consequence of instability of the ycoo3, which decomposes in air at t ≥ 900  °c with formation of y2o3 and coo [11–13, 22, 23]. similar behavior is well-known for the perovskite-type cobaltites with small rare-earth elements [24, 25]. therefore formation of ybaco2o6–δ at 1000 °c in air seems to proceed according table 1 crystallographic parameters of synthesized cobaltites in comparison with literature data compound space group a*, å b*, å c*, å reference ycoo3–δ pbnm 5.139 5.137 5.132 5.419 5.420 5.411 7.365 7.364 7.360 this work [17] [18] bacoo3 p-6m2 5.683 5.645 5.652 5.683 5.645 5.6525 4.552 4.752 4.763 this work [19] [20] bacoo2.63 p63/mmc 5.666 5.665 5.671 5.666 5.665 5.671 28.494 28.493 28.545 this work [16] [21] * uncertainty ±0.001 å. fig. 3. xrd patterns of ycoo3–δ and bacoo3–δ equimolar mixtures after annealing in air (a) and pure oxygen (b) at 900 °c for 72 h 186 to the two-stage process. first ycoo3 decomposes into y2o3 and coo upon heating of the equimolar mixture of ycoo3–δ and bacoo3-δ up to 1000 °c in air ycoo3 = ½y2o3 + coo + ¼o2. (1) then a mixture of y2o3, bacoo3 and coo slowly reacts at 1000 °c with formation of the required double perovskite ½y2o3 + bacoo3–δ + coo = = ybaco2o6–δ + ¼o2. (2) at the same time annealing the ycoo3–δ and bacoo3–δ equimolar mixture at 1000 °c in oxygen for 72 h leads to formation of the single phase ybaco2o6–δ as seen in fig. 5 where appropriate xrd pattern is shown. this pattern was refined as a mixture of two phases having 3×2×2 and 1×2×2 superstructures. the former has tetragonal structure (s. g. p4/mmm) with cell parameters a = b = 11.596(4) å and c = 7.509(7) å whereas the latter has orthorhombic structure (s. g. pmma) with cell parameters a = 3.821(4) å, b = 7.846(2) å, c = 7.515(8) å in full agreement with available structural data [5, 7, 12, 26, 27]. detailed step-by-step investigation of the ybaco2o6–δ synthesis in oxygen at this temperature revealed that the resultant mixture at each step except last one contained bacoo3–δ, y2o3, coo, ycoo3–δ and the product ybaco2o6–δ. this result can be understood, first of all, based on the analysis of the thermodynamics of reaction eq. (1). although for this particular reaction thermodynamic functions are unknown similar reactions for hoand er-contained cobaltites have already been studied in this respect [24, 25]. required thermodynamic data for them are given in table 2. as seen hocoo3 decomposition starts at 1051  °c in air whereas ercoo3 decomposes already at 866 °c in the same atmosphere. ycoo3 as mentioned above is somewhere between these two compounds since its decomposition in air starts at 900–950  °c [11–13, 22, 23]. therefore standard enthalpy and entropy of reaction eq. (1) for ycoo3 may be roughly estimated by averaging corres ponding standard enthalpies and entropies for erand ho-containing cobaltites. the thermodynamic quantities of reaction eq. (1) obtained in this way are also fig. 4. xrd pattern of ycoo3–δ and bacoo3–δ equimolar mixtures annealed in air at 1000 °c for 72 h fig. 5. x-ray diffraction pattern and its matching refinement plot of ybaco2o6–δ obtained by annealing at 1000 °c in oxygen for 72 h: observed x-ray diffraction intensity – points and calculated curve – line. the bottom curve is the difference of patterns, yobs − ycal, and the small bars indicate the angular positions of the allowed bragg reflections for ybaco2o6–δ with 3×2×2 superstructure (blue) and 1×2×2 superstructure (red) 187 shown in table 2. they allow estimating corresponding equilibrium decomposition temperatures for ycoo3 in air and oxygen. as seen in table 2 this estimation gives 953  °c as the decomposition temperature of ycoo3 in air, which is in line with that reported earlier [11–13, 22, 23]. the value of decomposition temperature in oxygen is around of 1060 °c. taking into account that this is only a very rough estimation one may expect the real decomposition temperature for ycoo3 in oxygen in the range of 1000–1100  °c, i. e. during annealing of the ycoo3–δ and bacoo3–δ equimolar mixture at 1000  °c in pure oxygen atmosphere its first component is in equilibrium with oxides y2o3 and co o. therefore synthesis of the ybaco2o6–δ double perovskite under these conditions can be described by the following parallel reactions ycoo3 + bacoo3 = ybaco2o6 (3) ½y2o3 + coo + ¼o2 = ycoo3 (4) the equilibrium of reaction eq. (4) is shifted to the right due to consumption of ycoo3 as a reagent of reaction eq. (3). comparison of the results of synthesis at 1000 °c in two atmospheres, i. e. air and oxygen, shows that in the second case formation of the double perovskite occurs apparently faster. one may speculate on the reasons of the observed positive influence of high oxygen pressure. intuitively it seems quite expected that the combination (or interaction) of two ‘simple’ perovskites representing elementary ‘building’ units of the double perovskite structure is a faster process then a combination of barium cobaltite with two oxi des. significant diffusion difficulties are quite expected in the last case. however the exact reasons and detailed microsco pic mechanism of an interaction in oxygen or air atmosphere should be studied in order to make meaningful conclusions. we only would like to emphasize once again the key role, which thermodynamic stability of ycoo3 plays in the optimization of synthesis routine for the ybaco2o6–δ double perovskite. table 2 thermodynamics of reaction eq. (1) for the selected cobaltites at 927 °c δh°, kj·mol–1 δs°, j·mol–1·k–1 tair*, °c to2**, °c reference hocoo3 44.88 30.63 1051 1192 [24, 25] ercoo3 51.34 41.3 866 970 [24, 25] ycoo3 48 36 953 1060 estimated in this work * equilibrium temperature for rcoo3 (r = y, ho, er) decomposition in air ** equilibrium temperature for rcoo3 (r = y, ho, er) decomposition in oxygen fig. 6. xrd patterns of ycoo3–δ and bacoo3–δ equimolar mixture step-by-step annealed at 1000 °c in pure oxygen 188 conclusions synthesis of ybaco2o6–δ from equimolar mixture of ycoo3 and bacoo3–δ was studied at 900  °c and 1000  °c in air and pure oxygen atmosphere. it was shown that synthesis at 1000  °c in pure oxygen atmosphere is an optimal way of obtaining the single phase ybaco2o6–δ. detailed step-by-step investigation of the synthesis was carried out at 1000 °c in po2 = 1 atm. the mechanism of ybaco2o6–δ synthesis in different gas atmospheres was proposed based on thermodynamics of ycoo3 and crucial role of this 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2017;4(3):183–90. doi:10.15826/chimtech/2017.4.3.03. cta_v4_№1.cdr 45 nechaev a.v., nechaev a.a., timina a.a. chimica techno acta. 2017. vol. 4, no. 1. p. 45–53. issn 2409-5613 d o i: 1 0. 15 82 6/ ch im te ch .2 01 7. 4. 1. 02 3 5 44 .6 5 a. v. nechaev, a. a. nechaev, a. a. timina institute of fundamental education, ural federal university, 28 mira str., ekaterinburg, 620002, russia. tel. (343) 375–45–68. email: a. v.nechaev@urfu.ru anodic behaviour of aluminium and its alloys in sodium chlorate solutions the e ect of chlorate ions on the anodic dissolution of aluminium and its alloys with magnesium under conditions of high current densities and intensive electrolyte mixing is investigated using the method of anodic polarisation curve removal on a rotating disk electrode. it is shown that at relatively low anodic potential values the process is limited by the capacity of the electrochemical reaction, but with a further potential shi and a venting of the reaction products from the surface of the anode. the e ective smoothing of the surface microrelief of aluminium alloys in solutions of chlorates is due to the periodic formation and destruction on the treated surface of a speci c oxide lm and inhibition due to the electrochemical heterogeneity of the structural components of the alloys. key words: anode potential; aluminium alloys; anodic polarization curves; sodium chlorate. received: 25.11.2016; accepted: 29.01.2017; published: 14.04.2017. а. в. нечаев, а. а. нечаев, а. а. тимина институт фундаментального образования уральский федеральный университет, россия, 620002, екатеринбург, ул. мира, 28. тел.(343) 375–45–68. email: a. v.nechaev@urfu.ru . , , . . : ; ; ; . : 25.11.2016; : 29.01.2017; : 14.04.2017. © nechaev a. v., nechaev a. a., timina a.a, 2017 46 introduction in solving problems associated with the electrochemical machining of aluminium alloys, an important role is played by an understanding of the laws of their anodic dissolution in an intensive electrolyte fl ow. th erefore, knowledge of these laws will allow the optimal composition of the electrolyte to be chosen for the best mode for electrochemical machining of aluminium alloys, providing high accuracy and surface quality. research methodology in this paper, the study of the behaviour of aluminium alloy anodes used a rotating disc electrode to simulate the actual hydrodynamic conditions of the electrochemical process and provide an intense fl ow of electrolyte at the electrode surface [1]. in order to eliminate the resistive component in the measurement of the electrode potential, a rotating electrode design was created at the chemical-technological institute of the ural federal university for the studied vertical movement relative to the very thin tip of the salt bridge of the reference electrode. th e capillary of the reference electrode, having an external diameter of 0.1 mm, was led into the centre of the disk by a distance not exceeding 0.07 mm. in order to control the value of the resistive component in the values of the electrode potential, polarisation curves were taken at consecutive removing of the capillary from the surface of the electrode and then extrapolated to zero distance. moulded ptfe cylindrical rods with a diameter of 2 mm, which had been degreased with ethanol directly prior to the experiment, were used for removing the polarization curves. in order to reduce dissolution of the electrode and thereby increase the distance between the working electrode and the reference electrode capillary, anodic polarisation curves were recorded in potentiodynamic mode with linear scanning potential of 4b/min in a temperature controlled three-electrode glass cell with the divided anode and cathode spaces in solutions naclo3 at 25 °c. a silver chloride electrode in a saturated solution of potassium chloride served as a reference electrode. for the auxiliary electrode, a platinum element was used. technological research was carried out on a pilot plant for electrochemical hole cutting in metals. in the experiments, the current density was varied between 50 and 250 a/cm2 with an electrode gap of 0.05 to 0.1 mm, electrolyte fl ow rate from 10 to 40 m/sec and temperature between 20 and 60 °c. highly pure grade a995 aluminium and aluminium alloys amg1, amg3, amg6, having varying magnesium content, formed the objects of study. experimental part in sodium chlorate solutions, the anodic behaviour of aluminium and its alloys, like sodium chloride solutions, is characterised by areas of active dissolution and passivation. polarisation curves obtained for aluminium alloys in sodium chlorate solutions show a sharp increase in the anodic current density following activation of the anode potential. 47 however, when it reaches a certain density, the current reaches a limit in the speed of the anode process of dissolution of aluminium alloys – the current density falls with anode off set potential into the positive area and no further increases take place (fig. 1). a slight difference in the chemical composition of alloys is considered here in terms of the main alloying components (magnesium) having no signifi cant impact on their anodic behaviour; this is determined by the base alloy component, i. e. aluminium. along with the concentration of the electrolyte, the infl uence of the electrolyte temperature and speed of rotation of the disc electrode on the intensity of anodic dissolution of aluminium alloy (fig. 2) were also studied. in the study of the anodic behaviour of the investigated aluminium alloys depending on the temperature of the solution, the rotating speed of the disk electrode showed that the maximum current density on the anodic polarisation curves increases with a decreasing concentration of sodium chlorate solution from 5m to 3m (fig. 1), as well as with an increase in electrolyte temperature (fig. 2) and with an increase in the rotational speed of the disk electrode (fig. 2). it can be assumed that in sodium chlorate solutions, as in chloride solutions, the passivation of aluminium and aluminium alloys of amg6 type occurs due to the formation of a salt fi lm on the surface of the electrode. results and discussion processing of the experimental data using the temperature-kinetic method showed that the value of the eff ective activation energy of the dissolution process of the alloy in amg6 naclo3 solutions decreases from 7.05 to 7 > 2.4 kcal / mol with increasing fig. 1. potentiodynamic polarisation curves for amg6 alloy captured on a rotating disk electrode in sodium chlorate solutions of various concentrations (mol / l): 1-0,5; 2-1,0; 3-5,0; 4-4,0; 5-2,0; 6-3,0. fig. 2. eff ect of temperature (1) and speed of rotation of disc electrode (2) on the maximum current density dissolution of aluminium alloy amg6 in 4m sodium chlorate 48 polarisation from 0.8 to 1.7 b. th erefore, at relatively low anode potential values, the alloy dissolution process is limited by the electrochemical reaction, and, when a certain potential is reached – withdrawal of the reaction products from the surface of the anode [2]. th e presence of diff usion limitations at the time of active dissolution of the alloy also shows the maximum dependence of the current density on the polarisation curve on the speed of the rotation disc electrode (fig. 2). th is may also indicate the fact that the maximum current value before the beginning of passivation increases almost linearly with an increase in temperature of the electrolyte owing to increased solubility of the salt fi lm. with a further shift of the potential of the aluminium electrode to a positive region in sodium chlorate solutions, no new sharp increase in current density was observed after reaching the maximum current density, as was the case in the solutions of sodium chloride. th is behaviour of the aluminium anode in solutions of naclo3 can be explained by the fact that fi lm passivation of a more complex nature may occur aft er the formation of a salt fi lm on the electrode. to some extent this shows the dependence of current on time (fig. 3.). although they were in evidence in the sodium chloride solution, no clearly expressed peaks were present with potentiostatic closure in the region of signifi cant polarisations. more complex secondary passivation layers, probably on the part of aluminium oxide compounds, are formed in sodium chlorate solutions. th e formation of a number of diff erent oxide fi lms on the metals in the sodium chlorate solutions was noted in [3]. since in the passive region, the current of the anodic dissolution is only somewhat less than the maximum it is possible to assert that the resultant oxide fi lm on the anode does not prevent the anodic dissolution of aluminium alloys in the solutions of sodium chlorate. when directly viewed through a microscope, a fi lm can be clearly seen forming on the surface of the aluminium electrode during dissolution; this almost immediately disintegrates into fragments, exposing the surface of the electrode. moreover, transportation of metal ions from the anode surface may occur by migration through the fi lm. according to [4] structural defects are present in an ionic oxide lattice: either cationic and anionic components are unoccupied, or, alternatively, ions introduced in the interstices of the lattice, whereby the diff usion of ions and electrons can occur in the oxide layer. th e intensity of the dissolution of the metal fig. 3. anodic polarisation curve of current density – time at diff erent potentials, taken on a rotating disk electrode for amg6 alloy in 4m sodium chlorate solution 1 – forward stroke of polarisation curve, 2 – return stroke of polarisation curve 49 will depend on the speed of movement of ions through the atomic lattice of the oxide. in electrochemical treatment of aluminium alloys in sodium chlorate solutions, a high purity of the treated surface is achieved. effective smoothing of the microrelief and high purity of the treated surface following electrochemical treatment of aluminium alloys in sodium chlorate solutions can be linked to the formation of specifi c oxide fi lms on the surface of the electrode and suppression thereby of the electrochemical heterogeneity of structural components of aluminium alloys by an additional potential barrier at the metal boundary, consisting of a fi lm that also reduces the extent of etching. in this case, there is a redistribution of the potentials of various structural components of the alloy, which leads to their levelling and a consequent smoothing of the microrelief. th is is to some extent confi rmed by metallographic studies of the aluminium alloy surface following electrochemical treatment in sodium chlorate solutions, which showed the absence of any intergranular violations of the grain boundary. in nitrate solutions, the activation potential of aluminium and its alloys with magnesium is almost two volts higher than in sodium chlorate solutions. th erefore, from the standpoint of energy consumption, treatment of aluminium alloys using a sodium chlorate based electrolyte is preferable. th us, along with high quality electrochemical machining in the complete absence macroscopic defects on the treated surface, a high level of productivity in processing aluminium alloys is achievable using chlorate solutions. in russian в решении проблем электрохимической обработки алюминиевых сплавов немаловажную роль играют закономерности их анодного растворения в интенсивном потоке электролита. поэтому знание этих закономерностей позволит выбрать состав электролита и оптимальный режим для обработки алюминиевых сплавов, обеспечивающий высокую точность и качество обрабатываемой поверхности. в данной работе при изучении анодного поведения алюминиевых сплавов был применен вращающийся дисковый электрод, реально имитирующий гидродинамические условия электрохимической обработки и обеспечивающий интенсивный поток электролита у поверхности электрода [1]. для элиминирования омической составляющей при измерении электродного потенциала в химико-технологическом институте уральского федерального университета специально была создана конструкция установки вращающегося электрода, обеспечивающая вертикальное перемещение изучаемого электрода относительно очень тонкого носика электролитического ключа электрода сравнения. капилляр электрода сравнения с внешним диаметром не более 0,1 мм подводился к центру диска на расстояние, не превышаю50 щее 0,07 мм. для контроля величины омической составляющей в значения величины потенциала электрода снимались поляризационные кривые при последовательном удалении капилляра от поверхности исследуемого электрода с последующей экстраполяцией их на нулевое расстояние. для снятия поляризационных кривых использовались запрессованные во фторопласт цилиндрические стержни диаметром 2 мм, которые непосредственно перед экспериментом обезжиривались этанолом. с целью уменьшения растворения электрода и в связи с этим увеличения расстояния между рабочим электродом и капилляром электрода сравнения анодные поляризационные кривые снимались в потенциодинамическом режиме при линейной развертке потенциала 4в/мин в термостатированной трех электродной стеклянной ячейке с разделенным анодным и катодным пространствами в растворах naclо3 при температуре 25 °c. электродом сравнения служил хлорсеребряный электрод в насыщенном растворе хлорида калия. вспомогательным электродом служила платина. технологические исследования проводились на опытной установке для электрохимической прошивки отверстий в металлах. при проведении экспериментов плотность тока менялась от 50 до 250 а/см2, межэлектродный зазор – от 0,05 до 0,1 мм, скорость течения электролита – от 10 до 40 м/с, температура – от 20 до 60 °c. в качестве объектов исследования использовалась алюминий марки а995 и алюминиевые сплавы амц, амг1, амг3, амг6, содержащие в своем составе различное содержание магния. в растворах хлората натрия анодное поведение алюминия и его сплавов, подобно растворам хлорида натрия, характеризуется областью активного растворения и пассивацией. поляризационные кривые, полученные для алюминиевых сплавов в растворах хлората натрия, свидетельствуют, что после потенциала анодной активации наблюдается резкий рост анодной плотности тока. однако при до с тижении опр еделенной плотности тока наступает ограничение скорости анодного процесса растворения алюминиевых сплавов – плотность тока падает при смещении потенциала анода в положительную область и в дальнейшем не увеличивается (рис. 1). незначительное отличие химического состава рассматриваемых нами сплавов по основному легирующему компоненту (магнию) не повлияло существенно на их анодное поведение, которое определяется основным компонентом сплава – алюминием. наряду с концентрацией электролита исследовано влияние температуры электролита и скорости вращения дискового электрода на интенсивность анодного растворения алюминиевых сплавов (рис. 2). изучение анодного поведения исследуемых алюминиевых сплавов в зависимости от температуры раствора скорости вращения дискового электрода показало, что максимальная плотность тока на анодных поляризационных кривых с понижением концентрации 51 раствора хлората натрия от 5м до 3м (рис. 1), а также с ростом температуры электролита (рис. 2) и увеличением скорости вращения дискового электрода (рис. 2) возрастает. можно предположить, что в растворах хлората натрия, как и в растворах хлоридов, пассивация алюминия и алюминиевых сплавов типа амг6 наступает вследствие образования на поверхности электрода солевой пленки. обработка полученных экспериментальных данных температурно-кинетическим методом показала, что значение эффективной энергии активации процесса растворения сплава амг6 в растворах naclo3 уменьшается от 7,05 до 7 > 2,4 ккал/моль с ростом поляризации от 0,8 до 1,7 в. следовательно, при сравнительно низких значениях анодных потенциалов процесс растворения сплава лимитируется собственно электрохимической реакцией, а при достижении определенного потенциала – отводом продуктов реакции от поверхности анода [2]. о наличии диффузионных ограничений в момент активного растворения сплава свидетельствует и зависимость максимальной плотности тока на поляризационной кривой от скорости вращения дискового электрода (рис. 2). об этом может также свидетельствовать и то, что с повышением температуры электролита, вследствие увеличения рис. 1. потенциодинамические поляризационные кривые для сплава амг6, снятые на вращающемся дисковом электроде в растворах хлората натрия различной концентрации (моль/л): 1 – 0,5; 2 – 1,0; 3 – 5,0; 4 – 4,0; 5 – 2,0; 6 – 3,0 рис. 2. влияние температуры (1) и скорости вращения дискового электрода (2) на максимум плотности тока растворения алюминиевого сплава амг6 в 4м раствора хлората натрия 52 растворимости солевой пленки, величина максимального тока до начала пассивации возрастает практически линейно. при дальнейшем сдвиге потенциала алюминиевого электрода в положительную область в растворах хлората натрия не наблюдалось нового резкого повышения плотности тока после достижения максимума плотности тока, как это имело место в растворах хлорида натрия. такое поведение алюминиевого анода в растворах naclo3 может быть связано с тем, что вслед за образованием солевой пленки на электроде может возникать пассивная пленка более сложной природы. об этом в какой-то мере свидетельствует зависимость ток – время (рис. 3). при потенциостатическом включении в области больших поляризаций отсутствовали ярко выраженные пики, в то время как в растворе хлорида натрия они имели место. в растворах хлората натрия вторичные более сложные пассивирующие слои, по всей вероятности, образованы оксидными соединениями алюминия. образование различных по природе оксидных пленок на металлах в растворах хлората натрия отмечалось в работе [3]. поскольку в пассивной области ток анодного растворения лишь немного меньше максимального, можно утверждать, что образующаяся на аноде оксидная пленка не препятствует анодному растворению алюминиевых сплавов в растворах хлората натрия. при наблюдении в микроскоп за поверхностью алюминиевого электрода непосредственно в процессе его растворения отчетливо было видно образование на поверхности электрода пленки, которая почти сразу же разрушалась на отдельные фрагменты, оголяя поверхность электрода. кроме того, транспорт металлических ионов с поверхности анода может происходить и посредством их миграции через эту пленку. в ионной решетке оксида имеются структурные дефекты: незанятые катионные и анионные узлы, или, наоборот, ионы, внедренные дополнительно в междуузлия решетки, в результате чего может происходить диффузия ионов и электронов в слое оксида [4]. интенсивность растворения металла будет зависеть и от скорости движения ионов сквозь атомную решетку оксида. при электрохимической обработке алюминиевых сплавов в растворах хлората натрия достигается высокая чистота обрабатываемой поверхности. эффективное сглаживание микрорельефа и высокая чистота обрабатываемой рис. 3. анодная поляризационная кривая и зависимости плотность тока – время при различных потенциалах, снятые на вращающемся дисковом электроде для сплава амг6 в 4м растворе хлората натрия: 1 – прямой ход поляризационной кривой; 2 – обратный ход поляризационной кривой 53 поверхности после электрохимической обработки алюминиевых сплавов в растворах хлората натрия могут быть связаны с образованием на поверхности электрода специфической оксидной пленки и подавлением вследствие этого электрохимической гетерогенности структурных составляющих алюминиевых сплавов за счет дополнительного потенциального барьера на границе металл – пленка, что и приводит к уменьшению масштабов травления. в этом случае происходит перераспределение потенциалов различных структурных составляющих сплава, приводящее к их выравниванию и сглаживанию микрорельефа. это в определенной степени подтверждается металлографическими исследованиями поверхности алюминиевых сплавов после их электрохимической обработки в растворах хлората натрия, которые показали отсутствие какихлибо межкристаллитных нарушений по границам зерен. в растворах нитратов потенциал активации алюминия и его сплавов с магнием почти на два вольта больше, чем в растворе хлората натрия. поэтому с точки зрения энергетических затрат использование для обработки алюминиевых сплавов электролита на основе хлората натрия предпочтительно. таким образом, в растворах хлоратов наряду с хорошим качеством электрохимической обработки алюминиевых сплавов достигается высокая производительность процесса при полном отсутствии макродефектов на обрабатываемой поверхности. references 1. davydov a. d., knotz l. l., kashcheev v. d., kuchnev v. v. study of electrode processes potentiokinetic method with respect to electrochemical processing of metals. electronic processing of materials. 1969;2:82–87. 2. amirkhanova n. a., khaydarov r. r. determination of the limiting stages of the highspeed dissolution of aluminum alloy with cz and ump structure. vestnik ufi mskogo gosudarstvennogo aviazionnogo tekhnicheskogo universiteta. 2007:9(1);117–121. 3. romashkan a. d., davydov d. a., kashcheev v. d., kabanov b. n. dissolution of iron in solutions of sodium chlorate at high anodic potentials. electrochemistry. 1974;10(1):109– 112. 4. bernard d. j. oxidation of metals. vol. 1. metallurgiya, 1968. cite this article as (как цитировать эту статью): nechaev a. v., nechaev a. a., th ymina a. a. anodic behavior of aluminium and its alloys in solutions of sodium chlorate. chimica techno acta. 2017;4(1):45–53. 247 a. v. melnikova, f. p. figilyantov, a. b. shein perm state university, russia, 614990, perm, bukireva str., 15 e-mail: ashein@psu.ru investigation of industrial compositions sonkor as corrosion inhibitors of mild steel in neutral media containing hydrogen sulfide electrochemical and corrosion behavior of mild steel in neutral media containing hydrogen sulfide has been investigated by weight-loss and electrochemical methods and protective effect of industrial compositions sonkor has been determined. it has been shown that in 3 % nacl compositions sonkor have weak protective effect but it increases greatly in presence of hydrogen sulfide in the solution. at concentration of h 2 s = 0,6 gram per liter maximal protective effect has sonkor 9801 (85.57 %) and sonkor 9920а (81.97 %). inhibitors sonkor 9021с (70.82 %), 9510а (73.11 %) и 9701 (67.87 %) show less protective effect. key words: electrochemistry; corrosion behavior; of industrial compositions sonkor; hydrogen sulfide © melnikova a. v., figilyantov f. p., shein a. b., 2015 introduction the corrosion of metals causes a great harm to many industries, primarily to the enterprises of oil and gas production and petroleum refining. this is due to the aggressive properties of corrosive environments in oil, which are caused by the presence of mineralized water, hydrogen sulfide and sulphate-reducing bacteria, and carbon dioxide. some of the most economical and efficient methods of metal protection methods are associated with the use of corrosion inhibitors [1]. inhibitors in these industries are applied at all stages of processing, transportation of oil, gas and petrochemicals. protection of metals from corrosion inhibitors based on the property of some individual chemical compounds or their mixtures when introduced in low concentrations in the corrosive environment to reduce the rate of corrosion of the process or completely suppress it. the aim of this work was to study the effectiveness of a range of industrial compositions series sonkor as inhibitors of the corrosion of s31600 steel in neutral hydrogen sulfide-containing environments. d o i: 1 0. 15 82 6/ ch im te ch .2 01 5. 2. 3. 02 6 248 № 3 | 2015 chimica techno acta experimental technique the studies of inhibitors was carried out by the gravimetric and electrochemical methods. the gravimetric method is to determine the corrosion rate by the mass loss of the samples. the electrochemical method consists in removing the polarization curves using a potentiostat-galvanostat with built in frequency analyzer solartron 128  °c (solartron analytical), the calculation coefficients, which determine the mechanism of action of corrosion inhibitors of tested metal, as well as in determining the corrosion rate of metal by extrapolation plots of the polarization curve at the corrosion potential of ecor. the chemical compounds were studied in the work as inhibitors of the industrial composition of domestic production series sonkor (company “neftehim”, ufa). the gravimetric method was studied the protective action of inhibitors at concentrations: 0.025; 0.050; 0.100; 0.200 g/l. in the electrochemical studies was chosen as the optimal concentration of the inhibitor is 0.100 g/l. the experiment was carried out in 3 % nacl solution, and, when introduced into a solution of various concentrations of h2s (0.1; 0.2; 0.4; 0.6 g/l). the working solutions were prepared with distilled water. a hydrogen sulfide is received directly in the working solution by introducing appropriate quantities of na2s and hcl. results and discussions the results of gravimetric determination of corrosion rate of mild steel s31600 in 3 % nacl and the impact of hydrogen sulfide and the studied inhibitors sonkor are shown in table 1. it is seen that in the absence of hydrogen sulfide inhibitors have a weak protective effect (z), and sonkor 9701 and does not have any effect. the introduction of hydrogen sulfide into a solution of 3  % nacl significantly increases the corrosion rate of steel (0.149 g/(m2.h) to 0.578 g/(m2.h)) at h2s concentration of 0.4 g/l and up to 0.747 g/(m2.h) at h2s concentration of 0.6 g/l. the protective effect of inhibitors also significantly increased in the presence of hydrogen sulfide and the increase of its concentration in solution. among the investigated compositions proved to be most effective composition sonkor 9801 and sonkor a, a protective effect which increased to 85.57 and 81.97 %, respectively. the average protective effect (z < 75 %) were showed by the inhibitors sonkor 9021c, 9510a and 9701. the protective effect of inhibitors of sonkor markedly increased in a neutral environment in the presence of hydrogen sulfide, which in itself is a powerful stimulant corrosion. this is probably due to the synergistic action of the inhibitors and the hydrogen sulfide. it is known that organic amendments enter into a chemical reaction with hydrogen sulfide, forming on the steel surface protective film of insoluble or sparingly soluble compounds. there is a joint effect of the inhibitor and the shielding layer of corrosion products on the development of the corrosion process. the results of the study of protective action of the inhibitors sonkor method of polarization curves presented in tables 2–4. the polarization curves is widely used in corrosion the for the study of corrosion inhibitors because it allows you to melnikova a. v., figilyantov f. p., shein a. b. 249 № 3 | 2015 chimica techno acta calculate the corrosion rate cor in units of current density, to determine a slopes of the polarization curves bk and ba, the corrosion potential of ecor, and also to determine what type of inhibitor is part of the test substance: which of the partial electrode reactions (release of hydrogen, the ionization of oxygen or ionization of metal) mainly slows down the inhibitor. the results showed that inhibitors of sonkor 9510a and 9021c increase the polarizability of the anode process, therefore they can be classified as anodic type inhibitors. the concor 9701, 9801 and 9920a inhibitors are mixed type of one. introduction to the nacl solution of hydrogen sulfide leads to a parallel shift of the polarization curves at higher currents, which ultimately accelerates the overall corrosion of the s31600 steel. the electrochemical studies were performed in solutions containing 0.6 g/l of h2s, because the concentration of hydrogen sulfide is most strongly accelerated corrosion of steel. in inhibited h2s-containing solutions catigny and anodic currents decreased markedly, which confirmed the results of gravimetric test the higher efficiency of the inhibitors sonkor in the presence of hydrogen sulfide. the discrepancy between the values of the protective action of inhibitors in gravimetric (zgr) and electrochemical methods (ze/x) is due to the fact that in the weight table 1 the corrosion of steel and the protective action of inhibitors sonkor (0.1 g/l) in 3 % nacl + h2s the inhibitor 3 % nacl 3 % nacl + h2s 0.2 g/l h2s 0.4 g/l h2s 0.6 g/l h2s к, g/m2 · h z, % к, g/m2 · h z, % к, g/m2 · h z, % к, g/m2 · h z, % not 0.150 – 0.368 – 0.578 – 0.748 – sonkor 9021с 0.123 18.03 0.186 49.33 0.201 65.25 0.218 70.82 sonkor 9510а 0.125 16.39 0.189 48.67 0.213 63.14 0.201 73.11 sonkor 9701 0.152 0 0.150 59.33 0.189 67.37 0.240 67.87 sonkor 9801 0.135 9.83 0.120 67.33 0.125 78.39 0.108 85.67 sonkor 9920а 0.125 16.39 0.142 61.33 0.152 73.73 0.135 81.97 table 2 the corrosion-electrochemical properties of steel in 3 % nacl solution in the presence of 0.1 g/l inhibitors the inhibitor (0, 1 г/л) –ecor, v ba, mv bк, mv icor, a/m 2 zгр, % ze/x, % – 0.545 138 245 0.105 – – sonkor 9021с 0.408 64 263 0.101 18.03 3.45 sonkor 9510а 0.413 65 162 0.088 16.39 15.94 sonkor 9701 0.418 76 259 0.072 0 31.58 sonkor 9801 0.432 79 240 0.069 9.83 34.26 sonkor 9920а 0.458 76 151 0.030 16.39 71.56 investigation of industrial compositions sonkor as corrosion inhibitors of mild steel in neutral media containing hydrogen sulfide 250 № 3 | 2015 chimica techno acta measurements to determine the average corrosion rate over 24 h and during the electrochemical measurements of the corrosion rate at the moment. the system metal– water–hydrogen sulfide is a very complex and even equilibrium can be many reactions to form a variety of compounds. when considering the mechanism of hydrogen sulfide corrosion, it should be borne in mind that, depending on ph in solutions of electrolytes, the hydrogen sulfide may be present in different forms at ph < 6 the main part is in the form of molecular dissolved gas, at ph > 6 in the form of sh-, in alkaline electrolytes – s2-. a significant effect of ph on the rate of hydrogen sulfide corrosion is determined by kinetic reasons associated with resistance resulting from corrosion of the films. the presence of sulfide and hydrosulfide ions in corrosive environment contributes to a dramatic stimulation of both partial electrochemical reactions at the steel2 . the presence in a corrosive environment h2s and o2 leads to further destruction of the metal, possibly because of the reaction in which the intermediate product н2s2 is a depolarizer which is equal to the oxygen3 . table 3 the corrosion-electrochemical properties of steel in 3 % nacl solution + h2s (c = 0.1; 0.2; 0.4; 0.6 g/l) concetration of н2s, g/l –ecor, v ba, mv bк, mv icor, a/m 2 0 0.545 138 245 0.105 0.1 0.428 89 870 0.304 0.2 0.403 77 384 0.397 0.4 0.397 89 419 1.057 0.6 0.397 111 440 1.371 table 4 the corrosion-electrochemical properties of steel in 3 % nacl solution+ h2s (0.6 g/l) in the presence of 0.1 g/l inhibitors the inhibitor (0, 1 г/л) –ecor, v ba, mv bк, mv icor, a/m 2 zгр, % zэ/х, % – 0.397 111 440 1.371 – – sonkor 9021с 0.399 92 369 0.409 70.82 70.16 sonkor 9510а 0.407 94 465 0.370 73.11 73.00 sonkor 9701 0.410 92 506 0.334 67.87 75.62 sonkor 9801 0.412 98 764 0.408 85.57 70.88 sonkor 9920а 0.383 87 546 0.342 81.97 75.10 melnikova a. v., figilyantov f. p., shein a. b. 251 № 3 | 2015 chimica techno acta conclusion in the environment of hydrogen sulfide inhibitors series sonkor dramatically increase its effectiveness in neutral solution. they can be attributed to the class of mixed-type inhibitors, because they inhibit both the partial electrochemical process, but more particularly inhibitors inhibit the cathodic process that occurs with a mixed oxygen-hydrogen depolarization. 1. kim ya. r., tsygankova l. e., kichigin v. i. korrozija: materially, zaschita. 2005;8: 30. 2. i. l. rosenfeld, ingibitory korrozii, khimiya, moscow, 1978. 300 pp. (in russian). 3. yashina g. m., bobov s. s., smolenskaya e. a. korrozija i zaschita v neftegaz. promyshl. 1980;8: 24. investigation of industrial compositions sonkor as corrosion inhibitors of mild steel in neutral media containing hydrogen sulfide 252 а. в. мельникова, а. п. фигильянтов, а. б. шеин пермский государственный национальный исследовательский университет 614990, пермь, ул. букирева, 15. e-mail: ashein@psu.ru изучение промышленных композиций серии сонкор в качестве ингибиторов коррозии малоуглеродистой стали в нейтральных сероводородсодержащих средах методами гравиметрических испытаний и поляризационных измерений изучено коррозионно-электрохимическое поведение малоуглеродистой стали марки ст. 3 в нейтральных и нейтральных сероводородсодержащих средах, исследовано защитное действие ряда отечественных ингибирующих композиций в данных условиях. установлено, что в 3 % растворе nacl-ингибиторы проявляют слабое защитное действие, а в присутствии н 2 s в основном обладали средним z (до 50 %), заметно возрастающим с увеличением концентрации сероводорода в растворе. максимальным защитным действием при концентрации 0,6 г/л н 2 s в растворе обладали ингибиторы сонкор 9801 (85,57 %) и 9920а (81,97 %). ингибиторы сонкор 9021с (70,82 %), 9510 а (73,11 %) и 9701 (67,87 %) обладали средним защитным эффектом. ключевые слова: электрохимия, коррозионно-электрохимическое поведение, композиция сонкор, сульфид водорода. © мельникова а. в., фигильянтов а. п., шеин а. б., 2015 введение коррозия металлов наносит огромный вред многим отраслям промышленности, и  в  первую очередь предприятиям нефтегазодобычи и  нефтегазопереработки. это объясняется агрессивными свойствами коррозионных сред при добыче нефти, которые обусловлены наличием в  них большого количества минерализованной воды, сероводорода и  сульфатредуцирующих бактерий, а  также диоксида углерода. одними из наиболее экономичных и эффективных методов защиты металлов являются методы, связанные с  использованием ингибиторов коррозии [1]. ингибиторы в  этих отраслях промышленности применяются на всех стадиях переработки, транспортировки нефти, газа и  продуктов нефтехимии. защита металлов от коррозии ингибиторами основана на свойстве некоторых индивидуальных химических соединений или их смесей при введении их в  незначительных концентрациях в  коррозиону д к : 5 44 .6 53 .2 2: 5 44 .6 .0 18 .4 214 3 253 № 3 | 2015 chimica techno acta ную среду уменьшить скорость коррозионного процесса или полностью его подавлять. чтобы судить о защитных свойствах того или иного ингибитора, необходим комплексный подход к  изучению его свойств. цель данной работы  – исследование эффективности действия ряда промышленных композиций серии сонкор в качестве ингибиторов коррозии стали ст. 3 в нейтральных сероводородсодержащих средах. методика эксперимента исследования ингибиторов проводили гравиметрическим и  электрохимическим методами. гравиметрический метод заключается в определении скорости коррозии по убыли массы образцов. электрохимический метод заключается в  снятии поляризационных кривых с  помощью потенциостата-гальваностата с  встроенным частотным анализатором solartron 1280c (solartron analytical), расчете тафелевых коэффициентов, по которым определяют механизм действия ингибиторов коррозии исследуемого металла, а  также в  определении скорости коррозии металла путем экстраполяции тафелевых участков поляризационной кривой на потенциал коррозии екор. химические соединения, исследованные в работе в качестве ингибиторов, – промышленные композиции отечественного производства серии сонкор (зао «нефтехим», г. уфа). гравиметрическим методом было изучено защитное действие ингибиторов в  концентрациях: 0,025; 0,050; 0,100; 0,200 г/л. при электрохимических исследованиях была выбрана оптимальная концентрация ингибитора – 0,100 г/л. эксперимент выполнялся в  3 % растворе nacl, а  также при введении в  раствор различных концентраций н2s (0,1; 0,2; 0,4; 0,6 г/л). рабочие растворы готовили на дистилляте. сероводород получали непосредственно в рабочем растворе путем введения соответствующих количеств na2s и hcl. результаты и их обсуждение результаты гравиметрического определения скорости коррозии ст. 3 в  3 % nacl и  влияния на нее сероводорода и  исследуемых ингибиторов сонкор приведены в  таблице 1. видно, что в  отсутствии сероводорода ингибиторы обладают слабым защитным действием (z), а сонкор 9701 и  вовсе не обладает никаким эффектом. введение сероводорода в  раствор 3 % nacl существенно увеличивает скорость коррозии стали (с  0,149 г/м2·ч до 0,578 г/м2·ч при концентрации h2s 0,4  г/л и  до 0,747 г/м2·ч при концентрации h2s 0,6 г/л. защитное действие ингибиторов также существенно увеличивается в  присутствии сероводорода и  с  увеличением его концентрации в  растворе. среди исследованных композиций наиболее эффективными оказались композиции сонкор 9801 и  сонкор 9920а, защитное действие корорых возросло до 85,57 и  81,97 % соответственно. ингибиторы сонкор 9021с, 9510а и  9701 показали среднее защитное действие (z < 75 %). таким образом, защитное действие ингибиторов сонкор заметно увелиизучение промышленных композиций серии сонкор в качестве ингибиторов коррозии малоуглеродистой стали в нейтральных сероводородсодержащих средах 254 № 3 | 2015 chimica techno acta чивается в  нейтральной среде в  присутствии сероводорода, который сам по себе является сильным стимулятором коррозии. это, вероятно, обусловлено синергетическим действием ингибиторов и сероводорода. известно, что органические добавки вступают в  химическое взаимодействие с  сероводородом, образуя на поверхности стали защитную пленку из нерастворимых или труднорастворимых соединений. при этом наблюдается совместное влияние ингибитора и экранирующего слоя продуктов коррозии на развитие коррозионного процесса. результаты исследования защитного действия ингибиторов сонкор методом поляризационных кривых представлены в  таблицах 2–4. метод поляризационных кривых широко используется в коррозиологии для изучения ингибиторов коррозии, поскольку он позволяет рассчитать скорость коррозии iкор в  единицах плотности тока, определить тафелевы наклоны поляризационных кривых bk и  ba, потенциал коррозии екор, а  также определить, к какому типу ингибиторов относится исследуемое вещество, т. е. какую из парциальных электродных реакций (выделение водорода, ионизацию кислорода или ионизацию металла) преимущественно замедляет ингибитор. результаты показали, что ингибиторы сонкор 9510а и  9021с увеличивают поляризуемость анодного процесса, следовательно их можно отнести к  анодному типу ингибиторов. ингибиторы сонкор 9701, 9801 и  9920а являются ингибиторами смешанного типа. введение в  раствор nacl сероводорода приводит к  параллельному сдвигу поляризационных кривых в область более высоких токов, что в  конечном счете ускоряет общую коррозию ст.  3. электрохимические исследования проводили в  растворах, содержащих 0,6 г/л h2s, т. к. данная концентрация сероводорода наиболее сильно ускоряла коррозию стали. в ингибированных сероводородсодержащих растворах катиодные и  анодные токи заметно уменьшились, что подтвердило результаты гравиметрических испытаний более высокой эффективности ингибиторов сонкор в  присутствии сероводорода. несовпадение значений таблица 1 показатели коррозии стали ст.3 и защитного действия ингибиторов сонкор (0,1 г/л) в 3 % nacl + h2s ингибитор 3 % nacl 3 % nacl + h2s 0,2 g/l h2s 0,4 g/l h2s 0,6 g/l h2s к, г/м2 · ч z, % к, г/м2 · ч z, % к, г/м2 · ч z, % к, г/м2 · ч z, % нет 0,150 – 0,368 – 0,578 – 0,748 – сонкор 9021с 0,123 18,03 0,186 49,33 0,201 65,25 0,218 70,82 сонкор 9510а 0,125 16,39 0,189 48,67 0,213 63,14 0,201 73,11 сонкор 9701 0,152 0 0,150 59,33 0,189 67,37 0,240 67,87 сонкор 9801 0,135 9,83 0,120 67,33 0,125 78,39 0,108 85,67 сонкор 9920а 0,125 16,39 0,142 61,33 0,152 73,73 0,135 81,97 мельникова а. в., фигильянтов а. п., шеин а. б. 255 № 3 | 2015 chimica techno acta защитного действия ингибиторов в  гравиметрическом (zгр) и  электрохимическом методах (zэ/х) связано с  тем, что в  весовых измерениях определяется средняя скорость коррозии за 24 ч, таблица 2 коррозионно-электрохимические характеристики ст.3 в 3 % растворе nacl в присутствии 0,1 г/л ингибиторов ингибитор(0,1 г/л) –eкор, в ba, мb bк, мв iкор, а/м 2 zгр, % zэ/х, % без ингибитора 0,545 138 245 0,105 – – сонкор 9021с 0,408 64 263 0,101 18,03 3,45 сонкор 9510а 0,413 65 162 0,088 16,39 15,94 сонкор 9701 0,418 76 259 0,072 0 31,58 сонкор 9801 0,432 79 240 0,069 9,83 34,26 сонкор 9920а 0,458 76 151 0,030 16,39 71,56 таблица 3 коррозионно-электрохимические характеристики ст. 3 в 3 % растворе nacl+ н2s (с = 0,1; 0,2; 0,4; 0,6 г/л) концентрация н2s, г/л –eкор, в ba, мb bк, мв iкор, а/м 2 0 0,545 138 245 0,105 0,1 0,428 89 870 0,304 0,2 0,403 77 384 0,397 0,4 0,397 89 419 1,057 0,6 0,397 111 440 1,371 таблица 4 коррозионно-электрохимические характеристики ст. 3 в 3 % растворе nacl + н2s (0,6 г/л) в присутствии 0,1 г/л ингибиторов ингибитор (0,1 г/л) –eкор, в ba, мb bк, мв iкор, а/м 2 zгр, % zэ/х, % без ингибитора 0,397 111 440 1,371 – – сонкор 9021с 0,399 92 369 0,409 70,82 70,16 сонкор 9510а 0,407 94 465 0,370 73,11 73,00 сонкор 9701 0,410 92 506 0,334 67,87 75,62 сонкор 9801 0,412 98 764 0,408 85,57 70,88 сонкор 9920а 0,383 87 546 0,342 81,97 75,10 изучение промышленных композиций серии сонкор в качестве ингибиторов коррозии малоуглеродистой стали в нейтральных сероводородсодержащих средах 256 № 3 | 2015 chimica techno acta а при электрохимических измерениях – скорость коррозии в данный момент. система «металл – вода – сероводород» является очень сложной, и  в  ней даже в  равновесных условиях могут протекать многие реакции с  образованием разнообразных соединений. при рассмотрении механизма сероводородной коррозии следует иметь в виду, что в  зависимости от рн-среды в  растворах электролитов сероводород может присутствовать в  разных формах: при рн < 6 основная часть находится в  виде молекулярно-растворенного газа, при рн > 6 в  виде sh–, в  сильнощелочных электролитах  – s2–. существенное влияние рн на скорость сероводородной коррозии определяется кинетическими причинами, связанными со стойкостью образующихся в  результате коррозии пленок. присутствие сульфиди  гидросульфид-ионов в  коррозионной среде способствует резкому стимулированию обоих парциальных электрохимических реакций на стали [2]. одновременное присутствие в  коррозионной среде н2s и  о2 приводит к  еще большему разрушению металла, поскольку возможно протекание реакции, в  которой промежуточный продукт н2s2 является деполяризатором, равным по силе кислороду [3]. заключение таким образом, в  среде сероводорода ингибиторы серии сонкор резко увеличивают свою эффективность в  нейтральных средах. их можно отнести к  классу ингибиторов смешанного типа, поскольку они тормозят оба парциальных электрохимических процесса, однако в  большей степени ингибиторы тормозят катодный процесс, протекающий со смешанной кислородно-водородной деполяризацией. 1. kim ya. r., tsygankova l. e., kichigin v. i. korrozija: materially, zaschita. 2005;8: 30. 2. rosenfeld i. l., ingibitory korrozii, khimiya, moscow, 1978, 300 pp. (in russian). 3. yashina g. m., bobov s. s., smolenskaya e. a. korrozija i zaschita v neftegaz. promyshl. 1980;8: 24. мельникова а. в., фигильянтов а. п., шеин а. б. preparation and characterization of bi4–xprxti3o12 solid solutions 210 klyndyuk a.i., chizhova e.a., poznyak a.i. chimica techno acta. 2017. vol. 4, no. 4. p. 210–217. issn 2409–5613 d o i: 1 0. 15 82 6/ ch im te ch /2 01 7. 4. 4. 01 a.i. klyndyuk, e.a. chizhova, a.i. poznyak belarus state technological university 13a sverdlova st., minsk, 220006, republic of belarus preparation and characterization of bi 4–x pr x ti 3 o 12 solid solutions the bi 4–x pr x ti 3 o 12 (bpt) solid solutions (x = 0.05, 0.10, 0.15) with small praseodymium content were prepared by solid-state method. thermal, electric, and dielectric properties of bpt were studied. it was revealed that bpt titanates crystalize in аn orthorhombic structure and exhibit p-type semiconductivity. dielectric constant of bpt increased, curie temperature (t c ), electrical conductivity and dielectric losses decreased, but lattice parameters and thermo-emf coefficient remained practically unchanged with the increase of praseodymium content in layered bi 4–x pr x ti 3 o 12 . it was determined that activation energy of direct current (dc) electrical conductivity and linear thermal expansion coefficient (ltec) of bpt changes at ferroelectric (fe) → paraelectric (pe) phase transition. the activation energy and ltec changed below and above t c from 1.08–1.56 ev to 0.45–0.86 ev and from (9.10–10.80)·10–6 k–1 to (13.12– 14.61)·10–6 k–1, respectively. the ac electrical conductivity studies of bpt illustrated short-range order with ionic translations assisted by small-polaron hopping. keywords: layered bismuth titanates; dielectric constant; dielectric losses; electrical conductivity; thermo-emf; thermal expansion. received: 20.10.2017; accepted: 15.11.2017; published: 25.12.2017. © klyndyuk a.i., chizhova e.a., poznyak a.i., 2017 introduction bi4ti3o12 belongs to the aurivillius phase family bi2an–1bno3n+3, structure of which consists of alternated fluoritelike [bi2o2] 2+ layeres and perovskite-like [an–1bno3n+1] 2– blocks, where n – number of octahedral layers in the perovskite-like block [1]. this triple-layered (n  = 3) aurivillius phase is ferroelectric with high curie temperature (tc  = 948 к  [2]). the possibility to preserve the ferroelectric properties within a wide temperature range lets us to consider layered bismuth titanate as a promising material for radio-, acusto-, and optoelectronics; and thus can be used for production of optical displays, piezoelectric transducers, filters, capacitors, and different types of memory devices. so, for example, as a material for non-volatile memory devices the lanthanum-substituted bi3.25la0.75ti3o12 bismuth titanate is proposed, functional characteristics of which are better than of traditional ferroelectrics, such as pbti1–xzrxo3 or srbi2ta2o9 [3]. crystal structure, physico-chemical, and functional properties of the solid solutions bi4–xlnxti3o12 (ln  = rare-earth element) were studied in a number of pa211 pers [1, 3–8]. in [4] it was found that partial substitution of bi by la in bi4ti3o12 leads to decrease of orthorhombic distortion degree of bi4–xlaxti3o12 solid solutions at x  ≤ 1.0, and at x > 1.0 they had tetragonal structure and were paraelectrics. according to the [1, 4] results, at x ≤ 0.75 la3+ ions substitute bi3+ in perovskite-like [bi2ti3o10] 2– blocks, and at x > 0.75 they can substitute bi3+ ions in fluorite-like [bi2o2] 2+ layers too, so formula of bi4–xlaxti3o12 solid solutions at x ≤ 0.75 and x > 0.75 should be written as [bi2o2][bi2–xlaxti3o10] and [bi2–ylayo2] [bi2–x+ylax–yti3o10], respectively. authors of [5] established that partial substitution of bi with la or ce in bi4ti3o12 leads to the decrease of curie temperature of cera mics (tc  values for bi3.5la0.5ti3o12 and bi3.5ce0.5ti3o12 samples were 798 and 813 k, respectively, both being lower than tc for bi4ti3o12 phase). at the same time, la2o3 addition to the layered bismuth titanate improved its dielectric properties; by authors’ opinion, it was caused by decreasing of oxygen vacancy concentration in ceramics. partial substitution of bi with nd in bi4ti3o12 leads to the decrease of curie temperature, dielectric losses, and electrical conductivity of bi4–xndxti3o12 ceramic; and impoves its polarization properties because of reduction of bismuth and oxygen vacancy concentrations [7]. in [8] the bi4–ytbyti3o12 phase formation in the powder mixtures of bi2o3, tb4o7, and tio2 was investigated. it was found that partial replacing of bi by tb results in shrinking of unit cell of bi4–ytbyti3o12 solid solutions, decrease of orthorhombic distortion degree of their crystal lattice, and, as a consequence, leads to the decrease of temperature of fe → pe (ferroelectric → paraelectric) phase transition (up to ≈28 k for y = 0.4). in this work the results of investigation of crystal structure, thermal, electric, and dielectric properties of ceramic samples of bi4–xprxti3o12 (bpt) solid solutions with small praseodymium oxide content (x ≤ 3.75 mol.%) are presented. experimental bi4–xprxti3o12 (x  = 0.00, 0.05, 0.10, 0.15) ceramic samples were prepared by solid-state reactions method from mixtures of bi2o3 (99.0%), pr6o11 (99.0%), and tio2 (99.5%) powders taken in appropriate stoichiometric ratios. precursor mixtures were calcuned in air within temperature interval of 923–1223  k for 17 hours with some intermediate regrindings, according to procedure described in details in [6]. identification of the samples was performed using x-ray diffraction analysis (xrd) (bruker d8 xrd advance diffractometer, cu kα radiation) and ir absorption spectroscopy (ir  fourierspectrometer nexus of thermonicolet). relative density (ρrel) of the samples was calculated as ρrel = (ρapp/ρxrd) · 100%, (1) where ρapp – apparent density, determined from the mass and dimensions of the samples; ρxrd – x-ray density. thermal expansion of the samples was studied using dil 402 pc (netzsch) dilatometer within 290–1130 k with heating-cooling rate of 1–5 k/min. dielectric measurements were carried out in the temperature range 300–1090 k for frequencies between 100 hz and 1 mhz using immittance meter e7–25. dc electrical conductitivy and thermo-emf of sintered ceramics were studied within the temperature ranges of 470–1090  k and 780–1090  k, 212 respectively, according to the procedure described elsewhere [9]. values of linear thermal expansion coefficient (ltec, α) and activation energy of dc electrical conductivity (еa) of the samples were determined from linear parts of δl/l0 = f(t), and lgσdc = f(1/t) dependences, respectively. all measurements were performed in air. results and discussion all bi4–xprxti3o12 samples after final stage of annealing were found single phase within xrd reliability (fig. 1), and crystallized in orthorhombic structure like parent compound bi4ti3o12 (space group b2cb) [10]. lattice constants of bi4tio12 (a = 5.449(9) å, b = 5.422(9) å, and c = 32.85(4) å) were in a close agreement with an earlier studies: 5.444(1), 5.413(1), and 32.858(1) å [10], 5.4403, 5.4175, and 32.7862 å [11], and 5.4438(1), 5.4105(1), and 32.8226(5) å [8]. lattice constants of bi4–xprxti3o12 solid solutions were close to the bi4ti3o12 ones (for example, for bi3.90pr0.10ti3o12 a = 5.449(7)  å, b = 5.420(9) å, and c = 32.80(3) å), which agrees with the fact that sizes of substituting and substituted ions are close to each other (for c.n. = 6 according to [12] bi3+ and pr3+ ionic radii are 1.11 and 1.013 å, respectively). it should be noted that 0014 reflection in the bi4–xprxti3o12 diffractograms was the most intensive, in contrast with 117 peak for bi4ti3o12. other 00l peaks had higher intensity as well (i006/i117 ratio was equal to 0.6, 1.7, 3.0, and 2.8 for x = 0.00, 0.05, 0.10, and 0.15, respectively). this fact shows that partial substitution of bi with pr in bi4ti3o12 leads to the texturing of the samples. the nature of this phenomenon is not clear yet and will be studied in the future. three absorption bands occurring at 810–818 cm–1 (ν1), 573–582 cm –1 (ν2), and 474 cm–1 (ν3) were observed in the absorption spectra of bi4–xprxti3o12 powders. according to [7, 11], these bands correspond to the stretching (ν1 and ν2) and bending (ν3) vibrations of bi–o (ν1 and ν3) and ti–o (ν2) bonds, respectively. the peak positions did not change with x increasing, so partial replacing of bi by pr in layered bi4ti3o12 did not affect practically the metal-oxygen interactions in its crystal structure. the relative density values for bi4–xprxti3o12 ceramics varied within 77–80% and increased with x, being essentially larger than for unsubstituted bismuth titanate (60%). these results show that addition of praseodymium oxide to the layered bismuth titanate improves its sinterability. note that according to the literature data [6, 7] addition of lanthanum or neodymium oxides to the bi4ti3o12, on the contrary, had lowered its sinterability. on the temperature dependences of relative elongation an inflection point near 940–970  k was observed (fig. 2). it is related to the fe → pe phase transition [8] and is accompanied by the increase of ltec values of the samples (table 1). fig. 1. x-ray powder diffractograms (cu kα radiation) of bi4–xprxti3o12 solid solutions 213 an inflection point, which was determined as an intersection of linear parts of δl/l0 = f(t) dependences at low (fe region) and high temperatures (pe region), corresponds to the curie temperature and decreases with x (fig. 2, inset). it is in a good agreement with the literature data, according to which substitution of bi with ln in bi4ti3o12 leads to lowering of its curie temperature [4–8]. the ltec values of bi4–xprxti3o12 titanates in fe state decreased, but in pe state increased with x (table 1). the ltec values in pe state can be explaned by anharmonicity of metal-oxygen vibrations in disordered cationic sublattice of pr3+-substituted bismuth titanate bi4–xprxti3o12. the ltec values in fe state could be caused either by increase of dipole-dipole interactions or by decrease of oxygen and bismuth vacancy concentrations in the bpt. the first explanation is in contrast with the fact that tc of bi4–xprxti3o12 solid solutions decreases with x. so, the decrease of ltec values of bpt ceramics in fe region is due to the decrease of the vacancy concentration in it [3]. bi4–xprxti3o12 compounds are p-type semiconductors (fig. 3), which confirms previous data [7, 14]. according to [7, 14] electrical conductivity of layered bismuth titanate increases with temperature [7,14] and thermo-emf coefficient of bi4ti3o12 phase at high temperatures is positive [14]. seebeck coefficient va lues of bpt ceramics were close to each other (fig. 3b), which corresponds to the isovalent character of substitution of bi with pr. but dc electrical conductivity of the samples decreased with x (fig. 3a) due to the defect concentration decrease as was mentioned above. near tc there is a change in the slope of linear sections at the arrhenius plots lgσdc = f(1/t). va lues of activation energy of the samples’ dc electrical conductivity in pe region are essentially less than in fe one (table  1). similar results were obtained in [15] for bi4ti2nb0.5fe0.5o12 ceramics, activation energy values of which were equal to 1.21  ev and 0.50 ev below and above tc, respectively (ac, ω = 10 5  hz). partial substitution of bi with pr in bi4ti3o12 increases ea of bpt in fe state and lowtable 1 values of apparent activation energy of dc electrical conductivity (ea) and linear thermal expansion coefficient (α) of bi4–xprxti3o12 titanates x ea, ev α·106, k–1 fe pe fe pe 0.00 1.08±0.02 0.86±0.02 10.80±0.06 13.12±0.02 0.05 1.24±0.01 0.46±0.02 09.62±0.01 14.61±0.02 0.10 1.23±0.02 0.45±0.01 09.31±0.01 13.53±0.01 0.15 1.56±0.04 0.49±0.01 09.10±0.01 13.48±0.01 fig. 2. temperature dependences of relative elongation of bi4–xprxti3o12 sintered ceramics. inset shows concentration dependences of tc 214 ers it in pe state (table 1). note that ea value of layered bismuth titanate below tc obtained in this work coincides with the data given in [14]: 1.0 ev for bi4ti3o12 ceramics. in the temperature dependences of dielectric constant of bi4–xprxti3o12 titanates abrupt maxima near 930–940 k was observed (fig. 4a). it was caused by fe → pe phase transition, and phase transition temperature (tc) lowered with increasing praseodymium content in the samples (fig. 4d) and was close to the tc values determined from the dl/l0 = f(t) dependences (fig. 2, inset). dielectric constant values of bpt ceramics increased with x, which was more prominent at high temperatures (fig. 4a, c). diеlectric losses of investigated samples increased with temperature and decreased when pr concentration (fig. 4b, e). besides, on the tgd = f(t) dependences two anomalous regions were observed: near 760–820 k and 930– 940 k. the second anomaly is related to the fe → pe phase transition, but the first one is probably due to the oxygen vacancy movement out (migration) of the domain walls [16]. the values of curie temperature of the samples are frequency independent (fig.  5a, b), which indicates that bi4–xprxti3o12 phases are normal ferroelectrics [15]. when the testing frequency increased from 100 hz to 100 khz, the dielectric constant and dielectric losses of bpt ceramics decreased substantially due to the suppression of relaxing polarization at high frequencies. the dielectric constant of normal ferroelectrics follows the curie–weiss law ε = с/(t – tθ), (2) where c is curie–weiss constant and tθ is curie–weiss temperature. the curie– fig. 3. dependences of dc electrical conductivity (a) and thermo-emf coefficient (b) of bi4–xprxti3o12 samples vs temperature fig. 4. temperature (a, b) and concentration (c–e) dependences of dielectric constant (a, c), dielectric losses (b, e), and tc (d) of bi4–xprxti3o12 ceramics (ω = 1 khz) 215 weiss plot for bi3.85pr0.15ti3o12 phase at 100 khz is shown in the fig. 5c. the parameters obtained from the linear fit are c = 1.63×105 k and tθ = 821 k. the magnitude of curie–weiss constant is of the same order as of well-known displasivetype ferroelectrics, such as batio3 (c  = 1.7·105 k [15]). the frequency dependences of ac electrical conductivity of bi3.85pr0.15ti3o12 at various temperatures are given in fig. 6. the frequency independent plateau at low frequencies is attributed to the long-range translational motion of ions contributing to dc conductivity (σdc) [17, 18]. at high frequencies (>104 hz) the ac electrical conductivity shows ωn dependence which corresponds to the short-range translation ion hopping [15, 18]. the frequency dependent ac electrical conductivity of bpt ceramics obeys jonscher’s power law [19] at all temperatures σ(ω) = σ(0) + aωn, (3) where σ(ω) is the total conductivity, σ(0) is the dc conductivity, a is the temperature-dependent constant which determines the strength of polarizability, and n represents the degree of interaction between the mobile ions and the lattice around them [15, 19]. the values of n are less than one, which indicates that motion of charge carriers is translational [18, 20]. the shape of n vs. t dependence suggests hopping mechanisms of charge carriers [18, 19]. in case of small-polaron hopping, n increases with temperature, while for a large polaron hopping, n decreases with temperature. as shown in inset of fig. 6, the values of n are less than 1 and are found to increase with temperature; fig. 5. temperature dependences of dielectric constant (a) and dielectric losses (b) of bi3.85pr0.15ti3o12 at different frequencies. inset (c) shows the inverse dielectric constant as a function of temperature at 100 khz fig. 6. frequency dependences of ac electrical conductivity of bi3.85pr0.15ti3o12 at different temperatures. inset shows the variation of jonscher’s power law parameters (n, a) as a function of temperature 216 hence we conclude that ac electrical conductivity arises mainly due to the shortrange order translation hopping assisted by small-polaron hopping mechanism. conclusions the bi4–xprxti3o12 solid solutions (x = 0.05, 0.10, 0.15) with small substitution degree were synthesized and their thermal expansion, dc and ac electrical conductivity, dielectric constant and dielectric losses were measured. the samples crystallized in orthorhombic structure and possessed p-type semiconductive and normal ferroelectric properties. lattice constants and thermo-emf coefficient of bpt were practically composition independent, but curie temperature, electrical conductivity and dielectric losses decreased with x. activation energy of dc electrical conductivity and linear thermal expansion coefficient of bi4–xprxti3o12 changed at the temperature of ferroelectric to paraelectric phase transition, and their values were 1.08–1.56 ev and 0.45– 0.86 ev, and (9.10–10.80)·10–6 k–1 and (13.12–14.61)·10–6 k–1 below and above curie temperature, respectively. ac electrical conductivity investigations illustrate short-range order ionic translation hopping assisted by small-polaron hopping mechanism. acknowledgements this work was carried out within the framework of state program of scientific investigations of belarus republic «physical materials science, new materials and technologies» (subprogram «materials science and technologies of materials», task 1.17). references 1. hyatt nc, hriljac ja, comyn tp. cation disorder in bi2ln2ti3o12 aurivillius phases (ln  = la, pr, nd and sm). mat res bull. 2003;38:837–46. doi:10.1016/s0025– 5408(03)00032–1. 2. scott jf, araujo ca. ferroelectric memories. science. 1989;246(4936):1400–5. doi:10.1126/science.246.4936.1400. 3. park bh, kang bs, bu sd, noh tw, lee j, jo w. lanthanum-substituted bismuth titanate for use in non-volatile memories. nature. 1999;401:682–4. doi:10.1038/44352. 4. wu d, yang b, li a. structural phase transition due to la substitution in bi4ti3o12. 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dielectric response. nature. 1977;267:673–9. doi:10.1038/267673a0. 20. sadykov sa, palchaev dk, murlieva zk, alikhanov nm, rabadanov mk, gadzhimagomedov sk, kallaev sn. ac conductivity of bifeo3 ceramics obtained by spark plasma sintering of nanopowders. phys solid state. 2017;59(9):1771–7. doi:10.1134/ s1063783417090268. cite this article as: klyndyuk ai, chizhova ea, poznyak ai. preparation and characterization of bi4–xprxti3o12 solid solutions. chimica techno acta. 2017;4(4):211–7. doi:10.15826/ chimtech/2017.4.4.01. cta_v4_№1.cdr 29 v. ya. sosnovskikh1, g.-v. roschenthaler2 1institute of natural sciences and mathematics, ural federal university, 51 lenina str., ekaterinburg 620000, russia; 2jacobs university, bremen 28759, germany e-mail: vy.sosnovskikh@urfu.ru nucleophilic conjugate tri uoromethylation of chromones and activated alkenes under the action of ruppert’s reagent this review summarizes data on the reactions of chromones and activated alkenes with trimethyl(tri uoromethyl)silane (ruppert’s reagent), which occures as a nucleophilic 1,4-tri uoromethylation with high regioselectivity and good yields. the most important chemical properties of the formed products are also considered. key words: chromones; activated alkenes; nucleophilic 1,4-trifluoromethylation; trimethyl(tri uoromethyl)silane. received: 28.02 .2017; accepted: 03.03.2017; published: 14.04.2017. в. я. сосновских1, г.-в. рошенталер2 1институт естественных наук и математики уральского федерального университета, екатеринбург 620000, пр. ленина, 51, россия; 2университет якобса, бремен 28759, германия e-mail: vy.sosnovskikh@urfu.ru ( ) ( ), 1,4 . . : , , 1,4, ( ) . : 28.02.2017; : 03.03.2017; : 14.04.2017. © sosnovskikh v. ya., roschenthaler g.-v., 2017 sosnovskikh v. ya., roschenthaler g.-v. chimica techno acta. 2017. vol. 4, no. 1. p. 29–44. issn 2409-5613 d o i: 1 0. 15 82 6/ ch im te ch .2 01 7. 4. 1. 02 2 5 47 .6 69 30 th e nucleophilic trifl uoromethylation of organic compounds is complicated by the instability of free trifl uoromethyl anion, which easily breaks down into the fl uoride anion and difl uorocarbene [1]. th e use of trimethyl(trifl uoromethyl)silane (ruppert’s reagent) in the presence of fl uoride anion as an initiator allows to avoid this unwanted reaction and to realize the direct introduction of the cf3 group to organic substrates. it is well known that the ruppert’s reagent interacts easily with both saturated and α, β-unsaturated carbonyl compounds via 1,2-nucleophilic addition with formation of the corresponding trifl uoromethyl carbinols [2–4]. it is important to note that in the case of α, β-unsaturated ketones, the formation of products of nucleophilic 1,4-trifl uoromethylation (michael addition) was not observed (scheme 1). th e fi rst example of the conjugate trifl uoromethylation of α, β-enone system was discovered by us on the example of the reaction rfsime3 (r f = cf3, c2f5) with 2-trifl uoromethylchromones 1 [5, 6]. monitoring using 19f nmr spectroscopy showed that chromones 1 in the presence of the nucleophilic initiator me4nf (thf, 0 °c, 4 h) almost quantitatively and with high regioselectively react with cf3sime3 towards the way of 1,4-addition, giving trimethylsilyl ethers 2 (the content in the reaction mixture of 1,2-addition products 3 does not exceed 5–10 %). when processing of the reaction mixture with diluted hcl only the products of 1,4-addition 2 are subjected to hydrolysis to give 2-trifl uoromethyl-2-perfl uoroalkylchroman-4-ones 4. as expected, when increasing of the length of the rf group to c2f5 the regioselectivity of the reaction is reduced to 80–85 % (scheme 2). th e optimal conditions of 1,4-trifl uoromethylation (me4nf, thf, 0 °c, 24 h) were used by us for the preparative synthesis of chromanones 4a–f, the yields of which ranged 50–86 % (scheme 3) [6]. currently, this reaction represents the shortest and most eff ective way of synthesis of partially fl uorinated analogues of natural chromanones, chromanes and chromenes scheme 1 scheme 2 31 with gem-dimethyl group at the atom c(2). th us, 4-oxo-2,2-bis(trifl uoromethyl)chroman-6-carbaldehyde 5a, an analogue of natural lactarochromal, metabolite of lactarius deliciosus mushrooms [7], in which both methyl groups are replaced by cf3 groups, was synthesized by oxidation of 6-me group of chromanone 4b by the mixture of cuso4 and k2s2o8 in acetonitrile with the yield 17 % [8]. in addition to hexafl uorolactarochromal 5a was obtained and the corresponding acid 5b (yield 35 %), which is also a fl uorinated analogue of the natural acid, isolated from chrysothamnus viscidifl orus [9] (scheme 4). another example of the use of the 1,4-trifl uoromethylation reaction is the synthesis of 2,2-bis(trifl uoromethyl)-6-methoxychromene 6 [6], a partially fl uorinated analogue of the natural 2,2-dimethyl-6-methoxychromene, antijuvenile hormone precocene i, isolated from plant ageratum houstonianum [10] (scheme 5). th e reaction mechanism of nucleophilic 1,4-trifl uoromethylation is presented in scheme 6 and involves fl uoride ion initiation to form the trifl uoromethylated enolate scheme 3 scheme 4 scheme 5 32 anion a, which then via hypervalent silicon intermediate b catalyzes the subsequent reaction [2, 3]. further we have shown that the found reaction has a fairly wide scope of applications. it is found that trifl uorokhellin [11], n-substituted 2-polyfl uoroalkylquinolines [12, 13] and 8-aza-5,7-dimethyl-2-polyfl uoroalkylchromones [14] react with ruppert’s reagent via the nucleophilic 1,4-addition and give compounds 7–9, respectively [6, 15]. note that in the latter case the regioselectivity falls and the ratio of products of 1,4and 1,2-addition is ~3: 2. as a result, 8-azachromanones were isolated only with the moderate yield (27–35 %). at the same time, 2-trifl uoromethyl-3-chlorochromone gives the expected michael adduct 10 in 58 % yield (scheme 7). it is interestingly, that thioanalogue of chromone 1a, 2-trifl uoromethyl-4h-thiochromen-4-one 11 [16] and its acyclic analogue, 4,4,4-trifl uoro-1-phenyl-2-butene-1-one 12, react with ruppert’s reagent scheme 6 scheme 7 33 under the same conditions exclusively towards 1,2-addition with the formation of trimethylsilyl derivatives 13 and 14 [6, 15] (scheme 8). th e presence of the electron withdrawing rf group at the β-c-atom of enone system is desirable, but not indispensable, if to carry out the reaction in the presence of bulky lewis acids, which under coordination at the carbonyl oxygen atom complicate 1,2-addition and increase the electrophilicity of the β-c atom. so, in the presence of tris(2,6-diphenylphenoxide) aluminum and me4nf 1,4-trifl uoromethylation of cyclohex-2-enone, chromone and coumarin could exercise and obtain the compounds 15–17 in 35–55 % yields [17] (scheme 9). recently, chinese chemists [18] in the course of work on the study of antitumor activity of trifl uoromethylated fl avonoids held trifl uoromethylation of fl avone 18 and isofl avone 19 in our conditions and found that in the fi rst case is a 1,2-addition and in the second is 1,4-addition with the formation of products 20 and 21, respectively (scheme 10). th us, both electronic and steric factors are greatly infl uenced to the successful course of the discussing reaction, the most favorable combination of which is observed in the case of 2-cf3and 2-cf2h-chromones. along with the conjugate 1,4-trifl uoromethylation and 1,6-addition of trifl uoromethyl anion is possible. recently, we have shown [19] that methylidene derivatives 22a, b obtained by knoevenagel condensation from chromone 1a, diethyl malonate and ethyl cyanoacetate react with excess of scheme 8 scheme 9 34 cf3sime3 in the presence of me4nf with the formation of 4-substituted 2,2-bis(trifl uoromethyl)-2h-chromenes 23a, b (scheme 11). th is reaction is the fi rst and the only example of regioselective nucleophilic 1,6-trifl uoromethylation that extends the synthetic possibilities of this method. in the works of dilman with coworkers [20–22], the method of nucleophilic conjugated trifl uoromethylation using the ruppert’s reagent in the presence of basic activators was further developed. since 2008, in the orbit of this reaction the various electron defi cient alkenes, such as arylidene derivatives of malononitrile, meldrum’s acid and nitroacetic ester, were involved. it was shown that arylidene malononitriles 24 react with cf3sime3 in scheme 10 scheme 11 35 the presence of sodium acetate in dmf at room temperature according to the type 1,4-addition and give products 25 in high yields (75–98 %) regardless of the nature of the substituent in the aromatic ring of the substrate. in addition to trifl uoromethyl group, benzylidene malononitrile 24 was also able to attach pentafl uoroethyl, pentafl uorophenyl and dichlorofl uoromethyl groups, to give compounds 26 in 81–99 % yields [20] (scheme 12). despite the fact that arylidene malonates not enter into this reaction due to their lower electrophilicity, arylidene derivatives of meldrum’s acid 27 smoothly added trifl uoromethyl anion and aft er acidic hydrolysis give the acids 28, which in their pure form were not isolated but were immediately methylated with methyl iodide in the presence of potassium carbonate to esters 29 or reduced by sodium borohydride and boron trifl uoride etherate to alcohols 30 [21] (scheme 13). in the work [22] the interaction of 2-nitrocinnamates 31 with the silicon reagents rfsime3 (r f = cf3, c2f5, c6f5) in the presence of sodium acetate in dmf (method a) or tetrabutylammonium acetate in dichloromethane (method b) was described. th e reaction proceeds as the conjugated addition of fl uorinated carbanion on the с=с bond and with good yields leads to obtaining of 3-aryl-2-nitroalkanoates with perfl uorinated substituents. th ese compounds are formed in the form of an isomeric mixture with a ratio of diastereomers from 1:1 to 1.6:1, and the possibility of their transformation to the corresponding amino derivative is shown by the example of methyl 4,4,4-trifl uoro-2-nitro-3-phenylbutanoate 32 (rf = cf3, ar = ph). reduction was carried out at atmospheric pressure with pd/c in the presence of acylating agent and gave n–boc-protected product 33 in 79 % yield (scheme 14). thus the high electrophilic alkenes (arylidene derivatives of malononitrile, meldrum’s acid and nitroacetic ester) as 2-polyfl uoroalkylchromones are able to add the ruppert’s reagent via nucleophilic scheme 12 36 1,4-addition, which signifi cantly expands the range of simple cf3-containing molecules of interest for subsequent syntheses on their base. th e work is executed at fi nancial support of the government of the russian federation, the program 211, agreement no. 02.a03.21.0006. in russian нуклеофильное трифторметилирование органических соединений осложнено нестабильностью свободного трифторметильного аниона, коscheme 14 scheme 13 37 торый легко распадается на фторид анион и дифторкарбен [1]. использование триметил(трифторметил)силана (реагента рупперта) в присутствии фторид аниона в качестве инициатора позволяет избежать этой нежелательной реакции и осуществить прямое введение cf3-группы в органические субстраты. хорошо известно, что реагент рупперта легко взаимодействует как с насыщенными, так и α, β-ненасыщенными карбонильными соединениями по типу 1,2-нуклеофильного присоединения с образованием соответствующих трифторметилированных карбинолов [2–4]. при этом важно отметить, что в случае α, β-непредельных кетонов образования продуктов нуклеофильного 1,4-трифторметилирования (присоединения по михаэлю) не наблюдалось (схема 1). первый пример сопряженного трифторметилирования α, β-еноновой системы обнаружен нами на примере реакции rfsime3 (r f = cf3, c2f5) с 2-трифторметилхромонами 1 [5, 6]. мониторинг с помощью спектроскопии ямр 19f показал, что хромоны 1 в присутствии нуклеофильного инициатора me4nf (тгф, 0 °c, 4 ч) почти количественно и с высокой региоселективностью реагируют с cf3sime3 по пути 1,4-присоединения, давая триметилсилиловые эфиры 2 (содержание в реакционной смеси продуктов 1,2-присоединения 3 не превышает 5–10 %). при обработке реакционной смеси, разбавленной hcl, гидролизу подвергаются только продукты 1,4-присоединения 2, которые дают при этом 2-трифторметил-2-перфторалкилхроман-4-оны 4. как и ожидалось, при увеличении длины rf группы до c2f5 региоселективность реакции уменьшается до 80–85 % (схема 2). оптимальные условия 1,4-трифторметилирования (me4nf, тгф, 0 °c, 24 ч) использованы нами для препаративного получения хроманонов 4a–f, выходы которых составляли 50–86 % (схема 3) [6]. в  настоящее время эта реакция представляет собой самый короткий и эффективный путь синтеза частично фторированных аналогов природных схема 1 схема 2 38 хроманонов, хроманов и хроменов с гемдиметильной группировкой при атоме с(2). так, 4-оксо-2,2-бис(трифторметил) хроман-6-карбальдегид (5а), аналог природного лактарохромаля, метаболита грибов lactarius deliciosus [7], в котором обе метильные группы замещены на cf3-группы, был синтезирован путем окисления 6-ме-группы хроманона 4b смесью k2s2o8 и cuso4 в ацетонитриле c выходом 17 % [8]. кроме гексафторлактарохромаля 5а, была получена и соответствующая кислота 5b (выход 35 %), которая также является фторированным аналогом природной кислоты, выделенной из chrysothamnus viscidifl orus [9] (схема 4). еще одним примером использования реакции 1,4-трифторметилирования является синтез 2,2-бис(трифторметил)6-метоксихромена (6) [6] – частично фторированного аналога природного 2,2-диметил-6-метоксихромена, антиювенильного гормона прекоцена i, выделенного из растения ageratum houstonianum [10] (схема 5). механизм реакции нуклеофильного 1,4-трифторметилирования представлен на схеме 6 и включает инициируемое анионом фтора образование трифторметилированного енолят аниона а, который через гипервалентный кремниевый интермедиат в катализирует последующую реакцию [2, 3]. в дальнейшем нами было показано, что найденная реакция имеет достаточно широкие границы применения. установлено, что с реагентом рупперта по типу 1,4-присоединения реагируют трифторкеллин [11], n-замещенные 2-полифторалкилхинолоны [12, 13] и 8-аза-5,7-диметил-2-полифторалкилхромоны [14], которые дают соединения 7–9, соответственно [6, 15]. отметим, что в последнем случае региоселективность падает и соотношение продуктов схема 3 схема 4 39 1,4и 1,2-присоединения составляет ~3: 2, в результате чего 8-азахроманоны 9 были выделены лишь с умеренным выходом (27–35 %). в то же время 2-трифторметил-3-хлорхромон дает ожидаемый аддукт михаэля 10 с выходом 58 % (схема 7). интересно, что тиоаналог хромона 1а, 2-трифторметил-4н-тиохромен-4-он 11 [16], а также его ациклический аналог – 4,4,4-трифтор-1-фенил-2-бутен-1-он 12 – реагируют с реагентом рупперта в аналогичных условиях исключительно по пути 1,2-присоединения с образованием триметилсилильных производных 13 и 14 [6, 15] (схема 8). присутствие электроноакцепторной rf-группы при β-с атоме еноновой системы желательно, но не обязательно, если проводить реакцию в присутствии объемных кислот льюиса, которые, координируясь по карбонильному атому кислорода, затрудняют 1,2-присоединение и повышают электрофильность β-с атома. так, в присутствии трис(2,6дифенилфеноксида) алюминия и me4nf удается осуществить 1,4-трифторметилирование циклогекс-2-енона, хромона схема 5 схема 6 40 и кумарина и с выходами 35–55 % получить соединения 15–17 (схема 9) [17]. недавно китайские химики [18] в ходе работы по изучению противоопухолевой активности трифторметилированных флавоноидов провели трифторметилирование флавона 18 и изофлавона 19 в наших условиях и установили, что в первом случае имеет место 1,2-, а во втором – 1,4-присоединение с образованием продуктов 20 и 21, соответственно (схема 10). таким образом, на успешное протекание обсуждаемой реакции большое влияние оказывают как электронные, так и стерические факторы, наиболее благоприятное сочетание которых наблюдается в случае 2-cf3и 2-cf2hхромонов. схема 7 схема 8 схема 9 41 наряду с сопряженным 1,4-трифторметилированием возможно и 1,6-присоединение трифторметильного аниона. так, недавно нами было показано [19], что метилиденовые производные 22a, b, полученные по кневенагелю из хромона 1а, диэтилмалоната и этилцианоацетата, реагируют с избытком cf3sime3 и me4nf с образованием 4-замещенных 2,2-бис(трифторметил)-2н-хроменов 23a, b (схема 11). эта реакция является первым и пока единственным примером региоселективного нуклеофильного 1,6-трифторметилирования, расширяющего синтетические возможности данного метода. в работах дильмана с сотр. [20–22] метод нуклеофильного сопряженного трифторметилирования с использованием реагента рупперта в присутствии основных активаторов получил дальнейшее развитие. так, начиная с 2008 года, в орбиту этой реакции удалось вовлечь различные электронодефицитные алкены, такие как арилиденовые производные малононитрила, кислоты мельдрума и нитроуксусного эфира. было показано, что арилиденмалононитрилы 24 реагируют с cf3sime3 в присутствии ацетата натрия в дмфа при комнатной температуре по типу 1,4-присоединения и дают продукты 25 с высокими выходами (75–98 %) независимо от природы заместителя в ароматическом кольце субстрата. кроме трифторметильной группы, к бензилиденмалононитрилу 24 удалось также присоединить пентафторэтильную, пентафторфенильную и дихлорфторметильную группы, в результате чего были получены соединения 26 с выходами 81–99 % [20] (схема 12). несмотря на то, что арилиденмалонаты не вступают в эту реакцию из-за их меньшей электрофильности, арилиденовые производные кислоты мельдрума 27 гладко присоединяют трифторметильный анион и после кислотного гидролиза дают кислоты 28, которые в чистом виде не выделяли, а сразу метилировали йодистым метилом в присутствии поташа до эфиров 29 или восстанавливали боргидридом натрия и эфиратом трехфтористого бора до спиртов 30 [21] (схема 13). описано взаимодействие 2-нитроциннаматов 31 с кремниевыми реагентами rfsime3 (r f = cf3, c2f5, c6f5) в присутствии ацетата натрия в дмфа схема 10 42 (метод а) или ацетата тетрабутиламмония в дихлорметане (метод в) [22]. реакция протекает как сопряженное присоединение фторированного карбаниона по связи с=с и с хорошими выходами приводит к получению 3-арил-2-нитроалканоатов 32 с перфторированными заместителями. эти соединения образуются в виде изомерной смеси с соотношением диастереомеров от 1:1 до 1,6:1, а возможность их трансформации до соответствующего аминопроизводного продемонстрирована на примере метил – 4,4,4-трифтор-2-нитро-3-фенилбутаноасхема 11 схема 12 43 та 32 (rf = cf3, ar = ph). восстановление проводилось при атмосферном давлении на pd/c в присутствии ацилирующего агента и давало n–boc защищенный продукт 33 с выходом 79 % (схема 14). таким образом, высокоэлектрофильные алкены (арилиденовые производные малононитрила, кислоты мельдрума и нитроуксусного эфира), как и 2-полифторалкилхромоны, способны присоединять реагент рупперта по типу нуклеофильного 1,4-присоединения, что существенно расширяет ассортимент простых cf3-содержащих молекул, представляющих интерес для последующих синтезов на их основе. работа выполнена при финансовой поддержке правительства рф, программа 211, соглашение № 02.a03.21.0006. схема 13 схема 14 44 references 1. langlois b. r., billard t. synthesis. 2003:185–194. 2. prakash g. k. s., yudin a. k. chem. rev. 1997;97:757–786. 3. singh r. p., shreeve j. m. tetrahedron. 2000;56:7613–7632. 4. prakash g. k. s., mandal m. j. fluorine chem. 2001;112:123–131. 5. sosnovskikh v. ya., sevenard d. v., usachev b. i., roschenthaler g.-v. 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2005;180:1315–1319. 17. sevenard d. v., sosnovskikh v. ya., kolomeitsev a. a., konigsmann m. h., roschenthaler, g.-v. tetrahedron lett. 2003;44:7623–7627. 18. wang c.-l., li h.-q., meng w.-d., qing f.-l. bioorg. chem. lett. 2005; 15:4456–4458. 19. сосновских в. я., усачев б. и., пермяков м. н., севенард д. в., рошенталер г.-в. изв. ан. сер. хим. 2006:1628–1630. 20. dilman a. d., levin v. v., belyakov p. a., struchkova m. i., tartakovsky v. a. tetrahedron lett. 2008;49:4352–4354. 21. zemtsov a. a., levin v. v., dilman a. d., struchkova m. i., belyakov p. a., tartakovsky v. a. tetrahedron lett. 2009;50:2998–3000. 22. zemtsov a. a., levin v. v., dilman a. d., struchkova m. i., tartakovsky v. a. j. fluorine chem. 2011;132:378–381. cite this article as (как цитировать эту статью): коzshevnikov d. n., коzshevnikov v. n. combinatorial approach to the synthesis of substituted 1,2,4-triazines. chimica techno acta. 2016;4(1):29–44. the synthesis of 1,2,4-triazines bearing the residues of higher alcohols in the 5-position via the ipso-substitution of cyano group under the solvent-free conditions a. p. krinochkin1, d. s. kopchuk1,2, e. s. starnovskaya1, ya. k. shtaiz1, a. f. khasanov1, i. s. kovalev1, o. s. taniya1, g. v. zyryanov1,2, v. l. rusinov1,2, o. n. chupakhin1,2 1ural federal university, 19 mira st., ekaterinburg, 620002, russia tel./fax: +7 (343) 375-45-01 2 postovsky institute of organic synthesis ub ras, 22 kovalevskaya st. / 20 akademicheskaya st., ekaterinburg, 620990, russia tel./fax: +7 (343) 369-30-58, e-mail: dkopchuk@mail. the synthesis of 1,2,4-triazines bearing the residues of higher alcohols in the 5-position via the ipso-substitution of cyano group under the solvent-free conditions ipso keywords: ipso reactions а. п. криночкин1, д. с. копчук1,2, е. с. старновская1, я. к. штайц1, а. ф. хасанов1, и. с. ковалев1, о. с. тания1, г. в. зырянов1,2, в. л. русинов1,2, о. н. чупахин1,2 1уральский федеральный университет, ул. мира, 19, г. екатеринбург, 620002, россия тел./факс: +7 (343) 375-45-01 2 институт органического синтеза им. и. я. постовского уро ран ул. ковалевской, 22 / ул. академическая, 20, г. екатеринбург, 620990, россия тел./факс: +7 (343) 369-30-58. e-mail: dkopchuk@mail.ru results and discussion 5-alkoxycontaining 1,2,4-triazines are of practical interest as receptors of gene expression [1] and inhibitors of enzymes of the mth1-type in the treatment of cancer [2]. in order to obtain these compounds the following synthetic approaches were previously proposed: the alkylation of the hydroxyl group in the corresponding position of the 1,2,4-triazine [1, 3–6], and the ipso-substitution of a chlorine atom [7–9], trichloromethyl group [10], methylthio group [11] or fluorine atom [12]. the ipso-substitution of a cyanogroup deserves a special attention because 5-cyano-1,2,4-triazines are highly affordable compounds due to previously developed convenient method of obtaining them by using the direct nucleophilic substitution of hydrogen in the series of 1,2,4-triazine-4-oxides [13]. the different variations of the ipso-substitution of a cyanogroup are reported in a literature [14–21]. typically, mineral or organic bases (potassium hydroxide, sodium alcoholate, sodium hydride, triethylamine) were used in this reaction. additionally, there are examples of heating of the starting 5-cyano-1,2,4-triazines with excess of alcohols without additional activation (in particular, the use of such procedures was reported for the introduction of the residues of methanol, ethylene glycol and glycerin). in this article we proposed the modified method of introducing of the residues of higher alcohols into 1,2,4-triazines as a result of ipso-substitution of cyano group in the absence of solvents. it should be noted that fragments of such alcohols have never been introduced into 1,2,4-triazines before. the initial 5-cyano-1,2,4-triazines 1 were obtained as described previously [15]. the substitution of cyano group in 1,2,4-triazines under the action of aromatic and aliphatic amines in heat was also reported by our group [22]. based on the experimental data it was demonstrated that the residues of higher alcohols, such as decanol and tetradecanol, could be also successfully introduced into 1,2,4-triazines under the solvent-free conditions during the heating for 10 h at 150  °c. the reaction proceeds easily and with high yields of products 2. thus, in this paper we reported a new method for the modification of the c5position in 1,2,4-triazines by means of ipso-substitution of c5-cyanogroup by the residues of higher alcohols. and the obtained reaction products have never been previously reported in a literature. experimental nmr1h spectra were recorded on the spectrometer «bruker-avance-400» (400 mhz), internal standard is sime4. the melting points were measured on the «boetius» device. mass spectra (type of ionization is electrospray) were recorded on the device of series «microtof-q ii» of «bruker daltonics» (bremen, germany). elemental analyses were performed on chn analyzer pe2400, series ii by perkin elmer. the starting compounds: 3,6-diphenyl-1,2,4-triazine-5-carbonitrile 1a [15] and 6-(4-tolyl)-3-(4-fluprophenyl)-1,2,4triazine-5-carbonitrile 1b [23] were synthesized according to previously described methods, other compounds are commercially available. 3,6-di(4-tolyl)-1,2,4-triazine-5-carbonitrile (1c) was obtained according to the method described earlier for similar compounds [15]. yield 80 %. mp 225–227 °c. 1h-nmr spectrum (dmsod6), δ, ppm: 2.48 (s, 3h, me), 2.50 (s, 3h, me), 7.40 (m, 2h, tol), 7.45 (m, 2h, tol), 7.97 (m, 2h, tol), 8.41 (m, 2h, tol). ms, m/z ((icomp., %): 287.13 [m+h]+ (100). found,  %: c, 75.67; h, 4.79; n, 19.65. c18h14n4. calculated, %: c, 75.50; h, 4.93; n, 19.57. general procedure for the synthesis of 5-alkoxysubstituted 1,2,4-triazines 2. a mixture of the corresponding 1,2,4-triazine-5-carbonitrile (0.4 mmol) and an appropriate alcohol (0.5 mmol) was stirred at 150  °c for 10 h under the argon. the resulting reaction mixture was cooled to room temperature, treated with hexane, and the precipitate formed was filtered off, washed with hexane and dried. analytical samples were obtained by recrystallization from butanol. 5-tetradecyloxy-3,6-diphenyl-1,2,4triazine (2a). yield 142 mg (0.32 mmol, 80 %). mp 197–199  °c. 1h-nmr spectrum (cdcl3), δ, ppm: 0.88 (t, 3h, j  6.8 hz, сн2сн3), 1.20–1.44 (m, 22н, (ch2)11сн3), 1.92 (m, 2h, осн2сн2), 4.65 (t, 2h, j 6.8 hz, осн2), 7.48–7.57 (m, 6h, ph), 8.19 (m, 2h, ph), 8.55 (m, 2h, ph). ms, m/z (icomp., %): 446.32 [m+h]+ (100). found, %: c, 78.26; h, 8.74; n, 9.22. c29h39n3o. calculated, %: c, 78.16; h, 8.82; n, 9.43. 5-dec yloxy-3,6-di(4-tolyl)-1,2,4triazine (2b). yield 125 mg (0.3 mmol, 75 %). mp 205–207  °c. 1h-nmr spectrum (cdcl3), δ, ppm: 0.88 (t, 3h, j 6.8 hz, сн2сн3), 1.20–1.45 (m, 14n, (ch2)7сн3), 1.91 (m, 2h, осн2сн2), 2.44 and 2.45 (both s, 3h, tol-me), 4.63 (t, 2h, j = 6.8 hz, осн2), 7.32 (m, 4h, tol), 8.10 (m, 2h, tol), 8.43 (m, 2h, tol). ms, m/z (icomp. %): 418.29 [m+h]+ (100). found, %: c, 77.87; h, 8.57; n, 9.90. c27h35n3o. calculated, %: c, 77.66; h, 8.45; n, 10.06. 5 te t r a d e c y l o x y 3 ( 4 t o l y l ) 6 (4-fluorophenyl)-1,2,4-triazine (2c). the yield is 134 mg (0.28 mmol, 70 %). mp 208–210  °c. the 1h-nmr spectrum (cdcl3), δ, m. d.: 0.88 (t, 3н, j 6.8 hz, сн2сн3), 1.20–1.45 (m, 22н, (сн2)7сн3), 1.91 (m, 2н, осн2сн2), 2.45 (с, 2н, tol-me), 4.62 (t, 2н, j 6.8 hz, осн2), 7.26 (m, 2н, 4-fph), 7.34 (m, 2н, tol), 7.73 (m, 2н, tol), 8.59 (m, 2н, 4-fph). mass spectrum, m/z (icomp.,  %): 478.67 [m+h]+ (100). found, %: с, 75.22; h, 8.29; n, 9.02. c30h40fn3o. calculated, %: с, 75.44; h, 8.44; n, 8.80. acknowledgements the authors thank d. sc. d. n. kozhevnikov (zao nph vmp) for suggestions on the synthesis of substituted 1,2,4-triazines. this work is supported by russian science foundation (grant no. 16–43–02020). in russian 5-алкоксисодержащие 1,2,4-триазины представляют практический интерес в  качестве рецепторов экспрессии генов [1], а  также ингибиторов энзимов типа mth1 при терапии раковых заболеваний [2]. для получения этих соединений ранее были предложены следующие синтетические подходы: алкилирование гидроксигруппы в  соответствующем положении триазина [1, 3–6], ипcо-замещение атома хлора [7–9], трихлорметильной группы [10], метилтиогруппы [11] или атома фтора [12]. отдельного внимания заслуживает ипсо-замещение циано группы, поскольку 5-циано-1,2,4-триазины являются весьма доступными соединениями ввиду разработанного ранее удобного метода их получения с  использованием методологии нуклеофильного замещения водорода в  ряду 1,2,4-триазин-4-оксидов [13]. в  публикациях [14–21] представлены различные варианты такого ипсозамещения. обычно в  ходе реакции используются основания (гидроксид калия, алкоголят натрия, гидрид натрия, триэтиламин), помимо этого имеются примеры нагревания исходного 5-циано-1,2,4-триазина в избытке спирта без дополнительной активации (в частности, использование подобной процедуры предложено в случае введения остатков метанола, этиленгликоля и  глицерина). в  рамках данной статьи мы предлагаем модифицированный метод введения остатков высших спиртов в  результате ипсо-замещения цианогруппы в  условиях отсутствия растворителя. следует отметить, что фрагменты подобных спиртов таким образом ранее в  состав 1,2,4-триазинов не вводились. исходные 5-циано-1,2,4-триазины 1 были получены по описанному ранее методу [15]. замещение цианогруппы в  составе 1,2,4-триазинов в  условиях отсутствия растворителя ранее было нами показано на примере ароматических и  алифатических аминов [22]. эксперименты показали, что аналогичным образом возможно введение остатков высших спиртов, что продемонстрировано нами на примере деканола и  тетрадеканола. нами были использованы аналогичные условия реакции (нагрев в  течение 10 ч при 150  °с). реакция протекает легко и с высокими выходами продуктов 2. таким образом, в  данной статье нами предложена новая модификация ипсо-замещения цианогруппы в  положении 5 1,2,4-триазинов остатками высших спиртов, что ранее в литературе представлено не было. спектры ямр 1h были записаны на спектрометре «bruker avance-400» (400  мгц), внутренний стандарт – sime4. температуры плавления были измерены на приборе boetius. массспектры (тип ионизации – электроспрей) записаны на приборе серии microtof-q ii фирмы bruker daltonics (бремен, германия). элементный анализ выполнен на chn анализаторе модели ре 2400, серия ii фирмы perkin elmer. исходные соединения: 3,6-дифенил-1,2,4-триазин-5-карбонитрил 1a [15] и  6-(4-толил)-3-(4-фторфенил)1,2,4-триазин-5-карбонитрил 1b [23] были получены по описанным ранее методам, остальные соединения коммерчески доступны. 3 , 6 д и ( 4 т о л и л ) 1 , 2 , 4 т р и а зин-5-карбонитрил (1c) был получен согласно описанному ранее методу для подобных соединений [15]. выход 80 %. тпл. 225–227  °c. спектр ямр 1н (dmso-d6), δ, м. д.: 2,48 (с, 3н, ме), 2,50 (с, 3н, ме), 7,40 (м, 2н, tol), 7,45 (м, 2н, tol), 7,97 (м, 2н, tol), 8,41 (м, 2н, tol). масс-спектр, m/z (iотн.,  %): 287,13 [m+h]+ (100). найдено, %: с, 75,67; h, 4,79; n, 19,65. c18h14n4. вычислено, %: с, 75,50; h, 4,93; n, 19,57. общая методика получения 5-алкоксизамещенных 1,2,4-тризинов 2 смесь соответствующего 1,2,4-триазин-5-карбонитрила (0,4  ммоль) и  соответствующего спирта (0,5 ммоль) перемешивают в отсутствие растворителя при 150 ºс в атмосфере аргона в течение 10 ч. реакционную массу охлаждают до комнатной температуры, обрабатывают гексаном, осадок отфильтровывают, промывают гексаном и  сушат. аналитические образцы получают перекристаллизацией из бутанола. 5 те т р а д е ц и л о к с и 3 , 6 д и ф е нил-1,2,4-триазин (2а). выход 142  мг (0,32  ммоль, 80 %) тпл. 197–199 ºс. спектр ямр 1н (cdcl3), δ, м. д.: 0,88 (т, 3н, j 6,8 гц, сн2сн3), 1,20–1,44 (м, 22н, (сн2)11сн3), 1,92 (м, 2н, осн2сн2), 4,65 (т, 2н, j 6,8 гц, осн2), 7,48–7,57 (м, 6н, ph), 8,19 (м, 2н, ph), 8,55 (м, 2н, ph). масс-спектр, m/z (iотн., %): 446,32 [m+h]+ (100). найдено, %: с, 78,26; h, 8,74; n, 9,22. c29h39n3o. вычислено, %: с, 78,16; h, 8,82; n, 9,43. 5 д е ц и л о к с и 3 , 6 д и ( 4 т о л и л ) 1,2,4-триазин (2b). выход 125  мг (0,3  ммоль, 75 %). тпл. 205–207 °с. спектр ямр 1н (cdcl3), δ, м. д.: 0,88 (т, 3н, j 6,8 гц, сн2сн3), 1,20–1,45 (м, 14н, (сн2)7сн3), 1,91 (м, 2н, осн2сн2), 2,44 и  2,45 (оба с, 3н, tol-me), 4,63 (т, 2н, j 6,8 гц, осн2), 7,32 (м, 4н, tol), 8,10 (м, 2н, tol), 8,43 (м, 2н, tol). массспектр, m/z (iотн.,  %): 418,29 [m+h] + (100). найдено,  %: с, 77,87; h, 8,57; n, 9,90. c27h35n3o. вычислено, %: с, 77,66; h, 8,45; n, 10,06. 5-те т р а децилокси-3-(4-толил)6-(4-фторфенил)-1,2,4-триазин (2с). выход 134  мг (0,28  ммоль, 70 %). тпл. 208–210 °с. спектр ямр 1н (cdcl3), δ, м. д.: 0,88 (т, 3н, j 6,8 гц, сн2сн3), 1,20–1,45 (м, 22н, (сн2)7сн3), 1,91 (м, 2н, осн2сн2), 2,45 (с, 2н, tol-me), 4,62 (т, 2н, j 6,8 гц, осн2), 7,26 (м, 2н, 4-fph), 7,34 (м, 2н, tol), 7,73 (м, 2н, tol), 8,59 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tekhnicheskogo universiteta – upi, seriya khimiya. 2003;3:79–81. russian. 20. prokhorov am, shumkov aa, ustinova mm, kozhevnikov dn, rusinov vl, chupakhin on. vestnik ural’skogo gosudarstvennogo tekhnicheskogo universiteta – upi, seriya khimiya. 2003;3:82–4. russian. 21. kozshevnikov dn, kozshevnikov vn. combinatorial approach to the synthesis of substituted 1,2,4-triazines. chimica techo acta. 2016;4(1):25–8. doi:10.15826/ chimtech.2017.4.1.021. 22. kopchuk ds, chepchugov nv, kovalev is, santra s, rahman m, giri k, zyryanov gv, majee a, charushin vn, chupakhin on. solvent-free synthesis of 5-(aryl/alkyl)amino-1,2,4-triazines and α-arylamino-2,2'-bipyridines with greener prospects. rsc adv. 2017;7(16):9610–9. doi:10.1039/c6ra26305d. 23. kopchuk ds, chepchugov nv, taniya os, khasanov af, giri k, kovalev is, santra s, zyryanov gv, majee a, rusinov vl, chupakhin on. 3-cyano-2-azaanthracene-based «push-pull» fluorophores: a one-step preparation from 5-cyano-1,2,4-triazines and 2,3-dehydronaphthalene, generated in situ. tetrahedron lett. 2016;57(50):5639–43. doi:10.1016/j.tetlet.2016.11.008. cite this article as (как цитировать эту статью) krinochkin ap, kopchuk ds, starnovskaya es, shtaiz yak, khasanov af, kovalev is, taniya os, zyryanov gv, rusinov vl, chupakhin on. the synthesis of 1,2,4-triazines bearing the residues of higher alcohols in the 5-position via the ipso-substitution of cyano group under the solvent-free conditions. chimica techno acta. 2017;4(2):112–119. doi: 10.15826/chimtech.2017.4.2.026. oxygen content and defect structure of the perovskite la0.5ba0.5coo3 117 d o i: 10 .1 58 26 /c hi m te ch .2 01 8. 5. 4. 04 malyshkin d. a., novikov a. yu., tsvetkov d. s. chimica techno acta. 2018. vol. 5, no. 2. p. 117–124. issn 2409–5613 d. a. malyshkin, a. yu. novikov, d. s. tsvetkov institute of natural sciences and mathematics, ural federal university, 19 mira st., 620002, ekaterinburg, russian federation e-mail: dmitry.malyshkin@urfu.ru oxygen content and defect structure of the perovskite la 0.5 ba 0.5 coo 3–δ perovskite-type complex oxide la 0.5 ba 0.5 coo 3–δ , promising cathode material for solid oxide fuel cells and precursor for synthesis of double perovskite labaco 2 o 6–δ , was prepared as a single-phase material. its oxygen content was measured by two independent techniques in the temperature range 1000– 1100 °c and at oxygen partial pressures corresponding to the stability field of cubic phase. the defect chemistry of this material was studied using the measured δ = f(po 2 , t) dependences. the defect structure model based on the localized nature of the electronic defects was proposed and successfully verified. keywords: oxygen nonstoichiometry, perovskite, defect structure, coulometric titration. received: 28.06.2018. accepted: 25.07.2018. published: 30.07.2018. © malyshkin d. a., novikov a. yu., tsvetkov d. s., 2018 introduction the perovskite-type oxide la0.5ba0.5coo3–δ was first prepared in 1979 [1, 2]. by a number of techniques it was shown to have cubic crystal structure with pm3m space group (s. g.), at least when synthesized in air atmosphere with oxygen partial pressure, po2, ≥ 0.21 atm [3–17]. depending on the synthesis method, the final annealing temperature, t, reported in the literature, varies within the fairly wide limits – from 750 [18] to 1300 °c [2]. however, the samples of la0.5ba0.5coo3–δ obtained at  t ≤ 850  °c are usually found to contain some impurities [8, 18, 19]. hence, regardless of  the synthesis method, a  single-phase cubic perovskite la0.5ba0.5coo3–δ can be prepared only at temperatures above 850 °c in air [16]. according to the results of in situ hightemperature x-ray diffraction studies [14], the crystal structure of la0.5ba0.5coo3–δ remains cubic (s. g. pm3m) in the temperature range 300–800 °c and under different gas atmospheres (o2, air and n2). on the other hand, annealing of la0.5ba0.5coo3–δ at  900–1200  °c under reducing conditions led to the formation of the double perovskite labaco2o6–δ[3, 5, 10–15, 20–23]. thus, according to the results of  studying the ordering-disordering phenomenon in  labaco2o6–δ  – la0.5ba0.5coo3–δ system [23], the stability field of cubic perovskite at 1000–1100 °c corresponds to the po2 range –1.3 ≤ log (po2 / atm) ≤ –0.68. 118 t h e o x y g e n c o n t e n t i n   t h e la0.5ba0.5coo3–δ was measured as a function of  po2 and temperature using coulometric titration [24] and thermogravimetric technique [6, 7, 11, 12, 14, 17]. however, the results obtained are discrepant, as  evidenced by  the comparison in table 1 and in fig. 1. moreover, sometimes even the data reported by the same scientific group [6, 7] turn out to be inconsistent with each other, as seen in fig. 1. unfortunately, in most cases it is difficult to understand the origin of these discrepancies because of  the incomplete and often only superficial description of  the specific experimental conditions (heating / cooling rate, equilibration time etc.) used by different authors. the only available attempt to describe the defect structure of la0.5ba0.5coo3–δ reported in [17] should also be considered as unsuccessful due to obvious errors in the charge neutrality and mass balance conditions given in [17]. table 1 comparison of the available literature data on the absolute oxygen content in la0.5ba0.5coo3–δ at room temperature the oxygen content in sample at room temperature, 3–δ cooling rate, °c / h 60 300 unknown po2, atm 0.21 1 3.00 [7] 2 [6] 2 2.98 [14] 1, [17] 2 2.96 [11] 2 2.94 [17] 2 2.91 [12] 1 method for determining the absolute value of δ: 1 – reduction by hydrogen flux 2 – iodometric titrations fig. 1. a) the oxygen content in la0.5ba0.5coo3–δ as a function of temperature in air; b) the oxygen content in la0.5ba0.5coo3–δ vs. po2 at different temperatures. the curves are shown as guides to the eye only 119 therefore, the priority purposes of this work were (i) to  prepare single-phase la0.5ba0.5coo3–δ oxide, (ii) to get reliable data on its oxygen content as a function of t and po2 and (iii) to carry out the analysis of the defect structure of la0.5ba0.5coo3–δ. experimental powder sample of the la0.5ba0.5coo3–δ was prepared by means of the glycerol-nitrate method using la2o3, baco3 and co as starting materials. all of the materials used had a purity of 99.99 %. a stoichiometric mixture of  the starting materials was dissolved in concentrated nitric acid (99.99 % purity) and the required volume of glycerol (99 % purity) was added as  a  complexing agent and a  fuel. the glycerol quantity was calculated according to  the amount required for  the full reduction of  the corresponding nitrates to molecular nitrogen n2. the as-prepared solution was heated continuously at 100 °c until complete water evaporation and pyrolysis of the dried precursor had occurred. the resulting ash was subjected to  stepwise calcination at temperatures between 900 and 1100 °c in air with intermediate regrindings. annealing at the last stage was carried out for 30 hours. the sample was then cooled to room temperature at a rate of 100 °c / h. the phase composition of the powder samples prepared accordingly was studied at  room temperature by  means of  xrd with a shimadzu xrd 7000s diffractometer (shimadzu, japan) using cu kα radiation. the xrd spectra showed no indication for the presence of a second phase in the as-prepared samples. t h e ox y ge n n ons toi ch i om e t r y of la0.5ba0.5coo3–δ was measured as a function of  po2 and temperature by  means of thermogravimetric (tg) and coulometric titration techniques. the absolute value of  δ in  la0.5ba0.5coo3–δ was determined by direct reduction of the oxide samples by hydrogen flux in the tg setup. the details can be found elsewhere [25]. results and discussion the absolute oxygen content in  the sample of la0.5ba0.5coo3–δ slowly (100 °c / h) cooled to  room temperature was found to be 2.992±0.005, in agreement with available literature data [6, 7]. the xrd pattern of the as-prepared single-phase perovskite la0.5ba0.5coo2.992 is shown in fig. 2. it was indexed using the cubic pm3m space group. the cell parameter a = 3.888 (6) å determined as a result of the rietveld refinement of the xrd profile (also shown in fig. 2) is in good agreement with those reported for la0.5ba0.5coo3–δ previously [3–5, 9, 26]. the oxygen content in la0.5ba0.5coo3–δ measured as a function of po2 and temperature is given in fig. 3. as seen, the data obtained by coulometric titration and tg are in good agreement with each other. it is worth noting that the presented range of  po2 corresponds to  the stability field of the cubic phase as determined in [23]. for the sake of comparison, fig. 3 also shows the results reported in ref. [17]. it is noteworthy that the values of the oxygen content measured in the present study exceed those found in ref. [17] on about 0.052 under the same conditions, whereas the slope of the po2 dependences of 3–δ is practically the same in the both data sets. in order to analyze the defect structure of la0.5ba0.5coo3–δ using the quasichemical approach, lacoo3 with fully occupied 120 oxygen sublattice was chosen as  a  reference crystal in the same way as for related compounds [27]. in this case, the regular constituents are la cola co × ×, and oo × , whereas the defect species can be defined as ba v cola o co� � ��, , and coco • , where the last two point defects correspond to cobalt in the oxidation state +2 (electron localized on cobalt site) and +4 (hole localized on cobalt site), respectively. the following quasichemical reactions were taken into account: oxygen exchange with ambient gas atmosphere with simultaneous reduction / oxidation of cobalt (1) o co o v co v co o o co o co o o co o � � � � � � � � �� ���� �� 2 212 2 1 0 5 2 2 i ii ii � , . k p ��� ���� ��coco i 2 (1) and the charge disproportionation involving the transfer of an electron between adjacent sites (2) 2 2 2 co co co co co co co co co co co co � � � � � �� �� ��� �� �� �� � i i , .k (2) equilibrium constants of the proposed quasichemical reactions along with conditions of mass balance and electroneutrality form the following set of nonlinear equations: k p h rt s 1 0 5 2 2 1 0 2� �� ���� �� �� ���� �� � � � � � � � o o co o co v co o co exp .   11 0 2 2 2 0 2 0 r k h rt s r � � � � � � � ��� ���� �� �� �� � � � � � � co co co exp co co co  �� � � � � � ��� �� � ��� �� � �� �� � �� �� �� �� � � � co ba co v co c co la co o co  2 oo co o v co co o o �� �� � �� �� � �� �� � � �� �� � � � � �   1 3 � � (3) the analytical solution of  the set (3) yields the model function: p k k k a a o2 0 25 1 2 2 3 12 4 16 1 2 2 . , � � � � � � � � �� � � � � � (4) where fig. 2. rietveld refined xrd pattern of the la0.5ba0.5coo2.992 sample slowly (100 °c / h) cooled from 1100 °c to room temperature in air: observed x-ray diffraction intensity (points) and calculated curve (line). the bottom curve is the difference of patterns, yobs − ycal, and the small bars indicate the angular positions of the allowed bragg reflections fig. 3. oxygen content in la0.5ba0.5coo3–δ vs. po2 at different temperatures. note that the data of stingaciu [17] were shifted upward by 0.052 121 a k k k � � � � � �16 32 12 64 82 2 2 2 2� � � �. (5) note that defect formation enthalpies were treated as constants, since the oxygen nonstoichiometry of la0.5ba0.5coo3–δ was measured in  the relatively narrow temperature range. this assumption enabled the substitution of  the equilibrium constants in the eq. 4 by their thermodynamic temperature dependences (see eq. 3) and, as a consequence, simultaneous treatment of the data on oxygen nonstoichiometry obtained at  different temperatures according to the proposed defect structure model. the result of  the least square fit of the model eq. 4 to the experimental data on the oxygen content in la0.5ba0.5coo3–δ is shown in fig. 4. as seen, there is a good agreement between the fitted surface and the measured values. the fitted parameters of the model are summarized in table 2. it is worth noting that the standard entropy of charge disproportionation ∆s2 0 , obtained as a result of the least square fit, was close to zero with relatively large error margin. within this margin fit results were found to  be relatively insensitive to  the particular value of  ∆s2 0 . furthermore, it is known that the value of  ∆si 0 corresponds to the vibrational entropy change [28] which should be very small for reaction (2) since it does not involve the gaseous species. in addition, the average point defects” coordination environment also does not change significantly in the course of the reaction (2). as a result, the magnitude of  ∆s2 0 can be expected to be rather low. therefore, during the final fitting procedure the standard entropy of charge disproportionation, ∆s2 0 , was assumed to be zero. similar reasoning was also presented in ref. [29]. conclusions oxygen nonstoichiometry of the perovskite oxide la0.5ba0.5coo3–δ was measured as a function of po2 and temperature in the range 1000–1100 °c by means of  thermogravimetric and coulometric titration techniques. the defect structure fig. 4. the result of the least square fit of the defect structure model for la0.5ba0.5coo3–δ. points – experimental data on oxygen nonstoichiometry of la0.5ba0.5coo3–δ. surface – model eq. 4 fitted table 2 the result of the least square fit of the defect structure model for la0.5ba0.5coo3–δ defect reaction ∆hi 0 , kj·mol–1 ∆si 0 , j·k–1·mol–1 r2 o co o v co o co o co � �� � �2 21 2 2 ii ii� 50.9 ± 2.1 35.4 ± 1.8 0.973 2co co co co co co � � �� i 30.1 ± 0.5 0.0 122 model of la0.5ba0.5coo3–δ based on the localized nature of the electronic defects was proposed and successfully verified using the measured δ = f (po2, t) dependences. references 1. kobussen agc, van buren fr, van den belt tgm, van wees hja. oxygen evolution on lacoo3-type 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doi:10.1007 / s10853-006-0345-8 28. kofstad p. nonstoichiometry, diffusion, and electrical conductivity in binary metal oxides. new york: wiley-interscience; 1972. 382 p. 29. lee y-l, morgan  d.  ab initio and empirical defect modeling of  lamno3+δ for  solid oxide fuel cell cathodes. phys chem chem phys. 2012;14(1):290–302. doi:10.1039 / c1cp22380a manipulating the grain boundary properties of baceo3-based ceramic materials through sintering additives introduction 38 d o i: 1 0. 15 82 6/ ch im te ch .2 01 9. 6. 2. 01 vdovin g. k., rudenko a. o., antonov b. d., malkov v. b., demin a. k., medvedev d. a. chimica techno acta. 2019. vol. 6, no. 2. p. 38–45. issn 2409–5613 g. k. vdovina, a. o. rudenkoa, b. d. antonova, v. b. malkova, a. k. deminab, d. a. medvedevab a institute of high temperature electrochemistry, yekaterinburg 620990, russia b graduate school of economics and management, ural federal university, yekaterinburg 620002, russia e-mail: dmitrymedv@mail.ru manipulating the grain boundary properties of baceo3‑based ceramic materials through sintering additives introduction baceo3-based materials represent a well-known family of proton-conducting electrolytes, which can be used in different solid oxide electrochemical devices. an effective operation of the latter across an intermediate-temperature range requires improved transport of pces, including their grain (g) and grain boundary (gb) components. in the present work, some 3d-elements in a small amount were used as sintering additives to verify the possibility of improving the gb conductivity of bace0.9gd0.1o3–δ. it is shown that copper oxide (cuo) can be considered as one of the most effective sintering agents, since its use enables decreasing the gb density of the bcg ceramic material at the reduced sintering temperatures. the obtained results form a new tactic for designing new protonic electrolytes, whose conductivity might be prevail over ones containing ni-based modifiers. keywords: baceo3; sofcs; soecs; sintering additives; impedance spectroscopy; protonconducting electrolytes. received: 11.06.2019. accepted: 28.06.2019. published: 05.08.2019. © vdovin g. k., rudenko a. o., antonov b. d., malkov v. b., demin a. k., medvedev d. a., 2019 introduction p r o t o n c o n d u c t i n g o x i d e (pco) materials occupy a  special place in the high-temperature electrochemistry due to its unique features consisting in proton transportation in an oxide matrix [1–5]. these features allows pcos to be utilized as electrolytes for various types of electrochemical devices (eds) such as solid oxide fuel cells (sofcs), solid oxide electrolysis cells (soecs), pumps and sensors [6–9]. as a result of high realizable conductivity levels of pcos, the mentioned devices can operate at  reduced temperatures (below 600 °c) compared with the conventional systems based on oxygen-ionic electrolytes [10, 11]. in  order to  further improve the  eds’ performance and efficiency, different strategies aimed at the electrolyte modifications can be exploited [1–3, 12–14]: the decrease of their thickness, designing the structures with a higher ionic mobility, purposeful modification of  ceramics morphology. the latter is a highly promising strategy, since the overall conductivity of  polycrystalline pcos is  known to  be determined by a high resistance of grain boundaries [14]. one of the most obvious 39 ways to modify the grain boundaries rests on  adding the  low-melting phases [15], which intensify mass transport and promotes grain growth. nickel oxide (nio) is often used as such an additive. however, no improvement (or even deterioration) of grain boundary transport is observed [16–20]; this is  due to  two undesirable effects: very low solubility of  ni2+-ions in  a  ce-sublattice of  baceo3-based materials and, consequently, the sedimentation of  proton-blocking ni-containing phases (nio, bay2nio5) along the grain boundaries. therefore, a  rational search of possible alternative to nio is a matter of fundamental and applied interests associated, respectively, with design of pcos with optimized properties and their successful application in eds. in the present work, on a well-known example of  pcos, bace0.9gd0.1o3–δ, possibility of  improving its grain boundary transport was checked via an addition of cuo, co3o4 and nio as second dopants. to launch bridges between structural, microstructural and transport properties of the materials obtained, the x-ray diffraction (xrd), scanning electron microscopy (sem) and electrochemical impedance spectroscopy (eis) analyses were used. experimental bace0.9gd0.1o3–δ (bcg) material and its doping derivatives (bace0.89gd0.1m0.01o3–δ, bcgm, where m = cu, co and ni) were prepared using traditional solid state synthesis method. baco3, ceo2, gd2o3, cuo, co3o4 and nio powders (with purity not less than 99.5 %) were taken in stoichiometric amounts and thoroughly mixed via a mortar and pestle. the obtained mixtures were first pre-synthesized at 1100 °c for 5 h. the resulting powders were again mechanically activated, uniaxally pressed into discs and then sintered at 1450 °c for 3 h. one part of  the  obtained ceramic samples was crushed and characterized by xrd (diffractometer rigaku d / max2200vl / pc, japan), while another part was studied by sem (jeol jsm-5900 lv, japan). electrochemical characterization was performed for  the  ag|bcg|ag or ag|bcgm|ag symmetrical cells by utilizing an  amel 2550 potentiostat / galvanostat (italy) and a  materialsm 520 frequency response analyser (italy). these cells were fabricated in the following sequence: polishing the discs, an ag paste painting and its sintering at 800 °c for 1 h. the impedance spectra were obtained for  wet (ph2o = 0.03 atm) air atmosphere in a frequency range of 10–2–106 hz with an amplitude of 30 mv. the spectra were analysed by  an  equivalent circuit method, using a zview software for model processing. results and discussion the  xrd pattern of  the  sintered bcg material (fig.  1) shows the  formation of a single-phase product, the crystal structure of  which can be indexed as an orthorhombically-distorted perovskite with lattice parameters of a = 6.221 å, b = 8.770 å, c = 6.244 å and space group of  pmcn. the  doping with 3d-elements does not change symmetry of  the  perovskite structure, while the  lattice parameters of bcgm are virtually constant (a = 6.220 ± 0.003 å, b = 8.766 ± 0.005 å, c = 6.237 ± 0.007 å). these results can be explained by the extremely small amount of  sintering additives introduced into the baceo3 structure, 0.005 mol.%. 40 despite of small concentrations used, the m-doping affects considerably the microstructural parameters of  the  sintered materials that can be seen from qualitative (fig.  2) and quantitative (table  1) analyses. in  detail, the  processes associated with grains growth, their close package, pores disappearance and densification occur in all the cases. nevertheless, a  degree of  these processes is  different and increases in the sequence of bcgco– bcgcu–bcgni, indicating dissimilar nature of the sintering additives. to reveal grain (σg.) and grain boundary (σg.b.) contributions of the total conductivity (σtotal), the eis analysis was successfully performed. the  electrochemical characterization was carried out in different temfig. 1. xrd patterns of the sintered bcg and bcgm materials (a) and example of refinement for bcg (b) fig. 2. surface morphology of the sintered ceramic materials: bcg (a), bcgco (b), bcgcu (c) and bcgni (d) 41 perature ranges, boundaries of which were determined by  accuracy of  the  analysis. the  obtained spectra (fig.  3) were analyzed using an equivalent circuit scheme of  ro–(r1q1)–(r2q2)–(r3q3), where r is the resistance, q is the constant phase element,  indexes of  1, 2, 3 correspond to  grain, grain boundary and electrode processes, respectively. correlation of hodographs’ elements with these processes is performed analyzing the characteristic capacitance (c) and frequency (f) values calculated as follows: ( )1/ 1nc r q r−= ⋅ ⋅ (1) ( ) ( )1/ 12nf r q − −= ⋅ ⋅ π (2) here, n is the power index in a frequency dependence part of the constant phase element. depending on the temperature, the c value varies between 20 and 80 pf for  the  first arc and between 3 and 8  nf for the second one, while the f values amount hundreds khz and hundreds hz, respectively. both levels of these parameters relate with grain and grain boundary properties. it should be noted that ro  = 0.001  ω was purposefully introduced in the equivalent circuit scheme; it imitates the origin of the coordinates, providing a correct fitting. as  can be seen from fig.  4a, cu and ni-doping of  bcg results in  an  increase of  σg., while co-doping has an opposite (but minor) effect. for example, the  σg. value at  200  °c reaches 5.01·10–5, 3.27·10–5 and 2.61·10–4  s  cm–1 for bcg, bcgco and bcgcu, respectively. this parameter cannot be precisely determined for the bcgni material at 200 °c, but its σg. level is by ~2 times lower than that of bcgcu at the lower temperatures (100–150 °c). table 1 microstructural parameters of the bcg and bcgm materials sintered at 1450 °c for 3 h: ρ is the relative density, l is the total shrinkage, d is the average grain size, γ is the grain boundary density a composition ρ, % l, % d ± 5 %, µm γ ± 5 %, µm–1 bcg 86 8.2 0.8 4.66 bcgco 91 12.3 3.4 1.10 bcgcu 94 17.5 6.9 0.54 bcgni 97 22.3 9.6 0.39 a estimated on the base of the following equation: γ = 3.722·d–1, see ref. [21]. fig. 3. impedance spectra obtained for the ag|bcg|ag symmetrical cell at different temperatures in wet air atmosphere (a) and example of the fitting procedure for the spectra obtained at 250 °c (b) 42 discussing the grain boundary transport (fig. 4b), the σg.b. improvement is observed for  all the  bcg-modified materials and can be related with decreasing the grain boundary density (table 1). comparison of the bcgcu and bcgni samples allows formulation of the assumption that nickel is only partially dissolved in the cesublattice of bcg, while another part localizes onto grain boundaries. this proposal is based on the fact that bcgni exhibits the lowest grain boundary density, which should provide the highest σg.b.; however, this is not confirmed experimentally. the resulting conductivity (σtotal, fig. 4c) of the bcgm samples is higher than that of bcg, showing that the grain boundary transport determines the overall properties even for bcgco (at least in the entire studied temperature range). the bcgcu material exhibits the maximal achievable σtotal values, ranging from 6.33·10 –6 s cm–1 at 100 °c to 1.86·10–4 s cm–1 at 200 °c. as shown in fig. 5, the apparent activation energies (ea) of σg. fall in the range of  0.45–0.49  ev, being in  close agreement with a characteristic value of 0.5 ev for proton transportation of pcos [22–24]. according to  these data, the  m-doping does not affect the grain transport properties of bcg. another scenario is observed for the grain boundary transport properties, when ea of σg.b. decreases by 25–40 % comparatively 0.92 ev reaching for the basic bcg oxide. it might be also associated with the  meaningful decrease of  grain boundary density serving as  a  barrier to ionic charge transfer. fig. 6 displays the most interesting result — a ratio between the grain boundary (rg.b.) and total (rtotal) resistances of bcg and bcgm. this ratio decreases significantly for  the  latter samples as  a  result of weakening the effect of grain boundaries on the overall transport of bcgm. a vivid example can be seen when rg.b. / rtotal = = 0.5: for  bcg this level is  reached at ~250 °c, whereas for bcgm — at 100– 125 °c. in terms of real operation of pcos (400–600 °c), the introduction of 3d-elemetns in small amounts can improve the outfig. 4. grain (a), grain boundary (b) and total (c) conductivities of the bcg and bcgm ceramic materials fig. 5. apparent activation energy values calculated for different types of conductivities 43 put properties (power density, current density) of pco-based electrochemical devices by tens of percent. considering transport properties of bcgm and data on low-melting phases in corresponding systems [25–27], it can be concluded that the studied dopants behave differently respectively each other. for example, cobalt is assumed to act as a dopant, fully incorporated in the ce-site of baceo3; nickel is mostly localizes at grain boundary region due to the mentioned low solubility in the ce-sublattice, although a certain amount can be nonetheless incorporated; finally, copper demonstrates dual nature: it has a high solubility (at least, more than 5  mol.% [21]), but can be also formed as a sediment at grain boundaries because of very low melting temperatures detected for a ba–cu–o system [15, 27]. conclusions this work shows that the doping strategy of barium cerate with transition elements is one of the simplest and most 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2409–5613 d o i: 1 0. 15 82 6/ ch im te ch /2 01 7. 4. 3. 01 ajay shankar1, alexander safronov2,3, igor beketov3 1indira gandhi national tribal university, amarkantak, madhya pradesh, 484886, india e-mail: ajayshankar0@gmail.com 2ural federal university, 19 mira st., ekaterinburg, 620002, russian federation e-mail: safronov@iep.uran.ru 3institute of electrophysics ub ras, 106 amundsen st., ekaterinburg, 620016, russian federation e-mail: beketov@iep.uran.ru encapsulation of metallic iron magnetic nanoparticles by polyacrylamide in water suspensions theoretical consideration of the factors of the stability of metallic iron magnetic nanoparticles (mnps) in water suspensions was done using extended dlvo (derjaguin-landau-verwey-overbeek) approach based on the balance among van der waals, electrostatic, magnetic and steric interactions. magnetic and steric interactions dominate over other in suspensions of fe mnps. to test the theory fe mnps with average diameter 84 nm were synthesized by electrical explosion of wire and encapsulated by polyacrylamide in water suspension to provide steric repulsion. it was shown that encapsulation resulted in the efficient diminishing of the aggregation of metallic iron mnps in water. keywords: iron nanoparticles; encapsulation; polyacrylamide. received: 28.06.2017; accepted: 24.07.2017; published: 20.10.2017. © shankar a., safronov a., beketov i., 2017 introduction magnetic nanoparticles (mnps) are the subject of intensive research due to the special properties required for technological and biomedical applications such as magnetic fluids, catalysis, magnetic resonance imaging, data storage, and environmental remediation [1–3]. in these applications magnetic material is to be dispersed in a solid phase giving a composite material, or in a liquid giving a ferrofluid or a suspension. among others iron-based mnps attract special attention due to their relatively low cost and comparatively low toxicity for the living systems, which is of the major importance for the biotechnological and biomedical applications. in this respect iron oxide mnps are mostly studied. there are a lot of different methods for their synthesis, a  variety of actual and prospective applications [3], and numerous studies of their compatibility [4]. at the same time metallic iron mnps are less studied. meanwhile, from the viewpoint of their magnetic properties metallic iron has indisputable advantages over its oxides. its saturation 159 magnetization is at least three times higher than that of magnetite. if used in magnetic sensors, actuators, contrast agents for mrs iron mnps might provide higher sensitivity, better response, and lower detectable doses. however, there are several unresolved problems of the application of metallic iron mnps in suspensions. the major one is strong aggregation of metallic iron mnps. it is known, that the aggregation of nanoparticles is thermodynamically favo rable process. the surface between coexisting phases carries on excess free energy, which might be very high for the nanosystem as its specific surface is also high due to small dimensions. the aggregation of mnps diminishes the surface of the direct contact among the phases and leads to the minimization of the free surface energy [5]. in order to overcome the thermodynamic force for the aggregation and to provide the stability of disperse systems with nanoparticles, such approaches as electrostatic or steric stabilization are used. unfortunately, the variety of stabilizers, which proved to be successful for the stabilization of iron oxide suspensions, are not such for the suspensions of metallic iron particles in water. it is the result of the enhanced magnetic properties of iron, which dominate over other forces in colloid suspensions. the objective of the present study was to examine the problem of the stability of magnetic iron nanoparticles from theoretical point of view and experimentally test the possibility of the stabilization of the suspension of spherical iron mnps in water, using their encapsulation by watersoluble polymer – polyacrylamide. experimental materials metallic iron magnetic nanoparticles (mnp) were synthesized by the method of electric explosion of wire (eew). the detailed description of eew equipment designed at the institute of electrophy sics of ras (ekaterinburg, russia) is given elsewhere [6–8]. the method is based on the evaporation of a portion of metal wire by the electric high power pulse in the explosion chamber filled with the inert atmosphere. further condensation of the expanding metal vapors resulted in the formation of spherical mnps. the applied voltage was 30 kv and the length of the exploded portion of wire was 70 mm. the wire was continuously fed to the explosion chamber by the feeding device, the high voltage source was concurrently recharged after each explosion, and the process was repeated in the pulsed manner resulted in rapid production of mnps (200 g/h). the reaction chamber was filled with a circulating mixture of 70 % of ar and 30 % of n2 providing the working gas pressure of 0.12 mpa. polyacrylamide (paam) was synthesized by the radical polymerization reaction of acrylamide (aam) (applichem, darmstadt) in 1.6 m water solution at 80  °c. ammonium persulfate (psa) in 5  mm concentration was used as an initiator. the reaction mixture was kept at 80  °c for 1  h. the obtained paam solution was then diluted with distilled water down to 5 % concentration by weight. the resulted solution was then used as a stock for the encapsulation of iron mnps. the molar weight of paam determined by viscometry was m = 1.46*105 g/mol. 160 methods the powder x-ray diffraction (xrd) patterns were recorded using bruker d8 discover with cu kα radiation (λ = 1.542  å) with graphite monochromator. the rietveld refinement of xrd patterns were performed using topas-3 software. the morphology of mnps was exami ned using jeol jem2100 transmission electron microscope (tem) operating at 200 kv. the specific surface area of mnps was measured by the low-temperature adsorption of nitrogen (brunauer-emettteller (bet) approach) using micromeri tics tristar3000 analyzer. the magnetic measurements were carried out using (cryogenics ltd. vsm) vibrating sample magnetometer (vsm) at room temperature for powder samples placed in a gelatine capsule. the magnetization values in a field of 1.8 t were designated as the satu ration magnetization values (ms). thermal analysis was done using netzsh sta409 thermal analyzer operated in li near heating mode from 40 to 1000 °c at 10 k/min in the air. dynamic light scattering (dls) and electrophoretic light scattering (els) measurements were performed using brookhaven zetaplus particle size analyzer: 5 and 3 runs were recorded for hydrodynamic size and zetapotential measurements, respectively. results and their discussion theory the aggregation features of iron mnps in water suspension can be qualitatively modeled by the extended dlvo approach. in classical dlvo theory, the attractive and repulsive interactions are modeled for van der waals and electrostatic interactions only. in case of the magnetic colloidal dispersions where both steric and magne tic interactions are also present, they must also be taken into account. the modified approach to consider all these interactions is known as xdlvo approach [9]. this theory was elaborated to study the stability of iron mnps in water suspension. the van der waals interaction energy (vvdw) between mnps with radius r at a distance s was calculated as [10]: v a r r s r s r r s s r s r s vdw = − +( ) +     + + + + +     ( ) ( ) ln ( ) ( ) 6 2 4 2 2 4 2 2 2 2 2      , (1) where a(r) = 1.77 × 10–19 + 1.60 × 10–19e–r/3.05 + + 6.35 × 10–20e–r/10.75 + 2.05 × 10–20 e–r/52.18 [j]. the electrostatic repulsions under constant charge boundary condition were taken as [11]: v ee o o s= +( )−2 12π ε ε ψ κr r ln , (2) where κ ε ε = ∑       − k t q n z c b r a i i 0 2 2 1 2/ . here εr is the relative dielectric constant of water, ε0 is the permittivity of free space, ψ0 is the surface potential, q is the elementary charge, zi is the charge of simple ions, ci is their molar concentration, na, kb, and t have their usual meanings. we used the value of electrokinetic (zeta) potential of –16 mv for iron mnps in water (by els) as an approximation for the surface potential. the steric repulsion was taken into account through a hard core combined with a soft tail potential, as modeled previously under self-consistent field (scf) theory. 161 this originating overall steric term for two identical stabilized mnps was taken as [12]: where, δ is thickness of adsorbed lpaam layer, σp is surface density of adsorbed chains, np is number of free segments and l is the length of one free segment. the maximum magnetic attraction energy (vm) between mnps was taken as [10]: v m r s r m o= − +      8 9 2 2 3πµ (4) the total energy of interaction between iron mnps was calculated as a combination of equations (1)–(4). v(s) = vvdw(s) + ve(s) + vst(s) + vm(s) (5) considering contributions from different terms in equation (5) it was found out that steric (equation (3)) and magnetic (equation (4)) terms are dominating for iron mnps. these two terms in turn strongly depend on such parameters of mnps as the radius, the thickness of the steric protective layer, and the magnetization of particle. fig. 1 presents the dependence of the energy of interpar ticle interaction at different combinations of these parameters. the parameters are taken close to that characteristic for the mnps studied below. it is noticeable that each curve in fig. 1 has a minimum, which is the result of the balance among attractive magnetic force and repulsive steric interaction. it is convst = ∞ for < 0s r kt n l sp p π δ σ δ 3 3 212 2       − ln      − −       + −             − −       9 5 1 2 1 3 1 2 1 30 1 2 3 s s s δ δ δ 66 0               for 0 < < 2 s δ for >s 2 δ        (3) fig. 1. energy of interaction as a function of the distance between iron mnps: a – the influence of the diameter of mnps at constant thickness of steric layer (30 nm) and constant magnetization (100 ka/m); b – the influence of the thickness of steric layer of mnps at constant diameter (84 nm) and constant magnetization (100 ka/m); c – the influence of the magnetization of mnps at constant diameter (84 nm) and constant thickness of steric layer (30 nm) 162 ventionally accepted that the aggregates can be disrupted by the thermal motion if the corresponding minimum is less than 20 kbt, as statistically only a few particles will cross barrier in this case [13]. thus, the depth of the minimum indicates the tendency of the ensemble of mnps to aggregation. it is obvious that the depth of the minimum increases with the increase of particle radius, with the increase in magnetization, and the diminishing of the thickness of protective layer. based on these results, we analyzed the possibility of de-aggregation of fe mnps by their encapsulation by polyacrylamide. characterization of metallic iron mnps fig. 2 presents tem image of metallic iron mnps synthesized by eew. they are spherical in shape and non-aglomerated. the spherical shape of mnps is the result of the eew conditions. the electrical pulse, which passes the portion of wire, provides its overheating to ca 104 k and complete vaporization. then iron mnps are condensed in a vapor phase under the thermodynamic condition for the minimization of free energy. the sphere has a minimal surface among other possible geometrical figures with a constant volume. hence, the obtained iron mnps condense in a shape of spheres. the density of vaporized metal in the eew explosion chamber is kept low by constant circulation of inert working gas; it minimizes the probability of collisions among condensing mnps and prevents their coalescence in liquid phase. the particle size distribution (psd) (fig. 2, inset), which was obtained by the graphical analysis of more than 2000 images of mnps, fits well the following lognormal equation: psd d d e d ( ) (ln ln( . )) * .= − − 10.70 83 9 2 2 0 4022 (6) the specific surface area of mnps (ssp) measured by the low-temperature adsorption of nitrogen was 9.0 m2/g. the surface average diameter of mnps, calculated from this value using the equation ds = 6/(ρssp) (ρ = 7.87 g/cm 3 being iron oxide density) was 84.7 nm. it was in a good agreement with the median diameter 83.9 nm in psd described by equation (6) (the latter value was used a basic level in the theoretical calculations given above). fig. 3 shows xrd patterns of iron particles. mnps contain 93 % of α-fe with а  = 2.867(2) å and coherent length 82(5) nm and 7 % of cubic phase of γ-fe with а  = 3.591(3) å and coherent length 27(2) nm. the coherent length of α-fe phase perfectly correlates with the average diameter of fe mnps obtained both by the analysis of tem images and by the calculation based on bet sorption results. it means that each singular mnp is a monocrystalline particle. the coherent length of γ-fe phase is much lower. most fig. 2. tem image of metallic iron magnetic nanoparticles synthesized by electric explosion of wire. inset: histogram – calculation of particle weight fraction from the image analysis, line – fitting of psd by equation (6) 163 likely it means that γ-fe phase predominantly corresponds to the smallest mnps in the ensemble. magnetic hysteresis loops of iron mnps (see fig. 4) are typical for the magnetically soft materials. the low field behavior (inset in fig. 4) reveals the existence of magnetic hysteresis and coercivity. it can be understood taking into account that although in the ensemble of spherical iron mnps with average diameter of about 82 nm the majority of them are in multi domain state, one cannot exclude the presence of a small fraction of single domain mnps contributing to non-zero coercivi ty. the value of the saturation magnetization in bulk state for pure iron is ms = 1710 (ka/m) [14] for room temperature. the obtained value for ms for mnps is about 30 % lower. most likely this difference stems from two reasons. first, there is a thin oxide layer on the surface of iron mnps, which appear inevitably if the active surface of mnps is exposed to the air. the layer 5 nm in thickness can not be detected by xrd but as the magnetization of iron oxide is lower, it certainly contributes to the diminishing of ms values for mnps. another possibility is the disturbance of the crystalline structure of iron in several layers adjacent to the surface of a spherical nanoparticle. these layers are not contributing to the ferromagnetic response due to the insufficient number of the nearest neighbours [15]. both processes are contributing to ms reduction but it is difficult to make more precise analysis first of all due to the existence of the mnps size distribution. encapsulation of fe mnps by paam encapsulation of iron mnps was performed by grinding in an agate mortar with 5 % water solution of paam at 25 °c. then the slurry was diluted by the excess of distilled water. the supernatant was decanted and the precipitant was washed several times by distilled water; after that it was collected and tested. the total amount of paam, which adsorbed onto fe mnps was determined by tg/dsc thermal analysis. fig. 5 presents fig. 3. xrd diffractogram of iron mnps synthesized by eew fig. 4. magnetic hysteresis loop of fe mnps at 25 °c. inset – enlarged view of hysteresis loop in low fields fig. 5. thermograms of the heating of pristine mnps (1) and encapsulated mnps (2) in the air 164 the thermograms for the initial fe mnps and mnps encapsulated by paam. both pristine mnps and encapsulated mnps exhibit weight gain (fig. 5a) in the process of heating. it is the result of the oxidation of iron by the atmospheric oxygen. there is clear difference in the total weight gain of these two samples. it stems from the decomposition of paam deposit on the surface of mnps, which effectively decreases the weight gain. the difference of the weight gain is ca 14 %. this value corresponds to the paam deposit on the surface of mnps. the thickness of this layer can be estimated using the residual amount of lpaam on the surface of mnps determined by thermal analysis. corresponding conversion into volume fraction taking into account the difference in densities of paam and fe core gives 40 % of polymer. the calculation of the thickness of a layer at the surface of the spherical particle with the diameter 90 nm gives ca 8 nm for the layer. meanwhile, this value corresponds to the dry layer of polymer on the surface. if the mnps are dispersed in water the polymeric layer swells and its thickness increases. if we assume that the conformation of paam macromolecules in the layer is a random gaussian coil, the volume fraction of a polymer in a coil is given by the following relation: ϕg n = 6 8 3 2/ (7) n is the number of monomeric segments in the chain. the number of kuhn segments for the molecular weight of paam (143.6 kda) is n = 500, which in turn gives φg = 0.08. it is a reasonable estimation for the volume fraction of paam in a swollen gaussian coil. thus, in water the volume of paam layer increases by a factor of 1/0.08 = 12.5. then, the thickness of a layer increases up to ca. 30 nm. (this value was used as a basic level in the theoretical calculations given above) fig. 6 presents multimodal distribution of particles/aggregates in water suspension of iron mnps encapsulated by paam. psd of iron mnps in water suspension comprises two peaks. the first one is positioned at 160–200 nm. this peak most likely corresponds to individual fe mnps in suspension. the estimation of the characteristic dimensions of encapsulated particle, which comprises 84 nm fe core and 30 nm paam steric protective layer on the surface gives ca 144 nm for the diameter. it is rather close to the position of the first peak at the psd plot. the second mode is positioned at ca 1000 nm. this peal obviously stans for the aggregates of mnps. the relative number fractions of these two peals are 90 % for the individual mnps and 10 % for large aggregates. it means that individual mnps dominate over aggregates in iron mnps suspension. qualitatively, this result is in agreement with the conclusions made based on the theoretical consideration, which favoured the possibility of de-aggregation of iron mnps if sterically stabilized by protective layers. fig. 6. multimodal psd of iron mnps in water suspension by dls 165 however, full de-aggregation was not achieved. the fraction of aggregates is still substantial. most likely it is due to high polydispersity of mnps. as it was shown in theory section the energy of interaction among mnps strongly depends on their radius. if the ensemble of mnps is polydisperse, then there is a large fraction of particles with enhanced interaction. this fraction obviously provides aggregation which can not be prevented by 30 nm paam layers. conclusions the factors of aggregation of fe magnetic nanoparticles (mean diameter 84  nm) in water suspension were analyzed using extended dlvo (derjaguinlandau-verwey-overbeek) approach. it is based on the balance among van der waals, electrostatic, magnetic and steric interactions. it was shown that attractive magnetic and repulsive steric interactions dominate over other in suspensions of fe mnps. as a result of their superposing the dependence of the energy of interaction between mnps exhibits minimum, which corresponds to the formation of aggregates of mnps. if the depth of the minimum is less than 20 kt, the aggregates can be disrupted by the thermal motion. the depth of the minimum is very sensitive to the size of mnp, to its magnetization, and to the thickness of the layer on its surface. it was shown that for fe mnps 84 nm in diameter and magnetization 100 ka/m the threshold of the stability corresponds to the protective layer 30 nm. to test the theory fe mnps synthesized by electrical explosion of wire were encapsulated by polyacrylamide in water suspension to provide steric repulsion. it was shown that the fraction of paam in the protective layer is around 14 % and it resulted in the efficient diminishing of the aggregation of metallic iron mnps in water. acknowledgement authors thank dr. k. balymov for performing the magnetic characterization of mnps, dr. a. i. medvedev and dr. a. m. murzakayev for special support. references 1. huber dl. synthesis, properties, and applications of iron nanoparticles. small. 2005;1(5):482-501. doi:10.1002/smll.200500006. 2. llandro j, palfreyman jj, ionescu a, barnes chw. magnetic biosensor technologies for medical applications: a review. med biol eng comput. 2010;48(10):977–98. doi:10.1007/s11517-010-0649-3. 3. lu ah, salabas el, schuth f. magnetic nanoparticles: synthesis, protection, functionalization, and application. angew chem int ed engl. 2007;46(8):1222–44. doi:10.1002/anie.200602866. 4. liu g, gao j, ai h, chen x. applications and potential toxicity of magnetic iron oxide nanoparticles. small. 2013;9(9–10):1533–45. doi:10.1002/smll.201201531 5. hiemenz pc, rajagopalan r. principles of colloid and surface chemistry. new york: marcel dekker, 1997. 499 p. isbn9780824793975. 166 6. kurlyandskaya gv, bhagat sm, safronov ap, beketov iv, 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b, de la cruz mo, grzybowski ba. electrostatics at the nanoscale. nanoscale. 2011;3(4):1316–44. doi:10.1039/c0nr00698j. 12. lim jk, majetich sa, tilton rd. stabilization of superparamagnetic iron oxide core−gold shell nanoparticles in high ionic strength media. langmuir. 2009;25(23):13384–93. doi:10.1021/la9019734. 13. rosensweig re. ferrohydrodynamics. usa: dover books on physics, 2014. 344 p. isbn9780486678344. 14. o’handley rc. modern magnetic materials. new york: john wiley & sons, 1972. 740 p. isbn978-0471155669. 15. jun yw, seo jw, cheon j. nanoscaling laws of magnetic nanoparticles and their applicabilities in biomedical sciences. acc chem res. 2008;41(2):179–89. doi:10.1021/ar700121f. cite this article as: shankar a, safronov a, beketov i. encapsulation of metallic iron magnetic nanoparticles by polyacrylamide in water suspensions. chimica techno acta. 2017;4(3):158–66. doi:10.15826/chimtech/2017.4.3.01. 6 d o i: 1 0. 15 82 6/ ch im te ch .2 01 8. 5. 1. 01 grivel j.-c. chimica techno acta. 2018. vol. 5, no. 1. p. 6–15. issn 2409–5613 j.-c. grivel department of energy conversion and storage, technical university of denmark, 399 frederiksborgvej, roskilde, dk-4000, denmark jean@dtu.dk subsolidus phase equilibria of the cuo – sro – zno pseudoternary system in air at 900 °c the subsolidus phase equilibria of the cuo – sro – zno system were determined at 900 °c in air. the pseudoternary section does not contain ternary oxide phases but is made of 5 three-phase regions and 2 narrow two-phase regions linked to a sr 14 cu 24–x zn x o 41–y solid solution. the maximum solubility of zn in this phase is limited to x ≈ 0.1, but this low doping level results in a significant decrease of the electrical resistivity by about one order of magnitude compared to the undoped compound. the other binary oxide phases srzno 2 , sr 2 cuo 3 , and srcuo 2 do not form solid solutions extending into the ternary system. srzno 2 was found to decompose upon contact with ambient air. keywords: phase equilibria, isothermal section, oxide systems, pseudoternary, cuo, sro, zno, spin-ladder, electrical resistivity received: 15.11.2017. accepted: 01.12.2017. published: 10.05.2018. © grivel j.-c., 2018 introduction the discovery of high-temperature superconductivity in the ba-doped la2cuo4 insulator [1] has initiated a wealth of research aiming at finding new compounds with ever higher superconducting critical temperatures, in particular among cuprate compounds. one of the strategies used for this purpose consists in studying the phase equilibria of pseudoternary and higher dimensional systems con taining cuo and an alkaline earth oxide, in particular bao, sro or cao. nevertheless, whereas ternary sections involving these oxides with rare-earth oxides have been systematically determined (refe rence [2] and references therein), combinations of cuo and (bao, sro or cao) with a transition metal oxide are still poorly investigated. in the case of sro, the exceptions encompass systems in which the transition element is v [3], nb [4, 5], fe [6], ti [7, 8], zr [8], hf [8], ta [9], w [10] and co [11]. the cuo – sro – zno system does not appear to have been stu died. however, zn being not magnetic, it represents a favo rable case for high-temperature superconductors. furthermore, the use of zno in association with sro or cuo for various applications [12–19] as well as that of srzno2 as a catalyst for pet depolymerization under microwave irradiation [20] or as host material for red or blue emitting phosphors [21, 22] make the study of this system interesting in view of optimizing the processing parameters of samples aimed at various technological 7 applications. the equilibration conditions for the present study (air atmosphere and 900 °c) correspond to conditions similar to those used for the synthesis of various high temperature superconductors [23, 24]. surprisingly, searches in databases such as the acers-nist phase equilibria diagrams database (version 4.0) or web of science did not deliver references to cuo – zno or sro – zno pseudobinary systems, not even as side-systems in ternary or higher dimensional systems so that even these simple combinations call for investigations. experimental cuo (alfa aesar, 99.995% purity), srco3 (sigma aldrich, 99.95) and zno (alfa aesar, 99.9%) powders were used as starting reagents. 33 different nominal compositions were selected and studied. after the powders were weighted in proper amounts, they were thoroughly mixed in an agate mortar and calcined at 900 °c for 60 h. after this first treatment and further grinding, 1 g pellets with 12 mm diameter were pressed under a pressure of 1.8 kbar and sintered at least twice at 900  °c for 100  h with intermediate grinding and re-pressing. the pellets were quenched in air at the end of each heat treatment. all manipulations were performed in air. the phase composition of the samples was determined using x-ray diffraction (xrd) patterns recorded in a bruker d8 robot diffractometer using cu kα radiation (λ  = 1.54  å). equilibrium was considered as achieved when no differences were detectable in the xrd patterns after two consecutive heat treatments. si powder was added as an internal standard after the heat treatments for lattice parameter calculations. low temperature electrical resistivity measurements were conducted in a displex setup with a dc current of 1 ma by the 4-contact method on samples cut from the pellets into parallelepipeds with 1.5 × 1.5 mm2 cross section and 8 mm length. gold wires were attached with silver paste cured at 200 °c. results and discussion as expected, the “zno” sample annealed at 900 °c consists of the zno (zincite) phase. its hexagonal lattice parameters were calculated as a = 3.250(1) å and c = 5.206(1) å, in close agreement with the values reported by mcmurdie et al. [25]. including small amounts (1 at.%) of either sr or cu in the nominal composition resulted in two-phase mixtures, as shown in fig. 1a, with the appearance of srzno2 or cuo peaks, respectively. the lattice parameters of these samples are compared with those of the pure zno composition in table 1. for the zn0.99sr0.01o2 nominal composition, the lattice parameters are unchanged within the standard deviation, whereas for zn0.99cu0.01o2, a slight decrease of the c-axis length seems to take place. the possibility of introducing sr into the zincite structure has been explored within various contexts such as modification of the optical and electrical properties of zno [12, 13], improving its photocatalytic properties [14, 15], or using sro as a sintering aid [15, 16]. conclusions on the actual doping of sr into zno are contradictory, probably due to the widely different preparation routes used for these various applications. güntürkun and toplan [16] (solid state reaction at 1000  °c to 1300  °c) found 8 a two-phase equilibrium between zno and srzno2 even for 1 wt.% sro in zno. harish et al. [14] (hydrothermal synthesis) reached a similar conclusion. in contrast, vijaran et al. [13] (thin films made by chemical bath deposition) as well as srivastava et al. [12] (thin films made by solution spin coating and annealing at 400 °c) claim that sr enters the zno structure. however, the lattice constants of zno show a nonmonotonic behavior versus doping level, with the c-axis parameter first decreasing before increasing. on the other hand, das et al. [15] (solid-state reaction at 1100 °c) observed a broadening of some zno xrd peaks at low sr doping level and concluded that two distinct zno phases with different lattice constants coexist. besides the fact that processing condicitons may induce different metastable situations, it is worth mentioning that the relatively low signal-to-noise ratio in the xrd patterns of the thin film samples [12, 13] makes the detection of low intensity impurity peaks difficult, while some high intensity xrd reflections of srzno2 have a near overlap with several zno reflections. the latter fact may partly be responsible for the reported behavior of the zno c-axis parameter upon sr doping [12, 13, 15]. in any case, there is a clear need for more systematic investigations in order to assess the actual solubility of sr in zno and its dependence on processing parameters. the present study allows concluding that for equilibration at 900 °c in air, the solubility of sr is clearly lower than 1 at.%. concerning cu substitution in zno, some recent publications, in which 5 at.% cu doped samples systematically show a clear cuo xrd impurity peaks [17, 18, 26], claim that a non-negligible amount of cu actually enters the zincite structure. again, the very different processing parameters, including hydrothermal systhesis [17], xerogel route [18] or sol-gel [26], all with relatively brief heat treatments at 600 °c or lower temperatures, certainly have an influence on the conclusions. moreover, no precise studies based on systematic lattice parameters variation were presented. the results of the present equilibration study at 900 °c are in fact more in line with other studies, including tem characterization showing that cuo nanoparticles segregate on the surface of zno crystallites even for 1 at.% cu doping [19]. the slight decrease of the zno c-axis length could be due to very low level cu doping (ppm range) as observed in zno samples exhibiting green luminescence [27]. the presence of cuo in the xrd pattern of the sample with zn0.99cu0.01o2 nominal stoichiometry indicates that there are no binary oxide compounds between zno and cuo. this is further confirmed by the fact that zno is detected in the xrd pattern of a sample with zn0.01cu0.99o2 overall composition (fig. 1b). in spite of this two-phase equilibrium, it is clear, as shown in table 1, that the presence of zn has resulted in changes in the lattice parameters of cuo, with, in particular, a significant fig. 1. xrd patterns of samples with zno (a), zn0.99cu0.01o2 (b), zn0.99sr0.01o2 (c), cuo2 (d) and cu0.99zn0.01o2 (e) nominal compositions: u – zno, l – cuo, m – srzno2 9 decrease of the b-axis length and increase of the a-axis parameter (as well as an increase of the β-angle from 99.5° to 99.7°). the unambiguous detection of low-intensity zno reflections in the xrd pattern of the cu0.99zn0.01o2 sample, however, indicates that at 900 °c the solubility limit of zn into cuo is lower than 1 at. %. similar lattice parameter variations upon zn doping in cuo had beed reported previously [28]. prabhakaran and boothroyd [29] report up to 5 at. % zn doping, but the pro cessing conditions in that case (single crystals grown by the floating-zone method under 4 to 8 atm pressure) mostly provide a hint that the solubility limit of zn in cuo might increase with temperature and may also show some dependence on the oxygen pressure. in the sro – zno binary oxide side system, srzno2 was the only binary oxide phase detected in the xrd patterns. the lattice parameters of samples with sr0.98zn1.02o2, sr1.00zn1.00o2 and sr1.02zn0.98o2 (table 1) show little variation that is well inside the confidence interval. this observation, coupled with evidence for two-phase equilibria in the two samples with nominal composition deviating from srzno2 (fig.  2), indicates that the latter phase has a very narrow solid-solution range, if any. it is worth mentioning that the formation on sro in the sr-rich table 1 phases observed in selected samples after equilibration and crystallographic data for the majority phases. phases listed between brackets are minority phases. z = zno, c = cuo, sz = srzno2, soh = sr(oh)2·h2o, s2c = sr2cuo3, sc = srcuo2, s14c = sr14cu24o41–y nominal composition phases space group a [å] b [å] c [å] zno z p63mc 3.250(1) – 5.206(1) zn0.99cu0.01o z (c) p63mc 3.251(1) – 5.203(1) zn0.99sr0.01o z (sz) p63mc 3.251(1) – 5.206(1) sr1.00zn1.00o2 sz pnam 5.843(9) 3.339(7) 11.33(4) sr0.98zn1.02o2 sz (z) pnam 5.841(9) 3.340(8) 11.33(4) sr1.02zn0.98o2 sz (soh) pnam 5.843(9) 3.340(7) 11.33(4) sr1.00zn0.98cu0.02o2 sz (z, s2c) pnam 5.843(9) 3.339(7) 11.33(4) sr0.98zn1.00cu0.02o2 sz (z, s2c) pnam 5.841(9) 3.339(7) 11.33(4) cuo c c2/c 4.686(2) 3.424(1) 5.129(1) cu0.99zn0.01o c (z) c2/c 4.702(1) 3.410(1) 5.132(1) sr2cuo3 s2c immm 12.70(1) 3.912(1) 3.499(1) sr2cu0.95zn0.05o3 s2c (sz, soh) immm 12.71(1) 3.914(2) 3.501(1) srcuo2 sc cmcm 3.572(1) 16.328(3) 3.913(2) srcu0.95zn0.05o2 sc (z, s2c) cmcm 3.571(1) 16.329(2) 3.912(1) sr14cu24o41 s14c cccm 11.467(3) 13.395(7) 27.649(6) sr14cu23.9zn0.1o41 s14c cccm 11.468(4) 13.396(10) 27.552(8) sr14cu23.75zn0.25o41 s14c cccm 11.475(5) 13.391(11) 27.564(14) sr14cu23.5zn0.5o41 s14c (z, sc) cccm 11.467(3) 13.394(8) 27.532(7) sr14cu23zn1o41 s14c (z, sc) cccm 11.469(3) 13.394(6) 27.532(5) 10 composition is assumed from the detection of sr(oh)2·h2o [30] in the xrd pattern. this assumption is supported by the fact that a sample with a composition closer to pure sro (sr0.99zn0.01o – not shown), still contained some identifiable sro reflections. the sr(oh)2·h2o compound appears to form quickly upon exposure to the atmosphere. the xrd pattern of the sr1.02zn0.98o2 sample (fig. 2b) was recorded within less than 1 hour after quenching from 900 °c. in view of potential applications of srzno2, it is also important to note that this compound degrades at a moderate rate when exposed to ambient air. after two weeks, formation of srco3 was ascertained in the originally single-phase srzno2 sample. in the cuo – sro pseudobinary side system, the three binary oxide phases sr2cuo3, srcuo2 and sr14cu24o41–y were found as expected [31–36]. replacing 5 at. % of cu by zn in the respective compositions of these compounds resulted in samples with equilibrium between three phases. the lattice parameters of sr2cuo3 and srcuo2 (table 1) were not affected by the presence of zn within the confidence interval. in contrast, while the aand b-axis lengths of sr14cu24o41–y were not influenced, it appears that the c-axis lattice parameter became significantly shorter at a zn substitution level for cu of 0.4 at. % only. the xrd patterns of samples with sr14cu24–xznxo41–y (x = 0.00; 0.10; 0.50 and 1.00) nominal compositions are shown in fig. 3, where it is observed that zno and srcuo2 reflections appear beyond x = 0.10 in agreement with the saturation of the c-axis parameter value (table 1 and inset in fig. 4). the effect of zn substitution on the sr14cu24o41–y phase was studied further by means of electrical conductivity measurements. as demonstrated by fig. 4, the room-temperature resistivity of sr14cu23.9zn0.1o41–y is lower than that of sr14cu24o41–y, the difference increasing at lower temperatures to reach one order of magnitude at 175 k. in the sr14cu23.75zn0.25o41–y sample, the resistivity is even lower. although the lattice parameters are not changed as compared with the sr14cu23.9zn0.1o41–y composition, it is likely that this further decrease in resistivity is related to a little more zn doping into the sr14cu24o41–y lattice (albeit not all the zn has entered the structure), instead of being due to minute amounts of impufig. 2. details of the xrd patterns of samples with sr0.98zn1.02o2 (a) and sr1.02zn0.98o2 (b) nominal compositions showing 2θ ranges, where the appearance of secondary phases is most evident: m – srzno2, u – zno, q – sr(oh)2·h2o. fig. 3. xrd patterns of sr14cu24–xznxo41–y samples with x = 0.00 (a), 0.10 (b) 0.50 (c) and 0.10 (d): l – sr14cu24o41–y, m – srcuo2, u – zno 11 rity phases. this hypothesis is based on the fact that the samples with higher nominal zn contents, i.e. sr14cu23.5zn0.5o41–y and sr14cu23zn1o41–y, exhibit higher resistivities (not shown in fig. 4). nominal compositions situated further within the pseudoternary section resulted in two-phase or three-phase equilibria, without any evidence for the formation of ternary oxide phases. based on all these observations, the phase equilibria and tieline compatibilities of phases in the cuo – sro – zno system at 900 °c in air can be summarized as shown in fig. 5. the section contains 5 three-phase regions and 2 narrow two-phase fields associated to the sr14cu24–xznxo41–y solid solution. this system is dominated by zno, which is in equilibrium with all other binary oxide phases. the overall structure of this section is rather different from those of the other systems involving cuo, sro and a transition element oxide [37–51]. the solubility limit of co in the sr14cu24o41–y structure (up to sr14cu19co5o41–y) is significantly larger than that of zn. in cuo – sro – re2o3 systems (re = rare earth element), re substitution in sr14cu24o41–y also takes place to various extents [37–51], however on the sr sites rather than on the cu sites, and the pseudoternary sections are dominated by srre2o4 compounds. conclusions the subsolidus relationship and phase formation of compounds in the cuo  – sro  – zno system were determined at 900  °c in air. the pseudoternary phase diagram is divided into 5 three-phase fields and two narrow two-phase fields are induced by the narrow sr14cu24znxo41–y (0 ≤ x ≈ 0.1) solid solution. some zn substitution in cuo can also be inferred from the variation of the lattice parameters of cuo, but the solubility limit of zn in cuo under the present equilibration conditions is lower than 1 at. %. substitution of zn for cu in the sr14cu24o41–y structure has a very strong effect on its electrical resistivity. the fact that zno is in equilibrium with all the other phases save sro represents a  favorable situation for processing and testing various properties of zno-based multiphase nanoparticles and films. fig. 4. low-temperature electrical resistivity of samples with nominal compositions belonging to the sr14cu24–xznxo41–y solid solution. inset: c-axis lattice parameter of the sr14cu24o41–y phase in samples with nominal sr14cu24–xznxo41–y (0.0 ≤ x ≤ 1.0) compositions fig. 5. phase diagram of the cuo – sro – zno pseudoternary system at 900 °c in air. the studied compositions are marked by symbols. the sro – srzno2 – sr2cuo3 area was not studied in details due to the fast reaction of sro with ambient air 12 references 1. bednorz jg, muller ka. possible high-tc superconductivity in the ba-la-cu-o system. zeitschrift für physik. 1986; b64:189–93. doi: 10.1007/bf01303701. 2. grivel jc. subsolidus phase relations of the cao – reox – cuo systems (re = eu, tb, dy, ho, er, lu and sc) at 900 °c in air. j 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grivel jc, andersen nh. subsolidus phase relations of the sro – re2o3 – cuo systems (re  = tm, lu and sc). j alloys compd. 2005;391:292–5. doi: 10.1016/j.jallcom.2004.08.077. 51. grivel jc, andersen nh. subsolidus phase relations of the sro – reox – cuo systems (re  = ce, pr and tb). j alloys compd. 2007;436:261–5. doi: 10.1016/j.jallcom.2006.07.020. 28 do i: 1 0. 15 82 6/ ch im te ch .2 01 5. 2. 1. 00 3 lyagaeva ju. g., medvedev d. a. institute of high-temperature electrochemistry ub ras, 20 akademicheskaya street, 620990 ekaterinburg fax: +7(343) 374 5992; phone: +7(343)3623263; e-mail: yulia.lyagaeva@ya.ru structure and transport properties of composite materials on a basis of ce 0.8 nd 0.2 o 2–δ and bace 0.8 nd 0.2 o 3–δ * in the present work the synthesis of materials was carried out by one-step citrate-nitrate method. the optimal synthesis temperature of the powders was chosen on the base of tg-dsc data. phase nature of the synthesized materials was investigated by xrd and rietveld refinement data analyzes. the influence of the perovskite phase content in the system of (1–x)ce 0.8 nd 0.2 o 2–δ – xbace 0.8 nd 0.2 o 3–δ (x = 0 , 0.25, 0.5 , 0.75 and 1) on the crystallite and particle size of powders and structure properties of ceramics (relative density, porosity, grain size) were investigated. measurements of the electrical conductivity of materials in a wide ranges of temperatures (550–900 °c) and oxygen partial pressure (10-23 ≤ po 2 /atm ≤ 0,21) revealed features of transport in the composite system. *this work was done underfinancial support rfbr grant 13-03-00065, 12-03-33002) and council for grants of the president of the russian federation (nsp-44.2012.1) introduction materials based on barium cerate and ceria attract attention as potential electrolytes for intermediate temperature solid oxide fuel cells (it-sofc). a new trend in the development of electrolyte systems appeared recently: creation of composite materials such as perovskitefluorite. composite electrolytes have the advantage compared to the reference materials: reduced electronic conductivity in reducing and oxidizing atmospheres(1), thermodynamic stability in reducing environments and co2 and h2o-containing atmospheres(2). relatively equal values of thermal coefficients of linear expansion (cte)-of oxides based on ceo2 and baceo3 also favorable for their joint use as composites(3). the purpose of this paper is to i) synthesize and study the peculiarities of obtaining previously non-researched composites (1–x) ce0.8nd0.2o2–δ– xbace0.8nd0.2o3–δ (x = 0, 0.25, 0.5, 0.75 and 1) and ii) study their mechanothermal, electrical and electrochemical properties. © lyagaeva ju. g., medvedev d. a., 2015 30 № 1 | 2015 chimica techno acta results and discussion in this paper we obtain the materials by the one-step citrate-nitrate method. based on tga-dsc analysis and mass spectroscopy it was indicated that the mass of powders stops changing at 1150 °c (see fig. 1). since the tga was carried out in the dynamic mode, the materials synthesis temperatures have been slightly lowered to 1100 °c with exposure to these conditions for 3 h. xrf results for the synthesized powders (1–x) ce0.8nd0.2o2–δ– xbace0.8nd0.2o3–δ are shown in fig. 2 for materials ce0.8nd0.2o2–δ and bace0.8nd0.2o3–δ on x-ray reflections only related to the phases of fluorite (fm3m) and perovskite (orthorhombic distortion, pmcn), respectively, are present. composite materials according to xrf are biphasic and contain no contaminants or phase interaction. however, it should be noted that the composition with x = 0.75 intensity of reflections corresponding to fluorite phase, is small compared to the expected level. this may be due to the partial dissolution of fluorite phase in perovskite. indeed, for the interval 0.75 <h≤1 (see fig. 2) radiographs recorded only reflections corresponding to the isostructural phase of orthorhombic baceo3. refinement of the structure and the lattice parameters for the materials of the system (1–x) ce0.8nd0.2o2–δ– xbace0.8nd0.2o3–δ was carried out by rietveld method. the convergence of the theoretical curves with the experimental data was estimated by bregg-and structural factors that do not exceed 0.87 and 1.02 for the cubic structure, and 1.64 and 2.10 for the orthorhombic structure, respectively. with the increase in concentration of the perovskite phase, the crystal lattice parameters of the orthorhombic structure are almost unchanged, whereas the parameters of the cubic structure are reduced. perhaps this is connected to the assumption about the solubility of a certain amount of cerium phase in barium cerate. part of fluorite with perovskite can form a solid fig. 1. tga and the ion current to the powder bace0.8nd0.2o3-δ, prepared by citrate-nitrate method fig. 2. radiographs of the synthesized powders (1–x) ce0.8nd0.2o2–δ–xbace0.8nd0.2o3–δ at 0≤h≤1 (top) and 0.75≤h≤1 (bottom) structure and transport properties of composite materials on a basis of ce 0.8 nd 0.2 o 2-δ and bace 0.8 nd 0.2 o 3-δ 32 № 1 | 2015 chimica techno acta solution of varied formulation with the same lattice parameters. simultaneously with this solution fluorite phase coexists, which may be enriched with neodymium, which causes a slight increase in the lattice parameter due to the influence of the size factor. ceramic samples were prepared by hydrostatic pressing of the powders, followed by sintering at 1500 °c for 3 hours (see fig. 3). all materials have a high relative density (93.2–96.5% depending on the formulation). for a qualitative evaluation of the microstructure surface of the sintered ceramics the size of each grain was determined, based on which histograms of particle size distribution and average grain size were calculated. the average grain size does not depend significantly for composites and varies from 1.2 to 1.7 microns. in contrast, for the ceramic base ce0.8nd0.2o2–δ materials and bace0.8nd0.2o3–δ the mean grain size is increased to 3.7 and to 7.8 microns, respectively. the temperature dependence of the conductivity of (1–x) ce0.8nd0.2o2–δ– xbace0.8nd0.2o3–δ materials is shown in fig. 4. it shows that the total conductivity of the composite material in a wet air is lower as compared to the basic oxides. a similar trend was observed for composite systems of (100–x) ce0.8y0.2o2–δ–bace0.7zr0.1y0.2o3–δ (x = 0, 20, 30, 50, 70 and 100 wt.%) and 4 (1–x) ce0.8gd0.2o2–δ–xbace0.8gd0.2o3–δ (x = 0, 0.2, 0.3 and 0.4) 1. in the first case, low conductivity of composite materials in comparison with the base ce0.8y0.2o2–δ and xbace0.7zr0.1y0.2o3-δ is attributed by the authors to the appearance of poorly conducting phases based on ba2yzro6 and ba2zro4, which appear to localize at grain boundaries and limit the process of electrotransport(4). in the second case, a low conductivity as compared to ce0.8gd0.2o2–δ and bace0.8gd0.2o3–δ composites is associated with high contact resistance of phase(1) interface that may be implemented in this case. high contact resistance at the interface of two different sorts of grain must necessarily lead to fig. 3. microphotograph of the surface of (1–x) ce0.8nd0.2o2–xbace0.8nd0.2o3–δ: x = 0 (a), x = 0.25 (b), x = 0.5 (c), x = 0.75 (d), x = 1 (e) fig. 4. temperature dependence of the conductivity of the (1–x) ce0.8nd0.2o2–δ– xbace0.8nd0.2o3–δ ceramics in the humid air. inset: concentration dependence of the conductivity activation energy in the low-and high-temperature ranges lyagaeva ju. g., medvedev d. a. 34 № 1 | 2015 chimica techno acta an increase in activation energy of the overall conductivity of composites (inset in fig. 4). note that the sample with x = 0.5 has the maximum ea, and at the same time has the lowest conductivity in (1–x) ce0.8nd0.2o2–δ–xbace0.8nd0.2o3–δ. thus, the concentration dependence of the activation energy in the composite system of the growth of the perovskite phase passes through a maximum. by the level of activation energy in the low and high ranges the sample with x = 0.25 is similar to ce0.8nd0.2o2–δ. this may indicate that the conductivity of the material is controlled primarily by fluorite phase. for composites with x = 0.5 and 0.75, the conductivity is apparently controlled by perovskite phase. the decrease in the grain size of ceramics (or an increase in their unit area of contact) can also be considered as the cause of the overall conductivity reducing of the composite systems. materials conductivity has also been investigated in relation to partial pressure of oxygen (po2) at 600, 700, 800 and 900 °c. the dependences obtained were processed using the emperic equation, σtotal = σe,o ∙ (po2) –1/4 + σion,o + σp,o ∙ (po2) 1/4, where σtotal – total conductivity, σion, o – ionic conductivity (const.), σp, o – hole conductivity at po2 = 1 atm. the analysis results are presented in the form of concentration dependences of partial conductivities (see fig. 5). the concentration dependence of the ionic conductivity at 600–900 °c (fig. 5a) corresponds to the data shown above (see fig. 4). comparison of ea and total ionic conductivity (see fig. 4) indicates predominantly ionic conductivity type as for the composite materials and for basic systems. electronic conductivity decreases with increasing content of the perovskite phase in the system of (1–x) ce0.8nd0.2o2–δ– xbace0.8nd0.2o3–δ to x = 0.5 (see fig. 6b). for samples with x = 0.75 and 1 electronic conductivity, according to the analysis data, is less than 1% in the total. hole conductivity appears for samples with 0.5≤h≤1 and increases with the increase of x (see fig. 6c). the activation energy of the hole and electron conductivity for fig. 5. concentration dependence of the ion (a), electron (b) and hole (c) conductivity and activation energy for (1–x) ce0.8nd0.2o2–δ– xbace0.8nd0.2o3–δ ceramics in the wet air a b c structure and transport properties of composite materials on a basis of ce 0.8 nd 0.2 o 2-δ and bace 0.8 nd 0.2 o 3-δ 36 № 1 | 2015 chimica techno acta the system «perovskite-fluorite» tend to be higher than for basic oxides as ce0.8nd0.2o2–δ and bace0.8nd0.2o3–δ, which confirms the phenomenon of blocking both the electron and hole conductivity in composites(1–3). despite lower ionic conductivity of composites, they show better thermodynamic and kinetic stability under longterm tests and in redox cycles (see fig. 6) than basic materials. it was found that after two redox cycles at 900 °c conductivity of ce0.8nd0.2o2–δ decreases lower to 85% relatively the initial level. possible reason for the sharp drop of conductivity is fractures in ceramics fixed by sem, which appear due to the partial reduction/ oxidation of cerium ions (see fig. 7). changing of the cerium oxidation state is accompanied by resolution of the crystal lattice vibrations, so repetition of redox cycles leads to mechanical instability of ceramics. for bace0.8nd0.2o3–δ material conductivity after 2 cycles is reduced to 30% relatively the initial level. perhaps this is due to the localization of different types of point defects at the grain boundaries. during several redox cycles three-dimensional defects (microcracks) are formed along grain boundaries due to congestion and interaction of point defects. degradation of composite materials in terms of conductivity does not exceed 15%. according to sem of ceramic samples, localized pores are noticed on the surface, which lead to an substantial decrease in conductivity. conclusion in this paper we have obtained new composite materials based on cerium oxide and barium cerate by using citratenitrate method, and studied their transport properties. the total composite electrolyte conductivity in wet air is lower than that of the base materials due to high specific resistance and interfacial contact area of the grains. the concentration dependence of the activation energy of conductivity for (1–x) ce0.8nd0.2o2–δ–xbace0.8nd0.2o3–δ has a minimum at x = 0.5. despite the low conductivity of the composite ceramics, they are characterized by small contributions of electronic components (conductivity of nand p-types), as well as betfig. 6 time dependence of the conductivity of (1–x) ce0.8nd0.2o2–δ–xbace0.8nd0.2o3–δ materials at 900 °c. a corresponds to an atmosphere with po2 = 0.21 atm, b-po2 = 1 atm ∙ 10–18 fig. 7 chemical expansion of ceramic (1–x) ce0.8nd0.2o2–δ–xbace0.8nd0.2o3–δ materials at 900 °c lyagaeva ju. g., medvedev d. a. 38 № 1 | 2015 chimica techno acta ter thermodynamic and kinetic stability, which suggests that such materials are promising electrolytes for it-sofc. the experimental part materials of formulation of (1–x) ce0.8nd0.2o2–δ–xbace0.8nd0.2o3–δ (x = 0, 0.25, 0.5, 0.75 and 1) were prepared by citrate-nitrate technology which features are presented in (3). the powders of the desired formulation were was synthesized and sintered on the basis of tga-dsc analysis and dilatometry at 1500 °c, respectively. crystal, microstructural properties of materials have been studied by rfa (dmax-2500 rigaku) and sem (jsm-5900 lv), respectively. materials conductivity has been examined by 4 probe method at constant current over a wide range of temperatures (550–900 °c) and oxygen partial pressure (atm 10-230.21) using zirconia-controller 3185. 1. venkatasubramanian a., copalan p., prasanna t. synthesis and characterization of electrolytes based on bao–ceo2–gdo1.5 system for intermediate temperature solid oxide fuel cells. international journal of hydrogen energy. 2010; 35(10):4597– 4605. doi: 10.1016/j.ijhydene.2010.02.037. 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[google scholar]. structure and transport properties of composite materials on a basis of ce 0.8 nd 0.2 o 2-δ and bace 0.8 nd 0.2 o 3-δ 29 ю. г. лягаева, д. а. медведев фгбун институт высокотемпературной электрохимии уро ран, 620990, г. екатеринбург, ул. академическая, 20. факс: (343) 374-59-92; тел.: (343) 362-32-63; e-mail: yulia.lyagaeva@ya.ru структура и транспортные свойства композитных материалов на основе ce 0,8 nd 0,2 o 2-δ и bace 0,8 nd 0,2 o 3-δ * в настоящей работе проведен синтез материалов путем одностадийного цитрат-нитратного метода. с привлечением данных тг-дск анализа установлены оптимальные температуры синтеза порошков. фазовые особенности синтезированных материалов изучены рфа с привлечением метода ритвелда. установлено влияние содержания перовскитной фазы в системе (1–x)ce 0,8 nd 0,2 o 2–δ –xbace 0.8 nd 0,2 o 3-δ (х = 0; 0,25; 0,5; 0,75 и 1) на размеры кристаллитов и частиц порошка. исследованы керамические свойства (относительная плотность, пористость, размеры зерен) образцов, спеченных при 1500 °с. исследование электропроводности материалов в широких интервалах температур (550–900 °с) и парциальных давлений кислорода (10-23 ≤ ро 2 /атм ≤ 0,21) позволило выявить особенности электропереноса в системе (1–x)ce 0,8 nd 0,2 o 2–δ –xbace 0,8 nd 0,2 o 3–δ . *работа выполнена при поддержке рффи (№ 13-03-00065, 12-03-33002), а также совета по грантам президента рф (№ сп-44.2012.1). у д к 6 61 .7 41 +6 61 .7 23 -1 3 введение материалы на основе церата бария и оксида церия привлекают повышенное внимание как потенциальные электролиты для среднетемпературных твердооксидных топливных элементов (it-sofc). в последнее время новой тенденцией в области развития электролитных систем является создание композитных материалов типа перовскит-флюорит. композитные электролиты имеют преимущество по сравнению с базовыми материалами: сниженную электронную проводимость в восстановительной и окислительной атмосферах [1], термодинамическую устойчивость в восстановительных средах и со2 и н2о-содержащих атмосферах © лягаева ю. г., медведев д. а., 2015 31 № 1 | 2015 chimica techno acta [2]. близкие значения термических коэффициентов линейного расширения (тклр) оксидов на основе ceo2 и baceo3 также благоприятны для их совместного использования в качестве композитов [3]. целью данной работы является 1) синтез и исследование особенностей получения ранее не изученных композитных (1–x)ce0,8nd0,2o2–δ–xbace0,8nd0,2o3–δ (х = 0; 0,25; 0,5; 0,75 и 1) материалов, и 2) исследования их механотермических, электрических и электрохимических свойств. результаты и обсуждение в настоящей работе получение материалов проведено путем одностадийного цитрат-нитратного метода. на основании тг-дск анализа и масс-спектроскопии установлено, что изменение массы порошков заканчивается при 1150 °с (рис. 1). поскольку тг-анализ был проведен в динамическом режиме, температуры синтеза материалов были несколько снижены и составляли 1100 °с с выдержкой в этих условиях в течение 3 ч. результаты рфа для синтезированных порошков (1–x)ce0,8nd0,2o2–δ– xbace0,8nd0,2o3–δ представлены на рис. 2. для материалов ce0,8nd0,2o2–δ и bace0,8nd0,2o3–δ на рентгенограммах присутствуют только рефлексы, относящиеся к фазам флюорита (fm3m) и перовскита (орторомбическое искажение, pmcn), соответственно. композитные материалы, согласно рфа, являются двухфазными и не содержат примесей или фаз взаимодействия. однако стоит отметить, что для состава х = 0,75 интенсивность рефлексов, соответствующих фазе флюорита, мала по сравнению с ожидаемым уровнем. это может быть связано с частичным растворением флюоритной фазы в перовскитной. действительно, для интеррис. 1. тг и ионный ток для порошка bace0,8nd0,2o3–δ, полученного цитрат-нитратным методом рис. 2. рентгенограммы синтезированных порошков (1–x)ce0,8nd0,2o2–δ–xbace0,8nd0,2o3–δ при: а – 0 ≤ х ≤ 1; б – 0,75 ≤ х ≤ 1 структура и транспортные свойства композитных материалов на основе ce 0,8 nd 0,2 o 2-δ и bace 0,8 nd 0,2 o 3-δ 33 № 1 | 2015 chimica techno acta вала 0,75 < х ≤ 1 (рис. 2) на рентгенограммах фиксируются только рефлексы, соответствующие фазе, изоструктурной орторомбическому baceo3. уточнение структуры и параметров кристаллической решетки для материалов системы (1–x)ce0,8nd0,2o2–δ– xbace0,8nd0,2o3–δ было проведено по методу ритвелда. сходимость теоретических кривых с экспериментальными данными оценивалась брэгги структурным факторами, которые не превышали 0,87 и 1,02 для кубической структуры и 1,64 и 2,10 для орторомбической структуры соответственно. с увеличением концентрации перовскитной фазы в системе параметры кристаллической решетки орторомбической структуры практически не изменяются, в то время как параметры кубической структуры уменьшаются. возможно, это связано с предположением о растворимости некоторого количества цериевой фазы в церате бария. часть флюорита с перовскитом может образовывать твердый раствор переменного состава с неизменными параметрами кристаллической решетки. одновременно с данным раствором сосуществует флюоритная фаза, которая может быть обогащена неодимом, что и вызывает некоторое увеличение в параметрах кристаллической решетки из-за влияния размерного фактора. керамические образцы были получены путем гидростатического прессования порошков с последующим спеканием при 1500 °с в течение 3 ч (рис. 3). все материалы характеризуются высокой относительной плотностью (93,2–96,5 % в зависимости от состава). для качественной оценки микроструктуры поверхности спеченной керамики были определены размеры каждого зерна, на основании чего построены гистограммы распределения частиц по размерам и вычислен средний размер зерен. средний размер зерен не зависит значимо для композитных материалов и изменяется с 1,2 до 1,7 мкм. напротив, для базовых керамических материалов ce0,8nd0,2o2–δ и bace0,8nd0,2o3–δ средний размер зерен увеличивается до 3,7 и 7,8 мкм соответственно. температурные зависимости проводимости материалов (1–x)ce0,8nd0,2o2–δ– xbace0,8nd0,2o3–δ представлены на рис. 4. видно, что общая проводимость композитных материалов во влажном воздухе ниже по сравнению с базовыми оксидами. аналогичная тенденция была отмечена для композитных систем состава (100–x)ce0,8y0,2o2–δ– xbace0,7zr0,1y0,2o3–δ (x = 0; 20; 30; 50; 70 и 100 мас.%) [4] и (1–x)ce0,8gd0,2o2–δ– xbace0,8gd0,2o3–δ (х = 0; 0,2; 0,3 и 0,4) рис. 3. микрофотографии поверхности (1–x)ce0,8nd0,2o2–xbace0,8nd0,2o3–δ: а – x = 0, б – x = 0,25, в – x = 0,5, г – x = 0,75, д – x = 1 лягаева ю. г., медведев д. а. 35 № 1 | 2015 chimica techno acta [1]. в первом случае более низкую проводимость композитных материалов по сравнению с базовыми ce0,8y0,2o2–δ и xbace0,7zr0,1y0,2o3–δ авторы связывают с появлением плохопроводящих фаз на основе ba2yzro6 и ba2zro4, которые, по-видимому, локализуются на границах зерен и лимитируют процесс электропереноса [4]. во втором случае низкая проводимость композитов по сравнению с ce0,8gd0,2o2–δ и bace0,8gd0,2o3-δ связана с высоким контактным сопротивлением границы раздела фаз [1], что может реализовываться и в нашем случае. высокое контактное сопротивление на границе двух зерен различного сорта непременно должно приводить к увеличению энергии активации общей проводимости композитов (вставка на рис. 4). отметим, что максимальный ea имеет образец с х = 0,5, который в тоже время обладает наименьшей проводимостью в (1–x)ce0,8nd0,2o2–δ–xbace0,8nd0,2o3–δ. таким образом, концентрационная зависимость энергии активации в композитной системе с ростом перовскитной фазы проходит через максимум. по уровню энергии активации в низко и высокотемпературных интервалах образец с х = 0,25 сходен с ce0,8nd0,2o2-δ. это может указывать на то, что проводимость данного материала контролируется преимущественно флюоритной фазой. для композитов с х = 0,5 и 0,75, по-видимому, проводимость контролируется перовскитной фазой. уменьшение размеров зерен керамики (или увеличение их удельной площади контакта) может также рассматриваться причиной снижения общей проводимости композитных систем. проводимость материалов также была исследована в зависимости от парцаильного давления кислорода (pо2) при 600, 700, 800 и 900 °с. полученные зависимости были обработаны с помощью эмперического уравнения σtotal = σe,o ∙ (po2) –1/4 + σion,o + σp,o ∙ (po2) 1/4, где σtotal – общая проводимость, σion,o – ионная проводимость (const), σp,o – дырочная проводимость при pо2 = 1 атм. результаты анализа представлены в виде конценрационных зависимостей парциальных проводимостей (рис. 5). концентрационные зависимости ионной проводимости при 600–900 °с (рис. 5a) соответствует представленным выше данным (рис. 4). сопоставление еа ионной и общей проводимости (рис. 4) свидетельствует о преимущественно ионном типе проводимости как для композитных материалов, так и для базовых систем. электронная проводимость уменьшается с ростом содержания перовскитной фазы в системе (1–x) ce0,8nd0,2o2–δ–xbace0,8nd0,2o3–δ до х = 0,5 (рис. 6б). для образцов с х = 0,75 и 1 электронная проводимость, согларис. 4. температурные зависимости проводимости керамики (1-x)ce0,8nd0,2o2-δ xbace0,8nd0,2o3-δ во влажном воздухе. вставка: концентрационные зависимости энергии активации проводимости в низко и высокотемпературном интервалах структура и транспортные свойства композитных материалов на основе ce 0,8 nd 0,2 o 2-δ и bace 0,8 nd 0,2 o 3-δ 37 № 1 | 2015 chimica techno acta сно проведенному анализу, составляет менее 1 % от общей. дырочная проводимость проявляется для образцов с 0,5 ≤ х ≤ 1 и увеличивается с ростом х (рис. 5в). энергии активации дырочной и электронной проводимости для системы «перовскит – флюорит», как правило, выше, чем для базовых оксидов ce0,8nd0,2o2–δ и bace0,8nd0,2o3–δ, что подтверждает явление блокирования как электронной, так и дырочной проводимости в композитах [1–3]. несмотря на более низкую ионную проводимость композитов, они показывают лучшую термодинамическую и кинетическую устойчивость в условиях долговременных испытания и редокс-циклах (рис. 6), чем базовые материалы. было установлено, что после 2 редокс-циклов при 900 °с проводимость ce0,8nd0,2o2–δ уменьшается на 85 % относительно начального уровня. возможной причиной резкого падения проводимости является зафиксированные методом рэм трещины в керамике, которые появляются вследствие частичного восстановления/окисления ионов церия (рис. 7). изменение степени окисления церия сопровождается рис. 5. концентрационные зависимости ионной (а), электронной (б) и дырочной (в) проводимости и их энергии активации для керамики (1–x)ce0,8nd0,2o2–δ– xbace0,8nd0,2o3–δ во влажном воздухе рис. 6. временная зависимость проводимости материалов (1–x) ce0,8nd0,2o2-δ-xbace0,8nd0,2o3-δ при 900 °c. a соответствует атмосфере с po2 = 0,21 атм, b – рo2=1·10 -18 атм рис. 7. химическое расширение керамических материалов (1–x) ce0,8nd0,2o2–δ–xbace0.8nd0,2o3–δ при 900 °c а б в лягаева ю. г., медведев д. а. 39 № 1 | 2015 chimica techno acta колебаниями размера кристаллической решетки, поэтому многократное повторение редокс-циклов приводит к механической нестабильности керамики. для материала bace0,8nd0,2o3–δ проводимость после 2 циклов уменьшается на 30 % относительно начального уровня. возможно, это связано с локализацией точечных дефектов различных типов на границах зерен. в процессе нескольких редокс-циклов происходит образование трехмерных дефектов (микротрещин) вдоль границ зерен вследствие скопления и взаимодействия точечных дефектов. деградация композитных материалов в терминах проводимости не превышает 15 %. согласно рэм этих керамических образцов, на поверхности фиксируются локальные поры, которые приводят к несущественному уменьшению проводимости. заключение в настоящей работе получены новые композитные материалы на основе оксида церия и церата бария цитратнитратным методом, а также изучены их транспортные свойства. общая проводимость композитных электролитов во влажном воздухе ниже, чем для базовых материалов вследствие высокого межфазного сопротивления и удельной площади контакта зерен. концентрационная зависимость энергии активации проводимости для (1–x)ce0,8nd 0,2o 2–δ–xbace 0,8nd 0,2o 3–δ имеет минимум при х = 0,5. несмотря на более низкую проводимость композитной керамики, они характеризуются малыми вкладами электронных составляющих (проводимоть nи p-типа), а также лучшей термодинамической и кинетической устойчивостью, что позволяет считать такие материалы перспективными электролитами для it-sofc. экспериментальная часть материалы состава (1–x) ce0.8nd0.2o2–δ–xbace0.8nd0,2o3–δ (х = 0; 0,25; 0,5; 0,75 и 1) были получены по цитрат-нитратной технологии, особенности которой представлены в [3]. порошки требуемого состава синтезировали и спекали на основании данных тг-дск анализа и дилатометрии при и 1500 °с, соответственно. кристаллические, микроструктурные свойства материалов были изучены рфа (dmax-2500 rigaku) и рэм (jsm-5900 lv) соответственно. проводимость материалов исследовали 4-зондовым методом на постоянном токе в широких интервалах температур (550–900 °с) и парциальных давлений кислорода (10–23–0,21 атм) с помощью регулятора zirconia-318 [5]. 1. venkatasubramanian a., gopalan p., prasanna t. r. s. // international journal of hydrogen energy. 2010. v. 35. p. 4597. 2. sun w., jiang y., wang y., fang s., zhu z., liu w. // journal of power sources. 2011. структура и транспортные свойства композитных материалов на основе ce 0,8 nd 0,2 o 2-δ и bace 0,8 nd 0,2 o 3-δ 41 № 1 | 2015 chimica techno acta v. 196. p. 62. 3. medvedev d., maragou v., pikalova e., demin a., tsiakaras p. // journal of power sources. 2013. v. 221. p. 217. 4. huang j., zhang l., wang c., zhang p. // international journal of hydrogen energy. 2012. v. 37. p. 13044. 5. http://zirconiaproject.wordpress.com/ devices/zirconia-318/. лягаева ю. г., медведев д. а. 1095-2574-1-pb 1095-2575-1-pb cta_v3_№1.cdr 85 d o i: 1 0. 15 82 6/ ch im te ch .2 01 6. 3. 1. 00 7 vladimir v. tkach1,2, silvio с. de oliveira2, severino k.b. de oliveira3, reza ojani4, о.v. elenich1, p. i. yagodynets´1 1chernivtsi national university, ukraine 2federal university of mato grosso do sul, brazil 3federal agricultural university of pernambuco, brazil 4mazandaran university, islamic republic of iran e-mail: nightwatcher2401@gmail.com the mechanism for the electrooxidation of procarbazine pharmaceutical preparation in alkaline media and its mathematical description the mechanism for the electrooxidation of procarbazine in alkaline media has been proposed. the process is realized completely on the electrode surface and is adsorption-controlled. the oscillatory behavior in this case is more probable, than for neutral media and may be caused by influences of electrochemical oxidation and salt dissolution from the electrode surface. © tkach v. v., de oliveira s. c., de oliveira s.k.b. , ojani r., elenich о.v.,yagodynets´ p. i., 2016 introduction procarbazine, i.e. n-isopropyl-α(2-methylhydrazino)-p-toluamide is one of the drugs commonly used in chemotherapy at different types of cancer [1–2]. the exact mechanism of action of the pharmaceutical preparation is still not determined. however, it is already known that its interaction with various substances (such as enzymes or compounds of transition metals) in the human organism leads to the formation of toxins (aldehydes, hydrazine and metal complexes) [3]. therefore, search of sensitive, precision and expeditious method for determining the concentration of the compound is a really actual task [4]. on the other hand, the use of electrochemical methods of analysis is one of reliable modern approaches to pharmaceutical (and not only) analytics since it has advantages over spectral and chromatographic methods such as sensitivity, accuracy, easy interpretation of the analytical signal and speed of analysis [5– 10]. however in some cases there occur problems of high anode voltage, the lack of data on the most likely mechanism for the electrooxidation of preparation and 86 № 1 | 2016 chimica techno acta electrochemical instabilities characteristic of the electrooxidation of small organic molecules (including electropolymerization of heterocyclic compounds) and hydrogen [11–16]. in the case of procarbazine the main problem is the small amount of data on the electrooxidation of said compound [4, 17] and a lack of theoretical works on the subject. in [4] an attempt to determine based on a purely experimental data the mechanism of the electrooxidation of the preparation under neutral conditions has been made. however the study was hindered by the lack of a solid theoretical foundation which is provided only as a result of construction and analysis of mathematical model that can adequately describe this process. the aim of this work is the mechanistic study of the procarbazine electrooxidation in alkaline medium. achievement of this aim is based on achieving the following specific objectives: the construction of a mathematical model, the analysis of the mathematical model, the study of steady state stability conditions and electrochemical instabilities (self-oscillatory or monotonic) and the comparison of the behavior of the system with the behavior of ones similar to it [18–21]. system and its model according to [4] the procarbazine electrooxidation consists in four steps: 1. oxidation of procarbazine to an azo derivative: 2. isomerization of the azo derivative in a schiff base: 3. hydrolysis of the schiff base to form an aldehyde: 4. electrooxidation of the aldehyde to form terephthalic acid n-isopropyl monoamide (in alkaline media a salt is formed): since the electrochemical reactions occur with elimination of proton in alkaline medium, they must occur faster than in neutral medium. tkach v. v., de oliveira s. c., de oliveira s.k.b., ojani r., elenich о.v.,yagodynets´ p. i. 87 № 1 | 2016 chimica techno acta the process takes place entirely at the anode surface and it can shown that the behavior of the system in this case is described by the following system of equations: d dt g r d dt h r d dt j r q q q 1 1 2 2 2 3 3 3 4 1 1 1 = − = − = −      (r ) (r ) (r )  (1) wherein parameters θ being the anode filling degree with the azo compound, the schiff base and the aldehyde, g, h and j being their maximum surface concentrations and parameters r being velocities of corresponding reactions can be calculated according to the following equations: r k f rt1 1 1 2 3 01 2 = − − −       ( ) expθ θ θ ϕ r2 = k2θ1 r3 = k3θ2 r k f rt a4 4 3 0 3 2 =       −θ ϕ θexp exp( ) results and discussion in order to investigate the behavior of the system with the procarbazine electrooxidation in alkaline medium, the system of differential equations (1) taking into account algebraic relations (2–5) using a linear stability theory has been analyzed. the functional jacobi matrix, whose elements are calculated for steady state, is written as follows: g g g g g g g g g 11 12 13 21 22 23 31 32 33       (6) wherein: self-oscillating instability of the system is possible since necessary conditions of hopf bifurcation can be fulfilled in fact in the main diagonal of jacobian there are positive elements responsible for the (2–5) (7–15) g g k f rt jk f 11 1 0 1 1 2 3 1 2 1 2 = −          + + − − − exp ( ) exp ϕ θ θ θ ϕ00 2rt k       −    g g k f rt lk f 12 1 0 1 1 2 3 1 2 1 2 = −          + + − − − exp ( ) exp ϕ θ θ θ ϕ00 rt          g g k f rt mk f 13 1 0 1 1 2 3 1 2 1 2 = −          + + − − − exp ( ) exp ϕ θ θ θ ϕ00 rt          g h k g h k g21 2 22 2 22 1 1 0= = − =( ) ( ) g j jk f rt31 4 3 01 2= −             θ ϕ exp g j k lk f rt32 3 4 3 01 2= −             θ ϕ exp g j k f rt a mk f r 33 4 0 2 4 3 0 1 2 2 = −       −    − exp exp( ) exp ϕ θ θ ϕ tt a ak f rt a       − + +       − exp( ) exp exp( ) θ θ ϕ θ 3 4 3 0 3 2    the mechanism for the electrooxidation of procarbazine pharmaceutical preparation in alkaline media and its mathematical description 88 № 1 | 2016 chimica techno acta positive feedback. in addition to element ak f rt a4 3 0 3 2 θ ϕ θexp exp( )       − responsible for self-oscillations when attracting the adsorbed molecules of a salt during its passing into a solution, members lk f rt1 1 2 3 01 2 ( ) exp− − −       θ θ θ ϕ and −       −mk f rt a4 2 0 3 2 θ ϕ θexp exp( ) describing self-oscillations caused by influence of electrochemical processes on the structure of the electrical double layer (edl) may also have positive values. these factors are the cause of the self-oscillatory behavior for other similar systems [19– 21], but it should be noted that if for alkaline medium both factors are possible then for neutral medium, in which the salt formation and passing of the acid anion in the solution does not virtually take place, only the latter factor is the cause of the self-oscillatory behavior. steady state stability study on the basis of the routh-hurwitz criterion shows that said reaction is controlled by a procarbazine adsorption factor as well as the state of the edl during the reaction. if in order to avoid cumbersome mathematical expressions to enter new variables so that the determinant of the jacobian matrix is written as follows: then at the opening parenthesis the condition det j<0 will be written as follows: –φ(k2k3 – k2θ – κk3) – –p(κ1k3 + k2k3 + πk2) < 0 (17) this inequality is guaranteed to be satisfied if parameters φ, κ, π, θ and κ describing the influence of electrochemical reactions on the edl as well as the interaction of adsorbed molecules in salt formation and passing to the solution are positive that is achieved by the absence or weakness of influences of electrochemical reactions on the structure of the edl and by the repulsive interaction of adsorbed molecules. in this case the left-hand side of the inequality reaches more negative values. since chemical and electrochemical reactions described above are faster than the procarbazine adsorption onto the anode surface the process is controlled by the procarbazine adsorption in case of equality of the influence of destabilizing and stabilizing factors on the stability of the steady state then monotonic instability appears which is presented as n-shaped segment in a voltammogram. the condition of its appearance is described as follows: –φ(k2k3 – k2θ– κk3) – –p(κ1k3 + k2k3 + πk2) = 0 (18) conclusion in alkaline medium the procarbazine electrooxidation to some extent is faster than in neutral medium but appearance of self-oscillations in it is more likely due to the presence of a salt formation factor and dissolution of the salt of terephthalic acid n-isopropyl monoamide. the reaction itself is controlled by the procarbazine adsorption and the state of the edl. 1. newton h. b. handbook of brain tumor chemoterapy. elsevier, 2006 tkach v. v., de oliveira s. c., de oliveira s.k.b., ojani r., elenich о.v.,yagodynets´ p. i. 1 0 1 2 2 3 3 ghj k k k k k p − − − − − − − − κ θ π ф (16) 89 № 1 | 2016 chimica techno acta 2. shiba d. a., weinkam r. j. the in vivo cytotoxic activity of procarbazine and procarbazine metabolites against l1210 ascites leukemia cells in cdf1 mice and the effects of pretreatment with procarbazine, phenobarbital, diphenylhydantoin, and methylprednisolone upon in vivo procarbazine activity. cancer chemoter. pharmacol. 1983;11(2):124-129. doi: 10.1007/bf00254261. 3. aronson j. k. meyler’s side effects of drugs in cancer and immunology. elsevier, 2010 4. oliveira s. c. b., mendes c. h. s., filho f. f. s., queiroz n. l.,nascimento j. a. m., nascimento v. b. electrochemical oxidation mechanism of procarbazine at glassy carbon electrode. j. electroanal. chem. 2015;746(1):51-56. doi: 10.1016/j.jelechem.2015.02.033. 5. mahanthesha k. r., swamy b. e. k., pai k.v. poly (alizarin) modified glassy carbon electrode for the electrochemical investigation of omeprazole: a voltammetric study. anal. bioanal. electrochem. 2014;6(2):234-244. 6. ojani r., raoof j., ahmady a., hosseini s. r. casp. j. chem. 2013;2:45. 7. raoof j., ojani r., hosseini s. r. an electrochemical investigation of methanol oxidation on nickel hydroxide nanoparticles. south afr. j. chem. 2013;66:47-53. 8. ojani r., raoof j. b., zavvarmahalleh s. r. h. electrocatalytic oxidation of methanol on carbon paste electrode modified by nickel ions dispersed into poly (1,5-diaminonaphthalene) film. electrochimica acta. 2008;53(5):2402-2407. doi: 10.1016/j. electacta.2007.10.004. 9. shu h. applications of poly(3-hexylthiophene) thin film as a hydrazine-sensitive chemoresistor. m. sc. thesis. alburn. alabama, 2006 10. tosar j. p. rovira. estudio de la inmovilización de oligonucleótidos a eléctrodos modificados de oro:polipirrol, y detección electroquímica de secuencias complementarias. tes. lic. bioquím. universidad de la república. montevideo, 2008. 11. pagitsas m., sazou d. the improved franck-fitzhugh model for the electrodissolution of iron in sulphuric acid solutions: linear stability and bifurcation analysis. derivation of the kinetic equations for the forced franck-fitzhugh model. electrochimica acta. 1991;36(8):1301-1308. doi: 10.1016/0013-4686(91)80009-w. 12. a. j. pearlstein, j. a. johnson. j. electrochem. soc. 1991;136:1290. 13. das i., agrawal n. r., ansari s. a., gupta s. k. pattern formation and oscillatory electropolymerization of thiophene. ind. j. chem. 2008;47(12):1798-1803. 14. rahman s. u., ba-shammakh m. s. thermal effects on the process of electropolymerization of pyrrole on mild steel. synth. met. 2004;140(2-3):207-223. doi: 10.1016/s0379-6779(03)00369-2. 15. liu a. s., oliveira m. a. s. electrodeposition of polypyrrole films on aluminum from tartrate aqueous solution. j. braz. chem soc. 2007;18(1):143-152. 16. sazou d. the dynamical behavior of the electrochemical polymerization of indole on fe in acetonitrile-water mixtures. synth. met. 2002;130(1):45-54. doi: 10.1016/ s0379-6779(02)00110-8. 17. mccue j. p., kennedy j. h. oxidation of procarbazine in the presence of ti(iv). bioinorg. chem. 1977;7(1):5-21. doi: 10.1016/s0006-3061(00)80125-8. 18. tkach v., kumara swamy b., ojani r. et. al. orbital elec. j. chem. 2015;7:1. 19. tkach v., ojani r., nechyporuk v., yagodynets´ p. rev. fac. ing. ucv. 2015;30:65. 20. tkach v., nechyporuk v., yagodynets p. med. j. chem. 2015;3:1122. 21. tkach v. v., nechyporuk v. v., yagodynets´ p.  i., kushnir v. m. afinidad. 2015;72:218. the mechanism for the electrooxidation of procarbazine pharmaceutical preparation in alkaline media and its mathematical description 90 у д к 6 68 .2 43 .8 8 в. в. ткач1, 2, силвио с. де оливейра2, северино к. б. де оливейра3, реза ожани4, о. в. еленич1, п. и. ягодинец1 1черновицкий национальный университет, украина 2федеральный университет штата мату-гроссу-ду-сул, бразилия 3федеральный сельскохозяйственный университет штата пернамбуку, бразилия 4университет мазендерана, исламская республика иран e-mail: nightwatcher2401@gmail.com механизм электрохимического окисления фармацевтического препарата прокарбазин в щелочной среде и ее математическое описание был предложен механизм электроокисления прокарбазина в щелочной среде. процесс реализуется полностью на поверхности электрода и является адсорбционно-контролируемым. осцилляторное поведение в этом случае более предпочтительно, чем в нейтральной среде и может быть вызвано влияниями электрохимического окисления и растворением соли на поверхности электрода. © ткач в. в., де оливейра c. с., де оливейра c. к. б., ожани р., еленич о. в. , п. и. ягодинец, 2016 введение прокарбазин, то есть n-изопропил-α-(2-метилгидразино)-птолуамид, – одно из часто используемых лекарственных средств в химиотерапии при различных видах рака [1–2]. точный механизм фармацевтического действия препарата все еще не определен. однако уже известно, что его взаимодействие с различными веществами (например, энзимами или соединениями переходных металлов) в организме человека приводит к образованию токсинов (альдегидов, гидразина и металлических комплексов) [3]. посему поиск чувствительного, точного и быстродейственного метода определения концентрации этого соединения действительно актуальная задача [4]. 91 № 1 | 2016 chimica techno acta с другой стороны, использование электрохимических методов анализа – один из надежных современных подходов к фармацевтической (и не только) аналитике, ибо имеет преимущества перед спектральными и хроматографическими методами – чувствительность, точность, легкая интерпретация аналитического сигнала и скорость анализа [5–10]. однако в некоторых случаях появляются проблемы высокого анодного перенапряжения, отсутствия данных о наиболее вероятном механизме электроокисления препарата, а также электрохимических неустойчивостей, характерных для электроокисления малых органических молекул (включая электрополимеризацию гетероциклических соединений) и водорода [11–16]. в случае прокарбазина основной проблемой является небольшое количество данных об электроокислении данного соединения [4, 17] и отсутствие теоретических работ по теме. была совершена попытка установить на основе чисто экспериментальных данных механизм электроокисления препарата в нейтральной среде [4]. однако исследованию мешало отсутствие твердого теоретического фундамента, который дается только вследствие построения и анализа математической модели, способной адекватно описать данный процесс. целью данной работы является механистическое исследование электроокисления прокарбазина в щелочной среде. достижение этой цели зиждется на достижении следующих специфических целей: построение математической модели, анализа математической модели, исследования условий устойчивости стационарного состояния и электрохимических неустойчивостей (автоколебательной, или монотонной), сравнения поведения данной системы с поведением ей подобных [18–21]. система и ее модель согласно [4], электроокисление прокарбазина состоит из четырех этапов: 1. окисление прокарбазина до азопроизводного: 2. изомеризация азосоединения в основание шиффа (гидразон): 3. гидролиз основания шиффа с образованием альдегида: механизм электрохимического окисления фармацевтического препарата прокарбазин в щелочной среде и ее математическое описание 92 № 1 | 2016 chimica techno acta 4. электроокисление альдегида с образованием n-изопропилмоноамида терефталевой кислоты (в щелочной среде образуется соль): так как электрохимические реакции происходят с отщеплением протона, в щелочной среде они должны протекать быстрее, чем в нейтральной. процесс полностью происходит на поверхности анода и можно показать, что поведение системы в данном случае описывается системой следующих уравнений: d dt g r d dt h r d dt j r q q q 1 1 2 2 2 3 3 3 4 1 1 1 = − = − = −      (r ) (r ) (r )  (1) где параметры θ – степени заполнения поверхности анода диазосоединением, основанием шиффа и альдегидом, g, h и j – их максимальные поверхностные концентрации, а параметры r – скорости соответствующих реакций, которые могут быть вычислены согласно следующим уравнениям: r k f rt1 1 1 2 3 01 2 = − − −       ( ) expθ θ θ ϕ r2 = k2θ1 r3 = k3θ2 r k f rt a4 4 3 0 3 2 =       −θ ϕ θexp exp( ) результаты и обсуждения для того чтобы исследовать поведение системы с электроокислением прокарбазина в щелочной среде, проанализируем систему дифференциальных уравнений (1), с учетом алгебраических отношений (2) – (5) с помощью линейной теории устойчивости. функциональная матрица якоби, элементы которой вычислены для стационарного состояния, записывается как: g g g g g g g g g 11 12 13 21 22 23 31 32 33       (6) где (2–5) g g k f rt jk f 11 1 0 1 1 2 3 1 2 1 2 = −          + + − − − exp ( ) exp ϕ θ θ θ ϕ00 2rt k       −    g g k f rt lk f 12 1 0 1 1 2 3 1 2 1 2 = −          + + − − − exp ( ) exp ϕ θ θ θ ϕ00 rt          g g k f rt mk f 13 1 0 1 1 2 3 1 2 1 2 = −          + + − − − exp ( ) exp ϕ θ θ θ ϕ00 rt          g h k g h k g21 2 22 2 22 1 1 0= = − =( ) ( ) (7–15)g j jk f rt31 4 3 01 2= −             θ ϕ exp g j k lk f rt32 3 4 3 01 2= −             θ ϕ exp ткач в. в., де оливейра c. с., де оливейра c. к. б., ожани р., еленич о. в. , п. и. ягодинец 93 № 1 | 2016 chimica techno acta автоколебательная неустойчивость для данной системы возможна, поскольку могут выполняться необходимые условия бифуркации хопфа – ведь в главной диагонали якобиана имеются положительные элементы, ответственные за положительную обратную связь. помимо ответственного элемента, за автоколебания при притяжении адсорбированных молекул соли при переходе ее в раствор ak f rt a4 3 0 3 2 θ ϕ θexp exp( )       − положительные значения также могут иметь члены lk f rt1 1 2 3 01 2 ( ) exp− − −       θ θ θ ϕ и −       −mk f rt a4 2 0 3 2 θ ϕ θexp exp( ) , описывающие автоколебания, причиной которых являются влияния электрохимических процессов на структуру двойного электрического слоя (дэс). эти факторы являются причиной автоколебательного поведения для других подобных систем [19–21], однако стоит заметить, что если для щелочной среды возможны оба фактора; для нейтральной, в которой солеобразования и перехода аниона кислоты в раствор практически не происходит, причиной автоколебательного поведения служит лишь последний фактор. исследование устойчивости стационарного состояния по критерию рауса – гурвица показывает, что данная реакция контролируется фактором адсорбции прокарбазина, а также состоянием дэс во время реакции. если ввести, с целью избежать громоздких математических выражений, новые переменные таким образом, что определитель матрицы якоби запишется как: (16) то при открытии скобок условие det j < 0 запишется как: –φ(k2k3 – k2θ – κk3) – –p(κ1k3 + k2k3 + πk2) < 0 (17) это неравенство гарантированно удовлетворяется, если параметры φ, κ, π, θ и κ описывающие влияние электрохимических реакций на дэс, а также взаимодействие адсорбированных молекул при солеобразовании и переходе в раствор, имеют положительные значения, что достигается отсутствием или слабостью влияний электрохимических реакций на структуру дэс, а также отталкивающим взаимодействием адсорбированных молекул. в таком случае выражение в левой части неравенства достигает более отрицательных значений. поскольку химические и электрохимические реакции, описанные выше, быстрее адсорбции прокарбазина на поверхность анода, то процесс будет контролироваться адсорбцией прокарбазина. в случае равенства влияния дестабилизирующих и стабилизирующих факторов на устойчивость стационарного состояния появляется монотонная неустойчивость, которая проявляется n-образным отрезком на g j k f rt a mk f r 33 4 0 2 4 3 0 1 2 2 = −       −    − exp exp( ) exp ϕ θ θ ϕ tt a ak f rt a       − + +       − exp( ) exp exp( ) θ θ ϕ θ 3 4 3 0 3 2    механизм электрохимического окисления фармацевтического препарата прокарбазин в щелочной среде и ее математическое описание 1 0 1 2 2 3 3 ghj k k k k k p − − − − − − − − κ θ π ф 94 № 1 | 2016 chimica techno acta вольтамперограмме. условие ее появления описывается как: –φ(k2k3 – k2θ– κk3) – –p(κ1k3 + k2k3 + πk2) = 0 (18) выводы в щелочной среде электроокисление прокарбазина проходит в некоторой мере быстрее, чем в нейтральной, однако в ней более вероятно появление автоколебаний, ввиду присутствия фактора солеобразования и растворения соли n-изопропилмоноамида терефталевой кислоты. сама реакция при этом контролируется адсорбцией прокарбазина и состоянием дэс. 1. newton h. b. handbook of brain tumor chemoterapy. elsevier, 2006. 2. shiba d. a., weinkam r. j. the in vivo cytotoxic activity of procarbazine and procarbazine metabolites against l1210 ascites leukemia cells in cdf1 mice and the effects of pretreatment with procarbazine, phenobarbital, diphenylhydantoin, and methylprednisolone upon in vivo procarbazine activity. cancer chemoter. pharmacol. 1983;11(2):124-129. doi: 10.1007/bf00254261. 3. aronson j. k. meyler’s side effects of drugs in cancer and immunology. elsevier, 2010. 4. oliveira s. c. b., mendes c. h. s., filho f. f. s., queiroz n. l.,nascimento j. a. m., nascimento v. b. electrochemical oxidation mechanism of procarbazine at glassy carbon electrode. j. electroanal. chem. 2015;746(1):51-56. doi: 10.1016/j. jelechem.2015.02.033. 5. mahanthesha k. r., swamy b. e. k., pai k.v. poly (alizarin) modified glassy carbon electrode for the electrochemical investigation of omeprazole: a voltammetric study. anal. bioanal. electrochem. 2014;6(2):234-244. 6. ojani r., raoof j., ahmady a., hosseini s. r. casp. j. chem. 2013;2:45. 7. raoof j., ojani r. hosseini s. r. an electrochemical investigation of methanol oxidation on nickel hydroxide nanoparticles. south afr. j. chem. 2013;66:47-53. 8. ojani r., raoof j., zavvarmahalleh s. r. h. electrocatalytic oxidation of methanol on carbon paste electrode modified by nickel ions dispersed into poly (1,5-diaminonaphthalene) film. electrochimica acta. 2008;53(5):2402-2407. doi: 10.1016/j.electacta.2007.10.004. 9. shu h. applications of poly(3-hexylthiophene) thin film as a hydrazine-sensitive chemoresistor. m. sc. thesis, alburn, alabama, 2006. 10. tosar rovira j. p.. estudio de la inmovilización de oligonucleótidos a eléctrodos modificados de oro:polipirrol, y detección electroquímica de secuencias complementarias. tes. lic. bioquím. universidad de la república. montevideo, 2008. 11. pagitsas m., sazou d. the improved franck-fitzhugh model for the electrodissolution of iron in sulphuric acid solutions: linear stability and bifurcation analysis. derivation of the kinetic equations for the forced franck-fitzhugh model. electrochimica acta. 1991;36(8):1301-1308. doi: 10.1016/0013-4686(91)80009-w. ткач в. в., де оливейра c. с., де оливейра c. к. б., ожани р., еленич о. в. , п. и. ягодинец 95 № 1 | 2016 chimica techno acta 12. pearlstein a. j., johnson j. a. j. electrochem. soc. 1991;136:1290. 13. das i., agrawal n. r., ansari s. a., gupta s. k. pattern formation and oscillatory electropolymerization of thiophene. ind. j. chem. 2008;47(12):1798-1803. 14. rahman s. u., ba-shammakh m. s. thermal effects on the process of electropolymerization of pyrrole on mild steel. synth. met. 2004;140(2-3):207-223. doi: 10.1016/s0379-6779(03)00369-2. 15. liu a. s., oliveira m. a. s. electrodeposition of polypyrrole films on aluminum from tartrate aqueous solution. j. braz. chem soc. 2007;18(1):143-152. 16. sazou d. the dynamical behavior of the electrochemical polymerization of indole on fe in acetonitrile-water mixtures. synth. met. 2002;130(1):45-54. doi: 10.1016/ s0379-6779(02)00110-8. 17. mccue j. p., kennedy j. h. oxidation of procarbazine in the presence of ti(iv). bioinorg. chem. 1977;7(1):5-21. doi: 10.1016/s0006-3061(00)80125-8. 18. tkach v., kumara swamy b., ojani r. et al. orbital elec. j. chem. 2015;7:1. 19. tkach v., ojani r., nechyporuk v., yagodynets´ p. rev. fac. ing. ucv. 2015;30:65. 20. tkach v., nechyporuk v., yagodynets p. med. j. chem. 2015;3:1122. 21. tkach v. v., nechyporuk v. v., yagodynets´ p. i., kushnir v. m. afinidad. 2015;72:218. механизм электрохимического окисления фармацевтического препарата прокарбазин в щелочной среде и ее математическое описание 343 d o i: 1 0. 15 82 6/ ch im te ch .2 01 5. 2. 4. 03 1 a. yu. zuev, d. s. tsvetkov 1 ural federal university 620000, ekaterinburg, lenin ave. 51, (343) 251-79-27 e-mail: andrey.zuev@urfu.ru oxygen non-stoichiometry and defect structure of lamn 1-z cu z o 3+δ the quantitative model analysis of the defect structure of copper doped lanthanum manganites lamn 1-z cuzo 3+δ (z = 0.05 and 0.1) was performed. in the framework of the model, the independent course of the three reactions of defect formation, including the electronic exchange between manganese and copper, completion of a lattice by the absorption of oxygen and the disproportionation of manganese was considered. it is shown that the increase in the dopant content leads to a change in the dominant electronic process. this is reflected in the lock and disproportionation and leads to the increase in the concentration of holes and decrease the concentration of electrons localized on the manganese atoms. keywords: lanthanum manganites; oxygen non-stoichiometry; thermodynamic characteristics of reactions; disproportionation © zuev a. yu., tsvetkov d. s., 2015 introduction the study of lanthanum manganite lamno3±δ started with published in 1950, the work of jonker and van santena santena [1] and has continued at present. the reason is that lanthanum manganites, partially doped alkaline earth metals, mainly calcium or strontium, are today indispensable cathode materials for high-temperature fuel cells [1, 2, 3]. lanthanum manganites with partial substitution of manganese for other 3d-metals have been studied less. however, the isomorphic substitution of manganese for copper leads to a substantial change of the magnetic and catalytic performance of lanthanum manganite [4], most likely due to the increased lability of the oxygen sublattice [5] and presence of 3d-metal in mixed oxidation states [4]. in his early work [6] we have analyzed the oxygen non-stoichiometry lamn1-zcuzo3+δ and proposed a model of its defect structure. however, quantitative analysis of this model was not performed. in this paper, we present the results of this analysis. 344 № 4 | 2015 chimica techno acta theory as oxygen non-stoichiometry of copper substituted lanthanum manganites are studied exclusively in the area of excess oxygen, the modeling of the defect structure in these manganites is only for this area. according to jonker [7], if in lamno3+δ mn is substituted for copper, which is more electronegative 3d-metal, we should expect the reaction. mn cu mn cumn mn mn mn × ×+ = + / (1) with the equilibrium constant k mn cu mn cu mn mn mn mn 1 = × × [ ][ ] [ ][ ] , / where cumn ´ и cumn / – cu+3 и cu+2, accordingly recorded in the system of kroger-vinca. taking into account the reaction of completing the grid 6 3 2 3 62mn o v v o mnmn la mn o mn × ×+ ⇔ + + +/// ///  (2) with the equilibrium constant k o v v mn mn o la mn mn mn 2 3 6 =     ⋅ ′′′  ⋅ ′′′    ⋅         × ×   ⋅ 6 3 2 2 po , where mnmn ´ и mnmn  – mn+3 и mn+4, respectively, as well as the disproportionation of manganese 2mn mn mnmn mn mn × ⇔ + / (3) with the equilibrium constant k mn mn mn mn mn mn 3 2=    ⋅         ×  / , where 2mn mn mnmn mn mn × ⇔ + / , together with the relevant conditions of mass balance and electroneutrality, we obtain the system of equations that defines the model of the defect structure of lamn1-zcuzo3+δ (4) the solution of system (5) is rather complicated dependence of the general form, log( / ) ( ), ( ), ( ), ( ) po f k f t k f t k f t 2 3 1 2 atm = = = = d (5) the explicit form which because of its bulkiness was omitted in the text. results and discussion in fig. 1, 2 there are the dependences of the absolute oxygen non stoichiometry of substituted manganites lamn1zcuzo3+δ, where z = 0.05 and 0.10, respectively, from the partial pressure of oxygen and temperature. it follows from these figures that in the whole studied range of temperatures and pressures of oxygen manganite lamn0.95cu0.05o3+δ and lamn0.90cu0.10o3+δ remain beyond stoichiometric on oxygen. for lamn0.80cu0.20o3±δ was set to [6], that the value of the oxygen content varies slightly, decreasing from 3.024 at 1173 k in a pure oxygen atmosphere to a value almost equal to three for lоg(po2/ атм)= -2.76 and t = 1373 k. the sample lamn0.70cu0.30o3+δ has been investigated [6] only in the environment of air in the k mn cu mn cu kmn mn mn mn 1 1 0=    ⋅        ⋅     = − × ×  / exp ∆hh rt k o v v mno la mn mn 1 2 3       =     ⋅ ′′′  ⋅ ′′′    ⋅ ×         ⋅ = −       = × 6 6 3 2 2 0 2 3 2 mn p k h rt k mn mn o mn exp ∆    ⋅         = ⋅ −      × mn mn k h rt mn mn / exp2 3 0 3 3 ∆ ′′′′   ′′′        =         v v mn mn mn mn la mn mn mn 3 /         = − ⋅         × × mn mn z cu cu mn mn mn mn / / ( )1 3 3 d = ⋅ ′′′  = ′′′    =    = × z v v o la mn o 3 3 3 3 d d d . zuev a. yu., tsvetkov d. s. 345 № 4 | 2015 chimica techno acta temperature interval 1173 – 1473 k. the obtained data showed that in all investigated temperature interval, the sample remained stoichiometric relative to the oxygen. in fig. 1 and 2 the results of the verification of the model, according to equation (5), lamn1-zcuzo3+δ are shown using temperature dependences of the equilibrium constants (see system (4)). the parameters of the corresponding temperature dependences obtained by minimizing the deviation of model surfaces from experimental data, together with correlation coefficients are summarized in table 1. as can be seen from this table and fig. 1, between the values of po2 calculated by the proposed model and defined experimentally, good agreement is observed. it follows from table 1 that the addition of copper (z=0.05 and 0.10) in lamno3+δ practically does not change the thermodynamic characteristics of reactions of completion of construction of the lattice of perovskite (2) compared with neoperabelny manganite of lanthanum [8]. a small addition of copper (z = 0.05) in lamno3+δ has little impact on the course of the disproportionation of manganese (3), as this enthalpy of this reaction increases slightly. however, the increase in copper (z = 0.10) is expressed in a dramatic change in the process of disproportionation (3), which acquires a pronounced thermally activated character, as evidenced by the anomalously large value of enthalpy, k j 6000, compared to almost zero enthalpy of disproportionation to unsubstituted lamno3+δ [8]. it should be noted that the equilibrium constant of reaction (4) for lamn0.90cu0.10o3+δ in the temperature interval investigated takes extremely low values, varying from 10 to 60 at 1173 k up to 1373 k. therefore, the equilibrium in the disproportionation of (3) is almost completely shifted to manganese ions mn+3. therefore, is reasonable to simplify the model of the defect structure of lamn0.90cu0.10o3+δ by removing from consideration the disproportionation of manganese. the corresponding simplification of the system (4) leads to a relatively simple model equation. log( / ) ( ) p a o 2 1 3 3 3 6 3 2 3 atm =− +       ⋅ ⋅ ⋅ + −      ⋅ + d d d d d (( . . )− + − − ⋅2 7 6 9 3 2 1 2 2 1 6d da a k , (6) fig. 1. the result of the model analysis of the defect structure of lamn0.95cu0.05o3+δ. filled symbols – experiment [6]; surface corresponds to the equation (5) fig. 2. the result of the model analysis of the defect structure of lamn0.9cu0.1o3+δ. filled symbols – experiment [6]; surface corresponds to the equation (5) oxygen non-stoichiometry and defect structure of lamn 1-z cuzo 3+δ 346 № 4 | 2015 chimica techno acta where a k k b k mn cu mn cu mn cu = − − + − ⋅ + 7 6 3 1 3 2 2 2 d d d( ) ( ) и b k k mn cu mn c = + − + + + − ( . . . ) ( . . . ) 46 24 5 76 32 64 26 64 3 24 81 24 2 2 2 2 2 d d d d uu +36 2d . the results of the verification of a simplified model of the defect structure of lamn0.90cu0.10o3+δ according to equation (6) are also presented in table 1. as can be seen, for this model the correlation coefficient r2 was significantly closer to 1 compared with a model taking into account reaction (3). it should be added that the sum of squared deviations for the model which corresponds to equation (6) is 0.068, while for the sought model considering reaction (3) is 0.224. therefore further calculations of concentrations of defects for lamn0.90cu0.10o3+δ was carried fig. 3. the dependence of the concentration of electronic defects in lamno3+δ from oxygen non stoichiometry [8] at different temperatures fig. 4. the dependence of the concentration of electronic defects lamn0.95cu0.05o3+δ from oxygen non stoichiometry at different temperatures table 1 the values of thermodynamic parameters temperature dependences of the equilibrium constants of the processes of disordering lamn1-zcuzo3+δ z e qu at io n r ea ct io n δh, kj mol ln(k0)i r 2 0. 05 5 3 85.1 1.53 0.9961 52.8 14.2 2 –293.4 –38.0 0. 1 5 3 6000 477 0.9761 118.0 29.3 2 –242.6 –34.2 0. 1 6 1 178±33 14.9±3 0.994 2 –163±30 –29.5±3 zuev a. yu., tsvetkov d. s. 347 № 4 | 2015 chimica techno acta out on the basis of results of model analysis of equation (6). as an example in fig. 3–6 the dependencies of the concentration of localized electronic defects from oxygen nonstoichiometry lamn1zcuzo3+δ are z = 0, 0.05 and 0.1, respectively. for comparative purposes, based on the concentration of holes localized on the manganese atoms, the magnitude of δ for various compositions lamn1zcuzo3+δ is shown in fig. 6. as can be seen from these drawings, the addition of copper in lamno3+δ leads to a noticeable change in the electronic disordering manganese sublattice, which is reflected in the increase in the concentration of holes and decrease of the concentration of electrons localized on the manganese atoms. the concentration of electrons localized at the copper atoms is almost constant in the whole area of excess oxygen for manganite lamn0.95cu0.05o3+δ and does not depend on temperature, being equal to the total copper content, whereas this value for lamn0.90cu0.10o3+δ varies in a wide interval when changing the oxygen content and temperature. the observed increase in the content of mn+4 in the lanthanum manganite when it is doped with copper is consistent with the findings of [9], made on the basis of the redox titration of samples of copper substituted lanthanum manganites. found in the present work, the change in the concentration of cu+2 for lamn0.90cu0.10o3+δ depending on the oxygen index and temperature beyond stoichiometric indirectly supported by the results of [10], which is obtained for this composition range x-ray photoelectron spectroscopy was unable to decipher in the assumption that all copper is located only in the state +2. at the same time the authors [10] found the absence of mn+2 in lamn0.90cu0.10o3+δ is consistent with the results of the model analysis of the defect structure of the manganite which is made in the present work. conclusions doping of the lanthanum manganite of copper has a significant impact primarily on the oxygen content and its electronic subsystem. this is observed in the consecutive change of the dominant electronic process from the disproporfig. 5. the dependence of the concentration of electronic defects lamn0.9cu0.1o3+δ from oxygen non stoichiometry at different temperatures fig. 6. the dependence of the concentration of electronic defects lamn1-zcuzo3+δ from oxygen non stoichiometry at different temperatures oxygen non-stoichiometry and defect structure of lamn 1-z cuzo 3+δ 348 № 4 | 2015 chimica techno acta tionation of manganese to the reaction of the electronic exchange between the manganese and copper increases the content in lamn1-zcuzo3+δ, and decrease in oxygen content. when the concentration of the dopant is z = 0.3, the response of the electronic exchange between manganese and copper, apparently, is the only process of disordering lamn1-zcuzo3, that is expressed in its stoichiometric composition of oxygen in the whole studied range of temperature. 1. jonker g. h., van santen j. h. ferromagnetic compounds of manganese with perovskite structure. physics. 1950;16;337–349. 2. n. h. menzler, f. tietz, s. uhlenbruck, h. p. buchkremer, d. stöver. materials and manufacturing technologies for solid oxide fuel cells. j. mater. sci. 2010;45:3109– 3135. 3. santen j. h. van jonker g. h. electrical conductivity of ferromagnetic compounds of manganese with perovskite structure. physics. 1950;16:599–600. 4. royer s., duprez d. catalytic oxidation of carbon monoxide over transition metal oxides. chemcatchem. 2011;3:24–65. 5. chan k. s., jaenicke s., chuah g. k. and lee j. y. catalytic carbon monoxide oxidation over strontium, cerium and copper-substituted lanthanum manganates and cobaltates. applied catalysis a: general. 1994;107:201–207. 6. petrov a. n., zuev a. yu., tikchonova i. l. voronin v. i. crystal and defect structure of the mixed oxides lamn1-zcuzo3±y (0£ z ≤0.4). solid state ionics. 2000;129:179–188. 7. jonker g. h. magnetic and semiconducting properties of perovskites containing manganese and cobalt. j. appl. phys. 1966;37:1424–1430. 8. zuev a. yu., tsvetkov d. s. oxygen nonstoichiometry, defect structure and defectinduced expansion of undoped perovskite lamno3±δ. solid state ionics. 2010;81:557– 563. 9. porta p., de rossi s., faticanti m., minelli g., pettiti i., lisi l., turco m. perovskitetype oxides i. structural, magnetic, and morphological properties of lamn1-x cuxo3-d and laco1-xcuxo3-d solid solutions with large surface area. j. of solid state chemistry. 1999;146:291-304. 10. tabata k., hirano y., suzuki e. xps studies on the oxygen species of lamn1xcuxo3+λ. applied catalysis a: general. 1998;170:245–254. zuev a. yu., tsvetkov d. s. 349 у д к 5 44 .2 2. 02 2. 34 2: 54 -3 1/ 54 4. 22 5. 3: [5 46 .6 5+ 54 6. 71 ’3 02 +5 49 .7 46 .3 ] а. ю. зуев, д. с. цветков 1 уральский федеральный университет, 620000, екатеринбург, пр. ленина 51, тел. (343) 251-79-27 e-mail: andrey.zuev@urfu.ru кислородная нестехиометрия и дефектная структура lamn 1–z cu z o 3+δ выполнен количественный модельный анализ дефектной структуры допированных медью манганитов лантана lamn 1–z cu z o 3+δ (z = 0,05 и 0,1). в рамках модели рассмотрено независимое протекание трех реакций дефектообразования, включая электронный обмен между марганцем и медью, достраивание решетки при поглощении кислорода и диспропорционирование марганца. показано, что увеличение содержания допанта приводит к смене доминирующего электронного процесса. это выражается в блокировке диспропорционирования и ведет к увеличению концентрации дырок и уменьшению концентрации электронов, локализованных на атомах марганца. ключевые слова: манганит лантана; кислородная нестихиометрия; термодинамические характеристики реакций; диспропорционирование. © зуев а. ю., цветков д. с., 2015 введение исследование манганита лантана lamno3±δ началось с опубликованной в 1950 г. работы джонкера и ван сантена [1] и продолжается в настоящее время. это определяется тем, что манганиты лантана, частично допированные щелочноземельными металлами, главным образом кальцием или стронцием, являются сегодня незаменимыми катодными материалами для высокотемпературных топливных элементов [1, 2, 3]. манганиты лантана с частичной заменой марганца на другие 3d-металлы изучены в меньшей степени. однако изоморфное замещение марганца на медь приводит к существенному изменению магнитных и каталитических характеристик манганита лантана [4], что, наиболее вероятно, связано с увеличением лабильности кислородной подрешетки [5] и нахождением 3d-металлов в смешанных степенях окисления [4]. в своей ранней работе [6] мы проанализировали кислородную нестехиометрию lamn1–zcuzo3+δ и предложили модель его дефектной структуры. однако количественного анализа этой модели не выполняли. в настоящей рботе мы приводим результаты этого анализа. 350 № 4 | 2015 chimica techno acta теория так как кислородная нестехиометрия медью замещенных манганитов лантана исследована исключительно в области избытка кислорода, то моделирование дефектной структуры этих манганитов приводится только для этой области. согласно джонкеру [7], если mn в lamno3+δ замещается на медь, которая является более электроотрицательным 3d-металлом, то следует ожидать протекания реакции mn cu mn cumn mn mn mn × ×+ = + / (1) с константой равновесия k mn cu mn cu mn mn mn mn 1 = × × [ ][ ] [ ][ ] , / , где cumn ´ и cumn / – cu+3 и cu+2, соответственно, записанные в системе крёгера – винка. приняв во внимание реакцию достраивания решетки 6 3 2 3 62mn o v v o mnmn la mn o mn × ×+ ⇔ + + +/// ///  (2) с константой равновесия k o v v mn mn o la mn mn mn 2 3 6 =     ⋅ ′′′  ⋅ ′′′    ⋅         × ×   ⋅ 6 3 2 2 po , где mnmn ´ и mnmn  – mn+3 и mn+4, соответственно,  а  также диспропорционирование марганца 2mn mn mnmn mn mn × ⇔ + / (3) с константой равновесия k mn mn mn mn mn mn 3 2=    ⋅         ×  / , , где mn mnmn / − +2 , вместе с соответствующими условиями баланса массы и электронейтральности, получаем систему уравнений, определяющую модель дефектной структуры lamn1–zcuzo3+δ (4) решением системы (5) является достаточно сложная зависимость общего вида, log( / ) ( ), ( ), ( ), ( ) po f k f t k f t k f t 2 3 1 2 atm = = = = d , (5) явный вид которой в силу своей громоздкости опущен в тексте. результаты и обсуждение на рис. 1, 2 приведены зависимости абсолютной кислородной нестехиометрии замещенных манганитов lamn1zcuzo3+δ, где z = 0,05 и 0,10, соответственно, от парциального давления кислорода и температуры. из этих рисунков следует, что во всем исследованном интервале температур и давлений кислорода манганиты lamn0,95cu0,05o3+δ и lamn0,90cu0,10o3+δ остаются сверхстехиометричными по кислороду. для lamn0,80cu0,20o3±δ было установлено [6], что величина кислородного содержания варьируется незначительно, уменьшаясь от 3,024 при k mn cu mn cu kmn mn mn mn 1 1 0=    ⋅        ⋅     = − × ×  / exp ∆hh rt k o v v mno la mn mn 1 2 3       =     ⋅ ′′′  ⋅ ′′′    ⋅ ×         ⋅ = −       = × 6 6 3 2 2 0 2 3 2 mn p k h rt k mn mn o mn exp ∆    ⋅         = ⋅ −      × mn mn k h rt mn mn / exp2 3 0 3 3 ∆ ′′′′   ′′′        =         v v mn mn mn mn la mn mn mn 3 /         = − ⋅         × × mn mn z cu cu mn mn mn mn / / ( )1 3 3 d = ⋅ ′′′  = ′′′    =    = × z v v o la mn o 3 3 3 3 d d d . зуев а. ю., цветков д. с. 351 № 4 | 2015 chimica techno acta 1173 k в атмосфере чистого кислорода до величины практически равной трем для lоg(po2/атм) =  –2,76 и т = 1373 k. образец lamn0,70cu0,30o3+δ был исследован только в среде воздуха в температурном интервале 1173–1473 k [6]. полученные данные показали, что во всем изученном температурном интервале образец оставался стехиометричным по отношению к кислороду. на рис. 1 и 2 приведены результаты верификации модели, согласно уравнению (5), для lamn1-zcuzo3+δ с использованием температурных зависимостей констант равновесия (см. систему (4)). параметры соответствующих температурных зависимостей, полученные в результате минимизации отклонения модельных поверхностей от экспериментальных данных, вместе с коэффициентами корреляции сведены в табл. 1. как следует из данных этой таблицы и рис.  1, между величинами po2, вычисленными по предложенной модели и определенными экспериментально, наблюдается хорошее согласие. из данных табл. 1 видно, что добавление меди (z = 0,05 и 0,10) в lamno3+δ практически не меняет термодинамические характеристики реакции достраивания решетки перовскита (2) по сравнению с недопированным манганитом лантана [8]. небольшое добавление меди (z = 0,05) в lamno3+δ также имеет небольшое влияние на протекание реакции диспропорционирования марганца (3), так как при этом энтальпия этой реакции увеличивается незначительно. однако увеличение содержания меди (z = 0,10) выражается в драматическом изменении процесса диспропорционирования (3), который приобретает резко выраженный термически активированный характер, о чем можно судить по аномально большому значению энтальпии, 6000 кдж, по сравнению с практически нулевой энтальпией диспропорционирования для незамещенного lamno3+δ [8]. стоит отметить, что константа равновесия реакции (4) для lamn0,90cu0,10o3+δ в исследованном температурном интервале принимает чрезвычайно низкие значения, изменяясь от 10–60 при 1173 k рис. 1. результат модельного анализа дефектной структуры lamn0,95cu0,05o3+δ. заполненные символы – эксперимент [6]; поверхность соответствует уравнению (5) рис. 2. результат модельного анализа дефектной структуры lamn0,9cu0,1o3+δ. заполненные символы – эксперимент [6]; поверхность соответствует уравнению (5) кислородная нестехиометрия и дефектная структура lamn 1–z cuzo 3+δ 352 № 4 | 2015 chimica techno acta до 10–22 при 1373  k. следовательно, равновесие в реакции диспропорционирования (3) практически полностью смещается на ионы марганца mn+3. поэтому обоснованным предоставляется упрощение модели дефектной структуры lamn0,90cu0,10o3+δ путем исключения из рассмотрения реакции диспропорционирования марганца. соответствующее упрощение системы (4) приводит к относительно простому модельному уравнению log( / ) ( ) p a o 2 1 3 3 3 6 3 2 3 atm =− +       ⋅ ⋅ ⋅ + −      ⋅ + d d d d d (( , , )− + − − ⋅2 7 6 9 3 2 1 2 2 1 6d da a k , (6) где a k k b k mn cu mn cu mn cu = − − + − ⋅ + 7 6 3 1 3 2 2 2 d d d( ) ( ) и b k k mn cu mn c = + − + + + − ( , , , ) ( , , , ) 46 24 5 76 32 64 26 64 3 24 81 24 2 2 2 2 2 d d d d uu +36 2d результаты верификации упрощенной модели дефектной структуры lamn0,90cu0,10o3+δ согласно уравнению (6) приводятся также в табл. 1. как видно, для этой модели коэффициент корреляции r2 заметно ближе к 1 по сравнению с моделью, учитывающей реакцию (3). следует добавить, что сумма квадратов отклонений для модели, которой соответствует уравнение (6), составляет 0,068, тогда как искомое для модели, учитывающей реакцию (3) – 0,224. поэтому дальнейшие расчеты концентраций дефектов для lamn0,90cu0,10o3+δ выполняли на основе результатов модельного анализа уравнения (6). в качестве примера на рис. 3–6 приводятся зависимости концентрации локализованных электронных дефектов от кислородной нестехиометрии lamn1–zcuzo3+δ для z = 0; 0,05 и 0;1, соответственно. в целях сравнения таблица 1 значения термодинамических параметров температурных зависимостей констант равновесия процессов разупорядочения lamn1-zcuzo3+δ z ур ав не ни е ре ак ци я δh, кдж моль ln(k0)i r 2 0,05 5 3 85,1 1,53 0,9961 52,8 14.2 2 -293,4 -38,0 0,1 5 3 6000 477 0,9761 118,0 29,3 2 -242,6 -34,2 0,1 6 1 178±33 14.9±3 0,994 2 -163 ± 30 -29,5 ± 3 зуев а. ю., цветков д. с. 353 № 4 | 2015 chimica techno acta зависимости концентрации дырок, локализованных на атомах марганца, от величины δ для различных составов lamn1–zcuzo3+δ приведены на рис. 6. как следует из этих рисунков, добавление меди в lamno3+δ приводит к заметному изменению электронного разупорядочения марганцевой подрешетки, что выражается в увеличении концентрации дырок mnmn  и уменьшении концентрации электронов mnmn ´ , локализованных на атомах марганца. как следует из данных этих рисунков, добавление меди в lamno3+δ приводит к заметному изменению электронного разупорядочения марганцевой подрешетки, что выражается в увеличении концентрации дырок mnmn  и уменьшении концентрации электронов mnmn ´ , локализованных на атомах марганца. при этом концентрация электронов, локализованных на атомах меди cumn / , практически не изменяется во всей области избытка кислорода для манганита lamn0,95cu0,05o3+δ, и не зависит от температуры, оставаясь равной общему содержании меди, тогда как эта величина для lamn0,90cu0,10o3+δ варьируется в широком интервале при изменении содержания кислорода и температуры. наблюдаемое увеличение содержания mn+4 в манганите лантана при его допировании медью согласуется с выводами работы [9], сделанными на основании окислительно-восстановительного титрования медью образцов замещенных манганитов лантана. обнаруженное в настоящей работе изменение концентрации cu+2 для lamn0,90cu0,10o3+δ в зависимости от индекса кислородной сверхстехиометрии и температуры косвенно поддерживается результатами работы [10], в которой полученный для этого состава спектр рентгеновской фотоэлектронной спектроскопии не удалось расшифровать в предположении того, что вся медь находится только в состоянии +2. в то же время, установленное авторами [10] отсутствие mn+2 в lamn0,90cu0,10o3+δ полностью согласуется с результатами модельного анализа дефектной структуры этого манганита, выполненного в настоящей работе. рис. 3. зависимость концентрации электронных дефектов lamno3+δ от кислородной нестехиометрии [8] при различных температурах рис. 4. зависимость концентрации электронных дефектов lamn0,95cu0,05o3+δ от кислородной нестехиометрии при различных температурах кислородная нестехиометрия и дефектная структура lamn 1–z cuzo 3+δ 354 № 4 | 2015 chimica techno acta выводы допирование манганита лантана медью оказывает заметное влияние прежде всего на содержание кислорода и его электронную подсистему. это наблюдается в последовательной смене доминирующего электронного процесса с реакции диспропорционирования марганца на реакцию электронного обмена между марганцем и медью по мере увеличения содержания последней в lamn1–zcuzo3+δ при одновременном уменьшении содержания кислорода. при достижении концентрации допанта z = 0,3, реакция электронного обмена между марганцем и медью, по всей видимости, становится единственным процессом разупорядочения lamn1–zcuzo3, что выражается в его стехиометрическом составе по кислороду во всем исследованном интервале температуры. 1. jonker g. h., van santen j. h. ferromagnetic compounds of manganese with perovskite structure. physics. 1950;16:337–349. 2. menzler n. h., tietz f., uhlenbruck s., buchkremer h. p., stöver d. materials and manufacturing technologies for solid oxide fuel cells. j. mater. sci. 2010;45:3109– 3135. 3. santen j. h. van, jonker g. h. electrical conductivity of ferromagnetic compounds of manganese with perovskite structure. physics. 1950;16:599–600. 4. royer s., duprez d. catalytic oxidation of carbon monoxide over transition metal oxides. chemcatchem. 2011;3:24–65. 5. chan k. s., jaenicke s., chuah g. k. and lee j. y. catalytic carbon monoxide oxidation over strontium, cerium and copper-substituted lanthanum manganates and cobaltates. applied catalysis a: general. 1994;107:201–207. 6. petrov a. n., zuev a. yu., tikchonova i. l. voronin v. i. crystal and defect structure of the mixed oxides lamn1–zcuzo3±y (0£ z ≤0,4). solid state ionics. 2000;129:179–188. рис. 5. зависимость концентрации электронных дефектов lamn0,9cu0,1o3+δ от кислородной нестехиометрии при различных температурах рис. 6. зависимость концентрации электронных дефектов lamn1–zcuzo3+δ от кислородной нестехиометрии при различных температурах зуев а. ю., цветков д. с. 355 № 4 | 2015 chimica techno acta 7. jonker g. h. magnetic and semiconducting properties of perovskites containing manganese and cobalt. j. appl. phys. 1966;37:1424–1430. 8. zuev a. yu., tsvetkov d. s. oxygen nonstoichiometry, defect structure and defectinduced expansion of undoped perovskite lamno3±δ. solid state ionics. 2010;81:557– 563. 9. porta p., de rossi s., faticanti m., minelli g., pettiti i., lisi l., turco m. perovskitetype oxides i. structural, magnetic, and morphological properties of lamn1−x cuxo3−d and laco1−xcuxo3−d solid solutions with large surface area. journal of solid state chemistry. 1999;146:291−304. 10. tabata k., hirano y., suzuki e. xps studies on the oxygen species of lamn1–xcuxo3+λ. applied catalysis a: general. 1998;170:245–254. кислородная нестехиометрия и дефектная структура lamn 1–z cuzo 3+δ arsenate and arsenite reaction kinetics with ferric hydroxides using quantum chemical calculations 144 d o i: 1 0. 15 82 6/ ch im te ch .2 01 8. 5. 03 .0 3 cijin j. george, sougata santra, zyryanov g. v., kousik giri chimica techno acta. 2018. vol. 5, no. 3. p. 144–149. issn 2409–5613 cijin j. george1, sougata santra2, g. v. zyryanov2,3, kousik giri1* 1department of computational sciences, central university of punjab, bathinda, punjab, india 2department of organic and biomolecular chemistry, chemical engineering institute, ural federal university, 19 mira st., ekaterinburg, 620002, russian federation 3i. ya. postovskiy institute of organic synthesis, ural branch of the russian academy of sciences, 22 s. kovalevskoy st., ekaterinburg, 620219, russian federation *e-mail: kousikgiri@gmail.com arsenate and arsenite reaction kinetics with ferric hydroxides using quantum chemical calculations the knowledge of the mechanism involved in the process of adsorption and desorption of arsenate and arsenite with ferric hydroxides is important to address the water toxicity problems and to tackle the adverse effect of these substances in nature. an essential outcome of previous studies on the kinetics of the arsenate adsorption on aluminum and iron oxide was that the adsorption is a two-phase (bi-phase) process. quantum mechanical calculations using density functional theory were used to determine the thermodynamic variables governing the adsorption process to get an insight into the stability of the complexes formed. the previous investigation showed that the positively charged ferric hydroxide cluster had better stability at neutral ph. the chemisorbed charged monodentate complexes had gibbs free energy of reaction –55.97 kcal/mol where the bidentate complex formation had gibbs free energy of reaction –62.55 kcal/mol. the bidentate complex having a negative charge had more gibbs free energy of reaction compared to uncharged one. the results of the study indicate that gibbs free energy for the reaction has a significant role in controlling the kinetics of the adsorption and sorption process of arsenate on ferric hydroxide clusters. keywords: received: 01.10.2018. accepted: 25.10.2018. published: 31.10.2018. © cijin j. george, sougata santra, zyryanov g. v., kousik giri, 2018 introduction arsenic is a significant contaminant present in the groundwater due to natural processes like weathering of rocks, discharge of effluents and waste disposal from industries, arsenical herbicides and pesticides used in agricultural activities and many other sources [1]. the various oxidation states arsenic exhibits are –3, 0, +3, and +5, where the inorganic forms +3 (arsenite) and +5 (arsenate) states of as are 145 predominant depending on the reducing and oxidizing conditions, respectively. the relatively strong adsorption affinity of as shown towards ferric hydroxides has a vital role in the detoxification of as, thereby controlling the arsenic water pollution and employed in techniques for purification of drinking water. several works were done on the structural determination of arsenate-ferric hydroxide complex. the studies of arsenic (iii) stability on goethite using x-ray absorption spectroscopy and batch techniques indicated that there is inner sphere bidentate complexation through ligand exchange [2]. monodentate and bidentate complexes are observed in the adsorption of arsenate on goethite [3–5]. the models produced by molecular modeling and the x-ray absorption fine structure spectroscopy (exafs) results are compared, and the nature of the chemisorption complex is determined [6, 7]. an essential outcome of previous studies on the kinetics of the arsenate adsorption on aluminum and iron oxide was the two-phase adsorption process constituting a fast phase of the time order of a minute or less and slow phase which attains an equilibrium within a time scale greater than 162 hours [5, 8–10]. the factors responsible for this phenomenon are considered to be slow diffusion mass transport [9, 11, 12], availability of heterogeneous sites, monodentate to bidentate complex conversions, the surface precipitate formation and the rearrangement of surface complexes. further, the studies on the arsenate desorption by use of different extractants like phosphate or high ph solutions indicate a slow release of arsenate from the adsorbed complexes. the conclusion from these studies implies that only a small portion of arsenate is released by the use of extractants like phosphate or hydroxide ions. this leads to the interesting fact that a part of arsenate-ferric hydroxide complex may be irreversible in nature. despite the studies done on arsenateferric hydroxide complex formation, a little is known about the mechanism of this reaction. in this regard, the motive of this theoretical study is to get an insight into the mechanism governing the arsenateferric hydroxide complex formation. the thermodynamic parameters and reaction rates governing the mechanism are determined by quantum chemical calculations. materials and methods all calculations were carried out using the gaussian 09 software [13]. full geometry optimizations and corresponding harmonic vibrational frequency computations, to confirm their minima on the potential energy surface, were carried out using the austin-frisch-petersson functional with dispersion (apfd) [14] and m06 hybrid functional of truhlar and zhao [15] suite of density functional theories (dft) as implemented in gaussian 09. apfd functional has been used as a primary method in gaussian 09 for its best trade-off between accuracy and computational cost for the largest range of molecular systems and chemical problems. m06 functional perform better for a model system with dispersion and ionic hydrogen-bonding interactions. for both structural optimizations and frequency calculations the balanced basis set of triple zeta valence from ahlrichs and coworkers (def2tzvp) [16] was employed. for all calculations, solvent effects of water were introduced using the polarizable continuum model (pcm) using the integral equation formalism variant 146 (iefpcm) with apfd functional and the smd variation of iefpcm of truhlar and workers with m06 functional. quantum-chemical calculations involving dft were used to calculate the heat of formation of reactants and products and their corresponding gibbs free energies. the ferric hydroxides clusters were modeled following the previous studies. the ferric hydroxides clusters consisted of two iron atoms, ten oxygen atoms which were octahedrally coordinated to the iron atoms. the clusters can be represented by the general formula fe2o3 (h2o)7. the numbers of the protons were varied to calculate the effect of binding of arsenate with the cation and anion cluster’s binding sites. to minimize the effect of gross distortions of the di-octahedral geometry observed in previous studies [17], the coordinates of six peripheral oxygen atoms which were not part of the binding reaction was fixed to simulate the binding sites of the iron hydroxide clusters also including bound arsenic species. the enthalpies of the reaction are determined by calculating the heats of formation. the equation used is as follows: ∆r h0(298k) = = σ(e0 + hcorr)products – (e0 + hcorr)reactants similarly, gibbs free energy change of the reaction is computed by the key equation: ∆r g0(298k) = = σ(e0 + gcorr)products − (e0 + gcorr)reactants results and discussion the heat of formation of the clusters at 0k was determined and is given in table 1. table 1 calculated heat of formation for three different possible species cluster charge heat of formation (kcal/mol) fe2o10h13 – –1 –1261.64 fe2o10h14 0 –1186.33 fe2o10h15 + +1 –1087.94 the results indicate that the heat of formation of the positive charged ferric hydroxide has the least value at 0k, whereas the other clusters are more stable than fe2o10h15 +. the previous investigation showed that the positively charged ferric hydroxide cluster had better stability at neutral ph [17]. this may be possible due to the better stabilization of the fe2o10h15 + at neutral ph and hence increase in the heat of formation at the neutral ph. the optimized geometry of the fe2o10h15 + is represented by fig. 1. the reaction of fe2o10h15 + with haso4 2– resulted in the formation of charged (–1 charge) monodentate (fig. 2) and bidentate complex (fig. 3). meanwhile, the reaction of fe2o10h15 + with h2aso4 resulted in the formation of uncharged monodentate (fig.  4) and bidentate complex (fig. 5). the corresponding gibbs free energy for the reaction was determined for the monodentate and bidentate complexes formed. the values are in given in table two and three, respectively. the monoand bidentate complex bearing a negative charge showed higher stability than the uncharged complexes formed. this indicates that the charge on the species improved the stability of the complex. the chemisorbed charged monodentate complexes had gibbs free energy of reaction –55.97 kcal/mol, whereas the bidentate complex formation had gibbs free energy of reaction –62.55 kcal/mol. thus, the desorption process of arsenate with com147 petitive ligands would depend on gibbs free energy of the reaction. the process is feasible only when the higher gibbs free energy values are attained. the results of the study indicate that gibbs free energy for the reaction has a significant role in controlling the kinetics of the adsorption and sorption process of arsenate on ferric hydroxide clusters. fig. 1. structure of fe2o10h15 + complex carrying a net positive charge fig. 3. structure of negatively charged bidentate complex fig. 2. structure of negatively charged monodentate complex fig. 4. structure of uncharged monodentate complex fig. 5. structure of uncharged bidentate complex 148 acknowledgments k. giri acknowledges financial support from ugc, govt. of india for start-up project funding. s.  santra and g. v.  zyryanov thank russian science foundation (ref # 18-73-00301) for financial help. references 1. bhumbla dk, keefer rf. arsenic mobilization and bioavailability in soils. arsenic in the environment. part i: cycling and characterization. nriagu jo, editor. john wiley & sons: new york, 1994. pp 51−82. 2. manning ba, fendorf se, goldberg s. surface structures and stability of arsenic (iii) on goethite: spectroscopic evidence for inner-sphere complexes. environmental science & technology. 1998;32(16):2383–8. doi: 10.1021/es9802201. 3. waychunas ga, davis ja, fuller cc. geometry of sorbed arsenate on ferrihydrite and crystalline feooh: re-evaluation of exafs results and topological factors in predicting sorbate geometry, and evidence for monodentate complexes. geochimica et cosmochimica acta. 1995;59 (17):3655–61. doi: 10.1016/0016–7037(95) 00276–6. 4. waychunas ga, rea ba, fuller cc, davis ja. surface chemistry of ferrihydrite: part 1. exafs studies of the geometry of coprecipitated and adsorbed arsenate. geochimica et cosmochimica acta. 1993;57(10):2251–69. doi: 10.1016/0016–7037(93)90567-g. 5. grossl pr, eick m, sparks dl, goldberg s, ainsworth cc. arsenate and chromate retention mechanisms on goethite. 2. kinetic evaluation using a pressure-jump relaxation technique. environmental science & technology. 1997;31(2):321–6. doi: 10.1021/es950654l. 6. kubicki jd. comparison of as (iii) and as (v) complexation onto aland fe-hydroxides. advances in arsenic research. acs symposium series. 915: american chemical society; 2005. p. 104–17. table 2 thermochemical analysis of negatively charged monodentate and bidentate complexes method product i–mono dentate product-ii bidentate δre (kcal/mol) δrh (kcal/mol) δrg (kcal/mol) δre (kcal/mol) δrh (kcal/mol) δrg (kcal/mol) apfd –61.3202283 –106.9803296 –55.9700823 –57.8908889 –57.0832842 –62.5564221 m06 –30.9876741 –30.0162894 –36.3949235 table 3 thermochemical analysis of uncharged monodentate and bidentate complexes method product i–mono dentate product-ii bidentate δre 0 (kcal/mol) δrh (kcal/mol) δrg (kcal/mol) δre (kcal/mol) δrh (kcal/mol) δrg (kcal/mol) apfd –32.0525578 –31.7544907 –28.0741475 –38.3383204 –37.5514235 –43.1638684 m06 –16.7174805 –15.8289271 –13.6307614 –20.3865286 –18.4719972 –27.6141831 149 7. sherman dm, randall sr. surface complexation of arsenic (v) to iron (iii) (hydr) oxides: structural mechanism from ab initio molecular geometries and exafs spectroscopy. geochimica et cosmochimica acta. 2003;67(22):4223–30. doi: 10.1016/s0016–7037(03)00237–0. 8. zhang h, selim hm. kinetics of arsenate adsorption−desorption in soils. environmental science & technology. 2005;39(16):6101–8. doi: 10.1021/es050334u. 9. fuller cc, davis ja, waychunas ga. surface chemistry of ferrihydrite: part 2. kinetics of arsenate adsorption and coprecipitation. geochimica et cosmochimica acta. 1993;57(10):2271–82. doi: 10.1016/0016–7037(93) 90568-h. 10. yang w, zhao n, zhang n, chen w, kan at, tomson mb. time-dependent adsorption and resistant desorption of arsenic on magnetite nanoparticles: kinetics and modeling. desalination and water treatment. 2012;44(1-3):100–9. doi: 10.1080/19443994.2012.691808. 11. raven kp, jain a, loeppert rh. arsenite and arsenate adsorption on ferrihydrite: kinetics, equilibrium, and adsorption envelopes. environmental science & technology. 1998;32 (3):344–9. doi: 10.1021/es970421p. 12. luengo c, brigante m, avena  m.  adsorption kinetics of phosphate and arsenate on goethite. a comparative study. journal of colloid and interface science. 2007;311(2):354–60. doi: https://doi.org/10.1016/j. jcis. 2007.03.027. 13. austin a, petersson ga, frisch mj, dobek fj, scalmani g, throssell k. a density functional with spherical atom dispersion terms. journal of chemical theory and computation. 2012;8(12):4989–5007. doi: 10.1021/ct300778e. 14. gaussian09, revision d. 01, gaussian, inc., wallingford ct, 2013. 15. zhao y, truhlar dg. the m06 suite of density functionals for main group thermochemistry, thermochemical kinetics, noncovalent interactions, excited states, and transition elements: two new functionals and systematic testing of four m06-class functionals and 12 other functionals. theoretical chemistry accounts. 2008;120(1):215–41. doi: 10.1007/s00214-007-0310-x. 16. weigend f, ahlrichs r. balanced basis sets of split valence, triple zeta valence and quadruple zeta valence quality for h to rn: design and assessment of accuracy. phys chem chem phys. 2005;7(18):3297–305. doi: 10.1039/b508541a. 17. farrell j, chaudhary bk. understanding arsenate reaction kinetics with ferric hydroxides. environmental science & technology. 2013;47(15):8342–7. doi: 10.1021/es4013382. 46 d o i: 1 0. 15 82 6/ ch im te ch .2 01 6. 3. 1. 00 4 i. zvereva1*, t. pavlova1, v. pantchuk1, v. semenov1, y. breard2, j. choisnet2 1 institute of chemistry, st. petersburg state university, 198904 petrodvorets, saint petersburg, russia 2 laboratoire crismat, umr 6508 cnrs ensicaen and caen university, 6 bd maréchal juin14050 caen cedex 4 france *corresponding author: tel.: +7 (904) 330-50-19 e-mail: irina.zvereva@spbu.ru the solid solution sr 3 ti 2–x fe x o 7–δ (x ≤ 0.5): characterization of fe (iii) – fe (iv) mixed valences** the results of a magneto chemical and mössbauer characterization are reported for the solid solution sr 3 ti 2–x fe x o 7–δ (x ≤ 0.5), the intergrowth of a double perovskite block and one rock-salt layer type. the charge compensation mechanism induced by the introduction of iron atoms in the matrix of sr 3 ti 2 o 7 is sensitive to the conditions of synthesis, namely an oxidation process triggers the formation of mixed fe(iii)–fe(iv) valences. the crystallographic characterization variation of the cell parameters and structure calculations – brings evidence for the respective occurrence of mixed valences and oxygen vacancies which form in the middle plane of the double perovskite block. ferromagnetic exchange interactions which are absent in the fe(iii) containing compositions, appear and progressively strengthen depending on the oxidizing treatment. they are ascribed to the presence of an increasing amount of fe(iv) species. remarkably, a mixed valence state of iron forms during annealing in air with an increasing contribution of the fe(iv) species for the larger iron contents, as deduced from mössbauer data. keywords: layered oxides; solid solutions; iron; mixed valence; magnetic susceptibility; mössbauer spectrometry. **the authors (1) are grateful to the russian fund of basic research for its financial support (grant 15-03-05981). © zvereva i., pavlova t.,pantchuk v., semenov v., breard y., choisnet j., 2016 47 № 1 | 2016 chimica techno acta introduction mixed valence states of 3d transition metals such as ni, co, cu and mn [1–7] can be stabilized in perovskite like oxides when working partial non-isovalent cationic substitutions. the fascinating electrical and magnetic properties of these oxide materials is strongly connected to the existence of these mixed valence states. of importance to stabilize unusual oxidation degrees of 3d transition metals is the lowering of their site symmetry in the perovskite layers. in this respect the intergrowths of perovskite (p) layers and rocks-salt (rs) layers are favourable to get mixed valence states of the transition metal, whereas in the high symmetry field of the tridimensionnal perovskite structure such unusual oxidation degrees can disproportionate. in the manganites la1+xsr2-xmn2o7 with the p2/rs intergrowth of a double perovskite block and one rock-salt layer, the existence of a colossal magnetoresistance (cmr) strongly depends on the mixed valence state of the manganese atoms [5, 6]. as to the oxygen content of these layered perovskite like phases, even if it has no concern to the oxygen stoichiometric lnsr2mn2o7 phases which contain mn (iii) and mn (iv) [8], in most cases the oxygen deficiency properties are involved in the existence of the physical properties, as regularly checked in the cuprates and nickelates [1–4]. in the same way, systematic attention has been focused on the rich electrical and magnetic properties of perovskite like intergrowth structures of ferrites and their solid solutions [9–14]. as an example the existence of two p2/rs type iron strontium mixed oxide is reported, namely the fe(iv) one sr3fe2o7 [12] and the fe(iii) one sr3 fe2o6 [9]. due to this and in the frame of our previous work on p/rs type chromium doped aluminates [15] and p2/rs chromium doped titanates [16], it was decided to look for compositions where it is possible to create mixed valence fe(iii) and fe(iv) state of the iron atoms. in this paper, we report on the partial substitution of iron atoms for titanium atoms in the p2/rs type strontium titanate sr3ti2o7 [17] (fig. 1) in terms of a structural analysis (xrpd) and a magnetic and mössbauer characterization of iron low compositions of the solid solution sr3ti2-xfexo7-δ (x ≤ 0.5). the entire solid solution exists but up to now the reported results have a concern with iron richer compositions (2 ≥ x ≥ 0.5) [18, 19]. even more iron diluted compositions (x ≤ 0.2) were never considered for crystal chemical and physical studies, as well. consequently, the main goal of the present work consisted in clearing up the crystal chemical mechanism of charge compensation induced by the introduction of iron atoms in the matrix of sr3ti2o7: formation of the fe (iii) and fe (iv) mixed valences together with the creation of oxygen vacancies. experimental eight compositions sr3ti2-xfexo7-δ (0 ≤ x ≤ 0.5) were synthesized from solid state reaction of the mixtures of precursor oxides tio2, fe2o3 and carbonate srco3 (johnson matthey, purity ≥ 99.95 %). according to the ceramics methods, the samples were pelletized and calcined in air at 1200 °c and then at 1350 °c for 40 h each. the solid solution sr 3 ti 2–x fe x o 7–δ (x ≤ 0.5): characterization of fe (iii) – fe (iv) mixed valences 48 № 1 | 2016 chimica techno acta the compositions x ≥ 0.2 were considered for x-ray structural analysis from cell parameters to structure calculations. the diluted compositions 0 < x ≤ 0.2 were retained for the magnetic and the mössbauer study. in order to receive relevant information regarding the oxygen stoichiometry, different heating conditions were worked for some compositions asprepared in air: – an oxidizing treatment: 850 °c for 10 h and 150 bars oxygen pressure (x = 0.2 and x = 0.5) – a reducing treatment: a dta setaram device used with an hydrogen-argon atmosphere from room temperature up to 850 °c for 8 h. this was applied specifically to the richest iron composition x = 0.5. the iron content of the as-prepared samples was determined from atomic emission spectrometry. the maximum deviation between the theoretical and the experimental value of the iron content of a given sample does not exceed 5 %. xrpd diffractograms were recorded with a philips pw3020 diffractometer using the cu kα radiation in the 2q angular range 5–110 °, step size 0.04 ° and counting time 12s. structure calculations were carried out with the fullprof code [20]. the magnetic susceptibility was measu red according to the faraday method in the temperature range 77–400 k. the precision is better than 2 %. mössbauer spectra were recorded at room temperature by using spectrometer wissel (57fe in a rhodium matrix), the isomeric shifts being calculated with respect to α fe. in order to evaluate the part of paramagnetic species, the intensity of the signals was determined precisely up to the resonance factor. xrpd results: cell constants and structure calculations xrpd phase analysis ensured the existence of iron containing mixed oxide isotypic of sr3ti2o7 (fig.  1) which forms within the whole range of compositions (0 ≤ x ≤ 0.5). when the iron content of the sr3ti2-xfexo7-δ compositions does not exceed the value x = 0.3 no extra phase is observed. in the range of compositions 0.3 < x ≤ 0.5 some faint amount of a sr4 ti3o10 type phase i.e. a p3/rs intergrowth phase accompanies the major p2/rs phase. the values of the tetragonal unit cell constants a, c and volume v for x = 0.2 air prepared and after oxidation, x = 0.3 air prepared and x = 0.5 (air prepared, after oxidation and after reduction) are reported in table 1. the corresponding variation versus x is shown in fig.  2. in order to better understand the meaning of such a variation in terms of the crufig. 1: (a) p2/rs intergrowth structure of sr3ti2o7: p perovskite block; rs rock-salt layer. (b) connection of octahedra and mo9 and mo12 polyhedra zvereva i., pavlova t.,pantchuk v., semenov v., breard y., choisnet j. 49 № 1 | 2016 chimica techno acta cial problem of the mixed valences of fe atoms, it was decided to include the variation which can be modelled in the cases of a fe (iii) and a fe (iv) solid solution i.e. the lines which connect the oxides sr3ti2o7 – sr3fe2o7 and sr3ti2o7 – sr3fe2o6, respectively. at first it should be stated that the nearly perfectly linear variation of vair the unit cell volume of the as-prepared compositions (fig. 2a) brings evidence for the existence of a solid solution in the entire range of compositions 0 ≤ x ≤ 0.5. moreover the variation of v strongly depends on the heating conditions: the oxidized compositions – fe (iv) – exhibit a value of vox smaller than the reduced one vred – fe (iii) whereas vair takes intermediate valu es. more precisely, the latter result is the combination of two different trends in the crystal chemical evolution of the solid solution sr3ti2-xfexo7-δ herein investigated: – in the oxidized compositions, the substitution of the smaller fe4+ cations (rcnvi = 0.585 å) [21] for the ti 4+ one (rcnvi = 0.605 å) results in a decrease of v. – in the reduced compositions, the creation of oxygen vacancies cancels the effect of the substitution of bigger fe3+ cations (rcnvi = 0.645 å) for the ti 4+ one, resulting in an overall decrease of v whose slope is weaker than in the oxidized compositions. the precise contribution of a (fig. 2b) and c (fig. 2c) parameters to the variation of the unit cell volume is rather difficult to ensure. at least one can assume the parameter a to be more sensitive to the decrease of size of the cations sitting in the octahedral sites. this result fully agrees with that is reported in the study of the compositions x ≥ 0.5 i.e. annealing at high oxygen pressure triggers a decrease table 1 unit cell parameters (å) and volume (å3) in the solid solution sr3ti2-xfexo7-δ x 0 [15 ] 0.2 air 0.2 oxid. 0.3 air 0.5 air 0.5 oxid. 0.5 red. *1oxid. *1red. a 3.902 3.8988(3) 3.8956(4) 3.8968(2) 3.8941(2) 3.8910(4) 3.8974(4) 3.877 3.898 c 20.371 20.334(4) 20.310(5) 20.323(2) 20.306(1) 20.272(5) 20.305(2) 20.26 20.20 v 310.2 309.1 308.2 308.6 307.9 306.9 308.4 304.5 307.0 *1: calculated values as the average of sr3ti2o7 and sr3fe2o7 (oxid.) [12] and sr3fe2o6 (red.) [9]. fig. 2: variation of the cell volume (å3) and cell parameters (å) in the solid solution sr3ti2-xfexo7-δ the solid solution sr 3 ti 2–x fe x o 7–δ (x ≤ 0.5): characterization of fe (iii) – fe (iv) mixed valences 50 № 1 | 2016 chimica techno acta of the parameter a [19]. on the contrary, the existence of a large amount of oxygen vacancies induces a pronounced lowering of the value of the parameter c. as a main result of the observed variation of the unit cell volume, it must be stated that the solid solution sr3ti2-xfexo7-δ which forms by heating in air contains a mixed valence state of the iron atoms. in order to learn about some modifications which are expected in the p2/rs intergrowth of the iron containing solid solution, it was decided to carry out a profile analysis of the xrpd difractograms of the compositions x ≥ 0.2. for x = 0.5 three cases were considered: as-prepared in air, oxidized and reduced samples and for x = 0.2 the as-prepared and the oxidized sample. the structure of sr3ti2o7 [17] was retained: s.g. i4/mmm. concerning the oxygen non-stoichiometry, xrpd is rather unsensitive to a small variation of the oxygen content. consequently, only in a final step of the calculations of the air prepared compositions, a value of δ the oxygen deficiency arbitrarily fixed to the half of the maximum value corresponding to a full reduction was considered (δ = x/4). the results of the mössbauer characterization here after reported ensured a value of δ close or lower than the half of a full reduction. as it was previously performed in the chromium containing solid solution sr3ti2-x crxo7-δ [16] we did an attempt to find the likely location of the oxygen vacancies in one of the three possible sites, namely the inner apical o1, the equatorial o2 and the outer apical o3 (fig. 1b). in this respect, the main results to be received from the structural analysis are as follows: – the oxygen deficiency of the air prepared and reduced compositions occurs in the inner apical o1 positions i.e. in the middle plane of the double perovskite block. this meets the different data obtained in the p2/rs cuprates [22] and the solid solution sr3ti2-xcrxo7-δ [16]. – the equatorial m-o2 distances (table 2), within the precision of the calculation procedure are unsensitive to the substitution of iron atoms for titanium. – as regularly observed in the intergrowth structures, there is an apical distorsion of the octahedra, as visible from the obtained values of the corresponding inner apical m-o1 and outer apical m-o3 distances (table 2). the main data observed in sr3ti2o7 i.e. the coupling of a longer inner m-o1 distance with a smaller outer m-o3 one is saved for the whole series of compositions. magneto chemical and mossbauer results the temperature dependence of the molar magnetic susceptibility in four air prepared compositions (x = 0.02; 0.08; 0.12; 0.18) of the solid solution table 2 metal oxygen distances (å) in the (ti, fe)o6 octahedra in the solid solution sr3ti2-xfexo7-δ m-o dist. m = ti, fe sr3ti2o7 air prep.[17] x = 0.2 oxidized x = 0.2 air prep. x = 0.3 air prep. x = 0.5 oxidized x = 0.5 air prep. x = 0.5 red. m-o1 x1 1.995 2.02(1) 2.02(1) 2.00(1) 2.03(1) 2.00(1) 2.02(1) m-o2 x4 1.949 1.95(1) 1.95(1) 1.95(1) 1.95(1) 1.95(1) 1.95(1) m-o3 x1 1.887 1.91(2) 1.92(2) 1.94(2) 1.91(2) 1.91(2) 1.96(2) zvereva i., pavlova t.,pantchuk v., semenov v., breard y., choisnet j. 51 № 1 | 2016 chimica techno acta sr3ti2-xfexo7-δ is shown in fig.3. within the temperature range 77–400 k there is a monotonic decrease of χ versus t and for given temperature the observed value of χ systematically increases when x, the iron content, gets larger. the experimental data of the molar magnetic susceptibility have been used for calculating a paramagnetic value per one mole of iron, by subtracting the diamagnetic contribution of sr3ti2o7 and iron atoms. the thermal variation of the paramagnetic susceptibility is described by a curie-weiss law χ = c/(t-q) over the whole temperature range under consideration. curie constant c takes a value close to 4 emu.k, where as weiss temperature q, slightly increases versus x (table 3). table 3 curie constant c and weiss temperature q in the air prepared) sr3ti2-xfexo7-δ x c, emu. q, k 0.02 4.07 -18 0.08 4.00 -1.1 0.12 4.04 2.8 0.18 4.01 7.8 the calculated effective magnetic moment meff shows a complex dependence on both temperature and iron content, as visible in fig. 4 for the air prepared compositions x = 0.02, 0.08; 0.12; 0.18. such behaviour cannot be explained on the basis of one paramagnetic species and consequently, a mixed valence state of the iron cations which are introduced in the diamagnetic matrix of sr3ti2o7 is likely to occur in the solid solution. concerning the magnetic interactions, it can be reasonably assumed that they progressively change from an antiferromagnetic property to a ferromagnetic one, depending on an increasing of iron content. the concentration dependence of meff in the temperature range 298–400 k can be modelled in the following way: 298к 400к µ µ = + = + 5 44 2 11 5 47 1 82 , , , , x x (1) by extrapolating these equations at zero concentration of iron, the value of the effective magnetic moment mx→0 of a single iron cation in the solid solution above the room temperature (rt) can be estimated as nearly constant and equal to 5.45 mb. the theoretical values of meff of a single iron cation are 5.92 mb and 4.9 mb, for fe3+ (s = 5/2) and fe4+ (s = 2), respectively. clearly, the observed value 5.45 mb gives evidence for the presence of iron cations with a number of unpaired electrons smaller than 5, very likely 4 as in the fe4+ species. if the exchange interactions between the paramagnetic iron species above rt are assumed to be weak enough not to induce a deviation of the effective magnetic moment with respect to the value of meff for a single paramagnetic iron fig. 3. temperature dependence of cm the molar magnetic susceptibility for the air prepared solid solution sr3ti2xfexo7-δ. 1. x = 0.02; 2. x = 0.08; 3. x = 0.12;4. x = 0.18 the solid solution sr 3 ti 2–x fe x o 7–δ (x ≤ 0.5): characterization of fe (iii) – fe (iv) mixed valences 52 № 1 | 2016 chimica techno acta cation, the existence of a fe(iii)-fe(iv) mixed valence state of the iron atoms in the solid solution is ensured. the observed effective magnetic moment in the solid solution with a zero concentration of iron can be modelled in terms on the only fe3+ and fe4+ cations, according to the following formula: x fe fe fe fe fe fe → = + + = + + + + + + 0 2 2 2 3 3 4 4 3 4 1 µ µ µ0 a a a (2) where mi and ai are the magnetic moment and the concentration of a given iron cation. introducing into this equation the calculated value of mx→0 = 5.45 mb allows to calculate the concentration of fe4+ as equal to 0.48(4). the presence of the two species fe3+ and fe4+ in the diluted solid solution looks unambiguous. considering the temperature dependence of the effective magnetic moment allows to point to the following statements: – for the lowest iron concentrations (x ≤ 0.08) the magnetic properties, up to a large extent, correspond to what is expected from antiferromagnetic exchange interactions. – for larger iron concentrations (x > 0.08) ferromagnetic exchange interactions take an increasing part depending on an increasing iron concentration (fig. 4). the fe(iii) – fe(iv) mixed valence state of the iron atoms in the solid solution triggers three kinds of magnetic exchange interactions, namely fe3-o-fe3+, fe3+-o-fe4+ et fe4-o-fe4+. exchange interactions between fe3+ cations in the layered perovskite like phases are antiferromagnetic [23, 24]. when atoms with different electronic configuration are concerned, the exchange interactions are always ferromagnetic. as regards the fe4+-o-fe4+ exchange interactions, they are either antiferromagnetic or ferromagnetic depending on the site symmetry of the iron atoms. in order to learn about the cha racter of the exchange interactions in the fe4+-o-fe4+ clusters, an analysis of the influence of the experimental heating conditions on the magnetic properties was carried out in the limiting composition x = 0.5 of the solid solution. the temperafig. 4. variation of the effective magnetic moment versus temperature in the air prepared solid solution sr3ti2-xfexo7-δ. 1. x = 0.02; 2. x = 0.08; 3. x = 0.12; 4. x = 0.18 fig. 5: variation of the effective magnetic moment versus temperature in the composition x = 0.5. 1. oxidizing treatment; 2. air prepared; 3. reducing treatment; ––: single fe3+ cation zvereva i., pavlova t.,pantchuk v., semenov v., breard y., choisnet j. 53 № 1 | 2016 chimica techno acta ture dependence of the effective magnetic moment observed in sr3ti1.5fe0.5o7-δ as prepared in air and heated in oxidizing or reducing conditions, is shown in fig. 5. in the latter case, the sample contains only fe3+ species, as checked by thermal ana lysis, and the exchange interactions are antiferromagnetic. above rt (fig.  6) meff in the reduced sample takes a value very similar to that of the fe3+ cation 5.92 mb. in the air prepared sample the value of meff is intermediate between the reducing and the oxidizing cases, which result ensures the existence of two different exchange interactions. finally, in the oxidized sample the fe4+ species are responsible of the strong ferromagnetic character of the exchange interactions, in agreement with the results reported for the ferrate sr3fe2o7 [12]. at this stage, one result remains not immediately understandable in a simple way: the value of meff even at temperatures higher than rt (fig. 5) largely exceeds the value of single fe4+ cations: approximately 7 mb to be compared with 4.9 mb. one must take into account that for such iron concentration in the solid solution (25 %) the tendency of the paramagnetic species to aggregate will be important. it was previously observed and modelled in the p/ rs intergrowth structure of the solid solution ycaal1-xcrxo4 [25]. consequently, the actual value of the magnetic moment will be due not only to the single monomeric iron species but it will include the contribution of the various clusters, at least up to tetramers which likely have a concern to the observed magnetic moment. as deduced from the temperature dependence of the effective magnetic moment, the ferromagnetism of the exchange interactions undoubtedly increases versus the increasing amount of iron in the solid solution. more precisely, this data gives evidence for the increasing part of the fe4+ species. in order to receive another evidence for the presence of fe4+ and even more to calculate its concentration, the solid solution was studied by mössbauer spectrometry. fig. 6 shows mössbauer spectra of three compositions a b c fig. 6. mössbauer spectra of air prepared compositions of the solid solution sr3ti2-xfexo7-δ: a – 0.12; b – 0.16; c – 0.2 the solid solution sr 3 ti 2–x fe x o 7–δ (x ≤ 0.5): characterization of fe (iii) – fe (iv) mixed valences 54 № 1 | 2016 chimica techno acta x = 0.12; 0.16; 0.20 prepared in air. in any case there is the superposition of two signals with very different isomeric shifts d1 = 0.431 mm/s and d2 = –0.08 mm/s – corresponding to the cations fe3+ and fe4+, respectively [26–28]. the observed value of the quadrupolar splitting for fe3+ dе1 = 0.29 mm/s is consistent with a lower site symmetry for fe3+ than for fe4+ dе2 = 0.22 mm/s. on the basis of the jahn-teller effect of the 3d4 fe4+ cations, a supplementary distortion of the corresponding (fe4+o6) octahedra is expected. in fact, the existence of oxygen vacancies in the inner apical positions of the double perovskite block, as ensured from the structure calculations, triggers a lowering of the site symmetry of the fe3+ cations. for comparison, the solid solution sr3-xlaxti2-xfexo7 was considered. in such case the fully charge compensated double substitution of the cationic couple x (la3+ + fe3+) for x (sr2+ + ti4+) allows to maintain the oxygen stoichiometry i.e. there are no oxygen vacancies. the mössbauer data observed for the composition x = 1 namely sr2.9la0.1ti1.9fe0.1o7 reveal the existence of one signal with an isomeric shift d = 0.32 mm/s which corresponds to an iron cation fe3+ in a high symmetry local field. clearly, this is another proof that the mössbauer spectrometry ensures the presence of the two species fe3+ and fe4+ in the air prepared solid solution sr3ti2-xfexo7-δ. the analysis of the iron concentration dependence of the intensity of the two mössbauer signals brings the opportunity to evaluate the respective parts of fe3+ and fe4+. in table 4 we report for the three compositions x = 0.12; 0.16; 0.20 the estimated values of the fe3+ and fe4+ concentration (%) and the corresponding values of y the (fe4+) composition and δ the oxygen deficiency. table 4 fe4+ and fe3+ concentration (%), y (fe4+) composition and estimated value of δ the oxygen deficiency in the solid solution sr3ti2-xfexo7-δ (air prepared) x fe4+(%) fe3+(%) y (fe4+) δ 0.12 41.5 58.5 0.05 0.035 0.16 46.7 53.3 0.07 0.045 0.20 66.5 33.5 0.13 0.035 we receive the confirmation that the amount of fe4+ increases versus x the iron composition i.e. when the iron concentration in the solid solution is large enough x ≥ 0.16 the air prepared samples contain the fe4+ cations as main species. these results are in good agreement with the main information obtained from the magnetic properties. finally an estimation of δ the oxygen deficiency in the solid solution sr3ti2-xfexo7-δ allows to ensure the oxygen non-stoichiometry property which is not large enough (δ < x/4) to be determined from xrpd calculations. conclusion the solid solution sr3ti2-xfexo7-δ within its homogeneity range shows a remarkable ability to promote an oxidation of fe(iii) to fe(iv) even annealed in air. the existence of a mixed valence state of the iron atoms with a major contribution of the fe(iv) species is well established. in this respect, these new data well compare with those previously obtained in the case of chromium atoms in the solid solution sr3ti2-xcrxo7-δ [16]. in both cases the significant trend to get fe(cr)(iv) species zvereva i., pavlova t.,pantchuk v., semenov v., breard y., choisnet j. 55 № 1 | 2016 chimica techno acta mainly results from the weak ability of these substituted titanates to tolerate the formation of oxygen vacancies in the middle plane of the double perovskite block. in this way, their crystal chemical properties are closer to that of the manganites la1+xsr2-xmn2o7 [8] than the cuprates la2-xsr(ca)xcu2o6-x/2+δ [20]. in the latter case, the middle plane of the double perovskite block is fully deprived of oxygen atoms. 1. nguyen n., choisnet j., hervieu m., raveau b. oxygen defect k2nif4-type oxides: the compounds la2−xsrxcuo4-x/2+d  . j. solid state chem. 1981;39:120-127. doi:10.1016/0022-4596(81)90310-8 2. ando y., sera m., yamagata s., kondoh s., onoda m., sato m. normal state properties of la2−xsrxcuo4 and la2srcu2oy. j. solid state comm. 1989;70:303-308. doi:10.1016/0038-1098(89)90332-3 3. kakol z., spalek j., honig j. m. superconductivity and antiferromagnetism in la2−xsrxnio4 j. solid state chem. 1989;79:288-292. doi:10.1016/00224596(89)90277-6 4. manthiram a., tang j. p., manivannan v. factors influencing the stabilization of ni+ in perovskite-related oxides. j. solid state chem. 1999;148:499-507. doi:10.1006/ jssc.1999.8487 5. seshadri r., martin c., maignan a., hervieu m., raveau b., rao c. n. r. structure and magnetotransport properties of the layered manganites re1.2sr1.8mn2o7(re = la, pr, nd). j. mater. chem. 1996;6:1585-1590. doi: 10.1039/jm9960601585 6. battle p. d., rosseinsky m. j. synthesis, structure, and magnetic properties of n = 2 ruddlesden–popper manganates. current opinion in solid state and materials science. 1999;4: 163-170. doi:10.1016/s1359-0286(99)00012-1 7. volkova n. e., kolotygin v. a., gavrilova l. ya., khartonv. v., cherepanov v. a. nonstoichiometry, thermal expansion and oxygen permeability of smbaco2− xcuxo6−δ solid state ionics. 2014;260:15-20. doi:10.1016/j.ssi.2014.03.003 8. battle p. d., green m. a., laskey n. s., millburn j. e., murphy l., rosseinsky m. j., sullivan s. p., vente j. f. layered ruddlesden−popper manganese oxides: synthesis and cation ordering. chem. mater. 1997;9:552-559. doi: 10.1021/cm960398r. 9. dann s. e., weller m. t., currie d. b. structure and oxygen stoichiometry in sr3fe2o7−y, 0 ≤  y  ≤ 1.0. j. solid state chem. 1992;97:179-185. doi:10.1016/00224596(92)90023-o 10. lee j. y., swinnea j. s., steinfink h., reiff w. m. the crystal chemistry and physical properties of the triple layer perovskite intergrowths lasr3fe3o10-δ  and lasr3(fe3-xalx)o10-δ. j. solid state chem. 1993;103:1-15. doi:10.1006/jssc.1993.1072 11. prado f., manthiram a. synthesis, crystal chemistry, and electrical and magnetic properties of sr3fe2−xcoxo7−δ  (0≤x≤0.8). j. solid state chem. 2001;158:307-314. doi:10.1006/jssc.2001.9111 12. mori k., kamiyama t., kobayashi h., torii s., izumi f., asano h. crystal structure of sr3fe2o7−δ. j. phys. chem. solids. 1999;60:1443-1446. doi:10.1016/s00223697(99)00158-4 the solid solution sr 3 ti 2–x fe x o 7–δ (x ≤ 0.5): characterization of fe (iii) – fe (iv) mixed valences 56 № 1 | 2016 chimica techno acta 13. ghosh s., adler p. competing magnetic interactions and large magnetoresistance effects in a layered iron(iv) oxide: citrate–gel synthesis and properties of sr3fe1.8co0.2o∼7. solid state com. 2000;116:585-589. doi:10.1016/s0038-1098(00)00400-2 14. hodges j. p., short s., jorgensen j. d., xiong x., dabrowski b., mini s. m., kimball c. w. evolution of oxygen-vacancy ordered crystal structures in the perovskite series srnfeno3n−1 (n = 2, 4, 8, and ∞), and the relationship to electronic and magnetic properties. j. solid state chem. 2000;151:190–209. doi:10.1006/jssc.1999.8640 15. zvereva i., zueva l., archaimbault f., crespin m., 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in  ruddlesden–popper ferrite-titanate sr3fe2−xtixo6+δ. j. solid state chem. 2002;168:275283. doi:10.1006/jssc.2002.9722 20. rodriguez-carvajal j. l. recent advances in magnetic structure determination by neutron powder diffraction. physica b. 1993;192:55-69. doi:10.1016/09214526(93)90108-i 21. shannon d. d. revised effective ionic radii and systematic studies of interatomic distances in halides and chalcogenides. acta cryst a. 1976;32:751-767. doi: 10.1107/ s0567739476001551 22. nguyen n., er-rakho l., michel c., choisnet j., raveau b. intercroissance de feuillets “perovskites lacunaires” et de feuillets type chlorure de sodium: les oxydes la2−xa1+xcu2o6−x/2 (a = ca, sr). mat. res. bull. 1980;15:891-897. doi:10.1016/00255408(80)90212-3 23. soubeyroux j., courbin p., fournes l., fruchart d., le flem g. la phase srlafeo4: structures cristalline et magnétique. j. solid state chem. 1980;31:313-320. doi:10.1016/0022-4596(80)90093-6 24. sharma i. b., singh d., magotra s. k.. effect of 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a. d., widatallah h. m., al-harthi s. h., johnson c., gismelseed a. m., elzain m. e., yousif a. a. the formation and structure of mechano-synthesized nanocrystalline sr3fe2o6.4: xrd rietveld, mössabuer and xps analyses. mat. res. bull. 2015;65:142-148. doi:10.1016/j.materresbull.2015.01.026 the solid solution sr 3 ti 2–x fe x o 7–δ (x ≤ 0.5): characterization of fe (iii) – fe (iv) mixed valences 190 а. v. suzdaltsev, a. p. khramov, yu. p. zaikov, o. v. limanovskaya, v. n. nekrasov institute of high-temperature electrochemistry ub ras, 20 akademicheskaya street, 620990, ekaterinburg. e-mail: suzdaltsev_av@mail.ru chronopotentiometry at platinum electrode in kf-naf-alf 3 -al 2 o 3 melt* some features of the mechanism of the anode process on platinum in kf–naf–alf 3 –al 2 o 3 melt at 750–780 °c depending on the of anodic current density (0.5 ma/cm2 to 2.0 a/cm2) and anodic pulse duration have been studied using chronopotentiometry method. in curves of change in the platinum anode potential a small peak at current densities of 10–30 ma/cm2 and a clear peak at current densities of 0.5–2.0 a/cm2 are recorded when the current is cut on. analysis of dependencies of the transition time on the current density indicates that the first peak in curve is associated with the formation of an oxide compound on the platinum surface, and the second one is related to hindering the diffusion for delivery of electroactive particles to its surface. key words: chronopotentiometry, mechanism of the anode process, platinum anode, aluminium * the study was supported by the russian foundation for basic research (grant № 13–03–00829 a). © suzdaltsev a. v., khramov a. p., zaikov yu. p., limanovskaya o. v., nekrasov v. n., 2015 introduction at the present time research is directed to the development of physicochemical bases of technology for production of aluminum by electrolysis of kf–naf–alf3–al2o3 melt at 750–850 °c using non-consumable anodes conducting in the world [1–3]. in order to avoid a rapid corrosion of the anodes it is necessary to select both its formulation and a method of manufacturing, and optimal electrolysis modes. the latter implies the establishment of regularities of kinetics of oxygen release at the anode using electrochemical methods of analysis. platinum can serve as an experimental model of a non-consumable anode. earlier [4] a comparative analysis of experimental and modeling stationary polarization curves for platinum in kf–naf–alf3–al2o3 melt at 725–800 °c has been conducted. it has been shown that the primary charge transfer to form oads particles adsorbed on platinum is accompanied by d o i: 1 0. 15 82 6/ ch im te ch .2 01 5. 2. 3. 02 0 191 № 3 | 2015 chimica techno acta their desorption by physical or electrochemical mechanism. a more complete description of the mechanism features of the process under study can be achieved as the result of using the complex of electrochemical analysis methods, including non-stationary ones. the present work is devoted to the experimental study of non-stationary anode process on platinum by chronopotentiometry in kf–naf–alf3–al2o3 melt at 750–780 °c. experiment experiments were performed in alundum crucible [4], which was placed in a quartz cell purged with argon or oxygen. the auxiliary nichrome electrode was placed in a porous alundum tube that serves as a diaphragm. as the working electrode platinum purity of 99.9926 % (jsc “revda non-ferrous metals processing works”) was used. as the reference electrode a gas carbon electrode [5] in the equilibrium mixture of co and co2 served. measurements were carried out in the melt (wt. %): 39.6kf-7.1naf-47.3alf3–6.0al2o3 at temperature 750–780 °c. chronopotentiograms were obtained at anodic current densities from 0.05 ma/cm2 to 2.0 a/ cm2 with a sampling frequency up to 750 khz using pgstat autolab 320n and software nova 1.10 (eco chemie, the netherlands). to calculate the anode overvoltage using the procedure «i–interrupt» ohmic resistance in the section of polarizing circuit included in the measuring circuit were determined. results and discussion figure 1 shows typical curves of change in the potential of the platinum anode obtained on platinum in kf–naf– alf3–al2o3 melt at 750–780 °c when cutting on and cutting off the anode current. a peak in cut on curve is observed at low current densities (up to ≈30 ma/cm2). increasing the anode current density from 0.5 to 30 ma/cm2 results in shifting of a peak potential from ≈ 0.44 to 0.58 v in respect of the carbon electrode and reducing the transition time from 1.1 to 0.005 s. in our view, electrochemical platinum oxidation accompanied by filling its surface by oxidation product can act as the process in said section. despite the instability of platinum oxide at temperatures above 560 °c [6] electrochemical formation of platinum oxide was observed in a  cryolite-alumina melt at 1000 °c [7]. the diffusive character of the dependence of the transition time on the current density at that may be caused by limiting oxygen delivery to the platinum through the oxidized layer (or  the growth rate of the oxide film). increasing the length of the anode current pulses of value up to ≈30 ma/cm2 (fig. 1a), does not give rise to the second peak in the cut on curve associated with hindering the diffusion for delivery of electroactive oxygen-containing al-o-f component from the melt content to the layer near the anode. its expression is observed for the system under study with an increase in the magnitude of anode current density from 0.5 a/cm2 (fig. 1b), at that the transition times are from 2 ms to 10–15 s. chronopotentiometry at platinum electrode in kf-naf-alf 3 -al 2 o 3 melt 192 № 3 | 2015 chimica techno acta analysis of curves of change in the platinum potential under current interruption points indicates a long period of term relaxation of the platinum potential as after the anode current density pulse of value of 30 ma/cm2 (30–35 s), so after pulses of value of 0.5–2.0 a/cm2 (10–15 s). data from curves of change in the platinum potential for small (1, 2) and high (3) anodic current density values were built in the coordinates it1/2 to i (fig. 2). enhancement of it1/2 (1) with increasing i for small values of anode current densities indicates the electrode process (platinum oxidation) followed by slow desorption of products [8], whereas at high anodic current densities constancy of it1/2 value (3) is observed, which points at slow diffusion of electroactive particles to the electrode surface. the value of the diffusion coefficient of the electroactive particles for high anode current densities at 750–780  °c estimated from the sanda equation [8] amounted to 0.7–1.5 × 10–5 cm2/s. the presence of the electrochemical oxidation of platinum is supported by the following: the estimated value of the electric double layer capacity (cd) in the initial section of curves of change in the platinum potential (times to ≈ 5 × 10–4 s) when the current is cut on according to expression cd = i/(dη/dt) [1] was 400–560 uf/ cm2, which is characteristic of the formation of several oxide compound layers; dependence of it3/2 on i (fig.2, 2) is linear at low current densities, that points at the growth of the oxide film resulting from the electrochemical process [7]. conclusion nonstationary anodic process on platinum in kf–naf–alf3–al2o3 melt at 750–780 °c depending on the duration and magnitude of anode current density (from 0.5 ma/cm2 to 2.0 a/cm2) have been studied using chronopotentiometry method. it is shown that when the anodic current densities are from 0.5 a/cm2 the process under study is limited by diffusion of the electroactive particles to the surface of the platinum anode, while at low current densities preceding stage is recorded. analysis of dependencies of it1/2 on i from curves of changes of the potential platinum when anode current is cut on according to equations describing the slow diffusion of electroactive particles and the growth of the oxide film on the electrode surface indicates the electrochemical oxidation of platinum. fig. 1. cut on and cut off curves of current on platinum in kf–naf–alf3–al2o3 melt at 780 °c and current densities of 0.5–30 ма/cm2 (a) and 0.5–2.0 а/cm2 (b). atmosphere is argon, the reference electrode is a carbon electrode suzdaltsev а. v., khramov a. p., zaikov yu. p., limanovskaya o. v., nekrasov v. n. 193 № 3 | 2015 chimica techno acta for high current densities values of the diffusion coefficient of electroactive particles to the platinum anode and the capacity of the electrical double layer were estimated, which amounted to, respectively, 0.7–1.5 × 10–5 cm2/s and 400–560 uf/cm2. the new obtained data can be used to specify the scheme of the process under study and create a theoretical model enabling estimation of the effect of the parameters of the anodic process on platinum and other oxygen-releasing electrodes in kf–naf–alf3–al2o3 melt and other oxide-fluoride melts in a wide temperature range. 1. nekrasov  v. n., suzdaltsev  a. v., limanovskaya  o. v., khramov  a. p., zaikov yu. p.  theoretical and experimental study of anode process at the carbon in kf-alf3al2o3 melts. electrochim. acta. 2012;75: 296. 2. yang j., hryn j. n., davis b. r., roy a., krumdick g. k., pomykala jr. j. a. new opportunities for aluminum electrolysis with metal anodes in a low temperature electrolyte system. light metals. 2004;321. 3. helle  s., pedron  m., assouli  b., davis  b., guay  d., roue  l.  structure and hightemperature oxidation behaviour of cu-ni-fe alloys prepared by high-energy ball milling for application as inert anodes in aluminium electrolysis. corrosion science. 2010;52: 3348. doi: 10.1016j.corsci.2010.06.011. 4. nekrasov  v. n., limanovskaya  o. v., suzdaltsev  a. v., khramov  a. p., zaikov yu. p.  stationary anodic process at platinum in kf-naf-alf3-al2o3 melts. rus. metallurgy. 2014;8: 664. doi: 10.1134s0036029514080084. 5. suzdaltsev a. v., khramov a. p., zaikov yu. p. carbon electrode for electrochemical studies in electrolite-alumina melts at 700–960 °c. rus j electrochemistry. 2012;48: 1141. doi: 10.1134s1023193512120117. 6. livingstone s. rhenium, rhodium, palladium, osmium, iridium and platinum. pergamon, oxford, 1975. fig. 2. dependencies of it1/2 and it3/2 on i, built up from cut on curves on platinum for small (1, 2) and high (3) anode current densities chronopotentiometry at platinum electrode in kf-naf-alf 3 -al 2 o 3 melt 194 № 3 | 2015 chimica techno acta 7. dewing e. w., van der kouwe e. anodic phenomena in cryolite-alumina melts. th. j. electrochem. soc. 1977;124: 58. 8. bard  a. j., faulkner  l. r.  electrochemical methods: fundamentals and applications. 2nd ed. n.y.: john wiley & sons inc. 2001, 833 p. suzdaltsev а. v., khramov a. p., zaikov yu. p., limanovskaya o. v., nekrasov v. n. 195 а. в. суздальцев1, а. п. храмов1, ю. п. зайков1, 2, о. в. лимановская1, 2, в. н. некрасов1 1институт высокотемпературной электрохимии уро ран, 620990, екатеринбург, ул. академическая, 20. e-mail: suzdaltsev_av@mail.ru 2уральский федеральный университет, 620002, екатеринбург, ул. мира, 19. e-mail: limanovskaya@yandex.ru хронопотенциометрия на платине в расплаве kf-naf-alf 3 -al 2 o 3 * методом хронопотенциометрии были исследованы некоторые особенности механизма анодного процесса на платине в расплаве kf–naf–alf 3 –al 2 o 3 при 750–780 °c в зависимости от анодной плотности тока (от 0,5 ма/см2 до 2,0 а/см2) и длительности анодного импульса. на кривых изменения потенциала платинового анода при включении тока фиксируется небольшой перегиб при плотностях тока 10–30 ма/см2 и четкий перегиб при плотностях тока 0,5–2,0 а/см2. анализ зависимостей переходных времен от плотности тока указывает на то, что первый перегиб связан с образованием оксидного соединения на поверхности платины, а второй – с диффузионными затруднениями по доставке электроактивных частиц к ее поверхности. ключевые слова: хронопотенциометрия, механизм анодного процесса, платиновый электрод, алюминий. * исследование выполнено при финансовой поддержке российского фонда фундаментальных исследований (проект № 13–03–00829 а). © суздальцев а. в., храмов а. п., зайков ю. п., лимановская о. в., некрасов в. н., 2015 у д к : 5 44 .6 53 .2 2: 5 44 .6 .0 18 .4 214 3 введение в настоящее время в  мире ведутся исследования, направленные на разработку физико-химических основ технологии получения алюминия электролизом расплава kf–naf– alf3–al2o3 при 750–850 °c с  использованием малорасходуемых анодов [1–3]. во избежание быстрой коррозии анодов необходимо подобрать как состав и  способ их изготовления, так и  оптимальные режимы электролиза. последнее предполагает установление закономерностей кинетики выделения кислорода на аноде при помощи элек196 № 3 | 2015 chimica techno acta трохимических методов анализа. экспериментальной моделью малорасходуемого анода может служить платина. ранее был проведен сравнительный анализ экспериментальных и  модельных стационарных поляризационных кривых для платины в  расплаве kf– naf–alf3–al2o3 при 725–800 °c [4]. было показано, что первичный перенос заряда с  образованием адсорбированных частиц оадс на платине сопровождается их десорбцией по физическому или электрохимическому механизму. более полное описание особенностей механизма исследуемого процесса может быть достигнуто в результате применения комплекса электрохимических методов анализа, в том числе нестационарных. данная работа посвящена экспериментальному исследованию нестационарного анодного процесса на платине методом хронопотенциометрии в  расплаве kf–naf–alf3–al2o3 при 750–780 °c. эксперимент эксперименты проводили в  алундовом тигле [4], который размещали в  кварцевой ячейке, продуваемой аргоном или кислородом. вспомогательный электрод из нихрома был размещен в  пористой алундовой трубке, выполняющей роль диафрагмы. в  качестве рабочего электрода использовали платину чистотой 99,9926 % (оао «рз оцм»). электродом сравнения служил газовый углеродный электрод [5] в равновесной смеси co и co2. измерения проводили в расплаве (мас.%): 39,6kf-7,1naf-47,3alf3–6,0al2o3 при температуре 750–780 °c. хронопотенциограммы получали при анодных плотностях тока от 0,05 ма/см2 до 2,0 а/см2 с  частотой дискретизации до 750 кгц, используя pgstat autolab 320n и  по nova 1.10 (eco chemie, the netherlands). для расчета анодного перенапряжения при помощи процедуры «i–interrupt» определяли омическое сопротивление участка поляризующей цепи, входящего в измерительную цепь. результаты и обсуждение на рис. 1 представлены типичные кривые изменения потенциала платинового анода при включении и  отключении анодного тока, полученные на платине в  расплавах kf–naf–alf3–al2o3 при 750–780 °c. при малых плотностях тока (до  ≈30 ма/см2) на кривых включения наблюдается перегиб. увеличение анодной плотности тока с  0,5 до 30 ма/см2 приводит к  смещению потенциала перегиба с  ≈ 0,44 до 0,58  в относительно углеродного электрода и  уменьшению переходного времени с  1,1 до 0,005  с.  на наш взгляд, процессом на данном участке может выступать электрохимическое окисление платины, сопровождаемое заполнением ее поверхности продуктом окисления. несмотря на нестабильность оксидов платины при температурах выше 560 °c [6], электрохимическое образование оксида платины было отмечено в  криолит-глиноземном расплаве при 1000 °c [7]. диффузионный характер зависимости переходного времени от плотности тока при этом может быть суздальцев а. в., храмов а. п., зайков ю. п., лимановская о. в., некрасов в. н. 197 № 3 | 2015 chimica techno acta вызван ограничением доставки кислорода к  платине через окисленный слой (или скоростью роста оксидной пленки). увеличение длительности анодных импульсов тока величиной до ≈30 ма/см2 (рис. 1, а) не приводит к появлению на кривой включения второго перегиба, связанного с  диффузионными затруднениями по доставке электроактивного кислород-содержащего компонента al–o–f из объема расплава в прианодный слой. его проявление для исследуемой системы наблюдается при повышении величины анодной плотности тока от 0,5 а/см2 (рис. 1, б), при этом переходные времена составляют от 2 мс до 10–15 с. анализ кривых изменения потенциала платины при отключении тока указывает на длительную релаксацию потенциала платины как после импульса анодной плотности тока величиной 30 ма/см2 (до 30–35 с), так и после импульсов величиной 0,5–2,0 а/см2 (до 10–15 с). данные из кривых изменения потенциала платины для малых (1, 2) и высоких (3) значений анодной плотности тока были построены в координатах it1/2 от i (рис. 2). увеличение it1/2 (1) при повышении i для малых значений анодных плотностей тока указывает на электродный процесс (окисление платины), сопровождаемый замедленной десорбцией продуктов [8], в  то время как при высоких анодных плотностях наблюдается постоянство величины it1/2 (3), которое указывает на замедленную диффузию электроактивных частиц к поверхности электрода. оцененное из уравнения санда [8] значение коэффициента диффузии электроактивных частиц для высоких анодных плотностей тока при 750–780 °c составило 0,7–1,5×10–5 см2/с. наличие стадии электрохимического окисления платины подтверждается следующим: – оцененное значение емкости двойного электрического слоя (cd) на начальном участке кривых изменения потенциала платины (времена до ≈  5×10–4 с) при включении тока по выражению cd = i/(dη/dt)[1] составило 400–560 мкф/см2, что характерно для образования нескольких слоев оксидного соединения; – зависимость it3/2 от i (рис. 2, 2) линейна при малых плотностях тока, что указывает на рост оксидной пленки в результате электрохимического процесса [7]. рис. 1. кривые включения и отключения тока на платине в расплаве kf–naf–alf3– al2o3 при 780 °c и плотностях тока 0,5–30 ма/см2 (a) и 0,5–2,0 а/см2 (б). атмосфера – аргон, электрод сравнения – углеродный хронопотенциометрия на платине в расплаве kf-naf-alf 3 -al 2 o 3 198 № 3 | 2015 chimica techno acta заключение методами хронопотенциометрии исследован нестационарный анодный процесс на платине в  расплаве kf–naf–alf3–al2o3 при 750–780 °c в зависимости от длительности и величины анодной плотности тока (от  0,5 ма/см2 до 2,0 а/см2). показано, что при анодных плотностях тока от 0,5 а/см2 исследуемый процесс лимитируется диффузией электроактивных частиц к  поверхности платинового анода, в то время как при низких плотностях тока фиксируется предшествующая стадия. анализ зависимостей it1/2 от i из кривых изменения потенциала платины при включении анодного тока по уравнениям, описывающим замедленную диффузию электроактивных частиц и  рост оксидной пленки на поверхности электрода, указывает на электрохимическое окисление платины. для высоких плотностей тока оценены значения коэффициента диффузии электроактивных частиц к  платиновому аноду и  емкость двойного электрического слоя, которые составили, соответственно, 0,7–1,5×10–5 см2/с и 400–560 мкф/см2. полученные новые данные могут быть использованы для уточнения схемы исследуемого процесса и  создания теоретической модели, позволяющей оценивать влияние параметров анодного процесса на платине и других кислород-выделяющих электродах в расплаве kf–naf–alf3–al2o3 и  других оксидно-фторидных расплавах в  широком интервале температур. 1. nekrasov  v. n., suzdaltsev  a. v., limanovskaya  o. v., khramov  a. p., zaikov yu. p. electrochim. acta. 2012;75: 296. 2. yang j., hryn j. n., davis b. r., roy a., krumdick g. k., pomykala jr. j. a. light metals. 2004, 321. 3. helle s., pedron m., assouli b., davis b., guay d., roue l. corrosion science, 2010, 52, 3348. рис. 2. зависимости it1/2 и it3/2 от i, построенные из кривых включения на платине для малых (1, 2) и высоких (3) анодных плотностей тока суздальцев а. в., храмов а. п., зайков ю. п., лимановская о. в., некрасов в. н. 199 № 3 | 2015 chimica techno acta 4. nekrasov  v. n., limanovskaya  o. v., suzdaltsev  a. v., khramov  a. p., zaikov yu. p. rus metallurgy. 2014;8: 664. 5. suzdaltsev a. v., khramov a. p., zaikov yu. p. rus j electrochemistry, 2012, 48, 1141. 6. livingstone s. rhenium, rhodium, palladium, osmium, iridium and platinum. pergamon, oxford, 1975. 7. dewing e. w., van der kouwe e. th. j. electrochem. soc. 1977;124: 58. 8. bard  a. j., faulkner  l. r.  electrochemical methods: fundamentals and applications. 2nd ed. n.y.: john wiley & sons inc., 2001. 833 p. хронопотенциометрия на платине в расплаве kf-naf-alf 3 -al 2 o 3 97 d o i: 1 0. 15 82 6/ ch im te ch .2 01 6. 3. 2. 00 8 уд к 66 1. 86 v. v. kurysheva, e. v. ivanova, p. e. prohorova ural federal university, 620002, ekaterinburg, 19, mira st, russia. e-mail: p.e.prokhorova@urfu.ru extractants for rare earth metals the separation of trivalent rare earth metals is perhaps the most serious challenge associated with a closed fuel cycle. the choice of ligand as extractant, which must be selective and efficient in conditions of high radiation environment, plays an important role. in this review there are the main examples of extractants for f-elements used in the present 10–20 years. key words: rare earth metals, organophosphorus compounds, crown ethers, podands, calixarenes, amides of diglycolic acid. в. в. курышева, е. а. иванова, п. е. прохорова уральский федеральный университет, россия, 620002, екатеринбург, ул. мира, 19. e-mail: p.e.prokhorova@urfu.ru. экстрагенты для редкоземельных металлов разделение трехвалентных редкоземельных металлов, возможно, является самым серьезным вызовом, связанным с замкнутым топливным циклом. важную роль играет выбор лиганда в качестве экстрагента, который должен быть селективным и надежным в условиях повышенной радиации среды. в данном обзоре приведены основные примеры экстрагентов для f-элементов, применяющихся в последнии 10–20 лет. ключевые слова: редкоземельные металлы; фосфорорганические соединения; краунэфиры; поданды; каликсарены; амиды дигликолевой кислоты. © kurysheva v. v., ivanova e. v., prohorova p. e., 2016 kurysheva v. v., ivanova e. v., prohorova p. e. chimica techno acta. 2016. vol. 3, no. 2. p. 97–120. issn 2409-5613 introduction in recent decades the rare earth metals (rem) are required for creating of advanced materials and technologies using catalysts, alloys, magnets, optics and lasers, rechargeable hydride batteries, electronics, efficient lighting, conversion to wind and solar energy, bio-analysis and modeling [1]. the main method of extraction of rare earth metals in the world is mineral processing [2]. however, scientists had developed ways to obtain rare earth metals from secondary raw materials, for example, from defective fluorescent lights [3], worn out hard drives of computers [4], etc. the extraction of rare earth metals from mineral raw materials is produced by leaching with nitric, sulfuric or hydrochloric acids or by direct chlorination, the resulting phase from the leaching of rare earth metals is separated by extraction [5]. regardless of the type of raw material from which rare earth metals were got, the actual problem today is the search of 98 the most effective extractants for separation of rare earth metals. analysis of literature data showed that the following well known and thoroughly described in the literature complexing agents such as crown-ethers, azacrownesters, calixarenes, schiff bases, porphyrins, phthalocyanines and tributylphosphates and tetraoctyldiglycolamides (todga) can be used as extractants for rare earth metals cations. crown ethers as extractants of rare earth metals cations the first representatives of the crown ethers class were described by pederson in 1967 [6]. since then, chemists had synthesized many new compounds with similar to crown-ethers structure and properties, for example, azacrown-esters, open chain crown-ethers (podands). many applications of crown ethers were based on their ability to form complexes with cations of different metals. the extraction properties of the crown ethers towards the rare earth metals were discovered during the development of new methods of extraction of radioactive elements from radioactive waste, which contained a significant number of ions of the lanthanides [7]. f. riahi and m. bagherzadeh [8] investigated and described the extraction of some lanthanides (iii): la3+, ce3+, pr3+, eu3+, er3+ by derivatives of 18-crown-6ether 1-4 in the presence of trichloroacetic acid in acidic solutions in the system of dmso/water [8]. it was established that the efficiency of cations extraction by compounds 1-4 increases in the following order: 1 > 2 > 3 > 4. this is understandable from the point of view of the rigidity of the molecule structure, which cyclohexyl and aromatic fragments attach to the molecules of the crown ethers. s. v. demin and colleagues conducted the series of studies on the extraction of alkyl derivatives by crown ethers 5 and 6 from acidic solutions in the system chloroform/water [9]. it is shown that extraction of cations of rare earth metals by dicyclohexano-18-crown-6-ether 2 and its alkyl derivatives in the presence of trichloroacetic acid is more effective than with nitric or acetic acids. the value of the recovery factor for the cerium cation was much higher than for the yttrium cation. such regularity was observed for all derivatives of the compounds 5 and 6. the ratio of the metal cation : crown ether in all complexes is 1:1. simplified technology of extraction of metal cations provides its implementa99 tion in the system solid phase-liquid. so during multi-step synthesis [10] the solid phase polymer 11-13 was obtained by polymerization of the monomer 10. the number of units of crown ether n could vary from two to four. the experimental data obtained by j. rey and employees, when carrying out extraction of lanthanides in acetonitrile and water, showed that compounds 12 and 13 are capable of extracting cations of lanthanides in acetonitrile to a lesser extent than compound 14. it is the best extractant for cation la3+ in acetonitrile and in water, in comparison with the other lanthanide cations. it should be noted that the compounds 12 and 13 in contrast to the 14 are not able to bind the cations of the lanthanides in the aquatic environment. modified diazacrown-esters can be used along with crown ethers as extractants of rare earth metals. for example, the extraction activity of compound 15 in relation to the lanthanides in the presence of 1-butyl-3-methylimidazole[(triflorometh yl)sulfonyl]imide is modified as follows: first, it decreases for a range of metals from la to ho and then it increases with increasing atomic number of the element [11]. thus, crown ethers are a class of extractants with variable selectivity in relation to extractable cations. the required level of selectivity of the crown ether is achieved by changing of the number of links of the glycol chain and introducing of a variety of substituents to its structure. crown-ethers show the greatest efficiency under the extraction of lanthanides from solutions of trichloroacetic, acetic and nitric acids. 100 podands as extractants for cations of rare earth metals the open chain crown ethers or podands are considering as analogues of complexing crown ethers. sour phosphoryl-containing podands 16, 18, 19 were described in 1989 as complexing agents for alkali metals [12]. compound 17 and its analogues with r1 = tert-butyl has been proposed as a reagent for the selective extraction of th(iv) from solutions of nitric acid [13, 14]. the extraction of rare earth metals cations from solutions of nitric, hydrochloric and perchloric acids by acidic phosphoryl-containing podands 16-19 was described by turanov a.v. and employees [15]. they found that the efficiency of extraction of rare earth metals cations (from la(iii) to lu(iii)) from 0.01 m solution of nitric acid with 0.01 m solution of the extractant in dichloroethane increases in the order of 18 < 16 < 17 < 19 moreover with the increase of concentration of nitric acid the extraction efficiency is reduced. neutral phosphoryl-containing compounds 20-22 slightly extracted rare earth metals cations under these conditions. the authors also note the change of the extraction ability of the compounds 22 in used acids solutions with a concentration of 0.01 m in the following order hcl < hno3 < hclo4. the process of extraction of cations of rare earth metals are affected by both: the nature of the used acids and the nature of the organic solvents. for example, the efficiency of extraction of eu (iii) with a solution of podand 23e in various organic solvents was increased in the next row of the solvents chloroform < 2-ethylhexanol < toluene < methylene chloride < dichlorobenzene < dichloromethane < nitrobenzene, it is due to the specific solvation of the podand molecules by solvent (chloroform or aliphatic alcohol) and the formation of hydrogen bonds, for example, p=o•••hccl3 or p=o•••hor1. the nature of the organic solvent also affects to the selectivity of extraction. turnov and staff discovered that under increasing the solvated ability of organic solvent for the system with extractant 24e the selectivity of extraction of cations of rare earth metals increases in the following order: toluene <chloroform <methylene chloride. perhaps this is due to the fact that the complexes of heavy rare earth metals cations solvated by organic solvents to a greater extent. during the extraction of cations by the compound 24e 101 with the use of polar solvent, the extraction efficiency increases with increasing of the atomic number of rare earth element in the periodic table. for toluene (a less polar solvent), the extraction efficiency is increased only for a number of elements from lanthanum to europium, then it was fallen from terbium to lutetium. the selectivity of the extraction may depend on the number of oxygen atoms m in the polyester chain of podands. the increase m in podands 24a-d from one to three reduced the efficiency and selectivity of extraction of lanthanides. increasing m to four led a slight decrease of extraction efficiency for lanthanum, for the rest rare earth elements the extraction efficiency increases, which leads to higher selectivity of extraction by podand 24d. for podands 23a-f with the number m to 6 atoms the non-linear increase in extraction efficiency of lanthanides and its sharp decrease in the event of a connection with the compound 23f (m = 7) were observed. selectivity of extraction is changed in the same direction for the extraction of rare earth metals cations by podans 23a-f [16]. based on the podand with open polyester chains 25, similarly as in the case of crown-ether 7-9, it is possible to obtain a polymer 26-28 for the extraction of cations of rare earth metals in the system solid phase-liquid [10]. however, unlike the crown esther-containing polymers, polymers containing podands are able to more effective extraction of lanthanides in water. the increase of extraction efficiency of lanthanides both in water and in acetonitrile has been observed in a number of polymers 26<27<28. in summary above, it is worth noting that the most effective extractants for rare earth metals are phosphoryl-containing podands, the selectivity of which may depend on the number of oxygen atoms in the polyester chain of the podand as well as the nature of organic solvent. 102 extraction of rare earth metals cations by modified calix[n]arenes with the development of the nuclearpower industry the question about the elimination and reprocessing of nuclear waste arose acutely. the separation of actinides from lanthanides is an important step before the implementation of the transmutation technology of actinides transformation. therefore, for extraction of radioactive elements from nuclear waste a number of selective extractants, for example, monodentate organophosphorus extractants (trioctylphosphine, tofo) [17] were tested. however, they showed low efficiency and insufficient selectivity. therefore, the idea of joining of phosphoryl group on the hard platform of calixarene arose to take advantage of synergistically effect for increasing the efficiency and selectivity of extraction [18]. previously it has already been well studied and calixarene derivatives containing carbamoylmetylphosphin oxides in different positions of the calixarene fragments were described [19, 20], as well as some calixarenes with their phosphine oxides at the lower rim [21, 22]. m. karavan and colleagues examined complexing properties of phosphonate derivatives of calix[n]arenes 29-36 in relation to some actinides and lanthanides [23]. analysis of experimental data of the cations extraction from nitric acid solution in m-nitrobenzotrifluoride (mnbtf) showed that the efficiency of extraction by calixarenes with phosphinic substituents in the upper rim of 29b and of 29d for cations 152eu exceeds it for 241am. however, increasing of the concentration of nitric acid in the solution leads to a decrease in the values of extraction n r1 r2 4 propyl methyl 29а ethyl 29b propyl 29c iso-propyl 29d butyl 29e 4 hexyl ethyl 30а butyl 30b 6 methyl ethyl 31а butyl 31b n r 4 h 32a 4 tert-butyl 32b 5 tert-butyl 33а 6 h 34а r metyl 35а ethyl 35b propyl 35c iso-propyl 35d butyl 35e 103 ratio for compounds 29e; for 29b there is a gradual increase of the coefficient up to 0.9 m hno3, which is then followed by a sharp decrease. from a number of calixarenes with phosphine substituents at the lower rim 32a, 32b, 33a and 34a, p-tertbutylcalix[5] arene 33a has the highest extraction efficiency for 241am and 152eu. among calixarenes with phosphonate substituents in the upper rim 35a-e has the maximum value of the extraction coefficient of europium and americium. the coefficients of extraction of 241am and 152eu were determined radiometrically using γ-radiation of the corresponding isotopes [23]. another example of the synthesis of selective extractants based on calix[4] arene to separate actinides from lanthanides has been described by ansari and employees [24, 25]. they received the series of pyrazine-substituted calixarenes 37-39 and examined their efficiency for the extraction of the cation eu3+ from an aqueous solution of nitric acid. according to research data the efficiency of extraction of cations of europium by compounds 37-39 can be displayed in the following sequence: 37<<38<39. these results can be explained by the influence of the nature of the substituent of pirazine fragment in compounds 37-39. the researchers also found that the ratio between the compounds 37-39 and cation eu3+ in the formed complexes is 1:1. however, according to h. huang and employees, the presence of the phosphorus atom in the structure of the extractant molecule does not allow to fully burn it, turning into accumulated solid waste [26]. the best extractants, in this case, are compounds only consisting of the atoms c, h, o and n, which will turn into gaseous products after disposal. the promising easily synthesized compounds for extraction of actinides from acid solutions were considered to fit «principle chon» – diglycolamides (dga) [27]. but due to their low selectivity dga may not be used for the separation of actinides and lantha104 nides. the introduction of diglycolamide to the molecule of calix[4]arene is a way to obtain promising compounds 43 for separation of actinides and lanthanides, which huang and staff chose. the synthesis of calix[4]arene-bdga 43 was carried out in accordance with a  scheme where the compounds 40 and 42 were obtained by previously described methods [28, 29]. the study of the extraction of am(iii) and eu(iii) from the solution of nitric acid by the compound 43 was conducted using 95% kerosene/5% n-octanol as diluent. the results showed that the value of the extraction factor for am(iii) and eu(iii) increases with increasing concentration of nitric acid in the range from 0.5-5.0 mol/l. ligand 43 showed higher selectivity for eu(iii) than for am(iii) with separation factor sfam(iii)/ eu(iii) in the range 4.5-7.3, that indicates its effectiveness in separation of cations of the lanthanides and actinides [30]. thus, modified calixarenes occupy one of leading positions among highly efficient and selective extractants of cations of rare earth metals. diglycolamides are extractants for separation of actinides and lanthanides diglycolamides and their derivatives, which are promising extractants for the extraction of the lower actinides from solutions of nitric acid, have been described by h. stephan and colleagues in 1991 [31]. the presence of ether oxygen between the two amide groups in the dga increases the extraction of lower actinides due to the active education of tridentate complexes. n,n,n',n'-tetraoctyldiglycolamide (todga) 44g and n,n,n',n'tetra-2-ethylhexyldiglycolamide (tehdga) 44j [32, 33] were considered as the most promising extractants for the lower actinides among diglycolamides. it is due to the influence of the nature of the alkyl substituents of diglycolamide. the influence of alkyl substituents and the nature of diluent on the extraction of lanthanides and actinides by diglycolamides 44a-l was studied by y. sasaki and colleagues [34]. they found that compounds with the branched alkyl chain and asymmetric alkyl-phenyl amide groups have the relatively low coefficient of extraction of the cations than glycolamides with a linear hydrocarbon substituents. an extraction study of the lanthanides by 105 thdga, todga, tdddga, tehgda and dmdpdga was conducted in six solvents (nitrobenzene, dichloroethane, octanol, chloroform, toluene, dodecane) using 0.04-0.1 m diglycolamide and 1m nitric acid solution. in every case except of thdga in toluene, dmdpdga in chloroform and toluene and tegdga in 6 diluents there was a gradual increase in the coefficient of extraction of lanthanides in increasing order of their atomic number from la to ho, then the value of the coefficient decreases for cations erlu. it is also worth noting that todga or tdddga dissolved in nitrobenzene, octanol and dodecane have separation factor sf(lu/la) more 100 than confirms the use of these diglycolamides for the selective separation of lanthanides. the extraction of lanthanides into chloroform or toluene showed a low value of not only recovery ratio, but also the separation factor sf (ln/la). thus, an important condition affecting the extraction efficiency of lanthanides by diglycolamides is the nature of the alkyl substituents of diglycolamide and used diluent. extraction of lanthanides by organophosphorous extractants since the tributyl phosphate tbp and triphenylphosphineoxide tppo are the objects for study of extractive activity in relation to the rare earth metals cations. e. jorjani and colleagues [35] examined the effectiveness of cations extraction of yttrium, lanthanum, cerium and neodymium by tributyl phosphate which are the main components of the waste of processing of iron ore. studies have shown that using different concentrations of solution of tbp in kerosene (from 0.73 to 3.65 mol·l–1), an increase in the rate of extraction factor to tbp concentration of 3.65 mol·l–1 was observed [36]. in the study of extraction of rare earth metals cations by organophosphorus extractants, researchers pay attention to the synergetic effect. synergistic extraction of trivalent lanthanides is of great interest due to the high efficiency of cations extraction by chelating agent in the presence of the neutral donor. many of studied liquid-phase extraction processes, which have a synergistic character, were made using monodentate compounds (for example, trioctylphosphine oxide, topo and β-diketones). umetani and freiser r, r1 tert-methyl тмdgа 44а tert-ethyl тedgа 44b tert-propyl тpdgа 44c tert-butyl тbdgа 44d tert-amyl таdgа 44e tert-hexyl тhdgа 44f tert-octyl тоdgа 44g tert-decyl тddgа 44h tert-dodecyl тdddgа 44i tert-2-ethylhexyl тehdgа 44j n,n'-dimethyl n,n'-diphenyl dмdpdgа 44k tert-phenyl тpdgа 44l 106 studied the mixed ligand-chelate extraction of lanthanides with 1-phenyl-3-methyl-4-(trifluoroacetyl)-5-pyrazolones and some phosphine oxides [37]. the extraction of lanthanides with the mixture of picrolonic acid 45 with various neutral organophosphorus donors have been studied by a. ali and staff [38]. in one of their works they have published research data of synergistic extraction of eu(iii) from mixture of cations of divalent transition metals using dissolved mixture of picrolonic acid and topo, tppo and tbp [39] in chloroform. the extracted particles were characterized as eu(pa)3•2тоpо, eu(pa)3•2тppo and eu(pa)3•tbp [40]. the most effective extracting mixture for europium was the mixture of picrolonic acid and topo, the mixture of pa and tpo is less effective. a mixture of pa and tbp [41]4 showed the least ability to extraction of europium. conclusion organophosphorous extractants has gained its popularity due to relatively simple synthetic methods and low cost. for selectivity, they are largely inferior to crown-ethers and calixarenes. however, the ability of organophosphorous compounds to synergistic extraction of cations causes for further study [42]. today the most promising extractants for rare earth metals are crown-ethers, calixarenes, podands, diglycolamides and organophosphorous compounds [43, 44]. modification (including the association) of their structures enables to obtain wide range of extractants which can selectively bind cations of rare earth metals. 107 in russian введение в последние десятилетия редкоземельные металлы (рзм) становятся необходимыми для создания усовершенствованных материалов и технологий с использованием катализаторов, сплавов, магнитов, оптики и лазеров, перезаряжаемых гидридных аккумуляторов, электроники, экономичного освещения, конверсии ветряной и солнечной энергии, биоанализа и моделирования [1]. основным способом добычи рзм в мире является переработка минерального сырья [2]. однако учеными разработаны способы получения рзм из вторичного сырья, например, из вышедших из строя флуоресцентных ламп [3], пришедших в негодность жестких дисков компьютеров [4] и т. д. извлечение редкоземельных металлов из минерального сырья производят выщелачиванием азотной, серной или соляной кислотами или прямым хлорированием, полученные в результате выщелачивания рзм разделяют экстракцией [5]. независимо от вида сырья, из которого получают рзм, актуальной проблемой на сегодняшний день является поиск наиболее эффективных экстрагентов для разделения рзм. анализ литературных данных показал, что в качестве экстрагентов для катионов рзм могут быть использованы следующие хорошо известные и достаточно подробно описанные в  литературе комплексообразователи, такие как краун-эфиры, азакраун-эфиры, каликсарены, основания шиффа, порфирины, фталоцианины, трибутилфосфаты и тетраоктилдигликольамиды (todga). краун-эфиры как экстрагенты катионов рзм в 1967 году педерсоном были описаны первые представители класса краун-эфиров [6]. с тех пор химиками было синтезировано множество новых соединений, обладающих схожим с краун-эфирами строением и свойствами. например, азакраун-эфиры, открытоцепные краун-эфиры (поданды). большинство способов применения краун-эфиров основано на их способности образовывать комплексы c катионами различных металлов. экстракционные свойства краун-эфиров по отношению к рзм были обнаружены при разработках новых способов экстракции радиоактивных элементов из радиоактивных отходов, которые содержали значительное количество ионов лантанидов [7]. f. riahi и m. bagherzadeh [8] исследовали и описали экстракцию некоторых лантанидов (iii): la3+, ce3+, pr3+, eu3+, er3+ производными 18-краун6-эфира а-д в присутствии трихлоруксусной кислоты в кислых растворах, в  системе дмсо/вода. установлено, что эффективность экстракции катионов соединениями 1-4 увеличивается в следующем порядке: 1 > 2 > 3 > 4. это объяснимо с точки зрения жесткости структуры молекулы, которую придают молекулам краун-эфиров циклогексильные и ароматические фрагменты. 108 s. v. demin и коллеги провели ряд исследований экстракции алкилированными производными краун-эфиров 5 и 6 из кислых растворов в системе хлороформ/вода [9]. показано, что экстракция катионов редкоземельных металлов дициклогексано-18-краун6-эфиром 2 и его алкилированными производными в присутствии трихлоруксусной кислоты является более эффективной, чем с использованием азотной или уксусной кислот. значение коэффициента извлечения для катиона церия намного превышало таковое для катиона иттрия. такая закономерность была замечена для всех производных соединений 5 и 6. соотношение катион металла c краун-эфиром во всех комплексах равно 1:1. упрощенная технология экстракции катионов металлов предусматривает ее проведение в системе твердая фаза-жидкость. так в ходе многостадийного синтеза [10] удалось получить твердофазный полимер 11-13 при полимеризации мономера 10. количество звеньев краун-эфира n может варьироваться от двух до четырех. экспериментальные данные, полученные j. rey и сотрудниками при проведении экстракции лантаноидов в ацетонитриле и воде, показали, что соединения 12 и 13 способны извлекать катионы лантаноидов в ацетонитриле в меньшей степени, чем соединение 14. оно является наилучшим экстрагентом для катиона la3+ как в ацетонитриле, так и в воде, в сравнении с остальными катионами лантаноидов. стоит отметить, что соединения 12 и 13, в отличие от 14, не способны связывать катионы лантаноидов в водной среде. наряду с краун-эфирами в качестве экстрагентов рзм могут быть использованы модифицированные диазакраун-эфиры. например, экстракционная активность соединения 15 по отношению к лантаноидам в присутствии 1-бутил-3-метилимидазолбис[(трифто рметил)сульфонил]имида изменяется 109 следующим образом: сначала понижается в ряде металлов от la до ho, а затем повышается с увеличением атомного номера элемента [11]. таким образом, краун-эфиры представляют собой класс экстрагентов с варьируемой селективностью по отношению к экстрагируемым катионам. требуемый уровень селективности краун-эфира достигается изменением количества звеньев гликольной цепи и введением разнообразных заместителей в его структуру. наибольшую эффективность краун-эфиры проявляют при экстракции лантаноидов из растворов трихлоруксусной, уксусной и азотной кислот. поданды как экстрагенты для катионов рзм в качестве комплексообразующих аналогов краун-эфиров рассматривают открыто-цепные краун-эфиры или поданды. кислые фосфорил-содержащие поданды 16, 18, 19 были описаны в 1989 году как комплексообразователи для щелочных металлов [12]. со единение 17 и его аналоги с r1 = третбутил было предложено как реагент для селективной экстракции th(iv) из растворов азотной кислоты [13, 14]. экстракция катионов рзм из растворов азотной, соляной и хлорной кислот кислыми фосфорил-содержащими подандами 16-19 была описана 110 а.в. турановым и сотрудниками [15]. ими установлено, что эффективность экстракции катионов рзм от la(iii) до lu(iii) из 0,01 м раствора азотной кислоты с 0,01 м раствором экстрагента в дихлорэтане увеличивается в порядке 18 < 16 < 17 < 19, причем при повышении концентрации азотной кислоты эффективность экстракции снижается. нейтральные фосфорил-содержащие соединения 20-22 незначительно экстрагировали катионы рзм при этих условиях. также авторы отмечают изменение экстракционной способности соединения ii в используемых растворах кислот с концентрацией 0,01 м в следующем порядке hcl < hno3 < < hclo4. на процесс экстракции катионов рзм влияет как природа используемых кислот, так и природа органических растворителей. например, при экстракции eu(iii) раствором поданда iie в различных органических растворителях наблюдалось увеличение эффективности экстракции eu (iii) в следующем ряду растворителей: хлороформ < 2-этилгексанол < толуол < метиленхлорид < дихлорбензол < дихлорэтан < нитробензол, что объясняется специфической сольватацией молекул поданда растворителем (хлороформ или алифатический спирт) и образованием водородных связей. например, p = o•••hccl3 или p = o•••hor [16]. природа органического растворителя также влияет и на селективность экстракции. турановым и сотрудниками обнаружено, что при увеличении сольватирующей способности органического растворителя для системы с экстрагентом 24д увеличивается селективность экстракции катионов рзм в следующем порядке: толуол < < хлороформ < метилен хлорид. возможно, это связано с тем, что комплексы катионов тяжелых рзм сольватированы органическими растворителями в большей степени. при экстракции катионов соединением 24д с применением полярного растворителя эффективность экстрации увеличивается с увеличением атомного номера рз элемента в периодической таблице. для толуола (менее полярного растворителя) эффективность экстракции повышается только для ряда элементов от лантана до европия, затем понижается от тербия до лютеция. селективность экстракции может зависеть и от количества атомов кислорода m в полиэфирной цепи подандов. увеличение m в подандах 24а-24г от одного до трех понижает эффективность и селективность экстракции лантаноидов. увеличение m до четырех вызывает незначительное понижение эффективности экстракции для лантана, для остальных рз элементов эффективность экстракции увеличи111 вается, что приводит к повышению селективности экстракции подандом 24г. для подандов 23а-23ж с количеством m до шести атомов наблюдается нелинейное увеличение экстрактивной эффективности лантаноидов и ее резкое понижение в случае с соединением 23ж (m = 7). селективность экстракции меняется в аналогичном направлении при экстракции катионов рзм подандами 23а-23ж [15]. на основе поданда с открытыми полиэфирными цепочками 25, аналогично, как и в случае с краун-эфиром 7-9, можно получить полимер 26-28 для экстракции катионов рзм в системе твердая фаза-жидкость [9]. однако, в отличие от краун-эфирсодержащих полимеров, полимеры, содержащие поданды, способны к более эффективной экстракции лантаноидов в  воде. увеличение эффективности экстракции лантаноидов как в воде, так и в  ацетонитриле наблюдается в ряду полимеров 26 < 27 < 28. резюмируя вышеизложенное, стоит отметить, что наиболее эффективными экстрагентами для рзм являются фосфорил-содержащие поданды, селективность которых может зависеть как от количества атомов кислорода в полиэфирной цепочке поданда, так и от природы органического растворителя. экстракция катионов рзм модифицированными каликс[n]аренами с развитием атомно-энергетической отрасли остро возник вопрос о ликвидации и переработке ядерных отходов. разделение актиноидов от лантаноидов является важным этапом перед осуществлением трансмутационной технологии превращения актиноидов. поэтому для экстракции радиоактивных элементов из ядерных отходов был испытан ряд селективных экстрагентов, например, монодентант ные фосфорорганические экстрагенты (триоктилфосфиноксид, тофо) [17]. однако они проявляли низкую эффективность и недостаточную избирательность. поэтому возникла идея присоединения фосфорильной группы на жесткую платформу каликсарена, чтобы воспользоваться синергетическим эффектом для увеличения эффективности и селективности экстракции [18]. ранее уже были хорошо изучены и описаны производные каликсарена, содержащие карбомо112 илметилфосфин оксиды в различных положениях фрагментов каликсарена [19, 20] так же, как и некоторые каликсарены с фосфиновыми оксидами по нижнему ободу [21, 23]. m. karavan и сотрудники изучили комплексообразующие свойства фосфонат производных каликс[n]аренов 29-36 по отношению к некоторым актиноидам и лантаноидам [23]. анализ экспериментальных данных экстракции катионов из раствора азотной кислоты в m-нитробензотрифториде (m-nbtf) показал, что эффективность экстракции каликсаренами с фосфиновыми заместителеми в верхнем ободе 29б и 29д для катионов 152eu превышает таковую для 241am. однако увеличение концентрации азотной кислоты в растворе приводит к уменьшению значения коэффициента извлечения для соединения 29е; для 29б наблюдается постепенное увеличение коэффициента до 0,9 м hno3, которое затем сменяется резким уменьшением. из ряда каликсаренов с фосфиновыми заместителями по нижнему ободу 32а, 32б, 33а и 34а наибольшей экстракционной эффективностью для 241am и 152eu обладает n-третбутилкаликс[5]арен 33а. среди каликсаренов с фосфонатными заместителями в верхнем ободе 35а-35д максимальным значением коэффициента извлечения для европия и америция обладает 35в. коэффициенты извлечения 241am и 152eu были определены радиометричеn r1 r2 4 пропил метил 29а этил 29б пропил 29в изопропил 29г бутил 29д 4 гексил этил 30а бутил 30б 6 метил этил 31а бутил 31б n r 4 h 32a 4 третбутил 32б 5 третбутил 33а 6 h 34а r метил 35а этил 35б пропил 35в изопропил 35г бутил 35д 113 ски используя γ-излучение соответствующих изотопов [22]. еще один пример синтеза селективных экстрагентов на основе ка ликс[4]арена для разделения актиноидов от лантаноидов был описан ansari и сотрудниками [24, 25]. они получили серию пиразин-замещенных каликсаренов 37-39 и изучили их эффективность для экстракции катиона eu3+ из водного раствора азотной кислоты. по данным исследований, эффективность экстракции катиона европия соединениями 37-39 можно отобразить в следующей последовательности: 37 << 38 < 39. такие результаты можно объяснить влиянием природы заместителя пиразинового фрагмента соединений 37-39. исследователями также установлено, что соотношение между соединениями 37-39 и катионом eu3+ в образовавшихся комплексах равно 1:1. однако, по мнению h. huang и сотрудников, присутствие атома фосфора в структуре молекулы экстрагента не позволяет полностью его сжечь, превращаясь в накапливающиеся твердые отходы [26]. наилучшими экстрагентами в таком случае являются соединения, состоящие только из атомов с, н, о и n, которые превратятся в газообразные продукты после утилизации. подходящими под «принцип сноn» считались перспективные, легко синтезируемые соединения для экстракции актиноидов из растворов кислот – дигликольамиды (dga) [27]. но вследствие их низкой избирательности dga не могут быть использованы для разделения актиноидов и лантаноидов. введение в молекулу каликс[4]арена дигликольамида – способ получения перспективного соединения 43 для разделения актиноидов и лантаноидов, который выбрали huang и сотрудники. синтез каликс[4]арен-bdga 43 осуществлен в соответствии со схемой, где соединения 40 и 42 были по114 лучены по ранее описанным методикам [28, 29]. исследование экстракции am(iii) и eu(iii) из раствора азотной кислоты соединением 43 проводилось, используя 95 % керосин / 5 % н-октанол как дилюент. результаты показали, что значение коэффициента извлечения для am(iii) и eu(iii) увеличивается с повышением концентрации азотной кислоты в интервале от 0,5–5,0 моль/л. лиганд 43 проявил более высокую селективность для eu(iii), чем для am(iii) с фактором разделения sfam(iii)/ eu(iii) в пределах 4,5–7,3, что свидетельствует о его эффективности при разделении катионов лантаноидов и актиноидов [30]. таким образом, модифицированные каликсарены занимают одну из лидирующих позиций среди высокоэффективных и селективных экстрагентов катионов редкоземельных металлов. дигликольамиды – экстрагенты для разделения актиноидов и лантаноидов дигликольамиды и их производные, являющиеся перспективными экстрагентами для извлечения низших актинидов из растворов азотной кислоты, были описаны h. stephan и коллегами в 1991 году [31]. присутствие эфирного кислорода между двумя амидными группами в dga повышает извлечение низших актиноидов вследствие активного образования тридентантных комплексов. как наиболее перспективные экстрагенты для низших актинидов среди дигликольамидов рассматриваются n,n,n',n'тетраоктилдигликольамид (тодга) 44ж и n,n,n',n'-тетра-2-этилгексилдигликольамид (тэгдга) 44к [32, 33]. это объясняется влиянием природы алкильных заместителей дигликоль амида. влияние алкильных заместителей и природы дилюента на экстракцию лантаноидов и актиноидов дигликольамидами 44а-м было изучено y.  sasaki и коллегами [34]. ими установлено, что соединения с разветвленной алкильной цепью и несимметричными алкил-фенильными амидными группами имеют сравнительно низкий коэффициент извлечения катионов, чем глигольамиды с линейными углеводородными заместителями. исследование экстракции лантанидов тфдга, тодга, тдддга, тэгдга и 115 дмдфдга проводились в шести растворителях (нитробензол, дихлорэтан, октанол, хлороформ, толуол, додекан), используя 0,04–0,1 м дигликольамида и 1 м раствор азотной кислоты. за исключением экстрагирования тфдга в толуоле, дмдфдга в хлороформе и толуоле и тэгдга в шести дилюентах наблюдалось постепенное увеличение коэффициента извлечения лантанидов в порядке увеличения их атомного номера от la до ho, затем значение коэффициента понижается для катионов er-lu. также стоит отметить, что тодга или tдддга, растворенные в нитробензоле, октаноле и додекане, имеют фактор разделения sf(lu/la) более 100, чем подтверждают использование этих дигликольамидов для селективного разделения лантаноидов. экстракция лантаноидов в хлороформ или толуол показала не только низкое значение коэффициента извлечения, но и фактора разделения sf(ln/la). таким образом, важным условием, влияющим на эффективность экстракции лантаноидов дигликольамидами, является природа алкильных заместителей дигликольамида и используемого дилюента. экстракция лантанидов органофосфорными экстрагентами трибутилфосфат tбф и трифенилфосфиноксид toфo с давних времен являются объектами для изучения их экстрактивной активности по отношению к катионам редкоземельных металлов [35]. e. jorjani и сотрудники изучили эффективность экстракции трибутилфосфатом катионов иттрия, лантана, церия и неодима – главных компонентов отходов переработки железной руды. исследования показали, что при использовании различных концентраций раствора тбф в керосине (от 0,73 до 3,65 моль·л–1) наблюдалось увеличение значения коэффициента извлечения до концентрации тбф 3,65 моль·л–1 [36]. при изучении экстракции катионов рзм органофосфорными экстрагентами исследователи уделяют внимание синергетическому эффекту. синергетическая экстракция трехвалентных лантанидов представляет большой интерес благодаря высокой эффективности экстракции катионов хелатирующим агентом в присутствии нейтрального донора. множество изученных жидкофазных экстракционных процессов, которые имели сиr, r1 тетраметил тмдга 44а тетраэтил тэдга 44б тетрапропил тпдга 44в тетрабутил тбдга 44г тетраамил тадга 44д тетрагексил тгдга 44е тетраоктил тодга 44ж тетрадецил тддга 44з тетрадодецил тдддга 44и тетра-2-этилгексил тэгдга 44к n,n'-диметил n,n'-дифенил дмдфдга 44л тетрафенил тфдга 44м 116 нергетический характер, выполнены с использованием монодентантных соединений (например, триоктилфосфин оксид, toфo и β-дикетоны). umetani и freiser изучили смешанную лиганд-хелат экстракцию лантанидов с 1-фенил-3-метил-4-(трифторацетил)5-пиразолоном и некоторыми фосфин оксидами [37]. экстракция лантанидов смесью пикролоновой кислоты 45 с различными фосфорорганическими нейтральными донорами была изучена а.  али и сотрудниками [38]. в одной из своих работ они опубликовали данные исследований синергетической экстракции eu(iii) из смеси катионов переходных двухвалентных металлов с применением растворенной в хлороформе смеси пикролоновой кислоты и toфo, tффo и tбф [39]. извлеченные частицы были охарактеризованы как eu(pa)3·2toфo, eu(pa)3·2tффo, и eu(pa)3·tбф [40]. наиболее эффективной экстрагирующей смесью для европия оказалась смесь пикролоновой кислоты и toфo, менее эффективной – пк и tффo. наименьшую способностью к экстракции европия показала смесь пк и tбф [41]. заключение органофосфорные экстрагенты обрели свою популярность благодаря относительно простым методам получения и дешевизне. по селективности они во многом уступают краун-эфирам и каликсаренам. однако способность органофосфорных соединений к синергетической экстракции катионов служит причиной для дальнейшего их изучения [42]. наиболее перспективными экстрагентами для рзм на сегодняшний день являются краун-эфиры, каликсарены, поданды, дигликольамиды и органофосфорные соединения [43, 44]. модификация (в том числе и объединение) их структур дает возможность получить широкий спектр экстрагентов, избирательно связывающих катионы рзм. 117 references 1. eliseeva s. v., bunzli j.-c. g. rare earths: jewels for functional materials of the future. new j. chem. 2011; 35(6):1165–1176. doi: 10.1039/c0nj00969e. 2. pyrzynska k., kubiak a., wysocka i. application of solid phase extraction procedures for rare earth elements determination in environmental samples. talanta. 2016;154:15-22. doi: 10.1016/j.talanta.2016.03.022. 3. tan q., li j., zeng x. rare earth elements recovery from waste fluorescent lamps: a review. critical reviews in environmental science and technology. 2015;45 (7):749-776. 4. abrahami s. t., xiao y., yang y. rare-earth elements recovery from post-consumer hard-disc drives. transactions of the institutions of mining and metallurgy, section c: mineral processing and extractive metallurgy. 2015;124 (2):106-115. 5. 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44. mincher b. j., modolo g., mezyk s. p. review article: the effects of radiation chemistry on solvent extraction 3: a review of actinide and lanthanide extraction. solvent extraction and ion exchange. 2009;27(5-6):579-606. doi: 10.1080/07366290903114098. cite this article as (как цитировать эту статью): v. v. kurysheva, e. v. ivanova, p. e. prohorova. extractants for rare earth metals. chimica techno acta. 2016; 3(2):97–120. doi: 10.15826/chimtech.2016.3.2.008. 326 d o i: 1 0. 15 82 6/ ch im te ch .2 01 5. 2. 4. 03 0 n. v. kosova, o. a. podgornova institute of solid state chemistry and mechanochemistry sb ras, kutateladze 18, 630128 novosibirsk, russia tel: +7 383 2332410*1115 fax: +7 383 3322847 e-mail: kosova@solid.nsc.ru supervalent doping of lifepo 4 for enhanced electrochemical performance* vanadium and titanium doped orthophosphates life 0.9 m 0.1 po 4 with an olivinetype structure (space group pnma) were prepared by mechanochemically assisted solid state synthesis using a high-energy ago-2 planetary mill and post-annealing at 750 °c. it has been established that the v and ti ions do not fully substitute for fe2+ in the lifepo 4 structure. the other part of these ions participate in the formation of the secondary phases with the open nasicon-type structures: monoclinic li 3 v 2 (po 4 ) 3 (space group p2 1 /n) and rhombohedral liti 2 (po 4 ) 3 (space group r-3c). according to tem, the average particle size of the nanocomposites is about 100–300 nm. edx microanalysis reveals that the small particles of the secondary phases are segregated on the surface of the larger lifepo 4 particles. on the charge-discharge profiles of life0.9m0.1po4, the plateaus corresponding to lifepo 4 and the secondary phases are observed. v doping improves cycleability and rate capability of lifepo 4 to a greater extent than ti. keywords: lifepo 4 ; supervalent doping; mechanical activation; electrochemical cycling *this work is executed at partial financial support of rfbr (grant № 14-03-01082). © kosova n. v., podgornova o. a., 2015 introduction many efforts have been made to turn insulating compounds into attractive electrode materials, including nanosizing, carbon nanopainting and metal doping [1–3]. this allows the olivine-type lithium iron phosphate lifepo4 with inherent low electronic conductivity and slow lithium diffusion [3,  4] to become a promising cathode material exhibiting favorable electrochemical properties and to be commercialized. li ions migration in lifepo4 is found to occur preferably down the [010] channels, following a curved trajectory. the most favorable intrinsic defects in lifepo4 are the cation antisite defects, in which li and fe ions exchange positions. according to ab initio simulations of the lifepo4 doping, low favorable energies are found only for divalent dopants on the fe sites, whereas substitution energy for supervalent cations is energetically unfavorable [5]. meanwhile, it has been 327 № 4 | 2015 chimica techno acta shown experimentally that supervalent doping of lifepo4 on li sites increases its electronic conductivity by a factor of ~108 and results in superior electrochemical performance [3]. later on, these results were explained by the formation of the conductive impurity phases. the studies on the enhancement of life stability and rate capability of lifepo4 are still highlighted. vanadium and titanium are very attractive dopants for lifepo4 since they readily form corresponding lithium metal phosphates. although several reports have been published on vanadium [6-12] and titanium [13-16] substitution, there is much disagreement regarding the formation of the life1–yvypo4 and life1-ytiypo4 solid solutions. some authors insist that v3+ substitutes for fe2+ on fe sites within the solid solubility limit 0<x<0.08 [9] or at x<0.1 [7]. according to [7], the solidsolution limit depends on the preparation method and heat-treatment temperature. when synthesis temperature is increased to 700 °c, the decreased v solubility and the formation of the second phase – li3v2(po4)3 – are observed. similarly, when lifepo4 was doped with ti, titanium phosphate impurities like tip2o7 and liti2(po4)3 at higher doping level (y>0.05) were formed [14]. vand ti-doped lifepo4 samples are reported to show excellent reversible capacity and rate capability. however, there is no common viewpoint on the mechanism of the improvement. in many previous studies, cationic substitution to the fe site (m2 site) in lifepo4 usually results in higher ionic mobility and li+ diffusion coefficient due to the cell volume expansion and the probable weakening of the li-o interactions. the latter lowers the charge transfer resistance and thus improves the reversibility of the lithiation process. only a limited number of reports show that cationic substitution to the li site (m1 site) is probable, resulting in the production of li vacancies that increases the capacity of lifepo4 [11]. it remains essential to develop the synthetic routs with an appropriate cation doping of lifepo4 along with decreased particle size and optimized carbon coating. the aim of the present work was the study of vand ti-doping of lifepo4 prepared by mechanochemically assisted carbothermal reduction. experimental li2co3, fe2o3, v2o5, tio2 and (nh4)2hpo4 were used as reagents for the synthesis of life0.9v0.1po4 and life0.9ti0.1po4, further labeled as lfvp and lftp. soot was used as a reducing and coating agent (5%). the reagent mixtures were undergone a mechanochemical activation (ma) by means of a highenergy ago-2 planetary mill (900 rpm). the activated mixtures were annealed at 750 °c in ar flow. x-ray powder diffraction (xrd) was performed using d8 advance bruker diffractometer, cukα irradiation. the structural refinement of the xrd data was carried out by the rietveld method using the gsas software package. particle size and morphology were characterized by transmission electron microscopy (tem) using a jem-2200 fs transmission electron microscope. microanalysis was performed by means of energy dispersive x-ray analyzer ex-230 bu. for electrochemical testing, the supervalence doping to improve the electrochemical characteristics of lifepo 4 328 № 4 | 2015 chimica techno acta the composite cathodes were fabricated using 75 wt.% active material, 20 wt.% super p (conductive carbon) and 5 wt.% pvdf/ nmp binder. the as-mixed slurry was then pasted on the aluminum foil to obtain working electrodes. the loading density of the prepared samples was 2–3 mg·cm-2, and the electrode diameter of 10 mm was used throughout. the working electrodes were dried at 120  °c. swagelok-type cells were assembled in an argon-filled glove box with li as an anode, 1m lipf6 solution in a mixture of ethylene carbonate and dimethylcarbonate (1:1 by weight) as an electrolyte, and a glass fiber filter (whatman, grade gf/c) as a separator. results and discussion figure 1 shows the rietveld refined xrd patterns of the as-prepared samples lfvp and lftp. it is evident that both of them are well fitted by a two-phase model: lfp with an orthorhombic olivine-type structure (space group pnmb) and lvp with a monoclinic structure (space group p21/n) or ltp with a rhombohedral structure (space group r-3c). the observed and calculated patterns match well, and the reliability factor (rw) is good. the olivine structure of lfp consists of corner-shared feo6 octahedra running parallel to the b-axis, which are linked together by the po4 tetrahedra. the monoclinic structure of lvp comprised of metal octahedra and phosphate tetrahedra sharing oxygen vertices. li ions are situated in the cavities within the framework [17]. the occurrence of corner-shared chains of li polyhedra along the b-axis and open diffusion pathways in the other directions provide rapid, isotropic ionic transport similar to the fast-ion conduction in nasicon phases. the rhombohedral structure of ltp consists of a three-dimensional network made of tio6 octahedra sharing all their corners with po4 tetrahedra and vice versa to form so-called ‘lantern units’, all oriented in the same direction (along the c-axis) [18]. the conduction channels are generated along the c-axis direction. the results of structural analysis of the composites obtained from xrd rietveld refinement are shown in table 1. the lattice parameters of lfp in the lfvp composite are slightly smaller than those of pure lfp. the slight changes of lattice parameters can be ascribed to the small incorporation of v ions with smaller ionic radius (rv3+=0.64 å, rv4+=0.53 å) into the structure of lfp. the calculated mol.% of lfp and lvp phases are about 96.3 and 3.7 mol.%, respectively. in the lftp composite, the changes of lattice parameters kosova n. v., podgornova o. a. fig. 1. rietveld refined xrd patterns o f v(a) and ti-doped (b) lifepo4 329 № 4 | 2015 chimica techno acta of lfp are smaller than in lfvp. the calculated lfp/ltp ratio is 95.8/4.2 mol.%, evidencing lower degree of ti4+/fe2+ substitution. incorporation mechanism of supervalent ions in the structure of lfp is debatable. according to [5], it is unfavorable in all the limpo4 systems. this strongly suggests that these ions are unstable within the crystal lattice of limpo4 and unlikely to be incorporated beyond low concentration (>3%). the compensation mechanism for supervalent dopants was found to be the formation of m2+ vacancies, whereas compensation by a change in charge state of the transition metal ion was much higher in energy. according to the literature, the electronic state of fe ions in lfp does not change upon vand ti-doping. the authors of refs. [13–15] have found the oxidation state of doped ti ions as 4+, whereas the oxidation state of v ions is between 3+ and 4+ [9-11]. the m3+ and m4+ substitution for fe2+ in the structure of lfp compound along with the formation of li vacancies and ‘anti-site’ pair defects can be represented by the following equations in kroger-vink notation: lili x → vli' + lii • fefe x + lili x → life' + feli • 1/2m2o3 + 3/2fefe x → mfe • + 1/2vfe" + 3/2feo mo2 + 2fefe x → mfe •• + vfe" + 2feo it was supposed that iron ions can migrate from feli • sites to vfe" vacancies. thus, the main defects in the vand tidoped lfp should be li vacancies and mn+ ions in fe sites [5]. according to tem, the lfvp and lftp samples consist of the irregular shaped nanosized particles with an average particle size of about 100–300 nm similar to pure lfp (fig. 2). the surface of the particles is coated by a thin carbon layer. edx microanalysis confirms the targeted concentration of the elements in the as-prepared composites. the maps of fe and v distribution in lfvp are shown individually and overlaid with the original image in fig. 2c-e. it is evident that lvp forms smaller particles, preferably on the surface of larger lfp particles, thus, probably enhancing surface li ion mobility in the composite. electrochemical behavior of lfvp and lftp was studied within the 2.5–4.3 v voltage window at c/10 charge-discharge rate. charge-discharge profiles and the correspondent dq/dv vs. voltage plots table 1 results of structural analysis obtained from xrd rietveld refinement lattice parameters lfp lfvp lftp lfp lvp lfp ltp a, å 10.3052(1) 10.2935(3) 8.583(6) 10.3053(3) 8.491(2) b, å 5.9946(1) 5.9886(1) 8.574(6) 5.9947(2) 8.491(2) c, å 4.6833(1) 4.6843(1) 12.018(8) 4.6828(1) 20.855(9) ☐ 90.56(6) v, å3 289.32(1) 288.76 884.4(7) 289.29(2) 1302.1(4) rwp, % 6.60 8.52 9.29 χ2 1.290 2.205 2.214 lfp/lmp (mol. %) 96.3/3.7 95.8/4.2 the supervalence doping to improve the electrochemical characteristics of lifepo 4 330 № 4 | 2015 chimica techno acta are shown in fig. 3. the profiles, as well as the number and the position of the redox peaks agree with the literature data for the pure phases. the plateau at around 3.4  v is based on the fe2+/fe3+ redox couple corresponding to one li (de)intercalation from/in lfp via a two-phase mechanism. v-doped sample is characterized by the appearance of some additional distinct plateaus at higher voltage, which have been attributed to the operation of v3+/ v4+ and v4+/v5+ couples in lvp. according to ref. [17], lvp exhibits three oxidation plateaus around 3.62, 3.70, and 4.09 v when charged to 4.3 v, corresponding to a sequence of two-phase transitions li3v2(po4)3 → li2.5v2(po4)3 → li2v2(po4)3 → li1v2(po4)3. very close position of the oxidation and reduction peaks for pure lvp upon cycling in the 2.5–4.3 v points to low degree of polarization and that the electron and ion transport is facile [17]. ti-doped lfp also exhibits additional plateau, but at lower voltage. this plateau was ascribed to operation of the ti4+/ ti3+ couple in ltp. it has been found earlier that ltp can insert two additional li ions at ~2.5 v corresponding to reduction of two ti4+ ions to ti3+ [19]. li insertion in ltp is realized by a two-phase mechanism. it should be emphasized that ltp serves as an insertion host to accommodate the li ions that could not be inserted back into the lfp structure. note that the position of the redox peaks on the dq/dv plots well corresponds to those of pure lfp, lvp and ltp, evidencing that low degree of substitution and the composite formation do not noticeably influence voltage of the redox processes upon cycling. on the contrary, in the case of the olivine-type solid solutions, e.g., life1-y mnypo4 and life1-ycoypo4, the fe2+/fe 3+ and mn2+/mn3+ (co2+/co3+) redox potentials progressively increase/decrease vs. dopant content [20, 21]. figures 4a and 4b present discharge profiles of the doped samples at different rates, whereas fig. 4c and 4d display the dependence of the specific discharge capacity vs. cycle number at c/10 rate and cycling rate, respectively. the initial discharge capacity was 152 mah·g-1 for lfvp and 135 mah·g-1 for lftp, however it gradually decreases at the following cycles. rate capability of lfvp is superior to that of lftp. the enhancement of the fig. 2. edx (a), tem (b) and element distribution images (c-e) of v-doped lifepo4. a kosova n. v., podgornova o. a. 331 № 4 | 2015 chimica techno acta fig. 3. charge-discharge profiles (a) and dq/dv vs. voltage plots (b) for pure, vand ti-doped lifepo4 fig. 4. discharge profiles (a,b), specific discharge capacity vs. cycle number (c) and cycling rate (d) for vand ti-doped lifepo4 the supervalence doping to improve the electrochemical characteristics of lifepo 4 332 № 4 | 2015 chimica techno acta electrochemical performance of lfvp was considered to be a result of the presence of lvp phase with high li ion mobility and suitable amount of point defects in the structure of lfvp. conclusion vand ti-doped lifepo4 samples were synthesized using fe2o3 and v2o5 or tio2 as the raw materials with carbon both as a reductive and covering agent by a simple mechanochemically assisted carbothermal reduction. it has been established that the as-prepared samples are comprised of two finely mixed phases: lifepo4 with a small degree of fe/v(ti) substitution and the impurity phases: li3v2(po4)3 or liti2(po4)3. small particles of the secondary phases are segregated on the surface of larger lifepo4 particles. v-doped lifepo4 exhibits better cycleability and rate capability than ti-doped one. this should be due to higher lithium diffusion arose from the presence of li3v2(po4)3 with high li ion mobility and suitable amount of defects due to partial v substitution for fe. the increase in a number of voltage plateaus and the mean intercalation voltage due to the presence of the li3v2(po4)3 secondary phase should be advantageous for improving the cell performance of lifepo4. 1. yamada a., chung s. c., hinokuma k. optimized lifepo4 for lithium battery cathodes. j. electrochem. soc. 2001;148(3):a224-a229. 2. ravet n., chouinard y., magnan j. f., besner s., gauthier m., armand m. electroactivity of natural and synthetic triphylite. j. power sources. 2001;97-98:503507. doi: 10.1016/s0378-7753(01)00727-3. 3. chung s. y., chiang y. m. microscale measurements of the electrical conductivity of doped lifepo4. electrochem. solid-state lett. 2003;6(12):a278-a281.doi: 10.1149/1.1621289. 4. prosini p. p., lisi m., zane d., pasquali m. determination of the chemical diffusion coefficient of lithium in lifepo4. solid state ionics. 2002;148(1-2):45-51. doi: 10.1016/s0167-2738(02)00134-0. 5. fisher c. a. j., prieto v. m. h., islam m. s. lithium battery materials limpo4 (m = mn, transport fe, co, and ni): insights into defect association, mechanisms, and doping behavior.chem. mater. 2008;20(18):5907-5915. doi: 10.1021/cm801262x. 6. wang l., li z., xu h., zhang k. j. phys. chem. c. 2008;112:308. 7. omenya f., chernova n. a., upreti s., zavalij p. y., nam k. w., yang x. q., whittigham  m.  s. can vanadium be substituted into lifepo4? chem. mater. 2011;23(21):4733-4740. doi: 10.1021/cm2017032. 8. xiang j. y., tu j. p., zhang l., wang x. l., zhou y., qiao y. q., lu y. improved electrochemical performances of 9lifepo4·li 3v2(po4)/c composite prepared by a simple solid-state method. j. power sources. 2010;195(24):8331-8335. doi: 10.1016/j.jpowsour.2010.06.070. 9. ma j., li b., du h., xu c., kang f. j. electrochem. soc. 2011;158:a26. 10. zhang l. l., liang g., ignatov a., croft m. c., xiong x. q., hung i. m., kosova n. v., podgornova o. a. 333 huang y. h., hu x. l., zhang w. x., peng y. l. effect of vanadium incorporation on electrochemical performance of lifepo4 for lithium-ion batteries. j. phys. chem. c. 2011;115(27):13520-13527. doi: 10.1021/jp2034906. 11. chiang c. y., su h. c., liu p. j., hu c. w., sharma n., peterson v. k., hsieh h. w., lin y. f., chou w. c., lee c. h., lee j. f., shew b. y. vanadium substitution of lifepo4 cathode materials to enhance the capacity of lifepo4-based lithium-ion batteries. j. phys. chem. c. 2012;116(46):24424-24429. doi: 10.1021/jp307047w. 12. zhong s., wu l., liu j. electrochim. acta. 2012;74:8. 13. wang g. x., bewlay s., needham s. a., liu h. k., liu r. s., drozd v. a., lee j. f., chen j. m. synthesis and characterization of lifepo4 and liti 0.01fe0.99po4 cathode materials. j. electrochem. soc. 2006;153(1):a25-a31. doi: 10.1149/1.2128766. 14. wang z. h., pang q. q., deng k. j., yuan l. x., huang f., peng y. l., huang y. h. electrochim. acta. 2012;78:576. 15. fang h., liang g., zhao l., wallace t., arava h., zhang l. l., ignatov a., croft m. c. j. electrochem. soc. 2013;160:a3148. 16. koenig g. m., jr., ma j., key b., fink j., low k. b., shahbazian-yassar r., belharouak i. composite of lifepo4 with titanium phosphate phases as lithium-ion battery electrode material. j. phys. chem c. 2013;117:21132. doi:10.1021/p4074174. 17. huang h., yin s. c., kerr t., taylor n., nazar l. f. nanostructured composites: a high capacity, fast rate li3v2(po4)3/carbon cathode for rechargeable lithium batteries. adv. mater. 2002;14(21):1525–1528. doi: 10.1002/1521-4095 (20021104) 14;21<1525:aid-adma1525>3.0.co;2–3. 18. belous a. g., novitzkaya g. n., polyanetzkaya s. v., gornikov yu. i. study of complex oxides of composition la//2/////3// minus //xli//3//xtio//3. russ. izvestiya an sssr, neorgan. materialy. 1987;23(3):470–472. 19. patoux s., masquelier c. lithium insertion into titanium phosphates, silicates, and sulfates. chem. mater. 2002;14(12):5057-5068. doi: 10.1021/cm0201798. 20. kosova n. v., devyatkina e. t., slobodyuk a. b., petrov s. a. submicron life 1-ymn y po4 solid solutions prepared by mechanochemically assisted carbothermal reduction: the structure and properties. electrochim. acta. 2012;59(1):404-411. doi  : 10.1016/j.electacta.2011.10.082. 21. kosova n. v., podgornova o. a., devyatkina e. t., podugolnikov v. r., petrov s. a. effect of fe2+ substitution on the structure and electrochemistry of licopo4 prepared by mechanochemically assisted carbothermal reduction. j. mater. chem. a. 2014;2(48):20697-20705. doi: 10.1039/c4ta04221b. the supervalence doping to improve the electrochemical characteristics of lifepo 4 334 у д к 5 44 .0 21 :[ 54 6. 18 5’ 34 +5 46 .8 2+ 54 6. 88 ] н. в. косова, о. а. подгорнова институт химии твердого тела и механохимии со ран, 630128 новосибирск, россия, кутателадзе, 18 e-mail: kosova@solid.nsc.ru супервалентное допирование для улучшения электрохимических характеристик lifepo 4 * ортофосфаты life 0,9 m 0,1 po 4 со структурой оливина, допированные ванадием и титаном, были получены с помощью механохимически стимулированного твердофазного синтеза с использованием высокоэнергетической планетарной мельницы аго-2 и последующего отжига при 750 °c. показано, что ионы v и ti не полностью замещают ионы fe2+ в структуре lifepo 4 . оставшаяся часть этих ионов участвует в образовании второй фазы с насиконоподобной структурой: моноклинной li 3 v 2 (po 4 ) 3 (пространственная группа p2 1 /n) и ромбоэдрической liti 2 (po 4 ) 3 (пространственная группа r-3c). согласно пэм, средний размер частиц нанокомпозитов около 100–300 нм. эдс микроанализ показал, что мелкие частицы вторичных фаз сегрегированы на поверхности более крупных частиц lifepo 4 . на зарядно-разрядных кривых life 0,9 m 0,1 po 4 присутствуют плато, соответствующие lifepo 4 и второй фазе. допирование ванадием повышает устойчивость циклирования lifepo 4 и улучшает его циклируемость при высоких скоростях в большей степени, чем в случае допирования титаном. ключевые слова: lifepo 4 ; супервалентное допирование; механохимическая активация; электрохимическое циклирование. *данная работа выполнена при частичной финансовой поддержке рффи (грант № 14-03-01082). © косова н. в., подгорнова о. а., 2015 введение много попыток было предпринято, чтобы превратить плохо проводящие соединения в привлекательные электродные материалы, включая получение материала в наноразмерном состоянии, создание наноуглеродного покрытия и допирование ионами металлов [1–3]. это позволило железофосфату лития lifepo4 со структурой оливина, обладающему низкой электронной проводимостью и медленной диффузией лития [3, 4], стать перспективным катодным материалом с необходимыми электрохимическими свойствами и способствовало его внедрению в промышленность. было показано, что диффузия ионов li в lifepo4 происходит преимуществен335 № 4 | 2015 chimica techno acta но вдоль каналов [1] по криволинейной траектории. наиболее предпочтительными собственными дефектами в lifepo4 являются катионные антиструктурные дефекты, в которых ионы li и fe обмениваются местами. в соответствии с ab initio расчетами по допированию lifepo4 низкие значения энергии характерны только для двухвалентных допантов в позициях fe, в то время как замещение супервалентными катионами энергетически невыгодно [5]. между тем экспериментально было показано, что супервалентное допирование lifepo4 в позиции li увеличивает его электронную проводимость в ~108 раз и приводит к превосходным электрохимическим характеристикам [3]. в дальнейшем эти результаты были объяснены образованием проводящих примесных фаз. исследованиям по повышению стабильности циклирования lifepo4 и его циклированию при высоких скоростях до сих пор придается большое значение. ванадий и титан являются чрезвычайно привлекательными допантами для lifepo4, поскольку они легко образуют соответствующие литий-металлофосфаты. несмотря на то, что было опубликовано несколько работ по допированию lifepo4 ванадием [6– 12] и титаном [13–16], существует много разногласий по поводу образования твердых растворов life1-yvypo4 и life1-y tiypo4. некоторые авторы утверждают, что v3+ замещает fe2+ в позициях fe в пределах области растворимости 0 < х < 0,08 [9] или при х < 0,1 [7]. согласно [7], предел растворимости в твердой фазе зависит от метода синтеза и температуры. когда температура синтеза увеличивается до 700 °c, наблюдается понижение растворимости v и образование второй фазы – li3v2(po4)3. аналогично, когда производится допирование lifepo4 ионами ti, то при высоком уровне допирования (х > 0,05) образуются примеси, такие как tip2o7 и liti2(po4)3 [14]. сообщается, что образцы lifepo4, допированные v и ti, показывают отличную обратимую емкость и хорошую циклируемость при высоких скоростях. тем не менее нет общей точки зрения относительно механизма этого улучшения. в большинстве предыдущих исследований катионное замещение в позициях fe (позиция м2) в lifepo4, как правило, приводит к более высоким ионной подвижности и коэффициенту диффузии li+ в связи с увеличением объема элементарной ячейки и вероятного ослабления взаимодействий li-о. последнее снижает сопротивление при переносе заряда и тем самым улучшает обратимость процесса литирования. только в нескольких работах показано, что возможно катионное замещение в позициях li (позиции m1), в результате чего происходит образование вакансий li, что увеличивает емкость lifepo4 [11]. в связи с этим необходима разработка методов синтеза lifepo4 с подходящим катионным допированием наряду с уменьшением размера частиц и  созданием оптимального углеродного покрытия. целью данной работы было изучение vи ti-допированого lifepo4, синтезированного механохимически стимулированным карботермическим восстановлением. супервалентное допирование для улучшения электрохимических характеристик lifepo 4 336 № 4 | 2015 chimica techno acta экспериментальная часть life0,9v0,1po4 и life0,9ti0,1po4, далее обозначенные как lfvp и lftp, были синтезированы с использованием в качестве исходных реагентов li2co3, fe2o3, v2o5, tio2 и (nh4)2hpo4. в качестве восстанавливающего и покрывающего агента использовали сажу (5 %). смесь исходных реагентов подвергали механической активации (ма) в высокоэнергетической планетарной мельнице аго-2 (900 об./мин.). отжиг мехактивированной смеси осуществляли в токе ar при 750 °c. рентгенофазовый анализ (рфа) проводили с помощью дифрактометра d8 advance bruker, излучение cuka. для структурных уточнений данных рфа использовали пакет программного обеспечения gsas. размер и морфологию частиц определяли с помощью просвечивающей электронной микроскопии (пэм) с использованием просвечивающего электронного микроскопа jem-2200 fs. микроанализ проводили с помощью энергодисперсионного рентгеновского спектрометра ex-230 bu. для электрохимического тестирования были приготовлены композиционные катодные материалы, состоящие из 75 вес.  % активной составляющей, 20 вес.  % проводящего углерода super p и 5 вес.% связующего pvdf/nmp. полученная суспензия затем наносилась на алюминиевую фольгу для получения рабочих электродов. плотность приготовленных образцов составляла 2–3 мг × см–2, а диаметр электрода 10 мм. рабочий электрод высушивали при 120 °c. электрохимические ячейки собирали в аргоновом боксе, используя литий в качестве анода, 1м lipf6 в смеси этилени диметилкарбоната (1:1) в качестве электролита и стекловолоконный фильтр whatman, grade gf/c в качестве сепаратора. результаты и обсуждение на рис. 1 представлены дифрактограммы синтезированных образцов lfvp и lftp, уточненные по методу ритвельда. видно, что они хорошо описываются двухфазной моделью: lfp с орторомбической структурой оливина (пространственная группа pnmb) и lvp с моноклинной (пространственная группа p21/n) или ltp с ромбоэдрической структурой (пространственная группа r-3c). наблюдаемые и расчетные дифрактограммы хорошо коррелируют между собой; фактор достоверности (rw) имеет приемлемые значения. структура оливина lfp состоит из соединенных вершинами октаэдров feo6, расположенных вдоль оси b, которые связаны друг с другом посредством тетраэдров ро4. моноклинная структура lvp содержит октаэдры металлов и тетраэдры фосфата, имеющие общие атомы кислорода в вершинах. ионы лития расположены в полостях структуры [17]. наличие цепочек полиэдров лития, соединенных вершинами вдоль оси b и открытых диффузионных каналов в других направлениях, обеспечивает быстрый, изотропный ионный транспорт, подобный суперионной проводимости в соединениях со структурой nasicon. ромбоэрическая структура ltp представляет из себя трехмерную сеть из октаэдров tio6, соединенных косова н. в., подгорнова о. а. 337 № 4 | 2015 chimica techno acta всеми своими вершинами с тетраэдрами ро4, и наоборот, формируя так называемые «фонарики», ориентированные в том же направлении (вдоль оси с) [18]. каналы проводимости формируются вдоль оси с. результаты структурного анализа композитов, полученные после уточнения дифрактограмм методом ритвельда, представлены в табл.  1. параметры решетки lfp в композите lfvp несколько меньше, чем у чистого lfp. небольшие изменения параметров могут быть вызваны незначительным внедрением ионов v с меньшим ионным радиусом (rv3+ = 0,64 å, rv4+ = 0,53 å) в структуру lfp. рассчитанное соотношение фаз lfp/lvp около 96,3/3,7 мол.  %. в композите lftp изменения параметров решетки lfp меньше, чем в композите lfvp. рассчитанное соотношение lfp/ ltp – 95,8/4,2 мол.  %, что свидетельствует о меньшей степени замещения ti4+/fe2+. вопрос о механизме внедрения супервалентных ионов в структуру lfp является дискуссионным. в соответствии с [5], этот процесс неблагоприятен для всех ортофосфатов limpo4. это указывает на то, что супервалентные ионы нестабильны в кристаллической решетке limpo4 и вряд ли могут встраиваться в концентрациях, превышающих 3 %. установлено, что механизмом компенсации для супертаблица 1 результаты структурного анализа с уточнением по методу ритвельда параметры решетки lfp lfvp lftp lfp lvp lfp ltp a, å 10,3052(1) 10,2935(3) 8,583(6) 10,3053(3) 8,491(2) b, å 5,9946(1) 5,9886(1) 8,574(6) 5,9947(2) 8,491(2) c, å 4,6833(1) 4,6843(1) 12,018(8) 4,6828(1) 20,855(9) ☐ 90,56(6) v, å3 289,32(1) 288,76 884,4(7) 289,29(2) 1302,1(4) rwp, % 6,60 8,52 9,29 χ2 1,290 2,205 2,214 lfp/lmp (мол. %) 96,3/3,7 95,8/4,2 рис. 1. дифрактограммы v(a) и ti-допированного (б) lifepo4, уточненные по методу ритвельда супервалентное допирование для улучшения электрохимических характеристик lifepo 4 338 № 4 | 2015 chimica techno acta валентных допантов является формирование вакансий m2+, в то время как изменение зарядового состояния ионов переходного металла более энергозатратно. по литературным данным, электронное состояние ионов fe в lfp не меняется при допировании v и ti. авторы работ [13–15] установили, что степень окисления допированных ионов ti 4+, в то время как ионов v – между 3+ и 4+ [9–11]. замещение ионов fe2+ ионами м3+ и м4+ в структуре lfp одновременно с образованием вакансий li и «антиструктурных» парных дефектов может быть представлено следующими уравнениями в системе крёгера – винка: lili x ® vli' + lii ∙ fefe x + lili x ® life' + feli ∙ 1/2m2o3 + 3/2fefe x ® mfe · + 1/2vfe''+ + 3/2feo mo2 + 2fefe x ® mfe ∙∙ + vfe'' + 2feo. предполагается, что ионы железа могут мигрировать из положений feli · в вакансии vfe''. таким образом, основными дефектами в lfp, допированном ионами v и ti, должны быть вакансии li и ионы mn + в позициях fe [5]. согласно пэм, образцы lfvp и lftp состоят из наноразмерных частиц неправильной формы со средним размером около 100–300 нм, аналогично чистому lfp (рис. 2). поверхность частиц покрыта тонким слоем углерода. энергодисперсионный рентгеновский микроанализ подтверждает заданную концентрацию элементов в синтезированных композитах (рис. 2, а). на рис. 2, в–г приведены индивидуальные карты распределения элементов fe и v для образца lfvp при наложении с исходным изображением (рис. 2, б). очевидно, что lvp образует более мелкие частицы, предпочтительно на поверхности более крупных частиц lfp, таким образом, вероятно, увеличивая поверхность для диффузии ионов li в композите. электрохимическое поведение lfvp и lftp изучали в диапазоне напряжений 2,5–4,3 в при скорости циклирования c/10. зарядно-разрядные профили и соответствующие зависимости dq/dv от напряжения показаны на рис. 3. профили, а также количество и положение окислительрис. 2. edx (а), tem (б) и карты распределения элементов (в–д) lifepo4, допированного ванадием a косова н. в., подгорнова о. а. 339 № 4 | 2015 chimica techno acta но-восстановительных пиков согласуются с литературными данными для чистых фаз. плато около 3,4 в относится к окислительно-восстановительной паре fe2+/fe3+, соответствующей (де)интеркаляции li из/в lfp по двухфазному механизму. образец, допированный v, характеризуется появлением нескольких дополнительных отчетливых плато при более высоком напряжении, которые относятся к рабочим парам v3+/v4+ и v4+/v5+ в lvp. согласно [17], для lvp характерны три окислительных плато около 3,62; 3,70; 4,09 в при заряде до 4,3 в, соответствующие последовательным двухфазным переходам li3v2(po4)3 ® li2.5v2(po4)3 ® li2v2(po4)3 ® li1v2(po4)3. очень близкое расположение окислительных и восстановительных пиков для чистого lvp при циклировании в диапазоне напряжений 2,5–4,3 в указывает на низкую степень поляризации и облегченный электронный и ионный транспорт. lfp, допированный титаном, также имеет дополнительное плато, но при более низком напряжении. это плато соответствует рабочей паре ti4+/ti3+ в ltp. ранее было обнаружено, что ltp может внедрять два дополнительных иона li при напряжении ~2,5 в, соответствующем восстановлению двух ионов ti4+ до ti3+ [19]. внедрение li в ltp реализуется по двухфазному механизму. следует подчеркнуть, что ltp служит матрицей для размещения ионов li, которые не могут быть внедрены обратно в структуру lfp. отметим, что положение окислительно-восстановительных пиков на dq/dv зависимостях соответствует пикам для чистых lfp, lvp и ltp, свидетельствуя, что низкая степень замещения и образование композитов не оказывают заметного влияния на напряжение окислительно-восстановирис. 3. зарядно-разрядные профили (а) и зависимости dq/dv от напряжения (б) для чистого, vи ti-допированного lifepo4 супервалентное допирование для улучшения электрохимических характеристик lifepo 4 340 № 4 | 2015 chimica techno acta тельных процессов при циклировании. с другой стороны, в случае твердых растворов со структурой оливина, например, life1-ymnypo4 и life1-ycoypo4, окислительно-восстановительные потенциалы fe2+/fe3+ и mn2+/mn3+ (co2+/ co3+) постепенно понижаются/повышаются в зависимости от содержания допанта [20, 21]. на рис. 4, а, б представлены разрядные профили допированных образцов при различных скоростях, а на рис. 4, в, г – зависимость удельной разрядной емкости от номера цикла при скорости с/10 и от скорости циклирования, соответственно. начальная разрядная емкость составляет 152 мач × г-1 для lfvp и 135 мач × г -1 для lftp, однако постепенно уменьшается на последующих циклах. lfvp лучше циклирует при повышенных скоростях, чем lftp. на наш взгляд, улучшение электрохимических характеристик lfvp является следствием присутствия фазы lvp с высокой подвижностью ионов лития и приемлемого количества точечных дефектов в структуре lfvp. заключение образцы lifepo4, допированные ванадием и титаном, были синтезированы с помощью простого механохимически стимулированного карботермического восстановления с использованием fe2o3, v2o5 и tio2 в качестве исходных реагентов и сажи для восстановления и создания углеродного покрытия. было установлено, что синтезированные материалы рис. 4. разрядные профили (a, б), зависимость разрядной емкости от номера цикла (в) и скорости циклирования (г) для vи ti-допированного lifepo4 косова н. в., подгорнова о. а. 341 № 4 | 2015 chimica techno acta состоят из двух тонко перемешанных фаз: lifepo4 с малой степенью замещения fe/v(ti) и примесной фазы – li3v2(po4)3 или liti2(po4)3. маленькие частицы вторичных фаз сегрегированы на поверхности более крупных частиц lifepo4. lifepo4, допированный ванадием, обладает лучшей стабильностью при циклировании и циклируемостью при повышенных скоростях, чем образец, допированных титаном. это в большей степени связано с более высокой диффузией лития, вызванной присутствием li3v2(po4)3 с высокой мобильностью ионов li и приемлемым количеством дефектов вследствие частичного замещения v на fe. увеличение числа плато и среднего напряжения интеркаляции благодаря присутствию li3v2(po4)3 должно иметь преимущества в улучшении циклирования ячеек с lifepo4. 1. yamada a., chung s. c., hinokuma k. optimized lifepo4 for lithium battery cathodes. j. electrochem. soc. 2001;148(3):a224-a229. 2. ravet n., chouinard y., magnan j. f., besner s., gauthier m., armand m. electroactivity of natural and synthetic triphylite. j. power sources. 2001;97-98:503– 507. doi: 10.1016/s0378-7753(01)00727-3. 3. chung s. y., chiang y. m. microscale measurements of the electrical conductivity of doped lifepo4. electrochem. solid-state lett. 2003;6(12):a278-a281. doi: 10.1149/1.1621289. 4. prosini p. p., lisi m., zane d., pasquali m. determination of the chemical diffusion coefficient of lithium in lifepo4. solid state ionics. 2002;148(1–2):45–51. doi: 10.1016/s0167-2738(02)00134-0. 5. fisher c. a. j., prieto v. m. h., islam m. s. lithium battery materials limpo4 (m = mn, transport fe, co, and ni): insights into defect association, mechanisms, and doping behavior. chem. mater. 2008;20(18):5907–5915. doi: 10.1021/cm801262x. 6.wang l., li z., xu h., zhang k. j. phys. chem. c. 2008;112:308. 7. omenya f., chernova n. a., upreti s., zavalij p. y., nam k. w., yang x. q., whittigham  m.  s. can vanadium be substituted into lifepo4? chem. mater. 2011;23(21):4733–4740. doi: 10.1021/cm2017032. 8. xiang j. y., tu j. p., zhang l., wang x. l., zhou y., qiao y. q., lu y. improved electrochemical performances of 9lifepo4·li 3v2(po4)/c composite prepared by a simple solid-state method. j. power sources. 2010;195(24):8331–8335. doi: 10.1016/j. jpowsour.2010.06.070. 9. ma j., li b., du h., xu c., kang f. j. electrochem. soc. 2011;158:a26. 10. zhang l. l., liang g., ignatov a., croft m. c., xiong x. q., hung i. m., huang y. h., hu x. l., zhang w. x., peng y. l. effect of vanadium incorporation on electrochemical performance of lifepo4 for lithium-ion batteries. j. phys. chem. c. 2011;115(27):13520–13527. doi: 10.1021/jp2034906. 11. chiang c. y., su h. c., liu p. j., hu c. w., sharma n., peterson v. k., hsieh h. w., lin y. f., chou w. c., lee c. h., lee j. f., shew b. y. vanadium substitution of lifepo4 cathode materials to enhance the capacity of lifepo4-based lithium-ion batteries. j. phys. chem. c. 2012;116(46):24424-24429. doi: 10.1021/jp307047w. супервалентное допирование для улучшения электрохимических характеристик lifepo 4 342 № 4 | 2015 chimica techno acta 12. zhong s., wu l., liu j. sol-gel synthesis and electrochemical properties of 9lifepo 4 li3v2(po4)3 / c composite cathode material for lithium ion batteries.electrochim. acta. 2012;74(15):8–15. doi: 10.1016/j.electacta.2012.03.181. 13. wang g. x., bewlay s., needham s. a., liu h. k., liu r. s., drozd v. a., lee j. f., chen j. m. synthesis and characterization of lifepo4 and liti 0.01fe0.99po4 cathode materials. j. electrochem. soc. 2006;153(1):a25-a31. doi: 10.1149/1.2128766. 14. wang z. h., pang q. q., deng k. j., yuan l. x., huang f., peng y. l., huang y. h. electrochim. acta. 2012;78:576. [15] fang h., liang g., zhao l., wallace t., arava h., zhang l. l., ignatov a., croft m. c. j. electrochem. soc. 2013;160:a3148. 16. koenig g. m., jr., ma j., key b., fink j., low k. b., shahbazian-yassar r., belharouak i. composite of lifepo4 with titanium phosphate phases as lithium-ion battery electrode material. j. phys. chem c. 2013;117:21132. doi:10.1021/p4074174. 17. huang h., yin s. c., kerr t., taylor n., nazar l. f. nanostructured composites: a high capacity, fast rate li3v2(po4)3/carbon cathode for rechargeable lithium batteries. adv. mater. 2002;14(21):1525–1528. doi: 10.1002/1521-4095(20021104)14;21<1525::aid-adma1525>3.0.co;2-3. 18. belous a. g., novitzkaya g. n., polyanetzkaya s. v., gornikov yu. i. study of complex oxides of composition la//2/////3// minus //xli//3//xtio//3. russ. izvestiya an sssr, neorgan. materialy. 1987;23(3):470–472. 19. patoux s., masquelier c. lithium insertion into titanium phosphates, silicates, and sulfates. chem. mater. 2002;14(12):5057–5068. doi: 10.1021/cm0201798. 20. kosova n. v., devyatkina e. t., slobodyuk a. b., petrov s. a. submicron life 1-ymn ypo4 solid solutions prepared by mechanochemically assisted carbothermal reduction: the structure and properties. electrochim. acta. 2012;59(1):404–411. doi : 10.1016/j. electacta.2011.10.082. 21. kosova n. v., podgornova o. a., devyatkina e. t., podugolnikov v. r., petrov s. a. effect of fe2+ substitution on the structure and electrochemistry of licopo4 prepared by mechanochemically assisted carbothermal reduction. j. mater. chem. a. 2014;2(48):20697–20705. doi: 10.1039/c4ta04221b. косова н. в., подгорнова о. а. 234 n. p. medvedeva1, i. s. sapozhnikova1, v. l. rusinov1, 2, e. n. ulomskii1 1 ural federal university, 19 mira street, 620002, ekaterinburg, russia. e-mail: nataly-medvedeva@yandex.ru 2 institute of organic synthesis ural division of ras, 22 kovalevskaya street/20 academicheskaya street, 620990, ekaterinburg, russia. e-mail: v. l.rusinov@urfu.ru the redox transformations and nucleophilic replacements as possible metabolic reactions of the drug “triazaverin”. the chemical modeling of the metabolic processes as a model of metabolic transformations of antiviral drug “triazaverin” and its analogues-2-alkylthio-6-nitro-1,2,4-triazolo[5,1-c][1,2,4]triazine-7-ones 1a-d examined the oxidation of alkylthio groups to the corresponding sulfoxides 2a-d and sulfones 3a-d, as well as the process of nucleophilic substitution sulfonyloxy group of cysteine and cysteamine with the formation of compounds 5 and 6. key words: biological active compounds; heterocycles; triazine; triazaverin; antiviral drug. © medvedeva n. p., sapozhnikova i. s., rusinov v. l., ulomskii e. n., 2015 introduction the relevance of creating new antiviral drugs due to the joint action of such operating factors as the spread of socially significant, particularly dangerous infections, and the emergence of pathogenic viral strains resistant to existing drugs. the antiviral drug “triazaverin” and its analogues are highly effective in experiments in vivo and decreased activity in experiments on cell cultures, suggesting that the antiviral effect is not the “triazaverin”, and products of its transformations in the body. one way to identify such transformations in the organism is to predict the possible products of modifications of the compounds and chemical synthesis models. based on the molecular structure of compounds 1a and study of chemid o i: 1 0. 15 82 6/ ch im te ch .2 01 5. 2. 3. 02 5 235 № 3 | 2015 chimica techno acta cal properties of nitroazolo[5,1-c][1,2,4] triazines [1] can assume various variants of metabolism: redox transformations in the body (directions a, b) as the reduction of the nitro group under the action of a reductases (direction a), oxidation of alkylthio fragment under the action of oxidases (direction b) and its further transformation. the part transferases under the action of n  – and s-nucleophils, such as lysine, arginine, cysteine could lead to the replacement of alkylthioor nitro groups (directions c, d). the hydrolytic enzymes are also quite capable to lead the transformation of “triazaverin” accompanying the degradation of triazine cycle with the break of bond c-n (direction e). the alkylation on the n-atom is possible too (direction f). with regard to the redox transformations of “triazaverin” that we previously established that after the intragastric administration of laboratory animals of the drug substance, there is a reduction of the nitro group with the formation of 2-methylthio-6-amino-1,2,4-triazolo[5,1c][1,2,4]triazine-7-one [2], does not exhibit antiviral action in vitro and, most likely, which is not applicable metabolite. results and discussion considering the possibility of oxidation of alkylthio groups under use “triazaverin” and its analogues, it should be noted that in the majority of viral infections at an early stage of the process is increased generation of reactive oxygen species [3]. based on the foregoing, it is natural to assume that in these conditions can occur in the oxidation reaction of s-methyl group of “triazaverin” characteristic, for example, for sh-containing amino acids of methionine under oxidative stress. in the present communication present data on the production model experiments with the drug “triazaverin”  – the study of the oxidation of s-methyl group and the behavior of oxidation products under the action of s-nucleophils. this approach allows, on the one hand, to predict the course of chemical reactions related to the behavior of the drug in the body, and on the other hand, by the synthesis of the respective compounds to simulate the process of formation of covalent bonds of azolo[5,1-c]1,2,4-triazines with s-key fragments of proteins as cells and virus. redox-transformations of “triazaverin” and its derivatives the first aspect of this work was the synthesis of model compounds  – oxidation of sulfhydryl groups in molecules of sodium salts of 2-alkylthio-6-nitro-1,2,4triazolo[5,1-c]1,2,4-triazine-7-ones 1a-d or in the associated n-h-acids comprising the formation of heterocyclic sulfoxides 3a-d and sulfones 4a-d. sulfoxides scheme 1 the redox transformations and nucleophilic replacements as possible metabolic reactions of the drug “triazaverin”. the chemical modeling of the metabolic processes 236 № 3 | 2015 chimica techno acta 3a-d (scheme 1) were obtained under the treatment of the compounds 1a-d or 2a-d by the equimolar quantity of 18 % hydrogen peroxide in the trifluoroacetic acid. further oxidation to the corresponding sulfones 4a-d with the yields 62–71 % carried out by gradual addition of excess 2.2 equivalent of 30 % hydrogen peroxide to the suspension of 2-alkylthio-1,2,4triazolo[5,1-c]-triazines in the trifluoroacetic acid at room temperature. the represented reactions model the possible metabolic transformations of “triazaverin” and its derivatives under the action of the active forms of oxygen including hydrogen peroxide. nucleophilic replacement of methylsulfonilic group. it is known that alkylsulfonyl fragments are susceptible to the substitution reactions when interacting with nucleophiles [4]. with regard to the behavior of nitro group in “triazaverin” but the susceptibility of the nitro group associated with aromatic (heteroaromatic) cycle to the displacement under the nucleophiles [5] is well known. thus in the structure of 2-alkylsulfony l-1,2,4-t r i azolo[5,1-c]1,2,4-t r i azine-7-ones 4a-d there are two groups that are susceptible to nucleophilic displacement. this situation is of interest for the research of the comparative reactive ability of the easy outgoing groups ch3so2in 1,2,4-triazole and no2 in1,2,4-triazine cycles in the compounds 4a-d and also as the model of the behavior of “triazaverin” in the organism. as the nucleophilic reagents in this work were used s-nucleophiles(cysteine and cysteamine), which can be regarded as models of protein fragments containing cysteine fragment. the substitution sulfonylic fragment in 2-methylsulfonyl-1,2,4-triazolo[5,1c]1,2,4-triazine 4a under the influence, as cysteine and cysteamine, occurs in dry methanol in the presence of triethylamine in a few days with the formation of compounds 5 and 6substitution products methylsulfonyl group with the yields 41– 46 % (scheme 2). the date of nmr 1h, ir-spectroscopy and elemental analysis for the compounds 5, 6 correspond to the attributed structures. the described displacement of alkyl sulfonyl group in the compound 4a is the argument in favor of the assumption about the possible participation of this fragment in the metabolic transformations of “triazaverin”. experiment part nmr1h and 13c spectra were recorded on a spectrometer bruker drx-400 (400 and 100 mhz, respectively) in dmso-d6 and d2o. the chemical shifts are recorded in σ scale relatively internal standard tms for nmr1h spectra. elemental analyses were performed on chns-analyzer “perkin elmer 2400-ii”. ir spectra (4000–400 cm–1) of the received compounds were recorded on a spectrophotometer “perkin elmer spectrum one bftir” in thin layer of a scheme 2 medvedeva n. p., sapozhnikova i. s., rusinov v. l., ulomskii e. n. 237 № 3 | 2015 chimica techno acta sample (dra). reaction monitoring and the individuality of the synthesized compounds was performed by tlc plates sorbfil in the systems: ethyl acetate and butanol-acetic acid-water 4:1:1. general methods 1 for preparation of 2-alkylsulfinyl-6-nitro-1,2,4-triazolo[5,1c]1,2,4-triazin-7-ones (3a-d). to a suspension 0.01 mol of sodium salt 2-alkylthio-6-nitro-1,2,4triazolo[5,1-c]1,2,4-triazin-7-one (1) in 10 ml of trifluoroacetic acid by mixing was added 1.78 ml (1 eq.) of 18 % hydrogen peroxide. the reaction mass is mixed at room temperature during 3 hours. the resulting solid precipitate was filtered and was crystallized from iso-propanol. 2 m e t h y l s u l f i n y l 6 n i t r o 1 , 2 , 4 triazolo[5,1-c]1,2,4-triazine-7-one (3a) was obtained on the general methods 1 from compound 1a in terms of beige crystalline solid, yield 70 %, mp 256 °c, 1h nmr (dmso-d6, 400 mhz): 9.84 (1h, уш.с., nh), 3.05 (3н, с, ch3); 13c nmr (dmso-d6, 100 mhz): 169.09 (c2), 157.32 (c3a), 144.05 (c7), 143.57 (c6), 25.58 (сн3so); ir (ν/sm -1): 1750 (с=o); 1036 (–so-); 1553,1340 (no2); elemental analysis, calculated for с5h4n6o4s %: с  24.59, h 1.65, n 34.42. found, %: c 24.62, h 1.43, n 34.28. 2 e t h y l s u l f i n y l 6 n i t r o 1 , 2 , 4 triazolo[5,1-c]1,2,4-triazine-7-one (3b) was obtained on the general methods 1 from compound 1b in terms of beige crystalline solid. yield 74 %, mp 227 °c, 1h nmr (dmso-d6, 400 mhz): 11.16 (1h, br.s., nh), 3.36–3.16 (2н, m, сн2), 1.24 (3h, t, j = 7.4, ch3); 13c nmr (dmsod6, 100 mhz): 168.34 (c2), 157.58 (c3a), 144.36 (c7), 143.87 (c6), 46.64 (ch2so), 6.15 (сн3); ir (ν/sm -1): 1748 (с=o); 1022 (–so-); 1552, 1336 (no2); elemental analysis, calculated for с6h6n6o4s, %: с  27.91, h 2.34, n 32.55. found, %: c 27.87, h 2.27, n 32.31. 2 p r o p y l s u l f i n y l 6 n i t r o 1 , 2 , 4 triazolo[5,1-c]1,2,4-triazine-7-one (3c) was obtained on the general methods 1 from compound 1c in terms of beige crystalline solid. yield 72 %, mp 222 °c, 1h nmr (dmso-d6, 400 mhz): 8.41 (1h, br.s., nh), 3.29–3.18 (2н, m, soch2), 1.78–1.55 (2н, m, сн2), 1.01 (3h, t, j = 7.4, сн3); 13c nmr (dmso-d6, 100 mhz): 168.19 (c2), 157.87 (c3a), 144.19 (c7), 143.46 (c6), 54.15 (ch2so), 15.21 (сн2), 12.94 (сн3); ir (ν/sm -1): 1748 (с=o); 1013 (–so-); 1556, 1336 (no2); elemental analysis, calculated for с7h8n6o4s, %: с  30.88, h 2.96, n 30.87. found, %: c 30.82, h 3.12, n 30.77. 2 i s o propy l su l f i ny l 6 n itro 1 , 2 , 4 triazolo[5,1-c]1,2,4-triazine-7-one (3d) was obtained on the general methods 1 from compound 1d in terms of beige crystalline solid. yield 77 %, mp 239 °c, 1h nmr (dmso-d6, 400 mhz): 7.60 (1h, br.s., nh), 3.49–3.38 (1н, m, сн), 1.27 (6h, dd, j = 6.8, 2сн3); 13c nmr (dmso-d6, 100 mhz): 167.79 (c2), 157.42 (c3a), 144.33 (c7), 143.86 (c6), 53.07 (chso), 15.92 (сн3), 14.59 (сн3); ir (ν/ sm–1): 1752 (с=o); 992(–so–); 1555, 1342 (no2); elemental analysis, calculated for с7h8n6o4s, %: с  30.88, h 2.96, n 30.87. found, %: c 31.07, h 2.95, n 30.89. the general methods 2 for preparation of 2-alkylsulfonyl-6-nitro-1,2,4triazolo[5,1-c]1,2,4-triazin-7-ones (4a-d). to a suspension 0.01 mol of sodium salt 2-alkylthio-6-nitro-1,2,4-triazolo[5,1c]1,2,4-triazin-7-one (1) in 14 ml of trifluoroacetic acid by mixing dropwise was added 4 ml (2 eq.) of 30 % hydrogen peroxide in order that a temperature wasn’t the redox transformations and nucleophilic replacements as possible metabolic reactions of the drug “triazaverin”. the chemical modeling of the metabolic processes 238 № 3 | 2015 chimica techno acta above 80 oc. then the reaction mass was mixed at a room temperature during 3  hours, the precipitate was filtered and crystallized from iso-propanol. 2 m e t h y l c u l f o n y l 6 n i t r o 1 , 2 , 4 triazolo[5,1-c]1,2,4-triazine-7-one (4a) was obtained on the general methods 2 from compound 1a in terms of beige crystalline solid. yield 66 %, mp 275 °c, 1h nmr (dmso-d6, 400 mhz): 7.57 (1h, br.s., nh), 3.41 (3н, s, ch3); 13c nmr (dmso-d6, 100 mhz): 163.86 (c2), 158.41 (c3a), 144.69 (c7), 143.64 (c6), 41.84 (сн3so2); ir (ν/sm -1): 1759 (с=o); 1347, 1138 (–so2-); 1570, 1323 (no2);); elemental analysis, calculated for с5h4n6o5s, %: с  23.08, h 1.55, n 32.30. found, %: c 23.21, h 1.31, n 32.33. 2 e t h y l s u l f o n y l 6 n i t r o 1 , 2 , 4 triazolo[5,1-c]1,2,4-triazine-7-one (4b) was obtained on the general methods 2 from compound 1b in terms of beige crystalline solid. yield 64 %, mp 259 °c, 1h nmr (dmso-d6, 400 mhz): 9.71 (1h, br.s., nh), 3.52 (2h, qv., j = 7.4, сн2), 1.33 (3h, t, j = 7.4, ch3); 13c nmr (dmsod6, 100 mhz): 162.82 (c2), 158.93 (c3a), 145.06 (c7), 144.02 (c6), 48.54 (ch2so2), 7.25 (сн3); ir (ν/sm -1): 1759 (с=o); 1311, 1140 (–so2-); 1557, 1332 (no2); elemental analysis, calculated for с6h6n6o5s, %: с  26.28, h 2.21, n 30.65. found, %: c 26.44, h 2.20, n 30.43. 2 p r o p y l s u l f o n y l 6 n i t r o 1 , 2 , 4 triazolo[5,1-c]1,2,4-triazine-7-one (4c) was obtained on the general methods 2 from compound 1c in terms of beige crystalline solid. yield 71 %, mp 264 °c, 1h nmr (dmso-d6, 400 mhz): 11.98 (1h, br.s., nh), 3.53 (2н, t, j = 7.6, so2ch2), 1.76–1.67 (2н, m, сн2), 0.98 (3h, t, j = 7.4, сн3); 13c nmr (dmso-d6, 100 mhz): 163.22 (c2), 158.44 (c3a), 144.91 (c7), 143.99 (c6), 55.35 (ch2so2), 16.20 (сн2), 12.94 (сн3); ir (ν/sm –1): 1748 (с=o); 1293, 1139 (–so2 –); 1556, 1326 (no2); elemental analysis, calculated for с7h8n6o5s, %: с 29.17, h 2.80, n 29.16. found, %: c 29.01, h 2.88, n 29.24. 2 i s o propy l su l f i ny l 6 n itro 1 , 2 , 4 triazolo[5,1-c]1,2,4-triazine-7-one (4d) was obtained on the general methods 2 from compound 1d in terms of beige crystalline solid. yield 62 %, mp 282 °c, 1h nmr (dmso-d6, 400 mhz): 8.27 (1h, br.s., nh), 3.73–3.63 (1н, m, сн), 1.35 (6h, d, j = 6.8, 2сн3); 13c nmr (dmso-d6, 100 mhz): 161.91 (c2), 158.80 (c3a), 144.98 (c7), 144.02 (c6), 54.30 (chso2), 15.02 (2сн3); ir (ν/sm -1): 1749 (с=o); 1311, 1135 (–so2-); 1556, 1326 (no2); elemental analysis, calculated for с7h8n6o5s, %: с  29.17, h 2.80, n 29.16. found, %: c 29.11, h 2.69, n 29.00. the general methods 3 of nucleophilic replacement in 2-methylsulfonyl-6-nitro-1,2,4-triazolo[5,1-c]1,2,4-triazin-7-one. to a suspension 0.001 mol of cysteine (or cysteamine) in 20 ml of methanol were added triethylamine and were mixed at the argon atmosphere during 5 min, then to a reaction mass were added equivalent of 2-alkylsulfonyl-triazolotriazin and were refluxed. the end of reaction is determined by tlc in system: butanolacetic acid-water 4:1:1. the resulting solid precipitate was washed with iso-propanol. triethylammonium salt of (2’-amino-2’-c arb o et hoxyet hy lt hio)6-nit ro-1,2,4-t r iazolo[5,1-c]t r iazine hydrochloride (5) was obtained with use of the general methods 3 and 3 equivalent of triethylamine. the product was crystallized from the water ethanol in terms of canary crystalline solid. yield 46 %, medvedeva n. p., sapozhnikova i. s., rusinov v. l., ulomskii e. n. 239 № 3 | 2015 chimica techno acta mp 158 °c, 1h nmr (d2o, 400 mhz): 4.27 (1н, dd, j = 7.5, 3.8, chn), 3.98 (1н, dd, j = 15.2, 3.8, нa in sch2), 3.66 (1н, dd, j = 15.2, 7.5, нb in sch2), 3.21 (6h, qv., j = 7.28, 3сн2), 1.29 (9h, t, j = 7.28, 3ch3); 13c nmr (d2o, 100 mhz): 172.02 (coo-), 166.09 (c2), 159.16 (c3a), 144.55 (c7), 143.06 (c6), 54.47 (chn), 46.71 (3ch2), 31.67 (sch2), 8.27 (3ch3); ir (ν/sm–1): 1682, 1615 (с=о); 1504, 1361 (no2); elemental analysis, calculated for с13h22n8o5s*н2о, %: с 37.10, h 5.71, n 26.63. found, %: c 36.96, h 5.56, n 26.72. 2-(2’-amino-ethylthio)-6-nitro-1,2,4triazolo[5,1-c]1,2,4-triazine hydrate (6) was obtained with use of the general methods 3 and 2 equivalent of triethylamine. the product was crystallized from the water ethanol in terms of canary crystalline solid. yield 41 %, mp 285 °c, 1h nmr (d2o, 400 mhz): 3.58 (2h, t, j = 7.03, nch2), 3.49 (2h, t, j = 7.03, sch2); 13c nmr (dmso-d6, 100 mhz): 163.95 (c2), 160.12 (c3a), 144.77 (c7), 142.94 (c6), 38.69 (ch2n), 27.87 (sch2); ir (ν/sm -1): 1690 (с=о); 1514, 1371 (no2); 3521 (broadened) (–nh3 +); elemental analysis, calculated for с6h7n7o3s*н2о, %: с  26.18, h 3.27, n 35.64. found, %: c 25.91, h 2.98, n 35 1. rusinov  v. l., ulomskii  е. n., chupakhin  о. n., charushin  v. n.  azolo[5,1-c]-1,2,4-triazines as a new class of antiviral compounds. russ. chem. bull., int. ed. 2008; 57(5): 985–1014. doi: 10.1007/s11172–008–0130–8. 2. karpenko  i., deev  s., kiselev  o., charushin  v., rusinov  v., ulomsky  e., deeva  e., yanvarev d., ivanov a., smirnova o., kochetkov s., chupakhin o., kukhanova m. antiviral properties, metabolism, and pharmacokinetics of a novel azolo-1,2,4-triazine-derived inhibitor of influenza a and b virus replication. antimicrobial agents and chemotherapy. 2010; 54(5): 2017–2022. doi: 10.1128/aac.01186–09. 3. denicola a., radi r. peroxynitrite and drug-dependent toxicity. toxicology. 2005; 208(2): 273–288. doi: 10.1016/j.tox.2004.11.023. 4. liu j., dang q., wei z., zhang h., bai x. parallel solution-phase synthesis of a 2,6,8,9-tetrasubstituted purine library via a sulfur intermediate. j. of combinatorial chemistry. 2005; 7(4): 627–636. doi: 10.1021/cc049819p. 5. rusinov  v. l., ulomskii  е. n., chupakhin  о. n., petrov  а.  yu., sharonov  е. а.  nitroazines. 9. characteristic features of nucleophilic substitution of the nitro group in dihydroazolo[5,1-c] [1,2,4]triazines. chemistry of heterocyclic compounds. 1989; 25(2): 209–213. doi: 10.1007/bf00479921. the redox transformations and nucleophilic replacements as possible metabolic reactions of the drug “triazaverin”. the chemical modeling of the metabolic processes 240 н. р. медведева1, и. с. сапожникова1, в. л. русинов1,2, е. н. уломский1 1 уральский федеральный университет 620002 екатеринбург, ул. мира, 19. e-mail: nataly-medvedeva@yandex.ru 2 институт органического синтеза уро ран 620990 екатеринбург ул. с. ковалевской, 22 / академическая, 20. e-mail: v. l.rusinov@urfu.ru редокс превращения и нуклеофильные замещения как возможные метаболические реакции препарата «триазавирина». химическое моделирование процессов метаболизма в качестве модельных метаболических превращений противовирусного препарата «триазавирин» и его аналогов – 2-алкилтио-6-нитро-1,2,4-триазоло-[5,1-c][1,2,4]триазин-7-онов 1a-d рассмотрены реакции окисления алкитиогруппы с образованием соответствующих сульфоксидов 2a-d и сульфонов 3a-d, а также процесс нуклеофильного замещения сульфонильной группы цистеином и цистеамином с образованием соединений 5 и 6. ключевые слова: биологически активные соединения, гетероциклы, триази, триазаверин, антивирусные препараты. © медведева н. р., сапожникова и. с., русинов в. л., уломский е. н., 2015 у д к : 5 44 .6 53 .2 2: 5 44 .6 .0 18 .4 214 3 введение актуальность создания новых противовирусных средств обусловлена совместным действием таких постоянно действующих факторов, как распространение социально значимых, особо опасных инфекций, а  также появление патогенных вирусных штаммов, устойчивых к  действию существующих лекарственных средств. противовирусный препарат «триазавирин» и  его аналоги обладают высокой эффективностью в  опытах in vivo [1] и  пониженной активностью в  экспериментах на клеточных культурах, что позволяет предположить противовирусное действие не самого 241 № 3 | 2015 chimica techno acta «триазавирина», а  продуктов его превращений в  организме. одним из способов выявления таких превращений является прогнозирование возможных продуктов модификаций соединений и химический синтез моделей. исходя из молекулярной структуры соединения 1а и  изучения химических свойств нитроазоло[5,1-c][1,2,4] триазинов, можно предположить различные варианты метаболизма [1]. редокс-превращения в  организме: (направления a, b) как восстановление нитрогруппы под действием редуктаз (направление a); окисление алкилтиофрагмента под действием оксидаз (направление b) и  его дальнейшие превращения. участие трансфераз при действии nи  s-нуклеофилов, таких, например, как лизин, аргинин, цистеин способно приводить к  замещению алкилтиоили нитрогрупп (направления c, d). гидролитические ферменты также вполне способны обусловливать превращения «триазавирина®», сопровождающиеся деструкцией триазинового цикла с  разрывом связи с-n (направление e). возможно и  алкилирование по атому азота (направление f). что касается редокс-превращений «триазавирина», то ранее нами было установлено, что при внутрижелудочном ведении лабораторным животным субстанции препарата происходит восстановление нитрогруппы с  образованием  – 2-метилтио-6-амино-1,2,4триазоло[5,1-c][1,2,4]триазин-7-она [2], не проявляющего противовирус ного действия в экспериментах in vitro и, скорее всего, не являющегося действующим метаболитом. результаты и обсуждение рассматривая возможность окисления алкилтиогрупп при использовании «триазавирина®» и  его аналогов, нужно отметить, что при большинстве вирусных инфекций уже на ранней стадии процесса происходит усиление генерирования активных форм кислорода [3]. исходя из изложенного естественно предположить, что в  этих условиях могут происходить реакции окисления s-метильной группы «триазавирина», свойственные, например, для sh-содержащей аминокислоты метионина при окислительном стрессе. в настоящем сообщении приводятся данные о  постановке модельных экспериментов с  препаратом «триазавирин»  – изучение окисления s-метильной группы и  поведения продуктов окисления под действием s-нуклеофилов. такой подход позволяет, с  одной стороны, предсказать течение химических реакций, сопутствующих поведению препарата в  организме, а  с  другой стороны, путем синтеза соответствующих соединений смоделировать процесс образования ковалентных связей азоло[5,1-c]-1,2,4триазинов с  s-фрагментами ключевых белков как клетки, так и вируса. редокс-превращения «триазавирина» и его производных первым аспектом работы стал синтез модельных соединений – окисление сульфгидрильной группы в  молекулах натриевых солей 2-алкилтио-6-ниредокс превращения и нуклеофильные замещения как возможные метаболические реакции препарата «триазавирина». химическое моделирование процессов метаболизма 242 № 3 | 2015 chimica techno acta тро-1,2,4-триазоло[5,1-c]-1,2,4-триазин-7-онов 1a-d или сопряженных с  ними n-h кислот 2a-d, включающее образование гетероциклических сульфоксидов 3a-d и  сульфонов 4a-d. при обработке соединений 1a-d или 2а-d эквимолярным количеством 18 %-го пероксида водорода в  трифторуксусной кислоте получены сульфоксидоы 3a-d (схема 1). дальнейшее окисление до соответствующих сульфонов 4а-d с  выходами 62–71 % осуществлено постепенным прибавлением избытка 2,2 эквивалента 30 % h2o2 к  суспензии 2-алкилтио-1,2,4-триазоло[5,1-с]триазинов 1а-d в  трифторуксусной кислоте при комнатной температуре. представленные реакции моделируют возможные метаболические превращения «триазавирина» и  его производных под действием активных форм кислорода, включая h2o2. нуклеофильное замещение метилсульфонильной группы. известно, что алкилсульфонильные фрагменты восприимчивы к  реакциям замещения при взаимодействии с  нуклеофилами [4]. что касается поведения нитрогруппы в  «триазавирине», то хорошо известна склонность no2-группы, связанной с  ароматическим (гетероароматическим) циклом к замещению под действием нуклеофилов [5]. таким образом, в  структуре 2-алкилс ульф онил-1,2,4-т риа з оло-[5,1c]-1,2,4-триазин-7-онов 4a-d присутствуют две группировки, склонные к  нуклеофильному вытеснению. эта ситуация представляет интерес для исследования сравнительной реакционной способности легкоуходящих групп  – ch3so2в  1,2,4-триазольном и  no2в  1,2,4-триазиновом циклах в  соединениях 4a-d, а  также как модель поведения «триазавирина» в  организме. в  качестве нуклеофильных реагентов в  настоящей работе использовались s-нуклеофилы (цистеин и  цистеамин), которые можно рассматривать как модели фрагментов белков, содержащих цистеиновый фрагмент. замещение сульфонильного фрагмента в  2-метилсульфонил-1,2,4триазоло[5,1-с]-1,2,4-триазине 4а под действием как цистеина, так и  цистеамина происходит при кипячении в  сухом метаноле в  присутствии триэтиламина в  течение нескольких дней с  образованием соединений 5 и  6  – продуктов замещения метилсульфонильной группы с  выходами 41–46 % (схема 2). данные ямр, ик-спектроскопии и элементного анализа для соединений схема 2 схема 1 медведева н. р., сапожникова и. с., русинов в. л., уломский е. н. 243 № 3 | 2015 chimica techno acta 5, 6 соответствуют приписываемым структурам. описанное замещение алкилсульфонильной группы в  соединении 4а является аргументами в  пользу предположения о  возможном участии этого фрагмента в  метаболических превращениях «триазавирина». экспериментальная часть спектры ямр 1h и  13с получены на приборе bruker drx-400 (400 мгц для 1h и  100 мгц для 13с) в  дмсоd6, и  d2o, химические сдвиги приведены в  δ-шкале относительно внутреннего стандарта для спектров 1h ямр  – тмс. элементные анализы (с, h, n) были проведены на анализаторе «perkin elmer 2400-ii chns/o». ик спектры (4000–400 см–1) полученных соединений записаны на спектрометре «perkin elmer spectrum one b ftir» в  тонком слое образца (dra). контроль за ходом реакций и  чистотой синтезированных соединений осуществляли с  помощью тсх на пластинках sorbfil (фирма зао «сорбполимер») в  системах этилацетат и  бутанол-уксусная кислота-вода 4:1:1. общая методика 1 получения 2-а лки лс ульфини л-6-ни т р о-1,2,4триазоло[5,1-с]-1,2,4-триазин-7-онов (3a-d). к  суспензии 0,01 моль натриевой соли 2-алкилтио-6-нитро-1,2,4триазоло[5,1-с]1,2,4-триазин-7-она (1) в 10 мл трифторуксусной кислоты при перемешивании добавляют 1,78 мл (1  экв) 18 %-й перекиси водорода. реакционную массу перемешивают при комнатной температуре три часа, осадок отфильтровывают и  кристаллизуют из изо-пропанола. 2-ме тилс ульфинил-6-нит ро-1,2,4триазоло[5,1-с]1,2,4-триазин-7-он (3a) был получен из соединения 1а с  использованием общей методики 1 в виде бежевых кристаллов, выход 70 %, mp 256 °c, 1h nmr (dmso-d6, 400 mhz): 9,84 (1h, уш.с., nh), 3,05 (3н, с, ch3); 13c nmr (dmso-d6, 100 mhz): 169,09 (c2), 157,32 (c3a), 144,05 (c7), 143,57 (c6), 25,58 (сн3so); ir (ν/sm –1): 1750 (с=o); 1036 (–so-); 1553,1340 (no2); элемент. анализ с5h4n6o4s, вычислено %: с  – 24,59, h  – 1,65, n  – 34,42, найдено, %: c – 24,62, h – 1,43, n – 34,28. 2 э т и л с у л ь фи н и л 6 н и т р о 1 , 2 , 4 триазоло[5,1-с]1,2,4-триазин-7-он (3b) был получен из соединения 1b с  использованием общей методики 1 в виде бежевых кристаллов, выход 74 %, mp 227 °c, 1h nmr (dmso-d6, 400 mhz): 11,16 (1h, уш.с., nh), 3,36–3,16 (2н, м, сн2), 1,24 (3h, т, j = 7,4, ch3); 13c nmr (dmso-d6, 100 mhz): 168,34 (c2), 157,58 (c3a), 144,36 (c7), 143,87 (c6), 46,64 (ch2so), 6,15 (сн3); ir (ν/sm -1): 1748 (с = o); 1022 (–so-); 1552, 1336 (no2); элемент анализ с6h6n6o4s, вычислено %: с – 27,91, h – 2,34, n – 32,55, найдено, %: c – 27,87, h – 2,27, n – 32,31. 2-пропилс ульфинил-6-нитро-1,2,4триазоло[5,1-с]1,2,4-триазин-7-он (3c) был получен из соединения 1c с  использованием общей методики 1 в виде бежевых кристаллов, выход 72 %, mp 222 °c, 1h nmr (dmso-d6, 400 mhz): 8,41 (1h, уш.с., nh), 3,29–3,18 (2н, м, soch2), 1,78–1,55 (2н, м, сн2), 1,01 (3h, т, j = 7,4, сн3); 13c nmr (dmsod6, 100 mhz): 168,19 (c2), 157,87 (c3a), 144,19 (c7), 143,46 (c6), 54,15 (ch2so), 15,21 (сн2), 12,94 (сн3); ir (ν/sm –1): 1748 (с = o); 1013 (–so–); 1556, 1336 редокс превращения и нуклеофильные замещения как возможные метаболические реакции препарата «триазавирина». химическое моделирование процессов метаболизма 244 № 3 | 2015 chimica techno acta (no2); элементный анализ с7h8n6o4s, вычислено %: с  – 30,88, h  – 2,96, n  – 30,87, найдено, %: c  – 30,82, h  – 3,12, n – 30,77. 2 изо п р о п и л с у л ь ф и н и л 6 н и т р о-1,2,4-т риа з оло[5,1-с]-1,2,4-т риазин-7-он (3d) был получен из соединения 1d с  использованием общей методики 1 в  виде бежевых кристаллов, выход 77 %, mp 239 °c, 1h nmr (dmso-d6, 400 mhz): 7,60 (1h, уш.с., nh), 3,49–3,38 (1н, м, сн), 1,27 (6h, дд, j = 6,8, 2сн3); 13c nmr (dmso-d6, 100 mhz): 167,79 (c2), 157,42 (c3a), 144,33 (c7), 143,86 (c6), 53,07 (chso), 15,92 (сн3), 14,59 (сн3); ir (ν/sm -1): 1752 (с=o); 992 (–so-); 1555, 1342 (no2); элементный анализ с7h8n6o4s, вычислено %: с  – 30,88, h  – 2,96, n  – 30,87, найдено, %: c  – 31,07, h  – 2,95, n  – 30,89. общая методика 2 получения 2-а лки лс ульф они л-6-ни т р о-1,2,4триазоло[5,1-с]-1,2,4-триазин-7-онов (4a-d). к  суспензии 0,01 моль натриевой соли 2-алкилтио-6-нитро-1,2,4триазоло[5,1-с]-1,2,4-триазин-7-она (1) в  14 мл трифторуксусной кислоты при перемешивании по каплям добавляют 4 мл (2 экв) 30 % перекиси водорода так, чтобы температура не превышала 80 °c. далее реакционную массу перемешивают при комнатной температуре еще три часа, осадок отфильтровывают и  кристаллизуют из изо-пропанола. 2-ме тилс ульфонил-6-нит ро-1,2,4т ри а з ол о [ 5 , 1 с ] 1 , 2 , 4 т ри а з и н 7 он (4a) был получен из соединения 1а с  использованием общей методики 2 в  виде бежевых кристаллов, выход 66 %, mp 275 °c, 1h nmr (dmso-d6, 400 mhz): 7,57 (1h, уш.с., nh), 3,41 (3н, с, ch3); 13c nmr (dmso-d6, 100 mhz): 163,86 (c2), 158.41 (c3a), 144,69 (c7), 143,64 (c6), 41,84 (сн3so2); ir (ν/sm–1): 1759 (с = o); 1347, 1138 (–so2 –); 1570, 1323 (no2); элементный анализ с5h4n6o5s, вычислено %: с  – 23,08, h  – 1,55, n  – 32,30, найдено, %: c – 23,21, h – 1,31, n – 32,33. 2 э т и л с у л ь ф он и л 6 н и т р о 1 , 2 , 4 триазоло[5,1-с]-1,2,4-триазин-7-он (4b) был получен из соединения 1b с  использованием общей методики 2 в виде бежевых кристаллов, выход 64 %, mp 259 °c, 1h nmr (dmso-d6, 400 mhz): 9,71 (1h, уш.с., nh), 3,52 (2h, кв., j = 7,4, сн2), 1,33 (3h, т, j = 7,4, ch3); 13c nmr (dmso-d6, 100 mhz): 162,82 (c2), 158,93 (c3a), 145,06 (c7), 144,02 (c6), 48,54 (ch2so2), 7,25 (сн3); ir (ν/ sm-1): 1759 (с=o); 1311, 1140 (–so2-); 1557, 1332 (no2); элементный анализ с6h6n6o5s, вычислено %: с – 26,28, h – 2,21, n  – 30,65, найдено, %: c  – 26,44, h – 2,20, n – 30,43. 2-пропилс ульфонил-6-нитро-1,2,4т ри а з ол о [ 5 , 1 с ] 1 , 2 , 4 т ри а з и н 7 он (4c) был получен из соединения 1c с  использованием общей методики 2 в  виде бежевых кристаллов, выход 71 %, mp 264 °c, 1h nmr (dmso-d6, 400 mhz): 11,98 (1h, уш.с., nh), 3,53 (2н, т, j = 7,6, so2ch2), 1,76–1,67 (2н, м, сн2), 0,98 (3h, т, j = 7,4, сн3); 13c nmr (dmso-d6, 100 mhz): 163,22 (c2), 158,44 (c3a), 144,91 (c7), 143,99 (c6), 55,35 (ch2so2), 16,20 (сн2), 12,94 (сн3); ir (ν/sm–1): 1748 (с=o); 1293, 1139 (–so2 -); 1556, 1326 (no2); элементный анализ с7h8n6o5s, вычислено %: с – 29,17, h – 2,80, n  – 29,16, найдено, %: c  – 29,01, h – 2,88, n – 29,24. 2 изо п р о п и л с у л ь ф и н и л 6 н и т р о-1,2,4-т риа з оло[5,1-с]-1,2,4-т риамедведева н. р., сапожникова и. с., русинов в. л., уломский е. н. 245 № 3 | 2015 chimica techno acta зин-7-он (4d) был получен из соединения 1d с  использованием общей методики 3 в  виде бежевых кристаллов, выход 62 %, mp 282 °c, 1h nmr (dmso-d6, 400 mhz): 8,27 (1h, уш.с., nh), 3,73–3,63 (1н, м, сн), 1,35 (6h, д, j = 6,8, 2сн3); 13c nmr (dmso-d6, 100 mhz): 161,91 (c2), 158,80 (c3a), 144,98 (c7), 144,02 (c6), 54,30 (chso2), 15,02 (2сн3); ir (ν/sm -1): 1749 (с=o); 1311, 1135 (–so2-); 1556, 1326 (no2); элементный анализ с7h8n6o5s, вычислено %: с  – 29,17, h  – 2,80, n  – 29.16, найдено, %: c – 29,11, h – 2,69, n – 29,00. общая методика 3 нуклеофильного замещения в  2-метилсульфонил-6-нитро-1,2,4-триазоло[5,1-с]1,2,4-триазин-7-оне. к суспензии 0,001 моль цистеина (или цистеамина) в  20 мл метанола прибавляют триэтиламин и  перемешивают в  атмосфере аргона в  течение пяти минут, затем в  реакционную массу вносят эквивалент 2-алкилсульфонил-триазолотриазина и  кипятят. окончание реакции определяют по тсх в  системе бутанол-уксусная кислота-вода 4:1:1, после чего реакционную массу упаривают досуха. полученный осадок промывают изопропиловым спиртом и  очищают от примесей. триаэтиламмониевую соль (2'-амино-2'-кар б оксиэ тил тио)-6-нитро-1,2,4-триазоло[5,1-с]-1,2,4-триазина гидрат (5) получают с использованием общей методики 3 и  3 экв. триаэтиламина. продукт кристаллизуют из водного этанола в  виде ярко-желтых кристаллов, выход 46 %, mp 158 °c, 1h nmr (d2o, 400 mhz): 4,27 (1н, дд, j = 7,5, 3,8, chn), 3,98 (1н, дд, j = 15,2, 3,8, нa в  sch2), 3,66 (1н, дд, j = 15,2, 7,5, нb в  sch2), 3,21 (6h, кв., j = 7,28, 3сн2), 1,29 (9h, т, j = 7,28, 3ch3); 13c nmr (d2o, 100 mhz): 172,02 (coo -), 166,09 (c2), 159,16 (c3a), 144,55 (c7), 143,06 (c6), 54,47 (chn), 46,71 (3ch2), 31,67 (sch2), 8,27 (3ch3); ir (ν/sm –1): 1682, 1615 (с=о); 1504, 1361 (no2); элементный анализ с13h22n8o5s × н2о, вычислено %: с – 37,10, h – 5,71, n – 26,63, найдено, %: c – 36,96, h – 5,56, n – 26,72. 2-(2'-амино-этилтио)-6-нитро-1,2,4триазоло[5,1-с]-1,2,4-триазин гидрат (6) получают с использованием общей методики 3 и  2 экв. триаэтиламина. продукт кристаллизуют из водного метанола в  виде ярко-желтых кристаллов, выход 41%, mp 285 °c, 1h nmr (d2o, 400 mhz): 3,58 (2h, т, j = 7,03, nch2), 3,49 (2h, т, j = 7,03, sch2); 13c nmr (dmso-d6, 100 mhz): 163,95 (c2), 160,12 (c3a), 144,77 (c7), 142,94 (c6), 38,69 (ch2n), 27,87 (sch2); ir (ν/sm –1): 1690 (с = о); 1514, 1371 (no2); 3521 (broadened) (–nh3 +); элементный анализ с6h7n7o3s × н2о, вычислено %: с – 26,18, h  – 3,27, n  – 35,64, найдено, %: c – 25,91, h – 2,98, n – 35,57. 1. rusinov  v. l., ulomskii  е. n., chupakhin  о. n., charushin  v. n.  azolo[5,1-c]-1,2,4-triazines as a new class of antiviral compounds. russ. chem. bull., int. ed. 2008, 57(5): 985–1014. doi: 10.1007/s11172–008–0130–8. 2. karpenko  i., deev  s., kiselev  o., charushin  v., rusinov  v., ulomsky  e., deeva  e., yanvarev d., ivanov a., smirnova o., kochetkov s., chupakhin o., kukhanova m. antiviral properties, metabolism, and pharmacokinetics of a novel azolo-1,2,4-triazine-derived редокс превращения и нуклеофильные замещения как возможные метаболические реакции препарата «триазавирина». химическое моделирование процессов метаболизма 246 № 3 | 2015 chimica techno acta inhibitor of influenza a and b virus replication. antimicrobial agents and chemotherapy. 2010, 54(5): 2017–2022. doi: 10.1128/aac.01186–09. 3. denicola a., radi r. peroxynitrite and drug-dependent toxicity. toxicology. 2005, 208(2): 273–288. doi: 10.1016/j.tox.2004.11.023. 4. liu j., dang q., wei z., zhang h., bai x. parallel solution-phase synthesis of a 2,6,8,9-tetrasubstituted purine library via a sulfur intermediate. j. of combinatorial chemistry. 2005, 7(4): 627–636. doi: 10.1021/cc049819p 5. rusinov  v. l., ulomskii  е. n., chupakhin  о. n., petrov  а.  yu., sharonov  е. а.  nitroazines. 9. characteristic features of nucleophilic substitution of the nitro group in dihydroazolo[5,1-c] [1,2,4]triazines. chemistry of heterocyclic compounds. 1989, 25(2): 209–213. doi: 10.1007/bf00479921. медведева н. р., сапожникова и. с., русинов в. л., уломский е. н. interaction of iron oxide nanoparticles synthesized by laser target evaporation with polyacrylamide in composites and ferrogels f. scharf1, e. mikhnevich2, a. safronov2,3 1tu dresden, 10 helmholtz st., dresden, 01062, germany e-mail: scharf.franziska@gmail.com 2ural federal university, 19 mira st., ekaterinburg, 620002, russia e-mail: koyoto4ka@rambler.ru 3institute of electrophysics ub ras, 106 amundsen st., ekaterinburg, 620016, russia e-mail: safronov@iep.uran.ru interaction of iron oxide nanoparticles synthesized by laser target evaporation with polyacrylamide in composites and ferrogels keywords: introduction novel advanced polymeric composites with embedded magnetic particles attract special attention due to their prospective applications in biomedical applications, which include magnetic sensors, actuators, and systems for the controlled drug delivery [1–3]. such materials are based on the matrix of a biocompatible polymer with magnetic particles, which are embedded into it. iron oxides – magnetite and maghemite are widely used for this purpose. considering the practical application in biomedicine and bioengineering it is important to ensure well controlled shape of iron oxide particles and a large single batch of their production. the fabrication techniques providing enhanced batch sizes [4, 5] attract special attention as the properties of mnps can vary from batch to batch. one of the methods of mnps synthesis providing a high production rate is the physical method of the laser target evaporation (lte) [6–9]: it provides 10 to 50 nm spherical mnps at ca. 100 g per hour production rate. a magnetic polymeric composite for biomedical application might be a twocomponent system, which consists of a polymeric matrix and dispersed magnetic particles, and as well might be a threecomponent system which contains water in its structure as well. in the latter case the composite is called ferrogel. the polymeric matrix of a ferrogel constitutes of chemically and of physically cross-linked polymeric network swollen in water. water-based gels (hydrogels) are extensively studied as biocompatible and biomimetic materials which closely resembles not only the molecular structure of biological tissues but the response of these tissues to such stimuli as ph, temperature, salt concentration as well [10, 11]. polyacrylamide (paam) is often used for the synthesis of ferrogels with iron oxide mnps [12–14]. paam is a water soluble biocompatible polymer and it can form chemically cross-linked networks of homogeneous hydrogels with the network density varying in a broad range. the application of paam ferrogels as a potential material for biosensors had been demonstrated [15]. the conventional approach in the studies on polyacrylamide ferrogels is focused on their magnetic properties and their response to the applied magnetic field. it is obvious that the response of a polymeric composite material like ferrogel depends not only on the magnetic properties of the dispersed mnps but also on their interaction with polymeric matrix. meanwhile, the studies on the interactions at the interface between polymer and embedded solid particle in composites and ferrogels are lacking. the main objective of this paper was to analyze interaction of polyacrylamide with embedded iron oxide nanoparticles in a binary composite and in ternary systems including ferrogels. the adsorption of polyacrylamide polymeric chains from water solutions on the surface of iron oxide mnps as well as the enthalpy of interaction at the interface was studied. it gave the basis for the analysis of the molecular structure of polyacrylamide ferrogel and its basic properties: uptake of water (the swelling degree) and the compression modulus, which to a large extent govern its biomedical applicability. experimental: materials iron oxide mnps iron oxide (feox) magnetic nanoparticles (mnp) were synthesized by laser target evaporation (lte) – the method of high temperature physical dispersion based on the evaporation of a solid pellet by the laser beam with consequent condensation of vapors in the gas phase. lte was performed using laboratory installation with ytterbium (yb) fiber laser with 1.07 μm wavelength operated in a pulsed regime with pulse frequency 4.85 khz and pulse duration 60 μs. average output power of irradiation was about 212 w. the target pellet 65 mm in diame ter, 20 mm in height was made of the commercial magnetite (fe3o4) (alfa aesar, ward hill, ma, usa) powder (specific surface area 6.9 m2/g). the laser beam was focused onto the target pellet surface by optical system optoscand d25 f60/200 with 200 mm focal length. the driving mechanism provided 20 cm/s beam scan rate on the target surface, which ensured uniform wear-out of the target surface. the working gas (a mixture of n2 and o2 in the volume ratio 0.79:0.21) was blown into the evaporation chamber by the fan. the oxide vapors were driven away from the focal spot and condensed in spherical nanoparticles. polyacrylamide/feox magnetic composites linear polyacrylamide (lpaam) which served as a polymeric matrix for the magnetic composites was synthesized by the radical polymerization reaction of acrylamide (aam) (applichem, darmstadt) in 1.6 m water solution at 80  °c. ammonium persulfate (psa) in 5 mm concentration was used as an initiator. the reaction mixture was kept at 80  °c for 1h. the obtained lpaam solution was then diluted with distilled water down to 5 % concentration by weight. the resulted solution was then used as a stock for the preparation of magnetic composites. the molar weight of lpaam determined by viscometry was m = 1.0∙106 g/mol. the stock solution of lpaam was used for the preparation of lpaam/feox magnetic composites. therefore mnps were mixed with the stock solution in the pre-calculated proportions to obtain composites with different lpaam/ feox ratios, which cover the entire composition range 0–100 % of feox at 10 % steps. weighted sample of dry powder was wetted by a few drops of water and vigorously stirred in a mortar. then the weighted amount of 5 % lpaam stock solution was added. the mixed suspension was stirred in a mortar to homogeneity and then cast onto ptfe plate. the cast mixture was then dried in an oven at 85  °c down to the constant weight, and the composite films of different lpaam/ feox ratio were obtained. ferrogels prior to the synthesis of ferrogels a stable ferrofluid of mnps in water was obtained. therefore feox was suspended into 5 mm sodium citrate solution. the suspension was subjected to an ultra-sonic treatment for dispersion. the process of mnps de-aggregation every 15 minutes was monitored by the dynamic light scattering (dls). as soon as hydrodynamic diameter did not change any more significantly, the suspension was placed in a centrifuge at 9000 rpm for 5 minutes to remove remaining aggregates. the final suspension had an effective hydrodynamic diameter 65.7 nm (intensity average). the weight concentration of the mnps in suspension was estimated to 8.66 % by drying a sample of the ferrofluid. ferrogels were synthesized by the radical polymerization of aam in the obtained ferrofluid. the total concentration of aam in the reaction mixture was kept at two levels: 0.8 m and 1.6 m, which formed two series of ferrogels with increasing content of feox mnps up to 4 % (wt). methylene diacrylamide (merck, schuchardt) was used as a cross-linker in a molar ratio 1:100 to aam. ammonium persulfate was used as an initiator in 5 mm concentration. to start and to accelerate the polymerization, few droplets of the catalyst temed (sigma-aldrich) were added to the reaction mixture. then it was filled into plastic molds closed with parafilm. the synthesis lasted 1h at 25 °c. after that the ferrogels were taken out from the molds and placed in glass containers filled with distilled water and they were kept in it for two weeks period with daily water renewal. during this period the gels were swollen to the equilibrium. experimental: methods the powder x-ray diffraction (xrd) patterns were recorded on bruker d8 discover with cu kα1.2 radiation (λ  = 1.542 å) with graphite monochromator. the rietveld refinement of xrd patterns were performed using topas-3 software. the morphology of mnps was exami ned using jeol jem2100 transmission electron microscope (tem) operating at 200 kv. the specific surface area of mnps was measured by the low-temperature adsorption of nitrogen (brunauer-emettteller (bet) approach) using micromeri tics tristar3000 analyzer. dynamic light scattering (dls) and electrophoretic light scattering (els) measurements were performed using brookhaven zetaplus particle size analyzer: 5 and 3 runs were recorded for hydrodynamic size and zetapotential measurements, respectively. the adsorption of lpaam on the surface of feox from water solutions was estimated from the difference of lpaam concentration before and after the adsorption measured with the use of the refracto meter atago dr-1a. calibration was done using lpaam solutions with increasing concentration. microcalorimetry measurements of the enthalpy of dissolution of lpaam/feox composites in distilled water were performed at 25 °c using setaram c80 microcalorimeter. the glass ampoule technique was elaborated. the weighted sample of composite film (20–40 mg) in a thin glass ampoule was placed in a stainless steel cell filled with 10 ml of distilled water. after thermal equilibration the ampoule was broken by a special rod and the enthalpy of dissolution was measured with 2 % accuracy. the equilibrium swelling degree of ferrogels was determined as a ratio of the content of water in the gel to the weight of the dry residue which was measured gravimetrically. the swelling degree was corrected by the weight percentage of mnps in the ferrogel. the compression modulus was measured using a laboratory setup providing compressive loading of gel samples and their simultaneous optical registration during deformation. results and their discussion fig. 1 presents tem image of feox mnps synthesized by laser target evaporation. they are spherical in shape and non-aglomerated. the particle size distribution (psd) fits well the following lognormal equation: psd d d e d ( ) (ln ln( )) = − − ⋅2.46 11.7 0.423 2 2 2 (1) the specific surface area of mnps (ssp) measured by the low-temperature adsorption of nitrogen was 78 m2/g. the surface average diameter of mnps, calculated from this value using the equation ds = 6/( ssp) (   = 4.6 g/cm 3 being iron oxide density) was 16.7 nm. it was in a good agreement with the value ds = 15.9 nm, obtained using equation (1). fig. 2 presents xrd plot for feox mnps. the crystalline structure of mnps corresponded to the inverse spinel lattice with a space group fd3m. the lattice period was found a = 0.8358 nm, which was larger than that for maghemite ( -fe2o3, a = 0.8346 nm) but lower than that for magnetite (fe3o4, a = 0.8396) [16] based on the dependence between the lattice period of the spinel cell and the effective state of oxidation of fe the composition of mnps contained 76 % of -fe2o3, and 24 % of fe3o4. the coherence length of monocrystalline domains estimated using the scherrer approach was 11 nm. this value correlates well with the median value of psd (11.7 nm) obtained by tem. the isotherms of the adsorption of lpaam on the surface of feox from water solutions at 25 °c are depicted in fig. 3. curve 1 in fig. 3 corresponds to the case if the adsorption occurs on the surface of non-stabilized feox mnps which is presumably formed by iron oxide crystalline lattice. curve 2 corresponds to a quite common case if electrostatic stabilizer nacit was used to provide the stabili ty of mnps in suspension. in the latter case the surface of mnps is covered by adsorbed citrate anions. these two cases were found to be significantly different considering the adsorption of lpaam. let us first discuss the adsorption on the intact oxide surface (fig. 3, curve 1). it is recognizable that the adsorption depends on the concentration of paam. in the range of paam concentration from 0 % to ca. 1.5 % the measured adsorption increases. at concentrations higher than ca. 1.5 % it is declining. the course of the curve is characteristic for moderate concentrated solutions of linear flexible macromolecules. in solution such chains have a conformation of a coil, which is an equilibrium one for a flexible polymer. at low concentration these coils do not overlap with each other and can adsorb on the particle surface separately. the typical threshold of coil overlapping is around 1–2 %. at concentration above the threshold lpaam coils are overlapping and their adsorption decreases due to the steric limitations. the results of the adsorption measurement with the surface of feox covered with citrate as a stabilisator are very diffig. 1. tem image of feox magnetic nanoparticles synthesized by laser target evaporation. inset: histogram – calculation of particle number fraction from the image analysis, line – fitting of psd by equation (1) fig. 2. xrd diffractogram of feox mnps synthesized by laser target evaporation fig. 3. adsorption of lpaam on feox mnps from water solution at 25 °c. 1 – intact feox surface; 2 – citrate covered feox surface ferent (fig. 3, curve 2). in contrary to the case of the intact feox surface, all the values of the measured adsorption are negative. the lowest value is reached at ca 2 % concentration of lpaam. it is worth to note that the values of adsorption correspond to the excess of the concentration of the adsorbing molecules over the average concentration in the system. thus the negative values of the adsorption simply mean that the content of lpaam in the layer attached to the surface of mnps in lower than that in the bulk solution. in other words it means that the paam mole cules are repelled by the surface of the iron oxide particles. the concentration of paam in access of mnps is lower than at places where no mnps are. nacit is subjected to be decisive for the repulsion of paam. by the use of nacit the suspension was stabilized and particles were covered with a double electrical layer. it might be assumed that the electrical layer causes the repulsion of paam. to clarify the influence of surface nature on the interaction between lpaam and feox mnps, calorimetric study on the enthalpy of interaction between lpaam and mnps was performed. by these measurements the enthalpy of mixing δhm was calculated for model composites lpaam/feox. the model composites were made once in the presence of nacit and once in the absence. the enthalpy (δhm) of mixing for the polyacrylamide composite filled with iron oxide mnps has to be calculated, because it is not measurable directly. for the calculation the thermochemical cycle is used [17]. it includes the following steps: 1) lpaam + h2o (excess) = lpaam dilute solution + δh1 2) feox + h2o (excess) = feox ferrofluid + δh2 3) lpaam/feox + h2o (excess) = = lpaam solution in ferrofluid + δh3 4) lpaam solution + ferrofluid = = lpaam solution in ferrofluid + δh4 combination of these steps gives the following equation for the formation of the composite from the components: lpaam + feox = = lpaam/feox composite + δhm (2) according to hess law the enthalpy of mixing is the following combination of enthalpies of the steps: δhm = 1δh1 + 2δh2 + + δh3 – δh4, (3) here 1, 2 – are the weight fractions of lpaam and feox in composite. the calculated values of δhm correspond to the temperature at which calorimetry measurements were performed (25 °c). fig. 4 presents the dependence of δh3 values, which were measured directly in calorimeter, on the weight fraction of feox mnps in composite. the values of the enthalpy of dissolution (δh3) are negative in all cases. the value at zero weight concentration of mnps corresponds to the enthalpy of dissolution of pure lpaam (δh1). it is fig. 4. enthalpy of dissolution of lpaam/ feox composite in water at 25 °c. 1 – feox mnps with intact surface; 2 – feox mnps treated with sodium citrate. lines are for eye-guide only strongly exothermic – 120 j/g. the enthalpy of wetting of feox mnps (δh2) is low, –5.5 j/g. with increasing of weight fraction (ω2) of mnps the enthalpy of dissolution declines. at ω2 = 1 it is equal to δh3. it is noticeable that the dependences of the enthalpy of dissolution for the composites with intact feox and citratecovered feox are different. the values of δh3 in the latter case are more negative. the results of the calculation δhm using equation (3) are presented in fig. 5. it is apparent that the enthalpy of mixing strongly depends on the surface of feox mnps which are interacting with lpaam chains. in case of feox mnps with intact surface the values of δhm are negative in the broad composition range (weight fraction 0.2–1.0), whereas they are positive over the entire composition range if the surface of feox mnps is covered with citrate. this result is consistent with the adsorption measurements presented above. based on thermochemical data we may conclude that negative adsorption of lpaam at the surface of feox mnps co vered with citrate is the result of positive enthalpy of interaction at the surface. experimental data in fig. 5 were fitted by the thermodynamic model developed for the polymeric composites filled with solid particles [18] δ δh h k s k s s ads sp sp coh pol sp m = − − + − − − − ∞ ( ) ( ) exp 1 1 1 2 2 2 2 2 ω ω ε ω ω ϕ γ ω ω22ρpol l ⎛ ⎝ ⎜⎜ ⎞ ⎠ ⎟⎟ . (4) here δhads ∞ is the characteristic enthalpy of polymer adsorption at the solid surface per 1 m2, k is the apparent constant of adsorption, εcoh is the cohesion enthalpy of polymer matrix per 1 g of polymer, φpol is the volume fraction of polymer in composite, ρpol is the density of polymer, l is the characteristic thickness of the adsorption layer, γ is the excess fraction of metastable voids in the glassy structure of polymer at the surface. solid lines in fig. 5 are the results of fitting of experimental data by equation (3). concerning the objective of the present study the fitting parameter δhads ∞ is of major importance as it stands for the interaction at the surface. the fitting procedure gave the values –10.5 and +14.7  j/m2 for the adsorption of lpaam at the intact feox surface and at the surface covered with citrate respectively. these values might be taken as quantitative evaluation for the difference between enthalpy of interaction of lpaam with these two types of surfaces. based on the presented results on the interaction between feox mnps and polyacrylamide let us consider the pro perties of ferrogels, which constitute the network of paam chains with embedded feox mnps. the question, which immediately arises while considering ferrogels is whether mnps can or can not change their location inside the network. in prinfig. 5. enthalpy of mixing of lpaam/feox composites at 25 °c: 1 – feox mnps with intact surface; 2 – feox mnps treated with sodium citrate. lines correspond to fitting of experimental data by equation (3) ciple, there are two factors that influence the mobility of mnps: the mesh size of the network and the adhesion of mnps to the subchains of the network. as for the latter, it was clearly shown above that interaction of paam chains to the surface of feox mnps strongly depended on the nature of the surface. if mnps with intact surface would be used in ferrogels one might assume strong adhesion of subchains to the surface. in case of citrate-coated mnps, on the contrary, one would expect no adhesion of subchains to the surface of mnps. in fact, electrostatic stabilization by sodium citrate is the most common way to prevent aggregation of ferrofluid in preparation of ferrogels. we have used the same procedure in the synthesis of ferrogels in the present study (see materials section). thus, in the ferrogels we have synthesized feox mnps were not interacting with paam subchains. as for the mesh size of the network, it can be estimated based on the equilibrium swelling degree of a gel, which is the uptake of water by the dry polymeric network. the degree of swelling related solely to the polyacrylamide network in ferrogels was 30.0 if the concentration of aam in synthesis was 0.8 m and it was 13.2 if such concentration was 1.6 m. based on the equilibrium degree of swelling of poly meric network ( ) the average number of monomer units in linear sub-chains between cross-links (nc) was evaluated using flory-rehner equation [19]: n v vc = − − + + − − − − − 1 1 1 3 2 1 1 2 0 5 1 ( . ) (ln( ) ) /α α α α χα , (5) where v1, v2 – are molar volumes of solvent and of polymer respectively, – is flory-huggins parameter for a polymer – solvent mixture. we used v1=18 cm 3/mol (water), v2 = 56.2 cm 3/mol (polyacrylamide) and = 0.12. the last two values were obtained by means of quantum mechanics molecular modeling software package cache7.5. equation (5) gave the number of monomer units in linear subchains nc = 225 if aam concentration was 0.8 m and nc = 53 if aam concentration was 1.6 m. the equilibrium conformation of electrically neutral polyacrylamide subchain in water is a random gaussian coil with hindered rotation. its mean square endto-end distance <r2>, which corresponds to the distance between adjacent crosslinks can be calculated according to the equation [20]: r2 = − + na2 1 1 cos cos ϑ ϑ , (6) where n is the number of bonds in the polymeric chain, a is the bond length, is the bond angle. we took a = 0.154 nm for the ordinary c–c bond, 109.5° for the bond angle, and n = 2nc for the number of bonds (it  is two fold larger than nc as it includes the bonds in monomer units and bonds between them). the distance between the cross-links, calculated using equation (6) is 10.6 nm for the network synthesized in 0.8 m aam and it is 1.6  nm for the network synthesized in 1.6 m solution of aam. the former value is close to the average diameter of mnps (11.7 nm), the latter value is substantially smaller. it means that the molecular structure of two series of ferrogels is different. the essential structural features of studied polyacrylamide/feox ferrogels may be illustrated by fig. 6. further on these two types of ferrogels will be denoted as 0.8 m series and 1.6 m series. fig. 7 presents the swelling degree of paam ferrogels in the dependence on the content of feox mnps. it is noticeable that the swelling degree of ferrogels of 0.8 m series is higher than in the case of 1.6 series. it is due to the larger mesh size of the network in the former case as it was shown above. it is worth to mention that the swelling degree corresponds exclusively to paam network among mnps. although the subchains do not adsorb on the surface of mnps, their presence influences the swelling. it gives a certain dependence of the swelling degree on the weight fraction of feox mnps. this dependence is more evident in 0.8 m series of ferrogels. the first portion of mnps diminishes the swelling degree. then it increases, goes through the maximum and gradually decreases. the same depen dence can be noticed in case of 1.6 m series but the variation is close to the experimental error. fig. 8 presents the compression mo dulus of the ferrogels of both series. there is the same trend for the dependence on weight fraction of mnps: the modulus strongly increases at the first portions of mnps embedded in the gel network and then comes to saturation. the initial raise up of modulus is quite substantial: the fig. 6. schematic presentation of molecular structure of polyacrylamide ferrogels with citrate-coated feox mnps: a – 0.8 m series; b – 1.6 m series. lines schematically show polyacrylamide subchains in the network, black dots indicate the crosslinks fig. 7. swelling degree of paam ferrogels with citrate-covered feox mnps. circles –0.8 m series, triangles –1.6 m series fig. 8. compression modulus of paam ferrogels with citrate-covered feox mnps. circles –0.8 m series, triangles 1.6 m series embedding of 0.5 % of feox mnps, which correspond to ca. 0.1 % volume fraction, resulted in two-fold elevation of modulus above the value for the paam hydrogel without mnps. such a trend certainly contradicts with the conventional consideration of the modulus of continuous medium (e) with dispersed solid spheres based on the einstein equation: e e= +⎛ ⎝ ⎜ ⎞ ⎠ ⎟ <<0 ( ,1 5 2 1ϕ ϕ (7) the reasons for this effect are not clear so far. meanwhile, it is noticeable that the initial raise up of the modulus correlates with the decrease of the swelling degree of ferrogel, so one may assume the connection between them. the influence of the network density on the modulus is quite reasonable: the dense network of ferrogels of 1.6 m series (see fig. 6) provide much higher values of modulus as compared to the loose network of ferrogels of 0.8 m series. conclusions iron oxide magnetic nanoparticles (feox mnps) synthesized by laser target evaporation can be succefully embedded in composites and ferrogels based on polyacrylamide (paam). the enthalpy of interaction between the surface of mnps and paam depends strongly on the pretreatment of mnps. in the case of the intact feox particles taken per se the interaction is strong and the adsorption of paam chain onto the surface takes place. meanwhile, if the surface of mnps is coated with citrate anions, which act as a common electrostatic stabilizer for feox suspensions, interaction of paam with the surface vanishes: the enthalpy of interaction becomes positive and paam chains are repelled from the surface. however, the use of citrate might be necessary to provide the synthesis of paam ferrogels in the stable ferrofluids of feox mnps. the network density of such ferrogels, their water uptake, and the compression modulus can be efficiently controlled by the concentration of aam monomer in the reaction mixture. the increase in aam concentration from 0.8 m up to 1.6 m results in ten-fold decrease in mesh-size of the network, in 2.5-fold decrease in the swelling degree and in 2.5-fold elevation of the compression modulus. references 1. llandro j, palfreyman jj, ionescu a, barnes chw. magnetic biosensor technologies for medical applications: a review. med biol eng comput. 2010;48(10):977–8. doi:10.1007/s11517–010–0649–3. 2. hamidi m, azadi a, rafiei p. hydrogel nanoparticles in drug delivery (review). adv drug delivery rev. 2008;60(15):1638–49. doi:10.1016/j.addr.2008.08.002. 3. li y, huang g, zhang x, li b, chen y, lu t, lu tj, 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structure of a polymer on the enthalpy of mixing of polystyrene-based filled composites. polym sci, ser a. 2012;54(3):214–23. doi:10.1134/s0965545x12030108. 19. quesada-perez m, maroto-centeno ja, forcada j, hidalgo-alvarez r. gel swelling theories: the classical formalism and recent approaches. soft matter. 2011;7(22):10536–47. doi:10.1039/c1sm06031g. 20. rubinstein m, colby rh. polymer physics. new york: oxford university press; 2003. 442 p. cite this article as (как цитировать эту статью) scharf f, mikhnevich e, safronov a. interaction of iron oxide nanoparticles synthesized by laser target evaporation with polyacrylamide in composites and ferrogels. chimica techno acta. 2017;4(2):128–139. doi: 10.15826/chimtech.2017.4.2.028. cta_v3_№2.cdr 213 d o i: 1 0. 15 82 6/ ch im te ch .2 01 6. 3. 3. 01 5 уд к 66 1. 77 :5 47 .8 32 .7 +5 47 .8 36 .1 a. a. poluikova. a. yu. platonova north kazakhstan state university named m. kozybaev pushkina st., 86, petropavlovsk, 150000, kazakhstan e-mail: alena-platonova@mail.ru technology of the pilot production of the tetrahydroquinoline derivative (3as*,4r*)-4-cyano-1,2,3,3а,4,5-hexahydro-1нpyrrolo[1,2-а]quinoline-4-carbothioamide the regulations of the pilot production of (3as*,4r*)-4-cyano-1,2,3,3а,4,5-hexahydro-1нpyrrolo[1,2-а]quinoline-4-carbothioamide designed in ltd. u-synthesis is presented in the present work. main steps of the production are considered, the material balance of the process, specification of main production steps and applied equipment are given. key words: tert-amino effect, cyclization, ortho-vinyl-n,n-dialkylanilines, knoevenagel condensation, tetrahydroquinolines, ch-active compound. received: 17.07.2016; accepted: 24.29.2016; published: 01.12.2016. a. a. полуйкова, а. ю. платонова северо-казахстанский государственный университет им. м. козыбаева 150000, ул. пушкина, 86, петропавловск, казахстан e-mail: alena-platonova@mail.ru технология опытного производства тетрагидрохинолина: (3as*,4r*)-4-циано-1,2,3,3а,4,5-гексагидро-1нпирроло[1,2-а]хинолин-4-карботиоамида в работе представлен разработанный в ооо «у-синтез» регламент опытного производства (3as*,4r*)-4-циано-1,2,3,3а,4,5-гексагидро-1н-пирроло[1,2-а]хинолин-4-карботиоамида. рассмотрены основные стадии производства, приведены материальный баланс процесса, описание основных стадий производства и применяемого оборудования. ключевые слова: трет-амино эффект; циклизация; орто-винил-n,n-диалкиланилины; конденсация кнёвенагеля; тетрагидрохинолины; сн-активное соединение. поступило: 17.07.2016; приянято: 24.09.2016; опубликовано: 01.12.2016. © a. a. poluikova. a. yu. platonova, 2016 poluikova a. a., platonova a. yu. chimica techno acta. 2016. vol. 3, no. 3. p. 213–241. issn 2409-5613 introduction rationale of the work. quinoline systems are attractive, primarily, due to their biological activities [1]. so, according to the literature data, tetrahydroquinolines and related compounds have exhibited antibacterial activity against a wide range of pathogens, including grampositive and gram-negative aerobic bacteria and anaerobic organisms [2]. some of these compounds are naturally occurring. for example, 2-methyl1,2,3,4-quinoline is present in a human brain. discohabdin c being a polycyclic system based on tetrahydroquinoline is a marine alkaloid [3]. dynemycin, which is 214 a natural antitumor antibiotic, has a complex structure built on the tetrahydroquinoline system [4, 5]. the 2,4,6-trisubstituted tetrahydroquinoline 1 isolated from martinella iquitosensis (bignoniaceae family) exhibits activity as an antagonist of physiologically and pharmacologically active peptide lowering blood pressure bradykinin [6]. plenty of relatively simple synthetic 1,2,3,4-tetrahydroquinolines are already used or studied as potential drugs. among them the most well-known are oxamniquine 2, schistosomicide [7], nicainoprol 3 as well as a novel antibiotic virantmycin 4 [8, 9]. one of the most efficient synthetic routes for preparing of such systems is a three-step consequence starting from ortho-substituted benzaldehydes and including cyclization of ortho-vinyldialkylanilines via tert-amino effect mechanism. the aim of the present work is development of the method for synthesis of tetrahydroquinoline derivative using cyclization via tert-amino effect mechanism. procedure for of the laboratory synthesis synthesis of 2-pyrrolidine-1-ylbenzaldehydes 5. to a solution of 1.0 ml (9.49 mmol) of 2-fluorobenzaldehyde in 8.0 ml of dmf, 9.88 mmol of dialkylamine and 1.38 g (9.88 mmol) of potassium carbonate are added. the reaction mixture is heated on a glycerin bath at 150 °c for 20 hours. the end of the reaction is determined by tlc. further, the crude reaction mixture is cooled to room temperature and 75 ml of water are added. the product is extracted by ethyl acetate (3×60 ml). combined organic layers are washed with an ammonium chloride solution (3×75 ml). the organic layer is dried over mgso4, the solvent is removed under reduced pressure. yield: 1.53  g (93 %). brown oil. 1h nmr: (dmso-d6), δ (j, hz): 10.01 (1н, s., сно), 7.61 (1н, d. d., j1 = 8.0, j2 = 7.2, arh), 7.35–7.29 (1н, m., arh), 6.89 (1н, d., j = 8.0, arh), 6.75 (1н, t., j1 = j2 = 7.2, arh), 3.33–3.30 (4н, m., 2сн2), 1.99–1.96 (4н, m., 2сн2). found, %: n, 7.5. c11h13no. calculated, %: n, 7.99. synthesis of (3as*,4r*)-4-cyano-1,2, 3,3а,4,5-hexahydro-1н-pyrrolo[1,2-а] quinoline-4-carbothioamide. 2-dialkylaminobenzaldehyde 5 (0.5 mmol), n-butanol (0.25 m) and cyanothioacetamide (1 equiv.) are placed into a 10-ml reaction flask. the reaction vessel is enclosed with a silicone cap with perforated septum and heated in a microwave 215 reactor. after cooling with compressed air the reaction mixture is transferred to a round-bottom flask. the solvent is removed in vacuo. solid residue is crystallized from ethanol. yield: 0.41 g (79 %). red-brown crystals. the second diastereomer is not observed in 1h nmr spectrum. m.p. 222–223  °c. 1h nmr of the main diastereomer: (dmso-d6), δ (j, hz): 1.73–1.85 (1h, m., сhax); 1.88–202 (1h, m., сhax); 2.05–2.18 (2h, m., 2сheq); 3.18 (1н, d., j = 16.2, 5-снax); 3.22 (1н, d. t., j1 = 9.0, j2 = 6.2, 1-сhax); 3.47-3.58 (2h, m., 3а-снax, 5-снeq); 3.86 (1h, d. d., j1 = 9.0, j2 = 5.8, 1-cheq); 6.57 (1н, d., j = 8.4, arh); 6.60 (1н, d. d., j1 = 7.4, j2 = 7.6, arh); 7.03-7.16 (2н, m., 2 arh); 9.19 (1н, s., nh); 10.23 (1н, s., nh). 13c nmr (100 мhz, dmso-d6), δ (j, hz): 23.1 (ch2); 29.0 (ch2); 39.5 (ch2); 47.9 (c-5); 53.3 (с-4); 63.6 (c-3a); 111.7 (ch ar); 116.2 (ch ar); 117.8 (c ar); 118.3 (c ar); 128.4 (ch ar); 129.1 (ch ar); 142.8 (csnh2); 200.4 (сn). ir, v, cm -1: 752; 1370; 1418; 1456; 1602; 1632 (c=s); 2237 (сn); 2854; 3148; 3271; 3373. ms (ei, 70 ev), m/z (irel %): 257 [m] + (43); 224 (10); 197 (22); 196 (27); 195 (100); 168 (8); 140 (8); 130 (12); 128 (10); 60 (8). ). found, %: с 64.8; н 6.0; n 16.1. c14h15n3s. calculated, %: с 65.34; н 5.87; n 16.33. characteristics of the final product product name: 4-cyano-1,2,3,3а,4,5hexahydro-1н-pyrrolo[1,2-а]quinoline4-carbothioamide. molecular weight: 257.355 g/mol structural formula: characteristics of an initial sample: 1. the standard sample is approved in accordance with the established procedure. 2. the standard sample should be replaced by newly prepared and approved after 6 months. 3. validity period, its extension and storage of the standard sample is established according to “the instruction for selection, study, approvement, storage and consumption of standard samples” approved in accordance with the established procedure. 4. the standard sample is stored in a hermetically closed container in a dry darkened place at 0–20 °с. characteristics of feedstock and materials are given in table 1–2. steps and chemistry of the process 1. preparation of 4-cyano-1,2,3,3а,4,5hexahydropyrrolo[1,2-а]quinoline-4-carbothioamide: 2. filtration and washing. 3. drying of a product. 4. recrystallization of the product in ethanol. 5. drying of the product. the technological diagram is given in fig. 1. table 1 characteristics of crude product name of an index standard 1. appearance brown powder 2. impurity content no more than 1.0 % 3. melting point 223 °с 4. solubility с4н9он chcl3 216 the scheme of material flows is shown in fig. 2. critical control points of the production are given in table 3. description of steps of the technological process preparation of equipment and feedstock before starting production works planned preventive maintenance of all equipment is carried out, its pressurization and reliability of grounding is checked, adjustment of balances is made. all control and instrumentation devices, control consoles serving the technological process are undergone a monitoring. apparatus are carefully washed by water, dried, correct operation of a mixer and a driver is checked. initial data for the production are given in tables 4–8. process is started with preparation of raw materials and equipment for work. raw materials are checked for necessary quality indicators: authenticity, content of the main substance. equipment is checked for purity, dryness, pressurization. material balances of units 1-4 are shown in table 9–17. tp 1. obtainment of carbothioamide preliminary storages stor-1, stor-2 and stor-11 are filled with pyrrolidinbentable 2 characteristic of feedstock and materials name gost (state standard), ost (branch standard), the regulations and technique for the preparation of feedstock grade or article indicators obligatory for check notes 1. pyrrolidinebenzaldehyde – react. mass fraction > 85 % from a storage stor-1 2. 2-cyanoacetothioamide – react. mass fraction > 60 % from a warehouse 3. n-butanol gost 6006-78 solv., pure mass fraction > 99,5 % boiling point 117 °с from a storage stor-2 4. ethanol gost 18300-87 solv., pure mass fraction > 96 % from a storage stor-11 mw=175 mw=100 mw=257 ortho-pyrrolidinbenzaldehyde cyanoacetothioamide hexahydroquinoline carbothioamide 217 fig. 1. the principal instrumental diagram of 4-cyano-1,2,3,3а,4,5-hexahydropyrrolo[1,2-а] quinoline-4-carbothioamide production fig. 2. graph diagram and material flows of the technological process 218 table 7 molar mass of reagents and reaction products pba та but et cta 175.23 100.14 74.12 46.07 257.36 table 4 abbreviations pyrrolidinbenzaldehyde pba cyanoacetothioamide та butanol but ethanol et carbothioamide cta table 5 initial data for calculation formulation of technical pba pure pba 0.98 water in the technical product 0.01 other impurities 0.01 formulation of technical та pure та 0.99 other impurity 0.01 formulation of technical cta pure cta 0.995 water 0.001 other impurities 0.004 table 6 yields for steps tp(technological process) 1 chemical reaction η1= 0.89 tp 2 filtration and washing η2 = 0.87 tp 3 drying η3 = 0.85 tp 4 recrystallization η4 = 0.99 tp 5 filtration and washing η5 = 0.87 tp 6 drying η6 = 0.91 total yield ση = 0.65 table 3 main technological parameters control point name of a subject of control controlled parameter and dimension standard method and control means rp 1 thioamide solution in n-butanol solubility of the thioamide the complete dissolution of the substance visually rp 2 reaction mixture completeness of the reaction absence of starting thioamide and aldehyde in the reaction mixture tlc rp 3 paste moisture content, % no more than 0.3 electroconductometric method of measurement of humidity rp 4 solution of product in ethanol solubility thioamide the complete disolution of substance visually rp 5 paste moisture content, % no more than 0.3 electroconductometric method of humidity measurement rp 6 commercial product content of the main substance, % no less than 99 1н-nmrspectroscopy, ms spectrometry, elemental analysis 219 zaldehyde, n-butanol and ethanol, respectively. a screw feeder bin s-3 is charged with cyanoacetothioamide. benzaldehyde is fed from the stor-1 into a measurer m-5 by compressed nitrogen. into a measurer m-6 n-butanol is fed from the stor-2 by compressed nitrogen. in a clean and checked reactor r-4 table 8 the material balance of units loading raw materials, including g γ pyrrolidinbenzaldehyde 1.0 0.980 cyanoacetothioamide 1.0 0.985 n-butanol 0.5 0.97 ethanol 0.6 0.97 table 9 material balance of unit 1 loaded received r aw m ate ri al s an d se m i pr od uc ts c on te nt , % (m as s. ) te ch ni ca l w ei gh t, kg w ei gh t 10 0  % , k g pr od uc ts , w as te , l os se s c on te nt , % (m as s. ) te ch ni ca l w ei gh t, kg w ei gh t 10 0  % , k g 1. pyrrolidine benzaldehyde, including: 100.0 1.037 1. reaction mixture, including: 100.0 3.021   pba 100 % 97.975   1.016 cta 56.5   1.708 water 0.964   0.010 pba residual 3.7   0.112 admixtures 1.061   0.011 та residual 5.5   0.165 2. cyanoacetothioamide, including: 100.0 0.985   but 100 % 32.1   0.970 та 100 % 98.477   0.970 water 1.3   0.040 admixtures 1.523   0.015 admixtures 0.9   0.026 3. n-butanol, including: 100.0 1.000           but 100 % 97.000   0.970         water 3.000   0.030         total (summary)  3.022 total 100.0 3.021 table 10 additional initial data the formulation of the precipitate after washing precipitate, including: γ 100 % cta 0.988 water in precipitate 0.01 admixtures in precipitate 0.002 the formulation of a mother liquor b: solution, including: γ 100 % but 0.942 water in solution 0.008 admixtures in solution 0.05 220 table 12 material balance of unit 3 loaded received r aw m at er ia ls an d se m ipr od uc ts c on te nt , % (m as s. ) te ch ni ca l w ei gh t, kg w ei gh t 10 0 % , k g pr od uc ts , w as te , lo ss es c on te nt , % (m as s. ) te ch ni ca l w ei gh t, kg w ei gh t 10 0 % , k g 1. precipitate, including: 100.00 1.504   1. dried cta, including: 100.00 1.273   cta 98.80   1.486 cta 99.74   1.2694 water 1.00   0.015 water 0.10   0.0013 admixtures 0.20   0.003 admixtures 0.16   0.0021 2. volatile, including: 100.00 0.015 water 93.81 0.0138 admixtures 6.19 0.0009 3. loss 0.223 total   1.504   total   1.505   table 11 material balance of unit 2 loaded received r aw m at er ia ls an d se m ipr od uc ts c on te nt , % (m as s. ) te ch ni ca l w ei gh t, kg w ei gh t 10 0 % , k g pr od uc ts , w as te , lo ss es c on te nt , % (m as s. ) te ch ni ca l w ei gh t, kg w ei gh t 10 0 % , k g 1. reaction mixture, including: 100.00 3.021   1. precipitate, including: 100.00 1.504   cta 56.538   1.708 cta 98.80   1.486 water 1.324   0.040 water 1.00   0.015 but 100 % 32.109   0.970 admixtures 0.20   0.003 admixtures 10.030   0.303 2. mother liquor, including: 100.00 1.030   2. but for washing   0.854   b 100 % 94.20   0.970 water 0.80   0.008 admixtures 5.00   0.051 3.filtrate, including: 100.00 1.117   b 100 % 76.45   0.854 water 1.52   0.017 admixtures 22.02   0.246 4. losses   0.222   total   3.875   total   3.873   221 butanol is poured by gravity from a measurer m-6, a stirrer is turned on, then benzaldehyde is charged by gravity from the measurer m-5. thioamide is fed into the reactor by the screw feeder s-3 after feeding alcohol and benzaldehyde. after loading thioamide the screw feeder is turned off, a loading hatch is closed hermetically. after loading of starting materials the reactor is completely pressurized, leaving only an open valve on the line connecting the reactor with the atmosphere. further live steam is fed into the jacket heating the reaction mixture to 115–120 °c and it is held with a running stirrer for 6 hours. a heat exchanger e-7 provides solvent condensation under heating of the reaction mixture during the whole step of the chemical reaction. after 6 hours feeding of steam is stopped, the reaction mixture is cooled with cold water fed into the jacket. further suspension is transferred to a centrifuge c-8 for the precipitate separation. table 13 material balance of unit 4 loaded received r aw m at er ia ls an d se m ipr od uc ts c on te nt , % (m as s. ) te ch ni ca l w ei gh t, kg w ei gh t 10 0  % , k g pr od uc ts , w as te , lo ss es c on te nt , % (m as s. ) te ch ni ca l w ei gh t, kg w ei gh t 10 0  % , k g 1. dried cta, including: 100.00 1.273 1. suspension, including: 100.00 1.263 cta 99.74 1.2694 cta 100 % 99.73 1.2601 water 0.10 0.0013 water 0.10 0.0013 admixtures 0.16 0.0021 admixtures 0.17 0.0021 2. et technical, including: 0.785 2. et technical, including: 100.00 0.785 et 100 % 0.761 et 100 % 96.943 0.7610 water 0.024  water 3.057 0.0240 3. losses 0.0096 total 2.058 total 2.058 table 14 additional initial data the composition of the precipitate after washing: precipitate, including. γ 100 % cta 0.995 water in precipitate 0.003 admixtures in precipitate 0.002 the composition of the mother liquor et: solution, including. γ 100 % et 0.994 water in solution 0.002 admixtures in solution 0.004 222 table 16 material balance of unit 6 loaded received r aw m at er ia ls an d se m ipr od uc ts c on te nt , % (m as s. ) te ch ni ca l w ei gh t, kg w ei gh t 10 0  % , k g. pr od uc ts , w as te , lo ss es c on te nt , % (m as s. ) te ch ni ca l w ei gh t, kg w ei gh t 10 0  % , k g. 1. precipitate, including 100.00 1.1021 1. cta (commercial), including: 100.00 1.000 cta 99.50 1.0962 cta 0.995 water 0.33 0.0036 residual water 0.001 admixtures 0.20 0.0022 admixturses 0.004 2. volatiles, including 100.00 0.0020 water 65.00 0.0013 admixturess 60.00 0.0012 3. losses 0.100 total 1.1021 total 1.102 table 15 material balance of unit 5 loaded received r aw m at er ia ls an d se m ipr od uc ts c on te nt , % (m as s. ) te ch ni ca l w ei gh t, kg w ei gh t 10 0 % , k g pr od uc ts , w as te , lo ss es c on te nt , % (m as s. ) te ch ni ca l w ei gh t, kg w ei gh t 10 0 % , k g 1. suspension, including: 100.00 1.263 1. precipitate, including: 100.00 1.102 cta 100 % 99.73 1.2601 cta 99.50 1.0962 water 0.10 0.0013 water 0.33 0.0036 admixtures 0.17 0.0021 admixtures 0.20 0.0022 2. et technical, including: 100.00 0.785 2. mother liquor, including: 100.00 0.766 et 100 % 96.943 0.7610 et 100 % 99.40 0.7610 water 3.057 0.0240 water 0.20 0.0015 3. et for washing 0.756  admixtures 0.40 0.0031 3. filtrate, including: 100.00 0.778 et 100 % 97.21 0.7560 water 2.64 0.0205 admixtures 0.15 0.0012 4. losses 0.068 total 2.804   total 2.803 223 table 17 sheet specification of the equipment name quantity of units material of a working zone technical data reactors r-4 1 12х18н10т оsт 26-01-1246-75. internal volume of the apparatus is 0.315 m3. execution of the apparatus 0010-1.0.6, inner diameter d = 660 mm, height h = 920 mm. a vertical apparatus with a mixing device used for conducting various technological processes in liquid single-phase and multiphase environments. material execution of the cylinder of the device is steel of 12х18н10т brand in accordance with gosт 5632-72. nominal overpressure in the cylinder is 0.6 mpa. engine power is 0.6 kw. admissible external pressure is 0.576 мpа. it is equipped with a smooth welded jacket in accordance with оsт 26-01-984-74, a frame stirrer мп01-10-5.74-3/167ао2-41-6 r-12 1 12х18н10т оsт 26-01-1246-75. internal volume of the apparatus is 0.315 m3. execution of the apparatus 0010-1.0.6, inner diameter d = 660 mm, height h = 920 mm. vertical apparatus with mixing device used for conducting various technological processes in liquid single-phase and multiphase environments. material execution of the cylinder of the device is steel of 12х18н10т brand in accordance with gosт 5632-72. nominal overpressure in the cylinder is 0.6 mpa. engine power is 0.6 kw. admissible external pressure is 0.576 мpа. it is equipped with a smooth welded jacket in accordance with оsт 26-01-984-74, a frame stirrer мп01-10-5.74-3/167ао2-41-6 measurers м-5 1 12х18н10т gost 9931-79. denomination vee1-1-1-0.6. nominal volume is 0.040 m3. a vertical all-welded apparatus with elliptic bottoms. the diameter of the apparatus d = 400 mm, h = 400 mm. the area of the inner surface is 0.59  m2. designed for receiving, storing and feeding liquid and gaseous media. the pressure in the apparatus is 0.6 мpа. liquid media feeding is performed by gravity м-6 1 12х18н10т gost 9931-79. denomination vee1-1-1-0.6. nominal volume is 0.040 m3. a vertical all-welded apparatus with elliptic bottoms. the diameter of the apparatus d = 400 mm, h = 400 mm. the area of the inner surface is 0.59  m2. designed for receiving, storing and feeding liquid and gaseous media. the pressure in the apparatus is 0.6 мpа. liquid media feeding is performed by gravity 224 the rest of table 17 name quantity of units material of a working zone technical data м-15 1 12х18н10т gost 9931-79. denomination vee1-1-1-0.6. nominal volume is 0.040 m3. a vertical all-welded apparatus with elliptic bottoms. the diameter of the apparatus d = 400 mm, h = 400 mm. the area of the inner surface is 0.59 m2. designed for receiving, storing and feeding liquid and gaseous media. the pressure in the apparatus is 0.6 мpа. liquid media feeding is performed by gravity storages stor-1 1 12х18н10т gost 9931-79. denomination gee1-1-0.063-0.6. a horizontal apparatus with two ellipsoidal bottoms. designed for receiving, storing and feeding liquid and gaseous media under conventional pressure in the apparatus of 0.6 мpа. the diameter of the apparatus d = 400 mm, h = 550 mm. the area of the inner surface is 0.78  m2. liquid media feeding is carried out by displacement by compressed air, technological or inert gas stor-2 1 12х18н10т gost 9931-79. denomination gee1-1-0.10-0.6. a horizontal apparatus with two ellipsoidal bottoms. designed for receiving, storing and feeding liquid and gaseous media under conventional pressure in apparatus of 0.6 мpа. the diameter of the apparatus d = 400 mm, h = 850 mm. the area of the inner surface is 1.15  m2. liquid media feeding is carried out by displacement by compressed air, technological or inert gas stor11 1 12х18н10т gost 9931-79. denomination dee1-1-0.063-0.6. a horizontal apparatus with two ellipsoidal bottoms. designed for receiving, storing and feeding liquid and gaseous media under conventional pressure in apparatus of 0.6 мpа. the diameter of the apparatus d = 400 mm, h = 550 mm. the area of the inner surface is 0.78  m2. liquid media feeding is carried out by displacement by compressed air, technological or inert gas condenser tank ct-9 1 12х18н10т gost 9931-79. denomination gkk1-1-1.60-0.07. a horizontal, all-welded device with conic unbeaded bottoms. nominal volume is 1.60 m3. designed for receiving, storing and feeding liquid and gaseous media at the operating pressure of not more than 0.07 мpа. the diameter of the device d = 1000 mm, h = 2150 mm. the area of the inner surface 7.34 m2 225 tp 2. filtration and washing preliminary n-butanol is fed into the measurer m-6 from the stor-2 by compressed nitrogen. after that a suspension from the reactor r-4 is transferred into the top discharge automated centrifuge c-8. the precipitate is filtered and washed with minimal amount of cold alcohol, fed from the measure m-6. the precipitate is transferred into a dryer d-10 after washing. the filtrate (n-butanol) is collected in a condenser tank ct-9 and transferred to regeneration. tp 3. drying the precipitate is manually transferred into the tray drier d-10 after filtering. the paste is placed on shelves, vacuum of 250 mm hg is created in the system, and steam of 0.4 mpa is fed inside the shelves. the drying time is 2 hours at temperature 70 °c. the dried product is sent to the the end of table 17 name quantity of units material of a working zone technical data ct-16 1 12х18н10т gost 9931-79. denomination gkk1-1-1.25-0.07. a horizontal, all-welded device with conic unbeaded bottoms. nominal volume is 1.60 m3. designed for receiving, storing and feeding liquid and gaseous media at the operating pressure of not more than 0.07 мpа. the diameter of the device d = 1000mm, h = 1800 mm. the area of the inner surface is 6.25 m2 filtering equipment c-8 1 12х18н10т tc (technical conditions) 26-01-387-80. denomination fgn-633к-01. it is intended for the separation of hazardous suspensions with medium and fine-grained insoluble solid phase. the centrifuge is sealed, with explosion-proof electrical equipment; it is worked under positive pressure of an inert gas. engine power is 18.5 kw. shaft speed is 1455 rev/min c-14 1 12х18н10т тc 26-01-387-80. denomination фгн-633к-01. it is intended for the separation of hazardous suspensions with medium and fine-grained insoluble solid phase. the centrifuge is sealed, with explosion-proof electrical equipment; it is worked under positive pressure of an inert gas. engine power is 18.5 kw. shaft speed is 1455 rev/min drying equipment d-10 1 вст3пс3 оsт 26-01-78-78. pv4.5-0.63nu-01. a vacuum tray dryer is a horizontal cylindrical apparatus with one or two pivoting end caps. there are shelves inside the cylinder. apparatus of periodic action with shelves having charging area of 4.5 and 16 m2. apparatus volume is 0.63 m3 d-17 1 вст3пс3 оsт 26-01-78-78. pv4.5-0.63nu-01. a vacuum tray dryer is a horizontal cylindrical apparatus with one or two pivoting end caps. there are shelves inside the cylinder. apparatus of periodic action with shelves having charging area of 4.5 and 16 m2. apparatus volume is 0.63 m3 226 recrystallization for further purification from impurities. tp 4. recrystallization recrystallization of the product is conducted for increasing the yield and additional purification of the final product. for this ethanol is preliminary fed into the measurer m-15 from the storage stor-11 by compressed nitrogen. then the stirrer is turned on, the dried precipitate is transferred from the c-10 into the reactor r-12, the loading hatch is closed hermetically. after loading the precipitate the reactor is completely pressurized, leaving only an open valve on the line connecting the reactor with the atmosphere. hot brine, which heats the reaction mixture to 78–80 °c, is fed into the jacket. heating continues for about 15–20 min to complete dissolution of the precipitate in alcohol. further feeding of hot brine is stopped; solution is cooled by feeding cold water supplied into the jacket of the reactor r-12. the cooled suspension is transferred to filtration. tp 5. filtration and washing the suspension from the reactor r-12 is fed into the automated centrifuge c-14, a solid phase is filtered and washed with a minimal amount of cold alcohol, supplied from the measure m-15. after filtering the precipitate is transferred into the dryer d-17. the filtrate (ethanole) is collected in the condenser tank ct-16 and transferred to regeneration. tp 6. drying the precipitate is manually transferred into a tray drier d-17 after filtering. the paste is placed on shelves, vacuum of 250 mm hg is created in the system, and steam of 0.4 mpa is fed inside the shelves. the drying time is 2 hours at temperature 70 °c. the dried product undergoes a final control. if results of the analysis were satisfactory, the product is packed and transported. сonclusion production of (3as*,4r*)-4-cyano1 , 2 , 3 , 3 а , 4 , 5 he x a hyd ro 1 н py r rol o [1,2-а]quinoline-4-carbothioamide has been developed. the graph diagram and principal instrumental diagram of the product production have been designed. calculation of the material balance on 1 kg of the product, technological calculations have been carried out, then appropriate equipment has been choosed. in russian введение актуальность работы. хинолиновые системы привлекают внимание прежде всего благодаря своей биологической активности [1]. так, согласно литературным данным, тетрагидрохинолины и родственные им соединения проявили антибактериальную активность против широкого ряда патогенов, включая грамположительные и грамотрицательные аэробные бактерии, а также анаэробные организмы [2]. некоторые из этих соединений представляют собой продукты природного происхождения. так, 2-метил1,2,3,4-хинолин содержится в мозге человека. дискохабдин c, представляющий собой полициклическую систему на основе тетрагидрохинолина, является морским алкалоидом [3]. ди227 немицин, который представляет собой природный противоопухолевый антибиотик, имеет сложную структуру, построенную на основе тетрагидрохинолиновой системы [4, 5]. 2,4,6-тризамещенный тетрагидрохинолин 1, выделенный из тропического растения martinella iquitosensis (семейство бигнониевые), проявляет активность как антагонист физиологически и фармакологически активного пептида, снижающего кровяное давление, брадикинина [6]. множество относительно простых синтетических 1,2,3,4-тетрагидрохинолинов уже используется или тестируется в качестве потенциальных лекарственных средств. среди них наи более хорошо известны оксамнихин 2, шистозомицид [7], никаинопрол 3, а также новый антибиотик вирантмицин 4 [8, 9]. один из наиболее эффективных синтетических путей получения таких систем представляет собой трехстадийную последовательность исходя из орто-замещенных бензальдегидов, включающую циклизацию орто-винилдиалкиланилинов по механизму трет-амино эффекта. целью работы является разработка метода синтеза производного тетрагидрохинолина с использованием циклизации, протекающей по механизму трет-аминоэффекта. методика проведения лабораторного синтеза синтез 2-пирролидин-1-ил-бензальдегидов 5. к раствору 1,0 мл (9,49  ммоль) 2-фторбензальдегида в 8,0 мл дмфа добавляют 9,88 ммоль диалкиламина и 1,38 г (9,88 ммоль) поташа. кипятят на глицериновой бане при температуре 150 °с в течение 20  ч. окончание реакции определяют при помощи тсх. далее реакционную массу охлаждают до комнатной температуры, добавляют 75 мл воды и продукт экстрагируют этилацетатом (360 мл). объединенный органический экстракт промывают раствором хлористого аммония. органический слой сушат над mgso4, растворитель упаривают под вакуумом. выход 1,54 г (93  %). коричневое масло. спектр ямр 1н (дмсо-d6), δ, м. д. (j, гц): 10.01 (1н, с., сно), 7.61 (1н, д. д., j1 = 8.0, j2 = 7.2, arh), 7.35–7.29 (1н, м., arh), 6.89 (1н, д., j = 8.0, arh), 6.75 (1н, т., j1 = j2 = 7.2, arh), 3.33–3.30 (4н, м., 2сн2), 1.99–1.96 (4н, м., 2сн2). 228 найдено, %: n 7.5. c11h13no. вычислено, %: n 7.99. синтез (3as*,4r*)-4-циан о 1 , 2 , 3 , 3 а , 4 , 5 г е к с а г и д р о 1 н пирроло[1,2-а]хинолин-4-карботиоамида. в реакционный сосуд объемом 10 мл помещают 2-диалкиламинобензальдегид 5 (0,5 ммоль), н-бутанол (0,25 m) и циантиоацетамид (1 экв.). реакционный сосуд закрывают силиконовой крышкой с перфорированной септой и нагревают в микроволновом реакторе. после охлаждения сжатым воздухом реакционную массу перемещают в круглодонную колбу. растворить удаляют in vacuo. твердый остаток кристаллизуют из этанола. выход 0,41 г (79 %). красно-коричневые кристаллы. второй диастереомер в спектре ямр 1н не наблюдается. т. пл. – 222–223 °с. спектр ямр 1н основного диастереомера (дмсо-d6), δ, м. д. (j, гц): 1.73–1.85 (1h, м., сhax); 1.88–2.02 (1h, м., сhax); 2.05–2.18 (2h, м., 2сheq); 3.18 (1н, д., j = 16.2, 5-снax); 3.22 (1н, д. т., j1 = 9.0, j2 = 6.2, 1-сhax); 3.47-3.58 (2h, м., 3а-снax, 5-снeq); 3.86 (1h, д. д., j1 = 9.0, j2 = 5.8, 1-cheq); 6.57 (1н, д., j = 8.4, arh); 6.60 (1н, д. д., j1 = 7.4, j2 = 7.6, arh); 7.03–7.16 (2н, м., 2 arh); 9.19 (1н, с., nh); 10.23 (1н, с., nh). спектр ямр13c (100 мгц, дмсо-d6), δ, м. д. (j, гц): 23.1 (ch2); 29.0 (ch2); 39.5 (ch2); 47.9 (c-5); 53.3 (с-4); 63.6 (c-3a); 111.7 (ch ar); 116.2 (ch ar); 117.8 (c ar); 118.3 (c ar); 128.4 (ch ar); 129.1 (ch ar); 142.8 (csnh2); 200.4 (сn). ик-спектр, v, см–1: 752; 1370; 1418; 1456; 1602; 1632 (c=s); 2237 (сn); 2854; 3148; 3271; 3373. массспектр (эу, 70  эв), m/z (iотн, %): 257 [m]+ (43); 224 (10); 197 (22); 196 (27); 195 (100); 168 (8); 140 (8); 130 (12); 128 (10); 60 (8). найдено, %: с 64.8; н 6.0; n 16.1. c14h15n3s. вычислено, %: с 65.34; н 5.87; n 16.33. характеристика готового продукта наименование продукта: 4-циано1,2,3,3а,4,5-гексагидропирроло[1,2-а] хинолин-4-тиокарбоксамид. молекулярная масса: 257,355 г/моль. структурная формула: характеристика исходного образца: стандартный образец утверждается в установленном порядке. стандартный образец подлежит замене вновь приготовленным и утверж денным через 6 месяцев. срок действия, его продление и хранение стандартного образца устанавливается в соответствии с инструкцией по отбору, испытанию, утверждению, хранению и расходованию стандартных образцов, утвержденных в установленном порядке. таблица 1 характеристика технического продукта наименование показателя норма 1. внешний вид порошок коричневого цвета 2. содержание примесей не более 1,0 % 3. температура плавления 223 °с 4. растворимость с4н9он chcl3 229 стандартный образец хранится в герметично закрытой таре в сухом затемненном месте при 0–20 °с. характеристика сырья и материалов джана в табл. 1–2. стадии и химизм процесса 1. получение 4-циано-1,2,3,3а,4,5гексагидропирроло[1,2-а]хинолин4-тиокарбоксамида: 2. фильтрация и промывка. 3. сушка продукта. 4. перекристаллизация продукта в этаноле. 5. фильтрация и промывка. 6. сушка продукта. технологическая схема приведена на рис. 1. схема материальных потоков показана на рис. 2. основные контрольные точки производства приведены в табл. 3. описание стадий технологического процесса подготовка оборудования и сырья перед началом производственных работ осуществляют планово-предупредительный ремонт всего оборудования, проверяют его герметичность и надежность заземления, производят регулировку весов. контролю подвергаются все приборы кипиа, пульты управления, обслуживающие технологический процесс. аппараты тщательтаблица 2 характеристика сырья и материалов наименование гост, ост, регламент и методика на подготовку сырья сорт или артикул показатели, обязательные для проверки примечания 1. пирролидинбензальдегид – реакт. массовая доля > 85 % из хранилища хр-1 2. 2-цианотиоацетамид – реакт. массовая доля > 60 % со склада 3. н-бутиловый спирт гост 6006-78 раств., ч. массовая доля > 99,5 % ткип = 117 °с из хранилища хр-2 4. этиловый спирт гост 1830087 раств., ч. массовая доля > 96 % из хранилища хр-11 м.м. 175 орто-пирролидинбензальдегид м.м. 100 циантиоацетамид м.м. 257 гексагидрохинолин карботиоамид 230 рис. 1. принципиальная аппаратурная схема производства 4-циано-1,2,3,3а,4,5гексагидропирроло[1,2-α]хинолин-4-тиокарбоксамида таблица 3 основные технологические параметры контрольная точка наименование объекта контроля контролируемый параметр и размерность норматив метод и средство контроля кт 1 раствор тиоамида в н-бутаноле растворимость тиоамида полное растворение вещества визуально кт 2 реакционная масса полнота прохож дения реакции отсутствие в р-ре исходных тиоамида и альдегида и гг тсх кт 3 паста содержание влаги, % не более 0,3 электрокондуктометрический метод измерения влажности кт 4 раствор продукта в этаноле растворимость тиокарбоксамида полное растворение вещества визуально кт 5 паста содержание влаги, % не более 0,3 электрокондуктометрический метод измерения влажности кт 6 товарный продукт содержание основного вещества, % не менее 99 спектроскопия 1н ямр, массспектрометрия, элементный анализ 231 но промывают водой, сушат, проверяют исправность работы мешалки и привода. в табл. 4–8 приведены исходные данные для производства. процесс начинают с подготовки сырья и оборудования к работе. сырье проверяют на необходимые качественные показатели: подлинность, содержание основного вещества. оборудование проверяют на чистоту, сухость, герметичность. материальные балансы узлов 1–4 приведены в табл. 9–17. тп 1. получение тиокарбоксамида предварительно хранилища хр-1, хр-2 и хр-11 заполняют пирролидинбензальдегидом, н-бутанолом и этанолом, соответственно. в бункер шнекового питателя ш-3 загружают цианоацеттиоамид. в мерник м-5 с помощью сжатого азота из хранилища хр-1 подают бензальдегид. из хранилища хр-2 с помощью сжатого азота в мерник м-6 подают н-бутанол. в чистый и проверис. 2. схема-граф и материальные потоки технологического процесса таблица 4 условные сокращения пирролидинбензальдегид пба циантиоцетамид та бутанол б этанол э тиокарбоксамид тка таблица 5 исходные данные для расчета состав технического пба пба чистый 0,98 воды в техническом продукте 0,01 прочие примеси 0,01 состав технического та та чистый 0,99 прочие примеси 0,01 состав технического тка тка чистый 0,995 воды 0,001 прочие примеси 0,004 232 ренный реактор р-4 из мерника м-6 c сливают бутанол, включают мешалку, затем самотеком загружают бензальдегид из м-5. после подачи спирта и бензальдегида шнеком ш-3 в реактор подают тиоамид. по окончании загрузки тиоамида отключают шнековый питатель, герметично закрывают люк, откуда подавалось сырье. после загрузки исходных веществ реактор полностью герметизируют, таблица 6 выходы по стадиям тп 1 химическая реакция η1 = 0,89 тп 2 фильтрация и промывка η2 = 0,87 тп 3 сушка η3 = 0,85 тп 4 перекристаллизация η4 = 0,99 тп 5 фильтрация и промывка η5 = 0,87 тп 6 сушка η6 = 0,91 общий выход ση = 0,65 таблица 7 мольные массы реагентов и продуктов реакции пба та б э тка 175,23 100,14 74,12 46,07 257,36 таблица 8 материальный баланс по узлам загрузка сырья, в т. ч. g γ пирролидинбензальдегида 1,0 0,980 тиоамида 1,0 0,985 н-бутанола 0,5 0,97 этанола 0,6 0,97 таблица 9 материальный баланс узла 1 загружено получено с ы рь е и по лу пр од ук ты с од ер ж ан ие , % (м ас с. ) м ас са т ех н. , к г м ас са 1 00 % , к г п ро ду кт ы , от хо ды , п от ер и с од ер ж ан ие , % (м ас с. ) м ас са т ех н. , к г м ас са 1 00 % , к г 1. пирролидинбензальдегид, в том числе: 100,0 1,037 реакционная масса, в том числе: 100,0 3,021 пба 100 % 97,975 1,016 тка 56,5 1,708 вода 0,964 0,010 пба ост 3,7 0,112 примеси 1,061 0,011 та ост 5,5 0,165 2. тиоамид, в том числе: 100,0 0,985 б 100% 32,1 0,970 та 100 % 98,477 0,970 вода 1,3 0,040 примеси 1,523 0,015 примеси 0,9 0,026 3. бутанол, в том числе: 100,0 1,000 б 100 % 97,000 0,970 вода 3,000 0,030 итого 3,022 итого 100,0 3,021 233 оставляя лишь открытым кран на линии, связывающей реактор с атмо сферой (воздушка). далее в рубашку подают острый пар, нагревая реакционную смесь до 115–120 °с и выдерживают при включенной мешалке в течение 6 ч. теплообменник т-7 обеспечивает конденсацию растворителя при нагревании реакционной смеси в течение всей стадии химической реакции. по истечении 6 ч прекращают подачу пара и охлаждают реакционную смесь холодной водой, подаваемой в таблица 10 дополнительные исходные данные состав осадка после промывки осадок, в т. ч. γ 100 % тка 0,988 воды в осадке 0,01 примеси в осадке 0,002 состав маточного раствора б раствор, в т. ч. γ 100 % б 0,942 воды в растворе 0,008 примеси в растворе 0,05 таблица 11 материальный баланс узла 2 загружено получено с ы рь е и по лу пр од ук ты с од ер ж ан ие , % (м ас с. ) м ас са т ех н. , к г м ас са 1 00 % , к г п ро ду кт ы , от хо ды , п от ер и с од ер ж ан ие , % (м ас с. ) м ас са т ех н. , к г м ас са 1 00 % , к г 1. реакционная масса, в том числе: 100,00 3,021 1. осадок, в том числе: 100,00 1,504 тка 56,538 1,708 тка 98,80 1,486 вода 1,324 0,040 вода 1,00 0,015 б 100 % 32,109 0,970 примеси 0,20 0,003 примеси 10,030 0,303 2. маточный раствор, в том числе: 100,00 1,030 2. б на промывку 0,854 б 100 % 94,20 0,970 вода 0,80 0,008 примеси 5,00 0,051 3. фильтрат, в том числе: 100,00 1,117 б 100 % 76,45 0,854 вода 1,52 0,017 примеси 22,02 0,246 4. потери 0,222 итого 3,875 итого 3,873 234 рубашку. далее передают суспензию в центрифугу для отделения осадка. тп 2. фильтрация и промывка предварительно из хранилища хр-2 с помощью сжатого азота пода ют в мерник м-6 н-бутанол. после этого в автоматизированную центрифугу с верхней выгрузкой осадка ц-8 принимают суспензию из реактора р-4, твердую фазу отфильтровывают и таблица 12 материальный баланс узла 3 загружено получено с ы рь е и по лу пр од ук ты с од ер ж ан ие , % (м ас с. ) м ас са т ех н. , кг м ас са 10 0 % , к г п ро ду кт ы , от хо ды , по те ри с од ер ж ан ие , % (м ас с. ) м ас са т ех н. , кг м ас са 10 0  % , к г 1. осадок, в том числе: 100,00 1,504 1. тка сухой, в том числе: 100,00 1,273 тка 98,80 1,486 тка 99,74 1,2694 вода 1,00 0,015 вода 0,10 0,0013 примеси 0,20 0,003 примеси 0,16 0,0021 2. летучие, в том числе: 100,00 0,015 вода 93,81 0,0138 примеси 6,19 0,0009 3. потери 0,223 итого 1,504 итого 1,505 таблица 13 материальный баланс узла 4 загружено получено с ы рь е и по лу пр од ук ты с од ер ж ан ие , % (м ас с. ) м ас са т ех н. , кг м ас са 10 0 % , к г п ро ду кт ы , от хо ды , по те ри с од ер ж ан ие , % (м ас с. ) м ас са т ех н. , кг м ас са 10 0 % , к г 1. тка сухой, в том числе: 100,00 1,273 1. суспензии, в том числе: 100,00 1,263 тка 99,74 1,2694 тка 100% 99,73 1,2601 вода 0,10 0,0013 вода 0,10 0,0013 примеси 0,16 0,0021 примеси 0,17 0,0021 2. э технического, в том числе: 0,785 2. э технический, в том числе: 100,00 0,785 э 100 % 0,761 э 100 % 96,943 0,7610 вода  0,024 вода 3,057 0,0240 3. потери 0,0096 итого 2,058 итого 2,058 235 промывают минимальным количеством холодного спирта, подаваемым из мерника м-6. после промывки осадок передают в сушилку с-10. фильтрат (н-бутиловый спирт) собирают в сборнике сб-9 и передают на регенерацию. таблица 15 материальный баланс узла 5 загружено получено с ы рь е и по лу пр од ук ты с од ер ж ан ие , % (м ас с. ) м ас са т ех н. , кг м ас са 10 0  % , к г п ро ду кт ы , от хо ды , по те ри с од ер ж ан ие , % (м ас с. ) м ас са т ех н. , кг м ас са 10 0  % , к г 1. суспензии, в том числе: 100,00 1,263 1. осадок, в том числе: 100,00 1,102 тка 100 % 99,73 1,2601 тка 99,50 1,0962 вода 0,10 0,0013 вода 0,33 0,0036 примеси 0,17 0,0021 примеси 0,20 0,0022 2. э технический, в том числе: 100,00 0,785 2. маточный раствор, в том числе: 100,00 0,766 э 100 % 96,943 0,7610 э 100% 99,40 0,7610 вода 3,057 0,0240 вода 0,20 0,0015 3. э на промывку 0,756 примеси 0,40 0,0031 3. фильтрат, в том числе: 100,00 0,778 э 100% 97,21 0,7560 вода 2,64 0,0205 примеси 0,15 0,0012 4. потери 0,068 итого 2,804 итого 2,803 таблица 14 дополнительные исходные данные состав осадка после промывки осадок, в т. ч. γ 100 % тка 0,995 воды в осадке 0,003 примеси в осадке 0,002 состав маточного раствора б раствор, в т. ч. γ 100 % э 0,994 воды в растворе 0,002 примесей в растворе 0,004 236 тп 3. сушка после фильтрования осадок вручную выгружают в полочную сушилку с-10. пасту размещают на полках, в системе создают вакуум 250 мм рт. ст. и внутрь полок подают пар 0,4 мпа. продолжительность сушки составляет 2 ч, при температуре 70 °с. высушенный продукт отправляют на перекристаллизацию для дальнейшей очистки от примесей. тп 4. перекристаллизация с целью увеличения выхода и дополнительной очистки конечного продукта производится перекристаллизация его из этанола. для этого предварительно в мерник м-15 с помощью сжатого азота из хранилища хр-11 подают этиловый спирт. затем включают мешалку, помещают высушенный осадок из с-10 в реактор р-12, и герметично закрывают люк, через который подавался осадок. после загрузки осадка реактор полностью герметизируют, оставляя открытым кран, связывающей реактор с атмосферой (воздушка). в рубашку реактора подается горячий рассол, который нагревает реакционную смесь до 78–80 °с. нагрев продолжается около 15–20 мин до полного растворения осадка в спирте. далее прекращают подачу горячего рассола и охлаждают раствор, подавая в рубашку реактора р-12 холодную воду. охлажденную суспензию передают на фильтрование. тп 5. фильтрация и промывка в автоматизированную центрифугу с верхней выгрузкой осадка ц-14 принимают суспензию из реактора р-12, твердую фазу отфильтровывают и промывают минимальным количеством спирта, подаваемым из мерника м-15. после фильтрации осадок передают в сушилку с-17. фильтрат (этитаблица 16 материальный баланс узла 6 загружено получено с ы рь е и  по лу п ро ду кт ы с од ер ж ан ие , % (м ас с. ) м ас са т ех н. , кг м ас са 10 0 % , к г п ро ду кт ы , от хо ды , по те ри с од ер ж ан ие , % (м ас с. ) м ас са т ех н. , кг м ас са 10 0 % , к г 1. осадок, в том числе: 100,00 1,1021 1. тка (товарный), в том числе: 100,00 1,000 тка 99,50 1,0962 тка 0,995 вода 0,33 0,0036 ост. вода 0,001 примеси 0,20 0,0022 примеси 0,004 2. летучие, в том числе: 100,00 0,0020 вода 65,00 0,0013 примеси 60,00 0,0012 3. потери 0,100 итого 1,1021 итого 1,102 237 ловый спирт) собирают в сборнике сб-16 и передают на регенерацию. тп 6. сушка после фильтрования осадок вручную выгружают в сушильный шкаф с-17. пасту размещают в поддонах на полках шкафа, в системе создают вакуум 250 мм рт. ст. и внутрь полок подают пар 0,4 мпа. продолжительность сушки составляет 2 ч, при температуре 70 °с. далее высушенный продукт проходит конечную проверку. при удовлетворительных результатах анализа продукт упаковывают и транспортируют. таблица 17 ведомость-спецификация оборудования наименование кол-во единиц материал рабочей зоны техническая характеристика реакторы р-4 1 12х18н10т ост 26-01-1246-75. внутренний объем аппарата – 0,315 м3. исполнение аппарата 0010-1.0,6, внутренний диаметр d = 660 мм, высота h = 920 мм. вертикальный аппарат с перемешивающим устройством предназначен для проведения различных технологических процессов в жидких однофазных и многофазных средах. материальное исполнение корпуса аппарата – сталь марки 12х18н10т в соответствии с гост 5632-72. условное избыточное давление в корпусе – 0,6 мпа. мощность двигателя – 0,6 квт. допустимое наружное давление 0,576 мпа. оснащен гладкой приварной рубашкой в соответствии с ост 26-01-984-74, рамной мешалкой мп01-10-5,74-3/167-ао2-41-6 р-12 1 12х18н10т ост 26-01-1246-75. внутренний объем аппарата – 0,315 м3. исполнение аппарата 0010-1.0,6, внутренний диаметр d = 660 мм, высота h = 920 мм. вертикальный аппарат с перемешивающим устройством предназначен для проведения различных технологических процессов в жидких однофазных и многофазных средах. материальное исполнение корпуса аппарата – сталь марки 12х18н10т в соответствии с гост 5632-72. условное избыточное давление в корпусе – 0,6  мпа. мощность двигателя – 0,6 квт. допустимое наружное давление – 0,576  мпа. оснащен гладкой приварной рубашкой в соответствии с ост 26-01-984-74, рамной мешалкой мп01-10-5,74-3/167-ао2-41-6 238 продолжение табл. 17 наименование кол-во единиц материал рабочей зоны техническая характеристика мерники м-5 1 12х18н10т гост 9931-79. обозначение вээ1-1-1-0,6. номинальный объем – 0,040 м3. вертикальный цельносварный аппарат с эллиптическими днищами. диаметр аппарата d = 400 мм, h = 400 мм. площадь внутренней поверхности – 0,59 м2. предназначены для приема, хранения и выдачи жидких и газообразных сред. давление в аппарате – 0,6 мпа. выдача жидких сред осуществляется самотеком м-6 1 12х18н10т гост 9931-79. обозначение вээ1-1-1-0,6. номинальный объем – 0,040 м3. вертикальный цельносварный аппарат с эллиптическими днищами. диаметр аппарата d = 400 мм, h = 400 мм. площадь внутренней поверхности – 0,59 м2. предназначены для приема, хранения и выдачи жидких и газо образных сред. давление в аппарате – 0,6 мпа. выдача жидких сред осуществляется самотеком м-15 1 12х18н10т гост 9931-79. обозначение вээ1-1-1-0,6. номинальный объем – 0,040 м3. вертикальный цельносварный аппарат с эллиптическими днищами. диаметр аппарата d = 400 мм, h = 400 мм. площадь внутренней поверхности – 0,59 м2. предназначены для приема, хранения и выдачи жидких и газообразных сред. давление в аппарате – 0,6 мпа. выдача жидких сред осуществляется самотеком хранилища хр-1 1 12х18н10т гост 9931-79, обозначение гээ1-1-0,063-0,6. горизонтальный аппарат с двумя эллипсоидными днищами. предназначен для приема, хранения и выдачи жидких и газообразных сред при условном давлении в аппарате 0,6 мпа. диаметр аппарата d = 400 мм, h = 550 мм. площадь внутренней поверхности – 0,78  м2. выдача жидких сред осуществляется передавливанием сжатым воздухом, технологическим или инертным газом хр-2 1 12х18н10т гост 9931-79, обозначение гээ1-1-0,10-0,6. горизонтальный аппарат с двумя эллипсоидными днищами. предназначен для приема, хранения и выдачи жидких и газообразных сред при условном давлении в аппарате 0,6 мпа. диаметр аппарата d = 400 мм, h = 850 мм. площадь внутренней поверхности – 1,15  м2. выдача жидких сред осуществляется передавливанием сжатым воздухом, технологическим или инертным газом 239 продолжение табл. 17 наименование кол-во единиц материал рабочей зоны техническая характеристика хр-11 1 12х18н10т гост 9931-79, обозначение гээ1-1-0,063-0,6. горизонтальный аппарат с двумя эллипсоидными днищами. предназначен для приема, хранения и выдачи жидких и газообразных сред при условном давлении в аппарате 0,6 мпа. диаметр аппарата d = 400 мм, h = 550 мм. площадь внутренней поверхности – 0,78  м2. выдача жидких сред осуществляется передавливанием сжатым воздухом, технологическим или инертным газом сборники сб-9 1 12х18н10т гост 9931-79, обозначение гкк1-1-1,60-0,07. горизонтальный цельносварный аппарат с коническими неотбортованными днищами. номинальный объем – 1,60 м3. предназначен для приема, хранения и выдачи жидких и газообразных сред при рабочем давлении не более 0,07 мпа. диаметр аппарата d = 1000 мм, h = 2150 мм. площадь внутренней поверхности – 7,34 м2 сб-16 1 12х18н10т гост 9931-79, обозначение гкк1-1-1,25-0,07. горизонтальный цельносварный аппарат с коническими неотбортованными днищами. номинальный объем – 1,60 м3. предназначен для приема, хранения и выдачи жидких и газообразных сред при рабочем давлении не более 0,07 мпа. диаметр аппарата d = 1000 мм, h = 1800 мм. площадь внутренней поверхности – 6,25 м2. фильтровальное оборудование ц-8 1 12х18н10т ту 26-01-387-80, обозначение фгн-633к-01. предназначена для разделения взрывоопасных суспензий со среднеи мелкозернистой растворимой твердой фазой. центрифуга герметизирована, со взрывозащищенным электрооборудованием; работает под избыточным давлением инертного газа. мощность двигателя – 18,5 квт. частота вращения вала – 1455 об/мин ц-14 1 12х18н10т ту 26-01-387-80, обозначение фгн-633к-01. предназначена для разделения взрывоопасных суспензий со среднеи мелкозернистой растворимой твердой фазой. центрифуга герметизирована, со взрывозащищенным электрооборудованием; работает под избыточным давлением инертного газа. мощность двигателя – 18,5 квт. частота вращения вала – 1455 об/мин 240 заключение разработано производство 4-циано-1,2,3,3а,4,5-гексагидропирроло[1,2а ] х и н о л и н 4 т и о к а р б о к с а м и д а . составлена схема-граф и принципиальная аппаратурная схема производства продукта. выполнен расчет материального баланса на 1 кг продукта, технологические расчеты и сделан выбор оборудования. bibliography 1. balasubramanian, m., keay, j. g. in comprehensive heterocyclic chemistry ii. katritzky, a. r., rees, c. w., scriven, e. f. v., eds.; pergamon: oxford, 1996; vol. 5, 245 р. 2. patent us 7,208,490 b2. tricyclic tetrahydroquinoline antibacterial agents / barbachyn m. r., dobrowolski p. j., hurd a. r., mcnamara d. j., palmer j. r., romer a. g., ruble j. c., sherry d. a., thomasco l. m., toogood p. l. pharmacia & upjohn company llc. 03.10.2003, 24.04.2007 3. r. barbachyn, p. j. dobrowolski, a. r. hurd, d. j. mcnamara, j. r. palmer, a. g. romero, j. c. ruble, d. a. sherry, t l. m. homasco, p. l. toogood. pharmacia&upjohn company llc. 03.10.2003; 24.04.2007. 4. perry n.b., blunt j.w., munro m.h.g. cytotoxic pigments from new zealand sponges of the genus latrunculia : discorhabdins a, b and c. tetrahedron. 1988;44(6):17271734. doi: 10.1016/s0040-4020(01)86737-5. 5. miyoshi m., morisaki n., tokiwa y., kobayashi h., iwasaki s., konishi m., oki t. facile reductive rearrangement of dynemicin a to dynemicin h: the direct evidence for the p-phenylene diradical intermediate. tetrahedron letters. 1991;32(42):60076010. окончание табл. 17 наименование кол-во единиц материал рабочей зоны техническая характеристика сушильное оборудование с-10 1 вст3пс3 ост 26-01-78-78. пв4,5-0,63ну-01. полочная вакуумная сушилка представляет собой горизонтальный цилиндрический аппарат с одной или двумя поворотными торцевыми крышками. внутри корпуса аппарата смонтированы полки. аппарат периодического действия с полками площадью загрузки 4,5 и 16 м2. объем аппарата – 0,63 м3 с-17 1 вст3пс3 ост 26-01-78-78. пв4,5-0,63ну-01. полочная вакуумная сушилка представляет собой горизонтальный цилиндрический аппарат с одной или двумя поворотными торцевыми крышками. внутри корпуса аппарата смонтированы полки. аппарат 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virantmycin, a novel antiviral antibiotic. tetrahedron letters. 1981;22(3):2199-2202. doi: 10.1016/s0040-4039(01)90497-6. 10. williamson n. m., march d. r., ward, a. d. an improved synthesis of 2,2-disubstituted-1,2-dihyroquinolines and their conversion to 3-chloro-2,2-disubstituted-tetrahydroquinolines. tetrahedron letters. 1995;36(42):7721-7724. doi: 10.1016/0040-4039(95)01572-y. cite this article as (как цитировать эту статью): poluikova a. a., platonova a. yu. technology of the pilot production of the tetrahydroquinoline derivative (3as*,4r*)-4-cyano-1,2,3,3а,4,5-hexahydro-1нpyrrolo[1,2-а]quinoline-4-carbothioamide. chimica techno acta. 2016;3(3):213– 241. doi: 10.15826/chimtech.2016.3.3.015. investigations into the structure of la3ni2−xfexo7±δ 51 d o i: 1 0. 15 82 6/ ch im te ch .2 01 9. 6. 2. 03 kiselev e. a., gaczynski p., eckold g., feldhoff a., becker k.-d., cherepanov v. a. chimica techno acta. 2019. vol. 6, no. 2. p. 51–71. issn 2409–5613 e. a. kiseleva, p. gaczynskib, g. eckoldc, a. feldhoffd, k.-d. beckerb, v. a. cherepanova a department of physical and inorganic chemistry, institute of natural sciences and mathematics, ural federal university, kuybysheva st. 48, 620026, yekaterinburg, russia b institute of physical and theoretical chemistry, technische universität braunschweig, rebenring 56. 10, d-38106, braunschweig, germany c institute of physical chemistry, georg-august-universität göttingen, tammannstr. 6, 37077, göttingen, germany d institute of physical chemistry and electrochemistry, leibniz universität hannover, callinstr. 3a, d-30179, hannover, germany eugene.kiselyov@urfu.ru investigations into the structure of la3ni2–xfexo7±δ the room-temperature (rt) 57fe mössbauer spectra of the la3ni2–xfexo7±δ oxide solid solutions of ruddlesden-popper-type (x = 0.05, 0.10) reveal two doublets for fe3+ ions in octahedral coordination by oxygen. the existence of two inequivalent sites for fe at rt is at variance with the space groups fmmm and cmcm (amam) which have been reported for la3ni2o7±δ. this unexpected finding is discussed in connection with patterson analyses and rietveld refinements of powder xrd data for x = 0, 0.05, and 0.10. alternative structural models have been proposed which can explain the spectroscopic findings and which are compatible with the results from x-ray diffraction. keywords: la3ni2o7; complex oxides; ruddlesden-popper phases; mössbauer spectroscopy; crystal structure; patterson analysis; rietveld refinement. received: 15.07.2019. accepted: 01.08.2019. published: 05.08.2019. © kiselev e. a., gaczynski p., eckold g., feldhoff a., becker k.-d., cherepanov v. a., 2019 introduction layered ruddlesden-popper (r-p) lanthanum nickelates of the general formula lan+1nino3n+1 have recently been studied for potential application as sofc cathodes [1–5] for the members with n = 1, 2, 3. the structure is characterized by n perovskite-type layers, n·lanio3, stacked up in c-direction and separated by a single rock-salt-type layer of lao, lao(lanio3) n. presently, however, la2nio4+δ with n = 1 is the most studied within the series; data concerning la3ni2o7±δ and la4ni3o10–δ are still insufficient and sometimes contradictory. in the present paper, the focus will be on la3ni2o7±δ (n = 2). la3ni2o7±δ was first reported by brisi et al. [6] as an intermediate phase in an attempt to synthesize la4ni3o10–δ at 1100 °c. drennan et al. [7] could directly obtain the  n = 2 compound by  annealing at 1150  °c in  air for 5  h with intermediate re-grindings. the unit-cell parameters were approximately determined as a = 5.42 å, b = 5.47 å, and c = 20.58 å. however, electron microscopy revealed intergrowth of all members of the series with n = 2, 3, and 4. later, the  existence of  la3ni2o7±δ was confirmed by odier et al. [8] in the temperature range 900–1150  °c. however, small amounts of secondary phases were 52 still found present. mohan ram et al. [9] obtained la3ni2o7±δ by decomposing stoichiometric amounts of  lanthanum and nickel nitrates and annealing at 1420 k for 10  h with frequent grindings. although the x-ray diffraction patterns showed no evidence for the presence of other members of the series, hrem studies showed intergrowth of  small extent of  members with n = 3 and n = 5. similar problems were also reported by sreedhar et al. [10] who stated that intergrowth can be minimized by  annealing samples at  a  suitable temperature (1150  °c). according to  zhang et al. [11], single phase la3ni2o7±δ can be obtained by  solution synthesis followed by heat treatment and final annealing of the pressed pellets for 4–5 days at 1150–1200 °c. these authors determined the oxygen content of the as-prepared n = 2 lanthanum nickelate by iodometric titration and tga to la3ni2o6.92 [11]. zhang et al. [11] were the  first to  refine (x-ray) diffraction data of la3ni2o6.92 in the orthorhombic space group fmmm which provides only a single site for nickel cations. this space group was also used by carvalho et al. [12] in their refinement of  the  unit-cell parameters of  the  compound. these authors also showed that the oxygen content of as prepared samples depends on the  synthesis route: nitrate precursors usually were found to  yield oxygen-deficient materials, e. g. la3ni2o6.93 which is close to results reported in ref. [11]. on the other hand, slightly oxygen excess samples, e. g. la3ni2o7.03, could be produced by the citrate technique. generally, least-square refinements of xrd data within the  fmmm space group showed good agreement in the unit cell parameters [1, 11–13]. however, neutron diffraction data by ling et al. [14] on la3ni2o7.02 and la3ni2o7.05 revealed a number of weak but clearly resolved peaks which could not be indexed by the fmmm structural model, but could satisfactorily be refined within the amam space group (a nonstandard setting of the cmcm space group). the main features of this structure, which also provides a  single unique site for nickel, are significantly distorted nio6 octahedra and an elongation of ni–o bonds in c-direction towards to the rock salt layers [14]. these results were confirmed by voronin et al. [15] using single-phase la3ni2o7±δ. in this work, the standard cmcm space group was used for refinement of neutron diffraction data and for exafs spectral analysis. the unit cell parameters and the  oxygen content of the la3ni2o7±δ powder samples obtained by various authors [1, 6, 7, 9–17] are listed in table 1 for comparison. the temperature dependence of  the  oxygen content of the n = 2 r-p compound in air has been studied by bannikov and cherepanov [16] in the temperature range 900–1150 °c. it was shown that the stoichiometric parameter δ of  la3ni2o7–δ changes from about 0.057 at 900 °c to 0.072 at 1150 °c which is in good agreement with the results presented in refs. [1, 11, 12] for the samples prepared by nitrate route, table 1. at  elevated temperatures, la3ni2o7±δ has been found to  undergo a  structural phase transition. sasaki et al. [13] observed a  discontinuous change in  the  temperature dependence of the lattice parameter for the  c-axis of  the  unit cell at  about 550  k. the  transition has also been detected in lattice expansion [1], in magnetic [18], infrared [19], electrical conductivity [1, 18, 19], and in thermal measurements [18, 20]. from all these experiments, transition temperatures between 550 and 600 k have been reported. more recently, amow et al. [1] monitored changes in the hightemperature x-ray diffraction patterns 53 of la3ni2o6.95 which led them to the conclusion that at about 590 k a transformation occurs from orthorhombic fmmm to a higher symmetry tetragonal phase. mössbauer spectroscopy has already been applied to  the  neighboring ruddlesden-popper phases la2nixfe1–xo4+δ (n  =  1)  [21–24] and la4ni3–xo10–δ (n  =  3)  [24–26] in  a  number of studies. the 57fe mössbauer spectra of these compounds are composed of one and of two doublets, respectively. this observation is in full agreement with the layered structures of these compounds which provide one unique site and two non-equivalent sites for nickel in the r-p phases with n = 1 and n = 3, respectively. this has been considered strong evidence for the conjecture that fe is incorporated on the transition metal sites in  the  r-p lanthanum nickelates. under this condition  — and provided that la3ni2–xfexo7±δ crystallizes in space group fmmm or cmcm (amam) — the mössbauer spectrum of la3ni2–xfexo7±δ is expected to consist of a single signal only. among the layered ruddlesden-popper lanthanum nickelates, la3ni2o7±δ is special in that the average oxidation state of nickel cations for the stoichiometric composition with δ = 0 is 2.5, indicating equal number of ni2+ and ni3+ ions. at low temperatures, this can open the possibility for charge ordering of the nickel cations. nevertheless, all structural models existing to date for la3ni2o7±δ (fmmm [1, 11–13], amam [14], and cmcm [15]) do not account for this special aspect in  providing only a  single site for ni. the present mössbauer study was undertaken in order to shed light into the  local structure of  la3ni2–xfexo7±δ. in contrast to the neighboring r-p phases la2ni1–xfexo4+δ and la4ni3–xfexo10–δ which have already been well studied by mössbauer spectroscopy [21–26], the present work to our knowledge appears to be the first mössbauer study of la3ni2–xfexo7±δ. table 1 structural data of la3ni2o7±δ obtained from x-ray and neutron diffraction, rt a (å) b (å) c (å) space group oxygen content 7±δ ref. 5.404(2) 5.452(2) 20.442(7) fmmm 6.95 [1] 5.407(4) 5.454(4) 20.54(2) — — [6] 5.402(2) 5.453(7) 20.537(1) — — [7] 5.412 5.456 20.94 — — [9] 5.41 5.46 20.54 — — [10] 5.3961(6) 5.4498(5) 20.522(2) fmmm 6.92 [11] 5.393(2) 5.451(2) 20.54(1) fmmm 6.93 [12] nitrate route 5.400(2) 5.452(2) 20.52(1) fmmm 7.03 [12] citrate route 5.3922(1) 5.4488(1) 20.5288(6) fmmm 6.92 [13] 5.3928(1)* 5.4486(1)* 20.5185(5)* amam* 7.02 [14] 5.3971(2)* 5.4501(2)* 20.507(1)* amam* 7.05 [15] 20.502(1)* 5.4494(7)* 5.3981(7)* cmcm* — [16] 5.409(2) 5.452(2) 20.537(3) — 6.72 [17] * neutron diffraction at 300 k. space groups amam and cmcm differ only by the setting of the crystallographic axes. 54 experimental in order to prepare the la3ni2–xfexo7±δ (x  = 0, 0.05, 0.10) powder samples for our study, stoichiometric amounts of la(no3)3 · 6h2o (chemical pure grade), ni(ch3coo)2 · 4h2o (chemical pure grade), and of metallic iron were dissolved in an aqueous solution of nitric acid prepared from concentrated nitric acid (extra pure grade) and deionized water in the ratio 1:3 while heating and mixing on a hot plate. metallic iron enriched in 57fe was obtained by reduction of fe2o3 (with iron enriched by 96.6 % in  the  isotope 57fe) in  flowing h2 at 925  k for 6  hours and then quantitatively transferred into solution. subsequently, citric acid monohydrate c6h5o4(oh)3 · h2o (chemical pure grade) was added to  the  solution as  a  chelating and gelling agent. the thus-prepared precursor solution was dried and decomposed forming a brown powder. the powder was calcined in  air at 1273  k for 30  minutes to  remove organic and carbon residuals and then cooled down to  rt. the  dark grey product was ground, pressed into pellets and annealed in  air at 1373  k for 24 h. in order to obtain single-phase la3ni2–xfexo7±δ materials (x  = 0, 0.05, 0.10), 5–6 intermediate cycles of regrinding, pelletizing and annealing at 1373  k were required. sample purity and morphology was checked by  rem/edx analysis (jeol jsm-6510, bruker nano xflash 410). the measurements confirmed the absence of  any impurities and secondary phases in noticeable concentrations. phase composition and crystal structure of the synthesized samples were examined by powder x-ray diffraction using an equinox 3000 diffractometer (inel, france) with cu-kα radiation (λ  = 1.54178  å); data were collected in  the  asymmetric reflection mode. the  scattered radiation from the flat-plate samples was registered by  a  curved position-sensitive detector (cps-590) within the angle interval 10–90° in 2θ. the  detector was calibrated using na2al2ca3f14 as standard. the data acquisition time was 1 h for phase analysis and 17–21 h for structural analysis. all calculations including the rietveld refinements and determinations of crystal structure of samples studied were performed using the  fullprof package [27]. the following structural parameters were varied in the refinement procedure: scale factor, unit cell parameters, zero shift, atomic positions, overall displacement parameters (b-factors, bov), background, peak shape, and width parameters. the  peak profiles were described by  the  thompson-cox-hasting pseudo-voigt function within the anisotropic strain broadening model. the instrumental resolution function was determined by means of diffraction experiments with a  ceo2 reference sample which had been annealed twice at 1473 k for 48 h with intermediate regrinding and then slowly cooled down to  rt. the background was estimated by linear interpolation between manually selected background points with refinable heights. transmission 57fe mössbauer spectra were taken using a  standard mössbauer system (halder) in  the  sinusoidal driving mode employing a 57co/rh γ-source with a  maximum activity of 1.91  gbq. the relatively low iron content and high electronic mass-absorption coefficient of la3ni2–xfexo7±δ for the 14.4 kev mössbauer γ-radiation necessitated the  use of  samples enriched in 57fe, see above. the least square fits of the spectra using lorentzian line shapes were performed by  means of  the  recoil mössbauer data evaluation software [28] yielding the fol55 lowing parameters: isomershift is (mm·s‒1) relative to  α-fe at  rt, quadrupole splitting qs (mm·s‒1) of  doublets, full width γ (mm·s‒1) at half maximum of lines, and (relative) spectral area a (%) of spectra. mössbauer spectroscopy the  rt 57fe mössbauer spectra of la3ni2–xfexo7±δ (x = 0.05, 0.10) are displayed in fig. 1. the highly symmetric spectra are composed of  two quadrupole-split doublets of almost identical intensity. this observation gives evidence of the fact that iron cations are incorporated on two inequivalent lattice sites which at present will be denoted by a and b for the site with the smaller and the larger quadrupole splitting (qs), respectively, qs(fea) < qs(feb). the parameters obtained from the  least square fits of the spectra are presented in table 2. the isomer shifts (is) of 0.31 mm·s–1 of the two subspectra of la3ni2–xfexo7±δ are identical in the two solid solutions studied (x = 0.05 and 0.10). it is also to be noted that these values are in close agreement with the 57fe isomer shifts observed for the other octahedrally coordinated lan+1nino3n+1 r-p phases with n = 1 and n = 3 [21–26]. according to numerous mössbauer studies, e. g. refs. [29, 30], such is-values are characteristic for high-spin fe3+ ions octahedrally coordinated by oxygen. the  rt quadrupole splittings (qs) of the two doublets in la3ni2–xfexo7±δ are found to  differ significantly with values of about 0.43 mm·s–1 and 0.95 mm·s–1 for iron incorporated on sites of type a and b, respectively, table 2. as also seen, fig. 1, transmission can assume values as  low as  about 90 % in  parts of  the  spectra. therefore, the absorbers used in the present study have to  be characterized as “thick”. this conclusion is also supported by the rt line widths of the two samples which take values ranging between 0.26 and 0.31  mm·s–1 and, thus, reveal significant broadening in  comparison with the theoretical width of a 57fe mössbauer line of  about 0.20  mm·s–1 for “thin” fig. 1. 57fe mössbauer spectra of la3ni2−xfexo7±δ (x = 0.05 and 0.10) at rt table 2 parameters of the rt 57fe mössbauer spectra of la3ni2−xfexo7±δ (x = 0.05 and 0.10): is — isomer shift (vs α-fe), qs — quadrupolar splitting, г — full line width at half maximum (fwhm), a — experimental area fraction compound is (mm·s−1) qs (mm·s−1) γ (mm·s−1) a (%) site la3ni1.95fe0.05o7±δ 0.31 0.41 0.30 50 a 0.31 0.97 0.26 50 b la3ni1.90fe0.10o7±δ 0.31 0.46 0.31 47 a 0.31 0.93 0.28 53 b 56 absorbers. in addition to line broadening, the thickness effect can also give rise to intensity distortion in the spectra as will be discussed below. predominantly, low transmission and broadening of the experimental mössbauer lines can be attributed to the substitution of nickel by iron strongly enriched in 57fe (96.6 %) which causes large values for the total absorber thickness ta of the samples. in the present case with 57fe on two sites of the structure, ta it is defined as ta = (fa na + fb nb)∙σ0 [31]. here, fε represents the debye-waller factor of atoms of type ε (ε = a, b) and nε their number per cm 2 of absorber; σ0 = 2.56·10 –18 cm2 is the absorption cross section of  a  mössbauer atom. in the present work, an estimate of 0.75 can be assumed for the  rt debyewaller factor. using this approximate value, estimates of about ta = 4.0 and 8.0 are obtained for total absorber thicknesses of the la3ni2–xfexo7±δ samples with x = 0.05 and 0.10, respectively, fig. 1. for non-overlapping doublets of  lorentzian shape, these ta-values would give rise to  theoretical line widths of  about 0.23 mm·s–1 and 0.25 mm·s–1 for x = 0.05 and 0.10, respectively, see e. g. refs. [29, 31]. however, as seen, fig.1, doublets are overlapping to  various degree. notably the inner doublet a is almost fully overlapped by  doublet b. in  the  limit of  full overlap, theoretical line widths amount to about 0.25 mm·s–1 and 0.30 mm·s–1 for x = 0.05 and x = 0.1, respectively [29, 31]. indeed, in agreement with these expectations, line widths observed for the inner doublet, a, are always larger than those of doublet b, table 2. remaining discrepancies between theoretical and experimental line widths can easily be attributed to the fact that quadrupolar interactions of the iron nuclei possess a distribution, see below, which provides an  additional source for line broadening. as  a  further consequence of  the  present large values of total absorber thickness ta, spectra undergo intensity distortion which always causes an underestimation of large spectral contributions on the basis of experimental signal areas. as has been demonstrated by  rancourt [31], such intensity corrections can be very large. in the present case, however, they are almost nonexistent (x = 0.05) or very moderate (~ 2 % for x = 0.10) due to the (almost) equal areas of the two experimental doublets. thus, in the present case corrections to experimental signal intensities can well be neglected. crystal structure as  discussed in  the  introduction, to date the crystal structure of la3ni2o7±δ has been assigned to  the  orthorhombic space groups fmmm (№ 69) [1, 11–13] or cmcm (№ 63) [14, 15]. according to these structural models, lanthanum cations occupy two different crystallographic positions, but the nickel cations are located on a single site exclusively. this is in striking contrast with the present results of the mössbauer measurements which clearly indicate the  existence of  two nonequivalent lattice sites for iron/nickel in  the  studied la3ni2–xfexo7±δ solid solutions at  rt. in order to explain the unexpected observations made in mössbauer spectroscopy for the  n  =  2 member of  the  r-p series, in  the  following an  attempt will be undertaken to search for adequate structural models of la3ni2–xfexo7±δ (x ≥ 0) accounting for two inequivalent ni/fe sites. the xrd patterns of the  synthesized la3ni2–xfexo7±δ (x  = 0, 0.05, 0.10) powder samples were indexed in orthorhom57 bic symmetry. unit cell parameters a = 20.52298 å, b = 5.45805 å, c = 5.40101 å, (α = β = γ = 90°) of la3ni1.9fe0.1o7±δ were obtained with the help of the dicvol04 program [32] and the figures of merit provided by this analysis amounted to m(20) = 56.2, f(20) = 60.7. calculations by means of the ito program [33] resulted in a preferable face-centered space group with almost the same unit cell parameters of a = 5.4577å, b = 20.5225å, and c = 5.4020 (α = β = γ = 90°), and a figure of merit f(20) = 59.3. after preliminary profile-matching refinement within primitive orthorhombic pmmm, probable space groups were searched for by means of the checkgroup program interfaced by winplotr [34]. thus, 48 possible space groups were obtained for consideration. most of them are primitive with quite low values for figures of merit (<1.35). in  order to  reduce the  number of space groups, we focused on those which can be deduced from group-subgroup relations keeping both unit cell dimensions and orthorhombic crystal system of the parent group unchanged. referring to  international tables for crystallography [35] only 6 subgroups remained: ccca (no  68), cmma (no  67), cccm (no  66), cmmm (no  65), cmca (no  64), and cmcm (no  63). bearing in  mind the  results of mössbauer spectroscopy that reveal the existence of two nonequivalent sites for iron/nickel ions, the list of possible space groups shortens to three: cmmm (no 65), cmma (no 67), and bmmb (non-standard setting of cmcm space group) (no 63). the next step of our study was an attempt to determine the crystal structure of  la3ni1.9fe0.1o7±δ from xrd patterns by  constructing the  patterson maps using observed structure amplitudes and the peak search procedure of the gfourier program [34]. the  patterson maps were constructed from the structural amplitudes extracted during the profile-matching fit according to the le bail algorithm for each chosen space group. note that the  simplest crystal structure solutions should be expected for both fmmm and cmmm models because these space groups correspond to exactly the same patterson space groups fmmm and cmmm [35]. this means that one has exactly the  same symmetry both in  real space and patterson space. as  far as  for x-ray diffraction, both nickel and iron atoms are indistinguishable and, thus, la3ni1.9fe0.1o7±δ contains three types of atoms with substantially different numbers of electrons. consequently, the observed peaks on the patterson map might be resolved except for those having the  same interatomic distances, for example the la1la1 and ni-ni bond lengths in the perovskite layers of the fmmm structure. additionally, if the heaviest atom (la) is placed into the origin of the unit cell with coordinates (0, 0, 0) — as we did in the present case — then the peaks observed in patterson space relate to interatomic vectors with coordinates (u = ±{x-0}, v = ±{y-0}, w = ±{z-0}) and coincide with atomic positions (±x, ±y, ±z) in real space. accounting for these considerations, we were able to solve the  crystal structure for la3ni1.9fe0.1o7±δ in the framework of fmmm and cmmm space groups directly from the  peaks observed in  patterson maps. the  results of  the  crystal structure solutions for la3ni1.9fe0.1o7±δ, which are summarized in table 3, confirm our above mentioned expectations. as can be seen from table 3, only a single crystallographic position is  available for nickel/iron cations within the fmmm crystal structure of la3ni1.9fe0.1o7±δ. this is  in  agreement with the  earlier pro58 posed fmmm space group for undoped la3ni2o6.92 by zhang et al. [11]. the main difference is that we place lanthanum into position (4a) at the origin of the unit cell (0, 0, 0). zhang puts one of  the  oxygen anions in that position (4a) and the lanthanum cations in position 4b with relative coordinates (0, 0, 0.5). in  contrast, the cmmm space group possesses two different crystallographic sites (4k and 4l) for nickel cations. thus, the cmmm model can provide an explanation for the observed rt mössbauer spectra of the la3ni2–xfexo7±δ solid solutions (x = 0.05, 0.1). in  addition, it is  worth noting that the  space groups under consideration are subgroups of the space group fmmm. thus, if the  wyckoff positions of  each atom in  fmmm are known, we can easily deduce the wyckoff positions of each atom in  the  corresponding subgroup. the transformation of atomic coordinates from fmmm (table 3) to the corresponding subgroups was performed by the powtable 3 crystal structure solutions for la3ni1.9fe0.1o7±δ according to fmmm and cmmm models obtained from patterson maps using peak search procedure of gfourier program [34] peak no relative atomic coordinates occupation peak height wyckoff position type of atomx y z fmmm (69): a = 5.4020å, b = 5.4570å, c = 20.5170 å general multiplicity 32 1 0 0 0 0.125 9872 4a la1 2 0 0 0.1837 0.25 6488 8i la2 3 0 0 0.4067 0.25 4024 8i ni 4 0 0 0.5 0.125 1293 4b o1 5 0 0 0.3076 0.25 1238 8i o2 6 0.25 0.25 0.0922 0.5 1067 16j o3 cmmm (65): a = 5.4014å, b = 5.4576å, c = 20.5182 å general multiplicity 16 1 0 0 0 0.125 9892 2a la1 2 0 0.5 0.5 0.125 8427 2c la2 3 0 0.5 0.3158 0.25 6163 4l la4 4 0 0 0.1830 0.25 5778 4k la3 5 0 0.5 0.0907 0.25 3864 4l ni2 6 0 0 0.4035 0.25 3855 4k ni1 7 0 0.5 0.1990 0.25 1105 4l o4 8 0.25 0.25 0.0925 0.5 1028 8m o6 9 0.25 0.25 0.4030 0.5 992 8m o5 10 0 0.5 0 0.125 937 2b o1 11 0 0 0.4922* 0.25* 987 4l* o2 12 0 0 0.2992 0.125 881 4k o3 * here z should be 0.5, the occupancy equal to 0.125 and the wyckoff position should be 2d according to the chemical composition la3ni1.9fe0.1o7 59 dercell program [36] in  order to  reveal the possibility for the appearance of nonequivalent positions for nickel cations. as a result, of the six subgroups considered, only three would meet the latter criterion, namely cmma (№ 67), cmmm (№ 65), and bmmb (№ 63) — a non-standard setting of the cmcm space group. the rietveld analysis of xrd patterns for la3ni2–xfexo7±δ within the  suggested crystal structure models as  well as  thorough search for additional reflections with even tiny intensities which could definitely be attributed to a particular space group did not allow us to arrive at a final conclusion. as an example, fig. 2 illustrates the  refined rietveld powder profiles of  la3ni2–xfexo7±δ solid solutions within space groups cmmm (a), cmma (b), and bmmb (c). table 4 summarizes r-factors and chi-square values (χ2) for all refined patterns in the framework of the proposed structural models with two inequivalent sites for ni/fe  — space group fmmm which provides only a single site for ni/fe is included for comparison. on the basis of these r-factor and χ2 data, the following observations can be made: (i) fmmm appears the least probable space group, (ii) fits within cmmm and cmma appear slightly superior to bmmb, (iii) no significant differences can be observed between cmmm and cmma. therefore, no valid conclusion can be drawn in respect to the true space group of la3ni2–xfexo7±δ on the basis of the present x-ray diffraction data. table  5 and table  6 report the  results of  the  rietveld refinements for la3ni2–xfexo7±δ in the two most probable space groups cmma and cmmm, respectively. the crystal structures of la3ni2–xfexo7±δ (x  = 0, 0.05, 0.10) solid solutions confined to space groups cmmm, cmma, and bmmb with two inequivalent sites (ni1 and ni2) for ni/fe are shown in  fig.  3. for reason of comparison, the graph also shows the structural model for space group fmmm. as can be seen from fig. 3, in all cases the  lattice is  built up from double perovskite layers 2[la(ni/fe)o3] which are stacked between single rock-salt lao layers along the c-axis. in cmmm, cmma, and bmmb, the double perovskite layers consist of two different ni/feo6 octahedra (ni1, ni2) with slightly different distortions. within the double perovskite layers the differently distorted octahedral ni/fe sites are arranged in different ways, fig. 3b-d. fig. 2. rietveld refined xrd powder patterns of la3ni2−xfexo7±δ solid solutions within space groups cmmm for x = 0 (a), cmma for x = 0.05 (b), and bmmb for x = 0.10 (c) 10 20 30 40 50 60 70 80 90 0 2000 4000 6000 8000 10000 in te ns ity , a .u . 2θ, degree observed calculated yobs – ycal bragg positions observed calculated yobs – ycal bragg positions observed calculated yobs – ycal bragg positions a 10 20 30 40 50 60 70 80 90 -5000 0 5000 10000 15000 20000 25000 30000 35000 in te ns ity , a .u . 2θ, degree b 10 20 30 40 50 60 70 80 90 0 10000 20000 30000 40000 50000 in te ns ity , a .u . 2θ, degree c 60 finally, aand b-parameters and the unit cell volume v of the la3ni2–xfexo7±δ solid solutions are found to increase with fe content (x), (see tables 5 and table 6) which are in good agreement with size factor for 3d-metal cations: r(fe3+) = 79 pm > r(ni3+) = 74 pm [37]. table 5 rietveld refined atomic coordinates and bond lengths l(ni-o) for la3ni2−xfexo7 (x = 0, 0.05, 0.10) solid solutions within the cmma model: 4g: la1 — (0,0.25,0.25), o3 — (0,0.25,0.75), la2,3/ni1,2/o1,2 — (0,0.25,z); 8l:o4,5 — (0.25,0,z), rt refined parameter x = 0 x = 0.05 x = 0.10 zero point 0.025(1) -0.0044(8) 0.0038(8) bov, å 2 1.66(4) 1.50(3) 1.58(3) a, å 5.3895(1) 5.3970(1) 5.4019(1) b, å 5.4462(1) 5.4521(1) 5.4574(1) c, å 20.5250(3) 20.5280(2) 20.5192(2) v, å3 602.46(1) 604.04(1) 604.91(1) z(la2) 0.06994 0.06994 0.07007 z(la3) 0.43006 0.43006 0.42993 z(ni1) 0.8476(2) 0.8472(1) 0.8469(1) z(ni2) 0.6524(2) 0.6528(1) 0.6531(1) z(o1) 0.9526(6) 0.9454(7) 0.94918 z(o2) 0.5474(6) 0.54719 0.55082 z(o4) 0.6448(9) 0.6415(5) 0.6439(6) table 4 comparison of r-factors and χ2-values obtained for structural models of la3ni2−xfexo7±δ solid solutions after rietveld refinement iron content space group rp rwp rexp χ 2 x = 0 fmmm 4.65 6.02 4.56 1.74 cmma 4.38 5.71 4.59 1.55 cmmm 4.36 5.69 4.58 1.54 bmmb 4.51 5.86 4.58 1.64 x = 0.05 fmmm 2.85 3.89 2.19 3.16 cmma 2.55 3.51 2.17 2.62 cmmm 2.56 3.54 2.17 2.68 bmmb 2.64 3.66 2.18 2.83 x = 0.1 fmmm 2.95 4.17 1.90 4.82 cmma 2.84 3.99 1.89 4.46 cmmm 2.96 4.15 1.91 4.72 bmmb 2.82 4.03 1.89 4.53 61 table 6 rietveld refined relative atomic coordinates and bond-lengths l(ni-o) for la3ni2−xfexo7 (x = 0, 0.05, 0.10) solid solutions within the cmmm model: 2a: la1 — (0, 0, 0), 2b: o1 — (0, 0.5, 0) 2c: la2 — (0,0.5,0.5), 2d:o2 – (0, 0, 0.5), 4k: la3/ni1/o3 — (0, 0, z), 4l: la4/ni2/o4 — (0, 0.5, z), 8m: o5/o6 — (0.25, 0.25, z), rt refined parameter x = 0 x = 0.05 x = 0.10 zero point 0.025(1) -0.0043(8) 0.0038(8) bov, å 2 1.66(4) 1.47(3) 1.61(3) a, å 5.3895(1) 5.3971(1) 5.4019(1) b, å 5.4462(1) 5.4521(1) 5.4574(1) c, å 20.5250(3) 20.5279(2) 20.5191(2) v, å3 602.46(1) 604.044(8) 604.91(1) z(la3) 0.18006 0.18016 0.17993 z(la4) 0.31994 0.31984 0.32007 z(ni1) 0.4024(2) 0.4029 (1) 0.4031(1) z(ni2) 0.0976(2) 0.0971 (1) 0.0969(1) z(o3) 0.298(1) 0.30079 0.2952(9) z(o4) 0.20267 0.2049 (8) 0.19918 z(o5) 0.3943(9) 0.4016 (3) 0.4021(4) z(o6) 0.087(1) 0.0984 (3) 0.0979(4) l(ni1/ni2-o2/o1), å 2.003(4) 1.994(2) 1.989(3) l(ni1-o3), å 2.15(3) 2.095(2) 2.21(2) 4l(ni1/ni2-o5/o6), å 1.923(2) 1.9181(1) 1.9198(1) average l(ni1-o), å 1.974(4) 1.9603(5) 1.980(3) l(ni2-o4), å 2.157(4) 2.21(2) 2.099(3) average l(ni2-o), å 1.979(1) 1.980(3) 1.944(4) сontinuation of table 5 refined parameter x = 0 x = 0.05 x = 0.10 z(o5) 0.838(1) 0.8370(7) 0.8389(8) l(ni1-o3), å 2.003(4) 1.995(2) 1.988(3) l(ni1/ni2-o1/o2), å 2.16(1) 2.01(1) 2.099(3) 4l(ni1-o5), å 1.926(2) 1.929(2) 1.927(2) average l(ni1-o), å 1.977(2) 1.954(3) 1.9657(8) l(ni2-o3), å 2.003(4) 2.169(2) 1.988(3) 4l(ni2-o4), å 1.922(2) 1.932(1) 1.929(2) average l(ni2-o), å 1.974(2) 1.9818(7) 1.967(5) 62 fig. 3. crystal structures of la3ni2−xfexo7 solid solutions within space groups fmmm (a), cmmm (b), cmma (c), and bmmb (d): grey balls — la3+, blue and dark grey octahedra represent oxygen environments of nickel/iron cations on ni1and ni2-sites, respectively 63 discussion t h e   rt m ö s s b a u e r s p e c t r a of la3ni2–xfexo7±δ reveal that the sites for iron are characterized by two significantly different quadrupolar interactions, table 2. in general, the 57fe mössbauer quadrupole splitting is given by [29] 21 11 2 3zz qs = eqv + η (1) where the so-called asymmetry parameter η is defined as η = (vxx – vyy)/vzz (0 ≤ η ≤ 1) and where vαα (α = x, y, z) represent the electric field gradients (efgs) at the nucleus in the principal axis system with |vzz| ≥ |vyy| ≥ |vxx|. q denotes the quadrupole moment of the first excited nuclear state of 57fe and e is the proton charge. in the case of  fe3+ ions possessing the  d5 electronic configuration it is reasonable to assume that the experimental quadrupole splittings are dominated by the so-called lattice contribution to the electric field gradient which is determined by the positions and charges of the ions surrounding the mössbauer atoms in the lattice. according to eq. (1), the quadrupole interaction is sensitive to local symmetry around the nuclear probes in that η = 0 for local tetragonal symmetry and that the interaction vanishes for local cubic symmetry, vzz = 0. thus, the splittings reflect an asymmetry of the charge distribution in the crystal lattice around the nuclear probes and notably also the local distortion of their coordination polyhedra. the rt mössbauer data clearly reveal that the two sites, a and b, occupied by iron differ significantly in respect to the quadrupolar interactions experienced by the probe nuclei, qs(fea) < qs(feb), table 2. under the  assumption that iron substitutes for nickel, this experimental finding is in conflict with the structural assignments made to  date for la3ni2o7±δ, i. e. space groups fmmm [1, 11–13], amam [14], and cmcm [15], which provide only one unique site for ni/fe in  the  structure. the  assumption made here that iron adopts nickel sites is strongly supported by successful predictions made in respect to the neighboring r-p phases la2ni1–xfexo4+δ [21–24] and la4ni3–xfexo10–δ [24,26]. their 57fe mössbauer spectra are composed  — as  predicted on the  basis of  their layered r-p structures — of one and of two doublets, respectively. further on, this assumption is also supported by crystal chemical arguments for the transition metal cations which make high-spin fe3+ ions with their intermediate ionic radius of 79 pm a  perfect substitute for both high-spin ni3+ (74  pm) and ni2+ (83  pm) cations [37]. thus, provided that iron substitutes for nickel and that one of the aforementioned space groups applies, only one signal is expected in the mössbauer spectrum of la3ni2–xfexo7±δ (x > 0) which is in contrast with experiment. two possible explanations can be offered for this unexpected observation of  two nonequivalent sites for fe/ni. the  first would be the  conjecture that the  la3ni2–xfexo7±δ solid solutions at  rt adopt a lower symmetry than hitherto assumed. this approach has been followed in crystal structure section, where possible structural models have been indicated. the second explanation, which will be discussed below, involves a local reconstruction of the r-p layer structure. indeed, a low-symmetry phase at rt cannot be unexpected in view of the fact that the mixed-valent la3ni2–xfexo7±δ contains ni3+ and ni2+ cations in similar concentrations 64 [ni2+] = 1  2δ and [ni3+] = 1 ± 2δ – x (2) where square brackets denote the number of  species per formula unit. the  validity of eq. (2) is based on the assumption that iron is always in the trivalent charge state as revealed by the present mössbauer spectra (see mössbauer spectroscopy section) and discussion below. the close agreement of [ni2+] and [ni3+] could give rise to charge ordering and to the formation of some kind of lower symmetry structure. indeed, charge ordering in la3ni2o7–δ at low temperatures has already been discussed by taniguchi et al. [38] where it was proposed that ordering of electronic charge on nickel was induced by ordering of oxygen vacancies. in the same context, electrical conductivity, which is intimately related with electronic materials properties, has given clear evidence of a transition from temperature-activated behavior to metal-type conduction at high temperatures with reported transition temperatures of 550 k [1, 18] and 600 k [19]. as  evidenced by  the  rt mössbauer spectra, fe3+ cations are almost evenly distributed between the  two nonequivalent ni1and ni2-sites for ni/fe in the lattice, table 2. this can easily be explained as follows. during their synthesis, samples have been exposed to high temperatures (up to 1373 k) where according to the above discussion there is only one unique site for ni/fe and the fe dopant will be randomly distributed on this unique site. electronic charge ordering on the  nickel cations leading to  less symmetric structure occurs at  much lower temperatures where fe3+ cations are not mobile anymore and, due to their random distribution on available sites, show up in  almost equal proportions on the ni1and ni2-sites which occur in equal numbers in the alternative structures previously discussed, tables 4–6 and fig. 3. due to their fixed valence (see mössbauer spectroscopy section) and discussion below, fe3+ cations are not part of  the  electronic ordering process and, thus, serve as “spectators” of the structural changes induced by the evolving electronic charge order-disorder. in  an  ideally stoichiometric system, where x = 0 and δ = 0, ni2+ and ni3+ ions are present in exactly equal numbers, eq. (2), and distributed over the two nonequivalent sites, ni1 and ni2, of the structure. thus, two limiting cases of the cation distribution are to be considered. in one case — cation distribution (i) — all sites of ni1type are occupied by (all) ni2+ ions and, correspondingly, all ni2-sites are occupied by (all) ni3+ ions. in the case of cation distribution (ii), all ni1-sites are occupied by ni3+ and all ni2-sites by ni2+. in both situations, different, but single-valued electric field gradients (efg) are expected at the two inequivalent sites of the structure due to the fully ordered distribution of charges in the lattice. however, already the  introduction of  fe3+ ions into sites of  the  ni2+ sublattice will create charge disorder which will cause a  distribution of efgs at both sites leading to line broadening. the variable oxygen content — deficit or excess — is associated with changing concentrations of oxygen anions and changing amounts of ni3+ and ni2+ cations. this will also contribute to charge disorder in the lattice and, hence, contribute to line broadening in mixed crystals with x > 0 and |δ| > 0. thus, charge disorder — in addition to  absorber thickness  — explains the larger line widths for the sample with the higher dopant level, table 2. in  an  alternative explanation for the  observation of  two sites for fe/ni in la3ni2–xfexo7±δ, the possibility is to be 65 envisaged that a temperature-dependent reconstruction (intergrowth) of the ruddlesden-popper structure may occur. locally, three perovskite-type layers of iron/nickel atoms may be formed, like in la4ni3–xfexo10–δ, which would provide two inequivalent sites for nickel (iron). with increasing temperatures, the  local three-layer intergrowth (n = 3) could change to  the  higher symmetric n = 2  two-layer structure of  la3ni2o7. such a  structural complexity could be a  consequence of  the  fact that for the  off-stoichiometric, iron-doped la3ni2–xfexo7±δ (δ > 0, x > 0) the number of ni3+ and ni2+ cations no longer obeys the ideal 1:1 ratio but, instead, is given by [ni3+]:[ni2+] = 1  (x4δ)/(12δ). in this context, it is also interesting to recall mössbauer results reported for la4ni3–xfexo10–δ with x = 0.03 [25]. here, the two quadrupole doublets at rt show splittings of 0.43 mm·s–1 and 0.95 mm·s–1 which is very close to the rt qs-values observed for la3ni2–xfexo7±δ in  the  present study, table  2. however, the  above scenario is  difficult to  accept in view of the fact that diffusional motion of all cations, la, ni, and fe, would be required for changing the local intergrowth situation. this conclusion is also supported by experience gathered by many authors in the (sluggish) high-temperature synthesis of la3ni2o7±δ, see e. g. refs. [7, 8, 11]. the  discussion of  the  results from x-ray diffraction in crystal structure section has led to  the  successful identification of several space groups which provide two nonequivalent sites for ni/fe in equal numbers. it must be admitted, however, that a final decision about the prevailing structure type could not be reached. therefore, in the following another approach will be taken by considering the 57fe quadrupolar interactions at the two inequivalent sites in la3ni2o7. in this discussion it will be assumed that the  electric field gradients at the iron nuclei, eq. (1), arise from the so-called lattice contribution, vαα(latt), i. e. from charges located on the ions surrounding the mössbauer atom in the crystal lattice. thus, the framework of the point charge model, the efgs at the two sites for iron can be calculated in the principal axis system according to [29]: ( ) ( ) ( )2 2 5 0 1 (1 ) 3 4 i i i ii v v latt e z r r αα ∞ αα ∞ − = − γ = − γ = α − πε ∑ (3) here, the  summation extends over the surrounding lattice ions of charge number zi, and (1 – γ∞) and ε0 denote the sternheimer factor and the vacuum permittivity, respectively. the lattice efgs were calculated using the unisoft program package [39] and quadrupole splittings were obtained by using a sternheimer factor for fe3+ ions of 1 – γ∞ = 10.42 [40] and a quadrupole moment of q = 0.209·10–28 m2 [41]. in  an  approximation to  the  complex situation in real la3ni2–xfexo7±δ solid solutions, the efgs at the ni1and ni2-sites have been calculated for an  ideal rigid la3ni2o7 lattice (x = 0, δ = 0) employing the crystallographic rt data of la3ni2o7 obtained from the  rietveld refinements partially reported in tables 5 and 6. in all cases, the  assumption was made that the  formal charge number of  oxygen is –2. in the case of the fmmm space group it was assumed that all ni-sites are occupied by nickel cations possessing an average charge of +2.5 — corresponding to no charge ordering. for the lower-symmetric space groups, the two above defined cation distributions, (i) and (ii), have been considered with charge numbers +2 for ni2+ and +3 for ni3+ and la3+. table 7 reports the results of these calculations according 66 to eqs. (1) and (3). it is to be noted that the  calculations neither account for fe3+ cations introduced into the lattice by doping nor for possible deviations from exact stoichiometry. because of their small numbers and their random distribution, it can be expected that the  iron dopants and defects will not influence significantly the average electric field gradients at cation nickel sites, but will lead to a distribution of quadrupole interactions about the structure-determined averages. as can be seen from table 7 these admittedly simplistic point charge calculations, which also neglect lattice relaxation around the nuclear fe probes and any effect of chemical bonding of the ferric cations, successfully yield 57fe quadrupole splittings of the right order of magnitude, i. e. 0.1 < qs/mm·s–1 < 1. calculated quadrupole splittings in the orthorhombic space groups cmmm and cmma, table  7, are in  reasonable agreement with the experimental splittings of qs(feb) ≈ 0.95 mm·s ‒1 and qs(fea) ≈ 0.45 mm·s‒1, table 2, for both types of cation distributions. however, calculated qs-values are always found smaller than experimental ones by about 20 %, table 7. in  view of  the  deficiencies of  the  point charge model in general and the simplifying assumptions made in the calculations, such deviations cannot be unexpected. in  contrast, for orthorhombic bmmb no acceptable agreement is observed between experiment and calculated values. in addition to consideration of the absolute values of quadrupolar interactions, special relevance is attributed to the ratio of splittings, rq = qs(feb)/qs(fea), because of possible error cancellation in the calculations. table 7 quadrupolar interactions in la3ni2o7: 57fe quadrupole splitting, qs, and splitting ratios rq, at the nickel sites of la3ni2o7 for space groups fmmm, cmmm, cmma, and bmmb and for the cation distributions, (i) and (ii), which can be adopted by nickel in the lower symmetric structures. calculations were performed in the framework of the point charge model according to eqs. (1,3) with lattice parameters taken from respective rietveld refinements space group cation distribution site qs mm·s−1 rq fmmm — ni 0.74 — cmmm (i) ni1 0.86 3.0 (i) ni2 0.29 (ii) ni1 / a 0.36 2.2 (ii) ni2 / b 0.79 cmma (i) ni1 / b 0.81 2.3 (i) ni2 / a 0.35 (ii) ni1 0.28 3.1 (ii) ni2 0.88 bmmb (i) ni1 0.83 1.1 (i) ni2 0.75 (ii) ni1 0.92 1.4 (ii) ni2 0.66 67 at  rt, the  experimental ratio assumes values of  about rq = 2.3 (x  = 0.05) and rq = 2.0 (x = 0.10), table 2. as can be seen from table 7, such values are not consistent with those calculated for bmmb where this ratio amounts to 1.1 or 1.4 for cation distributions (i) and (ii), respectively. for cmmm(i) as well as for cmma(ii) calculated ratios are significantly larger than the experimental rq-values. however, for cmmm(ii) and for cmma(i) close agreement is  observed with calculated ratios of 2.2 and 2.3, respectively, indicated in “bold” in table 7. because we see no further means for differentiation between the two structures, we arrive at the conclusion that space group cmmm with a cation distribution of  type (ii) as  well as  space group cmma with cation distribution (i) represent good structural models for la3ni2–xfexo7±δ solid solutions at rt. in  the  present combined approach involving diffraction and spectroscopic work, aand b-sites can be even be assigned to the ni1and ni2-sites in these space groups according to the quadrupole splittings calculated for the  respective types of cation distribution, see table 7. this conclusion on the  crystal structure of la3ni2–xfexo7±δ, which is in agreement with the space groups arrived at on the basis of general structural considerations and rietveld refinements of the materials, narrows down considerably the number of possible combinations of space groups and cation distributions of la3ni2–xfexo7±δ at rt. conclusions at  rt, local probe 57fe mössbauer spectroscopy has provided indisputable evidence for the  existence of  two nonequivalent sites for fe3+ in la3ni2–xfexo7±δ with site populations closely corresponding to the 1:1 ratio. this unexpected result is in contrast to the hitherto existing structure determinations of  la3ni2o7±δ. the latter assumed space groups fmmm or cmcm (amam) which both provide only a single unique site for nickel/iron. in view of the spectroscopic findings, the rt structure of la3ni2–xfexo7±δ has been reconsidered and x-ray diffraction patterns for samples with x = 0, 0.05, and 0.10 have been measured and refined by  the  rietveld method. the interest was in the identification of alternative structural models which could replace the previously used space groups. from general considerations, we have selected the orthorhombic space groups cmma, cmmm, and bmmb which fulfill the  spectroscopic requirements of providing two sites in equal numbers for ni/f. according to rietveld refinements, cmma and cmmm can be considered the preferred space groups. calculations of the quadrupolar interactions at the iron nuclei in  la3ni2o7 in  the  framework of the point charge model have confirmed this conclusion and provided additional information on the  specific distribution of ni2+ and ni3+ cations in these structures at rt. acknowledgements k.-d.b. and p.g. would like to  thank the  volkswagen-foundation and the  state of lower saxony (germany) for financial support of the present work. e.k. and v.c. acknowledge support of their work by the ministry of education and science of the russian federation. a.f. is grateful to the deutsche forschungsgemeinschaft (dfg) for financial support in the frame of grant fe928/7–1. thanks are also due to prof. th. gesing 68 (u bremen, germany) for chemical edx analyses of samples. e.k and v. ch. work was supported by act 211 government of the russian federation, agreement 02.a03.21.0006. references 1. amow g, davidson ij, skinner sj. a comparative study of the ruddlesden-popper series, lan+1nino3n+1 (n = 1, 2 and 3), for solid-oxide fuel-cell cathode applications. 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sternheimer quadrupole factors in ferric compounds. phys. status solidi b. 1982;111(2):469–475. doi: 10.1002/pssb.2221110207. thermodynamic assessment of oxide system in2o3-sno2-zno 166 d o i: 1 0. 15 82 6/ ch im te ch .2 01 8. 5. 4. 02 jantzen t., hack k., yazhenskikh e., müller m. chimica techno acta. 2018. vol. 5, no. 4. p. 166–188. issn 2409–5613 t. jantzena, k. hacka, e. yazhenskikhb, m. müllerb a gtt-technologies, kaiserstraße 103, d-52134 herzogenrath, germany b forschungszentrum jülich gmbh, iek-2, d-52425 jülich, germany e-mail: tj@gtt-technlogies.de thermodynamic assessment of oxide system in2o3‑sno2‑zno the in2o3-sno2-zno system is of special interest for applications as transparent conducting oxides and also transparent semiconductors. in the present work, a thermodynamic assessment for this system is discussed using all available experimental data on phase equilibria and thermodynamic properties. all subsystems including elemental combinations were considered in order to generate a self-consistent gibbs energy dataset for further calculation and prediction of thermodynamic properties of the system. the modified associate species model was used for the description of the liquid phase. particular attention was given to two significant solid solution phases: spinel with the formula zn(2–x)sn(1–x)in2xo4 based on zn2sno4 and bixbyite based on in2o3 and extending strongly toward the snzno3 composition according to the formula in(2–2x)snxznxo3. in addition to the component oxides, nine quasi-binary compounds located in the in2o3-zno binary subsystem have also been included in the database as stoichiometric phases. keywords: phase diagram; thermodynamic modeling; indium oxide; bixbyite; spinel received: 28.11.2018. accepted: 14.12.2018. published: 31.12.2018. © jantzen t., hack k., yazhenskikh e., müller m., 2018 introduction compositions in  the in2o3– sno2–zno ternary oxide system are of interest owing to their optical transparency combined with high electrical conductivity [1, 2]. transparent conducting oxides (tcos) can be used as electrodes in solar cells, flat panel displays and other commercial devices. although tcos are applied usually in film form, the study of bulk phase relations and physical properties can be useful for understanding fundamental materials properties. at the present time, ito (tin-doped indium oxide) is the material of choice for tco layers (e.g. in review [3]), but the increasing cost of indium metal and the development of new technologies will require alternative tcos. according to  palmer [4] both sno2 and zno are good tcos with conductivities comparable to  ito. compositions from the in2o3–zno system with high zn concentration are attractive due to their high electrical conductivity, optical transparency and excellent chemical stability [5, 6]. the materials from the system zito (zn-in-sn-o) [2] are promising replacements for  ito as  tco layers in  many opto-electronic applications. zito contains less indium than ito, which lowers the cost, and it has a  broad window of compositions that allow the tco layer to be adjusted (conductivity, etc.) for each 167 application. the bulk equilibrium phases of  zito have been defined and exhibit two transparent and conductive regions: the bixbyite solid solution in2–2xznxsnxo3 and the homologous series of compounds in2znkok+3. thermodynamic modelling on the basis of reliable experimental data and appropriate gibbs energy models for solid and liquid phases is a powerful tool for calculation and prediction of the thermodynamic properties and phase equilibria for various systems. furthermore, such data can be applied for heat balance calculations, i.e. for information on the energetics of possible production processes. the quality and completeness of the thermodynamic databases used is a key prerequisite for reliable calculations. according to  calphadtype modelling all available experimental data (phase equilibria, mixing properties, component activities, etc.) are critically analyzed in terms of their consistency. each phase in the system is treated by an appropriate gibbs energy model with adjustable parameters (gibbs energy of constituents, interaction parameters, etc.), which are optimized in accordance with the experimental information in order to generate a self-consistent dataset of gibbs energies of all phases in a system. in the present study the thermodynamic assessment of  the oxide system in2o3–sno2–zno is presented using all available experimental data on phase equilibria and thermodynamic properties. the calculation of phase equilibria and the prediction of thermodynamic properties using the database for the in2o3-sno2-zno system can be helpful for developing and manufacturing tcos for  optoelectronic devices. the experimental information on the available thermodynamic properties (phase diagram, phase transition etc.) is used for the generation of self-consistent gibbs energy datasets for all known phases and compounds in this ternary system. the gibbs energy of the liquid phase has been modelled using a non-ideal associate solution model proposed by besmann and spear [7]. this model has been successfully applied for  the description of melts containing oxides and sulphides in our previous studies, e.g. in [8–10]. solubilities in the solid state have been treated using the multi-sublattice approach which allows the description of experimentally determined solubilities. in the present study there are two solid solution series with different structure. the spinel phase with formula (zn+2,in+3)2(sn +4, zn+2)1(o –2)4 includes zn2sno4, in2sno4, zn2zno4, in2zno4 as  end-members. the model for bixbyite in form of in(2–2x)snxznxo3 using the formula (in, zn, va)1(in, sn)1(o)3 allows description of the limited solubility from pure indium oxide extending to snzn compounds. the present database contains a  gas phase, a multi-component liquid phase, 7 solid solutions and 27 solid stoichiometric compounds. thermodynamic models the gibbs energies of the elements were taken from the sgte unary database [11] while the pure component oxides were taken from the sgte pure substance database [12], the thermodynamic descriptions of  the metallic systems were taken from the sgte solution database [13]. the thermodynamic data sources used in the present work are collected in table 1. the thermodynamic descriptions of the assessed stoichiometric compounds are presented in table 2. 168 the solid solution phases in  the in2o3-sno2-zno system considered in the present work are given in table 3 and are described below in more detail. the molten oxide phase the gibbs energy of the liquid phase in the system is represented by the modified non-ideal associate species model [7]. the basic species in2o3, sno2 and zno along with one (quasi)binary species (snzn2o4) have been introduced as  liquid components. although the corresponding metallic species were added for the systems me-o, the present work will attend to the melt oxide species only; the interactions between these oxides and other oxide species are responsible for the thermodynamic properties of the liquid phase. to provide equal weighting of each associate species with regard to  its entropic contribution in the ideal mixing term, each species contains a total of two cations in its formula based on [7]. in addition, interactions between associate species were introduced in order to fine tune the thermodynamic description. the molar gibbs energy of  the solution is presented by a three-term expression with contributions of  the reference part, the ideal and the excess part taking into account binary interactions as follows: g x g rt x x x x l x x m i i i i i j i j v ij v i j v � � � � � � �� �� � � � � �� � ln 0 (1) where xi is the mole fraction of phase constituent i (including the associate species), °gi is the molar gibbs energy of the pure phase constituent i and is an interaction coefficient between components i and j, according to the redlich — kister polynomial. the lij v� � with v = 0, 1, 2 and °gi are temperature dependent in the same way according to: � � � � � � � � �� � � � � � � � � � g l a b t c t t d t e t f t i ij v, ln 2 1 3 (2) thermodynamic data for  the liquid components are summarized in table 3. the elemental systems in–o and zn–o contain one stable oxide, in2o3 and zno, respectively, while in the system sn-o two oxides were considered, sn2o2 and sn2o4. the liquid phase of the quasi-binary oxide systems will contain the basic oxides along with one (quasi)binary species (snzn2o4 · 3 / 2). no ternary species were necessary. the gibbs energy of the binary species are taken from the sgte pure substance database [12] without modifications. the g function of the liquid species snzn2o4 · 3 / 2 was derived using the melting data of the table 1 thermodynamic data sources used in present work system source system source in-sn [13] in2o3–sno2 this work in-zn [13] in2o3–zno this work sn-zn [13] sno2–zno this work in-o this work in2o3–sno2–zno this work sn-o this work – – zn-o this work – – 169 table 2 thermodynamic properties of stoichiometric compounds assessed in this work compound ∆fh 298, j / mol s298 0 , j / mol · k t (k) cp, j / mol·k sno –289853 48.95 298–1250 43.7399+0.01356023·t+ 10·t–2–1.06·10–10·t2 [13] sn3o4 –1155713 151.23 298–1250 163.5208+0.03448263·t – 2223847·t–2+5.57·10–10·t2 snin2o5 –1439306.47 187.51 298–1903 197.5511+0.01742532·t – 4485329·t–2+3.968488·10–10·t2 1903–2186 213.5101 +0.01006315·t – 2261462·t–2–3.721512·10–10·t2 sn3in4o12 –3458277.2 426.23 298–1903 471.1432+0.04221281·t – 11194525·t–2+3.968488·10–10·t2 1903–2186 213.5101 +0.01006315·t – 2261462·t–2+1.5626976·10–9·t2 zn3in2o6 –1975291.24 231.8 298–2186 264.2621+0.02177245·t – 4512542·t–2 +3.8375878488·10–6·t2 zn4in2o7 –2326518.2 274.79 298–2186 311.8461+0.02567555·t – 4512542·t–2 +3.8375878488·10–6·t2 zn5in2o8 –2678001 317.6 298–2186 359.4301+0.02957865·t – 6013262·t–2 +6.3962278488·10–6·t2 zn6in2o9 –3028592 360.86 298–2186 407.0141+0.03348175·t – 6763622·t–2 +7.6755478488·10–6·t2 zn7in2o10 –3379500 403.92 298–2186 454.5981+0.03738485·t – 7513982·t–2 +8.9548678488·10–6·t2 zn9in2o12 –4080212 490.44 298–2186 549.7661+0.04519105·t – 9014702·t–2 +1.15135078488·10–5·t2 zn11in2o14 –4781168.4 576.79 298–2186 644.9341+0.05299725·t – 10515422·t–2 +1.40721478488·10–5·t2 zn13in2o16 –5482137.2 663.13 298–2186 644.9341+0.05299725·t – 10515422·t–2 +1.40721478488·10–5·t2 zn15in2o18 –6183104.984 749.4702 298–2186 835.2701+0.06860965·t – 13516862·t–2 +1.91894278488·10–5·t2 snzn2o4 –1282630 151 298–1903 171.209+0.01516837·t – 3724587·t–2 +2.55940900002·10–6·t2 1903–2250 187.168+0.0078062·t – 1500720·t–2 +2.55864·10–6·t2 170 corresponding constituent oxides. the interactions between liquid species are listed in table 3. spinel normal spinels can be described using the formula ab2o4, where a is a divalent metallic cation and b represents a trivalent cation placed on the second sublattice. for example, zinc aluminate (znal2o4) and zinc ferrite (znfe2o4) are normal spinels. on the other hand, zinc stannate zn2sno4 is an inverse spinel and has the chemical formula a2bo4 where a are divalent zinc cations and b tetravalent tin cations, as in (zn2+)2(sn 4+)(o2–)4. the inverse spinel zn2sno4 has the cubic spinel structure (space group ) and pearson symbol cf56 [14]. this inverse spinel structure is present in  many systems, e.g. as  ülvöspinel fe2tio4, manganese titanate mn2tio4 and gandilite mg2tio4. all of them can be treated with the same common formula table 3 thermodynamic descriptions of the liquid and solid solution phases parameter value, j / mol reference liquid: (in, in2o3, sn, sn2o2, sn2o4, zn, zn2o2, snzn2o4 / 1.5) � � � �g gin liq in sgps � � � �g gin o liq ti o sgps 2 3 2 3 � � � �g gsn liq sn sgps � � � �g gsn o liq sno sgps 2 2 2 � � � �g gsn o liq sno sgps 2 4 2 2 � � � �g gzn liq zn sgps � � � � �g g tsnzn o snzn o spinel 2 4 2 4 163400 80 81806. • � �lin in o liq , � 2 3 +27600 � �lsn sno liq , � +39000 1lsn sno liq , = +11200 � �lsn sno liq , � 2 +44000 � �lin o sno liq 2 3 2, � –11000 � �lin o zno liq 2 3 , � –11000 � �lin o sno sn liq 2 3 2, , –187000 * [11] [12] [11] [12] [12] [11] * * * * * * * * spinel: (zn2+, sn4+)1(zn 2+, in3+)2(o 2–)4 � � �� � �� �� � �g g gzn zn o snzn o spinel znin o spinel 2 2 2 2 4 2 4 0 5 0 5 95 : : . . 000 � � � � � �� �� � �g g g g spinel zn in o znin o zno sgps in o sgps 2 3 2 2 4 2 3 2700 : : 00 � � �� � �g gsn zn o snzn o spinel 4 2 2 2 4: � � �� � �� �� � �g g gsn in o snzn o spinel znin o spinel 4 3 2 2 4 2 4 0 5 0 5 95 : : . . 000 * * * * * 171 (a2+)2(b 4+)(o2–)4. in the in2o3–sno2–zno ternary system the spinel phase zn2sno4 dissolves a significant amount of indium and extends toward the fictive zno·in2o3 composition, having constant zn:sn ratio [1] according to the formula zn(2–x)sn(1–x) in2xo4. the proposed multi sublattice formula reads (zn2+, in3+)2(sn 4+, zn2+)1(o 2–)4 and allows to describe the deviation from the stoichiometric composition towards higher in2o3-contents keeping the zn:sn ratio to 2:1. the molar gibbs energy of the phase spinel was expressed using the compound energy formalism derived by hillert and staffansson [15] and generalized by sundman and ågren [16] under the condition y o iii � �2 1 as follows: g y y g y y g y m o o � � � � � � � � � �� � zn i sn ii zn sno zn i zn ii zn zno in 2 4 2 4 2 2 2 4 2 33 4 2 4 3 2 2 4 2 2 2 � � � � � �� � � �� � i sn ii in sno in i zn ii in zno zn y g y y g rt y o o ii zn i in i in i sn ii sn ii zn ii ln ln ln ln y y y rt y y y y 2 3 3 4 4 2 � � � � � � �� �� � � zzn ii 2�� �� gmex g y y g y y g y m o o � � � � � � � � � �� � zn i sn ii zn sno zn i zn ii zn zno in 2 4 2 4 2 2 2 4 2 33 4 2 4 3 2 2 4 2 2 2 � � � � � �� � � �� � i sn ii in sno in i zn ii in zno zn y g y y g rt y o o ii zn i in i in i sn ii sn ii zn ii ln ln ln ln y y y rt y y y y 2 3 3 4 4 2 � � � � � � �� �� � � zzn ii 2�� �� gmex (3) where yi s represents the site fractions of sublattice component i on sublattice s. � �gi j o: : 2 are the gibbs energy of real (zn2sno4) or hypothetical compounds where the first and second sublattices are occupied by appropriate components i and j, is the excess gibbs energy which depends on the site fractions yi n and on temperature. bixbyite indium oxide in2o3 exists in  form of two crystalline phases, the cubic form (bixbyite type like mn2o3) with pearson symbol ci80, and the rhombohedral form (corundum type like cr2o3) with pearson symbol hr30. the rhombohedral modification is metastable under normal parameter value, j / mol reference bixbyite: (in, zn, va)(in, sn)(o)3 � � �g gin in o in o sgps : : 2 3 � � �� � �� � � �g g g tin sn o in o sgps znsno bixbyite : : . .0 5 0 5 20000 112 3 3 � � �� � �� � � �g g g tzn in o in o sgps znsno bixbyite : : . .0 5 0 5 119044 32 3 3 � � � � � �� �g g g gzn sn o znsno bixbyite zno sgps sno sgps : : 3 2 10800 � � ��g gva in o in o sgps : : .0 5 2 3 � � � � �g gva sn o sno sgps : : 2 12000 0 46403 13l tin in sn o bixbyite : , : •� � � 0 10 52l tin zn in o bixbyite , : : . •� � 0 1700lin zn sn o bixbyite , : : � � 0 318000lin zn in sn o bixbyite , : , : � � 1 97000lin zn in sn o bixbyite , : , : � � * [12] * * * * * * * * * * — this work. сontinuation of table 3 172 conditions, but can be produced at high temperatures and pressures [17]. in the present work this modification has been ignored. the solubility of tin in the stable form of in2o3 (bixbyite) was investigated by  gonzalez and mason [18], ohya and ito [19], enoki and echigoya [20], as well as  heward and swenson [21] using different methods. all investigations are in general agreement and confirm a significant solubility of sno2 in bixbyite. in contrast, the solubility of  zinc in  bixbyite appears to  be relatively small. in the ternary in2o3-sno2-zno system bixbyite is enriched with tin and zinc extending toward to  the composition znsno3 and can be described as  in(2–2x)snxznxo3 (0 < x < 0.40) [1]. bixbyite is described in this work as solid solution phase based on in2o3 using the atomic sublattice model (in, zn, va)1(in, sn)1(o)3 assuming that the first and second sublattices can be occupied by  metal atoms while the third contains oxygen atoms only. the atomic model is chosen, because the use of ions would require more additional unknown gibbs energies to describe the solubility of tin oxide in bixbyite. the molar gibbs energy of this phase was expressed using the compound energy formalism [15, 16] as follows: g y y g y y g y y g y m o o o � � � � �in i in ii in o in i sn ii insno zn i in ii znino 2 3 3 3 zzn i sn ii znsno va i in ii ino va i sn ii sno in y g y y g y y g rt y o o o 3 3 3 � � � � � ( ii in i zn i zn i va i va i in ii in ii va ii v lnln ln ) ( ln ln y y y y y rt y y y y � � � � � aa ii ) � gm ex (4) where yi i and yi ii represent the site fractions of the component i and j in the first respectively second sublattices. ogin o2 3 corresponds to the gibbs energy of the indium oxide and is taken from the sgps database [12], the gibbs energy ogino3 is estimated to be one half of the gibbs energy of the appropriate oxide in2o3. ogznsno3 is the gibbs energy of the hypothetical compound znsno3, while the gibbs energies for  the also hypothetical compounds oginsno3 and ogznino3 could be estimated using the following reciprocal equation o o o o g g g g in o znsno insno znino 2 3 3 3 3 � � � � (5) and accepting that the species on the righthand side have identical gibbs energies o o o o g g g g insno znino in o znsno 3 3 2 3 3 0 5 0 5 � � � � � �. . (6) assessments thermodynamic descriptions for  the binary metal systems are taken from the sgte solution database [13], the thermodynamic descriptions of binary metal-oxygen systems are proposed in this work. the data for the binary oxide systems in2o3– sno2, in2o3–zno and sno2–zno as well as the ternary system in2o3-sno2-zno are optimized using available experimental information. the calculated phase diagrams are in good agreement with the experimental data. the thermodynamic data for the ternary compounds assessed in this work are given in  table 2. the gibbs energies of  (me1ox)a(me2oy)b have been based on stoichiometric combinations of me1ox and me2oy using a  neumann-kopp approach. the values for  ∆h298 0 and s298 0 have been assessed according to available experimental data. the end-member gibbs-energies g° as well as the various binary and ternary 173 interaction parameters between species both in the liquid and solid solutions have been assessed in  order to  obtain correct representations of  the solubility regions. the optimization of  the chosen solution parameters based on the available experimental data was performed using the optimizer module optisage included in the factsage software [22, 23]. results and discussion the metallic subsystems as indicated above, the data for  the three metallic subsystems have been taken from the sgte solution database [13]. the resulting binary phase diagrams as well as the ternary liquidus surface are given below for reasons of completeness. the in–o system the binary in-o system contains one stoichiometric compound, in2o3. the crystal structure of stable indium oxide is the cubic form (bixbyite type), whereas the rhombohedral modification (corundum type) is metastable. according to schneider [24], the melting point of bixbyite in2o3 is 1910 ± 10 °c. the solubility of oxygen in liquid indium was investigated first by fitzner and jacob [25] in the temperature range 650– 820 °c using a phase equilibration technique. later investigations using different techniques [26, 27] did not confirm these results [25]. otsuka, sano and kozuka [26] determined the solubility of oxygen using coulometric titrations and later otsuka, kozuka and chang [27] have used an isopiestic equilibration technique. both measurements are in good agreement and show lower solubility of oxygen in liquid indium than determined by fitzner and jacob [25]. isomäki, hämäläinen et al. [28] in their assessment of the in-o binary system used the experimental data fitzner and jacob [25] applying the ionic liquid model. figure 5 shows the calculated phase diagram of the in-o binary system calculated from the present database compared with the experimental melting temperature of in2o3 [24]. figure 6 shows the indiumrich part of the phase diagram compared fig. 1. calculated in-sn phase diagram fig. 2. calculated in-zn phase diagram fig. 3. calculated sn-zn phase diagram te tr ag o n al _a 6 tet_alpha1 tet_alpha1 + insn_gamma in sn _g am m a bc t_ a5 liquid mole fraction sn 0 0.2 0.4 0.6 0.8 1 0 50 100 150 200 250 300 t( c) liquid + hcp_zn liquid hcp_zn + tetragonal_a6 tetragonal_a6 hcp_zn mole fraction zn 0 0.2 0.4 0.6 0.8 1 0 100 200 300 400 500 t( c) hcp_zn + bct_a5 liquid + hcp_zn liquid bct_a5 hcp_zn mole fraction zn 0 0.2 0.4 0.6 0.8 1 0 100 200 300 400 500 t( c) 174 with the experiments [25–27], the agreement is very good. the sn-o system the sn-o phase diagram used for the optimization was taken from massalski [17], which is based on the experimental data reported by mcpherson, hansen [29] and spandau, kohlmeyer [30]. the system is characterized by a large region of liquid immiscibility between pure tin and “tin oxide” — rich compositions. the monotectic reaction between metal-rich and tin oxiderich liquid is assumed to have a temperature of 1040 °c and liquid compositions of 3.3 and 50.3 at. % o according to [17]. it was confirmed by later investigations carried out by cahen, david et al. [31] using dsc and xrd experiments. the sn-o binary system contains three intermediate compounds sno, sno2 and sn3o4. although the experimentally determined melting temperatures of  sno2 vary enormously, all investigations agree that this compound melts congruently. acfig. 5. calculated in-o phase diagram fig. 6. calculated phase equilibria in the in-rich part of the in–o diagram compared with experimental data [25–27] fig. 4. calculated liquidus surface in the in-sn-zn system 0.1 0 .2 0.3 0.4 0.5 0.6 0.7 0.8 0. 9 0.10.20.30.40.50.60.70.80.9 0.1 0.2 0. 3 0.4 0.5 0 .6 0.7 0.8 0. 9 zn in sn mole fraction t(min) = 379.19 k, t(max) = 692.67 k 456.70 395.76 379.19 1 3 300 400 500 600 700 800 900 1000 1100 1200 t(k) hcp_zn bct_a5 insn_gamma tet_alpha1tetragonal_a6 620 600 580 640 560 540 520 liquid + in 2 o 3 (s) in(s) + in 2 o 3 (s) liquid gas_ideal + + in 2 o 3 (s) gas_ideal + in 2 o 3 (s) gas_ideal liquid gas_ideal + liquid gas_ideal + liquidgas_ideal + liquid [24] mole fraction o 0 0.2 0.4 0.6 0.8 1 0 200 400 600 800 1000 1200 1400 1600 1800 2000 2200 2400 t( c) in 2 o 3 (s) liquid liquid + in 2 o 3 in(s) + in 2 o 3 [25] [27] [26] mole fraction o 0 0.002 0.004 0.006 0.008 0.01 0.012 0.014 0.016 0.018 0.02 0 200 400 600 800 1000 1200 1400 t( c) 175 cording to [31] this compound melts congruently at 2000 °c in contradiction to the sgps database [12] which gives a melting temperature of 1630 °c. in the present work the thermodynamic properties of  pure sno2 were taken from [12]. moh [32] have reported the existence of the compound sno which is formed by a peritectoid reaction at 270 °c (βsn) +sn3o4→sno. sn3o4 is not stable at room temperature and decomposes at 450 °c [32]. a first thermodynamic assessment of the binary sn-o system was given by cahen, david et al. [31]. they assumed the melting temperature of sno2 to be 2000 °c and have modelled also the stoichiometric compounds sno and sn3o4 using the thermal stabilities experimentally determined by  moh [32]. later, a  thermodynamic assessment was carried out by  isomäki, hämäläinen et al. [28] where the thermodynamic data for sno2 were taken from the sgps database [12] with the lower melting temperature of 1630 °c. the other two compounds were not considered in  this work. in both assessments, the liquid phase was described using the ionic liquid model. in the assessment by cahen [31], the entropies of  formation for  the compounds sno and sno2 were determined to be 96.347 j / mol·k and 183.114 j / mol·k, respectively, which is in contradiction with the values published by barin [33] (56.48 and 52.34 j / mol·k) and also the sgps database [12] (57.17 and 49.01 j / mol·k). in the present work the thermodynamic data for sno2 were taken from the sgps database [12]. also, the heat capacity of the compound sno was taken from this source. the heat of formation of sno determined by li-zi et al. [34] (–285920 j / mol) was used for the optimization combined together with the phase diagram data [32]. the assessed value is –289853 j / mol, the difference to  the measured value being about 1.37 %. sn3o4 is modeled to be stable till 450 °c according to the experimental value of 450 °c [32]. the calculated sn–o phase diagram is presented in figure 7 compared with available experimental information; the agreement is good. the zn-o system for the binary zn–o system no phase diagram is available. the information on this system including thermodynamics and structure of zno has been summarized by wriedt [35]. the system contains one stoichiometric compound zno with known melting temperature (1972 °c) [17] but unknown melting behavior. no solubility of oxygen in pure zinc was reported. the binary zn-o phase diagram resulting from the present dataset is shown in figure 8 compared with the experimental data given in [17]. zinc monoxide decomposes congruently by  sublimation to  the gaseous elements according to the following reaction: zno(s)  zn(g) + 0.5o2(g). the sublimation / vaporization of zinc oxide has been investigated by  knudsen effusion mass-spectroscopy (kems) [36– 39]. at temperatures below 1500 k the vapor above zno consists almost exclusively gas_ideal + sno 2 (s) gas_ideal gas_ideal + liquid [29] sn 3 o 4 (s) sno(s)sn(s) + sno(s) [32] liquid + sno(s) liquid + liquid#2 gas_ideal + liquid liquid liquid liquid + sno 2 (s) gas_ideal + liquid mole fraction o 0 0.2 0.4 0.6 0.8 1 0 500 1000 1500 2000 2500 3000 t( c) sno 2 (s) fig. 7. calculated sn-o phase diagram compared with experimental data [29, 32] 176 of zn atoms and o2 molecules, which confirms the congruent vaporization of zno. the oxygen partial pressure, which could not be measured correctly in the experiment, was estimated in agreement with the congruent sublimation condition by  the above reaction as  p(o2)  =  1 / 2  ·  p(zn). under the conditions of  gas phase effusion from the cell, this relation takes the form p(o2)= 1 / 2[m(o2) / m(zn)] 1 / 2 · p(zn), where m(o2) and m(zn) designate the oxygen and zinc molar masses. the sublimation enthalpy can be obtained from the temperature dependence of p(zn) [38, 39] or calculated using the third-law [39]. the latter value is considered as more exact. the selected data on the partial pressure of atomic zn from the literature [37– 41] are presented in figure 9 (points and dashed lines) compared with the present equilibrium calculations (solid lines). the deviation between the experimental datasets is notable especially in  case of  oxygen. it should be noted that the thermodynamic data for  pure zn, zno, o2 were taken from the sgte databases [11, 12] without changes. therefore, the discrepancy can be explained by  differences with respect to both the thermodynamic data of individual gaseous species and the sublimation enthalpy of zno. for this, a value of 465.66 kj / mol is used in the sgps database. it is, however, in  good agreement with the literature, i.e. 461.9 (via third-law calculations in [39]) or 467.66 in [37, 38]. the me1-me2-o systems predicted isothermal sections at 500 °c for  the ternary in–sn–o, in–zn–o and sn–zn–o systems are given in  figures 10–12. the pseudo-binary systems in2o3– sno2, sno2–zno and in2o3–zno are considered as a part of the corresponding systems me1–me2–o. it should be noted liquid + zno(s) zn(s) + zno(s) gas_ideal + zno(s) gas_ideal + zno(s) gas_ideal zno(s) [17] a) mole fraction o 0 0.2 0.4 0.6 0.8 1 0 200 400 600 800 1000 1200 1400 1600 1800 2000 2200 t( c) fig. 8. calculated zn–o phase diagram: a — with participation of the gas phase, b — without liquid + zno(s) zn(s) + zno(s) gas_ideal + zno(s) zno(s) [17] liquid b) mole fraction o 0 0.2 0.4 0.6 0.8 1 0 200 400 600 800 1000 1200 1400 1600 1800 2000 2200 t( c) o 2 (g) o 2 (g) zn(g) zn(g) partial pressure of o 2 (g) over zno in different systems [39-41] temperature dependence of partial pressure of zn(g) [39] partial pressure of zn(g) over zno in different systems [39-41] partial pressure of zn(g) via kp [37] partial pressure of zn(g) and o 2 (g) calculated in present work partial pressure of zn(g), o 2 (g) from [37] cited in [38] zn(g) partial pressure of zn(g), o 2 (g) [38] t(k) 1200 1250 1300 1350 1400 1450 1500 –8 –7 –6 –5 –4 –3 –2 lo g 1 0( pa rt ia l p re ss ur e) , at m fig. 9. partial pressure of zn and o2 over zno: comparison of literature data (points, dashed, dotted lines) with calculations solid (lines) 177 that the data for the ternary metallic system in-sn-zn and its binary subsystems were taken from the sgte alloy database [13] and are not given in this paper. only in the liquid metal phase a small solubility of o is calculated from the present data. the behaviour of the respective systems along the oxide pseudo-binary systems is discussed below. the in2o3–sno2 system the pseudo binary system in2o3–sno2 is characterized by  the presence of  two intermediate phases stable at  high temperatures, a  significant solubility of  tin in  indium oxide and a  eutectic reaction close to the tin-rich side. the system was investigated by enoki and echigoya [20] between 1200 and 1600 °c by tem observations. heward and swenson [21] studied the phase diagram in the temperature range 1000–1650 °c using electron probe microanalysis (epma) and x-ray diffraction (xrd) analysis of solid-state sintered samples. the solubility ranges of tin oxide in bixbyite solid solution were investigated by ohya, ito et al. [19], gonzales and mason [18] and harvey [1]. the experimentally determined solubility limits and phase boundaries for  the bixbyite solid solution contradict each other. according to heward and swenson [21], the maximal solubility of sno2 in in2o3 was found to be 13.1 mol.% at 1650 °c, whereas ohya [19] reported 5 % at 1500 °c. in contrast, the solubility of indium in sno2 appears to be negligibly small [18, 21], which differs from the phase diagram obtained by enoki [20]. in the in2o3-sno2 system two intermediate compounds, sn3in4o12 and snin2o5, were observed. both are stable at high temperatures and decompose eutectoidally at 1325 and 1575 °c, respectively [21]. the stoichiometric compound sn3in4o12 was reported to be stable at temperatures above 1300 °c [18, 20] but was not observed by harvey [3] at 1275 °c. the data on the experimentally determined thermal stability of the compound in4sn3o12 are collected in table 4. the in-sn-o system has been thermodynamically modelled by  isomäki, fig. 10. the calculated in-sn-o isothermal section at 500 °c 0.1 0 .2 0.3 0.4 0.5 0.6 0.7 0.8 0. 9 0.10.20.30.40.50.60.70.80.9 0.1 0.2 0. 3 0.4 0.5 0 .6 0.7 0.8 0. 9 bixbyite sno 2 liquid + bixbyite o sn mole fraction in 178 hämäläinen et al. [28] who applied an ionic liquid two-sublattice model for the description of the liquid phase (sn+2, in+3) (sno2,o –2,va). only one compound (sn3in4o12) was modeled in this work, the solubility of tin in in2o3 were optimized using the data of enoki [20] which are significantly higher than those reported by ohya fig. 11. the calculated in-zn-o isothermal section at 500 °c 0. 1 0.2 0.3 0. 4 0.5 0.6 0 .7 0.8 0.9 0.10.20.30.40.50.60.70.80.9 0 .1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 o in mole fraction bixbyite zno in 2 zn 7 o 10 in 2 zn 5 o 8 liquid + zno zn fig. 12. the calculated sn-zn-o isothermal section at 500 °c o sn mole fraction 0.1 0 .2 0.3 0.4 0.5 0.6 0.7 0.8 0. 9 0.10.20.30.40.50.60.70.80.9 0.1 0.2 0. 3 0.4 0.5 0 .6 0.7 0.8 0. 9 liquid + zno zno snzn 2 o 4 sno 2 zn 179 [19], harvey [1] and gonzalez [18]. the values by enoki [20] were not used for the optimization in the present work. the calculated in2o3-sno2 binary system in air is presented in figure 13 compared with the experimentally determined phase boundaries. the tin solubility in in2o3 increases with temperature and reaches 4.6 at. % at 1730 °c. the system contains furthermore two intermediate high-temperature compounds sn3in4o12 and snin2o5, the transition temperatures of which could be taken from the literature [20, 21, 42]. the calculated decomposing temperature of  sn3in4o12 is 1333  °c, very close to the experimental values 1325 [21] and 1335 °c [18] while the calculated t2-temperature (1646  °c) agrees well with the experimental data by [21] and [42]. the in2o3-zno system in the pseudo-binary system in2o3-zno kasper [43] found that zinc oxide and indium oxides reacted at 1100 °c with formation of a series of homologous oxides in2znkok+3 where k = 2–5 and 7. based on  high-resolution electron microscopy results, cannard and tilley [44] proposed that the structures consist of k zno layers separated by two ino1.5 layers. zno has the wurtzite structure, in2o3 crystallizes in the cubic bixbyite structure, and these two structures intergrow along the hexagonal c-axis direction. according to [44], at high zno concentrations in2znkok+3 form compositions with k = 4–11 at 1100 °c. later, nakamura [45] and kimizuka [46] suggested that the compounds are isostructural with lufeo3(zno)k. although the two models are not identical, both exhibit wurtzite-type layers perpendicular to the c-axis of the in2znkok+3 structures. compounds with k = 3–11, 13, 15, 17, 19 were characterized by nakamura [45, 47] using xrd and scanning electron microscopy (sem). moriga et al. [6] presented the sub-solidus phase diagram for the system in2o3-zno over the temperature range 1100–1400 °c. homologous compounds in2znkok+3 with k = 3–7, 9, 11, 13, and 15 were reported based on xrd. at 1100 °c, in2zn5o8 and in2zn7o10 only were found to  be stable along with zno and in2o3, whereas the number of stable compounds increased as  the temperature increased. table 4 thermal stability of ternary stoichiometric compound sn3in4o12 t1, oc t2, oc t1, °c in this work t2, °c in this work 1300 enoki [20] – 1333 1646 1365 ohya [19] – 1335 gonzalez [18] – 1325 heward [21] 1650 heward [21] – 1652 bates [42] fig. 13. the calculated in2o3-sno2 phase diagram in air compared with experimental data [1, 18–21, 42] slag + bixbyite [21] [42] bixbyite liquid bixbyite + sno 2 (s) [19] [20] [18] [1] mole fraction sno 2 0 0.2 0.4 0.6 0.8 1 0 500 1000 1500 2000 2500 t( c) snin 2 o 5 (s) sn 3 in 4 o 12 (s) sn 3 in 4 o 12 (s) + sno 2 (s) 180 the temperature ranges of  stability determined in [6] agree with the previously reported information [43, 45, 46]. the difference was that the compounds with k = 4 and 8 were not observed by moriga [6] over the temperature range studied. moreover, the presence of  the compound with k = 15 of the in2znkok+3 series was almost impossible to detect with the xrd technique used in [6]. the formation of homologues series in2znkok+3 (where k = 3–7, 9, 11) was confirmed at  1275  °c in  the study on the ternary system in2o3–sno2–zno [1], while the compounds with k = 6, 13, 15 became stable at higher temperatures. the lattice constant, microstructure and electrical characteristics of in2o3 ceramic doped by zno were investigated by park et al. [48]. the solubility limit of zno in in2o3 was reported to  be close to  1 at.% when izo (indium zinc oxide) was sintered in oxygen atmosphere. sintering in nitrogen decreased the solubility limit to below 1 at.%. no previous assessments on  the system in2o3–zno were found in the literature. the present description of the system in2o3–zno is based on the data reported by moriga [6]. the series of phases with the general formula in2znkok+3 with k = 3–7, 9, 11, 13, 15 was modelled in form of stoichiometric oxides. the thermodynamic data of these compounds are given in table 2. heat capacities of these compounds were generated according to neumann — kopps rule based on the component oxides; the enthalpies and entropies of formation were optimized in accordance with the stability ranges of  the phases. the formation enthalpy for the compounds with k = 5 and 7 optimized in the present work are in very good agreement with those reported in [41] as shown in figure 14. the literature data have been derived from a vaporization study of the system in2o3–zno with the kems technique. it is worth noting that all compounds show a very consistent trend with increasing content of sn. the solubility limit of  zno in  in2o3 ( bi x by it e p h a s e ) w a s c a l c u l at e d at 1.56 mol.% and 1698 °c using the following atom-based model description of  the phase: (in, zn, va)1(in, sn)1(o)3. the liquid phase is assumed to  consist of the component oxides, zn2o2 and in2o3, i.e. following the rule of two cations per molecule. the gibbs energies of the stoichiometric homologous compounds are summarized in  table 2. the calculated phase diagram for the system in2o3–zno [41] amounts of zn atoms 2 4 6 8 10 12 14 16 300 400 500 600 700 zn 3 in 2 o 6 –∆ fh 29 8 , k j/ g – at om zn 4 in 2 o 7 zn 5 in 2 o 8 zn 6 in 2 o 9 zn 7 in 2 o 10 zn 9 in 2 o 12 zn 11 in 2 o 14 zn 13 in 2 o 16 zn 15 in 2 o 18 [6]liquid liquid + bixbyite bixbyite liquid + zno 1 mole fraction zno 0 0.2 0.4 0.6 0.8 1 1100 1200 1300 1400 1500 1600 1700 1800 1900 2000 2100 t( c) bixbyite + zn 3 in 2 o 6 bixbyite + zn 4 in 2 o 7 bixbyite + zn 5 in 2 o 8 zn 3 in 2 o 6 zn 4 in 2 o 7 zn 6 in 2 o 9 zn 5 in 2 o 8 zn 7 in 2 o 10 zn 15 in 2 o 18 zn 13 in 2 o 16 zn 11 in 2 o 14zn 9 in 2 o 12 fig. 14. heat of formation of the stoichiometric compounds in the in2o3–zno system fig. 15. the calculated in2o3–zno phase diagram in air compared with experimental data [6] 181 is presented in fig. 15 compared with the experimental data [6]. the sno2-zno system enoki [49] proposed a  preliminary phase diagram for the system sno2–zno with the spinel phase only. the oxide mixtures were equilibrated at 1200 and 1400 °c and characterized by xrd. most of the experimental studies [4, 49, 50] on this system agreed that there is one stable compound with the composition snzn2o4. this compound has inverse spinel structure and can be obtained by solid state reaction from the component oxides or by decomposition of the salts zinc acetate (zn(ch3coo)2 and tin tetrachloride (sncl4). in contrast, the information on the second phase, znsno3, is contradictory. shen and zhang [51] reported that this compound has a perovskite structure, whereas inagaki [52] proposed an ilmenite structure which is more reasonable due to the fact that the ionic radius of zn2+ radius is too small to form a stable perovskite structure as has been confirmed later by kovacheva and petrov [53]. palmer and poeppelmeier [4] studied sub-solidus phase equilibria in the system ga2o3–sno2–zno at 1250 °c using solid state synthesis and xrd. the zno–sno2 binary system contains one intermediate compound, snzn2o4 with two-phase regions between the end-members and the spinel. according to [4], the lattice parameters of snzn2o4 were unchanged (from the nominal value) in two-phase mixtures with zno or sno2, indicating minimal solubility of  either oxide into the spinel phase. hansson et al. [50] investigated phase equilibria for  sno2-zno system in  air in the temperature range 1200 to 1400 °c using high-temperature equilibration and quenching techniques followed by electron probe x-ray microanalysis (epma). the maximum solubility of zno in sno2 was found to be approximately 1.5 mol.% in the range of conditions investigated. the concentration of tin oxide in zincite (zno) is negligible between 1300 and 1400 °c in air within the limits of experimental uncertainty. a slight solubility of zno in the stoichiometric snzn2o4 spinel can be observed at all temperatures. later harvey et al. [1] did not observe a change of lattice parameter between pure zno or pure sno2 and doped compositions. mihaiu et al. [54] undertook a systematic study of the phase formation over the whole compositional range of  the zno-sno2 binary system in  the temperature range 500–1500 °c. starting with 900 °c, the formation of the snzn2o4 with inverse spinel type structure was found in all samples. the formation of the znsno3 was not observed under the experimental conditions used. in the temperature ranges 1000–1500 °c, no change in the phase composition was observed. vaporization processes in  the zno– sno2 system have been studied by  the knudsen effusion technique in  combination with mass spectrometric analysis (kems) of the vapor phase in the temperature range 1360 k to 1460 k [39]. complete isothermal sublimation experiments have been performed to determine the partial pressures of  vapor components over the whole system. the elemental composition of samples was quantified using laser mass spectrometry. by isothermal sublimation, the change of partial pressure of zn over the system is caused by  phase transformations in the solid state from pure zno through two heterogeneous fields (zno + zn2sno4 and zn2sno4 + sno2) to pure tin oxide. it has been found that the gas phase mainly consists of zn(g), o2 and sno(g). the partial pressures of the vapor species were determined at 1450 k. 182 in the present work, the compound snzn2o4 is treated as stoichiometric according to [3, 6] and calculated to be stable up to its melting point of 1675 °c. this compound is considered as the end-member constituent in the spinel phase for the ternary system. the heat capacity of snzn2o4 was based on the data of the component oxides according to neumann-kopp (table 2), the standard enthalpy of formation was optimized based on the experimental value from gribchenkova [39]. the entropy was adjusted in order to represent the melting point of  spinel. the compound znsno3 was omitted from consideration according to literature data on its instability [39]. the liquid phase in the system sno2– zno includes the associate snzn2o4 / 1.5 along with the basic oxides according to the modified associate species model. the melting properties of the spinel compound were based on those for liquid oxides. the two eutectics (spinel and zno as well as spinel and sno2) are calculated at  1647 and 1425  °c, respectively. the calculated phase diagram of  the system sno2-zno is given in figure 16. the calculated activities across the system sno2–zno at 1450 k are compared in figure 17 with those measured in [39] using kems. the thermodynamic data on the gas phase are taken from the sgps database [12]. the following main gas species are found by calculation of equilibrium between the condensed phases and gas – zn, sno and o2. the ratio between these species agreed with the measurements [39]; however, the absolute values of  the partial pressures (especially for zn) differ from the experimental data due to scattering of experimental data on p(zn) obtained by using such a complicated method as kems. moreover, the disagreement can be explained by possible small inconsistencies concerning the thermodynamic data of the gas components in the sgte database, as was already mentioned above regarding the zn–o system. the in2o3-sno2-zno system the ternary in2o3-sno2-zno system does not exhibit any ternary compounds, but presents two significant solid solution phases, the snzn2o4 spinel phase enriched with indium with the formula zn(2–x)sn(1–x)in2xo4 and the bixbyite solid solution based on  in2o3 and extending far toward the snzno3 composition with the formula in(2–2x)snxznxo3. palmer, poeppelmeier and mason [55] studied the solid solubility of zno and sno2 in bixbyite at 1100 and 1250 °c using x-ray diffraction and determined a very strong coupled snzn 2 o 4 (s) + sno 2 (s) zno(s) + snzn 2 o 4 (s) snzn 2 o 4 (s) liquid liquid + zno(s) liquid + snzn 2 o 4 (s) liquid + sno2(s) mole fraction sno 2 0 0.2 0.4 0.6 0.8 1 0 200 400 600 800 1000 1200 1400 1600 1800 2000 t( c) exp. kems: zn(gas), p in pa [39] exp. kems: sno(gas), p in pa [39] exp. kems: o 2 (gas), p in pa [39] exp. zn in gas exp. sno in gas solid lines are calculated 1450 k, total pressure 101325 pa zn(g) sno(g) 0 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 0.90 1.00 –1 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 ac ti vi ty ( pa rt ia l p re ss ur e) , pa exp. o 2 in gas o 2 (g) fig. 16. calculated sno2–zno phase diagram in air fig. 17. calculated and experimental activities in sno2–zno system at 1450 k 183 solubility of sno2 and zno. the maximum combined solubility of zn and sn can reach 40 cation %, the resulting material at this point can be described as in1.2sn0.4zn0.4o3. later investigations by kammler et al. [56] using x-ray powder diffraction confirmed high solubility of  zinc and tin in  in2o3 at 1250 °c. kammler reported also a wide spinel solution range, zn2–xsn1–xin2xo4 (0 < x < 0.45) and also a significant solubility of tin in zn3in2o6 which was, however, not confirmed by later investigations [1, 2]. the phase diagram data published in [56] are constructed schematically and were not used for the present optimization work. the present assessment of the ternary system is mainly based on the phase equilibria data published in [1]. harvey, poeppelmeier and mason [3] investigated the subsolidus phase relationships at 1275 °c using x-ray diffraction. they reported the existence of two extended solid solutions and preliminary phase relations between them and other coexisting compounds. both solid solution phases exhibit constant zn:sn ratio and appear on the phase diagram as  long vertical lines. the one significant solid solution phase is bixbyite in2o3, enriched by tin and zinc, where up to 40 % of indium can be replaced by tin and zinc. according to  harvey [1], the bixbyite phase can be described using the formula in(2–2x)snxznxo3, where x can reach a maximum of 0.4. at 1275 °c, bixbyite is in general in equilibrium with the spinel phase, compound (zno)k(in2o3), where k = 3, and also with the tin oxide sno2. the other important solid solution phase reported by harvey [1] is the spinel phase, which extends from the binary composition snzn2o4 towards the in2zno4 composition. harvey confirmed spinel phase boundaries and formula experimentally found by kammler [56] to describe this indium-doped spinel as zn(2–x)sn(1–x)in2xo4,(0 < x ≤ 0.45), whereby at x = 0.45 the spinel composition corresponds to the formula zn1.55sn0.55in0.90o4. harvey investigated also very intensively a zinc-oxide-rich region at 1275 °c and corresponding phase equilibria. as mentioned before, along the binary zno-in2o3 edge at 1275 °c there is a  series of  homologous compounds (zno)k(in2o3) (where k = 3–5, 7, 9, 11), all of  which are in  equilibrium with the phase spinel, starting with the first one (zno)11(in2o3) and finishing with the last (zno)3(in2o3) which is in equilibrium with spinel maximally enriched in indium. the compounds with k > 11 were not found in equilibrium with spinel at 1275 °c due to sluggish kinetics in the zno-rich composition range [1]. figure 18 shows the calculated isothermal section at 1275 °c in the ino1.5– sno2–zno system in air compared with experimental data [1]. the experimentally determined extensions of the solid solution phases bixbyite and spinel, the two-phase regions and also the compatibility triangles could be reproduced satisfactorily by the calculations. conclusions a thermodynamic dataset containing all phases in the system in2o3-sno2-zno has been generated using the available experimental information (phase diagrams, phase transitions, structure, enthalpies of formation). the liquid and solid phases have been introduced into the 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cta_v4_№1.cdr 8 d o i: 1 0. 15 82 6/ ch im te ch .2 01 7. 4. 1. 01 9 6 21 .3 91 zhijin fan, research team chimica techno acta. 2017. vol. 4, no. 1. p. 8–10. issn 2409-5613 th e eleventh of january, 2017 was bound to be an extraordinary day in my life! th is day, i lost one of my best friends, the best teacher and the best comrade in the area of organic chemistry, one of the most talented genius chemists. even now, i really do not know how to say any words to express my sadness, i felt so sad, because i have no chance to see him in his laboratory when i visit his university. let you know, we just discussed the future collaborations in october, 2016 when he visited my laboratory! no matter what kind of a day i am having, i can not forget his contribution to organic chemistry and collaborative scientifi c studies and friendship between china and russia. i can not forget the days when i visited th e ural state technical university, especially between the 14th of september and the 12th of october, 2007 by the invitation of professor bakulev vasiliy alekseevich, when i worked all the way zhijin fan, research team state key laboratory of elemento-organic chemistry, nankai university, tianjin 300071, p. r. china tel.:+86-22-23499464; e-mail: fanzj@nankai.edu.cn memorize organic chemist professor yuri yurievich morzherin исследовательская группа фан жиджина государственная лаборатория элементо-органической химии нанкайского университета, тяньцзинь, 300071, китай , © zhijin fan, research team, 2017 9 in the laboratory of professor morzherin for one month. his intelligence in organic chemistry especially in heterocyclic chemistry and calixarene chemistry gave me strong impressions, in my opinion, he had a strong will, active mind and was full of creativity in his study area. his careful consideration in every detail of my research made me to feel so warm-hearted! when i synthesized 5-methyl-1,2,3-thiadiazole-4-carboxylic acid as an intermediate, he conducted the step he thought to be risky by himself and he arranged all the team members in the laboratory to guide me in the garden near the university to wait for the reaction completion. i also can not forget the weekends during my visit in his laboratory, his arrangement for the picnic with research team members near the lake and the visit for the beautiful mountain in the forest let me having the feeling of coming home. i also heard the same impressions from the mouths of other students especially the bs students who worked in his laboratory, his laboratory is one of the most open access laboratories beloved by students because of his kind guidance and generosity. in this case, he cultured and protected the curiosities and dreams of organic chemistry of the students, his laboratory then became one of their cradles on the successfull road to the kingdom of organic chemistry. i do not know if he felt the misery when he left us, but i’m a strong believer that there is no pain in the heavens, i wish he will be good and happy in another world! as if i heard his voice in the poetry of mary elizabeth frye: «do not stand at my grave and weep, i am not there, i do not sleep. i am the soft ly falling snow, of beautiful birds in circling fl ight, i am the starshine of the night, i am in a quiet room, i am not there, i do not die». th e analects of confucius says: ‘may the deceased rest in peace, while the living must move on with their lives’. i appreciate each moment i spent with you. i will hold my tears with sorrow and continue the collaboration with your laboratory and do what i do. i hope you can feel our achievements in the havens, you will settle in my memory and heart, your thought and spirit will live with me forever, respectable professor yuri yurievich morzherin. in russian 11 января 2017 года стал необычным днем в моей жизни. в этот день я потерял моего лучшего друга, лучшего учителя и лучшего товарища в области органической химии, одного из самых талантливых и гениальных химиков. даже сейчас я действительно не знаю, как найти слова, чтобы выразить мою печаль, потому что у меня нет никаких шансов увидеть его в своей лаборатории, когда я приезжаю в свой университет. в октябре 2016 года мы обсудили будущее сотрудничество, когда он приезжал в мою лабораторию! как бы ни сложилась моя жизнь, я не забуду юрия юрьевича и его вклад в органическую химию и совместные научные исследования и дружбу между китаем и россией. я не могу забыть те дни, когда я посетил уральский государственный технический университет (особенно с 14 сентября по 12 октября 2007 года) по приглашению профессора бакулева василия алексеевича, где я работал в лаборатории профессора ю. ю. моржерина в течение месяца. его интеллект в области органической, особенно гетероциклической, 10 химии и химии каликсаренов произвел на меня сильное впечатление. на мой взгляд, он обладал сильной волей, умом и был полон творческих замыслов. он был внимателен к моей работе: когда я синтезировал 5-метил-1,2,3-тиадиазол-4-карбоновую кислоту в качестве промежуточного продукта, он сам провел синтез, который считал рискованным, и он организовал всех членов команды своей лаборатории вести меня в сад рядом с университетом для того, чтобы дождаться завершения реакции. я также не могу забыть выходные в ходе своего визита в его лабораторию, его договоренность о пикнике с членами своей исследовательской команды у озера и посещение прекрасной горы в лесу – все это позволило мне почувствовать себя как дома. я слышал те же впечатления из уст других студентов, особенно студентов bs, которые работали в его лаборатории. его лаборатория является одной из самых открытых лабораторий, которые любят студенты за его приветливое руководство и щедрость. он всегда поддерживал интерес студентов к органической химии, его лаборатория стала этапом на пути в царство органической химии. я не знаю, почувствовал ли он страдания, когда он покинул нас, но я твердо верю, что на небесах нет боли, я желаю ему счастья и добра в другом мире! словно я услышал его голос в поэзии марии элизабет фрай: «не стойте у могилы и не плачьте, меня нет, я не сплю. я – мягко падающий снег. из красивых птиц в круговом полете я ночной свет звезд, я в тихой комнате, меня там нет, я не умираю». в «анализах конфуция» говорится: «пусть покойник будет в мире, а живые должны жить дальше». я ценю каждый момент, который я провел с вами. я буду сдерживать свои слезы с горечью и продолжать сотрудничество с вашей лабораторией и делать то, что я делаю. надеюсь, вы увидите наши достижения на небесах, вы останетесь в моей памяти и сердце, ваши мысли и дух будут жить со мной навсегда, уважаемый профессор юрий юрьевич моржерин. 83 е. а. саватеева1, в. в. емельянов1, а. в. мусальникова1, л. п. сидорова1, н. е. максимова1, н. н. мочульская1, в. а. черешнев1, 2 1уральский федеральный университет, 620002, екатеринбург, ул. мира, 28. e-mail: evvd@list.ru 2институт иммунологии и физиологии уро ран, 620049, екатеринбург, ул. первомайская, 106. серосодержащие гетероциклические соединения с потенциальной противодиабетической активностью* существенным звеном патогенеза сахарного диабета и его осложнений является неферментативное гликозилирование белков (нгб). однако современная эндокринология испытывает нехватку клинически эффективных лекарственных средств для его коррекции. проведен скрининг 23 производных 1,3,4-тиадиазина на способность ингибировать реакцию нгб in vitro, исследована взаимосвязь «структура – активность». среди 23 соединений, подвергнутых скринингу, мы выделили 11 наиболее активных веществ, подавлявших накопление фа на 20–70 %, против контроля. лидерами среди этих веществ были соединения l-17, 2-г-5-ф и н-10, снижавшие накопление фа в 2–2,5 раза, по сравнению с контролем, и превосходившие по ингибирующей способности вещество сравнения g-sh. таким образом, в проведенном исследовании впервые продемонстрирована способность ряда серосодержащих гетероциклических соединений класса 1,3,4-тиадиазинов ингибировать накопление начального продукта нгб фруктозамина при инкубации бычьего сывороточного альбумина с глюкозой, проведена оценка взаимосвязи между структурой соединений и противогликозилирующей активностью. выявленный биохимический механизм может иметь значение в реализации противодиабетической активности производных 1,3,4-тиадиазина. * работа выполнена при поддержке гранта рффи 12-04-31852-мол_а и средств программы развития урфу на 2010–2020 гг. у д к 6 61 .1 2. 01 +6 15 .2 72 © саватеева е. а., емельянов в. в., мусальникова а. в., сидорова л. п., максимова н. е., мочульская н. н., черешнев в. а., 2014 84 cta | № 3 | 2014 введение возрастающая распространенность сахарного диабета (сд) в современном мире определяет высокую актуальность поиска новых противодиабетических средств с различными механизмами действия. существенным звеном патогенеза сд и его осложнений является неферментативное гликозилирование белков спонтанная химическая реакция между карбонильными группами моносахаридов и аминогруппами белков. нашими предыдущими исследованиями показана способность веществ, имеющих тиольную группу, ингибировать накопление начального продукта нгб фруктозамина. в связи с этим представляет интерес исследовать противогликозилирующую активность веществ, способных трансформироваться в тиольные производные. к таким соединениям относятся 1,3,4-тиадиазины – шестичленные гетероциклические соединения, содержащие два атома азота и один атом серы [1]. представители класса 1,3,4-тиадиазинов обладают различными видами фармакологической активности: антиагрегантной, антикоагулянтной, анестезирующей, гипометаболический, противовоспалительной, радиопротекторной [2, 3]. результаты и обсуждение в модельной системе в течение 7 недель инкубации происходит накопление фруктозамина (фа), наиболее интенсивное – в первые 2 недели. ингибиторы процесса снижают максимальный уровень накопления фа и замедляют его достижение. так, восстановленный глутатион (g-sh) снижал накопление фа в 1,5–2 раза в первые 4 недели эксперимента. однако к окончанию инкубации g-sh утрачивал ингибирующую активность, что, возможно, связано с окислением его тиольных групп [4]. исследованные производные 1,3,4-тиадиазина обладали различной способностью блокировать накопление фа в модельной системе (рис. 1). среди 23 соединений, подвергнутых скринингу, мы выделили 11 наиболее активных веществ, подавлявших накопление фа на 20–70 %, против контроля. лидерами среди этих веществ были соединения l-17, 2-г-5-ф и н-10, снижавшие накопление фа в 2–2,5 раза, по сравнению с контролем, и превосходившие по ингибирующей способности вещество сравнения g-sh. ингибирование реакции нгб тиолами мы связываем с их способностью к образованию полутиоацеталей и тиоацеталей при взаимодействии с глюкорис. 1. накопление фруктозамина при инкубации бычьего сывороточного альбумина с глюкозой и производными 1,3,4-тиадиазина, в процентах к уровню контрольного опыта е. а. саватеева, в. в. емельянов, а. в. мусальникова, л. п. сидорова, н. е. максимова, н. н. мочульская, в. а. черешнев 85 2014 | № 3 | cta серосодержащие гетероциклические соединения с потенциальной противодиабетической активностью зой и промежуточными карбонильными продуктами нгб [4, 5]. окисление тиольной группы с образованием дисульфида является конкурирующим процессом, выводит тиолы из реакции с карбонильными соединениями и лишает их противогликозилирующей способности. в этих условиях преобладает образование фа по аминогруппе g-sh, в связи с чем уровень фа в модельной системе на поздних сроках инкубации повышался. механизм противогликозилирующего действия соединений класса 1,3,4-тиадиазина возможно связан с их способностью трансформироваться в sh-замещенные пиразолы, как это наблюдается при нагревании некоторых 1,3,4-тиадиазинов в кислых и щелочных средах [2, 3], или присоединять глюкозу к фрагменту тиадиазинового кольца после его раскрытия (рис. 2). при анализе взаимосвязи «структура – противогликозилирующая активность» производных 1,3,4-тиадиазина установлено, что среди активных ингибиторов нгб преобладали производные 5-арил-1,3,4-тиадиазина, содержащие амины и циклоалкиламины в положении 2 тиадиазинового кольца. напротив, среди веществ со слабой ингибирующей способностью преобладали 5-гетерил-1,3,4-тиадиазины. таким образом, в проведенном исследовании впервые продемонстрирована способность ряда серосодержащих гетероциклических соединений класса 1,3,4-тиадиазинов ингибировать накопление начального продукта нгб фруктозамина при инкубации бычьего сывороточного альбумина с глюкозой, проведена оценка взаимосвязи между структурой соединений и противогликозилирующей активностью. выявленный биохимический механизм может иметь значение в реализации противодиабетической активности производных 1,3,4-тиадиазина. экспериментальная часть в данной работе впервые исследована способность 23 серосодержащих гетероциклических соединений класса 1,3,4-тиадиазинов блокировать реакцию нгб. в модельной системе, включавшей бычий сывороточный альбумин (sigma, сша) в концентрации 5 г/л, d-глюкозу и исследуемое вещество в эквимолярной концентрации 20 ммоль/л, определяли концентрацию первичного продукта нгб фруктозамина (фа) спектрофотометрическим методом по реакции с тиобарбитуровой кислотой через 1, 2, 4 и 7 недель инкубации. в качестве вещества сравнения, содержащего тиольную группу, в тех же условиях использовали восстановленный глутатион (merck, германия). в контрольном опыте бычий сывороточный альбумин инкубировали с d-глюкозой без ингибиторов нгб. рис. 2. возможный механизм блокады нгб производными 1,3,4-тиадиазниа 86 cta | № 1 | 2014 e. a. savateeva1, v. v. emelyanov1, a. v. musalnikova1, l. p. sidorova1, n. e. maksimova1, n. n. mochulskaya1, v. a. chereshnev1,2 1ural federal university, 28, mira street, 620002, ekaterinburg. e-mail: evvd@list.ru 2institute of immunology and physiology ubras, 106, pervomaiskaya street, 620049, eekaterinburg sulfur-containing heterocyclic compounds with potential antidiabetic activity the essential link in the pathogenesis of diabetes mellitus and its complications is a non-enzymatic glycosylation of proteins. however, modern endocrinology lacks of clinically effective pharmaceuticals for its correction. the screening of 23 derivatives of 1,3,4-thiadiazine the ability to inhibit the reaction of non-enzymatic glycosylation of proteins in vitro was held, and 11 the most active compounds of them were selected, also the relationship «structure – activity» was investigated. an essential part of the pathogenesis of diabetes mellitus and its complications is non-enzymatic glycosylation of proteins. however, modern endocrinology lacks clinically effective medicines for its correction. 1. pfeiffer w.-d. comprehensive heterocyclic chemistry iii, 2010, 9, 401. 2. patent ru2157210. 3. patent ru2379306. 4. emeliyanov v. v., savateeva e. a., maksimova n. e., mochulskaya n. n. chershnev v. a. materials of the annual conference “pharmacy and public health”, 25 feb 2010, ekaterinburg, 27. 5. emeliyanov v. v., maksimova n. e., mochulskaya n. n., chereshnev v. a. voprosy boil. medic. pharm. khimii, 2010, (1), 3. е. а. саватеева, в. в. емельянов, а. в. мусальникова, л. п. сидорова, н. е. максимова, н. н. мочульская, в. а. черешнев synthesis and properties of vanadium substituted bismuth tungstates with fluorite-like structure 46 d o i: 1 0. 15 82 6/ ch im te ch .2 01 9. 6. 2. 02 kaimieva o. s., sabirova i. e., buyanova e. s., petrova s. a. chimica techno acta. 2019. vol. 6, no. 2. p. 46–50. issn 2409–5613 o. s. kaimievaa, i. e. sabirovaa, e. s. buyanovaa, s. a. petrovab a institute of natural sciences and mathematics, ural federal university, 19 mira st., ekaterinburg 620002, russia b institute of metallurgy, ural branch of academy of sciences, 101 amundsena st., ekaterinburg 620026, russia e-mail: kaimi-olga@mail.ru synthesis and properties of vanadium substituted bismuth tungstates with fluorite‑like structure the samples of vanadium substituted bismuth tungstates with a cubic structure were obtained by solid state method. the unit cell volume of the compounds slightly contracts with increasing tungsten content and in case of vanadium doping. thermal expansion coefficient of bismuth tungstate is equal to 13·10–6 °c–1. the electrical conductivity was investigated using ac impedance spectroscopy. the results showed that the substitution of tungsten with vanadium ions increased electrical conductivity values by one order of magnitude. keywords: bismuth tungstate; fluorite-like structure; oxide-ion conductivity; solid electrolyte. received: 05.07.2019. accepted: 23.07.2019. published: 05.08.2019. © kaimieva o. s., sabirova i. e., buyanova e. s., petrova s. a., 2019 introduction δ-bi2o3 has the  highest value of electrical conductivity (1–1.5 ohm–1cm–1) among all known complex oxide electrolyte materials for electrochemical devices [1, 2]. the main disadvantage of this phase is that it is stable only within a limited temperature range (730–825 °c). a large number of  studies are connected with searching for the best way of its stabilization at room temperature preserving its characteristics. for this purpose, substitution with various suitable ions (nb5+, mo6+, ta5+, ti4+, w6+ etc.) is usually used [1–4]. it is found for bi2o3-wo3 system that the introduction of tungsten oxide (more than 9 wt.%) is a necessary condition for stabilization of δ-phase bi2o3 [5]. otherwise, β-bi2o3 appears. on the  other hand, a  homogeneity area of cubic structure on the phase diagram exists between compounds with compositions 2:1 and 5:1. bi6wo12 has fluorite-like structure as well. this compound melts congruently at 1040 °c and has reversible phase transition at 900 °c. so, as  it was shown by  wind [6, 7], bismuth tungstates with a fluorite-like structure are promising as compounds which have values of  electrical conductivity comparable with those of yttria-stabilized zirconia. three more stable cubic phases, bi22w5o48, bi22w4.5o47.25, and bi23w4o46.5, were obtained at  room temperature via quenching [6, 7]. in  case of  low cooling rate, a phase transition from cubic to tetragonal structure occurs at 700 °c. until now, many authors have agreed that the phase diagram of bi2o3–wo3 system is  complex enough and requires a  de47 tailed study. takahashi and iwahara [8] have done research on ionic properties of (bi2o3)1–x(wo3) x (x  = 0.05–0.5) and found extremely high oxide-ion conductivity for the  fcc structure over the  wide range of temperatures, up to at least 850 °c. the  conductivities in (bi2o3)0.78(wo3)0.22 are 0.01 and 0.15 ohm–1cm–1 at 500 and 880 °c, respectively. the oxide ion transfer number is close to 1 down to oxygen partial pressure p(o2) = 10 –15 atm [8]. there data on substituted bismuth tungstates bi22w5o48, bi22w4.5o47.25, bi23w4o46.5 have not been found in literature. therefore, the aim of this work is to obtain and study of the structure and physicochemical properties of bismuth tungstates doped with vanadium ions. experimental s a m p l e s b i 2 2 w 5 – x v x o 4 8 – δ , bi22w4.5–xvxo47.25–δ, bi23w4–xvxo46.5–δ (x = 0.0; 0.1) were prepared by solid-state method. metal oxides bi2o3 (99.99 %), wo3 (99.9 %), v2o5 (99.9 %) were taken as  precursors. the multi-step synthesis was carried out in  the  temperature range 400–1000  °c. annealing time was 8 hour at each stage. the synthesis into pressed bars was performed after annealing of powder samples at 700 °c. the samples were quenched after the last stage of the synthesis. the phase composition of  the  powders was determined by means of x-ray powder diffraction (dron3 diffractometer, russia, cu kα radiation). the phase purities of the compounds were confirmed by  comparing their xrd patterns with those in the pdf2 database. the density of sintered bars was estimated by archimedes method. dilatometric measurements were carried out on rectangular bars with the length of 23 mm using a dil 402 c netzsch dilatometer in the temperature range 20–900 °c with a heating rate of 2 °c/min. the electrical conductivity values were found by ac impedance spectroscopy method (impedance meter z-3000 “elins”, russia) using two-probe cell. the  measurements were performed in the temperature range 850– 200 °c and frequency span 3 mhz — 1 hz at the cooling mode. obtained impedance spectra were treated with “zview” software and equivalent circuits were fitted to them. using these data, the temperature dependences of  electrical conductivity (σ) were plotted in arrhenius coordinates –lgσ — 1000/t. results and discussion according to results of x-ray diffraction analysis, all obtained compounds were single-phase with cubic structure (space group fm3m). x-ray diffraction patterns of the bi22w5–xvxo48–δ, bi22w4.5–xvxo47.25–δ, bi23w4–xvxo46.5–δ (x  = 0.0–0.1) are given in fig. 1. the unit cell parameters are listed in table 1. as the radius of vanadium ions is smaller than that of tungsten ions (r(bi3+) = 0.60 å; r(w6+) = 0.60 å; r(v5+) = 0.54 å [9]), one can observe slight contraction of unit cell volume of the substituted compounds. the same tendency is found for the samples with increasing tungsten content and is reported in [6, 7]. on the whole, all experimental data which are obtained in the present work for matrix compounds are in a good agreement with previous results [6, 7]. for the further dilatometric and electrical conductivity measurements, the bismuth tungstates were pressed and sintered 48 into bars. volume porosity of the ceramics obtained at 850 °c was estimated by archimedes method. the average value was 10 %. for the bi23w4o46.5 sample, a peak was observed on the cooling curve of thermal expansion coefficient (tec) near 430 °c (fig. 2). this peak can be related to  the  presence of  the  phase transition from cubic to tetragonal structure [6, 7]. tec value of  the  bi23w4o46.5 equals to 13·10–6  °c–1 and is  close to  that for lanthanum manganite cathode materials. as  the  temperature of  the  measurement (900 °c) was higher than that for sintering of the bar (850 °c), there is hysteresis between the  heating and cooling curves on the temperature dependence of linear thermal expansion (fig. 2). the electrical conductivity was investigated by ac impedance spectroscopy using two-probe method. introducing of vanadium ions into the structure of bismuth tungstate leads to significant reduction of samples’ resistance. the equivalent circuits were matched to impedance spectra to describe processes taking place in the samples during the measurements (fig. 3). the circuits can be divided into two types. for the hightemperature range, general resistivity of the samples can be defined (r1) (fig. 3). other elements of this circuit (r2+cpe1, r3+cpe2) are related to electrode processes because the value of their capacity is equal to 4×10–4 f. but at low temperatures it is possible to estimate volume and grain boundary contribution to the electrical conductivity value (fig. 3). for example, for the composition bi22w4.9v0.1o48–δ, the volume resistance (r1) equals to 14 kohm at capacity (cpe1) table 1 the unit cell parameters of the bismuth tungstates composition а ± 0.001, å v ± 0.03, å3 bi23w4o46.5 5.569 172.73 bi23w3.9v0.1o46.5–δ 5.569 172.60 bi22w4.5o47.25 5.562 172.05 bi22w4.4v0.1o47.25–δ 5.558 171.72 bi22w5o48 5.549 170.85 bi22w4.9v0.1o48–δ 5.546 170.60 fig. 2. temperature dependence of linear thermal expansion and tec for the sample bi23w4o46.5 fig. 1. x-ray diffraction pattern of the bismuth tungstates 49 3×10–11  f, the  grain boundary resistance (r2) to 185 kohm at 2×10–5 f (cpe2). temperature dependences of the general electrical conductivity of the bismuth tungstates were plotted using the data of the impedance spectra (fig. 4). the results show that the substitution of tungsten with vanadium ions increases electrical conductivity values by one order of magnitude. the activation energy values for all bismuth tungstates are between 0.88–1.02 ev (table 2), indicating that the samples have ionic type of conductivity. according to our measurements, bi23w3.9v0.1o46.5–δ possesses the  highest conductivity of all oxides studied (σ850 = 0.13 ohm–1cm–1). conclusions to sum up, the solid solutions based on bismuth tungstates with fluorite-like structure were obtained by solid state method. the  unit cell volume of  the  compounds slightly contracts with increasing tungsten content and in case of vanadium doping. fig. 4. temperature dependences of the general electrical conductivity of the bismuth tungstates fig. 3. impedance spectra of the bi22w4.9v0.1o48–δ at 800 °c and 400 °c table 2 electrical conductivity (σ) and activation energy (ea) values of the bismuth tungstates composition еa, ev σ750, ohm –1cm–1 σ500, ohm –1cm–1 bi23w4o46.5 0.99 7.74·10 –2 1.30·10–2 bi23w3.9v0.1o46.5–δ 0.88 2.85·10 –1 6.69·10–2 bi22w4.5o47.25 1.00 5.92·10 –3 7.66·10–5 bi22w4.4v0.1o47.25–δ 1.02 7.84·10 –3 1.30·10–4 bi22w5o48 0.92 1.01·10 –1 1.91·10–2 bi22w4.9v0.1o48–δ 0.95 1.82·10 –1 3.50·10–2 50 tec of the bi23w4o46.5 sample is equal to 13·10–6 °c–1. a small peak on the cooling curve was observed at 430 °c, which can be contributed to the phase transition from cubic to tetragonal phase. the introduction of vanadium ions into bismuth tungstate structure has a positive effect on the electrical conductivity (the bi23w4.9v0.1o46.5–δ has the highest value σ850 = 0.13 ohm –1cm–1). acknowledgements this work was performed within the state assignment of the ministry of education and science of the russian federation no. 4.2288.2017/4.6. powder x-ray diffraction studies were performed on the equipment of the ural-m shared facility center of the institute of metallurgy of the ural branch of the russian academy of sciences (imet ub ras). references 1. shuk p, wiemhöfer h-d, guth u, göpel w, greenblatt m. oxide ion conducting solid electrolytes based on bi2o3. solid state ionics. 1996;89:179–96. doi: 10.1016/0167–2738(96)00348–7. 2. azad am, larose s, akbar sa. bismuth oxide-based solid electrolytes for fuel cells. journal of materials science. 1994;29:4135–51. doi: 10.1007/bf00414192. 3. ling cd, johnson m. modelling, refinement and analysis of the ‘type iii’ δ-bi2o3related superstructure in the bi2o3–nb2o5 system. journal of solid state chemistry. 2004;177:1838–46. doi: 10.1016/j.jssc.2004.01.003. 4. firman k, tan kb, khaw cc, zainal z, tan yp, chen sk. doping mechanisms and electrical properties of bismuth tantalite fluorites. journal of materials science. 2017;52:10106–18. doi: 10.1007/s10853–017–1216–1. 5. mokhosoev mv, alekseev fp, lutsyk vi. diagrammy sostoyaniya molibdatnykh i vol’framatnykh system [state diagrams of molybdate and tungstate systems]. novosibirsk: nauka, 1978. 320 p. russian. 6. wind j, auckett je, withers rl, piltz ro, maljuk a, ling cd. type ii bi1–xwxo1.5+1.5x: a (3+3)-dimensional commensurate modulation that stabilizes the fast-ion conducting delta phase of bismuth oxide. acta crystallographica b. 2015;71:679–87. doi: 10.1107/s2052520615018351. 7. wind j, kayser p, zhang z, evans ir, lind cd. stability and range of the type ii bi1–xwxo1.5+1.5x solid solution. solid state ionics. 2017;308:173–80. doi: 10.1016/j.ssi.2017.07.015. 8. takahashi t, iwahara h. high oxide ion conduction in sintered oxides of system bismuth oxide — tungsten oxide. journal of applied electrochemistry. 1973;3:65–72. doi: 10.1007/bf01119469. 9. shannon rd. revised effective ionic radii and systematic studies of interatomie distances in halides and chalcogenides. acta crystallographica a. 1976;32:751–67. doi: 10.1107/s0567739476001551. phase equilibria in the tl2moo4–r2(moo4)3–zr(moo4)2 (r = al, cr) systems: synthesis, structure and properties of new triple molybdates tl5rzr(moo4)6 and tlrzr0.5(moo4)3 218 grossman v.g., bazarov b.g., bazarova zh.g. chimica techno acta. 2017. vol. 4, no. 4. p. 218–223. issn 2409–5613 d o i: 1 0. 15 82 6/ ch im te ch /2 01 7. 4. 4. 02 v.g. grossman1, b.g. bazarov1,2, zh.g. bazarova2 1baikal institute of nature management, siberian branch of russian academy of sciences, 8 sakh’yanovoi st., ulan-ude, 670047, russian federation e-mail: grossmanv@mail.ru 2buryat state university, 24a smolinast., ulan-ude, 670000, russian federation phase equilibria in the tl 2 moo 4 –r 2 (moo 4 ) 3 –zr(moo 4 ) 2 (r = al, cr) systems: synthesis, structure and properties of new triple molybdates tl 5 rzr(moo 4 ) 6 and tlrzr 0.5 (moo 4 ) 3 the tl 2 moo 4 –r 2 (moo 4 ) 3 –zr(moo 4 ) 2 (r = al, cr) systems were studied in the subsolidus region using x-ray powder diffraction and differential scanning calorimetric (dsc) analysis. quasi-binary joins were revealed, and triangulation was carried out. new ternary molybdates tl 5 rzr(moo 4 ) 6 (5:1:2) and tlrzr 0.5 (moo 4 ) 3 (1:1:1) (r = al, cr) were prepared. the unit cell parameters for the new compounds were calculated. keywords: phase equilibria, synthesis, systems, thallium, zirconium, iron, aluminum, crystal structure, space group. received: 23.10.2017; accepted: 01.12.2017; published: 25.12.2017. © grossman v.g., bazarov b.g., bazarova zh.g., 2017 introduction this paper is a continuation of our systematic studies of phase relations in the tl2moo4–r2(moo4)3–a(moo4)2 (r – trivalent metals, а = zr, hf ) ternary salt systems [1]. earlier we studied phase equilibria in the tl2moo4–fe2(moo4)3– hf(moo4)2 system [2]. subsolidus phase diagrams for this system and constituent double systems were constructed, and triple molybdates tl5fehf(moo4)6 and tlfehf0.5(moo4)3 had been detected. the aims of the present study include (1) investigation of phase equilibria in the ternary salt systems tl2moo4–r2(moo4)3– zr(moo4)2 (r = al, cr), (2) determination of optimal condition for the solid state synthesis of ternary molybdates found in these systems, and (3) determination of crystallographic and thermal characteristics of the obtained compounds. experimental subsolidus phase relations in the tl2moo4–r2(moo4)3–zr(moo4)2 (r = al, cr) systems were studied in the subsolidus region (500–550  °c) using the intersecting joins method. the corresponding molybdates of thallium, aluminum, chromium and zirconium were used as initial components for studying the phase equilibria in the tl2moo4–r2(moo4)3–zr(moo4)2 (r = al, 219 cr) systems. synthesis of tl2moo4 was carried out according to the reaction tl2o3+moo3→tl2moo4+o2↑ at gradually increasing temperature in the range 400–550  °с for 50  h. the high temperature modification of zr(moo4)2 was prepared by annealing of stoichiometric mixture of binary oxides zro2 and moo3 at 400–700  °с for 100 h. aluminum molybdate and chromium molybdate were obtained by calcination of stoichiometric mixtures of precursors al(no3)3·9h2o, сr2o3, and moo3 in the temperature range 400–650 °с for 100 h. the initial stage of each synthesis was chosen as 400 °с since moo3 possesses high volatility at tempera ture about 600  °с. to ensure better homogenization, the reaction mixtures were ground in ethanol every 20–30 h during firing. after annealing, the samples were slowly cooled in the furnace. the nonequilibrium samples were additionally annealed. it was assumed that equilibrium is reached if the phase composition of the samples remains unchanged during two consecutive anneals. the crystallographic parameters of the synthesized compounds were close to those reported in literature [3–5]. x-ray powder diffraction (xrd) measurements were performed using bruker d8 advance diffractometer (bragg–brentano geometry, cu kα radiation, secondary monochromator, maximum angle 2θ=100°, scan step 0.02°). the differential scanning calorimetric (dsc) analysis of the samples was carried out using netzch sta 449c (jupiter, germany) thermoanalyzer. compounds’ pellets were placed in a pt-crucible, heated up and then cooled down in argon atmosphere with the heating and cooling rate of 10 k/min. results and discussion the information about the phase formation in the tl2moo4–r2(moo4)3– zr(moo4)2 (r = al, cr) systems, which represent the bounding sides of the stu died system, were taken from previous papers [3–5]. the formation of double molybdates with general composition tlr(moo4)2 was detected in the boundary tl2moo4–r2(moo4)3 systems [3]. two double molybdates tl8zr(moo4)6 and tl2zr(moo4)3 were formed in the tl2moo4–zr(moo4)2 system [4]. no intermediate compounds were found in the r2(moo4)3–zr(moo4)2 systems [5]. in order to find new triple molybdates, the subsolidus phase equilibria in the tl2moo4–r2(moo4)3–zr(moo4)2 (r = al, cr) systems were studied at 500–550  °c and its triangulated phase diagrams were constructed. solid-state interactions between tl2moo4, r2(moo4)3, and zr(moo4)2, which occurred over wide ranges of temperature and concentration, led to the formation of new triple molybdates tl5rzr(moo4)6 (5:1:2 mole ratio) s1 and tlrzr0.5(moo4)3 (1:1:1 mole ratio) s2. compound s2 was found at the intersection point of the r2(moo4)3–tl2zr(moo4)3 and tlr(moo4)2–zr(moo4)2 joins. the triple molybdate (s1) locates inside the triangle with the double molybdates tlr(moo4)2, tl8zr(moo4)6 and tl2zr(moo4)3 in its vertices. the phase relations in the tl2moo4– r2(moo4)3–zr(moo4)2 (r = al, cr) systems are shown in fig. 1. individual tl5rzr(moo4)6 (r = al, cr) oxides were prepared by firing at 450– 550 °с for 150–200 h, and the molybdates tlrzr0.5(moo4)3 (r = al, cr) were obtained by firing at temperatures from 500 to 600 °с for 100–150 h. 220 the single phase tl5alzr(moo4)6 was not synthesized under the conditions of our experiment. the analysis of x-ray diffraction patterns of the compounds obtained shows that the reflection positions and their intensity ratio for tlrzr0.5(moo4)3 and tl5rzr(moo4)6 (r = al, cr) are similar to tlfehf0.5(moo4)3 [2] and rb5erhf(moo4)6 [6], respectively. it could be concluded that tlrzr0.5(moo4)3 is isostructural to tlfehf0.5(moo4)3 and tl5rzr(moo4)6 is isostructural to rb5erhf(moo4)6. three dimensional framework of the tlfehf0.5(moo4)3 crystal structure (a = b = 13.0324(2) å, c = 11.8083(3) å, v = 1736.87(6) å3, ρcalc=4.757 g/cm 3, space group r3, z = 6) is composed of the motetrahedra sharing o vertices with the (fe, hf )o6 octahedra, with thallium atoms occupying wide channels in the framework [2] (figs. 2 and 3). the arrangement of tl atoms (pink spheres) in the structural channel in tlfehf0.5(moo4)3 is shown in fig. 3. rb5erhf(moo4)6 possesses the trigonal crystal structure: a = 10.7511(1) å, c = 38.6543(7) å, v = 3869.31(9) å3, ρcalc=4.462 g/cm 3, z = 6, space group r3c [6]. the three-dimensional framework of the structure is formed of the moo4 tetrahedra, which are sharing corners with two ero6 and hfo6 octahedra (fig. 4). two types of rb atoms occupy large cavities in the framework. the particular arfig. 2. the framework of tlfehf0.5(moo4)3 crystal structure that consists of moo4 tetrahedra and (fe, hf )o6 octahedra in the projection of layer onto the (001) plane (tl atoms are represented by pink spheres) fig. 3. the fragment of the tlfehf0.5(moo4)3 crystal structure that is projected onto the (010) plane fig. 1. subsolidus phase relations in the tl2moo4–r2(moo4)3–zr(moo4)2 (r = al, cr) systems: s1 −tl5rzr(moo4)6 (5:1:2 mole ratio) and s2 – tlrzr0.5(moo4)3 (1:1:1 mole ratio) tl2moo4 zr(moo4)2 r2(moo4)3 s1 s2 1:1 4:1 1:1 221 rangement of rb atoms in the structural channel is shown in fig. 5. the distribution of the er3+ and hf4+ cations over two positions is obtained during the structure refinement. the unit cell parameters for the synthesized triple molybdates tlrzr0.5(moo4)3 (r = al, cr) were refined using uniquely-indexed lines for the tlfehf0.5(moo4)3 single crystal [2]. the lines for tl5crzr(moo4)6 were indexed using rb5erhf(moo4)6 [6] as analogous isostructural compound. the unit cell parameters that were refined using the topas-4 software are listed in table 1 along with the melting points of the corresponding compounds. fig. 6 illustrates good coincidence of the experimental and calculated profiles. as shown in table 1, the unit cell parameters and volume of tlrzr0.5(moo4)3 (r = al, cr) and tl5crzr(moo4)6 increase with the substitution of 6-coordinated aluminum cations (r = 0.535 å) with a larger chromium cation (r = 0.615  å) [7]. the linear dependence of the unit cell volume on the trivalent element radii is also in accordance with tlrzr0.5(moo4)3 (r = al, table 1 the unit cell parameters and melting points of tlrzr0.5(moo4)3 (r = al, cr) and tl5crzr(moo4)6 in comparison with literature data compound unit cell parameters (å) t, °c a, å c, å v, å3 space group; z tlfehf0.5(moo4)3 [2] tlalzr0.5(moo4)3 tlcrzr0.5(moo4)3 13.0324(2) 12.5935(6) 12.6961(6) 11.8083(3) 11.5946(8) 11.7022(9) 1736.87(6) 1592.5(2) 1633.6(2) r3; 6 811 751 842 rb5erhf(moo4)6 [6] tl5crzr(moo4)6 10.7511(1) 10.4047(8) 38.6543(7) 37.5322(3) 3869.31(9) 3518.8(6) r3c; 6 730 599 fig. 4. complex framework of the rb5erhf(moo4)6 crystal structure built of the moo4 tetrahedra and (er, hf )o6 octahedra. red parallelogram shows the projection of a layer onto the (001) plane. the rb atoms are represented by the orange spheres fig. 5. crystal structure of rb5erhf(moo4)6 as projected on plane (133) 222 cr) and tl5crzr(moo4)6 belonging to one structural family. two endothermic effects are observed on the dsc curves (fig. 7). the first one corresponds to some structural changes that, however, are not accompanied by the change of a structural type. the last endothermic effect corresponds to the melting of the studied compounds. conclusions new triple molybdates with general compositions tl5rzr(moo4)6 (5:1:2) and tlrzr0.5(moo4)3 (1:1:1) (r = al, cr), respectively, were obtained in the thalliumcontaining systems with trivalent metals and zirconium. the formation of these triple molibdates occurs similarly to the formation of ternary molibdate tl(fehf0.5) fig. 7. dsc curves for tlrzr0.5(moo4)3 (r = al, cr) and tl5crzr(moo4)6 fig. 6. measured (red), calculated (black) and differential (blue) powder diffraction patterns for tlcrzr0.5(moo4)3 (a), tlalzr0.5(moo4)3 (b) and tl5crzr(moo4)6 (c) a b c 223 (moo4)3 in previously studied tl2moo4– fe2(moo4)3−hf(moo4)2 system [2]. the phase relations do not change with hafnium (r = 0.71  å) being substituted with zirconium (r = 0.72 å) [7]. acknowledgements this work was carried out according to the state assignment binm sb ras (project no. 0339-2016-0007). references 1. grossman vg, bazarov bg, bazarova zhg. subsolidus phase diagrams for the tl2moo4–ln2(moo4)3–hf(moo4)2 systems, where ln = la–lu. russ j inorg chem. 2008;53(11):1788–94. doi:10.1134/s003602360811020x 2. grossman vg, bazarov bg, klevtsova rf, glinskaya la, bazarova zhg. phase equilibria in the tl2moo4–fe2(moo4)3–hf(moo4)2 system and the crystal structure of ternary molybdate tl(fehf0.5)(moo4)3. russ chem bull. 2012;61(8):1546–9. doi:10.1007/s11172-012-0202-7 3. pleskov my, morozov va, lazoryak bi, zhizhin mg, burdakova ib, khalbaeva km, tsyrenova gd, khaikina eg. structures of double molybdates tlr(moo4)2 (r = in, sc, fe, cr, al). russ j inorg chem. 2005(4);50:604–14. 4. bazarov bg, klevtsova rf, bazarova tst, glinskaya la, fedorov kn, bazarova zhg, chimitova od. systems tl2moo4–e(moo4)2, where e = zr or hf, and the crystal structure of tl8hf(moo4)6. russ j inorg chem. 2006;51(5):794–9. doi:10.1134/ s0036023606050184 5. tushinova yul, bazarova zhg, archincheyeva si. abstracts of the reports. ulanude (russia): publishing house of bsc sb ras; 2002. p. 90–1. russian. 6. bazarov bg, klevtsova rf, chimitova od, glinskaya la, fedorov kn, tushinova yul, bazarova zhg. phase formation in the rb2moo4–er2(moo4)3–hf(moo4)2 system and the crystal structure of new triple molybdate rb5erhf(moo4)6. russ j inorg chem. 2006;51(5):800–4. doi:10.1134/s0036023606050196 7. shannon rd. revised effective ionic radii and systematic studies of interatomic distances in halides and chalcogenides. acta cryst. 1976;a32:751–67. doi:10.1107/ s0567739476001551 cite this article as: grossman vg, bazarova bg, bazarova zhg. phase equilibria in the tl2moo4– r2(moo4)3–zr(moo4)2 (r = al, cr) systems: synthesis, structure and properties of new triple molybdates tl5rzr(moo4)6 and tlrzr0.5(moo4)3. chimica techno acta. 2017;4(4):218–23. doi:10.15826/chimtech/2017.4.4.02. phase relations in the me2moo4?in2(moo4)3?hf(moo4)2 systems, where me = li, k, tl, rb, cs 126 d o i: 1 0. 15 82 6/ ch im te ch .2 01 8. 5. 3. 01 j. g. bazarova*, yu. l. tushinova, v. g. grossman, ts. t. bazarova, b. g. bazarov, r. v. kurbatov baikal institute of nature management siberian branch of the russian academy of sciences 8 sakh’yanovoi st., ulan-ude, buryat republic, russian federation *e-mail: jbaz@binm.ru phase relations in the me2moo4–in2(moo4)3–hf(moo4)2 systems, where me = li, k, tl, rb, cs the me2moo4–in2(moo4)3–hf(moo4)2 systems where me = li, k, tl, rb, cs were studied in the subsolidus region using an x-ray powder diffraction. quasi-binary joins were revealed, and triangulation carried out. the formation of ternary molybdates me5inhf (moo4)6 for me = k, tl, rb, cs and мe2inhf2(moo4)6.5 for me = rb, cs was established. keywords: phase relations, triangulation, solid-phase reactions, x-ray phase diffraction, molybdates. received: 26.09.2018. accepted: 12.10.2018. published: 31.10.2018. © bazarova j. g., tushinova yu. l., grossman v. g., bazarova ts. t., bazarov b. g., kurbatov r. v., 2018 introduction ternary molybdates attract attention due to their catalytic and ionexchange properties and the diversity of their crystal structures. the moo6 octahedra are usually highly distorted because of the relatively small effective radius of the mo6+ ion in the oxygen environment, which is favorable for the formation of low-symmetry crystal structures. systematic studies of multicomponent systems allow obtaining the large amount of  data which make it possible to  identify regularities of  the phase formation in related systems. in our previous works, the phase equilibria in the me2moo4–r2 (moo4)3–hf(moo4)2 (me = rb, cs; r — trivalent metals) systems were studied [1, 2]. the purpose of this work was to establish the phase formation in the me2moo4– in2(moo4)3–hf (moo4)2 systems where me = li, k, tl, rb, cs. experimental subsolidus phase relations in  the me2moo4–in2(moo4)3–hf(moo4)2 (me = li, k, tl, rb, cs) systems were studied within the temperature range 450–550 °c using the intersecting joins method. the correspondent molybdates of lithium, potassium, thallium, rubidium, cesium, indium and hafnium were used as  starting components for  studying the phase equilibria in  the me2moo4– in2(moo4)3–hf(moo4)2 (me  = li, k, tl, rb, cs) systems. in order to avoid moo3 losses due to the sublimation, annealing was started at  400 °c.  synthesis of  thalbazarova j. g., tushinova yu. l., grossman v. g., bazarova ts. t., bazarov b. g., kurbatov r. v. chimica techno acta. 2018. vol. 5, no. 3. p. 126–131. issn 2409–5613 127 lium molybdate tl2moo4 was performed according to the following reaction: tl2o3+moo3 → tl2moo4+o2↑ while the temperature was gradually increased in the range of 400–550 °с for 50 h. binary alkali molybdates me2moo4 (me  = li, k, rb, cs) were synthesized by  the solid-state reaction using stoichiometric mixtures of alkali carbonates or  nitrates with molybdenum trioxide for 80–100 h. hafnium molybdate was prepared by step annealing of stoichiometric mixtures of hfo2 and moo3 within the temperature range 400–700 °c for 100–150 h. indium molybdate was synthesized from indium oxide (iii) in2o3 and molybdenum oxide (vi) moo3 by  solid-state reaction at 500–700 °c. x-ray powder diffraction (xrd) measurements were performed using a bruker d8 advance diffractometer (bragg — brentano geometry, cu kα radiation, secondary monochromator, maximum angle 2θ = 100°, scan step 0.02°). results and discussion information about the known phases in  the side quasi-binary systems, which formed studied quasi-ternary me2moo4– in2(moo4)3–hf(moo4)2 (me = li, k, tl, rb, cs) systems, required for triangulation, was taken from the literature. according to solodovnikov et al. [3], the li2moo4– hf(moo4)2 system contains a lithium hafnium molybdate li10–4xhf2+x(moo4)9 (0.21 ≤ x ≤ 0.68). two types of  double molybdates, me8hf(moo4)6 and me2hf(moo4)3 (me  = k, tl, rb, cs), are formed inside the me2moo4–hf(moo4)2 systems [4–6]. an existence of  the double molybdates, namely: li3in(moo4)3, mein(moo4)2 (me = li, k, tl, rb, cs), and me5in(moo4)4 (me = tl, rb) was confirmed in the me2moo4– in2(moo4)3 systems [7–10]. no intermediate compounds were found inside the in2(moo4)3–hf(moo4)2 system [11]. taking into account the aforementioned data, the phase formation in the me2moo4– in2(moo4)3–hf(moo4)2 (me = li, k, tl, rb, cs) systems were studied by means of socalled “intersection joins method”. within this approach, we analyzed the xrd results for the samples representing the intersection points of  the joins that connect the starting components and phases inside the quasi-binary systems. this makes it possible to  establish the quasi-binary joins and, as  a  result, to  implement the triangulation of  the system. since the phase relations in the k2moo4–in2(moo4)3 and cs2moo4–in2(moo4)3 systems enriched by either potassium molybdate or by cesium molybdate were found to  be nonquasibinary, the studies of the me2moo4– in2(moo4)3–hf(moo4)2 (me  = k, cs) systems were limited to the hf(moo4)2– me8hf(moo4)6–mein(moo4)2–in2(moo4)3 (me = k, cs) regions. the results obtained are presented in fig. 1 and fig. 2. all systems under investigation can be categorized into three groups depending on the phase compositions of the binary subsystems and triple molybdates. the first group comprises the li2moo4– in2(moo4)3–hf(moo4)2 simple eutectic system without intermediate phases inside. the second group consists of  the me2moo4–in2(moo4)3–hf(moo4)2 systems where me = k and tl, with one intermediate phase, denoted in  fig.  1 as s — me5inhf(moo4)6 (5:1:2 mole ratio). the third group includes the me2moo4– 128 in2(moo4)3–hf(moo4)2 systems where (me  = rb, cs), with two intermediate phases: s1 − me5inhf(moo4)6 (5:1:2 mole ratio) and s2  — me2inhf(moo4)6 (2:1:4 mole ratio). s i n g l e p h a s e s a m p l e s o f me5inhf(moo4)6 (me  = k, tl, rb, cs) fig. 1. subsolidus phase relations in the me2moo4–in2(moo4)3–hf (moo4)2 (me = li, k, tl) systems: s − me5inhf(moo4)6 (5:1:2 mole ratio) fig. 2. subsolidus phase relations in the me2moo4–in2(moo4)3–hf(moo4)2 (me = rb, cs) systems: s1 − me5inhf (moo4)6 (5:1:2 mole ratio); s2 — me2inhf(moo4)6 (2:1:4 mole ratio) 129 and me2inhf(moo4)6 (me = rb, cs) were prepared by  annealing the stoichiometric mixtures of quasi-binary molybdates at 450–600 °c for 80–100 h. ternary molybdates me5inhf(moo4)6 (me  = k, tl, rb, cs) and me2inhf(moo4)6 (me = rb, cs) are insoluble in  water and usual organic solvents, but were found to be soluble in hcl aqueous solution. t h e t e r n a r y m o l y b d a t e s me5inhf(moo4)6 (me = k, tl, rb, cs) are located inside the triangle that is formed by  the double molybdates mer(moo4)2, me8hf (moo4)6 and me2hf(moo4)3 in its vertices. the number of  phases formed in  the systems under consideration increases as  the size of  the singly charged alkali cation increases. the only exception is thallium-containing system. a distinctive feature of thallium is that it combines properties of alkali metals, such as potassium, rubidium, and cesium, together with those related to heavy metals, such as copper (i), silver, and lead [12]. the single crystals of  new ternary potassium indium hafnium molybdate k5inhf(moo4)6 were grown by  fluxedmelt crystallization with spontaneous nucleation [13]. the composition and crystal structure of  as-grown single crystals were refined using x-ray diffraction data (a cad-4 automated diffractometer, mo kα radiation, 1498 reflections, r = 0.0252). the crystal structure was solved as trigonal with the following unit cell parameters: a = 10.564 (1) å, c = 37.632 (4) å, v = 3637.0 (6) å3, z = 6, space group r3c. a threedimensional mixed framework of  the structure is formed by mo tetrahedra and two independent (in, hf ) octahedra, which are connected through the shared vertices. two types of potassium atoms occupy the large voids within the framework. the distribution of in3+ and hf 4+ cations over two different sites was refined as  presented in the caption for fig. 3. fig.  4 illustrates the ir and raman spectra for  the triple rubidium indium fig. 3. mixed framework of moo4 tetrahedra (blue color) and two types of octahedra (in, hf )o6 in the k5inhf(moo4)6 crystal structure. m(1) = 0.413(1)hf + 0.587(1)in (olive color); m(2) = 0.587(1)hf + 0.413(1)in (burgundy color) 130 hafnium molybdate rb2inhf2(moo4)6.5. since the oscillation frequencies in the ir and raman spectra differ from each other, one can assume that ternary molybdate rb2inhf2(moo4)6.5 and its analogues are centrosymmetric. conclusions the phase equilibria in quasi-ternary salt systems were studied; six new compounds were identified inside the studied systems. the phase relations in  the me2moo4–in2(moo4)3–hf(moo4)2 (me = li, k, tl, rb, cs) systems are influenced by  the size factor and the nature of  the singly charged alkali cation. acknowledgements the work was carried out according to the state assignment binm sb ras (project no. 0339-2016-0007) and rfbr, grants nos. 18-03-00799. references 1. bazarov bg, klevtsova rf, bazarova tst, glinskaya la, fedorov kn, tsyrendorzhieva ad, chimitova od, bazarova jg. phase equilibria in  the systems rb2moo4–r2(moo4)3–hf(moo4)2 (r = al, in, sc, fe (iii)) and the crystal structure of double molybdate rbfe(moo4)2. russ j inorg chem. 2006;51(7):1111–5. doi: 10.1134 / s0036023606070151. 2. bazarova jg, tushinova yl, bazarov bg, oyun be, angarhayev jd. phase equilibrium in the systems cs2moo4–r2(moo4)(3)–hf(moo4)(2) (r = al, cr, fe, bi, la-lu). izvestiya vuzov prikladnaya khimiya i biotekhnologiya. 2018;8(2):19–28. doi: 10.21285 / 2227-2925-2018-8-2-19-28. 3. solodovnikov sf, balsanova lv, bazarov bg, zolotova es, bazarova zhg. phase formation in the rb2moo4–li2moo4–hf(moo4)2 system and the crystal structure of rb5(li1 / 3hf5 / 3)(moo4)6. russ j inorg chem. 2003;48(7):604–14. 4. bazarov bg, klevtsova rf, bazarova tst, glinskaya la, fedorov kn, bazarova zhg, chimitova od. systems tl2moo4–e(moo4)2, where e = zr or  hf, and the crystal structure of  tl8hf(moo4)6. russ j inorg chem. 2006;51(5):794–9. doi: 10.1134 / s0036023606050184. fig. 4. ir and raman spectra of rb2inhf2(moo4)6.5 131 5. trunov vk, efremov va, velikodny yua. crystal chemistry and properties of double molybdates and tungstates. leningrad: nauka; 1986. 173 p. russian. 6. klevtsova rf, zolotova es, glinskaya la, klevtsov pv. synthesis of double zirconium and hafnium molybdenum with cesium and crystal structure cs8zr(moo4). kristallografiya. 1980;25 (5):972. 7. velikodny yua, trunov vk, markelova ni. reaction of alkali metal molybdates (li, na, k) with indium molybdate. russ j inorg. chem. 1970;15(11):1587–1592. 8. velikodny yua, efremov va, trunov vk. crystal structure of high temperature α-liin(moo4)2. kristallografiya. 1980;25(1):165–8. 9. khaikina eg. synthesis, peculiarities of phase formation and the structure of double and triple-molibdate one — and trivalent metals [dissertation]. novosibirsk (russia); 2008. 39 p. 10. pleskov my, morozov va, lazoryak bi, zhizhin mg, burdakova ib, khalbaeva km, tsyrenova gd, khaikina eg. structures of double molybdates tlr (moo4)2 (r = in, sc, fe, cr, al). russ j inorg chem. 2005;4 (50):604–14. 11. tushinova yul, bazarova zhg, archincheyeva si. abstracts of  the reports  — ulan-ude: publishing house of bsc sb ras. 2002:90–91. russian. 12. nekrasov bn. principles of general chemistry. moscow: khimiya; 1967. 216 p. russian. 13. bazarov bg, klevtsova rf, bazarova tt, glinskaya la, fedorov kn, bazarova zg. synthesis and crystal structure of triple molybdate k5inhf(moo4)6. russ j inorg chem. 2005;50(8):1146–9. sodium intercalation into αand β-voso4 31 d o i: 1 0. 15 82 6/ ch im te ch .2 01 9. 6. 1. 04 deriouche w., anger e., amdouni n., pralong v. chimica techno acta. 2019. vol. 6, no. 1. p. 31–36. issn 2409–5613 w. deriouchea,b, e. angera, n. amdounib, v. pralonga,* a normandie univ, ensicaen, unicaen, cnrs, crismat, 14000 caen, france b unite de recherche physico-chimique des materiaux condenses, universite tunis el manar, faculte des sciences de tunis, campus universitaire, 2092 el manar tunis, tunisia e-mail: valerie.pralong@ensicaen.fr sodium intercalation into αand β-voso4 na-ion battery is one of the best alternatives to li-ion battery. abundance of sodium on earth is three orders of magnitude higher than lithium, which should make na-ion battery technology cheaper. but alkaline-ion battery prices, which tend to increase because of the massive world demand, also depend on the choice of electrode materials. therefore, cost-effective electrode development remains an important subject of research because this will allow na-ion battery to be even more competitive. electrochemical performances of anhydrous voso4 as electrode for na-ion battery are reported in this letter. two anhydrous phases of vanadyl sulfate have been studied. the first one, α-voso4, shows that up to 0.8 sodium per formula unit (na / f.u.) can be intercalated in this phase, and a reversible intercalation of 0.4 na / f.u. has been observed with a strong polarization. the second one, β-voso4, can intercalate up to 0.9 na / f.u. with a reversible intercalation of 0.4 na / f.u. leading to a reversible capacity of 64 mah / g. keywords: voso4; na-ion batteries; cathode; vanadium sulfate. received: 12.02.2019. accepted: 19.03.2019. published: 29.03.2019. © deriouche w., anger e., amdouni n., pralong v., 2019 introduction the search for new materials that could be used as electrode material for the na-ion batteries is one of today’s most challenging issues. many families of transition metal oxides as well as transition metal polyanionic frameworks have been proposed these last five years. among them, nasuper-ionic-conductors (nasicon) are one the most popular materials due to their good cycling ability and na+ mobility. however, sulfates represent an interesting and low-cost class with only few reported members. therefore, few sodiated iron sulfates [1–4] can be found in the literature and only one example of sodiated vanadate sulfate has been reported up to date (na2vo(so4)2) as an electrode material for na-ion battery [5]. this material delivers a reversible capacity of 60 mah / g at 4.5 v vs na+ / na. in this work, we report the use of anhydrous vanadyl sulfate as  an electrode material for  na-ion battery. anhydrous voso4 exists in two forms at room temperature: α-voso4 is tetragonal and is formed by dehydration of its hydrate below 280 °c [6], β-voso4 is orthorhombic and may be prepared either from the reaction of h2so4 and v2o5 [7] or by dehydration 32 above 280 °c, although decomposition occurs when using this last method [8]. the charge-discharge profile of  both known phases, αand β-voso4, will be discussed. experimental the alpha form, α-voso4, was prepared by a simple dehydration of voso4·xh2o (5 g, sigma aldrich) at 260 °c for 2 days, then stored in a glove-box to prevent rehydration from air moisture. on the other hand, β-voso4 was prepared by  a  precipitation reaction starting from stoichiometric amounts of  hydrated vanadium oxysulfide voso4·xh2o (1.8 g) heated at  140  °c in  100 ml of  sulphuric acid solution (0.1m h2so4) for  2 hours. the resulted green mixture was then filtered and washed with water. the obtained powder is then left overnight at 160 °c in an oven before being stored in  argon-filled glove-box. the compounds were characterized by x-ray powder diffraction (xrd) using a  philips x’pert 2 diffractometer with bragg-brentano geometry (cu kα radiation). note that due to their instability in  air, the reduced phases’ xrd patterns were registered under vacuum using a  chamber attached to  the xrd instrument. the electrochemical characterization was performed in cells build in swagelok compression tube fitting with a  solution 1m naclo4 in propylene carbonate (pc) as electrolyte and metallic sodium as counter electrode. the working electrode was prepared from a mixture of active material with acetylene black in a weight ratio of 50:50. the electrochemical cells were cycled at constant current between 1.0–3.0 v at different galvanostatic rates on a vmp iii potentiostat / galvanostat (biologic sa, claix, france) at room temperature. results and discussion first report on preparation of the phase alpha of  anhydrous vanadyl sulfate was published in 1965 by j. tudo [6]. its crystal structure was optimized and its magnetic properties studied by r. j. arnott and j. m. longo in 1970 [9]. they suggest that trace of water was present in tudo’s sample. this phase crystallizes within a tetragonal structure (space group: p4 / n) with a  = 6.258 å, c = 4.122 å and a volume of v = 161.42(3) å3. along the c-axis, we can observe continuous chains of corner-shared vo6 octahedra, as shown in fig. 1. all these chains are corner-shared with so4 tetrahedra forming a three-dimensional network. first report on the phase beta of anhydrous vanadyl sulfate was published in 1927 by a. sieverts and e. l. müller [7]. in 1970, its crystal structure and its magnetic properties have been studied in the same paper than α-voso4 [9]. this phase crystallizes within an orthorhombic structure (space group: pnma) with a = 7.384 å, b = 6.275 å, c = 7.078 å and a volume of v = 327.92(3) å3. β-voso4 is described by  gaubicher et al. as chains of corner-sharing distorded vanadium oxygen octahedra along the aaxis. those chains are linked to sulphate groups which alternately point in opposite directions along the c-axis [10]. interestingly, gaubicher et al. published the reversible intercalation of 0.6 lithium ions into β-voso4 at 2.84 v vs li + / li. after a first intercalation of 0.9 lithium through a biphasic process at 1.75 v, a solid solution reaction takes place. the structure of the reduced phase li0.9voso4 has not been solved [10]. we investigated the charge-discharge profile of  α-voso4 carried out at  c / 20 33 between 1.0 and 3.0 v (fig. 2a). th e slope of the curve suggests that a solid solution process occurs during both charge and discharge. th e theoretical capacity for the intercalation of  1 sodium per voso4 is 160 mah / g. th e fi rst discharge allows the intercalation of 0.8 na / f.u. at an average voltage of  1.58  v with an average of  0.6 na / f.u. reversibly deintercalated aft er 4 cycles. th is corresponds to  a  reversible capacity of  96 mah / g. th e intercalation and deintercalation of sodium occur in two distinct processes centered respectively at  1.45 then 1.15 v for  the intercalation and 2.42 then 2.68 v for the deintercalation, as observed on fig. 2b. t h e c h a r g e d i s c h a r g e p r o f i l e of β-voso4 carried out at c / 20 between 1.0 and 3.0 v is depicted in  fig.  2c. th e slope of the curve suggests also that a solid solution process occurs during both charge and discharge. th e fi rst discharge allows the intercalation of 0.9 na / f.u. at an average voltage of 1.58 v, but only 0.4 na / f.u. were reversibly deintercalated, corresponding to a reversible capacity of 64 mah / g. th is potential characterizes the v4+ / v3+ redox potential. th e capacity remains almost unchanged aft er 4 cycles. th e intercalation 0 20 40 60 80 -800 -600 -400 -200 0 200 400 600 800 1000 1200 1400 c ou nt s 2θ 2θ p4/n a = 6.2673(2) c = 4.1068(2) v = 161.313(9) χ2 = 2.36 α-voso4 β-voso4 a 0 50 100 -4000 -2000 0 2000 4000 6000 8000 10000 c ou nt s pnma a = 7.3837(2) b = 6.2750(2) c = 7.0776(2) v = 327.925(9) χ2 = 4.81 b fig. 1. (a) rietveld refi nement of the xrd pattern for α-voso4 and its structure along the c-axis; (b) rietveld refi nement of the xrd pattern for β-voso4 and its structure along the a-axis 34 and deintercalation of sodium occur in two distinct processes centered respectively at 1.90 and 2.40 v for the intercalation and 2.30 and 2.85 v for the deintercalation process, as observed in fig. 2d. according to the electrochemical study (lower polarization and almost no shift on  capacity after few cycles), β-voso4 seems more suitable for the intercalation of na and therefore should be more deeply investigated. best performance of β-voso4 can be explained by the channels observed in α-voso4 structure (1.5 å) being smaller than in b-voso4 structure (2 å) (see fig.  1). the difference in  channel sizes comes from a difference of configuration of  so4 tetrahedra in  these structures. in the α-voso4 structure, so4 tetrahedra are linked to four channels of vo6 octahedra. in contrast, only three channels of vo6 octahedra are connected to the so4 channels in the β-voso4 structure. consequently, the structure is more constrained with less space between vo6 octahedra chains in avoso4 than in β-voso4. to complete our study, we decreased the size of  the particles of  α-voso4 by  using a  mechanochemical process (250 rpm / 1.5 hrs). although this ball milling process effectively nanostructured our 0.0 0.2 0.4 0.6 0.8 1.0 0.5 1.0 1.5 2.0 2.5 3.0 x in naxvoso4 v ol ts v s n a+ /n a a 0 50 100 150 capacity (mah/g) 1.0 1.5 2.0 2.5 3.0 -2 -1 0 1 2 derivative curve 1.451.15 2.68 2.42 d( q –q 0) /d e (m a h/ v ) e (v vs na+/na) b 0.0 0.2 0.4 0.6 0.8 1.0 1.0 1.5 2.0 2.5 3.0 v ol ts v s n a+ /n a 0 50 100 150 x in naxvoso4 capacity (mah/g) c 1.0 1.5 2.0 2.5 3.0 -5 -4 -3 -2 -1 0 1 2 derivative curve 1.90 2.40 1.58 2.852.30 d( q –q 0) /d e (m a h/ v ) e (v vs na+/na) d fig. 2. (a) potential-capacity curves of α-voso4 at the galvanostatic rate of c / 20 between 3.0 and 1.0 v; (b) corresponding derivative curves; (c) potential-capacity curves of β-voso4 at the galvanostatic rate of c / 20 between 3.0 and 1.0 v; (d) corresponding derivative curves 35 material, as shown on the following x-ray pattern (fig. 3, middle line), this did not improve the electrochemical properties of our material. attempts to chemically reduce either α or β-voso4 using sodium naphthalenide in thf have been unsuccessful due to the dissolution of the material in thf. finally, ex situ xrd pattern has been obtained after the first reduction of α-voso4. this shows that an amorphization process occurred during the intercalation of  sodium into α-voso4 phase (fig. 3, upper line). conclusions in this work, we demonstrated that α and β-voso4 can be used as an electrode material in  na-ion battery. to the best of our knowledge, this is only the second vanadyl sulfate based material used in naion battery. the β phase exhibits smaller polarization than the α phase. intercalation and deintercalation of 0.4 na / f.u. have been observed, which correspond to a capacity of  65  mah / g. this reversible capacity is quite low, but could be improved by  playing with the particle size as  well as carbon coating, even though nanosizing has been unsuccessful on the α phase. then, due to  its attractive price and its cycling capability, further investigations on the intercalation of sodium in β-voso4 are in progress. acknowledgements the authors gratefully acknowledge the cnrs, the minister of education and research, the region of normandy and labex “energy materials & clean combustion center” for funding this work. we also thank j. thuillier, s. duffour and s. gascoin for technical help. references 1. singh p, shiva k, celio h, goodenough jb. eldfellite, nafe(so4)2: an intercalation cathode host for  low-cost na-ion batteries. energy environ  sci. 2015;8:3000–5. doi:10.1039 / c5ee02274f. 2. mason cw, gocheva i, hoster he, yu dyw. iron(iii) sulfate: a stable, cost effective electrode material for sodium ion batteries. chem commun. 2014;50:2249–51. doi:10.1039 / c3cc47557c. 3. meng y, zhang s, deng c. superior sodium — lithium intercalation and depressed moisture sensitivity of a hierarchical sandwich-type nanostructure for a graphene — sulfate composite: a case study on na2fe(so4)2·2h2o. j mater chem a. 2015;3:4484–92. doi:10.1039 / c4ta06711h. 20 40 60 80 na intercalation ball milling starting material 2θ fig. 3. powder x-ray diffraction pattern of as prepared a-voso4 phase (lower curve); powder x-ray diffraction pattern of a-voso4 phase after ball milling (middle curve); powder x-ray diffraction pattern of a-voso4 phase after na intercalation (upper curve) 36 4. barpanda p, oyama g, nishimura s, chung sc, yamada a. a 3.8-v earth-abundant sodium battery electrode. nat commun. 2014;5:4358. doi:10.1038 / ncomms5358. 5. sun m, rousse g, saubanère m, doublet ml, dalla corte d, tarascon jm. a2vo(so4)2 (a = li, na) as electrodes for li-ion and na-ion batteries. chem mater. 2016;28:6637–43. doi:10.1021 / acs.chemmater.6b02759. 6. tudo j. vanadyl sulfate and its reduction by hydrogen sulfide: vanadium sulfides. rev chim miner. 1965;2(1):58–177. 7. sieverts a, müller el. vanadinverbindungen und siedende schwefelsäure. z für anorg allg chem. 1928;173(1):313–23. german. doi:10.1002 / zaac.19281730128. 8. paufler p, filatov sk, bubnova rs, krzhizhanovskaya mg. synthesis and thermal behaviour of pauflerite, β-voso4, and its α-modification. z kristallogr — cryst mater. 2014;229:725–9. doi:10.1515 / zkri-2014–1752. 9. longo jm, arnott rj. structure and magnetic properties of voso4. j solid state chem. 1970;1(3-4):394–8. doi:10.1016 / 0022–4596(70)90121–0. 10. gaubicher j, chabre y, angenault j, lautié a, quarton m. lithium electrochemical intercalation in β-voso4. j alloys compd. 1997;262–3:34–8. doi:10.1016 / s0925-8388(97)00325–3. effect of alkylation on the kinetic stability of arsenodiester and organoarsenicals against hydrolysis: a theoretical study 96 d o i: 1 0. 15 82 6/ ch im te ch .2 01 8. 5. 2. 01 boota singh, rohan ranjan waliya, sougata santra, zyryanov g. v., kousik giri chimica techno acta. 2018. vol. 5, no. 2. p. 96–103. issn 2409–5613 boota singh1, rohan ranjan waliya1, sougata santra2, g. v. zyryanov2,3, kousik giri1* 1department of computational sciences, central university of punjab, bathinda, punjab, india 2department of organic and biomolecular chemistry, chemical engineering institute, ural federal university, 19 mira st., ekaterinburg, 620002, russian federation 3i. ya. postovskiy institute of organic synthesis, ural branch of the russian academy of sciences, 22 s. kovalevskoy st., ekaterinburg, 620219, russian federation *e-mail: kousikgiri@gmail.com effect of alkylation on the kinetic stability of arsenodiester and organoarsenicals against hydrolysis: a theoretical study arsenic diesters have same structural and chemical properties as p i (phosphate) diester. beside this structural similarity, arsenate is not considered by cellular processes to replace phosphate. quantum calculation reveals that this happens due to very high hydrolysis rate of as i diester (as–o-bond-based compounds) as compared to p i , but how organoarsenicals (as–c-bond-based compounds) that are produced by alkylation of as i survive in highly aqueous tissues of marine organisms? we found that this alkylation results in lower hydrolysis rate of as i diester. our work concluded that alkylating effort by our body on as i is to avoid structural ambiguity with phosphate and excrete out arsenic in the form of organoarsenicals from body. keywords: arsenic, arsenobetaine, arsenocholine, arsenosugar, dma, mma, arsenate organoarsenicals, arsonic acid, hydrolysis received: 14.06.2018. accepted: 27.07.2018. published: 30.07.2018. © boota singh, rohan ranjan waliya, sougata santra, zyryanov g. v., kousik giri, 2018 introduction arsenic (as) is one position below phosphorus (p) in  the same group of the periodic table, that is why it shares the fundamental chemical properties with phosphorus. in the environment arsenic exists in  four oxidation states:  –3, 0, 3, and 5, while the elemental arsenic occurs rarely [1]. arsenite [as (iii)] is the most toxic form of  inorganic arsenic, mainly found in anoxic environments, whereas less toxic arsenate [as (v)] occurs in aqueous, aerobic environments [1]. due to  structural similarities of arsenate and phosphate, phosphate transporters cannot easily distinguish between asi and pi, which results in the substitution of asi in many pi-based metabolic pathways (table 1) [2]. however, asi-based compounds are hydrolysed much 97 faster than phosphate compounds [3], but the kinetics of hydrolysis decreases by increasing size of alkyl substituent on arsenate due to steric effect [4]. alkylation is also utilised by marine organisms to produce organoarsenical products from arsenate, like arsenobetaine (me3as +ch2coo –), arsenocholine (me3as +ch2ch2oh) and arsenosugar [1]. even different pathways, proposed for arsenic metabolism in mammals, also lead to methylated end product of asi [5]. a very high percentage (> 70 % of total arsenic) of these organoarsenicals is found in kidney and muscles of marine animals [1]. the quantum chemical calculations performed by mlàdek et al. [11] reveals that neither steric hindrance nor polarity of the solvent is able to reduce the high hydrolysis rate of arsenate monoesters as compared to monoesters of phosphate. but mlàdek et al. [11] performed the theoretical modelling on the kinetics of the arsenate-ester hydrolysis by using mono-alkyl-arsenates only, whereas arsenate in organisms occurs as diester forms. chemically, diester has a very profound role in the kinetics of asi hydrolysis because of steric hindrance and electronic effect as compared to mono ester, where asi is enclosed by a single ester linkage. one interesting fact about protecting hydrolysis of asi is itself provided by organoarsenicals produced by marine organisms. these organic asi compounds have a direct as–c bonding as compared to inorganic asi which have as–o bonding. because as–c bond is less polar as compared to as–o bond due to lesser electronegativity of c than o, this would leads to the decrease in the reactivity of nucleophilic water towards as–c-bond-based compounds. the process of converting as– o-bond-based compounds to  as–c was also proposed in  mammals, where liver cell first reducts asi diester by using glutathione and then, after methyl transferases for methylation, finally produced various species of arsenic acid from asi diester (see fig. 1). in this regard, a  theoretical model based study is essential to  compare the hydrolysis rate of  alkylated asi diester with diester of  pi and to  understand the mechanism behind the alkylation of  asi during metabolism in mammals that differ from alkylation in diester where arsenic is directly (and not through the oxygen atom) bonded to carbon atom. table 1 evidence of arsenate substitution for phosphate in biochemical processes reaction or enzyme arseno-analogue phosphate compound reference adenylate deaminase 5’amas 5’amp [6] adenylate kinase 5’am (ch2) as amp [7] chloroplastic electron transport adp-as atp [8] glucose-6-phosphate dehydrogenase glucose-6-arsenate glucose-6-phosphate [9] hexokinase adp-as atp [9] human red blood cell sodium pump asi pi [2] purine nucleoside phosphorylase asi pi [10] 98 methods hydrolysis pathways for asi diester are well documented in the literature [4, 12]. the associative pathway was claimed to be dominated over dissociative pathway [4]. this pathway follows sn2 mechanism, where the attack of water nucleophile on ester results in a reaction intermediate having a pentacoordinated centre with trigonal bipyramidal geometry. further internal proton transfer leads to the breaking of as–o bond carrying the alkyl substituents. to see the effect of  alkyl substituent on  hydrolysis rate of  both as–oand as–c-bond-based compounds, prototypes of  chemical species in  fig.  3 were modelled. pbe1pbe functional from dft (density functional theory) was used for the quantum chemical calculation in this work because it was recommend after benchmarking of  dft functionals for  the hydrolysis of  phosphodiester bonds [13]. 6-31g+ (d, p) basis set was selected for the calculation of  hydrolysis rate constant. polar solvent (ε  = 78.4, water) was employed with the polarizable continuum model (pcm) using the integral equation formalism variant (iefpcm) [14]. since fig. 1. a general outline depicting mechanism of arsenate metabolism in mammals: mma – monomethyl arsonic acid, dma – dimethyl arsenic acid fig. 2. reaction pathways for hydrolysis of arsenate ester (ts – transition state) 99 we already described that the hydrolysis of asi follows sn2 mechanism where rate determining step is the attack of nucleophile, we modelled structures for reactants and ts only (see fig. 2) for the determination of  rate constant of  hydrolysis reaction. both optimization and frequency calculation of  reactants” structures were performed by  using pbe1pbe / 6-31g+ (d, p). transition state structure was modelled first by using lower methods like hf (hartree-fock) with less computationally demanding gaussian basis set 3-21g with redundant internal coordinates geometry where we applied bond constrained on one proton of  water molecule, which tunnel between negatively charged oxygen atom of  ester and oxygen atom of  water. hessian displays negative eigenvalues, which verify the nature of a transition state that has been optimized, and shows the correct vibration of  proton along a  bond vector where we applied constrained (see fig. 4) further optimization of ts geometry, followed by frequency calculation by using ultrafine grid and pbe1pbe dft method with 6-31g+ (d, p) basis set. aside from display of  negative vibrational frequency, it is also necessary to identify the minima connected through the transition state. this latter part is performed through the intrinsic reaction coordinate (irc), defined as the minimum energy reaction pathway in mass-weighted cartesian coordinates between the transition state of  a  reaction and its reactants and products [15]. irc is basically a path that the molecule takes while moving down the product and reactant valleys with zero kinetic energy [15]. we calculate irc with maximum 50 steps on both side with each step size of 0.0750 bohr (see fig. 5). the key equation for calculating reaction rates is k h k t hc eb g rt o 298, . � � � � � we use c0 = 1 for the concentration. because of  the final geometry, cartesian force constants and electronic energy are independent of the masses of the atoms, and only the vibrational analysis is massdependent [16]. the first step in  calculating the rates of these reactions is to compute the free energy of activation, � � � g ho of reaction at 298 k, which is calculated by using eq. 1: � � � � � � �� � � �� �� � , g k e g e g o o corr products o corr reactants 298 (1) where � �� � � �� �e g e go corr products o corr reactants, is sum of electronic and thermal free energies for products and reactants, respectively.fig. 3. as–cand as–o-bond-based arsenic compounds 100 fig. 4. bond constrains, applied along bond vector a, b and c in transition state structure geometry optimization of dimethylarsenate fig. 5. intrinsic reaction coordinates pathway for the rate-determining step in hydrolysis of arsenate with 50 steps on each side and step size of 0.0750 bohr 101 results and discussion hydrolysis rate for both as–oand as– c-bond-based compounds summarized in tables 2 and 3. we also calculated the hydrolysis rate of alkyl-o-phosphate diester. on average, it was found to be ~10–18 sec–1, whereas for alkyl-o-arsenate diester it was ~10–4 sec–1. it is clear that arsenate diester is less stable as compared to phosphate diester. this is because as have higher metallic character than p in diester and that is why it is a  stronger site for  a  nucleophilic attack as  compared to  p. in  fig.  6 we provide esp (electrostatic potential) charges for arsenate and phosphate in  their respective diester. we use esp charges in place of conventional mulliken charges because fig. 6. esp (electrostatic potential) charges on central atom of diester of arsenic and phosphorous. arsenic atom is more positively charged in its diester as compared with p. polarizable continuum model (pcm) using the integral equation formalism variant (iefpcm) was used to mimic effect of solvent (ε = 78.4, water). atomic charge is given in units of e table 2 hydrolysis rate for as–o-bond-based compounds № arsenic compounds rate of hydrolysis (in sec – 1) 1 dimethyl-o-arsenate 2∙10–4 2 diethyl-o-arsenate 6∙10–4 3 dipropyl-o-arsenate 1∙10–2 table 3 hydrolysis rate for as–c-bond-based compounds № arsenic compounds rate of hydrolysis (in sec–1) 1 arsenate 8.0∙10–2 2 monomethyl-arsenate 4.49∙10–5 3 dimethyl-arsenate 1.18∙10–6 4 trimethyl-arsenate 6.0∙10–7 102 they are much less dependent on the choice of basis set [17]. about 10 to 100 times fall in hydrolysis rate of as–c-bond-based compounds as  compared to  as–o-bond-based compounds was observed. this fall is due to the decrease in positive charge on central as atom (1.54e in case of dimethyl) because of the direct bonding of alkyl substituents to as, which are potent electron donating groups. now, because as in as–c-bondbased compounds has lower positive charge as  compared with charge on  as in  as– o-bond-based compounds, attack of nucleophilic water is less favoured over as in  as–c compounds compared to  as–o compounds. our findings directly support the proposed mechanisms for the metabolism of arsenate in mammals [5] because arsenate needs to be stabilized first, then, to support excretion of methylated arsenic products by highly aqueous excretory organs, some polar groups must be attached, like carboxylic acid, hydroxyl, etc. after that, arsenate is fully metabolized and ready to excrete in form of becomes organoarsenicals (see a, b, and c in fig. 3). conclusions in our study we found that asi diester is highly prone to hydrolysis under physiological conditions as  compared with pi diester, whereas organoarsenicals products are formed to protect asi from hydrolysis, otherwise it would be converted further to toxic asiii (arsnite). hence, methylation followed by  attachment of  a  polar group to arsenate is a way to excrete out 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scrocco e, tomasi j. electrostatic interaction of a solute with a continuum. a direct utilization of ab initio molecular potentials for the prevision of solvent effects. chem phys. 1981;55:117–29. doi:10.1016 / 0301–0104(81)85090–2. 15. fukui  k.  the path of  chemical reactions-the irc approach. acc chem  res. 1981;14(12):363–8. doi:10.1021 / ar00072a001. 16. ochterski jw. thermochemistry in gaussian [internet]. c2000 [cited 2018 june 14]. available from: http://gaussian.com / thermo / . 17. martin f, zipse  h.  charge distribution in  the water molecule  – a  comparison of methods. j comput chem. 2005;26(1):97–105. doi:10.1002 / jcc.20157. 156 d o i: 1 0. 15 82 6/ ch im te ch .2 01 6. 3. 2. 01 2 уд к 54 3. 63 v. a. shevyrin1,2 1 management of federal drug control service of russia in sverdlovsk region. stepan razin str., 31, ekaterinburg, 620142, russia. 2 ural federal university, institute of chemical technology, mira str., 19, ekaterinburg, 620002, russia. differentiation of 2and 6-isomers of (2-dimethylaminopropyl)benzofuran by tandem mass spectrometry reliable identification of new psychoactive substances of 2-(2-methylaminopropyl) benzofuran and 6-(2-methylaminopropyl)benzofuran is problematic when analyzing by gas chromatography–mass spectrometry method. it found that these two isomers can be reliably differentiated by ms/ms spectra obtained by collision-induced dissociation of their protonated molecules. key words: new psychoactive substances; amphetamine derivatives; chromatography – mass spectrometry method; high-resolution mass spectrometry; ei spectra; cid spectra. в. а. шевырин1,2 1управление фскн россии по свердловской области. россия, 620142, екатеринбург, ул. степана разина, 31. 2уральский федеральный университет, химико-технологический институт. россия, 620002, екатеринбург, ул. мира, 19. дифференциация 2и 6-изомеров (2-метиламинопропил)бензофурана методом тандемной масс-спектрометрии достоверная идентификация новых психоактивных соединений 2-(2-метиламинопропил) бензофурана и 6-(2-метиламинопропил)бензофурана проблематична при проведении анализа методом хроматомасс-спектрометрии. установлено, что эти два изомера могут быть надежно дифференцированы по мс/мс спектрам, полученным в результате диссоциации, индуцируемой соударением, их протонированных молекул. ключевые слова: психоактивные соединения; производные амфетамина; хроматомассспектрометрия; масс-спектрометрия высокого разрешения, масс-спектры электронной ионизации, мс/мс спектры. © shevyrin v. a., 2016 shevyrin v. a. chimica techno acta. 2016. vol. 3, no. 2. p. 156–162. issn 2409-5613 the compounds of 2-aminopropylbenzofuran appeared on the illegal market of new psychoactive substances (nps) starting in 2010 [1, 2]. among the most known (fig. 1) there are two isomers: 5-(2-aminopropyl)benzofuran (5-apb) and 6-(2-aminopropyl)benzofuran (6-apb) as well as their n-methyl derivatives (5-mapb and 6-mapb, respectively). the compounds 5-apb and 157 6-apb are serotonin receptor agonists and their pharmacological effects are similar to amphetamine-type stimulants [3, 4]. in the territory of the russia the circulation of 5-apb, 6-apb and these n-methyl derivatives is controlled by legislation. since mass spectra of electron ionization (ei) of isomeric compounds of 2-aminopropylbenzofuran have very significant similarity, the question of differentiation of these compounds is the important practical problem associated with the reliable identification of the compounds and their metabolites. when conducting analysis by gas chromatography–mass spectrometry using typical gas chromatography columns for drug identification with dimethylpolysiloxane nonpolar stationary phase (such as hp–5) the differentiation of compounds 5-apb and 6-apb or 5-mapb and 6-mapb is possible due to the differences in the values of parameters of the chromatographic retention of these compounds (fig. 2) or their acyl derivatives [3, 4]. first in autumn of 2015 we found in the illegal trafficking another compound, isomeric 5-mapb and 6-mapb, namely 2-(2-methylaminopropyl)benzofuran (2-mapb), whose structure was reliable established using high-resolution mass spectrometry and two-dimensional nmr spectroscopy. compound 2-mapb (fig. 3) has not only very similar to the 6-mapb ei mass spectrum (match factor more than 900) but the same chromatographic retention parameters (retention index of the fig. 1. chemical structures of most common derivatives of 2-aminopropylbenzofuran on the illegal market fig. 2. comparison ei mass spectra and chromatographic retention indices (gi) of compounds 5-mapb (top) and 6-mapb (bottom) according ekbdrugs library [5] 158 compounds gi=1546) [5], which does not allow to distinguish reliably between these compounds. the same values of retention indices were registered by us [5] for methyl (gi=1611) and trifluoroacetyl (gi=1749) derivatives of 2-mapb and 6-mapb. to address the question about the possibility of accurate differentiation of 2-mapb and 6-mapb using mass spectrometry we have considered different method of mass spectrometric ionization of compounds. as this method the ionization by electrospray was chosen, which is increasingly used in the determination of drugs and their metabolites. registered in terms of collision-induced dissociation (cid), high resolution ms/ms spectra of protonated molecules of compounds 2-mapb and 6-mapb (fig. 4) and their methyl derivatives had significant differences that allow to identify these compounds easily. thus, in the ms/ms spectrum of 2-mapb as the main product ions with m/z 58,0654 (100 %) and 159,0804 (1 %) were observed but in ms/ms spectrum of 6-mapb ions with m/z 159,0804 (100 %) fig. 3. the chemical structure of the compound 2-mapb and the comparison of its ei mass spectrum with mass spectrum of 6-mapb (bottom) fig. 4. comparison of cid spectra of protonated molecules of the compounds 2-mapb and 6-mapb 159 and 131,0492 (36 %) were observed. the intensity of the ion with m/z 58,0644 in the spectrum of 6-mapb did not exceed 1 %. the differences in the spectra can be explained by the advantageous formation of stable cyclic structures for ions with m/z 159,0804 and 131,0492 in the case of compound 6-mapb (fig. 5). in the case of compound 2-mapb alternative process with the formation of ion with m/z 58,0654 is favorable. thus, additional check cid spectra of protonated molecules of compounds 2-mapb and 6-mapb allow to differentiate these isomers reliably. in russian соединения 2-аминопропилбензофурана появились на нелегальном рынке новых психоактивных соединений (нпс), начиная с 2010 года [1, 2]. среди них наиболее известны (рис.  1) два изомера, 5-(2-аминопропил)бензофуран (5-apb) и 6-(2-аминопропил)бензофуран (6-apb), а также их n-метильные производные (5-mapb и 6-mapb, соответственно). соединения 5-арв и 6-арв являются антагонистами серотониновых рецепторов и по своему фармакологическому действию подобны стимуляторам амфетаминового ряда [3, 4]. на территории россии оборот 5-арв, 6-арв и их n-метильных производных контролируется законодательством. поскольку масс-спектры электронной ионизации изомерных соединений 2-аминопропилбензофурана обладают весьма значительным сходством, вопрос дифференциации этих соединений представляет собой важную практическую проблему, связанную с  достоверной идентификацией как самих соединений, так и их метаболитов. при проведении анализа методом хроматомасс-спектрометрии с использованием типичных для определения наркотиков газохроматографических колонок с неполярной диметилполисилоксановой неподвижной фазой (типа нр-5) дифференциация соединений 5-арв и 6-арв, или 5-mapb и 6-mapb возможна за счет различия fig. 5. the probable structure of the major fragment ions in the cid spectra of the compounds 2-mapb and 6-mapb 160 значений параметров хроматографического удерживания этих соединений (рис. 2), а также их ацильных производных [3, 4]. осенью 2015 года в нелегальном обороте нами впервые было обнаружено еще одно соединение, изомерное 5-mapb и 6-mapb, а именно 2-(2-метиламинопропил)бензофуран (2-мapb), структура которого была достоверно установлена с использованием масс-спектрометрии высокого разрешения и двумерной ямр-спектроскопии. соединение 2-мapb (рис.  3) обладает не только очень сходным с 6-мapb масс-спектром электронной ионизации (match фактор более 900), но и одинаковыми параметрами хроматографического удерживания (индекс удерживания соединений gi=1546) [5], что не позволяет надежно различить эти соединения. одинаковые значения индексов удерживания зарегистрированы нами [5] также для метильных (gi=1611) и трифторацетильных (gi=1749) производных 2-мapb и 6-мapb. для решения вопроса о возможности достоверной дифференциации 2-мapb и 6-мapb с использованием масс-спектрометрии нами был рассмотрен иной масс-спектрометрический метод ионизации соединений. в  карис. 1. химические структуры наиболее распространенных на нелегальном рынке производных 2-аминопропилбензофурана рис. 2. сравнение масс-спектров электронной ионизации и индексов хроматографического удерживания (gi) соединений 5-марв (вверху) и 6-марв (внизу), по данным библиотеки ekbdrugs [5] 161 честве такого метода была выбрана ионизация электрораспылением, все более активно применяемая при определении наркотических средств и их метаболитов. зарегистрированные в условиях диссоциации, индуцируемой соударением (дис), мс/мс спектры высокого разрешения протонированных молекул соединений 2-мapb и 6-мapb (рис. 4), а также их метильных производных, имели существенные различия, позволяющие легко идентифицировать эти соединения. так, в мс/мс спектре 2-мapb в качестве основных ион-продуктов наблюдаются ионы с m/z 58,0654 (100 %) и 159,0804 (1 %), а в мс/мс спектре 6-мapb – ионы с m/z 159,0804 (100 %) и 131,0492 (36 %). интенсивность иона с m/z 58,0644 в спектре 6-мapb не превысила 1 %. различия в спектрах могут быть объяснены выгодным образованием стабильных циклических структур для ионов с m/z 159,0804 и 131,0492 в случае соединения 6-mapb (рис. 5). в случае соединения 2-mapb благоприятен альтернативный процесс с образованием иона с m/z 58,0654. рис. 3. химическая структура соединения 2-марв и сравнение его масс-спектра электронной ионизации с масс-спектром 6-марв (внизу) рис. 4. сравнение спектров дис протонированных молекул соединений 2-mapb и 6-mapb 162 рис. 5. вероятные структуры основных фрагментных ионов в спектрах дис соединений 2-mapb и 6-mapb таким образом, дополнительная регистрация спектров дис протонированных молекул соединений 2-мapb и 6-мapb позволяет достоверно дифференцировать эти изомеры. references 1. king l. a. new phenethylamines in europe. drug test. anal. 2014;6(7-8): 808–818. doi: 10.1002/dta.1570. 2. casale j. f., hays p. a. the characterization of 6-(2-aminopropyl)benzofuran and differentiation from its 4-, 5-, and 7-positional analogues. microgram j. 2012;9(2):61–74. 3. welter j., kavanagh p., meyer m. r., maurer h. h. benzofuran analogues of amphetamine and methamphetamine: studies on the metabolism and toxicological analysis of 5-apb and 5-mapb in urine and plasma using gc-ms and lc-(hr)-msn techniques. anal. bioanal. chem. 2015;407:1371–1388. doi: 10.1007/s00216-014-8360-0. 4. welter j., brandt s. d., kavanagh p., meyer m. r., maurer h. h. metabolic fate, mass spectral fragmentation, detectability, and differentiation in urine of the benzofuran designer drugs 6-apb and 6-mapb in comparison to their 5-isomers using gc-ms and lc-(hr)-msn techniques. anal. bioanal. chem. 2015;407:3457–3470. doi: 10.1007/s00216-015-8552-2. 5. electronic library of mass spectra of electron ionization «ekbdrugs» (ms library ekbdrugs): certificate of state registration database no. 2015621086 russia / v. p. melkozerov, v. a. shevyrin. cite this article as (как цитировать эту статью): shevyrin v. a. differentiation of 2and 6-isomers of (2-dimethylaminopropyl)benzofuran by tandem mass spectrometry. chimica techno acta. 2016;3(2):156–162. doi: 10.15826/chimtech.2016.3.2.012. 49 l. b. vedmid’, v. m. dimitrov, o. m. fedorova institute of metallurgy, ural branch of russian academy of sciences, 101 amundsena st., ekaterinburg, 620016, russian federation elarisa100@mail.ru low-temperature synthesis under low oxygen pressure and thermodynamic properties of ybfe 2 o 4–δ the mixed-valence compound ybfe 2 o 4–δ was synthesized using a modified method that allows employing gaseous atmosphere with a controlled ratio of inert gas and oxygen. the stability range for ybfe 2 o 4–δ was determined at 1090 °c under reducing conditions. thermodynamic characteristics for the formation of ybfe 2 o 4–δ from the simple oxides and from elements in the temperature range 700–910 °c have been calculated. the obtained results allow specifying the low-temperature part of р-т-х diagram for the yb-fe-o system. keywords: oxygen partial pressure, mixed-valence compound, thermodynamic properties, complex oxides, oxygen nonstoichiometry received: 27.11.2017. accepted: 26.03.2018. published: 10.05.2018. © vedmid’ l. b., dimitrov v. m., fedorova o. m., 2018 d o i: 1 0. 15 82 6/ ch im te ch .2 01 8. 5. 1. 03 vedmid’ l. b., dimitrov v. m., fedorova o. m. chimica techno acta. 2018. vol. 5, no. 1. p. 49–54. issn 2409–5613 introduction complex oxides rfe2o4 (r = er, tm, yb, lu), which demonstrate both ferroelectric and ferromagnetic properties, are presenting a special class of materials called multiferroics. these materials are promising for application in energy-saving and storage devices [1]. the information concerning physicochemical properties for these complex oxides is important for their synthesis and practical applications. one of the representatives of such materials is ybfe2o4. taking into account that ybfe2o4 contains iron in two oxidation states, fe3+ and fe2+, it is obvious that one of the important parameters for its synthesis is oxygen partial pressure in gaseous phase. since the compound is stable only within narrow interval of temperature and oxygen partial pressure [2, 3], it is very important to establish a synthesis protocol and to find the temperature and oxygen partial pressure ranges of its stability. based on the ionic radii of rare earth ions r3+ [2], the whole set of r-fe-o systems can be divided into four groups. the yb-fe-o system belongs to the forth group d, in which r2fe3o7 exists together with rfeo3, r3fe5o12 and rfe2o4. the decrease of temperature may cause a decomposition of r2fe3o7 and, as a result, the yb-fe-o system would be converted to the group c [4]. the synthesis of mixed-valence compounds in the r-fe-o systems belonging to the c and d groups is traditionally performed under low oxygen partial pressure employing h2 and co2 mixtures [2–4]. in works [2–4] raw mixtures of r2o3 and fe2o3 were annealed at temperature 1200 °c in flow of gas with low oxygen activity. a precise 50 control and maintenance of oxygen partial pressure in such gaseouse mixtures in contact with oxide sample is not an easy task. the information about the possib ility of ybfe2o4 synthesis at temperatures lower than 1200 °c is absent. the purpose of the present study is the determination of conditions for preparation of ybfe2o4 at temperatures lower than 1200 °c, and investigation of its physicochemical properties in the low-tempearture range. experimental ybfe2o4–δ was synthesized by the advanced method in which gas mixture of argon and oxygen was used. reducing conditions were provided by maintaining the required value of oxygen partial pressure using the electrochemical method [5]. an interaction of a sample with the gaseous ar-o2 mixture can only result in oxygen exchange, while using of co2-h2 mixture may lead to the formation of carbides. preliminarily dried powders of fe2o3(purity ≥ 98%) and yb2o3(purity 99,9%) were mixed in equimolar amounts and grinded in an agate mortar for an hour, and then pressed into pellets with the diameter of 10 mm. the heat treatment was performed inside the airtight apparatus with a confined internal space (fig.  1). a  sample in a crucible 1 was placed in the quartz reactor 2 mounted in the furnace 3. air was evacuated by the vacuum pump 4 out of the apparatus which was followed by refilling with argon. oxygen partial pressure in the gas phase inside the apparatus was maintained and controlled by the oxygen cell 5, which consists of the oxygen sensor 6 and the oxygen pump 7. the oxygen cell was operated by the programmable oxygen pressure controller 8. since the thermal condition for each sample synthesis was tuned individually, but the oxygen cell worked at the limited tempearture range 600–900  °c (the optimal temperature is about 800  °c) two temperature zonesin the apparatus were created: one for the oxygen cell (furnace 9) and another for samples (furnace 3), retaining a common gas space. syntheses of ybfe2o4–δ were carried out at 1090 °c for 48 hours. it should be noted that it is the highest possible temperature that can be used in this apparatus because quartz was used as the reactor material. the value of oxygen partial pressure in the furnace 9 was set in the interval po2 = 10 –11.04–10–12.84 atm. it’s worth to note that in the region of low oxygen pressures po2 is defined by the equilibrium constant of reaction (1) and also depends on temperature [6]: h2o  ½ o2 +h2 (1) due to this fact the oxygen pressure in the furnace 3 differed from po2 which was achieved and measured in the furnace 6. the syntheses of samples in the furnace 3 at 1090 °c were performed in the interval po2 = 10 –11.04–10–12.84 atm. the circulation pump 10 was utilized to distribute the gas mixture with a controlled oxygen pressure evenly inside the apparatus. manometervacuummeter 11 was used to measure the total gas pressure. the samples were quenched by pulling them out of the high temperature zone of the reactor into the space cooled by the flow of cold water. the phase composition of quenced samples was determined by x-ray diffraction (xrd) using a shimadzu xrd7000c diffractometer (cu  kα radiation) in the range of angles 20°< 2θ < 80° with a step of 0.2°. the primary processing of diffraction data was performed with the software 51 package for the diffractometer xrd-7000, and calculation of the unit cell parameters was carried out using the x-ray diffraction tabulated process (rtp) program. thermodynamic characteristics of ybfe2o4–δ in relatively low temperature range and the values of oxygen nonstoichiometry for the samples obtained at various oxygen partial pressure were determined with the vacuum circulation apparatus [7]. results and discussion according to the xrd data, the obtained ybfe2o4–δ samples were single-phase (fig. 2). all of them possess rhombohedral structure (space group r3m). the unit cell parameters were in a good agreement with those collected from the database icdd, pdf4, card no 01–070–1734 [8] (fig. 2). the stability range for ybfe2o4 with respect to the oxygen partial pressure was determined at the fixed temperature 1090 °c. the decrease in oxygen pressure down to po2 = 10 –12.84 atm leads to the partial decomposition of initial ybfe2o4 oxide to yb2o3 and feo phases. on the other hand, when the oxygen partial pressure had been increased up to po2 = 10 –11.04 atm, xrd indicated that ybfe2o4 coexisted with the oxidized phases ybfeo3 and fe3o4 (fig. 3). fig. 2. initial x-ray diffraction patterns of ybfe2o4 fig. 3. a fragment of the phase diagram for the yb–fe–o system at 1090 °c. the phases are: а–ybfe2o4±δ, р–ybfeo3±δ, g – yb3fe5o12, w – feo, m – fe3o4 fig. 1. a scheme of the apparatus for synthesis of materials at the required value of oxygen partial pressure. 1 – a crucible with a sample, 2 – quartz reactor, 3 – big furnace, 4 – vacuum forepump, 5 – oxygen cell, 6 – oxygen sensor, 7 – oxygen pump, 8 – oxygen partial pressure controller, 9 – small furnace, 10 – circulation pump, 11 – manometer-vacuum meter 52 thus, it was experimentally determined that in the yb–fe–o system at 1090  °c ybfe2o4–δ exists within the range of oxygen pressures po2 = 10 –11.04–10–12.84 atm. this result significantly widens the temperature range for ybfe2o4–δ stability, as compared to previous studies [2]. the absolute values of oxygen nonstoichiometry for samples prepared at various oxygen partial pressures were determined by means of gravimetric analysis via the hydrogen reduction of the samples to the stable simple oxides in the vacuum circulation setup as follows: ybfe2o4–δ + 0.5 h2 = 0.5 yb2o3 + + 2 feo + (0.5 – δ)h2o (2) the absolute value of oxygen nonstoichiometry was calculated using equation (3): δ = − ⋅ ⋅ m m m m15 9994 15 9994. . ,red red (3) where м is the molecular weight of the studied oxide, мred is the total molecular weight of solid products in the reduction reaction with allowance for the stoichiometric coefficients, 15.9994 is the atomic weight of oxygen, mred is the weight of solid products after reduction reaction at the temperature of the experiment and m is the sample weight. detailed description of the procedure is given in [7]. a decrease of the oxygen partial pressure during synthesis results in formation of oxygen vacancies and consequent change of the fe2+/fe3+ ratio. at the same time the unit cell parameter a increases while the oxygen partial pressure is reduced (fig. 4, table 1). the obtained relationship between oxygen nonstoichiometry δ, which is influenced by oxygen partial pressure and the unit cell parameter a (fig. 5), might be used as a criterion for oxygen nonstoichiometry δ estimation using only xrd results. the measurements of ybfe2o4–δ thermodynamic stability have been carried out using the vacuum circulation apparatus by static method [7] in the temperature range 700–910 °c. the high temperature table 1 conditions of ybfe2o4–δ synthesis sample lg(po2) (atm) at 1090 °c unit cell parameter a, c (å) oxygen nonstoichiometry δ 1 –11.4 а = 3.4506(4) с = 25.0773(19) v = 258.576 0.033 2 –11.6 а = 3.4519(4) с = 25.0655(20) v = 258.656 0.038 3 –11.8 а = 3.4528(4) с = 25.0865(20) v = 259.011 0.041 4 –12 а = 3.4538(4) с = 25.0855(21) v = 259.157 0.048 5 –12.2 а = 3.4547(4) с = 25.0715(20) v = 259.133 0.061 53 dissociation process of ybfe2o4 at low oxygen partial pressure within the range po2 = 10–16.4–10–20.8 atm as a first approximation was written neglecting oxygen nonstoichiometry of ytterbium ferrite and oxygen nonstoichiometry of simple iron oxide as follows: ybfe2o4= 0.5 yb2o3 + + 2 feo + 0.25 o2 (4) a linear function was fitted to the measured values of equilibrium oxygen partial pressure of the reaction (4) vs temperuture (filled point in fig. 6), and the following equation was obtained: lg(po2, pa) = 11.78–27350/t±0.04 (5) unfilled point 2 (fig. 6) corresponds to the equilibrium oxygen partial pressure measured at 1200 °c by kimizuka et al. [3]. one can observe good agreement of our results with those obtained earlier. finally, eq. (5) was recalculated to the standard gibbs energy for reaction (4): δgot = 130.895 – 0.0564t ± ± 0.99 kj/mol (6) since the coefficients in eq. (6) can be treated as δh0t and δs 0 t , respectively, for reaction (4), the changes of standard entropy and enthalpy for ybfe2o4 formation from elements can be calculated taken into account the values of the thermodynamic functions for the simple oxides’ (yb2o3 and feo) formation [9,10]: δh0f (ybfe2o4) = –1575.767 kj/mol, δs0f = 274.23 kj/mol/k. conclusions it was found that ybfe2o4 can be prepared at 1090 °c within the oxygen partial pressure range po2 = 10 –11.04–10–12.84 atm. the obtained results allow specifying the low-temperature part of р-т-х diagram for the yb-fe-o system, which is very important from the practical point of view since it allows choosing the conditions for ybfe2o4 synthesis and usage. using the static method in the vacuum circulafig. 5. dependence of oxygen nonstoichiometry on unit cell parameter a for ybfe2o4–δ 3.451 3.452 3.453 3.454 3.455 0.030 0.035 0.040 0.045 0.050 0.055 0.060 0.065 a δ fig. 6. equilibrium oxygen partial pressure of ybfe2o4 dissociation (reaction 4) versus reciprocal temperature: 1 – our data, 2 –reported in [3] 6.5 7.0 7.5 8.0 8.5 9.0 9.5 10.0 -20 -18 -16 -14 -12 104/t,k 1 2 fe 3 o 4 /feo lg p o2 , atm fig. 4. dependence of the unit cell parameter a and c on oxygen partial pressure for ybfe2o4±δ synthesis 54 tion apparatus, the decomposition oxygen partial pressure was measured. finally, the changes of standard entropy and enthalpy of ybfe2o4 formation from elements in the temperature range 700–910  °c were calculated. acknowledgements the study was done in accordance with the state quota for imet ub ras, theme no. 0396-2015-0075, using equipment of ccu “ural-m”. references 1. pyatakov ap, zvezdin ak. magnitoelektricheskiye materially i  multiferroiki [magnetoelectric materials and multiferroics]. uspekhi fizicheskih nauk [achievements in physical sciences]. 2012;182(6):593–620. russian. doi: 10.3367/ ufnr.0182.201206b.0593. 2. kimizuka n, katsura t. the standard free energy of formation of ybfe2o4, yb2fe3o7, ybfeo3, and yb3fe5o12 at 1200 °c. j solid state chem. 1975;15:151–7. doi: 10.1016/0022-4596(75)90238-8. 3. kimizuka n, takenaka a, sasada y, katsura t. a series of new compounds a3+fe2o4 (a=ho, er, tm, yb, and lu). solid state commun. 1974;15:1321–3. doi: 10.1016/0038-1098(74)91372-6. 4. katsura t, sekine t, kitayama k, sugihara t, kimizuka n. thermodynamic properties of fe-lanthanoid-o compounds at high temperatures. j solid state chem. 1978;23:43–57.doi.org/10.1016/0022-4596(78)90052-x. 5. yankin am, vedmid’ lb. inventors; institute of metallurgy ub ras, assignee. isobaric console to synchronous thermoanalyzer. russian federation patent ru88452. 2009 nov 11. russian. 6. chufarov gi, men’ an, zhuravleva mg, balakirev vf, shchepyotkin aa. termodinamika processov vosstanovleniya okislov metallov [thermodynamics of metal oxides’ reduction processes]. moscow: metallurgy; 1970. 480 p. russian. 7. yankin am, balakirev vf, vedmid’ lb, fedorova om. a static method for studying heterogeneous equilibria. russ j phys chem. 2003;77(11):1899–1902. 8. kato k, kawada i, kimizuka n, katsura t. die kristallstruktur von ybfe2o4. zeitschrift für kristallographie. 1975;141:314–20. doi: 10.1524/zkri.1975.141.3-4.314. 9. portnoy ki, timofeeva ni. kislorodnye soedineniya redkozemelnyh elementov [oxygen compounds of rare-earth elements]. moscow: metallurgy; 1986. 480 p. russian. 10. tret’yakov yu d. khimiya nestekhiometricheskikh okislov [chemistry of nonstoichiometric oxides]. moscow: mgu; 1974. 364 p. russian. materials based on bifevox and bismuth or iron simple oxides nanopowders 202 krylov a.a., emelyanova yu.v., buyanova e.s., morozova m.v., vylkov a.i., chuykin a.yu. chimica techno acta. 2017. vol. 4, no. 3. p. 202–208. issn 2409–5613 d o i: 1 0. 15 82 6/ ch im te ch /2 01 7. 4. 3. 05 a.a. krylov1, yu.v. emelyanova1, e.s. buyanova1, m.v. morozova1, a.i. vylkov2, a.yu. chuykin2 1ural federal university 19 mira st., 620000, ekaterinburg, russia 2institute of high temperature electrochemistry ub ras 20 akademicheskaya st, 620137, ekaterinburg, russia materials based on bifevox and bismuth or iron simple oxides nanopowders compositions of composite materials based on bifevox and nanopowders of bismuth and iron oxides have been obtained. the absence of chemical interaction between the components has been proved, the total electrical conductivity of materials in the average temperature region has been determined. it has been shown that under the selected formation conditions, it has not yet been possible to achieve significant improvement of the functional characteristics of heterogeneous compositions in comparison with individual phases. however positive results on chemical and structural stability give way to further investigations. keywords: bimevox; oxygen-ion conductors; electrical conductivity; impedance spectroscopy. received: 22.09.2017; accepted: 17.10.2017; published: 20.10.2017. © krylov a.a., emelyanova yu.v., buyanova e.s., morozova m.v., vylkov a.i., chuykin a.yu., 2017 introduction the family of solid electrolytes with the general formula bi4v2–xfeхo11-δ (bifevox) is characterized by high oxygen-ion conductivity at intermediate temperatures 550–950 k [1–5]. the high-temperature γ-modification of the bifevox solid solutions with tetragonal structure (space group i4/mmm) is obtained at 0.3  ≤ x ≤ 0.5 iron concentration range. for this modification, the electrical conductivity versus temperature dependence is linear, and the activation energy at high temperatures has a value of 0.2–0.4 ev, which is characteristic of bifevox. the transition to an ordered γʹ modification with decreasing temperature is accompanied by a small change of slope of the lg σ – 103/t dependence and, accordingly, an increase in the activation energy to 0.5– 0.7 ev. the tetragonal γ-modification of the bi4v2–xfexo11–δ is sufficiently stable in a wide range of thermodynamic parame ters (t = 298 – 1073 k, lg po2 (atm) = –0.68 to –18.0) [4, 5]. the change of the structure into the orthorhombic one occurs in atmosphere with low oxygen content (lg po2 (atm) <–14.0) at temperatures above 773 k. however, decomposition of the sample does not occur. evaluation of the structural and thermal stability of bifevox in air at long time exposures (at least two weeks at the same temperature) 203 in the temperature range 723–1083 k revealed no changes in the structure or appearance of any additional phases [6]. in the last decade composite electrolytes are actively studied as alternative electrolyte materials. it has been shown that in this way it is possible to improve the quality of the material and remove some disadvantages of individual electrolytes [7]. there are examples of creating composite materials with bimevox as their components [8–11]. for the modification of bifevox based electrolyte materials, the approach using simple oxides nanopowders is used in this paper. experimental samples of bi4v2–xfexo11–δ (x = 0.3, 0.5) solid solutions were synthesized according to the standard ceramic technolo gy [2]. the preparation of nanopowders of bismuth and iron oxides was carried out by laser evaporation of a target and condensation of vapors in a working gas stream at the institute of electrophysics of the ural branch of the russian academy of sciences. in this method a fiber ytterbium laser ls-1 with diode pumping was used. the average radiation power was 1000 w with a smooth adjustment from 20 to 100  %, the wavelength 1070 nm, and the radiation regime continuous or modulated. the evaporation targets were prepared by pressing from a coarse-grained oxide powder followed by annealing at a temperature providing a partial sintering of the powder to provide mechanical strength of the compact. composites were prepared by mechanically mixing of the corresponding powders with a simple oxide content of 10 to 50 wt.%. the powders were pressed into pellets with a diameter of 10 mm on a hydraulic press in the form of pellets and annealed at 1073 k. the phase composition of the final solid oxide products was checked by x-ray powder diffraction (dron-3 diffractometer, cukα radiation, pyrolytic carbon monochromator, reflected beam). the particle size of the powders was determined using a laser dispersion analyzer sald-7101 shimadzu. the morpholo gy of the obtained powders and their chemical composition were studied using a jeol jsm6390 la scanning electron microscope equipped with a jed-2300 energy dispersive x-ray detector. thermal dilatometric analysis was performed on a dil 402 c netzsch dilatometer equipped with a vacuum furnace. electrical conductivity measurements of the ceramic samples were performed on elins z-3000 impedance spectrometer in the temperature range 1073–473 k. results and discussion 1.  synthesis and characterization of the materials bi4v2–xfexo11–δ (x = 0.3, 0.5) samples, obtained by the standard ceramic technology, are single-phase and have the structure of high-temperature tetragonal γ-modification (space group i4/mmm). the average particle size of bi4v2–xfexo11–δ is in the range of 0.5–10 μm. the bismuth oxide nanopowder is single-phase, and is β-bi2o3 with tetragonal structure. iron oxide nanopowder contains three crystalline phases where iron is in different oxidation states, so its composition is denoted as feox. this is composed of fe3o4 (magnetite) with its content 69 %, fe2o3 204 (hematite, 10 %) and ε-fe2o3 (21 %). the average particle size of nanopowders is in the range of 50–100 nm. in accordance with the results of the xrd, the calculation of the unit cell parameters was carried out for β-bi2o3 in the tetragonal structure (space group i4/mmm), for fe3o4 in cubic (fd-3m), fe2o3 for rhombohedral (space group r-3c), ε-fe2o3 for orthorhombic (space group pna21) structure. the results are shown in table 1. taking into account that the bimevox materials are non-stable in a reducing atmosphere as well as bi4v2–xfexo11–δ undergoes transition from tetragonal structure to orthorhombic one in air at ca. 773 k without decomposition [4, 5] the sample of bi4v1.5fe0.5o11–δ prepared accordingly was investigated in the reducing atmosphere with log(po2/atm) < –14.0 by means of dilatometry equipped with special chamber in order to reveal a  possible structure transition. the study was carried out with sequential change of gas atmosphere from air via argon to mixture of argon and hydrogen, and back to air in the heating and cooling cycles. when the sample was found to be heated in air a slight change in the slope of curve 1 at 890 k (see fig. 1) corresponding to an order-disorder type γ ↔ γʹ phase transition [12] is observed. however, there is no such transition upon heating in the reducing atmosphere while a γ ↔ β phase transition is observed at ca. 850 k. it is worth noting that final cooling curve recorded in air after reduction-oxidation cycling did not show indication of any transition. the unit cell parameters a = 3.919 and c = 15.509 å of the cooled sample were found by xrd to remain practically unchanged as compared to those of bi4v1.5fe0.5o11–δ before the reduction-oxidation treatment. aforementioned results indicate obvioustable 1 crystal structure parameters of the materials composition a ± 0.001, å b ± 0.001, å c ± 0.004, å bi4v1.7fe0.3o11–δ 3.919 3.919 15.468 bi4v1.5fe0.5o11–δ 3.918 3.918 15.524 β-bi2o3 7.729 7.729 5.648 fe3o4 8.356 8.356 8.356 fe2o3 5.034 5.034 13.727 ε-fe2o3 5.091 8.804 9.446 fig. 1. thermal strain of the bi4v1.5fe0.5o11–δ sample: 1 – heating up to 1023 k in air; 2 – 30 minutes holding in air at 1023 k; 3 – 1 hour holding in argon at 1023 k; 4 – 2 hours holding in argon-hydrogen mixture at 1023 k (50 % h2 and 50 % ar for this and next three steps); 5 – cooling in argon-hydrogen mixture, 6 – second heating in air-argon mixture; 7 – 30 minutes holding in argon-hydrogen mixture at 1023 k; 8 1 hour holding in argon at 1023 k; 9 – 3.5 hours holding in air at 1023 k, 10 – cooling in air 205 ly in favor of high resistance of the bifevox structure to alteration under reducing conditions. the value of the linear thermal expansion coefficient (ltec) of the bifevox before and after the oxidation-reduction cycle also did not change significantly and remained in the range 17–19∙10–6 k–1 (fig. 2). annealing in hydrogen atmosphere of the bi4v1.7fe0.3o11–δ sample at 1073 k for 8 hours was carried out to estimate the possibility of decomposition of the bi4v2–xfexo11–δ series at lgpo2 (atm) <–14.0. in addition to the bi4v2–xfexo11–δ lines, peaks corresponding to bivo4 and bi2o3 (or solid solutions based on them) as well as to metallic iron were found on the x-ray diffraction pattern of the sample. these results show that samples of the bifevox system, being annealed in air after the reduction, return to their original state with the same crystal structure. 2. preparation and characterization of composite materials. x-ray phase analysis was used to test the possible interactions in the compo site by annealing pellets of bi4v1.7(1.5) fe0.3(0.5)o11–δ/x wt.%. bi2o3 (feox) composites at 1073 k. all x-ray diffraction patterns contain only composite components lines, without extra reflexes. as an additional method for determining the phase and element composition of composites, the scanning electron microscopy (sem) method with the energy-dispersive microanalysis was used. for the sintered samples, the surface and cross-section of the composite pellets were examined. it was established that the surface of the samples is porous, consists of grains of various shapes and sizes, the visual contrast is determined by the topography of the sample surface (fig. 3). large grains of bifevox and fine grains of nanopowder particles are clearly fig. 2. ltec change versus temperature: 1 – first heating in air, 2 – cooling in air after reduction-oxidation cycle, 3 – heating in argon-hydrogen mixture, 4 – cooling in argon-hydrogen mixture fig. 3. the images of the surface of the composite samples: a – bi4v1.5fe0.5o11–δ/40 wt.%. bi2o3; b – bi4v1.7fe0.3o11-δ/10 wt.%. feox a b 206 visible, the iron oxide particles being aggregated to a lesser extent and covering the coarse grains of the bimevox complex oxide. the particles of bismuth oxide are combined into aggregates and fill the space between the coarse bimevox particles. the chemical composition of the particles was estimated by energydispersive x-ray spectroscopy (edx), and results correspond to the nominal ratio of elements in simple and complex oxides, which additionally indicates the absence of interaction in the composi tes under the selected processing conditions. an example of the x-ray dispersion energy spectrum of a surface of the bi4v1.7fe0.3o11–δ/10 wt.%. feox composite is shown in fig. 4. determination of the electrochemical characteristics of the composite materials was carried out by the impedance spectroscopy method. complex plane plots of the bifevox solid solutions consist of two joint half-circles, showing behavi or typical for the bimevox family ionic conductors [2]. fitting of the cole-cole plots was performed using the equivalent electrical circuits method [2]. typical temperature dependences of the total conductivity are shown in fig. 5. the dependences of the total conductivity on temperature for the composites studied have the form cha racteristic for the γ-modification of bifevox. the change of slope is observed in the dependencies at the temperature range 750–850 k. it corresponds to the transition of bifevox to an ordered γʹmodification with decreasing temperature and is accompanied by the increase of the activation energy from 0.4 to 0.7–0.8 ev. the behavior of all lg σ – 103/t dependencies, corresponding to the composites with different content and nature of the simple oxide added is similar. as the concentration of the simple oxide increases, the conductivity decreases. this situation is typical for the entire temperature range. this is probably due to an increase in the concentration of the less conducting phase, which are the simple oxides used in comparison with pure bifevox. for example, according to [13, 14], for the β-bi2o3 at 873  k the value of the total electrical conductivity is fig. 4. edx spectrum of the bi4v1.7fe0.3o11–δ/10 wt.%. feox composite surface c ou nt s 0.00 013 0 100 200 300 400 500 600 700 800 o k a v l l v l a fe l l fe l a 1.00 2.00 fe l su m b im z b im 3.00 4. v k es c b im a b im b b im r 00 5.00 kev v k a v k b fe k es c 6.00 7.00 fe k a fe k b 8.00 fig. 5. total electrical conductivity versus temperature: 1 – bi4v1.7fe0.3o11–δ; 2 – bi4v1.5fe0.5o11–δ; 3 – bi4v1.5fe0.5o11–δ/wt.% feox; 4 – bi4v1.5fe0.5o11–δ/wt.% feox; 5 – bi4v1.5fe0.5o11–δ/40 wt.% bi2o3; 6 – bi4v1.7fe0.3o11–δ/10 wt.% bi2o3 207 ~10–3 ohm–1 cm–1, for bi4v1.7fe0.3o11–δ in our work it is 1.5 × 10–2 ohm–1 cm–1. the effect of an increase of the overall electrical conductivity values of composite samples, which could be associated with a possible increase in the sintering quality of the bars, is not observed. conclusions thus, compositions of composite materials based on bifevox and nanopowders of bismuth and iron oxides have been obtained, the absence of interaction between them has been proved, the total electrical conductivity of materials in the region of average temperatures has been determined. it has been shown that, under the selected formation conditions, it has not yet been possible to achieve significant improvement of the functional characteristics of heterogeneous compositions in comparison with individual phases. however, the results obtained can serve as a basis for further searching for optimal solutions. acknowledgements the work was partially supported by the scholarship of the president (sp-3376.2016.1) and russian foundation for basic research (project no 17-53-04098). references 1. garcia-gonzalez e, arribas m, gonzalez-calbet jm. short-range-long-range order transformation in the bi4v2–xfexo11–y series. chem mater. 2001;13(1):96–102. doi:10.1021/cm0003929. 2. buyanova es, petrova sa, emel’yanova yuv, blinova al, morozova mv, zhukovskii vm, zhuravlev vd. preparation, structure, and charge transport characteristics of bifevox ultrafine powders. russ j inorg chem. 2009;54(8):1193–204. doi: 10.1134/s0036023609080051. 3. pena v, rivera a, leon c, santamaria j, garcia-gonzalez e, gonzalez-calbet jm. correlated oxygen diffusion in bifevox. chem mater. 2002;14(4):1606–9. doi:10.1021/cm010743z. 4. zhukovskii vm, buyanova es, emel’yanova yuv, morozova mv, shafigina  rr, zakharov rg, zhuravlev vd. synthesis, structure, and conductivity of bimevox oxide ceramics. russ j electrochem. 2009;45(5):512–9. doi:10.1134/ s1023193509050024. 5. morozova mv, buyanova es, emelyanova juv, zhukovskiy vm, petrova sa. highconducting oxide ceramics bimevox: synthesis, structure, properties. solid state ionics. 2011;192(1):153–7. doi:10.1016/j.ssi.2010.04.020. 6. morozova mv, buyanova es, petrova sa, khisametdinova vv, emel’yanova yuv, shatokhina an, zhukovskii vm. structural and thermal stability of bimevox oxygen semiconductors. russ j electrochem. 2011;47(4):448–52. doi:10.1134/ s1023193511040100. 7. rondao aib, patrıcio sg, figueiredo fml, marques fmb. composite electrolytes for fuel cells: long-term stability under variable atmosphere. int j hydrogen energy. 2014;39:5460–9. doi:10.1016/j.ijhydene.2013.12.125. 208 8. fuierera p, maiera m, exner j, moos r. anisotropy and thermal stability of hot-forged bicutivox oxygen ion conducting ceramics. j eur ceram soc. 2014;34(4):943–51 doi:10.1016/j.jeurceramsoc.2013.10.016. 9. sunarso j, baumann s, serra jm, meulenberg wa, liu s, lin ys, diniz da costa jc. mixed ionic-electronic conducting (miec) ceramic-based membranes for oxygen separation. j membrane science. 2008;320(1-2):13–41. doi: org/10.1016/j.memsci.2008.03.074. 10. sabolsky em, razmyar s, sabolsky k. nano-ceria enhancement of bi2cu0.1v0.9o5.35 (bicuvox) ceramic electrolytes. mater lett. 2012;76:47–50. doi:10.1016/j.matlet.2012.02.048. 11. piva rh, piva dh, venturini j, floriano r, morelli mr. inhibition of order–disorder phase transition and improvements in the bicuvox.1 properties by using yttria-stabilized zirconia particles. ceram int. 2014;41(1):171–7. doi:10.1016/ j.ceramint.2014.08.055. 12. buyanova es, shafigina rr, morozova mv, emel’yanova yuv, khisametdinova vv, zhukovskii vm, petrova sa, tarakina nv. electrochemical characteristics, thermal and chemical compatibility in the la0.7sr0.3coo3 electrode-γ-bifevox electrolyte system. russ j inorg chem. 2013;58(5):554–8. doi:10.1134/s0036023613050033. 13. sammes nm, tompsett ga, näfe h, aldinger f. bismuth based oxide electrolytes— structure and ionic conductivity. j eur ceram soc. 1999;19(10):1801–26. doi:10.1016/s0955-2219(99)00009-6. 14. kharton vv, marques fmb, atkinson a. transport properties of solid oxide electrolyte ceramics: a brief review. solid state ionics. 2004;174:135–49. doi:10.1016/j. ssi.2004.06.015. cite this article as: krylov aa, emelyanova yuv, buyanova es, morozova mv, vylkov ai, chuykin ayu. materials based on bifevox and bismuth or iron simple oxides nanopowders. chimica techno acta. 2017;4(3):202–8. doi:10.15826/chimtech/2017.4.3.05. 218 d o i: 1 0. 15 82 6/ ch im te ch .2 01 5. 2. 3. 02 3 o. v. kylosova, a. b. ilbuldina, o. v. yaroslavtseva ural federal university, 19 mira street, 620002 ekaterinburg e-mail: o. v.yaroslavceva@urfu.ru study of instantaneous rate of corrosion of aluminum in media with different acidity instantaneous rate of aluminum corrosion in media with different acidity has been studied using a method of polarization and the electrical resistance. a resulting time series of instantaneous corrosion rate have been analyzed using the standardized range. as a result, it has been found that in all studied media corrosion process has a stochastic character, and time series of instantaneous rate are anti-persistent. key words: electrochemistry, corrosion, aluminum. © kylosova o. v., ilbuldina a. b., yaroslavtseva o. v., 2015 introduction from the viewpoint of observation of the development of corrosion process of greater interest is the differential characteristic of the rate of corrosion, socalled instantaneous rate of corrosion [1]. since the corrosion process on the metal surface is likely to develop very unevenly, so fixing the instantaneous values of the corrosion rate one can be trace the alternation of its activation followed by temporary decay, which could again be replaced by reactivation. observations of such changes in instantaneous rate at the initial stage of the corrosion process development can be used as the basis for the development of long-term corrosion forecast model. therefore the choice of methodology of instantaneous corrosion rate research is actual. experimental part as an object of the study aluminum wire (al  not less than 99.6–99.7 % (wt.)) has been used. the instantaneous rate of corrosion of aluminum has been studied in three solutions: h2so4, na2so4 and naoh, a ph of which was 0.78, 5.71 and 11.11 respectively. the instantaneous rate of corrosion has been evaluated by two methods: polarization and electrical resistances. measurement of polarization resistance and recording polarization curves have been performed in a standard electrochemical cell with divided cathode and anode spaces using solartron 1280 c test station. a measurement design is shown in fig. 1. a program of measurement of the polarization resistance has included 219 № 3 | 2015 chimica techno acta 300 cycles, which consisted of measuring the currentless potential for 10 seconds, followed by potential sweep from –15 to +15 mv relative to the stationary potential, sweep rate is 3 mv/s. polarization curves for determining tafel coefficients have been recorded by polarization from the cathode region to the anode one at linear potential sweep of 3 mv/s. measurement of electrical resistance has been carried out by means of highresistance voltmeter. a measurement design is shown in fig. 2. the time interval between measurements was 30 seconds, in each solution up to 300 measurements have been performed. results and discussion a typical curve of the time dependence of the experimental polarization resistance of the aluminum sample is shown in fig. 3. according to experimental data of the polarization resistance (rp) values of instantaneous corrosion rate in current units (ikorr, а/см 2) have been calculated by the stern-geary equation [2]: i b b b b rkorr a k a k p = ⋅ ⋅ + ⋅2 3, ( ) , (1) wherein ba and bk are the tafel slopes of the anodic and cathodic processes. in all solutions under study oscillations have presented on the time dependence of the instantaneous corrosion rate. the presence of oscillations proves that the corrosion process has a stochastic character. the amplitude of oscillations and the general trend of change of polarization resistance suggest the following features of the corrosion process: – in a neutral salt solution dissolving aluminum occurs in pores existing on the surface of the oxide film; – in sulfuric acid solution the initial more or less active dissolution is replaced by the reduction of the oxide film, and the dissolution process slows down and localizes in pores of the oxide film; fig. 1. apparatus for polarization measurements: 1 – computer; 2 – electrochemical station; 3–3-way stopcock; 4 – silver chloride reference electrode; 5 – saturated solution of kcl; 6 – working electrode; 7 – working solution; 8 – platinum auxiliary electrode; 9 – haber-luggin capillary; 10 – support for the cell; 11 – salt bridge fig. 2. the electric resistance measuring circuit 1 – glass with the test solution, 2 – sample (in the form of wire spiral), 3 – thermocouple, 4 – high-resistance voltmeters study of instantaneous rate of corrosion of aluminum in media with different acidity 220 № 3 | 2015 chimica techno acta – in alkali medium dissolution of aluminum observed in cracks of fast-growing aluminate film. experimental curves of the change in time of the aluminum sample electrical resistance also had characteristic oscillations in all studied media (fig. 4). the instantaneous rate of corrosion (v, µm/s) can be calculated from the dependence of the electrical resistance on the radius of the wire sample [3]: v r t l r t r t =− ∂ ∂ = ⋅      ⋅ ⋅ ∂ ∂ −ρ π4 1 2 3 2 / /( ) , (2) wherein r is the radius of aluminum wire; ρ is the electrical resistivity of aluminum; l is the length of aluminum wire; r(t) is the resistance value at time t. the resulting time dependencies of the corrosion rate have oscillations regardless of the composition of the corrosive solution. this indicates that despite the significantly different values of the electric resistance and oscillation amplitude in different solutions the stochastic character of dissolution maintains. in order to identify the character (random or fractal) the time series have been processed by the method of hurst. the method involves the standardization of data to zero, mean and standard deviation. the calculated values of the hurst exponent for the time series of polarization and electrical resistances in the studied media (table 1) are in the range from 0 to 0.5. accordingly, all of the analyzed experimental time series are anti-persistent, so observed at the initial time moment the growth of corrosion rate subsequently may give place to a decrease. table 1 the hurst exponent for the time series of polarization and electrical resistance time series solution h2so4 na2so4 naoh polarization resistance 0.42 ± 0.21 0.27 ± 0.13 0.27 ± 0.08 electrical resistance 0.29 ± 0.02 0.29 ± 0.05 0.33 ± 0.04 conclusion 1. studies of electrochemical behavior of aluminum by electrical and polarization resistance in solutions with different ph have been carried out. 2. on the basis of the obtained time dependencies of the instantaneous corrosion rate it was confirmed that the process of corrosion on the surface of fig. 3. the polarization resistance of the aluminum sample in sodium sulfate solution fig. 4. the electric resistance of the aluminum sample: 1 – in sulfuric acid; 2 – in alkali medium kylosova o. v., ilbuldina a. b., yaroslavtseva o. v. 221 № 3 | 2015 chimica techno acta the aluminum sample develops nonmonotonically: oscillations presented on graphs suggest the stochastic character of the process. 3. when processing time series of polarization and electrical resistance it was revealed that the corrosion process on the aluminum surface has anti-persistent character regardless of the presence of the passive film. the results of the measurement of the polarization resistance data have confirmed known data on aluminum corrosion resistance in media with different ph, more specifically: – destruction of the passive film and intensive dissolution in alkaline solution; – passivation of the oxide film in a neutral solution; – reduction by the present in the solution oxygen of the oxide film dissolving upon contact with an acidic solution. 5. the analysis of experimental data has revealed that the corrosion rate determination by the electric resistance is possible in case of active dissolution of the metal in a corrosive medium, for example aluminum in an alkaline medium. in the presence of the growing passive film this method is not applicable. 1. gerasimov v. v. corrosion of aluminum and its alloys. m., metallurgiya, 1988. 113 pp. 2. zhuk  n. p. a course of the theory of corrosion and protection of metals. m., metallurgiya, 1976. 472 pp. 3. peters  e.  fractal analysis of financial markets: the application of chaos theory to investment and economics. m., internet trading, 2004. 304 pp. study of instantaneous rate of corrosion of aluminum in media with different acidity 222 о. в. кылосова, а. б. илбулдина, о. в. ярославцева уральский федеральный университет 620002, екатеринбург, ул. мира, 28. e-mail: o. v.yaroslavceva@urfu.ru исследование мгновенной скорости алюминия в средах с разной кислотностью методом поляризационного и электрического сопротивления исследована мгновенная скорость коррозии алюминия в средах с различной кислотностью. полученные временные ряды мгновенной скорости коррозии проанализированы методом нормированного размаха. в результате установлено, что во всех исследованных средах процесс коррозии имеет стохастический характер, причем временные ряды мгновенной скорости антиперсистентны. ключевые слова: электрохимия, коррозия, алюминий. © кылосова о. в., илбулдина а. б., ярославцева о. в., 2015 у д к : 5 44 .6 53 .2 2: 5 44 .6 .0 18 .4 214 3 введение с точки зрения наблюдения за развитием коррозионного процесса, больший интерес представляет дифференциальная характеристика скорости коррозии, так называемая мгновенная скорость коррозии [1]. поскольку коррозионный процесс на металлической поверхности, скорее всего, развивается крайне неравномерно, то фиксируя мгновенные значения скорости коррозии, можно проследить чередование его активации с  последующим временным затуханием, которое вновь может сменяться реактивацией. наблюдения за подобными изменением мгновенной скорости на начальном этапе развития коррозионного процесса могут быть положено в основу при разработке долгосрочной прогнозной модели коррозии. поэтому актуальным является выбор методологии исследования мгновенной скорости коррозии. экспериментальная часть в качестве объекта исследования использовали алюминиевую проволоку (al не менее 99,6–99,7 %(масс.)). мгновенную скорость коррозии алюминия изучали в  трех растворах: h2so4, na2so4 и  naoh, рн которых составляла 0,78, 5,71 и  11,11 соответ223 № 3 | 2015 chimica techno acta ственно. мгновенную скорость коррозии оценивали двумя методами: поляризационного и  электрического сопротивлений. измерение поляризационного сопротивления и  снятие поляризационных кривых осуществляли в  стандартной электрохимической ячейке с разделенными катодным и  анодным пространствами при помощи измерительной станции solartron 1280c. схема измерения представлена на рис. 1. программа измерения поляризационного сопротивления включала 300 циклов, которые состояли из измерения бестокового потенциала в  течение 10 с, с последующей разверткой потенциала от –15 до +15 мв относительно стационарного потенциала, скорость развертки 3 мв/с. поляризационные кривые для определения коэффициентов тафеля снимали поляризацией из катодной области в  анодную при линейной развертке потенциала 3 мв/с. измерение электрического сопротивления осуществляли при помощи высокоомного вольтметра. схема установки приведена на рис. 2. временной интервал между измерениями составлял 30 с, в каждом растворе осуществляли по 300 измерений. результаты и их обсуждение типичная кривая временной зависимости экспериментального поляризационного сопротивления алюминиевого образца приведена на рис. 3. по экспериментальным данным поляризационного сопротивления (rp) были рассчитаны значения мгновенной скорости коррозии в  токовых единицах (ikorr, а/см 2) по уравнению штерна – гири [2]: i b b b b rkorr a k a k p = ⋅ ⋅ + ⋅2 3, ( ) , (1) рис. 1. схема установки для поляризационных измерений: 1 – компьютер; 2 – электрохимическая станция; 3–3-ходовой краник; 4 – хлоридсеребряный электрод сравнения; 5 – насыщенный раствор kcl; 6 – рабочий электрод; 7 – рабочий раствор; 8 – платиновый вспомогательный электрод; 9 – капилляр гебера – луггина; 10 – подставка под ячейку; 11 – электролитический ключ рис. 2. схема измерения электрического сопротивления: 1 – стакан с исследуемым раствором, 2 – исследуемый образец (в виде спирали из проволоки), 3 – термопара, 4 – высокоомные вольтметры исследование мгновенной скорости алюминия в средах с разной кислотностью 224 № 3 | 2015 chimica techno acta где ba и  bk  – тафелевские наклоны анодного и катодного процессов. во всех исследуемых растворах на временной зависимости мгновенной скорости коррозии присутствовали колебания. наличие колебаний свидетельствует о  том, что коррозионный процесс имеет стохастический характер. амплитуда колебаний и  общий тренд изменения поляризационного сопротивления позволяют предположить следующие особенности коррозионного процесса: – в  нейтральном растворе соли растворение алюминия происходит в  порах имеющейся на поверхности оксидной пленки; – в  растворе серной кислоты первоначальное более или менее активное растворение сменяется восстановлением оксидной пленки, и  процесс растворения замедляется и  локализуется в порах оксидной пленки; – в  щелочи наблюдается растворение алюминия в  трещинах быстрорастущей пленки алюмината. экспериментальные кривые изменения во времени электрического сопротивления алюминиевого образца также имели характерные колебания во всех исследованных средах (рис. 4). мгновенная скорость коррозии (v, мкм/с) может быть рассчитана исходя из зависимости электрического сопротивления от радиуса проволочного образца [3]: v r t l r t r t =− ∂ ∂ = ⋅      ⋅ ⋅ ∂ ∂ −ρ π4 1 2 3 2 / /( ) , (2) где r  – радиус алюминиевой проволоки; ρ  – удельное электрическое сопротивление алюминия; l  – длина алюминиевой проволоки; r(t)  – значение сопротивления в момент времени t. полученные временные зависимости скорости коррозии имеют колебания вне зависимости от состава коррозионного раствора. это свидетельствует о том, что, несмотря на значительно отличающиеся значения электрического сопротивления и  амплитуды колебаний, в  разных растворах стохастический характер растворения сохраняется. с целью выявления характера (случайный или фрактальный) временные ряды были обработаны по методике херста. метод предполагает нормирование данных к  нулевому, среднему и  стандартному отклонению. рассчитанные значения показателя херста для временных рядов поляризационрис. 3. поляризационное сопротивление алюминиевого образца в растворе сульфата натрия рис. 4. электрическое сопротивление алюминиевого образца: 1 – в серной кислоте; 2 – в щелочи кылосова о. в., илбулдина а. б., ярославцева о. в. 225 № 3 | 2015 chimica techno acta ного и  электрического сопротивлений в  исследуемых средах (табл. 1) лежат в  интервале от 0 до 0,5. соответственно, все проанализированные экспериментальные временные ряды антиперсистентны, то есть наблюдаемый в  начальный момент времени рост скорости коррозии в  дальнейшем может смениться уменьшением. таблица 1 показатель херста временных рядов поляризационного и электрического сопротивления временной ряд solution h2so4 na2so4 naoh поляризационное сопротивление 0,42 ± 0,21 0,27 ± 0,13 0,27 ± 0,08 электрическое сопротивление 0,29 ± 0,02 0,29 ± 0,05 0,33 ± 0,04 выводы 1. проведены исследования электрохимического поведения алюминия методами электрического и  поляризационного сопротивления в  растворах с разным рн. 2. на основании полученных временных зависимостей мгновенной скорости коррозии подтверждено, что процесс коррозии на поверхности алюминиевого образца развивается немонотонно: имеющиеся на графиках колебания свидетельствуют о  стохастическом характере процесса. 3. при обработке временных рядов поляризационного и  электрического сопротивлений выявлено, что коррозионный процесс на поверхности алюминия имеет антиперсистентный характер вне зависимости от наличия пассивной пленки. результатами измерения поляризационного сопротивления подтверждены известные данные о коррозионной стойкости алюминия в  средах с  различным рн, а именно: – разрушение пассивной пленки и  интенсивное растворение в  щелочном растворе; – пассивация оксидной пленкой в нейтральном растворе; – восстановление присутствующим в  растворе кислородом, оксидной пленки, растворяющейся при контакте с кислым раствором. 5. в  ходе анализа экспериментальных данных установлено, что определение скорости коррозии методом электрического сопротивления возможно в  случае активного растворения металла в коррозионной среде, как например алюминий в щелочной среде. при наличии растущей пассивной пленкой этот метод не применим. 1. герасимов в. в. коррозия алюминия и его сплавов. м. : металлургия, 1988. 113 с. 2. жук  н. р.  курс теории коррозии и  защиты металлов. м.  : металлургия, 1976. 472 с. 3. петерс э. фрактальный анализ финансовых рынков: применение теории хаоса в экономике / пер. с англ. м.: интернет-трейдинг, 2004. 304 с. исследование мгновенной скорости алюминия в средах с разной кислотностью crystal structure and properties of novel oxide sm0.9ca1.1fe0.7co0.3o4-d 159 d o i: 1 0. 15 82 6/ ch im te ch .2 01 8. 5. 4. 01 galayda a. p., volkova n. e., dyagileva a. i., gavrilova l. ya., cherepanov v. a., battle p. d. chimica techno acta. 2018. vol. 5, no. 4. p. 159–165. issn 2409–5613 a. p. galaydaa*, n. e. volkovaa, a. i. dyagilevaa, l. ya. gavrilovaa, v. a. cherepanova, p. d. battleb a institute of natural sciences and mathematics, ural federal university, 19 mira st., ekaterinburg, 620002, russian federation b inorganic chemistry laboratory, university of oxford, south parks road, oxford ox1 3qr, uk *e-mail: anastasia.galaida@urfu.ru crystal structure and properties of novel oxide sm0.9ca1.1fe0.7co0.3o4–δ sm0.9ca1.1fe0.7co0.3o4–δ oxide with the k2nif4-type structure was prepared using a glycerin-nitrate technique. the xrd pattern of sm0.9ca1.1fe0.7co0.3o4–δ was refined by the rietveld method within an orthorhombic structure (space group bmab). the electrical conductivity, seebeck coefficient, and thermal expansion of sm0.9ca1.1fe0.7co0.3o4–δ were measured depending on temperature in air. the change of oxygen nonstoichiometry determined by tga in air does not exceed 0.01. the oxygen content in sm0.9ca1.1fe0.7co0.3o4–δ determined by the reduction in a hydrogen flux is equal to 3.96 ± 0.01. the positive value of seebeck coefficient indicates that the predominant charge carriers in the oxide studied are electron holes. keywords: complex oxide; ruddlesden-popper phase; crystal structure; oxygen nonstoichiometry, electroconductivity; thermal expansion. received: 13.11.2018. accepted: 05.12.2018. published: 31.12.2018. © galayda a. p., volkova n. e., dyagileva a. i., gavrilova l. ya., cherepanov v. a., battle p. d., 2018 introduction c omplex oxides with the k2nif4-type structure based on rare earth, alkaline earth and 3d-transition metals are known as materials with high mixed electronic-ionic conductivity and oxygen mobility, and also thermodynamic stability at high temperature under an oxidizing atmosphere [1–4]. for this reason, k2nif4-type oxides have attracted much attention as  promising sofc cathodes [1–3], oxygen-separation membranes [5] and catalysts [6]. the crystal structure of  a  k2nif4-type oxide is built up by  alternating the perovskite layer (abo3) and rock salt layer (ao) [7]. depending on the nature of the metals in the a and b sublattices, the crystal structure of  oxides with overall composition a2bo4 can be described using a  tetragonal (sp. gr. i4 / mmm) or orthorhombic (sp. gr. bmab) unit cell [3–13]. compared with sr-substituted phases, very little is known about ca-doped analogues with the k2nif4-type structure. it has been reported previously that metastable lanthanum calcium ferrite calafeo4–δ decomposes at 1100 °c to lanthanum ferrite lafeo3–δ and calcium oxide cao [14]. one can expect that variation of the ln / ca ratio and partial substitution of  more electronegative co for  fe ions 160 in  the b-site position will stabilize the k2nif4-type structure. the present study has focused on the structure and properties of the novel sm0.9ca1.1fe0.7co0.3o4–δ oxide with the k2nif4-type structure. experimental the complex oxide was prepared using a glycerin nitrate technique. samarium oxide sm2o3 (99.99 % purity), calcium carbonate caco3 (“pure for  analysis” grade), metallic cobalt co, iron oxalate fec2o4·2h2o (“pure for analysis” grade), nitric acid (“special purity” grade) and glycerin were used as the starting materials. metallic cobalt was obtained by reducing cobalt oxide co3o4 (“special purity” grade) in the hydrogen flow at 400–600 °c for 6 h. the appropriate stoichiometric amounts of starting materials were dissolved in nitric acid, and then glycerin was added to the solution. the resulting gel was dried in a porcelain cup, decomposed to the dark powder, then placed in  an alumina crucible and calcined in air at 700–1000 °c for 8–10 h. the final annealing was performed at  1100  °c in  air for  120 h with intermediate grindings, followed by slow cooling to  room temperature at  a  rate of  ~100  °c / h. the phase composition of the annealed samples was determined by  x-ray diffraction u sing a   s himadzu xrd-7000 (cukα-radiation, angle range 2θ = 20–90°, step 0.03°, 5 s / step) in air. the s tructural p arameters w ere r efined by the rietveld profile method using t he fullprof-2008 package. thermogravimetric analysis (tga) was carried out using an sta 409 pc instrument (netzsch) over the temperature range 25–1100 °с in air in dynamic (heating / cooling rate 2 k / min) mode. the absolute values of oxygen content were determined by a reduction of the samples in a hydrogen flux inside the tga cell at  1200  °c [15]. thermal expansion measurements were carried out within the temperature range of  25–1100  °c in  air using a dilatometer dil 402c (netzsch) at a heating / cooling rate of 5k / min. the total conductivity and seebeck coefficients of ceramic samples were measured in air by a 4-probe method with platinum electrodes. a bar-shaped sample (3×4×25 mm) for  thermal expansion coefficient (tec) and conductivity measurements was obtained by pressing powder that was mixed with 2–3 drops of ethanol using a manually-operated press. afterwards, the samples prepared accordingly were slow heated and then sintered at 1200 °c for 14 h in air followed by slow cooling (the rate of heating and cooling was 50 k / h). the relative density of the sample was evaluated by a comparison of measured values to those calculated from the xrd-data. the relative density was found to be 90 %. results and discussion in contrast with previously reported smcacoo4–δ [10] and lnsrfeo4–δ (ln=la [16], nd [17, 18], gd [19], sm [13]), we have failed to synthesize samarium-calcium ferrite with an equimolar sm / ca-ratio at 1100 °c in air. it is known that the homogeneity range limits for such solid solutions depend significantly on temperature, ionic radius of dopants and oxygen partial pressure. the decrease of temperature from 1500 °c to 1100 °c leads to decomposition of calafeo4–δ to lafeo3–δ and cao [14]. t h e c o m p l e x o x i d e sm0.9ca1.1fe0.7co0.3o4–δ was prepared 161 by  a  standard glycerin-nitrate technique with annealing temperature 1100 °c in air. diffraction data for sm0.9ca1.1fe0.7co0.3o4–δ analyzed by  the rietveld method are shown in  fig. 1. xrd pattern of sm0.9ca1.1fe0.7co0.3o4–δ was indexed in the orthorhombic structure (sp. gr. bmab). the value of  the oxygen content in sm0.9ca1.1fe0.7co0.3o4–δ at room temperature determined by the tga reduction was found to be 3.96 ± 0.01, and is consistent with that for smcacoo4–δ [10]. the tga measurements within the temperature range of 25–1100 °с in air revealed a small change in oxygen content, 4-δ, that is less than 0.01 (fig. 2). t h e t e mp e r at u r e d e p e n d e n c e of  the thermal expansion in  air for sm0.9ca1.1fe0.7co0.3o4–δ is given in  fig. 3 in comparison with smcacoo4–δ [10]. as can be seen, the shape of the measured dependence is non-linear. since this phenomenon cannot be explained by a noticeable oxygen exchange, we suggest that the non-linearity of the dilatometric plot is mainly associated with redistribution of  electron density between co and fe and / or  changes in  co spin states with the temperature. similar behavior was observed in  smfe1–xcoxo3–δ (x  =  0.2, 0.5, 0.8) [10]. however, additional research is needed to clarify this behavior. the dependence of  δl / l=f(t) has been described by two linear equations in the temperature ranges of  25–400  °c and 730–1000 °c. lowand high-temperature tec values for  sm0.9ca1.1fe0.7co0.3o4–δ in comparison with those of smcacoo4–δ and most common sofc electrolytes are listed in table 1. the decrease in the tec value with the increase of iron content can be explained by  the higher bond energy fig. 1. rietveld refined xrd pattern of sm0.9ca1.1fe0.7co0.3o4–δ. circles are the experimental xrd data, upper continuous line is the calculated profile, lower continuous line is the difference plot, vertical lines are indicating the bragg positions fig. 2. oxygen content, 4–δ, in sm0.9ca1.1fe0.7co0.3o4–δ as a function of temperature in air fig. 3. thermal expansion of the sm0.9ca1.1fe0.7co0.3o4–δ and smcacoo4–δ [10] ceramics in air 162 for fe–o (409 kj / mol) compared to co–o (368 kj / mol) [20]. t h e t o t a l c o n d u c t i v i t y of sm0.9ca1.1fe0.7co0.3o4–δ versus temperature is shown in fig. 4. t h e c o n d u c t i v i t y of  sm0.9ca1.1fe0.7co0.3o4–δ monotonously increases with temperature up to 23 s / cm at 1100 °c. in contrast, the seebeck coefficient decreases with temperature. the positive value of the seebeck coefficient (see fig. 5) indicates that electron holes are the predominant charge carriers in the oxide studied. the conductivity activation energies calculated from two linear segments of  arrhenius plot (see insert in  fig.  4) are equal to 0.193 ev and 0.283 ev in the temperature ranges 50–250 °c and 300– 1100 °c, respectively. both values are typical for a hopping conduction mechanism. a comparison of  the temperature dependences of  the total conductivity of sm0.9ca1.1fe0.7co0.3o4–δ and smcacoo4–δ [10] (see fig. 4) visually shows that they coincide in practical term up to 600 °c and the conductivityhas thermally activated character for both oxides. a strong increase in the conductivity of smcacoo4–δ above 600 °c can be explained by the pronounced charge disproportionation process at higher temperatures: 2co co coco co � � � � co (1) fig. 5. seebeck coefficient for sm0.9ca1.1fe0.7co0.3o4–δ vs. temperature in air table 1 the average thermal expansion coefficients for sm0.9ca1.1fe0.7co0.3o4–δ, smcacoo4–δ [10] and sofc electrolytes zr0.85y0.15o2–δ [22] and ce0.8sm0.2o2–δ [23] in air composition temperature range, °c tec×106, k–1 sm0.9ca1.1fe0.7co0.3o4–δ 25–400 4.4 730–1000 20.2 smcacoo4–δ [10] 25–580 17.7 580–1100 20.2 zr0.85y0.15o2–δ [22] 30–1000 10.9 ce0.8sm0.2o2–δ [23] 30–1000 12.5 fig. 4. total conductivity of sm0.9ca1.1fe0.7co0.3o4–δ and smcacoo4–δ [10] versus temperature in air. the insert shows the arrhenius plot for sm0.9ca1.1fe0.7co0.3o4–δ 163 in contrast, simultaneous presence of co and fe at the b-sites suppress disproportionation of iron and cobalt by the following process: fe co fe cofe fe fe � �� � � � fe , (2) where iron seems to be a hole trap [21]. conclusions single-phase sm0.9ca1.1fe0.7co0.3o4–δ was successfully synthesized by a glycerin nitrate technique. the structural parameters of  the oxide prepared were refined by  the rietveld method. the oxygen content, 4–δ, at  room temperature was found to be 3.96 ± 0.01 and its decrease with temperature does not exceeded 0.01. the lower value of the total conductivity of sm0.9ca1.1fe0.7co0.3o4–δ compared to that of  smcacoo4–δ was explained in  terms of an electronic exchange process. the seebeck coefficient of sm0.9ca1.1fe0.7co0.3o4–δ was shown to be positive over the entire temperature range investigated, indicating predominantly p-type conductivity. acknowledgements this work was supported in parts by act 211 government of the russian federation, agreement 02.a03.21.0006. references 1. istomin sya, antipov ev. cathode materials based on perovskite-like transition metal oxides for intermediate temperature solid oxide fuel cells. russ chem rev. 2013;82(7):686–700. doi: 10.1070 / rc2013v082n07abeh004390. 2. dailly j, fourcade s, largeteau a, mauvy f, grenier jc, marrony m. perovskite and a2mo4-type oxides as new cathode materials for protonic solid oxide fuel 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1. the system la0.8sr0.2co1–yfeyo3. solid state ionics. 1995;76:259–71. doi: 10.1016 / 0167–2738(94)00244-m. 22. tsipis ev, kharton vv. electrode materials and mechanisms in  solid oxide fuel cells: brief review. j solid state electrochem. 2008;12(11):1367–91. doi: 10.1007 / s10008-008-0611-6. 165 23. pikalova eyu, murashkina aa, maragou vi, demin ak, strekalovsky vn, tsiakaras pe. ceo2 based materials doped with lanthanides for applications in intermediate temperature electrochemical devices. int j hydrogen energy. 2011;36:6175–83. doi: 10.1016 / j.ijhydene.2011.01.132. conjugated addition of amines to electron deficient alkenes: a green approach anindita mukherjee1, rana chatterjee2, aramita de2, satyajit samanta2, sachinta mahato2, nirnita chakraborty ghosal2, g. v. zyryanov1,3, adinath majee2* 1institute of chemical engineering, ural federal university, 19 mira st., ekaterinburg, 620002, russia 2department of chemistry, visva-bharati university, santiniketan, 731235, india 3postovsky institute of organic synthesis ub ras, 22 kovalevskaya st., ekaterinburg, 620219, russia е-mail: adinath.majee@visva-bharati.ac.in conjugated addition of amines keywords: introduction the formation of carbon-nitrogen bond is very important task in organic synthesis and conjugate addition of amines to electron deficient alkenes is an efficient route to develop the carbonnitrogen bond [1]. as a consequence, β-amino ketone, nitriles, amide and carboxylic ester functionalities occur in many natural products [2–4]. it provides an easy route to produce β-amino derivatives, which are attractive for their use as synthetic intermediates of anticancer agents, antibiotics and other drugs [5, 6]. it is noteworthy to mention that the classical method for the preparation of β-amino derivatives is via mannich reaction [7]. the conjugate addition of amine to electron deficient alkenes is an alternate route to synthesize β-amino derivatives. in comparison with michael reaction the conjugate addition of amine to electron deficient alkenes is, in contrast, atom economical and easy to operate. but usually both these additions are carried out in presence of a strong base or acid [8, 9]. several methods are available in the literature by using different catalysts such as yb(otf )3 [10], cecl3·7h2o-nai [11], incl3 [12], cu(otf )2 [13, 14], can [15], kf/alumina [16,17], liclo4 [18], bi(otf )3 [19], bi(no)3 [20], smi2 [21], cu(acac)2/ionic liquid [22], ionic liquid/ quaternary ammonium salt [23, 24], boric acid [25], borax [26], zrocl2.8h2o [27], β-cyclodextrin [28], bromodimethylsulfonium bromide [29], [hp(hnch2ch2)3n] no3 [30], mncl2 [31]etc. although these methods have their own advantages and quite useful, but some of these methods used a large excess of reagents, hazardous solvents such as acetonitrile or 1,2-dichloroethane, require long time and harsh reaction. ranu et al. reported these addition in the absence of catalysts or water as the reaction medium, but due to the solubi lity problem of organic compounds the scope of the method is limited [32, 33]. so far, the reported methodologies are effective for either aromatic amines or aliphatic amines. so, in a consequence, development of a general, simple and environmentally benign method is highly desirable. considering the environmentally consciousness in chemical research, reactions in water have attracted much attention in recent times [34, 35]. in 2008, varma et al. reported that tea and coffee extract can be used as good stabilizer for green synthesis of silver and palladium nanoparticles [36]. the authors first synthesized nanoparticles in presence of tea and coffee extract. this observation promoted us to consider the tea extract for some organic reactions. interestingly, from the recent research we observed according to normal expectation that the extraction of normal tea is acidic in nature [37]. this observation motivated us to investigate the catalytic role of tea extract for simple organic reaction. so, in continuation of our research to develop green methodo logy [38–41], we have observed that tea extract is very useful as solvent as well as catalyst for conjugate addition of a variety of amines to different michael acceptors (fig. 1). results and discussion first of all, we prepared the required tea extract. in a typical experimental procedure, 2 g of tea leaves were dissolved in 20 ml of water and boiled it for 10–15 min. after filtration we got the extract which was used for the said reactions. it was observed that 2 ml of tea extract is sufficient to get the best result. several structurally varied amines were coupled with the wide range of α, β-ethylenic compounds and the results are summarized in table 1. a variety of aliphatic amines was examined to prove the general applicabi lity of this present procedure and the corresponding michael adducts were isolated in excellent yields within a short reaction time. the aliphatic primary amines such as benzylamine, butylamine and cyclohexylamine were treated with different michael acceptors and corresponding monoadducts were isolated in good yields (table 1, entries 1–5). the reaction of open chain bulky secondary amine like diisopropylamine proceeded very well (entries 6, 7). cyclic secondary amines such as piperidine and morpholine underwent facile additions with acrylonitrile and acrylic esters respectively (table  1, entries 6, 7). aromatic amines are less reactive than aliphatic amines and took long reaction time. both activated and weakly activated anilines were investiga ted. the reactions proceeded smoothly at room temperature and the products were fig. 1. tea extract mediated conjugated addition of amines to electron deficient alkenes obtained in excellent yields. several substituted anilines such as methyl and me thoxy anilines underwent efficient additions with acrylonitrile and methyl acrylate giving only monoadduct in high yields under present reaction conditions (table  1, entries 10–14). acid sensitive functional group in aniline such as 3,4-(methylenedioxy)aniline also reacted well to give the desired product in good table 1 tea extract-mediated michael addition of amines to conjugated alkenesa areaction conditions: 2 mmol of amine and 2 mmol of alkene were stirred in 2 ml of tea extract at room temperature; bisolated yields. yields keeping methylenedioxy group unaffected (table  1, entry 14). with regard to michael acceptors, a wide range of structurally diverse electron deficient alkenes was used such as α, β-unsaturated nitrile and carboxylic ester. in general, the reactions are very clean. both aliphatic and aromatic amines give the products in equally fair yields. in particular, in the case of primary amines the method produces the corresponding β-amino derivatives without the problem of double-conjugate addition. we have not observed any by-products for all reaction combinations which are supported by high yields of the protocol. all of the known synthesized compounds have been characterized by spectral data and the new compounds by spectral and analytical data. conclusions in conclusion, we have developed a tea extract-mediated a highly efficient methodology for the synthesis of β-amino derivatives under milder reaction conditions at room temperature. general applicability, operational simplicity, aqueous media, mild reaction conditions, environment friendly, high yields, and applications of inexpensive and easily available catalyst are the advantages of the present procedure. we believe this aza-michael reactions are of significant importance in both synthetic chemistry and industrial processes for the synthesis of β-amino derivatives. experimental general: 1h nmr (300 mhz) and 13c nmr (75 mhz) spectra were run in cdcl3 solutions. ir spectra were taken as kbr plates. elemental analyses were done by perkin-elmer autoanalyzer. co lumn chromatography was performed on silica gel (60–120 mesh, srl, india). mncl2.4h2o was purchased from nice chemicals, india. tea leaves were purchased from market. amines and alkenes are all commercial materials. all liquid reagents were distilled before use. preparation of tea extract: 2 g of tea leaves (any marketed) were dissolved in 20 ml of water and boiled it for 10–15 min. after filtration we got the extract which was used for the reactions. general procedure for the synthesis of β-amino derivatives: a mixture of amine (2 mmol) and alkene (2 mmol) was stirred in 2 ml of tea extract at room temperature as required for completion (tlc). after completion of the reaction the reaction mixture was extracted with ethyl acetate (40 ml). the extract was washed with water (2 × 10 ml) and brine solution (1 × 10 ml) and dried over anhydrous sodium sulphate. evaporation of solvent followed by short column chromatography of the crude product over silica gel (hexane/ ethyl acetate) furnished the analytically pure product. the known compounds have been identified by comparison of spectra data (ir  and nmr). the spectral and analytical data of the compounds which are not readily found provided below. 3-(cyclohexylamino)propanenitrile (table 1, entry 4): colorless oil; ir2928, 2246, 1722, 1666, 1558, 1455 cm-1; 1h nmr δ 2.85 (t, j = 5.1 hz, 2h), 2.45 (t, j = 5.1 hz, 2h), 2.43(m, 1h) 1.80–1.63 (m, 5h), 1.25–1.16 (m, 6h). calculated for c9h16n2: c, 71.01; h, 10.59; n, 18.40 %. found: c, 60.82; h, 10.35; n, 18.13 %. 3-(4-methoxy-phenylamino)-propanenitrile (table 1, entry 12): colorless liquid; ir3377, 2244, 1842, 1617, 1514, 1289 cm-1; 1h nmr δ 6.80 (d, j = 5.1 hz, 2h). 6.61 (d, j = 5.1 hz, 2h), 3.75 (s, 3h), 3.47 (t, j = 4.8 hz, 2h), 2.61 (t, j = 4.8 hz, 2h), (n-h) not identified; 13c nmr δ 152.9, 140.3, 118.5, 115.1 (2c), 114.8 (2c), 55.8, 40.8, 18.2. calculated for c10h12n2o: c, 68.16; h, 6.86; n, 15.90 %. found: c, 67.98; h, 6.53; n, 15.62 %. 3 ( 4 me t hy l p h eny l am i n o ) pro panenitrile (table 1, entry 13): colorless liquid; ir3559, 2253, 1615, 1522, 1404 cm-1; 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chatterjee r, zyryanov gv, hajra a, majee a. brønsted acidic ionic liquid-catalyzed tandem reaction: an efficient approach towards regioselective synthesis of pyrano[3,2-c]coumarins under solvent-free conditions bearing lower e-factors. green chem. forthcoming 2017. doi:10.1039/c7gc01158j. 41. santra s, rahman m, roy a, majee a, hajra a. nano-indium oxide: an efficient catalyst for one-pot synthesis of 2,3-dihydroquinazolin-4(1h)-ones with a greener prospect. catal commun. 2014;49:52–7. doi:10.1016/j.catcom.2014.01.032. cite this article as (как цитировать эту статью) mukherjeel a, chatterjeel r, de a, samantal s, mahatol s, ghosal nc, zyryanov gv, majee a. conjugated addition of amines to electron deficient alkenes: a green approach. chimica techno acta. 2017:4(2);140–147. doi: 10.15826/ chimtech.2017.4.2.029. 67 введение кремний – материал, который широко используется в современных полупроводниковых устройствах. морфология кремниевых материалов существенным образом влияет на их физико-химические свойства, а следовательно, на возможности применения в различных отраслях современной промышленности. последние годы внимание исследователей сосредоточено на создании кремниевых наноматериалов, которые открывают новые возможности повышения эффективности литий-ионных химических источников тока и фотоэлектрических элементов. основным способом получения кремния высокой чистоты и наноматериалов на его основе является осаждение из газовой фазы. процессы газофазного синтеза энергоемки требуют использования дорогостоящих реагентов и сложного оборудования. альтернативным методом получения кремния и наноматериалов на его основе является электролиз кремнийсодержащих расплавов солей [1, 2]. с. и. жук, л. м. минченко, о. в. чемезов, в. б. малков, а. в. исаков, ю. п. зайков фгбун ивтэ уро ран, 620990, екатеринбург, ул. академическая, 20. факс: (343) 362-34-62; тел: (343) 362-34-97. e-mail: chem@ihte.uran.ru. фазозарождение кремния на стеклоуглероде в расплаве kf-kcl-k 2 sif 6 методом хроноамперометрии изучено зарождение кремния на стеклоуглеродной подложке в расплаве kf-kcl-k 2 sif 6 при температуре 675 ºс. выявлено прогрессивное фазозарождение кремния. из sem-микрофотографий зародышей кремния, выращенных на стеклоуглеродной подложке в потенциостатическом режиме в интервале потенциалов от –0.005 до –0.03 в в расплаве kf-kcl-k 2 sif 6 при т = 675 ºс, видно, что в условиях одного эксперимента они имеют размеры, различающиеся в несколько раз, что подтверждает прогрессирующий характер возникновения зародышей кремния. показано, что когда к рабочему электроду при прочих равных условиях прикладывается более отрицательное значение потенциала относительно кремниевого электрода сравнения, то количество сформировавшихся зародышей на поверхности электрода растет. у д к 6 61 .6 86 © жук с. и., минченко л. м., чемезов о. в., малков в. б., исаков а. в., зайков ю. п., 2014 68 cta | № 2 | 2014 электрохимический метод позволяет сравнительно легко контролировать структуру электролитических осадков si. электролизом расплавов солей могут быть получены как сплошные кремниевые покрытия, так и si-наноструктуры: нанопорошки и нановолокна. для целенаправленного получения осадков кремния заданной формы необходимо понимание механизма зарождения и начального роста кристаллов si. теоретические представления о механизме зарождения и роста кристаллов металлов в процессе электролиза хорошо разработаны [3, 4]. однако по особенностям фазозарождения полупроводниковых материалов, в частности кремния, при элек-троосаждении из расплавов солей в литературе имеются лишь отрывочные сведения. исследовали зарождение кремния на серебряной подложке в расплаве naf-kf-na2sif6 в интервале температур от 850 до 900 ºс и сделали вывод, что оно протекает в мгновенном диффузионном режиме [5]. исследование фазозарождения кремния методом хроноамперометрии на молибденовой подложке в расплаве nacl-kcl-naf-sio2 при 800 °c проведено и показано, что при электрокристаллизации кремния образование трехмерных зародышей идет постепенно [6]. целью данной работы является исследование процесса фазозарождения электролитического кремния методом хроноамперометрии на стеклоуглеродном электроде из расплава kfkcl-k2sif6 в инертной атмосфере при т = 675 oc. экспериментальная часть электрохимические исследования проводили методом хроноамперометрии в расплаве kf-kcl-k2sif6 c мольным соотношением kf/kcl = 2 и концентрацией кремния в расплаве, равной 5,7 · 10–4 моль/см3. расплавы для исследования готовили из индивидуальных солей kf·hf, kcl, k2sif6 по ранее описанной методике [7]. эксперименты проводили в атмосфере аргона в трехэлектродной ячейке [8]. в качестве контейнера для расплава солей использовали стеклоуглеродный тигель. рабочим электродом служила пластина из стеклоуглерода (су-2000). в качестве противоэлектрода и электрода сравнения использовали пластины из монокристаллов кремния высокой чистоты (уд. сопротивление 0.01 ом·см). перед началом эксперимента проводили очистной электролиз на вспомогательном графитовом электроде. после очистного электролиза графитовый электрод извлекали из ячейки через шлюзовое устройство и меняли на стеклоуглеродный рабочий электрод. хроноамперометрические измерения производили при помощи потенциостата/гальваностата autolab с использованием программного обеспечения nova 1.5. зарождение кремния на стеклоуглеродной подложке вели в потенциостатическом режиме. микрофотографирование образцов проводили на сканирующем электронном микроскопе jms-5900lv. с. и. жук, л. м. минченко, о. в. чемезов, в. б. малков, а. в. исаков, ю. п. зайков. 69 2014 | № 2 | ctaфазозарождение кремния на стеклоуглероде в расплаве kf-kcl-k2sif6 результаты и обсуждение на начальных участках хроноамперометрических кривых был зарегистрирован пик, относящийся к зарядке двойного электрического слоя (рис. 1). этот пик спадал за короткое время (от 10–4 до 10–3 с). затем на хроноамперометрических кривых формировался второй пик тока в интервале времен от 1·10–1 до 5·10–1 с. полученные хроноамперометрические зависимости в расплаве kf-kcl-k2sif6 при т = 675 ºс в зависимости от приложенных потенциалов в интервале от –0.05 до –0.15 в относительно кремниевого электрода сравнения представлены на рис. 2. участок хроноамперограммы до второго максимума кривой связан с процессом фазозарождения. по-следующий участок снижения тока обусловлен обеднением приэлектрод-ного слоя по кремнийсодержащему иону. зависимость тока второго возрастающего участка хроноамперограммы от времени позволяет определить режим фазозарождения и подчиняется уравнению (1): j = ά t x, (1) где ά и х зависят от геометрии зародыша и режима фазозарождения. в случае полусферического 3d зародышеобразования, контролируемого диффузией для мгновенного режима зарождения, значение степенной функции x равно 1/2, для прогрессирующего – 3/2 [5]. анализ первичных данных, полученных при потенциале, приложенном к рабочему электроду из стеклоуглерода, равному значению –0.05 в относительно кремниевого электрода сравнения, в координатах i – t3/2, показал, что экспериментальные точки хорошо ложатся на линейную зависимость (рис. 3). отсюда можно сделать вывод, что режим образования зародышей кремния на стеклоуглеродной подложке в условиях наших опытов носит прогрессирующий характер. другими словами, не вся масса зародышей кремния появляется одновременно и сохраняет приблизительно одинаковые размеры в процессе роста. рис. 1. типичный начальный участок хроноамперометрической зависимости (стекло-углеродный электрод, т = 655 °с, расплав kf-kcl-k2sif6, с0 = 5,7·10 –3 моль/см3, sэл = 0.35 см 2) рис. 2. типичные хроноамперометрические зависимости (стеклоуглеродный электрод, расплав kf-kcl-k2sif6, с0 = 5,7·10 –4 моль/см3, т = 675 °с, sэл = 0.6 см 2) 70 cta | № 2 | 2014 в нашем случае процесс фазозарождения растянут во времени, поэтому зародыши кремния, возникшие первыми, имеют большие размеры в процессе роста, по сравнению с зародышами si, образовавшимися с некоторой задержкой во времени. зарождение кремния на стеклоуглеродной подложке проведено при разных, приложенных к рабочему электроду потенциалах (от –0.005 до –0.03 в) и разных временах процесса электролиза (от 0.001 с до 1 с). на микрофотографиях (рис. 4–6) видно, что размеры зародышей кремния в каждом эксперименте различаются между собой в несколько раз. это подтверждает ранее сделанный вывод о прогрессирующем процессе рис. 4. микрофотография (sem) зародышей кремния, полученных в расплаве kf-kcl-k2sif6, с0 = 5,7·10 –4 моль/см3, т = 675 °с на стеклоуглеродном электроде при приложенном значении потенциала –0,05 в в течение 1 с рис. 5. микрофотография (sem) зародышей кремния, полученных в расплаве kf-kcl-k2sif6, т = 675 °с на стеклоуглеродном электроде при приложенном значении потенциала –0,03 в течение 0,01 с рис. 6. микрофотография (sem) зародышей кремния, полученных в расплаве kf-kcl-k2sif6, с0 = 5,7·10 –4 моль/см3, т = 675 °с на стеклоуглеродном электроде при приложенном значении потенциала –0,005 в в течение 0,001 с рис. 3. линейная зависимость i-(t3/2), полученнная в расплаве kf-kcl-k2sif6, с0 = 5,7 · 10 –4 моль/см3, т = 675 ºс на стеклоуглеродном электроде при приложенном значении потенциала –0,05 в с. и. жук, л. м. минченко, о. в. чемезов, в. б. малков, а. в. исаков, ю. п. зайков. 71 2014 | № 2 | ctaфазозарождение кремния на стеклоуглероде в расплаве kf-kcl-k 2 sif 6 фазозарождения кремния в условиях наших экспериментов. оценку влияния потенциала зарождения на количество зародышей проводили при помощи анализа данных методом сканирующей электронной микроскопии подложек с si. показано, что когда к рабочему электроду при прочих равных условиях прикладывается более отрицательное значение потенциала относительно кремниевого электрода сравнения, то количество сформировавшихся зародышей на поверхности электрода растет. выводы по данным хроноамперометрии показано, что процесс фазозарождения кремния на стеклоуглеродной подложке в расплаве kf-kcl-k2sif6, при т = 675 ºс на стеклоуглеродном электроде имеет прогрессирующий характер. из sem-микрофотографий зародышей кремния, выращенных на стеклоуглеродной подложке в потенциостатическом режиме в интервале потенциалов от –0.005 до –0.03 в в расплаве kf-kcl-k2sif6 при т = 675 °с, видно, что в условиях одного эксперимента они имеют размеры, различающиеся в несколько раз, что подтверждает прогрессирующий характер возникновения зародышей кремния. 1. patent 2427526 ru. chemezov o. v., batukhtin v. p., apisarov a. p., isakov a. v., zaikov yu. p. publ. 27.08.2011. 2. chemezov o. v., vinogradov-zhabrov o. n., apisarov a. p., isakov a. v., povolotsky i. m., murzakaev a. m., maolkov v. b., zaikov yu. p., advanced mat., 2010, (9), 277 [чемезов о. в., виноградов-жабров о. н., аписаров а. п., исаков а. в., поволоцкий и. м., мурзакаев а. м., малков в. б., зайков ю. п. // перспективные материалы. 2010. № 9. с. 277–282]. 3. grishenkova o. v., semerikova o. l., isaev v. a., rasplavy, 2010, (5), 56 [гришенкова о. в., семерикова о. л., исаев в. а. // расплавы. 2010. № 5. с. 56–61]. 4. baraboshkin a. n. electrocrysstalizatiom from melt salts. moscow, nauka, 1976, 279 p. [барабошкин а. н. // электрокристаллизация металлов из расплавленных солей. м.: наука. москва, 1976. 279 с.]. 5. bieber a. l., massot l., gibilaro m., cassayre l., taxil p., chamelot p., electrochimica acta. 2012, 62, 282. 6. cai z., li y., he x., liang j. metallurgical and material transaction b., 2010, 41b, 1033. 7. apisarov a., redkin a., zaikov yu., chemezov o., isakov a. j. chem. engineering data, 2011, 56, 4733. 8. zhuk s. i., minchenko l. m., chemezov o. v., zaikov yu. p., voprosy chem. chem. technol., 2011, (4), 195. [жук с. и., минченко л. м., чемезов о. в., зайков ю. п. // вопросы химии и химической технологии. 2011. № 4 (1). с. 195–196]. 72 cta | № 2 | 2014 s. i. zhuk, l. m. minchenko, o. v. chemezov, v. b. malkov, a. v. isakov, yu. p. zaikov institute of high-temperature electrochemistry ub ras, 20, akademicheskaya street, 620990, ekaterinburg. e-mail: chem@ihte.uran.ru silicon phase origin on glassy carbon in kf-kcl-k 2 sif 6 fusion silicon nucleation process was invesigated in melt kf-kcl-k 2 sif 6 on glassy carbon substrates at 675 ºс by chronoamperometric method. using data of the chronoamperograms the linear dependence i – τ3/2 was constructed. that fact testified the progressive nucletion mode of silicon. as seem from sem micrographs silicon crystals obtained by a single pulse had different sizes, that also confirmed the progressive nucletion mode. с. и. жук, л. м. минченко, о. в. чемезов, в. б. малков, а. в. исаков, ю. п. зайков. страница 1 139 d o i: 1 0. 15 82 6/ ch im te ch .2 01 5. 2. 20 15 a. s. urusova, a. v. bryuzgina, t. v. aksenova, v. a. cherepanov institute of natural sciences, kuybisheva 48 st., ekaterinburg phone: +79527271271; e-mail: anastasiyapodzorova@yandex.ru crystal structure and oxygen nonstoichiometry of oxides in the ba-me-me’-y-o (me, me’=co, fe) system polycrystalline baмe 1–x y x o 3–δ (me=co, fe) samples were synthesized by a conventional route and glycerol–nitrate technique. according xrd patterns of single phase solid solutions baco 1–x y x o 3–δ (0.1≤x≤0.4) and bafe 0.9–y y 0.1 co y o 3–δ (0.05≤y≤0.15) were indexed using pm3m space group. the unit cell parameters were refined using rietveld full-profile analysis. oxygen non-stoichiometry of these solid solutions was measured by means of thermogravimetric technique within the temperature range 298–1273 k in air. * the work was supported under financial support from rfbr № 13-03-00958 and ministry of science and education of russian federation within the limits of the federal target program "scientific and scienceeducational cadres of innovative russia for 2009–2013" © urusova a. s., bryuzgina a. v., aksenova t. v., cherepanov v. a., 2015 introduction compounds with a perovskite structure currently provoke great interest, due to the unique physical and chemical properties. the prospect of using these compounds as electrode materials of hightemperature fuel cells and catalysts for exhaust gas after burning, pose aims for optimizing the conditions of their synthesis and complex study of their properties. the objects of this study are doped by bsublattice cobaltites baco1–xyxo3–δ and barium ferrite bafe1–x(co, y)xo3–δ. the experimental part synthesis of samples for research in system ba-me-me’-y-o (me, me ‘= co, fe) was carried out by standard ceramic technology, and mortar method with the use of glycerine as the organic precursor. under the standard ceramic technology, the mixture of raw materials with defined components ratio was thoroughly grinded and subjected to a graduated graded thermal treatment. the final annealing was carried out for 120 hours at 1373 k in air with intermediate chafing. in the synthesis with precursors, linkages of the initial components were dissolved in nitric acid while heated. next, an equimolar amount of glycerine was added to the solution, and it was evaporated. the dry residue was slowly heated over the 140 № 2 | 2015 chimica techno acta urusova a. s., bryuzgina a. v., aksenova t. v., cherepanov v. a. temperature range 873–1373 k. further annealing was carried out at a temperature of 1373 k during 60 hours, followed by its cooling the samples to room temperature with the speed 100° per hour. for determining the phase composition, the samples were analyzed by x-ray powder diffraction, using dron-6 and inelequinox 3000 in cuka-radiation (λ= 1.5418 å). filming was carried out in a range of angles 10° ≤ 2 θ ≤ 100° at speed from 1.0 to 0.02 degree per minute with a shutter at a point from 1 to 10 seconds. identification of the phases was carried out using filing jspds and software "fpeak". the unit cell parameters of single-phase oxides were calculated in the program "celref 3" and refined by full-profile rietveld analysis in the program "fullprof 2008". oxygen non-stoichiometry of complex oxides in the system ba-me-me'-y-o (me, me '= co, fe) was studied by hightemperature thermogravimetry as a function of the temperature in the range of 298 ≤ t, k ≤ 1373, at a pressure of po2 = 0.21 atm, on the machine sta 409 pc. the absolute values of the oxygen nonstoichiometry were determined by direct recovery of samples in hydrogen flow and iodometric titration. results and discussion barium cobaltite and ferrite, bacoo3–d, bafeo3–d, respectively, were synthesized by solid-phase synthesis. according to xrd, it was revealed that the complex oxides slowly cooled from 1373 k to room temperature in air are single phased. x-ray data for bacoo3–d were well described in the hexagonal cell (pr. c. p63 / mmc), with parameters: a = b = 5.665 å, c = 28.493 å. whereas barium ferrite bafeo3–d radiographic data were described in the orthorhombic cell (pr. c. p21212), with parameters: a = 5.958 å, b = 16.502 å, c = 11.008 å. it has been found that administration of yttrium into cobalt or iron sublattice leads to the formation of solid solutions bame1–xyxo3–δ (me = co, fe), stabilizing a cubic perovskite structure. for determining the homogeneity of oxides bame1–xyxo3–δ (me = co, fe) by solid-phase synthesis, the samples in the composition range 0.0 ≤ x ≤0.6 in steps of 0.05 were prepared. according to the results of xrd, it was found that the one-phase complex oxides baco1–xyxo3–δ are formed in the range of 0.1≤x≤0.4 (fig. 1.); the replacement of ferrum into yttrium, there is formed only one single-phase oxide bafe0.9y0.1o3–δ. diffraction patterns of single-phase samples were indexed within the cubic cell, space group pm3m1. as an example, fig. 2 shows the x-ray baco0.8y0.2o3–δ, treated by the method of full-profile rietveld analysis. increase of yttrium content replacing cobalt in complex oxides baco1-xyxo3-δ, leads to an increase of the parameter a and the unit cell volume, which can be attributed to the size effects: ry 3+ = 0.9 å (cn = 6) and rco 3+ /co 4+ = 0.61 / 0.53 å (cn = 6)2. to determine the feasibility of the substitution of iron into cobalt and formation of solid solutions of bafe0.9–yy0.1coyo3–δ, by solid-phase synthesis, the samples were prepared in the composition range 0.0≤x≤0.2 in steps of 0.05. x-ray data states that the substitution of iron for cobalt leds to the formation of solid solutions of bafe0.9–yy0.1coyo3–δ. 141 № 2 | 2015 chimica techno acta crystal structure and oxygen nonstoichiometry of oxides in the ba-me-me’-y-o (me, me’=co, fe) system homogenous spectrum of complex oxides bafe0.9–yy0.1coyo3–δ extends to the content of cobalt in 0.15. with the introduction of cobalt in the same sublattice in bafe0.9y0.1o3–δ, a monotonic decrease of the parameters and scope of the cells of solid solutions bafe0.9–yy0.1coyo3–δ is observed, which is explained by the size effect. change in the oxygen non-stoichiometry (d) in baco1–xyxo3–δ and bafe0.9–y y0.1coyo3-δ from the factual temperature (in the range of 273–1373 k) was studied by thermogravimetric analysis (tga) in air. the absolute value of the oxygen deficit in baco1–xyxo3–δ and bafe0.9–yy0.1coyo3–δ is determined by iodometric titration. for the composition of ba-feo3–δ value of the oxygen content was determined by direct reduction of the sample in a stream of hydrogen. with the gradual substitution of cobalt into yttrium in baco1–xyxo3–δ within the cubic structure at temperatures <700 k a monotonous decrease in oxygen is observed3. it has been shown that the introduction of cobalt in iron position in bafe0.9y0.1o3–δ leads to a decrease in the oxygen content of the samples, (see fig. 3). because injected in b-sublattice cobalt facilitates vacant disordering of the oxygen lattice, it becomes fully or partially electron acceptor (eoco = 1.7; eofe = 1.64) 4. to compensate for the excess negative charge of the acceptor defects in the structure of the oxide, an equivalent number of positive ones appears from the oxygen vacancies and / or electronic holes. fig. 1 x-ray data of solid solutions baco1–yyyo3–δ fig. 2 x-ray pattern of the sample composition baco0.8y0.2o3–δ, treated by the method of rietveld fig. 3 the dependence of the oxygen content of the cobalt content in bafe0.9–xy0.1coxo3–δ 142 № 2 | 2015 chimica techno acta urusova a. s., bryuzgina a. v., aksenova t. v., cherepanov v. a. conclusions methods of synthesis are worked out and the boundaries of the existence of solid solutions baco1–xyxo3–δ (0.0≤x≤0.4), bafe1–xyxo3–δ (x = 0.1) and bafe0.9–yy0.1coyo3–δ (0≤x≤0.15) at 1373 k in air are determined. the parameters of the unit cells studied in solid solutions are calculated and their dependences on the composition of complex oxides are built. it is found that by increasing the degree of substitution of cobalt into yttrium in baco1–yyyo3–δ, a monotonic increase in lattice parameters is happening, when substituting iron for cobalt in bafe0.9–yy0.1coyo3–δ the reduction of parameters and volume of the cells of solid solutions is happening that is explained by the size effect. for baco1–yyyo3–δ and bafe0.9–yy0.1coyo3–δ the dependence on the temperature of the oxygen non-stoichiometry in the air is obtained. it is shown that the oxygen content in complex oxides decreases with increasing temperature. by gradually replacing cobalt into yttrium in baco1– yyyo3–δ oxygen content within the cubic structures decreases monotonically. in bafe0.9–yy0.1coyo3–δ with increasing cobalt content oxygen decreases. 1. lomakov m. v., istomin, s. ya., abakumov a. m., van tendeloo g., antipov e. v. synthesis and characterization of oxygen-deficient oxides baco1–xyxo3–y, x = 0.15, 0.25 and 0.33, with the perovskite structur. solid state ionics. 2008;179(3334):1885–1889. doi: 10.1016/j.ssi/2008.05.004. 2. shannon r. d. revised effective ionic radii and systematic studies of interatomic distances in halides and chalcogenides. acta cryst. 1976;32:751-767. 3. urusova a. s., cherepanov v. a., aksenova t. v., gavrilova l.y ., kiselev e. a. phase equilibria, crystal structure and oxygen content of intermediate phases in the y-ba-co-o system. j.solid state chemistry. 2013;202:207-214. doi: 10.1016/j. ssc.2013.03.037. 4. allred a. l., rohow e. g. a scale of electronegativity based on electrostatic force. journal of inorganic and nuclear chemistry. 1958;5(4):264–268. 143 у д к 5 74 .3 44 .0 11 -1 6: 54 6. 43 1/ 54 6. 7 а. с. урусова, а. в. брюзгина, т. в. аксенова, в. а. черепанов институт естественных наук, екатеринбург, ул. куйбышева, 48. e-mail: anastasiyapodzorova@yandex.ru кристаллическая структура и кислородная нестехиометрия сложных оксидов в системе ba-me-me’-y-o (me,me’=co, fe) введение иттрия в подрешетку кобальта или железа приводит к образованию твердых растворов baмe 1–x y x o 3–δ (me=co, fe), стабилизируя кубическую перовскитовую структуру. рассчитаны параметры элементарных ячеек всех исследуемых твердых растворов и построены их зависимости от состава сложных оксидов. для всех исследуемых составов получены зависимости кислородной нестехиометрии от температуры на воздухе. * работа выполнена при финансовой поддержке гранта рффи (проект № 13-03-00958) и министерства науки и образования рф в рамках федеральной целевой программы «научные и научно-педагогические кадры инновационной россии на 2009–2013 годы» © урусова а. с., брюзгина а. в., аксенова т. в., черепанов в. а., 2015 введение соединения с перовскитоподобной структурой в настоящее время вызывают повышенный интерес, благодаря уникальным физико-химическим свойствам. перспектива использования данных соединений в качестве материалов электродов высокотемпературных топливных элементов и катализаторов дожига выхлопных газов ставит задачи по оптимизации условий их синтеза и комплексному изучению свойств. объектами настоящего исследования являются допированные по b-подрешетке кобальтиты baco1–xyxo3–δ и ферриты бария bafe1–x(co,y)xo3–δ. экспериментальная часть синтез образцов для исследования в системе ba-me-me’-y-o (me,me’=co, fe) был проведен по стандартной керамической технологии и растворным методом с использованием глицерина в качестве органического прекурсора. по стандартной керамической технологии смесь исходных веществ с определенным соотношением компонентов тщательно перетирали и подвергали ступенчатой термообработке. заключительный отжиг проводили в течение 120 ч при 1373 k на воздухе с промежуточными перетираниями. при синтезе через прекурсоры навески исходных компонентов растворя144 № 2 | 2015 chimica techno acta урусова а. с., брюзгина а. в., аксенова т. в., черепанов в. а. ли в азотной кислоте при нагревании. далее к раствору добавляли эквимолярное количество глицерина и раствор выпаривали. полученный сухой остаток медленно нагревали в интервале температур 873–1373 k. дальнейший отжиг проводили при температуре 1373 k в течение 60 ч, с последующим охлаждением образцов до комнатной температуры со скоростью 100°/час. для определения фазового состава образцы анализировали методом рентгеновской порошковой дифракции, с использованием дифрактометров дрон-6 и inelequinox 3000 в cuka-излучении (λ = 1,5418 å). съемку проводили в интервале углов 10° ≤ 2 θ ≤ 100° со скоростью от 1,0° до 0,02° в минуту с выдержкой в точке от 1 до 10 с. идентификацию фаз осуществляли при помощи картотеки “jсpds” и программного пакета “fpeak”. параметры элементарных ячеек однофазных оксидов были рассчитаны в программе “сelref-3” и уточнены методом полнопрофильного анализа ритвелда в программе “fullprof-2008”. кислородная нестехиометрия сложных оксидов в системе ba-me-me’-y-o (me,me’=co, fe) изучена методом высокотемпературной термогравиметрии как функция температуры в интервале 298 ≤ t, k ≤ 1373 при давлении pо2 = 0,21 атм. на установке sta 409 pc. абсолютные значения кислородной нестехиометрии были определены путем прямого восстановления образцов в токе водорода и йодометрическим титрованием. результаты и обсуждение кобальтит и феррит бария bacoo3–d и bafeo3–d, соответственно, были синтезированы методом твердофазного синтеза. по данным рфa установлено, что сложные оксиды, медленно охлажденные с 1373 k до комнатной температуры на воздухе, были однофазными. рентгенографические данные для bacoo3-d хорошо описывались в гексагональной ячейке (пр. гр. p63/mmс), с параметрами: а = b = 5,665 å, c = 28,493 å. тогда как для феррита бария bafeo3-d рентгенографические данные описывались в орторомбической ячейке (пр. гр. p21212), с параметрами: а = 5,958 å, b = 16,502 å, c = 11,008 å. было установлено, что введение иттрия в подрешетку кобальта или железа приводит к образованию твердых растворов baмe1–xyxo3–δ (me=co, fe), стабилизируя кубическую перовскитовую структуру. для определения области гомогенности оксидов baмe1–xyxo3–δ (me=co, fe) методом твердофазного синтеза были приготовлены образцы в интервале составов 0,0 ≤ x ≤ 0,6 с шагом 0,05. по результатам рфа установлено, что однофазные сложные оксиды baco1–xyxo3–δ образуются в интервале составов 0,1 ≤ x ≤ 0,4 (рис. 1), а при замещении железа на иттрий образуется единственный однофазный оксид состава bafe0,9y0,1o3–δ. дифрактограммы однофазных образцов были проиндексированы в рамках кубической ячейки, пространственная группа pm3m [1]. в качестве примера на рис. 2 представлена рентгенограмма baco0,8y0,2o3–δ, обработанная по методу полнопрофильного анализа 145 № 2 | 2015 chimica techno acta кристаллическая структура и кислородная нестехиометрия сложных оксидов в системе ba-me-me’-y-o (me,me’=co, fe) ритвелда. увеличение содержания иттрия, замещающего кобальт в сложных оксидах baco1–xyxo3–δ, приводит к увеличению параметра a и объема элементарной ячейки, что можно связать с размерными эффектами: ry 3+ = 0,9 å (к.ч. = 6) и rco 3+ /co 4+ = 0,61/0,53 å (к.ч. = 6)2. для определения возможности замещения железа на кобальт и образования твердых растворов состава bafe0,9-yy0,1coyo3-δ методом твердофазного синтеза были приготовлены образцы в интервале составов 0,0 ≤ x ≤ 0,2 с шагом 0,05. из рентгенографических данных установлено, что замещение железа на кобальт привело к образованию твердых растворов состава bafe0,9–yy0,1coyo3–δ. область гомогенности сложных оксидов bafe0,9–yy0,1coyo3–δ простирается до содержания кобальта в 0,15. при введении кобальта в подрешетку железа в bafe0,9y0,1o3-δ наблюдается монотонное уменьшение параметров и объема ячеек твердых растворов bafe0,9–yy0,1coyo3–δ, что объясняется размерным эффектом. изменение кислородной нестехиометрии (d) в baco1–xyxo3–δ и bafe0,9–yy0,1coyo3–δ от температуры (в диапазоне 273–1373 k) изучали методом термогравиметрического анализа (тга) на воздухе. абсолютное значение кислородного дефицита в baco1–xyxo3–δ и bafe0,9–yy0,1coyo3–δ определяли методом йодометрического титрования. для состава bafeo3-δ значение содержания кислорода было определено методом прямого восстановления образца в токе водорода. при постепенном замещении кобальта на иттрий в baco1–xyxo3–δ в рамках кубической структуры при температурах < 700 кk наблюдается монотонное уменьшение содержания кислорода [2]. показано, что введение кобальта в позицию железа в bafe0,9y0,1o3–δ приводит к уменьшению содержания кислорода в образцах (рис. 3). вследствие того, что внедряемый в b-подрешетку кобальт облегчает вакансионное разупорядочение кислородной решетки, так как становится полностью или частично акцептором электронов (эоco = 1,7; эоfe = 1,64) [3]. для компенсации избыточного отрицательного заряда акцепторных дефектов в структуре оксида появляетрис. 1. рентгенографические данные твердых растворов baco1–yyyo3–δ рис. 2. рентгенограмма образца состава baco0,8y0,2o3–δ,обработанная по методу ритвелда 146 № 2 | 2015 chimica techno acta урусова а. с., брюзгина а. в., аксенова т. в., черепанов в. а. ся эквивалентное количество положительных зарядов – кислородных вакансий и/или электронных дырок. выводы отработаны методы синтеза и определены границы существования твердых растворов baco1–xyxo3–δ (0,0 ≤ x ≤ 0,4), bafe1–xyxo3–δ (x = 0,1) и bafe0,9–yy0,1coyo3–δ(0 ≤ x ≤ 0,15) при 1373 k на воздухе. рассчитаны параметры элементарных ячеек исследуемых твердых растворов и построены их зависимости от состава сложных оксидов. установлено, что при увеличении степени замещения кобальта на иттрий в baco1–yyyo3–δ происходит монотонное увеличение параметров решетки, а при замещении железа на кобальт в bafe0,9–yy0,1coyo3–δ происходит уменьшение параметров и объема ячеек твердых растворов, что объясняется размерным эффектом. для baco1–yyyo3–δ и bafe0,9–y y0,1coyo3–δ получены зависимости кислородной нестехиометрии от температуры на воздухе. показано, что содержание кислорода в сложных оксидах уменьшается с ростом температуры. при постепенном замещении кобальта на иттрий в baco1–y yyo3–δ содержание кислорода в рамках кубической структуры монотонно уменьшается. в bafe0,9–y y0,1coyo3–δс увеличением содержания кобальта содержание кислорода уменьшается. 1. lomakov m. v., istomin, s. ya., abakumov a. m., van tendeloo g., antipov e. v. synthesis and characterization of oxygen-deficient oxides baco1–xyxo3–y, x = 0.15, 0.25 and 0.33, with the perovskite structur. solid state ionics. 2008;179(3334):1885–1889. doi: 10.1016/j.ssi/2008.05.004. 2. shannon r. d. revised effective ionic radii and systematic studies of interatomic distances in halides and chalcogenides. acta cryst. 1976;32:751-767. 3. urusova a. s., cherepanov v. a., aksenova t. v., gavrilova l. y., kiselev e. a. phase equilibria, crystal structure and oxygen content of intermediate phases in the y-ba-co-o system. j.solid state chemistry. 2013;202:207-214. doi: 10.1016/j. ssc.2013.03.037. 4. allred a. l., rohow e. g. a scale of electronegativity based on electrostatic force. journal of inorganic and nuclear chemistry. 1958;5(4):264-268. рекомендуем при цитировании данно статьи следующую ссылку: urusova a. s., bryuzgina a. v., aksenova t. v., cherepanov v. a. crystal structure and oxygen nonstoichiometry of oxides in the ba-me-me’-y-o (me, me’=co, fe) system / chimica techno acta. 2015. vol. 2. № 2. p. 139–146. рис. 3. зависимость содержания кислорода от содержания кобальта в bafe0,9–xy0,1coxo3–δ hopping conductivity in a system with zns crystal lattice by non-constant force field molecular dynamics 153 d o i: 1 0. 15 82 6/ ch im te ch .2 01 8. 5. 3. 05 a. a. raskovalov institute of high-temperature electrochemistry, ural branch of the russian academy of sciences, 20 akademicheskaya st., ekaterinburg, 620137, russian federation e-mail: other@e1.ru hopping conductivity in a system with zns crystal lattice by non-constant force field molecular dynamics in the paper non-constant force field molecular dynamics was used to study conductivity behavior on zns crystal lattice. the considered conductivity provided by electron hopping between localization centers placed randomly according to zns geometry. it was shown that the conductivity behavior depends on the maximal hopping distance. for the small distances the conductivity passes through the maximum around equimolar concentrations of electron donors and acceptors. increasing in the maximal hopping distance leads to increasing in conductivity values and change shape of its concentration dependence. keywords: molecular dynamics; non-constant force field; polaron hopping; zns lattice. received: 08.10.2018. accepted: 26.10.2018. published: 31.10.2018. © raskovalov a. a., 2018 raskovalov a. a. chimica techno acta. 2018. vol. 5, no. 3. p. 153–157. issn 2409–5613 introduction concentration dependences of  conductivity in  different systems has already for a long time obtained the attention of researchers [1–3]. such questions are often referred as percolation problems, including conductivity provided by polaron hopping between localization cen ters [2, 3]. at the moment a big amount of equations were suggested for describing concentration dependences of conducti vity in various systems. however, analytical solutions can not account all multiplicity of factors acting on  conductivity: thermal motion of ions, their mobilities, sizes and etc. an attempt to consider all microscopic picture of the conductivity process can be made with numerical methods which began to develop with progress in computer engineering. one of the most widespread methods for studying of many-boded systems on a microscopic level is molecular dynamics simulation (md) [4, 5]. unfortunately, classical md can not deal with polaron hopping conductivity, because this phenomenon has quantum-mechanical nature. early we have suggested scheme which allows including hopping conducti vity into md [6]. this approximation is possibility of  particles to  change their oxidation degree (and, consequently, properties and interaction laws) runtime. thus force field becomes variable and method can be called as “non-constant force field molecular dynamics” (ncffmd). the method is implemented in “aztotmd” software which is available on website http://ncffmd.ru / [7]. in our previous work we have demonstrated possibilities of the method and 154 the software for simulation of redox processes in liquid media [8]. the aim of the present paper is to study percolation behavior of a system with polaron hopping between localization centers placed according to zns crystal lattice. simulation details md simulations were performed with “aztotmd” software [7] in  canonical (nvt) ensemble. newton’s equations of motion were integrated by velocity verlet algorithm [9] with timestep of 1 fs during 100’000 steps (0.1 ns). equilibration time was 1 ps (1000 timesteps). electrostatic interactions were accounted using the ewald summation. nosé-hoover thermostat [10] with relaxation time of 0.2 ps was used for maintaining the temperature around 298 k.  the considered system consists of electron donors (a+), electron acceptors (a2+) and counterions (x-). the number of xions was chosen equal to 500 for all studied systems. amounts of a+ and a2+ cations were given in such way to keep electroneutrality and obtain desired ratio of a+ / a2+ concentrations. short range interactions were given by pair potential suggested for cucl-cucl2 binary system [11] since solid cucl has a zns structure. initial configurations were generated with the abovementioned site [7]. the starting ion coordinates correspond to zns crystalline structure with some vacant sites. the box was cubic with the edge length of 25.7 å for  all studied systems. this box length roughly corresponds to  a  cell parameter of cucl. the sizes of boxes was the same for simplification and, in addition, ionic radii of cu+ and cu2+ (which are prototypes of ions a+ and a2+) are close to each other and equal to 0.77 and 0.73 å, correspondingly [12]. for activation of electron transfer routine during the simulation value of ejump directive was set as 1 in control.txt file (one of input files for the program). the program performs electron transfer if the system decreases energy by this transfer. the difference in system energy before and after electron transfer is determined according to formula [6]: �u v v v v c q q q r q ij ik ii ik i jk ii jk i k i j k i ii i i ik j i � � � ��� �� � � � � � � , 1 � ii j i jkk i j x i j q r e a x x �� � � � � � � � � � �� � � , , � (1) where ∆uij is energy difference after electron transfer from i-th particle to j-th particle, vik is the van der waals energy of interaction between i-th and k-th par ticles, provided by corresponding pair potentials, q is the electric charge of the particle, r is the distance between par ticles, c is the constants in coulomb’s law, ε is the relative permittivity of the media, δex is the voltage drop on  the x axis, a  is the box length and upper indices i and ii mean states of particles before and after electron transfer, correspondingly. electronic current (i) was determined through a  time derivative of  difference in  the number of  electrons transferred in  positive and negative directions: i e d n n dt � �� �� � , (2) where e is the electron’s charge, n+ and n are the numbers of electron hops through oyz edge in positive and negative directions along x-axis. 155 results and discussion at first let us discuss a structure of the system. the numerical experiments showed that with the presented here force field the crystal lattice is stable only in  the case of the even numbers of both a+ and a2+ cations. in this case one can observe crystal lattice with zns structure independent of the time of the system evolution, fig. 1. one can see some vacant sites in  cation sublattice, because every a2+ ion demands one cation vacancy to save electroneutrality. despite of this voids the system keeps own crystal lattice right up to composition of 0.2ax·0.8ax2. examples of radial distribution functions (rdf) are given in fig. 2. the rdfs are characteristic for crystalline systems; there are a number of well-resolved maxima. distance for  the first maximum determines more probable distance between ions in the first coordination sphere for a chosen pair. the position of the first maximum for  a+–a2+ pair does almost not depend on  composition and electric field and equals to  ~3.7 å.  the distance at which rdf for a+–a2+ pair starts to exceed 0.1 is also almost constant and equal to ~2.7 å. this means that if length of  electron hopping is lesser than 2.7  å, the system will not have electronic conductivity. for this reason, we set maximal hopping distance to be much higher than 2.7 å by specifying of relec directive in the control.txt file. usually, the number of electron hops through some plane is a  linear function of time, fig. 3. without external electric field these numbers are the same for positive and negative directions, but in the case of the field the slopes of these lines differs from each other (fig. 3). the corresponding value of current can be obtained from expression (2). note that for observation of noticeable current we need to apply an external electric field with a colossal voltage, because current density of 1 a·cm–2 is approximately equal to 0.625·10–9 singlecharged particles per picosecond, per square angstrom (in units more conve nient for  md). to see the noticeable number of particles for the simulation time we need to obtain high current which requires high fig. 1. the structure of the simulated system 0.5ax·0.5ax2 obtained after simulation under 1v electric field during 100 000 timesteps. big green spheres denote xanions, small red and orange ones — a2+ and a+ cations, correspondingly fig. 2. the radial distribution functions, g(r), of the simulated system 0.5ax·0.5ax2 for a+–x– and a2+–a+ ion pairs 1 2 3 4 5 6 7 8 9 0,0 0,5 1,0 1,5 2,0 2,5 3,0 3,5 4,0 4,5 5,0 5,5 g( r) , å r, å pair a+ – x– pair a2+ – a+ 156 voltages. however, extremely high voltages can lead to the destruction of a system. in our simulations we used voltage of  1  v, higher voltages led to breaking of crystal lattice and liquid-like structure of the system. electronic current as a function of composition for different values of the maximal hopping distance is presented in fig. 4. as expected, the current grows with this parameter. at small values of the distance the current passes through the maximum around x = 0.5. from statistical point of view the current will be maximal if pro bability of finding the electron acceptor (a2+) near the electron donor (a+) is maximal. this probability is proportional to the product of their concentrations which is maximal at x = 0.5. the difference of observed position of maximum from 0.5 can be caused by some reasons: asymmetry in pair potentials, different mobility of a+ and a2+ ions and etc. at high values of the maximal hopping distance the current grows with concentration of a+ species. this implies that if electron can hop on enough long distances the conductivity will be limited by the concentration of electron donors. in other words, if there is an electron donor, an electron acceptor always can be found. so the maximal length of the electron hop determines the shape of the concentration dependence of the conductivity. conclusions non-constant force field molecular dynamics is able to  simulate electron hops between electron donors and acceptors affected by  thermal movement. thus, it is possible to study polaron conductivity of a given system by this method. in this work concentration dependence of  conductivity was considered in the case of zns geometry for electron localization cen ters. it was shown that the position of the conductivity maximum depends on the maximal hopping distance. fig. 3. the number of electron hops through the oyz plane in positive and negative directions (and their difference) as a function of time. the simulated system is 0.5ax·0.5ax2, the maximal hopping distance is 4.5 å, the applied voltage is 1 v fig. 4. electronic current (i) as a function of composition (x) in the xax–(1–x)ax2 system under external electric field of 1 v and different maximal hopping distance (re) 0 10 20 30 40 50 60 70 80 90 100 0 500 1000 1500 2000 2500 di�erence in negative direction n τ, ps in positive direction 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0 1 2 3 4 5 6 7 x(ax) re = 3.5å re = 3.8å re = 4.0å re = 4.5å i, e · p s– 1 157 acknowledgements the reported study was funded by russian foundation for basic research (rfbr), according to the research project no. 16-33-60095 mol_а_dk. references 1. kirkpatrick s. percolation and conduction. rev mod phys. 1973; 45(4):574–88. doi: 10.1103 / revmodphys.45.574. 2. kurkijarvi j. conductivity in random systems. ii. finite-size-system percolation. phys rev b. 1974; 9(15):770–4. doi: 10.1103 / physrevb.9.770. 3. shklovskii bi, éfros al. percolation theory and conductivity of  strongly inhomogeneous media. sov phys  usp. 1975; 18(11):845–62. doi: 10.1070 / pu1975v018n11abeh005233. 4. allen mp, tildesley dj. computer simulation of liquids. oxford: clarendon press; 1987. 385 p. 5. frenkel d, smit b. understanding molecular simulation from algorithms to applications. san diego, california: academic press; 1996. 638 p. 6. raskovalov aa. a new extension of classical molecular dynamics: an electron transfer algorithm. j comp chem. 2017; 38(5):926–32. doi: 10.1002 / jcc.24755. 7. non-constant force field molecular dynamics. available from: http://ncffmd.ru / set. php?lang=en (accessed: 22.02.2017). 8. raskovalov aa, latypov aa. simulation of red-ox reactions in liquid media with non-constant force field molecular dynamics. rasplavy [melts]. 2018; 6. in press. doi: 10.1134 / s0235010618060063. 9. verlet l. computer “experiments” on classical fluids. i. thermodynamical properties of lennard-jones molecules. phys rev. 1967; 159(1):98–103. doi: 10.1103 / physrev.159.98. 10. martyna gj, tuckerman me, tobias dj, klein ml. explicit reversible integrators for  extended systems dynamics. mol phys. 1996; 87(5):1117–57. doi: 10.1080 / 00268979600100761. 11. raskovalov aa, shevelin pyu. physico-chemical properties of the molten cucl — cucl2 system: experiment, thermodynamics and molecular dynamics simulations. j sol chem. 2018. in press. doi: 10.1007 / s10953-018-0817-x. 12. shannon rd. revised effective ionic radii and systematic studies of  interatomic distances in halides and chalcogenides. acta cryst. 1976;a32:751–67. doi: 10.1107 / s0567739476001551. preparation and characterization of bi26–2xmn2xmo10o69-d and bi26.4mn0.6mo10–2yme2yo69-d(me = v, fe) solid solutions z. a. mikhaylovskaya1, m. v. morozova1, e. s. buyanova1, s. a. petrova2, i. v. nikolaenko3, d. g. kellerman3 1 ural federal university, 19 mira st., ekaterinburg, 620000, russia 2 institute of metallurgy ub ras, 101 amundsen st., ekaterinburg, 620016, russia 3 institute of solid state chemistry ub ras, 91 pervomayskaya st., ekaterinburg, 620990, russia preparation and characterization of bi 26–2x mn 2x mo 10 o 69-d and bi 26.4 mn 0.6 mo 10–2y me 2y o 69-d (me = v, fe) solid solutions ∙ ∙cm ∙ ∙cm ∙ ∙cm ∙ ∙cm keywords: introduction bi2o3-based complex oxides exhibit a variety of properties including high oxide-ion conductivity and/or electronic conductivity at medium temperatures (573–973 k), ferroelectric and magnetic effects, as well as catalytic activity. these compounds crystallize in a number of different structure types, for example fluorite-type structures (δ-bi2o3 -based complex oxides [1]), layered aurivillius type structures (the bimevox family [2]) or unique columnar structures (bi26mo10o69 [3]). the latter is reported to contain [bi12o14]∞ columns oriented along the y-axis, moon polyhedrons and «isolated» bi3+ ions [4]. bi26mo10o69 exhibits pure one-dimensional oxide ion transport along the columnar fragments (y axis) [5]. the values of ionic conductivity are close to that observed in the bimevox and stabilized zirconia oxide ion conductors [6]. hence bi26mo10o69-based materials are being considered as alternative electrolytic materials for gas conversion membranes, separators, sensors and fuel cells. bi26mo10o69 is part of a small solid solution range in the bi2o3-moo3 system (2.57  ≤  bi/mo  ≤  2.77) [5]. a reversible monoclinic to triclinic phase transition is observed on cooling at c.a. 310  °c, resulting in a significant decrease in ionic conductivity and an increase in activation energy. the structure of the monoclinic form was described in [5] with the following unit cell parameters: a = 11.74 å, b = 5.80 å, c = 24.79 å, β = 102.84° with p2/c space group symmetry. the monoclinic model includes bismuthate columns, «isolated» bi3+ ions and moo4 tetrahedra. however, the model only accounted for 68 of the 69 oxygen atoms per formula unit required to maintain electroneutra lity. the structure of the triclinic form with one additional oxygen position was suggested in [7]. it includes moo5 polyhedra as well as moo4 tetrahedra. solid solution formation in the bi26mo10o69 system can be realized by substitution of either bi3+ or mo6+ cations. bi26mo10-2yme2yo69-δ solid solutions have been reported for me = li, mg, al, si, ge [8]; co [9]; v, p, w [6], while, larger cations can be substituted for bismuth including pb [10]; ln [11]; ca, sr, ba [6] and mn [12]. it was shown previously that the best conductivity properties of bi26-2xmn2xmo10o69-d series was related to the x = 0.3 compound [12]. the present work is devoted to the following investigation of bi26-2xmn2xmo10o69-d series and the synthesis, and electrical cha racterization of new substituted bismuth molybdates bi26-2xmn2xmo10-2yv2yo69-d and bi26-2xmn2xmo10-2yfe2yo69-d. experimental polycrystalline samples of general formula bi26-2xmn2xmo10o69-d and bi26-2xmn2xmo10-2yme2y o69-d were prepared using bi2o3 (99.9 %), moo3 (99.5 %), mno (99.7 %), v2o5 (99.5 %) fe2o3 (99.5 %) as precursors. in each case, stoichiometric mixtures of the starting materials were thoroughly ground in an agate mortar with ethanol as a dispersant. after drying in air, pellets were pressed and placed on a bed of unreacted powder in an alumina crucible. the pellets were heated to 823 k for 48 h, followed by quenching, regrinding and re-pelletizing. the samples were then heated at 1123  k for 24 h, followed by slow cooling in air to the room temperature. the solubility limits (x and y) and crystal structure of bi26-2xmn2xmo10o69-d, bi26-2xmn2xmo10-2yv2yo69-d and bi26-2xmn2xmo10-2yfe2yo69-d were determined by x-ray powder diffraction (xrpd). x-ray powder diffraction data were obtained on a bruker advance d8 diffractometer with a våntec1 detector using the cuk radiation ( 1 = 1.54056 å and 2  = =  1.54439  å). data were collected in flat plate / geometry and calibrated against external si standard in the 2 range 5–70 , in steps of 0.021356 , with an effective scan time of 1 s per step. xrpd data were obtained using the equipment of the centre for shared use «ural-m» (institute of metallurgy ub ras, ekaterinburg). the size of the particles of the powders was studied by means of the laser diffraction method using a sald-7101 shimadzu analyzer. the morphology of the obtained powders and their chemical composition were studied using the jeol jsm 6390la with a jed 2300 edx-analyzer. hydrostatic weighting (archimedes method) was used for investigation of density of ceramic pellets covered with a thin layer of waterproof coating. the volume porosity of ceramic samples was obtained by comparing for the experimental and theoretical (x-ray) densities of the samples. the variable temperature measurements of magnetic susceptibility were collected on squid magnetometer mpms xl7, quantum design (ural center for shared use «modern nanotechnology», ural federal university, ekaterinburg). the impedance spectroscopy method was used for electrochemical characterization of the ceramic samples of substituted bi26mo10o69 in the range of 523–1123  k using elinz-3000 impedance spectro meter. for the impedance measurements the samples were pelletized at 20 bar to yield pellets of 10 mm in diameter and ca. 2.5 mm thickness. the pressed pellets were then heated to 1123  k for 24 h, before slow cooling in air to room temperature. platinum electrodes were applied to the pellets by covering them with a thin layer of nh4(ptcl6) following its decomposition at ca. 673  k. for the analysis of impedance plots the equivalent electrical circuits method was used (zview software, version 2.6b, scribner associates, inc.). results and discussion characterization of ceramic and powder samples the solid solutions limit for bi26-2xmn2xmo10o69-d determined by xrpd is x = 0.8. the solubility limits of bi26-2xmn2xmo10-2yv2yo69-d and bi26-2xmn2xmo10-2yfe2yo69-d are y = 0.4 and y = 0.2, respectively. compositions with low dopant content crystallized in the triclinic structure (y = 0.1), whereas the compositions with higher dopant content showed the monoclinic structure of bi26mo10o69-d [5]. the refined unit cell parameters of the mn + fe and mn+v doped bismuth molybdates are given in tables 1 and 2, respectively. they show general compression of unit cell with increase of y and a good adherence to vegard’s law in the ranges of monoclinic modification. decrease of homogeneity ranges as compared with bi26mo10-2yfe2yo69-d (y < 0.3 [13]) and bi26mo10-2yv2yo69-d (y < 0.7 [6]) can be extable 1 unit cell parameters of bi26-2xmn2xmo10-2yv2yo69-d y modifi-cation a±0.002, å b±0.001, å c±0.005, å α±0.01, ° β±0.01, ° γ±0.01, ° v±0.01, å3 0.1 tricl 11.751 5.858 24.561 89.80 102.19 89.20 1652.59 0.2 monocl 11.851 5.856 24.560 90 102.19 90 1666.02 0.3 monocl 11.847 5.851 24.540 90 102.27 90 1662.18 0.4 monocl 11.847 5.845 24.535 90 102.23 90 1660.39 table 2 unit cell parameters of bi26-2xmn2xmo10-2yfe2yo69-d y modifi-cation a±0.002, å b±0.001, å c±0.005, å α±0.01, ° β±0.01, ° γ±0.01, ° v±0.01, å3 0.1 monocl 11.731 5.796 24.772 90 102.82 90 1642.333 0.2 monocl 11.728 5.795 24.764 90 102.74 90 1641.619 plained by the distortion of moon polyhedra, caused by mn presence. in the present work, as well as in [12], mn ions were assumed to have an oxidation state of +2. th e measurements of magnetic susceptibility vs. temperature gave a good adherence to curie–weiss law (fig. 1). th e calculated parameters of curie–weiss law are given in the table 3. calculated magnetic moment for mn is 5.95 while the theoretical value assuming mn+2 is 5.92. th us manganese is a bivalent dopant, which is typical for bismuth sublattice. representative electron micrographs of powdered and ceramic samples are shown in fig.  2. sem micrographs of powdered samples showed a homogenous distribution of large and small grains (fig.  2  a to d), with grain sizes in the range ~0.1–10  μm for all samples, which correlates well with the results of laser dispersion analysis. aft er sintering of pellets, dense ceramic samples were formed (fig.  2  a to  c). th e majority of pores is isolated and has a spherical form. sintered ceramic pellets’ densities of more than 97 % of the theoretical (x-ray) density were confi rmed by the archimedes method. th e edx analysis showed that the concentration of dopants was close to theoretical, whereas concentrations of bismuth and molybdenum couldn’t be determined separately because of the overlapping of analytical peaks. th e concentration of all dopants confi rms the theoretical formula within the experimental errors. electrical conductivity impedance spectroscopy was used for the electrochemical characterization of the ceramic samples. fig.  3  (a,  b) shows examples of complex plane plots of bi26.4mn0.6mo9.6v0.4o69-d at diff erent temperatures. th is shape of complex plane plots is typical for all studied compositions. equivalent electrical circuits for every temperature gave good agreement between calculated and experimental impedance curves. it can be seen that the shape of the complex plane plots appears to be diff erent in diff erent temperature regions. in general, two types of complex plane plots can be distinguished: at relatively high temperatures and at relatively low temperatures. at high temperatures (higher than a.c. 823–873 k) the impedance plots of all investigated complex oxides correspond to a broadened semicircle or two separate semicircles (fig.  3a), the high frequency intercept is non zero. th e equivalent electrical circuit used for the high temperature table 3 values for curie–weiss law χ = ao+c/(t-θ) and μ for bi24.4mn1.6mo10o69-d sample ао cm3/mol с, cm3*k/mol θ, k μ calc μ(mn +2)teor –0.00187 3.55 –4.7685 5.95 5.92 fig. 1. th e magnetic susceptibility of bi24.4mn1.6mo10o69-d sample vs temperature. points are experimental data, solid line – model curve (curie–weiss law) fig. 3. characteristic impedance plots and equivalent electrical circuits of bi26.4mn0.6mo9.2v0.8o69-d at: a – high temperature region (973 k); b – low temperature region (623 k) fig. 2. sem-images of bi25.4mn0.6mo9.6v0.4o69-d: a – ceramic pellet surface, secondary electrons imaging, scale 1:5000; b – ceramic pellet surface, backscattering electrons imaging, scale 1:6500; c – ceramic pellet cross-section, secondary electrons imaging, scale 1:5000; d – powder surface, secondary electrons imaging, scale 1:1000 region is shown in fig.  3a. it can be described as r1 – r2(cpe1) – r3(cpe2) serial connection, where r2 (cpe1) and r3 (cpe2) fragments are parallel connections of resistor (r) and constant phase element (cpe). th e r2(cpe1) and r3(cpe2) parallel connections correspond to electrochemical processes at the electrodes (the ionic migration and interfacial processes at the electrodes), what can be confi rmed by cpe1 and cpe2 capacity parameters values [14], and r1 describes bulk resistance of the sample. grain boundary resistance wasn’t observed for all compounds. th e similar results were presented in [15] for bi26mo10-xgexo69-d compounds, when only bulk resistance was observed. at low temperatures the complex plane plots of bi26-2xmn2xmo10-2yv2yo69-d and bi26-2xmn2xmo10-2yfe2yo69-d and their equivalent electrical circuits change (fig. 3b). th e impedance plot in this case consists of one separate distinct semicircle and two adjacent semi-circles. th e high frequency intercept of the high-frequency semicircle is equal to zero. th e equivalent electrical circuits can be described as r1(c1)–r2(cpe2)–r3(cpe3) serial connection, where ri (cpei or ci) are parallel connections of resistor (r) and constant phase element (cpe) or capacitor (c). th e r1(c1) connection describes the high frequency semi-circle, the c1 capacitance value is about 10–11 f, therefore r1 can be attributed to the total conductivity of the sample [14]. th e r2(cpe2) element can be attributed to electrochemical processes at the electrodes (the «capacitance» value of cpe2 is about 10–6  f), r3 (cpe3) can describe complicated diff usion processes at low temperatures (the «capacitance» value of cpe2 is about 10–5 f). according to the results of the impedance measurements, electrical conductivity vs. temperature dependences were plotted for bi26-2xmn2xmo10-2yv2yo69-d and bi26-2xmn2xmo10-2yfe2yo69-d ceramic samples. fig.  4 and 5 show arrhenius plots of total conductivity of bi26-2xmn2xmo10-2yv2yo69-d and bi26-2xmn2xmo10-2yfe2yo69-d. th e characteristic arrhenius plots (log (σ)–1000/t) have linear shape, and activation energy values (0.7–0.8 ev) are typical for the oxygenion conductors. for the parent compound bi26mo20o69-d, a signifi cant drop in conductivity and increase in activation energy (from 0.5–0.65 ev to 0.9 ev) is seen at temperatures below ca. 623 k due to the monoclinic to triclinic phase transition. th is is not the case for the solid solutions, and it can be concluded that substitution lowers fig. 4. arrhenius plots of total conductivity for selected bi26-2xmn2xmo10-2yv2yo69-d compounds fig. 5. arrhenius plots of total conductivity for selected bi26-2xmn2xmo10-2yfe2yo69-d compounds the monoclinic to triclinic phase transition to the temperatures below 523  k, which is the lower limit of the electrical measurements. a conductivity maximum occurs in single-phase compositions with maximum values of y = 0.2-0.4. the conductivity of bi26.4mn0.6mo9.6fe0.4o69–d was 1.2∙10–2  s∙cm–1 at 973  k and 2.2∙10–4  s∙cm–1 at 623  k, and the conductivity of bi26.4mn0.6mo9.2v0.8o69–d was 2.2∙10–3 s∙cm–1 at 973 k and 2.2∙10–5 s∙cm–1 at 623  k, respectively. in general, the change of electroconductive properties can be explained by the increase of the electronic part of total conductivity due to the mn doping, and by the raise of the oxygen-ion mobility due to the distortion of mo(fe/v)on polyhedra. conclusions the solid solutions limit for bi26-2xmn2xmo10o69-d is x = 0.8, and the solubility limits of bi26-2xmn2xmo10-2yv2yo69-d and bi26-2xmn2xmo10-2yfe2yo69-d are y = 0.4 and y = 0.2, respectively. compositions with low dopant content crystallize in the triclinic structure (y = 0.1), and compositions with higher dopant content – in the monoclinic structure. mn+fe and mn+v doped systems were synthesized for the first time and the formation of dense ceramics of these systems has been demonstrated. in general, the change of electroconductive properties depends of dopant concentration and is influenced by the metal-oxygen polyhedra distortion and the increase of the electronic part of total conductivity. acknowledgements this work was financially supported by the russian foundation for basic research (projects № 16-33-60026, 17-53-04098). the equipment of the ural center for shared use «modern nanotechnology» (ural federal university, ekaterinburg) was used. xrpd data were obtained using the equipment of the centre for shared use «ural-m» (institute of metallurgy ub ras, ekaterinburg). references 1. boivin jc. structural and electrochemical features of oxide ion conductors. int j inorg mat. 2001;3:1261-6. doi:10.1016/s1466-6049(01)00118-0. 2. abraham f, boivin jc, mairesse g, nowogrocki g. the bimevox series: a new family of high performances oxide ion conductors. solid state ionics. 1990;40-1:934-7. doi:10.1016/0167-2738(90)90157-m. 3. fonseca fc, steil mc, vannier rn, mairesse g, muccillo r. grain-sized influence on the phase transition of bi26mo9wo69: an x-ray diffraction and impedance spectroscopy study. solid state ionics. 2001;140:161-71. doi:10.1016/s0167-2738(01)00705-6. 4. buttrey dj, vogt t, yap gpa, rheingold al. the structure of bi26mo10o69. mater res bull. 1997;32:947-62. doi:10.1016/s0025-5408(97)00063-9. 5. vannier rn, mairesse g, abraham f, nowogorski g. bi26mo10oδ solid solution type in the bi2o3–moo3–v2o5 ternary diagram. j solid state chem. 1996;122:394-406. doi:10.1006/jssc.1996.0133. 6. vannier rn, danze s, nowogrocki g, huve m, mairesse g. a new class of mono-dimensional bismuth-based oxide anion conductors with a structure based on [bi12o14]∞ columns. solid state ionics. 2000;136-7:51-9. doi:10.1016/s01672738(00)00351-9. 7. ling cd, miiller w, johnson mr, richard d, rols s, madge j, evans ir. local structure, dynamics, and the mechanisms of oxide ionic conduction in bi26mo10o69. chem mater. 2012;24:4607-14. doi:10.1021/cm303202r. 8. bastide b, enjalbert r, salles p, galy j. ionic conductivity of the oxide family bi[bi12o14][(mo,m)o4]5 with m=li, mg, al, si, ge and v. solid state ionics. 2003;158:351-8. doi:10.1016/s0167-2738(02)00910-4. 9. mikhailovskaya za, buyanova es, petrova sa, morozova mv, zhukovskiy vm, zakharov rg, tarakina nv, berger if. cobalt-doped bi26mo10o69 : crystal structure and conductivity. j solid state chem. 2013;204:9-15. doi: 10.1016/j.jssc.2013.05.006. 10. enjalbert r, hasselmann g, galy j. a new mixed oxide with (bi12o14)n columns: pbbi12mo5o34. acta crystallogr, sect c: struct chem. 1997;53:269-72. doi:10.1107/ s0108270196013698. 11. galy j, salles p, rozier p, castro a. anionic conductors ln2/3[bi12o14](moo4)5 with ln=la, nd, gd, ho, yb. synthesis–spark plasma sintering–structure–electric properties. solid state ionics. 2006;177:2897-902. doi:10.1016/j.ssi.2006.07.059. 12. mikhaylovskaya za, buyanova es, morozova mv, petrova sa, nikolaenko iv. mn-doped bi26mo10o69-d: synthesis and characterization. ionics. 2017;23:1107-14. doi:10.1007/s11581-016-1917-5. 13. mikhaylovskaya za, morozova mv, buyanova es, petrova sa abrahams i. irondoped bi26mo10o69 bismuth molybdate:synthesis, properties and structure. in: abstract book of the 11th international symposium on systems with fast ionic transport. 2014 jun 25-29; gdańsk university of technology, gdańsk-sobieszewo, poland. 2014. p. 78. 14. irvine jts, sinclair dc, west ar. electroceramics: characterization by impedance spectroscopy. adv mater. 1990;2:132-8. doi:10.1002/adma.19900020304. cite this article as (как цитировать эту статью) mikhaylovskaya za, morozova mv, buyanova es, petrova sa, nikolaenko iv, kellerman dg. preparation and characterization of bi26-2xmn2xmo10o69-d and bi26.4mn0.6mo10-2yme2yo69-d(me = v, fe) solid solutions. chimica techno acta. 2017;4(2):120–127. doi:10.15826/chimtech/2017.4.2.027 16 s. a. decterov centre for research in computational thermochemistry, department of chemical engineering, ecole polytechnique, 2900 edouard-montpetit blvd., montréal, qc h3t 1j4, canada sergei.decterov@polymtl.ca thermodynamic database for multicomponent oxide systems a state-of-the-art thermodynamic database has been developed for multicomponent oxide systems. it can be used in combination with factsage software to calculate the properties of metallurgical slags, glasses, ceramics, refractories, minerals, cements, etc. the database has been developed by collecting all available structural, thermodynamic, and phase equilibria data for a particular chemical system, critical evaluation of this information, developing a thermodynamic model for each solution phase and optimization of model parameters to reproduce the experimental data. then the models are used to estimate the thermodynamic properties of multicomponent solutions from the properties of lower-order subsystems. oxide phases often exhibit complex structures and strong interactions between components, which require more sophisticated models than are normally used, for example, for metal alloys. short-range ordering is rather common and random mixing is often not a good approximation. the models for multicomponent liquid and solid solutions have been developed within the modified quasichemical formalism and compound energy formalism. optimized model equations are consistent with thermodynamic principles and fully characterize a chemical system, requiring much less experimental work to achieve this goal since only a few measurements are needed in higher-order systems to validate the model estimates. the database can be readily used in conjunction with the factsage gibbs energy minimization software to calculate any stable or metastable phase equilibria and phase diagrams. the present article outlines the major components and phases that are currently available in the oxide database, as well as the most important features of the models that have been developed. the model and database have also been developed for the viscosity of oxide melts and glasses. the model links the viscosity to the structure of the liquid phase, which is estimated using the thermodynamic database. keywords: thermodynamic; database; oxide; slag; glass; ceramics; refractory; minerals; cement; viscosity received: 21.02.2018. accepted: 22.03.2018. published: 10.05.2018. © decterov s.a., 2018 d o i: 1 0. 15 82 6/ ch im te ch .2 01 8. 5. 1. 02 decterov s.a. chimica techno acta. 2018. vol. 5, no. 1. p. 16–48. issn 2409–5613 17 1. introduction nowadays, development of new valueadded products and materials, as well as creation of cost-effective, environmentallyfriendly and energy-efficient production processes, starts with the physicochemical modeling of phase and chemical transformations in a particular chemical system. the optimal conditions for important chemical reactions are evaluated, the effects of temperature, pressure, overall composition, impurities are assessed, and the most promising values of input variables are selected for further experimental studies. computational thermodynamics is increasingly used for evaluation of phase and chemical equilibria and thermodynamic properties of phases, providing the basis for physicochemical modeling. oxide phases encompass metallurgical slags, fly ashes and slags that are produced in combustion and gasification of coal, biofuels and municipal wastes, many important minerals that make up most of the earth crust, magmas and lavas, conventional and functional ceramic materials, glasses, building materials, etc. most of oxides that we encounter are multicomponent solutions. we need to know the thermodynamic and physical properties of these solutions as functions of temperature, pressure and composition to understand what is going on in the inaccessible depths of the earth, how planets and nebulae form, and to optimize industrial processes and develop novel high-tech materials. however, it is essentially impossible to study experimentally the thermodyna mic and physical properties of all important solutions because the necessary amount of work increases exponentially with the number of components. hence, we need to develop a model for each particular solution that is calibrated based on available data and can then accurately predict the properties of the multicomponent solution. this work was carried out systematically over the last 30 years and resulted in the development of a comprehensive thermodynamic oxide database, which can be used to perform various calculations in combination with the factsage thermodynamic software and database computer package. the present article provides a brief overview of the factsage oxide database. thermodynamic databases are developed by critical evaluation and optimization of available thermodynamic and phase equilibrium data by a technique that has become known as the “calphad method”. this technique is summarized in section 3. the subsequent sections provide a list of the major components and phases that are currently present in the database. the chemical subsystems that are most important for applications are outlined. thermodynamic description of oxi de solutions requires more sophisticated models than normally used in the other computer packages. the choice of the appropriate model is very important: unless the mathematical model is based upon a realistic physical model, interpolations, extrapolations and predictions have little chance of success. section 5 gives an idea about the peculiarities of thermodynamic models that are used for liquid and solid multicomponent oxide phases. the quantitative thermodynamic description of multicomponent oxide melts provides insight into their structure, which can be used to model other physical properties that are strongly structure-dependent. this is how a new viscosity model was developed for oxide melts and glasses. the major features of the viscosity model are outlined in section 6. 18 the applications of the oxide database are many and varied, so it is not possible to provide an exhaustive list in the present article. however, some representative examples are referenced in section 7. 2. integrated software and databases computer packages for computational thermodynamics several powerful thermodynamic software and database computer packages have evolved over the last 40 years that enable accurate calculations in multicomponent chemical systems. thermocalc [1], mtdata [2], pandat [3] and factsage [4, 5] are among the largest packages with applications in metallurgy and materials science. these packages combine large evaluated and optimized thermodynamic databases with advanced gibbs energy minimization software as shown schematically in fig. 1. thermodynamic databases contain the gibbs energies, g, of all phases as functions of temperature, pressure, composition and model parameters. this is a complete description because all the other thermodynamic properties (enthalpies, heat capacities, chemical potentials, activities, etc.) can be calculated by taking the appropriate derivatives of the g functions. the software calculates the phase and chemical equilibrium for a given set of constraints, for example at fixed t, p and overall composition. this is done by minimizing the total gibbs energy of the chemical system. the thermodynamic properties of all relevant phases are automatically retrieved from the databases. performing an equilibrium calculation is similar to making an actual experiment when certain amounts of chemicals are placed in a crucible and allowed to react and equilibrate for a sufficient amount of time at a certain temperature and pressure. the software can also calculate various types of phase diagrams and any phase diagram section for a multicomponent system, for example isothermal or isoplethal sections. furthermore, it is po ssible to calculate what happens when an equilibrated chemical system, for example a metal alloy, fig. 1. schematic representation of a thermodynamic software and database package 19 is cooled down under various assumptions, e.g. equilibrium or nonequilibrium “scheil– gulliver” cooling. this, in turn, provides the means for estimating the amounts and composition of microstructural constituents. the thermodynamic databases permit the calculation of chemical potentials, which are the driving force for diffusion, precipitation kinetics, etc. this can be combined with databases of diffusion coefficients and software for calculating diffusion, phase field modeling and other kinetic calculations. in particular, such calculations proved to be a powerful tool for the study of the heat treatment of alloys. 3. development of thermodynamic databases the thermodynamic databases of thermocalc, mtdata, pandat and factsage are extensive. they contain self-consistent thermodynamic properties for hundreds of solution phases and thousands of stoichiometric compounds. the databases are prepared by the following procedure: 1. all available experimental data are collected from the literature for a particular chemical system, including structural data, thermodynamic properties of all phases, phase equilibria and phase diagram data. these data are obtained by a multitude of experimental techniques. in particular, heat capacities, heat contents, enthal pies of formation and enthalpies of mixing are obtained by various calorimetric measurements; vapour pressures, chemical potentials and activities are measured by mass spectrometry, isopiestic methods and electrochemical cells; integral gibbs energies are derived from emf measurements; phase equilibria and various types of phase diagrams are studied by dta, dsc, annealing and quenching followed by metallographic examination or electron probe x-ray microanalysis (epma). these diverse kinds of data are not independent of each other, but are interrelated through the laws of thermodynamics. it should be noted that it is desirable to have data on both thermodynamic properties and phase diagrams, because phase equilibria and distributions of minor elements among phases are very sensitive to thermodynamic functions. for example, normal experimental errors in calorimetric measurements of the enthalpy of formation will produce too large errors in calculated phase equilibria. on the other hand, even though it is possible to calculate phase diagrams from the gibbs energies of all phases, it is not possible to derive the gibbs energies solely from the phase diagrams because this problem does not have a unique solution. 2. an appropriate thermodynamic model is developed for each phase based upon the physical nature and structure of the solution. the model gives the functional dependence of the gibbs energy of the solution on temperature, pressure, composition and model parameters ai. the latter are optimized by fitting avai lable experimental data. the challenge is to produce a model that, on one hand, reflects the major structural features of a solution to ensure good predictive ability, but on the other hand, is relatively simple and suitable for the database development. if a model becomes too cumbersome in an attempt to describe the extremely complicated structure of some solutions, it will be impractical because there will never be enough experimental data to calibrate it. availability of experimental data should be taken into account in model development from the very beginning, in other words, the formulation of a practical model 20 depends on what data are available for a particular solution. 3. experimental data are almost always contradictory and must be critically evaluated. experimental uncertainties reported in the literature are rarely realistic. a good knowledge of all experimental methods is required for the critical evaluation, while the use of thermodynamic software and database computer packages greatly speeds up cumbersome thermodynamic calculations that are often needed for comparison of different data sets. 4. next, the model parameters for all phases in a given chemical system are simultaneously optimized to fit all available thermodynamic and phase equilibrium data from the literature. a self-consistent set of model parameters for all phases is obtained. this is done for all two-component, three-component and, if data are available, higher order subsystems. finally, the mo dels are used to estimate the thermodynamic properties of multicomponent solutions from the properties of lower-order subsystems. the optimized model equations are consistent with thermodynamic principles and with theories of solutions. they describe simultaneously all the thermodynamic properties and the phase diagrams. this technique greatly reduces the amount of experimental data needed to fully characterize a chemical system. all data can be tested for internal consistency. the data can be interpolated and extrapolated more accurately. all the thermodynamic properties and the phase diagram can be represented and stored by means of a relatively small set of model parameters. 5. this technique permits the estimation of phase diagrams of multicomponent systems based only upon data from lowerorder subsystems and allows any desired phase diagram section or projection to be calculated and displayed rapidly. 4. components of the thermodynamic database for oxide systems factsage stands out among the other computer packages due to its databases for inorganic non-metallic systems, such as oxides, sulfides and salts. the factsage database for oxide systems is called ftoxid. it contains the following oxide components: al2o3, as2o3, b2o3, bao, cao, coo, cro, cr2o3, cu2o, feo, fe2o3, geo2, k2o, mgo, mno, mn2o3, na2o, nio, p2o5, pbo, sio2, sno, sro, ti2o3, tio2, zno, zro2. critical evaluation of experimental data and optimization of model parameters for all possible combinations of these components over the whole temperature and composition range would be an enormous task, which is not even possible for many combinations due to the lack of reliable experimental information. instead, only specific sets of components were optimized at temperatures and compositions that are most important for various applications. the system fe2o3–feo–sio2–cao– al2o3–mgo forms the basis for smelting and refining slags in most metallurgical processes. it is also essential for simulating interactions of refractories with slags and metals, as well as for many other industrial applications. this chemical system has been optimized from 25 °c to above the liquidus temperatures at all compositions and oxygen partial pressures from equilibrium with metals to equilibrium with oxygen [6–20]. the ftoxid database has been further expanded by adding other components to this core six-component system over the ranges of temperature and composition that 21 are most important for particular applications, as is shown schematically in fig. 2. in particular, copper was added to the molten oxide phase over the range of oxygen partial pressures from 10–12 to 10–3 bar. this completely covers the range of oxygen potentials of interest to the production of copper. under these reducing conditions, the presence of cu+2 in the slag can be neglected, so that all copper in the slag is assumed to be cu+1 [21–25]. experimental information in the li t erature on the pboand zno-containing systems relevant to zinc and lead smelting slags and sinters was rather limited. hence, the addition of pbo and zno to the oxide database was done by a comprehensive research program that involved experimental studies and thermodynamic modelling [9, 26]. the phase equilibria in low-order systems that are most important for constraining parameters of thermodynamic models were studied experimentally using equilibration, quenching, and electron probe x-ray microanalysis [27–30]. then thermodynamic optimization was carried out [30–32] and the predictive ability of the developed database was validated against additional experimental measurements that were made for specific ranges of compositions in the multicomponent system, which are most important for production of lead and zinc [33, 34]. pb and zn are also important for copper smelting, because these detrimental elements are always present in sulfide concentrates and must be eliminated. several cu2o–pboand cu2o–zno-containing subsystems were optimized so that the database can be used to calculate the distribution of lead and zinc among the slag, matte, copper and gas phases during copper smelting and converting [35, 36]. the addition of nio to the oxide database was done for simulation of nickel extraction from laterite ores. it required a combination of experimental and modeling work [37–40]. cobalt is mostly produced as a byproduct of nickel and copper mining and smelting. the co–fe–si–o system was optimized to describe the solubility of co in fayalite slags [41, 42]. this made possible the calculation of co distribution among slag, matte and metal phases [43]. chromium was added to the oxide database by optimization of several subsystems of the cr–al–fe–ca–mg–si–o fig. 2. combinations of components in the oxide database that have been optimized for various applications 22 system [44–47], which are important for evaluating interactions of various slags with refractories. it was assumed that only cro and cr2o3 occur in the liquid. at high concentrations of cao and mgo, oxidation states of cr greater than (+3) can be present in the liquid phase under relatively oxidizing conditions. hence, the database is valid in the basic region for oxygen potentials lower than about 10–3 bar. to add manganese to the oxide database, the mno–al2o3–cao–sio2 system and all its binary and ternary subsystems were optimized [48–50]. this is important for production of ferromanganese and for inclusion control in steelmaking. alkali oxides, b2o3, sro and bao are essential for applications in the glass industry, but these components can be present also in mold fluxes. systematic addition of na2o and k2o to the al2o3–feo–fe2o3– cao–mgo–sio2 system was started by jak et al. [51] and is currently the subject of several phd projects. the whole b2o3– al2o3–cao–mgo–sio2 system has been optimized even though optimizations of only a few key subsystems have been published so far [52, 53]. all sroand baocontaining subsystems of the sro–bao– b2o3–al2o3–cao–mgo–sio2 system were optimized to add sro and bao to the oxide database [54–56]. the validity range of the oxide database can be deduced from the list of optimized systems mentioned above. a few other components, such as oxides of as, ge, p, sn, ti and zr, are discussed in more detail in the factsage documentation for ftoxid database on the factsage website www.factsage.com. 5. thermodynamic modeling of oxide solutions the oxide database contains the liquid oxide phase, which includes all database components mentioned above, and about ninety solid solutions. it is important to select a proper thermodynamic model for each solution. the simplest and best known model is a random-mixing bragg-williams model with a polynomial expression for the excess gibbs energy. this model assumes that the atoms or molecules of each component are randomly distributed over the sites of a lattice or quasilattice. the resulting equation for the molar gibbs energy is g x g rt x x x x g i i i i i i i j ij ji = + + + ∑ ∑ ∑∑ <  ln (1) where xi denotes the mole fraction of pure component i, g i  is the gibbs energy of pure component i, and the last term is the excess gibbs energy, which can be interpreted as the sum of nearest-neighbour pair energies. in turn, gij can be expressed as a polynomial in composition g x x aij i m j n ij mn m n = ≥ ≥ ∑ 0 0, (2) where the empirical binary model parameters aij mn can be functions of temperature and are found by evaluation and fitting the available data on the binary sub-system i–j. if data are available for ternary systems, then additional empirical ternary terms of the form x x x gi j k ijk can be added to eq.  (1). finally, the gibbs energy of the multicomponent solution is estimated from the optimized binary (and ternary) parameters by means of eq. (1). this model is internally contradictory in a sense that as gij becomes larger, the assumption of random mixing becomes less accurate, e.g. very negative gij should result in formation of substantially more 23 i–j pairs than would be present in the random mixture at a given composition. the preferential formation of i–j pairs is often called short-range ordering (sro). for the oxide solutions discussed in the present article, the assumptions of the random-mixing bragg-williams model are normally far too simplistic. this can be understood from the comparison of the enthalpies of mixing for different systems shown in fig. 3. as can be seen from fig. 3, the interactions between similar components fe and ni are not strong and the fe–ni liquid alloy can be well described by the random-mixing bragg-williams model. this is more problematic for the ni–al liquid where the two metals have quite different nature, which is manifested in much more negative enthalpy of mixing. even though the bragg-williams model can still be applied, it requires more empirical parameters, including excess entropy terms to compensate for the inadequate entropy expression. the interactions between components and the resulting sro in the fe–o, nao0.5–sio2 and nao0.5–bo1.5 liquids are so strong that the random-mixing bragg-williams model cannot be used. the angular shape of the enthalpy of mixing is essentially impossible to reproduce even with a very large number of model parameters. more sophisticated models are required as will be discussed in the following sections. 5.1. liquid phase the liquid oxide phase is an ionic melt where metal cations are almost exclusively surrounded by oxygen anions and vice versa, i.e. it exhibits almost full first-nearestneighbour (fnn) short-range ordering. this is the result of very strong interactions between metal atoms and oxygen as shown in fig. 3 for the fe–o system. the interactions with oxygen are even stronger for other elements such as na, ca, al, b, si, etc. furthermore, there is a strong tendency for second-nearest-neighbour sro of some cations in melts. in particular, basic cations such as na+1 or fe+2 form strong secondnearest-neighbour (snn) pairs with acidic cations such as si+4 or b+3. for example, this is manifested in the very negative enthalpy of mixing in the nao0.5–sio2 and nao0.5– bo1.5 liquids as shown in fig. 3. the model for the liquid oxide phase was developed within the modified quasichemical formalism [62, 63]. it is assumed that cations occupy one quasilattice, while anions such as o-2 and s-2 are located on the other quasilattice. in other words, the ordering between cations and anions is assumed to be complete and the deviations from the oxide stoichiometry towards the metal-rich region are neglected. this assumption greatly simplifies the model, increasing its predictive ability. the dissolution of excess metal in oxide liquid that may take place at very high temperatures fig. 3. enthalpies of mixing for liquid solutions at 1600 °c based on the thermodynamic assessments of the corresponding systems: fe–o [57], ni–fe [58], ni–al [59], nao0.5–sio2 [60] and nao0.5–bo1.5 [61]. the enthalpies of mixing for the latter two systems are shown per mole of cations 24 is not important for most practical applications of the oxide database. the model also explicitly takes into account the snn sro by considering pair exchange reactions such as na o na si o si na o si +1 +1 +4 +4 +1 +4 − −( )+ + − −( ) = = − −( )2 (3) and by using the nonconfigurational gibbs energy change for this quasichemical reaction in the mathematical formulation of the model. this reaction can also be viewed as the reaction of breaking si–o–si “oxygen bridges” by sodium atoms. since the gibbs energy of reaction is very negative, the reaction is shifted to the right, resulting in strong sro and a sharp minimum in the gibbs energy and enthalpy of mixing near the orthosilicate composition. 5.1.1. taking into account the charge compensation effect certain amphoteric oxides such as al2o3 can behave in profoundly different ways in a silicate melt depending on the overall composition. when added to a pure silica melt, al2o3 acts as a network-modifier, breaking the oxygen bridges of the pure silica network. on the other hand, when al2o3 and an alkali or an alkali-earth oxide (me2o or meo) are added simultaneously to sio2, some of the al cations assume tetrahedral coordination and replace si in the silica network, so that al acts as a networkformer. the missing charge is compensated by me cations that stay close to the al ions. due to this “charge compensation effect”, the properties of the liquid phase change drastically when the molar ratio of al2o3 to meo or me2o approaches unity. it should be noted that this is a fairly strong ternary effect that cannot be predicted from the binary interactions or fitted adequately by the ternary model parameters. hence, it is taken explicitly into account in the model for the liquid phase by introducing additional components me+1al and me+2al2 on the cation quasilattice. as a result, the thermodynamic pro perties of the me2o–al2o3–sio2 ternary system, which becomes a pseudoquaternary, cannot be extrapolated with any reasonable accuracy from the properties of the binary subsystems and must be described by fitting model parameters to the available experimental data. 5.1.2. borate and borosilicate melts borosilicate melts have particularly complex structure due to the presence of two network formers, b2o3 and sio2. boron is known to assume both triangular and tetrahedral coordination against oxygen, but it is believed that mostly triangular coordination is present in pure b2o3 melts. as an alkali oxide me2o is added to b2o3, more and more tetrahedraly-coordinated boron appears as a result of the charge compensation effect, whereby an additional charge provided by the fourth oxygen is compensated by an alkali cation, which is located in the vicinity of the bo4 group. boron atoms in tetrahedral and triangular coordination can co-polymerize to form various clusters. in particular, clusters at the tetraborate composition, me: b = 1 : 4, and diborate composition, me: b = 1 : 2, have been proposed based on stu dies by raman and infrared spectroscopy, 11b nmr, and x-ray and neutron diffraction [64]. it should be noted that meb4 and meb2 are simply the overall compositions where stable clusters seem to form. the average size of these clusters is not known. the formation of different clusters essentially means that there are several compositions of maximum sro in the me2o–b2o3 sys25 tem. many physical properties show abnormal behaviour at these compositions, e.g. the viscosity [65], density and thermal expansion [66, 67]. there is no experimental evidence for the formation of similar clusters in meo– b2o3 systems, where me is a divalent cation such as ca+2, most likely because one divalent cation must provide the charge compensation for two bo4 groups simultaneously, creating a strain in the structure and making the formation of diborate and tetraborate clusters much less favourable. in the model for the liquid phase, the presence of tetrahedrally-coordinated boron is explicitly taken into account by introducing an additional component, me+1b, on the cation quasilattice. the me2o–b2o3 binary system becomes then a pseudo-ternary, which makes it pos sible to have more than one composition of maximum sro in this system [61]. 5.1.3. solubility of non-oxide components in oxide liquid the solubility of sulfides and fluorides in the oxide liquid was modeled by placing s–2 and f–1 species on the anionic quasilattice [68]. the database can accurately calculate phase equilibria up to more than 50% of non-oxide components, sometimes up to pure sulfides and fluorides. a simple “capacity” model was developed [69] to predict solubilities of sulfates, carbonates, halides and water/hydroxide, up to about 10 wt%. the model is based on the thermodynamic properties of pure liquid non-oxides and the knowledge of the activities of components in multicomponent oxide liquid. in most cases no adjustable parameters are needed. 5.2. solid solutions there are about 90 solid solutions in the ftoxid database. modeling of oxide solid solutions is a challenging task. oxide and particularly silicate solutions are quite extraordinary in their ability to incorporate many different cations by adjusting the structure. complex oxide solutions often have several sublattices and reveal a strong tendency to interand intrasublattice short-range ordering, which is responsible for specific physical properties. for example, the distribution of cations and defects between different sublattices defines volumetric, electrical and magnetic properties of ceramic phases. in order to be physically meaningful, thermodynamic models for oxides and silicates must take into account crystallographic information. in most solid solutions, the oxygen anions occupy one sublattice, while metal cations are located on one or several cation sublattices, which can also contain vacant sites. the distribution of cations between different sublattices define the overall stoichiometry of the solution and its configurational entropy. hence, it is very important for thermodynamic modeling to obtain information on the number of sublattices and on cation occupancies from the structural data. in principle, crystallographically different sites should be modeled as different sublattices. however, if two nonequivalent sites are similar and the distribution of cations between the two sites is not well known, one can combine them into one sublattice as a first approximation. 5.2.1. compound energy formalism many different models have been used for thermodynamic modeling of oxide solid solutions. fortunately, most of these can be reduced to the compound energy formalism (cef) [70–73], which assumes random mixing of species on several sublattices. consider a solid solution having three sublattices and the following formula unit: ( , , ...) [ , , ...] { , , ...}a b c d e f zu v w α β γ (4) 26 where species a, b, … occupy sublattice α that has u sites per formula unit, species c, d, … occupy sublattice β that has v sites, species e, f, … occupy sublattice γ that has w sites and z denotes the rest of the formula unit that remains unchanged. the gibbs energy expression in the cef per formula unit is g y y y g ts g i j k kji ijk conf e = − − + ∑∑∑ α β γ (5) where yi α , yj β and yk γ represent the site fractions of constituents i, j and k on each sublattice, gijk is the gibbs energy of an end-member ( ) [ ] { } ,i j k zu v w α β γ sconf is the configurational entropy s r u y y v y y w y y conf i i i j j j k k k = − +    + +    ∑ ∑ ∑ α α β β γ γ ln ln ln (6) and ge is the excess gibbs energy g y y y y l y y y y l e i j k l lkji ij k l i j k l lkji i jk = + + ∑∑∑∑ ∑∑∑∑ α α β γ α β β γ : : : :ll i j k l lkji i j kly y y y l + + ∑∑∑∑ α β γ γ : : (7) where lij: k: l is the interaction energy between cations i and j on the first sublattice when the second and third sublattices are occupied only by k and l, respectively. terms containing higher powers of y, as well as ternary interaction terms and reciprocal terms such as y y y y y li j k l m ij kl m α α β β γ : : can also be added. of course, similar equations can be written for any number of sublattices. for oxide solid solutions, the species that mix on each sublattice are normally cations, while oxygen is included in the z part of the solution. the application of the cef to modeling oxide solutions is relatively straightforward when all end-members are neutral, even though some neutral end-members may not exist and therefore cannot be studied experimentally, e.g. due to disordering when the same cation can be present on more than one sublattice. if cations that mix on a sublattice have different charges, e.g. na+1 and ca+2, at least some end-members will be charged. clearly, only the compositions that obey the condition of electroneutrality can exist in reality. hence, the gibbs energy of one charged end-member can be selected arbitrarily as a reference state. however, when endmembers are charged, it normally becomes inappropriate to use the gibbs energies of end-members as model parameters because there are never enough experimental data to constrain all of them. instead, a model should be developed within the framework of the cef for each complex solid solution, which specifies a set of model parameters and a sequence of their optimization based on a physically meaningful model, so that if only a few parameters are needed to reproduce the experimental data, the rest of them are kept equal to zero. the selection of model parameters must not be made arbitrarily, for example by setting the gibbs energies of some of the end-members equal to zero, even though certain meaningful combinations of these gibbs energies can normally be used as the most important model parameters. development of a physically reasonable model is very important. although there is generally no problem in reproducing all data in simple systems, it becomes very easy to unbalance the model by using too many arbitrarily selected parameters and obtain unreasonable extrapolations of lower-order subsystems into a multicomponent solution. that is, in lower-order 27 subsystems, different choices of parameters can give equally good or, sometimes, even mathematically equivalent fits. however, extrapolations into multicomponent systems are different. this problem is most pronounced for solutions, such as spinels, where the same cations can be present on more than one sublattice [19, 30, 72]. the aforesaid reflects the fact that the cef is not a model, but a formalism, which can be conveniently used to mathematically represent many different models without the need to program each model separately into general thermodynamic software. in other words, the cef is so symmetric and general, that many reasonable sublattice models can be reduced to it. however, not every model written within the framework of the cef is reasonable. one more complication related to the presence of charged end-members is the difficulty of combining several independently optimized subsystems into one multicomponent solution. this can be done only if the same reference state for charged end-members was used for each subsystem, which is rarely the case. the major oxide solid solutions, for which the models were developed within the framework of the cef, are listed below: ȥ spinel: (al, co+2, co+3, cr+2, cr+3, cu+2, fe+2, fe+3, mg, mn+2, ni+2, zn)tet [al, ca, co+2, co+3, cr+3, cu+2, fe+2, fe+3, mg, mn+2, mn+3, mn+4, ni+2, zn, va]2 oct o4 ȥ pyroxenes: (ca, sr, mg, fe+2, ni, na) m2 (fe+2, fe+3, mg, ni, al)m1 (fe+3, al, si)t1 sit2 o6 ȥ olivine: (ca, fe+2, mg, mn, ni, co, cr+2, zn) [ca, fe+2, mg, mn, ni, co, cr+2, zn] sio4 ȥ melilite: (ca  , sr, ba, pb, na, k)2 [mg, zn, ni, fe+2, fe+3, al, b] {fe+3, al, b, si}2o7 ȥ walstromite: (ca, ba, sr) [ba, ca, sr] casi3o9 ȥ willemite: (zn, fe+2, mg) [zn, fe+2, mg] sio4 ȥ mullite: (al, fe)2 [al, si, b, fe] [o, va]5 where cations enclosed by parentheses occupy the same sublattice, and where va denotes a lattice vacancy. 5.2.2. short-range ordering in the cef, cations are assumed to mix randomly on each sublattice. however, many oxide solutions are likely to exhibit substantial short-range ordering. for example, the most common pyroxene compositions are located on the so-called “quadrilateral” (ca, mg, fe+2) m2 (fe+2, mg)m1 (si)t1 sit2 o6 (8) non-quadrilateral, or “supersystem” components may be of considerable importance and can be obtained from the quadrilateral compositions by coupled substitutions, such as: ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ca mg na al ca fe na al mg m2 m1 m2 m1 m2 m1 m2 m1 m1  +2 (( ) ( ) ( ) ( ) ( ) ( ) ( ) si al al mg si al fe t1 m1 t1 m1 t1 m1 t1   +       3 (9) it is widely believed that inter-lattice sro results from these coupled substitutions. for example, if na replaces ca on m2 sites and al replaces mg on m1 sites, the na and al cations tend to stay close to each other to preserve local electroneutrality. there are many indications of such sro. the tendency to sro often results in an order-disorder transition at lower temperatures accompanied by a reduction in spacegroup symmetry. for example, this happens in omphacitic pyroxenes near the composition in the middle of the diopside–jadeite join, camgsi2o6–naalsi2o6 [74, 75]. 28 in a number of systems, the optimized entropy of mixing appears to be much smaller than the entropy calculated under the assumption of ideal mixing. this also suggests sro. for example, the clinopyroxene solution along the jadeite – catschermak join, naalsi2o6 – caal2sio6, can be attributed to the coupled substitution ( ) ( ) ( ) ( )na si ca alm2 t1 m2 t1 . the availability of both phase equilibrium and enthalpy of mixing data for this solution made it possible to calculate the entropy of mixing [76], so in this particular case it was possible to correct the inadequate ideal mixing entropy with temperaturedependent excess terms. various approaches have been proposed for estimating the configurational entropy of pyroxenes and other minerals exhibiting similar coupled substitutions. in the simplest molecular mixing approximation, the molar configurational entropy is assumed to originate from permutations of charge-balanced end-member components. another simple approximation assumes that positions of cations on one sublattice uniquely define the distribution of cations on the other sublattice because of the local charge-balance constraint. therefore, the configurational entropy of a solution is given by random mixing on just one sublattice. these approximations have been used by geochemists with some success to describe coupled substitutions in simple solutions. clearly, they are not adequate for multicomponent reciprocal solutions. in most cases, these approximations underestimate the actual configurational entropy. it is possible to calculate the configurational entropy more accurately based on the assumption of local charge balance [77]. the formulas can be best demonstrated using pyroxene [na, ca]m2 [mg, fe+3, al]m1 si2o6 as an example. it is assumed that the solution consists of locally chargebalanced clusters: na(fe+3) si2o6, na(al) si2o6, ca(mg)si2o6. these clusters are of two types: a+1b+3si2o6 and a +2b+2si2o6. the configurational entropy can be expressed as a sum of three terms [77] sconf = s1 + s2 + s3 where s1 is the entropy from permutations of the clusters of different types: s1 = –r (yna ln yna + yca ln yca) s2 is the entropy from permutations of atoms of the same valencies: s2 = –r {yfe ln [yfe/(yfe + yal)] + + yal ln [yal/(yfe + yal)]} and s3 is the entropy from various crystallographically distinct orientations of the locally charge-balanced clusters, which are consistent with the symmetry s3 = r yna yca ln km1–m2 km1–m2 is a coordination number, which is equal to 3 in this case, and yi is a site fraction of cation i. the first and second terms in the entropy expression can be written in a very general way suitable for programming in general thermodynamic software. however, the third term is structure dependent, and it is not possible to derive a general formula for this term. furthermore, this model does not take into account the reduced possibilities of different geometric arrangements due to interactions between sro clusters. more importantly, the model does not take into account partial dissociation of sro clusters and does not reduce to random mixing at infinite dilution of al, fe+3, ca and na cations. nevertheless, similar formulations are often used in the geochemical literature. except for inter-lattice sro, there can be also intra-lattice sro. one example is the “al-avoidance principle” in pyroxenes and other minerals. a tetrahedral al–o– al linkage is known to be unfavorable to 29 the stability of crystal structures; therefore, al–o–si and si–o–si second-nearestneighbor pairs predominate. under certain simplifying assumptions [78], the al-avoidance principle can be explicitly taken into account to derive the configurational entropy of mixing of al and si on the tetrahedral sites. however, it is essentially impossible to formulate such a model for multicomponent solutions, which would be suitable for general thermodynamic software and databases. the overestimated configurational entropy resulting from the random mixing of al and si on the tetrahedral sites can be corrected to some extent by selecting a model that artificially splits the tetrahedral sublattice into two sublattices, one of which is occupied only by si. this is equivalent to approximating the strong sro by assuming that it creates the long-range ordering. in particular, this can be done for clinopyroxene, which has only one tetrahedral sublattice at high temperatures, but undergoes a phase transition to the structure with two distinct tetrahedral sites at low temperature. it should be noted that both ortho and protopyroxene have two tetrahedral sublattices, one of which is predominantly occupied by si. another, and more general approach, is to develop a model within the framework of the modified quasichemical formalism (mqf) [62, 63, 79, 80], which can explicitly take into account the sro. the mqf in the quadruplet approximation can treat simultaneously interand intra-sublattice sro. it operates with quadruplets just as the quasichemical model in the pair approximation operates with pairs. however, the mqf is limited to not more than two sublattices. accumulation of sro often finally results in a phase transition with lowering of long-range symmetry. this is illustrated by fig. 4 [81], which shows the enthalpy change due to ordering of cordierite, mg2[al4si5]o18, versus time of annealing. the enthalpy changes linearly with ln(t) as cordierite proceeds from the disordered hexagonal phase through a set of modulated structures to the fully ordered orthorhombic phase. the lowering of symmetry thus occurs during the last stages of ordering, and the gibbs energy of the long-range ordered orthorhombic phase is very close to that of the metastable shortrange ordered hexagonal phase. hence, if the sro is modeled properly, but the long-range ordered phase is not modeled, the results of equilibrium calculations will still be reasonable for most practical purposes. of course, the disordered phase is predicted instead of the ordered one, but the compositions of all other phases will be nearly correct. 5.2.3. simple models for complex solutions sometimes it is impossible to develop a model that, on the one hand, adequately reflects the structure of a solution, and on the other hand is suitable for practical calculations in multicomponent systems. fig. 4. enthalpy of dissolution in molten 2pbo·b2o3 of synthetic cordierite annealed for various times at 1473 k to produce ordering [82] 30 normally this happens when there is not enough experimental data to calibrate a model that would reflect a very complex structure, while the structural comple xity does not have a profound effect on the thermodynamic properties. feldspar and monoxide are two examples. feldspar is a very ubiquitous mineral, which composes about 60% of the earth’s crust. it is not one phase, but rather a family of structurally related phases. feldspar is a framework aluminosilicate: a three-dimensional framework is formed by corner-linked tetrahedra sio4 or alo4, i.e. si and al mix on the tetrahedral sites. larger alkali and alkaline-earth cations are located in the interstices, which are called m sites (or a sites). most natural feldspars lie within the triangle albite–orthoclase–anorthite (naalsi3o8–kalsi3o8–caal2si2o8). two types of simultaneously occurring processes reduce the symmetry of feldspars: the very sluggish al–si ordering and rapid secondorder displacive transformations. as a result, geochemists distinguish many phases within the feldspar family, which may have up to 8 distinct tetrahedral sites and up to 4 m sites. furthermore, one can expect the inter-sublattice sro due to the coupled substitutions ( ) ( ) ( ) ( )na si ca alm t m t and ( ) ( ) ( ) ( )k si ca alm t m t , as well as the intra-sublattice sro of al and si on the tetrahedral sites. on the other hand, the cation occupancies of different sites are poorly understood because they are difficult to measure. moreover, the samples used for structural and thermodynamic studies are often metastable and do not have equilibrium cation distributions among sublattices. fortunately, the measured thermodynamic properties seem to be insensitive to the structural complexity of feldspars. in particular, if the composition of feldspars is expressed in terms of charge-balanced components naalsi3o8, kalsi3o8 and caal2si2o8, the enthalpy of mixing is of the order of 10 kj/mol [83], while the activities of these components are close to ideal [84]. the phase transitions among different phases in the feldspar family can be of the second (or higher) order based on the structures of the phases, i.e. the symmetry constraints are satisfied. if there are first-order phase transitions, the heat of transition is very small. hence, since for most practical applications it does not matter which particular feldspar phase forms, the differences among the structures were ignored and feldspar was modeled as one continuous solution. the simple braggwilliams model in terms of the following components was used: naalsi3o8–kalsi3o8–caal2si2o8– –sral2si2o8–baal2si2o8–nafesi3o8 wüstite is another example where a simple model is used for the phase with a complex structure. the structure [85] is a highly defective form of an ideal nacl-type lattice. oxygen ions form an fcc lattice and fe2+ cations are located on the interstitial sites. the wüstite solid solution always contains more oxygen than the stoichiometric composition “feo”. the iron deficiency is normally attributed to formation of neutral vacancies on cation sublattices together with fe3+ cations, which provide charge compensation. even though the presence of vacancies on the oxygen sublattice cannot be ruled out, the concentration of these vacancies is definitely much smaller than the ones on the cation sublattice. originally it was assumed that iron and vacancies are located only on the octahedral sites, but subsequent detailed neutron diffraction studies indicated that some iron cations, mostly fe3+, occur interstitially 31 on the tetrahedral sites, but subsequent detailed neutron diffraction studies indicated that some iron cations, mostly fe3+, occur interstitially on the tetrahedral sites, which are normally vacant in the nacltype structures. the basic defect is formed by a tetrahedral fe ion surrounded by four octahedral vacancies positioned relative to one another at the comers of a tetrahedron. these defects form clusters, in which vacancies are shared among the conjoined defects. description of the defect structures is further complicated by the incompletely understood long-range ordering of the defect clusters at lower temperatures and higher o/fe ratios. three metastable forms of wüstite were observed at and above room temperature, but below the temperature of wüstite decomposition into spinel and bcc iron at about 570 °c. presumably, these superstructures, which have unit cell dimensions larger than the value of the basic nacl-type unit cell, originate from long-range ordering of defects. in the many papers of vallet and his associates (see, e.g. [86]), it was proposed to subdivide the wüstite field into ten regions separated by transformations of the second (or higher) order. these structural changes have not been detected by other authors who worked within the stability field of wüstite and vallet’s findings remain controversial. since there is no reliable quantitative information on the occupancies of tetrahedral and octahedral sites and on the compositions and amounts of clusters formed by defects, it is not practical to develop a comprehensive thermodynamic model reflecting the complex structure of wüstite. several simplified thermodynamic models were tested for wüstite [87]. the entropies of metastable wüstite at four different compositions were obtained by integrating from 0 k to room temperature the low-temperature heat capacities measured for single-phase samples [88, 89] and a three-phase sample containing wüstite of the fe0.99o composition [90]. when these data were used to calibrate the tested models for wüstite, all the models gave almost identical results. even though the models assumed quite different configurational entropies, the lattice entropies of pure endmembers of the wüstite solution had to be adjusted accordingly for the calculated curve to pass through the experimental entropies, so that the total calculated entropy became almost identical over the stabi lity range of wüstite. the random-mixing bragg-williams model with a polynomial expression for the excess gibbs energy was accepted for the wüstite/monoxide phase, using the following components: feo–mgo–cao–sro–bao–mno– –coo–nio + [cuo–zno–alo1.5– –cro1.5–feo1.5–mno1.5–zro2–nao0.5] where the pure components enclosed by square brackets can only be present in dilute solutions because they have structures different from that of wüstite. several other multicomponent solid solutions were also described by model: ȥ α-(ca, sr) 2sio4 + [fe2sio4, mg2sio4, mn2sio4, ba2sio4, ca3b2o6] ȥ αʹ-(ca, sr, ba)2sio4 + [fe2sio4, mg2sio4, mn2sio4, pb2sio4, zn2sio4, ca3b2o6] ȥ wollastonite: casio3 + [fesio3, mnsio3, mgsio3, srsio3, basio3] ȥ pseudo-wollastonite: (ca, sr)sio3 + [basio3] ȥ corundum: al2o3–cr2o3–fe2o3 + [mn2o3, ti2o3] ȥ zincite: zno + [coo, feo, feo1.5, mgo, mno, nio] ȥ rhodonite: mnsio3 + [casio3, cosio3, fesio3, mgsio3] 32 5.3. estimation of the gibbs energy of a multicomponent solution from binary and ternary subsystems among 27 oxide components that are currently present in the ftoxid database, 27!/(3!24!) = 2925 ternary systems and 17550 quaternary systems are formed. the american ceramic society estimates that it takes on average one man/year to construct experimentally a binary phase diagram of an oxide system. a ternary diagram takes five times longer. in view of the amount of work involved in measuring all ternary diagrams and just one isothermal section of each quaternary phase diagram, it is clear that there is no alternative but to use computational thermodynamics for predicting phase equilibria in multicomponent systems. hence, it is very important to have a means of estimating thermodynamic properties of ternary and multicomponent solutions from binary subsystems. several “geometric” models have been proposed for estimating thermodynamic properties of a ternary solution from optimized data for its binary subsystems. the most common are the muggianu, kohler, and kohler/toop models. the latter is “asymmetric” in that one component is singled out, whereas the first two are “symmetric”. the shape of the gibbs energy surface for a ternary solution can be substantially affected by the choice of the “geometric” model, which can change drastically the ternary phase diagram. clearly, a “symmetric” model should be used when all three components are similar, and an “asymmetric” model will be more reasonable if one component is quite different from the other two, but the choice becomes less obvious when all three components are of substantially different nature. all thermodynamic models mentioned above, i.e. the modified quasichemical formalism, compound energy formalism and random-mixing bragg-williams model with a polynomial expression for the excess gibbs energy, can be combined with different “geometric” models. the muggianu, kohler, and kohler/ toop models are illustrated in fig. 5 using the bragg-williams model given by eqs. and as an example. consider a composition point p in the ternary system a–b–c. the lines can be drawn through the point p to each binary subsystem as shown in fig. 5. in each “geometric” model, the function gij from eq. (1) at the point p in the ternary system is assumed to be equal to the value of gij in the binary system i-j at the point where the line drawn through the point p intersects this binary. for example in the kohler model, gab is constant along the line passing from component c through the fig. 5. kohler, kohler/toop and muggianu “geometric” models for estimating thermodynamic properties of a ternary solution from the properties of its binary subsystems 33 point p; in the toop model with component b being asymmetric, gab is constant along the line passing through the point p at the constant mole fraction of component b; and in the muggianu model, gab is constant along the line perpendicular to the a–b side of the gibbs triangle. it is easy to deduce from these assumptions that if gab is expanded as polynomial in the binary system a–b, the following equations should be used instead of eq.  (2) in the ternary system a–b–c: kohler model: g x x x x x x a m m n n mn ab a a b b a b ab = +       × × +       ≥ ≥ ∑ 0 0, (10) toop model, b asymmetric: g x x a m n mn m n ab b b ab= −( ) ( ) ≥ ≥ ∑ 1 0 0, (11) muggianu model: g x x x x a m m n n mn ab a b b a ab = + −      × × + −      ≥ ≥ ∑ 1 2 1 2 0 0, (12) naturally, these equations reduce to eq. (2) in the a–b binary system. similar equations can be written for gac and gbc. eq.  (2) can be re-arranged into “redlich-kister” form: g x x lij i j m ij m m = − ≥ ∑( ) 0 (13) the “redlich-kister” coefficients lij m may be less correlated than the coefficients aij mn . clearly, the set of coefficients lij m can be calculated from the set of aij mn and vice versa. if redlich-kister polynomials are used in combination with the muggianu “geometric” model, the same eq. (13) applies both in the binary and ternary system without any modifications. this happens because 1 2 1 2 + −     − + −      = = − x x x x x x i j j i i j (14) the redlich-kister / muggianu combination is currently most popular due to this simplicity. one drawback of the muggianu model can be seen from fig. 6: the properties of a ternary solution that is dilute in component b are estimated from the properties of the binary solutions a–b and c–b that are not dilute. furthermore, the use of the muggianu model, as well as any other symmetric model, can give rise to errors when an asymmetric model is more appropriate. for example, fig. 7 illustrates how the symmetric kohler model predicts a spurious and incorrect miscibility gap in the cao–al2o3–fe2o3 liquid. cao is a very basic oxide, while al2o3 and fe2o3 are amphoteric. hence, there are strong negative deviations from ideality in the cao–al2o3 and cao–fe2o3 binary liquids with a min in the enthalpy of mixing at about 50 mol% cao. clearly, the kohler/toop model with component cao being asymmetric is preferable for the cao–al2o3–fe2o3 liquid. this method would estimate the properties at the point p in fig. 7 from the properties of the binary liquids at 50 mol% cao, resulting in negative enthalpy of mixing which is intermediate between that of the cao–al2o3 and cao–fe2o3 liquids. however, if the enthalpy at the point p is estimated by the kohler model, the en34 thalpies of the binary melts at higher cao concentrations will be used, which are less negative than at 50 mol% cao. hence, the enthalpy of mixing at the point p will be less negative than in the binary liquids at the same cao content, which results in the miscibility gap with tie-lines approximately parallel to the al2o3–fe2o3 binary as shown in fig. 7. the application of the muggianu model gives a similar miscibility gap. a proper choice of “geometric” models is much more important for oxide systems than for metal alloys because oxide components are more diverse and the deviations from ideality in oxide systems can be much stronger than in metals as was illustrated in fig. 3. it should be noted that many other “geometric” models are conceivable in addition to the ones shown in fig. 5. in general, rather than speaking of a model for a ternary a–b–c system, we should instead define the approximation used for each of the three gij functions. for example, gab can be extrapolated into the ternary by four models: kohler, muggianu, the toop model with component b being asymmetric and the toop model with component a being asymmetric. similarly, the a–c and b–c binaries can be approximated in four different ways each. all possible combinations of these approximations give 64 possible “geometric” ternary models. equations were developed to calculate the thermodynamic properties of a multicomponent solution in a rational manner while permitting complete flexibility to choose any of the 64 possible geometric models for any ternary subsystem [91]. an improved general functional form for ternary terms in the excess gibbs energy expression was also proposed based on the notion that a ternary term represents the effect of a third component upon the energy gij, which made it possible to develop an equally general and flexible method for extrapolation of ternary terms into a multicomponent solution [91]. fig. 6. kohler, kohler/toop and muggianu “geometric” models applied for estimating thermodynamic properties of a ternary solution that is dilute in component b fig. 7. spurious and incorrect miscibility gap in the cao–al2o3–fe2o3 liquid predicted by the symmetric kohler model 35 factsage stands out among the other large thermodynamic software and database computer packages due to the complete flexibility of using several geometric models in one multicomponent solution [91]. for example, many ternary systems have already been evaluated/optimized with the muggianu model. if future optimizations of other ternary systems are performed with the kohler or toop models, then these can all be immediately combined in one large multicomponent database. no re-optimization is required. hence, the fact that certain subsystems have already been optimized with one model does not mean that other models cannot be used for other subsystems. these general and flexible methods for extrapolation of binary and ternary terms into a multicomponent solution can be used in factsage in combination with the randommixing bragg-williams model, compound energy formalism and modified quasichemical formalism. 6. viscosity of oxide melts and glasses the ability to predict accurately the viscosities of oxide melts and glasses is important in many industrial areas such as iron, steel and non-ferrous metal production, glassmaking, enamels, coal combustion and gasification, waste disposal, geological magmas, etc. the availability of the large multicomponent thermodynamic oxide database made it possible to develop a new model for the viscosity of liquid slags [65, 92–98]. it is distinct from other viscosity models in that it directly relates the viscosity to the structure of the melt, and the structure, in turn, is calculated from the model parameters of the thermodynamic database for molten oxides. the model takes into account the following structural features, which have the most pronounced effect on the viscosity: ȥ formation of a three-dimensional network by network formers such as sio2 and b2o3; ȥ the “charge compensation effect” when al+3 cations assume tetrahedral coordination and enter the silica network, while the additional negative charge resulting from the fourth oxygen is compensated by the pre sence of a second cation, such as na+1, in the vicinity of al+3; ȥ formation of large clusters in solutions of alkali oxides with sio2 or b2o3. for the binary systems sio2–meox and b2o3–meox, where meox is a basic oxide, the model requires very few optimized parameters. this is all the more remarkable as the viscosity of silicate slags spans over 20 orders of magnitude as a function of composition. each ternary system which exhibits the “charge compensation effect” requires 2 temperature-independent ternary parameters. the viscosities of all other subsystems and higher-order systems are predicted from these parameters within experimental uncertainty without additional model parameters. all available experimental data have been considered. so far the model has been applied successfully to multicomponent oxide melts containing si, b, al, ca, mg, na, k, mn, ni, fe+2, fe+3, pb, zn, ti+3, ti+4 and f. the resulting viscosity database is valid for temperatures above the liquidus and for slightly supercooled liquids. the viscosity model was further expanded to describe and predict the viscosi36 ties of glasses [99]. the structure of glasses quenched from the molten state is similar to that of melts, and is calculated from the thermodynamic description of the melt given by the modified quasichemical formalism. the non-arrhenian temperature dependence of the viscosity is illustrated in fig. 8 for several compositions in the na2o–sio2 system. as can be seen from the figure, the curves become increasingly more concave as the mole fraction of silica decreases. this is described by additional unary and binary parameters. the second viscosity database that applies to the whole temperature range from melts to glasses has been developed for the al2o3–b2o3– cao–k2o–mgo–na2o–pbo–sio2 system. this database contains fewer components and may be slightly less accurate in the melt region than the database mentioned above, which was developed only for melts. the connectivity of the three-dimentional silica network has the most profound effect on the viscosity. the composition dependence of the viscosity for the k2o– sio2 melts and glasses is shown in fig. 9. as k2o is added to silica, it breaks the si– o–si bonds of the silica network, causing a drastic decrease in the viscosity. fig. 10 shows the maximum on the viscosity curves for melts and glasses caused by the “charge compensation effect”. clearly, the maximum amount of al+3 in tetrahedral coordination forms at about equal concentrations of al2o3 and na2o. the formation of clusters in the na2o– b2o3 melts and glasses is evident from fig. 11. the maximum on the viscosity at lower temperatures is caused by the clusters forming at the diborate composition, while the maximum at high temperatures can be attributed to the clusters at the tetraborate composition. 7. applications of the oxide database the factsage database for oxide systems, ftoxid, is compatible with the other factsage databases for metal alloys, sulfides, salts, etc. in particular, complex phase and chemical equilibria among metal, oxide and gas phases can be calculated for applications in ferrous process metallurgy, such as ironmaking, steelmaking and inclusion engineering [51, 127, 128]. thermodynamic calculations were also used to simulate fig. 8. temperature dependence of the viscosity for several compositions in the na2o–sio2 system: experimental points [100–106] and calculated lines fig. 9. viscosity of the k2o–sio2 melts and glasses as a function of composition at different temperatures: experimental points [101–103, 105, 107–112] and calculated lines 37 corrosion of refractories [129–131] and treatment of wastes [132]. non-ferrous pyrometallurgical processes are characterized by reactions among oxide, sulfide, metal and gas phases, including matte–slag equilibria. a few examples of the application of computational thermodynamics to non-ferrous pyrometallurgy can be found in references [9, 51, 133]. numerous examples of applications of the oxide database in metallurgy, coal and biomass gasification, development of ceramic materials, cement and concrete, etc. can be found in the posters and publications section on the factsage website www.factsage.com. almost every issue of metallurgical and materials transactions b contains several articles on applications in ferrous and non-ferrous metallurgy. the sgte casebook [134] illustrates, through many examples, how thermodynamic calculations can be used as a basic tool in the development and optimization of materials and processes of many different types. in general, the oxide database is indispensable for understanding and visualizing phase equilibria and phase diagrams in multicomponent systems. for binary and ternary systems, this can be done, at least qualitatively, just from a sufficient amount of experimental data, but for quaternary and higher-order systems, computational thermodynamics has no alternative. the gibbs energy minimization software can access the database and, for a given set of conditions (e.g. t, p, composition), can calculate the compositions and amounts of all phases at equilibrium. by calculating the equilibrium state as the conditions are varied systematically, the software generates any desired phase diagram section of a multicomponent system. the computer calculation of phase diagrams presents many advantages. for example, metastable phase boundaries can be readily calculated by simply removing one or more stable phases from the calculation. other software can follow the course of equilibrium cooling or of nonequilibrium “scheil–gulliver cooling”. the relationship between phase diagrams and thermodynamics, different types and topology of phase diagrams are discussed in more detail by pelton [135]. the applications are not limited to calculations of phase and chemical equilibria. for example, one can calculate the composition of the mgo–al2o3–cao– pbo–zno–sio2 oxide system while fixing, within a given tolerance, the liquidus temperature and the mass fraction of solid fig. 10. viscosity of the na2o–al2o3– sio2 melts and glasses at 50 mol% sio2: experimental points [113–115] and calculated lines fig. 11. viscosity of the na2o–b2o3 melts and glasses as a function of composition at various temperatures: experimental points [116–126] and calculated lines 38 phases 100 ºc below the liquidus temperature [5]. this is done using the factoptimal module [136, 137] that computes optimal conditions for material and process design by coupling factsage with the mesh adaptive direct search (mads) algorithm for nonlinear optimization [138]. factoptimal minimizes and/or maximizes a set of two functions, f1 and f2, subject to several constraints, where ȥ the functions fi (e.g. t, p, v, heat, mass, density, conductivity, etc.) are calculated by factsage or computed from the formula provided by the user ȥ the functions may be non-smooth (e.g. liquidus temperature) ȥ the estimation of derivatives may be problematic ȥ the evaluations of fi may be timeconsuming ȥ the function calculation may fail unexpectedly at some points ȥ the constraints may be non-linear, non-smooth or boolean the ftoxid thermodynamic database can also be used in combination with chemapp [139] to include robust thermodynamics in process simulation software or integrated computational materials engineering (icme) approaches. chemapp is a programmer’s library consisting of a comprehensive set of subroutines, which permit the calculation of complex, multicomponent, multiphase chemical equilibria and their associated extensive property balances. chemapp is available as an object code for a wide range of platforms and as a dynamic link library (dll). chemapp can be linked to third-party process simulation packages for modeling new or optimizing existing processes, for example, to commercial computational fluid dynamics programs such as phoenics and cfx®, or to general simulation programs, including aspen plus®, or to user’s own process simulation software. 8. conclusions physicochemical modeling is gradually replacing the “trial-and error” approach to designing or improving new materials or industrial processes. with far fewer experimental measurements required to completely characterize the chemical system for a particular application, thermodynamic calculations allow considerable time and 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о. в. чемезов, в. б. малков, а. в. исаков, ю. п. зайков фгбун ивтэ уро ран, 620990, ул. академическая, 20, екатеринбург. факс: (343) 362-34-62; тел.: (343) 362-34-97; e-mail: chem@ihte.uran.ru фазозарождение кремния на стеклоуглероде в расплаве kf–kcl–k 2 sif 6 методом хроноамперометрии изучено зарождение кремния на стеклоуглеродной подложке в расплаве kf-kcl-k 2 sif 6 при температуре 675 ºс. выявлено прогрессивное фазозарождение кремния. из sem-микрофотографий зародышей кремния, выращенных на стеклоуглеродной подложке в потенциостатическом режиме в интервале потенциалов от –0,005 до –0,03 в в расплаве kf–kcl–k 2 sif 6 при т = 675 ºс, видно, что в условиях одного эксперимента они имеют размеры, различающиеся в несколько раз, что подтверждает прогрессирующий характер возникновения зародышей кремния. показано, что когда к рабочему электроду при прочих равных условиях прикладывается более отрицательное значение потенциала относительно кремниевого электрода сравнения, то количество сформировавшихся зародышей на поверхности электрода растет. введение кремний – материал, который широко используется в современных полу-проводниковых устройствах. морфология кремниевых материалов существенным образом влияет на их физико-химические свойства, а следовательно, на возможности применения в различных отраслях современной промышленности. последние годы внимание исследователей сосредоточено на создании кремниевых наноматериалов, которые открывают новые возможности повышения эффективности литий-ионных химических источников тока и фотоэлектрических элементов. основным способом получения кремния высокой чистоты и наноматериалов на его основе является осаждение из газовой фазы. процессы газофазного синтеза энергоемки, требуют использования дорогостоящих реагентов и сложного оборудования. альтернативным методом получения кремния и наноматериалов на его основе является электролиз кремнийсодержащих расплавов солей [1, 2]. © жук с. и., минченко л. м., чемезов о. в., малков в. б., исаков а. в., зайков ю. п., 2015 re tr ac te d 45 № 1 | 2015 chimica techno acta электрохимический метод позволяет сравнительно легко контролировать структуру электролитических осадков si. электролизом расплавов солей могут быть получены как сплошные кремниевые покрытия, так и si-наноструктуры: нанопорошки и нановолокна. для целенаправленного получения осадков кремния заданной формы необходимо понимание механизма зарождения и начального роста кристаллов si. теоретические представления о механизме зарождения и роста кристаллов металлов в процессе электролиза хорошо разработаны [3, 4]. однако по особенностям фазозарождения полупроводниковых материалов, в частности кремния, при электроосаждении из расплавов солей в литературе имеются лишь отрывочные сведения. bieber a. l. и др. исследовали зарождение кремния на серебряной подложке в расплаве naf–kf–na2sif6 в интервале температур от 850 до 900 ºс и сделали вывод о том, что зарождение кремния протекает в мгновенном диффузионном режиме [5]. исследование фазозарождения кремния методом хроноамперометрии на молибденовой подложке в расплаве nacl–kcl–naf–sio2 при 800 oc провели cai z. с соавт. и показали, что при электрокристаллизации кремния образование трехмерных зародышей идет постепенно [6]. целью данной работы является исследование процесса фазозарождения электролитического кремния методом хроноамперометрии на стеклоуглеродном электроде из расплава kf–kcl–k2sif6 в инертной атмосфере при т = 675 oc. экспериментальная часть электрохимические исследования проводили методом хроноамперометрии в расплаве kf–kcl–k2sif6 c мольным соотношением kf/kcl = 2 и концентрацией кремния в расплаве, равной 5,7·10–4 моль/см3. расплавы для исследования готовили из индивидуальных солей kf·hf, kcl, k2sif6 по ранее описанной методике [7]. эксперименты проводили в атмо сфере аргона в трехэлектродной ячейке [8]. в качестве контейнера для расплава солей использовали стеклоуглеродный тигель. рабочим электродом служила пластина из стеклоуглерода (су-2000). в качестве противоэлектрода и электрода сравнения использовали пластины из монокристаллов кремния высокой чистоты (уд. сопротивление 0,01 ом·см). перед началом эксперимента проводили очистной электролиз на вспомогательном графитовом электроде. после очистного электролиза графитовый электрод извлекали из ячейки через шлюзовое устройство и меняли на стеклоуглеродный рабочий электрод. хроноамперометрические измерения производили при помощи потенциостата/гальваностата autolab с использованием программного обеспечения nova 1.5. зарождение кремния на стеклоуглеродной подложке вели в потенциостатическом режиме. микрофотографирование образцов проводили на сканирующем электронном микроскопе jms-5900lv. фазозарождение кремния на стеклоуглероде в расплаве kf–kcl–k 2 sif 6 re tr ac te d 47 № 1 | 2015 chimica techno acta результаты и обсуждение на начальных участках хроноамперометрических кривых был зарегистрирован пик, относящийся к зарядке двойного электрического слоя (рис. 1). этот пик спадал за короткое время (от 10–4 до 10–3 с). затем на хроноамперометрических кривых формировался второй пик тока в интервале времен от 1·10–1 до 5·10–1 с. полученные хроноамперометрические зависимости в расплаве kf–kcl– k2sif6 при т = 675 ºс в зависимости от приложенных потенциалов интервале от –0,05 до –0,15 в относительно кремниевого электрода сравнения представлены на рис. 2. участок хроноамперограммы до второго максимума кривой связан с процессом фазозарождения. последующий участок снижения тока обусловлен обеднением приэлектродного слоя по кремнийсодержащему иону. зависимость тока второго возрастающего участка хроноамперограммы от времени позволяет определить режим фазозарождения и подчиняется уравнению (1): j = ά t x, (1) где ά и х зависят от геометрии зародыша и режима фазозарождения. в случае полусферического 3d-зародышеобразования, контролируемого диффузией для мгновенного режима зарождения, значение степенной функции x равно 1/2, для прогрессирующего – 3/2 [5]. анализ первичных данных, полученных при потенциале, приложенном к рабочему электроду из стеклоуглерода, равному значению –0,05 в относительно кремниевого электрода сравнения, в координатах i – t3/2, показал, что экспериментальные точки хорошо ложатся на линейную зависимость (рис. 3). отсюда можно сделать вывод, что режим образования зародышей кремния на стеклоуглеродной подложке в условиях наших опытов носит прогрессирующий характер. другими словами, не вся масса зародышей кремния появляется одновременно и сохраняет приблизительно одинаковые размеры в процессе роста. в нашем случае процесс фазозарорис. 1. типичный начальный участок хроноамперометрической зависимости (стеклоуглеродный электрод, т = 655 ºс, расплав kf–kcl–k2sif6, с0 = 5,7·10 –3 моль/см3, sэл = 0,35 см 2) рис. 2. типичные хроноамперометрические зависимости (стеклоуглеродный электрод, расплав kf–kcl–k2sif6, с0 = 5,7·10 –4 моль/см3, т = 675 ºс, sэл = 0,6 см 2) с. и. жук, л. м. минченко, о. в. чемезов, в. б. малков, а. в. исаков, ю. п. зайков re tr ac te d 49 № 1 | 2015 chimica techno acta ждения растянут во времени, поэтому зародыши кремния, возникшие первыми, имеют большие размеры в процессе роста, по сравнению с зародышами si, образовавшимися с некоторой задержкой во времени. зарождение кремния на стеклоуглеродной подложке проведено при разных приложенных к рабочему электроду потенциалах (от –0.005 до –0.03 в) и разных временах процесса электролиза (от 0,001 до 1 с). на микрофото графиях (рис. 4–6) видно, что размеры зародышей кремния в каждом эксперименте различаются между собой в несколько раз. это подтверждает ранее сделанный вывод о прогрессирующем процессе фазозарождения кремния в условиях наших экспериментов. оценку влияния потенциала зарождения на количество зародышей проводили при помощи анализа данных методом сканирующей электронной микроскопии подложек с si. показано, что когда к рабочему электроду при прочих равных условиях прикладывается более отрицательное значение потенциала относительно кремниевого электрода сравнения, то количество сформировавшихся зародышей на поверхности электрода растет. рис. 4. микрофотография (sem) зародышей кремния, полученных в расплаве kf–kcl–k2sif6, с0 = 5,7·10 –4 моль/см3, т = 675 ºс на стеклоуглеродном электроде при приложенном значении потенциала –0,05 в в течение 1 с рис. 6. микрофотография (sem) зародышей кремния, полученных в расплаве kf–kcl–k2sif6, с0 = 5,7·10 –4 моль/см3, т = 675 ºс на стеклоуглеродном электроде при приложенном значении потенциала –0,005в в течение 0,001 с рис. 5. микрофотография (sem) зародышей кремния, полученных в расплаве kf– kcl–k2sif6, т = 675 ºс на стеклоуглеродном электроде при приложенном значении потенциала –0,03 в течение 0,01 с рис. 3. линейная зависимость i – (t3/2), полученнная в расплаве kf–kcl– k2sif6, с0 = 5,7·10 –4 моль/см3, т = 675 ºс на стеклоуглеродном электроде при приложенном значении потенциала –0,05 в фазозарождение кремния на стеклоуглероде в расплаве kf–kcl–k 2 sif 6 re tr ac te d 51 № 1 | 2015 chimica techno acta выводы по данным хроноамперометрии показано, что процесс фазозарождения кремния на стеклоуглеродной подложке в расплаве kf–kcl–k2sif6, при т = 675 ºс на стеклоуглеродном электроде имеет прогрессирующий характер. из sem-микрофотографий зародышей кремния, выращенных на стеклоуглеродной подложке в потенциостатическом режиме в интервале потенциалов от –0,005 до –0,03 в в расплаве kf–kcl–k2sif6 при т = 675 ºс, видно, что в условиях одного эксперимента они имеют размеры, различающиеся в несколько раз, что подтверждает прогрессирующий характер возникновения зародышей кремния. 1. patent 2427526 ru. o. v. chemezov, v. p. batukhtin, a. p. apisarov, a. v. isakov, yu. p. zaikov. publ. 27.08.2011. 2. чемезов о. в., виноградов-жабров о. н., аписаров а. п., исаков а. в., поволоцкий и. м., мурзакаев а. м., малков в. б., зайков ю. п. // перспективные материалы. 2010. № 9. с. 277– 282. 3. гришенкова о. в., семерикова о. л., исаев в. а. // расплавы. 2010. №. 5.с. 56–61. 4. барабошкин а. н. // электрокристаллизация металлов из расплавленных солей. м.: наука, 1976. 279 с. 5. bieber a. l., massot l., gibilaro m., cassayre l., taxil p., chamelot p. // electrochimica acta. 2012. v. 62. p. 282–289. 6. cai z., li y., he x., liang j. // metallurgical and material transaction b. 2010. v. 41b. p. 1033–1037. 7. apisarov a., redkin a., zaikov yu., chemezov o. and isakov a. // journal of chemical and engineering data. 2011. v. 56. № 12. p. 4733–4735. 8. жук с. и., минченко л. м., чемезов о. в., зайков ю. п. // вопросы химии и химической технологии. 2011. №. 4 (1). с. 195–196. с. и. жук, л. м. минченко, о. в. чемезов, в. б. малков, а. в. исаков, ю. п. зайков re tr ac te d 42 do i: 1 0. 15 82 6/ ch im te ch .2 01 5. 2. 1. 00 4 zhuk s.i., minchenko l.m., chemezov o.v., malkov v.b., isakov a.v., zaikov yu.p. institute of high-temperature electrochemistry ub ras, 20 akademicheskaya street, 620990 ekaterinburg fax: +7(343) 3623462; phone: +7(343)3623497; e-mail: chem@ihte.uran.ru silicon phase origin on glassy carbon in kf-kcl-k 2 sif 6 fusion silicon nucleation process was invesigated in melt of kf-kcl-k 2 sif 6 on glassy carbon substrates at 675 ºс by chronoamperometric method. using data of the chronoamperograms the linear dependence i – τ3/2 has been constructed. that fact testified the progressive nucletion mode of silicon. as seem from sem micrographs silicon crystals obtained by a single pulse had different sizes, that also confirmed the progressive nucletion mode. introduction silicon is a material that is widely used in modern semiconductor devices. the morphology of the silicon material significantly affects their physical and chemical properties, and consequently the possibility of applying them in modern industries. currently, the attention of researchers is focused on the creation of silicon nanomaterials which offer new opportunities for increasing the efficiency of the lithium-ion chemical sources of current and photovoltaic elements. the basic method of production of high purity silicon and nanomaterials on its basis is vapor deposition. the processes of vaporphase synthesis are energy-intensive, require the use of expensive reagents and complicated equipment. an alternative method for the preparation of silicon and nanomaterials on its basis is the electrolysis of silicon-containing molten salts(1,2). electrochemical method makes it relatively easy to control the structure of the electrolyte precipitation of si. with the help of electrolysis of molten salts solid silicon coating, si-nanostructures nanopowders and nanofibers may be obtained. for preparation of targeted precipitates of silicon of given shape it is necessary to understand the mechanism of nucleation and initial crystal growth of the si. theoretical understanding of the mechanisms of nucleation and crystal growth of metals in the process of electrolysis are well developed (3.4). however, there is only fragmentary information about features of phase initiation of semiconductor materials in literature, in © zhuk s. i., minchenko l. m., chemezov o. v., malkov v. b., isakov a. v., zaikov yu. p., 2015 re tr ac te d 44 № 1 | 2015 chimica techno acta silicon phase origin on glassy carbon in kf-kcl-k 2 sif 6 fusion 44 particular silicon, with electrodeposition of molten salts. a.l.bieber et al. investigated nucleation of silicon on a silver base in melt of naf-kf-na2sif6 at temperatures ranging from 850 to 900° c, and concluded that the silicon nucleation occurs in an instantaneous diffusion mode(5). investigation of silicon phase initiation using chronoamperometry method on a molybdenum substrate in melt of naclkcl-naf-sio2 at 800 °c held by z.cai et al showed that during electrocrystallazation of silicon, formation of three-dimensional nucleation is gradual(6). the aim of this work is to study the process of electrolytic silicon phase initiation using chronoamperometry method on glassy carbon electrode from kf-kclk2sif6 melt in an inert atmosphere at t = 675 °c. the experimental part electrochemical studies were carried out using chronoamperometry method in melt of kf-kcl-k2sif6 with molar ratio kf / kcl = 2 and concentration of the silicon melt equal to 5,7·10–4 mol per cm3. melts for the experiment were prepared from individual salts of kf·hf, kcl, k2sif6 based on a previously described method(7). experiments were performed in argon atmosphere in a three-electrode cell(8). glassy carbon crucible was used as a container for the salt melt. the working electrode was glassy carbon plate (su-2000). as the counter-electrode and a reference electrode we used plates from mono-crystal silicon of high purity (resistivity equals 0.01 om per cm). before the starting of the experiment refinery electrolysis was carried out on the auxiliary graphite electrode. after refinery electrolysis graphite electrode was removed from the cell through the gateway device, and was replaced with a glassy carbon working electrode. chronoamperometric measurements were performed using a potentiostat/ galvanostat autolab, using software nova 1.5. nucleation of silicon on a glassy carbon substrate was conducted in a potentiostatic mode. microphotography of the samples was carried out using a scanning electron microscope jms-5900lv. results and discussion in the initial sections of chronoamperometric curves, a peak relates to charging of the double electric layer was registered (see figure 1). this peak was subsiding for a short time (from 10–4 to 10–3 seconds). then the second voltage peak was formed on chronoamperometric curves in the time interval from 1·10–1 to 5·10–1 s. received chronoamperometric dependence in the melt of kf-kcl-k2sif6 at t = 675 ° c, depending on the applied fig.1. typical initial section chronoamperometric dependence (glass carbon electrode, t = 655 °c, the melt of kf-kcl-k2sif6, c0 = 5,7*10 –3 mol per cm3, sel = 0.35 cm2) re tr ac te d 46 № 1 | 2015 chimica techno acta potentials ranging from –0.05 to –0.15 v with respect to the silicon electrode are shown in figure 2. chronoamperogramme section before the second peak of the curve is associated with the process of phase initiation. following section of current reduction is due to depletion of the layer on the silicon containing ion. dependence of the current of the second decreasing section of chronoamperogramme from time helps to determine the mode of phase initiation and conforms to the equation (1): j = ά t x, (1) where ά and x depend on the geometry of the nucleating center and the phase initiation mode. in the case of a hemispherical diffusion-controlled 3d-nucleation, for instantaneous nucleation mode, the value of the value of x function is 1/2, for progressive it is 3/2(5) analysis of primary data collected at a potential applied to the working glassy carbon electrode, equal to the value of -0.05 v with respect to the silicon electrode in the coordinates i – t3/2, showed that the experimental points are well in linear dependence (figure 3). it can be concluded that the mode of nucleation of silicon on a glassy carbon substrate under our experimental conditions is progressive in nature. in other words, not the whole mass of silicon nucleating centers appears at the same time and saves approximately the same size in the process of growing. in this case, the process of phase initiation is extended in time, so the silicon nucleating centers that arose first have larger size in the process of growing, as compared with nuclei of si, formed with a certain time delay. nucleation of silicon on a glassy carbon substrate was held at different potentials applied to the working electrode (from –0.005 to –0.03 v) and of different times of the electrolysis process (from 0.001 s to 1 s). presented photomicrographs (figure 4–6) show that the size of nucleating centers of silicon in each experiment differs in several times. this confirms the earlier conclusion of the progressive process of silicon phase zhuk s. i., minchenko l. m., chemezov o. v., malkov v. b., isakov a. v., zaikov yu. p. fig. 2. typical chronoamperometric dependence (glassy carbon electrode, the melt of kf-kcl-k2sif6, c0 = 5,7·10 –4 mol per cm3, t = 675 °c, sel = 0.6 cm2) fig.3. the linear dependence i – (t3/2), taken in the melt of kf-kcl-k2sif6, c0 = 5,7·10 –4 mol per cm3, t = 675 ºc on glassy carbon electrode at an applied potential value equal to –0,05v re tr ac te d 48 № 1 | 2015 chimica techno acta initiation in the conditions of our experiments. assessment of the impact of potential nucleation on the number of nucleating centers was performed using a data analysis by scanning electron microscopy of si substrates. it is shown that when a more negative potential in comparison with reference silicon electrode is applied to the working electrode with all other conditions being equal, the number of nucleating centers formed on the electrode surface increases. conclusions according to the chronoamperometry data, it is shown that the process of silicon phase initiation on a glassy carbon substrate in melt of kf-kcl-k2sif6, at t = 675 ºc on a glassy carbon electrode has a progressive character. sem-micrographs of the nucleating centers of silicon grown on a glassy carbon substrate in potentiostatic mode in the potential range from –0.005 to –0.03 in the melt of kf-kcl-k2sif6 at t = 675 ºc make it clear that under the conditions of a single experiment, they have sizes differing by several times, that confirms the progressive mode of the nucleation of silicon. 1. patent 2427526 ru. chemezov o. v., batukhtin v. p., apisarov a. v., isakov a. v., zaikov yu. p. publ. 27.08.2011. [google scholar]. 2. chemezov о. v., vinogradov-zhabrov о. n., аpisarov а. p., isakov а. v., povoloszhkiy i. m., мyrzakaev а. м., malkov v. b., zaikov yu. p. perspektivnye materialy. 2010; 9:277–282. [google scholar]. 3. grishenkova o. v., semerikova o. l., isaev v. a. rasplavy. 2010; 5:56–61. [google scholar]. 4. baraboshkin a. n. electrocrystallization from melted salts. moscow: nauka, 1976. 279 p. [google scholar]. figure 4. micrograph (sem) of silicon nucleating centers obtained in the melt of kfkcl-k2sif6, c0 = 5,7·10 –4 mol per cm3, t = 675 °c on a glassy carbon electrode at an applied potential value of –0.05 v for 1s. figure 5. micrograph (sem) of silicon nucleating centers obtained in the melt of kfkcl-k2sif6, t = 675 °c on a glassy carbon electrode at an applied potential value of –0.03 for 0.01s figure 6. micrograph (sem) of silicon nuclei obtained in the melt of kf-kcl-k2sif6, c0 = 5,7·10 –4 mol per cm3, t = 675 °c on a glassy carbon electrode at an applied potential value of –0,005 v for 0,001 s. silicon phase origin on glassy carbon in kf-kcl-k 2 sif 6 fusion re tr ac te d 50 № 1 | 2015 chimica techno acta 5. bieber a. l., massot l., gibilaro m., cassayre l., taxil p., chamelot p. silicon electrodeposition in molten fluorides. electrochimica acta. 2012; 62:28–289. doi: 10.1016/j.electacta.2011.12.039. [google scholar]. 6. cai z., li y., he x., liang j. metallurgical and material transaction b. 2010; 41b:1033–1037. [google scholar]. 7. apisarov a., redkin a., zaikov yu., chemezov o., isakov a. electrical conductivity of molten fluoride-chloride electrolytes containing k2sif6 and sio2. journal of chemical and engineering. data 2011; 56(12):473–4735. doi: 10.1021/je200717n. [google scholar]. 8. zhuk s.i., minchenko l.m., chemezov o.v., zaikov yu.p. questions of chemistry and chemical technology. 2011;4(1):195–196. [google scholar]. zhuk s. i., minchenko l. m., chemezov o. v., malkov v. b., isakov a. v., zaikov yu. p. re tr ac te d 1096-2577-1-pb(1) 1096-2576-1-pb 200 e. a. dolmatova, a. d. dayanov, t. n. ostanina ural federal university, 28, mira str., ekaterinburg, russia. e-mail: arcfan@yandex.ru simulation of an electrolytic bath for electrodeposition of multilayer shielding coatings in this the calculation work galvanic bath of cu/(ni+cu) multilayer shielding coatings formation from an acetate electrolyte containing 0,03 mol/l of cuac 2 , 0,3 mol/l of niac 2 and 1,66 mol/l of acetic acid were made. according to the results of polarization studies values of coatings deposition pulse mode current density have been chosen and current efficiency of copper and nickel during deposition of cu-ni alloy has been determined. to ensure a constant formulation of the electrolyte it has been proposed to use insoluble anodes made of stainless steel and continuous circulation of the electrolyte. the scheme of steams enabling the adjustment of the solution formulation with the use of an additional collecting vessel has been developed. the formulation of the correcting stream continuously fed into the collecting vessel has been calculated. key words: electrochemistry; simulation; cuprum acetate; nickel acetate; multilayer shielding coatings. © dolmatova e. a., dayanov a. d., ostanina t. n.. 2015 d o i: 1 0. 15 82 6/ ch im te ch .2 01 5. 2. 3. 02 1 introduction currently, there is an acute problem of protection devices and the environment from the effects of electromagnetic radiation. to ensure effective protection of the surface of plastics from which basic parts of devices are generally made, it is necessary to apply shielding coating. multilayer coatings consisting of alternating layers of magnetic (e.g., nickel) and nonmagnetic (e.g., copper) metals are the most effective screens. as shown by previous studies [1], copper filled composites consisting of an organic polymeric binder and a filler of copper powder can be used to create a conductive basis for a plastic for subsequent deposition of metal coatings. shielding coatings consisting of alternating layers of copper and nickel, can be obtained by the «single-bath» method [2] from the electrolyte containing cations of the two metals cu2+ and ni2+. conditions for preparing of individual layers are provided with a pulsed electrolysis, in which an alternation of pulses with different values of current takes place. during odd pulses ions of the most electroposi201 № 3 | 2015 chimica techno acta tive nonmagnetic metal (copper) are recovering cu2++2ē→cu0, and during the even pulses ions of copper and nickel presented in the electrolyte are discharging to give a magnetic layer, and hydrogen gas is exhaling. cu2+ + 2ē → cu0 ni2+ + 2ē → ni0 2h+ + 2ē → h2 the purpose of the present work consisted in simulation of a galvanic bath for forming multilayer shielding coatings. for electrodeposition layered cu/(ni+cu) coating acetate electrolyte of the following composition: 0.03 mol/l of cuac2, 0,3 mol/l of niac2 and 1.66 mol/l of acetic acid [2] has been used. monitoring of value ph = 4.7 has been periodically conducted. experimental part to select the parameters of the galvanic bath to be designed experimental studies were conducted. polarization measurements were carried out using a zive sp5 electrochemical station with a linear change in the potential in the cell, connected by a threeelectrode circuit. the potential has been measured with respect to a silver chloride reference electrode. when dotting the cathodic polarization curve (fig. 1) the pin type working electrode made of copper wire with a diameter of 2 mm and a height of 10 mm has been used. the area on the curve corresponds to the limiting diffusion current of discharge of copper ions, and the subsequent rise of the current corresponds to recovery processes of nickel ions and hydrogen. according to the results of polarization studies current densities: for deposition of copper layer equals to 7 a/m2 and a magnetic alloy ni-cu equals to 90 a/m2 were selected. the use of soluble anodes will lead to the enrichment of the electrolyte by nickel or copper ions, so it was proposed to use insoluble anodes made of stainless steel 12x18h10t. during polarization studies it was found that anodes made of steel are passivated and not dissolved in the solution. for technological calculations current efficiency of metal has a great significance. during odd pulses copper recovery with 100 % current efficiency occurs. to determine the current efficiency of metals during deposition of the magnetic layer experiments on deposition of a ni-cu coating to sample of stainless steel pre-coated by a copper layer were conducted. at a current density of 90 a/m2 current efficiency of ni-cu alloy was 70.6 %. the resulting precipitate of alloy and the copper underlayer have been dissolved in concentrated nitric acid. the concentration of ni2+ ions in the resulting solution has been determined by photometry allowing estimating the mass of nickel in the alloy. the analysis was fig. 1. cathode polarization curve of the recovery of copper in acetate electrolyte simulation of an electrolytic bath for electrodeposition of multilayer shielding coatings 202 № 3 | 2015 chimica techno acta conducted by employees of the department of analytical chemistry, cti, urfu. from the known weight of the precipitate alloy formulation was calculated as comprising 60 wt. % of ni and 40 wt. % of cu. the current efficiency of metals has been calculated taking into account proportion of the appropriate metal in the alloy bmni = bmalloy · ωni = 70 · 0,6 = 42 %, bmcu = bmalloy · ωcu = 70 · 0,4 = 28 %. the summarized reaction occurring during the even pulses based on the current efficiency looks as follows: втcu·cuac2+втni·niac2+ h2o = втcu·cu+втni·ni+(1-втcu-втni)·h2↑+ +(2–1+втcu+втni)·hac from the latter equation it follows that when using insoluble anodes in the electrolysis process a reduction in the concentration of copper and nickel acetates in a solution will be observed, and the concentration of acetic acid will increase. discussion of the calculations results for the stable operation of the galvanic bath and preparing precipitates of high quality it is necessary to maintain the formulation of the electrolyte unchanged. in the projected bath it can be achieved by adjusting the formulation of continuous circulating flow at the inlet to the bath. a scheme has been proposed (fig. 2), which includes a collecting vessel intended for the organization of continuous circulation of the solution and adjusting its formulation. electrolyte discharged from the bath is divided into two streams, one is directed to the collecting vessel (½ ϑ1), and the second one is directed to neutralize acid excess (½ ϑ1). simultaneously, correcting stream (ϑcor) is fed to the collecting vessel, wherein the concentration of copper and nickel acetates is higher than in the bath. the effluent solution from the collecting vessel is fed into a galvanic bath (ϑ'1). furthermore, during the process calculations speed of pseudocontinuous streams (ϑ'1 and ϑ2), which are solutions transferred on details, was considerd. as the result of the calculation of the stationary mass balance of the galvanic bath it was found that for stable operation it is necessary that the electrolyte is fed to the bath, wherein the acetic acid concentration (c'hac = 1,48 mol/l) is below, and the concentrations of copper acetate (c'hac2 = 0,033 mol/l) and nickel acetate (c'hac2 = 0,304 mol/l) is higher than in the bath. in view of water evaporation rate defined was a volume rate of effluent stream from which then stream feeding to the collecting vessel is formed. while calculating the different values of intensities of components sources in periods of even and odd pulses were taken into account. the correcting stream is needed to maintain in the collecting vessel a constant formulation of the solution corresponding by components concentrations to a stream directed to the bath of multilayer coating deposition. simulation of the stationary mass balance of the collecting vessel has allowed fig. 2. correcting streams in the technological scheme of multilayer coating deposition dolmatova e. a., dayanov a. d., ostanina t. n. 203 № 3 | 2015 chimica techno acta determining the rate of the correcting stream and its formulation: ϑ ϑ ϑ ϑ ϑ ϑ cor cor i i i cor c c c = − = ⋅ − ⋅ 1 2 1 1 1 1 2 2 ’ , ’ ’ , / . the calculation has showed that the solution containing 1.45 mol/l of acetic acid, 0.037 mol/l of copper acetate and 0.307 mol/l of nickel acetate should be continuously added at a rate equal to ϑcor = 5,0 · 10 –6 m3/s to the collecting vessel. conclusion during the experimental studies the parameters of pulse mode of multilayer coating deposition, and current efficiency of copper and nickel have been determined. for preparing layered cu/cu-ni coatings by the single-bath method it has been proposed to use a continuous flow bath with insoluble anodes. the possibility of using stainless steel as an insoluble anode in an acetate electrolyte has been shown. using the method of mathematical modeling of mass balances of galvanic baths and the collecting vessel the formulation of the circulating stream incoming to the bath as well as the speed and formulation of the correcting stream incoming to the collecting vessel have been determined. 1. rudoi v. m. , ostanina t. n., darintseva a. b., ostanin n. i., alikhanova i. a., demakov s. l., et al. electrodeposition of copper on metal-filled composite support. russian journal of electrochemistry. 2010; 46(6):702–706. doi: 10.1134/ s1023193510060157. 2. ovchnnikova s. n., poddubnyi n. p., masliy a. i., boldyrev v. v. schwazacher w. mutual influence of electrode processes during electrodeposition of layered structures by the single-bath method: the effect of nickel deposition and hydrogen evolution on the transport of copper ions in acetate and sulfamate electrolytes. russian journal of electrochemistry. 2002; 38(11):1210–1206. doi: 10.1023/a:1021153827310. simulation of an electrolytic bath for electrodeposition of multilayer shielding coatings 204 е. а. долматова, а. д. даянов, т. н. останина уральский федеральный университет 620002, екатеринбург, ул. мира, 28. e-mail: arcfan@yandex.ru моделирование электролитической ванны нанесения многослойных экранирующих покрытий в работе проведен расчет гальванической ванны формирования многослойных экранирующих покрытий cu/(ni+cu) из ацетатного электролита, содержащего 0,03 моль/л cuac 2 , 0,3 моль/л niac 2 и 1,66 моль/л уксусной кислоты. по результатам поляризационных исследований выбраны значения плотностей тока импульсного режима нанесения покрытий и определен выход по току меди и никеля в период осаждения сплава cu-ni. для обеспечения постоянного состава электролита предложено использовать нерастворимые аноды из нержавеющей стали и непрерывную циркуляцию электролита. разработана схема потоков, позволяющая проводить корректировку состава раствора с использованием дополнительной сборной емкости. рассчитан состав корректирующего потока, непрерывно подаваемого в сборную емкость. ключевые слова: электрохимия, моделирование, ацетат меди, ацетат никеля, гальваническая ванна. © долматова е. а., даянов а. д., останина т. н., 2015 у д к : 5 44 .6 53 .2 2: 5 44 .6 .0 18 .4 214 3 введение в настоящее время остро стоит проблема защиты приборов и окружающей среды от воздействия электромагнитных излучений. для обеспечения эффективной защиты на поверхность пластмассы, из которой, как правило, выполнены корпусные детали приборов, необходимо наносить экранирующие покрытия. наиболее эффективными экранами являются полислойные покрытия, состоящие из чередующихся слоев магнитного (например, никель) и немагнитного (например, медь) металлов. как показали проведенные ранее исследования, медьнаполненные композиты, состоящие из органического полимерного связующего и наполнителя медного порошка, можно использовать для создания электропроводной основы на пластмассе с целью последующего нанесения металлических покрытий [1]. экранирующие покрытия, состоящие из чередующихся слоев меди и никеля, можно получать методом «одной ванны» из электролита, содержащего катионы двух металлов cu2+ и ni2+ [2]. условия для получения 205 № 3 | 2015 chimica techno acta индивидуальных слоев обеспечиваются импульсным электролизом, в ходе которого происходит чередование импульсов с разными значениями тока. во время нечетных импульсов восстанавливаются ионы наиболее электроположительного немагнитного металла (медь) cu2++2ē→cu0, а во время четных импульсов разряжаются присутствующие в электролите ионы меди и никеля, давая магнитный слой, и выделяется газообразный водород. cu2++2ē→cu0 ni2++2ē→ni0 2h++2ē→h2. цель настоящей работы состояла в моделировании гальванической ванны формирования многослойных экранирующих покрытий. для электроосаждения слоистых покрытий cu/(ni+cu) использовали ацетатный электролит следующего состава: 0,03 моль/л cuac2, 0,3 моль/л niac2 и 1,66 моль/л уксусной кислоты [2]. периодически проводили контроль величины рн = 4,7. экспериментальная часть для выбора параметров работы проектируемой гальванической ванны были проведены экспериментальные исследования. поляризационные измерения проводили с помощью электрохимической станции zive sp5 при линейном изменении потенциала в ячейке, подключенной по трехэлектродной схеме. потенциал измеряли относительно хлоридсеребряного электрода сравнения. при съеме катодной поляризационной кривой (рис. 1) использовали рабочий электрод штырькового типа, изготовленный из медной проволоки диаметром 2 мм и высотой 10 мм. площадка на кривой соответствует предельному диффузионному току разряда ионов меди, а последующий подъем тока – процессам восстановления ионов никеля и водорода. по результатам поляризационных исследований были выбраны плотности тока: для осаждения слоя меди 7 а/м2 и магнитного сплава ni-cu – 90 а/м2. использование растворимых анодов приведет к обогащению электролита по ионам никеля или меди, поэтому было предложено использовать нерастворимые аноды из нержавеющей стали марки 12х18н10т. в ходе поляризационных исследований было установлено, что аноды из стали в данном растворе пассивируются и не растворяются. для проведения технологических расчетов большое значение имеет выход по току металла. во время нечетных импульсов происходит восстановление меди с выходом по току 100 %. рис. 1. катодная поляризационная кривая восстановления меди в ацетатном электролите моделирование электролитической ванны нанесения многослойных экранирующих покрытий 206 № 3 | 2015 chimica techno acta для определения выхода по току металлов при осаждении магнитного слоя были проведены эксперименты по осаждению покрытия ni-cu на образец из нержавеющей стали, предварительно покрытий слоем меди. при плотности тока 90 а/м2 выход по току сплава ni-cu составил 70,6 %. полученный осадок сплава и подслой меди растворяли в концентрированной азотной кислоте. концентрацию ионов ni2+ в полученном растворе определяли методом фотометрии, что позволило оценить массу никеля в сплаве. анализ проведен сотрудниками кафедры аналитический химии хти урфу. по известной массе осадка рассчитали состав сплава: 60 мас.% ni и 40 мас.% cu. выход по току металлов считали с учетом доли соответствующего металла в сплаве bmni = bmalloy · ωni = 70 · 0,6 = 42 %, bmcu = bmalloy · ωcu = 70 · 0,4 = 28 %. суммарная реакция, протекающая в период четных импульсов, с учетом выходов по току выглядит следующим образом: втcu·cuac2+втni·niac2+ h2o = втcu·cu+втni·ni+(1-втcu-втni)·h2↑+ +(2–1+втcu+втni)·hac из последнего уравнения следует, что при использовании нерастворимых анодов в процессе электролиза будет наблюдаться уменьшение концентрации ацетатов меди и никеля в растворе, а концентрация уксусной кислоты будет возрастать. обсуждение результатов расчетов для стабильной работы гальванической ванны и получения осадков высокого качества необходимо поддерживать неизменным состав электролита. в проектируемой ванне этого можно добиться, регулируя состав непрерывного циркуляционного потока на входе в ванну. была предложена схема (рис. 2), в которую входит сборная емкость, предназначенная для организации непрерывной циркуляции раствора и корректировки его состава. электролит, выходящий из ванны, делится на два потока: один направляется в сборную емкость (½ ϑ1), а второй – на нейтрализацию избытка кислоты (½ ϑ1). одновременно в сборную емкость подается корректировочный поток (ϑкорр), в котором концентрация ацетатов меди и никеля выше, чем в ванне. выходящий из сборной емкости раствор подается в гальваническую ванну (ϑ'1). кроме того, при проведении технологических расчетов учитывали скорость псевдонепрерывных потоков (ϑ'1 и ϑ2), которые представляют собой растворы, переносимые на деталях. в результате расчета стационарного материального баланса гальванической ванны было установлено, что для стабильной работы необходимо, чтобы в ванну поступал электролит, в котором концентрация уксусной кислоты (c'hac = 1,48 моль/л) ниже, а концентрации рис. 2. корректирующие потоки в технологической схеме нанесения многослойных покрытий долматова е. а., даянов а. д., останина т. н. 207 № 3 | 2015 chimica techno acta ацетата меди (c'hac2 = 0,033 моль/л) и ацетата никеля (c'hac2 = 0,304 моль/л) выше, чем в ванне. с учетом интенсивности испарения воды определена объемная скорость выходящего потока, из которого затем формируется поток, поступающий в сборную емкость. при расчете учитывали разные значения интенсивностей источников компонентов в периоды четных и нечетных импульсов. корректировочный поток необходим для обеспечения постоянного состава раствора в сборной емкости, соответствующего по концентрациям компонентов потоку, направляемому в ванну нанесения полислойного покрытия. моделирование стационарного материального баланса сборной емкости позволило определить скорость корректировочного потока и его состав: ϑ ϑ ϑ ϑ ϑ ϑ корр корр корр = − = ⋅ − ⋅ 1 2 1 1 1 1 2 2 ’ , ’ ’ , / .c c c i i i расчет показал, что в сборную емкость необходимо непрерывно добавлять со скоростью ϑкорр = 5,0 · 10 –6 м3/с раствор, содержащий 1,45 моль/л уксусной кислоты, 0,037 моль/л ацетата меди и 0,307 моль/л ацетата никеля. заключение в ходе экспериментальных исследований определены параметры импульсного режима нанесения многослойных покрытий и выходы по току меди и никеля. для получения слоистых покрытий cu/cu-ni методом одной ванны предложено использовать проточную ванну с нерастворимыми анодами. показана возможность использования нержавеющей стали в качестве нерастворимого анода в ацетатном электролите. с помощью метода математического моделирования материальных балансов гальванической ванны и сборной емкости определены состав входящего циркуляционного потока в ванну, а также скорость и состав корректирующего потока в сборную емкость. 1. rudoi v. m., ostanina t. n., darintseva a. b., ostanin n. i., alikhanova i. a., demakov s. l., et al. electrodeposition of copper on metal-filled composite support. russian journal of electrochemistry. 2010; 46(6):702–706. doi: 10.1134/s1023193510060157. 2. ovchnnikova s. n., poddubnyi n. p., masliy a. i., boldyrev v. v., schwazacher w. mutual influence of electrode processes during electrodeposition of layered structures by the single-bath method: the effect of nickel deposition and hydrogen evolution on the transport of copper ions in acetate and sulfamate electrolytes. russian journal of electrochemistry. 2002; 38(11):1210–1206. doi: 10.1023/a:1021153827310. моделирование электролитической ванны нанесения многослойных экранирующих покрытий 98 d o i: 1 0. 15 82 6/ ch im te ch .2 01 5. 2. 2. 01 0 а. а. poluikova, а. yu. platonova, т. v. glukhareva, yu. yu. morzherin y-synthesis, 60 lunacharsky street, 620027, ekaterinburg phone: +7(343)3882378; e-mail: annapoluikova200@mail.ru synthesis of 5-thiocarbomoyland 5-(thiazole-2-yl)-2,3,4,4a,5,6-hexahydro 1н-pyrido[1,2-a]quinoline-5-carbonitriles the tert-amino effect cyclizations are an efficient and convenient route to synthetically as well as biologically important ring-fused tetrahydroquinolines. the method is operationally simple and highly diastereoselective. herein we represent our studies of the tert-amino effect reaction ortho-dialkylaminobenzaldehydes and cyanthioacetamide or [4-aryl-1,3-thiazole-2yl]acetonitrile. it was found 9-chloro-5-(4-phenylthiazole-2-yl)-2,3,4,4a,5,6-hexahydro-1нpyrido[1,2-a]quinoline-5-carbinitrile can easily be obtained from 9-chloro-5cyano-2,3,4,4а,5,6-hexahydro-1h-pyrido[1,2-a] quinoline-5-carbothioamide and α-bromoacetophenone by condensation. © poluikova а.а., platonova а.yu., glukhareva т.v., morzherin yu.yu., 2015 introduction reactions on tert-amino mechanism are of interest to organic chemists in terms of the directed synthesis of a wide variety of nitrogen-containing heterocycles1,2. these include the cyclization of conjugate n, n-disubstituted amines, a key stage in which is the transfer of hydrogen from the formally non-activated α-carbon atom of the dialkylamino group to one of the atoms of an unsaturated substituent such as, for ex-ample, c = c, c = n, n = o , c = o, etc. depending on the nature of the unsaturated substituent, there are met-kon.3 and reynhoudt4 reactions. we are interested in the transformations of the first type, which resulted in converting the new c-c bond. the general scheme of transformations which we study is shown below. according to the analysis of literature data, there were mainly investigated cyclizations of compounds in which the 99 № 2 | 2015 chimica techno acta synthesis of 5-thiocarbomoyland 5-(thiazole-2-yl)-2,3,4,4a,5,6 hexahydro-1н-pyrido[1,2-a]quinoline-5-carbonitriles terminal carbon atom of the vinyl group has two cyano or ester groups. cyclization of compounds in which β-carbon atom of the vinyl group has two different substituents was investigated to a lesser extent. besides, the only example of such transformation with cyanacetamide was described by our group. analogous reactions of [4-aryl-1,3-thiazole-2-yl] acetonitrile has not previously been performed. in this study, we demonstrated for the first time the possibility of synthesizing of 5-(4-phenylthiazole-2-yl)-9-chloro2,3,4,4а,5,6-hexahydroquinoline-5carbonitrile from the corresponding thioamide by reaction hantzsch6. results and discussion we have studied the interaction of 2-piperidinobenzaldehyde 1 with [4 (4-chlorophenyl)-1,3-thiazole-2-yl] acetonitrile 2. the starting ch-active compound (thiazole derivative 2) was synthesized by reaction of cyanthioacetamide with α-bromoacetophenone representing a known method for the hantzsch synthesis of thiazoles. the reaction was allocated vinil-derivative 3 in 87% yield. however, we could not cyclize 3-[2-(piperidine-4-yl)phenyl]2-[4-(4-chlorophenyl)-1,3-thiazole-2-yl] prop-2-ennitrile (3). alternatively 5-(4-phenylthiazole-2yl)-2,3,4,4а,5,6-hexahydroquinoline-5carbonitrile, similar to compound 4, may be synthesized from the corresponding 5-hexahydroquinolinecarbothioamide by hantzsch reaction. the source 9-chloro-5-cyano2,3,4,4а,5,6-hexahydroquinoline-5carbothiamide 7 was obtained by reacting with 2 cyanthioacetamide(piperidin-1yl)-4 5-chlorobenzaldehyde with heating at 200 °c for 10 minutes in a microwave reactor. the condensation of benzaldehyde 5 with ch-acid formed vinil-derivative 6 that under the high temperature is cyclized to form a tandem reaction product 7 (yield of compound 7 was 73%). the reaction proceeds diastereoselectively to form a single isomer (according to 1h nmr). it has been shown that as a result of condensation 9-chloro-5-cyano2,3,4,4а,5,6-hexahydroquinoline-5carbothiamide 7 α-bromoacetophenone is formed 5-(4-phenylthiazole-2-yl)9-chloro-2,3,4,4a,5,6-hexahydro-1нpiride[1,2-a]quinoline-5-carbonitrile 8 during the conversion at 150 °c for 25 minutes in a microwave reactor. the yield of the reaction product is 70 %. as a result, the conversion produces two diastereomers (ratio ~ 2:1). 100 № 2 | 2015 chimica techno acta poluikova а.а., platonova а.yu., glukhareva т.v., morzherin yu.yu. it should be noted that numerous attempts to carry out a similar condensation in boiling ethanol (even after prolonged heating) did not yield any results. thus, it was shown that only a single one approach to the synthesis of 5-(4-phenylthiazole-2-yl)-2,3,4,4а,5,6hexahydroquinoline-5-carbonitrile. ring formation in thiazole occurs only in a microwave reactor. the experimental part monitoring of the progress of the reaction and the individuality of the synthesized compounds was performed by tlc plates 254 solufoluv system: chloroform (manifestation uv lamp). ir spectra were recorded on a spectrophotometer bruker alpha. 1hnmr and 13c recorded on a spectrometer bruker avanceii (400 and 100 mhz, respectively), internal standard – tms, in the laboratory of comprehensive research and expert assessment of organic materials in the ccu ufu. mass spectra were recorded on a spectrometer mat 11 (ei, 70 ev). reactions under microwave irradiation were performed in reactors antonpaarmonowave 300. melting points were determined on the instrument stuartsmp3 and are uncorrected. elemental analysis was performed on a chns-analyzer pe 2400 seriesii. the starting ortho-dialkylaminobenzaldehydes 1 and 5 were obtained in yields of 60–80 % by nucleophilic substitution of fluorine atoms in the respective 2-fluoro-benzaldehyde with piperidine as by described previously method7, 2-fluoro-benzaldehyde – commercial preparations of acros firm. procedure for the preparation of compound 2 to a solution of 2.0 mmol cyanacethioamide in 8.0 ml of ethanol was added 2.0 mmol of α-bromoacetophenone. this solution was boiled for 1–3 hours. reaction completion is determined by tlc. the reaction mass is cooled down to room temperature. solvent was removed in vacuo. the resulting solid precipitate was recrystallized from ethanol. [4 (4-chlorophenyl)-1,3-thiazole-2-yl] acetonitrile (2) yield 0.64 g (93%). brown shine crystals. mp. 126–127 °c8, 1h nmr spectrum (dmso-d6), δ, ppm.: 8.03 (1h, s., hthiazole), 7.98–7.93 (2h, m., arh), 7.44–7.39 (2h, 101 № 2 | 2015 chimica techno acta synthesis of 5-thiocarbomoyland 5-(thiazole-2-yl)-2,3,4,4a,5,6 hexahydro-1н-pyrido[1,2-a]quinoline-5-carbonitriles m., arh), 4.48 (2h, s., ch2). found, %: n 11.87. c11h7cln2s. calculated, %: n 11.94. method for producing 2-vinyl-n, ndialkyl anilinium 3 to a solution of 1.0 mmol of benzaldehyde in 10 5 ml of toluene was added 1.0 mmol of [4 (4-chlorophenyl)-1,3-thiazole-2-yl] acetonitrile 6 and the reaction mixture refluxed for 10–30 h. end of the reaction is determined by tlc. the reaction mixture was cooled to room temperature. the solvent was removed in vacuo, the residue was crystallized from ethanol. 3-[2-(piperidine-4-yl)phenyl]-2-[4-(4-chlorophenyl)-1,3-thiazole-2-yl] prop-2-ennitrile (3) yield 0.245 g (87%). orange yellow crystals. t.dec. 145 °c. 1h nmr spectrum (dmso-d6), δ, ppm.: 8.41 (1h, c., ch), 8.16 (1h, c., hthiazole), 8.07 (1h, br. d, j = 7.5, arh) , 8.05-8.00 (2h, m., ph), 7.51-7.41 (3h, m., arh + ph), 7.21– 7.11 (2h, m., arh), 3.01–2.93 (4h, m., сн2nсн2), 1.83–1.74 (4h, m., 2сн2), 1.67–1.59 (4h, m. 2сн2). found, %: c 68.00, h 4.93, n 10.30. c23h20cln3s. calculated, %: c 68.05, h 4.97, n 10.35. technique to obtain tetrahydroquinoline 7 to a solution of 0.5 mmol of benzaldehyde in 5 ml of 2-butanol 1 in a vessel equipped with an anchor stir-ring was added 0.5 mmol cyanacethioamide. the vessel was sealed with a roof perforated with septum and heated in a microwave reactor at 200 °c for 10 minutes. closing of the reactions is determined by tlc. the reaction mixture was cooled to room temperature. the solvent was removed in vacuo. obtained solid residue is recrystallized from ethanol. (4as*,5r*)-9-chloro-5-cyano-2,3,4,4а,5,6-hexahydro-1н-piride[1,2-а] quinoline-5-carbothiamide (7) yield 0.11 g (73 %). the second diastereomer in the h1 nmr spectrum is not observed. brown crystals. mp. 187–189 °c. ir spectrum, ν, cm–1: 3333 (nh), 3153 (nh), 2245 (cn). h1 nmr spectrum (dmso-d6), δ, ppm.: 10.19 (1h, s., nh), 9.10 (1h, s., nh), 6.97 (1h, d., j = 8.0, h-7, arh ), 6.91 (1h, d., j = 1.7, h-10 arh), 6.65 (1h, d. g., j1 = 8.0, j2 = 1.8, h-8, ar), 4.01 (1h, bd , j = 12.1, 1 sheq), 3.63 (1h, d., j = 16.0, 6 sneq), 3.51-3.42 (1h, m., 4a-chax), 3.04 (1h, d., j = 16.2 6-chax), 2.74 (1h, d. g. g., j1 = 12.4, j2 = j3 = 2.8, 1-chax), 1.99-1.77 (3h, m. 2,3,4-cheq), 1.69-1.52 (1h, m. chax), 1.49-1.28 (2h, m. 2chax). found, %: c 58.88, h 5.25, n 13.65. c15h16cln3s. calculated, %: c 58.91, h 5.27, n 13.74. technique to obtain tetrahydroquinoline 8 to a solution of 0.5 mmol of 9-chloro-5-cyano-2,3,4,4а,5,6-hexahydro-1нpiride[1,2-а]quinoline-5-carbothiamide 7 in 2 ml of ethanol in a vessel equipped with an anchor for remixing is added 0.5 mmol of α-bromoacetophenone. the vessel is capped with a perforated septum and heated in a microwave reactor at temperature of 150 °c for 25 minutes. the end of the reaction is determined by tlc. then repromotional mass is cooled to room temperature. the solvent was removed in vacuo. the resulting solid precipitate was recrystallized from ethanol. 102 № 2 | 2015 chimica techno acta poluikova а.а., platonova а.yu., glukhareva т.v., morzherin yu.yu. (4as*,5r*)-5-(4-phenylthiazole-2-yl)-9-chloro-2,3,4,4a,5,6-hexahydro1н-pirido[1,2-a]quinoline-5-carbonitrile (8) yield 0.142 g (70%). prepared as a mixture of two diastereoisomers (ratio ~ 2:1). brown crystals. mp. 92–94 °c. h1 nmr spectrum (dmso-d6), δ, ppm.: 8.02 (1h, s., hthiazole), 7.99–7.89 (2h, m., ph), 7.46–7.37 (2h, m., ph), 7.36–7.28 (1h, m., ph), 7.03 (1h, d., j = 8.0, arh), 6.95 (1h, c., arh), 6.71–6.66 (1h, m., arh), 4.06 (1h, bd, j = 13.0, 1-cheq), 3.74-3.60 (2h, m. 6-cneq, 4a-chax), 3.41 (1h, d., j = 16.3, 6-cnax), 2.85 (1h, d.d.d., j1 = 12.3, j2 = j3 = 2.1, 1-chax), 1.91-1.72 (3h, m. 2,3,4-cheq), 1.72-1.42 (3h , m. 2,3,4-chax). found, %: c 59.99, h 4.96, n 10.32. c23h20cln3s. calculated, %: c 68.05, h 4.97, n 10.35. 1. meth-cohn o., suschitzky h. heterocycles by ring closure of ortho-substituted t-anilines (the t-amino effect). advances in heterocyclic chemistry. 1972;114(14(c)):211-278. doi: 10.1016/s0065-2725(08)60954-x. 2. matyus p., elias o., tapolcsanyi p., polonka-balint a., halasz-dajka b. ringclosure reactions of ortho-vinyl-tert-anilines and (di)aza-heterocyclic analogues via the tert-amino effect: recent developments synthesis. 2006:2625-2639. doi: 10.1055/s-2006-942490. 3. meth-cohn o. the t-amino effect: heterocycles formed by ring closure of orthosubstituted t-anilines. advances in heterocyclic chemistry. 1996;65:1-377. doi: 10.1016/s0065-2725(08)60954-x. 4. verboom w., reinhoudt d. recueil des travaux chimiques des pays-bas 1990;109:311. 5. glukhareva t. v. , klimova e. p., platonova a. yu., morzherin yu. yu. interaction of 2-piperazinobenzaldehyde with cyano-acet(thio)amide: stereoselective cyclization by the "tert-amino effect" mechanism. chemistry of heterocyclic compounds. 2008;44(8):759-761. doi: 10.1007/s10593-008-0097-2. 6. li dzh. named reactions. the mechanisms of organic reactions 2006, 456 p. 7. deeva e. v., gluhareva t. v., zybina n. a., morzherin yu. yu.stereoselective synthesis of spiro derivatives of 2,4-dimethyl-2,3,4,4a,5,6-hexahydro-6h-benzo[c] quinolizine. russian chemical bulletin 2005;54(6):1537-1538. doi: 10.1007/ s11172-005-0444-8. 8. novuspharma s, ernesto m, giovanni d, mario g. derivatives of chromen-2-one as inhibitors of vegf production in mammalian cells. patent no. w003105842 (al). 2003. 103 у д к : 6 61 .7 7: 54 7. 83 1+ 54 7. 83 2. 7 а. а. полуйкова, а. ю. платонова, т. в. глухарева, ю. ю. моржерин ooo у-синтез, 620027, екатеринбург, ул. луначарского, 60, хти; тел.: (343) 388-23-78; e-mail: annapoluikova200 @mail.ru синтез 5-тиокарбомоили 5-(тиазол-2-ил)2,3,4,4a,5,6-гексагидро-1н-пиридо[1,2-a] хинолино-5-карбонитрилов реакции циклизации, протекающие по механизму трет-аминоэффекта, являются удобным методом синтеза конденсированных частично гидрированных хинолинов. в данной работе мы представляем исследование взаимодействия орто-диалкиламинобензальдегидов с циантиоацетамидом и [4-арил-1,3-тиазол-2-ил]ацетонитрилом, протекающего по механизму трет-аминоэффекта. конденсацией синтезированного 9-хлор-5-циано2,3,4,4а,5,6-гексагидрохинолино-5-карботиоамида с α-бромацетофеноном был получен 5-(4-фенилтиазол-2-ил)-9-хлор-2,3,4,4a,5,6-гексагидро-1нпиридо[1,2-a]хинолино-5-карбонитрил. © полуйкова а. а., платонова а. ю., глухарева т. в., моржерин ю. ю., 2015 введение реакции, протекающие по механизму трет-аминоэффекта, представляют интерес для химиков-органиков с точки зрения направленного синтеза широкого ряда азотсодержащих гетероциклов [1, 2]. к ним относятся реакции циклизации сопряженных n,n-дизамещенных аминов, ключевой стадией которых является перенос водорода от формально неактивированного α-углеродного атома диалкиламиногруппы к одному из атомов ненасыщенного заместителя, такого, например, как с = с, с = n, n = o, c = o и т. д. в зависимости от характера ненасыщенного заместителя выделяют реакции мет-кона [3] и реакции рейнхоудта [4]. для нас представляют интерес превращения первого типа, в результате которых происходит прев104 № 2 | 2015 chimica techno acta полуйкова а. а., платонова а. ю., глухарева т. в., моржерин ю. ю. ращение новой с-с связи. общая схема изучаемых нами превращений показана ниже. согласно анализу литературных данных, в основном были исследованы циклизации соединений, у которых терминальный атом углерода винильной группы имеет две циано или сложноэфирные группы. циклизация соединений, у которых при β-углеродном атоме винильной группы два различных заместителя, исследована в гораздо меньшей степени. при этом единственный пример подобного превращения с циантиоацетамидом описан нашей группой [5]. аналогичные реакции с [4-арил-1,3-тиазол-2-ил] ацетонитрилом ранее не проводились. в данной работе нами впервые показана возможность синтеза 5-(4-фенилтиазол-2-ил)-9-хлор-2,3,4,4а,5,6гексагидрохинолин-5-карбонитрила из соответствующего тиоамида реакцией ганча [6]. результаты и обсуждение нами было исследовано взаимодействие 2-пиперидинобензальдегида 1 с [4-(4-хлорфенил)-1,3-тиазол-2-ил] ацетонитрилом 2. исходное сн-активное соединение (производное тиазола 2) было синтезировано взаимодействием циантиоацетамида с α-бромацетофеноном, представляющим собой известный метод синтеза тиазолов по ганчу. в результате реакции было выделено винилпроизводное 3 с выходом 87 %. однако нам не удалось зациклизовать 3-[2-(пиперидин-4-ил)фенил]2-[4-(4-хлорфенил)-1,3-тиазол-2-ил] проп-2-еннитрил (3). альтернативным образом 5-(4-фенилтиазол-2-ил)-2,3,4,4а,5,6-гексагидрохинолин-5-карбонитрилы, подобные соединению 4, могут быть синтезированы из соответствующих гексагидрохинолино-5-карботиоамидов реакцией ганча. исходный 9-хлор-5-циано2 , 3 , 4 , 4 а , 5 , 6 ге кс а г и д р ох и н ол и н о 5-карботиоамид 7 был получен взаимодействием циантиоацетамида с 2-(пиперидин-1-ил)-4-хлорбензальдегидом 5 при нагревании при 200 °с в течение 10 мин. в микроволновом реакторе. в результате конденсации бензальдегида 5 с сн-кислотой происходит образование винилпроизводного 6, который под действием высокой температуры циклизуется с образованием продукта тандемной реакции 7 (выход соединения 7 составляет 73 %). реакция протекает диастереоселективно с образованием одного изомера (соглас но данным ямр 1н). было показано, что в результате конденсации 9-хлор-5-циано-2,3,4,4а,5,6гексагидрохинолино-5-карботиоамида 7 с α-бромацетофеноном происходит образование 5-(4-фенилтиазол-2-ил)105 № 2 | 2015 chimica techno acta синтез 5-тиокарбомоили 5-(тиазол-2-ил)-2,3,4,4a,5,6-гексагидро 1н-пиридо[1,2-a]хинолино-5-карбонитрилов 9-хлор-2,3,4,4a,5,6-гексагидро-1нпиридо[1,2-a]хинолино-5-карбонитрила 8 при проведении превращения при 150 °с в течение 25 мин. в микроволновом реакторе. при этом выход продукта реакции составляет 70 %. в результате превращения образуется два диастереомера (соотношение ~2:1). стоит отметить, что многочисленные попытки провести подобную конденсацию при кипячении в этаноле (даже при продолжительном нагревании) не дали никаких результатов. таким образом, было показано, что реализуется только один подход к синтезу 5-(4-фенилтиазол-2-ил)2,3,4,4а,5,6-гексагидрохинолин-5-карбонитрилов. причем образование тиазольного цикла происходит только в микроволновом реакторе. экспериментальная часть контроль за ходом реакции и индивидуальностью синтезированных соединений проводили методом тсх на пластинках solufol uv 254 в системе: хлороформ (проявление уф-лампой). ик-спектры записаны на спектрофотометре bruker alpha. спектры ямр 1h и 13с записаны на спектрометре bruker avanceii (400 и 100 мгц, соотвественно), внутренний стандарт – тмс, в лаборатории комплексных исследований и экспертной оценки органических материалов при цкп урфу. масс-спектры зарегистрированы на спектрометре mat 11 (эу, 70 эв). реакции под действием микроволнового облучения были выполнены в реакторах antonpaarmonowave 300. температуры плавления были определены на приборе stuartsmp3 и не корректировались. элементный анализ выполнен на chns-анализаторе ре 2400 seriesii. исходные орто-диалкиламинобензальдегиды 1 и 5 были получены с выходами 60–80 % путем нуклеофильного замещения атома фтора в соответствующих 2-фторбензальдегидах пиперидином по описанной ранее методике [7]. 2-фторбензальдегиды – коммерческие препараты фирмы acros. методика получения соединения 2 к раствору 2,0 ммоль цианацеттиоамида в 8,0 мл этанола добавляют 2,0 ммоль α-бромацетофенона. кипятят в течение 1–3 ч. окончание реакции определяют при помощи тсх. далее реакционную массу охлаждают до комнатной температуры. растворитель удаляют in vacuo. полученный твердый осадок перекристаллизовывают из этанола. 106 № 2 | 2015 chimica techno acta полуйкова а. а., платонова а. ю., глухарева т. в., моржерин ю. ю. [4-(4-хлорфенил)-1,3-тиазол-2-ил]-ацетонитрил (2) выход 0,64 г (93 %). коричневые блестящие кристаллы. т. пл. 126–127 с [8]. спектр ямр1н (дмсо-d6), δ, м. д.: 8,03 (1н, с., thiazolh), 7,98–7,93 (2н, м., arh), 7,44–7,39 (2н, м., arh), 4,48 (2н, с., сн2). найдено, %: n 11,87. c11h7cln2s. вычислено, %: n 11,94. методика получения 2-винил-n,nдиалкиланилина 3 к раствору 1.0 ммоль бензальдегида 5 в 10 мл толуола добавляют 1,0 ммоль [4-(4-хлорфенил)-1,3-тиазол-2-ил]ацетонитрила 6 и кипятят реакционную массу в течение 10–30 ч. окончание реакции определяют по тсх. затем реакционную массу охлаждают до комнатной температуры. растворитель удаляют in vacuo, остаток кристаллизуют из этанола. 3-[2-(пиперидин-4-ил)фенил]-2-[4-(4-хлорфенил)-1,3-тиазол-2-ил] проп-2-еннитрил (3) выход 0,245 г (87 %). желто-оранжевые кристаллы. т. разл. 145 °с. спектр ямр1н (дмсо-d6), δ, м. д.: 8,41 (1н, c., сh), 8,16 (1н, c., thiazolh), 8,07 (1н, уш.д., j = 7,5, arн), 8,05–8,00 (2н, м., ph), 7,51–7,41 (3н, м., arh + ph), 7,21–7,11 (2н, м., arh), 3,01–2,93 (4н, м., сн2nсн2), 1,83–1,74 (4н, м., 2сн2), 1,67–1,59 (4н, м., 2сн2). найдено, %: с 68,00, н 4,93, n 10,30. c23h20cln3s. вычислено, %: с 68,05, н 4,97, n 10,35. методика получения тетрагидрохинолина 7 к раствору 0,5 ммоль бензальдегида 5 в 2 мл бутанола-1 в сосуде, снабженном якорем для перемешивания, добавляют 0,5 ммоль цианацеттиоамида. сосуд закрывают крышкой с перфорированной септой и нагревают в микроволновом реакторе при температуре 200 °с в течение 10 мин. окончание реакции определяют по тсх. затем реакционную массу охлаждают до комнатной температуры. растворитель удаляют in vacuo. полученный твердый осадок перекристаллизовывают из этанола. (4as*,5r*)-9-хлор-5-циано-2,3,4,4а,5,6-гексагидро-1н-пиридо[1,2-а] хинолино-5-карботиоамид (7) выход 0,11 г (73 %). второй диастереомер в спектре ямр 1н не наблюдается. коричневые кристаллы. т. пл. 187–189 °с. ик спектр, ν, см–1: 3333 (nh), 3153 (nh), 2245 (cn). спектр ямр1н (дмсо-d6), δ, м. д.: 10,19 (1н, с., nh), 9,10 (1н, с., nh), 6.97 (1н, д., j = 8,0, н-7 arh), 6,91 (1н, д., j = 1,7, н-10 arh), 6,65 (1h, д. д., j1 = 8,0, j2 = 1,8, h-8 ar), 4,01 (1h, уш.д., j = 12,1, 1-сheq), 3,63 (1н, д., j = 16,0, 6-снeq), 3,51–3,42 (1h, м., 4a-chax), 3.04 (1н, д., j = 16,2, 6-снax), 2,74 (1h, д. д. д., j1 = 12,4, j2 = j3 = 2,8, 1-сhax), 1,99–1,77 (3h, м., 2,3,4-сheq), 1,69– 1,52 (1h, м., сhax), 1,49–1,28 (2h, м., 2сhax). найдено, %: с 58,88, н 5,25, n 13,65. c15h16cln3s. вычислено, %: с 58,91, н 5,27, n 13,74. методика получения тетрагидрохинолина 8 к раствору 0,5 ммоль 9-хлор5-циано-2,3,4,4а,5,6-гексагидро-1нп и р и д о [ 1 , 2 а ] х и н о л и н о 5 к а р 107 № 2 | 2015 chimica techno acta синтез 5-тиокарбомоили 5-(тиазол-2-ил)-2,3,4,4a,5,6-гексагидро 1н-пиридо[1,2-a]хинолино-5-карбонитрилов ботиоамида 7 в 2 мл этанола в сосуде, снабженном якорем для перемешивания, добавляют 0,5 ммоль α-бромацетофенона. сосуд закрывают крышкой с перфорированной септой и нагревают в микроволновом ракторе при температуре 150 °с в течение 25 мин. окончание реакции определяют по тсх. затем реакционную массу охлаждают до комнатной температуры. растворитель удаляют in vacuo. полученный твердый осадок перекристаллизовывают из этанола. (4as*,5r*)-5-(4-фенилтиазол-2-ил)-9-хлор-2,3,4,4a,5,6-гексагидро-1нпиридо[1,2-a]хинолино-5-карбонитрил (8) выход 0,142 г (70 %). получен как смесь двух диастереомеров (соотношение ~2:1). коричневые кристаллы. т. пл. 92–94 °с. спектр ямр1н (дмсо-d6), δ, м. д.: 8,02 (1н, с., thiazolh), 7,99–7,89 (2н, м., ph), 7,46–7,37 (2н, м., ph), 7,36–7,28 (1н, м., ph), 7,03 (1н, д., j = 8,0, arh), 6,95 (1н, c., arh), 6,71–6,66 (1н, м., arh), 4,06 (1h, уш.д., j = 13,0, 1-сheq), 3,74–3,60 (2н, м., 6-снeq, 4a-chax), 3,41 (1н, д., j = 16,3, 6-снax), 2,85 (1h, д. д. д., j1 = 12,3, j2 = j3 = 2,1, 1-сhax), 1,91–1,72 (3h, м., 2,3,4-сheq), 1,72–1,42 (3h, м., 2,3,4-сhax). найдено, %: с 59,99, н 4,96, n 10,32. c23h20cln3s. вычислено, %: с 68,05, н 4,97, n 10,35. 1. meth-cohn o., suschitzky h. // advances in heterocyclic chemistry. 1972. v. 114. p. 211. 2. matyus p., elias o., tapolcsanyi p., polonka-balint a., halasz-dajka b. // synthesis. 2006. № 16. р. 2625. 3. meth-cohn o. // advances in heterocyclic chemistry. 1996. v. 65. p. 1 verboom w., reinhoudt d. n. // recueil des travaux chimiques des pays-bas. 1990. v. 109. p. 311. 4. глухарева т. в., климова е. п., платонова а. ю., моржерин ю. ю. // химия гетероциклических соединений. 2008. № 44. c. 942. 5. ли дж. именные реакции. механизмы органических реакций. м.: бином. лаборатория знаний, 2006. 456 с. 6. деева е. в., глухарева т. в., зыбина н. а., моржерин ю. ю. // известия академии наук. серия химическая. 2005. т. 54, № 6. с. 1492. 7. патент wo03105842 (a1). derivatives of chromen-2-one as inhibitors of vegf production in mammalian cells / novuspharma s. p. a., ernesto m., giovanni d. r., mario g. заявлено 12.06.2003; опубл. 24.12.2003. бюлл. № pct/ep2003/006191 2003, с. 114. рекомендуем при цитировании данно статьи следующую ссылку: poluikova а. а., platonova а. yu., glukhareva т. v., morzherin yu. yu. synthesis of 5-thiocarbomoyland 5-(thiazole-2-yl)-2,3,4,4a,5,6-hexahydro-1н-pyrido[1,2-a] quinoline-5-carbonitriles // chimica techno acta. 2015. vol. 2. № 2. p. 98–107. heat of fusion of na3alf6 eutectic mixtures with caf2 and al2o3 104 d o i: 1 0. 15 82 6/ ch im te ch .2 01 9. 6. 3. 03 a. a. redkina, s. v. pershinaa, e. a. il’inaa, a. a. kataeva, yu. p. zaikova,b ainstitute of high-temperature electrochemistry of ural branch of ras, 20 akademicheskaya st., 620137, ekaterinburg, russian federation bural federal university, 19 mira st., ekaterinburg, 620002, russian federation a.redkin@ihte.uran.ru heat of fusion of na3alf6 eutectic mixtures with caf2 and al2o3 the heat of fusion of eutectic mixtures of sodium cryolite with alumina and calcium fluoride was measured using differential scanning calorimetry. melting temperatures were found to be in good agreement with literature data. the molar heat of fusion of cryolite salts and eutectic mixtures was found to be directly dependent on melting temperature. the temperature dependence coefficient is the same as that of alkali halides. keywords: heat of fusion; melting point; cryolite; heat balance; differential scanning calorimetry. received: 01.08.2019. accepted: 11.10.2019. published: 15.10.2019. © redkin a. a., pershina s. v., il’ina e. a., kataev a. a., zaikov yu. p., 2019 introduction molten cryolites are applied as  electrolytes in  industrial production of  aluminum due to  high alumina solubility and high electrical conductivity [1]. however, it is difficult to  use them due to  their relatively high corrosion activity. one means of  avoiding this issue is to  create protective layer of  frozen salts on  the walls of  electrolytic cell, but this layer, or ledge, is unstable due to high heat flows in the salt bath. in order to control the thickness of a side ledge, the knowledge of thermophysical properties of both liquid and frozen electrolyte is very important, as  well as  freezing and melting processes themselves. the heat that is absorbed or realized at melting or freezing is determined by the enthalpy of fusion. the main component of  an aluminium bath is sodium cryolite, and its enthalpy of fusion was investigated by many researches. the very first results were very different from later data. malinovsky [2] analyzed all results available in  mid-eighties. his own results on heat of fusion were given as  115.4 kj·mol–1 (considering cryolite as na3alf6) or 28.83 kj·mol –1 (considering cryolite as 75 naf — 25 alf3 in mol %.the data obtained by malinovsky do not differ essentially from the previous ones [3, 4]. latest results are also close to these data [5]. along with sodium cryolite, the other cryolites were studied in works of holm and bjorge [3, 6]. the real bath consists not only of cryolite but also of  the other components such as  alumina and calcium fluoride. the composition of electrolyte is usually close to some eutectic mixture of sodium cryolite with alumina, calcium fluoride redkin a. a., pershina s. v., il’ina e. a., kataev a. a., zaikov yu. p. chimica techno acta. 2019. vol. 6, no. 3. p. 104–110. issn 2409–5613 105 and aluminium fluoride plus some small quantities of initial components. eutectic mixture behaviour at melting (freezing) is similar to that of individual substance, and it is possible to perform a precise measurement of the heat related to melting of such mixture. heat of fusion measurements can be carried out by differential scanning calorimetry (dsc) and drop calorimetry. in drop calorimetry, the measured parameter is the enthalpy of the sample. the temperature dependence of enthalpy is discontinuous at a melting point. the difference between values for solid and liquid states is the heat of fusion. with the dsc method, the heat of  fusion is calculated from the melting area. the aim of  the work was to  measure the melting points and heats of  fusion of  some eutectic mixtures of  cryolite with aluminium oxide and calcium fluoride. the measurements were carried out by dsc method, which can provide precise results. experimental the chemicals used for  the sample preparation are listed in  table  1. aluminum fluoride was purified from oxygen containing admixtures by ammonium fluoride in a glassy carbon crucible. part of nh4f (10 % of alf3) was placed on the bottom of  the crucible, and the other part was mixed with aluminum fluoride in proportion as follows: 12 g of nh4f per 100 g of alf3. the mixture was heated up to 723–773 k and kept for about 6 hours at that temperature. the reaction between aluminum oxide and ammonium fluoride is given below: 6nh4f+al2o3 = = 2alf3+6nh3+3h2o (1) the analysis on oxygen after purification had been made using leco element analyzer (usa). the mass content of oxygen was less than 0.1 %. the purity of other reagents was higher than 99.5 % content of main component (table 1); therefore, their purification was not required. for preparation of cryolites with calcium fluoride and alumina, the aluminum fluoride was mixed with the other components of  eutectic mixture, placed into platinum crucible and heated up to 1323 k. to avoid the oxidation, a  small amount of nh4f was added to the mixture. ammonium fluoride was decomposed at 513 k and did not influence the composition of the mixture. after melting, the sample was poured into a graphite mould. the investigations were carried out using a sta 449c jupiter synchronous thermal analyzer (netzsch, germany). the experimental setup ensures high accuracy of the measuring parameters: temperature (< 1 k); mass (± 1∙10–6 g); base line reproducibility (± 2.5 mw); enthalpy (± 3 %). the apparatus was calibrated using pure table 1 materials used in this work compound mass fraction purity, % supplier purification naf 99.5 vecton — alf3 95 vecton treatment by nh4f al2o3 99.5 achinsk alumina plant — caf2 99.5 vecton — 106 salts supplied by netzsch (cscl, agso4, baco3, rbno3, kclo4). monocrystalline sapphire was used to calibrate the sensitivity. the measurements were performed under following conditions: temperature interval  — 308–1300  k; heating rate  — 10  k min–1; atmosphere  — pure argon; crucibles with lids — pt–rh. all measurements were carried out under the same conditions. all calculations were performed with netzsch proteus software. results and discussion some eutectic compositions of cryolite with calcium fluoride and alumina were investigated; their compositions are given in table 2. the phase diagrams of  these systems were widely studied and can be found in  works [7–11]. the dsc curves are shown in fig. 1. the weight loss was observed only after melting, and its value varied from 0.6 to 3 %. there are some solidsolid transitions on  the curves. the α–β cryolite solid transition is present in samples 1 and 4 (figs. 1, a, d). the temperature of this transition is in good agreement with literature [12]. all curves containing calcium fluoride have endothermic peaks in the interval of 1060–1080 k. fedotieff and iljinsky found two temperature halts in  the cooling curves in this region for calcium fluoride containing compositions [7]. there are no α / β transitions of cryolite in samples 2 and 3. the transitions occur in  mixtures which are quasi-binary such as  na3alf6–al2o3, na3alf6–alf3 and na3alf6–caf2. the sample 1 is such quasi-binary na3alf6– al2o3 and sample 4 is close to  quasi-binary na3alf6–caf2 due to  the low concentration of alumina in this sample. the multi-component mixtures manifest other dsc peaks. craig [9] investigated 8 eutectic mixtures of  na3alf6–alf3–caf2– al2o3. the lowest dsc peak temperature for these mixtures was found to be equal to  948  k. melting peaks are very broad, but the same lines were observed by other scientists [8, 10]. melting points of  mixtures under investigation are in  the interval of  1200– 1220  k. it is in  good agreement with the results presented in  the article [11]. the values of  melting points and heats of fusion are given in table 3. the literature data on  heats of  fusion and melting points of cryolite salts are given in table 4. na3alf6 is a  coordination compound. coordination compounds are inorganic salts formed by  the combination of  two or  more simple compounds in  stoichiometric ratio. in order to  compare molar properties of  coordination compounds and simple compounds, one must consider a  coordination compound (in  our case na3alf6) as a combination of simple table 2 the composition of samples under investigation no composition / mass% composition / mol% naf alf3 caf2 al2o3 naf alf3 caf2 al2o3 1 56.4 37.6 0.0 11.7 70.5 23.5 0.0 6.0 2 50.1 33.4 14.8 3.1 66.1 18.5 10.2 1.7 3 50.5 33.6 10.0 5.9 67.2 22.4 7.2 3.2 4 46.2 30.8 19.9 3.1 62.8 21.0 14.6 1.7 107 compounds, i.e. 3 molecules of  naf and 1 alf3. in order to to equalize cryolite with simple compounds its molecular weight must be given for  1 molecule (0.75 molecular weight of naf and 0.25 molecular weight of alf3). fig. 1. dsc and thermogravimetric (tg) curves of cryolites with different composition: 1 (a), 2 (b), 3 (c), 4 (d) (see table 2) table 3 heats of fusion and melting points of eutectics under investigation comp. no transition point / k ∆htr / j g–1 ∆htr / kj mol–1 melting point / k ∆hm / j g–1 ∆hm / kj mol–1 1 831 43.3 2.4 1202 476.6 26.4 2 1080 95.5 5.1 1210 501.8 26.6 3 1075 71.7 4.0 1219 477.2 26.7 4 835 44.2 2.5 1204 455 26.0 1063 84.3 4.8 — — — table 4 heats of fusion and melting points of cryolites compound tmp / k hfus / kj mol –1 compound tmp / k hfus / kj mol –1 li3alf6 1058 [4] 21.0 [4] na3alf6 1284 [2] 28.3 [2] li3alf6 1058 [2] 22.0 [2] na3alf6 1284 [1] 28.9 [1] na3alf6 1284 [3] 28.8 [3] k3alf6 1273 [2] 30.8 [2] 800 900 1000 1100 1200 1300 -0.4 -0.2 0.0 0.2 0.4 90 92 94 96 98 100 tg [% ] h ea t flo w [m w /m g] temperature [k] tons = 831 k exo tons = 1202 k (a) 800 900 1000 1100 1200 -3 -2 -1 0 1 2 60 70 80 90 100 tons = 1210 k tons = 1080 k tg [% ] h ea t flo w [m w /m g] temperature [k] exo (b) 800 900 1000 1100 1200 -4 -3 -2 -1 0 1 2 80 85 90 95 100 tons = 1219 k tons = 1075 k (c) tg [% ] h ea t flo w [m w /m g] temperature [k] tg exo 800 900 1000 1100 1200 -1.0 -0.5 0.0 0.5 1.0 80 85 90 95 100 tons = 1204 k tons = 1063 k tons = 835 k tg [% ] h ea t flo w [m w /m g] temperature [k] exo (d) 108 thus, the literature data were recalculated using the molecular mass of mixture as a sum of 75 % of molecular mass of alkali halide and 25 % of molecular mass of aluminium fluoride. it allows comparing results with data on individual salts. all the results are presented in fig. 2 in coordinates as follows: heat of fusion — melting point. there is a clear correlation between the enthalpy of melting and the melting point. the nature of this correlation is in thermodynamics, because tm=δhm / δsm, (2) where tm is the melting temperature, δhm is the enthalpy of  fusion, and δsm is the entropy of fusion. the correlation between the enthalpy of melting and the melting point for alkali halide salts was found in our previous article [13]. the same correlation was shown for nitrates, carbonates and sulphates [14]. this trend is the part of more broad relationship known as trouton’s rule, which connect enthalpy of phase transition with its temperature. it is valid both for vaporization of pure elements [15] and for melting [16, 17]. according to lsm (least-squares method) estimations, the coefficients in  the equation h = a+b·t are as follows: bsq = 0.034 kj mol–1 k–1; asq = –14.25 kj mol –1; t — temperature, k. the standard deviation σsq is equal to 0.815 kj mol –1, and the determination coefficient r2=0.94. thus, the equation is: δhm / kj mol –1 = =bsq·tm – asq = 0.034 tm – 14.25 (3) the heat of  fusion temperature coefficient of cryolites is close to that of alkali halides. thus, the temperature dependence of heat of fusion is the same for halide compounds and equal to the value for alkali halide salts. the values of temperature coefficients are close to 4r. it is the same number as heat capacity of halide salts per atom [18]. thus, the heat of fusion is directly proportional to the melting point for simple halide salts, salts compounds and eutectic mixtures. the fusion properties of all these substances are possibly connected due to the fact that the main components of these compounds are halide salts. conclusions 1. heats of  fusion were measured for some eutectic mixtures of sodium cryolite with alumina and calcium cryolite. 2. the heat of fusion was found to be directly proportional to the melting point. table 5 the values of coefficients in equations for heat of fusion dependence on the melting point compounds parameter asq / kj mol –1 parameter bsq / kj mol –1 k–1 cryolites –14.25 0.034 alkali halides [7] –12.12 0.036 fig. 2. heat of fusion dependence on the melting point for cryolites and alkali halides 700 800 900 1000 1100 1200 1300 12 16 20 24 28 32 36 cryolites alkali halides h ea t o f f us io n [k j/ m ol ] t melting [k] 109 acknowledgements the work was supported by rfbr. grants no 18-03-00785 а. the authors are grateful to o. reznitskikh from solid state 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gheribi a, salanne m, chartrand p. formulation of temperature-dependent thermal conductivity of  naf, β-na3alf6, na5al3f14, and molten na3alf6 supported by equilibrium molecular dynamics and density functional theory. j phys chem c. 2016;120(40):22873–86. doi: 10.1021 / acs.jpcc.6b07959. 110 13. redkin a, korzun i, reznitskikh o, yaroslavtseva t, zaikov yu, kumkov s. heat of fusion of halide salts and their eutectics. j therm anal calorim. 2018;131:2021–26. doi: 10.1007 / s10973-017-6650-4. 14. badenhorst h, bohmer t. enthalpy of fusion prediction for the economic optimisation of salt based latent heat thermal energy stores. journal of energy storage. 2018;20:459–72. doi: 10.1016 / j.est.2018.10.020. 15. wisniak j. frederick thomas trouton: the man, the rule and the ratio. j chem educator. 2001;6:55–61. doi: 10.1007 / s00897000448a. 16. sawamura h. the relation between entropy of fusion or heat of fusion of metallic elements and their crystal structure. trans jim. 1972;13:225–30. doi: 10.2320 / matertrans1960.13.225. 17. kaptay g. on the solid / liquid interfacial energies of metals and alloys. j. mat. sci. 2018;53: 3767–84. doi: 10.1007 / s10853-017-1778-y. 18. redkin a, zaikov y, korzun i, reznitskikh o, yaroslavtseva t, kumkov s. heat capacity of molten halides. j phys chem b. 2015;119:509–12. doi: 10.1021 / jp509932e. sol-gel synthesis and crystal chemical properties of the pigment zn1.9cu0.1sio4 205 d o i: 1 0. 15 82 6/ ch im te ch .2 01 8. 5. 4. 05 samigullina r. f., rotermel m. v., ivanova i. v., krasnenko t. i. chimica techno acta. 2018. vol. 5, no. 4. p. 205–209. issn 2409–5613 r. f. samigullina, m. v. rotermel*, i. v. ivanova, t. i. krasnenko institute of solid state chemistry, ural branch of the russian academy of sciences, 91 pervomaiskaya st., ekaterinburg 620990, russian federation *e-mail: rotermel@ihim.uran.ru sol‑gel synthesis and crystal chemical properties of the pigment zn1.9cu0.1sio4 the pigment zn1.9cu0.1sio4 was obtained by the method of sol-gel synthesis. the crystallization temperature was set at 776 °c, ∆h ≈ –16.3 kj / mol. thermal expansion of the individual zn2sio4 and zn1.9cu0.1sio4 solid solutions was studied by in situ high-temperature x-ray diffraction. it is shown that the substitution of zn2+ → cu2+ does not lead to significant changes in the lattice parameters; in the range from room temperature to 800 °c the structure expands monotonically when heated. the coefficients of volumetric thermal expansion for zn2sio4 and zn1.9cu0.1sio4 are αv = 8.05 · 10 –6 and 8.81 · 10–6 1 / k, respectively. the colorimetric coordinates in the rgb system are 71.8 % red, 72.9 % green and 79.6 % blue, which corresponds to the gray-blue pigment. keywords: pigment; willemite; sol-gel synthesis; thermal expansion. received: 06.12.2018. accepted: 21.12.2018. published: 31.12.2018. © samigullina r. f., rotermel m. v., ivanova i. v., krasnenko t. i., 2018 introduction divalent metal silicates are widely used as luminescent, corrosion protecting, electrical insulating materials, catalysts, pigments. thus, the emergence of the chemical manufacturing of synthetic pigments began with the production of dyed double silicates, known as egyptian blue cacusi4o10, han blue bacusi4o10 [1–3]. the continued interest to the silicate pigments is caused due to  the pure intense color, as  well as  by  their high thermal and chemical resistance. therefore, it is possible to  use them for  dyeing ceramic products that exposed to high temperature calcination in the manufacturing process. transition metal orthosilicates containing copper, nickel, and cobalt ions are well known as blue pigments. dopant m2+ ions (m = cu, ni, co) in zn2–2xm2xsio4 solid solutions are coordinated by four oxygen atoms, which causes the blue color of the compounds due to  the splitting of  electron levels of m2+ ions in the crystal field. since the information about zn2–2xm2xsio4 (m = cu, ni, co) is limited, the purpose of this work is a disclosure of sol-gel synthesis mechanism for  zn1.9cu0.1sio4 and determination of main pigment characteristics, such as colorimetric parameters and thermal expansion coefficient. 206 experimental the precursors used in  the sol-gel synthesis of  zn1.9cu0.1sio4 were zinc acetate zn(ch3coo)2·2h2o, copper acetate cu(ch3coo)2·h2o, and tetraethyl orthosilicate (teos) si(oc2h5)4. the phase composition within the range from room temperature up to 800 °c was controlled in  situ by  the x-ray powder diffraction (xrpd) method (shimadzu diffractometer, cuka1 radiation, 2θ angle interval from 10 to 60° with a step of 0.02°), comparing the xrd data with the x-ray characteristics of the possible impurity oxides and zinc silicates (pdf2 database, icdd, usa, release 2009). the temperature was controlled using an anton paar ttk-450 attachment. the unit cell parameters were refined by the rietveld method using the fullprof 2010 software. thermogravimetric (tg) analysis together with differential thermal analysis (dta) were performed using a setsys evolution thermal analyzer (setaram) in air at a temperature scan rate of 10 ° / min in the temperature range 20–1100 °c, with alumina as a reference substance. colorimetric analysis was performed using an slr olympus e-420 (light source temperature of 5400 k; iso = 200; light camera parameters l×w×h = 35×25×32 cm) photo impact 12 program, through a calibrator monitor one-eye pro. the colorimetry results are given in  the rgb color coordinates system. results and discussion the synthesis method used in our work allowed us to obtain the cu2+ dopant concentration equal to  5 at.%. hydrolysis of  [si(c2h5o)4] in  the mixture with the ratio h2o:teos = 1:1 took place within 30 min. the alcohol solutions of metal acetates and hydrolized teos were mixed. after the solutions were poured together the mixture was stirred on a magnetic stirrer for 1 h. the precursor for the final stage of synthesis was obtained by evaporation of  the mixture for  2 hours at  65  °c.  the gel was formed after 2 days at room temperature. in order to determine the temperature range of zn1.9cu0.1sio4 formation, thermogravimetric and differential thermal analyses of the obtained precursor were carried out (fig. 1). the mass loss of 2–3 %, accompanied by a small endothermic effect at 100 °c, corresponds to the removal of water and ethanol residual. the weight loss of about 20 % with a simultaneous exothermic signal on the dta curve within the region of 250–410 °c is caused by the decomposition of  organic components. the dta curve shows the sharp exothermic effect (∆h ≈ –16.3 kj / mol) with a  maximum at  776  °c, while the mass of  the sample remains constant. the assignment of this effect was determined by  the thermal analysis of  zn2sio4 precursor, prepared from zinc acetate and teos (fig. 2). the exothermic effect recorded on  the dta curve in the temperature range 320–500 °c with simultaneous mass loss on  the tg curve corresponded to the decomposition of  organic components. the exothermic effect at 786 °c (∆h ≈ –15.5 kj / mol) with a constant sample mass is similar to that observed on the dta curve for the precursor with the nominal composition zn1.9cu0.1sio4 (fig. 1). consequently, one can conclude that the exothermal effects on  the compared dta curves for  the zn2sio4 and zn1.9cu0.1sio4 precursors are of the same nature, and both are related 207 to the process of a phase with the willemite structure formation. thus, a comparative analysis of the thermal behavior of these samples showed that at temperatures above 776 °c the process of forming a long-range order at sol-gel synthesis of zn1.9cu0.1sio4 was completed. xrd data of the zn1.9cu0.1sio4 precursor annealed at 800 °c does indicate the formation of the phase with the willemite structure; however, an insignificant admixture of copper (ii) oxide is present in the sample (fig. 3). the single-phase product was obtained by firing the precursor sample at 900 °c (fig. 3). x-ray pattern of  the single phase zn1.9cu0.1sio4 sample taken at room temperature was indexed in the willemite type structure with the trigonal space group r3. the refined unit cell parameters, unit cell volume and number of formula units are: a = 13.927(1) å, c = 9.305(3) å, v = 1563.03(8) å3, z = 18. one of the most important characteristics of the pigment is the volumetric thermal expansion coefficient (vtec), which should be comparable to the thermal expansion of  the coated material. colored zinc orthosilicate doped with copper may be suitable as a pigment for ceramics made of porcelain, earthenware, majolica. manufacturing and operation proceeds in wide temperature range, therefore, the coincidence vtec of the matrix and the pigment will allow to avoid cracking of the coating. fig. 1. tg and dta curves (on heating) of the z1.9cu0.1sio4 precursor fig. 2. heating tg and dta curves of the zn2sio4 precursor fig. 3. x-ray diffraction profiles of zn1.9cu0.1sio4 powder annealed at different temperatures 0 200 400 600 800 1000 t, °c 0 2 4 6 8 10 h ea tf lo w ,w /g -50 -40 -30 -20 -10 0 t g ,% exo 776°c 0 200 400 600 800 1000 t, °c -1 0 1 2 3 4 h ea tf lo w ,w /g -40 -30 -20 -10 0 t g ,% exo 786°c 10 20 30 40 50 60 zn2sio4 icdd 00-079-2005 2θ, degree 900oc 800oc in te ns ity (a .u .) 600oc cuo icdd 00-041-0254 208 the values of  vtec were calculated from the experimental results for  the zn2–2xcu2xsio4 unit cell parameters (x = 0; 0.05) in the range from room temperature up to  800  °с  (fig. 4). it was shown that the sizes of the unit cell for the zinc orthosilicate zn2sio4 and zn1.9cu0.1sio4 solid solution monotonically expanded with increasing temperature. doping of  zinc orthosilicate with the cations with similar size, like cu2+ (for c.n.= 4 r zn2+ = 0.74 å, r cu2+ = 0.71 å) does not lead to  significant differences in the polyterms of unit cell parameters. a comparison of vtec for zn2–2xcu2xsio4 (x = 0; 0.05) with that for the ceramic substrate [4], most often used as a coated material (table 1), shows their proximity. colorimetric coordinates of blue-gray zn1.9cu0.1sio4 in the rgb color space consists of 71.8 % red, 72.9 % green and 79.6 % blue (the percentages are relative to pure color), the color saturation is 16.1 %. conclusion the gray-blue pigment zn1.9cu0.1sio4 was obtained by  the sol-gel synthesis method. the consequence of phase transformations during the synthesis of  the zn1.9cu0.1sio4 solid solution was disclosed with the help of x-ray diffraction and thermal analysis. in situ high-temperature x-ray study for zn2–2xcu2xsio4 (x = 0; 0.05) in the range of 25–800 °c showed that the volume thermal expansion of the ceramic pigment reveals monotonic character. the calculated vtec value for zn2–2xcu2xsio4 is close to vtec reported for porcelain, earthenware, majolica. acknowledgements the work was supported by ub ras (project 18-10-3-32). references 1. berke h. the invention of blue and purple pigments in ancient times. chem. soc. rev. 2007;36:15–30. doi: 10.1039 / b606268g. fig. 4. the unit cell parameters and unit cell volume for zn2–2xcu2xsio4 (x = 0, 0.05) versus temperature 0 200 400 600 800 1566 1569 1572 1575 1578 9,31 9,32 9,33 9,34 9,35 9,36 13,92 13,93 13,94 13,95 13,96 13,97 v ,å 3 t, o c c, å zn2sio4 zn 1,9 cu 0,1 sio 4 a, å table 1 volume thermal expansion coefficients for the often used ceramics and zn2–2xcu2xsio4 material αv∙10 –6, 1 / k zn2sio4 8.05 zn1.9cu0.1sio4 8.81 porcelain 5.5–7.0 earthenware 7.0–8.1 majolica 8.5–10.0 209 2. pozza g., ajo` d., chiari g., de zuane f., favaro m. photoluminescence of the inorganic pigments egyptian blue, han blue and han purple. j. cultural heritage. 2000;1:393–8. doi: 10.1016 / s1296-2074(00)01095–5. 3. sidorov v. i., malayvskyi n. i., pokid`ko b. v. poluchenie nizkoosnovnikh silikatov nekotorikh perekhodnikh metallov metodom osadzenizya. vestnik mgsu. 2007;1:163–6. russian. 4. khleborodova o. a. tablica sootvetstviya keramicheskikh mass i bazovikh glazurei [internet]. 2017. russian. available from: https://www.ceramistam.ru / blog / keramicheskie_massy / tablitsa-sootvetstviya-keramicheskikh-mass-i-bazovykh-glazurey / . 66 do i: 1 0. 15 82 6/ ch im te ch .2 01 5. 2. 1. 00 7 terenteva yu.v.1, fomina l.v.2, beznosyuk s.а.1 1 altai state university, 61 lenin street, 656049 barnaul fax: +7(385) 266-66-82; phone: +7(385) 266-66-82; e-mail: bsa1953@mail.ru 2 angarsk state technical academy, 60 chaikovskogostreet, 665835 angarsk fax: +7(3955) 67-17-32; phone: +7(3955) 67-17-32; e-mail: flvbaan@mail.ru physicochemical conditions for the stability of manganese-doped nanolayers of gallium arsenide and its isoelectronic analogues in this paper research of stability of nanolayers of manganese doped materials of aiiibv and aiibivсv 2 types holding much promise as spintronic semiconductor compounds is described. the method of non-local density functional has been applied to calculate bonding energies {ε ij (r)} in atomic pairs for structures of aiiibv and aiibivсv 2 types and for mnas. according to the calculations of internal energy, entropy and free energy of helmholtz (т = 298 к), in the context of used models, addition of manganese to the arsenide’s aiiibv and aiibivсv 2 nanolayers affects its stability in different ways depending on its morphology and substitution mode. however, a critical instability in nanofilm leading to the tendency of growing of a new phase germ may be formed under any manganese concentrations. this leads to deterioration of electrophysical parameters of magnetic semiconductor compounds that is agreed with experimental data. © terenteva yu. v., fomina l. v., beznosyuk s. а., 2015 introduction one of the rapidly developing areas of solid state physics in the last decade is investigation into the possibility of transferring the spin-oriented electrons from a ferromagnet into a nonmagnetic semiconductor1. this line of research has been called spintronics, which aims at developing devices that can simultaneously control the charge and spin properties of carriers. to create new functional spintronic devices it is required to increase allowed ranges of magnetic impurities in semiconductor. the main obstacle for producing saturated with magnetic ions nanolayers of semiconductors is their tendency to separate into the magnetic and semiconducting phase even with a small (about 3–5%) amount of dopants. in order to identify the range of existence of single-phase magnetic semiconductor various experimental techniques can be used, for example dta, xrf, and computer simulation techniques that allow us to study objects that are for some 68 № 1 | 2015 chimica techno acta reasons not available for the study with instrumental methods. computer simulation allows us to investigate the stability of nanolayers of semiconductor systems doped with, for example, manganese, by molecular mechanics with the entropy factor that allows us to detect the onset of nucleation of a new phase at the level of a few unit cells. computer simulation of nanolayer heterostructures aiiibv doped with manganese nowadays, the most studied diluted magnetic semiconductors (dms) are materials ga1-xmnxas with x <9.10 wt.% and corresponding heterostructures2. another promising class of spintronic materials are considered to be semiconductor type compounds aiibivsv2 mainly possessing the struture of copper pyrites3. for building of exact geometric model of nanostructured layers aiiibv, mnas in «crystals» module of software package hyperchem 6.0, the parameters of crystal cells gaas, alas, inas, mnas were used. in the external environment of the isothermal-isochoric thermostat thermodynamic resistance of nanofilms with a constant number of atoms of each type is described by the minimality of helmholtz free energy4. nanolayers internal energy was determined in the pair of atomic interaction5: e s rij ij ij j m i m = == ∑∑12 11 ε ( ) , (1) where m is the total number of atoms in a cluster, sij is the element of the adjacency matrix of the graph bonds of the atoms, εij is interaction potentials of the i-th to the j-th atoms, rij is interatomic distances. to calculate the parameters {εij (r)} of pair binding energy of atoms in structures aiiibv mnas, the method of non-local functional density was used6. in the framework of quantum statistical mechanics, entropy of s nanolayer was calcualated in the standard way, namely, by the number of its indistinguishable transposition of the manganese atoms microstates by formula: s = k ln ω, (2) where k is boltzmann constant, ω is the number of microstates that are indistinguishable and present a given macroscopic state of a nanosystem (statistical weight of the state). for each concentration of the manganese atoms in nanofilms of greatness ω defined as the number of options permutation unit cells or clusters containing manganese atoms on the assumption that the structure of a diamond-like lattice of manganese atoms is free to migrate. this allows calculating the number of microstates of the formula for the state of an ideal solution. on the contrary, if we consider the matrix lattice aiiibv with mnas inclusions in the lattice, the free movement of manganese atoms is difficult, making it necessary to use in the calculation of the number of microstates of different models of correlated microstates. investigation of thermodynamic stability of nanolayers with different concentration of the manganese atoms was performed at different temperatures ranging from cryogenic (the temperature of liquid nitrogen). however, the most interesting are the normal conditions under which the natural experiments took place. therefore, this paper presents an analysis physicochemical conditions for the stability of manganese-doped nanolayers of gallium arsenide and its isoelectronic analogues 70 № 1 | 2015 chimica techno acta of the results of numerical experiments at t = 298 k. structure of gaas, alas, inas and mnas were a film with a size 20×20×2 unit cells, which stood at 6400 atoms. as shown by test calculations, this size is quite representative for these nanofilms representativeness, as with an increase in the size, binding energy per atom in the calculation was varied within the error of the computer experiment. for the simulation of small concentrations of dopant atoms instead of aiii, aiiibv was introduced into the matrix from 48 to 400 atoms of manganese in different ways. 1. change in the structure of atoms aiii aiiibv performed while maintaining diamond-like structure in the layers (model 1). 2. replacement of fragments of structures aiiibv fragmented structure of mnas. and the change is implemented as a uniform distribution of fragments of the lattice-division mnas on re-lattice of the semiconductor, as well as with the formation of larger embryos to complete the collection of all manganese incorporated into the structure in a single cluster with the structure of mnas (model 2). in a study of the mechanical stability of nanostructures compounds we used the method of steepest descent. relaxation of nanostructures by molecular mechanics was carried out with the use of software “kompnanoteh” 7. analysis of the results of computer experiments calculations of the internal energy, entropy, and helmholtz free energy (t = 298 k) within the claimed models are that the administration of manganese nanoilms alas, gaas and inas is different, affecting their resilience is based on the morphology and substitution model. when over-displaced atoms in a diamond-aiii con-figuration of aiiibv atoms of manganese doped nanolayers energy weakly depends on the morphology of the substitution and is the same for the various cluster sizes. energy of nanolayer changes only on the number of manganese atoms, introduced in the system. for manganese-doped nanolayers alas the decrease in stability of the layer with respect to clear alas is observed. instability increases with increase in the number of manganese atoms in the nanolayer. for layers containing clusters with the structure of mnas size of 2 elementary cells resistance decreases with increase in the number of manganese atoms. this phenomenon is explained by the fact that the magnitude of the energy of the interatomic bond involving atoms, atoms of aluminum and arsenic exceeds the similar parameter in the case of the manganese atoms and arsenic. stability of nanolayers alas, doped with manganese, increases only in the case of the maximum size of the clusters with the structure of mnas. this can be explained by the formation of additional bonds within the cluster due to distortion of the structure mnas. for nanolayers gaas a different dependence in stability of layers is observed, depending on the number of manganese atoms, the cluster size, containing manganese and structural features of the clusters. for example, for diamond structures, similarly to the case of alas, stability depends weakly on the cluster size and morphology distribution, but depends only on the number of manganese atoms imposed on nanolayer. however, doped systems exhibit relative stability comterenteva yu. v., fomina l. v., beznosyuk s. а. 72 № 1 | 2015 chimica techno acta pared to the undoped layer of gaas, with a tendency to stabilize with the increase in the number of manganese atoms. unstable systems with a cluster size of two unit cells of the structure mnas indicate that the structure with the cluster size is to be re-presenting a diamond nanolayer. for a cluster of 4 unit cells stability of clusters with a diamond-like structure or the structure of the mnas depends on the number of atoms mn, introduced in the system topic. for the manganese concentration to 1.9 at.% crystallization of the cluster will present a diamond-like structure, but at concentrations of mn, greater than 1.9 at.%, the crystal structure of the cluster will follow the structure of mnas, while nanolayer stability of gaas, doped with manganese, with the dimension of clusters 4 unit cells will raise with increasing concentration of mn. however, the most stable clusters will be nanolayers with maximum size at the expense of additional bonds in the cluster with the structure of mnas. nanolayers inas are structures for which the most stable one is a cluster of mnas with a diamond lattice. the stability of clusters with a diamond-like structure increases with the concentration of manganese in the system. clusters with the structure of mnas and size 2 unit cells tend to decrease with increasing stability of the manganese concentration in the system. clusters with the structure of mnas and the size of 4 unit cells stabilize the system with increasing concentration of manganese, but not enough to form them into the system, because are the most stable system with diamond-like clusters. however, as in the case of nanolayers alas and gaas, doped with manganese, the most stable yet is nanolayers with clusters of maximum size at the expense of additional bonds in the cluster with the structure of mnas. but the realization of this configuration in the epitaxial layers of the prm is highly unlikely. computer simulation-monolayers aiibivsv 2 doped with manganese based on the example znsnas 2 structure znsnas2 and znsnas2: mn representing a film 20×20×1 dimensions of the unit cells, which amounted to 6400 atoms. in the doped systems administered from 48 to 400 atoms of manganese in different ways. 1. replacement of zn and sn atoms in structures znsnas2 was carried out while maintaining the diamond-like structure in layers (model 1). 2. replacement of fragments of structures znsnas2 fragmented structure of mnas. and the change is implemented as a uniform distribution of fragments mnas lattice on semiconductor lattice and to form larger nuclei, until the complete collection of all the manganese introduced into the structure in a single cluster with the structure of mnas (model 2). 3. the system model is analogous to 1, but only atoms zn are replaced (model 3). 4. the system, similar to the model 2, but only atoms zn are replaced (model 4). structures corresponding to models 1 and 3 do not show respect to the stability of non-alloy system. in this case, structures built on the model of 3 exhibit greater stability. moreover, the stability decreases with increasing of cluster size and concentration of manganese. structures constructed in accordance with the 2 and 4 models, behave differphysicochemical conditions for the stability of manganese-doped nanolayers of gallium arsenide and its isoelectronic analogues 74 № 1 | 2015 chimica techno acta ently in dependence of the size of the cluster. structures with time-clusters of mnas measures in 1 and 2 elementary cells exhibit instability concerning nonalloy structures, and structures with a diamond crystal lattice. as the concentration of manganese increases, the stability of structures decreases. in this case, the lower stability have structures corresponding to the model structure with 4 clusters in the size of 1-element unit cell is less stable than the structure with a cluster size of 2 elementary cells. when there are 4 unit cells observed, there is stability to non-alloy system. structures relevant to model 4 are more energy efficient compared with structures constructed by models 1–3. when the concentration of manganese in the 1.2 at.% (0.79 wt.%), the system is able to move from the structure, co-responsible with the size of model 4 with 4 elementary cells in the system corresponding to the model 2 with integration of cluster mnas to its maximum size. however, at all concentrations of manganese may form a critical nonstability in nanofilms and the emergence of thermodynamic trend towards growth of the embryo of a new phase of mnas by model 4, which leads to a deterioration of electro-physical parameters of magnetic semi-conductor. 1. ivanov v. a., aminov t. g., novotorztev v. m., kalinnikov v. t. izvestiya akademii nauk. seriya chim. 2004; 11:2255–2303. 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[google scholar]. 7. beznosuyk s. a., zshukovsky m. s., vazshenin s. v., lerh ya. v. svidetel'stvo about state registration of program for evm № 2009613043 from 10 june 2009. [google scholar]. terenteva yu. v., fomina l. v., beznosyuk s. а. 67 у д к 5 43 .7 :5 46 .2 2/ 24 ю. в. терентьева1, л. в. фомина2, с. а. безносюк1 1 алтайский государственный университет, пр. ленина, 61, 656049, барнаул. факс: (3852) 66-66-82; тел. 8 (3852) 66-66-82; e-mail: bsa1953@mail.ru 2 ангарская государственная технологическая академия, ул. чайковского, 60, 665835, ангарск. факс: (3955) 67-17-32; тел. (3955) 67-17-32; e-mail: flvbaan@mail.ru физико-химические условия устойчивости нанослоев арсенида галлия и его изоэлектронных аналогов, легированных марганцем в работе представлено исследование устойчивости нанослоев полупроводниковых соединений типа aiiibv и aiibivсv 2 легированных марганцем. для расчета параметров {ε ij (r)}энергий связей пар атомов в структурах – aiiibv и aiibivсv 2 и mnas использовался метод нелокального функционала плотности. расчеты внутренней энергии, энтропии и свободной энергии гельмгольца (т = 298 к) в рамках заявленных моделей свидетельствуют о том, что введение марганца в нанопленки арсенидов aiiibv и aiibivсv 2 по-разному сказывается на их устойчивости в зависимости от морфологии и модели замещения. однако при любых концентрациях марганца возможно образование критической неустойчивости в нанопленке и появление термодинамической тенденции в сторону роста зародыша новой фазы mnas, что ведет к ухудшению электрофизических параметров магнитного полупроводника в согласии с экспериментальными данными. © терентьева ю. в., фомина л. в., безносюк с. а., 2015 введение одним из активно развивающихся направлений физики твердого тела в последние десятилетия является исследование возможности переноса спин-ориентированного электрона из ферромагнетика в немагнитный полупроводник [1]. данное направление исследований получило название спинтроники, целью которой является разработка устройств, способных одновременно управлять зарядовыми и спиновыми свойствами носителей. 69 № 1 | 2015 chimica techno acta физико-химические условия устойчивости нанослоев арсенида галлия и его изоэлектронных аналогов, легированных марганцем для создания новых функциональных спинтронных устройств требуется расширение допустимого диапазона содержания магнитных примесей в матрице полупроводника. основным препятствием для получения насыщенных магнитными ионами полупроводниковых нанослоев является их тенденция к расслоению на магнитную и полупроводниковую фазы уже при небольшом (порядка 3–5 %) количестве легирующих добавок. для выявления диапазона существования однофазного магнитного полупроводника могут использоваться различные экспериментальные методы, например дта, рфа, а также методы компьютерного моделирования, которые позволяют исследовать объекты, по каким-либо причинам недоступные для исследования инструментальными методами. компьютерное моделирование позволяет исследовать устойчивость нанослоев полупроводниковых систем, легированных, например, марганцем, методом молекулярной механики с учетом энтропийного фактора, что позволяет обнаружить начало зародышеобразования новой фазы на уровне нескольких элементарных ячеек. компьютерное моделирование нанослоевых гетероструктур aiiibv, допированных марганцем на сегодняшний день наиболее изученными разбавленными магнитными полупроводниками (рмп) являются материалы ga1-xmnxas с х < 9–10 мас.% и гетероструктуры соответствующего состава [2]. еще одним перспективным классом спинтронных материалов считаются полупроводниковые соединения типа aiibivсv2, в основном обладающие структурой халькопирита [3]. для построения точной геометрической модели наноструктурных слоев aiiibv, mnas в модуле crystals программного пакета hyperchem 6.0 использованы параметры ячеек кристаллов gaas, alas, inas, mnas. во внешних условиях изотермического-изохорического термостата термодинамическая устойчивость нанопленок с постоянным числом атомов каждого сорта описывается минимальностью свободной энергии гельмгольца [4]. внутренняя энергия нанослоя была определена в приближении парных атомных взаимодействий [5]: e s rij ij ij j m i m = == ∑∑12 11 ε ( ) , (1) где m – общее число атомов кластера, sij – элемент матрицы смежности графа связей атомов, εij – потенциалы взаимодействия i-го с j-м атомов, rij – меж атомные расстояния. для расчета параметров {εij (r)} энергии связи пар атомов в структурах aiiibv и mnas использовался метод нелокального функционала плотности [6]. в рамках квантовой статистической механики энтропия s нанослоя определялась стандартно, а именно числом ее неразличимых по перестановке атомов марганца микросостояний по формуле: s = k ln ω, (2) где k – постоянная больцмана, ω является числом микросостояний, которые неразличимы и представляют заданное макроскопическое состояние наноси71 № 1 | 2015 chimica techno acta стемы (статистический вес состояния). для каждой концентрации атомов марганца в нанопленке величина ω определялась как количество вариантов перестановки элементарных ячеек или кластеров, содержащих атомы марганца, исходя из предположения, что в структуре с алмазоподобной решеткой атомы марганца могут свободно мигрировать. это позволяет использовать для расчета количества микросостояний формулы для состояния идеального раствора. напротив, если рассматривать матрицу решетки aiiibv с включениями зародышей решетки mnas, свободное движение атомов марганца затруднено, что приводит к необходимости использовать в расчете числа микросостояний различные модели коррелированных микросостояний. исследование термодинамической устойчивости нанослоев с различной концентрацией атомов марганца было выполнено для различных температур, начиная от криогенных (температур жидкого азота). однако наибольший интерес представляют нормальные условия, при которых были выполнены натурные эксперименты. поэтому в настоящей работе представлен анализ результатов численных экспериментов при т = 298 k. структуры gaas, alas, inas и mnas представляли собой пленки с размерами 20×20×2 элементарных ячеек, что составило 6400 атомов. как показали тестовые расчеты, такой размер нанопленки является вполне презентативным для рассматриваемых соединений, так как при увеличении ее размера энергия связи в расчете на атом изменялась в пределах ошибки компьютерного эксперимента. для моделирования малых концентраций допанта вместо атомов aiii в матрицу aiiibv было введено от 48 до 400 атомов марганца разными способами. 1. замена атомов aiii в структурах aiiibv осуществлялась при сохранении алмазоподобной структуры в слоях (модель 1). 2. замена фрагментов структур aiiibv на фрагменты структуры mnas. причем замена осуществлялась как с равномерным распределением фрагментов решетки mnas по решетке полупроводника, так и с образованием более крупных зародышей, до полного собирания всего марганца, введенного в структуру, в единый кластер со структурой mnas (модель 2). в исследовании механической устойчивости наноструктур соединений использован метод наискорейшего спуска. релаксация наноструктур методом молекулярной механики проводилась с использованием средств программного комплекса «компнанотех» [7]. анализ результатов компьютерных экспериментов расчеты внутренней энергии, энтропии и свободной энергии гельмгольца (т = 298 k) в рамках заявленных моделей свидетельствуют о том, что введение марганца в нанопленки alas, gaas и inas по-разному сказывается на их устойчивости в зависимости от морфологии и модели замещения. при замещении атомов aiii в алмазоподобной конфигурации aiiibv на атомы марганца энергия допированных нанослоев слабо зависит от морфологии терентьева ю. в., фомина л. в. , безносюк с. а. 73 № 1 | 2015 chimica techno acta замещения и оказывается фактически одинаковой для кластеров различного размера. энергия нанослоя изменяется лишь от количества атомов марганца, введенных в систему. для нанослоев alas, допированных марганцем, наблюдается снижение устойчивости слоя относительно чистого alas. не устойчивость возрастает с увеличением числа атомов марганца в нанослое. для слоев, содержащих кластеры со структурой mnas размером в 2 элементарные ячейки, устойчивость снижается с увеличением числа атомов марганца. данное явление объясняется тем, что величина энергии межатомной связи с участием атомов алюминия и мышьяка превышает аналогичный параметр в случае атомов марганца и мышьяка. устойчивость нанослоев alas, допированных марганцем, возрастает только в случае максимального размера кластеров со структурой mnas. это можно объяснить образованием дополнительных связей внутри кластера за счет искажения структуры mnas. для нанослоев gaas наблюдается иная зависимость устойчивости слоев в зависимости от числа атомов марганца, размера кластеров, содержащих марганец и структурных особенностей кластеров. так, для алмазоподобных структур, аналогично случаю с alas, устойчивость слабо зависит от размера кластеров и морфологии их распределения, а зависит только от количества атомов марганца, введенных в нанослой. однако допированные системы проявляют относительную устойчивость по сравнению с недопированным слоем gaas, с тенденцией стабилизации с увеличением числа атомов марганца. нестабильность систем с размером кластера в 2 элементарные ячейки со структурой mnas свидетельствуют о том, что структуры с таким размером кластера будут представлять собой алмазоподобные нанослои. для кластера в 4 элементарные ячейки устойчивость кластеров с алмазоподобной структурой или со структурой mnas зависит от количества атомов mn, введенных в систему. для концентрации марганца до 1,9 атм.% кристаллизация кластера будет представлена алмазоподобной структурой, но при концентрациях mn, превышающих 1,9 атм.%, кристаллическая структура кластера будет соответствовать структуре mnas, причем устойчивость нанослоя gaas, допированного марганцем, с размерностью кластера в 4 элементарные ячейки будет возрастать с ростом концентрации mn. однако наиболее устойчивыми окажутся нанослои с кластерами максимального размера за счет дополнительных связей внутри кластера со структурой mnas. нанослои inas представляют собой структуры, для которых наиболее устойчивой оказывается кластер mnas с алмазоподобной решеткой. устойчивость кластеров с алмазоподобной структурой возрастает с ростом концентрации марганца в системе. кластеры со структурой mnas и размером в 2 элементарные ячейки имеют тенденцию к снижению устойчивости с ростом концентрации марганца в системе. кластеры со структурой mnas и размером в 4 элементарные ячейки стабилизируют систему с ростом концентрации марганца, но недостаточно для образования их в системе, т. к. наиболее устойчивыми оказываются системы с алмазоподобными кластерафизико-химические условия устойчивости нанослоев арсенида галлия и его изоэлектронных аналогов, легированных марганцем 75 № 1 | 2015 chimica techno acta ми. однако, как и в случае нанослоев alas и gaas, допированных марганцем, наиболее устойчивыми все же окажутся нанослои с кластерами максимального размера за счет дополнительных связей внутри кластера со структурой mnas. но реализация такой конфигурации в эпитаксиальных слоях этих рпм весьма маловероятна. компьютерное моделирование нанослоев aiibivсv 2 , легированных марганцем, на примере znsnas 2 структуры znsnas2 и znsnas2:mn представляли собой пленки размерами 20х20х1 элементарных ячеек, что составило 6400 атомов. в легированные системы введено от 48 до 400 атомов марганца разными способами. 1. замена атомов zn и sn в структурах znsnas2 осуществлялась при сохранении алмазоподобной структуры в слоях (модель 1). 2. замена фрагментов структур znsnas2 на фрагменты структуры mnas. причем замена осуществлялась как с равномерным распределением фрагментов решетки mnas по решетке полупроводника, так и с образованием более крупных зародышей, вплоть до полного собирания всего марганца, введенного в структуру в единый кластер со структурой mnas (модель 2). 3. система, аналогичная модели 1, но замещаются только атомы zn (модель 3). 4. система, аналогичная модели 2, но замещаются только атомы zn (модель 4). структуры, соответствующие моделям 1 и 3, не проявляют стабильности относительно нелегированной системы. при этом наибольшую стабильность проявляют структуры, построенные по модели 3. причем стабильность падает с увеличением размера кластера и концентрации марганца. структуры, построенные согласно моделям 2 и 4, ведут себя по-разному в зависимости от размера кластера. структуры с размерами кластеров mnas в 1 и 2 элементарных ячейки проявляют нестабильность относительно нелегированной структуры и структур с алмазоподобной кристаллической решеткой. с ростом концентрации марганца стабильность структур уменьшается. при этом наименьшей стабильностью обладают структуры, соответствующие модели 4. структура с кластерами размером в 1 элементарную ячейку оказывается менее стабильной, чем структура с размером кластера в 2 элементарных ячейки. при размере кластера в 4 элементарные ячейки уже наблюдается стабильность относительно нелегированной системы. структуры, соответствующие 4 модели, энергетически более выгодны по сравнению со структурами, построенными по моделям 1–3. при концентрации марганца в системе 1,2 атм.% (0,79 мас.%) система способна перейти от структуры, соответствующей модели 4 с размером кластера в 4 элементарных ячейки, в систему, отвечающую модели 2 с укрупнением кластера mnas до максимального размера. однако при любых концентрациях марганца возможно образование критической неустойчивости в нанопленке и появления термодинатерентьева ю. в., фомина л. в. , безносюк с. а. 77 № 1 | 2015 chimica techno acta мической тенденции в сторону роста зародыша новой фазы mnas по типу модели 4, что ведет к ухудшению электрофизических параметров магнитного полупроводника. 1. иванов в. а., аминов т. г., новоторцев в. м., калинников в. т. // известия академии наук. серия химическая. 2004. № 11. с. 2255–2303. 2. ohno h. // journal of magnetism and magnetic materials. 2004. v. 272–276. part 1. p. 1. 3. wolf s. a., awschalom d. d., buhrman r. a., daughton j. m., von molnár s., roukes m. l., chtchelkanova a. y., treger d. m. // science. 2001. v. 294, n 5546. p. 1488– 1495. 4. васильевский а. с., мултановский в. в. статистическая физика и термодинамика. м.: просвещение, 1985. 256 с. 5. безносюк с. а., потекаев а. и., жуковский м. с., жуковская т. м., фомина л. в. многоуровневое строение, физико-химические и информационные свойства вещества. томск: изд-во нтл, 2005. 264 с. 6. beznosjuk s. a., dajanov r. d., kuljanov a. t. // international. journal of quantum chemistry. 1990. v. 38, n 5. p. 691–698. 7. свидетельство о государственной регистрации программы для эвм № 2009613043 от 10 июня 2009 г. // с. а. безносюк, м. с. жуковский, с. в. важенин, я. в. лерх. физико-химические условия устойчивости нанослоев арсенида галлия и его изоэлектронных аналогов, легированных марганцем 1099-2582-1-pb 1099-2583-1-pb cta_v4_№1.cdr 11 e. n. ulomsky1,2, d. n. lyapustin1, v. v. fedotov1, o. s. el’tsov1, i. m. sapozhnikova1, d. n. kozhevnikov3, e. m. mukhin2 1ural federal university, mira str., 28, ekaterinburg, 620002, russia e-mail: ulomsky@yandex.ru; 2institute of organic synthesis named i. ya. postovskii ural division of ras, 22 kovalevskaya str./20 academicheskaya str., 620990, ekaterinburg, russia; 3zao nph vmp, 105 amundsen’s str., ekaterinburg, russia the features of nucleophilic substitution of the nitro group in 4-alkyl-6-nitro-1,2,4-triazolo[5,1-c][1,2,4]triazines the nucleophilic substitution of the nitro group of 4-alkyl-6-nitro-4,7-dihydro-1,2,4-triazolo[5,1-c][1,2,4]triazine-7-ones on the example of interaction with morpholine was studied. it is established that under the action of excess cycloalkylimine at room temperature the unusual easy disclosure of triazine cycle with the formation of sterically hindered hydrazones occurs which are the key intermediates for further transformations. the carrying of reaction at elevated temperatures leads to the formation of products of substitution of the nitro group with the amine and also with morpholyl hydrazones which are the products of hydrolysis of amides of hydrazones and subsequent decarboxylation. thus, the nucleophilic substitution of the nitro group in the described triazolotriazines ows through the anrorc mechanism. key words: nucleophilic substitution; anrorc; the transformation of 4-alkyl-6-nitro-1,2,4triazolo[5,1-c][1,2,4]triazine-7-ones; morpholine. received: 13.02.2017; accepted: 20.02.2017; published: 14.04.2017. е. н. уломский1,2, д. н. ляпустин1, в. в. федотов1, о. с. ельцов1, и. м. сапожникова1, д. н. кожевников3, е. м. мухин2 1уральский федеральный университет, 620002, россия, екатеринбург, ул. мира, 28; e-mail: ulomsky@yandex.ru 2 институт органического синтеза имени и. я. постовского уро ран, 620990, россия, екатеринбург, ул. софьи ковалевской, 20–22; 3зао нпх вмп, россия, екатеринбург, ул. амундсена, 105 e-mail: dnk@fmp.ru ulomsky e. n., lyapustin d. n., fedotov v. v., el’tsov o. s., sapozhnikova i. m., kozhevnikov d. n., mukhin e. m. chimica techno acta. 2017. vol. 4, no. 1. p. 11–24. issn 2409-5613 d o i: 1 0. 15 82 6/ ch im te ch .2 01 7. 4. 1. 02 0 5 47 .7 92 .9 12 4-6-1,2,4[5,1-c][1,2,4] 46-4,7-1,2,4[5,1][1,2,4] -7 . , – . , – . , anrorc. : ; anrorc; 4-6-1,2,4[5,1-c][1,2,4] -4; . : 13.02.2017; : 20.02.2017; : 14.04.2017. © ulomsky e. n., lyapustin d. n., fedotov v. v., el’tsov o. s., sapozhnikova i. m., kozhevnikov d. n., mukhin e. m., 2017 introduction th e nucleophilic substitution of easily leaving groups is one of the major synthetic approaches in the construction of organic compounds. th e principles of nucleophilic heteroaromatic transformations are few and well known. th e fi rst of the conventional mechanisms of the type snhet is ipso-substitution of easily leaving groups and hydrogen [1, 2]. another variant of the substitutive functionalization on the principle of fgi are the transformations on arine mechanism (e, a) [3, 4]. finally, chronologically the last of the studied processes of substitution by nucleophiles is anrorc – multistage process involving in the fi rst stage the disclosure of azine by nucleophile [5]. in fact, the disclosure of azines under the action of n-nucleophiles are not uncommon [6–8], however not all of these transformations culminate in the substitution of leaving group and reverse cyclization. in the present work we have given the results of the study of the main stages of the transformation of 4-alkyl-6-nitro-1,2,4triazolo[5,1-c][1,2,4]triazine-7-ones under the action of morpholine and the nature of substitution of the nitro group according to the anrorc type was installed. previously, we described the reaction of 4-alkyl-6-nitro-1,2,4-triazolo[5,1-c] [1,2,4]triazine-7-ones in the substitution of the nitro group under the action of n-, o-, s – and c-nucleophiles [9], but the sequence of transformations remains obscure. in this study we investigated the features of substitution of nitro group in 13 4-alkyl-6-nitro-1,2,4-triazolo[5,1-c][1,2,4] triazine-7-ones (1) containing methyl (1a) and tert-butyl fragments (1b) in the cycle triazine, creating a minimum and maximum steric eff ect to determine its eff ect on the reaction. th e nucleophile was used n-morpholine as the least reactive reagent, allowing us to identify key intermediates. we have found that under the action of three-fold excess of morpholine at room temperature the unusual for stable nitrous heterocycles disclosure of triazine cycle with the formation of adducts with the structure of the hydrazones (2) occurs. the compounds (2) are sustainable, so that their structure is set on the basis of nmr spectroscopy data and elemental analysis (see experimental part). on the other hand, to obtain the holistic integral data of chromatography-mass spectrometry for compounds (2) failed because the hydrazones are converted to the parent compounds (1) and this occurs in the conditions column chromatography on silica gel. a common feature of the 1h nmr spectra for compounds (2) is the unusual diff erentiation of the proton signals of the amide fragment, where all eight protons are magnetically nonequivalent (fig. 1). such spectral pattern is determined fi rst of all by the peculiarities of the spatial structure of the whole hydrazone fragment of the compounds (2). another common feature for the hydrazones (3) is the diff erentiation of signals fig. 1. th e fragment of 1h nmr spectrum of 1’-(1”,2”,4”-triazolyl-3”)-1’-tert-butylhydrazone-1morpholinyl-2-nitroethanone morpholine (2b) 14 morpholine-amide fragment in the spectrum of 13c nmr. th e number of carbon resonance peaks in the spectrum belonging to this doubled fragment (fig. 2) are doubled. the sp ec tral cor relation patter n hmbc of 1h-13c nmr of hydrazone (3b) confirms the attributed structure, because obviously the interaction of protons of morpholine-amide fragment as with unequal c-atoms cycloalkylamine as and carbonyl (fig. 3). another aspect of the studied transformations was the nucleophilic substitution of the nitro group. th us, the heating of triazolothiadiazoles (1) in excess morpholine leads to the formation of two products (3) and (4) in comparable proportions. the data of chromato-mass spectrometry of the reaction masses show the presence of the n-nitrosomorpholine, the product of substitution of the nitro group (3) and product of substitution of decarboxylation (4). th e structure of 4-alkyl-6-morpholyl-1,2,4-triazolo[5,1-c] [1,2,4]triazine-7-ones (3) is set based on the data of 1h nmr spectroscopy and elemental analysis (see experimental part). th e structure of 1’-(1”,2”,4”-triazolyl-3”)-1’alkylhydrozonomorpholylmethane (4) is also identifi ed on the basis of data 1h nmr spectroscopy and elemental analysis (see experimental part). in the 1h nmr spectra of compounds (4) is the characteristic resonant peak in region 7,7 m. d. corresponding to the resonance of formyl proton, a fig. 2. th e fragment of the 13c nmr spectrum of 1’-(1”,2”,4”-triazolyl-3”)-1’-tertbutylhydrazine-1-morpholinyl-2-nitroethanone morpholine (2b) 15 singlet proton of the triazole ( 7.5 m. d.) and a broadened signal of heterocyclic nh group ( 12 m. d.). th e possibility of formation of hydrazone (4) is due to two features of the reaction mechanism, including the disclosure of triazolothiadiazole structure and the allocation of water under the formation of nitrosomorpholine, causing hydrolysis of the amide (2) followed by decarboxylation. th us, it is established that the nucleophilic substitution of the nitro group in 4-alkyl-6-nitro-1,2,4-triazolo[5,1-c][1,2,4] triazine-7-ones is not the type of ipsosubstitution and in accordance with the anrorc mechanism, including the disclosure of triazine cycle under the action of nucleophile, substitution of the nitro group with the formation of nitrosomorpholine and subsequent cyclization. the experimental part nmr spectra 1h and 13c were recorded on the spectrometer bruker avance ii spectrometer (400 mhz for 1h and 13c) in dmso-d6, internal standard for 1h nmr spectra is tms. elemental analyses were performed on sspa automatic analyzer «carlo erba 1108». ir spectra were recorded on the fourier-ir spectrometer «bruker alpha, znse». th e data on gas chromatography-mass spectrometry were obtained on a gas chromatography-mass spectrometer «gcms-qp2010 ultra» (shimadzu, japan, 2013). monitoring for the progress of reactions and purity of synthesized compounds was performed by tlc on plates «sorbfi l» (fi rm zao «sorbpolimer») in the system ethyl acetate. for preparative column chromatography the same eluent and silica gel sigma-aldrich 60 å were used. 4-methyl-6-nitro-4,7-dihydro-1,2,4-triazolo[5,1-c][1,2,4]triazine-7-it is obtained by the method described in [10]. 4-tert-butyl-6-nitro-4,7-dihydro-1,2,4triazolo[5,1-c][1,2,4]triazine-7-one (1b) 20 mmol of 6-nitro-4,7-dihydro-1,2,4triazolo[5,1-c][1,2,4]triazine-7-one in 10 ml fig. 3. th e fragment of the hmbc correlation spectrum 1h-13c nmr of compound (3b) 16 trifl uoroacetic acid were suspended, 20 mmol of tert-butanol were added and were heated with the refl ux condenser at 80 ос within 2 hours. th e solution is evaporated in vacuum, 10 ml of ethanol added and again evaporated. th e residue was triturated with 15 ml of tert-butylmethyl ether, fi ltered and dried. yield 2.4g (46 %). th e 1h-nmr spectrum, , m. d.: 1.77 (9h, s, 4-c(ch3)3); 8,63 (1h, s, 2-n). th e 13c nmr spectrum, , m. d.: 13,60 (с2’); 42,42 (c1’); 140,94 (с-no2); 141,85 (c=o); 152,36 (с3а); 166,99 (с2). th e ir spectrum , cm-1: 3125, 2999, 2948, 1737, 1549, 1522, 1466, 1447, 1355, 1263, 1229, 1173, 1151, 987, 920, 889, 793, 758, 743, 723, 704, 639, 517. th e mass spectrum m/z: m/z: 238 (м+), 223, 208, 180, 166, 152, 108, 96, 70, 57, 41. elemental analysis (calculated molecular formula, found, %): c – 40,34; h – 4,20; n – 35,29; o – 20.17. с8h10n6o3. с – 40,50; h – 4,09; n – 35,32; о – 20,09. 1’-(1”,2”,4”-triazolyl-3”)-1’-methylhydrazono-1-morpholinyl-2-nitroethanone morpholinium (2a) a mixture of 2.5 mmol (1a) and 7.5 mmol morpholine was stirred at room temperature for 15 minutes. 3 ml of tert-butylmethyl ether was added and filtered. the yield of 0.81 g (86,5 %). th e 1h-nmr spectrum, , m. d.: 2,68 (4н, t, n-ch2); 3,29–3,72 (8н, m, n-ch2-ch2-o); 3,50 (4н, t, ch2-o), 3,66 (3h, s, 1 i–ch3); 8,41 m. d. (1н, s, 2-н). th e 13c nmr spectrum, , m. d.: 38,15 (n-ch3), 41,87; 46,44 (o=c-n-ch2-ch2o); 45,06 (с3iv); 65,29; 65,36 (o=c-n-ch2ch2-o); 66,20 (c2 iv); 135,44 (c-no2); 144,95 (c5ii); 158,93 (c=o); 161,08 (c3ii). t h e i r s p e c t r u m , c m 1: 2 9 6 3 , 2917, 2858, 1924, 1652, 1599, 1566, 1524, 1430, 1322, 1274, 1253, 1215, 1 1 1 5 , 1 0 9 4 , 1 0 1 1 , 9 3 9 , 8 8 7 , 8 6 1 , 8 4 7 , 8 2 0 , 7 2 3 , 6 9 4 , 6 6 5 , 6 1 2 , 5 6 4 . elemental analysis (calculated molecular formula, found, %) c – 42,16; h – 5,95; n – 30,27; o –21,62. с13h22n8o5. c – 42,03; h – 5,87; n – 30,35; o – 21,75. 1’-(1”,2”,4”-triazolydyl-3”)-1’-tert-butylhydrazone-1-morpholinyl-2-nitroethanone morpholinium (2b) th e mixture of 3 mmol (1b) and 9 mmol morpholine at room temperature were stirred for 15 min, 5 ml of tert-butyl methyl ether were added and fi ltered. th e yield of 0.84 g (67,8 %). th e 1h-nmr spectrum, , m. d.: 1,39 (9н, s, 4-с(сн3)3); 2,70–3,76 (16н, m, nch2-ch2-o); 2,72 (4h, t, n-ch2); 3,52 (4h, t, сн2-о); 8,44 m. d. (1н, s, 2-н). th e 13c nmr spectrum, , m. d.: 28,32 (с2iii); 41,53; 46,56 (o=c-n-ch2-ch2o); 45,99 (c3v); 64,13 (c1iii); 65,48; 65;63 (o=c-n-ch2-ch2-o); 67,22 (c2 v); 135,47 (c-no2); 145,38 (c5 ii), 156,27 (c3ii), 157,35 (c=o). th e ir spectrum, , сm-1: 2978, 2853, 2730, 2208, 2165, 1645, 1585, 1455, 1309, 1279, 1197, 1109, 1019, 877. th e mass spectrum m/z (intensity, %): c327 (м+) 281, 252, 196, 140, 113, 110, 84. elemental analysis (calculated molecular formula, found,%): с – 46,60; h – 6,80; n – 27,18; о – 19,42. с16h28n8o5. с – 46,66; h – 6,83; n – 26,07; о – 20,44. 4 me t h y l 6 m o r p h o l i n 4 , 7 d i hydro-1,2,4-triaz ol o[5,1-c][1,2,4] triazine-7-on monohydrate (3a) and 1’-(1”,2”,4”-triazolyl-3”)-1’-methylhydrozonomorpholylmethan (4a). th e mixture of 2 mmol of (1a) and 6 mmol morpholine refl uxed for 5 h. when added to the reaction mass 10 ml of a mixture of chloroform: tert-butylmethyl ether (1:1) precipitated the product (4a) is fi ltered. th e fi ltrate is evaporated in vacuo, the products are separated by chromatography. 17 4 m e t h y l 6 m o r p h o l y l 4 , 7 d i hydro-1,2,4-triazolo[5,1-c][1,2,4]triazine-7-on monohydrate (3a) th e 1h-nmr spectrum, , m. d.: 3,43 (4h, t, ch2-n); 3,78 (4н, t, ch2-o); 3,91 (3н, s, 4-сн3); 8,09 (1н, sс, 2-н). th e 13c nmr spectrum: 40,51 (n-ch3); 47,94 (n-ch2); 65,59 (ch2-o); 143,48 (c6); 146,79 (c=o); 151,13 (c3a); 153,83 (c1). th e mass spectrum m/z (intensity,%): 236 (m+), 209, 193, 179, 151, 123, 110, 96, 83, 69. elemental analysis (calculated molecular formula, found, %): с – 45,71; h – 6,67; n – 40,00; о – 7,62. с9h11n6o2*н2о. с – 42,48; h – 5,59; n – 33,00; о – 18,93. 1’-(1”,2”,4”-triazolyl-3”)-1’-methylhydrazonomorpholylmethan (4a). th e 1h-nmr spectrum, , m. d.: 3,21 (3н, s, 1i–сн3); 3,31 (4н, t, сн2-n); 3,64 (4н, t, ch2-o); 7,29 (1н, s, 5 ii-н); 7,59 (1h, s, с-н); 12,10 (1н, br. s, nh). th e 13c nmr spectrum, , m. d.: 37,13 (n-ch3); 45,97 (n-ch2); 65,71 (ch2-o); 149,17 (c5ii); 151,13 (c1iii); 158,80 (c3ii). th e ir spectrum, , сm-1: 2970, 2858, 1615, 1567, 1509, 1272, 1236, 1217, 1161, 1113, 1070, 1030, 1009, 950, 739, 615. th e mass spectrum m/z (intensity, %): 210 (м+) 124, 98, 97, 70, 56, 42, 41. elemental analysis (calculated molecular formula, found, %): с – 45,71; h – 6,67; n – 40,00; о – 7,62. с8h14n6o. с – 45,59; h – 6,57; n – 40,07; о – 7,77. 4 t e r t b u t y l 6 m o r p h o l y l 4 , 7 dihydro-1,2,4-triazolo[5,1-c][1,2,4] triazine-7-one monohydrate (3b) and 1’-(1”,2”,4”-triazolyl-3”)-1’-tert-butylhydrazonomorpholylmethan (4b) make a mixture of 2 mmol (1b) and 6 mmol morpholine and is boiled for 5 hours. th e reaction mass is evaporated to dryness in vacuum. th e products are separated chromatographically on silica gel. 4-ter t-butyl-6-morpholyl-4,7-dihydro-1,2,4-triazolo[5,1-c][1,2,4]triazine-7-one (3b). th e 1h-nmr spectrum, , m. d.: 1,27 (9h, s, c-(ch3)3); 3,36 (4н, t, ch2-n); 3,65 (4н, t, сн2-о); 8,12 (1н, sс, 2-н). th e mass spectrum m/z (intensity, %): 278 (м+), 222, 207, 195, 179, 165, 137, 111, 82. elemental analysis (calculated molecular formula, found, %): с – 48,65; h – 6,76; n – 28,38; o – 16,22. c12h18n6o2*h2o. c – 48,59; h – 28,42; n – 28,42; o – 16,25. 1’-(1”,2”,4”-triazolyl-3”)-1’-tert-butylhydrazonomorpholylmethan (4b). th e 1h-nmr spectrum, , m. d.: 1,26 (9н, s, 1’-с(сн3)3); 3,35 (4н, t, сн2-n); 3,61 (4н, t, сн2-о); 7,52 (1н, s, 5”-h); 7,73 (1н, s, с-н); 12,04 (1н, br.s., nh). th e 13c nmr spectrum, , m. d.: 27,48 (c2iii); 45,64 (n-ch2); 59,16 (с1 iii); 65,81 (ch2-o); 149,35 (с3 ii); 159,58 (c5ii); 163,25 (c1iv) th e ir spectrum, , сm-1: 2971, 2860, 1610, 1554 1533, 1502, 1237, 1199, 1112, 1068, 1030, 962, 870, 726, 645. th e mass spectrum m/z (intensity, %): 252 (m+), 196, 195, 140, 113, 110, 84, 83, 57. elemental analysis (calculated molecular formula, found, %): с – 52,38; h – 7,94; n – 33,33; о – 6,35. с11h20n6o. с – 52,29; h – 8,02; n – 33,41; о – 6,28. 18 in russian нуклеофильное замещение легкоуходящих групп является одним из важнейших синтетических подходов в построении органических соединений. принципы нуклеофильных гетероароматических превращений немногочисленны и хорошо известны. первым из общепринятых механизмов типа snhet является ипсо-замещение легкоуходящих групп и водорода [1, 2]. другим вариантом заместительной функционализации по принципу fgi являются превращения по ариновому механизму (e, a) [3, 4]. наконец, хронологически последним из исследованных процессов замещения нуклеофилами является anrorc – многостадийный процесс, включающий на первой стадии раскрытие азина нуклеофилом [5]. в действительности раскрытие азинов при действии n-нуклеофилами встречается нередко [6–8], однако не все эти превращения завершаются замещением уходящей группы и обратной циклизацией. в настоящей работе нами приведены результаты исследования основных этапов превращения 4-алкил-6-нитро-1,2,4триазоло[5,1-c][1,2,4]триазин-7-нов под действием морфолина и установлен характер замещения нитрогруппы по типу anrorc. ранее нами описаны реакции 4-алкил-6-нитро-1,2,4-триазоло[5,1-c] [1,2,4]триазин-7-нов в замещении нитрогруппы под действием n-, o-, sи  c-нуклеофилов [9], однако сама последовательность превращений осталась неочевидной. в настоящей работе нами исследованы особенности замещения нитрогруппы в 4-алкил-6-нитро-1,2,4триазоло[5,1-c][1,2,4]триазин-7-нах (1), содержащих в триазиновом цикле метильный (1а) и трет-бутильный фрагменты (1b), создающих минимальный и максимальный стерический эффект для определения его влияния на протекание реакции. в качестве n-нуклеофила использован морфолин как наименее реакционноспособный реагент, позволяющий выделить ключевые полупродукты. нами установлено, что под действием трехкратного избытка морфолина при комнатной температуре происходит необычное для стабильных азотистых гетероциклов раскрытие триазинового цикла с образованием аддуктов со структурой гидразонов (2). соединения (2) являются устойчивыми настолько, что их структура установлена на основании данных ямр спектроскопии и элементного анализа (см. экспериментальную часть). с другой стороны, получить для соединений (2) целостные данные хроматомасс-спектрометрии не удалось, поскольку гидразоны 19 превращаются в исходные соединения (1), что происходит и в условиях колоночной хроматографии на силикагеле. общей особенностью спектров 1н ямр для соединений (2) является необычная дифференциация протонных сигналов амидного фрагмента, где все восемь протонов оказываются магнитно неэквивалентны (рис. 1). такая спектральная картина обусловлена, скорее всего, особенностями пространственной структуры всего гидразонного фрагмента соединений (2). другой общей особенностью для гидразонов (3) является дифференциация сигналов морфолинового амидного фрагмента в спектре 13с ямр. количество углеродных резонансных пиков в спектре, принадлежащих этому фрагменту, удвоено (рис. 2). спектральная корреляционная картина hmbc 1н-13с ямр гидразона (3b) подтверждает приписываемое строение, поскольку очевидно взаимодействие протонов морфолинового амидного фрагмента как с неэквивалентными с-атомами циклоа лкилимина, так и с карбонилом (рис. 3). следующим аспектом исследованных превращений стало нуклеофильное замещение нитрогруппы. так, нагревание триазолотриазинов (1) в избытке морфолина приводит к образованию двух продуктов (3) и (4) в соизмеримом соотношении. рис. 1. фрагмент спектра 1н ямр 1’-(1”,2”,4”-триазолидил-3”)-1’-трет-бутилгидразоно1-морфолинил-2-нитроэтанона морфолиния (2b) 20 данные хроматомасс-спектрометрии реакционных масс показывают присутствие n-нитрозоморфолина, продукта замещения нитрогруппы (3) и продукта замещения – декарбоксилирования (4). строение 4-алкил-6-морфолил1,2,4триазоло[5,1-c][1,2,4]триазин-7-онов (3) установлено на основании данных рис. 3. фрагмент корреляционного спектра hmbc 1н-13с ямр соединения (3b) рис. 2. фрагмент спектра 13с ямр 1’-(1”,2”,4”-триазолидил-3”)-1’-трет-бутилгидразоно1-морфолинил-2-нитроэтанона морфолиния (2b) 21 1н ямр спектроскопии и элементного анализа (см. экспериментальную часть). структура 1’-(1”,2”,4”-триазолил-3”)-1’алкилгидразономорфолилметанов (4) также определена на основании данных 1н ямр спектроскопии и элементного анализа (см. экспериментальную часть). в спектрах 1н ямр соединений (4) присутствуют характерный резонансный пик в области 7, 7 м. д., соответствующий резонансу формильного протона, синглет триазольного протона ( 7,5 м. д.) и уширенный сигнал гетероциклической nh группы ( 12 м. д.). возможность образования гидразона (4) объясняется двумя особенностями механизма реакции, включающего раскрытие триазолотриазиновой структуры и выделение воды при образовании нитрозоморфолина, вызывающей гидролиз амида (2) с последующим декарбоксилированием. таким образом, установлено, что нуклеофильное замещение нитрогруппы в 4-алкил-6-нитро-1,2,4-триазоло[5,1-c] [1,2,4]триазин-7-нах протекает не по типу ипсозамещения, а в соответствии с anrorc механизмом, включающим раскрытие триазинового цикла под действием нуклеофила, замещение нитрогруппы с образованием нитрозоморфолина и последующую циклизацию. спектры ямр 1h и 13с получены на приборе «bruker avance ii spectrometer» (400 мгц для 1h и  13с) в дмсо-d6, внутренний стандарт для спектров 1н ямр – тмс. элементные анализы были проведены на автоматическом снnо анализаторе «carlo erba 1108». ик спектры записаны на ик-фурье спектрометре «bruker alpha, znse (нпво)». данные по хроматомасс-спектрометрии получены на хроматомасс-спектрометре «gcms-qp2010 ultra» (шимадзу, япония, 2013). контроль за ходом реакций и чистотой синтезированных соединений осуществляли с помощью тсх на пластинках sorbfi l (фирма зао «сорбполимер») в системе этилацетат. для препаративной колоночной хроматографии использовали тот же элюент и силикагель sigma-aldrich 60 å. 4-метил-6-нитро-4,7-дигидро-1,2,4триазоло[5,1-c][1,2,4]триазин-7-он получен по методике, описанной в работе [10]. 4-трет-бутил-6-нитро-4,7-дигидро-1,2,4-триазоло[5,1-c][1,2,4]триазин-7-он (1b) суспендируют 20 ммоль 6-нитро-4,7дигидро-1,2,4-триазоло[5,1-c][1,2,4]триазин-7-она в 10 мл трифторуксусной кислоты, добавляют 20 ммоль третбутанола и греют с обратным холодильником при 80 ос в течение 2 ч. раствор упаривают в вакууме, добавляют 10 мл этанола и снова упаривают. затирают осадок с 15 мл трет-бутилметилового эфира, фильтруют, сушат. выход 2,4 г (46 %). спектр ямр 1н, , м. д.: 1,77 (9н, с, 4-с(сн3)3); 8,63 (1н, с, 2-н). спектр ямр 13с, , м.д: 13,60 (с2’); 42,42 (c1’); 140,94 (с-no2); 141,85 (c=o); 152,36 (с3а); 166,99 (с2). ик спектр, , см-1: 3125, 2999, 2948, 1737, 1549, 1522, 1466, 1447, 1355, 1263, 1229, 1173, 1151, 987, 920, 889, 793, 758, 743, 723, 704, 639, 517. масс-спектр m/z: 238 (м+), 223, 208, 180, 166, 152, 108, 96, 70, 57, 41. элементный анализ (рассчитано, брутто-формула, найдено, %): с – 40,34; h – 4,20; n – 35,29; о – 20,17. с8h10n6o3. с – 40,50; h – 4,09; n – 35,32; о – 20,09. 22 1’-(1”,2”,4”-триазолидил-3”)-1’-метилгидразоно-1-морфолинил-2-нитроэтанон морфолиния (2a) смесь 2,5 ммоль (1a) и 7,5 ммоль морфолина перемешивают при комнатной температуре 15 мин. добавляют 3 мл трет-бутилметилового эфира, фильтруют. выход 0,81 г (86,5 %). спектр ямр 1н, , м. д.: 2,68 (4н, т, n-ch2); 3,29–3,72 (8н, м, n-ch2-ch2-o); 3,50 (4н, т, ch2-o), 3,66 (3h, c, 1 i–ch3); 8,41 м. д. (1н, с, 2-н). спектр ямр 13с, , м. д.: 38,15 (nch3), 41,87; 46,44 (o=c-n-ch2-ch2-o); 45,06 (с3iv); 65,29; 65,36 (o=c-n-ch2ch2-o); 66,20 (c2 iv); 135,44 (c-no2); 144,95 (c5ii); 158,93 (c=o); 161,08 (c3ii). ик спектр, , см-1: 2963, 2917, 2858, 1924, 1652, 1599, 1566, 1524, 1430, 1322, 1274, 1253, 1215, 1115, 1094, 1011, 939, 887, 861, 847, 820, 723, 694, 665, 612, 564. элементный анализ (рассчитано, брутто-формула, найдено,%): с – 42,16; h – 5,95; n – 30,27; о – 21,62. с13h22n8o5. с – 42,03; h – 5,87; n – 30,35; о – 21,75. 1’-(1”,2”,4”-триазолидил-3”)-1’трет-бутилгидразоно-1-морфолинил-2-нитроэтанон морфолиния (2b) смесь 3 ммоль (1b) и 9 ммоль морфолина при комнатной температуре перемешивают 15 мин. добавляют 5 мл трет-бутил-метилового эфира и фильтруют. выход 0,84 г (67,8 %). спектр ямр 1н, , м. д.: 1,39 (9н, с, 4-с(сн3)3); 2,70–3,76 (16н, м, n-ch2ch2-o); 2,72 (4h, т, n-ch2); 3,52 (4h, т, сн2-о); 8,44 м. д. (1н, с, 2-н). спектр ямр 13с, , м. д.: 28,32 (с2iii); 41,53; 46,56 (o=c-n-ch2-ch2-o); 45,99 (c3v); 64,13 (c1iii); 65,48; 65;63 (o=cn-ch2-ch2-o); 67,22 (c2 v); 135,47 (cno2); 145,38 (c5 ii), 156,27 (c3ii), 157,35 (c=o). ик спектр, , см-1: 2978, 2853, 2730, 2208, 2165, 1645, 1585, 1455, 1309, 1279, 1197, 1109, 1019, 877. масс-спектр m/z (интенсивность, %): 327 (м+) 281, 252, 196, 140, 113, 110, 84. элементный анализ (рассчитано, брутто-формула, найдено, %): с – 46,60; h – 6,80; n – 27,18; о – 19,42. с16h28n8o5. с – 46,66; h – 6,83; n – 26,07; о – 20,44. 4 м е т и л 6 м о р ф о л и л 4 , 7 д и гидро-1,2,4-триазоло[5,1-с][1,2,4] т р и а з и н 7 о н м о н о г и д р а т ( 3 a ) и 1’-(1”,2”,4”-триазолил-3”)-1’-метилгидразономорфолилметан (4a). смесь 2 ммоль (1a) и 6 ммоль морфолина кипятят 5 ч. при добавлении к реакционной массе 10 мл смеси хлороформ: трет-бутилметиловый эфир (1:1) выпавший продукт (4a) фильтруют. фильтрат упаривают в вакууме, продукты разделяют хроматографией. 4-метил-6-морфолил-4,7-дигидро-1,2,4-триазоло[5,1-с][1,2,4]триазин-7-он моногидрат (3a) спектр ямр, , м. д.: 3,43 (4h, т, ch2-n); 3,78 (4н, т, ch2-o); 3,91 (3н, с, 4-сн3); 8,09 (1н, с, 2-н). спектр ямр 13с, , м. д. (дмсо-d6): 40,51 (n-ch3); 47,94 (n-ch2); 65,59 (ch2o); 143,48 (c6); 146,79 (c=o); 151,13 (c3a); 153,83 (c1). масс-спектр m/z (интенсивность, %): 236 (m+), 209, 193, 179, 151, 123, 110, 96, 83, 69. элементный ана лиз (расс читано, бру тто-форм ула, найдено,  %): с – 45,71; h – 6,67; n – 40,00; о – 7,62. с9h11n6o2*н2о. с – 42,48; h – 5,59; n – 33,00; о – 18,93. 1’-(1”,2”,4”-триазолил-3”)-1’-метилгидразономорфолилметан (4a) спектр ямр 1н, , м. д.: 3,21 (3н, с, 1i–сн3); 3,31 (4н, т, сн2-n); 3,64 (4н, т, 23 ch2-o); 7,29 (1н, с, 5 ii-н); 7,59 (1h, с, с-н); 12,10 (1н, уш. с, nh). спектр ямр 13с, , м. д.: 37,13 (nch3); 45,97 (n-ch2); 65,71 (ch2-o); 149,17 (c5ii); 151,13 (c1iii); 158,80 (c3ii). ик спектр, , см-1: 2970, 2858, 1615, 1567, 1509, 1272, 1236, 1217, 1161, 1113, 1070, 1030, 1009, 950, 739, 615. масс-спектр m/z (интенсивность, %): 210 (м+) 124, 98, 97, 70, 56, 42, 41. элементный анализ (рассчитано, брутто-формула, найдено, %): с – 45,71; h – 6,67; n – 40,00; о – 7,62. с8h14n6o. с – 45,59; h – 6,57; n – 40,07; о – 7,77. 4-трет-бу тил-6-морфолил-4,7дигидро-1,2,4-триазоло[5,1-с][1,2,4] т р и а з и н 7 о н м о н о г и д р а т ( 3 b ) и 1’-(1”,2”,4”-триазолил-3”)-1’-третбутилгидразономорфолилметан (4b) делают смесь 2 ммоль (1b) и 6 ммоль морфолина и кипятят в течение 5 ч. реакционную массу упаривают досуха в вакууме. продукты разделяют хроматографически на силикагеле. 4-трет-бутил-6-морфолил-4,7дигидро-1,2,4-триазоло[5,1-с][1,2,4] триазин-7-он (3b) спектр ямр 1н, , м. д.: 1,27 (9h, c, c-(ch3)3); 3,36 (4н, т, ch2-n); 3,65 (4н, т, сн2-о); 8,12 (1н, с, 2-н). масс-спектр m/z (интенсивность, %): 278 (м+), 222, 207, 195, 179, 165, 137, 111, 82. элементный ана лиз (расс читано, бру тто-форм ула, найдено,  %): с – 48,65; h – 6,76; n – 28,38; o – 16,22 c12h18n6o2*h2o. c – 48,59; h – 28,42; n – 28,42; o – 16,25. 1’-(1”,2”,4”-триазолил-3”)-1’-третбутилгидразономорфолилметан (4b) спектр ямр 1н, , м. д.: 1,26 (9н, с, 1’-с(сн3)3); 3,35 (4н, т, сн2-n); 3,61 (4н, т, сн2-о) 7,52 (1н, с, 5”-h); 7,73 (1н, с, с-н); 12,04 (1н, уш. с, nh). спектр ямр 13с, , м. д.: 27,48 (c2iii); 45,64 (n-ch2); 59,16 (с1 iii); 65,81 (ch2-o); 149,35 (с3ii); 159,58 (c5ii); 163,25 (c1iv) ик спектр, , см-1: 2971, 2860, 1610, 1554 1533, 1502, 1237, 1199, 1112, 1068, 1030, 962, 870, 726, 645. масс-спектр m/z (интенсивность, %): 252 (m+), 196, 195, 140, 113, 110, 84, 83, 57. элементный анализ (рассчитано, брутто-формула, найдено, %): с – 52,38; h – 7,94; n – 33,33; о – 6,35. с11h20n6o. с – 52,29; h – 8,02; n – 33,41; о – 6,28. references 1. linga r. p., khan s. i., ponnan p., tripathi m., rawat d. s. design, synthesis and evaluation of 4-aminoquinoline-purine hybrids as potential antiplasmodial agents. european journal of medicinal chemistry. 2017;126:675–686. 2. metal free c-h functionalisation of aromatics. nucleophilic displacement of hydrogen / eds v. n. charushin, o. n. chupakhin, in topics heterocycl. chem. / eds b.u.w. maes, j. cossy, s. polanic, springer, switzerland, 2014, 37, 283 p. 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mukhin e. m. th e features of nucleophilic substitution of the nitro group in 4-alkyl-6-nitro-1,2,4-triazolo[5,1-c][1,2,4]triazines. chimica techno acta. 2017;4(1):11–24. tert-butyl-diphenylmethylnitroxyl radical formation with the reaction of triphenylbismuth dicrotonate and c-phenyl-n-tert-butylnitrone in benzene a. v. gushchin1, o. s. kalistratova1, a. i. maleeva1, v. a. kuropatov2, d. n. yemelyanov1 1lobachevsky state university of nizhny novgorod, 23 gagarin av., nizhny novgorod, 603950, russia, 2 g. a. razuvaev institute of organometallic chemistry ras, 49 tropinina st., nizhny novgorod, 603137, russia e-mail: gushchin4@yandex.ru tert-butyl-diphenylmethylnitroxyl radical formation with the reaction of triphenylbismuth dicrotonate and c-phenyl-n-tert-butylnitrone in benzene ph bi(v) ph ph chn(o )bu -3 hv pbn 2⎯ →⎯ ⎡⎣ ⎤⎦⎯ →⎯• • t tert t tert t t keywords: electron tert а. в. гущин1, о. с. калистратова1, а. и. малеева1, в. а. куропатов2, д. н. емельянов1 1нижегородский государственный университет им. н. и. лобачевского, пр. гагарина, 23, г. нижний новгород, 603950, россия 2институт металлорганической химии им. г. а. разуваева ран, ул. тропинина, 49, г. нижний новгород, 603137, россия e-mail: gushchin4@yandex.ru ph bi(v) ph ph chn(o )bu -3 hv pbn 2⎯ →⎯ ⎡⎣ ⎤⎦⎯ →⎯• • t t t t introduction polymethylmethacrylate with organobithmuth compounds additives was known to be obtained with the radical polymerization in the presence of peroxide initiators [1, 2]. it was established that bi(v) acrylates accelerated the polymerization reaction. it was suggested that the acceleration was caused by decomposition of organometallic compounds on exposure by diffused light, as the polymer ization slowed in the dark. the character of the process was not studied. when various diacyl derivatives of triphenyl bismuth were used, no significant change in polymerization rate or molar mass was observed, indicating the predominant role of the ph3bi(v) fragment. besides, the previous study of the photo-induced cation polymerization of oxiranes and vinyl monomers was carried out with triaryl(1-pyrenyl)bismuth salts as initiators [3, 4]. when such compounds were irradiated by visible light, the homolysis of bi–c(pyrene) bond occured with the formation of pyrenyl radical and cation radical of triarylbismuth, which subsequently initiated polymerization. it is also known that organometallic compounds of bismuth(iii) can cause the controlled living radical polymerization [5, 6]. recently a phenyl-tert-butylnitroxyl stable radical was fixed in the triphenylbismuth dicrotonate reaction with 2-methyl-2-nitrosopropane [7]. that result isn’t clear proof of the phenyl radical formation by light discharge of organometallic compounds, because of spin trap 2-methyl-2-nitrosopropane in diffused light can be cleavaged to give initial tert-butyl radicals. so, phenyl radical could be a secondary product of homolytic substitution reaction: t-bun=o → t-bu• + no t-bu• + phbi(v) t-bubi(v) + ph• that is why the aim of present work was investigation of triphenylbismuth dicrotonate decomposition reaction in light in the presence of another spin trap c-phenyl-n-tert-butylnitrone which is stable for sun light. the triphenylbismuth dicrotonate was chosen as organobismuth(v) derivative with good solubility in benzene, hydrolitical and oxidative stability on air. the structure of this compound has been studied [8]. the thermal stability of this compound was investigated by thermogravimetric analysis. the experimental data were used to calculate the standard thermodynamic functions: heat capacity, enthalpy, entropy and gibbs energy over the range from t = 0 to 400–420 k. for the compounds under study the standard entropy of formation was calculated at t = 298.15 k [9]. experimental esr spectra were registered on the bruker er200d9.5 ghz in degassed tubes. benzene, et2o and thf were dried over anhydrous calcium chloride, then distilled and kept over sodium wire. chloroform was dried over anhydrous calcium chloride and distilled. hexane was used without previous purification. anhydrous bicl3 was purified by sublimation (350 °c, 0.5 torr). triphenylbismuth was synthesized according to conventional procedure [10] from bicl3 and phmgbr with the use of the benzene and thf (1:2) mixture as the solvent. the synthesis of triphenylbismuth dicrotonate was carried out according to conventional procedure [11] by the oxidative addition reaction at room temperature in et2o from triphenylbismuth, crotonic acid and tert-butylhydroperoxide (reagent ratio 1:2:1). the product was purified by recrystallization from the medium hexane – chloroform (4:1). the yield of the purified reaction product was 73 %, melting point 153 °c. the synthesis of pbn performed [12] from benzaldehyde, tert-butylamine and hydrogen peroxide. triphenylbismuth dicrotonate decomposition in diffused light was prepared as follows: in one elbow of tube a sample of pbn (0.2 mmol) was placed, while the other elbow was filled by the benzene solution of triphenylbismuth dicrotonate (1 ml, 0.2 mol/l concentration). the ampoule was degassed, sealed and after mixing the esr spectrum was registered. results and discussion we have investigated the decomposition of triphenylbismuth dicrotonate in benzene in the presence of pbn phch=n(o)bu-t by esr method in a sealed and degassed ampoule in diffuse light. the choice of the solvent is due to its low activity in radical reactions at the chosen conditions. we recorded esr spectrum of the mixture and found an adduct of spin trap phch(ph)n(o•)bu-t with phenyl radical, formed by decomposition reaction: ph3bi(o2cch=chch3)2 → → 2 ph• + phbi(o2cch=chch3)2 ph• + phch=n(o)bu-t → → phch(ph)n(o•)bu-t the esr spectrum of triphenylbismuth dicrotonate in benzene (with pbn as the spin trap) is show in fig. 1. for the adduct phch(ph)n(o•)bu-t the values of hyperfine interaction constants have been determined: an = 14.4 oe, ah = 2.2 oe, g = 2.0060, which are in agreement with the literature data for the addition compound generated in benzene by photolysis of ph3bi (an = 14.5 oe, aн = 2.3 oe), ph3sb (an = 13.2 oe, aн = 2.2 oe), ph3as (an = 13.4oe, aн = 2.2 oe) [13]. fig. 1. the esr spectrum of triphenylbismuth dicrotonate in benzene, the spin trap is pbn conclusions decomposition of triphenylbismuth dicrotonate in diffused light in benzene solution in the presence of c-phenyl-ntert-butylnitrone leads to formation of phenyl radicals which are registered in the form of the adduct phch(ph)n(o•)bu-t. acknowledgements this research was supported by gos zadanie rf. in russian ранее методом радикальной полимеризации в  присутствии инициаторов был получен полиметилметакрилат (пмма) с  добавками различных металлоорганических соединений bi(v) [1, 2]. было установлено, что наличие акрилатов bi(v) ускоряет протекание полимеризации. предположили, что это ускорение вызвано распадом металлоорганических соединений под действием рассеянного света, т. к. в  темноте полимеризация замедлялась. при этом характер процесса изучен не был. при использовании различных диацилатных производных трифенилвисмута не наблюдалось значительных изменений в  скорости полимеризации и  их молекулярной массе, что свидетельствует о  превалирующей роли фрагмента ph3bi(v). также ранее была изучена фотоиндуцированная катионная полимеризация оксиранов и  виниловых мономеров, в  которой инициаторами выступали соли триарил(1-пиренил)висмута [3, 4]. при облучении таких соединений видимым светом происходит гомолиз связи bi–c(пирен) с образованием пиренильного радикала и  катион-радикала триарилвисмута, который в дальнейшем и инициирует полимеризацию. также известно, что металлорганические соединения висмута(iii) способны вызывать контролируемую живую радикальную полимеризацию [5, 6]. недавно, фенил-трет-бутилнитроксильный стабильный радикал был зафиксирован в  реакции дикротоната трифенилвисмута с  2-метил-2-нитрозопропаном [7]. этот результат не является четким доказательством образования фенильного радикала при распаде металлоорганического соединения на рассеянном свету, т. к. спиновая ловушка 2 -метил-2-нитрозопропан может распадаться с образованием исходных трет-бутильных радикалов. таким образом, фенильный радикал может быть вторичным продуктом реакции гомолитического замещения: t-bun=o → t-bu• + no t-bu• + phbi(v) t-bubi(v) + ph• поэтому целью настоящей работы было исследование реакции разложения дикротоната трифенилвисмута на свету в  присутствии другой спиновой ловушки c-фенил-n-трет-бутилнитрона, которая стабильна на солнечном свету. дикротонат трифенилвисмута был выбран в качестве металлоорганического производного висмута(v) с хорошей растворимостью в бензоле, гидролитической и окислительной стабильностью на воздухе. структура этого соединения изучена [8]. термостабильность этого соединения исследовалась с  помощью термогравиметрического анализа. экспериментальные данные были использованы для расчета стандартных термодинамических функций: теплоемкости, энтальпии, энтропии и  энергии гиббса в диапазоне от t = 0 до 400–420 k. для изучаемых соединений стандартная энтропия образования рассчитывалась при t = 298,15 k [9]. эпр-спектры регистрировали на приборе bruker er200d-src с  рабочей частотой 9,5 ггц в дегазированных трубках. бензол, et2o и  тгф сушили над безводным хлоридом кальция, перегоняли и хранили над натриевой проволокой. хлороформ сушили над безводным хлоридом кальция и  перегоняли. петролейный эфир использовали без предварительной очистки. безводный bicl3 очищали сублимацией (350  °c, 0,5 мм рт. ст.). трифенилвисмут синтезировали по известной методике [10] из bicl3 и  phmgbr с  использованием смеси бензола и тгф (1:2) в качестве растворителя. синтез дикротоната трифенилвисмута проводили по известной методике [11] по реакции окислительного присоединения при комнатной температуре в  et2o из трифенилвисмута, кротоновой кислоты и трет-бутилгидропероксида (соотношение реагентов 1:2:1). полученный продукт очищали перекристаллизацией из системы: петролейный эфир–хлороформ (4:1). выход очищенного продукта реакции составил 73 %, температура плавления 153 °c. фбн синтезировали из бензальдегида, трет-бутиламина и пероксида водорода [12]. приготовление растворов для исследования распада ph3bi(o2cch=chch3)2 на рассеянном свету проводили следующим образом. в  одно колено н-образной ампулы для эпр помещали навеску фбн (0,2  ммоль), в  другое – раствор ph3bi(o2cch=chch3)2 в  бензоле (1  мл, концентрация 0,2 моль/л). ампулу дегазировали, запаивали и  после смешения содержимого регистрировали спектр эпр. исследовали распад дикротоната трифенилвисмута методом эпр в бензоле в  присутствии фбн phch=n(o) bu-t. выбор растворителя обусловлен тем, что он малоактивен в  радикальных реакциях в данных условиях. мы зарегистрировали спектр эпр смеси и обнаружили аддукт phch(ph) n(o•)bu-t спиновой ловушки с  фенильным радикалом, образованный в результате реакции разложения: ph3bi(o2cch=chch3)2 → → 2 ph• + phbi(o2cch=chch3)2 ph• + phch=n(o)bu-t → → phch(ph)n(o•)bu-t эпр спектр дикротоната трифенилвисмута в  бензоле (спиновая ловушка фбн) представлен на рис. 1. для аддукта phch(ph)n(o•)bu-t определены значения констант сверхтонкого взаимодействия an = 14,4 э, aн = 2,2 э, g = 2,0060, что согласуется с  литературными данными по этому аддукту, генерируемому в  бензоле в  ходе фотолиза ph3bi (an  = 14,5 э, aн = 2,3 э), ph3sb (an = 13,2 э, aн = 2,2 э), ph3as (an = 13,4 э, aн = 2,2 э) [13]. распад дикротоната трифенилвисмута на рассеянном свету в  бензоле в  присутствии c-фенил-n-трет-бутилнитрона протекает с образованием фенильных радикалов, которые зафиксированы в  форме аддукта phch(ph) n(o•)bu-t. работа выполнена при поддержке госзадания рф. references 1. dodonov va, gushchin av, kuznetsova jl, morugova va. [triphenylbismuth and triphenylantimony diacrylates in the synthesis of metal-containing polymethylmethacrylate]. vestnik nizhegorodskogo universiteta im. n. i. lobachevskogo, seriya khimiya [vestnik of lobachevsky university of nizhni novgorod, ser chemistry]. 2004;1(4):86–94. russian. 2. gushchin av, shashkin dv, shcherbakova ts, somov nv, baranov ev, fukin gk, shavyrin as, rykalin vi, dodonov va. 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korshunova, r. f. tukhvatullina, o. s. el'tsov ltd «stc-immuno analisys» blukhera st., 43, ekaterinburg, 620137, russia e-mail: o.s.eltsov@urfu.ru the study of the curing of the polyurethane coating by method of ir spectroscopy the results of the study of the curing process of polyurethane compositions with participation of two different catalysts by the method of ir spectroscopy are given. the time dependences of curing of polyurethane coatings from concentrations of catalysts were determined, on the basis of which the most effective catalyst was selected. key words: polyurethane, polyol, isocyanate, chemical curing, ir spectroscopy. received: 04.10.2016; accepted: 11.10.2016; published: 30.12.2016. н. а. коршунова, р. ф. тухватулина, о. с. ельцов ооо «итп иммуноанализ» 620137, ул. блюхера, 43, екатеринбург, россия e-mail: o.s.eltsov@urfu.ru изучение отверждения полиуретановых покрытий методом ик-спектроскопии приведены результаты исследования процесса отверждения полиуретановых композиций с участием двух различных катализаторов методом ик-спектроскопии. определены временные зависимости отверждения полиуретанового покрытия от концентраций катализаторов, по которым выбран наиболее эффективный катализатор. ключевые слова: полиуретан; полиол; изоционат; химическое отверждение; ик-спектроскопия. поступило: 04.10.2016; принято: 11.10.2016; опубликовано: 30.12.2016. © korshunova n. a., tukhvatullina r. f., el'tsov o. s., 2016 korshunova n. a., tukhvatullina r. f., el'tsov o. s. chimica techno acta. 2016. vol. 3, no. 4. p. 268–277. issn 2409-5613 one of the most common plastic materials today is polyurethane. the widespread use of this polymer is due to the wide scope and high rates of physicalmechanical properties as strength, wear resistance, resistance to swelling in various oils and solvents and ozoneand radiation resistance and others [1, 2]. the combination of high elasticity with wide range of hardness defines the excellent operational properties of the products based on them. the polymer is 269 able to withstand heavy loads, less subject to aging than other substances. it is resistant to temperature extremes, sunlight, salts, solvents on organic base. therefore, the establishment of the protective anti-corrosion polyurethane coatings, used in large industrial objects (bridges, overpasses, etc.) is an actual task today. the obtaining of the polyurethane occurs by the reaction of diand polyfunctional isocyanates with diand polyfunctional alcohols: since the curing time of the composition is sufficiently large, there is a need for its acceleration, while maintaining the properties of the very protective coating. in many experiments thermal processing is used for acceleration of curing of polyurethane, which is difficult to implement in a coating outdoor environments [3–5]. in this case it seems more profitable variant of use of a catalyst which initially is added to the reaction mixture, accelerating the process of chemical curing of the coating. one of the most common catalytic systems is the combination of organometallic compounds and tertiary amines. often this combination is due to the synergistic effect of these compounds. the purpose of work is the determination of the influence of the concentration of tertiary amine as a catalyst on the rate of binding process of the components in the reaction for producing the polyurethane at room temperature by the method of ir spectroscopy. materials and methods of study spectra of prepared samples were recorded on a ir-fourier spectrometer bruker alpha prefix diffusive reflection. as starting components for the preparation of the samples were taken:* aliphatic polyisocyanate on the basis of isocyanurate hexamethylenediisocyanate (desmodur n3390 of firm bayer) 90  % solution in n-butyl acetate with a mass content of isocyanate groups of 19.6 % was represented in the sale: pho o oh n m k oobu therefore, the establishment of the protective anti-corrosion polyurethane coatings, used in large industrial objects (bridges, overpasses, etc.) is an actual task today. the obtaining of the polyurethane occurs by the reaction of diand polyfunctional isocyanates with diand polyfunctional alcohols: o n r 1 n o oh r 2 oh o n r 1 n o oh r 2 oh ...+ + + + ... o n h r 1 n h o o r 2 o o n h r 1 n h o o r 2 o ... since the curing time of the composition is sufficiently large, there is a need for its acceleration, while maintaining the properties of the very protective coating. in many experiments thermal processing is used for acceleration of curing of polyurethane, which is difficult to implement in a coating outdoor environments [3–5]. in this case it seems more profitable variant of use of a catalyst which initially is added to the reaction mixture, accelerating the process of chemical curing of the coating. one of the most common catalytic systems is the combination of organometallic compounds and tertiary amines. often this combination is due to the synergistic effect of these compounds. the purpose of work is the determination of the influence of the concentration of tertiary amine as a catalyst on the rate of binding process of the components in the reaction for producing the polyurethane at room temperature by the method of ir spectroscopy. materials and methods of study. spectra of prepared samples were recorded on a ir-fourier spectrometer bruker alpha prefix diffusive reflection. as starting components for the preparation of the samples were taken:* nn n o o o ocn ocn nco the hydroxyl-bearing polyacrylate (setalux da 160x) with a mass content of hydroxyl groups of 1.6 % in the sale form. represented as 60 % solution in xylene: as organometallic catalyst was used 1 % solution of dilaurate dibutylamine in butyl acetate, the tertiary amines are variable amounts of triethanolamine and diazobicycloundezen. pho o oh n m k oobu therefore, the establishment of the protective anti-corrosion polyurethane coatings, used in large industrial objects (bridges, overpasses, etc.) is an actual task today. the obtaining of the polyurethane occurs by the reaction of diand polyfunctional isocyanates with diand polyfunctional alcohols: o n r 1 n o oh r 2 oh o n r 1 n o oh r 2 oh ...+ + + + ... o n h r 1 n h o o r 2 o o n h r 1 n h o o r 2 o ... since the curing time of the composition is sufficiently large, there is a need for its acceleration, while maintaining the properties of the very protective coating. in many experiments thermal processing is used for acceleration of curing of polyurethane, which is difficult to implement in a coating outdoor environments [3–5]. in this case it seems more profitable variant of use of a catalyst which initially is added to the reaction mixture, accelerating the process of chemical curing of the coating. one of the most common catalytic systems is the combination of organometallic compounds and tertiary amines. often this combination is due to the synergistic effect of these compounds. the purpose of work is the determination of the influence of the concentration of tertiary amine as a catalyst on the rate of binding process of the components in the reaction for producing the polyurethane at room temperature by the method of ir spectroscopy. materials and methods of study. spectra of prepared samples were recorded on a ir-fourier spectrometer bruker alpha prefix diffusive reflection. as starting components for the preparation of the samples were taken:* aliphatic polyisocyanate on the basis of isocyanurate hexamethylenediisocyanate (desmodur n3390 of firm bayer) 90 % solution in n-butyl acetate with a mass content of isocyanate groups of 19.6 % was represented in the sale: nn n o o o ocn ocn nco the hydroxyl-bearing polyacrylate (setalux da 160x) with a mass content of hydroxyl groups of 1.6 % in the sale form. represented as 60 % solution in xylene: pho o oh n m k oobu therefore, the establishment of the protective anti-corrosion polyurethane coatings, used in large industrial objects (bridges, overpasses, etc.) is an actual task today. the obtaining of the polyurethane occurs by the reaction of diand polyfunctional isocyanates with diand polyfunctional alcohols: o n r 1 n o oh r 2 oh o n r 1 n o oh r 2 oh ...+ + + + ... o n h r 1 n h o o r 2 o o n h r 1 n h o o r 2 o ... since the curing time of the composition is sufficiently large, there is a need for its acceleration, while maintaining the properties of the very protective coating. in many experiments thermal processing is used for acceleration of curing of polyurethane, which is difficult to implement in a coating outdoor environments [3–5]. in this case it seems more profitable variant of use of a catalyst which initially is added to the reaction mixture, accelerating the process of chemical curing of the coating. one of the most common catalytic systems is the combination of organometallic compounds and tertiary amines. often this combination is due to the synergistic effect of these compounds. the purpose of work is the determination of the influence of the concentration of tertiary amine as a catalyst on the rate of binding process of the components in the reaction for producing the polyurethane at room temperature by the method of ir spectroscopy. materials and methods of study. spectra of prepared samples were recorded on a ir-fourier spectrometer bruker alpha prefix diffusive reflection. as starting components for the preparation of the samples were taken:* nn n o o o ocn ocn nco 270 the experimental part in advance 12 metal dies of a given size of 25.5×4,5×6,0 mm had been prepared. the sizes of dies were determined by measuring of the geometric parameters of the set of elements of the sample preparation for the recording of spectra of diffuse reflection. metal dies on one side were mirror polished. half the polished side was covered with the prepared sample using a special device enabling the thickness of the polyurethane coatings of 0.01–0.03 mm, the other half surface was used as a standard of comparison. the ratio was calculated by the following formula (calculated to anhydrous polyol): p p m b m c b a 1 3 = ⋅ ⋅ where pa is the number of polyol, g; pb is the number of isocyanate derivatives, g; m1 is the molecular weight of isocyanate groups 42.e.m.; m3 is the molecular weight of the hydroxyl groups 17.e.m.; b is the content of hydroxyl groups in the polyol, 1,6 %; с is the content of isocyano groups in the isocyanate, 19,6 %. the founding ratio of isocyanate derivatives was to poliol by mass is 30,63:100. given the content of solvents the mass ratio used 20,47:100. the experiment was conducted in 4 parallel: without catalyst of tertiary amine, with content of catalyst of tertiary amine, 0.50 %, 0.75 %, 1.00 % of the mass of the mixture. isocyanate and polyol were mixed in a specific ratio, were added 1 % by mass of the mixture dilaurate dibutylamine 1 % solution in butyl acetate and the variable number of catalyst of tertiary amine was poured. so 4 parallels were got, where as the catalyst there was used triethanolamine, and 4 parallels, where the catalyst was diazobicycloundecen. the reaction mixture was prepared by stirring for 10 minutes at room temperature. ir spectra were recorded with the frequency of once per day for 25 days. additional treatment except correction of base line was not carried out. results and discussion the assessment of chemical bonding of the components was based on changes in the concentration of isocyanate, which is determined by the intensity of the absorption band of the isocyanate group at 2291 cm–1 [6]. the process of formation of polyurethane was considered complete when the absorption band is not visible in the spectrum (fig. 1). in fig. 2 and 3 show graphs of the content of the absorption band of nco-groups in time are shown. as can be seen in the graphs, the speed of curing increases with increasing concentration of catalyst. isocyanate groups sn o oo o n oh oh oh n n as organometallic catalyst was used 1 % solution of dilaurate dibutylamine in butyl acetate, the tertiary amines are variable amounts of triethanolamine and diazobicycloundezen. the experimental part in advance 12 metal dies of a given size of 25.5×4,5×6,0 mm had been prepared. the sizes of dies were determined by measuring of the geometric parameters of the set of elements of the sample preparation for the recording of spectra of diffuse reflection. metal dies on one side were mirror polished. half the polished side was covered with the prepared sample using a special device enabling the thickness of the polyurethane coatings of 0.01–0.03 mm, the other half surface was used as a standard of comparison. the ratio was calculated by the following formula (calculated to anhydrous polyol): where pa is the number of polyol, g; pb is the number of isocyanate derivatives, g; m1 is the molecular weight of isocyanate groups 42.e.m.; m3 is the molecular weight of the hydroxyl groups 17.e.m.; b is the content of hydroxyl groups in the polyol, 1,6%; с is the content of isocyano groups in the isocyanate, 19,6%. the founding ratio of isocyanate derivatives was to poliol by mass is 30,63:100. given the content of solvents the mass ratio used 20,47:100. the experiment was conducted in 4 parallel: without catalyst of tertiary amine, with content of catalyst of tertiary amine, 0.50 %, 0.75 %, 1.00 % of the mass of the mixture. isocyanate and polyol were mixed in a specific ratio, were added 1 % by mass of the mixture dilaurate dibutylamine 1 % solution in butyl acetate and the variable number of catalyst of tertiary amine was poured. so 4 parallels were got, where as the catalyst there was used 271 are extremely reactive and rapidly interact with substances that contain hydroxyl and amino groups. this interaction of isocyanate groups and hydroxyl or amino groups of agents of chain growth leads to the formation of a larger number of urethane linkages. therefore, the time for chemical curing of the reaction mixture of the polymer requires less at higher content of the catalyst. it should be noted that the physical curing is observed within hours after applying of the sample, whereas chemical curing was leaking much longer. physical curing was evaluated by leaving of the nail strip on the sample of polyurethane fig. 1. comparison of the ir spectra of the sample containing no triethanolamine at the beginning and end of the experience fig. 2. dependence of the intensity of the absorption bands from the time in the sample containing various concentrations of triethanolamine: № 1 – 0 %; № 2 – 0,5 %; № 3 – 0,75 %; № 4 – 1 % triethanolamine, and 4 parallels, where the catalyst was diazobicycloundecen. the reaction mixture was prepared by stirring for 10 minutes at room temperature. ir spectra were recorded with the frequency of once per day for 25 days. additional treatment except correction of base line was not carried out. results and discussion the assessment of chemical bonding of the components was based on changes in the concentration of isocyanate, which is determined by the intensity of the absorption band of the isocyanate group at 2291 cm–1 [6]. the process of formation of polyurethane was considered complete when the absorption band is not visible in the spectrum (fig. 1). in fig. 2 and 3 show graphs of the content of the absorption band of nco-groups in time are shown. 500100015002000250030003500 wavenumber cm-1 0. 0 0. 2 0. 4 0. 6 0. 8 1. 0 1. 2 1. 4 a bs or b an ce u n its fig. 1. comparison of the ir spectra of the sample containing no triethanolamine at the beginning and end of the experience 272 in the resulting study the chemical curing of the polymer composition was observed faster when used as a catalyst triethanolamine. it should be noted also that the triethanolamine is cheaper than diazobicycloundecen, which explains its wide spread in industrial production. the obtained experimental data can be used to optimize the technology of applying of polyurethane protective coatings and will predict the time to complete bonding of the components of the reaction mixture to achieve optimal physical-mechanical indicators. * the authors thank the head of r@d division prof. kozhevnikov d. n of jsc sih vmp for scientific and innovative work. for the objects of study and their interest in scientific research activity of students, hit urfu. in russian одним из самых распространенных полимерных материалов современности является полиуретан. широкое применение данного полимера обусловлено широкой областью применения и высокими показателями таких физико-механических свойств как прочность, износостойкость, устойчивость к набуханию в различных маслах и растворителях, а также озонои радиационностойкость и другие [1, 2]. сочетание высокой эластичности с широким диапазоном твердости определяет превосходные эксплуатационные свойства изделий на их основе. полимер способен выдерживать большие нагрузки, меньше подвергается старению, чем другие вещества. он устойчив к температурным перепадам, солнечным лучам, соли, растворителям на органической основе. поэтому создание защитных антикоррозионных полиуретановых покрытий, используемых в крупногабаритных промышленных объектах fig. 3. dependence of intensity of absorption bands from time in the sample containing different concentrations of diazobicycloundecen: № 1 – 0 %; № 2 – 0,5 %; № 3 – 0,75 %; № 4 – 1 % 273 (мосты, эстакады и т. д.) является актуальной задачей на сегодняшний день. получение полиуретана происходит по реакции дии полифункциональных изоцианатов с дии полифункциональными спиртами: поскольку время отверждения композиции достаточно большое, возникла необходимость его ускорения при сохранении свойств самого защитного покрытия. во многих опытах для ускорения отверждения полиуретана используется термическая обработка, которую трудно осуществить в условиях нанесения покрытий вне помещений [3–5]. в данном случае представляется более выгодным вариант использования катализатора, который изначально добавляется в реакционную смесь, ускоряя процесс химического отверждения покрытия. одной из распространенных каталитических систем является сочетание органометаллических соединений с третичными аминами. причем зачастую такая комбинация обусловлена синергетическим эффектом этих соединений. цель работы: определение влияния концентрации третичного амина как катализатора на скорость процесса связывания компонентов в реакции получения полиуретана при комнатной температуре методом ик-спектроскопии. материал и методы исследования спектры подготовленных образцов были записаны на ик-фурье спектрометре bruker alpha, приставка диффузионного отражения. в качестве исходных компонентов для подготовки образцов были взяты*: – алифатический полиизоционат на основе изоцианурата гексаметилендиизоционата (desmodur n3390 компании bayer). в продаже представлен как 90 % раствор в н-бутилацетате с массовым содержанием изоционатных групп 19,6 %: pho o oh n m k oobu therefore, the establishment of the protective anti-corrosion polyurethane coatings, used in large industrial objects (bridges, overpasses, etc.) is an actual task today. the obtaining of the polyurethane occurs by the reaction of diand polyfunctional isocyanates with diand polyfunctional alcohols: o n r 1 n o oh r 2 oh o n r 1 n o oh r 2 oh ...+ + + + ... o n h r 1 n h o o r 2 o o n h r 1 n h o o r 2 o ... since the curing time of the composition is sufficiently large, there is a need for its acceleration, while maintaining the properties of the very protective coating. in many experiments thermal processing is used for acceleration of curing of polyurethane, which is difficult to implement in a coating outdoor environments [3–5]. in this case it seems more profitable variant of use of a catalyst which initially is added to the reaction mixture, accelerating the process of chemical curing of the coating. one of the most common catalytic systems is the combination of organometallic compounds and tertiary amines. often this combination is due to the synergistic effect of these compounds. the purpose of work is the determination of the influence of the concentration of tertiary amine as a catalyst on the rate of binding process of the components in the reaction for producing the polyurethane at room temperature by the method of ir spectroscopy. materials and methods of study. spectra of prepared samples were recorded on a ir-fourier spectrometer bruker alpha prefix diffusive reflection. as starting components for the preparation of the samples were taken:* nn n o o o ocn ocn nco – гидроксилсодержащий полиакрилат (setalux da 160x) с массовым содержанием в продажной форме гидроксильных групп 1,6 %. в продаже представлен как 60 % раствор в ксилоле: pho o oh n m k oobu therefore, the establishment of the protective anti-corrosion polyurethane coatings, used in large industrial objects (bridges, overpasses, etc.) is an actual task today. the obtaining of the polyurethane occurs by the reaction of diand polyfunctional isocyanates with diand polyfunctional alcohols: o n r 1 n o oh r 2 oh o n r 1 n o oh r 2 oh ...+ + + + ... o n h r 1 n h o o r 2 o o n h r 1 n h o o r 2 o ... since the curing time of the composition is sufficiently large, there is a need for its acceleration, while maintaining the properties of the very protective coating. in many experiments thermal processing is used for acceleration of curing of polyurethane, which is difficult to implement in a coating outdoor environments [3–5]. in this case it seems more profitable variant of use of a catalyst which initially is added to the reaction mixture, accelerating the process of chemical curing of the coating. one of the most common catalytic systems is the combination of organometallic compounds and tertiary amines. often this combination is due to the synergistic effect of these compounds. the purpose of work is the determination of the influence of the concentration of tertiary amine as a catalyst on the rate of binding process of the components in the reaction for producing the polyurethane at room temperature by the method of ir spectroscopy. materials and methods of study. spectra of prepared samples were recorded on a ir-fourier spectrometer bruker alpha prefix diffusive reflection. as starting components for the preparation of the samples were taken:* nn n o o o ocn ocn nco – в качестве органометаллического катализатора был использован 1 % раствор дилаурат дибутилолова в бутилацетате, третичные амины – варьируемые количества триэтаноламина и диазобициклоундецена: pho o oh n m k oobu therefore, the establishment of the protective anti-corrosion polyurethane coatings, used in large industrial objects (bridges, overpasses, etc.) is an actual task today. the obtaining of the polyurethane occurs by the reaction of diand polyfunctional isocyanates with diand polyfunctional alcohols: o n r 1 n o oh r 2 oh o n r 1 n o oh r 2 oh ...+ + + + ... o n h r 1 n h o o r 2 o o n h r 1 n h o o r 2 o ... since the curing time of the composition is sufficiently large, there is a need for its acceleration, while maintaining the properties of the very protective coating. in many experiments thermal processing is used for acceleration of curing of polyurethane, which is difficult to implement in a coating outdoor environments [3–5]. in this case it seems more profitable variant of use of a catalyst which initially is added to the reaction mixture, accelerating the process of chemical curing of the coating. one of the most common catalytic systems is the combination of organometallic compounds and tertiary amines. often this combination is due to the synergistic effect of these compounds. the purpose of work is the determination of the influence of the concentration of tertiary amine as a catalyst on the rate of binding process of the components in the reaction for producing the polyurethane at room temperature by the method of ir spectroscopy. materials and methods of study. spectra of prepared samples were recorded on a ir-fourier spectrometer bruker alpha prefix diffusive reflection. as starting components for the preparation of the samples were taken:* aliphatic polyisocyanate on the basis of isocyanurate hexamethylenediisocyanate (desmodur n3390 of firm bayer) 90 % solution in n-butyl acetate with a mass content of isocyanate groups of 19.6 % was represented in the sale: nn n o o o ocn ocn nco the hydroxyl-bearing polyacrylate (setalux da 160x) with a mass content of hydroxyl groups of 1.6 % in the sale form. represented as 60 % solution in xylene: 274 экспериментальная часть предварительно были подготовлены 12 металлических плашек заданного размера 25,5×4,5×6,0 мм. размеры плашек были определены путем измерения геометрических параметров набора элементов пробоподготовки для записи спектров диффузного отражения. металлические плашки с одной стороны были зеркально отполированы. половина полированной стороны была покрыта подготовленным образцом с помощью специального устройства, обеспечивающего толщину полиуретанового покрытия 0,01–0,03 мм, другая половина поверхности использовалась в качестве эталона сравнения. соотношение компонентов рассчитывали по следующей формуле (в пересчете для безводного полиола): p p m m ca 1 3 б б= ⋅ ⋅ где ра – количество полиола, г; рб – количество изоционата, г; м1 – молекулярная масса изоционатных групп, 42 а.е.м.; м3 – молекулярная масса гидроксильных групп, 17 а.е.м.; б – содержание гидроксильных групп в полиоле, 1,6 %; с – содержание изоционатных групп в изоционате, 19,6 %. найденное соотношение изоционата к полиолу по массе составляет 30,63:100. учитывая содержание растворителей, использовали массовое соотношение 20,47:100. эксперимент проводился в четырех параллелях: без катализатора третичного амина, с содержанием катализатора третичного амина 0,50 %, 0,75  %, 1,00 % от массы смеси. смешивали в определенном соотношении изоционат и полиол, добавляли 1 % от массы смеси дилаурата дибутилолова 1 % раствор в бутилацетате и приливали варьируемое количество катализатора третичного амина. таким образом получили четыре параллели, где в качестве катализатора использовали триэтаноламин, и четыре параллели, где катализатор диазобициклоундецен. реакционную смесь готовили перемешиванием в течение 10 минут при комнатной температуре. ик-спектры записывались с периодичностью раз в сутки в течение 25 дней. дополнительной обработки, кроме коррекции базовой линии, не проводилось. sn o oo o n oh oh oh n n as organometallic catalyst was used 1 % solution of dilaurate dibutylamine in butyl acetate, the tertiary amines are variable amounts of triethanolamine and diazobicycloundezen. the experimental part in advance 12 metal dies of a given size of 25.5×4,5×6,0 mm had been prepared. the sizes of dies were determined by measuring of the geometric parameters of the set of elements of the sample preparation for the recording of spectra of diffuse reflection. metal dies on one side were mirror polished. half the polished side was covered with the prepared sample using a special device enabling the thickness of the polyurethane coatings of 0.01–0.03 mm, the other half surface was used as a standard of comparison. the ratio was calculated by the following formula (calculated to anhydrous polyol): where pa is the number of polyol, g; pb is the number of isocyanate derivatives, g; m1 is the molecular weight of isocyanate groups 42.e.m.; m3 is the molecular weight of the hydroxyl groups 17.e.m.; b is the content of hydroxyl groups in the polyol, 1,6%; с is the content of isocyano groups in the isocyanate, 19,6%. the founding ratio of isocyanate derivatives was to poliol by mass is 30,63:100. given the content of solvents the mass ratio used 20,47:100. the experiment was conducted in 4 parallel: without catalyst of tertiary amine, with content of catalyst of tertiary amine, 0.50 %, 0.75 %, 1.00 % of the mass of the mixture. isocyanate and polyol were mixed in a specific ratio, were added 1 % by mass of the mixture dilaurate dibutylamine 1 % solution in butyl acetate and the variable number of catalyst of tertiary amine was poured. so 4 parallels were got, where as the catalyst there was used 275 результаты и обсуждение оценка химического связывания компонентов проводилась на основании изменения концентрации изоцианата, которая определялась по интенсивности полосы поглощения изоцианатной группы при 2291 см–1 [6]. процесс образования полиуретана считался законченным, когда данная полоса поглощения не просматривалась на спектре (рис. 1). на рис. 2, 3 представлены графики изменения содержания полосы поглощения ncoгруппы во времени. как видно на графиках, скорость химического отверждения увеличивается при повышении концентрации рис. 1. сравнение ик-спектров образца, не содержащий триэтаноламин, в начале и в конце опыта рис. 2. зависимость интенсивности полосы поглощения от времени в образце, содержащем различные концентрации триэтаноламина: № 1 – 0 %; № 2 – 0,5 %; № 3 – 0,75 %; № 4 – 1 % 276 катализатора. изоцианатные группы крайне реакционноспособны и быстро взаимодействуют с веществами, которые содержат гидроксильные и аминогруппы. это взаимодействие изоцианатных групп и гидроксильных или аминогрупп агентов роста цепи приводит к образованию большего числа уретановых связей. следовательно, время на химическое отверждение реакционной смеси полимера требуется меньше при большем содержании соответствующего катализатора. стоит отметить, что физическое отверждение наблюдается через сутки после нанесения образца, тогда как химическое протекало намного дольше. физическое отверждение оценивали по оставляемой ногтем полосе на образце полиуретана. в полученном исследовании химическое отверждение полимерной композиции наблюдалось быстрее при использовании в качестве катализатора триэтаноламина. стоит отметить также, что триэтаноламин стоит дешевле, чем диазобициклоундецен, что объясняет его широкую распространенность в промышленном производстве. полученные экспериментальные данные могут быть использованы для оптимизации технологии нанесения полиуретановых защитных покрытий и позволят прогнозировать время полного связывания компонентов реакционной смеси для достижения оптимальных физико-механических показателей. * авторы благодарят руководство зао нпх вмп в лице вице-президента по научно-инновационной работе д. х. н. д. н. кожевникова за предоставленные объекты исследования и проявленный интерес к научно-исследовательской активности студентов хти урфу. рис. 3. зависимость интенсивности полосы поглощения от времени в образце, содержащем различные концентрации диазобициклоундецена: № 1 – 0 %; № 2 – 0,5 %; № 3 – 0,75 %; № 4 – 1 % 277 bibliography 1. wright p., cumming a. polyurethane elastomers. per. from english. under the editorship of doctor. chem. sciences n. p. apukhtina. l., «chemistry». 1973. 304 p. 2. lipatov yu. s., kercha yu. yu., sergeeva l. m. structure and properties of polyurethane. «naukova dumka». kiev, 1970. p. 37–52. 3. melent’ev s. v., malinovskaya t. d., volokitin o. g. the investigation of the polyurethane bindering composite fuel coating by the method of ir spectroscopy. the collection of materials of the x international conference of students and young scientists «prospects of fundamental sciences». tomsk, 2013. p. 388–390. 4. lipatova t. e., bakalo l. a. progress in the chemistry of polyurethanes. kiev: sciences. dumka, 1972. p. 195–213. 5. todosiichuk t. t., kosyanchuk l. f., antonenko o. i., yashchenko l. n., menieres g. ya., getmanchuk i. p., gorbatenko a. n. optimization of polyurethane curing opticallytransparent compositions. journal of physical chemistry. 2012;2(20121):49–52. 6. dechant i., dance r. infrared spectroscopy of polymers. m.: chemistry. 1976. 459 p. cite this article as (как цитировать эту статью): korshunova n. a. tukhvatullina r. f., el’tsov o. s. the study of the curing of the polyurethane coating by method of ir spectroscopy. chimica techno acta. 2016;3(4): 268–277. cta_v3_№1.cdr 30 d o i: 1 0. 15 82 6/ ch im te ch .2 01 6. 3. 1. 00 3 v. tkach1,2, c. s. de oliveira 2, j. maia 2, soares b. gunter 3, r. ojani 4, p. i. yagodinez1 1 chernovitsky national university, ukraine 2 federal university of state of mato grosso do sul, brazil 3 federalny the state university of rio de janeiro, brazil 4 university of mazandaran, islamic republic of iran e-mail: nightwatcher2401@gmail.com the mathematical description of the electrosynthesis of composites of oxy-hydroxycompounds cobalt with polypyrrole overooxidazed the electrosynthesis of the composite with of the overoxidized polypyrrole with cobalt oxy-hydroxide in strongly acidic media has been described mathematically, using linear stability theory and bifurcation analysis. the steadystates stability conditions and oscillatory and monotonic instability requirements have been described too. the system´s behavior was compared with behavior of other systems with overoxidation, electropolymerization of heterocyclic compounds and electrosynthesis of the cobalt oxy-hydroxides. keywords: cobalt, polypyrrole, overoxidation, oscillations, stable steady-state. © tkach v., de oliveira c. s., maia j., gunter soares b., ojani r., yagodinez p. i., 2016 introduction electrically conducting or conducting polymers (cp) occupy their place among the most studied materials during the last 50 years [1–4], due to their ability to combine the properties of plastics (flexibility and corrosion resistance) with metallic conductivity, so they are called synthetic metals. another advantage that they possess is the ease of modification, giving them a wide and rich range of applications, from anticorrosive coatings to sensors and biosensors [5–12]. on the other hand cobalt is one of the most commonly used metals [13-14]. its oxy-hydroxycompounds, in the form of films, can be used as anticorrosion coatings, as well as the surfaces for photoelectrocatalysis, due to to their intensively black color [15–16], therefore, their composites with conducting polymers should also exhibit interesting properties. however, the oxidation of compounds of bivalent cobalt to trivalent occurs at relatively high potentials (from +1.6 v), 31 № 1 | 2016 chimica techno acta in which some conducting polymers, such as polypyrrole [17–18], undergo a process of so-called “overoxidation”, known as reconfiguration of the conjugated system in the polymer according to the following mechanism. thus overoxidative polypyrrole conducts electricity worse than neutral. another problem may be caused by electrochemical oscillatory and monotonic instabilities, capable to accompany the processes of electrochemical oxidation of small organic molecules (including electropolymerization [19–28]), and conducting polymers [29–32]. the oscillations also accompany the process of coo(oh) formation [15–16]. the study of their causes is one of the key stages to determine the most probable mechanism of this process. so far, such phenomena has gained only phenomenological interpretation, which, though it may proceed from a logical conviction, has no solid theoretical justification, that can be given only by analyzing mathematical models, can adequately describe the process, which will be done in this work. this analysis can explain the behavior of such systems and (as a consequence of the theorem of kirpichev and guchman) compare them with other similar systems are described, for example in [33–49]. system and model for the mathematical description of potentiostatic electrosynthesis of the composite of the overoxidized polypyrrole with coo(oh), from neutral polypyrrole in strongly acidic media without fluorine ions, we introduce three variables: c – concentration of ions of bivalent cobalt in the surface layer; θ – degree of surface filling overoxidized polypyrrole; h is the concentration of protons in the surface layer. to simplify the model, we suppose that the reactor is intensively stirring, and the supporting electrolyte is in excess, allowing neglect the influence of convective and migration flows. the thickness of the surface layer, the concentration profile of cobalt salts and protons, assumed to be linear, is constant and equal to δ. the protons diffuse in surface layer by their diffusion and are formed as a result of the process of overoxidation, their concentration in the surface layer decreases due to proton attack of overoxidative polypyrrole. thus, considering the first law and fick coefficient modeling related to electric double layer (edl), the balance equation of the concentration of protons will look like: dh dt d h h r ro a= −( )+ −       2 0d d , (1) where h0 is the concentration of protons in the bulk solution, ro is the speed of the process of overoxidation, ra is the rate of proton attack of overoxidative polymer. the conventional conductive polymer, occupying in the beginning of the reaction the entire electrode, overoxidizes. thus, overoxidated polymer interacts with the cobalt salt, forming a composite with the product of its oxidation, and is attacked by protons. thus, the balance equation for the concentration of the overoxidative polymer can be written as (1–2) the mathematical description of the electrosynthesis of composites of oxy-hydroxycompounds cobalt with polypyrrole overooxidazed 32 № 1 | 2016 chimica techno acta d dt r r ro a c q = − −( ) 1 г . (2) in which rc is the reaction rate of the composite formation, and г is the polymer maximum surface concentration. the cobalt salt diffuses to the anode, and then oxidized in the overoxidative polypyrrole with the formation of the composite and the overoxidation product. thus, the balance equation of its concentration in the subsurface layer can be written as: dc dc c c rc= −( )−       2 0d d ∆ , (3) being c0 is the concentration of the cobalt salt in the solution bulk. the rate of the correspondent reactions can be expressed as: r k h n f rt o o= −      ( ) exp1 1 0θ ϕ r ka a h= q . r k n f rt c c c=      θ ϕ exp ,2 0 (4–6) where the k parameters represent rate constants of respective reactions, parameters n is the number of electrons transferred in electrochemical processes, φ0 is the potential drop of the edl, in comparison with the potential of zero charge f = na · e is the number of faraday. differential equations (1–3) resemble the systems of equations, described for the case of polypyrrole overoxidation in a strongly acidic media [33], and for the case of the electrosynthesis of oxyhydroxycompounds of cobalt [34], so it is possible to confirm the third theorem of similarity. however, in order to prove the behavior of such systems, it is necessary to compare the investigation of the mentioned systems with the system of equations (1–3), as will be illustrated below. results and discussion in order to research the behavior of the system with potentiostatic electrosynthesis of composite of coo(oh) – the overoxidative polypyrrole in strongly acidic media, it is necessary to investigate the system of differential equations (1–3), taking in account the algebraic relations (4–6), using linear stability theory. functional jacobi matrix, the elements of which are computed for a stationary state is represented in the form: a a a a a a a a a 1 1 1 2 2 2 3 3 3 1 2 3 1 2 3 1 2 3       , (7) where: a d k n f rt ko a1 1 0 1 2 1= − + −      −      δ δ θ ϕ θ( ) exp . a k h n f rt k h n f rt o o1 1 0 1 0 2 2 =      +      −δ ϕ θα ϕ exp exp kk ha       . a13 0= . a k n f rt ko a2 1 0 1 1 1= −( )      −      г θ ϕ θexp . a k h n f rt k h n f rt o o 2 1 0 1 0 2 1 =      +    +    г exp exp ϕ θα ϕ   − − −      −    k h k c n f rt k c n f rt a c cexp exp 2 0 2 0ϕ αθ ϕ       . a k n f rt c2 2 0 3 1 = −            г θ ϕ exp a31 0= . tkach v., de oliveira c. s., maia j., gunter soares b., ojani r., yagodinez p. i. 33 № 1 | 2016 chimica techno acta a k c n f rt k c n f rt c c3 2 0 2 0 2 2 = −      −      δ ϕ αθ ϕ exp exp       a k n f rt c3 2 0 3 2 = −      −      δ θ ϕ δ exp . ∆ (8–15) the oscillatory instability in this system is possible, because the necessary conditions of hopf bifurcation may be satisfied. they are performed in the case of the main diagonal of the jacobian positive elements: in this system there are three positive elements: k n f rt o ( ) exp ,1 0 1 0−      >θ ϕ in case of strong effects of the process of overoxidation on del, leading to the autocatalytic filling of the electrode surface with the overoxidated polypyrrole. this can happen if the polypyrrole derivative is a strong reducing agent and thus can form fluctuations k h n f rt o exp , 1 0 0 ϕ     > because of the possibility of autocatalytic formation of protons in the process of overoxidation of polypyrrole. this factor was considered as a factor self-oscillating behavior of the overoxidative polypyrrole in [33, 35–36], and this system it also presents. −      >k c n f rt c αθ ϕ exp ,2 0 0 n the case of strong influences on the dec process of oxidation of cobalt salts to hydroxy-hydroxycobalamine, which, incidentally, has already been described in [15, 16, 34]. in this case because of the greater possibility of positive feedback, the probability of self-oscillations in this system will be higher than in case of simple potentiostatic overoxidation of polypyrrole or the anodic oxidation of cobalt salts. the stability of the stationary state we analyzed according to the criterion of routh-hurwitz. to avoid cumbersome expressions, we introduce new parameters so as the determinant of the jacobian matrix can be written as: 4 0 0 2 1 3 3 2 δ κ κ г − + − − − − − χ σ χ σ σ λ σ λ . (17) using the condition det j < 0, which can be derived from the criterion of routh-hurwitz, we obtain the condition of stability of stationary state in the form of inequalities that can be resolved relative to the diffusion coefficient of cobalt salt κ2: − < − − − κ κ κ κ2 3 1 3 1 1 3 λς χ σ σ χς ( ) . (18) or: κ κ κ κ2 > − − − − λς χ σ σ χς λ3 1 3 1 1 3 ( ) . (18) thus, the stability of the stationary state, in this case, is supported by the more rapid diffusion of cobalt salts than protons and by high oxidation rate, which shifts the right part of inequality towards more negative values (in this case, the left part of the inequality is positive). so, at high concentrations of cobalt salts, the ph-dependence of stability of the stationary state decreases drastically. thus, for an optimal synthesis of the composite, it is necessary to use a concentration of cobalt salts with a small margin relative to the concentration of pyrrole and ph, but the composite will contain a quite significant proportion of the oxy-hydroxy cobalt compound. the mathematical description of the electrosynthesis of composites of oxy-hydroxycompounds cobalt with polypyrrole overooxidazed 34 № 1 | 2016 chimica techno acta the ph-decreasing leads to an increase in the value of the fraction in the right part of the inequality and, at relatively low concentrations of cobalt salts, also reduces the stabilization trend of a stationary state, even including the system leave from the stationary state, which is displayed at the point of a monotonic instability, occurring in the condition of: κ κ κ κ2 3 1 3 1 1 3 > − − − − λς χ σ σ χς λ ( ) , (19) represented by a n-shaped part of the voltamperogram. in a common system with potentiostatic overoxidation of polypyrrole, contrarily to this system, it is impossible. del factors also strongly affect the stability of the stationary state in this system. for example, in case of strong effects of electrochemical oxidation of cobalt salts on the structure of the dec, the parameter λ will have negative values which will lead to the exit of the stationary state of the field of stability. this factor is also present in other similar systems. the presence of fluoride ions. as known, oxy-hydroxycompound of cobalt is unstable in the presence of fluoride ions, and dissolves with the formation of the complex [cof6] 3– , according to the total equation: coo(oh) + 6hf → → h3[cof6] + 2h2o. 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description of the electrosynthesis of composites of oxy-hydroxycompounds cobalt with polypyrrole overooxidazed 38 у д к 6 69 -9 7+ 55 491 .2 в. ткач1,2 , с. с. де оливейра2, ж. майя2, б. гюнтер соарес3, р. ожани4, п. и. ягодинец1 1черновицкий национальный университет, украина 2федеральный университет штата мату-гроссу-ду-сул, бразилия 3федеральный университет штата рио-де-жанейро, бразилия 4университет мазендерана, исламская республика иран e-mail: nightwatcher2401@gmail.com математическое описание электросинтеза композитов окси-гидроксисоединений кобальта с переокисленным полипирролом электросинтез композита переокисленного полипиррола с окси-гидроксисоединениями кобальта в сильнокислой среде был описан математически, с использованием линейной теории устойчивости и бифуркационного анализа. были описаны условия устойчивости стационарного состояния, а также автоколебательной и монотонной неустойчивости. поведение системы было сравнено с поведением других систем с переокислением, электрополимеризацией гетероциклических соединений, а также электросинтезом окси-гидроксисоединений кобальта. ключевые слова: кобальт, полипиррол, переокисление, автоколебания, устойчивое стационарное состояние. © ткач в., де оливейра с. с., майя ж., гюнтер соарес б., ожани р., ягодинец п. и., 2016 введение электропроводящие или проводящие полимеры (пп) являются одними из наиболее изучаемых материа лов на протяжении последних 50 лет [1–4], что связано с их способностью соединять в себе свойства пластмасс (гибкость и противокоррозионную устойчивость) с металлической проводимостью, благодаря чему их называют синтетическими металлами. другим их преимуществом является легкость в модификации, благодаря чему у них широкий и богатый спектр применения, начиная от противокоррозионных покрытий и заканчивая сенсорами и биосенсорами [5–12]. с другой стороны, кобальт – один из наиболее часто применяемых ме39 № 1 | 2016 chimica techno acta таллов [13–14]. его окси-гидроксисоединения в форме пленок могут применяться в качестве противокоррозионных покрытий, а также в качестве поверхностей-носителей для фотоэлектрокатализа, благодаря своему интенсивно черному цвету [15–16], поэтому их композиты с проводящими полимерами также должны проявлять интересные свойства. однако окисление соединений двухвалентного кобальта до трехвалентного происходит при довольно высоком потенциале (от +1,6 в), при котором некоторые проводящие полимеры, такие как полипиррол [17–18], проходят процесс так называемого «переокисления», то есть смены конфигурации сопряженной системы в  полимере согласно следующему механизму: при этом переокисленный полипиррол проводит ток хуже, чем непереокисленный. другой проблемой являются электрохимические неустойчивости – автоколебательная и (или) монотонная, которые могут сопровождать процессы электроокисления как малых органических молекул, в том числе электрополимеризацию [19–28], так и проводящих полимеров [29–32]. автоколебания также сопровождают процесс образования coo(oh) [15– 16]. изучение их причин является одним из ключевых этапов определения наиболее вероятного механизма данного процесса. до сих пор такие явления получали исключительно феноменологическую трактовку, которая, хоть и может исходить из логических убеждений, не имеет твердых теоретических обоснований, которые могут быть даны только с помощью анализа математической модели, способной адекватно описать процесс, что и будет показано в данной работе. этот анализ может объяснить поведение подобных систем (как следствие из теоремы кирпичева – гухмана), а  также сравнить их с другими аналогичными системами, описанными, например в [33–49]. система и ее модель для математического описания потенциостатического электросинтеза композита переокисленного полипиррола с coo(oh) из обычного полипиррола в сильнокислой среде без ионов фтора введем три переменные: c – концентрация ионов двухвалентного кобальта в приповерхностном слое; θ – степень заполнения поверхности переокисленным полипирролом; h – концентрация протонов в приповерх ностном слое. с целью упрощения модели мы вводим допущения того, что реактор находится при постоянном перемешивании, а фоновый электролит находится в избытке, что позволяет пренебречь влиянием конвективного и миграционного потока. при этом толщина приповерхностного слоя, концентрационный профиль солей ко(1-2) математическое описание электросинтеза композитов окси-гидроксисоединений кобальта с переокисленным полипирролом 40 № 1 | 2016 chimica techno acta бальта и протонов в котором по допущению является линейным, постоянна и равна δ. протоны попадают в диффузионный приповерхностный слой вследствие диффузии и образуются в результате процесса переокисления, их концентрация в приповерхностном слое уменьшается из-за протонной атаки переокисленного полипиррола. таким образом, учитывая первый закон фика и коэффициент моделирования, относящийся к двойному электрическому слою (дэс), уравнение баланса концентрации протонов будет выглядеть как: dh dt d h h r ro a= −( )+ −       2 0d d , (1) где h0 – это концентрация протонов в  объеме раствора, ro – скорость процесса переокисления, ra – скорость протонной атаки переокисленного полимера. обычный проводящий полимер, который в начале реакции занимает весь электрод, переокисляется. при этом переокисленный полимер взаимодействует с солью кобальта, образуя композит с продуктом ее окисления, а также атакуется протонами. таким образом, балансовое уравнение для концентрации переокисленного полимера запишется как: d dt r r ro a c q = − −( ) 1 г . (2) где rc – реакция образования композита, а γ – максимальная поверхностная концентрация полимера. соль кобальта диффундирует к  аноду, а потом окисляется на переокисленном полипирроле с образованием его композита с продуктом переокисления. таким образом, уравнение баланса ее концентрации в приповерхностном слое запишется как: dc dc c c rc= −( )−       2 0d d ∆ , (3) где с0 – концентрация соли кобальта в объеме раствора. скорости соответствующих реакций можно вычислить как: r k h n f rt o o= −      ( ) exp1 1 0θ ϕ r ka a h= q . r k n f rt c c c=      θ ϕ exp ,2 0 (4–6) где параметры k отображают константы скоростей соответствующих реакций, параметры n – количество электронов, переданных в электрохимических процессах, φ0 – перепад потенциала дэс, по сравнению с потенциалом нулевого заряда, f = na · e – число фарадея. дифференциальные уравнения (1–3) напоминают по виду уравнения систем, описанных как для случая переокисления полипиррола в сильнокислой среде [33], так и для случая электросинтеза окси-гидроксисоединений кобальта [34], что, можно сказать, подтверждает действие третьей теоремы подобия. однако для того, чтобы доказать подобное поведение систем, нужно сопоставить исследования указанных систем и системы уравнений (1–3), что будет показано ниже. результаты и обсуждение чтобы исследовать поведение системы с потенциостатическим электросинтезом композита coo(oh) – переокисленный полипиррол в сильткач в., де оливейра с. с., майя ж., гюнтер соарес б., ожани р., ягодинец п. и. 41 № 1 | 2016 chimica techno acta нокислой среде, нужно разобрать сис тему дифференциальных уравнений (1–3) с учетом алгебраических соотношений (4–6) с помощью линейной теории устойчивости. функциональная матрица якоби, элементы которой вычислены для стационарного состояния представляется в виде: a a a a a a a a a 1 1 1 2 2 2 3 3 3 1 2 3 1 2 3 1 2 3       , (7) где a d k n f rt ko a1 1 0 1 2 1= − + −      −      δ δ θ ϕ θ( ) exp . a k h n f rt k h n f rt o o1 1 0 1 0 2 2 =      +      −δ ϕ θα ϕ exp exp kk ha       . a13 0= . a k n f rt ko a2 1 0 1 1 1= −( )      −      г θ ϕ θexp . a k h n f rt k h n f rt o o 2 1 0 1 0 2 1 =      +    +    г exp exp ϕ θα ϕ   − − −      −    k h k c n f rt k c n f rt a c cexp exp 2 0 2 0ϕ αθ ϕ       . a k n f rt c2 2 0 3 1 = −            г θ ϕ exp a31 0= . a k c n f rt k c n f rt c c3 2 0 2 0 2 2 = −      −      δ ϕ αθ ϕ exp exp       a k n f rt c3 2 0 3 2 = −      −      δ θ ϕ δ exp . ∆ (8–15) автоколебательная неустойчивость в данной системе возможна, так как могут выполняться необходимые условия бифуркации хопфа. они выполняются в случае наличия в главной диагонали якобиана положительных элементов. в данной системе есть три положительных элемента: k n f rt o ( ) exp ,1 0 1 0−      >θ ϕ в случае сильных влияний процесса переокисления на дэс, приводящих к самоускоренному заполнению поверхности электрода переокисленным полипирролом. это может произойти, если данное производное полипиррола является сильным восстановителем, и таким образом могут образовываться колебания k h n f rt o exp , 1 0 0 ϕ     > ввиду возможности автокаталитического образования протонов в процессе переокисления полипиррола. этот фактор рассматривался как фактор автоколебательного поведения при переокислении полипиррола в [33, 35–36] и в данной системе он тоже присутствует. −      >k c n f rt c αθ ϕ exp ,2 0 0 в случае сильных влияний на дэс процесса окисления соли кобальта до окси-гидроксисоединения, что, кстати, уже было описано и в [15, 16, 34]. при этом ввиду большей возможности положительной обратной связи, вероятность автоколебаний в данной системе будет выше, чем в случае простого потенциостатического пере окисления полипиррола или анодного окисления соли кобальта. устойчивость стационарного состояния анализируем по критерию рауса – гурвица. для этого, чтобы математическое описание электросинтеза композитов окси-гидроксисоединений кобальта с переокисленным полипирролом 42 № 1 | 2016 chimica techno acta избежать появления громоздких выражений, вводим новые параметры таким образом, что определитель матрицы якоби запишется как: 4 0 0 2 1 3 3 2 δ κ κ г − + − − − − − χ σ χ σ σ λ σ λ . (17) используя условие det j < 0, которое можно вывести из критерия рауса – гурвица, мы получим условие устойчивости стационарного состояния в виде неравенства, которое можно разрешить относительно параметра диффузии соли кобальта κ2: − < − − − κ κ κ κ2 3 1 3 1 1 3 λς χ σ σ χς ( ) . (18) или: κ κ κ κ2 > − − − − λς χ σ σ χς λ3 1 3 1 1 3 ( ) . (18) таким образом, устойчивость стационарного состояния поддерживается более быстрой диффузией соли кобальта, чем протонов, а также высокой скоростью ее окисления, которая смещает правую часть неравенства в сторону более отрицательных значений (при этом левая часть неравенства остается положительной). при этом при высокой концентрации соли кобальта рн-зависимость устойчивости стационарного состояния резко убывает. таким образом, для оптимального синтеза композита нужно использовать концентрацию соли кобальта с небольшим запасом относительно концентрации пиррола и рн, однако в композите будет довольно значительная доля окси-гидроксисоединения кобальта. понижение рн приводит к увеличению значения дроби в правой части неравенства и, при относительно малых концентрациях соли кобальта и уменьшении вероятности стабилизации стационарного состояния, включая даже выход системы из стационарного состояния, который отображается в точке монотонной неустойчивости, условие появления которой: κ κ κ κ2 3 1 3 1 1 3 > − − − − λς χ σ σ χς λ ( ) . (19) для обычной системы с потенцио статическим переокислением полипиррола, в отличие от данной системы, она невозможна. факторы дэс тоже сильно влияют на устойчивость стационарного состояния в данной системе. например, в случае сильных влияний электроокисления соли кобальта на структуру дэс, параметр λ будет иметь отрицательные значения, которые приведут к выходу стационарного состояния из области устойчивости. этот фактор присутствует и в других подобных системах. присутствие ионов фтора. как известно, окси-гидроксисоединение кобальта неустойчиво в присутствие ионов фтора, ибо растворяется с образованием комплекса [cof6] 3– по суммарному уравнению: coo(oh) + 6hf → → h3[cof6] + 2h2o. (20) в таком случае данная модель уже не описывает поведение композита. устойчивость композита в присутствие ионов фтора будет рассмотрена в одной из наших следующих работ. ткач в., де оливейра с. с., майя ж., гюнтер соарес б., ожани р., ягодинец п. и. 43 № 1 | 2016 chimica techno acta выводы устойчивость стационарного состояния для данной системы поддерживается относительно высоким рн и высокой концентрацией ионов кобальта в приповерхностном слое, а также общим для всех подобных систем фактором отсутствия сильных влияний электрохимических процессов на дэс. автоколебательное поведение для данной системы является возможным, будучи вызванным не только автокаталитическим образованием протонов, как для общего случая переокис ления проводящих полимеров, но и  влиянием на дэс электрохимических реакций – переокисления и окисления соли кобальта. монотонная неустойчивость для данной системы реализуется при относительно низких рн и сильных влияниях электрохимических реакций на дэс. 1. sadki s. 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isomerization sensors, based on conduction polymers. anal. bioanal. electrochem. 2014;6(3):273–283. 47. tkach v., kumara swamy b., ojani r., blanes m., yagodynets´ p. orbital elec. j. chem. 2015;7:1. 48. tkach v., ojani r., nechyporuk v., yagodynets p. rev. colomb. cien. quím. farm. 2014;43:35. 49. tkach v., ojani r., nechyporuk v., yagodynets´ p. orbital. elec. j. chem. 2014;6:142. математическое описание электросинтеза композитов окси-гидроксисоединений кобальта с переокисленным полипирролом structure of the solubility diagram in the na2so4-na2co3-nahco3-h2o system at 0, 25 and 50 ?? 104 l. soliev, m. t. jumaev, r. o. turaev, h. r. makhmadov, b. b. dzabborov tajik state pedagogical university named after s. ayni 121 prospect rudaki, dushanbe, 734003, tajikistan e-mail: soliev.lutfullo@yandex.com; jumaev_m@bk.ru structure of the solubility diagram in the na 2 so 4 ‑na 2 co 3 ‑nahco 3 ‑h 2 o system at 0, 25 and 50 °с the solubilities in invariant points of na 2 so 4 -na 2 co 3 -nahco 3 -h 2 o system were investigated at 0, 25 and 50 °с. the phase equilibria in the said system were discussed, and phase diagrams at given temperatures were constructed. keywords: solubility, phase equilibria, liquid phase, chemical analysis, crystallo-optical analysis, phase diagram received: 07.07.2018. accepted: 23.07.2018. published: 30.07.2018. © soliev l., jumaev m. t., turaev r. o., makhmadov h. r., dzabborov b. b., 2018 introduction four-component system na2so4na2co3-nahco3-h2o is a part of more complex six-component system na, са// so4, co3, hco3, f-h2o. equilibria in the latter determine the conditions of  aluminium production liquid waste disposal. the waste water of cryolite recycling plants contains fluorides, carbonates, bicarbonates and sulphates of sodium and calcium [1, 2]. crystallization and dissolution processes in such waste water are governed by the phase equilibria both in  six-component system na, са//so4, co3, hco3, f-h2o and in its constituents, fiveand four-component systems. in our earlier studies [3, 4] the phase diagrams in similar systems were constructed. this study presents the results of investigation of na2so4-na2co3-nahco3-h2o system at 0, 25 and 50 °c using solubility method. the main goal of this work was to establish the concentration parameters of geometrical images and separation of the crystallization fields of individual equilibrium solids in the phase diagrams. results and discussion the system investigated contains the following equilibrium solid phases: nk – nahcolite nahco3 (0, 25, 50 °c); mb – mirabilite na2so4·10h2o, с·10 – na2co3·10h2o (0, 25 °c); tr – throne nahco3·na2co3·2h2o (25, 50  °c); th  – thenardite na2so4, bur  – burkeite 2na2so4·na2co3, с·1  – na2co3·h2o (50 °c) [5, 6]. the following reagents were used in  xperiments: na2so4·10h2o (“chemically pure” grade), na2со3 (“pure” grade), nahсо3 (“pure” grade). the xperiments were carried out according to “saturation method” described in detail elsewhere [8]. based on the data available [5, 6], we prepared the mixtures of precipitates with saturated solutions according to the invarid o i: 1 0. 15 82 6/ ch im te ch .2 01 8. 5. 2. 02 soliev l., jumaev m. t., turaev r. o., makhmadov h. r., dzabborov b. b. chimica techno acta. 2018. vol. 5, no. 2. p. 104–108. issn 2409–5613 105 fig. 1. micrographs of equilibrium solid phases, corresponding to the invariant points of system na2so4-na2co3-nahco3-h2o at 0 (1, 2, 3, 8), 25 (1, 2, 3, 4, 9, 10) and 50 (2, 4, 5, 6, 7, 11, 12, 13) °c 106 ant points in the three-component systems na2so4-na2co3-h2o, na2so4-nahсо3h2o and na2co3-naнсо3-н2о at 0, 25 and 50 °c. then, transferring the non-variant points from the three-component section to the four-component section [3, 4], the saturated solutions prepared had been kept in a thermostat at a given temperature until the equilibrium was reached. thermostating was carried out in u-8 ultra-thermostat. stirring was performed using a  pd-09 magnetic stirrer for  50– 120 h. temperature was maintained with 0.1 °c accuracy using a contact thermometer. crystallization of solid phases was observed with a  polam-r 311 microscope. after the equilibrium in  a  given system was achieved, the solid phases were photographed with a sony-dsc-s500 digital camera. equilibrium was assumed to be attained when the phase composition of the precipitates was constant. a buchner funnel with an ash-free filter paper (blue band) connected to  a  vacuum pump has been used for  separation of  the liquid phase and solid phase. the precipitate after filtration was washed with 96 % ethanol and then dried at 120 °с. the table 1 solubility in central (invariant) points in system na2so4-na2co3-nahco3-h2o № of points structure of a liquid phase, mas. % phase composition of depositsna2so4 na2со3 naнсо3 h2o 0 °c e1 3 2.73 – 5.58 91.69 mb+nk e2 3 – 5.6 4.6 89.8 nk+ с·10 e3 3 2.8 6.0 – 91.2 с·10+mb e1 4 2.12 5.13 4.37 88.38 mb+nk+с·10 25 °c e1 3 16.4 18.3 – 65.3 mb+с·10 e2 3 20.68 – 4.16 75.16 nk+mb e3 3 – 17.62 4.62 77.76 tr+nk e4 3 – 22.46 2.84 74.7 с·10+tr e1 4 21.2 20.07 5.51 50.22 mb+tr+с·10 e2 4 20.9 22.54 4.77 50.68 nk+tr+mb 50 °c e1 3 29.65 – 4.05 66.30 тh+nk e2 3 22.47 10.52 – 67.61 тh+bur e3 3 5.87 28.52 – 65.61 bur+с·1 e4 3 – 16.92 6.30 76.78 nk+tr e5 3 – 31.80 0.85 67.35 tr+с·1 e1 4 12.64 21.31 2.51 54.76 тh+nk+bur e2 4 4.30 24.36 0.64 58.03 bur+tr+с·1 e3 4 7.52 9.14 3.24 60.08 tr+nk+bur 107 standard techniques used for the chemical analysis of products are described elsewhere [8–10]. results of  the crystallooptical analysis [11] of equilibrium solid phases (microphoto) are presented in fig. 1, and the results of the chemical analysis of the saturated solutions are given in table 1. on the basis of  the data obtained, the diagrams of solubility in the na2so4na2co3-nahco3-h2o system at 0, 25 and 50 °c were constructed. salt parts of these diagrams are shown in  fig.  2. the location of non-variant points on the diagrams were determined by  the center of  mass method [12]. fig. 2. solubility diagrams in na2so4-na2co3nahco3-h2o system: а – at 0 °c; b – at 25 °c; c – at 50 °c a b c 108 references 1. morozova va, rzhechitskii ep. [solubility in the naf – na2so4 – nahco3 – h2o system at 0 °c]. zhurnal prikladnoi khimii [journal of applied chemistry]. 1976;49(5):1152–4. russian. 2. morozova va, rzhechitskii ep. [solubility in the systems naf – nahco3 – h2o, naf – na2so3 – h2o and naf –na2co3 – h2o at 0 °c]. zhurnal neorganicheskoi khimii [russ j inorg chem]. 1977;22(3):873–4. russian. 3. soliev l, tursunbadalov sh. phase equilibria in the na, k||so4, co3, hco3-h2o system at 25°c. russ j inorg chem. 2008;53(5):805–11. 4. soliev l, dzhumaev mt, turaev ro. fazovye ravnovesiya sistemy na2so4-na2co3nahco3-h2o pri 50 °c [phase equilibria in na2so4-na2co3-nahco3-h2o system at 50 °c]. vestnik tadjikckogo natsional᾿nogo universiteta (seriya estesvennikh nauk) [bulletin of the tajik national university (series of natural sciences)]. 2016;1(3):200. russian. 5. spravochnik eksperimental”nykh dannykh po rastvorimosti mnogokomponentnykh vodno-solevykh system [reference book on experimental data for solubility in multicomponent water-salt systems]. vol. 1. saint-petersburg: khimizdat, 2003. 1151 p. russian. 6. spravochnik eksperimental”nykh dannykh po rastvorimosti mnogokomponentnykh vodno-solevykh system [reference book on experimental data for solubility in multicomponent water-salt systems]. vol. ii., books. 1–2. saint-petersburg: khimizdat, 2004. 1247 p. russian. 7. goroshchenko yag, soliev l, gornikov yui. opredelenie polozheniya nonvariantnykh tochek na diagrammakh rastvorimosti metodom donasyshcheniya [determination of the invariant points” positions on solubility diagrams using the presaturation method]. ukrainskii khimicheskii zhurnal [ukrainian journal of chemistry]. 1987;53(6):568–71. russian. 8. aleksandrova ea. analiticheskaya khimiya [analytical chemistry]. moscow: klass, 2011. 350 p. russian. 9. knipovich yun, morachevskiy yuv. analiz mineral’novo syr’ya [analysis of raw minerals]. leningrad (ussr): goskhimizdat, 1959. 947 p. russian. 10. orlova tn, ganzha bb. metody analiza i ochistki prirodnykh i stochnykh vod. tomsk (russia): tomsk polytechnical university publishing house, 2007. 168 p. russian. 11. marakushev аа, bobrov аv, partsev nn, fenogenov an. osnovy kristallooptiki. porodoobrazuyushchie mineraly. moscow: nauchnyy mir, 2000. 316 p. russian. 12. goroshchenko yag. masstsentricheskiy metod izobrazheniya mnogokomponentnykh system [the center of mass method for multi-component systems imaging]. kiev: naukova dumka, 1982. 264 p. russian. phase equilibria in the na,ca//so4,co3,hco3–h2o system at 0 °c 24 d o i: 1 0. 15 82 6/ ch im te ch .2 01 9. 6. 1. 03 soliev l., jumaev m. t. chimica techno acta. 2019. vol. 6, no. 1. p. 24–30. issn 2409–5613 l. soliev, m. t. jumaev tajik state pedagogical university named after s. ayni, dushanbe, 734025, republic of tajikistan e-mail: soliev.lutfullo@yandex.com; jumaev_m@bk.ru phase equilibria in the na,ca//so4,co3,hco3–h2o system at 0 °c phase equilibria in the na,ca//so4,co3,hco3-h2o system have been studied at 0 °c. the studied system at 0 °c involves 4 invariant points, 13 monovariant curves and 15 divariant fields. the obtained results served as a basis for the construction of phase diagram (phase complex) of the studied system at 0 °c. keywords: system; phase equilibria; diagram; geometric images received: 12.02.2019. accepted: 05.03.2019. published: 29.03.2019. © soliev l., jumaev m. t., 2019 results and discussion the laws of  phase equilibria in the na,ca//so4,co3,hco3-h2o system are not only of scientific interest, but also necessary for elaboration of optimal conditions for halurgicol processing of natural mineral raw materials and industrial wastes containing sulfates, carbonates, hydrocarbonates of sodium and calcium. however, these equilibria have not been studied yet, and necessary information is absent in the available literature [1]. we have studied phase equilibria in the na,ca,//so4,co3,hco3-h2o system at 0 °c by the translation method which follows from the principle of compatibility of  the structural elements for  the n and n+1 component systems in one diagram [2]. according to the translation method, the subsequent (n+1) component is added to the n-component system, and the latter is translated to the n+1 component state by the transformation of geometric images of the n-component system. transformed geometric images have formed corresponding phase diagram components on  the n+1 level, according to their topological properties (fields, curved, points), taking into account the gibbs phase rule for the n+1 component system. more detailed description of  the translation method that can be used for predicting and constructing of equilibrium phase diagrams for the multicomponent water — salt systems are considered in the works [3–5]. previously, this method was used to  study the fivecomponent system [6]. five-component na,ca,//so4, co3, hco3–h2o system includes the following four 4-component systems: na2so4– na2co3–nahco3–h2o; caso4–caco3-ca(hco3)2–h2o; na,ca,//so4, co3–h2o; na,ca,//so4, hco3–h2o; na,ca,//co3, hco3–h2o. phase composition of invariant points in the aforementioned 4-component systems have been determined by both the solubility method [1] and the translation method [7–10] described earlier. 25 coexisting equilibrium solid phases, representing the invariant points in  the 4-component systems, are listed in table 1. in table 1 and further, e denotes an invariant point where the superscript denotes its multiplicity (component of  the system), and the subscript denotes its sequence number. the following notation for  the equilibrium solid phases have been used: mb  — mirabilite, na2so4  · 10h2o; cag — calcium hydrocarbonate, ca(hco3)2; gp — gypsum caso4·2h2o; nk — nakhcolite, nahco3; gl — gaylussite na2co3·caco3·5h2o; cc  — calcite caco3, c  ·  10  — tenfold hydrogenated sodium carbonate na2co3 · 10h2o. fig.  1, which is drawn based on  the data from table 1, illustrates the equilibrium phase diagram (phase complex) for the na,ca,//so4,co3,hco3-h2o system at 0 °c at the four-component compositional level, where the salt part of the system forms four-sided prism sweep. after its unification (combining identical crystallization fields of the opposite four-component systems), we obtained a schematic diagram [11] for the phase equilibrium in the na,ca//so4,co3,hco3-h2o system at 0 °c at the four-component compositional level, which is shown in fig. 2. the constructed diagram contains various geometric images (invariant points, multi-variant curves, divariant fields) for  the studied system and correspondent equilibrium solid phases at the fourcomponent compositional level. the phase composition of the precipitation of quadruple invariant points is given in table 1. the phase composition of the precipitates inside the divariant fields is shown in fig. 2. the phase composition of the sediments, corresponding to the multi-variant curves that connect four-phase invariant points, can be represented as follows: e1 4 e2 4 = mb+nk; e1 4 e5 4 = mb+c·10; e1 4 e8 4 = c·10+nk; e2 4 e3 4 = nk+gp; e2 4 e7 4 = gp+mb; e3 4 e4 4 = cag+gp; e3 4 e10 4 = nk+cag; e4 4 e6 4 = gp+cc; e4 4 e9 4 = cc+cag; e5 4 e7 4 = mb+gl; e5 4 e8 4 = gl+c·10; e6 4 e7 4 = gp+gl; e6 4 e9 4 = gl+cc; e8 4 e10 4 = nk+gl; e9 4 e10 4 = gl+cag. table 1 phase composition of precipitates for the invariant points in the 4-component systems, which are compile the complex 5-component na,ca,//so4,co3,hco3-h2o system at 0 °c invariant points solid phases in equilibrium invariant points solid phases in equilibrium na2so4–na2co3–nahco3–h2o system na,ca||so4,co3–h2o system e1 4 mb+nk+c·10 e5 4 gl+mb+c·10 na,ca||so4,hco3-h2o system e6 4 gp+gl+cc e2 4 gp+mb+nk e7 4 gl+gp+mb e3 4 gp+nk+cag na,ca||co3,hco3–h2o system caso4–caco3–ca(hco3)2–h2o system e8 4 gl+nk+c·10 e4 4 gp+cc+cag e9 4 gl+cc+cag e10 4 nk+gl+cag 26 a translation procedure [3–5] of  invariant points from the four-component compositional level to a five-component level leads to the formation of the following five invariant points with the following coexisted in equilibrium solid phases: e1 4 + e5 4 + e8 4 e1 5 = nk + mb + + c·10 + gl; e2 4 + e7 4 e2 5 = nk + mb + gp + + gl; e3 4 + e10 4 e3 5 = nk + cag + gp + + gl; e4 4 + e6 4 + e9 4 e4 5 = gp + cc + + cag + gl. the equilibrium phase diagram for the na,ca//so4,co3,hco3-h2o system at 0 °c constructed by the translation method is shown in fig. 3. the thin solid lines in fig. 3 indicate the multivariant curves belonging to the four-component compositional level. the correspondent solid phases that coexisted in  equilibrium have been shown above. the dashed lines with arrows indicate monovariant curves belonging to the fivecomponent compositional level. the equilibrium solid phases, which corresponded to these monovariant curves, are identical to the equilibrium solid phases of the translated invariant points in  the corresponding quadruple systems. the arrows on  these curves indicate the directions fig. 1. prism sweep of the salt part of equilibrium phase diagram for the na,ca// so4,co3,hco3-h2o system at 0 °c at the four-component composition level 2nahco3 2nahco32nahco3 nk nk nk e1 4 mb mb mb c·10 c·10 c·10 na2so4 na2co3 gp gp gp ca(hco3)2 ca(hco3)2ca(hco3)2 caso4 caco3 gl gl cc cc cc cagcag cag e2 4 e3 4 e5 4 e7 4 e6 4 e4 4 e10 4 e8 4 e9 4 27 fig. 2. schematic diagram for the phase equilibrium in the na,ca//so4,co3,hco3-h2o system at 0 °c at the four-component compositional level, constructed by the translation method nk e1 4 e2 4 e1 4 mb c·10 gp gl cc cag e2 4 e3 4 e3 4 e8 4 e10 4 e5 4 e7 4 e6 4 e4 4 e10 4 e8 4 e9 4 fig. 3. schematic phase diagram for the na,ca//so4,co3,hco3-h2o system at 0 °c at the five-component compositional level constructed by the translation method e1 5 e3 5 e1 4 e2 4 e2 5 e3 4 e4 5 e5 4 e7 4 e6 4 e4 4 e10 4 e8 4 e9 4 28 table 2 equilibrium solid phases and contours of the divariant fields in the na,ca//so4,co3,hco3-h2o system at 0 °c equilibrium solid phases in the fields field contours in the diagram (fig. 3) equilibrium solid phases in the fields field contours in the diagram (fig. 3) mb+nk e1 4 e1 5 e2 4 e2 5 cc+cag e4 4 e4 5 e9 4 mb+c·10 e1 4 e1 5 e5 4 mb+gl e5 4 e1 5 e7 4 e2 5 c·10+nk e1 4 e1 5 e8 4 gl+c·10 e1 4 e1 5 e8 4 nk+gp e2 4 e2 5 e3 4 e3 5 gl+gp e6 4 e4 5 e7 4 e2 5 e3 5 mb+gp e2 4 e2 5 e7 4 gl+cc e6 4 e4 5 e9 4 cag+gp e3 4 e3 5 e4 4 e4 5 gl+nk e8 4 e1 5 e2 5 e10 4 e3 5 cag+nk e3 4 e3 5 e10 4 gl+cag e9 4 e4 5 e10 4 e3 5 cc+gp e4 4 e4 5 e6 4 29 of translation. the bold lines also denote monovariant curves belonging to the fivecomponent compositional level. these lines connect five-phase invariant points; equilibrium solid phases correspondent to these lines are: e1 5 e2 5 = nk + mb + gl; e2 5 e3 5 = gp + nk + gl; e3 5 e4 5 = cag + gl + gp. table 2 shows the equilibrium solid phases and contours of the divariant fields in the na,ca//so4,co3,hco3–h2o system at 0 °c. all 15 divariant fields that characterized phase equilibria in the studied system at 0 °c were formed as a result of the translation procedure transforming monovariant curves to the five-component composition level. conclusions finally, we can conclude that studied na,ca//so4,co3,hco3-h2o system at 0 °c has been described at the four-component compositional level (a) and the five-component compositional level (b) by particular amounts of specific geometric images. compositional level a b nonvariant points 10 4 monovariant curves 15 13 divariant fields 7 15 references 1. experimental solubility data for multinary water — salt systems: handbook. st. petersburg: khimizdat; 2004. russian. 2. goroshchenko yag. the center-of-mass method for  imaging multicomponent systems. kiev: naukova dumka; 1982. russian. 3. soliev l. prediction of structure of multicomponent water-salt systems phase equilibria diagram by means of translation method. viniti № 8990-b87, 1987. 28 p. russian. 4. soliev l. prediction of phase equilibria in a marine type multinary system by the translation method, part 1. dushanbe: tspu; 2000. russian. 5. soliev l. prediction of phase equilibria in a marine type multinary system by the translation method, part 2. dushanbe: tspu; 2000. russian. 6. tursunbadalov sh., soliev l. phase equilibria in the quinery na,k||so4,co3,hco3–h2o system at 75 °c. j solution chem. 2015;44(8):1626–39. doi:10.1007 / s10953-015-0368-3. 7. soliev l, dzhumaev mt, avloev shh, iqbol  g. [phase equilibria in  the na,ca||co3,hco3–h2o system at 0 °c]. bulletin of the tajik national university (series of natural sciences). 2013;1(1):151. russian. 8. soliev l, dzhumaev mt, avloev shh. solubility in the caso4–caco3–ca(hco3)2– h2o system at 0 °c. reports of the academy of sciences of the republic of tajikistan. 2015;58(2):139. russian. 9. soliev  l, dzhumaev  mt,  dzhabbrov  bb. solubility and phase equilibria in  the na,ca||co3,hco3–h2o system at 0 °c. chimica techno acta. 2017;4(3):191. doi:10.15826 / chimtech / 2017.4.3.04. 30 10. soliev l, dzhumaev mt, turaev iro. phase equilibria in the na2so4–na2co3– nahco3–h2o system at  50  °c. bulletin of  the tajik national university (series of natural sciences). 2016;1(3):202. russian. 11. soliev l. schematic phase equilibria diagrams for multicomponent systems. russ j inorg chem. 1988;33(5):1305. russian. 88 do i: 1 0. 15 82 6/ ch im te ch .2 01 5. 2. 1. 00 9 patrushev a. v.1, ostanina t. n.1, rudoy v. m.1, vereshchagina a. v.1, zalesova o. l.2, soloviev a. s.2, shtirba n. i.2 the choice of the conditions to receive the electrolytic zinc powders for metal-rich compositions* 1ural federal university, 19 mira street, 620002 ekaterinburg 2scientifically industrial holding vmp closed joint stock company, 105 amundsen street, 620016 ekaterinburg the paper presents a method of obtaining high-dispersed zinc powders by electrolysis and comparison of the properties of zinc-rich compositions prepared using as a pigment zinc powders obtained by different methods. measurements have shown that the electrical conductivity of zinc-rich coatings containing electrolytic zinc powder, not inferior to the conductivity of the film with powder pzhd-0 obtained by the method of evaporation-condensation, despite the significant difference in the amount of zinc pigment. on the basis of the received data we can conclude that the use of electrolytic zinc powder as a pigment will significantly save zinc. *this work was supported by rfbr, project number 11-03-00226 © patrushev a. v., ostanina t. n., rudoy v. m., vereshchagina a. v., zalesova o. l.,soloviev a. s., shtirba n. i., 2015 introduction the main structural material of modernity is steel, which actively corrodes and therefore requires anticorrosive protection. for the prevention of destruction of metal structures, passive defense is used: the surface is covered by various isolating coatings: bituminous mastics, polyethylene and epoxy film, and isolation. however, in places where the integrity of such coating is broken, metal active corrodes. in contrast to the isolating coatings, tread zinc-rich coatings possess complex mechanism of protective actions. with the penetration of moisture into the film pigment, zinc powder acts as protector, providing a cathode-term protection of steel substrates. currently, the production of zinc-rich compositions uses zinc powder, which is produced by the evaporation-condensation (1). the powder particles obtained by this method have a spherical shape and size of 3–8 micron (2). prerequisite of zinc-rich coating effectiveness is its conductivity (3) that occurs with the introduction of a large amount of 90 № 1 | 2015 chimica techno acta the choice of the conditions to receive the electrolytic zinc powders for metal-rich compositions pigment to the composites. substitution of zinc particles of spherical form with ‘scaly’ ones enhances conductivity in coatings. electrolytic zinc powders are without doubt advantageous in terms of the properties of the pigment, as they are characterized by a branched structure and high degree of purity of the metal. however, the mean particle size after zinc removal from the cathode is substantially higher than that of powders obtained by metallurgical method; therefore, there requires an additional operation for grinding dendritic precipitation. the advantage of electrolytic method of producing dendritic metal precipitation is the ability to influence the dynamic of growth and structure of the particles, changing the composition of the solution, the amount of current or potential, or polarization mode. in industry, powder precipitation is obtained under conditions of polarization by constant current exceeding the value of the limiting diffusion current. quantitative description of the process of electrocrystallisation of metal dendrites using model representations provides the opportunity for reasonable choice of the conditions for obtaining powder precipitation with specified characteristics (4). the aim of this study was in obtaining high-dispersed dendritic zinc precipitation and comparing the properties of zincrich compositions prepared using zinc as pigment powders obtained by different methods. the experimental procedure to select the conditions for obtaining a high-dispersed zinc powder, studies of the dynamics of growth of dendritic percipitation of zinc in solutions of different concentrations (0.12, 0.24, 0.36 and 0.45 mol / l zno, and 4 mole / l naoh) at the depletion rate (dr) 3, 6, 9 were carried out. depletion factor dr is the ratio of a given current to the limit one on a smooth electrode. investigations were carried out at the facility, which allows simultaneous recording of the amount of capacity, conducting videorecording of percipitation growth and determining the amount of generated hydrogen. cylindrical rod cathode made from zinc with diameter of 1.8 mm was put in the cell center. the edge of the cell was covered with anode from zinc sheet. electrochemical measurements were performed using an electrochemical station zivesp5; sony dsr-200se4 was used for video-recording of the development of dendrites. experimental batch of zinc powder was obtained in laboratory electrolysis unit by setting a dc. after powder trimmings from the cathode, powder was washed off the electrolyte, dried and milled in a porcelain mortar. for a comparative study of conductivity of zinc-rich coatings, compositions were prepared using powders produced by electrolysis and evaporation-condensation method. films resistance was defined by the currentvoltage curves (3). experiment results intensive growth of dendrites in the initial stages of electrodeposition was gradually slowing down. termination of active extension of dendrites is due to a 92 № 1 | 2015 chimica techno acta patrushev a. v., ostanina t. n., rudoy v. m., vereshchagina a. v., zalesova o. l.,soloviev a. s., shtirba n. i. decrease of the current density amid the growth to the limiting diffusion, which confirms a sharp decrease in the absolute value of the polarization observed in the chronopotentiograms, and termination of hydrogen gas emission. significant impact on the dynamics of dendritic precipitation is played by electrodeposition conditions. increasing the current and the concentration of the solution increases the rate of elongation of precipitation with simultaneous reduction in time of active growth of dendrites. maximum length of dendritic precipitation with increasing dr is growing, but is little affected by concentration. differential (instantaneous) current output, which was calculatedfrom the change of the amount of emitted hydrogen in time period δt, is of great importance for the exploration of the kinetics of electrodeposition of dendrite metal precipitations. differential current output increases with decreasing of given current and with increase in the concentration of metal ions in solution. at the end of the elongation of the active precipitation, its value is close to 1. model description for selection of the conditions for obtaining high-dispersed zinc powders, structural properties of growing dendrite precipitation were calculated: the tip radius of rb branches of dendrites and the density of their placement amid the growth of n percipitation using model representations [3]. analysis of the experimental data has proved that the change in dendrites length in time (t) can be described with high level of accuracy with exponential relationship y t y t ( ) = − −            0 1 exp τ , (1) where yo and τ are empirical parameters. for approximation of the change in differential current output, empirical relationship of the following form can be used: b tt a b t c d t ( ) = + ⋅ + ⋅ . (2) when receiving the dendritic precipitations, crystallization of metal occurs, primarily, on tops of dendrites generating the precipitation growth front. the current density on the tops can be calculated from the equation of mixed kinetics (4): 1 1 1 i i iв = + кин сф . (3) at high cathodic polarization kinetic current (ikin) is much larger than the diffusion (isf), so in equation (3), the first addend can be neglected. then it can be written for the current density on the tops of the dendrites: i t i t zfdc r t в в ( ) ( ) ( ) = =сф 0 , (4) where: d is the diffusion coefficient of zinc ions, c0 is the concentration of zinc ions in the solution. in accordance with faraday’s law the rate of precipitation elongation is proportional to current density on the tops: i t dy dt zf v b me ( ) = ⋅ , (5) where vme me me a = ρ is the molar metal vol94 № 1 | 2015 chimica techno acta ume. the joint solution of the equations (4) and (5), and differentiation of dependence of the length of the dendrites from the time (1) allowed to calculate the radius of tops: r t dc v y tb o me( ) = −       τ τ0 exp , (6) some part of the current goes onto the reduction of the metal; this part is derived from the magnitude of instant current output (2): i bm t i r n d y hb b⋅ ( ) = ⋅ ⋅ +( )2 22 0π π . (7) from equation (7) with (1) and (5) we have obtained an expression for the calculation of density of peaks layout peaks at the growth front: n i вт t zf r y t d y t h me b = ⋅ ( )⋅( )       −       + ( )( ) ν τ τ π / exp2 0 2 02 2 . (8) the calculations showed that during electrolysis an increase of the dendrites peaks radius (figure 1), and a decrease in their number. increase in depletion rate (values of given current) and decrease in the concentration of the solution help to ensure receiving of a dendrite with a small peaks radius. based on these results the following electrolysis conditions were selected to receive an experimental batch of zinc powder: zinc ion concentration of 0.1 mol / l, dr = 9. deposition was led on copper cylindrical electrodes with diameter of 11mm and height of 40mm, which were beforehand covered with a zinc layer with thickness of 20 microns. comparative studies of the properties of electrolytic zinc powder and powder of brand ptsdv-0 prepared by evaporation-condensation method, as well as the properties of zinc-rich coatings prepared using these powders were carried out on the cjs scientifically industrial holding vmp. it was established that oil-absorption of ptsvd-0 powder is 5 times less than oil absorption of zinc powder obtained by electrolysis, which indicates a high specific surface of the latter. the consequence of this is that the use of a pigment of electrolytic zinc powder leads to a significant reduction in the critical pigment volume fraction (cpvc)) in the paint (table. one). table 1 properties of zinc powders, obtained by different methods parameter electrolytic powder ptsvd-0 oil absorption mg / 100g 65,8 12,6 cpvc% 25,3 28,0 the measurements showed that the conductivity of zinc-rich coatings containing an electrolytic zinc powder is not inferior to the conductivity of the film with a powder ptsvd-0, despite the significant difference in the amount of zinc pigment. comparison of protective properties of zinc-rich films requires additionfig.1. time variation of the radius of the peaks of zinc dendrites at a concentration 0,12mol / l (1,2,3) and 0,24mol / l (1 ‘, 2’, 3 ‘) and dr 3 (1,1’), 6 (2 2 ‘), 9 (3,3’) the choice of the conditions to receive the electrolytic zinc powders for metal-rich compositions 96 № 1 | 2015 chimica techno acta al investigation; however, based on these data we can conclude that the usage of the electrolytic zinc powder as a pigment allows cutting costs. 1. subbotina o. yu., pirogov v. d., samsonova a. i., balahnina l. a. compounded coating zves and zinol for protection from corrosion at ship building and ship repair. varnish-and-paint materials and their use. 1998; 9:25–30. [google scholar]. 2. frishberg i. v., yurkina l. p., subbotina o. yu., posohinyu. p. modern domestic zncompounded paints. practice of their use. varnish-and-paint materials and their use. 1997; 12:8–13. [google scholar]. 3. rudoy v. m., yaroslavzeva o. v., ostanina t. n., yurkina l. p., subbotina o. yu. electroconductivity of me-compounded polymer compositions. protection of metals. 1998; 3(5):527–532. [google scholar]. 4. darinzeva a. b., patrushev a. v., ostanina t. n., malkov v. b. electrocristallzation of dendritic precipitates of zn and ni at the galvanostatistic conditions. vestnik kazanskogo technologicheskogo universiteta. 2012; 15(b19):62–66. [google scholar]. patrushev a. v., ostanina t. n., rudoy v. m., vereshchagina a. v., zalesova o. l.,soloviev a. s., shtirba n. i. 89 а. в. патрушев1, т. н. останина1, в. м. рудой1, а. в. верещагина1, о. л. залесова2, а. с. соловьев2, н. и. штырба2 1 уральский федеральный университет, 620002, екатеринбург, ул. мира, 19. 2 зао нпх вмп, 620016, екатеринбург, ул. амундсена, 105 выбор условий получения электролитических порошков цинка для металлнаполненных композиций* в работе представлен способ получения высокодисперсных порошков цинка электролизом и сравнение свойств цинкнаполненных композиций, приготовленных с применением в качестве пигмента цинковых порошков, полученных разными методами. проведенные измерения показали, что удельная электропроводность цинкнаполненных покрытий, содержащих электролитический порошок цинка, не уступает по проводимости пленкам с порошком пцвд-0, полученного методом испарения-конденсации, несмотря на существенное различие в количестве цинкового пигмента. на основании полученных данных можно сделать вывод, что использование электролитического порошка цинка в качестве пигмента позволит значительно экономить цинк. *работа выполнена при поддержке рффи, проект № 11-03-00226 © патрушев а. в., останина т. н., рудой в. м., верещагина а. в., залесова о. л., соловьев а. с., штырба н. и., 2015 введение основной конструкционный материал современности – сталь, которая активно подвергается коррозии и поэтому нуждается в противокоррозионной защите. для предотвращения разрушения металлических сооружений используют пассивную защиту – на поверхность наносят различные изолирующие покрытия: битумные мастики, полиэтиленовую, эпоксидную и пленочную изоляции. однако в местах нарушения целостности такого покрытия металл активно корродирует. в отличие от изолирующих протекторные цинкнаполненные покрытия обладают комплексных механизмом защитного действия. при проникновении влаги в пленку пигмент – цинковый порошок – выступает в роли протектора, обеспечивая катодную защиту стальной основы. у д к 5 41 .1 35 :6 69 .6 21 91 № 1 | 2015 chimica techno acta в настоящее время при производстве цинкнаполненных составов используют цинковый порошок, который получают методом испарения-конденсации [1]. частицы порошка, полученные данным методом, имеют сферическую форму и размер 3–8 мкм [2]. обязательным условием эффективности цинкнаполненных покрытий является электропроводность [3], которая возникает при введении в состав композитов большого количества пигмента. замена части частиц цинка сферической формы на чешуйчатую способствует повышению проводимости покрытий. несомненным преимуществом с точки зрения свойств пигмента обладают электролитические порошки цинка, так как они характеризуются разветвленной структурой и высокой степенью чистоты металла. однако средний размер частиц цинка после съема с катода существенно выше, чем у порошков, полученных металлургическим методом, поэтому требуется дополнительная операция по размолу дендритных осадков. достоинством электролитического метода получения дендритных осадков металла является возможность влиять на динамику роста и структуру частиц, изменяя состав раствора, величину тока или потенциала, режим поляризации. в промышленности порошкообразные осадки получают в условиях поляризации постоянным током, превышающим величину предельного диффузионного тока. количественное описание процесса электрокристаллизации дендритов металлов с помощью модельных представлений позволяет обоснованно выбирать условия получения порошкообразных осадков с заданными свойствами [4]. цель настоящей работы состояла в получении высокодисперсных дендритных осадков цинка и сравнении свойств цинкнаполненных композиций, приготовленных с применением в качестве пигмента цинковых порошков, полученных разными методами. методика эксперимента для выбора условий получения высокодисперсного порошка цинка были проведены исследования по изучению динамики роста дендритных осадков цинка в растворах разной концентрации (0,12; 0,24; 0,36 и 0,45 моль/л zno и 4 моль/л naoh) при коэффициентах истощения (ки) 3, 6, 9. коэффициент истощения ки – отношение заданного тока к предельному на гладком электроде. исследования проводили на установке, позволяющей одновременно регистрировать величину потенциала, проводить видеозапись роста осадка и определять объем выделяющегося водорода. в центр цилиндрической ячейки подводили стержневой катод, выполненный из цинка диаметром 1,8 мм. по краю ячейки располагали анод из цинкового листа. электрохимические измерения проводили с помощью электрохимической станции zivesp5, для видеозаписи процесса развития дендритов использовали видеокамеру sony dsr-200se [4]. опытную партию цинкового порошка получали в лабораторном электролизере при задании постоянного тока. после счистки с катода порошок отмывали от электролита, сушили и выбор условий получения электролитических порошков цинка для металлнаполненных композиций 93 № 1 | 2015 chimica techno acta измельчали в фарфоровой ступке. для сравнительного исследования электропроводности цинкнаполненных покрытий были приготовлены составы с применением порошков, полученных электролизом и методом испаренияконденсации. сопротивление пленок определяли по вольтамперным кривым [3]. результаты экспериментов интенсивный рост дендритов на начальных стадиях электроосаждения постепенно замедлялся. прекращение активного удлинения дендритов связано со снижением плотности тока на фронте роста до предельной диффузионной, что подтверждает резкое уменьшение абсолютной величины поляризации, наблюдаемое на хронопотенциограммах, и прекращение выделения газообразного водорода. существенное влияние на динамику развития дендритного осадка оказывают условия электроосаждения. повышение тока и концентрации раствора приводит к увеличению скорости удлинения осадка с одновременным уменьшением времени активного роста дендритов. предельная длина дендритного осадка с увеличением ки растет, но мало зависит от концентрации. большое значение для исследования кинетики электроосаждения дендритных осадков металлов имеет дифференциальный (мгновенный) выход по току, который рассчитывали по изменению объема выделившегося водорода за интервал времени δt. дифференциальный выход по току возрастает с уменьшением заданного тока и увеличением концентрации ионов металла в растворе. в момент окончания активного удлинения осадка его величина приближается к единице. модельное описание для выбора условий получения высокодисперсных порошков цинка был проведен расчет структурных свойств растущего дендритного осадка: радиуса вершин ветвей дендритов rв и плотности их размещения на фронте роста осадка n с помощью модельных представлений [3]. анализ экспериментальных данных показал, что изменение длины дендритов во времени (t) с высокой степенью точности может быть описано экспоненциальной зависимостью y t y t ( ) = − −            0 1 exp τ , (1) где y0 и τ – эмпирические параметры. для аппроксимации изменения дифференциального выхода по току может быть использована эмпирическая зависимость вида: b tt a b t c d t ( ) = + ⋅ + ⋅ . (2) при получении дендритных осадков кристаллизация металла протекает преимущественно на вершинах дендритов, образующих фронт роста осадка. плотность тока на вершинах может быть рассчитана по уравнению смешанной кинетики [4]: 1 1 1 i i iв = + кин сф . (3) патрушев а. в., останина т. н., рудой в. м., верещагина а. в., залесова о. л., соловьев а. с., штырба н. и. 95 № 1 | 2015 chimica techno acta при высокой катодной поляризации кинетический ток (iкин) много больше, чем диффузионный (iсф), поэтому в уравнении (3) первым слагаемым можно пренебречь. тогда для плотности тока на вершинах дендритов можно записать: i t i t zfdc r t в в ( ) ( ) ( ) = =сф 0 , (4) d – коэффициент диффузии ионов цинка, с0 – концентрация ионов цинка в растворе. в соответствии с законом фарадея скорость удлинения осадка пропорциональна плотности тока на вершинах: i t dy dt zf v b me ( ) = ⋅ , (5) где vme me me a = ρ – мольный объем металла. совместное решение уравнений (4) и (5) и дифференцирования зависимости длины дендритов от времени (1) позволило рассчитать радиус вершин: r t dc v y tb o me( ) = −       τ τ0 exp . (6) на восстановление металла идет часть тока, определяемая величиной мгновенного выхода по току (2): i bm t i r n d y hb b⋅ ( ) = ⋅ ⋅ +( )2 22 0π π . (7) из уравнения (7) с учетом (1) и (5) получили выражение для расчета плотности расположения вершин на фронте роста: n i вт t zf r y t d y t h me b = ⋅ ( )⋅( )       −       + ( )( ) ν τ τ π / exp2 0 2 02 2 . (8) проведенные расчеты показали, что в процессе электролиза происходит увеличение радиуса вершин дендритов (рис. 1) и уменьшение их числа. увеличение коэффициент истощения (величины заданного тока) и уменьшение концентрации раствора способствует получению дендритов с малым радиусом вершин. на основе полученных результатов были выбраны следующие условия электролиза для получения опытной партии цинкового порошка: концентрация ионов цинка 0,1 моль/л, ки = 9. осаждение вели на медных цилиндрических электродах диаметром 11 мм и высотой 40 мм, на которые предварительно наносили слой цинка толщиной 20 мкм. на предприятии зао нпх вмп были проведены сравнительные исследования свойств электролитического порошка цинка и порошка марки пцдв-0, полученного методом испарения-конденсации, а также свойств цинкнаполненных лакокрасочных покрытий, приготовленных с применением этих порошков. установлено, что рис. 1. изменение во времени радиуса вершин дендритов цинка при концентрации 0,12 моль/л(1,2,3) и 0,24 моль/л (1’,2’,3’) и ки 3(1,1’), 6(2,2’), 9(3,3’) выбор условий получения электролитических порошков цинка для металлнаполненных композиций 97 № 1 | 2015 chimica techno acta маслоемкость порошка марки пцвд-0 в 5 раз меньше маслоемкости цинкового порошка, полученного электролизом, что свидетельствует о большой удельной поверхности последнего. следствие этого использование в качестве пигмента электролитического порошка цинка приводит к существенному снижению критической объемной доли пигмента (кокп) в краске (табл. 1). проведенные измерения показали, что удельная электропроводность цинкнаполненных покрытий, содержащих электролитический порошок цинка, не уступает по проводимости пленкам с порошком пцвд-0 несмотря на существенное различие в количестве цинкового пигмента. для сравнения протекторных свойств цинкнаполненных пленок необходимы дополнительные исследования, однако на основании полученных данных можно сделать вывод, что использование электролитического порошка цинка в качестве пигмента позволит значительно экономить цинк. 1. субботина о. ю., пирогов в. д., самсонова а. и., балахнина л. а. наполненные покрытия цвэс и цинол для защиты от коррозии в судостроении и судоремонте // лакокрасочные материалы и их применение. 1998. № 9. с. 25–30. 2. фришберг и. в., юркина л. п., субботина о. ю., посохин ю. п. современные отечественные цинкнаполненные краски. опыт их применения // лакокрасочные материалы и их применение. 1997. № 2. с. 8–13. 3. рудой в. м., ярославцева о. в., останина т. н., юркина л. п., субботина о. ю. электропроводность металлнаполненных полимерных композиций // защита металлов. 1998. т. 34, № 5. с. 527–532. 4. даринцева а. б., патрушев а. в., останина т. н., малков в. б. электрокристаллизация дендритных осадков цинка и никеля в гальваностатических условиях // вестн. казан. технолог. ун-та. 2012. т. 15. в. 19. с. 62–66. таблица 1 свойства цинковых порошков, полученных разными методами параметр порошок электролитический пцвд-0 маслоемкость мг/100 г 65,8 12,6 кокп % 25,3 28,0 патрушев а. в., останина т. н., рудой в. м., верещагина а. в., залесова о. л., соловьев а. с., штырба н. и. 1183-2586-1-pb 1183-2587-1-pb determination of platinum group elements in catalysts recycling products by sem with energy dispersive spectrometer 13 d o i: 1 0. 15 82 6/ ch im te ch .2 02 0. 7. 1. 02 chebykin n. s., sandalov i. p., zamyatin d. a., votyakov s. l. chimica techno acta. 2020. vol. 7, no. 1. p. 13–16. issn 2409–5613 nikolai s. chebykina,*, ivan p. sandalovb, dmitry a. zamyatina, sergey l. votyakova a zavaritsky institute of geology and geochemistry ub ras, 15 vonsovskogo st., 620016, ekaterinburg, russia b plaurum ао “ekaterinburg non-ferrous metals processing plant”, 131 uspensky ave., verhnyaya pyshma, 624088, sverdlovsk region, russia *email: tchebykinnikolai@yandex.ru determination of platinum group elements in catalysts recycling products by sem with energy dispersive spectrometer analysis of platinum group elements (pge) extracted from various catalysts used in the car, petroleum and chemical industries requires use of microanalytical methods. pge content in the platinum powder concentrates k176 and k177 was studied by sem-eds. the content of main elements was determined using analytical lines fe kα1, si kα1, sn lα1, pt lα1, re lα1. the obtained data for the chemical composition are in good agreement with the result obtained by x-ray fluorescence analysis and icp-ms method. powdered platinum concentrates are considered to be ferrosilicide (fesi), where pge are localized at the phase boundaries and in separate patches of the k176 sample, or distributed over the volume of particles in the k177 sample. keywords: pge; platinum powder concentrate; sem-eds; microanalysis; x-ray lines received: 24.12.2019. accepted: 06.03.2020. published: 31.03.2020. © chebykin n. s., sandalov i. p., zamyatin d. a., votyakov s. l., 2020 introduction high cost of  platinum group elements (pge) dictates the  economic feasibility of their recovery from various catalysts which had been used in car, petroleum and chemical industries. in order to extract pge, plaurum ао “ekaterinburg non-ferrous metals processing plant” (jsc ezocm) applied a smelting technology on an iron collector using a tetronics plasma furnace with the  subsequent processing of  the  collector in  acids [1]. the  quantitative electron probe microanalysis of the processed powdered platinum concentrate, in order to determine its composition is difficult due to the rough surface of  the  particles and the  significant overlaps of  the  x-ray emission lines of  pge. therefore development of a microanalysis method for the determination of pge content in the products of catalyst recycling allow to optimize the technology and assess the efficiency of metal extraction. the aim of the work is to develop a microanalysis technique for the determination of pge content in platinum powder concentrate and in the products of its recycling using scanning electron microscopy (sem) equipped with an  energy disper14 sive spectrometer (eds), as well as to test the modified technique for the examination of  chemical composition and morphological characteristics of the samples. samples and methods the  powder concentrate samples, denoted as  k176–177 (see fig.  1) were obtained by  melting of  catalysts with lime, quartz sand, magnetite and coke. the samples differ in melting parameters and charge composition. the samples were placed on a conductive adhesive tape and studied using a scanning electron microscope jeol jsm-6390lv equipped with eds oxford inca x–max80. the  used working distance was equal to 10 mm, accelerating voltage of 30 kv and accumulation time of  60 s. the  refinement of  obtained x-ray spectra was performed using the aztec v.3.1 software (including modeling of background by integral line and x-ray peaks by voigt profile) [2]. results and discussion semi-quantitative analysis of the pge content was performed using a standard sample of metallic cobalt with consequent normalization of  total elements content to 100%. we used both reference materials (minerals hematite and diopside for analysis of fe and si content, respectively) and pure metal standards (such as, sn, pt, and re) for x-ray peak intensity calibration. the content of the main elements (fe, si, sn, pt, re) was determined using the following analytical lines of the x-ray spectrum: fe kα1, si kα1, sn lα1, pt lα1, re lα1 (see fig. 2b). the lines for the two last of the listed pges do not overlapped with x-ray lines for al, cr, ti, v, ca, cl, the  presence of  which is typical for studied samples (fig. 3); their content was measured by the corresponding x-ray lines al kα1, cr kα1, ti kα1, v kα1, ca kα1, cl kα1. in order to determine qualitatively (or semi-quantitatively) the  average chemical composition of the samples, we have studied a region with the area of 1.5 mm2 which contained about 300–400 particles of powder in scanning mode. the surface of  the  particles in  the  samples exhibited either complex branched structure (k176) or rounded shape with developed edges (k177). the size of particles in the samfig. 1. bse images of platinum concentrate particles (a, b — samples k176 and k177). the rectangle area separated in image (a) — corresponded to the plot for the sample k176, shown in fig. 3a 15 ples varied from 50 to  300 microns. the content of main elements in the k176 sample can be represented as: fe = 81.7, si = 12.1, pt = 2.4, sn = 1.3 wt.%; whereas the detected impurities are: al, cr, ti, v, cl. the  sample k177 contains fe = 77.7, si = 16.2, pt = 1.5, re = 2.3  wt.% as  main elements and the detected impurities are: al, ti, v, ca, cl. the  relative standard deviation (δ) for the  elements’ content in  the  samples determined in  the  scanning mode is 1.3 (1.1 wt.%), 5.0 (0.8 wt.%), 4.3 (0.1 wt.%), and 4.9 (0.1 wt.%) %, for fe, si, pt, and re respectively. the chemical composition of fe, si, pt, re obtained by  sem-eds within these standard deviations completely coincides with the values obtained in  the  ezocm laboratory using x-ray fluorescence analysis (xrf) (fe = 77.1 wt.%, si = 15.9 wt.%) and inductively coupled plasma mass spectrometry (icp-ms) (pt = 1.6  wt.%, re = 2.5  wt.%) fig. 2. x-ray spectra for the k176 (a) and k177 (b) samples. scanning mode, the scanning region area of 1.5 mm2 fig. 3. the bse image for the k176 (a) sample, x-ray spectra reflects the presence of three phases (b). 1 — dark-grey phase on bse image (the main phase in the volume); 2 — middlegrey (intermediate); 3 — bright-grey (blotches) 16 for sample k177 and is  close for sample k176 (fe = 77.3 wt.%, si = 15.6 wt.%, pt = 1.9 wt.%). the main reason for the discrepancy of the k176 sample is heterogeneity. in  order to  identify the  nature and chemical composition of phases that contained in different particles of the inhomogeneous k176 sample we used the mode of individual point analysis. the spatial resolution in this mode is 1–3 microns. three different phases inside the  k176 sample (see figs. 1, 3) with different bse brightness were clearly distinguished: dark-grey (main phase inside the volume), middlegrey (intermediate) and bright-grey (separate blotches). it was found that the chemical composition of  these phases varied significantly (see table 1). the main elements are: fe and si in a dark-grey phase, fe and pt in a middle-grey phase, pt and sn in a bright-grey phase. conclusions the results of the elaborated microanalysis technique by means of a scanning electron microscopy (sem) equipped with an energy dispersive spectrometer (eds) applied to measure the pge content in powder catalysts recycling products were in good agreement with the result obtained by other methods and allow to demonstrate the redistribution of pge after processing in plasma furnace and acids. based on the obtained data one can conclude that powdered platinum concentrates in the k176 and k177 samples are mainly ferrosilicide (fesi) [3], and the platinum group elements are localized at the phase boundaries and in separate patches of the k176 sample, or distributed over the volume of particles in the k177 sample. acknowledgements this work was supported by the theme of state agreement of igg ub ras (theme no. аааа-а19-119071090011-6). references 1. borbat vf, maslenitskij in, nikitin mv, strizhko ls, chugaev lv. metallurgiya blagorodnyh metallov. moscow: metallurgiya; 1987. 432 p. russian. 2. briggs d, seah mp. practical surface analysis: by auger and x-ray photoelectron spectroscopy. new york: john wiley & sons; 1983. 533 p. 3. bannykh oa, budberg pb, alisova sp et al. diagrammy sostoyaniya dvojnykh i mnogokomponentnykh sistem na osnove zheleza. moscow: metallurgiya; 1986. 440 p. russian. table 1 the chemical composition of the phases detected in the k176 sample by sem-eds phase brightness on bse concentration *, wt. % fe si sn pt 1 dark-grey 80.2–85.7 12.5–17.6 <1 0.7–1.3 2 middle-grey 60.0–85.7 3.0–9.2 1.1–13.7 6.9–16.0 3 bright-grey 8.5–16.0 <1 39.9–49.5 38.6–39.3 * the variation in the data obtained as a result of three measurements in each phase. 306 d o i: 1 0. 15 82 6/ ch im te ch .2 01 5. 2. 4. 02 9 e. s. buyanova1, yu.v. emelyanova1, m. v. morozova1, z. a. mikhailovskaya1, o. s. kaymieva1, v. m. zhukovskiy1, s.a. petrova2 1 ural federal university, 620002 ekaterinburg, mira str., 19, tel: (343) 261-75-53 e-mail: elena.buyanova@urfu.ru 2 institute of metallurgy ub ras, 620016 ekaterinburg, amundsen st., 101, tel: (343) 267-88-94 e-mail: danaus@mail.ru crystal structure and conductivity of bismuth-containing complex oxides in the paper, a comprehensive systematic study of different classes of bismuth containing oxide compounds was carried out. the relationship between composition, temperature and concentration regions of existence of stable, specific structure and properties of solid solutions on the basis of vanadates, molybdates, niobates and bismuth was found. the general regularities of synthesis of solid solutions with different variants of solid-phase and soluble methods were determined. on this basis, the optimal conditions for obtaining single-phase materials were formulated. for the first time the temperature and concentration boundaries of the regions of homogeneity and areas of stable existence of polymorphic modifications of solid solutions were defined and/or refined. the structural parameters of the synthesized phases were determined. by the method of electrochemical impedance spectroscopy the nature and features of impedance spectra, the temperature and concentration dependences of electrical conductivity of ceramic materials based on bismuth containing complex oxides were identified. key words: method of electrochemical impedance spectroscopy; bismuth containing oxides; oxygen-ionic conductivity; thermocycling. © buyanova e. s., emelyanova yu. v., morozova m. v., mikhailovskaya z. a., kaymieva o. s., zhukovskiy v. m., petrova s. a., 2015 introduction the complex oxides on the basis of bi2o3 provide a vast class of objects of interest from the point of view of both fundamental and applied science. among practically important physical and chemical properties can distinguish oxygen-ion 307 № 4 | 2015 chimica techno acta and mixed conductivity in middle temperature region (300–700 °c), ferroelectric and magnetic effects. bismuth-containing compounds crystallize in different structure types to a greater extent crystal – or perovskite-like, including having a layered structure. depending on the dimensionality of charge transfer process, the bismuth-containing complex oxides can be divided into 3 types: three-dimensional (family of complex oxides that is similar to δ-bi2o3); two-dimensional (bimevox family); and one-dimensional, represented by phases on the basis of bi26mo10o69, containing column [bi12o14]∞. an important feature of the compounds is the presence of the cation of bismuth 6s2 lone-pair electrons, which leads to a high polarizability of the cationic sublattice. the stereochemical activity of the electron pair of bismuth ions is manifested in the ability to the formation of highly disordered oxygen environment of bismuth, change in symmetry of the coordination polyhedras and the way to ensure the dissociation of oxygen molecules. this work presents the results of studies of bismuth-containing complex oxide compounds of different structural families, held at the ural university in recent years. the experimental part the series compounds of bi4v2-xmex o11-d or bimevox (me=cu, fe, ti, nb), bi13mo5-хmeхo34-δ and bi13-xmexmo5o34±δ, (me=mg, ca, sr, ba, сo, fe), bi6.95y0.05nb2ymeyo15,5±δ and bi3nb1-ymeyo7±δ (ме=fe, zr, w) were obtained by standard ceramic technology, or using different variants of synthesis of the mortar. the features of synthesis for each particular case are described in [1–15]. x-ray examination of samples was carried out using diffractometer dron-3 (cukα-radiation, monochromator of pyrolytic graphite on the reflected beam), d8 advance (cukα-radiation, β-filter, position sensitive detector våntec, high-temperature chamber anton paar htk 1200n). analysis of the phase composition and calculation of the crystallographic parameters was carried out using diffracplus eva, match-demo, celref and databases pdf4+ icdd, cod and amcsd. dilatometric analysis was performed using the dilatometer dil 402 c netzsch with a vacuum-tight oven, differential thermal analysis was performed using thermoanalyzer sta 409 pc luxx, netzsch. microscopic investigations were performed using scanning electronic (raster) microscope jeol jsm 6390la consoles and energy dispersive jeol jed 2300. elemental analysis of samples was performed by atomic emission spectroscopy with inductively coupled plasma and atomic absorption spectrometry on the spectrometer icap 6500 and m6 solar thermo scientific. the total conductivity of the samples was measured by the method of impedance spectroscopy (impedancemetry z-350m, z-3000 firm “elins”). results and discussion for all systems the processes of phase formation during their synthesis using a solid-phase, different versions of mortar methods, mechano-chemical activation were systematically investigated, the optimum conditions for obtaining singlecrystal structure and conductivity of bismuth-containing complex oxides 308 № 4 | 2015 chimica techno acta phase compositions were found. the phase formation in the systems bi2o3v2o5-oxides cu, fe, ti, nb is always in some series-parallel stages with formation of intermediate products of composition bi1.33v2o6 and bivo4, vanadates of the respective metals, for example, сu5v2o10, fe2v4o13, mixed oxides of bismuth and related cations (bi24ti2o40, bi20tio32, bi8nb18o57). it is established that the oxides of bismuth cations and the relevant cations the processes of formation of phases bimevox in the synthesis using liquid precursors is generally similar to the processes of phase formation during solidphase synthesis. the vanadate bismuth of the composition bivo4 is formed in all methods in the primary sludge. the interaction of the bismuth components with the formation of single-phase product in the field homogeneity during the synthesis phases bimevox using liquid precursors ends at temperatures 100–150 k lower than during solid-phase synthesis. when using the mechano-chemical method, the samples composition bi4v2o11, bi4v1.7cu0.15ti0.15o11-δ, bi4v1.8fe0.2o11-δ were obtained only after annealing of the mechanically activated mixture at a temperature of 873 k. under the same conditions of mechano-chemical synthesis of singlephase bi4v1.4nb0.6o11-δ was obtained after two minutes of activation. the phase formation by mechanical activation, as with other methods of synthesis goes through several series-parallel stages, which confirms the general complex nature of the interaction in the layered perovskite-like systems. however, at the final stage of the synthesis by any of the proposed options with appropriate concentrations of metal formed solid solutions belong to one of the possible polymorphic modifications of bismuth vanadate are formed [1–5]. the formation of solid solutions based on bismuth molybdate bi13mo5o34±δ during the synthesis of solid-phase method goes through the stage of formation of intermediate compounds bi38mo7o78 and bi2moo6; complex oxides of bismuth and a metal dopant. in the synthesis using soluble reagents as impurities has a significant amount of α–phase (bi2mo3o12), a hydroxide of bismuth, bi2moo6. analysis of reaction products after different stages of thermal processing has shown that in the case of the introduction in the process of synthesis procedures for the tempering of samples, the number and concentration of intermediates is significantly reduced, and single-phase final product forms at a temperature 1073–1123 k. the structural features of the different structural families of complex oxides are investigated, the boundaries of the regions of homogeneity, structural parameters and concentration intervals of existence of polymorphic modifications are defined. the high-symmetry complex oxides are formed on the basis of δ-bi2o3 with the fluorite structure with the occupancy of the oxygen sublattice at about 75 % (pr. gr. fm-3m) with partial substitution of metal ions for other cations. in this case, the region of homogeneity of solid solutions has a small length, for example, for a series bi3nb1-yzryo7±δ is the boundary located at x = 0.4, the series bi6.95y0.05nb2yzryo15.5±δ when y = 0.3. for bi6.95y0.05nb2yfeyo15.5±δ at a maximum temperature of 1073 k synthesis it is limited by the composition y = 0.2. outside the homogeneity region, or when the temperature changes often there is a mixture of two phases pseudokoningii buyanova e. s., emelyanova yu. v., morozova m. v., mikhailovskaya z. a., kaymieva o. s., zhukovskiy v. m., petrova s. a. 309 № 4 | 2015 chimica techno acta type bi3nbo7 with close lattice parameters and different content of metals. at low concentrations of dopant the stabilization of the tetragonal modification of solid solutions is possible, for example, for bi3nb1-ywyo7±δ or bi3nb1-yfeyo7±δ (y = 0.1). the existence regions of structural modifications phases bimevox vary depending on the composition and less – used method of synthesis. with a small content of operauser metal the solid solutions crystallize in the monoclinic (pr. gr. c2/m) or orthorhombic ((pr. gr. aba2 или amam) modification, by increasing the concentration of the dopant leads to the formation of tetragonal γ-modification. in the wide concentration interval of the tetragonal γ-modification (pr. gr i4/mmm) at room temperature is stable due to the substitution positions of vanadium to niobium (0.30 ≤ x ≤ 0.90), iron (0.20 ≤ x ≤ 0.50) and with a double substitution of iron and niobium (0.2 < x < 0.575). γ-modification bicutivox at room temperature was obtained for compositions with 0.25 ≤ x ≤ 0.50 only during rapid cooling (tempering) with the last stage of synthesis. the series of solid substitution solutions based on bismuth molybdate bi13mo5o34±δ crystallize in triclinic and monoclinic modifications. in particular, the triclinic modification of (pr. gr. p-1) forms by substitution in the sublattice of molybdenum and low concentrations of dopant for the series bi13mo5-ycoyo34±δ (y≤0.05) or bismuth for bi13-xmgxmo5o34±δ (x ≤ 0.1), bi13-xca(sr, ba)xmo5o34±δ (x ≤ 0.4), bi13-xcoxmo5o34±δ (x ≤ 0.05). monoclinic modification (pr. gr. p2/c) forms with the substitution in the sublattice of molybdenum compounds for bi13mo5-ycoyo34±δ (y ≤ 0.2) or bismuth, for example, bi13-x mgxmo5o34±δ (x ≤ 0.4), bi13-xca(sr, ba)x mo5o34±δ, (x ≤ 0.7), bi13-xcoxmo5o34±δ (x ≤ 0.2). an x-ray when you change the symmetry of the unit cell for different structural types is shown in fig. 1, an example of the dependence of unit cell parameters from the structure is shown in fig. 2. the regularities of the change of symmetry and the unit cell parameters of different polymorphic modifications of investigated series of samples depending on fig. 1. examples of radiographs of different structural types: : 1 – вi12.9ba0.1mo5o34±δ, (pr. gr. p-1); 2 – bi3nb0.8w0.2o7±δ, (pr. gr. fm⎯3m); 3 – bi3nb0.9fe0.1o7±δ, (pr. gr. i-4m2); 4 – γ-bimevox (pr. gr. i4/mmm); 5 – β-bimevox (pr. gr. amam), 6 – α-bimevox (pr. gr. c2/m) fig. 2. the dependence of the volume of the unit cell composition: 1 – bi13mo5-yfeyo34±δ; 2 – bi13-xcaxmo5o34±δ; 3 – bi4v2-xfex/2nbx/2o11-δ; 4 – bi4v2-xfexo11-δ crystal structure and conductivity of bismuth-containing complex oxides 310 № 4 | 2015 chimica techno acta temperature were revealed. for example, for phases bimevox family with increasing content of the dopant extends the temperature region of existence of the tetragonal γ-modification. the effect of the uneven change of parameters while maintaining the linearity of the change of unit cell volume with temperature for a series bicrfevox is found that is explained changes in vanadate layer structure. the study of the crystal structure of tetragonal bi4v2-xfexo11-δ depending on temperature and oxygen partial pressure revealed a significant stability of this modification in a fairly wide range of thermodynamic parameters. the change in the structure of the tetragonal modification bifevox in orthorhombic occurs in an environment with low oxygen content (at lgpo2 = –18.0 (atm.)) and at temperatures above 770 k. the baric dependences of the volume of the unit cell bi4v1.7fe0.3o11-δ at different temperatures are shown in fig.3. in addition, the samples of this series with x = 0.3–0.4 have the greatest stability under thermal cycling. using high-temperature x-ray studied the thermal behavior of the series bi13mo5-хmeхo34-δ and bi13-xmexmo5o34±δ with different dopants was studied. the changes of unit cell parameters in the phase transition from triclinic to monoclinic modification occurs abruptly and is accompanied by a small contraction of the unit cell. in the areas above and below the transition temperature the dependence is linear. however, at temperatures above 950 k there is a slight deviation from the linear behavior. an example of such dependencies for bi13mo4.9fe0.1o34±δ, obtained according to x-ray and neutron diffraction, are given in fig. 4. most likely this is due to the change in the mechanism of interaction between columnar elements and/or disordered polyhedra of molybdenum-oxygen framework of the same symmetry. with the increase in the concentration of the dopant the transition temperature from monoclinic to triclinic modification expected decreases: for example, with the composition bi12.9ca0.1mo5o34±δ the phase transition temperature was equal to ~593  k, for the composition bi12.6ca0.4mo5o34±δ ~523 k. the evaluation of the elemental composition of the investigated phases, taken in powder, or near the surface and in the fig. 3. the baric dependence of the volume of the unit cell bi4v1.7fe0.3o11-δ at different temperatures fig. 4. the dependence of the volume of the unit cell bi13mo4.9fe0.1o34±δ on temperature according to neutron and x-ray diffraction. the arrow shows a linear plot buyanova e. s., emelyanova yu. v., morozova m. v., mikhailovskaya z. a., kaymieva o. s., zhukovskiy v. m., petrova s. a. 311 № 4 | 2015 chimica techno acta bulk sintered pellets by atomic spectroscopy, and electron microscopy revealed that is not always realized even distribution of atoms in the structures of the solid solutions. this necessitates not only the phase, but the element of local and general control elements content in them. for example, for the system bicutivox regardless of the method of synthesis has been uneven joining of titanium atoms into the crystal lattice of the solid solution accompanied by the formation of uncontrolled trace impurities phases, enriched with titanium, which affects mechanical and electrical properties. such effect is absent for bifevox, binbvox. the uniform distribution of atoms in the structure is observed for all columnar series of molybdates of bismuth. for bismuth niobates with increasing concentration of the dopant is observed the formation of two structures pseudokoningii (let’s denote them as δ and δ/). for example, by the results of surface analysis and sample volume bi6.95y0.05nb1.4zr0.6o15.5±δ single-phase slightly is saturated with bismuth, and the other is saturated with niobium. the composition of one phase is δbi3nb0.72zr0.28o7-δ, and the second isδ/-bi1.7nb0.23zr0.07о3.30-δ. the coefficients of thermal expansion of both phases are close, the only difference between them is in the area 973–1073 k, where the phase δ/ is observed an anomaly of the unit cell parameters associated with the beginning of the collapse. according to the rfa above 973 k we observe the emergence of phase bi12nb0.29o18.7+x and a simultaneous decrease of the intensities of the reflexes of the phase δ/. for all series of samples the processes of non-isothermal sintering of ceramic briquettes were investigated that are allowed to establish their characteristics and the optimal values of the temperature-time characteristics of sintering. the samples were characterized by density, sintering, porosity, values of linear coefficients of thermal expansion. the highest value for lctr phases bimevox is ~20×10–6 k–1 and is characteristic of high-temperature γ-modification at low concentrations of dopant. for columnar of molybdates of bismuth it is a bit lower, 14–16×10–6 k–1. thus, unlike phases bimevox , size lctr for triclinic and monoclinic modifications are close, therefore, a sharp change in their volume during the phase transition does not occur, which is beneficial to the mechanical properties of the ceramic briquettes. the average values for lctr bismuth niobates are in the area of 11.7×10–6 – 11.8×10–6 k-1. by the method of electrochemical impedance spectroscopy identified the nature and features of impedance spectra, the temperature and concentration dependences of electrical conductivity of ceramic materials of all investigated series of samples were identified. the hodographs of the impedance of the studied compounds have the typical form of polycrystalline ionic conductors, and are composed of two or more combined semicircles, corresponding to the total resistance of the sample, the electrode and diffusion processes. the example of impedance diagram is shown in fig. 5. the corresponding equivalent circuit is based on a block-layered model that includes as mandatory elements of the impedance and the frequency-dependent component (examples in fig. 6). the course of temperature dependences of electrical conductivity is consistent with the concentration intervals of exiscrystal structure and conductivity of bismuth-containing complex oxides 312 № 4 | 2015 chimica techno acta tence of structural modifications: in the presence of phase transitions within the interval on politermo reflect the changes in the slope of the dependencie. for example, for phases bimevox at low concentrations of dopant (for example, x = 0.05), typical observed γ→β (853 k) and β→α (723 k) of successive phase transitions corresponding to the change of structure (i4/mmm → amam → c2/m) and is characterized by the change of activation energy of conductivity of solid solutions. for γ-modification phases bimevox solid solutions the values of activation energies at high temperatures are characteristic of the magnitude of 0.2–0.4 ev. the transition into an ordered γ/-modification with decreasing temperature is accompanied by a change of the tilt according to lgσ – 103/t and the increase of the activation energy to 0.5–0.7 ev. the electrical conductivity of ceramics made from powders obtained by the methods of synthesis using liquid precursors, is in average by 0.5 orders of magnitude higher compared with ceramics of the same composition obtained by a solid phase method. investigation of electrical conductivity of some compositions of the solid solution bifevox, binbvox depending on the partial pressure of oxygen showed that this dependence has a linear character, indicating a predominant oxygen-ion conductivity of this type of solid solutions. on the temperature dependence of conductivity of solid solutions on the basis of bi13mo5o34±δ are dedicated three ranges, characterized by different values of activation energy of conductivity: lowtemperature is inherent triclinic form еакт (нт) = 0.9–1.3 ev; mediumand hightemperature ((еакт (вт) = 0.5–0.6 эв; еакт (ст) = 0.65–0.8 эв is inherent to the monoclinic form. on the example of the samples of molybdates of bismuth-doped iron it is shown that the change in conductivity of materials in high-temperature and medium-temperature interval is correlated with changes in the oxygen sublattice of compounds within the life of the monoclinic modification, namely, due to the disordering of the oxygen polyhedra and the emergence of structure in the solid solution of the conjugate mo-o of trigonal bipyramid. for bismuth niobates the temperature dependence of electrical conductivity are linear, as determined by the absence of phase transitions in solid solutions of these compounds. the value of activation energy of conductivity is an average value of 0.9–1.1 ev. the highest conductivity have samples with a high concentration of phase δ/, which is a solid solution based on the highly conductive δ-modification fig. 6. examples of equivalent circuits used for analysis of impedance fig. 5. impedance diagrams for different compounds buyanova e. s., emelyanova yu. v., morozova m. v., mikhailovskaya z. a., kaymieva o. s., zhukovskiy v. m., petrova s. a. 313 № 4 | 2015 chimica techno acta of bismuth oxide. examples of the dependences are shown in fig. 7. the dependence of the conductivity on the concentration of the dopant usually has a parabolic type with a maximum at small concentrations of the dopant, which is typical for many oxide systems (fig. 8) and can be determined by the interaction of defects, or any structural factors. for example, the columnar bismuth molybdates the maximum value of conductivity is typical for the «transition state»: the area of occurrence of monoclinic or triclinic modifications modifications in the parameters is close to monoclinic. according to the results of the executed complex studies you can identify the most promising formulations from the viewpoint of conductive properties and stability under conditions of operation at elevated temperatures and variation of thermodynamic parameters. it is series of solid solutions bifevox, binbvox, bifenbvox with a dopant concentration of 25–30 mol.  % substituted columnar bismuth molybdate compositions bi12.8ba0.2mo5o34±δ и bi13mo4.7fe0.3o34±δ. 1. emel’yanova yu. v., shafigina r. r., buyanova e. s., zhukovskii v. m., zainullina v. m., petrova s. a. oxide ion conductors of the bimevox family: synthesis, structure, and conductivity. russian journal of physical chemistry. 2006;80(11):1725–1730. doi: 10.1134/s0036024406110057 2. zhukovskii v. m., emel’yanova yu. v., shafigina r. r., petrova s. a., zainullina v. m., buyanova e. s. oxide ceramics bimevox: conductivity, structure, and chemical bond. russian journal of electrochemistry. 2007;43(4):443–447. doi: 10.1134/ s1023193507040118 3. zhukovskii v. m., buyanova e. s., emel’yanova yu. v., morozova m. v., shafigina r. r., zakharov r. g., zhuravlev v. d. synthesis, structure, and conductivity of bimefig. 7. temperature dependence of conductivity of complex oxides: 1 – bi4v1.75fe0.125nb0.125o11-δ; 2 – bi4v1.9fe0.1o11-δ; 3 – bi12.8ba0.2mo5o34±δ; 4 – bi6.95y0.05nb1.7fe0.3o15.5±δ fig. 8. the dependence of the conductivity of complex oxides on: 1 – binbvox, 1023 k; 2 – bi13mo5-yfeyo34±δ; 1023 k; 3 – bi13-xcaxmo5o34±δ, 1023 k; 4 – bi13-x caxmo5o34±δ, 723 k; 5 – bifevox, 673 k crystal structure and conductivity of bismuth-containing complex oxides 314 № 4 | 2015 chimica techno acta vox oxide ceramics. russian journal of electrochemistry. 2009;45(5):512–519. doi: 10.1134/s1023193509050024. 4. buyanova e. s., petrova s. a., emel’yanova yu. v., blinova a. l., morozova m. v., zhukovskii v. m., zhuravlev v. d. preparation, structure, and charge transport characteristics of bifevox ultrafine powders. russian journal of inorganic chemistry. 2009;54(8):1193–1204. doi: 10.1134/s0036023609080051. 5. buyanova e. s., petrova s. a., emel’yanova yu. v., borodina n. a., zakharov r. g., zhukovskii v. m. crystal structure and conduction of bicutivox. russian journal of inorganic chemistry. 2009;54(6):864–872. doi: 10.1134/s0036023609060084 6. morozova m. v., buyanova e. s., petrova s. a., khisametdinova v. v., emel’yanova yu. v., shatokhina a. n., zhukovskii v.m. structural and thermal stability of bimevox oxygen semiconductors. russian journal of electrochemistry. 2011;47(4):448–452. doi: 10.1134/s1023193511040100 7. morozova m. v., buyanova e. s., emelyanova yu. v., zhukovskiy v. m., petrova s. a. highconducting oxide ceramics bimevox: synthesis, structure, properties. solid state ionics. 2011;192:153–157. doi: 10.1016/j.ssi.2010.04.020 8. morozova m. v., buyanova e. s., emelyanova ju. v., zhukovskiy v. m., petrova s. a., zakharov r. g., tarakina n. v. specific features in the synthesis, crystal structure and electrical conductivity of bicutivox. solid state ionics. 2011;201:27–34. doi: 10.1016/j.ssi.2011.07.010 9. buyanova e. s., shafigina r. r., morozova m. v., emel’yanova yu. v., khisametdinova v. v., zhukovskii v. m., petrova s. a., tarakina n. v. electrochemical characteristics, thermal and chemical compatibility in the la0.7sr0.3coo3 electrode–γ-bifevox electrolyte system. russian journal of inorganic chemistry. 2013;58(5):554–558. doi: 10.1134/s0036023613050033. 10. kaymieva o. s., tarasova o. a., shatokhina a. n., buyanova e. s., morozova m. v., zhukovskii v. m. structural and transport characteristics of substituted bismuth niobates. russian journal of electrochemistry. 2013;49(7):652–657. doi: 10.1134/ s1023193513070057. 11. mikhailovskaya z. a., buyanova e. s., petrova s. a., zhukovskiy v. m. oxygen–ionic conductors based on substituted bismuth molybdates with column-type structural fragments. russian journal of electrochemistry. 2013;49(7):658–664. doi:10.1134/ s1023193513070112. 12. buyanova e. s., morozova m. v., emelyanova yu. v., petrova s.a., zakharov r. g., tarakina n. v., zhukovskiy v. m. structure, thermal stability and electrical conductivity of binbvox. solid state ionics. 2013;243:8–17. doi: 10.1016/j.ssi.2013.04.009. 13. mikhailovskaya z. a., buyanova e. s., petrova s. a., morozova m. v., zhukovskiy v. m., zakharov r.g., tarakina n. v., berger i. f. cobalt-doped bi26mo10o69: crystal structure and conductivity. journal of solid state chemistry. 2013;204:9–15. doi: 10.1016/j.jssc.2013.05.006. 14. buyanova e. s., petrova s. a., mikhailovskaya z. a., kaymieva o. s., shatokhina a. n., emelyanova yu. v., morozova m. v. synthesis, structure, and conductivity buyanova e. s., emelyanova yu. v., morozova m. v., mikhailovskaya z. a., kaymieva o. s., zhukovskiy v. m., petrova s. a. 315 № 4 | 2015 chimica techno acta of substituted bismuth niobate bi7nb2o15.5. russian journal of inorganic chemistry. 2015;60(8):913–920. doi: 10.1134/s0036023615080045. 15. mikhaylovskaya z. a., buyanova e. s., morozova m. v., petrova s. a., zakharov  r.  g., nikolaenko i. v., abrahams i. bi13-xmexmo5o34±δ (me = mg, ca, sr, ba) solid solutions: synthesis and properties. ionics. 2015;21(8):2259–2268. doi: 10.1007/ s11581-015-1421-3. crystal structure and conductivity of bismuth-containing complex oxides 316 е. с. буянова,1 ю. в. емельянова,1 м. в. морозова,1 з. а. михайловская,1 о. с. каймиева,1 в. м. жуковский,1 с. а. петрова2 1 уральский федеральный университет, 620002 екатеринбург, ул. мира, 19, тел: (343) 261-75-53 e-mail: elena.buyanova@urfu.ru 2 институт металлургии уро ран, 620016 екатеринбург, ул. амундсена, 101, тел: (343) 267-88-94 e-mail: danaus@mail.ru кристаллическая структура и проводимость висмут-содержащих сложных оксидов в работе выполнено комплексное систематическое исследование различных классов висмут-содержащих оксидных соединений. найдена взаимосвязь состава, температурных и концентрационных областей устойчивого существования, специфики структуры и свойств твердых растворов на основе ванадатов, молибдатов, ниобатов висмута. установлены общие закономерности синтеза твердых растворов с использованием различных вариантов твердофазного и растворных методов. на этой основе сформулированы оптимальные условия получения однофазных материалов. определены впервые и/или уточнены температурные и концентрационные границы областей гомогенности и областей устойчивого существования полиморфных модификаций твердых растворов. установлены структурные параметры синтезированных фаз. методом спектроскопии электрохимического импеданса выявлены характер и особенности импедансных спектров, температурных и концентрационных зависимостей электропроводности керамических материалов на основе висмутсодержащих сложных оксидов. ключевые слова: метод спектроскопии электрохимического импеданса; висмутсодержащие оксиды; кислородно-ионная проводимость; термоциклирование. © буянова е. с., емельянова ю. в., морозова м. в., михайловская з. а., каймиева о. с., жуковский в. м., петрова с. а., 2015 у д к 5 44 .2 25 .3 /5 46 .0 3 /:5 46 .8 7 введение сложные оксиды на основе bi2o3 дают обширный класс объектов, представляющих интерес с точки зрения как фундаментальной, так и прикладной науки. среди практически значимых физико-химических свойств можно выделить кислородно-ионную и смешанную проводимость в средней области температур (300–700 °с), сегнетоэлектрические и магнитные эффекты. висмут-содержащие соединения кристаллизуются в различных 317 № 4 | 2015 chimica techno acta типах структур, в большей степени, флюоритоили перовскитоподобных, в том числе имеющих слоистое строение. в зависимости от мерности процесса переноса заряда висмут-содержащие сложные оксиды можно разделить на три типа: трехмерные (семейство сложных оксидов, подобных δ-bi2o3); двумерные (семейство bimevox) и одномерные, представленные фазами на основе bi26mo10o69, содержащими колонки [bi12o14]∞. важной особенностью соединений является наличие у катиона висмута неподеленной 6s2 пары электронов, что приводит к высокой поляризуемости катионной подрешетки. стереохимическая активность электронной пары ионов висмута проявляется в способности к образованию высоко разупорядоченного кислородного окружения висмута, изменению симметрии координационных полиэдров и возможности обеспечивать диссоциацию молекул кислорода. в настоящей работе представлены результаты исследований висмут-содержащих сложнооксидных соединений различных структурных семейств, проведенных в  уральском университете за последние годы. экспериментальная часть соединения серий bi4v2–xmexo11–d или bimevox (me = cu, fe, ti, nb), bi13mo5–хmeхo34–δ и bi13–xmexmo5o34±δ (me = mg, ca, sr, ba, сo, fe), bi6,95y0,05nb2–ymeyo15,5±δ и bi3nb1–ymeyo7±δ (ме = fe, zr, w) получены либо по стандартной керамической технологии, либо с использованием различных вариантов растворного синтеза. особенности синтеза для каждого конкретного случая описаны в [1–15]. рентгеновские исследования образцов проводили с использованием дифрактометров дрон-3 (cukα-излучение, монохроматор из пиролитического графита на отраженном пучке), d8 advance (cukαизлучение, β-фильтр, позиционночувствительный детектор våntec, высокотемпературная камера anton paar htk 1200n). анализ фазового состава и расчет кристаллографических параметров осуществляли с использованием программных пакетов diffracplus eva, match-demo, celref и баз данных pdf4+ icdd, cod и amcsd. дилатометрический анализ выполнен с помощью дилатометра dil 402 c netzsch с вакуум-плотной печью, дифференциальный термический анализ – с использованием термоанализатора sta 409 pc luxx, netzsch. микроскопические исследования проведены с помощью сканирующего электронного (растрового) микроскопа jeol jsm 6390la и энергодисперсионной приставки jeol jed 2300. элементный анализ образцов выполняли методом атомно-эмиссионной спектроскопии с индуктивно связанной плазмой и атомно-абсорбционной спектроскопии на спектрометрах icap 6500 и solar m6 thermo scientific. общую электропроводность образцов измеряли методом импедансной спектроскопии (импедансметры z-350м, z-3000 фирмы «elins»). кристаллическая структура и проводимость висмут-содержащих сложных оксидов 318 № 4 | 2015 chimica techno acta результаты и обсуждение для всех систем систематически исследованы процессы фазообразования при их синтезе с использованием твердофазного, различных вариантов растворного методов, механохимической активации, найдены оптимальные условия получения однофазных составов. фазообразование в системах bi2o3–v2o5-оксиды cu, fe, ti, nb всегда идет в несколько последовательно-параллельных стадий с образованием промежуточных продуктов состава bi1,33v2o6 и bivo4, ванадатов соответствующих металлов, например, сu5v2o10, fe2v4o13, сложных оксидов висмута и соответствующих катионов (bi24ti2o40, bi20tio32, bi8nb18o57). установлено, что процессы формирования bimevox при синтезе через жидкие прекурсоры в целом аналогичны процессам фазообразования при твердофазном синтезе. во всех методах в первичном осадке образуется ванадат висмута состава bivo4. взаимодействие компонентов с образованием однофазного продукта в области гомогенности при синтезе bimevox с использованием жидких прекурсоров заканчивается при температуре на 100–150 k ниже, чем при твердофазном синтезе. при использовании механохимического метода образцы состава bi4v2o11, bi4v1,7cu0,15ti0,15o11–δ, bi4v1,8fe0,.2o11–δ получены только после отжига механоактивированной смеси при температуре 873 k. при тех же условиях механохимического синтеза однофазный bi4v1,4nb0,6o11–δ получен уже после двух минут активации. фазообразование при механоактивации, как и при использовании других методов синтеза, идет через несколько последовательно-параллельных стадий, что подтверждает общий сложный характер взаимодействия в слоистых перовскитоподобных системах. тем не менее на конечном этапе синтеза любым из предложенных вариантов при соответствующих концентрациях металла образуются твердые растворы, относящиеся к одной из возможных полиморфных модификаций ванадата висмута [1–5]. образование твердых растворов на основе молибдата висмута bi13mo5o34±δ при синтезе твердофазным методом идет через стадии формирования промежуточных соединений bi38mo7o78 и bi2moo6; сложных оксидов висмута и металла-допанта. при синтезе с использованием растворимых реагентов в качестве примесей присутствует значительное количество α-фазы (bi2mo3o12), гидроксид висмута, bi2moo6. анализ продуктов реакции после различных стадий температурной обработки показал, что в случае введения в процесс синтеза процедуры закаливания образцов количество и концентрация промежуточных соединений значительно уменьшаются, и конечный однофазный продукт образуется при температуре 1073–1123 k. исследованы структурные особенности различных структурных семейств сложных оксидов, определены границы областей гомогенности, структурные параметры и концентрационные интервалы существования полиморфных модификаций. высокосимметричные сложные оксиды образуются на основе δ-bi2o3, имеющего структуру флюорита с заселенностью по подрешетке кислобуянова е. с., емельянова ю. в., морозова м. в., михайловская з. а., каймиева о. с., жуковский в. м., петрова с. а. 319 № 4 | 2015 chimica techno acta рода около 75 % (пр. гр. fm-3m) при замещении части ионов металла на другие катионы. при этом область гомогенности твердых растворов имеет небольшую протяженность, например, для серии bi3nb1–yzryo7±δ ее граница находится при х = 0,4, серии bi6,95y0,05nb2–yzryo15,5±δ – при у = 0,3. для bi6,95y0,05nb2–yfeyo15,5±δ при максимальной температуре синтеза 1073 k она ограничена составом у = 0,2. за пределами области гомогенности или при изменении температуры часто наблюдается смесь двух псевдокубических фаз типа bi3nbo7 с близкими параметрами элементарной ячейки и различным содержанием металлов. при малых концентрациях допанта возможна стабилизация тетрагональной модификации твердых растворов, например, для bi3nb1–ywyo7±δ или bi3nb1–yfeyo7±δ (y = 0.1). области существования структурных модификаций bimevox различаются в зависимости от состава и в меньшей степени – использованного метода синтеза. при небольшом содержании допирующего металла твердые растворы кристаллизуются в моноклинной (пр. гр. c2/m) или орторомбической (пр. гр. aba2 или amam) модификации, при увеличении концентрации допанта происходит образование тетрагональной γ-модификации. в наиболее широком концентрационном интервале тетрагональная γ-модификация (пр. гр i4/mmm) при комнатной температуре стабилизирована за счет замещения позиций ванадия на ниобий (0,30 ≤ x ≤ 0,90), железо (0,20 ≤ x ≤ 0,50), а также при двойном замещении на железо и ниобий (0,2 < x < 0,575). γ-модификация bicutivox при комнатной температуре получена для составов с 0,25 ≤ х ≤ 0,50 только при быстром охлаждении (закаливании) с последней стадии синтеза. серии твердых растворов замещения на основе молибдата висмута bi13mo5o34±δ кристаллизуются в триклинной и моноклинной модификациях. в частности, триклинная модификация (пр. гр. p-1) образуется при замещении в подрешетку молибдена и малых концентрациях допанта для серии bi13mo5–ycoyo34±δ (y ≤ 0,05) или висмута для bi13–xmgxmo5o34±δ (x ≤ 0,1), bi13–xca(sr, ba)xmo5o34±δ (x ≤ 0,4), bi13–xcoxmo5o34±δ (x ≤ 0,05). моноклинная модификация (пр. гр. p2/c) – при замещении в подрешетку молибдена для составов bi13mo5–ycoyo34±δ (y ≤ 0,2) или висмута, например, bi13–x mgxmo5o34±δ (x ≤ 0,4), bi13–xca(sr, ba)x mo5o34±δ, (x ≤ 0,7), bi13–xcoxmo5o34±δ (x ≤ 0,2). изменение вида рентгенограмм при изменении симметрии элементарной ячейки для различных структурных типов приведено на рис. 1, пример зависимости параметров элементарной ячейки от состава – на рис. 2. выявлены закономерности изменения симметрии и параметров элементарной ячейки различных полиморфных модификаций исследованных серий образцов в зависимости от температуры. например, для семейства bimevox при увеличении содержания допанта расширяется температурная область существования тетрагональной γ-модификации. обнаружен эффект неравномерного изменения параметров при сохранении линейности изменения объема элементарной ячейки с температурой для серии кристаллическая структура и проводимость висмут-содержащих сложных оксидов 320 № 4 | 2015 chimica techno acta bicrfevox, что объяснено изменениями в ванадатном слое структуры. исследование кристаллической структуры тетрагонального bi4v2-x fexo11-δ в зависимости от температуры и парциального давления кислорода выявило значительную устойчивость данной модификации в достаточно широком интервале термодинамических параметров. изменение структуры тетрагональной модификации bifevox в орторомбическую происходит в среде с низким содержанием кислорода (при lgpо2 = –18,0 (атм.)) и при температуре выше 770 k. барические зависимости объема элементарной ячейки bi4v1,7fe0,3o11–δ при различных температурах приведены на рис. 3. кроме того, образцы этой серии при x = 0,3–0,4 обладают наибольшей устойчивостью при термоциклировании. методом высокотемпературной рентгенографии изучено термическое поведение серий bi13mo5–хmeхo34–δ и bi13–xmexmo5o34±δ с различными допантами. изменения параметров элементарной ячейки в области фазового перехода из триклинной в моноклинную модификацию происходят скачкообразно, сопровождаясь небольшим сжатием элементарной ячейки. в областях выше и ниже температуры перехода зависимости линейны. однако при температуре выше 950 k наблюдается небольшое отклонение от линейного хода. пример подобной зависимости для bi13mo4,9fe0,1o34±δ, полученной по данным рентгеновской и нейтронной дифракции, приведен на рис. 4. вероятнее всего, это связано с изменением механизма взаимодействия колончатых элементов и/или разупорядоченных полиэдров молибден-кислород в рамках одной симметрии. с повышением концентрации допанта температура перехода из триклинной в моноклинную модификацию ожидаемо снижается: например, для состава bi12,9ca0,1mo5o34±δ температура фазового перехода составила ~593 k, для состава bi12,6ca0,4mo5o34±δ – ~523 k. рис. 1. примеры рентгенограмм различных структурных типов: 1– вi1,9ba0,1mo5o34±δ, (пр. гр. p-1); 2 – bi3nb0,8w0,2o7±δ, (пр. гр. fm⎯3m); 3 – bi3nb0,9fe0,1o7±δ, (пр. гр. i-4m2); 4 – γ-bimevox (пр. гр. i4/mmm), 5 – β-bimevox (пр. гр. amam), 6 – α-bimevox (пр. гр. c2/m) рис. 2. зависимость объема элементарной ячейки от состава: 1 – bi13mo5–yfeyo34±δ; 2 – bi13–xcaxmo5o34±δ; 3 – bi4v2–xfex/2nbx/2o11–δ; 4 – bi4v2–xfexo11-δ буянова е. с., емельянова ю. в., морозова м. в., михайловская з. а., каймиева о. с., жуковский в. м., петрова с. а. 321 № 4 | 2015 chimica techno acta оценка элементного состава исследуемых фаз, взятых в виде порошка, либо вблизи поверхности и в объеме спеченных брикетов методами атомной спектроскопии и электронной микроскопии выявила, что не всегда реализуется равномерное распределение атомов в структурах твердых растворов. это вызывает необходимость не только фазового, но элементного локального и общего контроля содержания элементов в них. например, для системы bicutivox независимо от метода синтеза наблюдается неравномерное вхождение атомов титана в кристаллическую решетку твердого раствора, сопровождающееся образованием неконтролируемых микропримесей фаз, обогащенных титаном, что сказывается на механических и электропроводящих свойствах. подобный эффект отсутствует для bifevox, binbvox. равномерное распределение атомов в структуре наблюдается для всех серий колончатых молибдатов висмута. для ниобатов висмута при росте концентрации допанта наблюдается образование двух псевдокубических структур (обозначим их как δ и δ/). например, по результатам анализа поверхности и объема образца bi6,95y0,05nb1,4zr0,6o15,5±δ одна фаза незначительно насыщена висмутом, а другая – ниобием. состав одной фазы – δ-bi3nb0,72zr0,28o7–δ, а второй – δ/-bi1,7nb0,23zr0,07о3,30–δ. коэффициенты термического расширения обеих фаз близки, единственным отличием между ними является область 973–1073 k, в которой для фазы δ/ наблюдается аномалия параметров элементарной ячейки, связанная с началом распада. по данным рфа выше 973 k наблюдается появление фазы bi12nb0,29o18,7+x и одновременное падение интенсивностей рефлексов фазы δ. для всех серий образцов исследованы процессы неизотермического спекания керамических брикетов, что позволило установить их особенности и оптимальные значения температурно-временных характеристик спекания. образцы охарактеризованы по плотности спекания, пористости, значениям линейных коэффициентов термического расширения. наибольшее рис. 3. барические зависимости объема элементарной ячейки bi4v1,7fe0,3o11–δ при различных температурах рис. 4. зависимость объема элементарной ячейки bi13mo4,9fe0,1o34±δ от температуры по данным нейтронной и рентгеновской дифракции. стрелкой показан линейный участок кристаллическая структура и проводимость висмут-содержащих сложных оксидов 322 № 4 | 2015 chimica techno acta значение лктр для bimevox составляет ~20×10–6 k–1 и характерно для высокотемпературной γ-модификации при низких концентрациях допанта. для колончатых молибдатов висмута оно немного ниже и равно 14-16×10–6 k–1. при этом, в отличие от bimevox, величины лктр для триклинной и моноклинной модификаций близки, следовательно, резкого изменения их объема при фазовом переходе не происходит, что благоприятно сказывается на механических свойствах керамических брикетов. средние значения лктр для ниобатов висмута находятся в области 11,7×10–6 – 11,8×10–6 k–1. методом спектроскопии электрохимического импеданса выявлены характер и особенности импедансных спектров, температурных и концентрационных зависимостей электропроводности керамических материалов всех исследованных серий образцов. годографы импеданса исследованных соединений имеют вид, типичный для поликристаллических ионных проводников, и состоят из двух или более сочетающихся полуокружностей, отвечающих общему сопротивлению образца, электродным и диффузионным процессам. пример импедансной диаграммы приведен на рис. 5. соответствующие эквивалентные схемы основаны на блочно-слоистой модели, включающей как обязательные элементы сопротивление и частотнозависимую компоненту (примеры на рис. 6). ход температурных зависимостей электропроводности согласуется с концентрационными интервалами существования структурных модификаций: при наличии фазовых переходов внутри интервала на политермах фиксируются изменения наклона зависимостей. например, для bimevox при малых концентрациях допанта (например, х  =  0,05), наблюдаются типичные γ→β (853 k) и β→α (723 k) последовательные фазовые переходы, отвечающие смене структуры (i4/mmm → amam → c2/m) и характеризующиеся изменением энергии активации проводимости твердых растворов. для γ-модификации твердых растворов bimevox значения энергии активации при высоких температурах составляют характерную величину 0,2–0,4  эв. переход в упорядоченную γ/-модификацию при понижении температуры сопровождается сменой наклона зависимости lgσ – 103/t и повышением энергии активации до 0,5– 0,7 эв. электропроводность керамики, рис. 5. импедансные диаграммы для различных соединений рис. 6. примеры эквивалентных схем, используемых при анализе импедансных диаграмм буянова е. с., емельянова ю. в., морозова м. в., михайловская з. а., каймиева о. с., жуковский в. м., петрова с. а. 323 № 4 | 2015 chimica techno acta изготовленной из порошков, полученных методами синтеза через жидкие прекурсоры, в среднем на 0,5 порядка выше по сравнению с керамикой того же состава, полученной твердофазным методом. исследование электропроводности некоторых составов твердых растворов bifevox, binbvox в зависимости от парциального давления кислорода показало, что зависимость носит прямолинейный характер, что свидетельствует о преимущественной кислородно-ионной проводимости данного типа твердых растворов. на температурных зависимостях электропроводности твердых растворов на основе bi13mo5o34±δ выделены три диапазона, характеризующиеся различными значениями энергии активации проводимости: низкотемпературный, присущий триклинной форме еакт (нт) = 0,9–1,3 эв; среднеи высокотемпературный (еакт (вт) = 0,5– 0,6 эв; еакт (ст) = 0,65–0,8 эв), присущие моноклинной форме. на примере образцов молибдатов висмута, допированных железом, показано, что изменение проводимости материалов в высокотемпературном и среднетемпературном интервале соотносится с изменениями в кислородной подрешетке соединений в рамках существования моноклинной модификации, а именно, обусловлено разупорядочением кислородных полиэдров и появлением в структуре твердого раствора сопряженных mo-o тригональных бипирамид. для ниобатов висмута температурные зависимости электропроводности имеют прямолинейный вид, что определяется отсутствием фазовых переходов у твердых растворов этих составов. значение энергии активации проводимости составляет в среднем величину 0,9–1,1 эв. при этом наибольшей проводимостью обладают образцы с высокой концентрацией фазы δ/, являющейся твердым раствором на основе высокопроводящей δ-модификации оксида висмута. примеры зависимостей приведены на рис. 7. зависимость электропроводности от концентрации допанта чаще всего имеет параболический вид с максимумом при небольших концентрациях допанта, что характерно для многих оксидных систем (рис. 8) и может определяться взаимодействием дефектов либо какими-либо структурными факторами. например, для колончатых молибдатов висмута максимальное значение проводимости характерно для «переходного состояния»: области появления моноклинной модификации или триклинной модификации, близкой по параметрам к моноклинной. по результатам выполненных комплексных исследований можно выдерис. 7. температурные зависимости проводимости сложных оксидов: 1 – bi4v1,75fe0,125nb0,125o11–δ; 2 – bi4v1,9fe0.1o11–δ; 3 – bi12,8ba0,2mo5o34±δ; 4 – bi6,95y0,05nb1,7fe0,3o15,5±δ кристаллическая структура и проводимость висмут-содержащих сложных оксидов 324 № 4 | 2015 chimica techno acta лить наиболее перспективные составы с точки зрения электропроводящих свойств и устойчивости в условиях работы при повышенных температурах и варьировании термодинамических параметров. это серии твердых растворов bifevox, binbvox, bifenbvox с концентрацией допанта 25–30 мол. %, замещенные колончатые молибдаты висмута составов bi12,8ba0,2mo5o34±δ и bi13mo4,7fe0,3o34±δ. 1. emel’yanova yu. v., shafigina r. r., buyanova e. s., zhukovskii v. m., zainullina v. m., petrova s. a. oxide ion conductors of the bimevox family: synthesis, structure, and conductivity. russian journal of physical chemistry. 2006;80(11):1725–1730. doi: 10.1134/s0036024406110057. 2. zhukovskii v. m., emel’yanova yu. v., shafigina r. r., petrova s. a., zainullina v. m., buyanova e. s. oxide ceramics bimevox: conductivity, structure, and chemical bond. russian journal of electrochemistry. 2007;43(4):443–447. doi: 10.1134/ s1023193507040118. 3. zhukovskii v. m., buyanova e. s., emel’yanova yu. v., morozova m. v., shafigina r. r., zakharov r. g., zhuravlev v. d. synthesis, structure, and conductivity of bimevox oxide ceramics. russian journal of electrochemistry. 2009;45(5):512– 519. doi: 10.1134/s1023193509050024. 4. buyanova e. s., petrova s. a., emel’yanova yu. v., blinova a. l., morozova m. v., zhukovskii v. m., zhuravlev v. d. preparation, structure, and charge transport characteristics of bifevox ultrafine powders. russian journal of inorganic chemistry. 2009;54(8):1193–1204. doi: 10.1134/s0036023609080051. 5. buyanova e. s., petrova s. a., emel’yanova yu. v., borodina n. a., zakharov r. g., zhukovskii v. m. crystal structure and conduction of bicutivox. russian journal of inorganic chemistry. 2009;54(6):864–872. doi: 10.1134/s0036023609060084. 6. morozova m. v., buyanova e. s., petrova s. a., khisametdinova v. v., emel’yanova yu. v., shatokhina a. n., zhukovskii v.m. structural and thermal stability of bimevox oxygen semiconductors. russian journal of electrochemistry. 2011;47(4):448–452. doi: 10.1134/s1023193511040100. рис. 8. зависимость электропроводности сложных оксидов от температуры: 1 – binbvox, 1023 k; 2 – bi13mo5–yfeyo34±δ, 1023 k; 3 – bi13-xcaxmo5o34±δ, 1023 k; 4 – bi13-xcaxmo5o34±δ, 723 k; 5 – bifevox, 673 k буянова е. с., емельянова ю. в., морозова м. в., михайловская з. а., каймиева о. с., жуковский в. м., петрова с. а. 325 № 4 | 2015 chimica techno acta 7. morozova m. v., buyanova e. s., emelyanova yu. v., zhukovskiy v. m., petrova s. a. high-conducting oxide ceramics bimevox: synthesis, structure, properties. solid state ionics. 2011;192:153–157. doi: 10.1016/j.ssi.2010.04.020. 8. morozova m. v., buyanova e. s., emelyanova yu. v., zhukovskiy v. m., petrova s. a., zakharov r. g., tarakina n. v. specific features 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i. bi13–xmexmo5o34±δ (me = mg, ca, sr, ba) solid solutions: synthesis and properties. ionics. 2015;21(8):2259–2268. doi: 10.1007/s11581-0151421-3. кристаллическая структура и проводимость висмут-содержащих сложных оксидов phase diagrams for the m2moo4–ln2(moo4)3–hf(moo4)2 systems, where m = li–cs, tl and ln = la–lu 224 bazarova zh. g., grossman v. g., bazarov b. g., tushinova yu. l., chimitova o. d., bazarova ts. t. chimica techno acta. 2017. vol. 4, no. 4. p. 224–230. issn 2409–5613 d o i: 1 0. 15 82 6/ ch im te ch /2 01 7. 4. 4. 03 zh.g. bazarova1,2, v.g. grossman1, b.g. bazarov1,2, yu.l. tushinova1,2, o.d. chimitova1, ts.t. bazarova1 1baikal institute of nature management, siberian branch of russian academy of sciences, 8 sakh’yanovoi st., ulan-ude, 670047, russian federation 2buryat state university, 24a smolinast., ulan-ude, 670000, russian federation e-mail: jbaz@binm.ru phase diagrams for the m 2 moo 4 –ln 2 (moo 4 ) 3 –hf(moo 4 ) 2 systems, where m = li–cs, tl and ln = la–lu in this paper, the results of systematic studies of complex molybdate systems m 2 moo 4 –ln 2 (moo 4 ) 3 –hf(moo 4 ) 2 (m = li–cs, tl; ln = la–lu) are presented. subsolidus phase diagrams of ternary systems were constructed and new triple molybdates were obtained. the optimum synthesis conditions for poly and monocrystalline form were determined. according to single-crystal data, the structure of one of the representatives of triple molybdates was determined. keywords: phase equilibria, synthesis, systems, lithium, sodium, potassium, rubidium, cesium, thallium, lanthanides, hafnium, crystal structure. received: 17.11.2017; accepted: 06.12.2017; published: 25.12.2017. © bazarova zh. g., grossman v. g., bazarov b. g., tushinova yu. l., chimitova o. d., bazarova ts. t., 2017 introduction the molybdates containing tetrahedrally coordinated anions moo4 2– are among the most exciting objects in inorganic and crystal chemistry. special attention has been paid to the molybdates that include luminescent elements, such as ce, pr, eu, tb, tm, in their composition. these compounds can be used as phosphors for white light emitting diodes. currently, numerous studies had been undertaken that aim to search for new effective phosphors for the creation of wled. these phosphors should possess high stability, compactness, high luminescence efficiency when excited by near uv, long lifetime and low cost. luminescent materials containing rare-earth elements are also within the scope of such studies [1–3]. in this paper, we present results on the study of phase equilibria in ternary molybdate systems containing single-, threeand tetravalent elements, as well as data on the crystal structure of complex molybdate structural types. experimental reagents li2moo4 (“pure” grade), na2moo4·2h2o (“pure for analysis” grade), k2moo4 (“pure” grade), cs2moo4 (“pure” grade), rb2co3 (“chemically pure” grade), tl2o3 (“chemically pure” grade), moo3 (“chemically pure” grade), hfo2 (“chemically pure” grade), and rare earth oxides of 99.9% purity 225 were used as starting materials. hf(moo4)2 and ln2(moo4)3 were synthesized by the solid state method. the annealing had started at 400–500  °c with the following temperature increase up to 800  °c in order to prevent moo3 losses due to its high volatility. the total calcination time was 100–150 h. rb2moo4 was prepared within the temperature range 350–650 °c during 100 h. tl2moo4 was synthesized during 50 h firing starting at 400 °c with final temperature equal to 550  °c. the samples were regrinded after each 24 h in the course of annealing in order to reach better homogeneity. the phase formation inside a subsolidus region of the ternary salt systems m2moo4–ln2(moo4)3–hf(moo4)2 (m  = li–cs, tl; ln = la–lu) in air were stu died using the intersecting joins method. the phase composition of the samples was monitored by x-ray diffraction (xrd) measurements using bruker d8 advance diffractometer (cu  kα radiation, vantec-1, maximum angle 2θ=100°, scan step 0.01–0.02°). primary fitting of the diffraction patterns was made using profan software from the csd package. results and discussion the data concerning phase equilibrium for the side systems of studied triangles (quasi-ternary systems) m2moo4– ln2(moo4)3–hf(moo4)2 (m  = li–cs, tl; ln = la–lu) are taken from the literature. the phase formation in the quasibinary li2moo4–ln2(moo4)3 systems was described in paper [4] in details. the aforementioned systems can be divided into two groups. the first group includes systems with ln = la–tb in which two intermediate phases liln5(moo4)8 and liln(moo4)2 possess a significant homogeneity range. the second group includes the systems with ln = dy–lu. inside these systems two intermediate compounds that did not exhibit any noticeable homogeneity ranges were detected: liln(moo4)2 and li7ln3(moo4)8. two intermediate compounds with the constituents mole ratio of 5:1 and 1:1 were detected inside the quasi-binary na2moo4–er2(moo4)3 systems similarly to the k2moo4–ln2(moo4)3 (ln = la, tb, dy, er), m2moo4–ln2(moo4)3 (m  = tl, rb; ln = la–lu) systems [4–8]. additionally to those two one more intermediate phase with the constituents mole ratio 1:5 was found to exist inside the na2moo4– ln2(moo4)3 (ln = nd, sm) and k2moo4– sm2(moo4)3 systems [4, 5]. the phases formed inside the cesiumcontaining rare-earth molybdate systems included those with the constituents mole ratio 3:1 and 1:1 with ln = nd, whereas the systems with ln = sm, tb, er revealed only 1:1 compound [4, 5]. lithium hafnium molybdate with the significant homogeneity range li10–4xhf2+x(moo4)9 (0.21 ≤ x ≤ 0.68) was formed in the li2moo4–hf(moo4)2 system [9], but in the oxide systems with larger alkali earth metals m2moo4–hf(moo4)2 (m  = k, tl, rb, cs) two types of compounds were confirmed – m8hf(moo4)6 and m2hf(moo4)3 [10–13]. it should be noted that na-containing system slightly differs from the aforementioned ones. it was found that along with phases with the constituents mole ratios equal to 4:1 and 1:1 one more compound is formed with the 3:1 composition. the phases that were isolated in the ln2(moo4)3–hf(moo4)2 systems 226 are ln2hf3(moo4)9 (ln  = la–tb), ln2hf2(moo4)7 (ln  = sm–ho), and ln2hf(moo4)5(ln = er–lu) [14]. the phase diagrams for various molybdate systems are shown in fig. 1–6, and the corresponding phase compositions are listed in table 1. no new compounds were detected in the lithium-containing and sodiumcontaining systems [15, 16]. in contrast, the new compounds listed in table 1 and shown in fig. 3–6 were confirmed in the m2moo4–ln2(moo4)3–hf(moo4)2 (m  = k, rb, tl, cs; ln = la–lu) systems [14, 17, 18]. the molybdates with the composition k5lnhf(moo4)6 were identified in the systems with ln = sm–lu. two types of compounds, namely m5lnhf(moo4)6 (5:1:2) and m2lnhf2(moo4)6.5 (2:1:4), were isolated in the tl2moo4–ln2(moo4)3–hf(moo4)2 (ln = ce–lu) and rb2moo4–ln2(moo4)3– hf(moo4)2 (ln  = ce–lu) systems. in case of the tl-containing systems, for ln = ce–nd one more phase except those mentioned above had been obtained – tllnhf0.5(moo4)3 (1:1:1). the phase with composition cs2lnhf2(moo4)6.5 (2:1:4) was found to fig. 1. subsolidus phase diagrams of the li2moo4–ln2(moo4)3–hf(moo4)2 systems (t li10–4xhf2+x(moo4)9, 0.21 ≤ x ≤ 0.68; shaded double-phase equilibrium region) [15] fig. 2. subsolidus phase diagrams of the na2moo4–ln2(moo4)3–hf(moo4)2 systems; shaded double-phase equilibrium region [16] 227 exist in the cs-containing rare earth molybdates with ln = pr–lu. the systems m2moo4–ln2(moo4)3– hf(moo4)2 (m  = k, rb, tl, cs; ln = la– lu) are characterized by the formation of a different number of phases with varying homogeneity ranges with respect to the lanthanide elements. one can see that m5lnhf(moo4)6 (m  = k, tl, rb) compounds were formed if the size difference for the single charged m+ cation and rare earth element cation ln3+ lies in the range of 0.682 å ≤ r(m+)(cn=12)–r(ln 3+)(cn=6) ≤ 0.859 å [19]. in the case of m+ = li+, na+, cs+ such radii difference lies outside this range. as a result, formation of m5lnhf(moo4)6 compounds for these cations is impossible. if the size difference for the single charged m+ cation and rare earth element cation ln3+ lies in the range 0.839 å ≤ r(m+)(cn=12) – r(ln 3+)(cn=6) ≤ 1.019 å, it fig. 3. subsolidus phase relations in the k2моо4–ln2(moo4)3–hf(moo4)2 systems (s1–k5lnhf(moo4)6 (5:1:2); shaded double-phase equilibrium region) [14] fig. 4. subsolidus phase diagrams for the tl2moo4–ln2(moo4)3–hf(moo4)2 systems where ln = la–lu. notations: s1–tl5lnhf(moo4)6 (5:1:2), s2–tl2lnhf2(moo4)6.5 (2:1:4), and s3– tllnhf0.5(moo4)3 (1:1:1); shaded double-phase equilibrium region [17] 228 fig. 6. subsolidus phase relations in the cs2моо4–ln2(moo4)3– hf(moo4)2 systems (s2–cs2lnhf2(moo4)6.5 (2:1:4); shaded double-phase equilibrium region) fig. 5. subsolidus phase diagrams for the rb2moo4–ln2(moo4)3–hf(moo4)2 systems where ln = la–lu. notations: s1–rb5lnhf(moo4)6 (5:1:2) and s2–rb2lnhf2(moo4)6.5 (2:1:4); shaded double-phase equilibrium region [18] table 1 compositions of triple molybdates in the m2моo4–ln2(моo4)3–hf(moo4)2 (m = li–cs, tl; ln = la–lu) systems la ce pr nd sm eu gd tb dy ho er tm yb lu lihf nahf khf k5lnhf(moo4)6 tlhf tl5lnhf(moo4)6 tl2lnhf2(moo4)6.5 tllnhf0.5(moo4)3 rbhf rb5lnhf(moo4)6 rb2lnhf2(moo4)6.5 cshf cs2lnhf(moo4)6.5 229 makes a formation of the m2lnhf2(moo4)6.5 molybdates possible. the complex molybdates m5lnhf(moo4)6 (m  = k, tl, rb) are isostructural to the earlier grown single crystals of rb5lnhf(moo4)6 (ln  = nd, eu, er), which possess the trigonal structure with r3c space group [18]. three-dimensional framework of this structure is built of the consequently alternating moo4 tetrahedra and (ln, hf )o6 octahedra linked with each other through the common o-vertices. one of the structural peculiarities for this class of compounds is a random distribution of ln3+ and hf4+ cations over two crystallographic sites with various distribution coefficients. rubidium cations fill two types of large cavities in the framework, forming differently oriented channels of a large diameter. it gives good expectations for the fast ionic transport in such structures (fig. 7). unfortunately, we have failed to prepare single crystals of m2lnhf2(moo4)6.5 (2:1:4) and tllnhf0.5(moo4)3 (1:1:1) in the condition used in the present work. acknowledgements this work was carried out according to the state assignment binm sb ras (project no. 0339-2016-0007.). this work was supported by the comprehensive program of basic research sb ras no ii.2 «integration and development» (project no. 0339-2015-0039). references 1. haque m, lee hi, kim dk. luminescent properties of eu3+-activated molybdatebased novel red-emitting phosphors for leds. j alloys compd. 2009;481:792–6. doi:10.1016/j.jallcom.2009.03.083. 2. haque m, kim dk. luminescent properties of eu3+ activated mla2(moo4)4 based (m  = ba, sr and ca) novel red-emitting phosphors. mater lett. 2009;3:793–6. doi:10.1016/j.matlet.2009.01.018. 3. liang y, noh hm, ran w, park sh, choi bc, jeong jh, kim kh. the design and synthesis of new double perovskite (na, li)ymg(w, mo)o6: eu 3+ red phosphors for white light-emitting diodes. j alloys compd. 2017;716:56–64. doi:10.1016/j.jallcom.2017.05.027. 4. evdokimov aa, efremov va, trunov vk, kleyman ia, tananaev iv. soedineniya redkozemel’nykh elementov. molibdaty, vol’framaty [rare-earth elements’ compounds. molibdates, wolframates]. moscow: nauka; 1991. 267 p. russian. 5. trunov vk, efremov va, velikodny yu a. [crystal chemistry and properties of double molybdates and tungstates.] leningrad (ussr): nauka; 1986. 173 p. russian. 6. basovich om. [new phases in m2moo4–ln2(moo4)3 (m  = ag, tl) and li2moo4– m2moo4–ln2(moo4)3 (m  = k, rb, tl) systems] [dissertation]. irkutsk (russia); 2006. russian. fig. 7. crystal structure fragment for rb5ndhf(moo4)6 230 7. spitsyn vi, trunov vk. [new data on double tungstates and molybdates of composition meln(eo4)2]. [reports of the academy of sciences of the ussr]. 1969;185(4):854– 5. russian. 8. savel’eva mv, shakhno iv, plyushchev ve. [synthesis and properties of molybdates of alkaline and some rare-earth elements]. izv an sssr: inorg mat. 1970;6(9):1665– 9. russian. 9. solodovnikov sf, balsanova lv, bazarov bg, zolotova es, bazarova zh g. phase formation in the rb2moo4–li2moo4–hf(moo4)2 system and the crystal structure of rb5(li1/3hf5/3)(moo4)6. russ j inorg chem. 2003;48(7):1084–8. 10. zolotova es. [synthesis and physico-chemical properties of double molybdates of alkali and tetravalent elements] [dissertation]. novosibirsk (russia); 1986. russian. 11. klevtsov pv, zolotova es, glinskaya la, klevtsova rf. synthesis, thermal stability and crystal structure of rubidium double molybdates with zirconium and hafnium. russ j inorg chem. 1980;25(7):1844–50. 12. bazarov bg, bazarova tst, fedorov kn, bazarova zhg, klevtsova rf, glinskaya la. systems tl2moo4–e(moo4)2 where e = zr, hf and crystal structure of tl8hf(moo4)6. russ j inorg chem. 2006;51(5):794–9. doi:10.1134/s0036023606050184. 13. klevtsova rf, antonova aa, glinskaya la. the crystal structure of cs2hf(moo4)3. crystallography. 1980;25(1):161–4. 14. romanova eyu. [new double and triple molybdates in the ln2(moo4)3–hf(moo4)2 and k2moo4–ln2(moo4)3–hf(moo4)2 (ln = la–lu, y) systems] [dissertation]. irkutsk (russia); 2007. russian. 15. grossman vg, bazarov bg, tushinova yul, bazarova zh g. phase equilibria in the li2moo4–ln2(moo4)3–hf(moo4)2 (ln  = la–lu) systems. russ j inorg chem. 2015;51(4):351–4. doi:10.1134/s0020168515030061. 16. tushinova yul, bazarova tst, bazarov bg. [phase relations in the na2moo4– ln2(moo4)3–zr(moo4)2 (ln = nd, sm, er, lu)]. vestnik buryatskogo gosudarstvennogo universiteta [bulletin of buryat state university]. 2014;3:3–6. russian. 17. grossman vg, bazarov bg, bazarova zh g. subsolidus phase diagrams for the tl2moo4–ln2(moo4)3–hf(moo4)2 systems, where ln = la–lu. russ j inorg chem. 2008;53(11):1788–94. doi:10.1134/s003602360811020x. 18. chimitova od. [phase equilibrium, crystalline structures and electrical properties of new triple molybdates in the rb2moo4–ln2(moo4)3–hf(moo4)2 (ln  = la–lu) systems] [dissertation]. krasnoyarsk (russia); 2008. russian. 19. shannon rd. revised effective ionic radii and systematic studies of interatomic distances in halides and chalcogenides. acta cryst. 1976; a32:751–67. doi:10.1107/ s0567739476001551. cite this article as: bazarova zhg, grossman vg, bazarov bg, tushinova yul, chimitova od, bazarova tst. phase diagrams for the m2moo4–ln2(moo4)3–hf(moo4)2 systems, where m = li– cs, tl and ln = la–lu. chimica techno acta. 2017;4(4):224–30. doi:10.15826/chimtech/2017.4.4.03. cta_v3_№1.cdr 5 d o i: 1 0. 15 82 6/ ch im te ch .2 01 6. 3. 1. 00 1 i. e. animitsa, n. a. kochetova ural federal university 620002, ekaterinburg, mira str., 19 phone: (343) 261-74-70 e-mail: irina.animitsa@urfu crystal structure and imperfection of the perovskite-like proton conductor ba 4 ca 2 nb 2 o 11 the crystal structure complex oxide ba 4 ca 2 nb 2 o 11 in anhydrous and hydrated forms was studied by the method of neutron diffraction, the preferred localizations of protons were set. the hydration process with temperature variation and the partial pressure of water vapor was studied. it is established that the crystallographic non-equivalence of oh-groups in the structure determines their different thermal stability. the quasi-chemical approach was proposed that describes the formation of proton defects in oxides with structural disordering. keywords: neutrongramma; quasichemical approach; high temperature proton conductors (htpc). © animitsa i. e., kochetova n. a., 2016 introduction proton conductors are widely used as components of electrochemical devices such as gas sensors, electrolysers, fuel cell membranes, etc [1–3]. the class of high temperature proton conductors (htpc) is presented of complex oxide compounds with perovskite structure аво3 or derived from it. in htpc hydrogen is not part of chemical formula, its appearance in the structure of the complex oxide is provided by the equilibrium with н2о/н2-containing atmosphere and is described as the process of dissociative dissolution of water vapor/hydrogen [4]. since the presence of oxygen vacancies is the main factor responsible for the appearance of proton defects, the value of the proton conductivity is determined by the complex oxide defectiveness. in complex oxide compounds with the structural typical disorder of the oxygen sublattice, in contrast to phases with impurity disordering, the number of vacancies in the oxygen sublattice may be considerably higher, therefore the high oxygen deficiency is able to provide a significant level of concentration of protons (and therefore, proton conductivity) [5]. such features allow us to consider these compounds as a distinct class of proton conductors and suggest the need to devise new ways to describe them. at the same time, a combination of properties, such as high concentrations of protons and high reversibility of the processes of hydration, gives ground to consider this class of proton conductors as a promising matrix for proton transport. 6 № 1 | 2016 chimica techno acta animitsa i. e., kochetova n. a. in the present work we report a detailed study of the crystal structure of proton conductor ba4ca2nb2o11 and set the preferred places of localization of protons, and also developed a quasichemical approach to describe the processes of formation of proton defects. experimental part the synthesis of the sample with a  nominal composition of ba4ca2nb2o11 was conducted by solid-phase synthesis from the pre-dried carbonates and niobium oxide at temperature endurances 800–1000–1200–1300 ос for 24 h with intermediate chafing. the hydrated samples were obtained by slow cooling (1 ос /min) with 1000 ос to 150-200 ос in the humid air (рн2о = 2 · 10 -2 atm). the amount of absorbed water was controlled by the method of thermogravimetry. the neutron diffraction studies were performed at the nuclear research reactor ivv-2m (zarechny town, sverdlovsk region) using diffractometer d-7a with a double monochromator. the first monocrystal is pyrolytic graphite with a reflective plane (002), the second is germanium, the reflection plane is 511. the wavelength of monochromatic neutrons is λ = 1.5255 å. data were obtained at room temperature in the angular range 9–130 оc with a step of 0.05 оc and angular resolution is δd/d = 0.02 %. the refinement of crystal structure was carried out using full-profile analysis on rietveld by using the software package fullprof [6]. the studies of surface morphology of the samples was performed by scanning electron microscope jeol jsm-6390la. for the quantitative determination of the elemental composition of the samples the energy dispersive microanalysis with energy dispersive console jeol jed 2300 was carried out. the limit of detection at normal energies (5–20 kv) was ~0.5 at. %. the error of concentration measurement is ±2 %. the management, monitoring and analysis of the received data were carried out using the software package analysis station jed series, version 3.7. the thermogravimetric studies were carried out in the heating process in the atmosphere of dry ar in thermoanalyzer tg sta 409 pc (netzsch) included with unit quadrupole mass spectrometer qms 403c aëlos. the shooting of isothermal dependences of the mass from the partial pressure of water vapor was performed with stepwise change of humidity from рh2o = 3 · 10 –5 atm to рh2o  =  2 · 10 –2 atm. under each value of the activity of water vapor the system was maintained to a state of equilibrium within a few days. results and discussion according to the results of local energy-dispersive x-ray microanalysis it is established that the stoichiometry of the synthesized sample was maintained within 1 at. %, there was a slight variation in the values of ratios of ba:ca:nb, the overall composition of the sample was characterized by a slight lack of ca. the study of the morphology of the powder sample did not reveal the presence of impurity phases, the homogene7 № 1 | 2016 chimica techno acta crystal structure and imperfection of the perovskite-like proton conductor ba 4 ca 2 nb 2 o 11 ous distribution of metal components was observed. the structure of the anhydrous sample ba4ca2nb2o11 was investigated by using neutron diffraction. fig. 1 shows experimental, calculated and differential profiles of neutronography. it is established that the crystal structure ba4ca2nb2o11 is described in the structural type of the double perovskite а2(вв’)о6, and is characterized by a cubic cell with space group fm3m, which corresponds well with x-ray diffraction studies carried out previously [7]. for four formula units а2(вв’)о6 the following distribution of hydrogen atoms in the positions is characterized: 8с-crystallographic positions are filled with cations of barium (a-sublattice), the cations b-sublattice (niobium and calcium) occupy two crystallographically nonequivalent positions 4a and 4b, the oxygen takes position 24e. the main results of calculations are presented in table 1. according to the data about the coordinates of the atoms and the unit cell parameters the interatomic distances were calculated (table 2). the structure is built from connected by vertices different octahedra nbo6 and сао6 formed by orderly arranged atoms of niobium and calcium and is oxygen-deficient, which is confirmed by the partial filling of oxygen positions. the location of oxygen vacancies is statistical, as the predominant places of their localization have not been identified. the next step was the study of the structure of the sample ba4ca2nb2o11 in hydrated form. the degree of hydration was established according to data of thermogravimetry, the overall composition is corresponded to the formula ba4ca2nb2o11·0.96н2о. table 1 the coordinates and isotropic thermal parameters (b) atoms of the anhydrous sample ba4ca2nb2o11 atom position the coordinates of the atoms coefficient of filling b×100, å2 x y z nb 4a 0 0 0 1.00 0.5(1) ca 4b 0 0 0.5 0.935(2) 1.76(4) ba 8c 0.25 0.25 0.25 1.00 1.59(9) o 24e 0.2347(5) 0 0 0.917(5) 2.54(8) rwp=5.14% rp=6.06% χ 2=1.36 r(f2)=3.37 characteristics of atoms: space group fm3m, cubic symmetry, z=4 the unit cell parameters: а = b = c = 8.4428(3) å; a = b = g = 90°; v = 601.80(3) å3; x-ray density 5.47 g/cm3 fig. 1. neutrongramma sample composition ba4ca2nb2o11, shows the experimental (points), calculated (line) and difference (bottom) data and the angular position of the reflexes for cubic phases (strokes) 8 № 1 | 2016 chimica techno acta table 2 interatomic distances (å) in the coordination polyhedra in the anhydrous sample ba4ca2nb2o11 interatomic distances bao12 cao6 nbo6 м–о 2.987 2.222 1.999 о–о 3.142 2.827 based on the data of neutron diffraction it was found that when hydrated niobate of barium-calcium the cell symmetry is reduced to monoclinic and can be described in the space group р21/n. neutrongramma is presented in fig. 2. as a result of absorption of water is the filling of oxygen vacancies by oxygen atoms from the water molecules, respectively, the total content of oxygen in hydrated sample increases, as evidenced by the corresponding fill coefficients. thus there is a distortion of the octahedra and the position of the oxygen atoms become non-equivalent. the data for the atomic coordinates and interatomic distances are in tables 3, 4. as can be seen, the distance from the atom of niobium up to four equatorial oxygen atoms is equal to 2.013 å and 2.115 å, and to the axial atoms is 2.066 å. in ca-octahedron these distances are slightly larger, respectively, to the equatorial oxygen atoms is 2.226 å and 2.125 å, and to the axial atoms is 2.254 å. fig. 2. neutrongramma of sample ba4ca2nb2o11·0.96н2о shows the experimental (points), calculated (line) and difference (bottom) data and the angular position of the reflexes for monoclinic phase (strokes) table 3 the coordinates and isotropic thermal parameters (b) atoms in ba4ca2nb2o11·0.96н2о according to data of neutron atom position the coordinates of the atom filling (abs.ed) b×100, å2 x y z ba nb 4e 2d –0.01312 0.50000 –0.00354 0.00000 0.7422 0.00000 4.00 2.00 1.893(2) 0.889(1) ca 2с 0.50000 0.00000 0.50000 1.815(7) 0.989(4) o1 4e 0.24055 0.26523 0.49187 4.000(0) 2.705(3) o2 4e 0.24067 –0.24146 0.49764 4.000(0) 3.069(8) o3 н1 н2 н3 4e 4e 4e 4e –0.02101 0.10214 0.27941 0.07867 0.47958 0.47503 0.15590 0.19818 0.73512 0.63517 0.20102 0.09212 3.616(0) 0.764 0.366 0.727 1.13(11) 1.13(11) 1.13(11) 1.13(11) rwp=3.16 %; rp=4.80 %; rf=5.39 %; χ 2=1.36 characteristics of atoms: space group р21/n, monoclinic symmetry the unit cell parameters: а = 5.9864(3) å; a = g = 90°; b = 5.9964(0) å; b = 89.838(15)°; c = 8.4958(2) å; v = 304.97(3) å3; x-ray density of 5.42 g/cm3 animitsa i. e., kochetova n. a. 9 № 1 | 2016 chimica techno acta the position of the protons is described by three possible positions h1, h2, h3. most of the protons (h1 and h2) is localized on axial oxygen atoms o3, forming oh--groups in which the distances oxygen-hydrogen are as follows: 1.125 å, 1.219 å (fig. 3). the h3 protons are localized at the equatorial oxygen atoms, shifting slightly above and below the equatorial plane and forming онˉ-groups with a sufficiently large connection lengths of 1.37 å (bond o2-h3). the positions of the h2 have a small filling, the main part of protons is distributed on the positions h1 and h3, which have approximately the same population (table 4). table 4 interatomic distance (å) in the structure ba4ca2nb2o11·0.96н2о polyhedron м−о1 м−о2 м−о3 сао6 2.226 (×2) 2.124 (×2) 2.254 (×2) nbо6 2.012(×2) 2.115(×2) 2.006 (×2) bao12 3.068 3.109 2.885 2.945 2.941 3.164 2.861 3.032 3.098 2.899 2.798 3.203 d o−h о3−н1 1.125 о3−н2 1.219 о2−н3 1.371 based on the data for fill factors, it can be concluded that there is a good correlation with the results of energy dispersive x-ray microanalysis on quantitative composition phase. the general formula can be written as h1.86ba4ca1.82nb2o4o4o3.62 or by highlighting hydroxo group ba4ca1.82(oh)1.86nb2o7.14. the hydration processes were studied by the method of thermogravimetry under the variations of temperature and partial pressure of water vapor in the gas phase рн2о (fig. 4, 5). on tg curves (fig. 4) there has been a dramatic change in mass of the sample at a temperature of 400–450 °c, which fig. 3. the fragment structure of the sample ba4ca2nb2o11·0.96н2о; shows the main interatomic distances (å) in the nbo6 octahedra and cao6 and the positions of the protons h1, h2, h3 fig. 4. tg curves and mass spectrum (ion current) water allocations in (1) ba4ca2nb2o11∙0.95h2o and (2) ba4ca2nb2o11∙0.50h2o (partial hydration) crystal structure and imperfection of the perovskite-like proton conductor ba 4 ca 2 nb 2 o 11 10 № 1 | 2016 chimica techno acta removed the main amount of water (0.65 mole), next there were more monotonous change in mass of up to 700 °c. the mass spectrum characterizing the allocation of water, for extremely hydrated composition ba4ca2nb2o11∙0.96h2o is presented by a peak in the temperature range 250–550 oc, its complex type indicates the superposition of several signals and reflects the presence of three overlapping effects. the mass spectrum of the allocation of water of partially hydrated sample ba4ca2nb2o11∙0.5h2o shows the redistribution of the peak intensities, primarily a decrease in intensity of low temperature peak of the allocation of water. the crystallographic non-equivalence of the он--groups is manifested in their different thermal stability. the isolated он--groups, that are remoted from the adjacent oxygen atoms at distances comparable to the size of the octahedron, are the most thermally resistant, and this fact reflects the greatest strength of bond o−h. the dependences of the concentration of protons from the partial pressure of water vapor lgcн = f(lgph2o) is presented in fig. 5. as you can see, in the area of investigated temperatures range 300–500 ос and рh2o = 3·10 -5÷2·10-2 atm there is an increase in the concentration of protons with increasing рh2o, the dependences in a logarithmic scale are characterized by a linear function with a slope of 1/3. to describe the process of dissociative dissolution of water vapour in a matrix of complex oxide we used the quasichemical approach, which allows to demonstrate the dependence of the concentration of proton defects from atmospheric humidity. the quasichemical description of the process of water absorption is sufficient detaily described for perovskite-like phases, in which oxygen vacancies are set acceptor doping. in these views, the formation of proton defects is considered as the appearance of the proton localized on oxygen, so it is represented as a particle он–, which occupies the anionic site (oh)o · . the corresponding equation of quasi-chemical reactions is as follows: v h o o 2(oh)o 2 газ o o •• × •+ + ⇔ , (1) where vo ·· – the oxygen vacancy, oo ´ – the oxygen atom in the regular position, (oh)o · – hydroxyl group in the oxygen sublattice with an effective positive charge. accordingly, the concentration of proton defects in the structure of the oxide increases with increasing partial pressure of water vapor as [oh ] рh oo 2 1/2• ∝ (t = const), where [oh ]o · is the concentration of the defect. usually the experimentally observed functional dependence lgcн = f(lgph2o) (ch – volume concentration of proton defects) for acceptare doped perovskites аво3-δ is characterized by the slope dlgc d рh oh 2lg »1 2 [8]. for phases with the structural disordering of the oxygen vacancies should be considered as neutral defects (vacant fig. 5. the dependence of the concentration of proton defects in the structure ba4ca2nb2o11∙nн2о from partial pressure of  water vapor animitsa i. e., kochetova n. a. 11 № 1 | 2016 chimica techno acta oxygen positions), therefore the water implementation process should be described otherwise. however, the emergence of neutral defects in quasi-chemical reactions creates uncertainty, since the concentration of this neutral defect cannot be made in the condition of electroneutrality (cen), and therefore it is impossible to establish its functional relationship with the concentrations of other defects. to avoid this situation it is usually proposed to take into account the equilibrium of the type: o v v oo o o vo × × ••+ ⇔ + ′′ , (2) where the formation of doubly ionized oxygen vacancies vo ·· occurs as a result of the migration of lattice oxygen on the place of structural vacancy, while the oxygen atom becomes formally effective negative charge corresponding to the charge of an atom in interstitial positions ¢¢ovo [9]. thus, the implementation process of the water is reduced to the equation (1). the experimental results obtained in the present work on studing of dependency lgcн = f(lgph2o) for ba4ca2nb2o11 with structural disordering showed that a previously proposed model cannot describe the observed dependence with a slope of 1/3. therefore, the following cases of dissociative dissolution of water in the matrix of the complex oxide with the structural disordering of the oxygen sublattice are considered below. if we consider the process of introducing water with the participation of oxygen vacancies as a neutral defect, it can be assumed that oxygen from water molecules is embedded in the place of structural vacancy, and the protons are placed at regular oxygen points: h o 2o v 2oh o2 o o o vо+ + ⇔ + ′′ × × • (3) the condition of electroneutrality (cen) can be written as: 2 o [ohv oо[ ] ]. ′′ = • the electronic defects are excluded from the cen, because it determines the conditions for dominance of atomic disordering. in addition, there is an additional relationship between the concentrations of neutral defects and oxygen vacancies. if we assume that initially, in the complex oxide the volumetric concentration of oxygen vacancies is characterized by some constant value, then the introduction of water it decreases as: o [vv ooa [ ] ] ′′ = × . the equilibrium constant of reaction (3) can be written as follows: k = ⋅ ′′ ⋅ = ⋅ ′′ ⋅ − ′′ • × •[oh ] [o ] ph o [v ] [oh ] [o ] ph o (a [o ] o 2 v 2 o o 2 v 2 v o o o )) (4) for analysis of the dependence of concentration of defects at a variation рн2о (t  =  const) we consider the conditions of approximation, corresponding to the three possible cases. 1) the low рн2о [ ] ; [ ], ]v o [oho v oо × •≈ >> ′′a 2) the middle рн2о 2 o [oh vv o oо[ ] ] [ ] ′′ = >>• × since [ ] ,′′ <ovo a then the concentration of defects will be: [ ] ,′′ <ovo a = (2ак) 1/3 . (рн2о) 1/3 [ ]¢¢ovo = (ak/4) 1/3 . (рн2о) 1/3 [ ]vo ´ = a – (ak/4) 1/3 . (рн2о) 1/3 that is, the concentration of dominant defects will be proportional рн2о 1/3. 3) the high рн2о in the case of complete filling of oxygen vacancies as a result of the implementation of the water we have: 2 o [ohv oо[ ] ] ′′ = =• 2 a , >> [ ]vo ´ . that is, the concentration of dominant defects do not depend on рн2о fig. 6а presents the dependence of concentration of defects from рн2о in logarithmic coordinates. crystal structure and imperfection of the perovskite-like proton conductor ba 4 ca 2 nb 2 o 11 12 № 1 | 2016 chimica techno acta thus, it can be expected that at low temperatures the concentration of proton defects will increase with increasing рн2о and in logarithmic coordinates it will have a slope of 1/3. in experiments on study of conductivity as a function рн2о, additionally taking that the mobility of the protons is much higher than the mobility of oxygen vacancies, in the simplest case, we should also expect the increase in the total conductivity as a function рн2о 1/3. the presented calculations for structural models of the oxygen vacancies show a contrast to the case of the introduction of water in complex oxides with impurity disordering. it should say that the equation (3) describing the penetration of water into structurally disordered complex oxides is not only. the appearance of oxygen on the place of structural vacancy as the defect with a negative charge ¢¢ovo creates conditions the preferential localization of the proton on the oxygen. therefore, in the framework of the quasichemical formalism, this process can be written as follows: h o o v oh oh2 o o o vo+ + ⇔ + ′ × × • (5) as can be seen, the formation of two types of proton defects with different charges takes place: localization of the proton on the oxygen, standing in a regular position, leads to the appearance of the defect oho · , and on the oxygen coming from water molecules leads to the appearance ohvo¢ . the seeming contradiction related to the appearance of proton defects of opposite sign occurs because in the quasichemical description the defect is attributed to an effective charge which is determined as a differential value relative to the charge of the corresponding structural element in an ideal lattice, which is taken for zero. this writing means that the position of the protons is energetically different. the possibility of reaction of proton exchange between lattice oxygen ions and oxygen ions, which has taken structural vacancy can be presented as follows: oh o o oho v o vo o • ×+ ′′ ⇔ + ′ . (6) we write equilibrium constants for reactions (5) and (6): k = ⋅ ′ ⋅ = ⋅ ′′ ⋅ − ′′ • × •[oh ] [oн ] ph o [v ] [oh ] [o ] ph o (a [o ]) o v 2 o o 2 v 2 v o o o (7) the condition of electroneutrality can be written as: 2 o oh [ohv v oo o[ ] [ ] ]. ′′ + ′ = • an additional relationship between the concentrations of defects and structural oxygen vacancies can be represented as: [ ] ([ ] / [ ]).v a o онo v vo o × = − ′′ + ′1 2 fig. 6. the dependence of defects concentration from рн2о (double logarithmic coordinates) for models of defect formation in equations (3) and (5) animitsa i. e., kochetova n. a. 13 № 1 | 2016 chimica techno acta the conditions of approximation will be represented by three possible cases (рн2о = var, т = const). 1) the low рн2о [ ] [ ], ],[ ].v a o [oh oho v o vo o × •≈ >> ′′ ′ 2) the middle рн2о 2 o [oh ohv o voo[ ] ] [ ] ′′ = >> ′• [oho · ] ~ (рн2о) 1/3 [ ]¢¢ovo ~ (рн2о) 1/3 [ohvo ¢ ] ~ (рн2о) 2/3. 3) the high рн2о. in the case of complete filling of oxygen vacancies as a result of introduction of water we have: oh [ohv oo[ ] ] ′ = ≈• 2 a . that is, the concentration of dominant defects does not depend on рн2о. the concentration [ ]vo ´ is low, а [ ]¢¢ovo ≈а. fig. 6b shows the calculated dependences in logarithmic coordinates. comparing the diagrams, it is seen that in general both approaches give a similar situation: the bulk of experimental data of the dependence of the concentration of proton defects from рн2о in logarithmic coordinate will be described by a slope of 1/3 with a gradual withdrawal to the plateau at high partial pressures of water vapor. thus, the differences in the quasichemical approaches of the description of oxygen vacancies formally define the different functional dependence of the concentration of resulting proton defects from рн2о. in the case of doubly ionized oxygen vacancies vo ·· , when the process of interaction with water is reduced to a quasi-chemical equation (1), the concentration of proton defects in the structure of the oxide increases with increasing water vapor activity under the law [oh ] рh oo 2 1/2• ∝ . for phases with neutral defects, the concentration of protons is proportional to рн2о 1/3. the authors thank k-phm.n. voronin, vladimir ivanovich (ipm ub ras) for helping in data processing for structural analysis. 1. norby t. ceramic proton and mixed proton-electron conductors in membranes for energy conversion applications. j. of chem. eng. of japan. 2007;40:1166-1171. 2. reijers r., haije w. literature review on high temperature proton conducting materials. energy research centre of the netherlands. 2008. ecn-e-08-091. 3. phair j. w., badwal s. p. s. review of proton conductors for hydrogen separation. ionics. 2006;12:103-115. 4. kreuer k. d. proton-conducting oxides. annu. rev. mater. res. 2003;33:333-359. 5. animitsa i. perovskites: structure, properties and uses. ed. maxim borowski, nova science publishers. inc. new york, 2010, pp. 501-524. 6. rodriguez-carvajal j. recent developments of the program fullprof. commission on powder diffraction, (iucr). newsletter. 2001;26:12-19. 7. animitsa i., neiman a., kochetova n., melekh b., sharafutdinov a. proton and oxygen-ion conductivity of ba4ca2nb2o11. solid state ionics. 2003;162-163:63-71. 8. pal’gyev s. f. high-temperature proton solid electrolytes. ekaterinburg, ub ras, 1998. 82 p. 9. smyth d. m. defects and order in perovskite-related oxides. ann. rev. mater. sci. 1985;5:329-357. crystal structure and imperfection of the perovskite-like proton conductor ba 4 ca 2 nb 2 o 11 14 у д к 5 44 .2 25 .3 /5 46 .0 3: 54 6. 87 и. е. анимица, н. а. кочетова уральский федеральный университет 620002, г. екатеринбург, ул. мира, 19 тел.: (343) 261-74-70 e-mail: irina.animitsa@urfu.ru кристаллическая структура и дефектность перовскитоподобного протонного проводника ba 4 ca 2 nb 2 o 11 методом нейтронографии изучена кристаллическая структура сложного оксида ba 4 ca 2 nb 2 o 11 в безводной и гидратированной формах, установлены предпочтительные места локализации протонов. изучен процесс гидратации при варьировании температуры и парциального давления паров воды. установлено, что кристаллографическая неэквивалентность он–-групп в структуре обуславливает их различную термическую устойчивость. предложен квазихимический подход, описывающий образование протонных дефектов в оксидах со структурным разупорядочением. ключевые слова: нейтронограмма; квазихимический подход; высокотемператуные протонные проводники (втпп). © анимица и. е., кочетова н. а., 2016 введение протонные проводники находят широкое применение в качестве компонентов электрохимических устройств, таких как газовые сенсоры, электролизеры, мембраны топливных элементов и др. [1–3]. класс высокотемпературных протонных проводников (втпп) представлен сложнооксидными соединениями со структурой перовскита аво3 или производной от нее. в втпп водород не является составной частью химической формулы, его появление в структуре сложного оксида обеспечивается равновесием с н2о/н2-содержащей атмосферой и описывается как процесс диссоциативного растворения паров воды/ водорода [4]. поскольку наличие вакансий кислорода является основным фактором, ответственным за появление протонных дефектов, то величина протонной проводимости определяется дефектностью сложного оксида. в сложнооксидных соединениях со структурной разупорядоченностью кислородной подрешетки, в отличие от фаз с примесным разупорядочением, число вакансий в кислородной подрешетке может быть существенно выше, поэтому высокий кислородный дефицит способен обеспечить значимый уровень концентрации протонов (и,  соответственно, протонной проводимости) [5]. именно такие особен15 № 1 | 2016 chimica techno acta ности позволяют рассматривать эти соединения как отдельный класс протонных проводников и предполагают необходимость разработки новых способов их описания. в то же время сочетание таких свойств, как высокие концентрации протонов и высокая обратимость процессов гидратации, дает основание рассматривать этот класс протонных проводников как перспективные матрицы для протонного транспорта. в настоящей работе проведено детальное исследование кристаллической структуры протонного проводника ba4ca2nb2o11 и установлены предпочтительные места локализации протонов, а также разработан квазихимический подход описания процессов образования протонных дефектов. экспериментальная часть синтез образца номинального состава ba4ca2nb2o11 проводился методом твердофазного синтеза из предварительно осушенных карбонатов и оксида ниобия при температурных выдержках 800–1000–1200–1300 °с по 24 ч. с промежуточными перетираниями. гидратированные образцы были получены медленным охлаждением (1 °c/мин) с 1000 °с до 150–200 °с в атмосфере влажного воздуха (рн2о = =  2 · 10–2 атм). количество поглощенной воды контролировалось методом термогравиметрии. нейтронографические исследования проводили на исследовательском атомном реакторе ивв-2м (г. заречный свердловской обл.) при использовании дифрактометра д-7а с двойным монохроматором. первый монокристалл – пиролитический графит с отражающей плоскостью (002), второй – германий, плоскость отражения (511). длина волны монохроматических нейтронов λ = 1,5255 å. данные были получены при комнатной температуре в угловом интервале 9–130 °c с  шагом 0,05 °c и угловым разрешением δd/d = 0,02 %. уточнение кристаллической структуры проводилось методом полнопрофильного анализа по ритвельду с использованием программного пакета fullprof [6]. исследования морфологии поверхности образцов проводили на сканирующем электронном микроскопе jeol jsm-6390la. для количественного определения элементного состава образцов был проведен энергодисперсионный микроанализ с помощью энергодисперсионной приставки jeol jed 2300. предел детектирования при обычных энергиях (5–20 кв) составил ~0,5  ат.%, ошибка измерения концентрации ±2 %. управление, контроль работы и анализ полученных данных осуществляли с использованием программного пакета analysis station, jed series, version 3.7. термогравиметрические исследования проводились в процессе нагрева в атмосфере сухого ar на термоанализаторе tg sta 409 pc (netzsch) в комплекте с блоком квадрупольного массспектрометра qms 403c aëlos. съемку изотермических зависимостей массы от парциального давления паров воды осуществляли при стадийной смене влажности от рh2o = 3 · 10 –5 атм до рh2o  =  2 · 10 –2 атм. при каждом значении активности паров воды система выдерживалась до состояния равновесия в течение нескольких суток. кристаллическая структура и дефектность перовскитоподобного протонного проводника ba 4 ca 2 nb 2 o 11 16 № 1 | 2016 chimica techno acta результаты и обсуждение по результатам локального энергодисперсионного рентгеновского микроанализа установлено, что стехиометрия синтезированного образца сохранялась в пределах 1 ат. %, наблюдался незначительный разброс в  значениях соотношений ba:ca:nb, общий состав образца характеризовался незначительным недостатком ca. исследование морфологии порошкового образца не выявило наличия примесных фаз, наблюдалось гомогенное распределение металлических компонентов. структура безводного образца ba4ca2nb2o11 была исследована методом нейтронной дифракции. на рис. 1 представлены экспериментальный, рассчитанный и разностный профили нейтронограммы. установлено, что кристаллическая структура ba4ca2nb2o11 описывается в  структурном типе двойного перовскита а2(вв’)о6 и характеризуется кубической ячейкой с пространственной группой fm3m, что хорошо соотносится с рентгенографическими исследованиями, проведенными ранее [7]. для четырех формульных единиц а2(вв’)о6 характерно следующее распределение атомов по позициям: 8с-кристаллографические позиции заполняются катионами бария (а-подрешетка), катионы в-подрешетки (ниобий и кальций) заселяют две кристаллографически неэквивалентные позиции – 4a и 4b, кислород занимает позиции 24e. основные результаты расчетов представлены в табл. 1. по данным о координатах атомов и параметрах элементарной ячейки были рассчитаны межатомные расстояния (табл.  2). структура построена из таблица 1 координаты и изотропные тепловые параметры (в) атомов безводного образца ba4ca2nb2o11 атом позиция координаты атомов коэффициент заполнения b×100, å2 x y z nb 4a 0 0 0 1,00 0,5(1) ca 4b 0 0 0,5 0,935(2) 1,76(4) ba 8c 0,25 0,25 0,25 1,00 1,59(9) o 24e 0,2347(5) 0 0 0,917(5) 2,54(8) rwp = 5,14 % rp = 6,06 % χ 2 = 1,36 r(f2) = 3,37 характеристики атомов: пространственная группа fm3m, кубическая симметрия, z = 4. параметры элементарной ячейки: а = b = c = 8,4428(3) å; a = b = g = 90°; v = 601,80(3) å3. рентгеновская плотность – 5,47 г/см3. рис. 1. нейтронограмма образца состава ba4ca2nb2o11, показаны экспериментальные (точки), расчетные (линия), разностные (внизу) данные и угловые положения рефлексов для кубической фазы (штрихи) анимица и. е., кочетова н. а. 17 № 1 | 2016 chimica techno acta связанных вершинами разноразмерных октаэдров nbo6 и сао6, образованных упорядоченно расположенными атомами ниобия и кальция, и является кислород-дефицитной, что подтверждается частичным заполнением позиций кислорода. расположение вакансий кислорода является статистическим, так как преимущественных мест их локализации не выявлено. на основе данных нейтронной дифракции было установлено, что при гидратации ниобата бария-кальция симметрия ячейки понижается до моноклинной и может быть описана в пространственной группе р21/n. нейтронограмма представлена на рис. 2. следующим этапом работы было исследование структуры образца ba4ca2nb2o11 в гидратированной форме. степень гидратации была установлена по данным термогравиметрии, общий состав соответствовал формуле ba4ca2nb2o11 · 0,96н2о. в результате поглощения воды происходит заполнение кислородных вакансий атомами кислорода от молекул воды, соответственно, общее содержание кислорода в гидратированном образце увеличивается, что подтверждается соответствующими коэффициентами заполнения. при этом происходит искажение окта эдров, и позиции атомов кислорода становятся неэквивалентными. данные по координатам атомов и меж атомным расстояниям – в табл. 3, 4. как видно, расстояния от атома ниобия до четырех экваториальных атомов кислорода равно 2,013 å и 2,115 å, а до аксиальных – 2,066 å. в са-октаэдре эти расстояния немного больше, соответственно, до экваториальных атомов кислорода – 2,226 å и 2,125 å, и до аксиальных – 2,254 å. положение протонов описывается тремя возможными позициями н1, н2, н3. бóльшая часть протонов (н1 и н2) локализуется на аксиальных атомах кислорода о3, образуя он ˉгруппы, в которых расстояния кислород-водород распределяются следующим образом: 1,125 å, 1,219 å (рис. 3). протоны н3 локализуются на экваториальных атомах кислорода, смещаясь немного выше и ниже экваториальной плоскости и образуя онˉ-группы с достаточно большими длинами связи 1,37 å (связь о2– н3). позиции н2 имеют небольшое заполнение, основная часть протонов распределяется по позициям н1 и н3, рис. 2. нейтронограмма образца ba4ca2nb2o11·0.96н2о; показаны экспериментальные (точки), расчетные (линия), разностные (внизу) данные и угловые положения рефлексов для моноклинной фазы (штрихи) таблица 2 межатомные расстояния (å) в координационных полиэдрах в безводном образце ba4ca2nb2o11 межатомные расстояния bao12 cao6 nbo6 м–о 2,987 2,222 1,999 о–о 3,142 2,827 кристаллическая структура и дефектность перовскитоподобного протонного проводника ba 4 ca 2 nb 2 o 11 18 № 1 | 2016 chimica techno acta которые имеют примерно одинаковое заполнение (табл. 4). исходя из данных по коэффициентам заполнения, можно заключить, что наблюдается хорошая корреляция с результатами энергодисперсионного рентгеновского микро анализа по количественному составу фазы. общая формула может быть записана как h1,86ba4ca1,82nb2o4o4o3,62 или, выделяя гидроксогруппу, ba4ca1,82(oh)1.86nb2o7,14. рис. 3. фрагмент структуры образца ba4ca2nb2o11 · 0,96н2о; показаны основные межатомные расстояния (å) в октаэдрах nbo6 и cao6 и позиции протонов н1, н2, н3 таблица 3 координаты и изотропные тепловые параметры (в) атомов в ba4ca2nb2o11 · 0,96н2о по данным нейтронной дифракции атом позиция координаты атома заполнение (абс. ед.) b×100, å2 x y z ba nb 4e 2d –0,01312 0,50000 –0,00354 0,00000 0,7422 0,00000 4,00 2,00 1,893(2) 0,889(1) ca 2с 0,50000 0,00000 0,50000 1,815(7) 0,989(4) o1 4e 0,24055 0,26523 0,49187 4,000(0) 2,705(3) o2 4e 0,24067 –0,24146 0,49764 4,000(0) 3,069(8) o3 н1 н2 н3 4e 4e 4e 4e –0,02101 0,10214 0,27941 0,07867 0,47958 0,47503 0,15590 0,19818 0,73512 0,63517 0,20102 0,09212 3,616(0) 0,764 0,366 0,727 1,13(11) 1,13(11) 1,13(11) 1,13(11) rwp=3,16% rp=4,80 % rf=5,39 % χ 2=1,36 характеристики атомов: пространственная группа р21/n, моноклинная симметрия. параметры элементарной ячейки: а = 5,9864(3) å; a = g = 90; b = 5,9964(0) å; b = 89,838(15)°; c = 8,4958(2) å; v = 304,97(3) å3. рентгеновская плотность – 5,42 г/см3. таблица 4 межатомные расстояния (å) в структуре ba4ca2nb2o11 · 0,96н2о полиэдр м−о1 м−о2 м−о3 сао6 2,226 (×2) 2,124 (×2) 2,254 (×2) nbо6 2,012(×2) 2,115(×2) 2,006 (×2) bao12 3,068 3,109 2,885 2,945 2,941 3,164 2,861 3,032 3,098 2,899 2,798 3,203 d o−h о3−н1 1,125 о3−н2 1,219 о2−н3 1,371 анимица и. е., кочетова н. а. 19 № 1 | 2016 chimica techno acta процессы гидратации изучались методом термогравиметрии при варьировании температуры и парциального давления паров воды в газовой фазе рн2о (рис. 4, 5). на тг-кривых (рис. 4) наблюдается резкое изменение массы образца при температуре 400–450 °с, в результате которого удалялось основное количество воды (0,65 моль), далее происходило монотонное изменение массы до 700 °с. масс-спектр, характеризующий выделение воды, для предельно гидратированного состава ba4ca2nb2o11 × × 0,96h2o, представлен пиком в области температур 250–550 °с, его сложный вид свидетельствует о наложении нескольких сигналов, причем хорошо прослеживается наличие трех перекрывающихся эффектов. масс-спектр выделения воды частично гидратированного образца ba4ca2nb2o11 ∙ 0,5h2o демонстрирует перераспределение интенсивности пиков, в первую очередь наблюдается уменьшение интенсивности низкотемпературного пика выделения воды. то есть кристаллографическая неэквивалентность он–-групп проявляется в их различной термической стойкости. изолированные он–-группы, то есть удаленные от соседних атомов кислорода на расстояния, сопоставимые с размерами октаэдра, являются наиболее термически стойкими, и это обстоятельство отражает наибольшую прочность связи о−н. зависимости концентрации протонов от парциального давления паров воды представлены на рис. 5. как можно видеть, в области исследованных температур 300–500 °с и рh2o = 3 · 10 –5  ÷ ÷ 2 · 10–2 атм наблюдается увеличение концентрации протонов с увеличением рh2o, зависимости в логарифмических координатах характеризуются линейной функцией с наклоном 1/3. для описания процесса диссоциативного растворения паров воды в  матрице сложного оксида нами использован квазихимический подход, который позволяет наглядно продемонстрировать зависимость концентрации протонных дефектов от влажности атмосферы. квазихимическое рис. 4. тг-кривые и масс-спектр (ионный ток) выделения воды в (1) ba4ca2nb2o11 × × 0,95h2o и (2) ba4ca2nb2o11 ∙ 0,50h2o (частичная гидратация) рис. 5. зависимость концентрации протонных дефектов в структуре ba4ca2nb2o11 × nн2о от парциального давления паров воды кристаллическая структура и дефектность перовскитоподобного протонного проводника ba 4 ca 2 nb 2 o 11 20 № 1 | 2016 chimica techno acta описание процессов поглощения воды достаточно подробно описано для перовскитоподобных фаз, в которых вакансии кислорода задаются акцепторным допированием. в рамках этих представлений, образование протонных дефектов рассматривается как появление протона, локализованного на ионе кислорода, поэтому его представляют как частицу он–, занимающую анионный узел – (oh)o · . соответствующее уравнение квазихимической реакции следующее: v h o o 2(oh)o 2 газ o o •• × •+ + ⇔ , (1) где vo ·· – вакансия кислорода, oo ´ – атом кислорода в регулярной позиции, (oh)o · – гидроксильная группа в подрешетке кислорода с эффективным положительным зарядом. соответственно, концентрация протонных дефектов в структуре оксида возрастает с увеличением парциального давления паров воды как [oh ] рh oo 2 1/2• ∝ (т = const), где [oh ]o · – концентрация дефекта. обычно экспериментально наблюдаемая функциональная зависимость lgcн = f(lgph2o) (ch – объемная концентрация протонных дефектов) для акцепторно допированных перовскитов аво3–δ характеризуется наклоном dlgc d рh oh 2lg »1 2 [8]. для фаз со структурным разупорядочением вакансии кислорода следует рассматривать как нейтральные дефекты (незанятые кислородные позиции), поэтому процесс внедрения воды следует описывать иначе. однако появление нейтральных дефектов в квазихимических реакциях создает неопределенность, поскольку концентрация такого нейтрального дефекта не может быть внесена в условие электронейтральности (уэн), и поэтому нельзя установить ее функциональную связь с концентрациями других дефектов. чтобы избежать такой ситуации обычно предлагается учитывать равновесие типа: o v v oo o o vo × × ••+ ⇔ + ′′ , (2) где образование двукратно ионизированной вакансии кислорода происходит в результате миграции решеточного кислорода на место структурной вакансии, при этом атом кислорода формально приобретает эффективный отрицательный заряд, соответствующий заряду атома в межузельной позиции [9]. таким образом, процесс внедрения воды сводится к уравнению (1). экспериментальные результаты, полученные в настоящей работе по изучению зависимостей для ba4ca2nb2o11 со структурным разупорядочением, показали, что предложенная ранее модель не может описать наблюдаемую зависимость с наклоном 1/3. поэтому ниже рассмотрены случаи диссоциативного растворения воды в матрице сложного оксида со структурным разупорядочением подрешетки кислорода. если рассматривать процесс внедрения воды с участием вакансии кислорода как нейтрального дефекта, то можно предположить, что   кислород от молекулы воды встраивается на место структурной вакансии, а протоны размещаются на регулярных узлах кислорода: h o 2o v 2oh o2 o o o vо+ + ⇔ + ′′ × × • . (3) условие электронейтральности (уэн) можно записать как: 2 o [ohv oо[ ] ]. ′′ = • электронные дефекты исключены из уэн, так как рассматриваются условия доминироанимица и. е., кочетова н. а. 21 № 1 | 2016 chimica techno acta вания атомного разупорядочения. кроме того, существует дополнительная связь между концентрациями дефектов и  нейтральными вакансиями кислорода. если предположить, что изначально в сложном оксиде объемная концентрация вакансий кислорода характеризовалась некоторой постоянной величиной а, то при внедрении воды она уменьшается как o [vv ooa [ ] ] ′′ = × . константа равновесия реакции (3) запишется следующим образом: k = ⋅ ′′ ⋅ = ⋅ ′′ ⋅ − ′′ • × •[oh ] [o ] ph o [v ] [oh ] [o ] ph o (a [o ] o 2 v 2 o o 2 v 2 v o o o )) . (4) для анализа зависимости концентрации дефектов при вариации рн2о (т = const) рассмотрим условия аппроксимации, соответствующие трем возможным случаям. 1) низкие рн2о [ ] ; [ ], ]v o [oho v oо × •≈ >> ′′a . 2) средние рн2о 2 o [oh vv o oо[ ] ] [ ] ′′ = >>• × . так как < a, то концентрации дефектов [ ] ,′′ <ovo a = (2ак) 1/3 . (рн2о) 1/3 [ ]¢¢ovo = (ak/4) 1/3 . (рн2о) 1/3 [ ]vo ´ = a – (ak/4) 1/3 . (рн2о) 1/3. то есть концентрации доминирующих дефектов будут пропорциональны рн2о 1/3. 3) высокие рн2о. в случае полного заполнения вакансий кислорода в результате внедрения воды имеем: 2 o [ohv oо[ ] ]′′ = = • 2 a , >> [ ]vo ´ . то есть концентрации доминирующих дефектов не зависят от рн2о. на рис. 6, а представлены зависимости концентрации дефектов от рн2о в логарифмических координатах. таким образом, можно ожидать, что в невысоких температурах концентрация протонных дефектов будет возрастать с увеличением рн2о и в логарифмических координатах иметь наклон 1/3. в экспериментах по изу чению проводимости как функции рн2о, дополнительно учитывая, что подвижность протонов значительно превышает подвижность вакансий кислорода, в простейшем случае также следует ожидать увеличение общей проводимости как функции рн2о 1/3. представленные расчеты для модели структурных вакансий кислорода демонстрируют отличие от случая внедрения воды в сложные оксиды с примесным разупорядочением. следует сказать, что уравнение (3), описывающее процесс внедрения воды в структурно-разупорядоченные сложные оксиды, не единственное. появление кислорода на месте структурной вакансии, как дефекта с  отрицательным зарядом ¢¢ovo , создает предпосылки преимущественной локализации протона на этом кислороде. поэтому в рамках квазихимического формализма данный процесс запишется следующим образом: h o o v oh oh2 o o o vo+ + ⇔ + ′ × × • . (5) как видно, происходит образование двух типов протонных дефектов с  разными зарядами: локализация протона на кислороде, стоящем в регулярной позиции, приводит к появлению дефекта, а на кислороде, пришедшем от молекулы воды, – к появлению. кажущееся противоречие, связанное с  появлением протонных дефектов противоположного знака, возникает потому, что в квазихимическом описании дефекту приписывается эффективный заряд, определяющийся как разностное значение по отношению кристаллическая структура и дефектность перовскитоподобного протонного проводника ba 4 ca 2 nb 2 o 11 22 № 1 | 2016 chimica techno acta к  заряду соответствующего структурного элемента в идеальной решетке, которое принимают за нуль. данная запись означает, что положение протонов энергетически различно. возможность протекания реакции протонного обмена между решеточными ионами кислорода и ионами кислорода, занявшими структурные вакансии, может быть представлена следующим образом: oh o o oho v o vo o • ×+ ′′ ⇔ + ′ . (6) запишем константы равновесия для реакций (5) и (6): k = ⋅ ′ ⋅ = ⋅ ′′ ⋅ − ′′ • × •[oh ] [oн ] ph o [v ] [oh ] [o ] ph o (a [o ]) o v 2 o o 2 v 2 v o o o . (7) условие электронейтральности запишется как: 2 o oh [ohv v oo o[ ] [ ] ]. ′′ + ′ = • дополнительная связь между концентрациями дефектов и структурными вакансиями кислорода может быть представлена в виде: [ ] ([ ] / [ ]).v a o онo v vo o × = − ′′ + ′1 2 условия аппроксимации будут представлены тремя возможными случаями (рн2о = var, т = const). 1) низкие рн2о [ ] [ ], ],[ ].v a o [oh oho v o vo o × •≈ >> ′′ ′ 2) средние рн2о 2 o [oh ohv o voo[ ] ] [ ] ′′ = >> ′• [oho · ] ~ (рн2о) 1/3 [ ]¢¢ovo ~ (рн2о) 1/3 [ohvo ¢ ] ~ (рн2о) 2/3. 3) высокие рн2о. в случае полного заполнения вакансий кислорода в результате внедрения воды имеем, oh [ohv oo[ ] ] ′ = ≈• 2 a . то есть концентрация доминирующих дефектов не зависит от рн2о. концентрация [ ]vo ´ мала, а [ ]¢¢ovo   ≈  а. на рис. 6, б представлены расчетные зависимости в логарифмических координатах. сравнивая представленные диа граммы, видно, что в общем случае оба подхода дают схожую ситуацию: основной массив экспериментальных данных зависимости концентрации протонных дефектов от рн2о в логарифмических координатах будет описываться наклоном 1/3 с постепенным выходом на плато в области высоких парциальных давлений паров воды. таким образом, различия в квазихимических подходах описания кислородных вакансий определяет формально различную функциональную зависимость концентрации образующихся протонных дефектов от рн2о. в случае двукратно ионизированных вакансий кислорода vo ·· , когда прорис. 6. зависимости концентрации дефектов от рн2о (двойные логарифмические координаты) для моделей дефектообразования по уравнениям (3) и (5) анимица и. е., кочетова н. а. а б 23 № 1 | 2016 chimica techno acta цесс взаимодействия с водой сводится к квазихимическому уравнению  (1), концентрация протонных дефектов в структуре оксида возрастает с увеличением активности паров воды по закону [oh ] рh oo 2 1/2• ∝ . для фаз с нейтральными дефектами концентрация протонов пропорциональна рн2о 1/3. авторы выражают благодарность к.  ф.-м.  н. владимиру ивановичу воронину (ифм уро ран) за помощь при обработке данных по структурному анализу. 1. norby t. ceramic proton and mixed proton-electron conductors in membranes for energy conversion applications. j. of chem. eng. of japan. 2007;40:1166–1171. 2. reijers r., haije w. literature review on high temperature proton conducting materials. energy research centre of the netherlands. 2008. ecn-e-08-091. 3. phair j. w., s. badwal p. s. review of proton conductors for hydrogen separation. ionics. 2006;12:103-115. 4. kreuer k. d. proton-conducting oxides. annu. rev. mater. res. 2003;33:333–359. 5. animitsa i. in perovskites: structure, properties and uses. ed. maxim borowski, nova science publishers. inc. new york, 2010. р. 501–524. 6. rodriguez-carvajal j.recent developments of the program fullprof. commission on powder diffraction, (iucr). newsletter. 2001;26:12–19. 7. animitsa i., neiman a., kochetova n., melekh b., sharafutdinov a. proton and oxygen-ion conductivity of ba4ca2nb2o11. solid state ionics. 2003;162-163:63–71. 8. пальгуев с. ф. высокотемпературные протонные твердые электролиты. екатеринбург: уро ран, 1998. 82 с. 9. smyth d. m. defects and order in perovskite-related oxides. ann. rev. mater. sci. 1985;5:329–357. кристаллическая структура и дефектность перовскитоподобного протонного проводника ba 4 ca 2 nb 2 o 11 226 a. g. titov, z. r. gil’vanova, e. a. shevchenko, m. k. masnaviev, a. a. bir ural federal university 28 mira street, 620002, ekaterinburg. e-mail: paht@yandex.ru quantitative assessment of reentrainment in the electrocyclone* the paper was devoted to the investigation of the reentrainment which was a parasitic effect incipient at the gas-cleaning systems – cyclones. it was demonstrated that the reentrainment arises at the speed of the aerosol from 14 to 27 m/sec. the quantitative characteristics of the reentrainment were determined. key words: the investigation of the reentrainment; cyclones; gas-cleaning systems; irrigation receiving electrode. •the research project has been supported by russian foundation for basic research (grant 14–08–00046а). © titov a. g., gil’vanova z. r., shevchenko e.  a., masnaviev m. k., bir a. a., 2015 d o i: 1 0. 15 82 6/ ch im te ch .2 01 5. 2. 3. 02 4 introduction the dust materials suppression at the chemical factories is the actual task [1]. the problem of the fine purification of the large gas volume from the disperse particles was existed. at present the applied multileaf lamellar electrostatic filters are too expensive, bulky and don’t ensure the required high purification efficiency to 99.5–97 %. the wet gas cleaning at the emulsifiers troubles the utilization of the product since its release from the pulp and the following drying is requested. the large heat costs are necessary for this. also the task of the elaboration of the high-performance equipment for the cleaning of the large gas volumes (hundred of thousands m3/hour) with the receipt of the product in the dry form is actual [2]. the reentrainment by the dust collecting is the parasitic fact. it depends on the material dispersion, the gas stream speed, the electrode voltage, the design philosophy of the materials and other. the identification of the efficiency dependence of the work of the electrocyclones from mentioned factors represents the scientific and practical interest [3]. early it was shown [4] experimentally that the gas purification efficiency decreases at the aerozol increasing speed above 15–17 m/sec on the entrance to the electrocyclone. the centrifugal force is increasing at the increasing of the gas speed in the active zone that favors to the precipitation of the particles but at the constant length of the machine the time of the aerozol stay is decreasing, the effi227 № 3 | 2015 chimica techno acta ciency of the charging of the particles is down, the ash ola increases. it’s result of that the particles don’t have time to settle on the receiving electrode. the reentrainment is increasing because the already settled particles especially small knocked out of the sediment layer of large particles and turbulent eddies. experiment part you want to exclude one of the factors to assess the degree of influence of the residence time of the gas flow in apparaten factor and the reentrainment on the decrease in the efficiency of particle collection in the electrocyclone. to exclude secondary reentrainment is necessary to irrigate the receiving electrode by film of water (wet mode). then the particles that touched the water film will not be able to go back into the gas stream, and will be permanently removed from the active zone. experiments were conducted in dry and wet mode of operation of the electrocyclone. for research was used an laboratory experimental setup (stand), shown in fig. 1. the stand included the electrocyclone 1, palpatation 2, tranporter tnzh 3, the high voltage source (model ivnr-20–10) 4, a u-shaped tube to determine the hydraulic resistance of the electrocyclone 5, the filter bag 6, inlet pipe to the collector 7, valves 8, rotameters 9, the pressure gauge  10, the filter holder (type ira-20–2) 11, the sampling tube 12. the test material was supplied by palpatation 2 in a disaggregated form on the inlet pipe 7 into the electrocyclone 1. caught ash was collected in the hopper of the electrocyclone 1, and the purified air in the duct was removed through the bag filter 6 into the atmosphere. for experiments with irrigation described above, the electrocyclone was supplemented with irrigation system and removal of the pulp (fig. 2). for irrigation receiving electrode of the electrocyclone 1 used located in the cochlea of the irrigation system, consisting of a distribution of ring 2 and the feed tube 3. the slurry from the hopper 4 is removed through the seal 5 in montego 6. the uniform irrigation of the wall at the translational-rotational motion of the gas was achieved when water flow was 8 l/min. fig. 1. scheme of the experimental setup quantitative assessment of reentrainment in the electrocyclone 228 № 3 | 2015 chimica techno acta results and discussion in the experiments on the capture of ash in the wet mode the reentrainment has been completely eliminated, however, the observed incomplete capture of ash, which can be explained by nagasarete particles and active turbulent mixing flow. the amount of ablation can imagine (1 – n) · 100 % what allowed us to estimate the values of ablation in terms of purity. the dependence of entrainment speed at a fixed concentration of ash 16.5 g/m3 are shown in fig. 3. from figure 3 it is seen that in wet mode at u = 17 kv (electrocyclone mode) carryover is less than 1 %, lowering the voltage to u = 0 kv (cyclone mode) ash reaches 5–7 %, whereas the ash in dry mode, when u = 17 kv matter 12–25 %. according to the experiment were also calculated values of the secondary ash as the difference between the degree of cleaning in wet and dry mode for corresponding points of the plan. the dependence of secondary reentrainment from the input speed and concentration of ash is shown in fig. 4. from fig. 4 shows that reentrainment varies in the interval from 5 to 35 %, the highest values are observed at gas velocities of more than 21 m/sec. the average value of the secondary ash is 10–15 %, which is significantly higher than the entrainment caused by necesarely. thus, reentrainment reduces the efficiency of ash fig. 2. diagram of the cyclone to work in wet mode. indicate in the figure: 1 – electro cyclone, 2 – distribution ring, 3 – feed tube, 4 – bunker, 5 – seal 6 – montagu fig. 3. the dependence of the amount of entrainment from the gas flow rate at different operating conditions of the electrocyclone titova. g., gil’vanova z. r., shevchenko e. a., masnaviev m. k., bir a. a. 229 № 3 | 2015 chimica techno acta in the electrocyclone at 5–35 % at velocities of aerosol 14.6–27.4 m/sec, respectively, by increasing the ablation is 10–50 times. conclusions the reentrainment is observed in the electrocyclone at a critical velocity of the aerosol at the inlet over 14–16 m/sec, which depends on the concentration and properties of the dust. the reentrainment is almost completely eliminated by irrigation receiving electrode film of water. the degree of purification is above 95 % without applying a voltage to the corona electrode and above 99 % at a supply voltage of 17 kv to the corona electrode. due to a secondary ablation of the degree of purification is reduced by 5–30 %. 1. lim k. s., kim h. s., lee k. w. comparative performances of conventional cyclones and a double cyclone with and without an electric field. j. of aerosol sciences. 2004, 35(1): 103–116. doi: 10.1016/j.jaerosci.2003.07.001 2. tsai r., mills a. f. a model of particle re-entrainment in electrostatic precipitators. j. of aerosol science. 1995, 26(2): 227–239. doi: 10.1016/0021–8502(94)00102–5. 3. xiangrong z., lianze w., keqin z. a simple criterion for particle-wall adhesion in a wire-plate electrostatic precipitator. j. of aerosol sciences. 2005, 36(3): 411–417. doi: 10.1016/j.jaerosci.2004.09.008. 4. titov  a. g., gil’vanova z. r., inyushkin  n. v., ermakov  s. a., shchelchkov  i. p., aitova a. i., man’kov m. g., tokareva n. a., perfilov s. a. efficiency of electrostatic cyclone operation. chemical and petroleum engineering. 2014, 49(9–10): 655–659. doi:10.1007/s10556–014–9814–0. fig. 4. the dependence of secondary ash at various initial concentrations of ash in the gas stream in the dry mode of operation of the cyclone from the gas flow rate at different operating conditions of the electrocyclone quantitative assessment of reentrainment in the electrocyclone 230 а. г. титов, з. р. гильванова, е. а. шевченко, м. к. маснавиев, а. а. бир уральский федеральный университет 620002 екатеринбург, ул. мира, 28. e-mail: paht@yandex.ru количественная оценка вторичного уноса в электроциклоне* статья посвящена исследованию вторичного уноса – паразитного явления, возникающего в газоочистных устройствах, – электроциклонах. показано, что вторичный унос возникает при скоростях аэрозоля от 14 до 27 м/с. определены количественные характеристики вторичного уноса. ключевые слова: исследование вторичного уноса, электроциклон, газоочистные устройства, орошение осадительного электрода. *исследование выполнено при финансовой поддержке рффи в рамках научного проекта № 14–08–00046а. © титов а. г., гильванова з. р., шевченко е. а., маснавиев м. к., бир а. а., 2015 у д к : 5 44 .6 53 .2 2: 5 44 .6 .0 18 .4 214 3 введение улавливание пылевидных материалов на химических предприятиях является актуальной задачей [1]. существует проблема тонкой очистки больших объемов газов от дисперсных частиц. применяемые в  настоящее время многопольные пластинчатые электрофильтры сравнительно дороги, громоздки и  не обеспечивают требуемую высокую степень очистки 99,5–99,7 %. мокрая очистка газов в  эмульгаторах затрудняет утилизацию продукта, т. к. требуется его выделение из пульпы и последующая сушка. для этого требуются большие затраты тепла. также актуальна задача разработки высокоэффективного оборудования для очистки больших объемов газов (сотни тыс. м3/ч) с  получением продукта в сухом виде [2]. вторичный унос при пылеулавливании  – паразитное явление. он зависит от дисперсности материала, скорости потока газа, напряжения на электродах, конструктивных особенностей аппаратов и  др. представляет научный и  практический интерес выявление зависимости эффективности работы электроциклона от указанных факторов [3]. ранее экспериментально было показано [4], что степень очистки газа снижается при увеличении скорости аэрозоля на входе в  электроциклон свыше 15–17 м/с. при увеличении скорости газа в активной зоне возрастает 231 № 3 | 2015 chimica techno acta центробежная сила, что благоприятствует осаждению частиц, но при постоянной длине аппарата время пребывания аэрозоля в активной зоне аппарата уменьшается, снижается эффективность зарядки частиц, увеличивается унос золы. это является следствием того, что частицы не успевают осесть на осадительный электрод. вторичный унос увеличивается, т. к. уже осевшие частицы, особенно мелкие, выбиваются из слоя осадка крупными частицами и турбулентными вихрями. экспериментальная часть чтобы оценить степень влияния времени пребывания газового потока в  аппарате и  вторичного уноса на снижение эффективности улавливания частиц в  электроциклоне, требуется исключить один из факторов. для исключения вторичного уноса необходимо орошать осадительный электрод пленкой воды (мокрый режим работы). тогда частицы, коснувшиеся пленки воды, не смогут вернуться обратно в  поток газа, а  будут необратимо удаляться из активной зоны. были проведены эксперименты в сухом и мокром режиме работы электроциклона. для проведения исследований была использована лабораторная экспериментальная установка (стенд), показанная на рис. 1. исследуемый материал пылеподатчиком 2 подавался в  дезагрегированном виде по входной трубе 7 в электроциклон 1. уловленная зола собиралась в бункере электроциклона 1, а очищенный воздух по воздуховоду удалялся через рукавный фильтр 6 в атмосферу. для проведения опытов с  орошением описанный выше электроциклон дополнялся системой орошения и  удаления пульпы (рис. 2). для орошения осадительного электрода электроциклона 1 применялась расположенная в  улитке ирригационная система, состоявшая из распрерис. 1. схема экспериментальной установки: электроциклон – 1, пылеподатчик – 2, тягонапоромер тнж – 3, источник высокого напряжения (модель ивнр-20–10) – 4, u-образную трубку для определения гидравлического сопротивления электроциклона – 5, рукавный фильтр – 6, подводящую трубу с коллектором – 7, вентили – 8, ротаметры – 9, манометры – 10, фильтродержатель (типа ира-20–2) – 11, пробоотборную трубку – 12 количественная оценка вторичного уноса в электроциклоне 232 № 3 | 2015 chimica techno acta делительного кольца 2 и  подающих трубок 3. суспензия из бункера 4 удалялась через гидрозатвор 5 в монтежю 6. равномерное орошение стенки при поступательно-вращательном движении газа достигалось при расходе воды 8 л/мин. результаты и обсуждение в экспериментах по улавливанию золы в  мокром режиме вторичный унос был полностью исключен, вместе с  тем наблюдалось неполное улавливание золы, которое можно объяснить недозарядкой частиц и  активным турбулентным перемешиванием потока. величину уноса можно представить как (1  – η) · 100 %, что позволило оценить значения уноса в  единицах степени очистки. зависимость величины уноса от скорости при фиксированной концентрации золы 16,5 г/м3 показана на рис. 3. на рис. 3 видно, что в  мокром режиме при u = 17 кв (электроциклонный режим) унос составляет менее 1 %, при снижении напряжения до u = 0 кв (циклонный режим) унос достигает 5–7 %, тогда как унос в  сухом режиме при u = 17 кв имеет значения 12–25 %. по данным эксперимента также были рассчитаны значения вторичного уноса как разница между степенью очистки в мокром и сухом режиме для рис. 2. схема электроциклона для работы в мокром режиме: 1 – электроциклон, 2 – распределительное кольцо, 3 – подающие трубки, 4 – бункер, 5 – гидрозатвор, 6 – монтежю рис. 3. зависимость величины уноса от скорости газового потока при различных режимах работы электроциклона а. г. титов, з. р. гильванова, е. а. шевченко, м. к. маснавиев, а. а. бир 233 № 3 | 2015 chimica techno acta соответствующих точек плана. зависимость величины вторичного уноса от входной скорости и  концентрации аэрозоля золы показана на рис. 4. на рис. 4 видно, что вторичный унос варьирует в  интервале от 5 до 35 %, наибольшие значения наблюдаются при скоростях газа более 21 м/с. среднее значение вторичного уноса составляет 10–15 %, что существенно выше уноса, вызванного недозарядкой. таким образом, вторичный унос снижает эффективность улавливания золы в  электроциклоне на 5–35 % при скоростях аэрозоля 14,6–27,4 м/с, соответственно увеличивая пылеунос в 10–50 раз. выводы вторичный унос наблюдается в  электроциклоне при критической скорости аэрозоля на входе свыше 14– 16 м/с, что зависит от концентрации и свойств пыли. вторичный унос практически полностью ликвидируется путем орошения осадительного электрода пленкой воды, степень очистки при этом выше 95 % без подачи напряжения на коронирующий электрод и  выше 99 % при подаче напряжения 17 кв на коронирующий электрод. вследствие вторичного уноса степень очистки снижается на 5–30 %. 1. lim k. s., kim h. s., lee k. w. comparative performances of conventional cyclones and a double cyclone with and without an electric field. j. of aerosol sciences. 2004, 35(1): 103–116. doi: 10.1016/j.jaerosci.2003.07.001 2. tsai r., mills a. f. a model of particle re-entrainment in electrostatic precipitators. j. of aerosol science. 1995, 26(2): 227–239. doi: 10.1016/0021–8502(94)00102–5. 3. xiangrong z., lianze w., keqin z. a simple criterion for particle-wall adhesion in a wire-plate electrostatic precipitator. j. of aerosol sciences. 2005, 36(3): 411–417. doi: 10.1016/j.jaerosci.2004.09.008. 4. titov  a. g., gil’vanova z. r., inyushkin  n. v., ermakov  s. a., shchelchkov  i. p., aitova  a. i., man’kov m. g., tokareva  n. a., perfilov  s. a.  efficiency of electrostatic cyclone operation. chemical and petroleum engineering. 2014, 49(9–10): 655–659. doi:10.1007/s10556–014–9814–0. рис. 4. зависимость величины вторичного уноса от скорости газа при различных начальных концентрациях золы в потоке газа при сухом режиме работы электроциклона количественная оценка вторичного уноса в электроциклоне 158 d o i: 1 0. 15 82 6/ ch im te ch .2 01 5. 2. 2. 01 7 i. a. khalymbadzha, s. l. deev, t. s. shestakova, v. l. rusinov, o. n. chupakhin chemical technology insitute, 19 mira street, ekaterinburg synthesis of acyclic nucleoside analogues by one-step vorbrüggen glyco-sylation of 1,2,4-triazolo[1,5-a]pyrimidine-7-ones new analogues of acyclovir have been prepared by reacting 1,2,4 -triazolo[1,5-a]pyrimidin-7-ones 1а-i and (2-acetoxyethoxy)methyl acetate 2 in the presence of trimethylsilyl trifluoromethanesulfonate as a catalyst. the interaction between the compounds 1а-е and 2 has led to a mixture of n3 and n4 isomers. in contrast, the reaction of compounds 1g-i and 2 proceeded selectively to form n3 isomers. in the case of compounds 1a-c the predominant product is the one with the acyclic moiety in azine ring (n4 isomer). interaction between 1d-f and 2 has led to mixtures comprising mainly n3 isomer. it has been found that the ratio of glycosylation products 1 and 2 are thermodynamically controlled. the structure of the obtained compounds has been proved by 1н, 13с, two-dimensional 1н-13с nmr spectroscopy and x-ray analysis. © khalymbadzha i. a., deev s. l., shestakova t. s., rusinov v. l., chupakhin o. n., 2015 1,2,4-triazolo[1,5-a]pyrimidines derivatives are the basis of many biologically active compounds1,2, and their n-substituted derivatives can be used to create antiviral and antitumor compounds3,4. considering that the therapeutic potential of nucleoside analogues based on 1,2,4-triazolo[1,5-a]pyrimidine7-ones, the development of effective synthetic procedures has become an actual task. as a continuation of our studies in the search for new inhibitors of the replication of herpes simplex virus, we have synthesized a series of new acyclic nucleoside analogues 3a-i and 4a-f on the basis of 1,2,4-triazolo[1,5-a]pyrimidines. reaction of 1,2,4-triazolo[1,5-a]pyrimidine-7-ones 1a-i with (2-acetoxyethoxy) methyl acetate in the presence of trimethylsilyl trifluoromethane sulphonate as a catalyst resulted in alkylated products 3 and 4. in the case of compounds 159 № 2 | 2015 chimica techno acta synthesis of acyclic nucleoside analogues by one-step vorbrüggen glyco-sylation of 1,2,4-triazolo[1,5-a]pyrimidine-7-ones 1a-c in the reaction mixture, n3 derivatives of 3a-c usually predominate. in the case of compounds 1d-f, conditions for selectively produce both n3 and n4 derivatives have been chosen. 1g-i gives only n3 alkylated products 3g-i (table 1). the structure of 3a-i and 4a-f was defined on the basis of two-dimensional 1h-13c hmbc nmr experiments. table 1 yield, ratio of isomers of acyclic nucleoside analogues yield, correlation of heterocycle r1 r2 r3 metoda ratiob yield (%) 1a h h me a 62:38 56 в 100:0 60 1b me h me а 51:49 59 b 75:25 49 1c sme h me а 52:48 63 b 94:6 80 1d h ph h a 5:95 86 b 75:25 48 1e me ph h a 40:60 70 b 70:30 43 1f sme ph h a 4:96 59 b 60:40 46 1g h h ph a 100:0 39 b 100:0 41 1h me h ph a 100:0 75 b 100:0 24 1i sme h ph a 100:0 35 b 100:0 34 a conditions a: mecn (7 ml), bsa (2 mmol), 1a-i (1.8 mmol), tmsotf (2 mmol), 0.5ch; b: mecn (7 ml), 1a-i (1.8 mmol), tmsotf (2 mmol) 0.2ch; b the 3:4 ratio was determined by 1h nmr. 160 № 2 | 2015 chimica techno acta khalymbadzha i. a., deev s. l., shestakova t. s., rusinov v. l., chupakhin o. n. compounds 3a-i have been characterized by presence of cross peaks between the protone signals at c1’ atom, and c2 and c3a carbon atoms. in the case of 4a-f derivatives, n4 position of acyclic fragment is confirmed by a cross peak between c5 and h1' atoms. furthermore, for crystals of the 3d and 4d compounds x-ray diffraction analysis has been performed, which is fully consistent with nmr data. deprotection of the substances 3a-i and 4a-f under the action of a methanolic solution of ammonia has led to novel acyclovir analogues 5a-i and 6a-f. the cytotoxicity and antiviral activity of compounds 5a-i and 6a-f have been investigated against herpes simplex virus type i in vero cells in accordance with the procedure [3]. the obtained compounds showed weaker activity against hsv compared to acyclovir. 1. ai y., chen y., tang c., yang g.-z., liang y.-j., fu l.-w., liu j.-c., he h.-w. synthesis and in vitro antiproliferative evaluation of pyrimido[5,4-c]quinoline-4(3h)-one derivatives. european journal of medicinal chemistry. 2012. 47; 206– 2013. doi:10.1016/j.ejmech.2011.10.044 2. boechat n., pinheiro l. c. s., silva t. s., carvalho a. s., bastos m. m., costa c. c., mendonca j. s., dutra k. d., santos-filho o. a., pinto a. c., aguiar a. c., ceravolo i. p., krettli a. u., pinheiro s., valverde a. l. new trifluoromethyl triazolopyrimidines as anti-plasmodium falciparum agents. molecules. 2012. 17:7; 8285–8302. doi:10.3390/molecules17078285. 3. sanchez r. m., erhard k., lin h., moore m. l., yu h., luengo j. i., tedesco r., rivero r. a., hardwicke m. a., plant r., rominger c. m., mcsurdy-freed j., spengler m. d., raha k., schaber m. d. synthesis and structure-activity relationships of 1,2,4-triazolo[1,5-a] pyrimidin-7(3h)-ones as novel series of potent β isoform selective phosphatidylinositol 3-kinase inhibitors. bioorganic and medicinal chemistry letters. 2012. 22:9; 3198–3202. doi: 10.1016/j.bmcl.2012.03.039 4. deev s. l., chupakhin o. n., shestakova t. s., ulomskii e. n., rusinov v. l., yasko m. v., karpenko i. l., korovina a. n., khandazhinskaya a. l., kukhanova m. k., andronova v. l., galegov g. a. 1,2,4-triazoloazine derivatives as a new type of herpes simplex virus inhibitors. bioorganic chem. 2010. 38:64; 265–270. doi: 10.1016/j.bioorg.2010.09.002 161 у д к 6 61 .7 7+ 54 7. 91 8: 54 7. 87 и. а. халымбаджа, с. л. деев, т. с. шестакова, в. л. русинов, о. н. чупахин уральский федеральный университет, 620002, екатеринбург, мира, 19 синтез ациклических аналогов нуклеозидов гликозилиированием 1,2,4-триазоло[1,5-а] пиримидин-7-онов по одностадийному методу форбрюггена новые аналоги ацикловира были получены при взаимодействии 1,2,4-триазоло[1,5-а]пиримидин-7-онов 1а-i с (2-ацетоксиэтокси)метилацетатом 2 в присутствии триметилсилилтрифторметансульфоната как катализатора. взаимодействие между соединениями 1а-е и 2 привело к смеси n3 и n4 изомеров. напротив, взаимодействие соединений 1g-i и 2 протекало избирательно с образованием n3 изомеров. в случае веществ 1a-c преобладает продукт с ациклическим фрагментом в азиновом кольце (n4 изомер). взаимодействие 1d-f и 2 привело к смесям, содержащим главным образом n3 изомер. было установлено, что соотношение продуктов гликозилирования 1 и 2 управляется термодинамически. структура полученных веществ была доказана 1н, 13с, двумерной 1н-13с ямр спектроскопией, а также рентгеноструктурным анализом. © халымбаджа и. а., деев с. л., шестакова т. с., русинов в. л., чупахин о. н., 2015 производные 1,2,4-триазоло[1,5а]пиримидинов представляют собой основу многих биологически активных веществ [1–2], а их n-замещенные производные могут использоваться для создания противовирусных и противоопухолевых соединений [3–4]. учитывая терапевтический потенциал аналогов нуклеозидов на основе 1,2,4-триазоло[1,5-а]пиримидин-7-онов, разработка эффективных синтетических процедур становится актуальной задачей. в продолжение наших работ по поиску новых ингибиторов репликации вируса простого герпеса мы синтезировали ряд новых ациклических аналогов нуклеозидов 3a-i и 4a-f на основе 1,2,4-триазоло[1,5-а] пиримидинов. взаимодействие 1,2,4-триазоло[1,5а]пиримидин-7-онов 1а-i с (2-ацетоксиэтокси)метилацетатом в присутствии триметилсилилтрифторметансульфоната в качестве катализатора привело к алкилированным продуктам 3 и 4. в случае соединений 1а-с в реакционной смеси, как правило, преобладают n3 производные 3а-с. в случае соедине162 № 2 | 2015 chimica techno acta халымбаджа и. а., деев с. л., шестакова т. с., русинов в. л., чупахин о. н. ний 1d-f, были подобраны условия для селективного получения как n3, так и n4 производных. 1g-i дают исключительно n3 алкилированные продукты 3g-i (табл. 1). структура 3a-i и 4a-f была установлена на основании двумерных ямр экспериментов 1h–13c hmbc. соединения 3a-i характеризовались наличием кросс-пиков между сигналами протонов при атоме с1' и атомами углерода c2 и c3a. в случае производных 4a-f, n4 позиция ациклического фрагмента подтверждается кросс-пиком между c5 и h1' атомами. кроме того, для кристаллов соединений 3d и 4d был проведен рентгеноструктурный анализ, который полностью согласуется с данными ямр. удаление защиты в веществах 3a-i таблица 1 выход, соотношение изомеров ациклических аналогов нуклеозидов гетероцикл r1 r2 r3 методa соотношениеb выход (%) 1a h h me a 62:38 56 в 100:0 60 1b me h me а 51:49 59 b 75:25 49 1c sme h me а 52:48 63 b 94:6 80 1d h ph h a 5:95 86 b 75:25 48 1e me ph h a 40:60 70 b 70:30 43 1f sme ph h a 4:96 59 b 60:40 46 1g h h ph a 100:0 39 b 100:0 41 1h me h ph a 100:0 75 b 100:0 24 1i sme h ph a 100:0 35 b 100:0 34 примечание: a условия a: mecn (7мл), bsa (2 ммоль), 1a-i (1,8 ммоль), tmsotf (2 ммоль), 0,5 ч; b: mecn (7 мл), 1a-i (1,8 ммоль), tmsotf (2 ммоль), 0,2 ч; bотношение 3:4 было определено по 1h ямр. 163 № 2 | 2015 chimica techno acta синтез ациклических аналогов нуклеозидов гликозилиированием 1,2,4-триазоло[1,5-а]пиримидин-7-онов по одностадийному методу форбрюггена и 4a-f под действием метанольного раствора аммиака привело к новым аналогам ацикловира 5a-i и 6a-f. цитотоксичность и противовирусная активность соединений 5a-i и 6a-f была исследована против вируса герпеса простого первого типа в клетках vero в соответствии с процедурой [3]. полученные соединения продемонстрировали слабую активность против вгп по сравнению с ацикловиром. 1. ai y., chen y., tang c., yang g.-z., liang y.-j., fu l.-w., liu j.-c., he h.-w. synthesis and in vitro antiproliferative evaluation of pyrimido[5,4-c]quinoline-4(3h)-one derivatives // european journal of medicinal chemistry. 2012. 47; 206– 2013. doi:10.1016/j.ejmech.2011.10.044 2. boechat n., pinheiro l. c. s., silva t. s., carvalho a. s., bastos m. m., costa c. c., mendonca j. s., dutra k. d., santos-filho o. a., pinto a. c., aguiar a. c., ceravolo i. p., krettli a. u., pinheiro s., valverde a. l. new trifluoromethyl triazolopyrimidines as anti-plasmodium falciparum agents // molecules. 2012. 17(7), 8285–8302. doi:10.3390/molecules17078285. 3. sanchez r. m., erhard k., lin h., moore m. l., yu h., luengo j. i., tedesco r., rivero r. a., hardwicke m. a., plant r., rominger c. m., mcsurdy-freed j., spengler m. d., raha k., schaber m. d. synthesis and structure-activity relationships of 1,2,4-triazolo[1,5-a] pyrimidin-7(3h)-ones as novel series of potent β isoform selective phosphatidylinositol 3-kinase inhibitors // bioorganic and medicinal chemistry letters. 2012. 22:9; 3198–3202. doi: 10.1016/j.bmcl.2012.03.039 4. deev s. l., chupakhin o. n., shestakova t. s., ulomskii e. n., rusinov v. l., yasko m. v., karpenko i. l., korovina a. n., khandazhinskaya a. l., kukhanova m. k., andronova v. l., galegov g. a. 1,2,4-triazoloazine derivatives as a new type of herpes simplex virus inhibitors // bioorganic chem. 2010. 38:6; 265–270. doi: 10.1016/j.bioorg.2010.09.002. рекомендуем при цитировании данно статьи следующую ссылку: khalymbadzha i. a., deev s. l., shestakova t. s., rusinov v. l. , chupakhin o. n. synthesis of acyclic nucleoside analogues by one-step vorbrüggen glyco-sylation of 1,2,4-triazolo[1,5-a]pyrimidine-7-ones // chimica techno acta. 2015. vol. 2. № 2. p. 158–163. cta_v4_№1.cdr 5 . . , , , 11 2017 , , , . (09.08.1964–11.01.2017) юрий юрьевич моржерин родился 9  августа 1964 году в  поселке азамар читинской области, но свое детство провел в военном поселке ясный оренбургской области. любовь к  химии привела его в  1981  году на химический факультет ургу, который он успешно окончил в 1986 году. в студенческие годы юрий юрьевич был также заядлым кавээнщиком с  отменным чувством юмора, которое пронес через всю жизнь, заражая им окружающих. многие помнят юрия юрьевича командиром студенческого уборочного отряда упи в колхозе. с 1986 года юрий юрьевич трудился на кафедре технологии органического синтеза хтф упи, где прошел путь от инженера до главного научного сотрудника. в 1991 году защитил диссертацию на соискание ученой степени кандидата химических наук «синтез и реакции гетероциклизации полифункциональных диазосоединений», подготовленную во время обучения в аспирантуре под руководством про6 фессора в. с. мокрушина и профессора в. а. бакулева, и начал преподавательскую деятельность в должности доцента. в 2004 году ю. ю. моржерин защитил докторскую диссертацию «перегруппировки 1,2,3-тиадиазолов и 1,2,3-триазолов в органическом синтезе» по специальности 02.00.03 «органическая химия» и продолжил работать на кафедре технологии органического синтеза уже профессором. за это время он впервые разработал и начал преподавать такие дисциплины, как «квантовая химия», «компьютерные информационные системы в химии, химической технологии и экологии», «моделирование органических соединений» и другие. он умел легко объяснять сложные вопросы, привлекать и заинтересовывать студентов, поддерживал высокий уровень мотивации изучения сложных дисциплин. юрий юрьевич шел в ногу со временем, он любил воплощать новые идеи и в науке, и в учебе. поэтому не удивительно, что первые магистранты в химико-технологическом институте работали под его руководством. так, ю. ю. моржерин впервые разработал и возглавил магистерскую образовательную программу «химическая технология природных энергоносителей, продуктов нефтехимии и полимеров» по направлению подготовки «химическая технология». юрий юрьевич проходил стажировки в университете твенте (энсхеде, нидерланды) под руководством профессора д. рейнхоудта, где начал изучение супрамолекулярной химии и реакций, протекающих по механизму трет-аминоэффекта; в католическом университете левена (бельгия) в группе профессора в. дэхаена. там юрий юрьевич познакомился с известными зарубежными учеными, с которыми в дальнейшем продолжал совместные исследования и внес значительный вклад в развитие этих тематик работами своей научной группы уже в стенах нашего университета. наряду с этим юрий юрьевич всегда поддерживал заграничные стажировки и развивал направление международного сотрудничества, а также творческие и научные инициативы своих учеников. так, студенты и аспиранты ю. ю. моржерина работали в университетах китая, сша, канады, великобритании, бельгии, германии, тайваня и австралии. поэтому в научной группе юрия юрьевича всегда было много увлеченной его идеями молодежи, под его руководством успешно защитили диссертации 11 кандидатов химических наук. активная и плодотворная деятельность юрия юрьевича распространялась не только на кафедре, но и в институте, и университете. с 2005 по 2014 год он был заместителем директора по науке химико-технологического института, работал в двух диссертационных советах, участвовал в проектировании химико-фармацевтического центра урфу. с 2014 года как главный научный сотрудник урфу занимался решением актуальных вопросов в научной и управленческой сфере университета. благодаря своему нестандартному мышлению юрий юрьевич выдвигал оригинальные предложения, многие из которых были воплощены в жизнь. в рамках программы развития урфу юрий юрьевич в 2013 году выступил с инициативой создания нового научного подразделения – научной лаборатории «нефтехимия», где он объединил совместные усилия научно-педагогических 7 работников нескольких кафедр хти. по результатам деятельности в 2016 году этой лаборатории присвоен статус центра превосходства урфу. для юрия юрьевича не было невыполнимых задач. при его активном участии в 1998 году, после почти десятилетнего перерыва, была проведена молодежная научная школа по органической химии, в рамках которой лекции по актуальным проблемам органического синтеза, строения, свойств и реакционной способности органических соединений, химии гетероциклических соединений, супрамолекулярной химии читали ведущие специалисты из научных центров россии и европы. юрий юрьевич не только принимал самое активное участие в организации школ-конференций в екатеринбурге, он был их вдохновителем, и можно смело сказать, что без него эти школы, если бы и существовали, то совершенно в другом, не нынешнем виде. в настоящее время школа стала ежегодной и приобрела общероссийскую значимость, собирая все больше участников. последними крупными проектами стали организация международной научно-практической конференции «химия в федеральных университетах» и создание научного журнала chimica techno acta, в котором он был и идейным вдохновителем, и главным редактором. на сегодняшний день в свет вышло 11 выпусков журнала. юрий юрьевич наряду с преподавательской и организационной деятельностью постоянно занимался научно-исследовательской работой, с его участием опубликовано 635 научных работ, в том числе 130 научных статей, а также 17 учебных пособий и 4 монографии. он принимал активное участие в работе международных научных конференций в различных странах мира, таких как сша, англия, португалия, бельгия, австрия, нидерланды, чехия, франция, германия, италия, япония, норвегия, китай и др. светлая память о юрии юрьевиче моржерине навсегда останется в наших сердцах как внимательном, отзывчивом, всегда готовом прийти на помощь коллеге, учителе и друге. 171 m. a. bezmaternikh, i. s. selezneva chemical technology institute 28 mira str., 620002, ekaterinburg, e -mail: max6669@rambler.ru milestones chemical technology institute: our past and present the article is devoted to the 95th anniversary of the chemical technological institute (cti) of the ural federal university named after the first president of russia b. n. yeltsin (urfu), which will be held in october 2015. over the years chemical technological institute (cti) has undergone many structure transformations in accordance with the tasks which were set before it the time and the development of our country. currently this is a fairly large educational and research institute, which employs more than 100 lecturers including more than 70 associate professors – candidates (phd), 30 professors – doctors of sciences (hb), 3 academics and 1 corresponding member of ras, trained more than 850 students. © bezmaternikh m. a., selezneva i. s., 2015 in october 2015 the chemical technology faculty (ctf) of the ural polytechnic institute named after s. m. kirov (upi), and now the chemical technology institute (cti) of the ural federal university named after the first president of russia  b. n.  yeltsin (urfu) celebrates its 95th foundation anniversary. let’s remember how it was in march 17, 1920 the chemical faculty was formed as a result of the division of the chemical-metallurgical faculty of the ural mining institute into separate faculties – chemical and metallurgical. in october 1920 it became part of the polytechnic institute, which, along with mining and other institutions was included in the newly created structure of the ural state university. in the first academic year in the chemistry department were enrolled 145 students. the first dean of the faculty was arrived in ekaterinburg professor of the petrograd institute of technology, electrochemist alexander evmenievich makovetskiy. he can rightly be called the father of the ural school of chemical engineers. thanks to the energy a. e.  makovetskiy in the chemistry department operated the laboratories for qualitative and quantitative analysis, organic and inorganic chemistry, physical chemistry, dry distillation of wood. and the laboratories were d o i: 1 0. 15 82 6/ ch im te ch .2 01 5. 2. 3. 01 9 172 № 3 | 2015 chimica techno acta bezmaternikh m.a., selezneva i.s. available to the students of all faculties and the workers’ school. on his initiative in germany and england were purchased thousands of books and dozens of magazines, which laid a solid foundation of the scientific library of the institute. in february 1922 the chemical and metallurgical faculties again united in the chemical-metallurgical faculty (cmf). the chemistry department cmf was training in six specialties, such as “the main chemical productions”, “technology of silicates”, “technological electrochemistry”, “technology of nonferrous, noble and rare metals,” “pyrogenic processes” and “pulp and paper industry”. in may 6, 1925 the ural state university was renamed the ural polytechnic institute. in june 11, 1929, by the decision of council of people’s commissars of the rsfsr the chemical branch of the cmf was converted into chemical faculty, the dean of which is approved by nikolai rogatkin. in 1929/1930 academic year to the first year of the chemistry department was taken 220 people. in 1930 the upi was transferred under the supervision of the supreme council of national economy, its faculties were transformed into a branch of the technical colleges and for some time have any of the ural institute of chemical technology (uict) subordinate to slavhimprom vsnkh of the ussr. in the 1930/1931 academic year uict began work composed of five departments of: the main chemical industry; pyrogenic productions; hardware and design; silicate; engineering and economics. in may 28, 1934 the branch technical colleges were merged into the ural industrial institute (uii), in its composition on the rights of the faculty of chemical technology entered uict, and in december 17, 1934 uii was named after s. m. kirov. at the beginning of the great patriotic war many teachers, researchers and students of the faculty went to the defense of our motherland. the remainder of the team together with the whole country worked under the motto: “all for front, all for victory!” students and lecturers of the chemistry department have been created and introduced in manufacture of sulfamide drugs, which contributed to the recovery of the wounded soldiers; developed new catalysts for the flameless combustion of gasoline to use in tactical aircraft to heat engines and cockpit; work on the development and intensification of production of coke and chemical products of coking on the plants of the urals. in february 1948 uii was renamed the ural polytechnic institute named after s. m. kirov. in december 24, 1992 upi was renamed the ural state technical university (ustu-upi). in april 2008, ustu-upi was named after the first president of russia b. n. yeltsin. in april 2010 the ural federal university named after the first president of russia  b. n.  yeltsin was created. in august 30, 2011 on the basis of the chemical technology faculty was established the chemical technology institute. the leaders of the cti were n. n.  rogatkin (1927–1929, 1937– 1938), s. g.  mokrushin (1930, 1937), i. g.  shcherbakov (1934–1937), i. y.  postovsky (1938–1942), a. i.  levin (1942– 1947), z. v.  pushkareva (1947–1949), v. l.  zolotavin (1949–1951), b. i.  timin (1951–1953), v. m.  cherkasov (1953– 173 № 3 | 2015 chimica techno acta milestones chemical technology institute: our past and present 1958), v. d. nikitin (1958–1962), b. v. berezin (1962–1965), a. v.  pomosov (1965– 1974), i. i.  kalinichenko (1974–1982), v. n.  desyatnik (1982–1987), o. n.  chupakhin (1987–1988), a. i.  matern (1988– 2007), from 2008 to present time the institute is headed by v. l. rusinov. currently at the institute for 10 departments work more than 100 teachers, including more than 70 associate professors  – candidates of sciences, 30 professors  – doctors of sciences, 3 academics and 1 corresponding member of russian academy of sciences, the institute has about 850 students. the institute has a wide creative relationships with ural branch of russian academy of sciences, a number of industrial enterprises of sverdlovsk, orenburg, chelyabinsk regions, the perm and stavropol territory. all departments are actively engaged in scientific work. more than 40 people are trained in graduate school. for the last five years at cti protected 4 doctoral and 47 master’s theses. in the ranking of hit consistently is in the top among three institutes of the ural federal university. teachers, postgraduates and students of the faculty work closely with the catholic university (leuven, belgium), karlaugust university (germany), with a number of foreign firms. many teachers, postgraduates and students of the institute were trained at the nankai university (tian-zhin, china), howard university (washington, usa), the university of maryland (usa), catholic university (leuven, belgium), the university of geneva (switzerland), the university of york (uk). just a 95-year history of the cti was released 15 461 specialists (engineers, bachelors, masters). in addition, faculty of the departments of the institute provide educational process at the institutes of materials science and metallurgy (imsmt), fundamental education (infe), ural power engineering (uralenin), physics and technology (ipt), mechanical engineering (ime), radio electronics and information technologies (irit-rtf). department of organic & biomolecular chemistry from 1924 to 1926 the department was headed by karmanov s. g., from 1926 to 1976 – by academician of the ras postovsky i. ya., from 1976 to the present – by academician of the russian academy of sciences, doctor of chemical sciences chupakhin o. n. the department offers two master programs: “comprehensive chemical and physical study and expert evaluation of organic materials” and “medical chemistry”, one profile bachelor – “chemical technology of synthetic biologically active substances, pharmaceutical preparations and cosmetics”. scientific directions of the department belong to different research areas of organic chemistry and organic synthesis, medicinal chemistry, materials science, namely:”integrated chemical and physical research and expert assessment of organic materials” and “medical chemistry”, and one bachelor’s degree program – “chemical technology of synthetic biologically active substances, chemical andpharmaceutical preparations and cosmetics.” research areas of the department belong to different fields of research including organic chemistry and organic synthesis, medicinal chemistry, materials science, namely: 174 № 3 | 2015 chimica techno acta ȥ nucleophilic aromatic substitution of hydrogen in heteroaromatic and aromatic systems; ȥ development of methods for the synthesis of heterocycles based on tandem nucleophilic reactions of various types; ȥ construction of heterocyclic compounds, including those having a fluorine atom in the side chain or the aromatic ring; ȥ development of methods for the synthesis of fluoroquinolone antibiotics and other inhibitors of dna gyrase; ȥ search for substances with antiviral activity; ȥ synthesis of substances with pharmacological activity, such as anticoagulants, antiplatelet agents, anesthetics, etc.; ȥ design of anti-tuberculosis drug; ȥ synthesis of isotope-labeled organic compounds; ȥ development of methods for preparing substances with a critically high nitrogen content; ȥ development of methods for the synthesis of effective complexing agents for special purposes; ȥ development of agents for the extraction of rare earth elements, highly sensitive sensors and fluorescent labels; ȥ development of highly effective catalytic systems, including systems for asymmetric synthesis. over the years, the department graduated 22 doctors and 135 candidates of chemical sciences. four employees of the department have been elected to the russian academy of sciences  – academicians  i.  ya. postovsky, o. n.  chupakhin, v. n. charushin and corresponding member of the ras v. l. rusinov. department of physical and colloid chemistry department of physical and colloid chemistry was founded in 1920. the department was headed by professor pershke  v. k. (1920–1931), docent zinoviev  e. i. (1931–1933), doctor of chemical sciences, professor, honored worker of science and technology of the rsfsr mokrushin  s. g. (1933–1971), professor, honored worker of science and technology of the rsfsr kitaev g. a. (1971–1996), doctor of chemical sciences, professor makurin yu.n. (1996–2002), and since 2002 to present time it is headed by professor, honored worker of higher school markov v. f. the department offers 3 master programs: “technology of materials and products of optoelectronics and sensorics”, “physicochemical technologies of crystals and infrared optical fibers”, “chemical thin-film technologies in optoelectronics and nanoelectronics”, and one bachelor’s degree program – “physicochemical technologies of materials of electronic technology and power industry”. academics, graduate and undergraduate students of the department are engaged in scientific research in the following areas: ȥ quantum chemical modeling of the structure, functional properties and reactivity of molecules; ȥ development of technology of hydrochemical synthesis of thin films of dielectric, semiconductor and metal materials; ȥ development of new, including nanostructured, sensor materials for infrared technology and chemical analysis; ȥ study and development of new fiber materials, scintillators, and based on them creation of optical fibers for infrared region of the spectrum; bezmaternikh m.a., selezneva i.s. 175 № 3 | 2015 chimica techno acta ȥ synthesis and study of properties of new x-ray contrast agents for medicine. the department has trained more than 90 candidates and 6 doctors of sciences. department of technology of inorganic substances department of technology of inorganic substances was founded in 1920. the department was headed by professor yushkevich  n. f. (1921–1923), professor makovetskiy  a. e. (1923–1929), professor shabalin k. n. (1929–1937), professor kuz’minykh i.n. (1937–1943), professor vilnyansky ya.e. (1943–1973), docent chukhlantsev  v. g. (1973–1978), professor desyatnik  v. n. (1978–2001), professor trifonov k. i. (1997–1999), and since 2001 to present time it is headed by professor katishev s. f. the department implements the master program “chemical technology of basic inorganic synthesis” and the bachelor’s degree program “chemical technology of inorganic substances”. scientific fields of the department are: ȥ physical chemistry and technology of melts containing rare earth elements; ȥ development of methods of physicochemical analysis of ionic equilibria in complex composition solutions; ȥ physicochemical basis of preparation of magnesium chloride feed to electrolysis; ȥ effective ways of using waste products of hydrofluoric and phosphoric acids and fluorides; ȥ development and simulation of technologies for processing man-made structures. to date the department has trained 2 academicians, 4 laureates of the state prize, 5 doctors and 50 candidates of sciences. department of processes and apparatus of chemical technology department of processes and apparatus of chemical technology was established in 1920. the department was headed by professor makovetskiy a. e. (1920–1932), professor plyusnin  v. g. (1932–1936), professor shabalin  k. n. (1936–1966), professor zaostrovsky  f. p. (1967–1991), professor pospelov  f. m. (1992–1995), professor ermakov  a. a. (1995–2010), and since 2011 to present time it is headed by professor ermakov s. a. the department trains bachelors in the profile “basic processes of chemical production and chemical cybernetics”. academics, staff, graduate and undergraduate students of the department are involved in fundamental and applied research in two areas: ȥ intensifying the mass and heat transfer under conditions of hydrodynamic instability of the phases contact surface in liquid-liquid systems; ȥ hydrodynamic separation of heterogeneous gas systems. department of technology of electrochemical production department of technology of electrochemical production was founded in 1923. the department was headed by professor shcherbakov  i. g. (1923–1938), professor esin  o. a. (1938–1944), professor levin  a. i. (1944–1978), professor pomosov  a. v. (1978–1988), professor rudoi  v. m. (1988–1998), professor milestones chemical technology institute: our past and present 176 № 3 | 2015 chimica techno acta samoilenko v. n (1998–2000), and since 2000 to present time it is headed by professor zaykov yu. p. currently, the department offers one bachelor’s degree program: “technology of electrochemical productions”, master programs: “electrochemical processes and productions”, “hydrogen and electrochemical power industry”, “technology of chemical and electrochemical materials protection”. the cooperation of the department with factories of ojsc “gazprom” has resulted in the opening a new form of specialists education which is applied bachelor’s program. the main scientific fields of the department are basic research in the field of electrodeposition and electrocrystallization of metals, protection against materials corrosion, production of current sources: ȥ model description of electrocrystallization of metals in the form of dendrites; ȥ electrolysis in nonferrous metallurgy; ȥ electrolytic molding of gold and silver articles; ȥ study of corrosion protective properties of paint coatings and protective alloys; ȥ improvition manufacturing processes and electrical characteristics of a lead accumulator. more than 40 graduates of the department became doctors of sciences and 170 are candidates of sciences. department of chemical technology of fuel and industrial ecology department of chemical technology of fuel and industrial ecology was founded in 1923. the department was headed by professor rogatkin  n. n. (1923–1944), professor syskov  k. i. (1944–1947), professor goftman  m. v. (1947–1967), professor kharlampovich  g. d. (1967–1997), docent shishov  m. g. (1997–2008), and since 2008 to present time it is headed by docent stakheev s. g. currently, the department offers the following bachelor’s degree programs: “chemical technology of natural energy resources” and “environmental protection and rational use of natural resources”, as well as the following master programs: “chemical technology of natural energy resources and carbon materials” and “industrial ecology and rational use of natural resources”. the main scientific fields of the department are: ȥ optimization of processes of coal processing and products produced from them in different pyrogenetic processes; ȥ environmental impact assessment of projects and the development of environmental design documentation. 22 graduates of the department became doctors of sciences and 130 are candidates of technical and chemical sciences. department of machines and apparatus for chemical productions department of machines and apparatus for chemical productions was organized in 1932. the department was headed by professor dal’-chumachenko v.i. (1932–1941), professor shabalin  k. n. (1941–1960), professor volgin  b. p. (1960–1977), berezin  b. v. (1977–1982), docent yugay  f. s. (1982–1996), profesbezmaternikh m.a., selezneva i.s. 177 № 3 | 2015 chimica techno acta sor chernomurov f. m. (1996–2006), and since 2006 to present time it is headed by professor khomyakov a. p. today, the undergraduate training is implemented on the bachelor’s degree programs «machines and apparatus for chemical productions”, “machines and apparatus for food production,” and on master’s degree program “machines and apparatus for chemical productions”. the main scientific research fields of the department relate to: ȥ development of heat and mass transfer apparatus based on the venturi tube; ȥ implementation of high-speed spray type apparatus for the treatment of process gases in a variety of productions; ȥ removal of harmful impurities, cooling, absorption; ȥ development of systems of gas purification from dust, mist, vapor, based on ejection type scrubbers; ȥ modernization of evaporation and heat exchange equipment, boiler deaerators; ȥ study of wear of parts of hydraulic machines at cavitation and hydroabrasive impact; ȥ development of apparatus in the field of resource and energy saving technologies; ȥ use of hydrodynamic cavitation systems for dissipative heating; homogenizing and pasteurizing liquids for food and industrial use; ȥ applying the principle of evaporation-condensation heat exchange to create technological and power equipment, utilization of secondary energy resources; ȥ development and implementation of energy technological complexes, providing the ultimate closure of material and energy flows within the unit, department, factory; ȥ investigation of processes and development of equipment for the food industry. the department has prepared 13 laureates of lenin and state prizes of the ussr council of ministers prize, 7 doctors of sciences, 107 candidates of sciences. department of analytical chemistry department of analytical chemistry was founded in 1933. the department was headed by docent levin  a. b. (1933– 1938), professor tananaev  n. a. (1938– 1959), professor podchaynova  v. n. (1960–1977), professor polezhaev yu.m. (1977–2000), since 2000 to present time it is headed by professor matern a. i. the department offers two master programs “electrochemical methods and sensors for environmental and biological objects monitoring”, “instrumental methods of research in the pharmaceutical industry”. from 2015 the department offers one bachelor’s degree program: “instrumental methods of analysis of natural and technical objects”. currently, the department of analytical chemistry of the cti conducts active scientific research. main research fields are: ȥ development of sensors, instruments and automated electrochemical complex for environmental monitoring of heavy metals in online mode; ȥ studies of antioxidant and anti-radical activity of solutions; ȥ non-enzymatic methods for determining diagnostically significant parameters; ȥ development of methods for electrochemical immunoassay; milestones chemical technology institute: our past and present 178 № 3 | 2015 chimica techno acta ȥ study of the toxicity of nanoparticles; ȥ study of mechanisms electro-transformations of organic compounds and pharmaceuticals; ȥ definition of basic substance and impurities in pharmaceuticals. department of technology for organic synthesis department of technology for organic synthesis was established in 1947. department was headed by professor, honored worker of science and technology of the rsfsr pushkareva z. v. (1947–1982), professor shishkina  v. i. (1982–1988), professor mokrushin  v. s. (1988–2008), from 2008 to present time it is headed by professor bakoulev v. a. the department of tos offers bachelors 3 bachelor’s degree programs: “chemical technology of organic substances”, “biotechnology” and “food biotechnology”. 6 master’s programs are implemented: “chemical technology of fine organic synthesis”, “chemical technology of biologically active substances”, “chemical technology of basic organic and petrochemical synthesis», «chemical technology of plastics,” “medical biotechnology”, “food biotechnology” (in  russian and english). the main research fields of the department are: ȥ fine organic synthesis in the field of heterocyclic and natural compounds; ȥ creation of new advanced materials; ȥ development of new and improvement of the known technological processes; ȥ nanotechnologies based on organic compounds; ȥ medical, food and environmental biotechnology. among the graduates and staff of the department 370 people defended their candidate’s dissertations, 40  – doctoral dissertations, 20 graduates received the state prize, 15 became heads of departments of various universities. department of immunochemistry department of immunochemistry was founded in 2000 on the initiative and with the participation of academician chereshnev  v. a., who heads the department from the first days of creation and to present time. the department offers master program “immunobiotechnology.” scientific activity of the department is connected with the research in the field of biochemistry and immunochemistry. one of the research fields is the study of non-enzymatic protein glycosylation reaction that underlies the pathogenesis of many social diseases. the second field is the study of mechanisms of cytokine regulation of physiological processes in blood cells and vascular walls in hyperglycemia. this work is done in collaboration with the institute of immunology of the russian academy of sciences. currently, the chemical technology institute offers three directions for undergraduate students: “biotechnology”, “chemical technology”, “energy and resource saving processes in chemical technology, petrochemistry and biotechnology”, as well as offers the same directions and the direction “chemistry” for masters. the institute implements 12 individbezmaternikh m.a., selezneva i.s. 179 № 3 | 2015 chimica techno acta ual bachelor’s degree programs within the undergraduate education and 24 master programs, including one in english. in 2008, the educational program “technology of electrochemical production” (tecp) passed the procedure of public and professional accreditation of the association of engineering education of russia. specialization tecp is the only specialization in the urals region, which is assigned a european quality mark eurace®. in june 2012 the basic education program “biotechnology” passed the procedure of public and professional accreditation of the public accreditation agency for higher education quality assurance and career development and confirmed the conformity of the quality of training of graduates of the program to quality standards and quality assurance, established on the basis of the recommendations of the european association for quality assurance in higher education. in addition to academic work lecturers and staff are actively engaged in scientific research. due to the internationalization the research received a powerful impetus for development. the number of articles and books published in international journals in english has been increased. original chemical compounds with biological activity have been synthesized. students under the guidance of lecturers are actively involved in implementation of sophisticated chemical experiments. foreign scientists from leading universities around the world often come to the institute to delivery lectures to staff and students. on the other hand, our undergraduate and graduate students regularly travel abroad (australia, austria, england, belgium, germany, china, usa and japan) for undertaking scientific internships. there they can get a new experience, gain new knowledge and improve spoken english. our staff and graduate students often win grants for the implementation of scientific research and participation in russian and international conferences. in conclusion we would like to congratulate all the academics, staff, students and graduates of the chemical technology institute with the upcoming anniversary! we wish you all success and new victories! we love cti! we wish cti all the best! milestones chemical technology institute: our past and present 180 м. а. безматерных, и. с. селезнева химико-технологический институт 620002 екатеринбург, ул. мира, 28. e-mail: max6669@rambler.ru этапы большого пути: наше прошлое и настоящее статья посвящена 95-летнему юбилею химико-технологического института (хти) уральского федерального университета имени первого президента россии б. н. ельцина (урфу), который состоится в октябре 2015 года. за эти годы химико-технологический институт (хти) претерпел множество структурных преобразований в соответствии с задачами, которые ставили время и развитие нашей страны. в настоящее время это достаточно большой учебный и исследовательский институт, в котором работают более 100 преподавателей, из них свыше 70 доцентов – кандидатов наук, 30 профессоров – докторов наук, 3 академика и 1 член-корреспондент ран, обучаются более 850 студентов. © безматерных м. а. , селезнева и. с. , 2015 в октябре 2015 года исполняется 95 лет химико-технологическому факультету (хтф), уральского политехнического института имени с. м. кирова (упи), а ныне – химикотехнологическому институту (хти) уральского федерального университета имени первого президента россии б. н. ельцина (урфу). вспомним, как это было 17 марта 1920 года образовался химический факультет в  результате разделения химико-металлургического факультета уральского горного института на отдельные факультеты – химический и металлургический. в октябре 1920 года он вошел в  состав политехнического института, который наряду с горным и другими институтами был включен в  структуру вновь созданного уральского госуниверситета. в  первом учебном году на химфаке обучалось 145 студентов. первым деканом факультета стал приехавший в  екатеринбург профессор петроградского технологического института, электрохимик александр евменьевич маковецкий. его по праву можно назвать отцом уральской школы инженеров-химиков. благодаря энергии а. е. маковецкого на химфаке действовали лаборатории качествен181 № 3 | 2015 chimica techno acta ного и  количественного анализа, органической и  неорганической химии, физической химии, сухой перегонки дерева. причем лаборатории были доступны для студентов всех факультетов и  рабфака. по его инициативе в германии и англии были закуплены тысячи книг и  десятки журналов, заложивших солидную основу научной библиотеки института. в феврале 1922 года химический и  металлургический факультеты снова объединены в  химико-металлургический факультет (хмф). на химическом отделении хмф осуществлялась подготовка специалистов по шести специальностям: «основные химические производства», «технология силикатов», «технологическая электрохимия», «технология цветных, благородных и  редких металлов», «пирогенные процессы» и  «целлюлозно-бумажное производство». 6 мая 1925 года уральский государственный университет был переименован в  уральский политехнический институт. 11 июня 1929 года решением снк рсфср химическое отделение хмф преобразовано в  химический факультет, деканом которого утвержден николай николаевич рогаткин. в  1929/1930 учебном году на первый курс химфака было принято 220 человек. в 1930 году упи был передан в ведение вснх, его факультеты преобразованы в  отраслевые втузы, и  на некоторое время возник уральский химико-технологический институт (ухти), подчиненный главхимпрому вснх ссср. в 1930/1931 учебном году ухти начал работу в  составе пяти отделений: основной химической промышленности; пирогенных производств; аппаратурно-конструкторского; силикатного; инженерно-экономического. 28 мая 1934 году отраслевые втузы были объединены в  уральский индустриальный институт (уии), в  его состав на правах химико-технологического факультета вошел ухти, а 17 декабря 1934 года уии было присвоено имя с. м. кирова. в начале великой отечественной войны многие преподаватели, научные работники и студенты факультета ушли на защиту нашей родины. оставшаяся часть коллектива вместе со всей страной трудилась под девизом: «все для фронта, все для победы!» преподавателями и  учеными химфака были созданы и  внедрены в  производство сульфамидные препараты, которые способствовали выздоровлению раненых воинов; разработаны новые катализаторы для беспламенного горения бензина с  целью применения во фронтовой авиации для обогрева моторов и  кабин самолетов; проведена работа по развитию и  интенсификации производства кокса и химических продуктов коксования на заводах урала. в феврале 1948 года уии был переименован в уральский политехнический институт имени с. м. кирова. 24 декабря 1992 года упи переименован в  уральский государственный технический университет (угту-упи). в апреле 2008 года угту-упи присвоено имя первого президента россии б. н. ельцина. в настоящее время в  институте на 10 кафедрах работают более 100 преподавателей, из них свыше 70 доцентов  – кандидатов наук, 30 профессоров  – докторов наук, 3 академика этапы большого пути: наше прошлое и настоящее 182 № 3 | 2015 chimica techno acta безматерных м.а., селезнева и.с. и  1  член-корреспондент ран, обучаются около 850 студентов. институт имеет широкие творческие связи с  уро ран, целым рядом промышленных предприятий свердловской, оренбургской, челябинской областей, пермского и  ставропольского края. все кафедры активно ведут научную работу. более 40 человек обучаются в  аспирантуре. за пять последних лет на хти защищено 4 докторских и  47 кандидатских диссертаций. в  общеуниверситетском рейтинге хти стабильно входит в  тройку лучших институтов урфу. преподаватели, аспиранты и  студенты факультета тесно взаимодействует с  католическим университетом (г. левен, бельгия), карл-август университетом (германия), с целым рядом зарубежных фирм. многие преподаватели, аспиранты и  студенты хти прошли стажировку в  нанкайском университете (г. тянь-жинь, китай), хавардском университете (г. вашингтон, сша), университете г. мэриленд (сша), католическом университете (г. левен, бельгия), женевском университете (швейцария), йоркском университете (великобритания). всего за 95-летнию историю хти было выпущено 15 461 специалист (инженеров, бакалавров, магистров). кроме того, преподаватели кафедр хти осуществляют образовательный процесс в  институтах материаловедения и  металлургии (имимт), фундаментального образования (инфо), уральском энергетическом (уралэнин), физико-технологическом (фти), механико-машиностроительном (мми), радиоэлектроники и  информационных технологий (ирит-ртф). кафедра органической химии с 1924 по 1926 год кафедру возглавлял с. г.  карманов, с  1926 по 1976 год  – академик ран и. я.  постовский, с  1976 года по настоящее время  – академик ран, доктор химических наук о. н. чупахин. на кафедре реализуется подготовка по двум магистерским программам: «комплексное химическое и  физическое исследование и экспертная оценка органических материалов» и  «медицинская химия», по одному профилю бакалавриата  – «химическая технология синтетических биологически активных веществ, химико-фармацевтических препаратов и  косметических средств». научные направления кафедры относятся к  разным областям исследований  – органической химии и  органического синтеза, лекарственной химии, материаловедения, а именно: ȥ ароматическое нуклеофильное замещение водорода в  гетероароматических и ароматических системах; ȥ создание методов синтеза гетероциклов, основанных на тандемных нуклеофильных реакциях различного типа; ȥ конструирование гетероциклических соединений, в  том числе имеющих атомы фтора в  боковой цепи или ароматическом ядре; ȥ разработка методов синтеза антибиотиков фторхинолонового ряда и других ингибиторов днк-гиразы; ȥ поиск веществ, обладающих противовирусной активностью; 183 № 3 | 2015 chimica techno acta этапы большого пути: наше прошлое и настоящее ȥ синтез веществ, обладающих фармакологической активностью – антикоагулянтов, антиагрегантов, анестетиков и др.; ȥ создание противотуберкулезных препаратов; ȥ синтез изотопно-меченых органических соединений; ȥ разработка методов получения веществ с  критически высоким содержанием азота; ȥ развитие способов синтеза эффективных комплексообразователей специального назначения, ȥ создание экстрагентов редкоземельных элементов, высокочувствительных сенсоров и  люминесцентных меток; ȥ создание высокоэффективных каталитических систем, в  том числе для асимметрического синтеза. за годы существования кафедрой подготовлено 22 доктора и  135 кандидатов химических наук. четыре сотрудника кафедры избраны членами ран  – академики и. я.  постовский, о. н.  чупахин, в. н.  чарушин и  членкорреспондент ран в. л. русинов. кафедра физической и коллоидной химии кафедра физической и коллоидной химии основана в  1920 году. кафедру возглавляли профессор в. к.  першке (1920–1931), доцент е. и.  зиновьев (1931–1933), д. х. н., профессор, заслуженный деятель науки и  техники рсфср с. г.  мокрушин (1933–1971), д. х. н., профессор, заслуженный деятель науки и  техники рсфср г. а.  китаев (1971–1996), д. х. н., профессор ю. н. макурин (1996–2002), а с 2002 г. – д. х. н., профессор, почетный работник высшей школы в. ф. марков. на кафедре открыты три магистерские программы: «технологии материалов и  изделий оптоэлектроники и  сенсорики», «физико-химические технологии кристаллов и  ик-световодов», «химические тонкопленочные технологии в  оптоэлектронике и  наноэлектронике» и один профиль бакалавриата  – «физико-химические технологии материалов электронной техники и энергетики». преподаватели, аспиранты и  студенты кафедры занимаются научной работой по следующим направлениям: ȥ квантово-химическое моделирование структуры, функциональных свойств и  реакционной способности молекул; ȥ разработка технологии гидрохимического синтеза тонких пленок диэлектрических, полупроводниковых и металлических материалов; ȥ разработка новых, в том числе наноструктурированных, сенсорных материалов для инфракрасной техники и химического анализа; ȥ исследование и разработка новых волоконных материалов, сцинтилляторов и создание на их основе световодов для ик-области спектра; ȥ синтез и  исследование свойств новых рентгеноконтрастных веществ для медицины. кафедрой подготовлено более 90  кандидатов и 6 докторов наук. 184 № 3 | 2015 chimica techno acta кафедра технологии неорганических веществ кафедра технологии неорганических веществ основана в 1920 году. заведующими кафедрой были профессор а. е. маковецкий (1923–1929), профессор н. ф.  юшкевич (1921–1923), профессор к. н.  шабалин (1929–1937), профессор и. н.  кузьминых (1937– 1943), профессор я. е.  вильнянский (1943–1973), доцент в. г.  чухланцев (1973–1978), профессор в. н. десятник (1978–2001), профессор к. и.  трифонов (1997–1999), с  2001 г.  – профессор с. ф. катышев. на кафедре реализуется магистерская программа «химическая технология основного неорганического синтеза» и профиль бакалавриата «химическая технология неорганических веществ». к научным направлениям кафедры относятся: ȥ физическая химия и  технология расплавов, содержащих редкоземельные элементы; ȥ разработка методов физико-химического анализа ионных равновесий в растворах сложного состава; ȥ физико-химические основы подготовки хлормагниевого сырья к  электролизу; ȥ эффективные направления использования отходов производства фтороводородной и  фосфорной кислот и фтористых солей; ȥ разработка и  моделирование технологий переработки техногенных образований. на сегодняшний день кафедра подготовила 2 академиков, 4 лауреатов государственной премии, 5 докторов наук и более 50 кандидатов наук. кафедра процессов и аппаратов химической технологии кафедра процессов и  аппаратов химической технологии организована в 1920 году. кафедрой заведовали профессор а. е.  маковецкий (1920–1932), профессор в. г.  плюснин (1932–1936), профессор к. н. шабалин (1936–1966), профессор ф. п.  заостровский (1967– 1991), профессор ф. м.  поспелов (1992–1995), профессор а. а.  ермаков (1995–2010), с  2011 года  – профессор с. а. ермаков. кафедра готовит бакалавров по профилю «основные процессы химических производств и  химическая кибернетика». преподаватели, сотрудники, аспиранты и  студенты кафедры проводят фундаментальные и  прикладные исследования по двум направлениям: ȥ интенсификация массои  теплообмена в условиях гидродинамической неустойчивости поверхности контакта фаз в системах жидкость-жидкость; ȥ гидродинамическое разделение неоднородных газовых систем. кафедра технологии электрохимических производств кафедра технологии электрохимических производств основана в  1923 году. кафедру возглавляли профессор и. г.  щербаков (1923–1938), профессор о. а. есин (1938–1944), профессор а. и.  левин (1944–1978), профессор а. в.  помосов (1978–1988), профессор в. м.  рудой (1988–1998), профессор безматерных м.а., селезнева и.с. 185 № 3 | 2015 chimica techno acta в. н.  самойленко (1998–2000), с  2000 года – профессор ю. п. зайков. в настоящее время кафедра готовит бакалавров по профилю «технология электрохимических производств», магистрантов по программам «электрохимические процессы и  производства», «водородная и электрохимическая энергетика», «технология химической и  электрохимической защиты материалов». результатом взаимодействия кафедры с  предприятиями оао «газпром» стало открытие новой формы обучения специалистов прикладного бакалавриата. основными научными направлениями кафедры являются фундаментальные исследования в  области электроосаждения и  электрокристаллизации металлов, защиты от коррозии материалов, производства источников тока: ȥ модельное описание электрокристаллизации металлов в  виде дендритов; ȥ электролиз в цветной металлургии; ȥ электролитическое формование изделий из золота и серебра; ȥ исследование коррозионно-защитных свойств лакокрасочных покрытий и протекторных сплавов; ȥ совершенствование технологических процессов производства и  электрических характеристик свинцового аккумулятора. более 40 выпускников кафедры стали докторами наук и  170  – кандидатами наук. кафедра химической технологии топлива и промышленной экологии кафедра химической технологии топлива и  промышленной экологии основана в 1923 году. кафедру возглавляли профессор н. н. рогаткин (1923–1944), профессор к. и.  сысков (1944–1947), профессор м. в.  гофтман (1947–1967), профессор г. д.  харлампович (1967–1997), доцент м. г. шишов (1997–2008), с 2008 года – доцент с. г. стахеев. в настоящее время кафедра готовит бакалавров по профилям «химическая технология природных энергоносителей» и  «охрана окружающей среды и  рациональное использование природных ресурсов», а  также магистрантов по программам «химическая технология природных энергоносителей и углеродных материалов» и «промышленная экология и  рациональное использование природных ресурсов». основными научными направлениями работы кафедры являются: ȥ оптимизация процессов переработки углей и  получаемых из них при различных пирогенетических процессах продуктов; ȥ экологическая экспертиза проектов и  разработка экологической проектной документации. 22 выпускника кафедры стали док торами наук и  130  – кандидатами технических и химических наук. кафедра машин и аппаратов химических производств кафедра машин и  аппаратов химических производств организована в  1932 году. кафедру возглавляли профессор в. и.  даль-чумаченко (1932–1941), профессор к. н. шабалин (1941–1960), профессор б. п.  волгин этапы большого пути: наше прошлое и настоящее 186 № 3 | 2015 chimica techno acta (1960–1977), б. в. березин (1977–1982), доцент ф. с.  югай (1982–1996), профессор ф. м. черномуров (1996–2006), с 2006 года – профессор а. п. хомяков. сегодня обучение в рамках бакалавриата ведется по профилям «машины и  аппараты химических производств», «машины и аппараты пищевых производств» и  в  магистратуре по программе ««машины и аппараты химических производств». к основным научным направлениям деятельности кафедры относятся: ȥ разработка теплои  массообменных аппаратов на основе трубы вентури; ȥ внедрение скоростных аппаратов распыляющего типа для обработки технологических газов в  различных производствах; ȥ очистка от вредных примесей, охлаждение, абсорбция; ȥ разработка систем очистки газов от пыли, тумана, паров на основе скрубберов эжекционного типа; ȥ модернизация выпарного и  теплообменного оборудования, котельных деаэраторов; ȥ исследования изнашивания деталей гидравлических машин при кавитационном и  гидроабразивном воздействии; ȥ разработка аппаратов в  области ресурсои  энергосберегающих технологий; ȥ применение гидродинамических кавитационных установок для диссипативного нагрева; гомогенизации и пастеризации жидких сред пищевого и технического назначения; ȥ применение принципа испарительно-конденсационного теплообмена для создания технологического и теплоэнергетического оборудования, утилизации вторичных энергоносителей; ȥ разработка и  внедрение энерготехнологических комплексов, обеспечивающих предельную замкнутость материальных и  энергетических потоков в  рамках агрегата, цеха, предприятия; ȥ исследование процессов и  разработка аппаратуры для пищевых производств. кафедрой подготовлено 13 лауреатов ленинской и  государственной премий ссср, премии совета министров, 7 докторов наук, 107 кандидатов наук. кафедра аналитической химии кафедра аналитической химии основана в  1933 году. кафедрой заведовали доцент а. б. левин (1933–1938), профессор н. а.  тананаев (1938–1959), профессор в. н.  подчайнова (1960– 1977), профессор ю. м.  полежаев (1977–2000), с  2000 года  – профессор а. и. матерн. на кафедре ведется подготовка магистрантов по двум программам «электрохимические методы и  сенсоры для мониторинга окружающей среды и  биологических объектов», «инструментальные методы исследования в  фармацевтике». в  2015 году кафедра открыла бакалавриат по профилю «инструментальные методы анализа природных и технических объектов». в настоящее время кафедра аналитической химии хти ведет активную научную работу. основные направления исследований: безматерных м.а., селезнева и.с. 187 № 3 | 2015 chimica techno acta ȥ разработка сенсоров, приборов и  автоматического электрохимического комплекса для экомониторинга тяжелых металлов в online-режиме; ȥ исследования антиоксидантной и  антирадикальной активности растворов; ȥ бесферментные методы определения диагностически значимых параметров; ȥ разработка методов электрохимического иммуноанализа; ȥ исследование токсичности наночастиц; ȥ исследование механизмов электропревращений органических соединений и фармпрепаратов; ȥ определения основного вещества и примесей в фармпрепаратах. кафедра технологии органического синтеза кафедра технологии органического синтеза (тос) организована в  1947 году. кафедрой заведовали профессор, заслуженный деятель науки и техники рсфср з. в.  пушкарева (1947–1982), профессор в. и. шишкина (1982–1988), профессор в. с.  мокрушин (1988– 2008), с 2008 года по настоящее время – профессор в. а. бакулев. кафедра тос выпускает бакалавров по трем профилям: «химическая технология органических веществ», «биотехнология» и  «пищевая биотехнология». реализуются шесть магистерских программ: «химическая технология тонкого органического синтеза», «химическая технология биологически активных веществ», «химическая технология основного органического и  нефтехимического синтеза», «химическая технология пластических масс», «медицинская биотехнология», «пищевая биотехнология» (на  русском и  английском языках). основными научными направлениями кафедры являются: ȥ тонкий органический синтез в  области гетероциклических и  природных соединений; ȥ создание новых перспективных материалов; ȥ разработка новых и  совершенствование известных технологических процессов; ȥ нанотехнологии на основе органических соединений; ȥ медицинская, пищевая и  экобиотехнология. из числа выпускников и  сотрудников кафедры 370 человек защитили кандидатские диссертации, 40  – докторские, 20 выпускников стали лауреатами государственной премии, 15 – заведующими кафедрами различных вузов. кафедра иммунохимии кафедра иммунохимии основана в  2000 году по инициативе и  при участии академика ран в. а.  черешнева, который с  первых дней создания и  по настоящее время возглавляет кафедру. кафедра ведет подготовку магистрантов по программе «иммунобиотехнология». научная деятельность кафедры связана с  исследованиями в  области биохимии и  иммунохимии. одним из этапы большого пути: наше прошлое и настоящее 188 № 3 | 2015 chimica techno acta научных направлений является изучение реакции неферментативного гликозилирования белков, которая лежит в основе патогенеза многих социально значимых заболеваний. второе направление – исследование механизмов цитокининовой регуляции физиологических процессов в  клетках крови и  сосудистой стенки в  условиях гипергликемии. эта работа выполняется совместно с институтом иммунологии ран. в настоящее время в  химико-технологическом институте ведется подготовка бакалавров по трем направлениям: «биотехнология», «химическая технология», «энергои  ресурсосберегающие процессы в химической технологии, нефтехимии и  биотехнологии», а  также магистрантов по этим же направлениям и  по направлению «химия». в  рамках бакалавриата реализуется подготовка по 12 индивидуальным траекториям (профилям) и  в  магистратуре открыто 24 магистерские программы, в  том числе одна на английском языке. в 2008 году образовательная программа «технология электрохимических производств» прошла процедуру общественно-профессиональной аккредитации ассоциации инженерного образования россии. специальность тэхп  – единственная специальность в  уральском регионе, которой присвоен европейский знак качества eurace®. в июне 2012 года основная образовательная программа «биотехнология» прошла общественно-профессиональную аккредитацию агентства по общественному контролю качества образования и  развитию карьеры и  подтвердила соответствие качества подготовки выпускников программы стандартам качества и  гарантий качества, установленным на основании рекомендаций европейской ассоциации гарантий качества в  высшем образовании. помимо учебной работы, преподаватели и  сотрудники кафедр активно занимаются научными исследованиями. благодаря интернационализации научные исследования получили мощный импульс к развитию. увеличилось количество статей и монографий, опубликованных в  международных журналах на английском языке. синтезированы оригинальные химические соединения с  биологической активностью. студенты под руководством преподавателей активно участвуют в  выполнении сложных химических экспериментов. к  нам часто приезжают иностранные ученые из ведущих университетов мира для чтения лекций сотрудникам кафедры и  студентам. с  другой стороны, наши студенты и  аспиранты регулярно выезжают за рубеж (австралия, австрия, англия, бельгия, германия, китай, сша и  япония) для прохождения научных стажировок за рубежом. там они приобретают новый жизненный опыт, получают новые знания и  совершенствуют разговорный английский язык. наши сотрудники и  аспиранты часто выигрывают гранты на выполнение научных работ и  для участия в  российских и  международных конференциях. в заключение хочется поздравить всех преподавателей, сотрудников, студентов и  выпускников химико-технобезматерных м.а., селезнева и.с. 189 № 3 | 2015 chimica techno acta логического института с  предстоящим юбилеем! желаем всем творческих успехов и  новых побед! мы любим тебя, хти! живи, процветай и крепни! этапы большого пути: наше прошлое и настоящее solubility in the na,ca||so4,hco3-h2o system at 25 °c 130 d o i: 1 0. 15 82 6/ ch im te ch .2 01 9. 6. 4. 02 soliev l., jumaev m. t., varkaeva a. m., makhmadov kh. r., sinoi g. chimica techno acta. 2019. vol. 6, no. 4. p. 130–137. issn 2409–5613 soliev l., jumaev m. t., varkaeva a. m., makhmadov kh. r., sinoi g. tajik state pedagogical university named after s. ayni 121 prospect rudaki, dushanbe, 734003, tajikistan e-mail: soliev.lutfullo@yandex.com, jumaev_m@bk.ru solubility in the na,ca||so4,hco3–h2o system at 25 °c water solubility at 25 °c was studied in the four-component water-salt system comprised of sodium and calcium sulfates and hydrocarbonates in order to determine the concentration parameters of solution and crystallization of the constituent salts and to experimentally verify the phase equilibria in the geometric images of the system predicted previously by the translation method. the prediction of possible phase equilibria in geometric images of the system, followed by plotting its phase diagram, appreciably decreases the time and material costs of experimentation and improves the reliability of results. our results can serve both as reference information and as a scientific base for optimizing the parameters of natural and artificial processes, in particular, the recycling of salt from liquid waste of aluminum production facilities. keywords: sodium; calcium; sulfate; hydrocarbonate; solubility diagram received: 07.10.2019. accepted: 10.12.2019. published: 30.12.2019. © soliev l., jumaev m. t., varkaeva a. m., makhmadov kh. r., sinoi g., 2019 introduction t h e   fou rc omp on e nt na , ca||so4, hco3–h2o system is a constituent of the more complex six-component na,ca||so4,co3,hco3,f–h2o system; the phase equilibria in the latter determines the conditions for recycling of aluminum liquid waste. the  wastewater after cryolite recovery in aluminum plants contains fluorides, carbonates, hydrocarbonates and sulfates of sodium and calcium [1, 2]. in this paper we have examined the concentration parameters of equilibrium solid phases for the particular crystallization fields in the na,ca||so4,hco3–h2o system studied by the solubility method at 25 °c. phase equilibria in the form of phase diagram established by the translation method were studied in our previous work [3]. the  use of  the  translations method for predicting and constructing of phase diagrams for various systems is based on the principle of compatibility of the structure of constituent n-component systems with elements of the structure of a common (n+1) component system in one diagram [4]. according to the translation method, while the components number in the system is increasing from n to n+1, the geometric images of constituent n-component systems (i.e. nonvariant points, monovariants curves, divariant fields) are increasing their dimension by one, i.e. they have transformed and translated into the general area of (n+1) component composition. at a level of (n+1) — component composition, transformed by the translation proce131 dure geometrical images of the n-component constituent systems involved in the formation of the phase complex of the overall system, in accordance with their topological properties and requirements of the gibbs phase rule [5]. based on the obtained data, it is possible to construct an isolated phase diagram of the studied system. the application of the translation method for predicting and constructing phase diagrams for multicomponent water-salt systems is described in detail elsewhere [6–7]. the  use of  the  translation method for prediction and construction of phase diagrams of multicomponent systems significantly reduces the  time and material expenses of  experimental study of  various systems [9–11] constituting the  sixcomponent na,ca||so4,co3,hco3,f– h2o system. the equilibrium solid phases of the system under study at 25 °c are calcium hydrocarbonate, nahcolite, mirabilite, and gypsum [12, 13]. experimental fol low ing re agents were us e d in  our work: na2so4 · 10h2o; nahco3; ca(hco3)2; caso4 · 2h2o. the  experiments were carried out according to  the  “until saturation” method in  accordance with the  following. based on the  data reported in  works [3–15], we preliminary prepared the  mixtures of  precipitates with saturated solutions corresponded to  the  nonvariant points of the ternary systems, namely: na2so4– nahco3–h2o; caso4–ca(hco3)2–h2o; na2so4–caso4–h2o and nahco3– ca(hco3)2–h2o at 25 °c, which are constituting the four-component system under study. then, according to the translation scheme, the nonvariant points of the level of  three-component system were transformed to  the  level of  four-component system [3] by  the  mixing of  appropriate amounts of the prepared saturated solutions with the corresponding equilibrium solid phases at 25 °c in an ultrathermostat u-8 with stirring using magnetic stirrers pd-09 for 50–100 h. the temperature was maintained with an  accuracy of  ±0.1  °c using a contact thermometer. the crystallization of the solid phases was detected using a polam-r 311 microscope. after reaching an equilibrium state in the system, the  equilibrium solid phases were photographed with a sony — psc 500 digital camera. the achievement of equilibrium was judged by the unchanged phase composition of precipitation. separation of liquid and solid phases was carried out with the help of a vacuum pump through a  desalted (blue ribbon) filter paper on a büchner funnel. the  precipitate after filtration was wasted with 96% ethyl alcohol and dried at 120 °c. chemical analysis of products was carried out using well-known methods described elsewhere [15–17]. results and discussion the  micrographs of the  crystalline equilibrium solid phases are presented in fig. 1, and the results of chemical analysis of  saturated solutions are presented in table 1. the phases are denoted as follows: cah  — calcium hydrocarbonate, ca(hco3)2; gp — gypsum, caso4 · 2h2o; mb — mirabilite, na2so4 · 10h2o; nh — nahcolite, nahco3; gb  — glauberite, na2so4 · caso4. 132 fig. 1. micrographs of equilibrium solid phases of the na,ca||so4,hco3-h2o system at 25 °c 133 based on the obtained results, the solubility diagram for the na,ca||so4,hco3–h2o system at 25 °c was constructed (fig. 2). the  location of  invariant points at each level of the diagram within threecomponent (en 3) and four-component (en 4) systems under study was established by  the  mass-centric method [19, 20]. the  mass-centric method which is  used for presentation of multicomponent systems allows changing the  scale of  one of  the  constituent parts without disturbance of the general diagram laws, and it also allows using the polygon area more rationally, i.e. to increase the length of small individual geometric images. this is especially important when the solubility of salts in water is small and the use of the same scale leads to the situation when the figurative point of  the  mixture is  shifted towards the water angle while constructing of water-salt system diagrams. fig. 2 shows the total (a) and salt (b) parts of  the  solubility diagram for the  na,ca||so4, hco3–h2o system at 25 °c, where the relative position and the relative sizes of the crystallization fields for the  corresponding equilibrium solid phases are reflected. as follows from fig. 2, the crystallization fields of ca(hco3)2 and caso4·2h2o occupy a  significant part of  the  solubility diagram for the  studied four-component system, which characterizes the low solubility of these salt in water solution of given content at 25 °c. a description of  content for the  geometric images (fields, curves, points) in  fig.  2 is given in table 2. table 1 the solubility values of various salts correspondent to the invariant points in the na,са||so4,нсо3–h2o system at 25 °с point no. liquid phase, wt. % phase composition of precipitates naнсо3 na2so4 са(нсо3)2 caso4 h2o е1 9.31 – – – 90.69 nh е2 – 21.9 – – 78.10 mb е3 – – 0.0160 – 99.984 cah е4 – – – 0.219 99.78 gp 3 1e 4.16 20.68 – – 75.16 nh+mb 3 2e 4.89 – 0.0109 – 95.09 nh+cah 3 3e – – 0.0168 0.186 99.797 cah+gp 3 4e – 21.75 – 0.197 78.05 mb+gp 3 5e – 25.78 – 0.188 74.03 gb+gp 4 1e 5.20 28.38 – 0.270 66.15 nh+mb+gb 4 2e – 25.14 0.0136 0.184 74.66 gb+gp+cah 4 3e 7.12 24.40 0.0163 – 68.46 nh+cah+gb 134 fig. 2. (a) general and (b) salt-area solubility diagrams for the na,ca||so4,hco4–h2o system at 25 °c b a 135 table 2 description of the content for the geometric images in fig. 2 designation content e1 solubility of sodium hydrocarbonate in water e2 solubility of sodium sulfate in water e3 solubility of calcium hydrocarbonate in water e4 solubility of calcium sulfate in water е1 3 joint crystallization point mb+nh in the system nahco3–na2so4–h2o е2 3 joint crystallization point nh+cah in the system nahco3–ca(hco3)2–h2o е3 3 joint crystallization point cah+gp in the system ca(hco3)2–caso4–h2o е4 3 joint crystallization point mb+gb in the system na2so4–caso4–h2o е5 3 joint crystallization point gp+gb in the system na2so4–caso4–h2o е1 4 joint crystallization point nh+mb+gb in the system na,ca||so4,hco3–h2o е2 4 joint crystallization point cah+gb+gp in the system na,ca||so4,hco3–h2o е3 4 joint crystallization point nh+gb+cah in the system na,ca||so4,hco3–h2o е1 3 е1 4 curve of the joint crystallization of nh+mb in system nahco3–na2so4–h2o е2 3 е3 4 curve of the joint crystallization of nh+cah in system nahco3–ca(hco3)2–h2o е2 3 е2 4 curve of the joint crystallization of cah+gb in system ca(hco3)2–caso4–h2o е4 3 е1 4 curve of the joint crystallization of mb+gb in system na2so4–caso4–h2o е5 3 е2 4 curve of the joint crystallization of gb+gp in system nahco3–na2so4–h2o е1 4 е3 4 curve of the joint crystallization of nh+gb in system na,ca||so4,hco3–h2o е2 4 е3 4 curve of the joint crystallization of cah+gb in system na,ca||so4,hco3–h2o nahco3e1 3e1 4e3 4e2 3nahco3 crystallization field nh ca(hco3)2e2 3e3 4e2 4e3 3 ca(hco3)2 crystallization field cah na2so4e1 3e1 4e4 3na2so4 crystallization field mb caso4e3 3e2 4e5 3caso4 crystallization field gp e4 3e1 4e3 4e2 4e5 3e4 3 crystallization field gb (i) notation of the figurative point of the mixture in the water-salt area of the diagram 136 references 1. morozova va, rzhechitskii ep. solubility in the naf–na2so4–nahco3–h2o system at 0 °c. russian journal of applied chemistry. 1976;49(5):1152–4. russian. 2. morozova va, rzhechitskii ep. solubility in the systems naf–nahco3–h2o, naf– na2so3–h2o and naf–na2co3–h2o at 0 °c. russ j inorg chem. 1977;22(3): 873–4. russian. 3. soliev  l., dzhumaev  m. t., nuri  v., avloev  sh. kh.  phase equilibria in na,ca||so4,hco3–h2o system at 25 °c. vestnik tadjikckogo natsional’nogo universiteta (seriya estesvennikh nauk) [bulletin of the tajik national university (series of natural sciences)]. 2012;1/3(85):221. russian. 4. goroshchenko yag. fiziko-khimicheskiy analiz gomogennykh i geterogennykh sistem [physicochemical analysis of homogeneous and heterogeneous systems]. kiev: naukova dumka; 1978. 490 p. russian. 5. anosov vya, ozerova mi, fialkov yuya. osnovy fiziko-khimicheskogo analiza [major methods of physicochemical analysis]. moscov: nauka; 1976. 504 p. russian. 6. soliev  l.  prediction of  phase equilibria in  multinary marine-type systems by the translation method, book 1. dushanbe: tspu; 2000. russian. 7. soliev  l.  prediction of  phase equilibria in  multinary marine-type systems by the translation method, book 2. dushanbe: tspu; 2011. russian. 8. soliev  l. [prediction of  phase equilibria in  multinary marine-type systems by the translation method, book 3]. dushanbe: r-graph; 2019. russian. 9. soliev l, dzhumaev mt, avloev shh, toshov af. solubility in the caso4–caco3– ca(hco3)2–h2o system at  0 °c.  doklady akademii nauk respubliki tajikistan [reports of the academy of sciences of the republic of tajikistan]. 2015;58(2):139. russian. 10. dzhumaev mt, soliev l, dzhabborov bb, ikbol g. solubility in the na,сa||со3, нсо3 — h2o system at 25 °с. russ j inorg chem. 2017;62(9):1245–51. doi:10.1134/s0036023617090169 11. soliev l, dzhumaev mt, dzhabborov bb. solubility and phase equilibria in  the  na,са||со3, нсо3–h2o system at  0 °с.  chimica techno acta. 2017;4(3):191–201. doi:10.15826/chimtech/2017.4.3.04. 12. spravochnik eksperimental’nykh dannykh po rastvorimosti mnogokomponentnykh vodno-solevykh system [reference book on experimental data for solubility in multicomponent water-salt systems]. vol. 1. saint-petersburg: khimizdat, 2003. 1151 p. russian. 13. spravochnik eksperimental’nykh dannykh po rastvorimosti mnogokomponentnykh vodno-solevykh system reference book on experimental data for solubility in multicomponent water-salt systems. vol. ii., books. 1–2. saint-petersburg: khimizdat, 2004. 1247 p. russian. 14. goroshchenko yag, soliev l, gornikov yui. opredelenie polozheniya nonvariantnykh tochek na diagrammakh rastvorimosti metodom donasyshcheniya [determination of the invariant points’ positions on solubility diagrams using the presaturation 137 method]. ukrainskii khimicheskii zhurnal [ukrainian journal of  chemistry]. 1987;53(6):568–71. russian. 15. kreshkov ap. osnovy analiticheskoy khimii [basics of analytical chemistry]. vol. 2. leningrad (ussr): khimiya, 1970. 456 p. russian. 16. knipovich yun, morachevskii yuv, editors. analiz mineral’nogo syr’ya [analysis of mineral raw materials]. leningrad: goskhimizdat, 1959. 947 p. russian. 17. reznikov aa, mulikovskaya ep, sokolov iyu. metody analiza prirodnykh vod [methods of natural water analysis]. moscow: nedra, 1970. 488 p. russian. 18. tatarskii vb. kristallooptika i immersionnyy metod analiza veshchestv [crystal optics and immersion method of substances analysis]. leningrad (ussr): izdatel’stvo lgu, 1948. 268 p. russian. 19. goroshchenko yag, soliev l, savchenko lt, mardanenko vkh, romanenko on, zharovskiy iv, borisenko la. sistema na, к, mg // so4, сl-н2o pri 100 °с [na, к, mg // so4, сl-н2o system at 100 °с]. zhurnal neorganicheskoy khimii [russ j inorg chem]. 1977;22(11):3129–34. russian. 20. goroshchenko yag. masstsentricheskiy metod izobrazheniya mnogokomponentnykh system [the center of mass method for multi-component systems imaging]. kiev: naukova dumka, 1982. 264 p. russian. synthesis, structure and electrical properties of mg-, ni-codoped bismuth niobates 231 d o i: 1 0. 15 82 6/ ch im te ch /2 01 7. 4. 4. 04 m.s. koroleva, i.v. piir, e.i. istomina institute of chemistry komi sc ub ras 48 pervomayskaya st., syktyvkar, 167982, russian federation e-mail: marikorolevas@gmail.com synthesis, structure and electrical properties of mg-, ni-codoped bismuth niobates mg-, ni-codoped bismuth niobates bi 1.6 mg 0.8–x ni x nb 1.6 o 7–δ (x = 0; 0.2; 0.4; 0.6; 0.8) were obtained by conventional solid-state reaction method. it was shown that the mg atoms are distributed at the nb sites while the ni atoms are distributed over the biand the nb-sites, according to the results of comparison of pycnometric and x-ray density of the bi 1.6 mg 0.4 ni 0.4 nb 1.6 o 7–δ pyrochlore. in this case, about 15–20% of the vacancies are formed at the bi sites. the obtained compounds are stable up to their melting point based on the dsc analysis data. real dielectric permittivity ε' of the bi 1.6 mg 0.8–x ni x nb 1.6 o 7–δ samples decreases from 80 to 65 with the temperature decrease from 25 to 700 °c and practically does not depend on frequency in the range of 1–1000 khz. oxi des bi 1.6 mg 0.8–x ni x nb 1.6 o 7–δ behave like insulators up to 280 °c, their conductivi ty increases with temperature (e a,dc ≈ 1.3 ev, dc) and with the ni content at a given temperature. keywords: pyrochlore; bi 1.6 mg 0.8–x ni x nb 1.6 o 7–δ ; dopant distribution; dielectric behavior; electrical conductivity. received: 14.11.2017; accepted: 12.12.2017; published: 25.12.2017. © koroleva m.s., piir i.v., istomina e.i., 2017 koroleva m.s., piir i.v., istomina e.i. chimica techno acta. 2017. vol. 4, no. 4. p. 231–241. issn 2409–5613 introduction ceramics in the bi2o3-mxoynb2o5 ternary system are interesting from the perspective of their dielectric properties. the most attention has been paid to the zn-, mg-containing bismuth niobates, which possess high dielectric constant (170–180) and low dielectric loss (~10-4) at 1 mhz (at room temperature) [1–9]. to search for the same properties fe[10], mn[11–12], co[13], ni[12, 14–15], cu[12] and the mixed zn-m (m – sr [16], ca [16–17], mn [16, 18], ti [19–22], sn [19, 22], zr [19, 21–22], ce [19,22], gd [21], ta [23], la [24]), mg-m (m – sr [25], nd [26], cu [27]) bismuth niobates and other ones were synthesized. the improved permittivity was achieved by ti doping of the nb sites in the pyrochlore structure [21–22] and by cu doping in bi1.5cuxmg1-xnb1.5o7 (x = 0.075) [27]. in most cases, doping leads to the permittivity decrease and to the tangent loss increase. however, electrical properties of several systems were investigated in the high temperature range (up to 700  °c) only in order to determine their conductivity mechanism [3, 9, 19–20, 27]. in our previous work [28–29] we have determined that the dielectric constant of the bi1.6cuxmg0.8-xnb1.6o7-δ pyrochlores behave 232 unusually passing through a maximum (250–350 °c) with temperature increasing. the value of the dielectric constant at the maximum is very high: ~106 (100 hz). second-type phase transition was found at 200 °c. to establish the reasons for such behavior, the distribution of doped me tals in the cation (a–, b–sites) positions in the pyrochlore structure (a2b2o6o’, the space group fd3m (no 227)) was studied by x-ray diffraction pattern refinement (rietveld analysis), and by comparison of pycnometric density with the calculated one. it has been determined that the electronegativity plays the crucial factor for the distribution of the mg atoms in the nb sites and the cu atoms – in the bi and the nb sites in equal ratios. in any case, there are 10–15% of vacancies in the bi sites. in accordance with the other systems’ investigations, the vacancy concentration always remains at about 5–10% in the bi sites in the pyrochlore structure [4, 10–11, 14, 30]. in this work we have a goal to determine a distribution of ni and mg dopants in the pyrochlore structure and investigate the temperature dependence of electrical properties of the bi1.6mg0.8-xnixnb1.6o7-δ. experimental mixed bismuth niobates bi1.6mg0.8-xnixnb1.6o7-δ (x = 0; 0.2; 0.4; 0.6; 0.8) were prepared by a conventional solid state reaction method [31–32] from the oxides with high degree of purity (>99.9%): bi2o3, nio, mgo, nb2o5. the oxides were weighted in an appropriate ratio (bi2o3:mgo:nio:nb2o5 = 0.8:(0.8x):x:0.8), grinded, pressed into pellets and calcined at 650 °с (8 h), 850 °c (6 h), 900 °c (6 h), 950 °c (12 h), 1000 °c (6 h), 1050  °c (12 h), 1070 (6 h), and 1100 °c (11 h) consequently in corundum crucibles. the annealing at 650 °c was carried out in order to avoid significant bismuth weight loss and the melting stage of вi2о3 at 824  °c. as the temperature and duration of the calcination increased, the impurity phase content decreased. after each firing step, the pellets were regrinded for 30 min and repressed. the pellets’ diameter and thickness varied from 12 to 14 mm and from 2.2 to 2.7 mm, respectively. the phase composition of the samples was examined by powder x-ray diffraction method on a shimadzu xrd-6000 diffractometer using cu kα emission within the angle range 10–80° (the step – 0.05°). distribution of nickel and magnesium atoms in the bi1.6mg0.4ni0.4nb1.6o7-δ pyrochlore was determined by rietveld analysis (fullprof software package [33]). scanning electron microscopy (sem) was carried out on a tescan vega 3 sbu microscope. the local composition of the samples was studied on polished pellets by energy dispersion spectroscopy (eds). differential scanning calorimetry (dsc) and thermogravimetric analysis (tg) of bi1.6mg0.4ni0.4nb1.6o7-δ powder were carried out in the air in platinum crucibles with heating up to 1300 °c and a heating rate of 5 °c/min (netzsch sta 409 pc/ pg). the electrical measurements were performed on the pellets, both sides of which were coated uniformly with a  silver paste. capacitance and dielectric loss tangent were measured by mt–4090 lcr meter in different gases (air, p(o2) = 0.21 atm and oxygen, p(o2) = 0.99 atm) at four frequencies (1, 10, 100, 200 khz) in the temperature range of 25–750  °c. the impedance plots were measured by immittance meter e7-28 at 0.5 v in the temperature and frequency ranges 25–700 °c and 24 hz – 10 mhz, respectively. the 233 electrical data were collected after 10 min after the thermal equilibrium was reached. the thermoelectric effect – seebeck coefficient – was determined in the temperature range 130–330 °c in a temperature gradient of 30–40 °c across the material. results and discussion synthesis and characterization the xrd patterns of bi1.6mg0.8-xnixnb1.6o7-δ (0 ≤ x ≤ 0.8) are shown in fig. 1. the pyrochlore structure is formed for the bi1.6mg0.4ni0.4nb1.6o7-δ composition only. the small amounts of second phases, identified as mgnb2o6 (pbcn space group) and as ninb2o6 (pbcn space group), were found in the samples with x = 0; 0.2 and with x = 0.6; 0.8, respectively. the surfaces of the bi1.6mg0.8-xnixnb1.6o7-δ (0 ≤ x ≤ 0.6) polished pellets after the last calcination are shown in the sem images (fig. 2a–2c). according to the eds data, the presence of additional phases such as mgnb2o6 (at x = 0) or as mixed mg-ni containing niobates (at x = 0.2; 0.6) can be seen. the amount of impurities is around 5%. the local compositions of the main and second phases are presented in the caption to fig. 2. the composition of the bi1.6mg0.4ni0.4nb1.6o7-δ ceramic determined by eds is bi1.60mg0.38ni0.45nb1.6o7-δ, which is close to the desired composition. the porosity of the pellets was around 35– 40%, as estimated from sem micrographs. dsc and tg curves of the bi1.6mg0.4ni0.4nb1.6o7-δ powder are shown in fig. 3. the endothermal effect was found on the dsc curve at 1261 °c. this effect may be associated with the melting of the sample. the reason for the weight rise during the heating process has not been established yet. it may be related to the partial oxidation of ni+2 to ni+3. the rietveld refinement of the xrd pattern of bi1.6mg0.4ni0.4nb1.6o7-δ was carried out. the occupations of atom sites were fixed in accordance with the quantitative composition of the compound. the possibility of displacement of the bismuth atoms (from 16c sites to 96h or 96g sites) and the oxygen atoms o′ associated with bismuth (from 8a sites to 32e sites) were considered, like in [bi0.833 mg0.11□0.04]2[mg0.24nb0.76]2o7 and in [bi0.833 ni0.125□0.04]2[ni0.25nb0.75]2o7 pyrochlores [14]. various models were studied to determine the distribution of doped atoms in the cation (bi, nb) sites of the pyrochlore structure. among the alternative models that were considered there are [bi1.56ni0.34□0.10][ni0.05mg0.39nb1.56]o7.02 and [bi1.56mg0.34□0.10][mg0.05ni0.39nb1.56]o7.02. in these models 5% of vacancies remain at the bi sites. the distribution of dopant atoms in equal ratio among two different cation sites causes formation of about 2.5% vacant sites both in the bi and nb sublattices. it is not typical for the pyrochlore structure. the best agreement between theoretical and observed x-ray patterns was obtained for the model designated as fig. 1. x-ray diffraction patterns of bi1.6mg0.8-xnixnb1.6o7-δ (0 ≤ x ≤ 0.8) 10 20 30 40 50 60 70 80 0 10 20 30 40 80 0 55 3, 73 1 64 242 2 62 0 53 3 62 2 44 4 55 1, 71 1 66 2 66 0, 82 2 64 4 22 0 31 1 2 22 40 0 33 1 33 3 44 0 53 1 11 1 * i 1 03 , c ps ∆ ∆ * mgnb2o6 ∆ ninb2o6 * 0.8 0.2 0.4 0.6 0.0 2θ, deg. x 234 [bi1.56ni0.34□0.10][ni0.05mg0.39nb1.56]o7.02. in this model, all mg atoms are distributed over the nb sites. several models were considered with different vacancy concentrations (10–25%) in the bi sites and mg atoms occupying the nb sites. the best values of rwp (%), rp (%), χ 2 factors can be obtained for the models with 15–20% vacancies in the bi sites. the refined crystallographic parameters of the [bi1.46ni0.18□0.36][ni0.18mg0.36nb1.46]o6.52 model are presented in table 1. this mo del corresponds to the equal distribution of ni atoms in the bi and the nb sites, whereas 18% of vacancies remain in the bi sites. displacement of bi and ni atoms (16c fig. 2. sem images of bi1.6mg0.8-xnixnb1.6o7-δ samples: a – x = 0 (1 – bi1.72mg0.78nb1.6o7-δ, 2 – mgnb2o6); b – x = 0.2 (1 – bi1.60mg0.44ni0.18nb1.6o7-δ, 2 – mg0.85ni0.11nb2o6); c – x = 0.4 (bi1.60mg0.38ni0.45nb1.6o7-δ); d – x = 0.6 (1 – bi1.68mg0.16ni0.56nb1.6o7-δ, 2 – mg0.35ni0.55nb2o6) a b c d 235 to 96h sites) is observed. the observed, calculated and difference x-ray diffraction profiles for the model are shown in fig. 4. to our mind, the distribution of dopant atoms in the cation sites is governed by the electronegativity values, apart from the ionic radii influence. so, mg2+ and ni2+ ionic radii are close (0.72 å and 0.70 å, respectively) [34]. the electronegativity of mg (1.23) by allred-rochow [35] is equal to that of nb (1.23), and the electronegativity of ni (1.75) is close to that of bi (1.67). obviously, the electronegativity values impact on the dopant distribution in the pyrochlore structure, like in the cu–mg substituted bismuth niobates [28–29]. the pycnometric density of the bi1.6mg0.4ni0.4nb1.6o7-δ powder is 6.50±0.24 g/cm3. the calculated density for the [bi1.56m0.34□0.10][m0.44nb1.56]o7.02 model where m – the dopant metals (5% of vacancies in the bi sites) is 7.02 g/cm3. the calculated density for the model with 18% vacancies in the bi sites ([bi1.46m0.18□0.36] [m0.54nb1.46]o6.52) is 6.53 g/cm 3 and is in agreement with the pycnometric density value. thus assumed amount of about 15– 20% vacant sites in bi sublattice seems to be in agreement with the experimental results obtained in the present study. electrical properties complex impedance plots of the bi1.6mg0.8-xnixnb1.6o7-δ ceramics were drawn from impedance spectroscopy data. the data were obtained during cooling from 700 to 160 °c to exclude proton conductivity. perfect semicircles are traced in fig. 4. observed, calculated and difference x-ray diffraction profiles for [bi1.46ni0.18□0.36][ni0.18mg0.36nb1.46]o6.52 fig. 3. dsc and tg curves of bi1.6mg0.4ni0.4nb1.6o7-δ 0 200 400 600 800 1000 1200 -0.5 -0.4 -0.3 -0.2 -0.1 0.0 0.1 1261 °ct, dsc, w/g tg, % 100 102 104 106 108 110 table 1 refined crystallographic parameters for bi1.6mg0.4ni0.4nb1.6o7-δ (space group fd3m) atom type site x y z biso, å 2 occupation [bi1.46ni0.18□0.36][ni0.18mg0.36nb1.46]o6.52 bi/ni 96h 0 0.015 0.985 0.708 0.725/0.09 nb/ni 16d 1/2 1/2 1/2 0.003 0.725/0.09 nb/mg 16d 1/2 1/2 1/2 0.003 0.725/0.18 o 48f 1/8 1/8 0.428 0.010 1 o’ 8a 1/8 1/8 1/2 0.010 0.52 a = 10.5204 å; rp = 4.51%, rwp = 5.86%, χ 2 = 2.22. 10 20 30 40 50 60 70 80 -2000 0 2000 4000 6000 8000 10000 iobs icalc iobs-icalc bragg position in te ns ity , a rb . u ni ts 2θ, deg. 236 the temperature range 320–700 °c. at the temperature less than 320 °c half semicircles may be observed. in fig. 5 impedance plots for the bi1.6mg0.8-xnixnb1.6o7-δ (x = 0.4; 0.6) ceramics are presented. the plots are well fitted by a single parallel rc element (inset of fig. 5) where r and c belong to bulk resistance and capacitance, respectively [36–38]. the measured parameters are listed in table 2. permittivity recalculated from the capacitance values for the samples with ni content x = 0.20, 0.40, and 0.60 is (70–81), (70–81), and (65–76), respectively, for the temperature range of 700–280 °c. calculated permittivity does not depend on the frequency in the range of 1–1000 khz and is close to the dc permittivity values. at room temperature, the permittivity is around 80 in the frequency range of 1–1000 khz. all ceramics under investigation behave like a dielectric (tan δ ≈ 0.002) up to 280 °с. calculated from arrhenius direct conductivity plots activation energy values are close to 1.2 ev (the third column in table 3). these values are almost equal to ones at 1 khz (the second column in table 3). the corresponding arrhenius config. 5. complex impedance plots at 500, 600 and 700 °c for the bi1.6mg0.8–xnixnb1.6o7–δ ceramics with x = 0.4; 0.6 0 50000 100000 150000 200000 250000 0 50000 100000 150000 200000 170.2 khz 24 hz 22.2 khz z ', ω -z '', ω 500 oc 600 oc 700 oc 0 10000 20000 30000 40000 50000 0 10000 20000 30000 662 khz z', ω 500 oc 600 oc 700 oc -z'', ω 86.3 khz a b table 2 rb and cb parameters of the rc elements in the temperature range 280–700 °c for the bi1.6mg0.8–xnixnb1.6o7–δ ceramics t, °c x = 0.20 (h = 0.265 cm; d = 1.280 cm) x = 0.40 (h = 0.235 cm; d = 1.300 cm) x = 0.60 (h = 0.220 cm; d = 1.325 cm) r, kω c, pf r, kω c, pf r, kω c, pf 280 (79±3)·104 34.77±0.08 (50±3)·104 40.61±0.18 (111.7±2.7)·103 42.03±0.26 320 (157.8±2.5)·103 34.32±0.11 – – (173±3)·102 41.4±0.3 360 (373±4)·102 33.99±0.15 (310±4)·102 39.77±0.20 2860±30 40.8±0.3 400 9420±60 33.57±0.14 7560±40 39.18±0.12 606.8±2.4 39.97±0.15 500 558.5±2.3 32.41±0.14 164.4±0.5 37.87±0.12 49.61±0.08 38.66±0.09 600 62.8±0.4 31.08±0.28 21.52±0.04 36.57±0.13 8.460±0.014 37.36±0.14 700 8.972±0.026 29.88±0.19 4.032±0.010 35.22±0.24 1.913±0.004 35.8±0.3 237 ductivity plots at 1 khz for all ceramics are shown in fig. 6a. the activation energy values, which are greater than 1 ev, may be associated with ionic conduction. the same activation energy values (~1.27 ev) are known for the (bi1.5zn0.5)(nb0.5m1.5)o7 (m – ti, sn, zr, and ce) ceramics [19] at t > 350 °c with the ionic type of conductivity. the conductivity dependences on the temperature for the bi1.6mg0.4ni0.4nb1.6o7-δ ceramic (160–750 °c) in the air and in the oxygen atmosphere are shown in fig. 6b. the conductivity of the ceramic does not dependent on the oxygen pressure, and the value of seebeck coefficient is near 0 mv/k in the temperature range of 200– 340 °c. these data indicate that there is no impurity-caused conductivity. for all ceramics, an electrical modulus (m") maximum is detected on the logarithmic scale of frequency (fig. 7), indicating the presence of a polarization process. these relaxation effects are characterized by the full width at half maximum (fwhm) peaks of m"(f) being ~ 1.2 decades. this value is close to an ideal debye response (1.14 decades) that characterizes the ceramics as electrically homogenous. at frequencies of the m" maximum value the relaxation time was calculated (fig. 7). frequency values at m" maxima were plotted vs temperature in an arrhenius-type fashion. obtained accordingly values of activation energy are a b fig. 6. electrical conductivities as functions of reciprocal temperature at 1 khz: a – bi1.6mg0.8-xnixnb1.6o7-δ; b – bi1.6mg0.4ni0.4nb1.6o7-δ table 3 activation energies of (dc, ac) conductivity and relaxation process of the substituted bismuth niobate pyrochlores compound ea (conductivity, 1 khz), ev ea (conductivity, dc), ev ea (relaxation), ev bi1.6mg0.8nb1.6o7–δ 1.03±0.06 – – bi1.6mg0.6ni0.2nb1.6o7–δ 1.09±0.03 1.25±0.03 1.38±0.03 bi1.6mg0.4ni0.4nb1.6o7–δ 1.14±0.03 1.20±0.03 1.38±0.03 bi1.6mg0.2ni0.6nb1.6o7–δ 1.10±0.03 1.20±0.04 1.23±0.04 bi1.6ni0.8nb1.6o7–δ 1.17±0.08 – – 0.8 1.0 1.2 1.4 1.6 1.8 2.0 -10 -9 -8 -7 -6 -5 -4 -3 ea = 1.03 ± 0.06 ev ea = 1.136 ± 0.009 ev 0.80 0.60 0.40 0.20 0.00 lg σ, σ (s cm -1 ) 103t -1, k-1 0,8 1,0 1,2 1,4 1,6 1,8 -8 -7 -6 -5 -4 -3 1.11 ev 103t -1, k-1 lg σ, σ (s cm -1 ) air o2 238 close to the ones obtained from the arrhenius conductivity plots (table 3). it points out that the hopping-type conductivity is typical for the bi1.6mg0.8–xnixnb1.6o7–δ ceramics, like for bi1.5znnb1.5o7 [36, 38] and bi3.55mg1.78ta2.67o13.78 [37] pyrochlores with ea (relaxation) are 0.94 ev and 1.37 ev, respectively. conclusions mixed mg–, ni–containing bismuth niobates bi1.6mg0.8-xnixnb1.6o7-δ (0 ≤ x ≤ 0.8) were synthesized by the conventional solid-state reaction method. for all samples the main crystal phase is the pyrochlore. the bi1.6mg0.4ni0.4nb1.6o7-δ ceramic is a single-phase compound and is stable up to its melting point (1261 ºc). based on structural analysis and the comparison of pycnometric and calculated densities of the bi1.6mg0.4ni0.4nb1.6o7-δ, it was found that mg atoms are distributed over the nb sites, ni atoms are distributed at the bi and nb sites almost in the equal ratio. in this case, there are about 15–20% vacant sites in the bi sublattice. the bi1.6mg0.8-xnixnb1.6o7-δ ceramics are characterized by the hopping type of conductivity (ea = 1.0–1.4 ev). it was determined that dielectric permittivity varies from 81 to 65 as the temperature increases from 280 to 700 °c, and practically does not depend on frequency in the range of 1–1000 khz. acknowledgements this study received the financial support of russian foundation for basic research (project no. 15-03-09173 а). the study was performed using the equipment of the center for shared use of scientific equipment “khimiya” of the institute of chemistry, komi science center, ural branch of the russian academy of sciences. references 1. nino jc, lanagan mt, randall ca. dielectric relaxation in bi2o3–zno–nb2o5 cubic pyrochlore. j appl phys. 2001;89(8):4512–6. doi:10.1063/1.1357468. a b fig. 7. imaginary part of electrical modulus as a function of frequency for the bi1.6mg0.8-xnixnb1.6o7-δ ceramics at x = 0.4 (a), x = 0.6 (b) 101 102 103 104 105 106 107 0.000 0.002 0.004 0.006 τ σ = 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with oxide shell in vapor condensation 93 d o i: 1 0. 15 82 6/ ch im te ch .2 01 9. 6. 3. 02 beketov i. v., safronov a. p., medvedev a. i., murzakaev a. m., zhidkov i. s., cholah s. o., maximov a. d. chimica techno acta. 2019. vol. 6, no. 3. p. 93–103. issn 2409–5613 i. v. beketova*, a. p. safronova,b, a. i. medvedeva,b, a. m. murzakaeva,b, i. s. zhidkovb, s. o. cholahb, a. d. maximova a institute of electrophysics ub ras, 106 amundsen st., yekaterinburg, 620016, russian federation b ural federal university, 19 mira st., yekaterinburg, 620002, russian federation *e-mail: beketov@iep.uran.ru encapsulation of ni nanoparticles with oxide shell in vapor condensation controlled input of oxygen into the inert working gas flow during the production of ni nanoparticles by the electrical explosion of wire (eew) method leads to the formation of a crystalline oxide shell on the surface of particles during their condensation from the vapor phase. resulting oxide shells encapsulating ni particles weaken their agglomeration processes as well as protect the surface of the ni nanoparticles from further oxidation. the influence of the amount of energy introduced during eew and the quantity of oxygen added to the working gas in eew process on the properties of resulting ni nanoparticles was studied. the obtained nickel nanopowders were characterized by x-ray diffraction (xrd), transmission electron microscopy (tem), x-ray photoelectron spectroscopy (xps), and n2 adsorption (bet) methods, which gave the specific surface area, the average diameter of nanoparticles, their phase composition, the morphology of the particles and the structure of the oxide shells. it was shown that the addition of oxygen leads to a decrease in the average diameter of ni nanoparticles and reduces the degree of their agglomeration. the encapsulation of ni nanoparticles with 3–5 nm thick gas-tight oxide shells protects the particles from oxidation and eliminates the pyrophoricity of the powder product. keywords: nickel nanoparticles, oxide shells, encapsulation, electrical explosion of wire. received: 10.07.2019. accepted: 16.09.2019. published: 15.10.2019. © beketov i. v., safronov a. p., medvedev a. i., murzakaev a. m., zhidkov i. s., cholah s. o., maximov a. d., 2019 introduction today, nanoparticles of transition metals are of considerable interest both from a scientific point of view due to their specific physical and chemical properties, and also in connection with promising practical applications [1]. in particular, such materials can be used as catalysts, as components in magnetic recording systems, in bioengineering and biomedicine, as components in sensors, actuators, scaffolds, etc. with a  decrease in  particle size their surface activity considerably increases, promoting agglomeration and aggregation of particles, which complicates their 94 further use. for instance, in the preparation of metal matrix composites or complex ceramic composites, the uniformity of the material is achieved only at the scale of  agglomerates with sizes varying from units to tens of micrometers. thus, the agglomeration of nanoparticles during their production limits the yield: with a decrease in the size of the particles, it is necessary to  reduce the productivity of  equipment to  prevent their agglomeration. in addition, it is known that metal nanoparticles, with the exception of  noble metals, are very pyrophoric at  low temperatures and simply combust if exposed to ambient air. usually, after the synthesis, the metal nanoparticles are passivated: a thin layer of oxide, which subsequently protects the metal from rapid oxidation, is formed on  their surface. however, some metals, such as  cu, even after the passivation do not form a  gas-tight oxide shell that protects them from further oxidation. in particular, it is shown [2] that the process of oxidation of copper nanoparticles during their storage in air results in complete formation of cuo. to prevent agglomeration and to protect the surface of  the particles, it is desirable to  form protective shells on  the particles during their formation. a choice of a material for a protective cover is a separate issue. on the one hand, the most acceptable material for  the protective shell is a material that reliably protects the surface of  the particle from rapid oxidation and does not interfere with, and in some cases even contributes to  the further use of such powders. on the other hand, nanoparticles with the structure of the metal core — protective shell are typically used as fillers in composite polymer materials and liquid disperse systems. therefore, the main property of the shell material is also to  ensure the compatibility of  core / shell nanoparticles with the dispersion medium, which depends on the energy of interaction between the dispersion medium and the surface of such nanoparticles. in the technology of synthesis of metal nanoparticles, their surface is typically covered with pure carbon, silicon carbide, or  polyethylene [3], which are not active at low temperatures. for instance, to create a carbon protective shell on the particles, various methods are used, such as annealing of metal particles in the atmosphere of hydrocarbon (gasoline) [4], filling carbon tubes with metal [5], annealing of a mixture of metal powder with carbon [6]. all these techniques involve the processing of the finished powder. the formation of a carbon shell on the surface of  the particles in  the process of  synthesis of fe, co, ni metal nanoparticles and their alloys using the method of  an arc discharge in  the methane atmosphere is described in ref. [7]. in our opinion, nickel monoxide (nio) is a  promising material of  the protective shell for ni nanoparticles. nio has a relatively high melting point, 1955 °c [8], and it forms a strong gas-tight protective film on the metal surface [9]. the objective of the present study is to develop an in-situ method of  the formation of  the protective oxide shells on  the surface of ni nanoparticles during their synthesis by the electric explosion of wire. electric explosion of wire (eew) is one of the most productive methods of synthesis of nanoparticles of metals, alloys and their chemical compounds. the productivity of eew method ranges from 50 to 500 g / h depending on  the nature of  nanoparticles. the method has low energy consumption, not exceeding 50 kw·h / kg; it is environmentally friendly; it provides high purity of the 95 resulting particles. experimental setups for eew method are compact and do not require separate facilities. this method has been described in detail elsewhere [10]. experimental production of nickel nanopowders was carried out in the installation of an electric explosion of  wire (eew). the discharge circuit had an inductance of 0.4 µh. the capacitance of the capacitor bank varied from 3.2 to 4.8 µf, and the charging voltage — from 20 to 30 kv, which provided a change in overheating ratio k (the ratio of  the energy introduced into the wire to  the sublimation energy of  the wire metal) in the range of 1–2.2. to obtain the powder, a wire of nickel (np2 grade) with a diameter of 0.3 mm and a length of 88 mm was used. the wire was fed into an explosion chamber continuously. wire explosions were carried out in argon at a pressure of 0.12 mpa at a frequency of 0.5 hz. the gas system of the installation consisted of an explosion chamber, two inertial traps with a gas flow rotation, a mechanical (cloth) filter and a fan connected in series. inertial traps were used to separate large micron-sized particles; the rest of the powder was collected in  the filter. as shown by  preliminary experiments, the output of the powder in the filter depends on the amount of energy introduced into the wire and averages 85 % of the mass of all resulting from the explosion powder. only the powders from the filter were studied in the present work. to create shells on the surface of the particles in the process of the powder production, oxygen was continuously introduced into the working gas (ar) flow directly before entering the explosion chamber. with the help of an adjustable flow-type throttle, the oxygen flow could vary from 0.3 to 20 cm3 / s. for the ease of comparison of powders obtained in different modes, the amount of oxygen is given below in grams per gram of nickel (g / g ni). at low oxygen consumption, after producing the powder, it was additionally passivated with oxygen flow (0.5 cm3 / s) supplied to the eew setup. the minimum oxygen consumption, which allows eliminating the pyrophoricity of  the powder, was determined experimentally. the passivation process was controlled by  the oxygen partial pressure sensor. passivation stopped when the partial pressure of  oxygen reached 2 kpa. after that, the powder was freely (without the risk of its self-combustion) removed to the air. the specific surface area of the obtained powders was determined by the bet method by low-temperature nitrogen adsorption using micromeritics tristar 3000. xray phase analysis (xrd) was performed on the bruker d8 discover diffractometer in cu kα radiation (λ = 1.54 å) with a graphite monochromator on the secondary beam. processing of diffractograms was performed using the program topas 3. high-resolution transmission electron microscopy (tem) was performed using the jeol jem2100 electron microscope at an accelerating voltage of 200 kv. the energy introduced into the wire was determined by  the oscillograms of  the current pulse passing through the exploding section of  the wire. measurements of  the x-ray photoelectron spectroscopy (xps) spectra of the main and valence levels of powders were carried out on the spectrometer phi 5000 versaprobe, based on  the classical scheme of x-rays with a quartz monochromator and a  hemispherical energy analyzer operating in the energy range from 0 to 1500 ev. electrostatic focusing with 96 magnetic shielding allows obtaining energy resolution δe ≤ 0.5 ev for  al kα radiation (1486.6 ev). pumping of the analytical chamber was carried out with the help of an ion pump, which provides a pressure lower than 10–7 pa. two-channel neutralization was used to compensate the local surface charge formed during the measurements. the diameter of the x-ray spot was 200 mcm and x-ray power — 50 w. calibration of spectra was carried out at the position of the 1s line of carbon e = 285.0 ev. processing of xps experimental data was carried out using the complex ulvac-phi multipak software 9.8. results and discussion the major variable to control the size of metal particles in eew method is the overheating ratio (k). it is a  dimensionless coefficient, which is equal to the electrical energy introduced into a  portion of a metal wire subjected to eew divided by the energy of sublimation of this metal. in case of ni, the energy of sublimation is 65.1 j / mm3. the experimental dependence of the specific surface area and the mean diameter of ni nanoparticles on overheating coefficient are shown in  fig.  1. the mean diameter of spherical particles (d) is related to the value of their specific surface area (ssp) by the following equation: d= 6 / ρ∙ssp, (1) with ρ being the effective density of the material (ni — 8.91 g / cm3, nio — 7.45 g / cm3). it is seen that the specific surface area of ni nanoparticles substantially increases from around 7 m2 / g up to 11 m2 / g if the overheating ratio is doubled. consequently, with the increase in the overheating ratio, the diameter of  ni particles diminishes from 100 down to 60 nm in average. further on, the results for two values of the overheating ratio will be systematically compared. these values are k = 1.2, which corresponds to large ni particles (low specific surface area) and k = 2 (small particles, high specific surface area). it is worth noting that overheating ratio k = 1 was not taken, because of the technical difficulties of maintaining stable eew process at zero overheating. using the given levels of  overheating ratio, several batches of ni particles were synthesized with the controlled addition of  oxygen to  the eew installation. the crystalline structure of obtained ni nanoparticles was characterized by xrd. fig. 2, a gives examples of xrd diffractograms for two ni batches synthesized at different amount of oxygen added to the working gas of the eew installation. in both cases, two cubic phases were identified: the major one corresponded to  ni with lattice parameter a = 3.523(1) å and the minor one corresponded to nio with a = 4.174(2) å. it means that the addition of oxygen to the working gas resulted in the in-situ oxidation of condensed ni nanoparticles. furfig. 1. the dependence of the specific surface area (left) and the average diameter (right) of ni nanoparticles synthesized by eew method on the overheating ratio 97 ther on, the obtained particles, which contain both the fraction of metallic ni and nio are denoted as ni@nio. using the diffractograms, the weight fraction of nio in all batches was evaluated. the dependence of nio content in nanoparticles on the amount of oxygen added to the working gas in eew installation is given in fig. 2, b. the amount of oxygen (in weight) is divided by the weight of ni wire consumed in the synthesis. further on it is denoted as q. experimental points in fig. 2, b relate to two values of overheating ratio, k = 1.2 and k = 2. it is seen that, despite the difference in  the level of  overheating ratio, the experimental points can be fitted well with the same linear dependence, %nio = 302·q. it means that in-situ oxidation does not depend on the average diameter of ni particles and is governed exclusively by the amount of oxygen in the working gas. fig. 3 presents experimental dependences of the specific surface area (fig. 3, a) fig. 2. a — selected xrd diffraction patterns of eew ni nanoparticles synthesized with the addition of oxygen; b — dependence of nio weight fraction on the amount of oxygen added to eew synthesis per ni wire consumption. closed circles correspond to overheating ratio 1.2, open circles — to overheating ratio 2 fig. 3. dependence of the specific surface area (a) and mean diameter (b) of ni particles on the amount of oxygen introduced into eew installation during the synthesis at overheating ratios 1.2 and 2 98 and the average diameter of nanoparticles (fig. 3, b) on the amount of oxygen added to  the working gas of  the eew installation at the values of overheating ratio equal to 1.2 and 2. as  shown in  fig.  3, a, the increase in oxygen consumption leads to an increase in the specific surface area of produced ni nanoparticles at both levels of overheating ratio. the experimental plots are nicely fitted by the linear dependences: 6.9+44.2·q (r2 =  0.981) for  k  =  1.2 and 9.2+82.4·q (r2 = 0.998) for k = 2. in general, the increasing trend in  specific surface area due to the addition of oxygen is equivalent to the same trend due to the increase in overheating ratio (see fig. 1). it is because the oxidation of  ni to  ni oxide is accompanied with the evolution of heat, which adds up to the electric energy introduced in eew. thus, the total amount of energy (electrical and oxidation) in eew process exceeds the sublimation energy of  ni significantly more in  the presence of oxygen than in the inert atmosphere. fig. 3, b presents the average diameter of ni@nio particles as a function of oxygen / ni ratio. the average diameter was calculated using eq. (1) taking into account that the density of ni@nio particles diminishes with the increase of nio content due to the difference in densities of ni and nio. it is seen that, at both levels of overheating ratio, the decreasing trend in the average diameter of ni@nio particles is observed. the reason is the same as for the increasing trend of the specific surface area. the oxidation reaction provides extra energy to the system, and the overheating effectively increases. it is noticeable that the slopes of the linear plots in fig. 3, a are different for two levels of overheating. the slope coefficient is 44.2 if k  =  1.2, and it is 82.4 if k  =  2. however, no evident difference in  the slopes of plots can be noticed in fig. 3, b. it is because the calculation of the average diameter of ni@nio particles according to eq. (1) includes the partial correction of  increasing ssp values by  the decreasing density of ni@nio particles with the increase in their oxidation. the plots are shifted one against the other by  the initial difference of average particle diameter for  k  =  1.2 (smaller particles) and k  =  2 (larger particles). it is known [9] that in  the oxidizing atmosphere the surface of  metallic ni is covered with dense oxide layer which efficiently prevents metal from further oxidation. the pilling-batworth criterium [11] for nio is 1.52, which means that ni particles should be covered with dense oxide shell in  the presence of  oxygen. during eew, the formation of oxide shells on the surface of ni particles can start only at the moment when the expanding cloud of metal vapor after the explosion mixes up with the working gas, which contains oxygen. it does not take place at the very first moments after the explosion, as the expanding cloud of vapors is substantially denser than the surrounding working gas. furthermore, the critical temperature of the thermodynamic stability of nio is lower than the temperature of condensation of ni vapors into liquid phase. therefore, oxidation begins when the condensation on ni liquid droplets has been already completed, and it takes place at the surface of ni particles (liquid or solid). fig. 4 presents high-resolution tem image of the surface of ni particle synthesized in the presence of oxygen. it is clearly noticeable that the surface of a particle is covered with a layer, whose crystal structure is different from that of the interior of the particle. the lattice 99 period in the surface layer evaluated from hrtem images is 2.4±0.1 å. this value corresponds to the lattice period for cubic or rhombohedric nio structure. according to xps analysis, the spectrum of the surface of ni particles synthesized in the presence of  oxygen contained signals of  elements ni and o.  ni is present in  the oxidation state ni+2, which is an indication of nio [12], and ni+3, which likely corresponds to ni2o3 [13] or niooh [14]. the surface also contained carbon, which is the result of carbon dioxide adsorption from the air. the  thickness of  oxide layers on  ni particles was evaluated by  the graphical analysis of  tem images obtained with 3.7∙106 and 7.4∙106 magnification. the average values of the thickness of oxide layers are given in  table 1. according to  table 1, the thickness of oxide layers increases with the increase in the amount of oxygen added to working gas in eew process. at the same time, the overheating ratio does not make a noticeable influence. table 1 average thickness of oxide layer on ni@nio particles qo2, g / g ni overheating, k thickness, nm 0.03 1.2 2.51 0.1 1.2 3.35 0.02 2 2.82 0.096 2 3.31 like other chemical reactions in  the eew process, oxidation of ni surface takes place in non-equilibrium conditions. it results in the non-uniformity of nio distribution on the surface of ni@nio particles. it becomes more evident at large amounts of  added oxygen. fig.  5 presents tem image of  ni@nio particles obtained at qo2 = 0.1 g / g ni. it is noticeable in  fig.  5, a  that the spherical shape of ni@nio particles became substantially distorted due to the formation of oxide layers with varied thickness. most likely, it is because oxidation took place at elevated temperature before the particles were cooled down to the ambient temperature. in these conditions of  intense non-equilibrium oxidation, the initially formed oxide layer could be fractioned, and spherical shape of particles would be distorted. such distortions might as well be taken as evidence in favor of oxidation of ni in liquid droplets, whose surface is easier to distort, rather than condensed solid particles. at the high level of oxygen in the working gas, the smallest ni particles, which are the most chemically active, could transform completely into nio. fig. 5, b shows such a particle with a diameter of 15 nm, which is completely formed by  nio. the fragment of crystal lattice noticeable in fig. 5, b has a lattice period of 2.4±0.1 å, which corresponds to nio. due to the presence of  separate nio particles and thickened oxide layers, the total nio content in ni@ fig. 4. high-resolution tem image of ni particle synthesized by eew at k = 1.2; qo2 = 0.033 g / g ni 100 nio particles according to xrd increases up to 30 % if oxygen content in the working gas is raised up to 0.1 g / g ni. as the oxidation of ni likely takes place on the surface of liquid droplets, the formation of  solid oxide layer can prevent the coalescence of droplets, which causes agglomeration of particles in the product powder. fig.  6 illustrates the influence of oxygen addition on agglomeration. in fig. 6, a it is evident that agglomeration of ni particles is high. almost all of them in the image are bonded into one cluster, which is certainly the result of coalescence of liquid ni droplets in gas phase at temperatures above crystallization. con a b fig. 5. a — ni@nio particles obtained by eew at qo2 = 0.1 g / g ni, k = 1.2; b — high resolution tem image of the surface with nio layer and small separate nio particle (d = 15 nm) а b fig. 6. a — ni nanoparticles synthesized in argon; b — ni@nio nanoparticles synthesized in argon with the addition of oxygen, qo2 = 0.033 g / g ni 101 trary to that, the majority of ni@nio nanoparticles in fig. 6, b are separated from each other. even if we see them on  top of  one another, we can also see distinct spherical boundaries. it means that ni@ nio particles are individual. some agglomeration can still be noticed, but it is not predominant in case of ni@nio particles. the residual agglomeration of ni@nio stems from the large difference  — 1223  k  — between the temperature of vaporization of ni, 3173 k [15], and the upper temperature of oxidation, 1950 k (calculated using the software chemical workbench, ver. 3, kinetic technologies ltd.). this temperature interval provides a time gap from the moment when liquid droplets of ni condense from the vapor phase until they are covered with solid oxide, which prevents their coalescence. in case of other metals, this interval is narrower: al — 350–400 k, cu — 500 k. in case of these metals, the addition of oxygen prevents agglomeration completely. nevertheless, despite the large temperature interval before oxidation, the addition of oxygen substantially decreases agglomeration of ni nanoparticles. nio layers on the surface of ni nanoparticles substantially enhance their stability to self-combusting in the air. it was found experimentally that at  an oxygen consumption greater than 0.015 g / g ni, the powdered product can be transferred from the eew setup to the ambient air without the risk of combustion. such oxygen additition leads to a significant reduction in the pyrophoricity of the powder, as ni@nio particles are covered with an oxide shell that reliably protects them from oxidation during storage. conclusions the  controlled oxygen injection into the inert working gas of the eew unit during the production of ni powder makes it possible to form a crystalline oxide shell on the particles in the process of their formation. it depresses the particle agglomeration, as well as protects the surface of ni particles from oxidation. the increase in oxygen consumption leads to an increase in the specific surface area of the powder. in the range of oxygen consumption from 0 to  0.1  g / g ni, the specific surface area varies almost linearly and increases by 60– 80 % depending on the overheating ratio. addition of oxygen to the working gas leads to the formation of a separate phase in the powdered product — crystalline ni oxide, the content of which increases with increasing oxygen consumption. at low consumption of oxygen, nio forms a dense crystalline shell on the surface of particles. the thickness of the shell is 2–5 nm and increases with increasing oxygen consumption. overheating ratio has no significant effect on the shell thickness. in the range of oxygen consumption 0–0.1 g / g ni the content of nio linearly increases up to 30 % independently of overheating ratio. at high oxygen consumption, spherical shape of ni@nio nanoparticles is substantially distorted, and small separate individual nio nanoparticles tend to appear. when the oxygen consumption is larger than 0.015 g / g ni, the powdered product becomes non-pyrophoric and can be subjected to the ambient air without the risk of combustion. 102 acknowledgements this work was performed as part of state task of iep ub ras and by ras program project no. 18-10-2-38. the study was performed using the equipment of the center for the common research of iep ub ras and using the x-ray spectrometer of the chair of electrophysics of the physical technological institute of the ural federal university. references 1. gusev ai. nanomaterialy, nanostructury, nanotekhnologii. moscow: fizmatlit, 2005. 416 p. russian. 2. kotov 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nikel. мoscow: nauka, 1975. 215 p. russian. synthesis, crystal structure and electrophysical properties of triple molybdates containing silver, gallium and divalent metals 132 d o i: 1 0. 15 82 6/ ch im te ch .2 01 8. 5. 3. 02 kotova i. yu., savina a. a., vandysheva a. i., belov d. a., stefanovich s. yu. chimica techno acta. 2018. vol. 5, no. 3. p. 132–143. issn 2409–5613 i. yu. kotovaa, a. a. savinaa*, a. i. vandyshevab, d. a. belovc, s. yu. stefanovichc abaikal institute of nature management, siberian branch, russian academy of sciences, 6 sakh’yanova st., ulan-ude, 670047, buryat republic, russian federation bburyat state university, 24a smolin st., ulan-ude, 670000, buryat republic, russian federation clomonosov moscow state university, leninskie gory, 1, moscow 119991, russian federation *e-mail: alex551112@mail.ru synthesis, crystal structure and electrophysical properties of triple molybdates containing silver, gallium and divalent metals a possibility of the triple molybdates formation with both nasicon-like and namg3in(moo4)5 structures in the ag2moo4–amoo4–ga2(moo4)3 (a = mn, co, zn, ni) systems was studied by powder x-ray diffraction analysis. it was established that nasicon-like phases ag1−xa1−xga1+x(moo4)3 are not formed. the triple molybdates aga3ga (moo4)5 (a = mn, co, zn) isostructural to triclinic namg3in(moo4)5 (sp. gr. p1, z = 2) were synthesized and characterized. the structure of the obtained compounds was refined for agzn3ga(moo4)5 according to the powder data by the rietveld method. the structure consists of moo4 tetrahedra, couples of edge-shared m(1)o6 octahedra, and trimers of edge-shared m(2)o6–, m(3)6– and m(4)o6 octahedra, which are linked by the common vertices to form a 3d framework. high-temperature conductivity measurements revealed that the conductivity of agmn3ga(moo4)5 at 500 °с reaches 10–2 s / cm, which is close to one of the known nasicon-type ionic conductors. keywords: triple molybdates; silver; gallium; solid-state synthesis; powder x-ray diffraction; rietveld refinement; ionic conductivity. received: 10.10.2018. accepted: 22.10.2018. published: 31.10.2018. © kotova i. yu., savina a. a., vandysheva a. i., belov d. a., stefanovich s. yu., 2018 introduction a synthesis and studying of complex oxide compounds, the development of  new materials with functionally significant properties based on  those are among the main areas of  the materials science. an important place in the study and obtaining of new phases with valuable physicochemical properties belongs to molybdates, in particular triple ones, which are among the fastest-growing groups of complex oxide compounds containing a  tetrahedral anion and three different cations. one of the largest families of these compounds is molybdates containing 1-, 2and 3-charged cations. in particular, silver-containing nasicon-like phases 133 ag1–xa1–xr1+x(moo4)3 (a = mg co, r = al; a = mg, r = in) with different homogeneity range and triclinic aga3r(moo4)5 (a = mg, r = cr, fe, ga; a = mn, r = al, cr, fe, sc, in) having high ionic conductivity (10–3–10–2 s / cm) are of interest. for a  number of  phases: agmg3r(moo4)5 (r  = cr, fe), agmnii3 (mn iii 0.26al0.74) (moo4)5, ag0.90al1.06co2.94(moo4)5 and agfeii3fe iii(moo4)5 single crystals were obtained and their crystal structures were determined [1–9]. the purpose of  this work is to  study the possibility of  forming triple molybdates ag1–xa1–xga1+x(moo4)3 and aga3ga(moo4)5 (a = mn, co, zn, ni) and investigate crystal structure and electrophysical properties of the obtained compounds. experimental the initial materials were simple molybdates of silver, manganese, cobalt, zinc, nickel, moo3 and ga2o3 (reagent grade). ag2moo4 and molybdates of divalent metals were obtained by the step annealing of stoichiometric mixtures of agno3 (analytical grade), mno, co(no3)2·6h2o, zno, moo3 (all chemically pure), nio (reagent grade) at 350−450 °с (ag2moo4), 400−750 °с (mnmoo4), 300−700 °с (comoo4), 500−700 °с (znmoo 4), 450−750 °с (nimoo4) in  the air with intermittent grindings every 15 hours for better sample homogenization. power x-ray diffraction (pxrd) patterns of the prepared compounds do not contain reflections of starting or impurity phases. pxrd and thermal characteristics of all prepared compounds agree well with corresponding data reported in [10−15]. sample compositions ag1–xa1–xga1+x (moo4)3 (0 ≤ x ≤ 0.7, δx = 0.1) and aga3ga(moo4)5 were prepared by  the annealing of  appropriate stoichiometric mixtures of ag2moo4, аmoo4, moo3 and ga2o3. the initial mixtures were annealed starting at 300 °c followed by raising the temperature by 20–50 °c (in some cases, 5–10 °c) with intermittent grindings every 20–30 hours for sample homogenization. the calcination time at each temperature was 30–70 h. the phase composition of the obtained products was controlled by the pxrd analysis before each increasing of the annealing temperature. pxrd patterns were collected at room temperature on a bruker d8 advance diffractometer using cu kα radiation in the 2θ range from 5° to 100° with a step of 0.02076°. possible impurity phases were checked by comparing their pxrd patterns with those in the powder diffraction file. the crystal structure refinement was carried out with the gsas [16] program suite using pxrd data. lattice parameters and individual scale factors were established, and five common peak-shape parameters of the pseudo-voigt function (no. 2), one asymmetry parameter and one parameter for  the zero-point correction were used to describe the powder patterns. the background level was described by a combination of 15-order chebyshev polynomials. isotropic displacement parameters (uiso) were refined, and grouped by  chemical similarity by used constrains. thermoanalytic studies were carried out on  a  sta 449 f1 jupiter netzsch thermoanalyser (pt crucible, heating rate of 10 °с / min in ar stream). ceramic disks for  dielectric investigations were prepared by the calcination of  pressed powder at  600 °с  for  2 h. the disks were of  9–10 mm in  diameter and 134 1–2 mm thick, the electrodes were deposited by painting the disk bases with colloid platinum followed by subsequent one hour annealing at  about 580 °с.  the direct current (dc) electric conductivity was measured with a  v7–38 microammeter. to study the ion transfer, electrical conductivity was measured on an alternating current (ac) by the two-contact method in the frequency range 1 hz–1 mhz in the temperature range 25–560 °c at  the rate of 4 °c / min at both heating and cooling using a  novocontrol beta-n impedance analyzer. the activation energy of electrical conductivity was calculated from the slope of the straight lines corresponding to the arrhenius dependence in lg (σt) – (103 / t) coordinates. results and discussion pxrd characteristics the presence of nasicon-like phases in the ag2moo4–amoo4–ga2(moo4)3 systems was determined according to pxrd analysis of samples ag1−xa1−xga1+x(moo4)3 (0 ≤ x ≤ 0.7, δх = 0.1) which were annealed in  the temperature range from 300 °c to melting point. the final annealed temperature was 550–700 °c and depended on both the composition of the reaction mixtures and the nature of  the divalent metal. it was established that, despite the close values of  the al3+ (0.53) and ga3+ (0.62 å [17]) radii, gallium containing triple molybdates with nasicon-like structure, apparently, do not exist. all our attempts to obtain rhombohedral phases ag1−xa1−xga1+x(moo4)3 by solid state synthesis did not lead to  a  positive result, probably this is due to the low reactivity of gallium in the molybdate systems. thus, the simple gallium molybdate ga2(moo4)3 has not yet been obtained by  ceramic techno logy, and only recently it was synthesized by the sol-gel method [18]. besides, silver-gallium double molybdate is not synthesized either by  ceramic technology or by co-precipitation. in [19] this compound was obtained by the calcining of mixtures of agno3, ga2o3, moo3 (in ratio 2:1:4) at  350–400 °c for  8–10 h, followed by cooling, homogenization, and the repeated 12–20 hours annealing at  500– 550 °c, but the pxrd data of the product are not given by the authors. it should be noted that in none of the later publications (including those of the same authors) additional information about this compound was found. at the same time, in  the ag2moo4– amoo4–ga2(moo4)3 systems triple molybdates of composition aga3ga(moo4)5 were found. these compounds were synthesized by the solid-state reactions at 550– 600 °с  (a = mn), 540–550 °с  (a  =  zn), 500–530 °с (a = co) for 80–100 h. however, nickel-containing compound was not obtained in the single-phase state, even after sintering at temperatures as high as 600– 650 °c for 250–300 hours. this may be due to the smallest radius of ni2+ cation (0.69 å for  cn = 6 [17]) in  the studied series of simple molybdates of divalent metals. the triple molybdates aga3ga(moo4)5 (a = zn, mn, co) were found to melt incongruently at temperatures of 644, 727, and 739 °c, respectively. the powder xrd patterns of  asprepared single-phase compounds aga3ga(moo4)5 are similar and show that these oxides are isostructural to triclinic namg3in(moo4)5 (sp. gr. p1, z = 2) [20]. the diffractograms of the aga3ga(moo4)5 (a = mn, co, zn) were indexed with taking into account our data obtained earlier in the course of single-crystal structure de135 termination of agmg3r(moo4)5, r = fe, cr [7]. the result of indexing the pxrd patterns for  aga3ga (moo4)5 (a = mn, co, zn) are given in table 1. unit-cell parameters are listed in table 2. crystal structure of agzn3ga(moo4)5 t h e c r y s t a l s t r u c t u r e of  agzn3ga(moo4)5 was refined according to  the rietveld method [21], starting with the atomic coordinates of agmg3fe(moo4)5 structure [7]. crystal data, data collection and structure refinement details are summarized in table 3. experimental, theoretical, and difference pxrd patterns for the agzn3ga(moo4)5 are shown in  figure 1. the fractional table 1 the calculated and observed values of pxrd data for aga3ga(moo4)5 (a = mn, zn, co) h k l agmn3ga(moo4)5 agzn3ga(moo4)5 agco3ga(moo4)5 i / i0 2θobs.,° 2θcal.,° i / i0 2θobs.,° 2θcal.,° i / i0 2θobs.,° 2θcal.,° 0 0 2 3 9.861 9.850 2 9.981 9.991 2 10.006 10.019 0 1 0 1 12.782 12.767 1 12.954 12.945 1l 12.956 12.943 1 0 0 9 12.903 12.894 9 13.058 13.064 9 13.112 13.108 0 1 1 1l 13.769 13.750 1 0 1 1l 13.654 13.637 1 13.778 13.808 1l 13.853 13.849 0 –1 1 1l 14.021 13.998 1l 14.005 14.017 –1 0 1 1l 13.974 13.977 2 14.170 14.175 1 14.231 14.226 0 0 3 1l 14.805 14.798 1 15.010 15.011 1l 15.061 15.052 1 0 2 1 15.924 15.959 1l 16.154 16.157 1 16.177 16.200 0 –1 2 1l 16.388 16.393 1l 16.577 16.576 1 16.625 16.619 –1 0 2 1l 16.529 16.538 1l 16.799 16.783 1l 16.819 16.844 1 1 1 1l 17.079 17.075 –1 –1 1 1l 17.541 17.562 1l 17.596 17.610 1 1 2 1l 18.728 18.728 1 0 3 1l 19.304 19.310 –1 –1 2 2 19.638 19.630 3 19.826 19.822 3 19.892 19.891 0 0 4 1 19.780 19.774 1l 20.127 20.115 –1 1 0 19.792 1l 20.115 20.122 20.154 –1 0 3 1l 20.025 20.033 1l 20.340 20.336 –1 1 1 1l 20.406 20.425 1l 20.774 20.790 1l 20.819 20.817 1 1 3 3 21.572 21.577 4 21.846 21.856 5 21.861 21.864 1 –1 2 6 22.117 22.117 10 22.419 22.427 10 22.483 22.482 –1 –1 3 1 22.959 22.996 1l 23.048 23.085 1 0 4 3 23.267 23.270 3 23.569 23.573 3 23.646 23.631 0 1 4 23.265 2 23.662 23.668 1 23.695 23.675 0 –1 4 1 23.959 23.944 10 24.193 24.222 3 24.313 24.306 –1 0 4 1 24.086 24.078 2 24.441 24.445 1 24.511 24.529 0 0 5 100 24.793 24.787 100 25.145 25.148 86 25.221 25.218 –1 1 3 6 24.869 24.848 16 25.307 25.312 16 25.344 25.346 136 h k l agmn3ga(moo4)5 agzn3ga(moo4)5 agco3ga(moo4)5 i / i0 2θobs.,° 2θcal.,° i / i0 2θobs.,° 2θcal.,° i / i0 2θobs.,° 2θcal.,° 1 1 4 3 25.122 25.119 5 25.459 25.465 6 25.480 25.478 0 2 0 3 25.701 25.697 2 26.072 26.058 2 26.055 26.054 2 0 0 73 25.959 29.954 83 26.307 26.302 100 26.396 26.392 0 2 1 23 26.036 26.025 38 26.417 26.422 26.403 2 0 1 10 26.255 26.250 20 26.596 26.590 18 26.679 26.676 0 –2 1 6 26.337 26.333 22 26.664 26.674 7 26.697 26.690 –1 –1 4 4 26.483 26.488 7 26.780 26.782 7 26.888 26.890 1 2 0 8 26.613 26.601 3 26.883 26.881 26.892 –2 0 1 26.614 7 26.984 26.984 7 27.079 27.081 1 2 1 11 26.835 26.829 25 27.132 27.137 18 27.133 27.131 2 1 1 2 27.007 27.001 5 27.283 27.278 3 27.350 27.345 –1 –2 1 11 27.307 27.306 26 27.575 27.575 19 27.613 27.609 0 2 2 27.285 4 27.712 27.731 3 27.705 27.703 –2 –1 1 3 27.507 27.503 4 27.790 27.784 3 27.880 27.879 0 1 5 6 27.622 27.611 10 28.081 28.084 8 28.109 28.105 0 –2 2 3 27.874 27.873 6 28.208 28.210 5 28.255 28.250 1 2 2 2 27.961 27.970 4 28.320 28.322 4 28.308 28.304 1 –1 4 2 28.066 28.064 6 28.423 28.425 5 28.512 28.510 2 1 2 2 28.114 28.121 28.423 3 28.454 28.481 –2 0 2 2 28.164 28.167 1 28.567 28.573 2 28.672 28.678 0 –1 5 6 28.342 28.336 16 28.678 28.676 13 28.782 28.778 –1 0 5 1 28.893 28.900 1 29.000 28.997 –1 –2 2 1 28.877 28.882 2 29.163 29.159 1 29.223 29.217 –2 –1 2 4 29.081 29.082 10 29.391 29.390 9 29.499 29.501 0 2 3 3 29.376 29.367 4 29.859 29.869 3 29.837 29.839 2 0 3 1l 29.525 29.516 2 29.898 29.888 1 29.985 29.973 0 0 6 1 29.860 29.850 1 30.300 30.287 1 30.383 30.372 1 2 3 1l 29.929 29.927 1 30.365 30.334 1 30.324 30.310 2 1 3 4 30.055 30.056 9 30.397 30.397 9 30.453 30.450 0 –2 3 1l 30.175 30.189 1 30.527 30.539 1 30.590 30.603 –2 0 3 1l 30.513 30.488 1 30.983 30.940 1l 31.055 31.055 –1 –1 5 1l 30.622 30.621 30.981 1 31.088 31.106 –1 2 0 1 30.953 30.949 2 31.460 31.462 1 31.483 31.484 –1 –2 3 2 31.213 31.207 4 31.501 31.509 4 31.594 31.592 –2 1 0 1 31.618 31.616 1l 31.691 31.698 –2 –1 3 2 31.748 31.755 18 31.865 31.883 –1 2 1 8 31.303 31.304 22 31.849 31.854 31.865 сontinuation of table 1 137 atomic coordinates, isotropic atomic displacement parameters, cation occupancies and main selected interatomic distances are presented in tables 4 and 5. the populations of  four independent positions m = (zn, ga) and three incompletely occupied ag sites were refined with keeping the electrical neutrality of the chemical formula. the final compositions of the crystals are close to stoichiometric agzn3ga(moo4)5 with a negligible silver deficiency. in the structure agzn3ga(moo4)5 all atoms are located in  general positions. coordination polyhedra of mo atoms are tetrahedra with mo–o distances of 1.714– 1.824  å, which are similar to  the values found in other molybdates containing a tetrahedral anion. cations zn2+ and ga3+ are statistically distributed on octahedral positions m1–m4 with the (zn, ga)–o bond lengths of 1.940–2.129 å. both ag1 and ag3 cations are coordinated by four o atoms (ag1–o 2.358 å, ag3–o 2.415 å), while ag2 cation has cn = 5 (ag2–o 2.495 å). the structure of  agzn3ga(moo4)5 consists of moo4 tetrahedra, couples of edgeshared m(1)o6 octahedra, and trimers of  edge-shared m(2)o6, m(3)o6 and сontinuation of table 1 h k l agmn3ga(moo4)5 agzn3ga(moo4)5 agco3ga(moo4)5 i / i0 2θobs.,° 2θcal.,° i / i0 2θobs.,° 2θcal.,° i / i0 2θobs.,° 2θcal.,° 1 –2 1 2 31.408 31.410 2 31.912 31.899 3 31.945 31.935 2 –1 1 1 31.440 31.428 31.914 1 31.996 31.999 1 –1 5 1 31.853 31.857 3 32.264 32.264 2 32.362 32.364 –1 1 5 1l 31.974 31.980 1 32.590 32.619 0 2 4 2 32.137 32.125 9 32.653 32.689 2 32.654 32.663 2 0 4 4 32.239 32.238 32.647 6 32.741 32.736 2 –1 2 1 32.512 32.535 11 33.027 33.015 1 33.127 33.106 1 2 4 3 32.569 32.567 33.038 7 33.020 33.014 1 –2 2 3 32.655 32.656 5 33.131 33.133 4 33.188 33.186 0 –1 6 2 33.363 33.368 0 –2 4 7 33.135 33.134 16 33.511 33.513 11 33.603 33.601 2 2 0 1 33.214 33.200 33.510 1 33.551 33.568 2 2 1 2 33.311 33.313 6 33.634 33.641 5 33.683 33.681 –2 0 4 1 33.426 33.434 4 33.935 33.941 1 34.059 34.066 1 1 6 1l 33.460 33.454 33.948 –2 –2 1 3 33.847 33.852 11 34.158 34.160 8 34.239 34.239 cu kα1 radiation (l = 1.54056 å) table 2 unit-cell parameters for aga3ga(moo4)5 (a = mn, zn, co) a a, å b, å c, å α° β° γ° v, å3 mn 6.9844 (3) 7.0519 (4) 17.9700 (8) 87.796 (4) 87.529 (5) 79.386 (4) 868.71 zn 6.9037 (3) 6.9639 (4) 17.7147 (8) 88.107 (4) 87.440 (4) 78.982 (4) 834.87 co 6.8810 (4) 6.9657 (4) 17.669 (1) 87.895 (5) 87.344 (5) 78.976 (5) 830.04 138 table 3 crystal data and structure refinement for agzn3ga(moo4)5 structural formula agzn3ga (moo4)5 formula weight, mr (g mol −1) 1172.58 temperature (k) 298(2) crystal system, space group (#) triclinic, p1 (2) unit-cell parameters: a (å) b (å) c (å) α (°) β (°) γ (°) 6.9035 (5) 6.9643 (5) 17.7160 (14) 88.1039 (11) 87.4338 (12) 78.9880 (9) unit-cell volume, v (å3) 835.0 (2) formula unit, z 2 calculated density, ρcal (g cm −3) 4.66 refinement r factors and goodness of fit: wrp rp rexp r(f2) χ2 0.0511 0.0382 0.0152 0.05815 3.40 table 4 structural parameters for agzn3ga(moo4) 5 atom occupancy x y z uiso mo1 1 0.2722(8) 0.3095(8) 0.5282(3) 0.030(2) mo2 1 0.2129(8) 0.8293(9) 0.2856(3) 0.028(2) mo3 1 0.6843(8) 0.2187(8) 0.3109(3) 0.023(2) mo4 1 0.2811(9) 0.0522(9) 0.9044(3) 0.029(2) mo5 1 0.2520(8) 0.5491(8) 0.0863(3) 0.021(2) m1 0.788(1)zn+0.212(1)ga 0.1834(12) 0.8241(11) 0.4938(5) 0.0126(3) m2 0.901(1)zn+0.099(1)ga 0.1704(14) 0.0855(16) 0.1145(5) 0.045(4) m3 0.798(1)zn+0.202(1)ga 0.7829(12) 0.4310(13) 0.1239(4) 0.014(3) m4 0.505(1)zn+0.495(1)ga 0.2546(12) 0.3014(13) 0.7370(4) 0.023(3) ag1 0.323(3)ag 0.149(3) 0.339(3) 0.2857(12) 0.062(5) ag2 0.328(3)ag 0.122(4) 0.308(4) 0.3155(13) 0.062(5) ag3 0.342(3)ag 0.097(3) 0.370(3) 0.3445(11) 0.062(5) o1 1 0.511(5) 0.194(5) 0.5163(18) 0.015(1) o2 1 0.289(4) 0.366(4) 0.6238(17) 0.015(1) o3 1 0.171(4) 0.545(5) 0.4601(18) 0.015(1) o4 1 0.130(5) 0.126(5) 0.4978(18) 0.015(1) 139 m(4)o6 octahedra, which are linked by the common vertices to form a 3d framework (fig. 2). in the large framework cavities, the silver cations are disordered on three close positions with the distances ag–ag 0.595(4) å and 1.101(2) å. such a  disordering is also typical of other compounds of this isostructural series [7, 9], suggesting a possible mobility of the ag+ cations in the compounds. this is favored not only by defects in ag positions along with their irregular coordinaсontinuation of table 4 atom occupancy x y z uiso o5 1 0.189(4) 0.872(4) 0.3866(18) 0.015(1) o6 1 0.477(5) 0.719(4) 0.2580(17) 0.015(1) o7 1 0.140(5) 0.053(5) 0.2220(19) 0.015(1) o8 1 0.098(5) 0.641(5) 0.2687(18) 0.015(1) o9 1 0.419(5) 0.280(4) 0.3590(17) 0.015(1) o10 1 0.804(5) 0.191(4) 0.3830(18) 0.015(1) o11 1 0.681(5) 0.995(5) 0.2696(17) 0.015(1) o12 1 0.774(4) 0.370(5) 0.237(2) 0.015(1) o13 1 0.198(4) 0.121(4) 0.997(2) 0.015(1) o14 1 0.468(5) 0.040(4) 0.0841(15) 0.015(1) o15 1 0.831(5) 0.202(5) 0.1174(16) 0.015(1) o16 1 0.238(4) 0.305(5) 0.8544(17) 0.015(1) o17 1 0.249(4) 0.546(4) 0.987(2) 0.015(1) o18 1 0.485(5) 0.488(5) 0.1153(17) 0.015(1) o19 1 0.171(4) 0.778(5) 0.1292(18) 0.015(1) o20 1 0.097(4) 0.410(5) 0.1173(18) 0.015(1) fig. 1. observed (black line) and calculated (red line) xrd patterns of agzn3ga(moo4)5. vertical bars indicate the positions of the bragg peaks. the lower trace depicts the difference between the experimental and calculated intensity values fig. 2. projection views of the structure of agzn3ga(moo4)5 along the a axis. the blue spheres and small red spheres indicate ag and oxygen atoms, respectively 140 table 5 selected interatomic distances(å) in agzn3ga(moo4) 5 mo1‑tetrahedron mo2‑tetrahedron mo1–o1 –o2 –o3 –o4 <mo1–o> 1.696(3) 1.764(3) 1.726(3) 1.858(3) 1.761 mo2–o5 –o6 –o7 –o8 <mo2–o> 1.819(3) 1.889(3) 1.891(3) 1.698(3) 1.824 mo3‑tetrahedron mo4‑tetrahedron mo3–o9 –o10 –o11 –o12 <mo3–o> 1.961(3) 1.739(3) 1.747(4) 1.812(3) 1.815 mo4–o13 –o14 –o15 –o16 <mo4–o> 1.749(3) 1.726(2) 1.922(3) 1.760(3) 1.789 mo5‑tetrahedron m1‑octahedron mo5–o17 –o18 –o19 –o20 <mo5–o> 1.758(4) 1.683(3) 1.773(3) 1.640(3) 1.714 m1–o1 –o3 –o10 –o4 –o5 –o4 <m1–o> 2.092(3) 2.068(3) 2.186(3) 2.070(2) 1.918(3) 2.124(3) 2.076 m2‑octahedron m3‑octahedron m2–o7 –o13 –o19 –o20 –o14 –o15 <m2–o> 1.918(3) 2.096(3) 2.144(3) 2.224(3) 2.066(3) 2.325(3) 2.129 m3–o18 –o17 –o15 –o16 –o12 –o20 <m3–o> 2.030(3) 1.99(4) 1.572(3) 1.869(3) 2.038(3) 2.143(3) 1.940 m4‑octahedron ag1‑polyhedron m4–o8 –o11 –o2 –o6 –o16 –o12 <m4–o> 2.398(4) 2.033(4) 2.053(3) 1.837(3) 2.079(3) 2.320(3) 2.120 ag1–o9 –o8 –o7 –o12 <ag1–o> 2.29(4) 2.080(3) 2.33(4) 2.73(4) 2.358 ag2‑polyhedron ag3‑polyhedron ag2–o9 –o10 –o8 –o7 –o12 <ag2–o> 2.19(4) 2.70(4) 2.41(4) 2.45(4) 2.725(3) 2.495 ag3–o9 –o8 –o10 –o3 <ag3–o> 2.22(4) 2.28(4) 2.62(4) 2.540(3) 2.415 ag1–ag2 ag1–ag3 0.595(4) 1.101(2) 141 tion, but also a rather flexible polyhedral framework of the namg3in(moo4)5 structure type, which involves interconnected cavities. electrophysical properties as was noted in the previous section, the structural features of  the obtained molybdates allow us to expect these compounds to have the increased ionic conductivity. this was already confirmed by us in the case of agmg3al(moo4)5 (σ = = 2.5 × 10−2 s / cm) and agmn3al(moo4)5 (σ = 7.1 × 10−3 s / cm) at 500 °c [7]. in this work as an example, the results of studying electrophysical properties for  agmn3ga (moo4) 5 are presented. it was found that the dc conductivity of ceramic sample agmn3ga(moo4)5, measured with the v7–38 device, is negligible as compared to the ac conductivity (fig. 3) in temperature region of 100–560 °c. as the platinum electrodes are blocking in the dc conductivity measurement mode, the dc conductivity of agmn3ga(moo4)5 corresponds to the electronic one. therefore, it can be concluded that the ac conductivity is almost equal to the ionic one. it is seen that near room temperature the conductivity is as small as 10–7 s / cm but quickly rises with temperature to va lues of about 10–2 s / cm. it is noteworthy that the conductivity in agmn3ga(moo4)5 increases with temperature in non-monotonic way showing distinct breaks on  lgσ  = f(1 / t) curves at 310 °c. above these temperature the lgσ = f(1 / t) dependences are almost linear with the small activation ener gy va lue еа = 0.26 ev. above 310 °с, the ionic conductivity of  agmn3ga(moo4)5 increases up to  2.03∙10–2 s / сm at  500 °с, which is close to the corresponding characte ristics of the known ionic conductors. conclusions the possibility of  the formation of  silver-containing gallium triple molybdates with mn, co, zn, ni, analogous to  the phases ag1–xa1–xr1+x(moo4)3 and aga3r(moo4)5 obtained by  us in  the ag2moo4−amoo4−r2(moo4)3 (a = mg, co; r = al; a = mg, r = in) systems, was studied. it was shown that in the ag2moo4− amoo4−ga2(moo4)3 (a = mn, co, zn, ni) systems the nasicon-like phases of the composition ag1–xa1–xr1+x(moo4)3 are not formed. the triple molybdates of the composition aga3ga(moo4)5 (a = mn, co, zn) were synthesized and characterized. agni3ga(moo4)5 was not obtained in the single-phase state. it was established that the obtained compounds incongruently melt and belong to  the structural type of triclinic namg3in(moo4)5 (sp. gr. p1, z = 2). the structure of the obtained compounds was refined by  the rietveld method using the powder diffraction data for agzn3ga(moo4)5. the structural features of the obtained molybdates allow us to  expect these compounds to  have the increased ionic conductivity. this was fig. 3. temperature dependences of the ionic conductivity on heating and cooling for agmn3ga(moo4)5 142 confirmed by  studying electrophysical properties of  agmn3ga(moo4)5. it was shown that the high-temperature electrical conductivity of this compound reaches 10–2  s / cm at  ea = 0.26 ev, which is close to the corresponding characteristics of the known ionic conductors. acknowledgments the research was carried out within the state assignment of binm sb ras, supported in part by the russian foundation for basic research (project no. 17-03-00333а) references 1. kotova iyu. phase formation in the ag2moo4–comoo4–al2(moo4)3 system. russ j inorg chem. 2014;59:844–8. doi:10.7868 / s0044457x14080133. 2. kotova iyu, korsun vp. phase in the ag2moo4–mgmoo4–al2(moo4)3. russ j inorg chem. 2010;55:955–8. 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oxygen diffusion; lanthanum-strontium cobaltite-ferrite; rate-determining stage received: 14.11.2018. accepted: 11.12.2018. published: 31.12.2018. © porotnikova n. m., antonova e. p., khodimchuk a. v., tropin e. s., farlenkov a. s., ananyev m. v., 2018 introduction over the last decades, complex oxides with the perovskite structure based on the lanthanum cobaltite attract much attention as  potential cathode materials for  solid oxide electrochemical devices [1–4]. variation of cations concentration in  these oxides results in  the physicalchemical properties changes in the oxidebased materials [5, 6]. complex oxides with a  common formula la1−xsrxco1− yfeyo3−δ are among the most perspective cathode materials. a sufficient amount of information available in the literature has focused on the study of phase equilibria and physicochemical properties of oxides in  this system [7–13]. in order to  create the effectively operating cathodes based on lanthanum-strontium cobaltite-ferrites, it is vital to understand in detail the oxygen exchange and diffusion mechanisms in these materials. the main purpose of  the present work was to  study oxygen diffusion and surface exchange kinetics in la0.6sr0.4co0.8fe0.2o3–δ oxide. 197 experimental the la0.6sr0.4co0.8fe0.2o3–δ oxide was prepared using the citrate-nitrate technology. lanthanum oxide (lao-d, 99,99635 %), strontium carbonate srco3 (acs), cobalt nitrate co(no3)2·6h2o (chemically pure), iron citrate c6h5feo7·h2o (fluka analytical) were used as initial reagents. the synthesis was performed at the temperature of 1100 °с for 5 hours. in order to perform the oxygen isotope exchange measurements, dense ceramic was fabricated. the obtained powders were ground and compacted into the form of disks using 1 % water solution of polyvinyl alcohol that served as  a  bounding agent. the final sintering was performed at the temperature of 1250 °с for 5 hours in  air. a relative density of  the obtained ceramics was about ~ 92 %. finally, the sintered dense specimens were polished using diamond pastes, such as асм 7 / 5 nvmc (federal standard 25593–83) and асм 1 / 0 nom (federal standard 16377–71). the phase composition of  the la0.6sr0.4co0.8fe0.2o3–δ sample was determined before and after the isotope experiments using a rigaku d / max-2200v diffractometer in the cu ka emission at room temperature. according to the x-ray analysis, the sample was single phase after synthesis (r3c space group, cell parameters a = 5.4270(4) å, c = 13.239(2) å) and after completing measurements at high temperatures and low oxygen pressures (fig. 1), which confirms its stability during longterm tests. the analysis of the particle size distribution for powder materials was performed by the laser scattering method using a malvern mastersizer 2000. to grind the agglomerated particles, the slurry was mixed using a stirrer with the rate of ~2000 rpm, as well as subjected to an ultrasound treatment. fig. 2 illustrates the volume fraction versus particle size distribution function. the microphotographs of the ceramics cross-section were made by  a  scanning electron microscope tescan mira 3. fig. 3 presents the microphotograph obtained in a beam of back-scattered electrons. the contrast of the images is mainly due to the chemical composition of the studied material surface. as can be seen from fig. 4, there are small inclusions of  cobalt-rich phase at the grains boundaries (probably cobalt oxide); however, the fraction is insignificant, it is less than 0.5 %. fig. 1. xrd patterns for la0.6sr0.4co0.8fe0.2o3–δ oxide before and after isotope experiments fig. 2. particle size distribution function for the la0.6sr0.4co0.8fe0.2o3–δ powder 15 30 45 60 75 in te ns it y, a .u . 2θ before experiment aster experiment 0,1 1 10 100 1000 0 1 2 3 4 5 6 7 8 vo lu m e fr ac ti on , % particle size, µm 198 the oxygen exchange kinetics between the gas phase and oxide was studied by the oxygen isotope exchange method with gas phase equilibration in  the experimental rig [12]. enriched oxygen 18o, whose fraction was 83.6 %, served as a match mark. during the experiment, the changes in  concentrations of  three mass numbers  — с32, с34, с36  — were recorded depending on  time using a  quadrupolar mass-spectrometer agilent 5973n. the detailed description of  the experiment methodology, evaluation of  the interphase exchange rate detection accuracy (rh, atom·cm –2 · s–1) and oxygen diffusion coefficient (d, cm2·s–1) has been reported elsewhere [14, 15]. the oxygen interphase exchange rate is numerically equal to the number of oxygen atoms, which exchange at  the surface of  a  unit area per unit of time. the isotope exchange method is one of the few direct methods of oxygen exchange kinetics study, which advantage is a possibility to obtain information fig. 4. edx mapping for la0.6sr0.4co0.8fe0.2o3–δ ceramics fig. 3. sem image of cross-section of la0.6sr0.4co0.8fe0.2o3–δ ceramics in bse mode 199 on  the oxygen redistribution between a  solid oxide and gaseous phase in  the adsorption-desorption equilibrium. this allows obtaining high accuracy for the kinetics characteristic values. to compare the obtained values of the interphase exchange rate with the literature data the following translation formula was used: k r m nh r a � �( ) , 3 � � (1) where rh is the oxygen interphase exchange rate (atom∙cm–2 ∙ s–1), k is the oxygen exchange coefficient (cm ∙ s–1), mr is the molecular mass, δ is the oxygen non-stoichiometry, na is the avogadro constant, ρ is the sample crystallographic density. results and discussion the oxygen exchange kinetics for the la0.6sr0.4co0.8fe0.2o3–δ oxide was studied at the temperatures of 600–800 °с and the oxygen pressure interval 0.27–2.13 kpa. during the experiment, the changes in ionic current, which correspond to the weight of 32, 34 and 36, versus the exchange time were recorded. then the obtained values were recalculated into the mass numbers concentrations (see fig. 5). typical time dependence for  the 18о oxygen isotope fraction changes in a particular experimental condition is presented in  fig. 6. the obtained data can be described using the model developed by ezin et al. [16] on the basis of the solution suggested by klier et al. [17]. fig. 7 illustrates the dependencies of  the interphase exchange rate versus oxygen pressure in  logarithmic coordinates at  different temperatures for  the la0.6sr0.4co0.8fe0.2o3–δ oxide. the values of exchange rate increase noticeably as the oxygen pressure and temperature rise. the dependence of  interphase exchange rate versus oxygen pressure exhibited a form of the exponential function: r ph o n~ 2 . the exponent values that were calculated from the line slopes decreased from 1.03 ± 0.04 down to  0.52 ± 0.03 as  the temperature rose. boreskov et al. [18] proved that the oxygen exchange occurs at  the elevated temperatures according to the oxygen dissociative adsorption-desorption mechanism for a number of simple oxide systems. in particular, the oxides with equilibrium 0 5000 10000 15000 20000 0,0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 co nc en tr at io n с 3 2, c 34 , c 3 6 time, s c 32 c 34 c 36 fig. 5. experimental concentrations of c32, c34, c36 in the gas phase versus time (t = 800 °с, рo2 = 0.53 kpa) fig. 6. fraction of 18o-isotope in the gas phase vs. time in the typical isotope exchange experiment at т = 800 °с, рo2 = 0.53 kpa. points are experimental data, and the line is the fitting result 200 oxygen concentration do not obey the first type of the exchange mechanism, according to which oxygen atom from the surface does not involved. the isotope exchange proceeds mainly according to the second and third exchange types with the participation of one or two oxygen atoms from the surface. recently, for the complex oxide systems [15, 19–23] we have demonstrated that the exponents in the equations for the oxygen interphase exchange versus oxygen pressure varies depending on the process which is a rate-determining stage. often the exchange at high temperature occurs according to the oxygen dissociative adsorption mechanism. depending on  the relation of three exchange types contribution, the oxygen exchange mechanism differs for oxides. fig. 8 demonstrates the dependence of the tracer diffusion coefficients of oxygen versus oxygen pressure at  various temperatures. the value of the oxygen diffusion coefficient is almost independent of oxygen pressure. earlier [15] we demonstrated the influence of the oxygen nonstoichiometry on the value of the oxygen tracer diffusion coefficient, for  example in lanthanum strontium cobaltites. almost constant value of oxygen tracer diffusion coefficient in  the fe-doped lanthanum strontium cobaltite is likely associated with the insignificant changes in the oxygen vacancies concentration within the oxygen pressures range of 0.27 ≤ ро2 ≤ 2.13 kpa, which was also confirmed earlier [24–26]. figs. 9, 10 illustrate the temperature dependencies of  oxygen exchange coefficient and oxygen diffusion coefficient, respectively, in  comparison with literary data for different oxides [22, 26–29]. the values of  activation energy for  the exchange and diffusion processes are listed in  table 1. it should be noted that relatively high values of oxygen diffusion and exchange coefficients for the studied la0.6sr0.4co0.8fe0.2o3–δ oxide are comparable with the values for barium praseodymium cobaltite [29] and are greater by the value of  magnitude than those for  lanthanum strontium manganite [22]. therefore, it may be assumed that la0.6sr0.4co0.8fe0.2o3–δ is a perspective oxide for the sofc cathode materials, because of  its high values of  exponents in  the equation for  oxygen exchange reaction and good stability in the reducing atmosphere. the substitution of iron for cobalt results in the insignififig. 7. the oxygen interphase exchange for la0.6sr0.4co0.8fe0.2o3–δ plotted as a function of oxygen partial pressure at different temperatures, рoо2 = 101.3 kpa (n ~ tgβ) fig. 8. oxygen diffusion coefficients versus oxygen partial pressure at different temperatures for  the la0.6sr0.4co0.8fe0.2o3–δ oxide -2,6 -2,4 -2,2 -2,0 -1,8 -1,6 15,2 15,4 15,6 15,8 16,0 16,2 16,4 16,6 16,8 600°c, n=1.03 700°c, n=0.88 800°c, n=0.52 lo g( r h , at om c m 2 c –1 ) log(po2/p°o2) -2,6 -2,4 -2,2 -2,0 -1,8 -1,6 -9,0 -8,5 -8,0 -7,5 -7,0 -6,5 600°c 700°c 800°c log(po2/p°o2) lo g( d , c m 2 s –1 ) 201 cant decrease in the oxygen exchange rate; however, its introduction into the cobalt sublattice increases the stability of  oxide in the reducing atmospheres [6]. conclusions the oxygen exchange kinetics for the la0.6sr0.4co0.8fe0.2o3–δ oxide was studied using the isotope exchange method with gas phase equilibration. the values of the interphase exchange rate and oxygen diffusion coefficient in la0.6sr0.4co0.8fe0.2o3–δ were calculated. the values of effective activation energies for the oxygen interphase exchange and diffusion were calculated. the exponents in the equations for the oxygen interphase exchange rate were found within the range of  0.52–1.03 at the temperatures of 600–800 °с in the oxygen pressures range of 0.27–2.13 kpa. table 1 the apparent activation energy values for the oxygen surface exchange and oxygen diffusion processes in the mixed conducting oxides oxide oxygen pressure, kpa ∆т, °с activation energy, ev sourceexchange diffusion la0.6sr0.4co0.8fe0.2o3–δ 2.13 600–800 0.57 ± 0.05 0.92 ± 0.05 this work la0.6sr0.4coo3±δ 0.67 600–850 0.11 1.08 [26] la0.6sr0.4mno3±δ 0.67 700–850 0.71 1.42 [22] pr2nio4±δ 0.67 600–700 700–800 2.0 1.4 2.0 [27] la2nio4±δ 1.33 600–800 1.38 1.41 [28] prbaco2o6–δ 1.33 600–800 0.76 0.75 [29] fig. 9. temperature dependences of the oxygen exchange coefficient for various mixed conducting oxides fig. 10. temperature dependences of the oxygen tracer diffusion coefficient for various mixed conducting oxides 0,9 1,0 1,1 1,2 -9 -8 -7 -6 la 0.6 sr 0.4 co 0.8 fe 0.2 o 3±δ la 0.6 sr 0.4 coo 3±δ [26] la 0.6 sr 0.4 mno 3±δ [22] pr 2 nio 4±δ [27] la 2 nio 4±δ [28] prbaco 2 o 6-δ [29] lo g (k ,c m s1 ) 1000/t, к–1 0,9 1,0 1,1 1,2 -12 -11 -10 -9 -8 -7 la 0.6 sr 0.4 co 0.8 fe 0.2 o 3±δ la 0.6 sr 0.4 coo 3±δ [26] la 0.6 sr 0.4 mno 3±δ [22] pr 2 nio 4±δ [27] la 2 nio 4±δ [28] prbaco 2 o 6-δ [29] 1000/t, к–1 lo g (d ,c m 2 s1 ) 202 based on  these results, it can be concluded that the exchange in  the case of la0.6sr0.4co0.8fe0.2o3–δ occurs according to the mechanism of the molecular oxygen dissociative adsorption at the oxide surface. the obtained results demonstrate that la0.6sr0.4co0.8fe0.2o3–δ possesses high values of  oxygen interphase exchange rate and oxygen diffusion coefficient as compared to other oxide materials with mixed conductivity. acknowledgements this work is partly supported by  the 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non-stoichiometric oxides] saarbrucken: lambert academic publishing; 2012. 205 p. russian. 27. porotnikova nm, khodimchuk av, ananyev mv, eremin va, tropin es, farlenkov as, pikalova eyu, fetisov av. j solid state electrochem. 2018;22(7):2115–26. doi: 10.1007 / s10008-018-3919-x. 28. ananyev mv, tropin es, eremin va, farlenkov as, smirnov as, kolchugin aa, porotnikova  nm, khodimchuk  av, berenov  av, kurumchin  ek. oxygen isotope exchange in la2nio4±δ. phys chem chem phys. 2016;18(13):9102–11. doi: 10.1039 / c5cp05984d. 29. ananyev mv, eremin va, tsvetkov ds, porotnikova nm, farlenkov as, zuev ayu, fetisov  av, kurumchin  ekh. oxygen isotope exchange and diffusion in  lnbaco2o6 − δ (ln = pr, sm, gd) with double perovskite structure. solid state ionics. 2017;304:96–106. doi: 10.1016 / j.ssi.2017.03.022. potassium carbonate supported efficient synthesis of new diethyl arylphosphoramidates p. v. ramana1, b. s. krishna1, n. b. reddy1,2, g. sravaya1,2, g. v. zyryanov2,3, c. s. reddy1 1 department of chemistry, sri venkateswara university, tirupati, 517502, india tel: + 91-9849694958; fax: + 918772289555 e-mail: csrsvu@gmail.com 2 department of organic and biomolecular chemistry, institute of chemical engineering, ural federal university, 19 mira st., ekaterinburg, 620002, russia 3 postovsky institute of organic synthesis ub ras, 22 kovalevskaya st. / 20 akademicheskaya st., ekaterinburg, 620990, russia of new diethyl arylphosphoramidates keywords: introduction phosphoramidates have gained considerable interest in the last few deca des as they have various applications in organic synthesis such as catalytic conversions like aldol and allylation reactions [1]. in addition to catalytic applications, n-arylphosphoramidates have been used as precursors for the synthesis of various heterocycles such as azetidines, aziridines, quinazolinediones and imines [2–3]. beside this, they are also used to synthesize phosphate esters in nucleotides chemistry [4]. in analytical chemistry, phosphoramidates improve ionization efficiency and suppress matrix-related ion effects in malditof mass spectrometry [5]. in medicinal chemistry, it is reported that phosphoramidates can be used as prodrug moieties to improve therapeutic potential of the parent drug [6]. phosphoramidates have also served as surrogates for amide bond in the synthesis of peptide based protease inhibitors [7]. they represents some key structure in a number of biologically active natural products like agrocin 84 [8], phosmidosine (ii) [9] and gs-6620 (iii) [10]. they also form important pharmacophore of many biologically potent compounds e. g. sofosbuvir (iv) (fda approved drug) used for the treatment of hepatitis c virus (hcv) [11], evofosfamidum (th-302) (v) which is in clinical trials for cancer treatment (fig. 1) [12]. recently, phosphoramidates have also been used in the field of plant hormone as abscisic acid (aba) agonists that play role in plant growth regulators [13]. among literature methods, direct phosphorylation of different amines with phosphorus halides is one of the most attractive and synthetically accessible methods [14]. coming to the reactivity, n-phosphorylation of the nh moiety of few n-heterocycles like indoles, imidazoles, and benzimidazole derivatives was reported with the similar reactivity as we expected in alkylations [15]. these phosphoramidates featuring a p-n bond are used as pesticides in agriculture and prodrugs in therapeutic development, and for other synthetic applications [16]. furthermore, they have been utilized as ligands for metal-catalyzed organic transformations, as flame retardants, and as labelling groups to improve sensitivity in mass spectroscopy [17]. the phosphorylation of a series of amines was studied under different conditions involving the application of the various methods. our aim was to find the best set of conditions for the preparation of some of these phosphoramidates. experimental general: all reagents were obtained from sigma-aldrich and alfa aesar and were used directly without further purification. melting points were recorded on guna digital melting point apparatus. ir spectra were recorded on bruker alpha – eco atr – ftir interferometer with single reflection sampling module equipped with znse crystal. 1h, 13c and 31p nmr spectra were recorded on bruker amx 500 mhz nmr spectrometers ope rating at 400 mhz for 1h, 100 mhz for 13c and 160 mhz for 31p nmr in dmso and were referenced to tms (1h and 13c) and 85 % h3po4 ( 31p) and their chemical shifts were reported in δ scale. mass spectra were recorded on a jeol sx 102 da/600 mass spectrometer and elemental analyfig. 1. some representative bioactive phosphoramidates sis was performed on a thermo finnigan instrument. melting points were determined in open capillaries using ez-melt automated melting point apparatus. all solvents used for spectroscopic and other physical studies were reagent grade and were further purified by methods reported in the literature. chemistry: initially 0.127 mg (1  mmol) of 4-chloro aniline (1a) was added to 0.144 ml (1 mmol) diethyl chlorophosphate (2) along with k2co3 (5 mol%) into a 50 ml round bottom flask in 8ml of dmso. then it is equipped with a reflux condenser and the contents were heated to 80  °c and reaction was continued at the same temperature and the reaction progress was monitored with tlc (3:7 ratio of ethylacetate and hexane mixture). after completion of the reaction the crude contents of diethyl (4-chlorophenyl) phosphoramidate (3a) formed were cooled to room temperature and was cooled to room temperature conditions. then the filtrate was concentrated by removing the solvent by rota-evaporation and then it was purified by column chromatography (1:9 ratio of ethylacetate and hexane mixture) and the pure product 3a was collected. similarly various amines amines (1a-n) as listed above were used to synthesize corresponding diethyl arylphosphoramidates (3a-n) with good reaction yields by the catalytic action of k2co3 (5 mol %) in dmso at 80 °c (fig. 2). diethyl (4-chlorophenyl)phosphoramidate (3a): yield: 92 %; brown solid; ir (znse): 3312 (nh  aromatic), 1172 (p=o), 935 (p-o-caliphatic) cm -1; 1h nmr (500 mhz, dmso-d6): δ 1.17–1.33 (6h, m, 2ch3), 3.95 (1h, s, nh), 4.26–4.34 (4h, m, 2ch2), 7.06–7.72 (4h, m, arh) ppm; 13c nmr (125 mhz, dmso-d6): δ 16.48, 63.32, 119.26, 127.08, 129.54, 142.22 ppm; 31p nmr (200 mhz, dmso-d6): δ 2.856 ppm; lc–ms m/z (%): 263 (100) [m+]; anal. calcd. for c10h15clno3p (%): c, 45.55; h, 5.73; n, 5.31. found: c, 45.51, h, 5.69; n, 5.28. diethyl (4-fluorophenyl)phosphoramidate (3b): yield: 89 %; brown solid; ir (znse): 3325 (nh  aromatic), 1225 (p=o), 942 (p-o-caliphatic) cm -1; 1h nmr (500 mhz, dmso-d6): δ 1.20–1.28 (6h, m, 2ch3), 3.87 (1h, s, nh), 4.22–4.26 (4h, m, 2ch2), 6.65–7.06 (4h, m, arh) ppm; 13c nmr (125 mhz, dmso-d6): δ 16.42, 62.96, 118.52, 125.85, 132.34, 148.44 ppm; 31p nmr (200 mhz, dmso-d6): δ 2.824 ppm; lc–ms m/z (%): 247 (100) [m+]; anal. calcd. for c10h15clno3p (%): c, 48.59; h, 6.12; n, 5.67. found: c, 48.51; h, 6.06; n, 5.63. diethyl (4-methoxyphenyl)phosphoramidate (3c): yield: 90 %; brown solid; ir (znse): 3321 (nh  aromatic), 1212 (p=o), 938 (p-o-caliphatic) cm -1; 1h nmr (500 mhz, dmso-d6): δ 1.18–1.29 (6h, m, 2ch3), 3.78–3.84 (3h, m, -och3), 3.89 (1h, s, nh), 4.01–4.12 (4h, m, 2ch2), 6.59–6.94 (4h, m, arh) ppm; 13c nmr (125 mhz, dmso-d6): δ 16.38, 55.82, 62.96, 117.33, 121.48, 132.94, 152.31 ppm; 31p nmr (200 mhz, dmsod6): δ 2.836 ppm; lc–ms m/z (%): 259 (100) [m+]; anal. calcd. for c11h18no4p (%): c, 50.96; h, 7.00; n, 5.40. found: c, 50.92; h, 6.95; n, 5.33. diethyl (5-nitropyridin-2-yl)phosphoramidate (3d): yield: 90 %; brown solid; ir (znse): 3332 (nh  aromatic), 1194 (p=o), 945 (p-o-caliphatic) cm -1; 1h nmr (500 mhz, dmso-d6): δ 1.24–1.31 (6h, m, 2ch3), 3.98 (1h, s, nh), 4.35– 4.46 (4h, m, 2ch2), 7.06–8.72 (4h, m, arh) ppm; 13c nmr (125 mhz, dmsod6): δ 16.36, 62.21, 110.96, 132.08, 136.22, 144.78, 169.14 ppm; 31p nmr (200 mhz, dmso-d6): δ 2.842 ppm; lc–ms m/z (%): 275 (100) [m+]; anal. calcd. for c9h14n3o5p (%): c, 39.28; h, 5.13; n, 15.27. found: c, 39.24; h, 5.09; n, 15.21. diethyl (3-fluoro-5-nitrophenyl) phosphoramidate (3e): yield: 92 %; brown solid; ir (znse): 3348 (nh  aromatic), 1209 (p=o), 944 (p-o-caliphatic) cm-1; 1h nmr (500 mhz, dmso-d6): fig. 2. synthesis of diethyl arylphosphoramidates δ 1.19–1.32 (6h, m, 2ch3), 4.02 (1h, s, nh), 4.42–4.48 (4h, m, 2ch2), 7.02–7.42 (3h, m, arh) ppm; 13c nmr (125 mhz, dmso-d6): δ 16.08, 62.04, 102.05, 104.54, 111.22, 142.08, 150.65, 165.84 ppm; 31p nmr (200 mhz, dmso-d6): δ 2.816 ppm; lc–ms m/z (%): 292 (100) [m+]; anal. calcd. for c10h14fn2o5p (%): c, 41.10; h, 4.83; n, 9.59. found: c, 41.03; h, 4.80; n, 9.55. tetraethyl ((phenylazanediyl) b i s ( m e t hy l e n e ) ) d i p h o sp h o r ami d at e (3f ): yield: 84 %; brown solid; ir (znse): 3345 (nh  aromatic), 1246 (p=o), 922 (p-o-caliphatic) cm -1; 1h nmr (500 mhz, dmso-d6): δ 1.21–1.32 (12h, m, 4ch3), 1.98 (1h, s, nh), 4.46–4.54 (8h, m, 4ch2), 4.76–4.84 (4h, m, 2ch2), 6.86–7.32 (5h, m, arh) ppm; 13c nmr (125  mhz, dmso-d6): δ 16.08, 58.02, 62.22, 115.22, 122.05, 129.44, 150.66 ppm; 31p nmr (200  mhz, dmso-d6): δ 2.824 ppm; lc–ms m/z (%): 423 (100) [m+]; anal. calcd. for c16h31n3o6p2 (%): c, 45.39; h, 7.38; n, 9.92. found: c, 45.35; h, 7.32; n, 9.85. diethyl thiazol-2-ylphosphoramidate (3g): yield: 87 %; brown solid; ir (znse): 3356 (nh  aromatic), 1206 (p=o), 938 (p-o-caliphatic) cm -1; 1h nmr (500 mhz, dmso-d6): δ 1.28–1.32 (6h, m, 2ch3), 3.95 (1h, s, nh), 4.46–4.54 (4h, m, 2ch2), 6.76–7.62 (2h, m, arh) ppm; 13c nmr (125 mhz, dmso-d6): δ 16.36, 62.92, 115.21, 135.48, 169.82 ppm; 31p nmr (200 mhz, dmso-d6): δ 2.821 ppm; lc–ms m/z (%): 236 (100) [m+]; anal. calcd. for c7h13n2o3ps (%): c, 35.59; h, 5.55; n, 11.86. found: c, 35.53; h, 5.52; n, 11.81. diethyl (5-ethyl-1,3,4-thiadiazol-2-yl) phosphoramidate (3h): yield: 86 %; brown solid; ir (znse): 3315 (nh  aromatic), 1242 (p=o), 944 (p-o-caliphatic) cm -1; 1h nmr (500 mhz, dmso-d6): δ  1.27–1.32 (6h, m, 2ch3), 1.34–1.37 (3h, m, ch3), 2.57–2.62 (2h, m, ch2), 4.05 (1h, s, nh), 4.46–4.54 (4h, m, 2ch2) ppm; 13c nmr (125 mhz, dmso-d6): δ 11.56, 16.52, 22.36, 62.96, 167.86, 174.14 ppm; 31p nmr (200 mhz, dmso-d6): δ 2.842 ppm; lc–ms m/z (%): 265 (100) [m+]; anal. calcd. for c8h16n3o3ps (%): c, 36.22; h, 6.08; n, 15.84. found: c, 36.17; h, 6.05; n, 15.75. diethyl benzo[d][1,3]dioxol-5-ylphosphoramidate (3i): yield: 82 %; brown solid; ir (znse): 3352 (nh  aromatic), 1222 (p=o), 953 (p-o-caliphatic) cm-1; 1h nmr (500 mhz, dmso-d6): δ 1.27–1.33 (6h, m, 2ch3), 4.01 (1h, s, nh), 4.48–4.54 (4h, m, 2ch2), 6.06–6.09 (2h, m, och2o), 6.12–6.65 (3h, m, arh) ppm; 13c nmr (125 mhz, dmsod6): δ 16.08, 62.22, 100.52, 101.33, 109.26, 113.02, 132.88, 139.04, 149.12 ppm; 31p nmr (200 mhz, dmso-d6): δ 2.836 ppm; lc–ms m/z (%): 273 (100) [m+]; anal. calcd. for c11h16no5p (%): c, 48.36; h, 5.90; n, 5.13. found: c, 48.33; h, 5.85; n, 5.05. diethyl (2-(1h-indol-3-yl)ethyl) phosphoramidate (3j): yield: 84 %; brown solid; ir (znse): 3344 (nh  aromatic), 1251 (p=o), 958 (p-o-caliphatic) cm-1; 1h nmr (500 mhz, dmso-d6): δ 1.28–1.34 (6h, m, 2ch3), 2.04 (1h, s, nh), 2.78–2.84 (2h, m, ch2), 2.92–2.94 (2h, m, ch2), 4.47–4.52 (4h, m, 2ch2), 7.16–7.42 (5h, m, arh), 10.04 (1h, s, indole nh) ppm; 13c nmr (125 mhz, dmso-d6): δ 16.05, 31.02, 43.95, 62.32, 111.23, 114.26, 118.98, 119.84, 122.08, 124.54 ppm; 31p nmr (200 mhz, dmsod6): δ 10.252 ppm; lc–ms m/z (%): 296 (100) [m+]; anal. calcd. for c14h21n2o3p (%): c, 56.75; h, 7.14; n, 9.45. found: c, 56.71; h, 7.10; n, 9.39. diethyl (5-nitrothiazol-2-yl)phosphoramidate (3k): yield: 80 %; brown solid; ir (znse): 3352 (nh  aromatic), 1216 (p=o), 946 (p-o-caliphatic) cm -1; 1h nmr (500 mhz, dmso-d6): δ 1.27–1.31 (6h, m, 2ch3), 4.01 (1h, s, nh), 4.50– 4.54 (4h, m, 2ch2), 8.62 (1h, s, arh) ppm; 13c nmr (125 mhz, dmso-d6): δ 16.54, 62.32, 136.26, 147.38, 165.94 ppm; 31p nmr (200 mhz, dmso-d6): δ 2.812 ppm; lc–ms m/z (%): 281 (100) [m+]; anal. calcd. for c7h12n3o5ps (%): c, 29.90; h, 4.30; n, 14.94. found: c, 29.85; h, 4.26; n, 14.90. diethyl (2-(piperidin-2-yl)ethyl) phosphoramidate (3l): yield: 82 %; brown solid; ir (znse): 3362 (nh  aromatic), 1214 (p=o), 953 (p-o-caliphatic) cm-1; 1h nmr (500 mhz, dmso-d6): δ 1.28–1.35 (6h, m, 2ch3), 1.56–1.64 (8h, m, 4ch2), 2.04 (1h, s, nh), 2.66 (1h, s, ch), 2.76–2.82 (4h, m, 2ch2), 4.45–4.52 (4h, m, 2ch2), ppm; 13c nmr (125 mhz, dmso-d6): δ 16.28, 23.32, 26.85, 32.82, 35.06, 39.32, 47.02, 59.02, 62.22 ppm; 31p nmr (200 mhz, dmso-d6): δ 10.232 ppm; lc–ms m/z (%): 264 (100) [m+]; anal. calcd. for c11h25n2o3p (%): c, 49.99; h, 9.53; n, 10.60. found: c, 49.95; h, 9.50; n, 10.54. diethyl (furan-2-ylmethyl)phosphoramidate (3m): yield: 86 %; brown solid; ir (znse): 3348 (nh  aromatic), 1209 (p=o), 968 (p-o-caliphatic) cm -1; 1h nmr (500 mhz, dmso-d6): δ 1.22–1.32 (6h, m, 2ch3), 1.96 (1h, s, nh), 3.72–3.76 (2h, m, ch2), 4.49–4.54 (4h, m, 2ch2), 6.46–7.62 (3h, m, arh) ppm; 13c nmr (125 mhz, dmso-d6): δ 16.22, 35.01, 62.12, 110.26, 110.48, 142.54, 148.82 ppm; 31p nmr (200 mhz, dmso-d6): δ 7.824 ppm; lc–ms m/z (%): 233 (100) [m+]; anal. calcd. for c9h16no4p (%): c, 46.35; h, 6.92; n, 6.01. found: c, 46.30; h, 6.88; n, 5.94. diethyl 1h-benzo[d]imidazol-1-ylphosphonate (3n): yield: 84 %; brown solid; ir (znse): 3356 (nh  aromatic), 1198 (p=o), 959 (p-o-caliphatic) cm-1; 1h nmr (500 mhz, dmso-d6): δ 1.26–1.34 (6h, m, 2ch3), 4.50–4.53 (4h, m, 2ch2), 7.26–7.62 (4h, m, arh), 8.18 (1h, s, n=ch-n) ppm; 13c nmr (125 mhz, dmso-d6): δ 16.22, 60.12, 115.26, 124.08, 137.84, 139.05, 142.25 ppm; 31p nmr (200 mhz, dmso-d6): δ –6.724 ppm; lc–ms m/z (%): 254 (100) [m+]; anal. calcd. for c11h15n2o3p (%): c, 51.97; h, 5.95; n, 11.02. found: c, 51.93; h, 5.91; n, 10.96. results and discussion at the onset of our investigation for the synthesis of phosphoramidate derivatives, 4-chloro aniline and diethyl chlorophosphate were taken as model substrates to optimize the experimental conditions. initially, 4-chloro aniline and diethyl chlorophosphate were heated at 80 °c in dmso without any catalyst, but the reaction was unable to produce the product even after the prolonged heating for 48 h (table 1, entry 1). hence, we have traced the activity of various catalysts for the synthesis of diethyl(4-chlorophenyl) phosphoramidate (3a). the catalytic effect of such inorganic and organic bases (table 1, entries 2–11) afforded the pro ducts with low yield, where k2co3 only afforded maximum product yields in 8  h of reaction time (table 1, entries 12–14). in the catalyst optimization studies with 2, 5 and 10 mol% of k2co3, we obtained the yields were 68, 94 and 94 respectively (table 1, entries 12–14). therefore, 5 mol % of k2co3 was sufficient for completion of the reaction and excess amount of catalyst did not increase the yields and the reusability of the catalyst has not also been observed with the mark of satisfaction. then several solvents, such as dmf, 1,4-dioxane, acetone, mecn, thf, ch3no2, ch3ch2oh, and dimethylsulfoxide were screened in the presence of 5 mol% of k2co3 at 80  °c (table 2, entries 1–8), and the results showed that dimethylsulfoxide (dmso) was the best choice. conclusions we have been successful in accomplishing a new synthetic protocol for the construction of phosphoramidates scaffold under sustainable condition applying k2co3 catalysis. developed synthetic protocol offers various advantages like operational simplicity, low catalyst loading, an extensive substrate scope, and a high product yield. the use of dmso as the reaction medium and application of k2co3 catalyst make this protocol truly a practical one for synthetic chemistry. acknowledgements acknowledgements: we thank prof. c. devendranath reddy, department of chemistry, s. v. university, tirupati for his helpful discussions and science and engineering research board (serb), new delhi – 110 070 india for providing financial assistance through a research project grant f. no.: sb/s1/oc-96/2013, dt: 05–11–2014. table 1 influence of various catalysts on the synthesis of compound 4a at 80 °c entry catalyst catalyst (mol %) time (h) yield (%) 1 none – 48 nr 2 cs2co3 5 10 65 3 na2co3 5 12 45 4 naoh 5 24 nr 5 t-buoh 5 10 42 6 nahco3 5 10 38 7 k3po4·3h2o 5 24 nr 8 acok 5 24 nr 9 dbu 5 14 trace 10 et3n 5 10 24 11 pyridine 5 10 15 12 k2co3 2 8 68 13 k2co3 5 8 94, 89, 82 14 k2co3 10 8 94 table 2 effect of various solvents on the synthesis of compound 4a entry solvent time (h) yield (%) 1 dmf 8 74 2 1,4-dioxane 8 72 3 acetone 8 68 4 mecn 8 75 5 thf 8 82 6 ch3no2 8 42 7 ch3ch2oh 8 84 8 dmso 8 94 references 1. egron d, imbach jl, gosselin g, aubertin am, perigaud c. s-acyl-2-thioethyl phosphoramidate diester derivatives as mononucleotide prodrugs. j med chem. 2003;46(21):4564–71. doi:10.1021/jm0308444. 2. denmark se, chung wj. lewis base activation of lewis acids: catalytic 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цитировать эту статью) ramana pv, krishna bs, reddy nb, sravaya g, zyryanov gv, reddy c s. potassium carbonate supported efficient synthesis of new diethyl arylphosphoramidates. chimica techno acta. 2017;4(2):148–156. doi:10.15826/chimtech.2017.4.2.030. 52 do i: 1 0. 15 82 6/ ch im te ch .2 01 5. 2. 1. 00 5 khazhieva i. s., glukhareva t. v., morzherin yu. yu. y-synthesis, ltd, 60 lunacharskogo street, 620027 ekaterinburg phone: +7(343) 375-48-18; e-mail: his_inna@mail.ru reaction of 4-acetyl-1,2,3-triazol-5-olate with hydrazine derivatives 1,2,3-triazoles attract attention because of thein ability to ring open leading to α-diazoimin and intramolecular rearrangements to form various heterocyclic systems. previously, the interaction of the 1h-1,2,3-triazole-5-ol sodium salt with amine hydrochloride resulting in the formation of isomeric 1,2,3-triazoles has been studied. in this paper, we present a study of the interaction of 4-acetyl-1,2,3-triazole-5-ol sodium salt with hydrazine derivatives. as result, 5-methyl-1,2,3-triazol-4-phenylcarboxamide-phenylamide and bis 5,5’-dimethyl-[1,1’]bi[[1,2,3] triazolyl]-4,4’-dicarboxylic acid derivatives were synthesized. introduction among 1,2,3-triazoles there are some compounds which exhibit various biological activities (antibacterial, antitumoral, anti-fungal1, immunosuppressive2), and various technical properties. currently, the search continues for new 1,2,3-triazole derivatives which have biological activity, and, consequently, there is an increase in number of publications dedicated to 1,2,3-triazoles. furthermore, 1,2,3-triazoles exhibit interesting chemical properties, such as ring-chain isomerisation, rearrangement and transformation of the ring. this is determined by the ability of 1,2,3-triazoles to ring opening with the formation of α-diazoimine. we have previously shown that reaction of sodium 4-acetyl-1,2,3-triazolate 1 with amine hydrochlorides proceeds with the formation of 5-methyl-1,2,3-triazol4-carboxamides 23. in this study, we investigated reaction of sodium 4-acetyl-1,2,3-triazolate 1 with hydrazine derivatives. © khazhieva i. s., glukhareva t. v., morzherin yu. yu., 2015 54 № 1 | 2015 chimica techno acta reaction of 4-acetyl-1,2,3-triazol-5-olate with hydrazine derivatives results and discussion it was shown that the reaction of sodium 1,2,3-triazolate 1 with equimolar amount of hydrazine hydrochlorides 3 a-g leads to 1-amino-5-methyl-1,2,3-triazol4-yl-carboxamides, 4 a-g . however, bistriazole 5 was isolated using unsubstituted hydrazine in the reaction. in this case, one molecule of hydrazine reacts with two molecules of triazolate, accompanied by rearrangement of two triazole rings. perhaps, this course of the reaction is due to slow dissolving of hydrazine hydrochloride in ethanol. 1-amino-1,2,3-triazol 6 was prepared in the reaction of 2-diazoacetoacetanilid hydrazine hydrate 7 obtained after acidification of sodium 1,2,3-triazolate aqueous solution. thus we obtained previously undescribed phenylamide derivatives 5-methyl-1(r-amino) -1 h [1,2,3] triazole-4-carboxylic acid and bis-phenylamid-5,5’-dimethyl-[1, 1’] bi [[1,2,3] triazolyl] -4,4’-dicarboxylic acid. the experimental part reaction monitoring and the individuality of the synthesized compounds was performed by tlc plates solufoluv 254 in the system: chloroform (visualisation under uv lamp). ir spectra were recorded on a spectrophotometer bruker alpha. nmr 1h and 13c spectra were recorded on a spectrometer bruker avanceii (400 and 100 mhz, respectively), internal standard is tms, in the laboratory of comprehensive research and evaluation of organic materials at ccu ufu. mass spectres were recorded on a spectrometer mat 11 (ei, 70 ev). melting points were measured using art stuartsmp3 apparatus and were not corrected. elemental analysis was performed on a chns-analyzer pe 2400 seriesii. methods for preparation of 4 a-g and 5 (1.43 mmol) hydrazine hydrochloride 3 a-d is added to an alcohol solution of sodium triazolate 1 0.29 g (1.3 mmol). the reaction mixture was heated for 24 hours. after cooling, the precipitation was filtered off, washed with ethanol and dried. phenylamide 5-methyl-1-phenylamino-1h-[1,2,3] triazole-4-carboxylic acid (4a) white crystalline solid 0.36 g (94.74%). tm = 147.3 ° c. nmr 1h: (dmso-d6,d, ppm, j / hz): 10.41 (1h, c, -nh), 10,39 (1h, c, -nh), 7,85 (2h , d, j = 8,4, o-ar-h), 7,33 (2h, dd, j = 7,5; j = 8,4, m-ar-h), 7,23 (2h, dd, j = 7,5; j = 56 № 1 | 2015 chimica techno acta 8,4, m-ar-h), 7,09 (1h, dd, j = 8,4; j = 7,5, p -ar-h), 6,92 (1h, dd, j1 = 8,4; j2 = 7,5, p-ar-h), 6,51 (2h, d, j = 8,4, a-arh), 2,47 (3h, s, ch3). nmr 13c specter: (dmso-d6,d, ppm): 159.61, 146.76, 139.02, 138.59, 137.67, 124.16, 121.82, 120.88, 113 37 8.7. found, %: c 65,50, h 5,17, n 23,91. calculated for c16h15n5o, %: c 65,52, h 5,15, n 23,88, o 5,45. phenylamide 5-methyl-1-(2-hydroxy-ethylamine)-1н-[1,2,3]triazole-4carboxylic acid (4b) dark yellow oil, 0.36 g (89.45%). nmr 1h: (dmso-d6, d, ppm, j / hz): 9.99 (1h, c, -nh), 7,82 (2h, d, j = 7,6 o-arh), 7,31 (2h, dd, j = 7,6; j = 8,3, m-ar-h), 7,20 (1h, t., j = 5,4, -nh ), 7.05 (1h, dd., j = 7,4; j = 7,4, p-ar-h), 4,06 (1h, bs, -oh) 3,56 (2h, b.t., j = 5,5, ch2), 3.26 (1h, dd, j = 5,5, j = 5,4, ch2) 2,56 (3h, s, ch3). found, %: c 55,15 h 5,80 n 26,80. calculated for c12h15n5o2, %: c 55,16, h 5,79, n 26,80, o 12,25. phenylamide 5-methyl-1-dimethylamino-1h-[1,2,3] triazole-4-carboxylic acid (4c) dark yellow oil, 0.34 g (92.73%). nmr 1h: (dmso-d6, d, ppm, j / hz): 10.06 (1h, c, -nh), 7,82 (2h, d, j = 7,6, o-ar -h), 7,29 (2h, dd, j = 7,6; j = 7,4, m-ar-h), 7,05 (1h, dd, j = 7,4 ; j = 7,4, p-ar-h), 3,02 (3h, s, ch3) 3,06 (3h, s, ch3) 2,54 (3h, s, ch3). found, %: c 55,77 h 6,15 n 28,57. calculated for c12h15n5o,%: c 58,76, h 6,16, n 28,55, o 6,52.% (5-methyl-4-phenylcarboxamide [1,2,3] triazole-1-yl)-amide 4-methyl [1,2,3] thiadiazole-5-carboxylic acid (4a) white crystalline solid of 0.52 g (82.35%). tm = 175,6ºc. nmr 1h: (dmso-d6, d, ppm, j / hz): 13.23 (1h, c, -nh), 10,28 (1h, c, -nh), 7,84 (2h , d, j = 7,8, o-ar-h), 7,30 (2h, dd, j = 7,8; j = 7,9, m-ar-h), 7,07 (1h, t., j = 7,9; j = 7,9, p-ar-h), 2,96 (3h, s, ch3) 2,55 (3h, s, ch3). found, %: c 48,98 h 3,81 n 28,53. calculated for c14h13n7o2s, %: c 48,97; h 3,82, n 28,55; o 9,32, s 9,34. bis-phenylamide 5,5’-dimethyl-[1,1 ‘] bi [[1,2,3] triazolyl] -4,4’-dicarboxylic acid (5) white crystalline solid 0.30 g (84.35%). tm = 217 ° c (180oc years). nmr 1h: (dmso-d6, d, ppm, j / hz): 9.02 (2h, c, -nh), 7,74 (4h, d, o-ar-h j = 8, 0), 7.44 (4h, dd, j = 7,6; j = 8,4 mar-h), 7,23 (2h, dd, j = 7,2, p-ar -h). ir, (v, cm-1) 3308,98 (-nh), 1666,04 (c = o). mass specter (ei, 70 ev), m / z (ires (%)): [m]+ 402 (9.14). found, %: c 59,71 h 4,47 n 18,04. calculated for c20h8n8o2, %: c 59,70; h 4,48 n 27,86; o 7,96. sinthesis of 6 hydrazine hydrate 0.07g (1.43 mmol) is added to an alcohol solution of 2diazoacetanilid 7 0.26 g (1.3 mmol). the reaction mixture was refluxed for a day. after cooling the priecipitate was filtered, washed with ethanol, and dried. reaction of 4-acetyl-1,2,3-triazol-5-olate with hydrazine derivatives 58 № 1 | 2015 chimica techno acta phenylamid 5-methyl-1-amino-1h-[1,2,3] triazole-4-carboxylic acid (4c) white crystalline solid of 0.32 g (83.39%). tm = 199 ° c (120oc years). nmr 1h: (dmso-d6, d, ppm, j / hz): 9.96 (1h, b.c., -nh), 7,80 (2h, d., o-arh j = 8,0), 7,2 (2h, dd, j = 8,0 m-arh), 7,04 (2h, dd, j = 8,0, p-ar -h), 6,76 (2h, c., -nh2), 2,54 (1h, c, -3). mass spectrum3 (ei, 70 ev), m / z (irel (%)): [m ]+217. found, %: c 55,28 h 5,07 n 25,80. calculated for c10h11n3o, %: c 55,29; h 5,06 n 25,81; o 7,37 1. tome a. c. five-membered hetarenes with three or more heteroatoms. science of synthesis. 2004; 13:415–602. [google scholar]. 2. alvarez r., velazquez s., felix a., aquaro s., clercq e., perno c.-f., karsson a., balzarini j., camarasa m.j. 1,2,3-triazole-[2,5-bis-o-(tert-butyldimethylsilyl)-. beta.-d-ribofuranosyl]-3'-spiro-5''-(4''-amino-1'',2''-oxathiole 2'',2''-dioxide) (tsao) analogs: synthesis and anti-hiv-1 activity. journal of medical chemistry. 1994; 4185(37):4185–4194. doi: 10.1021/jm00050a015. [google scholar]. 3. khazhieva i.s., glukhareva t.v., morzherin yu.yu. xxiii russian molodezhnaya scientific conference «problems of theoretical and experimental chemistry». ekaterinburg, urfu: 23–26 april 2013:506–507. [google scholar]. khazhieva i. s., glukhareva t. v., morzherin yu. yu. 53 и. с. хажиева, т. в. глухарева, ю. ю. моржерин ооо «у-синтез» 620027, г. екатеринбург, ул. луначарского, 60; тел.: (343) 375-48-18; e-mail: his_inna@mail.ru исследование реакции 4-ацетил-1,2,3-триазол-5-олата натрия с производными гидразина 1,2,3-триазолы привлекают внимание своей способностью к раскрытию цикла с образованием α-диазоимина и внутримолекулярным перегруппировкам и трансформациям с образованием различных гетероциклических систем. ранее нами было изучено взаимодействие 1,2,3-триазолата натрия с гидрохлоридами аминов, приводящее к образованию изомерных 1,2,3-триазолов. в данной работе мы представляем исследование взаимодействия 4-ацетил-1,2,3-триазол-5-олата натрия с производными гидразина. были получены производные 5-метил-1,2,3-триазол-4-фенилкарбоксамидов и бис-фениламид 5,5’-диметил-[1,1’]би[[1,2,3]триазолил]-4,4’-дикарбоновой кислоты. у д к 5 47 .7 91 :6 61 .7 7 введение среди производных 1,2,3-триазола обнаружены вещества, обладающие различными видами биологической активности: бактерицидной, противоопухолевой, фунгицидной [1], иммуноподавляющей [2], а также разнообразными техническими свойствами. в последнее время активно продолжается поиск новых производных 1,2,3-триазола, обладающих биологической активностью, и, как следствие этого, наблюдается рост количества публикаций, посвященных 1,2,3-триазолам. кроме того, 1,2,3-триазолы проявляют интересные химические свойства, такие как кольчато-цепная изомерия, перегруппировки и трансформации цикла. это обусловенно способностью 1,2,3-триазолов к раскрытию кольца с образованием α-диазоимина. © хажиева и. с., глухарева т. в., моржерин ю. ю., 2015 55 № 1 | 2015 chimica techno acta исследование реакции 4-ацетил-1,2,3-триазол-5-олата натрия с производными гидразина ранее нами было показано, что взаимодействие 4-ацетил-1,2,3-триазолата натрия 1 с гидрохлоридами аминов протекает с образованием 5-метил1,2,3-триазол-4-карбоксамидов 23. в данной работе было исследовано взаимодействие 4-ацетил-1,2,3-триазолата натрия 1 с производными гидразина. результаты и обсуждение было показано, что реакция 1,2,3-триазолата натрия 1 с эквимолярным количеством гидрохлоридов гидразинов 3 а-г приводит к 1-амино5-метил-1,2,3-триазол-4-ил-карбоксамидам 4 а-г. однако при использовании незамещенного гидразина гидрохлорида в результате реакции был выделен бистриазол 5. в данном случае одна молекула гидразина взаимодействует с двумя молекулами триазолата, что сопровождается перегруппировкой двух триазольных циклов. возможно такое протекание реакции связано с медленным растворением гидразина гидрохлорида в этаноле. 1-амино-1,2,3-триазол 6 удалось получить при взаимодействии с гидразингидратом 2-диазоацетоацетанилида 7, полученного подкислением водного раствора 1,2,3-триазолата натрия. таким образом, нами были получены неописанные ранее производные фениламидов 5-метил-1-(r-амино)1 н [ 1 , 2 , 3 ] т р и а з о л 4 к а р б о н о в о й кислоты и бис-фениламид 5,5’-диметил-[1,1’]би[[1,2,3]триазолил]-4,4’дикарбоновой кислоты. экспериментальная часть контроль за ходом реакции и индивидуальностью синтезированных соединений проводили методом тсх на пластинках solufoluv 254 в системе: хлороформ (проявление уф лампой). ик-спектры записаны на спектрофотометре bruker alpha. спектры ямр 1h и 13с записаны на спектрометре bruker avanceii (400 и 100 мгц соотвественно), внутренний стандарт – тмс, в лаборатории комплексных исследований и экспертоной оценки органических материалов при цкп урфу. массспектры зарегистрированы на спектрометре mat 11 (эу, 70 эв). температуры плавления определены на приборе 57 № 1 | 2015 chimica techno acta stuartsmp3 и не исправлены. элементный анализ выполнен на chns-анализаторе ре 2400 seriesii. методика получения 4 а-г и 5 к спиртовому раствору триазолата натрия 1 0,29 г (1,3 ммоль) добавляют (1,43 ммоль ) гидрохлорида гидразина 3 а-д. реакционную массу кипятят в течение суток. охлаждают, выпавший осадок отфильтровывают, промывают этанолом и сушат. прохождение реакции отслеживают методом тсх. фениламид 5-метил-1-фениламино-1н-[1,2,3]триазол-4-карбоновой кислоты (4а) осадок белый кристаллический 0,36 г (94,74 %). тпл = 147,3 ºс. спектр ямр 1н: (dmso-d6, d, м.д., j/гц): 10,41 (1н, c, -nh), 10,39 (1н, c, -nh), 7,85(2h, д, j=8,4, о-ar-h), 7,33 (2н, д.д., j = 7,5; j = 8,4, м-ar-h), 7,23 (2h, д.д., j = 7,5; j = 8,4, м-ar-h), 7,09 (1н, д.д., j = 8,4; j = 7,5, р-ar-h), 6,92 (1н, д.д., j1 = 8,4; j2 = 7,5, р-ar-h), 6,51 (2h, д, j = 8,4, о-ar-h), 2,47 (3h, с, сн3). спектр ямр 13c: (dmso-d6, d, м.д.): 159,61, 146,76, 139,02, 138,59, 137,67, 124,16, 121,82, 120,88, 113,37, 8,7. найдено, %: c 65,50, h 5,17, n 23,91. вычислено для с16h15n5o, %: c 65,52, h 5,15, n 23,88, o 5,45. фениламид 5-метил-1-(2-гидрокси-этиламино)-1н-[1,2,3]триазол-4карбоновой кислоты (4б) темно-желтое масло 0,36 г (89,45 %). спектр ямр 1н: (dmso-d6, d, м.д., j/гц): 9,99 (1н, c, -nh), 7,82 (2h, д, j = 7,6 o-ar-h), 7,31 (2н, д.д., j = 7,6; j = 8,3, м-ar-h), 7,20 (1н, т., j = 5,4, -nh), 7,05 (1н, д.д., j = 7,4; j = 7,4, р-arh), 4,06 (1н, уш.с., -oh ) 3,56 (2н, уш.т., j = 5,5, -сн2), 3,26 (1н, д.д., j = 5,5, j = 5,4, -сн2) 2,56 (3h, с, сн3). найдено, %: c 55,15 h 5,80 n 26,80. вычислено для c12h15n5o2, %: c 55,16, h 5,79, n 26,80, o 12,25. фениламид 5-метил-1-диметиламино-1н-[1,2,3]триазол-4-карбоновой кислоты (4в) темно-желтое масло 0,34 г (92,73 %). спектр ямр 1н: (dmso-d6, d, м.д., j/гц): 10,06 (1н, c, -nh), 7,82 (2h, д, j = 7,6, o-ar-h), 7,29 (2н, д.д., j = 7,6; j = 7,4, м-ar-h), 7,05 (1н, д.д., j = 7,4; j = 7,4, р-ar-h), 3,02 (3h, с, сн3) 3,06 (3h, с, сн3) 2,54 (3h, с, сн3). найдено, %: c 55,77 h 6,15 n 28,57. вычислено для c12h15n5o, %: c 58,76, h 6,16, n 28,55, o 6,52%. (5-метил-4-фенилкарбоксамоил--[1,2,3]триазол-1-ил)-амид 4-метил-[1,2,3]тиадиазол-5-карбоновой кислоты (4г) осадок белый кристаллический 0,52 г (82,35 %). тпл = 175,6 ос. спектр ямр 1н: (dmso-d6, d, м.д., j/гц): 13,23 (1н, c, -nh), 10,28 (1н, c, -nh), 7,84 (2h, д, j = 7,8, o-ar-h), 7,30 (2н, д.д., j = 7,8; j = 7,9, м-ar-h),7,07 (1н, т., j = 7,9; j = 7,9, р-ar-h), 2,96 (3h, с, сн3) 2,55 (3h, с, сн3). найдено, %: c 48,98 h 3,81 n 28,53. вычислено для c14h13n7o2s, %: c 48,97; h 3,82, n 28,55; o 9,32, s 9,34. исследование реакции 4-ацетил-1,2,3-триазол-5-олата натрия с производными гидразина 59 № 1 | 2015 chimica techno acta бис-фениламид 5,5’-диметил-[1,1’]би[[1,2,3]триазолил]-4,4’дикарбоновой кислоты (5) осадок белый кристаллический 0,30 г (84,35 %). тпл = 217 ос (лет 180 ос). спектр ямр 1н: (dmso-d6, d, м.д., j/гц): 9,02 (2н, c, -nh), 7,74 (4h, д, o-ar-h j=8,0), 7,44 (4н, д.д. , j = 7,6; j = 8,4 м-ar-h), 7,23 (2h, д.д., j = 7,2, p-ar-h) ик спектр, v, см-1 3308,98 (-nh), 1666,04 (с=о) массспектр (эу, 70 эв), m/z (iотн (%)): [m]+402(9,14). найдено, %: c 59,71 h 4,47 n 18,04. вычислено для с20h8n8o2, %: c 59,70; h 4,48 n 27,86; o 7,96. методика получения 6 к спиртовому раствору 2-диазоацетанилида 7 0,26 г (1,3 ммоль) добавляют 0,07 г (1,43 ммоль) гидразин гидрата. реакционную массу кипятят в течение суток. охлаждают, выпавший осадок отфильтровывают, промывают этанолом и сушат. прохождение реакции отслеживают методами тсх. фениламид 5-метил-1-амино-1н-[1,2,3]триазол-4-карбоновой кислоты (4в) осадок белый кристаллический 0,32 г (83,39 %). тпл = 199 ос (лет 120 ос). спектр ямр 1н: (dmso-d6, d, м.д., j/гц): 9,96 (1н, уш.c., -nh), 7,80 (2h, д., o-ar-h j = 8,0), 7,2 (2н, д.д., j = 8,0 м-ar-h), 7,04 (2h, д.д., j = 8,0, p-ar-h), 6,76 (2h, c., -nh2), 2,54 (1h, c, -3). масс-спектр (эу, 70 эв), m/z (iотн (%)): [m]+217. найдено, %: c 55,28 h 5,07 n 25,80. вычислено для с10h11n3o, %: c 55,29; h 5,06 n 25,81; o 7,37. 1. tome a. c. // five-membered hetarenes with three or more heteroatoms // science of synthesis. 2004 v. 13. new york. р. 415–602. 2. alvarez r., velazquez s., felix a. s., aquaro s., de clercq e., perno c.-f. karlsson a., balzarini j. and camarasa m. j. // journal of medicinal chemistry. 1994. № 37. р. 4185–4194. 3. хажиева и. с., глухарева т. в., моржерин ю. ю. // xxiii рос. молодеж. науч. конф. «проблемы теоретической и экспериментальной химии», екатеринбург, 23–26 апреля 2013 г. : сб. тезисов докладов. екатеринбург: урал. ун-т, 2013. с. 506–507. хажиева и. с., глухарева т. в., моржерин ю. ю. 1097-2578-1-pb 1097-2579-1-pb 16 farlenkov a. s., anan’ev m. v. ural federal university, 19 mira street, 620002 ekaterinburg fax: +7(343) 375-97-78; phone: +7(343) 375-44-72; e-mail: rector@urfu.ru institute of high-temperature electrochemistry ubras, 20 akademicheskaya street, 620990 ekaterinburg fax: +7(343) 374-59-92; phone: +7(343) 374-50-89; e-mail: dir@ihte.uran.ru modeling of a microstructure and calculation a tortuosity factor for cathodic materials of lsm–ysz* in this work changes in physico-chemical properties (oxygen interphase exchange rate and specific resistance) and microstructure parameters (tpb length and tortuosity factor) with time have been analyzed to find the quantitative relationships on the example of composite cathode material lsm-ysz. 3d microstructure of lsm-ysz materials has been reconstructed and tortuosity factor has been calculated on the basis of sem image analysis using the original software. *this work was done under financial support from rfbr grant № 12-03-31847 / 12 and the federal program № 2012-1.3.1-12-000-2006-004, number 8713. do i: 1 0. 15 82 6/ ch im te ch .2 01 5. 2. 1. 00 2 introduction one of the most important areas of the global energy and energy efficiency is the development and study of the solid oxide fuel cells (sofcs), they belong to class of chemical power sources, in which the chemical energy reagents (fuel and oxidizer) electrochemically converted into electricity. oxygen from the air is usually in the role of oxidizer and hydrogen as fuel. sofc retains the ability to generate electricity as long as reagents come from the outside and the results of their interaction are taken away. a significant advantage of the sofcs is its silent operation and a lack of emissions during its operation, but there are several problems associated with the degradation of the materials that make up sofcs. it is known that the microstructure of functional materials is a determining factor in the kinetics of the processes occurring during operation of the sofc. the source of the information about it is the images obtained by scanning electron microscopy (sem). to estimate the parameters of the microstructure, analysis of two© farlenkov a. s., anan’ev m. v., 2015 18 № 1 | 2015 chimica techno acta dimensional micrographs of sections or the surface of the material is not enough. there are a number of parameters of the microstructure, which can only be calculated from the three-dimensional model: the length of the three-phase (tfg) and interphase (fig) boundaries; proportion of active tfg, open pores; tortuosity factor, etc. in this paper we present the main directions and results in the analysis of microstructure parameters on the example of the composite lsm-ysz, and comparison of time changes in the physicochemical properties of this material (the rate of the interfacial exchange of oxygen and resistivity) and the parameters of its microstructure (tfg length and tortuosity factor) in order to find quantitative relationships. results and discussion the isotopic exchange of oxygen and microstructure of lsm-ysz. in this paper, tests of two symmetrical cells were carried out at t = 850 ° c, po2 = 10 -2 atm. first symmetrical cell was tested for 300 hours, and the other – for 1000 hours. during long-term tests by isotopic exchange of oxygen [1] the kinetics of the interaction of gas-phase oxygen with the test symmetric cells was studied. the parameters of the microstructure of the samples before and after the test was determined by the digital processing of photomicrographs of cross-sections obtained with the scanning electron microscope tescan mira 3 lmu. fig. 1 and fig. 2 show photomicrographs of the cell structure of symmetric lsm-ysz | ysz | lsm-ysz (la0,8sr0,2mno3-0,82zro2 ∙ 0,08y2o3) before the test. since the contrast between the phases of lsm and ysz in the image is absent (fig. 2), image analysis method was used [2], in which it was established that the distribution function of particles sizes is different, and these changes are due to coarsening of the phase lsm (fig. 3). conducted by 3d-reconstruction of the microstructure of the electrode symmetric cells (fig. 4), the dependence of tfg (contact between the lsm | ysz | o2) from time was obtained. the tfg length was defined as referred to the volume number of connections between voxels (voxel = volume pixel) of three types, corresponding to the phases lsm, ysz and pores [4, 5]. it was established that the length of tfg decreased by approximately 15% (fig. 5), whereas the constant of interfacial oxygen exchange k decreased by about 16% after 1000 hours (fig. 6). apparently, the process of interfacial oxygen exchange by tfg is sufficiently fast compared with the exchange of oxygen on individual components lsm and ysz. as a result, a decrease in tfg lenght eventually leads to a reduction of interfacial oxygen exchange constant of the composite cathode material lsm-ysz [7]. conductivity and tortuosity factor of composite materials lsm-ysz. tortuosity factor is statistically calculated by modeling the process of random walk of particles by monte carlo method. n number of stray particles is generated in the required volume. in one step of the program, each particle performs n walks with a given length l. after wandering the amount of mean-square displacements of all particles of a given ensemble is calmodeling of a microstructure and calculation a tortuosity factor for cathodic materials of lsm–ysz 20 № 1 | 2015 chimica techno acta fig. 1. photomicrographs of the cell lsm–ysz | ysz | lsm–ysz, electrolyte thickness is 140 ± 5 μm, electrode – 41 ± 10 μm fig. 2 photomicrographs of the cell lsm– ysz | ysz | lsm–ysz fig. 3 differential forms of distribution function of particles′ sizes fig. 4. 3d-reconstruction of microstructure lsm–ysz, grey – ysz, white – lsm, black – pores; 1 μm = 20 voxels fig. 5. the dependence of relative change of tgf length from time fig. 6. the dependence of relative change of exchange constant from time т = 850 °с, po2 = 10 –2 atm farlenkov a. s., anan’ev m. v. 22 № 1 | 2015 chimica techno acta culated (1). this procedure is repeated a required number of times [3]. tortuosity factor is defined as the ratio of the mean square displacement of the particle in free space to the mean square displacement of the particles in a porous medium (2), see. fig. 7. < > = 1 ({ } + { } + { })2 0 2 0 2 0 = 1 r n x x y y z zt i i i i i i i n ⋅∑ − − − , < > = 1 ({ } + { } + { })2 0 2 0 2 0 = 1 r n x x y y z zt i i i i i i i n ⋅∑ − − − , (1) < > = < > < > 2 2 τϕ r r t free t pore (2) it should also be noted that the magnitude of the tortuosity factor is different from the tortuosity defined as the ratio of the average pore length to the thickness of the porous material. unlike integral microstructure characteristics, such as porosity, the proportion of the phases and their average diameter, tortuosity factor value, depending on the environment for which it is considered to be proportional to the physico-chemical quantities. in the case of pores, tortuosity factor is proportional to the coefficient of permeability; for oxygen-ion electrolyte the diffusion coefficient (ionic conductivity); for electronic conductor the conductivity of the material [5]. for example, the dependence of the diffusion coefficient and the mean-square of displacement from the time is described by the expression (3). d d dt rt= 1 6 < >2⋅ (3) in this part of present work it is shown that the resistivity is reduced by one order of magnitute in the example of the composite material la0,6sr0,4mno3-0,9zro2 ∙ 0,1y2o3 shown that for 1000 hours at t = 800 °c, po2 = 10-2 atm (fig. 10). during the tests, the samples were taken after 40, 500 and 1000 hours of exposure. on the basis of segmentation results of sem images (fig. 8) for the cross sections of the samples before and after testing using the developed original software, the tortuosity factors are calculated for both the porous structure and the phases of lsm and ysz (fig. 9). a decrease in tortuosity factors phase lsm and ysz was discovered; it correlates with the drop in resistivity of the test composite material (fig. 9, 10). the monotonic dependence could not be found for the porous structure. image analysis showed that as a result of the exposure diffusive propagation of lsm and ysz phases occurs, which leads to the enlargement of particles at constant linear dimensions of the sample. process of diffusion growth of ysz phase goes faster than that of lsm, apparently due to the fact that ysz was initially taken in the form of nanopowder (fig. 8). formation of more coherent phase structure comprised in the composite material is the cause of resistivity (fig. 10). prolonged exposure under experimental conditions leads to improved contact between the grains of the components that make up the composite. quantitative parameter characterizing the process of diffusive propagation of lsm and ysz phase is the tortuosity factor. conclusions 3d-reconstruction of the microstructure based on the analysis and sem imaging was carried out, lengths of tfg and fig were calculated, proportion of active tfg and open pores was found in this work. modeling of a microstructure and calculation a tortuosity factor for cathodic materials of lsm–ysz 24 № 1 | 2015 chimica techno acta for symmetric cells (la0,8sr0,2mno30,82zro2 ∙ 0,08y2o3) the relationship between the constant interfacial exchange of oxygen and length tfg was obtained. for a composite material (la0,6sr0,4mno3-0,9zro2 ∙ 0,1y2o3) a correlation between the tortuosity factors of lsm and ysz phases and their resistivity was found. the approach used in this study may be useful in the study of electrochemical fig. 7. evolution of tortuosity factor data in dependence from algorithm steps lsm–ysz before tests lsm–ysz after 1000 hours exposure with t = 800 °с and po2 = 10 –2 atm fig 8. the result of micrographs processing of the cross-section of the composite material lsm–ysz, sem (grey – ysz, white – lsm, black – pores) fig. 9. the dependence of the tortuosity factor of cathode material lsm–ysz from time, т = 800 °c, po2 = 10 –2 atm fig. 10. the dependence of resistivity of the composite material lsm–ysz from time, t = 800 °c, po2 = 10 –2 atm farlenkov a. s., anan’ev m. v. 26 № 1 | 2015 chimica techno acta degradation of materials, where the direct changes in the physical and chemical parameters are difficult, but it is possible to analyze the microstructure parameters. it is necessary for selection of the optimum conditions for the formation and operation of electrochemical devices such as: sofc, electrochemical reformer, electrolysers, sensors etc. acknowledgements the authors thank porotnikova nm, eremin va, medvedev da, and pankratov aa for prodviding us with experimental data, based on which the modeling was carried out. 1. porotnikova n. m. isotopic exchange of oxygen and microstructure of materials on the basis of manganite of lanthanum-strontium and zirconium-itrium electrolyte. ekaterinburg: 2013. 153 p. 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[google scholar]. modeling of a microstructure and calculation a tortuosity factor for cathodic materials of lsm–ysz 17 а. с. фарленков 1, 2, м. в. ананьев 1, 2 1 уральский федеральный университет, 620002, екатеринбург, мира, 19. факс: (343) 375-97-78; тел.: (343) 375-44-72; e-mail: rector@urfu.ru 2 институт высокотемпературной электрохимии уро ран, 620990, екатеринбург, академическая, 20. факс: (343) 374-59-92; тел.: (343) 374-50-89; e-mail: dir@ihte.uran.ru моделирование микроструктуры и расчет фактора извилистости для катодных материалов lsm–ysz* в работе на примере композиционного материала lsm–ysz сравнивается изменение физико-химических свойств (скорости межфазного обмена кислорода и удельного сопротивления) и параметров микроструктуры (протяженности тфг и фактора извилистости) от времени с целью нахождения количественных взаимосвязей. для электродных материалов lsm–ysz проведена 3d-реконструкция микроструктуры и рассчитан фактор извилистости на основе результата анализа изображений рэм с использованием оригинального программного обеспечения. *работа выполнена при финансовой поддержке грантов рффи № 12-03-31847/12 и фцп № 20121.3.1-12-000-2006-004, соглашение № 8713. введение одним из важнейших направлений развития мировой энергетики и энергосбережения является разработка и изучение твердооксидных топливных элементов (тотэ), они относятся к классу химических источников тока, в которых химическая энергия реагентов (топлива и окислителя) электрохимическим способом преобразуется в электрическую. в роли окислителя обычно выступает кислород из воздуха, в роли топлива – водород. тотэ сохраняет способность генерировать электроэнергию все время, пока в него извне поступают реагенты, и отводятся продукты их взаимодействия. существенным преимуществом тотэ является бесшумность работы и отстутствие вредных выбросов при их функционировании, но существует ряд проблем, связанных с деградацией материалов, из которых состоит тотэ. известно, что микроструктура функциональных материалов являету д к 6 61 .7 41 +6 61 .7 23 -1 3 © фарленков а. с., ананьев м. в., 2015 19 № 1 | 2015 chimica techno acta ся определяющим фактором кинетики процессов, протекающих при работе тотэ. источником информации о ней являются изображения, полученные методом растровой электронной микроскопии (рэм). для оценки параметров микроструктуры, анализа двумерных микрофотографий сечений или поверхности исследуемого материала бывает недостаточно. существует ряд параметров микроструктуры, которые можно рассчитать только из трехмерной модели: протяженность трехфазных (тфг) и межфазных (мфг) границ; доля активных тфг, открытых пор; фактор извилистости и т. п. в настоящей работе приводятся основные направления и результаты в области анализа параметров микроструктуры на примере композиционного материала lsm–ysz, а также сравнивается изменение физико-химических свойств этого материала (скорости меж фазного обмена кислорода и удельного сопротивления) и параметров его микроструктуры (протяженности тфг и фактора извилистости) от времени с целью нахождения количественных взаимосвязей. результаты и обсуждение изотопный обмен кислорода и микроструктура lsm–ysz. в работе проводили испытания при t = 850 °с, pо2 = 10 –2 атм двух симметричных ячеек. первую симметричеую ячейку испытывали в течение 300 часов, другую – в течение 1000 часов. в процессе длительных испытаний методом изотопного обмена кислорода [1] исследовали кинетику взаимодействия кислорода газовой фазы с исследуемыми симметричными ячейками. параметры микроструктуры образцов до и после испытаний определяли с помощью цифровой обработки микрофотографий поперечных шлифов, полученных с помощью растрового электронного микроскопа tescan mira 3 lmu. на рис. 1 и на рис. 2 приведены микрофотографии структуры симметричной ячейки lsm– ysz | ysz | lsm–ysz (la0,8sr0,2mno3– 0,82zro2 ∙ 0,08y2o3) до испытаний. поскольку контраст между фазами lsm и ysz на изображении отсутствует (рис. 2), то был применен метод анализа изображений [2], в ходе которого установлено, что функции распределения размеров зерен частиц различны, и эти изменения связаны с огрублением фазы lsm (рис. 3). по проведенной 3d-реконструкции микроструктуры электродов симметричных ячеек (рис. 4), получена зависимость тфг (контакт между lsm | ysz | o2) от времени. протяженность тфг определяли как отнесенное к объему количество соединений между вокселями (от англ. voxel = volume pixel) трех типов, соответствующих фазам lsm, ysz и порам [4, 5]. установлено, что протяженность тфг уменьшилась примерно на 15 % (рис. 5), тогда как константа межфазного обмена кислорода k уменьшилась примерно на 16 % в течение 1000 часов (рис. 6). по-видимому, процесс межфазного обмена кислорода на тфг протекает достаточно быстро по сравнению с обменом кислорода на индивидуальных компонентах lsm и ysz. в результате уменьшение протяженности тфг моделирование микроструктуры и расчет фактора извилистости для катодных материалов lsm–ysz 21 № 1 | 2015 chimica techno acta рис. 1. микрофотография сечения lsm–ysz | ysz | lsm–ysz, толщина электролита 140 ± 5 мкм, электрода – 41 ± 10 мкм рис. 6. зависимость относительного изменения константы обмена от времени, т = 850 °с, pо2 = 10 –2 атм рис. 5. зависимость относительного изменения протяженности трехфазной границы от времени рис. 4. 3d-реконструкция микроструктуры lsm–ysz, серый – ysz, белый – lsm, черный – поры; 1 мкм = 20 вокселей рис. 3. дифференциальные формы функций распределения размеров зерен фаз рис. 2. микрофотографии сечения ячейки lsm–ysz | ysz | lsm–ysz фарленков а. с., ананьев м. в. 23 № 1 | 2015 chimica techno acta со временем приводит к уменьшению константы межфазного обмена кислорода композиционных катодных материалов lsm–ysz [7]. электропроводность и фактор извилистости композиционных материалов lsm–ysz. фактор извилистости статистически рассчитывается с помощью моделирования процесса случайного блуждания частиц методом монте-карло. в интересующем объеме генерируются блуждающие частицы в количестве n штук. за один шаг работы программы каждая частица совершает n блужданий с заданной длиной блуждания l. после этого рассчитывается сумма среднеквадратичных смещений всех частиц заданного ансамбля (1). данная процедура повторяется требуемое количество раз [3]. фактор извилистости определяется как отношение среднеквадратичного смещения частиц в свободном пространстве к среднеквадратичному смещению частиц в пористой среде (2) (рис. 7). < > = 1 ({ } + { } + { })2 0 2 0 2 0 = 1 r n x x y y z zt i i i i i i i n ⋅∑ − − − , < > = 1 ({ } + { } + { })2 0 2 0 2 0 = 1 r n x x y y z zt i i i i i i i n ⋅∑ − − − , (1) < > = < > < > 2 2 τϕ r r t free t pore . (2) здесь стоит также отметить, что величина фактора извилистости отличается от извилистости, которая определяется как отношение средней длины пор к толщине пористого материала. в отличие от интегральных характеристик микроструктуры, таких как пористость, доля фаз и их средний диаметр, величина фактора извилистости, в зависимости от того, для какой среды она считается, может быть пропорциональна физико-химическим величинам. в случае пор фактор извилистости пропорционален коэффициенту газопроницаемости; для кислород-ионного электролита – коэффициенту диффузии (ионной проводимости); для электронного проводника – удельной электропроводности материала [5]. к примеру, зависимость коэффициента диффузии и среднеквадратичного смещения от времени описывается выражением (3). d d dt rt= 1 6 < >2⋅ . (3) в данной части работы на примере композиционного материала la0,6sr0,4mno3–0,9zro2 ∙ 0,1y2o3 показано, что в течение 1000 часов при t = 800 °с, pо2 = 10 –2 атм удельное сопротивление уменьшается в пределах порядка (рис. 10). во время испытаний извлекались образцы-свидетели после 40, 500 и 1000 часов выдержки. на основе результатов сегментации изображений рэм (рис. 8) для сечений образцов до и после испытаний с помощью разработанного оригинального программного обеспечения рассчитаны факторы извилистости, как для пористой структуры, так и для фаз lsm и ysz (рис. 9). обнаружено уменьшение факторов извилистости фаз lsm и ysz, что коррелирует с падением удельного сопротивления исследуемого композиционного материала (рис. 9, 10). для пористой структуры монотонной зависимости обнаружить не удалось. анализ изображений показал, что в результате выдержки происходит дифмоделирование микроструктуры и расчет фактора извилистости для катодных материалов lsm–ysz 25 № 1 | 2015 chimica techno acta фузионное распространение фаз lsm и ysz, приводящее к укрупнению частиц при неизменных линейных размерах самого образца. процесс диффузионного роста фазы ysz протекает быстрее по сравнению с lsm, по-видимому, из-за того, что изначально ysz взят в форме нанопорошка (рис. 8). образование более связной структуры фаз, входящих в состав композиционного материала, служит причиной снижения сопротивления (рис. 10). рис. 7. эволюция значений фактора извилистости в зависимости от шага работы алгоритма lsm–ysz до испытаний lsm–ysz после выдержки в течение 1000 часов при t = 800 °с и pо2 = 10 –2 атм рис. 8. результат обработки микрофотографии сечения композиционного материала lsm–ysz, sem (серый цвет – ysz, белый цвет – lsm, черный цвет – поры) рис. 9. зависимость фактора извилистости катодного материала lsm–ysz от времени, т = 800 °c, pо2 = 10 –2 атм рис. 10. зависимость удельного сопротивления композиционного материала lsm–ysz от времени, t = 800 °c, pо2 = 10 –2 атм фарленков а. с., ананьев м. в. 27 № 1 | 2015 chimica techno acta длительная выдержка в условиях эксперимента приводит к улучшению контакта между зернами компонентов, входящих в состав композиционного материала. количественным параметром, характеризующим процесс диффузного распростронения фаз lsm и ysz, является фактор извилистости. выводы в ходе работы проведена 3d-реконструкция микроструктуры на основе анализа и обработки изображений рэм, рассчитана протяженность тфг и мфг, определены доли активных тфг и открытых пор. для симметричных ячеек (la0,8sr0,2mno3 – 0,82zro2 ∙ 0,08y2o3) получена взаимосвязь между константой межфазного обмена кислорода и протяженностью тфг. для композиционного материала (la0,6sr0,4mno3 – 0,9zro2 ∙ 0,1y2o3) найдена корреляция между факторами извилистости фаз lsm и ysz и удельным сопротивлением. подход, использованный в данной работе, может быть полезным при исследовании процессов деградации электрохимических материалов, где прямое изменение физико-химических параметров затруднено, но возможен анализ параметров микроструктуры. это необходимо для выбора оптимальных условий формирования и эксплуатации электрохимических устройств, таких как тотэ, электрохимические риформеры, электролизеры, сенсоры и др. благодарности авторы выражают благодарность поротниковой н. м., ерёмину в. а., медведеву д. а. и панкратову а. а. за предоставление экспериментальных данных, на основе которых проводилось моделирование. 1. поротникова н. м. // изотопный обмен кислорода и микроструктуры материалов на основе манганитов лантана-стронция и цирконий-итриевого электролита. екатеринбург, 2013. 153 с. 2. ananev m. v., gavrilyuk a. l., bronin d. i., steinberger-wilckens r., mertens j. sofc degradation quantification using image analysis // proceedings of 15th european fuel cell forum. chapter 13 – section b04. lucerne, switzerland, 28 june – 1 july 2011. p. 21–34. 3. ананьев м. в., гаврилюк а. л. // 42-я всероссийская молодежная школа-конференция «современные проблемы математики». екатеринбург, россия, 30 января – 6 февраля 2011. с. 276−279. 4. janardhanan v. m., etc. // journal of powersources. 2008. № 178. p. 368−372. 5. iwai h. etc. // journal of power sources. 2010. № 195. p. 955−961. 6. faes a. etc. // fuel cells. 2009. № 6. p. 841−851. 7. фарленков а. с., ананьев м. в. // проблемы теоретической и экспериментальной химии / xxiii российская молодежная научная конференция. екатеринбург, россия, 23–26 апреля 2013. с. 311−312. моделирование микроструктуры и расчет фактора извилистости для катодных материалов lsm–ysz 1094-2572-1-pb 1094-2573-1-pb 116 d o i: 1 0. 15 82 6/ ch im te ch .2 01 5. 2. 2. 01 2 o. g. reznikova, a. b. darintseva, i. b. murashova chemical technology institute, 28 mira street, 620002 ekaterinburg phone: +7(343) 3754463; e-mail: a.b.darintseva@ustu.ru about the stabilization of the dendritic structure of gg brand copper powder in industry copper powder is recieved under constant current load. surface roughening occurs during evolution of the dendritic particles. it is suggested to create a new impulse of current equal to the initial current density of 3200 a/m2 in order to obtain uniform structure of the precipitate. current load was evaluated by the result of chronopotentiometry research of the dynamics of the dendritic precipitate on cylindrical electrode. four-impulse galvanostatic electrolysis was investigated for the copper powder gg. new current impulse shifts the electrode potential to the cathodic area, crystallization process flows more rapidly. * this work was done under financial support from rfbr № 11-03-002296. © reznikova o. g., darintseva a. b., murashova i. b., 2015 introduction electrolytic metal powders are widely used in many industries. metal powders allow manufacturing by powder metallurgy products with unique characteristics1. in the industrial production of metal powders it is carried out while maintaining a constant current load which is several times higher than the limit. during the industrial electrolysis dendritic sediment was crystallized on cathodes. properties of the finished powders depend on postelectrolysis processing: grinding, sieving, but the main characteristics of the powder are laid at the stage of electrolysis. in galvanostatic electrolysis, sufficiently small particles are formed on the electrode surface that further either stop their growth or develop into dendrites. as the surface of dendritic sediment increases the diameter of the electrode with the sediment y thickness, cathode overvoltage of metal release is reduced2. with the decrease in cathode overvoltage diffusion limitations are reduced, the growth of dendritic sediment is suspended. it was stated3 with the help of studies that achieving the field voltage equalling to 0,54-0,59 b leads to crystallization at the growth in front of solid globules, which are then fused to form a solid crust of a chained sediment. it is offered at certain points in time to submit a new electrode current pulse equal to the initial current density on the electrode. increasing the 117 № 2 | 2015 chimica techno acta about the stabilization of the dendritic structure of gg brand copper powder surge will lead to more intensive deve lopment of cathode surface on the growth front the thin branched particles will again start to crystallize4. with the development of dendritic sediment on the growth front, overvoltage will fall again; then it is necessary to submit a new current pulse on to the electrode. the experimental part studies were carried out in an electrolyte solution to obtain a copper powder brand gg, which contains 23 g/l cu2+ and 150 g/l h2so4. limiting stationary current density was determined using a potentiostat ipc-pro by chrono-voltammetry with linear variation of the potential (fig. 1). according to the calculations steadylimit-stationary current density is ipr.st = 370 a/m 2. then we define the current load, which must be maintained at an electrode of diameter of 2.6 mm and a height of 8 mm. electrolysis was carried out under laboratory conditions with a current density equal to the factory one, which is 3200 a/m2, while it was necessary to set the current i = 226 ma. in the course of galvanostatic electrolysis, a continuous recording of growth of dendritic sediment was conducted with a video camera panasonicsdr-s150gc-s. electrolysis results are shown in fig. 2. when the current is on, overvoltage abruptly shifts to more negative values, followed by a period of small oscillations of the potential, which is followed by a period of large fluctuations. at the time of stopping of active growth of dendritic sediment (1440), overvoltage is significantly reduced. the diameter of the electrode with sediment is increasing until the overvoltage reaches the area of about 0.6 v, which is close to the precipitate ceases to lengthen. actively growing dendritic precipitate was decided to divide into 4 equal lengths of 6 minutes each. through stated interval new current pulse was applied to the electrode, equal to the initial current density. for determining the magnitude current pulse, dynamics studies were conducted at two growth precipitate pulses of current (fig. 3), three (fig. 4) and four (fig. 5). each subsequent pulse of current was calculated from the results of processing video precipitate dendritic growth. current value was determined by the formula i = i · (d0 + 2y)t · h, fig.1. dependence for the determination of the maximum steady-state current density fig. 2. dynamics of changes in the diameter of the electrode with sediment (o) and cathodic overvoltage (line) in the single-pulse electrolysis 118 № 2 | 2015 chimica techno acta reznikova o. g., darintseva a. b., murashova i. b. where i is the initial current density of 3200 a/m2; (d0 + 2y)t is the diameter os an electrode with the sediment at the time of current; h is the height of the electrode, which is assumed to be constant, and equal to 8 mm. when there is 226 ma current after 6 minutes from start of the electrolysis, the electrode diameter was 3.73 mm (fig. 2). in the second pulse at a given initial density, it was necessary to supply current of i = 335 ma. at the time of switching current from 226 ma to 335, overvoltage abruptly increased from 0.68 to 0.79 v. when the same pulse electrolysis is used, the period of active growth was increased and amounted to 2100; the diameter of the electrode with a deposit at the time of stopping the process has reached 5.5 mm. two-pulse electrolysis further increases the time of active growth of dendritic solid (fig. 4), the diameter of the pellet electrode is also increasing. according to the video processing of the growth of the dendritic precipitate after 6 minutes and after the second pulse current electrode had the diameter of 4.91 mm; therefore, the value of the third current pulse is 455 ma. galvanostatic electrolysis with three pulses of current (fig. 4) increases the growth of the active sludge to 2500, the diameter of the electrode with the precipitate at the time the process is stopped is 6 mm. the magnitude of the current load on the fourth pulse is equal to i = 531 ma. amperogram of four-pulse electrolysis is shown in fig. 6. duration of four-staged electrolysis (fig. 5) before the reset of the surge was 3900 sec; diameter of electrode with prefig. 3. changing the diameter of the electrode with sediment (o) and cathodic overvoltage (line) during the two-pulse electrolysis fig. 4. changing the diameter of the electrode with the precipitate (g) and cathode overvoltage (line) in the three-pulse electrolysis fig. 5. changing the diameter of the electrode with sediment (o) and cathodic overvoltage (line) during electrolysis four pulses 119 № 2 | 2015 chimica techno acta about the stabilization of the dendritic structure of gg brand copper powder cipitation has increased to 6.6 mm. current pulse increases the cathode overvoltage; dendritic precipitate at the time of switching current begins to develop more actively. increasing the current load leads to the rapid development of dendritic precipitate in height, which is characterized according to bend d0 + 2y (fig. 3–5). to study the structure of the sediment there were carried dendrit micrographs of thin cross-section of the electrode with the sediment (fig. 7), made with a digital metallographic microscope altamimet 1m. at the time of switching current pulse, more subtle elements of sediment are formed at the growth front. fig. 7b shows a photograph of 1.5 min after the third switching current. cylindrical electrode with dendrit sediment is 3d electrode. the surface of the three-dimensional electrode works unevenly, electrochemical process occurs on the outer surface of the active electrode. speed of electrode process decreases from the outer surface into the thickness of the sediment. the penetration depth λ is the characteristic length of the distance which the speed of the process is reduced by 2.7 times. the penetration depth of the electrode process was calculated from the results of processing of the chronopotentiograms and videos dendritic growth of sediment (fig. 8). when the new current pulse is sent, overvoltage increases abruptly but does not reach its maximum value at the previous pulse. this phenomenon is due to the different penetration depth of electrochemical process in the dendritic layer of sediment. the depth of penetration is defined as half the difference of electrode diameter with sediment at the maximum overvoltage when switching less electrode diamfig. 6. amperogram of four-pulse electrolysis fig. 7. micrographs of a cross section of the electrode with dendritic precipitate. electrolysis time, min: a – 18; b – 19.5. increase x10 120 № 2 | 2015 chimica techno acta reznikova o. g., darintseva a. b., murashova i. b. eter with sediment, corresponding to the value of surge suppressors, equal to the maximum by setting the previous current pulse. for a given current pulses λ was calculated. at current load of 335 ma λ335 = 0,5 · (3,48 – 2,68) = 0,4 mm; at 455 ma λ455 = 0,5 · (4,68 – 3,49) = 0,595 mm; at 531 ma λ531 = 0,5 · (5,47–4,74) = 0,365 mm. unambiguous results in penetration depth values could not be obtained. at the same conductivity of electrolyte solution, the specific surface area of the electrode displaced electro-chemical process on an outer surface of a porous electrode in the case of a larger current5. results and discussion increasing the load current to create the initial current density on the growth front of sediment raises cathode overvoltage, accelerates the process of elongation of dendrites and again leads to the crystallization of thin branched particles. using this mode of the process a significant increase in sediment build-up period can be achieved, while maintaining its structure. 1. neikov o. d., nabojchenko s. s., murashova i. b., gopienko v. g., frishberg i. v., lotsko d. v. handbook of non-ferrous metal powders. technologies and applications. london, n-y. amsterdam: elsevier 2009, 634 p. 2. murashova i. b., darinzeva a. b., rudoy v. m. analysis of growth dynamics of dendrite copper deposit in copper sulfate solutions under the galvanostatic conditions. russian j. of electrochemistry 2010;46(6):611-618. doi: 10.1134/ s10231935100600300. 3. murashova i. b., sokolovskaya e. e., lebed’ a. b., yun’ a. a., bodrova m. l. the formation of dendritic precipitation in the production of electrolytic copper powder. zvetnye metally 2007; 10:46. 4. darinzeva a. b., osipova m. l., murashova i. b. the regulation patterns of dendritic copper sludge gg during electrolysis by changing the cathode surface of the cell. vestnik kazanskogo technologicheskogo universiteta 2012;15:129. 5. ksenzhek o. s., shembel’ e. m., kalinovsky e. m., shustov v. a. electrochemical processes in porous matrixes. kiev: vysshaya shkola; 1983, 220 p. fig. 8. chronopotentiogram (line) and the diameter of the electrode with the precipitate (a) at four-pulse electrolysis. the numbers in the diagram show the number of periods 121 у д к 5 41 .1 35 :6 69 .6 21 о. г. резникова, а. б. даринцева, и. б. мурашова химико-технологический институт, мира, 28, 620002, екатеринбург. тел.: (343) 375-44-63; e-mail: a.b.darintseva@urfu.ru о стабилизации дендритной структуры порошка меди марки gg* в промышленности порошок меди получают при поддержании постоянной токовой нагрузки. по мере развития дендритного осадка происходит огрубление поверхности. для получения более равномерного по структуре осадка предложено через определенные промежутки времени задавать новый импульс тока, равный исходной плотности тока 3200 а/м2. токовую нагрузку определяли по результатам хронопотенциометрических исследований динамики развития дендритного осадка на цилиндрическом электроде. проведено исследование четырехимпульсного гальваностатического электролиза для порошка меди марки gg. новый импульс тока сдвигает потенциал электрода в более отрицательную область, процесс кристаллизации металла начинает протекать более интенсивно. * работа выполнена при финансовой поддержке рффи грант № 11-03-00226. © резникова о. г., даринцева а. б., мурашова и. б., 2015 введение электролитические порошки металлов находят широкое применение во многих областях промышленности. порошки металлов позволяют изготавливать методами порошковой металлургии изделия с уникальными свойствами [1]. в промышленности получение порошков металлов проводят при поддержании постоянной токовой нагрузки, в несколько раз превышающей предельную. в ходе промышленного электролиза на стержневых катодах кристаллизуется дендритный осадок. свойства готовых порошков зависят от послеэлектролизной обработки: размол, рассев, но основные характеристики порошка закладываются именно на стадии электролиза. при гальваностатическом электролизе на поверхности электрода формируются достаточно мелкие частицы, которые в дальнейшем либо останавливают свой рост, либо развиваются в дендриты. по мере развития поверхности дендритного осадка увеличивается диаметр электрода с осадком толщиной у, уменьшается катодное перенапряжение выделения металла [2]. по мере уменьшения катодного перенапряжения снижаются диффузи122 № 2 | 2015 chimica techno acta резникова о. г., даринцева а. б., мурашова и. б. онные ограничения, рост дендритного осадка приостанавливается. исследованиями установлено [3], что достижение области перенапряжения, равной 0,54–0,59 в, приводит к кристаллизации на фронте роста сплошных глобул, которые затем срастаются, образуя сплошную корку закованного осадка. предлагается в определенные моменты времени на электрод подавать новый импульс тока, равный исходной плотности тока на стрежневом электроде. увеличение перенапряжения приведет к более интенсивному развитию катодной поверхности, на фронте роста вновь начнут кристаллизоваться тонкие разветвленные частицы [4]. по мере развития дендритного осадка на фронте роста перенапряжение будет снова снижаться, тогда на электрод необходимо подать новый импульс тока. экспериментальная часть исследования проводили в растворе электролита для получения порошка меди марки gg, который содержит 23 г/л cu2+ и 150 г/л h2so4. предельную стационарную плотность тока определяли с помощью потенциостата ipcpro методом хроно вольтамперометрии при линейном изменении потенциала (рис. 1). согласно расчетам предельная стационарная плотность тока iпр.ст = = 370 а/м2. затем определяем токовую нагрузку, которую необходимо поддерживать на электроде диаметром 2,6 мм и высотой 8 мм. электролиз в лабораторных условиях проводили при плотности тока, равной заводской 3200 а/м2, при этом необходимо было задавать ток i = 226 ма. в ходе гальваностатического электролиза проводили непрерывную видеозапись роста дендритного осадка с помощью видеокамеры panasonicsdr-s150gc-s. результаты электролиза представлены на рис. 2. при включении тока перенапряжение скачком сдвигается в область более отрицательных значений, затем следует период малых колебаний потенциала, который сменяется периодом больших колебаний. к моменту остановки активного роста дендритного осадка рис. 1. зависимость для определения предельной стационарной плотности тока рис. 2. динамика изменения диаметра электрода с осадком (о) и катодного перенапряжения (линия) в ходе одноимпульсного электролиза 123 № 2 | 2015 chimica techno acta о стабилизации дендритной структуры порошка меди марки gg (1440 с) перенапряжение резко снижается. диаметр электрода с осадком увеличивается до тех пор, пока перенапряжение не достигает области около 0,6 в, вблизи которой осадок перестает удлиняться. время активного роста дендритного осадка было решено разбить на 4 равных отрезка по 6 мин. каждый. через указанный интервал времени на электрод подавать новый импульс тока, равный начальной плотности тока. для определения величины импульса тока были проведены исследования динамики роста осадка при двух импульсах тока (рис. 3), при трех (рис. 4) и при четырех (рис. 5). каждый следующий импульс тока рассчитывали исходя из результатов обработки видеозаписи роста дендритного осадка. величину тока определяли по формуле i = i·(d0 + 2y)t · h, где i – исходная плотность тока, равная заводской 3200 а/м2; (d0 + 2y)t – диаметр электрода с осадком к моменту переключения тока; h – высота электрода, которую принимали постоянной, равная 8 мм. при токе 226 ма через 6 мин. от начала электролиза диаметр электрода составил 3,73 мм (рис. 2). на втором импульсе при начально заданной плотности тока необходимо подавать ток i = 335 ма. в момент переключения тока с 226 на 335 ма перенапряжение увеличилось скачком с 0,68 до 0,79 в при одноимпульсном электролизе период активного роста увеличился и составил 2100 с, диаметр электрода с осадком к моменту остановки процесса достиг 5,5 мм. двухимпульсный электролиз еще больше увеличивает время активного роста дендритного осадка (рис. 4), при этом диаметр электрода с осадком также увеличивается. согласно результатам обработки видеозаписи роста дендритного осадка через 6 мин. после второго импульса тока диаметр электрода с осадком составил 4,91 мм, следовательно, величина третьего импульса тока составляет 455 ма. гальваностатический электролиз с тремя импульсами тока (рис. 4) увеличивает время активного роста осадка рис. 3. изменение диаметра электрода с осадком (о) и катодного перенапряжения (линия) в ходе двухимпульсного электролиза рис. 4. изменение диаметра электрода с осадком (о) и катодного перенапряжения (линия) в ходе трехимпульсного электролиза 124 № 2 | 2015 chimica techno acta резникова о. г., даринцева а. б., мурашова и. б. до 2500 с, диаметр электрода с осадком к моменту остановки процесса составляет 6 мм. величина токовой нагрузки на четвертом импульсе равна i = 531 ма. амперограмма для четырех импульсного электролиза представлена на рис. 6. продолжительность четырехступенчатого электролиза (рис. 5) до сброса перенапряжения составила 3900 с, диаметр электрода с осадком увеличился до 6,6 мм. импульс тока увеличивает катодное перенапряжение, дендритный осадок в момент переключения тока начинает более активно развиваться. увеличение токовой нагрузки приводит к быстрому развитию дендритного осадка в высоту, что характеризуется перегибами зависимости d0+2y (рис. 3–5). для исследования структуры дендритного осадка выполнены микрофотографии шлифов поперечного среза электрода с осадком (рис. 7), выполненные с помощью цифрового металлографического микроскопа altamimet 1м. в момент переключения импульса тока на фронте роста образуются более тонкие элементы осадка. на рис. 7б представлена фотография через 1,5 мин. после третьего переключения тока. цилиндрический электрод с дендритным осадком представляет собой трехмерный электрод. поверхность трехмерного электрода работает неравномерно, электрохимический процесс протекает активно на внешней поверхности электрода. скорость электродного процесса снижается от внешней поверхности вглубь толщины осадка. глубина проникновения λ – это характеристическая длина на расстоянии которой скорость процесса снижается в 2,7 раза. глубину проникновения электродного процесса рассчитывали исходя из результатов обработки полученных хронопотенциограммы и видеозаписи роста дендритного осадка (рис. 8). при включении нового импульса тока перенапряжение скачком увеличивается, но не достигает максимального значения при предыдущем импульсе. рис. 5. изменение диаметра электрода с осадком (о) и катодного перенапряжения (линия) в ходе четырехимпульсного электролиза рис. 6. амперограмма четырехимпульсного электролиза 125 № 2 | 2015 chimica techno acta о стабилизации дендритной структуры порошка меди марки gg предположительно, такое явление связано с различной глубиной проникновения электрохимического процесса в слое дендритного осадка. глубину проникновения определяли как половину разности диаметра электрода с осадком при максимальном значении перенапряжения в момент переключения за вычетом диаметра электрода с осадком, соответствующий значению перенапряжения, равного максимальному при задании предыдущего импульса тока. для заданных импульсов тока выполнен расчет λ. при токовой нагрузке 335 ма λ335 = 0,5·(3,48 – 2,68) = 0,4 мм; при 455 ма λ455 = 0,5·(4,68 – 3,49) = 0,595 мм; при 531 ма λ531 = 0,5·(5,47 – 4,74) = 0,365 мм. однозначных результатов в значениях глубины проникновения получить не удалось. при одинаковой электропроводности раствора электролита, удельной поверхности электрода электрохимический процесс вытесняется на внешнюю поверхность пористого электрода в случае задания большего тока [5]. результаты и обсуждение повышение токовой нагрузки до создания первоначальной плотности тока на фронте роста осадка поднимает катодное перенапряжение, ускоряет процесс удлинения дендритов и приводит вновь к кристаллизации тонких разветвленных частиц. используя такой режим проведения процесса можно добиться значительного увеличения периода наращивания осадка с сохранением его структуры. рис. 7. микрофотографии поперечного среза электрода с дендритным осадком. время электролиза, мин.: а – 18; б – 19,5. увеличение х10 рис. 8. хронопотенциограмма (линия) и диаметр электрода с осадком (о) при четырехимпульсном электролизе. цифрами на диаграмме показаны номера периодов 126 № 2 | 2015 chimica techno acta резникова о. г., даринцева а. б., мурашова и. б. 1. neikov o. d., nabojchenko s. s., murashova i. b., gopienko v. g., frishberg i. v., lotsko d. v. handbook of non-ferrous metal powders. technologies and applications. london, n-y, amsterdam: elsevier, 2009. 634 p. 2. мурашова и. б., даринцева а. б., рудой в. м. анализ динамики роста дендритного медного осадка в гальваностатических условиях в растворах сульфата меди // электрохимия. 2010. т. 46. с. 649. 3. мурашова и. б., соколовская е. е., лебедь а. б., юнь а. а., бодрова м. л. формирование дендритных осадков при производстве электролитических медных порошков // цветные металлы. 2007. № 10. с. 46. 4. даринцева а. б., осипова м. л., мурашова и. б. регулирование структуры дендритного медного осадка gg в ходе его электролиза изменением катодной поверхности электролизера // вестн. казан. технолог. ун-та. 2012. т. 15. с. 129. 5. ксенжек о. с., шембель е. м., калиновский е. а., шустов в. а. электрохимические процессы в пористых матрицах. киев: высшая школа, 1983. 220 с. рекомендуем при цитировании данно статьи следующую ссылку: reznikova o. g., darintseva a. b., murashova i. b. about the stabilization of the dendritic structure of gg brand copper powder // chimica techno acta. 2015. vol. 2. № 2. p. 116–126. 78 do i: 1 0. 15 82 6/ ch im te ch .2 01 5. 2. 2. 00 8 komarovskih n. v.*1, fomina l. v.2, beznosyuk s. а.1 1altai state university, 61 lenin street, 656049 barnaul. fax: +7(385) 266-66-82; phone: +7(385) 266-66-82; e-mail: bsa1953@mail.ru 2angarsk state technical academy, 60 chaikovskogo street, 665835 angarsk fax: +7(3955) 671832; phone: (3955) 671 832; e-mail: flvbaan@mail.ru physicochemical conditions of gaas/gaas x n y /gan nanochips stability in this work the study of the stability nanochips gaas / gaas x n y / gan is presented. for the calculation of parameters used quantum-chemical and thermodynamic approaches. the calculations of the surface free energy nanochips within the models used show that a significant contribution to the crystalline structure stability of the gan layer is the molar concentration of nitrogen atoms in the intermediate layer gaas x n y nanochips gaas / gaas x n y / gan. introduction interest to wide-band semiconductors based on iii-nitride compounds is associated with high chemical, thermal and radiation resistance of these compounds. the most demanded out of them is gallium nitride (gan), which is obtained in the form of films by heteroepitaxial growth method. structur of gan films is a function of the properties used for the growth of its substrates. among the materials used as substrate for the growth of the films of gallium nitride (1), attention is attracted by gallium arsenide (gaas). its advantage is in its low cost compared to other mate-als and in the use of new technological solutions for the formation of the gan films on its surface (2). another advantage of gaas substrates is the possibility to use different crystallographic surfaces for gan film growth, which allows setting epitaxial growth orientation of the surface layer of gan crystal structure of gan at the initial stage. nitridation process of gaas surface occurs as a result of its processing with active nitrogen radicals, which are produced in a powerful high-frequency plasma charge (2). the peculiarity of this method is that the active nitrogen radicals © komarovskih n. v., fomina l. v., beznosyuk s .а., 2015 80 № 1 | 2015 chimica techno acta physicochemical conditions of gaas/gaas x n y /gan nanochips stability do not violate the crystalline structure of the substrate-lattice and at the same time having a high mobility in its surface-layer, perform atoms substitution, similar to the growth of monolayers of liquid phase. as a result of this substitution heterostructure gaas / gaasxny / gan, which at the nanoscale can be called nanochips (from «chip» – a piece) is formed. in connection to the noted above, the results of theoretical research by means of quantum-chemical methods and thermodynamic stability of nanochips gaas / gaasxny / gan, formed on the crystallographic surfaces of gaas (001) and (111), are presented in the paper. this study was conducted as computer experiment. fundamentals of computer experiment based on the characteristics of the cubic and hexagonal structure type of gan films (1), it can be assumed that the use of either gaas (001) surface for epitaxial growth of gan film, gan (001) cubic structure should be formed; using gaas (111), gan (111); it is likely that of gallium nitride film with hexagonal structure (0001) will be formed as well. in this paper, for modeling of nanochips gaas / gaasxny / gan, two structures of substrates gaas were adopted: 1) a structure containing 9600 atoms, which has thickness of ~ 4.5 nm in the orientation [001] (surface area of forming a nitride film is ~ 48 nm2); a structure containing 9096 atoms, which has thickness of ~ 3.8 nm in the orientation [111] (surface area of forming a nitride film is ~ 27 nm2). for the formation of the transition layer of gaasxny a chaotic substitution of the as atoms into n atoms in the anion sublattice of gallium arsenide of both structures was performed on the maximum depth of 4 anion layers in the amount from 40% to 90%. as a result of this substitution heterostructure gaas / gaasxny was formed. then in order to produce the final formation of nanochips of gaas / gaasxny / gan layer on gaas / gaasxny, a layer of gan was placed by overlapping. as a result, we obtained model with the following compositions: gaas (001) / gaasxny / gan (001); gaas (001) / gaasxny / gan (0001); gaas (111) / gaasxny / gan (111); gaas (111) / gaasxny / gan (0001) for each of the models, nanochips x, y are changed in the range from 40 to 90%. computer experiment on the properties of nanochips was conducted using complex computer programs «computer nanotechnology» (3). in the adiabatic approximation with the help of the method of steepest descent on the surface of potential energy of the nuclei stable positions of the atoms in nanochips were found. energy of the system of nuclei is represented within the pair approximation. for a system of m atoms energy has the form: e s rij ij ij j m i m = == ∑∑12 11 ε ( ) (1) where m is the total number of atoms in the nanosystem; sij is atoms adjacency matrix, containing information about the atomic structure of the bond graph; εij is the energy of pair interaction between iatom and j-atom, depending on the distance between the atoms – rij (4). the matrix of the adjacency graph of bond graph of nanochips gaas / gaasxny / gan is determined by the topology of the 82 № 1 | 2015 chimica techno acta komarovskih n. v., fomina l. v., beznosyuk s .а. covalent bonds of the atoms of the structures on their first coordination sphere. to calculate the parameters of the potential interactions of the atoms in the simulated nanostructures, the method of nonlocal orbital-shell density function (osdf) (5) was used; using it energy u0 and length r0 of chemical bonds were found. for a pair of atoms of ga-n: r0 = 0,201 nm; u0 = –1,249 ev (–120.30 kj / mol) (6), for a pair of atoms for ga-as: r0 = 0,260 nm, u0 = –2,217 ev (–196.7 kj / mol) (5). then nanochips gaas / gaasxny / gan resistance was viewed from the position of equilibrium thermodynamics. since nanochips gaas / gaasxny / gan were formed by the superposition of two crystal structures, it is necessary to introduce the concept of the surface the interface between two contacting bodies. one of the properties of such a surface is the surface energy (helmholtz free energy), which is the excess of the energy of the surface layer between the contacting phases per unit of area dividing the surface. in general terms, this energy is defined by: f = u – ts, (2) where u is internal nanochip energy, s is nanochip entropy, t is absolute temperature of the thermostat. the internal energy u of the nanostructures is determined by the method of steepest descent on the potential energy surface (1). the entropy of the studied systems can be calculated within the framework of statistical thermodynamics, where it is given by the boltzmann equation: s = k ln w, (3) where k is boltzmann constant, w is statistic weight or equilibrium thermodynamic probability of the nanosystem. under the assumption that the nitrogen atoms are identical indistinguishable particles and their distribution in the surfacelayer of gallium arsenide will determine the macrostate for thewhole of the transition layer gaasxny. this macrostate can be realized in a large number of microstates by rearrangement of the atoms of nitrogen and arsenic. at its core, the distribution of the nitrogen atoms in the surface layer of gaas and, consequently, the formation of the transition layer gaasxny, obey the laws of statistical mechanics. free surface energy of the heterostructure gaas / gaasxny / gan can be defined by the formula: u e e e / /x y x y = − − − gaas gaas n gan gan gaas gaas n/ . (4) for the calculation of the helmholtz free energy the temperature range from 500 c to 900 °c was selected. the choice of this temperature range is due to the experimental data for obtaining gan films on the gaas substrate. the helmholtz free energy at absolute zero (f = u) and at room temperature were also calculated. analysis of the results of the computer experiment the calculation results show that at a certain concentration of nitrogen atoms in the layer gaasxny with increasing of the temperature, energy stability of the nanochip gaas / gaasxny / gan itself is raising. such dependence is observed for each of the computational models. in our model, we can assume that the formation of a particular crystal structure (hexagonal or cubic) of nanolayer gan does not depend on the temperature of the process, as suggested by the authors of the experimental works (2). the molar concentration of nitrogen in the intermediate layer gaasxny of gaas / gaasxny / gan nanochip can be seen as an influencial factor 84 № 1 | 2015 chimica techno acta in this case. consider the dependence of the helmholtz free energy of gaas / gaasxny / gan nanochips from mole fraction of nitrogen in the intermediate layer gaasxny. (fig. 1, 2). figure 1 represents the variation of the helmholtz free energy of gaas / gaasxny / gan nanochip with the original orientation of the substrate gaas (001); figure 2, with the original orientation of the substrate gaas (111). analysis of the curves in figure 1 reveals that it is more preferable to form a cubic gan structure onthe substrate gaas (001) with the account for the formation of the gaasxny intermediate layer in the range of molar concentrations in this layer of nitrogen atoms to about 45% of energy; when the concentration of nitrogen is above 45%, energatically favored is the hexagonal gan structure. in case of gaas (111) substrate gaas (see fig. 2): at a mass concentration of nitrogen in the interlayer gaasxny to ~60% and more than 75%, most preferable is the cubic structure of gan nanolayer on the substrate; when nitrogen concentration is in the range of 60–75% more stable is the hexagonal gan nanolayer structure on the substrate gaas (111). conclusion computer experiment showed that the formation of gallium nitride nanolayer both of hexagonal and cubic structures is possible on the surface of gallium arsenide. this is consistent with the known experiment results (2). in this case, the main influencing factor is the molar concentration of nitrogen atoms in the intermediate layer gaasxny, which is formed as a result of the substitution of arsenic atoms on the nitrogen atoms in the surface layer of the gaas substrate of gaas / gaasxny /gan nanochip. 1. bahtizin r. z., schue ch.-zh.,schue ch.-k., sakurai, t. ufn. 2004; 174:383–405. [google scholar]. fig. 1 the dependence of the helmholtz free energy of heterostructure gaas (001) / gaasxny / gan form mole fraction of nitrogen in the intermediate layer gaasxny fig. 2 the dependence of the helmholtz free energy of heterostructure gaas (111) / gaasxny / gan from mole fraction of nitrogen in the intermediate layer gaasxny physicochemical conditions of gaas/gaas x n y /gan nanochips stability 86 № 1 | 2015 chimica techno acta 2. sukach g. a., kidalov v. v., kotlyarovskiy m. b., potapenko e. p. zhurnal technicheskoy phiziki. 2003; 73:59–62. [google scholar]. 3. beznosyuk s. a., zhukovsky m. s., vazhenin s. v., lerh ya. v. svidetel'stvo about state registration of program for evm no. 2009613043 from 10 june 2009. [google scholar]. 4. zhukovsky m. s., beznosyuk s. a., potekaev a. i., starostenkov m. d. theory of computer nanoinzhenering of biomimetic system. tomsk: ntl; 2011:236 p. [google scholar]. 5. beznosyuk s. a., potekaev a. i., zhukovsky m. s., zhukovskaya t. m., fomina l. v. multilevel structure, physico-chemical and informational properties of substance. tomsk: ntl; 2005:264 p. [google scholar]. 6. komarovskih n. v., beznosyuk s. a., fomina l. v. fundamental problems of modern materials technology. 2009; 6:91–94. [google scholar]. komarovskih n. v., fomina l. v., beznosyuk s .а. 79 у д к 5 43 .7 +5 39 .2 н. в. комаровских1, л. в. фомина2, с. а. безносюк1 1алтайский государственный университет, пр. ленина, 61, 656049, барнаул. факс: (3852) 66-66-82; тел: (3852) 66-66-82; e-mail: bsa1953@mail.ru 2 ангарская государственная техническая академия, ул. чайковского, 60, 665835, ангарск. факс: (3955) 67-18-32; тел: (3955) 67-18-32; e-mail: flvbaan@mail.ru физико-химические условия устойчивости наночипов gaas/gaas x n y /gan в работе представлено исследование устойчивости наночипов gaas/ gaas x n y /gan. для расчетов параметров применялись квантово-химический и термодинамических подходы. расчеты свободной поверхностной энергии наночипов в рамках используемых моделей показывают, что существенный вклад на кристаллическую структуру слоя gan носит мольная концентрация атомов азота в промежуточном слое gaas x nнаночипа gaas/gaas x n y /gan. © комаровских н. в., фомина л. в., безносюк с. а., 2015 введение интерес к широкозонным полупроводниковым соединениям iii-нитридов связан с высокой химической, термической и радиационной стойкостью этих соединений. наиболее востребован среди них нитрид галлия (gan), который получают в виде пленок методом гетероэпитаксиального роста. структура пленок gan является функцией свойств используемых для его роста подложек. среди материалов, используемых в качестве подложки для роста пленок нитрида галлия [1], внимание привлекает арсенид галлия (gaas). его преимущество заключается в дешевизне по сравнению с другими материалами и использование новых технологических решений для формирования пленки gan на его поверхности [2]. другое преимущество подложек gaas – возможность применения разных кристаллографических поверхностей для роста пленок gan, что позволяет задавать уже на первоначальном этапе эпитаксиального роста ориентацию поверхности кристаллической структуры слоя gan. процесс нитридизации поверхности gaas происходит в результате ее 81 № 1 | 2015 chimica techno acta обработки активными радикалами азота, которые получают в мощном высокочастотном плазменном разряде [2]. особенность этого метода заключается в том, что активные радикалы азота не нарушают структуры кристаллической решетки подложки и в то же время, имея высокую подвижность в ее поверхностном слое, осуществляют замещение атомов, аналогичное росту монослоев из жидкой фазы. в результате такого замещения образуется гетероструктура gaas/gaasxny/gan, которую в наномасштабе можно назвать наночипом (от «чип» – кусок) в связи с отмеченным выше в работе представлены результаты теоретического исследования с помощью квантово-химических и термодинамических методов устойчивости наночипов gaas/gaasxny/gan, сформированных на кристаллографических поверхностях арсенида галлия (001) и (111). данное исследование было проведено в виде компьютерного эксперимента. основы компьютерного эксперимента исходя из особенностей кубического и гексагонального структурного типа пленок gan [1], можно предположить, что при использовании поверхности gaas (001) для эпитаксиального роста пленки gan должна формироваться кубическая структура gan ориентацией (001), при использовании поверхности gaas (111) – структура gan ориентацией (111), а также вполне вероятно образование пленки нитрида галлия с гексагональной структурой ориентацией (0001). в данной работе для моделирования наночипов gaas/gaasxny/gan, были приняты две структуры подложек gaas: 1) структура, содержащая 9600 атомов, имеющая в направлении [001] толщину ~ 4,5 нм (площадь поверхности формирования нитридной пленки ~ 48 нм2); структура, содержащая 9096 атомов, имеющая в направлении [111] толщину ~ 3,8 нм (площадь поверхности формирования нитридной пленки ~ 27 нм2). для формирования переходного слоя gaasxnyбыло произведено хаотическое замещение атомов as на атомы n в анионной подрешетке арсенида галлия обеих структур на максимальную глубину в 4 анионных слоя в количестве от 40 до 90 %. в результате такого замещения была сформирована гетероструктура gaas/gaasxny. далее для окончательного формирования наночипа gaas/gaasxny/gan на слой gaas/gaasxny путем наложения был помещен слой gan. в итоге получены модели следующего состава: gaas(001)/gaasxny/gan(001); gaas(001)/gaasxny/gan(0001); gaas(111)/gaasxny/gan(111); gaas(111)/gaasxny/gan(0001) для каждой из моделей наночипов x, y изменяются в пределах от 40 до 90 %. компьютерный эксперимент по исследованию свойств наночипов проводился с использованием комплекса программ для эвм «компьютерная нанотехнология» [3]. в адиабатическом приближении методом наискорейшего спуска по поверхности потенциальной энергии ядер находились устойчивые положения атомов в наночипах. энергия системы ядер представляется в рамках парного приближения. для системы м атомов энергия имеет вид: физико-химические условия устойчивости наночипов gaas/gaas x n y /gan 83 № 1 | 2015 chimica techno acta e s rij ij ij j m i m = == ∑∑12 11 ε ( ) , (1) где m – общее число атомов наносистемы; sij – матрица смежности атомов, содержащая информацию о связевом графе атомной структуры; εij – энергия парного взаимодействия i-атома с j-атомом, зависящая от расстояния между атомами – rij [4]. матрица графа смежности связевого графа наночипов gaas/gaasxny/gan определялась топологией ковалентных связей атомов изучаемых структур на их первой координационной сфере. для расчета параметров потенциалов взаимодействий атомов в моделируемых наноразмерных структурах был использован метод нелокального орбитально-оболочечного функционала плотности (оофп) [5], с помощью которого найдены энергии u0 и длины r0 химических связей. для пары атомов ga–n: r0 = 0,201 нм; u0 = –1,249 эв, (–120,30 кдж/моль) [6], для пары атомов ga-as: r0 = 0,260 нм, u0 = –2,217 эв (–196,7 кдж/моль) [5]. далее устойчивость наночипов gaas/gaasxny/gan рассматривалась с позиции равновесной термодинамики. так как наночипы gaas/gaasxny/gan были сформированы путем наложения двух кристаллических структур, то следует ввести понятие поверхности – границы раздела между двумя контактирующими структурами. одним из свойств такой поверхности является поверхностная энергия (свободная энергия гельмгольца), представляющая собой избыток энергии поверхностного слоя между соприкасающимися фазами, приходящегося на единицу площади разделяющей поверхности. в общем виде эта энергия определяется соотношением: f = u – ts, (2) где u – внутренняя энергия наночипа, s – энтропия наночипа, t – абсолютная температура термостата. внутренняя энергия u наноструктур определяется в рамках метода наискорейшего спуска по поверхности потенциальной энергии (1). энтропию изучаемых систем можно рассчитать в рамках статистической термодинамики, где она задается формулой больцмана: s = k ln w, (3) здесь k – постоянная больцмана, w – статистический вес или термодинамическая вероятность равновесного состояния наносистемы. в предположении того, что атомы азота являются тождественно неразличимыми частицами и их распределение в поверхностном слое арсенида галлия будет задавать макросостояние всего переходного слоя gaasxny. такое макросостояние может быть реализовано большим числом микросостояний за счет перестановки атомов азота и мышьяка. по своей сути распределение атомов азота в приповерхностном слое gaas и, соответственно, формирование переходного слоя gaasxny, подчиняется законам статистической механики. свободную поверхностную энергию гетероструктур gaas/gaasxny/ gan можно определить по формуле: u e e e / /x y x y = − − − gaas gaas n gan gan gaas gaas n/ . (4) для вычисления свободной энергии гельмгольца был выбран температурный интервал от 500 до 900 °с. выбор такого температурного интеркомаровских н. в., фомина л. в., безносюк с. а. 85 № 1 | 2015 chimica techno acta вала обусловлен экспериментальными данными по получению пленок gan на подложке gaas. также была рассчитана свободная энергия гельмгольца при абсолютном нуле температур (f = u) и при комнатной температуре. анализ результатов компьютерного эксперимента результаты расчета показывают, что при определенной концентрации атомов азота в слое gaasxny с ростом температуры увеличивается энергетическая стабильность собственно наночипа gaas/gaasxny/gan. такая зависимость наблюдается для каждой из расчетных моделей. в рамках нашей модели можно предположить, что формирование определенной кристаллической структуры (гексагональной или кубической) нанослоя gan не зависит от температуры технологического процесса, как это было предложено авторами экспериментальных работ [2]. влияющим фактором в нашем случае, вероятно, выступает мольная концентрация азота в промежуточном слое gaasxny наночипа gaas/gaasxny/gan. рассмотрим зависимость свободной энергии гельмгольца наночипов gaas/ gaasxny/gan от мольной доли азота в промежуточном слое gaasxny. (рис. 1, 2). рисунок 1 представляет изменение свободной энергии гельмгольца наночипов gaas/gaasxny/gan с исходной ориентацией подложки gaas (001); рисунок 2 – с исходной ориентацией подложки gaas (111). анализ кривых на рисунке 1 показывает, что на подложке gaas (001) с учетом образования промежуточного слоя gaasxny в интервале мольной концентрации в этом слое атомов азота до ~ 45 % энергетически более предпочтительно формирование кубической структуры gan; при концентрацих азота выше 45 % энергетически предпочтительной является гексагональная структура gan. в случае подложки gaas (111) (рис. 2): при массовой концентрации азота в промежуточном слое gaasxny до ~60 % и свыше 75 % наиболее предпочтительно формирование кубической структуры рис. 1. зависимость свободной энергии гельмгольца гетероструктур gaas(001)/ gaasxny/gan от мольной доли азота в промежуточном слое gaasxny рис. 2. зависимость свободной энергии гельмгольца гетероструктур gaas(111)/ gaasxny/gan от мольной доли азота в промежуточном слое gaasxny физико-химические условия устойчивости наночипов gaas/gaas x n y /gan 87 № 1 | 2015 chimica techno acta нанослоя gan на подложке; в интервале концентрации азота 60–75 % более устойчивой на подложке gaas (111) является нанослой gan в гексагональной структуре. заключение компьютерный эксперимент показал, что на поверхности арсенида галлия возможно формирование нанослоя нитрида галлия как в гексагональной, так и в кубической структурах. это согласуется с известными результатами эксперимента [2]. при этом основным влияющим фактором является мольная концентрация атомов азота в промежуточном слое gaasxny, который формируется в результате замещения атомов мышьяка на атомы азота в поверхностном слое подложки gaas, наночипа gaas/gaasxny/gan. 1. бахтизин р. з., щуе ч.-ж., щуе ч.-к., ву к.-х., сакурай т. // уфн. 2004. т. 174. с. 383–405. 2. сукач г. а., кидалов в. в., котляровский м. б., потапенко е. п. // жтф. 2003. т. 73. с. 59–62. 3. свидетельство о государственной регистрации программы для эвм № 2009613043 от 10 июня 2009 г. // с. а. безносюк, м. с. жуковский, с. в. важенин, я. в. лерх. 4. жуковский м. с., безносюк с. а., потекаев а. и., старостенков м. д. теоретические основы компьютерного наноинжиниринга биомиметических наносистем. томск: нтл, 2011. 236 с. 5. безносюк с. а., потекаев а. и., жуковский м. с., жуковская т. м., фомина л. в. многоуровневое строение, физико-химические и информационные свойства вещества. томск: изд-во нтл, 2005. 264 с. 6. комаровских н. в., безносюк с. а., фомина л. в. // фундаментальные проблемы современного материаловедения. 2009. т. 6. с. 91–94. комаровских н. в., фомина л. в., безносюк с. а. 1100-2584-1-pb 1100-2588-1-pb cta_v3_№1.cdr 24 d o i: 1 0. 15 82 6/ ch im te ch .2 01 6. 3. 1. 00 2 m. g. ivanov, a. v. nechaev, v. s. mokrushin, o. i. ostroukhova institute of fundamental education, institute of chemical technology, mira 28, 620002, ekaterinburg. phone: (343) 375-45-68. e-mail: a.v.nechaev@urfu.ru the effect of fluorine-containing inhibitors of corrosion of copper in atmospheric conditions the effect of fluorine-containing inhibitors of corrosion of copper in atmospheric conditions was studied by method of removing anodic polarization curves and corrosion of full-scale tests. the introduction of the inhibiting compositions as corrosion inhibitor of copper polyfluorinated amines leads to a decrease of the peak current of active dissolution of copper, which increases the corrosion resistance of copper wire rod during transportation in various climate conditions. key words: polarization curves, polyfluorinated amines, copper wire rods, corrosion inhibitor. © ivanov m. g., nechaev a. v., mokrushin v. s., ostroukhova o. i., 2016 introduction the various amines are the effective corrosion inhibitors of copper in aggressive media. the inhibitory effect of some derivatives of triazole is caused by their adsorption and formation of the insoluble complex of copper on the copper surface [1, 2]. therefore, the use of amines in the composition of the inhibiting composition can provide the protection from corrosion of copper rod for transportation. experimental part the paper studies the anodic behavior of copper deposited on its surface preservative coating the inhibitory composition, containing polyfluorinated amine – amine polyferrocenylsilane: нсf2-cf2cf2-cf2-o-ch2-ch2-nh2, which was synthesized at the department of technology of organic synthesis, chemical technology institute, urals federal university. for accelerated evaluation of the protective action of inhibiting compositions and optimization of the composition of the preservative coating was used the method of removing anodic polarization curves. the polarization curves were recorded on a potentiostat-galvanostat ipc-pro in potentiometric mode at a linear scan rate of potential of 2 mv/s in a three-electrode glass cell with sepa25 № 1 | 2016 chimica techno acta rated anode and cathode spaces in 0.5 m nacl solution at 25 °c. the silver chloride electrode was served as the reference electrode in a saturated solution of potassium chloride. the potentials were calculated on present n.v.sh. the platinum sheet was served as the auxiliary electrode. as object of study was used copper brand m00k (99.99 % pure) for the manufacture of copper wire rod. to remove the polarization curves were used cylindrical rods of copper by diameter 8 mm with a total working area of 4 cm2. the field corrosion tests were conducted on samples of copper rod of length 150 mm and diameter 8 mm in the salt spray chamber ascott 120 plus. the protective constitutions of inhibiting compositions were applied on a degreased with acetone, the working surface of the copper electrodes by dipping them in the solutions of inhibiting compositions for 15 seconds. results and discussion the studies have shown that in the absence of inhibiting on the metal surface films anodic polarization curve for copper has the form characteristic of soluble active metal, followed by passivation. when potentials are of about 0.18-0.19 changing to the passive state starts in copper electrode starts. the polarization curves for copper, pre-treated in solutions of isopropanol with different content of polyfluorinated amine (pfa) are presented in the below figure. as can be seen from fig. when applied to a metal surface of the copper protective film from solutions containing the pfa, there was a significant decrease of peak current of active dissolution of copper on the polarization curve, indicating a slowing of the rate of anodic dissolution of copper and the inhibition of anodic reaction. from these data it follows that the magnitude of the limiting current of anodic dissolution of copper depends on the concentration of the pfa. the maximum anodic current density observed on polarization curves decreases with increasing concentrations of pfa and reaches a minimum value of 3.32 % solution of inhibiting compositions on the basis of the pfa, which may indicate the increased corrosion resistance of copper is inhibited. however, only the character of the polarization curves does not allow us to judge the influence of inhibitor on the corrosion resistance of copper in atmospheric conditions. so in addition to the electrochemical measurements were conducted in situ corrosion testing of samples of copper wire rod in the salt spray chamber ascott 120 plus. the results of electrochemical measurements are consistent with the data fig. the polarization curves for copper, inhibiting composition treated with different concentration of pfa in isopropanol, 0.5 m sodium chloride solution: 1 – pure copper; 2 – 0% the pfa; 3 – 0,25 % pfa; 4 – 0.5% and the pfa; 5 – 0,75 % pfa; 6 – 1 % pfa; 7 – 1.25% of the pfa; 8 – 1,66 % pfa; 9 – 3,32 % pfa the effect of fluorine-containing inhibitors of corrosion of copper in atmospheric conditions 26 № 1 | 2016 chimica techno acta of corrosion tests. the corrosion tests showed that pockets of corrosion on the copper samples without inhibiting compositions and treated with clean isopropanol appear already in the first days of exposure of samples in the chamber. at the same time on the samples treated in an anhydrous solution of inhibiting compositions on the basis of the pfa, corrosion lesions appear in 2-4 days depending on the concentration of the pfa. of investigated compounds inhibiting compositions the best results (up to 4 days) were achieved for 3,32 % solution of inhibiting compositions on the basis of the pfa. thus, when used in inhibiting compositions as corrosion inhibitor of copper polyfluorinated amines can increase the corrosion resistance of copper wire rod during transportation in extreme conditions. 1. tsygankova l. e., rumiantsev a. f. the effect of oil coating and anionic composition of electrolyte on the corrosion inhibition of copper by benzotriazole in acidic media corrosion: materials, protection. 2006;12:31–36. 2. kuznetsov y. i., agafonkin m. o., shikhaliev h. s., andreeva n. p., potapov a. y. adsorption and passivation of copper by triazoles in neutral aqueous solutions corrosion: materials, protection. 2014;7:33–39. ivanov m. g., nechaev a. v., mokrushin v. s., ostroukhova o. i. 27 у д к 6 65 .6 68 .4 м. г. иванов, а. в. нечаев, в. с. мокрушин, о. и. остроухова институт фундаментального образования, химико-технологический институт, 620002, екатеринбург, ул. мира, 28 тел.: (343) 375-45-68 e-mail: a.v.nechaev@urfu.ru влияние фторсодержащих ингибиторов на коррозию меди в атмосферных условиях методом снятия анодных поляризационных кривых и натурных коррозионных испытаний изучено влияние фторсодержащих ингибиторов на коррозию меди в атмосферных условиях. введение в состав ингибирующих композиций в качестве замедлителя коррозии меди полифторированных аминов приводит к снижению максимума тока активного растворения меди, что повышает коррозионную стойкость медной катанки при ее транспортировке в различных климатических условиях. ключевые слова: поляризационные кривые, полифторированные амины, медная катанка, замедлитель коррозии. © иванов м. г., нечаев а. в., мокрушин в. с., остроухова о. и., 2016 введение различные амины являются эффективными ингибиторами коррозии меди в агрессивных средах. тормозящее действие производных ряда триазола обусловливается их адсорб цией и образованием на поверхности меди нерастворимого комплекса меди [1, 2]. поэтому использование аминов в составе ингибирующей композиции может обеспечить защиту от коррозии медной катанки при ее транспортировке. экспериментальная часть в работе изучено анодное поведение меди с нанесенным на ее поверхность консервационным покрытием ингибирующей композицией, содержащей в своем составе полифторированный амин – полифторалкилметиленоксиэтилен амина: нсf2cf2-cf2-cf2-o-ch2-ch2-nh2, который был синтезирован на кафедре технологии органического синтеза химикотехнологического института уральского федерального университета. для ускоренной оценки защитного действия ингибирующих композиций и оптимизации состава консервационного покрытия использовался ме28 № 1 | 2016 chimica techno acta тод снятия анодных поляризационных кривых. поляризационные кривые снимались на потенциостате-гальваностате ipc-pro в потенциодинамическом режиме при линейной развертке потенциала 2 мв/с в трехэлектродной стеклянной ячейке с разделенным анодным и катодным пространствами в 0,5 м растворе nacl при температуре 25 °с. электродом сравнения служил хлорсеребряный электрод в насыщенном растворе хлорида калия. потенциалы пересчитаны на н.в.ш. вспомогательным электродом служила листовая платина. в качестве объектов исследования использовалась медь марки м00к (99,99 % чистоты), идущая на изготовление медной катанки. для снятия поляризационных кривых использовались цилиндрические стержни из медной катанки диаметром 8 мм с суммарной рабочей площадью 4 см2. натурные коррозионные испытания проводились на образцах из медной катанки длиной 150 мм и диаметром 8 мм в камере солевого тумана ascott 120 plus. защитные составы ингибирующих композиций наносились на обезжиренную ацетоном рабочую поверх ность медных электродов путем окунания их в растворы ингибирующих композиций в течение 15 с. результаты и их обсуждение исследования показали, что в отсутствие на поверхности металла ингибирующих пленок анодная поляризационная кривая для меди имеет вид, характерный для активно растворяющегося металла с последующей пассивацией. при потенциалах около 0,18–0,19 в медный электрод начинает переходить в пассивное состояние. поляризационные кривые для меди, предварительно обработанной в раст ворах изопропанола с различным содержанием полифторированного амина (пфа), представлены на рисунке. как видно на рисунке, при нанесении на металлическую поверхность меди защитной пленки из растворов, содержащих пфа, наблюдается значительное снижение максимума тока активного растворения меди на поляризационной кривой, что свидетельствует о замедлении скорости анодного растворения меди и торможении анодной реакции. из приведенных данных следует, что величина предельного тока анодного растворения меди зависит от концентрации пфа. причем максимум анодной плотности тока, наблюдаемый на поляризационных кривых, уменьшается с повышением рис. поляризационные кривые для меди, обработанной ингибирующей композицией с различной концентрацией пфа в изопропаноле, в 0,5 м растворе хлорида натрия: 1 – чистая медь; 2 – 0 % пфа; 3 – 0,25 % пфа; 4 – 0,5 % пфа; 5 – 0,75 % пфа; 6 – 1 % пфа; 7 – 1,25 % пфа; 8 – 1,66 % пфа; 9 – 3,32 % пфа иванов м. г., нечаев а. в., мокрушин в. с., остроухова о. и. 29 № 1 | 2016 chimica techno acta концентрации пфа и достигает минимального значения для 3,32 % раствора ингибирующей композиции на основе пфа, что может свидетельствовать о  повышении коррозионной стойкости ингибированной меди. однако только характер поляризационных кривых не позволяет одно значно судить о влиянии ингибитора на коррозионную стойкость меди в атмосферных условиях. поэтому в  дополнение к электрохимическим измерениям были проведены и натурные коррозионные испытания образцов медной катанки в камере солевого тумана ascott 120 plus. результаты электрохимических измерений согласуются с данными коррозионных испытаний. коррозионные испытания показали, что очаги коррозии на медных образцах без ингибирующей композиции, обработанных чистым изопропанолом, появлялись уже в первые же сутки выдержки образцов в камере. в то же время на образцах, обработанных в безводном растворе ингибирующей композиции на основе пфа, коррозионные поражения появляются на 2–4 сутки в зависимости от концентрации пфа. из исследованных составов ингибирующих композиций лучшие результаты (до 4 суток) были достигнуты для 3,32 % раствора ингибирующей композиции на основе пфа. таким образом, при использовании в ингибирующих композициях в качестве замедлителя коррозии меди полифторированных аминов можно повысить коррозионную стойкость медной катанки при ее транспортировке в экстремальных условиях. 1. цыганкова л. е., румянцев ф. а. влияние масляного покрытия и анионного состава электролита на ингибирование коррозии меди бензотриазолом в кислых средах // коррозия: материалы, защита. 2006;12:31–36. 2. кузнецов ю. и., агафонкина м. о., шихалиев х. с., андреева н. п., потапов  а.  ю. адсобция и пассивация меди триазолами в нейтральных водных растворах // коррозия: материалы, защита. 2014;7:33–39. влияние фторсодержащих ингибиторов на коррозию меди в атмосферных условиях simulation of borosilicate glasses with non-constant force field molecular dynamics 4 d o i: 1 0. 15 82 6/ ch im te ch .2 01 9. 6. 1. 01 raskovalov a. a. chimica techno acta. 2019. vol. 6, no. 1. p. 4–11. issn 2409–5613 a. a. raskovalov the institute of high-temperature electrochemistry, ural branch of the russian academy of sciences, 20 akademicheskaya st., yekaterinburg, 620137, russian federation e-mail: other@e1.ru simulation of borosilicate glasses with non-constant force field molecular dynamics in this study the simulation of microscopical behavior of borosilicate glasses was conducted with non-constant force field molecular dynamics. the suggested model consists of classical pair potentials in the buckingham form, long range coulomb interaction, intramolecular bonded interactions and possibility of bond breaking and formation. the latter effects are accompanied by changes in the types of the bond-forming particles. the simulated system corresponds to the structure of borosilicate glasses with predominantly four-coordinated boron atoms. different structure groups are formed due to the dissociation / formation of intramolecular bonds, and the processes of the glass network rearrangement intensifies with temperature increasing. keywords: molecular dynamics; non-constant force field; glass; borate; silicate. received: 11.12.2018. accepted: 28.12.2018. published: 29.03.2019. © raskovalov a. a., 2019 introduction borosilicate glasses are materials with a wide range of applications. they can be used for nuclear waste utilization [1], as implants for tissue repair [2], in electrochemical devices as  ionic conductors [3–5], as sealants for solid oxide fuel cells [6] and in  many other areas of  human activity. from this point of  view, microscopical behavior of these glasses comes to researchers’ attention. glasses consisting of  several network former oxides (b2o3, sio2, p2o5 and some others) can contain a  colossal amount of  possible structure groups and their combinations. for this reason numerical simulations of  mixed glasses are very promoting because it can “view” glass structure at molecular level. to date, a molecular dynamics (md) simulation of silicate, borate and mixed borosilicate glasses was conducted in series of papers [1–5, 7–19]. most of these works deal with classical md, except researches [2, 17] performed with car-parinello (md) [20] and reax force field [21] (reaxff), correspondingly. the car-parinello method brings quantum mechanical calculation into md simulation. the reaxff is constucted to provide chemical reactivity during md simulation. the last two methods are used to include effects of chemical bonds dissociation and recombination to the simulation. these effects are needed to  be considered for  correct simulation of glass behavior. to perform such calculations with classical md is an ambiguous and complicated, if not impossible, task. 5 in the present paper i demonstrate how one can perform md simulation of borosilicate glass with non-constant force field methodology. this approximation consists of possibility of bond breaking and formation (including changing in particle types of bond forming atoms) runtime. simulation details md simulations were performed with an original program written in c in canonical (nvt) ensemble. newton’s equations of motion were integrated by velocity verlet algorithm [22] with timestep of 0.5 fs during 100’000 steps. equilibration time was 0.5 ps (1000 timesteps). electrostatic interactions were accounted using the ewald summation. nosé-hoover thermostat [23] with relaxation time of  0.02 ps was used for maintaining the temperature around desired temperature. there was tested three temperatures: 298, 500 and 1000 k.  the considered system consists of 94 si atoms, 80 b atoms, 429 o atoms and 242 alkaline metal (me) atoms (the total number of particles is 845). the oxygen atoms were divided into bridging (oc) and non-bridging (ot) species. bridging oxygen connects with two atoms of glass-forming element (si / b) and non-bridging — with only one. initial configuration of the system was generated with own special code. the box was cubic with the edge length of 20.4 å to match an approximate density of glassy silicates. van der waals interactions in the system were given by buckingham pair potential: u a r c rij ij ij ij ij ij � � � � �� � � �� �exp , � 6 (1) where uij is the potential energy between the i-th and the j-th atoms, rij is the distance between them, and aij, ρij and cij are empirical parameters. besides the van der waals short-range interactions, covalent bonds between oxygen and silicon / boron were set in the form of an intramolecular harmonic potential: u k r rij ij ij ij� �� �2 0 2 , (2) where kij is the spring constant and r0ij is the equilibrium distance between particles. unlike interactions provided by eq. (1), this potential is applied only to  covalent bonded pairs (s – ot, si – oc, b – ot and b – oc) listed separately. in addition, a  three-body potential energy term was applied to maintain a feasible valent angle for si – oc – si, b – oc – b and si – oc – b bonds: u k ijk tb ijk� �� �2 0 2 cos cos ,� � (3) where ktb is the spring constant of the threebody potential, 100.0 ev, θijk is the angle between ij and ik bonds, θ0 is the equilibrium angle, 148.3° (taken from [15] for si – o – si angle); i, j and k are the indexes of oc atom and its covalent-bonded neighbors, correspondingly. the values of aij, ρij and cij were taken from papers [1, 11, 12, 15, 19]. simulations were performed with different combination of these parameters. the more suitable for the glass structure description set of the parameters is summarized in table 1 with corresponding references. the parameters of the valent bond potential (2) are given in table 2. the atomic charges were suggested to be found as 4δ, 3δ, a, — 2δ and -δ-a for si, b, me, oc and ot, correspondingly. the values of δ and a are set to 0.4e and 1.0e. our md program allows deleting 6 (adding) valent bonds from (to) the corresponding list to mimic processes of bonds dissociation and glass forming: … ≡ si – oc – r ↔ ≡si+ ot – r (4) and … ≡ b – oc – r ↔ –b + ot – r. (5) if the bonds automatically break (form) then the interatomic distance is higher (lower) than a maximal bond distance parameter (rm). the values of this parameter are given in table 2. the further dissociation with participation of si+ or b+ species is not allowed. the charges of si+ and b+ species are chosen to keep electroneutrality during reactions (4) and (5). table 2 valent bonds parameters (including the maximal bond distance, rm) used in this study pair k, ev r0, å rm, å si — ot 10 –4 1.625 — si — oc 10 –4 1.650 2.0 b — ot 10 –5 1.400 — b — oc 10 –5 1.430 1.9 results and discussion the obtained structure of  the system is presented in fig. 1. one can see that the simulated glass consists of branchy chains of si — o / b — o bonds which can form various combinations and loops. in principle, there are two possible boron coordinations in borate glasses, triangular and tetrahedral [24]. in our case almost all boron in the glass is four-coordinated, fig. 1. radial distribution functions (rdfs) are presented in  fig.  2. all rdf-curves consist of  one sharp and several broad maximums. this is typical of  liquids or amorphous systems and indicates the presence of  the short-range and the absence of the long-range orders. there are no series of well-resolved maxima, specific for crystalline solids. the first maximum of  rdf-curve corresponds to  the most probable distance in the near-neighbor coordination. according to fig 2(a), the distance between me and ot is less than that between me and oc. it can be explained by  more negative charge of  ot species (simulation details section) and, therefore, stronger coulomb interaction. rdfs almost do not depend on temperature, the differences are observed only for the rdfs table 1 the buckingham pair potential parameters used in this study pair a, ev ρ, å c, evå6 reference si – ot / oc 13702.905 0.193817 54.681 [19] b – ot / oc 206941.81 0.124 35.0018 [19] me – ot / oc 4383.7555 0.243838 30.700 [5] ot / oc – ot / oc 352.56 0.35 0 [1] si – b 337.584 0.29 0 [1] si – me 861.744 0.29 0 [1] si – si 836.16 0.29 0 [1] b – b 121.056 0.29 0 [1] me – me 9500.0 0.23 0 [12] 7 with the sharpest maxima, for  example, si – o. for these rdfs the value of the first maximum decreases with temperature increasing and the peak becomes broader, fig. 2(b). this process occurs, most likely, due to the thermal motion. the first maximum for b – ot / oc and si – ot / oc pairs locates at  distance of  1.375–1.425 and 1.575–1.675 å, correspondingly, which is close to b – o и si – o interatomic distances in borosilicate glasses [15]. as the system initially does not have crystalline lattice and a  corresponding look of rdf-curves, it is necessary to find another criterion of  transition between liquid and solid states. such a  criterion can be, for  example, mean square displacement (msd), which characterizes fig. 2. some radial distribution functions, g(r) of the simulated glass: (a) for 298 k; (b) for pair si – ot at 298 and 1000 k fig. 1. the structure of the simulated system after 30’000 timesteps at 298 k in (a) stick-and-ball and (b) polyhedral representation. blue polyhedra correspond to boron central atom, gray — to silicon 1 2 3 4 5 6 7 8 0 1 2 3 4 5 6 me – ot me – si ot – oc g( r) r, å me – oc 1 2 3 4 5 6 0 2 4 6 8 10 12 14 16 18 20 22 298 k g( r) r, å 1000 k a b 8 a  mobility of  ions. in the simulated borosilicate glass, msds of  most ions tend to  reach a  plateau with some oscillation at temperature of 298 k, except one for me ions increased linearly, fig. 3(a). the time derivative of  msd grows with temperature increasing, fig. 3(b). this means that all species start to diffuse and the system behavior becomes liquid-like. analogous effects can be seen on trajectories of the ion motion. at temperature of 298 k most ions vibrate around one point (although with big enough amplitude), fig. 4(a). an exception is the me ion, its trajectory consists of a series of hops between positions with long enough oscillation time. with temperature increasing, me ion spends less time in one position, more often hops and covers greater distance, fig. 4(b). its movement character becomes more and more liquid-like. fig. 5 demonstrates the number of si and b species as a function of time. the changes in these quantities are provided by dissociation of b – oc and si – oc bonds according to equations (4) and (5). since dissociation in  the suggested model occurs upon reaching the determined distance (table 2), the observed fluctuations of the particles numbers are related with fig. 3. the mean square displacement (msd) of the simulated borosilicate glass: (a) for different ions at 298 k; (b) for me and si ions at different temperatures fig. 4. trajectories of motion in the simulated borosilicate glass for: (a) different ions at 298 k; (b) the same me ion at different temperatures 5 10 15 20 25 30 35 40 45 50 0 2 4 6 8 10 12 14 16 ot oc b si m sd , å 2 time, ps me 5 10 15 20 25 30 35 40 45 50 0 10 20 30 40 50 60 si (500 k) me (298 k) me (500 k) me (1000 k) si (1000 k) m sd , å 2 time, ps si (298 k) a b 7 8 9 10 11 12 13 14 15 8 9 10 11 12 13 boc o c y , å x, å me 10 11 12 13 14 15 16 17 18 19 20 21 4 5 6 7 8 9 10 11 12 500 k 298 k y , å x, å 1000 k a b 9 changing in  the b / si – oc distances. according to fig. 5, the suggested pair potentials provide stronger b — oc bonding, then si – oc one, as the amplitude of the si number oscillation is bigger. also, fig. 5 demonstrates that the amplitudes of these oscillations increase with temperature. this is a result of thermal motion which promotes overcoming of forces of interatomic attraction, as noted above in the discussion of  the radial distribution functions. the bonds breaking and formation realized by methodology of non-constant force field allow glass structure to be “dynamical,” i.e. to destroy ones atomic groups and to create others. a variety of formed molecular groups can see in fig. 1. conclusions in the paper 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ab, d. s. kopchuk ab, s. santraa, m. rahmana, g. v. zyryanov ab, v. l. rusinov ab, o. n. chupakhinab a ural federal university named after the first president of russia b. n. yeltsin, 620002, 19 mira st., ekaterinburg, russia b i. ya. postovsky institute of organic synthesis of ras (ural branch), 620990, 22/20 s. kovalevskoy/akademicheskaya st., ekaterinburg, russia *email: g.v.zyrianov@urfu.ru direct synthesis of 5‑arylethynyl‑1,2,4‑triazines  via direct ch‑functionalization an efficient synthetic approach towards 5-arylethynyl-1,2,4-triazines via direct c-h-functionalization of 5-h-1,2,4-triazines in reaction with lithium acetylenes is reported. keywords: c-h-functionalization, 1,2,4-triazines; acetylenes lithium salts; 5-arylethynyl1,2,4-triazines received: 05.08.2020. accepted: 01.09.2020. published: 07.10.2020. © m. i. savchuk, e. s. starnovskaya, y. k. shtaitz, a. p. krinochkin, d. s. kopchuk, s. santra, m. rahman, g. v. zyryanov, v. l. rusinov, o. n. chupakhin, 2020 introduction heterocyclic acetylenes are widely used in various heterocyclization reactions [1], especially via click reactions [2]. acetylene spacers are presented in a number of  conjugated heterocyclic chromophores [3]. additionally, some heterocyclic acetylenes are known posses with biological activities, for instance as antihypertensive agents [4]. the object of study of this work — 5-arylethynyl-1,2,4-triazines — are promising substrates for the preparation of various classes of compounds with unique applied properties. for example, by the transformation of the 1,2,4-triazine ring into the pyridine one via the aza-diels-alder reaction with vatious dienophiles, the corresponding pyridines can be obtained, including 2,2’ — bipyridine ligands [4]. in addition, arylethynyl substituted 1,2,3-triazoles were obtained in the reaction of the corresponding 3(2-pyridyl)  — 1,2,4-triazines with aryne intermediates [5–6]. also, by the chemical transformation of 5-arylethynyl the  corresponding 5-phenacyl1,2,4-triazines could be obtained [7–8], which in  turn can be transformed into 5-methyl-1,2,4-triazines [9]. among the  reported methods for the synthesis of 5-arylethynyl-1,2,4-triazines, the use of the sonogashira cross-coupling can be highlighted [10], and in this case 5-iodine or 5-chloro-1,2,4-triazines were used as reactants in addition, the direct introduction of an arylethynyl moiety via the c-h functionalization of 1,2,4-triazine-4-oxides in the reaction with the lithium salt of acetylene are described by using 105 deoxygenative aromatization pathway, and the benzoyl chloride was used as an acylating agent [5,11]. the interaction of non-activated 1,2,4-triazines with the lithium salt of arylacetylene is also described, however, the corresponding 5-styryl-1,2,4-triazines were the main reaction products [12–13]. in this aspect, it should be noted the greater availability of 1,2,4-triazines compare to 1,2,4-triazine-4-oxides; and the preparation of ethynyl derivatives starting from 1,2,4-triazines looks more attractive. in this article, we wish to report an efficient synthesis of 5-arylethynyl-1,2,4-triazines 1 via direct c-h-functionalization of 5-h-1,2,4-triazines 2 with lithium arylacetylenes. experimental part 1h nmr spectra were recorded on a  bruker avance-400 spectrometer (400 mhz), the internal standard was sime4. mass spectra (ionization type — electrospray) were recorded on a microtof-q ii instrument from bruker daltonics (bremen, germany). elemental analysis was performed on a perkin elmer pe 2400 ii chn analyzer. the starting 1,2,4-triazine 2 was obtained according to the described method [14]. a general procedure for the synthesis of of arylethynyl‑1,2,4‑triazines 1: a solution of n-buli in hexane (2.5 m, 0.8 ml) was added to a solution of the corresponding arylacetylene (2 mmol) in dry thf (4 ml) in a schlenk flask at a temperature of –78 °c in an argon atmosphere, and the resulting mixture was stirred for 5 min. then the  solution of  the  corresponding 1,2,4-triazine 1 (1.6 mmol) in dry toluene (35 ml) was added, and a minute later a solution of ddq (305 mg, 1.34 mmol) in dry toluene (10 ml) was added. the resulting mixture was stirred for 3 h at 78 °c to room temperature. after that methanol (10 ml) was added, and the reaction mixture stirred for 5 min and the solvents were removed under reduced pressure. the resulting oily residue was purified by column chromatography (neutral alumina, eluent: dichloromethane) to afford the desired products. 3‑ (2‑pyridyl) — 6‑phenyl‑5‑pheny‑ lethynyl‑1,2,4‑triazine (1а). yield 565 mg (1.7 mmol, 85%). rf 0.6. m.p. 142–144 °с. nmr 1h (cdcl3, δ, ppm): 7.37–7.41 (m, 2h, phc≡c), 7.43–7.55 (m, 4h, phc≡c, h-5 (py)), 7.59–7.63 ( m, 3h, ph), 7.94– 7.99 (ddd, 1h, 3j 8.0, 8.0 hz, 4j 2.0 hz, h-4 (py)), 8.19–8.22 (m, 2h, ph), 8.75 (dd, 1h, 3j 8.0 hz, 4j 1.0 hz, h-3 (py)), 8.96 (dd, 1h, 3j 4.8 hz, 4j 2.0 hz, h-6 (py)). 13c  nmr (cdcl3, δ, ppm): 86.5 (c-sp), 100.8 (c-sp), 120.8, 124.2, 125.7, 128.5, 128.7, 129.5, 130.7, 132.6, 133.9, 137.2, 142.6, 150.6, 152.4, 157.7, 160.7. esi–ms, m/z: 335.13 (m + h)+. found, %: c 78.82, h 4.01, n 16.55. c22h14n4. calculated, %: c 79.02, h 4.22, n 16.76. 5  ‑ ((4‑methoxyphenyl) ethynyl)  — 3‑ (pyridin‑2‑yl) — 6‑phenyl‑1,2,4‑tria‑ zine (1b). yield 515 mg (1.41 mmol, 88%). nmr 1h (cdcl3, δ, ppm): 3.85 (m, 3h, och3), 6.89 (m, 2h, c6h4), 7.45–7.54 (m, 3h, c6h4, h-5 (py)), 7.55–7.64 (m, 3h, ph), 7.95 (ddd, 1h, 3j 7.6 hz, 7.6 hz, 4j 1.6 hz, h-4 (py)), 8.17–8.23 (m, 2h, ph), 8.74 (d, 1h, 3j 8.0 hz, h-3 (py)), 8.94 (d, 1h, 3j 4.8 hz, h-6 (py)). esi–ms, m/z: 365.14 (m + h)+. found, %: c 75.70, h  4.30, n 15.25. c23h16n4o. calculated,%: c 75.81, h 4.43, n 15.37. 106 results and discussion the  previously proposed mechanism [14] for the  reaction of  1,2,4-triazines and lithium-acetylenes is  presented on the scheme 1. according to  the  mechanism, at the first stage, the corresponding σh-adduct a  is  formed, which further undergoes a  1,2-hydride shift affording the  formation of  the  corresponding styryl substituent. and the  treatment of  the  reaction mixture with methanol at  the  final stage leads to the products 3. obviously, to block the pathway a for the reaction, the σh-adduct a need to be treated with and oxidant to  form 5-ethynyl-1,2,4-triazine 1, which no longer turn into 5-styryl derivative 3 indeed, it was found that the  addition of  an  oxidizing agent, such as 2,3-dichloro-5,6-dicyanobenzoquinone (ddq), 10 minutes after the  initiation of the reaction between 1,2,4-triazine and the arylacetylene lithium salt allowed us to obtain the corresponding 5-phenylethynyl1,2,4-triazines 1 in up to 88% yields (way b), and they were isolated using column chromatography. the structure of products 1 was confirmed based on the data of nmr 1h, 13c spectroscopy, mass spectrometry, and elemental analysis. thus, in  the  13c nmr spectra, the signals of sp-hybrid carbon atoms in the range of 86.5–100.8 ppm can be observed. the spectral data of compound 1а correspond to  those previously published during its synthesis by an alternative method [5]. conclusions an efficient synthetic approach towards 5-arylethynyl-1,2,4-triazines via direct ch-functionalization of 5-h-1,2,4-triazines in reaction with lithium-acetylenes was reported. this method could serve as a possible pd-free alternative to the sonogashira cross-coupling. acknowledgements this work was supported by the russian science foundation (grant # 20-13-00142) and grants council of the president of the russian federation (no. nsh-2700.2020.3). n n nph li ar n n nph ar h n n nph ar meoh li+ bli+ -meoli a h n n nph ar h h ddq n n nph ar w ay a w ay b n n n nn 2 1a,b 3 ar = ph (a), 4-meoc6h4 (b) scheme 1. mechanism of reaction of 5-h-1,2,4-triazines 2 with lithium-acetylenes 107 references 1. a) heravi mm, sadjadi s. recent advances in the application of the sonogashira method in the synthesis of heterocyclic compounds. tetrahedron. 2009;65:7761– 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zn(ii) and ru(ii) complexes. tetrahedron. 2008;64:8963–8973. doi: 10.1016/j.tet.2008.06.040 tio2 paste for dssc photoanode: preparation and optimization of application method 140 d o i: 1 0. 15 82 6/ ch im te ch .2 02 0. 7. 4. 01 selyanin i. o., steparuk a. s., irgashev r. a., mekhaev a. v., rusinov g. l., vorokh a. s. chimica techno acta. 2020. vol. 7, no. 4. p. 140–149. issn 2409–5613 tio2 paste for dssc photoanode: preparation and optimization of application method i. o. selyanin ab*, a. s. steparukc, r. a. irgashevbс, a. v. mekhaevc, g. l. rusinovbс, a. s. vorokhab a institute of solid state chemistry, ural branch of the russian academy of sciences, 91 pervomaiskaya st., ekaterinburg 620990, russia b ural federal university, 19 mira st., 620002, ekaterinburg, russia с postovsky institute of organic synthesis, ural branch of the russian academy of sciences, s. kovalevskoi/akademicheskaya 22/20 st., 620137, ekaterinburg, russia *email: theselyanin@yandex.ru abstract. we propose a simple method of tio2 paste preparation from titania powder (degussa) and organic binders (terpineol, ethyl cellulose) for making a continuous photoactive layer of a dye-sensitized solar cell (dssc). the prepared paste was characterized by using thermogravimetric and x-ray diffraction methods for comparison with commercial paste (solaronix). the tio2 layer parameters for applying and annealing were optimized by varying the layer thickness and using different masks. the surface morphology of annealed layers was controlled by optical microscopy. before tio2 paste applying and after annealing, the conductive glass (fluorine-tin oxide — fto) was treated by ticl4 hydrochloric acid solution. the structure of dsscs were composed ftoglass / tio2 layer sensitized ruthenium complex (n719 dye)/ iodide-based electrolyte / pt counter electrode/ fto glass. the dssc photovoltaic characteristics were measured under am 1.5g irradiation and demonstrated to be close to those of photoanodes based on the prepared and commercial pastes. keywords: dssc; gratzel cell; tio2 paste; photoanode; open-circuit photovoltage; short-circuit photocurrent density; i–v characteristics received: 27.03.2020. accepted: 20.10.2020. published:30.12.2020. © selyanin i. o., steparuk a. s., irgashev r. a., mekhaev a. v., rusinov g. l., vorokh a. s., 2020 introduction over the  past two decades, dsscs (dye-sensitized solar cells or gratzel cells) have become widely known due to  their environmental friendliness and low cost of  manufacture [1]. improving the efficiency of the solar irradiation conversion into electrical energy can be reached by modifying every individual cell element. a photoactive anode layer based on wide-band semiconductor oxides (usually, nanocrystalline tio2) plays the most important role [2, 3]. titania matrix can be sensitized by organic molecules or quantum dots to  allow the  efficient injection of  light-excited electrons from dyes [4]. the combination of tio2 phases (anatase, 141 rutile, brookite, and amorphous) improves the  conducting and catalytic properties of  anode material. for commercial and laboratory investigation of  photoanode, a crystalline phase of anatase or a mixture of anatase and rutile phases (for example, degussa p25 with the ratio of anatase:rutile = 3:1) are used as sources of tio2 for paste making [5, 6]. together with the tio2 phase composition and electronic structure, the layer’s geometrical and morphological characteristics play an important role in electricity generation. in particular, the photoanode tio2 layer thickness affects the photovoltaic cell characteristics directly: the thick oxide layer is  prone to  cracking after shrinkage [6]. the cracks impede the electron transfer, provoke the short circuit, and reduce the area of the photoactive surface. a  balance between oxide layer continuity and thickness should be found to optimize the  dssc operation. when tio2 nanocrystalline layer thickness increases from 0.5 to 2 μm, the solar cell characteristics behave as follows: the short-circuit current density increases by a third, and the open-circuit voltage increases by 5% [7]. the dependence of photoelectrochemical characteristics on tio2 layer thickness (6, 10, 14 μm) demonstrates that the optimal layer thickness is 10 μm for good light absorption, minimal charge recombination, and the low resistance to charge transfer [8]. the short-circuit current and conversion efficiency decrease when the tio2 layer thickness exceeds 15  μm [9–12]. the  good anode layer continuity and its certain thickness are necessary to obtain the high efficiency of dssc. the purpose of this work is to develop methods for producing a paste based on tio2 powder and forming a  continuous layer of optimal thickness on a conductive substrate. the phase and chemical composition of commercial and prepared pastes were studied by x-ray diffraction and thermogravimetric analysis. the  search for optimal parameters of heat treatment and formation of the layer of a given thickness was carried out by studying the behavior (preservation of  continuity or cracking) of commercial paste on laboratory glass. the obtained parameters were used to create dssc anodes, the photoactive layers of which are formed from both commercial and prepared pastes. a  dye n719 based on a ruthenium complex was adsorbed on the tio2 layer. the photovoltaic properties of the collected dssc were studied under the conditions of illumination of am 1.5g by a xenon light source. experimental paste preparation and characterization. for the  paste preparation, 1.0  g of  tio2 (degussa p25, sigma-aldrich), 3.8  g of  α-terpineol (70% ps, panreac), 0.5  g of ethyl cellulose (48.0–49.5% (w/w) ethoxyl basis, sigma-aldrich), 0.15 g of nitric acid (65%, vecton) in 20 ml of ethyl alcohol were mixed. the mixture was stirred for 30  minutes at  room temperature. the titania-containing paste was obtained by  distilling excess volatile components on a heidolph hey-vap precision rotary evaporator at  a  water bath temperature of 60 °c and reduced pressure (175 mbar) for 30  minutes. commercial paste tinanoxide d/sp (solaronix sa) was used as  a  reference for comparison of  viscosity and homogeneity. the standard doctor blade method was used for applying pastes in all cases. the area of the applied layer was 2.0 × 2.0 cm. 142 the morphology of samples with pastes was studied using a  carl zeiss neophot 30 optical microscope equipped with a  digital camera everfocus eq500a/pir. x-ray diffraction (xrd) studies were performed on the  shimadzu maximax xrd-7000 x-ray diffractometer (with cu kα radiation, λ=1.5406 å) in the geometry of  bragg-brentano with a  step of 0.03° at the angle of 2θ and an exposure time of 3 seconds. particle size was determined by  the  igor pro multipeak2 program using the scherrer formula d = kλ/ (fwhm·cosθ), where k is the form factor, λ is the x-ray wavelength, fwhm is full width at half maximum and θ is the bragg angle corresponding to  reflection. thermogravimetric studies of commercial and prepared pastes based on titanium dioxide were performed on a mettler toledo tga / dsc 1 device in the air (30 ml/min) with a heating rate of 10 °c/min in the range of 30–500 °c. optimization of  annealing and paste application. glass substrates were kept in  a  sulfochromic mixture for 24  hours, after ward rinsed with distilled water and isopropyl alcohol and dried at  100  °c.  to  regulate the  thickness of the paste layer, masks made of various materials were used, namely: adhesive tape (hereinafter  — a.t., 35  μm), aluminum foil (9 and 14 μm), screen printing mesh sefar e-mesh 61/156-64w pw (thread thickness 64  μm, cell size 100×100  μm). the paste application onto the cover glass was made using a doctor blade technique. samples with the paste were dried at 120 °c for 5  minutes, then annealed in  a  muffle furnace (snol with oven trm-10 regulator) in the air at temperatures from 350 to 450 °c for 30 minutes (the heating rate was 5  °c/min). the  study of  the  effect of 0.30 g nitric and perchloric acids on the continuity of the formed layer was carried out by adding hno3 (65%, vecton, >90% sigma-aldrich) or hclo4 (65%, vecton) to the commercial paste. the  formation of  photoanodes. fto (fluorine-doped tin oxide) conductive glasses (size 2.5 × 2.5 cm, surface resistivity ~ 8 ω/cm2, sigma-aldrich) were treated with isopropyl alcohol for 30 minutes and then dried at  50  °c.  then fto glasses were treated by holding in the ticl4 hydrochloric acid solution (≥ 98.0%, fluka) for 30  minutes at  a  solution temperature of  70  °c, followed by  washing with isopropyl alcohol and distilled water. after applying the  oxide paste, the  samples were annealed in  a  muffle furnace for 30  minutes at  450  °c.  the  resulting layer was re-treated by  holding in  ticl4 hydrochloric acid solution according to the method described above. adsorption of the dye n719 [di-tetrabutylammonium cis-bis(isothiocyanato)-bis(2,2-bipyridyl-4,4-dicarboxylate)ruthenium(ii)] (solaronix sa) onto the  tio2 layer was carried out by holding the layer in a 5·10–4 m methanol solution of n719 for 18 hours. the cell elements and assembly. to create a counter electrode, a thin layer of platinum was applied to the fto glass using the following method: a  few drops of  h2ptcl6 solution in ethanol were distributed over the  surface and annealed at  450  °c for 30 minutes. a mixture of 0.5 m lii (99%, sigma-aldrich) + 0.05 m i2 (sublimated for analysis, sigma-aldrich) in acetonitrile (99.9%, npo reaktivy osc) or 3-methoxypropionitrile (≥98.0%, sigma-aldrich) was used as the electrolyte. the assembly of the elements was performed as follows: the pt cathode was placed on top of the photoanode side soaked tio2 layer, then a few drops of electrolyte were added in the gap 143 between the two glasses, and then the glasses were stuck together using office clips. measurement of  i–v characteristics. the assembled cell was illuminated with a  xenon source zolix gloria-x500a (the  illumination power at  a  distance of  25 cm is  100 mw/cm2, determined using a  silicon calibration element zolix qe-b1). the  source radiation spectrum was in the 250–1000 nm band with the  maximum intensity in  the  range of 350 to 550 nm. the illuminated surface of  the  photoanode was 4 cm2. lightening was performed from the photoanode side with the adsorbed dye. the i–v characteristic was recorded using a  keithley 2450 source-meter with a 50 mv step with a measurement error of ±10 na for current and ±1 μv for voltage. results and discussion the prepared paste characterization and comparison with the  commercial analog. the paste was made of tio2 degussa p25 with the addition of α-terpineol, ethyl cellulose, and nitric acid (hereinafter “prepared”). three stages are distinguished on thermogravimetric curves (fig.  1): the evaporation of volatile components (1st stage), oxidation of α-terpineol (2nd stage, tb.p. = 215 °c), and the combustion of cellulose derivatives (3rd stage, tautoignit. = 370 °c). after annealing, with the organic components removed, the remaining weight (pure tio2) was found to be ~15% of the initial one. the result obtained for the laboratory paste is comparable to the commercial paste ti-nanoxide d/sp (solaronix sa). the samples annealed at temperatures of 350–400 °c have a brownish tinge associated with incomplete burning of organic components. this result is consistent with the tga data. based on the obtained data, a temperature of 450 °c was used for further research. it is evident from table 1 that annealing leads to cracking of the resulting layer, which can be avoided by varying the thickness of the applied layer. according to  xrd, the  composition of  the  obtained layers at  450  °c is  nanocrystalline tio2 powder (fig.  2). the  combustion of  organic components defined from thermogravimetric data is  proved by  the  absence of  any reflections or amorphous halo onto the diffracfig. 1. thermogravimetric curves of prepared and commercial pastes 144 tion pattern. the  powder obtained from the  annealed commercial paste consists of anatase nanoparticles with an average particle size of 20.7 nm. the prepared paste is based on tio2-p25 and consists of a mixture of anatase (92 mass %) and rutile (8 mass %) phases. the size of anatase particles in tio2-p25 was 19.8 nm, and the size of rutile particles was 27.9 nm. we proposed that titania nanoparticles can be ordered along chains of organic molecules (ethyl cellulose) and can form anisotropic agglomerates during heat treatment. this process can provoke the texturizing of the tio2 layer. in support of this proposition, annealing was performed directly on the glass substrate used in the xrd experiment. the peak intensities of both layer and powder are the same as the standard peak intensities defined by pdf cards (21–1272 for anatase, and 21–1276 for rutile). the difference curve between the layer and powder diffraction patterns shows a lack of crystallographic orientations of the layer. we can conclude that the  procedure of  heat treatment allows decomposing organic compounds and obtaining the titania layer with a random orientation of nanostructured grains. an amorphous halo occurs for both the prepared powder pattern and the difference curve because of the very thin oxide layer and the reflection from the glass substrate. fig. 2. diffraction patterns of commercial and prepared tio2 layers and initial tio2 powder table 1 microphotographs of the tio2 layer surface, the insets show layer surfaces on the glass substrate 145 effect of various masks on the thickness of  the  tio2 layer. the  commercial paste was used as a reference for searching the optimal method of applying the paste to  form a  continuous tio2 layer. this paste has a uniform small particle size and a verified ratio between the components of the paste: tio2, thickener, and binder. to vary the thickness of the resulting layer on glass substrates, various combinations of  a.t., aluminum foil of  different thicknesses, and sefar screen printing mesh were used. a.t. and foil were used as masks that were applied to the glass. the squeegee was used to apply the paste evenly. the screen mesh was applied on top of  a  glass or a mask, a layer was applied on top of a mask, and then the mesh was removed. the samples were exposed to temperature treatment corresponding to  the  “annealing” stage discussed in the previous section. various “mask-mesh” combinations for applying tio2 paste to glass substrates and corresponding microscopic images of samples are shown in table 2 (sections i–iii). a n a ly s i s of   m i c rophoto g r aphs of the obtained layers showed that the best results are obtained when using one layer of a.t. in the case of using the only a.t. it corresponds to the thickness of the applied paste of  ~ 35  μm. in  this case, the  layer remains continuous; almost no cracks emerge (table  2, section i). a  comparative study by optical microscopy showed that the layer thickness after annealing was ~10 μm. the experiment with using more than one layer of the adhesive tape showed that the  increase in  the  layer’s thickness results in intense cracking of the tio2 layer after annealing. it negatively affects the efficiency of the cell. foil without mesh does not allow getting a  layer of  appropriate quality, the combination of foil and mesh produces an effect similar to the combination of mesh and a.t. (table 2, section ii). besides, the  foil deforms easily when it overlays the glass. this suggests that the use of a foil mask is problematic. applying two layers of paste with intermediate drying, in contrast, demonstrates good continuity (table 2, section iii). to  test the  hypothesis that cracking is  primarily caused by  uneven evaporation of the liquid phase and the formation of bubbles, an experiment with the addition of an oxidizer to a commercial paste to accelerate the oxidation process of organic components was performed. hno3 and hclo4 acids were used as  oxidants. based on microphotographs of photoanode surfaces, it can be concluded that the layers have the best appearance after adding 65% hno3, and adding hclo4, on the contrary, leads to greater cracking of the photoanode layer (table 2-iv). in general, adding 65% and 90% hno3 oxidizer reduces the cracking of the oxide layer. having established the optimal mode of application, the samples were obtained with the prepared paste with combinations of  masks presented in  table  2-v.  from the presented images it is clear that the laboratory paste during the  application has good continuity. the  fabrication of  the  photoanodes and the assembly of gratzel cells. based on the above experiments, the application and annealing conditions were selected for the preparation of photoanodes. in all cases, the commercial and the prepared pastes were applied through a mesh to a conductive fto glass. to improve the continuity of the layer, preliminary (before applying the paste to the glass) and final (after applying and annealing the paste) treatments with ticl4 hydrochloric acid solution were performed. 146 strong adhesion of oxide layers plays an  important role when they have been immersed in a dye solution for a long time. in the presence of microcracks and poor adhesion, even in the presence of distilled water, it is possible to observe the peeling of the oxide layer. for this reason, an additional experiment was performed to test the adhesion properties. the prepared photoanode was immersed in distilled water for 24 hours, after which there was no delamination, the layer showed good resistance even under the mechanical influence. according to optical microscopy data, the  morphological differences between the layers of commercial and the prepared table 2 micrographs of the surface of tio2 layers under various conditions for applying commercial paste (i–iii) and its modification (iv), as well as methods for applying laboratory paste (v). the annealing temperature is 450 °c, the scale is shown on the upper-left microphotograph i 1 layer a.t. 2 layer a.t. 3 layer a.t. 4 layer a.t. ii 9 μm foil 14 μm foil 9 μm foil– mesh 14 μm foil — mesh iii mesh 1 layer a.t. — mesh 2 layer a.t. — mesh 1+1 layer a.t. — mesh* iv without oxidizer hno3 (~65%) hno3 (~90%) hclo4 v 1 layer a.t. mesh 1 layer a.t. — mesh ticl4 treatment * 1 layer of a.t. — mesh, then drying at ~120 °c for 5 minutes, adding the 2nd layer of a.t, applying the 2nd layer of paste through the grid, followed by drying 147 pastes are minor in comparison with other layers shown in table 2. both layers have good continuity, but in the case of prepared paste (fig. 3a) there are cracks and slight heterogeneity caused by  the  aggregation of tio2 nanoparticles in the initial powder, while for commercial paste, small bubbles can be observed (fig. 3b). а pt thin layer applied to the conductive glass was used as a counter electrode (fig. 3c). the surface of the assembled cell is shown in fig. 3d. fig.  4 shows the  i–v characteristics of  the  dsscs. the  value of  the  opencircuit photovoltage voc for the  cell with prepared paste was 0.33  v, for the  commercial paste voc was slightly higher  — 0.38 v. at the same time, the short-circuit current density isc for the cell with prepared paste was 0.96 ma/cm2, which is noticeably higher than for the element based on commercial paste — 0.6 ma/cm2. to prevent the evaporation of acetonitrile from the electrolyte, the solvent was replaced with 3-methoxypropionitrile with a  higher boiling point. the  change of the electrolyte led to an increase in voc for both the cell with prepared paste — 0.5 v, and for the cell with commercial paste — 0.47 v. the isc values for the cell with prepared paste decreased to  0.9 ma/cm2, while for the cell with commercial paste, on the contrary, increased to 0.68 ma/cm2. according to  the  data obtained, we conclude that i–v characteristics of dsscs based on the  prepared paste are close to the characteristics of dsscs based on the commercial paste under the same conditions, namely: counter electrode, electrolyte, and assembly method. replacing fig. 3. microscopic images of surfaces: photoanodes based on (a) prepared and (b) commercial pastes, (c) a cathode coated with a layer of pt, (d) a cell assembled from the resulting electrodes 148 the solvent in the electrolyte increases both the current values and the voltage between the cell electrodes. conclusions to produce a homogeneous paste of nanodisperse tio2, a combination of α-terpineol and ethyl cellulose as binding components was used. applying the  prepared paste to the pretreated glasses using a screen printing mesh and annealing at a temperature of 450 °c allows forming a continuous layer of tio2 on the glass substrate. the  dsscs assembled from the  prepared and the commercial pastes demonstrated comparable photovoltaic characteristics of photoanodes. the open-circuit photovoltage value reaches 0.4–0.5  v; the short-circuit current density reaches 1 ma/cm2. the tio2 layers produced by using either prepared or commercial paste have similar properties, but the prepared paste is  less expensive to  manufacture. by changing other components (electrolyte, a counter electrode, etc.) and improving the assembly method, higher efficiency of dssc can be achieved. acknowledgements the team of authors is grateful to the russian science foundation for financial support, grant no. 17-79-20165. a. s steparuk would like to acknowledge the financial support for the analytical studies of synthesized compounds from the ministry of education and science of the russian federation within the framework of the state assignment for research (project no. aaaa-a19-119012490006-1). references 1. gratzel m. mesoporous oxide junctions and nanostructured solar cells. curr. opin. colloid interface sci. 1999;4(4):314–21. doi:10.1016/s1359-0294(99)90013–4 fig. 4. i–v characteristics of assembled solar cells with various electrolytes: e1 — acetonitrile, e2–3-methoxypropionitrile 149 2. joshi ph, korfiatis dp, potamianou sf, thoma k-at. selected parameters leading to an optimized dssc performance. russ. j. electrochem. 2013;49(7):628–32. doi:10.1134/s1023193513070045 3. amit k, sharma r, pransu g, boxman rl. evaluation of the photo electrode degradation in dye sensitized solar cells. russ. j. electrochem. 2019;55(9):829–40. doi:10.1134/s1023193519090039 4. o’regan 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dioxide absorbents 167 d o i: 1 0. 15 82 6/ ch im te ch /2 01 7. 4. 3. 02 уд к 66 .0 92 .5 7 (5 46 .2 63 .3 -3 1+ 54 6. 26 431 ) efremov v. n., golosman e. z., каshinskaya a. v., мugenov t. i., zolotareva v. e., polivanov b. i., polushin a. p. chimica techno acta. 2017. vol. 4, no. 3. p. 167–182. issn 2409–5613 v. n. efremov1, e. z. golosman1, a. v. каshinskaya1, t. i. мugenov2, v. e. zolotareva2, b. i. polivanov1, a. p. polushin3 1ooo «niap-katalizator» 10 svyazi st., novomoskovsk, tul’skaya obl., 301660, russia 2 novomoskovsk institute (branch) of the dmitry mendeleev university of chemical technology of russia 8 druzhby st., novomoskovsk, tul’skaya obl., 301665, russia 3jsc «novomoskovsk joint stock company azot» svyazi st., novomoskovsk, tul’skaya obl., 301660, russia e-mail: evgolosman.niap@yandex.ru resistance of industrial nickel-containing methanation catalysts to the poisoning by organic carbon dioxide absorbents we report the results of studies on the influences of the organic carbon dioxide absorbent – aqueous solution of activated methyldiethanolamine (mdea) – on the physico-chemical and mechanical characteristics of nickel-alumina catalyst niap-07-01 (nkm-1) and cement-containing catalysts niap-0707 (nkm-7), meth-134 and meth-135 for the hydrogenation of carbon oxide (methanation). it is established that for the nickel-alumina and nickel-cementcontaining catalysts subjected to activated methyldiethanolamine (mdea) it’s possible to restore their strength and catalytic properties. in order to increase the time of operation of the methanator it is recommended to apply a new nickel cement-containing catalyst niap-07-07 (nkm-7), which can be produced as tablets, rings or extrudates. keywords: nickel-containing catalyst; calcium aluminate; methantion; solution of methyldiethanolamine; hydrogenation; carbon oxides; catalytic activity; mechanical strength. received: 16.06.2017; accepted: 06.09.2017; published: 20.10.2017. 168 в. н. ефремов1, е. з. голосман1, а. в. кашинская1, т. и. мугенов2, в. е. золотарева2, б. и. поливанов1, а. п. полушин3 1ооо «ниап-катализатор» ул. связи 10, г. новомосковск, тульская обл., 301660, россия 2 новомосковский институт (филиал) российского химико-технологического университета имени д. и. менделеева ул. дружбы 8, г. новомосковск, тульская обл., 301665, россия 3ао «новомосковская акционерная компания «азот» ул. связи, г. новомосковск, тульская обл., 301660, россия e-mail: evgolosman.niap@yandex.ru устойчивость никелевых промышленных катализаторов метанирования к воздействию органических абсорбентов удаления диоксида углерода из синтез-газа приведены результаты исследований воздействия органического абсорбента в виде водного раствора активированного метилдиэтаноламина (мдэа), являющегося абсорбентом диоксида углерода при его удалении из азото-водородной смеси, на физико-химические и физико-механические характеристики никельалюминиевого марки ниап-07-01 (нкм-1) и цементсодержащих марки ниап-07-07 (нкм-7), meth-134 и meth-135 катализаторов гидрирования оксидов углерода (метанирования). установлено, что никельалюминиевые и никельцементсодержащие катализаторы, подвергнутые воздействию активированного метилдиэтаноламина (мдэа), восстанавливают свои прочностные и каталитические свойства. для увеличения времени эксплуатации метанатора рекомендуется применять новый никелевый цементсодержащий катализатор марки ниап-07-07 (нкм-7), который может изготавливаться в виде таблеток, колец или экструдатов. ключевые слова: никелевый катализатор; алюминат кальция; метанирование; раствор метилдиэтаноламина; гидрирование; оксиды углерода; каталитическая активность; механическая прочность. поступило: 16.06.2017; принято: 06.09.2017; опубликовано: 20.10.2017. © efremov v. n., golosman e. z., каshinskaya a. v., мugenov t. i., zolotareva v. e., polivanov b. i., polushin a. p., 2017 introduction in the ussr, russia and cis the most commonly used catalysts of the hydrogenation of carbon oxide (methanation) are those developed by «niapkatalizator»: nickel-aluminum catalyst niap-07-01 (nkm-1), nickel cement-containing ones – niap-07-02, niap-07-03 (nkm-4a), and nickel-chromia-alumina169 containing to-2m [1–5]. these catalysts are manufactured according to tu2178003-00209510-2006 by the «niap-katali zator» factory, and until recently they were also produced by dorogobuzhskiy catalyst factory and severo-donetsk catalyst production plant. as for now, these catalysts are produced solely by «niapkatalizator». their planned service life is usually about 15–16 years, while the actual service life amounted to 22–24 years [6] on the three jsc «azot» factories (nevinnomyssk, voronezh, grodno). note that there are some imported catalysts of methanation supplied by «haldor topsoe», «johnson matthey» and «clariant» (sud-chemie). the «niap-katalizator»-made catalysts are being produced as tablets or rings in accordance with the technical requirements of tu2178-003-00209510-2006 (catalysts of methanation). for the russian market the imported catalysts are also available as tablets, and in addition – as extrudates and beads. the methanation catalysts must have high activity in the hydrogenation process, leaving no more than 5–10 ppm of residual co after the methanation of 0.3– 0.7 % co and 0.02–0.1 % co2 mixture. they have to possess increased thermal stability without reducing their catalytic activity (overheating up to 550-650  °c can occur in cases of increasing the co content in the source gas to more than 1 %), high mechanical strength and low gas flow resistance. the quality of the methanation catalysts is largely determined by their support. in the domestic and imported industrial methanation catalysts various supports are used, for example, γ-al2o3, calcium aluminates, compounds of caomgo, γ-al2o3-сr2o3, γ-al2o3, calcium aluminate, boehmite (alooh) – γ-al2o3 [7–9]. the content of active component (nio) in the industrial methanation catalysts varies in the range of 25.0 to 45.0  wt.  %. catalysts niap-07-02, niap-07-03, and katalko-11-4r, мeth-134 and мeth-135, in which calcium aluminate plays the role of the adhesive, have a minimum level of internal microstresses, which contributes to the high mechanical strength after the catalyst’s activation and during its operation. note that the service life of a catalyst is primarily determined by its catalytic activity and mechanical strength. the experience of running industrial catalytic plants used in various chemical, petrochemical, metallurgical and other industries, as well as available literature data and our long-term monitoring of the industrial catalytic set-ups developed by «niap-katalizator» allowed us to assess the reasons for their deactivation. the deactivation of the methanation catalysts may occur due to: 1. irreversible poisoning associated with the interaction of the active component with the common catalyst poisons (sulfur compounds, chlorides etc.) present in the reaction medium. 2. consequences of the thermal treatment, such as recrystallization, caking, the chemical interactions of active component with the support (e. g. resulting in the formation of the nickel-aluminum spinel nial2o4). 3. loss of the active component due to the formation of volatile compounds such as tetracarbonylnickel. 4. carbon deposition on the catalyst’s surface. 5. catalyst’s surface contamination by various impurities. 170 the structural changes of the industrial porous catalysts are accelerated if the phase transformations occur upon the exposure to the reaction medium. under the working conditions of the large-capacity catalytic unit, the absorbents used to remove co2 from syngas or their decomposition products could possibly poison the catalyst. in industrial conditions this process occurs in the absorbers with absorbents such as aqueous alkaline solutions («banfield» and «karsol»), and organic absorbents such as aqueous solutions of activated monoethanolamine (mea) or methyldiethanolamine (mdea) [10, 11]. during the operation, carbon dioxide absorbents could get into the methanation reactor. as a result, a gradual decrease of catalytic activity may occur [12, 13]. to determine the causes of this phenomenon, we conducted studies in which the methanation catalysts were influenced by the organic absorbent mdea. experimental industrial catalysts niap-07-01 (nkm-1) and the niap-07-07 (nkm-7), the latter being recommended for industrial use, were chosen as the objects of this research. niap-07-07 (nkm-7) was obtained in two states: 1 – non-calcined; 2 – calcined at 400 °c. it can be manufactured as cylindrical tablets, extrudates or in toroidal form from the same non-calcined catalyst mixture. the catalyst in the form of rings has a low gas flow resistance, which leads to significant savings of natural gas in the operation of the ammoniasynthesis units. in addition, imported catalysts мeth-135 (c13-03-3) and мeth-134 (c13-04-4) were investigated. x-ray diffraction (xrd) studies of the phase composition and size of crystallites were performed using dron-3 diffractometer (cukα-radiation with graphite monochromator on reflected beam). for the phase analysis icdd pdf-2 (1999) database was used. thermogravimetric analysis (tga) was performed using the optical derivatograph od-103 with the heating rate of 5  °c/min. total specific surface area was determined by the low-temperature nitrogen sorption in the vacuum adsorption setup. total porosity was calculated from the data of real and theoretical density. mechanical strength was determined on the «mп-2c» setup by crashing the granules with the uniaxial compressive force. the chemical composition and catalytic activity during the methanation were determined in the original setup at a pressure of 3 mpa by means of the techniques described in the tu2178-003-00209510. according to this internal standard, we adopt the following definition of a catalytic activity: it’s a minimum temperature in °c, at which the volume fraction of co at the output of the catalytic reactor is less than 1·10–3 % at a pressure of 3 mpa. the other important experiment conditions are as follows: feed gas with 0.6–0.7 vol. % of co, space velocity of the feed gas should be equal to 4000 h–1, and the catalyst in the catalytic reactor should be pre-heated for 10 h at 550 °c. the treatment of all investigated catalysts by 50 % aqueous solution of mdea absorbent in the flow of nitrogen-hydrogen mixture (75 vol. % h2, 25 vol. % n2) was carried out in the original setup, schematic of which is shown in fig. 1. before the experiments catalysts were activated in a stream of nitrogen-hydrogen mixture (nhm) at 400 °c for 5 h. at 171 the end of the activation process the samples were exposed to aqueous solution of mdea in the stream of nhm in the layer catalyst at a temperature of 320 °c. results and discussion in order to determine the infl uence of the absorbents on the catalysts’ properties their initial characteristics were determined (table 1). data given in table 1 show that the catalysts under investigation possess 27–40 wt. % of the ni-containing active component with weight percentage calculated implying that nio is the active component’s only form. th e average nio particle size in niap-07-01 (nkm1) and niap-07-07 (nkm-7) is around 60–80  å. total porosity is almost equal for all catalysts, its value being around 48– 57 %. th e only exception is niap-07-07, for which it’s 29 %. note that the porous structure of this catalyst forms during the combined calcination and activation process, which could explain this unique porosity value. all catalysts have quite large total surface area, with the largest value of 180 m2/g corresponding to niap-07-01 (nkm-1). it should be noted that the mechanical strength of studied samples, which is one of the parameters determining the service life of a catalyst, varies signifi cantly. th e «strongest» catalyst is niap-07-07 (nkm-7) – 60 mpa, followed by niap-07-01 (nkm-1) – 29 mpa. strength of the мeth-134 and мeth-135 is almost equal. phase composition and nio particle size analysis (table 1) shows that the aluminate cement is one of the components of the support for мeth-134, мeth-135 and niap-07-07 (nkm-7) catalysts. as the second component of the support for niap-07 (nkm) is γ-al2o3, for the мeth134 and мeth-135 catalysts it consists of the mixture of boehmite (alooh) and γ-al2o3. boehmite as a support constituent could impede the catalyst’s activity as it inhibits the interaction between support and the active component. th e active component of raw niap07-07 catalyst is a complex compound – nickel hydroxocarboaluminate (nhca). it’s the main diff erence between the raw niap-07-07 and niap-07-01, fi red niap-07-07 and meth catalysts. activation of niap-07-07, coupled with the nhca decomposition, occurs at the lower temperatures (thus – at milder conditions) as compared to the other industrial catalysts with nio as an active component. since the industrial catalytic reactors are operated at about 280–320  °c, we had to determine the thermal stability of fig. 1. schematic diagram of a setup for catalyst treatment by the aqueous solution of the absorbent in the fl ow of nitrogenhydrogen mixture (nhm): 1 – mdea solution; 2 – fl ow regulators; 3 – evaporator; 4 – temperature regulators; 5 – reactor; 6 – catalyst 172 mdea in this temperature range. therefore, the sample of α-al2o3 impregnated with the aqueous solution of mdea was investigated by means of thermogravimetric analysis. on the differential thermogravimetric (dtg) curve, shown in fig. 2, two distinct minima at the temperatures of 100  °c and 210  °c can be observed. they correspond to the maximum speed of removal of water from the sample and the decomposition of mdea, accordingly. the process of decomposition of mdea in air, accompanied by the mass loss, starts at about 150 °c and ends at 300 °c. in order to determine the optimal activation temperature of a catalyst a temperature-programmed reduction experiments were employed. it was determined that the activation is a multistage process. it should be noted that niap-07-07 (nkm-7) catalyst is activated at about 100 °c lower temperatures than the other studied catalysts. xrd analysis shows that at 400  °c the activation process is virtually complete. comparison of the ni-containing particle sizes shows that for all catalysts after the activation it still is in the range of 60–80 å. physico-chemical and mechanical properties of the activated catalysts treated with mdea solution are listed in the table 2 along with their catalytic activities table 1 physico-mechanical and physico-chemical characteristics of the original catalysts for the methanation: p – porosity, s – specific surface area brand of the catalyst the geometric dimensions, mm bulk density, kg/dm3 mechanical strength, mpa pavg/pmin s, m2/g p, % xrd phase analysis results lnio, å chem. composition, % mass. nio al2o3 cao niap-07-01 (nkm-1) tablet 6×5 1.08 29/20 180 57 γ-al2o3, nio, graphite 60 33.6 61.3 – niap-07-07 (nkm-7) tablet 6×5 1.2 60/52 102 29 nhca, graphite, сасо3 (aragonite) – not much, al(oh)3, cao·2al2o3 – not much – 30.3 25.2 7.9 niap-07-07 (nkm-7) fired at 450 °с tablet 6×5 1.1 49/32 160 53 nio, γ-al2o3, cao·al2o3, cao·2al2o3, graphite 75 30.3 meth-134 (c13-04-4) sphere d = 4.3 0.95 8/4 150 48 nio, alooh, γ-al2o3, caco3 (boehmite) 80 27.2 57.3 10.0 meth-135 (c13-03-3) sphere d = 5.3 0.99 6/1 120 54 nio, alooh, γ-al2o3, caco3 (boehmite) 80 40.4 42.9 11.2 fig. 2. tga curve of the sample of α-alumina, impregnated with water solution of mdea 173 towards the methanation. characteristic feature of the interaction between mdea solution and the catalyst is the initial rise of the temperature at the beginning of the reaction. it could be related to the passivation of a catalyst by the water vapor, which is formed during the evaporation of mdea aqueous solution. xrd pattern analysis confirmed that in this case passivation of the active component occurs, effectively removing part of it from the catalysis process. the activated catalysts treated with mdea solution in nhm gas flow contain the mixture of ni and nio phases, which is an evidence in favor of our assumption. particular ratio of the mentioned phases should depend on how reduced the catalyst was and how much of metallic ni it contains. hence the samples before the catalytic activity measurements have been pre-treated at 400 °с for 8 h. according to xrd, mdea does not chemically alter the supports of the investigated catalysts for methanation. however, due to the fact that mdea (tertiary amine) is an adsorbtion-active agent, it could negatively affect the properties of catalysts, namely, mechanical strength, specific surface area, porosity and catalytic activity. the results of our studies given in table 2 show that after exposure to the aqueous solution of mdea in the nitrogen-hydrogen gas mixture flow the mechanical strength and specific surface area were only insignificantly reduced. the one exception is niap-07-07 (nkm-7), for which the microstructure forms during the activation process. total porosity is almost equal for all samples. phase changes occurred during the reaction with mdea are related to the catalysts’ passivation. comparison of the catalytic activity data show that the catalysts treated with aqueous mdea solution in nhm flow at 320 °c retain their catalytic properties almost completely. the particular catalytic activities are comparable to those defined in our tu2178-003-00209510-2006 internal standard (typically being in the range from 170  °c to 200  °c) for methanation catalysts containing 31–40 % of active component (nio). table 2 physico-chemical and mechanical characteristics of the catalysts for methanation after exposure to mdea brand of catalyst mechanical strength, mpa rsr/pmin s, m2/g p, % phase composition catalytic activity, °с initial samples after exposure to mdea niap-07-01 nkm-1 27/19 155 54 nio, ni, graphite, γ-al2o3 160 165 niap-07-07 nkm-7 41/35 168 41 nio, ni, γ-al2o3, cao·2al2o3, caco3 165 170 meth 134 (c13-04-4) 5/3 120 50 nio, ni, γ-al2o3, caco3 180 180 meth 135 (c13-03-3) 5/2 66 57 ni, nio, γ-al2o3, caco3 175 180 174 summary in the present study raw ni-alumina catalyst niap-07-01 (nkm-1) and nicement-containing catalysts niap-07-07 (nkm-7), meth-134 (c13-04-4) and meth-135 (c13-03-3), as well as the same catalysts activated and pre-treated with aqueous mdea solution in the flow of nitrogen-hydrogen gas mixture (nhm), were investigated. after the exposure to mdea investigated catalysts almost completely retain their values of mechanical strength, specific surface area, porosity and catalytic activity, the latter being around 165–180  °c. the active component (ni) in the catalysts subjected to the mdea solution exposure is highly dispersed after the subsequent activation, which contributes to the elevated catalytic activity. during the treatment of a catalyst by the mdea aqueous solution in the flow of nhm at 320 °c its passivation takes place. by using the temperatureprogrammed reduction it was proven that the surface of catalysts is blocked by mdea. during the reduction of the cata lysts treated with mdea co2 – one of the mdea decomposition products – is released to the gas phase, which further reinforces our assumptions. regeneration of the activated methanation catalysts subjected to (and inhibit ed by) mdea should be carried out by drying them in the nhm at temperatures higher than 150–200  °c, followed by additional reduction at temperatures of 350–400 °c. in russian введение в  течение длительного времени в  ссср, рф и  снг основными катализаторами, применяющимися в  процессе гидрирования оксидов углерода (метанирования), являются разработанные в  «ниап-катализатор» никель-алюминиевый катализатор марки ниап-07-01 (нкм-1), никель-цементсодержащий – ниап-07-02, ниап-07-03 (нкм-4а) и  никель-алюмохромовый то-2м [1–5]. катализаторы изготавливаются по ту 2178-003-00209510-2006 катализаторным производством «ниап-катализатор», а до недавнего времени выпускались также дорогобужской катализаторной фабрикой и  северо-донецким катализаторным производством. в  настоящее время в  рф катализаторы изготавливаются только катализаторным производством «ниап-катализатор». катализаторы, произведенные в «ниап-катализатор», при соблюдении регламентных режимов эксплуатации работают по 15–16  лет, а  на трех по «азот» (невинномысск, тольятти, гродно) срок их службы составил 22–24 года [6]. кроме того, применяются импортные катализаторы, основными поставщиками которых являются такие фирмы, как haldor topsoe, johnson matthey и  clariant (sud-chemie). отечественные катализаторы изготавливаются в  форме таблеток или колец (таблетирование) в  соответствии с  техническими требованиями ту 2178-003-00209510-2006 (катализаторы метанирования). для российского рынка импортные катализаторы предлагаются в виде таблеток, а также в форме экструдатов и шариков. 175 катализаторы метанирования должны иметь высокую активность в  процессе гидрирования 0,3–0,7 % со и  0,02–0,1 % со2 до остаточного содержания со 5–10 ppm, термостабильность без снижения активности при перегревах до 550–650 °с, которые могут возникать в  случае повышения содержания оксидов углерода в исходном газе ≥ 1 %, высокую механическую прочность и  пониженное гидравлическое сопротивление. качество катализаторов метанирования в  значительной степени определяется носителем, используемым в  процессе его приготовления. в  отечественных и  импортных промышленных катализаторах метанирования в качестве носителя, как правило, применяют γ-al2o3, алюминаты кальция, композиции саоmgo, γ-al2o3-сr2o3, γ-al2o3-алюминат кальция, бемит (alooh) – γ-al2o3 [7–9]. содержание активного компонента (nio) в  промышленных катализаторах метанирования варьируется в  пределах 25,0–45,0 масс.%. катализаторы ниап-07-02, ниап-07-03, а  также katalko-11-4r, мeth-134 и мeth-135, в которых алюминат кальция выполняет роль гидравлического вяжущего, имеют минимальный уровень внутренних микронапряжений, что способствует сохранению на высоком уровне механической прочности после стадии активации и  последующего периода эксплуатации. срок эксплуатации катализаторов определяется в первую очередь такими показателями, как каталитическая активность и механическая прочность. мировой опыт эксплуатации промышленных катализаторов, применяющихся в  различных процессах химической, нефтехимической, металлургической и  др. отраслях, а  также имеющиеся в  литературе данные и  наши многолетние наблюдения за работой в  промышленных условиях катализаторов, разработанных в  «ниап-катализатор», позволили во многом оценить причины их дезактивации. дезактивация катализаторов метанирования может происходить, например, вследствие: 1. необратимого отравления, связанного с  взаимодействием активного компонента с  каталитическими ядами (сернистые соединения, хлориды и т. д.), присутствующих в реакционной среде. 2. термического воздействия – рекристаллизация, спекание, взаимодействие активного компонента с носителем. например, образование никель-алюминиевой шпинели (nial2o4). 3. унос активного компонента за счет образования летучих соединений (например, образование карбонила никеля). 4. зауглероживание. 5. загрязнение поверхности механическими примесями. структурные изменения промышленных катализаторов, которые представляют собой пористые высокодисперсные тела, ускоряются, если в  них происходят фазовые превращения при воздействии реакционной среды. в  условиях работы агрегатов большой единичной мощности по производству синтетического аммиака источником катализаторных ядов могут служить абсорбенты, применяющиеся для удаления со2 из синтезгаза или продукты их разложения. в  промышленных условиях этот процесс происходит в  абсорберах с  помощью таких абсорбентов, как вод176 ные щелочные растворы («бенфийлд» и  «карсол»), а  также органических поглотителей в  виде водных растворов активированных моноэтаноламина (мэа) или метилдиэтаноламина (мдэа) [10, 11]. в процессе эксплуатации наблюдаются уносы абсорбентов диоксида углерода в  реактор метанирования. результатом этого нарушения технологического процесса, как правило, является увеличение газодинамического сопротивления метанатора и постепенное падение каталитической активности [12, 13]. для выяснения причин этого явления нами были проведены исследования, в  которых катализаторы метанирования были подвергнуты максимально жесткому воздействию органического абсорбента мдэа. экспериментальная часть в  качестве объектов исследований были взяты промышленный катализатор ниап-07-01 (нкм-1) и  рекомендуемый для промышленного внедрения катализатор ниап-07-07 (нкм-7) в двух его состояниях: 1 – непрокаленный; 2 – прокаленный при 400 °с. из одной и той же непрокаленной катализаторной шихты он может изготавливаться в  виде цилиндрических таблеток, экструдатов или в кольцевидной форме. катализатор в форме колец обладает низким газодинамическим сопротивлением, что приводит к существенной экономии природного газа при эксплуатации агрегата синтеза аммиака. кроме того, были исследованы импортные катализаторы марки мeth-135 (c13-03-3) и мeth-134 (c13-04-4). рентгенографические исследования с  определением фазового состава и  дисперсности кристаллитов проводили с  использованием дифрактометра дрон-3 (cukα-излучение с  графитовым монохроматором на отраженном пучке). для идентификации фаз использовали базу данных международного комитета порошковых дифракционных стандартов (icdd pdf-2, 1999  г.). комплексные термические исследования осуществляли с  применением оптического дериватографа марки оd-103 (линейная скорость нагрева 5 °с/мин). общую удельную поверхность определяли по низкотемпературной адсорбции азота на вакуумной адсорбционной установке. общую пористость рассчитывали по данным истинной и  кажущейся плотности. механическая прочность определялась на приборе «мп-2с» раздавливанием гранул с  приложением нагрузки на торец. химический состав и  каталитическую активность в  процессе метанирования на пилотной установке при давлении 3 мпа определяли по методикам, приведенным в ту 2178-003-00209510. химический состав и  каталитическую активность в процессе метанирования на пилотной установке при давлении 3 мпа определяли по методикам, приведенным в ту 2178-003-00209510. за меру каталитической активности принята минимальная температура (°с), обеспечивающая объемную долю со на выходе не более 1·10–3 об.% при давлении 3 мпа, объемной скорости 4000 ч–1, объемной доле в  исходном газе 0,6–0,7 об.% со после предварительного перегрева катализатора при температуре 550 °с в течение 10 ч. 177 обработку всех исследуемых катализаторов 50 %-м водным раствором абсорбента мдэа в потоке азото-водородной смеси (75 об.% h2, 25 об.% n2) проводили на установке, принципиальная схема которой приведена на рис. 1. перед проведением экспериментов осуществляли активацию катализаторов в  потоке азото-водородной смеси (авс) при температуре 400 °с в  течение 5 ч. по окончании процесса активации образцы подвергали при температуре 320 °с воздействию водного раствора мдэа в  потоке авс в  слое катализатора. результаты и обсуждение для определения степени воздействия абсорбентов на катализаторы были определены их основные исходные характеристики (табл. 1). из данных, приведенных в  табл.  1, видно, что исследуемые катализаторы имеют концентрацию активного компонента в пересчете на nio в пределах 27–40 масс.%. дисперсность nio в  катализаторах ниап-07-01 (нкм-1) и  ниап-07-07 (нкм-7) находится на уровне 60–80 å. показатель общей пористости практически одинаков для всех катализаторов и  находится на уровне 48–57 %. исключение составляет катализатор ниап-07-07, для которого значение общей пористости составляет 29 %. это явление объясняется тем, что формирование пористой структуры этого катализатора происходит в совмещенном процессе прокаливания и  активации. сопоставление данных по общей удельной поверхности показывает, что все катализаторы имеют высокоразвитую общую удельную поверхность. максимальное ее значение равное 180 м2/г имеет катализатор ниап-07-01 (нкм-1). можно отметить значительный разброс для катализаторов по такому показателю, как механическая прочность, которая во многом определяет срок службы катализаторов. по этому показателю наибольшее предпочтение можно отдать катализатору ниап-07-07 (нкм-7), для которого ее значение равно 60 мпа. на второе место можно поставить катализатор ниап-07-01 (нкм-1) – 29 мпа. катализаторы мeth-134 и мeth-135 по своим прочностным показателям практически одинаковы. анализ фазового состава и  дисперсности nio (табл.  1) свидетельствует о  том, что в  качестве одного из компонентов носителя катализаторов мeth-134, мeth-135 и  ниап-07-07 рис. 1. принципиальная схема установки для обработки катализатора в потоке азота или азото-водородной смеси с водными растворами абсорбентов: 1 – раствор мдэа; 2 – регуляторы расхода; 3 – испаритель; 4 – регулятор температуры; 5 – реактор; 6 – катализатор 178 (нкм-7) применяется алюминатный цемент. если в  катализаторах серии ниап-07 (нкм) вторым компонентом носителя является γ-al2o3, то в  катализаторах мeth-134 и  мeth-135 применяется смесь гидрооксида алюминия в  виде его модификации «бемит» (alooh) и  γ-al2o3. применение в  катализаторах мeth-134 и  мeth-135 гидрооксида алюминия в виде его модификации «бемит» приводит к  недостаточно глубокому его взаимодействию с  прекурсором активного компонента, что неизбежно будет сказываться на каталитической активности. отличие исходного образца катализатора ниап-07-07 от ниап-07-01 (нкм-1), прокаленного ниап-07-07 (нкм-7) и  катализатора марки мeth состоит в том, что его активный компонент находится в виде сложного химического соединения (гидроксокарбо алюминат никеля – гкан). активация этого катализатора, совмещенная с разложением гкан, происходит при более низких температурах и  в  более мягких условиях по сравнению с  другими промышленными катализаторами, в  которых активный компонент находится в оксидной форме. так как эксплуатация катализаторов в  промышленных условиях агрегатов синтеза аммиака осуществляется при температурах 280–320 °с, в  этом же температурном интервале была определена термическая устойчивость мдэа, данные по которой в  справочной литературе отсутствуют. с  этой целью образец α-al2o3 был пропитан до состояния насыщения водным раствором мдэа, который затем был исследован дериватографическим методом анализа. на рис. 2 приведена дериватограмма данного образца. таблица 1 физико-механические и физико-химические характеристики исходных катализаторов метанирования: п – пористость, sуд – удельная поверхность, lnio – дисперсность частиц nio марка катализатора геометрические размеры, мм насыпная плотность, кг/дм3 механическая прочность, мпа на торец рср./рmin sуд., м2/г п, % рфа lnio, å хим. состав, % масс. al2o3 cao ниап-07-01 (нкм-1) таблетка 6×5 1,08 29/20 180 57 γ-al2o3, nio, графит 60 33,6 61,3 – ниап-07-07 (нкм-7) таблетка 6×5 1,2 60/52 102 29 гкан, графит, сасо3 (арагонит) – мало, al(oh)3, cao·2al2o3 – мало – 30,3 25,2 7.9 ниап-07-07 (нкм-7) прокален при 450 °c таблетка 6×5 1,1 49/32 160 53 nio, γ-al2o3, cao·al2o3, cao·2al2o3, графит 75 30,3 – – meth-134 (c13-04-4) шарик d = 4,3 0,95 8/4 150 48 nio, alooh, γ-al2o3, caco3 (бемит) 80 27,2 57,3 10,0 meth-135 (c13-03-3) шарик d = 5,3 0,99 6/1 120 54 nio, alooh, γ-al2o3, caco3 (бемит) 80 40,4 42,9 11,2 179 на дериватограмме имеются два ярко выраженных эффекта с  характеристическими температурами тmax  = 100  °c и  тmax = 210 °с, которые соответствуют удалению из образца физически связанной влаги и  разложению мдэа. процесс разложения мдэа в  среде воздуха сопровождается убылью массы. начинается он при температуре 150 °с, а  его максимальная скорость достигается при 210 °с. заканчивается разложение мдэа при 300 °с. для определения оптимальной температуры активации катализаторов были проведены исследования температурно-программированного восстановления. было установлено, что этот процесс является многостадийным. кроме того, было обнаружено, что катализатор ниап-07-07 (нкм-7) активируется ~ на 100 °с ниже всех исследованных образцов. рентгенографические данные показали, что при температуре 400 °с происходит практически полная активация. сопоставление данных по дисперсности ni свидетельствует о том, что она для всех исследуемых катализаторов практически одинакова и находится в пределах 60÷80 å. в  табл.  2 приведены физико-механические и  физико-химические характеристики активированных исследуемых катализаторов метанирования с  последующим воздействием на них водного раствора мдэа в потоке авс, а  также их каталитическая активность в  процессе метанирования. характерной особенностью экспериментов по воздействию водного раствора мдэа на активированные катализаторы метанирования было то, что в начальный рис. 2. дериватограмма образца α-al2o3, пропитанного до состояния насыщения раствором мдэа таблица 2 физико-механические и физико-химические характеристики катализаторов метанирования после обработки мдэа марка катализатора механическая прочность, мпа на торец рср./рmin sуд., м2/г п, % рфа активность, тпр., °с исходных образцов после воздействия мдэа ниап-07-01 нкм-1 27/19 155 54 nio, ni, графит, γ-al2o3 160 165 ниап-07-07 нкм-7 41/35 168 41 nio, ni, γ-al2o3, cao·2al2o3, caco3 165 170 meth-134 (c13-04-4) 5/3 120 50 nio, ni, γ-al2o3, caco3 180 180 meth-135 (c13-03-3) 5/2 66 57 ni, nio, γ-al2o3, caco3 175 180 180 период подачи мдэа в  потоке авс наблюдался рост температуры в  слое катализатора, что связано с пассивирующим действием водяного пара, образующегося при испарении водного раствора мдэа. анализ дифрактограмм подтвердил что, в  данном случае происходит пассивация активного компонента ni и  определенная его часть выводится из каталитического процесса. свидетельством этого является наличие в  фазовом составе активированных катализаторов, подвергнутых воздействию водного раствора мдэа в  потоке авс, фаз ni и  nio. соотношение этих фаз, по всей видимости, зависит от степени восстановленности и от содержания металлического никеля в каждом конкретном катализаторе. исходя из этого, образцы перед проведением испытаний активности были предварительно восстановлены при 400 °с в течение 8 ч. по данным рфа, мдэа не оказывает химического воздействия на носители исследуемых катализаторов метанирования. однако в  связи с  тем, что мдэа (третичный амин) является адсорбционно-активным веществом, он может негативно сказаться на свойствах катализаторов, и  в  первую очередь на таких его характеристиках, как механическая прочность, общая удельная поверхность, пористость и  каталитическая активность. результаты исследований, приведенные в  табл.  2, показывают, что после воздействия на активированные катализаторы водного раствора мдэа с одновременным потоком авс произошло незначительное снижение механической прочности и общей удельной поверхности. исключение составляет катализатор ниап-07-07 (нкм-7), у  которого формирование текстуры происходит в  процессе активации. общая пористость для всех образцов практически одинакова. произошли изменения в  фазовом составе, связанные с  процессом пассивации катализаторов. сравнение данных по каталитической активности, полученных в  данном эксперименте, показывает, что катализаторы, подвергнутые при 320 °с воздействию водного раствора мдэа в  потоке авс после предварительной активации, практически не теряют своих каталитических свойств. данный показатель хорошо сопоставим со значениями активности (по ту 2178-003-00209510-2006) катализаторов метанирования, имеющих содержание активного компонента (nio) от 31 до 40 %. для катализаторов с  таким содержанием активного компонента каталитическая активность находится в пределах от 170 до 200 °с. выводы комплексом физико-механических и  физико-химических методов исследованы характеристики ni-al катализатора ниап-07-01 (нкм-1) и ni-цементсодержащих катализаторов марки ниап-07-07 (нкм-7), meth-134 (c1304-4) и meth-135 (c13-03-3) как исходных катализаторов, так и  активированных с  последующим воздействием на них водного раствора мдэа в  потоке авс. исследуемые катализаторы после воздействия на них водного раствора мдэа в  потоке авс практически сохраняют высокие значения механической прочности, общей удельной поверхности, пористости 181 и каталитической активности, которая находится на уровне 165–180 °с. установлено, что активный компонент (ni) в катализаторах, обработанных мдэа с последующей активацией, находится в  дисперсном состоянии, что предопределяет их высокую каталитическую активность. в  процессе воздействия на активированные катализаторы при температуре 320 °с водного раствора мдэа в  потоке авс происходит их пассивация. методом температурнопрограммированного восстановления установлено, что поверхность катализаторов блокируется мдэа. это предположение подтверждается выделением в процессе восстановления обработанных катализаторов в  газовую фазу со2, являющегося одним из продуктов разложения мдэа. регенерация в  промышленных условиях активированных катализаторов метанирования, подвергшихся воздействию водного раствора мдэа, должна осуществляться путем их сушки в потоке авс при температурах не ниже 150–200 °с с  последующим довосстановлением при температурах 350–400 °с. references 1. golosman ez, efremov vn, kreyndel’ ai, mironov yuv, obysov av, sobolevskiy vs, yakerson vi, inventors; men’shov vn, assignee. russian federation patent ru2143320. 27.12.1999. russian. 2. golosman ez, efremov vn. promyshlennye katalizatory gidrirovaniya oksidov ugleroda [industrial catalysts for the carbon oxides hydrogenation]. kataliz v promyshlennosti. 2012;(5):36-55. russian. doi:10.18412/1816–0387-2012-5-36-55. 3. alekseev am. iz istorii kataliza [history of catalysis]. moscow: kal’vis, 2005. [chapter], giap v istorii katalizatornoy promyshlennosti sssr i rossii [giap in the history of catalysis industry of ussr and russia]; p. 481–532. russian. 4. melnikov eya, editor. spravochnik azotchika. 2nd ed. moscow: chemistry, 1987. 512 p. russian. 5. demidenko im, yankovskiy na, stepanov va, nikitina ef, kravchenko bv. katalizatory i  protsessy s ikh primeneniem v azotnoy promyshlennosti [catalysts and processes with their application in the nitric industry]. gorlovka: gorlovskaya tipografiya, 1998. 198 p. russian. 6. efremov vn, kashinskaya av, polivanov bi, boevskaya ea, golosman ez. o razrushenii katalizatora metanirovaniya pod vozdeystviem vodnogo rastvora potasha [destruction of the methanation catalyst by water solution of koh. part i: the nickel-alumina catalyst niap-07-01 (nkm-1)]. neftegazokhimiya. 2015;4:62–6. russian. 7. takenara s, shimizu t, otsuka k. complete removal of carbon monoxide in hydrogen-rich gas stream through methanation over supported metal catalysts. int j hydrogen energy. 2004;29(10):1065–73. doi:10.1016/j.ijhydene.2003.10.009. 8. men y, kolb g, zapf r, hessel v, love h. selective methanation of carbon oxides in a microchannel reactor-primary screening and impact of gas additives. catal today. 2007;125(1-2):81–7. doi:10.1016/j.cattod.2007.02.017. 182 9. liu q, dong x, mo x, lin w. selective catalyc methanation of co in hydrogen-rich gases over ni/zro2 catalyst. j natur gas chem. 2008;17(3):268–72. doi:10.1016/ s1003-9953(08)60062-6. 10. leites il, avetisov ak, yazvikova nv, suvorkin sv, baichtok ck, dudakova nv, deev kn, kosarev gv. issledovanie fiziko-khimicheskikh svoystv modifitsirovannogo meda-absorbenta dlya tonkoy ochistki gaza ot dioksida ugleroda v proizvodstve ammiaka [investigation of physico-chemical properies of modified mdeaabsorbent for fine purification of gas from carbon dioxide in ammonia production]. khimicheskaya promyshlennost’ segodnya. 2003;1:34–41. russian. 11. аvetisov ak, kononov sm, sokolov am, baichtok ck, suvorkin sv, leites il, deripasov vv, sokolinskiy ca, yazvikova nv. opyt modernizatsii otdeleniya absorbtsionnoy ochistki agregata sinteza ammiaka am-70 na oao «nevinnomysskiy azot» s zamenoy mea-rastvora na mdea-absorbent rossiyskogo proizvodstva [experience of modernization of absorption purification unit of the ammonia-synthesis plant am-70 at jsc «nevinnomysskiy azot»: replacement of the mea solution by mdea-absorbent made in russia]. khimicheskaya promyshlennost’ segodnya. 2003;2:22–4. russian. 12. vakk eg, shuklin gv, leites il. poluchenie tekhnologicheskogo gaza dlya proizvodstva ammiaka, metanola, vodoroda i  vysshikh uglevodorodov. teoreticheskie osnovy, tekhnologiya, katalizatory, oborudovanie, sistemy upravleniya [obtaining of gas for production of ammonia, methanol, hydrogen and higher hydrocarbons. theoretical foundations, technology, catalysts, equipment, management: a textbook]. moscow, 2001. 478 p. isbn978-5-98801-033-3. russian. 13. efremov vn, golosman ez, polivanov bi, kashinskaya av, polushin ap. ustoychivost’ nikelevykh promyshlennykh katalizatorov metanirovaniya k vozdeystviyu aktivirovannogo metildietanolamina – absorbent co2 [stability of industrial nickel catalysts for methanation against the action of activated methyldiethanol amine used as co2 absorbent]. kataliz v promyshlennosti. 2016;16(4):67–76. russian. doi:10.18412/1816-0387-2016-4-67-76. cite this article as: efremov vn, golosman ez, каshinskaya av, мugenov ti, zolotareva ve, polivanov bi, polushin ap. resistance of industrial nickel-containing methanation catalysts to the poisoning by organic carbon dioxide absorbents. chimica techno acta. 2017;4(3):167– 82. doi:10.15826/chimtech/2017.4.3.02. using the profiled elements to increase electrocyclone effectiveness 173 d o i: 1 0. 15 82 6/ ch im te ch .2 02 0. 7. 4. 06 anton trinkunas, lidia pomortseva, anatolii titov, zalina rusinova chimica techno acta. 2020. vol. 7, no. 4. p. 173–176. issn 2409–5613 using the profiled elements to increase electrocyclone effectiveness anton trinkunas*, lidia pomortseva, anatolii titov, zalina rusinova ural federal university, 19 mira st., ekaterinburg, 620002, russia *email: trinkunas.anton@yandex.ru abstract. the article is devoted to flue gas cleaning, using fly ash as an example. electrocyclone can be employed as gas-cleaning equipment. the electrocyclone operation can be intensified by reducing re-entrainment. the laboratory model of the annular channel of the electrocyclone is used to show the possibility of reducing re-entrainment by using the shaped elements of various designs on the collecting electrodes. aerosol industrial emissions can be reduced by using an electrocyclone with modified collecting electrodes. keywords: gas treatment; re-entrainment; shaped elements; electrocyclone received: 18.10.2020. accepted: 07.12.2020. published:30.12.2020. © anton trinkunas, lidia pomortseva, anatolii titov, zalina rusinova, 2020 introduction technological advancement implies a continuous increase in the capacities of industrial companies. industrial enterprises use solid materials for production purposes. many of  the  thermal power stations supplying electricity to industrial companies also operate on solid fuels. increasing volumes of emitted flue gases require high-performance gas-cleaning devices [1, 2]. aerosols can be purified in  various types of devices [3–5]. an electrocyclone is  a  combined dust collector that combines the centrifugal and electrostatic effects for cleaning aerosols. there has been unreasonably little focus on the  electrocyclone research. a comprehensive study of this type of gas cleaning devices could lead to the introduction into the industry of a new type of highly efficient gas cleaning devices. it is  possible to  intensify the  operation of  electrocyclones by  optimising the various parameters and characteristics. the main of this is reduction of re-entrainment [6]. this work is devoted to the intensification of the work of the electrocyclone by reducing re-entrainment. the effectiveness of the profiled elements of different shapes is considered. experimental for visual observation and quantification of the effectiveness of the profiled elements, a stand was assembled. a schematic diagram of the experimental stand is shown in fig. 1. the stand is designed as a prototype (in a first approximation) of the annular channel model. 174 the  stand consist of: 1 is  the  corona electrode, 2 is  the  external collecting electrode, 3 is the internal collecting electrode, 4 is  the  body, 5 is  the  collector, 6 is  the  inlet pipe, 7 is  the  exhaust pipe, 8 is the glass plate, 9 is the settling chamber. the walls (smooth aluminum plates) were connected to the positive pole of an external source of high voltage and grounded. the  discharge electrodes are connected to the negative pole of the external highvoltage source. 4 most common structural elements were selected (fig. 2): c-shaped element (a), double c-shaped element (b), rounded c-shaped elements (c), z -shaped elements (d). re-entrainment is associated with ejection of the entrapped materials on the collecting electrodes. fig. 3 shows a top view of the settling chamber with a besieged ash layer. it can be seen that on the deposited layer there are jagged areas. the photo taken from the side shows that the  largest number of  holes are opposite the fixed points of the corona discharge. the same can be said about other areas. in  all cases, the  observed jags are opposite the  corona electrode, namely in front of the needles located thereon. the shape of the holes is irregular, and they do not form a  perfect cone or any spherical/elliptical surface. such an irregular shape of the edge and surface of holes due to large particles hitting the material layer at an angle rather than strictly in a radial manner. numerous traces of particles in front of the fixed points of the corona discharge can be attributed to the high concentration of  charged ions moving to  the  collecting electrode and the  greater intensity of  the  electric field in  that domain. a larger concentration of ions and larger electric field strength contribute to increasing the maximum possible charge as well as  more intense particle charging. this increases the rate of the large particles migration to the collecting electrode by a few to a few dozen times. fig. 1. a stand for the re-entrainment process study fig. 2. profiled elements 175 the  second part of  the  study was the visual and partly quantitative evaluation of the installation of profiled elements on the external collecting electrodes of the annular channel. photographs of the profiled elements placed in the model of the active area channel with ashes settled on them are shown in fig. 4. the ash was deposited on the surface of the collecting electrodes and the surface of the profiled elements. moreover, the ash was on the outside and inside surfaces of the profiled elements. ash distribution on the  external collecting electrodes is the same in all cases. parts of low spots of the z-shaped profiled elements are covered by  a  thicker layer of material, although there were areas not covered with ashes due to partial shielding of the corona discharge. visually, the ash layer thickness on the electrodes seemed larger in all cases of the profiled elements, while the thickness of the layer on the smooth settling electrode without any elements seemed to be thinner. on the stand the dust collection efficiency was also quantitatively studied in the presence of the profiled elements in the active area channel. evaluated was the amount of material accumulated on the collecting electrodes by passing a sample of 50 g of ash (table 1). it is  shown that the  most effective (13.8 g per 1 element) are double c-shaped elements; the lowest efficiency is demonstrated by c-shaped elements along the gas (13.0 g). z-shaped ones catch only 11.3 g and the  rounded c-shaped ones catch 5.6 g. this can be explained by the developed parasitic vortices in the radial cavity of the blades and between the blades. anyway, the  profiled elements can reduce re-entrainment. this happens through the  removal of  large particles of the aerosol flow path due to delays and deposition and at expense of conservation on the surface of the particle layer in view of the wind shadow. fig. 3. photograph of the deposited material layer. channel without the profiled elements fig. 4. c photograph of the deposited material layer. channel with the profiled elements 176 conclusions some research was conducted in a gas treatment process of  the  annular channel model of an electrocyclone. to assess the effectiveness of the profiled elements, an experimental stand was manufactured and exploratory tests were conducted. the  design of  the  stand can be used for further experimentation. a technique of physical modeling of reentrainment was tested. the effectiveness of the profiled elements was demonstrated qualitatively and quantitatively. the most effective are the double c-shaped profiled elements. references 1. yan p, zheng c, zhu w, xu x et al. an experimental study on the effects of temperature and pressure on negative corona discharge in high-temperature esps. applied energy. 2016;164:28–35. doi:10.1016/j.apenergy.2015.11.040 2. oh j, choi s, kim j. numerical simulation of an internal flow field in a uniflow cyclone separator. powder technology. 2015;274:135–45. doi:10.1016/j.powtec.2015.01.015 3. chen cj, wang lfs. cost-benefit analysis of electrocyclone and cyclone. resources, conservation and recycling. 2001;31:285–92. doi:10.1016/s0921-3449(00)00086–0 4. zhuohan l, shao c, an y. et al. energy-saving optimal control for a factual electrostatic precipitator with multiple electric-field stages based on ga. journal of process control. 2013;23(8):1041–51. doi:10.1016/j.jprocont.2013.06.007 5. shrimpton js, crane ri. small electrocyclone performance. chemical engineering & technology. 2001;24(9):951–5. doi:10.1002/1521–4125(200109)24:9<951::aid–ceat951>3.0.co;2–9 6. titov a. the impact of re-entrainment on the electrocyclone effectiveness. separation and purification technology. 2015;156(2):795–802. doi:10.1016/j.seppur.2015.11.004 table 1 comparative effectiveness of the profiled elements № element type collected ash mass, g quantity of elements, piece collected ash mass corresponding on 1 element, g 1 no elements 16.2 2 8.1 2 c-shaped 26.0 2 13.0 4 c-shaped double 27.6 2 13.8 5 c-shaped rounded 22.4 4 5.6 6 z-shaped 34.0 3 11.3 creating a virtual device for processing the results of sorption measurements in the study of zinc oxide nanorods 154 d o i: 1 0. 15 82 6/ ch im te ch .2 02 0. 7. 4. 03 maraeva e. v., permiakov n. v., kedruk y. y., gritsenko l. v., abdullin h. a. chimica techno acta. 2020. vol. 7, no. 4. p. 154–158. issn 2409–5613 creating a virtual device for processing the results of sorption measurements in the study of zinc oxide nanorods e. v. maraevaa*, n. v. permiakova, y. y. kedrukb, l. v. gritsenkob, kh. a. abdullinс a department of micro-and nanoelectronics, saint petersburg electrotechnical university «leti», prof. popova st., 5, saint petersburg 197376, russsia b satbayev university, satpaeva st, 22, almaty 050013, kazakhstan c al-farabi kazakh national university, al-farabi ave, 71, almaty 050040, kazakhstan *email: jenvmar@mail.ru abstract. the work is devoted to the creation of a virtual device (computer program) for processing the results of sorption analysis of nanomaterials, including for estimating the size of nanoparticles based on the specific surface area. the obtained evaluation results were compared with the scanning electron microscopy data. photocatalytically active zinc oxide samples were chosen as the object of the study. keywords: zinc oxide; nanorods; sorption measurements; virtual device; received: 15.10.2020. accepted: 09.12.2020. published:30.12.2020. © maraeva e. v., permiakov n. v., kedruk y. y., gritsenko l. v., abdullin kh. a., 2020 introduction sorption analysis methods, as a rule, are used to characterize porous materials at  the  mesoporous (diameter 2–50  nm), as  well as  microporous (diameter ≤ 2  nm) levels. however, such a characteristic of the material as the specific surface area, determined on the basis of  analysis of  inert gas adsorption isotherms, in  some cases characterizes not only the  surface development due to  the  porous structure of  the  material, but also the  surface of  the  particles of the fragmented phase of the dispersed system. in this case, the data of a sorption study provide an express estimation of the sizes of  nanoparticles, while the  sorption analysis methods have some advantages over other methods. such advantages are the possibility of studying a large amount of material in one step (unlike local methods where individual sections of the sample are analyzed and the results of the study are averaged), as  well as  the  possibility of studying materials with high roughness, where other methods of surface analysis are not applicable or undesirable. the  aim of  this work was to  create a virtual device (computer program) for processing the results of sorption analysis of nanomaterials, including for assessing the size of nanoparticles based on the specific surface area determined by the standard bet method. as the object under study 155 photocatalytically active zinc oxide samples [1] obtained by annealing zinc acetate dihydrate (ch3coo)2zn∙2h2o in a muffle furnace were chosen. experimental zno nanoparticles (nps) were synthesized by  annealing zinc acetate dihydrate (ch3coo)2zn∙2h2o in  a  muffle furnace at  temperatures of  400  °c and 700 °c; the annealing time was 2, 4, and 10 hours. zinc acetate was placed in a ceramic crucible covered with a ceramic lid. the mass of the obtained zno nps sample was from a quarter to a third of the mass of zinc acetate. according to [2], the main weight loss occurs due to the combustion of acetone ((ch3)2co) and carbon dioxide (co2) in the precursor. particle sizes were determined based on the  processing of  sorption analysis data implemented on a sorbi ms device, which allows one to study the parameters of the porous structure of nanomaterials [3], including determining the size distribution of mesopores and specific surface area. the obtained evaluation results were compared with the data of scanning electron microscopy. to develop a virtual program, the labview environment was used. the input to the analysis was a fragment of the adsorption isotherm of the selected inert gas on the test sample, the density of the test material, and the  aspect ratio of  the  nanorods. results and discussion in  this work, five types of  zinc oxide samples were investigated. the  parameters of their heat treatment and the results of determining the specific surface area are shown in table 1. the  data presented in  fig.  1 were the initial ones for determining the particle sizes, which was carried out in two stages. the first stage was to determine the specific surface according to  the  method of brunauer, emmett, teller (sbet, table 1). at the second stage, the average particle size was determined from the specific surface area in the framework of the model that the particles are nanorods with a given ratio of length and diameter l/d. the l/d ratio was selected on the basis of processing the experimental data of scanning electron microscopy, individually for each series of samples obtained by varying the annealing modes. fig. 1. plots of adsorption isotherms for samples 1–5 table 1 zno specific surface area vs. heat treatment temperature and duration № heat treatment parameters sbet, m 2/g t, °c t, hours 1 400 2 13 2 400 4 9 3 400 10 10 4 700 2 5 5 700 4 5 156 fig. 1 shows the nitrogen adsorption isotherm for a series of zinc oxide samples 1–5. according to the data of scanning electron microscopy, the particles had a rodlike shape, and it was noted that the samples synthesized at 400 °c had a shorter length and thickness than those obtained at 700 °c with the corresponding annealing duration. for example, fig. 2 shows sem images of the surface of a samples 1 and 4, and table 2 shows the results of processing the  experimental sem data for all types of samples. the diameter of the nanorods was calculated according to the formula: bet 4 2n d n s + = ρ⋅ ⋅ (1) where n — the aspect ratio, ρ — the density, sbet — specific surface area of the material. fig.  3 shows for example a  fragment of a block diagram (graphic code) of a program that calculates a  fragment of  nanorods for a given aspect ratio n. to calculate the size of the core particles by the sorption method, we used the approximation that the diameter of the rod d refers to its height l according to the data presented in table 2. the results of the sorption analysis are presented in table 3. table 2 zno particle characteristics № thickness d, nm length l, nm average l average d n = l/d 1 43–81 300–539 420 63 7 2 54–88 400–690 545 71 8 3 48–88 400–688 544 66 8 4 80–136 260–400 330 98 3 5 108–113 109–358 234 111 2 fig. 2. morphology of zno samples obtained during annealing of zinc acetate in the atmosphere, annealing for 2 hours at temperatures: a — 400 °с sample 1, b — 700 °с sample 4 157 as can be seen from table 3, the diameter of the rods will vary from 50 to 190 nm, and its height — from 0.4 to 0.7 microns, depending on the conditions of receipt. it was noted that the  height and diameter of the rods, determined by sem and sorption data, differ significantly for some samples. one possible reason is the recrystallization of the material during annealing. it is likely that the annealing process changed the density of the material, which was the reason for the discrepancy between the data of sorption analysis and sem for 2, 4, and 5 samples. another reason may be the heterogeneity of particles in size and shape in the samples. conclusions series of photocatalytically active zinc oxide samples were studied. according to the data of scanning electron microscopy, it was found that the particles have a rodshaped shape, while the  heat treatment conditions significantly affect the size and aspect ratio of the nanorods. a program has been developed that automates the process of calculating the size of nanorods based on sorption analysis data. the program can also be used to analyze nanoparticles of a different shape, however, keep in mind, that several assumptions are the basis of the calculations: all particles are the same in size and shape (if it is, for example, the shape of nanorods, then when calculating their diameter it is assumed that the aspect ratio of all the rods in the sample are the same); particles have no internal pores and cavities. the program can be used for approximate express analysis of particle sizes and in the educational process. fig. 3. a fragment of a program’s block diagram for selecting an adsorbate gas, calculating the specific surface area and determining the size of nanorods according to sorption analysis table 3 sorption analysis results № heat treatment parameters l, μm d, μm t, °c t, hours 1 400 2 0.402 0.057 2 400 4 0.693 0.087 3 400 10 0.576 0.072 4 700 2 0.521 0.174 5 700 4 0.38 0.19 158 references 1. ualikhanov re, kedruk eyu, gritsenko lv, chichero j, abdullin ha. [photocatalytic properties of nanostructured zinc oxide.] vestnik kaznrtu. 2019;133(3):542. russian 2. labuayai s, promarak v, maensiri s. synthesis and optical properties of nanocrystalline zno powders prepared by a direct thermal decomposition route. applied physics a. 2009;94:755. doi:10.1007/s00339-008-4984-2 3. belorus ao, maraeva ev, spivak yum, moshnikov va. the study of porous silicon powders by  capillary condensation. journal of  physics: conference series. 2015;586:012017. doi:10.1088/1742–6596/586/1/012017 8-hydroxy-5-nitroquinoline as a c-nucleophilic reagent in the reaction of c, c-coupling with quinazoline 237 d o i: 1 0. 15 82 6/ ch im te ch .2 02 0. 7. 4. 18 yuri a. azev, olga s. koptyaeva, oleg s. eltsov, anton n. tsmokalyuk, tatyana a. pospelova chimica techno acta. 2020. vol. 7, no. 4. p. 237–241. issn 2409–5613 8-hydroxy-5-nitroquinoline as a c-nucleophilic reagent in the reaction of c, c-coupling with quinazoline yuri a. azev,* olga s. koptyaeva, oleg s. eltsov, anton n. tsmokalyuk, tatyana a. pospelova ural federal university, 19 mira st., ekaterinburg, 620002, russian federation *email: azural@yandex.ru abstract. the first example of the reaction of 5-nitro-8-hydroxyquinoline as a c-nucleophile with quinazoline is described. as a result of the reaction of c, c-coupling, a stable σ-adduct containing the drug nitroxalin on a heterocyclic carrier was obtained. the structure of the resulting adduct was confirmed by 2d 1h-13c hsqc, 1h-13c hmbc, and 1h-15n hmbc spectra. keywords: 5-nitro-8-hydroxyquinoline; quinazoline; c, c-coupling received: 20.11.2020. accepted: 23.12.2020. published:30.12.2020. © yuri a. azev, olga s. koptyaeva, oleg s. eltsov, anton n. tsmokalyuk, tatyana a. pospelova, 2020 introduction 5-nitro-8-hydroxyquinoline (nitroxaline) is an antimicrobial agent from the  group of  hydroxyquinolines. it has a wide spectrum of action, including selectively suppressing the synthesis of bacterial dna, forms complexes with metal-containing enzymes of the microbial cell [1, 2]. preparations containing 8-hydroxyquinoline are highly toxic. in this regard, the  search for new derivatives of  these compounds that are less toxic is urgent. it seems promising to carry out the synthesis of new derivatives of 8-hydroxyquinolines by  means of  environmentally friendly c–c coupling reactions, during which the  addition of  a  c-nucleophile to the 8-hydroxyquinoxaline molecule occurs, followed by the replacement of a hydrogen atom [3]. theoretically, this type of transformation is waste-free and possible under conditions of acid activation of heterocyclic azines. reactions of nucleophilic substitution of hydrogen in 5-nitroquinolines have been described, which proceed in  the  orthoposition to the nitro group in interaction with nucleophiles containing a vicarious group (vicarious substitution) [4]. the reaction of  amination of  nitroquinolines with trimethylhydrazinium iodide occured in a solution of anhydrous dmso in the presence of potassium tert-butylate [5]. vicarious amination of nitroquinolones with 4-amino-1,2,4-triazole was carried out under similar conditions and occured at the c6 atom of nitroquinolone [6]. it was known that 5-nitro-8-hydroxyquinoline 1 reacted with formaldehyde in the presence of amines, to form 7-substituted aminomethyl derivatives of 5-nitroquinoline-8-ol 2 [7] (scheme 1). 238 experimental all reagents used were commercially available and were used without further purification (sigma aldrich, merck). the  reaction progress and purity of  the  obtained compounds were controlled by tlc method on sorbfil uv-254 plates, using visualization under uv light. melting points were determined on a stuart smp10 melting point apparatus. 1h, 13c and 19f nmr spectra were acquired on bruker bruker avance neo — 600 spectrometer in dmso-d6 solutions, using tms as internal reference for 1h and 13c nmr or cfcl3 for 19f nmr. massspectra (ei, 70ev) were recorded on microtof-q instrument (bruker daltonics) at 250 °c. elemental analysis was performed using a perkin-elmer 2400 series ii chns / o analyzer. to  calculate molecular orbitals, we used the  b3lyp exchange correlation functional in the 6-31g++ (d, p) basis set, in the framework of the density functional theory. the energy of solvation in acetonitrile was taken into account when calculating. the  calculations were performed using the gaussian09 package similarly to work [8]. 4 ( 8 h y d r ox y 5 n i t r o q u i n o l i n 7-yl)-1,4-dihydroquinazolin-3-ium 2,2,2-trifluoroacetate 4 0.095  g (0.5 mmol) of  quinazoline 3 is heated with 0.5 mmol of 5-nitro-8-hydroxyquinoline 1 in  2.0 ml of  trifluoroacetic acid for 70 hours at 110 °c. the reaction mixture is evaporated under vacuum. the residue was treated with 3 ml of alcohol, the precipitate of product 4 was filtered off, washed with 2–3 ml of ethanol, 0.105 g (32%) was obtained, m.p. > 300 °c. 1h nmr (600  mhz, dmso-d6, δ, ppm): 6.93 (s, 1h), 6.94 (d, j = 7.9 hz, 1h), 7.20 (d, j = 8.1 hz, 1h), 7.23 (t, j = 7.7 hz, 1h), 7.38 (t, j = 7.8 hz, 1h), 8.23 (s, 1h), 8.30 (dd, j = 9.0, 5.4 hz, 1h), 8.58 (s, 1h), 9.22 (d, j = 5.2 hz, 1h), 10.00 (d, j = 8.9 hz, 1h), 11.60 (s, 9h), 13c nmr (151  mhz, dmso-d6, δ, ppm): 50.23, 111.39, 114.21 (q, j = 283.5 hz, cf3), 117.88, 123.80, 125.54, 127.59, 128.43, 129.14, 129.31, 130.60, 130.72, 136.63, 144.46, 144.68, 148.27, 151.08, 160.72 (q, j = 43.2 hz, cocf3), 180.20. 15n nmr (61 mhz, dmso-d6, δ, ppm): 118.48, 125.63, 184.09, 364.34. mass spectrum (ei), 321 (20), 320 (100) [m]+, 301(20), 288 (24), 272 (56), 271 (59). found, %: c 52.54; h 3.02; n 12.90. c19h13n4o5f3 calculated, %: c 52.68; h 3.08; n 13.01. n no2 oh n no2 oh n r1 r2hn r1 r2 (ch2o)n 1 2 r1 = h; r2 = ch2ch2oh, (ch2)2-c6h5 scheme 1 239 results and discussion the data presented in the literature confirm the presence of an electrophilic center on the c6 atom and a nucleophilic center on the c7 atom in the 5-nitro-8-hydroxyquinoline molecule. it is obvious that the oxygen-containing substituents (8-hydroxy and 5-nitro group) cause a polarization of the electron density in the aromatic nucleus that is higher than that in the heterocyclic part of the nitroxaline molecule. this has been confirmed using quantum chemical calculations. the electron density in the high occupied molecular orbital (homo, fig. 1a) is most localized on the c5, c7, and c8 atoms of the aromatic nucleus. in this case, due to  the  absence of  steric hindrances, the  c7 atom of  the  nitroxaline can be the most effective nucleophilic center. the lowest unoccupied molecular orbital (lumo, fig.  1b) are localized on the nitrogen atoms of the nitro group, c6 and c8 atoms of nitroxaline. these positions of molecule 1 are characterized by increased electrophilic properties. taking into account the  absence of  steric hindrances to the formation of a stable c–c bond at the c6 position of nitroxaline, it can be assumed that this electrophilic center is the most active when interacting with nucleophiles, which is confirmed by data from the literature [4–6]. in  this work, it was found that 5-nitro-8-hydroxyquinoline 1 interacts with quinazoline 3 in the presence of trifluoroacetic acid to  form a  stable σ-adduct 4 (scheme 2). an ion peak corresponding to the molecular weight of  compound 4 was observed in the mass spectrum of electron impact. in the 1h nmr spectrum of adduct 4, the signal of the h4’ atom of the quinazoline nucleus was found at 6.93 ppm, and the signal of the corresponding sp3-hybridized c4’ atom in the 13c nmr spectrum was observed at 50.23 ppm. the assignment of signals from 1h, 13c, and 15n atoms of adduct 4 was carried out in the analysis of 2d 1h-13c hsqc, 1h-13c hmbc, and 1h-15n hmbc spectra. 2d fig. 1. distribution of electron density in the nitroxoline 1: (a) homo, (b) lumo. n no2 oh n n + 1 3 4 3 2 n 1 4 8 7 6 5 4' ho n 3' 2' nh 1' 8' 7' 6' 5' h no2 tfa, 110 oc, 70 h h cf3coo scheme 2 240 1h-15n hmbc spectrum with assignment of  signals of  1h and 15n atoms is  shown in fig. 2. apparently, 5-nitro-8-hydroxyquinoline 1 reacted as a c-nucleophile at the c7 position of the molecule to form a stable adduct under conditions of acid activation of the quinazoline nucleus. conclusions in conclusion, it should be noted that a stable σ-adduct consisting of a biologically active drug (nitroxaline) on a heterocyclic quinazoline carrier was obtained for the first time by means of the c,c-coupling reaction under the conditions of acid catalysis. references 1. mashkovsky md. lekarstvennyye sredstva [medicines]. moscow: nauka; 1993. 347 p. russian. 2. ragno r, gioia u, laneve p, bozzoni i, mai a, caffarelli e. identification of smallmolecule inhibitors of the xendou endoribonucleases family. chem med chem. 2011;6:1797–1805. doi:10.1002/cmdc.201100281 3. charushin vn, chupakhin on. topics in heterocyclic chemistry: metal-free c-h functionalization of aromatic compounds through the action of nucleophilic reagents. eds.: charushin vn, chupakhin on. switzerland: springer; 2014;37:1–50. 4. makosza m, wojciechowski k. topics in heterocyclic chemistry: nucleophilic substitution of hydrogen in arenes and heteroarenes. eds.: charushin vn, chupakhin on. switzerland: springer; 2014;37:51–105. 5. grzegozek m. vicarious nucleophilic amination of nitroquinolines by 1,1,1trimethylhydrazinium iodide. j heterocyclic chem. 2008;45:1879–82. doi:10.1002/jhet.5570450652 fig. 2. 1h-15n hmbc spectrum of adduct 4 241 6. szpakiewicz b, grzegozek m. vicarious nucleophilic amination of nitroquinolines with 4-amino-1,2,4-triazole. can j chem. 2008;86:682–685. doi:10.1139/v08–051 7. movrin m, maysinger d, marok e. biologically active mannich bases derived from nitroxoline. pharmazie. 1980;35:458–60. 8. azev yua, koptyaeva os, eltsov os, yakovleva yua, tsmokalyuk an, ivoilova av, seliverstova ea, pospelova ta, bakulev va. indole-3-carbaldehydes arylhydrazones as multisite c-nucleophiles in the reactions with quinazoline. j gen chem. 2020;9:1601–10. doi:10.1134/s1070363220090030 thermodynamics of formation of solid solutions between bazro3 and bapro3 42 d o i: 1 0. 15 82 6/ ch im te ch .2 02 0. 7. 2. 01 dmitry s. tsvetkov, vladimir v. sereda, dmitry a. malyshkin, anton l. sednev-lugovets, andrey yu. zuev, ivan l. ivanov chimica techno acta. 2020. vol. 7, no. 2. p. 42–50. issn 2409–5613 dmitry s. tsvetkov, vladimir v. sereda, dmitry a. malyshkin, anton l. sednev-lugovets, andrey yu. zuev, ivan l. ivanov* institute of natural sciences and mathematics, ural federal university, 620002, 19 mira st., ekaterinburg, russia *email: ivan.ivanov@urfu.ru thermodynamics of formation of solid solutions between bazro3 and bapro3 a linear relationship between the standard enthalpy of formation from binary oxides, δfh°ox, and the goldschmidt tolerance factor, t, for some a iibivo3 (a = ca, sr, ba; b = ti, zr, hf, ce, pr, tb, u, pu, am) perovskite oxides was used for estimation of δfh°ox of pr-substituted barium zirconates bazr1–xprxo3. a dependence of the relative change of the standard entropies, s°298, on the relative change of the molar volumes in the reactions of formation of aiibivo3 (a = ca, sr, ba; b = ti, zr, hf, ce) from binary oxides was also found to be linear. using this dependence, a relatively precise method of estimating s°298 was proposed, and s°298 of bapro3 was calculated as (162.8 ± 2.8) j·mol –1·k–1. knowing s°298 of bapro3 and using the literature data for s°298 of bazro3, the values of s°298 of bazr1–xprxo3 were predicted on the assumption that bazr1–xprxo3 is a regular or ideal solution of bapro3 in bazro3 as evidenced by the very small enthalpy of mixing calculated based on the estimated δfh°ox. the values of standard entropy changes, δfs°ox, and gibbs energy changes, δfg°ox, for the reactions of formation of bazr1–xprxo3 from bao, zro2 and pro2 were also estimated. substituting pr for zr in bazr1–xprxo3 results in δfh°ox and δfg°ox becoming more positive, indicating the decrease of the relative stability with respect to the corresponding binary oxides. expanded uncertainties of the estimated values of δfh°ox and δfg°ox are equal to 14 kj · mol–1, and those of s°298 and δfs°ox — less than 2.8 j · mol –1·k–1 and 3.5 j · mol–1·k–1, respectively, for bazr1–xprxo3 (x = 0.0–1.0). keywords: doped barium zirconate; thermodynamics; thermodynamic properties prediction received: 30.03.2020. accepted: 11.05.2020. published: 30.06.2020. © dmitry s. tsvetkov, vladimir v. sereda, dmitry a. malyshkin, anton l. sednev-lugovets, andrey yu. zuev, ivan l. ivanov, 2020 introduction partially substituted barium zirconates, bazr1–xmxo3–δ (m = rare-earth or alkaline-earth element), are the state-ofthe-art proton-conducting electrolyte materials for intermediate-temperature solid oxide fuel cells [1–3]. these complex oxides possess high proton conductivity upon hydration, good chemical and mechanical stability. among their known drawbacks are high grain boundary resistance, slow 43 grain growth and, as a consequence, very high sintering temperatures (1900–2000 k) required for obtaining dense ceramics [4– 8]. praseodymium doping was suggested as  a  possible way not only to  overcome these drawbacks [9] but also, due to potentially mixed-valent state of pr, to obtain triple-conducting (electron-proton-oxide ion) and catalytically active electrode materials for highly efficient proton-conducting solid oxide fuel cells (pc sofcs) [10, 11]. in spite of the promising electrochemical properties of the bazr1–xprxo3 zirconates [10, 11], the influence of pr doping on their thermodynamics of formation is still unknown. at the same time, understanding the thermodynamics of key materials for pc  sofcs is  of  utmost importance for the assessment of the long-term behavior of the whole device. some thermodynamic properties of bazr1–xprxo3 oxides such as enthalpy increments and constant-pressure heat capacities have been studied by us earlier [12]. this work continues systematic investigation of the influence of pr doping on the thermodynamics of barium zirconates and was aimed to estimate the standard thermodynamic functions (enthalpy, entropy and gibbs free energy) of formation of bazr1–xprxo3 oxides. results and discussion typically, when it is necessary to experimentally determine the standard formation enthalpy of a compound, the solution calorimetry is the most straightforward method of choice. however, the dissolution of zirconates is quite a hard task, as our preliminary experiments showed. it requires using either highly corrosive mixtures of acids such as, for example, hf and hno3 employed by huntelaar et al. [13], or high-temperature melts [14]. importantly, in the latter case the solvent stirring is necessary since the dissolution kinetics is slow. unfortunately, neither of  the  above mentioned possibilities was available for the authors. indeed, the measurements on mhtc 96 (setaram, france) calorimeter, in  which the solvent stirring is not implemented, resulted in irreproducible solution enthalpies of bazr1–xprxo3. besides, the hydrofluoric acid resistant measurement cell for the solution calorimeter has to be custom-made and was not readily available. because of these reasons, the standard formation enthalpies of bazr1–xprxo3 zirconates were estimated using the  well-known strong correlation between the formation enthalpy and goldschmidt’s tolerance factor [15–18]. this correlation was shown to allow predicting reasonably good, i.e. very close to the experimental values, estimates of the formation enthalpies for many perovskite oxides. the  standard enthalpy of  formation at 298.15 k, ∆fh°ox, corresponding to the reaction ao+ bo2 = abo3 (1) calculated for a number of aiibivo3 perovskite-type oxides, is  shown in  fig.  1 as a function of goldschmidt’s tolerance fac tor, ( ) 0 0 . 2 a b r r t r r + = + the  va lues of the tolerance factor were calculated using the crystal radii reported by shannon [19] with the following coordination numbers: 12 — a2+ cation, 6 — for both b4+ cation and o2– anion. the necessary thermodynamic data were taken from [20–27]. it should be noted that while the ao oxides (namely, cao, sro and bao) belong to  the  same rock-salt crystal structure class, it is  not the case for bo2 and abo3 oxides which possess different crystal structure depending on the nature of the a and b cations. 44 however, the  differences in  the  crystal structure of both bo2 and abo3 with different cations were not taken into account. the  enthalpies of  slight distortions of the perovskite structure in abo3 are generally small and were thought to be much less than the standard deviation of the estimated values. in turn, even though the crystal structure of bo2 varies more than that of  abo3, judging by  the  good linearity of the ∆fh°ox,(t) dependence in fig. 1, its influence should also be rather small. the  linear dependence observed in fig. 1 was least squares fitted. the resulting equation is the following: ( )1f ox kj mol 793.8 907.2h t−∆ ⋅ = − ⋅ (2) with the  coefficient of  determination r2 = 0.98. the standard formation enthalpies of bazr1–xprxo3 oxides calculated according to eq. (2) are summarized in table 1. the  standard deviation of  the  fitted line from the points in fig. 1 was found to be 7 kj·mol–1; therefore, the expanded uncertainty (95% confidence level) of the ∆fh°ox values reported in  table  1 is  equal to  14  kj·mol–1. however, since the  experimental points corresponding to both bazro3 and bapro3 in fig. 1 deviate from the fitted line (i.e. from eq. (2)) by less than 5.6 kj·mol–1, the accuracy of our predicted ∆fh°ox values is likely to be somewhat better than this rather conservative estimate of 14 kj·mol–1. as  follows from fig.  1 and table  1, the  standard formation enthalpy of  zirconates bazr1–xprxo3 increases with doping level, x, becoming less negative. this corresponds to  increasing distortions of  the  perovskite lattice, as  evidenced by the results of the structural studies [28, 29] and the gradual decrease of the tolerance factor, t, from the  value of  1, characteristic of undoped bazro3 possessing ideal cubic perovskite structure, to 0.946 for bapro3 with orthorhombic distortions of the lattice. similar, but significantly more pronounced trend — the decrease in ∆fh°ox with the increase in x — was also reported for bazr1–xyxo3–δ (x  =  0.0–0.3) [14]. in contrast with bazr1–xprxo3, the structure of  bazr1–xyxo3–δ is  destabilized not only by the difference in crystal radii of zr and y, but also by the formation of the oxygen vacancies. moreover, ba-loss during synthesis procedure and associated y redistribution between aand b-sublattice, not to mention of ordering of oxygen vacancies, are also influencing the stability of bazr1–xyxo3–δ. these additional factors should be responsible for more abruptly increasing ∆fh°ox of  bazr1–xyxo3–δ with the  dopant concentration, as  compared to bazr1–xprxo3. it is  also of  interest that the  mixing enthalpy of  bazr1–xprxo3 solid solution, calculated as ( ) ( ) ( ) mix f ox 1 3 f ox 3 f ox 3 bazr pr o (1 ) bazro bapro , x xh h x h x h −∆ ° = ∆ − − − ⋅∆ − − ⋅∆    (3) fig. 1. standard enthalpy of formation from binary oxides vs tolerance factor for some aiibivo3 oxides. points — calculation using the literature data [20–27], line — linear fit. the reference thermodynamic data values are also given in supplementary 45 is slightly positive, as seen in table 1, most probably, as a result of both the abovementioned difference in the crystal structure of the end members and the size mismatch between zr4+ and pr4+cations. however, the absolute value of δmixh° is well within the estimated level of uncertainty, indicating the behavior close to that of the ideal or regular (the maximum of δmixh° corresponds to x = 0.5) solution. this is consistent with a very small positive change of the molar volume upon mixing bazro3 and bapro3 [28]. the  ideal (or regular) solution behavior opens up a  possibility to  estimate the  entropy of  bazr1–xprxo3 solid solution as ( ) [ ] 1 3 3 3 bazr pr o (bazro ) (bapro ) ln( ) (1 ) ln(1 ) (1 ) , x x s r x x x x x s x s − = = − ⋅ + − ⋅ − + + − ⋅ + ⋅    (4) where r is  the  universal gas constant, the  first term in  the  right hand side is the entropy of ideal mixing and 3(bazro ) s and 3(bapro ) s   — the  standard entropies of  bapro3 and bapro3, respectively. table 1 estimated standard thermodynamic functions of bazr1 — xprxo3 (x = 0.0–1.0) x ta δfh°ox b / kj·mol–1 δfh°el c / kj·mol–1 δmixh° d / kj·mol–1 s°298 e / j·mol–1·k–1 δfs°ox f / j·mol–1·k–1 δfg°ox g / kj·mol–1 0.0 1.004  — 117.0* –1762.5 0.00 125.5 5.1 –118.5 0.1 0.998 –111.4 –1742.1 0.29 131.9 8.5 –113.9 0.2 0.992 –106.0 –1721.8 0.51 137.1 10.7 –109.2 0.3 0.986 –100.5 –1701.6 0.67 141.8 12.3 –104.2 0.4 0.980 –95.2 –1681.4 0.76 146.0 13.5 –99.2 0.5 0.974 –89.9 –1661.3 0.78 149.9 14.3 –94.2 0.6 0.968 –84.7 –1641.3 0.75 153.5 14.8 –89.1 0.7 0.963 –79.5 –1621.3 0.65 156.7 15.0 –84.0 0.8 0.957 –74.4 –1601.4 0.49 159.5 14.8 –78.8 0.9 0.951 –69.4 –1581.5 0.28 161.8 14.0 –73.6 1.0 0.946  — 64.4** –1561.7 0.00 162.8 12.0 –68.0 a goldschmidt’s tolerance factor, (crystal radii, coordination numbers: 12 — for a2+ cation, 6 — for b4+ cation and o2– anion). b standard enthalpy of formation from binary oxides at 298.15 k, the expanded uncertainty (95% confidence level) is ±14 kj·mol–1. c standard enthalpy of formation from elements at 298.15 k, the expanded uncertainty (95% confidence level) is ±14 kj·mol–1. d standard enthalpy of mixing at 298.15 k, the expanded uncertainty (95% confidence level) is ±14 kj·mol–1. e standard entropy at 298.15 k, the expanded uncertainty (95% confidence level) linearly scales with x from ±1 j·mol–1·k–1 for bazro3 (x = 0) to ±2.8 j·mol –1·k–1 for bapro3 (x = 1). f standard entropy of formation from binary oxides at 298.15 k, the expanded uncertainty (95% confidence level) linearly scales with x from ±1.2 j·mol–1·k–1 for bazro3 (x=0) to ±3.5 j·mol –1·k–1 for bapro3 (x = 1). g standard gibbs free energy of formation from binary oxides at 298.15 k, the expanded uncertainty (95% confidence level) is ±14 kj·mol–1. * experimental formation enthalpy f oxh∆   = ( — 115.12 ± 3.69) kj·mol –1 [14], (–117.44 ± 3.7) kj·mol–1 [13] ** experimental formation enthalpy f oxh∆   = ( — 70 ± 10) kj·mol –1 [20], (–147 ± 8) kj·mol–1 [21] 46 the only unknown parameter in the eq. (4) is the standard entropy of bapro3, 3(bapro ) ,s  which has to  be estimated since no experimental value has been reported so far. to do this, we, first, tried to correlate the standard entropies available for some of the aiibivo3 oxides with their molar volumes in  line with the  so-called volumebased approach introduced by glasser and jenkins [30]. however, it was found that much better correlation can be established using relative changes of entropy and molar volume instead of  their absolute values. these relative changes correspond to the formation from binary oxides (reaction (1)) and can be calculated as follows: 2 f ox ao bo ,s s s s ∆ ω = +    (5) 2 f (ox) (ao) (bo ) ,mv m m v v v ∆ ω = + (6) where ωs and ωv are the relative changes of entropy and molar volume; f oxs∆  and f (ox)mv∆ are the absolute changes of standard entropy and molar volume in the formation reaction (1); 2ao bo ,s s  and vm(ao), 2(bo )m v  — are standard entropies and molar volumes of constituting binary oxides, respectively. ωs as a function of ωv is shown in fig. 2 for the aiibivo3 oxides for which we have managed to find the literature values of the absolute entropies. surprisingly good linear correlation can be observed between ωs and ωv. the two outliers are cahfo3 and batio3. the reason for these deviations is unclear, but, taking into account the  good linear trend for the  rest of  the  aiibivo3 oxides, it seems that one can suggest some errors in the reference data reported for batio3 and cahfo3. the observed ωs(ωv) linear dependence (see fig. 2) was least squares fitted. the resulting equation is the following: 27.99 10 0.51 .s v −ω = ⋅ + ⋅ω (7) the  coefficient of  determination is  r2  =  0.97. the  standard deviation of the fitted line from the points in fig. 2 is  0.006 (note that batio3 and cahfo3 were not taken into account). the absolute entropy of  the  perovskite oxide aiibivo3 can be calculated using the eq. (7) as ( ) ( )( ) 3 2 2 abo ao bo f ox ao bo 1.0799 0.51 .v s s s s s s = + + ∆ = = + + ⋅ω       (8) the standard deviation of the as-estimated entropy from the experimental reference data does not exceed 0.5 j·mol–1·k–1. for the  outliers, batio3 and cahfo3, calculation according to  eq.  (8) leads to the standard entropies 120.6 j·mol–1·k–1 and 107.0 j·mol–1·k–1, respectively, with the  deviations from the  reference thermodynamic data [20–27,31–34] equal to  +12.7  j·mol–1·k–1 (i.e. +11.8%) and –6.4 j·mol–1·k–1 (i.e. –5.7%), respectively. the absolute entropy of bapro3, calculated using eq. (8), equals 162.8 j·mol–1·k–1 fig. 2. relative change of entropy vs relative change of molar volume in the reaction (1) for some aiibivo3 perovskites. points — calculation using the literature data [20–27, 31, 32], line — linear fit. the reference thermodynamic and structural data values are also given in supplementary 47 with probable expanded uncertainty (95% confidence level) of 2.8 j·mol–1·k–1. here, rather high uncertainty of the  3pr o s value (2.0 j·mol–1·k–1 [34]) has the most influence on the  expanded uncertainty of  3ba pr o .s with this value in hand, it is now possible to estimate the entropies of bazr1–xprxo3 solid solutions, 298 ,s according to eq. (4). the  calculated values are summarized in table 1. the combined uncertainty of  298s depends on the amount of dopant x in bazr1–xprxo3, and can be evaluated using the following expression: ( ) ( ) 3 3 298 2 2 bazro bapro ( ) (1 ) ( ) ( ) , s x s x s δ = = − ⋅δ + ⋅δ    (9) where δ(s) is the uncertainty of the corresponding entropy value s. with the values of  3bazro ( )sδ    =  1.0  j·mol–1·k–1 [32], which is less than our predicted value of  3bapro ( )sδ   = 2.8 j·mol–1·k–1, 298( )sδ  is also less than 2.8  j·mol–1·k–1 for any possible value of x. the  entropies of  formation from oxides, f ox ,s∆  listed in  table  1, obviously, also depend on the concentration of praseodymium: ( )f ox 298 1 3 298 298 2 298 2 bazr pr o (bao) (1 ) (zro ) (pr o ), x xs s s x s x s −∆ = − − − − ⋅ − − ⋅      (10) and so does their uncertainty, which increases with x from 1.2  j·mol–1·k–1 for bazro3 to 3.5 j·mol –1·k–1 for bapro3. the standard gibbs free energy of formation at 298.15 k of bazr1–xprxo3 oxides, calculated as f ox f ox f ox298.15 ,g h s∆ = ∆ − ⋅∆   (11) using estimated enthalpies and entropies, is  also given in  table  1. the  combined expanded uncertainty of  f ox ,g∆  is determined by the uncertainty of  f ox ,h∆  which is much higher than that of the entropic term, and is equal to 14 kj·mol–1. as seen, all the solid solutions studied are stable against their constituting binary oxides. however, the  relative stability of  bazr1–xprxo3 decreases with the amount of pr. conclusions the  dependence of  the  standard enthalpy of formation from binary oxides on the goldschmidt tolerance factor, f ox ( ),h t∆  was shown to  be linear for a  number of  perovskite-type aiibivo3 (a  = ca, sr, ba; b = ti, zr, hf, ce, pr, tb, u, pu, am) oxides. this dependence was used to predict the  f oxh∆  values for praseodymiumsubstituted barium zirconates bazr1–xprxo3. the increase in x results in the distortions of the crystal lattice, decreasing the tolerance factor and making f oxh∆  more positive. the values of the enthalpies of mixing, calculated regarding bazr1–xprxo3 as a solid solution of bapro3 in bazro3, were found to be indicative of the regular or ideal solution behavior. thus, to estimate the absolute entropy of bazr1–xprxo3 using the expression for the entropy of ideal mixing, the absolute entropy of bapro3, not yet reported in the literature, had to be estimated first. we found that for some of  the  aiibivo3 (a = ca, sr, ba; b = ti, zr, hf, ce) perovskites, for which the entropy values are known, an almost perfectly linear relationship exists between the  relative changes of entropy and molar volume in the reaction of formation of aiibivo3 from ao and bo2. this relationship allowed predicting the  entropy of  bapro3 with relative uncertainty of  less than 2% of  its value, the uncertainty being virtually determined 48 by the uncertainties of the reference s°298 data for the corresponding binary oxides. with the knowledge of s°298(bapro3), not only the absolute entropy values, but also the standard entropies and gibbs energies of formation of bazr1–xprxo3 from binary oxides were calculated. the latter, though increasing with x in bazr1–xprxo3, are negative for all x from 0.0 to 1.0, so bazr1–xprxo3 should be stable with respect to bao, zro2 and pro2. the methodology employed in predicting the enthalpy, f ox ,h∆  and, especially, the absolute entropy of bazr1–xprxo3 can be applied to other similar oxides. we believe that, especially in the absence of experimental data, our work would be of interest to  the  researchers who are studying the  thermodynamics and stability issues of substituted barium zirconates, and that it could provide the  data for the  future thermodynamic assessments and phase diagram calculations in bao–zro2–pro2 and related oxide systems. acknowledgements this work was supported by the russian science foundation (project no. 18-73-00022). references 1. kreuer kd. proton-conducting oxides. annu rev mater res. 2003;33(1):333–59. doi:10.1146/annurev.matsci.33.022802.091825 2. norby t. proton conductivity in perovskite oxides. boston, ma: springer us; 2009. 217 p. 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and actinide oxides. j phys chem ref data. 2014;43(1):013101. doi:10.1063/1.4825256 synthesis and research of photocurable protective coatings on the basis of olygoesteracrylates 229 d o i: 1 0. 15 82 6/ ch im te ch .2 02 0. 7. 4. 16 karsakova o. a., kuzmin m. v. chimica techno acta. 2020. vol. 7, no. 4. p. 229–232. issn 2409–5613 synthesis and research of photocurable protective coatings on the basis of olygoesteracrylates o. a. karsakova*, m. v. kuzmin chuvash state university named after in ulyanov, 15 moskovsky pr., cheboksary, 428015, russia *email: karsakova.lesya@yandex.ru abstract. in this work, photocurable protective coatings based on methacrylic acid esters have been developed and their physical and mechanical properties have been investigated. the photocurable compositions were obtained by mixing at different ratios the following methacrylic acid esters: polyethylene glycol dimethacrylate 400 and triethylene glycol dimethacrylate ether, polyethylene glycol dimethacrylate 400 and oligourethane dimethacrylate, polyethylene glycol dimethacrylate 400 and pentaerythritol tetraacrylate. for the obtained compositions, the viscosity was studied using a brookfield rotary viscometer. to initiate polymerization, a mixture of initiators was used: benzoyl peroxide and benzoin. curing of the obtained compositions was carried out under the influence of uv rays for 2–5 minutes. for photo-cured compositions, their physical and mechanical properties have been studied. it was found that the composition based on polyethylene glycol dimethacrylate modified with triethylene glycol dimethacrylate at a ratio of 70:30 has the highest strength. keywords: photocuring; protective coatings; polyethylene glycol dimethacrylate 400; triethylene glycol dimethacrylate ether; pentaerythritol tetraacrylate; oligourethane dimethacrylate; benzoyl peroxide; benzoin received: 30.10.2020. accepted: 09.12.2020. published:30.12.2020. © karsakova o. a., kuzmin m. v., 2020 introduction currently, photoinitiated polymerization is really relevant; this is due to  the  fact that the  field of  application of  photo-cured materials is  increasing. this method of curing is used in the manufacture of  lacquers, paints, adhesives, coatings, in  stereolithography, 3d printing, dentistry, laser image printing, and microelectronics [1]. an important component of photopolymerizing compositions (photopolymers) are oligomers, which determine the main characteristics of the photo-cured material  — chemical resistance, abrasion resistance, hardness, elasticity, tensile and flexural strength. under the  influence of uv rays, three-dimensional insoluble polymer systems are formed from the contained functional groups of the oligomer. for radical photopolymerization initiated by ultraviolet radiation, unsaturated polyethyracrylates are used: epoxyacrylates, complex polyester acrylates, simple polyester acrylates, aminomodified polyester acrylates, urethanacrylates [2]. another component is  monomers and diluents. they are used to  regulate the viscosity of the system. the meaning 230 of the mechanism of action of monomers in the process of ultraviolet curing is embedded in the polymer structure. acrylic acid esters are considered more popular: tripropylene glycol diacrylate, hexadiol diacrylate and dipropylene glycol diacrylate. also widely used are glycidylmethacrylates, low-viscosity derivatives of glycidylmethacrylate or methyl methacrylate and polyatomic alcohols, polyphenols, polyether polyols, polycarboxylic acids, their esters or anhydrides. when the functionality of  acrylic monomers increases, their reactivity increases, but the elasticity of the product decreases [3]. the  third component of  the  photocured composition is the initiators (photoinitiators). in  the  composition you need to  enter the  matter, that the  absorption radiation of a certain wavelength will go into an excited state, followed by molecular breakdown, leading to the emergence of radicals and initiate thereby the polymerization reaction of the monomer and oligomer, providing a transition of the composition from liquid to solid, with a spatial mesh stitched structure. thus, due to  the  intensive development of  new technologies for the  use of photo-cured polymers, it became necessary to create new special compositions based on materials with lower cost for 3d printers. in this regard, the purpose of this work is to develop and study the physical and mechanical properties of photo-cured compositions based on methacrylic acid esters. experimental polymer binders were prepared on the basis of acrylic monomers by mixing at a certain ratio of polyethylene glycol-400 dimethacrylate and triethylene glycol dimethacrylate, polyethylene glycol 400 dimethacrylate and oligourethandimethacrylate, polyethylene glycol-400 dimethacrylate and pentaerythritol tetraacrylate. to  initiate polymerization, benzoyl peroxide and benzoin were used. benzoyl peroxide and benzoin were dissolved in polyethylene glycol-400 dimethacrylate. next, to the obtained solution was added olygoethyleneamines, dimethacrylates ether of  triethylene glycol, tetraacrylate of pentaerythritol and permissively until smooth. for the obtained compositions, the viscosity was studied using a rotational brookfield viscometer. compressive strength was tested according to  gost 4651–82 on a tensile testing machine rem-10-a-2. results and discussion the initialization mechanism is shown in fig. 1. the  results of  studying the  viscosity of the photocurable compositions according to the brookfield viscometer and the compressive strength of the obtained photocurable protective coatings are given in table 1 and table 2. from table  1 it can be seen that the highest viscosity at room temperature is the composition obtained on the basis of polyethylene glycol dimethacrylate and triethylene glycol dimethacrylate ether at a ratio of 70:30. curing of the binder obtained was carried out under the action of uv light for 2–5 min. then the cured samples were kept for 14 days and their physical and mechanical properties were studied. 231 from table.  2 it can be seen that the  composition based on polyethylene glycol dimethacrylate modified with triethylene glycol dimethacrylic ether at a ratio of 70:30 has the greatest strength. table 1 the viscosity of the photocurable compositions on the basis of olygoesteracrylates at room temperature № the name of the modifier the content of the modifier, % 0 10 20 30 viscosity ηср, mpa∙s 1 dimethacrylic triethylene glycol ether 13262 15003 14755 13964 2 oligourethandimethacrylate 13262 34896 33268 35194 3 tetraacrylate of pentaerythritol 13262 12647 14945 21669 table 2 physical and mechanical properties of photocurable formulations, based on olygoesteracrylates № the name of the modifier the content of the modifier, % 0 10 20 30 uniform compressive strength δ, mpa 1 dimethacrylic triethylene glycol ether 44.41 47.37 90.19 140.96 2 oligourethandimethacrylate 44.41 48.96 54.62 73.94 3 tetraacrylate of pentaerythritol 44.41 56.19 71.75 81.98 o oh c o + oh o+ o + n r1 r2 ch2 r hv hv o n+ r2 r1 ch2 r n c+ oh + r ch+ n r1 r2 fig. 1. the mechanism of photoinitiation 232 conclusions thus, in this work we have developed a photocurable coating based on the amalgam of  polyethylene glycol and various cooligomers. it was found that the compositions modified with triethylene glycol dimethacrylic ether have the highest curing rate and maximum strength. acknowledgements the research was carried out under a grant for students from the foundation for support of  youth startups of  the  fsbei he “chuvash state university named after i. n. ulyanov”. references 1. deng l, tang l, qu  j.  synthesis and photopolymerization of  novel uv-curable macrophotoinitiators. progress in organic coatings. 2020;141:105546. doi:10.1016/j.porgcoat.2020.105546 2. quan h, zhang t, xu h, luo sh, nie j, zhu x. photo-curing 3d printing technique and its challenges. bioactive materials. 2020;5(1):110–5. doi:10.1016/j.bioactmat.2019.12.003 3. babkin o. e. polimernye pokrytiya uf-otverzhdeniya [polymer coatings of uvcuring]. saint-petersburg: spbgukit, 2012. 39 p. russian. 278 d o i: 1 0. 15 82 6/ ch im te ch .2 01 6. 3. 4. 01 8 уд к 55 4. 63 8: 54 7. 76 4 v. tkach1,2, s. c. de oliveira 2, r. ojani3, o. v. elenich1, p. i. yagodynets1 1 chernivtsi national university named fedkovych, ukraine 2 federal university of mato-gross-do-sul, brazil 3 university of mazandaran, islamic republic of iran e-mail: nightwatcher2401@gmail.com mathematical description of «polythiophene paradox» for potentiostatic electropolymerization of electrochemically modified thiophenes the phenomenon of "polythiophene paradox" for insoluble polythiophenes based on electrochemically modified monomers has been described theoretically. the corresponding mathematical model was examined using linear theory of stability and bifurcation analysis. stability conditions of steady state, monotonic and oscillatory instabilities have also been obtained. key words: polythiophene; electrochemical modification; positively paradox; electropolymerization; stable steady state. received: 08.10.2016; accepted: 22.10.2016; published: 30.12.2016. в. в. ткач1,2, с. с. де оливейра2, р. ожани3, о. в. еленич1, п. и. ягодинец1 1черновицкий национальный университет им. ю. федьковича, украина 2федеральный университет штата мату-гроссу-ду-сул, бразилия 3университет мазендерана, исламская республика иран e-mail: nightwatcher2401@gmail.com математическое описание «политиофенового парадокса» для потенциостатической электрополимеризации электрохимически модифицированных тиофенов явление «политиофенового парадокса» для нерастворимых политиофенов на основе электрохимически модифицированных мономеров было описано теоретически. соответствующая математическая модель была рассмотрена с помощью линейной теории устойчивости и бифуркационного анализа. условия устойчивости стационарного состояния, монотонной и автоколебательной неустойчивостей также были получены. ключевые слова: политиофен; электрохимическая модификации; политиофеновый парадокс; электрополимеризация; устойчивое стационарное состояние. поступило: 08.10.2016; принято: 22.10.2016; опубликовано: 30.12.2016. © tkach v., de oliveira s. c., ojani r., elenich o. v., yagodynets p. i., 2016 tkach v., de oliveira s. c., ojani r., elenich o. v., yagodynets p. i. chimica techno acta. 2016. vol. 3, no. 4. p. 278–288. issn 2409-5613 279 polythiophene (pt) is one of the most used conductive polymers (pp) of heterocyclic compounds, since the potential polymerization of its monomer is lower than that of unsubstituted benzene, and its stability in different environments is higher than that of pyrrole and furan. [1–8]. it is also worth mentioning that pt was the first conducting polymer, commercially used in electrostatic brushes produced by the company “xerox”. in the synthesis of the pp the choice of the monomer is guided by the properties of the resulting polymer and sometimes it is more convenient to obtain monomers by electrochemical methods than chemically [9–12]. moreover, some electrochemical transformations of organic compounds do not have the purely chemical analogies. pt can be obtained either chemically or electrochemically and the latter method has some advantages over the first – for example, the best conductivity of the polymer and coplanarity between the monomer fragments in it. however, the electrochemically synthesized polythiophene may undergo partial overoxidation due to the fact that its potential of overoxidation may be equal or lower than the potential of polymerization of the corresponding monomer. this phenomenon discovered in 1989 was named “polythiophene paradox” and is manifested in the appearance of oxygen-containing functional groups and the decrease in conductivity in the polymer, due to changes in the configuration of the conjugated system [13–14]. further researches showed that the “polythiophene paradox” is also possible for some of polypyrroles [15–17], making the explanation of this phenomenon is important not only to determine the exact mechanism of electropolymerization of thiophenes, but in general for the synthesis of polymers of five-membered heterocyclic compounds. this phenomenon is manifested among other things and in electrochemical instabilities – fluctuations in current or potential or the multiplicity of the stationary states [15–17]. the phenomenon of “polythiophene paradox” has been described by many experimental methods and electrochemical instabilities basically obtained a phenomenological interpretation. the main disadvantage of this explanation is that despite the fact that it can be derived from the point of view of purely logical reflections, it is not based on the solid theoretical basis, which can only be given through development and analysis of mathematical models able to adequately describe the processes in the system. we have attempted to describe the processes of overoxidation (including “polythiophene paradox”) for polymers of monomers present in the solution [18–20]. now the aim of our work is to describe the same phenomenon for the monomers, obtained electrochemically, the study of the behavior of the given process and comparison with the general case “polythiophene paradox”. the system and its model with the purpose of the mathematical description of potentiostatic (u > umod > > upol > uov) electropolymerization of thiophene, electrochemically modified with the help of the substances present in solution in excess, we introduce two variables: –  θ1 – the degree of coverage of the electrode by modified monomer; 280 –  θ2 – the degree of coverage of the electrode by nonoveroxidation polythiophene. to simplify the model we assume that non-modified monomer at the initial moment of the reaction covers the surface of the anode completely (θ0 t = 0 = 1). the modified monomer is obtained by electrochemical oxidation of the starting monomer and then electropolymerizes. in turn, the polymer overoxidizes at the same time with their own synthesis. thus, the balance equations for their concentrations will be written as: d dt r r θ1 1 2 1 = −( ) γmax (1) d dt g r r θ2 2 3 1 = −( ) max (2) where r1, r2 and r3 are speeds of modification, polymerization and overoxidation which can be described as: r k z f rt r k f z 1 1 1 2 1 0 2 2 1 2 2 1= − − −       = − ( ) exp , ( ) exp θ θ ϕ θ θζ � � ff rt r k z f rt ϕ θ ϕ 0 3 3 2 3 0       = −       exp (3–5) where k1, k2, k3 are the rate constants of the corresponding reactions, z1, z2, z3 is the number of electrons transferred in each of them, φ0 is the potential jump relative to the zero charge potential, ξ is the reaction order of electropolymerization on the monomer, f (θ2) is a function of the possible autocatalytic growth of the polymer chain, rising to the order of reaction with respect to the polymer. autocatalytic growth of the chain occurs due to the acceleration of electrochemical reaction at transition from monomer through oligomers to the polymer. mathematically equations (1–2) remind of equations (2–3) of general model for polythiophene paradox for the case of the presence of monomer in solution [19] that shows the similarity of the systems. however, due to the fact that in this case the process occurs completely on the surface and also in view of the presence of the greater number of electrochemical steps the system behavior will be slightly different from the general case that will be described and discussed below. results and discussion to analyze the behavior of the system with “polythiophene paradox” under electropolymerization of electrochemically generated polymers we analyze the system of differential equations (1–2) using linear stability theory. functional jacobian matrix whose elements are calculated for the stationary state can be shown as: a a a a 11 12 21 22       , (5) a a r r r f a r r 11 1 1 1 1 2 2 2 2 2 2 1 1 1 = − − − −    − −     γmax ( ) ’( ) θ θ θ ξ θ      a b r r b r12 1 1 1 1 2 2 2 1 1 = − − − −      γmax ( )θ θ a g a r r a r21 2 2 2 1 3 3 1 = + −       max ζ θ (6–9) 281 a g r f b r r b r r 22 2 2 2 2 2 1 3 3 3 2 1 = −       − −       max ’( )θ ξ θ θ  here ax and bx are parameters describing the effect of the electrochemical reactions in the electric double layer (edl). the necessary conditions for the oscillatory behavior described by andronov-hopf bifurcation are tr j = 0, det j > 0 (simultaneously); where tr j = a11 + a22 is the trace of the jacobian matrix and det j is its determinant. since the second condition is satisfied in most cases, the first one is the main at calculation which for this system are written as: 1 1 1 1 1 1 2 2 2 2 2 2 1 γmax ( ) ’( ) a r r r f a r r − − − −    − −       θ θ θ ξ θ     1 2 2 2 2 2 1 3 3 3 2 g r f b r r b r r max ’( )θ ξ θ θ −          − − −    ==0. (10) this condition can be satisfied only in case of presence in the main diagonal of the jacobian matrix of positive elements, describing the positive feedback. you can see that the elements axrx and bxrx, where x is the phase number can be positive (or negative under the sign minus), depending on the impact of the electrochemical stages of the reaction on the capacity of des and the strength of oxidising substances as reducing agents. this factor is common to all systems with electropolymerization [18–20]. the second factor responsible for the oscillatory behavior can be autocatalytic chain growth, the impact of which is described by the positivity of the elements containing the derivative of the function f that describes this growth. thus, in this system self-oscillatory behavior is caused by two factors – electrochemical and autocatalytic. there are temporal dissipative structures in this system the existence of which maintained by steady “supply” of the initial monomer and by the excess of the modifying substance in the solution (input entropy) and by the overoxidation of the polymer formed by (output entropy). the factor of interaction of particles on the surface of the electrode by adsortion – desorption, which is the reason of self-oscillations in such systems [18–20] does not apply here owing to the purely superficial nature of the process. for two-dimensional systems the conditions of stability of stationary states are described as: tr j < 0, det j > 0. herewith the latter condition is main. for analysis of the determinant of the jacobian matrix without cumbersome expressions we introduce new variables so that the determinant of a matrix was written as: 1 1 2 1 2 2 3 2 3 1 1γmax max . g r r x x r r x x − − − − (11) opening the straight brackets and solving the inequality det j>0 relative to r1, we obtain the condition of stability of stationary state for the system in the form: r r x x r x x x x1 2 3 1 3 1 2 2 3 > − − − − ( ) ( ) . (12) this inequality is satisfied, in the case of the growth of effects of modification of the monomer and overoxidation of the corresponding polymer (increase r1 and r3) on des and the fall of the effects of electropolymerization on it (drop r2). also the stability of the stationary state is determined by the stability of the polymer 282 (x2>x3). the process is controlled by adsorption of unmodified monomer as in the similar case of electrooxidation of procarbazine [21–22]. the critical value of the parameter r1 which is on topological limit of stability of stationary state corresponds to the multiplicity of steady states, the condition of which is: r r x x r x x1 2 3 1 3 1 2 2 3 = − − − − ( ) ( ) . x x (13) it appears by n-shaped plot of voltamperogramme and explains the equality of the stabilizing and destabilizing influences of the electrochemical processes at del. the reaction in galvanostatic and potentiometric modes is described by system based on the described above, while the variable introduces in the sdr that describes the change in charge density of the anode. the behavior of such system is more complex and will be described in future works. effect of ph is an important factor in the behavior of the system, because the process of electropolymerization and the process of overoxidation are highly dependent on ph. this system describes the electrosynthesis of polythiophene at neutral ph. in the case of more acidic ph third variable introduces in the above described des that describes the behavior of protons. addition to the above factors it can also be responsible for the appearance of electrochemical instabilities in this system. conclusion from the analysis of the system with polythiophene paradox under electropolymerization of electrosynthesized monomers, we can conclude that: – as for all similar systems with “poly thiophene paradox” the temporal dissipative structures present in this system, the existence of which is maintained by steady “supply” of the initial monomer and by an excess of the modifying substance in the solution and by overoxidation of the formed polymer. – the stability of the stationary state is determined by the distribution of the effects of electrochemical processes on the del so that the polymer remained stable. the process is controlled by the adsorption of initial monomer. – in case of equality of stabilizing and destabilizing influences in del, the monotonic instability, manifested in the multiplicity of the stationary states realizes. – the oscillatory instability in this system can be caused by the action of the factor of influence of electrochemical processes on the del and autocatalytic factors. in russian политиофен (пт) является одним из наиболее используемых проводящих полимеров (пп) гетероциклических соединений, ибо потенциал полимеризации его мономера ниже, чем для незамещенного бензола, а устойчивость в различных средах выше, чем у пиррола и фурана. [1–8]. стоит также упомянуть, что пт был первым проводящим полимером, получившим коммерческое применение в электро283 статических щетках производства компании xerox. при синтезе пп при выборе мономера руководствуются свойствами результирующего полимера и иногда получать мономеры по электрохимическим методикам более удобно, чем химически [9–12]. при этом некоторые электрохимические превращения органических веществ не имеют чисто химических аналогий. пт можно получить как химически, так и электрохимически, и последний метод имеет некоторые преимущества перед первым – к примеру, лучшая проводимость полимера и компланарность между мономерными фрагментами в нем. однако электрохимически синтезированный политио фен может подвергаться частичному переокислению ввиду того, что его потенциал переокисления может быть равным потенциалу полимеризации соответствующего мономера. данное явление, открытое в 1989 году, получило название «политиофенового парадокса» и проявляется в появлении в полимере кислородсодержащих функ циональных групп и снижении проводимости, ввиду изменения конфигурации сопряженной системы [13–14]. дальнейшие исследования показали, что «политиофеновый парадокс» возможен также для некоторых полипирролов [15–17], что делает объяснение данного феномена важным не только для определения точного механизма электрополимеризации тиофенов, но и вообще для синтеза полимеров пятичленных гетероциклических соединений. это явление проявляется, среди прочего, и в электрохимических неустойчивостях – колебаниях тока или потенциала или множественности стационарных состояний [15–17]. явление «политиофенового парадокса» было описано множеством экспериментальных методов, и электрохимические неустойчивости в  основном получали феноменологическую интерпретацию. главным недостатком такого объяснения является то, что, несмотря на то, что его можно вывести с точки зрения сугубо логических размышлений, оно не зиждется на прочном теоретическом основании, которое может быть дано только с помощью разработки и анализа математической модели, способной адекватно описать процессы в системе. мы уже предприняли попытку описать процессы переокисления (в том числе «политиофеновый парадокс») для полимеров мономеров, присутствующих в растворе [18–20]. сейчас же целью нашей работы является описание того же явления для мономеров, полученных электрохимически, изучение поведения данного процесса и его сравнение с общим случаем «политиофенового парадокса». система и ее модель с целью математического описания потенциостатической (u > umod > upol > > uov) электрополимеризации тиофена, электрохимически модифицированного с помощью вещества, присутствующего в растворе в избытке, мы вводим две переменные: – θ1 – степень покрытия электрода модифицированным мономером; – θ2 – степень покрытия электрода непереокисленным политиофеном. 284 с целью упрощения модели мы предполагаем, что немодифицированный мономер в начальный момент реакции полностью покрывает поверхность анода (θ0 t = 0 = 1). модифицированный мономер получается электрохимическим окислением начального мономера, а затем электрополимеризируется. в свою очередь, полимер переокисляется одновременно с собственным синтезом. таким образом, балансовые уравнения для их концентрации запишутся как: d dt r r θ1 1 2 1 = −( ) γmax (1) d dt g r r θ2 2 3 1 = −( ) max , (2) где r1, r2 и r3 – скорости модификации, полимеризации и переокисления, которые могут быть описаны как: r k z f rt r k f z 1 1 1 2 1 0 2 2 1 2 2 1= − − −       = − ( ) exp , ( ) exp θ θ ϕ θ θζ � � ff rt r k z f rt ϕ θ ϕ 0 3 3 2 3 0       = −       exp (3–5) где k1, k2, k3 – константы скоростей соответствующих реакций, z1, z2, z3 – количество электронов, переданных в  каждой из них, φ0 – скачок потенциала относительно потенциала нулевого заряда, ξ – порядок реакции электрополимеризации по мономеру, f (θ2) – функция возможного автокаталитического роста полимерной цепи, восходящая к порядку реакции по полимеру. автокаталитический рост цепи возникает ввиду ускорения электрохимической реакции при переходе от мономера через олигомеры к полимеру. математически уравнения (1–2) напоминают уравнения (2–3) общей модели для политиофенового парадокса для случая присутствия мономера в растворе [19], что отображает подобность систем. однако в связи с тем, что в данном случае процесс полностью происходит на поверхности, а также ввиду присутствия бóльшего количества электрохимических стадий, поведение данной системы будет несколько отличаться от общего случая, что будет описано и обсуждено ниже. результаты и обсуждения с целью анализа поведения системы с «политиофеновым парадоксом» при электрополимеризации электрохимически генерированных полимеров, мы анализируем систему дифференциальных уравнений (1–2) с использованием линейной теории устойчивости. функциональная матрица якоби, элементы которой вычислены для стационарного состояния, может быть показана как: a a a a 11 12 21 22       , (5) где a a r r r f a r r 11 1 1 1 1 2 2 2 2 2 2 1 1 1 = − − − −    − −     γmax ( ) ’( ) θ θ θ ξ θ      a b r r b r12 1 1 1 1 2 2 2 1 1 = − − − −      γmax ( )θ θ 285 a g a r r a r21 2 2 2 1 3 3 1 = + −       max ζ θ (6–9) здесь ax и bx – параметры, описывающие влияние электрохимических реакций на двойной электрический слой (дэс). необходимые условия для автоколебательного поведения, описываемого бифуркацией андронова – хопфа, – tr j = 0, det j > 0 (одновременно), где tr j = a11 + a22 – след матрицы якоби, а det j – ее определитель. поскольку второе условие удовлетворяется в большинстве случаев, главным в расчете является первое, которое для данной системы запишется как: 1 1 1 1 1 1 2 2 2 2 2 2 1 γmax ( ) ’( ) a r r r f a r r − − − −    − −       θ θ θ ξ θ     1 2 2 2 2 2 1 3 3 3 2 g r f b r r b r r max ’( )θ ξ θ θ −          − − −    ==0. (10) данное условие может быть удовлетворено только в случае присутствия в главной диагонали матрицы якоби положительных элементов, описывающих положительную обратную связь. можно увидеть, что элементы axrx и bxrx, где x – номер стадии, могут быть положительными (или отрицательными под знаком минус), в зависимости от влияния на емкость дэс электрохимических стадий реакции и от силы окисляющихся веществ как восстановителей. данный фактор общий для всех систем с электрополимеризацией [18–20]. вторым фактором, ответственным за автоколебательное поведение, может быть автокаталитический рост цепи, влияние которого описывается положительностью элементов, содержащих производную функции f, описывающей этот рост. таким образом, в данной системе автоколебательное поведение вызывается действием двух факторов – электрохимического и автокаталитического. в системе присутствуют временные диссипативные структуры, существование которых поддерживается устойчивым «запасом» начального мономера и избытком модифицирующего вещества в растворе (вход энтропии) и переокислением образованного полимера (выход энтропии). фактор взаимодействия частичек на поверхности электрода при адсорбции – десорбции, который является причиной автоколебаний в других подобных системах [18–20] здесь не действует ввиду чисто поверхностной природы процесса. для двуразмерных систем условия устойчивости стационарного состояния описываются как: tr j < 0, det j > 0. при этом последнее условие считается главным. с целью анализа определителя матрицы якоби без громоздких выражений мы вводим новые переменные таким образом, чтобы определитель матрицы записался как: 1 1 2 1 2 2 3 2 3 1 1γmax max . g r r x x r r x x − − − − (11) раскрывая прямые скобки и решая неравенство det j > 0 относительно r1, мы получаем условие устойчивости стационарного состояния для данной системы в виде: r r x x r x x x x1 2 3 1 3 1 2 2 3 > − − − − ( ) ( ) . (12) 286 данное неравенство удовлетворяется в случае роста влияний на дэс модификации мономера и переокисления соответствующего полимера (рост r1 и r3), а также падения влияния на него электрополимеризации (падение r2). также устойчивость стационарного состояния определяется устойчивостью полимера (x2 > x3). процесс при этом контролируется адсобцией немодифицированного мономера, как и в  аналогичном случае электроокисления прокарбазина [21–22]. критическое значение параметра r1, находящееся на топологическом пределе устойчивости стационарного состояния, соответствует множественности стационарных состояний, условием которого является: r r x x r x x1 2 3 1 3 1 2 2 3 = − − − − ( ) ( ) . x x (13) оно отображается n-образным участком вольтамперограммы и объяс няется равенством стабилизирующих и дестабилизирующих влияний электрохимических процессов на дэс. реакция в гальваностатическом и  потенциодинамическом режимах описывается системой, базирующейся на описанной выше, при этом в сдр вводится переменная, описывающая изменение плотности заряда анода. поведение такой системы является еще более сложным и будет описано нами в следующих работах. влияние рн является важным фактором поведения данной системы, ибо как процесс электрополимеризации, так и процесс переокисления сильно зависят от рн. данная система описывает электросинтез политиофена при нейтральном рн. в случае более кислых рн в описанную выше сдр вводится третья переменная, описывающая поведение протонов. оно помимо указанных факторов также может быть ответственным за появление электрохимических неустойчивостей в системе. выводы из анализа системы с политиофеновым парадоксом при электрополимеризации электросинтезированных мономеров можно сделать выводы о том, что: – как и для всех аналогичных систем с «политиофеновым парадоксом», в данной системе присутствуют временные диссипативные структуры, существование которых поддерживается устойчивым «запасом» начального мономера и избытком модифицирующего вещества в растворе и переокислением образованного полимера. – устойчивость стационарного состояния определяется таким распределением влияний электрохимических процессов на дэс, чтобы полимер при этом оставался устойчивым. процесс контролируется адсорбцией начального мономера. – в случае равенства стабилизирующих и дестабилизирующих влияний в дэс, реализуется монотонная неустойчивость, проявляющаяся во множественности стационарных состояний. – автоколебательная неустойчивость в данной системе может быть вызвана действием фактора влияния электрохимических процессов на дэс и автокаталитических факторов. 287 bibliography 1. yamamoto t. molecular assembly and properties of polythiophenes. npg asia materials. 2010;2(2):54-60. doi: 10.1038/asiamat.2010.37. 2. shirakawa h. the discovery of polyacetylene film: the dawning of an era of conducting polymers(nobel lecture). angewandte chemie international edition. 2001;40(14):2575-2580. 3. macdiarmid a. g. “synthetic metals”: a novel role for organic 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substituted 1,2,4-triazines a. p. krinochkinab, m. r. gudaa, a. rammohana, d. s. kopchukab, g. v. zyryanovab*, v. l. rusinov ab, o. n. chupakhinab a ural federal university named after the first president of russia b. n. yeltsin, 19 mira st., ekaterinburg, 620002, russian federation bi.ya. postovsky institute of organic synthesis of ras (ural branch), 22/20 s. kovalevskoy/akademicheskaya st., ekaterinburg, 620990, russian federation *email: g.v.zyrianov@urfu.ru abstract. a convenient synthesis of 1,2,4-triazines bearing the moieties of (hetero) arylhydrazines at the position of c5 of the 1,2,4-triazine core is reported. keywords: 1,2,4-triazines; (hetero)arylhydrazines; 5-cyano-1,2,4-triazines; ipso-substitution received: 09.09.2020. accepted: 20.12.2020. published:30.12.2020. © krinochkin a. p., guda m. r., a. rammohan, kopchuk d. s., zyryanov g. v., rusinov v. l., chupakhin o. n., 2020 d o i: 1 0. 15 82 6/ ch im te ch .2 02 0. 7. 4. 12 krinochkin a. p., guda m. r., a. rammohan, kopchuk d. s., zyryanov g. v., rusinov v. l., chupakhin o. n. chimica techno acta. 2020. vol. 7, no. 4. p. 204–208. issn 2409–5613 introduction 1,2,4-triazines with moieties of (hetero)arylhydrazines at с5 position are of  interest as  substrates for further heterocyclizations for the  synthesis of different condensed triazines, e.g., 2hpyrazolo[3,4-e][1,2,4]triazin-7(6h)  — ones, 2,6-dihydro-[1,2,4]triazino[5,6-d] [1,2,3]triazin-4-amines [1] or 2,6-dihydro-[1,2,4]triazino[6,5-e][1,2,4]triazines [2]. as for the methods for the synthesis of  similar compounds it was previously proposed ipso-substitution of  (methyl) sulfanyl group by arylhydrazine [2]. also, there is  a  number of  heterocyclizations of 1,2,4-triazine ring with the desired substituent at c5 position [1, 3, 4]. in addition, the opening of the condensed furan ring at the positions of c5 and c6 of the triazine ring is possible under the action of arylhydrazine [5]. at the same time, a known approach to  the  preparation of  various 1,2,4-triazines with the  residues of  various nucleophiles at  position c5 is  the  ipsosubstitution of the c5-cyano group. this is due to the easy availability of 5-cyano1,2,4-triazines obtained via the  nucleophilic substitution of  hydrogen process [6]. thus, the possibility of the substitution of  the  c5-cyano group by  the  residues of such nucleophiles as alcohols [7–9], amines [7,10,11], anilines [12–14], lithiumcarboranes [15], various ch acid residues [16, 17], hydrazides of carboxylic acids [18, 19] etc. was demonstrated earlier. in this article we wish to  report the  synthesis of 1,2,4-triaizines bearing (hetero)arylhydrazine moieties at position c5 by means of  ipso-substitution of  c5-cyanogroup in 1,2,4-triazines under the action of (het) arylhydrazines. 205 experimental part nmr 1h and 19f spectra were recorded on a  bruker avance-400 spectrometer (400  mhz), the  internal standard was correspondingly sime4 or cfcl3. mass-spectra (ionization type  — electrospray) were recorded on a microtof-q ii instrument from bruker daltonics (bremen, germany). elemental analysis was performed on a perkin elmer pe 2400 ii chn analyzer. the  starting 5-cyano-1,2,4-triazines 1 were obtained according to the described method [8]. a general procedure for the synthesis of  5-(het)arylarylhydrazinyl substituted 1,2,4-triazines 2 the mixture of corresponding 5-cyano1,2,4-triazine 1 (1 mmol) and the corresponding (het)arylhydrazine (1.05 mmol) was stirred at  150  °c for 8  h in  argon atmosphere. after cooling down the obtained residue was crashed and dissolved in chloroform (5-10ml). the final products were isolated by flash chromatography on sio2 using chloroform as eluent. 2-(2-(3,6-diphenyl-1,2,4-triazin5-yl)hydrazinyl)benzo[d]thiazole (2a). yield 305 mg (0.77 mmol, 77%). nmr 1h (dmso-d6, δ, ppm): 2.42 (s, 3h, me), 7.02– 7.09 and 7.22–7.28 (both m, 1h, h-5,6 (benzothiazole)), 7.43–7.47 (m, 1h, h-7 (benzothiazole)), 7.50–7.60 (m, 5h, ph), 7.61–7.65 (m, 1h, ph), 7.66–7.71 (m, 1h, h-4 (benzothiazole)), 8.16–8.22 (m, 2h, ph), 8.35–8.40 (m, 2h, ph), 10.84 (s, 1h, nhnh), 13.02 (s, 1h, nhnh). esi–ms, m/z: 397.12 (m+h)+. 2-(2-(3-(4-fluorophenyl)-6-(p-tolyl)1,2,4-triazin-5-yl)hydrazinyl)benzo[d] thiazole (2b). yield 310 mg (0.72 mmol, 72%). nmr 1h (dmso-d6, δ, ppm): 2.42 (s, 3h, me), 7.07 and 7.28 (both ddd, 3j 7.6, 7.6 hz, 4j 1.2 hz, h-5,6 (benzothiazole)), 7.33–7.36 (m, 2h, ch3c6h4), 7.40–7.45 (m, 2h, c6h4f), 7.45–7.48 (m, 1h, h-7 (benzothiazole)), 7.77–7.80 (m, 1h, h-4 (benzothiazole)), 8.03–8.06 (m, 2h, ch3c6h4), 8.49–8.54 (m, 2h, c6h4f), 11.33 (s, 1h, nhnh), 13.07 (s, 1h, nhnh). esi–ms, m/z: 429.13 (m+h)+. 5-(2-(4-fluorophenyl)hydra zinyl)3,6-di-p-tolyl-1,2,4-triazine (2c). yield 310  mg (0.80 mmol, 80%). nmr 1h (cdcl3, δ, ppm): 2.43 (s, 3h, me), 2.45 (s, 3h, me), 6.90–6.96 (m, 2h, c6h4f), 6.98–7.02 (m, 2h, c6h4f), 7.25–7.28 (m, 2h, ch3c6h4), 7.25–7.28 (m, 2h, ch3c6h4), 7.29–7.33 (m, 2h, ch3c6h4), 7.75–7.78 (m, 2h, ch3c6h4), 7.96–8.00 (m, 2h, ch3c6h4), 8.79 (s, 1h, nhnh), 9.22 (s, 1h, nhnh). nmr 19f (cdcl3, δ, ppm): –126.51 (s, 1f). esi–ms, m/z: 386.18 (m+h)+. 5-(2-phenylhydrazinyl)-3,6-di-ptolyl-1,2,4-triazine (2d). yield 280  mg (0.76 mmol, 76%). nmr 1h (dmso-d6, δ, ppm): 2.44 (s, 3h, me), 2.46 (s, 3h, me), 6.61–6.67 (m, 1h, ph), 7.03–7.08 (m, 2h, ph), 7.10–7.16 (m, 2h, ph), 7.24–7.30 (m, 2h, ch3c6h4), 7.32–7.37 (m, 2h, ch3c6h4), 8.00–8.05 (m, 2h, ch3c6h4), 8.09–8.13 (m, 2h, ch3c6h4), 9.10 (s, 1h, nhnh), 12.34 (s, 1h, nhnh). esi–ms, m/z: 368.19 (m+h)+. results and discussion the starting 5-cyano-1,2,4-triazines 1 were synthesized as  described in  literature [8]. ipso-substitution reaction was carried out under the solvent-free conditions, as reported earlier for anilines and hydrazides [12, 18] (scheme 1). the structure of the obtained products 2 was confirmed by using nmr 1н, mass206 spectrometry and elemental analysis. thus, nmr 1h spectra of compound 2 contains two characteristic broadened singlets for n-h-protons in  the  area of  8.79–13.07 ppm, signals of protons of the substituents at the positions of с3 and с6 of the triazine moiety, as  well as  the  signals of  protons of (hetero)aromatic substituents of hydrazines. it is worth to mention that, di(het)aryl hydrazine moieties are found in  many natural and synthetic biologically active compounds [20–22]. therefore, further studies are needed to evaluate the reactivity, biological activity and chelating properties of the obtained products 2. conclusions in conclusion, we have reported herein a convenient method for the synthesis of  3,6-disubstituted 1,2,4-triazines bearing moieties (het)arylhydrazine residues at the position of c5 of the triazine core by  means of  ipso-substitution of  cyanogroup in 1,2,4-triazine-5-carbonitriles by (het)arylhydrazines under the solvent-free conditions. references 1. al-matar hm, khalil kd, al-dorri dm, elnagdi mh. efficient routes to  pyrazolo[3,4-e][1,2,4]triazines and a  new ring 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polina v. notina c , sergey v. zvonarev b , evgeniya a. il’ina d , vyacheslav yu. churkin b a: samara state technical university, 244 molodogvardeiskaya st., samara, 443001, russia b: ural federal university, 19 mira st., yekaterinburg, 620000, russia c: clausthal university of technology, 2a adolph-roemer-strasse, clausthal-zellerfeld, 38678, germany d: institute of high temperature electrochemistry of the ural branch of the russian academy of sciences, 20 academicheskaya st., yekaterinburg, 620990, russia * corresponding author: frolov_zhenya@inbox.ru this article belongs to the pcee-2020 special issue. © 2021, the authors. this article is published in open access form under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). abstract the article describes in detail alumina powder synthesis by different methods at varying parameters. the technique of obtaining ceramics and the research of the optical properties for determining the materials with the maximum luminescence efficiency is presented. the concentration of the luminescence intrinsic centers and various defects differ for ceramics synthesized by different methods. it is determined that ceramics based on the powder synthesized by a sol-gel method has the maximum thermoluminescence intensity in the fcenter peak, whereas for the peak of 360 °c it is obtained with the powder prepared by precipitation of aluminum nitrate with a peg-20000 stabilizer. keywords aluminum oxide synthesis thermal decomposition chemical precipitation sol-gel method thermoluminescence received: 27.10.2020 revised: 18.12.2020 accepted: 18.12.2020 available online: 21.12.2020 1. introduction material optical properties are studied to create on their basis high-performance luminophores, in particular, based on aluminum oxide, which is widely used in various fields of science and technology. aluminum oxide is used in production of ceramics obtained from the artificially synthesized substances (pure oxides, nitrides, carbides, etc.) by forming the powder followed by sintering. one of the most important stage in preparing ceramic samples is obtaining the powders which must meet a number of requirements for morphology, agglomeration, impurity and phase composition [1]. for obtaining powders with a high purity degree such synthesis methods as a precipitation method, a method of thermal decomposition and a sol-gel method are used. the precipitation method is based on the selective distribution of components between liquid and solid phases, accompanied by the separation of one or more components from the solution in the form of a precipitate. the principle of the precipitation method is that differences in the solubility of the compounds employed are used for effective separation. optimum separation conditions are mainly determined by the value of the solubility product. the precipitation method [2, 3] can include additional thermal processing. moreover, inoculating can be used for the alumina particle agglomeration process and peg-20000 can be employed as a stabilizer [3]. thermal decomposition of aluminum nitrate (al(no3)3∙9h2o) is possible in two versions: using the original salt or its saturated solution. obtaining al2o3 by the decomposition is reported in [4], according to which the phase transfer in modification occurs at a temperature higher than 1200 °с. the problem of particle sintering during nano-structures formation by the annealing method [5] under high temperatures is actively studied. a sol-gel process was developed specifically for obtaining oxide ceramics. the process involves the following stages: preparation of alkoxide solutions, their catalytic interaction with subsequent hydrolysis, condensation polymerization, further hydrolysis [6–9]. an oxide polymer (gel) is obtained as a product. the authors of [10] describe the process of polycondensation into a gel after the hydrolysis of the polymer chains as a result of their formation upon dissolution of aluminum isopropoxide in isopropanol with the formation of complexes. after polymer chains formation their hydrolysis is carried out which results in their polycondensation into a gel. then the gel undergoes aging, flushing out, drying and thermal processing. in [11] a modified sol-gel method for obtaining http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2021.8.1.02 http://creativecommons.org/licenses/by/4.0/ chimica techno acta 2021, vol. 8(1), № 20218102 article 2 of 5 al2o3is described where urea is used as a sol stabilizer (nh2)2co. the disadvantage of the method is a complexity of the hardware design, and its advantage is the high purity and homogeneity of the synthesized compounds, as well as the possibility of obtaining various nanopowders [12]. thus, the purpose of the study is to obtain aluminum oxide by various synthesis methods, to produce ceramics on its basis and to research the optical properties of the ceramics obtained. 2. experimental in the present work the experimental samples were obtained by the three methods described above. the main stages and their characteristics for each method are presented in table 1. next, each of them will be considered in more detail. 2.1. precipitation method the alumina oxide was obtained by the method of aluminum nitrate precipitation by the alkali (potassium hydroxide) up to ph = 9–10. then, the “aging” took place – the exposure of the resulting mixture to air for a certain period of time. two durations of the sample aging were taken: 2 and 48 h. a part of the samples was prepared both with inoculating and with peg-20000. to analyze the influence of each component added, the samples were additionally prepared either only with inoculating or only with peg20000. however, it should be noted that the sample prepared only with inoculating was hygroscopic and its use for luminescent properties analysis was impossible. at the next stage the obtained suspensions of the samples were first filtered on a water-jet pump, and then dried at 100 °c for 12 h. the last step was a sintering process, which was conducted in two stages. the alumina synthesized powders were annealed at 700 °c for 30 min and then at 1150 °c for 4 h. the first stage is carried out for the full decay of the coprecipitation product up to the aluminum oxide. the second stage is necessary for the transition of the alumina into α-phase. after two-stage sintering, the powders were pressed into compacts by cold static pressing at a pressure of 0.42 gpa. the compacts were of a disk shape with a diameter of 6 mm and a thickness of 1 mm. to increase the mechanical strength of the compacts, they were additionally thermally tempered in air at a temperature of 450 °c for 30 min. for these compacts, the thermoluminescence (tl) curves were measured on an experimental setup “gray” with linear heating within the temperature range from 25 to 450 °c at a rate of 2 °/s. in order to fill the luminescence centers, before measuring tl, the samples were exposed to pulsed electron irradiation with the following characteristics: the pulse width of ≈2 ns, the average electron energy of 130 kev, the number of pulses was 10. to compare tl curves for the samples annealed at various temperatures the compacts were subjected to the additional high temperature annealing at 1200 °с, corresponding to the transfer of al2o3 into -phase. the synthesized samples of al2o3 were examined by xray diffraction method (xrd). the phase analysis was done using a rigaku d/max-2200vl/pc diffractometer (rigaku, japan) at room temperature. a curved graphite crystal was used to monochromate cu kα radiation. the data were collected over a 2 range of 15–75 in a continuous mode at a scan rate of 3 /min. 2.2. thermal decomposition direct thermal decomposition of al(no3)3∙9h2o (“chemically pure”) was conducted in two ways. the first way was to use the initial inorganic salt, to carry out thermal decomposition to amorphous alumina the temperature was first gradually raised to 250 °c (evaporation process) and then annealing took place in air at 700 °c for 30 min. the second way involved obtaining a saturated solution of aluminum nitrate by dissolving the original salt in water at its first stage. table 1 conditions of obtaining al2o3 samples sample no. synthesis method synthesis conditions annealing stages, °с (h) aging, h additives aggregate state of the initial mixture thermal preprocesssing, °с (h.) 1 2 3 1 precipitation method (with the drying stage after precipitation for 12 h at 100 °с) 2 700 (0.5) 1150 (4) 1200 (4) 2 48 3 inoculum + + peg-20000 4 peg-20000 5 thermal decomposition solid salt 250 (0.5) 700 (0.5) 1200 (4) 6 saturated solution 7 sol-gel (with a stage of evaporation to a transparent gel) 200 (3) 700 (1) 800 (1) 1200 (4) chimica techno acta 2021, vol. 8(1), № 20218102 article 3 of 5 then, similar to the previous sample, evaporation and the first stage of annealing were carried out. before annealing at the second stage, the powders were compacted at a temperature of 1200 °c for 4 h by the method described above. tl curves were measured at a temperature of 1200 °c after annealing. 2.3. sol-gel method as the initial compounds for the alumina synthesis, al(no3)3∙9h2o and c6h8o7∙h2o (“reagent grade”), previously dissolved in a small amount of distilled water, were used. the obtained solutions were mixed and evaporated to a transparent gel. the gel was dried at ~200 °c for 3 h. the product obtained was annealed in air at temperatures of 700 °c (1 h), 800 °c (1 h) and 1200 °c (4 h) to remove any organic residues and soot, as well as to form the main phase of aluminum oxide. after each annealing stage the powder was ground in an agate mortar to homogenize the powder. at the final stage, similar to the previous methods, the compacts were obtained, and tl curves were measured. 3. results and discussion the luminescent properties of the materials under study are determined by the presence and concentration of the luminescent centers and defects, which are responsible for the luminescence at various peaks of tl curves. fig. 1 shows ceramic tl curves annealed in air at 1150 °c produced from the alumina powder synthesized by the precipitation method at various synthesis parameters. it is observed that two distinct peaks with maxima in the ranges 225–230 °c and 360–400 °c are recorded. the first tl peak is mostly likely to correspond to the main dosimetric peak for which various f-type alumina centers are responsible [13]. the second peak is usually associated with chromium ions which, as a rule, is found in super low concentrations in the studied oxide and has a high luminescence [14]. it should be noted that for single-crystal alumina these peaks are observed with maxima at 170 and 300 °c [15] and for the ceramics synthesized from nanopowder obtained by the sol-gel method at 140 and 330 °c [16]. the sample under study obtained by aluminum nitrate precipitation at a low aging duration without any additives has the maximum tl peak intensity at 225 °c. moreover, the comparison of the samples with equal aging time shows that peg-20000 additive allows the creation of ceramics with a large number of intrinsic defects, such as f-centers. in addition, such synthesis method results in creation of ceramics with the maximum luminescence intensity at the tl peak at 400 °c. annealing at a temperature of 1200 °c leads to a single-phase material containing only alumina -phase. fig. 2 demonstrates ceramic tl curves shown in the previous figure (samples no. 1–4) which were additionally annealed for 4 h at a temperature of 1200 °c. it is seen that for sample no. 1 only high temperature peak intensity changes. for the samples with the longer aging duration the intensity of the both peaks increases from 1.4 to 12.1 times. in this case, the position of the peaks does not change. as the previous experiments showed, the transfer to alumina -phase (i.e. annealing at a temperature of 1200 °c) leads to a significant increase of luminescence in all the peaks recorded. in this regard, for the ceramics, for which the initial powder al2o3 was obtained by the thermal decomposition, tl curves were also measured after the last stage of annealing at 1200 °c for 4 h (fig. 3). it is shown that the maximum concentration of f-centers occurs in a sample synthesized from a solid phase. in addition, compared to the precipitation method the position of the maximum of this peak shifts to the low-temperature region and corresponds to the range 200–215 °c. for a high-temperature peak a similar situation is observed when the peak maximum shifts to a low-temperature region and corresponds to the range 350–360 °c. fig. 1 ceramic tl curves synthesized by the precipitation method (samples no. 1–4 from table 1) after the second annealing stage (1150 °c) fig. 2 tl curves of alumina ceramics synthesized by the precipitation method at various parameters (samples no. 1–4) after additional annealing for 4 h at a temperature of 1200 °c chimica techno acta 2021, vol. 8(1), № 20218102 article 4 of 5 to compare luminescent properties of ceramics synthesized by various methods, fig. 4 shows tl curves of the samples obtained by the methods of precipitation, thermal decomposition and sol-gel method, which have the highest luminescence intensity in f-centers luminescence band. the graph demonstrates that tl peaks of the samples mentioned differ in shape, which indicates a different nature of these centers or a possible contribution to this luminescence of additional defects of the structure obtained. thus, the ceramics obtained by the precipitation method has the smallest peak half-width at half maximum, and the largest value is recorded for the ceramics synthesized by the sol-gel method. the xrf analysis was carried out to assess the influence of the structural condition on the luminescence at the recorded tl peaks. its results are shown in fig. 5. 4. conclusions during the study the alumina powders were obtained by various methods, such as thermal decomposition, chemical precipitation and sol-gel. the position of fwhm tl peaks with their maxima within the ranges of 200–215 °c and 350–370 °c for the ceramics obtained by various methods is different. this fact can evidence that along with the fcenters for the first peak and the luminescence centers of chrome ions for the second peak additional defects of the obtained structure are found. thus, in the study at the synthesis of the alumina ceramics by various methods it is determined that powder-based ceramics synthesized by the sol-gel method has the maximum tl intensity during annealing under vacuum at 1200 °c at 200 °c peak, whereas for the peak of 360 °c it occurs when the powder is prepared by the aluminum nitrate precipitation with a peg-20000 stabilizer. 10 20 30 40 50 60 70 0 4000 8000 12000 16000 * * * *** ** * *** c) b) in te n s it y , a .u . 2, o a) * al2o3 fig. 5 diffractogram and bar-diffractogram of al2o3 powders: a – precipitation method, b – thermal decomposition, c – sol-gel method; * – phases other than α-al2o3 acknowledgments this work was financially supported by the russian science foundation, project no. 18-72-10082. references 1. garanin sg, rukavishnikov nn, dmitryuk av, zhilin aa, mikhaĭlov md. laser ceramic. 1. production methods. journal of optical technology. 2010;77(9):565–76. doi:10.1364/jot.77.000565 2. li h, lu h, wang s, jia j, sun h, hu x. preparation of a nanosized α-al2o3 from a supersaturated sodium aluminate solution. ceramics international. 2009;35(2):901–4. doi:10.1016/j.ceramint.2008.01.030 3. bugaeva ayu. ceramic matrix filled composite prepared by the sol-gel method. glass physics and chemistry. 2012;38:149–54. doi:10.1134/s108765961106006x 4. yakovlev iv, volodin am, zaikovskii vi, stoyanovskii vo, lapina ob, vedyagin aa. stabilizing effect of the carbon shell on phase transformation of the nanocrystalline alumina particles. ceramics international. 2018;44:4801–6. doi:10.1016/j.ceramint.2017.12.066 5. xu r, xu y. modern inorganic synthetic chemistry: second edition. changchun (china): elsevier; 2017. 785 p. fig. 3 tl curves of alumina ceramics, synthesized by thermal decomposition (samples no. 5–6 from table 1) after annealing for 4 h at 1200 °c fig. 4 tl curves of alumina oxide synthesized by different methods: the method of precipitation (sample no. 1), thermal decomposition (sample no. 5) and a sol-gel method (sample no. 7) https://doi.org/10.1364/jot.77.000565 https://doi.org/10.1016/j.ceramint.2008.01.030 https://doi.org/10.1134/s108765961106006x https://doi.org/10.1016/j.ceramint.2017.12.066 chimica techno acta 2021, vol. 8(1), № 20218102 article 5 of 5 6. rivera t, azorin j., barrera m., soto am. nanostructural processing of advanced thermoluminescent materials. radiat e def sol. 2007;162:731–6. doi:10.1080/10420150701482675 7. pierre a. introduction to sol-gel processing. new york: kluwer academic publishers; 1998. 685 p. 8. bitencourt jfs, ventieri k, gonçalves ka, pires el, mittani jc, tatumi ha. comparison between neodymium doped alumina samples obtained by pechini and sol-gel methods using thermo-stimulated luminescence and sem. j non-crystal. 2010;356:2956–59. doi:10.1016/j.jnoncrysol.2010.03.047 9. khrushcheva аа. sol-gel synthesis of composite nanoparticles based on aluminum, cerium and zirconium oxides [dissertation]. moscow (russia): baikov institute of metallurgy and materials science of the russian academy of sciences; 2016. 170 p. 10. pietrzyk b, miszczak s, kaczmarek ł, klich m. low friction nanocomposite aluminum oxide/mos2 coatings prepared by sol-gel method. ceramics international. 2018;44:8534–9. doi:10.1016/j.ceramint.2018.02.055 11. vinogradov vv, agafonov av, vinogradov av, gulyaeva ti, drozdov va, likholobov va. sol-gel synthesis, characterization and catalytic activity of mesoporous γ-alumina prepared from boehmite sol by different methods. journal of sol-gel science and technology. 2010;56:333–9. doi:10.1007/s10971-010-2310-x 12. rempel’ aa, valeeva aa. materialy i metody nanotekhnologiy [materials and methods of nanotechnology]. yekaterinburg: ural. un-ta; 2015. 136 p. russian. 13. grigorjeva l., zolotarjovs a, millers d, smits k, krug p, stollenwerk j, osman a, tenostendarp t. magnetron sputtering fabrication of α-al2o3:cr powders and their thermoluminescence properties. radiation measurements. 2018;119:140–3. doi:10.1016/j.radmeas.2018.10.009 14. kortov v., kiryakov a., pustovarov v. luminescent properties of alumina ceramics doped with chromium oxide. iop conf series: j phys: conf series. 2016;741:012195. doi:10.1088/1742-6596/741/1/012195 15. kortov vs, zvonarev sv, pustovarov va, slesarev ai. features of thermoluminescence in anion-defective alumina single crystals after highdose irradiation. radiation measurements. 2014;61:74–7. doi:10.1016/j.radmeas.2013.12.010 16. zvonarev sv, kortov vs, shtang tv, ananchenko dv, petrovykh ka. effect of structural changes on luminescent and dosimetric properties of nanoscale aluminum oxide. applied radiation and isotopes. 2015;95:44–7. doi:10.1016/j.apradiso.2014.10.003 https://doi.org/10.1080/10420150701482675 https://doi.org/10.1016/j.jnoncrysol.2010.03.047 https://doi.org/10.1016/j.ceramint.2018.02.055 https://doi.org/10.1007/s10971-010-2310-x https://doi.org/10.1016/j.radmeas.2018.10.009 https://doi.org/10.1088/1742-6596/741/1/012195 https://doi.org/10.1016/j.radmeas.2013.12.010 https://doi.org/10.1016/j.apradiso.2014.10.003 improving the environmental production of electrodes for solar panels 186 d o i: 1 0. 15 82 6/ ch im te ch .2 02 0. 7. 4. 09 patianova a. o., ivanova k. yu., rogozhina l. g., kuzmin m. v., semenov v. l. chimica techno acta. 2020. vol. 7, no. 4. p. 186–191. issn 2409–5613 improving the environmental production of electrodes for solar panels a. o. patianova*, k. yu. ivanova, l. g. rogozhina, m. v. kuzmin, v. l. semenov chuvash state university named after i. n. ulyanov, 15 moskovsky av., cheboksary, 428015, russia *email: alisa.patyanova@yandex.ru abstract. biodegradable aminosiloxanes have been synthesized by the interaction of 3-aminopropyltriethoxysilane with monoethanolamine in the presence of a binary antioxidant and an alkali metal alcoholate. the synthesized compounds were used to develop flux compositions for tinning copper wire and producing electrodes for solar panels. the wetting ability, fluxing activity and biodegradability of the flux were investigated. the possibility of using a flux for hot tinning of copper wire is shown, which makes it possible to increase the environmental friendliness of the production of electrodes for solar panels. keywords: flux; lead-free solder; solar panels; electrode; tinning; copper wire; biodegradable aminosiloxanes received: 29.10.2020. accepted: 09.12.2020. published:30.12.2020. © patianova a. o., ivanova k. yu., rogozhina l. g., kuzmin m. v., semenov v. l., 2020 introduction currently, the  most attractive and promising of  renewable energy sources is the use of photovoltaic modules [1]. the quality of photovoltaic modules directly determines the  efficiency of  solar energy production, so the production of  photovoltaic modules becomes especially important [2–5]. a relatively large number of  lead-free solders have been proposed for replacement of  lead-based ones. most of these alloys contain metals such as sn, in and bi, with the dominant sn content [6]. long-term reliability data is extremely important for the successful application of these alloys, namely properties such as the ability to withstand thermal fatigue, corrosion, changes in  mechanical properties during thermal aging and the  ability to  withstand mechanical stress. also the  cost, manufacturability, availability, melting point and the  effect of temperature on polymer components are important [7, 8]. the most promising solder is a low-melting lead-free one based on tin and indium of poin-52 grade, which is used to impart high physical, mechanical and operational properties. the  product with high antifriction and wear-resistant properties to contacts with a low transient resistance and higher corrosive properties in  acidic and alkaline solutions, as  well as  mineral oils, which is  not typical for products made of pure metals is the result of  using such alloy. the  reason of  using indium is its ability to reduce the oxidizability of alloys in the molten state, which is very important for increasing the reliability of final products. to ensure good 187 adhesion between the tin or tin alloy and the copper wire manufacturers need to use a suitable flux [8]. a significant drawback of such fluxes is  the  impossibility of  complete removal of  its components from the  brazed surface, which leads to its corrosion, as well as the inevitability of wastewater pollution with salts of heavy metals, amines and other substances when washing products after soldering. this process is environmentally harmful. the  aim of  the  work was to  increase the environmentally friendly production of electrodes for solar modules by using harmless flux compositions that meet the existing requirements for solar modules’ electrodes. it is  known that organosilicon compounds are biodegradable, they can increase the  intensity of  biological processes with oxidation of organic pollution of wastewater and thereby reduce the anthropogenic load on environmental objects [9]. for this, we synthesized aminosiloxanes, organosilicon compounds, which can reduce the corrosivity of the flux, improve the solder spreading, ensure the required fluxing activity, increase the contact angle with the tinning surface, reduce the surface tension and eliminate the solder surface oxidation and the base material to be tinned. experimental aminoalkoxysilanes i–iii were prepared by reacting 3-aminopropyltriethoxysilane with monoethanolamine at different molar ratios in the presence of a binary antioxidant and an alkali metal alcoholate. to this end, (ν1, mol) 3-aminopropyltriethoxysilane, (ν2, mol) pre-distilled monoethanolamine are loaded into a reactor equipped with a stirrer, the reaction is carried out in the presence of an antioxidant table 1 the structure and properties of aminosiloxanes formula and name ν1 : ν2 efficiency, % nd 20 ir spectrum, ν, cm–1: s i o-ch2-ch2-nh2 (o-ch2-ch3)2 h2n-h2c-h2c-h2c 3-aminopropyl(2-aminoethoxy) diethoxysilane (i) 1:1 89.7 1.4440 3373, 3294 (nh2), 2974, 2927, 2883 (ch3, ch2), 1083 (si-o-c) si (o-ch2-ch2-nh2)2 o-ch2-ch3 h2n-h2c-h2c-h2c 3-aminopropyl-di(2-aminoethoxy) ethoxysilane (ii) 2:1 95.7 1.4521 3366, 3293 (nh2), 2971, 2927, 2875 (ch3, ch2), 1081 (si-o-c) si (o-ch2-ch2-nh2)3h2n-h2c-h2c-h2c 3-aminopropyl-tri(2-aminoethoxy) silane (iii) 3:1 97.6 1.4650 1590 (si-o-c); 3362,3293 (nh2); 1083–1020 (si-o) 188 and an alkali metal alcoholate. the mixture is kept at room temperature for 10 minutes, then evacuated at  temperature up to 100 °c for 10–20 minutes, until the alcohol is completely removed. data on the  synthesis of  aminosiloxanes are given in table 1. the process was monitored by ir spectroscopy on an ft-801 fourier spectrophotometer. in the ir spectra of the obtained products, there are intense absorption bands at  1081–1085 cm–1, characteristic of  si-o-c bonds. the  bands of  the  hydroxyl group directly bonded to the silicon atom are absent, and the bands corresponding to the nh2-group are observed at  3275–3373 cm–1. aminosiloxanes are clear to light yellow oily liquids. further, with the  use of  synthesized aminosiloxanes, flux compositions were obtained. citric acid is dissolved in an isopropyl alcohol, glycerol is  added, and synthesized aminosiloxane of the general formula is  introduced into the  resulting mixture, si (o-ch2-ch2-nh2)n (o-ch2-ch3)(3-n) h2n-h2c-h2c-h2c mixed well. citric acid, isopropyl alcohol and glycerin are classified as  hazard class 4, are of  natural origin and biodegradable, so they have a minimal impact on the environment. the compositions of the flux for soldering and tinning are given in table 2. the  viscosity of  the  flux for soldering and tinning copper wire, according to  the  compositions (table  2) are determined in accordance with gost 6258–85. the activity of the flux (spreading coefficient) of poin-52 solder on copper plates at a temperature of 150±30 °c is calculated as the ratio of the spreading area of the solder under the action of the inventive flux to the spreading area of the solder under the action of the inventive flux in the form of  a  20% solution in  isopropyl alcohol. the absolute error in determining the activity of fluxes at a probability of 0.95 is ± 0.03, the error in measuring the temperature of the solder is ±2 °c. results and discussion the test results are shown in table 3. according to above data the proposed flux compositions have good fluxing activity, which provides a significant increase in  the  adhesion strength of  the  coating, improves the quality of tinning due to bettable 2 compositions of flux for soldering and tinning copper wire components, wt. % flux 1 2 3 citric acid 12 15 18 glycerol 10 8 5 aminosiloxane 1 3 aminosiloxane 2 2 aminosiloxane 3 1 isopropyl alcohol others others others 189 ter spreading of  the  solder, that ensures continuous tinning of the copper plate and the absence of corrosion and are also easily biodegradable. the use of flux to obtain an electrode for the solar module showed that during the  production process, smoke does not accumulate over the tinning bath, splashing of tin and its alloys decreases. when the tinned copper wire is twisted, cracks and chips do not form, and the  coating does not peel off. table 4 shows the test results of tinned copper wire using a flux. table 3 test results of flux for soldering and tinning copper wire flux test results of flux for soldering and tinning copper wire biodegradation after 28 days, %fluxing activity, mm spread coefficient wettability θ, o 1 95.56 2.86 14 72 2 99.16 2.91 12 64 3 110.47 2.97 10 60 table 4 tinned copper wire test results indicator name, unit of measurement tinned wire poin-52 alloy normalized value (тт) test results appearance smooth surface and continuous coating along the entire length of the wire the surface is smooth and clean, the coating is continuous the surface is smooth and clean, the coating is continuous the surface is smooth and clean, the coating is continuous diameter, mm 0.0050.0050.25 + ‑ 0.249 0.254 0.252 coating thickness, microns 0.001 0.0013.5 + ‑ 3.3 3.5 3.4 density, g/cm3 8.9±0.2 9.0 9.0 9.0 tensile strength of wire, n/mm2 200–290 240 244 244 relative extension, % +5-1025 21 21 21 dc electrical resistance at 20 °c, ohm/m. 0.35±0.03 0.35 0.35 0.35 direct current electrical resistivity at 20 °c, ohm mm2/m. 0.017±0.002 0.0176 0.0176 0.0176 190 conclusions according to  the  above data, test results show that the obtained data of the finished tinned copper wire fully comply with the  standards, and the  flux can be used in the manufacture of electrodes for solar cells. in this way, 1. biodegradable aminosiloxanes have been synthesized and used as active fluxing additives in the development of flux. 2. the qualitative and quantitative composition of the flux for tinning copper wire and the production of electrodes for solar modules was selected, which is based on the use of environmentally friendly substances based on natural, biodegradable raw materials. 3.  it has been found that the  synthesized aminosiloxanes increase the wetting ability, fluxing activity and also the biodegradability of the flux. 4.  as  a  result of  using the  developed compositions of fluxes, the gas contamination of  industrial premises decreases, the  likelihood of  injury and burns decreases. 5.  using the  developed flux for hot tinning of copper wire with low-melting lead-free solder poin-52 allows obtaining an electrode for solar panels with high physical, mechanical and operational properties. 6.  improving the  environmental friendliness of  the  production of  electrodes for solar panels is achieved by a set of the above measures. acknowledgements the research was carried out by chuvash state university within the implementation of a comprehensive project under the contract no. 2019/0837/1202–19 dated september 19, 2019 with the financial support of the ministry of education and science of russia under the agreement no. 075-11-2019-047 dated november 25, 2019. references 1. zarmai mt, ekere nn, oduoza cf, amalu eh. a review of interconnection technologies for improved crystalline silicon solar cell photovoltaic module assembly. applied energy. 2015;154:173–82. doi:10.1016/j.apenergy.2015.04.120 2. miles rw. photovoltaic solar cells: choice of materials and production methods. vacuum. 2006;80(10):1090–7. doi:10.1016/j.vacuum.2006.01.006 3. saga  t.  advances in  crystalline silicon solar cell technology for industrial mass production. npg asia mater. 2010;2(3):96–102. doi:10.1038/asiamat.2010.82 4. fazal ma, liyana nk, rubaiee s, anas a. a critical review on performance, microstructure and corrosion resistance of pb-free solders. measurement. 2019;134:897– 907. doi:10.1016/j.measurement.2018.12.051 5. li g, akram mw, jin y, chen x, zhu c, ahmad a, arshad rh, zhao x. thermomechanical behavior assessment of smart wire connected and busbar pv modules 191 during production, transportation, and subsequent field loading stages. energy. 2019;168:931–45. doi:10.1016/j.energy.2018.12.002 6. campeau z, anderson m, hasselbrink e, kavulak d, shen yc, lacerda r. sunpower® module degradation rate [internet]. sunpower corpor. 2013 [cited 29.10.2020]; p. 1–61. available from: https://energyhub.org/wp-content/uploads/2018/05/sunpowermodule-degredation-pdf.pdf 7. jeong js, park n, han c. field failure mechanism study of solder interconnection for crystalline silicon photovoltaic module. microelectronics reliability. 2012;52(9– 10):2326–30. doi:10.1016/j.microrel.2012.06.027 8. chen ym, chiu yp, wu h. improved testing of soldered interconnects quality on silicon solar cell. gpem. 2020;1(2):51–8. 9. ryzhova og, fokina iv, mukhamedzhanova tg, churmasova li, indisova ge, shanenko ef. kremniyorganicheskie soedineniya, povishayushchie effektivnost’ ochistki stochnykh vod [organosilicon compounds that increase the  efficiency of wastewater treatment]. khimicheskaya promyshlennost’ segodnya [chemical industry today]. 2018;6:9–12. russian. 164 d o i: 1 0. 15 82 6/ ch im te ch .2 01 6. 3. 3. 01 3 уд к 54 7. 62 1: 54 7. 62 2+ 66 1. 78 2 v. v. mitin, e. a. ivanova, p. e. prokhorova, yu. yu. morzherin lев «y-synthes», lunacharskogo st., 60, ekaterinburg, 620027, russia chlorophenols in organic synthesis this article reviews the alternatives for modifications of p-chlorophenols, p-chloroanisoles with the formation of c-c, c-n, c-s and c-b bonds. it is worth noting the high fundamental as well as practical importance of these reactions due to the availability and cheapness of initial chlorine substituted derivatives of phenol. key words: phenol, chlorophenols, biphenyls, reactions combination, the palladiumcatalyzed reaction. received: 17.08.2016; accepted: 11.10.2016; published: 01.12.2016. в. в. митин, е. а. иванова, п. е. прохорова, ю. ю. моржерин ооо «у-синтез», 620027, ул. луначарского, екатеринбург, россия хлорфенолы в органическом синтезе в данном обзоре рассмотрены варианты модификаций п-хлорфенолов и п-хлоранизолов с образованием связей c-c, c-n, c-s и c-b. стоит отметить высокую не только фундаментальную, но и практическую значимость данных реакций, ввиду доступности и дешевизны исходных хлорзамещенных производных фенола. ключевые слова: фенол; хлорфенолы; дифенилы; реакции сочетания; палладий-катализируемые реакции. поступило: 17.08.2016; приянято: 11.10.2016; опубликовано: 01.12.2016. © mitin v. v., ivanova e. a., prokhorova p. e., morzherin yu. yu., 2016 mitin v. v., ivanova e. a., prokhorova p. e., morzherin yu. yu. chimica techno acta. 2016. vol. 3, no. 3. p. 164–192. issn 2409-5613 introduction derivatives of p-chlorophenol have a lot of possibilities for further modifications of the chlorine atom with the formation of bonds c-c, c-n, c-s and c-b. also these compounds are the most advantageous for use in the industrial synthesis, as they are inexpensive and readily available in large quantities. 165 reactions with the formation of c-c bonds the formation of biaryls biaryl fragment is the common structural component of many biologically active compounds [1–2]. therefore the synthesis of asymmetric biaryl compounds is an important issue. palladium-catalyzed reactions of organic boron compounds with arylclorides are one of common synthetic methods for forming new carbon-carbon bonds [3]. organic boron reagents are readily available, stable to air and non-reactive to various active fragments for which usually the protective groups introduction requires. the palladium-catalyzed reactions were studied by a group of chinese researchers [4]. mil-101 was used as ligand. the reaction of 0.5 mmol of 4-chloroanisole 1a and 0.75 mmol of phenylboronic acid 2 was carried out in nitrogen atmosphere for 20 h. water solution of 1.5  mmol of base, 0.3 mmol of tetrabutylammoniumbromide (tbab) was also used. the product 3 was obtaineded with 96 % yield. also this research group studied the arylclorides’ reaction on the ullmann mechanism. the same conditions were used, but phenylboronic acid was excluded. it should be noted that in the reaction with 4-chlorophenol 1b the normal air was used instead of nitrogen atmosphere. as a result the products 4a (96 %) and 4b (97 %) were formed from compounds 1a and 1b respectively [4]. independently of the previous group the interaction of p-chlorophenol derivatives and phenylboronic acid has been studied under the leadership of p. l. diaconescu [6]. the palladium nanoparticles were used as the catalyst, the interest to it increases because of the benefits offered by these “half-geterogenous catalysts”. these advantages combine the characteristics of heterogeneous catalysis (recovery and recirculation) and homogeneous catalysis (relatively low catalyst loading and good selectivity). in addition, because of their large surface area, metal nanoparticles usually have high reactivity under mild conditions [5]. palladium nanoparticles are prepared by adding palladium (ii) salts to the aqueous dispersion of polyaniline (pani). high surface area and porosity of paninanofibers are the ideal environment to make nanocomposites metal/polyaniline. in order to take advantage of these characteristics, pani-nanofibers were employed as the carriers of palladium nanoparticles. the products 3a (88 %) and 3b (92 %) were formed as a result of this catalyst using [6]. another method of p-phenylphenol synthesis was proposed by n. a. bumagin and v. v. bykov [7]. they described the large number of biaryl compounds which 166 were obtained, in particular from chlorophenol 1a with 92 % yield. 3 mol % of palladium catalyst, 4 mmol of the base and 1 mmol of borate 4 were used. the reaction was carried out during three hours. this method is not inferior to the efficiency of both the preceding and the following methods. the synthesis, including the use of simple and easily available catalytic system of cobalt and titanium, looks attractive because it takes place under mild conditions and has high selectivity and regioselectivity. the cobalt/titanium complex, which catalyzes the cross-coupling reactions between aryl derivatives of magnesium and arylchlorides, was presented by x. f. duan and his team [8]. this reaction easily proceeds in the presence of 40  mol  % ti(oet)4 and 7.5 mol  % of cocl2, 15 mol % pbu3. the compounds 3a and 3b are formed with the yield 56 % and 86 %, respectively. the reactions involving organometallic reagents are very effective and practical way for the formation of the c-c bonds. and another group of researchers worked with grignard reagent [9]. the products 3a and 3b are formed with the yeild 95 % and 97 % when same starting materials 1a and 1b and reagents pd2(dba)3 (1 mol %), iprhcl (4 mol %) and phenyl magnesium bromide 6 (2.5 and 1 equivalent respectively) in tetrahydrofuran at temperature of 80 °c [9]. m.-j. jin and colleagues [10] also worked on getting of biaryl derivatives. they used complex of palladium and diketoiminophosphine as the catalyst. the results show that this catalytic system allows the use of less reactive substrates such as deactivated or sterically hindered arylchlorides. the 0.5 mol % catalyst was enough to achieve high efficiency under relatively mild reaction conditions. the products 3a and 3b are formed with a 89 % yield in carrying out these reactions for 4 and 5 hours respectively. the group of researchers under the supervision of a. albini [11] proposed to substitute the chlorine to durene 8 with 60 % yield of reaction product 9. the photoarylation was performed using 0.2 mol of durene 8 and 0.02 mol of 4-chlorophenol 1a in 30 ml of solvent for 7 hours. thus, the synthesis of biaryl compounds is quite popular reactions of cross-coupling of chlorophenols with the participation of the various catalitic systems. the most profitable for the getting of biaryls is the using of reactions involv167 ing boronic acid and palladium nanoparticles and tin organic reactions. introduction of other functional groups arylnitriles, which are included in the structure of dyes, herbicides, natural products and pharmaceuticals, are the following direction of the modifications. they are also useful intermediate products for the synthesis [12–13]. the reactions for obtaining aromatic nitriles were conducted by n. e. leadbeater with a colleague [14]. the process was carried out in the microwave reactor with installed power of 120 w and the threshold pressure of 200 pounds per square inch. in the experiments there were used 1 mmole of arylchloride, 2 mmol of sodium cyanide, 1 mmol of nickel bromide in 1 ml of n-methyl-2-pyrrolidone (nmp). as a result after 20 and 10 minutes respectively the products 10a (99 %) and 10b (61 %) were formed [14]. thus, this reaction is very useful to make p-cyanophenols, because using of 4-chlorophenol leads to the selective and high yield synthesis. the reactions of p-chlorophenol derivatives with aldehydes make it easy to obtain alkylarylketones with good yields. they are widely used in pharmaceutical and perfume industry, dye and agricultural chemistry. these compounds are synthesized usually under using reactions on the friedel-crafts mechanism. the reactions include dangerous reagents and does not work with the use of arenes containing electron-withdrawing substituents [15–17]. the group of researchers under the supervision of j. xiao [18] was offered more convenient method of synthesis. they carried out the reactions in the presence of palladium catalysts using different ligands, which showed high activity in relation to chlorophenols and chloroanisoles. it has been shown that the use of ligand l1 gives the highest yields. the use of dimethylamine as a solvent, the presence of molecular sieves 4å and pyrrolidine in the reaction mixture when heated to 140 °c also has a positive effect on selectivity and yield of the reaction. in the result they received the large number of compounds 12 with different substituents r’ (40–78 % yields), the nature of which does not affect to the product. α-arylcarbonyl derivatives are the important structural compounds in many natural products and pharmaceutically active substances. although arylation of simple monocarbonyl compounds is the well-known technique, the metal-catalyzed arylation of β-dicarbonyl derivatives is the more difficult task. sterically demanding ligand – di-tret-butylneopentylphosphin (dtbp) in combination with pd(dba)2 is an effective catalyst for the combination of arylchlorides 168 with diethylmalonate 13. as a result of experiments the compounds 14a (85 %) and 14b (83 %) were obtained [19]. the cross-coupling reaction on the sonogashira mechanism between arylhalides and terminal alkyne has become one of the most widely applicable reactions which used for the formation of carboncarbon bonds in organic chemistry. the reaction has been proposed as effective method for the synthesis of dendrimers, conjugated oligomers and polymers, substituted alkynes. they are also intermediates in the synthesis of natural products, pharmaceuticals, optical materials and other [20–24]. the group of researchers under the supervision of s. pal [25] was investigated the cross-coupling reactions of phenylacetylene and various arylhalogenides using the synthesized palladium – ligand complex l2 as a catalyst. the reactions were carried out in dmf in the presence of triethylamine at room temperature for 24 hours. the results were compounds 15a (50 %) and 15b (54 %) [25]. the arylhalogenides were also used for the formation of indazoles. indazoles are rare in nature, but they are the important class of heterocycles for pharmaceutical and agrochemical industries. in addition, the synthesis of 3-aryl-1h-indazoles by cross-combination of 1h-indazoles, having a methyl substituent in position 3, and arylhalogenides is attractive, because it allows to use the resulting compound in further modifications. b. a. egan and m. p. burton [26] synthesized these compounds. the starting substances were derivatives of arylhalogenides (1 equiv.) and borated indazole (1,3 eqiv.) obtained by the same researchers. the complex with palladium l3 was used as the catalyst. these reactions took place at 55 °c for 16 h (conditions a) and under the microwave radiation (100 °c for 20 min (conditions b)). the mixture of tert-butylmethyl ether (tbme) and water in a ratio of 10:1 was used as a solvent. the results were synthesized compounds 16a and 16b with a yield of 84 % and 76 %, respectively [26]. in addition the reactions with other derivatives of indazole were investigated 169 under the same conditions and the corresponding products were obtained. the results are presented in table 1. a fragment of the γ-lactone is presented in many biologically active natural compounds. in particular some of the benzyl and arylsubstituted γ-lactones exhibit anticancer activity or are used as intermediates for the synthesis of antitumor antibiotic agents [27–29]. the group of researchers under the suoervision of a. albini [30] studied photochemical reactions of arylchloride derivatives and acids k1, k2 and к3. since the use of polar (proton) solvents favors the photolysis, irradiation (310 nm, 254 nm for p-butoxybenzene) was carried out in the system acetonitrilewater in the ratio 5:1. the results of the reactions are presented in the table 2. the reactions of chlorophenol with other unsaturated acids were also examined. the results of the reactions are presented in the table 3 [30]. table 1 arylation of indazole derivatives starting compound the reaction product yield, % 1 2 3 65 70 89 170 the cross-coupling with formation of c-c bond is large area of the chlorophenols use. the products of synthesis are used in many areas, in particular as biologically active substances. reactions with formation of c-n bond the cross-coupling reactions of chlorophenols include not only the c-c bond formation, but c-n bond formation as well. moreover nitrogencontaining organic compounds possess diverse biological activity, but also they could be a building blocks for various macromolecules and new materials [31–34]. the group of indian researchers have studied reactions with participation of the copper based catalyst. the reaction was carried out using 1 mmol of arene, 1.1 mmol of amine, 1.5 mmol of base in 2 ml of solvent under nitrogen atmosphere. the results of the reactions are shown in the table 4 [35]. american researchers also studied the substitution of chlorine in arylchlorides to nitrogen-containing compounds, however instead of the copper catalyst they used the palladium complex with ligand l4. table 2 photoinduced synthesis of lactones substituent r time, h product yield, % н 14 23a-c 52 н 14 24a 95 сн3 14 24b 72 с4н9 8 24c 57 с4н9 14 25 57 table 3 photoinduced synthesis of lactones from chlorophenol acid time, h product yield, % 1 2 3 4 24 54 24 67 36 61, phenol (6 %) as byproduct 171 they investigated the influence of solvent, base and temperature and obtained following results (table. 5) [36]. it was noted that conditions 3 using lin(tms)2 in toluene at 50 °c for 2 hours are the best to produce compound 33. the yield of the target product was 94 %. the reactions with participation of aminoheterocycle 34 were also carried out. one from obtained compounds was the product 35 in 92 % yield. table 4 n-arylation of heterocyclic amines by arylhalides amine time, h product yield, % 1 2 3 4 8 70 4 82 6 84 4 92 table 5 n-arylation by chlorophenol № b as e so lv en t te m pe ra tu re , ° с t im e, h y ie ld % 1 lin(tms)2 tgf r.t. 46 94 2 lin(tms)2 tgf 40 24 94 3 lin(tms)2 toluene 50 2 94 4 naotbu toluene 100 24 89 172 these reactions are the important part of cross-coupling series with the formation of c-n bond. the group of american researchers also used the palladium catalyst. the compound l5 was used as ligand. the reaction results are given in the table 6. the reactions were carried out with 1:1 ratio of palladium acetate to ligand l5. 1.0 mmol of chloranisole 1b and 1.2 equiv. of amine, 1.4 equiv of naotbu in 1 ml of dme were used. in the case octylamine 36a 3.0 equiv. of this substance was required. all the reactions proceed with good yields. reactions with chlorophenol 1a were also studied and corresponding phenylamines 39a-b were obtained. the results of the studies listed in the table 7. the reaction was performed under same conditions [37]. thus, the reaction using chloroanisole has better yields in comparison with aniliration of chlorophenol and requires smaller amount of reagents. in addition to amination of chlorophenols and anisoles there are also the reactions of amidation. the group of researchers under the supervision of s.  l.  buchwald [36] studied these reactions. first, the effect of different conditions to the amidation of chloroanisoles 1b with benzamide 40 was studied. palladium catalyst and ligand l4 were used. the reaction was carried out with the use of 1.2 equiv of amide 40, 0.5 mol  % catalyst, 2.5 mol % ligand in 0.5 moles of solvent. the results are shown in the table 8. it was noted that the highest yields are produced in conditions 1 and 5. then, the series of compounds were obtained (table 9). 1.0–1.5 equiv. of amide, 1.2–1.5 equiv of base, 0.5 mol of solvent and the ratio kat/ligand = 1/2,5 were used. the high yields were observed with low amounts of reagents, except the reaction with carboxamide [38]. thus, the substitution of chlorine with the formation of c-n bond plays as important role in modifying of chloroarenes as the cross-coupling with the formation of c-c bond. 173 reactions with formation of c-s bond arylsulphides are valuable intermediate products in the synthesis of biologically and pharmaceutically active molecules, organic materials or intermediates in the production of these molecules. the number of arylsulphides showed potential clinical application, for example, for the treatment of alzheimer’s disease and parkinson’s disease, for the treatment of asthma and obstructive lung diseases, for the treatment of human immunodeficiency virus (hiv) [39–44]. the group of american researchers under the leadership of j. f. hartwig [37] studied the interaction of chloroarenes and thiol derivatives. the results of researches are shown in the table 10. all experiments were performed with a1:1 ratio of metal to ligand, with 1 mmol of both 4-chloroanisole 1b and 1-octanethiol 44 and 1.1 equiv. of base in 1.5 ml solvent. the compound l5 was selected as a ligand. in conditions 7 0,05 mol % of catalyst was used. in terms of 8 [pd(dba)2] was used as precursor of palladium acetate. it was noted that conditions under number 4 are the best. also, the number of reactions with 4-chloroanisole and thiophenol were carried out. in these conditions the reaction was not selective with the formation of byproducts 47b and 47c. as a result of the table 6 n-arylation by chloroanisole № reagent catalyst, mol% temperature, °с time, h product yield, % 1 36a 0,1 100 48 37a 92 2 36b 1,0 100 18-24 37b 94 3 36c 0,1 100 48 37c 90 table 7 amination of chlorophenol № reagent time, h product yield, % 1 38a 18 39a 72 2 38b 20 39b 66 table 8 amidation by benzamide № base solvent yield, % 1 k3po4 t-buoh 94 2 k3po4 toluene 89 3 k3po4 1,4dioxane 79 4 k3co3 t-buoh 45 5 cs2co3 t-buoh 97 6 t-buona t-buoh 28 7 lhmds toluene 1 table 9 amidation of chloroanisoles № r ea ge nt r ’ pd (m ol % ) pr od uc t y ie ld , % 1 42a me 1 43a 99 2 42b cy 1 43b 96 3 42c h 4 43c 82 4 42d о-phenyl 2 43d 92 174 optimizations, conditions for selective synthesis were found (table. 11). all experiments were performed with a 1:1 ratio of catalyst to ligand, 1 mmol of both starting compounds 1b and 46 and 1.1 equiv of base at 110 °c in 1.5 ml of solvent. it was noted that it is cheaper to use conditions under the number 11. the following reactions were held in these conditions and the corresponding products were obtained (table 12). all experiments were performed with a 1:1 ratio of catalyst to ligand, 1 mmol of both starting compounds 1b and 48a-c in toluene (1.5 ml) for 2-24 h at 110 °c. the reactions were also carried out with 4-chlorophenol and the corresponding products are obtained (table 13). all experiments were performed with a 1:1 ratio of catalyst to ligand, 1 mmol of both starting compounds in dme (1.5  ml) for 2–5 h under the heating at 110 °c [45–46]. thus, the cross-coupling with the formation of c-s bonds are the important reactions of the chlorine atom substitution. table 10 the interaction of chloroanisole and 1-octanethiol № base solvent temperature, °с time, h yield, % 1 naotbu dme 100 18 84 2 kotbu dme 100 18 80 3 nahmds dme 100 18 57 4 naotbu dme 110 <4 98 5 kotbu dme 110 18 87 6 naotbu 1,4-dioxane 110 5 94 7 naotbu dme 110 48 85 8 naotbu dme 110 7 96 table 11 the interaction of chloroanisole and 1-thiophenol № base solvent catalyst loading, % time, h 47:47b:47c, % 1 naotbu dme pd(oac)2 0,5 12 91:4:5 2 kotbu dme pd(oac)2 0,5 12 98:1:1 3 nahmds dme pd(oac)2 0,5 12 71:15:14 4 lihmds dme pd(oac)2 0,5 12 56:24:20 5 naotbu 1,4dioxane pd(oac)2 0,5 12 96:2:2 6 kotbu 1,4dioxane pd(oac)2 0,5 12 97:2:1 7 naotbu toluene pd(oac)2 0,5 12 98:1:1 8 kotbu toluene pd(oac)2 0,5 12 >98:1:<1 9 kotbu toluene pd(oac)2 1,0 6 >98:<1:<1 10 kotbu toluene [pd(dba)2] 0,5 12 >99,5:0,5:– 11 kotbu toluene [pd(dba)2] 1,0 <4 >99,5:0,5:– 175 reactions with formation of c-b bond arylboronic acids are the universal reagents for organic synthesis which used in the formation of c-o, c-n and c-c bonds [47]. in addition, the use of organoboranes is particularly attractive because of their high stability and low toxicity. s. l. buchwald and his team [48] have conducted researches in this area. they carried out the cross-coupling of 4-chlorophenol 1a or 4-chloroanisole 1b and bis(pinacolato)diboron 51. the ratio of catalyst and ligand was 1:2. using 2 mol % of palladium acetate the reaction was performed for 10 minutes with the formation of 97 % of the product 52b. in the case of 0.05 mol% pd2dba3 using the product 52b with 94 % yield was formed within 24 h and while increasing the amount of catalyst to 1 mol  % the product 52b was formed in 10 min. with 97 % table 12 thioarylation of 4-chloroanisole catalyst, mol% reagent r’ product yield, % 0,1 48a 49a 98 0,25 48b 49b 99 0,25 48c 49c 94 table 13 thioarylation of 4-chlorophenol catalyst, mol% reagent r’ product yield, % 2,0 48с 50a 91 1,0 48d 50b 91 176 yield and 52a was formed in 30 minutes with 82 % yield. the reaction with chloroanisole also was carried out in the presence of 2.0 mol% of palladium acetate, ligand l5 (in relation to the catalyst 3:1), potassium phosphate (3 equixv.) in 2 ml of solvent at room temperature. the result is the product with a 97 % yield [48]. thus, the cross-couplings with the formation of c-b bonds are no less important than the previous reactions. conclusion thus, in this review the high synthetic potential of the p-chlorophenols, p-chloroanisole was described. it is shown that due to the formation of new bonds c-c, c-n, c-s and c-b instead of c-cl the derivatives of chlorophenol found wide application in the synthesis of complex organic compounds. it is worth noting that there is the high not only fundamental but also practical importance of these reactions, due to the availability and cheapness of initial chlorine substituted derivatives of phenol. in russian введение производные п-хлорфенола имеют множество возможностей для дальнейших модификаций атома хлора с  образованием связей c-c, c-n, c-s и c-b. также эти соединения являются наиболее выгодными для применения в промышленном синтезе, так как они стоят недорого и легкодоступны в больших количествах. реакции с образованием c-c связи образование биарилов биарильный фрагмент является общим структурным компонентом многих биологически активных соединений [1–2]. следовательно, синтез несимметричных или замещенных несколькими алкильными фрагментами биарильных соединений является актуальной проблемой. катализируемые палладием реакции борорганических соединений с арилхлоридами являются одним из универсальных синтетических методов формирования новой углеродуглеродной связи [3]. борорганические реагенты легко доступны, стабильны на воздухе и инертны по отношению к различным функциональным группам, для которых требуется введение защитной группы и затем ее дальнейшее снятие. так, реакции с использованием палладиевого катализатора были изучены группой китайских исследователей. в  качестве лигандов использовалось 177 соединение mil-101, структура которого не раскрывалась. реакцию 0,5 ммоль 4-хлоранизола 1a и 0,75 ммоль фенилбороновой кислоты 2 проводили в атмосфере азота в течение 20 ч. использовалось 1,5 ммоль основания, 0,3 ммоль тетрабутиламмонийбромида (тбаб) в 4 мл воды. в результате образовался продукт 3 с выходом 96 %. также этой группой исследователей были изучены реакции арилхлоридов друг с другом по механизму ульмана. использовались те же условия, однако исключена фенилбороновая кислота. кроме того, в реакции с 4-хлорфенолом 1b вместо атмосферы азота использовался обычный воздух. в результате из соединений 1a и 1b образовывались продукты 4a (96 %) и 4b (97 %), соответственно [4]. независимо от предыдущей группы, взаимодействие производных п-хлорфенола и фенилбороновой кислоты было изучено под руководством p. l. diaconescu [5]. в качестве катализатора использовались наночастицы палладия, интерес к которым возрастает из-за преимуществ, предлагаемых этими «полугетерогенными катализаторами». эти преимущества сочетают в себе характеристики гетерогенного катализа (восстановление и рециркулируемость) и гомогенного катализа (относительно низкая каталитическая нагрузка и хорошая селективность). кроме того, из-за их большой площади поверхности, металлические наночастицы обычно имеют высокую реакционную способность в мягких условиях. наночастицы палладия получают путем добавления соли палладия (ii) к водной дисперсии полианилина (пани). высокая площадь поверхности и пористость пани-нановолокон служат идеальной средой, чтобы сделать нанокомпозиты металл/полианилин. для того чтобы воспользоваться этими характеристиками, были задействованы пани-нановолокна в качестве носителя наночастиц палладия. в результате использования такого катализатора образуются продукты 3a (88 %) и 3b (92 %) [6]. свой способ синтеза п-фенилфенолов был предложен н. а. бумагиным и в. в. быковым [7]. ими было описано получение большого числа биарильных соединений, получаемых в том числе, и из хлорфенолов 1a с 92 % выходом. использовалось 3 моль палладиевого катализатора, 4 ммоль% основа178 ния и 1 ммоль бората 4. реакцию проводилась в течение трех часов. данный метод не уступает по эффективности как предшествующим, так и нижеизложенным методам. привлекательным выглядит синтез, включающий в себя использование простой и легко доступной каталитической системы кобальта и титана, который проходит в мягких условиях, а также обладает высокой избирательностью и региоселективностью. x. f. duan и его сотрудниками был представлен комплекс кобальт/титан, который катализирует реакции кросссочетания между арилпроизводными магния и арилхлоридами [8]. эта реакция легко протекает в присутствии 40  моль  % ti(oet)4 и 7,5 моль% cocl2, 15 моль % pbu3. соединения 3a и 3b образуются с выходом 56 и 86 % соответственно. реакции с участием металлоорганических реагентов являются весьма эффективным и практичным способом для образования связей с-с. с магнийорганикой работала и другая группа исследователей [9]. при использовании тех же исходных веществ 1a и 1b и реагентов pd2(dba)3 (1 моль  %), iprhcl (4 моль  %), а также фенилмагнийбромида 6 (было использовано 2,5 и 1 эквивалента, соответственно) в тетрагидрофуране, при температуре 80 °с образуются продукты 3a и 3b с соответствующими выходами в 95 и 97 %. над получением биарильных производных работал также m.-j. jin с коллегами [10]. ими был использован в  качестве катализатора комплекс палладия и дикетоиминофосфина. результаты показывают, что эта каталитическая система позволяет использовать менее реакционноспособные субстраты, такие как неактивные или стерически затрудненные арилхлориды. загрузки катализатора, равной 0,5 моль %, было достаточно для достижения высокой эффективности при относительно мягких условиях реакции. при проведении данных реакций в течение 4 и 5 ч образовывались соответственно продукты 3a и 3b с выходом 89 %. группой исследователей под руководством a. albini было предложено замещать атом хлора на дурол 8 с 60 % выходом продукта реакции 9 [11]. фотоарилирование проводили с использованием 0,2 моль дурола 8 и 0,02 моль 4-хлорфенола 1a в 30 мл растворителя в течение 7 ч. однако данный способ уступает ранее описанным методам получения. таким образом, синтез биарильных соединений – это достаточно популярные реакции кросс-сочетания хлорфенолов с участием различных систем катализаторов. наиболее выгодно использовать для получения биарилов реакции с участием бороновой кисло179 ты и наночастиц палладия, а также реакции с оловоорганикой. введение других функциональных групп следующим направлением модификаций являются арилнитрилы, которые входят в структуру целого ряда красителей, гербицидов, натуральных продуктов и фармацевтических препаратов. также они являются полезными промежуточными продуктами синтеза [12–13]. реакции по получению ароматических нитрилов были проведены n.  e. leadbeater с коллегой [14]. процесс осуществлялся в микроволновом реакторе, с установленными значениями мощности 120 вт и порогового значения давления 200 фунтов на квадратный дюйм. в экспериментах использовали 1 ммоль арилхлорида, 2 ммоль цианида натрия, 1 ммоль бромида никеля в 1 мл n-метил-2-пирролидона (нмп). в результате через 20 и 10 мин. образуются соответственно продукты 10a (99 %) и 10b (61 %). таким образом, реакцию выгодно использовать для создания п-цианофенолов, так как с 4-хлорфенолом синтез протекает селективно и с высоким выходом. реакции производных 4-хлорфенолов с альдегидами позволяют легко получить алкиларилкетоны с хорошими выходами. они широко используются в фармацевтической и парфюмерной промышленности, промышленности красителей и агрохимии. такие соединения, как правило, синтезируют с помощью традиционных реакций по механизму фриделя – крафтса. реакции включают в себя работу с опасными реагентами и не идут с использованием аренов, содержащих электроноакцепторные заместители [15–17]. группой исследователей под руководством j. xiao был предложен свой более доступный метод синтеза [18]. ими были проведены реакции в присутствии палладиевых катализаторов с использованием различных лигандов, которые показали высокую активность по отношению к хлорфенолам и хлоранизолам. было показано, что использование лиганда l1 дает самые высокие выходы. также положительно влияет на селективность и выход реакции использование диметиламина в качестве растворителя, наличие молекулярных сит 4å и пирролидина в реакционной смеси при нагревании до 140 °с. в результате был получен большой ряд соединений 12, с различными заместителями r’, природа которых не влияет на протекание реакции, с выходами в 40–78 %. таким образом, данные реакции представляют значительный интерес для модификации хлоркаликсаренов. α-арилкарбонильные производные являются важными структурными со180 единениями во многих натуральных продуктах и фармацевтически активных веществах. хотя арилирование простых монокарбонильных соединений представляет собой хорошо известную методику, металл-катализируемое арилирование β-дикарбонильных производных является более сложной задачей. стерически требовательный лиганд – ди-трет-бутилнеопентилфосфин (дтбнпп) – в комбинации с pd(dba)2 является эффективным катализатором для сочетания арилхлоридов с диэтилмалонатом 13. в результате экспериментов были получены соединения 14a (85 %) и 14b (83 %) [19]. реакция кросс-сочетания по механизму соногаширы между арилгалогенидом и терминальным алкином стала одной из наиболее широко используемых реакций, которые применяют для образования углерод-углеродной связи в органической химии [20–24]. реакция была предложена в качестве эффективной методики для синтеза дендримеров, конъюгированных олигомеров и полимеров, замещенных алкинов. также они являются интермедиатами при синтезе натуральных продуктов, фармацевтических препаратов, оптических материалов и т. д. группой исследователей под руководством s. pal были исследованы реакции кросс-сочетания фенилацетилена и различных арилгалогенидов с использованием в качестве катализатора созданного ими комплекса с палладием l2 [25]. реакции проводились в дмфа в присутствии триэтиламина при комнатной температуре в течение 24 ч. результатами исследований стали соединения 15a (50 %) и 15b (54 %). арилгалогениды использовались также для образования индазолов. индазолы редко встречаются в природе, но они являются важным классом гетероциклов в фармацевтической и агрохимической отраслях. кроме того, синтез 3-арил-1н-индазолов путем перекрестного сочетания 1н-индазолов, имеющих метиловый заместитель в 3-м положении, и арилгалогенидов является привлекательным, так как он позволяет использовать полученное соединение в дальнейших модификациях. получением такого ряда соединений занимались b. a. egan и p.  m.  burton [26]. исходными веществами были производные арилгалогенидов (1  экв) и полученный этими же исследователями борированный индазол (1,3  экв). в качестве катализатора использовали комплекс с палладием l3. 181 эти реакции могут проходить как при 55 °с в течение 16 ч (условия a), так и в условиях микроволнового излучения (100 °с в течение 20 мин. (условия б)). в качестве растворителя использовали смесь трет-бутилметилового эфира (тбмэ) и воды в соотношении 10:1. в результате были синтезированы соединения 16a и 16b с выходом в 84 и 76 %, соответственно. кроме того, в тех же условиях были исследованы реакции с другими производными индазола и получены соответствующие продукты. результаты представлены в табл. 1. таким образом, вышеизложенные синтезы играют важную роль и позволяют предполагать создание подобного ряда соединений с п-хлоркаликсаренами. фрагмент γ-лактона присутствует во многих биологически активных природных соединениях. в частности, некоторые бензили арилзамещенные γ-лактоны проявляют противораковую активность или используются в качестве промежуточных продуктов таблица 1 борирование производных индазола и последующее арилирование исходное соединение продукт реакции выход, % 1 2 3 65 70 89 182 для синтеза антибиотических противоопухолевых агентов [27–29]. группа исследователей под руководством a. albini занималась фотохимическим синтезом производных арилхлоридов и кислот k1, k2 и k3. поскольку фотолизу благоприятствует использование полярных (протонных) растворителей, облучение (310 нм, 254 нм, для п-бутоксихлорбензола) проводили в системе ацетонитрил-вода в соотношении 5:1. результаты реакций представлены в табл. 2. также были исследованы реакции хлорфенола с другими ненасыщенными кислотами. результаты реакций представлены в табл. 3 [30]. все это позволяет указать на значимость изложенных реакций и использовать их для модификации хлоркаликсаренов. кросс-сочетание с образованием с-с связи – обширная область применения хлорпроизводных фенола. продукты синтеза применяют во многих отраслях, вплоть до биологически активных веществ. модифицированные каликсарены могут комбинировать свойства соединений, тем самым увеличив свою область применения. реакции с образованием c-n связи реакции кросс-сочетания хлораренов включают в себя не только образование с-с связи, но и не менее важное образование с-n связи. причем азотсодержащие органические соединения не только обладают разнообразной био логической активностью, но и служат в качестве строительного блока для различных макромолекул и новых материалов [31–34]. группа индийских исследователей изучала такого рода реакции с  участием катализатора на основе меди. реакции проводили с использованием 1 ммоль арена, 1,1 ммоль амина, 1,5 ммоль основания в 2 мл растворителя под атмосферой азота [36]. результаты реакций указаны в табл. 4 [35]. таблица 2 фотоиндуцированный синтез лактонов заместитель r время, ч продукт выход, % н 14 23a-c 52 н 14 24a 95 сн3 14 24b 72 с4н9 8 24c 57 с4н9 14 25 57 183 таблица 3 фотоиндуцированный синтез лактонов из хлорфенола кислота время, ч продукт выход, % 1 2 3 4 24 54 24 67 36 61, фенол (6 %) в качестве побочного продукта таблица 4 n-арилирование гетероциклических аминов арилхлоридами амин время, ч продукт выход, % 1 2 3 4 8 70 4 82 6 84 4 92 184 замещением хлора в арилхлоридах на азотсодержащие соединения также занимались американские исследователи, однако вместо медного катализатора они использовали палладиевый комплекс с лигандом l4. было исследовано влияние растворителя, основания и температуры и получены следующие результаты (табл. 5). было отмечено, что лучшими для получения соединения 33 являются условия под номером 3 с использованием lin(tms)2 в толуоле при температуре 50 °с в течение 2 ч. выход целевого продукта составил 94 %. также были проведены реакции с участием аминогетероцикла 34. одним из ряда полученных соединений стал продукт 35 с 92 % выходом. эти реакции являются важной составляющей ряда кросс-сочетаний с образованием c-n связи. следующая группа американских исследователей также использовала палладиевый катализатор. в качестве лиганда было использовано соединение l5 [37]. результаты реакции приведены в табл. 6. реакции проводили при соотношении 1:1 ацетата палладия к лиганду l5. использовали 1,0 ммоль хлоранизола 1b, 1,2 экв амина и 1,4 экв naotbu в  1  мл дмэ. в случае с участием октиламина 36a требуется 3,0 экв азотсодержащего вещества. все реакции идут с хорошими выходами. также были изучены реакции с хлорфенолом 1a и получены соответствующие фениламины 39a-b. результаты исследований занесены в табл. 7. реакции также проводили при соотношении 1:1 ацетата палладия к лиганду l5. использовались 1,0 ммоль хлорфенола 1a, 1,2 экв амина и 2,4 экв lihmds в 1 мл дмэ. таким образом, реакции с использованием хлоранизола имеют более хорошие выходы, по сравнению с анилированием хлорфенола, и требуют меньшего расхода реагентов. кроме аминирования хлорфенолов и анизолов, существуют также реакции амидирования. изучением этих 185 реакций занималась группа исследователей под руководством s. l. buchwald [38]. сначала было изучено влияние различных условий на амидирование хлоранизолов 1b с бензамидом 40 с участием палладиевого катализатора и лиганда l4. реакцию проводили с использованием 1,2 экв. амида 40, 0,5 моль% катализатора, 2,5 моль% лиганда в 0,5 моль растворителя: результаты исследований представлены в табл. 8. было отмечено, что самые высокие выходы образуются в условиях 1 и 5, а выгоднее использовать фосфат калия и трет-бутиловый спирт. затем в выбранных условиях был получен ряд соединений (табл. 9). использовали 1,0–1,5 экв. амида, 1,2–1,5 экв. основания, 0,5 моль растворителя и соотношение кат/лиганд равно 1/2,5. наблюдались высокие выходы продукта реакции с малыми затратами реагентов, за исключением реакции с использованием карбоксамида. таким образом, замещение хлора с  образованием связи c-n играет не менее важную роль в модифицировании хлораренов, как и кросс-сочетания с образованием с-с связи. реакции с образованием c-s связи арилсульфиды являются ценными промежуточными продуктами в органическом синтезе биологически и фармацевтически активных молекул, органических материалов или промежуточных продуктов в производсттаблица 5 n-арилирование хлорфенолом № основание растворитель температура, °с время, ч выход, % 1 lin(tms)2 тгф кт 46 94 2 lin(tms)2 тгф 40 24 94 3 lin(tms)2 толуол 50 2 94 4 naotbu толуол 100 24 89 таблица 6 n-арилирование хлоранизолом № реагент катализатор, моль% температура, °с время, ч продукт выход, % 1 36a 0,1 100 48 37a 92 2 36b 1,0 100 18-24 37b 94 3 36c 0,1 100 48 37c 90 таблица 7 аминирование хлорфенола № ре аг ен т в ре м я, ч п ро ду кт в ы хо д, % 1 38a 18 39a 72 2 38b 20 39b 66 186 ве этих молекул. ряд арилсульфидов показал потенциальное клиническое применение, например для лечения болезни альцгеймера и заболевания паркинсона, для лечения астмы и обструктивных заболеваний легких, для лечения вируса иммунодефицита человека (вич) [39–44]. группа американских исследователей под руководством j. f. hartwig занималась изучением взаимодействия хлораренов и тиолпроизводных [45–46]. результаты отмечены в табл. 10. все эксперименты проводились с соотношением 1:1 металла к лиганду, с 1 ммоль обоих 4-хлоранизола 1b и 1-октантиола 44 и 1,1 экв основания в 1,5 мл растворителя. в качестве лиганда было выбрано соединение l5. при проведении реакции в условиях под номером 7 использовали 0,05  %-ную загрузку катализатора. в условиях 8 [pd(dba)2] использовали в качестве предшественника ацетата палладия. было отмечено, что условия под номером 4 являются наиболее выгодными. также был проведен ряд реакций с 4-хлоранизолом и тиофенолом. в выбранных ранее условиях реакция шла неселективно, с образованием побочных продуктов 47b и 47c. в  результате оптимизаций удалось подобрать такие условия, чтобы образовывался только целевой продукт (табл. 11). все эксперименты проводились с соотношением 1:1 катализатора к лиганду, с 1 ммоль обоих исходных веществ 1b и 46, 1,1 экв основания при 110 °c в 1,5 мл растворителя. было таблица 8 амидирование бензамидом № основание растворитель выход, % 1 k3po4 t-buoh 94 2 k3po4 толуол 89 3 k3po4 1,4-диоксан 79 4 k3co3 t-buoh 45 5 cs2co3 t-buoh 97 6 t-buona t-buoh 28 7 lhmds толуол 1 таблица 9 амидирование хлоранизола № реагент r’ pd (моль%) продукт выход, % 1 42a me 1 43a 99 2 42b cy 1 43b 96 3 42c h 4 43c 82 4 42d о-фенил 2 43d 92 187 отмечено, что выгоднее использовать условия под номером 11. далее в этих условиях были проведены следующие реакции и получены соответствующие продукты (табл. 12). все эксперименты проводились с  соотношением 1:1 катализатора к лиганду, с 1 ммоль обоих исходных веществ 1b и 48a-c в толуоле (1,5 мл) в течение 2–24 ч при 110 °c. с 4-хлорфенолом также были проведены реакции и получены соответствующие продукты (табл. 13). все эксперименты проводились с соотношением 1:1 катализатора к лиганду, с 1 ммоль обоих исходных веществ в dme (1,5 мл) в течение 2–5 ч нагревания при 110 °с [45–46]. таким образом, кросс-сочетания с образованием c-s связи являются важными реакциями замещения атома хлора. таблица 10 взаимодействие хлоранизола и 1-октантиола № основание растворитель температура, °с время, ч выход, % 1 naotbu дмэ 100 18 84 2 kotbu дмэ 100 18 80 3 nahmds дмэ 100 18 57 4 naotbu дмэ 110 <4 98 5 kotbu дмэ 110 18 87 6 naotbu 1,4-диоксан 110 5 94 7 naotbu дмэ 110 48 85 8 naotbu дмэ 110 7 96 таблица 11 взаимодействие хлоранизола и тиофенола № основание растворитель катализатор загрузка, % время, ч 47:47b:47c, % 1 naotbu дмэ pd(oac)2 0,5 12 91:4:5 2 kotbu дмэ pd(oac)2 0,5 12 98:1:1 3 nahmds дмэ pd(oac)2 0,5 12 71:15:14 4 lihmds дмэ pd(oac)2 0,5 12 56:24:20 5 naotbu 1,4-диоксан pd(oac)2 0,5 12 96:2:2 6 kotbu 1,4-диоксан pd(oac)2 0,5 12 97:2:1 7 naotbu толуол pd(oac)2 0,5 12 98:1:1 8 kotbu толуол pd(oac)2 0,5 12 >98:1:<1 9 kotbu толуол pd(oac)2 1,0 6 >98:<1:<1 10 kotbu толуол [pd(dba)2] 0,5 12 >99,5:0,5:– 11 kotbu толуол [pd(dba)2] 1,0 <4 >99,5:0,5:– 188 реакции с образованием c-b связи арилбороновые кислоты представляют собой универсальные реагенты для органического синтеза, которые используются в образовании c-o, c-n и c-c связей [47]. кроме того, использование органоборанов особенно привлекательно из-за их высокой стабильности и низкой токсичности. s. l. buchwald и его группой были проведены исследования в этой области [48]. они проводили кросс-сочетания 4-хлорфенола 1a и 4-хлоранизола 1b и бис(пинаколато)диборона 51. соотношение катализатора и лиганда составляло 1:2. при использовании 2 моль% ацетата палладия реакцию проводили в течение 10 мин. с образованием 97 % продукта 52b. в случае же с участием 0,05 моль % pd2dba3 в течение 24 ч образовался продукт 52b с 94 % выходом, а при увеличении количества катализатора до 1  моль % – продукт 52b через 10 мин. с 97 % выходом, а 52a через 30 мин. с 82 %-ным выходом. таблица 12 тиоарилирование 4-хлоранизола катализатор, моль% реагент r’ продукт выход, % 0,1 48a 49a 98 0,25 48b 49b 99 0,25 48c 49c 94 таблица 13 тиоарилирование 4-хлорфенола катализатор, моль% реагент r’ продукт выход, % 2,0 48с 50a 91 1,0 48d 50b 91 189 также с хлоранизолом была проведена реакция в присутствии 2,0 моль% ацетата палладия, лиганда l5 (в соотношении к катализатору 3:1), фосфата калия (3 экв) в 2 мл растворителя и при комнатной температуре. в 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morzherin yu.yu. chlorophenols in organic synthesis. chimica techno acta. 2016;3(3):164–192. doi: 10.15826/ chimtech.2016.3.3.013. cta_v3_№1.cdr 58 d o i: 1 0. 15 82 6/ ch im te ch .2 01 6. 3. 1. 00 5 v. v. panteleeva, a. b. shein, o. yu. kamenschikov perm state national research university, russia, 614990, perm, bukireva st., 15 e-mail: vikpant@mail.ru; ashein@psu.ru the impedance of anodic processes on passive nisi-electrode in sulfuric fluoride containing electrolyte* the mechanism and kinetics of anodic oxidation of the ni-si electrode in solutions of 0.5 m h 2 so 4 + (0,005 – 0,05)m naf in the passive state were investigated by methods of polarization and impedance measurements. the impedance spectra are interpreted on the assumption about the formation of the bilayer oxide film on the surface of the silicide nickel, the outer layer which has a porous structure. the growth of the porous layer with the increase of the electrode potential in the investigated solutions is linearly (constant anodizing is 2.2 nm/v). the increase in naf concentration leads to a decrease in the thickness of the porous layer. the growth of the barrier layer of the oxide film was described in the framework of the model of point defects. the diffusion coefficient of oxygen vacancies inside the barrier layer of the film is 8.5 · 10–16 cm2/s and varies weakly with the potential and the content of sodium fluoride in solution. microscopic and profilometric studies show the development of the surface of the nisi electrode during anodic etching. keywords: the method of impedance measurements; two layer oxid; metal monosilicic. *the work is executed at financial support of rfbr under research project no. 14-03-31016. © panteleeva v. v., shein a. b. , kamenschikov o. yu., 2016 introduction in the study of anodic processes on the mono-silicides of metals of the iron triads in solution of 0.5 m h2so4 was found that a factor contributing to the high chemical resistance of the passive fesi, cosi, and nisi in sulfuric electrolyte is the surface chemically stable in acidic media film, similar in composition to sio2, for which characteristics such as impedance, electrical resistance, resisti vity and uniformity have a maximum value approximately in the middle of the passivation field [1–4]. however, when the content in the solution of hydrofluoric acid or its salts passivation influence of silicon dioxide is weakened: fluosilicic acid or a soluble ferrosilicates [4–7] are formed in the interaction of sio2 with hf or f-ions. the aim of the present study is to examine the concentration effect of sodium fluoride on the kinetics and mechanism of anodic 59 № 1 | 2016 chimica techno acta oxidation of the nisi electrode in sulfuric acid solution in the passive state. experimental technique the material for investigation was monosilicic nickel, which was obtained by the czochralski method from a silicon kpz-1 (99.99 wt. % si) and electrolytic nickel n-0 (99.99 wt. % ni). the electrochemical measurements were performed in solutions of 0.5 m h2so4 + (0,005 – 0,05)m naf at room temperature (~20 – 22 oc) in conditions of natural aeration in the fluoroplastic cell using a potentiostatgalvanostat with built-in frequency analyzer solartron 1280c (solartron analytical). for the preparation of solutions the deionised water was used (resistivity 18.2 mohm∙cm) and reagents h2so4 of brand “c.p.” and naf of brand “c.f.a”. all potentials in this work are presented in comparison to the normal hydrogen electrode. before measurement the working electrode surface was polished with abrasive papers with consequent reduction of grain size, degreased with ethanol, rinsed with working solution. after immersion in the solution the electrode was held at open-circuit potential before the establishment of the stationary value of the potential, then the current-voltage curves and impedance spectra were took. the range of frequency f (ω/2π) used in the impedance measurement was from 20 khz to (0,005 – 0,002) hz, the amplitude of the ac signal was (10 to 20) mv. the morphology of the sample surface before and after electrochemical testing was examined using a scanning electron microscope s-3400n (hitachi). the ima ges were obtained in a high vacuum at an accelerating voltage of 10 kv in the mode scattering of secondary electrons. the study of micro-roughness of the electrode surface was carried out at the interference microscope non–contact profilometer “new view 5000” (zygo). results and discussion the anodic potentiostatic curves of nisi electrode in solutions of 0.5 m h2so4 + (0 – 0,05)m naf are shown in fig.1. in the potential range from 0.40 to 1.70 v, corresponding to the passive state, the polarization curves of nisi there is a noticeable growth of i with increasing electrode polarization and with increasing the content of sodium fluoride in solution. in the passive potential state, the impedance hodographs nisi electrode in the investigated solutions consist of the capacitive semicircle at high frequencies and of the inclined line at low frequencies (fig. 2). the equivalent electric circuit descri bing the presence on the surface of the electrode the double-layer passivating film, consisting of an inner barrier and outer porous layers (fig. 3) was used for the simulation of impedance spectra of nisi (fig. 2). the film growth is associated with the transfer of the defects inside the barrier layer, which through the pores of the outer layer the electrolyte is accessed. at the interface of the barrier layer/electrolyte interface as a result of interaction of the substance of the oxide film with hydrofluoric acid is place of its partial transition to the solution and the the impedance of anodic processes on passive nisi-electrode in sulfuric fluoride containing electrolyte 60 № 1 | 2016 chimica techno acta formation of pores. in the circuit in fig. 3: rs is resistance of the electrolyte between the spout of the capillary loggia and the working electrode surface, r1 is the resis tance of the electrolyte in the pores of the outer layer, r2 is the resistance of charge transfer, zd is the warburg impedance describing the migration of defects within the barrier layer, the elements of constant phase cpe1 and cpe2 are modeling the heterogeneous capacity of the outer layer of an oxide film and boundary barrier layer/electrolyte interface, respectively. the parameter χ2 for the equivalent circuit in fig. 3 takes values (8-20) · 10–5, which show a good correlation between the model and experimental data. it follows from calculated by the equivalent circuit data in fig. 3, while developing the capacity nisi electrode in all solutions investigated, the thickness of the outer porous layer increases with e, approximately linearly, with the increase of porosity outstripping the growth of the layer thickness. under the assumption that the basis of oxide film on the surface of the silicide of nickel in fluoride containing electrolyte is nio (or hydrated oxide of ni(oh)2), estimated the thickness d of the porous layer of the oxide film: constant growth (k = dd/de) of the porous layer of the oxide film in the potential range from 0.8 to 1.6v equal to 2.2 nm (the thickness of the porous layer varies from 3.2 to 5.0 nm for solutions with different concentrations of naf). if we assume that the passive film is a mixed oxide and along with the nickel oxide also contains a certain amount of silicon dioxide, the constant anodizing will be somewhat less. the increasing of the concentration of sodium fluoride leads to a slight reduction in the thickness of the porous layer of the oxide film that, appa rently, is connected with the dissolution of the substance of the film in the presence of hf. the thickness of the barrier layer also increases with increasing e. the coefficient of the diffusion of oxygen vacancies d inside barrier layer of the passivating film on fig. 1. anodic potentiostatic curves of nisi in 0.5 m h2so4 + naf, m: 1 – 0; 2 – 0,005; 3 – 0,01; 4 – 0,02; 5 – 0,05 fig. 2. impedance spectra nisi in 0.5 m h2so4 + 0.02 m naf at e, in: 1 – 0,40; 2 – 0,50; 3 – 0,60; 4 – 0,80; 5 – 1,00; 6 – 1,20; 7 – 1,40; 8 – 1,60; 9 – 1,70 fig. 3. an equivalent electric circuit for nisi in 0.5 m h2so4 + (0,005 – 0,05) m naf in the passive state panteleeva v. v., shein a. b. , kamenschikov o. yu. 61 № 1 | 2016 chimica techno acta the nisi in the solution of 0.5 m h2so4 + 0,02 m naf at e = 1.2 v is 8.5∙10-16 cm2/s and varies weakly with increasing electrode polarization and the content of sodium fluoride in solution. a slight increase of the diffusion coefficient (but very weak) when the concentration of sodium fluoride in solution, probably due to the increase of defects in the structure of the barrier layer film formed in the presence of fluoride. the microscopic examination nisi before and after electrochemical testing shows that the anodic etching of silicide at e the passive condition in 0.5 m h2so4 + 0.05m naf leads to a significant deve lopment of the electrode surface (fig.  4 presents the comparison of photographs of the electrode surface before and after anodic etching in bestrides and fluoride containing solutions). the development of the surface of the electrode in sulfuric non-fluoride electrolyte may be due to restroom in the potential region of active dissolution and of active-passive transition. the introduction to the solution of sodium fluoride leads to an even more substantial irritation of the electrode surface due to dissolution of the oxides nio and sio2 in the presence of fluoride formed during anodic oxidation of nisi in the passive state. the results of measurement of microroughness of the surface of the nisi electrode fully correlate with the microscopic studies. the values of ra and rms change as follows: ra (nm)/rms (nm) = 25,5/34,3 (initial sample) : 79,8/119.4 p (anodic etching in 0.5 m h2so4 at e = 1.2 v) : 957,5/1240,8 (anodic etching in 0.5m h2so4 + 0.05m naf at e = 1.2 v). conclusion the investigation of the anodic behavi or of nisi electrode in sulfuric electrolyte containing a variable amount of hydrofluoric acid shows that the presence of hf in solution exerts a strong influence on current-voltage and impedance cha racteristics of the silicide. the latter is evident in the substantial weakening of the passivating action of oxygen-containing compounds of the alloy components and activation nisi of dissolution. fig. 4. photomicrographs of the surface of the nisi (×700) before (a) and after anodic etching in 0.5 m h2so4 (b) and 0.5 m h2so4 + 0.05m naf (b) at e = 1.2 v а b vc the impedance of anodic processes on passive nisi-electrode in sulfuric fluoride containing electrolyte 62 № 1 | 2016 chimica techno acta 1. panteleeva v. v., shein a. b. cosi impedance of the electrode in sulfuric acid solution. izv. vyssh. uchebn. zaved. khim. khim. tekhnol. 2012;55(7):35–39. 2. panteleeva v. v., shein a. b. the impedance of anodic processes on fesi electrode in sulfuric acid solution. izv. vyssh. uchebn. zaved., khim. khim. tekhnol. 2013;56(10):48–52. 3. panteleeva v. v., shein a. b. growth of anodic oxide films on iron-triad metal monosilicides in sulfuric acid electrolyte. russian j. electrochemistry. 2014;50(11):1036–1043. doi: 10.1134/s102319351411007x. 4. shein a. b. elektrokhimia silicidov i germanidov perehodnih metallov, perm, perm. gos. univ. 2009:269 pp. (in russian). 5. batenkov v. a. elektrokhimia poluprovodnikov. barnaul, alt. gos. univ. 2002:162 pp. (in russian). 6. panteleeva v. v., shein a. b. the anodic dissolution of monosilicide iron in sulfuric acid electrolyte containing sodium fluoride. vestn. tamb. univ. estestv. techn. nauk. 2013;18(5):2237–2240. 7. remi g. kurs neorganicheskoj khimii. moscow. 1972:824 pp. (in russian). panteleeva v. v., shein a. b. , kamenschikov o. yu. 63 у д к 6 68 .2 43 .8 8 в. в. пантелеева, а. б. шеин, о. ю. каменщиков пермский государственный национальный исследовательский университет россия, 614990, пермь, ул. букирева, 15 e-mail: vikpant@mail.ru; ashein@psu.ru импеданс анодных процессов на пассивном nisi-электроде в сернокислом фторидсодержащем электролите* методами поляризационных и импедансных измерений исследованы механизм и кинетика анодного окисления nisi-электрода в растворах 0,5 m h 2 so 4 + (0,005–0,05) m naf в области пассивного состояния. спектры импеданса интерпретированы в предположении о формировании на поверхности силицида никеля двухслойной оксидной пленки, внешний слой которой имеет пористое строение. рост пористого слоя при повышении потенциала электрода в исследованных растворах осуществляется по линейному закону (константа анодирования составляет 2,2 нм/в). увеличение концентрации naf приводит к снижению толщины пористого слоя. рост барьерного слоя оксидной пленки описан в рамках модели точечных дефектов. коэффициент диффузии кислородных вакансий внутри барьерного слоя пленки составляет 8,5 · 10-16 см2/с и слабо изменяется с потенциалом и содержанием фторида натрия в растворе. микроскопические и профилометрические исследования свидетельствуют о развитии поверхности nisi-электрода в ходе анодного травления. ключевые слова: метод импедансных измерений; двухслойная оксидная пленка; моносилициды металлов. * работа выполнена при финансовой поддержке рффи в рамках научного проекта № 14-03-31016 мол_а. © пантелеева в. в., шеин а. б., каменщиков о. ю., 2016 введение при изучении анодных процессов на моносилицидах металлов триады железа в растворе 0,5 m h2so4 было установлено, что фактором, обусловливающим высокое химическое сопротивление пассивных fesi, cosi и nisi в сернокислом электролите, является поверхностная химически стойкая в кислых средах пленка, близкая по составу к sio2, для которой такие характеристики, как импеданс, элект рическое сопротивление, удельное сопротивление и однородность имеют 64 № 1 | 2016 chimica techno acta максимальные значения примерно в середине области пассивации [1–4]. однако при содержании в растворе фтороводородной кислоты или ее солей пассивационное влияние диоксида кремния ослабляется: при взаимодействии sio2 с hf или f –-ионами образуются кремнефтористоводородная кислота или растворимые фторосиликаты [4–7]. целью настоящего исследования является изучение концентрационного влияния фторида натрия на кинетику и механизм анодного окисления nisiэлектрода в растворе серной кислоты в области пассивного состояния. методика эксперимента материалом для исследования служил моносилицид никеля, который был получен методом чохральского из кремния кпз-1 (99,99 мас.  % si) и электролитического никеля н-0 (99,99 мас. % ni). электрохимические измерения проводили в растворах 0,5  m h2so4 + (0,005–0,05)  m naf при комнатной температуре (~20–22 ос) в  условиях естественной аэрации во фторопластовой ячейке с помощью потенциостата-гальваностата с  встроенным частотным анализатором solartron 1280c (solartron analytical). для приготовления растворов использовали деионизованную воду (удельное сопротивление 18,2м ом ∙ см) и  реактивы h2so4 марки «х.ч.» и naf марки «ч.д.а.». все потенциалы в работе приведены относительно нормального водородного электрода. перед проведением измерений рабочую поверхность электрода шлифовали абразивными бумагами с  последовательным уменьшением размера зерна, обезжиривали этиловым спиртом, ополаскивали рабочим раствором. после погружения в раствор электрод выдерживали при потенциале разомкнутой цепи до установления стационарного значения потенциала, далее снимали вольтамперные кривые и спектры импеданса. диапазон используемых в импедансных измерениях частот f (ω/2π) – от 20 кгц до (0,005–0,002) гц – амплитуда переменного сигнала (10–20) мв. морфологию поверхности образца до и после электрохимических испытаний исследовали с помощью сканирующего электронного микроскопа s-3400n (hitachi). изображения были получены в высоком вакууме при ускоряющем напряжении 10 кв в режиме рассеяния вторичных электронов. исследование микрошероховатости поверхности электрода осуществляли на интерференционном микроскопе – бесконтактном профилометре new view-5000 (zygo). результаты и их обсуждение анодные потенциостатические кривые nisi-электрода в растворах 0,5 m h2so4 + (0–0,05) m naf приведены на рис. 1. при потенциалах от 0,40 до 1,70 в, соответствующих области пассивного состояния, на поляризационных кривых nisi наблюдается заметный рост i с увеличением поляризации электрода и с повышением содержания фторида натрия в растворе. пантелеева в. в., шеин а. б., каменщиков о. ю. 65 № 1 | 2016 chimica techno acta в области потенциалов пассивного состояния годографы импеданса nisiэлектрода в исследованных растворах состоят из полуокружности емкостного типа при высоких частотах и наклонной прямой при низких частотах (рис. 2). для моделирования спектров импеданса nisi (рис. 2) использована эквивалентная электрическая схема, описывающая присутствие на поверх ности электрода двухслойной пассивирующей пленки, состоящей из внутреннего барьерного и внешнего пористого слоев (рис. 3). рост пленки сопряжен с переносом дефектов внутри барьерного слоя, к которому через поры внешнего слоя осуществляется доступ электролита. на границе раздела барьерный слой/электролит в результате взаимодействия вещества оксидной пленки с фтороводородной кислотой происходит его частичный переход в раствор и формирование пор. в схеме на рис. 3: rs – сопротивление электролита между носиком капилляра луггина и рабочей поверхностью электрода; r1 – сопротивление элект ролита в порах внешнего слоя; r2 – сопротивление переноса заряда; zd – импеданс варбурга, описывающий перенос дефектов внутри барьерного слоя, элементы постоянной фазы cpe1 и cpe2 моделируют емкость неоднородного внешнего слоя оксидной пленки и границы раздела барьерный слой/электролит, соответственно. параметр χ2 для эквивалентной схемы на рис. 3 принимает значения (8–20) · 10–5, что говорит о хорошей корреляции между моделью и экспериментальными данными. из расчитанных по эквивалентной схеме на рис. 3 данных следует, что при повышении потенциала nisi-электрода во всех исследованных растворах толщина внешнего пористого слоя увеличивается с e примерно по линейному закону, при этом рост пористости рис. 2. спектры импеданса nisi в 0,5 m h2so4 + 0,02 м naf при е, в: 1 – 0,40; 2 – 0,50; 3 – 0,60; 4 – 0,80; 5 – 1,00; 6 – 1,20; 7 – 1,40; 8 – 1,60; 9 – 1,70 рис. 3. эквивалентная электрическая схема для nisi в 0,5 m h2so4 + (0,005–0,05) m naf в области пассивного состояния рис. 1. анодные потенциостатические кривые nisi в 0,5 m h2so4 + naf, м: 1 – 0; 2 – 0,005; 3 – 0,01; 4 – 0,02; 5 – 0,05 импеданс анодных процессов на пассивном nisi-электроде в сернокислом фторидсодержащем электролите 66 № 1 | 2016 chimica techno acta опережает рост толщины слоя. в предположении, что основу оксидной пленки на поверхности силицида никеля во фторидсодержащем электролите составляет nio (или гидратированный оксид ni(oh)2), оценена толщина d пористого слоя оксидной пленки: постоянная роста (k = dd/de) пористого слоя оксидной пленки в интервале потенциалов от 0,8 до 1,6 в равна 2,2 нм/в (толщина пористого слоя при этом изменяется от 3,2 до 5,0 нм для растворов с разным содержанием naf). если допустить, что пассивная пленка представляет смешанный оксид и наряду с оксидом никеля также содержит некоторое количество диоксида кремния, то константа анодирования окажется несколько меньше. повышение концентрации фторида натрия приводит к небольшому снижению толщины пористого слоя оксидной пленки, что, по-видимому, связано с растворением вещества пленки в присутствии hf. толщина барьерного слоя также повышается с ростом e. коэффициент диффузии кислородных вакансий d внутри барьерного слоя пассивирующей пленки на nisi в растворе 0,5 m h2so4 + + 0,02m naf при e = 1,2 в составляет 8,5 ∙ 10–16 см2/с и слабо изменяется с ростом поляризации электрода и содержанием фторида натрия в растворе. небольшое увеличение коэффициента диффузии (однако весьма слабое) при повышении концентрации фторида натрия в растворе, вероятно, связано с ростом дефектности структуры барьерного слоя пленки, образуемой в присутствии фторида. микроскопическое исследование nisi до и после электрохимических испытаний показывает, что анодное травление силицида при e области пассивного состояния в 0,5 м h2so4 + +  0,05м naf приводит к значительному развитию электродной поверхности (на рис. 4 для сравнения представлены фотографии поверхности электрода до и после анодного травления в бесфторидном и фторидсодержащем растворах). развитие поверхности электрода в сернокислом бесфторидном электролите может быть обусловлено растравом при потенциалах области активного растворения и активно-пассивного перехода. введение в раствор фторида рис. 4. микрофотографии поверхности nisi (×700) до (а) и после анодного травления в 0,5 м h2so4 (б) и 0,5 м h2so4 + 0,05 м naf (в) при e = 1,2 в а б в пантелеева в. в., шеин а. б., каменщиков о. ю. 67 № 1 | 2016 chimica techno acta натрия приводит к еще более существенному растравливанию электродной поверхности, что обусловлено растворением в присутствии фторида образующихся при анодном окислении nisi в области пассивного состояния оксидов nio и sio2. результаты измерения параметров микрошероховатости поверхности nisi-электрода полностью коррелируют с данными микроскопических исследований. значения ra и rms изменяются следующим образом: ra (нм)/rms (нм) = = 25,5/34,3 (исходный образец): 79,8/119,4 (анодное травление в  0,5  м h2so4 при e = 1,2в) : 957,5/1240,8 (анодное травление в 0,5  м h2so4 + 0,05 м naf при e = 1,2 в). заключение исследование анодного поведения nisi-электрода в сернокислом элект ролите, содержащем переменное количество фтороводородной кислоты, показывает, что присутствие hf в раст воре оказывает достаточно сильное влияние на вольтамперные и импеданс ные характеристики силицида. последнее проявляется в существенном ослаблении пассивирующего действия кислородсодержащих соединений компонентов сплава и активации раст ворения nisi. 1. panteleeva v. v., shein a. b. impedance of cosi-electrode in sulphuric acid solution. izv. vyssh. uchebn. zaved. khim. khim. tekhnol. 2012;55(7):35–40. 2. panteleeva v. v., shein a. b. impedance of anodic processes on fesi-electrode in sulphuric acid solution. izv. vyssh. uchebn. zaved., khim. khim. tekhnol. 2013;56(10):48–53. 3. panteleeva v. v., shein a. b. growth of anodic oxide films on iron-triad metal monosilicides in sulfuric acid electrolyte. russian j. electrochemistry. 2014;50(11):1036–1043. doi: 10.1134/s102319351411007x. 1. 4. shein a. b. elektrokhimia silicidov i germanidov perehodnih metallov. perm: perm. gos. univ., 2009. 269 pp. (in russian). 5. batenkov v. a. elektrokhimia poluprovodnikov. barnaul: alt. gos. univ., 2002. 162 pp. (in russian). 6. panteleeva v. v., shein a. b. anodic dissolution of iron silicide in sulfuric acid solution, containing sodium fluoride. vestn. tamb. univ. estestv. techn. nauk. 2013;18(5):2237–2240. 7. remi g. kurs neorganicheskoj khimii. moscow, 1972. 824 pp. (in russian). импеданс анодных процессов на пассивном nisi-электроде в сернокислом фторидсодержащем электролите synthesis, structure and magnetic properties of ti doped la2mnnio6 double perovskite 80 d o i: 1 0. 15 82 6/ ch im te ch .2 01 9. 6. 3. 01 uma dutta, ariful haque, md. motin seikh chimica techno acta. 2019. vol. 6, no. 3. p. 80–92. issn 2409–5613 uma dutta, ariful haque, md. motin seikh* department of chemistry, visva-bharati university, santiniketan-731235, west bengal, india *e-mail: mdmotin.seikh@visva-bharati.ac.in synthesis, structure and magnetic properties of ti doped la2mnnio6 double perovskite we report sol-gel synthesis, structural characterization and magnetic properties of la2mn1–xtixnio6 (0 ≤ x ≤ 1.0). ti doping removed the biphasic structure of la2mnnio6 by suppression of rhombohedral structure and all the ti containing samples crystallized in monoclinic p21 / n symmetry. la2mnnio6 exhibits multiple magnetic transitions. the high temperature ferromagnetic transition of la2mnnio6 gradually shifted to lower temperatures with increase in ti doping. la2tinio6 (x = 1.0) does not show any long-range magnetic ordering. the suppression of magnetic transition by ti doping is ascribed to the destruction of mn4+ – o – ni2+ superexchange interaction. however, the signature of ferromagnetic phase persists up to 70 % ti doping, indicating the robustness of magnetic ordering in la2mnnio6. these results suggest that the addition of ti 4+ truncates the ferromagnetic mn4+ – o – ni2+ superexchange path and it likely promotes ferromagnetic cluster formation. the robustness of ferromagnetic state towards ti substitution compared to the simple perovskite or spinel structure can be attributed to cationic ordering in double perovskite structure. both the pure and ti-doped samples exhibit magnetic frustration at lower temperatures due to partial cationic disordering. the absence of long-range ordering in la2tinio6, unlike la2ticoo6 or pr2ticoo6, could be related to cationic disordering. keywords: double perovskite; ferromagnetic; superexchange interaction; magnetic frustration; cationic disorder; magnetic cluster. received: 20.08.2019. accepted: 11.09.2019. published: 15.10.2019. © uma dutta, ariful haque, md. motin seikh, 2019 introduction oxides of transition metals with perovskite structure lnmo3 (where ln is rare earth elements or alkaline earth and m is transition element) exhibit various exotic physical properties related to the correlation between spin, charge, lattice and orbital degrees of  freedom [1–3]. these strongly correlated electronic systems show competing electronic and magnetic states. accordingly, compounds with perovskite structure have most extensively been studied by the physics and chemistry communities due to their magnetic, transport and magnetotransport properties [4]. presence of second transition metal in the perovskite structure further improves the characteristic 81 features of the so-called double perovskites, ln2mm’o6. the important features of double perovskite are cationic ordering, antiphase boundaries and multiple exchange interactions [5–7]. the rock salt ordering with alternate occupancy of  octahedra by different metal ions takes place when there is a large size mismatch or the charge difference is  greater than 2 [6, 8, 9]. all these are governed by the local electronic configuration of the transition metal ions. extensive investigations on double perovskites reveal that by virtue of wide m / m’ cationic range they exhibit multifunctional properties like insulating, metallic, ferromagnetic, magnetodielectric, multiferroic, etc., which are suitable for various technological applications [10–13]. among the  double perovskites, la2mnnio6 has attracted special attention due to its striking properties such as multiple structures, multiple magnetic ground states, spin frustration and ferromagnetic insulating behaviour near room temperature with giant magnetodielectricity and magnetoresistance [14–19]. la2mnnio6 is reported to crystallize in biphasic nature with rhombohedral (r3c) and monoclinic (p21 / n) [14, 15, 20–22] or rhombohedral and orthorhombic (pbnm) symmetry [17, 23]. the  high temperature synthesized sample is rhombohedral and low temperature one is monoclinic or orthorhombic, whereas for  intermediate temperature range it is biphasic [23]. the phase fraction in the sample is also sensitive to the synthesis condition and post annealing treatment [14, 15, 18]. it was reported that the hightemperature phase transforms to  p21 / n phase at low temperature [14]. the magnetic ordering temperatures are different for  different phases. the r3c phase shows ferromagnetic ordering at relatively higher temperature (~280  k) compared to  the  p21 / n or  pbnm phase (~150  k) [16, 17]. the high temperature magnetic phase is governed by mn4+ – o – ni2+, where for  low temperature it is  mn3+ – o – ni3+ superexchange interactions [15–17, 23, 24]. there is  also report on  ferromagnetic transition at tc~100  k in  partially disordered sample, which was attributed to the mn3+ – o – ni3+ interaction [15]. furthermore, there is also appearance of spin glass behaviour in la2mnnio6 associated with the  competing interaction between ferromagnetic superexchange and disorder induced antiferromagnetic mn4+ – o – mn4+ and ni2+ – o – ni2+ interactions [15, 18, 25]. this suggests that the cationic disordering suppressed the high temperature ferromagnetic mn4+ – o – ni2+ interaction of  perfectly ordered phase. another extensively studied compound is  la2mncoo6 with ferromagnetic tc~230 k [26]. the double perovskites in which both metal ions are magnetic exhibit ferromagnetic ordering. however, for the ordered perovskite with single magnetic ion the long-range magnetic ordering is  antiferromagnetic and the  interaction is  supersuperexchange with separation of magnetic centres larger than 5  å [27, 28]. such interaction also becomes weaker as reflected from the ordering temperatures. the  observed tn values for la2cotio6 and pr2cotio6 are respectively, 15 k and 17 k [28, 29]. thus, it would be interesting to investigate the ferromagnetic to antiferromagnetic crossover starting from an  ordered ferromagnetic system by gradual replacing one magnetic ion by a nonmagnetic one. in the present studies we have gradually replaced mn4+ in la2mnnio6 by ti 4+ to better understand the role of mn4+ in determining the  structural and magnetic properties. to the best of our knowledge there is no report in the literature on in82 vestigation of  ti doping in  la2mnnio6. the ionic radius of ti4+ (0.605 å) is larger than that for mn4+ (0.530 å) [30]. in addition, there are other aspects of this substitution. the replacement of magnetic mn4+ by nonmagnetic ti4+ will make magnetic dilution in  system, which in  turn will truncate the ferromagnetic exchange path. thus, substitution of  ti4+ in  la2mnnio6 is  expected to  rapidly destroy the  ferromagnetic state. furthermore, by  considering the retention of cationic ordering it will bring antiferromagnetic supersuperexchange ni2+ – o – ti4+ – o – ni2+ in place of ferromagnetic ni2+ – o – mn4+ – o – ni2+ exchange path. we observed that the ferromagnetic ground state of  la2mnnio6 is  very robust and it persists up to  70 % doping of  ti4+. we did not observe any antiferromagnetic ordering in la2tinio6 could be due to cationic disordering. experimental polycr ystalline l a 2mn 1–xti xnio 6 (0 ≤ x ≤ 1) samples were prepared by modified sol-gel technique. at  first, stoichiometric amounts of metal nitrates (la, ni) and acetate (mn) were dissolved in 100 ml double distilled water followed by the addition of about 5 ml concentrated nitric acid to  prevent the  hydrolysis of  the  aquated metal ions. in another small beaker stoichiometric amount (1:1) of titanium isopropoxide [ti{och(ch3)2}4], and acetyl acetone were mixed and stirred for about several minutes. these two different solutions were mixed in  one single beaker and were stirred for about one hour using a magnetic stirrer to get a clear solution. citric acid was then added to  the  solution at four times mole ratio of the total metal ions. the  final ph of  the  solution was found to be ~2. the resulting solution was stirred overnight followed by evaporation of solvent at 100 °c to obtain the gel. the  obtained gel was dried by  increasing the temperature of hotplate to 150 °c to transform the gel into crude precursor. the  crude powders were ground thoroughly by using an agate mortar-pestle and calcined at 500 °c for 6 h in air. the final calcination was performed at 700 °c for 6 h in air to achieve the pure phase samples. the powder x-ray diffraction (pxrd) patterns were registered with a bruker d8 advance x-ray diffractometer using cu kα radiation (λ = 1.5418 å) operating at 40 kv and 40 ma. the pxrd patterns were recorded in the 2θ range of 10–120° using lynxeye detector (1d mode) with a step size of  0.02° and a  dwell time of  1s per step. iodometric titration of the samples confirms the oxygen stoichiometry fixed to ‘‘o6” within the limit of accuracy ±0.05. the  dc magnetization measurements were performed using a superconducting quantum interference device (squid) magnetometer with a  variable temperature cryostat (quantum design, san diego, usa). the magnetic ac susceptibility, χac(t) was measured with a  ppms (quantum design, san diego, usa) with the  frequency ranging from 10  hz to  10  khz. all the magnetic measurements were performed on powder samples putting inside a teflon capsule. results and discussion the  pxrd patterns for  all the la2mn1–xtixnio6 (x = 0, 0.2, 0.3, 0.5, 0.7 and 1.0) samples recorded in the 2q-range 10–120° are shown in fig. 1. all the pat83 terns are refined by rietveld method using fullprof suit program [31]. the pattern of the parent compound (x = 0) la2mnnio6 can only be refined properly by considering a mixed rhombohedral r3c and monoclinic p21 / n phases. the biphasic nature composed of  rhombohedral and monoclinic phases for la2mnnio6 sample was reported in the literature by several researchers [14, 15, 18, 32]. however, the  phase fraction depends on  synthesis condition as  well as on post-synthesis annealing treatment. we observed predominant monoclinic phase (80 %) over rhombohedral (20 %) one for the sol-gel synthesized la2mnnio6 with final heat treatment in air at 700 °c for 6 h. however, all the ti doped samples can be nicely indexed with monoclinic structure (sp. gr. p21 / n) (fig. 1). thus, the ti doping suppressed the  rhombohedral phase of la2mnnio6. the detailed structural and refinement parameters are given in table 1. from the table, one can see the systematic increase in cell volume with the increase in  ti4+ content as  expected for  its larger ionic radius compared to that of mn4+ [30]. we observed that the size of nio6 octahedra are slightly larger than that of mno6 as reported in the literature [33]. fig. 2 shows the temperature dependent dc-magnetization measured in  both the  zero field-cooled (zfc) and fieldcooled (fc) protocols under an  applied magnetic field of 500 oe for the temperature range 5–300  k. the  magnetization data of x = 0 parent phase exhibit ferromagnetic transition (tc~280 k) just below room temperature (fig. 2, a). one should notice the large thermomagnetic irreversibility between zfc and fc data branch immediate below tc~280  k, where zfc data show a  hump. the  zfc data also fig. 1. powder x-ray diffraction patterns of la2mn1–xtixnio6 (x = 0, 0.2, 0.3, 0.5, 0.7 and 1.0). the open red circles, black lines, the bottom blue lines and vertical bars represent the experimental data, calculated pattern, difference curve and bragg position, respectively 84 ta bl e 1 st ru ct ur al re fin em en t p ar am et er s fo r ln 2m n 1 -x t i xn io 6 ( 0 ≤ x ≤ 1) c er am ic s x = 0 x = 0. 2 x = 0. 3 x = 0. 5 x = 0. 7 x = 1 p2 1/ n r 3c a (å ) 5. 47 1 (4 ) 5. 51 6 (2 ) 5. 48 3 (9 ) 5. 49 0 (8 ) 5. 51 1 (8 ) 5. 52 4 (5 ) 5. 54 2 (6 ) b (å ) 5. 49 3 (3 ) 5. 51 6 (1 ) 5. 50 6 (4 ) 5. 51 3 (6 ) 5. 52 7 (2 ) 5. 53 8 (6 ) 5. 55 3 (6 ) c (å ) 7. 74 2 (4 ) 13 .2 37 (7 ) 7. 76 0 (4 ) 7. 76 7 (4 ) 7. 78 3 (7 ) 7. 80 2 (5 ) 7. 82 1 (6 ) v (å 3 ) 23 2. 72 34 8. 78 23 4. 34 2 23 5. 15 6 23 7. 11 0 23 8. 74 5 24 0. 77 8 β (o ) 89 .3 69 γ = 12 0 89 .5 40 89 .7 19 89 .7 20 90 .1 97 90 .2 44 r b (% ) 10 .4 13 .6 10 .8 11 .9 9. 20 12 .3 r f ( % ) 14 .5 22 23 .4 17 .0 24 .4 26 .8 χ2 2. 97 2. 63 2. 38 2. 28 2. 26 2. 30 b on d le ng th 2× m n— o 1: 1. 93 0  å 2× m n— o 2: 1. 87 5  å 2× m n— o 3: 1. 95 6  å 2× n i— o 1: 1. 99 1  å 2× n i— o 2: 2. 03 7  å 2× n i— o 3: 2. 00 7  å la — o 1: 2 .3 18  å m n1 — o 1: 1. 89 9  å n i2 — o 1: 2. 02 9  å la 1— o 1: 3× 2. 45 3  å 6× 3. 05 6  å 3× 2. 77 1  å ×m n/ t i— o 1: 1. 93 4  å 2× m n/ t i— o 2: 1. 88 5  å 2× m n/ t i— o 3: 1. 90 6  å 2× n i— o 1: 2. 02 3  å 2× n i— o 2: 2. 04 6  å 2× n i— o 3: 2. 03 3  å 2× m n/ t i— o 1: 1. 93 5  å 2× m n/ t i— o 2: 1. 88 8  å 2× m n/ t i— o 3: 1. 90 9  å 2× n i— o 1: 2. 01 9  å 2× n i— o 2: 2. 04 8  å 2× n i— o 3: 2. 03 5  å 2× m n/ t i— o 1: 1. 93 9  å 2× m n/ t i— o 2: 1. 89 4  å 2× m n/ t i— o 3: 1. 91 4  å 2× n i— o 1: 2. 02 3  å 2× n i— o 2: 2. 05 4  å 2× n i— o 3: 2. 04 1  å ×m n/ t i— o 1: 1. 94 1  å 2× m n/ t i— o 2: 1. 89 9  å 2× m n/ t i— o 3: 1. 92 0  å 2× n i— o 1: 2. 03 1  å 2× n i— o 2: 2. 05 8  å 2× n i— o 3: 2. 04 4  å 2× t i— o 1: 1. 94 6  å 2× t i— o 2: 1. 90 5  å 2× t i— o 3: 1. 92 6  å 2× n i— o 1: 2. 03 7  å 2× n i— o 2: 2. 06 4  å 2× n i— o 3: 2. 05 0  å 85 x = 0 x = 0. 2 x = 0. 3 x = 0. 5 x = 0. 7 x = 1 p2 1/ n r 3c la — o 1: 3. 12 1  å la — o 1: 2. 72 3  å la — o 1: 2. 82 9  å la — o 2: 2. 78 7  å la — o 2: 2. 72 9  å la — o 2: 3. 01 0  å la — o 2: 2. 46 3  å la — o 3: 2. 71 3  å la — o 3: 2. 45 5  å la — o 3: 2. 76 7  å la — o 3: 3. 05 7  å 2l a— o 1: 2. 33 8  å la — o 1: 2. 72 1  å la — o 1: 2. 82 6  å la — o 1: 3. 14 8  å la — o 2: 2. 47 6  å la — o 2: 2. 73 3  å la — o 2: 2. 79 2  å la — o 2: 3. 02 4  å la — o 3: 2. 45 9  å la — o 3: 2. 72 7  å la — o 3: 2. 78 0  å la — o 3: 3. 06 3  å la — o 1: 2. 34 1  å la — o 1: 2. 72 5  å la — o 1: 2. 83 0  å la — o 1: 3. 15 2  å la — o 2: 2. 48 0  å la — o 2: 2. 73 5  å la — o 2: 2. 79 3  å la — o 2: 3. 02 9  å la — o 3: 2. 46 0  å la — o 3: 2. 73 2  å la — o 3: 2. 78 4  å la — o 3: 3. 06 4  å la — o 1: 2. 34 9  å la — o 1: 2. 73 2  å la — o 1: 2. 83 8  å la — o 1: 3. 16 3  å la — o 2: 2. 48 7  å la — o 2: 2. 74 2  å la — o 2: 2. 80 0  å la — o 2: 3. 03 7  å la — o 3: 2. 46 7  å la — o 3: 2. 73 9  å la — o 3: 2. 79 1  å la — o 3: 3. 07 2  å 2l a— o 1: 2. 35 5  å la — o 1: 2. 73 7  å la — o 1: 2. 84 3  å la — o 1: 3. 17 2  å la — o 2: 2. 50 0  å la — o 2: 2. 74 1  å la — o 2: 2. 79 8  å la — o 2: 3. 05 2  å la — o 3: 2. 46 5  å la — o 3: 2. 75 4  å la — o 3: 2. 80 5  å la — o 3: 3. 07 0  å la — o 1: 2. 36 7  å la — o 1: 2. 74 5  å la — o 1: 2. 85 1  å la — o 1: 3. 18 2  å la — o 2: 2. 50 8  å la — o 2: 2. 74 8  å la — o 2: 2. 80 5  å la — o 2: 3. 06 1  å la — o 3: 2. 47 2  å la — o 3: 2. 76 2  å la — o 3: 2. 81 3  å la — o 3: 3. 07 8  å b on d an gl e (° ) m n— o 1— n i: 15 8. 44 m n— o 2— n i: 16 1. 16 m n— o 3— n i: 16 2. 62 m n— o — n i: 16 2. 67 m n— o 1— n i: 15 8. 31 m n— o 2— n i: 16 2. 61 m n— o 3— n i: 16 1. 20 m n— o 1— n i: 15 8. 3 m n— o 2— n i: 16 2. 6 m n— o 3— n i: 16 1. 21 m n— o 1— n i: 15 8. 26 m n— o 2— n i: 16 2. 62 m n— o 3— n i: 16 1. 22 m n— o 1— n i: 15 8. 27 m n— o 2— n i: 16 2. 57 m n— o 3— n i: 16 1. 27 m n— o 1— n i: 15 8. 25 m n— o 2— n i: 16 2. 57 m n— o 3— n i: 16 1. 28 c on tin ua tio n of ta bl e 86 show a  second broad hump at  low temperature centred around 25 k. below tc, fc data show a plateau followed by a definite slope change below 100 k (fig. 2, a). such magnetic behaviour of  the  parent phase is  in  good agreement with the  reported data which supports the  prevalence three magnetic phases in  the  temperature window 5–300 k [15–17, 23, 24]. the high temperature tc is associated with the ferromagnetic mn4+ – o – ni2+ superexchange interaction of  cation ordered state. the transition below 100 k ascribed to the mn3+ – o – ni3+ superexchange interaction and lowest temperature anomaly was attributed to the magnetic frustration arising out of partial cationic disordering [15, 18, 25] for the ti doped sample with x = 0.2, the high temperature magnetic transition largely shifted (~60 k) to lower temperature at  tc~220  k (fig.  2, a). however, the  shape of  the  curve remains similar to that of the parent phase, though the thermomagnetic hysteresis loop shrinks compared to the x = 0 sample (fig. 2, a). however, the upturn in magnetization below 100 k is not much shifted for x = 0.2 sample compared to x = 0. this result indicates that the high temperature magnetic transition associated with mn4+ – o – ni2+ superexchange interaction is  largely hampered compared to  the  mn3+ – o – ni3+ superexchange interaction. this could be due to preferential isovalent substitution effect. thus, it can be suggested that for 20 % ti doped sample the cationic ordering persists. for x = 0.5 the tc value comes down to 150 k and still one can observe the double humps in  zfc branch data, upturn in fc data below 50 k as well as the thermomagnetic irreversibility (fig.  2, b). it is  worth mentioning that the  parent phase sample with orthorhombic pbnm or  monoclinic p21 / n structures exhibits ferromagnetic transition at tc~150 k ascribed to the mn3+ – o – ni3+ superexchange interaction [15–17, 24]. however, we believe that the tc~150 k for x = 0.5 sample is not associated with mn3+ – o – ni3+ superexchange interaction like in parent phase, rather it is related to the weakening of mn4+ – o – ni2+ superexchange interaction due to substitution of nonmagnetic ti4+ in place of mn4+. the second magnetic phase further shifted below 50 k as indicated by the upturn in fc data in x = 0.5 sample (fig. 2, b). this indicates that still there is possible cationic ordering up to 50 % ti doping in la2mnnio6. on further increase in ti doping to x = 0.7, there is only one broad hump in  zfc data around 20  k and fc data show up turn below 100 k (fig. 2, b). this indicates that the high and fig. 2. temperature dependent dcmagnetization of la2mn1–xtixnio6: a — for x = 0 and 0.2 and (b) for x = 0.5 and 0.7. inset in (b) shows the data for la2tinio6 87 low temperature transitions as well as low temperature magnetic frustration merged together. for complete substitution of mn by ti i.e. x = 1.0 sample does not show any anomaly in  the  magnetization data and zfc-fc superimposed as  shown in  inset of fig. 2, b. this behaviour is typical for a paramagnetic material. this suggests that la2tinio6 does not show any kind of long-range ordering. the gradual change in magnetic properties with replacement of magnetic mn4+ by nonmagnetic ti4+ in la2mnnio6 is also supported from the isothermal magnetization data measured at 5 k under an applied field of ±5 t (fig. 3). there is also a systematic decrease in magnetization as expected for magnetic dilution, but all the samples up to x = 0.7 exhibit clear hysteresis loop suggesting the  prevalence of  ferromagnetic component in the system. however, the opening of the loop is small as reported for the parent phase [15, 24]. there is no hysteresis loop for x = 1.0 sample (see inset in  fig.  3) which practically shows a  linear increase in  magnetization with field as  expected for  a  paramagnet (see inset in fig. 3). let us discuss the  observed change in  magnetization in  la2mn1–xtixnio6. the  substitution of  mn4+ by  nonmagnetic ti4+ will truncate the ferromagnetic ni2+ – o – mn4+ – o – ni2+ superexchange path to ni2+ – o – ti4+ – o – ni2+. this doping not only destroy the  ferromagnetic exchange path, but also results in  weak antiferromagnetic interaction between the  ni2+ cation. the  weak antiferromagnetic interaction between ni2+ takes place via super superexchage interaction mediated through o – ti4+ – o linker. this type of  antiferromagnetic interaction is  observed in  half doped lani0.5al0.5o3 through ni – o – al – o – ni exchange path [34]. thus, with increase in ti doping the ferromagnetism in la2mnnio6 becomes more and more weaker as reflected by the change in tc shown in fig. 4. this result is  very contrasting with the  effect of ti doping in single perovskite manganite sm0.55sr0.45mno3, where just 4 % of ti doping leads for disappearing of the ferromagnetic state [35]. the robustness of ferromagnetism towards magnetic dilution in double perovskite la2mnnio6 may be related to the cationic ordering. most likely the disruption of ni2+ – o – mn4+ – o – ni2+ superexchange path leads to fragmented fig. 3. isothermal magnetization of la2mn1–xtixnio6 (x = 0, 0.2, 0.5 and 0.7) recorded at 5 k. inset shows the data for la2tinio6 -40 -20 0 20 40 -4 -2 0 2 4 la2mn1-xtixnio6 m ag ne tiz at io n (µ β/ f.u ) h (koe) x = 0 x = 0.2 x = 0.5 x = 0.7 0 20 400.00 0.05 0.10 x=1 m (µ b/f .u ) h ( koe ) 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 50 100 150 200 250 300 la2mn1-xtixnio6 t c (k ) x fig. 4. variation of ferromagnetic curie temperature (tc) with x in la2mn1–xtixnio6 88 ferromagnetic clusters which are responsible for  observed magnetic behaviour of the ti doped samples even for 70 % doping. this is even higher than the effect of ti doping in spinel structure. mn1+xfe2−2xtixo4 has been reported to exhibit ferrimagnetic ordering up to 50 % ti doping [36, 37]. however, one cannot rule out the  cationic disordering with the  increase in  ti doping. la2cotio6 and pr2cotio6 have been reported to show long-range antiferromagnetism at  15 k and 17  k, respectively, in cationic ordered state. the antiferromagnetic exchange interaction path is co2+ – o – ti4+ – o – co2+ in cationic ordered samples [28, 29]. however, we did not observe any such long range antiferromagnetic ordering in la2tinio6. the absence of such long range ordering can be related to the cationic disordering. to look at the magnetic features above tc we have fitted the high temperature data with curie-weiss law. the calculated effective paramagnetic moments also found to  decrease with the  increase in  ti doping. the µeff value for the parent phase is 6.30 µb / f.u. which is  slightly larger than the calculated value 5.97 µb / f.u., which has been attributed to the possible formation of ferromagnetic cluster above tc [38, 39]. the  µeff value decreases from 4.8 µb / f.u. for x = 0.2 to 1.72 µb / f.u. for x = 1.0 sample revealing the effect of magnetic dilution. finally, to confirm the association of low temperature magnetic anomaly with spin glass behaviour as  reported for  the  parent phase we have measured the  ac-susceptibility of  x = 0 and x = 0.5 samples at different driving frequencies in the low temperature regions. fig. 5 shows the real and imaginary parts of the ac-susceptibility data for these two samples. the χ’(t) for x = 0 sample is too broad to uniquely identify the glass transition temperature tg fig. 5. temperature dependent ac-susceptibilities of la2mn1–xtixnio6 for x = 0 and 0.5. panels (a, b) show real part, χ’(t), and (c, d) show imaginary part, χ”(t), at selected frequencies 89 (fig. 5, a). however, the χ”(t) revealed two frequency dependent peak around 20 k and 50 k (fig. 5, c), respectively, suggesting the  magnetic frustration. the  multiglass behaviour of la2mnnio6 has been reported in the literature [18]. this magnetic frustration is  associated with the  competing interaction between the antisite disorder induced antiferromagnetic mn4+ – o – mn4+ and ni2+ – o – ni2+ interactions and ferromagnetic clusters [18]. the x = 0.5 sample exhibit only one peak around 20 k, which is frequency dependent as revealed from both χ’(t) and χ”(t) data (figs. 5, b, d). this indicates the  presence of  magnetic frustration in pure and ti doped samples. conclusions in  the  present study, we have synthesized la2mn1–xtixnio6 (0 ≤ x ≤ 1.0) by modified citrate-based sol-gel method. rietveld analysis of the pxrd patterns revealed that the parent phase (x = 0) is biphasic in nature composed of rhombohedral r3c and monoclinic p21 / n structures, whereas ti doped samples crystalized in  single phase monoclinic p21 / n structure with the  suppression of  rhombohedral phase. the cell volume of the ti doped samples increased due to larger size of ti4+ compared to mn4+ ion. the magnetic measurements suggest the  multiple magnetic transition in la2mnnio6. the high temperature ferromagnetic transition with tc~280  k associated with the  cationic ordered ferromagnetic superexchange interaction ni2+ – o – mn4+ becomes weaker by replacement of mn4+ by nonmagnetic ti4+. there is  a  gradual shift in  tc with increase in ti doping eventually leading to  a  paramagnetic state in  la2tinio6. the ferromagnetic state of double perovskite exhibits robustness towards ti substitution compared to the simple perovskite manganite as  well as  spinels, which may be related to  the  cationic ordering. unlike other ti containing double perovskite, la2tinio6 fails to  show long-range antiferromagnetic ordering probably due to cationic disordering. both the pure and ti doped samples show magnetic frustration at lower temperatures. acknowledgements the  authors acknowledge the  financial support from indo-russian project (int / rus / rfbr / p-239), department of science and technology (dst), government of india. references 1. raveau b, seikh  md. m. cobalt oxides: from crystal chemistry to  physics, john wiley & sons; 2012. 2. kobayashi ki, kimura t, sawada h, terakura k, tokura  y.  room-temperature magnetoresistance in an oxide material with an ordered double-perovskite structure, nature. nature. 1998; 395(6703):677–680. doi: 10.1038 / 27167. 3. von helmolt r, wecker j, holzapfel b, schultz l, samwer k. giant negative magnetoresistance 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education "chuvash state university named after i.n. ulyanov ", 19 moskovsky ave., cheboksary, russia, 428015 * corresponding author: mlimait@rambler.ru this short communication (letter) belongs to the mosm2020 special issue. © 2021, the authors. this article is published in open access form under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). abstract the parameters of the continuous technological process of leaching copper from fine copper waste using nitric acid as an oxidizer are studied. optimal conditions for a continuous leaching process were established, in which solutions with a mass concentration of copper ions greater than 25 g/dm 3 were obtained. keywords copper leaching copper waste treatment received: 20.10.2020 revised: 25.12.2020 accepted: 25.12.2020 available online: 13.04.2021 1. introduction copper is one of the most popular metals for human economic activity and has been used since ancient times. in the global structure of copper consumption, 30% is used in construction, 30% for equipment production, 13% in the transport industry, and the remaining 27% is distributed among other sectors of the economy. in 2019 there were produced 23.72 million tons of copper. in the copper market, russia provides about 4.7% of world production. currently, there is an excess of demand over supply in the amount of 94 thousand rubles·tons and according to analysts ' estimates, a further increase in demand for copper is forecast [1]. unfortunately, the extraction of copper from natural sources is expensive and not very environmentally friendly, so it is more cost-effective to get copper from copper waste. hydroelectrometallurgical processes are widely used for processing copper waste to produce metallic copper. these processes can be divided into electrolytic refining and electroextraction [2,3]. electrolytic refining is used as the final stage in pyrometallurgical processes for producing copper, including the processing of copper waste by melting. the technology of this process is well studied and covered in detail in many monographs and textbooks. as a result of electrofining, cathode copper with a purity of 99.7–99.9% and a spent electrolyte are obtained, in which copper sulfate and impurities of other metals accumulate. the spent electrolyte is periodically sent for regeneration, which is a process of electrical extraction of copper. electroextraction is carried out in electrolyzers with an insoluble anode. the electroextraction method can also be used for processing copper waste from previously obtained solutions of copper salts. it is known that copper dissolves only in the presence of substances with oxidizing properties: concentrated sulfuric acid, oxygen, hydrogen peroxide and nitric acid. high values of redox potentials of nitric acid solutions allow dissolving copper. with concentrated nitric acid (mass fraction of acid more than 45%), the reaction proceeds according to equation (1), and with dilute acid (mass fraction of acid less than 40 %) – according to equation (2) [4]: cu + 4hno3 → cu(no3)2 + 2no2 + 2h2o, (1) 3cu + 8hno3 → 3cu(no3)2 + 2no + 4h2o. (2) in this paper, the possibility of conducting a continuous process of copper dissolution with nitric acid while excluding the formation of toxic nitrogen dioxide is studied. 2. experimental the diagram of the experimental laboratory installation is shown in fig. 1 a cylindrical reactor 1 with a diameter of 50 mm and a height of 250 mm with a false bottom located at a height of 20 mm has a jacket heated by water vapor obtained in a laboratory steam generator 5. copper chips with a particle size of about 2×2×2 mm were loaded into the reactor until a 200 mm high copper column was obtained. seven compositions of working solutions with different fixed concentrations of nitric acid were prepared for the experiments 10, 15, 20, 25, 30, 40 and 45% (mass). before each experiment, working solutions with a volume of 500 cm 3 were prepared, heated to a set temperature and thermostated. http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2021.8.1.09 http://creativecommons.org/licenses/by/4.0/ chimica techno acta 2021, vol. 8(1), № 20218109 letter 2 of 3 1 4 5 2 3 initial working solution waste gas steam ready solutionnitrogen fig. 1 scheme of an experimental laboratory installation: 1 – a tank for preparing the working solution; 2 – a reactor with loaded copper chips; 3– a jacket for heating the reactor; 4 – a steam generator; 5 – an absorption tank to stabilize the temperature in the reactor, the reactor was initially filled with water, the water was heated to a set temperature by applying steam to the jacket, then the water was drained and a hot working solution was immediately supplied. the working solution was fed to the upper part of the reactor through a sprinkler. the contact time was regulated by the flow rate of the working solution from 60 to 300 cm 3 /s. the liquid level in the reactor was regulated by lowering the finished solution. the first 50 cm 3 of the finished solution was discarded. the content of copper ions in the solution was controlled by the iodometric method [5]. waste gases from the reactor were displaced by a nitrogen current into an absorption flask filled with 50 cm 3 of a 10% solution of potassium iodide. at the end of the experiment, a qualitative test was made for the content of nitrogen dioxide in the absorption solution for the formation of pink staining with the griessilosvaya reagent [6]. to obtain reliable results, all experiments were repeated three times and the arithmetic mean values of the measurement results were calculated. in each experiment, the reactor was filled with a new sample of copper and a freshly prepared working solution was used. the relative error of the results does not exceed ±5%. 3. results and discussion the main criteria for the effectiveness of the process of leaching copper with nitric acid are the concentration of copper ions in the solution at the reactor outlet and the formation of nitrogen dioxide. during the experiment, it was found that the solubility of copper is mainly influenced by three factors: the contact time, the concentration of nitric acid and the temperature of the solution. to determine the optimal contact time, experiments were performed with a working solution containing 30% nitric acid when the temperature and flow rate of the solution changed (fig. 2). the data presented in fig. 2 show that the solubility of copper increases with decreasing consumption of the working solution and, accordingly, with increasing contact time. it follows that in production conditions, when the process is carried out in an industrial reactor, the efficiency of the leaching process will increase, since the contact time will increase at the same costs. it should be noted that at the same flow rates, the dissolution rate increases with increasing temperature and reaches a maximum value at 60 °c. to determine the effect of nitric acid in the working solution on the amount of dissolved copper at a constant flow of the working solution of 60 cm 3 /s, experiments were conducted which varied the temperature and composition of the working solution found that the mass fraction of nitric acid, 10 and 15% copper is not dissolved even when the temperature rises to 80 °c. with a further increase in the concentration of nitric acid in the solution, the solubility of copper increases (fig. 3). the results show that with an increase in the content of nitric acid in the working solution, the rate of copper dissolution also increases, but with a mass fraction of nitric acid of 40% and 45%, the absorption solution turns fig. 2 dependence of the concentration of copper ions in the solution on the flow rate of the working solution and temperature: a – 20 °c; b – 30 20 °c; c – 40 °c; d – 50 °c; e – 60 °c fig. 3 dependence of the concentration of copper ions in the solution on the content of nitric acid and the temperature of the solution: a – 20 °c; b – 30 20 °c; c – 40 °c; d – 50 °c; e – 60 °c chimica techno acta 2021, vol. 8(1), № 20218109 letter 3 of 3 pink when the griss–ilosvay reagent is added, which indicates the formation of nitrogen dioxide. therefore, it is optimal to use working solutions with a mass fraction of nitric acid of 30-35%. an increase in temperature also contributes to an increase in the rate of the copper oxidation reaction, but at temperatures above 60 °c, there is a significant entrainment of nitric acid with the nitrogen current and the cost of heat energy increases. 4. conclusions the experimental data obtained show that the process of copper leaching can be carried out in a continuous manner to produce solutions containing more than 25 g/dm 3 of copper ions. it was found that the maximum concentration of copper ions without the formation of nitrogen dioxide is achieved when using working solutions with a mass fraction of nitric acid of 25-30%, a temperature of 60 °c and a flow rate of 60 cm 3 /s of the working solution. 5. references 1. wbms: proizvodstvo medi v 2019 godu neznachitel’no vyroslo [wbms: copper production in 2019 increased insignificantly] [internet]. moscow: jsc “metallservis”; c2020 [cited 2020 oct 10]. russian. available from: https://mc.ru/news/nw/news_id/11688 2. naboichenko ss. smirnov vi. gidrometallurgiya medi [hydrometallurgy of copper]. moscow: metallurgiya; 1974. 272 p. russian. 3. bredikhin vn, manyak nk, kaftanenko aya. med’ vtorichnaya: monografiya [secondary copper: monograph]. donetsk: donntu; 2006. 416 p. russian. 4. lidin ra, molochko va, andreeva ll. khimicheskie svoystva neorganicheskikh veshchestv [chemical properties of inorganic substances]. moscow: khimiya; 2000. 408 p. russian. 5. lurie yy. analiticheskaya khimiya promyshlennykh stochnykh vod [analytical chemistry of industrial waste waters]. moscow: khimiya; 1984. 448 p. russian. 6. bykhovskaya ms, ginzburg sl, halizova od. metody opredeleniya vrednykh veshchestv v vozdukhe i drugikh sredakh [methods for determining harmful substances in the air and other environments]. moscow: medgiz; 1960. 312 p. russian. https://mc.ru/news/nw/news_id/11688 phase formation processes and synthesis of solid solutions in ca-r-nb-m-o systems 17 d o i: 1 0. 15 82 6/ ch im te ch .2 02 0. 7. 1. 03 levina a. a., tadevosyan n. o., petrova s. a., buyanova e. s., morozova m. v. chimica techno acta. 2020. vol. 7, no. 1. p. 17–25. issn 2409–5613 a. a. levinaa, n. o. tadevosyana, s. a. petrovab, e. s. buyanovaa, m. v. morozovaa a ural federal university, 19 mira st., 620002, ekaterinburg, russia b institute for metallurgy, ural branch of the russian academy of sciences, 101 amundsen st., 620016, ekaterinburg, russia email: anastasia.levina@urfu.ru phase formation processes and synthesis of solid solutions in ca–r–nb–m–o systems during the study of the phase formation process in ca–r–nb–m–o systems (r = la, bi, m = mo, w), an attempt was made to obtain single-phase compounds of carnbmo8 composition by the standard ceramic technique. in addition, samples based on lanbo4, cawo4, binbo4 were also synthesized by the standard ceramic technique. the phase composition of the samples was studied by xrd analysis. the electrical conductivity of the obtained solid solutions and potential composite materials was investigated by impedance spectroscopy. keywords: sheelite; fergusonite; solid solutions; electrical conductivity received: 18.02.2020. accepted: 12.03.2020. published: 31.03.2020. © levina a. a., tadevosyan n. o., petrova s. a., buyanova e. s., morozova m. v., 2020 introduction currently, there is  an  active search for new materials that can be used as electrodes and electrolytes of solid oxide fuel cells, oxygen sensors and membranes of electrochemical devices. modern technology uses well-established materials with highly symmetric (usually cubic) structure such as  fluorite or perovskite, where ionic conductivity is  based on the migration of oxygen vacancies [1–3]. recently, it has been demonstrated that structures with lower symmetry achieve high oxygen ion conductivity, which is due to  the  presence of  oxygen ions in  interstitial positions in  materials with both ionic and mixed conductivity [4]. such materials include a  number of  complex oxides that have sheelite or fergusonite structure and correspond to the formula abo4 (a = me 2+/me3+, b = me5+/me6+). thus, lanbo4 is  characterized by  insufficiently high values of electrical conductivity (at 1000 °c σ ≈ 5.5 · 10–5 ohm–1 · cm–1), but some solid solutions based on it show an increase in conductivity by 1–3 orders of magnitude both with an acceptor [5] and a donor doping [6]. in addition, new materials with promising characteristics can be found based on the  results of  studies on the  preparation of complex oxide solid solutions. for example, vu et al. [7] investigated the phase diagram la2o3-wo3-nb2o5 and to  date discovered and studied a  new composition la3nbwo10, which is  characterized by  a  relatively high oxygen conductivity due to the transport of oxygen ions. 18 deepa et al. [8] studied the system ca– ce–nb–m–o (where m = mo or w). all samples ca2cenbm2o12, cacenbmo8, and cace2nb2moo12 have cubic structure with a  space group (sg)  i41/a. electrical conductivity increases with increasing cerium concentration, which is  due to the variable valence of cerium. excess oxygen is released into the atmosphere upon heating, leaving electron in the lattice, which is further responsible for the conductivity of the compound [8]. thus, the establishment of mechanisms of formation and study of the characteristics of complex oxides in the systems calcium — bismuth (lanthanum) — niobium — molybdenum (tungsten) — oxygen is very relevant and is in line with current trends in the search for new materials for various functional applications and technologies for their production. experimental all samples were synthesized using a standard ceramic technique with several heating stages and intermediate grinding after every 50–100 °c of  heating. initial components were taken in stoichiometric quantities to  obtain products according to the equations 1–6: caco3 + r2o3 + nb2o5 + mo3 = = carnbmo8, (1) la2o3 + bi2o3 + nb2o5 + wo3 = = la1–xbixnb1–ywyo4±δ, (2) caco3 + r2o3 + wo3 = = ca1–uruwo4+δ, (3) caco3 + wo3 + nb2o5 = = caw1–znbzo4–δ, (4) bi2o3 + caco3 + nb2o5 = = bi1–vcavnbo4–δ, (5) bi2o3 + nb2o5 + wo3 = = binb1–wwwo4+δ, (6) where r = la or bi, m = mo or w; x, y, u, z, v, w are the quantities of the dopant element. stoichiometric amounts of dried precursors were weighed and mixed in an agate mortar as dispersion in ethanol. powders were heated at  500–1000 °c (up to 1400 °c for lanb1–ywyo4+δ samples) for ~8 hours at each stage. the phase composition of the powders was controlled by  means of  x-ray powder diffraction in the range of 5–75° of 2θ (d8 advance diffractometer (bruker, germany), cu kα radiation, β-filter, psd vantec1). the phase composition and structure of the compounds was examined by comparing xrd patterns with the pdf2 database entries. surface morphology and local chemical composition of the powders and ceramic specimens annealed at 1200–1270 °с were determined by scanning electron microscopy (sem) using jeol jsm 6390la (jeol, japan) microscope. for conductivity measurements the ceramic pellets of  10 mm in  diameter and 2.5 mm thickness were used. the flat surfaces of pellets were covered with pt. impedance spectra were obtained in two-electrode measurement cell on elins z-3000 impedance spectrometer, over the  frequency ranges 3 mhz to  10 hz at  stabilized temperatures from 850 °c to 250 °c in the cooling run. impedance spectra were treated with “zview” software. using these data, the temperature dependences of electrical conductivity (σ) were plotted in arrhenius coordinates lgσ – 1000/t. 19 results and discussion for a series of ca–r–nb–m–o at a ratio of metal components 1:1:1:1 the analysis of  phase formation during the  synthesis and search for the proposed single-phase compositions of the carnbmo8 type complex oxides was carried out. according to the xrd data, the samples after a series of annealing are not single-phase, but have a variable phase composition throughout the  temperature range. in  each system, compounds based on complex oxides with the general formula abo4 (rnbo4, camo4) are predominantly formed. qualitative change in  the  phase composition with temperature is presented in table 1. thus, the expected compounds of the total composition carnbmo8 in the analyzed systems at  the  applied temperature and time conditions of synthesis were not yet detected. in the la1–xbixnbo4 series within single-phase regions with increasing bismuth concentration, the  lattice is  compressed at x = 0.0–0.3 (monoclinic, sg i2/b) and expands at  x = 0.775–1.0 (triclinic, sg p-1). a  disproportionately modulated structure was found for the lanb1–ywyo4+δ solid solutions, previously mentioned by li et al. [9] when describing the  properties of  the  lanb0.92w0.08o4.04 compound. in the present study, after prolonged exposure of samples at t = 1400 °с (32 hours), additional peaks on the diffraction patterns (see fig. 1) were detected only for the compositions with y = 0.10 and above. solid solutions are formed throughout the studied concentration range, and at y≤0.15, a montable 1 phase composition of ca–r–nb–m–o systems at different sintering stages т, oc r = bi, m = mo r = la, m = mo r = bi, m = w r = la, m = w 500 caco3, nb2o5, bi2moo6, bi2mo3o12 caco3, la2o3, nb2o5, mo4o11, lanbo4, la4mo2o11, la2(moo4)3, camoo4 caco3, nb2o5, wo3, bi2o3, canb2o6 caco3, wo3, la2wo6, nb2o5, cawo4 600 caco3, nb2o5, bi2moo6, camoo4 caco3, nb2o5, la2mo2o9, camoo4 wo3, ca3bi8o15, canb2o6, cawo4 wo3, la2wo6, la3nbo7, cawo4 700 binbo4, nb2o5, bi2moo6, camoo4 cao, nb2o5, la2mo2o9, camoo4, la2moo6 binbo4, canb2o6, cawo4 la2wo6, la3nbo7, cawo4 800 binbo4, camoo4 nb2o5, la3nbo7, camoo4, la2moo6 binbo4, cawo4 la2wo6, la3nbo7, cawo4 900 binbo4, camoo4 canb2o6, la3nbo7, camoo4, la2moo6 binbo4, cawo4 canb2o6, la3nbo7, cawo4, la14w8o45 1000 binbo4, camoo4 canb2o6, la3nbo7, lanbo4, camoo4, la2moo6 binbo4, cawo4 canb2o6, cawo4, la14w8o45 20 oclinic phase with a  sg i2/b is  formed; at y > 0.15 the tetragonal phase with sg. i41/a is formed. reflections on the diffraction patterns of double substituted samples (la1–xbixnb1–ywyo4±δ) correspond to  additional phases listed in table 2. all samples of  ca1–ubiuwo4+δ and caw1–znbzo4–δ systems are not singlephase. the main phase in ca1–uruwo4+δ system is based on calcium tungstate cawo4 with tetragonal structure (sg i41/a). homogeneity range of the ca1–ulauwo4+δ solid solution is limited by the la concentration u = 0.0–0.05. the  following phases were additionally detected in  ca1–uruwo4+δ and caw1–znbzo4–δ samples with subsequent substitution to  a  small extent: la22w9o60, r2wo6, la0.14wo3, la2(wo4)3. in  caw1–znbzo4–δ samples, the  second phase of ca2nb2o7 (monoclinic, sg p21) was found and its concentration increased with the degree of substitution of tungsten in the b-sublattice. the unit cell parameters of the samples were calculated. the values vary slightly within the error of determination (fig. 2), so the formation of the solid solution even within the range u = 0.0 – 0.05 is still under discussion. to resolve this issue, an additional xrd is required with an increase in the exposure time. the  change in  the  phase composition in the binbo4-based system is presented with binb 0.95w 0.05o 4.025 and bi0.95ca0.05nbo3.975 as an example. tungstencontaining sample at 500 °с, in addition to  the  initial phases, contains bi14w2o27 (tetragonal, sg i41/a). an  increase in  temperature from 700 °с to  800 °с leads to the formation of the orthorhomfig. 1. xrd patterns of samples lanb1–ywyo4+δ (additional reflections are marked) table 2 phase composition of the la1–xbixnb1–ywyo4+δ samples dopant concentration crystal structure x=0.1, y=0.1 lanbo4, monoclinic, i2/b lanbo4, monoclinic, i2/a la0.33nbo3, orthorhombic, pmmm x=0.1, y=0.2 lanbo4, tetragonal, i41/a x=0.2, y=0.1 lanbo4, monoclinic, i2/a la0.33nbo3, orthorhombic, pmmm x=0.2, y=0.2 x=0.3, y=0.1 x=0.3, y=0.2 x=0.4, y=0.1 binbo4, triclinic, p-1 x=0.4, y=0.2 lanbo4, monoclinic, i2/a x=0.5, y=0.1 binbo4, triclinic, p-1 x=0.5, y=0.2 lanbo4, monoclinic, i2/a 21 bic phase binbo4 (sg pnna), bi5nb3o15 (tetragonal, sg p4/mmm), bi2wo6 (orthorhombic, sg pcan). at  850 °с the  reflections of  bi5nb3o15 disappear. the  calcium-containing sample undergoes changes from the initial composition (bi2o3, nb2o5) to  binbo4 (orthorhombic, sg pnna), bi5nb3o15 (tetragonal, sg p4/mmm), canb2o6 (orthorhombic, sg pcan). the formation of a new phase cabi2nb2o9 with orthorhombic structure (sg pbcn) was found for the compositions bi1–vcavnbo4–δ (v = 0.15 – 0.30). from the concentration dependence of the unit cell parameters (fig. 3) it can be seen that a significant change in the lattice parameters occurs when the dopant content increases from 0.00 to 0.05, which may indicate the formation of a solid solution in this concentration range. further increase of the ca and w content in the samples practically does not result in any changes in the values of the unit cell parameters. the  particle size of  the  powdered samples is in the range of 1.0–14 μm (for example lanb0.9w0.1o4+δ  — fig.  4); for the sintered monoclinic briquettes the values increase to 5.0–20 μm. in the region of tetragonal phase existence, the particle size range of  sintered samples is  wider 1.0–20 μm. the  sem scan (figs. 4–5) shows that the grains are tightly adjacent to each other only in the monoclinic phase of lanb1–ywyo4+δ compositions. the general shape of the temperature dependences of conductivity for lanbo4based samples is linear and is typical for ionic conductors (figs. 6–9). in addition, small change of  slope is  seen on the  dependencies which may be due to the presence of slight structural phase transitions (at  a.c. 600–700 °с); these are typical for lanthanum niobate. in bismuth-containing samples conductivity increases within the  monoclinic phase existence fig. 2. the unit cell parameters of ca1–uruwo4+δ and caw1–znbzo4–δ systems, calculated according to the tetragonal structure of cawo4 (sg i41/a) fig. 3. the unit cell parameters of binbo4-based systems calculated in orthorombic structure of binbo4 (sg pnna) 22 range and decreases within the  triclinic phase with increasing x. a similar trend is observed for lanb1–ywyo4+δ: at y ≤ 0.15 with increasing dopant concentration, the conductivity values increase sharply, exceeding those of the parent compound by three orders of magnitude at the maximum point, and then gradually decrease fig. 6. temperature dependencies of electrical conductivity la1–хbixnbo4 fig. 7. temperature dependencies of electrical conductivity lanb1–ywyo4+δ a b fig. 4. micrographs of the sample lanb0.9w0.1o4+δ obtained by scanning (a) the surface or (b) the cross-section of the briquettes in the secondary (left) and reflected electrons (right) a b fig. 5. micrographs of the sample lanb0.8w0.2o4+δ obtained by scanning (a) the surface or (b) the cross-section of the briquettes in the secondary (left) and reflected electrons (right) 23 fig. 8. temperature dependencies of electrical conductivity la1–хbixnb0.9w0.1o4+δ fig. 9. temperature dependencies of electrical conductivity la1–хbixnb0.8w0.2o4+δ table 3 activation energy values of samples based on lanbo4 composition ea (tlow), ev ea (thight), ev lanbo4 0.91 1.21 la0.9bi0.1nbo4 1.00 1.00 la0.8bi0.2nbo4 0.88 0.88 la0.7bi0.3nbo4 1.18 0.88 la0.225bi0.775nbo4 1.33 1.08 (1.76 *) la0.2bi0.8nbo4 0.88 1.05 la0.1bi0.9nbo4 0.89 1.06 lanb0.9w0.1o4+δ 1.24 1.24 lanb0.85w0.15o4+δ 1.44 1.44 lanb0.8w0.2o4+δ 0.60 1.50 lanb0.75w0.25o4+δ 0.41 1.53 lanb0.7w0.3o4+δ 0.92 1.44 la0.9bi0.1nb0.9w0.1o4+δ 1.28 1.10 la0.8bi0.2nb0.9w0.1o4+δ 1.22 1.12 la0.7bi0.3nb0.9w0.1o4+δ 1.28 1.13 la0.6bi0.4nb0.9w0.1o4+δ 1.28 1.08 la0.5bi0.5nb0.9w0.1o4+δ 1.26 1.04 la0.9bi0.1nb0.8w0.2o4+δ 1.28 1.28 la0.8bi0.2nb0.8w0.2o4+δ 1.25 1.25 la0.7bi0.3nb0.8w0.2o4+δ 1.26 1.26 la0.6bi0.4nb0.8w0.2o4+δ 1.21 1.21 la0.5bi0.5nb0.8w0.2o4+δ 1.19 1.19 * the value of ea in the high-temperature region on the graph of the temperature dependence of the conductivity of the solid solution la0.225bi0.775nbo4. 24 within the  tetragonal phase. samples la1–xbixnb1–ywyo4±δ show high conductivity comparable to the maximum values of the lanb1–ywyo4+δ conductivity. the activation energy values (table 3) were calculated according to the plots of the conductivity temperature dependencies; the average value is around 1.1 ev, which is consistent with the values of activation energies typical for ionic conductors. in ca1–ubiuwo4+δ and caw1–znbzo4–δ series, conductivity increases slightly with increasing dopant concentration. as can be seen in figs. 10–11 the total conductivity value for all samples is rather low. therefore, the measurement error in the temperature range below 500 °с is very large, which does not allow to  uniquely determine the values of –lg(σ) for all samples. the values of electrical conductivity of samples ca1–ubiuwo4+δ are higher than that of  the  matrix by  no more than one order of magnitude. despite the  absence of  single-phase samples in  the  binbo4-based series, the  conductivity of  these compositions as  composite materials were evaluated. in comparison with the matrix composition binbo4 (σ = 7.77 · 10 –7 ohm–1 · cm–1, at t = 800 °с) it was possible to increase the conductivity for the sample of the nominal composition binb0.9w0.1o4.05 (at t = 800 °с it is  9.61 · 10–6 ohm–1 · cm–1). when the  temperature decreases to 500 °с, it is possible to observe an equalization of the  conductivity values to 8 · 10–8 om–1 · cm–1 for all samples containing tungsten. for calcium doped bismuth niobates, no significant conductivity changes occur. the highest value shows the sample with nominal composition bi0.85ca0.15nbo3.925 at t = 800 °с σ = 1.41 · 10–6 ohm–1 · cm–1, and the smallest sample of bi0.9ca0.10nbo3.95 σ = 2.71 · 10–7 ohm–1 · cm–1 at t = 800 °с. conclusions this work demonstrates the  processes of  phase formation in  ca-r-nbm-o. in each system, compounds based on complex oxides of  the  general formula abo4 (lanbo4, binbo4, camo4) are predominantly formed. a  number of  samples based on lanbo4, binbo4, cawo4 substituted with bismuth, tungsten, calcium, lanthanum and niobium were obtained. solid solutions are formed in  the  range x = 0.0–0.3 and x = 0.775– 1.0 for la1–xbixnbo4, y = 0.0–0.3 for fig. 10. temperature dependencies of electrical conductivity ca1–zbizwo4+δ fig. 11. temperature dependencies of electrical conductivity caw1–ynbyo4–δ 25 lanb1–ywyo4+δ, u = 0.0 – 0.05, z = 0.0–0.05 for ca1–ulauwo4+δ and caw1–znbzo4–δ. a significant increase in the conductivity is observed mainly for lanthanum niobates substituted with tungsten. acknowledgements this work was financially supported by grant of russian foundation for basic research, project № 18-33-00921. references 1. goodenough jb. oxide-ion electrolytes. annu rev mater res. 2003;33:91–128. doi:10.1146/annurev.matsci.33.022802.091651 2. fergus jw. electrolytes for solid oxide fuel cells. j power sources. 2006;162(1):30–40. doi:10.1016/j.jpowsour.2006.06.062 3. malavasi l, fisher caj, islam ms. oxide-ion and proton conducting electrolyte materials for clean energy applications: structural and mechanistic features. chem soc rev. 2010;39: 4370–87. doi:10.1039/b915141a 4. orera a, slater pr. new chemical systems for solid oxide fuel cells. chem mater. 2010;22(3):675–90. doi:10.1021/cm902687z 5. haugsrud r, norby t. proton conduction in rare-earth ortho-niobates and orthotantalates. nat mater. 2006;5:193–6. doi:10.1038/nmat1591 6. cava rj, roth rs, negas t, parker hs, minor db. crystal chemistry, modulated structure, and electrical conductivity in the oxygen excess scheelite-based compounds la1–xthxnbo4+x/2 and lanbl–xwxo4+x/2. j solid state chem. 1981;40(3):318–29. doi:10.1016/0022–4596(81)90398–4 7. vu td, barre m, adil k, jouanneaux a, suard e, goutenoire  f.  investigation of the la2o3 — nb2o5 — wo3 ternary phase diagram: isolation and crystal structure determination of the original la3nbwo10 material. j solid state chem. 2015;229:129–34. doi:10.1016/j.jssc.2015.05.022 8. deepa m, rao pp, sumi s, radhakrishnan anp, koshy p. new negative temperature coefficient ceramics in ca — ce — nb — m — o (m = mo or w) system. j am ceram soc. 2010;93(6):1576–9. doi:10.1111/j.1551–2916.2010.03616.x 9. li c, bayliss rd, skinner sj. crystal structure and potential interstitial oxide ion conductivity of lnnbo4 and lnnb0.92w0.08o4.04 (ln = la, pr, nd). solid state ionics. 2014;262:530–5. doi:10.1016/j.ssi.2013.12.023 relevance of application of irradiated starter cultures to production of fermented milk products 242 d o i: 1 0. 15 82 6/ ch im te ch .2 02 0. 7. 4. 19 zhuravleva d. a., kazakov a. v., selezneva i. s., baranova a. a. chimica techno acta. 2020. vol. 7, no. 4. p. 242–249. issn 2409–5613 relevance of application of irradiated starter cultures to production of fermented milk products d. a. zhuravlevaa, a. v. kazakovb*, i. s. seleznevaa, a. a. baranovaa a ural federal university, 19 mira st., yekaterinburg, 620002, russian federation b ural state university of economics, 62/45 8 marta st./ narodnoy voli st., yekaterinburg, 620144, russian federation *email: prof_kazakov@mail.ru abstract. nowadays yogurt, fermented milk products, enriched with biologically active substances, acquire increasingly important significance in people’s diets. the traditional method for producing fermented milk products and yogurt is to ferment the milk using starter cultures. the purpose of this research was to figure out if it is possible to use suspensions of probiotic microbial cultures irradiated with ionizing radiation to produce yoghurt products. liquid live suspensions of bifidobacteria and lactobacilli, as well as a mixture of bifidobacteria, lactobacilli, propionibacteria and lactic acid streptococci were taken as a research model. the goal was achieved by receiving the yoghurt products enriched with active secondary metabolites due to using the suspensions of lysed cells of different microorganisms. we studied physico-chemical and organoleptic properties of the received products after 1, 7 and 14 days of storage. keywords: fermented milk products; probiotic microorganisms; secondary metabolites; ionizing radiation received: 10.10.2020. accepted: 27.12.2020. published:30.12.2020. © zhuravleva d. a., kazakov a. v., selezneva i. s., baranova a. a., 2020 introduction currently, it is generally accepted to use probiotics to produce a variety of  dietary supplements, fermented food products and drinks, and medicaments. it is  enough to  mention that almost all fermented milk products are obtained using lactic acid and probiotic microorganisms. all over the world, for decades this approach has been defined as  fully justified in  terms of  preserving and improving the health of people and animals. at the same time, most researchers, as well as wide public trained by them, undoubtedly identify probiotic microorganisms with exceptionally useful ones, which do not cause any side effects and have no contraindications to their unlimited use [1, 2]. few people realize that production strains of bifidobacteria, lactobacilli, propionibacteria and other probiotic microorganisms are selected from specific donors, such as astronauts, or from some environmental objects. it means that biomaterial, which represents just a part and is endowed with specific individual properties, applies to  the  entire community of  animal and human populations without any restrictions or control. but, after all, it is known 243 that there is  a  huge variety of  races and strains of probiotic microorganisms, and every human or animal has got its unique microbial “landscape” and it is not really a correct measure to artificially plant someone else’s heterogeneous microflora [3]. on the  other hand, it is  true that the benefits of liquid probiotics have been proven by numerous studies and experiments, or at least the apparent harm to human and animal health from them has not been confirmed. the  purpose of  this research was to develop more physiological application of  production strains of  liquid probiotic microorganisms without any even hypothetical possibility of replacing their own beneficial microflora inherent in everyone. experimental liquid live suspensions of  bifidobacteria and lactobacilli, as well as a mixture of  bifidobacteria, lactobacilli, propionibacteria and lactic acid streptococci were taken as  a  research model. a  positive impact of liquid probiotics on the organism is  diverse. improvement of  all parts of  the  gastrointestinal and urogenital tracts, skin surface, and mucous membranes of the upper respiratory tract; normalization of digestive functions; immunostimulating and anti-allergic effects — it is not a complete list of health-improving properties of the abovementioned probiotics in various age groups of the population, and also of  domestic and farm animals, confirmed by us with a dozen patents for inventions [4]. we have attempted to  convert liquid probiotics into more physiological forms with the elimination of any possible alien influence on the organisms of humans and animals, while increasing the nutritional value, as we have confirmed in our earlier works, and maintaining antimicrobial activity against opportunistic and pathogenic microflora [5]. this was achieved by lysis live cellular probiotic cultures of microorganisms through the irradiation and with subsequent application of  the  obtained cell-free suspensions as  starter cultures to produce sour-milk yogurt-like products. the  processing of  the  probiotic cultures with ionizing radiation was carried out on the  linear electron accelerator model uelr-10-10c2 in  the  innovative-introduction center of radiation sterilization of  the  physical-technological institute (ural federal university, yekaterinburg). there were used liquid probiotics, received at the production equipment, since in  almost all cases there is  a  statistically significant difference in  the  quality and safety criteria of  any products, received using laboratory and industrial methods. the br-30 bioreactor (fig. 1) was used to produce liquid live probiotics. this reactor allows carrying out sterilization of initial nutrient hydrolysate-milk medium in  automatic mode (temperatures 106– 108 °с and excess pressure 0.3–0.4 atm for 60 min); cooling till 38–40 °с and holding at this temperature of mixture of nutrient medium with preliminarily prepared liquid starter material for 24 hours, based on the following proportions: 3–5% of starter culture to the volume of seeded sterile environment [6]. the following raw materials were used to  prepare unfermented products: cow milk “irbitsky” 2.5% fat, pasteurized, homogenized, standardized in  the  package volume of  1 l was manufactured by  jsc “irbitsky milk factory” (yekaterinburg, russia) according to  the  russian state standard 31450–2013 [7]. it was bought 244 from supermarkets in yekaterinburg, russia. the milk ingredients were marked on the package as the following: fat — 2.5%, protein — 3.0%, and carbohydrate — 4.7%. biologically active additives “euflorine-l” (liquid lactobacillus), (liquid bifidumbacterin) (fig. 2a,b); non-alcoholic drink “euflorine-plus” (protein hydrolysate — metabolic) (fig. 2c) in 100 ml dark glass bottles were selected as probiotic starter culture for yoghurt products preparation. they were produced by llc npc “priority” (yekaterinburg, russia). weighing was performed on the laboratory analytic balance and hr-60 of the i accuracy class. the  рн was measured according to  the  requirements of  state standard 33776–2016 [8] using electronic рн-meter kelilong ph-911. the inoculation process was carried out under a sterile condition of  microbiological laminar flow (ii  class, в2 type bмb-ii  — “laminar-s-1.2”, lamsystem company, russia) (a thermostable incubator). the milk was fermented in  yogurt maker marta mt-1854 marta trade inc., united kingdom, equipped with the  timer and thermometer. all experiments and sample analysis were carried out in two parallels. results and discussion comparative chemical analysis to determine the  qualitative and quantitative spectrum of  amino acids, containing in  whole cell and lysed by  irradiation of the respective microbial cultures, was carried out in the scientific-research laboratory of united laboratory complex at ural state university of economics using highly efficient liquid chromatograph agilent 1260 infinity ii (germany), equipped with multi-wave detector and analytic tube with reversed phase agilent zorbax eclipse aaa 4.6 * 150 mm 3.5-micron. gradient elution with two eluents was used during the research process. we used the phosphate buffer based on na2hpo4 with 0.5 м concentration as the first eluent, and a mixture of acetonitrile:methanol:water with 45:45:10 ratio was used as  the  second eluent. elution speed was 2 ml/min, and temperature of  the  tube was maintained at the level of 40 °с. before startfig. 2. models of starter cultures for fermented milk products: a — euflorine-l, b — euflorine-b, c — euflorine-plus fig. 1. the br-30 bioreactor to produce liquid live probiotics 245 ing the measurements, the chromatograph was calibrated using the standard of amino acids produced by  agilent technologies company. in the calibration the following non-essential amino acids were used: alanine, aspartic and glutamic acids, serine; conditionally essential  — arginine, cysteine, glycine, proline, tyrosine, and essential amino acids, such as histidine, threonine, valine, methionine, phenylalanine, isoleucine, leucine, lysine. the  performed research showed that in  the  irradiated liquid probiotic microbial cultures, the total content of the abovementioned amino acids, expressed in mg per 100 g of sample, is 1.6–2.2 times higher than in live whole-cell monocultures of bifidobacteria, lactobacilli and their mixtures in the 1:1 ratio. in the average values, cellular microbial cultures, destroyed by radiation, contained 1.8 times more amino acids than the  corresponding live whole cell cultures. besides, studies were carried out to determine the number of live colony-forming microorganisms in  liquid probiotic cultures after various modes of their irradiation. during this, the nmafam parameter was determined (number of  mesophilic aerobic and facultative anaerobic microorganisms) [9]. when determining this value, we used the scales vmk-622, automatic single-channel dispenser biohit, рн-meter “anion 7000”. it was found that before irradiation the content of probiotic microorganisms in  liquid live whole-cell microbial cultures was from 1∙108 to  1∙1010 cfu/cm3. after irradiation with the  dose 10 kgr the nmafam parameter was at the level of values from 1.6∙104 to 2.0∙102 cfu/cm3. at  the  same time, colony-forming microbial units in the culture of lactobacilli were not determined at all (the parameter matched the value less than 1.0∙101 cfu/ cm3). at a higher radiation dose of 15 kgr the  nmafam parameter in  all studied cultures of microorganisms was less than 1.0∙101 cfu/cm3; it means that the microbial cells have been completely lysed in this case. the next stage of our work was to study the possibility of using biologically active additives of brands “euflorine-b”, “euflorine-l” and “euflorine-plus”, produced by  llc npc “priority”, as  a  starter in  the  production of  yoghurt products using probiotic cultures lysed by ionizing radiation and their secondary metabolites, as well as living microorganisms. at  first it was identified that the  рн value of  the  original milk was 6.65 ± 0.75%. the milk was pasteurized at 85 °c for 15 min and subsequently cooled to 38– 40 °c (fermentation temperature), then 125 ml of it was poured into clean, numbered 150 ml containers. after that the milk was divided in models inoculated by the dose 15 kgr and non-irradiated models of starter cultures, with a dose of 100 g/l of milk. containers with fermented milk and with reference samples were closed with lids, put into a yogurt maker at 40 °с for 8 hours. the  control sample was prepared using the previous method without the addition as a starter culture to the pasteurized milk neither the living culture, nor the suspension of lysed cells of microorganisms, their secondary metabolites. analysis of  the  appearance, organoleptic and physical parameters of quality of yoghurt products, made by adding irradiated, as well as live cultures of microorganisms, was performed after 1, 7 and 14 days of storage. while determining the рн of the samples after 8 hours of fermentation, it was established that only in case of milk fer246 mentation by  not irradiated euflorine-l the value lowered to рн = 4.4, the texture of this product was dense, homogeneous (fig. 3), while the other samples were less dense, and the рн value varied from 4.9 to 5.8. consequently, the samples were again placed into the yogurt maker for another 3 h and suddenly cooled to 4 °c after the fermentation time was determined. after 6-hour cooling, gelation was observed in  all samples (figs. 4a, 4b, 5a, 5b), although the рн values remained at the same level. t h e re f o re , m i l k f e r m e nt at i o n in the samples with not irradiated starters is carried out due to the activity of microorganisms, as well as the activity of their metabolites; when using sterile starters, fermentation process is conditioned by solely the interaction of secondary metabolites and milk components. the control sample during fermentation and the consequent cooling has not changed even for 24  hours, so it can be argued the fermentation due to microorganisms contained in milk, without adding the model starters, does not occur. during the  research there were determined physical and organoleptic indicators of yoghurt product samples quality, received using irradiated starters and mixtures with living microorganisms and during 1, 7 and 14 days of storage (see table 1). determination of sensory indicators — appearance and consistency, taste and smell, color of received products was performed according to the requirements of state standard 31981–2013 [10]. the sensory evaluation of yogurt product samples was provided by 5 volunteers expert panel members from professors and students in  the  department of  technologies of  organic synthesis according fig. 3. yoghurt products with the addition of not irradiated (а) and irradiated (b) euflorine-l fig. 4. fermented products with the addition of not irradiated (а) and irradiated (b) euflorine-в 247 to scoring scale (0–5) for its appearance (color and syneresis), flavor (aroma and taste), consistency (firmness and texture) and overall acceptability. the samples were served to panelist cold at 4 °c by random order. samples no. 2 and no. 6 have shown the  best organoleptic parameters during 7 days of storage; after 14 days of storage the taste characteristics of all the samples have been decreased. it was determined that with the increase in the storage period of all the samples, ph value decreased, titratable acidity (from 55 °т to  145 °т [11]) and whey separation (syneresis) increased. this is well correlated with the fact that during storage, the protein-lipid complex is destroyed due to acidification of the medium by the forming lactic acid, which results in compaction of the yoghurt product structure and separation of the whey [12]. conclusions in conclusion, it should be noted that during the  performed research live cell probiotic cultures of the microorganisms were irradiated by different doses at the linear electron accelerator. microbiological analysis showed that microbe cells were completely lysed after radiation by the dose 15 kgr. fermented products were received using irradiated mixtures instead of traditional starters. it should be also noted fig. 5. yoghurt products, made of not irradiated (а) and irradiated (b) euflorine — plus table 1 results of determination of рн, density and sensory indicators of fermented products samples number euflorine type рн density, g/ml evaluation of sensory indicators (1, 7 days) 1 day 7 days 14 days taste smell appearance 1 euflorine-в 5.8 5.6 5.2 0.9780 3.0 3.4 3.6 2 euflorine-в irrad. 4.9 4.7 4.3 0.9820 4.0 4.0 4.4 3 euflorine-l 4.4 4.0 3.8 0.9860 3.6 3.8 3.8 4 euflorine-l irrad. 5.3 5.0 4.8 0.9750 3.4 3.4 3.6 5 euflorine-plus 5.1 4.7 4.6 0.9630 4.0 4.4 3.8 6 euflorine-plus irrad. 5.4 4.9 4.5 0.9450 3.8 4.0 4.6 248 that irradiated euflorin-b and euflorinplus are preferable for this purpose. they can improve the  texture, viscosity, and the  rheological charteritics of  yogurt effectively, ensure the formation of a denser and more uniform structure and consistency of yogurt products. this fact can be explained, apparently, the formation by bifidobacteria of  exopolysaccharide (eps), which can act as thickeners and stabilizers [13]. we produced fermented milk products soured by unirradiated live probiotic mixtures as control samples. thus, we have shown the basic possibility to transform liquid probiotics into more physiological forms and eliminate any possible unwanted influence on the organisms of people and animals along with the  increase in  their nutritional value. references 1. shchekina mi. [healthy food as a way of life. role and place of probiotic products. gastroenterology]. consilium medicum. 2011;2:61–4. russian. 2. bel’mer sv. kislomolochnye produkty: ot istorii k sovremennosti [fermented milk products: from history to the present]. russian bulletin of perinatology and pediatrics. 2019;6(64):119–25. russian. doi:10.21508/1027-4065-2019-64-6-119-125 3. ardatskaya md. metabiotiki kak estestvennoe razvitie probioticheskoy kontseptsii [metabiotics as a natural development of the probiotic concept]. trudnyy patsient [difficult patient]. 2017;6–7(15):35–9. russian. 4. kazakov av. velikoe v malom [the great in the small]. yekaterinburg: amb publishing house; 2010. 150 p. russian. 5. kazakov av. sravnenie antimikrobnoy aktivnosti zhidkikh form probioticheskogo i postbioticheskogo produktov [comparison of antimicrobial activity of liquid forms of probiotic and postbiotic products]. molochnaya promyshlennost’ [dairy industry]. 2016;9:56–8. russian. 6. kazakov av. [modern liquid starter culture materials based on probiotic bacteria and principles of their production organization]. yekaterinburg: ural state economy university publishing house; 2019. 52 p. russian. 7. gost 31450–2013 moloko pit’evoe. tekhnicheskie usloviya [drinking milk. specifications]. international standard. moscow: standartinform; 2019. 10 p. russian. 8. gost 33776–2016 metody ispytaniy khimicheskoy produktsii, predstavlyayushchey opasnost’ dlya okruzhayushchey sredy [methods of test for of chemicals of environmental hazard. determination of ph, acidity and alkalinity]. international standard. moscow: standartinform; 2019: 11 p. russian. 9. gost 10444.15–94 produkty pishchevye. metody opredeleniya kolichestva mezofil’nykh aerobnykh i fakul’tativno-aerobnykh mikroorganizmov [food products. methods for determination of quantity of mesophilic aerobes and facultative anaerobes]. international standard. moscow: standartinform; 2010. 7 p. russian. 10. gost 31981–2013 yogurty. obshchie tekhnicheskie usloviya [yogurts. general specifications]. international standard. moscow: standartinform; 2014. 18 p. russian. 249 11. tablitsa perevoda ph i ternera [ph and turner translation table] [internet]. moscow: apkimpulse [cited 2020]. russian. available from: http://ekomilk.ru/laborotornoeoborudovanie-news/113 12. abbasi h, mousavi me, ehsani mr, jomea ze, vaziri m, rahimi j, aziznia s. influence of starter culture type and incubation temperature on rheology and microstructure of  low-fat set yoghurt. international journal of  dairy technology. 2009;62(4):549–55. 13. cartasev a, rudic v. the effect of starter culture producing exopolysaccharide on physicochemical properties of yoghurt. chemistry journal of moldova. 2017;12(2):7–12. 356 d o i: 1 0. 15 82 6/ ch im te ch .2 01 5. 2. 4. 03 2 g. e. khaikina1,2, s. f. solodovnikov3,4, o. m. basovich1, z. a. solodovnikova3, y. m. kadyrova1, a. a. savina1,2, e. s. zolotova3, v. n. yudin3,4, t. s. spiridonova1,2 1 fsbun baikal institute of nature management sb ras, 670047, ulan-ude, sakhyanovoy str., 6 2 fsbgu hpe “buryat state university”, 670000, ulan-ude, smolina str., 24a 3 institute of inorganic chemistry sibiryan branch ras, 630090, novosibirsk, prospect akademika lavrentyeva, 3 4 federal state autonomous educational institution “novosibirsk national research state university”, 630090, novosibirsk, pirogov str., 2 egkha@mail.ru, solod@niic.nsc.ru triple molybdates one-, one and three(two)valence metals the review summarizes experimental data on the phase formation, structure and properties of new complex oxide compounds group – triple molybdates containing tetrahedral molybdate ion, two different singly charged cation, together with trior divalent cation. the several structural families of these compounds were distinguished and it shown that many of them are of interest as luminescent, laser, ion-conducting or nonlinear optical materials. keywords: triple molybdates, one-, two and trivalent metals, phase formation, structure, functional properties. the authors thank ph. d. m. k. alibaeva, ph. d. i. a. gudkova and ph. d. i. v. korolkova for participation in the research. the work is executed at partial support of the russian foundation for basic research (projects no. 08-0300384, 13-03-01020 and 14-03-00298). © khaikina g. e., solodovnikov s. f., basovich o. m., solodovnikova z. a., kadyrova y. m., savina a. a., zolotova e. s., yudin v. n., spiridonova t. s., 2015 the molybdates and tungstates are among the most popular objects of inorganic chemistry, crystal chemistry and solid state chemistry, as well as a base for developing of functional materials for various purposes, which maintains a constant interest in these compounds and explains a significant number of publications on this subject. 357 № 4 | 2015 chimica techno acta in 1960-80 the focus of the scientists was double molybdates and tungstates phases with the general formula axby(xo4)z, on the basis of which laser, ferroelectric, scintillation, nonlinear optical and other materials were later developed [1-5]. the main contribution to the formation of this group of compounds and their comprehensive study was made of the russian scientific school: professor kovba l. m., professor trunov v. k. (moscow state university named m. v. lomonosov), professor zhukovsky v. m, professor tkachenko e. v. (ural state university named a. m. gorky, sverdlovsk), corresponding member of academy of sciences of ussr mokhosoev m. v. (donetsk state university; buryat institute of natural sciences, sibiriyan brunch of academy of sciences ussr, ulan-ude), professor mayer a. a (moscow chemical-technological institute named d. i. mendeleev), professor golub a. m. (kiev state university), candidate of physico-mathematical sciences klevtsova p. v., candidate of physico-mathematical sciences klevtsova r. f. (institute of inorganic chemistry of sibiriyan brunch of academy of sciences ussr, novosibirsk) and etc. in the last two decades there has been a shifting of the centre gravity of studies from double molybdates and tungstates on triple molybdates. to date, this group of compounds has more than 550 individuals and is the fastest growing of complex oxide phases containing tetrahedral anion and cation. the large part of triple molybdates is prepared and is characterized by the employees of the baikal institute of nature management sb ras (ulan-ude) and the institute of inorganic chemistry named a.  v. nikolaev sb ras (novosibirsk). a brief overview of the different types of triple molybdates, different combinations of the charges of their constituent cations is earlier presented in [6]. the aim of this work is a detailed consideration of the phase formation, structure and properties of triple molybdates, containing two different singly mono-charged cation along with triple-charged (type 1-1-3) or doubly charged (type 1-1-2) cation. triple molybdates of the type 1-1-3 the first systematic searching researches of triple molybdates of one-, one-, and trivalent metals were conducted for lithium-containing systems li2moo4– m2moo4–r2(moo4)3 (m = k–cs, tl, ag, r = bi, ln, y, in, sc, fe, ga, cr, al). their result was the identification, synthesis and characterization of about 40 compounds of compositions limr2(moo4)4, lim2r(moo4)3, li2m3r(moo4)4, lim4r(moo4)4, li2mr(moo4)3 which initiated the formation of an extensive group of triple molybdates of the type 1-1-3. the typical variants of systems triangulation in which these phases are formed are represented in fig. 1. the belonging of the considered compounds to eight structural types is set, for representatives of five of whom crystals were obtained and the crystal structures are determined triple molybdates of the most numerous isostructural series of compounds of the composition limr2(moo4)4 are formed with the bismuth and lanthanides on some quasi-binary sections of lir(moo4)2–mr(moo4)2 of systems li2moo4–m2moo4–r2(moo4)3 (m = k, rb, tl). the domains of existence of these 358 № 4 | 2015 chimica techno acta phases in a series of ree vary significantly and with increasing size of singly charged cations move in the direction to the light lanthanides (fig. 2). the analysis of experimental data allows to draw a conclusion about the decisive influence of dimensional factor on the possibility of the formation of monoclinic triple molybdates of this family: limln2(moo4)4 are formed, if the difference in sizes of ions of large singly charged cation and rare earth element lies in the interval. 0.48 ǻ ≤ r(m+) – r(ln3+) ≤  0.60 ǻ. at lower values of dr in the cut of liln(moo4)2–mln(moo4)2 there is the formation of solid solutions. when dr > 0.60 å the consider phase is either not formed or its formation is so complicated that the connection cannot be allocated in single-phase condition using conventional methods of solid-phase synthesis [11]. within the prescribed time interval the isothermally and isostructural copper compounds cukln2(moo4)4 with gd, tb, ho are prepared and characterized in [12, 13] are stacked. the closeness of r(cu+) and r(li+) with a high degree of probability allows to predict a significant expansion of the triple molybdates m’m’’r2(moo4)4 due to containing cu(i) phases of this type with k, tl, rb, and those of trivalent elements, the difference in dimensions which will satisfy the proposed criterion. the structure of triple molybdates limr2(moo4)4 is defined by the examfig. 1. subsolidus structure of some systems li2moo4–m2moo4–r2(moo4)3 [7–10]: s1 – limr2(moo4)4; s2 – lim2r(moo4)3; s3 – li2mr(moo4)3; s4 – li2m3r(moo4)4.region limmoo4–m2moo4–mfe(moo4)2 систем li2moo4–m2moo4–fe2(moo4)3 (m = k, rb, cs) is not a quasi-threefold. ln m la ce, pr nd sm, eu gd–lu, y k tl rb fig. 2. the domains of existence of triple molybdates limln2(moo4)4 (shaded) khaikina g. e., solodovnikov s. f., basovich o. m., solodovnikova z. a., kadyrova y. m., savina a. a., zolotova e. s., yudin v. n., spiridonova t. s. 359 № 4 | 2015 chimica techno acta ple lirbbi2(moo4)4, the only compound of this family which congruently melting [14]. other compounds limr2(moo4)4 decompose in the solid phase at the corresponding double molybdates [7, 15] and their structure (for example limnd2(moo4)4, m = k, tl, rb) was refined by the rietveld method for powder data [16]. the structures limr2(moo4)4 are close to the structure of triple molybdates li3ba2ln3(moo4)8 [17] and are derived from the structural type band2(moo4)4 [18]. a characteristic features of structures limr2(moo4)4 are the laced layers of the ro8 polyhedron and connected to them through common vertices moo4-tetrahedra. the neighbouring layers are interconnected by octahedra and lio6 polyhedra mo10 (fig. 3). the presence in compounds limr2(moo4)4 ions li +, filling the interstitial voids of the structural type band2(moo4)4 suggests that they have lithium ionic conductivity. the results [19, 20] indicate the possibility of using these triple molybdates as sensitive elements of sensors of sensor systems for operational environmental monitoring. spectral-luminescent characteristics limln2(moo4)4: eu 3+(nd3+) give the basis to speak about the possibility of the application of triple molybdates of this family to create luminophors with high contrast colors, as well as active media of lasers [8, 21]. the data obtained in [22] show the availability of using likgd2(moo4)4: in the capacity of: eu3+ is as a red phosphor for wled. as in the previous case, the possibility of formation of other isostructural series of triple molybdates li2m3r(moo4)4 (mr = csfe, csga, rbga, csal, rbal, tlal) is largely determined by a dimensional factor: compounds are formed by small cations fe3+, ga3+, al3+ with tetrahedral coordination and quite major ions tl+, rb+ and cs+. the absence li2m3cr(moo4)4 is apparently due to the high preference of cr3+ in octahedral coordination. these tetragonal compounds have a frame structure and are ordered derivatives of the cubic cs6zn5(moo4)8 [23, 24]. with the increasing of size of r3+, the region of existence of these phases shifts towards larger singly charged cations m+, which can be explained by the compliance of the sizes of the tetrahedral framework and the size of the extra framework cation. obviously with namely dimensional discrepancy the crystallization li2k3al(moo4)4 is bound in a different structural type [10]. it is shown that lik2in(moo4)3, lirb2fe(moo4)3, lics4al(moo4)4 and lics4al(moo4)4 form new structural types that have not other members (table 1). get fit for x-ray crystallographic fig. 3. projection patterns lirbnd2(moo4)4 along the axis a fig. 4. t–x-diagram of a cut libi(moo4)2–agbi(moo4)2 [29] triple molybdates one-, one and three(two)valence metals 360 № 4 | 2015 chimica techno acta studies single crystals of lik2fe(moo4)3, li2kfe(moo4)3 and li2k3al(moo4)4 or to find structural prototypes of these compounds have not yet succeeded. in none of the systems li2moo4–ag2 moo4–r2(moo4)3 triple molybdates are not found [28-30]. the incisions lir(moo4)2–agr(moo4)2 in the bismuthand lanthanoid-containing systems are characterized by the formation of extended boundary solid solutions (fig. 4). made in recent years the researches of systems m2moo4–cs2moo4–r2(moo4)3 (m = na, ag) allowed significantly to fill the group of triple molybdates of one-, oneand trivalent metals due to the sodium and silver-containing phases. the compositions and the fields of the existence of thus obtained compounds are shown in table. 2, the data of the rsa of the obtained single crystals are presented in table. 3. studied sodium compounds have, as a rule, difficult structures and frame structures (fig. 5, 6), different in structure from the triple molybdates formed in the systems li2moo4–m2moo4–r2(moo4)3 (m = k–cs, tl). in the structures of the sodium-containing triple molybdates моo4tetrahedra and ro6-octahedra are present and sodium has an octahedral or trigonalprismatic coordination or generates polyhedra with lower cn. in these structures the na+ and r3+ quite often jointly occupy one crystallographic position; along with them there are positions which partially filled with sodium cations that leads to the deviation of composition from stoichiometry. the phases of variable composition are widely distributed among the complex (double and triple) sodium molybdates [33, 34], due to the proximity of sizes of ions na+ and и a2+ or r3+. according to the data of rsa, all triple molybdates found in the systems ag2 moo4–cs2moo4–r2(moo4)3 are isoformular to sodium analogs and are built on the same structural basis [32]. table 1 data rsa single crystals lik2in(moo4)3, lirb2fe(moo4)3 and lics4al(moo4)4 [25–27] compound pr. gr.; z a, ǻ b, ǻ c, ǻ β, ° r, % lik2in(moo4)3 p21; 2 7.0087(2) 9.2269(3) 10.1289(3) 107.401(1) 22.80 lirb2fe(moo4)3 pnma; 4 24.3956(6) 5.8306(1) 8.4368(2) – 2.11 lics4al(moo4)4 p2; 2 15.940(3) 8.266(2) 8.319(2) 105.13(3) 2.85 table 2 triple molybdates in systems m2moo4–cs2moo4–r2(moo4)3 (m = na, r = bi, ln, in, sc, fe; m = ag, r = bi, ln, in, sc) [31, 32] m = na phase m = ag bi tm yb lu in sc fe bi yb lu in sc s1 * * m13–3xcs11r2+x(moo4)15 s2 * m5cs7r2(moo4)9 s3 * mcs2r(moo4)3 ◆ s4 *в/т m3cs3r2(moo4)6н/т s5 * * * m25cs8r5(moo4)24 fields of compounds, based on common structural basis, equally shaded * – the resulting crystals and structure was determined on single crystal data by method rsa; ◆ – the resulting crystals and settings of cells were determined on single crystal data. khaikina g. e., solodovnikov s. f., basovich o. m., solodovnikova z. a., kadyrova y. m., savina a. a., zolotova e. s., yudin v. n., spiridonova t. s. 361 № 4 | 2015 chimica techno acta in practical terms, triple molybdates na25cs8r5(moo4)24 are the most interesting which the closely related structures are solved by single crystal data in the framework of pr. gr.  p21/c (in), p212121  (sc), p`1  (fe) [38, 39]. the mo atoms in all three structures are coordinated tetrahedral, trivalent metal is octahedral, all or some of them occupy their positions together with the atoms of sodium. the remaining na atoms have rather distorted oxygen coordination (cn = 5 and 6); the atoms of cesium are cn = 9-10 (in), 11 (sc), 10-12 (fe); some positions of the sodium cations may be partially settled. in all structures it is possible to allocate polyhedral layers which formed by pairs of articulated along edges of the octahedra (r, na)o6 and (r, na)o6 (or ro6) that are connected by vertices with bridging moo4-tetrahedra (fig. 6, a–c). the layers contact bridging moo4-tetrahedra in the table 3 data rsa of single crystals of triple molybdates of sodium, cesium and trivalent metals [31] compound pr. gr.; z lattice parameters r s1 na7.23cs11tm3.92(moo4)15 p63/mcm; 2 a = 10.5849(1), c = 37.4867(6) å 0.029 na7.72cs11bi3.76(moo4)15 p63/mcm; 2 a = 10.5507(1), c = 37.6640(1) å 0.038 s2 na5cs7yb2(moo4)9 r32; 3 a = 10.5107(2), c = 36.358(7) å 0.035 s3 nacs2bi(moo4)3 r3c; 12 a = 10.6435(2), c = 40.9524(7) å 0.020 s4 в/т-na3cs3in2(moo4)6 r 3 ; 12 a = 17.5753(2), c = 29.4333(3) å 0.032 s5 na25cs8in5(moo4)24 p21/c; 4 a = 12.6392(2), b = 21.4601(4), c = 14.0313(3) å, β = 90.017(1)° 0.030 na25cs8sc5(moo4)24 p212121; 2 a = 28.6452(6), b = 14.0043(3), c = 12.6482(2) å 0.072 na25cs8fe5(moo4)24 p`1; 2 a = 12.5814(5),b = 13.8989(5), c = 28.4386(9) å, α = 90.108(2), b = 90.064(2), g = 90.020(2)° 0.044 fig. 5. structures na7.23cs11tm3.92(moo4)15 (а), na5cs7yb2(moo4)9 (b), nacs2bi(moo4)3 (c) [35–37] triple molybdates one-, one and three(two)valence metals 362 № 4 | 2015 chimica techno acta three-dimensional skeleton the voids of which are cations сs+ and na+. in all cases the structure of the layers goes back to the polyhedral layer of patterns na5sc(moo4)4 (fig. 6, d), related to the type alluaudite (na, ca)(fe, mn, mg) 3(po4)3 [40]. the rhombic or pseudorhombic metric of cells of triple molybdates occurs due to some mutual shift of the layers in comparison with monoclinic na5sc(moo4)4 and alluaudite (pr. gr.  c2/c), which may be due to the presence of cesium cations between the layers. structural features of this group of triple molybdates suggests that this is not the kind of structural type of alluaudite and a separate, let closely related structural family. the study of alluaudite-like ion-conductive properties of triple molybdates showed that these compounds undergo reversible phase transitions of type i, followed by an abrupt increase of conductivity. above the temperatures of phase transitions, the electrical conductivity reaches values of 10-2–10-3 sm/sm, which gives an opportunity to consider na25cs8r5(moo4)24 (r  =  in,  sc,  fe) as the promising objects for the development of new materials with high ionic conductivity [38, 39]. the structural features of the other described above triple molybdates also allow to expect the existence of them increased the sodium (silver)-ionic conductivity and improve their conductive characteristics that apparently it is possible to achieve by suitable heterovalent substitutions with replacing part of the sodium (silver) or other cation in the structure on more high strength field and education vacancies. fig. 6. polyhedral fragments (layers) in the structures na25cs8in5(moo4)24 (а), na25cs8sc5(moo4)24 (b), na25cs8fe5(moo4)24 (c), na5sc(moo4)4 (d) [38] khaikina g. e., solodovnikov s. f., basovich o. m., solodovnikova z. a., kadyrova y. m., savina a. a., zolotova e. s., yudin v. n., spiridonova t. s. 363 № 4 | 2015 chimica techno acta triple molybdates of type 1-1-2 among triple salt systems m’2moo4– m’’2moo4–amoo4 to date, the most studied systems are that consist of lithium molybdate, heavy alkali elements (k, rb, cs) and mg, mn, co, ni, co, zn, cd, ca, sr, ba, pb. most of these systems are not phaseforming, the solid solutions are formed in some of them on the basis of double molybdates. one triple molybdate was found in the six systems; their characteristics are presented in table. 4. in the triple systems li2moo4– k2moo4–amoo4 (a = mg, mn, co) in quasi-binary sections li2a2(moo4)3k2a2(moo4)3 (fig. 7) the rhombohedral triple molybdates k3+xli1-xa4(moo4)6 (0 ≤ x ≤ 0.3) are revealed [42, 43]. they crystallized in the structural type iina3fe2(aso4)3 [49], in which the cations are distributed as follows: (na5£) ix(m1) vi(m2)vi(m3)3 vi(aso4)6 = (na5£)(na) (fe3+)(fe3+)3(aso4)6 (here the roman numerals denote the cn of the cations in the positions m1, m2 and m3). in the structures of the triple molybdates cations li, a2+ and k+ are placed at the positions m1, m2 and m3 (fig. 8), and the main part of the potassium is in a position with cn = 9, busy half due to short contacts c–c. the presence of potassium in the same position with the cations mg2+, mn2+, co2+, li+ is rare case for crystal chemistry. found on the structural data the compositions of the crystals are confirmed by good convergence of the local balance of valence efforts. the basis of all structures are three dimensional frames from octahedra around m1, m2 and m3 and tetrahedra table 4 crystallographic and thermal properties of triple molybdates of the type 1-1-2 [41–48] compound pr. gr.; z the unit cell parameters тmelt, oca, å b, å c, å b, o k3.11li0.89mg4(moo4)6 r`3 c; 6 14.3541(2) – 19.7338(4) – 730* k3.07li0.93mn4(moo4)6 r`3 c; 6 14.5896(3) – 19.9773(8) – 720 k3.14li0.86mn4(moo4)6 r`3 c; 6 14.607(2) – 19.992(4) – – k3.30li0.70co4(moo4)6 r`3 c; 6 14.4391(3) – 19.891(1) – 710* k3nani4(moo4)6 r`3 c; 6 14.2790(2) – 19.7589(4) – 750 k3namg4(moo4)6 r`3 c; 6 14.4528(2) – 19.8894(3) – 720 k3naco4(moo4)6 r`3 c; 6 14.4638(1) – 19.8369(3) – 530 * rb3lizn2(moo4)4 i`4 3 d; 4 11.902(1) – – – 580 cs3lico2(moo4)4 i`4 3 d; 4 12.2239(2) – – – 740** cs3lizn2(moo4)4 i`4 3 d; 4 12.2100(1) – – – 690 cs3nazn2(moo4)4 i`4 3 d; 4 12.3134(1) – – – 510 cs3agzn2(moo4)4 i`4 3 d; 4 12.3049(2) – – – 530 csna5mn3(moo4)6 с2/с; 2 13.3659(3) 13.6897(3) 7.1692(2) 112.727(1) 701 cs4na10mn5(moo4)12 p21/c; 4 13.8597(3) 12.5719(2) 28.4209(3) 90.097(1) 576 csna5co3(moo4)6 с2/с; 2 13.0917(8) 13.5443(8) 7.1217(4) 112.331(2) 615 cs4na10co5(moo4)12 pbca; 4 13.6572(3) 12.5063(3) 27.9898(5) – – csna5ni3(moo4)6 с2/с; 2 13.212(3) 12.458(3) 7.120(1) 112.245(3) 636 * the compound decomposes in the solid phase of the double molybdates. ** compound decomposes in the solid phase at cs2co2(moo4)3 и cslimoo4. triple molybdates one-, one and three(two)valence metals 364 № 4 | 2015 chimica techno acta moo4 in large extra-framework cavities there are potassium ions. in the systems na2moo4–k2moo4–amoo4 (a = ni, mg, co) there are formed triple molybdates k3naa4(moo4)6 similar in structure [44], figurative points are located on quasi-binary sections of k3na(moo4)2–amoo4. in the structures of these compounds the positions m1, m2 and m3 are occupied by the cations na+, a2+ and a2+, respectively, and the positions of potassium, as in the previous case are occupied only half. the data on these triple molybdates are given in table. 4. the isostructurality of considered triple molybdates to sodium-ion conductor iina3fe2(aso4)3 gives reason to expect the presence of increased ionic conductivity. it is assumed that the ways of transport of ions in these phases are similar to found in the structure of iina3fe2(aso4)3, where na + cations are moved through the defective positions of sodium with cn = 9 and octahedral site m1, in the neighbouring coordination polyhedra and form three-dimensional network. in the systems li2moo4–rb2moo4– amoo4 (a = mg, mn, co, ni) and li2 moo4–cs2moo4–amoo4 (a = mg, mn, ni) triple molybdates aren’t formed. in systems with rb and zn (fig. 9, a) and cesium-containing systems with co and zn (fig. 9, b) rb3lizn2(moo4)4 и cs3lia2(moo4)4 (a = co, zn) are found [41-43], the isostructural cubic cs6zn5(moo4)8 [23, 24]. the uniqueness of the composition and structure cs6zn5(moo4)8 is connected with the incompleteness of the tetrahedral positions of the zinc, where the sixth part is vacant. the filling of vacancies by ions li+ and other singly charged cations m+ according to scheme zn2+ + ☐ → 2m+ creates the conditions for the synthesis of new compounds. an introduction to the structure of cubic cs6zn5(moo4)8 of singly charged cations m+ = na, ag with close to zn2+ ionic radius obtained cubic phases cs3mzn2(moo4)4 with disordered distribution of cations m+ on the positions of the zn2+. the features cs3mzn2(moo4)4 (m = na, ag) are given in table. 4. according to our data [43, 50], between cs3mzn2(moo4)4 (m = li, na) and cs6zn5(moo4)8 there are continuous solid solutions (fig. 9, b) with the gradual filling of the cationic vacancies in the fig. 7. subsolidus triangulation of li2moo4-k2moo4- mgmoo4 at 550 °c. s – k3+xli1-xmg4(moo4)6 fig. 8. the projection of the fragment of structure of triple molybdate k3+xli1-xa4(moo4)6 (a = mg, mn, co) on the plane (001). khaikina g. e., solodovnikov s. f., basovich o. m., solodovnikova z. a., kadyrova y. m., savina a. a., zolotova e. s., yudin v. n., spiridonova t. s. 365 № 4 | 2015 chimica techno acta structure cs6zn5(moo4)8. it is likely that a similar phenomenon occurs in the case of cs3agzn2(moo4)4. the formation of such solid solutions gives the opportunity within certain limits to control the composition, stability and properties of phases on the basis of cs6zn5(moo4)8. it should be noted that the substitution and the simultaneous introduction into the position of zinc in the structure cs6zn5(moo4)8 different valent cations with very different ionic radius on the scheme 5zn2+ + ☐ → 2r3+ + 4li+ leads to the formation of the group of triple molybdates li2m3r(moo4)4 (mr = csfe, csga, rbga, csal, rbal, tlal) described above. in the latter case, the cations li+ and r3+ are distributed orderly in structure, which leads to a tetragonal distortion of the structure of the prototype. the basis of the structures of the triple molybdates of both series, as structures cs6zn5(moo4)8 are delicate three-dimensional frames. in phases with divalent metals they are formed by tetrahedrons of two sorts – around the molybdenum fig. 9. subsolidus triangulation of the triple systems at 510 °c: а – li2moo4-rb2moo4znmoo4; b – li2moo4-cs2moo4-znmoo4. s – m3lizn2(moo4)4 (m = rb, cs) fig. 10. the structure of triple molybdates derived from patterns cs6zn5(moo4)8 [23, 24]: а – структура lics3co2(moo4)4 (pr. gr. i`43d) [41]; b – структура li2cs3ga(moo4)4 (pr. gr. i`42d) [42] triple molybdates one-, one and three(two)valence metals 366 № 4 | 2015 chimica techno acta and “mixed” position of lithium (sodium, silver) and a divalent cation; in the compounds with trivalent metals tetrahedra moo4, lio4 and ro4. in large voids of the framework there are large singly charged cations with cn = 12 (fig. 10). all phases of family cs6zn5(moo4)8 have acentric structure and perspective to create materials for nonlinear optics. moreover, an open frame structure leads to the manifestation of these compounds ion-conductive properties. the most significant results were obtained for rb3lizn2(moo4)4 and tl3li2al(moo4)4, the values of ionic conductivity (of the order of 2∙10-2 sm/sm at 520 and 350 °c, respectively), bring them closer to superionic conductors. in the systems li2moo4–m2moo4– amoo4 (m = na, k, rb, cs; a = ca, sr, pb, ba, cd) triple molybdates aren’t formed, however, there are areas of solid solutions (up to 15 mol. %) on the basis of double molybdates from faceting systems m2moo4–amoo4 [51]. in the study of solution-melt crystallization (solvent – cs2mo2o7) in the systems na2moo4–cs2moo4–amoo4 (a = ni, co, mn) the crystals csna5m3(moo4)6 [47] related to the type alluaudite were isolated and structurally were investigated. the oxygen octahedra around the cations a2+ and na+ are connected with common edges and faces, and then by common vertices with the moo4 tetrahedra into a three-dimensional frame, which is parallel (100) is divided into two kinds of layers (fig. 11). in one of these layers (fig. 11) the wide channels filled with cesium ions pass parallel to the axis c, which occupy half their positions and have cn = 8. the comparison of eludicating structures csna5a3(moo4)6 and na4–2xa1+x(moo4)3 (a = ni, co, mn) shows that in the triple molybdates part of the cations na+ in the channels was replaced with cs+, significantly increased the parameters of the cell along the axis a and accordingly the width of the channels were significantly increased. view as along these channels the transport of sodium ions may be, it may increase the ionic conductivity. the close relationship of phases csna5a3(moo4)6 and na4–2xa1+x(moo4)3 (a = ni, co, mn) can indicate the formation of solid solutions between them, which requires additional researches. the features csna5a3(moo4)6 (a = ni, co, mn) are given in table. 4. fig. 11. structure csna5mn3(moo4)6: a – general view; b,c two types of layers of polyhedra projected on (100) khaikina g. e., solodovnikov s. f., basovich o. m., solodovnikova z. a., kadyrova y. m., savina a. a., zolotova e. s., yudin v. n., spiridonova t. s. 367 № 4 | 2015 chimica techno acta in the systems na2moo4–cs2moo4– amoo4 (a = co, mn) also highlighted the triple molybdates of composition cs4na10a5(moo4)12 [46, 48] (fig. 12, table 4) also were highlighted, which were very similar in structure to the above compounds na25cs8r5(moo4)24 (r = in, sc, fe), forming together with them obviously the single family of phases with similar metrics of cells and different symmetry. the structure cs4na10co5(moo4)12 (pr. gr. pbca) is most symmetrical, which can be regarded as the ancestor of this family. the symmetry the other compounds may be raised at phase transitions, which must be accompanied by disordering of the structure and the possible increase in the mobility of sodium cations. in this regard, we can expect high ionic conductivity at triple molybdates cs4na10a5(moo4)12 (a = co, mn, as this is the case for na25cs8r5(moo4)24 (r = in, sc, fe). concluding remarks our carried studies of triple molybdates of the type 1-1-2 and 1-1-3 show that among them there are several families of isostructural or closely related in structure phases. the systems with trivalent metals have higher phase-forming ability, the large stoichiometric and structural diversity in which the triple molybdates belonging to 14 structural types (families) form, whereas triple molybdates of the type 1-1-2 belong only to four isostructural series. one from these explanations for this may be the wider range of cations r3+ and their sizes compared to the ions a2+ in the phase-forming systems m’2moo4–m’’2moo4–amoo4 (m’ = li, na; m’’ = k, rb, cs; a = mg, mn, co, ni, zn). a number of identified families of triple molybdates of types 1-1-3 and 1-1-2 may be promising as functional materials. this is especially true of the family of compounds limr2(moo4)4 with interesting spectral-luminescent properties, as well as lithiumand sodiumcontaining triple molybdates of different structures, which may show an increased ion conductivity. among the latest the compounds of families cs6zn5(moo4)8, ii-na3fe2(aso4)3 and alluaudito-similar phase na25cs8r5(moo4)24 (r = in, sc, fe) and cs4na10m5(moo4)12 (m = co, mn) for which the relevant researches have already conducted. from the crystallochemical point of view in this regard the compounds limr2(moo4)4 are also interesting, where the ions li+ fill internodic voids of structural type band2(moo4)4 and the hexagonal or trigonal phases s1–s4 (table. 2, 3), in which the sodium ions have a nonstandard (trigonal-prismatic or lower) coordination that can contribute to ionic conductivity. nonlinear optical properties fig. 12. subsolidus triangulation of the na2moo4–cs2moo4–comoo4 at 480 oc triple molybdates one-, one and three(two)valence metals 368 № 4 | 2015 chimica techno acta can be expected 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solodovnikova z. a. the search and study of triple molybdates of sodium with cesium and trivalent metals. mater. vseros. youth scientific and practical conference. with the intern. participation «resource-saving and environment-friendly technologies and materials». 12–14 may 2011, ulan-ude. ulan-ude: bsu, 2011. p. 57–59. 36. basovich o. m., uskova a. a., solodovnikov s. f., solodovnikova z. a., khaikina e. g. formation of phase in the systems na2moo4–cs2moo4–ln2(moo4)3 and crystal structure of new triple molybdate cs7na5yb2(moo4)9. bulletin of the buryat state university. vol. 3. chemistry, physics. 2011;24-29. 37. savina a. a., atuchin v. v., solodovnikov s. f., solodovnikova z. a., krylov a. s., maximovskiy e. a., molokeev m. s., oreshonkov a. s., pugachev a. m., khaikina e. g. synthesis, structural and spectroscopic properties of acentric triple molybdate cs2nabi(moo4)3. j. solid state chem. 2015;225:53–58. doi: 10.1016/j. jssc.2014.11.023. 38. savina a. a., solodovnikov s. f., belov d. a., basovich o. m., solodovnikova z. a., gudkova i. a., stefanovich s. yu., lazoryak b. i., khaikina e. g. new ion-conducting triple molybdates with eludito-similar structure. «environment-friendly and resource-saving technologies and materials». mater. ii vseros. young. scientific. conf. with the intern. participation (ulan-ude, on may 15-16, 2014). ulan-ude: publishing house of the buryat state university, 2014. p. 93–94. 39. savina a. a., solodovnikov s. f., belov d. a., basovich o. m., solodovnikova z. a., khaikina g. e., solodovnikov s. f., basovich o. m., solodovnikova z. a., kadyrova y. m., savina a. a., zolotova e. s., yudin v. n., spiridonova t. s. 371 № 4 | 2015 chimica techno acta pokholok k. v., stefanovich s. yu., lazoryak b. i., khaikina e. g. synthesis, crystal structure and properties of alluaudite-like triple molybdate na25cs8fe5(moo4)24. j. solid state chem. 2014;220:217–220. doi: 10.1016/j.ssc.2014.09.004. 40. moore p. b. crystal chemistry of the alluaudite structure type: contribution to the paragenesis of pegmatite phosphate giant crystals. amer. miner. 1971;56(11–12):1955. 41. solodovnikova z. a., solodovnikov s. f., zolotova e. s. new triple molybdates cs3lico2(moo4)4 and rb3lizn2(moo4)4, filled derivatives of the cs6zn5(moo4)8 type. acta crystallogr. 2006;c62(1):i6-i8. doi: 10.1107/s0108270105037121. 42. solodovnikov s. f., khaikina e. g., solodovnikova z. a. kadyrova yu. m., khal'baeva k. m., zolotova e. s. new families of lithium-containing triple molybdates and stabilizing role of lithium in their structure. reports of russian academy of sciences. 2007; 416(1):60–65. 43. solodovnikova z. a. phase formation and structure of triple molybdate and related compounds in the systems li2moo4–a + 2moo4–m 2+moo4 (a + = k, rb, cs; m2+ = mg, mn, co, ni, zn). dis. candidate. chem. sciences. novosibirsk, 2008. 219p. 44. solodovnikova z. a., solodovnikov s. f., gudkova i. a., zolotova e. s. synthesis and structure of new triple molybdate k3nam4(moo4)6 (m = ni, mg, co). mater. vseros. scientific. conf. with the intern. participation “baikal materials science forum”. 9–13 july 2012, ulan-ude. ulan-ude: izd-vo bnts sb ras, 2012. part 2. p. 143–144. 45. solodovnikov s. f., solodovnikova z. a., zolotova e. s., yudin v. n., gudkova i. a., kadyrova, yu. m., khaikina e. g., triple molybdates (tungstates) of the family cs6zn5(moo4)8 tez dokl. the 9th seminar of sb ras – urb ras “thermodynamics and material science”]. the memory of acad. f. a. kuznetsov. 30 june – 4 july 2014, novosibirsk, russia. novosibirsk: publishing house of the institute of inorganic chemistry sb ras, 2014. p. 108. 46. yudin, v. n., zolotova e. s., solodovnikova z. a., solodovnikov s. f., gudkova i. a. formation of phase and structure of triple molybdate in the system cs2moo4– na2moo4–. tez dokl. the 9th seminar of sb ras – urb ras “thermodynamics and material science”]. the memory of acad. f. a. kuznetsov. 30 june – 4 july 2014, novosibirsk, russia. novosibirsk: publishing house of the institute of inorganic chemistry sb ras, 2014. p. 151. 47. yudin v. n., zolotova e. s., shkerin s. n., tolkacheva a. s., uporov s.  a., solodovnikova z. a., solodovnikov s. f. structure and properties of triple molybdates csna5m3(moo4)6 (m = ni, co, mn. mater. vseros. scientific. conf. with the intern. “ii baikal materials science forum”. 29 june – 5 july 2015, ulan-ude. ulanude: publishing house of buryat scientific center sb ras, 2015. part 1. p. 146–148. 48. yudin v. n., zolotova e. s., solodovnikova z. a., solodovnikov s. f., tolkacheva  a.  s. formation of phase, structure and properties of triple molybdates in the system cs2moo4–na2moo4–comoo4. proc. dokl. school-conference of young scientists “inorganic compounds and functional materials (icfm-2015)”. novosibirsk: publishing house of the institute of inorganic chemistry sb ras, 2015. p. 139. triple molybdates one-, one and three(two)valence metals 372 № 4 | 2015 chimica techno acta 49. d’yvoire f., bretey e., collin g. crystal structure, non-stoichiometry and conductivity of ii-na3m2(aso4)3 (m = al, ga, cr, fe). solid state ionics. 1988;28–30:1259– 1264. doi: 10.1016/0167-2738(88)90367-0. 50. zolotova e. s., solodovnikova z. a., yudin v. n., solodovnikov s. f., khaikina e. g., basovich o. m., korolkov i. v., filatova i. yu. phase relations in the na2moo4-cs2moo4 and na2moo4-cs2moo4-znmoo4 systems, crystal structures of cs3na(moo4)2 and cs3nazn2(moo4)4. j. solid state chem. 2015 (accepted for publication). 51. gudkova i. a. phase equilibria, synthesis, structure and properties of compounds formed in ternary systems li2moo4–a2moo4–mmoo4 (a = na, k, rb, cs; m = ca, sr, pb, ba, cd). dis. cand. chem. sci., novosibirsk, 2014. 192 p. khaikina g. e., solodovnikov s. f., basovich o. m., solodovnikova z. a., kadyrova y. m., savina a. a., zolotova e. s., yudin v. n., spiridonova t. s. 373 у д к 5 49 .7 61 .5 е. г. хайкина1,2, с. ф. солодовников3,4, о. м. басович1, з. а. солодовникова3, ю. м. кадырова1, а. а. савина1,2, е. с. золотова3, в. н. юдин3,4, т. с. спиридонова1,2 1 фгбун байкальский институт природопользования со ран, 670047, г. улан-удэ, ул. сахьяновой, 6 2 фгбоу впо «бурятский государственный университет», 670000, г. улан-удэ, ул. смолина, 24а 3 фгбун институт неорганической химии им. а.в. николаева со ран, 630090, г. новосибирск, пр. акад. лаврентьева, 3 4 фгаоу во «новосибирский национальный исследовательский государственный университет», 630090, г. новосибирск, ул. пирогова, 2 egkha@mail.ru, solod@niic.nsc.ru тройные молибдаты одно-, однои трех(двух)валентных металлов в обзоре обобщен экспериментальный материал по фазообразованию, структуре и свойствам новых групп сложнооксидных соединений – тройных молибдатов, содержащих тетраэдрический молибдат-ион, два различных однозарядных катиона наряду с трехили двухзарядным катионом. выделено несколько структурных семейств данных соединений и показано, что многие из них представляют интерес как люминесцентные, лазерные, ионопроводящие или нелинейно-оптические материалы. ключевые слова: тройные молибдаты; одно-, двухи трехвалентные металлы; фазообразование; структура; функциональные свойства. авторы благодарят к.х.н. к. м. хальбаеву, к.х.н. и. а. гудкову и к.х.н. и. в. королькова за участие в исследованиях. работа выполнена при частичной поддержке российского фонда фундаментальных исследований (проекты № 08-03-00384, 13-03-01020 и 14-03-00298). © хайкина е. г., солодовников с. ф., басович о. м., солодовникова з. а., кадырова ю. м., савина а. а., золотова е. с., юдин в. н., спиридонова т. с., 2015 молибдаты и вольфраматы являются одними из наиболее востребованных объектов неорганической химии, кристаллохимии и химии твердого тела, а также базой для разработки функциональных материалов различного назначения, что поддерживает постоянный интерес к данным соедине374 № 4 | 2015 chimica techno acta ниям и объясняет значительное число публикаций по этой тематике. в 1960–1980 гг. в центре внимания ученых оказались двойные молибдаты и вольфраматы – фазы с общей формулой axby(xo4)z, на основе которых были впоследствии разработаны лазерные, сегнетоэлектрические, сцинтилляционные, нелинейно-оптические и другие материалы [1–5]. определяющий вклад в формирование этой группы соединений и их всестороннее изучение внесли отечественные научные школы: профессора л. м. ковбы, профессора в.  к.  трунова (московский государственный университет им. м.  в.  ломоносова), профессора в. м. жуковского, профессора е. в. ткаченко (уральский государственный университет им. а.  м.  горького, г. свердловск), чл.корр. ан ссср м. в. мохосоева (донецкий государственный университет; бурятский институт естественных наук со ан ссср, улан-удэ), профессора а.  а.  майера (московский химико-технологический институт им. д.  и.  менделеева), профессора а.  м.  голуба (киевский государственный университет), к. ф-м. н. п. в. клевцова, к.ф.-м.н. р. ф. клевцовой (институт неорганической химии со ан ссср, г. новосибирск) и др. в последние два десятилетия произошло перенесение центра тяжести исследований с двойных молибдатов и вольфраматов на тройные молибдаты. к настоящему времени эта группа соединений насчитывает более 550 представителей и является наиболее быстро растущей среди сложнооксидных фаз, содержащих тетраэдрический анион и три различных катиона. большая часть тройных молибдатов получена и охарактеризована сотрудниками байкальского института природопользования со ран (г. уланудэ) и института неорганической химии им. а.  в.   николаева со ран (г. новосибирск). краткий обзор различных типов тройных молибдатов, отличающихся комбинациями зарядов входящих в них катионов, был ранее представлен в [6]. целью настоящей работы является более подробное рассмотрение фазообразования, строения и свойств тройных молибдатов, содержащих в своем составе два различных однозарядных катиона наряду с трехзарядным (тип 1-1-3) или двухзарядным (тип 1-1-2) катионом. тройные молибдаты типа 1-1-3 первые систематические поисковые исследования тройных молибдатов одно-, одно-, трехвалентных металлов были проведены для литийсодержащих систем li2moo4– m2moo4–r2(moo4)3 (m = k–cs, tl, ag, r = bi, ln, y, in, sc, fe, ga, cr, al). их результатом стали выявление, синтез и характеризация около 40 соединений составов limr2(moo4)4, lim2r(moo4)3, li2m3r(moo4)4, lim4r(moo4)4, li2mr(moo4)3, что положило начало формированию обширной группы тройных молибдатов типа 1-1-3. типичные варианты триангуляции систем, в которых эти фазы образуются, представлены на рис.  1. установлена принадлежность рассматриваемых соединений к восьми структурным типам, для представителей пяти из которых получены кристаллы и определены кристаллические структуры. хайкина е. г., солодовников с. ф., басович о. м., солодовникова з. а., кадырова ю. м., савина а. а., золотова е. с., юдин в. н., спиридонова т. с. 375 № 4 | 2015 chimica techno acta тройные молибдаты самой многочисленной изоструктурной серии соединений состава limr2(moo4)4 образуются с висмутом и некоторыми лантаноидами на квазибинарных разрезах lir(moo4)2–mr(moo4)2 систем li2moo4–m2moo4–r2(moo4)3 (m = k, rb, tl). области существования этих фаз в ряду рзэ существенно различаются и с ростом размера однозарядного катиона сдвигаются в сторону легких лантаноидов (рис. 2). анализ экспериментальных данных позволяет сделать вывод об определяющем влиянии размерного фактора на возможность формирования моноклинных тройных молибдатов данного семейства: limln2(moo4)4 образуются, если разница в размерах ионов крупного однозарядного катиона и редкоземельного элемента заключена в интервале 0,48 ǻ ≤ r(m+) – r(ln3+) ≤ 0,60 ǻ. при более низких значениях dr на разрезе liln(moo4)2–mln(moo4)2 происходит формирование твердых растворов. при dr >  0,60  ǻ рассматриваемая фаза либо не образуется, либо ее формирование настолько затруднено, что соединение не удается выделить в однофазном состоянии при использовании обычных методик твердофазного синтеза [11]. в установленный интервал укладываются и изоформульные и изоструктурные медьсодержащие соединения рис. 1. субсолидусное строение некоторых систем li2moo4–m2moo4–r2(moo4)3 [7–10]: s1 – limr2(moo4)4; s2 – lim2r(moo4)3; s3 – li2mr(moo4)3; s4 – li2m3r(moo4)4. область limmoo4–m2moo4–mfe(moo4)2 систем li2moo4–m2moo4–fe2(moo4)3 (m = k, rb, cs) ln m la ce, pr nd sm, eu gd–lu, y k tl rb рис. 2. области существования тройных молибдатов limln2(moo4)4 (заштрихованы) тройные молибдаты одно-, одно и трех(двух)валентных металлов 376 № 4 | 2015 chimica techno acta cukln2(moo4)4 с gd, tb, ho, полученные и охарактеризованные в [12, 13]. близость r(cu+) и r(li+) позволяет с высокой степенью вероятности прогнозировать существенное расширение семейства тройных молибдатов m’m’’r2(moo4)4 за счет содержащих cu(i) фаз подобного типа с k, tl, rb и теми трехвалентными элементами, разница в размерах с которыми будет удовлетворять предложенному критерию. строение тройных молибдатов limr2(moo4)4 определено на примере lirbbi2(moo4)4, единственного соединения данного семейства, плавящегося конгруэнтно [14]. остальные соединения limr2(moo4)4 разлагаются в твердой фазе на соответствующие двойные молибдаты [7, 15]1 и их структуры (на примере limnd2(moo4)4, m = k, tl, rb уточняли методом ритвельда по порошковым данным [16]. структуры limr2(moo4)4 близки к строению тройных молибдатов li3ba2ln3(moo4)8 [17] и производны от структурного типа band2(moo4)4 [18]. характерной особенностью структур limr2(moo4)4 являются ажурные слои из полиэдров ro8 и присоединенных к ним через общие вершины moo4тетраэдров. соседние слои связаны между собой посредством октаэдров lio6 и полиэдров mo10 (рис. 3). наличие в соединениях limr2(moo4)4 ионов li +, заполняющих междоузельные пустоты структурного типа band2(moo4)4, позволяет предполагать у них литий-ионную 1 распад limce2(moo4)4 при нагревании на воздухе сопровождается частичным окислением ce3+ до ce4+. проводимость. результаты указывают на возможность использования этих тройных молибдатов как чувствительных элементов датчиков сенсорных систем оперативного мониторинга окружающей среды [19, 20]. спектрально-люминесцентные характеристики limln2(moo4)4:  eu 3+(nd3+) дают основание говорить о возможности применения тройных молибдатов этого семейства для создания люминофоров, обладающих высокой контрастностью цветов, а также активных сред лазеров [8, 21]. о перспективности использования likgd2(moo4)4:  eu 3+ в качестве красного люминофора для wled-свидетельствуют данные, полученные в [22]. как и в предыдущем случае, возможность образования другой изоструктурной серии тройных молибдатов li2m3r(moo4)4 (mr = csfe, csga, rbga, csal, rbal, tlal) в значительной мере определяется размерным фактором: соединения образованы малыми катионами fe3+, ga3+, al3+ с тетраэдрической координацией и достаточно крупными ионами tl+, rb+ и cs+. отсутствие li2m3cr(moo4)4 связано, видимо, с высокой предпочтительностью cr3+ к октаэдрической координации. рис. 3. проекция структуры lirbnd2(moo4)4 вдоль оси а хайкина е. г., солодовников с. ф., басович о. м., солодовникова з. а., кадырова ю. м., савина а. а., золотова е. с., юдин в. н., спиридонова т. с. 377 № 4 | 2015 chimica techno acta эти тетрагональные соединения обладают каркасным строением и являются упорядоченными производными кубического cs6zn5(moo4)8 [23, 24]. с увеличением размера r3+ область существования подобных фаз смещается в сторону более крупных однозарядных катионов m+, что можно объяснить соответствием размеров тетраэдрического каркаса размерам внекаркасного катиона. очевидно, именно с размерным несоответствием связана кристаллизация li2k3al(moo4)4 в другом структурном типе [10]. показано, что lik2in(moo4)3, lirb2fe(moo4)3 и lics4al(moo4)4 формируют новые структурные типы, не имеющие пока других представителей (табл.  1). получить пригодные для рентгеноструктурных исследований монокристаллы lik2fe(moo4)3, li2kfe(moo4)3 и li2k3al(moo4)4, либо найти структурные прототипы этих соединений пока не удалось. ни в одной из систем li2moo4– ag2moo4–r2(moo4)3 тройные молибдаты не выявлены [28–30]. разрезы lir(moo4)2–agr(moo4)2 в висмути лантаноидсодержащих системах характеризуются формированием прорис. 4. t–x-диаграмма разреза libi(moo4)2–agbi(moo4)2 [29] таблица 1 данные рса монокристаллов lik2in(moo4)3, lirb2fe(moo4)3 и lics4al(moo4)4 [25–27] соединение пр. гр.; z a, ǻ b, ǻ c, ǻ b, ° r, % lik2in(moo4)3 p21; 2 7.0087(2) 9.2269(3) 10.1289(3) 107.401(1) 22.80 lirb2fe(moo4)3 pnma; 4 24.3956(6) 5.8306(1) 8.4368(2) – 2.11 lics4al(moo4)4 p2; 2 15.940(3) 8.266(2) 8.319(2) 105.13(3) 2.85 таблица 2 тройные молибдаты в системах m2moo4–cs2moo4–r2(moo4)3 (m = na, r = bi, ln, in, sc, fe; m = ag, r = bi, ln, in, sc) [31, 32] m = na phase m = ag bi tm yb lu in sc fe bi yb lu in sc s1 * * m13–3xcs11r2+x(moo4)15 s2 * m5cs7r2(moo4)9 s3 * mcs2r(moo4)3 ◆ s4 *в/т m3cs3r2(moo4)6н/т s5 * * * m25cs8r5(moo4)24 поля соединений, построенных на единой структурной основе, заштрихованы одинаково; * – получены кристаллы и по монокристальным данным методом рса определена структура; ◆ – получены кристаллы и по монокристальным данным определены параметры ячейки тройные молибдаты одно-, одно и трех(двух)валентных металлов 378 № 4 | 2015 chimica techno acta тяженных граничных твердых растворов (рис. 4). выполненные в последние годы исследования систем m 2 m o o 4 – c s 2 m o o 4 – r 2 ( m o o 4 ) 3 (m = na, ag) позволили значительно пополнить группу тройных молибдатов однои трехвалентных металлов за счет натрийи серебросодержащих фаз. составы и области существования полученных при этом соединений приведены в табл.  2, данные рса полученных монокристаллов – в табл. 3. изученные натриевые соединения имеют, как правило, сложные составы и каркасные структуры (рис.  5, 6), отличные по своему строению от тройных молибдатов, образующихся в системах li2moo4–m2moo4–r2(moo4)3 (m = k–cs, tl). в структурах натрийсодержащих тройных молибдатов присутствуют моo4-тетраэдры и ro6-октаэдры, а натрий обладает октаэдрической или тригонально-призматической координацией, либо формирует полиэдры с более низким кч. в этих структурах na+ и r3+ достаточно часто совместно заселяют одни кристаллографические позиции; наряду с ними имеются позиции, частично заполненные катионами натрия, что приводит к отклонению составов от стехиометрических. фазы переменного состава широко распространены среди сложных (двойных и тройных) натриевых молибдатов [33, 34], что обусловлено близостью размеров ионов na+ и a2+ или r3+. согласно данным рфа, все тройные молибдаты, обнаруженные в системах ag2moo4–cs2moo4–r2(moo4)3, изоформульны натриевым аналогам и построены на единой с ними структурной основе [32]. в практическом плане наиболее интересны тройные молибдаты na25cs8r5(moo4)24, близко родственные структуры которых решены по монокристальным данным в рамках пр.  гр.  p21/c (in), p212121  (sc), p`1  (fe) [38, 39]. атомы mo во всех трех структурах координированы тетраэдрически, трехвалентного металла – октаэдрически, причем все или часть из таблица 3 данные рса монокристаллов тройных молибдатов натрия, цезия и трехвалентных металлов [31] соединение пр. гр.; z параметры решетки r s1 na7.23cs11tm3.92(moo4)15 p63/mcm; 2 a = 10.5849(1), c = 37.4867(6) å 0,029 na7.72cs11bi3.76(moo4)15 p63/mcm; 2 a = 10.5507(1), c = 37.6640(1) å 0,038 s2 na5cs7yb2(moo4)9 r32; 3 a = 10.5107(2), c = 36.358(7) å 0,035 s3 nacs2bi(moo4)3 r3c; 12 a = 10.6435(2), c = 40.9524(7) å 0,020 s4 в/т-na3cs3in2(moo4)6 r 3 ; 12 a = 17.5753(2), c = 29.4333(3) å 0,032 s5 na25cs8in5(moo4)24 p21/c; 4 a = 12.6392(2), b = 21.4601(4), c = 14.0313(3) å, β = 90.017(1)° 0,030 na25cs8sc5(moo4)24 p212121; 2 a = 28.6452(6), b = 14.0043(3), c = 12.6482(2) å 0,072 na25cs8fe5(moo4)24 p`1; 2 a = 12.5814(5),b = 13.8989(5), c = 28.4386(9) å, α = 90.108(2), b = 90.064(2), g = 90.020(2)° 0,044 хайкина е. г., солодовников с. ф., басович о. м., солодовникова з. а., кадырова ю. м., савина а. а., золотова е. с., юдин в. н., спиридонова т. с. 379 № 4 | 2015 chimica techno acta них заселяют свои позиции совместно с атомами натрия. оставшиеся атомы na имеют довольно искаженную кислородную координацию (кч  =  5 и 6); у атомов цезия кч  =  9–10  (in), 11  (sc), 10–12  (fe); некоторые позиции катионов натрия могут быть заселены частично. во всех структурах можно выделить полиэдрические слои, образованные парами сочлерис. 5. структуры na7.23cs11tm3.92(moo4)15 (а), na5cs7yb2(moo4)9 (б), nacs2bi(moo4)3 (в) [35–37] а б в рис. 6. полиэдрические фрагменты (слои) в структурах na25cs8in5(moo4)24 (а), na25cs8sc5(moo4)24 (б), na25cs8fe5(moo4)24 (в), na5sc(moo4)4 (г) [38] тройные молибдаты одно-, одно и трех(двух)валентных металлов 380 № 4 | 2015 chimica techno acta ненных по ребрам октаэдров (r,  na) o6 и (r,  na)o6 (или ro6), которые соединены вершинами с мостиковыми moo4-тетраэдрами (рис.    6,  а–в). слои связываются мостиковыми moo4-тетраэдрами в трехмерный каркас, в пустотах которого расположены катионы сs+ и na+. во всех случаях строение слоев восходит к полиэдрическому слою из структуры na5sc(moo4)4 (рис.  6, г), относящейся к типу аллюодита (na,  ca)(fe,  mn,  mg)3(po4)3 [40]. ромбическая или псевдоромбическая метрика ячеек тройных молибдатов возникает из-за некоторого взаимного сдвига слоев по сравнению с моноклинными na5sc(moo4)4 и аллю одитом (пр.  гр.  c2/c), что может быть связано с наличием катионов цезия между слоями. особенности строения данной группы тройных молибдатов позволяют считать ее не разновидностью структурного типа аллюодита, а отдельным, хотя и близко родственным, структурным семейством. исследование ионопроводящих свойств аллюодитоподобных тройных молибдатов показало, что данные соединения претерпевают обратимые фазовые переходы i рода, сопровождаемые скачкообразным увеличением проводимости. выше температур фазовых переходов электропроводность достигает значений 10–2–10–3  см/см, что дает возможность рассматривать na25cs8r5(moo4)24  (r  =  in,  sc,  fe) как перспективные объекты для разработки новых материалов с высокой ионной проводимостью [38, 39]. особенности строения ряда других описанных выше тройных молибдатов также позволяют ожидать проявления ими повышенной натрий(серебро)ионной проводимости, причем улучшения их проводящих характеристик, по-видимому, можно добиться подходящими гетеровалентными замещениями с заменой части натрия (серебра) или другого катиона в структуре на более высокозарядный и образованием вакансий. тройные молибдаты типа 1-1-2 среди тройных солевых систем m’2moo4–m’’2moo4–amoo4 к настоящему времени наиболее изучены системы, образованные молибдатами лития, тяжелых щелочных элементов (k, rb, cs) и mg, mn, co, ni, co, zn, cd, ca, sr, ba, pb. большинство этих систем не являются фазообразующими, в некоторых формируются твердые растворы на основе двойных молибдатов. в шести системах найдено по одному тройному молибдату; их характеристики представлены в табл. 4. в тройных системах li2moo4– k2moo4–amoo4 (a = mg, mn, co) на квазибинарных разрезах li2a2(moo4)3-k2a2(moo4)3 (рис.  7) выявлены ромбоэдрические тройные молибдаты k3+xli1-xa4(moo4)6 (0 ≤ x ≤ 0,3) [42, 43]. они кристаллизуются в структурном типе ii-na3fe2(aso4)3 [49], в котором катионы распределяются следующим образом: (na5£) ix(m1)vi(m2) vi(m3)3 vi(aso4)6 = (na5£)(na)(fe 3+) (fe3+)3(aso4)6 (здесь римские цифры обозначают кч катионов в позициях м1, м2 и м3). в структурах тройных молибдатов катионы li, a2+ и часть k+ размещены в позициях м1, м2 и м3 (рис. 8), а основная часть калия нахайкина е. г., солодовников с. ф., басович о. м., солодовникова з. а., кадырова ю. м., савина а. а., золотова е. с., юдин в. н., спиридонова т. с. 381 № 4 | 2015 chimica techno acta ходится в позиции с кч = 9, занятой наполовину из-за коротких контактов k–k. присутствие калия в одной позиции с катионами mg2+, mn2+, co2+, li+ является редким для кристаллохимии случаем. найденные по структурным данным составы кристаллов подтверждены хорошей сходимостью локальных балансов валентных усилий. основой всех структур являются трехмерные каркасы из октаэдров вокруг м1, м2 и м3 и тетраэдров таблица 4 кристаллографические и термические характеристики тройных молибдатов типа 1-1-2 [41–48] соединение пр. гр.; z параметры элементарной ячейки тпл, ocb, å c, å b, o k3,11li0,89mg4(moo4)6 r`3 c; 6 14,3541(2) – 19,7338(4) – 730* k3,07li0,93mn4(moo4)6 r`3 c; 6 14,5896(3) – 19,9773(8) – 720 k3,14li0,86mn4(moo4)6 r`3 c; 6 14,607(2) – 19,992(4) – – k3,30li0,70co4(moo4)6 r`3 c; 6 14,4391(3) – 19,891(1) – 710 * k3nani4(moo4)6 r`3 c; 6 14,2790(2) – 19,7589(4) – 750 k3namg4(moo4)6 r`3 c; 6 14,4528(2) – 19,8894(3) – 720 k3naco4(moo4)6 r`3 c; 6 14,4638(1) – 19,8369(3) – 530 * rb3lizn2(moo4)4 i`4 3 d; 4 11,902(1) – – – 580 cs3lico2(moo4)4 i`4 3 d; 4 12,2239(2) – – – 740 ** cs3lizn2(moo4)4 i`4 3 d; 4 12,2100(1) – – – 690 cs3nazn2(moo4)4 i`4 3 d; 4 12,3134(1) – – – 510 cs3agzn2(moo4)4 i`4 3 d; 4 12,3049(2) – – – 530 csna5mn3(moo4)6 с2/с; 2 13,3659(3) 13,6897(3) 7,1692(2) 112,727(1) 701 cs4na10mn5(moo4)12 p21/c; 4 13,8597(3) 12,5719(2) 28,4209(3) 90,097(1) 576 csna5co3(moo4)6 с2/с; 2 13,0917(8) 13,5443(8) 7,1217(4) 112,331(2) 615 cs4na10co5(moo4)12 pbca; 4 13,6572(3) 12,5063(3) 27,9898(5) – – csna5ni3(moo4)6 с2/с; 2 13,212(3) 12,458(3) 7,120(1) 112,245(3) 636 * соединение разлагается в твердой фазе на двойные молибдаты. ** соединение разлагается в твердой фазе на cs2co2(moo4)3 и cslimoo4. рис. 7. субсолидусная триангуляция системы li2moo4-k2moo4-mgmoo4 при 550°c. s – k3+xli1-xmg4(moo4)6 рис. 8. проекция фрагмента структуры тройных молибдатов k3+xli1-xa4(moo4)6 (a = mg, mn, co) на плоскость (001) тройные молибдаты одно-, одно и трех(двух)валентных металлов 382 № 4 | 2015 chimica techno acta moo4, в больших внекаркасных пустотах размещаются ионы калия. в системах na2moo4–k2moo4–amoo4 (a = ni, mg, co) образуются аналогичные по строению тройные молибдаты k3naa4(moo4)6 [44], фигуративные точки которых расположены на квазибинарных разрезах k3na(moo4)2– amoo4. в структурах этих соединений позиции м1, м2 и м3 заняты катионами na+, a2+ и a2+, соответственно, а позиции калия, как и в предыдущем случае, заняты только наполовину. данные по этим тройным молибдатам приведены в табл. 4. изоструктурность рассматриваемых тройных молибдатов натрий-ионному проводнику ii-na3fe2(aso4)3 дает основание ожидать наличия повышенной ионной проводимости. предполагается, что пути транспорта ионов в этих фазах аналогичны обнаруженным в структуре ii-na3fe2(aso4)3, где катионы na + перемещаются через дефектные позиции натрия с кч = 9 и октаэдрическую позицию м1, которые находятся в соседних координационных полиэдрах и образуют трехмерную сеть. в системах li2moo4–rb2moo4– amoo4 (a = mg, mn, co, ni) и li2– moo4–cs2moo4–amoo4 (a = mg, mn, ni) тройные молибдаты не образуются. в системах с rb и zn (рис.  9,  а) и цезийсодержащих системах с co и zn (рис.  9,  б) найдены rb3lizn2(moo4)4 и cs3lia2(moo4)4 (a = co, zn) [41– 43], изоструктурные кубическому cs6zn5(moo4)8 [23, 24]. уникальность состава и строения cs6zn5(moo4)8 связана с некомплектностью тетраэдрических позиций цинка, где их шестая часть вакантна. заполнение вакансий ионами li+ и другими однозарядными катионами m+ по схеме zn2+ + ☐ → 2m+ создает условия для получения новых соединений. введением в структуру кубического cs6zn5(moo4)8 однозарядных катионов m+ = na, ag с близкими к zn2+ ионными радиусами получены кубические фазы cs3mzn2(moo4)4 с неупорядоченным распределением катионов m+ по позициям zn2+. характеристики cs3mzn2(moo4)4 (m = na, ag) приведены в табл. 4. по нашим данным [43,  50], между cs3mzn2(moo4)4 (m = li, na) и cs6zn5(moo4)8 существуют непрерывные твердые растворы (рис.  9,  б) с постепенным заполнением катионных вакансий в структуре cs6zn5(moo4)8. вполне вероятно, что аналогичное явление имеет место и в случае cs3agzn2(moo4)4. образование таких твердых растворов дает возможность в определенных пределах управлять составом, стабильностью и свойствами фаз на основе cs6zn5(moo4)8. нельзя не отметить, что замещение и одновременное внедрение в позиции цинка в структуре cs6zn5(moo4)8 разновалентных катионов с сильно различающимися ионными радиусами по схеме 5zn2+ + ☐ → 2r3+ + 4li+ приводит к образованию группы тройных молибдатов li2m3r(moo4)4 (mr = csfe, csga, rbga, csal, rbal, tlal), описанных выше. в последнем случае катионы li+ и r3+ упорядоченно распределены в структуре, что приводит к тетрагональному искажению структуры прототипа. основу структур тройных молибдатов обеих серий, как и структуры cs6zn5(moo4)8, составляют ажурные трехмерные каркасы. в фазах с двухвалентными металлами они образованы тетраэдрами двух сортов – вокруг хайкина е. г., солодовников с. ф., басович о. м., солодовникова з. а., кадырова ю. м., савина а. а., золотова е. с., юдин в. н., спиридонова т. с. 383 № 4 | 2015 chimica techno acta молибдена и «смешанной» позиции лития (натрия, серебра) и двухзарядного катиона; в соединениях с трехвалентными металлами – тетраэдрами moo4, lio4 и ro4. в больших пустотах каркаса размещаются крупные однозарядные катионы с кч = 12 (рис. 10). все фазы семейства cs6zn5(moo4)8 обладают ацентричным строением и перспективны для создания материалов нелинейной оптики. кроме того, открытая каркасная структура обусловливает проявление этими соединениями ионопроводящих свойств. наиболее значимые результаты получены для rb3lizn2(moo4)4 и tl3li2al(moo4)4, величины ионной проводимости которых (порядка 2∙10–2 см/см при 520 и 350 °c, соответственно), приближают их к суперионным проводникам. рис. 9. субсолидусная триангуляция тройных систем при 510 °c: а – li2moo4–rb2moo4–znmoo4; б – li2moo4–cs2moo4–znmoo4. s – m3lizn2(moo4)4 (m = rb, cs) б б а а рис. 10. структуры тройных молибдатов, производных от структуры cs6zn5(moo4)8 [23, 24]: а – структура lics3co2(moo4)4 (пр. гр. i 43d) [41]; б – структура li2cs3ga(moo4)4 (пр. гр. i 42d) [42] тройные молибдаты одно-, одно и трех(двух)валентных металлов 384 № 4 | 2015 chimica techno acta в системах li2moo4–m2moo4– amoo4 (m = na, k, rb, cs; a = ca, sr, pb, ba, cd) тройные молибдаты не образуются, однако имеются области твердых растворов (до 15 мол.  %) на основе двойных молибдатов из ограняющих систем m2moo4–amoo4 [51]. при исследовании раствор-расплавной кристаллизации (растворитель – cs2mo2o7) в системах na2moo4– cs2moo4–amoo4 (a = ni, co, mn) выделены и структурно изучены кристаллы csna5m3(moo4)6 [47], относящиеся к типу аллюодита. кислородные октаэдры вокруг катионов a2+ и na+ соединяются между собой общими ребрами и гранями, а далее по общим вершинам с тетраэдрами moo4 в трехмерный каркас, который параллельно (100) разбивается на два вида слоев (рис. 11). в одном из таких слоев (рис.  11,  в) параллельно оси c проходят широкие сквозные каналы, заполненные ионами цезия, которые занимают свои позиции наполовину и имеют кч = 8. сравнение аллюодитоподобных структур csna5a3(moo4)6 и na4–2xa1+x(moo4)3 (a = ni, co, mn) показывает, что в тройных молибдатах часть катионов na+ в каналах замещена cs+, существенно увеличены параметры ячеек вдоль оси a и, соответственно, ширина каналов. так как вдоль этих каналов может осуществляться транспорт ионов натрия, это может способствовать увеличению ионной проводимости. близкое родство фаз csna5a3(moo4)6 и na4–2xa1+x(moo4)3 (a = ni, co, mn) может означать образование между ними твердых растворов, что требует дополнительного исследования. характеристики csna5a3(moo4)6 (a = ni, co, mn) приведены в табл. 4. в системах na2moo4–cs2moo4– amoo4 (a = co, mn) также выделены тройные молибдаты состава cs4na10a5(moo4)12 [46, 48] (рис.  12, табл.   4), которые оказались очень близки по строению с вышеописанными соединениями na25cs8r5(moo4)24 (r = in, sc, fe), образуя вместе с ними, очевидно, единое семейство фаз с близкими метриками ячеек и разной симметрией. наиболее симметрична структура cs4na10co5(moo4)12 (пр. гр. рис. 11. структура csna5mn3(moo4)6: а – общий вид; б, в – два вида слоев полиэдров в проекции на (100) а б в хайкина е. г., солодовников с. ф., басович о. м., солодовникова з. а., кадырова ю. м., савина а. а., золотова е. с., юдин в. н., спиридонова т. с. 385 № 4 | 2015 chimica techno acta pbca), которую можно считать родоначальником данного семейства. симметрия остальных соединений может повышаться при фазовых переходах, что должно сопровождаться разупорядочением структуры и возможным ростом подвижности катионов натрия. в связи с этим можно ожидать у тройных молибдатов cs4na10a5(moo4)12 (a = co, mn) повышенной ионной проводимости, как это имеет место для na25cs8r5(moo4)24 (r = in, sc, fe). заключительные замечания проведенные нами исследования тройных молибдатов типа 1-1-3 и 1-1-2 показывают, что среди них имеются несколько семейств изоструктурных или близко родственных по строению фаз. более высокой фазообразующей способностью, большим стехиометрическим и структурным разнообразием обладают системы с трехвалентными металлами, в которых формируются тройные молибдаты, принадлежащие к 14 структурным типам (семействам), тогда как тройные молибдаты типа 1-1-2 относятся только к четырем изоструктурным рядам. одним из объяснений этого может быть более широкий спектр катионов r3+ и их размеров по сравнению с ионами a2+ в фазообразующих системах m’2moo4– m’’2moo4–amoo4 (m’ = li, na; m’’ = k, rb, cs; a = mg, mn, co, ni, zn). ряд выявленных семейств тройных молибдатов типов 1-1-3 и 1-1-2 могут быть перспективными в качестве функциональных материалов. это прежде всего относится к семейству соединений limr2(moo4)4 с интересными спектрально-люминесцентными свойствами, а также литийи натрий-содержащим тройным молибдатам различного строения, которые могут проявлять повышенную ионную проводимость. среди последних можно выделить соединения семейств cs6zn5(moo4)8, ii-na3fe2(aso4)3 и аллюодитоподобные фазы na25cs8r5(moo4)24 (r = in, sc, fe) и cs4na10m5(moo4)12 (m = co, mn), для которых уже проведены соответствующие исследования. с  кристаллохимической точки зрения в  этом плане также интересны соединения limr2(moo4)4, где ионы li + заполняют междоузельные пустоты структурного типа band2(moo4)4, а также гексагональные или тригональные фазы s1–s4 (табл. 2, 3), в которых ионы натрия обладают нестандартной (тригонально-призматической или более низкой) координацией, что может способствовать ионной проводимости. нелинейно-оптические свойстрис. 12. субсолидусная триангуляция системы na2moo4–cs2moo4–comoo4 при 480 oc тройные молибдаты одно-, одно и трех(двух)валентных металлов 386 № 4 | 2015 chimica techno acta ва можно ожидать у ацентричных тройных молибдатов lik2in(moo4)3, lics4al(moo4)4, na5cs7yb2(moo4)9, nacs2bi(moo4)3 и их аналогов, а также фаз семейства cs6zn5(moo4)8. 1. трунов в. к., ефремов в. а., великодный ю. а. кристаллохимия и свойства двойных молибдатов и вольфраматов. л.: наука, 1986, 173 с. 2. евдокимов а. а., ефремов в. а., трунов в. к., клейман и. а., тананаев и. в. соединения редкоземельных элементов. молибдаты, вольфраматы. м.: наука, 1991, 267 с. 3. каминский а. 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10.1016/j.jssc.2012.01.010. 26. khal’baeva k. m., solodovnikov s. f., khaikina e. g., kadyrova yu. m., solodovnikova z. a., basovich o. m. phase formation in the li2moo4–rb2moo4–fe2(moo4)3 system and crystal structure of a novel triple molybdate lirb2fe(moo4)3. j. solid state chem. 2013;203:227–231. doi: 10.1016/jjssc.2013.04.020. тройные молибдаты одно-, одно и трех(двух)валентных металлов 388 № 4 | 2015 chimica techno acta 27. солодовников с. ф., солодовникова з. а., кадырова ю. м., хайкина е. г., басович о. м. фазообразование в системе li2moo4–cs2moo4–al2(moo4)3 и  кристаллическая структура lics4al(moo4)4 // матер. всерос. науч. конф. с междунар. участием «байкальский материаловедческий форум». 9–13 июля 2012 г., г. улан-удэ. улан-удэ: изд-во бнц со ран, 2012. ч. 2. с. 141–142. 28. хайкина е. г., басович о. м., хальбаева к. м. фазообразование в серебросодержащих молибдатных системах с участием трехвалентных металлов // iii  всерос. науч. конф. по физико-химическому анализу. 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li2moo4–a + 2moo4–m 2+moo4 (a + = k, rb, cs; m2+ = mg, mn, co, ni, zn) : дис. … канд. хим. наук. новосибирск, 2008. 219 с. 44. солодовникова з. а., солодовников с. ф., гудкова и. а., золотова е. с. синтез и строение новых тройных молибдатов k3nam4(moo4)6 (m = ni, mg, co) : материалы всерос. науч. конф. с междунар. участием «байкальский материаловедческий форум». 9–13 июля 2012 г., г. улан-удэ. улан-удэ: изд-во бнц со ран, 2012. ч. 2. с. 143–144. 45. солодовников с. ф., солодовникова з. а., золотова е. с., юдин в. н., гудкова и. а., кадырова ю. м., хайкина е. г. тройные молибдаты (вольфраматы) семейства cs6zn5(moo4)8 // тез. докл. 9-го семинара со ран – уро ран «термодинамика и материаловедение», посвящ. памяти акад. ф. а. кузнецова. 30 июня – 4 июля 2014 г., г. новосибирск. новосибирск: изд-во инх со ран, 2014. с. 108. 46. юдин в. н., золотова е. с., солодовникова з. а., солодовников с. ф., гудкова и. а. фазообразование и строение тройных молибдатов в системе cs2moo4– na2moo4–mnmoo4 // 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ран, 2015. с. 139. 49. d’yvoire f., bretey e., collin g. crystal structure, non-stoichiometry and conductivity of ii-na3m2(aso4)3 (m = al, ga, cr, fe). solid state ionics. 1988;28–30:1259– 1264. doi: 10.1016/0167-2738(88)90367-0. 50. zolotova e. s., solodovnikova z. a., yudin v. n., solodovnikov s. f., khaikina e. g., basovich o. m., korolkov i. v., filatova i. yu. phase relations in the na2moo4-cs2moo4 and na2moo4-cs2moo4-znmoo4 systems, crystal structures of cs3na(moo4)2 and cs3nazn2(moo4)4. j. solid state chem. 2015 (принята в печать). 51. гудкова и. а. фазовые равновесия, синтез, строение и свойства соединений, образующихся в тройных системах li2moo4–a2moo4–mmoo4 (a = na, k, rb, cs; m = ca, sr, pb, ba, cd) : дис. … канд. хим. наук. новосибирск, 2014. 192 с. хайкина е. г., солодовников с. ф., басович о. м., солодовникова з. а., кадырова ю. м., савина а. а., золотова е. с., юдин в. н., спиридонова т. с. investigation of alternative materials as bifunctional catalysts for electrochemical applications 120 d o i: 1 0. 15 82 6/ ch im te ch .2 01 9. 6. 4. 01 vayenas m., vaitsis c., sourkouni g., pandis p. k., argirusis c. chimica techno acta. 2019. vol. 6, no. 4. p. 120–129. issn 2409–5613 vayenas m.a, vaitsis c.a, sourkouni g.b, pandis p. k.a, argirusis c.a,* a school of chemical engineering, national technical university of athens, 9 iroon polytechniou st, 15780 zografou, athens, greece. b clausthal university of technology, clausthaler zentrum für materialtechnik (czm), 9 leibnizstr., 38678 clausthal-zellerfeld, germany *e-mail: amca@chemeng.ntua.gr investigation of alternative materials as bifunctional catalysts for electrochemical applications a lab-scale custom made zinc-air battery cell was manufactured and tested with a variety of cathode catalysts. mno2 has been examined both as an oxygen reduction reaction (orr) and oxygen evolution reaction (oer) catalyst, with more promising results as an orr catalyst. mno2 as well as a combination of mno2 and mwcnts (mocn-10) has been examined in this work. in addition, two different metal organic frameworks (mofs), specifically hkust-1 and mof-74, based on cu and ni, respectively, were investigated as an alternative and novel cathode catalyst directly on the battery cell. a power output of 20 mw · cm–2 was achieved by using mocn-10, along with stability in prolonged discharge cycling at 5 ma · cm–2. furthermore, mof-loaded battery demonstrated astonishing performance in pulse cycling for more than 120 hours. moreover, no dendrite formation was observed during long term pulse cycling. keywords: rechargeable zinc-air battery; orr; oer; polarization; cycling; mofs received: 25.10.2019. accepted: 18.11.2019. published: 30.12.2019. © vayenas m., vaitsis c., sourkouni g., pandis p. k., argirusis c., 2019 introduction advancement in  energy storage systems have recently been on high demand due to  the  vast development of  portable electronic devices, as  well as to the forthcoming outburst of electrical vehicles. lithium-ion batteries have attracted a lot of attention and have been extensively developed [1, 2]. however, high cost of raw materials used in these batteries and public safety concerns have led to explore alternative storage systems. zinc-air batteries (zabs) are seen as a promising candidate for next generation energy storage devices. the needed oxygen is not stored within the zab and can be supplied from ambient air; therefore, they offer a high theoretical energy density of 1353 wh/kg [3]. zinc itself is a low-cost anode material and is also available in sufficient amounts in nature. during discharge, the zinc — air battery functions as a power generator, while electrochemical coupling of the zinc metal to the air electrode is oc121 curring in the presence of an alkaline media. metal zinc is oxidized at the negative electrode, producing zinc cations, and the liberated electrons leave the zinc electrode and travel through an external load to the air electrode. at the same time, oxygen from the surrounding air diffuses into the porous air electrode and is ready to be reduced to hydroxide ions via the oxygen reduction reaction (orr). orr is occurring at  the  three-phase (gas oxygen, liquid electrolyte, and solid electrocatalysts) boundary as a reaction site. generated anions oh– then migrate from the reaction site to the zinc electrode, forming zincate ions (zn(oh)4 2−), which at supersaturated concentrations, further decompose into insoluble zinc oxide (zno) [2]. upon charging, these reactions may be reversed. the zinc — air battery is capable of storing electric energy through the oxygen-evolution reaction (oer), which is occurring at the positive electrode-electrolyte interface. at the same time, zinc is deposited at the positive electrode surface. however, the redox reactions of oxygen during the  charging and discharging cycles are kinetically hindered; thus, it is  common to use catalysts to accelerate the process [4]. manganese oxide (mnox) has been previously reported as  an  efficient, costeffective catalyst for orr and oer catalysis [5, 6]. it is considered as a potential candidate for replacing traditional catalysts, such as noble metals (pt, pd, ru, ir), as well as their oxides and alloys. metal-organic frameworks (mofs) are also examined as alternative electrocatalysts [7, 8]. mofs are hybrid crystalline materials, which consist of a metal-based centers and organic ligands. their chemical versatility can lead to various morphologies (cubes, spheres, rods, etc.) depending on the target application. their facile synthesis, high surface areas and open metal sites have made them highly desirable in the field of catalysis, gas storage/adsorption and gas separation, while recently they have been shown to be very promising in biomedical and electrochemical applications [9]. mofs have been traditionally prepared via a solvothermal synthesis at high temperatures for a prolonged time (hours or even days). in  order to  avoid these harsh conditions, alternative methods have emerged, such as  microwaves, electrochemistry, mechanochemistry and sonochemistry [10]. mofs described in this work have been prepared by a high intensity sonicator. in this work, a custom-made, lab-scale zinc-air battery has been constructed in order to investigate two different types of materials as catalysts. more specifically, mno2-containing materials and mof structures were used as  orr and oer electrocatalysts. experimental section materials and equipment all reagents were used as received without further purification. potassium hydroxide (koh, purity ≥ 98%), copper chloride dihydrate (cucl2·2h2o, purity ≥ 99%), 2,5-dihydroxyterephthalic acid (dhtp, purity 98%), ethanol (purity ≥ 98%), acetone (purity ≥ 99%), hydrochloric acid (hcl, concentration 37%) were purchased from sigma-aldrich. nickel nitrate hexahydrate (ni(no3)2·6h2o, purity ≥ 97%) was purchased from honeywell. 1,3,5-benzenetricarboxylic acid (trimesic acid, purity 98%) was purchased from alfa-aesar. dimethylformamide (dmf, purity > 99.5%), methanol (purity > 99.8%) were purchased from 122 chem-lab. manganese oxide (mno2) was purchased from tosoh hellas. nafion solution (5%) was purchased from quintech. cooh functionalized multi-walled carbon nano-tubes (mwcnts) were purchased from hongwunematerial. widely commercially available zn sheets (purity >  99.9%) and celgard-3401 membranes were also used without any modification, while carbon cloth was pretreated as described below. the sonicator used for mof synthesis and carbon cloth pre-treatment was vibra cell vcx 750  w (20  khz). the potentiostat used for electrochemical measurements was biologic sp-150. catalyst preparation synthesis of ni-mof-74 the solution was prepared by dissolving a mixture of ni(no3)2 · 6h2o (3.14 mmol) and dhtp (0.949  mmol) in  a  15:1:1 mixture of dmf (75 ml), ethanol (5 ml) and deionized water (5  ml), while stirring. the mixture was transferred to a 3-neck round-bottom flask, and synthesis was carried out in  a  nitrogen environment via a  continuous flow under ultrasound irradiation for 1  hour at  a  power output of  65%. after letting the  vessel cool down to room temperature, the solid was recovered by  centrifugation and washed once with dmf, and then with methanol. the solid was kept immersed in methanol for 4 days; the solvent was refreshed once a day. finally, ni-mof-74 was activated in vacuo for 12 hours at 100 °c. synthesis of hkust-1 the solution was prepared by dissolving a mixture of cucl2 · 2h2o (3.75 mmol) and trimesic acid (3.75 mmol) in a 2:1:2 mixture of dmf (30 ml), ethanol (15 ml) and deionized water (30  ml), while stirring. the mixture was transferred to a 3-neck round-bottom flask and synthesis was carried out in  a  nitrogen environment via a  continuous flow under ultrasound irradiation for 1 hour at a power output of 65%. after letting the vessel cool down to room temperature, the solid was recovered by  centrifugation and washed once with dmf, then with water and then ethanol within 4 days; the solid was kept immersed in water for 2 days and ethanol for 2 more days; the solvents were refreshed once a day. finally, hkust-1 was activated in vacuo for 12 hours at 100 °c. air electrode preparation mof catalysts were used as prepared and described above, mno2 was used as purchased, while mno2-mwcnts combination was prepared by  mixing 18  mg mno2 and 2 mg mwcnts. in order for as-prepared catalysts to be loaded on cathode, 20 mg of each catalyst were dispersed in 1 ml ethanol and underwent sonication in an ultrasound bath for 10 min. 150 μl of nafion solution (5%) were also added and the  final mixture was sonicated for 10 min. finally, the dispersion was poured onto a pretreated carbon cloth (1.5 cm × 1.5 cm). carbon cloth pre-treatment the catalyst support used for our battery cells was sonicated in three different solutions before being loaded by the catalyst [11]. carbon cloth (1.5 cm × 1.5 cm) was successively immersed into 20% hcl, acetone and deionized water. each sonication lasted 15 min with a power output of 33%, while the carbon cloth was fully immersed. results and discussion different types of materials were prepared as  described above in  order to  be examined as zn-air battery electrocatalysts. mno2 and mocn-10 (mixture of mno2 123 and mwcnts) were electrochemically compared with each other. furthermore, mof structures were also examined as electrocatalysts. as-prepared catalysts were directly loaded on carbon cloth in order to catalytically activate the three-phase boundaries. a  home-made rechargeable zn-air battery was built (see fig. 1) to  evaluate the  performance of  as-prepared electrocatalysts of  the  air electrode. in  fig. 2a, a  stable open circuit voltage (ocv) is  exhibited regardless using mno2 or mno2-cnts catalysts. ocv for mno2 catalyst cell is equal to 1.48 v, while 1.44 v ocv is monitored for mocn-10 catalyst. fig. 2b shows the  galvanodynamic polarization curves of  batteries loaded with mno2 and mocn-10 catalysts on the anode. the exhibited potential is monitored for increasing current density, while charging (positive current) or discharging (negative current) the cell with a scan rate of 0.5 ma · sec–1. corresponding power curves for cells using different air catalysts are depicted in  fig. 2c. mocn-10 catalyst shows the highest power pick at 20 mw/cm2. energy efficiency curve for the same battery was also calculated by dividing the values of charge polarization by the values of discharge polarization. comparing to the corresponding power curve, it is apparent that the energy efficiency is reduced to 29.1% while power peak is observed. that means that the battery’s energy efficiency has been reduced by 70.9% (see fig. 2d). to  evaluate the  c ycling stability of  the  battery, a  low current density of 2 ma · cm–2 was first applied for pulsed and non-pulsed cycles. during non-pulsed cycling, 2 ma · cm–2 were applied for 2 h of charging and 4 ma · cm–2 were applied for 1 h of discharging while 13 cycles were obtained without any obvious deterioration. therefore, the  capacity output was equal for charge and discharge. the different currents applied are due to the better orr activity of various manganese oxide forms compared to  the  oer [5]. with the utilization of mno2 as a catalyst, cell potential during the  orr process was 1.10 v, while the respective potential during oer process was 2.00 v (see fig. 3 a, b). surprisingly, both the orr and oer potentials of the mocn-10 battery were 1.20 v and 2.10 v, respectively (see fig. 3 c, d). however, for both catalysts the voltage gap was equal. a  charge-discharge voltage gap (δη) of less than 900 mv has been fig. 1. photograph of zinc-air battery 124 observed while cycling regardless of the air catalyst. fig. 4 shows a discharge profile plot for the cell where mocn-10 acted as the cathode catalyst. after increasing the current density on 20 ma/cm2 discharge and successively reducing the  applied current density until 0.5 ma/cm2, only 49 mv reduction has been observed, corresponding to 96.2% potential retention. furthermore, mof crystals were examined as orr and oer catalysts directly on zn-air batteries. due to their high porosity and large surface areas, mofs can contribute to the reaction area between the threephase sites on cathode. utilization of hkust-1 as air catalyst shows increased battery performance, as the battery is able to remarkably perform for over 350 consecutive cycles on pulse charging of 20 min without any apparent deterioration (see fig. 5). battery cell using ni-mof-74 has also been evaluated through galvanostatic cycling (see fig. 6). however, the observed δη between charging and discharging is greater than 1 v. in fig. 7, zn sheets that have been used during cycling can be seen. the formation a b c d fig. 2. electrochemical performance of zinc-air batteries using mno2 (blue) and mno2-cnts (black) as air catalysts: a — ocv plots; b — polarization curves and c — the corresponding power density; d — energy efficiency curve for mocn-10 cell (red) regarding its power density curve (black) vs current density 125 of zno structures that increase the polarization and lead to degradation can easily be observed [12, 13]. although, much less zno formed during pulsed cycling than during non-pulsed cycling, even if the total time of pulsed cycling was longer. conclusions in this work, a lab scale rechargeable zinc-air battery has been developed, and different material structures have been investigated as orr and oer catalysts. mno2 has already been reviewed in the literature as an excellent orr catalyst, but further testing needs to be done for the oer catalytic process. hereby, we prepared mno2 and mwcnts mixture — loaded cathode and compare the respective battery’s performance with the mno2 loaded battery. relative to mno2 — loaded cells, battery cells with mocn-10 mixture show higher power output. in particular, we achieved 20  mw · cm–1 utilizing the  mno2-cnts mixture as air catalyst for orr and oer. additionally, mof structures were evaluated as  catalysts. cathode was prea b c d fig. 3. a — discharge and charge cycling at 2 ma · cm–2 for cell with mno2 as electrocatalyst; b — discharge (at 4 ma · cm–2) and charge (at 2 ma · cm–2) cycling for cell with mno2 as electrocatalyst; c — discharge (at 4 ma · cm–2) and charge (at 2 ma · cm–2) cycling for cell with mocn-10 as electrocatalyst; d — discharge and charge at 5 ma · cm–2 of mocn-10 loaded cell 126 pared in the same way as with mno2 catalysts and nafion acted as binder between catalyst and gas diffusion layer (gdl). galvanodynamic polarization curves in the mof-loaded cell, with current step of  0.5  ma · s–1, showed performance comparative to  that of  the  mno2 catalysts. in particular, battery cell with hkust-1 on the cathode, performed at 7 mw · cm–1 and surpassed the  3.5  mw · cm–1 power output of  ni-mof-74 loaded cell. what is  more, great cycling stability has been achieved during short cycles (pulsed cycling). while utilizing hkust-1 cell, more than 360 successive cycles (120 hrs) were fig. 4. discharge profile of the battery cell with mno2-cnts air catalyst for 0.5, 2, 5, 10 and 20 ma · cm — 2 and vice versa a b c fig. 5. electrochemical performance of zinc-air batteries using hkust-1 as air catalyst: a — discharge polarization curve and the corresponding power curve; b — charge polarization curve; c — discharge and charge cycling at 2 ma · cm–2 127 performed at 2 ma · cm–1 without deterioration of the cell, indicating great stability during both orr and oer operation. in the future, more mof structures might be candidates for utilization as air catalysts including mn-based mofs. a b c fig. 6. electrochemical performance of zinc-air batteries using ni-mof-74 as air catalyst: a — discharge polarization curve and the corresponding power curve; b — charge polarization curve; c — discharge and charge cycling at 2 ma · cm–2 fig. 7. zinc electrode after cycling performance for long and pulse cycling at 2 ma · cm–2 128 references 1. menictas c. advances in batteries for medium and large-scale energy storage. boston, ma: elsevier; 2015. 2. reddy t, linden d. linden’s handbook of batteries (4th edition). new york, usa: mcgraw-hill professional publishing; 2010. 3. fu j, cano zp, park mg, yu a, fowler m, chen  z.  electrically rechargeable zinc-air batteries: progress, challenges, and perspectives. advanced materials. 2017;29(7):1604685. doi:10.1002/adma.201604685 4. xiong m, clark mp, labbe m, ivey dg. a horizontal zinc-air battery with physically decoupled oxygen evolution/reduction reaction electrodes. journal of power sources. 2018;393:108–18. doi:10.1016/j.jpowsour.2018.05.004 5. sumboja a, ge x, goh fwt, li b, geng d, hor tsa, et al. manganese oxide catalyst grown on carbon paper as an air cathode for high-performance rechargeable zinc-air batteries. chempluschem. 2015;80(8):1341–6. doi:10.1002/cplu.201500183 6. sumboja a, ge x, zheng g, goh fwt, hor tsa, zong y, et al. durable rechargeable zinc-air batteries with neutral electrolyte and manganese oxide catalyst. journal of power sources. 2016;332:330–6. doi:10.1016/j.jpowsour.2016.09.142 7. zhao r, liang z, zou r, xu q. metal-organic frameworks for batteries. joule. 2018;2(11):2235–59. doi:10.1016/j.joule.2018.09.019 8. wang z, hu j, han l, wang z, wang h, zhao q, et al. a mof-based single-ion zn2+ solid electrolyte leading to dendrite-free rechargeable zn batteries. nano energy. 2019;56:92–9. doi:10.1016/j.nanoen.2018.11.038 9. butova vv, soldatov ma, guda aa, lomachenko ka, lamberti c. metal-organic frameworks: structure, properties, methods of synthesis and characterization. russian chemical reviews. 2016;85(3):280–307. doi:10.1070/rcr4554 10. vaitsis c, sourkouni g, argirusis c. metal organic frameworks (mofs) and ultrasound: a review. ultrasonics sonochemistry. 2019;52:106–19. doi:10.1016/j.ultsonch.2018.11.004 11. mou k, chen z, yao s, liu l. enhanced electrochemical reduction of carbon dioxide to formate with in-situ grown indium-based catalysts in an aqueous electrolyte. electrochimica acta. 2018;289:65–71. doi:10.1016/j.electacta.2018.09.026 12. cheng y, zhang l, xu s, zhang h, ren b, li t, et al. ionic liquid functionalized electrospun gel polymer electrolyte for use in a high-performance lithium metal battery. j mater chem a. 2018;6(38):18479–87. doi:10.1039/c8ta06338a 129 13. jin y, chen f. facile preparation of ag-cu bifunctional electrocatalysts for zinc-air batteries. electrochimica acta. 2015;158:437–45. doi:10.1016/j.electacta.2015.01.151 obtaining cyclopentanone from acidic wastewater of caprolactam production 177 d o i: 1 0. 15 82 6/ ch im te ch .2 02 0. 7. 4. 07 tsvetkova i. v., golovanov a. a., reznikova n. s., chirkunova n. v. chimica techno acta. 2020. vol. 7, no. 4. p. 177–179. issn 2409–5613 obtaining cyclopentanone from acidic wastewater of caprolactam production i. v. tsvetkova*, a. a. golovanov, n. s. reznikova, n. v. chirkunova togliatti state university, 14 belorusskaya st., tolyatti, samara region, 445020, russia *email: irina.cvetkova.56@mail.ru abstract. it has been shown that adipic acid released from the by-products of caprolactam production is a promising raw material for the production of cyclopentanone. the thermal stability of calcium adipate was investigated by the derivatographic method and the conditions were selected that ensure the yield of at least 50% of the target cyclopentanone with a purity of at least 99%. keywords: wastes from caprolactam production; adipic acid; cyclopentanone; derivatography; calcium adipate; gas chromatography received: 22.10.2020. accepted: 08.12.2020. published:30.12.2020. © tsvetkova i. v., golovanov a. a., reznikova n. s., chirkunova n. v., 2020 results and discussion the process of oxidation of cyclohexane with oxygen from air, carried out in  the  production of  caprolactam as a separate step is characterized by a large amount of oxygen-containing side-products concentrated in  acidic wastewater. one of these compounds is adipic acid [1]. the adipic acid is converted to a calcium salt, and the calcium salt decomposes to cyclopentanone during the high-temperature treatment (fig. 1). cyclopentanone is an important intermediate in the production of insecticides, pharmaceuticals, and fragrance chemistry (synthesis of jasmon). in  the  pharmaceutical industry, cyclopentanone is a precursor in the production of cyclopentobarbital, a sedative barbiturate derivative. cyclopentanone is  also used to  produce cyclopentamine, which is an intermediate in the synthesis of fungicides such as pencycuron [2]. the solid concentrate of acidic wastewater was methylated with diazomethane to obtain methyl esters of carboxylic acids. the  analysis of  the  methylated products was carried out on a  kristallux 4000m chromatograph with a  flame ionization detector (capillary column, helium carrier gas, quartz, db-wax (peg), 30 m / 0.32 mm / 0.5 µm, maximum thermostat temperature is 240 °c) showed that the solid residue of the acidic wastewater from the production of caprolactam contains up to 94% of adipic acid (fig. 3). calcium adipate was synthesized from the resulting product. the thermal stability (ch2)4(co2 -)2ca 2+ ∆ o + caco3 fig. 1. decomposition reaction of calcium adipate 178 of the calcium adipate was studied on a shimadzu dtg-60/60h thermal analyzer, and the initial temperature of its decomposition was determined as 400 °c. th e thermal eff ect of the decomposition reaction is 5.68 kj/g (fig. 3). the  pyrolysis of  calcium adipate in  a  quartz reactor was carried out, and the yield of cyclopentanone was calculated as 51%. th e  resulting product was subjected to chromatographic analysis. th e retention time of the technical sample of cyclopentanone (96.4% purity) is 6.24 minutes versus 6.20 minutes for the standard sample of cyclopentanone of 99.6% purity. th e difference in the retention times of the standard sample (fig. 4) and the technical one (fig. 5) may be due to the presence of impurities in the second one. as a result, the possibility of obtaining cyclopentanone from by-products of caprolactam production with good yield and high concentration in liquid products has been shown. fig. 2. chromatogram of the content of dimethyladipate in methylation products fig. 3. th e derivatogram of calcium adipate 179 references 1. kisil im, preobrazhensky va, zolin vs, gorodetskaya ni, davydov yui, polikarpov av, salomykov vi. method of utilization of acidic wastewater of caprolactam production: pat. 2039740 rus. federation. 93009600/04; declared 02.24.1993; publ. 07.20.1995 2. carbonyl compounds in the synthesis of heterocycles: k82 coll. scientific. tr. / ed. prof. a. p. krivenko. saratov: publishing house “scientific book”, 2008. 324 p. fig. 4. chromatogram of the standard sample of cyclopentanone fig. 5. chromatogram of the technical sample of cyclopentanone evaluation of different extraction techniques for the assay of anti acetylcholinesterase activity of olive leaves (olea europaea) chimica techno acta article published by ural federal university 2021, vol. 8(4), № 20218403 eissn 2411-1414; chimicatechnoacta.ru doi: 10.15826/chimtech.2021.8.4.03 1 of 5 evaluation of different extraction techniques for the assay of anti acetylcholinesterase activity of olive leaves (olea europaea) s.s. khizrieva* , s.n. borisenko, e.v. maksimenko , n.i. borisenko research institute of physical and organic chemistry of the southern federal university, 194/2 stachki ave., rostov-on-don 344090, russia * corresponding author: hizrieva@sfedu.ru this article belongs to the regular issue. © 2021, the authors. this article is published in open access form under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). abstract the total phenol content and the anti-acetylcholinesterase activity were compared in olive leaf (ol) extracts obtained using both subcritical water extraction (sbwe) and conventional solvent extraction (ethanol-water). the method proposed by ellman (in vitro) was used to study the inhibitory activity of acetylcholinesterase (ache). the total content of phenolic compounds and ache activities of ol extracts varied depending on the used extraction method. thus, the extract obtained using the subcritical water technique (220 °c) showed the highest amounts of total phenolic components, expressed as gallic acid equivalents, (70.4 mg/g raw material) and the highest inhibitory ache-activity (ic50 = 0.35 mg/ml). the obtained values of the anti-ache activity of the extracts of ol demonstrated that the inhibitory activity for sbw-extract 120 °c (ic50 = 2.92 mg/ml) and sbwextract 180 °c (ic50 = 0.8 mg/ml) is higher than that of the traditional extract (ic50 = 3.6 mg/ml), respectively. these results indicate a great potential of the subcritical water technique to develop the techniques to produce commercial extracts of ol, and these results could encourage improved utilization of the ol. the collected data on the anti acetylcholinesterase activity of olive leaves clearly demonstrate the prospects for use of ol extracts in the development of novel pharmaceutical substances and nutraceuticals for the prevention and/or the treatment of alzheimer's disease as well as some other neurodegenerative diseases. keywords olive leaves subcritical water extracts polyphenols alzheimer's disease anti-acetylcholinesterase activity ellman’s method received: 19.05.2021 revised: 21.09.2021 accepted: 08.11.2021 available online: 09.11.2021 1. introduction alzheimer's disease (ad) is a neurodegenerative disease that usually affects the elderly. ad is charac terized by memory loss, impaired behavior, decreased performance, and slowed-down thinking. at present according to the world health organization about 50 million people worldwide are struggle from ad dementia, and over 152 million people may be affected by 2050 globally [1, 2]. in recent years, a growing number of works aimed at the finding of new pharmaceutical substances based on secondary plant metabolites [3–6] for the treatment of various neurodegenerative diseases, including ad. one of these promising groups of plant metabolites are polyphenols, which are common components of plant raw materials and agricultural wastes. in the presented work, the medium of subcritical water (in the temperature range from 100 to 220 °c) [7] was used to obtain extracts from the leaves of olive (olea europaea l.) [8] – the most common waste of the olive oil industry. the antioxidant and neuroprotective effect of plant extracts depends on their qualitative and quantitative composition. the phenolic group is found in the structure of many medicinal plants and substances and largely determines their pharmacological, physicochemical, and chemical properties [9]. polyphenolic derivatives in ol (fig. 1) are represented by five main groups of phenolic compounds [10]. http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2021.8.4.03 http://creativecommons.org/licenses/by/4.0/ http://orcid.org/0000-0001-7064-2402 http://orcid.org/0000-0002-8715-4517 http://orcid.org/0000-0003-4733-1985 chimica techno acta 2021, vol. 8(4), № 20218403 article 2 of 5 1) hydroxytyrosol, c8h10o3 caffeic acid, c9h8o4 2) oleuropein, c8h10o3 verbascoside, c29h36o15 3) luteolin 7-glucoside, c21h20o11 apigenin 7-glucoside, c21h20o10 4) 5) rutin, c27h30o16 catechin (flavan-3-ol), c15h14o6 fig. 1 structural formulas of phenolic compounds in olive leaves (ol): 1 – substituted phenols: tyrosol (2-4-hydroxyphenylethanol), hydroxytyrosol (2-3,4-dihydroxyphenylethanol) and caffeic acid (3,4-dioxycinnamic acid); 2 – oleuroposides (oleuropein and verbascoside); 3 – flavones (luteolin-7-glucoside, apigenin-7-glucoside, diosmethin-7-glucoside, luteolin and diosmetin); 4 – flavonoids (rutin); 5 – flavan-3-ols (catechin) olive polyphenols are known to have anticholinesterase activity [11]. therefore, in this work, the assessment of the sum of polyphenols in ol extracts obtained both by the traditional method and in the medium of subcritical water will be carried out using the folin-ciocalteu method [12]. also, the anti-acetylcholinesterase (anti-ache) activity of the obtained extracts in vitro will be estimated according to the ellman method [13]. therefore, the purpose of the present work is the evaluation of different extraction techniques for the assay of anti-ache activity, and the determination of total amount of phenolic components of ol extracts obtained using both subcritical water extraction (sbwe) and traditional solvent extraction (tse). 2. experimental 2.1. materials and method materials. as an object of study, the olive leaves of the o. europaea obtained from the oleaf company («okvel», russia) were used. acetylcholinesterase (ache) was obtained from electrophorus electricus (electric eel) (type vi-s, 3.1.1.7, 200–1000 units/mg protein), acetylthiocholine iodide (atchi) (≥98%, usa), 5.5’-dithiobis (2-nitrobenzoic) chimica techno acta 2021, vol. 8(4), № 20218403 article 3 of 5 acid (dtnb) (99%, usa), folin-ciocalteu reagent (2 m) were supplied by sigma-aldrich company. gallic acid (not less than 98%, mw = 170.12) was purchased from dia-m company (russia). na2co3 (anhydrous, gost 83–79) and glacial acetic acid (ch3cooh, gost 61–75, chemically pure: puriss.) were supplied by jsc vekton company (russia). hydrochloric acid (hcl, gost 14261–77, ultra-high purity: puriss. spec.) was purchased from sigma tech company. instrumentation. a speks ssp 705 spectrophotometer (uv-vid, 190–1100 nm) (manufactured by zao spectroscopic systems, rf) was used for the measurements. methods. in this work the ways for preparation of extracts from leaves of olive (olea europaea l.) included two different extraction techniques: 1) the traditional solvent (ethanol-water) extraction techniques and 2) the techniques using the medium of subcritical water, as described earlier [8]. the traditional extraction. a 1.0 g sample of the dry olive leaves of o. europaea (particle size 0.5–3.0 mm) was boiled under reflux with the addition of 15 ml of 70% aqueous solution of ethanol for 90 min (bath temperature 82 °c). the boiling procedure was repeated 3 times (extraction time 270 min). the obtained extracts were filtered, combined, and analyzed by hplc. sbw-extraction. the treatment of olive leaves in sbw was carried out using a custom-made stainless-steel reactor (autoclave) [8]. the reactor has inner volume of 10 ml (dinner = 12 mm). a portion of ground olive leaves (particle size 0.5–3.0 mm) weighing 0.5 g was placed in a reactor, to which 7 ml distilled water was then added. the reactor was hermetically sealed and placed in an oven, where it was kept at a certain temperature (accuracy ±1 °c) for 1 h. then the reactor cooled to room temperature (15 min) in a tank filled with cold water. the contents of the reactor were filtered through a paper filter into a graduated cylinder, washing the reaction mixture with 70% ethanol until the color was washed out (~v = 40 ml, 60 min). aliquots of the resulting solutions were dried at room temperature under a fan. then, the anti-acetylcholinesterase activity of the extracts, as well as the sum of polyphenols and flavonoids in the dry product, were determined using direct and differential spectrophotometry methods. 2.2. anti-acetylcholinesterase (anti-ache) assay the activity of ache (in vitro) was measured by the modification [11] of ellman's method [13]. this method measures the activity of ache serving acetylcholine as the substrate. stock solutions of olive leaf extracts in 50% ethanol and then diluted to working concentrations with phosphate buffer (ph = 7.4) were prepared. the ache enzyme inhibitory assay was carried out according to ellman's method [13], as described elsewhere [11], with slight modifications. olive extracts (0.6 ml) in various concentrations (0.05–4 mg/ml) were added to the 1.88 mm atchi substrate (0.36 ml), followed by addition of 1.44 ml of ellman's reagent (0.25 mm). sodium phosphate buffer (0.1 m, ph 7.4) was used for all the preparations and reaction mixture; however, the ache enzyme (2 units/ml) was prepared in sodium phosphate buffer (0.02 m, ph 7.0). after incubation of the reaction mix for 5 min at room temperature, ache enzyme (0.12 ml) was added to the reaction mixture. this mixture was stirred (5 s) and after that the optical density was measured at a wavelength of 412 nm within 6 minutes from the start of the reaction on a spectrophotometer (uv-vid, 190–1100 nm). to exclude the influence of the absorption of extract solutions on the absorption in the reaction mixture control (blank) solutions of the extracts were prepared. that is, the values of its absorption at a wavelength of 412 nm were subtracted from the values of the absorption of the reaction mixture. phosphate buffer (ph 7.4) was added to the control reaction mixture instead of the test substance solution. the assay was performed in triplicate (n = 3). the percentage inhibition was calculated using the formula: % inhibition = 1 − [ absorption of the test sample at 412 nm absorption control at 412 nm ] × 100 (1) the results of ache inhibition were expressed as ic50: concentration of extracts (mg/ml) that resulted in 50% inhibition of enzyme activity. the values of ic50 were obtained from the dose-response curves. total phenolic content assay. total phenolic content was evaluated spectrophotometrically by the modified folin-chocalteu method [12]. the total phenolic contents of the ol were expressed as gallic acid equivalents in milligram per gram of dried leaves. gallic acid as a polyphenol standard was used. the optical density of the solutions was measured after 30 minutes in a 1 cm quartz cuvette at a wavelength of 750 nm. based on the obtained data, a calibration curve was plotted (y = 107.3x + 0.003, r² = 0.997). in addition, the total phenolic content was evaluated in the extracts of ol obtained in different ways. 3. results and discussion as a first stage of this study, the total phenolic content (tpc) of the tse-extract was determined. it was found that the tse extract contained 42.6 mg/g of tpc (in terms of standard gallic acid). the value of the inhibitory activity of the ache enzyme of the tse extract, based on the dose-response curves, was ic50 = 3.6 mg/ml, respectively. as a next stage, the set of the sbw-extracts (at 120 °c, 180 °c, and 220 °c) were obtained. also, the yields of the tpc of the sbw-extracts, obtained in the temperature range 120–220 °c, were determined. the yields of the tpc of sbw-extracts at 120 °c, 180 °c, and 220 °c were 32.7 mg/g, 41.8 mg/g, and chimica techno acta 2021, vol. 8(4), № 20218403 article 4 of 5 70.4 mg/g, respectively (table 1). after that, the values of the ache-activity for the obtained sbw-extracts were determined. the calculated values of the ache activity, expressed as ic50, were: ic50 = 2.92 mg/ml (120 °c); ic50 = 0.8 mg/ml (180 °c); ic50 = 0.35 mg/ml (220 °c), respectively. the obtained results are presented in table 1. as can be seen from table 1, the total content of phenolic compounds and ache activities of ol extracts varied depending on the used extraction method. the extract obtained using the subcritical water technique (220 °c) showed the highest amounts of total phenolics (70.4 mg/g raw material) and the highest ache inhibitory activity (ic50 = 0.35 mg/ml). also, the obtained values of the antiache activity of the extracts ol demonstrated that the inhibitory activity for sbw-extract 120 °c (ic50 = 2.92 mg/ml) and sbw-extract 180 °c (ic50 = 0.8 mg/ml) are higher than those observed for the traditional extract (ic50 = 3.6 mg/ml), respectively. the obtained results indicated that a percentage (%) of inhibition of the ache enzyme activity by ol extracts is determined by the total content of polyphenols in the investigated extracts. at the same time, it should be noted that an increase of the temperature of subcritical water from 120 to 220 °c causes a change in the physicochemical characteristics of water [7, 14]. therefore, one can expect an increase in the solubility of plant metabolites, on the one hand, and the chemical transformation of polyphenols from the native ol, on the other hand. recently, the authors have shown that in a subcritical water medium in a temperature range 180–220 °c a hydrolysis of rutin to quercetin took place (fig. 2) [14–16]. table 1 the values ic50 and total phenolic content of ol extracts, obtained by different extraction techniques: the tse and the sbwe the methods of extraction tpc in terms of standard gallic acid, mg/g of raw material anti-ache activity (ic50), mg/ml tse 42.6 3.6 sbwe – 120 °c 32.7 2.92 sbwe – 180 °c 41.8 0.8 sbwe – 220 °c 70.4 0.35 fig. 2 hydrolysis of rutin in a medium of subcritical water according to the literature [17], quercetin is more active against the ache enzyme than its glycoside rutin. the latter circumstance suggests that in sbw-extracts (180 and 220 °c) the aglycons, such as quercetin, are the main components to determinate the anti-ache activity of the corresponding extracts. thus, it was shown that the solution of the extract obtained in sbw at 220 °c has the best effect of inhibition of ache, in contrast to the extract obtained by the traditional method. 4. conclusions for the first time, the total phenol content and the antiacetylcholinesterase activity were studied in the extracts of olive leaves obtained using both subcritical water and conventional (ethanol-water) extraction. it was shown that the total content of phenolic compounds and the anti-ache activity of ol extracts varies depending on the extraction method used. the obtained sbw-extract (220 °c) showed the highest amounts of total phenolics, expressed as gallic acid equivalents, (70.4 mg/g raw material), and the highest inhibitory ache-activity (ic50 = 0.35 mg/ml). the obtained values of the anti-ache activity of the extracts of olive’s leaves demonstrated that the inhibitory activities for sbwe 120 °c (ic50 = 2.92 mg/ml) and sbwe 180 °c (ic50 = 0.8 mg/ml) are higher than that of the traditional extract (ic50 = 3.6 mg/ml), respectively. the obtained research results demonstrate the prospects for widespread use of the extracts of olive leaves in the development of pharmaceutical substances and nutraceuticals for the prevention or the treatment of alzheimer's disease, as well as other neurodegenerative diseases. acknowledgements this work was supported by the ministry of science and higher education of the russian federation (state assignment in the field of scientific activity, project no 08522020-0031) and the russian foundation for basic research (rfbr, grant no. 19-33-90211-aspiranty (s.s. khizrieva)). references 1. mahadik vj, chavare mn, patil ss, wadkar ka. cognition enhancing potential of sesbania grandiflora fruit extract in scopolamine induced amnesia in mice. res j pharm technol. 2020;13(11):5057–62. doi:10.5958/0974-360x.2020.00886.0 2. sharma vk. current therapeutic strategies for alzheimer’s disease: a lost direction or a hope remains? res j pharm pharmacodynamics. 2010;2(3):215–20. available from: https://www.researchgate.net/publication/343682407_curr ent_therapeutic_strategies_for_alzheimer%27s_disease_a_l ost_direction_or_a_hope_remains 3. savateev kv, borisov ss, voinkov ek, ulomsky en, rusinov vl, chupakhin on. 6-aminotriazolo[1,5-a]pyrimidines as 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complementary altern. med. 2016;21(4):np11–7. doi:10.1177/2156587215610032 https://doi.org/doi:10.15826/chimtech.2015.2.2.013 https://doi.org/doi:10.5958/0974-360x.2019.00521.3 https://rjppd.org/abstractview.aspx?pid=2014-6-1-24 https://doi.org/doi:10.5958/0974-360x.2020.00613.7 https://doi.org/doi:10.1070/rc2005v074n01abeh001167 https://doi.org/doi:10.34984/scftp.2020.15.4.006 https://doi.org/doi:10.15826/chimtech.2021.8.1.10 https://doi.org/doi:10.3305/nh.2015.31.3.8400 https://doi.org/doi:10.1016/j.fitote.2018.05.011 https://doi.org/doi:10.1016/0006-2952(61)90145-9 https://doi.org/doi:10.4103/0976-9668.210009 https://doi.org/doi:10.1134/s1990793118080092 https://doi.org/doi:10.4103/jnsbm.jnsbm_161_17 https://doi.org/doi:10.1177/2156587215610032 electrodialysis concentration of sulfuric acid chimica techno acta article published by ural federal university 2021, vol. 8(1), № 20218106 journal homepage: chimicatechnoacta.ru doi: 10.15826/chimtech.2021.8.1.06 1 of 5 electrodialysis concentration of sulfuric acid s.a. loza * , n.a. smyshlyaev, a.n. korzhov, n.a. romanyuk kuban state university, stavropolskaya st., 149, krasnodar, 350049, russia * corresponding author: s_loza@mail.ru this article belongs to the pcee-2020 special issue. © 2021, the authors. this article is published in open access form under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). abstract an urgent task is the development of new resource-saving technologies for deep processing of wastes from the hydrometallurgical industry for the purpose of their reuse. membrane technologies make it possible to create closed technological cycles with the reuse of recovered components in production, which allows solving many environmental problems. at the abinsk electric steel works ltd. (russia), during the production of copper-coated steel wire, a large amount of waste containing sulfuric acid and heavy metal salts is generated. the chemical treatment of such effluents with slaked lime and alkali produces a large amount of sludge, which causes environmental problems and leads to the irreversible loss of sulfuric acid. the problem of separating acids and salts can be solved using diffusion dialysis through anion-exchange membranes, however, to return the acid to the production cycle, the purified acid must be additionally concentrated. in this work, we studied the process of electrodialysis concentration of sulfuric acid using heterogeneous ion-exchange membranes ralex ® cmhpp and ralex ® amhpp (manufactured by mega a.s., czech republic) which have a polypropylene reinforcing mesh resistant to acids. the main parameters of the electrodialysis concentration process have been determined – the dependence of the concentration of the regenerated sulfuric acid on the concentration at the inlet to the electrodialysis cell and on the current density, as well as the energy consumption for the process. it is shown that with the help of electrodialysis concentration it is possible to obtain sulfuric acid with a concentration of up to 180 g/l, which makes it possible to return it to the production cycle. keywords ion exchange membrane diffusion dialysis electrodialysis concentration sulfuric acid recovery received: 31.12.2020 revised: 30.03.2021 accepted: 30.03.2021 available online: 31.03.2021 1. introduction one of the urgent tasks of the industry is the development of new resource-saving technologies for the deep processing of wastes from the metallurgical industry for the purpose of their reuse. the key task in solving the problem of protecting the environment and creating closed technological cycles is the development of effective methods for separating technological mixtures into components and further concentrating the resulting solutions. typical waste products from the hydrometallurgical industry are acidic effluents containing heavy metal salts. currently, industrial wastewater treatment is most often performed using chemical precipitation methods. this method is relatively cheap and undemanding from a technological point of view. purification of acidic effluents is carried out by adding slaked lime, sodium hydroxide and soda, followed by the separation of precipitation [1]. however, this cleaning method has a lot of disadvantages – precipitated substances can dissolve after their disposal, which leads to secondary pollution of the environment. it is also negative that the amount of sludge formed significantly exceeds the amount of contamination in waste water, and acids are irretrievably lost as a result of the neutralization reaction. the problem of disposal of the resulting acidic waste can be solved using membrane methods, which are currently widely used for purification, separation and concentration of technological solutions and gas mixtures. they allow you to create environmentally friendly, waste-free, energy-saving technological processes that can be easily automated, facilitating the solution of many social and http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2021.8.1.06 http://creativecommons.org/licenses/by/4.0/ https://orcid.org/0000-0002-3316-5413 chimica techno acta 2021, vol. 8(1), № 20218106 article 2 of 5 environmental problems. the number of scientific publications on this topic has increased significantly in recent years [2]. also, in recent time, the number of industries using electrodialysis technologies has grown significantly [3]. most often, for processing solutions containing ionic impurities, the method of electrodialysis with ionexchange membranes is used. if it is necessary to concentrate impurities in a small volume, and electrodialysis is preferred among all membrane methods, because allows to obtain solutions with high concentrations, which cannot be achieved using baromembrane technologies. membrane technologies for processing solutions are environmentally friendly and efficient and allow solving such problems as the creation of closed technological cycles, as well as the return of valuable components to production, which reduces the environmental burden of production on the environment [4, 5]. therefore, it is urgent to increase the efficiency of membrane technologies. electrodialysis allows to desalt and concentrate various technological solutions and wastewater which containing electrolytes [6]. electrodialysis with bipolar membranes [7-9] or its combination with ion exchange [10] is often used to recover acids or heavy metal salts. a combination of ion exchange with classical electrodialysis is also used to recover sulfuric acid from wastewater generated during the processing of chalcopyrite [11]. in addition, electrodialysis and metathesis electrodialysis are used to recover organic acids [12]. however, the problem of separation of mixed solutions of electrolytes is still urgent. despite the fact that in recent years there has been a large number of works devoted to imparting specific selectivity to membranes in the processes of electromembrane separation, the separation coefficients of ions of the same charge sign on such membranes have low values or membranes are experimental laboratory samples [13-16]. in addition, at current densities above the limiting value, the selectivity of such membranes is significantly reduced, which reduces the practical significance of the application of such processes in industry [17]. in this regard, a promising method for the separation of ternary electrolytes is the diffusion dialysis using ionexchange membranes, since it does not require high energy costs for its implementation. this separation method can have several advantages over electrodialysis. one can expect high efficiency of separation of acids and salts in the case of using anion-exchange membranes due to the extremely high mobility of hydrogen ions, which as a coion will determine the rate of diffusion transfer [18-20]. such processes will be in demand for the processing of spent galvanic solutions, as well as in hydrometallurgical processes. in addition, diffusion dialysis has a number of advantages over electrodialysis – low energy consumption, simplicity of instrumental design, and the use of membranes of the same polarity [21]. in work [22], diffusion dialysis, electrodialysis, and electrodialysis were compared with bipolar membranes for the recovery of sulfuric acid and tetrabutylammonium. despite the fact that bipolar electrodialysis requires significantly fewer membranes than diffusion dialysis, the costs of bipolar electrodialysis are very high due to the high cost of bipolar membranes and significant electricity consumption. also, electrodialysis with ion-exchange membranes is used for processing organo-mineral mixtures [23]. to increase the efficiency of electrodialysis processing of acidic solutions, ionexchange membranes with various modifiers are used. thus, the use of polyaniline for the modification of cationexchange membranes reduces the current efficiency and reduces energy consumption in the process of electrodialysis processing of sulfuric acid solutions [24]. the process of concentrating sulfuric acid with electrodes made of various materials was studied in [25]. it is shown that the graphite anode is stable at low current densities and provides a high current efficiency; however, at high current densities, the anode was destroyed. for the concentration of acids, it is preferable to use titanium electrodes coated with ruthenium dioxide or platinum. the use of rhodium-plated titanium electrodes in the process of hi concentration in the sulfur-iodine thermochemical cycle has also proven itself well [26]. at the abinsk electric steel works ltd., during the production of copper-coated steel wire, electrochemical deposition of copper from a sulfuric acid solution is used, while the solution is contaminated with iron sulfate. with an increase in the concentration of iron (ii) in the electrolyte above 50 g/l, the quality of the copper coating deteriorates and this electrolyte is replaced. in this case, it is necessary to dispose of a large amount of a solution containing 150 g/l h2so4 and 20 g/l cu 2+ and 50 g/l fe 2+ . to create a closed technological cycle, it is necessary to separate sulfuric acid from metal salts and return it to production. electrodialysis with standard ion-exchange membranes is unable to solve this problem due to the low separation factor of various electrolytes. high separation coefficients of metal sulfates and sulfuric acid are observed during diffusion dialysis through anion exchange membranes. however, there are a set of problems when dialysis is used to process such solutions. when carrying out dialysis in a countercurrent mode of circulation of solutions with a low flow rate, it is possible to recover sulfuric acid with a sufficiently high concentration of 60-70% of the original. a significant disadvantage is that with such a hydraulic mode, a low concentration gradient is maintained over the entire length of the dialysis machine. this leads to the need to increase the number of expensive anion-exchange membranes several times. when carrying out dialysis in distilled water with its frequent replacement, it is possible to intensify the process by maintaining a high concentration gradient. this leads to a decrease in the amount of required anion-exchange membranes, but the volume of regenerated acid is several times greater than that of the original solution. the acid thus obtained has a low concentration and is not suitable for reuse in the elecchimica techno acta 2021, vol. 8(1), № 20218106 article 3 of 5 trolytic copper refining. the use of electrodialysis concentration can increase the acid concentration to the desired level. in this work, the process of electrodialysis concentration of sulfuric acid for its return to the production cycle was studied. 2. experimental the process of electrodialysis concentration of sulfuric acid was performed on a laboratory cell consisting of alternating 5 cation-exchange and 5 anion-exchange membranes with a working area of 5×20 cm 2 , the gap between the membranes was 0.1 cm. the volumetric flow rate through the desalination path was 8.6 l/h (linear velocity 0.013 m/s). the concentration chambers were made without circulation of solution, which makes it possible to increase the concentration of the recovered sulfuric acid. heterogeneous electrodialysis membranes ralex ® cmh-pp were used as the cation exchange membrane, and ralex ® amh-pp as the anion exchange membrane (mega a.s., czech republic). this membranes was chosen because it is reinforced with an acid-resistant polypropylene mesh. membranes mk-40 and ma-41, produced by llc “innovative enterprise shchekinoazot”, tula region, russia are reinforced with capron, which is unstable in acidic solutions. the appearance of the electrodialysis cell is shown in fig. 1a, the schematic drawing of the membrane package is shown in fig. 1b. the concentration process was carried out in a potentiostatic mode at a voltage drop of 16 v to the pair chamber, the acid concentration at the inlet was varied from 1 to 10 g/l. the resulting concentrate was collected 1 time per hour, and the acid concentration was determined by acid-base titration. the concentration chambers of the cell are filled due to the transfer of hydration water together with ions, as well as due to the osmotic and electroosmotic transfer of water. dotted arrows in fig. 1b show non-selective proton leakage through the anion-exchange membrane, which makes it difficult to obtain a high concentration of acid. fig. 1 the view of the electrodialysis cell (a) and the schematic drawing of the membrane package (b). c – cation exchange membrane, a – anion exchange membrane, cc – concentration chamber, dc – desalination chamber 3. results and discussion fig. 2 shows the dependence of the volume of h2so4 concentrate (vk) flowing out from the concentration chamber on the current density. all points fall on one curve, despite the fact that in different experiments the acid concentration at the inlet to the apparatus varied from 1 to 10 g/l. fig. 3 shows the dependence of the concentration of sulfuric acid in the concentrate (ck) on the voltage drop on the electrodialysis cell. the inlet concentration varied from 1.0 g/l to 10 g/l. analysis of fig. 3 allows us to conclude that increasing the inlet acid concentration significantly affects the concentration of the resulting concentrate. in fig. 4, the same data are plotted not from voltage drop, but from current density and all experimental points can be fitted by one curve. thus, an increase in the acid concentration at the inlet of the electrodialysis cell increases the electrical conductivity of the desalting chambers, which leads to an increase in the current density and increases the concentration of sulfuric acid. based on the experiments performed, the energy consumption for the concentration of sulfuric acid was determined and are shown in table 1. the data are given for various acid concentrations at the inlet to the apparatus (cin) and voltage drop across the cell (u). analysis of the data in table 1 allows us to conclude that when the voltage drop on the electrodialysis cell increases, the energy consumption for fig. 2 dependence of the volume of the formed sulfuric acid concentrate on the current density fig. 3 dependence of the concentration of recovered sulfuric acid on the voltage at the electrodialysis cell (the numbers in the legend show the concentration of sulfuric acid at the inlet to the apparatus, g/l) chimica techno acta 2021, vol. 8(1), № 20218106 article 4 of 5 fig. 4 dependence of the concentration of sulfuric acid in the concentrate on the current density on the apparatus table 1 energy consumption (w·h/mol) for the process of concentration of the sulfuric acid сin, g/l u, v 5 10 15 20 25 1.0 548 810 – 2006 2940 1.8 – 565 – 1429 1794 2.5 – 458 – 867 1258 5.0 429 680 1083 – 10.0 219 449 616 – – the sulfuric acid concentration process decreases. it should be noted that when the salts are concentrated, energy consumption usually increases with increasing voltage. the anomalous dependence for sulfuric acid appears to be related to proton leakage through the anion exchange membranes (fig. 1b), as well as acid loss by diffusion. therefore, when the voltage is increased, due to the fact that the time required for the transfer of 1 mole of sulfuric acid is reduced, the energy consumption also decreases. the maximum possible voltage drop (and current density) is limited by the ohmic heating of the solution and the electrodialysis cell. since the concentration chambers are non-flowing, the composition of the solution in them is determined by the transfer of ions and water through cation and anion exchange membranes. the electrolyte and water flows can be described by the equations: 𝑗e = −𝑃s(𝐶k − 𝐶in) + 𝜂 𝑖 𝐹 (1) 𝑗w = 𝑃w(𝐶k − 𝐶in) + ℎ𝜂 𝑖 𝐹 (2) where 𝑗e is the electrolyte flow; 𝑗w is the water flow; 𝑃s = 𝑃s a + 𝑃s k, 𝑃w = 𝑃𝑤 a + 𝑃𝑤 k are the diffusion and osmotic permeability of the membrane pair, respectively; ℎ – salt hydration number, ℎ – current efficiency. these equations can be linearized by dividing by δ𝐶 = 𝐶k − 𝐶in: 𝑗e δ𝐶 = −𝑃s + 𝜂 𝐹 ∙ 𝑖 δ𝐶 (3) 𝑗w δ𝐶 = 𝑃w + 𝑡𝑤 𝐹 ∙ 𝑖 δ𝐶 (4) where 𝑡𝑤 = ℎ𝜂 – water transport number. table 2 сalculated characteristics of the membrane pair ralex ® cmh-pp / ralex ® amh-pp 𝜂,% 𝑃s ·10 8 , m/s 𝑃w·10 6 , m/s 𝑡w, mol(h2o)/f 14 1.38 1.78 1.15 the data obtained were processed using the method of least squares in coordinates 𝑗s δ𝐶 − 𝑖 δ𝐶 and 𝑗w δ𝐶 − 𝑖 δ𝐶 , which made it possible to determine the characteristics of the membrane pair. analysis of the data in table 2 shows that the current efficiency values are low due to the proton leakage through the anion-exchange membrane and the high diffusion rate of acid from the concentration chamber to the desalination chamber. the calculated water transfer number is significantly lower than observed during salt concentration, which is caused to the relay-race mechanism of proton transfer. 4. conclusions thus, the process of electrodialysis concentration of sulfuric acid has been studied using heterogeneous electrodialysis membranes ralex ® cmh-pp and ralex ® amh-pp (mega a.s., czech republic) and it has been shown that it is possible to obtain a concentrate of up to 180 g/l, which makes it possible to use this acid in the production of copper-coated steel wire. the process of concentrating sulfuric acid must be carried out at the highest possible current density, because this reduces energy consumption, increases the concentration of regenerated sulfuric acid and reduces the required amount of membranes. the diffusion and osmotic permeability of the studied 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https://doi.org/10.1016/j.seppur.2011.12.017 https://doi.org/10.1023/a:1026187823767 https://doi.org/10.1016/j.scitotenv.2019.05.481 https://doi.org/10.1016/j.jenvman.2019.01.028 https://doi.org/10.1016/j.hydromet.2017.07.005 https://doi.org/10.1016/j.jhazmat.2009.12.043 https://doi.org/10.5004/dwt.2018.23077 https://doi.org/10.1134/s102319351909009x https://doi.org/10.1134/s0965544115090054 https://doi.org/10.1080/00986445.2019.1587611 https://doi.org/10.3390/chemengineering3020050 the development of technology for production of zeolites from fly-ash from troitskaya power plant chimica techno acta letter published by ural federal university 2021, vol. 8(1), № 20218111 journal homepage: chimicatechnoacta.ru doi: 10.15826/chimtech.2021.8.1.11 1 of 5 the development of technology for production of zeolites from fly-ash from troitskaya power plant v.a. snegirev, v.m. yurk * chemical-technological institute, ural federal university, mira str., 28, ekaterinburg, russia * corresponding author: v.yurk@yandex.ru this short communication (letter) belongs to the mosm2020 special issue. © 2021, the authors. this article is published in open access form under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). abstract the study examines the technology of processing fly ash from troitskaya power plant for the production of zeolite. the paper presents the results of laboratory studies evaluating the suitability of fly ash from troitskaya power plant for the production of zeolites and the development of the zeolite production process. fly ash contains a small amount of heavy metals that can complicate processing, but contains a large amount of silicon oxide. the technology consists of high-temperature alkaline activation of fly ash and hydrochemical synthesis. the resulting powder has a specific surface area of 89.7 m 2 /g, determined by the bet method, and an average pore diameter of 0.345 μm. the static exchange capacity was 220 mg/g. keywords fly ash metals zeolites waste treatment thermal power plant residues received: 03.11.2020 revised: 25.12.2020 accepted: 25.12.2020 available online: 16.04.2021 1. introduction thermal power plant residues are divided into the fly ash, collected on electrostatic air cleaner, and slag formed under the combuster. due to physical and chemical properties (small powdery particles of spherical shape, often hollow), fly ash is widely used in the production zeolites. however, their use may be limited by the high content of toxic metals [1]. the chemical and mineral-phase components of the flyash depend on the composition of the mineral part of the fuel, its calorific value, the combustion mode, the method of their capture and removal, and the place of selection from dumps. but, despite this, in the composition of all ashes, the same set of mineral components is observed. the main components of fly ash are silicon oxides, aluminum, iron, calcium, potassium, sodium and titanium, the main content of which in all ash is 50-60% sio2, 20-30% al2o3, 5-10% fe2o3 [2,3]. such composition makes the ash an attractive raw material for the production of sorption materials such as zeolites. the issue of obtaining zeolites from ash is not new and has long been studied by various researchers. it is possible to obtain zeolites of nax, nay, naa, and phillipsite modifications from fly ash. one of the methods of zeolite synthesis is the separation of fly ash into components – silicon oxide and aluminum oxide – by multi-stage leaching of the ash and then their crystallization in alkaline solutions in autoclaves at high pressures [4]. the purpose of this work is to determine the possibility of using the ash of troitskaya power station for the production of zeolites, taking into account the toxic effect of metals. 2. experimental fly ash from troitskaya state district power station is captured by eight electrostatic air cleaner and mixed. the granulometric composition was determined by the sieve method (state standard 2093-82). the density determination was carried out by hydrostatic weighing (state standard 2160-2015). the phase analysis was performed using an xrd-7000 x-ray diffractometer (shimadzu, japan) in filtered copper radiation. the survey was carried out in the range of bragg angles 2θ = 3-80° at a speed of 0.5 °/min., u = 40 kv, i = 30 ma. a semi-quantitative assessment of the content of mineral phases in the sample was performed. chemical analysis of ash was performed in "vukhin" corp. (state standard 10538-87). the metal concentration was determined by atomic absorption method (aas) using a double beam atomic absorption spectrometer aa-7000 (shimadzu, japan) (state standard 32977-2014) and inductively coupled plasma mass spectrometry (icp-ms). zeolite was obtained by hydrochemical method with preliminary high-temperature activation. a heated magnetic stirrer, heidolph mr hei-standard, was used for desilting. high-temperature activation of fly ash was performed in a laboratory electric furnace snol 6,7/1300 at a http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2021.8.1.11 http://creativecommons.org/licenses/by/4.0/ chimica techno acta 2021, vol. 8(1), № 20218111 letter 2 of 5 temperature of 550 °c. at all stages of the process, a sodium hydroxide (hc) reagent was used. zeolite crystallization took place in a liquid thermostat loip lt-316b with an accuracy of maintaining the temperature of ±0.1 °c. the total pore volume was measured by mercury porometry using a modernized pore meter pa-3mv at a pressure range of 0.1-200 gpa, which corresponded to pore radii from 6520 to 3.75 nm. the morphology of the resulting product was studied by scanning electron microscopy using a jsm 6490 (jeol, japan) scanning electron microscope. the static exchange capacity for ca 2+ ions, converted to cao, was determined by the following method: a solution containing a calcium salt was added to 1 g of the sorbent, mixed and kept for 24 h. next, 10 cm 3 of the solution was selected over the sorbent, the content of calcium ions was determined by complexometric titration. the ion exchange capacity of the zeolite was calculated by cao. 3. results and discussion the x-ray diffraction (xrd) pattern of troitskaya ash is shown in fig. 1. the main components of the ash are quartz, mullite and magnetite, typical for this type of raw material. the amorphous phase is about 37% (calculated with respect to the ratio of the halos of the 1st and 2nd orders to the total scattered density in the range of angles 2θ = 15-60°). the density of the ash is 1.85 kg/m 3 . the results of the chemical analysis of the ash components are presented in table 1. the total content of silicon oxide in ash is 55.2%, and of aluminum oxide 26.8%, based on which, the ash can be classified as high-silica. this also suggests that the main part of alumina is most likely represented in the composition of mullite, while the amorphous phase consists mainly of silica. the presence of any additional macroscopic inclusions and minerals in the composition of the studied ash was not found. the obtained results are in good agreement with the data of [5]. the initial fly ash contains a large amount of the crystalline phase represented by the minerals mullite and quartz. the optimal technology for producing zeolite from ash of this composition is high-temperature activation with solid alkali and subsequent hydrochemical synthesis [6-8]. the data shown in table 2 provide an indication of the potential toxicity of fly ash and its processed products. in addition, metal ions can reduce the adsorption capacity of zeolites [9,10]. however, the content of any metal does not exceed the established standards [11]. the content of silicon oxide in the ash is significantly more than required to obtain alkaline sodium hydroaluminate, so it was decided to conduct a pre-procedure of fly ash. the fly ash was leached in a solution of sodium hydroxide under constant stirring and heated to 90 °c to isolate excess silicon oxide of an amorphous phase. silica is dissolved in an alkaline solution. process parameters such as the alkali concentration, the liquid-to-solid ratio, and the duration of desilicization varied to achieve the maximum value for removing excess sio2. the results of the experiments are shown in table 3. the table shows that the main influence on the process is the amount of alkali, respectively: the more alkali, the higher the result. this is because the amorphous silica interacts better with concentrated solutions to form sodium silicate. the average maximum extraction value is 25%, which corresponds to the dissolution of most of the amorphous phase. based on the research conducted, the optimal process conditions were: naoh concentration – 5 mol/l, liquid-tosolid ratio – 10, process duration – 5 h. the selected technological parameters allow achieving the maximum reproducible extraction of silica without additional time and material costs. the resulting filtrate was analyzed for aluminum content. it was found that, under the selected conditions, aluminum oxide practically does not pass into the solution, concentrating in the composition of the treated material. fig. 1 xrd pattern of the initial troitskaya ash table 1 granulometric composition of fly ash from troitskaya thermal power plant particle size, μm 1– 0.5 0.5– 0.25 0.25– 0.125 0.125– 0.063 0.063– 0.04 0.04 % 2.0 13.4 30.6 34.8 12.2 7.0 table 2 trace element content of fly ash from troitskaya thermal power plant method for determining the concentration metal content, mass. % be cr cu mn ni pb v zn aas 0.001 0.010 0.155 0.001 0.001 0.010 0.008 icp-ms 0.001 0.008 0.162 0.001 0.002 0.011 0.007 chimica techno acta 2021, vol. 8(1), № 20218111 letter 3 of 5 table 3 results of the silicon removal experiment № naoh concentration, mol/l solid-to-liquid ratio t, h removal, % 1 2 8 3 16 2 2.5 8 3 20 3 3 6 4 16 4 3 8 3 22 5 4 8 4 24 6 5 10 4 23 7 5 10 5 26 8 8 10 7 32 9 8 8 3 26 10 8 10 10 28 the next stage of processing was opening the mineral phase of the ash and converting it into soluble compounds. we have chosen a method of temperature activation with alkali that does not require high pressure and ultrahigh temperatures, and is widely used by many researchers. high-temperature activation of the fly ash was carried out by sintering with solid sodium hydroxide. the process took place at a temperature of up to 550 °c for 2 h. the essence of this activation is the dissolution of quartz and mullite minerals with alkali, which under normal conditions does not occur as a result of this process, sodium silicate and aluminate are formed. the resulting sinter was then ground, dissolved in water, and the zeolite was crystallized. to confirm the need for pretreatment of ash, high-temperature activation was performed for both untreated and desilicized materials. the ratio of reacting components required for the dissolution of the crystal phase and the production of zeolite was determined experimentally. based on the data from [6-8], the first experiments selected a mass ratio of naoh/ash from 1 to 2.5. the result of sintering and subsequent repulpation of sinters obtained from both desilicated and untreated ash were powders containing a large amount of mullite and quartz, which indicates an insufficient amount of alkali for their dissolution. zeolite was not found in these samples. in subsequent experiments, the alkali content was increased. the required amount of naoh was calculated from stoichiometric equivalent ratios required for mineral dissolution. the experiments were carried out at a naoh / fly ash ratio equal to their stoichiometric amounts and with a one-and-a-half excess of hydroxide. under the selected activation conditions, the specks of both types of ash had a uniform laurel-green color, without obvious signs of underburning of the fly ash. they were characterized by high strength, and therefore they had to be ground in a wet mortar. as a result, after performing the repulpation and crystallization stages, zeolite powders with a pale beige color were obtained. xrd patterns of zeolite powders obtained with a 1.5 excess of alkali from desilicated and untreated ash are shown in fig. 2. the powders in both samples do not contain the original ash minerals. the zeolite composition in both cases can be characterized by the formula na1.84al2si2.88o9.68 (pdf 00-048-0731). such composition is difficult to attribute to any particular type of zeolite; most likely, a mixture of them was obtained. the closest in composition are the zeolites nax and nay. the powder obtained from desilicized ash (fig. 2b) has a higher crystallinity than the sample synthesized from raw materials (fig. 2a), which also indicates a smaller amount of the amorphous phase in the powder composition. increased crystallinity has a beneficial effect on the functional properties of the material. it can be concluded that the pretreatment of ash, namely the desilicization stage, is a necessary stage in the process of processing ash into zeolite from the ash of the troitskaya power plant. fig. 3 shows the morphology of zeolite powder particles obtained by high-temperature activation of desilicized fly ash in the presence of 1.5 excess of alkali. the average a b fig. 2 xrd patterns of the zeolite obtained from: a – non desilicated ash, b –desilicated ash chimica techno acta 2021, vol. 8(1), № 20218111 letter 4 of 5 a b c fig. 3 sem images of the obtained zeolite size of the powder particles is about 70 μm in length and 40 μm in width (fig. 3b). the powder also contains particles with smaller sizes, up to 10 μm in length (fig. 3a). fig. 3c shows the surface morphology of one of these particles. they are cubic microcrystallites of zeolite surrounded by a structureless mass of the amorphous phase. zeolite crystallizes in a cubic phase, with a rib length of about 1 μm. the specific surface of obtained zeolite, determined by the bet method, is 89.7 m 2 /g. for comparison, the values of this parameter for zeolites synthesized from fly ash in other researchers range from 62.01 m 2 /g [12] to 213.2 m 2 /g [13]. as shown by the results of mercury porometry, the surface of zeolite particles is characterized by the presence of a large number of micropores. the volume fraction of pores with a diameter from 0.1 to 5 μm is 84.89%. the total pore volume of the sample was 17.67 cm 3 /g, and their average diameter was 0.345 μm. synthesized from fly ash zeolites are used in the purification of water from metal ions. the main parameter that characterizes the material for adsorption purposes is the ion exchange capacity. the ion exchange capacity of zeolite for the sorption of ca 2+ ions in terms of cao was 220 mg/g. the obtained value shows the applicability of the synthesized zeolite for sorption of heavy metal ions from an aqueous medium. the synthesized zeolite is not soluble in dilute solutions of hydrochloric and sulfuric acids, as well as in concentrated sulfuric acid. it is half dissolved in concentrated hydrochloric acid. as a result of the research, a technology for processing fly ash from troitskaya gres into zeolite was developed. the processing technology consists of operations for extracting excess silicon from ash, high-temperature activation, and hydrochemical crystallization, which require the use of available reagents and easy-to-use equipment. prospective technology for processing fly ash from troitskaya power plant into zeolite consists of operations for extracting excess silicon from ash, high-temperature activation, and hydrochemical crystallization, which require the use of available reagents and easy-to-use equipment. by its structure, the resulting zeolite can be attributed to a mixture of zeolites of the naa and nax types. the zeolite also has good ion exchange properties, typical of this material, which makes it attractive for use as a sorbent for wastewater treatment (removal of metal ions). references 1. bukhari ss, jamshid behin j, kazemian h, rohani s. conversion of coal fly ash to zeolite utilizing microwave and ultrasound energies: a review. fuel. 2015;140:250-66. doi:10.1016/j.fuel.2014.09.077 2. ilica m, cheeseman c, sollars c, knight j. mineralogy and microstructure of sintered lignite coal fly ash. fuel. 2003;82:331-6. doi:10.1016/s0016-2361(02)00272-7 3. adeeva ln, borbat vf. zola tets – perspektivnoe syr’yo dlya promyshlennosti [thermal power plant fly ash is a promising raw 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based on menadione 81 d o i: 1 0. 15 82 6/ ch im te ch .2 02 0. 7. 2. 05 aleksey s. antipov, vasily a. nizov, anna yu. antipova chimica techno acta. 2020. vol. 7, no. 2. p. 81–86. issn 2409–5613 aleksey s. antipova, vasily a. nizovb, anna yu. antipovaab allc “novokhrom”, 462353, 51 industrial st., novotroitsk, orenburg region, russia bural federal university named after the first president of russia b. n. yeltsin, 620002, 19 mira st., yekaterinburg, russia e-mail: lexrus91@bk.ru technology for the industrial production of k3 series vitamins based on menadione an improved technology for the industrial production of k3 series vitamins based on menadion is reported. the procedure involves the cr(vi) — promoted oxidation of the corresponding methyl-naphtahelenes with the following purification by precipitation/recrystallization. the best results were obtained under the process temperature between 20–40 °c, solution ph after dilution of mnb in a range of 5.5–5.7, and mnb content in initial solution of 25–30%. keywords: vitamin k3; methyl-naphalenes; cr(vi) — compounds; menadione; industrial scale received: 15.04.2020. accepted: 27.06.2020. published: 30.06.2020. © aleksey s. antipov, vasily a. nizov, anna yu. antipova, 2020 introduction for the  industrial production of vitamins of the k family, the most accessible and important precursor is 2-methylnaphthalene-1,4-dione, (menadione) [1]. in some sources, menadione is called vitamin k3 [2], although derivatives 1,4-naphthoquinone are not natural chemicals and therefore cannot be qualified as vitamins. menadione can be considered as  provitamin due to  the  possibility of  its metabolism in the human body into vitamins k2, menaquinones, [3] containing various alkyl fragments at the position of c3 of the naphthalene-1,4-dione. according to the literature, the simplest and most cost-effective industrial method for producing menadione in the form of sodium bisulfite (msb) or nicotinamide bisulfite (mnb) is the cr(vi) compoundsmediated oxidation reaction of  2-methylnaphthalene-containing raw materials in an acidic medium with the release of menadione as an intermediate product [4], and the  subsequent crystallization of the msb from water or the precipitation of  nicotinamide mnb from the  mother liquor. since 2012, a domestic technology implemented according to this principle has been developed at  the  novochrom llc enterprise (novotroitsk, orenburg region). the main problem of this technology is associated with a strict restriction on the content of impurity components in final consumer products, such as k3 series vitamins. for example, eu regulation no. 1831/2003 limits the  chromium content in sodium menadione bisulfite to 45 mg/ kg, and in  the  menadione nicotinamide bisulfite 142 mg/kg. even trace amounts 82 of 2-methylnaphthalene, 1-methylnaphthalene, indole(s) are also excluded. in connection with the above, the initial stages of industrial production of k3 series vitamins are burdened with a  significant accumulation of substandard and intermediate products, as  well as  high costs for their recycling. namely, the level of such important technical and economic indicator, as  the  volume of  substandard mnb with a chromium content from 300 to 2500 mg/kg in an amount of more than 30 tons for 2016 makes the industrial production of  k3 series vitamins to  be not competitive in the global msb market [5]. the aim of this work was to develop a methodology for the processing of menadione nicotinamide bisulfite on an industrial scale. experimental part research methodology industrial grade mnb with a  chromium content of  2250 mg/kg was used for research. sulfuric acid, sodium carbonate, butanol-1 of technical grade were purchased from commercial sources. analytical researches were carried out according to the methods certified by novochrom ltd. investigations of the method of processing mnb by carrying out the reactions of direct and reverse synthesis 50 g of mnb was re-pulped in 125 ml of  water containing 12 ml of  butanol-1. sodium carbonate was slowly, in  small portions, added to the resulting suspension to  achieve a  stable ph of  5.5–5.7. the reaction volume was maintained until the  mnb was completely dissolved, followed by  filtration to  remove insoluble particles. after the filtration the obtained solution was acidified with 65% sulfuric till the ph of 2.0–2.2. the precipitated mnb was filtered, washed and air-dried. investigation of the influence of the ph on the fractionation size of the impurities the influence of the ph of the medium on the fractionation size of chromium-containing impurities was checked similarly to the first method, except that before filtering the ph of the solution was reduced to 4.5 with the following addition of 5 g of diatomite to improve filtration. investigation of  the  cyclic method of mnb processing to  study the  cyclic processing process, 50 g of mnb was re-pulped in 125 ml of water containing 12 ml of butanol-1. sodium carbonate was slowly, in small portions, added to  the  resulting suspension to reach a stable ph value in a range of 5.5– 5.7. the reaction volume was maintained until the mnb was completely dissolved. the ph of the solution was reduced to 4.4– 4.6 by the addition of 65% sulfuric acid. after that the 5 g of diatomite was added, and the  insoluble particles were filtered out. the filtered solution was acidified with 65% sulfuric acid till the  ph of  2.0–2.2, and the resulted solution was stirred for 15 minutes. after the filtration the precipitate was washed and dried. the next cycle was carried out similarly to the first one, except using a filtrate after the separation of the mnb instead of water. at the end of  the  third cycle, all the  washings and the  filtrate were collected together and made alkaline with sodium bicarbonate to reach a ph of >10, followed by filtration and washing of the precipitated menadione. investigation of the influence of water amount on the  chromium content in the recycled mnb the study of the effect of the amount of water on the fractionation of chromium 83 was carried out according to the methodology of the first cycle of the cyclic process, except that the amount of water was 50, 80, 100 and 130 ml. results and discussion the technology for producing k3 vitamins consist of  three separate stages: synthesis of  menadione with cr(vi) compounds, isohydric crystallization [6] of  msb, and the  precipitation of  mnb by  reaction of  the  mother liquor with nicotinamide in  an  acidic media. based on the classical positions of fractionation of impurity components in the isohydric crystallization mode [6], we refined the dependence of the solubility of msb in water in  the  operating temperature range and compiled a nomogram for assessing the  possible effects of  purification from chromium during crystallization [7]. we have previously shown that the use of  additives of  water-soluble aluminum salts [8] leads to  a  decrease in  the  chromium content during the synthesis of msb, while using liquid extraction with butanol-1 leads to  the  production of  highquality mnb [9]. the  return of  substandard mnb to the scope of implementation is expected to be achieved through the sequential processes presented in schemes 1–3. the dissociation of mnb into the starting reagents under the action of alkaline reagents, in particular sodium carbonate in  the  ph range of  5.5–5.7 (scheme 1), makes it possible to efficiently obtain a solution of msb and nicotinamide, as well as  impurities, which are highly soluble in  water. a  further decrease of  the  ph of the medium to 4.4–4.6 leads to the precipitation of chromium-containing impurities, the removal of some of which from the solution was made by the filtration, and scheme 1. decomposition of mnb into the starting reagents scheme 2. synthesis of mnb scheme 3. dissociation of msb to menadione 2 o o so3h ch3 n nh2 o na2co3 o o so3na ch32 2 n nh2 o h2o co2 o o so3na ch32 2 n nh2 o h2so4 2 o o so3h ch3 n nh2 o na2so4 o o so3na ch3 ohoo s o o o o o ch3 so3 2– 84 this step was followed by the direct synthesis of mnb. this allows to obtain a product with a chromium content of less than 142 mg/kg. processing the mother liquor after the separation of mnb with alkaline reagents allows additional extraction of msb menadione and its return to  the  stage of  the  synthesis of  mnb. the  cleavage of  msb to  menadione was carried out by the action of alkaline reagents at a ph of more than 11. it should be noted that earlier it was shown that in the ph range from 6 to 10 the equilibrium is shifted towards the formation of msb [10]. from the data collected it follows that the sequential reverse reaction of the cleavage of mnb into initial products at a ph of  5.5–5.7 with filtration of  undissolved particles, followed by  a  direct synthesis reaction, leads only to  a  slight decrease in the chromium content in the final product. in the course of studies, it was found that when alkaline reagents, in particular sodium carbonate and sodium bicarbonate, are added to the suspension of the initial mnb to adjust a ph to 5.5–5.7 all mnb decomposes into the  starting products. when the  solution is  acidified with sulfuric acid to adjust a ph of less than 5.0 a fine precipitate is formed. the precipitation of  mnb usually begins at  the  ph of  the  solution of  less than 4.2. studies, carried out with a high dilution of the solution to prevent the deposition of mnb, showed that the precipitation of the impurities continues until the ph of the solution is  reduced till 2.9–3.0, and with further acidification no precipitation is observed. also, the color of the solution changes from dark brown at ph 5.6 to light yellow at ph 2.5, after filtering the precipitate of impurities. to avoid precipitation of mnb at ph less than 4.2, the precipitation of impurities was carried out in a range of ph range of 4.4–4.6. from the  results of  cyclic processing it follows that it is not possible to obtain mnb using the filtrate from the previous stage with a low chromium content while maintaining the regime of the first cycle. apparently, an increase in the salt content of the solution leads to a different distribution of the impurity between the aqueous and organic phases. this is confirmed by  the  fact that dilution of  the  solution of  the  second cycle after the  filtration of the insoluble residue leads to cloudiness of the solution and precipitation of the impurities. from the  results of  a  study of  the  effect of  the  amount of  water on the chromium content in the final mnb it follows that an increase in the amount of water leads to a decrease in the chrofig. 1. chromatogram of the processed mnb 85 mium content in  the  final product due to a more complete deposition of chromium-containing impurities from the solution upon decreasing ph. additional extraction of  menadione from the  mother liquor is  achieved by  changing the  ph of the medium above 10.0 by adding sodium carbonate. chromatographic studies of the resulting mnb (fig. 1) to demonstrate the absence of 2-methylnaphthalene and other organic impurities in  it, which confirms the effectiveness of the described purification method. conclusions in  conclusion, a  technical solution is developed for the processing of menadione nicotinamide bisulfite with a high content of chromium and organic impurities, as  well as  for one with an  expired shelf life to produce a high quality menadione with low chromium content. the best results were obtained at the temperature of the reaction mixture of 20–40 °c, the ph after dilution in  a  range of  5.5–5.7, and the initial mnb content of 25–30%. this technical solution is  also applicable well for the accumulated previously substandard commercial products, and it finalizes the cycle of the improvement of the existing industrial production of k3 series vitamins based on menadione. references 1. weber f., rüttimann a. vitamin k. ullmann’s encyclopedia of industrial chemistry. weinheim: wiley-vch, 2012. 38. pp. 211–31. 2. scott gk, atsriku c, kaminker p, held j, gibson b, baldwin ma, benz cc. vitamin k3 (menadione) — induced oncosis associated with keratin 8 phosphorylation and histone h3 arylation. molecular pharmacology. 2005;68:606–15. 3. belikov vg. farmatsevticheskaya khimiya. chast’ 2. spetsial’naya farmatsevticheskaya khimiya. pyatigorsk. 1996. pp. 152–5. russian. 4. antipov as, nizov va. sintez menadiona (2-metil-1,  — naftokhinona) s ispol’zovaniyem soyedineniy cr6+. bashkirskiy khimicheskiy zhurnal. 2019;26(2):100–5. russian. 5. antipov as, nizov va. analiz vozmozhnostey polucheniya menadiona s naimen’shim soderzhaniyem primesey khroma. bashkirskiy khimicheskiy zhurnal. 2018;25(1):27– 32. russian. 6. stepin bd, gorshteyn ig, blyum gz, kurdyumov gm, ogloblina ip. metody polucheniya osobo chistykh neorganicheskikh veshchestv. leningrad: khimiya; 1969. 480 p. russian. 7. antipov as, nizov va. fraktsionirovaniye khroma v protsesse izogidricheskoy kristallizatsii menadiona natriya bisul’fita (2-metil-1,4-diokso-1,2,3,4-tetragidro2-naftalinsul’fonat natriya). bashkirskiy khimicheskiy zhurnal. 2018:25(4):11–5. russian. 8. antipov as, nizov va, gvozdev av, antipova ayu, inventors; federal institute of the industrial property, assignee. sposob polucheniya vitaminov serii k3. russian federation patent ru 2696493. 2018. russian. 86 9. antipov as, nizov va, gvozdev av, antipova ayu, inventors; federal institute of the industrial property, assignee. sposob polucheniya vitaminov serii k3. russian federation patent ru 2696776. 2018. russian. 10. bicker m, bierstedt a, amouzegar k, mahdavi b, stamant g, assignee. recovery of vitamin k3 from mother liquor. european patent wo2010121638. 2010. overview of sorption analysis capabilities for mesoand microporous zeolites nanomaterials chimica techno acta article published by ural federal university 2021, vol. 8(3), № 20218302 eissn 2411-1414; chimicatechnoacta.ru doi: 10.15826/chimtech.2021.8.3.02 1 of 4 overview of sorption analysis capabilities for mesoand microporous zeolites nanomaterials s. tokmeilova * , e.v. maraeva saint petersburg electrotechnical university «leti», prof. popova st., 5, saint petersburg 197376, russia * corresponding author: ak_saya@mail.ru this article belongs to the regular issue. © 2021, the authors. this article is published in open access form under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). abstract in this paper we consider the main application features of the thermal desorption method of inert gases, implemented on the sorbi ms (meta, russia) device, for the analysis of mesoand microporous materials. recommendations on the choice of measurement modes for stable operation of the sorbi ms device are offered (including recommendations on mass, sample preparation mode). the article presents the results of the micropores analysis by the t-plot and sing method. keywords micropores mesopores capillary condensation sorption hysteresis received: 27.04.2021 revised: 12.06.2021 accepted: 30.06.2021 available online: 07.07.2021 1. introduction gas sorption methods are commonly used to characterize porous materials. porous materials are widely used in microand nanoelectronics. according to the classification of pores by size, micropores are less than 2 nm in size, mesopores are in the range from 2 to 50 nm [1]. at present, nitrogen sorption at 77 k has become a standard tool for the analysis of materials with pores in a range of 0.5– 50 nm. the mechanism of nitrogen sorption at 77 k occurs in the following way. at a low relative pressure (0.02– 0.1), the filling of micropores with adsorbate begins. the monolayer adsorption occurs after the completion of adsorption in micropores. capillary condensation is observed in relatively small mesopores when the relative pressure and pore width correspond to the kelvin equation. the desorption isotherm is obtained by reversing the adsorption process, releasing the liquid adsorbate and decreasing the equilibrium relative pressure [2]. the evaporation process takes place from the meniscus of the condensed liquid. in the case of polymolecular adsorption, the adsorption potential interaction does not change with the distance from the surface of micropores, as a result of dispersion potentials overlapping of closely spaced pore walls [3]. as a result, adsorption in the entire volume of micropores becomes equiprobable to adsorption on their surface (micropores volumetric filling). the adsorption potential interaction of adsorptive molecules with microporous materials is much higher than with the surface of mesoscale materials. all this together determines some peculiarities and imposes certain restrictions on the applicability of the brunauer-emmett-teller (bet) method. therefore, other procedures are used for the micropore adsorption isotherms analysis, the so-called comparative methods of analysis, which make it possible to isolate the contribution of adsorption in the volume of micropores and to calculate the size of the mesopores and macropores surface. currently, a large number of comparative methods are known that are used to determine the specific surface area of a microporous material and to estimate the volume of micropores in the presence of mesopores: t-method, sing’s αs-method and others. the works [4-7] illustrating the current state of the question of the specific surface area analysis of mesoporous materials are presented. mesoporous materials are widely used in practice (bioengineering, sensorics of gaseous media and environmental monitoring, power engineering, lithium-ion batteries), are used as adsorbents and catalysts for oil refining processes. in all cases, the porous structure parameters play a key role. the paper [4] presents and discusses the kinetic results of nitrogen adsorption and desorption experiments performed at 77 k on one aluminum-based and three materials based on carbon, differing in their microporous and mesoporous nature. the paper is devoted to the study of transport phenomena during adsorption / desorption experiments in pores of various sizes. the authors of the article noted that the rates of transport phenomena http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2021.8.3.02 http://creativecommons.org/licenses/by/4.0/ https://orcid.org/0000-0001-6180-7359 chimica techno acta 2021, vol. 8(3), № 20218302 article 2 of 4 change significantly with the gradual filling / emptying of the pores. the authors of [5] synthesized and investigated coo3d ordered mesoporous carbon nitride (coo@mpgcn) catalyst. the authors managed to find out that the significant catalytic performance of coo@mpgcn was due to its uniformly distributed mesopores, large specific surface area, and high electron transferability at the active coo sites. the textural parameter and the mesoporous extent of materials originated from parent template were examined by nitrogen adsorption-desorption isotherm along with corresponding bet surface area and pore distribution analyses. the authors of [6] aimed to explore a facile route to synthesize mesoporous zinc silicate composites. the specific surface area and the pore properties of the samples were tested by the brunauer-emmett-teller (bet) method based on n2 adsorption / desorption measurements on quantachrome autosorb-iq2. the authors provided the n2 adsorption / desorption isotherms and pore size distributions of zs-3 and zs-5 that are rather different in structure. the fact that the structure is mesoporous is indicated by the increase of adsorbed nitrogen at relative pressure p > 0.45 and related to the multilayer adsorption and capillary condensation of n2. the excellent adsorption property endows the composite with potential application in the field of dye wastewater treatment. the authors of [7] attempted to enhance nitrogen adsorption capacity modified x zeolite adsorbent. for this, procedures including both nh4 + treatment and ca 2+ ionexchange were carried out. these modifications lead to a hierarchical mesopore-micropore structure with a multilayer n2 adsorption capacity. the properties of adsorbents are characterized by n2 adsorption–desorption in 77 k, xrd, and xrf analysis. in paper [7] adsorption isotherms are modeled by langmuir, dual-site langmuir (dsl), freundlich, and langmuir-freundlich (sips) models, and the corresponding parameters are determined. these adsorbents can be used effectively in the helium purification by the pressure swing adsorption (psa) process, which is based on nitrogen adsorption. it is known that the zeolites considered in this work are microporous materials. however, catalytic processes require materials containing both mesoand macropores. at the same time, the advanced system of zeolite micropores has a significant effect on the rate of the reactions. in this regard, it is necessary to develop analysis techniques that provide simultaneous control of the micro and mesoporous structure of materials. the aim of this paper is to consider the application peculiarities of the thermal desorption method of inert gases, implemented on the sorbi ms (meta, russia) device, for the analysis of mesoand microporous zeolite materials. 2. experimental in this work, zeolites of the type zsm-5 (samples 1,3) and beta (samples 2,4–6) were investigated. aluminum hydroxide (ah), including silica addition, was selected as the binder. the sample synthesis features and the selection of the peptizers are shown in table 5. zeolites were synthesized at the irkutsk national research technical university. in the previous paper [8], the results of the studying the properties of compositions in the mesopore range are presented; here we will emphasize the analysis of micropores. adsorption isotherms were built on the basis of the sorption study data obtained. the samples were studied by nitrogen sorption at 77 k on the sorbi ms device. the device works by comparing the volumes of adsorbate gas sorbed by the test sample and the standard sample. the specific surface area is measured using the 4-point bet method. micropores volume was determined on the basis of analysis of inert gas adsorption isotherms. 3. results and discussion 3.1. investigation of capillary condensation processes, sorption hysteresis a characteristic feature of adsorption in mesopores is associated with capillary condensation, which leads to filling the mesopores volume with a liquid adsorbate phase at a relative pressure, for example, nitrogen vapor at 77 k, 0.4 < p/p0 < 1. as a rule, the process of capillary condensation is irreversible. this means that the magnitude of sorption with increasing pressure of the sorbent does not coincide with the magnitude of sorption with decreasing pressure. in this case, a characteristic hysteresis is formed on the sorption isotherm, formed by mismatched branches of adsorption and desorption (fig. 1) [3]. 3.2. recommendations on the choice of measurement modes of the sorbi ms device during researching the parameters of the nanomaterials porous structure by the sorption method, it is important to correctly estimate the mass of the adsorbent material required for the study, select the sample preparation mode, and set the range of the relative partial pressure variation of the adsorbate gas at which the measurement will be carried out. fig. 1 characteristic types of capillary-condensation hysteresis loops according to the iupac classification. adapted from [3] chimica techno acta 2021, vol. 8(3), № 20218302 article 3 of 4 3.2.1. determination of the analyzed material mass and sample preparation the features of the thermal desorption method realized in sorbi ms are discussed in [9,10]. when studying compositions by the thermal desorption method of nitrogen, the choice of the analysed material mass is determined by two factors: the possibility of obtaining a stable desorption signal, which is used to calculate the volume of desorbed gas, and the range of the total measured surface s = ssp∙m. for example, the selected masses for various series of zeolite compositions that provide a stable desorption signal are shown in table 1. 3.2.2. modes selection and sample preparation of the analyzed material sample preparation of the analysed material, as a rule, consists in controlled heating of the sample in a flow of inert gas (helium). preparation is necessary, first of all, to remove moisture and surface contamination. variable sample preparation modes are heating temperature and time. table 2 shows, for example, the results of measuring the parameters of the porous structure of some samples depending on the conditions of preliminary degassing. also all samples were subjected to a single annealing procedure in a muffle furnace for 1 hour. this procedure is required in case of long-term storage or transportation of samples in high humidity conditions. the results of measuring the specific surface area for a sample of the bea type are presented in table 3. as can be seen from table 3, in the case of long-term storage of zeolite samples in high humidity conditions, the measured specific surface area of the samples decreases by 2–3 times. zeolites annealing at a temperature of 500 °c restores the specific surface area by removing moisture from the microand mesoporous system. in the study of zeolites, such heat treatment is similar to the annealing at the final stage of their preparation does not lead to structure destruction and is recommended. 3.2.3. measurement in the given range of the relative partial pressures of the adsorbate gas p/po the range selection of p/po values is determined by the investigated porous structure parameter. the measurement of the specific surface area by the bet method, the external surface and the construction of the size distribution of mesopores suggest the choice of different study modes. for example, the p/po parameters that are selected on the sorbi ms device used in this work are listed in table 4. 3.3. the micropores volume determination of a series of zeolite compositions by the sing and t-plot methods for the successful and high-quality application of porous materials, the control of their parameters and properties is an important criterion. analysis of microporous structure parameters in zeolite compositions was carried out in table 1 selected masses for various series of zeolite compositions series bea+2mnaoh bea mass, mg 83 150 49 211 ssp value at standard conditions of sample preparation, m 2 / g 296.6 exceeding the maximum measurable desorption signal 303.4 exceeding the maximum measurable desorption signal table 2 specific area values for different sample preparation modes t prep, °с t prep, min ssp, m 2 /g bea+2mnaoh 99.79 150 20 296.6 150 45 399.2 300 15 434.4 table 3 specific area values for different sample preparation modes before and after annealing at 500 °c t prep, °с t prep, min ssp, m 2 /g bea before annealing 170 150 60 366.1 bea after annealing 453 bea after annealing, 3 days later 300 150 60 470 table 4 the value range of p/p0 investigated parameter method range of relative partial pressures of adsorbate gas p/p0 specific surface area bet 6% to 20% micropore indication t-plot method 15% to 40% external surface of mesopores, size distribution of mesopores capillary condensation of an inert gas 6% to 97% this paper. zeolites of the type zsm-5 (samples 1,3 in table 5) and beta (samples 2,4–6 in table 5) were used. studies of the zeolites porous structure were carried out by low-temperature nitrogen adsorption on a sorbi ms device (t-plot method). as an alternative method for estimating the micropores volume, a comparative sing method is proposed. it is based on the use of the relative adsorption value αs on the reference sample. the value αs is calculated from the ratio of the current adsorption value v to adsorption at the relative pressure p/p0 = 0.4. the reference is a non-porous zeolite (without heating) of the same chemical nature as the sample under study. using normalized value we rebuild previously constructed adsorption isotherms into dependence of type v = f(v/v0.4), replacing relative pressure by value αs. the segment, cut off on the ordinate axis, is the value by which the micropores volume is then calculated. the obtained t-plot and sing micropore volume values are shown in table 5. chimica techno acta 2021, vol. 8(3), № 20218302 article 4 of 4 table 5 micropore volume values by the t-plot and sing method sample № sample composition zeolite/ah, wt% ah producer peptizer micropores volume (t-plot method), cm 3 /g micropores volume (sing method), cm 3 /g 1 zsm-5 0.07 0.07 2 bea 0.066 0.09 3 70 zsm -5/30 ah sasol aqueous solution of nitric acid 0.053 0.065 4 70 bea /30 ah-1 sasol aqueous solution of nitric acid 0.039 0.074 5 70 bea /30 ah-2 oao azk and os aqueous solution of nitric acid 0.1 0.1 6 70 bea /30 ah-3 oao azk and os mixture of aqueous solutions of nitric acid and ammonia (1:1) 0.072 0.097 as it can be seen, the micropore volume values calculated by sing do not differ significantly compared to the values taken from the sorbi ms device. thus, it is possible to estimate the volume of micropores by both the t-plot method and the comparative sing method. the analysis showed that the largest micropores volume (0.1 ml/g) is typical for samples of series 5, where in the synthesis process an aqueous solution of nitric acid was used as a peptizer, and aluminum hydroxide from the manufacturer oao azk and os was used as a binder. replacement of the peptizer (sample 6 in table 5) led to a slight decrease in the micropores volume in the composition. however, such a replacement results in an increase in the total specific surface area [8] and the total pore volume. 4. conclusions the paper considers the method application features of nitrogen thermal desorption for the study of micromesoporous materials on the example of zeolite composition. the recommended mass values for obtaining a stable desorption signal and the recommended modes of sample preparation of zeolite compositions were selected. as a rule, in the study of materials by the thermal desorption method of inert gases, an insufficient mass of the sample can act as a significant limitation for the analysis. in the case of studying zeolite compositions, on the contrary, too large an adsorbent mass can lead to an incorrect sensor signal for thermal conductivity and peak truncation. nitrogen adsorption at 77 k on a series of zeolite compositions was investigated. it was shown that using analysis sorption methods, it is possible to estimate the volume micropores by the t-plot and sing method. references 1. everett d. manual of symbols and terminology for physicochemical quantities and units, appendix ii: definitions, terminology and symbols in colloid and surface chemistry. pure and applied chemistry. 1972;31(4):577-638. doi:10.1351/pac197231040577 2. wang g, wang k, ren t. improved analytic methods for coal surface area and pore size distribution determination using 77k nitrogen adsorption experiment. int j min sci technol. 2014;24(3):329-334. doi:10.1016/j.ijmst.2014.03.007 3. gavrilov vy. fiziko-himicheskie osnovy adsorbcionnogo analiza dispersnyh i poristyh materialov [physicochemical bases of adsorption analysis of dispersed and porous materials]. novosibirsk: nctc; 2007. 67 p. russian. 4. zelenka t. adsorption and desorption of nitrogen at 77 k on microand mesoporous materials: study of transport kinetics. journal of microporous and mesoporous materials. 2016;227:202-209. doi:10.1016/j.micromeso.2016.03.009 5. nguyen tb, huang cp, doong ra, chen cw, dong cd. coo-3d ordered mesoporous carbon nitride (coo@mpgcn) composite as peroxymonosulfate activator for the degradation of sulfamethoxazole in water. journal of hazardous materials. 2021;401:123320. doi:10.1016/j.jhazmat.2020.123326 6. dong gy, tian gy ,gong ll, tang qg. mesoporous zinc silicate composites derived from iron ore tailings for highly efficient dye removal: structure and morphology evolution. journal of microporous and mesoporous materials. 2020;305:110352. doi:10.1016/j.micromeso.2020.110352 7. hadis m, jafar t, babak m. enhanced nitrogen adsorption capacity on ca 2+ ion-exchanged hierarchical x zeolite. separation and purification technology. 2021;264:118442. doi:10.1016/j.seppur.2021.118442 8. kononova ie, maraeva ev, skornikova sa, moshnikov va. influence of binder on porous structure of zeolite compositions and their catalytic activity. glass physics and chemistry. 2020;46(2):162-169. doi:10.1134/s1087659620020066 9. gracheva ie, moshnikov va, maraeva ev, karpova ss, alexsandrova oa, alekseyev ni, kuznetsov vv, olchowikc g, semenov kn, startseva av, sitnikov av, olchowikc jm. nanostructured materials obtained under conditions of hierarchical self-assembly and modified by derivative forms of fullerenes. journal of non-crystalline solids. 2012;358(2):433-439. doi:10.1016/j.jnoncrysol.2011.10.020 10. maraeva ev, permiakov nv, kedruk yy, gritsenko lv, abdullin kha. creating a virtual device for processing the results of sorption measurements in the study of zinc oxide nanorods. chimica techno acta. 2020;7(4):154-158. doi:10.15826/chimtech.2020.7.4.03 https://doi.org/10.1351/pac197231040577 https://doi.org/10.1016/j.ijmst.2014.03.007 https://doi.org/10.1016/j.micromeso.2016.03.009 https://doi.org/10.1016/j.jhazmat.2020.123326 https://doi.org/10.1016/j.micromeso.2020.110352 https://doi.org/10.1016/j.seppur.2021.118442 https://doi.org/10.1134/s1087659620020066 https://doi.org/10.1016/j.jnoncrysol.2011.10.020 https://doi.org/10.15826/chimtech.2020.7.4.03 cta_v3_№1.cdr 68 d o i: 1 0. 15 82 6/ ch im te ch .2 01 6. 3. 1. 00 6 a. f. guseva, m. v. trifonova, n. n. pestereva a ural federal university, 620000, ekaterinburg, mira 19, phone:+79126373816 e-mail: anna.guseva@urfu.ru surface reactions with participation of oxides of molybdenum and tungsten: the influence of external factors this work is a continuation of the article “surface reactions with participation of oxides of molybdenum and tungsten”, published in the previous issue of the journal. the influence of the electric field and the pressure of oxygen in the gas phase on the rate of surface reactions for the synthesis of molybdates of manganese and copper were investigated. it’s found that for the synthesis reaction of molybdate of copper the nature of the dependency of the rate of synthesis and rate of surface reactions from the external parameters are the same, indicating the crucial contribution of surface diffusion to the reactive mass transfer. for the synthesis reaction of molybdate of manganese the dependences of the rate of synthesis and of rate of surface reactions by external parameters differ, indicating that for this reaction, surface diffusion isn’t the main mechanism of mass transfer. keywords: mass transfer; reaction surface diffusion; surface reactions; molybdates; tungstates. © guseva a. f., trifonova m. v., pestereva n. n., 2016 introduction in a number of experiments to study solid state reaction of synthesis of molybdates and tungstates it was observed that the reaction product is not only in the place of the direct contact of the briquettes of reagents (diffusant and substrate), but also outside it, on the free surface of the substrate briquette, fig. 1. this phenomenon, as well as the results of experiments on the effect of substrate porosity on the rate of solid state reactions [1] prompted us to conduct a special study of the surface reaction diffusion (srd), the results of which we published earlier in [2–4]. the reaction diffufig. 1. the disposition layout of the briquettes of the starting materials and the layer of product 69 № 1 | 2016 chimica techno acta sion in the synthesis of molybdates and tungstates, as with many other complex oxides, includes bulk, grain boundary and surface mass transfer. to explore the features of the mechanism of surface mass transfer and to assess its contribution to the reaction stream has been tasked to studying of the influence of external factors on the rate of surface reaction, characterized by the length of the surface layer ℓs, and on reaction rate in general, characterized by the thickness of layer of product in the place of contact of the briquettes reagents ℓ. the experimental part we used cuo, moo3, mn2o3, (qualifying “h.p.”). the samples for investigation were prepared in the form of briquettes by pressing and subsequent sintering. sintering conditions of the samples are given in table 1. table 1. sintering conditions of the samples. compound temperature of sintering, °c time of sintering, hour mn2o3 900 24 cuo 950 18 moo3 600 3 when studying of srd in the electric field the bars of the substrate with a height of 3–5 mm and tablets of diffusant with a diameter of 15 mm and a thickness of 1.5–2.0 mm were used. surface of the reagents was carefully polished before experiments to remove surface contamination. the reaction couple, which is of constant thickness, with platinum electrodes were placed in a corundum cell, which, in turn, was placed in the furnace preheated to the required temperature, then a constant voltage from the power source is supplied into the system. the control for the development process was performed by the measurement of the length of the surface layer ℓs and the thickness of the layer of product ℓ in the place of contact the briquettes. the layout of the briquettes of the starting materials and of the layer of product in the study of srd in an electric field are presented in fig. 2. the diffusion anneals under reduced oxygen pressure were performed in the interval of po2 =  1÷10 –5 atm. the oxygen pressure in the system was setting by the electrochemical oxygen pump from stabilized zirconia (zro2 + 10 mol % y2o3) and was controlling using an oxygen sensor made of the same material. x-ray analysis of the reaction product was carried out on diffractometer drf2.0 by radiation сокa. the survey was conducted at a speed of 2.0 °/min in the range of angles 2q from 5 to 35 °. microscopic analysis of the surface and of chips of the briquettes after annealing was performed using microscope mbs-9 fig. 2. the layout of the briquettes of the starting materials and of the layer of product in the study of srd in an electric field (u = const). surface reactions with participation of oxides of molybdenum and tungsten: the influence of external factors 70 № 1 | 2016 chimica techno acta with magnification in 16 to 56 times and optical microscope polam-112 in transmitted light at magnification of 300–420 times. the measurement of the mass of briquettes before and after diffusion annealings was carried out on an analytical balance sartorius – bl60s with an accuracy of 0.0001 g the effective density of samples was determined by the volume and mass of samples and hydrostatic weighing. its value ranged from 60 to 85 %. the morphology of the substrate and product, as well as their elemental composition was investigated using the electron microscope jsm-3 with a microanalyzer at magnification of 300 3000 times. results and discussion the influence of an electric field. the influence of the electric fields at srd (ℓs) and the rate of solid-phase reactions in general (ℓ) for two systems сuomoo3 и mn2o3-moo3, in which the reactions occur: 2mn2o3 + 4moo3 → 4mnmoo4 + o2 (1) 2cuo + moo3 → cu2moo5 (2) (cumoo4) in brackets there is the minor product of the reaction. the experiment was conducted at a temperature of 600 °с with potentiostatic conditions; the voltage on the reaction cell was varied from –400 to +400 v when the thickness of the assembly of briquettes was 5 mm. for the positive direction of passing of the electric current it’s adopted such direction when the briquette of moo3 is positively polarized, and the substrate ((сuo, mn2o3) is negative: (–) substrate|moo3 (+), u > 0. the dependence of characteristics of the process velocity from the voltage is presented in fig. 3–4. for the system сuo-moo3 was found that electric field significantly influences the rate of surface reaction and the overall rate of synthesis. the length of the surface layer depending on the voltage level and direction of transmission of the electric current varies from 90 to 1300 μm, and the thickness of the layer in the place of contact varies from 10 to 130 µm (fig. 3). thus, the influence of an electric field in the range of values of u = –400...+400 allows to change the value of 14 times and to change the value of 13 times. this shows that the intensity of influence of the electric field on the rate of surface reaction and reaction rate in general is about the same. as can be seen from fig. 3, the nature of the effect of electric field on the rate of surface reaction and speed of interaction in the place of contact is similar. this indicates a similar mechanism of the srd and interaction at the site of contact of the briquettes of the reagents. in place of fig. 3. the dependence of the length of the surface layer (1) and the thickness of the layer (2) in the place of contact of the briquettes reagents from the voltage on the cell of the cuo-moo3, t = 600 °c, τ = 3 hours guseva a. f., trifonova m. v., pestereva n. n. 71 № 1 | 2016 chimica techno acta the contact the mass transfer is carried out both by surface and by grain boundary and bulk diffusion. the same nature of the impact of electric field on the srd and on the speed of interaction at the site of contact, it seems, may be an indication that surface diffusion is the main mode of mass transfer in this system. the complex non-monotonic character of the dependences can be explained within the framework of the hypothesis about electroosmotic entrainment of moo3 by counterions of the double electric layer arising at the interfaces, along which there is a transfer diffusant. the essence of this hypothesis is described in detail in [1–2, 5]. for the system mn2o3/moo3 the strong effect of electric field on the rate of surface reaction (ℓs) and reaction in general (ℓ) is also found, fig.4. the length of the surface layer depending on the voltage level and direction of transmission of the electric current ranges from 1200 to 2000 μm, and the thickness of the layer in the place of contact ranges from 3 to 24 μm thus, the influence of the electric field in the range of values of u = –300 ...+300 v allows to change ℓs 1.7 times, and ℓ allows to change 8 times. this shows that the intensity of the influence of the electric field on the rate of surface reaction is much less than the rate of reaction in general. the shape of curves ℓs, ℓ = f(u) is also very different (fig. 4). in the field of values of voltage -80...+50v the nature of the influence of the electric field ℓ on and ℓs is opposite: an increase in the voltage increases the layer thickness at the site of contact of the reagents and decrease of the length of the surface layer. this shows the difference of the mechanism of mass transfer at the surface and at the site of contact. apparently, in this system, the surface diffusion isn’t the main transport stream, which presumably can be grainboundary diffusion. influence of oxygen activity in the gas phase on the rate of surface reactions. the layout of the briquettes of the reagents and reaction product in studies of the reaction diffusion at the different pressures of oxygen is presented in fig. 5. in these series of experiments there was radial (two-dimensional) distribution of diffusant on the substrate surface. to discuss the results of experimental values ℓ and ℓs the rate constants of fig. 4. the dependence of the thickness of the layer at the site of contact of briquettes of the reagents (1) and the length of the surface layer(2) of the voltage on the cell mn2o3-moo3, t = 600 °c, τ = 3 hours fig. 5. the layout of the briquettes of the reagents and reaction product surface reactions with participation of oxides of molybdenum and tungsten: the influence of external factors 72 № 1 | 2016 chimica techno acta the interaction at the site of contact of the briquettes of reagents (k) were calculated by the equation k = ℓ2/τ and the rate constant of surface reaction (ks) were calculated according to the equation k x y z= + +  3 2 3 τ. this type of constant кs is due to fact that for radial diffusion the growth of the surface layer is described the third-order polynomial as shown in our article published in the previous issue of the magazine: x y z gs s s  + + = 2 3 ∆ τ (3) the dependences of the rate constants from po2 in logarithmic coordinates are presented on fig. 6. for the system mn2o3-moo3 values of d gk d gps o  2 and d gk d gpo  2 are respectively –1/6 and –1/4, and for the system сuo-moo3 are respectively –1/8 and –1/9 thus, for both systems, the decrease of the oxygen pressure increases the speed of interaction, both on the surface and at the site of contact. as was proved earlier in [1–2], the main mechanisms of mass transfer during the synthesis of molybdates are the surface and grain-boundary diffusion. the speed of these reactions is proportional to the concentration of extended defects and, apparently, little depends on the concentration of point defects. about the veracity of this claim the following fact is evidenced. the diffusion coefficient of molybdenum in monocrystal pbmoo4, determined by the method of radioactive indicators, increases with growth po2: dmo = k · po2 +1/7 [6], which indicates the growth of point defects in molybdenum sublattice with growth po2. at the same time, the reaction rate of the formation of pbmoo4 decreases with increasing po2 [6]. the chemical nature and mechanism of formation of extended defects in complex oxides are poorly understood to date. therefore, the quantitative interpretation of the dependence of the rate of surface reactions and reactions at the site of contact of the synthesis of molybdates is not possible to the present moment. on a qualitative level the increase in the rate of surface interaction with decreasing po2 can be explained as follows. according to [7], in the lattice of complex oxides меmoo4, especially at the interfaces the defects of the type o xmoo4 capable fig. 6. the dependence of the constants кs and к from the pressure of the oxygen in the gas phase in the system mn2o3-moo3 (t = 600 °c, τ = 3 hours) fig. 7. the dependence of the constants кs and к from the pressure of the oxygen in the gas phase in the system cuo-moo3 (t = 600 °c, τ = 3 hours) guseva a. f., trifonova m. v., pestereva n. n. 73 № 1 | 2016 chimica techno acta of migration of the component mo in the following manner can contain: moo o moox x x4 44 3 4 4moo moo moo moo+ + . (4) the mobile form is triangular pyramid (моо3) which has properties that potentially facilitate the migration of mo: first, can rotate around the mo-peaks due to the oxygen exchange with the vacant position, secondly, a pyramidal center moo3 with a tricoordinated atom mo can in principle change its shape by passing mo through the center of the base of the pyramid, fig. 8 [7]. it is logical to assume that with increasing defect the concentration of the type o xmoo4 will increase the rate of mass transfer of molybdenum oxide through the layer of reaction product and, consequently, the rate of reaction. defects o xmoo4 may form at the exit of moo3 from the crystal lattice меmoo4 into the gas phase on the reaction: memoo moo meme x 4 3û ( .газ)+ (5) in order to evaluate the effect of reducing the partial pressure of oxygen at equilibrium (5) the following experiment was carried out. the pre-weighed briquettes of molybdenum oxide were annealed in an oxygen 10-5 atm) at ×atmosphere (po2 = 1 atm) and in the helium atmosphere (po2 = 3×10-5 atm) and at the°temperature of 600 °с during 15 hours and the change in mass after annealing was determined. since the briquettes have different weight and volume, the change in mass was resulted in the area of the entire surface of the briquettes. the results of the experiment are shown in table 2. table 2 the mass decrease of the moo3 briquettes, annealed in an atmosphere of oxygen and helium, t = 600 °c, τ = 15 hours. po2, atm 1 (oxygen) 3·10-5 (helium ) ∆m s ⋅100 %, g/sm3 0,24% 0,39% the results in table show that the mass decrease of the briquettes in an atmosphere of helium at about 1.6 times more than in the atmosphere of oxygen. likely the increase of the volatility of molybdenum oxide at low oxygen pressure shifts the equilibrium (5) in the direction of the products, i.e. increasing the concentration of defects o xmoo4. this, in turn, leads to an increase in the rate of mass transfer of molybdenum oxide through the layer of reaction product and to increase the of the reaction rate, as observed experimentally. assessing the results of impact pressure of oxygen in the gas phase on the reaction rate in the investigated systems, we also note that the proximity coefficients d gk d gps o  2 and d gk d gpo  2 for the system of сuo-moo3 may be an indication that surface diffusion is the main mode of mass transfer in this system. the difference of these coefficients for the system mn2o3-moo3, likely is due to the fact that surface diffusion is the main transport stream in the synthesis of mnmoo4. these findings are in good agreefig. 8. the inversion center of moo3 [7] surface reactions with participation of oxides of molybdenum and tungsten: the influence of external factors 74 № 1 | 2016 chimica techno acta ment with the conclusion made by us above, according to the data of the effects of electric fields on the reaction rate. study of the morphology of the substrate and reaction product by electron microscopy. the morphology of the substrate and the reaction product was examined by electron microscopy to determine possible differences for the studied systems. system cuo-moo3 under the interaction of cuo and moo3 the formation of two individual chemical compounds cumoo4 and cu2moo5 may occur. the main product of the interaction is cu2moo5 and only after prolonged annealing (more than 30 hours) at the site of contact of the briquettes by means of xpa recorded trace amounts of the second phase cumoo4 were recorded. studies by electron microscopy gave the following information. the grains of cuo substrate have the form of irregular polygons; the size 5.5– 13 µm, fig. 9. the grains of reaction product cu2 moo5 have an elongated shape, their size varies from 2 to 5 microns in width and from 8 to 20 µm in length, fig. 10. thus, in this system the grains of the product and substrate are quite similar in size but differ shape. system mn2o3-moo3 the grains of the substrate mn2o3 have a rounded shape, their average size is of 2.5 μm, fig. 11. the grains of reaction product mnmoo4 also have a rounded shape, but their average size (10 μm) was approximately 4 times larger than the grain size of the substrate, fig. 12. thus, the fundamental differences in the morphology of the grains of the product and the substrate (the form of grains, the ratio of the grain size of the substrate/ product) are revealed for the two studied systems this fact indirectly indicates differences in the mechanism of the reaction diffusion in the investigated systems. conclusions in terms of the results of this work we can draw the following conclusions: 1. it is established that the nature of the impact of electric field on the rate of surface interactions and reaction speed in general is the same for the synthesis fig. 9. the sem image of the cuo substrate fig. 10. sem image of product cu2moo5 guseva a. f., trifonova m. v., pestereva n. n. 75 № 1 | 2016 chimica techno acta of copper molybdate and is varied for the synthesis of manganese molybdate. 2. it is established that decreasing of oxygen pressure leads to increased speed of interaction both on the surface and in the region of contact of the reagents for the systems cuo/moo3 and mn2o3/ moo3, which may be associated with an increase in the concentration of defects of type o xmoo4 under decreasing of oxygen pressure. the intensity of the impact on the speed of surface interactions and reaction speed in general is close for the synthesis of copper molybdate and differs for the synthesis of manganese molybdate. 3. by electron microscopy the morphology of the substrates and reaction product in the systems cuo/moo3 and mn2o3/moo3 was researched. the differences in the form of grains, and the ratio of the grain sizes of the product/substrate in the investigated systems were determined. 4. the educated guess was made about that the main traffic stream in the synthesis of copper molybdate is surface diffusion, in contrast to the synthesis of manganese molybdate. 1. a. ya. neiman, a. f. guseva. new data on mechanism of mass transfer in solid-state reactions i. reactions in an electric field. kinetics and catalysis. 1994;35(ii):188-194. 2. a. ya. neiman, a. f. guseva. new data on the mechanism of mass transfer in solidphase reactions: ii. chemical and electrochemical surface phenomena. kinetics and catalysis. 1999;40(i):38-49. 3. a. ya. neiman, a. f. guseva, m. v. trifonova surface reaction in the course of molibdates and tungstates formation. solid state ionics. 2001;141-142:321-329. 4. a. ya. neiman, a. f. guseva, m. v. trifonova, i. v. sukhankina. reactive surface diffusion durin synthesis of molybdates and tungstates: the role of phase constitution of product. russian journal of inorganic chemistry. 2005;50:319-324. 5. a. ya. neiman, a. f. guseva. electrochemical approach to solid state reactions and interphase phenomena. russian j. of electrochemistry. 1993;29(11):1388-1395. 6. a. ya. neiman, l. m. fedorova, a. a. afanasyev. point defect interaction in pbmoo4. inorgan. materials. 1986;22(5):811-815 7. a. ya. neiman. cooperative transport in oxides: diffusion and migration processes involving mo (vi), w (vi), v (v) and nb (v). solid state ionics. 1996;83:263-273. fig. 11. sem image of substrate mn2o3 fig. 12. sem image of product mnmoo4 surface reactions with participation of oxides of molybdenum and tungsten: the influence of external factors 76 у д к 6 61 .8 78 +5 46 .7 8: 54 4. 22 7 а. ф. гусева, м. в. трифонова, н. н. пестерева уральский федеральный университет, 620000, г. екатеринбург, ул. мира, 19 тел.: +7 (912) 637-38-16, e-mail: anna.guseva@urfu.ru поверхностные реакции с участием оксидов молибдена и вольфрама: влияние внешних факторов данная работа является продолжением статьи «поверхностные реакции с участием оксидов молибдена и вольфрама», опубликованной в предыдущем номере журнала. исследовано влияние электрического поля и давления кислорода в газовой фазе на скорость поверхностных реакций синтеза молибдатов марганца и меди. установлено, что для реакции синтеза молибдата меди характер зависимостей скорости синтеза и скорости поверхностной реакции от внешних параметров одинаков, что свидетельствует об определяющем вкладе поверхностной диффузии в реакционный массоперенос. для реакции синтеза молибдата марганца зависимости скорости синтеза и скорости поверхностной реакции от внешних параметров отличаются, что свидетельствует о том, что для этой реакции поверхностная диффузия не является основным механизмом массопереноса. ключевые слова: массоперенос; поверхностная реакционная диффузия; поверхностные реакции; молибдаты; вольфраматы. © гусева а. ф., трифонова м. в., пестерева н. н., 2016 введение в ряде экспериментов по изу чению твердофазных реакций синтеза молибдатов и вольфраматов было замечено, что продукт реакции располагается не только в месте непосредственного контакта брикетов реагентов (диффузанта и подложки), но и вне его, на свободной поверхности брикета подложки, рис. 1. рис. 1. схема расположения брикетов исходных веществ и слоя продукта 77 № 1 | 2016 chimica techno acta это явление, а также результаты экс периментов по влиянию пористости подложки на скорость твердофазных реакций [1] побудили нас провести специальное исследование поверхностной реакционной диффузии (прд), основные результаты которого опубликованы нами ранее в [2–4]. реакционная диффузия при синтезе молибдатов и вольфраматов, как и многих других сложных оксидов, включает объемный, зернограничный и поверхностный массоперенос. с целью исследовать особенности механизма поверхностного массопереноса и оценить его вклад в реакционный поток была поставлена задача изучить влияние внешних факторов на скорость поверхностной реакции, характеризующейся длиной поверхностного слоя ℓs, и на скорость реакции в  целом, характеризующейся толщиной слоя продукта в месте контакта брикетов реагентов ℓ. экспериментальная часть в работе использовались cuo, moo3, mn2o3 (квалификации «ос.ч.»). образцы для исследования готовили в виде брикетов преccованием и последующим спеканием. условия спекания образцов приведены в табл. 1. таблица 1 условия спекания образцов вещество температура отжига,°c время отжига, час mn2o3 900 24 cuo 950 18 moo3 600 3 при изучении прд в электрическом поле использовали бруски подложки высотой 3–5 мм и таблетки диффузанта диаметром 15 мм и толщиной 1,5–2,0  мм. поверхность реагентов тщательно шлифовали перед опытом для удаления загрязнения поверхности. реакционную пару, имеющую постоянную толщину, вместе с платиновыми электродами помещали в алундовую ячейку, которую, в свою очередь, помещали в печь, заранее разогретую до необходимой температуры, после этого на систему подавалось постоянное напряжение от источника тока. контроль за развитием процесса осуществляли измерением длины поверхностного слоя и толщины слоя ℓs продукта ℓ в месте контакта брикетов. схема расположения брикетов исходных веществ и слоя продукта при изучении прд в электрическом поле представлена на рис. 2. диффузионные отжиги при пониженном давлении кислорода проводили в интервале po2 = 1÷10 –5 атм. давление кислорода в системе задаварис. 2. схема расположения брикетов исходных веществ и слоя продукта при изучении прд в электрическом поле (u = const) поверхностные реакции с участием оксидов молибдена и вольфрама: влияние внешних факторов 78 № 1 | 2016 chimica techno acta ли электрохимическим кислородным насосом из стабилизированного диоксида циркония (zro2 + 10 мол. % y2o3); контролировали при помощи кислородного датчика, изготовленного из того же материала. рентгенофазовый анализ продукта реакции выполняли на дифрактометре дрф-2.0 в сокa излучении. съемку проводили со скоростью 2 °/мин в интервале углов 2q от 5 до 35 °. микроскопический анализ поверхности и сколов брикетов после отжигов проводили с помощью микроскопа мбс-9 при увеличении в  16–56 раз и оптического микроскопа полам с-112 в проходящем свете при увеличении в 300–420 раз. измерение массы брикеты до и после диффузионных отжигов проводили на аналитических весах sartorius – bl60s с точностью 0,0001г. эффективную плотность образцов определяли по объему и массе образцов, а также методом гидростатического взвешивания. ее величина варьировалась от 60 до 85 %. морфологию подложки и продукта, а также их элементный состав исследовали с помощью электронного микроскопа jsm-3 с микроанализатором при увеличении 300–3000 раз. результаты и обсуждение воздействие электрического поля. исследовано влияние электрического поля на прд (ℓs) и скорость твердофазной реакции в целом (ℓ) для двух систем: сuo-moo3 и mn2o3-moo3, в которых протекают реакции: 2mn2o3 + 4moo3 → 4mnmoo4 + o2 (1) 2cuo + moo3 → cu2moo5 (2) (cumoo4) в скобках указан неосновной продукт реакции. эксперимент проводили при температуре 600 °с в потенциостатических условиях; напряжение на реакционной ячейке варьировали от –400 до +400 в при толщине сборки брикетов 5 мм. за положительное направление пропускания электрического тока приняли такое, когда брикет moo3 положительно поляризован, а подложка (сuo, mn2o3) – отрицательно: (–) подложка|moo3 (+), u>0 зависимости характеристик скорости процесса от напряжения представлены на рис. 3–4. для системы сuo-moo3 было обнаружено, что электрическое поле весьма существенно влияет на скорость поверхностной реакции и суммарную скорость синтеза. длина поверхностного слоя в зависимости от величины напряжения и направления пропускания электрического тока варьируется от 90 до 1300 мкм, а толщина слоя в месте контакта от 10 до 130 мкм (рис.  3) таким образом, воздействие электрического поля в диапазоне значений u = –400…+400в позволяет изменить значение ℓs в 14 раз, а ℓ – в 13 раз. это показывает, что интенсивность воздействия электрического поля на скорость поверхностной реакции и  скорость реакции в целом примерно одинакова. как видно на рис. 3, характер воздействия электрического поля на скорость поверхностной реакции и  скорость взаимодействия в месте контакта аналогичен. это свидетельствует о сходном механизме прд гусева а. ф., трифонова м. в., пестерева н. н. 79 № 1 | 2016 chimica techno acta и  взаимодействия в месте контакта брикетов реагентов. в месте контакта массоперенос осуществляется как за счет поверхностной, так и за счет зернограничной и объемной диффузии. одинаковый характер воздействия электрического поля на прд и на скорость взаимодействия в месте контакта, по-видимому, может быть свидетельством того, что поверхностная диффузия является основным способом массопереноса в данной системе. сложный немонотонный характер зависимостей ℓs, ℓ = f(u) можно объяснить в рамках гипотезы об электроосмотическом увлечении moo3 противоионами двойного электрического слоя, возникающего на межфазных границах, вдоль которых происходит перенос диффузанта. суть этой гипотезы подробно изложена в работах [1–2, 5]. для системы mn2o3/moo3 также обнаружено сильное влияние электрического поля на скорость поверхностной реакции (ℓs) и реакции в целом (ℓ), рис. 4. длина поверхностного слоя в зависимости от величины напряжения и направления пропускания электрического тока варьируется от 1200 до 2000 мкм, а толщина слоя в месте контакта от 3 до 24 мкм таким образом, воздействие электрического поля в диапазоне значений u = –300 …+300в позволяет изменить ℓs в 1,7 раз, а ℓ – в 8 раз. это показывает, что интенсивность воздействия электрического поля на скорость поверхностной реакции значительно меньше, чем на скорость реакции в целом. вид ℓs, ℓ = f(u) кривых также весьма различен (рис. 4). в области значений напряжения –80…+50в характер воздействия электрического поля на ℓ и ℓs противоположен: с увеличением напряжения происходит увеличение толщины слоя в месте контакта реагентов и уменьшение длины поверхностного слоя. это свидетельствует о различии механизма массопереноса на поверхности и в месте контакта. по-видимому, в данной системе поверхностная диффузия не является основным транспортным потоком, которым, предположительно может быть зернограничная диффузия. рис. 3. зависимость (1) длины поверхностного слоя и (2) толщины слоя в месте контакта брикетов реагентов от напряжения на ячейке cuo-moo3, t = 600 °c, τ = 3 час. рис. 4. зависимость (1) толщины слоя в месте контакта брикетов реагентов и (2) длины поверхностного слоя от напряжения на ячейке mn2o3-moo3, t = 600 °c, τ = 3 ч поверхностные реакции с участием оксидов молибдена и вольфрама: влияние внешних факторов 80 № 1 | 2016 chimica techno acta влияние активности кислорода в  газовой фазе на скорость поверхностных реакций. схема расположения брикетов реагентов и продукта реакции при исследованиях реакционной диффузии при различных давлениях кислорода представлена на рис. 5. в данной серии экспериментов происходило радиальное (двумерное) распространение диффузанта по поверхности подложки. для обсуждения результатов из экспериментальных значений ℓ и ℓs были рассчитаны константы скорости взаимодействия в месте контакта брикетов реагентов (k) по уравнению и константы скорости поверхностной реакции (ks) по уравнению k x y z= + +   3 2 3 τ. такой вид константы ks обусловлен тем, что при радиальной диффузии рост поверх ностного слоя описывается, как было показано в нашей статье, опубликованной в предыдущем номере журнала, полиномом третьей степени: x y z gs s s  + + = 2 3 ∆ τ . (3) зависимости констант скорости от po2 в логарифмических координатах представлены на рис. 6. для системы mn2o3-moo3 значения d gk d gps o  2 и d gk d gpo  2 соответственно составляют –1/6 и –1/4, а  для системы сuo-moo3 –1/8 и –1/9, соответственно. таким образом, для обеих систем понижение давления кислорода приводит к увеличению скорости взаимодействия как на поверхности, так и в месте контакта. как было убедительно доказано ранее в работах [1–2], основными механизмами массопереноса при синтезе молибдатов являются поверхностная и зернограничная диффузия. скорость этих реакций пропорциональна концентрации протяженных дефектов и, по-видимому, мало зависит от концентрации точечных дефектов. о справедливости этого утверждения свидетельствует следующий факт. коэффициент диффузии молибдена в монокристалле pbmoo4, определенный методом радиоактивных индикаторов, увеличивается с ростом po2: dmo = k · po2 +1/7 [6], что свидетельствует о росте точечных дефектов в молибденовой подрешетке с ростом po2. в то же время, скорость реакции образования pbmoo4 уменьшается с увеличением po2 [6]. рис. 5. схема расположения брикетов реагентов и продукта рис. 6. зависимость констант ks и k от давления кислорода в газовой фазев системе mn2o3-moo3 (t = 600 °c, τ = 3 ч) гусева а. ф., трифонова м. в., пестерева н. н. 81 № 1 | 2016 chimica techno acta химическая природа и механизм образования протяженных дефектов в сложных оксидах к настоящему моменту мало изучены. поэтому количественная интерпретация зависимости скорости поверхностных реакций и реакций в месте контакта синтеза молибдатов к настоящему моменту не представляется возможной. на качественном уровне увеличение скорости поверхностного взаимодействия с уменьшением po2 можно объяснить следующим образом. согласно [7], в решетке сложных оксидов меmoo4, особенно на межфазных границах, могут содержаться дефекты типа o xmoo4 , способные обеспечить миграцию компонента мо по следующей схеме: moo o moox x x4 44 3 4 4moo moo moo moo+ + . (4) подвижная форма – трехгранная пирамида (моо3) – обладает свойствами, потенциально облегчающими миграцию мо: – во-первых, может вращаться вокруг мо – вершины за счет обмена кислорода с вакантной позиции; – во-вторых, пирамидальный центр моо3 с трехкоординированным атомом мо принципиально может менять свою форму путем прохождения мо через центр основания пирамиды, рис. 8 [7]. логично предположить, что с ростом концентрации дефектов типа o xmoo4 возрастет скорость массопереноса оксида молибдена через слой продукта реакции и, следовательно, скорость реакции. дефекты o xmoo4 могут образоваться при выходе moo3 из кристаллической решетки меmoo4 в газовую фазу по реакции: memoo moo meme x 4 3û ( .газ)+ (5) для того чтобы оценить, как влияет уменьшение парциального давления кислорода на равновесие (5), был проведен следующий эксперимент. предварительно взвешенные брикеты оксида молибдена отожгли в атмосфере кислорода (po2 = 1 атм) и в атмосфере гелия (po2 = 3 ⋅ 10 –5 атм) при температуре 600 °с и времени 15 час и определили изменение их массы после отжига. так как брикеты имели разную массу и объем, то изменение массы привели к площади всей поверхности брикетов. результаты эксперимента приведены в табл. 2. результаты, приведенные в таблице, показывают, что убыль массы брикетов в атмосфере гелия примерно в  1,6 раз больше, чем в атмосфере кислорода. вероятно, увеличение летучести оксида молибдена при понижении рис. 7. зависимость констант ks и k от давления кислорода в газовой фазев системе cuo-moo3 (t = 600 °c, τ = 3 ч) рис. 8. инверсия центра моо3 [7] поверхностные реакции с участием оксидов молибдена и вольфрама: влияние внешних факторов 82 № 1 | 2016 chimica techno acta давления кислорода смещает равновесие (5) в сторону продуктов, т.  е. увеличивается концентрация дефектов o xmoo4 . это, в свою очередь, приводит к увеличению скорости массопереноса оксида молибдена через слой продукта реакции и к увеличению скорости реакции, что и наблюдали экспериментально. таблица 2 убыль массы брикетов моо3, отожженных в атмосфере кислорода и гелия, t = 600 °c, τ = 15 ч. po2, атм 1 (кислород) 3·10–5 (гелий) ∆m s ⋅100 %, г/см3 0,24 % 0,39 % оценивая результаты воздействия давления кислорода в газовой фазе на скорость реакций в исследованных системах, отметим также, что близость коэффициентов d gk d gps o  2 иd gk d gpo  2 для системы сuo-moo3 может быть свидетельством того, что поверхностная диффузия является основным способом массопереноса в данной системе. различие этих же коэффициентов для системы mn2o3-moo3, вероятно, связано с тем, что поверхностная диффузия не является основным транспортным потоком при синтезе mnmoo4. эти выводы хорошо согласуются с заключением, сделанным нами выше по данным воздействия электрического поля на скорость реакции. исследование морфологии подложки и продукта реакции методом электронной микроскопии морфология подложки и продукта реакции была исследована методом электронной микроскопии с целью выяснения возможных отличий для исследованных систем. система cuo-moo3 при взаимодействии cuo и moo3 возможно образование двух индивидуальных химических соединений cumoo4 и cu2moo5. основным продуктом взаимодействия является cu2moo5, и лишь при длительных отжигах (более 30 ч) в месте контакта брикетов методом рфа зафиксированы следовые количества второй фазы – cumoo4. исследования методом электронной микроскопии дали следующую информацию. рис. 9. рэм-изображение подложки cuo рис. 10. рэм-изображение продукта cu2moo5 гусева а. ф., трифонова м. в., пестерева н. н. 83 № 1 | 2016 chimica techno acta зерна подложки cuo имеют форму неправильных многогранников; размер 5,5–13 мкм, рис. 9. зерна продукта реакции cu2moo5 имеют вытянутую форму, размер их варьируется от 2 до 5 мкм в ширину и от 8 до 20 мкм в длину, рис. 10. таким образом, в данной системе зерна продукта и подложки довольно близки по размерам, но отличаются формой. система mn2o3 -moo3 зерна подложки mn2o3 имеют округлую форму, их средний размер 2,5 мкм, рис. 11. зерна продукта реакции mnmoo4 также имеют округлую форму, но средний размер их (10 мкм) приблизительно в 4 раза больше, чем размер зерен подложки, рис. 12. таким образом, для двух исследованных систем выявлены коренные отличия в морфологии зерен продукта и  подложки (форма зерен, соотношение размеров зерен подложка/ продукт). этот факт также косвенно свидетельствует о различии механизма реакционной диффузии в исследованных системах. выводы по результатам проделанной работы можно сделать следующие выводы: 1.  установлено, что характер воздействия электрического поля на скорость поверхностного взаимодействия и скорость реакции в целом одинаков для синтеза молибдата меди и различен для синтеза молибдата марганца. 2.  установлено, что понижение давления кислорода приводит к росту скорости взаимодействия как на поверхности, так и в месте контакта реагентов для систем cuo/moo3 и  mn2o3/moo3, что может быть связано с ростом концентрации дефектов типа o xmoo4 с уменьшением давления кислорода. интенсивность воздействия po2 на скорость поверхностного взаимодействия и скорость реакции в целом близка для синтеза молибдата меди и различается для синтеза молибдата марганца. 3.  методом электронной микроскопии исследована морфология подложки и продукта реакции в системах cuo/moo3 и mn2o3/moo3. установлерис. 12. рэм-изображение продукта mnmoo4. рис. 11. рэм-изображение подложки mn2o3 поверхностные реакции с участием оксидов молибдена и вольфрама: влияние внешних факторов 84 № 1 | 2016 chimica techno acta ны различия в форме зерен, а также соотношении размеров зерен продукт/ подложка в исследованных системах. 4.  сделано обоснованное предположение, что основным транспортным потоком при синтезе молибдата меди является поверхностная диффузия, в отличии от синтеза молибдата марганца. 1. neiman a. ya., guseva a. f. new data on mechanism of mass transfer in solid-state reactions i. reactions in an electric field. kinetics and catalysis. 1994;35(ii):188– 194. 2. neiman a. ya., guseva a. f. new data on the mechanism of mass transfer in solidphase reactions: ii. chemical and electrochemical surface phenomena. kinetics and catalysis. 1999;40(i):38–49. 3. neiman a. ya., guseva a. f., trifonova m. v. surface reaction in the course of molibdates and tungstates formation. solid state ionics. 2001;141–142:321–329. 4. neiman a. ya., guseva a. f., trifonova m. v., sukhankina i. v. reactive surface diffusion durin synthesis of molybdates and tungstates: the role of phase constitution of product. russian journal of inorganic chemistry. 2005;50:319–324. 5. neiman a. ya., guseva a. f. electrochemical approach to solid state reactions and interphase phenomena. russian j. of electrochemistry. 1993;29(11):1388–1395. 6. neiman a. ya., fedorova l. m., afanasyev a. a. point defect interaction in pbmoo4. inorgan. materials. 1986;22(5):811–815 7. neiman a. ya. cooperative transport in oxides: diffusion and migration processes involving mo (vi), w (vi), v (v) and nb (v). solid state ionics. 1996;83:263-273. гусева а. ф., трифонова м. в., пестерева н. н. phase equilibria in the yfeo3 – yсoo3 system in air chimica techno acta article published by ural federal university 2021, vol. 8(1), № 20218108 journal homepage: chimicatechnoacta.ru doi: 10.15826/chimtech.2021.8.1.08 1 of 7 phase equilibria in the yfeo3 – yсoo3 system in air a.v. bryuzgina, a.s. urusova * , i.l. ivanov, v.a. cherepanov institute of natural science and mathematics, ural federal university, lenin av. 51, yekaterinburg, 620000 russia * corresponding author: anastasia.podzorova@urfu.ru this article belongs to the regular issue. © 2021, the authors. this article is published in open access form under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). abstract yfe1-xсоxo3 solid solutions were prepared by glycerol-nitrate technique. the homogeneity range of solid solutions was studied within the temperature range 1173 – 1573 k. a continues series of solid solution below the decomposition temperature of yсоo3, which was shown to be equal to 1266  6 k, begins to narrow at higher temperatures and becomes equal to 0 ≤ x ≤ 0.1 at 1573 k. the phase diagram of the yfeo3 – yсoo3 system in the “t – composition” coordinates was divided into three fields. similar to the parent ternary oxides, all single-phase yfe1-xсоxo3 solid solutions possess orthorhombically distorted perovskite structure (pnma space group). unusual behavior of orthorhombic distortions in yfe1-xсоxo3 with temperature was explained by probable changes in spin state of co 3+ ions. keywords solid solutions perovskite crystal structure phase diagram received: 14.03.2021 revised: 10.04.2021 accepted: 11.04.2021 available online: 13.04.2021 1. introduction yttrium ferrite and yttrium cobaltite with the perovskite structure and their mixed derivates attract much attention due to a set of electrical and magnetic properties [1-12]. although their structural features and some functional properties were widely studied [1-16], there is lack information concerning phase equilibria and homogeneity ranges of yfe1-xсоxo3 solid solutions. it is worth noting that phase equilibria in the y – fe – o system as well as thermodynamic characteristics of ternary oxides inside including yfeo3 were studied in detail [17-21]. also, detailed information available for the fe – co – o system [22-24]. much less information can be found for the y – co – o system and the thermal stability of ycoo3 [16, 25]. thus, the aim of present work was determination of homogeneity ranges of yfe1-xсоxo3 solid solutions as a function of temperature in air and establishing of phase equilibria in the yfeo3 – yсoo3 system. 2. experimental the samples were prepared via the glycerol-nitrate technique. the starting materials — y2o3, metallic co, fec2o4·2h2o — were dissolved in nitric acid and then glycerol was added. metallic cobalt was prepared from co3o4 by reduction in hydrogen flow at 923 k. the solution was carefully heated to dryness. the obtained residue was slowly heated up and annealed at 1173 k for 20 h. final annealing of the samples were performed at required temperatures in air for 96 h with grinding after each 12 h. the samples were quenched to room temperature (rt) by removing them from a furnace and placing them to a cold massive copper plate. phase identification was carried out by means of x-ray powder diffraction (xrd) using a shimadzu xrd 7000 diffractometer (cu kα radiation, 2θ = 20°–90°, 0.02 deg/min, 5 s/point). high temperature xrd measurements were performed using a htk 1200n (anton paar, austria) high temperature chamber installed at the diffractometer. unit cell parameters were calculated using celref 3 software. the structure was refined by full-profile rietveld analysis using fullprof 2017 software. tga measurements were performed using a sta 409 pc instrument (netzsch) within the temperature range of 300 – 1373 k in air. 3. results and discussion first, the parent oxides of the studied system yfeo3 and yсоo3 were prepared and examined. yttrium ferrite quenched from high temperature within the entire range (1173 – 1473 k) or slowly cooled to rt possesses orthorhombically distorted perovskite structure, which is in good agreement with the results reported earlier [1-4]. fig. 1 illustrates xrd patterns of yfeo3 prepared at various conditions and evaluated values of unit cell parameters, as an example. the xrd pattern refined by the rietveld method and structural model of yfeo3 designed http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2021.8.1.08 http://creativecommons.org/licenses/by/4.0/ chimica techno acta 2021, vol. 8(1), № 20218108 article 2 of 7 fig. 1 xrd patterns of yfeo3 quenched from various temperatures in air: (a) 1373 k; (b) 1173 k and (c) slowly cooled to room temperature and unit cell parameters evaluated by the rietveld refinement using the “diamond 3.2” software is shown in fig. 2. single-phase yttrium cobaltite yсоo3 was obtained only at relatively low temperatures 1173 and 1223 k. like ferrite it possesses the orthorhombic structure (sg pnma). the structural parameters of yсоo3 quenched from 1173 and 1223 k refined by the rietveld method are listed in table 1. to preliminarily estimate the decomposition temperature of yсоo3, tga measurements in a dynamic mode with a heating rate of 3.2 k/min were performed. a sharp drop in the mass of the sample was detected at 1300 k (fig. 3). table 1 the structural parameters of yсоo3 quenched from 1173 and 1223 k refined by the rietveld method sg pnma: y(4c)(x; 0.25; z); co(4a)(0; 0; 0); o1(4c)(x; 0.25; z); o2(8d)(x; y; z) т, к 1173 1223 a, å 5.41656(5) 5.41784(5) b 7.36230(7) 7.36195(7) c, å 5.13591(5) 5.13604(5) v, (å) 3 204.811(1) 204.855(3) x(y) 0.4316(2) 0.4315(2) z(y) 0.0183(3) 0.0184(3) x(o1) 0.5287(1) 0.5285(2) z(o1) 0.5956(2) 0.5972(1) x(o2) 0.2002(1) 0.1988(1) y(o2) 0.0487(8) 0.0487(8) z(o2) 0.3051(2) 0.3047(1) d(y)–(o1), å 2.234(8) 2.227(7) d(y)–(o2), å 2.437(6) 2.439(6) d(y)–(o2), å 2.266(6) 2.263(6) d(y)–(o2), å 2.558(6) 2.557(6) d(co)–(o1), å 1.911(2) 1.913(2) d(co)–(o2), å 1.939(6) 1.933(6) d(co)–(o2), å 1.941(7) 1.949(6) rp, % 10.7 13.2 rwp, % 12.3 15.5 rexp, % 9.18 11.3 rbr, % 3.58 3.10 rf, % 6.85 3.11 χ 2 1.783 1.877 fig. 2 xrd pattern refined by the rietveld method and structural model of yfeo3 along the b axis designed using the “diamond 3.2” software. to refine the decomposition temperature in tga measurements, a static mode was used. the following protocol was used: a single-phase sample was heated at a rate of 1 k/min to 1110 k and equilibrated at this temperature for 8 h. then the temperature was increased in a step of 20 k and the sample was kept at a fixed temperature until a constant mass was established. no significant mass changes were detected at t  1260 k. the next step to 1280 k results in a dramatic weight loss. xrd analysis of the sample quenched after annealing at 1273 k, which was originally a single-phase yсоo3, showed the presence of significant amounts of yttrium oxide and cobalt oxide (ii) as secondary phases (fig. 4). it should be mentioned that small amount of co3o4 forms due to partial oxidation of coo while cooling since latter is thermodynamic stable form of cobalt oxide at 1273 k in air. thus, one can conclude that yсоo3 decomposes according the reaction yсоo3 = ½ y2o3 + coo + ¼ o2 (1) within the range 1260 < tdec, k < 1273. this allows us to evaluate tdec (ycoo3) = 1266  6 k. fig. 3 tga curve for single-phase yсоo3 in air measured in a dynamic mode with a heating rate of 3.2 k/min chimica techno acta 2021, vol. 8(1), № 20218108 article 3 of 7 fig. 4 xrd patterns of the samples with nominal composition of ycoo3, fired and quenched from various temperatures in air: (a) 1373 k; (b) 1323 k; (c) 1273 k; (d) 1223 k; (e) 1173 k. prolonged annealing of the sample with nominal composition corresponding to ycoo3 at 1373 k reveals coexisting of two binary simple oxides y2o3 and coo. since yсоo3 is only stable below 1266 k, it is likely that a continuous series of yfe1-xcoxo3 solid solutions cannot be obtained at higher temperatures. indeed, continuous series of yfe1-xcoxo3 solid solutions in the range of 0  x  1 was obtained at 1173 k. the homogeneity range at 1273 k was evaluated as 0  x  0.9. the sample with x=0.95 contained together with perovskite phase also y2o3 and enriched by cobalt fe1-ycoyo with the rock salt structure (fig. 5). further increase of temperature leads to a decrease in co content in the limiting yfe1-xcoxo3 solid solution (table 2). table 2 the homogeneity range value for the yfe1-xcoxo3 solid solutions at various temperatures т, k homogeneity range т, k homogeneity range 1173 0x1 1373 0x0.45 1273 0x0.9 1423 0x0.3 1323 0x0.68 1473 0x0.2 fig. 5 xrd patterns for yfe1-xcoxo3 (x=0.9, 0.95) equilibrated at 1273 к and quenched to rt thermal decomposition of co-saturated solid solution with the temperature increase can be shown by following reaction: yfe1-x’cox’o3  yfe1-x’’cox’’o3 + co1-y’fey’o +y2o3 + zo2 (2) were x’ > x’’ and y’ corresponds to the fe-saturated solid solution at a fixed temperature. it is worth noting that the process described by scheme (2) differs significantly from the one occurs according to equation (1). the latter corresponds to a nonvariant thermodynamic equilibrium, when all participating phases coexist at fixed t and po2. in contrast, scheme (2) represents the situation when cosaturated single-phase yfe1-x’cox’o3 solid solutions in the left-hand side exist at t’, and an increase of temperature to t’’ = t’ + t causes a depletion of cobalt in solid solution and displacement of its composition yfe1-x’’cox’’o3 as well as appearance of two secondary phases, namely, y2o3 and co1-y’fey’o. the left-hand side and the right-hand side in the scheme (2) represent the phase composition in the system at different temperatures, t’ and t’’=t’+t, respectively. thus, scheme (2) describes nonequilibrium process that occurs due to the change in thermodynamic parameter, in this case it is temperature. a similar process can take place at fixed temperature due to the decrease in po2. based on the results of phase composition of all studied samples the “t-composition” phase diagram of the yfeo3 – yсoo3 system in air was drawn (fig. 6). all single-phase yfe1-xcoxo3 solid solutions quenched from all studied temperatures possess the orthorhombic structure, like parent ternary oxides. the influence of temperature on the crystal structure of yfe1-xcoxo3 (x = 0.35 and 0.45) was studied by in situ high temperature (ht) xrd measurements. the structural parameters of yfe1-xcoxo3 (x = 0.35 and 0.45) at various temperatures refined by the rietveld method are listed in tables 3 and 4. temperature dependencies of the unit cell parameters and unit cell volume demonstrate visible non-linearity (fig. 7). as a rule, the distortions of crystal structure tend to decrease with the temperature rise; however, the ortho fig. 6 phase diagram of the yfeo3 – yсoo3 system in air chimica techno acta 2021, vol. 8(1), № 20218108 article 4 of 7 table 3 the structural parameters of yfe0.65со0.35o3 at various temperatures refined by the rietveld method using ht-xrd measurements sg pnma : y(4c)(x; 0.25; z); fe/co(4a)(0; 0; 0); o1(4c)(x; 0.25; z); o2(8d)(x; y; z) т, k 298 473 623 673 973 1273 1373 a, å 5.53089(6) 5.53716(4) 5.54493(4) 5.54861(4) 5.58349(4) 5.61551(6) 5.62316(5) b, å 7.51120(8) 7.52574(5) 7.54017(6) 7.54575(6) 7.59046(6) 7.63524(8) 7.64818(6) c, å 5.23159(6) 5.24225(4) 5.25323(4) 5.25755(4) 5.29060(4) 5.32228(6) 5.33169(4) v, (å) 3 217.339(4) 218.451(3) 219.636(3) 220.125(3) 224.222(3) 228.197(4) 229.300(3) x(y1) 0.4316(2) 0.4324(2) 0.4332(2) 0.4330(2) 0.4339(2) 0.4347(2) 0.4350(2) z(y1) 0.0181(3) 0.0182(3) 0.0174(3) 0.0174(3) 0.0172(3) 0.0165(3) 0.0163(3) x(o1) 0.534(1) 0.533(1) 0.532 (1) 0.531(1) 0.533(1) 0.531(2) 0.5329(2) z(o1) 0.603 (1) 0.605(2) 0.604(2) 0.605(2) 0.605(2) 0.606(2) 0.606(2) x(o2) 0.196(1) 0.195(1) 0.195(1) 0.194(1) 0.193(1) 0.192(1) 0.192(1) y(o2) 0.054(7) 0.053(7) 0.053(7) 0.053(7) 0.055(7) 0.054(7) 0.054(7) z(o2) 0.307(1) 0.306(1) 0.307(1) 0.309(9) 0.309(1) 0.308(1) 0.307(1) d(y)–(o1), å 2.287(7) 2.307(7) 2.314(7) 2.323(7) 2.331(7) 2.360(8) 2.371(8) d(y)–(o2), å 2.479(5) 2.490(5) 2.503(5) 2.512(6) 2.529(6) 2.553(6) 2.557(6) d(y)–(o2), å 2.270(5) 2.271(5) 2.272(6) 2.267(6) 2.268(6) 2.282(6) 2.287(6) d(y)–(o2), å 2.633(5) 2.634(5) 2.635(5) 2.633(5) 2.657(6) 2.666(6) 2.672(6) d(fe/co)–(o1), å 1.963(2) 1.969(2) 1.971(2) 1.973(2) 1.985(2) 1.997(2) 2.002(3) d(fe/co)–(o2), å 1.980(5) 1.976(5) 1.982(5) 1.987(5) 2.004(6) 2.003(6) 2.004(6) d(fe/co)–(o2), å 2.002(5) 2.010(5) 2.012(6) 2.016(5) 2.030(6) 2.052(6) 2.056(6) (fe/co)–(o1)–(fe/co),° 146.09(3) 146.25(2) 146.07(7) 146.00(1) 145.92(3) 145.8(2) 145.61(7) (fe/co)–(o2)–(fe/co),° 145.91(6) 145.62(2) 145.92(2) 145.47(9) 144.92(6) 145.15(4) 145.25(7) rp, % 11.8 12.2 12.5 12.9 13.4 13.8 14.0 rwp, % 15.0 15.2 15.2 15.7 15.8 16.0 16.2 rexp, % 10.6 10.6 10.7 10.7 11.0 11.3 11.4 rbr, % 4.25 4.83 4.98 4.91 5.01 5.38 5.09 rf, % 3.43 3.87 4.05 3.89 4.26 4.80 4.91 χ 2 1.985 2.057 2.036 2.148 2.043 2.002 2.019 table 4 the structural parameters of yfe0.55со0.45o3 at various temperatures refined by the rietveld method using ht-xrd measurements sg pnma : y(4c)(x; 0.25; z); fe/co(4a)(0; 0; 0); o1(4c)(x; 0.25; z); o2(8d)(x; y; z) т, k 298 623 723 873 1223 1373 a, å 5.51229(9) 5.52600(9) 5.53528(9) 5.55559(9) 5.60219(9) 5.61552(9) b, å 7.48536(13) 7.51456(13) 7.52654(13) 7.54977(13) 7.60614(13) 7.62717(13) c, å 5.21595(9) 5.23834(9) 5.24821(9) 5.26589(9) 5.30639(9) 5.32121(8) v, (å) 3 215.218(2) 217.524(4) 218.648(7) 220.869(6) 226.111(7) 227.910(7) x(y1) 0.4324(3) 0.4343(3) 0.4343(3) 0.4345(3) 0.4349(3) 0.4356(3) z(y1) 0.0178(4) 0.0170(4) 0.0168(5) 0.0166(4) 0.0164(5) 0.0158(5) x(o1) 0.5328(18) 0.5319(18) 0.5304(18) 0.5319(18) 0.5332(18) 0.5340(19) z(o1) 0.6004(19) 0.5999(20) 0.5984(20) 0.6031(20) 0.6030(20) 0.602(2) x(o2) 0.1935(15) 0.1929(15) 0.1926(15) 0.1952(15) 0.1925(15) 0.1948(16) y(o2) 0.0547(10) 0.0530(9) 0.0524(10) 0.0527(10) 0.0538(10) 0.0541(10) z(o2) 0.3050(15) 0.3045(15) 0.3062(15) 0.3039(15) 0.3070(15) 0.3053(16) d(y)–(o1), å 2.25(1) 2.25 (1) 2.26(1) 2.24 (1) 2.26(1) 2.27(1) d(y)–(o1), å 2.287(1) 2.306(1) 2.316 (1) 2.324(1) 2.338(1) 2.341(2) d(y)–(o2), å 2.4729(8) 2.4979(8) 2.512(8) 2.505(8) 2.540(8) 2.537(9) d(y)–(o2), å 2.250(8) 2.260(8) 2.263(8) 2.284(8) 2.278(8) 2.293(9) d(y)–(o2), å 2.629(8) 2.630(7) 2.626(8) 2.645(8) 2.662(8) 2.678(8) d(fe/co)–(o1), å 1.952(3) 1.958(3) 1.959(3) 1.972(3) 1.987(3) 1.992(3) d(fe/co)–(o2), å 1.959(8) 1.959(8) 1.968(8) 1.974(8) 1.996(8) 2.002(9) d(fe/co)–(o2), å 2.014 (8) 2.022(8) 2.021(8) 2.023(8) 2.046(8) 2.0447(9) (fe/co)–(o1)– (fe/co),° 147.017(6) 147.24(2) 147.798(6) 146.33(2) 146.222(6) 146.418(6) (fe/co)–(o2)– (fe/co),° 145.537(6) 145.995(6) 145.861(6) 146.534(6) 145.349(6) 145.868(6) rp, % 15.3 15.4 15.4 15.6 15.8 16.7 rwp, % 18.2 18.2 18.3 18.3 18.5 19.4 rexp, % 11.7 11.5 11.5 11.6 11.9 12.3 rbr, % 4.38 4.56 4.53 4.76 5.19 5.36 rf, % 3.53 3.92 3.81 4.53 4.99 5.30 χ 2 2.429 2.503 2.528 2.471 2.398 2.481 chimica techno acta 2021, vol. 8(1), № 20218108 article 5 of 7 fig. 7 the unit cell parameters and unit cell volume of yfe1-xcoxo3 (x=0.35 and 0.45) versus temperature rhombic distortion parameters calculated by the formula [26, 27]: 𝐷𝑜𝑟𝑡ℎ = 1 3 ∑ | 𝑎𝑖 − �̅� �̅� | × 100% 3 𝑖=1 (3) where 𝐷𝑜𝑟𝑡ℎ is the orthorhombic distortion parameter, %; 1 = a; 2 = b; 3 = c/√2 and �̅� = (a×b×c/√2) 1/3 , exhibit visible anomalies within 600 – 1200 k (fig. 8). such behavior could not be explained by the change in oxidation states of 3d metals. tga analysis of yfe1-xcoxo3 (x = 0.35 and 0.45) reveals tiny mass changes while heating, which means that both oxides possess almost stoichiometric oxygen content within entire temperature range. thus, the oxidation state of 3d atoms is equal to 3+ and remains unchanged with the increase of temperature. another reason that can induce structural transformations can be changes in spin states. such temperature-induced changes in the spin state of co 3+ ion in lncoo3 perovskites were reported by raccach and goodenough [28] and in later publications [7, 29-31]. low-spin (t 6 2g) state can transforms into intermediate-spin (t 5 2ge 1 g) state and finally into high-spin (t 4 2ge 2 g) state. although the possibility of spin state changes for fе 3+ ion is still questionable and its highspin state is more favorable [2, 5], possible spin-state transition of co 3+ ion can cause the observed anomalies. however, this needs to be checked by further independent experiments. it is worth noting that co substitution for fe reveals much stronger effect on changes in the unit cell volume due to the size effect (𝑟fe3+(hs) vi = 0.645 å, 𝑟co3+(ls) vi = 0.545 å, 𝑟co3+(hs) vi = 0.61 å [32]) rather than temperature. the decrease in the unit cell volume of yfe1-xcoxo3 with the cobalt content (fig. 9) is much more significant in comparison with the temperature dependence. fig. 8 the pseudo-cubic unit cell parameter (ap) and the orthorhombic distortion parameter (d) for yfe1-xcoxo3 (x = 0.35 and 0.45) versus temperature fig. 9 the unit cell volume of yfe1-xcoxo3 versus co content (x) chimica techno acta 2021, vol. 8(1), № 20218108 article 6 of 7 4. conclusions the homogeneity range and crystal structure of yfe1-xсоxo3 solid solution have been studied within the entire composition range (0≤x≤1) in 1173 – 1573 k temperature range. continuous series of yfe1-xcoxo3 solid solutions in air can be obtained only below decomposition temperature of ycoo3, which was evaluated equal to 1266  6 k. further temperature increase leads to a decrease of yfe1-xcoxo3 homogeneity range which is determined to be 0≤x≤0.1 at 1573 k. phase diagram of the yfeo3 – yсoo3 system in air comprise of 3 phase fields. partial substitution of co for fe has not changed the orthorhombic perovskite structure. possible change in the spin state of co 3+ ions is a presumable reason for the unusual behavior of orthorhombic distortions in yfe1-xсоxo3 (x = 0.35 and 0.45) with temperature. acknowledgments this work was supported in parts by the ministry of science and higher education of russian federation (№ аааа-а20-120061990010-7) and a.v.b. was supported with a stipend for young scientists and phd students from the president of russian federation (№ sp-3689.2019.1). references 1. rosales-gonzález o, sánchez-de jesús f, cortés-escobedo ca, bolarín-miró am. crystal structure and multiferroic behavior of perovskite yfeo3. ceram int. 2018; 4:15298-303. doi:10.1016/j.ceramint.2018.05.175 2. cheng zx, shen h, xu jy, liu p, zhang sj. magnetocapacitance effect in nonmultiferroic yfeo3 single crystal. j appl phys. 2012;111:034103-1–5. doi:10.1063/1.3681294 3. zhang y, yang j, xu j, gao q, hong z. controllable synthesis of hexagonal and orthorhombic 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academy of sciences, 20 academicheskaya st., yekaterinburg, 620137, russia * corresponding author: jelen456@yandex.ru this article belongs to the regular issue. © 2021, the authors. this article is published in open access form under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). abstract the electrophoretic deposition (epd) of coatings and bulk compacts in a wide range of thicknesses (from 23 to 1800 μm) from stable suspensions of a magnesium-doped aluminum oxide nanopowder with subsequent sintering of samples into dense ceramics was studied. the initial nanopowder was obtained by the method of electric explosion of an al-mg alloy wire with a mg content of 1.3 wt. %. the study of the dispersion composition, kinetics of deaggregation under the ultrasonic treatment and zeta potential in the nanopowder-based suspensions was carried out. it was shown that a nearly linear increase in the deposited mass and thickness of epd deposits occurred at a constant voltage of 20 v and an average deposition current of approximately 40 μa when the deposition time was varied from 1 to 180 min. drying of the coatings with a thickness of less than 35 μm led to the formation of a net of small cracks, while drying of the bulk compacts with a thickness of more than 1 mm occurred without cracking. the ceramic bulk sample with a thickness of 1.2 mm and the density of 98.7% td was successfully obtained by sintering at 1650 °c for 4 h. it was characterized by a dense grain structure with an average grain size of 5 μm and the presence of a small number of closed pores less than 1 μm in size. sintering of ceramics was revealed to be accompanied by the formation of a mgal2o4 crystalline spinel phase, localized mainly at grain boundaries. keywords aluminum oxide nanopowder stable suspension zeta potential electrophoretic deposition received: 06.04.2021 revised: 02.05.2021 accepted: 03.05.2021 available online: 07.05.2021 1. introduction corundum materials are widely used in many applications as high-frequency and high-voltage insulators, current inputs, resistance substrates and etc. thus, the development of methods for the formation of dense corundum ceramics both in the form of coatings as well as bulk compacts is a relevant and challenging task of ceramic technology. the known methods of the formation of al2o3based coatings are sol-gel method [1], chemical vapor deposition [2, 3], pulsed laser deposition [4, 5], and electrophoretic deposition (epd) [6-8]. the slip casting is known as one of the ceramic methods for producing corundum ceramics [9]. various pressing technologies such as isostatic and magnetic-pulse pressing were applied to compact powdered materials [10-12]. however, the features of these methods include the difficulty to obtain uniform density and the presence of internal stresses in the material [13]. the epd method is based on the formation of a deposited layer on an electrode from a liquid suspension under the action of an external electric field [14-17]. it is simple and cost-effective, and is characterized by high deposition rates. the advantages of the epd method also include flexibility in regulating the thickness of the formed deposits by varying the deposition time or electrical deposition modes. in this case, the kinetics of the deposited mass growth depending on time, the formation of cracks in the deposited layer during drying, the ratio between the achieved deposit’s density before and after sintering are http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2021.8.2.06 mailto:jelen456@yandex.ru http://creativecommons.org/licenses/by/4.0/ https://orcid.org/0000-0002-5637-7451 https://orcid.org/0000-0001-8176-9417 chimica techno acta 2021, vol. 8(2), № 20218206 article 2 of 6 the important issues to be addressed. the features of the epd method include the difficulty of achieving a high density of the formed deposit [18] and the formation of cracks during the deposit drying [19], which is influenced by many factors: the particle size distribution in the suspension, the thickness of coatings, drying conditions, the addition of binders and plasticizers. santanach carreras et al. [20] revealed the existence of a critical thickness of the coating, above which cracks may appear during its drying. the use of nanopowders is relevant in ceramic technology since it allows one to reduce the sintering temperature of ceramics [21]. however, in the epd technology, it is necessary to take into account the necessity of obtaining stable suspensions of nanoparticles suitable for the deposition and, thus, to find a way to diminish nanoparticle aggregation in a liquid dispersion medium [22]. the use of weakly aggregated nanopowders with a spherical shape of particles obtained by the method of electric explosion of wires (eew) [23, 24] makes it possible to avoid the use of dispersants and charging agents due to the spontaneous formation of a high zeta potential on the nanoparticles in the suspension [25]. however, during the epd formation of the compacts, the use of suspensions based on nanopowders during the epd formation of the compacts can be accompanied by a decrease in their density compared to those obtained using suspensions of submicron powders [18]. it is known that the addition of a small amount of mg to an oxide ceramic accelerates its sintering due to diffusion processes at the grain boundaries and makes it possible to achieve a high density of the sintered samples [2628]. in [28], the bulk ceramics of 98.5–99.2% of theoretical density (td) were obtained by the epd method from the suspensions of commercial submicron (330 and 470 nm) al2o3 powders with an addition of 0.05 wt. % mgo. the aim of this work was to study the conditions for obtaining epd deposits in a wide range of thicknesses (from 23 to 1800 μm) from stable suspensions of eew nanopowder of mg-doped al2o3 (22 nm) with subsequent sintering of samples into dense ceramics. the preparation of suspensions without the introduction of dispersants and binders was identified in this study as a necessary condition to obtain the epd deposits with high green densities (the density of as-obtained deposits). the developed technology allowed obtaining the bulk ceramics of high quality with the density of 98.7% td. 2. experimental an initial mg-doped al2o3 nanopowder was obtained by the eew method from an al-mg alloy wire with a mg content of 1.3 wt. % as described elsewhere [23, 29]. the morphology of aluminum oxide nanoparticles was studied using a jeol jem 2100 transmission electron microscope (tem) (jeol, tokyo, japan). x-ray phase analysis was carried out on a d8 discover diffractometer (bruker uk ltd, durham, uk) in a copper radiation with a graphite monochromator on a diffracted beam. the processing of the xrd data was carried out using the topas-3 program. the specific surface area was determined by the volumetric version of the bet method by a low-temperature equilibrium sorption of nitrogen vapor from a mixture with helium using a micromeritics tristar 3000 device (micromeritics instrument corporation, norcross, usa). the initial mg-doped al2o3 nanopowder was used for the preparation of suspensions for the epd in isopropanol (high purity grade). ultrasonic treatment of the suspensions was performed using an uzv-13/150-tn ultrasonic bath (reltek, yekaterinburg, russia) for 125 min. removal of large aggregates preserved in the suspension after the ultrasound processing was carried out by centrifugation using a hermle z383 centrifuge at a speed of 6000 rpm for 3 min. the electrokinetic zeta potential and ph in suspensions were measured by the electroacoustic method using a dt-300 analyzer (dispersion technology, ny, usa). particle size distribution in suspensions was obtained by dynamic light scattering (dls) using a zetaplus particle size analyzer (brookhaven instruments corporation, ny, usa). all measurements in suspensions were carried out under isothermal conditions in air at 25 c. electrophoretic deposition was performed in a constant voltage mode in a cell with a vertical arrangement of electrodes for the epd of coatings and with a horizontal arrangement of electrodes for the epd of compacts. an aluminum foil disk of 12 mm in diameter served as an electrode (cathode) for the deposition, the counter electrode (anode) was a stainless steel disk of the same diameter, the distance between the electrodes was 10 mm. during the epd, the voltage on the electrodes was set at 20 v; the deposition time varied from 1 to 180 min. the suspension was pumped from the bottom of the cell to its upper part for the deposition. the resulting deposits were dried on the electrode for several days in a desiccator with a small amount of isopropyl alcohol. the thickness of the dried coatings and bulk compacts was in a range of 23–1800 µm. the morphology of the dried epd deposits was examined using an st-vs-520 (russia) optical microscope. the bulk compacts were sintered in air at a temperature of 1650 °c for 4 h using a nabertherm lht-04/18 oven (nabertherm gmbh, lilienthal, germany). study of the microstructure of the sintered bulk samples and the edx analysis were performed using a tescan mira 3 lmu field-emission electron microscope (tescan, brno, czech republic) equipped with an inca energy 350 microanalysis system (oxford instruments, abingdon, uk). the deposition of conductive carbon coatings to improve the recording quality (thickness <10 nm) was carried out using a q150t es system (quorum technologies ltd., east sussex, uk). the density of the sintered bulk ceramic samples was determined by the method of hydrostatic weighing. chimica techno acta 2021, vol. 8(2), № 20218206 article 3 of 6 3. results and discussion 3.1. preparation and study of the dispersion composition and electrokinetic properties of the suspensions in agreement with the tem data, the particles of the initial mg-doped al2o3 nanopowder were of spherical shape (fig. 1a). the particle size distribution (fig. 1b) is characterized by a lognormal function: 𝑓(𝐷) = 1 𝐷𝜎√2𝜋 𝑒 − (ln𝐷−ln𝜇)2 2𝜎2 (1) where d particle diameter, μ mean value of the distribution,  dispersion of the normal distribution of the logarithm of diameter. the parameters’ values are μ = 19.0 nm and  = 0.632. according to the distribution data (eq. 1), the average diameter of nanoparticles was 22 nm. the specific surface of the nanopowder (𝑆bet) was determined to be equal to 40 m 2 /g. the analysis of the xrd data showed that the nanopowder contained four crystalline phases: 1) -al2o3 (68 wt. %) of an orthorhombic syngony (sp. gr. p222) with the unit cell parameters а = 7.934 å, b = 7.956 å, c = 11.711 å with a coherent scattering region (csr) value of (18 ± 2) nm; 2) -al2o3 (31.3 wt. %) of a cubic structure (sp. gr. fd3̅m) with the unit cell parameter а = (7.950 ± 0.010) å and csr = (26 ± 2) nm; 3) -al2o3 (0.4 wt. %) of a rhombohedral syngony (sp. gr. r3̅c) with the unit cell parameters a = (4.764 ± 0.004) å, c = (12.99 ± 0.02) å; 4) metallic al (0.3 wt. %) of a cubic structure (sp. gr. fm3̅m), a = (4.054 ± 0.004) å. to obtain a stable suspension of nanoparticles, isopropanol was used as a dispersion medium. the initial suspension with a concentration of 70 g/l was prepared from an accurate weighed portion of the nanopowder and then subjected to the ultrasonic treatment (ust). after the ust, the dispersion characteristics and fractional composition of particle aggregates in the suspensions were evaluated. fig. 2a shows the dependence of the effective hydrodynamic diameter of the aggregates (deff) in the suspension as a function of the ust time (with continuous cooling of the suspension). as derived from the data presented in fig. 2a, under the ust the size of aggregates in the nanopowder suspension significantly decreases from 410 nm to 250 nm. the large aggregates remaining after the ust were removed by centrifugation. the fractional composition of the suspension after the ust (25 and 125 min) and centrifugation is shown in fig. 2b. in accordance with the fractional composition data, in the initial suspension of the nanopowder (ust during 5 min), the presence of three fractions of particles and their aggregates in different weight ratios was established: 90 nm (5 wt. %), 420 nm (87 wt.%), and 2020 nm (8 wt. %). after the ust for 25 min, the size of aggregates of the main fraction was 440 nm (97 wt. %). after the ust for 125 min and centrifugation, the dispersion composition of the suspension was the following: 170 nm (44 wt. %) and 45 nm (56 wt. %). after centrifugation of the initial suspension (70 g/l), the concentration of nanoparticles decreased down to 62 g/l. the values of the electrokinetic zeta potential and ph obtained for the suspension of mg-doped al2o3 nanoparticles are presented in table 1. according to the data, when the initial suspension was centrifuged the zeta potential decreased from +55 to +48 mv with a simultaneous decrease in ph from 8.1 to 7.3, respectively. the obtained high value of the zeta potential ensures the stability of the suspensions and successful and stable implementation of the epd process [30, 31]. table 1 parameters of the suspensions based on mg-doped al2o3 nanoparticles suspension concentration, g/l zeta potential, mv рн initial 70 +55 8.1 after centrifugation 62 +48 7.3 fig. 1 morphology of aluminum oxide nanoparticles (tem images) (a) and numerical particle size distribution calculated using the tem data (b) chimica techno acta 2021, vol. 8(2), № 20218206 article 4 of 6 fig. 2 dependence of the effective hydrodynamic diameter of the aggregates on the ust time (a) and the fractional composition of the suspension with the ust for 25 min and 125 min with centrifugation (b). pw(d) — weight fraction (%) of particles with a diameter d (nm) 3.2. electrophoretic deposition of coatings and bulk compacts the formation of coatings and bulk compacts was carried out from a suspension after centrifugation with a concentration of 62 g/l. the use of centrifugation made it possible to exclude a fraction of large aggregates (fig. 2b), which is favorable for increasing the homogeneity of the resulting deposits. the characteristics of deposits obtained at different deposition times (at a constant voltage of 20 v and an average current of 40 μa) are shown in table 2. it can be seen from the data presented that almost linear dependence of the deposit thickness and weight on the deposition time is observed when obtaining coatings with a thickness of up to 35 μm and during the formation of bulk compacts with a thickness of up to 1800 μm. it was found that the formation of cracks in the deposits during their drying is associated with their thickness. with an increase in thickness of more than 1 mm, a compacted bulk deposit without cracks was formed, while coatings with a thickness of less than 1 mm tended to form a net of cracks, especially with the coating thicknesses less than 35 μm (fig. 3). 3.3. sintering of bulk compacts based on mg-doped al2o3 into dense ceramics crack-free bulk sample am_5 with a green thickness 1.8 mm (the thickness of as-obtained bulk sample deposited and dried) was sintered in air at a temperature of 1650 °c for 4 h. the thickness of the sintered ceramic sample was 1.2 mm. the relative density of the am_5 sample before sintering was about 30% td, while after the sintering it reached 98.7% td. as provided by the xrd data, the sintered am_5 ceramic sample contained two crystalline phases 2.5 wt. % of a mgal2o4 spinel phase (cubic, sp. gr. fd3̅m with a lattice parameter a = (8.080 ± 0.02) å and csr = (110 ± 40) nm) and 97.5 wt. % of a α-al2o3 phase (rhombohedral, sp. gr. r3̅c with lattice parameters a = (4.763 ± 0.002) å, c = (13.011 ± 0.005) å and csr > 200 nm). in the initial nanopowder obtained from the al-mg alloy, a separate magnesium containing crystalline phase, as it was noted in the experimental section, was not registered by the xrd analysis. magnesium was possibly presented in the initial powder in the form of interstitial or substitutional ions in the al2o3 crystal lattice. however, during longterm sintering of the compacted material into dense fig. 3 optical images of coatings and bulk compacts based on mgdoped al2o3: (a) sample am_1; (b) sample am_3; (c) sample am_4; (d) sample am_5 table 2 parameters of coatings and bulk compacts based on mg-doped al2o3 at different deposition times (obtained at a constant voltage of 20 v and an average current of 40 μa) sample deposition time, min weight, mg thickness, µm deposit characteristics am_1 1 3.2 23 net of small cracks am_2 2 5.5 35 net of small cracks am_3 15 25.4 340 uniform areas of the deposit separated by cracks am_4 90 90.6 1000 single cracks in the uniform deposit am_5 180 180.8 1800 uniform deposit without cracks chimica techno acta 2021, vol. 8(2), № 20218206 article 5 of 6 ceramics at a temperature of 1650 °c, the crystalline phase of mgal2o4 spinel was formed localized mainly at the grain boundaries of the ceramics. fig. 4 shows electron images of the surface (a) and in section (b), as well as an integrated map (c) and individual maps of elements (d) for the sintered am_5 ceramic sample (e). sintered ceramics are characterized by a dense grain structure with grain sizes up to 5 μm and a small number of closed pores less than 1 μm in size. the element distribution map (fig. 4d) demonstrates the segregation of magnesium along the grain boundaries. this is in good agreement with the results obtained in [26], where it was demonstrated that doping aluminum oxide with magnesium improves the sinterability of ceramics by accelerating diffusion processes at grain boundaries. 4. conclusions the study of electrophoretic deposition of coatings and bulk compacts from stable suspensions of the nanopowder of aluminum oxide doped with magnesium in an isopropyl alcohol media with subsequent sintering of samples into dense ceramics was carried out. an initial mg-doped al2o3 nanopowder was obtained by the method of electric explosion of an al-mg alloy wire with a mg content of 1.3 wt. %. a study of the dispersion composition and kinetics of ultrasonic disaggregation of aggregates in a nanopowder suspension was carried out. it was shown that the ultrasonic treatment effectively reduced the average hydrodynamic size of aggregates from 410 to 250 nm. a fraction of large aggregates in the suspension was excluded by means of centrifugation, thus, the suspension for the epd contained 170 nm (44%) and 45 nm (56%) fractions. the resulting suspension had a high zeta potential (+48 mv), sufficient to ensure its stability and successful epd. it was shown a nearly linear increase in the deposit weight and thickness observed during the epd process at a constant voltage of 20 v and varying the deposition time from 1 to 180 min. it was found that drying of coatings with a thickness of less than 35 μm led to the formation of a net of small cracks. an increase in the thickness of the epd deposit reduced cracking in such a way that drying of the samples with a thickness of more than 1 mm was not accompanied by their cracking. a criterion was established in concordance with that the thickness of the dried epd deposit should be at least 1 mm to exclude cracks during drying in the case of the implementation of the suspension preparation scheme without the use of dispersants and binders based on eew nanopowders, used in this study. high-quality dense ceramics (1.2 mm) of 98.7% td were obtained by sintering at 1650 с for 4 h. appearance of mgal2o4 spinel phase on the ceramics grain boundary validates increasing sinterability of mg-doped corundum ceramics by accelerating diffusion processes at grain boundaries. fig. 4 electron images of the am_5 bulk ceramic sample sintered at a temperature of 1650 с for 4 h: surface (a) and in section (b), integrated map (c), individual maps of elements (d) and a photo of the sintered ceramic sample (e) acknowledgements the work was partially carried out using the equipment of the shared access centers of the institute of electrophysics (iep ub ras) and institute of high temperature electrochemistry (ihte ub ras), composition of compounds. the authors are grateful to d.sc. prof. a.p. safronov (ural federal university) for valuable advice during the preparation of the manuscript, to the head of the laboratory of impulse processes dr. i.v. beketov and junior researcher mr. a.v. bagazeev (iep ub ras) for the development of the method for producing nanopowders (eew method), and to scientific researcher dr. a.s. farlenkov (ural federal university) for conducting electron microscopic studies. references 1. he j, avnir d, zhang l. sol-gel derived alumina glass: mechanistic study of its structural evolution. acta mater. 2019;174:418–26. doi:10.1016/j.actamat.2019.05.062 2. kelekanjeri vg, carter wb, hampikian jm. deposition of α-alumina via combustion chemical vapor deposition. thin solid films. 2006;515(4):1905–11. doi:10.1016/j.tsf.2006.07.033 https://doi.org/10.1016/j.actamat.2019.05.062 https://doi.org/10.1016/j.tsf.2006.07.033 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belongs to the regular issue. © 2021, the authors. this article is published in open access form under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). abstract the viscosity of cryolite melts of conventional composition naf–alf3–caf2–al2o3 was studied by rotational viscometry using the frs 1600 high-temperature rheometer. the cryolite ratio of the naf–alf3 melt was 2.1, 2.3, and 2.5; the al2o3 content varied from 2 to 6.6, and caf2 – from 0 to 8 wt%. the measurements were carried out in the temperature range from liquidus to 1200 °c. the conditions for the laminar flow of the investigated melts were determined, based on the measurements of the cryolite melts viscosity as a function of the shear rate at a constant temperature. a shear rate of 12 ± 1 s –1 was chosen for studying the viscosity temperature dependence for all samples. the viscosity temperature dependence of cryolite melts is described by a linear equation. the temperature coefficient b in this equation has negative values and varies in the range of (–0.01)–(–0.06) mpa·s/deg. it was found that the viscosity of cryolite melts of conventional composition in the range of operating temperatures of aluminum electrolysis (950–970 °c) varies from 2.5 to 3.7 mpa·s (depending on the composition and temperature). the viscosity of cryolite-alumina melts increases with the rise of alumina content: 1 wt% al2o3 increases the viscosity, on average, by 1%. however, the influence of caf2 is more significant: the addition of 1 wt% caf2 leads to an increase in viscosity by 3%. a decrease in the cr of the melt by 0.1 (in the range of 2.1–2.5) leads to a decrease in the viscosity of cryolite melts by 2.3%. a viscosity regression equation for the cryolite melts of conventional composition as a function of several independent parameters (temperature, cr, caf2 and al2o3 content) is obtained by the multivariable approximation of experimental data. the equation satisfactorily (within 1.5%) describes the viscosity of conventional industrial electrolytes and can be used for estimation of their viscosity. keywords molten cryolite alumina calcium fluoride viscosity rotary method received: 02.07.2021 revised: 16.08.2021 accepted: 13.09.2021 available online: 21.09.2021 1. introduction according to the international aluminum institute, the worldwide aluminum production amounted 65.296 million tons in 2020, of which 3.72 million tons were produced in russia. nonetheless, the classic hall–héroult process for producing aluminum is more than 140 years old. it is comprised on the electrolysis of dissolved aluminum oxide (alumina) in molten cryolite. the melting point of alumina is 2044 °c, therefore, in order to obtain primary aluminum, the alumina has to be dissolved in sodium cryolite, whereas electrolysis is carried out at 950–970 °c. the conventional electrolyte is composed on the base of sodium cryolite (na3alf6), besides the additions of alf3, caf2, mgf2 are added [1]. these electrolytes possess a high solubility of alumina [2]. the electrolyte is characterized by such parameter as the cryolite ratio (cr), expressed by the molar ratio of sodium fluoride to aluminum fluoride. the sodium cryolite has the cr = 3, and the cr of industrial electrolytes can vary from 2.1 to 2.7 [3]. http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2021.8.3.06 http://creativecommons.org/licenses/by/4.0/ https://orcid.org/0000-0001-5451-2915 chimica techno acta 2021, vol. 8(3), № 20218306 article 2 of 6 one of the main parameters defining the electrolysis process is the current efficiency. the current efficiency during electrolysis is influenced by many factors: process temperature, pole-to-pole distance, current density, composition and physicochemical properties of the electrolyte, cell design, etc. one of the most important characteristics of molten cryolite-alumina electrolytes, which determine the processes of mass and heat transfer in an aluminum cell, is viscosity. it also determines the following hydrodynamic processes: electrolyte circulation, rate of alumina dissolution, flotation and sedimentation of alumina particles, transfer of dissolved and undissolved alumina in the electrolyte balk, transfer and release of anode gas, nature of chemical and electrode reactions [4, 5]. nowadays, the most reliable and systematic data related to the viscosity of cryolite melts is considered to be the results obtained by torklep and oye in 1980 [6]. they measured the viscosity of cryolite melts in wide ranges of cr (the alf3 content was varied from 5 to 35 mol.%) and temperature by an oscillation method. the viscosity of cryolite melts depending on cr was obtained to be nonlinear. the maximum value (~ 2.3 mpa/s at 1000 °с) accumulated in the melt with cr = 4. abnormal behavior of melts with low cr was detected (random movements of the pendulum, very large differences between periodic viscosity and damping viscosity, irreproducibility of results, etc.). the authors suggest that one of the several possible reasons for the observed behavior of acidic melts is insufficient mixing. in the region of high crs, the difficulties in dissolving of oxide were noted. it was the reason for the increase in the duration of experiments in order to obtain completely reproducible values. the viscosity measurements were carried out from high temperature in every 10–20 degrees, lowering temperature to the expected liquidus point. the frequent overcooling of the cryolite-alumina melts was observed, which led to the fact that measurements of some compositions were conducted in the two-phase region. in cryolite-alumina melts with the al2o3 content up to 4 wt%, the viscosity temperature dependences were almost parallel to the curves obtained in the naf–alf3 binary system, especially for melts with low cr. the inflection point on the binary curve become even more pronounced with an increase in the al2o3 content. authors [6, 7, 8] measured the viscosity of the naf–alf3–al2o3 ternary system depending on cr and al2o3 concentration. it should be noted that some experimental results were presented at temperatures below the liquidus of the corresponding mixtures. this may explain why the measured viscosities of these two-phase samples (consisting of a suspension of some solid particles of aluminum oxide and corundum in the liquid phase) are significantly higher than the calculated viscosities of "hypothetical" liquid (single-phase) samples. in this case, no bends are observed on the curves. the viscosity of cryolite melts containing caf2 were described in articles [8, 9]. the viscosity values obtained by different authors differ significantly. moreover, the comparison of viscosity values is often difficult due to the significantly different multicomponent mixtures of cryolite melts. researchers [5] determined the temperature dependences of density, viscosity, surface and interfacial tension in a system with low cr: 55 mol.% naf + 45 mol.% alf3. the viscosity was measured in the temperature range from 725 to 840 °c, and a quadratic equation for the viscosity temperature dependence was obtained for the cryolite melts of eutectic composition (cr = 1.22). in paper [10] a thermodynamic model was suggested for calculating the viscosity of multicomponent fluoride systems. the authors used the thermochemical program factsage [11]. thus, despite the importance of viscosity for the technological process, the viscosity of cryolite melts of conventional electrolytes has not been properly studied yet. according to various authors, the viscosity of the conventional electrolyte naf–alf3–caf2–al2o3 in the cr range from 1.8 to 2.6 and 945–970 °с varies in the range from 1 to 5 mpa·s [10, 12]. the limited number of studies related to the viscosity of cryolite melts can be explained by the great experimental difficulties associated with the choice of structural materials, due to the aggressiveness of fluoride melts and high measurement temperatures (about 1000 °c), as well as with rather low values of the molten salts viscosity. the purpose of this work was to study the effect of temperature, cryolite ratio, caf2 and al2o3 content on the viscosity of cryolite melts of the conventional composition naf–alf3–caf2–al2o3 with the cr = 2.1–2.5 in a wide temperature range using the rotational viscometry; the focus was also set on the obtaining of the viscosity multiparameter regression equation for the molten conventional electrolytes. 2. experimental 2.1. composition and preparation of melts molten mixtures were prepared from individual substances naf (specifically pure grade), alf3 (highly pure grade), and caf2 (pure grade) (vekton). a weighed amount of components was loaded into a glassy carbon crucible and remelted at 990 °c for 2 hours in a shaft furnace. the prepared mixtures were stored in a closed container. the compositions of the studied samples are presented in table 1. 2.2. rotational viscometry method a liquid is placed in a small gap, necessary for the shear of the medium, between two cylinders: an inner cylinder with a radius r0 and an outer one with a radius ri. chimica techno acta 2021, vol. 8(3), № 20218306 article 3 of 6 table 1 composition of cryolite melts cr naf alf3 caf2, wt% al2o3, wt% wt% mol.% wt% mol.% 2.1 48.7 65.3 46.3 31.1 0 3.0 5.0 3.0 5.0 6.5 8.0 6.5 2.3 50.8 67.2 44.2 29.2 0 2.0 5.0 2.0 5.0 4.0 2.5 52.8 68.9 42.2 27.6 0 2.0 5.0 2.0 5.0 4.0 5.0 6.0 a schematic diagram of a rotating cylindrical viscometer is shown in fig. 1. during measurements, the outer cylinder rotates at a constant rate, while the inner cylinder is given a rotational torque, which is a measure of viscosity. the viscosity (𝜂) is calculated by the following equation: 𝜂 = 1 𝜔 ( 𝑀 4𝜋ℎ ) ( 1 𝑅𝑖 2 − 1 𝑅0 2 ) = 𝑘 𝑀 𝜔 (1) where m is the torque acting on the cylindrical surface, n·m; 𝜔 is the angular velocity, rad/s; h is the depth of immersion of the inner cylinder in a liquid medium, m; ri is the radius of the inner cylinder, m; r0 is the radius of the outer cylinder, m; k – is the constant of the device, rad/m 3 . the parallel plane model, schematically depicted in fig. 2, helps defining both shear stress (𝜏) and shear rate (�̇�) [13]. fig. 1 schematic diagram of a cylindrical viscometer fig. 2 the flow between two parallel planes the force f, applied to the area s located at the interface between the upper plane and the fluid below it, causes a flow in the fluid layer: 𝜏 = 𝐹 𝑆 (2) where 𝜏 is the shear stress, pa (n/m 2 ); f is the force applied to the area s, n; s is the area, m 2 . the shear stress produces a characteristic pattern of layer-by-layer rate distribution in the fluid layer. the maximum flow rate vmax is observed at the interface between the liquid and the moving plane [13]. the flow rate decreases with the distance from the moving plane, and at a distance y from it, at the boundary with the fixed plane, vmin = 0. the laminar flow means that the liquid layers of infinitesimal thickness slide over one another. one laminar layer is displaced relative to the other by some part of the total shear of the entire liquid layer between both planes. the velocity gradient across the gap is called the shear rate, which is mathematically expressed as a differential: �̇� = 𝑑𝜈 𝑑𝑦 , [ m/s m = s −1]. (3) the dynamic viscosity is defined as 𝜂 = 𝜏 �̇� , [ n/m2 s−1 = pa ∙ s]. (4) 2.3. measurement techniques the viscosity measurements of the cryolite melts with different cr and additive concentrations were carried out using an frs 1600 rheometer, the principle of operation of which is based on the rotary method. the studied sample is placed in an outer graphite cylinder (fig. 3). the inner cylinder slowly immerses and rests against the solid sample with a force of 3 n, after which the furnace starts heating. after reaching the liquidus temperature, the rotor begins rotating at a low rate in order to homogenize the melt. the fact that the sample has passed into a single-phase state can be judged by the steady-state values of the viscosity. the viscosity measurements can be performed either at a constant temperature or according to a given program for cooling the melt in a dynamic mode. 3. results and discussion 3.1. selecting the "shear rate" parameter in order to obtain the correct viscosity values, a laminar flow has to be established in the sample. this means that it takes time for the substance to start moving at a rate corresponding to the applied shear stress. in order to determine the conditions for the laminar flow the viscosity of all cryolite samples was measured as a function of the shear rate at a constant temperature. as chimica techno acta 2021, vol. 8(3), № 20218306 article 4 of 6 an example, the dependence of the viscosity of cryolite samples with the cr = 2.5 on the shear rate in logarithmic coordinates is presented in fig 4. the shear rate varies from 2 to 50 s –1 . it is seen in the fig. 4 that at low shear rate (up to 10 s –1 ), a large scatter of points is observed, which is due to the fact that the laminar flow was not established yet. the laminar flow is realized when the viscosity does not depend on the shear rate, that is, in the horizontal section in the shear rate range of 10–16 s –1 . with an increase in the shear rate above 16 s –1 , the viscosity rises sharply, which is associated with incipient turbulence. in order to study the temperature dependence of the viscosity of all samples, a shear rate of 12 ± 1 s –1 was chosen. 3.2. the viscosity temperature dependence of the cryolite melts the viscosity measurements were started at 1020 °c, then the temperature was decreased to a temperature few degrees above liquidus. the cooling rate was 2 °с/ min. the liquidus temperature was calculated using the equation given in [14]. the calculated values of the liquidus temperature are listed in table 2. the viscosity temperature dependence of the cryolite melts with the cr = 2.1 is given in fig. 5. the viscosity temperature dependence of all samples in the temperature range from the liquidus to 1200 °c is described by a linear equation of the type: η = a + bt (5) where a and b are experimental constants. the equations for the viscosity temperature dependence of the cryolite melts are summarized in table 2. for all equations, the coefficient of determination r 2 has a value of at least 0.97. the viscosity of the cryolite samples at the operating temperatures of aluminum electrolysis 950 and 970 °c are given in table 2. as the temperature rises the viscosity of the molten salt decreases. fig. 3 internal and external cylinders and the shaft furnace carbolite stf16/180 the temperature coefficient b in equation (5) has negative values and varies in the range of (–0.01)–(–0.06) mpa·s/deg for all tested samples. thus, the change in temperature has a decisive influence on the change in the viscosity of the electrolyte. 3.3. effect of cr, caf2 and al2o3 content the viscosity temperature dependence of the cryolitealumina melts with different cr is shown in fig. 6. the figure also demonstrates the literature data [6] and [15] on the viscosity of melts, which are the closest to ours in composition and temperature range of measurements. the data diverge quite significantly, although the temperature coefficients are close. it should be noted that due to the complex multicomponent compositions of electrolytes for aluminum production, it is difficult to find completely identical compositions in the references, and no generalizing equations have been found. moreover, the results of works [6] and [15] were obtained by the oscillation method, the disadvantages of which were described above. in addition, data on the density were used to calculate the dynamic viscosity of these compositions, which introduces an additional error in the result. fig. 4 the viscosity of cryolite melts with the cr = 2.5 depending on the shear rate at 1020 °с: – without additives; – 5 wt% caf2; – 5 wt% caf2 and 2 wt% al2o3; – 5 wt% caf2 and 2 wt% al2o3 fig. 5 the viscosity temperature dependence of the cryolite melts with cr = 2.1 and different content of caf2 and al2o3 (wt%): 1 – 0 caf2 + 3 al2o3; 2 – 5 caf2 + 3 al2o3; 3 – 5 caf2 + 6.5 al2o3; 4 – 8 caf2 + 6.5 al2o3 chimica techno acta 2021, vol. 8(3), № 20218306 article 5 of 6 table 2 viscosity (mpa·s) of the cryolite melts of conventional composition № cr caf2, wt% al2o3, wt% a b r 2 η (950 °с) η (970 °с) тliq [14] 1 2.1 0 3.0 9.837 –0.0075 0.985 – 2.56 958 2 5.0 3.0 11.716 –0.009 0.99 3.17 2.99 940 3 5.0 6.5 12.37 –0.0096 0.98 3.25 3.06 931 4 8.0 6.5 14.234 –0.0111 0.99 3.67 3.46 920 5 2.3 0 2.0 10.023 –0.0075 0.97 – 2.67 (980 °с) 975 6 5.0 2.0 9.011 –0.0063 0.97 – 2.90 960 7 5.0 4.0 9.832 –0.007 0.98 3.18 3.04 949 8 2.5 0 2.0 9.506 –0.0069 0.75 – – 990 9 5.0 2.0 9.9867 –0.0072 0.93 – – 978 10 5.0 4.0 10.168 –0.0073 0.96 – 2.97 (980 °с) 965 11 5.0 6.0 10.438 –0.0075 0.97 – 3.115 958 according to our data, the cr alteration by 0.1 changes the viscosity of cryolite-alumina melts in average by 0.1 mpa·s, which is 2.3%. the viscosity of cryolite melts in the temperature range of 950-970 °c varies from 2.5 to 3.7 mpa·s (depending on the composition). it can be concluded, based on the results presented in table 2, that both the caf2 and al2o3 additives effect the cryolite melts viscosity. the viscosity of cryolite-alumina melts rises with increasing alumina content. the addition of 1 wt% al 2o3 increases by 1% the viscosity of conventional electrolyte, on average. calcium fluoride significantly increases the viscosity of cryolite-alumina melts. the addition of 1 wt% caf2, on average, increases the electrolyte viscosity by 3%. considering that caf2 impacts the thermal conductivity of cryolite melts, and acts as a part of the side ledge of the electrolysis bath, that is, plays an important role in the thermal balance of an aluminum cell, its concentration in conventional electrolyte is an important value and requires special control. 3.4. multiparameter equation of the viscosity the general regression equation for the dependence of the conventional cryolite electrolyte viscosity on several parameters was derived by the multivariable data approximation. the data set included the following parameters: temperature, cryolite ratio, calcium fluoride and alumina content. the resulting equation for the viscosity of cryolite melts is the following: 𝜂 = 71.75 − 0.133 ∙ 𝑇 − 8.21 ∙ 10−3 ∙ 𝐶(al2o3) + +0.333 ∙ 𝐶𝑅 + 0.0796 ∙ 𝐶(caf2) − 0.625 ∙ 10 −5 ∙ 𝑇 2 − −2.08 ∙ ( 𝐶(caf2)+𝐶(al2o3) 𝐶(al2o3) ) 1.5 + 8.12 ∙ 10−5 ∙ 𝐶(al2o3) 3; r2 = 0.99 (6) where t is temperature, °с; c(al2o3) and c(caf2) are the content of components, wt%; cr is the cryolite ratio. the equation is valid within the temperature range from liquidus to 1020 °с at cr 2.1–2.5, the caf2 content 0–8 wt%, the al2o3 content 2–6.5 wt%. the equation is valid in the temperature range from liquidus temperature to 1020 °c, in the concentration ranges of cr 2.1–2.5, alumina from 2 to 6.5 wt%, and calcium fluoride from 0 to 8 wt%. a comparison of the experimental and calculated by equation (6) viscosity data for the cryolite melt with cr = 2.3 is shown in fig. 7. fig. 6 the viscosity temperature dependence of the naf–alf3 melt with different cr and al2o3 content (wt%):1 – cr = 2.1, al2o3 = 3; 2 – cr = 2.3, al2o3 = 4; 3 – cr = 2.5, al2o3 = 2; 4 – cr = 2.1 [15]; 5 – cr = 2.3, al2o3 = 4 [6]; 6 – cr = 2.3, al2o3 = 8 [6]; 7 – cr = 2.3, al2o3 = 12 [6] fig. 7 experimental and calculated viscosity for cryolite melts with cr = 2.3. concentration of additives – in wt%: 1 – caf2 = 0, al2o3 = 2; 2 – caf2 = 5, al2o3 = 2; 3 – caf2 = 5, al2o3 = 4; points – experiment, lines – calculation chimica techno acta 2021, vol. 8(3), № 20218306 article 6 of 6 the calculated viscosity is given as solid lines in fig. 4 and the experimental data – as dots. the experimental and calculated values of the viscosity of conventional cryolite electrolyte coincide within 1.5%. conclusions the viscosity of the conventional cryolite melts naf–alf3–caf2–al2o3 in the temperature range of 950–970 °c varies from 2.5 to 3.7 mpa·s (depending on the composition). the viscosity increases with the rise in the content of additives: per addition of 1 wt% al2o3 the viscosity, on average, increases by 1%, while the addition of 1 wt% caf2 increases the melt viscosity by 3%. a decrease in the cr of the melt by 0.1 results in a viscosity decrease (in the range of the cr 2.1–2.5) by 2.3%. the regression equation for estimating viscosity of cryolite melts on several independent parameters, obtained by approximating the experimental data, satisfactorily describes (within 1.5%) the viscosity of conventional electrolytes for aluminum production. references 1. kudryavtseva nt. prikladnaya electrockimiya [applied electrochemistry]. moscow: khimiya; 1975. 552 p. russian. 2. grjotheim k, krohn c, malinovsky m, matiasovsky k, thonstad j. aluminium electrolysis. fundamentals of the hallheroult process. 2nd ed. dusseldorf: aluminium-verlag; 1982. 443 p. 3. borisoglebskiy yuv, galevskiy gv, kulagin nm. metallurgiya alyuminia [metallurgy of aluminum]. novosibirsk: nauka; 1999. 438 p. russian. 4. haupin w. the influence of additives on hall-héroult bath properties. jom. 1991;43:28–34. 5. silny a, chrenkova m, danek v. density, viscosity, surface tension, and interfacial tension in the systems naf(kf) + alf3. j chem eng data. 2004;49:1542–1545. doi:10.1021/je0341965 6. torklep k, oye h. viscosity of naf–alf3–al2o3 melt mixtures. electrochimica acta. 1980;25:229–235. 7. hertzberg t, torklep k, oye h. viscosity of naf–alf3–al2o3 melt mixtures. selecting and fitting models in a complex system. in: essential readings in light metals: volume 2 aluminum reduction technology. bearne g, dupuis m, tarcy g (eds.). cham: springer. 2016. 19–24. 8. votava i, matiasovsky k. measurement of viscosity of fused salts. ii. viscosity of molten binary mixtures on the cryolite basis. chem zvesti. 1973;27(5):582–587. 9. nishihara k, matsumura y, komatsu k, noguchi h. suiyokaishi. 1964;15(6):311–315. 10. robelin c, chartrand p. a viscosity model for the (naf + alf3 + caf2 + al2o3) electrolyte. j chem thermodynamics. 2011;43:764–774. doi:10.1016/j.jct.2010.12.017. 11. bale cw, bélisle e, chartrand p, decterov sa, eriksson g, hack k. calphad: comput. coupling phase diagrams thermochem. 2009;33(2):295–311. doi:10.1016/j.calphad.2016.05.002 12. korenko m, vaskova z, priscak j. density, viscosity and electrical conductivity of the molten cryolite electrolytes (na3alf6–sio2) for solar grade silicon (si-sog) electrowinning. silicon. 2015;7:261–267. doi:10.1007/s12633014-9214-2 13. shramm g. osnovy prakticheskoy reologii i reometrii [fundamentals of practical rheology and rheometry] moscow: koloss; 2003. 312 p. russian. 14. solheim a, rolseth s, skybakmoen e. liquidus temperatures for primary crystallization of cryolite in molten salt systems of interest for aluminum electrolysis. metallurgical and materials transactions b. 1996;27b:739–745. 15. fellner p, silny a. viscosity of sodium cryolite-aluminium fluoride-lithium fluoridemelt mixtures. berichte der bunsengesellschaft für physikalische chemie. 1994;98:935–937. https://doi.org/10.1021/je0341965 https://doi.org/10.1016/j.calphad.2016.05.002 https://doi.org/10.1007/s12633-014-9214-2 https://doi.org/10.1007/s12633-014-9214-2 direct ch/ch functionalization of 1,3-dihydroxy-9h-xanthen-9-one and 1,3-dimethoxy-9h-xanthen-9-one with 1,2,4-triazines and quinazoline 233 d o i: 1 0. 15 82 6/ ch im te ch .2 02 0. 7. 4. 17 sharapov a. d., fatykhov r. f., khalymbadzha i. a., chupakhin o. n. chimica techno acta. 2020. vol. 7, no. 4. p. 233–236. issn 2409–5613 direct ch/ch functionalization of 1,3-dihydroxy-9hxanthen-9-one and 1,3-dimethoxy-9h-xanthen-9-one with 1,2,4-triazines and quinazoline a. d. sharapov*, r. f. fatykhov, i. a. khalymbadzha, o. n. chupakhin ural federal university, 19 mira st., ekaterinburg, 620000, russian federation *email: sharapovaienur27@mail.ru abstract. an electron-deficient series of 1,2,4-triazines and quinazoline have been used for cross-dehydrogenative coupling with 1,3-dihydroxy and 1,3-dimethoxyxanthones to give stable nucleophilic addition products. the adducts and their subsequent oxidation products were obtained in good yields and the structures of the compounds were confirmed by 1h nmr spectroscopy. these results expand the scope of the methodology of nucleophilic substitution of hydrogen with the participation of xanthones with azines. moreover, this methodology makes it possible to obtain new organic materials based on xanthones, which have a wide spectrum of biological activity. keywords: сross-dehydrogenative coupling reactions; 1,2,4-triazines; quinazolines; xanthones received: 20.10.2020. accepted: 19.12.2020. published:30.12.2020. © sharapov a. d., fatykhov r. f., khalymbadzha i. a., chupakhin o. n., 2020 introduction mangiferin is  a  representative of  xanthones. it is  present in  significant quantities in higher plants and in particular in  fruits, stems, leaves, bark and kernels of mangoes. it is a promising antioxidant with many health-related properties such as  antiviral, antineoplastic, antidiabetic, antioxidant, immunomodulatory, hepatoprotective, and analgesic (fig. 1) [1]. o o oh oh ho ho oh ho ho oh o fig. 1. mangiferin as a biologically active representative of xanthones the  transformation of  xanthones with azaheterocyclic compounds may be promising not only for obtaining new biological properties, but also for developing the methodology of nucleophilic substitution of hydrogen in chemistry of natural compounds. reactions of nucleophilic substitution of hydrogen (sn h) in a series of π-deficient heterocycles are one of the types of crossdehydrogenation coupling (cdc) and proceed as the addition of a nucleophile to  an  electrophile with the  formation of  the  so-called σh-adduct, which can subsequently be oxidized to  a  product with a  completely aromatic structure (scheme 1). 234 this direction makes it possible to  abandon the  preliminary functionalization of the initial reagents and to reduce the amount of side reagents-waste [2]. thus, the  present work is  devoted to  the  study of  the  reactivity of  naturally occurring nucleophilic systems such as  xanthones containing two active sites with 1,2,4-triazines and quinazoline. results and discussion 1,3-dihydroxyxanthones contain two different nucleophilic centers in the m-dihydroxybenzene ring (carbon atoms c2 and c4) and in reactions with electrophiles are capable of  producing two isomeric products. we found that when 1,3-dihydroxyxanthone 1 interacts with 1,2,4-triazines a or b and quinazoline c in trifluoroacetic acid a mixture of two σh-adducts 2 and 3 is formed. these are products of nucleophilic attack at the c4 and c2 positions with a ratio of 85:15, respectively, with total yields of 68–72% (scheme 2). the reaction of fully methylated 1,3-dihydroxyxanthone 4 with azines a, b and quinazoline c in the presence of meso3h in  acetic acid at  room temperature proceeds regioselective with the  formation of  с4 σh-adduct 5a-c. the  adducts are subsequently oxidized under the  action of  2,3-dichloro-5,6-dicyano-1,4-benzoquinone (ddq) to nucleophilic substitution of hydrogen products 6a-c in 60–71% yields (scheme 3). thus, using calculations in the “gaussian interface program”, in the case of 1,3-dihydroxanthone, carbon c2 has a more negative charge than carbon atom c4. it can be assumed in connection with the  data obtained that in  the  case of  xanthone 1 there is a competition between orbital and charge control, which leads to the formation of a mixture of products. experimental unless otherwise noted, all commercially available compounds were used without further purification. 1h nmr spectra was recorded at ambient temperature on a  bruker avance ii 400  mhz spectrometer at  400 and 100  mhz, respectively, in  dmso-d6 as a solvent. 1,3-di hydroxyxanthone 1 and 1,3-dimethoxyxantone 4 were prepared according to known procedures [3,4]. typical procedure for synthesis 2a-c and 3a-c. xanthone 1 (1 mmol) and azines a, b or c (1 mmol) were dissolved in tfa (10 ml). the mixture was allowed to stand for 72  h. the  mixture was diluted with nahco3 (5  ml), the precipitate formed was collected by filtration, and recrystallized from benzene. 4-(3-(methylthio)-4,5-dihydro-1,2,4-triazin-5-yl)-1,3-dihydroxy-9h-xanthen-9-one 2a. 1h nmr (dmso-d6): δ = 10.98 (s, 1h, 3-oh), 9.74 (s, 1h, 1-oh), 9.70 (s, 1h, nh), 7.84 (s, 1h, h’5), 7.67–7.77 (m, 4h, benzene), 6,51 (s, 1h, c2h), 5,30 (s, 1h, sp3-ch), 2.49 (s, 1h, ch3). h catalyst oxidizing reagent nu nu-nucleophilic particle h h nu σh-adduct h2onu scheme 1. general scheme of reaction of nucleophilic substitution of hydrogen 235 4-(3,6-diphenyl-4,5-dihydro-1,2,4-triazin-5-yl)-1,3-dihydroxy-9h-xanthen-9-one 2b. 1h nmr (dmso-d6): δ = 11.15 (s, 1h, 3-oh), 9.68 (s, 1h, 1-oh), 7.45–7.65 (m, 4h, ph), 7.43 (2m, 10h, ph) 6,12 (s, 1h, c2h), 3,52 (s, 1h, sp3-ch). 4-(3,4-dihydroquinazolin-4-yl)-1,3-dihydroxy-9h-xanthen-9-one 2c. 1h nmr (dmso-d6): δ = 11.15 (s, 1h, 3-oh), 9.68 (s, 1h, 1-oh), 7.84–7.95 (m, 4h, quin), 7.67–7.77 (m, 4h, ph), 6,12 (s, 1h, c2h), 5,52 (s, 1h, sp3-ch). typical procedure for synthesis of 5a-c. xanthone 4 (1 mmol) and azines a,b or c (1 mmol) were dissolved in acoh (10 ml) and was added meso3h (3 equiv). the mixture was allowed to stand for 72 h. the  mixture was diluted with nahco3 (5  ml), the  precipitate formed was collected by filtration, and recrystallized from benzene. 4-(3-(methylthio)–4,5-dihydro-1,2,4-triazin-5-yl)-1,3-dimetoxy-9h-xanthen-9-one 5a. 1h nmr (dmso-d6): δ = 9.75 (s, 1h, nh), 7.84 (s, 1h, h’5), 7.67–7.77 (m, 4h, ph), 6,51 (s, 1h, c2h), 4,35 (s, 1h, sp3-ch), 2.62 (s, 3h, ch3), 2.49 (s, 3h, ch3). 4-(3,6-diphenyl-4,5-dihydro-1,2,4-triazin-5-yl)-1,3-dimetoxy-9h-xanthen-9-one 5b. 1h nmr (dmso-d6): δ = 7.45–7.65 (2m, 10h, ph), 6,12 (s, 1h, c2h), 3,52 (s, 1h, sp3-ch), 2.74 (s, 3h, ch3), 2.67 (s, 3h, ch3). 4 ( 3 , 4 d i h y d r o q u i n a z o l i n 4-yl)-1,3-dimetoxy-9h-xanthen-9-one 5c. 1h nmr (dmso-d6): δ = 7.84–7.95 (m, 4h, quin), 7.67–7.77 (m, 4h, benzene), meso3h, acoh 4 n h o o ome ome nh o o ome ome a,b or c 5a-c 6a-c n n n n n n n n sme ph ph 6a (60%) 6b (63%) 6c (71%) o o ome ome n ddq dce, reflux scheme 3. interaction of 1,3-dimetoxyxanthone with 1,2,4-triazines and quinazoline o cf3cooh 1 o oh oh n h o o oh oh nh o o oh oh n h a or b or c 2a-c 3a-c n h n n n h n n n nh sme ph ph 2a, 3b (72%) 2b, 3b (68%) 2c, 3c (70%) nh = scheme 2. interaction of 1,3-dihydroxyxanthone with 1,2,4-triazines and quinazoline 236 6,12 (s, 1h, c2h), 4,53 (s, 1h, sp3-ch), 2.76 (s, h, ch3), 2.45 (s, h, ch3). typical procedure for oxidation of 5ac. to a solution of 5a-c (1 mmol) in dce (4 ml) was added ddq (3 equiv). the reaction mixture was heated at 65 °c for 6 h and diluted with dcm (5 ml). the solution was passed through an alumina pad and evaporated yielding pure 6a-c. 4 ( 3 m e t h y l t h i o 1 , 2 , 4 t r i a z i n 5-yl)-1,3-dimetoxy-9h-xanthen-9-one 6a. 1h nmr (dmso-d6): δ = 9.75 (s, 1h, nh), 7.84 (s, 1h, h’5), 7.67–7.77 (m, j = 2.44, 4h, benzene), 6,51 (s, 1h, c2), 2.62 (s, 6h, 2ch3), 2.49 (s, 3h, ch3). 4 ( 3 , 6 d i p h e n y l 1 , 2 , 4 t r i a z i n 5-yl)-1,3-dimetoxy-9h-xanthen-9-one 6b. 1h nmr (dmso-d6): δ = 9.75 (s, 1h, nh), 7.84 (s, 1h, h’5), 7.67–7.77 (m, 4h, ph), 6,51 (s, 1h, c2h), 2.62 (s, 3h, 2ch3), 2.44 (s, 3h, ch3). 4-(3,4-quinazolin-4-yl)-1,3-dimetoxy-9h-xanthen-9-one 6c. 1h nmr (dmso-d6): δ = 9.75 (s, 1h, nh), 7.84 (s, 1h, h’5), 7.67–7.77 (m, 4h, ph), 6,51 (s, 1h, c2h), 2.62 (s, 3h, ch3), 2.44 (s, 3h, ch3). conclusions in summary, we have developed a convenient method introduction of 1,3-dihydroxy and 1,3-dimetoxyxanthones into 1,2,4-triazines and quinazoline based on nucleophilic substitution of hydrogen sn h in these nitrogen-containing heterocycles. the direct reaction ch/ch-functionalization was performed using msoh or tfa as  catalyst for the  addition step, ddq as  oxidant. high yields of  the  coupling products, short reaction times, and mild conditions appear to be the main advantages of this promising synthetic approach. acknowledgements this work was finantionally supported by the presidential council on grants nsh2700.2020.3 and ministry of science and higher education of the russian federation (project feuz-2020-005). references 1. dar a, shaheen f. analgesic and antioxidant activity of mangiferin and its derivatives: the structure activity relationship. biol pharm bull. 2005;28:596–600. doi:10.1248/bpb.28.596 2. khalymbadzha ia, fatykhov rf, chupakhin on. functionalization of aromatic n-heterocycles via c(sp2)–h/c(sp2)–h cdc reactions. in: srivastava a., jana c. (eds) heterocycles via cross dehydrogenative coupling. singapore: springer nature: 2019. pp. 35–75. doi:10.1007/978-981-13-9144-6_2 3. radhakrishna km, prakash n. 1,3-dihydroxy-9h-xanthones and 1,3-dihydroxy-9hxanthenes. new methods of synthesis. j org chem. 1986;51(5):717–23. doi:10.1021/jo00355a024 4. fedunov rg. electronic structures and population dynamics of excited states of xanthione and its derivatives. j chem phys. 2017;494:1–10. doi:10.1016/j.chemphys.2017.07.007 new pathways for the synthesis of indolyl-containing quinazoline trifluoroacetohydrazides 109 d o i: 1 0. 15 82 6/ ch im te ch .2 02 0. 7. 3. 03 yu. a. azev, o. s. koptyaeva, o. s. eltsov, yu. a. yakovleva, t. a. pospelova chimica techno acta. 2020. vol. 7, no. 3. p. 109–115. issn 2409–5613 yu. a. azev,* o. s. koptyaeva, o. s. eltsov, yu. a. yakovleva, t. a. pospelova ural federal university 620002, 19 mira st., ekaterinburg, russian federation *email: azural@yandex.ru new pathways for the synthesis of indolyl‑containing quinazoline trifluoroacetohydrazides the reactions of indole-3-carbaldehyde arylhydrazones with quinazoline in tfa proceed at the 7’ position of the aryl part of the hydrazone molecule to form σ-adducts of quinazoline trifluoroacetohydrazides. keywords: arylhydrazones; indole-3-carboxaldehydes; с,с-coupling; trifluoroacetyl quinazoline hydrazides. received: 19.08.2020. accepted: 28.09.2020. published: 07.10.2020. © yu. a. azev, o. s. koptyaeva, o. s. eltsov, yu. a. yakovleva, t. a. pospelova, 2020 introduction it is  known that the  quinazoline core is part of natural alkaloids [1, 2]. among the quinazoline derivatives, compounds have been identified that have various types of biological activity, including antimicrobial, antiallergic, hypotonic, and antiviral [3]. quinazoline derivatives have been synthesized, which have shown antitumor [4] and radioprotective activity [5]. the  addition of  c-nucleophiles to  3-methylquinazolinium iodide with the formation of 4-substituted 3,4-dihydroquinazolines has been reported [6]. it is also known that unsubstituted quinazoline reacts with indole, 3-methyl-1-phenylpyrazolone-5, 1,3-dimethylbarbituric acid, and pyrogallol in the presence of acid to form 4-σ-adducts [7]. examples of  arylation of quinazoline with 1,3,5-trimethoxybenzene, 1-(4-methoxybenzylidene) — 2-phenylhydrazine, and o-phenylenediamine derivatives have been described [8]. to  create effective drugs based on quinazoline, it is  important to  be able to change substituents (pharmacophoric fragments) in  the  structure of  the  compound. theoretically, this will allow to affect their physicochemical properties (hydrophilicity, lipophilicity, etc.), changing their bioavailability and activity. indole is  part of  tryptophan and its metabolites and this one is  also present in a number of natural alkaloids and antibiotics [9]. indole derivatives exhibit antitumor, antiviral, anti-inflammatory, antidepressant, and other types of activity [10]. this work is a continuation of research related to the development of methods for the synthesis of biologically active derivatives of quinazoline [7]. it should be noted that within the framework of this direction, atomic-economical reactions corresponding to the principles of green chemistry are a particular value [11]. this type of interactions includes nucleophilic reactions of c,ccoupling under conditions of acid catalysis, which proceed without using of metal catalysts and are theoretically waste-free [12,13]. 110 experimental section unless otherwise indicated, all common reagents and solvents were used from commercial suppliers without further purification. the  reaction progress and purity of  the  obtained compounds were controlled by tlc method on sorbfil uv-254 plates, using visualization under uv light. melting points were determined on a stuart smp10 melting point apparatus. 1h, 13c and 19f nmr spectra were acquired on bruker avance-400 and bruker avance neo  — 600 spectrometers in dmso-d6 solutions, using tms as internal reference for 1h and 13c nmr or cfcl3 for 19f nmr. mass-spectra (ei, 70ev) were recorded on microtof-q instrument (bruker daltonics) at 250˚c. the  general method for the  reaction of  indole carbaldehyde 1 with hydrazines 2a-2d 2-methyl-1н-indole-3-carbaldehyde 1 (0.5 mmol) was dissolved in ethanol (3 ml). then this solution was added to mixture of the corresponding hydrazine 2 and hydrochloric acid (0.02 ml) in water (3.0 ml). the resulting mixture was refluxed for 5–10 minutes and then was cooled. the resulting solid was filter off and dried. the crude hydrazones were used directly in the next step without additional purification. spectral data for hydrazones 3a‑c were described earlier [14]. 2‑methyl‑3‑{[2‑(4‑methylphenyl) hydrazono]methyl}‑1h‑indole (3d) yield 55%, mp 185–186°c. 1h nmr spectrum (600 mhz, dmso-d6), δ, ppm: 2.21 s (3h, ch3), 2.48 s (3h, c 2ch3), 6.93 d (2h, j 8.4 hz, ho), 7.02 d (2h, j 8.4 hz, hm), 7.07–7.11 m (2h, h 5 and h6), 7.30 m (1h, h7), 8.12–8.15 m (2h, h1’ and h4), 9.61 br.s (1h, n3’h), 11.19 s (1h, n1h). ms, m/z (irel,%): 263 (m +, 100). 2‑methyl‑3‑[(2‑phenylhydrazinyl) methyl]‑1h‑indole (3e). yield 59%, m. p. 192–193 °c. 1h nmr spectrum (600 mhz, dmso-d6), δ, ppm: 2.49 s (3h, ch3), 6.67 t.t (1h, j 7.3, 1.2 hz, hp), 7.03 d.d (2h, j 8.5, 1.2 hz, ho), 7.08–7.12 m (2h, h5, h6), 7.21 d.d (2h, j 8.5, 7.3 hz, hm), 7.31 m (1h, h 7), 8.15 m (1h, h4), 8.17 с  (1h, h1’), 9.78 br.s (1h, n3’h), 11.23 s (1h, n1h). 13c nmr spectrum (151 mhz, dmso-d6), δ, ppm: 136.06 (c2), 118.04 (c3), 129.91 (c3a), 130.99 (c4), 127.76 (c5), 127.49 (c6), 127.78 (c7), 132.84 (c7a), 139.22 (c1’), 139.44 (ci), 124.4 (co), 129.27 (cm), 127.67 (cp), 115.98 (cf3), 155.28 (c=o). 15n nmr spectrum (61 mhz, dmso-d6), δ, ppm: 126.8 (n1), 305 (n3’), 218.5 (n3’). ms, m/z (irel,%): 249 (m +, 100). the  general method for the  reaction of hydrazones 3d-3e with quinazoline 4 a mixture of quinazoline 4 (0.5 mmol) and the  corresponding hydrazone 3d,e in  tfa (3.0 ml) was refluxed for 65–70 h. the  solvent was removed under reduced pressure. water (2.0 ml) was added to  the  residue; the  solid was filtered off. the resulting product 6a,b was analytically pure and no additional purification was required. 4‑(4‑(2‑((1h‑indol‑3‑yl)methyl‑ ene)  — 1‑(2,2,2‑trifluoroacetyl)hy‑ drazinyl)phenyl) — 1,4‑dihydroquina‑ zolinium‑3 2,2,2‑ trifluoroacetate (6a). yield 51%, m.p. 112–113 °c. 1h nmr spectrum (600 mhz, dmso-d6), δ, ppm: 6.24 s (1h, h4’’), 7.07 d (1н, j 7.4 hz, h5’’), 7.20–7.24 m (2h, h6’’, h7’’), 7.37 t (1н, j 7.7 hz, 1h, h5), 7.41 d (1н, j 6.7 hz, h4), 7.43–7.45 m (2h, h6,7), 7.61 d 111 (2н, j 8.4 hz, h5’), 7.69 d (2н, j 7.6 hz, h8’’), 7.92 d (2н, j 8.4 гц, h6’), 7.98 s (1h, h1’), 8.57 s (1h, h2’’), 8.80 s (1h, h2), 11.18 s (2h, n1h, n3’’h), 12.37 s (1h, cooh). 13c nmr spectrum (151 mhz, dmso-d6), δ, ppm: 54.61 (c 4’’), 116.39 q (1с, j 288.7 hz, cf3), 117.59 (c 8’’), 119.17 (c3), 121,42 (c6’), 122.42 (c4a), 126.86 (c7), 127.83 (c6’’), 128.22 (c7’), 128.60 (c5’), 128.73 (c5’’), 129.34 (c7’’), 129.48 (c4), 129.82 (c8a), 130.07 (c3a), 131.90 (c7a), 132.0 (c4’), 139.89 (c7), 140.54 (c5), 141.1 (c6), 149.14(c2’’), 156.00 q (1с, 2j 36.3 hz, cocf3), 158.44 q (1с, 2j 30.7 hz, cooh). 19f nmr spectrum (376 mhz, dmso-d6), δ, ppm: — 73.50, — 74.12. 15n nmr spectrum (61 mhz, dmso-d6), δ, ppm: 126.9 (n 1”, n3’’), 218.6 (n1, n3’), 301.6 (n2’). ms, m/z (irel,%): 461 (m+, 20), 369 (11), 131 (100). 4‑(4‑(2‑((2‑methyl‑1h‑indol‑3‑yl) methylene)  — 1‑(2,2,2‑trifluoroacetyl) hydrazinyl)phenyl)  — 1,4‑dihydroqui‑ nazolinium‑3 2, 2,2‑trifluoroacetate (6b). yield 55%, m.p. 121–122 °c. 1h nmr spectrum (600 mhz, dmso-d6), δ, ppm: 2.21 s (3h, ch3), 6.28 s (1h, h 4’’), 7.11 d (1h, char), 7.24 m (2h, char), 7.38 t (1н, j 7.7 hz, chаr), 7.44 s (5h, 4chind, char), 7.63 s (3h, char), 7.64 s (1h, h 1’), 8.57 s (1h, h2’’), 11.03 m (2h, nh), 12.37 br.s (1h, cooh). 13c nmr spectrum (151 mhz, dmso-d6), δ, ppm: 11.34 (сh3), 55.96 (c 4’’), 115.33 q (1с, j 147.38 hz, cf3), 118.06 (c 8’’), 119.17 (c3), 123.08 (c6’), 124.11 (c4a), 124.53 (c7), 127.50 (c6’’), 127.67 (c7’), 127.74 (c5’), 127.78 (c5’’), 127.95 (c7’’), 129.85 (c8a), 130.97 (c4), 132.86 (c7a), 136.05 (c3a), 138.50 (c4’), 138.87 (c7), 138.87 (c5), 144.98 (c6), 146.48 (c2’’), 155.30 q (1с, j 36.5 hz, cocf3), 158.17 q (1с, 2j 30.9 hz, cooh). 19f nmr spectrum (376 mhz, dmso-d6), δ, ppm: — 73.72, — 74.07. ms, m/z (irel,%): 475 (m +, 27), 345(25), 131 (100). general procedure for the  synthesis of compounds 7a,b 0.3 mmol of  corresponding hydrazone 3d,e was heated in tfa for 45–50 h. the solvent was removed under reduced pressure. the  solid residue was treated with water (2.0 ml) and ammonia solution (15%) to adjust ph to 7–8. the precipitate was filtered off and washed with water (2.0 ml). the resulting product 7a,b was analytically pure and no additional purification was required. 2,2,2‑trifluoro‑n’ — [(1h‑indolyl‑3) methylene] — n‑phenylacetylhydrazide (7а). yield 55%, m.p. 154–155 °c. 1h nmr spectrum (600 mhz, dmso-d6), δ, ppm: 7.34 t.t (1h, j 7.5, 1.0 hz, hp), 7.39 m (1h, h6), 7.43–7.46 m (2h, h5, h6), 7.54 d.d (2h, j 8.6, 7.5 hz, hm), 7.70 m (1h, h 4), 7.85 d.d (2h, j 8.6, 1.0 hz, hz, ho), 7.97 s (1h, h1’), 8.78 s (1h, h2), 11.15 s (1h, n1h). 13c nmr spectrum (151 mhz, dmso-d6), δ, ppm: 116.08 q (cf3, j 288.6 hz), 118.22 (co), 120.64 (c 3), 126.19 (c2), 126.49 (cp), 127.57 (c 6), 128.18 (c5), 128.18 (c7), 129.08 (c4), 129.64 (cm), 131.36 (c 7a), 139.39 (ci), 139.7 (c 1’), 155.52 q (c=o, j 36.2 hz). 19f nmr spectrum (376 mhz, dmso-d6), δ, ppm: 74,52 (s, cf3). ms, m/z (irel,%): 331 (m +, 100), 262 (44). 2,2,2‑trifluoro‑n’ — [(2‑methyl‑1h‑ ‑indolyl‑3)methylene] — n‑phenylace‑ tylhydrazide (7b). yield 64%, m.p. 164– 165 °c. 1h nmr spectrum (500 mhz, dmso-d6), δ, ppm: 2.21 s (3h, ch3), 7.43–7.47 m (5h, h4, h5, h6, h7 and hp), 7.52 d.d (2h, j  8.5, 1.4 hz, ho), 7.57 d.d (2h, j 8.5, 7.2 hz, hm), 7.63 s (1h, h 1’), 10.99 s (1h, n1h). 13c nmr spectrum (151 mhz, dmso-d6), δ, ppm: 115.98 q (cf3, j 288.8 hz), 118.04 (c 3), 124.4 112 (co), 127.49 (c 6), 127.67 (cp), 127.76 (c 5), 127.78 (c7), 129.27 (cm), 130.99 (c 4), 136.06 (c2), 132.84 (c7a), 139.22 (c1’), 139.44 (ci), 155.28 q (c=o, j 36.2 hz). 19f nmr spectrum (376 mhz, dmso-d6), δ, ppm: — 74,45 (s, cf3). ms, m/z (irel,%): 345 (m+, 80), 276 (100). results and discussion arylhydrazones of indole-3-carbaldehydes 3а‑е, which were obtained by heating indole-3-carbaldehydes 1a,b with phenylhydrazines 2а‑d in ethanol with the addition of hcl, were used as c-nucleophiles for the  studies (scheme 1). it is  known that the e-configuration of the c=n bond is more thermodynamically favorable for arylhydrazones. this was confirmed by the data of x-ray structural analysis [15, 16]. we previously described that heating of  quinazoline 4 with hydrazones 3a‑c in tfa resulted in the formation of products 5a‑c (scheme 2) [14]. in  current work, we have found that hydrazones 3d,e, which do not contain substituents in the phenyl fragment of the molecule, are added to quinazoline 4 at the c7’ atom. the reaction of quinazoline 4 with hydrazones 3d,e in tfa yielded adducts 6a,b (scheme 3). the  mass spectra of  compounds 6 contain molecular ions corresponding to  the  addition products of  hydrazones 3d,e to  quinazoline 4. the  mass spectra of  compounds 6 contain molecular ions corresponding to  the  addition products of hydrazone to quinazoline. the 1h nmr n h n hn 1 2 33a 4 5 6 7 7a 1' 2' 3' r1nh h2n hn r2r1 o 3a-e + r2 1a,b 3: a: r1 = me; r2 = no2 b: r1 = me; r2 = me c: r1 = me; r2 = f d: r1 = h; r2 = h e: r1 = me; r2 = h ∆, etoh, hcl 2a-d 4' 5' 6' 7' 1: a: r1 = h b: r1 = me 2: a: r2 = no2 b: r2 = me c: r2 = f d: r2 = h scheme 1 n n h n n nhh3cr nhn h n h ch3 n hn r n h n n o cf3 rch3 nhn h 4 3a-c a 5a-c 3,5: a r=no2, b r=ch3, c r=f 1'' 4'' 3''2'' 5'' 6'' 7'' 8'' 4a'' 8a'' 1 2 3 45 6 7 3a 7a 1' 2' 3' 4' 5' 6' 7' 8' 8 cf3coo tfa h 65–71% scheme 2 113 spectrum contain characteristic signals: the  h4’’ proton singlet at  6.24 ppm (6a) and a pair of two-proton doublets of aromatic protons h6’, h5’ (7.61 and 7.92 ppm, respectively (6a)). these data confirm the addition of hydrazones 3d,e to compound 4 by the p-position of the phenyl group. since the signal of the nh-proton of the indole fragment is retained in adducts 6, it is  obvious that the  hydrazine part of the molecule undergoes acylation. it should be noted that the 2d 1h-13c ghmbc spectra of adducts 6a,b contain intense cross peaks between the  characteristic quartet of  c8’ atom in  the  trifluoroacetyl group, in particular, at 155.9 ppm for compound 6а (2jс-f = 36.3 hz), and the  broadened signal of  the  n1h proton (see fig. 1), indicating the  presence of an intramolecular hydrogen bond n-h…o=c. due to the presence of an intramolecular hydrogen bond in the molecule, it can be assumed that the c=n bond of compounds 6а,b in dmso-d6 has the zconfiguration, as in adducts 5. we suggest that the formation of trifluoroacetyl derivatives of  quinazoline 6, as well as adducts 5, occurs in several stages. initially, the  addition of  hydrazone to quinazoline takes place, followed by  acylation of  the  adduct with tfa at  the  n3’h-group with the  formation of compounds 6. since acylation of  the  nh group occurred during the c,c-coupling described above, we assumed that the same reaction would take place upon heating hydrazones 3 in  tfa in  the  absence of  quinazoline. this was confirmed in  the  course of  experiments and hydrazides 7 were obtained (sheme 4). the  structure of  acylation products 7a,b was confirmed by  1h, 13c, 15n, and n n h n n nhr nhn h 4 3d,e a 6a,b 3: d r=h, e r=ch3 1 2 3 4 5 6 7 3a 7a 1'2' 3' 4' 5'6' 7' 8' 8 tfa 51-55% nh n n h r nhn h 1'' 3''2'' 5'' 6'' 7'' 8'' 4a'' 8a'' cf3coo h n n n f3c o h r 6: a r=h, b r=ch3 scheme 3 n n nn h n nh o o f3c h h h tfa n n n oh o cf3 h h n n n o f3c h 3d,e 7a,b -h2o r r r r d r=h; e r=ch3 a b a r=h; b r=ch3 scheme 4 fig. 1. fragment of the nmr 2d 1h-13c hmbc spectrum for compound 6a 114 19f nmr spectroscopy including 2d 1h-13c hsqc / hmbc correlation experiments. due to the fact, that the spectra of compounds 7a,b contain signals of  the  nhprotons of the indole fragment, it is obvious that the hydrazine part of the molecule undergoes acylation. 2d 1h-13c hmbc spectra of compounds 7a,b contain characteristic intense cross-peaks between the  carbon quartet of  the  trifluoroacetyl group (155.4 ppm, 2jc-f = 36.7 hz) and the  n1h proton of  the  indole fragment (11.01 ppm). we believe that these cross peaks are due to the spin-spin interaction through the hydrogen bond (see fig. 2). it should be mentioned that the  obtained hydrazides 7 do not react with quinazoline 4. heating of  quinazoline 4 with hydrazides 7a, b in tfa gave the starting compounds 7. the inertness of  hydrazides 7 in  the  studied reactions of  c,c-coupling confirms that the  first stage of  the  multistep reaction is  precisely the  addition of  the  hydrazone 3 to  the  quinazoline 4, and then the  stage of acylation with acid occurs. conclusions as a result of this work, it was found that the reactions of indole-3-carbaldehyde arylhydrazones with quinazoline can proceed either at 5or 7’ — position of the arylhydrazone molecule. it was shown that in the absence of substituents at both positions, the c7 atom is the most active nucleophilic center. acknowledgements the  authors are grateful to  the  russian foundation for basic research (grant 18-33-00727 mol_a) for financial support of the research. references 1. d’yakonov al, telezhenetskaya mv. quinazoline alkaloids in  nature. chem. nat. compd. 1997;33:221–267. doi: 10.1007/bf02234869 2. aniszewski t. alkaloids (second edition). helsinki: elsevier science, 2015. 496 p. 3. asif m. chemical characteristics, synthetic methods, and biological potential of quinazoline and quinazolinone derivatives. int. j. med. chem. 2014;id 395637:1–27. 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to indole hydrazone derivatives in tfa as a facile synthesis of trifluoroacetylhydrazide quinazoline σ-adducts. mend. comm. 2020;30:226–227. doi: 10.1016/j.mencom.2020.03.032 15. zabaleta n, uria u, reyes e, carrillo l, vicario jl. ion-pairing catalysis in the enantioselective addition of hydrazones to n-acyldihydropyrrole derivatives. chem. comm. 2018;54:8905–8908. doi: 10.1039/c8cc05311a 16. tung t, tezcan h, san m, bueykguengoer o, yagbasan r. n-(4-nitrobenzylidene) — n'-phenylhydrazine. acta cryst., sec. c. 2003;59:528–529. doi: 10.1107/s0108270103016019 55 d o i: 1 0. 15 82 6/ ch im te ch .2 01 8. 5. 1. 04 volkova n. e., khvostova l. v., galaida a. p., gavrilova l. ya., cherepanov v. a. chimica techno acta. 2018. vol. 5, no. 1. p. 55–79. issn 2409–5613 n. e. volkova, l. v. khvostova, a. p. galaida, l. ya. gavrilova, v. a. cherepanov department of physical and inorganic chemistry, ural federal university, 19 mira st., ekaterinburg, 620002, russian federation nadezhda.volkova@urfu.ru phase equilibria, crystal structure and oxygen nonstoichiometry of the complex oxides in sm – (sr, ba) – (co, fe) – o systems present paper contains available information on the phase equilibria in the sm – (sr, ba) – (co, fe) – o systems, including the synthesis routes used, crystal structure, which is often depended on oxygen nonstoichiometry, the data on thermodynamic stability of complex oxides, the obtained results on the homogeneity ranges of solid solutions, formed in the systems, and graphical presentation of phase relations in a form of phase diagrams. keywords: phase equilibrium; solid solutions; crystal structure; phase diagram received: 18.01.2018. accepted: 14.02.2018. published: 10.05.2018. © volkova n. e., khvostova l. v., galaida a. p., gavrilova l. ya., cherepanov v. a., 2018 introduction complex oxides based on samarium, alkali earth (sr, ba) and 3d transition (co, fe) metals have attracted great interest of researchers during the last few decades because of a variety of potential practical applications such as cathodes for the sofcs [1–6], membranes [7–9], magnets [10–12], catalysts [13–16], gas sensors [17–19]. traditionally, most of the publications devoted to the modern materials focus on their functional properties. at the same time, information concerning the phase equilibria and stability ranges often remains undisclosed or appears fragmentary. systematic studies of phase equilibria are rare. another important characteristic of these oxides, closely linked with their stability, is the value of oxygen nonstoichiometry. since the overall information concerning the crystal structure, phase equilibria, phase stability, oxygen nonstoichiometry and defect structure constitutes the physicochemical basis of the preparation and usage of these materials, it is vitally important. thus, the present work was aimed to overview the available data concerning the phase equilibria within the sm – (sr, ba) – (co, fe) – o system, as well as the crystal structure and oxygen nonstoichiometry of the complex oxides formed in these systems. phase equilibria in sm – co – o system a systematic study of phase equilibria in the sm – co – o system was performed for the first time by kropanev et al [20, 21], and later by kitayama [22]. samarium 56 cobaltate smcoo3 was the only phase found to exist in this system. this complex oxide was first described by wold and ward [23] as perovskite type with the cubic structure (a = 3.75±0.01 å), although later it was suggested that the ideal perovskite structure is orthorhombically distorted (table 1) [22, 24–28]. different techniques have been used for preparation of smcoo3: a conventional ceramic technique from oxides [20, 21], or from mixture of nitrates dried from their solution [24, 27], or from the mixture of cobalt carbonate and samarium nitrate [23]; via co-precipitation from the nitrates solution by na2co3 with following annealing in air [22]. the mechanism and kinetics of solid state smcoo3 synthesis from oxides has been studied in [29–32]. it was shown that the diffusion stage of synthesis occur by transport of con+ (n  = 2, 3) and o2– ions through the layer of product to the reaction zone that is located on the smcoo3 – sm2o3 interphase boundary [29, 30]. the kinetics of synthesis depends on the grain size, oxygen partial pressure and compacting pressure of oxides mixture for both sm2o3 – coo and sm2o3 – co3o4 systems [30, 31]. samarium cobaltate smcoo3 is stable in air up to the incongruent melting point equal to 1344±4 °c [21]. the subsolidus part of the “t – composition” phase diagram for the sm – co – o system in air is shown in fig. 1. thermodynamic properties and stability ranges measured by means of emf technique in the galvanic cells with solid electrolyte are presented in [20, 21, 33, 34] and those measured by thermogravimetric (tga) method – in [22]. the equilibrium oxygen partial pressure for the reaction: ½ sm2o3 + coo + ¼ o2 = smcoo3, (1) examined in the galvanic cell with the solid electrolyte (zro2 doped by y2o3) can be written as follows [20]: table 1 the values of unit cell parameter of orthorhombically distorted smcoo3 (pbnm space group) a, å b, å c, å treatment conditions ref. 5.284±0.006 5.343±0.006 7.506±0.006 prepared in air, with the excess of coo [22] 5.283±0.005 5.344±0.005 7.502±0.005 prepared in air, with the excess of sm2o3 [22] 5.289 5.354 7.541 treated in oxygen at 930 °c [24,25] 5.294±0.002 5.352±0.002 7.504±0.003 prepared at 930 °c and under pressure 60 kbar [26,27] 5.2831(1) 5.3502(1) 7.4962(1) standard solid state ceramic procedures at 1200 °c in air, with intermediate grindings [28] fig. 1. the cross-sections of phase diagram for the sm – co – o system “t – composition” in air [21] 57 lg , . , p p t k o o 2 2 14800 8 46          = − + (1076 ≤ t, k ≤1474). (2) where is a standard pressure, and standard gibbs energy corresponding to the reaction (1) is expressed by the equations: ref. [33]: ∆g j mol t k1 70820 40 47 ( / ) . ( ),= − + × (3) (1076 ≤ t, k ≤1474). ref. [34]: ∆g j mol t k1 52530 25 0 ( / ) . ( ),= − + × (4) (1080 ≤ t, k ≤1180). the standard gibbs energy of formation from elements δg°f (smcoo3) was presented in [33] by following equation: ∆g j mol t t f  ( / ) . lg . . = = − − × × +1215600 3 66 270 5 (5) the cross sections of phase diagram for the sm – co – o system corresponding to the different fixed parameters are shown in figs. 2–4. phase equilibrium in sm – fe – o system the detailed study of phase equilibria in the sm – fe – o system was performed by kitayama and katsura (fig. 5) [35] and later by parida et al [36]. two ternary oxides – smfeo3–δ and sm3fe5o12 – exist in the system. samarium ferrite smfeo3–δ possesses orthorhombically distorted perovskite structure (space group pbnm) [24, 35–41], sm3fe5o12 crystallizes in the cubic garnet structure (space group ia3d) [35, 36, 42–45]. it was shown that despite of sm2o3/ fe2o3 ratio smfeo3–δ always appears as the first product in the initial stages of synthesis within the temperature range 700–1300 °c; the reaction rate was greater in the mixtures with the iron oxide excess [46]. this is consistent with the fact that most of the samples with the nominal fig. 2. the cross sections of phase diagram for the sm – co – o system at fixed metal ratio (εsm): a – 0.75; b – 0.5 and c – 0.33. filled circles – single-phase, half-filled circles – double-phase samples [20]. dashed lines are smcoo3 decomposition oxygen partial pressure calculated from [34] 58 composition of sm3fe5o12 fired at 700 °c contained smfeo3–δ as the impurity phase, even if the citrate technique had been used as preparation method [43]. taking into account these findings, the temperature of final synthesis’ anneals in order to get a single phase samarium ferrite with garnet structure has to be high enough (≥ 1200 °c). the unit cell parameters for the samarium ferrites smfeo3–δ and sm3fe5o12 are listed in table 2. a detailed study of crystal structure performed on the single crystal of sm3fe5o12 within the range 20 ≤ t, k ≤ 297 reveals the second order phase transition at 68 and 40 k [44]. the coefficients for the temperature dependency of unit cell parameter for sm3fe5o12 a t a a a t( ) = + +0 1 2 2 (6) are listed in table 3. thermodynamic properties of samarium ferrites were reported in [35, 36, 47–49]. at 1200  °c smfeo3–δ is stable from air down to po2 = 10 –12.68 atm and sm3fe5o12 – down to po2 = 10 –3.72 atm [35]. fig. 4. gibbs triangle of phase equilibria in the sm – co – o system at 1273 k [20]. the values of equilibrium oxygen pressure in logarithmic scale are: 1) ≈ 5, 2) ≈1.3, 3) –3.17, 4) –11.8 fig. 3. the cross sections of phase diagram for the sm – co – o system at fixed temperatures: a – 1173 k; b – 1373 k [20]. the composition is represented by molar fraction of metal components 59 table 2 the values of unit cell parameter of smfeo3–δ and sm3fe5o12 smfeo3–δ sm3fe5o12 (3 – δ) a, å b, å c, å ref. a, å ref. – 5.394 5.592 7.711 [24, 37] 12.519±0.002 [35] 3.0 5.398±0.002 5.598±0.002 7.708±0.002 [35] 12.529±0.001 [42] 2.982 5.398±0.001 5.591±0.001 7.706±0.001 [35] – – – 5.400±0.001 5.597±0.001 7.711±0.001 [38] – – – 5.39853(4) 5.59683(4) 7.70715(5) [39] – – 3.034 5.588(3)* 7.710(6)* 5.392(3)* [40] – – – 5.39 5.58 7.71 [41] – – * pnma space group table 3 polynomial’s coefficients (eq. 6) for the single crystal sm3fe5o12 unit cell parameter [44] temperature range (k) a0 (å) a1×10 4 (å/k) a0×10 6 (å/k2) 20–297 12.5235 –1.53×10–1 2.21×10–1 20–40 12.5197 2.24 –3.18 40–68 12.5270 –1.407 1.35 68–297 12.5226 –4.9×10–2 1.95×10–1 fig. 5. phase equilibria in the fe – fe2o3 – sm2o3 system at 1200 °c (mol%) [35]. numbers in the figure mean values of –log po2 at which three crystalline phases are in equilibrium state. letters r, p, g, and m represent stoichiometric compositions of sm2o3, smfeo3, sm3fe5o12, and fe3o4, respectively. m1 is the end member of the magnetite solid solution with chemical composition fe2.957o4. pss, wss, and mss are the solid solutions of smfeo3 from p to p1, of feo from w to w2, and fe3o4 from m to m1, respectively. w and w2 are the end members of the wustite solid solution with chemical compositions feo1.049 and feo1.166, respectively. p1 is nonstoichiometric perovskite phase smfeo2.982 60 the limits of thermodynamic stability for smfeo3–δ and sm3fe5o12 that can be represented by the reactions (7) and (8) [36] are shown in fig. 6. 18 smfeo3 + 4 fe3o4 + o2 = = 6 sm3fe5o12 (7) 2/3 sm2o3 + 4/3 fe + o2 = smfeo3 (8) the temperature dependencies of gibbs energy that correspond to the processes (7) and (8) are written as follows [36]: ∆μ(o2)/kj×mol -1 (±0.8) = = –607.3 + 0.2333×(t/k) 1030 ≤ t/k ≤ 1252 (9) ∆μ(o2)/kj×mol –1 (±0.6) = =–590.7 + 0.1587×(t/k) 1005 ≤ t/k ≤ 1259 (10) the phase diagram for the sm – fe – o system in the “log(po2) – composition” coordinates at 1250 k is shown in fig 7. the heat capacity anomaly that was detected for smfeo3 at 673 k and for sm3fe5o12 at 560 k was attributed to the second-order magnetic order  disorder transformation [36]. phase equilibrium in sm – sr – co – o system two types of solid solutions were found to exist in the sm – sr – co – o system: with the perovskite structure and with the k2nif4 type structure. the perovskite-type solid solutions sm1–хsrxcoo3–δ can be prepared by the conventional ceramic technique [1, 50–52] or through the solution precursors me thods [53–59] within the temperature range 900–1200 °c in air or in the oxygen flow. it should be noted that using of conventional ceramic technique often yields the samples contaminated by small amounts of impurities, for example, they were detected in the sm0.5sr0.5coo3–δ sample after annealing at 1100 °c in air for 240 h. on the contrary, using the solution precursors routes allow to obtain single-phase samples much faster. fig.6. thermodynamic stability of the smfeo3 and sm3fe5o12, constructed from the data in [36] (straight line); circle points are taken from [47], square points are calculated from [48, 49] 61 the synthesis conditions, structure type and unit cell parameters for the various sm1–хsrхcoo3–δ compositions are listed in table 4. sm-enriched sm1–хsrхcoo3–δ (0 < х < 0.5) obtained at 1200 °c in air possesses the perovskite structure with orthorhombic [1, 52] or tetragonal [53] distortions. the increase of strontium content leads to the decrease of orthorhombic distortions [1]. it should be noted that annealing temperature not less than 1200 °c is important since the samples sm1–хsrхcoo3–δ with x ≤ 0.40 annealed at 1100 °c in air for 300 h were double-phase. depending on the preparation conditions, sr-enriched samples could be obtained either with tetragonal (2a×2a×4a) table 4 the synthesis conditions, structure type and unit cell parameters for the various sm1–хsrхcoo3–δ compositions composition synthesis route final treatment conditions crystal structure and unit cell parameters ref. smcoo3–δ ceramic route 1200 °c, in air orthorhombic a = 5.357(1), b = 5.294(1), c = 7.513(2) [1] sm0.9sr0.1coo3–δ orthorhombic a = 5.363(1), b = 5.298(2), c = 7.518(3) sm0.8sr0.2coo3–δ orthorhombic a = 5.361(1), b = 5.371(2), c = 7.577(2) sm0.75sr0.25coo3–δ nitrate route 800–1200 °c, in air, finally 1000 °c, 3 days a = 10.877(1), c = 7.716(1) [53] sm0.7sr0.3coo3–δ ceramic route 1200 °c, in air orthorhombic a = 5.366(1), b = 5.377(2), c = 7.583(1) [1] sm0.6sr0.4coo3–δ orthorhombic a = 5.369(2), b = 5.389(2), c = 7.588(2) sm0.5sr0.5coo3–δ ceramic route 1200 °c, in air orthorhombic a = 5.367(2), b = 5.406(1), c = 7.588(2) [1] fig. 7. the phase diagram for the sm – fe – o system at 1250 k [36] 62 composition synthesis route final treatment conditions crystal structure and unit cell parameters ref. sm0.5sr0.5coo3–δ nitrate route 1100 °c, in air orthorhombic a = 5.366(7), b = 5.370(9), c = 7.587(3) [57] edta-citrate complexing sol-gel process 900 °c, in air orthorhombic pnma a = 5.366, b = 5.398, c = 7.585 [58] ceramic route 1150 °c, in air cubic a = 3.8086(5) [50] nitrate route 800–1200 °c, in air, finally 1000 °c, 3 days cubic a = 3.795(1) [53] glycerinnitrate route 1100 °c, in air tetragonal (2a×2a ×4a), i4/mmm a = 7.587(1), c = 15.253(1) [59] sm0.45sr0.55coo3–δ glycerinnitrate route 1100 °c, in air tetragonal (2a×2a ×4a), i4/mmm a = 7.593(1), c = 15.333(1) [59] sm0.4sr0.6coo3–δ ceramic route 1150–1200 °c, in air cubic a = 3.808(2) a = 3.8178(5) [1] [50] glycerinnitrate route 1100 °c, in air tetragonal (2a×2a×4a), i4/mmm a = 7.582(1), c = 15.339(1) [59] sm0.35sr0.65coo3–δ glycerinnitrate route 1100 °c, in air tetragonal (2a×2a×4a), i4/mmm a = 7.596(1), c = 15.328(1) [59] sm0.33sr0.67coo3–δ citrate-nitrate route 1100 °c, oxygen flow tetragonal (2a×2a×4a), i4/mmm a = 7.6149(4), c = 15.3472(10) [54] sm0.3sr0.7coo3–δ ceramic route 1150–1200 °c, in air cubic a = 3.823(2) a = 3.8306(1) a =3.830 [1] [50] [51] glycerin nitrate route 1100 °c, in air tetragonal (2a×2a×4a), i4/mmm a = 7.625(1), c = 15.368(1) [59] sm0.25sr0.75coo3–δ nitrate route 800–1200 °c, in air, finally 1000 °c, 3 days orthorhombic gdfeo3 type a =5.363(1), b =5.353(1), c =7.592(1) [53] glycerin nitrate route 1100 °c, in air tetragonal (2a×2a×4a), i4/mmm a = 7.631(1), c = 15.364(1) [59] sm0.2sr0.8coo3–δ citrate nitrate route 1100 °c, oxygen flow tetragonal (2a×2a×4a), i4/mmm a = 7.6724(4), c = 15.3983(11) [54] ceramic route 1150–1200 °c, in air cubic a =3.846(2) a = 3.8407(3) [1] [50] glycerin nitrate route 1100 °c, in air tetragonal (2a×2a×4a), i4/mmm a = 7.669(1), c = 15.405(1) [59] сontinuation of table 4 63 [54, 59] or cubic [1, 50] structure. one can see that the samples with the tetragonal structure appear in the relatively more oxidizing conditions and the samples with the cubic structures formed in the relatively more reducing conditions (table 4). fig. 8 illustrates the xrd pattern for sr0.8sm0.2coo3–δ with the 2ap×2ap×4ap superstructure. electron diffraction measurements uncovered the formation of 2ap×2ap×4ap superstructure (sp. gr. i4/mmm) within the tetragonal cell, but the intensity of reflections corresponding to the superstructure decreases with the increase of strontium content [54, 55]. the superstructure forms because of the ordering of sm and sr cations in the a-site sublattice accompanied by the ordering of oxygen vacancies. for sr1–xsmxcoo3–δ with x < 0.25, sm atoms are first incorporated into the a1 position until substitution is complete, while the a2 and a3 sites remain fully occupied by sr2+. further increase of samarium content leads to the incorporation of sm cations into the a3 position, while a1 is fully occupied by sm3+ and a2 is completely filled with sr2+. the value of sm content, x = 0.5, corresponding to the limiting composition of solid solution, represents the situation when half of a3 positions are occupied by sm3+ and the other half – by sr2+ [54, 59]. thermodynamic stability of the sm1–хsrхcoo3–δ solid solutions has not been studied yet. usually partial substitution of alkaline-earth elements for rare-earth in the cobaltites with the perovskite structure decreases their thermodynamic stability [60]. the only information concerning the behavior of sm0.5sr0.5coo3–δ under extremely reducing conditions at low temperature is available [61]. it was found that at 250 °c under 4% h2o-96% h2 atmosphere samarium-strontium cobaltite decomposes to sro, co(oh)2 and coo on the surface composition synthesis route final treatment conditions crystal structure and unit cell parameters ref. sm0.15sr0.85coo3–δ glycerin nitrate route 1100 °c, in air tetragonal (2a×2a×4a), i4/mmm a = 7.678(1), c = 15.372(1) [59] sm0.1sr0.9coo3–δ citrate nitrate route 1100 °c, oxygen flow tetragonal (2a×2a×4a), i4/mmm a = 7.6968(8), c = 15.4672(16) [54] ceramic route 1150–1200 °c, in air cubic a = 3.848(2) a = 3.8531(4) [1] [50] glycerin nitrate route 1100 °c, in air tetragonal (2a×2a×4a), i4/mmm a = 7.668(1), c = 15.410(1) [59] sm0.05sr0.95coo3–δ glycerin nitrate route 1100 °c, in air tetragonal (2a×2a×4a), i4/mmm a = 7.668(1), c = 15.431(1) [59] fig. 8. xrd pattern for sr0.8sm0.2coo3–δ with the 2ap×2ap×4ap superstructure [59] сontinuation of table 4 64 of the reduced sm0.5sr0.5–αco1–βo3–γ layer. in the atmosphere of pure h2 at 350  °c sr0.5sm0.5coo3–δ completely decomposes into sm2o3, sro and coo [61]. the solid solutions sm2–хsrxcoo4 with k2nif4 type structure (sp. gr. i4/mmm) within the range 0.8 ≤ х ≤ 1.50 were prepared either by the conventional ceramic technique at 1200–1300 °c in air [56, 62], or at 1450 k in oxygen flow [63], or by the edta-citrate sol-gel method at 1000  °c in oxygen flow [64], or by the glycerinnitrate technique at 1100  °c in air [59]. the homogeneity range of sm2–хsrxcoo4 solid solutions, estimated by edx analysis, was reported as 0.79 ≤ х ≤ 1.68 [63]. the samples quenched in air from 1100 °c were single-phase within the range 0.7 ≤ x ≤ 1.1 [59]. the unit cell parameters for sm2–хsrxcoo4 are listed in table 5. another representative of the ruddlesden-popper series sm2srco2o7 was reported earlier [64]. it was prepared from sm2o3, srco3 and co2o3 by solid state synthesis at 1450 k in the flow of oxygen for 3 days [64]. according to the powder x-ray diffraction measurements, it possesses the tetragonal structure with the unit cell parameters: a = 0.3801 nm, c = 1.9562 nm, v = 0.2826 nm3. it was shown that thermal stability of this phase is limited. the x-ray diffraction of the sample after heating at 1550 k for 6 h indicated that the compound decomposes to smsrcoo4 and smcoo3 [64]. it worth to mention that sm2srco2o7 formation was not confirmed during the systematic study of phase equilibria in the ½ sm2o3 – sro – coo system at 1100 °c in air. the projection of isothermal–isobaric phase diagram for the sm – sr – co – o system to the compositional triangle ½ sm2o3 – sro – coo is shown in fig. 9 [59]. phase equilibria in sm – sr – fe – o system three types of solid solutions were reported to exist in the sm-sr-fe-o system: sm1–xsrxfeo3–δ [56, 65–70], sm2–ysryfeo4±δ [56, 62], and sr3–zsmzfe2o7–δ [71]. complex oxides with the overall composition sm1–xsrxfeo3–δ may be prepared by solid state [66], glycine nitrate [56, 68, 70], edta-citrate sol-gel [7, 67, 69] or coprecipitation [56] methods at 900–1300 °c. all samples of sm1–xsrxfeo3–δ solid solution range, whether as-prepared in air or treated at high oxygen pressure (100 bar at 600 °c table 5 the unit cell parameters and unit cell volumes for sm2–хsrxcoo4 [59, 62, 63] sample composition a, å c, å v, (å)3 ref. sm0.5sr1.5coo4–δ 3.761 12.234 173.4 [62] 3.7699(2) 12.4085(6) 176.35(1) [63] sm0.75sr1.25coo4–δ 3.7620(2) 12.3575(8) 174.89(2) [63] sm0.8sr1.2coo4–δ 3.753(1) 12.304(1) 173.36(2) [59] sm0.9sr1.1coo4–δ 3.756(1) 12.266(1) 173.04(2) [59] smsrcoo4–δ 3.7609(3) 12.2454(9) 173.20(2) [63] 3.752(1) 12.200(1) 171.76(2) [59] sm1.1sr0.9coo4–δ 3.765(1) 12.198(1) 172.95(2) [59] sm1.2sr0.8coo4–δ 3.768(1) 12.171(1) 172.77(2) [59] sm1.3sr0.7coo4–δ 3.777(1) 12.180(1) 173.74(2) [59] 65 [66]), possess orthorhombically distorted perovskite type structure (sp. gr. pbnm). the unit cell parameters for sm1–xsrxfeo3–δ are listed in table 6. single-phase sr2–ysmyfeo4±δ samples were synthesized by the glycine nitrate route [56] or by the solid-state technique [62] with the final annealing temperature within the range 1000–1250 °c. the homogeneity range of sr2–ysmyfeo4±δ solid solution was reported to be equal to 0.5 ≤ y ≤ 1.2 [62]. sr3–zsmzfe2o7–δ solid solutions were synthesized by the glycine-nitrate method at 1100 °c in air [71]. it was shown that single-phase sr3–zsmzfe2o7–δ formed in the composition range 0 ≤ z ≤ 0.3 and at z = 1.80. similarly to the undoped sr3fe2o7–δ, partially sm-substituted sr3–zsmzfe2o7–δ (z =0–0.3) possesses the tetragonal structure (sp. gr. i4/mmm). sm-enriched single phase sr1.2sm1.8fe2o7–δ also crystallizes in the tetragonal system, although the space group is different (p42/mnm). all attempts to synthesize sm-substituted strontium hexaferrite sr1–zsmzfe12o19 (0.06 ≤ z ≤ 0.5) solid solutions by hydrothermal [10, 11] or solid state [12] methods failed. it was found that all sm-containing powders were multiphase; together with srfe12o19 they contained fe2o3 and (sm, sr)feo3–δ as the impurity phases. phase equilibrium in sm – ba – co – o system relatively large difference in ionic radii between samarium and barium, in comparison with that between samarium and strontium, results in the formation of socalled “112 type” phase with the formula smbaco2o6–δ [72–74] instead of solid solution that is typical for the sr-containing system. the structure of smbaco2o6–δ is also called as double perovskite since sm and ba atoms are separated to the alternating layers along the c axis. therefore, the value of the c parameter is doubled fig. 9. the phase diagram of the ½ sm2o3 – sro – coo system at 1100 °c in air: 1 – smcoo3, coo, sr0.5sm0.5coo3–δ; 2 – coo, sr1–xsmxcoo3–δ (0.05 ≤ x ≤ 0.5); 3 – coo, sr0.95sm0.05coo3–δ, srcoo3–δ; 4 – smcoo3–δ, sr0.5sm0.5coo3, sr0.7sm1.3coo4+δ; 5 – sr1–xsmxcoo3–δ (0.05 ≤ x ≤ 0.5), sr2–ysmycoo4+δ (0.9 ≤ y ≤ 1.3); 6 – sr1.1sm0.9coo4+δ, srcoo3–δ, sr0.95sm0.05coo3–δ, srcoo3–δ; 7 – srcoo3–δ, sr3co2o7–δ, sr1.1sm0.9coo4+δ; 8 – sm2o3, smcoo3–δ, sr0.7sm1.3coo4+δ; 9 – sr2–ysmycoo4+δ (0.9 ≤ y ≤ 1.3), sm2o3; 10 – sm2o3, sm2sro4–δ, sr1.1sm0.9coo4+δ; 11 – sro, sm2sro4–δ, sr1.1sm0.9coo4+δ; 12 – sro, sr3co2o7–δ, sr1.1sm0.9coo4+δ [59] table 6 the unit cell parameters for the sr1–xsmxfeo3–δ solid solution x structure a, å b, å c, å ref. 0.5 orthorhombic sp. gr. pbnm 5.4622(1) 5.4627(4) 7.7249(1) [70] 0.667 5.4728(2) 5.4454(2) 7.6973(2) [66] 0.8 5.396 5.562 7.711 [69] 66 relatively to the ordinary perovskite structure, and the unit cell can be represented as ap×ap×2ap. another specific feature of this structure that is caused by the cation separation is the location of oxygen vacancies. it is generally acknowledged that oxygen vacancies are not distributed randomly in the lattice while the oxygen content changes within the range 5 < (6–δ) < 6, but are concentrated in the particular planes. according to the most widespread point of view, oxygen vacancies are located in the smoδ planes while bao planes remain completed [74–76], however, alternatively the opposite model was suggested in [77]. such accumulation of oxygen vacancies in the specific planes (doesn’t matter what they are – either smoδ or baoδ) results in the ordering of oxygen vacancies when the value of (6–δ) is equal approximately to 5.5, leading to the doubling of b-parameter and formation of the ap×2ap×2ap supercell. smbaco2o6–δ can be prepared by a conventional ceramic technique [3, 74, 78–81] and via solution methods using different precursors [82–84]. it possesses the orthorhombic structure (space group pmmm) with the ap×2ap×2ap supercell. the value of oxygen content at room temperature in the sample slowly cooled in air was found to be 5.61 [81]. this value corresponds to the orthorhombic structure. the x-ray diffraction pattern for smbaco2o5.61 refined by the rietveld analysis is shown in fig. 10 and the structural parameters are listed in table 7. the samples within the compositional range sm1–xbaxcoo3–δ with x < 0.5 annealed at 1100  °c in air were doublephase and consisted of smbaco2o5.61 and smcoo3–δ, while the samples with x > 0.5 were the mixtures of smbaco2o5.61 and bacoo3–δ [72, 73]. high temperature in situ xrd measurements reveals the structural transfortable 7 the unit cell parameters and atomic coordinates for smbaco2o5.61 [81] space group pmmm atom x y z sm 0.5 0.229(3) 0.5 ba 0.5 0.250(1) 0 co1 0 0.5 0.255(2) co2 0 0 0.254(2) o1 0 0 0 o2 0 0.5 0 o3 0 0.5 0.5 o4 0 0 0.5 o5 0.5 0 0.239(3) o6 0.5 0.5 0.247(3) o7 0 0.244(2) 0.238(2) a = 3.886(1) å; b = 7.833(1) å; c = 7.560(1) å; v = 230.22(2) (å)3; rbr = 10.7%; rp = 7.73%; rexp = 4.46% 67 mation from orthorhombic to tetragonal cell between 450 and 550 °c (fig. 11) that is in good agreement with the value of oxygen content in smbaco2o6–δ within this temperature range. temperature dependence of unit cell parameters for smbaco2o6–δ is shown in fig. 12. although the radius of samarium is significantly larger than radius of cobalt ions, it was found that the solid solutions represented by the formula baco1–zsmzo3–δ can be prepared by citrate-nitrate method at 1100 °c in air within the range 0.1≤ z ≤0.2. partial substitution of sm for co stabilized the cubic structure similarly to baco1–zyzo3–δ [85]. fig. 13 illustrates xrd pattern for the single-phase cubic solid solution baco0.85sm0.15o3–δ as an example. the unit cell parameters refined by the rietveld method are listed in table 8. the sample with nominal composition z = 0.05 consisted of cubic baco0.9sm0.1o3–δ and hexagonal bacoo3–δ. one more complex oxide with the formula sm2baco2o7 representing the ruddlesden-popper (rp) (n=2) phase was reported to exist in the sm – ba – co – o system [63, 86]. it was obtained by solidstate reaction from sm2o3, baco3 and co2o3 at 1300 k in the flow of oxygen for 2 weeks. the crystal structure was described by the orthorhombic cell with the parameters a = 3.821 å, b = 3.776 å and c = 19.426 å [85]. however, gillie et al. [87] using same preparation method with prolonged annealing in flowing oxygen at 1100 °c did not obtain the single phase but the mixture composed of two distinct phases: an oxyfig. 11. high-temperature in situ diffraction data for smbaco2o6–δ [84] fig. 12. temperature dependencies of the unit cell parameters and unit cell volume for smbaco2o6–δ in air [84] fig. 10. the x-ray diffraction pattern for smbaco2o5.61, refined by the rietveld method [72] fig. 13. xrd pattern for the cubic solid solution baco0.85sm0.15o3–δ, refined by the rietveld method [72] 68 genated 112-type phase smbaco2o5+x (x ≈ 0.5), and double-layered rp target compound. from a set of obtained results it was concluded that the composition of rp phase is probably close to sm2.1ba0.8co2.1o7-δ (where δ ≈ 1). the unit cell parameters refined within the pnnm space group were equal to a = 5.4371(4) å, b = 5.4405(4) å, and c = 19.8629(6) å [87]. the only one complex oxide sm2bao4±δ was described in the sm – ba – o system [73, 88, 89]. it can be prepared as a single phase by a conventional ceramic technique at 1500 °c in air for about 24 h [88]. sm2bao4±δ demonstrates low stability at room temperature due to high hygroscopicity and reactivity with co2 [88, 89]. however, dta curves in the temperature range 950–1400  °c in air indicated no phase transitions occurred. the presumed space group is pbna with the lattice parameters a = 12.313 å, b = 10.535 å, c = 3.564 å [88]. the standard gibbs energy of sm2bao4 formation from the binary oxides sm2o3 and bao, determined by the hightemperature caf2-based emf method, was evaluated as –110 kj/mol at 1100 k [89]. according to the xr results, partial dissolution of bao in sm2o3 at 1100  °c in air was about 15 mol% [72]. the unit cell parameters for the sm2–xbaxo3 solid solutions are listed in table 9. the phase diagram for the sm – ba – co – o system at 1100  °c in air [72] is shown in fig. 14. according to the obtained results, it could be assumed that rp phase is thermodynamically unstable at 1100 °c in air but could be synthesized in more oxidizing conditions. phase equilibria in sm – ba – fe – o system in contrast with smbaco2o6–δ, similar samarium-barium ferrite smbafe2o6–δ with the double perovskite structure can be obtained only under reduction conditions. karen et al. [90, 91] synthesized smbafe2o6–δ at 985–1020 °c in atmosphere with oxygen partial pressure po2 about 10–14.88–10–15.5 bar that was achieved by table 8 the unit cell parameters for baco1–zsmzo3–δ, refined by the rietveld method [72] z a, å v, (å)3 rbr,% rf ,% rp,% 0.1 4.108(1) 69.33(1) 2.04 1.72 13.4 0.15 4.131(1) 70.51(1) 1.59 1.50 9.76 0.2 4.143(1) 71.13(2) 1.30 1.09 16.4 table 9 the unit cell parameters for the sm2–xbaxo3 solid solutions sm2–xbaxo3 space group c2/m x a, å b, å c, å v, (å)3 rbr,% rf ,% rp,% 0.05 14.191(1) 3.628(1) 8.860(1) 449.22(2) 1.27 1.15 10.2 0.1 14.180(1) 3.626(1) 8.855(1) 448.39(1) 3.20 2.45 13.9 0.2 14.177(1) 3.625(1) 8.853(1) 448.08(1) 2.40 2.21 13.7 0.3 14.175(1) 3.625(1) 8.851(1) 447.92(2) 1.82 2.01 13.3 69 mixing of hydrogen, argon or oxygen and water vapor. moritomo et al. [92] prepared smbafe2o6–δ at 985 °c for 40 h in an evacuated fused-silica tube with fe metal grains put inside the tube, which served as a getter mixture (fe/feo) and provided the oxygen partial pressure of about 7.6×10–16 atm. although it is impossible to prepare smbafe2o6–δ in air, it remains single-phase after annealing at 900 °c in air [93] or even at 985ºc in pure oxygen [91]. the crystal structure of smbafe2o6–δ is well described within the tetragonal or the orthorhombic unit cell (ap×ap×2ap), depending on the oxygen content [90–93]. similarly to the co-containing double perovskite, the appearance of the (ap×2ap×2ap) supercell takes place in the vicinity of oxygen content equal to 5.5. the values of unit cell parameters and synthesis conditions for smbafe2o6–δ are listed in table 10. the complex oxide smba2fe3o8+δ can be obtained at 500 °c in oxygen flow [93] or at 1100 °c for 200 h [94]. the structural refinements were performed by the rietveld method within the ideal perovskite cubic structure (space group pm3m). the on ly sing le-phas e s ample sm0.375ba0.625feo3–δ was prepared at 1100 °c in air [95, 96] and described within a cubic unit cell (space group pm3m) with a = 3.934(1) å. however, transmission electron microscopy revealed that sm0.375ba0.625feo3–δ possesses tetragonal structure with 5-fold c para meter ap×ap×5ap. such complex structure is formed by alternation of the layers contai ning exclusively samarium and barium with the mixed layers, as follows: sm–ba– (sm, ba)–(sm, ba)–ba–sm [95, 96] (fig. 15). table 10 the values of unit cell parameters and synthesis conditions for smbafe2o6–δ [90] 6–δ a, å b, å c, å structure ar/h2 log(ph2o) log(po2) t, °c 4.980 3.963 3.946 7.609 orthorhombic ap×ap×2a (sp.gr. pmmm) 8.78 –4.1 –27.6 670 4.999 3.963 3.945 7.612 8.65 –4.4 –29.3 630 5.002 3.962 3.945 7.611 8.65 –4.2 –28.6 640 5.007 3.962 3.944 7.611 8.65 –4.3 –29.4 620 5.014 3.962 3.946 7.612 8.78 –4.1 –27.9 660 5.016 3.963 3.946 7.612 8.78 –4.1 –28.2 650 5.022 3.962 3.944 7.617 8.78 –4.1 –28.5 640 5.030 3.959 3.948 7.621 16.3 –1.68 –15.31 1000 5.064 3.953 7.628 tetragonal (sp.gr p4/ mmm) ap×2ap×2a 24.9 –1.67 –14.93 1000 5.095 3.952 7.636 41.3 –1.68 –14.53 1000 5.137 3.949 7.649 74.2 –1.68 –14.03 1000 5.142 3.950 7.654 83.2 –1.64 –13.85 1000 5.182 3.949 7.664 101 –1.68 –13.76 1000 5.202 3.947 7.671 137 –1.69 –13.51 1000 5.249 3.946 7.686 238 –1.66 –12.96 1000 5.320 3.943 7.705 398 –1.62 –12.44 1000 5.346 3.943 7.714 341 –1.65 –12.64 1000 70 phase equilibrium in sm – co – fe – o system the solid solutions between samarium ferrite and samarium cobaltite smfe1–xcoxo3–δ were extensively studied [52, 97–102] because of their possible application as gas sensors. polycrystalline samples of smfe1–xcoxo3–δ can be prepared by the pyrolysis of cyanide complexes [97, 99], sol–gel method [98, 100, 102] or conventional solid-state technique [52] at 800– 1100 °c. it was shown that the homogeneity range of smfe1–xcoxo3–δ solid solutions extended to the entire range of compositions (0 ≤ x ≤ 1). similarly to the undoped parent oxides smfeo3–δ and smcoo3–δ, the structure of all smfe1–xcoxo3–δ solid solutions was identified as orthorhombic. the unit cell parameters and unit cell volume values are listed in table 11 [98, 102]. another solid solution in the sm – fe – co – o system was obtained by partial substitution of sm for fe in the cobalt ferrite cofe2o4 with spinel structure [103–107]. the solid oxides with overall composition cofe2–ysmyo4 were prepared at 400– 1000 °c by co-precipitation [103–105] or sol-gel decomposition [105, 107] me thods. single-phase samples cofe2–ysmyo4 were obtained at temperatures 400–700  °c within the ranges 0 ≤ y ≤ 0.2 [105] and 0 ≤ y ≤ 0.4 [107] by sol-gel technology or fig. 14. a projection of isobaric-isothermal phase diagram of the sm–ba–co–o system to the metallic components triangle (t = 1100 °c, po2 = 0.21 atm): 1 – smcoo3–δ, coo and smbaco2o6–δ; 2 – coo, smbaco2o6–δ and bacoo3–δ; 3 – melt; 4 – sm2o3, smcoo3–δ and smbaco2o6–δ; 5 – smbaco2o6–δ and sm2–xbaxo3–δ (0 ≤ x ≤ 0.3); 6 – smbaco2o6–δ, bacoo3–δ and baco0.9sm0.1o3–δ; 7 – smbaco2o6–δ, baco0.9sm0.1o3–δ and sm1.7ba0.3o3–δ; 8 – sm1.7ba0.3o3–δ and baco1–zsmzo3–δ (0.1 ≤ z ≤ 0.2); 9 – sm1.7ba0.3o3–δ, sm2bao4 and baco0.8sm0.2o3–δ; 10 – bacoo3–δ, ba2coo4 and baco0.9sm0.1o3–δ; 11 – ba2coo4 and baco1–zsmzo3–δ (0.1 ≤ z ≤ 0.2); 12 – sm2bao4, ba2coo4 and baco0.8sm0.2o3–δ; 13 – sm2bao4, ba2coo4 and bao [72] fig. 15. crystal structure of five-layered ordered perovskite sm1.875ba3.125fe5o15–δ [95, 96] 71 table 11 the unit cell parameters and unit cell volume of the smfe1–xcoxo3–δ solid solutions [98, 102] x a, å b, å c, å v, å 3 ref. 0 5.5871 7.6977 5.3852 231.61 [98] 5.400 5.593 7.708 232.83 [102] 0.1 5.8551 7.5196 5.0739 223.40 [98] 5.390 5.557 7.691 231.19 [102] 0.2 5.8421 7.4964 5.0670 221.91 [98] 5.378 5.554 7.668 229.01 [102] 0.3 5.7916 7.4653 5.0618 218.85 [98] 5.364 5.520 7.634 226.03 [102] 0.4 5.7812 7.4689 5.0533 218.20 [98] 5.363 5.448 7.620 224.26 [102] 0.5 5.7189 7.4671 5.0649 216.29 [98] 5.340 5.453 7.584 220.83 [102] 0.6 5.324 5.422 7.554 218.09 [102] 0.7 5.316 5.412 5.548 217.17 [102] 0.8 5.6564 7.3754 4.9933 208.31 [98] 5.308 5.394 7.536 215.76 [102] 0.9 5.297 5.371 5.518 213.91 [102] 1.0 5.5148 7.2953 4.9582 199.48 [98] 5.286 5.353 7.499 212.18 [102] fig. 16. a projection of isobaric-isothermal phase diagram for the sm–fe–co–o system to the compositional triangle (t = 1100 °c, po2 = 0.21 atm): 1 – sm2o3, smfe1–xcoxo3–δ (0 ≤ x ≤ 1.0); 2 – co1–ufeuo (0 ≤ u ≤ 0.13), smfe1–xcoxo3–δ (0.2 ≤ x ≤ 1.0); 3 – co0.87fe0.13o, co1.35fe1.65o4, smfe0.8co0.2o3–δ; 4 – smfe1–xcoxo3–δ (0 ≤ x ≤ 0.2), co1+vfe2–vo4 (–0.1 ≤ v ≤ 0.35); 5 – smfeo3, sm3fe5o12, co0.9fe2.1o4; 6 – sm3fe5o12, co0.9fe2.1o4, fe1.985co0.015o3; 7 – sm3fe5o12, fe2–wcowo3 (0 ≤ w ≤ 0.03) [102] 72 within the range 0 ≤ y ≤ 0.5 [106] by coprecipitation by sodium hydroxide with following annealing at 800 °c. however, further increase of temperature (> 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studied by single crystal x-ray diffraction. the compound crystallizes in the orthorhombic system. the space group is pbca, with the following lattice constants: a = 9.7414(5) å, b = 7.4671(6) å, c = 16.5288(11) å, v = 1202.31(14) å3, z = 8. the asymmetric unit contains one β-alaninium cation (+nh3ch2ch2cooh) and one chloride anion. the structure was shown to consist of layers stacked along the c-axis and connected with each other by weak van der waals forces. each layer consists of two halves linked by hydrogen bonds between carbonyl and nh3 + groups and, also, between nh3 + groups and cl– anions. fourier transform infrared spectrum of β-alaninium chloride was recorded and analyzed. the spectroscopic results were found to support the conclusions of the structural study. keywords: β-alanine; amino acids; x-ray diffraction; ftir received: 20.04.2020. accepted: 28.05.2020. published: 30.06.2020. © dmitry s. tsvetkov, maxim o. mazurin, 2020 introduction β-alanine, nh2ch2ch2cooh, is  the  simplest and the  only naturally occurring β-amino acid participating (as a constituent of carnosine and anserine dipeptides as well as pantothenic acid) in some important biochemical processes in muscle and brain tissues of mammals, including humans [1]. the crystal structure of β-alanine and some of its derivatives has already been studied [1–9]. however, this is not the case for the simplest salts of  β-alanine such as  halides which can be considered as  promising precursors for the  development of  new hybrid organic-inorganic materials. to  the  best of our knowledge, the vibrational spectra of  these compounds also have not been reported yet, except in the narrow range of 1400–1500 cm–1 [10] for β-alanine hydrochloride (β-ala·hcl). therefore, the  main aim of  this work was to  study the  crystal structure of  β-ala·hcl and its vibrational properties in the wider range of frequencies. experimental the single crystals and the polycrystalline powder of β-ala·hcl were prepared by the following technique. 3.5 ml of concentrated hydrochloric acid, hcl, (mass fraction 36 wt. %, purity >99.99 wt.%), were combined with solution of  3.54 g of  β-alanine (purity >98 wt.%) in  20 ml of  distilled water. the  resulting solution 62 was evaporated to the final volume of 10 ml and left for cooling and crystallization in the petri dish for several days. after this, the crystals of β-ala·hcl were filtered out using glass filter. the largest crystals with the size up to 0.5×0.5×0.5 mm3 were handpicked, carefully dried by filter paper and left in the desiccator under p2o5 for 24 h. the precipitate containing smaller crystals was washed with small amount of acetone (purity >99 wt.%), dried under vacuum at  100 °c for 3–4 h, carefully powdered using an agate mortar and pestle and stored in the desiccator under p2o5. ir spectra of  the  powdered sample of  β-ala·hcl were recorded at  room temperature in  the  range from 400 cm–1 to  3500 cm–1 using nicolet 6700 ftir spectrometer (thermo scientific, usa) equipped with diamond smart orbit atr sampling accessory. x-ray data for β-ala·hcl single crystal were collected using four-circle diffractometer xcalibur sapphire3 (oxford diffraction limited, uk) equipped with fine-focus sealed mo tube, graphite monochromator and sapphire3 ccd plate detector. the crystal structure of β-ala·hcl was solved by direct methods as implemented in shelxs-97 program [11] and refined by the full matrix least squares method on all f2 data using the shelxl-97 programs [12]. the  non-hydrogen atoms were refined anisotropically, by means of the fullmatrix least squares procedure. the  hydrogen atoms of  the  methylene groups (–ch2–) were placed at  calculated positions (c–h = 0.97 å) and treated as riding on their parent atoms, with uiso(h) values set at 1.2–1.5 ueq(c). the rest of the h atoms (i.e. those corresponding to  –nh3 + and –cooh groups) were found from difference fourier maps and constrained with n–h ≤ 1.03 å (similar to ammonia) and o–h ≤ 0.98 å, and their displacement factors were refined isotropically. the basic crystallographic data and details of  the  measurement and refinement are summarized in table 1. a list of the observed and calculated structural factors and the anisotropic displacement factors is available in supplementary. table 1 basic crystallographic data, data collection and refinement parameters empirical formula c3h8no2cl a 9.7414(5) å b 7.4671(6) å c 16.5288(11) å v 1202.31(14) å3 z 8 d (calc.) 1.387·103 kg·m–3 crystal system orthorhombic space group pbca mr 125.55 cell parameters from 1876 reflections, θ = 4.165–29.036 t 293 k μ(mo kα) 0.534 mm–1 63 results and discussion β-ala·hcl, as  indicated in  table  1, crystallizes in  the  orthorhombic space group pbca with eight formula units per elementary cell. the refined atomic coordinates and atomic displacement parameters are given in tables 2 and 3, and the bond lengths and angles are summarized in table 4. the asymmetric unit of β-ala·hcl cont ains one β-a laninium cat ion (+nh3ch2ch2cooh) and one chloride anion. the arrangement of these species in the elementary cell is shown in fig. 1. the crystal structure may be considered as consisting of double layers connected with each other by  weak van der waals forces and stacked along the c-axis, as can be seen in fig. 2. each double layer consists of two halves which are mirror images of each other. they are shifted against each other along the a-axis by about one half of the translation. as a result, the –c=o groups of the one half layer are almost directly facing the –nh3 + groups of the other half layer. therefore, the  two halves of  the  double layer are linked together by the hydrogen bonds, whose length varies from 2.680 to 2.998 å, formed by –c=o and –nh3 + groups. in  addition,  –nh3 + groups of the one half layer form hydrogen bonds (length 2.613 å) with the closf(000) 528 crystal dimensions and shape, color 0.45 × 0.35 × 0.25 mm3 prism, colorless data collection diffractometer and radiation used xcalibur sapphire3, mo kα, λ= 0.71073 å scan technique ω — 2θ θ range 3.65°–30.91° index ranges  — 11≤h≤13, — 10≤k≤10, — 22≤l≤22 absorption correction multi-scan, crysalispro 1.171.39.38a (rigaku oxford diffraction, 2017). empirical absorption correction using spherical harmonics, implemented in scale3 abspack scaling algorithm tmin, tmax 0.75985, 1.00000 no. of measured, independent and observed [i > 2σ(i)] reflections 7329, 1573, 1124 rint 0.0315 refinement r[f2>2σ(f2)], wr(f2), s 0.0669, 0.1724, 1.003 no. of reflections 1573 no. of parameters 80 no. of restraints 0 δρmax, δρmin (e·å 3) 0.311, –0.335 end of table 1 64 est cl– anions of the other half layer. this is drawn in greater details in fig. 3. furthermore, each half layer itself is stabilized by  the  multidirectional hydrogen bonds between the cl– anions, on the one side, and both the closest –nh3 + groups (length 2.546 å) and the –oh part of the carboxyl group (–c(=o)oh) (length 2.316 å), on the other, as seen in fig. 4. there is also an intramolecular hydrogen bond (length 2.548 å) between the  –nh3 + and –c=o groups of the same β-alaninium cation. ir spectrum of β-ala·hcl is shown fig.  5. the  observed vibrational bands were tentatively assigned on the  basis of the comparison with published ir spectra of β-alanine [13], β-ala·hno3 [5] and 2(β-ala)·hcl [9]. table 2 fractional atomic coordinates and isotropic or equivalent displacement parameters atom site x y z ueq * / å 2 cl1 0.57555(6) 0.14434(9) 0.40265(3) 0.0481(3) n1 0.8957(2) 0.2305(3) 0.44022(12) 0.0470(5) h1a 0.894(3) 0.369(5) 0.433(2) 0.068(9) h1b 0.815(3) 0.203(4) 0.4584(19) 0.060(8) h1c 0.952(3) 0.216(4) 0.472(2) 0.071(10) c1 1.1833(2) 0.1496(3) 0.37117(14) 0.0453(6) c2 1.0566(2) 0.1977(4) 0.32491(14) 0.0520(6) h2a 1.0628 0.1459 0.2712 0.062 h2b 1.0532 0.3268 0.3188 0.062 c3 0.9247(2) 0.1359(4) 0.36360(17) 0.0507(7) h3a 0.8494 0.1557 0.3263 0.061 h3b 0.9304 0.0083 0.3741 0.061 o1 1.18503(18) 0.0817(3) 0.43693(11) 0.0605(5) o2 1.2945(2) 0.1964(3) 0.33036(12) 0.0645(6) h2 1.357(4) 0.173(5) 0.349(2) 0.076(11) * *1 3eq ij i j i j u u a a∗ = ∑∑ a ai j table 3 atomic displacement parameters atom site u11 / å 2 u22 / å 2 u33 / å 2 u23 / å 2 u13 / å 2 u12 / å 2 cl1 0.0354(4) 0.0540(6) 0.0549(4) 0.0009(2) 0.00071(19) 0.0004(2) c1 0.0397(11) 0.0542(16) 0.0418(11) –0.0072(9) 0.0000(8) 0.0028(9) c2 0.0393(11) 0.0741(19) 0.0426(11) –0.0032(11) –0.0012(8) 0.0078(10) c3 0.0395(12) 0.057(2) 0.0559(14) –0.0115(10) –0.0057(9) –0.0007(9) o1 0.0486(10) 0.0808(15) 0.0522(10) 0.0070(9) –0.0030(7) 0.0085(9) o2 0.0358(9) 0.1009(18) 0.0567(10) 0.0063(10) 0.0010(8) 0.0041(9) n1 0.0355(10) 0.0585(17) 0.0469(10) –0.0009(8) 0.0005(8) –0.0033(9) 65 the wide absorption band in the range 3300–2500 cm–1 is characteristic of stretching vibrations of the n–h and o–h groups, involved into the system of hydrogen bonds [5, 9]. stretching vibrations of ch2 are superimposed on top of the n–h and o–h bands [5, 9]. the  weak bands observed from ~2650 to  ~1850 cm–1 seem to  correspond to  the  overtones and combination bands of the fundamental vibrations. the  c=o stretching vibration is  located at about 1711 cm–1, confirming the existence of the β-alaninium cation in the lattice of β-ala·hcl. interestingly, this absorption band, in fact, seems to be splitted with the second minimum lying at about 1722 cm–1 and a shoulder — at 1680 cm–1. this may be related to  the  participation the c=o-groups in the hydrogen bonding. the  rest of  the  observed vibrational bands and their assignments are summarized in  table  5. in  general, it can be table 4 geometric parameters bond lengths, å bond value bond value c1–o1 1.199(3) o2–h2 0.71(4) c1–o2 1.323(3) n1–h1a 1.04(3) c1–c2 1.496(3) n1–h1b 0.87(3) c3–n1 1.477(3) n1–h1c 0.77(3) c3–c2 1.507(3) c2–h2a 0.9700 c3–h3a 0.9700 c2–h2b 0.9700 c3–h3b 0.9700 angles, ° angle value angle value o1–c1–o2 124.2(2) c3–n1–h1b 111(2) o1–c1–c2 125.2(2) h1a–n1–h1b 105(2) o2–c1–c2 110.6(2) c3–n1–h1c 112(3) n1–c3–c2 112.4(2) h1a–n1–h1c 103(3) n1–c3–h3a 109.1 h1b–n1–h1c 113(3) c2–c3–h3a 109.1 c1–c2–c3 114.4(2) n1–c3–h3b 109.1 c1–c2–h2a 108.7 c2–c3–h3b 109.1 c3–c2–h2a 108.7 h3a–c3–h3b 107.9 c1–c2–h2b 108.7 c1–o2–h2 115(3) c3–c2–h2b 108.7 c3–n1–h1a 112.7(19) h2a–c2–h2b 107.6 torsion angles, ° angle value angle value o1–c1–c2–c3 –6.3(4) n1–c3–c2–c1 67.5(3) o2–c1–c2–c3 175.3(2) 66 concluded that the character of the measured ir-spectrum of  β-ala·hcl, indicating the  compound containing β-alaninium cations involved in hydrogen bonds, is  in  agreement with the  results of the structural study. fig. 1. the elementary cell of β-ala·hcl in three projections. white balls — h, red balls — o, grey balls — c, blue balls — n, green balls — cl fig. 2. the structure of the β-ala·hcl in three projections with hydrogen bonds indicated as dashed blue lines and clearly seen stacking of double layers along the c-axis. color interpretation is the same as in fig. 1 67 fig. 3. the arrangement of the two halves of the double layer in the structure of β-ala·hcl: (a) view along the b-axis; (b) hydrogen bonds between the halves of the layer; (c) the half of the double layer with intrinsic hydrogen bonds. color interpretation is the same as in fig. 1 fig. 4. different views of the half layer with its intrinsic hydrogen bonds: (a) view along the b-axis as in fig. 3; (b) projection on the ab-plane. color interpretation is the same as in fig. 1 68 fig. 5. ir spectrum of β-ala·hcl at room temperature table 5 vibrational bands observed in the ir-spectrum of β-ala·hcl at room temperature ν, cm–1 assignment 3421 2×ν(c=o) 3172 νs(nh3 +), νa(ch2), νs(ch2), ν(n-h···o), ν(o-h···cl) 3122 3048 3016 2965 2947 2925–2902 2854 2834 2706 overtones, combinations 2607 2521 2490 2432 2395 2285 1981 1903 1830 1722 νa(c=o), νs(c=o) 1711 1680 69 conclusions mono-β-alanine hydrochloride was found to crystallize in the orthorhombic space group pbca with eight formula units per elementary cell. the  structure was shown to  consist of  double layers connected with each other by  weak van der waals forces and stacked along the  c-axis. each double layer, in  turn, consists of  two halves linked by hydrogen bonds between –c=o and –nh3 + groups. in addition, –nh3 + groups of the one half layer form hydrogen bonds with the  closest cl– anions of the other half layer. the results of  the  ir-spectroscopy were found to  be consistent with these conclusions. the ir-active vibrational bands were identified and their preliminary assignment was carried out based on the comparison with similar compounds reported previously. acknowledgements the authors would like to acknowledge dr. p. a. slepukhin (i. ya. postovsky institute of organic synthesis, ural branch of russian academy of sciences, ekaterinburg, russia) ν, cm–1 assignment 1587 δa(nh3 +) 1572 δa(nh3 +) 1493 δs(nh3 +) 1473 δs(ch2) 1402 νs(c-o) 1394 δ(ch2), ω(ch2) 1327 ω(ch2) 1306 τ(ch2) 1257 1186 ν(c–c), ρ(nh3 +) 1130 ρ(nh3 +) 1100 ρ(nh3 +) 1086 ν(c–c) 1053 νs(c-n) 953 ρ(nh3 +) 912 ρ(nh3 +) 860 ν(c–c) 831 ν(c-n), ν(c–c) 800 ρ(ch2) 636 δ(coo) 567 ω(coo) 509 τ(nh3 +) end of table 5 70 for his help in collecting the single crystal xrd data and dr. n. v. lakiza (ural federal university, ekaterinburg, russia) for spectroscopic measurements. this work was supported by the russian science foundation (grant no. 18-73-10059). references 1. fleck m., petrosyan am. salts of amino acids. crystallization, structure and properties. springer international publishing switzerland; 2014. 574 p. doi: 10.1007/978-3-319-06299-0 2. jose p, pant lm. the  crystal and molecular structure of  β-alanine. acta cryst. 1965;18:806–10. doi: 10.1107/s0365110x65001810 3. averbuch-pouchot mt, durif a, guitel jc. structures of β‐alanine, dl‐alanine and sarcosine monophosphates. acta cryst sect c. 1988;44:1968–72. doi: 10.1107/s0108270188000502 4. averbuch-pouchot mt. crystal structure of 3-ammonium propionic acid monohydrogen-phosphite, (h3nc2h4cooh)(hpo3h). z kristallogr. 1993;208:257–58. doi: 10.1524/zkri.1993.208.part-2.257 5. nemec i, gyepes r, micka z. the crystal structure, vibrational spectra and dsc measurements of mono-β-alaninium nitrate. j mol struct. 1999; 476:203–13. doi: 10.1016/s0022-2860(98)00545–6 6. sridhar b, srinivasan n, rajaram rk. bis(β‐alanine) hydrogen nitrate. acta cryst sect e. 2001;57:o1004–06. 7. rajagopal k, krishnakumar rv, natarajan  s. β-alaninium maleate. acta cryst sect e. 2001;57:o922–24. doi: 10.1107/s1600536801014672 8. pandiarajan s, sridhar b, rajaram rk. β-alaninium perchlorate. acta cryst sect e. 2001;57:o1130–32. 9. godzisz d, ilczyszyn m, ciunik z. β-alanine-hydrochloride (2:1) crystal: structure, 13c nmr and vibrational properties, protonation character. spectrochim acta pt a. 2003;59:235–44. doi: 10.1016/s1386-1425(02)00116–6 10. watson cc. infra-red identification of the n-methyl group in substituted amino acid hydrochlorides. spectrochim acta. 1960;16:1322–27. doi: 10.1016/s0371-1951(60)80005–7 11. sheldrick gm. phase annealing in shelx-90: direct methods for larger structures. acta cryst sect a. 1990;46:4674–73. doi: 10.1107/s0108767390000277 12. sheldrick gm. shelxl-97, program for crystal structure refinement. university of göttingen. 1997. 13. tulio m, rosado s, leonor m, duarte rs, fausto r. vibrational spectra (ft-ir, raman and mi–ir) of αand β-alanine. j mol struct. 1997;410–411:343–48. doi: 10.1016/s0022-2860(96)09695–0 new monomers for (bi)pyridine-containing polymers 209 new monomers for (bi)pyridine-containing polymers a. p. krinochkinab, m. i. savchuka, e. s. starnovskayaab, y. k. shtaitza, d. s. kopchuk ab, i. l. nikonovab, i. s. kovalev a, g. v. zyryanov ab*, v. l. rusinov ab, o. n. chupakhinab a ural federal university named after the first president of russia b. n. yeltsin, 19 mira st., ekaterinburg, 620002, russian federation b i. ya. postovsky institute of organic synthesis of ras (ural branch), 22/20 s. kovalevskoy/akademicheskaya st., ekaterinburg, 620990, russian federation *email: g.v.zyrianov@urfu.ru abstract. convenient methods for the synthesis of three monomers based on functionalized (bi)pyridines with using “1,2,4-triaizine” methodology have been developed. keywords: monomers; 1,2,4-triazines; (bi)pyridines; inverse demand diels-alder reaction received: 09.09.2020. accepted: 20.12.2020. published:30.12.2020. © krinochkin a. p., savchuk m. i., starnovskaya e. s., shtaitz y. k., kopchuk d. s., nikonov i. l., kovalev i. s., zyryanov g. v., rusinov v. l., chupakhin o. n., 2020 d o i: 1 0. 15 82 6/ ch im te ch .2 02 0. 7. 4. 13 krinochkin a. p., savchuk m. i., starnovskaya e. s., shtaitz y. k., kopchuk d. s., nikonov i. l., kovalev i. s., zyryanov g. v., rusinov v. l., chupakhin o. n. chimica techno acta. 2020. vol. 7, no. 4. p. 209–214. issn 2409–5613 introduction (2,2′-bi)pyridine containing polymers are of interest from the point of view of creating oled [1, 2] for redox catalytic reactions [3], as  electrolyte membrane fuel cell application [4] or anode materials components [5]. in this regard, the development of  convenient methods for the synthesis of compounds with the (poly) pyridine fragment and suitable for using as monomers, is an actual purpose. in this article we propose the convenient methods for the synthesis of three potential monomers of the (bi)pyridine series. experimental part 1h nmr spectra were recorded on a  bruker avance-400 spectrometer (400  mhz), the  internal standard was sime4. mass-spectra (ionization type — electrospray) were recorded on a  microtof-q ii instrument from bruker daltonics (bremen, germany). elemental analysis was performed on a perkin elmer pe 2400 ii chn analyzer. the  starting 4-bromophenylhydrazone 2 was obtained according to the described method [11]. general procedure for the  synthesis of 1,2,4-triazines 3 hydrazone 2 (605  mg, 2.5 mmol) was solved in  ethanol (30 ml) and solution of the corresponding carbaldehyde 1 (2.5 mmol) in ethanol (25 ml) was added. the  resulting mixture was kept at  room temperature for 12 h. the precipitate was filtered off, washed with ethanol and dried. then the obtained intermediate was suspended in acetic acid (30 ml) and mixture was heated to  reflux two times. solvent was removed under reduced pressure. 210 ethanol (30 ml) was added to the residue; the resulting crystals of 3 were filtered off, washed with ethanol and dried. the crude triazines were used directly in the next step without additional purification. 6-(4-bromophenyl)-3-(5-bromopyridin-2-yl)-1,2,4-triazine (3a). yield 630 mg (1.60 mmol, 64%). nmr 1h (dmso-d6, δ, ppm): 7.75–7.79 (m, 2h, c6h4br), 8.23 (dd, 1h, 3j 8.4 hz, 4j 2.4 hz, h-4(py)), 8.25–8.29 (m, 2h, c6h4br), 8.49 (d, 1h, 3j 8.4 hz, h-5(py)), 8.89 (d, 1h, 4j 2.4 hz, h-6(py)), 9.52 (s, 1h, h-5). esi–ms, m/z: 390.92 (m+h)+. 6-bromo-2-(6-(4-bromophenyl)1,2,4-triazin-3-yl)quinoline (3b). yield 800  mg (1.80 mmol, 72%). nmr 1h (dmso-d6, δ, ppm): 7.77–7.83 (m, 2h, c6h4br), 7.92 (dd, 1h, 3j 8.0 hz, 4j 2.0 hz, h-7(qui)), 8.15–8.20 (m, 2h, h-5,8(qui)), 8.30–8.35 (m, 2h, c6h4br), 8.56 and 8.70 (both d, 1h, 3j 8.4 hz, h-3 and h-4 (qui)), 9.61 (s, 1h, h-5). esi–ms, m/z: 440.94 (m+h)+. 3-(4-bromophenyl)-6-(thiophen2-yl)-1,2,4-triazine (7). a  mixture of  349  mg (1.7 mmol) of  2-bromo1-(thiophen-2-yl)ethanone 5, 732 mg (3.4 mmol) of hydrazide 6 and 25 ml of dmf was heated at 120 °c under argon for 10 h. the solvent was distilled off under reduced pressure, the  residue was treated with ethanol, and the  precipitate was filtered off. the crude triazine was used directly in the next step without addition purification. yield 343 mg (1.08 mmol, 63%). nmr 1h (dmso-d6, δ, ppm): 7.27 (dd, 1h, 3j 5.2 hz, 3.8 hz, h-4(thio)), 7.70–7.76 (m, 2h, c6h4br), 7.27 (dd, 1h, 3j 5.2 hz, 4j 0.8 hz, h-5 (thio)), 8.10 (dd, 1h, 3j 3.8 hz, 4j 0.8 hz, h-3(thio)), 8.37–8.42 (m, 2h, c6h4br), 9.43 (s, 1h, h-5). a general procedure for the synthesis of (bi)pyridines 4 and 8 the mixture of corresponding 1,2,4-triazine 3 or 7 (0.8 mmol) and 1-morpholinocyclo-pentene (0.64 ml, 4.0 mmol) was stirred at 200 °c for 2 h under argon atmosphere. then, the  additional portion of  1-morpholinocyclopentene (0.32 ml, 2.0 mmol) was added and the  resulting mixture was stirred for additional 1  h at the same conditions. the reaction mass was cooled to room temperature. the products were purified by flash chromatography (dcm as eluent) and then by recrystallization (ethanol). 4-(4-bromophenyl)-1-(5-bromopyridin-2-yl)-6,7-dihydro-5h-cyclopenta[c] pyridine (4a). yield 270 mg (0.63 mmol, 78%). nmr 1h (dmso-d6, δ, ppm): 2.08 (m, 2h, ch2-6), 3.04 (t, 2h, 3j 7.6 hz, ch2-7), 3.46 (t, 2h, 3j 7.6 hz, ch2-5), 7.48–7.54 (m, 2h, c6h4br), 7.64–7.70 (m, 2h, c6h4br), 8.11 (dd, 1h, 3j 8.4 hz, 4j 1.6 hz, h-4′), 8.30 (d, 1h, 3j 8.4 hz, h-5′), 8.47 (s, 1h, h-3), 8.75 (d, 1h, 4j 1.6 hz, h-6′). esi–ms, m/z: 428.96 (m+h)+. found, %: c 53.19, h 3.39, n 6.40. c19h14br2n2. calculated, %: c 53.05, h 3.28, n 6.51. 6-bromo-2-(4-(4-bromophenyl)6,7-dihydro-5h-cyclopenta[c]pyridin1-yl)quinoline (4b). yield 290 mg (0.60 mmol, 75%). nmr 1h (dmso-d6, δ, ppm): 2.14 (m, 2h, ch2-6), 3.08 (t, 2h, 3j 7.6 hz, ch2-7), 3.69 (t, 2h, 3j 7.6 hz, ch25), 7.51–7.57 (m, 2h, c6h4br), 7.66–7.71 (m, 2h, c6h4br), 7.86 (dd, 1h, 3j 8.8 hz, 4j 1.6 hz, h-7(qui)), 8.02 (d, 1h, 3j 8.8 hz, h-8(qui)), (d, 1h, 4j 1.6 hz, h-5(qui)), 8.40 and 8.56 (both d, 1h, 3j 8.8 hz, h-3 and h-4 (qui)), 8.54 (s, 1h, h-3). esi–ms, m/z: 478.98 (m+h)+. found, %: c 57.41, h 3.22, n 8.67. c23h16br2n2. calculated, %: c 57.53, h 3.36, n 8.53. 211 1-(4-bromophenyl)-4-(thiophen2-yl)-6,7-dihydro-5h-c yclopenta[c] pyridine (8). yield 228  mg (0.64 mmol, 80%). nmr 1h (dmso-d6, δ, ppm): 2.14 (m, 2h, ch2-6), 3.15 (t, 2h, 3j 7.6 hz, ch27), 3.20 (t, 2h, 3j 7.6 hz, ch2-5), 7.16 (dd, 1h, 3j 5.2 hz, 3.8 hz, h-4(thio)), 7.33 (dd, 1h, 3j 3.8 hz, 4j 0.8 hz, h-3(thio)), 7.41 (dd, 1h, 3j 5.2 hz, 4j 0.8 hz, h-5(thio)), 7.57–7.62 (m, 2h, c6h4br), 7.65–7.70 (m, 2h, c6h4br), 8.73 (s, 1h, h-3). esi–ms, m/z: 356.01 (m+h)+. found, %: c 60.53, h 3.81, n 4.07. c18h14brns. calculated, %: c 60.68, h 3.96, n 3.93. 1-(4-bromophenyl)-4-(5-bromothiophen-2-yl)-6,7-dihydro-5h-cyclopenta[c] pyridine (9). pyridine 8 (307  mg, 0.86 mmol) was dissolved in dmf (30 ml). nbromosuccinimide (184  mg, 1.0 mmol) was added and the  resulting mixture was stirred for 8  h at  50 ºc. then water (100  ml) was added to  the  mixture and precipitate formed was filtered off. the analytical sample was obtained by recrystallization (ethanol). yield 329 mg (0.76 mmol, 88%). nmr 1h (cdcl3, δ, ppm): 2.19 (m, 2h, ch2-6), 3.17 (t, 2h, 3j 7.6 hz, ch27), 3.20 (t, 2h, 3j 7.6 hz, ch2-5), 7.10 and 7.13 (d, 1h, 3j 3.8 hz, h-3 and h-4 (thio)), 7.61–7.65 (m, 2h, c6h4br), 7.67–7.71 (m, 2h, c6h4br), 8.69 (s, 1h, h-3). esi–ms, m/z: 433.92 (m+h)+. found, %: c 49.53, h 3.14, n 3.39. c18h13br2ns. calculated, %: c 49.68, h 3.01, n 3.22. results and discussion the “1,2,4-triazine” methodology has been used for the preparation of the target compounds [7–9]. in particular, we used the  modified synthetic route previously used for preparation of the luminophores of 2,2’-bipyridine [10] and 2-(2-pyridyl) quinoluine series [11]. namely, heterocyclization [6] of the corresponding commercially available aldehydes 1a,b and hydrazone of 4’-bromoisonitrosoacetophenone 2 [11] allowed to obtain the 1,2,4-triazine precursors 3, which are also of  interest as  monomers (scheme  1). the  further solvent-free inverse demand diels-alder reaction with 1-morpholinocyclopentene [12] allowed to synthesize compounds 4 of  2,2’-bipyridine and 2-(2-pyridyl)quinoluine series. we have also suggested an  approach for obtaining the  monomer of  monopyridine series. in this case we also used the “1,2,4-triazine” methodology. namely, br n n oh nh2 n o br n o br n n n n br n n n n br br br n n br n n br br br 1a 1b 2 3a 3b 4a 4b i i ii ii scheme 1. reagents and conditions: i) 12 h, r.t. / etoh, then acoh, 118 °c, 5 min; ii) 1-morpholinocyclopentene, 200 °c, neat, 3 h. 212 the  condensation of  2-bromoacetylthiophene 5 with two equivalents of hydrazide of 4-bromobenzoic acid 6 allowed to obtain the triazine precursor 7 (scheme 2). this heterocyclization has been known for a long time [13]. in this case reaction was realized during heating in dmf with no sodium acetate [14, 15]. the  further solvent-free inverse demand diels-alder reaction [12] with 1-morpholinocyclopentene allowed to obtain the condendes pyridine 8. for preparation of monomer 9 we used the bromination of thiophene ring of compound 8 at position c5 by nbromosuccinimide in dmf. this reaction is a well-known effective method [16, 17]. for the full conversion of compound 8 to 9 it is necessary the heating reaction mass at 50 °c. the structure of compounds 4 and 9 was confirmed by data of nmr 1н, mass-spectrometry and elemental analysis. the characteristics of compounds 4 correlate with ones for the previously published similar compounds [10, 11]. for compound 9 there are the signals of protons of thiophene ring as two doublets, protons of cyclopentene fragment, protons of 4-bromophenyl moiety, as well as proton of 6,7-dihydro-5hcyclopenta[c]pyridine as singlet. conclusions in conclusion, we have reported herein effective synthetic protocols for the preparation of  functionalized (bi)pyridines as  potential monomers for the  further synthesis of (bi)pyridines-based polymers for different applications. acknowledgements this work was supported by  the  russian foundation for basic research (grant #19-53-55002) and grants council of  the  president of  the  russian federation (no. nsh-2700.2020.3). references 1. li zr, editor. organic light-emitting materials and devices. boca raton: crc press, 2015. 813 p. 2. wang c, kilitziraki m, macbride jah, bryce mr., horsburgh le, sheridan ak, monkman ap, samuel idw. tuning the  optoelectronic properties of  pyridinecontaining polymers for light-emitting devices. adv mater. 2000;12:217–22. doi:10.1002/(sici)1521–4095(200002)12:3<217::aid-adma217>3.0.co;2-y o nh n br s br n br s n n n br s s o br br h2n 5 6 7 8 9 i ii iii scheme 2. reagents and conditions: i) dmf, 120 °c, 10 h; ii) 1-morpholinocyclopentene, 200 °c, neat, 3 h; iii) nbs, 50 °c, 8 h. 213 3. sato y, kagotani m, yamamoto t, souma y. novel effective poly(2,2′-bipyridine5,5′-diyl)-cucl2 catalyst for synthesis of dimethyl carbonate (dmc) by oxidative carbonylation of methanol. appl catal a-gen. 1999;185:219–26. doi:10.1016/s0926-860x(99)00175–1 4. xiao l, zhang h, jana t, scanlon e, chen r, choe e-w, ramanathan ls, yu s, denicewicz bc. synthesis and characterization of pyridine-based polybenzimidazoles for high temperature polymer electrolyte membrane fuel cell applicationsx. fuel cells. 2005;5:287–95. doi:10.1002/fuce.200400067 5. yang l, mihali v-a, brandell d, strømme m, sjödin m. conjugated pyridine-based polymers characterized as conductivity carrying components in anode materials. j phys chem c. 2014;118:25956–63. doi:10.1021/jp509606c 6. kozhevnikov vn, kozhevnikov dn, shabunina ov, rusinov vl, chupakhin on. an efficient route to 5-(hetero)aryl-2,4′and 2,2′-bipyridines through readily available 3-pyridyl-1,2,4-triazines. tetrahedron lett. 2005;46:1791–3. doi:10.1016/j.tetlet.2005.01.135 7. pabst gr, sauer j. a new and simple ‘lego’ system for the synthesis of 2,6-oligopyridines. tetrahedron lett. 1998;39:6687–90. doi:10.1016/s0040-4039(98)01437–3 8. rykowski a, branowska d, kielak j. a novel one-pot synthesis of annulated 2,2′-bipyridine ligands by inverse electron demand diels — alder reaction of  5,5′-bi1,2,4-triazines. tetrahedron lett. 2000;41:3657–9. doi:10.1016/s0040-4039(00)00436–6 9. kozhevnikov vn, shabunina ov, kopchuk ds, ustinova mm, könig b, kozhevnikov dn. facile synthesis of 6-aryl-3-pyridyl-1,2,4-triazines as a key step toward highly fluorescent 5-substituted bipyridines and their zn(ii) and ru(ii) complexes. tetrahedron. 2008;64:8963–73. doi:10.1016/j.tet.2008.06.040 10. starnovskaya es, kopchuk ds, khasanov af, tanya os, santra s, giri k, rahman m, kovalev is, zyryanov gv, majeed a, charushin vn. synthesis and photophysics of new unsymmetrically substituted 5,5′-diaryl-2,2′-bypiridine-based “push-pull” fluorophores. dyes pigm. 2019;162:324–30. doi:10.1016/j.dyepig.2018.10.040 11. kopchuk ds, chepchugov nv, starnovskaya es, khasanov af, krinochkin ap, santra s, zyryanov gv, das p, majee a, rusinov vl, charushin vn. synthesis and optical properties of new 2-(5-arylpyridine-2-yl)-6-(het)arylquinoline-based “pushpull” fluorophores. dyes pigm. 2019;167:151–6. doi 10.1016/j.dyepig.2019.04.029 12. kozhevnikov vn, ustinova mm, slepukhin pa, santoro a, bruce dw, kozhevnikov dn. from 1,2,4-triazines towards substituted pyridines and their cyclometallated pt complexes. tetrahedron lett. 2008;49:4096–8. doi:10.1016/j.tetlet.2008.04.138 214 13. saraswathi tv, srinivasan vr. a novel synthesis of 1,2,4-triazines. tetrahedron lett. 1971;12:2315–6. doi:10.1016/s0040-4039(01)96849–2 14. saraswathi tv, srinivasan vr. syntheses and spectral characteristics of 6-mono-, 3,6-di and 3,5,6-trisubstituted-1,2,4-triazines. tetrahedron. 1977;33:1043–51. doi:10.1016/0040–4020(77)80223–8 15. shtaitz yak, savchuk mi, kopchuk ds, taniya os, santra s, zyryanov gv, suvorova ai, rusinov vl, chupakhin on. efficient synthesis of methyl 6-(6-aryl-1,2,4-triazin-3-yl)pyridine-2-carboxylates. russ j org chem. 2020;56:548–51. doi:10.1134/s1070428020030306 16. khan ms, al-mandhary mra, al-suti mk. feeder n, nahar s, koehler a, friend rh, wilson pj, raithby pr. synthesis, characterisation and electronic properties of a series of platinum(ii) poly-ynes containing novel thienyl-pyridine linker groups. dalton trans. 2002;12:2441–8. doi:10.1039/b201073a 17. hu b, fu s-j, xu f, tao t, zhu h-y, cao k-s, huang w, you x-z. linear heterocyclic aromatic fluorescence compounds having various donor-acceptor spacers prepared by the combination of carbon-carbon bond and carbon-nitrogen bond cross-coupling reactions. j org chem. 2011;76:4444–56. doi:10.1021/jo200065d determination of phenolic compounds in medicinal preparations by galvanostatic coulometry chimica techno acta letter published by ural federal university 2021, vol. 8(1), № 20218110 journal homepage: chimicatechnoacta.ru doi: 10.15826/chimtech.2021.8.1.10 1 of 3 determination of phenolic compounds in medicinal preparations by galvanostatic coulometry n.n. yaschenko * , s.v. zhitar, e.g. zinovjeva chuvash state university, moskovsky ave., 15, cheboksary, chuvash republic, russia * corresponding author: n.yashenko.n@mail.ru this short communication (letter) belongs to the mosm2020 special issue. © 2021, the authors. this article is published in open access form under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). abstract in this work, the possibility of using reactions of electrogenerated titrants with phenolic compounds was studied and a method for their coulometric determination in medicaments by galvanostatic coulometry was developed. the research objects were: rutin, salicylic acid and drugs containing phenolic compounds such as «ascorutin», «salicylic paste» and «salicylic ointment» of russian manufacture. electrogenerated halogens (cl2, br2 and i2) and hexacyanoferrate(iii)ions were used as titrants. it was found that for the quantitative determination of phenolic acids, the optimal reagent is electrogenerated bromine, for rutin electrogenerated bromine and iodine, and for ascorbic acid any of the studied electrogenerated titrants (cl2, br2, i2 and [fe(cn)6] 3). the correct definition was checked by the «entered-found» method, the error does not exceed 2%. as experimental studies have shown, our method of coulometric titration with electrogenated bromine and iodine is characterized by good reproducibility of results, expression, accuracy and can be used to determine phenolic compounds in drugs, for example, «ascorutin» tablets. it should be noted that by our procedure it is possible to determine the spectrum of phenol-containing compounds (rutin, ascorbic and salicylic acids) in drugs without their preliminary separation. therefore, the coulometric method using electrogenerated titrants can be recommended for the determination of salicylic, ascorbic acids and rutin in dosage forms. the proposed method is accurate and eliminates the experiment error in comparison with the pharmacopoeic method. keywords galvanostatic coulometry phenolic compounds flavonoids received: 31.10.2020 revised: 25.12.2020 accepted: 25.12.2020 available online: 13.04.2021 1. introduction the phenolic group is found in the structure of many medicinal substances and largely determines their pharmacological, physicochemical and chemical properties. quality control of such medicinal substances requires the determination of indicators characterizing phenolic function. this makes it necessary to study the reactivity and methods of chemical analysis of drugs from the class of phenols. the guarantee of the effectiveness and safety of medicines is the creation of national standards for their quality. in order to establish the conformity of the quality of medicines to the regulated requirements, it is necessary to use various analytical methods. the conclusion about the quality of drugs depends to a large extent on the quality of the method itself. therefore, it is necessary to evaluate the suitability of analytical methods for their intended use. however, the state pharmacopoeia [1] does not always offer the most reliable method for determining the active ingredient in the dosage form. one of the promising methods of quantifying biologically active compounds is the galvanostatic coulometry method [2], characterized by simplicity of the experiment, expressiveness, high accuracy, lack of expensive equipment and use in a conventional control and analytical laboratory. the purpose of this work is to study the possibility of using reactions of electrogenerated titrants with phenolic compounds and to develop a reliable method for their coulometric determination in drugs. http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2021.8.1.10 http://creativecommons.org/licenses/by/4.0/ chimica techno acta 2021, vol. 8(1), № 20218110 letter 2 of 3 2. results and discussion the objects of the study were: rutin as a representative of the class of flavonoids and polyphenols; salicylic acid as a representative of phenolic acids and drugs containing phenolic compounds such as «ascorutin», «salicylic paste» and «salicylic ointmen». the titrants used were electrogenated halogens (cl2, br2 and i2) and hexacyanoferrate(iii)-ions. generation was carried out at a constant current strength of i = 10 ma, and the equivalence point was fixed biamperometrically with two polarized electrodes on the coulometric analyzer «expert-006». the selected halogens are not only capable of oxidizing phenolic compounds, but also enter into electrophilic substitution reactions of the benzene ring, while the hexacyanoferrate(iii)-ions [fe(cn)6] 3 are mild oxidizing agents. based on the studies, we found that the electrogenated hexacyanoferrate(iii)-ion and electrogenated iodine enter into redox reactions, but since the redox potential (0.356 v) is low, therefore their oxidative force is not enough to oxidize salicylic acid. salicylic acid is easily oxidized by chlorine, but this reaction proceeds nonstoichiometrically. therefore, to quantify phenolic acids, an electrogenerated bromine is chosen as the optimal reagent from all of us studied, which allows the reactions to be carried out quickly and stoichiometrically. analysis of salicylic acid content in real objects drugs «salicylic paste» and «salicylic ointment» confirmed the correctness of the choice of electrogenerated bromine as a titrant. there is no information on the mechanism of interaction of routine with halogens in the literature. we assume that together with the oxidation of hydroxyl groups, an electrophilic substitution reaction in the benzene ring is also possible. we found that rutin does not interact with the electrogenerated [fe(cn)6] 3, while with cl2 the reaction proceeds nonstoichiometrically; and with electrogenated bromine and iodine, the reactions are carried out at a molar ratio of rutin:titrant of 1:1 and 1:2, respectively. therefore, to quantify the routine in real objects, it is recommended to use electrogenerated br2 and i2 as titrants. in medicinal phenol-containing drugs, ascorbic acid is often contained, as for example, in the «ascorutin» preparation produced by ojsc «kiev vitamin plant». ascorbic acid is a potent antioxidant capable of stopping the growth of cancer stem cells. one «ascorutin» tablet contains ascorbic acid 0.05 g, routine 0.05 g and auxiliary substances (sugar, potato starch, calcium stearate, talc). therefore, we also studied the interaction of ascorbic acid with electrogenerated titrants and found that it with all titants is easily oxidized to dehydroascorbic acid at a molar ratio of ascorbic acid to titrant of 1:1. results of coulometric determination of ascorbic by reaction with electrogenerated titrant are given in table 1. the correctness of the determination was checked by the «entered – found» method, the number of tests conducted n = 4, statistical reliability p = 0.95. as can be seen from table 1, it is better to use halogen titants to quantify ascorbic acid, they are more reactive than [fe(cn)6] 3 and their use provides very good accuracy. the determination error, for all titrants as a whole, does not exceed 1.8%, and for halogen titrants within 1%. in living organisms and in dosage forms, the antioxidant properties of phenolic compounds always work in tandem with ascorbic acid, so there is a need to develop a method for determining them in the joint presence. we propose a method of joint determination of rutin and ascorbic acid in the preparation «ascorutin». i2 and br2 were used as electrogenerated titrants for «ascorutin». since the main active substances (rutin and ascorbic acid) in the «ascorutin» tablets differ in solubility, the following procedure can be proposed for quantitative determination. one «ascorutin» tablet was first treated with ethyl alcohol (96% by weight) and the resulting alcohol extract was titrated with electrogenated bromine and iodine. the titration results are used to calculate the rutin content of the preparation. the results are shown in table 2. another tablet «ascorutin» is treated with warm distilled water and the obtained water extract is titrated with electrogenated bromine and iodine. the content of ascorbic acid in the preparation is calculated from the titration results. the results are shown in table 3. as shown by the experimental data (tables 2 and 3), the developed coulometric titration technique with electrogenated bromine and iodine is characterized by good reproducibility of results, expressiveness, accuracy and can be used to determine the routine and ascorbic acid in drugs. table 1 results of coulometric determination ascorbic acid reaction with electrogenerated titrants (n = 4, р = 0.95) power generation titrant entered аscorbic acid, μg found ascorbic acid, μg sr, % br2 180 182 ± 4 0.99 i2 179 ± 3 0.89 cl2 185 ± 4 1.07 [fe(cn)6] 3– 191 ± 5 1.8 hereinafter, sr is the relative standard deviation. table 2 results of coulometric determination of the routine in «ascorutin» (n = 4, р = 0.95) power generation titrant entered tablets «ascorutin», μg found «ascorutin» tablets, μg sr,% br2 300 294 ± 2 0.99 i2 289 ± 4 0.89 table 3 results of coulometric determination of ascorbic acid in «askorutin» (n = 4, р = 0.95) power generation titrant entered tablets «ascorutin», μg found «ascorutin» tablets, μg sr,% br2 300 295 ± 3 1.08 i2 294 ± 2 1.16 chimica techno acta 2021, vol. 8(1), № 20218110 letter 3 of 3 3. conclusions thus, the coulometric method we have developed using electrogenerated titrants (cl2, br2 and i2 and hexacyanoferrate(iii)-ions) can be recommended for the determination of salicylic acid, ascorbic acid and rutin in their joint presence in dosage forms. the method is characterized by high reliability, accuracy and expression compared to the pharmacopoeia method [1], and also eliminates the error of the experiment. references 1. mashkovsky md, babayan ea, oboimakova an, bylaev vm, severtsev va, lybimov bi, sokolov sd, tentsova ai. gosudarstvennaya farmakopeya. obshchie metody analiza. lekarstvennoe rastitel’noe syr’yo. [state pharmacopoeia. general methods of analysis. medicinal plant raw materials]. moscow: medicina; 1990. v. 2. 453 p. russian. 2. gruzik tv. electrochemical determination of the total content of organic acids in wines, wine materials and juices [dissertation]. krasnodar (russia): kuban state university of technology; 2015. 123 р. in situ synthesis, structural chemistry and vibrational spectroscopy of zn-doped ca5mg4(vo4)6 chimica techno acta article published by ural federal university 2022, vol. 9(2), no. 20229201 eissn 2411-1414; chimicatechnoacta.ru doi: 10.15826/chimtech.2022.9.2.01 1 of 8 in situ synthesis, structural chemistry and vibrational spectroscopy of zn-doped ca5mg4(vo4)6 anna s. tolkacheva a* , sergey n. shkerin a , sofya a. petrova b , olga m. fedorova b , svetlana g. titova b , ivan i. leonidov a* a: institute of high-temperature electrochemistry, 620990 ekaterinburg, russia b: institute of metallurgy, 620016 ekaterinburg, russia * corresponding authors: asergeevnatolkacheva@gmail.com; ivanleonidov@ihim.uran.ru this paper belongs to the regular issue. © 2021, the authors. this article is published in open access form under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). abstract the phase formation of the solid solution ca5mg4–xznx(vo4)6 (0≤x≤4) was studied in situ using differential scanning calorimetry and hightemperature x-ray powder diffraction (xrpd). xrpd analysis shows the appearance of unavoidable secondary pyrovanadate phases using conventional synthesis methods. the local structure of the solid solution was verified by vibrational spectroscopy. the analysis of the infrared and raman spectroscopy data allows establishing the main features between vanadate garnets and their isostructural analogs among natural silicates. keywords crystal structure vibrational spectroscopy x-ray diffraction ceramics differential scanning calorimetry pyrovanadate garnet received: 18.08.2021 revised: 17.03.2022 accepted: 17.03.2022 available online: 23.03.2022 1. introduction a wide range of compounds with the general formula a3b2v3o12 that belong to calcium vanadate garnets is known nowadays. this system includes complex oxides with substitution of calcium ions in a position by alkaline, (li, na, k), alkaline-earth (sr) and other metal cations like cu, ag, cd, pb [1, 2]. heterovalent substitution in b position in the garnet structure a3b2v3o12 (b = mg2+, mn2+, co2+, ni2+, cu2+, zn2+, cd2+) has been analyzed by many research groups [1–3]. ca5mg3zn(vo4)6 was first characterized as a garnet having the crystal symmetry of space group 𝐼4̅3𝑑 [4]. the lattice comprises the vo4 tetrahedra sharing edges with deformed cao8 dodecahedrons. the crystal structure of most of garnet-related vanadates is described with the symmetry of space group 𝐼𝑎3̅𝑑 [1]. these compounds attract increasing attention due to a cation deficiency, where the vacancy concentration in a position varies from 1/10 to 3/10 [5–8]. the nonstoichiometry values in b position were evaluated for ca5co4(vo4)6 [9]. inorganic materials based on calcium vanadates have been studied as a new series of low-temperature co-fired ceramics [3] with promising microwave characteristics below 100 °с [10–14]. the optical and photophysical properties of compounds doped with in, ta [15], and lanthanide ions [16–18] have been considered in view of their application in solid-state lighting. ca5mg4(vo4)6 is characterized by cationic transport [19], whereas the vanadates ca5mg4−xcox(vо4)6 (1≤x≤4) demonstrate predominantly electronic conductivity about 10–2 s·cm−1 at 850 °c [20]. different chemical routes are used to synthesize vanadates as single crystals as well and in polycrystalline forms [11–14, 20, 21]. among them, solid-state method can be carried out in a quartz ampule upon annealing at 975 °c [4]. the melting point of v2o5 is, nevertheless, about 650 °c, and, typically, vanadium oxide melt interacts with quartz. some single-crystal fiber methods are also employed for preparation of calcium vanadates [22, 23]. however, most of the approaches for the synthesis of target compounds of this class of inorganic solids are highly time-consuming and require special equipment. the widely reported method implies a solid-state reaction [24–26]. for example, the synthesis of ca5m4(vo4)6 (m = mg and zn) can be done taking mgco3, zno, caco3 and either nh4vo3, or v2o5 as initial reagents with further annealing of the reaction mixture at 800–850 °c. the attempt to obtain ca5zn4−xmgx(vo4)6 (0≤x≤3) via a solid-state reaction results in the appearance http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2022.9.2.01 mailto:asergeevnatolkacheva@gmail.com mailto:ivanleonidov@ihim.uran.ru http://creativecommons.org/licenses/by/4.0/ https://orcid.org/0000-0002-7546-7807 https://orcid.org/0000-0003-4064-0670 http://orcid.org/0000-0002-9796-5794 https://orcid.org/0000-0002-0692-770x https://orcid.org/0000-0003-2891-3453 https://orcid.org/0000-0002-6635-4747 https://crossmark.crossref.org/dialog/?doi=https://doi.org/10.15826/chimtech.2022.9.2.01&domain=pdf&date_stamp=2022-3-23 chimica techno acta 2022, vol. 9(2), no. 20229201 article 2 of 8 of zno as a second phase [10]. the problems of synthesis of the single-phase powders are reported not only for the above-mentioned system but for other compositions of garnet-type vanadates [1, 27, 28]. wet-chemical synthesis procedure provides high homogeneity of its products [29, 30]. many modified sol-gel methods using the corresponding nitrates as initial reagents are often applied to prepare vadanate-based solid solutions [15, 31, 32]. other changes in the chemical routes to synthesize different inorganic solids include also mechanochemical treatment, variation of educts and raw materials, additional intermediate grindings and heat treatments, alternation in temperature of annealing. the observations listed above forces us to pay more attention to phase formation of the vadanate subclass of inorganic compounds. this can be accompanied by possible vaporization of vanadium oxides [33]. ca5mg4–xznx(vo4)6 (0≤x≤4) is chosen as a model solid solution among garnet-related vanadates. differential scanning calorimetry (dsc) analysis supplemented by gas emission analysis, in situ x-ray diffraction and evaluation of the local structure employing vibrational spectroscopy facilitate the solution of the problems in chemistry of vanadate-based materials more comprehensively than was reported earlier [4, 5, 10, 20, 31, 32]. the present study is also relevant to understanding of the synthesis processes of other garnettype compounds such as silicates, hafnates, zirconates, germanates, etc. 2. experimental 2.1. reagents the target ceramic samples of ca5mg4–xznx(vo4)6 (0≤x≤4) were synthesized via a salt decomposition reaction using caco3 (99%), mgco3 (99.999%), zno (99%), v2o5 (99.999%) or nh4vo3 (98%), hcooh (98%, concentration 99%) and c6h8o7·h2o (99%) as initial reagents. those taken in a stoichiometric ratio were dissolved in distilled water with hcooh. ethanol was used as a grinding medium. next, c6h8o7·h2o was added with subsequent stirring and heating at 70–80 °c on a hot plate. homogeneous water reagent solutions were slowly evaporated into a gel, which then formed a dry residue. 2.2. in situ synthesis dsc and thermal gravimetric analysis (tg) were performed to estimate the optimal temperature of heat treatment of the final product. thermal analysis was conducted with a netzsch sta 449c jupiter simultaneous analyzer operating with the heating rate of 10 k/min. in situ phase formation was studied by collecting of the x-ray powder diffraction (xrpd) patterns upon heating of the reagents 5cao:4mgo:3v2o5 and 5cao:4zno:3v2o5 taken with the stoichiometric ratios. room temperature xrpd patterns before heating and after the phase formation were recorded using a shimadzu xrd-7000 maxima diffractometer and cu kα radiation in the 2θ range between 10° and 90°. high temperature (ht) xrpd in the 2θ range between 15° and 60° was employed with ni-filter instead of a graphite monochromator and a shimadzu ha-1001 sample heating attachment (the scanning rate 1 °/min; the 2θ step of 0.02°). the temperature uncertainty was maintained at less than 1 °c. the xerogels obtained during the ht xrpd experiments were placed on a pt plate. the samples were heated from 20 °c up to 700 °c at the rate <10 °c/min. further heating was carried out from 700 °c to 785 °c in the steps of 15 °c and the rate <5 °c/min. the samples were maintained for 1 h prior to every measurement at the temperatures listed. heat treatment at 785 °c was continued for over 12 h. further heating was carried out on mgo-containing sample from 850 °c to 950 °c with the step 50 °c and the rate <5 °c/min with the dwell time of 1 h at every step. the scanning temperatures were selected according to the dsc curves of the precursor samples. the highest scanning temperature (820 °c) was chosen for ca5zn4(vo4)6. 2.3. characterization xrpd patterns were collected at room temperature using a rigaku dmax-2200 diffractometer operating with cu kα1 radiation over the angular range 15°≤2θ≤80° with the step increment δ2θ = 0.02°. the xrpd patterns were compared with those in the icsd-web database (2021). rietveld refinement of the crystal structures was performed using the xrpd data collected on a bruker d8 advance diffractometer with position-sensitive detector våntec-1 operating with cu kα1 radiation (the angular range 10°≤2θ≤134°; the step increment δ2θ=0.021°). the xrpd patterns were compared with those in the pdf4+icdd (2018) [34]. the crystallographic computing system jana2006 [35] was employed for rietveld refinements (figs. s1–s5). raman spectra were recorded on a renishaw ramascope u1000. this setup comprised a confocal leica dml microscope, 50× olympus objective lens (the numerical aperture of 0.55), a notch filter, and a cooled charge-coupled device detector. a renishaw hene laser operating at 632.8 nm and 4 mw at the sample was employed as an excitation source. typical spectra acquisition time was 300 s and the resolution was 1 cm−1. the raman spectrum of silica was used for spectral calibration. fourier transform infrared (ftir) measurements were carried out on a bruker vacuum spectrometer tensor 27 using kbr pellets. the ftir spectra were collected in a transmittance mode in the range from 400 cm–1 to 1000 cm–1 with the resolution of 2 cm−1. the ftir spectra in the range of 50–600 cm–1 were recorded using atr technique with a diamond optical element employed at a bruker vertex 70v spectrometer. vibrational spectroscopy was performed at room temperature. 3. results and discussion decomposition of the precursor colloidal solution upon heating in air is an exothermic process with the mass loss chimica techno acta 2022, vol. 9(2), no. 20229201 article 3 of 8 mainly between 200 °c and 730 °c (fig. 1). the total mass loss of the precursor mixture of ca5mg4(vo4)6 is 61.02 wt%, whereas the value of 52.57 wt% was obtained in the case of ca5zn4(vo4)6 up to 730 °c. following the dsc data of a dried mixture of reagents, one can observe the water desorption at ~220 °c (fig. 1) with the maximum of the dsc signal at 250 °c. it is accompanied by emission of со2 and no2 after decomposition of organics and (hn4)− groups with energy uptake. the slow exothermal process at 270 °c associated with the prolonged emission of h2o, со2, no2 and no was reported in earlier papers [31]. however, the next stages depicted in the dsc plots differ due to the other precursors chosen for synthesis. at 350 °c, there is an exothermal stage with the ongoing emission of the gases listed above (со2 and no2). after the known exothermal effect at 372 °c [31], a well pronounced exothermal peak near 450 °c correlates with emission of со2, no2 and h2o. this can evidently be explained by the exhaust that forms during the decomposition of the available organic matrix. the energy output at 510–528 °c is accompanied by emission of со2, no and no2. extraction of со2 and no2 occurs up to 730 °c with energy consumption. the observed disagreement between the obtained results and those reported earlier [31] arises from two main reasons. first, this difference may be caused by the reactants used to synthesize the target compositions. second, the dsc data are analyzed in this study, whereas only the dta results were presented previously [31]. the dsc curves of the dried precursor of ca5zn4(vo4)6 demonstrate several exothermal peaks at 396 °c, 451 °c, 528 °c and 727 °c and one endothermal one at 689.5 °c (fig. 1). some of the processes listed above can be evaluated more accurately employing in situ x-ray diffraction as an additional method. the xrpd patterns of dried sol-gel precursors show the phase formation of caco3 at 360 °c which is stable up to 785 °c (fig. 2 and 3). its appearance is accompanied by the emission of со2 from the decomposition of an organic matrix. the pyrovanadates camgv2o7 and mg2v2o7 are formed at 360 °c along with calcium carbonate (fig. 2). the exothermal process near 450 °c is assigned to the formation of the intermediates α-zn2v2o7 and ca2v2o7 whose crystal structures are characterized by monoclinic symmetry (fig. 1–3). the energy output at 510 °c (or 566 °c in ref. [31]) corresponds to the phase with a cubic structure (space group 𝐼𝑎3̅𝑑). extraction of со2 observed up to 730 °c with energy consumption is caused by the start of calcite decomposition, which ends at 785 °c, according to the xrpd data (fig. 1–3). the mixture of phases is observed from 460 °c to 950 °c in the magnesium-containing powder sample (fig. 2), whereas the zinc-containing sample is characterized by coexistence of the phases like caco3, pyrovanadates, garnet-type vanadate in the temperature range 460–820 °c (fig. 3). fig. 2 ht xrpd profiles of ca5mg4(vo4)6 prepared via a sol-gel process: * – ca5mg4(vo4)6, ♦ – mg2v2o7, ● – camgv2o7,  – ca2v2o7 (p21/c),  – ca2v2o7 (p1̅),  – caco3 fig. 1 dsc and tg curves with mass spectrometry analysis of the gaseous phase during heating of the xerogel powders ca5mg4(vo4)6 (left) and ca5zn4(vo4)6 (right) prepared by the sol-gel process (a) (b) chimica techno acta 2022, vol. 9(2), no. 20229201 article 4 of 8 in turn, the phase transition in zn2v2o7 implies the change of space group c2/c→c2/m at 620 °c [36]. ca2v2o7 undergoes also the phase transition p1̅→p21/c above 900 °c. camgv2o7 melts incongruently at 885 °c, whereas ca2v2o7 and mg2v2o7 are thermally stable even at 950 °c. the coexistence of ca5mg4(vo4)6 (space group ia3̅d) and camgv2o7 (space group p21/c) is detected at room temperature in the reaction products (fig. 2). in this way, one can carry out synthesis at 850 °c and, after shortterm heat treatment, can obtain the target product with contamination of ca2v2o7. the presence of satellite pyrovanadate phases was revealed in many earlier studies on evaluation of the most efficient chemical route to synthesize garnet-type vanadates [3, 5, 15]. the elimination of these satellite pyrovanadates is a complex problem which is often dismissed when the target chemical products of ca5m4(vo4)6 (m = mg, zn, co, etc.) are synthesized. fortunately, the impurity-free samples can be obtained. however, this usually requires a long duration of thermal treatment [4, 5]. indeed, the heat treatment at 980 °c for 150 h allows a single-phase sample of ca5mg4(vo4)6 to be prepared. this temperature of the final annealing during the synthesis procedure corresponds to the melting point of mg2v2o7. fig. 3 ht xrpd profiles of ca5zn4(vo4)6 prepared via a sol-gel process: * – ca5zn4(vo4)6,  – ca2v2o7 (p21/c),  – ca2v2o7 (p1̅),  – caco3,  – α-zn2v2o7,  – β-zn2v2o7 the xrpd analysis shows that polycrystalline ca5mg4–xznx(vo4)6 (0≤x≤4) with some quantity (2–3 wt%) of pyrovanadate phases is formed via the sol-gel process (fig. 4). the crystal structures of ca5mg4–xznx(vo4)6 (0≤x≤4) were refined using the rietveld method (table s1; supporting information). the solid solution ca5mg4-xznx(vo4)6 (0≤x≤4) crystallizes in the cubic space group ia3̅d, z = 8 (supporting information: fig. s1–s5). the fractional atomic coordinates and refinement parameters are listed in table 1. magnesium and zinc cations have close radii that promotes the formation of solid solutions [38]. both mg and zn ions occupy the octahedral position (16a) and the formation of the solid solutions is proved by a linear change in the cell parameter and volume when zinc concentration increases (fig. 4). the lattice parameter a refined for ca5mg3zn(vo4)6 deviates from the linear dependence because of a relatively large amount of camgv2o7 impurity (supporting information: table s1). the site occupancy factor of ca2+ positions is chosen to be about 5/6 that is close to the data reported by ronniger and mill [6]. cation deficiency from 1/10 to 3/10 is not surprising and was also observed in other garnet-type vanadates [6, 39]. therefore, a study of the local structure of these compounds becomes highly relevant in view of high deficiency in the cation sublattice. eight molecules of ca2.5mii2(vo4)3 (mii = mg, zn) per primitive cell in the 𝐼𝑎3̅𝑑, (𝑂h 10) structure support 3×8×19.5 = 468 modes of vibration with k=0 involving the zero-frequency translational motion of the crystal. these vibrations are classified according to irreducible representations of the point group of the elementary cell [40]. given that the number of equivalent sites in any set is defined by the order of the point group divided by the order of the site symmetry subgroup for the primitive or primitive rhombohedral lattices, the number is greater for the centered lattices. the body-centered unit cells have twice as many points as the primitive ones (table 1). fig. 4 xrpd patterns of ca5mg4–xznx(vo4)6 (0≤x≤4) (a), concentration dependence of the lattice parameters in ca5mg4–xznx(vo4)6 (0≤x≤4) (b) chimica techno acta 2022, vol. 9(2), no. 20229201 article 5 of 8 the vibration modes of the full symmetry group are characterized by the following irreducible representations of oh γ 𝑐𝑟𝑦𝑠𝑡 = 3𝐴1g + 5𝐴1u + 5𝐴 2g + 5𝐴 2u + 8𝐸g + 10𝐸u + 13𝐹 1g + 18𝐹 1u + 14𝐹 2g + 15𝐹2u (1) three acoustic modes are described by γacoust = f1u and the remaining ones, γ𝑣𝑖𝑏 𝑐𝑟𝑦𝑠𝑡 = 3𝐴1g + 5𝐴1u + 5𝐴2g + 5𝐴2u + 8𝐸g + 10𝐸u + 13𝐹1g + 17𝐹1u + 14𝐹2g + 15𝐹2u, (2) correspond to the optical modes, among which a1u, a2g, a2u, eu, f1g and f2u are inactive. the modes of the f1u symmetry are infrared active and the combination of a1g, eg and f2g is raman active. infrared and raman activities are presented in table 2. vibrational modes can be classified in two main categories [41, 42], i.e., internal modes of the tetrahedral vo4 unit with the molecular symmetry s4 and external modes, which include translations of ca2+, mg2+, zn2+ and [vo4]3− ions, and librations of [vo4]3−. in a lattice of a2.5b2(vo4)3, zone-center raman active vibrational modes can be distinguished for ca2+ cations (a-site in a2.5b2(vo4)3) and vo4 tetrahedra, whereas mg2+/zn2 cations (b-site) do not produce raman active vibrations. table 1 fractional atomic coordinates and isotropic thermal displacement parameters (b) of ca5mg4–xznx(vo4)6, 0≤x≤4 (sg ia3̅d, z = 8) atom wyckoff position x y z sof* b ca5mg4(vo4)6 rwp = 0.112, rp = 0.062, gof = 0.058 ca 24c 0.125 0 0.25 0.83 0.68(5) mg 16a 0 0 0 1.00 0.10(4) v 24d 0.375 0 0.25 1.00 0.18(3) o 96h 0.0980(2) 0.2001(1) 0.2887(1) 1.00 0.67(7) ca5mg3zn(vo4)6 rwp = 0.163, rp = 0.099, gof = 0.041 ca 24c 0.125 0 0.25 0.83 0.10(4) mg/zn 16a 0 0 0 0.75/0.25 0.57(5) v 24d 0.375 0 0.25 1.00 0.10(3) o 96h 0.0938(3) 0.2032(1) 0.2896(1) 1.00 0.39(6) ca5mg2zn2(vo4)6 rwp = 0.128, rp = 0.086, gof = 0.020 ca 24c 0.125 0 0.25 0.83 0.51(6) mg/zn 16a 0 0 0 0.5/0.5 0.09(3) v 24d 0.375 0 0.25 1.00 0.20(4) o 96h 0.0961(2) 0.1966(2) 0.2879(2) 1.00 0.58(8) ca5mgzn3(vo4)6 rwp = 0.162, rp = 0.089, gof = 0.037 ca 24c 0.125 0 0.25 0.83 0.16(2) mg/zn 16a 0 0 0 0.25/0.75 0.30(4) v 24d 0.375 0 0.25 1.00 0.25(3) o 96h 0.0929(2) 0.1969(1) 0.2891(1) 1.00 0.40(6) ca5zn4(vo4)6 rwp = 0.142, rp = 0.078, gof = 0.045 ca 24c 0.125 0 0.25 0.83 0.63(2) zn 16a 0 0 0 1.00 0.22(1) v 24d 0.375 0 0.25 1.00 0.10(2) o 96h 0.0955(5) 0.1977(3) 0.2885(1) 1.00 0.73(4) * sof stands for site occupancy factor table 2 classification of the k = 0 unit cell modes* for ca2.5m ii 2(vo4)3, m ii = mg, zn (sg 𝐼𝑎3̅𝑑, z = 8) factor group oh lattice modes internal modes [vo4] 3− selection rules acoustic librational translational infrared raman a1g 1 2 xx + yy + zz a1u 2 3 a2g 2 3 a2u 1 2 2 eg 1 2 5 xx + yy + 2zz, √3xx − √3yy eu 1 4 5 f1g 3 4 6 f1u 1 2 8 7 t f2g 2 5 7 xy, yz, xz f2u 3 6 6 overall 3 36 87 108 ∑ = 234 * the f1u modes are infrared and the a1g, eg and f2g modes are raman active. chimica techno acta 2022, vol. 9(2), no. 20229201 article 6 of 8 translations and librations of the vo4 unit are associated with the representations below: t′(vo4) = a1u + a2g + eg + eu + 2f 1g + 3f1u + 3f 2g + 2f 2u (3) l(vo4) = a1g + a2u + eg + eu + 3f 1g + 2f1u + 2f 2g + 3f 2u . (4) once acoustic modes are subtracted, the external modes are distributed among the irreducible representation a1g + 2a1u + 2a2g + 3a2u + 3eg + 5eu + 7f1g + 10f1u + 7f2g + 9f2u. therefore, the internal modes of the tetrahedral vo4 unit can be characterized by γ𝑣𝑖𝑏 𝑐𝑟𝑦𝑠𝑡 = 2𝐴1g + 3𝐴1u + 3𝐴2g + 2𝐴2u + 5𝐸g + 5𝐸u + 6𝐹1g + 7𝐹1u + 7𝐹2g + 6𝐹2u. (5) in ca2.5mii2(vo4)3 (mii = mg, zn), the symmetry of the vo4 tetrahedron changes due to the site symmetry and crystal field effects, and all the internal modes are split. the latter are summarized in table 3. ftir and raman spectroscopy techniques are employed to study possible structural changes when mg2+ cations are substituted for zn2+ in the solid solution ca5mg4−xznx(vo4)6. both types of vibrational spectra of ca5mg4−xznx(vo4)6 (0≤x≤4) are similar and do not indicate any significant changes in the crystal structure (fig. 5). whereas 25 raman and 17 infrared modes are active according to the group theory, not all of them can actually be detected [10]. this discrepancy originates from the negligible changes in polarizability and dipole moment, which do not give rise to observable raman and infrared modes [43]. according to the previous studies on garnet compounds [41, 44, 45], the raman lines between 910 cm−1 and 950 cm−1 and infrared bands in the range of 700–950 cm−1 correspond to the internal anti-symmetric (ν3) stretching vibrations of [vo4]3− ions, whereas the symmetric (ν1) stretching modes of [vo4]3− are revealed only in the raman spectra between 690 cm−1 and 875 cm−1. typical weak raman lines at ~450 cm−1 with the shoulder at ~430 cm−1 are expected for the vo4 bending vibrations. an observed general order of mode frequencies, i.e., l(vo4) > t′ (the metal cation) > t′(vo4) is also presented in most garnet-type silicates. a very strong raman peak (as well as some weak ones) at ~320 cm−1 is attributed to the librational vo4 modes which can be also distinguished as the infrared band in the range of 340–380 cm−1 (fig. 5). fig. 5 infrared (a) and raman (b) spectra of ca5mg4–xznx(vo4)6 (0≤x≤4) table 3 correlation table for the internal vibrations of [vo4] 3− in ca2.5m ii 2(vo4)3, m ii = mg, zn (sg 𝐼𝑎3̅𝑑, z = 8) normal modes of free [vo4] 3− with td symmetry [vo4] 3− site symmetry and factor group ν1 (a1) ν2 (e) ν3 (f2) ν4 (f2) splitting of normal modes of td symmetry due to site symmetry and factor group effects s4 a a + b b + e b + e oh a1g + a2u + eg + eu + f1g + f2u a1g + a1u + a2g + a2u + 2eg + 2eu + f1g + f1u + f2g + f2u a1u + a2g + eg + eu + 2f1g + 3f1u + 3f2g + 2f2u a1u + a2g + eg + eu + 2f1g + 3f1u + 3f2g + 2f2u chimica techno acta 2022, vol. 9(2), no. 20229201 article 7 of 8 the raman line at ~245 cm−1 is assigned to translation modes of ca2+. meanwhile, t′(ca2+) and t′(mg2+/zn2+) modes are associated with the infrared band at 190–250 cm−1. very weak raman lines below 200 cm−1 correspond to external translations of vo4 tetrahedrons. the latter stand in the line with the t′(sio4) modes analyzed previously for a3b2(sio4)3 (a = mg, ca, mn, fe; b = al, cr, fe) [44, 45]. substitution of mg2+ by zn2+ in ca5mg4−xznx(vo4)6 leads to the monotonic increase of the unit cell parameter (fig. 4b) and a slight shift (not exceeding ~10 cm−1) of most of the vibrational bands towards lower wavenumbers (fig. 5). the similar dependencies of vibrational frequencies on the lattice parameter were earlier found in silicate garnets [44, 45]. given that the density of modes is relatively high to allow a clear assignment of all the lines, it is obviously not complete. therefore, first-principle calculations in the density functional theory (dft) framework based on the geometry optimization of ca5m4(vo4)6 (m = mg, zn) are needed to perform an accurate assignment of vibrational bands and will be discussed elsewhere. 4. conclusions high-temperature x-ray diffraction supported by dsc technique allowed studying ca5mg4–xznx(vo4)6 (0≤x≤4) so as to provide more detailed and reliable data on the phase formation of garnet-type vanadates. the synthesis of zndoped ca5mg4(vo4)6 is accompanied by the appearance of ca2v2o7, mg2v2o7 or zn2v2o7. these satellite pyrovanadate phases are stable up to 950 °c and disappear only above their melting point. the single-phase samples of ca5mg4(vo4)6 and ca5zn4(vo4)6 can be obtained following heat treatment for 150 h at 980 °c and at 750 °c, respectively. the formation of the solid solution ca5mg4–xznx(vo4)6 (0≤x≤4) was confirmed by xrpd and vibrational spectroscopy. the findings in structural chemistry contribute to understanding of the impact of synthesis procedures on crystal engineering of vanadates and other garnet-type oxides. supplementary materials supplementary materials in the online format are available at the website of this paper. these data contain: table s1: phase composition and lattice parameters of ca5mg4–xznx(vo4)6 (0 ≤ x ≤ 4). fig. s1: rietveld refinement of ca5mg4(vo4)6 from xrpd data. fig. s2: rietveld refinement of ca5mg3zn(vo4)6 from xrpd data. fig. s3: rietveld refinement of ca5mg2zn2(vo4)6 from xrpd data. fig. s4: rietveld refinement of ca5mgzn3(vo4)6 from xrpd data. fig. s5: rietveld refinement of ca5zn4(vo4)6 from xrpd data. funding this study was funded by the research programs no. aaaa-a19-119020190042-7 and no. аааа-а19119020190044-1 (ihte ub ras). acknowledgments we are grateful to dr. olga g. reznitskikh (issc ub ras), dr. elena a. sherstobitova (imp ub ras) and dr. nikolai i. moskalenko (ihte ub ras) for technical assistance. the crystallographic and spectroscopic studies were carried out in the shared access centers at imet ub ras and ihte ub ras, respectively. author contributions conceptualization: a.s.t. data curation: i.i.l., a.s.t. formal analysis: s.a.p., o.m.f., i.i.l. funding acquisition: i.i.l., a.s.t. methodology: s.n.s. project administration: a.s.t. resources: s.g.t. supervision: s.g.t., s.n.s. validation: s.n.s. visualization: i.i.l., a.s.t. writing – original draft: a.s.t. writing – review & editing: i.i.l. conflict of interest the authors declare no conflict of interest. additional information webpages of institute of high-temperature electrochemistry: http://www.ihte.uran.ru/?page_id=3106; 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long tv. vibrational spectra of the common silicates: i. the garnets. am. mineral. 1971;56:54–71. https://doi.org/10.1016/j.ceramint.2017.07.127 https://doi.org/10.1016/j.ceramint.2018.07.035 https://doi.org/10.1016/j.ceramint.2016.06.085 https://doi.org/10.1016/j.ceramint.2013.05.041 https://doi.org/10.1016/j.ceramint.2015.10.163 https://doi.org/10.1016/j.jeurceramsoc.2014.03.026 https://doi.org/10.1038/srep10296 https://doi.org/10.1016/j.materresbull.2010.01.014 https://doi.org/10.1016/j.ceramint.2016.05.072 https://doi.org/10.1016/j.jlumin.2011.09.004 https://doi.org/10.1007/s10008-019-04202-y https://doi.org/10.1016/j.matlet.2021.130811 https://doi.org/10.1016/0025-5408(74)90156-1 https://doi.org/10.1016/s0022-0248(97)01070-1 https://doi.org/10.15826/chimtech.2020.7.1.03 https://doi.org/10.15826/chimtech.2020.7.1.04 https://doi.org/10.15826/chimtech.2021.8.3.01 https://doi.org/10.1016/j.jphotochem.2020.112765 https://doi.org/10.1107/s0108270107021233 https://doi.org/10.15826/chimtech.2019.6.3.01 https://doi.org/10.15826/chimtech.2020.7.2.02 https://doi.org/10.1016/j.ijleo.2017.11.046 https://doi.org/10.1007/s10973-018-7780-z https://doi.org/10.1515/zkri-2014-1737 https://doi.org/10.1134/1.1541739 https://doi.org/10.2320/matertrans.m2010027 https://doi.org/10.1107/s0567740869003220 https://doi.org/10.1002/jrs.1250100152 https://doi.org/10.1016/0022-2852(68)90043-x https://doi.org/10.1007/bf02838517 https://doi.org/10.1007/s002690050097 269 d o i: 1 0. 15 82 6/ ch im te ch .2 01 5. 2. 4. 02 7 vladimir mikhailovich zhukovsky vladimir mikhailovich zhukovsky was born on 13 may 1931 in the town of spas-demensk, kaluga region. he finished school in the urals, and then entered the first set of physical-technical faculty of upi (sverdlovsk), which he graduated in 1955, and in 1962 he was postgraduate student of the ural polytechnic institute (upi). he started engineering activities in the nuclear industry at the oldest russian radiochemical plant. in 1957 he entered into one of the first groups of the liquidators. from 1963 his work was related to the chemical faculty of the ural state university, where he passed the way from a candidate of sciences, associate professor to the doctor of chemical sciences, professor. during the 4 years he was the dean of the chemical faculty, during 11 years he was the pro-rector for scientific work, during 15 years old he was the head department of analytical chemistry. zhukovsky v.  m. developed and or the first time read the courses in the field of physical chemistry, chemical, statistical and nonequilibrium thermodynamics, physical chemistry and technology of solids, crystal chemistry, chemical metrology and analytical control, standardization and certification. for the conception of teaching of the natural sciences to the humanities, v. m. zhukovskiy in the team of authors was awarded the winner of the prize of the president of the russian federation of 2000 in the field of education. the extensive scientific school and the academic specialization in solid state chemistry has established by vladimir mikhailovich in the ural university. it was started in the mid 60th of xx century, when the department of physical chemistry of the ural state university has been active in scientific terms, a creative team of researchers. the students, and since the mid 60-ies and the first graduate students – a. n. petrov, t. m. yanushkevich, s. f. wexler, n. a. veselova were involved in the scientific research. 270 № 4 | 2015 chimica techno acta in 1964 the first graduation works on the physical chemistry of solids were protected, and in 1965 the first experimental setup of thermal and thermogravimetric analysis were created. in the 70th number studied in the group of oxide materials significantly increased – from traditional to the molybdates and tungstates of alkaline earth metals are added ferrites, niobates, vanadates, as well as the manganites, cobaltites, nicelty and cuprite of the rare earth elements and of the alkalineearth elements. currently all of these lines of research are continued by his disciples, and the disciples of his disciples. in fact, in three of the five departments of the chemical faculty of the institute of natural sciences (analytical chemistry, physical chemistry, inorganic chemistry) of ural federal university the researches successfully conducted, undergraduate and graduate students in the field of chemistry of solids continued. for more than 50 years of history, zhukovsky v. m. together with the staff made fundamental studies of the thermodynamic and structural characteristics of oxide materials, made a significant contribution to the development of experimental and theoretical approaches to the description of transport and electrical properties of individual chemical compounds and solid solutions. within the framework of the scientific school 10 doctors of sciences and, more than 60 candidates of science were prepared. vladimir mikhailovich, his colleagues and students always support the creative scientific contacts with institutes of the ras and a number of leading universities in the field of solid state chemistry in russia and abroad. vladimir mikhailovich was the inspirer and permanent head of the visiting winter school on solid state chemistry, traditional and well-known far beyond the department of chemistry. in 2016 xxv anniversary, the school dedicated to his memory will be held. vladimir mikhailovich was the shine lecturer, a renowned scholar and teacher with a capital letter, deservedly earned the love and respect of others. his rich spiritual world, humanity, the desire to understand and help, the ability to interact on equal terms with young and venerable scientists, comprehensive erudition, scholarly integrity and openness always will be remembered by all who were lucky enough to be in touch with him on his life journey. this edition of the magazine, which included articles by renowned experts in the field of solid state chemistry from yekaterinburg, novosibirsk, ulan-ude and st. petersburg, is dedicated to the memory of vladimir mikhailovich zhukovsky, which remains an example for us in science and life. 271 владимир михайлович жуковский отчизна, воля, тот горчайший дым, что нас разбудит поздно или рано, но дай хоть раз заплакать покаянно: «учитель, перед именем твоим…» да разве сердце позабудет того, кто хочет нам добра, того, кто нас выводит в люди, кто нас выводит в мастера владимир михайлович жуковский родился 13 мая 1931 года в г. спасдеменске калужской области. школу оканчивал на урале, затем поступил на физико-технического факультета упи (свердловск), первый набор, который окончил в 1955 г. и в 1962 г. – аспирантуру уральского политехнического института (упи). инженерно-техническую деятельность начинал в атомной промышленности на старейшем в россии радиохимическом заводе. в 1957 г. он входил в одну из первых групп ликвидаторов. с 1963 г. его деятельность была связана с химическим факультетом уральского государственного университета, где он прошел путь от кандидата наук, доцента до доктора химических наук, профессора. в течение четырех лет был деканом химического факультета, 11 лет – проректором университета по научной работе, 15 лет – заведующим кафедрой аналитической химии. в. м. жуковским разработаны и впервые прочитаны курсы в области физической химии, химической, статистической и неравновесной термодинамики, физикохимии и технологии твердого тела, кристаллохимии, химической метрологии и аналитического контроля, стандартизации и сертификации. за разработку концепции преподавания естествознания для гуманитариев в.  м.  жуковский в числе коллектива авторов стал лауреатом премии президента российской федерации 2000 г. в области образования. владимиром михайловичем в уральском университете создана разветвленная научная школа и учебная специализация по химии твердого тела. начало ей было положено в  середине 60-х гг. xx в., когда на кафедре физической химии ургу сложился активный в научном плане творческий коллектив исследователей. к научным изысканиям были привлечены студенты, а с се272 № 4 | 2015 chimica techno acta редины 60-х гг. и первые аспиранты – а. н. петров, т. м. янушкевич, с. ф. векслер, н. а. веселова. в 1964 г. были защищены первые дипломные работы по физической химии твердого тела, а в 1965 г. – созданы первые экспериментальные установки термического и термогравиметрического анализа. в 1970-е гг. существенно расширился круг изучаемых в группе оксидных материалов – к ставшим традиционными молибдатам и вольфраматам щелочноземельных металлов добавляются ферриты, ниобаты, ванадаты, а также манганиты, кобальтиты, никелаты и куприты редкоземельных элементов и щелочноземельных элементов. в настоящее время все эти направления исследований продолжаются его учениками и учениками его учеников. фактически на трех из пяти кафедр химического факультета института естественных наук (аналитической химии, физической химии, неорганической химии) уральского федерального университета успешно проводятся научные исследования, обучаются студенты и аспиранты по направлению химии твердого тела. за более чем 50-летнюю историю существования этого направления в.  м.  жуковским совместно с сотрудниками выполнены фундаментальные исследования термодинамических и структурных характеристик оксидных материалов, сделан существенный вклад в разработку экспериментальных и теоретических подходов к описанию транспортных и электрических свойств индивидуальных химических соединений и твердых растворов. в  рамках научной школы подготовлено 10 докторов наук, более 60 кандидатов наук. владимир михайлович, его коллеги и ученики постоянно поддерживают творческие научные контакты с институтами ран и рядом ведущих в области химии твердого тела университетов россии и дальнего зарубежья. владимир михайлович был идейным вдохновителем и бессменным руководителем выездной зимней школы по химии твердого тела, ставшей традиционной и известной далеко за пределами химического факультета. в 2016 г. состоится xxv юбилейная школа, посвященная его памяти. владимир михайлович – блестящий лектор, известный ученый и учитель с большой буквы, заслуженно снискавший любовь и уважение окружающих. его богатый духовный мир, человечность, стремление понять и помочь, способность на равных взаимодействовать как с молодыми, так и с маститыми учеными, всесторонняя эрудиция, научная принципиальность и открытость всегда останутся в памяти всех, кому посчастливилось соприкоснуться с ним на своем жизненном пути. это выпуск журнала, в который вошли статьи известных специалистов в области химии твердого тела из екатеринбурга, новосибирска, улан-удэ и  санкт-петербурга, мы посвящаем памяти владимира михайловича жуковского, который остается примером для нас в науке и жизни. synthesis and study of complexes of the novel russian antiviral drug camphecene with pentacyclic triterpenes of licorice 192 d o i: 1 0. 15 82 6/ ch im te ch .2 02 0. 7. 4. 10 khizrieva s. s., vetrova e. v., borisenko s. n., maksimenko e. v., borisenko n. i. chimica techno acta. 2020. vol. 7, no. 4. p. 192–198. issn 2409–5613 synthesis and study of complexes of the novel russian antiviral drug camphecene with pentacyclic triterpenes of licorice s. s. khizrieva*, e. v. vetrova, s. n. borisenko, e. v. maksimenko, n. i. borisenko research institute of physical and organic chemistry, southern federal university, 194/2 stachki ave., rostov-on-don, 344090, russia *email: hizrieva@sfedu.ru abstract. for the first time, the complexation of pentacyclic triterpenes of licorice (glycyrrhizic acid (ga) and its aglycone, glycyrrhetinic acid (gla)) with the novel russian antiviral drug camphecene (camph) was investigated. the complexes obtained at different molar ratios were studied using both uv/vis spectroscopy and mass spectrometry (esi ms). formation of the host:guest complexes were registered: ga and gla molecular complexes (camph+2ga; camph+2gla) with stability constants к = 6.94 · 106 м–2 and к = 2.89 · 106 м–2, respectively. the research results demonstrate a considerable potential of esi ms as a technique for simple and fast detection of formation of the complexes of ga /gla and the novel drugs. keywords: camphecene; glycyrrhizic acid; glycyrrhetinic acid; antiviral activity; supramolecular complexes received: 30.10.2020. accepted: 07.12.2020. published:30.12.2020. © khizrieva s. s., vetrova e. v., borisenko s. n., maksimenko e. v., borisenko n. i., 2020 introduction influenza is known to be the most common and dangerous respiratory viral infection. it causes annual epidemics and pandemics, leading to significant increases in morbidity and mortality in all regions of the world. in connection with the growing number of cases of viral infections and especially resistant viral strains, it is necessary to improve the available therapeutic methods, complementing them with the discovery of new antiviral agents. on the other fist, it is widely recognized that the  medical heritage of  plants is  a  valuable resource for the  treatment of  infectious disorders. this indicates a growing interest in antiviral products based on secondary plant metabolites [1–3]. the one of the unique plants used in both folk and traditional medicine is  licorice. licorice (glycyrrhiza glabra l.) is one of the oldest and most widely used medicinal plants [4, 5]. the major plant’s metabolite in licorice root is glycyrrhizic acid (ga, 1), pentacyclic triterpene, consisting of  one residue of  glycyrrhetinic acid (gla, 2) and two residues of glucuronic acid (fig. 1). licorice triterpenes 1 and 2 are attracting more and more attention of chemists and pharmacologists due to the wide spectrum of their biological activity [6–9]. ga and gla are active against a wide range of viruses, including herpes, corona, alpha, 193 flaviviruses and others [10]. at the same time, ga, gla and their derivatives exhibit a wide spectrum of antiviral activity both in the form of individual substances [1, 10] and in combination with antiviral drugs [11]. ga 1, due to its amphiphilicity, can form supramolecular complexes with various hydrophobic molecules, significantly increasing their solubility. this property was used in the approach of acad. g. a. tolstikov: to reduce therapeutic doses of drugs and prolong the action [12–13]. in this regard, the presented work considers the possibilities of synthesizing new supramolecular complexes of ga and gla with new antiviral drug camphecene for the development of low-dose pharmaceutical substances on their basis. the authors consider that these pharmaceutical substances can be used to suppress the multiplication of viruses in the early stages. camphecene 3 (fig. 1), has a broad spectrum of antiviral activity. it is proved to be active against influenza a strains and type b virus [14]. experimental for the  research we used ga and 18β-gla from aldrich. camphecene was synthesized at  the  novosibirsk institute of  organic chemistry (nioch sb ras) and kindly provided by  prof. n. f. salakhutdinov. solvents from merck, hplc/ms qualifications. the complexes were obtained by traditional mixing of solutions with different molar ratios of ga, gla, and camph in  a  70% aqueous-alcoholic solution. the  founding of  complexes of ga and gla with camph was recorded by  uv/vis spectroscopy using a  speks ssp 705 spectrophotometer (190–1100  nm) (manufactured by  cjsc spectroscopic systems, russia). measurements were performed in  a  quartz cell. the  formation of  the  complex was considered by  the  change in  optical density at a constant concentration of camph (c = 0.5 mm). in order to exclude the contribution of the absorption of triterpenes by ga and gla, respectively, their absorption spectrum was subtracted from the  total spectrum. the  composition of  supramolecular complexes of ga and gla with camph was investigated with direct injection on a  bruker daltonics microtof-q mass spectrometer with electrospray ionizaro o cooh h h h 1, 2 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 ooh oh oh ocooh ooh oh cooh2 : r = h 1 : r = a) ga (1) b) gla (2) c) camph (3) fig. 1. formulae of a) glycyrrhetinic acid (2), с30н46о4; b) glycyrrhizic acid (1), c42h62o16; c) camphecene (3), c12h21no 194 tion. the microtofcontroltm2.2 software was used to analyze the results. the mass spectrometer was calibrated using a fluka electrospray calibrant solution. detection of negative and positive ions was performed in the range of m/z from 50 to 3000. results and discussion in  accordance with the  objectives of the work, sets of complexes of licorice triterpenes ga and gla with an antiviral drug camphecene at different molar ratios “guest:host” were synthesized. in the first step, complexes of ga with camph were obtained at molar ratios: 1:1 and 2:1 and studied by uv / vis spectroscopy and mass spectrometry with electrospray ionization. as  demonstrated in fig. 2, with an increase in the concentration of ga from 0 to 1 mm, a bathochromic shift of  the  absorption maximum of  camph (201 → 212  nm) is  recorded in  the  uv / vis spectra, and a  decrease in optical density is observed. an increase in the concentration of ga (from 1.5 mm and higher) leads to the disappearance of  the  maximum absorption of camph, which indicates the complete binding of camph molecules in the presence of ga (fig. 3). from the  dependence of  the  optical density on the  concentration of  glycyrrhizic acid (fig. 3), over the entire range of  increase in  the  concentration of  ga, the value of the maximum optical density of camph decreases. the study of gla as a complexing agent demonstrated similarchanges in the uv / vis spectra of  the  obtained complexes. when the  gla concentration changes in  the  range from 0.05 to  0.125  mm, a  bathochromic shift of  the  absorption maximum of camph is recorded (201 → 206 nm). to  calculate the  stability constant of  the  complexes, we used the  benesihildebrand plot (1) [15]. the  stability constant of the nga-camph complex was estimated from the change in the optical density of camph (λmax1 = 201 nm) at its fixed concentration in solutions in which the ga (or gla) concentration was varied. eq. (1) allows, within the framework of  one experiment, not only to  estimate the stability constant of the complex (k), fig. 2. absorption spectrum of camphecene (ccamph = 0.5 mm) at different concentrations of ga 195 but also to  determine the  stoichiometry ratio “host:guest” (n) in the complex: d/∆d – 1 = (1/[ga]n) ∙ (1/k), (1) where ∆d = ∆ε∙[сcamph]  — change in the optical density of the solution, аnd к — the constant of stability of the complex, determined for the reaction: [ ] [ ] [ ] camph ga camph ga camph ga camph ga, . n n n n + ‑ = ‑ = ⋅  (2) the  absorption spectrum of  camph was recorded at a wavelength of 201 nm, while the camph concentration was constant and amounted to 0.5 mm. the obtained dependence of the absorption intensity of camphecene (λ = 201 nm) on the concentration of ga is shown in fig. 4. from the  slope of  the  straight-line d/dd, depending on 1/[ga]2 (fig.  4), the stability constant of the complex was calculated using eq. (1). the stability constant for the camph + ga complex is 1/k = 1.44 · 10–7 m2 or k = 6.94 · 106 m–2. recognizing the  value of  the  binding constant, the change in the gibbs energy was calculated. obtained from the binding constant, the change in gibbs energy ∆g = –38.4 kj. based on the obtained negative value, it can be concluded that the reaction proceeds spontaneously during the formation of ga and camph complexes. similarly, according to the eq. (1), the stability constant of the complex camph+gla was calculated, 1/k = 3.46 · 10–7 m2 or k = 2.89 · 106 m–2. using the value of the binding constant, the change in gibbs energy was calculated. the change in the gibbs energy ∆g = –36.2 kj, which allows us to conclude that the reaction proceeds spontaneously during the formation of a complex of gla with camph. the formation of complexes of camphecene with natural triterpenoids has also been studied using electrospray ionization mass spectrometry (esi ms). in the mass spectra of complexes of ga and gla with camph in the mode of positive ions, both the peaks of ga, gla, and camph ions and the peaks of heterocomplexes containing ga and camph or gla and camph are recorded. thus, in the gla and camph complexes synthesized both at a ratio of the components of  gla and camph in  1:1 and at  a  ratio of  2:1, a  peak with m/z 688.73 was recorded, corresponding to  a  single charged ion of  the  complex gla and camph [mgla + mcamph + na] +. a typical mass spectrum of the gla-camph complex is shown in fig. 5. the presence of peaks of heterocomplexes containing ga and camph, gla and camph confirm the formation of complexes of ga and gla with camph, respectively. the  results obtained demonfig. 3. dependence of optical density on the concentration of glycyrrhizic acid fig. 4. dependence of the absorption intensity of camphecene (λ = 201 nm) on the concentration of ga 196 strate the  high potential of  triterpenes ga and gla in the development of new pharmaceutical forms using the example of camphecene in the form of molecular complexes. conclusions in  the  presented work, complexes of  pentacyclic triterpenes of  the  licorice (glycyrrhizic acid (ga) and glycyrrhetinic acid (gla), its aglycone) with the antiviral drug camphecene (camph) were synthesized and studied. the  complexes obtained at  different molar ratios “host — ga (gla): guest — camph”: 1:1 and 2:1 were studied using both uv / vis spectrophotometry and mass spectrometry with electrospray ionization. formation of  the  host:guest complexes were registered: ga and gla molecules form molecular complexes (camph+2ga; camph+2gla) with stability constants k = 6.94 · 106 м–2 and k = 2.89 · 106 м–2, respectively. in the mode of positive ion, the mass spectra of mixture of ga and gla with camph showed peaks of  ga, gla, and camph ions and the peaks of heterocomplexes containing ga and camph, and gla and camph, respectively. the  research results demonstrated the  considerable potential of esi ms as a technique for simple and fast detection of formation of the complexes of ga /gla and the novel drugs. acknowledgements this work was supported by the russian foundation for basic research (rfbr, grant no. 19-33-90211-aspiranty). references 1. zarubaev vv, anikin vb, smirnov vs. anti-viral activity of glycyrrhetinic and glycyrrhizic acids. rus j of inf and imm = infektsiyaiimmunitet. 2016;6(3):199–206. doi:10.15789/2220-7619-20163-199-206 2. akram m, tahir im, shah sma, mahmood z, altaf a, ahmad k, munir n, daniyal m, nasir s, mehboob h. antiviral potential of medicinal plants against hiv, fig. 5. mass spectrum of a complex of camphecene (camph) + glycyrrhetinic acid (gla) 197 hsv, influenza, 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lighting applications chimica techno acta article published by ural federal university 2022, vol. 9(1), no. 20229107 eissn 2411-1414; chimicatechnoacta.ru doi: 10.15826/chimtech.2022.9.1.07 1 of 7 bright blue emissions on uv-excitation of labo3 (b=in, ga, al) perovskite structured phosphors for commercial solid-state lighting applications b.v. naveen kumar ab, t. samuel c, samatha bevara d, k. ramachandra rao e, satya kamal chirauri e* a: department of physics, acharya nagarjuna university, guntur, india b: shri vishnu college of engineering for women(a), bhimavaram, india c: gmr institute of technology, rajam, andhra pradesh, india d: chemistry division, vignan's foundation for science, technology and research, guntur, andhra pradesh, india e: crystal growth & nanoscience research center, government college (a), rajahmundry, india * corresponding author: satyakamal.ch@gmail.com this article belongs to the regular issue. © 2022, the authors. this article is published in open access form under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). abstract bright blue photoluminescence (pl) was obtained from bi3+-activated labo3 (b = in, ga, al) perovskite nanophosphors. a cost-effective and low-temperature chemical route was employed for preparing bi3+ doped labo3 (b=in, ga, al) which were then annealed at 1000 °c. the phase formation, morphological studies and luminescent properties of the as-prepared samples were performed by x-ray diffraction (xrd), scanning electron microscopy (sem), photoluminescence and optical absorption spectroscopy. comparison of emission intensities, lifetime studies, energy band gaps and color purity of all samples (pure and bi3+ doped) were investigated for promising applications in uv light-emitting diodes, variable frequency drive (vfd), field emission display (fed), and other photoelectric fields. keywords perovskites photoluminescence phosphor quenching solid-state lightning received: 08.07.2021 revised: 02.01.2022 accepted: 04.03.2022 available online: 11.03.2022 1. introduction blue emissive materials have attracted considerable attention because of their vast applications in the fields of sensors, solid-state lighting technology, and light fidelity (li-fi) [1–3]. in view of such applications, design and development of blue light-emitting materials is an exciting challenge. commercially available blue phosphors like gan and ingan, in thin-film form, have potential use in bright blue light emitters. preparation of such nitride materials requires an energy-expensive process and thus hinders the development of cost-effective blue light emitters [4]. perhaps, in blue light-emitting phosphors, rare-earth ions like eu2+ and ce3+ are commonly used as activator ions, owing to their 4f→5d transitions giving rise to an absorption band ranges in nuv to the blue region and a broad emission band covering blue to the red region [5–8]. however, phosphors doped with eu2+ or ce3+ shows some disadvantage in the view of high cost, high reabsorption and color deviation. therefore, developing potential luminescent phosphor materials doped with non-rare earth ions as activators is more promising. among many recent studies, it was found that bi3+ ion as an activator plays a crucial role in the generation of efficient blue-light emission [9–13]. alternatively, bi3+ ions with their excited state for electron transition and emission band of bi3+ ion at room temperature can be rationally attributed to the 3p1→1s0 transition, which avoids the reabsorption among phosphors. it is worth mentioning that oxide-based materials are preferred over nitride thin films due to low temperatures and simple methods of preparation. among many oxides, perovskite materials have been widely investigated for luminescence applications. for example, semiconductor laino3 revealed potential properties for the phosphor applications and as a surface for solid oxide fuel cells [14]. subsequently, laalo3 has intensive applications as a substrate for superconductors, magnetic and ferromagnetic thin films and luminescent host materials, and has high thermal stability and good dielectric properties [15–17]. lagao3 perovskite has received much attention as a leading host because of its potential use as substrate applications for phosphorus and solid oxide fuel cells [18]. in the last http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2022.9.1.07 http://creativecommons.org/licenses/by/4.0/ https://orcid.org/0000-0003-2562-244x https://crossmark.crossref.org/dialog/?doi=https://doi.org/10.15826/chimtech.2022.9.1.07&domain=pdf&date_stamp=2022-3-11 chimica techno acta 2022, vol. 9(1), no. 20229107 article 2 of 7 few years, a considerable amount of research was done on laino3, laalo3, lagao3 perovskite materials. a few research groups have also reported that bi3+ doped laino3 and lagao3 are efficient blue-emitting luminescent materials. however, to the best of our knowledge, there is no report on the optimization of bi3+ ions in laino3, laalo3, and lagao3 phosphors. therefore, in this article, we demonstrated a comparative study for bright blue emissions on uv excitation close to industrial standards (colour coordinates: x = 0.15 and y = 0.15) obtained from bi3+ ion doped labo3 (b=in, ga, al) samples. hence, from the photo luminescent results, these blue light emitters would be potential materials to increase the efficiency of white light-emitting solid-state devices. 2. experimental la(no3)36h2o [merck, germany], in(no3)3h2o [sigmaaldrich, 99.99%], al(no3)3h2o [alfa aesar 99.99%], gallium(iii)nitratehydrate (ga(no3)3h2o) [sigma-aldrich, 99.99%], bi(no3)35h2o [sigma-aldrich, 99.99%], were used as starting materials. for the synthesis of pure laino3 nanoparticles, stoichiometric amounts of la(no3)36h2o and in(no3)3h2o were mixed with 20 ml of distilled water in a two-necked round bottom flask. the solution was slowly stirred and ammonium hydroxide aqueous solution was added dropwise until the clear solution turned intoturbid; then the solution was maintained at 120 °c for 2 hours. the precipitate then formed in the round bottom flask was collected and thoroughly washed five times with methanol and allowed for drying. later, the samples were heated to 1000 °c at a heating rate of 10 °c per minute in a furnace that maintained the constant temperature for 5 h, then the furnace was turned off and the samples were allowed to settle naturally at room temperature to cool. finally, the samples were grounded for further investigation. the same procedure was used to prepare laino3: 0.5, 1, 2, 2.5, 3 at.% bi3+, lagao3: 1, 1.5, 2, 2.5, 3 at.% bi3+, laalo3: 0.5, 1, 2, 2.5, 3 at.% bi3+ doped nanophosphors, which were also annealed in air at 1000 °c. 3. results and discussion 3.1. xrd studies xrd patterns of undoped and selected bi3+ doped laino3, lagao3 and laalo3 samples calcined at 1000 °c are shown in fig. 1 (a–c). the diffraction peaks indicate that the calcined samples of laino3, lagao3 can be indexed in pure orthorhombic phase and laalo3 can be indexed in cubic or rhombohedral phase. all diffraction peaks are in good agreement with the previously reported phases of laino3, lagao3 and laalo3 samples, and it is observed that no second phase was detected for the samples indicating that bi3+ was completely dissolved in the host array, which is in good agreement with previously reported literature [19–23]. typically, the crystal size of the sample is calculated from the debye–scherer diffraction line width using the relation d = 0.9/cos, where d is the average crystal size,  is the x-ray wave length (1.5405 å), and  is the maximum amplitude, which is correlated to full width at half of the maximum intensity (fwhm) line, and  is the angle of diffraction. the average crystal sizes of undoped and doped laino3, lagao3 and laalo3 samples, which were calcined at 1000 °c, are in the range of 90–120 nm. the lattice parameters for both pure and doped laino3, lagao3 and laalo3 were calculated using powderx software and are listed in table l. table 1 unit cell parameters of pure and doped laino3, lagao3 and laalo3 samples composition a (å) b (å) c (å) volume (å)3 laino3 (jcpds: 08-0148) 5.7820 8.3360 5. 9990 289.14 laino3: 2.5 at.% bi 3+ 5.7240 8.2450 5.9280 279.76 lagao3 (jcpds: 024-1102) 5.4883 5.5248 7.7499 234.99 lagao3: 1.5 at.% bi 3+ 5.4963 5.4688 7.7149 231.90 laalo3 (jcpds: 01-085-0848) 3.7860 3.7860 3.7860 54.26 laalo3: 2 at.% bi 3+ 3.7810 3.7810 3.7810 54.05 3.2. morphological studies fig. 2 (a–f) shows the typical scanning electron microscope (sem) images of pure and laino3: 2.5 at.% bi3+, lagao3: 1.5 at.% bi3+, laalo3: 2 at.% bi3+ doped samples. a collection of crystalline granules and particles was observed in the sem images of the phosphorus. the sem images of pure labo3 (b = in, ga, al) samples are depicted in fig. 2 (a–c) and bi3+ doped samples in fig. 2 (d–f). all crystallites are spherical in nature ranging between 90–150 nm. fig. 1 xrd patterns of pure and bi3+ doped laino3 (a), lagao3 (b) and laalo3 (c) samples calcined at 1000 °c chimica techno acta 2022, vol. 9(1), no. 20229107 article 3 of 7 fig. 2 sem images of pure labo3 (b = in, ga, al) (a–c) and bi 3+ doped labo3 (b = in, ga, al) (d–f) samples the higher calcinations temperature facilitates the possible rapid arrangement of crystal structure followed by coalescence of particles leading to particle agglomeration causing a considerable reduction in crystallite size of bi3+ doped samples compared to undoped samples. to support this phenomenon, particle size distribution graphs for all the pure and doped samples were calculated using imagej software and are presented in fig. 3 (a–f). the energy dispersive x-ray spectrometer (eds) spectra used to determine the composition of the samples and show good agreement with the nominal sample compositions (fig. 4 (a–f)). 3.3. optical energy bandgap calculations fig. 5 (a–b) shows the plots of (αhυ)2 vs hυ for the asprepared nanophosphor uses, where α is the optical absorption coefficient and hυ is the energy of the incident photon. the band gap of the optical energy (for example) can be calculated by extending the linear part of the curve (αhυ)2 = 0. form the plots, it was found that the optical energy bandgaps are equal to 4.16 ev, 5.10 ev and 4.28 ev for laino3, lagao3 and laalo3 pure samples, respectively. the optimum laino3: 2.5 at.% bi3+, lagao3: 1.5 at.% bi3+, laalo3: 2 at.% bi3+ doped samples energy bandgap values are 3.81 ev, 4.90 ev and 3.90 ev, respectively. the value of energy gap is reduced considerably on doping with bi3+ ions, which is demonstrated in fig. 5. also, it was reported elsewhere that the energy gap of phosphor material decreased in presence of bi3+ ion [24–26]. the bi3+ ion renders some energy levels that have the 6s2 valence electrons together to form a continuous band. the decrease in optical energy band gap may result in an increase in the concentration of excited ions in higher energy states. thus, doping leads to the decrease in the energy of fermi level and, hence, a reduction in the optical band gap is observed [27]. 3.4. photoluminescence and lifetime decay studies emission spectra of laino3: 0.5, 1, 2, 2.5, 3 at.% bi3+, lagao3: 1, 1.5, 2, 2.5, 3 at.% bi3+, laalo3: 0.5, 1, 2, 2.5, 3 at.% bi3+ doped samples are shown in fig. 6 (a–c). all the samples have broad emission bands centered at 432 nm, 373 nm and 350 nm on excitation with 330 nm, 309 nm and 274 nm, respectively, which is attributed to the 3p1–1s0 transition of bi3+ ions [28]. it was evident that the intensity of the emission band increases as the bi3+ concentration increases, reaching a maximum at 2.5 at.% for laino3: bi3+, 1 at.% for lagao3: bi3+ and 2 at.% for laalo3: bi3+ samples, and then remarkably decreasing on increasing bi3+ content due to the concentration quenching. the concentration quenching can be triggered because the interactions between two ions increase as doping increases and the decrease in extent of the energy transfer process causes the decrease of the emission intensity [29]. the corresponding excitation spectra, a broad excitation band ranging from 300 to 500 nm with a maximum at about 330, 309, 274 nm, which was arising from 1s0–3p1 transition of bi3+, are illustrated in supporting information (fig. s1). further, it is noteworthy that in the emission spectra for undoped lagao3 a broad band peak maximum at 430 nm is observed, which is due to the gao6 octahedral site (fig. s2). of all the perovskites from the emission spectra trend, the highest emission intensity is observed for lagao3: bi3+ doped samples with a peak position at 375 nm on excitation with 309 nm, which is illustrated in fig. 6 (b) [30]. chimica techno acta 2022, vol. 9(1), no. 20229107 article 4 of 7 fig. 3 particle size distributions of pure labo3 (b = in, ga, al) (a–) and bi 3+ doped labo3 (b = in, ga, al) (d–f) samples fig. 4 eds spectra of pure labo3 (b = in, ga, al) (a–c) and bi 3+ doped labo3 (b = in, ga, al) (d–f) samples chimica techno acta 2022, vol. 9(1), no. 20229107 article 5 of 7 fig. 5 optical energy band gaps of pure labo3 (b = in, ga, al) (a) and bi 3+ doped labo3 (b = in, ga, al) (b) samples fig. 6 emission spectra of laino3: 0.5, 1, 2, 2.5, 3 at.% bi 3+ (a), lagao3: 0.5, 1, 1.5, 2, 2.5 at.% bi 3+ (b) and laalo3: 0.5, 1, 2, 2.5, 3 at.% bi3+ (c) doped samples the reason behind the enhanced intensity from lagao3:bi3+ doped sample is due to the energy transfer phenomena from gao6 octahedral sites to bi3+ ions. to confirm this energy transfer, spectral overlap between excitation spectra of lagao3:bi3+ sample and emission spectra of pure lagao3 is demonstrated in fig. 7. to verify the emission intensity pattern, the corresponding life time decay values (fig. 8 (a–d)) for the prepared phosphors were calculated according to the following equation: 𝐼 = 𝐴1𝑒 (−𝑡 𝜏1⁄ ) + 𝐴2𝑒 (−𝑡 𝜏2⁄ ), (1) where i is the luminescence intensity at the time t, τ1 and τ2 are two components of the decay time, a1 and a2 are the constants. the average decay times of the samples were found to be 215, 252, 269, 329, 273 ns of laino3:bi3+ (0.5, 1, 2, 2.5, 3 at.% bi3+), 734 ns, 806 ns and 693 ns oflaalo3: 0.5, 1, 2, 2.5, 3 at.% bi3+ and for lagao3: 1, 1.5, 2, 2.5, 3 at.% bi3+ samples decay life time value was found to be 702 ns and 989 ns, 745 ns, 643 ns and 567 ns, respectively. 3.5. cie chromatic coordinates quantification of the overall emitted colors was done with the help of commission international de i’eclairage (cie) chromaticity coordinates, where any color can be expressed in terms of (x, y) color coordinates, based on emission spectra [31]. fig. 7 spectral overlap of pure and 1.5 at.% bi3+ doped lagao3 samples chimica techno acta 2022, vol. 9(1), no. 20229107 article 6 of 7 fig. 9 (a–c) represents the cie coordinates of laino3, lagao3 and laalo3 as-prepared samples doped with bi3+. the cie diagram of laino3: 3 at.% bi3+ lies in bright blue [points (0.22, 0.18)], lagao3: 1 at.% bi3+ lies in blue [points (0.18, 0.15)] and laalo3: 1 at.% bi3+ lies in blue [points (0.26, 0.22)]. from the color coordinators, it is evident that laino3, laalo3 lies in nearly blue regions, whereas lagao3 samples lie in the blue region. so, from color purity analysis, the coordinates of lagao3: 1 at.% bi3+ lies very near to the industrial standard blue emission coordinates, i.e. (0.15, 0.15). 4. conclusions all the samples were prepared by a cost-effective and lowtemperature polyol route method and were heated to 1000 °c. from the xrd patterns and sem, it was observed that all samples range in nanoscale in agreement with the reported data. from pl studies, it was evident that all the emission peaks of as-prepared samples are attributed to 3p1–1s0 transition of bi3+ ions emitting strong bright blue luminescence. when excited by uv light, lagao3 (pure and bi3+) samples shows emissions. the emissions from the pure sample of lagao3 indicates that the host lattice itself is optically self-activated, whereas when the host lattice is doped with bi3+ the intensity of emissions are enhanced. this is beneficial for the development of optically selfactivated lighting devices. from the emission spectra and the data plotted for cie coordinates, out of all three samples, lagao3: 1 at.% bi3+ cie coordinates nearly meets the standard blue emission coordinates i.e. (0.15, 0.15). thus, in comparison with the other samples, we finally conclude that lagao3: 1 at.% bi3+ would be the best blue lightemitting phosphor that may be potentially used in solidstate lighting applications. acknowledgements the authors are very grateful to dr. r. david kumar, principal, government college (a), rajamahendravaram, for providing the lab facility. one of the authors, b.v. naveen kumar, is grateful to the principal and management of the shri vishnu college of engineering for women (a), bhimavaram, india. conflict of interest the authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. fig. 8 life time decay curves of laino3:bi 3+ (a), lagao3:bi 3+ (b), and laalo3:bi 3+ (c) doped samples fig. 9 cie chromatic coordinates of laino3 (a), lagao3 (b) and laalo3 (c) samples doped with bi 3+ chimica techno acta 2022, vol. 9(1), no. 20229107 article 7 of 7 references 1. ferreira rx, xie e, mckendry jj, rajbhandari s, chun h, faulkner g, et al. high bandwidth gan-based micro-leds for multi-gb/s visible light communications. ieee photonics technol lett. 2016;28(19):2023–2026. doi:10.1109/lpt.2016.2581318 2. peng s, zhao y, fu c, pu x, zhou l, huang y, et al. acquiring high‐performance deep‐blue oled emitters through an un‐ expected blue shift color‐tuning effect induced by electron‐ donating‐ome substituents. chem eur j. 2018;24(32):8056– 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author: vsuprunchuk@ncfu.ru this short communication (letter) belongs to the mosm2021 special issue. © 2021, the authors. this article is published in open access form under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). abstract ultrasonic exposure can be used for depolymerization of brown algae polysaccharides. however, its effectiveness depends on several factors, including cavitation activity in the treatment medium. therefore, the purpose of the work was to determine the cavitation activity and the effectiveness of the ultrasonic exposure to fucoidan in order to optimize the processing processes of polysaccharide from brown algae. a change in cavitation activity was revealed depending on the composition of the processing environment, as well as on the intensity of ultrasonic exposure with a constant frequency of the ultrasonic wave. similar dynamics of change of cavitation activity were established at the intensity of ultrasonic treatment of 100 and 133 w/cm2 with amplification of electric signal at the increase of ultrasound intensity. the use of sds in the processing medium led to an increase in cavitation activity to 14.9±0.47 mv. treatment of the fucoidan solution for 40 minutes under various conditions allowed to obtain fractions with a change in the average hydrodynamic particle diameter from 113 nm (100 w/cm2) to 85 nm (200 w/cm2) and 124 nm (sds). keywords fucoidan cavitation nanoparticles depolymerization received: 02.11.2021 revised: 16.12.2021 accepted: 20.12.2021 available online: 23.12.2021 1. introduction fucoidans are of great interest among biopolymers of marine origin. fucoidan is a branched sulfated heteropolysaccharide isolated from brown algae and some marine invertebrates [1]. fucoidan has anticancer [2], antithrombic [3], anticoagulant [4], antioxidant [5], antiviral [6] activity and other pharmacologically important properties and its use is approved by the fda. however, as a rule, this polysaccharide has a high molecular weight, which limits its industrial use. therefore, we can make a conclusion that depolymerization of fucoidan is considered an urgent task. ultrasonic treatment is often used in order to lower the molecular weight of polymers, in polysaccharides in particular [7, 8]. this method is simple and environmentally friendly. ultrasonic processing is based on the phenomenon of cavitation. when treated with ultrasonic, the cavities are formed in the environment – cavitation bubbles. as a result of the cavitation bubble collapse, a shock wave is created with the formation of an acoustic flow leading to the formation of turbulence due to the continuous formation and collapse of cavities in the system. in addition, shock waves, intense local heating (about 5000 °c) and high pressure (about 1000 atm) are created [9]. as a result of the collapse of such bubbles, sufficient energy is released to break bonds in any polymeric materials [10]. however, the effectiveness of ultrasonic treatment depends on a number of factors, one of which is the cavitation activity in the treatment medium. detection of cavitation activity will allow determining the optimal rate of destruction of the biopolymer. therefore, the purpose of the work was to determine the cavitation activity and the effectiveness of ultrasonic treatment to fucoidan in order to optimize the processing of polysaccharide from brown algae. the measurement of cavitation intensity was based on recording acoustic noise as an electrical signal. 2. experimental for ultrasonic treatment, polysaccharide obtained from brown algae fucus vesiculosus was used according to the procedure presented in [11] with some changes. subsequent cleaning was carried out in accordance with the work of a.m. urvantsev, i. yu. bakunin, n. yu. kim and others [12]. the resulting fucoidan was dispersed in deionized water at a concentration of 10 mg/ml. http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2021.8.4.14 https://orcid.org/0000-0002-5587-8262 http://creativecommons.org/licenses/by/4.0/ chimica techno acta 2021, vol. 8(4), № 20218414 letter 2 of 4 the ultrasonic waves generated by means of the ultrasonic uip1000hd processor with a power of 1 kw (hielscher ultrasonics gmbh, germany) with a frequency of 20 khz induced through sonotrode. in the first case, the sonotrode was placed in an aqueous fucoidan solution and the ultrasonic intensity was varied to 100, 133, 200 w/cm2. in the second case, the composition of the medium was varied by introducing auxiliary substances into an aqueous solution of fucoidan while maintaining the intensity of ultrasonic exposure. surfactants (sds, peg-400) were used as excipients. ultrasonic treatment of fucoidan was carried out for 40 minutes with constant cooling with the help of an ice bath with temperature control within the range of 45±5 °с. the size of the obtained particles was determined using photocor compact z (photoсor llc, russia). a cavitometer was used in order to determine the intensity of cavitation. the principle of the cavitometer is based on the analysis of cavitation noise with its conversion to an electric signal. the hydrophone was placed in a treatment medium at a depth of 45±2 mm below the surface of the liquid and an electrical signal was recorded. 3. results and discussion cavitation is the formation of bubbles experiencing local pressure fluctuations, the occurrence of which is possible under the influence of an ultrasonic wave [13]. cavitation measurements were carried out in the work using a cavitometer, the action of which is based on processing the spectrum of cavitation noise received by a broadband hydrophone, followed by converting an acoustic signal into an electric one. the more intense the shock wave, the wider the spectrum of cavitation noise and the larger the electric signal. the measurement of cavitation activity in the form of an electrical signal were carried out during ultrasonic exposure of the fucoidan solution. the work revealed that cavitation activity changes unevenly. this is because the volume fraction of the cavitation bubble plays an important role in cavitation. the large cavitation bubble in medium reduces acoustic transparency and can cause attenuation of the ultrasonic waves during their propagation [13]. however, when bubbles collapse, shock waves form, which can lead to an increase in acoustic emission. similar dynamics of change of cavitation activity were established at the intensity of ultrasonic exposure of 100 and 133 w/cm2, as well as when used in the sds processing medium. in addition, the amplification of the electric signal was revealed when the intensity of ultrasound increased. therefore, in the first minute, the average value of this signal increased from 7.94±0.21 mv (with an ultrasound intensity of 100 w/cm2), 9.2±0.47 mv (with an ultrasound intensity of 133 w/cm2) to 10.4±1.35 mv (with an ultrasound intensity of 200 w/cm2). at higher ultrasound power, a cone-shaped bubble structure [14] is formed which can lead to the effect of screening and scattering of ultrasound. this leads to a change in the shape of the acoustic emission plot compared to the acoustic emission plots at lower values of sound wave intensity (fig. 1). application in the treatment medium (sds) showed an increase in cavitation activity up to 14.9±0.47 mv. the use of saa peg-400 also led to an increase in the electric signal relative to the medium without the use of saa at the same ultrasonic wave intensity from 9.2±0.47 mv to 10.2±0.92 mv, but to a lesser extent than sds. in general, during ultrasonic exposure, a decrease in cavitation is observed during the first 500 ms. when used in the sds processing medium, there is a decrease in cavitation activity from 14.90±0.47 mv to 11.00±0.21 mv at the 30th minute of exposure (fig. 2). it is known that saa leads to a decrease in surface tension in liquids, as a result of which the number of collapse bubbles decreases and they accumulate [15]. fig. 1 graph of the cavitation activity change at ultrasonic exposure during the first 500 ms chimica techno acta 2021, vol. 8(4), № 20218414 letter 3 of 4 fig. 2 change in cavitation activity at ultrasonic exposure during 40 min when saa is used (* – results of 5 measurements) at the same time, the introduction of saa prevents the bjerknes force and leads to electrostatic repulsion of cavitation bubbles [16], thereby their fusion is prevented, growth slows down and the lifetime of the bubbles increases. the retention of bubbles, in turn, can block the transmission of sound through the liquid to the hydrophone [17], as a result of which the electrical signal is reduced. in general, there is a decrease in cavitation activity to 9.80±0.31 mv when used in a processing medium peg400 and to 14.20±0.22 mv when using sds. saas have been used in the treatment environment under the assumption that their action caused forced conformational changes, which are formed during the movement of polymer chains. in turn, this makes it possible to adopt the unwound shape of the chain and increase its sensitivity to the shear force of the shock wave when the cavitation bubble collapses [18]. fig. 3 dependence of size of nanoscale fraction of fucoidan on parameters of ultrasound and composition of processing environment according to fig. 3, there is a decrease in the particle size of the polysaccharide of the nanoscale fraction of fucoidan with an increase in the intensity of ultrasonic exposure. the average hydrodynamic diameter of the obtained particles, as in the case of molecular weight, has a certain value for a given intensity. it is known that in branched polysaccharides of the form "tangle", chain break is more difficult than in linear "stick-shaped" macromolecules (for example, chitosan). this is due to the fact that linear conformation leads to the accumulation of "pulling forces" throughout the entire chain [19]. it is possible that this difficulty can be overcome by increasing the intensity of the ultrasonic wave or introducing peg-400, allowing to obtain fractions with an average particle size of 85±33 and 83±25 nm, respectively. 4. conclusions cavitation activity in the treatment medium upon change of intensity of ultrasonic action and composition of the treatment medium was investigated. a direct proportional dependence of the ultrasound efficiency on the intensity of ultrasound wave was revealed. similar dynamics of change of cavitation activity at intensity of ultrasonic action of 100 and 133 w/cm2 with amplification of electric signal upon the increase of ultrasound intensity was established. in such a way, with an ultrasound intensity of 200 w/cm2 the electric signal increased to 10.40±1.35 mv. the use of sds in the processing medium led to an increase in cavitation activity to 14.90±0.47 mv. after 40 minutes of treatment of the fucoidan solution under various conditions, fractions with a change in average particle size from 113 nm (100 w/cm2) to 85 nm (200 w/cm2) and 124 nm (sds) were obtained. increasing the intensity of the ultrasonic wave or introducing peg-400 allows obtaining fractions with an average particle size of 85±33 and 83±25 nm, respectively. therefore, determination of ultrasonic impact efficiency will allow optimizing the technological process of fucoidan destructuring. funding sources scholarship of the president of the russian federation to young scientists and graduate students № sp-1758.2021.4 “development of a nanobiocomposite tpa carrier for targeted high-performance thrombolytic therapy”. references 1. wang y, xing m, cao q, ji a, liang h, song s. biological activities of fucoidan and the factors mediating its therapeutic effects : a review of recent studies. mar drugs. 2019;17:183. doi:10.3390/md17030183 2. jin jo, chauhan ps, arukha ap, chavda v, dubey a, yadav d. the therapeutic potential of the anticancer activity 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pathway. sci rep. 2017;7:1– 14. doi:10.1038/srep40760 7. mason j, cuthbert c, brookfield a. effect of ultrasound on the degradation of aqueous native dextran. ultrason sonochem. 1995;2:1–3. doi:10.1038/srep40760 8. tiwari bk, muthukumarappan k, donnell cpo, cullen pj. rheological properties of sonicated guar, xanthan and pectin dispersions. int j food prop issn. 2010;13:223–33. doi:10.1080/10942910802317610 9. suslik ks, fang m., hyeon t, mdleleni m. applications of sonochemestry to materials synthesis. sonochemistry and sonoluminescence. 1999;291–320. 10. mason tj, newman ap, phull s. sonochemistry in water treatment. 2nd international conference on advances in water and effluent treatment. professional engineering publishing. 1993. p. 243–50. 11. zvyagintseva tn, shevchenko nm, popivnich ib, isakov v v., scobun as, sundukova ev, et al. a new procedure for the separation of water-soluble polysaccharides from brown seaweeds. carbohydr res. 1999;322:32–9. doi:10.1016/s0008-6215(99)00206-2 12. urvantseva am, bakunina iu, kim nyu, isakov vv, glazunov vp, zvyagintseva tn. isolation of purified fucoidan from a natural complex with polyphenols and its characteristics. chem plant raw mater. 2004;15–24. russian. 13. frohly j, labouret s, bruneel c, looten-baquet i, torguet r. ultrasonic cavitation monitoring by acoustic noise power measurement. j acoust soc am. 2000;108:2012–20. doi:10.1121/1.1312360 14. moussatov a, granger c, dubus b. cone-like bubble formation in ultrasonic cavitation field. ultrason sonochem. 2003;10:191–5. doi:10.1016/s1350-4177(02)00152-9 15. iwai y, li s. cavitation erosion in waters having different surface tensions. wear. 2003;254:1–9. doi:10.1016/s0043-1648(02)00305-8 16. wood rj, lee j, wood rj, lee j, bussemaker mj. a parametric review of sonochemistry : control and augmentation of sonochemical activity in aqueous solutions. ultrason sonochem. 2017;38:351–70. doi:10.1016/j.ultsonch.2017.03.030 17. verhaagen b, fernández rivas d. measuring cavitation and its cleaning effect. ultrason sonochem. 2016;29:619–28. doi:10.1016/j.ultsonch.2015.03.009 18. caruso mm, davis da, shen q, odom sa, sottos nr, white sr, et al. mechanically-induced сhemical changes in polymeric material. chem rev. 2009;109:5755–98. doi:10.1021/cr9001353 19. czechowska-biskup r, rokita b, lotfy s, ulanski p, rosiak jm. degradation of chitosan and starch by 360-khz ultrasound. carbohydr polym. 2005;60:175–84. doi:10.1016/j.carbpol.2004.12.001 https://doi.org/10.1016/j.ijbiomac.2018.09.079 https://doi.org/10.1016/0049-3848(91)90114-c https://doi.org/10.1021/acsomega.0c04591 https://doi.org/10.1038/srep40760 https://doi.org/10.1038/srep40760 https://doi.org/10.1080/10942910802317610 https://doi.org/10.1016/s0008-6215(99)00206-2 https://doi.org/10.1121/1.1312360 https://doi.org/10.1016/s1350-4177(02)00152-9 https://doi.org/10.1016/s0043-1648(02)00305-8 https://doi.org/10.1016/j.ultsonch.2017.03.030 https://doi.org/10.1016/j.ultsonch.2015.03.009 https://doi.org/10.1021/cr9001353 https://doi.org/10.1016/j.carbpol.2004.12.001 investigation of borosilicate glasses with simulated hlw components and determination of their chemical durability chimica techno acta article published by ural federal university 2021, vol. 8(1), № 20218105 journal homepage: chimicatechnoacta.ru doi: 10.15826/chimtech.2021.8.1.05 1 of 7 investigation of borosilicate glasses with simulated hlw components and determination of their chemical durability s.m. shaydullin ab* , e.a. belanova b , p.v. kozlov bc , m.b. remizov b , e.m. dvoryanchikova b a: seversk technological institute – branch of nrnu mephi (sti nrnu mephi), 636036, kommunistichesky av. 65, seversk, tomsk region, russia b: fsue mayak production association, 456784, lenin str. 31, ozyorsk, chelyabinsk region, russia c: ozyorsk technological institute – branch of nrnu mephi (oti nrnu mephi), 456780, pobeda str. 48, ozyorsk, chelyabinsk region, russia * corresponding author: cpl@po-mayak.ru this article belongs to the pcee-2020 special issue. © 2021, the authors. this article is published in open access form under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). abstract the paper discusses the current status of the hlw vitrification technology applied at the radiochemical plant of the mayak pa. conceptual and technical solutions proposed to develop the technology of vitrification of various types of liquid hlw at the mayak pa are presented. compositions of borosilicate glasses with hlw components are described, temperatures of their melting and easy pouring are determined. chemical durability parameters obtained for the borosilicate glasses are provided. keywords borosilicate glass vitrification high-level waste chemical durability vitrification melter received: 25.11.2020 revised: 02.03.2021 accepted: 03.03.2021 available online: 04.03.2021 1. introduction isolation and safe storage of radioactive waste can by implemented by means of its immobilization with the use of durable, chemically resistant materials. while low-level and intermediate-level waste can be immobilized by means of cementation, solidification of high-level waste (hlw) requires more durable matrices, such as ceramics and glass. glass is a nonstoichiometric compound that can dissolve, when heated, and then reliably confine, at subsequent cooling, a complex mixture of nuclear fuel fission products. the resulting isotropic, nonporous product is characterized by high chemical durability, radiation resistance and heat conductivity [1]. the objective of this work was to produce borosilicate glasses based on calcined simulated hydroxide sludge with a complex composition that simulated hlw accumulated in the storage tanks of the radiochemical plant and glass frit in various ratios, to determine the melting temperature, the temperature of easy pouring and chemical durability of the glasses. as a part of this study, the borosilicate glasses with a weight content of calcined solid ranging from 15 to 60% were produced and investigated. acceptable chemical durability is demonstrated by the glasses with a mass fraction of the calcined solid of no more than 30%. 2. results and discussion two types of glasses are mainly applied for hlw immobilization; these include borosilicate and phosphate glasses [2]. as a rule, basic composition of borosilicate glass includes silicon, boron and sodium oxides, and aluminophosphate glass consists of aluminum, phosphorus and sodium oxides [3]. the glass composition is limited by solubility of individual hlw components in glass, on the one hand, and by the technological parameters of vitrification (waste denitration method, equipment applied for their calcination, heating method, solidification conditions, pouring from the melter, etc.), on the other hand. immobilization of the liquid hlw of the radiochemical plant in aluminophosphate glass has been carried out at the mayak pa on the industrial scale since 1987. this method is implemented using nonremovable direct electric heating melters (ep-500). over the past period of time, 4 such melters have reached the end of their design service life and have been decommissioned. since december 27, 2016, the fifth industrial-scale electric furnace ep-500/5 designed for vitrification of liquid hlw has been in operahttp://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2021.8.1.05 http://creativecommons.org/licenses/by/4.0/ chimica techno acta 2021, vol. 8(1), № 20218105 article 2 of 7 tion. its design service life is 6 years. the work is currently underway to develop the next melter of such type (ep250/6), the design of which will take into account the operational experience of the previous vitrification facilities, which is expected to prolong the service life of the new melter to approximately 8 years. commissioning of this electric melter is scheduled for 2023. plans are underway at the mayak pa to construct in 2028 a new vitrification complex that will enable solidifying a wide variety of liquid high-level waste. for example, small-size borosilicate glass melters with direct electrical heating are assumed to be used for solidification of liquid hlw generated as a result of reprocessing of snf from power reactors (vver-440, vver-1000, bn-600 and bn800) [4]. the design-basis dismantling, disassembling and removing procedures are to be developed for these electric melters to ensure compliance with environmental regulations and to provide cost saving at construction of new facilities due to the use of considerable part of the infrastructure [5]. solidification of other types of liquid hlw is planned to be implemented using ep melters, the design of which will provide for an inherent procedure of dismantling upon completion of the service life. thus, in the coming decade the main method for hlw solidification in russia will still be based on radioactive waste vitrification in the direct electric heating melters. it is worth noting that the range of glasses applied for vitrification and characteristics of waste to be solidified will be expanded [6]. in compliance with the iaea standards, liquid hlw is subject to solidification [7]. the main objective is to reduce the hlw volume as much as possible and to provide the hlw conditioning, i.e. conversion of the radioactive waste into chemically durable and radiation-resistant form that maintains its stability throughout the entire storage period. from the point of view of long-term environmental safety, chemical durability is of paramount importance. in spite of the fact that borosilicate glass has long been used abroad for radioactive waste solidification, systematic investigations of physical and chemical properties of this type of glass have been carried out in russia mainly during the recent 20 years. the objective of this work was to produce borosilicate glasses based on calcined simulated hydroxide sludge with a complex composition that simulated hlw accumulated in the storage tanks of the radiochemical plant and glass frit in various ratios, to determine the melting temperature, the temperature of easy pouring and chemical durability of the glasses. compositions of the investigated borosilicate glasses and the initial glass frit, melting temperatures and easy pouring temperatures are provided in table 1. these compositions were selected based on the variety of hlw vitrified into borosilicate glass. calcined solid is a product resulting from reprocessing of simulated hydroxide sludge from one of the storage tanks. the storage tanks are fourteen concrete compartments, 1170 m 3 each, isolated from each other and lined with stainless steel of 12х18н9т grade with a thickness of 3 mm. the storage tanks were actively filled with heterogeneous high-level waste (hlw) between 1968 and 1986. the storage tanks are located on the ground surface, which excludes the possibility of ground water ponding [8]. the storage tanks contain slightly alkaline and alkaline systems of precipitates, suspensions and clarified solutions. the precipitates mainly contain iron, aluminum, nickel and chromium hydroxides, iron and nickel sulfides, nickel-cesium and titanium-cesium ferrocyanides. the liquid phase contains high salinity solutions, chemical composition of which is determined mainly by sodium hydroxide, aluminate and nitrate. radionuclide composition is represented mainly by fission products and is different for the clarified phase and the precipitate. the liquid phase activity is conditioned mainly by cesium-137; the precipitate also contains considerable amount of strontium-90 (in equilibrium with yttrium-90), as well as fissionable components such as uranium and plutonium. the sludge composition is provided in table 2. as it is a challenging task to synthesize sludge of such composition under laboratory conditions, its ninefold dilution was assumed by convention. consequently, aluminum, iron, chromium, nickel, manganese, magnesium and calcium hydroxides were produced directly by precipitation of the elements from the nitric acid solution using sodium hydroxide. table 1 compositions of the investigated glasses, melting temperatures and easy pouring temperatures g la s s n o mass fraction of oxides in borosilicate glasses, % тm., °с тe.p., °с sio2 b2o3 li2o na2o al2o3 fe2o3 cr2o3 nio mno cao k2o mgo so3 glass frit 72.00 8.00 8.00 12.00 1200 1 61.43 6.80 6.80 18.69 3.19 0.56 0.26 0.67 0.18 0.09 0.67 0.13 0.54 1050 1150 2 50.85 5.60 5.60 25.37 6.37 1.13 0.52 1.33 0.36 0.19 1.34 0.26 1.07 1000 1100 3 40.28 4.40 4.40 32.06 9.56 1.69 0.77 2.00 0.55 0.28 2.01 0.39 1.61 950 1000 4 29.71 3.20 3.20 38.75 12.74 2.26 1.03 2.66 0.73 0.37 2.69 0.52 2.14 900 950 a тm. melting temperature b тe.p. easy pouring temperature chimica techno acta 2021, vol. 8(1), № 20218105 article 3 of 7 table 2 content of components in the hydroxide sludge on condition that the precipitate and the liquid phase are homogenized component concentration of components in the real sludge, g/l concentration of components in the ninefold diluted sludge, g/l na 170.3 18.9 al 181.5 20.2 fe 42.5 4.7 cr 19.1 2.1 ni 56.3 6.3 mn 15.0 1.7 si 11.4 1.3 mg 8.4 0.9 ca 7.3 0.8 k 60.0 6.7 so4 2 69.1 7.7 cl 0.37 0.04 no3 30.7 3.4 the sodium hydroxide solution with a concentration of 500 g/l was added to the nitric acid solution so that hydroxides of the above-mentioned elements precipitated completely; as a consequence, the simulated laboratory sludge turned out to have higher sodium content. potassium was introduced in the form of potassium nitrate, sulfate-ions in the form of sodium sulfate, chloride-ions in the form of sodium chloride and silicon in the form of colloidal silicon oxide (aerosil). upon completion of the precipitation, a system consisting of a solid and a liquid phase was obtained. the solid phase contained aluminum, iron, chromium, nickel, manganese, magnesium, calcium and silicon. the liquid phase was formed by potassium, sodium, nitrate-, chlorideand sulfate-ions. in the course of the investigations the sludge was evaporated to dry residue and thermally treated at 600 °с for 2 hours. to ensure more complete calcination, the sludge was additionally held for 2 hours at 800 °с. the final composition of the simulated hydroxide sludge produced under laboratory conditions and the related calcined solid composition are provided in table 3. the data were obtained using an inductively coupled plasma mass spectrometer. glass of four compositions was produced based on the calcined simulated hydroxide sludge with a complex composition and the glass frit in various ratios: calcined solid 15%, frit 85%; calcined solid 30%, frit 70%; calcined solid 45%, frit 55%; calcined solid 60%, frit 40%. the glass-forming calcined solid was melted at a temperature ranging from 800 °c to 1050 °c. as each glass composition is characterized by its individual melting temperature, the condition of the crucible contents was visually examined at intervals of 50 °c (starting from 800 °c). the glass melting temperature was recorded at the moment of the calcined solid conversion into melt. in order to reach complete homogenization of the melt, it was held at the abovementioned temperature for 2 hours. then the heating was continued at intervals of 50 °c to determine the temperature of easy pouring of the melt, which was assessed visually judging by the melt fluidity. quenched glass was produced by rapid cooling of the melt to room temperature at its discharge on the metal plate made of stainless steel. table 3 the composition of the hydroxide sludge produced under laboratory conditions and the corresponding calcined solid composition components of simulated hydroxide sludge component concentration in the sludge, g/l complete composition of the simulated hydroxide sludge component concentration in the sludge, g/l complete composition of the calcined simulated hydroxide sludge mass fraction of oxides in the calcined solid, % al 19.64 al(oh)3 56.76 al2o3 21.24 fe 4.60 fe(oh)3 8.82 fe2o3 3.76 cr 2.07 cr(oh)3 4.09 cr2o3 1.72 ni 6.09 ni(oh)2 9.61 nio 4.44 mn 1.62 mn(oh)2 2.64 mno 1.21 mg 0.91 mg(oh)2 2.18 mgo 0.87 ca 0.79 ca(oh)2 1.45 cao 0.62 k 6.49 koh 5.52 k2o 4.48 na 73.28 kno3 6.82 na2o 53.78 si 1.23 nano3 257.58 sio2 1.51 so4 2 7.48 sio2 2.64 so3 3.57 cl 0.04 na2so4 11.06 nacl 0.03 no3 187.9 nacl 0.06 chimica techno acta 2021, vol. 8(1), № 20218105 article 4 of 7 it was established that the glass melting temperature ranged from 900 °с to 1050 °с and the easy pouring temperature was from 950 °с to 1150 °с (see table 1), which is fully consistent with the temperature mode of operation of the vitrification furnaces designed at the mayak pa. the produced glass was homogenous and transparent throughout its entire volume. the glasses with compositions 1 to 4 were tested for chemical durability. to test the glasses according to the procedure described in state standard gost r 52126 [9], glass fractions with a particle size ranging from 0.16 to 0.25 mm were prepared. specific surface area of the powder was 120 cm 2 /g. before the testing, the glass powders were washed with ethyl alcohol to remove dust fraction and dried. according to a method of long-term leaching, weighed powder samples with a weight of 0.3 g with a total surface area of 36 cm 2 were placed into polyethylene containers with sealed lids, where 50 cm 3 of deionized water was added. the samples were held at a temperature of (23 ± 2) °с. the contact solution was replaced in 1, 3, 7, 10, 14, 21, 28, 35, 56 and 91 days after the testing was started. at the end of the specified period of time, the contact solution was decanted and analyzed to determine the element content using inductively coupled plasma massspectrometry (icp-ms). according to rules and regulations np-019-2015 [10], chemical durability of phosphate glasses is evaluated based on cesium-137 leaching, the standard leaching rate of which must not exceed 1∙10 -5 g/(cm 2 ∙day). in the framework of this research, chemical durability of the borosilicate glasses was determined based on the leaching rate of lithium, sodium and potassium that are chemical analogs of cesium. among the above-mentioned univalent elements, lithium and sodium are the most mobile elements due to their small ionic radius. besides, leaching of matrix components (silicon and boron) and hlw components (aluminum) was investigated to assess behavior of multivalent elements. the degree of element leaching is an additional criterion for evaluation of the chemical durability of the glass. this value is not normalized; however, it provides a more accurate estimate of the matrix quality. the rate of the element leaching from the matrix determined using the long-term leaching method is a differential quantity, while the leaching degree is an integral quantity. the results of the element leaching from the borosilicate glasses with compositions 1 to 4, produced using the long-term leaching method for 1, 3, 7, 10, 14, 21, 28, 35, 56 and 91 days from the beginning of the experiment, are provided in figs. 1 to 6 and in table 4. table 4 summarized data on leaching of elements from quenched borosilicate glasses obtained using the long-term leaching method glass number differential leaching rate, g/(cm 2 ∙day) leaching degree, % on the 1 st day on the 91 st day over 1 day over 91 days lithium 1 1.48∙10 -5 3.74∙10 -7 0.18 1.12 2 2.12∙10 -5 1.69∙10 -6 0.25 2.68 3 4.23∙10 -5 4.69∙10 -6 0.51 9.19 4 1.78∙10 -4 1.01∙10 -5 2.14 21.34 sodium 1 8.34∙10 -6 5.40∙10 -7 0.10 0.99 2 8.22∙10 -6 2.11∙10 -6 0.10 1.85 3 1.69∙10 -5 5.21∙10 -6 0.20 5.54 4 5.36∙10 -5 1.00∙10 -5 0.64 13.12 potassium 1 4.63∙10 -6 4.73∙10 -7 0.06 0.91 2 8.10∙10 -6 8.25∙10 -7 0.10 1.35 3 1.10∙10 -5 2.11∙10 -6 0.13 2.31 4 4.65∙10 -5 3.88∙10 -6 0.56 6.39 boron 1 7.42∙10 -6 5.35∙10 -7 0.09 1.13 2 6.13∙10 -6 2.68∙10 -6 0.07 2.83 3 2.65∙10 -5 7.18∙10 -6 0.32 9.52 4 6.95∙10 -5 1.43∙10 -5 0.83 23.08 silicon 1 2.54∙10 -7 1.41∙10 -8 0.003 0.035 2 2.72∙10 -7 3.41∙10 -8 0.003 0.051 3 2.58∙10 -6 1.57∙10 -6 0.03 2.02 4 8.26∙10 -6 1.82∙10 -6 0.10 4.60 aluminum 1 1.13∙10 -6 4.54∙10 -9 0.014 0.067 2 8.69∙10 -7 1.78∙10 -8 0.010 0.044 3 2.08∙10 -6 1.92∙10 -7 0.03 0.35 4 3.77∙10 -6 4.87∙10 -7 0.05 1.87 chimica techno acta 2021, vol. 8(1), № 20218105 article 5 of 7 (a) (b) fig. 1 rate (a) and degree (b) of lithium leaching from the quenched borosilicate glasses with compositions 1 to 4 versus the durati on of leaching (a) (b) fig. 2 rate (a) and degree (b) of sodium leaching from the quenched borosilicate glasses with compositions 1 to 4 versus the duration of leaching (a) (b) fig. 3 rate (a) and degree (b) of potassium leaching from the quenched borosilicate glasses with compositions 1 to 4 versus the dur ation of leaching chimica techno acta 2021, vol. 8(1), № 20218105 article 6 of 7 (a) (b) fig. 4 rate (a) and degree (b) of boron leaching from the quenched borosilicate glasses with compositions 1 to 4 versus the duration of leaching (a) (b) fig. 5 rate (a) and degree (b) of silicon leaching from the quenched borosilicate glasses with compositions 1 to 4 versus the duration of leaching (a) (b) fig. 6 rate (a) and degree (b) of aluminum leaching from the quenched borosilicate glasses with compositions 1 to 4 versus the duration of leaching as can be seen from the data provided in table 4, the chemical durability of the borosilicate glasses (from composition 1 to composition 4) decreases with an increase in the mass fraction of the calcined sludge (from 15 to 60%) in them. this phenomenon is associated with growth in sodium oxide concentration in the glass (due to the high chimica techno acta 2021, vol. 8(1), № 20218105 article 7 of 7 sodium content in the simulated hydroxide sludge) and with the decrease in concentration of other important components contained in the frit that form threedimensional framework of the glass material (silicon and boron oxides). the glasses with compositions 1 and 2 are characterized with maximum chemical durability. sodium and potassium leaching rates had already been below the standard level of (1∙10 -5 g/(cm 2 ∙day)) at the beginning of the testing, and the leaching rate of lithium reached the specified reference level at the end of the 3 rd day. it is worth noting that the leaching degree of the three elements over the entire testing period of 91 days did not exceed 3% [10]. it was noted that boron behavior at leaching was identical to that of sodium. as for silicon, it has the lowest leaching indices; and in compliance with rules and regulations np-019-2015 [10] they are comparable with a standard leaching rate of (1∙10 -7 g/(cm 2 ∙day)) for plutonium. such a level is reached at the end of the 7 th day, and the leaching degree for the entire testing period is not more than 0.051%. average initial rate of aluminum leaching from the glasses with compositions 1 and 2 is 1∙10 -6 g/(cm 2 ∙day), which is comparable with the standard leaching rate of strontium. besides, the degree of aluminum leaching over 91 days does not exceed 0.1%. an increase in the mass fraction of alkaline elements in glasses (compositions 3 and 4) causes an increase in their content in the leachate, which, in its turn, speeds up the dissolution of the silicon oxide. 3. conclusions as a part of this study, the borosilicate glasses with a weight content of calcined solid ranging from 15 to 60% were produced and investigated. the calcined solid contained the components of the hydroxide sludge with a complex composition that simulated hlw of the radiochemical plant. the melting temperature of the glasses ranges from 900 °c to 1050 °c, and the easy pouring temperature is in the range from 950 °с to 1150 °с, which is fully consistent with the temperature mode of operation of the vitrification furnaces designed at the mayak pa. the glasses with compositions 1 and 2 are characterized with maximum chemical durability. sodium and potassium leaching rates had already been below the standard level of (1∙10 -5 g/(cm 2 ∙day)) at the beginning of the testing, and the leaching rate of lithium reached the specified reference level at the end of the 3 rd day. it was noted that boron behavior at leaching was identical to that of sodium. as for silicon, it has the lowest leaching indices; they are comparable with a standard leaching rate of (1∙10 -7 g/(cm 2 ∙day)) for plutonium. acceptable chemical durability is demonstrated by the glasses with a mass fraction of the calcined solid of no more than 30%. references 1. goel a, mccloy js, pokorny r, kruger aa. challenges with vitrification of hanford high-level waste (hlw) to borosilicate glass – an overview. j non-cryst solids: x. 2019;4:100033. doi:10.1016/j.nocx.2019.100033 2. ozhovan mi, poluektov pp. primeneniye styokol pri immobilizatsii radioaktivnykh otkhodov [the use of glass for 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pererabotki nakoplennykh v yomkostyakh zhidkikh radioaktivnykh otkhodov slozhnogo himicheskogo sostava [main approaches, practices and problems of reprocessing of radioactive waste with complex chemical composition accumulated in the storage tanks]. radioaktivnye otkhody [radioactive waste]. 2018[cited 2020 november 25];4(5):55–64. russian. available from: http://ibrae.ac.ru/docs/radwaste_journal_4(5)18/055066_kozlov_basic%20approaches,%20experience%20 and%20problems.pdf 9. radioactive waste. opredeleniye khimicheskoy ustoychivosti otverzhdyonnnykh vysokoaktivnykh otkhodov metodom dlitelnogo vyshchelachivaniya. gost r 52126-2003 [determination of chemical stability of solidified high-level waste using long-term leaching method. state standard gost r 52126-2003]. moscow: ipk standards publishing house, 2003. 5 p. russian. 10. sbor, pererabotka, khranenye i konditsionirovaniye zhidkikh radioaktivnykh otkhodov. trebovaniya bezopasnosti. np-0192015 [collection, reprocessing, storage and conditioning of liquid radioactive waste. safety requirements. rules and regulations np-019-2015]. moscow: gosatomnadzor of russia, 2015. 22 p. russian. https://doi.org/10.1016/j.nocx.2019.100033 https://doi.org/10.1016/j.jnoncrysol.2004.07.040 http://ibrae.ac.ru/docs/radwaste_journal_4(5)18/055-066_kozlov_basic%20approaches,%20experience%20and%20problems.pdf http://ibrae.ac.ru/docs/radwaste_journal_4(5)18/055-066_kozlov_basic%20approaches,%20experience%20and%20problems.pdf http://ibrae.ac.ru/docs/radwaste_journal_4(5)18/055-066_kozlov_basic%20approaches,%20experience%20and%20problems.pdf oxidative destruction of anionite av-17×8 using the fenton reaction chimica techno acta article published by ural federal university 2021, vol. 8(4), № 20218406 eissn 2411-1414; chimicatechnoacta.ru doi: 10.15826/chimtech.2021.8.4.06 1 of 5 oxidative destruction of anionite av-17×8 using the fenton reaction m.m. kozlova a*, v.f. markov ab, l.n. maskaeva ab a: ural federal university, 620002 mira st., 19, ekaterinburg, russia b: ural state fire service institute of emergency ministry of russia, 620022 mira st., 22, ekaterinburg, russia * corresponding author: marina.kozlova2014@mail.ru this article belongs to the mosm2021 special issue. © 2021, the authors. this article is published in open access form under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). abstract the kinetic studies of av-17×8 strongly basic anionite’s oxidative destruction using the fenton reaction have been carried out. the effect of the process’s temperature and the concentration of catalysts of iron(ii) sulfate or copper(ii) sulfate on the oxidation of anion exchange resin with hydrogen peroxide is estimated. with an increase in temperature in the range of 323–348 k, a regular increase in the effective rate constant of oxidative anionite destruction is observed when using iron(ii) sulfate by 1.5 times, and when using copper(ii) sulfate – by 22 times. it was found that the obtained values of the activation energy of the anion exchanger’s oxidation with the addition of copper(ii) sulfate are 124.3–115.7 kj/mol and are characteristic of the process proceeding in the kinetic region. the nature of the change in the surface morphology of the anionite granules in the process of oxidative decomposition has been revealed . keywords anion exchanger av-17×8 hydrogen peroxide fenton process process rate constant activation energy received: 02.11.2021 revised: 22.11.2021 accepted: 23.11.2021 available online: 26.11.2021 1. introduction the ion exchange resins are widely used in the field of waste and wash water treatment at the nuclear power plants. as a result, the spent ion-exchange resins are formed, which are low-activity heterogeneous waste in the form of spherical granules from a cross-linked organic polymer. over the years, the significant amounts of waste resins have accumulated at nuclear power plants, which subsequently cannot be regenerated [1]. thus, an effective technology is needed for the disposal of the spent ionexchange resins in order to reduce their negative impact on the environment. at present, such technologies as immobilization (cementation, bitumization, vitrification) or incineration, pyrolysis, thermal vacuum drying, and supercritical water oxidation are used to dispose of waste resins [1, 2]. however, regular recycling technologies are characterized by significant economic costs, also there are difficulties with the transportation and storage of wastes that can be accompanied by the formation of explosive products associated with the radiolysis of organic substances and water. an effective way of the spent ion-exchange resins removal can be oxidative destruction, which significantly reduces the concentration of organic substances. a promising method is the fenton process, based on the oxidation of organic compounds under the action of hydrogen peroxide. the catalytic additive can be ions of divalent transition metals, for example, iron(ii) sulfate or copper(ii) sulfate. the fenton process is characterized by the formation of free hydroxyl radicals но• in the system, which have minimal selectivity to various organic substances. но• radicals are characterized by a high potential (2.80 v), and, therefore, have high oxidizing capacity [3]. the main mechanism of the classical fenton process can be represented in the form of a redox reaction with the ferrous ions [3]: fe2+ + h2o2 → fe3+ + он•+ oh¯. (1) as a result of chain reactions and an increase in the concentration of chemically active particles, a complex organic compound rh decomposes into small fragments [3]: но• + h2o2 → hoo• + н2о, (2) fe3+ + hoo• → fe2+ + н+ + o2, (3) fe2+ + hoo• → fe3+ + hoо¯, (4) fe2+ + но• → fe3+ + oh¯, (5) но• + rh → r• + h2o. (6) http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2021.8.4.06 http://creativecommons.org/licenses/by/4.0/ chimica techno acta 2021, vol. 8(4), № 20218406 article 2 of 5 the fenton process is characterized by a high reactivity, a deep oxidation state, and sufficiently mild operating conditions. the reaction efficiency is influenced by such factors as temperature, ph of the medium, concentration of hydrogen peroxide and catalyst. the oxidation of sulfonic acid cation exchangers with hydrogen peroxide, as well as strongly basic anion exchangers with tertiary trimethylammonium groups in the presence of catalytic additions of transition metal salts, was described in [4–14]. thus, in the study [4], the complete decomposition of domestic brand anionite av-17×8 was achieved by the action of a 30% solution of hydrogen peroxide with the addition of an iron(ii) salt in the temperature range 363–373 k. the works of the authors [5–14] are aimed at choosing the optimal conditions for the oxidative destruction of ion exchange resins of some foreign brands. the research [9] is devoted to the complete decomposition of a foreign brand of anion-exchange resin amberlite inr78 by exposure to a 30% hydrogen peroxide solution with the addition of a copper (ii) salt at a temperature of 368 k. in the above mentioned works the individual aspects of the influence such as the concentration of the oxidizing agent, the temperature of the solution, and the concentration of catalytic additives on the fenton process were studied. however, there is currently no information on kinetic s of the ion-exchange resins oxidative destruction using the fenton process. previously, the studies were carried out on the oxidation of hydrogen peroxide using the fenton reaction of the highly acidic universal cation exchanger ku-2-8 [15]. this works object is to the study of the kinetics of catalytic oxidative destruction of the domestic anionite av-17×8 using the fenton process. 2. experimental the object of the study was the strongly basic anion exchanger av-17×8 (gost 20301-74), the crosslinked copolymer of styrene and divinylbenzene. the diameters of spherical resin granules are in range of 315–1250 µm, the content of the working fraction is not less than 95%, the uniformity coefficient is 1.6, and the specific volume is 3.0±0.3 cm3/g. for the oxidation of the av-17×8 anionite, we used an environmentally friendly oxidizing agent — hydrogen peroxide h2o2, the concentration of which was determined by permanganatometry [16]. the preparation of 0.1 m catalyst solutions was carried out using salts of iron(ii) sulfate feso47h2o and copper(ii) sulfate cuso45h2o. in all experiments, the amount of anion-exchange resin was constant and was 0.5 g based on the weight of the airdry mass. to study the catalytic oxidation, a weighed portion of the av-17×8 anionite was introduced into the reactors, then 10 ml of a hydrogen peroxide solution with an h2o2 concentration of 20 vol.%, then 0.001–0.005 mol/l feso4 or cuso4 was added. the reactors were placed in the thermostat of the brand loip lt-105a. the process was carried out in the temperature range of 323–348 k. each reactor was removed from the thermostat after a certain time. the remaining av-17×8 anionite in the reactors was thoroughly washed, filtered, dried in air for a week at room conditions, then heated in a pm-1.0-7 electric furnace for 2.5 h at the temperature of 377±1 k. after that, it was weighed on an analytical balance vibra htr-220ce with a readability of ±0.0001 g. the study of the surface morphology of the granules of the anionite av-17×8 was carried out by scanning electron microscopy using a jeol jsm-6390 la microscope. 3. r esults and discussion to explain the physicochemical process of av-17×8 anionite oxidation, it is necessary to consider the patterns of the process in time, depending on the mechanism of the chemical reaction and on thermodynamic factors the temperature and concentration of the catalyst. let us consider the effect of temperature as a parameter that has the most significant impact on the rate of anion exchanger oxidative destruction. the kinetic studies of the av-17×8 anionite catalytic oxidation with hydrogen peroxide were carried out with the addition of 0.001–0.005 mol/l iron(ii) sulfate and copper(ii) sulfate. the dependences of the relative weight loss of the anion exchange resin on the exposure time of 20 vol.% hydrogen peroxide with the addition of 0.002 mol/l feso4 at temperatures from 323 to 343 k are shown in fig. 1a. it is observed that the process of the anionite destruction by hydrogen peroxide with iron(ii) sulfate proceeds relatively slowly, and with a decrease in the reaction temperature, the longer induction period occurs. so, at 343 k in 360 min, only 36% of the anion exchanger was dissolved. the lowering of the temperature to 333 k leads to the decomposition of 17% of resin within 210 min. at 323 k, 10% of the anion exchanger is oxidized in 270 min. with the use of copper(ii) sulfate as a catalytic additive at the temperatures in range of 323–348 k, the complete oxidation of the av-17×8 anionite was achieved (fig. 1b). the graph shows how the duration of the induction period decreases with increasing temperature. at 348 k the intense oxidation of the anion exchange resin is observed during the first 24 min. the decrease in the working temperature of the solution to 343 and 333 k leads to the complete decomposition of the resin after 35 and 110 min, respectively. at 323 k after 270 min, the resin mass loss was ~92%. thus, an increase in the process temperature from 323 k to 348 k significantly influences the rate of anion exchange resin decomposition. it should be noted that increasing the catalyst concentration that is iron(ii) sulfate or copper(ii) sulfate at a given temperature does not significantly accelerate the decomposition of the av-17×8 anionite. chimica techno acta 2021, vol. 8(4), № 20218406 article 3 of 5 fi g. 1 kinetic curves of the av-17×8 anionite relative weight loss in 20% h2o2 with the addition of 0.002 mol/l feso4 (a) and 0.003 cuso4 mol/l (b) at a temperature, k: 348 (1), 343 (2), 333 (3), 323 (4) the effect of catalytic additions of copper and iron salts, according to studies [6–9, 11, 14], is based on an increase in the concentration of active oxygen during the decomposition of hydrogen peroxide, which promotes more active resin oxidative destruction. in the works [6, 9], the activities of catalytic additives in the fe2+/h2o2 and cu2+/h2o2 solutions have been compared and it is concluded that copper(ii) ions have a stronger catalytic effect in the process of the anion exchanger oxidation compared to iron(ii) ions. to determine the rate of the heterogeneous process in the "anionite-solution" system, it is necessary to take into account the interfacial area that changes during oxidative destruction, as well as the geometry of the spherical particles of the anion-exchange resin. the reaction rate, that is, the loss of anionite’s mass, can be determined according to the equation: − 𝑑𝑚 𝑑𝜏 = 𝑘𝐹𝐶 (7) where m is the mass of the anionite av-17×8 granule at the time τ, f is its surface area, c is the concentration of н2о2, k is the rate constant of the oxidation reaction. by transforming eq. (7), it is possible to obtain the dependence of the change in the mass of the anion resin granule on the duration of the process of its oxidation "m1/3 – τ" [17]. the processing of the experimental results, carried out in coordinates "m1/3 – τ", allows taking into account the heterogeneous nature of the oxidation reaction and the spherical shape of the anionite av-17×8 granules. the effective rate constant of the process k was determined from the slope of the obtained straight line in the coordinates "m1/3 – τ". table 1 shows the calculated values of the effective rate constants of the anion exchanger oxidative destruction process depending on the temperature and the concentration of catalytic additives . from the calculated values with the addition of 0.002 mol/l feso4 catalyst, it shows that an increase in the process temperature from 323 to 343 k leads to an increase in the rate constant by a factor of 1.5. with an increase in the content of the cataly tic additive from 0.001 to 0.005 mol/l, the rate constant of the process increases by a factor of 1.2. according to the obtained values of the process effective rate constant with the addition of 0.002 mol/l cuso4, and with increase in the process temperature from 323 to 348 k the rate constant is increasing by a factor of 23. at 0.003, 0.004, and 0.005 mol/l cuso 4, the effective rate constant of the process increases by a factor of 22. with a decrease in the concentration of the catalytic additive to 0.001 mol/l cuso4, an increase in the rate constant by a factor of 18 is observed. an increase in the concentration of the cuso4 catalyst from 0.001 to 0.005 mol/l slows down the increase in the process rate constant, increasing it by no more than 1.3–2.2 times. t a ble 1 effective process rate constant (k×103, g1/3 min–1) oxidative destruction of the anionite av-17×8, depending on the temperature and concentration of catalytic additives when using 20 vol.% hydrogen peroxide т, к [feso4], mol/l [cuso4], mol/l 0.001 0.002 0.003 0.004 0.005 0.001 0.002 0.003 0.004 0.005 323 – 0.23 0.25 0.34 0.35 2.15 2.71 2.93 3.20 3.25 333 0.20 0.24 0.25 – – 5.82 7.88 9.13 10.29 12.67 343 0.27 0.34 – – – 32.07 33.49 35.99 42.13 41.83 348 – – – – – 38.41 63.73 65.96 70.67 72.75 chimica techno acta 2021, vol. 8(4), № 20218406 article 4 of 5 using the calculated values of the effective rate constants, the activation energy eа of the process of the anionite oxidative destruction was determined by the graphical solution of the arrhenius equation in the coordinates "lnk – 103/t". according to the data presented in table 2, the activation energies of the anionite oxidation process with the addition of the cuso 4 catalyst are in the range from 124.3 to 115.7 kj/mol, which indicates that the process is of the kinetic type. t a ble 2 activation energy of the process of oxidative destruction of the av-17×8 anionite in 20% hydrogen peroxide at various concentrations of the cuso4 catalyst [cuso4], mol/l 0.001 0.002 0.003 0.004 0.005 eа, kj/mol 124.3 118.1 116.4 115.7 116.2 the surface of the anionite av-17×8 granules in the process of catalytic oxidative destruction has been investigated. for comparison, fig. 2a shows a relatively smooth and practically undeformed surface of granules before oxidation. fig. 2b shows an electron microscopic image of a surface of granules after 2.5 h of contact at the temperature of 343 k with a 20 vol.% aqueous solution of hydrogen peroxide containing 0.002 mol/l feso 4, which corresponds to a loss of 20% of granule’s mass. fig. 2c shows a surface of anionite granules after exposure to a 20 vol.% aqueous solution of h2o2 containing 0.005 mol/l cuso 4. as a result of contact for 10 min at the temperature of 343 k, the weight loss of the anionite was 85%. in fig. 2(b, c), the local changes can be observed on the resin surface. at the same time, the sorbent granule changed its shape, volume, and its surface was covered with cracks, which may indicate the destruction of the crosslinks of the av-17×8 anionite in the process of oxidative destruction and a decrease in its mechanical strength. 4. conclusions thus, the kinetic studies of the av-17×8 anionite catalytic oxidative destruction by hydrogen peroxide showed that the introduction of 0.001–0.005 mol/l of the copper(ii) sulfate catalyst significantly increases the intensity of the oxidation process as compared to the addition of 0.001–0.005 mol/l of iron(ii) sulfate. it was found that in the presence of 0.002 mol/l catalytic additives in a 20% aqueous solution of hydrogen peroxide in the temperature range 323–348 k the rate constant of the oxidative decomposition of the anion exchanger increases by a factor of 1. 5 when using iron(ii) sulfate at an operating temperature of 343 k, and with the introduction of copper(ii) sulfate at 348 k – by a factor of 23. the calculated activation energies of the process of oxidative destruction of the av -17×8 anionite by hydrogen peroxide with the addition of copper(ii) sulfate are in the range 124.3–115.7 kj/mol, which is typical for the kinetic type process. fi g. 2 electron microscopic images of the surface of the anionite av-17×8 before oxidation (a), after exposure to 20% h2o2 with the addition of feso4 (b) and with the addition of cuso4 (c) r eferences 1. smolnikov mi, markov vf, maskaeva ln, bobylev ae, mokrousova oa. utilization problems of spent ion-exchange resins of nuclear power plants. butlerov commun. 2017;49(3):119–134. doi:jbc-01/17-49-3-119 2. wang j, wan z. treatment and disposal of spent radioactive ion-exchange resins produced in the nuclear industry. prog nucl energy. 2015;78:47–55. doi:10.1016/j.pnucene.2014.08.003 3. babuponnusami a., muthukumar k. a review on fenton and improvements to the fenton process for wastewater treathttps://doi.org/jbc-01/17-49-3-119 https://doi.org/10.1016/j.pnucene.2014.08.003 chimica techno acta 2021, vol. 8(4), № 20218406 article 5 of 5 ment. j environ chem eng. 2014;2(1):557–572. 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https://doi.org/10.1016/j.nucengdes.2015.05.009 https://doi.org/10.1016/j.cej.2015.09.004 https://doi.org/10.3390/environments5110123 https://doi.org/10.1016/j.cej.2018.09.169 https://doi.org/10.1016/j.pnucene.2020.103377 https://doi.org/10.32604/jrm.2020.011000 https://doi.org/10.1016/j.jece.2020.104740 https://doi.org/10.1134/s0036024420120146 391 d o i: 1 0. 15 82 6/ ch im te ch .2 01 5. 2. 4. 03 3 a. f. guseva, m. v. trifonova ural federal university 620000, ekaterinburg, mira 19, tel:+79126373816 e-mail: anna.guseva@urfu. surface reactions with participation of oxides of molybdenum and tungsten the kinetics of surface reactions in one-dimensional and radial (two-dimensional) distribution of diffusant moo 3 (wo 3 ) on the surface of the substrate meo (me is cd, ni, pb, mn, cu) were investigated. a kinetic equation satisfactorily describes the rate of surface reactions in the case of radial distribution of diffusant on the substrate. it’s found that when the radial distribution of diffusant the growth of layer on the substrate surface eventually slows down and stops almost completely, due to the outflow of the diffusant deeps into the substrate. when the one-dimensional distribution of diffusant the surface interaction is not slowed down and does not stop at an arbitrarily large times. keywords: diffusant; molybdates; complex oxides; surface reaction diffusion; scanning electron microscopy (sem) © guseva a. f., trifonova m. v., 2015 introduction the reaction diffusion in the synthesis of molybdates and tungstates, as well as many other complex oxides, includes bulk, grain-boundary and surface diffusion. the separation of these three streams and study of their mechanism is the most important task of the science of solid-phase reactions. in the synthesis of molybdates and tungstates the formation of the reaction product is found not only in the place of contact of the pellets of the reactants, but also outside it, on the surface of one of the reagents (substrate). this indicates a large contribution of surface reaction diffusion (srd) in a total reaction transfer and provides a unique opportunity to select and research one of three major streams of the reaction mass. one of the quantitative characteristics of the srd is the ratio of the length of the surface layer (ℓs) to the thickness of the layer of product at the place of contact of reagents (ℓ). the value of ℓs/ℓ for the same diffusants moo3 (wo3) varies in very wide limits from ℓs/ℓ ≈ 1…180. in papers [1–3] more than 20 surface reactions with the participation of moo3 (wo3) were studied and the following basic facts were installed: 1. a sharp slowdown in surface reactions, up to a full stop, after reaching a certain value of the length of the surface layer. 392 № 4 | 2015 chimica techno acta 2. the independence of the maximum length of the surface layer maxs from the temperature of the experiment; with changes in temperature, only the time to reach maxs changes. 3. the dependence of the rate of surface reactions on porosity of the substrate, which is localized on the surface layer. with increasing porosity ℓs decreases sharply. 4. the high sensitivity of the speed of srd to the influence of an electric field; a complex nonmonotonic dependencies ℓs (u) are observed. 5. the speed of surface reactions is significantly higher for those reaction pairs where the product of the interaction contains several phases. thus, the effect of srd has been studied well enough. however, the authors [1–3] noted that a number of experimental facts obtained in the study of this phenomenon (for example, termination of surface interaction when reaching a certain value of the length of the surface layer) can not be explained. further, up to the present time the research was conducted for this cell geometry, in which the proliferation of diffusant, and, consequently, the growth of the surface layer occurs radially with respect to the place of contact of the reactants. in this case, the diffusion is two-dimensional. at the same time, kinetic dependencies, linking some characteristic speed of the process over time, are obtained for one-dimensional diffusion. in connection with the foregoing, in the present work the following objectives are stated: 1) to obtain the growth equation of the surface layer in the radial distribution of diffusant, which satisfactorily describes the kinetics of surface interactions. 2) to investigate the kinetics of surface interactions in the case of one-dimensional distribution of diffusing into the systems cuo-moo3, mn2o3-moo3, niomoo3, nio-wo3, pbo-moo3. 3) using scanning electron microscopy (sem) to study the morphology of the reaction product on the surface and at the site of contact of the reactants. the experimental part we used nio, cuo, moo3, wo3, pbo, mn2o3, cdo (qualification “h.p.”). pb2moo5 was synthesized from simple oxides by standard ceramic technique in three stages with intermediate milling at temperatures of 550–750 °c; time of annealing at each stage was 15 hours. the phase composition was controlled by xray. the samples for investigation were prepared in the form of briquettes by pressing and subsequent sintering. the sintering conditions of the samples are given in table 1. the surface diffusion of the reaction was studied in one-dimensional and twodimensional distribution of diffusant. for this purpose we used cells with different geometry of the assembly of briquettes reagents. in one case, the disc diameter of the substrate briquette was 15 mm, and the diameter of the disc diffusant – 5 mm (fig. 1a); in another case substrate had a shape of a bar with a height of 5–10 mm and an area of contact with the surface diffusant 65–75 mm2, and the sample diffusant was made in the form of a disk with a diameter of 15 mm and a thickness of 2 mm (fig. 1b). the distribution scheme of diffusant on the substrate is shown by arrows. guseva a. f., trifonova m. v. 393 № 4 | 2015 chimica techno acta table 1 the sintering conditions of the samples compound annealing temperature, °c annealing time, hour nio 1200 6 mn2o3 900 24 pb2moo5 700 48 pbo 760 24 cuo 950 18 cdo 700 24 moo3 600 3 wo3 900 3 overseeing the development process was carried out by periodic measurement of the length of the surface layer ℓs, layer ℓ, formed in the contact area of the briquettes, the weight of the substrate. x-ray analysis of objects of research was carried out on diffractometer drf2.0 in the сокa radiation. the survey was conducted at a speed of 2 °c/min in the range of angles 2q from 5 to 35 °c. the interpretation of radiographs was carried out using the card file astm. the microscopic analysis of the surface and chipping of the pellets after annealing was performed using microscope mbs-9 with magnification 16 to 56 times and optical microscope polam s-112 in transmitted light at magnification of 300–420 time. the morphology of the substrate and product, as well as their elemental composition, was investigated using the electron microscope jsm-3 with a microprobe at magnification of 300–3000 times. the measurement of the mass of briquettes before and after diffusion annealing was carried out on an analytical balance sartorius – bl60s with an accuracy of 0.0001 g. the effective density of samples was determined by the volume and mass of samples and hydrostatic weighing. its value variated from 60 to 85 %. results and discussion the kinetic growth equation of the surface layer in the radial diffusion as shown earlier [1–3], one interesting feature of the srd is an atypical form of the kinetic dependences, which have the form of curves with saturation. when analyzing this phenomenon, we drew attention to the fact that a complete shutdown of surface interaction is recorded by conducting experiments for cells with such a geometry assembly of briquettes of reagents, which was radial (two-dimensional) distribution of diffusant on the surface of the substrate (fig. 1, a). it are obvious that the classical limit cases for the kinetic and diffusion regimes (ℓ = kτ and ℓ2 = kτ) is not consistent in the description of the kinetics of radial diffusion. when the radial distribution of diffusant, unlike the one-dimensional case, there is a constant increase in the length of the reaction front, which should fig. 1. the scheme of experiments for the investigation of kinetics of surface interactions: a – radial distribution of diffusant; b – one-dimensional distribution of diffusant. surface reactions with participation of oxides of molybdenum and tungsten 394 № 4 | 2015 chimica techno acta lead to change of time dependence of the parameter characterizing the rate of reaction (ℓs). therefore, in this work the task was to obtain a growth equation of the surface layer in the radial distribution of diffusant on the substrate surface. the derivation of the equation was not taken into account the outflow of diffusant deep into the substrate, i.e. the case of surface reaction diffusion was considered in pure form. according to the general principles of thermodynamics of nonequilibrium processes the speed of any non-equilibrium process (including chemical reactions) is proportional to some “driving force” of the process and is inversely proportional to a certain effective value of r* which is the resistance process [4]. the thermodynamic driving force of chemical interaction is the difference in isobaricisothermal potentials of the reaction δg. then the reaction rate of surface reaction is determined by the ratio: w g r = ∗ ∆ (1) on the other hand, the rate of surface reaction can be determined by the area change of a reaction product formed on the surface of the substrate, per unit time, fig. 2. the rate of surface reaction is determined by varying the amount of reaction product formed on the surface, per unit time: w dn d = пов τ (2) the amount of the substance on the surface is proportional to its volume: nпов ~ vпов.. in turn, the volume of the surface layer is equal to the mathematical product of its area by thickness: vпов = sпов · δ. as a first approximation we can assume that the thickness of the surface of the product (d) is a constant value, since it is less on orders than the length of the surface layer; then the number of product on the surface is proportional to the occupied of the area: nпов ~  sпов, which suggests that the reaction rate is equal to the change of the square of the reaction product formed on the surface, per unit time: w ds d = пов τ . (3) the resistance of the solid-phase reaction is the sum of resistance of separate stages, the main of which are actually chemical interaction (resistance rchem) and diffusion (resistance rdif): r* = rchem+ rdif (4) equating (1) and (3), we obtain: ds d g r r пов хим дифτ = + ∆ . (5) the size of the surface layer is determined by the expression: sпов = π((r+ ℓs) 2 – r2) = πℓs(2r + ℓs), (6) where r – the radius of the briquette diffusant. it is obvious that the resistance of the chemical stage rchem is proportional to the length of the front surface reactions, i.e. the length of a circle of radius (r + ℓs): fig.2. the lay ut of the surface layer (grey colour) on the substrate guseva a. f., trifonova m. v. 395 № 4 | 2015 chimica techno acta rchem = a · 2π(r + ℓs), (7) where а is a certain resistivity of the chemical stage, depending on the nature of the reacting substances. the resistance stage of diffusion is directly proportional to the length of the surface layer: rdif= b · ℓs (8) where b is the resistivity of the diffusion stage. substituting (6), (7) and (8) into (5), we obtain the expression: d r d g a r s s s [ ( )] ( ) π τ π    2 2 + = + ∆ , (9) which is converted to 2 2 π τ π d d r g a r b s s s s     ( ) ( ) + = + + ∆ . (10) separating variables and integrating (10), we obtain: 4 4 2 3 22 2 2 3  s s sar r b a a b gπ π π π π τ+ + + + =( ) ( ) ∆ (11) denoting the constant as follows: 4π2ar2 = x; πr(b +4πa) = y; ⅔π(2πa + b) = z, and substituting in (11), we finally obtain: x y z gs s s  + + = 2 3 ∆ τ (12) thus, the dependence of the length of the surface layer with time is described by a polynomial of the third degree. the derivation of this equation is not stated which of the stages (diffusion or kinetic) limits the entire process. let us now consider special cases. since and rchem, and rdif , according to the equations (7), (8), depend on the length of the surface layer, which increases with time, the resistance of chemical and diffusion stages also will be constantly expanding in the surface reaction. this means that in the case of two-dimensional (radial) diffusion at short times it cannot be neglected diffusion resistance, as in the one-dimensional case. then it is obvious that the mode of interaction will depend only on the resistivity which stage (diffusion or kinetic) is larger in magnitude. kinetic mode. when kinetic control of the process the resistivity of the diffusion stage is significantly smaller than the stage of chemical interaction: b<<a, hence rdif << rchem, that is the diffusion resistance can be neglected. then the expression (9) is converted to the following: d r d g a r s s s [ ( )] ( ) π τ π    2 2 + = + ∆ . (13) making a transformation similar to the above, we get: r r ks s s2 2 3 3    + + = химτ , (14) where k g aхим = ∆ 4 2π . thus, the dependence of the length of the surface layer from time to time in the case of kinetic control of the process is also described by a polynomial of the third degree. b) diffusion regime. under the diffusion control of process the resistivity of the diffusion stage is significantly greater than the stage of chemical interaction: b>>a, therefore rdif >> rchem , that is, the resistance stage, the chemical interaction can be neglected. then the expression (9) is converted to the following: d r d g b s s s [ ( )]π τ    2 + = ∆ . (15) after transformations we get the equation: surface reactions with participation of oxides of molybdenum and tungsten 396 № 4 | 2015 chimica techno acta r ks s   2 3 2 3 + = дифτ , (16) where k g bдиф = ∆ 2π . thus, when the diffusion control of process the time dependence of the length of the surface layer is described by a thirdorder polynomial with a zero coefficient for the first member of (ℓs). so, when the radial distribution of diffusant on the surface of the substrate the kind of dependence of the length of the surface layer with time is not fundamentally dependent on the interaction mode. in all cases the dependence ℓs = f(τ) is described by polynomial of third degree (12). however, equation (12) does not prescribe a termination surface interaction at sufficiently large times, what was observed experimentally earlier [1–3] for more than a dozen systems studied, as well as in the present work. the reason for the stop of the surface interactions, probably is associated with the outflow of diffusant deep into the substrate that were not considered in the derivation of this equation. the investigation of kinetics of surface interaction for radial and one-dimensional distribution of diffusant as noted previously, the study of the surface reaction diffusion in one-dimensional propagation of diffusant was conducted. therefore, in the present work we study the kinetics of surface reactions in the radial and one-dimensional distribution of diffusant (fig. 1) in comparison. the equations of the studied reactions are: nio + wo3 → niwo4 (t=850 °с) (17) nio + moo3 nimoo4 → (t=550 °с) (18) 2mn2o3 + 4moo3 → 4mnmo + o2 (t=600 °с) (19) cdo + moo3 → cdmoo4 (t=550 °с) (20) pb2moo5 + moo3 → 2pbmoo4 (t=600 °с) (21) pbo + moo3 → pbmoo4(t=600 °с) (22) (pb2moo5) the product pb2moo5 is in parentheses that can be formed according to the state diagram, but were not detected during this study by means of srd. the kinetic dependences of the length of the surface layer by one-dimensional and radial (two-dimensional) diffusion is presented in fig. 3. from fig. 3 it can be seen that the form of the kinetic curves in one-dimensional and radial (two-dimensional) srd is different. in the case of two-dimensional diffusion the curves go out of the saturation quickly (10–20 hours). in order to verify the applicability in the previous section, equation (12) to the description of the kinetics of the srd in the case of radial diffusion was carried out the processing of the experimental curves 2 (fig. 3) using equation (12), wherein the processing were taken as part of the curve (until saturation). the correlation coefficients are shown in table 2. table 2 correlation coefficients system correlation coefficients, % pbo/ моо3 95 mn2o3/moo3 93 nio/моо3 96 nio/wо3 92 cdo/моо3 97 high values of correlation coefficients (more than 90 %) show that the equation (12) satisfactorily describes the experimental kinetic data presented in terms of geometry for time that is less than the guseva a. f., trifonova m. v. 397 № 4 | 2015 chimica techno acta critical value τmax at which the maximum value of the length of the surface layer is achieved. when the one-dimensional distribution of diffusant during annealing over 70–100 hours the change in the length of the surface layer is still so that it is possible only to ascertain the slowing down at large times, which is reflected in the flattening out of the curve. at large times (over 100 hours) the boundary between the surface layer of the product and the substrate is very uneven and blurred, so it is very difficult to visufig.3. the dependence of the length of the surface layer from time to time: 1 – dimensional; 2 – radial (two-dimensional) distribution of diffusant surface reactions with participation of oxides of molybdenum and tungsten 398 № 4 | 2015 chimica techno acta ally determine the length of the surface layer. “blurring” of boundaries, probably associated with the formation of product on the surface not only by surface reactions, but also by gaseous diffusion of moo3. therefore, the error in determining the length of the surface layer at large times increases. therefore, the error in determining the length of the surface layer at large times increases, and using only the method of optical microscopy, it is impossible definitely to determine whether full stop the surface process, or only a sharp slowdown. to solve this problem, we used scanning electron microscopy in combination with x-ray microanalysis. the value of length of the surface layer in the two-dimensional distribution is always lower than the value in the onedimensional distribution for the same experiment time. the reason for this is the fact that when radial diffusion the constant increase is in the length of the three-phase boundary diffusant/substrate/product, which is carried on direct interaction. in the case of one-dimensional diffusion the length of this boundary is constant. that is, the difference of values for two types of geometries is not evidence of differences in the speeds of surface reactions, since in these two cases oneand two-dimensional diffusion is respectively. the relative area occupied by the surface layer (normalized to the contact area of the reactants) sпов / sконт is a more correct characterization of the speed of the process, in our opinion. this can be explained by the following considerations. the rate of surface reaction is determined by varying the amount of reaction product formed on the surface, per unit time: w ds d = пов τ (23) the amount of the substance on the surface is proportional to its volume: nпов ~ vsur. in turn, the volume of the surface layer is equal to the product of its area by thickness: . vпов = sпов ·δ. as a first approximation we can assume that the thickness of the surface of the product (d) is a constant value, then the amount of surface product is proportional to the occupied area: nпов ~  sпов, which suggests that the reaction rate is equal to the change of the square of the reaction product formed on the surface, per unit time: w ds d = пов τ . (24) in the case of one-dimensional and two-dimensional diffusion the square of the surface layer in different ways depend on ℓs. when radial diffusion area of the surface layer is determined by the expression: sпов = π((r+ ℓs) 2 – r2) = πℓs(2r + ℓs), (25) when one-dimensional diffusion is: sпов = ℓs · 2(a + b), (26) fig. 4. the scheme of change of the surface area of the reaction product: а –radial (twodimensional) disttribution of diffusant; b – dimensional distribution of diffusant guseva a. f., trifonova m. v. 399 № 4 | 2015 chimica techno acta where a and b are the length and width of the briquette of the substrate, fig.4. the area of the surface layer depends on the diffusant contact area and the substrate, so it is better to compare not the length, and even not size, and the relative area of the surface layer (i. e., the ratio of the area of the surface layer to the contact area of the reactants). the contact area of the reactants are equal sпов = a · b, where a and b are the sides of the base substrate in the case of one-dimensional diffusion and sконт =2πr 2, where r is the radius of diffusant, in the case of radial diffusion. the justice above considerations shows given as an example of the time dependence sпов / sконт for one-dimensional and two-dimensional diffusion in the system mn2o3-moo3, fig. 5. fig. 5 shows that the kinetic dependence sпов / sконт for one-dimensional and two-dimensional distribution of diffusant are close. thus, the relative area of the surface layer is a more correct characteristic of the speed of surface reactions: under the radial distribution the diffusant tends to spread out over the surface of the substrate, forming a layer of a shorter length, but approximately the same area as that for one-dimensional diffusion. to determine the mode of interaction the processing of the kinetic curves was carried out for the case of one-dimensional diffusion equation: ℓn= kτ. (27) the values of the coefficient n in equation (27) for the studied systems are shown in table 3. table 3 the values of the coefficient n in equation ℓn= kτ system coefficient n cdo/моо3 1.94 ± 0.1 nio/wо3 1.8 ± 0.1 nio/моо3 1.9 ± 0.1 mn2o3/moo3 2 ± 0.1 pb2moо5/ моо3 2 ± 0.1 the coefficient n for all systems is close to 2, therefore, the surface reactions occur in the diffusion mode. the study of the morphology of the surface layer by electron microscopy the morphology of the substrate and the layer of product formed as a result of surface reaction diffusion (one-dimensional and two-dimensional) was investigated by electron microscopy with the aim to clarify the following points. first, is it possible to stop the srd when onedimensional diffusion, or diffusion on the substrate surface does not stop until the source diffusion is not exhausted. for this purpose, in addition to rem, also x-ray microanalysis of sample was conducted. secondly, does the morphology of the product layer at the site of contact of the pellets of the reactants differ on the morphology of the surface layer? rem-studies were conducted for six systems: cdo-moo3, cuo-moo3, pbofig. 5. the dependence of the relative area surface layer to the time the system mn2o3moo3: 1 – dimensional, 2 – radial (two-dimensional) diffusion surface reactions with participation of oxides of molybdenum and tungsten 400 № 4 | 2015 chimica techno acta moo3, nio-moo3, nio-wo3, mn2o3moo3. as an example, the results of rem studies of one-dimensional diffusion in the system cdo-moo3 and radial (twodimensional) diffusion in the system nio-moo3 are given. the system cdo-moo3 the sample for the survey was obtained by means of contact diffusion couple annealing the pellets at the propagation of one-dimensional diffusing into the for 167 hours at a temperature of 550 °c. shooting direction is shown by the arrow from point 1 to point 2, fig. 6. rem-images of the product cdmoo4 in point 1 and 2 (fig. 6) are shown in fig. 7 a, b. the grain product have an average size of 4–5 µm (fig. 7a). when moving off from the contact points, the layer acquires a loose structure, sometimes peels off from the substrate (fig. 7 b). in place of the detachment of the product the fine grains of the substrate cdo size 1 2 µm are visible. product cdmoo4 completely covers the substrate cdo, as evidenced by both rem-images and x-ray microanalysis data, which show the presence of molybdenum on the entire surface of the sample (fig. 8). thus the conclusion made earlier is confirmed that in one-dimensional propagation of diffusant the growth of the surface layer does not stop at an arbitrarily large times, until the source diffusion is exhausted. the system niomoo3 the sample for the survey was obtained by means of contact diffusion couple annealing the pellets at the radial distribution of diffusant into the 4 hours at a temperature of 600 °c. fig.6. scheme of direction sem-photography of the sample fig.7. the pem image of the surface layer of the product cdmoo4 on the substrate cdo: a – in point 1, ×1000; b – in point 2, ×300 (fig. 6). guseva a. f., trifonova m. v. а b 401 № 4 | 2015 chimica techno acta the shooting direction is shown by the arrow (fig. 9). analysis of rem-images shows that the grain size of the product nimoo4 is approximately the same at all points of the sample and 1–2 µm, fig. 10. as mentioned earlier, it is impossible to determine the length of the surface layer by the method of optical microscopy. for more accurate determination by x-ray microanalysis the concentration profile [mo] and [ni] was withdrawn, fig. 11. the graph shows that the concentration of mo in place of the contact of the briquettes of diffusant/substrate is high and constant on size then as the distance from the contact is sharply reduced. this is due to the radial spread of diffusant on the surface of the substrate wherein the length of the reaction boundary is constantly growing whereby the front edge of the diffusion formation of a continuous layer of a product is not happended the product grains are alternated with the grains substrate, which physically corresponds to the descending order of the concentration of molybdenum as diffusant. product grains are alternated with the substrate, which physically corresponds to the descending order of the concentration of molybdenum as diffusant. fig. 8. the distribution of x-ray density of molybdenum on the surface of the substrate at a distance of 4.5 cm from the contact fig. 9. scheme of direction sem-photography of the sample fig. 10. the pem image of the surface layer of the product nimoo4 fig. 11. concentration profile (1) mo; (2) ni in the nio sample with a layer of nimoo4 (x-ray microanalysis data) surface reactions with participation of oxides of molybdenum and tungsten 402 № 4 | 2015 chimica techno acta the spot on the sample, where the fixed sharp decrease in the concentration of molybdenum is fixed, coincides with the length of the surface layer, determined by optical microscopy (1200 µm). similar results are obtained for the other investigated systems. conclusions the results of this work we can draw the following conclusions: 1. the resulting equation of growth of the surface layer in the radial distribution of diffusant satisfactorily describes the kinetics of surface interactions at times that are lower than the terminating surface reactions. 2. the kinetics of surface interactions in the case of one-dimensional distribution of diffusant is investigated. it is established that surface reactions occur in the diffusion mode and unlike radial diffusion surface interaction does not stop even at large times. 3. it is found that the length of the surface layer in one-dimensional diffusion is greater than when radial and the relative area occupied by the surface product is almost the same in both cases. the latter testifies to the same speed of surface reactions in the radial and one-dimensional distribution of diffusant. 4. the morphology of the substrate surface layer and the morphology of the product formed at the site of contact of the briquettes was investigated. it is established that the surface layer on the front lines of reaction diffusion is not continuous but consists of individual grains. 1. neiman a. ya., guseva a. f. new data on the mechanism of mass transfer in solidphase reactions: ii. chemical and electrochemical surface phenomena. kinetics and catalysis. 1999;40(i):38–49. 2. neiman a. ya., guseva a. f., trifonova m. v. surface reaction in the course of molibdates and tungstates formation. solid state ionics. 2001;141–142:321–329. 3. neiman a. ya., guseva a. f., trifonova m. v., sukhankina i. v. reactive surface diffusion durin synthesis of molybdates and tungstates: the role of phase constitution of product. russian journal of inorganic chemistry. 2005;50:319-324. 4. chebotin v. n., perphiluev m. v. electrochemistry of solyd electrolytes. khimiya. moscow, 1978. р. 67. (in russian). guseva a. f., trifonova m. v. 403 у д к 5 44 .7 2+ 54 4. 22 8/ 54 9. 76 1. 5 а. ф. гусева, м. в. трифонова уральский федеральный университет, 620000, г. екатеринбург, пр. мира 19, тел.+7 (912) 637-38-16 e-mail: anna.guseva@urfu.ru поверхностные реакции с участием оксидов молибдена и вольфрама исследована кинетика поверхностных реакций при одномерном и радиальном (двумерном) распространении диффузанта moo 3 (wo 3 ) по поверхности подложки meo (me–cd, ni, pb, mn, cu). предложено кинетическое уравнение, удовлетворительно описывающее скорость поверхностных реакций в случае радиального распространения диффузанта по подложке. установлено, что при радиальном распространении диффузанта рост слоя на поверхности подложки со временем замедляется и практически полностью прекращается, что связано с оттоком диффузанта вглубь подложки. при одномерном распространении диффузанта поверхностное взаимодействие не замедляется и не прекращается при сколь угодно больших временах. ключевые слова: диффузант; молибдаты; сложные оксиды; поверхностная реакционная диффузия. © гусева а. ф., трифонова м. в., 2015 введение реакционная диффузия при синтезе молибдатов и вольфраматов, как и многих других сложных оксидов, включает объемный, зернограничный и поверхностный массоперенос. разделение этих трех потоков и изучение их механизма является важнейшей задачей науки о твердофазных реакциях. при синтезе молибдатов и вольфраматов обнаружено образование продукта реакции не только в месте непосредственного контакта брикетов реагентов, но и вне его, на поверхности одного из реагентов (подложки). это свидетельствует о большом вкладе поверхностной реакционной диффузии (прд) в суммарный реакционный перенос и открывает уникальную возможность для выделения и исследования этого одного из трех важнейших потоков реакционного массопереноса. одной из количественных характеристик прд является отношение длины поверхностного слоя (ℓs) к толщине слоя продукта в месте контакта реагентов (ℓ). величина ℓs/ℓ для одних и тех же диффузантов moo3 (wo3) варьируется в весьма широких пределах от ℓs/ℓ ≈ 1…180. в работах [1–3] изучено более 20 поверхностных реакций с участием 404 № 4 | 2015 chimica techno acta moo3 (wo3) и установлены следующие основные факты: 1. резкое замедление поверхностной реакции, вплоть до полной остановки, после достижении определенного значения длины поверхностного слоя. 2. независимость значения максимальной длины поверхностного maxs слоя от температуры эксперимента; с изменением температуры меняется лишь время достижения maxs . 3. зависимость скорости поверх ностной реакции от пористости подложки, на которой локализуется поверхностный слой. с ростом пористости ℓs резко уменьшается. 4. высокая чувствительность скорости прд к воздействию электрического поля; сложный немонотонный характер зависимостей ℓs (u). 5. скорость поверхностных реакций существенно выше для тех реакционных пар, в которых продукт взаимодействия содержит несколько фаз. таким образом, эффект прд достаточно хорошо исследован. однако авторы [1–3] отмечают, что ряд экспериментальных фактов, полученных при исследовании этого явления (например, прекращение поверхностного взаимодействия при достижении определенного значения длины поверхностного слоя) не удается пока объяснить. далее, до настоящего времени, проводились исследования для такой геометрии ячейки, при которой распространение диффузанта, а следовательно, рост поверхностного слоя происходит радиально по отношению к месту контакта реагентов. в этом случае диффузия происходит двумерно. в то же время кинетические зависимости, связывающие какую-либо характеристику скорости процесса со временем, получены для одномерной диффузии. в связи с вышесказанным в настоящей работе поставлены следующие задачи: 1) получить уравнение роста поверхностного слоя при радиальном распространении диффузанта, удовлетворительно описывающее кинетику поверхностного взаимодействия. 2) исследовать кинетику поверхностного взаимодействия в случае одномерного распространения диффузанта в системах cuo-moo3, mn2o3moo3, nio-moo3, nio-wo3, pbomoo3. 3) методом растровой электронной микроскопии исследовать морфологию продукта реакции на поверхности и в месте контакта реагентов. экспериментальная часть в работе использовались nio, cuo, moo3, wo3, pbo, mn2o3, cdo (квалификации «ос.ч.»). pb2moo5 синтезировали из простых оксидов по стандартной керамической технологии в  три стадии с промежуточными перетираниями при температурах 550– 750  °с; время отжига на каждой стадии составляло 15 ч. фазовый состав контролировали рентгенографически. образцы для исследования готовили в виде брикетов преccованием и последующим спеканием. условия спекания образцов приведены в табл. 1. поверхностную реакционную диффузию изучали при одномерном и двугусева а. ф., трифонова м. в. 405 № 4 | 2015 chimica techno acta мерном распространении диффузанта. для этого использовали ячейки с разной геометрией сборки брикетов реагентов. в одном случае диаметр диска брикета подложки составлял 15 мм, а диаметр диска диффузанта – 5 мм (рис. 1, а); в другом подложка имела форму бруска высотой 5–10 мм и площадью контактирующей с диффузантом поверхности 65–75 мм2, а образец диффузанта выполнялся в виде диска диаметром 15 мм и толщиной 2 мм (рис. 1, б). схема распространения диффузанта по подложке показана стрелками. таблица 1 условия спекания образцов вещество температура отжига, °c время отжига, ч nio 1200 6 mn2o3 900 24 pb2moo5 700 48 pbo 760 24 cuo 950 18 cdo 700 24 moo3 600 3 wo3 900 3 контроль за развитием процесса осуществлялся периодическим измерением длины поверхностного слоя ℓs, слоя ℓ, образующегося в месте контакта брикетов, массы подложки. рентгенофазовый анализ объектов исследования выполняли на дифрактометре дрф-2.0 в соka излучении. съемку проводили со скоростью 2 °с/мин. в интервале углов 20 от 5 до 35 °с. расшифровку рентгенограмм проводили с помощью картотеки astm. микроскопический анализ поверхности и сколов брикетов после отжигов проводили с помощью микроскопа мбс-9 при увеличении в 16–56 раз и оптического микроскопа полам с-112 в проходящем свете при увеличении в 300–420 раз. морфологию подложки и продукта, а также их элементный состав, исследовали с помощью электронного микроскопа jsm-3 с микроанализатором при увеличении 300–3000 раз. измерение массы брикеты до и после диффузионных отжигов проводили на аналитических весах sartorius – bl60s с точностью 0,0001 г. эффективную плотность образцов определяли по объему и массе образцов, а также методом гидростатического взвешивания. ее величина варьировалась от 60 до 85 %. результаты и обсуждение кинетическое уравнение роста поверхностного слоя при радиальной диффузии как было показано ранее [1–3], одной из интересных особенностей прд является нетипичный вид кинетических зависимостей, которые имерис. 1. схема опытов по исследованию кинетики поверхностного взаимодействия: а – радиальное распространение диффузанта; б – одномерное распространение диффузанта поверхностные реакции с участием оксидов молибдена и вольфрама 406 № 4 | 2015 chimica techno acta ют вид кривых с насыщением. при анализе этого явления мы обратили внимание на то, что полную остановку поверхностного взаимодействия фиксировали, проводя эксперименты для ячеек с такой геометрией сборки брикетов реагентов, при которой происходило радиальное (двумерное) распространение диффузанта по поверхности подложки (рис. 1, а). очевидно, что классические предельные случаи для кинетического и диффузионного режимов (ℓ = kτ) и ℓ2 = kτ) не состоятельны в описании кинетики радиальной диффузии. при радиальном распространении диффузанта, в отличие от одномерного случая, происходит постоянное увеличение длины реакционного фронта, что должно привести к изменению вида временной зависимости параметра, характеризующего скорость реакции (ℓs). поэтому в настоящей работе была поставлена задача получить уравнение роста поверхностного слоя при радиальном распространении диффузанта по поверхности подложки. при выводе уравнения не учитывался отток диффузанта вглубь подложки, т. е. рассматривался случай поверхностной реакционной диффузии в чистом виде. согласно общим принципам термодинамики неравновесных процессов скорость любого неравновесного процесса (в том числе и химической реакции) пропорциональна некоторой «движущей силе» процесса и обратно пропорциональна некоторой эффективной величине r* – сопротивлению процесса [4]. движущей термодинамической силой химического взаимодействия является разность изобарно-изотермических потенциалов реакции δg. тогда скорость реакции поверхностной реакции определяется соотношением: w g r = ∗ ∆ (1) с другой стороны, скорость поверх ностной реакции можно определить по изменению площади продукта реакции, образующегося на поверхности подложки, в единицу времени, рис. 2. скорость поверхностной реакции определяется изменением количества продукта реакции, образующегося на поверхности, в единицу времени: w dn d = пов τ (2) количество вещества на поверхности пропорционально его объему: nпов ~ vпов. в свою очередь, объем поверхностного слоя равен произведению его площади на толщину: vпов = sпов · δ. в первом приближении можно считать, что толщина поверхностного продукта (d) величина постоянная, так как она на порядки меньше длины поверхностного слоя; тогда количество продукта на поверрис. 2. схема расположения поверхностного слоя (серый цвет) на подложке гусева а. ф., трифонова м. в. 407 № 4 | 2015 chimica techno acta хности пропорционально занимаемой им площади: nпов ~ sпов, откуда следует, что скорость реакции равна изменению площади продукта реакции, образующегося на поверхности, в единицу времени: w ds d = пов τ . (3) сопротивление твердофазной реакции складывается из сопротивления отдельных стадий, основными из которых являются собственно химическое взаимодействие (сопротивление rхим) и диффузия (сопротивление rдиф): r* = rхим+ rдиф. (4) приравняв (1) и (3), получим: ds d g r r пов хим дифτ = + ∆ . (5) площадь поверхностного слоя определяется выражением: sпов = π((r+ ℓs) 2 – r2) = πℓs(2r + ℓs), (6) где r – радиус брикета диффузанта. очевидно, что сопротивление химической стадии rхим пропорционально длине фронта поверхностной реакции, т. е. длине окружности радиусом (r + ℓs): rхим = a · 2π(r + ℓs), (7) где а – некое удельное сопротивление химической стадии, зависящее от природы реагирующих веществ. сопротивление диффузионной стадии прямо пропорционально длине поверхностного слоя: rдиф= b · ℓs (8) где b – удельное сопротивление диффузионной стадии. подставив (6), (7) и (8) в (5), получим выражение: d r d g a r s s s [ ( )] ( ) π τ π    2 2 + = + ∆ , (9) которое преобразуем в 2 2 π τ π d d r g a r b s s s s     ( ) ( ) + = + + ∆ . (10) разделив переменные и проинтегрировав (10), получим: 4 4 2 3 22 2 2 3  s s sar r b a a b gπ π π π π τ+ + + + =( ) ( ) ∆ (11) обозначив постоянные следующим образом: 4π2ar2 = x; πr(b +4πa) = y; ⅔π(2πa + b) = z, и, подставив в (11), окончательно получим: x y z gs s s  + + = 2 3 ∆ τ (12) таким образом, зависимость длины поверхностного слоя от времени описывается полиномом третьей степени. при выводе данного уравнения не конкретизировалось, какая из стадий (диффузионная или кинетическая) лимитирует весь процесс. рассмотрим теперь частные случаи. так как и rхим, и rдиф, согласно уравнениям (7), (8), зависят от длины поверхностного слоя, которая увеличивается во времени, то сопротивления химической и диффузионной стадий также будут постоянно расти в ходе поверхностной реакции. это означает, что в случае двумерной (радиальной) диффузии при малых временах нельзя пренебречь диффузионным сопротивлением, как в одномерном случае. тогда очевидно, что режим взаимодействия будет зависеть лишь от того, удельное сопротивление какой стадии (диффузионной или кинетической) больше по величине. а) кинетический режим. при кинетическом контроле процесса удельное сопротивление диффузионной стадии значительно меньше, чем стадии химического взаимодейстповерхностные реакции с участием оксидов молибдена и вольфрама 408 № 4 | 2015 chimica techno acta вия: b<<a, следовательно rдиф << rхим, т. е. диффузионным сопротивлением можно пренебречь. тогда выражение (9) преобразуется в следующее: d r d g a r s s s [ ( )] ( ) π τ π    2 2 + = + ∆ . (13) сделав преобразования, аналогичные вышеизложенным, получим: r r ks s s2 2 3 3    + + = химτ , (14) где k g aхим = ∆ 4 2π . таким образом, зависимость длины поверхностного слоя от времени в случае кинетического контроля процесса также описывается полиномом треть ей степени. б) диффузионный режим. при диффузионном контроле процесса удельное сопротивление диффузионной стадии значительно больше, чем стадии химического взаимодействия: b>>a, следовательно rдиф >> rхим, т.  е. сопротивлением стадии химического взаимодействия можно пренебречь. тогда выражение (9) преобразуется в следующее: d r d g b s s s [ ( )]π τ    2 + = ∆ . (15) после преобразований получим уравнение: r ks s   2 3 2 3 + = дифτ , (16) где k g bдиф = ∆ 2π . таким образом, и при диффузионном контроле процесса временная зависимость длины поверхностного слоя описывается полиномом третьей степени с нулевым коэффициентом при первом члене (ℓs). итак, при радиальном распространении диффузанта по поверхности подложки вид зависимости длины поверхностного слоя от времени принципиально не зависит от режима взаимодействия. во всех случаях зависимость ℓs = f(τ) описывается полиномом третьей степени (12). однако уравнение (12) не предписывает прекращение поверхностного взаимодействия при достаточно больших временах, что наблюдали экспериментально ранее [1–3] более чем для десятка исследованных систем, а также в настоящей работе. причина остановки поверхностного взаимодействия, вероятно, связана с оттоком диффузанта вглубь подложки, что не учитывалось при выводе настоящего уравнения. исследование кинетики поверхностного взаимодействия при радиальном и одномерном распространении диффузанта. как было отмечено, ранее исследование поверхностной реакционной диффузии при одномерном распространении диффузанта ранее не проводилось. поэтому в настоящей работе проведено исследование кинетики поверхностных реакций при радиальном и одномерном распространении диффузанта (рис. 1) в сравнении. уравнения исследованных реакций: nio + wo3 → niwo4 (t=850 °с) (17) nio + moo3 nimoo4 → (t=550 °с) (18) 2mn2o3 + 4moo3 → 4mnmo + o2 (t=600 °с) (19) cdo + moo3 → cdmoo4 (t=550 °с) (20) pb2moo5 + moo3 → 2pbmoo4 (t=600 °с) (21) гусева а. ф., трифонова м. в. 409 № 4 | 2015 chimica techno acta pbo + moo3 → pbmoo4(t=600 °с) (22) (pb2moo5) в скобках указан неосновной продукт pb2moo5, который может образовываться согласно диаграмме состояния, но не обнаружен при данном исследовании методом рфа. кинетические зависимости длины поверхностного слоя от времени при одномерной и радиальной (двумерной) диффузии представлены на рис. 3. на рис. 3 видно, что вид кинетических кривых при одномерной и рарис. 3. зависимость длины поверхностного слоя от времени: 1 – одномерное; 2 – радиальное (двумерное) распространение диффузанта поверхностные реакции с участием оксидов молибдена и вольфрама 410 № 4 | 2015 chimica techno acta диальной (двумерной) поверхностной диффузии различен. в случае двумерной диффузии кривые быстро (в течение 10–20 ч) выходят на насыщение. для того чтобы убедиться в применимости полученного в предыдущем разделе уравнения (12) к описанию кинетики прд в случае радиальной диффузии, была проведена обработка экспериментальных кривых 2 (рис. 3) с помощью уравнения (12), причем для обработки были взяты части кривых (до насыщения). коэффициенты корреляции приведены в табл. 2. таблица 2 коэффициенты корреляции система коэффициенты корреляции, % pbo/ моо3 95 mn2o3/moo3 93 nio/моо3 96 nio/wо3 92 cdo/моо3 97 высокие значения коэффициентов корреляции (более 90 %) показывают, что уравнение (12) удовлетворительно описывает экспериментальные кинетические данные в условиях представленной геометрии для времени, меньшем критического значения τmax, при котором достигается максимальное значение длины поверхностного слоя. при одномерном распространении диффузанта при отжиге более 70–100 ч все еще происходит изменение длины поверхностного слоя, так что можно лишь констатировать замедление процесса при больших временах, что выражается в выполаживании кривой. при больших временах (более 100  ч) граница между поверхностным слоем продукта и подложкой очень неровная и размытая, поэтому визуально очень сложно определить значение длины поверхностного слоя. «размытость» границы, вероятно, связана с образованием продукта на поверхности не только за счет поверхностной реакции, но также за счет газовой диффузии moo3. поэтому погрешность в определении длины поверхностного слоя при больших временах увеличивается, и, используя лишь метод оптической микроскопии, невозможно совершенно точно определить, происходит ли полная остановка поверхностного процесса или лишь его резкое замедление. для решения этой проблемы мы использовали растровую электронную микроскопию в комплексе с рентгеновским микроанализом. значение длины поверхностного слоя при двумерном распространении всегда ниже, чем значение ℓs при одномерном распространении при том же времени эксперимента. причиной этого факта является то обстоятельство, что при радиальной диффузии происходит постоянное увеличение длины трехфазной границы диффузант/подложка/продукт, на которой и осуществляется непосредственное взаимодействие. в случае же одномерной диффузии длина этой границы постоянна. то есть различие значений ℓs для двух типов геометрий не является свидетельством различий скоростей поверхностных реакций, т. к. в этих двух случаях имеет место соответственно однои двумерная диффузия. более корректной характеристикой скорости процесса, по нашему мнению, гусева а. ф., трифонова м. в. 411 № 4 | 2015 chimica techno acta является относительная площадь, занимаемая поверхностным слоем (нормированная к площади контакта реагентов) sпов  / sконт. это можно по яснить следующими соображениями. скорость поверхностной реакции определяется изменением количества продукта реакции, образующегося на поверхности, в единицу времени: w ds d = пов τ . (23) количество вещества на поверхности пропорционально его объему: nпов ~ vsur. в свою очередь, объем поверхностного слоя равен произведению его площади на толщину: vпов = sпов ·δ. в первом приближении можно считать, что толщина поверхностного продукта (d) величина постоянная, тогда количество продукта на поверхности пропорционально занимаемой им площади: nпов ~ sпов, откуда следует, что скорость реакции равна изменению площади продукта реакции, образующегося на поверхности, в единицу времени: w ds d = пов τ . (24) в случае одномерной и двумерной диффузии площадь поверхностного слоя различным образом зависит от ℓs. при радиальной диффузии площадь поверхностного слоя определяется выражением: sпов = π((r+ ℓs) 2 – r2) = πℓs(2r + ℓs), (25) а при одномерной диффузии: sпов = ℓs · 2(a + b), (26) где a и b – длина и ширина брикета подложки, рис. 4. площадь поверхностного слоя зависит от площади контакта диффузанта и подложки, поэтому более корректно сравнивать не длину и даже не площадь, а относительную площадь поверхностного слоя (т. е. отношение площади поверхностного слоя к площади контакта реагентов). площадь контакта реагентов равна sпов = a · b, где а и b – стороны основания подложки в случае одномерной диффузии и sконт =2πr 2, где r – радиус диффузанта в случае радиальной диффузии. справедливость приведенных выше соображений показывает приведенная в качестве примера зависимость sпов / sконт от времени для одномерной и двумерной диффузии в системе mn2o3-moo3, рис. 5. на рис. 5 видно, что кинетические зависимости sпов / sконт для одномерного и двумерного распространения диффузанта близки. таким образом, относительная площадь поверхностного слоя является более корректной характеристикой скорости поверхностной реакции: при радиальном распространении диффузант рассредоточивается по поверхности подложки, образуя слой меньшей длины, но приблизительно такой же рис. 4. схема изменения площади поверхности продукта реакции: а – радиальное (двумерное) распространение диффузанта; б – одномерное распространение диффузанта поверхностные реакции с участием оксидов молибдена и вольфрама 412 № 4 | 2015 chimica techno acta площади, что и при одномерной диффузии. с целью определить режим взаимодействия, была проведена обработка кинетических кривых для случая одномерной диффузии по уравнению ℓn= kτ. (27) значения коэффициента n в уравнении (27) для исследованных систем приведены в табл. 3. таблица 3 значения коэффициента n в уравнении ℓn= kτ система коэффициент n cdo/моо3 1,94±0,1 nio/wо3 1,8±0,1 nio/моо3 1,9±0,1 mn2o3/moo3 2±0,1 pb2moо5/ моо3 2±0,1 коэффициент n для всех систем близок к 2, следовательно, поверхностные реакции протекают в диффузионном режиме. исследование морфологии поверхностного слоя методом электронной микроскопии морфология подложки и слоя продукта, образованного в результате поверхностной реакционной диффузии (одномерной и двухмерной), была исследована методом электронной микроскопии, с целью прояснить следующие моменты. во-первых, происходит ли остановка прд при одномерной диффузии или же диффузия по поверхности подложки не прекращается до тех пор, пока не истощится источник диффузии. для этого, помимо рэм, проведен также рентгеновский микроанализ образцов. во-вторых, отличается ли морфология слоя продукта в месте контакта брикетов реагентов от морфологии поверхностного слоя. рэм-исследования провели для шести систем: cdo-moo3, cuo-moo3, pbo-moo3, nio-moo3, nio-wo3, mn2o3-moo3. в качестве примера приведены результаты рэм-исследований одномерной диффузии в системе cdomoo3 и радиальной (двумерной) диффузии в системе nio-moo3. система cdo-moo3 образец для съемки получен методом контактного диффузионного отжига пары брикетов при одномерном распространении диффузанта в течение 167 ч при температуре 550 °с. нарис. 5. зависимость относительной площади поверхностного слоя от времени в системе mn2o3-moo3: 1 – одномерная, 2 – радиальная (двумерная) диффузия рис. 6. схема направления рэм-съемки образца гусева а. ф., трифонова м. в. 413 № 4 | 2015 chimica techno acta правление съемки показано стрелкой, от точки 1 к точке 2, рис. 6. рэм-изображения продукта cdmoo4 в точке 1 и 2 (рис. 6) представлены на рис. 7, а, б. зерна продукта имеют средний размер 4–5 мкм (рис. 7, а). при удалении от места контакта, слой приобретает рыхлую структуру, местами отслаивается от подложки (рис. 7, б). в месте отслоения продукта видны мелкие зерна подложки cdo размером 1–2 мкм. продукт cdmoo4 полностью покрывает подложку cdo, о чем свидетельствуют как рэм-изображения, а также данные рентгеновского микроанализа, которые показывают наличие молибдена на всей поверхности образца (риc. 8). таким образом, подтверждается сделанное ранее заключение о том, что при одномерном распространении диффузанта рост поверхностного слоя не прекращается при сколь угодно больших временах, пока не исчерпается источник диффузии. система nio-moo3 образец для съемки получен методом контактного диффузионного отжига пары брикетов при радиальном а б рис. 7. рэм-изображение поверхностного слоя продукта cdmoo4 на подложке cdo: а – в точке 1, ×1000; б – в точке 2, ×300 (рис. 6). рис. 9. схема направления рэм-съемки образца поверхностные реакции с участием оксидов молибдена и вольфрама рис. 8. распределение рентгеновской плотности молибдена на поверхности подложки на расстоянии 4,5 см от места контакта 414 № 4 | 2015 chimica techno acta распространении диффузанта в течение 4 ч при температуре 600 °с. направление съемки показано стрелкой (рис. 9). анализ рэм-изображений показывает, что размер зерен продукта nimoo4 примерно одинаков во всех точках образца и составляет 1–2 мкм, рис. 10. как упоминалось ранее, методом оптической микроскопии невозможно с большой точностью определить длину поверхностного слоя. для более точного ее определения методом рентгеновского микроанализа был снят концентрационный профиль [mo] и [ni], рис. 11. на графике видно, что концентрация mo в месте контакта брикетов диффузант/подложка велика и постоянна по величине, затем, по мере удаления от места контакта, резко уменьшается. это связано с радиальным распространением диффузанта по поверхности подложки, при котором длина реакционной границы постоянно растет, вследствие чего на переднем фронте диффузии образования сплошного слоя продукта не происходит; зерна продукта чередуются с зернами подложки, что физически соответствует убыванию концентрации молибдена по мере продвижения диффузанта. то место на образце, где фиксируется резкое убывание концентрации молибдена, совпадает с длиной поверхностного слоя, которая определена методом оптической микроскопии (1200 мкм). аналогичные результаты получены и для других исследованных систем. выводы по результатам проделанной работы можно сделать следующие выводы: 1. получено уравнение роста поверхностного слоя при радиальном распространении диффузанта, удовлетворительно описывающее кинетику поверхностного взаимодействия при временах меньших, чем время прекращения поверхностной реакции. 2. исследована кинетика поверхностного взаимодействия в случае одномерного распространения дифрис. 10. рэм-изображение поверхностного слоя продукта nimoo4 рис. 11. концентрационный профиль (1) mo; (2) ni на образце nio со слоем nimoo4 (данные рентгеновского микроанализа) гусева а. ф., трифонова м. в. 415 № 4 | 2015 chimica techno acta фузанта. установлено, что поверхностные реакции протекают в диффузионном режим, и, в отличие от радиальной диффузии, поверхностное взаимодействие не прекращается даже при больших временах. 3. установлено, что длина поверхностного слоя при одномерной диффузии больше, чем при радиальной, а относительная площадь, занимаемая поверхностным продуктом, практически одинакова в обоих случаях. последнее свидетельствует об одинаковой скорости поверхностной реакции при радиальном и одномерном распространении диффузанта. 4. исследована морфология подложки, поверхностного слоя и морфология продукта, образующегося в месте контакта брикетов. установлено, что поверхностный слой на переднем фронте реакционной диффузии не является сплошным, а состоит из отдельных зерен. 1. neiman a. ya., guseva a. f. new data on the mechanism of mass transfer in solidphase reactions: ii. chemical and electrochemical surface phenomena. kinetics and catalysis. 1999; 40(1):38–49. 2. neiman a. ya., guseva a. f., trifonova m. v. surface reaction in the course of molibdates and tungstates formation. solid state ionics. 2001;141–142:321–329. 3. neiman a. ya., guseva a. f., trifonova m. v., sukhankina i. v. reactive surface diffusion durin synthesis of molybdates and tungstates: the role of phase constitution of product. russian journal of inorganic chemistry. 2005;50:319–324. 4. chebotin v. n., perphiluev m. v. electrochemistry of solyd electrolytes. khimiya. moscow, 1978. p. 67. (in russian). поверхностные реакции с участием оксидов молибдена и вольфрама corrigendum to morphological and structural features of the cdxpb1−xs films obtained by cbd from ethylenediamine-citrate bath chimica techno acta corrigendum published by ural federal university 2021, vol. 8(2), № 20218212 eissn 2411-1414; chimicatechnoacta.ru doi: 10.15826/chimtech.2021.8.2.12 1 of 1 corrigendum to morphological and structural features of the cdxpb1−xs films obtained by cbd from ethylenediamine-citrate bath a.d. kutyavina a,* , l.n. maskaeva a,b , v.i. voronin c , i.а. anokhina d , v.f. markov a,b a: ural federal university named after the first president of russia b.n. yeltsin, 620002, 19 mira st., yekaterinburg, russia b: ural institute of the state fire service of the emercom of russia, 620062, 22 mira st., yekaterinburg, russia c: m.n. miheev institute of metal physics, ural branch of russian academy of sciences, 620108, 18 s. kovalevskaya st., yekaterinburg, russia d: institute of high temperature electrochemistry, ural branch of the russian academy of sciences, 620990, 20 akademicheskaya st., yekaterinburg, russia * corresponding author: n-kutyavina@mail.ru © 2021, the authors. this article is published in open access form under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). the original article, “kutyavina ad, maskaeva ln, voronin vi, anokhina ia, markov vf. morphological and structural features of the cdxpb1−xs films obtained by cbd from ethylenediamine-citrate bath. chimica techno acta. 2021;8(2):20218210”, is available at: https://doi.org/10.15826/chimtech.2021.8.2.10 available online: 04.07.2021 in the acknowledgments of the original article, there was a missing funding source, state assignment of minobrnauki of russia (theme “flux”, no аааа-а18118020190112-8). thus, the revised acknowledgments should read as follows: the research was financially supported by 211 program of the government of the russian federation (no. 02.a03.21.0006) and the state assignment of minobrnauki of russia (theme “flux”, no аааа-а18-118020190112-8), was carried out within the state assignment of ministry of science and higher education of the russian federation (theme no. н687.42б.223/20) and supported by rfbr (projects no. 20-48-660041). the authors would like to apologize for any inconvenience this may have caused to the readers of the paper. http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2021.8.2.12 http://creativecommons.org/licenses/by/4.0/ https://doi.org/10.15826/chimtech.2021.8.2.10 https://orcid.org/0000-0002-1489-1137 147 d o i: 1 0. 15 82 6/ ch im te ch .2 01 6. 3. 2. 01 1 уд к 66 .0 87 .5 :5 46 .5 612 1 e. a. dolmatova, a. v. patrushev, t. n. ostanina ural federal university, 620002, ekaterinburg, 19, mira st, russia. tel.: (343) 37544-63; e-mail: arcfan@yandex.ru measurement of the specific surface area of loose copper deposit by electrochemical methods in the work the surface area of the electrode with dispersed copper deposit obtained within 30 seconds was evaluated by techniques of chronopotentiometry (cpm) and impedance spectroscopy. in method cpm the electrode surface available for measurement depends on the value of the polarizing current. at high currents during the transition time there is a change of surface relief that can not determine the full surface of loose deposit. the electrochemical impedance method is devoid of this shortcoming since the measurements are carried out in indifferent electrolyte in the absence of current. the area measured by the impedance is tens of times higher than the value obtained by chronopotentiometry. it is found that from a solution containing sulfuric acid the deposits form with a high specific surface area. based on these data it was concluded that the method of impedance spectroscopy can be used to measure in situ the surface area of the dispersed copper deposits. key words: current, chronopotentiometry, loose copper deposit, depletion factor, impedance spectroscopy. е. а. долматова, а. в. патрушев, т. н. останина измерение удельной поверхности рыхлого осадка меди электрохимическими методами в работе проведена оценка площади поверхности электрода с дисперсным осадком меди, полученным в течение 30 секунд методами хронопотенциометрии (хпм) и импедансной спектроскопии. в методе хпм поверхность электрода, доступная для измерения, зависит от величины поляризующего тока. при больших токах в течение переходного времени происходит изменение рельефа поверхности, что не позволяет определить полную поверхность рыхлого осадка. метод электрохимического импеданса лишен этого недостатка, так как измерения проводятся в индифферентном электролите в отсутствие тока. площадь, измеренная методом импеданса, в десятки раз превышает значения, полученные методом хронопотенциометрии. установлено, что из раствора, содержащего серную кислоту, формируются осадки с высокой удельной поверхностью. на основании полученных данных сделан вывод, что метод импедансной спектроскопии может быть использован для измерения in situ площади поверхности дисперсных осадков меди. ключевые слова: ток; хронопотенциометрия; осадок свободной меди; коэффициент истощения; импедансная спектроскопия. © dolmatova e. a., patrushev a. v., ostanina t. n., 2016 dolmatova e. a., patrushev a. v., ostanina t. n. chimica techno acta. 2016. vol. 3, no. 2. p. 147–155. issn 2409-5613 148 introduction copper powder is widely used in powder metallurgy, mechanical engineering, aviation, chemistry, electrical engineering industry. the production of copper powders was based on a process of electroreduction of copper ions from aqueous solutions at currents exceeding the limiting diffusive current. a feature of the process is the joint discharge of metal ions and hydrogen. the hydrogen evolution occurs so rapidly that the hydrogen absorption causes the «navodorazhivanie» of copper surface, affecting on deposit properties. the bubbles of gas shake the electrolyte in the electrode space, thus affecting the parameters of the electrode reaction. the study of the electrode processes mechanism at high current densities is of particular interest however to solve this problem it is necessary to know the electrode surface area with disperse deposit on which electrochemical processes take place. the aim of this study was the choice of the electrochemical method of determination in situ of electrode surface area with dispersed copper deposit. the experimental part to study the reduction process of copper ions the electrolytes were used: 1 – 0.12 mol/l cuso4 + 1 mol/l h2so4 2 – 0.12 mol/l cuso4 + 1 mol/l na2so4. polarization measurements were carried out using an electrochemical test system autolabpgstat 302n. the working electrode is a copper pin 1.5 mm in diameter with a working surface area s = 0.471 cm2. the counter electrode is made of copper foil. the potential was measured relative to unpolarized copper electrode in a suitable solution. the dendritic copper deposits were obtained under galvanostatic conditions if the setting current (i) exceeds the value of the limiting diffusion current on the smooth surface of electrode (id) to ki = 6 times. the concept of the depletion factor was introduced by a.v. pomosov [1] to determine the depth of the diffusion limitation of the discharge process of metal. the deposit was obtained within 30 seconds to development of the surface was not very large. during electrolysis the amount of evolved hydrogen was measured for this burette with a funnel on the end was set above the electrode. to determine the electrode surface area with a loose deposit (sdep) chronopotentiometry method at a constant current was used [2]. previously on the smooth electrode chronopotentiograms series at different currents were shooting (fig. 1) and a transition time (τ) was defined on them. in the investigated solutions the dependence of the current density (i) has a linear character [3]: i a b iτ= − ⋅ , (1) where a and b are empirical constants whose values are determined by the analysis of experimental data (tabl. 1). table 1 the coefficients a and b values solution 1 solution 2 а, а∙s1/2/m2 637.711 466.6 в, s1/2 0.369 0.168 after electrolysis the electrode with the dispersed deposit was kept in the solution for 10 minutes to restore concentration of the copper ions at the electrode 149 surface. then chronopotentiogram take off and the area of the electrode with the precipitate sdep [2] is determined on transition time value taking into account the constants a and b: s i b adep = +( )τ . (2) when determining the surface area of the electrode with the deposit by impedance spectroscopy the measurements were carried out in a solution of 0.5 mol/l na2so4 with the aid of electrochemical station zahner im6 in the frequency range from 1 hz to 500 khz. as the reference electrode a saturated silver chloride electrode was used, the counter electrode was a platinum plate. impedance spectra were recorded on a smooth electrode and on the electrode with loose deposit. experimental impedance hodographs were approximated using the equivalent circuit (fig. 2), which canadian scientists previously proposed [4] to simulate the behavior of porous electrodes. when analyzing of the electrode impedance with a loose deposit the circuit elements had the following physical meaning: r1 is the solution resistance in the cell; c is the capacity of the electrical double layer at the front of deposit growth; resistance r2 and constant phase element cpe are resistance and distributed capacitance within the layer of loose deposit. the schema options were selected using ec-lab. using the values of parameters of the equivalent circuit was calculated capacitance of the double layer of smooth electrode csm and the electrode with the deposit cdep. from the value csm the specific capacitance csp was measured considering the surface area of a smooth electrode ssm [2]: c c ssp sm sm = . (3) the surface area of loose deposit (sdep) was determined as the ratio of the electrode capacity with deposit to the specific capacity of the electrical double layer: s c cdep dep sp = . (4) results of the experiments 1. determination of the electrode surface area with the disperse deposit by chronopotentiometry method loose copper deposit is a complex structure consisting of a large number of branched dendritic particles. to deterfig. 1. chronopotentiograms obtained on a smooth electrode in solution 1 at different currents. the current values, a: 1 – 0.01; 2 – 0,012; 3 – 0.017 fig. 2. the equivalent circuit of the electrode impedance with a loose deposit 150 mine the electrode surface area with the deposit chronopotentiograms were recorded at different currents. at the same time with an increase in current the measured surface area increased (fig. 3). this fact can be explained by fractal properties of dispersed deposit: the thickness of diffusion layer is reduced with growth of the current and all finer details of the surface relief of loose electrode are available for the measurement. the dependence of the electrode surface area with the deposit from the current value was observed in both the investigated solutions. at high currents the transition time was not possible to measure due to changes of surface deposit in the process of record of chronopotentiograms. to quantify the deposit dispersion the coefficient of the surface development k = =  sdep /s (s is smooth electrode surface area) was calculated (table 2). it is found that within 30 seconds of electrolysis the surface area of loose copper deposit in solution 1 with sulfuric acid is higher than in solution 2 with sodium sulfate. values sdep and k measured at high currents are shown in tabl. 2. these results indicate the surface development during copper deposit growth. however the dependence of results on the current magnitude in the measurements shows the impossibility of measuring of the entire electrode surface with a loose deposit using the method chronopotentiometry. table 2 the values of the copper deposits surface area measured by chronopotentiometry method parameter solutions solution 1 solution 2 sdep · 104, m2 1.56 1.25 k 3.32 2.65 2. determination of the electrode surface area with the disperse deposit by impedance spectroscopy method comparison of experimental and calculated impedance spectra (fig. 4) shows a good approximation. the results of calculating the value of surface area on the equations 3–4 are presented in tabl. 3. the area disperse deposit measured by impedance is higher in ten times than the value obtained by chronopotentiometry (tabl. 2). fig. 3. current influence on the surface area of a disperse copper deposit measured by chronopotentiometry method. deposits of copper obtained by ki = 6 from solutions 1 (◊) and 2 (☐) fig. 4. the impedance spectrum of copper deposit obtained in solution 1. markers are experimental data, line is approximation according to the accepted the equivalent circuit 151 from a practical point of view such characteristic as specific surface is a very important ssp = sdep / mdep. table 3 the values of the copper deposits surface area measured by by impedance spectroscopy parameter solutions solution 1 solution 2 sdep·10 4, m2 20.825 6.348 k 44.214 13.478 current efficiency 0.78 0.23 m · 104, g 2.73 0.62 ssp, m 2/g 5.921 2.337 the weight of the deposit was determined by faraday's law: m a zf i t cedep = ⋅ ⋅ cu cu , (5) where acu is atomic weight of copper, t is time of electrolysis, i is current; cecu is current efficiency of copper. in the obtaining of copper disperse deposit on the electrode the reactions of reduction of the metal and hydrogen simultaneously take place. by the volume of evolved gas in the electrolysis process the current efficiency of hydrogen was determined and then the current efficiency of copper was calculated: ce v f i tcu sc h g = − ⋅ ⋅ ⋅ 1 2 ϑ , (6) where vsc h2 is the hydrogen volume, brought to standard conditions, ϑg is molar volume of gas. the conducted research has shown that when using a solution containing sulfuric acid the copper disperse deposits with high surface area form (tabl. 3). when electrodeposition from a solution with sodium sulfate less branched particles form as evidenced by the significantly lower surface area of the deposit and by low specific surface. based on these results we can conclude that the method of impedance spectroscopy allows to measure the surface area of the copper disperse deposit in situ with a high degree of reliability. in russian введение медный порошок достаточно широко применяют в порошковой металлургии, машиностроении, авиации, химии, электротехнической промышленности. получение медных порошков основано на процессе электровосстановления ионов меди из водных растворов при токах, превышающих предельный диффузионный. особенностью процесса является совместный разряд ионов металла и водорода. выделение водорода происходит настолько интенсивно, что вызывает наводораживание поверхности меди, влияя на свойства осадка. его пузырьки перемешивают электролит в приэлектродном пространстве, тем самым воздействуя на ход электродной реакции. особый интерес представляет исследование механизма электродных процессов в условиях высоких плотностей тока. однако для решения этой задачи необходимо знать площадь поверхности электрода с дисперсным осадком, на которой протекают электрохимические процессы. 152 цель настоящей работы состояла в выборе электрохимического метода определения in situ площади поверхности электрода с дисперсным осадком меди. методика эксперимента для исследования процесса восстановления ионов меди были использованы электролиты: 1 – 0,12 моль/л cuso4 + 1 моль/л h2so4. 2 – 0,12 моль/л cuso4 + 1 моль/л na2so4. поляризационные измерения проводили с помощью электрохимической станции autolabpgstat 302n. в качестве рабочего электрода использовали штырьковый электрод из меди диаметром 1,5 мм с площадью рабочей поверхности s = 0,471 см2. вспомогательный электрод был изготовлен из медной фольги. потенциал измеряли относительно неполяризованного медного электрода в соответствующем растворе. дендритные осадки меди получали в гальваностатических условиях при задании тока (i), превышающего величину предельного диффузионного тока на гладкой поверхности электрода (id) в ku = 6 раз. понятие коэффициента истощения ku = i/id было введено а. в. помосовым [1] для определения глубины диффузионных ограничений процесса разряда металла. осадок получали в течение 30 с, чтобы развитие поверхности было не очень большим. в процессе электролиза измеряли объем выделяющегося водорода, для чего над электродом устанавливали бюретку с воронкой на конце. для определения площади поверхности электрода с рыхлым осадком (sос) использовали метод хронопотенциометрии при постоянном токе [2]. предварительно на гладком электроде снимали серию хронопотенциограмм при разных токах (рис. 1) и определяли по ним переходное время (τ). в исследованных растворах зависимость от плотности тока (i) имела линейный характер [3]: i a b iτ= − ⋅ , (1) где a и b – эмпирические константы, значения которых определяли в ходе анализа экспериментальных данных (табл. 1). таблица 1 значения коэффициентов a и b коэффициент раствор 1 раствор 2 а, а∙с1/2/м2 637,711 466,6 в, с1/2 0,369 0,168 после электролиза электрод с дисперсным осадком выдерживали в растворе в течение 10 мин. для восстановления концентрации ионов меди у  поверхности электрода. затем снирис. 1. хронопотенциограммы, полученные на гладком электроде в растворе 1 при разных токах. величина тока, а: 1 – 0,01; 2 – 0,012; 3 – 0,017 153 мали хронопотенциограмму и по величине переходного времени с учетом констант а и b определяли площадь электрода с осадком sос [2]: s i b aос = +( )τ . (2) при определении площади поверхности электрода с осадком методом импедансной спектроскопии измерения проводили в растворе 0,5 моль/л na2so4 с помощью электрохимической станции zahner im6 в диапазоне частот от 1 гц до 500 кгц. в качестве электрода сравнения использовали насыщенный хлоридсеребряный электрод, вспомогательным электродом служила платиновая пластина. спектры импедансов снимали на гладком электроде и на электроде с рыхлым осадком. экспериментальные годографы импеданса аппроксимировали с помощью эквивалентной схемы (рис. 2), предложенной ранее канадскими учеными [4] для моделирования поведения пористых электродов. при анализе импеданса электрода с рыхлым осадком элементы схемы имели следующий физический смысл: r1 – сопротивление раствора в ячейке; с – емкость двойного электрического слоя на фронте роста осадка; сопротивление r2 и элемент постоянной фазы сре – сопротивление и распределенная емкость внутри слоя рыхлого осадка. параметры схемы подбирали с помощью программы ec-lab. используя значения параметров эквивалентной схемы, рассчитывали емкость двойного слоя гладкого электрода cгл и электрода с осадком cдэс. по величине cгл с учетом площади гладкого электрода sгл определяли удельную емкость суд [2]: c c уд гл гл = s , (3) площадь поверхности рыхлого осадка (sос) определяли как отношение емкости электрода с осадком к удельной емкости двойного электрического слоя: s c ос дэс удc = . (4) результаты экспериментов 1. определение площади поверхности электрода с дисперсным осадком методом хронопотенциометрии рыхлый осадок меди представляет собой сложную структуру, состоящую из большого количества разветвленных дендритных частиц. для определения площади поверхности электрода с осадком хронопотенциограммы снимали при разных токах. при этом с увеличением тока измеренная площадь поверхности возрастала (рис. 3). данный факт можно объяснить фрактальными свойствами дисперсного осадка: по мере роста тока уменьшается толщина диффузионного слоя и все более мелкие детали рельефа поверх ности рыхлого электрода становятся доступными для измерения. зависимость площади поверхности электрода рис. 2. эквивалентная схема импеданса электрода с рыхлым осадком электрода 154 с осадком от величины тока наблюдали в обоих исследованных растворах. при больших токах измерить переходное время не удавалось из-за изменения поверхности осадка в процессе съема хронопотенциограммы. для количественной оценки дисперсности осадка рассчитывали коэффициент развития поверхности k = = sос/s (s – площадь поверхности гладкого электрода) (табл. 2). установлено, что за 30 с электролиза площадь поверхности рыхлого осадка меди в растворе 1 с серной кислотой выше, чем в растворе 2 с сульфатом натрия. таблица 2 значения площади поверхности осадков меди, измеренные методом хронопотенциометрии параметр растворы раствор 1 раствор 2 sос · 10 4, м2 1,56 1,25 k 3,32 2,65 значения sос и k, измеренные при больших токах, представлены в табл. 2. полученные результаты указывают на развитие поверхности в процессе роста осадка меди. однако зависимость результатов от величины тока при проведении измерений свидетельствует о невозможности измерения всей поверхности электрода с рыхлым осадком с помощью метода хронопотенциометрии. 2. определение площади поверхности электрода с дисперсным осадком методом импедансной спектроскопии сравнение экспериментальных и расчетных спектров импеданса (рис. 4) свидетельствует о хорошей аппроксимации. результаты расчета величины площади поверхности по уравнениям (3), (4) представлены в табл. 3. площадь дисперсного осадка, измеренная методом импеданса, в десятки раз превышает значения, полученные методом хронопотенциометрии (табл. 2). с практической точки зрения большое значение имеет такая характеристика порошка, как удельная поверхность sуд = sос /mос. массу осадка определяли по закону фарадея: m a zf i t bmос cu cu= ⋅ ⋅ , (5) рис. 3. влияние тока на площадь поверхности дисперсного осадка меди, измеренную методом хронопотенциометрии. осадки меди получены при ku = 6 из раствора 1 (◊) и раствора 2 (☐) рис. 4. спектр импеданса осадка меди, полученного в растворе 1. маркеры – экспериментальные данные, линия – аппроксимация по принятой эквивалентной схеме 155 где acu – атомная масса меди, t – время электролиза, i – ток, втcu – выход по току меди. таблица 3 значения площади поверхности дисперсных осадков меди, измеренных методом импедансной спектроскопии параметр растворы раствор 1 раствор 2 sос · 10 4, м2 20,825 6,348 k 44,214 13,478 вт 0,78 0,23 m · 104, г 2,73 0,62 sуд, м 2/г 5,921 2,337 при получении дисперсного осадка меди на электроде одновременно протекают реакции восстановления металла и водорода. по объему выделившегося в процессе электролиза газа определяли выход по току водорода, а затем рассчитывали выход по току меди: bm v f i t h cu н.у г = − ⋅ ⋅ ⋅ 1 2 . , ϑ (6) где vн.у. h2 – объем водорода, приведенный к нормальным условиям ϑг – молярный объем газа. проведенные исследования показали, что при использовании раствора, содержащего серную кислоту, формируются дисперсные осадки меди с высокой удельной поверхностью (табл.  3). при электроосаждении из раствора с сульфатом натрия образуются менее разветвленные частицы, о чем свидетельствует существенно меньшая площадь поверхности осадка и низкая удельная поверхность. на основании полученных результатов можно сделать вывод: метод импедансной спектроскопии может быть использован для измерения in situ площади поверхности дисперсных осадков меди. references 1. pomosov a. v., krymakova e. e. predicting the properties of electrolytic copper powder, poroshk. metall. 1976;6:1–4. 2. ostanina t. n., rudoy v. m., nikitin v. s., darintseva a. b., zalesova o. l., porotnikova n. m. russian journal of non-ferrous metals. 2014;3:15-20. 3. vetter k. j. electrochemical kinetics, theoretical and experimental aspects, academic press. new york, 1967. 4. jurczakowski r., hitz c., lasia a. impedance of porous au based electrodes. journal of electroanalytical chemistry. 2004;572:355–366. cite this article as (как цитировать эту статью): dolmatova e. a., patrushev a. v., ostanina t. n. measurement of the specific surface area of loose copper deposit electrochemical methods. chimica techno acta. 2016;3(2):147–155. doi: 10.15826/chimtech.2016.3.2.011. spin–state transition in the layered barium cobaltite derivatives and their thermoelectric properties 26 d o i: 1 0. 15 82 6/ ch im te ch .2 02 0. 7. 1. 04 a. i. klyndyuk*, e. a. chizhova, s. v. shevchenko belarus state technological university, 13a sverdlova st., minsk, 220006, belarus republic e-mail: klyndyuk@belstu.by dedicated to the memory of professor l. a. bashkirov (1930–2020) spin-state transition in the layered barium cobaltite derivatives and their thermoelectric properties ba1.9me0.1co9o14 (me = ba, sr, ca) (bco) layered cobaltites were prepared by means of solid-state reactions method. crystal structure, microstructure, thermal expansion, electrical conductivity, and thermo-emf for the obtained oxides were studied; the values of their linear thermal expansion coefficient, activation energy of electrical transport, and power factor values were calculated. it was found that bco are p-type semiconductors, in which the spin-state transition occurs within 460–700 k temperature interval due to change in spin state of cobalt ions, which accompanied the sharp increase in electrical conductivity, activation energy of electrical conductivity, and linear thermal expansion coefficient, while thermo-emf coefficient decreased. partial substitution of barium by strontium or calcium in bco leads to the increase in spin-state transition temperature and electrical conductivity of the samples, and, at the same time, thermo-emf coefficient; consequently, their power factor values decrease. keywords: layered barium cobaltite; spin-state transition; thermal expansion; electrical conductivity; thermo-emf; power factor received: 29.02.2020. accepted: 20.03.2020. published: 31.03.2020. © klyndyuk a. i., chizhova e. a., shevchenko s. v., 2020 klyndyuk a. i., chizhova e. a., shevchenko s. v. chimica techno acta. 2020. vol. 7, no. 1. p. 26–33. issn 2409–5613 introduction layered sodium, calcium, or bismuth– calcium cobaltites (naxcoo2, ca3co4o9, bi2ca2co1.7ox) are prospective materials for producing of p-branches for high-temperature thermoelectric generators, since they possess high values of electrical conductivity (σ) and thermo-emf coefficient (s) and low thermal conductivity (λ), as well as high stability at elevated temperatures in air [1–4]. the common elements of crystal structure, which are present in all of these compounds, are the conducting [coo2] layers. layered barium cobaltite ba2co9o14, which belongs to the ba2n+1cono3n+3(co8o8) series [5], was also tested recently as a possible thermoelectric oxide [6]. crystal structure of ba2co9o14 consists of alternated [coo2] layers (cdi2–type) and octahedral trimers co3o12 that are interconnected by cornershared coo4 tetrahedra [6]. ba2co9o14 crystallizes in the rhombohedral syngony (space group r3m, z = 3) with the unit cell parameters: a = 5.6958(4) å, c = 28.909(4) å [6], a = 5.6963(8)  å, c = 28.924(6) å [7], 27 a = 5.69464(3) å, c = 28.9017(2) å [8]. layered barium cobaltite is  stable in  air up to 1303 k; it decomposes to coo and bacoo2 at higher temperatures [7]. it was reported that at room temperature ba2co9o14 is paramagnetic (tn = 39 k [7], ≈ 40 k [8]); its resistivity was evaluated as ρ300 > 2 ω · cm [7], or 20 ω · cm [8, 9]. the main charge carriers in ba2co9o14 are electronic holes [6, 7], so, similar to the other layered cobaltites, it is a p-type conductor [1–4]. electrical conductivity of layered barium cobaltite sharply increases within the  temperature range of  473–673 k [7] due to the spin-state transition of co3+ ions inside the co3o12 octahedral trimers from low spin-state (ls) into high spin-state (hs) near 570 k (spin-state transition) [8, 10]. studying of magnetic, electrotransport, and thermoelectric properties of ba1.9m0.1co9o14 (m = ba, la, na) materials below room temperature [9] allows us to conclude that they are p-type polaronic conductors; however, the values of their figure-of-merit are too small (zt = s2 · σ · t/λ << 1) to  consider them as  potential thermoelectric materials for low-temperature applications (at t < 300 k). it was also reported [11, 12] that ba2co9o14 can be used as a cathode material for intermediate-temperature solid oxide fuel cells in contact with various electrolytes, such as yttria stabilized zirconia (ysz) or cerium doped gadolinium oxide (gco). the  aim of  this work was to  study the effect of partial substitution of barium by strontium or calcium in ba2co9o14 on crystal structure, microstructure, thermal expansion, electrotransport and thermoelectric properties of layered barium cobaltite derivatives above room temperature. experimental ceramic samples of the ba1.9m0.1co9o14 (m = ba, sr, ca) composition have been prepared using solid-state reaction method from mixtures of starting materials baco3, srco3, caco3, co3o4 (99.0%), taken in  appropriate stoichiometric compositions, in air within the temperature range 1173–1273 k during 40 h with few intermediate grindings according to the method described earlier [13]. samples’ phase identification and determination of their unit cell parameters were performed using x-ray diffraction analysis (xrd) with a bruker d8 advance diffractometer (cu kα radiation, ni filter). the  microstructure of  sintered ceramics was studied by  means of  a  jsm  — 5610 lv scanning electron microscope (jeol, japan). relative density (ρrel) of the sintered ceramic samples was calculated as ρrel = (ρapp/ρxrd) · 100%, (1) where ρapp is apparent density, determined from the mass and dimensions of the samples; ρxrd is calculated x-ray density. thermal expansion, electrical conductivity and thermo-emf of the samples were measured within 300–1100 k in air according to the methods described in detail elsewhere [13–15]. values of  average linear thermal expansion coefficient (ltec, αav), activation energy of electrical conductivity (ea,av) and thermo-emf (es,av) were calculated from the linear parts of δl/l0 = f(t), ln(σ · t) = f(1/t), and s = f(1/t) plots, respectively. the true values of ltec (α) and activation energy for electrical conductivity (ea) were calculated as follows: α = d(δl/l0)/dt, (2) ea = (r/f) · dlnρ/d(1/t), (3) where r is  gas constant, f is  faraday constant, ρ is  the  electrical resistivity of the sample. 28 power factor values for the  ceramics studied were found using equation p = s2 · σ. (4) results and discussion all the bco samples after the final stage of annealing were found to be single phase within xrd accuracy; they possessed structure of layered barium cobaltite with unit cell parameters a ≈ 5.7 å, c ≈ 29.0 å (table 1). the obtained values are in good agreement within the experimental error with the data given in the literature [6–9]. the unit cell parameters for ba1.9m0.1co9o14 (m = sr, ca) solid solutions do not differ much from those reported for undoped ba2co9o14 (table  1), despite of  the  large difference in ionic radii between dopants and barium (for coordination number of 6 rba2+ = 1.36 å, rsr2+ = 1.16 å, rca2+ = 1.00 å [16]), which is probably due to the small substitution degree of strontium or calcium (x = 0.1) in these solid solutions. the  values of  relative density of the ba1.9m0.1co9o14 ceramics were equal to 75%, 68%, and 66% for m = ba, sr, and ca, respectively. this fact let us to  conclude that partial isovalent substitution of barium by other alkaline-earth elements in ba2co9o14 essentially decreases its sinterability. crystallites of  bco ceramics had a plate-like form, which is typical for ceramics of  layered cobaltites; their sizes varied within 2–5 μm and the  thickness changed within 0.5–1 μm (fig. 1). the temperature dependences of relative elongation of  the  studied samples demonstrate three obvious regions (fig. 2, table 1 the unit cell parameters for the ba1.9m0.1co9o14 cobaltites m a, å c, å c/a v, å3 ba 5.697 ± 0.006 28.97 ± 0.09 5.09 ± 0.02 814.4 ± 4.1 sr 5.696 ± 0.007 28.98 ± 0.11 5.09 ± 0.02 814.4 ± 4.9 ca 5.703 ± 0.005 29.03 ± 0.07 5.09 ± 0.02 817.7 ± 3.2 fig. 1. electron microscopy image of the ba1.9sr0.1co9o14 ceramics surface table 2 average values of ltec (αav) for the sintered ba1.9m0.1co9o14 ceramics m αav, ppm/k t1, k t2, k300 – t1 t1 – t2 t2 – 1000 ba 10.9 ± 0.7 36.6 ± 0.5 21.3 ± 0.2 475 650 sr 13.9 ± 0.6 43.9 ± 1.1 19.7 ± 0.2 500 640 ca 17.3 ± 0.5 28.1 ± 0.2 21.7 ± 0.1 500 700 29 table  2); the  second one characterized by  larger values of  ltec, corresponded to the broad spin-state transition of cobalt ions from low spin-state into high spinstate inside co3o12 trimers in the crystal structure [8, 10]. partial substitution of barium by strontium or calcium in ba2co9o14 raises αav values in  the  first region (before spin-state transition). this is caused by the increase in anharmonicity degree of metal-oxygen vibrations in the lattice, and resulted in the shift of the spin-state transition to the higher temperatures (table  2, fig.  2, light-gray rectangle area). the temperature of co3+(ls) → co3+(hs) transition, which was determined as a peak temperature on the  α = f(t) dependences for the  materials studied, was equal to 560 k, 575 k, and 600 k for ba2co9o14, ba1.9sr0.1co9o14, and ba1.9ca0.1co9o14, respectively (fig. 2, insets). the values of αav in the third region of the δl/l0 = f(t) dependences (t > t2) were essentially larger compared to those in the first one (t < t1). the  latter was caused by  destroying of charge-ordered state of co2+/co3+ ions in the coo2 layers after the spin-state transition in the layered barium cobaltite had completed [8]. it is worth noting that similar shape of δl/l0 = f(t) dependences was observed by us earlier for nd1–xgdxcoo3 solid solutions in  which a  semiconductor–metal phase transition took place within the temperature range 370–790 k due to the spin-state transition of co3+ ions from the low spin-state to the intermediate spin-state (is) [17]. ba1.9m0.1co9o14 (m = ba, sr, ca) compounds were p-type semiconductors (fig. 2), which is in good agreement with the results of [5, 7–9]. the values of electrical conductivity sharply (by more than two orders of magnitude) increased within 460–665 k temperature interval, which was accompanied by essential (up to three-five times) decrease in  the  seebeck coefficient (fig.  2) due to  the  change in  spin state of cobalt ions co3+(ls) → co3+(hs) fig. 2. temperature dependences of relative elongation (δl/l0), electrical conductivity (σ), and thermo-emf coefficient (s) for ba2co9o14 (a), ba1.9sr0.1co9o14 (b), and ba1.9ca0.1co9o14 (c). insets show the temperature dependences of true values for ltec (α) and for electrical conductivity activation energy (ea). light-gray rectangle area shows the temperature interval (t1 – t2), in which the spin-state transition of co3+ ions takes place 30 (spin-state transition) inside co3o12 trimers [8, 10]. we have observed earlier [17, 18] similar behavior of  σ = f(t) and s = f(t) dependences for the  nd1–xgdxcoo3, lnco1–xgaxcoo3 (ln = la, nd) solid solutions, in which semiconductormetal phase transitions occur within temperature intervals of 325–860 k and 550– 950 k, respectively, due to change of spin state of co3+ ions form the low spin-state to  the  intermediate spin-state. the  temperatures of  spin-state transition, which were determined as peak temperatures on the ea = f(t) dependences for the cobaltites studied, were equal to 560 k, 575 k, and 600 k for ba2co9o14, ba1.9sr0.1co9o14, and ba1.9ca0.1co9o14, respectively (fig. 2, insets); they coincided with those found from the  dilatometry results. the  values of room temperature electrical conductivity in bco ceramics increase when barium is partially substituted by strontium or calcium. ba1.9sr0.1co9o14 solid solution reveals highest conductivity within entire temperature interval studied (fig. 2). the  average values of  electrical conductivity activation energy for the  bco ceramics were maximal within the  middle temperature (t1–t2) region (fig.  3, table 3) where spin-state transition took place. at the same time, average ea values for the ba1.9m0.1co9o14 (m = sr, ca) solid solutions within the high temperature region (t2–1000 k) were larger than those at  low temperatures (300 k – t1), which is in good agreement with the results obtained earlier [7, 8]. thermo-emf values for the  ba1.9m0.1co9o14 (m = sr, ca) solid solutions were smaller than those for ba2co9o14 cobaltite, especially in the vicinity of room temperature (fig. 2). the shape of  the  σ = f(t) and s = f(t) dependences for bco ceramics as well as the fact that es,av < ea,av let us conclude that charge carriers in  the  studied materials can be described by the small polaron model [19]. the shape of power factor temperature dependences for the studied compounds were similar to that of the s = f(t) curves (fig. 2, 4). the maximum on the p = f(t) dependence for the ba1.9sr0.1co9o14 solufig. 3. dependences of ln(σ · t) = f(1/t) and s = f(1/t) for ba1.9sr0.1co9o14. the average values for electrical conductivity activation energy (ea,av) and thermo-emf activation energy (es,av) are given near the corresponding lines table 3 values of average activation energy of electrical conductivity (ea,av) and thermo-emf (es,av) of ba1.9m0.1co9o14 cobaltites m ea,av, ev t1, k t2, k es,av, ev300 — t1 t1 – t2 t2–1000 ba 0.166 ± 0.011 0.711 ± 0.035 0.143 ± 0.006 495 650 0.083 ± 0.003 sr 0.164 ± 0.012 0.884 ± 0.032 0.311 ± 0.003 525 665 0.065 ± 0.001 ca 0.119 ± 0.012 0.470 ± 0.020 0.128 ± 0.008 460 640 0.058 ± 0.001 31 tion was shifted towards the larger temperature, while that for ba1.9ca0.1co9o14 was shifted down to smaller temperature, as compared to the ba2co9o14 parent phase. the  maximal value of  power factor obtained for the ba2co9o14 cobaltite was equal to 3.36 μw/(m · k2) at 600 k; all p values of this phase within the entire temperature interval studied were larger than those for the ba1.9m0.1co9o14 (m = sr, ca) solid solutions, except the temperature interval 700– 950 k, in which ba1.9sr0.1co9o14 possessed maximal of the power factor values, mainly due to the fact that its seebeck coefficient was essentially smaller in comparison with unsubstituted ba2co9o14 phase. although the power factor values for the layered barium cobaltite ceramics synthesized in this work are too small to consider these oxide materials prepared using conventional solid-state reactions method as possible high-temperature thermoelectrics, they can be improved using special sintering methods (spark plasma sintering, hot pressing etc.), which can help to obtain low-porous textured ceramics with essentially larger values of electrical conductivity and, consequently, higher power factors. conclusions the ceramic samples of ba2co9o14 and its derivatives ba1.9me0.1co9o14 (ba, sr, ca) were prepared using solid-state reactions method. the values of unit cell parameters and microstructure, thermal expansion, electrotransport and thermoelectric properties were determined. it was shown that synthesized materials are p-type semiconductors, in which the spin-state transition occurs within 460–700 k temperature interval that caused by change of spin state of  cobalt ions. it was accompanied with sharp increase in  electrical conductivity value, activation energy of electrical conductivity, and linear thermal expansion coefficient, while the seebeck coefficient decreased. it was found that partial substitution of barium by strontium or calcium in ba2co9o14 leads to the increase of spinstate transition temperature and electrical conductivity of the oxides, while thermoemf coefficient and power factor values were decreased. acknowledgements this work was carried out in the frame of state program of scientific investigations «physical materials science, new materials and technologies» (subprogram «materials science and technologies of materials», task 1.55). fig. 4. temperature dependences of power factor (p) for ba1.9m0.1co9o14 compounds: m = ba (1), sr (2), and ca (3) 32 references 1. terasaki i, sasago y, uchinokura k. large thermoelectric power in naco2o4 single crystals. phys rev b. 1997;56(20):r12685–7. doi: 10.1103/physrevb.56.r12685 2. krasutskaya ns, klyndyuk aim evseeva le, tanaeva sa. synthesis and properties of naxcoo2 (x = 0.55, 0.89) oxide thermoelectrics. inorg mater. 2016;52(4):393–9. doi: 10.1134/s0020168516030079 3. masset ac, 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bashkirov la, klyndyuk ai. properties of nd1 — xgdxcoo3 solid solutions. inorg. mater. 2004;40(11):1224–8. 18. lubinsky nn, bashkirov la, petrov gs, klyndyuk ai. thermo-emf and electric conductivity of lanthanum and neodymium cobaltites — gallates solid solutions. j thermoelectricity. 2009;(1):47–54. 19. mott nf, davis ea. electronic processes in non-crystalline materials. 2nd ed. new york, usa: oxford university press; 1979. 605 p. synthetic route optimization of sumepirin antiepileptic drug candidate 159 d o i: 1 0. 15 82 6/ ch im te ch .2 02 0. 7. 4. 04 m. s. dzyurkevich, n. v. shtyrlin, y. g. shtyrlin chimica techno acta. 2020. vol. 7, no. 4. p. 159–168. issn 2409–5613 synthetic route optimization of sumepirin antiepileptic drug candidate m. s. dzyurkevich, n. v. shtyrlin, y. g. shtyrlin* kazan (volga region) federal university, 420008, kremlevskaya str. 18, kazan, russia *email: yurii.shtyrlin@kpfu.ru abstract. in this work we describe the transformation of synthetic route of the antiepileptic drug candidate sumepirin starting from discovery stage. initial method included six step process requiring two steps of purification using colon chromatography and has poor overall yield of target compound. the process developed is convenient, scalable, technological and meet the most of conditions of green chemistry. the overall yield was increased up to 62.5% in four steps without colon chromatography purification which allows to obtain the target compound with purity of 99.5+% which is especially important for the active ingredient. keywords: pyridoxine; synthetic route optimization; scale-up; purification; antiepileptic drug; technology received: 15.10.2020. accepted: 09.12.2020. published:30.12.2020. © m. s. dzyurkevich, n. v. shtyrlin, y. g. shtyrlin, 2020 introduction the  social and medical significance of epilepsy is determined by its high prevalence. epilepsy is  one of  the  most common chronic diseases of the nervous system in  the  world, which affects both children and adults. 5% of the population suffers at least one epileptic seizure during their lifetime. in 70% of cases, epilepsy debuts in childhood and adolescence. patients with epilepsy may have mental problems including personality changes specific to the disease associated with a mnesticintellectual defect, affective disorders and so-called epileptic psychoses. according to the who, about 50 million people suffer from epilepsy, which is about 0.5–1% of  the  world’s population (https://www. who.int/news-room/fact-sheets/detail/ epilepsy). approximately 5 million new cases are diagnosed worldwide each year. moreover, 30% of  patients with epilepsy are pharmacoresistant [1]. on the  other hand, existing antiepileptic drugs have a lot of side effects including ataxia, decreased mental ability, drowsiness, dizziness, digestive disorders, etc. [2]. development of effective and safe drugs may significantly improve the quality of life of patients suffering from epilepsy. sumepirin 1 is  a  novel antiepileptic drug candidate developed in  the  scientific and educational center of pharmaceutics of the kazan federal university and having pronounced antiseizure effect and improved safety profile. this compound is pyridoxine-based molecule with residue of methanesulfonic acid in the 6th position of pyridoxine ring (fig. 1). it has successfully passed preclinical studies in  the  framework of  state pro160 gram of  russian federation «development of  the  pharmaceutical and medical industry» and is planned to undergo the  clinical trials. as  sumepirin entered preclinical studies stage an  urgent need of the optimization of its method of synthesis arised. preclinical phase involves study of chronical toxicity of a drug candidate both in  small (e.g. mice or rats) and large (rabbits) animals. the duration of these experiments depends on the expected duration of the course of the drug. antiepileptic drugs are usually taken for an extended period of time: from months to years. that means that chronical toxicity should be studied at least for 6 month of everyday administration of a drug. during the discovery stage a general method of synthesis was used which allows preparation of diverse set of 6-substitued pyridoxine derivatives. this method is not suitable for large-scale synthesis as required at preclinical trials. this required the development of more convenient and scalable synthetic approach. experimental unless otherwise stated, chemicals are obtained from the commercial suppliers and were used without further purification. 1h and 13c nmr spectra were recorded on a “bruker avance 400” at operating frequencies of  400.13 and 100.62  mhz, respectively. chemical shifts were measured with reference to  the  residual peak of  the  solvent (dmso-d6, 1h, 2.50 ppm, 13c, 39.52 ppm; cdcl3, 1h, 7.26 ppm, 13c, 77.16 ppm). coupling constants (j) are given in hertz (hz). the following abbreviations are used to  describe coupling: s = singlet; d = doublet; t = triplet. melting points were determined using a stanford research systems mpa-100 optimelt melting point apparatus and are uncorrected. for tlc analysis, silica gel plates from sorbfil (krasnodar, russia) were used with uv light (254 nm) as a developing agent. column chromatography was performed on silica gel (60–200 mesh) from acros. high-resolution mass spectroscopy mass spectra were obtained on a  quadrupole time-of-flight (t, qtof) ab sciex triple tof 5600 mass spectrometer using turbo-ion spray source (nebulizer gas nitrogen, positive ionization polarity, needle voltage 5500 v). recording of the spectra was performed in “tof ms” mode with a collision energy of 10 ev, declustering potential of 100 ev and resolution more than 30,000 full-width half-maximum. samples with the analyte concentration 5 µmol/l were prepared by dissolving the test compounds in a mixture of methanol (hplcuv grade, labscan) and water (lc–ms grade, panreac) in 1:1 ratio. compounds 3, 4, 5 and 6 were obtained according to published procedures [3–5] without any modifications, unless otherwise is stated. i.  optimized method of  synthesis of  6-(hydroxymethyl)-3,3,8-trimethyl-1,5-dihydro-[1,3]dioxepino[5,6-c] pyridin-9-ol (4). 143 g (684 mmol) compound 3 is  added to  the  2-liter doublenecked round bottom flask equipped with n oh oh ho so3na sumepirin (1) fig. 1. structure of sumepirin 1 161 magnetic stirring bar and a thermometer. solution of  14  g (342 mmol) of  sodium hydroxide in 342 ml of distilled water and 120 ml of freshly distilled formaldehyde solution (37% wt., 1641 mmol, stabilized with 5% methanol) is added to the reaction vessel. mixture is flushed with argon and reaction is carried out under inert atmosphere at 70 °c for about 5 h. the reaction is  controlled by  tcl on silica (eluent chcl3:meoh = 10:1) until the  spot of starting material completely disappears. after reaction is finished, reaction mixture is cooled down to the room temperature and neutralized by the 1m solution of hydrochloric acid to  the  ph = 6.5. a  seed of  water-insoluble crystalline form of  4 (10 mg) is added to the solution. solution is then transferred into the 2-liter beaker and left overnight to  achieve complete crystallization. the  precipitate formed is filtered off, washed 3 times with the 100 ml of distilled water and dried to obtain 154 g (94%) of compound 4 as pale yellow solid; m.p. 182–183 °c. 1h nmr (dmsod6), δ, ppm: 1.41 (s, 6н), 2.33 (s, 3н), 4.42 (s, 2н), 4.80 (s, 2н), 4.82 (s, 2н). spectrum is in accordance with the previously published [4]. ii. synthesis of sodium (9-hydroxy3 , 3 , 8 t r i m e t hy l 1 , 5 d i hy d r o [ 1 , 3 ] dioxepino[5,6-c]pyridin-6-yl)metha n e s u l fo n ate ( 7 ) s t a r t i n g f r o m 6-(chloromethyl)-3,3,8-trimethyl-1,5-dihydro-[1,3]dioxepino[5,6-c]pyridin-9-yl acetate (6). in the 100 ml round bottom flask equipped with mechanical stirring bar a solution of 1.0 g (3.34 mmol) of compound 6 in 20 ml of dichloromethane and solution of 0.8 g (6.67 mmol) of sodium sulfite in 30 ml of water were added. 0.01 g (0.03 mmol) of tbab were added to the reaction mixture and the reaction was carried out at  room temperature while vigorous stirring for 10 h. then water layer is  separated from the  organic and water is removed under reduced pressure. dry solid residue is extracted with 3×100 ml of hot isopropyl alcohol. alcohol extract is evaporated until 30 ml left and white precipitate formed is filtered off and washed with 10 ml of cold isopropyl alcohol. after drying 0.66  g (61%) of  compound 7 was obtained as white solid; m.p. 197 °c (decomp.). nmr 1h (400 mhz, dmsod6), δ, ppm: 1.38 (s, 6н, c(сн3)2), 2.30 (s, 3н, сн3), 3.82 (s, 2н, сн2s), 4.79 (s, 2н, сн2), 4.90 (s, 2н, сн2). nmr 13с {1h} (100  mhz, dmso-d6), δ, ppm: 19.28, 23.73, 57.47, 59.11, 60.97, 101.45, 132.07, 134.18, 140.97, 143.25, 146.78. hrмs-esi: found [м+н]+ 326.0667, c12h16nnao6s, calculated [м+н]+ 326.0669. iii. synthesis of  sodium (5-hydroxy-3,4-bis(hydroxymethyl)-6-methylpyridin-2-yl)methanesulfonate (1) starting from sodium (9-hydroxy3 , 3 , 8 t r i m e t hy l 1 , 5 d i hy d r o [ 1 , 3 ] dioxepino[5,6-c]pyridin-6-yl)methanesulfonate (7). 0.66 g (2.03 mmol) of compound 7 is dissolved in 10 ml concentrated hydrochloric acid. the solution was stirred for 1 h at room temperature. after this insoluble nacl filtered off (solubility of nacl in concentrated hcl solution is 0.1% wt.) and 40 ml of isopropanol is added to the filtrate. after standing for 1 hour a crystalline precipitate is formed. the solid is filtered off, washed with 10 ml of cold isopropanol and dried. dry solid is dissolved in 15 ml of distilled water and titrated with 0.1 m naoh solution until ph = 7.2. after drying 0.57 g (98%) of compound 1 was obtained as  white solid; m.p. 265  °c (decomp.). nmr 1h (400 mhz, dmso-d6), δ, ppm: 2.31 (s, 3h, ch3), 4.04 (s, 2h, ch2), 4.51 (d, 3jhh = 6.3 hz, 2h, ch2), 4.78 (s, 2h, ch2), 5.17 (t, 3jhh = 6.3 hz, 1h, oh). nmr 162 13с {1h} (100  mhz, dmso-d6), δ, ppm: 19.33, 56.80, 57.16, 57.21, 132.07, 132.74, 143.31, 145.04, 148.94. hrмs-esi: found [м+н]+ 286.0354, c9h12nnao6s, calculated [м+н]+ 286.0356. iv. modified synthesis of  (9-acetoxy-3,3,8-trimethyl-1,5-dihydro-[1,3] dioxepino[5,6-c]pyridin-6-yl)methyl acetate (10). 1-liter double-necked round bottom flask equipped with magnetic stirring bar and effective reflux condenser is charged with 90 g (376 mmol) of compound 4, 55 ml of  triethylamine (395 mmol) and 400 ml of  dichloromethane. 28 ml of acetyl chloride (395 mmol) in 100 ml of dichloromethane is charged into drop funnel which is then attached to the flask. acetyl chloride is added dropwise to the reaction mixture while stirring to maintain slow boiling. after whole amount is added reaction mixture is stirred for additional 0.5  h and then extracted with 3×200 ml of distilled water and washed with brine. organic layer is separated, dried over anhydrous sodium sulfate and evaporated. residue is  dried under vacuum to  obtain 119  g (98%) of  10 as  viscous liquid of yellow to light brown color which may crystallize upon long standing. nmr 1h (400 mhz, dmso-d6), δ, ppm: 1.48 (s, 6h, ch3), 2.09 (s, 3h, ch3), 2.35 (s, 6h, ch3), 4.72 (s, 2h, ch2), 4.89 (s, 2h, ch2), 5.13 (s, 2h, ch2). spectrum is in accordance with the previously published [6]. v.  synthesis of  sodium (9-hydroxy3 , 3 , 8 t r i m e t hy l 1 , 5 d i hy d r o [ 1 , 3 ] dioxepino[5,6-c]pyridin-6-yl)methanesulfonate (7) starting from (9-acetoxy-3,3,8-trimethyl-1,5-dihydro-[1,3] dioxepino[5,6-c]pyridin-6-yl)methyl acetate (10). solutions of 100 g (309 mmol) of  bis-acetate 10 in  400 ml of  methanol and 59  g (464 mmol) of  sodium sulfite in 600 ml of distilled water are prepared separately. solutions are added to the 2 liter round bottom flask equipped with magnetic stirring bar while stirring. the  resulting mixture is stirred for 6 h at room temperature. the solvents are evaporated under vacuum following the same workup procedure as  described in  synthesis ii. the product is dried under vacuum to obtain 57 g (57%) of 7 as white solid; m.p. 197  °c (decomp.). nmr 1h (400  mhz, dmso-d6), δ, ppm: 1.38 (s, 6н, c(сн3)2), 2.30 (s, 3н, сн3), 3.82 (s, 2н, сн2s), 4.79 (s, 2н, сн2), 4.90 (s, 2н, сн2). nmr 13с {1h} (100 mhz, dmso-d6), δ, ppm: 19.28, 23.73, 57.47, 59.11, 60.97, 101.45, 132.07, 134.18, 140.97, 143.25, 146.78. hrмs-esi: found [м+н]+ 326.0667, c12h16nnao6s, calculated [м+н]+ 326.0669. v i . s y n t h e s i s o f   ( 5 h y droxy-3,4-bis(hydroxymethyl)-6-methylpyridin-2-yl)methanesulfonic acid (11) starting from 6-(hydroxymethyl)-3,3,8-trimethyl-1,5-dihydro-[1,3]dioxepino[5,6-c] pyridin-9-ol (4). 15 liter glass reactor equipped with anchor-type stirrer, reflux condenser, heating jacket, thermometer and ph-meter is loaded with 1565 g (6540 mmol) of compound 4 and solution of  1262  g (9810 mmol) if sodium sulfite in 5.5 liters of distilled water. the reaction mixture is stirred under reflux conditions for 5 h while maintaining ph at a range between 8.0 and 9.0 by the addition of small portions of concentrated hydrochloric acid (about 300 ml of acid was used). the reaction is  controlled by  tcl on silica (eluent chcl3:meoh = 3:1) until the  spot of  starting material completely disappears. then reaction mixture is  cooled down to the room temperature and neutralized with concentrated hydrochloric acid to the ph = 6.5 during 30 minutes. the  precipitate of  by-product is  formed and is  filtered off. filtrate is  acidified 163 to the ph = 1.0 with concentrated hydrochloric acid. acidified mixture is evaporated under vacuum until mushy residue is  obtained while absorbing so2 formed with solution of sodium hydroxide. residue is  heated up until boiling and small portions of water are added until clear solution obtained. after cooling to 0°c crystalline precipitate of product 11 is formed. it is filtered off and washed with 300 ml of  ice-cold distilled water. after drying 1120  g (65%) of  product 11 is  obtained as off-white to pale yellow solid. filtrate is evaporated until dryness and extracted with 1 liter of boiling water followed by hot filtration. after cooling this filtrate to 0 °c second portion 223  g (13%) of  product 11 was isolated additionally. overall yield 1343 g (78%); m.p. 250 °с (decomp). nmr 1h (400 mhz, dmso-d6), δ, ppm: 2.56 (s, 3н, сн3), 4.27 (s, 2н, сн2s), 4.70 (s, 2н, сн2), 4.90 (s, 2н, сн2). nmr 13с {1h} (100  mhz, dmso-d6), δ, ppm.: 14.74, 51.57, 55.52, 56.19, 136.44, 138.79, 141.50, 142.95, 151.62. hrмs-esi: found [м+н]+ 264.0537, c9h13no6s, calculated [м+н] + 264.0536. vi. synthesis of sodium (5-hydroxy3,4-bis(hydroxymethyl)-6-methyl pyridin2-yl)methanesulfonate (1) starting from (5-hydroxy-3,4-bis(hydroxymethyl)6-methylpyridin-2-yl)methanesulfonic acid (11). 15 liter glass reactor equipped with anchor-type stirrer is loaded with 1343 g (5100 mmol) of compound 11 and solution of 204 g (5100 mmol) of sodium hydroxide in 2.5 liters of water. mixture is stirred at room temperature during 6 minutes until clear solution is obtained. then 12 liters of  isopropyl alcohol is  added and white precipitate is  formed immediately. solid is filtered off, washed with twice with 1 liter of  isopropyl alcohol and dried to  obtain 1427 g (98%) of product 1 as a white solid with purity >99.5% (hplc); m.p. 265 °c (decomp.). nmr 1h (400 mhz, dmsod6), δ, ppm: 2.31 (s, 3h, ch3); 4.04 (s, 2h, ch2), 4.51 (d, 3jhh = 6.3 hz, 2h, ch2); 4.78 (s, 2h, ch2); 5.17 (t, 3jhh = 6.3 hz, 1h, oh). nmr 13с {1h} (100 mhz, dmso-d6), δ, ppm: 19.33, 56.80, 57.16, 57.21, 132.07, 132.74, 143.31, 145.04, 148.94. hrмs-esi: found [м+н]+ 286.0354, c9h12nnao6s, calculated [м+н]+ 286.0356. results and discussion the  starting point of  our research was synthetic method described below in scheme 1. as can be seen overall yield is slightly greater than 18%. moreover, two steps (c and d) require column chromatography. in case of intermediate 5 chromatography is needed to separate ester by the benzyl group from the desired compound. this also explains poor yield at this step. as  substance 3  has hydroxymethyl group in  the  paraposition in  relation to the phenol oh. it makes possible to investigate the possibility of functionalization of this scaffold via metaquinon methide intermediate. the reactivity of ortoand para-quinon methides intermediates is well studied in non-heterocyclic aromatic structures [7, 8]. but we can barely find any data on its heterocyclic analogs. acetyl esters 8 and 9 are among usual quinone methide precursors [9, 10] (fig. 2). in  this connection bis-acetic ester 8 that was synthesized earlier in  our research group [6] was a good starting point for the  optimization of  synthetic route. it has straightforward synthesis with no need of chromatographic purification. it was shown that use of acetyl chloride in164 stead of acetic anhydride as an acylating agent in synthesis of 8 dramatically reduces the reaction time from 30 hours [6] to only 0.5 hour with no need of refluxing conditions (scheme 2). it was shown that bis-acetyl ester 10 can react with primary and secondary amines in  alcohol media [11]. an  attempt was made to investigate reactivity of 10 toward sulfur-containing nucleophile such as sodium sulfite. very poor solubility of sodium sulfite in almost any organic media including alcohols became the main barrier for this reaction. usual methods like two-phase reaction system (h2o/ch2cl2) with phase transfer catalyst gave very low yields even after prolonged reaction time. however, it was an indication of the principal possibility of such a reaction. the best results (57% yield of 6) were achieved using mixed solvent water/meoh in 3:2 ratio by the volume. in  this mixture both components of the reaction have significant solubility. replacement of meoh with etoh or any other alcohol significantly reduces the solubility of sodium sulfite slowing the reaction and reducing the yield. the development of this synthetic step not only reduces total amount of steps, it allows to avoid chromatographic purification of  intermediates 5 and 6 which are no longer needed. with this implementation total yield was increased from 18% to 38% with no principal limitation for the scaling-up. another optimization was made during the scaling-up of the process. original method of the synthesis of 4 includes extraction with ethanol during the workup. after the evaporation of ethanol 4 is obtained as white solid with significant soluoh oac oor poac oac oor p8 9 fig. 2. structures of acetyl esters 8 and 9 as quinone methide precursors n oh oh ho hcl n o o ho n o o ho oh n o o aco oh n o o aco cl n o o ho so3na n oh oh ho so3na 2 3 (87%) 4 (80%)* 5 (49%) a b c ef d 6 (90%)7 (61%)1 (98%) scheme 1. reagents and conditions: (a) (ch3)2co, hcl, 0 °c, 12 h [3]; (b) ch2o, naoh, h2o, 70 °c, 60 h [4]; (c) ac2o, et3n, ch2cl2, r.t., 30 h [5]; (d) mscl, et3n, chcl3, 0 °c to r.t., 10 h [5]; (e) na2so3, tbab, ch2cl2/h2o, r.t., 10 h; (f ) hcl, h2o, r.t., 1 h * — yield according to non-optimized method [4] 165 bility in water and melting point of 161– 163  °c.  however, the  crystalline solid precipitates from water solutions of 4 after long standing. it was found to have similar nmr spectra as  4 and melting point of  182–183  °c which indicates another crystalline form of the same compound. this finding allows to alter the workup procedure of the synthesis of 4 which consists in  seed induces precipitation of  product from the neutralized mother liquor. this alteration not only simplified the  procedure but also improved the yield up to 94% at this step due to more complete precipitation. the use of freshly distilled formaldehyde solution and use of more concentrated reaction mixture (less solvent) allows to dramatically reduce the reaction time from 60 to 6 hours. in some examples oand phydroxymethylphenols may play a role of the quinon methide precursors. this examples are usually limited to the reaction with c-nucleophiles like base-activated 2-nitropropane [12] or potassium cyanide [13]. reactions of pyridoxine with different alcohols are described yielding corresponding 4’ — esters [14]. the latter do not have much practical significance due to very long reaction time (about 96 hours). the original work [15] and its modern reiteration [16] has evidence of the possibility of  direct reaction between p-hydroxymethylphenol and sodium hydrosulfite. this reaction has a good yield and requires refluxing in the water media for only 8 hours. possible application of this method to  the  direct synthesis of  compound 7 starting from 4 allows reducing the total amount of steps. it was found that reaction of  4 with sodium hydrosulfite is not possible as ph of  the  reaction mixture is  slightly acidic (ph = 4–5) and it is enough the remove the dimethylketal protecting group. the replacement of  hydrosulfite with sulfite gave the  first results as  it makes possible to achieve the partial conversion of 4 to  7. the  conversion was not complete even after prolonged refluxing. usually it reaches 60–70% in  6  hours and does not change after. this process is believed to  be reversible (fig.  3) and the  conversion observed corresponds to the equilibrium. the changes of ph of the reaction mixture were observed during the process: from ph = 11 at  the  start to  ph = 13.5 at the equilibrium. the addition of small amounts of  acid to  control ph makes it possible to reach complete conversion. it was found that optimal ph for the reaction is in range between 8.0 and 9.0. under this ph controlled conditions reaction completes in 5 hours of refluxing. it was found to be unpractical to isolate compound 7 before the deprotection n o o ho oh 4 a n o o o o ac ac 10 (98%) b n o o ho so3na 7 (57%) scheme 2. reagents and conditions: (a) accl, net3, ch2cl2, r.t. 0.5 h; (b) na2so3, h2o/meoh, r.t., 6 h 166 step as  it requires extraction with huge amount of  isopropyl alcohol. deprotection step may be done by the acidification of the reaction mixture from the previous step with the  isolation of  sulfonic acid 11 as it has limited solubility in cold water. the  overall optimized synthesis of  1 is shown in scheme 3. n o o ho oh n o o ho so3na na2so3 h2o, ∆ + naoh 4 7 fig. 3. preparation of compound 7 from 4 with sodium sulfite n oh oh ho ·hcl n o o ho n o o ho oh n oh oh ho so3h n oh oh ho so3na 2 3 (87%) 4 (94%)* a b c, d e 11 (78%)1 (98%) scheme 3. reagents and conditions: (a) (ch3)2co, hcl, 0 °c, 12 h [3]; (b) ch2o, naoh, h2o, 70 °c, 6 h; (c) na2so3, h2o, ph = 8.0–9.0, reflux, 5 h; (d) hcl, ph = 1.0, 0.5 h, r.t.; (e) naoh, h2o, r.t., 0.1 h * — yield according to optimized method of synthesis (see experimental) 167 conclusions thus, the total yield of the final method of synthesis of the antiepileptic drug candidate sumepirin 1 starting prom pyridoxine hydrochloride was increased from 18% to 62.5%. as the result of optimization the amount of steps was reduced from six to  four. it is  also important that this method is  environment-friendly: at  first step reagent (acetone) is used as a solvent and any other step is carried out in water media; good level of atom economy was achieved due to elimination of chloride and acetyl protecting or leaving groups from the synthetic route. unfortunately, it does not seem to be possible not to use the dimethylketal protecting group because oh groups in 4’ and 6’ positions of pyridoxine ring have very similar reactivity. acknowledgements this work was supported by subsidy allocated to kazan federal university for the state assignment in the sphere of scientific activities (project number 0671-2020-0053). references 1. janmohamed m, brodie mj, kwan p. pharmacoresistance — epidemiology, mechanisms, and impact on epilepsy treatment. neuropharmacology. 2020;168:107790 doi:10.1016/j.neuropharm.2019.107790 2. štuhec m. optimization of antiepileptic drug pharmacotherapy related 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doi:10.1016/j.tetlet.2017.04.082 15. shearing ea, smiles s. derivatives of o-hydroxybenzylsulphonic acid. j chem soc. 1937;1348–51. doi:10.1039/jr9370001348 16. jankowski p, poterała m, lindahl n, wieczorek w, johansson p. chemically soft solid electrolyte interphase forming additives for lithium-ion batteries. j mater chem a. 2018;6(45):22609–18. doi:10.1039/c8ta07936f effect of lithium borate coating on the electrochemical properties of licoo2 electrode for lithium-ion batteries chimica techno acta article published by ural federal university 2021, vol. 8(1), № 20218101 journal homepage: chimicatechnoacta.ru doi: 10.15826/chimtech.2021.8.1.01 1 of 6 effect of lithium borate coating on the electrochemical properties of licoo2 electrode for lithium-ion batteries victor d. zhuravlev a , ksenia v. nefedova a* , elizaveta yu. evshchik b , elena a. sherstobitova a , valery g. kolmakov b , yury a. dobrovolsky b , natalia m. porotnikova a , andrey v. korchun b , anna v. shikhovtseva b a: institute of solid state chemistry, ural branch of the russian academy of sciences, 91 pervomaiskaya st., ekaterinburg, 620990, russia b: institute of problems of chemical physics, russian academy of sciences, 1 ac. semenov ave, chernogolovka, moscow region, 142432, russia * corresponding author: nefedova@ihim.uran.ru, ksenia_nef@rambler.ru this article belongs to the regular issue. © 2021, the authors. this article is published in open access form under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). abstract the effect of a protective coating of fused lithium borate, li3bo3, on the physicochemical and electrochemical characteristics of licoo2 has been studied. a cathode material produced by the scs method using binary organic fuel, glycine and citric acid. the influence of the experiment conditions on the morphology, crystal structure and specific surface of lithium cobaltite was studied. electrochemical testing of licoo2∙nli3bo3 samples, n = 5 and 7 mass %, has been performed in the cathode li|li+-electrolyte|licoo2∙nli3bo3 half-cell using 1m lipf6 in ec/dmc mixture (1:1) as electrolyte in the 2.7-4.3 v range at normalized discharge current с/10, с/5, с/2. the maximal initial discharge capacity of 185 mah/g was detected for the samples with 5 mass % li3bo3. the coulomb efficiency of optimal materials in the 40 th cycle was 99.1%. keywords lithium-ion batteries lithium cobalt oxide solution combustion synthesis li3bo3 protective coating received: 13.10.2020 revised: 18.11.2020 accepted: 26.11.2020 available online: 21.12.2020 1. introduction lithium cobaltite licoo2 (lco) is used as a cathode material since 1990, and in spite of the appearance of such promising cathode materials as lini1/3mn1/3co1/3o2 (nmc), lini0.8co0.15al0.05o2 (nca), limn2o4 (lmo) etc. it is still employed as a component of lithium-ion batteries (lib) with low discharge rates in portable gadgets [1]. chemical interaction between the electrolyte and the cathode material leads to non-recoverable losses of lithium cations reduced service lifetime and accelerated capacity failure of lib. the manufacturers of lib materials try to eliminate this effect by decreasing the specific surface of dispersed materials, by using microgranulation processes or applying modifying coatings on cathode material particles, protecting them from the action of acid fluorine-containing components of electrolyte. in particular, al2o3, zro2, zno, sio2, tio2 and other oxides are used as protective coatings [2-5]. recently appeared publications reporting the application of glasses and boron and lithium based oxides as coatings [5-7]. a. nagasubramanian et al. [6] studied the effect of libo2 coating on the electrochemical performance of orthorhombic limno2 cathode. shuangyuan tan et al. [7] showed that using glass-coated nmc/li2o∙2b2o3 can increase the discharge capacity retention of the cathode from 22.5% to 57.8% at −40 °c. among compounds in the li2o-b2o3 system, lithium borate li3bo3 should be noted [8-10]. it has the lowest melting temperature, 715±15 °c [11], which allows applying it as a flux for more refractory compounds, creating dense protective coatings. in addition, li3bo3 is a lithium ion conductor [10], and its molecular mass is smaller than that of licoo2 and other cathode materials. li3bo3 coating also increases the concentration of li + in the contact layer with electrolyte. most coating strategies are based on the sol-gel method or impregnation of cathode materials powders with salt solutions with subsequent drying and annealing [1-3, 5-7]. however, the application of lithium borates via solutions guarantees neither synthesis of the nominal composition of lithium borate nor the density of the coating after annealing at 500 °с. it can be assumed that addition and distribution of libo2, li2b4o7 or li3bo3 compounds in the cathode bulk with subsequent annealing at melting temperatures of the corresponding eutectics may cause positive effect. http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2021.8.1.01 http://creativecommons.org/licenses/by/4.0/ https://orcid.org/0000-0001-5933-4310 https://orcid.org/0000-0002-5147-1414 http://orcid.org/0000-0002-3562-8805 https://orcid.org/0000-0002-4443-1318 https://orcid.org/0000-0001-9292-0266 https://orcid.org/0000-0002-2163-6863 https://orcid.org/0000-0001-5284-4553 https://orcid.org/0000-0003-1002-8114 https://orcid.org/0000-0003-4058-2968 chimica techno acta 2021, vol. 8(1), № 20218101 article 2 of 6 for the production of cathode materials, different modifications of solid-phase and hydrothermal methods are usually employed [12]. in laboratory studies for the obtaining of the cathode materials, in particular, lithium cobaltite, combustion reactions [13-18] are more often used [19-24]. the attraction of solution combustion synthesis (scs) reactions for industrial application is determined by the following characteristics: 1. cathode material can be produced almost without sewage; 2. energy consumption for the decomposition of precursors is reduced compared to conventional technologies, since the method employs internal exothermal processes requiring only relatively moderate energy consumption for evaporation of reaction solutions and preliminary heating of xerogel before the beginning of redox reaction; 3. dispersion and chemical activity of produced precursor may reduce the time of high-temperature annealing to attain the monophasic; 4. although the initial solutions contain nitrates, combustion proceeds with almost complete transformation of nitrogen dioxides into molecular nitrogen; 5. this method allows to control the dispersion of the material while reducing the costs for milling and lessening the risk of pollution of the material during milling. however, in the lino3-co(no3)2-glycine (urea) systems, a redox reaction of lco formation proceeds intensely with outflow of a considerable part of precursor with effluent gases outside the reactor. under stoichiometric combustion conditions, the combustion rate may have an explosive character. it is reasonable to expect that the described above effects detected under conditions of laboratory experiments will be multiply strengthened if the mass of the material is increased. this problem can be solved by using of less energetic fuel for controlled reduction of scs rate, for example, sucrose, ammonium acetate starch, citric acid and oxalic acid [24-28]. in this paper, we report structural, morphological, dimensional and electrochemical characteristics of lco powders produced in scs reactions with glycine and citric acid with subsequent coating with fused lithium borate li3bo3. 2. experimental 2.1. starting materials for the combustion synthesis of lco powders, cobalt(ii) nitrate hexahydrate (99%) and cobalt(ii) carbonate hydroxide hydrate coco3∙mco(oh)2∙nh2o (with cobalt content of 55.5%) (ural chemical reagents plant, russia) were used as cobalt sources, and lithium carbonate (unichim (russia), 99%) was used as a source of lithium. citric acid hydrate h3c6h5o7∙h2o (citrobel (russia), 99.8%) and amino acetic acid (glycine) h2n(ch2)cooh (kamhimkom (russia), 98.5%) were used as fuel, while double-distilled water served as a solvent for precursor solutions. the synthesis of lithium borate was carried out from boric acid (unichim (russia), 99.5%) and lithium carbonate (npf nevsky chemist (russia), 99.5 %). 2.2. synthesis lithium nitrate combined with cobalt nitrate imparts excessive combustion intensity to scs reactions. in the methods where glycine used as a fuel / reductant, the combustion rate during synthesis of cathode materials of lib can be considerably decreased by replacing lithium nitrate by lithium carbonate or lithium citrate [24]. besides, the reduction of the fraction of cobalt nitrate (oxidizer) due to its replacement by cobalt citrate also lowers the scs intensity allowing the yield increasing of the resulting material [24]. in this work, we used one-step mode of lco production. for this purpose, a 150 ml solution of cobalt nitrate (66.67 g/dm 3 co) and citric acid (237.5 g/dm 3 ) (solution 1) was placed into a 2 dm 3 reactor, to which 120 cm 3 lithium citrate solution (286.68 g/dm 3 li2hc6h5o7) was added. cobalt (ii) carbonate hydroxide hydrate and glycine successively added to the resulting solution (table 1). the reaction solution was heated on an electrical heater with a capacity of 1 kw (the temperature of the heater was 550–600 °с) for dehydration and initiation of scs reaction. the produced lco precursor was ground in a ball mill with grinding bodies made of stabilized zirconium oxide prior and between the annealing at 650, 800 and 850 °с. the annealing duration at each stage was 10 h. after certification, lco powders were coated with fused li3bo3 (lbo) produced preliminarily in a solid-phase reaction using lithium carbonate and boric acid at 560– 600 °с for 35 h with intermediate grinding. 5 and 7 mass % of lbo were added to the initial lco powder and mixed in a ball mill for 1 h, then they were annealed at 750 °с for 5 h. after the first annealing, the lco/lbo samples were repeatedly ground and annealed for the second time at 750 °с for 5 h to produce better uniform coating. 2.3. characterization of powder samples the diffraction patterns of the powders were taken at room temperature with a shumadzu xrd-700 (cu kα1 radiation, 2θ = 10-80°) diffractometer, equipped with pdf2 database. the refinement of the crystal structure according to the rietveld method carried out using the software package fullprof [29]. sem images obtained with a jeol jsm 6390 la microscope. specific surface area (s) of powders was determined by bet nitrogen desorption during heating in a sorbi n4.1 (meta, russia). the particle size distribution of the obtained powders was determined using a horiba la-950v2 laser particle meter. 2.4. electrochemical measurements the electrochemical properties of the lco powder samples were studied using two-electrode pouch cells. the composite electrodes were prepared by inkjet printing of a hochimica techno acta 2021, vol. 8(1), № 20218101 article 3 of 6 mogenized mixture of the synthesized material, a conductive additive (acetylene black) and a binder (polyvinylidene fluoride dissolved in n-methyl-2-pyrrolidone) (weight ratio of solid components 80:10:10) onto an aluminum foil. the electrodes were compacted in a rolling mill and then dried under vacuum at 120 °с for 12 h. the area of the prepared electrode was of 2.25 cm 2 . the active material loading of the electrode was about 3-6 mg cm -2 . the electrochemical test cells li│liquid electrolyte│lco were assembled in an argon-filled mbraun lab star glove box with o2 and h2o contents <0.1 ppm. lithium foil (99.9 %, alfa aesar) was used as a counter electrode. celgard 2300 film was used as a separator. the solution of 1 m lipf6 in ethylene carbonate (ec) and ethyl methyl carbonate (emc) (1:1 vol.) (sigma aldrich) was used as the electrolyte. the residual water content in the electrolyte solution did not exceed 30 ppm. cycling performance and rate capability of the cathode half-cells were examined at 25 °c by galvanostatic chargedischarge curves measured with p-20x80 multichannel potentiostat (“elins” llc, russia) in the voltage range of 2.7–4.3 vs. li 0 /li + . current density varied from 0.1 to 0.5c. 3. results and discussion scs as the chosen lco obtaining method allowed to increase the mass of the obtained product without growing the reaction temperature and rate, i.e. without discharge of the produced powder. evaporation of the solution led to the formation of a semi-sphered dried gel covered with a violet film. the dry outer layer gradually closed the whole semi sphere, inside which a wet gel remained (fig. 1а) also transforming gradually into dry precursor material. the redox reaction proceeded in the form of a heating wave (fig. 1b) with low violet flame. there was no discharge of the material outside the reactor, and no visible traces of nitrogen dioxide were present. when the combustion was completed, a bulky flake black powder of lco precursor was obtained. the lco powders obtained after combustion possessed high dispersion and revealed chemically non-equilibrium state due to incomplete crystal lattice formation processes. this is connected with a short combustion time (the reaction mass was in the high-temperature region for less than 3–5 min); low density of the material (as a result of large amount of gaseous products) hampers the completion of diffusion processes during lco formation. usually, the scs process is supplemented with high-temperature annealing, in this case in the range of 650–850 °с, to remove carbon-containing impurities and form the lco crystal structure (table 1, fig. 2). upon annealing, the crystal lattice parameters of the produced lco corresponded to the literature data [30]. reflections of the fused lbo coating were not recorded, probably due to its glassy character. the performed sedimentation analysis revealed that lco represents finely dispersed powders forming agglomerates with the maximal diameter, dmax, of <30 µm (table 2) and the average particle diameter, dav, of 8.4-11.5 µm. table 1 lco crystal lattice parameters after annealing at 850 °с sample a, å c, å v, å 3 r1 r2 1 2.8165 (2) 14.0604 (21) 96.5921 1.72 0.57 [30] 2.81619 14.05586 96.5382 1.35 0.44 fig. 1 formation of the product in scs reactions fig. 2 x-ray diffraction patterns of (а) lco, (b) lco+5% lbo, (c) lco +7% lbo chimica techno acta 2021, vol. 8(1), № 20218101 article 4 of 6 the fraction of particles less than 5 µm is rather large, from 6 to 30%. the application of borate coating considerably changes the particle size distribution in the material; dav increases to 11-45 µm and depends explicitly on the milling conditions and load. the fraction of particles with a diameter less than 5 µm decreases to 1.1-1.3% (table 2), which should have a positive effect on the cathode stability during the interaction with electrolyte. however, the presence of aggregate fractions larger than 30 µm required the classification of powders before applying the electrode mass. coating of lco with a layer of fused lithium borate practically does not change the specific surface of the material (table 2), remaining equal to 0.8-0.98 m 2 /g. this value is larger than the traditional values for commercial cathode materials, 0.4-0.6 m 2 /g, but possibly has positive impact on the electrochemical characteristics during cycling. the advantage of coating by fusion is that fusion and spreading of lbo on the surface of lco particles and agglomerates decreases the coating thickness and increases the probability of connection of small particles, reducing the influence of electrolyte. the sizes of lco-lbo powders are slightly larger than the base (lco) particles, it contain a smaller percent of fine fractions due to enhanced sintering into agglomerates and additional annealing time (growth of primary crystallites) (fig. 3). the charge-discharge characteristics of cathode materials based on lco were studied in the potential range of 2.75-4.3v vs li/li + . the charge and discharge rate of the first 10 cycles were 0.1c. then, at the same charge rate, 10 cycles performed with a discharge rate of 0.2c, 0.5c and again 0.1c. fig. 4 shows the capacity dependences on the cycle number based on a series of powders: lco, lco + 5% lbo and lco + 7% lbo as samples with the most stable characteristics. the discharge capacity of the sample without coating at the first cycle was 166 mah/g. a significant increase of the discharge capacity (up to 185 mah/g) was achieved by using a 5% lbo coating. when the lbo content of the sample increases to 7%, the discharge capacity drops to 164 mah/g. the negative effect probably related to the increasing thickness of the coating layer and/or the formation of less conducting glasses during the interaction of fused lbo with lco. all samples retain 94, 93 and 93% of the original discharge capacity after 40 cycles when the cycle rate returned to the original rate 0.1c. in addition, the coulomb efficiency of these samples is more than 99% throughout all 40 charge-discharge cycles (table 3). fig. 5 shows the charge-discharge curves of the first cycle for lco, lco+5% lbo and lco +7% lbo. the type of the charge-discharge curves corresponds to the typical charge-discharge curves obtained for lithium cobaltatebased cathodes [21, 31, 32]. the charge-discharge curves have a plateau at a potential of 3.9 v and two small quasi-plateaus at 4.1 and 4.2 v. these plateaus correspond to the peaks on the cyclic voltammograms (fig. 6). according to the literature data [3236], the main peak at 3.9 v is related to the first order transition from lco to li0.8coo2; the two less pronounced peaks at ~4.06 and ~4.17 v are associated with phase transitions to the monoclinic structure and back to the hexagonal structure. table 2 the results of sedimentation analysis of lco-lbo powders lco lbo dav, µm dmed, µm fraction < 5 µm, % dmax, µm fraction >30 µm, % fraction 30-100 µm, % s, m 2 /g lco 8.4 8.2 13.5 30 0 0 0.82±0.02 lco+5% lbo 43 14 1.3 300 24 11 0.86±0.04 lco+7% lbo 37 16 1.1 300 29 19 0.92±0.03 table 3 the cyclic performance of lco powders in the range of 2.75–4.3 v at different rates discharge capacity, mah/g (cycle number) coulomb efficiency, % (cycle number) 0.1с (10) 0.2с (20) 0.5с (30) 0.1с (40) (10) (20) (30) (40) lco 162 158 145 153 99.5 99.7 99.9 99.1 lco+5% lbo 185 180 173 172 99.5 99.7 99.9 99.1 lco+7% lbo 162 158 152 150 99.5 99.7 99.9 99.1 fig. 3 morphology of (а) lco, (b) lco+5% lbo, (c) lco +7% lbo powders chimica techno acta 2021, vol. 8(1), № 20218101 article 5 of 6 based on the obtained data, it is possible to conclude that borate coating does not affect the electrode polarization, as the discharge plateau does not change. according to the data obtained by the cyclic voltammetry method and based on the peaks intensity on the cyclic voltammograms, one may conclude that due to the presence of 5 mass % of lbo coating on the lithium cobaltite surface, it is possible to activate the electrode surface and increase the reversibility of lithium introduction and extraction processes into the electrode. wider peaks for the uncoated sample may be an indication of inhibition of lithiation and delithiation processes as compared to the modified samples. consequently, the presence of lbo coating may affect the rate of lithium diffusion into cathode material particles. thus, borate coating increases the stability of cobaltite cycling at elevated rates. when the rate increases to 0.5c, the capacity falls by 4% for coated samples and by 8% for uncoated samples. 4. conclusions the best electrochemical characteristics, discharge capacity of 185 mah/g at 0.1c and coulomb efficiency of 99.1% after 40 cycles, were demonstrated by the sample obtained in the scs 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o i: 1 0. 15 82 6/ ch im te ch .2 02 0. 7. 4. 08 yakovishin l. a., grishkovets v. i. chimica techno acta. 2020. vol. 7, no. 4. p. 180–185. issn 2409–5613 intermolecular interaction of glycyrrhizin with cholesterol l. a. yakovishina*, v. i. grishkovetsb a sevastopol state university, 33 university str., sevastopol, 299053, russia b v. i. vernadsky crimean federal university, 4 vernadsky ave., simferopol, 295007, russia *email: chemsevntu@rambler.ru abstract. the 1:1 molecular complex of licorice triterpene glycoside glycyrrhizic acid (in the form of monoammonium salt) with cholesterol was obtained in 80% aqueous isopropyl alcohol for the first time. the complexation was studied by 13c nmr, uv, and atr ir-fourier spectroscopy. the hydrogen bonds and hydrophobic interactions are formed in the molecular complex. keywords: triterpene glycosides; licorice; glycyrrhizin; glycyrrhizic acid; cholesterol; molecular complex received: 27.10.2020. accepted: 09.12.2020. published:30.12.2020. © yakovishin l. a., grishkovets v. i., 2020 introduction glycyrrhizin (glycyrrhizic acid, 3-о-β-d-glucuronopyranosyl-(1→2)о-β-d-glucuronopyranoside of 18β-glycyrrhetinic acid, ga; fig. 1) is the dominant triterpene saponin from licorice roots glycyrrhiza glabra l. and glycyrrhiza uralensis fisch. (fabaceae) [1, 2]. ga has anti-inflammatory, antioxidative, antiviral, anticancer, hypocholesterolemic, and hepatoprotective properties [1–3]. the most important derivative of ga is its monoammonium salt (monoammonium glycyrrhizinate, glycyram, gc; fig. 1). gc is used as an anti-inflammatory, hepatoprotective, antiallergic, mineralocorticoid, and antitussive drug [2–4]. some biological properties of saponins explain their molecular complexation with sterols [1, 2, 5–7]. ga increases permeability and reduces the  elastic modulus of cell membranes [8]. on the other hand, recent spectrophotometric titration did not confirm the complexation of gc with cholesterol (chol; fig. 1) and 1,2-dipalmitoylphosphatidylcholine [9]. the authors of  this paper have been suggested that the  presence of  11-oxo group in  the  gc aglycone part prevents its complexation. in  order to  consider the  possibility of complexation of gc with chol in various media, we studied their intermolecular interaction in aqueous isopropyl alcohol by nmr, ir, and uv spectroscopy. experimental gc (purity ≥95% by hplc) was purchased from calbiochem. chol and other chemicals in  the  highest grade of  purity were obtained from sigma-aldrich. 181 the complex of chol with gc was preparatively obtained by liquid-phase method. for this purpose, 1 mmol of the substances was mixed with 50  ml of  80% aqueous isopropyl alcohol (v/v). the obtained mixture was incubated at 50 °c for 1.5 h with continuous stirring. the organic solvent was removed by vacuuming. uv spectra of chol solutions (0.50  · ·  10–4 m = const) with different concentrations of gc (0, 0.125 · 10–4, 0.25 · 10–4, 0.50 · 10–4, 1.0 · 10–4 m) were recorded on a leki ss2110uv spectrophotometer using a quartz cuvette (l = 1 cm) at 25 °c. the  ir spectra were recorded on a simex fт-801 ir-fourier spectrometer in the 4000–550 cm–1 region (spectral resolution 4 cm–1; 50 scans) using the universal optical attenuated total reflection (atr) accessory with diamond crystal plate. ir spectrum of gc (ν, cm–1): 3197 (он, nh), 2928 (сн), 2907 (сн), 2868 (сн), 1719 (с=о), 1708 (с=о), 1641 (с(11)=о, c=c), 1587 (соо–), 1451 (сн), 1425 (nh4 +), 1416 (соо–), 1387 (сн), 1357 (сн), 1318 (сн), 1260 (сн), 1211 (сн), 1162 (с–о–с, с–он), 1037 (с–о–с, с– он), 980 (=ch), 946 (сн), 918 (monosaccharide ring), 880 (сн), 818 (сн), 793 (сн), 694 (сн), 687 (сн), 679 (=ch), 663 (он). ir spectrum of  chol (ν, cm–1): 3403 (он), 3337 (он), 2929 (ch), 2899 (ch), 2865 (ch), 2848 (сн), 1672 (c=c), 1460 (сн), 1434 (сн), 1377 (сн), 1364 (сн), 1341 (сн), 1333 (сн), 1318 (сн), 1275 (сн), 1268 (сн), 1253 (сн), 1234 (сн), 1220 (сн), 1190 (сн), 1169 (с–он), 1132 (с–он), 1106 (с–он), 1052 (с–он), 1022 (с–он), 986 (=ch), 953 (сн), 925 (=ch), 881 (сн), 839 (с–с–с), 799 (сн), 738 (сн), 720 (сн), 694 (сн), 687 (сн), 679 (=ch), 662 (он). ir spectrum of the complex of gc with chol (ν, cm–1): 3216 (он, nh), 2928 (ch), 2903 (ch), 2863 (ch), 1717 (с=о), 1698 (с=о), 1669 (с=сchol), 1648 (с(11)=о, c=cgc), 1586 (соо –), 1459 (сн), 1450 (сн), 1433 (сн), 1424 (nh4 +), 1418 (соо–), 1386 (сн), 1379 (сн), 1362 (сн), 1339 (сн), 1316 (сн), 1277 (сн), 1261 (сн), 1211 (сн), 1163 (с–о–с, с–он), 1038 (с–о–с, с–он), 1030 (с–о–с, с–он), 978 (=ch), 947 (сн), 919 (monosaccharide ring, =ch), 880 (сн), 818 (сн), 795 (сн), 741 (сн), 719 (сн), 692 (сн), 685 (сн), 679 (=ch), 662 (он). 13c nmr spectra were recorded on a bruker wm-250 spectrometer (62.9 mhz for 13с) in с5d5n at 30 °с. nmr spectra are reported in tables 1 and 2. cooh o o o hooc ho ho ho o ho o h rooc oh ho intermolecular hydrogen bond hydrophobic interactions3 23 12 28 30 20 17 ga: r=h gc: r=nh4 chol 1' 6' 1'' 3 19 5 6 21 20 2526 27 18 22 241 11 1 11 17 24 25 27 29 6'' chol gc .... . fig. 1. chemical structures of ga, gc, chol and schematic representation of the possible orientation of gc and chol molecules during their intermolecular interaction 182 results and discussion the intermolecular interaction of gc with chol was studied by  uv spectroscopy. as the gc concentration increases (at constant chol concentration), the optical density of  their solutions increases (hyperchromic effect) (fig. 2). the absorption maximum of the solutions increases (bathochromic shift) from 237 to 250 nm. similar spectral changes were previously noted for molecular complexes of  some triterpene glycosides [10] and cyclodextrins [11]. the  complex of  chol with gc was preparatively obtained by  liquid-phase method in  80% aqueous isopropyl alcohol. the potential centers of intermolecular interactions in the molecules are cooh groups of  gc and oh group of  chol. the lipophilic nature of the aglycone part of  gc and sterane system with the  hydrocarbon “tails” in chol may contribute to hydrophobic contacts between them. the nature of intermolecular interactions in the complex was confirmed by atr ft-ir spectroscopy. upon the formation of  complex in  the  ir spectra for the  absorption bands of  stretching vibrations of  chol o–h bonds are observed shifts from 3403 and 3337 cm–1 to  3216 cm–1, and for gc  — from 3197 to  3216 cm–1. we also found a  low-frequency shift of  the  absorption band of  c=o bond in one of gc carboxyl groups at 1708 cm–1 by  10 cm–1. similar shifts of  the  absorption bands of  c=o bonds in  ir spectra were previously observed during the interaction of ivy triterpene glycosides with chol [12], as well as during the formation of ga and gc complexes [11]. in addition, the band of stretching vibrations of c–o bonds in c–oh for gc at 1037 cm–1 shifts by –7 cm–1 and for chol at 1169, 1052, and 1022 cm–1 — by –6, –14, and +8 cm–1, respectively. ir spectroscopic data indicate about the formation of a hydrogen bond between chol oh group and c=o group in one of gc carboxyl groups: с=оgc…н–оchol. fig. 2. uv spectra of chol solutions (0.50 · 10–4 m = const) with different concentrations of gc: 0 m (curve 1), 0.125 · 10–4 (curve 2), 0.25 · 10–4 (curve 3), 0.50 · 10–4 (curve 4), 1.0 · 10–4 (curve 5) (a) and atr ft-ir spectra of gc, chol, and gc–chol molecular complex (b) 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 220 a 1 5 270 λ, nm a b 183 the complexation also causes changes in  certain frequencies of  absorption of ch bonds: 2868 → 2863 cm–1 and 2907 → 2903 cm–1 (for gc), and also 2899 → 2903 cm–1, 953 → 947 cm–1, and 799 → 795 cm–1 (for chol). these facts may indicate the presence of hydrophobic contacts between chol and gc molecules. the location of gc carboxyl group involved in  the  interaction with chol was determined by  13c nmr spectroscopy. the value of the chemical shift of the c-30 atom in  the  carboxyl group of  the  aglycone portion of  gc remains practically unchanged (table  1). however, there is a change in the chemical shift of the с-6″ table 1 13c nmr spectral data for free gc and gc in the molecular complex with chol (δ, ppm, 0 — tms, с5d5n, 30 °с) с -a to m g c g c in  c om pl ex w ith c ho l ∆ δ = =  δ g c –c ho l – δ g c с -a to m g c g c in  c om pl ex w ith c ho l ∆ δ = = δ g c –c ho l – δ g c aglycone part 1 40.03 40.04 0.01 16 26.78 26.75 –0.03 2 26.96 26.96 0 17 32.23 32.23 0 3 89.28 89.30 0.02 18 48.81 48.82 0.01 4 40.14 40.15 0.01 19 41.84 41.89 0.05 5 55.52 55.51 –0.01 20 44.19 44.19 0 6 17.66 17.68 0.02 21 31.72 31.71 –0.01 7 33.05 33.07 0.02 22 38.51 38.51 0 8 43.55 43.58 0.03 23 28.17 28.16 –0.01 9 62.20 62.19 –0.01 24 16.91 16.92 0.01 10 37.29 37.29 0 25 16.79 16.78 –0.01 11 199.62 199.63 0.01 26 18.87 18.87 0 12 128.75 128.75 0 27 23.66 23.65 –0.01 13 169.63 169.63 0 28 28.85 28.85 0 14 45.63 45.61 –0.02 29 28.85 28.85 0 15 26.78 26.75 –0.03 30 179.22 179.21 –0.01 carbohydrate part glcua′ glcua″ 1′ 105.10 105.12 0.02 1″ 106.63 106.61 –0.02 2′ 82.82 82.82 0 2″ 76.71 76.74 0.03 3′ 77.15 77.16 0.01 3″ 77.65 77.67 0.02 4′ 73.45 73.47 0.02 4″ 73.51 73.50 –0.01 5′ 78.02 78.00 –0.02 5″ 78.23 78.15 –0.08 6′ 172.92 172.94 0.02 6″ 174.19 174.03 –0.16 184 atom of the carboxyl group of the terminal residue of  glucuronic acid (glcua″) in the disaccharide fragment gc by –0.16 ppm compared to individual gc (fig. 1). a smaller effect was also noted on the neighboring c-5″ atom (∆δ = –0.08 ppm). in addition, it is noted ∆δ (up to 0.05 ppm) for a  number of  gc aglycone and chol c-atoms (tables 1 and 2). the greatest effects were found for some c-atoms in the b–e rings of gc, in the b–d rings, and side chain of chol, as well as all methyl groups of chol. these data may indicate about hydrophobic interactions between the aglycone part of gc and chol (fig. 1). conclusions the  results of  this work confirm the molecular complexation between gc and chol. the interaction is accompanied by bathochromic shift and a hyperchromic effect. the formation of an intermolecular hydrogen bond between oh group at c-3 of chol and c=o group of terminal glucuronic acid residue in the carbohydrate part of gc (c3–о–н…о=с6″) and hydrophobic contacts were confirmed by 13c nmr and atr ft-ir spectroscopy. the results of this work can be used to study of mechanisms of biological activity of ga, gc and other saponins. table 2 13c nmr spectral data for free chol and chol in the molecular complex with gc (δ, ppm, 0 — tms, с5d5n, 30 °с) с -a to m c ho l c ho l i n co m pl ex w ith g c ∆ δ = = δ g c –c ho l – δ c ho l с -a to m c ho l c ho l i n  co m pl ex w ith g c ∆ δ = = δ g c –c ho l – δ c ho l 1 37.92 37.94 0.02 15 24.59 24.62 0.03 2 32.71 32.71 0 16 28.58 28.61 0.03 3 71.35 71.38 0.03 17 56.49 56.52 0.03 4 43.59 43.58 –0.01 18 12.09 12.13 0.04 5 142.07 142.06 –0.01 19 19.68 19.72 0.04 6 121.29 121.31 0.02 20 36.11 36.13 0.02 7 32.31 32.34 0.03 21 19.02 19.06 0.04 8 32.26 32.29 0.03 22 36.57 36.59 0.02 9 50.60 50.62 0.02 23 24.22 24.24 0.02 10 36.99 37.02 0.03 24 39.80 39.83 0.03 11 21.45 21.48 0.03 25 28.29 28.32 0.03 12 40.12 40.15 0.03 26 22.74 22.78 0.04 13 42.60 42.63 0.03 27 22.99 23.03 0.04 14 57.00 57.04 0.04 185 acknowledgements this work was carried out in the frame of an internal grant of sevastopol state university (identifier 30/06-31). references 1. hostettmann k, marston a. saponins. cambrige: cambrige university press; 1995. 548 р. 2. tolstikov ga, baltina la, grankina vp, kondratenko rm, tolstikova tg. solodka: bioraznoobrazie, khimiya, primenenie v medicine [licorice: biodiversity, chemistry, and application in medicine]. novosibirsk: geo; 2007. 311 p. russian. 3. asl mn, hosseinzadeh h. review of pharmacological effects of glycyrrhiza sp. and its bioactive compounds. phytother res. 2008;22(6):709–24. doi:10.1002/ptr.2362 4. pavlova si, uteshev bs, sergeev av. licorice root: possible mechanisms of  antitoxicant, anticarcinogen, and antitumor properties (a review). pharm chem j. 2003;37(6):314–7. doi:10.1023/a:1026005931751 5. sidhu gs, oakenfull dg. a  mechanism for the  hypocholesterolaemic activity of saponins. brit j nutrit. 1986;55(3):643–9. doi:10.1079/bjn19860070 6. lorent jh, quetin-leclercq j, mingeot-leclercq mp. the amphiphilic nature of saponins and their effects on artificial and biological membranes and potential consequences for red blood and cancer cells. org biomol chem. 2014;12(44):8803–22. doi:10.1039/c4ob01652a 7. popov am. mechanisms of biological activity of ginsenosides: comparison with holothurian glycosides. vestnik dvo ran. 2006;6:92–104. 8. selyutina oyu, polyakov ne, korneev dv, zaitsev bn. influence of glycyrrhizin on permeability and elasticity of cell membrane: perspectives for drugs delivery. drug deliv. 2016;23(3):858–65. doi:10.3109/10717544.2014.919544 9. wojciechowski k, orczyk m, gutberlet t, geue t. complexation of phospholipids and cholesterol by triterpenic saponins in bulk and in monolayers. biochim biophys acta biomembr. 2016;1858(2):363–73. doi:10.1016/j.bbamem.2015.12.001 10. yakovishin la, grishkovets  v. i.  ivy and licorice triterpene glycosides: promising molecular containers for some drugs and biomolecules. stud nat prod chem. 2018;55:351–83. doi:10.1016/b978-0-444-64068-0.00011–5 11. li s, purdy wc. cyclodextrins and their applications in  analytical chemistry. chem rev. 1992;92(6):1457–70. doi:10.1021/cr00014a009 12. yakovishin la, grishkovets vi. molecular complexes of ivy triterpene glycosides with cholesterol. khimiya rastitel’nogo syr’ya. 2018;4:133–40. doi:10.14258/jcprm.2018043607 crystal structure, thermal and electrotransport properties of ndba1–xsrxfeco0.5cu0.5o5+δ (0.02 ≤ x ≤ 0.20) solid solutions chimica techno acta article published by ural federal university 2021, vol. 8(3), № 20218301 eissn 2411-1414; chimicatechnoacta.ru doi: 10.15826/chimtech.2021.8.3.01 1 of 5 crystal structure, thermal and electrotransport properties of ndba1–xsrxfeco0.5cu0.5o5+δ (0.02 ≤ x ≤ 0.20) solid solutions a.i. klyndyuk * , ya.yu. zhuravleva, n.n. gundilovich belarus state technological university, 13a sverdlova str., minsk, 220006, belarus republic * corresponding author: klyndyuk@belstu.by this article belongs to the regular issue. © 2021, the authors. this article is published in open access form under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). abstract using solid-state reactions method, the solid solutions of layered oxygen-deficient perovskites ndba1–xsrxfeco0.5cu0.5o5+δ (0.02 ≤ x ≤ 0.20) were prepared; their crystal structure, thermal stability, thermal expansion, electrical conductivity and thermopower were studied. it was found that ndba1–xsrxfeco0.5cu0.5o5+δ phases crystallize in tetragonal syngony (space group p4/mmm) and are p-type semiconductors, whose conductivity character at high temperatures changed to the metallic one due to evolution from the samples of so-called weakly-bonded oxygen. partial substitution of barium by strontium in ndbafeco0.5cu0.5o5+δ leads to the small decreasing of unit cell parameters, thermal stability and thermopower of ndba1–xsrxfeco0.5cu0.5o5+δ solid solutions, increasing of their electrical conductivity values and slightly affects their linear thermal expansion coefficient and activation energy of electrical transport values. keywords layered perovskites thermal stability thermal expansion electrical conductivity thermopower received: 02.06.2021 revised: 01.07.2021 accepted: 08.07.2021 available online: 08.07.2021 1. introduction layered oxygen-deficient double perovskites of lnbame’me”o5+ (ln  y, rare-earth element (ree), me’, me”  3d-metal) have a complex of unique properties, including large values of electrical conductivity and thermopower, and contain in their structure labile oxygen, so they may be used as functional materials for different purposes: high-temperature oxide thermoelectrics, electrode materials for solid-oxide fuel cells (sofc), materials for working elements of semiconducting chemical gas sensors, catalysts of hydrocarbons oxidation, etc. [16]. lnbaco2o5+ phases demonstrate high electrochemical performance in oxygen reduction reaction (orr) [48], but values of their linear thermal expansion coefficient (tec, ) are too large (circa (1529)10 6 k 1 [79]) in comparison to the tec of commonly used in sofc zirconia, ceria, or perovskite-like based solid electrolytes, which are equal to (1011)10 6 k 1 , (1213)10 6 , and (1013)10 6 k 1 respectively [10], which limits the practical implementation of these phases as cathode materials in sofc. many studies [8,9,1118] have demonstrated that partial substitution in lnbaco2o5+ of cobalt by other 3dmetal or barium by strontium essentially improves electrochemical performance of solid solutions forming at such substitution and reduces their tec value. so, partial substitution of cobalt by iron in lnbaco2o5+ (ln  pr, nd) leads to the reducing of tec and polarization resistance of materials forming at this substitution and also improves their long-term stability at implementation as cathode materials of sofc [12,13,15]. doping of barium by strontium and of cobalt by copper or iron in ybaco2o5+ lead to the reducing of tec of forming solid solutions, improving of their structural stability and electrochemical performance [9,16]. so, obtaining and studying of solid solutions, including complex substituted ones, on the basis of layered oxygendeficient double perovskites is an actual task, having scientific and practical interest. in this work we studied the effect of partial substitution of barium by strontium in ndbafeco0.5cu0.5o5+ on the crystal structure, thermal and electrotransport properties of ndba1xsrxfeco0.5cu0.5o5+ solid solutions as perspective cathode materials for intermediate-temperature sofc. http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2021.8.3.01 mailto:klyndyuk@belstu.by http://creativecommons.org/licenses/by/4.0/ chimica techno acta 2021, vol. 8(3), № 20218301 article 2 of 5 2. experimental ceramic samples of ndba1xsrxfeco0.5cu0.5o5+ (x = 0.02, 0.05, 0.10, and 0.20) solid solutions were prepared by means of solid-state reactions method from nd2o3 (no–l), baco3 (pure), srco3 (pure), fe2o3 (super pure 2–4), co3o4 (pure), and cuo (pure for analysis) in air at temperature of 1173 k within 40 h with consequent sintering during 9– 18 h in air at temperatures of 1223–1273 k according to the methods, described in [19,20]. identification of the samples and determination of their lattice constants was performed by means of x-ray diffraction analysis (xrd) (x-ray difrractometer bruker d8 advance xrd, cu k-radiation). ir-absorption spectra of powders were recorded in the mixtures with kbr within 300–1500 cm –1 (thermonicolet nexus fourier-transform infrared spectrometer). apparent (effective) density of the sintered ceramics (eff) was determined from the mass and dimensions of the samples, and their porosity (п) was calculated using eq. (1): п = (1 – eff/xrd)100%, (1) where xrd – x-ray density of the samples. thermal stability of the powdered samples was studied by means of thermoanalytical system of tga/dsc– 1/1600 hf in air within 300–1100 k temperature interval. thermal expansion of the sintered ceramics was investigated using dil 402 pc quartz dilatometer in air within temperature interval of 300–1100 k [21]. electrical conductivity and thermopower of ndba1xsrxfeco0.5cu0.5o5+ solid solutions were studied in air within 300–1100 k according to the methods, described in detail in [20]. values of tec and apparent activation energies of electrical conductivity (ea) and thermopower (es) were calculated from the linear parts of l/l0 = f(t), ln(t) = f(1/t), and s = f(1/t) dependences, respectively. 3. results and discussion after final stage of the synthesis, all the samples of the ndba1xsrxfeco0.5cu0.5o5+ solid solutions were single phase, within xrd accuracy (fig. 1a), and had a structure of tetragonally distorted double perovskite of ybacufeo5 type (a  ap,c  2ap) [1], and their reflections were indexed in the framework of the p4/mmm space group with unit cell parameters of a = 3.903–3.914 å and c = 7.707–7.715 å (table 1). as can be seen from the table 1, increasing of the substitution degree of larger ba 2+ ion by smaller sr 2+ one (for c.n. = 12 r(ba 2+ ) = 1.60 å, r(sr 2+ ) = 1.44 å [22]) leads to the decreasing of the size of the unit cell of the ndba1– xsrxfeco0.5cu0.5o5+δ phases. porosity of the sintered ceramics enlarged at x increasing (table 1), which let us conclude that partial substitution of barium by strontium in ndbafeco0.5cu0.5o5+δ slightly reduces sinterability of this perovskite. on the ir-absorption spectra of the samples were detected some absorption bands with extrema at 351– 353 cm –1 (1), 467–470 cm –1 (2), 576–582 cm –1 (3), and 660–665 cm –1 (4) (fig. 1b), which were attributed, according to [23], to the stretching (3, 4) and bending vibrations (1) of the (fe,co,cu)–o–(fe,co,cu) bonds in the [(fe,co,cu)o2] basal planes (1, 3), as well as stretching vibrations of apical oxygen of (fe,co,cu)–o–(fe,co,cu) bonds along c axis (4) in the structure of ndba1– xsrxfeco0.5cu0.5o5+δ phases. at x increasing the 3 and 4 bands shifted to the larger values, fig. 1 x-ray powder diffractograms (a) and ir-absorption spectra (b) of ndba1–xsrxfeco0.5cu0.5o5+δ solid solutions: x = 0.02 (1); 0.05 (2); 0.10 (3); 0.20 (4) chimica techno acta 2021, vol. 8(3), № 20218301 article 3 of 5 table 1 the unit cell parameters (a, c, c/2a, v), effective density (ρeff) and porosity (п) of ndba1–xsrxfeco0.5cu0.5o5+δ layered perovskites finally sintered at 1273 k x a, ǻ c, ǻ c/2a, ǻ v, ǻ 3 ρeff, g/cm 3 п, % 0.02 3.913(1) 7.715(1) 0.9860 118.1(1) 5.54 10 0.05 3.914(1) 7.711(1) 0.9851 118.1(1) 5.62 8 0.10 3.911(2) 7.707(2) 0.9853 117.9(1) 5.54 12 0.20 3.903(1) 7.708(1) 0.9876 117.5(1) 4.84 21 which pointed out to increasing of energy of metal–oxygen interactions in the crystal structure of these phases. results of ir-absorption spectrocopy correlate with the xrd results, showing that increasing of substitution degree of barium by strontium in ndba1–xsrxfeco0.5cu0.5o5+δ solid solutions leads to the shrinking of their unit cell. according to the results of thermal analysis, near the room temperature all the samples were thermally stable, but, beginning from the temperatures of 623–663 k (tb) the small mass loss (0.6–0.8%) was detected (fig. 2a), which took place due to the evolution of the labile (weakly-bonded) oxygen from the samples into environment [24]. values of tb decreased at x increasing (fig. 2c, table 2), which indicated increasing of mobility of weaklybonded oxygen in the structure of ndba1–xsrxfeco0.5cu0.5o5+δ solid solutions at increasing of substitution degree of barium by strontium. on the temperature dependences of the relative elongation (l/l0) of materials studied an anomaly in a kink near tk = 640– 680 k accompanied by the increase the tec value was detected (fig. 2b, table 2), which took place due to the rearrangement of oxygen sublattice of the samples with consequent evolution of oxygen from them in air [24]. tec values of ceramics in high-temperature region (ht, t > tk) were 15–24% larger than in the low-temperature one (lt, t < tk) (table 3). values of tec of ndba1–xsrxfeco0.5cu0.5o5+δ solid solutions in both temperature regions slightly varied but temperature of anomaly (tk) essentially decreased (fig. 2d) at x increasing. as can be seen from the data given in the fig. 3a,b, materials studied are p-type (s > 0) semiconductors (/t > 0). their conductivity character at high temperatures (t > tmax) changed to the metallic one (/t < 0), which was accompanied by the change of the sign of the s/t derivative (s/t < 0 at t < tmin and s/t > 0 at t >tmin). observed anomalies of electrotransport properties of ndba1–xsrxfeco0.5cu0.5o5+δ phases as well as described earlier anomaly of thermal expansion were due to the evolution of the weakly-bonded oxygen from the samples [24]. note that temperatures of  and s anomalies, tmax and tmin respectively, at x increasing shifted to the smaller temperatures (fig. 3c,d, table 2) like tb and tk temperatures. it is interesting that values of tb, tk, and tmin temperatures were rather close to each other, but tmax value was essentially larger (table 2, figs. 2c,d, 3c,d). values of all critical temperatures (tcr: tb, tk, tmax, and tmin) decrease at increasing of strontium content in the ndba1–xsrxfeco0.5cu0.5o5+δ solid solutions, hereby dependence tcr = f(x) was almost linear for tk, underlinear for tb and tmin, and overlinear for tmax increased despite of the table 2 values of critical temperatures (tb, tk, tmax, and tmin) of ndba1–xsrxfeco0.5cu0.5o5+δ ceramics x tb, k tk, k tmax, k tmin, k 0.02 663 680 734 685 0.05 631 670 733 665 0.10 631 660 730 650 0.20 623 640 709 650 fig. 2 temperature dependences of mass loss (a) and relative elongation (b) of ndba1–xsrxfeco0.5cu0.5o5+δ samples: x = 0.02 (1); 0.05 (2); 0.10 (3); 0.20 (4). dilatometric curves are shifted from each other by 0.1% for the clarity of presentation. insets shows concentration dependences of temperatures of mass loss onset (c) and kink of the δl/l0 = f(t) dependences (d) chimica techno acta 2021, vol. 8(3), № 20218301 article 4 of 5 fig. 3 temperature dependences of electrical conductivity (a) and thermo-emf coefficient (b) of ndba1–xsrxfeco0.5cu0.5o5+δ sintered ceramics: x = 0.02 (1); 0.05 (2); 0.10 (3); 0.20 (4). insets shows concentration dependences of temperatures of maximum on the σ = f(t) dependences (c) and minimum of the s = f(t) dependences (d) fact that porosity of the samples enlarged at increasing of strontium content (table 1). so, our results show that partial substitution of barium by strontium in ndbafeco0.5cu0.5o5+δ is an effective way to increase its electrical conductivity. layered oxygen-deficient double perovskites lnbame’me”o5+ possess polaronic character of charge transfer [1,19,24], and temperature dependences of their electrical conductivity and thermopower obey eqs. (2–3)  = (a/t)exp(ea/kt), (2) s = (k/e)(–es/kt + b), (3) where ea = es + em and es – activation energies of electrical conductivity and thermopower respectively, es is also activation energy of charge carriers – polarons, and em is energy of their transfer [25]. as can be seen from the data given in the table 3, values of energies of activation of electrical transport, in the whole, slightly varied at variyng strontium content in the samples. comparing obtained in this work results with the data of [24], where for ndbafeco0.5cu0.5o5+δ layered perovskite was found that ea = 0.245 ev, es = 0.048 ev, and em = 0.200 ev, we can conclude that partial substitution table 3 values of tec (α) and apparent activation energy of electrical transport (eσ, es, em) for the sintered ndba1–xsrxfeco0.5cu0.5o5+δ ceramics x 10 6 · αlt, k –1 10 6 · αht, k –1 eσ, ev (350– 700 k) es, ev (400– 650 k) em, ev 0.02 15.8 19.3 0.190 0.047 0.143 0.05 16.3 20.0 0.203 0.044 0.159 0.10 16.6 19.1 0.200 0.054 0.146 0.20 16.4 20.4 0.167 0.038 0.129 of barium by strontium in this parent phase does not affect practically the value of activation energy of charge carriers – polarons, but results in essential reducing of transfer energy of charge carriers. 4. conclusions by means of solid-state reactions method the ceramic samples of ndba1xsrxfeco0.5cu0.5o5+ (x = 0.02, 0.05, 0.10, and 0.20) solid solutions were prepared, and their crystal structure and physico-chemical properties were studied. in was found that obtained materials had tetragonal structure, whose unit cell parameters slightly depend on their cationic composition, and are p-type semiconductors, whose conductivity character changes to the metallic one at high temperatures due to the evolution of oxygen from their crystal structure into environment. it was established that partial substitution of barium by strontium in ndbafeco0.5cu0.5o5+ results in the increasing of electrical conductivity, reducing of energy activation of electrical 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7, no. 1. p. 4–12. issn 2409–5613 d. v. kiseleva a. n. zavaritsky institute of geology and geochemistry of urals branch of russian academy of sciences, 15 akademika vonsovskogo, 620016, ekaterinburg, russia kiseleva@igg.uran.ru matrix-matched calibration in la-icp-ms of silicate, phosphate and carbonate minerals: application of g-probe samples laser ablation (la) sampling provides fast microelement icp-ms analysis of a wide range of solid materials without their dissolution, thus decreasing contamination from water and reagents as well as reducing polyatomic isobaric interferences from acid solutions. however, the issue of matrix-matched calibration becomes crucial for la-icp-ms due to differences in behaviour during laser interaction and evaporation of solid samples. there are several approaches to la calibration: simultaneous supply of standard solutions into a spray chamber; calibration using a set of nist 61х synthetic glasses and glasses prepared from natural rocks and minerals (basalt, nephelinite, etc.) or pressed synthetic samples (calcium carbonates, phosphates and sulphides produced by usgs). a set of natural glasses for microanalysis is available from the international association of geoanalysts (iag) in co-operation with the usgs. the g-probe proficiency testing programme has been operating since 2008 and deals with solid samples for microanalysis (la-icp-ms, epma, eds-sem). a number of samples of different compositions were distributed: bbm-1g and bswir-1g natural basaltic glasses, gsm-1 gabbro; nist srm-based basaltic and diabase glasses; gp-macs synthetic pressed calcium carbonate, gp-maps phosphate and some others. the aim of the present work was to estimate the la-icp-ms analysis quality using matrix-matched calibration with g-probe samples of various composition. all g-probe samples were analysed using an elan 9000 q-icp-ms combined with a lsx-500 (nd:yag, 266 nm) laser ablation system. for silicate rocks, tb-1 basaltic glass was used for calibration; the remaining samples were analysed as unknowns. maps-4 calibration material were used for phosphate rock analysis. a combination of external matrix-matched calibration and internal normalisation was used for calculating element concentrations. la-icp-ms analysis quality was estimated using z-scores. most of the results obtained were in a good agreement with assigned values. keywords: laser ablation; inductively coupled plasma mass-spectrometry; geological glasses; matrix-matched calibration; internal standard received: 23.12.2019. accepted: 20.02.2020. published: 31.03.2020. © kiseleva d. v., 2020 5 introduction laser ablation (la) sampling in inductively coupled plasma mass spectrometric (icp-ms) analysis allows the rapid analysis of the trace element composition of solids to be carried out without their dissolution. at the same time, the contamination from the reagents used is minimised, and polyatomic isobaric interferences arising due to the presence of acid solutions are significantly reduced [1]. la-icp-ms is widely applied in the studies of microobjects with high spatial resolution, individual mineral grains, and spatial distributions of  trace elements. however, the issue of matrix-matched calibration becomes crucial for la-icp-ms of solids due to differences in behaviour during laser interaction and evaporation of  solid samples, especially when using 193 nm excimer and 213 and 266 nm nd:yag lasers [2]. to date, there are several widely practiced approaches to constructing calibration curves in the analysis of solid samples of various compositions using laser ablation sampling: some include the simultaneous supply of aqueous calibration solutions to the spray chamber of a mass spectrometer [3, 4]; others use synthetic glasses of the nist srm 61x series (manufactured by the national institute of standards and technology, usa), as well as glasses made by  fusion of  natural rocks and minerals (basalt, nephelinite, etc.) or pressed synthetic non-silicate samples (calcium carbonates and phosphates, sulphides, us geological survey, usa). the  first approach leads to  a  complication of  design features (for example, the  manufacturing, often in-house, of  chambers with additional inputs for solutions, the connection of an additional gas for spraying), as well as the formation of polyatomic isobaric interferences from the  solvents (water and acids). the  use of synthetic glasses for calibration provides a certain unification of the results obtained, but can be justified only in some cases (for example, for the analysis of silicate samples), while their composition does not reflect the natural sample composition with their wide range of trace element content [5]. for example, about 33 microelements with concentrations from 15 to  80 μg/g are certified in the most widespread nist srm 612 glass, which is insufficient when analysing the entire variety of rocks and minerals. taking into account the  above-mentioned, the most acceptable way to calibrate a mass spectrometer when analysing solid samples is to use matrix-matched calibration samples, and nist srm 612 glasses to  optimise the  analytic parameters of  the  device (adjusting the  interface, monitoring the level of oxides, etc.). the range of solid reference materials (rm) of natural composition has expanded significantly at the moment: the us geological survey produces 4 natural basalt glasses and 1 nephelinitic glass, which are the melts of powdered bcr-2, bhvo-2, bir-1, tb-1 and nkt-1 certified reference materials (srm) [5], respectively, as well as  synthetic pressed macs-3 calcium carbonate and maps-4 phosphate and mass-1 polymetallic sulphide. the  glass making procedure [5] involves the  fusion of  the  powdered rock material in an oven in a platinum crucible at 1325–1645 °c for 2–6 hours with several stirrings with a platinum rod and subsequent rapid cooling in  deionised water. the  pieces of  glass are then dried, fixed in epoxy resin and distributed to analytical laboratories. for pressed powdered sam6 ples [6], a specially developed procedure of trace element co-precipitation with pure calcium carbonate or phosphate in  a  reaction vessel is  used. the  resulting suspension is powdered to less than 40 μm, dried at  110 °с and pressed into pellets with a diameter of 19 mm. the homogeneity and composition of the samples obtained is confirmed by a number of studies in usgs laboratories (xrf, la-icp-ms, epma, etc.). thus, the samples described above are microanalytical reference materials (mrm), that is, they have passed the  certification procedure and issued certificates with certified concentrations of major and trace elements. an expanded set of natural glasses for microanalysis is presented as part of the gprobe interlaboratory testing programme, which combines the efforts of the us geological survey and the international association of geoanalysts (iag). the  main idea of  the  programme is to analyse the samples of unknown composition sent to  a  number of  interested laboratories around the world, after which the organisers provide the data on the composition of  these samples and protocols summarising the results obtained by all participants, and evaluate the quality of analysis in  a  particular laboratory. g-probe programme has been operating since 2008 and specialises in solid samples for microanalysis (la-icp-ms, epma, sem-eds); the number of participating laboratories has been ranged from 12 to 30 in various rounds with those providing the la-icp-ms results from 6 to 18, which reflects the complexity and specificity of mass spectrometric analysis of natural geological materials with high spatial resolution [7]. since 2008, 13 samples of  various composition and origin were distributed: natural basalt glasses based on samples taken by the usgs expeditions (bbm-1g, bswir-1g), gabbro (gsm-1); basalt glass based on the  geological nist srm 688; glass based on the  usgs w-2 diabase standard; sl factory soda-lime glass; synthetic pressed gp-macs calcium carbonate and gp-maps calcium phosphate et al. almost all g-probe samples are prepared and analysed in usgs laboratories in accordance with the procedures adopted for microanalytical standard samples, and very often they become certified reference materials after processing the results provided by the g-probe participants. since 2008, the  laboratory of  physical and chemical methods of  investigation of mineral substance (igg ub ras) has been taking part in the g-probe programme. the laboratory has all of the listed solid geological glasses and synthetic pressed pellets, as  well as  nist srm 612 glass. the aim of the present work is to estimate the la-icp-ms analysis quality using matrix-matched calibration with g-probe samples of various composition. experimental the  following geological glasses and microanalytical reference materials were studied (table 1). la-icp-ms trace element analysis was carried out using an elan 9000 quadrupole mass spectrometer (perkinelmer) with an  lsx-500 laser ablation system (cetac, nd:yag laser with a wavelength of 266 nm). the la-icp-ms analysis algorithm included daily tuning and selection of  the  operating parameters of  the  mass spectrometer using multi-element calibration solutions followed by laser ablation, while the  elan 9000 operating condi7 tions and gas flows were adjusted in  accordance with the highest possible intensity signal at  a  minimum level of  oxides (tho/th≤0.8%) using nist 612. the isotopes analysed were: 7li, 9be, 11b, 45sc, 51v, 53cr, 55mn, 59co, 60ni, 65cu, 66zn, 71ga, 74ge, 75as,85rb, 86sr, 89y, 90zr, 93nb, 95mo, 109ag, 111cd,115in, 118sn, 123sb, 128te, 133cs, 135ba, 139la, 140ce, 141pr, 146nd, 147sm, 153eu, 157gd, 159tb, 163dy, 165ho, 167er, 169tm, 172yb, 175lu, 178hf, 181ta, 184w, 205tl, 208pb, 209bi, 232th, 238u. the following la operational parameters (table 2) were used when analysing the samples of various compositions based on the previously obtained data taking into account the specific features of rock/mineral laser evaporation [8, 9]. la-icp-ms data were acquired in runs of up to 15 analyses. each run started and ended with two data acquisitions on a calibration material. the  15  analysis limit ensured that calibration was performed on no more than about an  hourly basis, in order to monitor and correct for the drift of the inter-element sensitivities (i.e., analyte-internal standard) with time. most often, for the  quantitative laicp-ms analysis, a combination of calibration by rm and internal standardisation is used [10], when the ratio of the analyte and the internal standard intensities is taken as the analytical signal. since the addition of internal standards is not easily and routinely carried out with solid samples, naturally occurring elements are used as internal standards. these are elements that are found table 1 g-probe samples and microanalytical reference materials used for the study g-probe round number name material origin gp-5 bbm-1g basalt usgs gp-6 bnv-1g basalt nist srm 688 gp-8 sl-1g soda-lime glass corning glass works, 1976 gp-10 gp-maps calcium phosphate usgs gp-11 dva-1g diabase w-2 usgs srm gp-12 gsm-1g gabbro san marcos mountains, southern california batholith, usa gp-14 bbrz-1g basalt brp-1 srm (university of campanias, brazil) gp-15 symp-1g syenite symp-1 usgs srm gp-16 bswir-1g mid-ocean ridge basalt (morb) southwest indian range, the border of the african and antarctic plates rm maps-4* calcium phosphate with trace elements usgs mrm rm tb-1g** basalt tb-1 usgs srm (golden, colorado, usa) *used for calibration for the analysis of phosphate rock samples. **used for calibration for the analysis of silicate rock samples. 8 in both the samples and calibration material, and for which the concentrations are known in both materials [10]. the concentration of the internal standard can be obtained from an analysis using an alternative method (for example, epma, eds-sem) or from the known elemental stoichiometry when crystalline materials are analysed. often, one of the major elements serves as the internal standard containing in the sample in sufficiently large quantities (e.g. silicon for silicate rocks, calcium and phosphorus for carbonate and phosphate minerals, zirconium, hafnium for zircons, etc.). in  this case, finding the  analyte content in the sample is carried out according to the formula: ( ) ( )’ c c ’ a a as s cala cal i k i = ⋅ ⋅ (1) where ( )’ a a iss s si i i= is  the  analyte relative intensity normalised to  the  internal standard intensity in  the  sample, both background subtracted, ( )’a a iscal cal cali i i= is  the  analyte relative intensity normalised to  the  internal standard intensity the in the calibration material, both background subtracted, cacal is  the  analyte concentration in the calibration material, c cis iss calk = is the coefficient taking into account the  ratio of  the  concentrations of the internal standard in the sample (c )iss and the calibration material .(c )iscal thus, the silicate samples were analysed using a tb-1g basalt glass for calibration with internal silicon standardisation. phosphate sample was analysed using maps-4 synthetic phosphate rm for calibration and internal calcium standardisation. table 2 la and icp-ms operational parameters during the analysis of silicate and phosphate samples la parameters phosphate rocks [8] silicate rocks [9] energy, mj 0.9 0.9 frequency hz 20 20 spot diameter, microns 50 50 pulse duration, ns <10 <10 icp-ms parameters rf power 1300 w plasma ar flow rate 16 l/min auxiliary ar flow rate 1.0 l/min sample ar flow rate 1 l/min data acquisition parameters dwell time 8 ms quadrupole settling time 1.5 ms sweeps for total analysis 480 (240 for background and 240 for ablation) sweeps per reading 3 points per peak 1 total analysis time ~240 s 9 results and discussion scoring and statistical analysis in geopt is undertaken according to the iso 13528 standard relating to  statistical methods used in proficiency testing [11] based on the earlier recommendations of the iupac international harmonised protocol [12]. according to the geopt protocol [13], the results of the analysis are evaluated using z-scores in the form: z = (xi – xpt)/σpt (2) where xi is the result of the analysis of a particular laboratory, xpt is the assigned value of the element content in the test sample, σpt is the corresponding standard deviation for proficiency testing (sdpt), or target precision, based on a  geopt fitness for purpose criterion. in the g-probe programme, the values of element concentrations obtained during analysis in usgs laboratories, as well as  the  data from nist srm certificates (in case glass was fused from a standard sample), and results of  analysis of  bulk powder samples from previous rounds are taken as xpt assigned elemental content. in  the  protocol of  the  g-probe programme, a model of the standard deviation dependency on concentration is adopted as  an  σh estimate of  the  target precision in the form of the horwitz function [14]: σpt = σh = 0.02 · xpt 0.8495 (3) where the  values of  concentrations and precision should be expressed in  mass fractions (for example, 1  ppm = 10–6, 1% = 0.01); the coefficient k = 0.02 corresponds to the results of the second category of results — applied geochemistry. accordingly, a z-score outside the range ±3 implies that an  unacceptable source of bias may be present in the participant’s analytical system and that the  need for remedial action should be considered. z-scores more extreme than ±2 carry the same message to a lesser degree [13]. however, an assumption has been made by [15] that the dependency of the standard deviation on concentration in the form of the horwitz function used in the geopt programme does not take into account the main source of analytical errors due to the distribution of the component being determined in  the  sample, while determining trace elements additional errors in the measurement results contribute to  the  heterogeneity of  the  distribution. thus, the dependence σh = f(x), based on approximation by the horwitz function, is too strict for the determination of trace elements. the authors [15] have proposed the  following approximations of  the  dependency of the permissible standard deviation for high and low concentrations: s = 0.005 · xpt 0.5 if xpt > 0.1% (4) s = 0.035 · xpt 0.8495 if xpt ≤ 0.1% (5) the results of la-icp-ms analysis and z-scores are given in supplementary table s1. the measurement result is the mean value of two measurements performed on two different sample fragments each consisting of two parallel measurements. for a number of samples studied (table  1), the  values of  the  z-scores were calculated in  accordance with the  protocol of the g-probe programme, as well as the z’ — scores using the dependency of the standard deviation for low concentrations s = 0.035 · c0.8495 (c ≤ 0.1%) since almost all the concentrations of determined elements in studied samples were less than 0.1% [15]. figure 1 shows the generalised distribution of a number trace elements depending on the z-scores (a) and the z’ — scores (b) for the samples studied. it can be seen that the results of the la-icp-ms analy10 sis of most trace elements are satisfactory, a certain amount falls outside the range ±3. when the quality assessment is performed using the  z’  — scores, a  greater number of  results are recognised as  satisfactory, and only some elements still fall outside the range ±3. most often, during la-icp-ms analysis of geological samples, a number of elements are of the greatest interest — these are the rare-earth elements (ree), yttrium, uranium, thorium and lead. to illustrate the  quality of  their analysis, z (z’) plots were constructed (fig. 2). figure  2 shows that when assessing the quality of analysis by the z’ — scores, the vast majority of the results of the determination of  ree, yttrium, uranium, thorium and lead fall within the  range not exceeding ±2 with the  insignificant number of outliers for sl-1g, symp-1g и bswir-1g, thus indicating the satisfactory results. the outliers for sl-1g and symp-1g samples can be explained by  its major element composition different from the tb-1g natural basaltic glass. sl-1g soda-lime glass contains ~71% of sio2, which is rather close to nist srm 612 glass (72% sio2). symp-1g syenite (55.3% sio2) has intermediate composition according to the igneous rock classification by silicon fig. 1. summary plots of element distribution versus z-scores (a) and z’ — scores (b) fig. 2. z (a) and z’ (b) plots for ree, y, u, th, and pb 11 dioxide content (52–63% of sio2), while all natural basaltic, gabbro and diabase glasses have mafic composition, and their silica content is generally 45–52%. thus, the difference in the composition of major elements especially if they are used as internal standards, can lead to  the  biased results. when analysing igneous rocks composed of  silicate minerals, a  careful selection of  calibration materials should be performed taking into account their composition classified by silicon dioxide content — mafic, intermediate or felsic. conclusions this study describes the  matrixmatched calibration approach to the analysis of geological samples by la-icp-ms using the  samples provided by  g-probe programme (international association of geoanalysts). a wide range of g-probe samples with the  composition of  major elements (matrix) similar to natural geological objects (silicates, phosphates and carbonates) can be used as  calibration samples especially in geoanalytical laboratories in order to correct for differences in behaviour during laser interaction and evaporation of  solid samples. the  conducted evaluation of the analysis quality for a number of geological samples using z-scores has proved that the combination of matrix-matched external calibration and internal standardisation in la-icp-ms microanalysis of rocks and minerals allows satisfactory results to be obtained for most of the determined elements. acknowledgements the study was carried out at the geoanalytic collective use centre and supported by rsf grant no. 16-17-10283. references 1. jackson se. the application of nd:yag lasers in la icp-ms. ed. p. sylvester. laser ablation icp-ms in the earth sciences: principles and applications. short course series. mineralogical association of canada. 2001;29:29–45. 2. jochum kp, stoll b, weis u, jacob de, mertz-kraus r, andreae mo. non-matrixmatched calibration for the multi-element analysis of geological and environmental samples using 200 nm femtosecond la-icp-ms: a comparison with nanosecond lasers. geostandards and geoanalytical research. 2014;38:265–92. doi:10.1111/j.1751-908x.2014.12028.x 3. o’connor c, sharp b, evans p. on-line additions of aqueous standards for calibration of laser ablation inductively coupled plasma mass 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mezhlaboratornyy kontrol’ kachestva pryamogo atomno-emissionnogo analiza s ispol’zovaniem serii gornykh porod programmy testirovaniya geoanaliticheskikh laboratoriy geopt [interlaboratory quality control of direct atomic emission analysis using the series of rock samples of geopt proficiency testing programme for geoanalytical laboratories]. analitika i kontrol’. 2005;3(9):230–9. annealing effect on temperature stability and mechanical stress at the “cdxpb1−xs film – substrate” interface 250 d o i: 1 0. 15 82 6/ ch im te ch .2 02 0. 7. 4. 20 maskaeva l. n., kutyavina a. d., pozdin a. v., miroshnikov b. n., miroshnikova i. n., markov v. f. chimica techno acta. 2020. vol. 7, no. 4. p. 250–258. issn 2409–5613 annealing effect on temperature stability and mechanical stress at the “cdxpb1−xs film — substrate” interface l. n. maskaevaab*, a. d. kutyavinaa, a. v. pozdina, b. n. miroshnikovc, i. n. miroshnikovac, v. f. markovab a ural federal university, 19 mira st., ekaterinburg, 620002, russia b ural institute of the state fire service of the emercom of russia 22 mira st., ekaterinburg, 620022, russia c national research university “moscow power engineering institute” 14 krasnokazarmennaya st., moscow, 111250, russia *email: larisamaskaeva@yandex.ru abstract. the article establishes the upper temperature steadiness limit of сdxpb1-xs supersaturated solid solutions obtained by chemical bath deposition. сdxpb1-xs (x = 0.06; 0.122; 0.176) and (x = 0.02–0.05) films remained stable under the heating up to 405– 410 and 450 k, respectively. sem studies have shown that heating of сdxpb1-xs films (x = 0.02–0.05) to 620 k leads to the structure destruction. internal mechanical compressive stresses at the “сdxpb1-xs film-substrate” interface was calculated in the range of 300–900 k for the first time ever, the highest values reached 2000–2750 kn/m2 for a number of the films compositions. in contrast to solid solutions, the expansion stresses up to 100 kn/m2 were derived for the cds layer at 900 k. the obtained temperature steadiness boundaries and the mechanical stresses of сdxpb1-xs films must be taken into account in the development of photonic devices based on such materials. keywords: chemical bath deposition (cbd); thin films; cdxpb1−xs solid solutions; annealing; mechanical stress received: 12.10.2020. accepted: 27.12.2020. published:30.12.2020. © maskaeva l. n., kutyavina a. d., pozdin a. v., miroshnikov b. n., miroshnikova i. n., markov v. f., 2020 introduction one of the most important places among photosensitive semiconductor compounds is occupied by сdxpb1‑xs substitutional solid solutions, which are used to  register visible and infrared radiation in the range of 0.4–3.0 μm. the most common areas of their practical use are the manufacture of ir detectors [1, 2], environmental control devices [3, 4], solar cells [5–7], as well as fast-response flame detectors [8]. the most effective method for the synthesis of films of cdxpb1-xs solid solutions is chemical deposition from aqueous media (chemical bath deposition cdb). during this process, layers are formed with a b1 structure that are strongly supersaturated with respect to  the  substituting component [9]. expansion of  the  temperature range of  using photonic devices based on cdxpb1-xs films presupposes a  clear 251 knowledge of the temperature boundaries of the solid solutions stability of various compositions, as  well as  their mechanical characteristics. given the  high level of  supersaturation in  chemically deposited films of cdxpb1-xs solid solutions, a significant increase in temperature can lead to  structural, morphological, and phase transformations in the layer [10], as well as the appearance of internal mechanical stresses at  the  “film  — substrate” interface [11]. the reason of their occurrence is the difference in the values of the crystal lattice constants, elastic moduli, and thermal expansion coefficients of the film and substrate. since the film and the substrate are rigidly connected to  each other, and the film is much thinner than the substrate, it can experience significant mechanical stress of compression or tension to match the geometry of the substrate [11]. even an approximate estimate of elastic stresses is important for practical application. it will make possible to qualitatively determine the  distribution of  stresses in a thin-film layer and evaluate their influence. thus, annealing of zns and znse films obtained by thermal discrete evaporation on nacl cleavages, quartz and silicon substrates, has led, in particular, to the vanishing of inclusions of the high-temperature wurtzite phase in the sphalerite matrix, to improvement of the structure and homogenization of the phase composition. in  this case, the  films heating to  200  °c for an hour has caused to the appearance of mechanical stresses in the layers, reaching approximately −170∙109 n/m2 [12, 13]. moreover, the authors of the works note that the  mechanical stresses in  the  films on the rock salt cleavage represent the expansion ones, and stresses in  the  films sedimented on quartz and silicon substrates are the  compressive ones. it was shown in  [14] that internal mechanical compressive stresses in znse films chemically deposited at 353 k are proportional to an increase in their thickness and depend on the thermal expansion coefficients of the film and substrate. in this regard, it is necessary to take into account the compatibility of the thermal expansion coefficients of the used substrates and the semiconductor layer for creating multilayer functional structures. in [15], we showed that the magnitude of  the  mechanical compressive stresses arising at the “film — substrate” interface are presumably related to various conditions of  nucleation and growth during the chemical deposition of cdxpb1-xs layers on silicon, sitall, fused quartz, ito, slide and porous glasses substrates. in this case, the magnitude of the internal elastic stresses in the layers is asymbatic to the temperature expansion coefficients for the studied substrate materials. at the same time, there are no data on temperature boundaries of stability and internal mechanical stresses in cdxpb1-xs supersaturated solid solutions films. thereby, in this work, we intend to establish the effect of annealing on the temperature stability and mechanical stresses at the “cdxpb1-xs film — substrate” interface for various phase compositions of solid solutions. experimental cdxpb1-xs (х ≤ 0.176) solid solutions films were obtained by chemical bath deposition from a  reaction mixture containing fixed concentrations of sodium citrate na3c6h5o7, an  aqueous solution of  ammonia nh4oh, and thiourea n2h4cs. 252 the  concentration of  cadmium chloride cdcl2 was varied from 0.01 to 0.1 mol/l. the content of lead acetate pb(ch3coo)2 was 0.04 and 0.06 mol/l. deposition was carried out in sealed reactors on previously degreased sitall substrates for 120 min in a ts-tb-10 thermostat at 353 k with an accuracy of maintaining the temperature of ± 0.1 k. the thickness of the obtained films was estimated using an interference microscope (linnik microinterferometer) mii-4m with a measurement error of 20%. the  degradation of  the  synthesized cdxpb1-xs (х = 0.06; 0.122; 0.176) solid solutions was studied by isothermal annealing in an argon atmosphere in the temperature range 298–673 k for 1 hour in a snol 7,2|1100l muffle furnace. in  parallel, the resistance of the cdxpb1-xs films (х = 0.02–0.05) was continuously monitored at heating from 300 to 900 k in air (rate ~ 12  k/min), followed by  slow cooling to room temperatures. the  crystal structure of  synthesized cdxpb1-xs solid solution films was studied by  x-ray diffraction method using diffractometer dron-4 with copper anode cu kα1,2. the structural and morphological characteristics of  the  as-deposited cdxpb1-xs films were studied using a mira 3 lmu scanning electron microscope at an electron beam accelerating voltage of 10 kv, and the annealed ones were investigated using a  vega ii sbu scanning electron microscope (tescan, czech republic) at  an  electron beam accelerating voltage of 20 kv. an  approximate estimate of  the  mechanical stresses σδα in the “cdxpb1-xs solid solution film — substrate” two-layer structure was carried out according to the equation proposed in [16]: ( ) ( ) ( ) cd pb s sub cd pb cd pb s cd pb s sub cd pb s 1 1 1 1 1 6 1 3 4 x x x x x x x x x x se h t h h ‑ ‑ ‑ ‑ ‑ dα ⋅ ⋅ α ‑α ⋅ ⋅d σ = ‑ν ⋅ ‑ (1) where cd pb1x x s e ‑  — young’s modulus of cdxpb1−xs solid solution; αsub, cd pb1x x s‑α  — thermal expansion coefficient of sitall substrate and film, respectively; δt  — setpoint temperature difference; cd pb1 x x s‑ ν — film poisson’s ratio; sub cd pb s1 , x x h h ‑  — thickness of substrate and films, respectively, upon condition hsub >> cd pb1x x sh ‑ . results and discussion the effect of the annealing temperature on the content of the substituent component (cadmium sulfide) in cdxpb1-xs solid solutions is shown in fig. 1, which images the equilibrium phase diagram of the cds– pbs system. cdxpb1-xs films with initial cds contents of 6.0, 12.2, and 17.6 mol.% were annealed at 403, 473, 573, and 673 k for 1 h. the layers were obtained from a reaction mixture containing 0.04 mol/l lead acetate with varying the cadmium chloride content from 0.02 to 0.1 mol/l. annealing for 1  hour at  673  k demonstrated almost complete correspondence of the composition of the annealed films to  the  equilibrium phase diagram of the pbs–cds system [17]. the obtained results confirm the supersaturated metastable character of the chemically deposited cdxpb1-xs solid solutions films (0.060 < x < 0.176). xrd studies of the annealed layers have revealed that, all samples retain diffraction reflections corresponding to the b1 structure. however, they shift to the region of smaller angles, which means an increase in the lattice period of the solid solution. in addition, the background intensity increases due to  the  formation of  an  indi253 vidual x-ray amorphous phase of  cds. at the same time, no additional reflections were detected on the xrd patterns. the established changes in the initial compositions of the cdxpb1-xs supersaturated solid solutions are a  consequence of  their decomposition into two phases: a  solid solution with a  lower cadmium content (x) and an individual cds phase. the decay indicator of the studied solid solutions is also a changing their electrophysical properties. for this purpose, we investigated the dependence of the resistance r of cdxpb1-xs films in the temperature range from 300 to 900 k (fig. 2). layers synthesized from a reaction mixture with a lead acetate concentration of 0.06 mol/l were used as  initial samples. the  initial content of cadmium chloride in the reactor was 0.01, 0.02, 0.04, 0.10  mol/l. according to  the  xrd data, the  resulting films had the compositions: cd0.02pb0.98s, cd0.03pb0.97s, cd0.04pb0.96s and cd0.05pb0.95s. as seen from fig. 2, as the temperature rises to 450 k, the films resistance decreases by about an order of magnitude. the behavior of the curves of all the films under discussion in the range of 300–450 k is approximately similar. however, a  slightly greater resistance decrease is observed for the  cd0.02pb0.98s solid solution (1) compared to other samples. it can be assumed that the  solid solution structure partial recrystallization occurs in  this temperature range. note that all the samples under study have a pronounced photosensitivity to visible and near-ir radiation. a  further temperature increase (up to 450–500 k) is accompanied by an abrupt resistance decrease by more than three orders of magnitude. in this case, the other electrophysical properties of the films also transform, the photoresponse disappears, and the  hall mobility sharply declines. the revealed effect is due to the decomposition beginning at т > 450 k of supersaturated solid solutions (b1 structure) with fig. 1. effect of the annealing temperature on the composition of cdxpb1–xs supersaturated solid solutions in the range 403–673 k and correspondence of obtained data to the equilibrium phase diagram of the cds — pbs system. initial content of cds in solid solution samples at 298 k, mol.%: 6.0 ( ), 12.2 (•), 17.6 (∇) 17.6. the duration of the annealing was 1 hour. phase equilibrium diagram of cds — pbs is given according to [17], dash line denotes extrapolated data [17] 254 separating the  individual b3 cadmium sulfi de phase from the  cdxpb1-xs crystal lattice. th e degradation of the supersaturated solid solution generally ends at t ≈ 600– 650  k.  th e  fi lm becomes two-phase, its residual resistance increases (a conductivity decreases) due to additional scattering of electrons at phase boundaries in accordance with nordheim’s rule. in  the  range 650–750 k the observed resistance increase by about an order of magnitude is a consequence of the oxidation process, fi rst of all, of lead sulfi de to the formation of oxygenated phases (pbo, pbso4) [18]. for comparison, fig. 3 shows sem images of as-deposited fi lms of solid solutions cd0.02pb0.98s (a) and cd0.04pb0.96s (c) and sem images of  these fi lms aft er heating in air to 893 k (b) and (d), respectively. it should be noted that the as-deposited fi lms morphology is  approximately the  same. th ey are diff erent only in the sizes of crystallites formed their surface: 0.4–0.6 μm for cd0.02pb0.98s and 0.4–0.8  μm for cd0.04pb0.96s. th e  annealing cd0.02pb0.98s fi lm consists mainly of 5–12 µm globules, formed by  smaller spherical particles (~ 0.50–1.0 µm). single ~ 1–2 μm crystallites are observed on its surface. fig. 3. sem images of cd0.02pb0.98s (a, b) and cd0.04pb0.96s (c, d) solid solutions fi lms before (a, c) and aft er annealing at 893 k in air (b, d). sem images of as-deposited layers were obtained using a mira 3 lmu scanning electron microscope at an electron beam accelerating voltage of 10 kv, and ones aft er annealing were received using a vega ii sbu scanning electron microscope (tescan, czech republic) at an electron beam accelerating voltage of 20 kv fig. 2. th e resistance dependence of cd0.02pb0.98s (1), cd0.03pb0.97s (2) cd0.04pb0.96s (3), cd0.05pb0.95s (4) solid solutions fi lms on the heating temperature in air 255 the cd0.04pb0.96s film globules with sizes from 4 to 20 μm are destroyed after heating to 893 k under the temperature and an increasing internal stresses. for example, structure of the film at the fig. 3d exhibits strongly deformed spherical particles or globules with broken edges. as  already noted [12, 13], annealing of  chemically deposited films even at  200  °c leads to  the  appearance of  internal mechanical stresses. therefore, in  this work, we performed a  quantitative assessment of the elastic mechanical stresses arising during annealing at  the “cdxpb1−xs film — substrate” interface according to eq. (1). the  main physical characteristics (young’s modulus e, temperature coefficient of  linear expansion tcle α, poisson’s ratio ν) of the cdxpb1−xs multicomponent compound films were determined by  the  additive change properties rule of  pbs and cds for each composition of  the  solid solution [16]. the  values of  physical characteristics for cdxpb1−xs solid solutions films and individual lead and cadmium sulfides with the indication of their thickness are given in table 1. as noted by many researchers, tcle differences between the film and the substrate plays decisive role in the occurrence of mechanical stresses in such systems. note that the temperature expansion coefficients values for the  synthesized compounds (table  1) change insignificantly: from 18.2·10−6  k−1 to  18.7·10−6  k−1. the  tcle of the sitall substrate is 5.0·10−6 k−1, and its thickness is 0.51 mm that are used for mechanical stresses calculating arising at the “film — substrate” interface. fig.  4 plots a  quantitative estimate of  elastic mechanical stresses at  the  “cdxpb1−xs solid solution film  — sitall substrate” interface for the temperature range 300–900  k.  the  calculation have taken into account the composition x and the layer thickness h. the thickness altered from 690 to 920 nm. for comparison, the figure also shows the temperature dependences of mechanical stresses arising in individual sulfides pbs and cds. as  seen from fig.  4, mechanical stresses in  the  discussion films increase with increasing temperature. nevertheless, the cds film does not practically has the mechanical stresses at 350–400 k temperature range. and upon reaching 900 k, insignificant expansion stresses 100 kn/ m2 are established. the reason of this fact is practically equal the tcle of substrate table 1 young’s modulus е, linear thermal expansion coefficient α, poisson’s ratio ν, thickness h of pbs, cds and cdxpb1−xs solid solution films parameter film pbs cd0.02pb0.98s cd0.03pb0.97s cd0.04pb0.96s cd0.05pb0.95s cds young’s modulus, e. 10−10, pa 7.02 6.96 6.94 6.91 6.88 4.20 linear thermal expansion coefficient, α∙106, k−1 19.0 18.7 18.5 18.3 18.2 2.5 poisson’s ratio, ν 0.280 0.282 0.283 0.284 0.285 0.380 films thickness, h, nm 400 740 690 920 870 360 256 and of cadmium sulfide (tcle of substrate is only 1.25 times greater than cds tcle). as  for the  film of  individual lead sulfide and solid solutions films based on pbs, elastic compressive stresses are created in them, that evidenced by the negative temperature dependences σ = f (t) in fig. 4. the  absolute value of  mechanical stresses of  these films increases with an increasing the annealing temperature from 350 to  893  k.  compressive stresses rise in absolute terms from about 200 to 1200 kn/m2 for pbs and from 150–250 to 2000–2750 kn/m2 for cdxpb1−xs under these conditions. the ambiguous change of this characteristic with the composition of the solid solution requires attention. it would seem that the mechanical compressive stresses of the cdxpb1−xs films should be lower with a cadmium content increasing due to  their partial compensation by  the  expansion stresses (the  contribution of cds). however, a more pronounce compressive stresses growth is  observed in the film of the cd0.02pb0.98s solid solution (4) compared with cd0.04pb0.96s (6). the reason of that case may be larger layer thickness of film with the cds content х = 0.04 (920 nm vs 740 nm). this is probably why crystallites just melted with the formation of  globules in  the  cd0.02pb0.98s layer at 893 k (fig. 3b), while there was a radical destruction of similar globular formations in the cd0.04pb0.96s film (fig. 3d). the increasing layer thickness by a factor of 1.25 led the rise of internal mechanical stresses by  1.5 times. the  same effect of  the  deposited film thickness on the magnitude of mechanical stresses was discovered for zinc selenide [14]. the  strong cracking of the znse film occurred due to compressive stresses at the site of globules adhesion formed it. conclusions we determined the upper temperature stability limit of chemically deposited films of сdxpb1-xs. it is in the range of 405–410 k for cds content (x) in supersaturated solid solutions equal to 0.06, 0.122 and 0.176, and about 450 k for x from 0.02 to 0.05, refig. 4. elastic mechanical stresses dependence in the systems “film — sitall substrate” on the annealing temperature in air for cds(1), pbs (2), cd0.03pb0.97s (3), cd0.02pb0.98s (4), cd0.05pb0.95s (5), cd0.04pb0.96s (6) films 257 spectively. solid solutions decompose into two phases at higher temperatures: a solid solution with the  equilibrium cadmium sulfide content at  the  given temperature and x-ray amorphous cds. the  quantitative assessment of internal mechanical stresses caused by annealing of сdxpb1-xs films was carried out for the first time ever in the range of 300–900 k. it is shown that the mechanical stresses at the “сdxpb1-xs film  — sitall substrate” interface increase with annealing temperature. thus, the compressive stresses under these conditions increase in  absolute terms from 150–250 to 2000–2750 kn/m2 depending on the composition of the solid solution. acknowledgements the  research was supported by  rfbr, projects no. 20-48-660041r_a and no. 18-29-11051mk, and was carried out within the state assignment of ministry of science and higher education of the russian federation (theme no. н687.42б.223/20). references 1. nichols pl, liu z, yin l, turkdogan s, fan f, ning cz. cdxpb1–xs alloy nanowires and heterostructures with simultaneous emission in  mid-infrared and visible wavelengths. nano lett. 2015;15:909–16. doi:10.1021/nl503640x 2. ahmada sm, kasima sj, latif la. effects of thermal annealing on structural and optical properties of nanocrystalline cdxpb1–xs thin films prepared by cbd. jordan journal of pharmaceutical sciences. 2016; 9:113–22. 3. zarubin iv, markov vf, maskaeva ln, zarubina nv, kuznetsov mv. 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grytsiv vi. diagrammy sostoyaniya v poluprovodnikovom materialovedenii : (sistemy na osnove khal’kogenidov si, ge, sn, pb) [state diagrams in semiconductor materials science : (systems based on si, ge, sn, pb chalcogenides)]. moscow: nauka; 1991. 368 p. russian. 18. kitaev ga, protasova lg, kosenko vg, markov vf. oxidation of chemically precipitated lead sulfide. inorganic materials. 1993;29:2017–8. 19. marvin jw. handbook of laser science and technology. crc press llc; 2003. 499 p. using the mineral component of building refuse in heavy metals sorption from their mixture chimica techno acta letter published by ural federal university 2021, vol. 8(1), № 20218112 journal homepage: chimicatechnoacta.ru doi: 10.15826/chimtech.2021.8.1.12 1 of 5 using the mineral component of building refuse in heavy metals sorption from their mixture v.m. yurk ab , o.b. zaytsev b , a.v. zaytseva b , n.a. malahova a a: ural federal university named after the first president of russia b.n. yeltsin, institute of chemical engineering, 620002, 19 mira st., ekaterinburg, russia b: ecology development of business (ekologiia razvitiia biznesa (erbi llc)), 620144, 195 moskovskaya st., ekaterinburg, russia * corresponding author: v.yurk@yandex.ru this short communication (letter) belongs to the mosm2020 special issue. © 2021, the authors. this article is published in open access form under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). abstract the sorption properties of the sand-breakstone mixture based on the mineral component of building refuse of the 0-10 mm fraction with respect to pb 2+ , zn 2+ , cu 2+ , ni 2+ , cd 2+ and hg 2+ ions were studied using atomic absorption spectroscopy. the mechanisms of accumulation of heavy metal ions on the surface of the mixture particles are described. it was found that after washing the contaminated material distilled water, the residual concentration of metals in the filtrate does not exceed the established sanitary and hygienic standards. the practical value of the work lies in the possibility of applying the results in reclamation of technogenic formations or production of materials for the technical stage of reclamation using technogenic soils. keywords contamination heavy metal building refuse soil pollution received: 03.11.2020 revised: 25.12.2020 accepted: 25.12.2020 available online: 16.04.2021 1. introduction the heavy metal pollution of the environment is a serious problem nowadays. soils nearby to plant facilities and industrial dumping sites are the most intensively affected by this type of exposure. the forming of geochemical barriers is a prospective way to prevent heavy metal migration in polluted soils and to protect ground water. in accordance with contemporary conceptions a geochemical barrier is an open, non-equilibrium, dynamic and selforganizing system with a quantity of factors conditioning a contaminant fixation [1,2]. thus, the investigation, description and modelling of geochemical barriers is really important. various materials are used to create artificial geochemical barriers. a choice of its components depends on pollutant properties and economic feasibility. at present, mining waste [3], organoclay [4], farm waste [5,6] have been proposed as basic materials for artificial geochemical barriers. however, the use of mineral part of the building refuse for that is of interest of soils tilling from heavy metals. the ability of building refuse to sorb heavy metal ions has been proved by a lot of studies. such barriers belong to physicochemical ones because ions fixation generally arises from coordination bond formation between metals and functional groups of barrier particles surface. also, it was reported [7] that basic properties of building refuse which cause a high receptivity are capillary pores and silicon and calcium minerals in the composition. the adsorption capacity of calcium-containing materials (concrete, foam concrete or brickbats) under dynamic conditions reaches 2.3 mg/g [8]. recent studies have shown that the dynamic capacity of building refuse is comparable to the capacity of most synthetic sorbents [9,10]. so, this type of waste is more attractive for geochemical barriers formation because of abundance and availability at low cost. also, calcium-containing materials have an alkaline reaction in water solution; therefore they can be used for soils disoxidation or neutralization of acidic tails. for example, calcium aluminate cement is good for reliable encapsulation and effective sorption of pb 2+ , zn 2+ and cu 2+ [11] and cd 2+ , mn 2+ , ni 2+ , fe 2+ , cr 2+ [12]. concrete has great geoecoprotective properties for protection of soil from radionuclides [13] and sulfide-rich tailings [3]. in [14], a concrete geoprotective embankment along the railroads to prevent contamination of adjacent soils with iron was proposed, and the paper [9] presents the recommendation to use of shungite-containing crushed stone waste for these purposes. the authors of [15,16] developed a model of a multilayer geochemical barrier based on flask, clay, and kaolin accumulating hg, pb, fe, and cs ions, as well as zn, cd, and cu. thus, the analysis of the literature data allows us to conclude that the use of building refuse as a raw material http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2021.8.1.12 http://creativecommons.org/licenses/by/4.0/ chimica techno acta 2021, vol. 8(1), № 20218112 letter 2 of 5 for the production of a geochemical barrier to the migration of heavy metal ions is promising. however, most of the adsorption studies have considered fixation of only one type of metal ions at once. actually, one has to deal with media containing more than one pollutant. the available information does not allow to estimate the geoprotective potential of the building refuse in multicomponent systems, which soils are. the results of our statistical study of soil contamination in the sverdlovsk region of russian federation [17] showed that four-five metals can be observed in contaminated soil at the same time. the present work belongs to the series of our studies on the development of a geochemical barrier based on building refuse for the reclaiming of industrial lands. the article presents the results of sorption studies of heavy metal ions from their mixture. 2. experimental 2.1. materials the building refuse used in this study was composed of cement, concrete, firebrick, sand, hardened building mortar and other building materials. cement and concrete composed a big part of this mixture. before we examined this building refuse, it had been prepared at first. utilizable components such as metal and wood ones were removed. after that, it was ground on a crusher. the basis of the derived sand-breakstone compound was a sand fraction with a particle size of up to 10 mm, the grain-size composition of which are shown in fig. 1. 2.2. sorption batch experiment the model solutions contained ions of heavy metals: lead, cadmium, zinc, copper, mercury and nickel. sorption of heavy metals from their nitrate solution was studied in static conditions. a 30 g of sand-breakstone mixture was put into a 250 ml cylindrical glass funnel and filled up by 30 ml of a model solution. this suspension was kept for seven days at 25 °c. after that the supernatant was filtered to analyze metal ions concentration. to determine fig. 1 the grain-size composition of sand-breakstone compound based on building refuse residual metals (pb, zn, cu, ni, hg and cd) concentrations, the atomic absorption spectrometry (aas) was used. for determination of capability of sand-breakstone mixture to hold fixed metal ions on a surface of its particles, the batch experiment was carried out in dynamic conditions. distilled water was leaked through a layer of building refuse mixture saturated by heavy metals. eluates were collected at every 100 ml and the residual metals concentrations were determined by aas (aa-7000, shimadzu, japan). 3. results and discussion the laboratory studies of the sorption properties of the sand-gravel mixture were carried out in an aqueous medium. this approach allows us to evaluate the full adsorption capacity of the material and its geoprotective properties. moreover, moisture is always present in the soil and the migration of heavy metal ions occurs with its active participation. therefore, the obtained data can be successfully adapted for use in soils. determining the initial concentration of metals in model solutions, we used the statistical data on soil pollution obtained by analyzing the ecological engineering surveys of capital construction objects in which erbi llc took part for 2015-2018. the sampling was carried out mainly on sites in yekaterinburg and the sverdlovsk region and included soils with the “extremely dangerous” category of pollution. these soils must not be used in any way and have to be neutralized. the model solution of the experiment 1 contained a concentration of metal ions, which corresponds to their maximum content in contaminated soils of the “extremely dangerous” category, discovered during engineering surveys of various sites for construction projects in yekaterinburg. one should bear in mind that soils in industrial areas can be exposed to increased anthropogenic pollution, as a result of which the heavy metals concentrations in them can exceed the values being detected during engineering surveys. such soils are also classified as “extremely dangerous” and must be utilized. the ability of a sandbreakstone mixture to exhibit geoprotective properties under these conditions were estimated in the experiment 2. also, as a result of various emergency situations, spills of reagents containing metal compounds on the soil may occur, contributing to their extreme pollution. material properties in the conditions of emergency soil contamination were evaluated during the experiment 3. the initial data on the metals concentrations in model solutions in accordance with the situations described above are presented in table 1. the ability of sand-breakstone mixture to sorb heavy metals was assessed in aqueous solutions because due to the dissolution processes, the ability to migrate to lower chimica techno acta 2021, vol. 8(1), № 20218112 letter 3 of 5 layers of the soil and further to aquifers increases in moisture medium. so, the most unfavorable environmental conditions for each of the considering situations were simulated, since in the experiments all metals are in their most mobile form, while under natural conditions the proportion of the mobile form of metals is far from 100% of the total content. the results of the sorption of heavy metals by the studied building refuse mixture modeling various levels of environmental pollution are shown in table 2. the experimental results demonstrate a high sorption activity of building refuse to all heavy metal ions presented in the model solutions. the sorption efficiency for each element in all experiments exceeds 99%. the adsorption capacity of cadmium is better because a minimal concentration of it in the filtrate is observed. the decrease in the residual concentration of metals in the filtrate with an increase in their concentration in the model solution has been noticed. this phenomenon can be explained by the alkaline reaction of an aqueous solution and leaching of calcium ions into the solution. as a result of calcium hydrolysis, ca(oh)2 particles are formed in solution. also, hydrolysis of metal salts occurs in the alkaline medium and a sol of the corresponding hydroxides is formed. the growth of the metals concentrations in the model solution increases the amount of hydrosol in the solution. joining to the particles of the material, it provides additional fixation of free metal ions from the solution that increases the purification efficiency of the process. in addition, ca(oh)2 and cao particles act as links which are capable to sorb metal hydroxide molecules on its surface and to agglomerate it. an indirect confirmation of the implementation of such mechanisms is the formation of a loose precipitate over the surface of the studied material, observed throughout the process. the metal hydroxides formation in soils and their transition from a mobile to a fixed form (hydroxide formation) begins at ph > 5.5 for lead and > 7.5 for other metals [18]. the ph value in the filtrates after the sorption process in all experiments was 11.5-12.0. therefore, most of the contaminants were in the meohn form after sorption. the mechanisms of metals interaction with the surface of the sorbent particles leading to their accumulation can be represented by the following reactions: 3сao∙sio2 + 2h2o + me 2+ → → meo∙sio2 + 2me(oh)n + ca 2+ (1) cao∙sio2∙h2o + me n+ + h2o → → me(oh)n + sio2∙h2o + ca 2+ (2) cao∙sio2∙h2o + me 2+ → meo∙sio2∙h2o + ca 2+ (3) 2сao∙sio2∙h2o + me 2+ + h2o → → meo∙sio2∙h2o + ca(oh)2 + ca 2+ (4) 2(2сao∙sio2∙h2o) + 3me 2+ + 2h2o → → meo∙sio2∙h2o + сao∙sio2∙h2o + 2me(oh)n + 3ca 2+ (5) 3сao∙sio2 + 2h2o → 2cao∙sio2∙h2o + ca(oh)2 (6) the mechanisms of heavy metals sorption demonstrate how the geochemical barrier based on the building refuse acts to prevent the migration of pollutants into deeper soils layers. however, it is necessary to bear in mind that soils are dynamic systems there are the processes of substance migration, such as aqueous solutions of organic components and inorganic compounds, continuously occur. water influences the migration of many elements and since the sorption of metal ions on the surface of silicon, calcium and magnesium-containing materials is a reversible process, (me n+ )sol ↔ (me n + )sorb, under corresponding conditions it washes out some of the ions being passed by the geochemical barrier. so, experiments to determine the ability of a sandbreakstone mixture to retain heavy metal ions adsorbed on the surface of its particles in dynamic conditions were carried out. the results of the studies for each sample are shown in fig. 2 as a dependence of the total content of metal ions in filtrates depending on the volume of water having passed through the sorbent layer. fig. 3 shows similar relationships for each metal in the mixture. as can be seen from the presented data, a small part of the metals was washed out from the surface of the particles. the total metal content in the filtrate did not exceed 1 mg/l, at that the highest concentration was typical for zinc, lead and mercury. the best resistance to leaching was possessed by cadmium ions, whose presence in the filtrate was practically not detected. fig. 2 the dynamics of leaching of sorbed metal ions (total) from contaminated material table 1 initial concentrations of metal ions in model solutions experiment № metals concentrations, mg/l pb zn cd cu ni hg 1 1888.17 1965.68 401.83 3773.37 3326.04 32.07 2 2454.62 2555.38 522.38 4905.38 4323.85 41.69 3 3191.00 3322.00 679.10 6377.00 5621.00 54.20 chimica techno acta 2021, vol. 8(1), № 20218112 letter 4 of 5 table 2 residual concentrations of heavy metals in filtrate after sorption experiment № concentrations of metal ions in filtrate, mg/l pb zn cd cu ni hg 1 0.57 0.165 0.0017 0.633 0.12 0.006 2 0.08 0.138 0.0022 0.299 0.13 0.02 3 0.05 0.041 0.0010 0.074 0.06 0.031 fig. 3 the dynamics of leaching of each sorbed metal ions from contaminated material it should be noted that there was no relationship between the initial concentration of metals in model solutions and the ability of particles of the sand-breakstone mixture to retain it. so, we can conclude that the strength of the adsorption depends on most of all the nature of the sorbent and the degree of affinity of elements to its surface, and to a lesser extent of concentration. it is known that sorption of cd ions on the surface of calciumcontaining materials most often occurs by the mechanism of ion exchange [16], which increases the strength of their retention. the remaining metals can be bound by the mineral part of the building refuse through chemisorption and surface deposition. such bond is less strong, since metals in hydrolyzed forms can change back to the mobile form when the external conditions of the process change. thus, part of the retained metals can enter the environment. metals are washed out in a mobile form capable of the migration. using the sand-breakstone mixture as a geochemical barrier, some of them will be accumulated by the organic matter of the soil. in order to assess the possible contamination of the underlying soils and the effectiveness of the barrier on the basis of the proposed sandbreakstone mixture, a comparison of the concentrations obtained with the sanitary and hygienic standards working in the russian federation was carried out. the maximum permissible concentration (mpc) values for acid soils were taken because of the most stringent values. a comparative analysis of the equilibrium concentrations of metals in the filtrates after washing the contaminated mixture with standard values mpc showed that their content did not exceed 0.01 part of mpc. consequently, using the sand-breakstone mixture for reclamation of contaminated areas or mixed with contaminated soil will prevent the migration of pollutants to lower soils and underground horizons. 4. conclusions thus, the present study shows the possibility of using the sand-breakstone mixture based on building refuse as geochemical barriers for the reclamation of technogenic formations, quarries, planning the territory. an analysis of the results showed a high sorption activity of the material to a mixture of heavy metals containing ions of lead, cadmium, nickel, zinc, copper and mercury both under static sorption conditions and in dynamic modeling conditions for soil filtration by surface runoff. the material studied in the work can be used during reclamation independently, or as a 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regional ecology. 2015;6(41):52-7. doi:10.30694/1026-5600-2019-1-5-12 17. azmatova e, myakisheva a, tashkinova i. theoretical and experimental justification of using construction and demolition wastes for disturbed areas rehabilitation. pnrpu bulletin, applied ecology. urban development. 2016;31:110-25. doi:10.15593/2409;5125/2016.03.08 18. nevedrov np, procenko ep, balabina ip, fomina mju. tjazhelye metally v pochvah goroda: zagrjaznenie i remediacija [heavy metals in city soils: pollution and remediation]. moscow: ru-science; 2017. 120 p. russian. https://doi.org/10.1016/0883-2927(86)90088-0 https://doi.org/10.1007/s12665-014-3099-7 https://doi.org/10.1180/minmag.2012.076.7.05 https://doi.org/10.1016/j.clay.2016.11.024 https://doi.org/10.1016/j.biortech.2013.08.124 https://doi.org/10.1002/clen.201100118 https://doi.org/10.1016/j.conbuildmat.2016.02.054 https://doi.org/10.1016/j.jhazmat.2013.04.048 https://doi.org/10.1016/j.proeng.2015.08.171 https://doi.org/10.1016/j.jenvrad.2013.04.009 https://doi.org/10.30694/1026-5600-2019-1-5-12 https://doi.org/10.15593/2409;5125/2016.03.08 composite materials based on dental acrylic plastic and chimica techno acta letter published by ural federal university 2021, vol. 8(4), № 20218413 eissn 2411-1414; chimicatechnoacta.ru doi: 10.15826/chimtech.2021.8.4.13 1 of 3 composite materials based on dental acrylic plastic and chitosan l.a. yakovishin * , e.v. tkachenko sevastopol state university, 299053 university st., 33, sevastopol, russia * corresponding authors: chemsevntu@rambler.ru this short communication (letter) belongs to the mosm2021 special issue. © 2021, the authors. this article is published in open access form under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). abstract chitosan and poly(methyl methacrylate) (pmma) composites were synthesized by polymerization with heating and mechanochemical method. the obtained polymer composites were analyzed by the atr ft-ir spectroscopy method. the presence of intermolecular hydrogen bonds and hydrophobic interactions in formation of pmma and chitosan polymer composites was shown. keywords polymer composites poly(methyl methacrylate) chitosan ft-ir spectroscopy received: 03.11.2021 revised: 16.12.2021 accepted: 16.12.2021 available online: 17.12.2021 1. introduction new composites are currently being actively studied [1–3]. such materials may be promising for use in various fields of medicine. for example, composite materials are widely used in modern dentistry [1]. poly(methyl methacrylate) or poly(methyl 2-methylpropenoate) (pmma) is one of the most important polymers in industry and medicine [1, 4]. pmma is widely used in dentistry practice for the fabrication of dentures [4]. on the basis of pmma, heat-curing acrylic resins for removable prostheses, cold-curing resins for frameworks and self-curing resins for denture repairs and for custom trays have been developed [5, 6]. however, pmma can have a toxic effect on the human body, which is accompanied by allergic reactions and impaired oral microflora [7]. polysaccharide chitosan is used for obtaining new biomedical materials [8, 9]. chitosan has antitumoral, antioxidative, bacteriostatic and fungistatic properties [8]. earlier, various composites of chitosan with gelatin [10], clay [9] and other substances were prepared. in addition, a block copolymer of chitosan with pmma was obtained [11]. this article is devoted to the preparation of composite materials based on pmma and chitosan. 2. experimental low-molecular water-soluble chitosan (freeze-dried powder; purity 88.4%; molecular weight 1–30 kda) was purchased from bioprogress (russia). the source of pmma was the villacryl h plus (zhermack s.p.a., poland). 2.1. preparation of composites preparation of composite 1. 1 g of chitosan and 1 g of villacryl h plus were stirred for 1 min, 0.44 ml of pmma monomer was added to the resulting mixture, stirred for 10 min at room temperature, and heated at 60 °c for 60 min. preparation of composite 2. 1 g of chitosan and 1 g of villacryl h plus were stirred for 1 min, 0.44 ml of pmma monomer was added to the resulting mixture, stirred for 10 min at room temperature and heated at 60 °c for 30 min. then the temperature was raised to 100 °с and the mixture was heated for another 30 min. preparation of composite 3. 1 g of chitosan and 1 g of villacryl h plus were grinded in an agate mortar for 120 min. to the resulting mixture was added 0.44 ml of pmma monomer, stirred for 10 min at room temperature and heated at 60 °c for 30 min. then the temperature was raised to 100 °c and the mixture was heated for another 30 min. the powders of the obtained composites were cooled to room temperature and investigated by the ft-ir spectroscopy method. the ir spectra were recorded on the simex fт801 ir-fourier spectrometer (russia) in the 4000–550 cm–1 region (spectral resolution 4 cm–1; 25 scans) using the atr accessory with diamante crystal plate. photos of the composites were obtained using the atr accessory with builtin lens (simex, russia) at 60x magnification. http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2021.8.4.13 https://orcid.org/0000-0002-8728-7950 https://orcid.org/0000-0002-7041-5792 http://creativecommons.org/licenses/by/4.0/ chimica techno acta 2021, vol. 8(4), № 20218413 letter 2 of 3 2.2. ir spectra ir spectrum of pмма (, cm–1): 2998 (сн), 2948 (сн), 2853 (сн), 1719 (с=о), 1474 (сн), 1458 (сн), 1432 (сн), 1387 (сн), 1364 (сн), 1322 (сн), 1268 (с–о–с), 1237 (с–о–с), 1188 (со–о–сн3, сн), 1140 (с–о–с), 1059 (с–о–с), 984 (с–с), 962 (с–с), 912 (сн), 839 (сн), 809 (с=о), 747 (с=о, сн), 692 (сн). ir spectrum of chitosan (, cm–1): 3310 (он, nh), 2869 (сн), 2836 (сн), 1655 (c=oamid i), 1619 (nh2), 1609 (nh2), 1602 (nh2), 1543 (n–h+с–namid ii), 1516 (n–h+с–namid ii), 1509 (n–h+с–namid ii), 1501 (n–h+с–namid ii), 1489 (сн), 1474 (ch), 1418 (сн), 1379 (сн), 1339 (ch), 1317 (n–h+с–namid iii, ch), 1260 (c–o–c, oh, с–n), 1244 (c–o–c, c–oh), 1149 (c–o–c, c–oh), 1057 (c–o–c, c–oh), 1015 (c–o–c, c–oh), 995 (c–o–c, c–oh, с–с), 889 (ch), 720 (nhamid v), 679 (nh2), 661 (oh), 635 (ch), 617 (o=c–namid iv), 603 (ch), 567 (nh, co). ir spectrum of composite 1 (, cm–1): 3297 (он, nh), 2989 (сн), 2948 (сн), 2888 (сн), 2836 (сн), 1731 (с=оpmma), 1715 (с=оpmma), 1654 (c=oamid i), 1636 (nh2), 1623 (nh2), 1610 (nh2), 1558 (nh2), 1542 (n–h+с–namid ii), 1517 (n–h+с–namid ii), 1508 (n–h+с–namid ii), 1488 (сн), 1474 (сн), 1451 (сн), 1433 (сн), 1418 (сн), 1397 (сн), 1387 (сн), 1379 (сн), 1363 (сн), 1339 (ch), 1318 (n–h+с–namid iii, ch), 1296 (сн), 1268 (с–о–с, oh, с–n), 1239 (с–о–с, c–oh), 1188 (со–о–сн3, сн), 1145 (с–о–с, c–oh), 1086 (с–о–с, c–oh), 1060 (с–о–с, c–oh), 1034 (c–o–c, c–oh), 1012 (c–o–c, c–oh), 991 (c–o–c, c–oh, с–с), 966 (с–с), 943 (сн), 838 (сн), 812 (с=о), 747 (с=о, сн), 720 (nhamid v), 686 (ch), 679 (nh2), 660 (oh), 636 (ch), 618 (o=c–namid iv), 602 (ch), 572 (сh), 558 (nh, co). ir spectrum of composite 2 (, cm–1): 3247 (он, nh), 2996 (сн), 2947 (сн), 2865 (ch), 1732 (с=оpmma), 1716 (с=оpmma), 1698 (с=оpmma), 1647 (c=oamid i), 1636 (nh2), 1623 (nh2), 1617 (nh2), 1609 (nh2), 1557 (nh2), 1541 (n–h+с–namid ii), 1522 (n–h+с–namid ii), 1507 (n–h+с–namid ii), 1497 (n–h+с–namid ii), 1489 (сн), 1473 (сн), 1456 (сн), 1435 (сн), 1419 (сн), 1396 (сн), 1387 (сн), 1374 (сн), 1362 (сн), 1339 (ch), 1319 (n–h+с–namid iii, ch), 1268 (с–о–с, oh, с–n), 1241 (с–о–с, c–oh), 1186 (со–о–сн3, сн), 1141 (с–о–с, c–oh), 1090 (с–о–с, c–oh), 1060 (с–о–с, c–oh), 1028 (c–o–c, c–oh), 1012 (c–o–c, c–oh), 985 (c–o–c, c–oh, с–с), 968 (с–с), 905 (сн), 839 (сн), 807 (с=о), 747 (с=о, сн), 720 (nhamid v), 696 (ch), 681 (nh2), 650 (oh), 617 (o=c–namid iv), 601 (ch), 572 (сh), 562 (nh, co). ir spectrum of composite 3 (, cm–1): 3239 (он, nh), 3031 (сн), 2993 (сн), 2951 (сн), 2801 (сн), 1720 (с=оpmma), 1655 (c=oamid i), 1638 (nh2), 1627 (nh2), 1619 (nh2), 1610 (nh2), 1561 (nh2), 1542 (n–h+с–namid ii), 1523 (n–h+с–namid ii), 1509 (n–h+с–namid ii), 1499 (n–h+с–namid ii), 1474 (сн), 1458 (сн), 1449 (сн), 1432 (сн), 1419 (сн), 1396 (сн), 1387 (сн), 1376 (сн), 1365 (сн), 1338 (ch), 1323 (n–h+с–namid iii, ch), 1297 (сн), 1267 (с–о–с, oh, с–n), 1239 (с–о–с, c–oh), 1185 (со–о–сн3, сн), 1139 (с–о–с, c–oh), 1102 (с–о–с, c–oh), 1082 (с–о–с, c–oh), 1062 (с–о–с, c–oh), 1029 (c–o–c, c–oh), 1016 (c–o–c, c–oh), 987 (c–o–c, c–oh, с–с), 961 (с–с), 917 (сн), 838 (сн), 814 (с=о), 798 (сн), 780 (сн), 747 (с=о, сн), 723 (nhamid v), 694 (ch), 684 (nh2), 654 (oh), 620 (o=c–namid iv), 607 (ch), 573 (сh), 561 (nh, co). 3. results and discussion composites of chitosan and pmma were obtained by in situ polymerization with heating at different temperatures (fig. 1). to obtain composite 3, mechanochemical activation was preliminarily carried out by grinding chitosan and pmma powders for 120 min. the source of pmma was the villacryl h plus heat-curing acrylic resin for denture bases [6]. the resulting composites were analyzed by atr ft-ir spectroscopy. it is often used to research composite materials [10]. a b fig. 1 photo of the pmma-chitosan composite 3 (a) and atr ft-ir spectra of pmma, chitosan and pmma-hitosan composite 3 (b) chimica techno acta 2021, vol. 8(4), № 20218413 letter 3 of 3 the ir spectra of chitosan and pmma composites show low-frequency shifts of the absorption band of stretching vibrations of о–н and n–h bonds in chitosan from 3310 cm–1 to 3297 cm–1 (for composite 1), to 3247 cm–1 (for composite 2) and to 3239 cm–1 (for composite 3; fig. 1). such changes in the spectra confirm the formation of hydrogen bonds. in addition, ir spectra of composites 1–3 show certain changes related to the absorption bands of stretching vibrations of с–о bonds in с–о–с and с–он groups, as well as to the in-plane bending vibrations of о–н bonds in chitosan: 12601268, 12441239, 11491145, 10571060, 10151012, 995991 cm–1 (for composite 1), 12601268, 12441241, 11491141, 10571060, 10151012, 995985 cm–1 (for composite 2), and 12601267, 12441239, 11491139, 10571062, 995987 cm–1 (for composite 3). in this case, the most significant shifts were noted for the composites 2 and 3. the main absorption band of c=o stretching vibrations in pmma ester bond was found at 1715 cm–1 (composite 1), at 1716 cm–1 (composite 2) and at 1720 cm–1 (composite 3). moreover, additional bands are observed at 1698 and 1732 cm–1 (for composite 1), and at 1731 cm–1 (for composite 2). the presence of low-frequency shifts in the ir spectra is indicative of involving с=о group of pmma in hydrogen bonding with chitosan. high-frequency shifts of some absorption bands of inplane bending vibrations of n–h bonds in the chitosan molecule are observed in the spectra of composites: 16021610 cm–1 (for composite 1), 16021609 cm–1 (for composite 2), 16231627 cm–1 (for composite 3). in addition, the ir spectra show shifts of the main absorption bands of stretching vibrations of ch bonds, which can be caused by hydrophobic interactions during the formation of composites. 4. conclusions polymer composites of pmma and chitosan were obtained by polymerization with heating and mechanochemical method. the composites 1–3 are formed due to hydrogen bonds (c=opmma…h–ochitosan and c=opmma…h–nhchitosan) and hydrophobic interactions. it is possible that the presence of chitosan in composite materials can change some of their mechanical properties and eliminate the toxicity of pmma. acknowledgements this study was carried out on the experimental equipment of the sevastopol state university (project pr/80742/2017). references 1. stein ps, sullivan j, haubenreich je, osborne pb. composite resin in medicine and dentistry. j long term eff med implants. 2005;15(6):641–654. doi:10.1615/jlongtermeffmedimplants.v15.i6.70 2. scharf f, mikhnevich e, safronov a. interaction of iron oxide nanoparticles synthesized by laser target evaporation with polyacrylamide in composites and ferrogels. chimica techno acta. 2017;4(2):128–139. doi:10.15826/chimtech/2017.4.2.028 3. mikhnevich ea, safronov ap, beketov iv, medvedev ai. carbon coated nickel nanoparticles in polyacrylamide ferrogels: interaction with polymeric network and impact on swelling. chimica techno acta. 2020;7(3):116–127. doi:10.15826/chimtech.2020.7.3.04 4. frazer rq, byron rt, osborne pb, west kp. pmma: an essential material in medicine and dentistry. j long term eff med implants. 2005;15(6):629–639. doi:10.1615/jlongtermeffmedimplants.v15.i6.60 5. liber-kneć a, łagan s. surface testing of dental biomaterials– determination of contact angle and surface free energy. materials (basel). 2021;14(11):2716. doi:10.3390/ma14112716 6. solutions for the dental laboratory. catalogue [internet]. zhermack s.p.a., 2019. p. 72–79. available from: https://www.zhermack.com/public/uploads/f300072_1907_catalogo_labo_en_low.pdf 7. leggat pa, kedjarune u. toxicity of methyl methacrylate in dentistry. int dent j. 2003;53(3):126–131. doi:10.1111/j.1875-595x.2003.tb00736.x 8. zargar v, asghari m, dashti a. a review on chitin and chitosan polymers: structure, chemistry, solubility, derivatives and applications. chem bio eng rev. 2015;2(3):204–226. doi:10.1002/cben.201400025 9. kusmono, abdurrahim i. water sorption, antimicrobial activity, and thermal and mechanical properties of chitosan/clay/glycerol nanocomposite films. heliyon. 2019;5(8):e02342. doi:10.1016/j.heliyon.2019.e02342 10. voron’ko n, sokolan n, kuchina y, berestova g. formation of polyelectrolyte complexes from chitosan and alkaline gelatin. kne life sciences. 2020;5(1):109–119. doi:10.18502/kls.v5i1.6031 11. smirnova nn, markin av, smirnova on, smirnov vf, knyazev av. effect of technogenic factors and biodestructive agents on the thermal behavior of chitosan and poly(methyl acrylate) block copolymer. russ j phys chem. 2020;94(6):1262–1267. doi:10.1134/s0036024420060254 https://doi.org/10.1615/jlongtermeffmedimplants.v15.i6.70 https://doi.org/10.15826/chimtech/2017.4.2.028 https://doi.org/10.15826/chimtech.2020.7.3.04 https://doi.org/10.1615/jlongtermeffmedimplants.v15.i6.60 https://doi.org/10.3390/ma14112716 https://www.zhermack.com/public/uploads/f300072_19-07_catalogo_labo_en_low.pdf https://www.zhermack.com/public/uploads/f300072_19-07_catalogo_labo_en_low.pdf https://doi.org/10.1111/j.1875-595x.2003.tb00736.x https://doi.org/10.1002/cben.201400025 https://doi.org/10.1016/j.heliyon.2019.e02342 https://doi.org/10.18502/kls.v5i1.6031 https://doi.org/10.1134/s0036024420060254 phase complex of the system na,ca||so4,co3,hco3-h2o at 100 ºc 71 d o i: 1 0. 15 82 6/ ch im te ch .2 02 0. 7. 2. 04 soliev l., jumaev m. t. chimica techno acta. 2020. vol. 7, no. 2. p. 71–80. issn 2409–5613 soliev l., jumaev m. t. tajik state pedagogical university named after s. ayni 121 prospect rudaki, dushanbe, 734003, tajikistan e-mail: soliev.lutfullo@yandex.com, jumaev_m@bk.ru phase complex of the system na,ca||so4,co3,hco3–h2o at 100 °c the article discusses the results of determining the possible phase equilibria in geometric images of a five-component reciprocal water-salt system of sulfates, carbonates, sodium bicarbonates and calcium at 100 °c with subsequent construction of its phase complex diagram. the laws that determine the structure of the phase complex diagram of this system are needed to be obtained for the production of scientific data used both as a reference material and also to create the optimal conditions for the recycling of liquid waste industrial production of aluminum-containing sulfate carbonate and bicarbonate salts of sodium and calcium. it was established that the system under study at 100 °c is characterized by the presence of 31 divariant double saturation fields, 25 monovariant trisaturation curves and 14 invariant points. keywords: translation method; phase complex diagram; geometric images received: 17.04.2020. accepted: 22.06.2020. published: 30.06.2020. © soliev l., jumaev m. t., 2020 introduction the phase diagrams for the complex systems are not only of scientific interest, but also necessary for creating optimal conditions for the galurgic processing of natural mineral raw materials and industrial wastes containing sulfates, carbonates, sodium and calcium bicarbonates [1]. the  na,ca||so4,co3,hco3-h2o system has not been studied yet at 100 °c. earlier we studied phase equilibria in this system by the translation method at temperatures of 0 and 50 °c [2, 3]. methods we have deduced phase equilibria in  the  na,ca||so4,co3,hco3–h2o system at 100 °c using translation methods [4, 5] which follows from the  principle of  compatibility of  structural elements of n and n + 1 component systems in one diagram [6, 7]. according to the translation method, the  addition of  one more component to  the  n-component system and its transition to the n + 1 component state is  accompanied by  transformation of the geometric image of the n-component system. the transformed geometric images are translated to the n + 1 level according to their topological property in accordance with the gibbs phase rule, forming correspondent geometric images (fields, curves, points) in  the  n  +  1 component system. the application of translation methods for predicting and constructing phase diagram 72 for multicomponent water-salt systems was considered in more details in our previous work [4]. earlier this method was successfully used for other multicomponent systems [8, 9]. t h e   f i v e c o m p o n e n t s y s t e m na,ca||so4,co3,hco3-h2o can be represented as  a  combination of  the  follow ing four comp onent systems: na2so4–na2co3–nahco3–h2o, caso4– caco3–ca(hco3)2–h2o, na,ca||so4,co3, – h 2 o , n a , c a | | s o 4 , h c o 3 – h 2 o , na,ca||co3,hco3–h2o. the phase equilibria of  invariant points in  these fourcomponent systems were studied earlier by the method of the multiple solubility [1, 10] and by the translational method [11– 15]. coexisted equilibrium solid phases inside the invariant four-component systems are listed in table 1. phase composition of these non-variant points was used to predict the phase equilibria and for construction of phase complex of the studied system by the translation method. in table 1 and further e denotes the invariant point, where the upper index indicates its multiplicity (the number of system’s component), and the  lower index indicates its serial number. the following notations for solid phases that were formed in the system were used: te — tenaedite, na2so4; cag  — calcium hydrocarbonat, ca(hco3)2; gp — gypsum, caso4·2h2o; nk — nakhcolite, nahco3; pr — gayluscite, na2co3·caco3·2h2o; cc — calcite caco3; na·1 — na2co3; ber — berkeite, 2na2so4·na2co3; table 1 phase composition of precipitates for the non-variant points in the na,ca||so4,co3,hco3-h2o system at 100 °c at the four-component composition level invariant points solid phase equilibrium invariant points solid phase equilibrium na2so4-na2co3-nahco3-h2o system na,ca||so4,co3-h2o system e1 4 te+nk+3na·c e10 4 te+br+gb e2 4 br+na·1+tr e11 4 5ca·na·3+gp+cc e3 4 te+br+tr e12 4 br+na·1+pr e4 4 te+tr+3na·c e13 4 gb+5ca·na·3+br system caso4-caco3-ca(hco3)2-h2o e14 4 pr+cc+5ca·na·3 e5 4 gp+cc+cag e15 4 br+pr+5ca·na·3 na,ca||so4,hco3-h2o system na,ca||co3,hco3–h2o system e6 4 nk+te+gb e16 4 na·1+tr+pr e7 4 gp+5ca·na·3+cag e17 4 pr+cc+cag e8 4 nk+cag+gb e18 4 nk+3na·c+cag e9 4 gb+cag+5ca·na·3 e19 4 tr+3na·c+pr e20 4 pr+3na·c+cag 73 tr — trona, na2co3·nahco3·2h2o; 3na·c — 3nahco3·na2co3; gb — glauberit, na2so4·caso4; 5ca·na·3 – 5caso4·na2so4·3h2o. results and discussion based on the  data listed in  table  1 the  phase diagram (phase complex) for the  na,ca||so4,co3,hco3-h2o system was constructed at  100  °c at  the  level of four component composition of the salt part, which is shown in the figure as projection of tetrahedral faces. a  unification of  the  salt part of the phase diagram (combining of identical crystallization fields of various constituent four-component systems), we obtain a schematic diagram for the phase equilibria in the na,ca||so4, co3,hco3-h2o fig. 1. projection of the salt part of the phase diagram for the na,ca||so4,co3,hco3–h2o system at 100 °c at level of the four-component composition 74 system at 100 °c at the level of four-components, which is shown in the fig. 2. the constructed diagram contains geometric images (invariant points, multi-variant curves, divariant fields) correspondent to the various states of the system under study as  a  function of  its composition at the level of four component composition. the phase compositions of the quadruple invariants are listed in table 1. the phase compositions of  the  precipitation for the divariant fields are shown in the figure. the phase composition for the monovariant curves connecting quadruple invariant are presented as follows: е1 4 е4 4 = te + 3na·c; е1 4 е6 4 = nk + te; е1 4 е18 4 = nk + 3na·c; е2 4 е3 4 = ber + tr; е2 4 е12 4 = ber + na·1; е2 4 е16 4 = tr + na·1; е3 4 е4 4 = te + tr; е3 4 е10 4 = te + ber; е4 4 е19 4 = tr + 3na·c; е5 4 е7 4 = cag + gp; е5 4 е11 4 = gp + cc; е5 4 е17 4 = cc + cag; е6 4 е8 4 = nk + gb; е6 4 е10 4 = te + gb; е7 4 е9 4 = cag + 5ca·na·3; fig. 2. the schematic diagram of phase equilibrium in the na,ca||so4,co3,hco3-h2o system at 100 °c at the level of four-component composition, constructed by the translation method 75 е7 4 е11 4 = gp + 5ca·na·3; е8 4 е9 4 = cag + gb; е8 4 е18 4 = cag + nk; е9 4 е13 4 = 5ca·na·3 + gb; е10 4 е13 4 = gb + ber; е11 4 е14 4 = gp + 5ca·na·3; е12 4 е15 4 = ber + pr; е12 4 е16 4 = na·1 + pr; е13 4 е15 4 = ber + 5ca·na·3; е14 4 е15 4 = cc + 5ca·na·3; е14 4 е17 4 = cc + pr; е16 4 е19 4 = tr + pr; е17 4 е20 4 = pr + cag; е18 4 е20 4 = 3na·c + cag; е18 4 е20 4 = 3na·c + pr. through and one-way translation procedure [4] of invariant points from the level of four component composition to the level of  five-component composition leads to the formation of the following invariant points: e1 4 + e6 4 e1 5 = nk + te + 3na·c + gb; e2 4 + e12 4 + e16 4 e2 5 = ber + na·1 + tr + pr; e3 4 + e10 4 e3 5 = te + ber + tr + gb; e4 4 + e19 4 e4 5 = te + tr + 3na·c + pr; e5 4 + e7 4 + e11 4 e5 5 = gp + cc + cag + 5ca·na·3; e8 4 + e18 4 e6 5 = nk + cag + gb + 3na·c; e9 4 + e13 4 e7 5 = gb + cag + 5ca·na·3 + ber; e14 4 + e17 4 e8 5 = pr + cc + 5ca·na·3 + cag; e15 4 + cag e9 5 = ber + pr + 5ca·na·3 + cag; e20 4 + gb e10 5 = pr + 3na·c + cag + gb; the  analysis of  phase equilibria in  the  na,ca||so4,co3,hco3-h2o system at 25 °c based on the obtained data at the level of five-component composition shows that the crystallization fields formed during the  translation of  monovariant curves of level four-component composition with their characteristic equilibrium solid phases, namely tr+pr, pr+cag, 3na·c+pr, ber+pr, gb+ber and cag+gb, do not closed for their closure by the “intermediate” translation [4] method: e11 5 = te + 3na·c + gb + pr; e12 5 = gb + ber + tr + cag; e13 5 = tr + pr + ber + te; e14 5 = pr + cag + 5ca·na·3 + gb the  displaced chart of  phase balance in  the  na,ca||so4,co3,hco3-h2o system at 100 °c the level of four-component system has been constructed taking into account all types of translations (fig. 3). bold lines indicate monovariant level curves of the five-component composition. these lines connected five various invariant points; they are characterized by the following phase composition of the precipitates: e1 5 e6 5 = nk + 3na·c + gb; e1 5 e11 5 = te + 3na·c + gb; e2 5 e12 5 = ber+ pr + tr; e3 5 e13 5 = ber+ te + tr; e4 5 e11 5 = te + pr + 3na·c; e5 5 e8 5 = cc + 5ca·na·3 + cag; e6 5 e10 5 = cag + gb + 3na·c; e7 5 e9 5 = cag + 5ca·na·3 + ber; e7 5 e12 5 = gb + ber + cag; e8 5 e9 5 = pr + cag + 5ca·na·3; e9 5 e14 5 = pr + cag + 5ca·na·3; e10 5 e11 5 = pr + 3na·c + gb; e10 5 e14 5 = pr + cag + gb. table  2 demonstrates the  solid phase equilibrium and contour of  the  divariant sodium-based system na,ca||so4,co3,hco3-h2o at  100 °c. among 31 divariant fields that characterized the  studied system at  100 °c, 30 fields are formed as a result of translation 76 of monovariant curves at the level of fourcomponent composition to  the  level of five-component composition and one more field with equilibrium solid phases gb+3na·c was obtained as  a  result of the contouring of five invariant points and monovariant curves. the  thin solid lines in  figure 3 indicate the  monovariant curves at  the  level of  four-component composition. the  equilibrium solid phases that are correspondent to these curves were presented above. dash lines with arrows (in  table  2) indicate monovariant curves at  the  level of five-component composition, they are formed as a result of translation therefore the  equilibrium phases corresponded to these monovariant curves are identical to the equilibrium solid phases of the invariant points of the corresponding quaternary systems. fig. 3. combined diagram of phase equilibria (phase complex) for the na,ca||so4,co3,hco3–h2o system at 100 °c at the level of four-component composition constructed by the translation method 77 table 2 equilibrium solid phases and contours of the divariante fields in the na,ca||so4,co3,hco3-h2o system equilibrium solid phases of fields field contours in the diagram (fig. 3) equilibrium solid phases of fields field contours in the diagram (fig. 3) 3na·c+nk e1 4 e1 5 e18 4 e6 5 cag+5ca·na·3 e7 4 e5 5 e1 5 e9 4 e2 5 e2 5 nk+te e1 4 e1 5 e6 4 cag+gb e8 4 e6 5 e14 5 e9 4 e7 5 e12 5 te+3na·c e1 4 e1 5 e4 4 e4 5 e11 5 cag+nk e8 4 e6 5 e18 4 na·1+tr e2 4 e2 5 e6 4 5ca·na·3+gb e9 4 e7 5 e13 4 na·+ber e2 4 e2 5 e12 4 gb+ber e10 4 e3 5 e12 5 e13 4 e7 5 cag+gp e2 4 e2 5 e13 5 e3 4 e3 5 gp+5ca·na·3 e11 4 e5 5 e14 4 e8 5 te+ber e3 4 e3 5 e10 4 na·1+pr e12 4 e2 5 e16 4 te+tr e3 4 e3 5 e13 5 e4 4 e4 5 ber+5ca·na·3 e13 4 e7 5 e15 4 e9 5 78 equilibrium solid phases of fields field contours in the diagram (fig. 3) equilibrium solid phases of fields field contours in the diagram (fig. 3) tr+3na·c e4 4 e4 5 e19 4 ber+pr e12 4 e2 5 e13 5 e4 5 e1 5 e15 4 e9 5 e14 5 e10 5 cc+cag e5 4 e5 5 e17 4 e8 5 cc+5ca·na·3 e14 4 e8 5 e15 4 e9 5 gp+cc e5 4 e5 5 e11 4 pr+cc e14 4 e8 5 e17 4 cag+gp e5 4 e5 5 e7 4 tr+pr e16 4 e2 5 e13 5 e19 4 e4 5 te+gb e6 4 e1 5 e11 5 e4 5 e10 4 e3 5 e13 5 pr+cag e17 4 e8 5 e9 5 e20 4 e10 5 e14 5 nk+gb e6 4 e1 5 e8 4 e6 5 3na·c+cag e18 4 e8 5 e20 4 e10 5 5ca·na·3 e7 4 e5 5 e11 4 3na·c+pr e19 4 e4 5 e11 5 e1 5 e20 4 e10 5 e14 5 e6 5 gb+3na·c e6 5 e10 5 e1 5 e11 5 end of table 2 79 conclusions the  translation method applied for the  na,ca||so4,co3,hco3-h2o system at  100 °c while transforming the  phase equilibria from the level of four-component (a) to the level of five-component (b) reveals following changes in the numbers of geometric patterns: component level a  b invariant point 20 14 monovariant curves 30 33 divariant fields 13 31 the decrease in the number of invariant points from 20 at  the  level of  fourcomponent composition to 14 at the level of  five-component composition is  due to  the  mutual combination (from mathematical approach) of quadruple invariant points, or mutual intersection of  monovariant curves (within the  graphical approach) formed during the transformation and subsequent translation of these quadruple invariant points to the level of fivecomponent composition and the formation of quintuple invariant points. the increase in the number of monovariant curves from 30 at the level of four-component composition up to 33 at the level of five-component composition is due to the fact that 20 of them are formed as a result of translation and quadruple invariant points, and another 13 connected five invariant points. the raise of components’ number by unity from four to five leads to the increase of divariant fields’ number from 13 at the level of  four-component composition to  31 at  the  level of  five-component composition. it was shown that 30 of  them were formed in a course of translation procedure of monovariant curves of the level of fourcomponent composition and one more was obtained as a result of the surface contouring in the system with five invariant points and monovariant curves connecting these points. references 1. spravochnik eksperimental’nykh dannykh po rastvorimosti mnogokomponentnykh vodno-solevykh system [reference book on experimental data for solubility in multicomponent water-salt systems]. vol. ii., books. 1–2. saint-petersburg: khimizdat, 2004. 1247 p. russian. 2. soliev l, jumaev mt. phase equilibria in the na,ca//so4,co3,hco3–h2o system at 0 °c. chimica techno acta. 2019;6(1):24. doi: 10.15826/chimtech.2019.6.1.03 3. soliev l, jumaev mt. phase equilibrium of na,ca||so4,co3,hco3-h2o systems at 50 °с. applied solid state chemistry. 2018;4(5):192–8. doi: 10.18572/2619-0141-2018-4-5-192-198 4. soliev  l. [prediction of  structure of  multicomponent water-salt systems phase equilibria diagram by means of translation method]. viniti № 8990-b87, 1987. 28 p. russian. 5. goroshenko yag, soliev l. [new trends in methodology of physicochemical analysis of complex and multicomponent systems (for 125th anniversary of n. s. kurnakov)]. zh. neorg. khim. 1987;32(7):1676. russian. 6. goroshchenko yag. masstsentricheskiy metod izobrazheniya mnogokomponentnykh system [the center of mass method for multi-component systems imaging]. kiev: naukova dumka, 1982. 264 p. russian. 80 7. tursunbadalov sh, soliev l. phase equilibria in the quinery na,k||so4,co3,hco3– h2o system at 75 °c. j solution chem. 2015;44(8):1626–39. doi: 10.1007/s10953-015-0368-3 8. tursunbadalov sh, soliev l. phas equilibria in multicomponent water-salt system. j chem eng data. 2016;61(7):2209–20. doi: 10.1021/acs.jced.5b00875 9. soliev l, jumaev мт, turaev rо, makhmadov khr. [solubility in  the  system na2so4–na2co3–nahco3–h2o at  50  °с]. chemical journal of  kazakhstan. 2017;4(60):29. russian. 10. soliev l, jumaev mt, nuri v, valantino n. phase equilibria system na,ca||so4,hco3– h2o at 25 °с. bulletin of the tajik national university (series of natural sciences). 2012;1(3)85:221. 11. s olie v l, jumae v mt, iqb ol g, nizomov im. phas e e qui libr ia in the na,ca||co3,hco3-h2o system at 25 °с. reports of the academy of sciences of the republic of tajikistan. 2012; 55(3):220. russian. 12. usmonov mb. fazovye ravnovesiya i rastvorimost’ v sisteme na,ca||so4,co3,f-h2o pri 0 i 25 °с [phase equilibria and solubility in the na,ca||so4,co3,f-h2o system at 0 and 25 °с] [dissertation]. tajik state pedagogical university; 2015. 126 p. russian. 13. valantena n. fazovye ravnovesiya i rastvorimost’ v sisteme na,ca||so4,hco3,f-h2o pri 0 i 25 °с [phase equilibria and solubility in the na,ca||so4,hco3,f-h2o system at 0 and 25 °с] [dissertation]. tajik state pedagogical university; 2016. 121 p. russian. 14. gulomiqbol g. [phase equilibria and solubility in the na,ca||co3,hco3,f-h2o system at 0 and 25 °с] [dissertation]. tajik state pedagogical university; 2018. russian. 15. soliev l. [schematic phase equilibria diagrams for multicomponent systems]. russ j inorg chem. 1988;33(5):1305. russian. influence of a binder on the electrochemical behaviour of si/rgo composite as negative electrode material for li-ion batteries 259 influence of a binder on the electrochemical behaviour of si/rgo composite as negative electrode material for li-ion batteries a. v. korchuna*, e. yu. evshchika, s. a. baskakova , o. v. bushkovaa,b, y. a. dobrovolskya a institute of problems of chemical physics of the russian academy of sciences, 1 academician semenov av., chernogolovka, moscow region, 142432, russia b institute of solid state chemistry of the ural branch of the russian academy of sciences, 91 pervomaiskaya st., ekaterinburg, russia *email: andrei_korchun@mail.ru abstract. a composite consisting of silicon nanoparticles and reduced graphene oxide nanosheets (si/rgo) was studied as a promising material for the negative electrode of lithium-ion batteries. commonly used polyvinylidene fluoride (pvdf) and carboxymethyl cellulose (cmc) served as a binder. to reveal the influence of the binder on the electrochemical behaviour of the si/rgo composite, binder-free electrodes were also prepared and examined. anode half-cells with composites comprising cmc as a binder demonstrated the best properties: capacity over 1200 mah·g–1, excellent cycling performance and good rate capability up to 1.0c. keywords: li-ion battery; negative electrode; nanocomposite; reduced graphene oxide; silicon nanoparticles received: 02.12.2020. accepted: 21.12.2020. published:30.12.2020. © korchun a. v., evshchik e. yu., baskakov s. a., bushkova o. v., dobrovolsky y. a., 2020 d o i: 1 0. 15 82 6/ ch im te ch .2 02 0. 7. 4. 21 korchun a. v., evshchik e. yu., baskakov s. a., bushkova o. v., dobrovolsky y. a. chimica techno acta. 2020. vol. 7, no. 4. p. 259–268. issn 2409–5613 introduction li-ion batteries (libs) are leading electrochemical energy storage systems among secondary batteries due to their high energy density. graphite, the most common material of the negative electrode, is widely used in libs production for several reasons: good cyclability, low cost, non-toxicity, low operating voltage [1]. commercial graphitised materials demonstrate specific capacity near 360 mah∙g–1 [2], which is very close to the limiting value of the theoretical capacity of graphite, 372 mah∙g–1. further improvements in the total capacity of libs require a material with a much higher capacity. silicon is a promising material for the negative electrode due to its high theoretical capacity of 3579 mah∙g–1 (which corresponds to the formation of li3.75si compound [3]); it is almost ten times more than that of graphite. unfortunately, individual macroscale silicon is not suitable for practical usage in libs as a negative electrode because of colossal volume changes during lithiation [4], causing cracks and leading to loss of material integrity [5]. silicon nanoparticles can withstand such volume changes without destruction, but they still have low electronic and ionic conductivity. moreover, the high surface area of si nanoparticles leads to excessive solid-electrolyte in260 terphase (sei) formation. all these peculiar properties hinder their application in libs as the negative electrode material [6]. a  promising way to  incorporate silicon into libs production is combining it with various carbonaceous materials (nanotubes, graphite, amorphous coatings, graphene and others) to obtain a composite [7]. carbon enhances electronic and ionic transport throughout a  composite and helps maintain material stability [8]. choice of a binder also plays a significant role in the stability improvement of the silicon-containing electrode, providing good adhesion to the current collector and reliable contact with carbonaceous particles for better electronic conductivity [9, 10]. reduced graphene oxide seems to be a suitable carbonaceous material to stabilize silicon nanoparticles during cycling and provide fast electron transfer in such a composite. few recent works describe design and modification of si/rgo composites to achieve better performance during cycling; some researchers tried to modify the silicon particle surface for better contact between si and rgo [11–14]. for example, covering with poly(diallyl dimethylammonium chloride) which can change the surface charge of silicon to positive was studied [11]. si/go composite was assembled by electrostatic attraction, and then go was reduced into rgo by heat treatment [11]. another approach to stabilize the composite structure is to cover si/rgo particles with pyrolyzed carbon [12, 13]. other researches also use simple routes to obtain si/rgo composites with good cycling stability [14]. in  this work, a  new approach to  obtain si/rgo composite was developed, and the influence of a binder on cycling behaviour of the si/rgo composite was investigated. experimental starting materials graphene oxide water suspension with a concentration of 14.6 mg∙cm–3 was provided by graphenox llc (russia). silicon nanoparticles were prepared by the destruction of monosilane in argon plasma, as described in [15]; average particle size was 50 nm (sem), and the specific area was 52 m2∙g–1 (by bet). composite preparation si/rgo composite with 50:50 ratio (by weight) was prepared by self-assembly in a water suspension. 100 cm3 of go suspension was ultrasonically dispersed for 5  minutes. then, 774  mg of  silicon nanoparticles were added to the suspension and again ultrasonically dispersed for 5 minutes. after that, the suspension was frozen in  cylindrical moulds with an inner diameter of 20 mm on a copper plate cooled by  liquid nitrogen. finally, the frozen suspension was freeze-dried for 72 hours at –55 °c (martin christ alpha 1–4 ldplus, germany). the resulting aerogel was then reduced in hydrazine vapour atmosphere at room temperature and dried in an oven at 65 °c. samples thus obtained were named as sirgo. electrode preparation active mass of electrode consisted of si/ rgo composite and a  binder (pvdf or cmc) at 90:10 ratio (by weight); electrode without binder was also prepared, for comparison. n-methyl-2-pyrrolidone (nmp) was used as a solvent for samples with pvdf binder, and water was used as a solvent for samples with cmc binder. pvdf and cmc binders were purchased from sigma-al261 drich. table 1 presents the type of polymer binder and the composition of electrode active mass. samples without binder were designated as sirgo1, with pvdf binder — as sirgo2, and with cmc binder — as sirgo3. the area of prepared electrodes was 2.25 cm2. the active material loading of the electrode was about 0.5 mg∙cm–2. electrode slurry was prepared by adding a suitable solvent to a composite powder with further homogenization by ika t10 ultra turrax equipment (10 min) and then by an ultrasonic bath (10 min). electrode slurry without binder was prepared by adding nmp to a composite powder with subsequent homogenization as described above. electrode slurry was applied onto a copper current collector using dr blade technology with subsequent calendering and vacuum drying at 120 °c for 12 h. methods the morphology of the composite samples was studied by scanning electron microscopy (sem) using zeiss leo supra 25 (germany) equipment with accelerating voltage of 12 kv. e l e c t ro che m i c a l char a c te r ist i c s of the si/rgo composite electrodes with various binders were measured in  twoelectrode pouch cells modelling anode half-element of lib. the cells were assembled in an argon-filled glove box. lithium metal foil on a  copper current collector served as a counter electrode, and a baseline 1 m solution of  lipf6 in  ethylene carbonate (ec)/ethyl methyl carbonate (emc) mixture (1:1 by  volume) served as an electrolyte; celgard 2300 film served as a separator. the residual water content in the electrolyte solution did not exceed 30 ppm. all components were supplied by sigma-aldrich. cyclic voltammetry (cv) and galvanostatic cycling (gst) were performed using a multi-channel potentiostat p20x8 (“elins” llc, russia). in cv measurements, the potential range was 10–2000 mv with a sweep rate of 0.1 mv/s. gst was performed in  two regimes: 1) with constant current throughout the whole cycling (0.1c); 2) with constant charge rate of 0.1c and different discharge rates of 0.1c, 0.2c, 0.3c, 0.5c and 1.0c. intermediate discharge at 0.1c for 10 cycles between every 10 cycles with different discharge rates was used. (0.1c rate corresponded to 0.1 a g–1; this value was estimated from the supposed capacity of the si/rgo active mass equal to 1000 mah∙g–1). results and discussion scanning electron microscopy fig.  1 illustrates the  morphology of the si/rgo composite studied by scanning electron microscopy. rgo provides a flexible interconnected matrix in which agglomerated silicon nanoparticles are randomly distributed. sem data demonstrate that some of  the  agglomerated si nanoparticles occupy the  surface positions, but most of them allocated between rgo sheets. as mentioned in introduction, rgo sheets can enhance the stability of si-based composite material during li+ insertion-extraction cycles since they provide fast electron transfer and mechanical support for silicon nanoparticles. voids table 1 compositions of electrode active mass sample binder composite:binder ratio sirgo1 none — sirgo2 pvdf 90:10 sirgo3 cmc 90:10 262 in the composite structure allow accommodating volume changes of  silicon nanoparticles during cycling, thus stabilising the electrode. cyclic voltammetry cv curves allow a better understanding of  the  electrochemical behaviour of the si/rgo electrodes during cycling. fig. 2 shows the initial three cycles for all samples under investigation. one can see that anode half-cells comprising si/rgo electrodes with and without polymer binder demonstrated different electrochemical behaviour. for the sirgo1 electrode without binder cathodic and anodic curves for the 1st, 2nd and 3rd cycle are practically the  same. in  contrast, for the  sirgo2 and sirgo3 electrodes with a  polymer binder, well-distinguishable peaks appear only in the second cycle and their intensity increases by the third cycle. the positions of the peaks are in good agreement with the literature data [16–19], according to which they can be attributed to the processes of  insertion/extraction of  lithium into silicon or rgo nanoparticles and to the sei formation. gradual appearance of the peaks on cycling (fig. 2(b, c)) can be attributed to the influence of polymer binder on the surface chemistry of silicon particles distributed in the carbon matrix. cmc can bind with silicon surface by formation of ester or hydrogen bonds [9, 10], -500 0 500 1000 1500 2000 2500 3000 3500 -600 -400 -200 0 200 ь anodic path i, µa e, mv 1st cycle 2nd cycle 3rd cyclecathodic pathю a -500 0 500 1000 1500 2000 2500 3000 3500 -600 -400 -200 0 200 cathodic pathю i, µ a e, mv 1st cycle 2nd cycle 3rd cycle ь anodic path b -500 0 500 1000 1500 2000 2500 3000 3500 -1200 -1000 -800 -600 -400 -200 0 200 400 600 ь anodic path i, µ a e, mv 1st cycle 2nd cycle 3rd cyclecathodic pathю c fig. 2. cyclic voltammograms of (a) sirgo1; (b) sirgo2; (c) sirgo3 fig. 1. si/rgo composite sem images with different magnifications 263 whereas pvdf forms with silicon surface van-der-vaals bonds only. chemical bonds formation caused by cmc influences on the positions and intensity of the typical peaks. galvanostatic cycling the  electrochemical performance of  anode half-cells comprising si/rgo nanocomposites was studied by galvanostatic charge-discharge cycling in the range 10 to  2000 mv under the  same conditions at  room temperature. fig.  3 shows the charge-discharge curves in the 1st, 2nd and 5th cycles for the  cells with sirgo1 (fig. 3a), sirgo2 (fig. 3c) and sirgo3 (fig.  3e) electrodes. in  the  first cycle, the initial discharge capacities of the electrodes were 573  mah∙g–1, 1350  mah∙g–1 and 249 mah∙g–1, the values of the coulomb efficiency were 56%, 69% and 21%, respectively. table 2 summarises the electrochemical behaviour of electrodes based on si/rgo nanocomposites with different binders. the  discharge curves of  the  1st cycle are typical for formation cycles in  libs. all the curves contain a step near 800 mv, which corresponds to the reduction of electrolyte components on the surface of active materials si and rgo resulting in a protective sei layer formation. this step disappeared in the next cycles (fig. 3). formation of sei is the well-known reason for low coulombic efficiency in the first cycle [7]. the enhanced surface electrochemical reactivity of si/rgo nanocomposites must be attributed to the large surface-to-volume ratio of both rgo and si [15, 20]. however, the sample sirgo3 with cmc binder differ from others: one can see that the first discharge curve contains one more step near 1500 mv. this new process is responsible for the largest decrease in coulomb efficiency at the first cycle (table 2). most likely, a polymer binder also participates in the reduction processes during the first cathodic polarisation of the si/rgo electrode. this conclusion is  in  good agreement with the cv data. as can be seen from fig. 3 (b, d, f), the cyclic behaviour of the cell comprising sirgo3 electrode is  fundamentally different from others. indeed, the  capacity of  electrodes without a  polymer binder (sirgo1, fig. 3b) and with pvdf as a binder (sirgo2, fig. 3d) drops upon cycling, while the capacity of an electrode with a  cmc binder (fig.  3e) increases rapidly during the first 8 cycles and then stabilises near 1200 mah∙g–1 (table 2). the theoretical capacity of composite samples si/rgo can be calculated based on the content of si nanoparticles and rgo in  the  composite using their theoretical capacity. as was mentioned above, si has the theoretical capacity of 3579 mah∙g–1 and graphene, by  different evaluations, has the theoretical capacity ranging from 500 to 1116 mah∙g–1 [21]. the composite contained 50 mass % si nanoparticles and 50 mass % rgo. the theoretical capacity (qth) of the composite is calculated using formula (1): ,th si si rgo rgoq q q= ⋅ω + ⋅ω (1) where qsi and qrgo are theoretical capacities of si and rgo, respectively; ωsi and ωrgo are mass fractions of  si and rgo in the composite, respectively. the resulting value of the theoretical capacity of the si/ rgo composite, using the minimum value of 500 mah∙g–1 as the theoretical capacity of rgo, was estimated as 2040 mah∙g–1. as can be seen from table 2, the capacity values of all samples under investigation fall below the theoretical one, which is typical for any si-based anode materials [2–7]. 264 fig. 3. charge-discharge curves (a, c, e) and dependences of discharge capacity and coulombic efficiency (b, d, f) on cycle number for sirgo1 (a, b), sirgo2 (c, d) and sirgo3 (e, f) 265 as follows from the obtained results, cmc binder can solely enhance the stability of silicon-carbon nanocomposite. this conclusion is in line with those presented in [22]. in [23], authors declare that cmc alone is too brittle to effectively stabilise sibased negative electrodes during cycling. however, in this work, cmc demonstrated excellent stabilisation properties. the observed effect can be attributed to the formation of hydrogen bonds between functional groups on the  surface of  silicon particles and carboxyl groups in  cmc and between cmc carboxyl groups and residual functional groups in the surface of  rgo nanosheets. such bonds can be broken during volume expansion of silicon nanoparticles during lithiation and restored during delithiation thus preventing the material from the isolation of particles and helps maintain material integrity [10]. rate capability was studied for the best sirgo3 electrode; different discharge rates of  0.1c, 0.2c, 0.3c, 0.5c and 1.0c were used. fig.  4 presents the  results of  these measurements. the first 10 cycles at 0.1c were used as  the  formation cycles. one can see that the sirgo3 electrode shows good rate capability up to 1.0c, which can be attributed to both small silicon particle size (50 nm) and presence of conductive rgo layers which support fast electron transfer through the composite and enables high power operation of  half-cell fig. 4. rate capability of the sirgo3 electrode with cmc binder table 2 the cycle performance of the si/rgo electrodes in the range of 0.01–2 v at 0.1c rate sample discharge capacity, mah∙g–1 coulombic efficiency, % capacity retention, % 1st cycle 60th cycle 100th cycle 1st cycle 60th cycle 100th cycle 60th cycle 100th cycle sirgo1 573 292 56 99 51 sirgo2 1350 512 334 69 98 99 38 25 sirgo3 249 1186 1200 21 99 100 100 100 266 [7]. the sirgo3 electrode demonstrated the capacity of ~1200 mah∙g–1 at any discharge rate with the  exception of  1.0c. at  1.0c, the  electrode capacity reached ~1200 mah∙g–1 only at the 4th cycle. perhaps this is due to some diffusion difficulties or rearrangement of  the  conducting paths. however, after that, the  capacity again stabilised at the ~1200 mah∙g–1 value. some anomalies were also observed at 0.5c, when the capacity first deviated towards higher values causing coulombic efficiency above 100%, and then stabilised at the previous level of 1200 mah∙g–1. the reasons for this behaviour are unclear and require additional examination. conclusions polymer binder plays a  crucial role in stabilising the si/rgo nanocomposite material during cycling. the electrode with pvdf binder demonstrated better initial coulombic efficiency of 69%, but the exponential capacity loss was observed down to capacity retention 25% after 100 cycles. the electrode with cmc binder exhibited low initial coulombic efficiency of  21% due to additional reduction process with binder participation. however, the resulting sei provided stable cycling with discharge capacity near 1200  mah∙g–1 and 100% capacity retention after 100 cycles at 0.1c. excellent rate capability up to 1.0c with no capacity fade during cycling was also observed. acknowledgements this work was performed with financial support from the ministry of science and higher education of russian federation, project id rfmefi60419x0235. references 1. asenbauer j, eisenmann t, kuenzel m, kazzazi a, chen z, bresser d. the success story of graphite as a lithium-ion anode material — fundamentals, remaining challenges, and recent developments including 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batteries: effectiveness of materials synthesis and electrode preparation. nano energy. 2016;27:359–76. doi:10.1016/j.nanoen.2016.07.023 cation-exchange resins as heterogeneous catalysts for the synthesis of 1,3-butadiene from propylene and formaldehyde chimica techno acta article published by ural federal university 2021, vol. 8(2), № 20218201 eissn 2411-1414; chimicatechnoacta.ru doi: 10.15826/chimtech.2021.8.2.01 1 of 5 cation-exchange resins as heterogeneous catalysts for the synthesis of 1,3-butadiene from propylene and formaldehyde t.m. kutuzova, o.m. kuznetzova, r.a. akhmedyanova * kazan national research technological university, 420015 karl marx st., 72, kazan, russia * corresponding author: achra108@rambler.ru this article belongs to the regular issue. © 2021, the authors. this article is published in open access form under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). abstract the possibility of using the cation-exchange resin lewatit k2420 as a catalyst for the synthesis of 1,3-butadiene from isopropyl alcohol and formaldehyde solution in one technological stage has been shown. the regularities of the process have been established and the influence of the formaldehyde form (a cyclic trimer 1,3,5-trioxane and a 37% solution in water) on the composition of the reaction mass and the yield of the main and by-products has been assessed. it has been shown that the lewatit k2420 heterogeneous catalyst showed catalytic activity in all reactions occurring in the synthesis of 1,3-butadiene, including the decomposition of 1,3,5-trioxane, dehydration of isopropyl alcohol into propylene, condensation of propylene and formaldehyde, dehydration of 3-butene-1-ol, decomposition of 4-methyl-1,3-dioxane, etc. keywords 1,3-butadiene cation exchange resin formaldehyde propylene monomer petrochemical synthesis received: 23.12.2020 revised: 13.04.2021 accepted: 20.04.2021 available online: 28.04.2021 1. introduction among the processes based on the acid-catalyzed interaction of formaldehyde (fa) with iso-olefins the synthesis of isoprene from fa and isobutylene could be named, which is one of the main methods of isoprene production in russia. sulfuric, phosphoric, and oxalic acids are used as a catalyst in this process. the current trend in improving the chemical technology processes is the replacement of homogeneous catalysts with heterogeneous ones. for acidic catalysts, such alternative is cation-exchange resins that meet all the requirements for catalytic systems (high activity, selectivity, dynamic stability and lifetime), while having a number of advantages over homogeneous catalysts, such as low corrosion activity towards equipment, no need to neutralize the catalyst after the synthesis completion, the possibility of multiple use of the catalyst without a significant decrease in its catalytic activity. the works [1-3] describe methods for producing isoprene from trimethyl carbinol and isobutylene sources in the presence of cation-exchange resins (cer) and show the efficiency of their use as acid catalysts for these reactions. the principal possibility of synthesizing the second most large-tonnage diene monomer, 1,3-butadiene (bd), from propylene (p) and fa by the prins reaction was shown in work [4] in 1946. the process was two-step with the use of sulfuric acid acting as a catalyst on the first step. recently, publications have appeared on synthetic methods for the obtaining of bd, for example, from ethanol [5]. these processes mainly use solid-phase catalysts containing a metal (silver, gold or copper) and a metal oxide (magnesium, titanium, zirconium, tantalum or niobium oxide), operating at a temperature of 200–400 °c and at least a three-fold excess of alcohol. the relevance of the development of a new energyefficient, sophisticated process based on the use of modern achievements of chemical science and technology, led us to study the regularities of bd synthesis from isopropyl alcohol (ipa) (propylene) and fa in the presence of cer – heterogeneous acid catalysts that allow reactions to proceed under mild conditions and are not corrosive. 2. experimental the following materials were used in the research: isopropyl alcohol, melting temperature -89.5 °с, boiling temperature 82.4 °с, d4 20 = 0.7855 g/cm 3 ; nd = 1.3776); 1,3,5-trioxane (acros organics, 99+%, melting temperature 61–62 °с, boiling temperature 115 °с); n-hexane, boilhttp://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2021.8.2.01 http://creativecommons.org/licenses/by/4.0/ chimica techno acta 2021, vol. 8(2), № 20218201 article 2 of 5 ing temperature 68.74 °c; crystallization temperature 95.32 °c; d4 20 = = 0.660 g/sm 3 ; nd = 1.3749. the brands and characteristics of cer are presented in table 1. 2.1. experimental procedures calculated amounts of ipa, to and cer were charged into stainless steel reactor-autoclave of 230 ml (berghof, germany). the reactor was closed and placed into thermal protection case which placed on magnetic stirrer with heating. the reaction was carried out at a temperature of 150 °с. the reaction time started, when a temperature in the reactor reached required value which was controlled by a thermocouple. the duration of experiments was from 1 to 4 hours. 2.2. analysis of products the composition of a reaction mass was identified on chromatograph kristalyux 4000м with flame-ionization detector. the column was supelco analytical petrocol dh (100 m × 0.25 mm х 0.5 µm); the carrier gas was helium. the temperature regime was as follows: constant temperature of 40 °c during 15 min, then heating from 40 to 250°c with a rate of 5°с/min. composition and structure of reaction products were determined by chromatography-mass spectrometry using agilent 5975 unit (column hp-5ms (5%-phenyl)methylpolysiloxane 30 m × 0.25 mm × 0.5 µm). reference mass-spectra presented in database nist11 were used to identify components. component contents were calculated based on chromatographic peak areas on total ion current chromatogram without ionization efficiency correction [6]. 3. results and discussion the creation of macroporous cer with increased thermal stability and mechanical strength has opened up wide possibilities for their use in large-scale industrial technologies. examples include the processes of obtaining methyl tert-butyl ether (mtbe), ethyl tert-butyl ether (etbe), tert-amyl methyl ether (tame), isobutylene separation from hydrocarbon с4 fractions, etc. one of these catalysts is a macroporous sulfonic acid cer with a high exchange capacity lewatit k2420, cer in the hydrogen form, the characteristics of which are presented in table 1. table 1 characteristics of the cation-exchange resin lewatit k2420 indicator units value total exchange capacity mg eq/g eq/l 5.4 1.4 granules effective size >90% mm 0.5–1.6 tap density (±5%) g/dm 3 740 pore volume cm 3 /g 0.40 average pore diameter nm 53 the synthesis of bd from p and fa is based on the following consecutive chemical reactions: we have used ipa as a source of p, which, under the conditions of synthesis in the presence of cer, very quickly dehydrates into p. in the work [6], the results of studies on the p source, ipa, interaction with an anhydrous source of fa, 1,3,5-trioxane (to), in the presence of lewatit k2420 cer are presented. in the case of using concentrated forms of fa, the reaction leads to the formation of 3-butene-1-ol. its subsequent intramolecular dehydration is accompanied by the release of the bd molecule. among possible side reactions is the interaction of 3-butene-1-ol with a molecule of free fa with the formation of tetrahydropyranol (a bd precursor). the dehydration of the latter leads to the formation of dihydropyran (a bd precursor) (scheme 1). in this work, the 37% aqueous solution of fa (f) is used as a source of fa. in this case, the reaction goes through the formation of butane-1,3-diol, the further interaction of which with a molecule of free fa leads to the formation of 4-methyl-1,3-dioxane, which traces are detected in the reaction mass. the decomposition of 4methyl-1,3-dioxane in the presence of cer under the conditions of synthesis releases the bd molecule, free fa, and water (scheme 2). thus, the form of fa used to obtain bd via the reaction with p in the presence of cer can have a noticeable effect on the reactions direction. our studies have confirmed this assumption. scheme 1 reaction of p with fa in the form of to chimica techno acta 2021, vol. 8(2), № 20218201 article 3 of 5 scheme 2 reaction of p with fa in the form of 37% solution in water in the process under study, cer is at the same time the catalyst for the decomposition of to, the ipa dehydration to p, the condensation of p with fa, and, finally, the dehydration of 3-butene-1-ol into bd or the decomposition of 4-methyl-1,3-dioxane. temperature is an important factor influencing the cer activity and selectivity. the increase of temperature from 130 to 150 °c is followed by the increase of the bd yield and the yield of byproducts, including 3,6-dihydro-2h-pyran, 4-methyl-1,3dioxane and tetrahydro-2h-pyran-4-ol (table 2). when an aqueous solution f is used, the bd yield is 52% higher than that of to. moreover, the yield of byproducts is lower. thus, the use of an aqueous solution f leads to the increase in the bd selectivity. despite the observed tendency for the target product yield to increase with the increase in the process temperature, the further increase in temperature is limited by the maximum possible operating temperature of cer. the catalyst concentration (the content of sulfonic acid groups in the cer) has a significant effect on the yield of bd and by-products, regardless of the formaldehyde form (fig. 1). the db yield is maximum at a concentration of 0.6 eq/l. the decrease in the target product yield with the increase in the catalyst amount is due to the increase in side reactions, which is shown in figs. 2–4. table 2 main products yield obtained at bd synthesis from ipa and fa at different temperatures: [fa]:[ipa] = 1:5 mol.; [so3h] = 0.6 eq/l, τ = 180 min t, °c bd synthesis products yield, % 1.3butadiene 3,6-dihydro2h-pyran 4-methyl1,3-dioxane tetrahydro2h-pyran-4ol to f to f to f to f 130 1.26 1.18 0.10 1.79 0.01 1.10 0.05 1.91 140 4.92 1.25 1.10 2.99 0.18 1.70 2.03 1.82 150 6.45 9.83 6.33 4.14 0.01 0.01 7.01 3.19 fig. 1 dependence of the butadiene yield on the so3h groups concentration: [fa]:[ipa] = 1:5 mol.; τ = 180 min; т = 150 °с, 1 – то, 2 – 37% aqueous solution of formaldehyde fig. 2 dependence of the tetrahydropyranol yield on the so3h groups concentration: [fa]:[ipa] = 1:5 mol.; τ = 180 min; т = 150 °с, 1 – то, 2 – 37 % aqueous solution of formaldehyde fig. 3 dependence of the dihydropyran yield on the so3h groups concentration: [fa]:[ipa] = 1:5 mol.; τ = 180 min; т = 150 °с, 1 – то, 2 – 37% aqueous solution of formaldehyde fig. 4 dependence of the methyldioxane yield on the so3h groups concentration: [fa]:[ipa] = 1:5 mol.; τ = 180 min; т = 150 °с, 1 – то, 2 – 37 % aqueous solution of formaldehyde chimica techno acta 2021, vol. 8(2), № 20218201 article 4 of 5 the yield of tetrahydropyranol is high in the region of low concentrations of acid sites for syntheses with anhydrous formaldehyde (fig. 2). the increase in the cer concentration in the reaction system leads to the decrease in the tetrahydropyranol yield, which is due to its conversion into bd and dihydropyran. when using an aqueous formaldehyde solution, the maximum tetrahydropyranol yield is observed at a concentration of so3h groups equal to 0.6 eq/l. this is due to the presence of water in the system, which leads to the hydrolysis reaction of dihydropyran with the formation of tetrahydropyranol. this is shown by the decrease in the dihydropyran yield at a concentration of so3h groups of more than 0.6 eq/l (fig. 3). moreover, depending on the form of formaldehyde, the maximum dihydropyran yield is observed at different concentrations of so3h groups. the maximum methyldioxane yield is observed at low cer concentrations – 0.2 eq/l (fig. 4). in this case, it is worth noting the higher md content in the syntheses using fa in an aqueous solution, since in this case the reaction of obtaining bd goes mainly through the formation of md, in contrast to the synthesis from anhydrous to, when the reaction goes through the formation of 3-butene-1-ol. therefore, in all syntheses using to, a low md content in the reaction medium is observed. increasing in the reaction time to 180 min leads to the increase in the bd yield. further increase in the reaction time in a periodic mode demonstrates the decrease in bd yield (fig. 5). at the same time, the dependences of the db precursors (by-products) yield in this case have a different character for different formaldehyde forms (table 3). it is important to note that at higher temperatures, cer, as well as other acid catalysts, accelerates the oligomerization reactions of unsaturated compounds, in our case propylene and 1,3-butadiene. this leads to the decrease in the catalyst activity due to the formation of resins that block the access to the active sites, as well as to an unproductive loss of monomers. the longer unsaturated compounds are in direct contact with active sites, the greater is the probability of oligomerization reactions occurring. this problem can be solved by introducing an inert organic solvent, n-hexane, which dissolves propylene and butadiene and removes them from the contact zone with the acid sites of cer, into the reaction mixture. it is demonstrated by the increase of the bd yield with the increase in n-hexane concentration (fig. 6). table 3 yield of the bd synthesis products reaction time, min yield of the synthesis products, % 3,6-dihydro2h-pyran 4-methyl-1.3dioxane tetrahydro2h-pyran-4-ol to f to f to f 60 2.0 1.2 0.003 0.1 4.1 0.90 120 6.5 2.49 0.004 0.06 7.00 1.99 180 6.33 4.14 0.006 0.04 7.19 3.19 240 8.49 3.49 0.038 0.03 11.27 2.00 fig. 5 dependence of the bd yield on reaction time; [fa]:[ipa] = 1:5 mol.; т = 150 °с, [so3h] = 0.6 eq/l, 1 – то, 2 – 37 % aqueous solution of formaldehyde fig. 6 dependence of the bd yield on n-hexane concentration: [fa]:[ipa] = 1:5 mol.; т = 150 °с, τ = 180 min, 1 – то, 2 – 37% aqueous solution of formaldehyde 4. conclusions thus, the regularities of the bd synthesis from ipa and an aqueous solution of fa in the presence of the lewatit k2420 heterogeneous catalyst have been studied, and the influence of the fa, a cyclic trimer 1,3,5-trioxane and a 37% solution in water, form has been evaluated. the lewatit k2420 heterogeneous catalyst has been shown to exhibit catalytic activity in all processes occurring in the db synthesis, including decomposition of 1,3,5-trioxane, dehydration of isopropyl alcohol into propylene, condensation of propylene and formaldehyde, dehydration of 3-butene-1-ol, decomposition of 4-methyl-1,3-dioxane etc. the use of cer as a catalyst made it possible to carry out the reaction in one technological stage under mild conditions, without the threat of equipment corrosion. the possibility of reusing the catalyst has been studied, and the need for its regeneration has been shown, which is associated with the processes of undesirable oligomerization of unsaturated compounds, leading to the formation of resins that block the catalyst active centers. the optimal conditions for the bd synthesis from ipa and fa were selected, providing the maximum yield of 1,3-butadiene of 9.83%: [fa]: [ipa] = 1:5 mol.; т = 150 о с; [so3h] = 0.6 eq/l, τ = 180 min. chimica techno acta 2021, vol. 8(2), № 20218201 article 5 of 5 it has been shown that the nature of the fa source affects the transformations mechanism; 2 possible routes of reactions occurring in the bd synthesis have been given. references 1. vavilov di, ahmedyanova ra, liakumovich ag, levin yaa. sintez isoprena iz 1,3-dioxolanf and trimethilcarbinola v prisutstvii sulfocationoobmennyh smol [synthesis of isoprene from 1,3-dioxolane and trimethylcarbinol in the presence of sulfonic cation exchange resins]. russian journal of chemistry and chemical technology. 2011;54(5):113-6. available from: https://www.elibrary.ru/download/elibrary_16388516_6010 0076.pdf 2. burkin ke, akhmedyanova ra. novel ecological and energy saving method of single-stage synthesis of isoprene novel ecological and energy saving method of single-stage synthesis of isoprene. chemistry for sustainable development. 2011;19:531-5. available from: https://www.sibran.ru/upload/iblock/d1d/d1d0d00d9ba88d e02aa3edc4dff43f6f.pdf 3. burkin ke, akhmedyanova ra, liakumovich ag. odnostadiynyy sintez izoprena iz 1,3,5-trioksana i trimetilkarbinola v prisutstvii kationoobmennykh smol [one-step synthesis of isoprene from 1,3,5-trioxane and trimethylcarbinol in the presence of cation exchange resins]. industrial production and use of elastomers. 2011;2:11-4. 4. workman ar, author; cities service oil co, assignee. manufacture of butadiene from propene and formaldehyde. united states patent us 2412762a, 1947 december 17. 5. ordomsky vv; sushkevich vl.; ivanova ii, inventors; limited liability company «unisit», assignee. odnostadiynyy sposob polucheniya butadiyena [one-step method for producing butadiene]. russian federation patent ru 2440962c1. 2010 july 29. russian. 6. bogаchevа tm, zevаkinа аo, аkhmedyаnovа rа, zenitovа lа. synthesis of butаdiene-1,3 from isopropyl аlcohol аnd trioxаne. processes of petrochemistry аnd oil refining 2018; 1: 46-58. available from: http://ppor.az/jpdf/tatyanabogacheva-1(2018).pdf https://www.elibrary.ru/download/elibrary_16388516_60100076.pdf https://www.elibrary.ru/download/elibrary_16388516_60100076.pdf https://www.sibran.ru/upload/iblock/d1d/d1d0d00d9ba88de02aa3edc4dff43f6f.pdf https://www.sibran.ru/upload/iblock/d1d/d1d0d00d9ba88de02aa3edc4dff43f6f.pdf http://ppor.az/jpdf/tatyanabogacheva-1(2018).pdf physical and chemical characterization of drag reducing polymer based on polyvinylpyrrolidone (pvp) in human blood flow chimica techno acta article published by ural federal university 2021, vol. 8(2), № 20218207 eissn 2411-1414; chimicatechnoacta.ru doi: 10.15826/chimtech.2021.8.2.07 1 of 6 physical and chemical characterization of drag reducing polymer based on polyvinylpyrrolidone (pvp) in human blood flow akram jassim jawad a,b,* , auda j. braihi a a: university of babylon, college of materials engineering, department of polymer and petrochemicals industries, al hillah, iraq b: queen mary university of london, school of engineering and materials science, london, uk * corresponding author: akrammaterials4@gmail.com this article belongs to the regular issue. © 2021, the authors. this article is published in open access form under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). abstract a new attempt to use polyvinylpyrrolidone (pvp) as a bio-drag reducing polymer agent for human blood flow has been studied. pvp was added at 0, 500, 750 and 1000 part per million (ppm) and mixed with human blood at room temperature for 2 minutes. then, a cone on plate rheometer was used to investigate the effectiveness of pvp agent on blood rheological properties. the results showed significant effecting of pvp on blood fluidity characteristics, where the viscosity decreased as the pvp content increased or as a shear rate increased. for a certain shear rate, the shear stress decreased as pvp content increased. these changes will lead to increased mixing efficiency within the capillaries, increased oxygen transportation, increased tissue perfusion, modified red blood cells (rbcs) distribution, reduced pressure drop gradients, enhanced turbulent flow tendency, enhanced viscoelasticity nature of the blood and its strengthened non-newtonian pattern. also, the results showed that the viscosityshear stress relationships become more linear at higher pvp concentrations. pvp addition caused no shifting in uv-absorbing positions and only moderate intensity changing. atomic force microscopy (afm) parameters provide other indicators about the role of pvp as a drag reduction agent for blood flow, where all of the amplitude, hybrid and special parameters decreased significantly. keywords polyvinylpyrrolidone (pvp) blood flow biorheology drag reducing polymers (drps) cone on plate atomic force microscopy received: 29.03.2021 revised: 28.04.2021 accepted: 06.05.2021 available online: 11.05.2021 1. introduction in the last few years, nano-amounts of drag reduction polymeric agents (drps) with high solubility, flexibility and molecular weight (mw>10 6 da) as bio-drag reduction agents in turbulent flow, due to tom’s effect, have been used in different biomedical applications, such as blood flow [1]. drps have interesting hemodynamics effects, such as an increase in tissue perfusion, tissue oxygenation, aortic and arterial blood flow, collateral blood flow in rabbits, the number of capillaries in normal and diabetic rats, the concentrations of red blood cells (rbcs) along the vessel wall [2, 3]. additionally, drps could introduce a decrease in vascular resistance, blood pressure, peripheral vascular resistance, turbulent flow resistance, mechanical damage to blood cells when the blood is in contact with circulatory assist devices, as well as the margination of leukocytes and platelets in the microcirculation. also, drps could modify dynamics of red blood cell (rbc) distribution in microcirculation, preventing them from moving toward the vessel center [4, 5]. different types of polymers were used as drps in literature, including high mw polyethylene oxide (peo) [2, 69], polyacrylamide (pam) [10-13], and certain polysaccharides [2, 8]. polyvinylpyrrolidone (pvp) is a vinyl-group polymer, in which the pendant group is the five-membered amide ring. the schematic chemical structure of pvp is shown in fig. 1. pvp was first patented with good adhesion, good complexation, low toxicity, biocompatibility and good solubility in non-polar and polar solvents. hence, it has been used in various fields, such as food, cosmetics, pharmaceuticals, adhesives, paints, detergents and energy storages; in last years, pvp was used as drag reduction agent in crude oil flow [14, 15]. http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2021.8.2.07 http://creativecommons.org/licenses/by/4.0/ https://orcid.org/0000-0002-4860-6082 chimica techno acta 2021, vol. 8(2), № 20218207 article 2 of 6 fig. 1 schematic chemical structure of pvp [15] in our present research, we tried to use polyvinylpyrrolidone (pvp) as a bio drag reducing agent and watersoluble polymer in blood flow at very tiny additive ratios. we added pvp in different concentrations, around 0, 500, 750 and 1000 ppm. cone on plate rheometer was applied to check flow characteristics of blood/pvp mixture. besides that, fourier-transform infrared (ftir) spectroscopy, ultraviolet-visible spectroscopy (uv-vis) and atomic force microscopy (afm) was utilized to deepen the understanding of physical and chemical interactions between blood ingredients and pvp chains, which have an effect on rheological properties. 2. experimental human blood was collected in containers with acidcitrate-dextrose (acd) added as an anticoagulant (10% by volume) at a local hospital. the drp used in this study was a polyvinylpyrrolidone with an average molecular weight of 60,000 da with glass transition temperature (tg) about 137 °c, supplied by bio basic inc. company, canada. pvp was added to human blood at 0, 500, 750 and 1000 part per million (ppm). the polymer solution was prepared by dissolving pvp directly in the blood. then, the solutions were mixed for about 5 min by using magnetic stirrer at 37 °c, as shown in fig. 2. then, the viscosity of blood samples with/without pvp were measured using a brookfield cone and plate rotational rheometer (dv iii-lv) by using the same procedures as in our previous works [16, 17], in which the cone model number was 40, so that the volume of the sample was 2 ml at 37 °c and 20-60 s -1 , temperature and shear rate range, respectively. also, ftir spectroscopy (shimadzu, japan) was applied by using a drop of the samples between a couple of nacl disks. meanwhile, the samples were characterized by uv-vis (shimadzu, japan) by using quartz double cells method. a drop of samples were dropped on glass substrate for afm (angstrom, usa) test by tapping mode procedure with scanning rate equal to 10 mm/min. afm images were analyzed by the by3000 spm 2.9 program following the iso 25178-2: 2012 and asme b46.1 standards. fig. 2 flow chart of procedure for experimental work 3. results and discussion it is clear from fig. 3 that, at a certain shear rate, the viscosity decreased as the pvp content increased. this can be attributed to the presence of bulky five membered amide ring within the polymeric chains, where these bulky five membered amide ring could decrease the internal friction between chain-chain, and blood-chain interactions, which leads to lower entanglements that reduce the turbulence flow due to free volume increasing between polymer chains [18]. therefore, these rings can increase the mixing efficiency within the capillaries, which leads to the increasing of the oxygen transporting due to enhancing the mixing of plasma in the near wall vessel regions. this effect, in turn, resulted in increasing the red blood cells (rbcs) traffic within the vessels. this means that the tissue perfusion will enhance, oxygen delivery, gas exchange will raise, the fahraeus effect will be reverse and the dynamics rbcs distribution will be modified in the microcirculation within the human body preventing them from accumulation in the vessel centre. the latter manner will improve the pressure levels across vessel regions and decrease the pressure drop gradients. this is due to the redirection of rbc in this section reducing the vascular resistance as a result of the increment of the wall shear stress, which enhances the endothelium mediated vasodilation [20]. this shear thinning tendency in blood increased as pvp content increased for a fixed shear rate. it can be concluded also that the presence of amide rings in pvp structure will decrease the turbulent flow tendency due to the inverse relationship between the reynolds number value and the viscosity, where the turbulence increases the apparent viscosity. chimica techno acta 2021, vol. 8(2), № 20218207 article 3 of 6 fig. 3 viscosity – concentration behaviour of human blood/pvp at different shear rates with different ratios of pvp the above rheological effects might alter the functional capillary density (fcd), which is the essential factor of survival in haemorrhagic shock. also, these effects could change the plasma skimming, local haematocrit and fahraeus-lindqvist effect. besides these effects, the presence of polymeric materials in the blood circulation system will enhance the viscoelasticity nature of blood and will strengthen its non-newtonian pattern in the velocity profile across the vessel. also, fig. 3 shows that the viscosity decreased as shear rate increased. this result coincides with the pribush et al. [19] findings, which indicate that high molecular weight polymers decrease the hydrodynamic resistance of blood, thereby improving impaired blood circulation [19]. this explains using pvp as a lubricant agent to reduce friction in contact lenses and eye drops. this proved the previous findings which were related to the increasing the mixing efficiency, especially, in the so called “unstirred boundary plasma layer”. this stable layer surrounded rbcs, through which oxygen will transfer by diffusion action. the increment in the mixing state will redistribute the rbcs across the blood vessel, making homogeneity in the velocities of the blood components by shifting the mean velocity of rbcs closer to the corresponding blood mean velocity. these findings agreed with marhefka et al. [20] results, which indicate that the additives reduce flow separations at micro channel expansions, deflecting rbc closer to the wall and eliminating the plasma recirculation zone [20]. the overall conclusion of fig. 3 coincides with the tom’s effect due to the reduction of the turbulent flow resistance in the presence of the polymeric material in blood circulation. for a certain shear rate, the shear stress decreased as the pvp content increased as in fig. 4. this finding coincides with the decreasing of viscosity as pvp content increased in the blood stream, which proved the drag reduction of the chosen polymer. at higher shear rates, above 40 s -1 , there is a relativity linear relationship with shear fig. 4 shear stress as a function of shear rate of human blood/pvp with different pvp ratios stresses for low concentrations only, (0-500) ppm; this increment in shear rate decreased at high concentrations (750-1000) ppm. these findings get in agreement with fig. 5 results, where for certain viscosity, the shear stress decreased as pvp content increased. also, the shear stressviscosity relationships become more linear at higher concentrations. fig. 6 shows the ftir spectra of blood, pvp and blood containing pvp particle. ftir spectrum of pure pvp shows an absorption band at 1279 cm −1 which is related to c–n bending vibration mode from the pyrrolidone structure, and an absorption band around 1644 cm −1 which belongs to the stretching vibration mode of the c=o in the pyrrolidone group. the band at 2885 cm -1 belongs to the ch stretching mode, the band at 2919 cm -1 – to ch2 symmetric stretching mode, the band at 2983 cm -1 – to asymmetric ch2 stretching mode, and the band around 3464 cm -1 refers to the oh group. the bands at 1371 cm −1 and 1423 cm −1 correspond to the ch deformation modes from the ch2 group. the ftir spectrum of pure blood shows bands for cooh, -nh, c-h and c=o group’s blood consists of haemoglobin. it is a tetramer protein, which means it has four fig. 5 shear stress behaviour as a function of viscosity of human blood/pvp with different pvp ratios chimica techno acta 2021, vol. 8(2), № 20218207 article 4 of 6 fig. 6 ftir absorption spectra of human blood, pvp and blood/pvp mixture parts. it is made up of 4 polypeptide chains, each polypeptide chain consisting of a linkage of amino acids also known as protein [21]. it is clear from fig. 6 that there are no new bands appear within the blood/pvp spectrum, which could mean that dissolving pvp polymeric chains within blood have no adverse effects. this is because there are not obvious chemical reactions that introduce new materials and products, which is confirmed by the absence of new bands. this result matching marhefka et al. [20] assumption that the effect of these drps on the drag is associated with their physical interactions with local irregularities of disturbed laminar blood flow [20]. figs. 7 and 8 represent absorption and transparence uv-vis spectra of blood, pvp, and blood/pvp, respectively. the pvp addition has a moderate effect on the absorption spectra of uv-vis by blood, where there is no shifting in the wavenumber, and only the intensity decreases from 3.79 to 3.00. this is due to the little absorbance of pvp for uv-vis, which is about 1.05 [22]. therefore, the uv-vis figures support the ftir results for biocompatibility of pvp within blood flow due to the blood colour not changing significantly. consequently, there are no risks from dissolving pvp in blood because it has high biocompatibility that has made it useful in different biomedical applications such as contact lenses and eye drops [15]. the 3d afm topography images, as in fig. 9, indicate the role of pvp in reducing the blood viscosity, where the plates seem to be smoother after the pvp addition. this decrease in the roughness of cells surfaces reduces the friction between these cells and makes their flow easier and faster. table 1, which was extracted from fig. 9, explains in detail these pvp effects, with all roughness parameters presented. after pvp addition, all amplitude parameters were affected significantly: the roughness average parameter (sa) decreased by 58.52%, the root mean square (sq) decreased by 59%, the peak-to-peak (sy) decreased by 53.6% and the ten-point height (sz) decreased by 80.9%. the hydride parameters decreased also, where the root mean square slop (sdq) by 86.67%. fig. 7 uv-vis absorption spectra of human blood, pvp and blood/pvp mixture fig. 8 transparence uv-vis spectra of human blood, pvp and blood/pvp mixture the topography of plates changed after the pvp addition, so that the summits density (sds) decreased by 99.44% and the reduced summit height parameter (spk) decreased by 63.9%. these findings coincide with the reduce in the core roughness depth (sk) by 50.31% and reduced valley depth (svk) by 59.62%, which means the surface possessed less grooves. these surface changes lead in the end to decrease in the core fluid retention index (sci) by 3.82% and the surface bearing index (sbi) by 32.8%. 4. conclusions pvp could be used as an effective drp within the flow of human blood, especially in high blood pressure conditions due to its high lubrication ability that introduces pressure drops. the blood viscosity decreased as pvp content increased with nano concentration at a certain shear rate. also, the blood viscosity decreased as shear rate increased at a certain pvp content with nano concentration. however, there is no change in the blood chemical composition and no shifting in the uv absorbing positions. consequently, pvp addition makes blood cells smoother, easier and the flow – faster. the possible recommendations could be measuring the haematocrit in each sample, and study the drag reduction in higher shear rates within the veins and compare it with the current range (20-60 s -1 ). also, studying of the drag reduction in arteries and atherosclerotic arteries and comparing them with the results for veins could be promising. chimica techno acta 2021, vol. 8(2), № 20218207 article 5 of 6 fig. 9 three-dimensional afm topography images of (a) human blood, (b) pvp and (c) blood/pvp mixture table 1 roughness report for amplitude, hybrid, functional and spatial parameters of human blood, pvp and blood/pvp mixture by using afm topography analysis acknowledgements we would like to thank the members of the laboratory of the department of polymers and petrochemical industries in babylon university for their great cooperation in accomplishing this work. also, we would like to thank dr. efstathios kaliviotis, department of mechanical engineering and materials science and engineering at the cyprus university of technology, for his great help. 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https://doi.org/10.3233/bir-2009-0543 https://doi.org/10.3390/ma13173675 80 i. a. zvereva, a* e. a. tugovab, v. f. popovac, o. i. silyukova, i. a. minicha a saint petersburg state university, 7/9 universitetskaya nab., st. petersburg, 199034, russian federation b saint petersburg state technological institute, 26 moskovsky pr., st. petersburg, 190013, russian federation c institute of silicate chemistry of ras, 2 makarova nab., st. petersburg, 199034, russian federation * irinazvereva@spbu.ru the impact of nd3+/la3+ substitution on the cation distribution and phase diagram in the la 2 sral 2 o 7 -nd 2 sral 2 o 7 system the effect of isovalent cation substitution of lanthanum atoms in the structure of la 2 sral 2 o 7 oxide, and phase equilibria (solidus-liquidus curves) in the binary system la 2 sral 2 o 7 -nd 2 sral 2 o 7 were studied. it was found that nd3+ substitution for la3+ has effect on the structure of la 2 sral 2 o 7 in respect of the character of cation distribution in the solid solution la 2–x nd x sral 2 o 7 from statistically disordered to the ordered one where strontium cations predominantly occupied the rock-salt layers, as reflected by the solidus-liquidus lines. keywords: perovskites, transition metal oxides, solid solutions, layered compounds, phase diagram received: 28.04.2018. accepted: 09.05.2018. published: 10.05.2018. © zvereva i. a., tugova e. a., popova v. f., silyukov o. i., minich i. a., 2018 d o i: 1 0. 15 82 6/ ch im te ch .2 01 8. 5. 1. 05 zvereva i. a., tugova e. a., popova v. f., silyukov o. i., minich i. a. chimica techno acta. 2018. vol. 5, no. 1. p. 80–85. issn 2409–5613 introduction the elements that occupy a-sites in the perovskite-related oxides play a significant role in both crystallographic and physical properties. a well-known fact is related to the heterovalent substitutions of large ap+ cations which can trigger mixed valence state of b transition elements and induced superconductivity in cuprates or giant magnetoresistance in manganites. it is also generally acknowledged that electrical properties of a perovskite-like solid solution depend significantly on the mean size of cations located in the a-site positions, and even more – on the size mismatch between them. the isovalent substitution of ca2+ for sr2+ was studied intensively in the superconducting cuprates la2–xsr(ca)xcu2o6–δ [1] and in the magnetoresistant manganites ln0.7a0.3mno3 (a = ca, sr) [2]. the crystal chemistry of such cationic substitution in the perovskite-like aluminates is quite similar, as exemplified by the results obtained for two structural types of layered aluminates – lasr(ca)alo4 and la2sr1–xcaxal2o7 [3, 4]. the most striking result is the evidence for the high destabilizing role of ca2+. it is confirmed by the fact that lacaalo4 is thermodynamically unstable, it has demixed to laalo3 and 81 cao instead of complex crystallographic transformation, which is originated in local ordering of ca2+ and la3+ ions [5, 6]. the substitution of ca2+ for sr2+ in la2sral2o7 is more crucial for the layered structure, and brings progressive instability when the amount of ca becomes more than x = 0.5 because of the positional ordering phenomena [4]. to clarify the different rare-earth (re) cations’ presence in layered perovskite type oxides, it is important to understand their crystal chemistry and stability of the intergrowth structure that influences their properties and potential applications. the size of re cation, as well as partial re and sr cation ordering, play a prominent role in the actual magnetotransport properties. this is the reason why it is worthwile to investigate the cation ordering and the stability of structure in the system where the redox processes for the transition metal are eliminated, as in the case of the isostructural aluminates. we herein report on the structure analysis for the series of solid solutions la1–xndx)2sral2o7 and the investigation of solidus-liquidus equilibria in system la2sral2o7-nd2sral2o7. both re strontium aluminates ln2sral2o7 (ln = la, nd) belong to the n = 2 member of so-called ruddlesden-popper phases (an+1bno3n+1) [7], in which double perovskite slabs (p2) alternate with the rocksalt layers (rs). the stability of the structure represented as (p2/ rs) intergrowth for the studied aluminates and their solid solutions at high temperatuteres are considered in the view of the re–sr cation ordering. experimental solid solutions (la1–xndx)2sral2o7 were prepared by a solid state reaction of the stoichiometric amounts of re2o3 (re  = la, nd), al2o3, and srco3 according to the following equation: (1 – x)la2o3 + xnd2o3 + srco3 + al2o3   (la1–xndx)2sral2o7 + co2. the mixtures were preheated at 900 °c in air, then grinded, pelletized and annealed at 1450 °c for 100 hours (140 hours for re = la), and cooled in air. the as-prepared compounds were characterized by the x-ray powder diffraction (xrpd) using a philips pw3020 diffractometer, in cu kα radiation. the structural analysis of the aluminates was made using the results collected in the angular range 2θ = 5–120°, with the step of 0.04° in 2θ and exposure time of 12 s. the structural parameters were refined by the rietveld method using the fullprof software. the melting points for the samples were determined by the differential thermal analysis (dta) using a vta-982 hightemperature thermal analyzer in helium atmosphere with heating rate of 10 k/min. results and discussion the results of x-ray diffraction (xrd) analysis show that the continuous series of solid solutions (la1–xndx)2sral2o7 (0 ≤ х ≤1), crystallizing in the sr3ti2o7 structural type, were obtained as single phases. the indexing of the xrpd patterns were performed within the conventional for the p2/rs intergrowth structure tetragonal unit cell (space group (s.g.) i4/mmm). the values of unit cell parameters (fig. 1) decrease monotonically with the increase of nd content in accordance with the difference in their ionic radii r(re3+). observed deviation from the vegard’s law might indicate 82 the nonrandom distribution of neodymium atoms in the lа2sral2o7 structure. it is worth to note that, contrary to the ca2+  sr2+substitution, the substitution of nd3+  la3+ does not limit the homogeneity range of the (la1–xndx)2sral2o7 solid solutions. it was shown earlier [8] that the distribution of ln3+ and sr2+atoms over two non-equivalent structural positions, namely 12-coordinated ao12 and 9-coordinated ao9, is different in lа2sral2o7 and nd2sral2o7. the distribution of la 3+ and sr2+ in lа2sral2o7 appears to be generally random, however, with some preferable la occupation of ao12 polyhedra in the perovskite layers. on the contrary, the visible deviation from the random distribution towards to the positional ordering of nd3+ ions in rock-salt layers is observed in nd2sral2o7. the situation is more complicated in (la1–xndx)2sral2o7 solid solutions where ao12 and ao9 polyhedra are occupied by the three types of ions: la3+, nd3+ and sr2+. in the case of the nd3+  la3+ substitution, the determination of the sites’ occupation by the rietveld refinement is more difficult, as compared to the case of the ca2+  sr2+ substitution, because of the smaller difference in the number of electrons between la3+ and nd3+ (three f-electrons). therefore, the full-profile x-ray diffraction analysis of solid solutions (la1–xndx)2sral2o7 provides only the information about the redistribution of sr atoms over two sites with the change in the neodymium content. although la3+ and nd3+ could not be distinguished by the rietveld refinement, one can take into account the general tendency obtained for the whole series of ln2sral2o7 oxides (ln  = la-ho) [8], which showed the evidence of favorable occupancy of ao9 polyhedra by the atoms with smaller atomic radii. nevertheless, the structure of (la1–xndx)2sral2o7 solid solutions was refined by means of the rietveld method. the occupancy values for the nonequivalent sites calculated for the random distribution of cations and obtained from the xrpd results for two solid solutions (la1–xndx)2sral2o7 and parent oxides la2sral2o7 and nd2sral2o7 are shown in table 1. it should be emphasized that the rietveld refinement gives only the occupancy for sr atoms. the distribution of la and nd atoms is undefinable; it could be assumed under consideration that redistribution of strontium from the rock-salt layers (ao9 polyhedra) into the perovskite layers (ao12 polyhedra) is compensated specifically by the transfer of nd to the rock-salt layers. it should be noted that deviation from the random distribution of cations is observed independently of the distribution of re atoms when neodymium content is х ≥ 0.6. no deviations for the random cation distribution were observed in the concentration range x ≤ 0.5. to summarize the aforementioned results one can conclude that the transition from random distribution of a-site cations (re3+ and sr2+) between non-equivalent positions to the ordered one with certain fig. 1. the unit cell parameters for the (la1–xndx)2sral2o7 solid solutions versus nd content (x) 83 preferred occupancy of perovskite layers by sr2+ ions with the nd content increase takes place in vicinity of x = 0.6. therefore, the distribution of la3+, nd3+, sr2+ cations between two non-equivalent sites (ao9 and ao12) could be presented by the structural diagram shown in fig. 2. bearing in mind that the positional ordering when lanthanide atoms preferably located in the rock-salt layers sites stabilizes the layered p2/rs type structure, one can conclude that solid solution (la2–xndx)2sral2o7 should be more stable than lanthanum strontium aluminate la2sral2o7, but less stable than neodymium-containing analog nd2sral2o7. the influence of cation ordering in the continuous series of solid solutions on the phase diagrams, which, in particular, can be observed on a shape of liquidus and solidus lines, was the issue of our further experimental study. we applied the ceramic technique followed by the xrpd analysis in order to examine the phase equilibria in the pseudo-binary system la2sral2o7– nd2sral2o7 within the entire concentration range. melting points were detected by means of a differential thermal analysis. the phase diagram (fig. 3) was constructed taking into account the particularities of the ln2sral2o7 melting mechanism [9]. it was found that both la2sral2o7 and nd2sral2o7 melt incongruently: ln2sral2o7  liquid + lnalo3, (ln = la, nd). as a result, two types of double-phase fields where liquid phase coexists with the solid, namely, (la2–xndx)2sral2o7) + liquid and (la1–xndxalo3) + liquid, appear on the phase diagram. the main feature of phase equilibria in the la2sral2o7–nd2sral2o7 system is the existence of the minimum on the solidus line. considering the phase equilibria in the pseudo-binary la2sral2o7– nd2sral2o7 system in combination with the structural transformations of cation coordination during the formation of the fig. 2. the structural diagram for the pseudobinary la2sral2o7–nd2sral2o7 system l a+ 3 a o 12 statisticallydisordered distribution la+3, nd+3, sr+2 ordering sr+2 ao12 0.4 0.6 0.8 la2sral2o7 nd2sral2o7 table 1 the occupancy for a-site cations in the ao12 and ao9 polyhedra in la2sral2o7, nd2sral2o7 and (la1–xndx)2sral2o7 solid solutions (x = 0.6 and 0.8) p2/rs ao12 ao9 lа+3 nd+3 sr+2 lа+3 nd+3 sr+2 ln2sral2o7 random 0.67 – 0.33 1.33 – 0.67 calculated 0.73 – 0.27 1.27 – 0.73 (la0.4nd0.6)2sral2o7 random 0.26 0.41 0.33 0.52 0.80 0.67 calculated 0.26 0.36 0.38 0.52 0.86 0.62 (la0.2nd0.8)2sral2o7 random 0.13 0.54 0.33 0.27 1.06 0.67 calculated 0.13 0.47 0.40 0.27 1.13 0.60 nd2sral2o7 random – 0.67 0.33 – 1.33 0.67 calculated – 0.54 0.46 – 1.46 0.54 84 (la2–xndx)2sral2o7 solid solution, it is noticeable that the minimum on the solidus line correlates with the disordering-ordering transition domain for la3+, nd3+, sr2+ distribution. the existence of minimum on the melting point plot may be related to the decrease of enthalpy of the solid solutions formation, which actually reflects the decrease in their stability. certainly, the studied solid solutions cannot be described in terms of regular solution model, since the entropy contribution to the gibbs energy of solid solutions formation, accompanied by the cation redistribution between the non-equivalent 12-coordinated (cuboctahedron ao12) and 9-coordinated (antiprism ao9) sites, should not be neglected. conclusions it was shown that nd3+  la3+ cation substitution in the crystal structure of la2sral2o7 allows to obtain continuous series of solid solutions (la1–xndx)2sral2o7 (0 ≤ х  ≤ 1). introduction of nd3+ instead of la3+ changes the character of cation distribution in the la2–xndxsral2o7 solid solutions from a statistically disordered to the ordered with respect to the strontium cations in the rock-salt layers. the latter causes the particularities in the phase diagram for the pseudo-binary la2sral2o7-nd2sral2o7 system. the minimum on the solidus line correlates with the cation disorderingordering transition in respect of the nd content. references 1. ohyama t, ohashi n, fukunaga o, ikawa h, izumi f, tanaka j. structural and electrical changes in ln1.9sr1.1–xcaxcu2o6+δ (ln = la, pr) systems. phys c supercond. 1995;249(3–4):293–303. doi: 10.1016/0921-4534(95)00307-x. 2. maignan a, simon c, caignaert v, raveau b. size of the interpolated cation and hole carrier density: two key parameters for the optimisation of colossal magnetoresistive properties of pr-based manganites. zeitschrift für phys b condens matter. 1995;99(3):305–10. doi: 10.1007/s002570050041. 3. zvereva i, zueva l, choisnet j. metastability of the k2nif4 type structure of the solid solution laca(crxal–x)o4 (0 < x < 0.10). j mater sci. 1995;30(14):3598–602. doi: 10.1007/bf00351871. 4. zvereva i, smirnov y, choisnet j. prominent part of calcium ordering in the formation and stability of the intergrowth type solid solution la2sr1–xcaxal2o7. int j inorg mater. 2001;3(1):95–100. doi: 10.1016/s1466-6049(00)00099-4. fig. 3. phase equilibria in the pseudo-binary la2sral2o7–nd2sral2o7 system 85 5. smirnov y, zvereva i, choisnet j. x-ray diffraction study of the decomposition process occurring in single crystals of the k2nif4-type aluminate lacaalo4. j solid state chem. 1997;134(1):132–7. doi: 10.1006/jssc.1997.7557. 6. zvereva i, smirnov y, choisnet j. demixion of the k2nif4 type aluminate lacaalo4: precursor role of the local ordering of lanthanum and calcium. mater chem phys. 1999;60(1):63–9. doi: 10.1016/s0254-0584(99)00072-3. 7. ruddlesden sn, popper p. the compound sr3ti2o7 and its structure. acta crystallogr. 1958;11(1):54–5. doi: 10.1107/s0365110x58000128. 8. zvereva i, smirnov yu, gusarov v, popova v, choisnet j. complex aluminates re2sral2o7 (re  = la, nd, sm-ho): cation ordering and stability of the double perovskite slab-rocksalt layer p2/rs intergrowth. solid state sci. 2003;5(2):343–9. doi: 10.1016/s1293-2558(02)00021-3. 9. popova vf, tugova ea, zvereva ia, gusarov vv. phase equilibria in the laalo3–lasralo4 system. glass phys chem. 2004;30(6):564–7. doi: 10.1007/s10720-005-0014-z. synthesis and research of polyfunctional silicon-containing amines – new promoters of adhesion 199 d o i: 1 0. 15 82 6/ ch im te ch .2 02 0. 7. 4. 11 k. yu. ivanova, kuzmin m. v., n. i. kol’tsov chimica techno acta. 2020. vol. 7, no. 4. p. 199–203. issn 2409–5613 synthesis and research of polyfunctional siliconcontaining amines — new promoters of adhesion k. yu. ivanova*, m. v. kuzmin, n. i. kol’tsov chuvash state university named after i. n. ulyanov 15 moskovskii pr., cheboksary, 428015, russia *email: cool.karakyrt@ya.ru abstract. currently, in order to obtain high-tech hybrid products, modern adhesives have high requirements for creating strong joints between dissimilar materials. it is known that adhesion depends on the compatibility of the adhesives with the surfaces of the materials. amine compounds are the main hardeners for epoxy compositions. that is why, in this article, we synthesized silicon-containing amines based on polyfunctional aminoalkoxysiloxanes for epoxy compositions. aminoalkoxysiloxanes were prepared by the interaction of 3-aminopropyltriethoxysilane with monoethanolamine in nitrogen at atmospheric pressure in the presence of a binary antioxidant and catalytic amounts of an alkali metal alcoholate. during the reaction in a homogeneous phase, the reaction mixture was heated to a temperature of 100–110 °c and distilled off to 90% of ethanol from the theoretically calculated amount. further, the reaction was carried out at a reduced temperature of 10–20 mmhg pressure until the release of alcohol stops. at the same time, gravimetric control was carried out and the refractive index of the reaction mixture was measured. as a result, aminoalkoxysilanes were obtained in the form of light-yellow oily liquids. the structure of the obtained compounds was investigated by ir spectroscopy on an fsm-1202 fourier spectrophotometer and 1h nmr spectroscopy on a high-resolution brukerwm-250 nmr spectrometer. it was found that under the selected synthesis conditions, aminopropyltri-(2-aminoethoxy)silane is obtained with the highest yield of 97.6% at a molar ratio of 3-aminopropyltriethoxysilane agm-9 with monoethanolamine 1:3. keywords: 3-aminopropyltriethoxysilane; aminoalkoxysiloxanes; adhesion promoters received: 30.10.2020. accepted: 07.12.2020. published:30.12.2020. © k. yu. ivanova, kuzmin m. v., n. i. kol’tsov, 2020 introduction various types of aminosiloxanes are used to improve the adhesion characteristics of coatings, since silicon-containing compounds can significantly improve the adhesion of polymer resins to substrates such as glass, silica, aluminum oxide and active metals [1, 2]. the advantage of epoxy compounds is their high adhesion capacity, low shrinkage, the possibility of curing in a wide temperature range [3]. however, epoxy compositions have a number of disadvantages: high brittleness, low heat resistance, which manifests itself in a decrease in strength and stiffness at elevated temperatures. an increase in temperature at the moment of formation of the adhesive 200 contact leads to a decrease in viscosity and contributes to the achievement of the highest adhesion strength. the  chemical nature of the adhesive plays a decisive role in the adhesion of the polymer to the metal. it is  not the  number of  polar groups that is important, but the ability to enter into intense interaction with the surface groups of  the  substrate and the  ability to act as electron donors. the more clearly expressed the  electron-donor properties of functional groups, the higher their adhesion to metal [4]. experimental it is  known that organosilicon compounds are biodegradable; they can increase the intensity of biological processes of oxidation of organic pollution of wastewater and thereby reduce the  anthropogenic load on the environment [5–7]. for this, we synthesized organosilicon compounds — aminosiloxanes — as adhesion promoters, which can significantly increase the adhesive strength and water resistance of the adhesive bonds of epoxyamine coatings on various metal surfaces. aminoalkoxysilanes i–iii were obtained by the interaction of 3-aminopropyltriethoxysilane with monoethanolamine at  different molar ratios in  the  presence of a binary antioxidant and an alkali metal alcoholate. to do this, (ν1, mol) 3-aminopropyltriethoxysilane, (ν2, mol) pre-distilled monoethanolamine are loaded into a reactor equipped with a stirrer, the reaction is carried out in the presence of an antioxidant and an alkali metal alcoholate, the mixture is kept at room temperature for 10  minutes, then evacuated at  temperature up to 100 °c for 10–20 minutes, until the alcohol is completely removed. the process was monitored by ir spectroscopy on an fsm-1202 fourier spectrophotometer. the structure of the obtained compounds was confirmed by the data of nmr spectroscopy, 1h nmr — high resolution spectra were obtained on a bruker wm250 spectrometer in dmso-d6, the internal standard was hexamethylenedisiloxane. results and discussion in  this work, we have studied for the  first time the  process of  obtaining silicon-containing amines by  addition of  alkanolamines to  ethoxy-substituted derivatives, for example, to aminopropyltriethoxysilane. aminoalkoxysilanes i–iii were obtained at different molar ratios of 3-aminopropyltriethoxysilane with monoethanolamine. for this, the calculated amount of  reagents was loaded into an  arbuzov flask and heated in a nitrogen flow. the reaction begins in  a  heterogeneous phase, when a  certain temperature is  reached, the reaction mixture is homogenized (for example, at a ratio of 1:4, the homogenization temperature of the mixture is 104 °c). with a  further increase in  temperature, distillation of ethyl alcohol begins. with a  slow increase in  temperature, 80–90% of  the  theoretically calculated amount of alcohol (ethanol) was distilled off. then, at  a  reduced pressure of  10–20 mmhg completed the  reaction until the  release of alcohol ceases. аt the end of the process were performed gravimetric control and measurement of the refractive index of the reaction mixture. as a result, aminoalkoxysilanes were obtained in the form of a light-yellow oily liquid. 201 reactions of  3-aminopropyltriethoxysilane with monoethanolamine in various mole ratios are presented below: data on the  synthesis of  aminosiloxanes are given in table. 1. aminoalkoxysiloxanes were obtained as clear to light yellow oily liquids. in the ir spectra of the obtained products, there are intense absorption bands at 1081– 1085 cm–1, which are typical for si-o-c bonds. the  absorption bands of  the  hydroxyl group directly bonded to the silicon atom are absent, and the bands corresponding to the nh2 group are observed at 3275–3373 cm–1. in 1h nmr spectra of compounds i–iii the signals related to the ch2si were obsereved at 0.563 ppm, and signals of amino groups protons were observed at 2.50 ppm. in 1h nmr spectra of compounds i, ii there were signals related to the vibrations of the si-o-ch2 bond of 2-aminoethoxy and ethoxy groups at  3.33 ppm and 3.44 ppm, respectively. in  the  spectrum si eto eto eto nh2 ho nh2 si o o o nh2h2n nh2 si eto eto eto nh2 ho nh2 si eto eto eto nh2 ho nh2 si o o o nh2h2n h2n nh2 si o o o nh2 h2n etoh1. 2. 2 etoh2 3. 3 etoh3 (i) (ii) (iii) table 1 the structure and properties of aminosiloxanes № name ν1:ν2 reaction yield, % nd 20 ir spectroscopy, ν, сm–1: nmr spectroscopy, d, ppm 1 3-aminopropyl(2-aminoethoxy) diethoxysilane (i) 1:1 89.7 1.4440 3373, 3294 (nh2), 2974, 2927, 2883 (ch3, ch2), 1083 (si-o-c) 0.563 s (2h, ch2si), 1.058 t (6h, 2ch3), 2.50 s (4h, 2nh2), 2.546 m (2h, ch2ch2ch2), 2.547 t (4h, 2nh2ch2), 3.334 t (2h, 2h2nch2ch2o), 3.443 (4h, 2 ch3ch2o). m 236.373 202 of compound iii there were no vibrations of  the  protons of  the  оch2ch3 groups, which indicates the complete replacement of  the  ethoxy groups in  3-aminopropyltriethoxysilane by 2-aminoethoxy groups. conclusions to  sum up, aminoalkoxysiloxanes  — p oly f u n c t i on a l s i l i c on c ont ai n i ng amines — have been synthesized, the structure of which was confirmed by ir and 1h nmr spectroscopy. these aminoalkoxysiloxanes are recommended for use as adhesion promoters. acknowledgements this study was supported by russian foundation for basic research (rfbr), project number 20-33-90269. references 1. rogozhina lg, kuzmin mv, ignatiev va, kolyamshin oa, koltsov ni. investigation of the effect of alkanolamines on the properties of epoxy anhydride compositions. journal of applied chemistry. 2016;89(11):1481–7. doi:10.1134/s1070427216110161 2. zagidullin ai, kolpakova mv, garipov rm, stoyanov ov. structure and properties of epoxy composites hardened with new silicon-containing amines. glue. sealants. technology. 2008. (1):17–9. doi:10.1134/s1995421208030052 № name ν1:ν2 reaction yield, % nd 20 ir spectroscopy, ν, сm–1: nmr spectroscopy, d, ppm 2 3-aminopropyl-di(2-aminoethoxy) ethoxysilane (ii) 2:1 95.7 1.4521 3366, 3293 (nh2), 2971, 2927, 2875 (ch3, ch2), 1081 (si-o-c) 0.56 s (2h, ch2si), 1.06 t (3h, ch3), 2.50 s (6h, 3nh2), 2.335 t (4h, 2h2nch2ch2o), 2.544 m (2h, ch2ch2ch2), 2.546 t (6h, 3nh2ch2), 3.334 ( 2h, ch3ch2o). m 251.388 3 3-aminopropyl-tri(2-aminoethoxy) silane (iii) 3:1 97.6 1.4650 1590 (sio-c); 3362, 3293 (nh2); 1083–1020 (si-o) 0.57 s (2h, ch2si), 2.50 s (8h, 4nh2), 2.544 m (2h, ch2ch2ch2), 2.546 t (8h, 4nh2ch2), 3.333 t (6h, 3h2nch2ch2o). m 270.384 end of table 1 203 3. pradhan s, mohanty s, nayak s. waterborne epoxy adhesive derived from epoxidized soybean oil and dextrin: synthesis and characterization. international journal of polymer analysis and characterization. 2017;22(4):318–29. doi:10.1080/1023666x.2017.1295516 4. rajan r, rainosalo e, thomas sp, ramamoorthy sk, zavasnik j, vuorinen j, skrifvars m. modification of epoxy resin by silane-coupling agent to improve tensile properties of viscose fabric composites. polymer bulletin. 2018;75(1):167–95. doi:10.1007/s00289-017-2022-2 5. kunal m, libin kb. influence of naturally occurring fiber (switchgrass) reinforcement on the mechanical properties of epoxy resin. biomedical journal of scientific & technical research. 2019;20(2):14861–3. doi:10.26717/bjstr.2019.20.003418 6. efremov aa, zagidullin ai, kolpakova mv. use of  organosilicon compounds as modifiers of epoxy compositions. polymer science, series d. 2008;(1):244–8. doi:10.1134/s19954 21208040060 7. yao h, hang j, sun x, jin l, shi l, zhang j. preparation and anticorrosive behavior of epoxy-polysiloxane hybrid coatings modified by polyetheramines. journal of adhesion science and technology. 2014;28(12):1103–16. doi:10.1080/016942 43.2013.87 5609 bispyrenylalkane chemosensor for the naked-eye detection of nitro-explosives chimica techno acta letter published by ural federal university 2021, vol. 8(2), № 20218209 eissn 2411-1414; chimicatechnoacta.ru doi: 10.15826/chimtech.2021.8.2.09 1 of 4 bispyrenylalkane chemosensor for the naked-eye detection of nitro-explosives i.s. kovalev a , l.k. sadieva a,b,* , o.s. taniya a,b , v.m. yurk a , a.s. minin a,b , d.s. kopchuk a,b , g.v. zyryanov a,b , v.n. charushin a,b , o.n. chupakhin a,b a: ural federal university, 19 mira st., yekaterinburg 620002, russia b: postovsky institute of organic synthesis, ural branch of the russian academy of sciences, 22 s. kovalevskoi / 20 akademicheskaya st., yekaterinburg 620219, russia * corresponding author: leilasad@yandex.ru this short communication (letter) belongs to the regular issue. © 2021, the authors. this article is published in open access form under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). abstract pyrene-based compounds have a great potential as fluorescent chemosensors for various analytes including common nitroexplosives, such as 2,4,6-trinitrotoluene (tnt). compounds having two pyrene units in one molecule, such as bispyrenylalkanes, are able to form stable, bright emissive in a visual wavelength region excimers both in non-polar and polar environments. in this work we wish to report that in non-polar solvents the excimer has poor chemosensing properties while in aqueous solutions it provides significant “turn-off” fluorescence response to tnt in the subnanomolar concentrations. keywords detection of explosives in aqueous media chemical sensors pyrene-based fluorophores fluorescence quenching received: 15.04.2021 revised: 20.05.2021 accepted: 20.05.2021 available online: 20.05.2021 1. introduction due to an increased terrorism threats, the remote detection of tnt and dnt as main components of explosive blends [1] has become an actual task. visual detection of explosives [2–5] is one of the oldest analytical techniques offering vast possibilities for the on-site, real-time analysis with a very fast response time. among the visual methods, fluorescence [6–9] “turn-off” [10–15] detection is the most convenient due to high sensitivity and fast response time; in the last two decades, various fluorescent sensors for many analytes, including (nitro)explosives, have been reported. among many fluorescent chemosensors [16], those based on polycyclic aromatic hydrocarbons (pahbased) have gained wide attention owing to their unique fluorescent properties, such as long-wavelength excimer emission [17] either in a solution [18] or in a solid state. and pyrene-based chemosensors can be ideal candidates to use in pah-based chemosensors because of the wellknown pyrene intense emission with long lifetime values [19–28], tendency to form excimers [29] and high sensitivity to electron-deficient molecules (e.g., nitroaromatics) [30,31]. in this manuscript we wish to report our study of the ability of the simple bispyrenylalkane chemosensor to effectively detect a common nitro-explosive, such as 2,4,6-trinitrotoluene (tnt). 2. experimental starting materials are commercially available. uv-vis absorption spectra were measured on the spectrophotometer shimadzu uv-1600 (japan). emission and excitation spectra were measured on the horiba fluoromax-4 (usa). the emission spectra were normalized automatically using the “normalize columns” option in the originpro 2015 software (64-bit) b9.2.196. fluorescence titration experiments were carried out by using the horiba-fluoromax-4 spectrofluorometer (usa). photos were taken with the canon d3000 kit camera. 3. results and discussion chemosensor 1 was prepared as reported earlier [32,33] by using the condensation reaction between the 1-pyrenecarboxaldehyde and acetone with the following reduction of the obtained condensation product (fig. 1). next, the photophysical properties of compound 1 in the absence and in the presence of tnt were studied. previously, the intensive excimer emission of 10 -5 m solutions of compound 1 in methylcyclohexane was reported [32]. http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2021.8.2.09 http://creativecommons.org/licenses/by/4.0/ chimica techno acta 2021, vol. 8(2), № 20218209 letter 2 of 4 fig. 1 synthetic scheme for sensor 1 however, in our experiments only a feeble response through the excimer fluorescence quenching with poor linearity in the stern-volmer plot was observed in cyclohexane. based on the earlier reports [34,35], we suggested that the polarity of a solvent can be the driving force for the geometry changes in the molecule of 1, which are highly soluble in non-polar solvents. in polar solvent media, this lipophilic molecule could act as a surfactant and the hydrophobic interactions would make molecule 1 to bend over the pentane linker. in this case, the proximity effect between two pyrene moieties will result in excimer emission, while the monomeric emission of 1 will be suppressed. in addition, the lipophilic nature of the interior of the cavity formed by molecule 1 would provide a driving force for the transport of tnt molecules from the polar solvent media inside the non-polar micellar chemosensor to cause the dramatic excimer fluorescence quenching. to prove that, the photophysical studies of compounds 1 (10 -6 m) in different solvent systems were carried out. the selected solvents were arranged in the order of their increasing polarity: cyclohexane, thf (tetrahydrofuran), dmso (dimethyl sulfoxide), and various solutions of dmso in water. as it was expected, upon the increasing the polarity of solvents, a gradual decrease in the absolute intensity of the monomer emission was observed (fig. 2), along with an increase in the intensity of the excimer emission. the highest excimer emission was observed for the 50% aqueous solution of dmso, and this solvent was selected for our experiments. the visual detection experiments were carried out for the solution of sensor 1 by using common borosilicate glass vials (10 ml), and the picture is presented below (fig. 3). thus, depending on the concentration of tnt (10 -4 m solution of in acetonitrile) added to the 10 -6 m solution of sensor 1 in dmso/h2o (1:1), different degree of fluorescence quenching was observed (λex = 365 nm). fig. 2 emission spectra (left) and normalized emission spectra (right) of sensor 1 (10 -6 m) in the solvents of different polarity fig. 3 the visual detection experiment for chemosensor 1 in dmso/h2o (1:1): pictures of sensor 1 under uv light (λ = 365 nm) after stepwise addition of nitro explosive (tnt) chimica techno acta 2021, vol. 8(2), № 20218209 letter 3 of 4 next, the fluorescence quenching titration was carried out. the fluorescence response of the chemosensor towards the nitro-analyte was quantitatively calculated using the stern-volmer static quenching model according to eq. (1): 𝐼0 𝐼 = 1 + 𝐾sv [q] . (1) the calculated stern-volmer constant value for tnt was determined to be as high as ksv = 4.67·10 5 m -1 for the static quenching model (fig. 4). at low concentration of tnt quencher the close to linear behavior of stern-volmer plots was observed, which suggests the prevalence of only one quenching mechanism, such as static quenching. the calculated limit of detection (lod) of 143 µg/l (136 ppb) for the sensor 1 was estimated as reported earlier [36]. 4. conclusions in summary, we described a tunable bispyrenylalkane chemosensor, which provides a simple, fast and convenient way for the detection of common nitroaromatic explosive (2,4,6-tnt) in aqueous solutions. its sensory response is visible enough to be detected even by the naked eye. the value of the stern-volmer constant of the fluorescence quenching for 2,4,6-trinitrotoluene was found to be high and equal to 4.67·10 5 m -1 . acknowledgements this work was supported by the russian foundation for basic research (project № 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chronicles young sci. 2011;2(1):21. doi:10.4103/2229-5186.79345 https://doi.org/10.1139/v95-240 https://doi.org/10.1007/bf00260432 https://doi.org/10.1063/1.1672406 https://doi.org/10.3390/molecules24224083 https://doi.org/10.1016/0301-4622(82)80011-2 https://doi.org/10.1039/c7ra08142a https://doi.org/10.1021/ma020784w https://doi.org/10.1080/10601329409351530 https://doi.org/10.1524/zpch.1954.1.5_6.275 https://doi.org/10.1002/ijch.197000029 https://doi.org/10.1021/ac001347n https://doi.org/10.1524/zpch.1976.101.1-6.267 https://doi.org/10.1021/ja00168a004 https://doi.org/10.1039/c5py00096c https://doi.org/10.1039/c6py01759b https://doi.org/10.4103/2229-5186.79345 quantum chemical study of heterocyclic organic compounds on the corrosion inhibition chimica techno acta review published by ural federal university 2022, vol. 9(2), no. 20229203 eissn 2411-1414; chimicatechnoacta.ru doi: 10.15826/chimtech.2022.9.2.03 1 of 11 quantum chemical study of heterocyclic organic compounds on the corrosion inhibition dyari mustafa mamand a, awat hamad awla a, twana mohammed kak anwer b, hiwa mohammad qadr a* a: department of physics, college of science, university of raparin, 46012 sulaymaniyah, iraq b: department of physics, college of science education, salahaddin university, erbil, iraq * corresponding author: hiwa.physics@uor.edu.krd this paper belongs to a regular issue. © 2021, the authors. this article is published open access under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). abstract corrosion damages all materials, necessitating replacement and inspection related expenses. thus, the demand has increased for new corrosion inhibitor materials. the ratios of corrosion inhibition of materials are different, but organic compounds have high efficiency in aqueous corrosion inhibition for various alloys and metals. this efficiency can increase in the presence of o, n and s. the molecule provides great inhibition with the presence of both s and n atoms in the same compound. this paper investigates the 1, 3, 4-thiadiazole molecule and electronic structure of several organic compounds such as r1 and r2 which consist of different substituent groups. they were united to the ring of 1, 3, 4-thiadiazole to provide nine different derivatives. quantum computations (density functional theory, dft) at 6-311g++ (d, p) basis set and becke’s three parameters hybrid (b3lyp) level were performed using gaussian program. the purpose of this study is to determine the chemical behaviour of several heterocyclic organic compounds and to understand the process of the corrosion inhibition. keywords dft humo lumo corrosion inhibition 1, 3, 4-thiadiazole received: 25.10.21 revised: 07.04.22 accepted: 09.04.22 available online: 17.04.22 1. introduction corrosion is the degradation of the material and it is generally a slow process [1]. but it can accelerate if incompatible materials are combined, e.g. when two materials with different electrochemical activity are in electrical contact with each other. in this process, more passive metal drives the corrosion of the active metal at the same time as the passive metal remains unharmed [2–4]. this process keeps going until the active metal has been completely gone or the electrical connections between the two metals have been broken. using corrosion inhibitors is one of the best and most effective ways to protect the surface of materials from corrosion in acid environments [5]. watery corrosion of metallic surfaces can be hindered with organic materials [6]. nowadays, these compounds have a good capability for the prevention of metallic surface abuse, which has caused their widespread usage [7]. decreasing the cathode reaction with the anodic process of destruction of the mineral in acid solution, these factors all stem from the inhibitors adsorbed on the surface of the metals [8]. this leads to the creation of a diffusion barrier between two sides. the electrical conductivity is drastically decreased due to forming a diffusion barrier that surrounds the reaction sites [9]. there are many ways to prevent metallic material from corrosion. some materials , such as those containing heteroatoms, are beneficial for preventing corrosion. organic compounds containing π bonds and n, o, s have been widely used [10]. in previous years, theoretical methods have been widely used in various fields [11]. quantum computational method is realized in the gaussian program [12]. a theoretical calculations in the gaussian program can be used to estimate corrosion inhibition performances of molecules [13]. the corrosion inhibition efficiencies are determined by the experimental method and allowed to estimate the corrosion inhibition mechanisms of composites in terms of weight loss [14]. nitrogen and sulfur are two important atoms for inhibition. it would be beneficial, if the two of them came together in the same molecule [14]. however, if the compounds consist of oxygen or nitrogen, the effect will be reduced. so, it will not provide an excellent inhibition [15]. the ability of these compounds to inhibit corrohttp://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2022.9.2.03 mailto:hiwa.physics@uor.edu.krd http://creativecommons.org/licenses/by/4.0/ https://orcid.org/0000-0001-5585-3260 https://crossmark.crossref.org/dialog/?doi=https://doi.org/10.15826/chimtech.2022.9.2.03&domain=pdf&date_stamp=2022-4-17 chimica techno acta 2022, vol. 9(2), no. 20229203 review 2 of 11 sion depends on the structure of the molecular [16]. the adsorption of these molecules on metallic surfaces is important in this regard, and it is possible to estimate it, as it depends on the lone electron pairs in the heteroatoms [17]. the computational method in quantum chemistry is able to predict some parameters such as hardness and softness [18, 19]. this paper investigates the molecular structure and electronic behaviour of some organic compounds by using quantum computational method based on dft. hardness, softness, electronegativity and chemical potential are important parameters for quantum chemical method. 2. computational details density functional theory (dft) is a computational quantum mechanical modelling method used in this study to calculate the electronic structure of atoms and molecules [20]. the quantum chemical calculations based on dft at 6-311g++ (d, p) basis set were used because this basis set is very popular for determining the electronic and molecular geometry accurately. all computations were performed with gaussian 09 package program. the 6-311g is the standard, splitvalence and double-zeta basis set use to describe the core and valence orbitals, (d, p) are polarization function to describe the chemical bonds and ++ are diffuse functions [21]. 6311g++ (d, p) basis set is very useful and can accurately calculate high occupied molecular orbital (homo), lower unoccupied molecular orbital (lumo), hardness, softness, electronegativity, chemical reaction, electrophilicity, proton affinity and nucleophilicity [22]. the use of fukui indices can predict the local molecular reactivity [23]. the fukui function 𝑓(𝑟) can be written with the following expression [24]: 𝑓(𝑟) = ( 𝜌(𝑟) 𝜕𝑁 ) 𝑣(𝑟) , (1) where 𝜌 is the electronic density of the system under consideration, 𝑁 is the number of electrons and 𝑣(𝑟) is the external potential. removal or addition of an electron in the relaxation effects is not measured approximately from the fukui function. the removal and addition of an electron can be expressed as follows: 𝜌−(𝑟) ≈ 𝜌𝐿𝑈𝑀𝑂 (𝑟), (2) 𝜌+(𝑟) ≈ 𝜌𝐻𝑂𝑀𝑂 (𝑟), (3) where 𝜌𝐿𝑈𝑀𝑂 (𝑟) is the density for the lowest unoccupied molecular orbital and 𝜌𝐻𝑂𝑀𝑂 (𝑟) is the density of the highest occupied molecular orbital [25]. condensed fukui functions are used for the local activity sites which are determined by using the infinitesimal change, limited variation and approximations of quantum computational chemistry from the mulliken population analysis of atoms, which depend on the direction of electron transfer of atoms in molecules [26]. there are two types of local active sites the nucleophilic and the electrophilic. in the nucleophile site, the electrons will transfer from the nucleophile to the electrophile. but, in the electrophile site, the electron will transfer to the end site of electrophile [27]. each of r1 and r2 consist of different substituent groups, which are united to the ring of 1, 3, 4-thiadiazole to provide nine various derivatives as shown in figure 1, where r1 consists of (h), hydrogen, and (–ch3), methyl, while r2 consists of a variety of substituents united to 1, 3, 4thiadiazole. the substituent groups consist of ethyl (–c2h5), methyl (–ch3), propyl (–c3h7), chloroethyl (–c2h5–cl), hydroxyethyl (–c2h5–oh), tioethyl (–c2h5–sh), carboxyethyl (–c2h5–cooh) and aminoethyl (–c2h5–nh2). figure 2 shows the chemical structure of 1, 3, 4-thiadiazole derivatives 1–9. figure 1 chemical structure of 1, 3, 4-thiadiazole ring with r1 and r2 substituents. 3. computational results quantum computational chemistry method optimized geometries of the compounds withnine various substitutions of the ring (1, 3, 4-thiadiazole) by using gaussian program with 6-311g++ (d, p) basis set as shown in figure 2 [28, 29]. the structures of these derivatives are presented in figure 3: (1) 2-methyl-1,3,4-thiadiazole (2) 2-propyl-5methyl-1,3,4-thiadiazole (3) 2,5-dimethyl-1,3,4-thiadiazole; (4) 2-ethyl-5-methyl-1,3,4-thiadiazole (5) 2-(2-hidroxy ethyl)-5-methyl-1,3,4-thiadiazole; (6) 2-aminoethyl-5-methyl1,3,4-thiadiazole; (7) 2-(2-chloroethyl)-5-methyl-1,3,4thiadiazole; (8) 2-(2-carboxy ethyl)-5-methyl-1,3,4thiadiazole; and (9) 2-(2-tioethyl)-5-methyl-1,3,4-thiadiazole. 4. quantum chemical calculations homo, lumo and frontier orbital gap are significant parameters in quantum computational chemistry. they are important for the kinetic stability and chemical reactivity of the molecules [30, 31]. table 1 shows the bandgap energies of nine different derivatives. the charge-transfer interaction inside the molecule is explained by the energy gap of homo and lumo [32]. they are two popular parameters in quantum chemistry. frontier orbitals are the main factors to describe the molecule's interaction with other species. chimica techno acta 2022, vol. 9(2), no. 20229203 review 3 of 11 inh 1 homo lumo inh 2 homo lumo inh 3 homo lumo inh 4 homo lumo inh 5 homo lumo inh 6 homo lumo inh 7 homo lumo inh 8 homo lumo inh 9 homo lumo figure 2 the optimized structures of lumo and homo using dft/b3lyp/6-31++g (d, p) of non-protonated inhibitor molecules 1 to 9 in gas phase. chimica techno acta 2022, vol. 9(2), no. 20229203 review 4 of 11 figure 3 chemical structure of 1, 3, 4-thiadiazole derivatives 1–9. the chemical interaction between homo and lumo decides the formation of transition states [33]. the ability of molecules to donate electrons can be found with the energy of ehomo [34]. the tendency to donate electrons in the molecules is related to the energy of ehomo [35]. if the molecule has a high ehomo, the tendency to donate an electron will increase to allow acceptor molecules with low energy and empty molecular orbital. facile adsorption of molecules (i.e. the inhibition) will increase with the increase in the value of ehomo due to adsorbed layer which influences the transportation process [36]. the probability of accepting electrons by the molecules is related to the value of elumo, the tendency of accepting electrons by molecules will increase with the lower value of elumo. materials have a good inhibition efficiency if they have lower bandgap energy. in this case, more energy is required to transfer the electron from the last lowest occupied orbital and the surface of the material [37]. in recent years, quantum chemical approaches have shown to be particularly beneficial in the assessment of prospective corrosion inhibitors. quantum chemical parameters based on the dft, such as chemical potential, chemical hardness, electrophilicity, electronegativity, and nucleophilicity, have been used to investigate the results of the computational chemistry works' consistency with experimental data [38]. indeed, koopmans theorem is one of the most significant contributions to the computational chemistry research. following that, it is possible to explain hard and soft acidbase (hsab) theory in detail. pearson developed the hsab theory as a result of studies on lewis acid bases in the 1960 [39]. bases and lewis acids were characterized as hard or soft, based on this hypothesis. the hard acids choose to correlate with hard bases, but soft acids prefer to associate with soft bases. the description for these purposes is that the soft-soft interactions are frequently covalent, but hard-hard interactions are electrostatic. because the corrosion inhibitors are lewis bases, the hsab theory should be included in corrosion research [13]. furthermore, the hsab theory is a significant advancement in quantum chemistry, which is useful in a variety of theoretical and experimental research involving corrosion inhibitors, chemical equilibrium, complex stability, precipitation 2-methyl-1, 3,4-thiadiazol 2-propyl-5-methyl-1,3,4-thiadiazole 2,5-dimethyl-1,3,4-thiadiazole 2-ethyl-5-methyl-1,3,4-thiadiazol 2-(2-hidroxyethyl)-5-methy1-1,3,4-thiadiazole 2-aminoethyl-5-methyl-1,3,4-thiadiazole 2-(2-chloroethyl)-5-methyl-1, 3,4-thiadiazole 2-(2-carboxyethyl)-5-methyl-1,3,4-thiadiazole 2-(2-tioethyl)-5-methyl-1, 3,4-thiadiazole chimica techno acta 2022, vol. 9(2), no. 20229203 review 5 of 11 titrations and gravimetry. the chemical potential (μ), chemical hardness (η) and reactivity indexes electronegativity (χ) are described as derivatives of the number of electrons (n) of the electron energy (e) at external potential (v) in the conceptual dft. the expression for the mathematical operations can be obtained as: 𝐼 = −𝐸𝐻𝑂𝑀𝑂 , (4) 𝐴 = −𝐸𝐿𝑈𝑀𝑂 , (5) 𝜒 = ( 𝐼 + 𝐴 2 ), (6) 𝜂 = ( 𝐼 − 𝐴 2 ), (7) 𝜎 = 1 𝜂 , (8) 𝜔 = 𝜇2 2𝜂 , (9) where i is the ionization energy, a is the electron affinity, σ is the softness and ω is the electrophilicity. 5. mulliken atomic charges and fukui function calculations in the gas phase the value of bandgap energy of each derivative reduces, evidencing the increase of corrosion inhibition of 1, 3, 4thiadiazole with substituents. the hardness and softness of molecules are related to elumo and ehomo. reactivity wards chemical species depends on the bandgap energy, where high reactivity wards chemical species indicates a small bandgap [40]. a hard molecule has lower reactivity than a soft molecule because a soft molecule has a small bandgap energy [41]. reactivity and stability of molecules are two parameters that can be determined by measuring the softness and hardness properties of molecules [42, 43]. the harness properties of the materials in a low perturbation of the reactions are the resistance to prevent deformation, preventing the polarization of the electron cloud of the molecules. inhibition properties of the molecules will rise with an increase in the value of softness. inhibition efficiency will be highest when the softness is the highest, which is in agreement with our conclusions [44]. all calculations were performed with quantum computational chemistry for the derivatives of 1, 3, 4-thiadiazole in the gas phase, as shown in tables 1 and 2. for each of derivatives of 1, 3, 4-thiadiazole molecule, fukui indices have been calculated. tables 1 and 2 are expressed in terms of ionization energy, where ∆𝐸, cp and 𝜀 are the energy gap, the chemical potential and the nucleophilicity. table 1 shows the calculated values of ehomo and elumo for the investigated derivatives 1–9 in non-protonated gas. the order of inhibition efficiency of the investigated inhibitors corresponds to the order established from theoretical data based on ehomo, which is 1<9<8<3<4<5<6<7<2. however, based on the results obtained for elumo in the gas phase, the value of elumo changes follows: 1>9>8>3>4>5>6>7>2. as a function of the reaction of the inhibitor molecule towards adsorption on the metal surface, the energy gap is an important descriptor. the reactivity of the molecule increases due to the reduction of ∆𝐸. it is known that corrosion inhibitors with small energy gaps are effective because the ionization energy needed to remove the electron from the final occupied orbital is low. according to bereket et al., organic compounds do not only donate electrons to empty metal orbitals, but also accept free electrons from metals [45]. furthermore, a molecule with a lower energy gap appears to be more polarizable and typically characterized by low kinetic stability and strong chemical activity. the results in table 1 shown that inhibitor 1 has the smallest energy gap under all conditions, which means the molecule can perform better as a corrosion inhibitor. absolute hardness and softness are well-known qualities to determine molecule stability and reactivity. according to obi-egbedi, chemical hardness is defined as the resistance to deformation or polarization of the electron cloud of atoms, ions, or molecules under minor perturbations of chemical reactions [46]. a soft molecule has a tiny energy gap, whereas a hard molecule has a big energy gap. as a result, molecules in the lowest global hardness values are supposed to be effective corrosion inhibitors for bulk metals in acidic environments. table 1 gas phase calculations with 6-311++(d, p) basis set and b3lyp level for molecular characteristics of compounds 1–9. no. homo (ev) lumo (ev) i a ∆𝑬 (ev) 𝜼 𝝈 𝝌 cp 𝝎 𝜺 1 –6.2861 –2.1850 6.28615 2.18509 4.1010 2.05053 0.48767 4.235 62 –4.235628 4.3745 0.22859 2 –6.8684 –6.4850 6.86847 6.48506 6 0.3834 0.19170 5.21632 6.676 77 –6.6767 116.27 0.00860 3 –7.1555 –3.5951 7.15556 3.59519 3.5603 1.78018 0.56174 5.375 37 –5.37537 8.1156 0.12321 4 –7.5808 –5.5582 7.58087 5.55824 2.0226 1.01131 0.98880 6.569 56 –6.56956 21.338 0.04686 5 –7.1955 –6.1615 7.19556 6.16152 1.0340 0.51702 1.93415 6.678 54 –6.6785 43.134 0.02318 6 –7.3011 –6.3490 7.30114 6.34901 0.9521 0.47606 2.10054 6.825 07 –6.8250 48.923 0.02044 7 –6.4091 –5.6156 6.40914 5.61565 0.7934 0.39674 2.52050 6.012 40 –6.01240 45.556 0.02195 8 –7.5982 –5.1299 7.59829 5.12993 2.4683 1.23418 0.81025 6.364 11 –6.36411 16.408 0.06094 9 –6.6184 –3.9364 6.61840 3.93643 2.6819 1.34098 0.74571 5.277 41 –5.27741 10.384 0.09629 chimica techno acta 2022, vol. 9(2), no. 20229203 review 6 of 11 table 2 gas phase calculations of fukui functions and mulliken atomic charges at 6-311g++ (d, p) basis set at b3lyp level for derivatives 1–9. no. atoms 𝒒𝑵 𝒒𝑵+𝟏 𝒒𝑵−𝟏 𝒇𝒌 + 𝒇𝒌 − 𝒇𝒌 𝟎 1 n4 –0.106 –0.030 –0.130 0.076 0.024 0.050 n5 0.065 0.166 –0.034 0.101 0.099 0.100 s6 0.082 0.228 –0.124 0.146 0.206 0.176 2 n4 0.025 0.061 0.011 0.036 0.014 0.025 n5 –0.315 –0.215 –0.329 0.100 0.014 0.057 s6 0.235 0.349 0.209 0.114 0.026 0.070 3 n4 –0.227 –0.148 –0.254 0.079 0.027 0.053 n5 –0.296 –0.218 –0.299 0.078 0.003 0.0405 s6 0.402 1.035 0.332 0.633 0.070 0.3515 4 n4 0.034 0.039 0.008 0.005 0.026 0.0155 n5 –0.354 –0.317 –0.362 0.037 0.008 0.0225 s6 0.266 0.359 0.235 0.093 0.031 0.062 5 n4 0.070 0.075 0.016 0.005 0.054 0.0295 n5 –0.303 –0.294 –0.312 0.009 0.009 0.009 s6 0.194 0.226 0.179 0.032 0.015 0.0235 o16 –0.353 –0.307 –0.365 0.046 0.012 0.029 n4 0.070 0.075 0.016 0.005 0.054 0.0295 6 n4 –0.144 –0.129 –0.181 0.015 0.037 0.026 n5 –0.318 –0.297 –0.331 0.021 0.013 0.017 s6 0.309 0.396 0.290 0.087 0.019 0.053 n16 –0.378 –0.290 –0.479 0.088 0.101 0.0945 7 n4 0.056 0.058 –0.012 0.002 0.068 0.035 n5 –0.237 –0.230 –0.240 0.007 0.003 0.005 s6 0.116 0.200 0.109 0.084 0.007 0.0455 cl12 0.764 0.822 0.639 0.058 0.125 0.0915 8 n4 –0.016 –0.011 –0.066 0.005 0.05 0.0275 n5 –0.250 –0.211 –0.256 0.039 0.006 0.0225 s6 0.195 0.298 0.181 0.103 0.014 0.0585 9 n4 –0.193 –0.191 –0.239 0.002 0.046 0.0240 n5 –0.356 –0.321 –0.365 0.035 0.009 0.0220 s6 0.253 0.286 0.213 0.033 0.040 0.0365 inhibitor adsorption occurs on a metal surface in the softest part of the molecule. table 1 shows the calculated values of the gas phases for the analysed derivatives 1–9. compared with other inhibitors, 1, 3, 9 and 8 have the highest levels of hardness. compared with the derivatives, the data for b3lyp/6-311++g (d, p) show that inhibitor 1 has the highest stiffness value of 2.05 ev in the nonprotonated gas phase. table 2 shows the gas phase calculations of fukui functions and mulliken atomic charges at 6-311g++ (d, p) basis set at b3lyp level for derivatives 1–9, where 𝑓𝑘 +, 𝑓𝑘 − and 𝑓𝑘 0 are the nucleophilic attack, the electrophilic attack and the radical attack. a high value of the nucleophilic attack site indicates the increased ability of the molecules to accept electrons, and the molecule will be more able to stabilize additional electrons [47]. the tendency of a molecule to donate electrons is defined by the high electrophilic site value. the ability of the metal surface to donate electrons increases with an increase in the inhibition efficiency [40]. figure 3 shows the optimized structures lumo and homo using dft/b3lyp/6-31++g (d, p) of nonprotonated inhibitor molecules 1–9. 6. mulliken atomic charges and fukui function for derivatives 1–9 in the presence of water only four atoms o, n, s, and cl were shown in mulliken charge and fukui function calculations to determine the effect of each of the atoms on the molecule because of the existence of electrochemical corrosion in the liquid phase. it is obvious that quantum computational calculations in the aqueous phase are necessary to show the effect of solvents on corrosion inhibition of organic compounds. for this purpose, gaussian program can describe the properties of organic compounds. in this case, the polarized continuum method pcm was used [48]. the solute is placed in a cavity of a roughly molecular shape. for determining the effect of solvent on geometry optimization calculations, the solvent in these models is defined by a continuum that interacts with charges on the cavity surface [49]. table 3 shows the aqueous phase calculations with 6-311++ (d, p) basis set and b3lyp level for molecular characteristics of the compounds 1–9. table 4 shows the aqueous phase calculations of fukui functions and mulliken atomic charges at 6-311g++ (d, p) basis set at b3lyp level for the derivatives 1–9. chimica techno acta 2022, vol. 9(2), no. 20229203 review 7 of 11 table 3 aqueous phase calculations with 6-311++ (d, p) basis set and b3lyp level for molecular characteristics of compounds 1–9. no. homo (ev) lumo (ev) i a ∆𝑬 (ev) 𝜼 𝝈 𝝌 cp 𝝎 𝜺 1 –8.26307 –4.0488 8.26307 4.04881 4.21426 2.10713 0.47457 6.15594 –6.1559 8.992 0.11120 2 –7.59611 –7.1969 7.59611 7.19692 0.39919 0.19959 5.01009 7.39652 –7.3965 137.04 0.00729 3 –7.23093 –5.7757 7.23093 5.77579 1.45514 0.72757 1.37443 6.50336 –6.5033 29.065 0.03440 4 –6.82249 –4.9440 6.8224 4.94407 1.87841 0.93920 1.06472 5.88328 –5.8832 18.426 0.05426 5 –6.44425 –5.4951 6.4442 5.49511 0.94914 0.47457 2.10716 5.96968 –5.9696 37.546 0.02663 6 –6.59527 –5.5862 6.59527 5.58626 1.00900 0.50450 1.98214 6.09077 –6.0907 36.766 0.02719 7 –6.40914 –5.6156 6.4091 5.6156 0.7934 0.3967 2.5205 6.01240 –6.0124 45.556 0.02195 8 –6.81324 –4.4303 6.8132 4.4303 2.3829 1.1914 0.8393 5.6217 –5.6217 13.262 0.07539 9 –6.61840 –3.9364 6.6184 3.9364 2.6819 1.3409 0.7457 5.2774 –5.2774 10.384 0.09629 table 4 aqueous phase calculations of fukui functions and mulliken atomic charges at 6-311g++ (d, p) basis set at b3lyp level for derivatives 1–9. no. atoms 𝒒𝑵 𝒒𝑵+𝟏 𝒒𝑵−𝟏 𝒇𝒌 + 𝒇𝒌 − 𝒇𝒌 𝟎 1 n4 –0.288 –0.114 –0.333 0.174 0.045 0.1095 n5 –0.219 –0.205 –0.238 0.014 0.019 0.0165 s6 0.633 1.189 0.575 0.556 0.058 0.307 2 n4 0.033 0.061 0.011 0.028 0.022 0.025 n5 –0.212 –0.215 –0.329 –0.003 0.117 0.057 s6 0.248 0.349 0.209 0.101 0.039 0.07 3 n4 –0.511 –0.441 –0.535 0.07 0.024 0.047 n5 –0.519 –0.430 –0.535 0.089 0.016 0.0525 s6 0.804 1.450 0.761 0.646 0.043 0.3445 4 n4 0.034 0.039 0.008 0.005 0.026 0.0155 n5 –0.354 –0.317 –0.362 0.037 0.008 0.0225 s6 0.266 0.359 0.235 0.093 0.031 0.062 5 n4 0.070 0.075 0.016 0.005 0.054 0.0295 n5 –0.303 –0.294 –0.312 0.009 0.009 0.009 s6 0.194 0.226 0.179 0.032 0.015 0.0235 o16 –0.353 –0.307 –0.365 0.046 0.012 0.029 6 n4 –0.144 –0.129 –0.331 0.015 0.187 0.101 n5 –0.318 –0.297 –0.181 0.021 –0.137 –0.058 s6 0.309 0.369 0.290 0.06 0.019 0.0395 n16 –0.378 –0.290 –0.479 0.088 0.101 0.0945 7 n4 0.056 0.058 –0.012 0.002 0.068 0.035 n5 –0.237 –0.230 –0.240 0.007 0.003 0.005 s6 0.116 0.200 0.109 0.084 0.007 0.0455 cl12 0.764 0.822 0.639 0.058 0.125 0.0915 8 n4 –0.016 –0.011 –0.066 0.005 0.05 0.0275 n5 –0.250 –0.211 –0.256 0.039 0.006 0.0225 s6 –0.195 0.298 0.181 0.493 –0.376 0.0585 9 n4 –0.193 –0.191 –0.239 0.002 0.046 0.024 n5 –0.356 –0.321 –0.365 0.035 0.009 0.022 s6 0.253 0.286 0.213 0.033 0.04 0.0365 the bond distance from the analyses of the optimized geometry at 6-311++g (d, p) basis set between c2 and r2 remained unchanged and equal to 1.54 å. the bond angle of the 1, 3, 4-thiadiazole internal ring for s6–c2–n4 and s6–c2–n4 is 111.10865–111.108660, respectively. at the first derivative, the difference between them is very small, but at the second derivative it is 0.0060. the bond angle between c1-n4 and c2–n4 is in the same range for all derivatives, about 1.349830 and 1.349820. the bond length between c1–n4 and c2–n4 shows just small variations. for this purpose, it is reasonable to arrange all the derivatives which showed a length of c1–n4 and c2–n4 bond of 1.34 å. the bond angle between s6–c1 and s6–c2 is 1.758050 for each of the optimized geometry calculations, indicating the formation of single bonds between these atoms. n4, n5, s6, o16 and cl12 have a high electronic density, which was calculated by mulliken population analysis for each derivative. due to the high electronic density, these atoms are nucleophilic when they interact with the metallic surface. the homo calculations in the presence of solvents (water) are shown in figure 3. in all compounds, homo is placed on both sides of the functional groups attached to the 1, 3, 4-thiadiazole ring. this calculation shows the positions of the approved active sites for an electrophilic attack. the active region is distributed around the molecule belonging to the 1, 3, 4-thiadiazole ring. the inhibitor with the lowest global hardness (and thus the highest global softness) is likely to have the best inhibition efficiency. the following anticorrosion efficiency was predicted in our study: the inhibitor 2 is more efficient than the inhibitor 7, 5 – than 6, 9 – than 1. according chimica techno acta 2022, vol. 9(2), no. 20229203 review 8 of 11 to hasanov et al., adsorption can occur in the part of the molecule where softness is at maximum [50]. an electrophile is a chemical species that accepts a pair of electrons. the molecule with the larger electrophilicity value has the greater ability to receive electrons, and its opposite will behave as a good nucleophile. tables 1 and 2 shows the compounds with low electrophilic values (good nucleophiles). table 3 shows both the electrophilic and nucleophilic data. the corrosion inhibition efficiency rating of the investigated compounds can be defined as follows: 1<9<8<4<3<6<5<7<2. when electronegativity and chemical potentials are equal, electrons flow from the lower-electronegative site to the higher as the inhibitor and iron come close to each other. the fraction of electrons transferred can be calculated from the following equation: δ𝑁𝑚𝑎𝑥 = 𝜒𝐹𝑒 − 𝜒𝑖𝑛ℎ 2(𝜂𝐹𝑒 − 𝜂𝑖𝑛ℎ ) . (10) the electronegativity of the inhibitor and the metal are represented by 𝜒𝐹𝑒 and 𝜒𝑖𝑛ℎ. the chemical hardness of the inhibitor is 𝜂𝑖𝑛ℎ and that of the metal – 𝜂𝐹𝑒. pearson has been demonstrated that electron transfer is driven by electronegativity differences and the aggregation of 𝜂 factors acts as a barrier [51]. as a result, the electronegativity of fe = 7 ev and a global 𝜂 of fe = 0 were used to calculate the ratio of electrons transferred assuming that for the metallic mass i is equal to a because it is softer than the neutral metal atoms [52]. tables 5 and 6 shows quantum chemical parameters of derivatives 1–9 in the gas and aqueous phases with 6-311++ (d, p) basis set and b3lyp level. the positive number δ𝑁𝑚𝑎𝑥 indicates that the molecules are electron acceptors, while the negative number of δ𝑁𝑚𝑎𝑥 indicates that the molecules are electron donors. as a result of that as the electron-donating capacity of these inhibitors increases on the metal surface, the inhibition efficiency also increases. moreover, as the electron-donating ability at the metal surface increases, the inhibition efficiency also increases if δ𝑁𝑚𝑎𝑥<3.6. the inhibitor molecules' capacity to accept electrons changes in the sequence 7>2>1>9>3>5>8>4>6 in the gas phase and in the aqueous phase – as follows: 7>8>9>6>4>8>3>1>2. the inhibitor 2 is a donor compound in the aqueous phase. figure 5 shows the optimized structures, homos of non-protonated inhibitor molecules using dft/b3lyp/6-31++g (d, p) in the aqueous phase. a study by gomez et al. postulated that an electronic back-donation mechanism can control the interaction between the metal surface and the inhibitor molecule, based on the charge transfer model for back-donation and donation of charges [53, 54]. according to this theory, if backdonation transfers from the molecule and electron to the molecule at the same time, the energy change δ𝐸𝑏−𝑑 is proportional to the molecule's hardness. that is, δ𝐸𝑏−𝑑 = − 𝜂 4 . (11) from the molecule to the metal, the back donation is strongly preferred when 𝜂 > 0 or δ𝐸𝑏−𝑑 < 0 . it indicates that charge transfer to the molecule is accompanied by the back donation from the molecule, which is energetically beneficial on the metal surface, if the higher adsorption of the molecule enhances inhibition effectiveness. then, the inhibition efficiency should arise with the increase in the stabilization energy induced by the contact between the inhibitor and the metal surface. in this study, the calculated δ𝐸𝑏−𝑑 values exhibit the tendency: 2>7>5>6>4>8>9>3>1 in the gas phase, and in the aqueous phase the tendency is: 2>7>5>6>3>4>8>9>1, as shown in tables 5, 6. tables 1 and 3 show aqueous phase calculations with 6311++ (d, p) basis set and b3lyp level for molecular characteristics of compounds 1–9. it is an important parameter that can predict the chemical reactive ratio of the molecule. consequently, the reactivity sequence for the derivatives in the liquid phase are: 1<9<8<4<3<6<5<7<2 liquid phase, 1<9<8<3<4<5<6<7<2 gas phase. 2-methyl-1, 3, 4-thiadiazole has a high hardness in the gas phase and aqueous phase, besides 2-propyl-5-methyl1, 3, 4-thiadiazole has the lowest value of hardness. tables 2 and 4 describe the fukui indices which are more significant to predict the lowest and highest susceptible site for electrophilic attack. the most susceptible sites are n4 and s6. n4 and n16 have the highest amount in 2-aminoethyl5-methyl-1, 3, 4-thiadiazole in the aqueous phase which are equal to 0.187 and 0.101. in the gas phase calculations, cl atom in 2-(2-chloroethyl)-5-methyl-1, 3, 4-thiadiazole and n16 in 2-aminoethyl-5-methyl-1, 3, 4-thiadiazole have the maximum value of electrophilic attack which are equal to 0.125 and 0.101 respectively. figure 4 variation of quantum chemical parameters with the nature of the inhibitor. chimica techno acta 2022, vol. 9(2), no. 20229203 review 9 of 11 table 5 quantum chemical parameters of derivatives 1–9 in the gas phase with 6-311++ (d, p) basis set and b3lyp level. inhibitors 1 2 3 4 5 6 7 8 9 δ𝑁 0.674 0.843 0.456 0.212 0.310 0.183 1.244 0.257 0.642 δ𝐸𝑏−𝑑 –0.512 –0.047 –0.445 –0.252 –0.129 –0.119 –0.099 –0.308 –0.335 table 6 quantum chemical parameters of derivatives 1–9 in the aqueous phase with 6-311++ (d, p) basis set and b3lyp level. inhibitors 1 2 3 4 5 6 7 8 9 δ𝑁 0.200 –0.99 0.341 0.594 1.085 0.901 1.244 0.578 0.642 δ𝐸𝑏−𝑑 –0.526 –0.049 –0.18 –0.23 –0.118 –0.126 –0.099 –0.297 –0.335 1 2 3 4 5 6 7 8 9 figure 5 the optimized structures, homos of non-protonated inhibitor molecules using dft/b3lyp/6-31++g (d, p) in aqueous phase. 7. conclusions quantum computational chemistry approach with 6-311++ (d, p) basis set and becke’s threeparameters hybrid exchange-correlation functional (b3lyp) using dft was used to perform the theoretical calculations. we carried out the geometry optimization of the investigated compounds resulting from the substitution of the ring of 1, 3, 4thiadiazole with various groups. homo and lumo are extremely useful to determine such parameters as bandgap energy, hardness, softness, ionization energy, electrophilicity, nucleophilicity and electronegativity of molecules to indicate chemical reactive behaviour. low bandgap and high softness indicate the interaction between inhibitor substituent and 1, 3, 4-thiadiazole. moreover, we predicted the adsorption abilities of the 1, 3, 4-thiadiazole surface of inhibitor molecules by considering eg and harness. in the gas phase and the aqueous phase, dynamic simulation approximations to demonstrated the corrosion inhibition performance of the studied inhibitors against the corrosion of 1, 3, 4-thiadiazole. the relative performance in the gas and aqueous phases can be given as 1<9<8<3<4<5<6<7<2, 1<3<9<8<3<4<5<6<7<2, respectively. the mulliken population analysis was used to determine the fukui indices to detect the reactive sites. in conclusion, the study shows that n4 has a more reactive site in the gaseous and aqueous phases of these derivatives. if these atoms – o, n, s – are present in the molecule, the corrosion inhibition increases. the highest value was found in the aqueous phase in the n4 atoms in 2aminoethyl-5-methyl-1, 3, 4-thiadiazole, which has a susceptible site for electrophilic attack. supplementary materials no supplementary materials are available. funding this research had no external funding. acknowledgments none. author contributions conceptualization: d.m.m., h.m.q. data curation: d.m.m. chimica techno acta 2022, vol. 9(2), no. 20229203 review 10 of 11 formal analysis: d.m.m, a.h.a., t.m.k. funding acquisition: d.m.m., h.m.q. investigation: d.m.m., h.m.q. methodology: d.m.m., h.m.q. project administration: d.m.m. resources: d.m.m., h.m.q. software: d.m.m. supervision: d.m.m. validation: d.m.m. visualization: h.m.q. writing – original draft: h.m.q., d.m.m. writing – review & editing: h.m.q. conflict of interest the authors declare no conflict of interest. additional 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https://doi.org/10.1073/pnas.83.22.8440 https://doi.org/10.1007/s40735-021-00566-9 https://doi.org/10.1021/jp057143y https://doi.org/10.17725/rensit.2020.12.451 molecular complexation of hederasaponin c with cholesterol in aqueous isopropyl alcohol 150 d o i: 1 0. 15 82 6/ ch im te ch .2 02 0. 7. 4. 02 yakovishin l. a., grishkovets v. i., korzh e. n., golovchenko i. v., nagirnyak a. a. chimica techno acta. 2020. vol. 7, no. 4. p. 150–153. issn 2409–5613 molecular complexation of hederasaponin c with cholesterol in aqueous isopropyl alcohol l. a. yakovishina*, v. i. grishkovetsb, e. n. korzha, i. v. golovchenkoa, a. a. nagirnyaka a sevastopol state university, 33 university str., sevastopol, 299053, russia b v. i. vernadsky crimean federal university, 4 vernadsky ave., simferopol, 295007, russia *email: chemsevntu@rambler.ru abstract. the 1:1 molecular complex of ivy triterpene glycoside hederasaponin c (hedc) with cholesterol (chol) was obtained in aqueous isopropyl alcohol. the stability constant of (3.3 ± 0.7) · 106 (mol/l)–1 was calculated for the complex. the complexation was studied by uvand atr ir-fourier spectroscopy, and method of isomolar series. the hydrogen bonds and hydrophobic interactions are formed in the molecular complex. keywords: triterpene glycosides; hederasaponin c; cholesterol; molecular complex received: 06.08.2020. accepted: 07.12.2020. published:30.12.2020. © yakovishin l. a., grishkovets v. i., korzh e. n., golovchenko i. v., nagirnyak a. a., 2020 introduction t r i t e r p e n e g l y c o s i d e h e d e r a s a p o n i n c ( h e d e r a g e n i n 3 o -αlrham nopy r ano s y l ( 1→2 ) o -αl a r a b i n o p y r a n o s y l 2 8 о -αl r h a m n o p y r a n o s y l ( 1→ 4 ) о -β d g l u c o p y r a n o s y l ( 1→6 ) о -βd glucopyranoside, hedc; fig.  1) was discovered in the most species of the ivy genus hedera  l. (araliaceae juss.) [1]. hedc is the dominant ivy saponin. hedc was also founded in plants of various species of kalopanax, in aralia elata, acanthopanax sieboldianus and schefflera octophylla [1]. h h oh h h 1 3 5 6 11 12 13 15 9 10 8 14 17 22 24 25 26 27 18 19 20 21 23 chol 1 3 12 23 28 16 20 30 9 18 o o oh oh o oh oh oh ch3 o coor oh 1'' 2' 5' hedc fig. 1. structures of hedc (r = ←βglcp-(6←1)-βglcp-(4←1)-αrhap) and chol 151 hedc is the component of antitussive drugs prospan, hedelix and other containing hedera helix l. leaves [1]. a characteristic feature of triterpene glycosides is their ability to form molecular complexes with sterols [1–4]. the complexation of saponins with sterols is responsible for hemolytic, antitumor, ichthyotoxic, molluscicidal, antifungal, hypocholesterolaemic, and embryotoxic activity of triterpene glycosides [1, 2]. on the other hand, it was reported that some triterpene glycosides do not form a molecular complex with cholesterol (chol; fig. 1) [3]. the interaction of hedc with chol has been studied by spectrophotometric titration in aqueous ethanol [3] and isomolar series [4]. a preparation of molecular complex of chol with hedc and bisdesmoside ivy triterpene glycoside hederacoside b mixture in aqueous ethanol and its analysis by planar chromatography [2] was previously reported. to  study the  complexation of  hedc with chol in various media we examined their interaction in 80% aqueous isopropyl alcohol. experimental hedc was preparatively isolated from leaves of hedera canariensis willd. (araliaceae juss.) by column chromatography on sio2 and its structure was confirmed using chemical and physical methods [5]. the  isomolar series were prepared by mixing 10–4 mol/l solutions of hedc and chol in 80% aqueous isopropyl alcohol (v/v) at 25 °c for 40 min with continuous stirring. spectroscopic analysis of isomolar series was performed on a leki ss2110uv spectrophotometer using a quartz cuvette (l = 1 cm) at  25  °c.  stability constant of the complex was calculated according to the a. k. babko method based on isomolar curves [4, 6]. the  complex of  chol with hedc was preparatively obtained by  liquidphase method. for this purpose, 1 mmol of the substances was mixed with 50 ml of  80% aqueous isopropyl alcohol (v/v). the  obtained mixture was incubated at 50 °c for 1.5 h with continuous stirring. the  organic solvent was removed under reduced pressure. synthesized complex was analyzed by ir spectroscopy. the  ir spectra were recorded on the  simex fт-801 ir-fourier spectrometer in the 4000–550 cm–1 region (spectral resolution 4 cm–1; 50 scans) using atr accessory with diamante crystal plate. ir spectrum of  hedc (ν, cm–1): 3333 (он), 2930 (сн), 2907 (сн), 2878 (сн), 1734 (с=о), 1624 (c=c), 1451 (сн), 1433 (сн), 1417 (сн), 1387 (сн), 1357 (сн), 1342 (сн), 1319 (сн), 1260 (сн), 1230 (сн), 1201 (сн), 1050 (с–о–с, с–он), 1024 (с–о–с, с–он), 979 (=ch). ir spectrum of  chol (ν, cm–1): 3403 (он), 3337 (он), 2929 (ch), 2899 (ch), 2865 (ch), 2848 (сн), 1672 (c=c), 1460 (сн), 1434 (сн), 1377 (сн), 1364 (сн), 1341 (сн), 1333 (сн), 1318 (сн), 1275 (сн), 1268 (сн), 1253 (сн), 1234 (сн), 1220 (сн), 1190 (сн), 1169 (с–он), 1132 (с–он), 1106 (с–он), 1052 (с–он), 1022 (с–он), 986 (=ch), 953 (сн). ir spectrum of  the  complex of  hedc with chol (ν, cm–1): 3316 (он), 2930 (сн), 2900 (сн), 2865 (сн), 1732 (с=о), 1670 (c=c), 1625 (c=c), 1458 (сн), 1434 (сн), 1378 (сн), 1363 (сн), 1339 152 (сн), 1316 (сн), 1261 (сн), 1230 (сн), 1199 (сн), 1128 (с–о–с, с–он), 1050 (с–о–с, с–он), 1024 (с–о–с, с–он), 983 (=ch), 958 (сн). results and discussion the  composition of  the  complex of  hedc with chol was determined by the isomolar series method. this method gave a molar ratio ≈1.0, which corresponded to a 1:1 complex (fig. 2). such ratio was obtained for complex of hedc with chol in 90% and 70% aqueous ethanol [3, 4], and for complexes of  hedc with several drugs [7]. stability constant of  complex (3.3 ± 0.7)  · · 106 (mol/l)–1 was calculated based on isomolar curves (a. k. babko method) [4, 6]. the stability constants of complex in aqueous ethanol were of the order 10–4 [3, 4]. thus, the  stability constant of  complex formed in 80% aqueous isopropyl alcohol was greater than in aqueous ethanol. as the hedc concentration increases (at constant chol concentration), the optical density of  their solutions increases (hyperchromic effect) (fig. 3). the absorption maximum of the solutions decreases insignificantly (hypsochromic shift) from 237 to 230 nm. similar spectral changes were previously observed for molecular complexation of hedc with caffeine [7]. the complexation of hedc with chol was studied by atr ft-ir spectroscopy. the  potential centers of  intermolecular interactions in  the  molecules of  hedc and chol are oh groups. indeed, upon the formation of complex in the ir spectra for the absorption bands of stretching vibrations of o–h bonds in chol are observed shifts from 3403 and 3337 cm–1 to 3316 cm–1, and in hedc — from 3333 to 3316 cm–1. this may indicate to formation of hydrogen bonds between hedc and chol. 0 0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.18 0.2 220 260 300 340 380 λ, nm a 1 4 fig. 3. uv spectra of chol solutions (0.50 · 10–4 m = const) with different concentrations of hedc: 0 m (curve 1), 0.125 · 10–4 (curve 2), 0.25 · 10–4 (curve 3), 0.50 · 10–4 (curve 4) 0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.1 0.11 0.12 0.13 0 1 2 3 4 5 6 7 8 9 10 c (hedc) / c (chol) ∆а 237 fig. 2. optical density change dа as a function of component ratio of isomolar series at 237 nm 153 the complexation also causes changes in certain frequencies of absorption of ch bonds. these facts may indicate the presence of  hydrophobic contacts between chol and hedc molecules in the molecular complex. the presence of hydrophobic interactions explains the high stability of triterpene glycosides molecular complexes [4]. conclusions the  1:1  molecular complex of  hedc with chol has been prepared for the first time in  aqueous isopropyl alcohol. the  presence of  molecular complexation of chol with hedc has been proved by uvand atr ir-fourier spectroscopy. intermolecular interaction in the complex is carried out by hydrogen bonds formation and hydrophobic contacts. the results can be used to  explain the  mechanisms of the biological activity of triterpene glycosides. acknowledgements this work was carried out within the framework of an internal grant of sevastopol state university (identifier 30/06-31). references 1. hostettmann k, marston a. saponins. cambrige: cambrige university press; 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1955. 328 p. russian. 7. yakovishin la, grishkovets  v. i.  ivy and licorice triterpene glycosides: promising molecular containers for some drugs and biomolecules. stud nat prod chem. 2018;55:351–83. doi:10.1016/b978-0-444-64068-0.00011–5 abo4 type scheelite phases in (ca/sr)moo4 bivo4 bi2mo3o12 systems: synthesis, structure and optical properties chimica techno acta article published by ural federal university 2021, vol. 8(2), № 20218204 eissn 2411-1414; chimicatechnoacta.ru doi: 10.15826/chimtech.2021.8.2.04 1 of 7 abo4 type scheelite phases in (ca/sr)moo4 bivo4 bi2mo3o12 systems: synthesis, structure and optical properties z.a. mikhaylovskaya a,b,* , e.s. buyanova b , s.a. petrova c , a.v. klimova a,b a: zavaritsky institute of geology and geochemistry of the ural branch of the russian academy of sciences, 15 ak. vonsovskogo st., ekaterinburg, 620016, russia b: ural federal university, 19 mira st., ekaterinburg, 620002, russia c: institute for metallurgy of the ural branch of the russian academy of sciences, 101 amundsena st., ekaterinburg, 620016, russia * corresponding author: zozoikina@mail.ru this article belongs to the regular issue. © 2021, the authors. this article is published in open access form under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). abstract the cation deficient complex oxides of (ca/sr)moo4 bivo4 bi2mo3o12 triple system are promising photocatalysts and pigments. compounds with general formula of ca1−1.5x-ybix+yфxmo1-yvyo4 and sr1−1.5x-ybix+yфxmo1-yvyo4 were synthesized by convention solid state technique in the range of 550-720 °c. two wide regions of the solid solutions (ordinary and superstructured scheelite-type phases respectively) were found for each system. the diffuse scatering of homogeneous samples was investigated in the range of 190-1100 nm. energy gaps calculated with linear approximation of kubelka-munk function decreases with bismuth and vanadium content. keywords strontium bismuth molybdate calcium bismuth molybdate kubelka-munk method energy gap received: 25.03.2021 revised: 12.04.2021 accepted: 28.04.2021 available online: 29.04.2021 1. introduction materials based on camoo4 and srmoo4 are of interest for science and technology as catalysts and photocatalysts, scintillation detectors, solid-state lasers, pigments as well as for using in photoluminescent and microwave devices due to a wide variety of functional properties [1-8]. the latter strongly depend on not only the nature of dopants [2-3] but also on synthesis techniques employed [2,3,8] and a place of doping. the doping in different sublattice (ca/sr or mo) and varying parameters of synthesis (temperatures, irradiation time, ph, speed of mixture, etc.) may cause distortion of moo4 polyhedra. this distortion, in turn, affects such physical and chemical properties as photocatalytic activity [8-10], optical and luminescence properties [2-3,11], conductivity [12], etc. the most common way of substitution in abo4 complex oxides with scheelite structure is doping a-sublattice by trivalent me 3+ cations [3-4,6-7,13]. in this case, three basic charge compensation mechanisms are possible in abo4 scheelites: (1) formation of oxide ion interstitials ( a1-xmxbo4+x/2) [12]; (2) co-substitution on a or b sites by subvalent cations (a1-2xme 3+ xme + xo4 or a1-xme 3+ xb1-xme 5+ xo4) [16-17,6]; (3) formation of cation vacancies (a1-3xm2xфxbo4) [13-17]. mechanism (3) was reported for rare earth molybdates ln2mo3o12 (ln2/3moo4, x=1/3) with scheelite-type structure [14] and for a small number of completely investigated a1−3xm2xфxmoo4 series where 0 < x ≤ 1/3 [13,17]. but cation vacancies (ф) and their ordering can influence not only structure, but also the physical and chemical properties of the molybdates, and, therefore, we pay close attention to them in the present work. the simultaneous use of mechanisms (2) and (3) have not been described yet. for this reason the present work is devoted to the synthesis and characterization bi and v co-doped camoo4 and srmoo4 obtained by mechanisms (2) and (3). previously, sleight et al. [18] reported the x = 0.04 compositions of (ca/sr)1−3xbi2xфxmoo4 series with the tetragonal scheelite structure (sp. g. i41/a). sleight assumed that solid solution limit could apparently go all the way to 0.333. the structure, microwave dielectric properties, conductivity and photocatalytic activity of ca1−3xbi2xфxmoo4 series were investigated in [13,19]. guo et al. [13] synthesized series of solid solutions ca1−3xbi2xфxmoo4 (0.005 ≤ x ≤ 0.20), using a conventional ceramic method, and examined their microstructure and microwave dielectric properties. the 0 ≤ x ≤ 0.15 compositions were found to be single-phase and to have scheelite structure with cationic vacancies [13,19] (the structural model of sr0.88bi0.08moo4 [18] was used). it was shown that bi-doped samples exhibit improved values of the mihttp://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2021.8.2.04 http://creativecommons.org/licenses/by/4.0/ https://orcid.org/0000-0002-0050-9216 chimica techno acta 2021, vol. 8(2), № 20218204 article 2 of 7 crowave quality factor (qf). vibrational spectroscopy results revealed large distortions of moo4 and bio8 polyhedra [13], with a strong correlation between substitutions in the cation (a n+ ) sublattice and microwave dielectric properties of the ca1−3xbi2xфxmoo4 series. later, the powder x-ray and neutron diffraction patterns for compositions with 0.15 < x ≤ 0.225 were shown to exhibit a tetragonal supercell with asup ≈ √5a, csup ≈ c where a and c are the tetragonal scheelite cell parameters [19]. this superstructural ordering results in the additional reflections on xrpd patterns detected by guo et al. [13] and provided by ordering of bi atoms and cationic vacancies [19]. samples described with supercell showed maximal photocatalytic activity due to complex microstructure at grain surface and also showed a decrease of total conductivity as compared to samples with normal scheelite structure [19]. the conductive properties and structure of sr1−3xbi2xфxmoo4 compositions (0.025 ≤ x ≤ 0.225) were described in [20]. the superstructural ordering was also observed for 0.15 ≤ x ≤ 0.4. in fourier-transformed infrared spectra of sr1−3xbi2xфxmoo4, the general shifting of absorption bands caused by deformation of moo4 tetrahedra was observed. an increase of overall electrical conductivity with x was also observed. the activation energy decreased with x insignificantly (from ~1.2 to ~1.1ev), indicating that the charge carriers and conduction mechanism in sr1−3xbi2xфxmoo4 generally were the same as in the parent compound srmoo4. probably, the increase of conductivity was caused by the increase in the oxygen ion mobility provided by the distortion of moo4 polyhedra [20]. synthesis of sr1-xbixmo1-xvxo4 results in the two-phase samples consisting of bivo4 (monoclinic) and srmoo4 phases [20]. in contrast, ca1-xbixmo1-xvxo4 single-phase solid solutions are observed for 0 ≤ x ≤ 0.9 [6]. one possible reason of such discrepancy is that the dopants influence differently the composition and structure of strontium and calcium molybdates. the simultaneous presence of bi and v in ca1-xbixmo1-xvxo4 oxide leads to the simultaneous expansion and contraction of its unit cell due to the replacement of calcium with bismuth and molybdenum with vanadium, respectively; as a result, the unit cell volume changes slightly [6]. in contrast, in sr1-xbixmo1-xvxo4 doping with both bi and v leads to the contraction of unit cell and by that means makes this oxide unstable. it can be assumed that such contraction decreases the distance between [bo4] n (b = mo,v) clusters and, consequently, increases the repulsion between them. as a result, decomposition of sr1-xbixmo1-xvxo4 oxide is observed [20]. in general, biand (bi+v) doped camoo4 and srmoo4 show the decreasing melting point temperature and, as a consequence, lower sintering temperature, as well as increasing conductivity, catalytic and photocatalytic activity. in addition, the shift of absorbance bands from uv to violet and blue parts of spectra was observed, and the energy gap decreases [6,22]. the last mentioned characteristics are important factors for such technical areas as photocatalytic oxidation under visible light or pigment technology. thus, the priority goal of the present work was to show the effects of bismuth and vanadium co-doping on the uv-vis spectral characteristics and eg values of the ca1−1.5x-ybix+yфxmo1-yvyo4 and sr1−1.5x-ybix+yфxmo1-yvyo4 complex oxides. 2. experimental samples of ca1−1.5x-ybix+yфxmo1-yvyo4 and sr1−1.5x-ybix+yфxmo1-yvyo4 (0 < x ≤ 0.4, 0 < y ≤ 0.5) were synthesised by conventional solid state methods from srco3 (99.5%) or caco3 (99.5%), bi2o3 (99.9%), v2o5 (98.5%) and moo3 (99.0%) as starting materials. stoichiometric amounts of dried precursors were weighed and mixed in an agate mortar as dispersions in ethanol. mixed powders were then pelletized and calcined in steps at 550– 720 c with duration about 10 hours at each step followed by regrinding and re-pelletizing. the overall time of calcination was about 30 hours. x-ray powder diffraction (xrd) data were obtained using a bruker advance d8 diffractometer with a vantec1 detector (ni filtered cu kα radiation, θ/θ geometry). xrd data were collected in the 2θ range of 6–120°, with steps of 0.02103° and an effective scan time of 200 s per step. the reflection spectra were obtained in the range of 190–1100 nm by using a spectrophotometer evolution 300 (termo sci) equipped with an integrating sphere. the absorption coefficient curves were derived from reflection curves using kubelka-munk model. energy gaps for direct interband transitions were calculated with linear approximation of kubelka-munk function [21]. 3. results and discussion as-prepared samples of nominal composition ca1−1.5x-ybix+yфxmo1-yvyo4 and sr1−1.5x-ybix+yфxmo1-yvyo4 (0 < x ≤ 0.5, 0 < y ≤ 0.5) were found to contain one phase for y ≤ 0.05 (x = 0) and y ≤ 0.2 (x = 0) for camoo4and srmoo4-based systems, respectively, although the solubility limit of vanadium in ca1−ybiymo1-yvyo4 is reported to be y = 0.9 [6,22]. bivo4 was also detected in camoo4-based samples with x = 0 and 0.2 < y ≤ 0.5. presence of bivo4 was also found in ca1−ybiymo1-yvyo4 (0.4 < y ≤ 0.9) [22], but this fact was disregarded by authors during solid solution limits discussion. at low x concentration the sheelite structure are observed. but for oxides with higher x values the additional peaks in the xrd patterns are evident. these oxides were found to have the tetragonal supercell with asup ≈ √5a, csup ≈ c, where a and c are the tetragonal scheelite cell parameters, like it was found earlier for ca1−3xbi2xmo1o4 [19] and sr1−3xbi2xmo1o4 [20]. the areas of solid solutions (ordinary scheelite and superstructured scheelite) and inveatigated fields of triple phase diagram are shown at fig. 1. it is seen that continuation of solid chimica techno acta 2021, vol. 8(2), № 20218204 article 3 of 7 fig. 1 the areas of scheelite-type solid solutions (red), superstructured scheelite solid solutions (blue) and tree-phases areas (gray) in camoo4 bivo4 bi2mo3o12 (a) and srmoo4 bivo4 bi2mo3o12 (b) ternary diagram. white regions are unstudied areas (x > 0.5, y > 0.5). solutions areas can be expected for {0.5 < x ≤ 0.7, 0.5 < y ≤ 0.6} values. compositions without solid solutions areas contain additional bi3moo12 and monoclinic bivo4. previously, free refinement of the occupancies in superstructured ca1−3xbi2xmo1o4 solid solutions showed the 4b site positions to be fully occupied by bismuth, the 16f site positions are partially occupied by both ca 2+ and bi 3+ [19]. in the present work, the refinement of the occupancies of 4b and 16f sites revealed the same pattern of doping. it can be clearly observed that high concentration of bismuth only (i.e. x+y values) does not lead to the superstructural ordering, but relatively high concentration of cationic vacancies accompanying high concentrations of bismuth provide the ordering of bismuth at 4b position. samples with superlattice ordering contain plains which include only bismuth and molybdenum atoms (fig. 2) and the formation of such planes can be associated with preferred orientation of 6s 2 lone pair electrons of bismuth along z axis. high concentration of cationic vacancies in 16f sr/bi position provides required geometrical factors of favourable orientation of 6s 2 lone pair and, as a result, the mentioned planes are formed. fig. 2 planes including bi 4b positions show the ordering of bismuth atoms in tetragonal supercell. “srbi” 16f positions are mixed with sr, bi and ф. the dependencies of the unit cell parameters for ca1−1.5x-ybix+yфxmo1-yvyo4 and sr1−1.5x-ybix+yфxmo1-yvyo4 compositions are shown in fig. 3. the compression and enlargement are caused by substitution by smaller of bigger cation, respectively (ionic radii 𝑟ca2+ = 1.12 å, 𝑟sr2+ = 1.26 å, 𝑟bi3+ = 1.17 å [23]). the ionic radius of vanadium is smaller than that of molybdenum (𝑟moiv 6+ = 0.41 å, 𝑟viv 5+ = 0.355 å), and vdoping impedes expansion of the unit cell in the case of ca1−1.5x-ybix+yфxmo1-yvyo4 and promotes the decrease of cell volume in the case of sr1−1.5x-ybix+yфxmo1-yvyo4. in both cases, the superstructural ordering is a “growth factor” of с-parameter. it leads to the sharp rise of c-parameter or local plateau on c-parameter dependence in the cases of ca1−1.5x-ybix+yфxmo1-yvyo4 and sr1−1.5x-ybix+yфxmo1-yvyo4, respectively. probably, it is caused by stereochemical activity of 6s 2 lone pair of bismuth in the planes parallel to (xoy) plane. typical diffuse scattering spectra of (ca/sr)1−1.5x-ybix+yфxmo1-yvyo4 compositions are similar (fig. 4). the scattering in the range of ~500–1100 nm is close to 100%. the spectra for camoo4 and srmoo4 contain a broad band in the range of wavelengths ~200– 300 nm that corresponds to electronic transition within the moo4 2 complex [24]. for bi-doped and (bi+v) -doped samples this band is located in higher wavelengths (see fig. 4). the separate absorbance bands that correspond to transitions in the vanadium-oxygen complex are not observed. the band gap calculations for (ca/sr)1−1.5x-ybix+yфxmo1-yvyo4 were carried out by using kublenka-munk theory and tauc relation. fig. 5 shows the tauc plot for some compositions. the graph consists of non-linear and linear regions. the value of eg can be obtained by drawing a tangent on the linear part. the point of inflection on the x-axis provides the value of band gap for the prepared powders. chimica techno acta 2021, vol. 8(2), № 20218204 article 4 of 7 fig. 3 the unit cell parameters depending on x and y parameters in ca1−1.5x-ybix+yфxmo1-yvyo4 (a,c,e) and sr1−1.5x-ybix+yфxmo1-yvyo4 (b,d,f) solid solutions chimica techno acta 2021, vol. 8(2), № 20218204 article 5 of 7 fig. 4 the diffuse scattering spectra for some ca1−1.5x-ybix+yфxmo1-yvyo4 (a) and sr1−1.5x-ybix+yфxmo1-yvyo4 (b) compositions fig. 5 tauc plots for some ca1−1.5x-ybix+yфxmo1-yvyo4 (a) and sr1−1.5x-ybix+yфxmo1-yvyo4 (b) compositions calculated values of the band gap (eg) for ca1−1.5x-ybix+yфxmo1-yvyo4 were found to be 3.83–2.64 ev for {x = 0, y = 0} – {x = 0.1, y = 0.5}compositions. eg values for sr1−1.5x-ybix+yфxmo1-yvyo4 were 4.25–2.87 ev for {x = 0, y = 0} – {x = 0.2, y = 0.3} compositions. it is seen that the band gap value decreases with x and y (fig. 6), and it reduces not only with bismuth content (x+y value) but with vanadium content (y) as well. for camoo4-based solid oxides, eg value slowly decreases with x and rapidly decreases with y, while for srmoo4-based solid oxides we observed the opposite trends (fig. 6). in general, the energy gap in (ca/sr)1−1.5x-ybix+yфxmo1-yvyo4 is reduced by additional bands of bi 6p electrons and by modification of states of mo 4d electrons caused by distortion of moo4 polyhedra. bands of bi 6p electrons lead to the significant decrease of eg even for low concentration of bismuth for both series of molybdates. in the case of distortion of moo4 polyhedra for srmoo4-based solid oxides, the sufficient contraction of the unit cell is observed, while for camoo4-based solid oxides the cell volume grows. therefore, the distortion of moo4 polyhedra caused by the formation of cation vacancies (represented by x while y = 0) is generally smaller for camoo4-based compounds than that for srmoo4-based compounds. strongly distorted moo4 polyhedra in srmoo4-based compounds do not change significantly at vanadium doping (y > 0), but weakly distorted moo4 polyhedra in camoo4-based compounds show a sharp alteration at the same time. meanwhile, some special effects for superstructured phases are not observed. for the purpose of eg minimization, therefore, the best compositions are found to be {x = 0.1–0.2, y = 0.4–0.5} and {x = 0.2–0.425, y = 0.1–0.2} for camoo4 chimica techno acta 2021, vol. 8(2), № 20218204 article 6 of 7 fig. 6 the eg changing in ca1−1.5x-ybix+yфxmo1-yvyo4 (a) and sr1−1.5x-ybix+yфxmo1-yvyo4 (b) series based and srmoo4-based compounds, respectively. these compositions are expected to be the most effective photocatalysts in (ca/sr)1−1.5x-y bix+yфxmo1-yvyo4 series because of absorption of energy in both uv and vis (i.e. blue) parts of spectra. 4. conclusions compounds with general formulae of ca1−1.5x-ybix+yфxmo1-yvyo4 and sr1−1.5x-ybix+yфxmo1-yvyo4 were synthesized by conventional solid state technique in the temperature range of 550–720 °c. the areas of solid solutions (ordinary scheelite and superstructured scheelite) were determined. it was observed that relatively high concentration of cationic vacancies accompanying high concentrations of bismuth provide the ordering of bismuth at 4b position. the diffuse scatering spectra of homogeneous samples contain a broad band in the range of ~200– 450 nm. energy gaps, calculated with linear approximation of kubelka-munk function, decrease with bismuth content. the compositions with minimal eg are found to be {x = 0.1–0.2, y = 0.4–0.5} and {x = 0.2–0.425, y = 0.1–0.2} for camoo4-based and srmoo4-based compounds, respectively. these compositions are expected to be the most effective photocatalysts in (ca/sr)1−1.5x-y bix+yфxmo1-yvyo4 series. acknowledgements the xprd data were obtained in ural-m center of institute for metallurgy, ural br. of ras this work is supported by grant of rsf, project № 20-73-10048. references 1. frank m, smetanin sn, jelínek m, vyhlídal d, kopalkin aa, shukshin ve, ivleva li, zverev pg, kubeček v. synchronously-pumped all-solid-state srmoo4 raman laser generating at combined vibrational raman modes with 26-fold pulse shortening down 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https://doi.org/10.1021/jp0608729 https://doi.org/10.1107/s0567739476001551 https://doi.org/10.1016/j.solidstatesciences.2019.105945 synthesis and study of complexes of the novel russian antiviral drug camphecene with plant’s flavonoids chimica techno acta article published by ural federal university 2021, vol. 8(2), № 20218202 eissn 2411-1414; chimicatechnoacta.ru doi: 10.15826/chimtech.2021.8.2.02 1 of 5 synthesis and study of complexes of the novel russian antiviral drug camphecene with plant’s flavonoids s.s. khizrieva * , e.v. vetrova, s.n. borisenko, e.v. maksimenko, n.i. borisenko research institute of physical and organic chemistry, southern federal university, stachki ave., 194/2, rostov-on-don, 344090, russia * corresponding author: hizrieva@sfedu.ru this article belongs to the regular issue. © 2021, the authors. this article is published in open access form under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). abstract traditionally, glycyrrhizic acid has been used to form polydentate complexes. for the first time in the presented paper, the complexation of the plant’s flavonoids (quercetin (qu) and its glycoside rutin (rut)) with the novel russian antiviral drug camphecene (camph) was investigated. the complexes obtained at different molar ratios were studied using uv/vis spectroscopy. formation of the host: guest complexes were registered: qu and rut molecular complexes (camph+2qu; camph+2rut) with a stability constant k = 3.3·10 8 m -2 . comparison of the binding constants of the obtained complexes shows that the efficiency of camphecene complexation with the participation of flavonoids is more efficient than with the participation of triterpenoids. besides, it was found that the complexes of camphecene with the quercetin and rutin are soluble in water, in contrast to the complexes with triterpenoids, which makes it possible to increase the bioavailability of both camphecene and flavonoids. the obtained results demonstrate the high potential of flavonoids qu and rut to the development of novel pharmaceutical forms using the example of camphecene in the form of molecular complexes, as the novel forms of delivery. keywords camphecene quercetin rutin antiviral activity supramolecular complexes received: 01.03.2021 revised: 22.04.2021 accepted: 27.04.2021 available online: 28.04.2021 1. introduction it is known that a decrease in therapeutic doses of medicinal substances and prolongation of action is possible when they are clathrate with plant glycosides. this property was used in the approach of academician g. a. tolstikov to reduce therapeutic doses of drugs and prolong the action [1-3]. in this regard, the presented work considers the possibilities of synthesizing new supramolecular complexes of qu and rut using the new antiviral drug camphecene for the development of low-dose pharmaceutical substances on their basis. the authors consider that these pharmaceutical substances can be used to suppress the multiplication of viruses in the early stages. it is known that camphecene 1 (fig. 1), has a broad spectrum of antiviral activity. it is proved to be active against the influenza virus strains type a and type b [4]. the purpose of this work is to synthesize and study supramolecular complexes based on the scaffold monoterpenoid camphecene and plant flavonoids to develop, in the future, previously unknown low-dose pharmaceutical substances with antiviral activity. influenza is known to be the most common and dangerous respiratory viral infection. it causes annual epidemics and pandemics, leading to significant increases in morbidity and mortality in all regions of the world. in connection with the growing number of cases of viral infections and especially resistant viral strains, it is necessary to improve the available therapeutic methods, complementing them with the discovery of new antiviral agents. on the other fist, it is widely recognized that the medical heritage of plants is a valuable resource for the treatment of infectious disorders. this indicates a growing interest in antiviral products based on secondary plant metabolites [5, 6]. one of the unique plant components used in traditional medicine is bioflavonoids quercetin and rutin (fig. 1). plant flavonoids 2 and 3 are attracting more and more attention of chemists and pharmacologists due to the wide spectrum of their biological activity. flavonoids have long attracted scientific interest as antiviral agents in a few http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2021.8.2.02 http://creativecommons.org/licenses/by/4.0/ https://orcid.org/0000-0001-7064-2402 chimica techno acta 2021, vol. 8(2), № 20218202 article 2 of 5 c12h21no a) camph(1) c15h10o7 b) qu (2) c27h30o16 c) rut (3) fig. 1 structures of a) camphecene (1), c12h21no; b) quercetin (2), c15h10o7; c) rutin (3), c27h30o16 studies, they have shown an inhibitory effect on proteases of various types of coronaviruses [7]. quercetin (qu) is one of the most important plant molecules, showing pharmacological activity such as antiviral and anti-inflammatory effects. it has also been demonstrated to have a wide range of anti-cancer properties, and several reports indicate its efficacy as a cancer‐preventing agent [8]. quercetin 2 (fig. 1), chemical name 2‐(3,4‐dihydroxy phenyl)‐3,5,7‐trihydroxychromen‐4‐one or 3,3′,4′,5,7‐pentahydroxyflavone, is classified as a flavonol, one of the six subcategories of flavonoid compounds, and is the major polyphenolic flavonoid found in various vegetables and fruits, such as berries, dill, apples, and onions [9]. according to research results [10], qu and other several substances exhibited better potential inhibition than hydroxy-chloroquine against covid-19 main protease active site and ace2. based on the results obtained by computational methods on molecular docking, it is anticipated that qu could affect sars‐cov‐2 by interacting with 3clpro, plpro, and/or s protein [8, 11]. thus, qu is currently promising as a biologically active substance of natural origin, capable of exerting a nonspecific complex effect on inflammatory and destructive processes in the body, and qu be considered promising in the treatment of allergic pathology, inflammatory and noninflammatory diseases (alzheimer's). one of the special effects of quercetin is its protective effect on the vascular endothelium, which is important in covid-19 since endothelial dysfunction inevitably develops in this pathology [7]. 2. experimental the following reagents were used in this study: quercetin (purity 98.2%) from dia-m (russia) and rutin (99.4% purity) from sichuan xieli pharmaceutical co., ltd. (china), and locally produced chemicals of the chemically pure grade. camphecene – 2-(e)-((1r,4r)-1,7,7-trimethylbicyclo [2.2.1] heptan-2-ylidene-aminoethanol was synthesized at the novosibirsk institute of organic chemistry (nioch sb ras) (fig. 2): а mixture of (1r)-(+)-camphor (1.0 equiv.), the appropriate amine (2.5 equiv.), and anhydrous zncl2 (0.1% mol on camphor) was reflux for 5–12 h. diethyl ether was added to the reaction mixture, after completion of the reaction. the organic layer was washed with brine, dried (na2so4), and evaporated. the crude product was subjected to vacuum distillation [12]. the complex of camph and qu and rut was formed by mixing 96% alcohol solution. the process of complex formation between qu and rut and camph was analyzed using electron-optical uv-vis spectroscopy (a speks ssp 705-pc spectrometer (cjsc spectroscopic systems, russia). the complexes of qu/rut and camph were formed by mixing an alcohol solution of qu/rut and camph at the molar ratio of 1:1 and 2:1 (using ethanol as alcohol). the stoichiometry of the complex was evaluated by the dependence of optical density of a camph solution (measured at 201 nm) on qu/rut concentration. a contribution of qu/rut to absorbance was corrected by subtracting the absorbance spectrum of qu/rut from the total absorbance spectrum. measurements were carried out in a quartz cell. 3. results and discussion following the objectives of the work, sets of complexes of bioflavonoids qu and rut with an antiviral drug camphecene at different molar ratios "guest: host" were synthesized. for a detailed study of the processes of complexation of qu and camph, the absorption spectra of camph in a mixture with different concentrations of qu were investigated. in the first step, complexes of qu with camph were obtained at molar ratios: 1:1 and 2:1 and studied by uv/vis spectroscopy. the binding of camph and qu after mixing of their solutions was accompanied by changes in the (+)-camphor 2-aminoethanol scaffold monoterpenoid–camphecene fig. 2 scheme of obtaining the scaffold monoterpenoid – camphecene [12] chimica techno acta 2021, vol. 8(2), № 20218202 article 3 of 5 absorbance spectrum of camph indicating the complex formation of these compounds (fig. 3). the uv-vis spectrophotometric analysis of the mixture of camph and qu has shown that the increase in qu concentration is accompanied by the change in the shape of the camph spectrum due to complex formation (its maximum of absorbance becomes lower). as demonstrated in fig. 3, with an increase in the concentration of qu from 0 to 0.125 mm, a bathochromic shift of the absorption maximum of camph (201  215 nm) is recorded in the uv/vis spectra, and a decrease in optical density is observed. fig. 3 shows the camph spectra, which are the difference absorption spectra of the mixture of camph and qu and the spectrum of qu at a given concentration. an increase in the concentration of qu (from 0.25 mm and higher) leads to the disappearance of the maximum absorption of camph, which indicates the complete binding of camph molecules in the presence of qu (fig. 4). fig. 4 demonstrates from the dependence of the optical density on the concentration of qu at the value of the maximum absorption band of camph λmax1= 201 nm: the optical density sharply decreases its values depending on the concentration of qu in the mixture. the study of rut (fig. 5) demonstrated similar changes in the uv/vis spectra of the obtained complexes. when the fig. 3 absorption spectrum of camphecene (ccamph = 0.5 mm) at different concentrations of qu* (in 96% alcohol solution). the upper spectrum line corresponds to the absorbance spectrum of camph in the absence of qu (c= 0.0 mm). fig. 4 dependence of optical density on the concentration of quercetin fig. 5 absorption spectrum of camphecene (ccamph = 0.5 mm) at different concentrations of rut (*rut 0.01 mm – standard solution of rutin) rut concentration changes in the range from 0.05 to 0.275 mm, a bathochromic shift of the absorption maximum of camph is recorded (201  213 nm). in this study, the stability constants for the complex of camph and qu/rut were analyzed by changes of optical density of camph solutions (with its constant concentration, ccamph = 0.5 mm) with variable concentrations of qu/rut. to calculate the stability constant of the complexes, we used the benesi-hildebrand plot (1) [13]. eq. (1) is applicable for certain experimental conditions (camph concentration < qu/rut concentration). the stability constant of the nqu-camph complex was estimated from the change in the optical density of camph (λmax1 = 201 nm) at its fixed concentration in solutions in which the qu (or rut) concentration was varied. eq. (1) allows, within the framework of one experiment, not only to estimate the stability constant of the complex (k) but also to determine the stoichiometry ratio "host: guest" (n) in the complex: ∆𝐷 𝐷⁄ − 1 = 1 [qu]𝑛⁄ ∙ 1 𝐾⁄ (1) where ∆𝐷 = ∆𝜀 ∙ [camph] – change in the optical density of the solution, к – the constant of stability of the complex, determined for the reaction camph + nqu ⇄ camph-nqu: 𝐾 = [camph − nqu] [camph] ∙ [nqu] (2) the absorption spectrum of camph was recorded at a wavelength of 201 nm, while the camph concentration fig. 6 dependence of the slope of the straight line d/d on 1/[qu] 2 chimica techno acta 2021, vol. 8(2), № 20218202 article 4 of 5 was constant and amounted to 0.5 mm. the obtained dependence of the absorption intensity of camphecene (λ = 201 nm) on the concentration of qu is shown in fig. 6. from the slope of the straight line ∆𝐷 𝐷⁄ depending on 1/[qu] 2 (fig. 6), the stability constant of the complex was calculated using eq. (1). the stability constant for the camph+qu complex is 1/k = 3 10 -9 m 2 or k = 3.3 10 8 m -2 . recognizing the value of the binding constant, the change in the gibbs energy was calculated. obtained from the binding constant, the change in gibbs’s energy ∆g = -47.8 kj. based on the obtained negative value, it can be concluded that the reaction proceeds spontaneously during the formation of qu and camph complexes. similarly, according to eq. (1), the stability constant of the complex camph+rut was calculated, 1/k = 3 10 -9 m 2 or k = 3.3 10 8 m -2 . using the value of the binding constant, the change in gibbs’s energy was calculated. the change in the gibbs energy ∆g =-47.8 kj, which allows us to conclude that the reaction proceeds spontaneously during the formation of a complex of rut with camph. thus, the values of the binding constant camph for qu and rut are comparable, and the same conclusion can be drawn about the change in the gibbs energy ∆g = -47.8 kj. comparison of the binding constants of the obtained complexes shows that the efficiency of camphecene’s complexation with the participation of flavonoids is more efficient (k = 3.3 10 8 m -2 for the camph+2qu; camph+2rut complexes) than with the participation of triterpenoids (k = 6.94 10 6 m -2 for camph+2ga) [14]. also, it was found that the complexes of camphecene with the quercetin and rutin are soluble in water, in contrast to the complexes with triterpenoids, which makes it possible to increase the bioavailability of both camphecene and flavonoids. 4. conclusions for the first time, the complexation of the plant’s flavonoids (quercetin (qu) and its glycoside rutin (rut)) with the novel russian antiviral drug camphecene (camph) was investigated. the complexes obtained at different molar ratios "host: guest" 1:1 and 2:1 were studied using uv/vis spectroscopy. formation of the "host: guest" complexes were registered: qu and rut molecular complexes (camph+2qu; camph+2rut) with a stability constant k = 3.3 10 8 m -2 . the obtained results demonstrate the high potential of flavonoids qu and rut to the development of novel pharmaceutical forms using the camphecene in the form of molecular complexes, as the novel forms of delivery. acknowledgements this work was supported by the ministry of science and higher education of the russian federation (state assignment in the field of scientific activity, project no 08522020-0031) and the russian foundation for basic research (rfbr, grant no. 19-33-90211-aspiranty). the authors are grateful to the corresponding member of the ras, doctor of chemical sciences, professor of nioch sb ras salakhutdinov n.f. for the kindly provided scaffold monoterpenoid camphecene. references 1. tolstikova tg, tolstikov ag, tolstikov ga. on the way to low-dose medicines. herald of the russian academy of sciences. 2007;77(10):447–53. doi:10.1134/s1019331607050012 2. vetrova ev, lekar av, filonova ov, borisenko sn, maksimenko ev, borisenko ni. study of molecular complexation of glycyrrhizic acid with chloramphenicol by electrospray ionization mass spectrometry. journal of natural science, biology, and medicine. 2015;6(suppl 1):40–3. doi:10.4103/09769668.166070 3. yakovishin la, grishkovets vi. intermolecular interaction of glycyrrhizin with cholesterol. chimica techno acta. 2020;7(4):180–5. doi:10.15826/chimtech.2020.7.4.08 4. zarubaev vv, garshinina av, tretiak ts, fedorova va, shtro aa, sokolova as, 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journal of medicinal chemistry. 2015;105:263–73. doi:10.1016/j.ejmech.2015.10.010 13. vavilin va, salakhutdinov nf, ragino yui, polyakov ne, taraban mb, leshina tv, stakhneva em, lyakhovich vv, nikitin yup, tolstikov ga. the cholesterol lowering properties of the complex compound simvastatin with glycyrrhizic acid (simvaglyzin) in experimental models. biochem (moscow) suppl series b: biomed chem. 2008;2(4):373–80. doi:10.1134/s1990750808040070 14. khizrieva ss, vetrova ev, borisenko sn, maksimenko ev, borisenko ni. synthesis and study of complexes of the novel russian antiviral drug camphecene with pentacyclic triterpenes of licorice. chimica techno acta. 2020;7(4):192–8. doi:10.15826/chimtech.2020.7.4.10 https://doi.org/10.1016/j.ejmech.2015.10.010 https://doi.org/10.1134/s1990750808040070 https://doi.org/10.15826/chimtech.2020.7.4.10 synthetic approaches to 2-aryl/hetaryland 2-(hetaryl)ylidene derivatives of fluorinated 1,3-benzothiazin-4-ones 96 d o i: 1 0. 15 82 6/ ch im te ch .2 02 0. 7. 3. 01 emiliya v. nosova, olga a. batanova, nataliya n. mochulskaya, galina n. lipunova chimica techno acta. 2020. vol. 7, no. 3. p. 96–103. issn 2409–5613 emiliya v. nosova,ab* olga a. batanova,a nataliya n. mochulskaya,a galina n. lipunovab a ural federal university 620002, 19 mira st., ekaterinburg, russia b i. ya. postovskii institute of organic synthesis, ural branch of russian academy of sciences, 620990, 22 kovalevskaya st. / 20 akademicheskaya st., ekaterinburg, russia *email: emilia.nosova@yandex.ru synthetic approaches to 2‑aryl/hetaryl‑ and 2‑(hetaryl)ylidene derivatives of fluorinated 1,3‑benzothiazin‑4‑ones  a series of 2-hetaryland 2-(hetaryl)ylidene substituted 5-fluoro-8 nitro-1,3-benzothiazin-4-ones was synthesized by interaction of 2,6-difluoro3-nitrobenzoylisothiocyanate with c-nucleophiles. cyclocondensation of polyfluorobenzoylchlorides with aryl and hetaryl thioamides represents new approach to 1,3-benzothiazin-4-ones. some compounds proved to be promising for further development of tuberculostatic agents. keywords: 1,3-benzothiazin-4-ones; 2-fluorobenzoylchloride; 2-fluorobenzoyl-isothiocyanate; indole; pyrrole; cyanomethylbenzimidazole; benzoylmethylbenzimidazole; thioamide; cyclocondensation; tuberculostatics. received: 28.06.2020. accepted: 25.08.2020. published: 07.10.2020. © emiliya v. nosova, olga a. batanova, nataliya n. mochulskaya, galina n. lipunova, 2020 introduction many synthetic benzothiazines are biologically actives, which play an  important role in  treatment of  various diseases. some 2-amino substituted 1,3-benzothiazin-4-ones (2-amino-1,3-benzothiazinones) represent a  promising new class of  antitubercular agents [1]. other 1,3-benzothiazin-4-one derivatives, mostly 2-aryl and 2-(pyridin2-yl) ones, are attractive due to their ability to suppress an oxidative stress-induced cardiomyocyte apoptosis [2]. synthetic approaches to  2-amino-1,3-benzothiazin-4-ones are sufficiently developed, whereas not many ones are available for incorporation of c–c bond into position 2 [3]. the  synthetic methods are limited to the following: • interaction of  2-mercaptobenzoic acids with aryl/hetaryl nitriles [2]; • rearrangement of n-arylthiomethylaroylamides catalyzed by phosphorus oxychloride, followed by oxidation of 4h-1,3-benzothiazines with potassium permanganate [4]; • addition of  c-nucleophiles to 2-fluorobenzoylisothiocyanates and subsequent intramolecular condensation [5]. the last approach opens wide opportunities for modification of  position 2 of 1,3-benzothiazin-4-ones. previously we 97 studied the interaction of polyfluorobenzoylisothiocyanates with ch-reactive benzimidazoles [5], 2,6-difluorobenzoylisothiocyanate with the same benzimidazoles and 2-cyanomethylpyridine [6], o-fluorobenzoylisothiocyanates with n-methylpyrrole and n-methylindole [7]. we presented only one example of  2-indolyl-5-fluoro8-nitro-1,3-benzothiazin-4-one in recent paper [8]. in this article, we wish to report new data on 2-substituted 5-fluoro-8nitro1,3-benzothiazinones and introduce efficient synthetic approach to 2-aryl/hetaryl derivatives of  1,3-benzothiazin-4-ones based on cyclocondensation of  polyfluorobenzoyl chlorides with thioamides. experimental 1h and 19f nmr (nuclear magnetic resonance) spectra were recorded in  dimethylsulfoxide-d6 (dmso-d6) on the  spectrometer “bruker-avance-400” (400 mhz), using tetramethylsilane as internal reference for 1h nmr and cfсl3 for 19f nmr. mass spectra were recorded on a shimadzu gcms-qp2010 ultra instrument with electron impact ionization (ei) of the sample. microanalyses (c, h, n) were performed using the perkin — elmer 2400 elemental analyzer. melting points were measured on the stuart melting point apparatus smp10 (ac/dc input 230 v ac, merck supplier). 2,6-difluorobenzoic acid 1, 2,3,4,5-tetrafluorobenzoyl chloride 10a and pentafluorobenzoyl chloride 10b were purchased from merck (cas numbers 385-00-2, 94695-48-4, 2251-50-5). 3-nitro-2,6-difluorobenzoic acid 2 was synthesized according to  the  literature [9]. procedure for toluene solution of 2,6-difluoro-3-nitrobenzoylchloride 3 was reported [8]. 2-benzoylmethylbenzimidazole was prepared from 2-methylbenzimidazole [5], 2-cyanomethyl-benzimidazole was synthesized by condensation of ethyl cyanoacetate with o-phenylenediamine [10]. thioamides 11 were prepared by the addition of hydrogen sulfide to the corresponding nitriles [11]. 5‑fluoro‑8‑nitro‑2‑(1‑methylpyrrol‑ 2‑yl)  — 1,3‑benzothiazin‑4‑one (5). the  solution of  ammonium isothiocyanate (0.4758 g, 6.26 mmol) in  acetonitrile (10 ml) was added to toluene solution of 2,6-difluoro-3-nitrobenzoylchloride  3 (0.88 ml, 6.26 mmol). reaction mixture was stirred at 40 °с for 5 min, the precipitate of nh4cl was filtered off and 1-methylpyrrole (0.761 g, 9.39 mmol) was added to a solution of 2,6-difluoro-3-nitrobenzoylisothiocyanate 3. the mixture was stirred at room temperature for 3 h, the precipitate of benzothiazinone 5 was filtered off and washed with hot ethanol (10 ml). yield 1.72 g (90%), mp 194–196 °с. 1н nmr, δ (ppm), j (hz): 4.09 s (3н, сн3), 6.30 dd (1н, h4’, 3jhh 4.1, 4jhh 2.3), 7.29 dd (1н, h 3’, 3jhh 4.2, 4jhh 1.3), 7.37 m (1н, h 5’), 7.62 dd (1н, н6, 3jhh 9.2, 3jfh 9.4), 8.70 dd (1н, h7, 3jhh 9.2, 4jfh 4.5). 19f nmr, δ (ppm), j (hz): — 99.05 dd (1f, 3jfh 9.5, 4jfh 4.0). ms (ei), m/z (irel (%)): 305 [m] + (14), 106 (100), 105 (15). found, %: c 51.17; h 2.60; n 13.74. с13h8fn3o3s. calculated, %: c 51.15; h 2.64; n 13.76. compounds 6–9 were synthesized by the same method. 5‑fluoro‑8‑nitro‑2‑(5‑methoxy‑ 1‑methylindol‑3‑yl) — 1,3‑benzothiazin‑ 4‑one (6). yield 80%, mp 274–276 °с. 1н nmr, δ (ppm), j (hz): 3.83 s (3н, nсн3), 3.93 s (3н, oсн3), 7.01 d (1н, н 6’ , 3jhh 98 8.8), 7.54 d (1н, н7’, 3jhh 8.8), 7.65 dd (1н, н6, 3jhh 9.3, 3jfh 9.5), 7.97 s (1н, н 4’), 8.66 s (1н, h2’), 8.70 dd (1н, h7, 3jhh 9.3, 4jfh 4.3). 19f{1h} nmr, δ (ppm):  — 99.27 s. ms (ei), m/z (irel (%)): 385 [m] + (31), 187 (12), 186 (100), 171 (41), 143 (28). found, %: c 56.13; h 3.15; n 10.87. с18h12fn3o4s. calculated, %: c 56.10; h 3.14; n 10.90. 5‑fluoro‑8‑nitro‑2‑(2‑methylindol‑ 3‑yl) — 1,3‑benzothiazin‑4‑one (7). yield 91%, mp 207–209 °с. 1н nmr, δ (ppm), j (hz): 2.87 s (3н, сн3), 7.25 m (2н, с6н4), 7.45 m (1н, с6н4), 7.66 dd (1н, н 6, 3jhh 9.3, 3jfh 9.6), 8.34 m (1н, с6н4), 8.71 dd (1н, h7, 3jhh 9.3, 4jfh 4.6), 12.5 br. s (1н, nh). 19f{1h} nmr, δ (ppm): — 98.42 s. ms (ei), m/z (irel (%)): 355 [m] + (21), 157 (12), 156 (100), 155 (50), 81 (10). found, %: c 57.43; h 2.82; n 11.85. с17h10fn3o3s. calculated, %: c 57.46; h 2.84; n 11.83. 1 ‑ ( 1 , 3 ‑ d i h y d r o b e n z i m i d a z o l ‑ 2‑yliden)  — 1‑(5‑fluoro‑8‑nitro‑4‑oxo‑ 4н‑1,3‑benzothiazin‑2‑yl)  — acetoni‑ trile (8). yield 75%, mp 319–321 °с. 1н nmr, δ (ppm), j (hz): 7.30 m (2н, c6h4), 7.50 dd (1н, н6, 3jhh 9.2, 3jfh 9.8), 7.64 m (2н, c6h4), 8.62 dd (1н, h 7, 3jhh 9.2, 4jfh 4.4), 13.31 br. s (2н, nh). 19f{1h} nmr, δ (ppm): — 97.49 s. ms (ei), m/z (irel (%)): 381 [m]+ (39), 183 (13), 182 (100), 155 (12), 103 (23), 81 (12). found, %: c 53.50; h 2.15; n 18.36. с17h8fn5o3s. calculated, %: c 53.54; h 2.11; n 18.37. 2 ‑ ( 1 , 3 ‑ d i h y d r o b e n z i m i d a z o l ‑ 2‑yliden)  — 2‑(5‑fluoro‑8‑nitro‑4‑oxo‑ 4н‑1,3‑benzothiazin‑2‑yl) — acetophe‑ none (9). yield 89%, mp 265–267 °с. 1н nmr, δ (ppm), j (hz): 7.36 m (5н, с6н5), 7.53 m (4н, с6н4), 7.60 dd (1н, н 6, 3jhh 9.2, 3jfh 9.5), 8.56 dd (1н, h 7, 3jhh 9.2, 4jfh 4.5), 13.36 br. s (2н, nh). 19f {1h} nmr, δ (ppm): — 98.39 s. ms (ei), m/z (irel (%)): 460 [m]+ (24), 432 (13), 431 (41), 355 (25), 261 (46), 260 (100), 206 (16), 156 (16), 105 (45), 77 (71), 51 (10). found, %: c 60.03; h 2.83; n 12.20. с23h13fn4o4s. calculated, %: c 60.00; h 2.85; n 12.17. 6,7,8‑trifluoro‑2‑phenyl‑1,3‑benzo‑ thiazin‑4‑one (12а). tetrafluorobenzoylchloride 10a (0.85 g, 4 mmol) was added to thiobenzamide 11a (0.397 g, 2.9 mmol) in dry toluene (8 ml), reaction mixture was refluxed for 3 h and then cooled. the precipitate of benzothiazinone 12a was filtered off and recrystallized from dmso. yield 0.646 g (76%), mp 160–162 0с. 1н nmr, δ (ppm), j (hz): 7.62 m (2н, ph), 7.73 m (1н, ph), 8.15 ddd (1н, h5, 3j 10.3, 4j 7.4, 5j 2.2), 8.19 m (2н, ph). 19f nmr, δ (ppm), j (hz): 151.84 ddd (1f, f7, 3j 22.5, 3j 21.5, 4j 7.4), 135.10 ddd (1f, f8, 3j 21.5, 4j 6.2, 5j 2.2), 132.50 ddd (1f, f6, 3j 22.5, 3j 10.3, 4j 6.2). ms (ei), m/z (irel (%)): 293 [m] + (11), 190 (100), 162 (30). found, %: c 57.51, h 1.88, n 4.62. c14h6f3nos. calculated, %: c 57.34, h 2.06, n 4.78. compounds 12b‑h were synthesized by the same method. 6,7,8‑trifluoro‑2‑(p‑chlorophenyl) — 1,3‑benzothiazin‑4‑one (12b). yield 59%, mp 204–206 0с. 1н nmr, δ (ppm), j (hz): 7.73 d (2н, h3’,5’, 3j 8.8), 8.23 d (2н, h2’,6’, 3j 8.8), 8.24 ddd (1н, h5, 3j 10.6, 4j 7.5, 5j 2.1). 19f nmr, δ (ppm), j (hz): 151.68 ddd (1f, f7, 3j 22.5, 3j 21.2, 4j 7.5), 135.02 ddd (1f, f8, 3j 21.5, 4j 6.3, 5j 2.1), 132.29 ddd (1f, f6, 3j 22.5, 3j 10.6, 4j 6.3). ms (ei), m/z (irel (%)): 327 [m]+ (4), 190 (100), 162 (27). found, %: c 51.42, h 1.66, n 4.13. c14h5f3noscl. calculated, %: c 51.31, h 1.54, n 4.27. 6,7,8‑trifluoro‑2‑(p‑tolyl) — 1,3‑ben‑ zothiazin‑4‑one (12c). yield 71%, mp 184–186 0с. 1н nmr, δ (ppm), j (hz): 2.46 s (3н, сн3), 7.43 d (2н, h 3’,5’, 3j 8.0), 8.09 d (2н, h2’,6’, 3j 8.0), 8.14 ddd (1н, h5, 3j 10.0, 4j 7.5, 5j 2.3). found, %: c 58.75, h 2.70, n 4.41. c15h8f3nos. calculated, %: c 58.63, h 2.62, n 4.56. 99 6,7,8‑trif luoro‑2‑(pyridyl‑2)  — 1,3‑benzothiazin‑4‑one (12d). yield 76%, mp 166–168 0с. 1н nmr, δ (ppm), j (hz): 7.75 dd (1н, h5’, 3j 8.0, 3j 4.0), 8.10 td (1h, h4’, 3j 8.0, 4j 1.8), 8.13 ddd (1н, н5, 3j 10.4, 4j 7.4, 5j 2.2), 8.38 d (1h, h3’, 3j 8.0), 8.79 dd (1н, h6’, 3j 4.0, 4j 1.8). 19f nmr, δ (ppm), j (hz): 151.95 ddd (1f, f7, 3j 22.5, 3j 21.1, 4j 7.4), 135.64 ddd (1f, f8, 3j 21.1, 4j 6.2, 5j 2.2), 132.70 ddd (1f, f6, 3j 22.5, 3j 10.4, 4j 6.2). found, %: c 52.95, h 1.63, n 9.67. c13h5f3n2os. calculated, %: c 53.06, h 1.71, n 9.52. 5,6,7,8‑tetrafluoro‑2‑phenyl‑1,3‑ben‑ zothiazin‑4‑one (12e). yield 80%, mp 165–167 0с. 1н nmr, δ (ppm), j (hz): 7.63 m (2н, ph), 7.76 m (1н, ph), 8.17 m (2н, ph). ms (ei), m/z (irel (%)): 311 [m] + (7), 208 (100), 180 (24), 111 (5). found, %: c 53.83, h 1.81, n 4.67. c14h5f4nos. calculated, %: c 54.02, h 1.62, n 4.50. 5,6,7,8‑tetrafluoro‑2‑(p‑chlorophe‑ nyl)  — 1,3‑benzothiazin‑4‑one (12f ). yield 62%, mp 186–188 0с. 1н nmr, δ (ppm), j (hz): 7.66 d (2н, h3’,5’, 3j 8.8), 8.20 d (2н, h2’,6’, 3j 8.8). found, %: c 48.83, n 3.97. c14h4f4noscl. calculated, %: c 48.64, h 1.17, n 4.05. 5,6,7,8‑tetrafluoro‑2‑(p‑tolyl)  — 1,3‑benzothiazin‑4‑one (12g). yield 74%, mp 191–193 0с. 1н nmr, δ (ppm), j (hz): 2.46 s (3н, сн3), 7.43 d (2н, h 3’,5’, 3j 8.4), 8.08 d (2н, h2’,6’, 3j 8.4). found, %: c 55.46, h 2.24, n 4.19. c15h7f4nos. calculated, %: c 55.39, h 2.17, n 4.31. 5,6,7,8‑tetrafluoro‑2‑(pyridyl‑2)  — 1,3‑benzothiazin‑4‑one (12h). yield 77%, mp 182–184 0с. 1н nmr, δ (ppm), j (hz): 7.76 ddd (1н, h5’, 3j 8.0, 3j 4.8, 4j 0.8), 8.10 td (1h, h4’, 3j 8.0, 4j 1.8), 8.36 dd (1h, h3’, 3j 8.0, 4j 0.8), 8.79 dd (1н, h6’, 3j 4.8, 4j 1.8). found, %: c 49.92, n 9.09. c13h4f4n2os. calculated, %: c 50.01, h 1.29, n 8.97. results and discussion we developed an efficient synthetic approach to 2-hetaryl/(hetaryl)ylidene-substituted fluorinated 1,3-benzothiazinones, for this purpose we studied the interaction of  the  range of с-nucleophiles (indoles, n-methylpyrrole, 2-cyanomethyland 2-benzoylmethylbenzimidazoles) with 2,6-difluoro-3-nitrobenzoylisothiocyanate 4 in acetonitrile at room temperature (figure 1). according to 1h and 19f nmr spectra, the reaction leads to the formation of  1,3-benzothiazin-4-ones 5–9, the  intermediate addition products were not isolated, and fluorine atom at с5 was not subjected to substitution with nucleophilic reagent. it is worth noting that the intramolecular cyclization proceeded at milder reaction conditions than in  the  case of 2,6-difluoroand 2,3,4,5-tetrafluorobenzoyl derivatives (refluxing in acetonitrile or dimethylformamide in the presence of trimethylamine [7]). the signals of н6 and н7 in  1h nmr spectra of  benzothiazinones 5–9 exhibit more complicated multiplicity than in  the  case of  2,5-diaminobenzothiazinones [8], which indicates that the fluorine atom remains in position 5. to prove that the alternative product of cyclization, 5-fluoro-6-nitro isomer, was not formed 19f nmr spectra without suppression of f-h spin-spin interaction were registered. in such spectra of compounds 5–9 double doublet signals with 3jfh = 9.5–10.1 hz and 4jfh = 3.9–4.0 hz are present, so the formation of  5-fluoro-8-nitroisomers was confirmed. the  peaks of  molecular ions in the mass spectra of benzothiazinones 5–9 have a relative intensity of 14–39%. 100 thus, we demonstrated the  difference in  behavior of  с-nucleophiles and n-nucleophiles under the  reaction with 2,6-difluoro-3-nitrobenzoylisothiocyanate 4: application of  с-nucleophiles allows to  obtain derivatives of  5-fluoro8-nitrobenzothiazinone, whereas the reaction with cycloalkylimines fails to avoid the  nucleophilic substitution of  fluorine at position 5. the proposed strategy opens wide opportunities for varying the substituent at position 2 of 8-nitrobenzothiazin4-ones. we presented novel one-stage synthetic approach to 2-substituted fluorinecontaining 1,3-benzothiazin-4-ones based on cyclocondensation of  polyfluorobenzoyl chlorides with thioamides as  s,ndinucleophiles. new 6,7,8-trifluoroand 5,6,7,8-tetrafluoro-derivatives of 1,3-benzothiazin-4-ones 12a‑h were obtained by the reaction of polyfluorobenzoylchlorides 10a,b and thioamides 11a‑d in boiling toluene for 3 h in 59–80% yields (figure 2), notably that intermediate n-aroylation products were not isolated. signals of nh groups are absent in  1h nmr spectra of compounds 12a‑h, spectra of 6,7,8-trifluorobenzothiazinones 12a‑d exhibited ddd signal of fluoroarene residue н5 proton at 8.13–8.24 ppm. the number of signals in  19f nmr spectra is in accordance with the structure of benzothiazinones 12. the peaks of molecular ions in the mass f o oh f o oh f no2 f f f o cl no2 h2so4 , hno3 socl2 , nh4ncs, mecn, f f no2 o ncs 1 2 3 4 s n f no2 o s n f no2 o s n f no2 o s n f no2 o s n f no2 o 7 6 8 5 nn n hn nh n n nh n o n o nh n h n nh o ph ph o hn nh mecn, room t mecn, room t mecn, room t mecn, room t mecn, room t 9 toluene toluene fig. 1. synthesis of 5-fluoro-8-nitro-1,3-benzothiazin-4-ones 5–9 101 spectra of benzothiazinones 12 have low relative intensity of 4–11%. the ions m/z 190 or m/z 208 with 100% intensity were observed for benzothiazinones 12, moreover, peaks m/z 162 or m/z 180 correspond to ions [м-rcn-co]+. the most abundant peak was reported to be characteristic for elimination of  rcn fragment from molecular ions of 2-r-6,7,8-trifluoro-1,3-benzothiazin-4-ones [5–7]. the presented approach allows to obtain a variety of 2-aryl/hetaryl-substituted 1,3-benzothiazinones and successfully complements the previously described cyclocondensation of polyfluorobenzoylchlorides with benzimidazol-2-thiones as cyclic s,n-dinucleophiles leading to [b]-annelated fluorobenzothiazinones [12]. unfortunately, we failed to  obtain 5-fluoroand 5-fluoro-8-nitro analogs using the method shown in figure 2. tuberculostatic activity of polyfluorinated benzothiazinnes 12 was studied at two laboratories, namely ural research institute for phthisiopulmonology (urip) and university of illinois, chicago institute for tuberculosis research (inr); the data are presented in table 1. table 1 data on tuberculostatic activity of fluorinated 2‑aryl/pyridyl‑1,3‑benzothiazin‑4‑ones 12 against mycobacterium tuberculosis h37rv* comp mic values (urip data), mg/ml % inhibition at 128 mg/ml (itr data) mic values, mg/ml (itr data) ic50, mg/ml (itr data) maba lora maba lora 12b 12.5 28 66 — 12c 12.5 95 100 58.0 52.3 >128 12d 0.3 — — >128 >128 — 12f 3.12 0 100 — 3.7 53.5 12g nd 74 99 — 26.3 — 12h 12.5 0 100 — 55.8 65.9 * mic–minimal inhibitory concentration; ic50 — the half maximal inhibitory concentration; urip — ural research institute for phthisiopulmonology; inr — chicago institute for tuberculosis research; maba — microplate alamar blue assay; lora — lowoxygen recovery assay. o f f f f cl y 10а,b 12а-h h2n r s r f f s n o f y toluene, t 11а-d 10: y = h (a), f (b); 11: r = ph (a), 4-cl-c6h4 (b), 4-me-c6h4 (c), 2-py (d); 12: y = h, r = ph (a), 4-cl-c6h4 (b), 4-me-c6h4 (c), 2-py (d); y = f, r = ph (e), 4-cl-c6h4 (f), 4-me-c6h4 (g), 2-py (h). fig. 2. synthesis of polyfluorinated 2-aryl/pyridyl-1,3-benzothiazin-4-ones 12a‑h 102 according to trials conducted in urip, benzothiazinone 12d exhibited the highest activity (mic 0.3 mg/ml, isoniazide as  reference compound with mic 0.15 mg/ml). data obtained in  itr revealed 12f as the most promising derivative towards the dormant multi-resistant strain of  micobacteria h37rv–ca-luxab (mic 3.7 mg/ml, rifampicinum as reference compound with mic 8.26 mg/ml). conclusions to sum up, we developed efficient synthetic approaches to fluorine-containing 1,3-benzothiazin-4-ones bearing aryl, hetaryl and (hetaryl)ylidene residues at position 2 and demonstrate that some of them are promising for design of new antitubercular agents. acknowledgements the work was carried out with financial support from the ministry of science and higher education of russian federation (project № feuz-2020–0058 (н687.42б.223/20)). references 1. chetty s, ramesh m, singh-pillay a, soliman m. recent advancements in the development of anti-tuberculosis drugs. bioorg med chem lett. 2017;27(3):370–86. doi: 10.1016/j.bmcl.2016.11.084 2. kimura h, sato y, tajima y, suzuki h, yukitake h, imaeda t, kajino m, oki h, takizawa m, tanida s. btzo-1, a cardioprotective agent, reveals that macrophage migration inhibitory factor regulates are-mediated gene expression. chem biology. 2010;17(12):1282–94. doi: 10.1016/j.chembiol.2010.10.011 3. nosova ev, lipunova gn, charushin vn, chupakhin on. synthesis and biological activity of 2-aminoand 2-aryl(hetaryl) substituted 1,3-benzothiazin-4-ones. minireviews in medicinal chemistry. 2019;19(12):999–1014. doi: 10.2174/1389557518666181015151801 4. szabo j, bani-akoto e, dombi g, gunther g, bernath g, fodor l. ring-closure reaction of n-arylthiomethylaroylamides to 1,3-benzothiazines. j. heterocyc. chem. 1992;29(5):1321–4. doi:10.1002/jhet.5570290545 5. nosova ev, lipunova gn, laeva aa, charushin vn. polyfluorobenzoyl chlorides and isothiocyanates in reactions with ch-reactive benzimidazoles. russ. chem. bull. 2005;54(3):733–7. doi: 10.1007/s11172-005-0312-6 6. nosova ev, laeva aa, trashakhova tv, golovchenko av, lipunova gn, slepukhin pa, charushin vn. fluorine-containing heterocycles: xviii. monofluoro derivatives of quinazolines and 1,3-benzothiazin-4-ones. russ j org chem. 2009;45(6):904–12. doi:10.1134/s1070428009060189 103 7. nosova ev, poteeva ad, lipunova gn, slepukhin pa, charushin vn. synthesis of fluorine-containing 2-pyrrolyland 2-indolyl-substituted 1,3-benzothiazin4-ones. russ j org chem. 2019;55(3):384–7. doi: 10.1134/s1070428019030205 8. nosova ev, batanova oa, lipunova gn, charushin vn. synthesis of novel 8-nitrosubstituted 1,3-benzothiazin-4-ones. mendeleev communications. 2020;30(4);427–9. doi: 10.1016/j.mencom.2020.07.007 9. yoshida y, barrett d, azami h, morinaga c, matsumoto s, matsumoto y, takasugi h. studies on anti-helicobacter pylori agents. part 1: benzyloxyisoquinoline derivatives. bioorg med chem. 1999;7(11):2647–66. doi: 10.1016/s0968-0896(99)00203–5 10. mohareb rm, abdallah aem, mohamed aa. synthesis of novel thiophene, thiazole and coumarin derivatives based on benzimidazole nucleus and their cytotoxicity and toxicity evaluations. chem pharm bull. 2018;66(3):309–18. doi: 10.1248/cpb.c17–00922 11. mochul’skaya nn, andreiko aa, kodess mi, vasil’eva eb, filyakova v. i, gubaidullin at, litvinov ia, sinyashin og, aleksandrov gg, charushin vn. annelation of the thiazole ring to 1,2,4-triazines by tandem an-an or sn h-sn h reactions. russ chem bull, int ed. 2004;53(6):1279–89. doi: 10.1023/b:rucb.0000042287.32992.54 12. lipunova gn, nosova ev, mokrushina ga, ogloblina eg, aleksandrov gg, charushin vn. fluorocontaining heterocycles: ix. derivatives of imidazo[2,1-b] [1,3]benzothiazine. russ j org chem. 2003;39(2):248–56. doi: 10.1023/a:1025548505109 reducing of industrial atmospheric emissions using electrocyclone 169 reducing of industrial atmospheric emissions using electrocyclone anatolii titova*, john shrimptonb, cheng shaoc, zhuohan lic a ural federal university, 19 mira st., ekaterinburg, 620002, russia b university of southampton, university road, southampton, so17 1bj, united kingdom c dalian university of technology, no. 2 linggong road, ganjingzi district, dalian city, liaoning province, 116024, china *email: a.g.titov@urfu.ru abstract. the article is focused on capturing process-related dust at industrial enterprises (in chemical, metallurgical and energy industries). an electrocyclone can be recommended for the purification of gases emitted into the atmosphere from particulates, such as sodium percarbonate (efficiency 97.5% — 99.9%), iron-vanadium concentrate (98.0% — 99.9%), fly ash (99.0% — 99.9%). however, the fumes from copper-smelting furnaces cannot be purified with high efficiency (less than 50–60%) because of their properties. using electrocyclone will reduce the amount of aerosol emissions, and in some cases, let the emission reach the values set by standards. keywords: gas purification; electrocyclone; cyclone; electrostatic precipitator received: 16.10.2020. accepted: 07.12.2020. published:30.12.2020. © anatolii titov, john shrimpton, cheng shao, zhuohan li, 2020 d o i: 1 0. 15 82 6/ ch im te ch .2 02 0. 7. 4. 05 anatolii titov, john shrimpton, cheng shao, zhuohan li chimica techno acta. 2020. vol. 7, no. 4. p. 169–172. issn 2409–5613 introduction the concept of sustainable development of the industry includes an important part of the responsibility for the environment, in particular, the commitment to  the  preservation of  clean air and water, narrowing down the amount of waste to the minimum. the urals is an industrially developed region of the russian federation. more than 1,500 enterprises representing the mining, metallurgical, energy and other industries are found in the urals. this neighbourhood cannot but affect the  environment [1]. the  urals is  one of russia’s leading regions in terms of environmental pollution [2]. it is quite an urgent objective now to reduce the amount of emissions, in particular, air emissions [3]. any type of gas-cleaning equipment has an area of optimum use. cyclones are high-performance but are ineffective for trapping micron particles [4]. electrofilters are effective for particles pm2.5 but are high costly [5, 6]. many researchers have attempted to combine two or even three types of  gas cleaning devices in  a  single unit to improve the performance of its operation [7, 8]. electrocyclone is a combined dust collector that combines the centrifugal and electrostatic effects for aerosol cleaning [9]. 170 experimental materials, which are the products and industrial wastes of  russia’s volga and ural regions, were chosen: 1. sodium percarbonate from the  first and second stages of the purification of exhaust gases of the spray dryer at jsc “percarbonate”, chuvash republic. 2. the iron-vanadium concentrate dust released during ore annealing at jsc “kachkanarskiy mining and processing plant”, sverdlovsk region. 3. sublimates of the blister smelting furnaces of the copper smelting shop of jsc “sredneuralsk copper plant”, sverdlovsk region. 4. the ash from the combustion of ekibastuz coal at reftinskaya tpp, sverdlovsk region. the characteristics of the substances are reported in table 1. the  main tool of  the  experimental equipment was a laboratory vertical electrocyclone. the  diagram of  it is  shown in  fig.  1. an  electrocyclone consists of a body 1, snails with an inlet 2, the central tube 3, a corona system 4, an exhaust pipe 5 and a hopper 6. results and discussion figs. 2–4 shows results of experiments. it is shown, that without an electric field, the degree of gas purification from particles with a size less than 50 microns detable 1 characteristics of the materials under research № material true density, k/gm3 specific electric resistance, ohm·m particle diameter, μm d10 d50 d90 1 sodium percarbonate 2144 <104 10 35 67 2 iron-vanadium concentrate 5100 103 16 73 90 3 sublimates of furnaces 4600 107 2.5 6 15 4 fly ash 2200 >108 15 32 64 fig. 1. electrocyclone (model ecv) 171 creases with a  decrease in  diameter; for micron particles it is virtually zero. when the voltage reaches 17 kv, the purification rate is higher than 90% for fine particles (less than 50 microns) in each case. capturing the fumes of copper-smelting furnaces electrocyclone yielded unsatisfactory results (no diagram). the degree of purification in the experiments at a voltage of  17  kv was 50–60%, and no more than 50% without voltage. conclusions studies have been held to  capture the  dispersed industrial materials. it is  shown that an  electrocyclone can be used like existing gas treatment units. for 0 20 40 60 80 100 η (e ff ic ie nc y) , % particle size, μm u=17 kv, w=11.6 m/s u=17 kv, w=14.9 m/s u=17 kv, w=17.7 m/s u=17 kv, w=21.1 m/s u=17 kv, w=23.6 m/s u=0 kv, w=11.6 m/s u=0 kv, w=14.9 m/s u=0 kv, w=17.7 m/s u=0 kv, w=21.1 m/s u=0 kv, w=23.6 m/s fig. 2. fractional efficiency (sodium percarbonate) 0 20 40 60 80 100 η (e ff ic ie nc y) , % particle size, μm u=17 kv, w=11.6 m/s u=17 kv, w=14.9 m/s u=17 kv, w=17.7 m/s u=17 kv, w=21.1 m/s u=17 kv, w=23.6 m/s u=0 kv, w=23.6 m/s u=0 kv, w=21.1 m/s u=0 kv, w=17.7 m/s u=0 kv, w=14.9 m/s u=0 kv, w=11.6 m/s fig. 3. fractional efficiency (iron-vanadium concentrate) 0 20 40 60 80 100 η (e ff ic ie nc y) , % particle size, μm u=17 kv, w=11.6 m/s u=17 kv, w=14.9 m/s u=17 kv, w=17.7 m/s u=17 kv, w=21.1 m/s u=17 kv, w=23.6 m/s u=0 kv, w=11.6 m/s u=0 kv, w=14.9 m/s u=0 kv, w=17.7 m/s u=0 kv, w=21.1 m/s u=0 kv, w=23.6 m/s fig. 4. fractional efficiency (fly ash) 172 example, in catching sodium percarbonate, the  efficiency reached 97.5–99.9%. the  iron-vanadium concentrate collection efficiency was up to 98–99.9%. the ash of  tpp can be caught with an  efficiency up to 99.9%. the optimum operating flow rate of aerosol at the inlet to electrocyclone lies in the range 15–17 m/s. in capturing the fumes of the copper-smelting furnaces some satisfactory data were received (the efficiency does not exceed 50–60%). this can be explained by the high dispersion and adhesion. the  factors have led to the termination of electrical purification. in general, the electrocyclone can reduce aerosol emissions from industrial plants into the atmosphere by a few digits to several tens of times. in each case, before choosing an electrocyclone as a gas treatment unit, individual characteristics of the material should be evaluated. references 1. bréchignac f, desmet g. equidosimetry: ecological standardization and equidosimetry for radioecology and environmental ecology. springer science & business media; 2005. 436 p. 2. linkov i, wilson r. air pollution in the ural mountains: environmental, health and policy aspects. springer science & business media; 2012. 455 p. 3. gafurova s. ecological problems of trans-ural zone come out to the forefront [internet]. 2011[updated 2011.02.17; cited 2020.10.12] http://www.bashinform.ru/eng/341343/. 4. ng sy, priestman gh, allen rwk. investigation of  flooding, re-entrainment and grade efficiency in axial flow cyclones. chemical engineering research and design. 2006;84:884–94. doi:10.1205/cherd05063 5. sudrajad a, yusof af. review of electrostatic precipitator device for reduce of diesel engine particulate matter. energy procedia. 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varaksin m. v., kopchuk d. s., kovalev i. s., taniya o. s., m. rahman, s. santra, zyryanov g. v., chupakhin o. n., charushin v. n. chimica techno acta. 2020. vol. 7, no. 4. p. 215–221. issn 2409–5613 synthesis of meso-2,2’-bipyridyl-substituted calix[4] arenes and their response to metal cations t. d. moseeva, a. f. khasanovab, m. v. varaksinab, d. s. kopchukab, i. s. kovaleva, o. s. taniyaab, m. rahmana, s. santraa, g. v. zyryanovab*, o. n. chupakhinab, v. n. charushinab a ural federal university named after the first president of russia b. n. yeltsin, 19 mira st., ekaterinburg, 620002, russian federation b i. ya. postovsky institute of organic synthesis of ras (ural branch), 22/20 s. kovalevskoy/akademicheskaya st., ekaterinburg, 620990, russian federation *email: g.v.zyrianov@urfu.ru abstract. a convenient synthetic approach to meso-substituted with 2,2’-bipyridine and 1-(pyridin-2-yl)isoquinoline residues calix[4]arenes is reported. this approach involves the reaction of generated in situ 2-lithio-calix[4]arene with 1,2,4-triazine precursor with the following aromatization of the obtained adduct, and the aza-dielsalder reaction of the 1,2,4-triazinyl-substituted calix[4]arene with 2,5-norbornadien or in-situ generated 1,2-dehydrobenzene. the uv/fluorescence response of thus obtained meso-pyridyl-substituted calix[4]arenes to metal cations is studied. keywords: calix[4]arene; 1,2,4-triazines; aza-diels-alder reaction; 2,2’-bipyridines; visual cations detection received: 16.09.2020. accepted: 20.12.2020. published:30.12.2020. © moseev t. d., khasanov a. f., varaksin m. v., kopchuk d. s., kovalev i. s., taniya o. s., m. rahman, s. santra, zyryanov g. v., chupakhin o. n., charushin v. n., 2020 introduction calix[4]arenes and their derivatives are, probably, the mostly studied supramolecular hosts for various applications for analytical chemistry [1], materials science [2], as well as environmental [3] and medicinal [4] applications. by means the proper synthetic modification various calixarene derivatives bearing extra heterocyclic ligand units or other receptor units at the upper or lower rim were obtained to be used for the recognition/supramolecular extraction of inorganic [5] and organic cations [6], anions [7], as well as some neutral molecules [8]. in  this article we wish to report a method for the preparation of  meso-2,2’-bipyridyl-substituted calix[4]arenes and their response to metal cations. experimental part 1h nmr spectra were recorded on a  bruker avance-400 spectrometer (400  mhz), the  internal standard was sime4. mass-spectra (ionization type — electrospray) were recorded on a  microtof-q ii instrument from bruker daltonics (bremen, germany). elemental analysis was performed on a perkin elmer 216 pe 2400 ii chn analyzer. fluorescence spectra were measured on horiba fluoromax-4 spectrofluorometer. absolute quantum yields were measured by using the  integrating sphere. uv-spectra were measured on shimadzu uv-1800 spectrometer. the  starting meso-triazinylsubstituted calix[4]arenes were prepared as reported [9]. mes o-2,2’-bipy ri dy l-substitute d calix[4]arene (3). in  a  50 ml roundbottom flask to  a  solution of  2-(6-phenyl-3-(2-pyridyl)-1,2,4-triazin-5-yl)25,26,27,28-tetramethoxycalix[4]arene 2 (0.106 g, 0.15 mmol) in 10 ml of o-xylene 2,5-norbornadiene (0.15 ml) was added and the  resulting solution was heated at a temperature of 130–150 °c for 12 hours under the argon atmosphere. then another 0.1 ml of 2,5-norbornadiene were added and the reaction mixture was heated for another 6 hours at a temperature of 130– 150  °c. o-xylene was distilled off under reduced pressure, and the column chromatography (eluent — ethyl acetate) resulted in the product 3 (rf = 0.55). yield 69 mg (0.097 mmol, 65%), mp >250°с. nmr 1h (cdcl3, δ, ppm): 8.64 (1h, d, j=4.9 hz, н-6 (2-ру)), 8.43–8.51 (1h, dd, j=8.2 hz, j=15.1 hz, н-3 (ру)), 8.33–8.37 (1н, dd, j=2.7 hz, j=8.2 hz, н-4 (ру)), 7.67–7.76 (2н, m, н-3 (2-ру)), н-4 (2-ру)), 7.35– 7.43 (2н, m, н-5 (2-ру), ph), 7.27–7.33 (2н, m, ph) 7.11–7.27 (5н, m, ph), 6.90– 6.97 (2н, m, ph), 6.80–6.86 (2н, m, ph), 6.67–6.77 (6н, m, ph), 6.28, 5.70 (1н, s, с(2)н), 4.25–4.32, 4.12–4.17 (2н, m, arch2ar), 3.72–3.77 (4н, m, 1н arch2ar + 3н оме), 3.65 (3н, s, оме), 3.57 (1н, m, arch2ar), 3.42–3.48 (4н, m, 1н arch2ar + 3н оме), 3.16 (3н, m, 3н оме), 2.85 (1h, m, arch2ar). found: с 81.27%, н 6.15%.c48h42n2o4. calculated: с 81.10%, н 5.96%. meso-1-(pyridin-2-yl)isoquinolinylsubstituted calix[4]arene (4). in a 100 ml three-necked flask equipped with a reflux condense 2-(6-phenyl-3-(pyridin-2-yl)1,2,4-triazin-5-yl)-25,26,27,28-tetramethoxycalix[4]arene (0.142 g, 0.2 mmol) was dissolved and 0.1 ml of  iso-amyl nitrite (0.7 mmol) in  40 ml of  dry toluene was added at once. under argon atmosphere the resulted solution was heated to a temperature of  105–110  °c, and a  solution of anthranilic acid (96 mg, 0.7 mmol) in 20 ml of 1,4-dioxane was added to dropwise for 30 minutes with an intensive stirring the reaction mixture. after that the reaction was kept under such conditions for 60 minutes. the reaction mixture was than cooled down to  room temperature and washed with a 30% aqueous alkali solution (4 times 50 ml each), the organic phase was separated, dried with an anhydrous sodium sulfate, filtered and the solvent was distilled off under reduced pressure. the product 4 was isolated by  column chromatography (dichloromethane: ethyl acetate in a ratio of 4: 1, rf = 0.85). yield 10 mg (0.012 mmol, 6.0%), mp >250°с. nmr 1h (cdcl3, δ, ppm): 8.89 (1h, d, j=4.9 hz, н-6 (2-ру)), 8.41–8.48 (1h, dd, j=8.2 hz, j=15.1 hz, н-3 (2-ру)), 8.79–8.88 (1h, dd, j=2.7 hz, j=8.2 hz, н-4 (2-ру)), 7.59–7.66 (2н, m, н-5 (2-ру), ph), 7.46–7.55 (4н, m, ph), 7.39–7.46 (3н, m,ph), 7.08–7.18 (2н, m, ph), 6.89–7.04 (2н, m, ph), 6.83– 6.88 (2н, m, ph), 6.65–6.76 (5н, m, ph), 6.57–6.64 (2н, m, ph), 6.35, 5.96 (1н, s, с(2)н), 4.25–4.32, 4.12–4.17 (2н, m, arch2ar), 3.72–3.77 (4н, m, 1н arch2ar + 3н оме), 3.65 (3н, s, оме), 3.57 (1н, m, arch2ar), 3.42–3.48 (4н, m, 1н arch2ar + 3н оме), 3.16 (3н, m, 3н оме), 2.85 (1h, m, arch2ar). found: с 81.91%, н 5.77%. c52h44n2o4. calculated: : с 82.08%, н 5.83%. 217 studies of  the  interactions of  calixarenes 3–4 with cations the studies of the interactions of compounds 3–4 with zn2+ and cd2+ cations were carried out at  the  concentrations of  3–4 of  (1-9)·10–6 m (depending on the  value of  the  absorption coefficient (a  ≤ 0.1)) in  anhydrous freshly distilled thf. the concentrations of cations were 10–3–10–4 m. results and discussion a  most common method for the  introducing of  (bi)pyridine moieties into the  calix[4]arenes is  the  modification of  upper or lower ring the  calixarene core with oligopyridine-attached spacer groups by means of acylation, alkylation or condensation reactions [9–17]. as an alternative approach our group reported the direct modification of an upper ring of calix[4]arene moiety with 3-(2-pyridyl)1,2,4-triazine-5(2h) — one residues [18]. for these modified calixarenes an  effectiveness for their transport of la3+ cations was confirmed. additionally, we reported recently an  effective synthetic approach to  meso-substituted with 1,2,4-triazine moieties calix[4]arenes via direct modification of 5-h-1,2,4-triazines by the reaction with generated in situ 2-lithio-calix[4] arene and the following aromatization [9] (scheme 1). from another hand the 1,2,4-triazines are suitable precursors for the preparation of multi-substituted (bi)pyridine ligands/ fluorophores via the inverse demand dielsalder/retro-diels-alder reaction sequence omeome meoome li h omeome meoome h n n n ph n omeome meoome h n ph n omeome meoome h n ph n 1 2 3 4 i,ii iii iv scheme 1. reagents and conditions: i) 1.6 m n-buli, tmeda, thf, –78 °c, 1h, then 25 °c overnight; ii) ddq (1.2 eq.), thf, 25 °c, 0.5 h; iii) 2,5-norbornadiene, o-xylene, 130–150 °c, 18 h; iv) anthranilic acid, iso-amylnitrite, 1,4-dioxane-toluene, 105–110 °c, 1.5 h. 218 with various dienophiles, such as 2,5-norbornadiene [20], enamines [21], acetylene equivalents [22] or aryne intermediates [23]. keeping in  mind all the  mentioned above we decided to prepare new calix[4] arenes meso-substituted with (benzo) pyridine moieties and study their response to  selected metal cations. to  do that as a first step we prepared the corresponding meso-1,2,4-triazine-substituted calixarene 2 using the previously reported procedure [9]. as a next step the id dielsalder reaction between 2 and 2,5-norbornadiene was carried out to afford smoothly meso-2,2’-bipyridyl-substituted calix[4] arene 3 in  up to  65% yield (scheme  1). the photophysical properties of calixarene 3 are presented below (table 1). the introduction of bipyridyl ligand/ fluorophore on the periphery of calix[4] arene caused the change in the photophysical properties of product 3. thus, in thf solution calixarene 3 has a strong absorbance band near 292 nm and an emission peak near 379  nm. calculated absolute fluorescence quantum yield was 1.1%. the response of calixarene 3 to zn2+ and cd2+ cations is shown below. thus, in uvspectra the addition of 1 eq. of these cations caused a strong decrease of the absorbance peak at 292 nm (fig. 1). the  same trend was obser ved in  the  emission spectra. thus, upon addition of  1 eq. of  cd2+ or zn2+ a  dramatic fluorescence quenching was observed along with the bathochromic shift of  the  emission maxima by  5–20  nm. it worth to mention that, the addition of zn2+ caused the stronger red-shift, while the addition of cd2+ caused stronger fluorescence quenching (fig. 2). as  a  last step the  isoqinoline-substituted calixarene 4 was obtained by using the reaction between 2 and benzyne generated in situ as reported before [23]. the retable 1 photophysical properties of calixarene 3(c3) in thf solution # λabs max a, nm λem max b, nm εm (at λabs max, 10 4 m–1 ·cm–1) stokes shift, nm φf, (%) c (λ ex, nm) d c3 292 379 1.60 113 1.1 (292 nm) a absorption maxima in thf at room temperature; b fluorescence maxima in thf at room temperature; c absolute photoluminescence quantum yield in thf; d excitation wavelength fig. 1. uv-spectra of calixarene 3 in the presence of cd2+ and zn2+ fig. 2. emission spectra of calixarene 3 in the presence of cd2+ and zn2+ 219 action afforded as low as 6% of the desired calixarene 4, while the rest of the reaction mixture contains several non-identified products. in  preliminary experiments in  a  solution of  thf in  the  presence of even trace amounts of cd2+ calixarene 4 exhibited a dramatic fluorescence quenching. however, a lesser response to zn2+ was observed. in our opinion, these results confirm the influence of a nature of pyridine substituents in the meso-position of the calix[4]arene core on the  fluorescence response of  whole calixarene molecule to the selected metal cations. conclusions in summary, meso-pyridyland mesoisoqunolinyl-substituted 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university 2021, vol. 8(4), № 20218401 eissn 2411-1414; chimicatechnoacta.ru doi: 10.15826/chimtech.2021.8.4.01 1 of 13 facile synthesis of some 5-(3-substituted-thiophene)pyrimidine derivatives and their pharmacological and computational studies s.h. sukanya a, talavara venkatesh a* , s.j. aditya rao b, n. shivakumara c, muthipeedika nibin joy d a: department of p.g. studies and research in chemistry, jnanasahyadri, kuvempu university, shankaraghatta 577451, karnataka, india b: plant cell biotechnology department, csir-central food technological research institute, mysore 570020, karnataka, india c: department of chemistry, ramaiah institute of technology, bangalore 560054, india d: innovation center for chemical and pharmaceutical technologies, institute of chemical technology, ural federal university, 19 mira st., yekaterinburg 620002, russia * corresponding author: venkateshatalwar@gmail.com this article belongs to the regular issue. © 2021, the authors. this article is published in open access form under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). abstract a series of 5-(3-substituted-thiophene)-pyrimidine derivatives (3a-d) were synthesized via knoevenagel condensation reaction in aqueous ethanol using h2o2:hcl as a catalyst. their pharmacological effects were evaluated. analytical and spectroscopic methods confirmed the structures of the target molecules. the antibacterial activity studies revealed that compounds 3b and 3d exhibited the most effective zone of inhibition against bacterial strains e. coli and s. aureus, respectively. the in vitro cytotoxicity was carried out by mtt assay against mcf-7 cell line. the results showed the excellent selectivity for all four compounds, among which the compound 3a exhibited remarkable cytotoxicity with a minimum cell viability range of 23.68 to 44.16%. the interaction of compounds with calf thymus dna was determined using uv-absorption spectroscopy. the results confirmed that all the synthesized compounds interacted strongly with ct dna through electrostatic or groove binding. in silico adme-toxicology studies indicated that all the molecules under investigation are nontoxic with good oral bioavailability. the drug-likeness score indicated that they are suitable as drug-leads. in silico molecular docking the specified compound 3b bounds with glcn-6-p and p38 mapk with a minimum binding energy of –7.9 and –6.4 kcal/mol, respectively. dft study demonstrated that the compound 3d was chemically and biologically more reactive due to less energy gap. keywords biological studies dna binding adme-toxicology study sar study molecular docking and dft studies received: 02.09.2021 revised: 11.10.2021 accepted: 12.10.2021 available online: 15.10.2021 1. introduction heterocyclic compounds play a predominant role in medicinal chemistry and synthetic organic chemistry due to their massive biological importance. the synthesis of nitrogen and sulphur containing fused heterocyclic compounds with multi-structures in one molecule has attracted the attention of medicinal chemists and researchers due to their multifaceted pharmacological activities [1–2]. among them, pyrimidine and thiophene have been recognized as key scaffolds owing to their important biological significances and interesting therapeutic properties including anti-tubercular [3], anticancer [4], anti-hiv [5], antibacterial [6], antifungal [7], antitumor [8], also used as potent egfr inhibitor [9, 10], protein kinase inhibitors [11–14] and 5-ht7 receptors [15]. moreover, the heterocyclic compounds increase the strength of the molecules by forming hydrogen bonds with dna. hence, the interactive study of heterocyclic moieties with dna is essential for estimating their anticancer activity and elucidates the viable mechanism of their action. therefore, dna binding is considered as an essential exhttp://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2021.8.4.01 http://creativecommons.org/licenses/by/4.0/ https://orcid.org/0000-0001-9637-3909 chimica techno acta 2021, vol. 8(4), № 20218401 article 2 of 13 perimental step to measure anticancer drugs activity because most anticancer drugs specifically target the dna [16]. heterocyclic compounds appear to be most effective against various cancers. around 60% of the medicines used for cancer treatment are based on heterocyclic moieties. among the various heterocyclic moieties, nitrogen and sulphur-based compounds are effective against different types of cancers [17–19]. cancer is a group of diseases in which the abnormal cells grow uncontrollably by disregarding the normal rules of cell division. cancer is caused by many external (tobacco, chemicals, radiation and infectious organisms) as well as some internal factors (inherited mutations, hormones, immune conditions and random mutations). there are different types of cancer such as breast cancer, bladder cancer, kidney cancer, leukaemia, liver cancer, lung cancer, melanoma, pancreatic cancer, prostate cancer, thyroid cancer etc. [20]. the breast cancer is one of the most frequently diagnosed cancers and the leading cause of death in females worldwide, with more than 1.5 million new cases recorded every year. it is also the fifthhighest cause of death in the world [21]. the modern methods of chemotherapy suffer from the main disadvantages: side effects and drug resistance. therefore, continued search for novel and safer anticancer drugs remains essential [22]. pollution is one of the critical problems that the synthetic organic chemist faces in designing the organic reactions for the synthesis of pharmacologically active compounds. thus, development of an environmentally-friendly chemical process that induces necessary organic transformation is one of the most important goal of sustainable progression [23]. therefore, "green chemistry" becomes a promising approach that meets the requirements of the chemical and pharmaceutical industries. the replacement of hazardous solvents with eco-friendly solvents is an acceptable and valuable approach in a chemical reaction. hence, the use of a hypochlorous acid (hocl) as a green halogenating agent [24] is highly advantageous over other catalysts, including cost-effectiveness, efficiency and readily availability. earlier, our research group has reported the synthesis of different pyrimidine derivatives and other biologically important heterocyclic compounds [25–27]. some of the drugs containing pyrimidine nucleus available in the market are depicted below (fig. 1). based on the above findings, we herein report the application of h2o2:hcl as a green halogenating catalyst for the synthesis of 5-(3-substituted-thiophene)-pyrimidine derivatives of considerable pharmacological relevance. 2. experimental 2.1. materials and method all chemicals and calf thymus dna were purchased from aldrich chemical company, and the reaction was performed at refluxed condition and solvents were used without further purification. analytical tlc was performed with e. merck silica gel gf254 glass plates. visualization of the developed chromatogram was performed by uv light (254 and 356 nm). the melting points of the products were determined in open capillary tubes and uncorrected. the atr-ir spectra were obtained using bruker ftir alpha spectrometer. the 1h nmr and 13c nmr spectra were recorded on bruker 400 mhz and 100 mhz in dmso-d6 as a solvent. mass spectra were obtained by agilent 1200 series lc and micromass q spectrometer. the dna binding studies were carried on elico sl 159 uv-visible spectrophotometer in 200–500 nm range equipped with 1.0 cm quartz cell at room temperature. the anticancer activity was carried out in the department of microbiology, maratha mandal's ngh institute of dental sciences and research centre, belgaum, karnataka. the computational studies were carried out by density functional theory (dft)/b3lyp method using gaussian 09 software using 631g (d, p) basis set at gaseous phase. 2.2. general procedure for the synthesis of 5-(3substituted-thiophene)-pyrimidine derivatives (3a-d) the synthesis of 5-(3-substituted-thiophene)-pyrimidine derivatives (3a-d) were carried out by the reaction of barbituric/thiobarbituric acid (1, 1mmol) with 3-substitutedthiophene-2-carboxaldehyde (2, 1mmol) in the presence of 15 ml aqueous ethanol using 6% h2o2:hcl (2:1) as a catalyst. the reaction mixture was refluxed at 80 °c for about 10–15 min and the progress of the reaction was monitored by tlc (ethyl acetate and petroleum ether). after the completion of the reaction, the reaction mixture was cooled to room temperature and poured into the 100 ml flake ice with vigorous stirring to get solid precipitated out. the crude mixture was filtered, washed and recrystallized with absolute ethanol to afford pure solid products. 2.2.1. 5-(thiophen-2-ylmethylidene)pyrimidine2,4,6(1h,3h,5h)-trione (3a) yield: 96%, yellow solid; mp: 280–282 °c. ir (atr, υ cm–1): 3373 (nh), 1654 (c=o), 1529 (c=c). 1h nmr (400 mhz, dmso-d6, δ ppm): 7.31–7.33 (t, j= 8 hz, 1h, ar-h), 8.13–8.24 (m, 2h, ar-h), 8.53 (s, 1h, ch), 11.17 (s, 1h, nh), 11.21 (s, 1h, nh). 13c nmr (100 mhz, dmso-d6, δ ppm): 112.035, 128.808, 136.776, 142.526, 146.116, 146.291, 150.679, 163.453 and 163.950 (c=o). hrms: m/z 221.9054 [m+h]+. anal. calcd for c9h6n2o3s: c 48.64, h 2.72 and n 12.61%. found: c 48.59, h 2.68 and n 12.53%. 2.2.2. 5-[(3-methylthiophen-2-yl)methylidene]pyrimidine2,4,6(1h,3h,5h)-trione (3b) yield: 94%, yellow solid; mp: 302–306 °c. ir (atr, υ cm–1): 3225 (nh), 2858 (ch3), 1703 (c=o), 1542 (c=c). 1h nmr (400 mhz, dmso-d6, δ ppm): 2.24 (s, 3h, ch3), 7.21–7.23 (d, j= 8 hz, 1h, ar-h), 8.16–8.18 (d, j= 8 hz, 1h, ar-h), 8.53 (s, 1h, ch), 11.17 (s, 1h, nh), 11.24 (s, 1h, nh). 13c nmr (100 mhz, dmso-d6, δ ppm): 19.922 (ch3), 114.870, 135.252, 136.011, 145.166, 147.180, 154.915, 158.106, 167.728 and 168.497 (c=o). hrms: m/z 235.9774 [m+h]+. anal. calcd for c10h8n2o3s: c 50.84, h 3.41 and n 11.86%. found: c 50.79, h 3.36 and n 11.80%. chimica techno acta 2021, vol. 8(4), № 20218401 article 3 of 13 hn h no o f 5-fluorouracil (anticancer) n h no o f o ho ho floxuridine (anticancer) n h nh n o o cl cl uramustine (anticancer) hn n o o o f tegafur (anticancer) hn n h sh o o 5-thiouracil (anticancer) n n nh2 o o o h2n trimethoprim (antibacterial) n n s n n o n n hn s o o pictilisib (anticancer) n n n o f n h o s lorediplon (insomnia) n n n o s n o indiplon (sedative & hypnotics) fig. 1 some of the drugs containing pyrimidine nucleus available in the market 2.2.3. 5-(thiophen-2-ylmethylidene)-2thioxodihydropyrimidine-4,6(1h,5h)-dione (3c) yield: 93%, green solid; mp: 320–322 °c. ir (atr, υ cm–1): 3106 (nh), 1760 (c=o), 1559 (c=c), 1156 (c=s). 1h nmr (400 mhz, dmso-d6, δ ppm): 6.86–6.88 (d, j = 8 hz, 1h, ar-h), 8.20 (s, 1h, ch), 8.34–8.36 (d, j = 8 hz, 2h, ar-h), 12.20 (s, 1h, nh), 12.30 (s, 1h, nh). 13c nmr (100 mhz, dmso-d6, δ ppm): 114.713, 116.139, 124.434, 139.254, 157.012, 160.480, 162.825, 164.168 (c=o) and 178.617 (c=s). hrms: m/z 237.9467 [m+h]+. anal. calcd for c9h6n2o2s2: c 45.36, h 2.54 and n 11.76%. found: c 45.30, h 2.49 and n 11.71%. 2.2.4. 5-[(3-methylthiophen-2-yl)methylidene]-2thioxodihydropyrimidine-4,6(1h,5h)-dione (3d) yield: 95%, green solid; mp: 310–312 °c. ir (atr, υ cm–1): 3108 (nh), 2852 (ch3), 1704 (c=o), 1516 (c=c), 1200 (c=s). 1h nmr (400 mhz, dmso-d6, δ ppm): 2.24 (s, 3h, ch3), 7.22–7.24 (d, j= 8 hz, 1h, ar-h), 8.17–8.19 (d, j = 8 hz, 1h, ar-h), 8.54 (s, 1h, ch), 11.18 (s, 1h, nh), 11.25 (s, 1h, nh). 13c nmr (100 mhz, dmso-d6, δ ppm): 26.806 (ch3), 114.280, 128.031, 128.903, 129.867, 130.391, 130.892, 142.472, 163.552 (c=o) and 173.358 (c=s). hrms: m/z 251.9608 [m+h]+. anal. calcd for c10h8n2o2s2: c 47.60, h 3.20 and n 11.10%. found: c 47.55, h 3.16 and n 11.06%. 2.3. pharmacological studies 2.3.1. antibacterial activity antibacterial activity of the synthesized compounds (3a-d) was carried out by the agar well diffusion method [28] using two bacterial strains (gram-negative and grampositive) escherichia coli (mtcc-1559) and staphylococcus aureus (mtcc-902). dmso was used as negative control and ciprofloxacin as standard drug. the test compounds were dissolved in dmso at two different concentrations, 20 and 40 µg/ml. 2.3.2. cytotoxicity in vitro cytotoxicity was assessed by the mtt assay method [29] against mcf-7 (breast cancer) cell line. the cells were seeded in a 96-well flat-bottom microplate and maintained at 37 °c in 95% humidity and 5% co2 overnight. different concentration (200, 100, 50, 25, 12.5 and 6.25 µg/ml) of samples were treated. the cells were incubated for another 48 h, and the wells were washed twice with pbs. 20 µl of the mtt staining solution was added to each well, and the plate was incubated at 37 °c for 4 h. the medium with mtt was discarded, and 100 µl of chimica techno acta 2021, vol. 8(4), № 20218401 article 4 of 13 dmso was added to each well to dissolve the formazan crystals. the absorbance was recorded at 570 nm using a microplate reader. the percentage of cell survival was calculated by using the following formula: % of cell survival = mean o. d. of test compound mean o. d. of negative control  100. (1) 2.3.3. dna binding study dna binding study was assessed by using electronic spectroscopy. a solution of ct dna in 50 mm tris-hcl/50 mm nacl buffer solution was prepared at ph 6.9–7.01. in buffer solution, the ratio of absorption values of ct dna at 260 and 280 nm is 1.8–1.9, indicating that dna was free of proteins [30]. then a concentrated stock solution of dna was prepared in 50 mm tris-hcl, 50 mm nacl in double distilled water at ph 6.9–7.01. the concentration of ct dna was determined per nucleotide by taking the absorption coefficient (6600 dm3 mol–1 cm–1) at 260 nm [31]. stock solutions were stored at 4 °c. 2 ml of the solution was taken containing a fixed concentration of the compounds (3a-d) with ct dna (0 to 350 µl of a 0.5025–6.067010–7 m stock ct dna solution). a blank solution containing the same concentration of dna was used as a reference. solutions were prepared by mixing the compound and ct dna in dmso medium and then recording the uv absorption spectra by adding 25 to 350 µl dna to the compound. the spectra were recorded against a blank solution containing the same concentration of dna (4.090910–6 mol l–1). the intrinsic binding constant kb was obtained by using the following equation [32]: [dna] (∈a−∈b) = [dna] (∈b−∈f ) + 1 kb(∈b−∈f) , (2) where, ∈𝐴 ,∈𝐵 and ∈𝐹 corresponds to the apparent, bound and free compound extinction coefficients, respectively. a plot of [dna] (∈a−∈f ) versus [dna] gave a slope of 1 (∈b−∈f) and y-intercept equal to 1 kb(∈b−∈f) . hence kb is the ratio of slope to intercept. the % of hyperchromicity or hypochromicity (% h) for the ct dna/[ligand] was obtained from (∈a – ∈f)/ ∈f 100. 2.3.4. in silico oral bioavailability assessment and admetoxicology studies the oral bioavailability of the synthetic molecules (3a-d) can be predicted by considering their structural properties to screen based on the rule of five or lipinski rule-of-five (ro5) filter [33]. rule of five employs the molecular properties necessary to filter candidate drug's pharmacokinetics (pk) and pharmacodynamics (pd) [34–36]. oral bioavailability assessment was done using osiris data warrior v.4.4.3 [37] based on total molecular weight, clogp, h-acceptors, h-donors, rotatable bonds as part of ro5 filters, along with tpsa (topological polar surface area) and drug-likeness assessment [38]. pharmacodynamic properties like mutagenicity, tumorigenicity, reproductive effects, irritancy, ames toxicity and hepatotoxicity were predicted using the admetsar server. bioactivity scores were predicted using the molinspiration server for gpcr ligand, ion channel modulator, kinase inhibitor, nuclear receptor inhibitor, protease inhibitor, enzyme inhibitor. pharmacokinetic properties like blood-brain barrier penetration, human intestinal absorption, caco-2 permeability and cyp450 2d6 substrate were predicted by submitting each molecule individually to the admetsar server [39]. 2.3.5. in silico molecular docking studies the docking of the synthesized compounds to the binding pocket of glucosamine-6-phosphate synthase (glcn-6-p) and p38 map kinase was carried out using the autodockvina program [40]. the co-crystallized structure of glcn6-p (pdb id: 2vf5) and p38 map kinase (pdb id: 1ouk) were retrieved from protein databank, and their substrate binding sites were identified using pdbsum server [41, 42]. a grid box of dimensions 40 x 50 x 40 å with x, y and z coordinates at 32.198, 16.709 and –3.151 for glcn-6-p and 56 x 60 x 48 å with x, y and z coordinates at 44.746, 34.234 and 32.603 for p38 mapk were created respectively. for the obtained molecules, all the torsions were allowed to rotate during docking. the grid box was set around the residues forming the active pocket. the binding interactions were visualized using biovia discovery studio visualizer v.20.1 and schrodinger-maestro v.12.7. the in silico studies were performed on a local machine equipped with amd ryzen 5 six-core 3.4 ghz processor, 8 gb graphics and 16 gb ram with microsoft windows 10 operating system. 2.3.6. computational studies computational studies of synthesized compounds (3a-d) were conducted by using the gaussian 09 software [43] with the help of the density functional theory at becke-3-lee-yang-parr (dft)/b3lyp level with 6-31g (d,p) basis set [44]. the energy minimization process has been conducted at the same level in the gas phase to obtain a stable structure. the 3d representation of the optimized structure was presented in a molecular visualization program gauss view 5.0 and the output was processed using the avogadro software [45]. 3. results and discussion 3.1. chemistry in this report, we developed a convenient and straightforward method for the synthesis of 5-(3-substitutedthiophene)-pyrimidine derivatives (3a-d) via knoevenagel condensation of barbituric/thiobarbituric acid (1) with 3-substituted-thiophene-2-carboxaldehyde (2) in aqueous ethanol using h2o2:hcl as catalyst (scheme 1). a possible mechanism for the formation of 5-(3-substituted-thiophene)-pyrimidine derivatives is shown in scheme 2. firstly, hypochlorous acid (hocl) forms by the reaction of h2o2 with hcl, and it acts as a chimica techno acta 2021, vol. 8(4), № 20218401 article 5 of 13 powerful oxidizing agent. then the reaction is initiated by the generation of carbanion 2 from active methylene compound 1. the carbanion 2 attacks the carbonyl carbon of aldehyde 3 to form intermediate 4, which undergo subsequent dehydration to desired knoevenagel product 5. hocl increases the abstraction of acidic proton from active methylene compound and electrophilicity of carbonyl group of aldehydes due to hydrogen bonding. firstly, we studied the effect of catalyst on the reaction. in the previous reports, the same reaction was carried out in the presence of different catalysts such as cuo nps, pvp-ni nps, fe3o4 nps, l-tyrosine, nh2so3h, ean, bi(no3)3.5h2o, and also in the absence of catalyst (table 1). we studied the influence of catalyst in the progress of reaction as well as on the increased product yield. the results were not very encouraging. therefore, we concluded that the best result was obtained in the presence of green halogenating catalyst 6% h2o2:hcl, where a further increase in the quantity of catalyst doesn't significantly affect reaction kinetics. consequently, to study the effect of temperature on synthesized compound 3a, we carried out the reaction at room temperature, 50 °c and 80 °c (table 2). as a result, an increase in the reaction temperature decreased the reaction time from 60 to 20 and 20 to 10 min, respectively. still, the yield of the product was not affected by an increase in temperature. the structures of the intended 5-(3-substitutedthiophene)-pyrimidine derivatives (3a-d) were confirmed by ir, 1h nmr, 13c nmr and hrms spectral data. ir spectrum of compound 3a showed that the absorption band in the region 3373 cm–1 is attributed to the amide stretching vibration, and the absorption band at 1654 cm–1 corresponds to stretching vibration of the carbonyl group (c=o). another stretching vibrational band at 1529 cm–1 corresponds to c=c bond. the 1h nmr spectrum of compound 3a exhibited two singlet peaks at δ 11.21 and 11.17 ppm, which corresponds to two nh protons of pyrimidine nucleus (s, 2h, nh) and another singlet peak at δ 8.53 ppm due to ch proton (s, 1h, ch). a multiplet peak was observed in the range of δ 8.24–8.13 ppm, corresponds to two aromatic protons (m, 2h, ar-h) and a triplet peak at 7.33–7.31 ppm due to one aromatic proton (t, j = 8 hz, 1h, ar–h). hn nh x o o s r h o hn n h o x o s r 1 2 3(a-d) + h2o2:hcl reflux/ 10-15min x= o & s, r= h & ch3 scheme 1 synthesis of 5-(3-substituted-thiophene)-pyrimidine derivatives (3a-d) n h n h o o x h h o h cl n h n h o o x _ s o h h o cl r n h nh s o x o oh h r n h nh s o x o r h 2 o 2 + hcl hocl + h2o 1 3 4 5 2 hocl h2o h2o scheme 2 possible mechanism of synthesized compounds (3a-d) in addition, the 13c nmr spectrum of compound 3a exhibited peaks at δ 163.950 and 163.453 ppm, which correspond to carbonyl carbons. the mass spectrum showed molecular ion peak [m+h]+ at m/z is 221. 9054 corresponds to the molecular weight of compound 3a (supporting information: s1 to s16). the physical and analytical data of synthesized compounds (3a-d) were appended in table 3. 3.2. pharmacological effect 3.2.1. antibacterial activity the synthesized 5-(3-substituted-thiophene)-pyrimidine derivatives (3a-d) were screened for their in vitro antibacterial activity at two different concentrations (20 and 40 µg/ml). all four compounds showed appreciable antibacterial activity with a varied zone of inhibition in the range of 3.3 to 3.8 and 7.1 to 7.8 mm against e. coli and 3.0 to 3.7 and 7.4 to 7.9 mm against s. aureus, respectively (table 4). table 1 effect of catalysts on synthesized compound 3a entry catalyst solvent temperature, °c time, min yield, % 1 h2o2: hcl etoh:h2o reflux 10 96 2 cuo nps – rt 10 93 [46] 3 pvp-ni nps ethylene glycol reflux 10 87 [47] 4 fe3o4 nps etoh reflux 30 70 [48] 5 l-tyrosine h2o rt 16 93 [49] 6 nh2so3h – grinding 120 96 [50] 7 – ionic liquids rt 10 96 [51] 8 bi(no3)35h2o etoh reflux 20 95 [52] 9 – etoh reflux 120 89 [53] chimica techno acta 2021, vol. 8(4), № 20218401 article 6 of 13 table 2 effect of temperature on synthesized compounds 3a entry temperature, °c time, min yield, % 1 rt 60 96 2 50 20 96 3 80 10 96 the results revealed that compounds 3b (3.8 and 7.8 mm) and 3d (3.7 and 7.9 mm) having electrondonating group (methyl) on c-3 of the thiophene ring exhibited the most inhibitory effect against bacterial strains e. coli and s. aureus, respectively, compared to the standard drug ciprofloxacin. 3.2.2. cytotoxicity all the four synthesized compounds were investigated for their in vitro cytotoxicity against mcf-7 (breast cancer) cell line (fig. 2). the plot details compound concentration versus the survival fraction (fig. 3). the percentages of cell survival of the tested compounds are listed in table 5. in vitro cytotoxicity results revealed that all four compounds displayed a superior selectivity against the mcf-7 cell line. among the compounds tested, compound 3a exhibited promising cytotoxicity with a minimum cell survival range of 23.68 to 44.16% at the concentration range of 200 to 6.25 µg/ml. whereas 3b, 3c and 3d displayed reliable selectivity at all the concentrations with cell survival ranges of 29.00 to 50.93%, 31.31 to 66.82% and 26.95 to 53.12%, respectively. 3.2.3. dna binding study dna binding was assessed using electronic spectroscopy. the uv-absorption spectral studies were employed to examine the binding mode of compounds to ct dna, which involves the changes in absorbance and wavelength [55]. the molecules are bound to dna with two modes (covalent or noncovalent) of binding. the covalent binding led to bathochromism and hyperchromism due to breaking the dna structure when a compound interacted with dna covalently. while in non-covalent binding, there are "electrostatic", "groove", and "intercalative" types of interactions. table 4 antibacterial activity results of synthesized compounds (3a-d) compd. zone of inhibition in mm escherichia coli staphylococcus aureus concentration in µg/ml 20 40 20 40 3a 3.5 7.8 3.0 7.5 3b 3.8 7.8 3.1 7.6 3c 3.3 7.2 3.5 7.4 3d 3.4 7.1 3.7 7.9 ciprofloxacin 4.0 8.0 4.2 8.4 table 3 physical and analytical data of synthesized compounds (3a-d) entry comp. x r product yield (%) mp (oc) observed reported 1 3a o h hn n h o o o s 98 278–280 271 [54] 2 3b o ch3 hn n h o o o s 95 302–306 – 3 3c s h hn n h o s o s 94 320–322 – 4 3d s ch3 hn n h o s o s 96 310–312 – chimica techno acta 2021, vol. 8(4), № 20218401 article 7 of 13 fig. 2 images of anticancer study of the synthesized compounds (3a-d) fig. 3 a graph of % of surviving cells of compounds (3a-d) at different concentration against mcf-7 cell line table 5 percentage of cell viability against mcf-7 cell line of the synthesized compounds (3a-d) concentration in µg/ml mean cell viability of mcf-7 3a 3b 3c 3d 6.25 44.16±0.76 50.93±0.42 66.82±0.41 53.12±0.34 12.5 38.11±0.82 48.68±0.31 58.1±0.13 46.88±0.52 25 34.09±1.2 43.72±0.52 48.6±0.23 43.93±0.42 50 32.37±0.82 40.23±0.61 40.03±0.82 40.03±0.62 100 30.06±0.62 36.80±0.20 37.38±0.61 37.85±0.34 200 23.68±0.41 29.00±0.16 31.31±0.42 26.95±0.52 values are mean ±se, n=3, *p<0.01 vs. control decreased absorption (hypochromic shifts) and redshift (bathochromic shift) revealed the intercalative binding of compounds with dna. lower hypochromic/hyperchromic effect with no or negligible bathochromic shift led to the electrostatic binding. minor or no effect and, rarely, some hyperchromism show the groove binding [56–58]. the dna binding efficiency of synthesized compounds (3a-d) was monitored by comparing their absorption spectra with and without ct dna. the absorption spectra were carried out at a fixed concentration of synthesized compounds and varying with dna concentrations (25–350 µl of 0.502510–7 to 6.067010–7 mol l–1) under the physiological condition of ph 7.01. the absorption spectra of all the synthesized compounds (3a-d) exhibited absorption bands at 235 to 240 nm due to π–π* transitions (fig. 4). the kb values of compounds (3a-d) are found to be 1.1216107, 1.4072107, 1.0634107 and 3.4872107 respectively are shown in table 6. these kb values confirm that all the synthesized compounds interacted strongly with ct dna. among the four compounds, compound 3d showed a prominent binding ability with ct dna compared to other compounds. the absorption bands of the compounds were affected due to the gradual increase of ct dna concentration resulting hyperchromism/hypochromism. no/or negligible blue/red shift indicates strong interaction of the compounds with ct dna mainly through electrostatic or groove binding [59]. the kinetics and thermodynamics of compounds-dna interaction in terms of binding constant (kb) and gibbs free energy change (δg) were evaluated using the classical van't hoff's equation, δg= –2.303rt logkb. the negative δg values confirmed spontaneous binding of compounds with ct dna through the formation of stable complexes. 3.2.4. in silico adme-toxicology studies the bioavailability and drug-likeness were estimated for all the synthesized compounds (3a-d) based on the molecular properties. the results indicated that all the four compounds under study could pass through lipinski's filter without any violation, demonstrating a positive druglikeness score indicating their suitability as drug-leads. in silico pharmacokinetic studies showed that all the molecules under investigation could penetrate the blood-brain barrier and are readily absorbed by the human intestine while they are impermeable to caco-2, and non-substrate cytochromes p450 (cyp450) group of enzymes (table 7). table 6 dna binding results of synthesized compounds (3a-d) compd. λmax, nm δλmax, nm % h kb, m–1 δg, kj/mol free bound 3a 240 239 1 6.187910–4 1.1216107 –40.205 3b 236 236 0 6.015710–4 1.4072107 –40.767 3c 239 239 0 1.156010–3 1.0634107 –40.073 3d 236 236 0 1.238810–3 3.4872107 –43.015 chimica techno acta 2021, vol. 8(4), № 20218401 article 8 of 13 fig. 4 the electronic absorption spectra of compounds (3a-d) in the absence and presence of increasing amounts of ct dna. arrow (↓) shows the change in the absorbance with increase the dna concentration. inset: plot of [dna]/( ∈a–∈f) vs [dna] table 7 bioavailability, drug likeness and in silico pharmacokinetic assessment of synthesized compounds (3a-d) comp. bioavailability and drug likeness in silico pharmacokinetics t o ta l m o le c u la r w e ig h t c l o g p h -a c c e p to r s h -d o n o r s r o ta ta b le b o n d s p o la r s u r fa c e a re a d r u g l ik e n e s s h u m a n i n te s ti n a l a b s o r p ti o n c a c o -2 p e r m e a b il it y b lo o d b r a in b a r ri e r c y p 4 5 0 2 d 6 s u b s tr a te 3a 222.224 0.2739 5 2 1 103.51 5.2698 +0.982 –0.779 +0.982 –0.873 3b 236.251 0.6178 5 2 1 103.51 4.9763 +0.728 –0.753 +0.980 –0.889 3c 238.291 0.6344 4 2 1 118.53 4.2229 +0.979 –0.698 +0.977 –0.871 3d 252.318 0.9783 4 2 1 118.53 3.9143 +0.987 –0.673 +0.976 –0.886 in silico pharmacodynamics studies revealed that all the four molecules are non-mutagenic, nontumorigenic, non-irritant, ames non-toxic with high reproductive effects with possible hepatotoxicity. the bioactivity assessment indicated that the molecules do not belong to the gpcr group of ligands, do not modulate ion channels, non-kinase inhibitors, non-nuclear receptor ligands, non-protease and non-enzyme inhibitors (table 8). 3.2.5. structure-activity relationship (sar) studies the evaluation of the antibacterial activity of the newly synthesized compounds (3a-d) revealed that the presence of electron-donating methyl group has a significant effect on enhancing their potency. the compounds 3b and 3d have a methyl group at c-3 of the thiophene ring. this could have improved their cell permeability, which improved their activity profile compared to 3a and 3c. the combination of heterocyclic rings like pyrimidine and thiophene is presumed to be the main reason for the profound cytotoxicity of the newly synthesized compounds (3a-d). furthermore, the presence of the urea group in the pyrimidine ring could have significantly contributed to the superior cytotoxicity of 3a and 3b compared to other synthesized molecules. chimica techno acta 2021, vol. 8(4), № 20218401 article 9 of 13 3.2.6. in silico molecular docking studies the results revealed that compound 3b bound with glcn6-p and p38 mapk with a minimum binding energy of –7.9 and –6.4 kcal/mol, respectively. 3a, 3d and 3c interacted with a binding energy of –7.6 and –6.4, –7.4 and –6.2 and –7.4 and –6.0 with glcn-6-p and p38 mapk targets, respectively. the interaction of all the molecules with glcn6-p and p38 mapk were compared with antibacterial agent ciprofloxacin (–7.7 kcal/mol) and anticancer agent 5-fluorouracil (–4.7 kcal/mol) (table 9, fig.5). the computational methods in drug discovery have gained enormous importance in modern drug research. they play a critical role in reducing the virtual chemical space in synthesizing, modifying, and screening chemical drugs against a specific disease target. their effectiveness can be validated using microbial pathogens due to their simpler and clearer cellular understandings. similarly, cell death modalities can also be studied using in vitro cell culture studies, particularly focusing on necrosis, apoptosis, necroptosis, autophagic cell death, etc. [42]. in the present study, in silico molecular docking studies were performed to predict the most effective binding among the synthesized molecules to appropriate targets [60, 61]. the studied molecules showed remarkable binding interactions with the selected target proteins, supporting their remarkable antimicrobial and anticancer effects. 3.2.7. dft studies frontier molecular orbitals (fmos) containing the highest occupied molecular orbital (homo) and lowest unoccupied molecular orbital (lumo), as well as the energy gap (δe = ehomo –elumo) were considered to be very effective parameters in chemical quantum chemistry [62]. fmos also delivered important information about chemical reactivity, biological activity and kinetic stability of the molecules [63]. the optimized homo and lumo structures of synthesized compounds (3a-d) are shown in fig. 6 and 7. the homo and lumo of compounds were helpful in determining of various global reactivity parameters such as ionization energy (i = –ehomo), electron affinity (a = –elumo), chemical hardness (ƞ = 1/2 (i – a)), chemical softness (σ = 1/ƞ), electronegativity (χ = 1/2 (i + a)), chemical potential (µ = –χ), and electrophilicity index (ω = µ2/2ƞ) helps to study about donor– acceptor interaction and intramolecular charge transfer (ict) ability of synthesized compounds [64]. the calculated homo-lumo energies and global reactivity parameters of the synthesized compounds (3a-d) are displayed in table 10. a smaller homo-lumo energy gap (δe) indicates a soft molecule, while a larger gap indicates a hard molecule. lower energy gap, less ionization potential, electron affinity, chemical hardness, electronegativity, electrophilicity index values and more softness values indicate that a molecule is more chemically and biologically active with low kinetic stability [65]. fig. 5 binding interaction of compounds 3a (a and b), 3b (c and d), 3c (e and f), and 3d (g and h) with glcn-6-p along with standard drug ciprofloxacin (i and j) (a) and binding interaction of compounds 3a (a and b), 3b (c and d), 3c (e and f), and 3d (g and h) with p38 mapk along with standard drug 5-fluorouracil (i and j) (b) table 8 in silico pharmacodynamics and bioactivity assessment of synthesized compounds (3a-d) comp. in silico pharmacodynamics bioactivity score m u ta g e n ic t u m o ri g e n ic r e p r o d u c ti v e e ff e c ti v e ir ri ta n t a e r o b ic b io d e g r a d a b il it y a m e s t o x ic it y h e p a to to x ic it y g p c r l ig a n d io n c h a n n e l m o d u la to r k in a s e in h ib it o r n u c le a r r e c e p to r li g a n d p r o te a s e i n h ib it o r e n z y m e i n h ib it o r 3a none none high none –0.590 –0.706 +0.925 –1.12 –1.58 –0.86 –1.26 –1.30 –0.69 3b none none high none –0.562 –0.694 +0.950 –1.07 –1.44 –0.90 –0.91 –1.32 –0.73 3c high none high none –0.859 –0.731 +0.900 –1.43 –1.77 –1.41 –1.73 –1.32 –1.00 3d high none high none –0.843 –0.711 +0.850 –1.35 –1.62 –1.42 –1.35 –1.34 –1.03 chimica techno acta 2021, vol. 8(4), № 20218401 article 10 of 13 dft studies data reveals that the energy gaps (δe) of compounds 3a, 3b, 3c and 3d are 0.16038 ev, 0.15988 ev, 0.12799 ev and 0.12636 ev, respectively. 3a, 3b and 3c, 3d moleculs show nearly similar energy gap due to the similar structure. among them 3d molecule shows less energy gap (0.12636 ev) and more softness value (15.8277 ev); hence, it is chemically more reactive compared to the other molecules. 3a molecule has more electronegative value (0.19923 ev); hence, it has more tendency to attract a bonding electron pairs compared to the other molecules. table 9 binding energies of synthesized compounds (3a-d) with glcn-6-p and p38 mapk targets antibacterial activity anticancer activity compd. binding energy in kcal/mol compd. binding energy in kcal/mol ciprofloxacin –7.7 5-fluorouracil –4.7 3a –7.6 3a –6.4 3b –7.9 3b –6.4 3c –7.4 3c –6.0 3d –7.4 3d –6.2 conclusions we described a mild, easy and green protocol for synthesizing 5-(3-substituted-thiophene)-pyrimidine derivatives (3ad) using h2o2:hcl as a catalyst under reflux condition. this synthetic approach has a short reaction time, excellent yield, and clean reactions make this procedure a magnificent alternative to the existing methods. furthermore, this method is environmentally greener and safer. the activity results revealed that the compounds 3b and 3d exhibited more potent antibacterial activity against e. coli and s. aureus than the standard drug ciprofloxacin. in vitro cytotoxicity results disclosed the outstanding selectivity on mcf-7 cell line, mainly compound 3a exhibiting the most effective cytotoxicity with a minimum cell survival range of 23.68 to 44.16%. dna binding results indicated that all the synthesized compounds interacted strongly with ct dna, and compound-dna complexes were stabilized by electrostatic or groove binding. in silico adme-toxicology results showed that all the four compounds are non-toxic and suitable for oral bioavailability and drug-likeness, indicating their suitability as drug-leads. table 10 chemical parameters of synthesized compounds (3a-d) entry ehomo (ev) elumo, ev δe ehomo– elumo, ev i, ev a, ev ƞ, ev σ, ev χ, ev µ, ev ω, ev d, debye 3a –0.27942 –0.11904 0.16038 0.27942 0.11904 0.08019 12.4703 0.19923 –0.19923 0.24749 4.6744 3b –0.27411 –0.11423 0.15988 0.27411 0.11423 0.07994 12.5093 0.19417 –0.19417 0.23581 5.2238 3c –0.25095 –0.12296 0.12799 0.25095 0.12296 0.06399 15.6274 0.18695 –0.18695 0.27310 5.4300 3d –0.24793 –0.12157 0.12636 0.24793 0.12157 0.06318 15.8277 0.18475 –0.18475 0.27012 5.9267 fig. 6 optimized structures of synthesized compounds (3a-d) chimica techno acta 2021, vol. 8(4), № 20218401 article 11 of 13 fig. 7 dft study of synthesized compounds (3a-d) in silico molecular docking results showed compound 3b bound with glcn-6-p and p38 mapk with a least binding energy of –7.9 and –6.4 kcal/mol, respectively. dft study result revealed that the compound 3d was chemically and biologically more reactive with low kinetic stability due to less energy gap. in future, the obtained compounds can be used as antibiotics, anticancer agents, dyes and pigments in compounds as food industries. acknowledgements the authors are thankful to the chairman, department of chemistry, kuvempu university, shankaraghatta, for providing the laboratory facilities and saif, mysore 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abstract in the present work, we report a convenient synthesis of 5and 7substituted-4-phenyl coumarins. in contrast to previous results obtained with 4-alkylcoumarins, nicotinoylation of 5,7-dihydroxy-4phenylcoumarin with nicotinoyl benzotriazole or nicotinoyl azide selectively provides 5-o protected ester. the combination of the nicotinoylation reaction followed by tosylation-denicotinoylation yields 5-hydroxy-7-tosyloxy-coumarin derivative, which may be useful in the synthesis of inophyllum, a tetracyclic hiv reverse transcriptase inhibitor, as well as its analogues. keywords 5,7-dihydroxy-4phenylcoumarin nicotinoylation esterification protecting group inophyllum received: 18.11.2021 revised: 21.12.2021 accepted: 21.01.2022 available online: 26.01.2022 1. introduction asymmetrically o-substituted 5,7-dihydroxycoumarins attract attention as important building blocks for the synthesis of biologically active compounds. compounds of this class are widespread both in nature, especially in plants in the form of monoand diterpenes, and in synthetic compounds with important biological activity [1–4]. they have anti-cancer, antibacterial [5, 6], anti-hiv, antiinflammatory and others activities, for example, inophyllums (fig. 1), a series of natural hiv reverse transcriptase inhibitors isolated from calophyllum inophyllum tree [7], comprise asymmetrically o-substituted 5,7dihydroxycoumarin scaffold. asymmetrically o-substituted 5,7-dihydroxycoumarins also can be used to prevent and treat parkinson’s disease, brain lesions, and dementia [8]. fig. 1 structure of naturally occurring inophyllums we have previously demonstrated that nicotinoylation of 5,7-dihydroxy-4-alkylcoumarins is a convenient method for the synthesis of both 5and 7-hydroxy-substituted coumarins [9,10]. in this case, the nicotinoylation reaction proceeds at the sterically less hindered hydroxy group at position c7 of coumarin system (scheme 1). subsequent modification of free 5-oh hydroxy group with a protective group orthogonal to nicotinoyl (tosyl or di(tertbutyl)phenylsilyl) and removal of the nicotinoyl moiety under acidic conditions allows the synthesis of complementary 5-oh protected coumarins [9]. in the presented work, we expand this methodology of selective nicotinoylation to 4-aryl-5,7-dihydroxycoumarins. 2. experimental unless otherwise noted, all commercially available compounds were used without further purification. 1-nicotinoyl benzotriazole [10], nicotinoyl azide [11], and 5,7-dihydroxy-4-phenylcoumarin [12] were prepared in accordance with published procedures. 1h and 13c nmr spectra were recorded at ambient temperature on a bruker avance ii 400 mhz spectrometer at 400 and 100 mhz, respectively, in dmso-d6 or dmsod6:ccl4 mixture as a solvent. chemical shifts (δ) are given in ppm relative to the dmso residual peak (2.50 ppm) as an internal standard. http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2022.9.1.05 https://orcid.org/0000-0003-1582-5462 http://creativecommons.org/licenses/by/4.0/ chimica techno acta 2022, vol. 9(1), no. 20229105 letter 2 of 4 scheme 1 nicotinoylation of 5,7-dihydroxy-4-alkylcoumarin the x-ray diffraction data for compound 2 were obtained from a 0.30×0.25×0.20 mm single crystal (colorless prism) at 295(2) k on an xcalibur e diffractometer with a ccd detector (cu kα radiation, λ = 154.184 pm, graphite monochromator). 2.1. procedure for synthesis of 2, 3, and 4 compounds 2.1.1. 7-hydroxy-2-oxo-4-phenyl-2h-chromen-5-yl nicotinate 2 5,7-dihydroxy-4-phenylcoumarin (2.540 g, 10.0 mmol), triethylamine (1.111 g, 11.0 mmol), and nicotinoyl azide or nicotinoylbenzotriazole (10.0 mmol) were dissolved in acetone (30 ml). the mixture was allowed to stand for 12 hours and the precipitate formed was filtered. yield 1.860 g (52%). 1h nmr (400 mhz, dmso-d6 + ccl4) δ 10.83, 8.67 (d, j = 4.9 hz, 1h), 8.57 (s, 1h), 7.78 (d, j = 8.0 hz, 1h), 7.33 (dd, j = 8.0 hz, j = 4.9 hz, 1h), 7.22–7.22 (m, 2h), 7.04–7.08 (m, 2h), 6.77–6.80 (m, 2h), 6.54 (s, 1h), 5.88 (s, 1h). 13c nmr (101 mhz, dmso) δ 162.62, 161.26, 158.68, 156.03, 153.50, 153.13, 149.99, 147.91, 137.59, 136.73, 127.79, 127.45, 126.72, 123.53, 122.81, 113.28, 108.29, 104.88, 101.44. anal. calcd. for c21h13no5: c, 70.19; h, 3.65; n, 3.90. found: c, 70.01; h, 3,75; n, 3.79. an empirical correction for absorption (μ = 0.875 mm–1) was applied. triclinic crystal system, space group p-1; unit cell parameters: a = 9.240(7), b = 9.946(8), c = 10.604(10) å; α = 83.33(7)°; β = 69.90(8)°; γ = 63.77(8)°; v = 820.2(12) å3; z = 2. total of 8848 reflection intensities were measured in the range 4.44<θ<65.28, including 2705 independent reflections (rint = 0.0517), and 1795 reflections with i>2σ(i); completeness 96.2% for θ = 65.28°. the structure was solved by the direct method and was refined by the least-squares method using shelxtl package [13]. all hydrogen atoms were placed in directly calculated positions which were refined according to the riding model in isotropic approximation. goodness of fit s = 1.005; final divergence factors: r1 = 0.0569, wr2 = 0.0942 for reflections with i>2σ(i); r1 = 0.0419, wr2 = 0.0971 for all independent reflections. the x-ray diffraction data for compound 2 were deposited to the cambridge crystallographic data centre (ccdc entry no. 2129495) [14]. 2.1.2. 2-oxo-4-phenyl-7-(tosyloxy)-2h-chromen-5-yl nicotinate 3 to a suspension of 7-hydroxy-2-oxo-4-phenyl-2hchromen-5-yl nicotinate 2 (1795 mg, 5.0 mmol) in dcm (35 ml) was added dimethylaminopyridine (2440 mg, 10.0 mmol) and tosyl chloride (1194 mg, 6.25 mmol). the mixture was stirred for 30 min., washed with water (3×50 ml), dried and evaporated to yield 3 (1.638 g, 65%) as a white solid. 1h nmr (400 mhz, dmso-d6) δ 8.74 (dd, j = 4.9 hz, j = 1.7 hz, 1h), 8.57 (d, j = 2.5 hz, 1h), 7.87 (d, j = 8.2 hz, 2h), 7.80 (dd, j = 8.0 hz, j = 2.0 hz, 1h), 7.52 (d, j = 8.2 hz, 2h), 7.41 (dd, j = 8.0 hz, j = 4.8 hz, 1h), 7.21–7.28 (m, 4h), 7.07–7.11 (m, 2h), 6.82 (dd, j = 7.51 hz, 1h), 6.27 (s, 1h), 2.43 (s, 3h). 13c nmr (101 mhz, dmso) δ 162.64, 158.09, 154.58, 153.99, 152.01, 150.35, 150.03, 147.70, 146.40, 137.04, 136.77, 130.90, 130.46, 128.31, 128.01, 127.90, 126.98, 123.33, 123.20, 117.90, 114.45, 112.04, 108.98, 21.18. anal. calcd. for c28h19no7s: elemental analysis: c, 65.49; h, 3.73; n, 2.73. found: c, 65.35; h, 3,58; n, 2.93. 2.1.3. 5-hydroxy-2-oxo-4-phenyl-2h-chromen-7-yl 4methylbenzenesulfonate 4 a suspension of 2-oxo-4-phenyl-7-(tosyloxy)-2h-chromen5-yl nicotinate 3 (1008 mg, 2.0 mmol) was stirred in a mixture of ethanol (20 ml) and 30% hydrochloric acid (12 ml) at 80 °c for 4 hours. the mixture was cooled and precipitate was filtered off. yield 710 mg, 87%. 1h nmr (400 mhz, dmso-d6) δ 10.77 (s, 1h), 7.82 (d, j = 8.0 hz, 2h), 7.50 (d, j = 8.0 hz, 2h), 7.32–7.38 (m, 5h), 6.57 (d, j = 2.4 hz, 1h), 6.43 (d, j = 2.4 hz, 1h), 6.04 (s, 1h), 2.43 (s, 3h). 13c nmr (101 mhz, dmso-d6) δ 158.89, 156.90, 155.37, 154.71, 151.29, 146.15, 138.63, 131.20, 130.38, 128.22, 128.06, 127.40, 127.32, 114.70, 106.42, 104.82, 101.03, 21.19. anal. calcd. for c22h16o6s: elemental analysis: c, 64.70; h, 3.95. found: c, 64.57; h, 4.02; n, 3.00. 3. results and discussion we found that nicotinoylation of 5,7-dihydroxy-4phenylcoumarin 1 with nicotinoylbenzotriazole (x = benzotriazolyl) or nicotinic acid azide (x = n3) leads to unexpected 5-nicotinoyloxy-4-phenylcoumarin 2 (scheme 2). chimica techno acta 2022, vol. 9(1), no. 20229105 letter 3 of 4 scheme 2 nicotinoylation of 5,7-dihydroxy-4-phenylcoumarin the reaction takes place at most sterically hindered 5-oh position as confirmed by x-ray structural analysis of compound (fig. 2). one may assume that the selectivity of this reaction is associated with non-covalent interactions in the transition state, such as π-π stacking between the pyridyl ring of nicotinoyl derivatives and the phenyl ring of coumarin. fig. 2 the x-ray structure (ccdc 2129495) of compound 2 to obtain 5-hydroxy-7-o-subsituted derivatives of coumarin 1, we carried out the exchange of hydroxy protective groups. thus, tosylation of 2 with p-toluenesulfonyl chloride followed by denicotinoylation of 3 in an acidic media provides 7-protected tosyloxy derivative 4 (scheme 3). compound 4 may be further converted to inophyllum or inophillum analogues using adapted procedures [9]. 4. conclusions thus, we presented a convenient synthesis of 5and 7substituted 4-phenyl coumarins. it was demonstrated that 4phenyl-5,7-dihydroxycoumarins, unlike 4-alkyl compounds, react with nicotinoylazide with the involvement of the 5hydroxy group in the reaction. the structure of the nicotinoyl derivative was proved by x-ray diffraction analysis. combination of the nicotinoylation with tosylation– denicotinoylation allows one to obtain 7-hydroxy protected 5,7-dihydroxycoumarins. acknowledgments this work is financially supported by russian science foundation (ref no. 21-13-00382). declaration of competing interests the authors declare 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renaissance of the bischler reaction a.d. sharapov * , r.f. fatykhov, i.a. khalymbadzha, o.n. chupakhin institute of chemical engineering, ural federal university, ekaterinburg 620002, russia * corresponding author: a.d.sharapov@urfu.ru this paper belongs to the mosm2021 special issue. © 2021, the authors. this article is published in open access under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). abstract in the present work, we have studied a modified bischler-möhlau reaction – synthesis of indoles from benzoin and aniline. our proposed modification of this method differs from that described earlier in that the reaction is carried out at a lower temperature, which made it possible to improve yields and reduce formation of tarry side products. in addition, unlike previous contradictory works, which described the preparation of a single 4-hydroxy or 6-hydroxy isomer in condensation of m-aminophenol and benzoin, we have obtained both 4-hydroxy and 6-hydroxy isomers. keywords 4-hydroxyindoles 6-hydroxyindoles bischler-möhlau reaction received: 02.11.21 revised: 09.04.22 accepted: 09.04.22 available online: 13.04.22 key findings ● this work reveals the possibilities for the synthesis of new 4-hydroxy and 6-hydroxyindoles under the conditions of the modified bischler-möhlau reaction. ● a distinctive feature of this work is the achievement regioselectivity in the synthesis of these hydroxyindoles. ● in addition, the one-step synthesis of two isomeric hydroxyindoles with good yields can be characterized as an undoubted advantage of this work. 1. introduction the creation of new potential medicinal agents based on hydroxyindoles fragments is one of the promising areas of medical and organic chemistry. for example, topsentin, first isolated from sponges of the genus spongosorites, has pronounced antiviral, antitumor, adrenergic, and antibacterial properties [1–3]. psilocin is an example of psychedelic tryptamines comprising 4-hydroxyindole moiety [4] (scheme 1). several alkaloids, in particular harmine, harmalol and harmol contained in the plant peganum harmala have a spectrum of antitumor activity on cancer cell lines[5, 6], exhibit antibacterial and neuroprotective properties and are also inhibitors of monoaminosidase a (mao-a) [7, 8]. the modified bischler reaction [9], a condensation reaction between aniline and benzoin, allows one to obtain indole with water as only by-product. this feature of the bischler reaction, combined with solventfree conditions, makes this reaction especially relevant to the aspect of green chemistry and atomic economy. hydroxyindoles are particularly convenient to prepare by the bischler reaction, since in some cases it is not necessary to use protecting groups in order to block the phenolic hydroxyl. however, the reaction described in the literature is usually carried out at high temperatures (140–160 °c). this factor reduces the applicability of this process for the synthesis of complex compounds with labile groups. in addition, some aspects of the regiochemistry of the formation of hydroxyindoles from meta-aminophenol and benzoin have remained unclear until now. so, in some works the structure of 2,3-diphenyl-6-hydroxyindole was attributed to the product of this reaction, in other works 2,3-diphenyl-4-hydroxyindole [10, 11]. in this work, we optimized the conditions for the bischler reaction, and put an end to the issue of regiochemistry of this process. 2. experimental section unless otherwise noted, all commercially available compounds were used without further purification. http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2022.9.2.s2 https://orcid.org/0000-0003-1582-5462 mailto:a.d.sharapov@urfu.ru http://creativecommons.org/licenses/by/4.0/ https://crossmark.crossref.org/dialog/?doi=https://doi.org/10.15826/chimtech.2022.9.2.s2&domain=pdf&date_stamp=2022-4-13 chimica techno acta 2022, vol. 9(2), no. 202292s2 letter 2 of 4 scheme 1 biologically active examples of 4and 6-hydroxyindole derivatives. 1h and 13c nmr spectra were recorded at ambient temperature on a bruker avance ii 400 mhz spectrometer at 400 and 100 mhz, respectively, in dmso-d6 as a solvent. chemical shifts (δ) are given in ppm relative to the dmso residual peak (2.50 ppm) as internal standard. aminophenol 1 was obtained from commercially available sources. 2.1. typical procedure for synthesis of 3a-d and 4b, c. benzoin 2 (1 equiv.) was added to aminophenol 1 (3 equiv.) and then hydrochloric acid (1.5 ml of 10m per 0.082 mmol of aminophenol). then the reaction mixture was heated for 30 minutes at 135 °c. during the reaction, water condensate was collected in a deanstark apparatus attached to a weak vacuum. at the end of the reaction, the resulting mass was treated with 15% hydrochloric acid. then the mixture was filtered off, washed with water and dried. the dry residue containing a mixture of 4 and 6-hydroxyindoles 3, 4 was separated using column chromatography with a mixture of solvents ch2cl2:c6h14 = 1:1. 2.2. 2,3-diphenyl-6-hydroxyindole 3a 1h nmr (400 mhz, dmso-d6): δ = 10.99 (s, 1h, oh), 8.81 (s, 1h, nh), 7.46–7.24 (m, 10h, 2ph), 7.25 (d, j = 8.6 hz, 1h, h-4), 6.80 (d, j = 2.1 hz, 1h, h-7), 6.54 (dd, j = 8.6, 2.1 hz, 1h, h-5). 2.3. 2,3-diphenyl-4-hydroxyindole 4a 1h nmr (400 mhz, dmso-d6): δ = 11.18 (s, 1h, oh), 8.80 (s, 1h, nh), 7.39–7.15 (m, 10h, 2ph), 6.93–6.83 (m, 2h, h-6, h-5), 6.34 (dd, j = 6.4, 2.1 hz, 1h, h-7). 2.4. 2,3-bis(3,4-dimethoxyphenyl)-6-hydroxyindole 3b 1h nmr (400 mhz, dmso-d6): δ = 10.80 (s, 1h, oh), 8.71 (s, 1h, nh), 7.22 (d, j = 8.5 hz, 1h, h-4), 7.05–6.81 (m, 6h, ph), 6.76 (d, j = 2.0 hz, 1h, h-7), 6.51 (dd, j = 8.5, 2.2 hz, 1h, h-5), 3.84–3.81 (s, 3h, 2ome ), 3.70 (s, 3h, ome), 3.65 (s, 3h, ome). 2.5. 2,3-bis(3,4-dimethoxyphenyl)-4-hydroxyindole 4b 1h nmr (400 mhz, dmso-d6): δ = 11.00 (s, 1h, oh), 8.59 (s, 1h, nh), 7.07–6.76 (m, 9h, ph), 3.80–3.75 (s, 3h, 2 ome), 3.68 (s, 3h, ome), 3.65 (s, 3h, ome). 2.6. 2,3-bis(3,4,5-trimethoxyphenyl)-6hydroxyindole 3c 1h nmr (400 mhz, dmso-d6): δ = 11.10 (s, 1h, oh), 9.07 (s, 1h, nh), 7.29 (d, j = 8.5 hz, 1h, h-4), 6.81 (d, j = 2.1 hz, 1h, h-7), 6.76 (s, 2h, ph), 6.63 (s, 2h, ph), 6.58 (dd, j = 8.5, 2.2 hz, 1h, h-5), 3.72–3.59 (s, 15h, ome), 3.33 (s, 3h, ome). 13c nmr (101 mhz, dmso-d6): δ = 153.77, 152.90, 152.52, 152.42, 151.98, 136.85, 136.47, 136.08, 131.58, 131.31, 127.92, 121.76, 119.30, 113.56, 110.29, 107.32, 104.88, 96.09, 64.88, 60.07, 60.03, 55.80, 55.49, 55.42, 30.64, 15.13. 2.7. 2,3-bis(3,4,5-trimethoxyphenyl)-4hydroxyindole 4c 1h nmr (400 mhz, dmso-d6): δ = 11.10 (s, 1h, oh), 9.03 (s, 1h, nh), 6.96–6.86 (s, 3h, ph), 6.70 (s, 2h, ph), 6.64 (s, 1h, ph), 3.84 (s, 3h, ome), 3.46–3.36 (s, 15h, ome). 2.8. 2,3-bis(2-chlorophenyl)-6-hydroxyindole 3d 1h nmr (400 mhz, dmso-d6): δ = 11.05 (s, 1h, oh), 8.83 (s, 1h, nh), 7.52–7.36 (m, 3h, ph), 7.36–7.26 (m, 3h, ph), 7.20 (m, 2h, ph), 7.09 (d, j = 8.6 hz, h-4), 6.81 (d, j = 2.2 hz, 1h, h-7), 6.56 (dd, j = 8.6, 2.2 hz, 1h, h-5). 3. results and discussion the use of a modified two-component reaction catalyzed by hydrochloric acid made it possible to isolate a mixture of new isomeric 4and 6-hydroxyindoles from the reaction mixture in high yields. for the synthesis of the starting benzoins 2b-d, the procedure described in the literature [12–14] was used (scheme 2). it was found that fusion according to the modified procedure of 3-aminophenol 1 (3 equiv.) with benzoins 2а-d (1 equiv.) at 135 °с under hydrochloric acid catalysis resulted in a mixture of isomeric 4 and 6-hydroxyindoles 3а-d, 4a-c. in this case, the formation of major 6-hydroxyindole was observed. 4-hydroxyindole derivatives 4a-c were separated using column chromatography (ch2cl2:c6h14 1:1). 6-hydroxyindole derivatives were isolated by elution with a mixture of solvents сh2cl2:meoh 20:1 (scheme 3). the course of condensation of benzoins with aminophenol can be observed by the distilled water removed using a weak vacuum (60–70 mm hg) and a deanstark apparatus. chimica techno acta 2022, vol. 9(2), no. 202292s2 letter 3 of 4 scheme 2 synthesis of starting benzoins 2b-d. scheme 3 interaction of aminophenol 1 with benzoins 2a-c. the structure of products 3 and 4 is confirmed by the data of 1h and 13c nmr spectroscopy. for example, in the 1h nmr spectrum of compound 3c, the signal of phenolic hydroxyl is recorded in the region of 11.1 ppm, the signal of the nh-proton is at 9.1 ppm, the signals of the proton h-5 are recorded as a doublet of doublets with 1j(h-5,h-6) = 8.5 hz and 2j(h-5,h-7) = 2.2 hz. 4. conclusions thus, in the search for new potential medicinal agents, we have developed a convenient modified method for the synthesis of new 4and 6-hydroxyindoles in good yields. the advantages of the modified procedure are characterized by a lower reaction temperature (which does not reduce the reaction yields), the convenience of isolating pure 4and 6-hydroxyindoles, and a decrease in the formation of resinous by-products. supplementary materials no supplementary materials are available. funding the russian science foundation (no. 21-13-00382) financially supported this research, https://rscf.ru/en. acknowledgment none. author contributions conceptualization: a.d.s., i.a.k. data curation: a.d.s. formal analysis: o.n.c., r.f.f., i.a.k. funding acquisition: a.d.s., r.f.f. investigation: a.d.s., i.a.k. methodology: o.n.c., i.a.k., r.f.f. project administration: a.d.s. resources: r.f.f., i.a.k. software: a.d.s., i.a.k. supervision: a.d.s. validation: i.a.k., r.f.f. visualization: a.d.s. writing – original draft: a.d.s., i.a.k. writing – review & editing: o.n.c. conflict of interest the authors declare no conflict of interest. additional information author id’s: a.d. sharapov, scopus id 57201740165; r.f. fatykhov, scopus id 57190761230; i.a. khalymbadzha, scopus id 18434200300; o.n. chupakhin, scopus id 7006259116. institute’s website: https://hti.urfu.ru/en. https://rscf.ru/en https://www.scopus.com/authid/detail.uri?authorid=57201740165 https://www.scopus.com/authid/detail.uri?authorid=57190761230 https://www.scopus.com/authid/detail.uri?authorid=18434200300 https://www.scopus.com/authid/detail.uri?authorid=7006259116 https://hti.urfu.ru/en chimica techno acta 2022, vol. 9(2), no. 202292s2 letter 4 of 4 references 1. gunasekera sp, kashman y, cross ss, lui ms, pomponi sa, diaz mс. topsentin, bromotopsentin, and dihydrodeoxybromotopsentin: antiviral and antitumor bis(indoly1)imidazoles from caribbean deep-sea sponges of the family halichondriidae. structural and synthetic studies. j org chem. 1988;53(23):5446–5453. doi:10.1021/jo00258a009 2. sakemi s, sun hh. nortopsentins a, b, and c. cytotoxic and antifungal imidazolediylbis[indoles] from the sponge spongosorites ruetzleri. j org chem. 1991;56(13):4304–4307. doi:10.1021/jo00013a044 3. phife dw, ramos, ra, feng m, king i, gunasekera sp, wright a, patel m, 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article published by ural federal university 2022, vol. 9(2), no. 20229205 eissn 2411-1414; chimicatechnoacta.ru doi: 10.15826/chimtech.2022.9.2.05 1 of 5 synthesis and luminescent properties of new double ln2zr(wo4)5 (ln = tb, dy) tungstates bair bazarov a,b* , sesegma g. dorzhieva a , roman yu. shendrik c,d , yunna l. tushinova a,b , tsirendyzhit t. bazarova a , dmitriy o. sofich c , olga d. chimitova a , jibzema g. bazarova a a: baikal institute of nature management sb ras, ulan-ude 670047, russia b: department of inorganic and organic chemistry, buryat state university, ulan-ude 670000, russia c: a.p. vinogradov institute of geochemistry sb ras, irkutsk 664033, russia d: irkutsk state university, irkutsk 664033, russia * corresponding author: info@binm.ru; bazbg@rambler.ru this paper belongs to a regular issue. © 2021, the authors. this article is published open access under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). abstract new polycrystalline powder samples of double ln2zr(wo4)5 (ln = dy, tb) tungstates were synthesized using high-temperature solid-phase and sol-gel methods. the conditions of the sol-gel synthesis of tungstates were optimized. the obtained phases were characterized by the x-ray powder diffraction on the basis of the crystallographic data of similar ln–zr molybdates. it is found that ln2zr(wo4)5 (ln = dy, tb) double tungstates crystallize in the orthorhombic crystal system, space group cmc21 (z = 4). the intensive luminescence in the green spectral region for tb2zr(wo4)5 and yellow spectral region for dy2zr(wo4)5 was shown. keywords solid-phase synthesis sol-gel technique framework structure luminescence tungstates lanthanides received: 08.11.21 revised: 19.04.22 accepted: 26.04.22 available online: 03.05.22 1. introduction the search and synthesis of new compounds are associated with the study of multicomponent systems. in terms of the formation of promising compounds, molybdate and tungstate systems are of great interest [1–19]. complex oxide compounds containing ree and elements of the iv b subgroup (ti, zr, hf) are the objects of intensive research in connection with the search of new materials used as solid-state electrolytes, phosphors and matrices for immobilizing radioactive waste. previously, we studied interactions in the ternary oxide systems in the subsolidus region by the intersecting cuts method and established the formation of three types of compounds with following formulas: ln2zr3(moo4)9 (1:3) (ln = la–tb), ln2zr2(moo4)7 (1:2) (ln = sm–dy), ln2zr(moo4)5 (1:1) (ln = tb–lu) [20–22]. the crystal structures for the double molybdate representatives were also studied [23]. this work was devoted to synthesis and luminescent characteristics of double tungstates ln2zr(wo4)5 (ln = tb, dy) obtained by a solidphase synthesis and sol-gel methods. it was established that the tungstate phases are isostructural to the molybdenum analogues. 2. experimental new ln2zr(wo4)5 (ln = tb, dy) tungstates were obtained by the solid-phase reaction and sol-gel technique. for solid-phase synthesis, ln2o3 (99.9% purity), zro2 obtained by calcining zro(no3)22h2o (analytical grade), wo3 (analytical grade) were used as starting reagents. the initial oxides, preliminary calcined at t=200 °c, were thoroughly mixed in appropriate ratios. the samples were annealed in porcelain crucibles in air in a muffle furnace. the initial annealing temperature was 450 °c. the final synthesis temperature was varied in the range of 750–800 °c with 50 h dwell time. in the course of synthesis, the samples were repeatedly ground in an agate mortar in ethanol. the phases were identified by x-ray phase analysis using a d8 advance bruker diffractometer. also, double tungstates ln2zr(wo4)5 (ln = tb, dy) were synthesized by the pechini method, where ethylene glycol is completely replaced by water, there by reducing the amount of organic compounds. the second difference is the formation of an amorphous gel-like substance instead of a polymer. as a complexing agent, as in the pechini method, an aqueous solution of citric acid (c6h8o7h2o) was used. http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2022.9.2.05 https://orcid.org/0000-0003-1712-6964 http://orcid.org/0000-0003-2071-1152 https://orcid.org/0000-0001-6810-8649 https://orcid.org/0000-0003-1032-8854 https://orcid.org/0000-0001-9697-6320 https://orcid.org/0000-0002-2836-3597 http://orcid.org/0000-0002-9381-8922 https://orcid.org/0000-0002-1231-0116 mailto:info@binm.ru mailto:bazbg@rambler.ru http://creativecommons.org/licenses/by/4.0/ https://crossmark.crossref.org/dialog/?doi=https://doi.org/10.15826/chimtech.2022.9.2.05&domain=pdf&date_stamp=2022-5-3 chimica techno acta 2022, vol. 9(2), no. 20229205 article 2 of 5 the excitation and emission spectra in the uv-ir range were measured using a mdr-2 laboratory monochromator and a sdl-1 dual monochromator. the absorption spectra were obtained using a perkin-elmer lambda 950 uv/vis/nir spectrophotometer, operating in the range of 180–3000 nm with a maximum resolution of 0.2 nm. to measure the absorption spectra of powder samples to the device, a prefix was connected to the integrating sphere with a diameter of 150 mm. powder was poured into a quartz ampoule and was fixed in the holder of the integrating sphere. the absorption of the test glass was subtracted from the absorption spectra. 3. results and discussion ln2zr(wo4)5 (ln = tb, dy) double tungstates were obtained by ceramic and sol-gel methods. the conditions of the sol-gel technique for obtaining of ln2zr(wo4)5 (ln = tb, dy) were optimized. the synthesis scheme is shown in figure 1. figure 1 block diagram of the sol-gel technique for obtaining of ln2zr(wo4)5 (ln = tb, dy) tungstates. according to the x-ray powder diffraction data, all compounds synthesized by two methods are isostructural. crystallographic parameters of double tungstates was determined using the topaz 4.2 program according to data of isostructural high-temperature phase of er2zr(moo4)5 molybdate [24]. the results of refinement are shown in table 1. ln2zr(wo4)5 (ln = tb, dy) are crystallized in orthorhombic crystal system, space group cmc21 (z = 4). the shape and intensity of the spectral lines indicate low symmetry of rare-earth ions coordination, which is in good agreement with the crystallographic data of molybdates. as an example, figure 2 shows an x-ray diffraction pattern for tb2zr(wo4)5 obtained by the solid state reaction. table 1 the refinement parameters for ln2zr(wo4)5 (ln = tb, dy). the crystal structure of the studied tungstates can be represented by a three-dimensional mixed framework consisting of three polyhedra: wo4 tetrahedra, ln(2)/zro6 octahedra and eight vertex polyhedra ln(1)o8 connected to each other through common oxygen atoms (figure 3). ln and zr atoms are distributed with equal probability over equivalent crystallographic positions. 2th degrees 100908070605040302010 c o u n ts 12 500 12 000 11 500 11 000 10 500 10 000 9 500 9 000 8 500 8 000 7 500 7 000 6 500 6 000 5 500 5 000 4 500 4 000 3 500 3 000 2 500 2 000 1 500 1 000 500 0 -500 -1 000 structure 100.00 % figure 2 measured and calculated powder diffraction patterns for tb2zr(wo4)5 together with the difference curve (cu kα1 radiation). empirical formula tb2zr(wo4)5 dy2zr(wo4)5 formula weight, g/mol 1648.31 1655.46 crystal system orthorhombic space group cmc21 cell parameters, å a = 21.078(1) b = 9.6844(4) c = 9.8164(6) a = 21.177(1) b = 9.6737(7) c = 9.8176(8) cell volume, å3 2003.8(1) 2011.3(2) z 4 calc. density, g/sm3 4.061 4.047 rwp, % 2.88 6.75 rp, % 2.24 5.34 gof 1.80 1.21 chimica techno acta 2022, vol. 9(2), no. 20229205 article 3 of 5 figure 3 the structural model of ln2zr(wo4)5 (ln = tb, dy), viewed along the b axis. light-lilac tetrahedra are formed by w atoms, dark-grey octahedra by ln(2)/zr atoms and turquoise polyhedra by ln(1)atoms. in the excitation spectra of the investigated tungstates tb2zr(wo4)5, two types of bands are observed – narrow, corresponding to transitions inside 4f shells of ree (rare earth elements) and broad bands associated with charge transfer bands in complexes wo42– on ree. the luminescence and excitation spectra of tb2zr(wo4)5 in the band with an energy of 26500 cm–1 (λ = 377 nm) are shown in figure 4. the position of the bands associated with transitions inside the 4f shell remains almost unchanged in the molybdate and the tungstate. the vertical lines in figure 4 represent the energies of corresponding terms according to carnall [25]. figure 4 excitation (1) and luminescence (2) spectra of tb2zr(wo4)5 tungstate. since tb2zr(wo4)5 is isostructural to the corresponding molybdate analogue tb2zr(moo4)5 [26], all their spectra (luminescence, excitation) are similar. the luminescence spectra are characterized by the band with a highest intensity and maximum in the region of 18500 cm–1 (λ = 540 nm) associated with the 5d4–7f5 magnetic dipole transition. the luminescence band with a maximum at 20500 cm–1 (λ = 488 nm) refers to the electric dipole transition 5d4–7f6 in a tb3+ ion and depends on the symmetry of the crystal field; it is more intense than the other bands (except for 5d4–7f5) and splits into three types, which indicates a spatial distortion of the 8-vertex tbo8 polyhedra with a decrease in symmetry. the absorption spectra of dy2zr(wo4)5 (figure 5) exhibit a number of bands corresponding to transitions from the ground term of the 4f15/2 and 4fstate to higher energy terms. the position of the bands associated with transitions inside the 4f shell remains almost unchanged in the molybdate and in the tungstate. upon excitation by a laser with a wavelength of 404.5 nm, three emission bands with energies of 15100 cm–1, 17400 cm–1, and 20600 cm–1 are observed (figure 6, curve 2), associated with transitions inside the dy3+ ions. the most intense is the band with a maximum at 17400 cm–1, associated with the transition from the 4f9/2 term to the 6h13/2 term (yellow region of the spectrum), the luminescence band at 20600 cm–1 is associated with transitions from the 4f9/2 to 6h15/2 term (blue spectral region), and the 15100 cm–1 band is associated with the 4f9/2–6h11/2 transition (red spectral region). figure 5 absorption spectrum of dy2zr(wo4)5. figure 6 excitation (1) and emission (2) spectra of dy2zr(wo4)5. chimica techno acta 2022, vol. 9(2), no. 20229205 article 4 of 5 the 4f9/2–6h15/2 transition is magnetic-dipole and its intensity weakly depends on the crystal environment. the 4f9/2–6h13/2 transition is of the electric-dipole type. due to low symmetry, the 4f9/2–6h13/2 transition becomes partially allowed and its intensity is higher or comparable to the intensity of the 4f9/2–6h15/2 transition in crystals without an inversion center. if a rare-earth ion occupies a position with an inversion center and its environment is sufficiently symmetric, then the transition intensity is significantly lower than 4f9/2–6h15/2. thus, we can conclude that the environment of the rare-earth ion has rather low symmetry, which is confirmed by the structural analysis data. in the excitation spectrum of yellow luminescence (figure 6, curve 1), there is a number of bands associated with the transition from the 4h15/2 term to higher energy terms with subsequent relaxation and luminescence from the 4f9/2 level. the most intense excitation bands correspond to transitions to the 4f3/2, 4l19/2 terms; upon excitation to a group of levels with lower energies: 6p5/2, 4m19/2, 5f7/2, 4i13/2, luminescence with a lower intensity is observed. 4. conclusions new ln2zr(wo4)5 (ln = tb, dy) double tungstates were obtained by ceramic and sol-gel techniques. the conditions of the sol-gel synthesis of tungstates were optimized. their crystallographic and luminescent properties were determined. it was established that ln2zr(wo4)5 (ln= dy, tb) double tungstates are crystallized in orthorhombic crystal system, space group cmc21 (z = 4). the luminescence properties of tb3+, dy3+ ions in tungstate matrices were investigated. the observed spectral lines and bands of luminescence and excitation were identified. the structural features of the considered double tungstates suggest the possibility of their use as matrices for obtaining effective laser materials and promising phosphors. supplementary materials no supplementary materials are available. funding this research was carried out within the state assignment of baikal institute of nature management sb ras no. 0273-2021-0008. acknowledgment the equipment of the centre for collective use of baikal institute of nature management sb ras. author contributions conceptualization: j.g.b., b.g.b. data curation: b.g.b., j.g.b., s.g.d., r.yu.sh. formal analysis: s.g.d., d.o.s., yu.l.t., ts.t.b., o.d.ch. funding acquisition: j.g.b. investigation: s.g.d., d.o.s., r.yu.sh. methodology: s.g.d., d.o.s., r.yu.sh. project administration: b.g.b., j.g.b. resources: b.g.b., j.g. b., r.yu.sh. software: s.g.d., d.o.s., r.yu.sh. supervision: b.g. b., j.g.b. validation: s.g. d., d.o. s., r.yu.sh. visualization: s.g.d., d.o.s., r.yu.sh. writing – original draft: b.g.b., j.g.b. writing – review & editing: s.g.d., d.o.s. conflict of interest the authors declare no conflict of interest. additional information author id’s: b.g. bazarov, scopus id 7004745799; s.g. dorzhieva, scopus id 52663542700; r.yu. shendrik, scopus id 24402065800; yu.l. tushinova, scopus id 6507295454; ts.t. bazarova, scopus id 6603469765; d.o. sofich, scopus id 57202072039; o.d. chimitova, scopus id 14059854100; j.g. bazarova, scopus id 6701747363. institute websites: baikal institute of nature management sb ras, https://www.binm.ru/en; buryat state university, https://en.bsu.ru; a.p. vinogradov institute of geochemistry sb ras, http://www.igc.irk.ru/en; irkutsk state university, https://isu.ru/en. references 1. sorokin ni. ionic conductivity of kmgcr(moo4)3 molybdate. crystallogr rep. 2017; 62:416–418. doi:10.1134/s106377451703021x 2. pavlova jet, tsyrenova g.d, lazorjak bi, solodovnikov sf. the structure and properties of double silver-containing molybdates of the composition ag2a2(moo4)3 (a = mg, mn, cu). vestn buryats gos univ khim fiz. 2015;3:3–7. russian. 3. savina aa, solodovnikov sf, belov da, basovich om, solodovnikova za, pokholok kv, stefanovich syu, lazoryak bi, khaikina eg. synthesis, crystal structure and properties of alluaudite-like triple molybdate na25cs8fe5(moo4)24. j solid state chem. 2014;220:217–220. doi:10.1016/j.jssc.2014.09.004 4. jena p, nallamuthua n, patro pk, venkateswarlu m, satyanarayana n. structural characterization and electrical conductivity studies of bamoo4 nanorods prepared by modified acrylamide assisted sol–gel process. adv appl ceram. 2014;113(6):372–379. doi:10.1179/1743676114y.0000000170 5. balsanova lv. synthesis of crystals of silver-containing 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https://doi.org/10.1016/j.jlumin.2010.02.052 https://doi.org/10.1016/j.materresbull.2017.09.053 https://doi.org/10.1016/j.jlumin.2019.03.052 https://doi.org/10.1016/j.jssc.2019.121143 https://doi.org/10.15826/chimtech/2017.4.4.03 https://doi.org/10.1007/s10973-013-3579-0 https://doi.org/10.1007/s10947-005-0091-9 https://doi.org/10.1007/s11172-017-1777-9 https://doi.org/10.1007/bf02741593 https://doi.org/10.1007/s10947-009-0086-z https://doi.org/10.1016/j.jallcom.2017.01.173 https://doi.org/10.1063/1.1669893 https://doi.org/10.17308/kcmf.2020.22/2831 carbon coated nickel nanoparticles in polyacrylamide ferrogels: interaction with polymeric network and impact on swelling 116 d o i: 1 0. 15 82 6/ ch im te ch .2 02 0. 7. 3. 04 e. a. mikhnevich, a. p. safronov, i. v. beketov, a. i. medvedev chimica techno acta. 2020. vol. 7, no. 3. p. 116–127. issn 2409–5613 e. a. mikhnevich,a* a. p. safronov,ab i. v. beketov,ab a. i. medvedevab a ural federal university, 620002, 19 mira st., ekaterinburg, russia b institute of electrophysics ub ras, 620016, 106 amundsen st., ekaterinburg, russia *email: emikhnevich93@gmail.com carbon coated nickel nanoparticles  in polyacrylamide ferrogels: interaction with polymeric network and impact on swelling polyacrylamide ferrogels with embedded magnetic nanoparticles of metallic nickel (ni) and nanoparticles of nickel coated with a carbon shell (ni@c) were synthesized by radical polymerization in water. the effect of the carbon shell on the interaction of ni and ni@c nanoparticles with polyacrylamide matrix and on swelling ratio of the ferrogels has been studied. the deposition of carbon on the surface of ni nanoparticles worsens their interaction with polyacrylamide but at the same time elevates the water uptake by ferrogels. keywords: nanoparticles; nickel; composites; ferrogels; polyacrylamide; carbon coatings. received: 26.08.2020. accepted: 06.10.2020. published: 07.10.2020. © e. a. mikhnevich, a. p. safronov, i. v. beketov, a. i. medvedev, 2020 1. introduction a hydrogel is a three-dimensional polymeric network swollen in water. the internal structure of a hydrogel includes flexible polymeric sub-chains, which are crosslinked in a certain number of points. due to the internal cross-linking the polymeric network of  a  hydrogel might be considered as a combined huge molecule. from the thermodynamic point of view hydrogel is a solution of this molecule in water. despite the fact that it contains large amount of water, hydrogel is not a fluid but an elastic material maintaining its shape. due to their unique properties such as mechanical elasticity, softness, and biocompatibility, hydrogels have been applied in a variety of fields, including smart devices that respond to stimuli and soft actuators in biomedicine and agriculture [1, 2]. hydrogels are often functionalized by  incorporating various physically, chemically, and biologically active moieties, which endows hydrogels with new functions, such as response to specific external stimuli and increased mechanical stability [3]. stimulus-responsive hydrogels can markedly change their physical and/or chemical properties when exposed to external triggers (ph, temperature, light, magnetic or electric field) [4]. for instance, the  inclusion of  magnetic nanoparticles (mnps) in such a polymer network gives magnetic hydrogels (ferrogels) that react to  an  external magnetic field [5]. ferro117 gels are usually obtained by crosslinking hydrophilic monomers in a stabilized aqueous dispersion of magnetic nanoparticles (ferrofluid), which, in turn, provides good dispersion of nanoparticles in a polymer matrix. one of the main advantages of ferrogels over traditional stimulus-responsive polymers is that they can be remotely activated by a non-contact force (magnetic field). this unique property makes ferrogels prospective advanced material in various fields such as drug delivery [6, 7], soft robotics [8], tissue reconstruction [9, 10] and environmental engineering [11, 12]. huang et al. [9] reported about a hydrogel formed by gelatin and β-cyclodextrin with embedded magnetic fe3o4 nanoparticles for pulsed electromagnetic field therapy. chondrogenesis of mesenchymal stem cells grown on a magnetic hydrogel was enhanced by a magnetic field. czichy et al. [13] investigated the  mechanical properties of alginate-methylcellulose hydrogels containing magnetite nanoparticles for the use in the additive manufacturing of implants. the study was an introduction to further research on the effect of an external magnetic field on the  mechanical stability of composites. the most extensive study on ferrogels was carried out by zrinyi et al. [14–16] on magnetic silicone elastomers filled with carbonyl iron or micronsized magnetite. the modulus of elasticity of these magnetoelastic gels was studied in both uniform and inhomogeneous magnetic fields. the influence of the content of magnetic particles and their distribution at various combinations of magnetic field orientation and deformation on the modulus has been systematically studied. meanwhile, studies of synthetic water-based ferrogels are very limited. in the literature most of the studies address ferrogels based on polyacrylamide (paam) chemically cross-linked polymeric network. thus, the series of works were performed by  the  group of  galicia et al [17–19] on ferrogels with embedded maghemite nanoparticles. maghemite nanoparticles were synthesized using ferrofluid obtained by co-precipitation of iron oxides from fe2+/fe3+ mixed solutions. ferrogels had weakly cross-linked polymeric network with monomer-to-cross-linker ratio 1000 and more and contained up to 7% (vol.) of nanoparticles. the structure of ferrogels in the swollen state and the mechanical properties were studied. it was shown that the young modulus of ferrogels enlarged from 4 to 16 kpa with the increase in nanoparticles content. in our previous works [20–22] we have studied paam ferrogels with embedded iron and nickel nanoparticles, which were synthesized by the high-power pulsed physical dispersion by the electrical explosion of  metal wire (eew) [23]. the  magnetostriction in the uniform magnetic field and the compression modulus of ferrogels were characterized. it was shown that ferrogels with iron nanoparticles contract by approximately 9% (vol) in the uniform magnetic field 420 mt applied for 4 hours. shear modulus of ferrogels with embedded iron nanoparticles increased from 0.5 to 2.5 kpa with the elevation of nanoparticles content up to 4% (vol.) [21]. in paam ferrogels with nickel nanoparticles it was shown [22] that the elastic modulus of ferrogels linearly depended on the content of the embedded nickel nanoparticles. the applied magnetic field 270 oe in the parallel direction to the compression increased the elastic modulus by 10% while the application of the magnetic field in the transverse direction decreased the modulus. although ferrogels with embedded metal nanoparticles show a potential for 118 their use as a smart material in soft sensors and actuators their application in bioengineering and medicine is  doubtful due to the toxicity of metallic iron and nickel. to overcome this shortcoming the surface of  metallic particles should be covered with a biocompatible layer, which prevents the contact of an open metallic surface with biological liquids. it our earlier report [24] it was shown that the  surface of  nickel nanoparticles produced via eew can be modified by the in-situ carbon deposition. such a deposition is provided by adding volatile hydrocarbons to the working gas of eew unit. in the process of the electrical explosion hydrocarbon molecules decompose to elements and carbon deposits on the surface of condensing metal nanoparticles. the modification of the surface of nickel nanoparticles opens a question on how would it influence the properties of ferrogels with embedded metal nanoparticles. in  the  present study we aimed to  clarify two aspects of this possible influence. first, we will focus on the interfacial interaction between polyacrylamide and modified nickel nanoparticles. second, we will address the influence of the carbon deposition on the volume swelling of ferrogels, which is a basic property for their performance in sensors and actuators. 2. experimental part 2.1. synthesis of mnps, composites, and ferrogels nickel magnetic nanoparticles (ni mnps) were synthesized by  the  electrical explosion of wire (eew). the essence of eew is the evaporation of a metal wire by  a  high-voltage electrical discharge in  an  inert atmosphere of  argon and the subsequent condensation of metal vapors into spherical nanoparticles. nickel nanoparticles coated with a carbon shell (ni@c mnps) were synthesized using a mixture of argon with the addition of butane as a working gas of eew unit. carbon content in the ni@c was 2% (wt.). the thickness of the carbon shell was 4–6 nm. the carbon was in an amorphous state. the details of the synthetic procedure can be found in our previous reports [25]. the mnps composites for microcalorimetry studies were prepared in the entire range of  weight fraction of  mnps. linear polyacrylamide (paam) was synthesized by  free radical polymerization in  1.6 m water solution. hydrogen peroxide in 18 mm concentration was an initiator of the reaction. polymerization was done at two steps: first at 60 °c for 30 min, second at  100 °c for 60 min. molecular weight of linear paam was 7.3∙105 as determined by viscometry of water solution at 25 °c. the stock solution of paam was then vigorously stirred with weighted amounts of ni and ni@c mnps in proportions to get resulted composites with certain mnps/paam ratio. the suspension of mnps in paam solution was homogenized by ultra-sound treatment and then cast upon teflon plate and dried to the constant weight at 70 oc. the obtained films of np/paam composites were then used for the  microcalorimetry measurements of the enthalpy of dissolution in distilled water. ferrogels were synthesized by radical polymerization of acrylamide (aa) (panreac quimica sa) of in 1.6 m water solution. methylene diacrylamide (mdaa) (merck) was a cross-linker in a molar ratio to monomer of 1:100. ammonium persulfate (aps) was used as the initiator of the polymerization. magnetic ni/ni@c 119 nanoparticles were added to the reaction mixture in portions of a weighed 20% water-based suspension stabilized with dispex a40 dispersant (r. t. vanderbilt). the suspension was homogenized in an ultrasonic bath for 20 minutes. polymerization was carried out for 60 minutes at 80 °c. synthesized ferrogels were washed in distilled water for two weeks with daily water renewal to  remove residual impurities. the equilibrium swelling ratio (maximum water uptake) was determined as the ratio of the water content in the gel to the weight of the dry gel by weighing the swollen sample of the gel and the dry residue after drying to a constant weight at 70 °c. 2.2. methods transmission electron microscopy (tem) was performed using a  jeol jem2100 microscope operated at 200 kv. the  specific surface area of  mnps was measured via low temperature adsorption of nitrogen (brunauer-emmett-teller approach) using a micromeritics tristar3000 analyzer. phase composition of mnps was examined using an x-ray diffractometer bruker d8 discover operated at  cu ka radiation (wavelength l = 1.5418 a) with a graphite monochromator and a scintillation detector. xrd results were processed using the built-in bruker software topas-3 provided the rietveld full-profile refinement. magnetic hysteresis loops were measured using a vibrating sample magnetometer (cryogenics). calorimetric measurements were done at 25 °c using a  calvet differential microcalorimeter of laboratory design. the sensitivity was 31.5 mv/w, cell volume was 10 cm3. the  stability of  a  baseline was ±0.5 mv. enthalpies of  dissolution of  paam/ni, paam/ni@c, and paam/c composites in  water were measured using glass ampoule cells. water was placed in a stainless steel cell and small portion of a composite film (approximately 10–30 mg by weight) was put into a thin-walled glass ampoule. this specimen was dried to  a  constant weight in vacuum and then the ampoule was sealed. a sealed ampoule was placed in the cell with water in it. after thermal equilibration until the baseline of calorimeter kept at a constant level the ampoule was broken inside the  cell and the  heat effect of  the  dissolution of  a  composite in water was measured. the absolute values of measured heat effects of dissolution were from 0.5 to 2 joule depended on the composition of a composite. the absolute error of calorimetric measurements was 0.05 joule. 3. results and discussion 3.1. characterization of ni and ni@c mnps fig. 1 shows the transmission electron microscopy (tem) images of ni and ni@c mnps. both batches of  mnps contain individual spherical particles. a  typical diameter of spherical ni mnps (fig. 1a) lay within 10–100 nm range. deposited thin carbon layers are clearly observed on the  surface of  ni@c nanoparticles (fig. 1b). the average diameter of mnps was estimated based on the value of the specific surface area of  mnps, which was determined by  low-temperature nitrogen adsorption. the specific surface area of ni and ni@c mnps obtained from the isotherms of nitrogen adsorption by the brunaueremmett-teller (bet) treatment were equal to 12.6 and 10.8 m2/g respectively. straightforward geometrical consideration of the surface of a sphere related to its 120 mass gives the following simple equation for the diameter (d) of the sphere in relation to its surface (s) and the density (r) of its material: 6 d s = r (1) if applied to  the  specific surface area of the mnps in air-dry powder equation (1) gives the average value of the diameter for the ensemble of mnps. if s is in m2/g and r is in g/cm3 equation (1) yields the average diameter in micron. calculated values for ni and ni@c mnps are presented in table 1. the average diameters are close to each other. the average diameter of ni@c nanoparticles is little higher than that for ni nanoparticles. it is consistent with the  presence of  a  deposited carbon layer on the surface of ni@c nanoparticles. the phase composition of ni and ni@c mnps was characterized by x-ray diffraction (xrd). according to x-ray powder diffraction data (fig. 2), the ni sample contained 100% α-ni phase with a cubic facecentered lattice; the  unit cell parameter а = 0.3523(2) nm. xrd pattern for ni@c mnps also revealed 100% α-ni phase with fig. 1. tem images of ni (a) and ni@c (b) mnps. table 1 characteristics of magnetic fillers mnps density, g/cm3 shape ssp, m 2/g dav, nm *ms, ka/m **hc, ka/m ni 8.9 spherical 12.6 58 454 20.7 ni@c 8.9 spherical 10.8 62 339 7.7 * — saturation magnetization; ** — coercive force fig. 2. xrd pattern of ni mnps 121 the unit cell parameter а = 0.3533(3) nm. carbon layer was not detected in xrd pattern for ni@c because the deposited layer was too thin and its content (2%) was below the sensitivity of xrd. fig. 3. shows magnetic hysteresis loops for ni and ni@c mnps. in  both cases magnetization reached saturation in high field range. the  parameters of  magnetic hysteresis loops — saturation magnetization and coercive force are given in table 2. according to  these data, ni and ni@c powders were soft magnetic materials with low coercive force. saturation magnetization of  ni@c nanoparticles was by  approximately 25% lower than saturation magnetization of ni mnps. it was likely due to the distortions of the crystalline lattice in the surface layer of ni@c particles under the influence of deposited carbon, which could happen because of limited dissolution of carbon in the lattice. the  structural characterization of  ni and ni@c mnps showed that these nanoparticles are very much alike despite the existence of the deposited carbon layer on the surface of ni@c mnps. meanwhile, this factor was of decisive importance for the  interfacial properties of  polymeric composites with ni and ni@c mnps. 3.2. interfacial adhesion of  paam to mnps the  basic thermodynamic property, which stands for the interaction of a polymeric chain of composite with an embedded solid particle, is the enthalpy of interfacial adhesion. the latter is the enthalpy change during the adsorption of a macromolecule on a solid surface. this process establishes adhesive contacts at the interface between a macromolecule and a particle due to molecular interactions. such enthalpy change cannot be measured directly in  calorimetric experiment as  ni, ni@c, and paam are solids. the enthalpy of interfacial adhesion was determined using an appropriate thermochemical cycle (hess cycle), which included quantities measurable in calorimeter. in case of polymeric composites with embedded solid particles the enthalpy of interfacial adhesion is equal to the enthalpy of composite mixing. since the solid particles have not dissolved in a polymeric matrix, the only source of enthalpy change is the interface interaction. the hess cycle for the enthalpy of mixing of paam/ni (or paam/ni@c) composite constitutes the  combination of the following processes. 1)  paam + ni mnps = composite paam/ni + dhadh 2) paam + water (excess) = paam solution + dhdis,p 3)  ni mnps + water (excess) = ni mnps suspension + dhwet 4) paam solution + ni mnps suspension = ni mnps suspension in paam solution + dhmix 5) composite paam/ni + water (excess) = ni mnps suspension in  paam solution + dhdis,c fig. 3. magnetic hysteresis loops for ni and ni@c mnps. inset — hysteresis loop in low field range for ni mnps 122 the combination of these steps gives for the enthalpy of adhesion: dhadh = wpaamdhdis,p + wnidhwet + + dhmix – dhdis,c (2) in  equation (2) wpaam and wni are weight fractions of paam and ni in a composite; dhdis,p is the enthalpy of dissolution of paam in water; dhwet is the enthalpy of  wetting of  air-dry ni mnps in  water; dhmix is the enthalpy of mixing of paam water solution with ni mnps water suspension; dhdis,c is the enthalpy of dissolution in water for a composite with wpaam and wni composition. fig. 4 (a) shows dependencies of the enthalpy of  dissolution in  water versus the  weight content of  embedded particles for paam composites. together with paam/ni and paam/ni@c composites we also took as  a  reference paam/carbon composite which was prepared using commercial sample of  carbon black with specific surface area 124 m2/g. the  value at  the  left-hand vertical axis corresponds to  the  enthalpy of  dissolution of  paam in  water, which is dhdis,p. the  value at  the  right-hand axis corresponds to the enthalpy of wetting of airdry particles, which is dhwet. the symbols at the field of the plot corresponds to dhdis,c values for the composites with certain fractions of paam and a filler. one can notice that the  dependence of dhdis,c for paam/ni composites is convex upward, while the  dependencies of dhdis,c for paam/ni@c and paam/ carbon are concave downwards. the data presented in fig. 4 (a) were used to calculate the  enthalpy of  interfacial adhesion in  composites dhadh using equation (2). it is worth noting that the values of dhmix (step (4) of  the  hess cycle) typically can be neglected as they lay within the experimental error of the other quantities of hess cycle. the dependence of the enthalpy of interfacial adhesion versus the content of solid particles in paam composites is shown in fig. 4 (b). there is a substantial difference between dependencies of the enthalpy of adhesion for paam/ni and paam/ ni@c composites. in  case of  paam/ni composite the enthalpy of adhesion is negative over the entire composition range. it fig. 4. a) — concentration dependence of the enthalpy of dissolution of paam composites with embedded ni, ni@c, and c particles; b) — concentration dependence of the enthalpy of interfacial adhesion in paam composites with embedded ni, ni@c, and c particles 123 means that the adhesion contact between paam chain and the surface of ni mnp is energetically favorable. such interaction promotes adsorption of paam chains on the surface of ni mnps. on the  contrary, in  case of  paam/ ni@c composite the  enthalpy of  adhesion is positive over the entire composition range. it means that paam chains do not interact with the surface of ni@c mnps. no doubts that such interaction is energetically unfavorable the deposited carbon layer on the surface of mnps. the results for the  reference system paam/carbon clearly confirm this fact. in the paam/carbon composites the enthalpy of adhesion is also positive over the entire composition range similar to the case of paam/ni@c composites. thus, the  obtained thermochemical data showed that the  deposition of  carbon on the surface of ni mnps worsened the adhesion of paam chains to modified ni mnps. 3.3. swelling of paam ferrogels with ni and ni@c fig. 5 (a) shows the  dependence of the relative degree of swelling of paam/ ni and paam/ni@c ferrogels versus the weight fraction of mnps in ferrogel. the relative degree of swelling is the swelling ratio (water uptake) of a ferrogel divided by the swelling ratio of a blank paam gel with the same composition. the data presented in  fig. 7 (a) refer to  gels with a network density of 100 monomer units in linear sub-chains per one cross-link. it is worth noting that the relative swelling decreases with mnps content in the case of ferrogels with ni mnps, and it increases in the case of ferrogels with ni@c mnps. the same trend is shown in fig. 5 (b), which presents the  swelling ratio of  ferrogels with different network density containing the 3.1% (wt.) of mnps. both in the case of ferrogels with ni mnps and in the case of ferrogels with ni@c mnps the swelling ratio increases if the network density of  a  gel decreases. it is  a  general trend in  gels. if a  number of  monomer fig. 5. a) — dependence of the relative degree of swelling of paam ferrogels with ni and ni@c mnps with respect to the unfilled gel matrix (monomer to cross-link ratio 100:1); b) — dependence of the swelling ratio of paam ferrogels with ni and ni@c mnps on the length of the linear sub-chains between the crosslinks (mnps content 3.1%) 124 units in  linear sub-chains enlarge and the number of cross-links diminishes, then the network loosens and it can absorb more water. thus the water uptake of a gel increases. although the basic trend in the dependence of the swelling ratio on the network density is  the  same for both types of ferrogels, there is s remarkable difference in the absolute values of the swelling ratio. it is much higher in the case of ni@c ferrogels. in ferrogels with the lowest network density (300 monomer units per one crosslink) the swelling ratio of paam ferrogel with embedded 3% ni@c mnps is  four times larger than that for the ferrogel with the same composition but with embedded ni mnps. the  reason for such a  difference in  swelling of  ferrogels with embedded ni or ni@c mnps apparently stems from the  different adhesion of  paam chains to the surface of particles. paam ferrogels differ from paam composites, because ferrogels contain water besides polymer and mnps. nevertheless, interaction between paam chains and the  surface of  mnps governs the  swelling of  ferrogel. if interaction between polymeric chains and mnps is strong, then the paam sub-chains in the network are adsorbing on the surface of the particles. adsorption of chains effectively increases the networking density and diminishes the water uptake of the gel matrix. it is the case of paam ferrogel with enbedded ni mnps. in turn, if paam chains do not interact with the surface of mnps, then the mnps will effectively repel the  sub-chains of the networks. it will increase the mobility of the network, and it will promote extra swelling of ferrogel. it is the case of paam ferrogel with embedded ni@c mnps. 4. conclusions metallic magnetic nanoparticles (mnps) are prospective for the  use in smart soft materials suitable for bioengineering and medical applications. however, to provide biocompatibility they need to be coated with protective layers. deposited carbon coating is among them. meanwhile, deposition of carbon affects functional properties of mnps and materials, in which they are embedded. in the present study the interfacial interaction of carbon coated ni mnps (ni@c) with polyacrylamide (paam) has been studied in comparison with ni mnps focusing on application in paam ferrogels. the interfacial adhesion of paam chains to the surface of mnps was studied by means of thermochemical cycle based on calorimetric measurements of  the  enthalpy of  dissolution of paam/ni and paam/ni@c composites in water, and the enthalpy of adhesion to  the  surface of  mnps was determined in  the  entire range of  mnps content in the composite. it turned out that while interaction of ni mnps with paam was energetically favorable and led to the evolution of heat (negative enthalpy change) during adhesion, deposited carbon layer provided poor interaction of paam with the surface of ni@c mnps. the enthalpy of interaction between paam and ni@c mnps was positive over the entire range of mnps content. it means that paam do not interact with the surface coated with carbon layer. it provided a  marked impact on the swelling ratio (water uptake) of paam ferrogels with embedded ni@c mnps in comparison with ferrogels with embedded ni mnps. the  swelling ratio of  paam gel matrix diminished with the embedding of ni mnps due to the adsorption of paam sub-chains on the sur125 face of mnps. on the contrary, the embedding of ni@c mnps in paam gel matrix resulted in the increase of its swelling ratio owing to the effective repelling of paam chains by the carbon layer on the surface of mnps. it means that poor interaction at  the  interface not necessarily worsens the functional properties of soft biocompatible materials. the increase of the swelling ratio might be an  advantageous feature in  certain applications of  ferrogels in  biocompatible sensors and actuators. in a whole, obtained results showed that coating of the surface of mnps not only provides biocompatibility of  mnps but might as well be a versatile tool to modify the functional properties of smart materials based on nanoparticles. acknowledgements the study was financially supported by rfbr, project number 19-38-90229. references 1. abasi s, 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and herbicides in aqueous media by using pyrene-based fluorescent chemosensors chimica techno acta letter published by ural federal university 2021, vol. 8(2), № 20218208 eissn 2411-1414; chimicatechnoacta.ru doi: 10.15826/chimtech.2021.8.2.08 1 of 3 detection of anti-viral drug riamilovir and herbicides in aqueous media by using pyrene-based fluorescent chemosensors i.s. kovalev a , l.k. sadieva a,b,* , o.s. taniya a,b , d.s. kopchuk a,b , g.v. zyryanov a,b , e.n. ulomsky a,b , v.l. rusinov a,b , o.n. chupakhin a,b a: ural federal university, 19 mira st., yekaterinburg 620002, russia b: postovsky institute of organic synthesis, ural branch of the russian academy of sciences, 22 s. kovalevskoi / 20 akademicheskaya st., yekaterinburg 620219, russia * corresponding author: leilasad@yandex.ru this short communication (letter) belongs to the regular issue. © 2021, the authors. this article is published in open access form under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). abstract two ethyleneglycol esters of 1-pyrene carboxylic acid were studied as chemosensors for the fluorescence “turn-off” detection of two nitro-containing analytes, such as antiviral drug riamilovir (triazavirin ®) and herbicidal agent dinitro-ortho-cresol (dnoc). in both cases the dramatic fluorescence quenching was observed with quenching constants as high as 3·10 4 m -1 and limits of detection (lod) as low as 100 ppb. keywords covid-19 riamilovir (triazavirin ®) dnoc detection in aqueous media chemical sensors pyrene-based fluorophores fluorescence quenching received: 19.04.2021 revised: 30.04.2021 accepted: 18.05.2021 available online: 20.05.2021 1. introduction one of the scourges of modern civilization is the coronavirus (sars-cov-2) pandemic that broke out in the end of the 2019. despite the fact that the antiviral drug riamilovir (triazavirin ®) is not a specific drug against sarscov-2, it has successfully shown itself among other drugs in reducing the incidence of respiratory, cardiac, hepatic, renal and other complications, associated with coronavirus infection (covid-19) [1,2]. for the pharmacokinetic studies of this drug as well as other ones, it is very important to determine the fate of these substances, administered to a living organism. once drugs are administered their concentration in target organs or biological liquids is changed. fluorescence-based methods are the robust and convenient methods of measuring drug concentration in the biological (water-based) liquids and target organs [3,4]. in addition to coronavirus infection, the problem of soil, air and rain pollution with herbicides and their decay products, has long been an acute problem [5]. despite the fact that at present in europe and the united states the use of such herbicide as dinitro-ortho-cresol (dnoc) is abandoned, accumulated over the years of previous use, it is still present [5,6]. dnoc has been identified in at least 56 of the 1854 hazardous waste sites that have been proposed for inclusion on the epa national priorities list (npl) [6]. it is also still widely used in russia and other countries. in this manuscript we would like to report our study of sensory abilities of the pyrene-based polyethyleneglycol water-soluble fluorescent “turn-off” chemosensors toward nitro-containing drug riamilovir and herbicide dnoc. 2. experimental chemosensors 1-2 (see fig. 1) were obtained as reported earlier [7]. starting materials are commercially available. fluorescence titration experiments were carried out by using the horiba-fluoromax-4 spectrofluorometer (usa). solutions of sensors 1-2 with concentration 10 -6 m in h2o : thf (99.9 : 0.1 (v/v)) and solutions of quenchers with concentration 10 -4 m in water (riamilovir) and in acetonitrile (dnoc) were prepared. next, fluorescence quenching http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2021.8.2.08 http://creativecommons.org/licenses/by/4.0/ chimica techno acta 2021, vol. 8(2), № 20218208 letter 2 of 3 fig.1 structure of chemosensors 1-2 was carried out via the method of single point [8]. the solution of sensor by volume of 3 ml was placed in quartz cuvette and intensity of its fluorescence was measured. after that 15 aliquots of solution of quencher (volume of each aliquot was 10 mkl) were added into cuvette one by one. after each addition of quencher, fluorescence intensity was measured. analysis of fluorescence quenching was performed on the basis of a stern-volmer equation of static quenching (1): 𝐼0 𝐼 = 1 + 𝐾sv [q] . (1) the stern-volmer constants (ksv) were calculated as the slope of the intensity plot (((𝐼0/𝐼) − 1)) versus the concentration of the quencher ([q]). 3. results and discussion as water soluble chemosensors, two pyrene-based chemosensors 1-2 (fig. 1) were selected, and their synthesis and photophysical properties were reported earlier [7]. based on these previous studies, chemosensors 1-2 have exhibited high sensitivity toward some common nitroexplosives, such as 2,4,6-trinitrotoluene (tnt) and pentaerythritol tetranitrate (petn) in aqueous media. so, we expected that these molecules will be suitable candidates for the detection of nitro-containing riamilovir and dnoc. to study sensory abilities of sensors 1-2 towards the abovementioned nitro-analytes, fluorescence quenching titration was carried out. the fluorescence response was quantitatively determined via the stern-volmer static quenching model, according to eq. (1). the stern-volmer constant values for riamilovir were calculated to be as high as ksv = 2.67·10 4 m -1 and 2.28·10 4 m -1 for the sensors 1 and 2, respectively, and, based on the linearity of the stern-volmer plots, the static quenching (table 1, fig. 2a,b) was suggested. fig. 2 stern-volmer plots of emission quenching for sensors 1 (a, c) and 2 (b, d): points – experimental data, lines – linear fitting results chimica techno acta 2021, vol. 8(2), № 20218208 letter 3 of 3 table 1 summary of the stern-volmer rate constants and lod for the chemosensors 1-2 sensor ksv riamil. , m -1 ksv dnoc , m -1 lod riamil. , ppb lod dnoc , ppb 1 2.67·10 4 3.07·10 4 101 122 2 2.28·10 4 3.14·10 4 252 223 under similar conditions, dnoc caused a slightly stronger response, which can be seen based on higher values of stern-volmer constants, such as ksv = 3.07·10 4 m -1 (for the sensor 1) and ksv = 3.14·10 4 m -1 (for the sensor 2) (table 1). again, linearity of stern-volmer plots was observed. in addition to linear behavior of stern-volmer plots, high values of the coefficient of determination (r 2 ) were obtained (fig. 2). thus, the prevalence of only one quenching mechanism, such as static quenching, in all the cases was suggested. for all titration experiments, limits of detection (lod) were calculated by using previously reported methods [9]. lod values are collected in table 1. 4. conclusions ethyleneglycol esters of 1-pyrene carboxylic acid were found to be promising chemosensors for the fluorescence “turn-off” detection of nitro-containing drugs, such as riamilovir, and ecotoxicants, such as dinitro-ortho-cresol, in aqueous solutions. in all the cases, dramatic fluorescence quenching and high quenching constants (2.28·10 4 – 3.14·10 4 m -1 ) were observed. acknowledgements this work was supported by the russian foundation for basic research (project № 19-33-90155). references 1. wu x, yu k, wang y, xu w, ma h, hou y, et al. efficacy and safety of triazavirin therapy for coronavirus disease 2019: a pilot randomized controlled trial. engineering. 2020;6(10):1185–91. doi:10.1016/j.eng.2020.08.011 2. sabitov au, belousov vv, edin as, oleinichenko ev, gladunova ep, tikhonova ep, et al. practical experience of using riamilovir in treatment of patients with moderate covid-19. antibiotiki i khimioterapiya. 2020;65(7–8):27–30. russian. doi:10.37489/0235-2990-2020-65-7-8-27-30 3. ayoob am, peppi m, tandon v, langer r, borenstein jt. a fluorescence-based imaging approach to pharmacokinetic analysis of intracochlear drug delivery. hear res. 2018;368:41–8. doi:10.1016/j.heares.2018.03.026 4. kuneš m, květina j, maláková j, bureš j, kopáčová m, rejchrt s. pharmacokinetics and organ distribution of fluorescein in experimental pigs: an input study for confocal laser endomicroscopy of the gastrointestinal tract. neuroendocrinol lett [internet]. 2010;31(suppl. 2):57–61. available from: https://www.nel.edu/userfiles/articlesnew/nel31s210a09.p df 5. lyle k. environmental health criteria 220 dinitro-orthocresol [internet]. 2000. available from: https://www.who.int/ipcs/publications/ehc/en/ehc220.pdf 6. toxicological profile for dinitrocresols. atsdr’s toxicological profiles [internet]. 2018. available from: https://www.atsdr.cdc.gov/toxprofiles/tp63.pdf 7. sadieva lk, taniya os, kovalev is, kopchuk ds, zyryanov gv, rusinov vl, et al. polietilenglikolevyye efiry piren-1karbonovoy kisloty: sintez i fotofizicheskiye issledovaniya [polyethylene glycol esters of 1-pyrenecarboxylic acid: synthesis and photophysical studies]. izv acad nauk. 2021;4. forthcoming 2021. 8. das-6 operation manual [internet]. horiba scientific; 117 p. available from: https://www.horiba.com/fileadmin/uploads/scientific/down loads/userarea/fluorescence/manuals/das67_manual.pdf 9. shrivastava a, gupta v. methods for the determination of limit of detection and limit of quantitation of the analytical methods. chronicles young sci. 2011;2(1):21. doi:10.4103/2229-5186.79345 https://doi.org/10.1016/j.eng.2020.08.011 https://doi.org/10.37489/0235-2990-2020-65-7-8-27-30 https://doi.org/10.1016/j.heares.2018.03.026 https://www.nel.edu/userfiles/articlesnew/nel31s210a09.pdf https://www.nel.edu/userfiles/articlesnew/nel31s210a09.pdf https://www.who.int/ipcs/publications/ehc/en/ehc220.pdf https://www.atsdr.cdc.gov/toxprofiles/tp63.pdf https://www.horiba.com/fileadmin/uploads/scientific/downloads/userarea/fluorescence/manuals/das67_manual.pdf https://www.horiba.com/fileadmin/uploads/scientific/downloads/userarea/fluorescence/manuals/das67_manual.pdf https://doi.org/10.4103/2229-5186.79345 determination of optimal parameters technological process of polling of copper wire with alloy pos-61 chimica techno acta letter published by ural federal university 2022, vol. 9(2), no. 202292s7 eissn 2411-1414; chimicatechnoacta.ru doi: 10.15826/chimtech.2022.9.2.s7 1 of 3 determination of optimal parameters for the technological process of polling of copper wire with alloy pos-61 v.v. aleksandrova * , m.v. kuzmin , a.o. patianova , v.l. semenov , r.i. alexandrov chuvash state university named after i. n. ulyanov, cheboksary 428015, russia * corresponding author: valek_1996@mail.ru this paper belongs to the mosm2021 special issue. © 2021, the authors. this article is published open access under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). abstract the development of the technique for the manufacture of round copper wire coated with "tin-lead" alloy is considered. the optimal parameters such as the temperature of the "tin-lead" alloy melt, the linear speed for tinning of the wire with a round copper alloy and the diameter of the diamond die were determined. the test results of the experimental wire samples are presented. keywords technological process alloy tin lead tinning round copper wire received: 03.11.21 revised: 14.06.22 accepted: 16.06.22 available online: 21.06.22 key findings ● the round copper wire coated with pos 61 alloy is used as shielding elements in cable and wire products. ● according to the results of tests the optimal technological process parameters of tinning the wire are determined. ● during the tests it turned out that 8 samples of experimental round copper wire meet the established requirements 075-11-2019-047-tt on consumer properties. 1. introduction the most important factor in ensuring and increasing an organisation's competitiveness is the development of innovative products with parameters that are ahead of existing consumer requirements at the time of market entry [1]. the developed products, according to their characteristics, must satisfy the consumers, needs in terms of the required and the desired parameters, thus forming the necessary “quality profile” [2]. chuvashkabel plant jsc is not an exception. the plant management and personnel are focused on the production of innovative and high technology products [3], in particular, wire with unique characteristics used as braiding in cable products for various purposes. this research is focused on round copper wire coated with pos-61 alloy. this wire is used as a shield in cable and wire products. the developed tinning technology must provide the wire with characteristics indicated in table 1. round copper wire samples with pos-61 coating are considered to have passed the tests if their indicators meet the requirements specified in table 1. the controlled parameters of the pos-61 coated round copper wire also include the appearance: the wire should have a smooth surface and a continuous coating along the entire wire length. table 1 list of required parameters for the round copper wire coated with pos-61. options values wire diameter, mm 0.12−0.003 +0.005 0.15−0.003 +0.005 0.20−0.003 +0.005 0.30−0.005 +0.007 coating thickness, microns 1.0−0.5 +0.2 tensile strength wire, n/mm2 not less 196 elongation at break, % 0.12 mm – 10–25%; 0.15 mm – 10–25%; 0.20 mm – 10–25%; 0.30 mm – 15–30% resistivity, оhmm10–6 no more 0.0180 http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2022.9.2.s7 http://creativecommons.org/licenses/by/4.0/ https://orcid.org/0000-0002-4278-4056 https://orcid.org/0000-0003-3880-9510 https://orcid.org/0000-0002-9785-4058 https://orcid.org/0000-0002-9869-6602 https://orcid.org/0000-0002-8335-9996 https://crossmark.crossref.org/dialog/?doi=https://doi.org/10.15826/chimtech.2022.9.2.s7&domain=pdf&date_stamp=2022-6-21 chimica techno acta 2022, vol. 9(2), no. 202292s7 letter 2 of 3 2. materials and methods research tests were carried out on 36 samples with a total weight of 50.4 kg and five parallel measurements for each wire sample. during the tests, five experimental wire samples with a length of at least 1000 mm were taken from each wire batch. during the tests, we were guided by the following documents:  preliminary technological documentation pbmi.05171.00002;  route map 075-11-2019-047-1.2.1-mk;  program and test procedure e pbmi.00002 pm2;  act of making experimental samples. each experimental sample of a round copper wire with a pos-61 coating was obtained under various technological modes of coating the wire mt 0.12, mt 0.15, mt 0.20 and mt 0.30 with the solder made of the pos-61 alloy. the production of high quality round copper wire coated with various alloys, including pos-61, is provided by:  the correct choice of wire grade as a raw material;  the correct choice of alloy (solder), which will be applied to the base, depending on the purpose, design features and materials used;  the optimal flux choice [4], which is designed to remove the oxide film from the surfaces of wire and alloy (solder), to protect the surface of wires and solder (alloy) from oxidation during the alloy (solder) deposition and to reduce the surface tension of the straightened alloy (solder) at the boundary metal – alloy (solder) – flux;  the surfaces, high-quality preparation of the base metal and alloy (cleaning, preliminary tinning);  temperature control, speed and time of alloy (solder) deposition on the base;  absence of foreign impurities and foreign inclusions in the alloy and the flux [5–6]. 3. results and discussion chuvashkabel plant jsc proposed to produce experimental wire samples to determine the optimal parameters of the technological mode of manufacturing round copper wire coated with pos-61 alloy. as mentioned above, it is based on variations in the temperature of the pos-61 alloy melt, linear velocity, diamond wire diameter and flux grades (table 2). table 2 technological modes of obtaining the round copper wire with pos-61 coating. nominal diameter of copper wire, mm melt temperature, °с linear speed, m/min diamond die diameter, mm 0.12−0.003 +0.005 0.15−0.003 +0.005 0.20−0.003 +0.005 0.30−0.005 +0.007 185 215 245 110 125 140 0.187 0.238 0.385 table 3 shows an example, which is one of the variations in the manufacturing modes of round copper wire with a pos-61 coating, used as a braid in cable products for various purposes. table 4 shows the tests results of an experimental prototype of a round copper wire with a pos-61 coating, manufactured with the parameters of the technological mode indicated in table 3. based on the 36 experimental sample results of the studies performed, obtained at different parameters of the tinning technological process, it is proposed to use the following optimal modes:  first mode: melt temperature – 185±5 °с, linear speed – 110±5 m/min;  second mode: melt temperature – 215±5 °с, linear speed – 125±5 m/min. the first mode allows increasing the productivity of manufacturing of the round copper wire coated with pure tin or pos61 alloy at lower power consumption. the second mode allows obtaining a better quality solder coating with a narrow range of variation in the coating thickness and wire diameter. table 3 modes of manufacturing the experimental samples of round copper wire with pos-61 coating at a temperature of 395 °c. no. wire sample diameter of copper wire, mm melt temperature pos-61, °с linear speed, m / min diamond die diameter, mm e-мт0.15pos61-31 0.15−0.003 +0.005 215±5 110±5 0.238 table 4 test results of an experimental sample of pos-61 e-mt-0.15-pos61-31 coated round copper wire. options meaning and tolerances sample test results no. 1 no. 2 no. 3 no. 4 no. 5 diameter of wire, mm 0.15−0.003 +0.005 0.156 0.155 0.156 0.156 0.156 quality and continuity of the coating the solution should be lighter than the control correct correct correct correct correct coating thickness, microns 1.0−0.5 +0.2 1.1 1.0 1.2 1.1 1.0 tensile strength of wire, n/mm2 not less 196 215 210 210 215 220 elongation at break, % 20−10 +5 23 22 22 23 24 specific resistance, оhmm10–6, no more 0.0180 0.01725 0.01714 0.01722 0.01716 0.01715 chimica techno acta 2022, vol. 9(2), no. 202292s7 letter 3 of 3 4. conclusions thus, during the tests, it turned out that 8 samples of experimental round copper wire with coatings pos61 e-mt0.12-pos61-12, e-mt-0.12-pos61-14, e-mt-0.15-pos61-30, e-mt-0.15-pos61-32, e-mt-0.20-pos61-48, e-mt-0.20pos61-50, e-mt-0.30-pos61-66 and e-mt-0.30-pos61-68 met the established requirements 075-11-2019-047-tt of consumer properties. supplementary materials no supplementary materials are available. funding the research was carried out by the chuvash state university within the implementation of a comprehensive project under the contract no. 2019/0837/1202–19 dated september 19, 2019 with the financial support of the ministry of education and science of russia under the agreement no. 075-11-2019-047 dated november 25, 2019 and russian foundation for basic research (rfbr), project number 2033-90269. https://www.rfbr.ru/rffi/eng. acknowledgments none. author contributions conceptualization: a.v.v., k.m.v., p.a.o., s.v.l., a.r.i. data curation: a.v.v., k.m.v., p.a.o. formal analysis: a.v.v., k.m.v., p.a.o., s.v.l., a.r.i. funding acquisition: k.m.v., s.v.l., a.r.i. investigation: a.v.v., k.m.v., p.a.o., s.v.l., a.r.i. methodology: k.m.v., s.v.l., a.r.i. project administration: a.v.v., k.m.v., p.a.o., s.v.l., a.r.i. resources: a.v.v., k.m.v., p.a.o., s.v.l., a.r.i. software: a.v.v., k.m.v., p.a.o., s.v.l., a.r.i. supervision: a.v.v., k.m.v., p.a.o., s.v.l., a.r.i. validation: a.v.v., k.m.v., p.a.o., s.v.l., a.r.i. visualization: a.v.v., k.m.v., p.a.o., s.v.l., a.r.i. writing – original draft: a.v.v., k.m.v., p.a.o., s.v.l., a.r.i. writing – review & editing: a.v.v., p.a.o. conflict of interest the authors declare no conflict of interest. additional information author ids: m.v. kuzmin, scopus id 55758896300; a.o. patianova, scopus id 57202283653; v.l. semenov, scopus id 57190025583; r.i. alexandrov, scopus id 57219838682. website: chuvash state university, https://www.chuvsu.ru/. references 1. semenov vl, patyanova ao. development of the mechanism of formation of factors of improvement of quality of products. kachestvo i iinovacii v xxi veke: materialy xv mezhdunar. nauch. prakt. konf. 2017. cheboksary, russia. p. 524– 529. 2. semenov vl. sovremennye «instrumenty» menedzhmenta. kachestvo i konkurentosposobnost' v xxi veke: materialy ix vseros. nauch. prakt. konf. 2010. cheboksary, russia. p. 293– 296. 3. danilov ip, semenov vl. sistema kachestva predpriyatiya i ee osnovnye cherty. kachestvo i konkurentosposobnost' v xxi veke: materialy ii vseros. nauch.-prakt. konf. 2003. cheboksary, russia. p. 63–67. 4. kuz'min mv. ignat'ev va, kol'cov ni. sintez i issledovanie zakonomernostej obrazovaniya alifaticheskih alkanolaminov i gidroksietilzameshchennyh mochevin. vestnik chuvashskogo univ. 2011;3:217–226. 5. nikolaeva np, kuz'min mv, kol'cov ni. sintez i issledovanie svojstv epoksiuretanov, poluchennyh psevdoforpolimernym metodom. vestnik kazanskogo tekhnol univ. 2013;16(1):136– 138. 6. nikolaeva np, kuzmin mv, koltsov ni, inventors; chuvash state university named after i. n. ulyanov, assignee. method of obtaining epoxy polyurethanes. russian federation patent ru 2457220 c1. 2012 jul 27. https://www.scopus.com/authid/detail.uri?authorid=55758896300 https://www.scopus.com/authid/detail.uri?authorid=57202283653 https://www.scopus.com/authid/detail.uri?authorid=57190025583 https://www.scopus.com/authid/detail.uri?authorid=57219838682 https://www.chuvsu.ru/ modern biotechnological methods in wastewater treatment: a review chimica techno acta review published by ural federal university 2022, vol. 9(2), no. 202292s3 eissn 2411-1414; chimicatechnoacta.ru doi: 10.15826/chimtech.2022.9.2.s3 1 of 6 modern biotechnological methods in wastewater treatment: a review c.l. beya ab*, o.n. kanwugu a , m.n. ivantsova a a: institute of chemical engineering, ural federal university, ekaterinburg 620002, russia b: polytechnic faculty, department of industrial chemistry, university of lubumbashi, lubumbashi 7110501, dr congo * corresponding author: borhomelwamba@gmail.com this paper belongs to the mosm2021 special issue. © 2021, the authors. this article is published open access under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). abstract given that water is the main solvent in living organisms as well as in domestic and industrial activities, it must be treated as carefully as possible after multiple uses to get a harmless water quality. to remove the undesirable materials (e.g. organic matters, surfactants, petroleum products, unwanted metals, dyes, et.), the physicochemical water treatment process is used as the common method. this method of wastewater treatment uses flocculation – coagulation technique, which consists of mixing coagulant matters with water to collect, in solid clusters, the materials in suspension by gravity. recently, environmental scientists have suggested biotechnology methods as the main alternatives in the treatment of wastewater, as they offer more benefits to the water quality and human health than chemical methods. this paper describes and assesses some modern biotechnology methods used in wastewater treatment. keywords wastewater and biological treatment bioadsorption membrane biofilm reactor bes received: 02.11.21 revised: 08.04.22 accepted: 09.04.22 available online: 16.04.22 1. introduction water is source of all life and a vital resource for all mankind in the sense that each human consists averagely of 65– 70% water. for the environment water remains the object par excellence, without which no life is possible [1]. after being used water is said to be waste due to the presence of some pollutants, which affect its quality. these pollutants include heat, sediments, inorganic chemicals, organic compounds, radioactive substances, and dead organic matter; it should be noted that most of the pollution from our wastewater is organic [2]. rivers can absorb and degrade these organic pollutants to a certain extent by the selfpurification process. even though nature is capable of selfcleansing, the amount of organic matter we produce far exceeds the self-purification capacity of the watercourse [3]. according to who, approximately 30% of all diseases and 40% of deaths throughout the world are due to polluted water [4]. it is, thus, essential to develop technologies capable of treating wastewater to allow its reuse without damaging the ecosystem. biotechnology finds a wide range of applications in many fields, such as the environmental decontamination, the food industry, and the mining sector [5]. as a modern technology and in comparison to the conventional physicochemical method, which uses mainly chemicals to treat wastewater, biotechnology methods consist of using microorganisms such as algae, fungi, bacteria or their parts, which interact with and remove unwanted matters within wastewater [6–7]. a successful use of biotechnology in the wastewater treatment, however, needs to properly integrate microorganisms with the modern bioreactors. this is because microbial communities require certain conditions to live (under aerobic or anaerobic conditions) and then to oxidize or incorporate organic matters in wastewater into cells that can be eliminated by a removal process or sedimentation [8]. the bioadsorption, the membrane biofilm reactor, microbial fuel cells and the biofilters are modern technologies allowing treating the wastewater using biotechnology methods. indeed, biotechnological treatment is extensively used for the removal as well as stabilization of biodegradable matters in wastewater [6–7]. scientists and environment engineers have realized that major issues for reclaiming water quality are concerned either with oxidized contaminants, or with those that do not share electrons, but receive them [6]. biotechnological processes for wastewater treatment are more suitable to achieve this goal than electrochemical treatment. in general, the wastewater treatment process relies on the combination http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2022.9.2.s3 https://orcid.org/0000-0003-3887-1058 https://orcid.org/0000-0002-2389-0523 mailto:borhomelwamba@gmail.com http://creativecommons.org/licenses/by/4.0/ https://crossmark.crossref.org/dialog/?doi=https://doi.org/10.15826/chimtech.2022.9.2.s3&domain=pdf&date_stamp=2022-4-16 chimica techno acta 2022, vol. 9(2), no. 202292s3 review 2 of 6 of separate treatment processes, which allow the generation of an effluent of specified characteristics from a wastewater of a known rate and composition [9]. this paper is intended to give a brief description of modern wastewater treatment technologies using biotechnological processes and some of their applications. 2. types of biological wastewater treatment systems according to some researches, biological wastewater treatment processes can be summarized in three main systems which include: bioremediation, phytoremediation and mycoremediation [10]. mycoremediation, thought to be an effective method of combating the ever-growing problem of water pollution, uses fungi's digestive enzymes or their derivatives to break down contaminants like heavy metals, pesticides, and hydrocarbons and remove pollutants from water [11]. phytoremediation, on the other hand, uses plants and some rhizosphere microorganisms to aid in the recovery of polluted water [12]. the former (microbial bioremediation) relies on aerobic and anaerobic microbial treatments such as oxidation ponds, aeration and anaerobic lagoons, aerobic and anaerobic bioreactors, activated sludge, percolating or trickling filters, rotating biological contactors, etc. [10]. besides these, biostimulation, which employs a combination of indigenous microorganisms and environmental modifications (e.g. additional mineral nutrients for the enhancement of pollutants’ metabolism by microbes) and bioaugmentation, where extra cultures of microbes with particular contaminant reducing abilities are added to a polluted area, have enjoyed wide utilization [13]. in addition, bioelectrochemical systems (bes) and bioadsorption can also be classified as modern biotechnological processes of wastewater treatment. in fact, bioelectrochemistry is a mix of biotechnology and electrochemistry incorporating electrodes within bioreactors where biological and electrochemical processes take place [14], while bioadsorption, which occurs along with biodegradation, is a special adsorption process using organic or biological matters as adsorbents in bioreactors [15]. 3. bioadsorption bioadsorption is an adsorption process that uses a biological material called bioadsorbent, which typically includes microorganisms and their components, seaweed, vegetables, industrial waste, agricultural waste, and natural waste as adsorptive medium [16–17]. this process aims to remove or recover organic and inorganic substances in aqueous solutions. the bioadsorption process occurs by interactions between contaminants such as metal oxides or metal hydroxides and specific active sites (carboxyl, amino, sulfate groups, among others), present in the coatings of the biomaterial [16]. in general, the chemical and physical structures of an adsorbent determine its adsorption and desorption performance [18–19]. for instance, the type of adsorption forces and the desorption capability of an adsorbent are influenced by chemical structures such as functional groups. on the other hand, physical structures, i.e. specific surface area and pore size, dictate the accessibility of an adsorbent to dyes [18]. bioadsorption processes for decontamination of wastewaters can be carried out either continuously, in fixedbed reactors/columns, or discontinuously, in batch reactors. this method is mostly used in marine oily and dye wastewater treatment. bioadsorption is mainly applied in dye wastewater treatment due to its technical feasibility, flexibility and operation simplicity (figure 1) [18–21]. 4. mechanism of adsorption in dye wastewater treatment the interaction between a cell surface and positive ions of dye is the underlying principle of bioadsorption in living biomass. polysaccharides, proteins, and lipids, which are parts of the cell surface of living biomass, have negative charges, that accumulate sufficient amount of positive ion of dyes present in wastewater [21–22]. the presence of hydroxyl, nitro, azo groups increase adsorption of dye, while sulfonic acid groups decrease adsorption. thus, ion-exchange mechanisms account for the efficiency and selectivity of adsorption by microbial biomass [21]. figure 1 interaction between microbial biomass and dye. reproduced with permission [21]; 2019, elsevier. chimica techno acta 2022, vol. 9(2), no. 202292s3 review 3 of 6 major factors affecting industrial-scale treatment of dye wastewater through bioadsorption technology include adsorption and desorption capability as well as reusability of the bioadsorbent, all of which are based on its chemical and physical structures (figure 2). however, industrial-scale treatment of dye wastewater via bioadsorption technologies remains stagnant, mainly due to its high costs [18]. 5. the membrane biofilm reactors treatment of wastewater with biofilm technology was inspired by the industrial operation of trickling filters in the early 1880 [23]. the biofilm method is a type of biological sewage treatment technology similar tothe activated sludge method in the sense that the treatment processes of activated sludge and aerobic biofilm reactors are less dependent on temperature, although temperature plays a decisive role in most wastewater treatment processes [24]. in fact, biofilm is formed by growing and breeding microorganisms on filter material or carrier. recently, new membrane reactors, including the micro porous membrane bioreactor (mbr), moving bed biofilm reactor (mbbr), sequential batch biofilm reactor (sbbr), and the up flow anaerobic sludge bed-anaerobic biological filter (uasb-bf) have been made [23–25]. biofilm processes in relation to wastewater treatment are divided into two groups: the moving-medium and the mixed-medium systems. in the former, the biofilm media are static in the reactors and the biological reactions take place in the biofilm developed on the static media (trickling filters and biological aerated filters), while the biofilm media are kept constantly in motion in the moving-medium systems. hydraulic, mechanical, or air forces (moving-bed biofilm reactors, vertically moving biofilm reactors, fluidized bed biofilm reactor, and rotating biological contactors) are employed to move the biofilm media in the moving-medium systems [23]. the use of biofilm systems in wastewater treatment is rapidly increasing because of its alluring approach of pollutant removal from wastewater, which is both cost-effective and environmentally sound [26]. the biofilm structures can be smooth or rough, fluffy or dense, as well as flat or filamentous; the structure is influenced by both the chemical composition of the surrounding medium and the hydrodynamics of the system [27]. 6. biofilm formation and mechanism usually, 3 steps are involved in the biofilm formation, namely, the biofilm attachment, growth, and detachment. surface, nutrients, and water are the minimum requirements for its formation (figure 4) [26]. once the sewage gets in contacts with the biofilm, organic pollutants in the wastewater are taken in as nutrients by the microorganisms on the biofilm, resulting in the purification of the sewage wastewater [29]. biofilms are hugely complex; they have a difficult structure for quantification and are heterogeneous consortia of cells which are significantly influenced by the environmental and mechanical conditions to which they are subjected. during the quantification, different parameters must be taken into account, including specific surface area, porosity, thickness, surface area coverage, thickness variability, fractal dimension, density, and pore radius [27]. table 1 presents the advantages and disadvantages of some of the membrane biofilm reactors used in wastewater treatment. 7. bioelectrochemical systems the bioelectrochemical systems (bes), as noted earlier, combine two sciences in industrial wastewater treatment. this technology uses the integration of electrodes within the biological reactors to regain resources present in the wastewater and takes advantage of a solid electron acceptor or donor interactivity with microorganisms to achieve bioenergy recovery from organic substances [14, 31]. figure 2 dye wastewater treatment. reproduced with permission [18]; 2019, elsevier. chimica techno acta 2022, vol. 9(2), no. 202292s3 review 4 of 6 figure 3 a biofilm reactor model used in wastewater treatment. reproduced with permission [28]; 2015, elsevier. 8. processes within the bioelectrochemical reactors the bes catalyze distinct oxidation and reduction reactions by using microorganisms attached to electrodes (anode and cathode) with the aim of recovering resources contained in the wastewater. bacteria in wastewater degrade organic matter and release electrons and protons, which are collected at the anode and cathode, respectively, while co2 is released [32]. the anode (negative or reducing electrode) transfers electrons to the external circuit but oxidizes during the electrochemical reaction, whereas the cathode (positive or oxidizing electrode) gains electrons from the external circuit but is reduced during the electrochemical reaction, necessitating additional contaminant treatment [33]. thus, electrons that result from oxidation are transmitted to the anode and are important to electrical energy generation [14]. three features are mainly focal while using bes technology in the wastewater treatment: trapping electrical power from organic pollutants in microbial fuel cells, collecting additional products like ch2, h2 and high standard water in microbial electrosynthesis cells, and eliminating contaminants such as perchlorate, heavy metal etc. [31]. 9. assessment of bes in wastewater treatment the bioelectrochemical systems allow the improvement of the current processes performance and are the potential alternative energy storage systems. these systems are particularly able to carry out the electromethanogenesis process, which consists in the conversion of co2 (carbon dioxide) to methane (figure 5). in addition, the bes present advantage in terms of: • stabilizing the biological process, increasing both quality and quantity of biogas produced; • reducing the high costs of wastewater treatment resulting from conventional water purification technologies; • reusing the products obtained during the process, as other sorts of sources of energy. table 1 comparison among bioreactors: merits and limitations. adapted from [30]. bioreactor merits limitations moving bed biofilm reactor (slurry reactor) heterogeneous version of stirred tank. high cell concentration in biofilm promotes rate of bioconversion. capacity wise inferior to column reactors. biofilm could get disturbed due to high rate of agitation. fluidized bed biofilm reactor operates at high capacities, provides high degree of bioconversion. once fully fluidized, pressured drop across the bed remains constant and does not increase with increase in feed flow rate. degree of bioconversion increases with increase in feed flow rate due to bed expansion. entrainment loss of particle-biofilm aggregates possible. operating cost higher than trickle bed (packed bed). semifluidized bed biofilm reactor higher degree of bioconversion (than fluidized beds) at higher capacities and low reactor volume requirement. degree of bioconversion increases with increase in feed flow rate, even if reactor volume is kept constant. higher operating cost than fluidized beds. continuous, circulating mode of operation not possible. inverse fluidized biofilm reactor low operating cost due to down flow mode of operation. larger size particles could be used. reasonably large degree of bioconversion. lower capacity than fluidized /semi-fluidized bed. larger reactor volume requirement. figure 4 biofilm life cycle. reproduced from [26]; 2019, intechopen. chimica techno acta 2022, vol. 9(2), no. 202292s3 review 5 of 6 it should be noted that actually the bes technology is still experimental and has not yet been proven in terms of its technical and economic viability on industrial scale [31]. 10. conclusions and recommendations the big problem in the wastewater treatment is to oxidize all soluble and insoluble organic compounds present. the use of microorganisms in sewage treatment through modern biological methods has shown to be more efficient at achieving this goal. compared to chemicals, microorganisms offer several benefits such as being environmentally friendly, cost-effective, and abundant in nature. although their use in bioreactors seems perfect, choosing the right microorganism remains difficult and tricky since it depends on areas of its use. in the papermaking and dying industry wastewater, which are the examples of alkaline wastewater, a detachment of a biofilm may happen, which could lead to a collapse of biological wastewater treatment systems. it would, thus, be much better and useful to make bioflocculant-producing strains that can form biofilm in alkaline conditions. nevertheless, it is still difficult to define a universal method that could be used for the elimination of all contaminants from wastewater. one of the major reasons is because, practically, only few industries have been successful in removing the production of all wastewater requiring disposal unit after treatment even if the theory of zero discharge is still popularly adopted. therefore, water treatment with both biotechnological and traditional methods must be monitored continuously to ensure that the desired water quality is always achieved. supplementary materials no supplementary materials are available. funding this research had no external funding. acknowledgments none. author contributions conceptualization: c.l.b., o.n.k., m.n.i. data curation: m.n.i. formal analysis: c.l.b., o.n.k., m.n.i. funding acquisition: c.l.b., o.n.k., m.n.i. investigation: c.l.b. methodology: c.l.b., o.n.k., m.n.i. project administration: o.n.k., m.n.i. resources: c.l.b., o.n.k., m.n.i. software: c.l.b., o.n.k., m.n.i. supervision: m.n.i. validation: c.l.b., o.n.k., m.n.i. visualization: c.l.b. writing – original draft: c.l.b. writing – review & editing: o.n.k., m.n.i. conflict of interest the authors declare no conflict of interest. figure 5 bes scheme. reproduced from [34]; 2019, infoanalítica. chimica techno acta 2022, vol. 9(2), no. 202292s3 review 6 of 6 additional information authors’ ids: beya, charles l.: ; kanwugu, osman n., scopus id 57195573903; ivantsova, maria n., scopus id 6507519617. websites of ural federal university: https://urfu.ru/en; university of lubumbashi: https://www.unilu.ac.cd. references 1. rockstrom j. 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infoanalítica, 2019. 7(2):15-37. doi:10.26807/ia.v7i2.100 https://www.researchgate.net/profile/charles-borome-beya https://twitter.com/borhomelwamba http://www.scopus.com/authid/detail.uri?authorid=57195573903 http://www.scopus.com/authid/detail.uri?authorid=6507519617 https://urfu.ru/en https://www.unilu.ac.cd/ https://doi.org/10.4324/9781849770521 https://doi.org/10.1016%2fb978-0-12-409548-9.09508-7 https://www.sdea.fr/index.php/fr/l-eau/les-eaux-usees/pourquoi-traiter-les-eaux-usees https://www.sdea.fr/index.php/fr/l-eau/les-eaux-usees/pourquoi-traiter-les-eaux-usees https://doi.org/10.5772/63499 https://ncert.nic.in/textbook/pdf/lebo112.pdf https://doi.org/10.1061/(asce)ee.1943-7870.0000140 https://doi.org/10.4314/ajb.v8i25 https://doi.org/10.1016/j.biortech.2016.05.098 https://doi.org/10.1007/s10311-018-0785-9 https://doi.org/10.5772/61250 https://doi.org/10.3390/w13060846 https://doi.org/10.15666/aeer/1501_033050 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https://doi.org/10.1016/j.bej.2014.10.006 https://doi.org/10.3390/w11122517 https://doi.org/10.1186/s42834-019-0036-1 https://doi.org/10.3390/w7010038 https://ec.europa.eu/environment/integration/research/newsalert/pdf/fb5_en.pdf https://ec.europa.eu/environment/integration/research/newsalert/pdf/fb5_en.pdf https://doi.org/10.1038/s41545-018-0022-x https://doi.org/10.26807/ia.v7i2.100 synthesis, crystal structure, and thermal stability of double borate na3erb2o6 chimica techno acta article published by ural federal university 2021, vol. 8(4), № 20218402 eissn 2411-1414; chimicatechnoacta.ru doi: 10.15826/chimtech.2021.8.4.02 1 of 5 synthesis, crystal structure, and thermal stability of double borate na3erb2o6 alexey k. subanakov * , evgeniy v. kovtunets , bair g. bazarov, jibzema g. bazarova baikal institute of nature management sb ras, 670047 sakhyanovoy st., 6, ulan-ude, russia * corresponding author: subanakov@binm.bscnet.ru this article belongs to the regular issue. © 2021, the authors. this article is published in open access form under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). abstract double borate na3erb2o6 was synthesized by the solid-state reaction. the crystal structure of na3erb2o6 was refined by the rietveld method: p21/c, a = 6.49775(14) å, b = 8.50424(17) å, c = 12.0067(3) å, β = 118.4797(9)°, z = 4. the crystal structure of na3erb2o6 consists of –[ero6]∞-chains along the "b" axis, which are linked by bo3 triangles in a three-dimensional framework. sodium atoms occupy empty positions inside the channels. the thermal behavior of na3erb2o6 was studied in detail in the range of 25–1150 °c range by dsc and tg methods. na3erb2o6 congruently melts at 1116 °c. based on the results of dsc measurements, three reversible phase transitions were found for na3erb2o6. keywords sodium rare-earth borate solid-state reaction crystal structure rietveld refinement thermal analysis received: 05.10.2021 revised: 18.10.2021 accepted: 18.10.2021 available online: 20.10.2021 1. introduction borates are considered to be attractive functional materials for non-linear optic and luminescence due to their wide variety of crystal structures, low synthesis temperature, and environmental benignity [1–13]. today commercially used nonlinear optical crystals of borates with superior optical properties are β-bab2o4 [14] and lib3o5 [15]. recent studies of borates are related to birefringent materials [16] and self-frequency-doubling (sfd) laser ones [17]. sfd crystals belong to multi-functional materials and possess both laser and frequency doubling properties. the basic requirements for an efficient sfd laser crystal are excellent laser properties and excellent nonlinear optical properties with suitable birefringence. therefore, sfd materials contained rare-earth elements and a nonlinear framework. to search new sfd materials, the oxide systems based on alkaline, rare earth, and boron were extensively studied. exploration of the na2o–r2o–b2o3 systems revealed the existence of a number of double borates: na2r2(bo3)2 [18–20], na3rb2o6 [21–23], na3r2b3o9 [21,24–26], na3y3b4o12 [27], na3r9o3b8o24 [28,29]. our attention was attracted by double borates with the general formula na3rb2o6. this family of compounds includes borates with large lanthanides such as na3lab2o6 [21], na3prb2o6 [22], na3smb2o6 [22], na3eub2o6 [22], na3yb2o6 [23] and na3gdb2o6 [23]. the subject of our study is the possibility of replacing large lanthanides with erbium. the crystal structure and thermal stability of double borate na3erb2o9 was studied in the present work. 2. experimental the title compounds were prepared by solid state reactions using high purity starting reagents: na2co3 (99.8%, sigma aldrich ltd.), er2o3 (99.9%, red chemist, ltd., russia), and h3bo3 (99.5%, sigma aldrich ltd.). before weighing, er2o3 had been preheated at 850 °c for 8 hours to remove absorbed water. the reagents were weighed on an analytical balance with an accuracy of 0.5 mg. the mixtures of na2co3, er2o3, and h3bo3 at molar ratio 3:1:2 were thoroughly ground in an agate mortar, slowly heated up to 300 °c, and were kept for 5 hours. then the samples were reground and annealed at 600 °c for 5 hours and finally at 700 °c for 40 hours with intermediate grindings until equilibrium was reached. temperature was measured with a pt–ptrh thermocouple. the temperatures up to 1200 °c were controlled with an accuracy of ±2 °c with an omron instrument. the equilibrium was considered to be reached only when two successive heat treatments resulted in identical x-ray diffraction patterns. powder x-ray diffraction data were recorded by a d8 advance bruker axs diffractometer (vantec-1 detector) at room temperature using cu kα radiation and scanning http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2021.8.4.02 https://orcid.org/0000-0002-1674-283x https://orcid.org/0000-0003-1301-1983 http://creativecommons.org/licenses/by/4.0/ chimica techno acta 2021, vol. 8(4), № 20218402 article 2 of 5 from 2θ = 8° to 100° in increments of 0.02° and a counting time of 0.1 s/step. phase purity was verified by powder x-ray diffraction (xrd) and the profile was compared to that reported for the isostructural phase na3ndb2o6. the topas 4.2 [30] software suite was used to analyze the experimental data and to perform the rietveld refinement of the obtained compound. all peaks in the x-ray powder diffraction pattern for na3erb2o9 were indexed satisfactory in a monoclinic cell (space group p21/c). differential scanning calorimetry (dsc) and thermogravimetric (tg) measurements were performed on an sta 449 f1 jupiter thermoanalyzer (netzsch) in the temperature range of 30–1150 °c in argon flow. pt crucibles were used as vessels. pt–ptrh thermocouples were used for temperature measurement. the precision of temperature measurement was ±1 °c. the heating and cooling rates were 10 °c/min. 3. results and discussion the synthesized sample of na3erb2o6 is pink powder, which is characteristic for the er-containing oxides. the structure of na3ndb2o6 was used as initial model for the rietveld refinement to define the positions of atoms. they were refined by isotropic approximation with “soft” limitations of the b–o distance and the b–o–b bond angles. the refined parameters were added sequentially with the graphical simulation of the background in continuous. the pearson vii function was used to describe the shape of peaks. the isotropic displacement parameters (biso) for the er and na atoms were refined separately, while for the o and b atoms they were taken as equivalent. the refinement process included corrections for the sample preferred orientation and anisotropic broadening of peaks within the model of spherical harmonics. the refinement was stable and gave low r-factors (fig. 1, table 1). na3erb2o6 was crystallized in the monoclinic system with the space group p21/c. the unit cell parameters are: a = 6.49775(14) å, b = 8.50424(17) å, c = 12.0067(3) å, β = 118.4797(9)°, z = 4. coordinates of atoms are given in table 2. further details of the crystal structure may be obtained from supplementary material. in the structure of na3erb2o6 (fig. 2a), er atoms are coordinated by seven o atoms in a distorted pentagonal bipyramid. the bipyramids share corners, forming a zigzag chain along the “b” direction, and the chain is reinforced by the b1o3 group, which uses all its three b–o bonds to join the neighboring bipyramids (fig. 2a). along with the “a” and “c” directions, these chains are connected via the b2o3 groups, thereby constructing a threedimensional framework. na1 and na3 atoms are located in the interlayer channels and na2 atom sits in the inlayer empty positions (fig. 2b–d). three na atoms are coordinated by seven, six, and four o atoms, respectively. the main bond lengths (å) and angles (°) of na3erb2o6 are shown in table 3. fig. 1 xrd data for na3erb2o6 refined by the rietveld analysis: measured (red points), calculated (black profile) and difference between experimental points and calculated profile (grey curve) table 1 crystallographic data for na3erb2o6 phase at room temperature chemical formula na3erb2o6 space group p21/c (14) formula weight, g/mol 353.9 unit cell dimensions, å α = γ = 90° a = 6.49775(14) b = 8.50424(17) c = 12.0067(3) β = 118.4797(9)° cell volume, å3 583.18(2) z 4 calculated density (g/cm3) 4.163 rp, % 2.571 rwp, % 3.534 rexp, % 1.572 bragg r-factor, % 1.864 χ2 2.249 table 2 fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters of na3erb2o6 structure x y z biso*/beq er 0.0970(3) 0.1261(1) 0.3287(1) 0.9(2) na1 0.380(2) 0.8039(8) 0.3841(7) 1.1(3) na2 0.058(2) 0.2963(8) 0.0802(8) 0.9(3) na3 0.331(2) 0.9488(8) 0.1134(7) 3.1(3) b1 0.139(3) 0.4379(7) 0.3695(8) 1.0(6) b2 0.351(1) 0.5864(8) 0.1209(5) 1.0(6) o1 0.255(2) 0.334(1) 0.4714(9) 0.5(2) o2 0.049(2) 0.373(2) 0.2513(7) 0.5(2) o3 0.137(2) 0.600(1) 0.3911(9) 0.5(2) o4 0.226(1) 0.674(1) 0.1611(5) 0.5(2) o5 0.251(2) 0.505(1) 0.0086(7) 0.5(2) o6 0.413(1) 0.080(1) 0.3075(5) 0.5(2) chimica techno acta 2021, vol. 8(4), № 20218402 article 3 of 5 fig. 2 the crystal structure of na3rb2o9: a, b) ero7 chains, bo3 triangles (a) and na atoms (b) along a axis; b, c) a general view along b and c axes the dsc curves recorded for na3erb2o6 are shown in fig. 3. four endothermic signals at 717, 907, 1014, and 1116 °с were detected during the sample’s first heating, as shown in fig. 3. the endothermic peak at 1116 °с corresponds to the melting point of na3erb2o6. the x-ray diffraction measurements indicate the congruent melting of the borate (fig. 4). to determine the nature of the endothermal effects at 717, 907, 1014 °с and prove congruent melting, the same sample was recorded in the ‘‘heating-cooling” mode over the temperature range of 100–1150 °с (with melting). at first cooling, na3erb2o6 shows exothermic effects at 712, 831, 1000, 1098 °с. the second cooling reveals a new exothermic effect at 706 °с that seems to correspond to na3erb2o6 partial decomposition, which is confirmed by x-ray analysis. the observed temperatures hystereses are about 5, 76, 14, 18 degrees. thus, the signature observed at 600–1150 °с reveals the existence of reversible phase transitions (type i) in na3erb2o6 and, respectively, additional experiments are needed to define the structure of the hightemperature modification of β, γ – na3erb2o6. table 3 main bond lengths (å) and angles (°) of na3erb2o6 er—o1 2.33(1) na2—o5 2.55(1) er—o2i 2.36(1) na2—o6 3.19(1) er—o2 2.26(2) na3—o1x 2.40(1) er—o3i 2.32(1) na3—o3x 2.38(1) er—o4i 2.20(1) na3—o4 2.57(1) er—o5ii 2.20(1) na3—o6vii 2.40(1) er—o6 2.22(1) b1—o1 1.40(1) na1—o1iii 2.50(1) b1—o2 1.37(1) na1—o2iv 2.53(1) b1—o3 1.40(1) na1—o3 2.38(1) b2—o4 1.35(1) na1—o4 2.61(1) b2—o5 1.37(1) na1—o5v 2.72(1) b2—o6v 1.36(1) na1—o5vi 2.60(1) o1—b1—o2 116(1) na1—o6vii 2.56(1) o1—b1—o3 120(1) na2—o1viii 2.48(1) o2—b1—o3 123(1) na2—o2 2.18(1) o4—b2—o5 123(7) na2—o3i 2.22(1) o4—b2—o6v 120(5) na2—o4ix 2.60(1) o5—b2—o6v 118(1) na2—o5ix 2.44(1) symmetry codes: (i) –x, y–1/2, –z+1/2; (ii) x, –y+1/2, z+1/2; (iii) –x+1, –y+1, –z+1; (iv) –x, y+1/2, –z+1/2; (v) –x+1, y+1/2, –z+1/2; (vi) x, –y+3/2, z+1/2; (vii) x, y+1, z; (viii) x, –y+1/2, z–1/2; (ix) –x, –y+1, –z; (x) x, –y+3/2, z–1/2. chimica techno acta 2021, vol. 8(4), № 20218402 article 4 of 5 it should be pointed out that the transition was not found in na3rb2o6 (r = pr, sm, eu) [22]. respectively, it can be reasonably assumed that the appearance of the phase transitions is observed only for the na3rb2o6 borates where rare earth elements have small ionic radius. an x-ray examination of solid-state interactions between the components of the na2o–er2o3–b2o3 system resulted in finding double borate na3erb2o6. na3erb2o6 was synthesized by solid-state reaction. the crystal structure of na3erb2o6 was refined by the rietveld analysis. na3erb2o6 consists of ero7 distorted pentagonal bipyramids and bo3 groups. na3erb2o6 congruently melts at 1116 °c. the dsc and tg experiments assume that after melting na3erb2o6 decomposing with formation of er2o3. the observed endothermic effects on the dsc curve are assumed to be attributed to high-temperature phase transitions of the title compound. this assumption prompts us to thoroughly investigate this family of compounds in the future. fig. 3 dsc measurement results fig. 4 x-ray patterns of unmelted and melted na3erb2o6 specimen conclusions an x-ray examination of solid-state interactions between the components of the na2o–er2o3–b2o3 system resulted in finding the double borate, na3erb2o6. na3erb2o6 was synthesized by solid-state reactions. the crystal structure of na3erb2o6 was refined by the rietveld analysis. na3erb2o6 consists of ero7 distorted pentagonal bipyramids and bo3 groups. na3erb2o6 congruently melts at 1116 °c. the dsc and tg experiments 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savchuk ab, еkaterina s. starnovskaya аb, igor l. nikonov ab , artem v. baklykov ab, ekaterina a. kudryashova a, svetlana s. rybakova a, evgeny d. ladin a, dmitry s. kopchuk ab , zhuo wang c,оleg n. chupakhin ab a: ural federal university, 620002 mira st., 19, yekaterinburg, russia b: i.ya. postovsky institute of organic synthesis of the ural branch of the ras, 620990 kovalevskoy/akademicheskaya st., 22/20, yekaterinburg, russia c: beijing university of chemical technology, 100029 beijing, china * corresponding author: yapet89@mail.ru this short communication (letter) belongs to the regular issue. © 2021, the authors. this article is published in open access form under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). abstract a new co-polymer based on fragments of 2-(2pyridyl)monoazatriphenylene and 2,5-bis (2-ethylhexyl)-3,6di(thiophen-2-yl)pyrrolo[3,4-c]pyrrole-1,4(2h,5h)-dione was prepared by using the sonogashira reaction. the photophysical properties of the polymer were studied. the presence of a strong bathochromic shift of the absorption and emission maxima in comparison with the previously described monomer units is shown. the polymer exhibits an intense “turn-off” response toward cu2+ cations. keywords sonogashira coupling polymer monoazatriphenylene 3,6-di(thiophen-2yl)pyrrolo[3,4-c]pyrrole1,4(2h,5h)-dione fluorescence cu2+ “turn-off” response received: 16.12.2021 revised: 19.12.2021 accepted: 23.12.2021 available online: 24.12.2021 1. introduction acetylene-based polymers find a variety of applications as functional materials for sensorics and molecular electronics [1]. in particular, conjugated polymers containing 2,2'-bipyridine moieties [2] as monomer units are of interest in terms of optical response to metal cations [3]. thus, the selective determination of cu2+ [4] and hg2+ [5] cations has been described with the help of such polymers. on the other hand, bis-pyrrolo[3,4-c]pyrrole-1,4(2h,5h)-diones (dpps) were widely used as components of donor–acceptor alternating co-polymers, which were reported as promising hole-transport materials [6,7], as materials for molecular electronics and photovoltaics [8,9], components of laser dyes [10], dyes for two-photon fluorescence microscopy [11], chemosensors for cu2+ [12] and hg2+ [13] cations, and many other applications [14]. one of the most important application of dpp-based materials was in their use as reagents for photothermal therapy of cancer [15], including photoacoustic imaging-guided photothermal therapy [16]. in this work, we wish to report the synthesis of a polymer containing fragments of 2-(2-pyridyl)monoazatriphenylene and 2,5-bis(2-ethylhexyl)-3,6-bis(thiophen-2-yl)pyrrolo[3,4c]pyrrole-1,4(2h,5h)-dione. 2. experimental 1h nmr spectra were recorded on a bruker avance-400 spectrometer (400 mhz), the internal standard was sime4. elemental analysis was performed on a perkin elmer pe 2400 ii chn analyzer. uv–visible absorption spectra were recorded on a perkin elmer lambda 45. luminescence spectra were obtained using a horiba scientific fluoromax-4 spectrofluorometer. gpc measurements were performed using a chromatograph agilent 1200 with an aerosol light scattering detector (elsd) (agilent technologies, http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2021.8.4.17 https://orcid.org/0000-0002-2493-0056 https://orcid.org/0000-0002-0397-4033 http://creativecommons.org/licenses/by/4.0/ chimica techno acta 2021, vol. 8(4), № 20218417 letter 2 of 4 usa). the starting monomers 1 [17] and 2 [18] were obtained as described in the literature. the chemical polymerization process was carried out in accordance with the modified method [19]. the compounds 1 (33 mg, 0.048 mmol) and 2 (19.1 mg, 0.048 mmol) were dissolved in the mixture of diisopropylamine/toluene (2:3, 4.0 ml). then cui (5.8 mg, 0.030 mmol), pd(tpp)2cl2 (3.4 mg, 0.0048 mmol) and pph3 (2.5 mg, 0.01 mmol) were added. the reaction mixture was stirred in an autoclave under argon atmosphere at 65 °c for 3 days. then the solvents were evaporated under reduced pressure. water (10 ml) was added to the residue and the product was extracted with methylene chloride (3×10 ml). the organic phase was washed with an aqueous solution of nh4cl and then dried over anhydrous na2so4. the solvent was evaporated under reduced pressure. the polymer was obtained as a purple powder. yield 32 mg (70%). nmr 1н (cdcl3, δ, ppm): 0.77–0.96 (m, 14h, 2-ethylhexyl), 1.14–1.40 (m, 28h, 2ethylhexyl), 1.49–1.63 (m, 9h, 2-ethylhexyl), 7.44–7.49 (ddd, 2h, 3j 7.6 hz, 7.6 hz, 4j 2.6 hz, charom), 7.52–7.58 (m, 1h, charom), 7.64–7.67 (m, 1h, charom), 7.67–7.70 (m, 1h, charom). ir (ν, cm–1): 1660 (c=o). 3. results and discussion the synthesis of monomers 1 [17] and 2 [18] was carried out according to the described methods. thus, compound 1 was obtained on the basis of commercially available precursor 3 as a result of successive n-alkylation and bromination of thiophene rings (scheme 1). in the case of pyridylmonoazatriphenylene 2, the starting compound is the previously described 3,11-dibromo-6-(pyridin-2-yl)-8,9dihydro-7h-dibenzo[f,h]cyclopenta[c]quinoline 4 [20]. the monomer was obtained as a result of the sonogashira reaction at two bromine atoms, followed by removal of the trimethylsilyl protection. the polymerization process was carried out in accordance with a modified technique under the conditions of the sonogashira reaction [19]. the data of the 1h nmr spectrum of the obtained polymer do not contradict its proposed structure. in the ir spectra, the presence of a vibration band corresponding to carbonyl groups in the region of 1660 cm–1 can be noted. next, we studied the photophysical characteristics of the obtained polymer 5. in the solution of acetonitrile this polymer demonstrates absorption maxima around 550 nm (table 1). analysis of the literature data showed that, in the case of polymer 5, there is a bathochromic shift of the absorption maximum relative to the monomer units. thus, for unsubstituted pyridylmonoazatriphenylene 6 [20], the longest wavelength absorption maximum corresponds to 357 nm, and in the case of 2,5-bis(2-ethylhexyl)-3,6di(thiophen-2-yl)pyrrolo[3,4-c]pyrrole-1,4-(2h,5h)-dione 7 [21] this parameter was 541 nm. a similar bathochromic shift is observed for the emission maxima of polymer 5 relative to compounds 6 and 7. for example, there is a shift from 541 nm to 55 nm. the absorption and emission spectra of the polymer are shown in fig. 1. next, we studied the fluorescent response of the new polymer 5 with respect to cations of a number of metals. thus, it was found that the addition of cu2+ cation to the solution of polymer 5 in acetonitrile results in almost complete quenching of its fluorescence, which is due to the influence of both monomer units on the supramolecular properties of the whole polymer. fig. 2 depicts gpc chromatography for the resulting polymer 5. according to the obtained data, the resulting product 5 is a mixture of oligomers/short polymers, among which there are structures with molecular weights of up to 3–4 kda. thus, the method reported herein for the preparation of the polymer 5 requires further development in order to increase its average molecular weight. table 1 the photophysical characteristics for polymer 5 and compounds 6 and 7 in mecn at room temperature compound absorption maxima, nm emission maxima, nm [20] 263, 313, 339, 357 364, 381, 403 (sh) [21] 341, 353, 508, 541 560, 600 polymer 5 550 571, 616 fig. 1 absorption and emission spectra of polymer 5 in acetonitrile at room temperature chimica techno acta 2021, vol. 8(4), № 20218417 letter 3 of 4 scheme 1 synthesis of polymer 5. reagents and conditions: i) cui, pph3, pd(tpp)2cl2/diisopropylamine, 65 °c, 3 days fig. 2 gpc chromatogram for polymer 5 chimica techno acta 2021, vol. 8(4), № 20218417 letter 4 of 4 4. conclusions in conclusion, a 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https://doi.org/10.1016/j.dyepig.2004.02.002 https://doi.org/10.1016/j.dyepig.2012.11.028 https://doi.org/10.1016/j.dyepig.2018.09.027 https://doi.org/10.1016/j.snb.2017.01.037 https://doi.org/10.1002/adom.201400559 https://doi.org/10.1016/j.dyepig.2020.108599 https://doi.org/10.1039/d1tb00193k https://doi.org/10.1039/c5ra00391a https://doi.org/10.1063/5.0018783 https://doi.org/10.1021/ja982293q https://doi.org/10.1007/s10593-014-1541-0 https://doi.org/10.1016/j.jphotochem.2020.113017 synthesis of highly stable luminescent molecular crystals based on (e)-2-((3-(ethoxycarbonyl)-5-methyl-4-phenylthiophen-2-yl)amino)-4-oxo-4-(p-tolyl)but-2-enoic acid chimica techno acta letter published by ural federal university 2021, vol. 8(4), № 20218411 eissn 2411-1414; chimicatechnoacta.ru doi: 10.15826/chimtech.2021.8.4.11 1 of 5 synthesis of highly stable luminescent molecular crystals based on (e)-2-((3-(ethoxycarbonyl)-5-methyl-4-phenylthiophen-2yl)amino)-4-oxo-4-(p-tolyl)but-2-enoic acid n.a. zhestkij a, e.v. gunina a, s.p. fisenko b, a.e. rubtsov c, d.a. shipilovskikh d, v.a. milichko ae* , s.a. shipilovskikh ac* a: itmo university, 197101 kronverksky pr., 49, st. petersburg, russia b: a. v. luikov, heat and mass transfer institute, nasb, 220072 brovki st., 15, minsk, belarus c: perm state university, 614068 bukireva st., 15, perm, russia d: perm national research polytechnic university, 614077 komsomolsky pr., 29, perm, russia e: universite de lorraine, cnrs, ijl, f-54000 nancy, france * corresponding authors: v.milichko@metalab.ifmo.ru (v.a. milichko), s.shipilovskikh@metalab.ifmo.ru (s.a. shipilovskikh) this short communication (letter) belongs to the mosm2021 special issue. © 2021, the authors. this article is published in open access form under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). abstract the synthesis of (e)-2-((3-(ethoxycarbonyl)-5-methyl-4phenylthiophen-2-yl)amino)-4-oxo-4-(p-tolyl)but-2-enoic acid was performed. this organic compound was used as a building block for the organic molecular crystals with highly stable photoluminescence at ambient conditions, which has been established during 10 years of exploitation. keywords organic molecular crystal photoluminescence structure rigidity substituted 2,4-dioxobutanoic acids gewald thiophenes received: 09.12.2021 revised: 14.12.2021 accepted: 14.12.2021 available online: 15.12.2021 1. introduction luminescent molecular crystals (mcs) based on organic molecules are the cornerstones of modern organic electronics and luminescent technologies. the utilization of such crystals as active components of displays and lasers [1–5] significantly decreases energy consumption and makes such devices recyclable. generally, organic crystals (ocs) are based on organic molecules packed in a specific order, where weak intermolecular interactions maintain the integrity of the crystal structure. for such a structure, the nature of luminescence is defined by intrinsic electronic transitions of individual organic molecules and generalized electronic states, which are directly determined by the type of molecular packing [6–8]. demonstrating unprecedented efficiency, light spectrum control [1, 3], scalability [2], flexibility [9] and enhanced time of emission (phosphorescence) [5, 7, 10–12], mcs still suffer from aging and poor structural stability [8, 11, 13, 14] at ambient conditions (in air atmosphere and room temperature). the reasons for this are, on the one hand, the violation of the integrity of the organic molecules during long-term excitation. this is due to the heatand photoinduced destruction of certain chemical bonds. on the other hand, the distortion of the weak intermolecular interactions under normal conditions disrupts the aggregation of molecules and negatively affects both the emission spectrum and the luminescence efficiency [13, 14]. what is important is that the latter effect is observed at lower excitation parameters at ambient conditions and, hence, more significantly affects the working capacity of corresponding organic devices. 2. experimental 2.1. chemical experiments the yields are given for the isolated products showing one spot on a tlc plate and no impurities detectable in the nmr spectrum. the identity of the products prepared by different methods was checked by comparison of their nmr spectra. 1h and 13c nmr spectra were recorded at 400 mhz for 1h and 100 mhz for 13c nmr at room temperature; the chemical shifts (δ) were measured in ppm with respect to http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2021.8.4.11 https://orcid.org/0000-0002-8461-0804 https://orcid.org/0000-0002-8917-2583 http://creativecommons.org/licenses/by/4.0/ chimica techno acta 2021, vol. 8(4), № 20218411 letter 2 of 5 the solvent (cdcl3, 1н: δ = 7.26 ppm, 13c: δ = 77.16 ppm; [d6] dmso, 1н: δ = 2.50 ppm, 13c: δ = 39.52 ppm). the coupling constants (j) are given in hertz. the splitting patterns of apparent multiplets associated with averaged coupling constants were designated as s (singlet), d (doublet), t (triplet), q (quartet), sept (septet), m (multiplet), dd (doublet of doublets) and br (broadened). the melting points were determined with a «stuart smp 30», the values are uncorrected. flash chromatography was performed on silica gel macherey nagel (40–63 m). the elemental analysis was performed on a leco chns-932 instrument. the reaction progress was monitored by gc/ms analysis and thin layer chromatography (tlc) on aluminum backed plates with merck kiesel 60 f254 silica gel. the tlc plates were visualized either by uv radiation at a wavelength of 254 nm or stained by exposure to a dragendorff’s reagent or potassium permanganate aqueous solution. all the reactions were carried out using dried and freshly distilled solvent. 2.2. synthesis of (z)-2-hydroxy-4-oxo-4-(p-tolyl)but2-enoic acid 3 a cooled mixture of 29.2 g (0.2 mol) diethyl oxalate and 26.8 g (0.2 mol) 1-(p-tolyl)ethan-1-one was slowly added with stirring to a solution of freshly prepared (0.4 mol) sodium methoxide in 100 ml of methanol. after one day, the precipitate that formed was dissolved in warm water (60 °с) and the solution was acidified with concentrated hydrochloric acid to ph = 3. the formed precipitate was filtered off and recrystallized from acetonitrile (scheme 1). scheme 1 synthesis of (z)-2-hydroxy-4-oxo-4-(p-tolyl)but-2-enoic acid 3 beige crystals (36.3 g, 88%), m.p. 141–143 °с (141– 142 °с [15]). 1h nmr (cdcl3, 400 mhz) δ (ppm): 2.48 (s, 3h, me), 7.16 (s, 1h, c=ch), 7.35 (m, 2h, har), 7.94 (m, 2h, har). 13c nmr (cdcl3, 100 mhz) δ (ppm): 21.8, 94.8, 128.0, 129.7, 129.8, 145.6, 161.6, 174.6. found, %: c 64.05, h 4.93. c11h10o4. calculated, %: c 64.08, h 4.89. 2.3. synthesis of ethyl 2-amino-5-methyl-4phenylthiophene-3-carboxylate 6 in a 100 ml three-necked flask equipped with a reflux condenser, a dropping funnel, an internal thermometer and a magnetic stirrer a solution of 13.4 g (0.1 mol) of propiophenone and 11.3 g (0.1 mol) of ethyl 2-cyanoacetate in 40 ml of ethanol was placed. to the resulting solution 3.2 g (0.1 mol) of finely ground sulfur was added. while stirring, 4 ml of morpholine was added dropwise to the resulting mixture, making sure that the reaction mixture did not overheat. after the end of the exothermic reaction, the mixture was heated in a water bath until the sulfur was completely dissolved. after cooling the solution to 0 °c, ethyl 2-amino-5methyl-4-phenylthiophene-3-carboxylate precipitated in the form of yellow crystals. the resulting product was filtered off and recrystallized from methanol (scheme 2). scheme 2 synthesis of ethyl 2-amino-5-methyl-4phenylthiophene-3-carboxylate 6 yellow crystals (22.47 g, 86%), m.p. 91–93 °с (93 °с [16]). 1h nmr (cdcl3, 400 mhz) δ (ppm): 1.35 (t, j = 7.1 hz, 3h, ме), 2.30 (s, 3h, ме), 4.29 (q, j = 7.1 hz, 2h, сн2), 6.05 (s, 2h, nh2), 7.29 (m, 5h, har). found, %: c 64.30, h 5.72, n 5.31. c14h15no2s. calculated, %: c 64.34, h 5.79, n 5.36. 2.4. synthesis of (e)-2-((3-(ethoxycarbonyl)-5methyl-4-phenylthiophen-2-yl)amino)-4-oxo-4-(ptolyl)but-2-enoic acid 7 to a solution of 2.06 g (0.01 mol) of (z)-2-hydroxy-4-oxo4-(p-tolyl)but-2-enoic acid 3 in 10 ml of ethanol was added 2.61 g (0.01 mol) of a solution of ethyl 2-amino-5-methyl4-phenylthiophene-3-carboxylate 6 in 10 ml of ethanol. аfter the resulting solution had been heated to boiling, it was refluxed. the resulting saturated red solution was kept for 24 hours at –18 °c, then the formed precipitate was filtered off and recrystallized from ethanol (scheme 3). the compound 7 was obtained according to the previously described method [17]. the new mcs and the old mcs were obtained by the same method and repeated after 10 years. red crystals (3.7 g, 82% «old mcs»), (3.6 g, 80% «new mcs»), m.p. 171–172 °с. 1h nmr (cdcl3, 400 mhz) δ (ppm): 0.87 (t, j = 7.1 hz, 3н, me), 2.13 (s, 3h, me), 2.39 (s, 3н, me), 4.00 (q, j = 7.1 hz, 2н, ch2о), 6.58 (s, 1h, c=ch), 7.20 (m, 2h, har), 7.36 (m, 5h, har), 7.92 (m, 2h, har), 12.74 (s, 1н, nh). found, %: c 66.84, h 5.21, n 3.10. c25h23no5s. calculated, %: c 66.80, h 5.16, n 3.12. 2.5. optical experiment the single mcs were placed on a 6.45 cm2 (0.2 mm thickness) glass substrate under normal conditions (in air atmosphere, room temperature, and 30% humidity). the absorption and pl spectra have been measured using a home-made confocal microscope setup [18, 19]. the single crystals have been irradiated by incoherent (halogen light source avalight-hal-s-mini, 300-900 nm spectral range, for absorbance) and coherent light (for pl) via 100x/0.9na mitutoyo objective. for pl measurement, femtosecond laser system (laser pharos ph1-sp-20w, 1030 nm pump, 220 fs pulse duration, 1 mhz repetition rate), associated with an optical parametric amplifier orpheus hp to emit 400, 450, and 500 nm (with 10 nm band width), has been utilized. chimica techno acta 2021, vol. 8(4), № 20218411 letter 3 of 5 scheme 3 synthesis of (e)-2-((3-(ethoxycarbonyl)-5-methyl-4-phenylthiophen-2-yl)amino)-4-oxo-4-(p-tolyl)but-2-enoic acid the pl signal was collected in the reflection regime via the same objective and then analyzed using a confocal raman spectroscopy system horiba labram with 600 g/mm diffraction gratings and a water-cooling camera andor. the absorption spectra a for the single crystals have been obtained in the transmission regime by transmission t spectroscopy (a = 1 − t) under the assumption that signals reflected from the crystal surface and scattered on its defects were small compared with the transmission signal. 3. results and discussion here we demonstrate the synthesis of a highly luminescent mcs based on (e)-2-((3-(ethoxycarbonyl)-5-methyl-4phenylthiophen-2-yl)amino)-4-oxo-4-(p-tolyl)but-2-enoic acid. the photoluminescent (pl) behavior of the old crystal has been verified over 10 years at ambient conditions. we discovered that aging of the crystals is accompanied by a 30 nm red shift of the absorption spectrum, while the shape and pl peaks positions have not changed after 10 years. fig. 1 the absorption spectra for single mcs (a); optical images of the corresponding single mcs and pl images of the corresponding thin films on 1 inch2 glass, excited by 400 nm; scale bars, 100 m (b); pl spectra for mc_new and mc_old compounds excited by 400, 450 and 500 nm with corresponding 0.25, 1.5 and 2 w laser power (c, d) chimica techno acta 2021, vol. 8(4), № 20218411 letter 4 of 5 the observed decrease in pl intensity by 30% can be explained by an enhanced self-absorption effect. also, an analysis of pl signal versus pumping wavelength (400 to 500 nm) showed an increase in efficiency when the aged crystal was excited with a green light. these results pave the way for utilization of new mcs based on (e)-2-((3(ethoxycarbonyl)-5-methyl-4-phenylthiophen-2-yl)amino)-4oxo-4-(p-tolyl)but-2-enoic acid as promising extended-life materials for optical application under normal operating conditions. the optical analysis of the mcs is summarized in fig. 1 in detail. as one can see, aging caused a 30 nm red shift in the absorption spectrum (fig. 1a) and the disappearance of small interference beats for approximately the same mc thickness. this process can be described by a partial violation of the long-range order in the crystal, which can cause an increase in absorption in the red region of the spectrum [20]. however, the shape of the pl spectrum and the positions of the peaks (610 and 660 nm) during aging were found to remain the same. this indirectly indicates both the molecular nature of the pl and the relative stability of the molecules packed in the mcs over time. in this case, the aging process is described by an approximately 30% decline in the integral pl intensity and a relative increase in the red tail by 10% (fig. 1c, d). also, we found that aging of the mcs causes a threefold increase in the intensity of pl excited by 500 nm (blue curves in fig. 1c, d). this effect can be also explained by a red shift of the absorption band and, hence, an increase in the absorption coefficient for the old mc. finally, the pl signal has been stimulated by extremely low laser power (0.25 w for 400 nm, 1.5 w for 450 nm, and 2 w for 500 nm) and observed up to 0.5 mw, confirming the mc structure rigidity with a change in the pump laser power by three orders of magnitude. 4. conclusions as a result, we report on the synthesis of (e)-2-((3(ethoxycarbonyl)-5-methyl-4-phenylthiophen-2-yl)amino)4-oxo-4-(p-tolyl)but-2-enoic acid. this organic compound was then utilized to create new organic molecular crystals in the form of single microcrystals and large scale thin films demonstrating highly efficient and stable photoluminescence at ambient conditions. moreover, the structure 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https://doi.org/10.1038/srep22918 mechanochemical synthesis of intermetallic compounds in the system gallium – ruthenium chimica techno acta article published by ural federal university 2021, vol. 8(1), № 20218104 journal homepage: chimicatechnoacta.ru doi: 10.15826/chimtech.2021.8.1.04 1 of 4 mechanochemical synthesis of intermetallic compounds in the system gallium – ruthenium t.f. grigoreva a* , e.a. pavlov b , p.a. vitiaz c , n.z. lyakhov a a: institute of solid state chemistry and mechanochemistry sb ras, kutateladze st. 18, novosibirsk, 630090, russia b: jsc “zelenyj gorod”, 60 let oktyabrya st. 126, krasnoyarsk, 660079, russia c: joint institute of mechanical engineering of the national academy of sciences of belarus, akademicheskaya st. 12, minsk, 220072, belarus * corresponding author: corresponding_grig@solid.nsc.ru this article belongs to the pcee-2020 special issue. © 2021, the authors. this article is published in open access form under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). abstract the interaction of a solid inert metal ru with liquid active metal ga during mechanical activation in a high-energy planetary ball mill was studied using the x-ray diffraction and the high resolution scanning electron microscopy with energy dispersive x-ray microanalyses. this paper considers mechanical activation effects on formation of intermetallic compounds gaxruy and their solubility in concentrated acids. gallium is a surface-active substance with respect to ruthenium. under intensive mechanical treatment, liquid gallium penetrates into grain boundaries of polycrystalline ruthenium particles and sharply reduces their strength. because of severe mechanical deformation, an intensive increase of contact surface between solid and liquid metals observed, which a place of rapid formation of intermetallic compounds. this processing leads to high reactive products of mechanical activation of ga + ru. their interaction with a mixed concentrated hydrochloric and nitric acid allows ruthenium (~37%) to pass into an acidic solution, forming complex compounds of the hxrucly type (h2rucl6). keywords mechanochemical synthesis intermetallics gallium ruthenium complex compounds of ruthenium received: 28.12.2020 revised: 05.02.2021 accepted: 05.02.2021 available online: 08.02.2021 1. introduction ruthenium is the most chemically and heat-resistant metal of the platinum group metals, so ru is applied as alloys additive for manufacturing turbine blades of jet engines, high temperature parts of missiles, equipment for aircraft devices [1]. a promising area for using ruthenium is solar energy. the ability of ruthenium to bind catalytically atmospheric nitrogen at room temperature is also unique. the alloys of ruthenium with platinum and iridium are used for manufacturing dies in the production of glass fibers and viscose. an efficient approach to obtain ultra-fine high purity metals can be their dissolution in acids with formation of ammonium salts and subsequent reduction. for ruthenium, there is a problem with the dissolution, because this metal does not interact even with highly concentrated acids. it is known that intermetallic compounds (imc) and alloys dissolve faster than their constituent inert metals, especially in case of well-developed interfacial or intergranular surface [2,3]. the conversion of an inert metal into a soluble form becomes possible when one of the components of the imc dissolves easily. this effect is much more pronounced for ultra-dispersed imc, and mechanochemical synthesis is one of the most promising techniques for their production. in systems with interacting solid and liquid metals, the adsorption–active properties of the liquid metal with respect to most hard solid metals were verified [4,5]. penetration of liquid metal along the grain boundaries sharply reduces the strength characteristics of the latter [6–9]. the work of destruction of polycrystalline metal in contact with the melt reduces by hundreds of times, which provides a high rate of formation of a "fresh" (native) surface of a solid metal. due to the high wettability of the solid surface with liquid metal, the contact surface of the solid– liquid metal can reproduce itself permanently, and imc synthesis continues [8,10–12]. from this point of view, it is very likely that the inert ruthenium should chemically interact with the active liquid gallium, since it is known http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2021.8.1.04 http://creativecommons.org/licenses/by/4.0/ http://orcid.org/0000-0002-7264-0862 chimica techno acta 2021, vol. 8(1), № 20218104 article 2 of 4 that ga3ru, ga2ru, and garu are able to form in the ga– ru system at high temperature and pressure. the full equilibrium state diagram of the ga–ru system has not been evaluated yet [13]. the presence of several intermetallic compounds in the ga–ru system is probably due to the negative enthalpy of mixing. in a pair of solid ru – liquid ga (with melting temperature 29.8 °c), the mechanochemical synthesis is possible thanks to formation of large contact surface ru/ga. gallium is highly soluble in acidic solutions [14]. this makes it possible to leach ga from intermetallic compounds gaxruy obtained mechanochemically, thus increasing the ability for ruthenium to dissolve in concentrated acids. analysis of scientific literature data shows that there are no studies of mechanical interaction of platinum satellite metals (ir, ru, rh) with liquid gallium, so this study is relevant. the aim of this is work to study the process of mechanochemical synthesis of intermetallic compounds in the ga–ru system, as well as the acid separation of gallium from synthesized imc in order to convert ruthenium into a soluble form. 2. experimental liquid gallium and ruthenium powder were used to prepare the intermetallics gaxruy. mechanochemical synthesis of intermetallic compounds in the inert solid metal (ruthenium) – active liquid metal (gallium) system was carried out in a high-energy planetary ball mill ago-2. the volume of milling drums was 250 cm 3 . steel balls of 5 mm diameter with total mass 200 g were used to achieve the ball-to-powder ratio 20:1. the rotation speed of the drums around the common axis was 1000 rpm. during milling, drums and balls were cooled with water [15]. to determine the degree of dissolution of the initial gallium and ruthenium, mechanochemically synthesized intermetallic compounds gaxruy, they were treated with a mixture of concentrated acids (60 ml hcl + 20 ml hno3), for three hours, at a temperature of 75 °c. samples of 1 g each were weighed directly in 400 ml glasses with analytical mettler toledo rt 503 balance (weighing accuracy of 0.001 g). separation of insoluble sediments from solutions was carried out in several stages using paper filters with a pore size of 2–3 μm. glass measuring cylinders were used to determine the volume of filtrate and washing water. x-ray phase analysis of the powders was carried out using an xpert-pro diffractometer (cu kα1 radiation, wavelength = 1.54051 å, the 2θ angle range from 3.0131° to 90.91°, step δ2θ = 0.001°). morphological characteristics and elemental composition of the initial ruthenium powder, as well as mechanochemically synthesized gaxruy intermetallides and gaxruy/ru composites, before and after treatment with a mixture of concentrated acids, were obtained on a scanning electron microscope jeol 6601 lv (accelerating voltage 20 kv, magnification up to ×10000) with an energydispersive x-ray microanalyzer (edxa). the error of the elemental content analysis on the edxa was 0.2-0.3 mass. %. 3. results and discussion according to scanning electron microscopy, the initial ruthenium powder consists of primary particles with size within 1–3 μm; round shaped particles form porous agglomerates with the size in between 5 to 20 μm (fig. 1). according to the results of edxa, the ru content is 100%. according to [16,17], for interacting metals an intermetallic compound with the maximum content of fusible metal is first formed on the contact surface. accordingly, in the interacting ga-ru system, some phases with the highest gallium content must be formed first, and when gallium is totally spent the mechanochemical interaction of the imc with ru will start forming intermetallic phases with a lower gallium content (garu) [18]. it can be expected that at the initial stage of the mechanical activation of the ga+ru mixture the bulk gallium will cover the ruthenium particles with an extremely thin layer, forming ga3ru or ga2ru on the contact surface of the compound, since, according to miedema calculations, the mixing enthalpy is about –8 kj/mol [19–21]. these imcs will further interact with ruthenium to form garu. by means of x-ray phase analysis, the products of the chemical interaction of ruthenium with gallium (with molar ratio ga:ru = 1:1) are detected only after 2 minutes of mechanical activation. (fig. 2, curve 1). a noticeable amount of this phase is formed in the mixture when activated for 14 min (fig. 2, curve 2), at the same time a weak diffraction peak appears on the x-ray pattern, which may be due to the formation of garu as a result of the interaction of ga2ru with ruthenium. as the activation time increases up to 20, 34, and 62 min, the newly formed ga2ru is consumed to form garu, resulting in the increasing diffraction peak intensities of secondary phase (fig. 2, curves 3–5). electron microscopic studies showed the small particles of ~0.2–0.5 μm after 2 min of activation (fig. 3, photo a). after activation for 14 min, the sample contains the fig. 1 sem image and particle size of the as received ru powder (×4000) chimica techno acta 2021, vol. 8(1), № 20218104 article 3 of 4 small particles of ~0.2–0.5 μm and agglomerates of different types: dense ~0.5-5 μm and porous (loose) up to 10 μm (fig. 3, photo b). in the sample activated 34 min, there are significantly fewer small particles of ~0.2–0.5 μm, and much more of agglomerates with a wide size distribution from ~0.5 to 5 μm (fig. 3, photo c). according to the edxa, the iron content in the samples increases from 0.5–0.7 to 6–8 wt. % due to the wear contaminations from balls and drums, depending on time of mechanical activation. preliminary experiments showed the starting gallium totally dissolved in a mixture of concentrated acids within 40 min. the highly dispersed ruthenium powder does not dissolve under the above conditions, remaining the same morphological features as the original ruthenium (figs. 1 and 4). it was found that the amount of ruthenium in a mixture of concentrated acids increases with the increase in the content of intermetallic compounds in mechanocomposites obtained. so, after 20 min of mechanical activation it was 27.09 wt.%, after 34 min the value increased to 36.78 wt. %. the insoluble precipitate after ma for 34 min is an ultrafine powder with an average particle size of less than 0.5–0.6 μm (fig. 5). we can expect that ruthenium is oxidized to form a complex acid hxrucly in the course of transition from a mechanocomposite to an acidic solution. 30 40 50 60 70 80 90    ru [6-663]  ga 2 ru: [23-261]  garu [17-440]                  in te n s it y , a rb . u n . 2 theta, degree 1 2 3 4 5                  fig. 2 x–ray patterns of the products of mechanochemical interaction of ru with ga in depending on the duration of mechanical activation (min): 2 (1), 14 (2), 20 (3), 34 (4), 62 (5). a b c fig. 3 sem images of the products of mechanochemical interaction of ru with ga depending on the duration of mechanical activation (min): 2 (a), 14 (b), 34 (c). fig. 4 sem image of the insoluble precipitate particles of the original ru powder after treatment with acid mixture (×6000) fig. 5 sem image of the insoluble precipitate obtained from ru– ga intermetallic (ma for 34 min) after treatment with concentrated acid mixture (×7000) chimica techno acta 2021, vol. 8(1), № 20218104 article 4 of 4 4. conclusions for metallic systems with platinum satellite metals, the example of the ru-ga system shows that the problem of converting chemically inert ruthenium into a soluble form can be solved by mechanochemical synthesis of intermetallic compounds ru with liquid ga and subsequent extraction of gallium into acidic solutions. being a surface-active substance in relation to ruthenium, liquid gallium penetrates into grain boundaries of polycrystalline ruthenium particles, which strongly reduces their strength. there is an increase in the contact surface between solid ruthenium and liquid gallium, which leads to the active formation of intermetallic compounds. it is shown that chemically active gallium passes from intermetallic to solution when treated with a mixture of concentrated acids hcl and hno3, while the reactivity of ruthenium increases and more than 36.7% of ruthenium passes into a soluble form. acknowledgments 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the influence of a silanol cover on the protolytic properties of aminopropyl silica gels 222 d o i: 1 0. 15 82 6/ ch im te ch .2 02 0. 7. 4. 15 filisteev o. v., sharov a. v. chimica techno acta. 2020. vol. 7, no. 4. p. 222–228. issn 2409–5613 to the question of the influence of a silanol cover on the protolytic properties of aminopropyl silica gels o. v. filisteev*, a. v. sharov kurgan state university 63 sovetskaya st., kurgan, 640020, russia *email: filisteev@kgsu.ru abstract. the paper proposes a model that describes the acid-base properties of amino groups grafted onto the surface, taking into account their interaction with silanol groups. for this, aminopropyl silica was chosen as an object with well-studied methods of preparation, structure and properties. the isotherms of sorption of hydrogen ions on aminopropyl silica were obtained by potentiometric method. the experimental points were analyzed numerically, taking into account the presence of an electric double layer, the presence of surface processes competing with the sorption of hydrogen ions, and the peculiarities of the behavior of silanol groups when the degree of surface filling with hydrogen ions changes. the resulting model makes it possible to carry out a preliminary calculation of the sorption of hydrogen ions on the surface of aminopropyl silica. keywords: functionalized sorbents; aminopropyl silica; protolytic properties; curves of potentiometric titration of sorbents received: 03.11.2020. accepted: 09.12.2020. published:30.12.2020. © filisteev o. v., sharov a. v., 2020 introduction to  describe the  reactivity of  the  surface groups of  sorbents, many numerical algorithms for the  analysis of complexation on the surface are used. they are based on the numerical solution of equations that make it possible to calculate the experimentally determined characteristics of surface equilibria. the equations are usually solved with respect to the values of the equilibrium constants. in addition to them, the roots of the equation can be other parameters of the system (capacity of des, the proportion of certain groups from the total concentration, etc.). in this case, it is possible to use models that take into account des (the theory of complexation on the surface, including the guy-chapman and stern models, the cd–music model [1–5], and those operating without taking into account des (models of chemical reactions, distribution of groups by equilibrium constants [6–9]). common materials, most often obtained by surface modification, are sorbents containing basic nitrogen [10, 11]. nitrogencontaining groups often interact with acidic groups on the surface, which makes it difficult to quantitatively analyze their acid-base and complexing properties. in such cases, the  equilibrium constants with the  participation of nitrogen-containing groups are conditional with respect to the content of  interfering groups. a  typical example is the acid-base and complexing properties on the surface of various types of aminosilicas. the presence of acidic silanol groups 223 leads to  the  fact that the  experimentally determined constants are significantly lower than the  tabulated ones for structures similar to those present on the surface. the processes of interaction of surface groups with each other lead to different interpretations of the initial data, depending on the model used: the presence of several types of nitrogen-containing groups, different in the energy of sorption interaction with ions in solution, the presence of interactions of nitrogen-containing groups with each other, etc. [6, 8, 11–13]. at the same time, a model of the interaction of basic nitrogen-containing groups with acidic ones on the surface has not yet been constructed. the available models require the involvement of a significant amount of preliminary obtained experimental data [14]. the presence of such a model would allow a preliminary calculation of the sorption properties of materials with the properties described above. in  this work, we propose a  variant of  describing the  interactions of  amino groups and silanol groups on the surface of aminopropyl silica gels during the adsorption of  hydrogen ions from a  solution. the model takes into account the effect of the diffusion double layer, as well as the direct chemical interaction of amino and silanol groups. experimental aminopropyl silicas were chosen as test objects as  materials with well-studied methods of  synthesis, surface structure, and acid-base properties [8]. for the synthesis of  aminopropyl silicas, industrial silica gels kskg and ksmg were used. silica gels were preliminarily crushed and divided into fractions by  sieving (used fraction 0.25–0.5 mm). the particles were separated from the dust by repeated washing in distilled water. before inoculation, the silica gels were heated at a temperature of  150 °с  to  constant weight. the  grafting of aminopropyl groups was carried out by impregnation of silica gels in solutions of  3-aminopropyltriethoxysilane (acros organics) in  anhydrous toluene [15]. to obtain samples with different surface concentration of amino groups, different temperatures and contact times were used. the  impregnation time was varied from 20  min to  24  hours, the  temperature  — from room temperature to 60 °c. the  moisture content of  the  samples was determined by  heating at  150  °c to  constant weight using an  automatic sartorius analyzer. the  specific surface area was determined by  the  multipoint bet method from nitrogen sorption isotherms at –196 °c on a sorbi ms analyzer. the  surface concentration of  aminopropyl groups was determined by the kjeldahl method. the  curves of  potentiometric titration of  the  samples were recorded using the  method of  one sample as  follows. a  weighed sample with a  known moisture content of  about 0.3  g, weighed on an  analytical balance, was mixed with 30 ml of a 0.1 m potassium chloride solution. the  cell with the  suspension was placed in  a  thermostat with a  temperature of  25  °c.  titration was carried out with 0.0500 m hydrochloric acid solution (fixanal). the indicator system was a glass electrode and a  silver chloride reference electrode. the measurement of ph up to 3 decimal places was carried out on an “expert 001” ionomer. the  time to  reach equilibrium after adding each portion of the titrant is not less than 15 minutes. equilibrium at each point was considered 224 to  be achieved if the  ph did not change within 5 min by more than 0.002 units. processing of experimental curves the  obtained experimental points were transformed into the  dependence of the surface charge on ph. the surface charge was calculated using eq. (1). ( )h e k h f c sc + + ‑   σ = (1) here σe is the surface charge calculated from the experimental data, c/m2; h c +  — total concentration of  hydrochloric acid in solution, mol/l; [h+] — concentration of hydrogen ions in solution, mol/l; s — specific surface area, m2/g; ck — concentration of silica suspension, g/l. the  concentration of  hydrogen ions in the solution was calculated from the ph values, taking into account the activity coefficients of hydrogen ions in the solution. when analyzing the  experimental points, the following surface chemical processes were taken into account. –nh2s + h + s = –nh3 + s (2) ≡siohs = ≡sio – s + h + s (3) the ‘s’ index indicates that the particles belong to the surface layer. from the charge balance condition, it follows that the  surface charge σ, calculated from the concentration of particles determining the charge, can be expressed by eq. (4): ( )s snh sio–3 – k f sc +   σ = ‑ ≡    (4) equilibrium concentrations of ammonium groups and deprotonated silanols were calculated based on the material balance conditions: [ ]nh s s snh nh2 2 3–c + ‑  = ‑ +   (5) [ ]siohs s ssioh sio–c≡  = ≡ + ≡  (6) where nh s2 c‑ and siohsc≡ are the total concentration of  surface amino groups and silanol groups, respectively. taking into account eqs. (5) and (6), expression (4) takes the form: nh s siohs k s s s h h 2 1 1 1 c cf sc k k ‑ ≡ + +       σ = ‑    + +     (7) in  eq.  (7), k and ks are the  equilibrium constants of eq. (2) and (3), respectively. the transition from the concentration of hydrogen ions in the surface layer to the concentration in the bulk of the solution was carried out using the well-known equation: sh h 0 , f rte ψ ‑ + +   =    (8) where ψ0 is the potential in the zero plane relative to the solution volume. it was determined through the equation of the diffuse des model: sinh0.1174 , 2 f i rt ψ σ = ‑ (9) where ψ is the potential of the beginning of the  diffuse layer, which is  taken to  be equal to the potential ψ0 [16]. eqs. (8) and (9) were substituted into (7), yielding the simplified expression: e 2 1 0 ( ) n i iis n = σ ‑σ = ∑ (10) in  eq.  (10), σei and σi are the  surface charges calculated by using eq. (1) and (7), respectively, and n is  the  number of  experimental points. numerical minimization was performed using the built-in tools 225 of  mathematica 10 software package. the  chosen parameter for minimization in all cases was the constant k. the acidity constant of  silanol groups, 7.67, was taken from [14]. the total concentration of  silanol groups, siohsc≡ , participating in the process is difficult to determine experimentally. therefore, this value was also an adjustable parameter during minimization. the evaluation of the results of minimization was also carried out according to the value of s0. results and discussion when choosing k and siohsc≡ by minimizing eq. (7), the following results were obtained. the  logk grows to  the  values in the range of 9.9–10.32 in comparison with conditional constants determined without taking into account the influence of silanol groups. in this case, the s0 distribution over the values of the surface concentration is observed, shown in fig. 1a. the shape of the points indicates an increase in  the  deviation of  the  calculated from the experimental points with an increase in  the  surface concentration (not a random nature of the distribution of s0 on the  nh s2 c‑ scale). fig. 1b shows examples of approximation of experimental points of charge versus ph dependence. for low concentrations of grafted groups, the deviation is not very significant. it is seen that the greatest deviation at high concentrations of amino groups is observed at low degrees of surface coverage with hydrogen ions. thus, eq. (7) is not suitable for fitting the points of titration curves. the non-random nature of the distribution of points in fig. 1a speaks of a regularity that we did not take into account when calculating. we assumed that an increase in the degree of saturation of the surface of  aminosilica with hydrogen ions leads to  a  change in  the  total surface concentration of silanol groups siohsc≡ , involved in process (2). in this case, the constancy of the constants of protonation of amino groups and acid dissociation of  silanol groups is postulated. to  reveal the  type of  dependence of the total concentration of silanol groups on the  degree of  titration of  the  surface from eq.  (7) with eqs. (8) and (9) subfig. 1. dependence of s0 values on the surface concentration of amino groups (a); examples of approximation of experimental points by eq. (7) (b): 1 — sample with nh s2c‑ = 0.67 μmol/m 2, 2 — sample with nh s2c‑ = 3.33 μmol/m 2 226 stituted there, we expressed siohs .c≡ we used different values of logk in the vicinity of the propylamine protonation constant in solution: logk = 9, 10 or 11. substituting the experimental values [h+] into the resulting equation, the desired dependence was obtained. examples of  the  obtained dependences are shown in fig. 2. for all samples in  the  range of  total hydrogen ion concentrations used by us, the dependences have a linear form. based on this, siohsc≡ in eq. (7) can be expressed as siohs ,bc a x≡ = + (11) where x is  a  parameter associated with the course of the titration process (titrant volume, total concentration of hydrogen ions), a and b are parameters selected for the  numerical minimization of  eq.  (7). the  approximation results are shown in fig. 3. the  curves in  fig.  3 indicate in  favor of the fact that the model used by us satisfactorily describes the  protonation of aminopropyl silicas with allowance for the  effect of  silanol groups on the  surface. the  mean value of  the  logarithm of the protonation constant is 10.55, which is  close to  the  thermodynamic constant of protonation of propylamine in an aqueous solution (logk = 10.5 [17]). comparison of  the  a  constant with the  concentration of  amino groups on the  surface indicates that a is equal to the concentration of grafted amino groups. thus, the interaction of  amino groups with silanol groups in a 1:1 ratio is confirmed within the framework of this model. the average value of  the  b constant is  –0.0014. most likely, its value corresponds to  the  rate of  decrease in  the  equilibrium concentration of amino groups with an increase in the degree of titration. from the  point of  view of  equilibria in  solutions, the  thesis of  a  decrease in the total concentration of one of the participants in  the  process does not stand up to criticism. however, on the surface of a solid, the groups are localized at specific points on the surface. the transformation of  an  amino group into an  ammonium one leads to  the  disappearance of  its interaction with silanol ones. accordingly, the  assumption of  a  decrease in the total number of silanol groups parfig. 2. examples of obtained siohs hcl( )f vc≡ = dependences fig. 3. approximations of surface charge points calculated from experimental data by calculated lines: 1 — nh s2 c‑ = 0.65 μmol/m 2, 2 — nh s2c‑ = 0.90 μmol/m 2, 3 — nh s2c‑ = 1.51 μmol/m 2 227 ticipating in equilibrium with an increase in the number of protonated amino groups seems logical. a change in the concentration of silanol groups during the process is equivalent to a different effect of silanol groups on amino groups that are unevenly distributed over the surface. the  model described in  the  work allows one to  carry out a  preliminary calculation of the isotherms of the sorption of hydrogen ions on aminosilica. for this, the  ionization constant of  propylamine in  an  aqueous solution and the  concentration of aminopropyl on the surface are used. the only empirical parameter is the b constant. conclusions our proposed model for describing protolytic equilibria is  based on the  following theses: 1. the process of protonation of amino silica is described using models of complexation on the surface, taking into account the effect of the electric double layer. 2. silanol surface groups are direct participants in  proton exchange processes. amino groups on the surface are capable of deprotonating silanol groups. to take into account the influence of silanol groups, the equations of charge balances and material balance are used. 3.  the  total concentration of  silanol groups involved in the process decreases during the process. references 1. davis ga, kent db. surface 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in nacl media: a cd–music model interpretation of combined experimental and density functional theory studies. langmuir. 2013;29(27):8572–83. doi:10.1021/la4011955 6. kholin yuv. kolichestvennyy fiziko-khimicheskiy analiz kompleksoobrazovaniya v rastvorakh i na poverkhnosti khimicheski modifitsirovannykh kremnezemov: soderzhatel’nyye modeli, matematicheskiye metody. khar’kov: folio; 2000. 290 p. russian. 228 7. khristenko iv, kholin yuv. the greement of the results of quantitative physicalchemical analysis and probing surfaces of aminosilicas by reichardt’s solvatochromic betaine indicators. kharkov university bulletin. 2007;13(38):245–50. 8. kobylinskaya ng, zaytsev vn. izucheniye protoliticheskikh svoystv kremnezemov, modifitsirovannykh 8-aminometilkhinolinom [study of the modified with 8-aminomethylquinoline silicas protolytic properties]. trudy odesskogo politekhnicheskogo universiteta. 2006;1(25):231–6. russian. 9. barkauskas j, dervinyte m. an investigation of the functional groups on the surface of activated carbons. j. serb. chem. soc. 2004;69(5):363–75. doi:10.2298/jsc0405363b 10. chen l. c., peng p. y., lin l. f., yang t. c., huang c. m. facile preparation of nitrogen-doped activated carbon for carbon dioxide adsorption aerosol air qual. res. 2014;14(3):916–27. doi:10.4209/aaqr.2013.03.0089 11. zaytsev vn. funktsionalizirovannyye materialy. tom 1. kompleksoobrazuyushchiye kremnezemy: sintez, stroyeniye privitogo sloya i khimiya poverkhnosti. seriya monogr. pod red. akad. v. v. skopenko [functionalized materials. volume 1. complexing silicas: synthesis, graft structure and surface chemistry. monogr. ed. acad. v. v. skopenko]. khar’kov: folio; 1997. 240 p. russian. 12. zhu m, lerum mz, chen w. how to prepare reproducible, homogeneous, and hydrolytically stable aminosilane-derived layers on silica. langmuir. 2012;28(1):416–23. doi:10.1021/la203638g 13. bol’bukh yun. vysokodispersnyye kremnezemy s binarnymi aminometil’nymi i kremniygidrometil’nymi modifitsiruyushchimi sloyami [highly dispersed silicas with the binary aminomethyl and silicon-hydromethyl modifying layers]. nanostrukturnoye materialovedeniye. 2011;(2):44–61. russian. 14. sharov av, morozova tv, kovyatkin yav, filisteev ov. kolichestvennoye opisaniye vliyaniya silanol’nogo pokrova na kislotno-osnovnyye svoystva 3-aminopropilsilikageley [quantitative description of silanol cover influence on the 3-aminopropyl silica acid-base properties]. sorbtsionnyye i khromatograficheskiye protsessy. 2015;15(2):243–50. russian. 15. koopal lk, yang y, minnaard aj, theunissen plm, van riemsdijk wh. chemical immobilization of humic acid on silica. colloids surf. a. 1998;141(3):385–95. doi:10.1016/s0927-7757(97)00170–2 16. vlasova nn. sravneniye modeley kompleksoobrazovaniya na poverkhnosti dlya kolichestvennogo opisaniya kislotnykh svoystv vysokodispersnogo kremnezema [a comparison of surface complexation models for quantitative description of acidic properties of fumed silica]. khimiya, fizika i tekhnologiya poverkhnosti. 2008;14:6– 15. russian. 17. nikolsky bp, editor. spravochnik khimika [chemist’s handbook]. vol 3. leningrad (ussr): khimiya; 1965. 1008 p. russian. synthesis and research of polyfunctional silylureas used in electric deposition of tin-indium alloy chimica techno acta letter published by ural federal university 2021, vol. 8(3), № 20218305 eissn 2411-1414; chimicatechnoacta.ru doi: 10.15826/chimtech.2021.8.3.05 1 of 5 synthesis and research of polyfunctional silylureas used in electric deposition of tin-indium alloy k.yu. ivanova * , m.v. kuzmin , l.g. rogozhina , a.o. patianova , v.l. semenov , r.i. alexandrov chuvash state university named after i. n. ulyanov, 428015, moskovskii pr., 15; cheboksary, russia * corresponding author: cool.karakyrt@ya.ru this short communication (letter) belongs to the regular issue. © 2021, the authors. this article is published in open access form under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). abstract polyfunctional silylureas were synthesized by the interaction of 3-aminopropyltriethoxysilane with isocyanates of various structures in an inert aromatic solvent. commercially available diisocyanates such as isophorone diisocyanate, hexamethylene diisocyanate, 2,4-toluene diisocyanate were used as isocyanates. in this case, freshly distilled toluene was used as a solvent. the structures of the obtained compounds were confirmed by the data of ir and nmr 1 h spectroscopy. using the synthesized compounds, formulations of compositions for electrodeposition of a tin-indium alloy on a copper wire were developed. the possibility of using silylureas of various structures as effective surfactants used in the electrodeposition of the tin-indium alloy is shown. the operational characteristics of the obtained wire were investigated, including the wire diameter, coating thickness, tensile strength, electrical resistance, and direct current electrical resistivity. keywords isophorone diisocyanate hexamethylene diisocyanate 2,4-toluene diisocyanate 3-aminopropyltriethoxysilane polyfunctional silylureas electrodeposition indium-tin alloy copper wire electrode solar panels received: 29.06.2021 revised: 28.08.2021 accepted: 31.08.2021 available online: 13.09.2021 1. introduction one of the most important tasks of increasing the efficiency of photovoltaic solar modules is the search and development of new electrodes that provide high reliability of contact with crystalline silicon, as well as charge transfer in the cell [1]. copper wire coated with various alloys, which is currently one of the main materials in electrical engineering, is widely used as conductive electrodes [2]. the use of such a wire ensures the reliability and protection of solar modules from any external influences and, as a result, the indicator of the durability of the product itself increases [3]. the use of a low-melting alloy on the surface of a copper wire makes it possible to obtain reliable electrical contact with a silver-containing contact grid, which helps to reduce the ohmic resistance between photovoltaic cells [4]. as a rule, wire coating is performed by electroplating or hot dipping [5]. the continuity of the contact of the electrode with monocrystalline silicon directly depends on the quality of the surface of the copper wire and the adhesion strength of the coating to the copper base, which ultimately affects the efficiency of transferring the converted light energy into electricity [6]. to obtain a microscopic adhesive layer of a copper wire coating, electrodeposition of a tin-indium alloy in various electrolytes can be used, but it is impossible to predict the effect of technological additives on the properties of the resulting coating; therefore, in most cases, the electrolyte composition is selected experimentally [6]. for the electrodeposition of the tin-indium alloy acidic and alkaline electrolytes are used. of acidic electrolytes the following are used: perchlorate, sulfamic, chloride, glycerol, sulfate, boron fluoride electrolytes and others [7]. in the electrical and radio engineering industry, contact-reactive soldering with low-melting eutectic solders based on tin with indium and cadmium is widely used. existing electrolytes based on sn 2+ salts have low stability, even in the presence of special organic additives [8]. at the same time, there is information in the literature on the successful coprecipitation of tin with indium from acidic and alkaline electrolytes based on sn 4+ salts [9], the stability of which is provided by oxyacids. the presence in the electrolyte of a hydroxy acid, for example citric acid, increases the content of the electronegative component of http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2021.8.3.05 http://creativecommons.org/licenses/by/4.0/ https://orcid.org/0000-0001-5982-0570 https://orcid.org/0000-0003-3880-9510 https://orcid.org/0000-0001-6014-3642 https://orcid.org/0000-0002-9785-4058 https://orcid.org/0000-0002-9869-6602 https://orcid.org/0000-0002-8335-9996 chimica techno acta 2021, vol. 8(3), № 20218305 letter 2 of 5 the alloy [10, 11]. to develop a stable, reproducible and controlled technological process for obtaining eutectic composition solders from electrolytes based on sn 4+ salts, information is needed on the mechanism and kinetics of the joint discharge of alloy-forming metal ions. the aim of the work was to increase the adhesion strength of the tin-indium alloy coating on a copper wire by using polyfunctional silylureas that meet the existing requirements for the production of electrodes for solar modules. it is known that organosilicon compounds are surfaceactive, they can increase the intensity of biological processes of oxidation of organic pollution of wastewater and thereby reduce the anthropogenic load on the environment [12, 13]. 2. experimental in this work, we synthesized organosilicon compounds polyfunctional silylureas, which make it possible to increase the affinity of copper wire coated with a tin-indium alloy, improve the spreading of the solder, ensure the necessary activity of the composition, increase the contact angle with the surface during electrodeposition, reduce the surface tension and eliminate the oxidation of the solder surface and a base material to be electrodeposited. silylureas i-iii received the interaction of 3-aminopropyltriethoxysilane with isocyanates of various structures in the presence of an antioxidant and toluene as a solvent at a temperature of 17-20 °c, while 2,4-toluene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate were used as isocyanates of various structures. fig. 1 shows a general scheme for the interaction of 3aminopropyltriethoxysilane with diisocyanates. the data on yields, melting points and confirmation of the structures of polyfunctional silylureas are given in table 1. ir spectra were obtained on ft-801 series spectrophotometer in liquid paraffin. 1 h nmr spectra were recorded on a bruker drx500 spectrometer (500.13 mhz) in dmsod6, the internal standard was tetramethylsilane. mass spectra were recorded on a finnigam mat incos-50 instrument (ionizing electron energy 70 ev). in the ir spectra of the obtained products, absorption bands are observed at 3309-3317, 1621-1632, 15621570 cm -1 , characteristic of nhc(o)nh groups and at 1072-1074 cm -1 si-o bonds. in the 1 h nmr spectra, there are characteristic signals belonging to the protons of the following groups (, ppm): 0.50-0.56 t (ch2ch2ch2si), 1.39-1.47 m (ch2ch2ch2si) and at 2.94-3.04 m (nhch2ch2ch2si). the protons of the urea group correspond to signals at 6.52 t and 8.22 s for compound (i) and 5.69-5.71 t and 5.76-5.78 t, for compounds (ii) and (iii), respectively. silylureas are crystalline substances that melt without decomposition. 3. results and discussion at the next stage, tin-plated copper wires were obtained with the poin-52 grade sn-in alloy, which is used as a solder in electrical engineering. it is produced according to tu 48-0220-40-90. the wire thickness is 250 μm, the coating thickness is from 3-5 μm, which is applied by hot tinning. electrolyte formulations have been developed using synthesized polyfunctional silylureas. the container for electrolyte preparation was filled by three quarters with distilled water, and sulfuric acid was added to it in small portions. then the solution was cooled to 20-22 °c, and the required amount of tin (ii) sulfate was added to it and vigorously stirred to dissolve it. as-obtained solution was filtered. then indium (iii) sulfate was added to the filtrate and stirred until complete dissolution. next, silylureas (iiii) (as surfactants to increase the affinity of the copper substrate with the alloy), previously dissolved in a small amount of isopropyl alcohol, were added to the solution, (c2h5o)3si nh2 r ncoocn+ r nhnh c c o o nh nh(c2h5o)3si si(oc2h5)3 iiii 2 h3c h3c h3c ch3 ch2 ch2 ch2 ch2 ch2 ch2 r= , , i ii iii fig. 1 interaction of 3-aminopropyltriethoxysilane with diisocyanates chimica techno acta 2021, vol. 8(3), № 20218305 letter 3 of 5 table 1 ir, nmr 1 h spectroscopy data and properties of polyfunctional silylureas name reaction yield, % tm, °с ir spectroscopy, сm -1 nmr spectroscopy, , ppm 2,4-toluylenebis[n-3(triethoxysilyl)propyl]urea (i) 94.1 135 ν 3309 (nh),  1632 (с=о amide i),  1562 (nh amide ii), ν 1072 (si-o), ν 1610 (arh),  765 (arh) 0.56 m (4h, 2ch2si), 1.15 m (18h, 6 ch3ch2о, 3 jhh 7), 1.47 m (4h, 2ch2ch2ch2si), 2.08 s (3h, ch3), 3.04 m (4h, 2 nhch2ch2ch2si, 3 jhh 6.8), 3.75 m (12h, 6 ch3ch2о, 3 jhh 7), 6.52 t (2н, 2 nhc(о)nh c6h3, 3 jhh 5.6), 7.11 d, 7.45 d, 7.70 s (3h, c6h3), 8.22 s (2н, 2 nhc(о)nh). m 616.89. 1,6-hexamethylenebis[n-3(triethoxysilyl)propyl]urea (ii) 95.9 122 ν 3312 (nh),  1691 (с=о amide i),  1570 (nh amide ii), ν 1072 (si-o) 0.50 t (4h, 2ch2si, 3 jhh 8.45), 1.14 t (18h, 6 ch3ch2о, 3 jhh 7), 1.22 m (4h, 2ch2), 1.33 m (4h, 2ch2), 1.39 m (4h, 2ch2ch2ch2si), 2.94 m (2 nhch2ch2ch2si, 2nhch2, 3 jhh 6.8), 3.73 k (12h, 6ch3ch2о, 3 jhh 7), 5.71 t, 5.76 t (4н, 2nhc(о)nhch2, 3 jhh 5.6). m 610.93. isophoronbis[n-3(triethoxysilyl)propyl]urea (iii) 94.3 171 ν 3317 (nh),  1624 (с=о amide i),  1563 (nh amide ii), ν 1070 (si-o) 0.51 m (4h, 2ch2si), 0.88-1.07 m (17h, 3 ch3, ch2, c6h6), 1.14 t (18h, 6 ch3ch2о, 3 jhh 7), 1.39 m (4h, 2ch2ch2ch2si), 2.94 m (4h, 2 nh ch2ch2ch2si), 3.43 k (1н, chcycle), 3.74 k (12h, 6 ch3ch2о, 3 jhh 7), 5.69 t, 5.78 k (4h, 2 nhc(о)nh ). m 636.97. 1,2-propylene glycol and the remaining amount of isopropyl alcohol were added to a predetermined level. co-deposition of sn-in occurs electrochemically using the following deposition mode: temperature, °c 18-35; cathode current density, a/dm 2 0.5-7.0; current output, % 80-98; the content of indium in the alloy, wt% 40.0-52.0. measurement of the wire diameter, its deviation and ovality, the degree of alignment was carried out according to gost 12177 using a video measuring system nvm2010d. the determination of the thickness and composition of the coating was carried out in accordance with gost 9.302 using an x-strata 920 x-ray fluorescence analyzer of coatings. the determination of the density was carried out by hydrostatic weighing. determination of tensile strength, yield strength, and relative elongation at breaking of the wire were carried out in accordance with gost 10446 using an optical non-contact video extensometer m-view and on a tensile testing machine rkm-1.1. the determination of the specific and electrical resistance was carried out according to gost 7229. the adhesion strength of the adhesion of the coating of the tin-indium alloy with the copper base was studied by examining the coated wire after twisting with using the video measuring system nvm-2010d. tables 2 and 3 show the comparative characteristics of the developed electrolyte compositions, the properties of the electrolyte compositions of copper wire coated with a tin-indium alloy and the modes of its electrodeposition. table 2 electrolyte compositions for the production of copper wire coated with tin-indium alloy components, g / l compositions prototype 1 2 3 tin sulphate (in terms of metal) (ii) 2-15 17 17 17 indium sulfate (in terms of metal) (iii) 5-30 20 20 20 sulfuric acid 90-100 80 85 80 laureth 9 1-2 2,4-toluylenebis [n-3-(triethoxysilyl)propyl] urea (i) 1 1,6-hexamethylenebis [n-3-(triethoxysilyl)propyl] urea (ii) 1 isophoronbis [n-3-(triethoxysilyl)propyl] urea (iii) 1 isopropyl alcohol 10 10 10 formalin (37% solution) 5-7 1,4-butanediol (35% solution) 10-15 propane-1,2-diol 20 25 15 chimica techno acta 2021, vol. 8(3), № 20218305 letter 4 of 5 table 3 properties of coatings obtained by electrodeposition of a tin-indium alloy properties compositions prototype 1 2 3 cathode current density, a/dm 2 0.5-7.0 20.0 20.0 20.0 temperature, ° c 15-30 18 18 18 alloy current output, % 37-97 87 85 80 indium content in the alloy,% 0.5-56.0 41.0 42.0 40.0 appearance of coatings shiny smooth shiny surface and continuous coating along the entire length of the wire leveling degree 0.20-0.60 0.85 0.80 0.80 adhesive strength test + + + wire diameter, μm 250 250 250 coating thickness, microns 6 0.1 0.1 0.1 coating density, g / cm 3 8.9 8.9 8.9 tensile strength of wire, n/ mm 2 242 238 240 relative extension, % 23 24 21 dc electrical resistance at 20 °с, ohm / m 0.35 0.35 0.35 specific electrical resistance for direct current at a temperature of 20 °с, ohm mm 2 / m 0.0172 0.0174 0.0176 as can be seen from tables 2 and 3, the copper wires obtained by this method with a coating based on a tinindium alloy from the proposed electrolyte have a smooth shiny surface and a continuous coating with a thickness of 0.1 – 1.0 μm along the entire length of the wire, strong adhesion to a copper base and the presented modes of electrodeposition can be used to obtain a microscopic adhesive layer of a copper wire coating based on a tinindium alloy. 4. conclusions polyfunctional silylureas were synthesized via the interaction of 3-aminopropyltriethoxysilane with isocyanates of various structures, which were used as active surfactants in the electrodeposition of a tin-indium alloy. the qualitative and quantitative composition of the electrolyte for the electrodeposition of the tin-indium alloy on copper wire and the production of electrodes for solar modules was selected based on the use of effective modifiers that increase the adhesive strength of the coating on a copper substrate. it was found that the synthesized polyfunctional silylureas increase the affinity of copper wire coated with a tin-indium alloy and, consequently, the binding power and adhesive strength. the use of the developed electrolyte with the polyfunctional silylureas in the electrodeposition of a tin-indium alloy on a copper wire makes it possible to obtain an electrode for solar panels with high physical, mechanical and operational properties. acknowledgments the research was carried out in chuvash state university within the implementation of a comprehensive project under the contract no. 2019/0837/1202–19 dated september 19, 2019 with the financial support of the ministry of education and science of russia under the agreement no. 075-11-2019-047 dated november 25, 2019 and russian foundation for basic research (rfbr), project number 20-33-90269. references 1. prospects for energy technologies 2008. scenarios and strategies until 2050 [internet]. international energy agency. oecd / iea, 2008. p. 10-15 [cited 29.07.2021]. available from: https://iea.blob.core.windows.net/assets/0e190efbdaec-4116-9ff7-ea097f649a77/etp2008.pdf 2. lobanov ml, kardonina ni, rossina ng, yurovskikh as. zashchitnye pokrytiya : uchebnoe posobie [protective coatings: textbook]. yekaterinburg: ural federal university publishing house; 2014. p. 87-89. russian. 3. 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voprosy ekologii v galvanotekhnike i proizvodstve pechatnykh plat» [book of abstracts of “progressive technology and environmental issues in electroplating and printed circuit board production” conference]. penza: dntp, 2000. p. 48-49. russian. 7. fursova nyu. elektroosazhdeniye splava sn-sb iz sulfata elektrolity s organicheskimi dobavkami [electrodeposition of sn-sb alloy from sulfate electrolytes with organic additives] [dissertation]. moscow: mendeleev university of chemical technology, 2000. 146 p. russian. 8. kryvtsov ak, khamaev va, gryaznova gi, pavelyeva la, karabinov yuv, inventors. elektrolit dlya osazhdeniya pokrytiy iz splava olovo-indiy. ussr patent su 865997 a1. 23 sep 1981. russian. 9. perelygin yup. elektroosazhdeniye indiya i splavov na ego sonove. raspredeleniye toka mezhdu sovmestnymi reaktsiami vosstanovleniya ionov na katode [plating indium and its alloys. current distribution between joint recovery reactions of ions reduction at the cathode] [dissertation]. moscow: mendeleev university of chemical technology. 1996. 235 р. russian. 10. kotov vl, gryaznova gl, chuvilyaeva tv, kryvtsov ak. izvestiya vysshikh uchebnykh zavedeniy seriya “khimiya i khimicheskaya tekhnologiya”. 1985;28(9):70-73. russian. 11. belevskiy ss. indutsirovannoe soosazhdenie nanokristallicheskikh co-w pokrytiy i ikh mekhanicheskie svoystva [induced coprecipitating of nano-crystalline co-w coatings and their mechanical properties] [dissertation]. chisinau: institute of applied physics; 2012. 142 p. russian. 12. patianova ao, ivanova kyu, rogozhina lg, kuzmin mv, semenov vl. improving the environmental production of electrodes for solar panels. chimica techno acta. 2020;7(4):186– 191. doi:10.15826/chimtech.2020.7.4.09 13. ivanova kyu, kuzmin mv, kol’tsov ni. synthesis and research of polyfunctional siliconcontaining amines new promoters of adhesion. chimica techno acta. 2020;7(4):199–203. doi:10.15826/chimtech.2020.7.4.11 https://doi.org/10.15826/chimtech.2020.7.4.09 https://doi.org/10.15826/chimtech.2020.7.4.11 improved method for the obtaining dtta-appended 2,2’-bipyridine ligands for lanthanide cations chimica techno acta letter published by ural federal university 2022, vol. 9(2), no. 20229210 eissn 2411-1414; chimicatechnoacta.ru doi: 10.15826/chimtech.2022.9.2.10 1 of 4 improved method for the obtaining dtta-appended 2,2’-bipyridine ligands for lanthanide cations dmitry s. kopchuk ab , alexey p. krinochkin ab * , мaria i. valieva ab , ekaterina s. starnovskaya аb , yaroslav k. shtaitz a , svetlana s. rybakova a , evgeny d. ladin a, ekaterina a. kudryashova a , elvira r. sharafieva aс, оleg n. chupakhin ab a: institute of chemical engineering, ural federal university, ekaterinburg 620009, russia b: postovsky institute of organic synthesis, ural brunch of russian academy of sciences, ekaterinburg 620990, russia c: ural state medical university, ministry of healthcare of the russian federation, ekaterinburg 620028, russia * corresponding author: a.p.krinochkin@urfu.ru this paper belongs to a regular issue. © 2022, the authors. this article is published open access under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). abstract the composition of the reaction mixture after dtta tert-butyl ester alkylation with 6'-halomethyl-5-phenyl-2,2'-bipyridines was studied. in addition to the target product, dtta-appended 2,2’-bipyridine, the corresponding 6'-hydroxymethyl-substituted 2,2’-bipyridine and (5'phenyl-[2,2'-bipyridin]-6-yl)methyl formate were isolated as byproducts in some cases. finally, an improved procedure for the dtta tert-butyl ester alkylation with 6'-halomethyl-5-phenyl-2,2'bipyridines by using finkelstein reaction was developed. keywords dtta tert-butyl ester 2,2'-bipyridines finkelstein reaction ligands for lanthanide cations alkylation received: 25.03.22 revised: 24.05.22 accepted: 24.05.22 available online: 30.05.22 key findings ● the composition of the reaction mixture after dtta ester alkylation with 6-bromomethyl-2,2'bipyridine was studied. ● an improved procedure for dtta ether alkylation with 6-halomethyl-2,2'-bipyridines was proposed. the yield of the target product was increased up to 80%. 1. introduction 2,2'-bipyridines are the commonly used ligands for different metal cations [1, 2]. in case of the presence of polyaminocarboxylic acid (dtta, do3a etc.) moiety at the c6 position, these compounds are of interest as effective ligands for lanthanide cations [3–6]. as for the luminescent chelates of lanthanide cations, the polyaminocarboxylic acid fragment as the chelating part of hard nature is necessary to saturate all lanthanide coordination bonds in order to prevent the incorporation of water molecules in the first coordination sphere of the lanthanide cation, which usually leads to a significant quenching of luminescence [7]. the 2,2’-bipyridine part of the ligand is necessary for the absorption of energy and its transmission to the lanthanide cation. early we reported on our progress in the development in this direction. e.g., the chromophore systems with aromatic substituent at position c6′ [8], c4 [9–11], c5 [12] and c5′ [6] have been researched for effectiveness of lanthanide cations sensibilization. as a result, the main regularities of the influence of the bipyridine chromophore structure on the properties of the complexes were revealed. the most common method for the preparation of such ligands involves direct alkylation of the dtta tert-butyl ester with the corresponding halomethyl derivatives of 2,2’bipyridine and subsequent cleaving of tert-butyl protection. however, the yields of target products at this stage do not exceed 35–40% with formation of by-products. in this manuscript we wish to report the results of the optimization of the reaction conditions and the analysis of the reaction mixture of the above mentioned reaction. http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2022.9.2.10 mailto:a.p.krinochkin@urfu.ru http://creativecommons.org/licenses/by/4.0/ http://orcid.org/0000-0002-0397-4033 http://orcid.org/0000-0002-6712-1136 https://orcid.org/0000-0001-5965-1527 http://orcid.org/0000-0002-9679-8269 http://orcid.org/0000-0002-4786-5568 https://orcid.org/0000-0003-2408-7166 https://orcid.org/0000-0002-7031-5230 http://orcid.org/0000-0002-1672-2476 https://crossmark.crossref.org/dialog/?doi=https://doi.org/10.15826/chimtech.2022.9.2.10&domain=pdf&date_stamp=2022-5-30 chimica techno acta 2022, vol. 9(2), no. 20229210 letter 2 of 4 2. experimental all reagents were purchased from commercial sources and used without further purification. nmr spectra were recorded on a bruker avance-400 spectrometer, 298 k, digital resolution ± 0.01 ppm, using tms as the internal standard. mass spectra were recorded on a microtof-q ii mass spectrometer (broker daltonics) with electrospray ionization. the starting (5'-phenyl-[2,2'-bipyridin]-6-yl)methanol 1 [6], 6'-(bromomethyl)-5-phenyl-2,2'-bipyridine 2a [6] and ester of dtta 3 [13, 14] were synthesized as described in literature. 6'-(chloromethyl)-5-phenyl-2,2'-bipyridine (2b). hydroxymethylbipyridine 1 (140 mg, 0.53 mmol) was dissolved in 1,2-dichloroethane (35 ml). then socl2 (0.08 ml, 1.07 mmol) was added to that solution and the mixture was stirred at 50 °c for 2 h. the resulting mixture was washed with aqueous solution of na2co3. the organic layer was dried with anhydrous sodium sulfate. the solvent was removed under reduced pressure. the analytical sample was obtained by recrystallization (ethanol). yield 116 mg (0.41 mmol, 77%). nmr 1н (cdcl3, δ, ppm): 4.78 (s, 2н, ch2), 7.41–7.46 (m, 1h, ph), 7.49–7.54 (m, 3h, ph, н-5'), 7.64–7.68 (m, 2h, ph), 7.88 (d, 1h, 3j 7.6, 7.6 hz, н-4'), 8.05 (dd, 1h, 3j 8.0 hz, 4j 1.6 hz, н-4), 8.39– 8.43 (m, 1h, н-3'), 8.53 (d, 1h, 3j 8.0 hz, н-3), 8.93 (d, 1h, 4j 1.6 hz, н-6). esi-ms, m/z: 281.08 (м+н)+. found, %: с 72.61, н 4.52, n 9.81. с17н13cln2. calculated, %: с 72.73, н 4.67, n 9.98. 2.1. the methods for the alkylation of dtta ester method a. the corresponding compound 2 (1.53 mmol), dtta tetra-tert-butyl ester 3 (946 mg, 1.69 mmol), and anhydrous potassium carbonate (1062 mg, 7.68 mmol) were mixed in dry acetonitrile (90 ml). the mixture was stirred under reflux for 48 h under argon atmosphere. then solvent was removed in vacuum and water (30 ml) was added, the product was extracted by chloroform (2x35 ml). the extract was dried with anhydrous sodium sulfate and solvent was removed under reduced pressure. the products were separated by column chromatography (eluent: acetonitrile). method b. the corresponding compound 2 (1.53 mmol), dtta tetra-tert-butyl ester 3 (946 mg, 1.69 mmol), potassium iodide (257 mg, 1.70 mmol), and anhydrous potassium carbonate (1062 mg, 7.68 mmol) were mixed in dry acetonitrile (90 ml). the resulted reaction mixture was stirred under reflux for 48 h under argon atmosphere. the following work-up was done similarly to the method a. tert-butyl 2,2',2'',2'''-(2,2'-((5'-phenyl-2,2'-bipyridin6-yl)methylazanediyl)bis(ethane-2,1-diyl)bis(azanetriyl))tetraacetate (4). rf 0.15. yield 0.56 g (0.7 mmol, 45%, method a); 0.98 g (1.224 mmol, 80%, method b from compound 2a); 0.92 g (1.148 mmol, 75%, method b from compound 2b). 1h nmr (cdcl3, δ, ppm): 1.42 (s, 36h, tbu), 2.75 (t, 4h, 3j 7.0 hz, ch2), 2.92 (t, 4h, 3j 7.0 hz, ch2), 3.45 (s, 8h, ch2cootbu), 3.93 (s, 2h, bipy-ch2), 7.42 (m, 1h, ph), 7.51 (m, 3h, ph, h-5'), 7.66 (m, 2h, ph), 7.77 (dd, 1h, 3j 8.0, 7.8 hz, h-4'), 8.00 (dd, 1h, 3j 8.2 hz, 4j 2.2 hz, h-4), 8.28 (d, 1h, 3j 7.8 hz, h-3'), 8.51 (d, 1h, 3j 8.4 hz, h-3), 8.91 (d, 1h, 3j 2.4 hz, h-6). esi-ms, m/z: found 804.48 (m+h)+, calcd 804.48. 5'-phenyl-2,2'-bipyridin-6-yl)methanol (1). rf 0.45. yield 80 mg (0.3 mmol, 20%) (method a). 1h nmr (cdcl3, δ, ppm): 4.66 (2h, d, 3j 5.5 hz, ch2oh), 5.24 (1h, t, 3j 5.5 hz, oh), 7.38–7.43 (1h, m, ph), 7.46–7.53 (2h, m, ph), 7.72 (2h, m, ph), 7.88 (1h, dd, 3j 7.8, 7.8 hz, h-4'), 8.10 (1h, dd, 3j 8.3, 4j 2.1 hz, h-4), 8.29 (1h, d, 3j 7.8 hz, h-3'), 8.49 (1h, d, 3j 8.3 hz, h-3), 8.90 (1h, d, 4j 2.1 hz, h6). esi-ms, m/z: found 263.12, calcd 263.12 [m+h]+. 5'-phenyl-[2,2'-bipyridin]-6-yl)methyl formate (5). rf 0.85. yield 30 mg (0.1 mmol, 7%) (method a). 1h nmr (cdcl3, δ, ppm): 5.42 (s, 2h, ch2), 7.39–7.45 (m, 2h, ph, h-3' (py)), 7.49–7.54 (m, 2h, ph), 7.64–7.68 (m, 2h, ph), 7.87 (dd, 1h, 3j 7.6, 7.6 hz, h-4' (py)), 8.03 (dd, 1h, 3j 8.0, 4j 2.4 hz, h-4 (py)), 8.28 (s, 1h, cho), 8.38–8.42 (m, 1h, h-5' (py)), 8.51 (d, 1h, 3j 8.0 hz, h-3 (py)), 8.89 (1h, d, 4j 2.1 hz, h-6). esi-ms, m/z: found 291.11, calcd 291.11 [m+h]+. 3. results and discussion thе starting 6'-bromomethyl-5-phenyl-2,2'-bipyridine 2a was obtained according to the described method [6]. the alkylation of the dtta ether [13, 14] using this compound was carried with the yield of the target product of 45%, as it was reported earlier [6]. a more detailed analysis of the reaction mass showed the presence of two side-products in the reaction mixture, and they were separated by column chromatography (scheme 1). one of the of products (20% yield) was identified as hydroxymethyl-substituted 2,2’-bipyridine 1. its structure was confirmed by comparing the data of 1h nmr spectrum with those described earlier in the literature [6], as well as by means of mass spectrometry and elemental analysis data. another product was identified as (5'-phenyl-[2,2'bipyridin]-6-yl)methyl formate 5 (yield 7%). the structure was confirmed by 1н nmr, mass spectrometry and elemental analysis data. e.g. the singlets of methylene group at 5.42 ppm and proton of formic acid moiety at 8.27 ppm can be observed in 1h nmr spectra. presumably, the formation of product 5 can be due to the presence of traces of potassium formate in potassium carbonate used as a base in this reaction. some examples of such transformations have previously been reported in the literature [15, 16]. chimica techno acta 2022, vol. 9(2), no. 20229210 letter 3 of 4 scheme 1 a detailed analysis of the reaction mass after dtta ester 3 alkylation. then the same reaction was carried out for the compound 2a in the presence of sodium iodide (1.70 eq.). in this case the desired compound 4 was isolated in yield up to 80% as the only product. this is due to the in situ conversion of the 6’-bromomethyl-5-phenyl-2,2’-bipyridine 2a to 6’-iodomethyl-5-phenyl-2,2’-bipyridine by means of the finkelstein reaction [17]. our further studies showed that the alkylation of dtta tert-butyl ester can also be successfully performed using 6'-chloromethyl-5-phenyl-2,2'bipyridine 2b, which was easily obtained by reacting the corresponding alcohol 1 with thionyl chloride. the yield of the target product 4 in this case was 75%. in all cases, when using this method, the corresponding alcohol 1 was practically absent from the composition of the reaction mixture, and, thus, the application of this method for the preparation of dtta-appended 2,2'-bipyridine ligands for lanthanide cations looks much more promising. 4. conclusions thus, we studied the alkylation reaction of dtta tertbutyl ester with 6'-halomethyl-5-phenyl-2,2'-bipyridines. in case of 6'-bromomethyl-5-phenyl-2,2'-bipyridine the reaction afforded the desired product in 45% yield along with the corresponding 6'-hydroxymethyl-substituted bipyridine (yield 20%) and (5'-phenyl-[2,2'-bipyridin]-6yl)methyl formate (7% yield) as by-products. in case of in situ formation of 6’-iodomethyl-5-phenyl-2,2’-bipyridine, the desired product was isolated in up to 80% yield, and both the corresponding 6’-bromomethyl or 6’chloromethyl-2,2’-bipyridines can be used as starting compounds. the article is based on the materials of the report presented at the v international conference “modern synthetic methodologies for the creation of drugs and functional materials” (november 8–12, 2021, ekaterinburg and perm). supplementary materials no supplementary materials are available. funding this work was supported by the russian science foundation (grant no. 18-73-10119-p), https://www.rscf.ru/en. acknowledgments none. author contributions conceptualization: d.s.k., o.n.c. data curation: a.p.k. formal analysis: m.i.v, a.p.k. funding acquisition: d.s.k. investigation: e.s.s., y.k.s., s.s.r. methodology: d.s.k. project administration: d.s.k. resources: d.s.k. software: a.p.k. supervision: d.s.k. validation: d.s.k. visualization: e.d.l. writing – original draft: d.s.k., a.p.k. writing – review & editing: a.p.k. https://www.rscf.ru/en chimica techno acta 2022, vol. 9(2), no. 20229210 letter 4 of 4 conflict of interest the authors declare no conflict of interest. additional information authors ids: dmitry s. kopchuk, scopus id 14123383900; alexey p. krinochkin, scopus id 56951324100; мaria i. valieva, scopus id 57204922642; еkaterina s. starnovskaya, scopus id 57197871733; yaroslav k. shtaitz, scopus id 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https://www.scopus.com/authid/detail.uri?authorid=7006259116 https://urfu.ru/en/ https://www.ios.uran.ru/ https://usma.ru/en/main/ https://doi.org/10.3390/molecules24213951 https://doi.org/10.3390/cryst10080671 https://doi.org/10.1016/j.jlumin.2004.05.004 https://doi.org/10.1021/ic025543j https://doi.org/10.1002/hlca.200900122 https://doi.org/10.1016/j.tet.2010.11.058 https://doi.org/10.1016/j.ccr.2009.07.025 https://doi.org/10.1016/j.poly.2017.05.030 https://doi.org/10.1016/j.ica.2018.03.016 https://doi.org/10.1002/slct.201901080 https://doi.org/10.1016/j.poly.2020.114962 https://doi.org/10.1016/j.poly.2020.114473 https://doi.org/10.1139/cjc-2015-0576 https://doi.org/10.1021/ja0111479 https://doi.org/10.1021/jm00087a023 https://doi.org/10.1002/cber.19100430257 metal-organic frameworks for metal-ion batteries: towards scalability chimica techno acta review published by ural federal university 2021, vol. 8(3), № 20218304 eissn 2411-1414; chimicatechnoacta.ru doi: 10.15826/chimtech.2021.8.3.04 1 of 8 metal-organic frameworks for metal-ion batteries: towards scalability semyon bachinin, venera gilemkhanova, maria timofeeva, yuliya kenzhebayeva, andrei yankin * , valentin a. milichko * school of physics and engineering, itmo university, 197101, st. petersburg, russia * corresponding authors: andrei.yankin@metalab.ifmo.ru, v.milichko@metalab.ifmo.ru this article belongs to the regular issue. © 2021, the authors. this article is published in open access form under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). abstract metal-organic frameworks (mofs), being a family of highly crystalline and porous materials, have attracted particular attention in material science due to their unprecedented chemical and structural tunability. next to their application in gas adsorption, separation, and storage, mofs also can be utilized for energy transfer and storage in batteries and supercapacitors. based on recent studies, this review describes the latest developments about mofs as structural elements of metal-ion battery with a focus on their industry-oriented and large-scale production. keywords metal-organic frameworks batteries spin coating vapour deposition received: 30.07.2021 revised: 23.08.2021 accepted: 25.08.2021 available online: 27.08.2021 1. introduction global energy consumption is growing every year, which is associated with active social and economic development. however, limited natural energy resources and climatic changes, caused by their extraction and use, call into question the previous pace of development. in this sense, the development of new green technologies that ensure the energy storage in batteries and energy transfer in an environmentally friendly way is becoming more relevant than ever. global industrial auto giants such as mercedes also support such transition to green energy. despite unprecedented successes in the development of such batteries and accumulators, chemical and physical limitations of existing (organic, inorganic and hybrid) materials yet hinder the wide commercial application and require new solutions in material science. for instance, limited life of the batteries and their cycle stability, physical and chemical stability of structural elements, limited charge/discharge rates, capacity, as well as recyclability of the batteries [1] are cornerstones of the future technology of the clean energy. in this sense, metal–organic frameworks (mofs) can be considered as new attractive candidates to meet the requirements of next-generation energy storage devices [2]. emerged over 20 years ago [3], mofs have become one of the key materials in chemistry and crystal engineering. being as a family of highly crystalline and porous materials, mofs are composed of metal nodes and organic ligands linked by coordination bonds. their "lego" nature possesses an unlimited structural and compositional versatility, providing the desired chemical and physical properties [4]. due to synthetic design, mofs' properties such as crystal structure, porosity, stability, and conductivity can be tailored for specific applications. therefore, such synthetic versatility of mofs allows one to optimize the functional properties for energy storage [5], since the needs of each device are different. today, mofs, depending on their designed properties, are utilized as the main structural elements of the batteries (fig. 1): electrodes, solid-state electrolyte, separator and potentially contacts with the metallic conductivity [610]. there are many reviews covering the design [5,11-16] fabrication, operation, limitations, and prospects of specific mofs as individual structural elements such as cathodes and anodes [17-26], electrolytes and separators [27-30]. however, the problem associated with the creation of scalable mofs for mass (as basf, mof-worx, and numat make [31-34]) and large-scale production with focus on energy applications has not been addressed. here we discuss the latest developments about mofs as structural elements of metal-ion battery focusing on their industryoriented production by thin film technology: spin coating and recently developed chemical vapour deposition. 2. discussion generally, metal-ion batteries are composed of three major components: anode and cathode with different chemical potentials, immersed in an ion-conducting and electri http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2021.8.3.04 http://creativecommons.org/licenses/by/4.0/ https://orcid.org/0000-0003-4221-5619 https://orcid.org/0000-0002-8461-0804 chimica techno acta 2021, vol. 8(3), № 20218304 review 2 of 8 fig. 1 schematic illustration of mofs (porous coordination polymers) as solid-state electrolytes (4), cathode (3) and anode (2) coating as well as potential electronic conductors (1) cally insulating electrolyte (fig. 1). the electrochemical reactions in such batteries are the following: metal ion diffusion within the electrode, charge transfer at the interface between the electrodes and electrolyte, and metal ion transport through the electrolyte. herein, the recharging of the batteries (i.e. current source) occurs in a “rockingchair” fashion: metal ions transfer between cathode and anode during charge/discharge cycles (fig. 1). during discharge (i.e. current consumer), metal ions travel from the anode to the cathode, while electrons move externally from the anode to the cathode. metal-organic frameworks demonstrate high potential to optimize the performance of metal-ion batteries. this is facilitated by a number of their distinctive properties such as porosity, redox behavior, various types of conductivity (ionic and electronic), encapsulation of various molecules and ions, etc. fig. 1 demonstrates a schematic diagram of a metal ion battery with highlighted areas corresponding to mofs as cathodes, anodes, solid-state electrolytes and separators. first, we consider mofs as cathodes and anodes. generally, metal-organic frameworks are semiconductors in nature, in some cases the band gap reaches up to 5 ev. nevertheless, there are compounds with the lower band gap possessing hopping electronic conductivity. the mechanisms of electronic transport in mofs are the following [35-37]: through-bond, through-plane, through-space, redox-hopping, and guest-promoted pathways. this provides an opportunity to utilize zif-8 (zn(mim)2, where mim = 2-methylimidazolate), metal-ion batteries, addressing two issues: providing electron transport and insertion/extraction of ions due to redox activity [38-40]. nam et al. [38] were able to combine these two properties and provide a prototype of the metal-ion battery with a cathode entirely made of two-dimensional mof (cu3(hhtp)2, where hhtp 2,3,6,7,10,11hexahydroxytriphenylene) with an electronic conductivity of 0.2 s cm –1 (fig. 2a). also, li et al. [40] demonstrated similar approach, but for the anode (fig. 2b). deposition of metal-organic frameworks on the anodes also allows one to improve the capacitive characteristics of metal-ion batteries due to insertion/extraction of various ions through the mof layer. this makes it possible to increase the effective anode area without changing the dimensional characteristics of the device, which, in its turn, promises miniaturization of existing batteries. a number of papers [41-48], considering such an approach, demonstrate the achievement of significant results in current densities, charge capacity, and cyclic stability. the mechanism of insertion/extraction of ions is also described in details in [44] using the example of aluminumbased mof (fig. 3). in addition, the deposition of mofs on the cathodes possesses the similar effect, which has been considered by the authors of [48-52]. fig. 2 the concept for the mof as a cathode (a) [38] and anode (b) [40] chimica techno acta 2021, vol. 8(3), № 20218304 review 3 of 8 fig. 3 the mechanism of insertion/extraction of various ions through mof layer [44] utilization of metal-organic frameworks as an active medium for ion transport is the other side of the story. the porous structure provides ion transport through the mof, which allows one to consider it as a solid-state electrolyte [53-59]. the reason to use mof as a solid-state electrolyte is dictated, first, by a decrease in the toxicity of the resulting metal-ion batteries. indeed, the common liquid electrolytes are extremely toxic, which makes the process of disposal quite difficult and expensive. such toxicity also makes existing batteries extremely unsafe for use in electronic devices for children. in this sense, the transition from the liquid electrolytes towards solid-state ones can improve this issue and allows the batteries to be recyclable. in addition, a number of metal-organic frameworks demonstrate promising operation characteristics under the extreme conditions: high temperatures, mechanical stress, directed thermal action, etc. a number of recent research works [54-59] prove the validity of this suggestions through the embedding of metal-organic frameworks as an additional layer [58] (fig. 4c) or making the energy device based on mof as an active layer [57] (fig. 4a,b). also, a review of potentially suitable compositions of mofs as solid-state electrolytes can be found in [59]. the increasing focus on industrially applicable mofs [31-34] for microelectronics and energy applications highlight significant limitations of common solution methods and emphasizes the need for more scalable technologies like roll-on approach, which is highly needed for production of portable batteries. the possibility of the scaling of the synthesis of functional mofs is directly related to the development of technologies for the growth of highquality crystals in the form of thin films. to address this issue, first, we consider spin coating approach [60-64]. this is one of the simplest methods for mof scalability allowing the deposition of mof films on different rigid and flexible substrates (metal, semiconductor or dielectric) with different morphologies. the method consists of the interaction of droplets of two solutions (an organic ligand and a metal salt) on the surface of a rotating substrate (fig. 5a) [60]. due to the high rotation speeds of the substrate, the resulting film has relatively good uniformity in thickness and composition (fig. 5b). the heating of the substrate can be also applied to increase both the rate of synthesis and the crystallinity. the authors of [61] obtained a 150 nm film on an aluminum electrode at a rotation speed of 3000 rpm and a substrate temperature of 140 °c, which can potentially fig. 4 mof as a solid-state electrolyte (a,b) [57] and separator film (c) [58] chimica techno acta 2021, vol. 8(3), № 20218304 review 4 of 8 fig. 5 schematic illustration of spin-coating approach (a) and cross-section view of mof thin film obtained by scanning electron microscopy (b) [60] be used for the process of modifying the electrodes of metal-ion batteries. chen et al. [62] also showed the possibility of spin-coating the flexible film with an electronic type of conductivity, which is interesting as electrode layers in the device of metal-ion batteries. also, direct evidence of the validity of the spin-coating technology application follows from the paper [63] where fan et al. modified the surface of the zn-mof anode by centrifugation. finally, considering the battery, whose structure consists of multilayer mofs as electrodes, electrolytes and separators (fig. 1), the specific technology is required. in this sense, the spin-coating makes it possible to fabricate such multilayer structures, as evidenced by the results obtained in [64]. next highly promising approach is chemical vapour deposition (cvd) [65-74]. indeed, cvd as a non-solvent method is a well-known industrial approach for obtaining surfaces suitable for microand optoelectronics since the corrosion and contamination issues are solved. a variant of cvd, mocvd (metal-organic cvd) is a standard process for laser diode, led, and semiconductor manufacturing, meaning it can be used for mof synthesis, as well. following the research works on mof cvd, common structures such as zif-8, zif-67 (co(mim)2, where mim = 2-methylimidazolate), hkust-1 (cu3(btc)2, where btc = benzene-1,3,5-tricarboxylic acid) and mil-53 (al-bdc, where bdc = 1,4 benzene dicarboxylic acid), recently utilized for energy storage [21], can be prepared as model thin films. however, in contrast to solution chemistry, the limited possibilities of cvd for using a variable concentration of various solvents significantly limit the resulting mof topologies, while it is not an insurmountable problem for the method. the general concept of mof cvd is illustrated in fig. 6. rob ameloot and co-workers describe this methods as a two-step procedure [65]: the deposition of the metal oxide layer on a support by, for instance, atomic layer deposition (ald), followed by the exposure of this oxide coating fig. 6 schematic illustration of mof cvd process [68] to a vaporized linker resulting in a vapor-solid reaction towards the formation of the desired mof structures. following this approach, zif-8 films were obtained by stassen et al. [65]. zif-8 was deposited on silicon pillars with a 25:1 aspect ratio by vapour-solid transformation of 25 nm ald zinc oxide films. it is vital to mention the possibility of obtaining conformal coatings by such approach on various, often fragile, surfaces. intriguing, the presence of water during synthesis promotes formation of a nonporous diamondoid zn(mim)2 polymorph, but under high temperatures the water evaporation eliminates the chances of amorphous material to form. similar effect of lack of solvent has been demonstrated by han et al. [66] who reported solvent-free hkust-1 film deposition under vacuum conditions. they combined cvd and physical vapour deposition processes using layer-bylayer (lbl) growth where after each h3btc deposition cycle a monolayer cu was grown again. the group of ameloot [67] also reported the growth of mof based on cu(ii) and linkers 1,4-benzenedicarboxylic acid (h2bdc) and trans-1,4-cyclohexanedicarboxylic acid (h2cdc). the mof-cvd method for these materials consists of two steps: vapour-phase deposition of copper or copper oxide films as a metal source, and a solid–vapour reaction between this precursor and the vaporised organic linker. it is important to note that depending on synthesis chimica techno acta 2021, vol. 8(3), № 20218304 review 5 of 8 conditions (dry or humid) diverse mofs’ structures were obtained. for h2cdc linker humidity did not play a major role and porous cucdc was normally formed. however, for h2bdc linker, depending on the humidity level, cubdc or cp-cubdc structure similar to coordination polymer [cu2(oh)2(bdc)] could be obtained. a number of emerging problems in the process of mofcvd, such as the incomplete conversion of the metal-oxide precursor to mof, and the degradation of the organic ligand during deposition at elevated temperature were described [68-71]. a possible solution was proposed by cruz et al. [68]: involving an increase of exposure time and decrease of the thickness of the metal-oxide precursor. furthermore, the use of low-temperature synthesis (80 °c) conditions to circumvent these challenges was explored for maf-6 (rho-zn(eim)2, where eim = 2-ethylimidazolate) [69], maf-252 (zn(dpt)2, where dpt = 3-(2-pyridyl)-5-(4-pyridyl)-1,2,4-triazolate)) [70] (fig. 7), zif-8 and zif-67 [71] structures. another issue comes from mof-cvd method itself that allows obtaining mofs with limited porosity [65-71]. this deteriorates a whole range of functional properties including ion transport. this issue can be overcome by accounting for the following factors [67,68]: (i) humidity has to be controlled since it can increase chances of amorphous intermediate formation, thus, affecting thin film roughness – the more humid conditions are, the rougher are the films produced; (ii) the thickness of metal-oxide precursor has to be controlled in order to fully convert it into mof. otherwise, it acts as a protecting shell that hampers further mof growth. so far, only model mofs with relatively simple topologies and short ligands have been synthesized by cvd, therefore, leaving room for further investigations of mofs with more complex hierarchy and variable ion/electron conductivity. the report by stassin et al. [72] creates a basis for the direct comparison of the solvothermal and vapour deposition methods for the synthesis of functional and polymorphic mofs. mofs al-mil-53-fum and al-mil-53-mes (al mil-68-mes) were synthesized with and without modulators. when formic acid was used as a modulator, mof crystallized at 80 ºc by cvd in the orthorhombic crystal system with pnma space group. at the same time, modula fig. 7 the scheme of maf-252 thin film fabrication with corresponding optical images of maf-252 powder and large-scale film [70] tor-free product crystallized by solvothermal method in the monoclinic space group p21/c. the change of the modulator from formic to mesaconic acid led to formation of al-mil-53-mes by cvd that crystallizes in the orthorhombic with pnma space group. this work highlighted the principle possibility of the controlled synthesis of structurally diverse compounds via conscious vapour deposition synthesis. similar message was conveyed by a very recent work by tu et al. [73], which described another approach to controlled mof-cvd synthesis by using the so-called template vapor that arranges the mof building blocks and promotes the formation of desired product. they found out that the reaction between zinc oxide and 4,5-dichloroimidazole (hdcim) leads to the formation of either porous kinetic phase zif-71 [zn(dcim)2] (dcim = 4,5-dichloroimidazolate) with rho topology, or thermodynamically stable phase zif-72 (the same chemical formula as zif-71) with lcs topology. the addition of template vapors enabled formation of zif-71 at lower temperatures (120 °c vs 160 °c); however, at temperatures above 120 °c it was impossible to avoid the phase transition from zif-71 to zif-72. 3. conclusions conventional solution chemistry certainly remain the key approach for the synthesis of mofs for diverse applications including electrochemical energy storage [74]. however, the increasing focus on industrially applicable mofs [31-34] for microelectronics, optics [75] and energy application highlight significant limitations of the solution methods and emphasizes the need for more scalable and industry-oriented technologies. here, we cover advanced methods, such as spin coating and vapour deposition techniques, allowing large-scale and fast productions of functional mofs. these industrially oriented and scalable methods demonstrate high potential for producing the functional mof thin films. specifically, the cvd technique appears as the most optimal and promising method for the industrial manufacture of mofs. the intense research during the past 5 years identified a number of technological challenges hampering the implementation of mof-cvd and indicated avenues for their solution. the key challenges include the incomplete conversion of the metal-oxide precursor to mof, the degradation of the organic ligand during deposition at elevated temperature [68-71], as well as growth of mofs with limited porosity [65-71]. all these issues can potentially be addressed. also, over the past year, the possibility of large-scale growth of mofs with a structural diversity has been also demonstrated [73,74], which, we believe, will be one of the driving forces in mof crystal engineering in the near future. concerning spin coating approach, there are still technological problems of mof thin film fabrication such as a poorly controlled growth process, the influence of external chimica techno acta 2021, vol. 8(3), № 20218304 review 6 of 8 factors (mechanical vibrations, convection flows and insufficient automation), and a limited list of structural elements (especially ligands) involved in the crystal growth. the latter is associated with the high growth rate of thin films during the spin coating, which does not allow sufficiently large ligands (porphyrins, tbapy etc.) to organize a porous periodic lattice. finally, inhomogeneity of the film (domain structure) and a high degree of surface roughness limit the applicability of the method. in our 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chimicatechnoacta.ru doi: 10.15826/chimtech.2021.8.2.11 1 of 11 structural changes in v2o5-p2o5 glasses: non-constant force field molecular dynamics and ir spectroscopy a.a. raskovalov a,* , n.s. saetova b , i.s. popov c a: institute of high temperature electrochemistry of ub ras, 620137 akademicheskaya st., 20, yekaterinburg, russia b: vyatka state university, 610000, moskovskaya st., 36, kirov, russia c: institute of solid state chemistry of ub ras, 620049 pervomayskaya st., 91, yekaterinburg, russia * corresponding author: other@e1.ru this article belongs to the regular issue. © 2021, the authors. this article is published in open access form under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). abstract quasi-binary phosphate-vanadate glasses have been studied by both ir spectroscopy and a novel method of molecular dynamics with a non-constant force field. this method is used for the self-assembly of structural models of glasses. the obtained models and the glass network structure are analyzed quantitatively using element distribution by the number of r–o–r bonds (r is phosphorous or vanadium) and 4-, 6-, and 8-membered cycles. the bends on the concentration dependences of atoms distribution in the second coordination sphere agree well with changing the shape of ir spectra. based on the cycle analysis, the formation of cycles is shown to be more characteristic for vanadate fragments that can form 4-membered cycles, which, according to zachariasen’s rule, negatively affects glass-forming ability. keywords phosphate-vanadate glasses ir spectroscopy non-constant force field molecular dynamics self-assembly received: 27.04.2021 revised: 07.06.2021 accepted: 09.06.2021 available online: 10.06.2021 1. introduction oxide semiconducting glasses possess electron conductivity due to the electron transfer between ions of transition metals (v 4+ /v 5+ , fe 2+ /fe 3+ , pb 2+ /pb 4+ , etc.) [1–3]. such glasses attract scientific attention because of the combination of electron conductivity and features of the vitreous state: glasses can be given any shape, and their composition can be varied in a wide range of concentrations, achieving the required properties. glasses containing transition metal oxides can be used as electrode materials of batteries, gas sensors, for the disposal of high-level waste, etc. [4–6]. vanadate glasses have the highest conductivity among semiconducting oxide glasses [7]; vanadate phosphate glasses are the most studied. at the same time, despite numerous works devoted to the study of vanadate-phosphate glasses in terms of their conductivity, insufficient attention has been paid to the explanation of some concentration dependence of non-electrical properties. for example, we have carried out a detailed study of the thermal and transport properties of xv2o5–(1-x)p2o5 (x = 35–95 mol %) glasses, and it appeared that the properties change non-linearly with vanadium content and their concentration dependences demonstrate several clearly distinguished ranges [8]. it has been suggested that the observed phenomena are connected with the structural changes of the glass network. vanadium glasses have a complex structure because vanadium ions can exist in four-, fiveand six-coordinated states (tetrahedron, square pyramid, trigonal bipyramid, and octahedron [9]). moreover, vanadium oxide is a transition metal which possesses at least fourand five-valent states in glasses, and ions with different valence can form the same structural groups [10]. according to [11], amorphous vanadium oxide consists of vo4 and vo5 structural units sharing edges and corners, while vo4 units dominate in the molted v2o5 and vo5 units are formed due to the transformation of vo4 ones at quenching. in binary vanadium phosphate glasses, vo4 structural units can substitute similar po4 units [12] forming a continuous glass network. the structure of binary v2o5–p2o5 glasses was studied in a wide composition range by nmr spectroscopy [13, 14], esr [15], and ir spectroscopy [16]. it was established that there are two types of vo5 units in glasses involving vo5 units sharing oxygen with only vo5 units and vo5 units sharing oxygen atoms with po4 units [14]. the structure of glasses containing 50 mol % p2o5 was proven to be similar to the structure of vpo5 crystalline compounds [17]. it was shown in [18] by studying the crystallization products of vanadium phosphate glasses that a http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2021.8.2.11 http://creativecommons.org/licenses/by/4.0/ https://orcid.org/0000-0002-6634-4135 https://orcid.org/0000-0002-0721-3944 https://orcid.org/0000-0001-8312-7071 chimica techno acta 2021, vol. 8(2), № 20218211 article 2 of 11 significant difference should be observed between the structures of glasses with compositions lying below and above 78 mol % v2o5. when v2o5 content is more than 78 mol %, the crystallization of v2o5 is observed; at v2o5 concentration below 78 mol %, the crystallization of vpo5 solid solution is possible, which is confirmed by ir spectroscopy. according to the recent research, main vanadium structural units in binary vanadate-phosphate glasses are presented by symmetric-v 5+ o4 (s-vo4), distorted-v 5+ o4 (d-vo4), v 5+ o6 (vo6), and v 5+ o5 units (vo5) [10]. in the present work, structural models of xv2o5– (1-x)p2o5 (x = 35–95 mol %) glasses were obtained by means of self-assembly using non-constant field molecular dynamics. this method simulates the formation of glasses from a completely dissociated state by creating covalence bonds, and its applicability was demonstrated on boratevanadate glasses [19]. the obtained models were analyzed by different structural criteria, and some quantitative factors connected with the network structure were obtained. it was shown that the bends on concentration dependences of these parameters correlate with the bends on such dependences of physicochemical properties. similar bends were observed in the ir spectra. 2. experimental glasses of the xv2o5–(1-x)p2o5 (x = 35–95 mol %) system were obtained by melt quenching by the technique described in [8]. their amorphous nature was confirmed by x-ray diffraction using a d/max 2200 diffractometer (rigaku, japan) with cu kα radiation (λ = 1.5418 å) in a 2θ range of 15–55°. to study the structural changes occurring at a change in v2o5/p2o5 ratio, infrared (ir) spectroscopy was used. the spectra were collected in the absorption mode at room temperature in a wavelength range of 400–4000 cm -1 using a tensor 27 fourier ir spectrometer (bruker, germany). before measurements, glass powders were mixed with kbr in a weight ratio of 1:500, and the pellets were compacted in an evacuated mold. then, pre-treatment (baseline subtraction) and deconvolution of the spectra into gaussian components were performed using the fityk software [20]. 3. simulation details molecular dynamics simulation was performed with cuda version of aztotmd software [21] (the latest version and user manual are available at http://aztotmd.ru/set.php?lang=en). the computations were performed on a geforce rtx 2080 ti video card with a clock rate of 1650 mhz. the xv2o5–(100-x)p2o5 glass compositions with x = 35–95 mol % were studied by simulation. the starting configurations consisted of v 5+ , p 5+ , and o 2 ions, and 10% of v 5+ ions were replaced by v 4+ ions with the corresponding correction of the o 2 number. this corrective was made according to some experimental evidence. the box sizes were chosen to match the earlier obtained density data [8]. a summary of the simulated system’s size is given in table 1. the following selfassembly procedure was performed in two stages. in the first stage, v 5+ and p 5+ ions can form double bonds with oxygen ions o 2– when the distance between couples of vanadium(phosphorus) and oxygen ions is short enough. this process leads to species conversion: v 5+ /p 5+ + o 2 → v 3+2δ /p 3+2δ = od -2δ (1) note that the formal oxidation degree of ions remains the same, but the partial charges are changed. v 3+2δ in eq. (1) means five-valent vanadium with two electron pairs shared with the double-bonded oxygen (od -2δ ). the value of δ was chosen as 0.6e, as in [22]. hereinafter, we will omit the partial part of the charges (multiple δ) for brevity. this stage was stopped after all pentavalent cations were bonded to oxygen. in the next stage, the obtained cations as well as the remained v 4+ cations are sequentially linked to oxygen in a similar way up to the formation of four bonds for each cation (v 5+ and p 5+ had one double bond and three single, v 4+ had four singles). the oxygen ions converted sequentially into the terminal (ot, one bond) and bridging (oc, two bonds): do = v 3+ /p 3+ + o 2/ot → do = v 2+ /p 2+ –ot/oc, (2) and v 4+ + o 2/ot → v 3+ –ot/oc. (3) in eq. (3), v 3+ means v 3+δ , not v 3+2δ as in eqs. (1,2). at these stages, covalent bonds were taken in the form of harmonic potentials with the spring constant of 10 table 1 the simulated system sizes: nv 5+ , nv 4+ , np 5+ , and no 2 are the amounts of the corresponding ions, ntot is the total amount of ions, and a is the box size x nv 5+ nv 4+ np 5+ no 2 ntot a, å 95 854 95 50 2450 3449 36.7 90 810 90 100 2455 3455 36.8 85 764 85 150 2455 3454 36.7 80 720 80 200 2460 3460 36.6 75 674 75 250 2460 3459 36.6 70 630 70 300 2465 3465 36.5 65 584 65 350 2465 3464 36.4 60 540 60 400 2470 3470 36.4 55 494 55 450 2470 3469 36.3 50 450 50 500 2475 3475 36.2 45 404 45 550 2475 3474 36.1 40 360 40 600 2480 3480 36.0 35 314 35 650 2480 3479 36.0 http://aztotmd.ru/set.php?lang=en chimica techno acta 2021, vol. 8(2), № 20218211 article 3 of 11 30 evå -2 and the corresponding equilibrium distance. the creation of bridging oxygen (oc) was accompanied by adding a valent angle potential. finally, after the selfassembly procedure, the main part of the simulation was provided during 3’000’000 steps with a timestep of 1 fs. the force field for this stage was replaced with the one from our previous work [8]. the electrostatics was calculated in a way suggested by fennel and gezelter [23]. in all cases, the temperature was kept around 298 k by the nose-hoover thermostat. 4. results and discussion fig. 1 presents the general appearance of ir spectra obtained for xv2o5–(1-x)p2o5 (x = 35–95 mol %) glasses in a wavelength range of 400–2000 cm –1 . it is seen that the shape of the spectra changes significantly depending on the p2o5/v2o5 ratio. the two most pronounced changes in the spectrum shape can be distinguished at x = 50 and 70 mol %. since the last meaningful peak is observed at ~1750 cm –1 , the considered wavelength range was reduced to 1800 cm –1 . the following peaks corresponding to the vibrations of the glass network can be distinguished in the spectra: ~480, 530, 665–690, 760, 800–820, 960–980, 1040–1060, 1230, 1370, and 1750 cm –1 . however, these peaks are broadened, and, in most cases, they are a superposition of several peaks, as typical for amorphous materials. a slight bend is seen near ~1010 cm –1 , after which a sharp growth of the intensity of the spectra is observed; such behavior might be connected with the presence of bound water in samples. therefore, the spectra were considered in two wavelengths of 400–1010 and 1010– 1800 cm –1 to increase the deconvolution accuracy. for clarity, the peaks observed in the spectra given in fig. 1 are listed in table 2. 4.1. wavelength range from 400 to 1010 cm –1 as was mentioned above, several concentration ranges with the same spectrum shape exist. as v2o5 content grows, a redistribution of intensity is observed between the wavelength ranges of 400–650 and 850–1010 cm –1 . fig. 1 ir spectra of xv2o5–(100-x)p2o5 glasses table 2 peaks observed in ir spectra (see fig. 1) wavenumber, cm –1 vibration type reference 475–490 δ o–p–o [24, 25] 530 δ o=p–o [25, 26] 665–690 νs o–p–o [26] 760 νs v–o–p; νs p–o–p [25] 800–820 νs p–o–p [26] 960–980 v–o [25] 1040–1060 v=o [27, 28] 1230 νs p=o (q 2 ) [24, 25] 1370 νas p=o (q 2 ) [26] for the middle of the spectra (650–850 cm –1 ), no strong correlation between the glass composition and peak intensity is observed; however, its shape depends on the glass composition: when v2o5 concentration is reduced from 95 mol %, the peak becomes smoother, and it almost disappears at v2o5 content of 70 mol %. the examples of deconvolution of the spectra in this area are given in fig. 2. according to the literature data, bending vibrations of v–o–v bonds are observed in the wavelength range of 400–650 cm –1 , as well as various vibrations of phosphate glass network, for example, vibrations of o–p–o and o=p–o bonds [29–31]. considering that the intensity of this peak increases as p2o5 content grows, the main contribution might be assigned to the vibrations of po2 structural units [24, 31]. in the wavelength range of 650–850 cm –1 , a gradual degeneration of the most intense peak is observed, and it shifts towards lower wavelengths (from 757 to 742 cm –1 for v2o5 content of 95 and 75 mol %, respectively). the following vibrations can be excited in this spectrum area: stretching vibrations of p–o–p [24, 31] and v–o–p [32] bonds and the vibrations of the vanadium-oxygen network such as asymmetric stretching vibrations of vo2 groups in vo4 tetrahedra [30, 33]. since the vibrations of phosphate and vanadate networks in this area are overlapped, it is complicated to unambiguously relate the peaks obtained by spectra deconvolution. it might be assumed that the main contribution to the intensity of the peak at ~750 cm –1 is made by the vibrations of the vanadium-oxygen network, as well as v–o–p vibrations, in the v2o5 concentration range from 85 to 95 mol %. as p2o5 content increases, this peak shifts towards the low-frequency area, which is followed by its vanishing; that may be connected with both a low intensity of vanadium-oxygen network vibration and restructuring of the glass network (transition from predominantly vanadate to mixed phosphatevanadate glass network). within the wavelength range of 850–1010 cm –1 , the most noticeable changes occur at v2o5 content of 80 mol %. in the 85 ≤ x ≤ 95 (mol %) composition range, three peaks are observed in the spectra deconvolution: ~985, 965, and 933 cm –1 . the intensity of the peak at 985 cm –1 remains the same within this v2o5 range, while the intensity is redistributed between the peaks at 933 and 965 cm –1 . the peak at 965 cm –1 can be attributed to the stretching vibrations of v–o bonds in vo4 structural units [29]. chimica techno acta 2021, vol. 8(2), № 20218211 article 4 of 11 fig. 2 deconvolution of ir spectra of xv2o5–(100-x)p2o5 glasses in the wavelength range of 400–1010 cm –1 . the spectra are plotted in the same ranges on the y-axis to demonstrate the intensity change. hence, decreasing its intensity is connected with the reduction of vanadium oxide concentration and, consequently, the number of bonds formed with vanadium ions. the peak at ~935 cm –1 is connected with the stretching vibrations of p–o–p bonds in q 0 structural units [29, 34–36]; therefore, the growth of its intensity is also natural. it is interesting to mention the peak at 985 cm –1, which vanishes with decreasing the v2o5 content from 95 to 80 mol %. according to the literature data, it can be caused by the vibrations of vanadium-oxygen tetrahedra vo4 [37], constituting the glass network at high vanadium oxide content [38], or vanadium clusters [37]. probably, the glass network changes drastically with the growth of p2o5 content, which results in the decay of vanadium clusters. as was mentioned above, a change in the shape of the spectra begins at v2o5 content of 70 mol %, which is accompanied by the disappearance of a number of peaks and redistribution of vibration intensities; this change finishes at x = 65 mol % (fig. 2). apparently, the transition from predominantly vanadate to mixed phosphate-vanadate glass network occurs. beginning from x = 85 mol %, there is a peak at ~530–540 cm –1 , whose intensity and position are kept with a further increase in p2o5 concentration. this indicates that this peak is attributed to the vibrations of the phosphate structural units. more noticeable changes in the shape of the spectra occur in the wavelength range of 650–900 cm –1 . the intensity of peaks in the area of 650–850 cm –1 increases sharply; the position of the peak at ~700 cm –1 observed for the glass with x = 70 mol % is almost unchanged, while the peak with the maximum at ~780 cm –1 shifts towards larger wavenumbers. the vibrations in this spectrum area are attributed to the symmetric stretching vibrations of p–o–p bonds in q 2 structural groups [39–42]. the growth of the intensity of these peaks clearly indicates increasing the connectivity of the phosphate network with an increase in p2o5 content. the peak at ~700 cm –1 appears in the spectra of glass with x = 70 mol % and maintains with the p2o5 content growth up to x = 55 mol %; in the spectrum of x = 50 mol % composition, this peak completely disappears. according to the literature data [26], this peak is typical for p–o– p vibrations and symmetric stretching vibrations of phosphate rings [25]. the peak near ~780 cm –1 arises for the composition with x = 70 mol % and persists up to the maximum p2o5 concentration shifting towards large wavenumbers (821 cm –1 ). this peak could be caused by symmetric stretching vibrations of p–o–p bonds in q 2 groups [39–42]. chimica techno acta 2021, vol. 8(2), № 20218211 article 5 of 11 further distortion of the spectrum shape begins at v2o5 content of 55 mol % and ends at x = 50 mol %. a slight narrowing of the top of the spectra accompanied by a redistribution of intensity of vibrations in all studied wavelength range is observed. the appearance of the peak at 488 cm –1 can be mentioned in the spectra of glasses with x = 55 mol %; this peak shifts to the low-frequency area as p2o5 content grows. this peak may be attributed to the bending vibrations of po4 tetrahedra [43]. its appearance indicates the formation of the metaphosphate chain with decreasing v2o5 content, which indirectly indicates the modifying role of v2o5 in this concentration range. the peak near 620–640 cm –1 becomes more pronounced, and it shifts towards the high-frequency area with the growth of p2o5 concentration (660–690 cm –1 ). in this area, bending vibrations of o–p–o bonds [43] and stretching vibrations of p–o–p bonds [44] are observed. increasing the intensity of this peak indicates the growth of connectivity of the phosphate network and the possible formation of this network with inclusions of vanadiumoxygen clusters. this suggestion is indirectly confirmed by the constancy of the peak near 980–990 cm –1 , whose appearance points up the existence of vanadium-oxygen clusters in the glass network [31]. 4.2. wavelength range from 1010 to 1800 cm –1 in the wavelength range of 1010–1800 cm –1 , changes in the shape and intensity of the spectra are similar to those observed in the 400–1010 cm –1 range. the broadening of the spectra is observed in this frequency range as the p2o5 content increases (fig. 1). this might be connected with the growth of hygroscopicity of glasses with an increase in p2o5 and, consequently, a large amount of bound water in the glass structure. it can cause a broadening of the spectrum associated with the absorption of water molecules and the appearance of p–oh bonds. for these reasons, unambiguous interpretation of the results of spectrum deconvolution is difficult; therefore, only a brief discussion of the peaks which can be interpreted based on the literature data is given below. the peaks at ~1230–1270 and 1350–1370 cm –1 are present in the spectra of all studied compositions (fig. 3), and they can be attributed to the vibrations of p=o bonds [45]. in addition, there is a peak at ~1040–1060 cm –1 , which indicates the vibrations of v=o bonds [46] or asymmetric stretching vibrations of pyrophosphate groups [47]; its intensity decreases with the growth of p2o5 content. a small peak at ~1745 cm –1 is likely connected with the vibrations of the oh groups [48]. the rest of the peaks in the range of 1400–1800 cm –1 are assigned to the vibrations of p–oh bonds and adsorbed water molecules [48]. 4.3. simulation results examples of snapshots of the simulated systems are given in fig. 4; for clarity, we presented only thin slices of the systems cut from the middle of the box. one can see phosphate-vanadate chains and valent angles r-o-r. the interatomic distances correspond to experimental data on single and double bond lengths, as was shown in detail in our fig. 3 deconvolution of ir spectra of xv2o5–(100-x)p2o5 glasses in the wavelength range of 1000–1800 cm –1 . the spectra are plotted in the same range on the y-axis to demonstrate the intensity change. chimica techno acta 2021, vol. 8(2), № 20218211 article 6 of 11 fig. 4 snapshots of the simulated xv2o5–(100-x)p2o5 glasses (thin slices) for (a) x = 35 and (b) x = 80 mol %. colors: magenta – p, gray – v, red – o. previous work [8]. fig. 5 shows distributions of vanadium ions by coordination number (at a cutoff of 2.21 å) and mean coordination number as a function of vanadium content. the dominated coordination is five (about 60%), and, in general, the proportion of four-coordinated vanadium decreases, and that of six-coordinated increases with an increase in vanadium content. to estimate the structure of the glass network, we analyzed the number of atoms with different quantities of triatomic bond sequences; for this purpose, we introduced r n or notation, where n is the number of r–o–r bonds starting from a given atom r, see fig. 6 for the explanation. fig. 7 shows the dependences of p n op as a percentage of the total number of p atoms; for example, p 2 op = 30% means that 30% of phosphorous atoms have exactly two bonds p–o–p starting from them. all r n or values are averaged over five final configurations. fraction of p 4 op (all surroundings are phosphate) is about 5% even at the highest p2o5 content and almost disappears at x = 70 mol %. p 0 op (all atoms in the second coordination sphere are vanadium) grows from 12 to 85 %, and this concentration dependence can be divided into three regions (x = 35– 50, 55–70, and 75–95 mol %) with the increasing slope. starting from x = 75 mol %, more than half of the phosphorous atoms are surrounded by vanadium. the dependence of p 1 op (single p–o–p clusters inside of the vanadate matrix) passes through the maximum. fraction of these units grows up to the point x = 50 mol % and then, after x = 65 mol % falls, i.e., initially dilution of the system by vanadium leads to breaking of the phosphate network with the creation of single clusters, and then they also disappear. 4 5 6 0 10 20 30 40 50 60 70 a p e rc e n t o f v c o o rd in a ti o n coordination number x = 35 x = 40 x = 45 x = 50 x = 55 x = 60 x = 65 x = 70 x = 75 x = 80 x = 85 x = 90 x = 95 35 40 45 50 55 60 65 70 75 80 85 90 95 4.70 4.72 4.74 4.76 4.78 4.80 4.82 4.84 4.86 b m e a n v c o o rd in a ti o n n u m b e r x, mol. % fig. 5 (a) distributions of vanadium ions by coordination number (at cutoff of 2.21 å) for different compositions and (b) mean coordination number as a function of vanadium content a b chimica techno acta 2021, vol. 8(2), № 20218211 article 7 of 11 fig. 6 explanation of r n or notation: p atom labeled “1” has two bonds with vanadium (via oxygen) and two bonds with phosphorous (via oxygen), so it can be indicated p 2 ov as well as p 2 op. similarly, the 2 nd atom is p 1 ov/p 3 op, and 3 rd is v 3 ov/v 2 op the fraction of vanadium fully surrounded by phosphorous (v 0 ov) falls with increasing of v2o5 content and disappears starting from x = 80 mol %, fig. 8. the numbers of isolated (v 1 ov) and “chained” (v 2 ov) vanadate fragments also fall. the fraction of v 3 ov passes through the maximum at x = 60 mol %, v 4 ov grows sigmoidal and reaches a plateau value of ~1/3 at x = 75 mol %. this coordination dominates up to x = 90 mol %, and then v 5 ov dominates. v 6 ov increases weakly and reaches values about 7% at x = 95 mol %. this fact is related to the vanadium coordination number. unlike phosphorous, vanadium coordination numbers can vary from 4 to 6, and v 4 ov may mean that vanadium has only four v–o–v bonds as well as more than four bonds, and only four of them are v–o–v. it is interesting that p 2 ov fluctuates around 30% for all studied compositions but two last, i.e., every third p atom has two p–o–v bonds, fig. 9. the fraction of p atoms without p–o–v bonds (p 0 ov) drops dramatically down to the value of 2.4% at x = 65 mol %, then decreases smoothly and disappears around x = 85 mol %. 35 40 45 50 55 60 65 70 75 80 85 90 95 0 20 40 60 80 p n o p , % x, mol.% n = 0 n = 1 n = 2 n = 3 n = 4 fig. 7 fraction of p n op as a function of vanadium oxide content for simulated xv2o5–(100-x)p2o5 glasses according to fig. 10, the number of vanadium atoms without connection with phosphorous (v 0 op) grows from ~5 to 85%. v 6 op is about zero for all compositions (is not shown in figures). comparison with fig. 8, which shows that isolated vanadate units still exist, one can conclude that v atoms, which are linked only to p atoms, have coordination less than 6. v 5 op almost disappears from x = 60 mol %, v 4 op – from x = 80 mol %. v 1 op passes through the maximum at x = 75 mol %. in addition, we analyzed the obtained configurations for 4-, 6and 8-membered cycles using the written script. the preliminary results, averaged over five configurations, are summarized in table 3. as one can see from the table, the total number of cycles, as well as the number of participated in cycles atoms, grows with increasing of v2o5 content. it is interesting that 4-membered cycles were detected. in terms of coordination polyhedra, such cycles mean that two coordination polyhedra have a shared edge, not a corner which is against zachariasen’s rule [49]. 30 40 50 60 70 80 90 100 0 5 10 15 20 25 30 35 a v n o v , % x, mol.% n = 0 n = 1 n = 2 30 40 50 60 70 80 90 100 0 10 20 30 40 50 b v n o v , % x, mol.% n = 3 n = 4 n = 5 n = 6 fig. 8 fraction of v n ov as a function of vanadium oxide content for simulated xv2o5–(100-x)p2o5 glasses: (a) n = 0–2 and (b) n = 3–6 chimica techno acta 2021, vol. 8(2), № 20218211 article 8 of 11 fig. 11(a) demonstrates the number of r–o–r–o cycles related to the number of corresponding atoms; these fractions directly correlate with the amount of phosphorous/vanadium in the system. however, the formation of 4-membered cycles is less typical for phosphorous than for vanadium. even at high p2o5 content, less than 5% of phosphorous participates in such cycles. one can conclude that phosphorous oxide obeys zachariasen’s rule strictly than vanadium oxide. this leads to the fact that p2o5 is the main glass former and v2o5 is an intermediate. in general, vanadium is more prone to form cycles due to higher coordination numbers and longer v–o bonds. fig. 11(b) shows the dependences of the number of 6membered cycles normalized to the total number of p and v atoms. here is also evident that vanadium tends to form cycles better than phosphorous. even at the equimolar ratio of the oxides in the glass (x = 50 mol %), the dominated cycle’s species is vvp. starting from x = 55 mol %, the numbers of the vvv and vvp cycles are comparable, and from x = 70 mol %, the vvv cycles become dominated among 6-membered cycles. examples of the found cycles are given in fig. 12. 35 40 45 50 55 60 65 70 75 80 85 90 95 0 5 10 15 20 25 30 35 40 p n o v , % x, mol.% n = 0 n = 1 n = 2 n = 3 n = 4 fig. 9 fraction of p n ov as a function of vanadium oxide content for simulated xv2o5–(100-x)p2o5 glasses 35 40 45 50 55 60 65 70 75 80 85 90 95 0 10 20 30 40 50 60 70 80 90 a v n o p , % x, mol.% n = 0 n = 1 n = 2 35 40 45 50 55 60 65 70 75 80 85 90 95 0 5 10 15 20 25 30 b v n o p , % x, mol.% n = 3 n = 4 n = 5 fig. 10 fraction of v n op as a function of vanadium oxide content for simulated xv2o5–(100-x)p2o5 glasses 35 40 45 50 55 60 65 70 75 80 85 90 95 0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 a p-o-p-ocycles n (r r c y c le s ) / n (r a to m s ) x, mol. % v-o-v-ocycles 35 40 45 50 55 60 65 70 75 80 85 90 95 0 2 4 6 8 10 12 14 16 ppp cycles vpp cycles vvp cycles n c y c le s / ( n p + n v ), % x, mol. % vvv cycles b fig. 11 (a) number of r–o–r–o cycles normalized per number of corresponding elements as a function of vanadium content and (b) the number of 6-membered cycles of each type normalized per sum of vanadium and phosphorous atoms chimica techno acta 2021, vol. 8(2), № 20218211 article 9 of 11 table 3 statistics by cycles: number of cycles (nc), number of atoms participated in cycles (nat) and number of each cycle (as a percentage of the total cycle number). the record vv means v–o–v–o– cycle, vp means v–o–p–o– cycle, etc. x nc nat vv vp pp vvv vvp vpp ppp vvvv vvvp vpvp vvpp vppp pppp 35 317.8 1258.2 11.0 21.9 8.2 2.5 9.7 9.5 2.3 2.4 6.5 4.2 7.7 10.8 3.2 40 394.0 1485.4 12.9 21.4 6.1 2.0 12.1 9.1 2.1 0.8 8.7 5.0 8.9 8.4 2.4 45 406.4 1446.4 17.3 18.1 4.0 3.9 13.6 9.0 0.6 2.9 12.5 2.8 9.2 5.5 0.5 50 368.0 1344.6 27.3 14.9 3.6 7.3 11.5 6.6 0.5 4.6 9.5 3.3 6.4 4.1 0.3 55 445.2 1559.6 23.3 15.8 3.6 10.3 10.6 6.2 0.9 7.0 12.1 2.3 4.6 3.0 0.2 60 506.6 1700.8 26.4 13.3 2.3 9.7 10.5 5.0 0.4 6.4 15.4 2.8 6.4 1.2 0.2 65 556.4 1803.0 27.5 15.4 0.8 9.6 10.4 4.1 0.2 11.3 11.7 1.0 6.6 1.4 0.0 70 557.4 1901.6 30.1 10.6 0.9 12.8 10.2 2.9 0.2 10.2 13.4 3.0 4.2 1.3 0.1 75 650.6 2026.8 28.9 8.3 0.5 16.3 9.6 1.8 0.1 14.9 15.1 1.5 2.4 0.5 0.1 80 697.2 2087.4 32.2 8.2 0.3 14.4 7.6 1.3 0.1 19.8 13.9 0.0 2.1 0.0 0.0 85 690.8 2109.0 33.1 4.5 0.2 19.2 5.4 0.9 0.0 24.6 9.4 1.0 1.6 0.1 0.0 90 775.8 2293.8 35.1 4.4 0.0 20.3 5.2 0.2 0.0 26.3 7.8 0.5 0.2 0.0 0.0 95 772.4 2302.6 40.4 1.6 0.1 18.7 1.9 0.1 0.0 32.4 4.4 0.0 0.4 0.0 0.0 fig. 12 examples of found 6and 8-membered cycles in the simulated xv2o5-(100-x)p2o5 glasses for (a) x = 35, (b) x = 50 and (c) x = 80 mol %. only atoms participating in the cycles are shown. colors: magenta – p, gray – v, red – o. 4.4. connectivity of structure and properties it was mentioned above that some intervals of v2o5 content can be distinguished by the spectrum shape, namely, 95–70, 65–55, and 50–35 mol % v2o5. observed structural changes agree well with the concentration dependences of other physicochemical properties of the xv2o5–(100-x)p2o5 glasses found earlier [8]. a bend was observed in the concentration dependence of glass transition temperature in the area of x = 65–70 mol % (fig. 13a). it was suggested that this effect could be explained by changing the glass structure, for example, by the transition from predominant vanadium-oxygen units to a mixed vanadiumphosphate network with a predominance of phosphate structural units. according to the ir spectroscopy results, a noticeable restructuring is observed in this range of v2o5 concentration which agrees with our hypothesis. it was confirmed by the simulation results (fig. 13a): above x = 65 mol %, phosphorous atoms without vanadium ones in the second coordination sphere are almost absent. when x < 65 mol %, the number of such phosphorous atoms sharply increases, i.e., isolated phosphorous clusters are formed (fig. 9). moreover, a change in conductivity behavior was observed in the same range of v2o5 concentrations which was expressed as a change in the impedance spectra shape and a sudden decrease in conductivity (fig. 13b). it was assumed that such behavior is connected with a change in the charge transfer mechanism in the studied glasses. based on the data on the structure of phosphate-vanadate glasses, one can assume that structural changes strongly affected the conductivity. similar changes were observed at x = 45–50 mol % that can also be explained by the change of the glass network from mixed to predominantly phosphate with vanadium-oxygen clusters. when x < 50 mol %, the number of phosphorous atoms with two bonds p–o–p (which could be considered as phosphate chains with vanadate branches) is about a third of all phosphorus atoms, and it decreases with the x growth (fig. 7). moreover, it is seen that at x = 50 mol %, a sharp increase in the fraction of phosphorus atoms isolated by the vanadate matrix begins. thus, it can be concluded that the observed deviations in the concentration dependences of some physicochemical properties of xv2o5–(100-x)p2o5 glasses can be explained by the detailed investigation of their structure by ir spectroscopy combined with the analysis of atomic configurations obtained by molecular simulation. a b c chimica techno acta 2021, vol. 8(2), № 20218211 article 10 of 11 fig. 13 (a) concentration dependences of glass transition temperature (tg) and p 3 op cycles and (b) concentration dependences of lgσ50 and v 5 ov cycles. data on glass transition temperature and electrical conductivity are taken from [8] 5. conclusions xv2o5–(100-x)p2o5 (x = 35–95 mol %) glasses were studied by ir spectroscopy. by means of deconvolution of the ir spectra, the data were obtained on changes in the glass structure, and the correlation of these changes with a number of physicochemical properties was shown. to obtain the structural models of the glasses, self-assembly was performed using non-constant field molecular dynamics. the models were analyzed to find the atom distribution by the number of defined triatomic sequences. bends and kinks are observed in their concentration dependences, which indicate the transitions between the main glassforming elements. these points coincide with the changes observed in the ir spectra. it was established from the analysis of obtained molecular configurations of glasses in the presence of cycles that the vanadate fragments are much more prone to the ring formation, including 4-membered cycles. according to zachariasen’s rule, systems with 4-membered cycles (edge connected coordination polyhedra) cannot have a strong tendency to vitrification. so, our results can explain why v2o5 has much lower glass-forming ability than p2o5 (melts enriched with vanadium require higher cooling rate to vitrify). acknowledgements the research was supported by the russian science foundation (project no. 18-73-10205). references 1. el-damrawi g, abdelghany am, hassan ak, faroun b. conductivity and morphological studies on iron borosilicate glasses. j non cryst solids. 2020;545:120233. doi:10.1016/j.jnoncrysol.2020.120233 2. kaur n, khanna a, fábián m, dutt s. structural and electrical characterization of semiconducting xcuo-(100-x)teo2 glasses. j non cryst solids. 2020;534:119884. doi:10.1016/j.jnoncrysol.2020.119884 3. ningthemcha rkn, biswas d, singh yb, sarkar d, mondal r, mandal d, et al. temperature and 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polytechnic university, 614990, perm, russia c: itmo university, 197101, saint petersburg, russia * corresponding author: s.shipilovskikh@metalab.ifmo.ru this short communication (letter) belongs to the mosm2021 special issue. © 2021, the authors. this article is published in open access form under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). abstract the diphenyl sulfoxide-catalyzed conversion of aldehydes to 1,1-dichlorides is reported. the reaction proceeds via a sulfurous (iv)-catalysis manifold in which diphenyl sulfoxide turnover is achieved using oxalyl chloride as a consumable reagent. keywords aldehydes lewis base catalysis organocatalysis diphenyl sulfoxide received: 31.10.2021 revised: 17.11.2021 accepted: 01.12.2021 available online: 03.12.2021 1. introduction nucleophilic substitutions sn are general chemical transformations, as they allow, for example, strategic building of c–cl, c–o, c–n and c–c bonds [1–10]. in addition, geminal dihalides, especially dichlorides, are important intermediates in chemical synthesis, and the traditional synthesis protocols are often limited in terms of cost efficiency and waste balance [11, 12]. however, research in this area is at an early stage in the study of such catalytic reaction. although by now several effective protocols for the preparation of dichlorides from aldehydes catalyzed by a lewis base have been disclosed [13, 14], all possibilities for studying these reactions have not yet been realized (scheme 1). dichlorides – important class of intermediates in organic synthesis. they were used for alkenylation of carbonyl compounds [15, 16], cyclopropanation and epoxidation [17–19], dimerization [20, 21] and others [22–25]. in addition, geminal dichlorides are encountered as structural motifs in polyhalogenated natural products [26, 27] (fig. 1). 2. experimental yields are given for isolated products showing one spot on a tlc plate and no impurities detectable in the nmr spectrum. the identity of the products prepared by different methods was checked by comparison of their nmr spectra. 1h and 13c nmr spectra were recorded at 400 mhz for 1h and 100 mhz for 13c nmr at room temperature; the chemical shifts (δ) were measured in ppm with respect to the solvent (cdcl3, 1н: δ = 7.26 ppm, 13c: δ = 77.16 ppm; [d6] dmso, 1н: δ = 2.50 ppm, 13c: δ = 39.52 ppm). coupling constants (j) are given in hertz. splitting patterns of apparent multiplets associated with an averaged coupling constants were designated as s (singlet), d (doublet), t (triplet), q (quartet), sept (septet), m (multiplet), dd (doublet of doublets) and br (broadened). melting points were determined with a «stuart smp 30», the values are uncorrected. flash chromatography was performed on silica gel macherey nagel (40–63 µm). reaction progress was monitored by gc/ms analysis and thin layer chromatography (tlc) on aluminum backed plates with merck kiesel 60 f254 silica gel. the tlc plates were visualized either by uv radiation at a wavelength of 254 nm, or stained by exposure to a dragendorff’s reagent or potassium permanganate aqueous solution. all the reactions were carried out using dried and freshly distilled solvent. 2.1. general method for synthesis of dichlorides from aldehyde diphenyl sulfoxide (ph2so) (40 mg, 0.2 mmol, 0.1 equiv, 10 mol.%) and aldehyde 1 (2 mmol, 1 equiv) were dissolved in 15 ml of anhydrous toluene in a 25 ml round bottom flask equipped with a magnetic stirring bar. the resulting solution was treated dropwise with neat oxalyl chloride (0.26 ml, 3 mmol, 1.5 equiv (chlorine source)) http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2021.8.4.08 http://creativecommons.org/licenses/by/4.0/ https://orcid.org/0000-0002-8917-2583 chimica techno acta 2021, vol. 8(4), № 20218408 letter 2 of 4 using an adjustable volume pipette (0.1–1.0 ml), followed by the temperature increase up to 100 °c; the mixture was stirred for 6 h. the reaction progress was monitored by gc-ms. after the reaction was complete, the solution was filtered and concentrated in vacuum. the crude mixture thus obtained was purified by flash chromatography on silica (petroleum ether/et2o – 19/1). 2.1.1. (dichloromethyl)benzene 4а obtained from 1a (212 mg, 2 mmol), diphenyl sulfoxide (ph2so) (40 mg, 0.2 mmol, 0.1 equiv, 10 mol.%), and oxalyl chloride (0.26 ml, 3 mmol, 1.5 equiv), in anhydrous toluene (15 ml). colorless oil (242 mg, 75%). 1h nmr (cdcl3, 400 mhz) δ (ppm): 6.75 (s, 1h, ch), 7.44 (m, 3h, har), 7.66 (m, 2h, har). 13c nmr (cdcl3, 100 mhz) δ (ppm): 72.0, 126.2, 128.8, 123.0, 140.4. 2.1.2. 1-(dichloromethyl)-4-methylbenzene 4b obtained from 1b (240 mg, 2 mmol), diphenyl sulfoxide (ph2so) (40 mg, 0.2 mmol, 0.1 equiv, 10 mol.%), and oxalyl chloride (0.26 ml, 3 mmol, 1.5 equiv), in anhydrous toluene (15 ml). colorless oil (278 mg, 80%). 1h nmr (cdcl3, 400 mhz) δ (ppm): 2.40 (s, 3h, ch3), 6.68 (s, 1h, ch), 7.23 (m, 2h, har), 7.48 (m, 2h, har). 13c nmr (cdcl3, 100 mhz) δ (ppm): 21.7, 71.6, 126.1, 129.3, 137.5, 140.9. 2.1.3. 1-bromo-4-(dichloromethyl)benzene 4с obtained from 1с (370 mg, 2 mmol), diphenyl sulfoxide (ph2so) (40 mg, 0.2 mmol, 0.1 equiv, 10 mol.%), and oxalyl chloride (0.26 ml, 3 mmol, 1.5 equiv), in anhydrous toluene (15 ml). colorless oil (345 mg, 72%). 1h nmr (cdcl3, 400 mhz) δ (ppm): 6.68 (s, 1h, ch), 7.46 (m, 2h, har), 7.55 (m, 2h, har). 13c nmr (cdcl3, 100 mhz) δ (ppm): 72.0, 124.3, 128.0, 131.9, 139.4. 2.1.4. 1-(dichloromethyl)-4-nitrobenzene 4d obtained from 1d (302 mg, 2 mmol), diphenyl sulfoxide (ph2so) (40 mg, 0.2 mmol, 0.1 equiv, 10 mol.%), and oxalyl chloride (0.26 ml, 3 mmol, 1.5 equiv), in anhydrous toluene (15 ml). colorless oil (259 mg, 63%). 1h nmr (cdcl3, 400 mhz) δ (ppm): 6.78 (s, 1h, ch), 7.78 (m, 2h, har), 8.29 (m, 2h, har). 13c nmr (cdcl3, 100 mhz) δ (ppm): 70.2, 124.5, 127.9, 146.6, 149.2. 2.1.5. (e)-(3,3-dichloroprop-1-en-1-yl)benzene 4e obtained from 1e (264 mg, 2 mmol), diphenyl sulfoxide (ph2so) (40 mg, 0.2 mmol, 0.1 equiv, 10 mol.%), and oxalyl chloride (0.26 ml, 3 mmol, 1.5 equiv), in anhydrous toluene (15 ml). colorless oil (286 mg, 77%). 1h nmr (cdcl3, 400 mhz) δ (ppm): 6.34 (d, j = 7.6 hz, 1h, ch), 6.39 (dd, j = 14.7 and 7.6 hz, 1h, ch), 6.72 (d, j = 14.7 hz, 1h, ch), 7.41 (m, 5h, har). 13c nmr (cdcl3, 100 mhz) δ (ppm): 73.5, 127.0, 128.2, 129.1, 129.3, 132.5, 134.9. scheme 1 deoxydichlorination of aldehydes to 1,1-dichlorides fig. 1 natural products including a fragment of dichlorides chimica techno acta 2021, vol. 8(4), № 20218408 letter 3 of 4 3. results and discussion the investigation commenced with establishing the best conditions for the deoxydichlorination of aldehydes, employing benzaldehyde 1a as a model substrate (scheme 2). first, the role of each reagent was evaluated. oxalyl chloride on its own did not produce (dichloromethyl)benzene 4a (table 1, entry 1). the use of stoichiometric quantities of ph2so and (cocl)2 in acetonitrile resulted in low conversion of 1a into 4a (entry 2). with 10 mol.% ph2so and 1 equiv of oxalyl chloride, 4a was formed in 15% conversion (entry 3), which increased to 51% after change the solvent on toluene (entry 4). the up of the temperature to 100 °c and use 1.5 equiv of oxalyl chloride to give the best results of conversion to 92% (entry 11). scheme 2 the reaction for optimization of the conditions table 1 optimization of the reaction conditions entry equiv of (cocl)2 ph2so, mol.% solvent t, °c t, h conv., %b 1 1 – mecn 50 1 0 2 1 100 mecn 50 1 19 3 1 10 mecn 50 6 15 4 1 10 tol 50 6 53 5 1 10 dcm 40 6 10 6 1 10 dce 50 6 18 7 1 10 thf 50 6 37 8 1 10 et2o 30 6 4 9 1 10 tol 100 6 85 10 1 10 tol 100 12 88 11 1.5 10 tol 100 6 92 ageneral conditions: 1a (0.2 mmol), ph2so, dry solvent (1 ml), dropwise addition of neat (cocl)2. the reactions were carried out for 1–12 h before an aliquot (50 μl) was taken, quenched with aqueous solvent (1 ml), and analyzed by gc. bconversion to 4a was calculated from gc. the substrate scope was investigated next. as shown in scheme 3, the reaction work well with different type of aromatic aldehydes, including donor and acceptor substituents at the fourth position of the ring. the use of cinnamaldehyde under the reaction conditions also showed good results. the proposed mechanism is depicted in scheme 4. we think that the catalytic cycle start with quick formation of the intermediate chlorodiphenylsulfonium chloride (b) upon treatment of diphenyl sulfoxide (a) with (cocl)2. previously, a similar process was carried out by denton with triphenylphosphine oxide as a catalyst [14]. next, in the catalytic cycle, the intermediate b reacts with the aldehyde 1 via oxygen to form the intermediate c, which then undergoes elimination to furnish the geminal dichloride 4 and regenerate the catalyst a. scheme 3 deoxydichlorination of aldehydes catalyzed by diphenyl sulfoxide 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https://doi.org/10.1055/s-0036-1588633 https://doi.org/10.1021/acscatal.0c03348 https://doi.org/10.1021/acs.orglett.7b03862 https://doi.org/10.1039/c9sc02126d https://doi.org/10.1002/ejoc.201800907 https://doi.org/10.1002/chem.201800588 https://doi.org/10.1021/acs.orglett.9b01687 https://doi.org/10.1016/s0040-4020(99)00021-6 https://doi.org/10.1021/jo980724h https://doi.org/10.1055/s-0037-1611798 https://doi.org/10.1016/j.tet.2013.07.100 https://doi.org/10.1021/jo070209w https://doi.org/10.1055/s-0029-1216880 https://doi.org/10.1016/j.tet.2013.12.016 https://doi.org/10.1002/anie.201511271 https://doi.org/10.1039/c5ob02617b https://doi.org/10.1021/jo062492p https://doi.org/10.1002/ejic.200601106 https://doi.org/10.1021/ja300743t https://doi.org/10.1021/ol302790e https://doi.org/10.1002/chem.201404668 https://doi.org/10.1021/acs.joc.8b01091 https://doi.org/10.1002/ejoc.201101525 121 a. a. uritskaya1, n. s. kozhevnikova2, t. v. yakubova3 1ural federal university, 19 mira st., 620002 еkaterinburg, russia 2institute of solid state chemistry urb ras, 91 pervomaiskaya st., 620990 еkaterinburg, russia 3ural institute of state fire service of emercom of russia, 22 mira st., 620002 еkaterinburg, russia теl.: (343) 362-35-64 e-mail: kozhevnikova@ihim.uran.ru kinetics of chemical bath deposition of zinc sulfide zns* the paper is devoted to kinetic methods of chemical bath deposition of zinc sulfide zns from aqueous alkaline solutions containing ehylenediamine complex zinc salt zn(en) n 2+ and diamide of thiocarbonic acid n 2 h 4 cs. it is established that the rate of formation of zns is weakly dependent on ph, depends on the concentration of the precipitant ((n 2 h 4 cs) and decreases with increasing concentration of ligand (ethylenediamine). the calculation of the theoretical curves on the experimentally obtained kinetic equation shows a satisfactory description of experimental data that allows to recommend it to calculate the rate of formation of zns in aqueous alkaline solutions of n 2 h 4 cs. кey words: chemical bath deposition, thiourea, ethylenediamine, detectors of ultraviolet radiation, the apparent rate constant of the reaction, the true rate constant of the reaction *this work was done under financial support from rfbr (project 16-03-00566). а. а. урицкая, н. с. кожевникова, т. в. якубова кинетика химического осаждения сульфида цинка zns* работа посвящена исследованию кинетическими методами химического осаждения сульфида цинка zns из водных щелочных растворов, содержащих этилендиаминовую комплексную соль цинка zn(en) n 2+ и диамид тиоугольной кислоты n 2 h 4 cs. установлено, что скорость образования zns слабо зависит от величины рн, зависит от концентрации осадителя (n 2 h 4 cs) и уменьшается с увеличением концентрации лиганда (этилендиамина). расчет теоретических кривых по полученному экспериментально кинетическому уравнению показывает удовлетворительное описание полученных экспериментальных данных, что позволяет рекомендовать его для расчета скорости образования zns в водных щелочных растворах n 2 h 4 cs. ключевые слова: химическое осаждение; тиомочевина; этилендиамин; детекторы ультрафиолетового излучения; кажущаяся константа скорости реакции; истинная константа скорости реакции. *работа выполнена при финансовой поддержке рффи (проект № 16-03-00566). © uritskaya a. а., kozhevnikova n. s., yakubova t. v., 2016 d o i: 1 0. 15 82 6/ ch im te ch .2 01 6. 3. 2. 00 9 уд к 54 4. 42 1: 54 4. 42 2: 54 9. 32 1 uritskaya a. а., kozhevnikova n. s., yakubova t. v. chimica techno acta. 2016. vol. 3, no. 2. p. 121–133. issn 2409-5613 122 introduction zinc sulfide zns, being one of the most important representatives of the wide-band-gap semiconductors, is studied intensively in recent time as a promising material for the creation of detectors of ultraviolet radiation [1]. zns is one of the first [2] and important compounds used as matrix for phosphors [3]. zns doped with ions of transition metals ((mn2+, cu2+) allows us to observe the luminescence under the influence of radiation with higher energies, e.g. x-ray and ultraviolet [4, 5]. the interest in zns as the optical material for photonic crystals is determined by its properties: high values of integral transmittance (~0.72) in the range 400–14000 nm and the refractive index (2.3 at a wavelength of 1 µm) [6, 7]. in this regard, a large number of works were devoted and dedicated to the synthesis of zns [8, 9]. among many problems in the synthesis of new compounds there is one of the most important. it’s determination of the flow rate of the transformations in the studied systems. the knowledge of the rate of chemical reaction allows creating technological scheme of production of new materials without solving complex problems of the reaction mechanism. the rate of any chemical reaction is determined experimentally [10]. the present work is devoted to study of kinetic methods of chemical deposition of zinc sulfide zns from aqueous alkaline solutions containing ehylenediamine complex zinc salt zn(en)n 2+ and diamide of thiocarbonic acid n2h4cs. with the introduction of n2h4cs in the solution of complex salt of zinc the formation of a solid phase zns begins according to reaction: zn(en)n 2+ + n2h4cs + 2oh – = = zns + nen + h2cn2 + 2h2o. (1) previously it was found [11, 12] that chemical precipitation of sulphides of metals from solutions of thiourea is a heterogeneous autocatalytic process. and the surface of the metal sulfide formed in the reaction is the catalyst of this process. therefore describing the kinetics of the process (1) in this article we proceeded from the assumption that the formation of zns can also be viewed as a heterogeneous process. in this paper we have confined the study of formal kinetic regularities. for the compilation of the kinetic equation it is necessary to determine the reaction order for each precursor. in application to heterogeneous catalytic processes we distinguish the true and apparent reaction order. true order is an order of the reaction regarding concentration of reagents on the surface of the solid phase and apparent order is the order of reaction with respect to varying volumetric concentrations of reagents in solution. in this work we determined the apparent orders of reaction (1) on the components. a formal kinetic equation for the rate w of process (1) can be written as follows: w k e rt sc c c cen n tm n n n = − × × − + 0 1 2 3 2 4 exp( / ) , oh zn (2) where cen, ctm, coh–, czn2+ are the current concentrations of reaction mixture components; n1, n2, n3, n4 are the kinetic orders of reaction by components: ethylenediamine, thiourea, alkali, salts of zinc, respectively; s is the surface of the solid phase on which the formation of zns occurs; k0 is the pre-exponential factor; е is activation energy; r is universal gas constant; т is temperature, k. at the kinetic description the rate of the heterogeneous process depends not 123 only on the concentration of reactants, ph value, temperature, which are easily measurable, but on the size of the surface of the solid phase which is continuously changing during the process due to nucleation, coagulation and sedimentation of the solid phase. therefore the study of the kinetic of the process (1) was conducted using pre-introduced solid phase with known surface value. the experimental part when conducting kinetic study the concentrations of the solutions were the following, mol/l: [znso4] = 0.5, [en] = 5.0, [n2h4cs] = 0.5, [naoh] = 1–4. the concentration of the precursors in the reaction mixtures was ranged: mol/l: [znso4] = 0.008–0.020, [en] = 0.10–0.25, [n2h4cs] = 0.08–0.20, рн = 11.5–12.5. with the aim of obtaining reproducible results the order of merging reagents has passed. the calculated volume of znso4 solution was poured into volumetric flask, en and water were added. the set value of ph was adjusted by the introduction of naoh and then a solution of n2h4cs was added. the reaction mixture was prepared at room temperature. at the next phase the solid phase with known surface value, which was created by the introduction of glass powder of sodium borosilicate composition into the reactor was added in the reaction mixture [13]. the glass powder was prepared in the laboratory according to the method described previously [14]. the obtained glass powder had a median particle size of 50 μm and a size of specific surface area of 24.5 m2/kg calculated from the known density of the glass 2450 kg/m3 [13]. the hitch of glass powder, 0.1 kg per 1 liter of solution, allowed localizing the process on the surface of the glass, i.e. eliminating the zns nucleation in the volume of the reaction solution was installed by the preliminary series of experiments [14]. the glass powder was preliminarily coated with a film of zns. to maintain particles in a suspended state, the process (1) was carried out under continuous stirring with a stirrer with flexible drive with a speed of 300 rev/min. to determine the order of reaction (1) on components the method of ostwald-neues was used [15]. for this purpose the conditions were created under which in reaction (1) the concentration of only one component would change and the concentrations of all other substances participating in the reaction were set in excess and their changes in time can be neglected. therefore equation (2) at a given temperature can be represented in the form: w k cn= +exp zn2 4 , (3) where k k sc c cen n tm n n exp = −’ 1 2 3 oh is the apparent rate constant of the reaction, k' is the true rate constant of reaction per unit surface zns and the unit of concentration of components with respect to orders of the reaction. equation (3) proved that to determine the reaction rate w it was sufficient to take down experimentally the dependence of concentrations of ions zn2+ on time in different reaction solutions. the measurement of concentrations of ions zn2+ was produced by the method of sampling from the reactor by chemical-analytical way, i.e. using complexometric direct titration with visual indication of the equivalence point by using an indicator eriochrome black t in a mixture with sodium chloride at ph = 10. to maintain a 124 constant temperature during the reaction (1) a liquid thermostat with a temperature support stability of 0.1 degrees was used. the control of ph was performed using ph meter hanna instruments hi 98130 with accuracy of the measurement of ph equal to 0.02. the mathematical treatment of kinetic curves obtained in the conditions when only one of the system parameters was changing while other parameters were constant (for example, the en concentration changes at constant concentrations n2h4cs, ph, temperature and degree of loading of the glass powder), allowed to determine the reaction rate constant under different conditions, as well as private orders of reaction (1) on components. the process (1) was controlled to achieve the equilibrium corresponding to the appearance of the horizontal section on the kinetic curve. the kinetic curves were described by the equation of two-sided reaction of first order. lg . , x x x k kpr form∞ ∞− = +( ) 2 3 τ (4) where x∞, x are the number of complex salt zn(en)n 2+ converted to the sulfide by the time to reach equilibrium and any time τ, respectively; kpr is the rate constant of the process of formation of zns; kform is the rate constant of the decay process of zns. the graphical solution of the equation (4) is a straight line in the coordinates lg(x∞/(x∞– x)) – τ with an angular coefficient а, equal to the sum of the constants of direct kpr and reverse kform reactions (fig. 2). to find the rate constant for the reaction of formation of zns kpr the ratio characterizing the equilibrium state kpr / kform = x∞/(c0 – x∞) was used, where с0 is the initial concentration of znso4 in solution. results and discussion the typical kinetic curves, taken off in the conditions of the controlled surface at a temperature 363 k, initial concentration [n2h4cs] = 0.1 mol/l and и s = 24500 sm2/l are presented on a fig. 1. the process of formation of zns was considered complete, when the equilibrium value of remaining concentration of salt of zinc at in solution was arrived: it’s horizontal area on a kinetic curve. the results of graphic calculation of kpr and kform of reaction (1) for the concentrations of en 0.15 and 0.20 mol/l. the results of calculation of kpr and kform for the concentrations of en 0.1, 0.15, 0.20 and 0.25 the mol/l show that with the increase of concentration of en kpr diminishes, consequently, the rate of reaction diminishes (fig. 2). the concentration of free ions of zn2+ diminishes with the increase of concentration of complexing agent that slows rate of reaction. on the experimental values of kpr at the different initial concentrations of znso4, en, n2h4cs, znso4, en and ph it is possible to define the order of reaction on every component. the calculation of kinetic orders of reaction on components was conducted on equalization lgkpr = lgki + + nilgci which in co-ordinates lgkpr – lgci presents a straight line with the angular coefficient of ni. the graphic decision of this equalization for determination of orders of reaction on components of en, n2h4cs and naoh is presented on a fig. 3–5. 125 thus, it is set as a result of kinetic researches that rate of reaction (1) is proportional the concentrations of components of reactionary solution, which are included in kinetic equalization with the followings indexes of degree: on the found values of seeming constant of rate the veritable constant of rate component znso4 en n2h4cs naoh the seeming private order of reaction (1) on the component of ni 1.0 –1.9 1.2 0.3 fig. 1. the dependence of rate of reaction of formation of zns on the concentration of ethylenediamine en. the kinetic curves are taken off in the conditions of the known surface of s = 24500 sm2/l at a temperature 363 k and initial concentration [n2h4cs] = 0.1 mol/l. theoretical curves are expected on equalization (6) fig. 2. the graphic determination of constants of rate of kpr and kform of process (1) on equalization of two-sided reaction of the first order (4). a process (1) was conducted in the conditions of the known surface of s = 24500 sm2/l at a temperature 363 k and [n2h4cs] = 0.1 mol/l fig. 3. the graphic determination of private order n1 of reaction of formation of zns (1) on ehylenediamine. a reaction was conducted in the conditions of the known surface of s = 24500 sm2/l at a temperature 363 k and и [n2h4cs] = 0.1 mol/l fig. 4. the graphic determination of private order n2 of reaction of formation of zns (1) on thiourea. a reaction was conducted in the conditions of the known surface of s = 24500 sm2/l at a temperature 363 k and [en] = 0.15 mol/l 126 of heterogeneous reaction of formation of zns was calculated at a temperature 363 k, attributed to unit of surface of hard phase of zns and unit of concentrations of every component taking into account the private orders of reaction: k k sc c cen tm ’ . . . . = − − exp 1 9 1 2 0 3 oh (5) the data got on equalization (5) show that at the changing concentrations of components of reaction rate of reaction mixture k' remain permanent within the limits of error of experiment. the mean value k' make (3.69±0.13)· ·10–7 l0.6·mol0.4·min–1·sm–2 under 363 k. to determine the experimental dependence of reaction rate of sulphide formation on temperature the series of experiments were conducted at temperatures 358, 363 and 369 k, that allowed graphically (fig. 6) determination of activation energy of process by arrhenius equation: lgk' = lgk0 – (e/2.3rt) which made e = 84.5±0.5 kj/mol. the found value of activation energy showed that the process of formation of zns in the system was not limited by the stage of diffusion as for diffusive processes the small values of energy of activating are from 8 to 30 kj/mol [15]. the pre-exponential multiplier of equalization of arrhenius is expected on the veritable rate constant at 363 k and at the known value of energy of activating of e: k0 = 5.39·10 5 mol0.4l0.6sm–2min–1. it is set as a result of the conducted research, that the process of formation of zns (1) is described formal kinetic equalization: w sc c cen tm = ⋅ −      × × − − 5 39 10 84500 8 3147 5 1 9 1 2 0 . exp . . . . oh 33 0c x−( ). (6) conclusion thus, in the terms chosen in this work the rate of process (1) depends weakly on the size of ph that is explained by the buffer action of ethylenediamine, depends on the concentration of precipitafig. 5. the graphic determination of private order n3 of reaction of formation of zns (1) to on он–-ions. a reaction was conducted in the conditions of the known surface of s = 24500 sm2/l at a temperature 363 k and [n2h4cs] = 0.1 mol/l fig. 6. graphic calculation of energy of activating of process of the chemical precipitation of zns (1) on equalization of arrhenius 127 tor (thiourea) and diminishes with the increase of concentration of ligand (ethylenediamine) from the decline of concentration of free ions of zinc in solution. the calculation of theoretical kinetic curves on equalization (8) shows satisfactory definition of the got experimental data (fig. 1), that allows recommending it for the calculation of formation rate of zns in water alkaline solutions of diamide of thiocarbonic acid. in russian введение сульфид цинка zns, являясь одним из важнейших представителей широкозонных полупроводников, интенсивно исследуется в последнее время как перспективный материал для создания детекторов ультрафиолетового излучения [1]. zns – одно из самых первых [2] и важных соединений, использующихся в качестве матрицы для люминофоров [3]. допирование zns ионами переходных металлов (mn2+, cu2+) позволяет наблюдать люминесценцию под воздействием излучений с повышенными энергиями, например рентгеновского и ультрафиолетового [4, 5]. интерес к zns как к оптическому материалу для фотонных кристаллов определяется его свойствами: высокими значениями интегрального пропускания (~0,72) в диапазоне 400– 14000  нм и коэффициента преломления (2,3 при длине волны 1 мкм) [6, 7]. в связи с этим большое количество работ посвящалось и посвящается синтезу zns [8, 9]. среди многих проблем при синтезе новых соединений существует одна из важнейших – определение скорости протекания превращений в изучаемых системах. знание скорости превращения позволяет создавать технологические схемы производства новых материалов, не решая сложных вопросов о механизме реакций. скорость любой химической реакции определяется экспериментальным путем [10]. настоящая работа посвящена исследованию кинетическими методами процесса химического осаждения сульфида цинка zns из водных щелочных растворов, содержащих этилендиаминовую комплексную соль цинка zn(en)n 2+ и диамид тиоугольной кислоты (тиомочевину) n2h4cs. при введении n2h4cs в раствор комплексной соли цинка, начинается образование твердой фазы zns по реакции: zn(en)n 2+ + n2h4cs + 2oh – = = zns + nen + h2cn2 + 2h2o. (1) ранее было установлено, что химическое осаждение сульфидов металлов из растворов тиомочевины является гетерогенным автокаталитическим процессом [11, 12]. а поверхность сульфида металла, образующегося в  результате реакции, является катализатором этого процесса. поэтому при кинетическом описании процесса (1) в данной работе исходили из предположения, что формирование zns также можно рассматривать как гетерогенный процесс. в данной работе мы ограничились исследованием формальных кинетических закономерностей. для составления кинетического уравнения необходимо определить по128 рядок реакции по каждому исходному компоненту. в применении к гетерогенным каталитическим процессам различают истинный и кажущийся порядок реакции, понимая под истинным порядок реакции относительно концентрации реагентов на поверхности твердой фазы, а кажущийся – порядок реакции по отношению к объемным изменяющимся концентрациям реагентов в растворе. определены кажущиеся порядки реакции (1) по компонентам. формальное кинетическое уравнение скорости w процесса (1) можно записать следующим образом: w k e rt sc c c cen n tm n n n = − × × − + 0 1 2 3 2 4 exp( / ) , oh zn (2) где cen, ctm, coh–, czn2+ – текущие концентрации компонентов реакционной смеси; n1, n2, n3, n4 – кинетические порядки реакции по компонентам, этилендиамину, тиомочевине, щелочи, соли цинка, соответственно; s – поверхность твердой фазы, на которой происходит образование zns; k0  – пред экспоненциальный множитель; е  – энергия активации процесса; r  – универсальная газовая постоянная; т  – температура, k. при кинетическом описании скорость гетерогенного процесса определяется не только концентрацией реагентов, величиной рн, температурой, которые легко измеримы, но и величиной поверхности твердой фазы, непрерывно изменяющейся в ходе процесса за счет зарождения, коагуляции и седиментации частиц твердой фазы. поэтому изучение кинетики процесса (1) проводили в условиях специально вводимой контролируемой поверхности твердой фазы. экспериментальная часть при проведении кинетических исследований концентрации исходных растворов были следующие, моль/л: [znso4] = 0,5, [en] = 5,0, [n2h4cs] = 0,5, [naoh] = 1–4. концентрации компонентов в реакционных смесях варьировали в пределах, моль/л: [znso4] = = 0,008–0,020, [en] = 0,10–0,25, [n2h4cs]= = 0,08–0,20, рн = 11,5–12,5. с целью получения воспроизводимых результатов выдерживали порядок сливания реагентов. в мерную колбу вливался рассчитанный объем раствора znso4, добавлялся en и вода. заданная величина рн корректировалась введением раствора naoh, и затем добавлялся раствор n2h4cs. реакционная смесь готовилась при комнатной температуре. на следующем этапе в реакционную смесь вводили контролируемую поверхность твердой фазы, которую создавали введением в реактор стеклянного порошка натрий боросиликатного состава [13]. стеклянный порошок готовился в лабораторных условиях по методике, описанной ранее [14]. полученный стеклянный порошок имел средний размер частиц 50 мкм и величину удельной поверхности 24,5 м2/кг, рассчитанную по известной плотности стекла 2450 кг/м3 [13]. предварительной серией экспериментов [14] была установлена навеска стеклянного порошка, равная 0,1 кг на 1  л раствора, позволяющая локализовать процесс на поверхности стекла, т. е. исключить зарождение zns в объеме реакционного раствора. стеклянный порошок предварительно покрывали 129 пленкой zns. для поддержания частиц во взвешенном состоянии процесс (1) проводили при непрерывном перемешивании с помощью мешалки с гибким приводом со скоростью 300 об/мин. для определения порядка реакции (1) по компонентам использовали метод оствальда – нойеса [15]. для этого создавали такие условия, при которых в реакции (1) изменялась бы концентрация только данного компонента, а концентрации всех остальных веществ – участников реакции задавались в избытке, и изменением их во времени можно было пренебречь. следовательно, уравнение (2) при заданной температуре можно представить в виде: w k cn= +эксп zn2 4 , (3) где k k sc c cen n tm n n эксп = −’ 1 2 3 oh – кажущаяся константа скорости реакции, k'– истинная константа скорости реакции, отнесенная к единице поверхности zns и единице концентрации компонентов с учетом порядков реакции по компонентам. анализируя уравнение (3), видно, что для определения скорости реакции w достаточно экспериментальным путем снять зависимость концентрации ионов zn2+ от времени в различных реакционных растворах. измерение концентрации ионов zn2+ произведено методом отбора проб из реактора химико-аналитическим путем, т. е. с использованием прямого комплексонометрического титрования с визуальной индикацией точки эквивалентности с помощью индикатора эриохрома черного т в смеси с хлоридом натрия при рн = 10. для поддержания постоянной температуры в ходе реакции (1) использовали жидкостный термостат со стабильностью поддержания температуры 0,1 градуса. контроль за величиной рн осуществляли с помощью измерителя рн hanna instruments hi 98130 с точностью измерения величины рн, равной 0,02. математическая обработка кинетических кривых, полученных в условиях, когда меняется только один из параметров системы при неизменных остальных (например, меняется концентрация en при постоянных значениях концентрации n2h4cs, рн, температуры и степени загрузки стеклянного порошка), позволила определить константы скорости реакции в разных условиях, а также частные порядки реакции (1) по компонентам. процесс (1) контролировали до достижения равновесия, соответствующего появлению горизонтального участка на кинетической кривой. кинетические кривые описывались уравнением двухсторонней реакции первого порядка: lg , , x x x k k ∞ ∞− = +( )пр обр 2 3 τ (4) где x∞, x – количества комплексной соли zn(en)n 2+, перешедшей в сульфид ко времени достижения равновесия и к любому моменту времени τ, соответственно; kпр – константа скорости процесса образования zns; kобр – константа скорости процесса распада zns. графическим решением уравнения (4) является прямая линия в координатах lg(x∞/(x∞– x)) – τ с угловым коэффициентом а, равным сумме констант прямой kпр и обратной kобр реакций (рис. 2). для нахождения константы скорости реакции образования zns kпр использовали соотношение, характеризующее состояние равновесия, 130 kпр/ kобр = x∞/(c0 – x∞), где с0 – начальная концентрация znso4 в растворе. результаты и обсуждение на рис. 1 представлены типичные кинетические кривые, снятые в условиях контролируемой поверхности при температуре 363 k, начальной концентрации [n2h4cs] = 0,1 моль/л и s = 24500 см2/л. процесс образования zns считался законченным, когда достигалось равновесное значение остаточной концентрации соли цинка в растворе: горизонтальный участок на кинетической кривой. результаты графического расчета kпр и kобр реакции (1) для концентраций en 0,15 и 0,20  моль/л. результаты расчета kпр и kобр для концентраций en 0,1; 0,15; 0,20 и 0,25  моль/л показывают (рис. 2), что с увеличением концентрации en kпр уменьшается, следовательно, уменьшается и скорость реакции. с увеличением концентрации комплексующего агента уменьшается концентрация свободных ионов zn2+, что замедляет скорость реакции. по экспериментальным значениям kпр при различных начальных концентрациях znso4, en, n2h4cs и рн можно определить порядок реакции по каждому компоненту. расчет кинетических порядков реакции по компонентам проводили по уравнению lgkпр = lgki + nilgci, которое в координатах lgkпр – lgci представляет прямую линию с угловым коэффициентом ni. графическое решение этого уравнения для определения порядков реакции по компонентам en, n2h4cs и naoh представлено на рис. 3–5. таким образом, в результате кинетических исследований установлено, что скорость реакции (1) пропорциональна концентрациям компонентов реакционного раствора, которые входят в кинетическое уравнение со следующими показателями степени: по найденным значениям кажущейся kэксп константы скорости была рассчитана истинная k' константа скорости гетерогенной реакции образования zns при температуре 363 k, отнесенная к единице поверхности твердой фазы zns и единице концентраций каждого компонента с учетом частных порядков реакции: k k sc c cen tm ’ . , , , = − − эксп 1 9 1 2 0 3 oh (5) полученные по уравнению (5) данные показывают, что при изменяющихся концентрациях компонентов реакционной смеси константы скорости реакции k' остаются постоянными в пределах ошибки эксперимента. среднее значение k' составляет (3,69 ± 0,13) × × 10–7 л0,6 · моль0,4· мин–1 · см–2 при 363 k. с целью определения экспериментальной зависимости скорости реакции сульфидообразования от температуры была проведена серия экспериментов при температурах 358, 363 и 369 k, что позволило графически (рис. 6) рассчитать компонент znso4 en n2h4cs naoh кажущийся частный порядок реакции (1) по компоненту ni 1,0 –1,9 1,2 0,3 131 энергию активации процесса по уравнению аррениуса: lgk' = lgk0 – (e/2,3rt), которая составила е = 84,5 ± 0,5 кдж/моль. найденное значение энергии активации показало, что процесс образования сульфида цинка в системе не лимитируется стадией диффузии, поскольку для диффузионных процессов характерны малые значения энергии активации от 8 до 30  кдж/моль [15]. предэкспоненциальный множитель уравнения аррениуса рассчитан по истинной константе скорости при 363 k и при известном значении энергии активации е: k0 = = 5,39 · 105 моль0.4л0.6см–2мин–1. рис. 1. зависимость скорости реакции образования zns от концентрации этилендиамина en. кинетические кривые сняты в условиях контролируемой поверхности s = 24500 см2/л при температуре 363 k и начальной концентрации [n2h4cs] = 0,1 моль/л. теоретические кривые рассчитаны по уравнению (6) рис. 2. графическое определение констант скорости kпр и kобр процесса (1) по уравнению двухсторонней реакции первого порядка (4). процесс (1) проводили в условиях контролируемой поверхности s = 24500 см2/л при температуре 363 k и [n2h4cs] = 0,1 моль/л рис. 3. графическое определение частного порядка n1 реакции образования zns (1) по этилендиамину. реакцию проводили в условиях контролируемой поверхности s = 24500 см2/л при температуре 363 k и [n2h4cs] = 0,1 моль/л рис. 4. графическое определение частного порядка n2 реакции образования zns (1) по тиомочевине. реакцию проводили в условиях контролируемой поверхности s = 24500 см2/л при температуре 363 k и [en] = 0,15 моль/л 132 в результате проведенного исследования установлено, что процесс образования zns (1) описывается формальным кинетическим уравнением: w sc c cen tm = ⋅ −      × × − − 5 39 10 84500 8 3147 5 1 9 1 2 0 , exp , , , , oh 33 0c x−( ). (6) заключение таким образом, в выбранных в данной работе условиях скорость процесса (1) слабо зависит от величины рн, что объясняется буферным действием этилендиамина, зависит от концентрации осадителя (тиомочевины) и уменьшается с увеличением концентрации лиганда (этилендиамина) из-за снижения концентрации свободных ионов цинка в растворе. расчет теоретических кинетических кривых по уравнению (8) показывает удовлетворительное описание полученных экспериментальных данных (рис. 1), что позволяет рекомендовать его для расчета скорости образования zns в водных щелочных растворах диамида тиоугольной кислоты. references 1. monroy e., omnes f., calle f. wide-bandgap semiconductor ultraviolet photodetectors. semicond. sci. technol. 2003;18(4):r33-r55. doi: 10.1088/02681242/18/4/201. 2. kroeger f. a., hellingman j. e. chemical proof of the presence of chlorine in blue fluorescent zinc sulfide. j. electrochem. soc. 1949;95(2):68-69. doi: 10.1149/1.2776738. 3. chen r., lockwood d. j. developments in luminescence and display materials over the last 100 years as reflected in electrochemical society publications. j. electrochem. soc. 2002;149(9):s69-s78. doi: 10.1149/1.1502258. рис. 5. графическое определение частного порядка n3 реакции образования zns (1) по он–-ионам. реакцию проводили в условиях контролируемой поверхности s = 24500 см2/л при температуре 363 k и [n2h4cs] = 0,1 моль/л рис. 6. графический расчет энергии активации процесса химического осаждения zns (1) по уравнению аррениуса 133 4. quan z., yang d., li c., kong d., yang p., cheng z., lin j. multicolor tuning of manganese-doped zns colloidal nanocrystals. langmuir 2009;25(17):10259-10262. doi: 10.1021/la901056d. 5. peng w. q., cong g. w., qu s. c., wan z. g. synthesis and photoluminescence of zns:cu nanoparticles. optic. mater. 2006;29(2-3):313-317. doi: 10.1016/j.optmat.2005.10.003. 6. debenham m. refractive indices of zinc sulfide in the 0.405–13-μm wavelength range. appl. opt. 1984;23(14):2238-2239. doi: 10.1364/ao.23.002238. 7. park w., king j. s., neff c. w., liddell c., summers c. j. zns-based photonic crystals. phys. stat. sol. 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chimicatechnoacta.ru doi: 10.15826/chimtech.2021.8.2.03 1 of 4 new possibilities of the functionalization of 6-hydrazino-1,3-dimethyluracils: one-pot synthesis of 5,7-dimethylpyrazolopyrimidine-4,6-dione and 1,3-dimethyl-5-arylidenebarbituric acid derivatives yu.a. azev * , o.s. koptyaeva, t.a. pospelova ural federal university, 19 mira st., ekaterinburg, 620002, russia * corresponding author: azural@yandex.ru this short communication (letter) belongs to the regular issue. © 2021, the authors. this article is published in open access form under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). abstract 3-aryl-5,7-dimethylpyrazolopyrimidine-4,6-diones and 5-benzylidene-1,3-dimethylpyrimidine-2,4,6-triones were obtained by heating hydrazones of 1,3-dimethyl-6 -hydrazinouraciles in trifluoroacetic acid (tfa). the same compounds were also obtained by heating the hydrazones of 1,3-dimethyl-6-hydrazinouraciles in aqueous ethanol in the presence of hydrochloric acid. keywords 1,3-dimethyl-6hydrazinouracil hydrazones pyrazolopyrimidine-6,8diones 1,3-dimethylbarbituric acid received: 07.04.2021 revised: 20.04.2021 accepted: 26.04.2021 available online: 28.04.2021 1. introduction derivatives of pyrimidine (uracil, cytosine, thymine) are part of nucleic acids, which are carriers of hereditary traits in living organisms and are involved in the synthesis of proteins. the pyrimidine core is a component of bicyclic systems such as purine and pteridine. it is known that pyrazolopyrimidine derivatives have a wide spectrum of biological activity, including antimicrobial[1, 2, 3], antiviral[4, 5], anti-inflammatory and etc. [6, 7, 8]. as a result of the cyclization of hydrazinouracils with the corresponding reagents, derivatives of pyrimidodiazoles and pyrimidotriazines were obtained [9]. 5,7-dimethyl-3-phenylpyrazolopyrimidine-4,6-dione was obtained by heating 6-arylidenehydrazine-1,3dimethyluracils with thionyl chloride in dry benzene from a mixture of reaction products [10]. as a result of boiling the derivatives of 1,3-dimethyl-6-hydrazinouracil with an equimolar amount of n-bromosuccinimide in acetic acid, the derivatives of the corresponding pyrimidoazoles were isolated [11]. the hydrazone of 3-methyl-5-nitro-6hydrazinouracil was cyclized on heating in dmf to form 3arylpyrazolopyrimidine-4,6-dione; the same compound was obtained by nitration of hydrazones of 3-methyl-6hydrazinouracil [12]. analysis of the literature showed that pyrimidopyrazoles were obtained in the presence of an easily leaving group in the hydrazinouracil molecule, which undergoes ipso-substitution followed by annulation of the pyrazole ring. in this work, we have studied the transformations of 6-hydrazino-1,3-dimethyluracil to find ways to synthesize new potentially biologically active compounds, as well as to improve the methods for preparing known compounds. 2. experimental unless otherwise indicated, all common reagents and solvents were used from commercial suppliers without further purification. the reaction progress and purity of the obtained compounds were controlled by tlc method on sorbfil uv-254 plates, using visualization under uv light. melting points were determined on a stuart smp10 melting point apparatus. 1 h, 13 c and 19 f nmr spectra were acquired on bruker bruker avance-400 spectrometer in dmso-d6 solutions, using tms as internal reference for 1 h and 13 c nmr or cfcl3 for 19 f nmr. mass-spectra (ei, 70 ev) were recorded on microtof-q instrument (bruker daltonics) at 250 °c. elemental analysis was performed using a perkinelmer 2400 series ii chns/o analyzer. 1,3-dimethyl-6-hydrazinopyrimidine-2,4-dione 1 was obtained according to the method described in [13]. http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2021.8.2.03 http://creativecommons.org/licenses/by/4.0/ chimica techno acta 2021, vol. 8(2), № 20218203 letter 2 of 4 the general method for the synthesis of hydrazones 2а-c 1.0 mmol of hydrazine 1 was dissolved in a mixture of 3 ml of water and 3 ml of alcohol, 1.0 mmol of aldehyde dissolved in 5 ml of alcohol was added to the resulting solution, and the mixture was heated for 1-2 minutes. the formed precipitate was filtered off, washed with 1 ml of alcohol. 6-(2-benzylidenehydrazinyl)-1,3dimethylpyrimidine-2,4(1h,3h)-dione 2а. yield 85 %, m.p. 260-261 °c. (ref. 261 °c [12]). 1 h nmr (400 mhz, dmso-d6, δ, ppm): 3.18 (s, 3h, ch3), 3.43 (s, 3h, ch3), 5.51 (s, 1h, ch), 7.38-7.41 (m, 3h, char), 7,70 (d, j = 6.4 hz, 1h, char), 8.34 (s, 1h, char), 10.38 (s, 1h, nh). mass spectrum (ei, 70 ev), m/z (%): 258 (100) [м] + , 142 (35), 104 (38), 90 (49). found (%): с, 60.51; н, 5.52; n, 21.71. calculated for с13н14n4o2 (%): с, 60.45; н, 5.46; n, 21.69. 6-(2-(4-(dimethylamino)benzylidene)hydrazinyl)1,3-dimethylpyrimidine-2,4(1h,3h)-dione 2b. yield 80 %, m.p. 251-252 °c. (ref. 252 °c [14]). 1 h nmr (400 mhz, dmso-d6, δ, ppm): 3.02 (s, 6h, 2ch3), 3.16 (s, 3h, ch3), 3.40 (s, 3h, ch3), 5.44 (s, 1h, ch), 6.67 (d, j = 8.8 hz, 2h, ch), 7.50 (d, j = 8.8 hz, 2h, сh), 8.17 (s, 1h, ch), 10.00 (s, 1h, nh). mass spectrum (ei, 70 ev), m/z (%): 301 (18) [м] + , 284 (2), 132 (48), 55 (100). found (%): с, 59.81; н, 6.40; n, 23.22. calculated for с15н19n5o2 (%): с, 59.79; h, 6.36; n, 23.24 1,3-dimethyl-6-(2-(4nitrobenzylidene)hydrazinyl)pyrimidine-2,4(1h,3h)dione 2с. yield 85 %, m.p. 285-286 °c. (ref. 285 °c [14]). 1 h nmr (400 mhz, dmso-d6, δ, ppm): 3.18 (s, 3h, ch3), 3.43 (s, 3h, ch3), 5.56 (s, 1h, ch), 7.98 (d, j = 8.8 hz, 2h, ch), 8.25 (d, j 8.8 hz, 2h, ch), 8.43 (s, 1h, ch), 10.74 (s, 1h, nh). mass spectrum (ei, 70 ev), m/z (%): 303 (18) [м] + , 256 (2), 218 (12), 142 (32). found (%): с, 51.52; н, 4.27; n, 23.13. calculated for с13н13n5o4 (%): с, 51.48; н, 4.32; n, 23.09. reactions of hydrazones 2a-c with tfa 0.5 mmol of hydrazone 2 was heated in 1.5 ml of tfa in a closed vessel at 110 ° c for 85-90 hours. the solvent was removed in vacuo. the solid residue was treated with 3 ml of ethanol. the resulting precipitate of product 4 was filtered off. the alcoholic mother liquor was treated with 1-2 ml of water, the precipitate that formed was filtered off to obtain product 3. 5,7-dimethyl-3-phenyl-1h-pyrazolo[3,4d]pyrimidine-4,6(5h,7h)-dione 3а. yield 20 %, m.p. 256-257 °c. (ref. 257 °c [11]). 1 h nmr (400 mhz, dmsod6, δ, ppm): 3.30 (s,3h, ch3), 3.49 (s, 3h, ch3), 7.46-7.50 (m, 3h, char), 8.14-8.16 (m, 2h, char), 13.64 (br.s, 1h, nh). mass spectrum (ei, 70 ev), m/z (%): 256 (92) [м] + , 199 (38), 171 (100). found (%): с, 60.96; н, 4.75; n, 21.83. calculated for с13н12n4o2 (%): с, 60.93; н, 4.72; n, 21.86. 3-(4-(dimethylamino)phenyl)-5,7-dimethyl-1hpyrazolo[3,4-d]pyrimidine-4,6(5h,7h)-dione 3b. yield 18 %, m.p. 272-273 °c. (ref. 273 °c [12]). 1 h nmr (400 mhz, dmso-d6, δ, ppm): 3.05 (s, 6h, 2ch3), 3.29 (s, 3h, ch3), 3.46 (s, 3h, ch3), 6.74 (d, j = 8.8 hz, 1h, char), 8.07 (d, j = 8.8 hz, 1h, ch), 13.2 (br.s, 1h, nh). mass spectrum (ei, 70 ev), m/z (%): 299 (100) [м] + , 242 (14), 134 (17). found (%): с, 60.24; н, 5.75; n, 23.42. calculated for с15н17n5o2 (%): с, 60.19; h, 5.72; n, 23.40. 5,7-dimethyl-3-(4-nitrophenyl)-1h-pyrazolo[3,4d]pyrimidine-4,6(5h,7h)-dione 3с. yield .45 % m.p. >300 °c. (ref. >300 °c [11]). 1 h nmr (400 mhz, dmsod6, δ, ppm): 3.31 (s, 3h, ch3), 3.49 (s, 3h, ch3), 8.34 (d, j = 8.8 hz, 2h, ch), 8.47 (d, j = 8.8 hz, 2h, ch), 14.08 (s, 1h, nh). mass spectrum (ei, 70 ev), m/z (%): 301 (100) [м] + , 244 (26), 216 (12), 142 (69). found (%): с, 51.86; н, 3.71; n, 23.28. calculated for с13н11n5o4 (%): с, 51.83; н, 3.68; n, 23.25. 5-benzylidene-1,3-dimethylpyrimidine2,4,6(1h,3h,5h)-trione 4а. yield 25 %, m.p. 159-160 °c. (ref. 160 °c [15]). 1 h nmr (400 mhz, dmso-d6, δ, ppm): 3.25 (s, 3h, ch3), 3.29(s, 3h, ch3), 7.45-7.53 (m, 3h, 3char), 8.05-8.07 (d, 2h, 2char), 8.38 (s, 1h, ch). mass spectrum (ei, 70 ev), m/z (%): 243 (100) [м-1] + , 186 (35), 130 (40), 102 (60). found (%): с, 63.96; н, 4.99; n, 11.53. calculated for с13н12n2o3 (%): с, 63.93; н, 4.95; n, 11.47. 5-(4-(dimethylamino)benzylidene)-1,3dimethylpyrimidine-2,4,6(1h,3h,5h)-trione 4b. yield 25% m.p. 240-242 °c. (ref. 241 °c [16]). 1 h nmr (400 mhz, dmso-d6, δ, ppm): 3.19 (s, 6h, 2ch3), 3.28 (s, 6h, 2ch3), 6.74-6.77 (d, 2h, 2char), 8.39-8.41 (d, 2h, 2char), 8.24 (s, 1h, ch). mass spectrum (ei, 70 ev), m/z (%): 287 (100) [м] + , 286(70), 144 (18). found (%): с, 62.21; н, 5.99; n, 14.67. calculated for с15н17n3o3 (%): с, 62.17; h, 5.96; n, 14.63. 1,3-dimethyl-5-(4-nitrobenzylidene)pyrimidine2,4,6(1h,3h,5h)-trione 4с. yield 17%, m.p. >300 °c. (ref. >300 °c [16]). 1 h nmr (400 mhz, dmso-d6, δ, ppm): 3.31 (s, 3h, ch3), 3.50 (s, 3h, ch3), 8.18 (s, 1h, ch), 8.34 (d, j = 9.2 hz, 2h, char), 8.49 (d, j = 9.2 hz, 2h, char). mass spectrum (ei, 70 ev), m/z (%): 288 (87) [м] + , 288 (100), 272 (64), 242 (58), 156 (55). found (%): с, 54.01; н, 3.85; n, 14.64. calculated for с13н11n3o5 (%): с, 53.98; н, 3.83; n, 14.53. conversions of hydrazones 2a-c in ethanol in the presence of acid. 0.02 mmol of the corresponding compound 2 in 3 ml of ethanol and the presence of 0.25 ml of concentrated hydrochloric acid was kept at reflux for 2.5-3 hours. the reaction mixture was cooled, precipitate 4 was filtered off. the melting points and spectral characteristics of the obtained compounds 4a-c were similar to those obtained earlier. 5-benzylidene-1,3-dimethylpyrimidine2,4,6(1h,3h,5h)-trione 4а. yield 48%. 5-(4-(dimethylamino)benzylidene)-1,3dimethylpyrimidine-2,4,6(1h,3h,5h)-trione 4b. yield 53%. chimica techno acta 2021, vol. 8(2), № 20218203 letter 3 of 4 1,3-dimethyl-5-(4-nitrobenzylidene)pyrimidine2,4,6(1h,3h,5h)-trione 4с. yield 54%. reaction of 1,3-dimethylbarbituric acid with aldehydes. 0.05 mmol of barbituric acid 5 was heated in 5.0 ml of ethanol with 0.05 mmol of the corresponding aldehyde in the presence of 0.25 ml of hcl for 25-30 minutes. the reaction mixture was cooled, the precipitate of the corresponding product 4 was filtered off. the melting points and spectral characteristics of the obtained compounds 4a-c were similar to those obtained earlier. 5-benzylidene-1,3-dimethylpyrimidine2,4,6(1h,3h,5h)-trione 4а. yield 60%. 5-(4-(dimethylamino)benzylidene)-1,3dimethylpyrimidine-2,4,6(1h,3h,5h)-trione 4b. yield 54%. 1,3-dimethyl-5-(4-nitrobenzylidene)pyrimidine2,4,6(1h,3h,5h)-trione 4с. yield 70%. 3. results and discussion we used hydrazones 2a-c, as objects of study, obtained by short-term heating of 1,3-dimethyl-6-hydrazinouracil 1 in aqueous-alcoholic solutions with the corresponding aldehydes in the presence of hcl (scheme 1). we found that heating hydrazones 2а-c in tfa gave 5,7-dimethylpyrazolopyrimidine-4,6-diones 3а-c and 5benzylidene-1,3-dimethylpyrimidine-2,4,6-trione derivatives 4а-c. considering the literature data, it can be assumed that the formation of pyrazolopyrimidines 3a-c occurs through the 5-trifluoroacyl intermediate a. the formation of intermediate a occurs as a result of acylation of the starting hydrazones 2a-c of tfa. during this process, water is released and the process of cleavage of hydrazones with the formation of compounds 4a-c is started. to confirm the proposed reaction mechanism, we investigated the transformations of hydrazones 2 upon heating in aqueous ethanol in the presence of hydrochloric acid. as a result of the reactions, derivatives of barbituric acid 4a-c were obtained (scheme 2). the formation of arylidene derivatives apparently occurred as a result of the transfer of the aldehyde group from the hydrazine fragment to the 5-position of the pyrimidine nucleus with the formation of intermediate a. then, acid hydrolysis of the hydrazino group of intermediate a took place, giving derivatives of barbituric acid 4. products 4a-c were also obtained by heating 1,3dimethylbarbituric acid 6 with the corresponding aldehydes. 4. conclusions thus, as a result of the conducted studies, a new one-pot method for the synthesis of derivatives of 5,7dimethylpyrazolopyrimidine-4,6-dione and 5-benzylidene1,3-dimethylpyrimidine-2,4,6-trione was discovered. scheme 1: scheme 2: chimica techno acta 2021, vol. 8(2), № 20218203 letter 4 of 4 references 1. rashad ae, shamroukh ah, ali hs, abdel-megeid fme. some new pyrazole and pyrazolopyrimidines: synthesis and antimicrobial evaluation. j heterocycl chem. 2013;50:758-65. doi:10.1002/jhet.1550 2. eweas af, swelam sa, fathalla oa. synthesis, anti-microbial evaluation, and molecular modeling of new pyrazolo[3,4d]pyrimidine derivatives. med chem res. 2012;21:3848-57. doi:10.1007/s00044-011-9911-y 3. aggarwal r, 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in aqueous media. chin j chem. 2010;28:791-6. doi:10.1002/cjoc.201090148 https://doi.org/10.1002/jhet.1550 https://doi.org/10.1007/s00044-011-9911-y https://doi.org/10.1016/j.ejmech.2011.04.041 https://doi.org/10.3390/molecules19055459 https://doi.org/10.1016/j.bmcl.2009.08.009 https://doi.org/10.1016/j.bmcl.2012.08.119 https://doi.org/10.3797/scipharm.1211-21 https://doi.org/10.1002/cmdc.201000165 https://doi.org/10.1016/0307-4412(80)90067-9 https://doi.org/10.1002/jhet.5570220233 https://doi.org/10.1002/jhet.5570210408 https://doi.org/10.1246/bcsj.48.1484 https://doi.org/10.1002/jlac.19586120117 https://doi.org/10.1016/j.tetlet.2005.07.111 https://doi.org/10.1002/cjoc.201090148 synthesis of 5h-chromeno[4,3-b]pyridin-5-one derivatives as a backbone of natural product polyneomarline c scaffolds in presence of et3n and nh4oac in etoh chimica techno acta article published by ural federal university 2022, vol. 9(2), no.20229211 eissn 2411-1414; chimicatechnoacta.ru doi: 10.15826/chimtech.2022.9.2.11 1 of 5 synthesis of 5h-chromeno[4,3-b]pyridin-5-one derivatives as a backbone of natural product polyneomarline c scaffolds in presence of et3n and nh4oac in etoh shrishnu kumar kundu a*, susanta patra b, chayan sardar c, sunil kumar bhanja d, prasanta patra b* a: department of chemistry, acharya prafulla chandra roy government college, siliguri 734 010, india b: department of chemistry, jhargram raj college, jhargram 721507, india c: techno-india university, kolkata 700091, india d: government general degree college, kharagpur-ii, paschim medinipur, india * corresponding authors: shrishnuk@gmail.com (s.k. kundu); prasantaanupama1983@gmail.com (p. patra) this paper belongs to a regular issue. © 2022, the authors. this article is published open access under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). abstract a green one-pot synthesis of 5h-chromeno[4,3-b]pyridin-5-one derivatives which are the main core of the natural product of polyneomarline c is described by the reaction of 4-chloro-3-formyl coumarin and different cyclic and acyclic compounds having active methylene group in presence of et3n and nh4oac in etoh. the advantages of this strategy are good yields, no need for the chromatographic separation and the absence of heavy metal catalysts and toxic by-products. the 4chloro-3-formyl coumarin is obtained by vilsmeier heck reaction of 4hydroxy coumarin. keywords 5h-chromeno[4,3-b]pyridin5-one green synthesis 4-chloro-3-formyl coumarin active methylene group polyalthia nemoralis c received: 21.04.22 revised: 07.06.22 accepted: 07.06.22 available online: 14.06.22 1. introduction in the last one or two decades, one-pot tandem chemical transformation without metal catalysts has been widely used for the synthesis of complex organic molecules. a variety of chemical conversion processes, such as oxidation, reduction, substitution, condensation, etc., has been developed using this principle [1–3]. a reaction undergoing without using toxic reagents (catalysts and solvents) has many advantages: a decrease of wastes, lower toxicity, maximum efficacy, a decrease in the energy requirements of the reactions, a possibility of designing biodegradable products, economic and time factors. hence, heterocyclic ring formation using this green protocol is an active and attractive field. coumarin derivatives represent the core structure of many naturally occurring compounds with significant biological activities [4– 7]. lamellarins and related pyrrole derived alkaloids isolated from diverse marine organisms are well known for their remarkable biological activities [8, 9]. the coumarin derivatives fused with azaheterocycles specially the pyridine nucleus have been reported to possess antiallergic, antidiabetic and analgesic properties [10–12]. santiagonamine is a naturally occurring pyridine fused coumarin derivatives found in the stems and branches of berberisdarwinii hook, which is a shrub that abounds in south america having wound-healing properties [13, 14]. goniothaline [15] is another a natural pyridocoumarin alkaloid, isolated from the australian rainforest plant goniothalamusaustralis, having antimalarial activity against a chloroquine-sensitive plasmodium falciparum line (3d7). polyneomarline c [16] is also a natural 6hchromeno[4,3-b]quinolin-6-one derivative, isolated from the polyalthia nemoralis a. dc, used as chinese herbal medicine. coumarin fused pyridine [17–19] derivatives have been reported to possess anti-hypertensive activities, anti-hiv activity, androgen receptor antagonist activity, and optoelectronic activity; they can also act as fluorescent dyes. all these observations highlight the importance and bioactivity of pyridine fused coumarin derivatives. so the interest towards the synthesis of pyridine fused comarin is trending among the organic chemists. many methods [20–30] have been developed to synthesize these types of compounds using different types of lewis acids/bases and metal catalysts with different solvents. the 5h-chromeno[4,3-b]pyridin-5-one skeleton constitutes the backbone of polyneomarline c. we were interested in the preparation of some non-natural analogs of this type of compounds by an easy process. many synthese of 5h-chromeno[4,3-b]pyridin-5-one derivatives have been dehttp://chimicatechnoacta.ru/ https://dx.doi.org/10.15826/chimtech.2022.9.2.11 mailto:shrishnuk@gmail.com mailto:prasantaanupama1983@gmail.com http://creativecommons.org/licenses/by/4.0/ https://orcid.org/0000-0002-2738-1216 https://crossmark.crossref.org/dialog/?doi=https://dx.doi.org/10.15826/chimtech.2022.9.2.11&domain=pdf&date_stamp=2022-6-14 chimica techno acta 2022, vol. 9(2), no. 20229211 article 2 of 5 scribed in the literature [31, 32] using different reagents, catalyst, solvents and ultrasound irradiation. in our present work, we reported a modified green approach for the synthesis of 5h-chromeno[4,3-b]pyridin-5-one derivatives from 4chloro-3-formyl coumarin and various compounds having an active methylene group. in this method there is no need for the chromatographic separation. 2. experimental 2.1. preparation of substituted pyridocoumarin derivatives a mixture of chloroaldehyde 1 of 4-hydroxy coumarin (1 mmol), 2 (1.2 mmol), et3n (1–2 drops) and nh4oac (2 mol%) with 10 ml etoh was taken in 50 ml r.b. the mixture was then heated on an oil bath at 60 °c for 2 h. it was then cooled to room temperature. then solvent was distilles out and residue was mixed with 20 ml water and filtered and washed with water and dried. the crude product which was purified by recrystalisation with etoh to furnish compound 3. 2.1.1. 3-acetyl-2-methyl-5h-chromeno[4,3-b]pyridin-5-one (3a) light pink solid, yield, 90%; mp 220–221 °c (etoh); 1h nmr (400 mhz, dmso-d6): 2.62 (s, 3h), 2.68 (s, 3h), 7.42 (m, 1h), 7.52 (d, 1h, j = 7.8 hz), 7.65 (d, 1h, j = 7.8 hz), 7.79 (m, 1h), 9.33 (s, 1h); hrms (esi, 70 ev): m/z = 254.0820 (m++h) [calcd mass for c15h12no3: 254.0817 (m++h)]. 2.1.2. ethyl 2-methyl-5-oxo-5h-chromeno[4,3-b]pyridine-3carboxylate (3b) light pink solid, yield, 82%; mp 230–231 °c (etoh); 1h nmr (400 mhz, dmso-d6): 1.3 (t, 3h, j = 7.2 hz) 2.62 (s, 3h), 4.8 (m, 2h), 7.30–7.33 (m, 1h), 7.65 (m, 1h), 7.92 (d, 1h, j = 7.2 hz), 7.78–7.80 (m, 1h), 8.90 (s, 1h); hrms (esi, 70 ev): m/z = 284.0929 (m++h) [calcd mass for c16h14no4: 284.0923 (m++h)]. 2.1.3. 10,11-dihydro-9h-chromeno[4,3-b]quinoline-6,8-dione (3c) light yellow solid, yield, 92%; mp 221–222 °c (etoh); 1h nmr (400 mhz, dmso-d6): 1.98 (m, 2h), 2.45 (t, 2h, j = 7.2 hz) 2.95 (m, 2h), 7.35 (m, 2h), 7.65–7.80 (m, 1h), 8.03 (d, 1h, j = 7.5 hz), 9.22 (s, 1h) ppm; hrms (esi, 70 ev): m/z = 266.0821 (m++h) [calcd mass for c16h12no3: 266.0817 (m++h)]. 2.1.4. 9,9-dimethyl-10,11-dihydro-9h-chromeno[4,3-b]quinoline-6,8-dione (3d) light yellow solid, yield, 85%; mp 239–240 °c (etoh); 1h nmr (400 mhz, dmso-d6): 1.38 (s, 6h), 1.91 (t, 2h, j = 7.8 hz), 2.92–2.95 (m, 2h), 7.45 (t, 2h, j = 8.0 hz), 7.7 (t, 1h, j = 7.7 hz), 8.13 (dd, 1h, j = 2.2 and 9.0 hz), 9.33 (s, 1h) ppm; 13c nmr (13c nmr 100 mhz, dmso-d6): 23.2 (2), 28.2, 32.9, 113.3, 117.2, 117.9, 123.8, 125.32, 125.6, 125.7, 127.3, 136.33, 153.0, 154.0, 160.5, 169.8, 196.7; hrms (esi, 70 ev): m/z = 294.1121 (m++h) [calcd mass for c18h16no3: 294.1130 (m++h)]. 3. results and discussion our first task was to find out an optimal condition to prepare the 5h-chromeno[4,3-b]pyridin-5-one derivatives in the best possible yield using different methodologies. a reaction between 4-chloro-3-formyl coumarin (1 equivalent) and acetyl acetone (1.2 equivalent) (scheme 1) was studied under different conditions with different temperatures and times (table 1). when 3-formyl 4-chloro coumarin, which was obtained from 4-hydroxy coumarins [33], was treated with different cyclic and acyclic compounds having active methylene group in the presence of et3n and nh4oac in etoh at 60 °c, within 2 h the corresponding 5hchromeno[4,3-b]pyridin-5-one derivatives were obtained. the 1h-nmr (400 mhz, dmso-d6) data is in conformity with the assigned structure for the 5h-chromeno[4,3b]pyridin-5-one derivatives. a reaction of the other cyclic and acyclic compounds having an active methylene group 2(b-d) and 4-chloro 3-formyl coumarin (1 equivalent) under identical condition produced the 5h-chromeno[4,3-b]pyridin-5-one derivatives 3(a-d), respectively, in excellent yields (scheme 2). scheme 1 synthesis of pyridocoumarin by condensation followed by cyclization reaction. table 1 optimization studies in the formation of pyridocoumarin derivatives.a entry reactant proportions (1:2a) solvent catalysts additives temp. (°c) time (h) yields (%) 1 1:1 h2o – – 100 10 - 2 1:2 h2o et3n nh4oac 100 10 trace 3 1:1 etoh et3n nh4oac 100 3 75 4 1:1 etoh et3n nh4oac 60 2 90 5 1:1 etoh et3n nh4oac 60 1 80 6 1:1 meoh et3n nh4oac 80 5 40 7 1:1 etoh nahco3 nh4oac 100 5 trace 8 1:1 dmf et3n nh4oac 100 2 trace 9 1:1 etoh/h2o et3n nh4oac 100 2 45 10 1:1 – – nh4oac 100 1 trace a reaction conditions: 4-chloro 3-formyl coumarin 1 (1 mmol), 2a (1.2 mmol), solvent (10 ml); et3n (cat), nh4oac (2 mmol), 60 °c. chimica techno acta 2022, vol. 9(2), no. 20229211 article 3 of 5 scheme 2 substrate scope of for the synthesis of 3(a-d). unfortunately, we did not have access to any other coumarin derivatives, but we believe our method will be applicable for other derivatives. a probable mechanism for the formation of compounds 3a is given in scheme 3. in general, the reactions are very clean, proceeding without any side product, with remarkable yields, and do not requiring any chromatographic separation. recrystallization from etoh provides an analytically pure sample. we believe that it is the first green approach reported for the synthesis of fused 5h-chromeno[4,3-b]pyridin-5-one derivatives. 4. conclusions in conclusion, we achieved the synthesis of poly-substituted pyridocoumarin derivative in one-pot three-component condensation and cyclization via an efficient, short and easy method. the method has a number of advantages: easy availability of the starting material, short time of the reaction, and the use of simple and inexpensive catalyst. we are planning a collaborative study into the photophysical and biological properties of the synthesized compounds in the near future. supplementary materials no supplementary materials are available. funding this work was financially supported by the department of science & technology and biotechnology (dstbt) of west bengal (34(sanc.)-st/p/s&t/15g-1/2018 date: 31/01/2019). acknowledgments p. patra is grateful to his supervisor prof. gandhi kumar kar, dean of science, presidency university, kolkata and dept. of chemistry, jhargram raj college. author contributions conceptualization: s.k.k., p.p. data curation: s.p., c.s., s.k.b. formal analysis: s.k.k., c.s. funding acquisition: p.p. investigation: s.k.k., p.p. methodology: s.p., c.s., s.k.b. project administration: p.p. resources: s.k.k. software: s.p. supervision: s.k.k., p.p. validation: s.k.k. visualization: p.p. writing – original draft: s.p. writing – review & editing: s.k.k., p.p. conflict of interest the authors declare no conflict of interest. additional information author ids: shrishnu kumar kundu, scopus id 15128586000; prasanta patra, scopus id 36182642900. scheme 3 probable mechanism for the formation of pyridocoumarin derivatives. https://www.scopus.com/authid/detail.uri?authorid=15128586000 https://www.scopus.com/authid/detail.uri?authorid=36182642900 chimica techno acta 2022, vol. 9(2), no. 20229211 article 4 of 5 websites: acharya prafulla chandra roy government college, 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chimicatechnoacta.ru article 2022, vol. 9(2), no. 202292s13 doi: 10.15826/chimtech.2022.9.2.s13 1 of 6 phosphorous-containing copolymers loaded with silver nanoparticles for biomedical purposes marina gorbunova a* , larisa lemkina b, yulia beloglazova a a: institute of technical chemistry of the ural branch of the russian academy of sciences, perm 614013, russia b: institute of ecology and genetics of microorganisms of the ural branch of the russian academy of sciences, perm 614081, russia * corresponding author: mngorb@yandex.ru this paper belongs to the mosm2021 special issue. © 2022, the authors. this article is published in open access form under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). abstract new silver nanocomposites (agncs) based on copolymers of tris(diethylamino)diallylaminophosphonium tetrafluoroborate (daap-bf4) and chloride (daap-cl) with n-vinylpyrrolidone (vp) were developed. the reduction of silver ions into silver nanoparticles was achieved using nabh4 as a reducing agent. uv-spectroscopy and scanning electron microscopy techniques were used to characterize the formation of silver nanoparticles in copolymers. the average silver particle size ranged from 10 to 20 nm, with the corresponding uv-vis absorption peak position at 395–405 nm. the agncs exhibited significant cytotoxic activity towards rhabdomyosarcoma and melanoma line cells and completely inhibited bacterial growth, including both grampositive and gram-negative bacteria. keywords phosphonium salts radical polymerization silver nanoparticles biocides cytotoxic activity received: 05.04.22 revised: 19.07.22 accepted: 20.07.22 available online: 08.08.22 1. introduction nowadays, the creation of nanomaterials from silver nanoparticles is the most promising, especially due to their outstanding significant chemical and biological properties [1–5]. numerous nanoparticle stabilizers are known, among which special attention is paid to polymers. on the one hand, the inclusion of nanoparticles in traditional polymers leads to the formation of materials with fundamentally new functional properties. on the other hand, the polymer matrix acts as a stabilizing component, preventing aggregation of metal nanoparticles. these factors determine the unique properties of nanocomposites (biological, catalytic, optical, magnetic, semiconductor) and, ultimately, determine the breadth of their application spectrum. it is known that the stability of particles is significantly affected by the chemical structure of the polymer [6]. a large number of studies were devoted to the use of (co)polymers of n-vinylpyrrolidone (vp) as a nanostabilizing matrices [7–12]. phosphoric polymer derivatives are of significant interest because they are used as extractants and complexing agents [13]. due to high selectivity, phosphorylated polyamines can be successfully employed in the isolation of cations which are in hardly separable combinations [14]. the ability of aminopolyphosphonic compounds to form complexes with various elements opened up the possibility for their use in the removal of metal from organisms [15]. that is why phosphorous-containing copolymers are promising for stabilizing silver particles, since they have a high sorption capacity with respect to metal ions due to the formation of chelate complexes. previously, by reducing silver nitrate with sodium borohydride, we obtained polymer nanocomposites that contained silver nanoparticles, stabilized with polysulfones based on tris (diethylamino)-diallylaminophosphonium salts [16]. it is important to continue and expand these studies aimed at the synthesis of phosphorous-containing copolymers used as stabilizing agents for silver nanoparticles. the article is devoted to the incorporation of silver nanoparticles into the matrices of vp copolymers with daap-bf4 and daap-cl. thorough structural and optical characterization of nanocomposites was performed using uv-spectroscopy, scanning electron microscopy, dls and xrd. antimicrobial activity and cytotoxic effect of nanocomposites were determined. 2. experimental 2.1. materials tris(diethylamino)diallylaminophosphonium tetrafluoroborate (daap-bf4) and chloride (daap-cl) were obtained as http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2022.9.2.s13 http://orcid.org/0000-0003-2639-6069 http://orcid.org/0000-0003-1141-6266 mailto:mngorb@yandex.ru http://creativecommons.org/licenses/by/4.0/ https://crossmark.crossref.org/dialog/?doi=https://doi.org/10.15826/chimtech.2022.9.2.s13&domain=pdf&date_stamp=2022-8-8 chimica techno acta 2022, vol. 9(2), no. 202292s13 article 2 of 6 described in our previous publications [13, 17]. the yield of daap-cl was 86.5%. (c18h40cln4p) (378.5): calcd. c 57.07, h 10.57, n 14.79. found c 56.82, h 11.06, n 14.55. the yield of daap-bf4 was 70.1%. (c18h40f4n4pb) (430): calcd. c 50.23, h 9.30, n 13.02; found c 49.72, h 10.03, n 12.83. n-vinylpyrrolidone (vp) (lancaster, reagent grade) was dried by potassium hydroxide and purified by vacuum distillation. a fraction with tb = 97 °c/13 mm hg, nd20 = 1.5117 was used. 2,2’-azobisisobutyronitrile (aibn) was recrystallized three times from methanol and dried in vacuum at room temperature until a constant weight; the melting temperature was тm = 103 °с (decomposition). all the other chemicals were obtained from commercial suppliers. the characteristics of applied solvents conformed to the reference data after purification by conventional methods. 2.2. copolymerization copolymerization of daap-bf4 and daap-cl with vp was conducted in bulk in the presence of aibn. copolymers were precipitated and purified by three-fold reprecipitation by diethyl ether from methanol solution. the purified copolymers were dried under vacuum at 50 °c until constant weight was achieved. the copolymer composition was calculated from the elemental analysis data. 2.3. synthesis of nanocomposites synthesis of silver nanocomposites was conducted as follows. the copolymer (10–2 mol) was dissolved in water (50 ml). then agno3 (10–4 mol of 1% aqueous solution) was added and the reactive mixture was stirred for one hour at room temperature. then nabh4 (2·10–4 mol) was added dropwise with the constant intensive stirring, and the reactive solution was stirred for ten hours at room temperature. nanocomposites were separated by dialysis. the purified nanocomposites were dried under vacuum at 50 °c until constant weight was achieved. 2.4. characterization fourier transform infrared spectra (ft-ir) were recorded using an ifs 66/s bruker spectrometer at a resolution of 4 cm−1. the 1h and 13c nmr spectra were recorded on a bruker avance ii spectrometer operating at 400 and 100 mhz, respectively, using a broad-band proton decoupling and in a jmod (j-modulated) mode. dmso-d6 was used as a solvent; tetramethylsilane was used as an internal standard. the optical properties of the nanocomposites were measured using a cf-2000 spectrophotometer in a wavelength range of 200–600 nm. concentration of ag in aqueous solutions was determined with using of atomic-absorption spectrometer ice 3500 («thermo fisher scientific», usa). the particle size was determined from the dynamic light scattering measurements using a zetapals analyzer (brookhaven, usa). the samples of nanocomposites were studied by means of an evex mini-sem hr-3000 microscope. the structure of produced nanocomposites was explored by x-ray phase analysis on the xrd-7000 difractometer (shimadzu, japan) using the cu kα radiations (λ = 1.54062 å) in the angular interval 2θ = 10–80°. 2.4.1. microbiological tests microbiological tests were performed by serial two-fold dilution. the test cultures were staphylococcus aureus, atcc 25923; staphylococcus epidermidis 33 gis; micrococcus luteus, ncimb 196; escherichia coli, atcc 25922. thee bacterial strains used in the work were obtained from the fsbi «scientific centre for expert evaluation of medicinal products» of the ministry of health of the russian federation (moscow). the microbial loads were 106 cells in 1 ml in lb medium. a bacterial culture was put into 96-well polystyrene microtiter plate for 24 h at 37 °c. the concentration of planktonic cells was evaluated by measuring the optical density at 570 nm (od570). duplicate sets of plates were prepared each time, and each experiment was repeated three times to obtain accurate results. 2.4.2. mtt tests cytotoxicity of compounds was measured as follows. cell lines of human lung carcinoma (a549), human rhabdomyosarcoma (rd te32) and human melanoma (ms) were obtained from the research institute of experimental tumor diagnostics and therapy, n.n. blokhin cancer research center, russian academy of medical sciences (moscow). the cells were kept in the dmem medium (for a549 and rd) and in the rpmi 1640 medium (for ms) supplemented with 10% fetal bovine serum, 2 mm l-glutamine and 1% gentamicin at 37 °c in the isotemp barnstead co2 incubator. the 50% cell growth inhibitory concentration (ic50) of the synthesized compounds was determined by the mtt method. a549, rd and ms cells were inoculated at 1.0·104 cells/200 ml in 96-well plates and incubated at 37 °c in a humidified atmosphere with 5% co2. after 24 h incubation, various concentrations of the tested compounds (1.00–1.56 µm) were added into each well, and these cells were incubated at 37 °c in a humidified atmosphere with 5% co2 for 72 h. all compounds were dissolved in dmso. the final dmso concentration in each well did not exceed 0.1% and was not toxic for the cells. the wells with a specific cell culture containing 0.1% dmso solution in the medium were monitored as control. after incubation, 20 µm mtt (3-(4,5-dimethylthiazol-2yl)-2,5-diphenyl tetrazolium bromide), at a final concentration of 5 mg/ml, was added into each well, and the cells were incubated for another 4 h. the medium was removed and 60 µl dmso was added to each well. the optical density was measured at 544 nm using a fluostar optima microplate reader. the concentrations (ic50) were calculated according to the dosechimica techno acta 2022, vol. 9(2), no. 202292s13 article 3 of 6 dependent inhibition curves. all experiments were performed for three times and the data were presented as means ± standard deviations (sd). to test the significance of observed differences between the study groups, student’s t-test was applied. a value of p<0.05 was considered to be statistically significant. 3. results and discussion 3.1. synthesis of copolymers the study of the activity of diallylaminophosphonium salts showed that these compounds do not enter the homopolymerization reaction by the radical mechanism. diallylaminophosphonium salts are also inactive during copolymerization with vinyl monomers (acrylonitrile, methyl methacrylate, acrylamide, n-vinylpyrrolidone, etc.) with low reaction rates and their insignificant entry into the polymer chain. in particular, during the copolymerization of daaf-bf4 with vp (70 mol.%) in dmso in the presence of aibn (3 wt.%) at 80 °c for 10 h, the vp content in copolymer is 93 mol.%. an analysis of the above results showed that the homoand copolymerization of daaf-bf4 and daap-cl is difficult, and a significant contribution to this process is made by the degradation chain transfer to the monomer. the activity of diallylaminophosphonium salts can be increased by changing the reaction medium. it is known that the nature of the solvent has a great influence on the vp polymerization [18]. in the vp molecule, the vinyl group through the nitrogen atom is conjugated with the c=o group, which is capable of forming bonds with the molecules of the proton-donor solvent. for this reason, the electronic state of the vinyl group and, consequently, the vp reactivity largely depends on the nature of the solvent. it was found that during the polymerization of daaf-bf4 with vp, the activity of the diallyl monomer in a proton-donor solvent (methanol) increases as compared to the polymerization in dmso. in particular, upon copolymerization of daaf-bf4 with vp (70 mol.%) in methanol under similar conditions, the vp content in copolymer is 85 mol.%. the higher activity of daaf-bf4 in methanol, as compared with polymerization in dmso, is associated with the formation of hydrogen bonds between comonomers and the solvent, while the formation of bonds between vp and methanol is more significant, which leads to the displacement of vp from the solvation layer and to a decrease in vp activity. the dependence of the composition of the daaf-bf4 with vp copolymer on the composition of the initial monomer mixture in methanol and dmso is shown in figure 1. the studies showed that during copolymerization the resulting products have a statistical distribution of comonomer units in the macromolecule. the values of the relative reactivities presented in table 1 indicate that, as expected, vp is characterized by a higher reactivity than the diallyl monomer. the structure of the copolymers obtained was investigated using both 1h and 13c nmr. the spectral parameters of copolymers are presented in table 1 in supporting information file. it was established that the copolymerization of diallylaminophosphonium salts with nvinylpyrrolidone proceeds, both double bonds participating, with formation of cis-, trans-stereoisomeric pyrrolidine structures in a cyclolinear polymer chain. block fragments of the vp with inclusions of daap units prevail in the structure of the copolymer. 3.2. synthesis of silver nanocomposites new silver nanocomposites based on new copolymers were obtained by the reduction of agno3 with nabh4 in the copolymer solution. the reaction proceeds via formation of the stable dark brown sols, from which silver nanocomposites are separated. in the ir spectra of nanocomposites, except for the signals of initial copolymers, there are no signals. this proves that the formation of silver polymer nanocomposites is not accompanied by a change in the chemical structure of the polymer matrix. the content of silver in the composites was found to be 8 and 11% for daap-cl-vp and daap-bf4-vp, respectively. uv-spectroscopy and scanning electron microscopy techniques were used to characterize the formation of silver nanoparticles in copolymers. the average silver particle size ranged from 10 to 20 nm, with the corresponding uv-vis absorption peak position at 395–405 nm (figure 2). sem results prove the obtaining of nanocomposites with regular narrow-dispersed distribution of silver nanoparticles of spheric and elliptic forms in the polymer matrix (figure 3). figure 1 composition of daap-bf4 with vp (m2) copolymers vs. the monomer ratio: [aibn] = 3 wt.%, t = 80 °c. 1 – dmso, 2 – methanol. table 1 relative reactivities of daap-bf4 and vp (m2) at bulk copolymerization (aibn, 80 °c). medium r1 r2 1/r2 r1 r2 methanol 0.023±0.001 1.928±0.411 0.52 0.04 dmso 0.072±0.022 7.638±0.135 0.13 0.54 chimica techno acta 2022, vol. 9(2), no. 202292s13 article 4 of 6 to obtain size distributions of the silver particles, approximately 100–200 particles were counted and then combined into histograms. the average particle sizes of silver nanoparticles ranged from 10 to 20 nm. this experimental result is consistent with dls measurements (figure 4). the average particle size of the silver nanoparticles was determined to be in the range of 14–16 nm for both copolymers. moreover, as it turned out, the colloidal solutions are stable at least further six months due to high stabilizing effect of daap copolymers. the xrd measurements of nanocomposites (figure 5) were also performed. the peaks at 2θ values of 38°, 44°, 65° and 78° are indexed in, respectively, (111), (200), (220) and (311) planes, signifying a face-centered-cubic (fcc) phase of metallic silver. figure 2 uv extinction spectra of nanocomposite: 1 – daap-cl-vp, water solution, c = 7.5·10–3 mol/l; 2 – daap-bf4-vp, alcoholic solution, c = 5·10–4 mol/l. figure 3 sem images of silver nanoparticles in daap-cl-vp (1) and daap-bf4-vp (2). figure 4 the particle size distribution histograms of agncs: 1 – daap-cl-vp, 2 – daap-bf4-vp. this is in agreement with the data reported for the pvp–ag nanocomposite [19]. the average crystallite sizes of silver nanoparticles were estimated using the scherrer equation and were found to be 16.5 and 17.4 nm for daap-cl-vp and daap-bf4-vp, respectively. it should be noted that the xrd data concerning the size of silver nanoparticles are in good agreement with the results of sem and dls analysis. 3.3. antimicrobial effect among biocide polymers, the polymeric phosphonium salts have gained importance as medical agents and antiseptics [16, 20–23]. they are believed to be effective in inhibiting the growth of bacteria. our studies of antimicrobial activity showed that new copolymers exhibit bactericidal effect (table 2). the copolymer concentration of 31.2–62.5 μg/ml ensured 100% reduction of staphylococcus aureus and micrococcus luteus. the daap-cl-vp at concentration of 125 μg/ml and daap-bf4-vp at concentration of 250 μg/ml inhibited 100 % escherichia coli. figure 5 x-ray powder diffractograms of agncs based on daapcl-vp (1), daap-bf4-vp (2). table 2 antimicrobial activity of copolymers and their nanocomposites. test cultures mic, µg/ml daap-clvp nano daapcl-vp daapbf4-vp nano daapbf4-vp staphylococcus aureus 62.5 7.8 62.5 15.6 staphylococcus epidermidis 62.5 7.8 31.2 7.8 micrococcus luteus 62.5 15.6 62.5 15.6 escherichia coli 125 31.2 250 31.2 chimica techno acta 2022, vol. 9(2), no. 202292s13 article 5 of 6 it is seen that our nanocomposites have a significant activity against both gram-positive and gram-negative bacteria. the biocide effect of new nanocomposites is higher as compared to initial copolymers. it should be kept in mind that the fraction of nanosilver is about one-tenth of the total composite concentration. 3.4. cytotoxic activity it is well-known that metal-polymer nanocomposites are considered as promising drugs for the treatment of cancer tumors [24]. cytotoxicity of agncs was evaluated in vitro by mtt-test using three cell lines, namely the bronchial carcinoma (а549), rhabdomyosarcoma (rd) and melanoma (ms) (table 3). the nanocomposites have a significant activity against both rd and ms line cells. moreover, cytotoxic effects of new nanocomposites with respect to rd and ms line cells are comparable to activity of camptothecin – an alkaloid with significant antitumor activity. with the initial copolymers exhibiting low cytotoxic activity, one may say of a decisive contribution of silver nanoparticles to the cytotoxic activity of the composites. 4. conclusions in summary, new silver nanocomposites based on copolymers of tris(diethylamino)diallylaminophosphonium tetrafluoroborate and chloride with n-vinylpyrrolidone have been developed. the copolymers provide a very good covering for silver particles and prevent particle growth or formation of large aggregates. the developed silver nanocomposites are well characterized by using different techniques to confirm the formation of silver nanoparticles with size of 10–20 nm. new silver nanocomposites possess significant antimicrobial properties against both gram positive and gram-negative microflora. also, they have a significant cytotoxic activity towards rd and ms line cells, and these cytotoxic effects are not inferior to activity of camptothecin. thus, the use of phosphorus-containing copolymers in the synthesis of silver nanoparticles opens up a number of opportunities for development of non-toxic functional materials for biomedical applications. supplementary materials spectral parameters of copolymers are provided in the supporting information file. funding the study was funded by russian foundation for basic research and government of the perm region according to the research project № 19-43-590019 r_a. https://www.rfbr.ru/rffi/eng; http://minobr.permkrai.ru. acknowledgments analytical, spectroscopic, and biological studies were performed at the "research of materials and substances" collective center of pfrc ub ras. the authors gratefully acknowledge dr. dmitriy kiselkov, itch ub ras, for his generous advice on sem analysis. author contributions conceptualization: м.n.g. data curation: l.m.l., y.a.b. formal analysis: m.n.g., l.m.l., y.a.b. funding acquisition: m.n.g. investigation: m.n.g., l.m.l., y.a.b. methodology: m.n.g., l.m.l., y.a.b project administration: m.n.g. resources: m.n.g., l.m.l., y.a.b. software: m.n.g., l.m.l., y.a.b. supervision: m.n.g. validation: m.n.g., y.a.b. visualization: m.n.g., l.m.l., y.a.b. writing – original draft: m.n.g. writing – review & editing: m.n.g., y.a.b. conflict of interest the authors declare no conflict of interest. additional information author ids: marina n. gorbunova, scopus id 7004005438; larisa m. lemkina, scopus id 6602343571; yulia a. beloglazova, scopus id 57221844232. websites: institute of technical chemistry of the ub ras, http://www.itcras.ru/index.php/ru/; table 3 cytotoxic activity of agncs. culture ic50, µm camptothecin daap-cl-vp nano daap-cl-vp daap-bf4-vp nano daap-bf4-vp rhabdomyosarcoma rd 2.79±0.08 101.26±0.36 25.83±11.26 97.16±2.26 5.73±0.15 bronchial carcinoma а549 2.26±0.01 no effect no effect 81.51±1.47 31.19±0.63 melanoma ms 1.63±0.00 91.25±0.03 1.27±0.00 no effect 1.87±0.02 https://www.rfbr.ru/rffi/eng http://minobr.permkrai.ru/ http://www.scopus.com/inward/authordetails.url?authorid=7004005438 http://www.scopus.com/inward/authordetails.url?authorid=6602343571 http://www.scopus.com/inward/authordetails.url?authorid=57221844232 http://www.itcras.ru/index.php/ru/ chimica techno acta 2022, vol. 9(2), no. 202292s13 article 6 of 6 institute of ecology and genetics of microorganisms of the ub ras, http://www.iegm.ru/. references 1. pandey s, goswami gk, nanda kk. 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https://doi.org/10.1134/s1070427208050224 https://doi.org/10.1016/s0009-2614(02)02036-5 https://doi.org/10.1016/j.ifset.2012.02.010 https://doi.org/10.1002/pola.1993.080310615 https://doi.org/10.1002/pola.1994.080321024 https://doi.org/10.1002/pola.1993.080310611 https://doi.org/10.1517/17425247.2012.668522 development of technology for deposition of thick copper layers onto ceramic substrates applied in power electronics published by ural federal university eissn 2411-1414; chimicatechnoacta.ru letter 2022, vol. 9(3), no. 20229307 doi: 10.15826/chimtech.2022.9.3.07 1 of 4 development of technology for deposition of thick copper layers onto ceramic substrates applied in power electronics yuri k. nepochatov a, pyotr m. pletnev b , vladimir f. kosarev c, тatiana s. gudyma d* a: hc pjsc nevz–soyuz, novosibirsk 630049, russia b: department of physics, siberian state transport university, novosibirsk 630049, russia c: laboratory of cold gas-dynamic spraying, institute of theoretical and applied mechanics sb ras, novosibirsk 630090, russia d: department of chemistry and chemical technology, novosibirsk state technical university, novosibirsk 630073, russia * corresponding author: gudymatan@mail.ru this paper belongs to the ctfm'22 special issue: https://www.kaznu.kz/en/25415/page. guest editors: prof. n. uvarov and prof. e. aubakirov. © 2022, the authors. this article is published in open access under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). abstract the basic element of the design of a power module is a metallized ceramic substrate. in this work, the formation of metallization coatings by the method of thermal transfer of metallization pastes (mo-mn-si + binder) for alumina and aluminum nitride ceramics was carried out. the fixing of the metallization coating on the ceramic substrate was performed by firing at a temperature of 1320 °c. the subsequent deposition of the copper layer was carried out by the method of cold gas-dynamic spraying (cgds) followed by annealing of the deposited coating. for high-quality adhesion, the optimum annealing temperature was 1000 °c. keywords ceramics metallization coating aluminum nitride copper adhesion received: 23.06.22 revised: 19.07.22 accepted: 19.07.22 available online: 26.07.22 key findings ● the technology of a two-layer metallization coating on ceramic substrates made of aluminum nitride and oxide was developed. ● the resulting copper coatings are characterized by a strong adhesive bond with the base and low electrical resistance (at the level of 3·10–6 ohm·cm). ● for high-quality adhesion, the optimum annealing temperature was 1000 °c. 1. introduction cold gas dynamic spraying (cgds) is a relatively new modification of cold spraying techniques that uses converging-diverging (de laval) nozzle at a supersonic velocity to accelerate different solid powders towards a substrate on which they are plastically deformed. this deformation results in adhesion to the surface. cgds is one of the innovative cold spraying processes with fast-growing scientific interests and industrial applications in the fields of aerospace, automotive and biotechnology. cold spray research and development efforts have doubled during the last decade and along with new industry applications and novel demands provide both a strong body of knowledge and market pull to identify and address these roadblocks. [1, 2]. due to the high strain rate deformation of particles in (cgds), in situ investigation is challenging. metallurgical bonding is one of the main adhesion mechanisms of particles during coating buildup [3]. the properties of the kinetically deposited coating layer are significantly affected by the microstructure of the coating. the most powerful influencing factors in microstructural evolution of kinetic-sprayed coating layers are instant generation of thermal energy and high-strain, high-strain-rate plastic deformation at the moment of particle impact [4]. heat treatment of the 316 l austenitic steel coating improves its mechanical properties [5]. in [6] the microstructure of the coating obtained by cold gas-dynamic spraying was investigated. a cu-al2o3-zn powder blend was sprayed onto a copper substrate to restore a worn copper contact wire. the coating thickness was 1–2.5 mm. improved adhesion http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2022.9.3.07 mailto:gudymatan@mail.ru http://creativecommons.org/licenses/by/4.0/ https://orcid.org/0000-0003-0190-7133 https://crossmark.crossref.org/dialog/?doi=https://doi.org/10.15826/chimtech.2022.9.3.07&domain=pdf&date_stamp=2022-7-26 chimica techno acta 2022, vol. 9(3), no. 20229307 letter 2 of 4 strength was achieved through substrate surface preprocessing with coarse al2o3 particles. to obtain the pattern of an electronic power module, ceramic substrates should be metallized. therefore, conducting layers, over 300 µm thick, are deposited by different techniques to form multilevel metallization [7]. while in production and operation, the metallized structures of power modules are exposed to thermal and mechanical stresses. the research objective is to optimize the technique of thick copper layers deposition onto ceramic substrates used in power electronics. we considered the use of finely-dispersed pmvd-0, pmvd-1 and coarse pmс-1 copper powders for their sputtering by gas dynamic cold spray technique (gdcs). after preliminary experimental studies of gas dynamic cold spray technique (gdcs), we made a choice of pmс-1 copper powder (gost 4960-2009) as the most appropriate, affordable and cheap. the basic element of the power module structure is considered to be a metallized ceramic substrate with the power semiconductor crystal, which is used for implementing two main functions: firstly, for electrical isolation of conductor buses patterned on one or both sides; secondly, for the conductance of heat emitted by the active elements of the electronic power module to heat radiators. besides their high heat conductivity, the substrates of power modules must be very strong, heatand chemically resistant. in this regard, we use the substrates made from different grades of aluminum oxide ceramics and aluminum nitride ceramics providing high dissipation capacity. based on the properties analysis carried out for ceramic materials applied by dbc technology abroad [8, 9], we come to the conclusion that aluminum oxide ceramics with the content of aluminum oxide exceeding 95% is more frequently used, but aluminum-nitride ceramics with the content of nitride oxide, which is more than 98%, is suitable for the circuits with high specific dissipation capacity. taking into account their main characteristics, aluminum-oxide ceramic substrates for dbc boards made by сетс (china) are comparable with вк96 substrates produced by jsc nevzceramics (russia). however, their characteristics are inferior to the ones of вк100 ceramics produced by jsc nevz-ceramics (russia), where the content of the basic substance is equal to 99.7% (in contrast to vк-96 ceramics with 96% content of the base material). with regard to their physical properties, aluminumnitride ceramics (aln) is characterized by high thermal conductivity (170–200 w/m·к) and electrical resistance stability (1013–1014 ohm·cm) when the temperature is increasing [10–13]. in russia jsc nevz-ceramics specializes in manufacture of aluminum-nitride ceramic substrates [9]. produced at this enterprise, aluminumnitride substrates are characterized by high thermal conductivity of 160–185 w/m·к, isolation and strength parameters at the level of world’s brands, such as maruva (japan), leatec (taiwan), clecgroup (china), ceramtec (germany). the substrates are produced by slip casting technique followed by annealing of aluminum-oxide ceramics at 1650 °с and aluminum-nitride ceramics at 1850 °с. 2. experimental metallized coatings (mc) formation was tested by the heat transfer of two metallization pastes compositions for aluminum-oxide and aluminum-nitride ceramics. pastes compositions: а. mo-mn-si+ta2o5+zro2+tih2+binder. b. mo-mn-si+ binder. the organic binder for the metallization pastes contains: ethylcellulose-100, α-terpineol, dibutylphthalate and oleic aсid. surface preparation is considered to be one of the main stages of metallized coating formation on ceramics. ceramic substrates had been mechanically polished before metallization to obtain alignment and surface roughness of ra = 0.15 µm. mc bonding on the ceramic substrates was achieved via its annealing. in this regard, nitrogen-hydrogen throughand pusher-type furnaces were used. the furnaces consist of 5 mullite muffles, which are 90 cm long. the muffles are located in series to provide a continuous channel with 3 temperature ranges. annealing was carried out with 30 minutes exposure at 1320 °с. the gdcs technique is based on acceleration of 1–150 µm particles with a supersonic gas flow up to the speed of 500–1200 m/s. the particles colliding with an obstacle tend to bond on it without melting [14, 15]. meanwhile, the substrates are not strongly affected by temperatures. sputtering was carried out on vk-96 aluminum oxide substrates with the dimensions of 30290.3 mm, and with a mo-mn-si sublayer being 10–20 μm thick. pмс-1 copper powder was used for sputtering. formation of metallized coatings from copper powders was carried out according to typical gdcs diagrams with the use of a planar contracting-expanding nozzle with 3.053.05 mm critical cross section and 9.53.05 mm exit geometry. the rate of powder consumption from a dispenser was set to 0.1 g/s. the distance of sputtering was equal to 30 mm; the nozzle scanning velocity against the substrate varied from 5 to 50 mm/sec. air was chosen as a carrier and working gas. the deposition was conducted on the gdcs itam sb ras test installation. the substrates were split into two batches after sputtering. then annealing was carried out in the hydrogen medium at different temperatures to determine the optimal thermal mode. chimica techno acta 2022, vol. 9(3), no. 20229307 letter 3 of 4 3. results and discussion since the products obtained are operated in air, the resistance of the coatings in aggressive media (acids or base solutions) was not determined. it is also known that semiconductor devices with these products are operated at low temperatures (not exceeding 125 °c). for this reason, the thermal stability of coatings was not studied. the most important performance characteristics of coatings are adhesion resistance and low electrical resistivity. the key parameters were determined after annealing as follows: the measured values of adhesion and intrinsic resistance were compared with the same parameters for dbc-substrates produced in germany and china (table 1). 1000 °с appeared to be the optimum annealing temperature for adhesion. the best results are peculiar to dbcsubstrates with the lowest resistance, which is close to the resistance of pure copper. the substrates with thick copper layers sputtered by the gdcs technique are characterized by the key parameters close to the values of dbcsubstrates, despite the use of copper powder to obtain the copper coatings. 4. conclusions the technology of applying a two-layer metallization coating on ceramic substrates made of nitride and aluminum oxide was developed. initially, a layer of molybdenummanganese-silicon was deposited on the surface of the substrates by burning in a nitrogen-hydrogen medium for 30 minutes at a temperature of 1320 °c. at the second stage, a layer of copper was deposited by the cgds method with a flat laval nozzle. the working gas was air. after deposition, annealing was carried out in hydrogen atmosphere. the optimal annealing temperature was 1000 °c. the obtained coatings are characterized by a stable adhesive bond of the copper coating with the base (the adhesion value exceeds 60 mpa) and low electrical resistance (at the level of 3·10–6 ohm·cm). supplementary materials no supplementary materials are available. funding the work was funded by the state task of ministry of science and higher education of russia (project no. fsun2020-0008). acknowledgments none. table 1 measurement results of adhesion and intrinsic resistance. no. sample adhesion mpa average value of intrinsic resistance ρ·106, ohm·cm 1 gdcs, al2o3 + momnsi + cu, 850 °с 63.7 2.95 2 gdcs, al2o3 + momnsi + cu, 850 °с 51.7 3.05 3 gdcs, al2o3 + momnsi + cu, 950 °с 65.3 3.18 4 gdcs, al2o3 + momnsi + cu, 1000 °с 66.2 3.22 5 gdcs, al2o3 + momnsi + cu, 1000 °с 67.2 3.30 6 gdcs, aln + momnsi + cu, 850 °с 8.3 2.91 7 gdcs, aln + momnsi + cu, 850 °с 6.3 2.81 8 gdcs, aln + momnsi + cu, 950 °с 20.2 2.92 9 gdcs, aln + momnsi + cu, 1000 °с 31.3 3.07 10 gdcs, aln + momnsi + cu, 1000 °с 33.0 2.98 11 dbc, al2o3 + cu, 1065– 1080 °с (germany) 59.0 2.40 12 dbc, al2o3 + cu, 1065– 1080 °с (china) 28.5 2.90 author contributions conceptualization: n.yu.k. data curation: n.yu.k. formal analysis: n.yu.k., p.p.m. investigation: n.yu.k., p.p.m., g.t.s. methodology: n.yu.k., p.p.m. project administration: n.yu.k. supervision: p.p.m., g.t.s. validation: n.yu.k., p.p.m., k.v.s. visualization: n.yu.k., p.p.m. writing – original draft: p.p.m., k.v.s. writing – review & editing: n.yu.k., g.t.s. conflict of interest the authors declare no conflict of interest. additional information author ids: yuri k. nepochatov, scopus id 56059064700; pyotr m. pletnev, scopus id 6603166237; vladimir f. kosarev, scopus id 7005349023; тatiana s. gudyma, scopus id 57220042373. websites: hc pjsc nevz–soyuz, https://nevz.xspe.ru; siberian state transport university, http://www.stu.ru; http://www.scopus.com/inward/authordetails.url?authorid=56059064700 https://www.scopus.com/authid/detail.uri?authorid=6603166237 https://www.scopus.com/authid/detail.uri?authorid=7005349023 https://www.scopus.com/authid/detail.uri?authorid=7005349023 https://www.scopus.com/authid/detail.uri?authorid=57220042373 https://nevz.xspe.ru/ http://www.stu.ru/ chimica techno acta 2022, vol. 9(3), no. 20229307 letter 4 of 4 institute of theoretical and applied mechanics sb ras, http://itam.nsc.ru; novosibirsk state technical university, https://en.nstu.ru. references 1. oyinbo st, jen t-c. a comparative review on cold gas dynamic spraying processes and technologies. manuf rev. 2019;6:25. doi:10.1051/mfreview/2019023 2. 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12. rounds r, sarkar b, alden d, guo q, klump a, hartmann c, nagashima t, kirste r, franke a, bickermann m, kumagai y, sitar z, collazo r. the influence of point defects on the thermal conductivity of aln crystals. j appl phys. 2018;123(18):185107. doi:10.1063/1.5028141 13. mccauley j. structure and properties of aluminum nitride and alon ceramics. elsevier's encycl of mater sci technol. 2001;127–132. doi:10.1016/b0-08-043152-6/00028-0. 14. roelison rn, vergy c, liao h. cold gas dynamic spray additive manufacturing today: deposit possibilities, technological solutions and viable applications. mater des. 2017;133:266– 287. doi:10.1016/j.matdes.2017.07.067 15. schmidt t, gartner f, assadi h, kreye h. development of generalizated parameter window for cold spray deposition. acta mater. 2006;54:729–742. doi:10.1016/j.actamat.2005.10.005 http://itam.nsc.ru/ https://en.nstu.ru/ https://doi.org/10.1051/mfreview/2019023 https://doi.org/10.1007/s11666-022-01363-7 https://doi.org/10.1007/s11666-021-01245-4 https://doi.org/10.1007/s11666-015-0223-5 https://doi.org/10.1007/s11666-022-01402-3 https://doi.org/10.3390/coatings11091067 https://doi.org/10.1361/105996398770350945 https://doi.org/10.1109/iecon.1998.724090 https://doi.org/10.1016/0257-8972(93)90106-x https://doi.org/10.1590/s0366-69132004000300012 https://doi.org/10.1016/0955-2219(93)90036-q https://doi.org/10.1063/1.5028141 https://doi.org/10.1016/b0-08-043152-6/00028-0. https://doi.org/10.1016/j.matdes.2017.07.067 https://doi.org/10.1016/j.actamat.2005.10.005 a method of mild deoxydichlorination of aldehydes catalyzed by triphenylphosphine oxide chimica techno acta article published by ural federal university 2022, vol. 9(2), no. 20229202 eissn 2411-1414; chimicatechnoacta.ru doi: 10.15826/chimtech.2022.9.2.02 1 of 7 a method of mild deoxydichlorination of aldehydes catalyzed by triphenylphosphine oxide d.a. shipilovskikh ab, m.f. konkova a, i.p. nikonov a, m.m. gladysheva a, s.a. shipilovskikh ac* a: perm state university, 614990 perm, russia b: perm national research polytechnic university, 614990 perm, russia c: itmo university, 197101 st. petersburg, russia * corresponding authors: s.shipilovskikh@metalab.ifmo.ru this paper belongs to the regular issue. © 2022, the authors. this article is published in open access form under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). abstract the catalytic system of triphenylphosphine oxide and phthaloyl dichloride catalysing conversion of aldehydes to 1,1-dichlorides is reported. the reaction proceeds via a p (v) catalysis manifold in which triphenylphosphine oxide turnover is achieved using phthaloyl dichloride as a consumable reagent. the application of the developed method on substrates of different structures was demonstrated. we showed the use of unsaturated compounds, including aromatics with and without electron donating / withdrawing groups, as well as saturated aliphatic compounds. the possibility of using the developed method on a gram scale was also demonstrated with the deoxydichlorination reaction of 0.03 mol of benzaldehyde catalyzed by triphenylphosphine oxide as an example. the proposed method may be of interest for the production of different herbicides, insecticides and fungicides for the agricultural industry. keywords aldehydes lewis base catalysis organocatalysis triphenylphosphine oxide nucleophilic substitution agricultural chemistry received: 15.02.2022 revised: 23.03.2022 accepted: 23.03.2022 available online: 25.03.2022 1. introduction the development of methods for nucleophilic substitution (sn) in sp3-hybridized carbon centers is the most significant and widespread problem of chemical transformations in organic synthesis [1–5]. nucleophilic substitutions are general chemical transformations, as they allow, for example, strategic building of c–cl, c–o, c–n and c–c bonds [6–15]. at the same time, compounds such as geminal dihalides are important intermediates in the chemical synthesis of useful natural substances, including active biological compounds. geminal dihalides, especially dichlorides, are an important class of intermediates in organic synthesis. they were used for alkenylation of carbonyl compounds [16, 17], cyclopropanation and epoxidation [18–20], dimerization [21, 22] and other purposes [23–26]. in addition, geminal dichlorides are also encountered as structural motifs in polyhalogenated natural products [27, 28]. at the same time, one of the main areas of application of such compounds is agriculture. herbicides, insecticides and fungicides are widely used for plant protection in the modern industry (fig. 1) [29–31]. most of the waste from such chemical industries contains various halogencontaining compounds, which are extremely toxic to both humans and the environment. also, the dichlorides are an important class of intermediates in organic synthesis. they were used for alkenylation of carbonyl compounds [32, 33], cyclopropanation and epoxidation [34–36], dimerization [37, 38], etc. [39–42]. in addition, geminal dichlorides are also encountered as structural motifs in polyhalogenated natural products such as caldariomycin, danicalipin a and undecachlorosulfolipids a [43–48]. however, traditional synthetic methods often have low selectivity and low atom economy, resulting in the different products of chemical reactions [49–51]. research in this area is at an early stage in the study of such catalytic reactions, but several efficient protocols for the production of dichlorides from aldehydes catalyzed by a lewis base have been disclosed to date (scheme 1). dr. denton with colleagues previously reported a method for the catalytic deoxydichlorination of aldehydes [52]. in this method, authors used a catalytic system of triphenylphosphine oxide (7.5–15 mol.%) and oxalyl chloride. the proposed method works well with different unsaturated compounds, but gives a lower yield of 32% with aliphatic compounds. http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2022.9.2.02 http://creativecommons.org/licenses/by/4.0/ https://orcid.org/0000-0002-8917-2583 https://crossmark.crossref.org/dialog/?doi=https://doi.org/10.15826/chimtech.2022.9.2.02&domain=pdf&date_stamp=2022-3-25 chimica techno acta 2022, vol. 9(2), no. 20229202 article 2 of 7 fig. 1 the most used herbicides, insecticides and fungicides in 2019, dr. p. huy showed new catalytic method transformation of aldehydes into geminal dichlorides using a catalytic system of n-formylpyrrolidine (5–10 mol.%) with phthaloyl dichloride (1.2–1.4 equiv). the proposed method exhibits the same catalytic activity as triphenylphosphine oxide [53]. later dr. shipilovskikh with colleges proposed an alternative method for deoxydichlorination of aldehydes catalyzed by diphenyl sulfoxide, using a catalytic system of diphenyl sulfoxide (10 mol.%) and oxalyl chloride (1.5 equiv). the developed method showed excellent yields with unsaturated aldehydes [54]. in this work, we use the combination of the previously reported catalytic system and optimization of the reaction condition. we found that the catalytic activity of triphenylphosphine oxide can be increased by a factor of 10 compared to previously described methods. in addition, in the proposed method, reducing the catalyst load did not affect the catalytic activity in case of unsaturated aldehydes and in case of aliphatic aldehydes, the reaction yield increased to 10%. 2. experimental yields are given for isolated products showing one spot on a tlc plate and no impurities detectable in the nmr spectrum. the identity of the products prepared by different methods was checked by comparison of their nmr spectra. the 1h and 13c nmr spectra were recorded at 400 mhz for 1h and 100 mhz for 13c nmr at the temperature of 303 k; the chemical shifts (δ) were measured in ppm with respect to the solvent (cdcl3, 1н: δ = 7.26 ppm, 13c: δ = 77.16 ppm; [d6] dmso, 1н: δ = 2.50 ppm, 13c: δ = 39.52 ppm). the coupling constants (j) are given in hertz. the splitting patterns of apparent multiplets associated with an averaged coupling constants were designated as s (singlet), d (doublet), t (triplet), q (quartet), sept (septet), m (multiplet), dd (doublet of doublets) and br (broadened). the melting points were determined with a «stuart smp 30», the values are uncorrected. flash chromatography was performed on silica gel macherey nagel (40–63 µm). scheme 1 catalytic deoxydichlorination of aldehydes to 1,1-dichlorides chimica techno acta 2022, vol. 9(2), no. 20229202 article 3 of 7 the reaction progress was monitored by gc/ms analysis and thin layer chromatography (tlc) on aluminum backed plates with merck kiesel 60 f254 silica gel. the tlc plates were visualized either by uv radiation at a wavelength of 254 nm or stained by exposure to a dragendorff’s reagent or potassium permanganate aqueous solution. all the reactions were carried out using dried and freshly distilled solvent. 2.1. general method for synthesis of dichlorides from aldehyde triphenylphosphine oxide (ph3po) (3 mg, 0.01 mmol, 0.01 equiv, 1 mol.%) and phthaloyl dichloride (203 mg, 1.00 mmol, 1 equiv) were dissolved in 8 ml of anhydrous toluene in a 25 ml round bottom flask equipped with a magnetic stirring bar. after wards, aldehydes 1a–e (1 mmol, 1 equiv) in 2 ml of anhydrous toluene were slowly added to this solution with vigorous stirring at 0 °c, followed by heating up to 100 °c and stirring the mixture for 3 h. the reaction progress was monitored by gc-ms. after the reaction was complete, the solution was filtered and concentrated in vacuum. the crude mixture thus obtained was purified by flash chromatography on silica (petroleum ether/et2o – 19/1). for gram-scale example , the mixture was purified by distillation. the general method for synthesis is shown in scheme 2. scheme 2 general method for synthesis 2.1.1. (dichloromethyl)benzene 4а obtained from 1a (106 mg, 1 mmol), triphenylphosphine oxide (ph3po) (3 mg, 0.01 mmol, 0.01 equiv, 1 mol.%), and phthaloyl dichloride (203 mg, 1.00 mmol, 1 equiv), in anhydrous toluene (10 ml). colorless oil (142 mg, 88%, for gram-scale 4.05 g, 84%). 1h nmr (cdcl3, 400 mhz) δ (ppm): 6.73 (s, 1h, ch), 7.44–7.46 (m, 3h, har), 7.64–7.66 (m, 2h, har). 13c nmr (cdcl3, 100 mhz) δ (ppm): 72.2, 126.0, 128.9, 123.0, 140.3 [55]. 2.1.2. 1-(dichloromethyl)-4-methylbenzene 4b obtained from 1b (120 mg, 1 mmol), triphenylphosphine oxide (ph3po) (3 mg, 0.01 mmol, 0.01 equiv, 2 mol.%), and phthaloyl dichloride (203 mg, 1.00 mmol, 1 equiv), in anhydrous toluene (10 ml). colorless oil (159 mg, 91%). 1h nmr (cdcl3, 400 mhz) δ (ppm): 2.42 (s, 3h, ch3), 6.69 (s, 1h, ch), 7.16–7.24 (m, 2h, har), 7.44–7.51 (m, 2h, har). 13c nmr (cdcl3, 100 mhz) δ (ppm): 21.8, 71.6, 126.0, 129.1, 137.2, 140.7 [56]. 2.1.3. 1-bromo-4-(dichloromethyl)benzene 4с obtained from 1с (185 mg, 1 mmol), triphenylphosphine oxide (ph3po) (3 mg, 0.01 mmol, 0.01 equiv, 1 mol.%), and phthaloyl dichloride (203 mg, 1.00 mmol, 1 equiv), in anhydrous toluene (10 ml). colorless oil (194 mg, 81%). 1h nmr (cdcl3, 400 mhz) δ (ppm): 6.70 (s, 1h, ch), 7.43–7.49 (m, 2h, har), 7.49–7.56 (m, 2h, har). 13c nmr (cdcl3, 100 mhz) δ (ppm): 72.0, 124.2, 128.1, 131.7, 139.5 [53]. the structures of 1-(dichloromethyl)benzene 4a, (dichloromethyl)-4-methylbenzene 4b and 1-bromo-4(dichloromethyl)benzene 4c are shown in fig. 2. fig. 2 1-(dichloromethyl)benzene 4a, (dichloromethyl)-4methylbenzene 4b and 1-bromo-4-(dichloromethyl)benzene 4c 2.1.4. 1-(dichloromethyl)-2-methoxybenzene 4d obtained from 1d (136 mg, 1 mmol), triphenylphosphine oxide (ph3po) (3 mg, 0.01 mmol, 0.01 equiv, 1 mol.%), and phthaloyl dichloride (203 mg, 1.00 mmol, 1 equiv), in anhydrous toluene (10 ml). colorless oil (143 mg, 75%). 1h nmr (cdcl3, 400 mhz) δ (ppm): 3.87 (s, 3h, ch3), 6.93–7.17 (m, 1h, ch, 2h, har), 7.29–7.32 (0, 1h, har), 7.71–7.83 (m, 2h, har). 13c nmr (cdcl3, 100 mhz) δ (ppm): 54.1, 64.5, 109.3, 120.1, 127.1, 128.3, 130.0, 152.4 [53]. 2.1.5. (3,3-dichloroprop-1-en-1-yl)benzene 4e obtained from 1e (132 mg, 1 mmol), triphenylphosphine oxide (ph3po) (3 mg, 0.01 mmol, 0.01 equiv, 1 mol.%), and phthaloyl dichloride (203 mg, 1.00 mmol, 1 equiv), in anhydrous toluene (10 ml). colorless oil (153 mg, 82%). 1h nmr (cdcl3, 400 mhz) δ (ppm): 6.33 (d, j = 7.6 hz, 1h, ch), 6.40 (dd, j = 14.7 and 7.6 hz, 1h, ch), 6.72 (d, j = 14.7 hz, 1h, ch), 7.30–7.50 (m, 5h, har). 13c nmr (cdcl3, 100 mhz) δ (ppm): 73.5, 127.1, 128.1, 129.0, 129.2, 132.5, 134.7 [53]. 2.1.6. 1,1-dichlorooctane 4f obtained from 1f (128 mg, 1 mmol), triphenylphosphine oxide (ph3po) (3 mg, 0.01 mmol, 0.01 equiv, 1 mol.%), and phthaloyl dichloride (203 mg, 1.00 mmol, 1 equiv), in anhydrous toluene (10 ml). colorless oil (77 mg, 42%). 1h nmr (cdcl3, 400 mhz) δ (ppm): 0.92 (t, j = 7.2 hz, 3h, ch3), 1.31 (m, 8h, ch2), 1.55 (m, 2h, ch2), 2.20 (m, 2h, ch2), 5.74 (t, j = 6.2 hz, 1h, chcl2). 13c nmr (cdcl3, 100 mhz) δ (ppm): 14.0, 22.9, 26.3, 28.7, 29.6, 32.0, 43.9, 73.7. the structures of 1-(dichloromethyl)-2methoxybenzene 4d, (3,3-dichloroprop-1-en-1-yl)benzene 4e and 1,1-dichlorooctane 4f are shown in fig. 3. chimica techno acta 2022, vol. 9(2), no. 20229202 article 4 of 7 fig. 3 1-(dichloromethyl)-2-methoxybenzene 4d, (3,3-dichloroprop-1-en-1-yl)benzene 4e and 1,1-dichlorooctane 4f 3. results and discussion the investigation commenced with establishing the best conditions for the deoxydichlorination of aldehydes, employing benzaldehyde 1a as a model substrate (table 1). first, the catalytic triphenylphosphine oxide was investigated. then, the effects of the solvent, temperature, and equivalents of phthaloyl dichloride on the conversion in the reaction were studied. phthaloyl dichloride on its own did not produce (dichloromethyl)benzene 4a (entry 1). the use of stoichiometric quantities of ph3po and 2 equiv of phthaloyl dichloride in dcm resulted in low conversion of 1a into 4a (scheme 3, table 1, entry 2). with 10 mol.% ph3po and 2 equiv of phthaloyl dichloride, 4a was formed in 16% conversion after 3 h (entry 3), which increased to 40% after changing the solvent to toluene (entry 4). raising the temperature to 100 °c with 10 mol.% ph3po and using 2 equiv of phthaloyl dichloride led to the best results of conversion to 95% (entry 9). we then studied the catalytic activity of ph3po at 100 °c for 3 hours and found that using 1 mol.% ph3po gives a similar result (95% conversion, entry 11). finally, we studied the effect of the equivalents of phthaloyl dichloride on the conversion of the reaction and found that the use of phthaloyl dichloride at an equivalent of 100 mol.% gives a similar conversion, 95% (entry 12). however, reducing the equivalents of phthaloyl dichloride to 50 mol.% yields the conversion of 43% (entry 13). table 1 optimization of the reaction conditionsa entry equiv of phthaloyl dichloride mol.% ph3po solvent t (°c) t (h) conv. (%)b 1 2 – dcm 40 1 0 2 2 100 dcm 40 1 8 3 2 10 dcm 40 3 16 4 2 10 tol 40 3 40 5 2 10 mecn 40 3 10 6 2 10 dce 40 3 18 7 2 10 thf 40 3 32 8 2 10 et2o 30 3 6 9 2 10 tol 100 3 95 10 2 5 tol 100 3 95 11 2 1 tol 100 3 95 12 1 1 tol 100 3 95 13 0.50 1 tol 100 3 43 ageneral conditions: 1a (0.01 mmol, 1 mol.%) ph3po, dry solvent, slowly addition of aldehydes. the reactions were carried out for 1–3 h before an aliquot (50 μl) was taken, quenched with aqueous solvent (1 ml), and analyzed by gc. bconversion to 4a was calculated from gc. scheme 3 the reaction for optimization conditions the substrate scope was investigated next. as shown, the reaction works well with different types of aromatic aldehydes, including donor and acceptor substituents at the fourth position of the ring. the use of cinnamaldehyde under the reaction conditions also showed good results. however, the use of aliphatic aldehydes led to the low catalytic activity, which is consistent with the research described previously. in addition, we studied the possibility of transferring the developed method from the milligram-scale to the gram-scale of (dichloromethyl)benzene, which shows the possibility of industrial application of the developed methods (scheme 4). the possibility of using 1 mol.% catalyst based on triphenylphosphine oxide, as well as the complete transition of chlorine into the final product, significantly reduces the amount of waste that is toxic to the environment and humans. also, the results obtained are superior to those described earlier, which indicates the prospects for further development of this catalytic system. scheme 4 gram-scale application of deoxydichlorination of benzaldehyde catalyzed by triphenylphosphine oxide the proposed mechanism is depicted in scheme 5. we believe that the catalytic cycle start with a quick formation of the intermediate dichlorotriphenylphosphane (b) upon treatment of triphenylphosphine oxide (a) with phthaloyl dichloride. next, in catalytic cycle, the intermediate b reacts with aldehyde 1 via oxygen to form the intermediate c, which then undergoes elimination to furnish geminal dichloride 4 and to regenerate the catalyst a. 4. conclusions we developed a highly atom economy protocol for a catalytic deoxydichlorination of aldehydes under modified appel conditions catalyzed by 1 mol.% of triphenylphosphine oxide. the salient features of the method are: (i) operationally simplicity, (ii) low catalyst loading (1 mol.%), (iii) medium reaction times and (iv) mild conditions and chimica techno acta 2022, vol. 9(2), no. 20229202 article 5 of 7 all transfer chlorine from phthaloyl dichloride. also, we showed applications of the developed method on the gram-scale. scheme 5 the proposed mechanism related to cyclic transformation of substances supplementary materials no supplementary data are available. funding this study was funded by the russian science foundation grant no. 20–73–00081, https://www.rscf.ru/en. acknowledgments none. author contributions conceptualization: s.a.s. data curation: m.f.k., i.p.n. formal analysis: m.f.k., i.p.n., m.m.g. funding acquisition: d.a.s., s.a.s. investigation: d.a.s., m.f.k., i.p.n., m.m.g. methodology: i.p.n., m.m.g. project administration: s.a.s. resources: d.a.s., s.a.s. software: d.a.s., s.a.s. supervision: s.a.s. validation: d.a.s., m.f.k., s.a.s. visualization: d.a.s., i.p.n., s.a.s. writing – original draft: d.a.s., s.a.s. writing – review & editing: d.a.s., s.a.s. conflict of interest the authors declare no conflict of interest. additional information authors’ ids: shipilovskikh, daria a., scopus id 57193555475; shipilovskikh, sergei a., scopus id 34168423100. website of perm state university, http://en.psu.ru; perm national research polytechnic university, https://pstu.ru/en; itmo university, https://en.itmo.ru. references 1. li j, huang chyu, li chj. deoxygenative functionalizations of aldehydes, ketones and carboxylic acids. angew chem int ed engl. 2021:202112770. 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relat elem. 2020;196(4):398–406. doi:10.1080/10426507.2020.1845680 https://doi.org/10.1016/s0040-4020(99)00021-6 https://doi.org/10.1021/jo980724h https://doi.org/10.2174/1570178617666200121110618 https://doi.org/10.1016/j.tet.2013.07.100 https://doi.org/10.1055/s-0037-1611798 https://doi.org/10.15826/chimtech.2021.8.4.08 https://doi.org/10.1002/chem.202101534 https://doi.org/10.1080/10426507.2020.1845680 experimental estimation of the diffusion spinodal position of binary mixture with lcst based on the method of isobaric pulse heating published by ural federal university eissn 2411-1414; chimicatechnoacta.ru article 2022, vol. 9(4), no. 20229408 doi: 10.15826/chimtech.2022.9.4.08 1 of 6 to the possibility of experimental estimation of the diffusion spinodal position of binary mixture with lcst via pulsed heating method alexander a. igolnikov ab , aleksandr d. yampol'skiy a a: institute of thermal physics ub ras, ekaterinburg 620016 russia b: ural federal university, ekaterinburg 620000, russia * corresponding author: alexander.igolnikov@bk.ru this paper belongs to a regular issue. © 2022, the authors. this article is published in open access under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). abstract in this paper, we present new data on non-stationary heating of a platinum wire probe, immersed in a binary partially-miscible liquid. a pressure value and a mass fraction of the a polymer in the mixture were the experimental parameters. the characteristic heating time was from 5 to 15 ms. the object of the research was the water/polypropylene glycol-425 (ppg-425) mixture having lower critical solution temperature (lcst). the position of the diffusion spinodal was estimated based on the obtained data on the liquid-liquid binodal in the framework of the flory-huggins approximation. an experimental technique to estimate the position of the spinodal of two-component mixtures with lcst on the scale of the mixture component ratio was developed. it was shown that the method of isobaric pulse heating can be used for this purpose. this representation is based on the threshold change in the heat transfer pattern when crossing the phase coexistence curve and the diffusion spinodal. keywords diffusion spinodal phase coexistence line partially-miscible mixture pulse heating flory-huggins approximation received: 30.05.22 revised: 07.07.22 accepted: 21.07.22 available online: 10.08.22 1. introduction polymer solutions are widely used in engineering, medicine, and agriculture. they are also closely related to the processes occurring in living organisms. the study of their physico-chemical properties is of crucial importance. however, phase diagrams (pd) of solutions are much more diverse than pd of pure substances, so the area of study is often limited by the phase coexistence boundary on the t–c diagram [1]. an analysis of the gibbs energy makes it possible to rigorously determine the binodal and spinodal equations for partially-miscible mixtures. the binodal determines the absolute stability limit of a single-phase system, beyond which the system becomes metastable. concentration fluctuations exceeding the critical size lead to the decay of the metastable system. the critical size of nuclei decreases with increasing degree of penetration into the metastable region. further growth of nuclei is caused by the diffusion of components from a nonequilibrium solution. the system becomes two-phase with a clear interface. the spinodal is the boundary of the instability of mixture, beyond which it becomes labile. in this case, the appearance of new phases is due to fluctuations of any size. it is not the linear size of the fluctuations that grows, but the deviation of the concentration from the equilibrium value. the decomposition is accompanied by the formation of two equilibrium liquid phases. the junction point at the pd where the binodal and the spinodal meet is called the critical solution temperature. there are upper (ucst) and lower (lcst) critical solution temperatures [1–3]. nowadays, methods of experimental determination of phase coexistence curve positions are being actively developed. among these are visual analysis, light scattering [4], and short-term heating of a platinum wire probe immersed in an investigated liquid [5, 6]. theoretical models have been developed that can be used to estimate the position of the binodal and the spinodal of two-component systems based on their physico-chemical properties. the theories of regular solution [7] and flory-huggins [8, 9] have received the most recognition. however, there are practically no experimental methods capable of determining the diffusion spinodal position of not too viscous systems with sufficient accuracy. research in this area of pd is accompanied by significant difficulties. indeed, in the region bounded by the binodal and spinodal, the multicomponent system is not in a fully stable state. thus, the http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2022.9.4.08 mailto:alexander.igolnikov@bk.ru http://creativecommons.org/licenses/by/4.0/ https://orcid.org/0000-0002-1894-6131 https://crossmark.crossref.org/dialog/?doi=https://doi.org/10.15826/chimtech.2022.9.4.08&domain=pdf&date_stamp=2022-8-10 chimica techno acta 2022, vol. 9(4), no. 20229408 article 2 of 6 characteristic time of the experiment should be comparable with the characteristic time of phase relaxation of the nonequilibrium solution. in this paper, an aqueous solution of polypropylene glycol-425 (ppg-425) having an lcst at approximately 50 °c and a ppg-425 content of 27 wt.% was chosen as the object of the study. the components of the mixture are non-toxic, easily available and can be used in relatively large volumes. the mixture is isopycnic, i.e. the components of the mixture have almost the same density, which eliminates the influence of the archimedes force on the process of phase separation. the aim of this work was to calculate the position of the diffusion spinodal of a water/ppg-425 mixture in the framework of the flory-huggins approximation and to develop an experimental technique for estimating the position of the spinodal of two-component mixtures with lcst based on the method of controlled pulsed heating of a wire probe – a resistance thermometer. this method has a number of characteristic advantages: the ability to control and change the heating parameters on a microsecond temporal scale, access to the primary experimental data obtained in the course of heating, and a wide range of temperatures and pressures (up to 800 oc and 100 mpa) available for the research [10]. 2. spinodal calculation earlier, the calculation of the spinodal of water/ppg-425 mixture based on the regular solution approximation was carried out in the work [11]. here, we will focus on the flory-huggins theory as the most commonly used for this purpose. according to the theory, the change in the chemical potential of the solvent during the formation of a linear polymer solution is determined by the equation: ∆𝜇1 = 𝑅𝑇[ln(1 − 𝜑2) + (1 + 1 𝑥)𝜑2 + 𝜑2 2⁄ ], (1) where 𝜑2 – the volume fraction of polymer in solution; x – the degree of polymerization; χ – the interchange energy normalized by rt.  = 𝛼 + 𝛽 𝑇⁄ , 𝛼, 𝛽 = 𝑐𝑜𝑛𝑠𝑡. (2) as a result of the phase separation, solutions diluted (i) and concentrated (ii) with respect to the polymer are formed. then, ∆𝜇1(𝐼) = 𝑅𝑇[ln(1 − 𝜑2 ′ ) + (1 + 1 𝑥)𝜑2 ′ + 𝜑2 ′ 2⁄ ], (3) ∆𝜇1(𝐼𝐼) = 𝑅𝑇[ln(1 − 𝜑2 ′′) + (1 + 1 𝑥)𝜑2 ′′ + 𝜑2 ′′ 2⁄ ]. (4) single and double apostrophes denote the concentration of the component in the dilute and the concentrated solution, respectively. changes in the chemical potentials of the polymer in coexisting phases are equal: ∆𝜇2(𝐼) = 𝑅𝑇[ln 𝜑2 ′ − (𝑥 − 1)𝜑1 ′ + 𝜑1 ′ 2], (5) ∆𝜇2(𝐼𝐼) = 𝑅𝑇[ln 𝜑2 ′′ − (𝑥 − 1)𝜑1 ′′ + 𝜑1 ′′ 2]. (6) the phase coexistence curve corresponds to the system of equations: ∆𝜇1(𝐼) = ∆𝜇1(𝐼𝐼), (7) ∆𝜇2(𝐼) = ∆𝜇2(𝐼𝐼). 0 substituting equations (3) and (4) into equation (7) and performing transformations, one can obtain the following expression for χ:  = 𝑙𝑛 1 − 𝜑2 ′ 1 − 𝜑2 ′′ + (1 − 1 𝑥⁄ )(𝜑2 ′ − 𝜑2 ′′) 𝜑2 ′′ 2 − 𝜑2 ′ 2 . (9) the equation for the spinodal is defined as: 𝜕∆𝜇1 𝜕𝜑2 = 0. (10) the critical point satisfies the condition: 𝜕2∆𝜇1 𝜕2𝜑2 = 0. (11) after performing the differentiation operation and transforming the resulting expressions, one can obtain the following equations: 𝜑2 2 + 1 2 (1 − 2 − 1 𝑥 ) 𝜑2 + 1 2𝑥 = 0, (12)  𝑐 = 1 2(1 − 𝜑2,𝑐 ) 2 , (13) 𝜑2,𝑐 = 1 1 + 𝑥1 2⁄  𝑥 = ( 1 𝜑2,𝑐 − 1) 2 . (14) knowing the parameters of the cst and the concentration of the polymer in the solution 𝜑2 ′ and𝜑2 ′′ (2 points on the binodal) at a given temperature, one can calculate the values of α, β and х. by substituting the obtained values into equation (12), one can estimate the position of the diffusion spinodal (figure 1). the data on the estimation of the solution binodal obtained by visual observation (the cloud point method) were used in the calculations [11]. 3. pulsed heating method experimental setup for pulsed heating of a wire probe – resistance thermometer comprises an analog microcircuit based on a pid controller [12]. the device is controlled by a specially developed software through adc/dac signal converters. the excess pressure was created and maintained by means of a wika cpp1200-x hydraulic press with a maximum allowable pressure of 120 mpa. the measurements of pressure value were carried out via a wika cpg1500 pressure gauge with a measurement limit of 100 mpa and accuracy class of 0.025. a simplified scheme of the experimental setup is shown in figure 2. chimica techno acta 2022, vol. 9(4), no. 20229408 article 3 of 6 the measuring cell containing the substance under study and the probe has flexible walls for pressure transmission. it is placed in a pressure chamber where excess pressure is created. the digital control signal from the computer is converted into the analog one and fed to the microcircuit contacts. as a result, the wire probe is heated under the given heat release conditions. the feedback system makes it possible to control the heat release parameters with high accuracy throughout the entire pulse. the analog signal-response from the platinum wire probe is converted to the digital one and transmitted back to the computer. the essence of the method is to maintain the specified conditions of heat release from the probe surface in the course of heating. the diameter of the probe is 22 µm and the length is approximately 1 cm. the primary values acquired in the experiment are as follows: the voltage drop across the probe u(t) and the current i(t) passing through the probe circuit (figure 3a). the software allows real-time monitoring and recording not only of the mentioned primary data, but also of the power dissipated by the probe p(t)=u(t)∙i(t) and its resistance r(t)=u(t)/i(t). the evolution of the average temperature of the probe t(t) is calculated based on the thermometric calibration of platinum (figure 3b). the heating power p(t) is maintained with an accuracy of 99.95%. the total measurement errors u(t) and i(t) do not exceed 0.2%. the total measurement error of the calculated probe resistance r(t) is 0.4%. the total calculation error t(t) is 1% [13]. 4. experimental results let us consider the main results obtained in the course of heating of the water/ppg-425 mixture. the mass content of ppg-425 in mixture and the excess pressure value served as parameters of the experiments. figure 1 phase diagram of water/ppg-425 mixture. the red squares indicate the measured position of the binodal by the cloud point method, the green circles indicate the calculated diffusion spinodal according to the regular solution approximation [11], and the blue triangles indicate the calculation result according to the flory-huggins approximation at α = 1.61 and β = –33.76. the initial temperature in the measuring cell was kept constant, at the level t0 = 25 oc. the first results were obtained for the mixture with a ppg content of 10 wt.% (figure 4a). the heating of the wire probe is accompanied by a perturbation of the temperature curves. this area is highlighted in figure 4a. a time differentiation operation was performed for a more detailed analysis of the temperature curves (figure 4b). in section i, the rate of temperature change slows down significantly, which is probably caused by the release of the latent heat of nucleation during the separation of the metastable mixture. figure 2 simplified scheme of the experimental setup. explanations are given in the text. figure 3 primary experimental data: voltage drop across the probe (red line) and current in the probe circuit (blue line) at a constant heating power and a pressure value of 60 mpa (a). the evolution of the probe temperature, immersed in a deionized water at a pressure value of 60 mpa, calculated from primary data (figure 3a) (b). chimica techno acta 2022, vol. 9(4), no. 20229408 article 4 of 6 then, the mixture decomposes according to the mechanism presented in the introduction. the rate of temperature change increases due to the heating of individual clusters adjacent to the heater with compositions close to equilibrium values. further heating is accompanied either by boiling up of one of the mixture components in the pressure range of 16–20 mpa, or by a supercritical transition in the pressure range of 22–30 mpa. a more detailed picture of heat transfer in the course of non-stationary heating in a wide pressure range is presented in [14]. as it can be seen, the supercritical transition occurs at an excess pressure of 22 mpa and a probe temperature of 370–380 oc. the phase transition parameters (spontaneous boiling-up temperature and supercritical transition parameters) correspond to the heat transfer to water, which is due to the content of the initial substance in the mixture (about 90 wt.%). similar results were obtained for the mixtures with a ppg content of 40 and 50 wt.% (figure 5). such a heat transfer pattern corresponds to superheating of an initially stable binary mixture relative to the liquid-liquid equilibrium line (figure 1). figure 4 heating curves for the mixture with a ppg content of 10 wt.% under constant power mode. the circle marks the area in which the course of the temperature curves changes (а). derivatives of the probe temperature with respect to time for the mixture with a ppg content of 10% wt.% under constant power mode (b). from the heat transfer point of view, more interesting results were obtained for the mixtures with a ppg content of 20 and 30 wt.%. an analysis of the pd lead us to assume that in this case the mixture is transferred to the region of unstable or labile states. let us consider the results obtained in the course of pulsed heating (figure 6). in this case, the characteristic heating curves tend to level off. moreover, the curves shift upwards with increasing pressure, i.e., lower values of the heat transfer intensity begin to correspond to higher pressure values. taking into account the presence of a limited mixing region on the pd, this phenomenon may be due to the action of spinodal decomposition (sd). the sd phenomenon is the most probable relaxation mechanism in this region of pd and, at the same time, the most powerful one. sd of an unstable mixture is accompanied by the formation of phase boundaries of individual domains, which begin to move towards each other under the influence of nonequilibrium thermocapillary forces [15]. similar results were also obtained for pressures up to 1 mpa. the study of the sd phenomenon for the water/ppg425 mixture at relatively low pressure values is complicated by premature spontaneous boiling-up of water. figure 5 heating curves for the mixture with a ppg content of 40 wt.% under constant power mode (а). heating curves for the mixture with a ppg content of 50 wt.% under constant power mode (b). chimica techno acta 2022, vol. 9(4), no. 20229408 article 5 of 6 figure 6 heating curves for the mixture with a ppg content of 20 wt.% under constant power mode (а). heating curves for the mixture with a ppg content of 30 wt.% under constant power mode (b). thus, based on the temperature history curves analysis, it is hypothetically possible to predict the position of the diffusion spinodal of the mixture on the scale of the mixture component ratio. the essence of the phenomenon is due to the threshold change in the heat transfer pattern to the mixture under study with a change in the content of components in it. despite the fact that the position of the diffusion spinodal was calculated at atmospheric pressure, the authors of this paper believe that such a comparison with experimental data is reasonable. indeed, the effect of external pressure on the key elements of pd for aqueous solutions of polypropylene glycols is insignificant [16]. 5. conclusions the physico-chemical properties of the water/ppg-425 mixture were analyzed. based on these data, the position of the diffusion spinodal was calculated by means of the regular solution and flory-huggins approximations. the heat transfer characteristics of the mixture were studied in a wide range of component contents and pressures via the method of pulsed heating of a wire probe. an analysis of the temperature curves suggests that the proposed method can be potentially used to estimate the position of the spinodal of two-component mixtures with lcst on the scale of the mixture component ratio. this representation is based on the threshold change in the heat transfer pattern when crossing the phase coexistence curve and the diffusion spinodal. the elaborate choice of the heating power variation as a function of time and pulse duration creates a practical basis to select the conditions under which the phase separation of the mixture will manifest itself as a temperature-confined signal at a sufficiently small depth of entry into the region of unstable states. the mastering of such a selection technique and its development will serve as the basis to improve the technique for predicting the position of a limited mixing region of components in temperature-concentration coordinates. supplementary materials no supplementary materials are available. funding this work was supported by the russian science foundation (grant no. 19-19-00115-p). acknowledgments the authors are grateful p.v. skripov and s.b. rutin for help in preparing the article. author contributions conceptualization: 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https://doi.org/10.1016/j.ijheatmasstransfer.2021.122290 https://doi.org/10.1016/0021-9797(74)90061-7 variability of pathogenicity factors representatives of the human microbiome under the influence of γ-fe2o3 iron oxide nanoparticles published by ural federal university eissn 2411-1414; chimicatechnoacta.ru article 2022, vol. 9(4), no. 20229401 doi: 10.15826/chimtech.2022.9.4.01 1 of 6 variability of pathogenicity factors representative of the human microbiome under the influence of γ-fe2o3 nanoparticles lyubov a. kokorina a, yana v. chernyavskaya b, tatiana p. denisova b* , elena v. simonova а, alexander p. safronov c, galina v. kurlyandskaya сd a: irkutsk state medical university moh, irkutsk 664003, russia b: irkutsk state university, irkutsk 664011, russia c: institute of natural sciences and mathematics, ural federal university, ekaterinburg 620002, russia d: university of the basque country upv/ehu, department of the electricity and electronics, leioa 48940, spain * corresponding author: denis_tp@inbox.ru this paper belongs to the regular issue. © 2022, the authors. this article is published in open access under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). abstract biomedical applications of nanoparticles require deep understanding of their interaction with normal human microflora. previously, the toxic and mutagenic properties of iron oxide nanoparticles as well as their effect on the growth and morphology of the microflora were extensively investigated. however, the studies related to the variability of microbial pathogenicity factors induced by iron oxide nanoparticles are very limited. meanwhile, this characteristic of microbes is genetically determined and is important for their survival and distribution in the human body. therefore, pathogenicity factors are significant indicators of the experimental studies. in this work, the effect of the presence of fe2o3 nanoparticles obtained by laser target evaporation (lte) on selected enzymes that demonstrate invasion and aggression factors was evaluated for three reference strains of candida albicans, staphylococcus aureus, and escherichia coli. it was found that the presence of lte fe2o3 nanoparticles supplied in the form of water-based suspensions does not induce changes of the above-mentioned parameters. keywords laser target evaporation iron oxide nanoparticles magnetic nanoparticles biomedical applications eukaryotic and prokaryotic microorganisms normal human microflora pathogenicity factors received: 17.05.22 revised: 16.06.22 accepted: 21.06.22 available online: 04.07.22 1. introduction magnetic nanomaterials are moving from the stage of scientific research to the stage of practical implementation in diagnostics, therapy and biotechnologies [1, 2]. many studies have been associated with proposals to use nanomaterials for targeted drug delivery, creating bone implants, wearable devices, etc. magnetic nanoparticles (mnps) are especially attractive as their movements inside the body can be controlled by application of gradient of the external magnetic field [3, 4], which can be also used to induce hyperthermia and thermal ablation [5]. magnetic nanoparticles can be produced by different chemical and physical techniques. interestingly, about 92% of mnps of iron oxides are prepared by chemical routes: co-precipitation, hydrothermal and solvothermal synthesis, sol-gel and polyol microemulsion methods, microwave-assisted synthesis electrochemical deposition and others [2, 6, 7]. about 6% of mnps of mnps are fabricated by physical techniques [8, 9], and about 2% by biological synthesis methods [2, 10]. the largest batches of the mnps can be obtained using electrophysical techniques such as electric explosion of the wire, laser target evaporation or spark discharge [2, 9]. in any case, biomedical applications require synthesis of large batches, since established protocols demand testing with an extended set experimental technique [11]. in addition, biological and biomedical applications are only possible with aqueous suspensions (not with the air-dry mnps). their fabrication also to some extent reduces the amount of available material. on the one hand, the composition of nanoparticles includes natural components: iron, silver, copper, aluminum, oxygen, etc. on the other hand, their size, shape, exact composition, and physicochemical properties make it possible to classify nanoparticles as xenobiotics, i.e. chemical substances found within an organism that is not http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2022.9.4.01 mailto:denis_tp@inbox.ru http://creativecommons.org/licenses/by/4.0/ https://orcid.org/0000-0002-1044-2916 https://crossmark.crossref.org/dialog/?doi=https://doi.org/10.15826/chimtech.2022.9.4.01&domain=pdf&date_stamp=2022-7-4 chimica techno acta 2022, vol. 9(4), no. 20229401 article 2 of 6 naturally produced or expected to be present in it. the question about the degree of safety of each particular nanomaterial for organisms and ecosystems in general is a very important one to be answered. an analysis of the experimental results presented in the scientific sources allows to distinguish three groups of effects of nanoparticles on biological systems: modifications, toxicity, and mutagenicity. for example, a change in the color of eukaryotic organisms was established in an experiment with iron-containing nanoparticles [12]. iron nanoparticles caused reversible changes in the biochemical activity of pseudomonas aeruginosa: a decrease in carbohydrate fermentation was observed [13]. the toxic effects of nanoparticles were found for organisms of different systematic groups [14]. copper nanoparticles caused the death of bacteria. nanoparticles based on aluminum oxide reduced the ability of escherichia coli (e.сoli) to form a biofilm [15]. iron nanoparticles had a toxic effect on pseudomonas aeruginosa [13]. the low toxicity of nanoparticles of silicon dioxide was shown for some strains of e.coli [16]. toxic effects were also found in different types of eukaryotic organisms [14, 17, 18]. deoxyribonucleic acid (dna) damage, including mitochondrial dna, and the formation of micronuclei in blood cells can be induced by silicon, nickel, and gold containing nanoparticles. metal nanoparticles cause excessive production of reactive oxygen species (peroxides, superoxide, singlet oxygen, etc.), which induce dna damage [14]. the mutagenicity of aluminum oxide nanoparticles for human cells was also proven [19]. it is important to take into account that, regardless the type of nanoparticles and biotests used in the experiment, the first interaction of the agent occurs with the normal microflora of the body, regardless of the method of administration. previously, the toxic and mutagenic properties of iron oxide nanoparticles as well as their effect on the growth and morphology of the microflora were extensively investigated. however, up to now, the studies of the microbial variability of pathogenicity factors related to the presence of the iron oxide nanoparticles were quite limited. the variability of pathogenicity factors is both genetically determined and important for the microbial survival and distribution in the body. therefore, pathogenicity factors are significant indicators of the experimental studies. in this work, the effect of the presence of iron oxide nanoparticles obtained by laser target evaporation supplied as water-based suspension was studied for selected enzymes that demonstrate invasion and aggression factors. three reference strains of candida albicans, staphylococcus aureus, and escherichia coli were used. 2. materials and methods electrophysical techniques allow fabrication of large batches of mnps (of the order of 100 g) required for biomedical research and applications [9]. one of these techniques is the laser target evaporation (lte) in which the solid target is evaporated by the high-power pulse of a laser beam. the beam energy transform into the kinetic energy of the evaporated products. in this study, the lte target was fabricated using the commercial fe3o4 iron oxide powder (alfa aesar). more details of the experimental procedure for the lte synthesis can be found elsewhere [9]. the x-ray diffraction investigation was performed using s discover d8 bruker diffractometer and topas software allowing rietveld full-profile refinement for the quantitative analysis. transmission electron microscopy (tem) was performed for the evaluation of the size and shape of mnps (jeoljem2100). for the measurements of the specific surface area (ssp) of the mnps ensemble, the low temperature sorption of nitrogen technique was used [1]. magnetic properties were studied with a mpmsxl-7 squid magnetometer. biomedical applications require supplying magnetic mnps as water-based suspensions. electrostatically stabilized water-based suspension of mnps was prepared with sodium citrate in 5 mm concentration via disaggregation by ultrasound treatment on a cole-parmer cpx-750 homogenizer at the power output 300 w and centrifuging using a hermle z383 apparatus in order to remove the largest aggregates. the final concentration of mnps in the stock suspension was 47.8 g/l, and the suspension was slightly acidic (ph=4.5) due to the specific adsorption of hydroxide ions on the surface. the stock suspension was then diluted with distilled water to provide the desired concentration of mnps therein. hydrodynamic diameters of the mnps and their aggregates were defined by dynamic light scattering technique (brookhaven zeta plus). the same instrument allowed measuring the electrokinetic zeta-potential of the suspensions by the electrophoretic light scattering. the fungus strain candida albicans атсс 10231 [20], staphylococcus aureus atcc 25923 [21] and escherichia coli atcc 25922 [22] strains, which belong to the normal human microflora, were used as bioassays. in the control group, the bacteria grew in a liquid nutrient medium mpa (meat-peptone agar), the ph of which was 7.4±0.4. the fungi were cultivated in a liquid sabouraud medium (ph 5.7±0.2). in the experimental group, a suspension of mnps was introduced into the liquid medium, the concentration of which reached 0.1, 1.0 and 10.0 mpd (maximum permissive dose) for fe+3. the microbial suspension was exposed for 144 hours for all groups. the experiments included the following stages. starting from the zero point, every 24 hours, microorganisms were inoculated from the culture liquid onto a solid nutrient medium (mpa, and nickerson agar). several clones were selected by random sampling among the grown colonies to determine pathogenicity factors. the clones were placed onto differential diagnostic media and cultivated at a temperature of 37 o c for 24 hours. after that, the presence or absence of pathogenicity factors was recorded chimica techno acta 2022, vol. 9(4), no. 20229401 article 3 of 6 similar to the way reported in the literature [23–25]. the analyzed indicators (pathogenicity factors) were provided by the presence of certain enzymes in microbes and their activity. respiratory, lecithinase, plasmacoagulase, hemolytic, and dnaase activities were taken into account. respiratory activity is assessed by changing the color of the culture in the medium with the dye congo red. lecithinase activity is assessed by the formation of a cloudy "corolla" around the colony on a nutrient yolk medium. the plasmacoagulating activity of s. aureus is determined by the presence of a gelatinous formation. hemolytic activity is manifested through the formation of a zone of enlightenment on a nutrient medium. determination of dnaase activity is associated with the formation of a cleavage zone, i.e. zones of enlightenment of the nutrient medium around the colony. it should be noted that qualitative indicators were collected; therefore, their presence “+” or absence “–” was recorded. depending on the severity of the symptom, the following states were noted: "–" – the indicator is negative, "+" – low activity, "++" – moderate activity, "+++" – pronounced activity, "++++" – maximum activity. 3. results x-ray diffraction analysis showed that obtained iron oxide powder have the inverse spinel structure (fd-3m space group). according to the tem studies, which included the graphical analysis (figure 1), the shapes of the mnps were very close to being spherical. the nanoparticles in the ensemble were size-distributed in accordance with the lognormal law with 17±3 nm average mean diameter. according to psd, 99% of mnps fell within the diameter range of 2–40 nm. the specific surface area was about 69 m2/g. magnetic measurements confirmed that nanoparticles had low coactivity of about 30 oe at room temperature and the saturation magnetization of about 37±2 emu/g (both numbers are consistent with existing sources for the fe2o3 mnps of this size) [1, 9]. the average hydrodynamic diameter, 51.4±0.4 nm, was determined for the species in mnps suspension. it was higher than that for the air-dry mnps. it meant that the suspension was in fact a mixture of individual mnps and their small aggregates. the value of zeta-potential of the suspension was –44±2 mv, which was well above the coagulation threshold (20 mv regardless of the sign). it meant that the aggregates were stable and no further aggregation occurred in the suspension. these parameters of the suspension did not change in storage for over a year. figure 2 shows the general view of the samples of the control groups of the fungus strain candida albicans атсс 10231, staphylococcus aureus atcc 25923 and escherichia coli atcc 25922 strains, belonging to the normal human microflora. in order to determine the effect of mnps on the variability of pathogenicity factors, 144 clones were isolated from the eukaryotic strain c.albicans atcc 10231, 144 clones from the gram-positive prokaryotic strain s.aureus atcc 25923 and 83 clones from the gramnegative prokaryotic strain e.coli atcc 25922. it was found that the reference strains under physiological conditions (control) retain a set of specific aggression factors (table 1), which they implement in a low virulent form. this corresponds to the levels of activity that are capable of being manifested by the microorganisms of these species, which are part of the structure of the normal human microbiome, without leading to the development of pathological processes in internal organs and tissues. this result is evidenced by the absence of dnase and hemolytic activities. figure 1 transmission electron microscopy: general view of γfe2o3 lte nanoparticles (a), tem microdiffraction confirming spinel structure (b). chimica techno acta 2022, vol. 9(4), no. 20229401 article 4 of 6 figure 2 candida albicans on nickerson's nutrient medium in petri dish (a), staphylococcus aureus on nutrient medium yolk-salt agar (b), escherichia coli on endo nutrient medium (c). table 1 evaluation of pathogenicity factors in reference strains in the control group. enzymatic activity тest objects c. albicans st. aureus e. coli. respiratory ++ ++++ ++++ lecithinase – + – plasmocoagulase – +++ – hemolytic – – – dnаase – – – the presence of lecithinase and plasma-coagulase activity, due to which they are able to realize their immunogenic properties in the human body, indicates the normally functioning work of plastic metabolism. respiratory activity in microorganisms is an indicator of a normally functioning energy metabolism system. the results of the experiments on the variability of factors of invasion and aggression of microorganisms in the presence of nanoparticles are shown in table 2. it was found that the activity of the reference strains of microorganisms after exposure to the nanoparticles does not change in all variants of the experiment. dnase and hemolytic activities were not detected. respiratory activity also remained unchanged in all variants of the experiment (figure 3a). lecithinase and plasmacoagulase activities were found only in staphylococcus, being at the same level as in the control group. c. albicans shows only respiratory activity (figure 3b). thus, the factors associated with the level of virulence of microorganisms remain stable in the experiment and do not differ from the control level. perhaps this is due to the fact that nanoparticles cannot affect the metabolic processes of a microbial cell due to their adhesion to the cell wall. 4. conclusions iron oxide fe2o3 nanoparticles were obtained by the lte technique. they had the inverse spinel structure (fd-3m space group), close to spherical shapes and the lognormal size-distribution, and they had 17±3 nm average mean diameter and magnetic parameters consistent with their size and composition. biological experiments resulted in the following findings: 1. dnase and hemolytic activities were not detected in all test samples, neither in the control nor in the experimental groups. 2. lecithinase and plasmacoagulase activities were recorded only in s. aureus in the control and in all experimental groups at the same level. 3. c. albicans showed moderate respiratory activity, and s. aureus and e. coli showed pronounced respiratory activity. the control and all experimental groups did not differ from each other. table 2 evaluation of pathogenicity factors in reference strains obtained in the experiments. тest objects mtd calculated on the basis of fe+3 content in mnps enzymatic activity dnаase respiratory hemolytic lecithinase plasmocoagulase c. albicans 0.1 – ++ – – – 1.0 – ++ – – – 10.0 – ++ – – – st. aureus 0.1 – ++++ – + +++ 1.0 – ++++ – + +++ 10.0 – ++++ – + +++ e. coli. 0.1 – ++++ – – – 1.0 – ++++ – – – 10.0 – ++++ – – – chimica techno acta 2022, vol. 9(4), no. 20229401 article 5 of 6 figure 3 pronounced respiratory activity of staphylococcus (a), a negative test for plasmocoagulase in c. albicans (no clot is formed) (b). 4. the induced variability of indicators of pathogenicity factors in the experiment was not established. given that pathogenicity factors are the genetically determined traits, it can be assumed that the studied nanoparticles either do not penetrate into the bacterial cell or have no effect on the genetic material. supplementary materials no supplementary materials are available. funding this research in part was supported by the university of the basque country upv/ehu research groups funding (gmmm). acknowledgments authors would like to thank the dr. i.v. beketov (institute of electrophysics ud ras) and dr. i. orue for special support. selected measurements were made at sgiker services of upv/ehu. author contributions conceptualization: e.v.s. data curation: l.a.k., t.p.d., ya.v.c. formal analysis: l.a.k., t.p.d., ya.v.c. funding acquisition: e.v.s., t.p.d., g.v.k. investigation: l.a.k., ya.v.c., a.p.s., g.v.k. methodology: e.v.s., l.a.k., a.p.s. project administration: e.v.s., g.v.k. resources: e.v.s., l.a.k., t.p.d., g.v.k. software: l.a.k., e.v.s., a.p.s. supervision: e.v.s., t.p.d., g.v.k. validation: e.v.s., g.v.k., l.a.k., t.p.d., a.p.s. visualization: l.a.k., t.p.d., ya.v.c., a.p.s. writing – original draft: l.a.k., t.p.d., ya.v.c., g.v.k., a.p.s. writing – review & editing: t.p.d., e.v.s., a.p.s., g.v.k. conflict of interest the authors declare no conflict of interest. additional information author ids: lyubov a. kokorina, scopus id 57194266259; tatyana p. denisova, scopus id 56443729400; elena v. simonova, scopus id 57194285465; alexander p. safronov., scopus id 35588399100; galina v. kurlyandskaya, scopus id 7004350808. websites of irkutsk state medical university moh, https://www.ismu.baikal.ru/ismu/news.php; irkutsk state university, https://isu.ru/ru/index.html; ural federal university, https://urfu.ru/en; university of the basque country, https://www.ehu.eus/es/. references 1. kurlyandskaya gv, blyakhman fa, makarova eb, buznikov na, safronov ap, 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simulation k.a. nekrasov ab* , a.e. galashev a , d.d. seitov b , s.k. gupta c a: institute of high-temperature electrochemistry of the ural branch of the russian academy of sciences, 22 s.kovalevskoy street/ 20 akademicheskaya street, yekaterinburg 620990, russian federation b: ural federal university, 19 mira street, yekaterinburg 620002, russia federation c: st. xavier’s college, ahmedabad 380009, india * corresponding author: kirillnkr@mail.ru this article belongs to the pcee-2020 special issue. © 2021, the authors. this article is published in open access form under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). abstract a molecular dynamic simulation of diffusion of intrinsic oxygen anions in the bulk of hypostoichiometric uo2x nanocrystals with a free surface was carried out. the main diffusion mechanism turned out to be the migration of oxygen by the anionic vacancies. it is shown that in the range of values of the non-stoichiometry parameter 0.05 x  0.275 the oxygen diffusion coefficient d is weakly dependent on temperature, despite the uniform distribution of the vacancies over the model crystallite. the reliable d values calculated for the temperature t = 923 k are in the range from 310 9 to 710 8 cm 2 /s, in quantitative agreement with the experimental data. the corresponding diffusion activation energy is in the range from 0.57 ev to 0.65 ev, depending on the interaction potentials used for the calculations. keywords uranium dioxide hypostoichiometry oxygen diffusion nanocrystals received: 04.02.2021 revised: 30.03.2021 accepted: 30.03.2021 available online: 31.03.2021 1. introduction recently, considerable efforts have been directed towards experimental research for the development of a nonaqueous technology for reprocessing irradiated nuclear fuel [1–4]. the key technology for highly efficient processing of such fuels is pyrolysis combined with molten salt electrolysis. this technology can be applied to highly burned fuel without long exposure time. the advantages of the electrochemical method are due to the high radiation resistance of inorganic molten salt, which makes it possible to dissolve highly radioactive nuclear fuel. the possibility of recycling the molten salt, and compactness of the equipment are also important. this study is related to the problem of reduction of crystalline uo2 to metallic uranium, which consists in the removal of oxygen from the crystal lattice. in the process of electrochemical reduction of uranium from uo2, oxygen is gradually released into the environment (for example, into the liclli2o molten salt surrounding the crystal surface). the crystal becomes hypostoichiometric, and the relative content of uranium increases in the course of uranium reduction up to the complete oxygen removal. the described technique has been well studied experimentally [1–6]; however, further optimization of the technology requires an understanding of the mechanisms of oxygen release at the atomic level. these mechanisms remain insufficiently studied to date. the rate of oxygen release is limited by the coefficient of its diffusion in the hypostoichiometric crystal uo2x. the experimental data on the diffusion of oxygen in uo2x relate mainly to values of x within 0.1 [7–9]. the values of the oxygen diffusion coefficient obtained in [7] and [8] for the temperature used in the electrochemical reduction of uranium (923 k) differ by two orders of magnitude (being in the range from 210 6 to 110 8 cm 2 /s at x = 0.03). higher values of x in uo2x are achievable only with increasing temperature. the oxygen diffusion coefficient for x  0.2 has been measured at relatively high temperatures of 20002100 с [10]. to clarify the features of oxygen diffusion at significant deviations of uo2x from stoichiometry, computational simulation of this process is of interest. to date, such studies have been performed mainly for hyperstoichiometric uo2 that contains excess oxygen [11–14]. oxygendepleted hypostoichiometric uranium dioxide has been studied much less [15–17]. let us note that correct accounting for the ion charge transfer in a non-stoichiometric crystal requires the use of ab initio calculations. nevertheless, the simulation of the http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2021.8.1.07 http://creativecommons.org/licenses/by/4.0/ https://orcid.org/0000-0002-1863-2597 https://orcid.org/0000-0002-2705-1946 https://orcid.org/0000-0003-2549-3027 https://orcid.org/0000-0002-3060-2104 chimica techno acta 2021, vol. 8(1), № 20218107 article 2 of 6 crystals within the framework of classical molecular dynamics also remains relevant. an important advantage of the latter approach is the ability to study large systems over a long time evolution. molecular dynamic modeling of oxygen diffusion in uo2 was previously carried out at temperatures significantly higher than 923 k [18-20], and in most of these studies, the periodic boundary conditions describing a quasi-infinite crystal were used. however, upon reduction in an electrochemical cell, the surface of uranium dioxide can become severely indented at the atomic level, which requires the presence of a free surface in the simulation. in this work, the presence of the surface was taken into account by modeling uo2-x nanocrystals isolated in vacuum. the results of classical modeling are fundamentally dependent on the choice of the particle interaction potentials. to simulate a uo2 crystal, a number of sets of empirical potentials have been proposed, optimized for different problems (see, for example, reviews [20–22]). the oxygen diffusion coefficients calculated using different potentials could differ significantly. the applicability of the existing potentials under hypostoichiometric conditions has not been sufficiently studied. in the present work, three such sets of potentials [17, 20, 23] are compared. 2. the model the molecular dynamics model in this work was a uo2x crystallite in the shape of an octahedron with a free surface. the specified stoichiometry was ensured by removing the required amount of oxygen anions, selected at random, from the crystal. in this case, the electroneutrality of the crystal was maintained by replacing part of the u q+ cations with u (q1)+ ions. here, q is the effective charge of the uranium cation within a specific set of interaction potentials. at x = 0, the crystallite consisted of 2720 uranium ions and 5440 oxygen ions. the x values for which the oxygen diffusion coefficients were calculated in this work varied from 0.003 to 0.275. this range is within the experimental existence of non-stoichiometric uranium dioxide (o/u from 1.65 to 2.25 [24]). values of x above 0.1 in uo2x are achieved only at temperatures above 1000 k [10-11, 25]. nevertheless, in the process of the electrochemical reduction of uranium at lower temperatures, the occurrence of local oxygendepleted regions at the boundary of the crystal with the electrolyte is not excluded. the temperature 923 k in this work has been chosen to match the common conditions of the electrolytic uranium reduction. to ensure the symmetry of the charge distribution over the surface of the nanocrystal, neutral uo2 molecules were used as "building" blocks. the two oxygen ions were placed on the same straight line with the uranium cation, using the displacements (0.25, 0.25, 0.25)a and (+0.25, +0.25, =0.25)a relative to the cation center, where a is the lattice constant. this made it possible to minimize the effect of surface charges on the bulk properties of the model crystals, which had to be taken into account considering the long-range character of the coulomb force. the interaction of the intrinsic ions was simulated by three sets of potentials [17, 20, 23], in order to compare the results of using each of the sets. set i (mox-07, s. potashnikov et al., 2011 [20]) is characterized by a relatively accurate reproduction of both the mechanical and thermophysical characteristics of the stoichiometric uo2 crystal and the energies of its own disordering [20–22]. set ii (yakub-09, e. yakub et al., 2009 [17]) provides the most accurate melting temperature of uo2. set iii (busker02, g. busker, 2002 [23]), in contrast to potentials i and ii, uses the whole charges of oxygen anions (2e) and uranium cations (+4e), which would allow, in a further study of the electrochemical cells, to simulate the transition of oxygen ions from the uo2x crystal to the liclli2o molten salt without changing their charge. note that along with the potentials listed above, there are a number of other sets of potentials of similar quality, such as basak-03 [26], morelon-03 [11], goel-08 [19]. most of these sets are characterized by non-integral effective charges of the intrinsic ions. the lesser-known busker potentials are studied in this work as an example of potentials with integral charges, which have acceptable quality at temperatures up to 1000 k, according to the review [20]. all the potentials were represented in general form 𝑈𝑖𝑗(𝑅) = 𝐾e 𝑞 𝑖 𝑞 𝑗 𝑅 + 𝐴𝑖𝑗𝑒 −𝐵𝑖𝑗𝑅 − 𝐶𝑖𝑗𝑅 −6 + 𝜀𝑖𝑗 ∙ ∙ (𝑒−2𝛽𝑖𝑗(𝑅−𝑅𝑚,𝑖𝑗) − 2𝑒−𝛽𝑖𝑗(𝑅−𝑅𝑚,𝑖𝑗)) (1) that takes into account the repulsion of overlapping electron shells, the van der waals attraction, and the possibility of chemical bond formation. the first term on the right-hand side corresponds to the long-range coulomb interaction, the second term is the repulsive potential between the ion cores, the third term is the dispersive (van der walls) attraction and the last term is the morse potential accounting the covalent bonding energy attributed to u–o interaction. the quantities qi and qj are the effective ion charges, ke is the coulomb's law constant, and the rest are fitting parameters that cannot be measured or computed separately. the parameter values are listed in table 1. the non-coulomb part of the potential uu was zero in the potential sets i and iii. for the model nanocrystals in this work, the longrange coulomb forces were calculated explicitly, due to the finite number of particles in the model. in order to avoid the non-physical effects of the long-range coulomb interaction, the charge distribution over the nanocrystal surface was made as symmetric as possible. the newtonian equations of motion were integrated by the leapfrog method with a time step t = 310 15 s. chimica techno acta 2021, vol. 8(1), № 20218107 article 3 of 6 table 1 the potential parameter values parameter potentials i potentials ii potentials iii oo ou oo ou u-u oo ou a, ev 50211.7 873.107 883.12 432.18 187.03 9547.96 1761.78 b, 10 10 m 1 5.52 2.78386 2.9223 2.9223 2.9223 4.562 2.806 c, ev10 60 m 74.7961  3.996   32  , ev    0.5055    , 10 10 m 1    1.864    rm, 10 10 m    2.378    q, e 1.37246 1.1104 2 q+, e +2.74492 +2.2208 +4 the berendsen thermostat was used, as well as an original procedure for correcting the crystallite rotation. simulation times reached 200 ns. to determine the oxygen diffusion coefficient in the bulk of the model crystals, we calculated the mean square of the displacement of anions that were separated from the surface by a distance no less than 1.75a, where a = 0.551 nm was the lattice constant of the uo2.00 crystal at t = 923 k. there were 895 such anions at x = 0. the indicated lattice constant is the experimental value [27]. it coincides with the calculated values for all the three sets of potentials used in this work with an accuracy of 0.001 nm. the simulations were carried out using an in-house developed software package, the same as in earlier works [2829]. the required high computing performance was obtained by parallelizing the calculations on cuda architecture graphics processing units. 3. results and discussion fig. 1 shows the characteristic dependence of the bulk anion mean square displacement <a 2 (t)> on the evolution time of the system. the curve is characterized by three sections. the first two sections correspond to the process of establishing an equilibrium concentration of the anion vacancies in the bulk of the crystal. this process included a rapid release of excess vacancies at the first stage, as well as a slower adjustment of the concentration during the second phase. the third section describes a linear increase in <a 2 (t)> with time under conditions of constant average concentration of the vacancies, in accordance with the direct vacancy mechanism of oxygen ion migration. the time dependence of the concentration of the vacancies relative to the sites of the anion sublattice in the bulk of the crystal [v], corresponding to fig. 1, is shown in fig. 2. in this work, the oxygen diffusion coefficient was determined from the slope of the latter section using a generalization of the well-known einstein relation in the form (2): 𝐷 = 1 6 ∙ 𝑑〈𝑎2〉 𝑑𝑡 (2) let us note that, at small deviations from stoichiometry x < 0.002, the equilibrium concentration of the vacancies in the bulk of the crystal turned out to be zero, so that in the equilibrium state of the crystallite diffusion of anions was not observed. an example of the corresponding graph <a 2 (t)> is shown in fig. 3. the dependence <a 2 (t)> fig 1 a characteristic time dependence of the mean square displacement of the oxygen anions in the bulk of the model nanocrystal. here, t = 923 k, x = 0.1625, and the set of potentials iii was used fig 2 a time dependence of the relative oxygen vacancy concentration in the bulk of the model nanocrystal. here, t = 923 k, x = 0.1625, and the set of potentials iii was used. <a2> = (0.0043t + 2.62), 1020 m2 0 0.5 1 1.5 2 2.5 3 3.5 0 30 60 90 120 150 < a 2 > , 1 0  2 0 m 2 time t, ns 0.08 0.082 0.084 0.086 0.088 0.09 0.092 0.094 0.096 0.098 0.1 0 30 60 90 120 150 v a c a n c ie s p e r a n io n s u b la tt ic e s it e [ v ] time t, ns chimica techno acta 2021, vol. 8(1), № 20218107 article 4 of 6 fig 3 the mean square displacement of the bulk oxygen anions of a model nanocrystal at small deviations of the composition uo2x from stoichiometry. here, t = 923 k, x = 0.0015, and the set of potentials ii was used. is shown within 150 ns in order to show the region of its increase in more detail. until the end of the simulation (200 ns), the mean square of the displacement remained constant. fig. 4 illustrates the relationship between the equilibrium bulk concentration of the anionic vacancies (referred to the concentration of sites of the anionic sublattice) and the non-stoichiometric parameter x, which specified the composition of the model crystallites uo2x as a whole, including the surface. these plots show that the distribution of the vacancies over the crystal was practically uniform, regardless of their concentration, for all the three sets of interaction potentials. ideally, the concentration of vacancies and the parameter x would be related as [v] = 0.5x. fig. 5 shows the results of calculating the oxygen diffusion coefficient at a temperature of t = 923 k depending on the stoichiometry of the uo2x. it can be seen that the potentials i, ii, and iii give significantly different values of the diffusion coefficient, the maximum divergence of which reaches almost 500 times. fig 4 the relative concentration of the oxygen vacancies in the bulk depending on the stoichiometry of the model nanocrystals uo2x the highest diffusion coefficients were obtained using potentials i, the lowest correspond to potentials iii. potentials ii made it possible to obtain a better agreement between the calculation and experiment [8]. the calculation with potentials i also does not contradict the experimental data, taking into account the high values of the diffusion coefficient obtained in [7]. potentials iii clearly underestimate the oxygen diffusion coefficient. however, they reproduce the tendency observed in [7] towards a decrease in the diffusion coefficient with an increase in the deviation of the crystal composition from stoichiometry. regardless of the set of interaction potentials, the simulation predicts the absence of a strong dependence of the oxygen diffusion coefficient d on stoichiometry at x above 0.05. experimental data [8] also indicate a weakening of the dependence of d on x with an increase in hypostoichiometry. similarly, in the experiment [9], at values of x near 0.2 and temperatures of 20002100 с, the oxygen diffusion coefficient was practically independent on x. to explain these results, it can be assumed that simultaneous diffusion jumps of many anions in a confined space are hindered. fig. 5 also shows the results of calculating the oxygen diffusion coefficient with periodic boundary conditions (6144 ions in the ideal supercell) for the potentials ii. these diffusion coefficients are overestimated in comparison with the rest of the calculations of this work, although they are within the spread of the experimental data. more research is needed to clarify the reason for the discrepancy. fig. 6 demonstrates the dependence of the oxygen diffusion coefficient in model nanocrystals uo20.0375 on the reciprocal temperature. when using potentials i and ii, the calculation corresponds to the temperature range from 923 k to 1750 k, and in the case of potentials iii, the upper temperature was t = 2500 k. the following values of the diffusion activation energy were obtained: ed[i] = 0.57 ev, ed[ii] = 0.65 ev, ed[iii] = 0.80 ev (the sets of potentials are indicated in square brackets). fig 5 the oxygen diffusion coefficient at t = 923 k 0 0.5 1 1.5 2 2.5 0 30 60 90 120 150 < a 2 > , 1 0  2 0 m 2 time t, ns [v] = (0.530  0.009)x + (9.57  0.001)104 0 0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16 0 0.05 0.1 0.15 0.2 0.25 0.3 v a c a n c ie s p e r a n io n s u b la tt ic e s it e [ v ] non-stoichiometric parameter x potentials i potentials ii potentials iii 0.0001 0.0010 0.0100 0.1000 1.0000 10.0000 100.0000 0 0.05 0.1 0.15 0.2 0.25 0.3 d 1 0 7 , c m 2 /s non-stoichiometric parameter x in uo2-x mox-07 (i) yakub-09 (ii) busker-02 (iii) experiment [7] experiment [8] pbc, yakub-09 (ii) chimica techno acta 2021, vol. 8(1), № 20218107 article 5 of 6 fig 6 temperature dependences of the oxygen diffusion coefficient in the model nanocrystals the effective activation energies of oxygen diffusion ed obtained in experiments [7] and [8] turned out to be very close to each other, and their values were practically independent of stoichiometry. in particular, at x = 0.03 ed = 0.56 ev in [7], while ed = 0.51 ev in [8]. it can be seen that the calculated energy ed[i] is close to these data, the energy ed[ii] is comparable with them, and only ed[iii] is overestimated in a significant way. the temperature dependences of the calculated diffusion coefficients can be represented in the following form: d[i] = 5.5510 5 exp{0.57 ev / kt) cm 2 /s, (3) d[ii] = 6.110 5 exp{0.65 ev / kt) cm 2 /s, (4) d[iii] = 5.5510 5 exp{0.80 ev / kt) cm 2 /s. (5) 4. conclusions according to the comparison of the calculation results with experimental data, the pair potential approximation has provided a quantitative accuracy of modeling of the oxygen diffusion process in hypostoichiometric uranium dioxide nanocrystals, despite the simplicity of the model. most reliable results were obtained using the sets of interaction potentials i and ii, which are characterized by realistic effective charges of intrinsic uranium and oxygen ions. the diffusion coefficient values calculated using these potentials at a temperature of t = 923 k were in the range from 310 9 to 710 8 cm 2 /s. the calculated dependence of the diffusion coefficient on the stoichiometry of the crystal uo2x at 0.05 x  0.275 is weak, in agreement with the experimental data [7–9]. a similar effect can take place in the process of electrochemical reduction of uranium from uo2 dissolved in a molten salt such as liclli2o. acknowledgments the work was financially supported by the 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molecular dynamics simulation. a molecular dynamics study. nuclear instruments and methods in physics research section b: beam interactions with materials and atoms. 2020;476:26–31. doi:10.1016/j.nimb.2020.04.040 https://doi.org/10.1016/j.jnucmat.2008.03.020 https://doi.org/10.1016/j.jnucmat.2011.08.033 https://doi.org/10.1016/j.jnucmat.2008.01.023 https://doi.org/10.1016/j.jnucmat.2017.07.067 https://doi.org/10.1039/f29878301121 https://doi.org/10.1016/j.jnucmat.2012.09.011 https://doi.org/10.1016/s0925-8388(03)00350-5 http://www.pub.iaea.org/mtcd/publications/pdf/te_1496_web.pdf http://www.pub.iaea.org/mtcd/publications/pdf/te_1496_web.pdf https://doi.org/10.1016/j.nimb.2020.04.034 https://doi.org/10.1016/j.nimb.2020.04.040 drop motion during mass transfer accompanied by interphase chimica techno acta letter published by ural federal university 2022, vol. 9(2), no. 202292s9 eissn 2411-1414; chimicatechnoacta.ru doi: 10.15826/chimtech.2022.9.2.s9 1 of 5 drop motion during mass transfer accompanied by interphase convection anatolii g. titov a* , zalina r. rusinova a, ekaterina a. kalimullina a, anatoliy m. vorobev b a: institute of chemical engineering, ural federal university, ekaterinburg 620009, russia b: engineering department, university of southampton, university road, southampton so17 1bj, united kingdom * corresponding author: a.g.titov@urfu.ru this paper belongs to the mosm2021 special issue. © 2021, the authors. this article is published open access under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). abstract the article deals with the experimental study of the mass transfer of acetic acid from the dispersed phase (butyl acetate) to the continuous phase (water). the experiments were carried out on a laboratory column with single floating drops. the presence of the marangoni effect during the movement of drops and its influence on the trajectories of movement of drops and the kinetics of mass transfer during extraction are shown. the influence of the marangoni effect is most clearly observed when the driving force of the process is 0.1...0.2 mol/l. keywords interphase convection mass transfer marangoni convection liquid droplet continuous phase received: 04.11.21 revised: 16.06.22 accepted: 16.06.22 available online: 22.06.22 key findings ● the work shows the presence of the marangoni effect when a drop of acetic acid solution moves in the extractor. ● small drops with a diameter of 2.5 mm should move straight like hard drops, but the marangoni effect causes the drops to deviate from a straight trajectory. ● the marangoni effect is clearly observed at acetic acid concentrations of 0.5 mol/l and below in a water/butyl acetate extraction system. 1. introduction extraction is used for the selective separation of a wide range of substances (aromatic hydrocarbons, pesticides, antibiotics, etc.) from reaction solutions, culture media, and liquid waste [1]. the calculation of extractors is carried out on the assumption that the mass transfer coefficient is independent of the driving force of the process – the difference between the equilibrium and current concentration of the transferred substance in the media [2, 3]. however, in a number of industrial processes, there is a deviation of the real parameters from the calculated ones [4, 5]. laterly, these facts have beenere studied by a number of researchers [6, 7]. it has turned out that the mass transfer coefficient can change several times at certain values of the driving force [8]. 2. experimental experiments to determine the velocities of the droplets and study the kinetics of mass transfer were carried out in a thermostated column (figure 1) made of borosilicate glass. the column was 1000 mm high and 75 mm in inner diameter. the dispersed phase was fed into the column through a steel capillary (pos. 5) using a syringe pump (pos. 3a). in order for the drops of a certain diameter to be detached from the capillary, the needle was connected to an electromagnetic device (pos. 4). this device generated fast pulses at specified time intervals, due to which the needle dropped sharply downward and droplets of the desired size were separated. before the experiments, the dispersed and continuous phases were mutually saturated in order to exclude additional mass transfer between them. in order to limit the influence of contamination, all parts of the setup in contact with the continuous or dispersed phases underwent a http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2022.9.2.s9 mailto:a.g.titov@urfu.ru http://creativecommons.org/licenses/by/4.0/ https://orcid.org/0000-0003-4511-627x https://orcid.org/0000-0002-6458-9390 https://crossmark.crossref.org/dialog/?doi=https://doi.org/10.15826/chimtech.2022.9.2.s9&domain=pdf&date_stamp=2022-6-22 chimica techno acta 2022, vol. 9(2), no. 202292s9 letter 2 of 5 thorough multi-stage cleaning procedure. for the same reason, stainless steel, glass and fluoropolymer-4 were used as materials for the setup. to obtain data on the instantaneous velocities of the ascent of the droplets, video recording of their movement was carried out using a canon 600d camera (pos. 9) with the possibility of high-speed video filming. in the work, the following settings were used for video filming: spatial resolution of 1280x720 pixels and a frame rate of 50 hz. the position of the camera relative to the column was determined so that the entire path of the droplet through the column could be captured during the shooting. to align the position of the camera vertically and horizontally, a two-axis spirit level was used. the required intensity and uniformity of illumination was achieved using a gasdischarge lamp (pos. 8) with a power of 21 w and a long tube of 850 mm. the recorded video fragments were transferred to a computer for analysis. the obtained fragments were processed using the media cybernetics image-pro plus software version 6.0. the first processing step was to determine the scale of the image. after that, the background image was subtracted from each image of the sequence of video frames. the track objects tool was applied to the sequence of frames processed in this way, with the help of which the coordinates of the drop center on each image from the sequence were automatically determined. as a result of the processing procedure, the instantaneous velocities of the droplets were calculated. to collect the dispersed phase, droplet separators with an inner diameter of 70 mm (item 7) were installed in the experimental setup. a small constant volume of the dispersed phase was accumulated in the droplet separator for the coalescence of droplets. the dispersed phase collected in the droplet separator was sampled using a second syringe pump (pos. 3b). the acid concentration was determined by titration with an aqueous solution of sodium hydroxide in the presence of phenolphthalein. 3. results and discussion the results of experiments on the mass transfer of acetic acid from butyl acetate droplets into water are presented. a series of experiments were carried out with different initial concentrations of acetic acid (0.1, 0.2, 0.3, 0.5, 0.7 mol/l). figures 2–6 show the trajectories of droplets with a diameter of 2.5 mm. the mass transfer at high values of the concentration of the transferred substance took place under practically stable conditions, the trajectories of the droplets coinciding with the symmetry axis of the column. at the final stage of the mass transfer process, the influence of interfacial convection was already noticeable. drops with a concentration of 0.1 mol/l almost immediately deviated from the axis; at concentrations up to 0.5 mol/l, this effect influenced the motion of particles in the upper parts of the trajectories. however, the acid concentration of 0.7 mol/l was too high, so the droplet deflection did not occur. figure 1 schematics of the experimental setup: 1 – borosilicate glass column; 2 – shirt; 3a, 3b – syringe pumps; 4 – electromagnetic device; 5 – capillary; 6 – thermostat; 7 – drop catchers; 8 – lamps; 9 – video camera; 10 – personal computer. . chimica techno acta 2022, vol. 9(2), no. 202292s9 letter 3 of 5 figure 2 trajectories of droplets (0.1 mol/l). figure 3 trajectories of droplets (0.2 mol/l). figure 4 trajectories of droplets (0.3 mol/l). the data on the ascent rate of drops are shown in figure 7. the upper horizontal line on the plot corresponds to the calculated ascent rate for a liquid droplet without mass transfer, the lower horizontal line corresponds to the calculated ascent rate for a rigid sphere. the experimental data for a liquid droplet with zero acid concentration practically coincide with the calculated data. the movement of droplets containing acid is different. as the acid concentration increases from 0.1 to 0.7 mol/l, the ascent rate decreases to the ascent rate of a rigid sphere. this dependence is explained by a change in the structure of flows inside the droplet. in an ordinary case, a drop squeezes through the thickness of the continuous medium due to the internal circulating toroidal currents. in the case of mass transfer with convection, the structure of streamlines in the droplet changes, convection disturbances impede the coordinated toroidal flow, reducing the speed of the droplet ascent. the kinetics of mass transfer (figures 8 and 9) is also highly dependent on the presence of interfacial convection. at small values of the driving force of the process (0.1...0.2 mol/l), the dependence is pronounced; it is observed in the form of an ascending line. at large values of the driving force (more than 0.2 mol/l), the dependence changes its character and approaches horizontal lines. the dependence of the acid concentration on the total contact time of the phases is inversely proportional, asymptotically approaching the horizontal line at the concentration level of 0.05...0.1 mol/l. figure 5 trajectories of droplets (0.5 mol/l). figure 6 trajectories of droplets (0.7 mol/l). chimica techno acta 2022, vol. 9(2), no. 202292s9 letter 4 of 5 figure 7 dependence of the ascent rate on the process time. figure 8 dependence of the acid concentration on the total contact time of the phases. figure 9 dependence of the mass transfer coefficient on the driving force. 4. conclusions the marangoni effect has a significant influence on the mass transfer of acetic acid from the dispersed phase (butyl acetate) to the continuous phase (water). the most pronounced effect is observed at a driving force of 0.1...0.2 mol/l. the drops with a concentration of 0.1 mol/l almost immediately deviated from the axis; at concentrations up to 0.5 mol/l, this effect influenced the motion of the particles in the upper sections of the trajectories. the marangoni effect also affects the ascent rate of a liquid droplet. the experimental data for a liquid droplet with zero acid concentration practically coincide with the calculated data. the movement of droplets containing acid is different. as the acid concentration increases from 0.1 to 0.7 mol/l, the ascent rate decreases to the ascent rate of a rigid sphere. supplementary materials no supplementary materials are available. funding this research had no external funding. acknowledgments none. author contributions conceptualization: a.g.t., z.r.r. data curation: z.r.r., e.a.k. formal analysis: a.g.t., a.m.v., e.a.k. investigation: z.r.r., e.a.k. methodology: a.g.t., z.r.r. project administration: a.g.t. resources: a.g.t., z.r.r., e.a.k. supervision: a.m.v. validation: a.g.t., a.m.v. visualization: a.g.t., z.r.r. writing – original draft: a.g.t., z.r.r. writing – review & editing: a.m.v. conflict of interest the authors declare no conflict of interest. additional information author ids: anatolii g. titov, scopus id 56010769800; zalina r. rusinova, scopus id 56662108900; ekaterina a. kalimullina, scopus id 56661917600; anatoliy m. vorobev, scopus id 15849342600. websites: ural federal university, https://urfu.ru/en/; university of southampton, https://www.southampton.ac.uk/. references 1. slater mj, godfrey jc. liquid–liquid extraction equipment. chichester: wiley; 1994. 792 p. https://www.scopus.com/authid/detail.uri?authorid=56010769800 https://www.scopus.com/authid/detail.uri?authorid=56662108900 https://www.scopus.com/authid/detail.uri?authorid=56661917600 https://www.scopus.com/authid/detail.uri?authorid=15849342600 https://urfu.ru/en/ https://www.southampton.ac.uk/ chimica techno acta 2022, vol. 9(2), no. 202292s9 letter 5 of 5 2. garner fh, foord a, tayeban m. mass transfer from circulating drops. j appl chem. 1959;9:315–323. doi:10.1002/jctb.5010090605 3. thorsen g, terjesen sg. on the mechanism of mass transfer in liquid – liquid extraction. chem eng sci. 1962;17:137–148. doi:10.1016/0009-2509(62)80025-6 4. kronig r, brink jc. on the theory of extraction from falling drops. appl sci res. 1950;a2:142–154. doi:10.1007/bf00411978 5. sheikholeslami m, chamkha aj. influence of lorentz forces on nanofluid forced convection considering marangoni convection. int commun heat mass transf. 2020;119. doi:10.1016/j.icheatmasstransfer.2020.104962 6. villers d, platten jk. coupled buoyancy and marangoni convection in acetone: experiments and comparison with numerical simulations. j fluid mech. 1992;234:487–510. doi:10.1017/s0022112092000880 7. tam d, arnim v, mckinley gh, hosoi ae. marangoni convection in droplets on superhydrophobic surfaces. j fluid mech. 2009;624:101–123. doi:10.1017/s0022112008005053 8. shevchenko e, mitra s, ermakov s, titov a, ermakov a, pattader p. joint mass transfer of two components associated with the spontaneous interfacial convection in the liquidliquid extraction system. chem eng sci. 2019;195:301–311. doi:10.1016/j.ces.2018.09.018 https://doi.org/10.1002/jctb.5010090605 https://doi.org/10.1016/0009-2509(62)80025-6 https://doi.org/10.1007/bf00411978 https://doi.org/10.1016/j.icheatmasstransfer.2020.104962 https://doi.org/10.1017/s0022112092000880 https://doi.org/10.1017/s0022112008005053 https://doi.org/10.1016/j.ces.2018.09.018 new 2,5-bis(2-ethylhexyl)pyrrolo[3,4-c]pyrrole-1,4(2h,5h)-dione-2,2’-bipyridine-based co-polymer, synthesis, photophysical properties and response to metal cations chimica techno acta letter published by ural federal university 2022, vol. 9(1), no. 20229101 eissn 2411-1414; chimicatechnoacta.ru doi: 10.15826/chimtech.2022.9.1.01 1 of 3 new molecular complex of ammonium glycyrrhizate with rutin l.a. yakovishin a* , v.d. ratnikov a , p.i. bazhan a, g.p. zaitsev b a: sevastopol state university, 299053 university st., 33, sevastopol, russia b: all-russian national research institute of viticulture and winemaking “magarach” of ras, 298600 kirova st., 31, yalta, russia * corresponding author: chemsevntu@rambler.ru this short communication (letter) belongs to the mosm2021 special issue. © 2021, the authors. this article is published in open access form under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). abstract a new 1:1 molecular complex of triterpene glycoside ammonium glycyrrhizate (gc) with flavonoid glycoside rutin (rut) was obtained in aqueous ethanol. the stability constant (9.70.2)104 (mol/l)–1 was calculated for the complex via isomolar curves. the complexation was studied by uvand atr ir-fourier spectroscopy and a method of isomolar series. the hydrogen bonds and hydrophobic interactions are formed in the molecular complex. a preliminary antioxidant activity assessment of the complex was made. keywords triterpene glycosides ammonium glycyrrhizate rutin molecular complex antioxidant capacity received:03.11.2021 revised: 21.12.2021 accepted: 21.12.2021 available online: 11.01.2022 1. introduction rutin (rut; fig. 1) is one of the most famous flavonols and glycosides [1]. its aglycone is quercetin. found in different plants, rut has p-vitamin activity and exhibits antimicrobial, antioxidant, anti-inflammatory, antidiabetic, antispasmodic, antisclerotic, diuretic, and anticancer effects [1]. rut has a low solubility in water and limited membrane permeability [1]. the therapeutic effect of rut is limited due to its bioavailability [1]. the study [2] showed that the solubility and bioavailability of bioactive compounds can be significantly increased by their molecular complexation with triterpene glycosides. triterpene saponins are amphiphilic multidentate ligands that are capable of molecular complexation with both polar and non-polar fragments of other molecules [2]. glycyrrhizic acid (ga) and its monoammonium salt (ammonium glycyrrhizate, glycyram, gc; fig. 1) are widely used as complexing agents [2–6]. ga is the main triterpene saponin of licorice roots [2]. ga increases permeability of cell membranes [5]. previously, we studied the molecular complex of quercetin with gc [6]. however, molecular complexes of rut with gc have not been described. this article reports the preparation of a new molecular complex of gc with rut. 2. experimental gc (purity ≥95% by high-performance liquid chromatography (hplc)) was purchased from calbiochem. other chemicals of the highest grade of purity were obtained from sigma-aldrich. the isomolar series were prepared by mixing 10– 4 mol/l solutions of gc and rut in 70% aqueous ethanol (v/v) with continuous stirring at 25 °c for 40 min. spectroscopic analysis of isomolar series was performed on a leki ss2110uv spectrophotometer using a quartz cuvette (l = 1 cm) at 25 °c. stability constant of the complex was calculated according to the a.k. babko method based on the isomolar curves [5, 7]. the complex of rut with gc was preparatively obtained by the liquid-phase method. for this purpose, 1 mmol of the substances was mixed with 50 ml of 70% aqueous ethanol (v/v). the obtained mixture was incubated with continuous stirring at 50 c for 1.5 h. the organic solvent was removed by vacuuming. the synthesized complex was analyzed by ir spectroscopy. the ir spectra were recorded on a simex fт801 ir-fourier spectrometer (russia) in the 4000–550 cm–1 region (spectral resolution 4 cm–1; 25 scans) using the atr accessory with a diamante crystal plate. ir spectrum of rut (, cm–1): 3415 (oh), 3343 (oh), 2954 (ch), 2914 (сн), 2847 (сн), 1656 (с=о), 1596 (c=car), 1572 (c=car), 1552 (c=car), 1502 (c=car), 1453 (c=car, сн), 1426 (сн), 1405 (с–он), 1360 (с–он, сн), 1313 (ch), 1294 (с–о–с, с–он), 1234 (с–о–с, с–он), 1203 (с–о–с, с–он), 1168 (с–о–с, с–он), 1149 (с–о–с, с–он), 1123 (с–о–с, с–он), 1093 (с–о–с, с–он), 1059 (с–о–с, с–он), 1041 (с–о–с, с–он), 1013 (с–о–с, с–он), 999 (с–о–с, с–он), 967 (сн), 943 (сн), 910 (monosaccharide ring), 880 (сн), 848 (сн), 826 (сн), 807 (сн), 794 (сн), 727 (сн), 719 (сн), 707 (сн), 688 (сн), 655 (он), 629 (сн), 594 (сн). http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2022.9.1.01 https://orcid.org/0000-0002-8728-7950 https://orcid.org/0000-0002-6673-5435 https://orcid.org/0000-0001-6416-8417 http://creativecommons.org/licenses/by/4.0/ chimica techno acta 2022, vol. 9(1), no. 20229101 letter 2 of 3 o ooh oh o oh oh o ch2 oh oh oh o ch3 oh ohoh o 1 3 2 45 7 6 8 1' 3' 5' 2' 4'6' o hooc o o oh oh cooh oh o oh oh coo o h nh 4 1 3 9 12 11 18 20 7 28 rut gc fig. 1 structures of rut and gc ir spectrum of gc (, cm–1): 3212 (он, nh), 2944 (ch), 2928 (сн), 2911 (ch), 2862 (сн), 1726 (с=о), 1710 (с=о), 1692 (с=о), 1642 (с(11)=о, c=c), 1588 (соо–), 1453 (сн2, сн3), 1428 (nh4+), 1414 (соо–), 1390 (сн), 1358 (сн), 1350 (сн), 1324 (ch), 1304 (сн), 1279 (ch), 1258 (сн), 1211 (сн), 1162 (с–о–с, с–он), 1032 (с–о–с, с–он),980 (=ch), 946 (сн), 918 (monosaccharide ring), 879 (сн), 868 (ch), 818 (сн), 786 (сн), 749 (ch), 692 (сн), 684 (сн), 677 (=ch), 657 (он). ir spectrum of the complex of rut with gc (, cm–1): 3284 (он, nh), 2956 (ch), 2919 (сн), 2850 (ch), 1730 (с=оgc), 1715 (с=оgc), 1682 (с=оgc), 1639 (с=оrut), 1584 (соо–, c=car), 1509 (c=car), 1451 (c=car, сн), 1424 (nh4+), 1411 (соо–), 1360 (с–он, сн), 1301 (с–о–с, с–он, ch), 1275 (с–о–с, с–он, сн), 1235 (с–о–с, с–он), 1201 (с–о–с, с–он), 1168 (с–о–с, с–он), 1073 (с–о–с, с–он), 1047 (с–о–с, с–он), 1030 с–о–с, с–он), 982 (=ch), 929 (сн), 878 (сн), 806 (сн), 786 ch), 717 (сн), 691 (сн), 655 (oh), 598 (сн). antioxidant activity was studied on a photochem analyzer (analytik jena ag, germany). determination of antioxidant capacity of lipid soluble compounds (acl) and water soluble compounds (acw) was carried out according to the manufacturer's standard protocols. acw = 161.2 nm and acl = 157.3 nm (in terms of trolox for 49.5 mg/l solutions of rut–gc complex in 70% aqueous ethanol (v/v)). 3. results and discussion the composition of the complex of gc with rut was determined by the isomolar series method (figs. 2, 3). this method gave a molar ratio 1.0 at 258 nm, which corresponded to a 1:1 complex (fig. 3). in addition, the isomolar curve shows a clear minimum at 361 nm at a 1:1 ratio of components (fig. 3). such ratio was obtained for complexes of ga and gc with several drugs [2]. however, a different composition (1:2) was found in the complex of gc with quercetin [6]. due to hypsochromic shift, the absorption maximum of the solutions decreases from 258 to 252 nm (fig. 2). stability constant of the complex (kgc–rut = (9.70.2)104 (mol/l)–1) was calculated based on the isomolar curves at 258 nm by a.k. babko method. the previously obtained 1:1 molecular complexes of different bioactive compounds with gc had stability constants of 103–105 (mol/l)–1 [2]. atr ft-ir spectra of gc and rut complex show lowfrequency shifts of the absorption band of stretching vibrations of о–н bonds in rut from 3415 and 3343 cm–1 to 3284 cm–1. fig. 2 absorption curves of isomolar series of solutions at 25 °c chimica techno acta 2022, vol. 9(1), no. 20229101 letter 3 of 3 0 0.5 1 0 1 2 3 4 5 6 7 8 9 10 c (gc)/c (rut) dа 258 -0.04 0 0.04 0.08 0.12 0 1 2 3 4 5 6 7 8 9 10 c (gc)/c (rut) dа 361 (a) (b) fig. 3 optical density change dа as a function of component ratio of isomolar series at 258 nm (a) and at 361 nm (b) such changes in the spectra confirm the formation of hydrogen bonds. ir spectrum of complex shows certain changes related to stretching vibrations, absorption bands of с–о bonds in с–о–с and с–он groups, for example 1059→1047 cm–1 for rut, 1162→1168 cm–1 for gc. the presence of lowfrequency shifts of c=o stretching vibrations, absorption band is indicative of с=о groups of rut and gc involvement in hydrogen bonding: 1656→1639 cm–1 for rut and 1692→1682 cm–1 for gc. in addition, the ir spectra show shifts of the main absorption bands of ch bonds, stretching vibrations, which can be caused by hydrophobic interactions in the complex. their presence explains the stability of the molecular complex of gc with rut. rut, ga and some complexes of ga have antioxidant activity [1, 8, 9]. for example, the antioxidant capacity of complexes of uracil derivatives with ga was studied in several oxidative systems, where they showed a higher activity than ionol [8]. a preliminary study of rut–gc complex antioxidant activity was performed. at the same time, the analysis of the complex antioxidant capacity (in terms of trolox) showed an increase of acw by 7.31%, but a slight decrease of acl by 2.73% in comparison with the rut standard. 4. conclusions a joint molecular complex of triterpene and flavonoid glycosides was obtained for the first time. the composition of the complex of rut with gc is 1:1. the complex has sufficient stability and is formed by hydrogen bonds (c=ogc…h–orut and c=orut…h–ogc) and hydrophobic contacts. complexation of rut with gc can improve its bioavailability and membrane permeability, and expand the spectrum of biological activity. acknowledgements this study was carried out with the experimental equipment of the sevastopol state university (project pr/80742/2017). declaration of competing interest the authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. references 1. gullón b, lú-chau ta, moreira mt, lema jm, eibes g. rutin: a review on extraction, identification and purification methods, biological activities and approaches to enhance its bioavailability. trends food sci technol. 2017;67:220–35. doi:10.1016/j.tifs.2017.07.008 2. yakovishin la, grishkovets vi. ivy and licorice triterpene glycosides: promising molecular containers for some drugs and biomolecules. stud nat prod chem. 2018;55:351–83. doi:10.1016/b978-0-444-64068-0.00011-5 3. khizrieva ss, vetrova ev, borisenko sn, maksimenko ev, borisenko ni. synthesis and study of complexes of the novel russian antiviral drug camphecene with pentacyclic triterpenes of licorice. chimica techno acta. 2020;7(4):192–98. doi:10.15826/chimtech.2020.7.4.10 4. yakovishin la, 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safronova og, lyakhovich vv, nikitin yup, tolstikov ga. antioxidant and endothelium-stabilizing effects of simvaglyzin on rabbits with experimental hypercholesterolemia. bull exp biol med. 2008;146(2):206–209. doi:10.1007/s10517-008-0252-x https://doi.org/10.1016/j.tifs.2017.07.008 https://doi.org/10.1016/b978-0-444-64068-0.00011-5 https://doi.org/10.15826/chimtech.2020.7.4.10 https://doi.org/10.15826/chimtech.2020.7.4.08 https://doi.org/10.2174/1573407215666191007111603 https://doi.org/10.1063/5.0018047 https://doi.org/10.15826/chimtech.2020.7.4.02 https://doi.org/10.1007/s10517-008-0252-x development of technology for obtaining electrodes based on copper wire using in the manufacture of solar modules chimica techno acta letter published by ural federal university 2022, vol. 9(2), no. 202292s1 eissn 2411-1414; chimicatechnoacta.ru doi: 10.15826/chimtech.2022.9.2.s1 1 of 4 development of technology for obtaining electrodes based on copper wire used in the manufacture of solar modules m.s. illarionova * , k.yu. ivanova , m.v. kuzmin , a.o. patianova , v.l. semenov chuvash state university named after i. n. ulyanov, 428015 cheboksary, russia * corresponding authors: illarionovamarina1995@mail.ru this paper belongs to the mosm2021 special issue. © 2021, the authors. this article is published in open access form under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). abstract to optimize the technological process of manufacturing copper wire coated with solder of the poin-52 brand, the optimal modes for the tinning temperature, linear velocity, diameter of the diamond die and flux were identified. it was found that the best wire tinning process is achieved when cleaning the surface of a copper wire by the method of electrochemical degreasing. the results of the tests showed that, in terms of mechanical and electrical parameters wire meets the requirements for electrodes in the manufacture of solar modules. the results of climatic tests of solar modules showed a high degree of reliability with a power loss of 0.86% and thermal cycling tests with a power loss of 0.4%, which is within tolerance. keywords smart wire connection technology poin-52 brand tin-indium alloy copper wire mechanical and electrical parameters solar module received: 09.11.2021 revised: 01.12.2021 accepted: 28.03.2022 available online: 31.03.2022 1. introduction in modern conditions of the russian economy development, one of the most important tasks is implementing the import substitution for reducing the cost of manufactured products. this issue is also relevant in the field of alternative energy sources, i.e. in the transition from non-renewable to renewable energy sources [1, 2]. it is known that photovoltaic solar modules are manufactured using smart wire connection technology (swct). on both surfaces of the photovoltaic cells, a film-wire electrode is glued, which consists of a wire and a film for the electrode. using a film-wire electrode, photovoltaic cells are connected in series [3]. one of the important tasks of increasing the efficiency of photovoltaic solar modules is the search and development of new electrodes that provide high reliability of contact with crystalline silicon, as well as charge transfer in the cell [4]. tinned copper wire, which is currently one of the main materials in electrical engineering, is widely used as conductive electrodes. the use of tinned copper wire ensures the reliability and protection of solar modules from any external influences and, as a result, increases the durability of the product itself [5]. the use of low-melting solder on the surface of the copper wire makes it possible to obtain reliable electrical contact with the siver-containing contact grid, which helps to reduce the ohmic resistance between the photovoltaic cells [6]. 2. experimental as a rule, tinning in the manufacture of wire is performed by the galvanic method. however, practice has shown that the necessary qualities of electrodes are achieved via hot tinning [7]. the continuity of the electrode contact with monocrystalline silicon directly depends on the surface quality of the tinned wire and the thickness of the solder based on the poin-52 alloy, which ultimately affects the efficiency of transferring the converted light energy into electricity [8]. in accordance with the requirements of the normative and technical documentation, hot tinning on the coating of copper wire of mt 0.25 brand with poin-52 brand solder was carried out on a hot tinning unit. at the first stage, we prepared the surface of the copper wire in order to remove oxides from the surface. we used the electrochemical degreasing to prepare the surface of the wire. the initial parameters of the wire were as follows: diameter – 0.25±0.001 mm; elongation – http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2022.9.2.s1 mailto:illarionovamarina1995@mail.ru http://creativecommons.org/licenses/by/4.0/ https://orcid.org/0000-0002-4893-7746 https://orcid.org/0000-0001-5982-0570 https://orcid.org/0000-0003-3880-9510 https://orcid.org/0000-0002-9785-4058 https://orcid.org/0000-0002-9869-6602 https://crossmark.crossref.org/dialog/?doi=https://doi.org/10.15826/chimtech.2022.9.2.s1&domain=pdf&date_stamp=2022-3-31 chimica techno acta 2022, vol. 9(2), no. 202292s1 letter 2 of 4 25%; specific electrical resistance – 0.016710–6 ohmm2. wire degreasing parameters are shown in table 1. hot tinning was carried out using flux deposition technology. a composition developed by a team of authors in work [9, 10] was used as a flux. the technological modes of hot tinning are given in table 2. during the coating process, it was found that the wire stretches slightly. the coating of the wire is even, smooth, shiny, the quality of adhesion is satisfactory. 3. results and discussion we experimentally studied the possibility of using wire as electrodes using swct technology in the manufacture of solar modules. reliability tests of soldering joints were carried out by testing for exposure to high humidity at high temperature and by thermal cycling. the results of the tests showed that, according to mechanical and electrical parameters, the wire coated with solder of the point-52 brand meets the requirements for electrodes in the manufacture of solar modules. the results of climatic tests of solar modules for exposure to high humidity at high temperature showed a high degree of reliability with a power loss of 0.86% and thermal cycling tests with a power loss of 0.4%, which is within tolerance. mechanical and electrical parameters of tinned wire are presented in table 3. the data in table 3 show that the mechanical parameters (mechanical strength and relative elongation) and electrical parameters (electrical resistance to direct current and specific electrical resistance) are within the specified tolerance ranges or within the normal range. the design parameters of the copper wire coated with poin-52 alloy is presented in table 4. the thickness of the coating was determined by metallographic method according to clause 3.14 of g ost 9.302-88 unified system of protection against corrosion and aging (eszks). metallic and non-metallic inorganic coatings. control methods (as amended). data analysis table 3 and 4 indicates that the most optimal characteristics are obtained with technological mode no. 2. the obtained sample of tinned wire is recommended as a current conducting electrode in the manufacture of solar modules using swct technology. at the next stage we carried out climatic tests of solar modules in order to determine the possibility of using tinned wire coated with poin-52 alloy according to iec 61215-1: 2016 “photovoltaic modules. assessment of compliance with technical requirements. test requirements". two different climatic tests were performed. the first test method involves exposure to high humidity at high temperatures. the test conditions are presented in table 5. the results of the tests are presented in table 6. table 6 shows that the power loss was 2.71 watts or 0.86%. the photo of the electroluminescence of the module at the end of the tests is shown in fig. 1. fig. 1 photo of the electroluminescence of the module at the end of the tests the second method of climate testing involves thermal cycling. the test conditions are presented in table 7. the results of the tests are presented in table 8. table 8 shows that the power loss was 1.29 w, or 0.4%. the photo of the electroluminescence of the module at the end of the tests is shown in fig. 2. table 1 technological mode of electrochemical degreasing brand and nominal diameter of copper wire, mm degreasing solution тemperature, °с electric current, а speed, m/min wire diameter after degreasing, mm мм 0.25±0.001 tg-19 38 20 50 0.25±0.001 table 2 technological mode of wire coating with poin-52 solder mode copper wire diameter according to technical specifications copper wire brand and actual diameter, mm melt temperature, °с linear velocity, m/min diamond die diameter, mm 1 1.0 1.025.0 + − мт 003.0 001.025.0 + − 130 130 0.265 2 1.0 1.025.0 + − мт 003.0 001.025.0 + − 150 100 0.265 3 1.0 1.025.0 + − мт 003.0 001.025.0 + − 175 105 0.278 chimica techno acta 2022, vol. 9(2), no. 202292s1 letter 3 of 4 table 3 mechanical and electrical parameters of copper wire coated with poin-52 solder tensile strength, н/ mm 2 relative extension, % specific electrical resistance to direct current at temperature 20 °с, ohm× mm 2/m electrical resistance to direct current at temperature 20 °с, ohm/m standard 1 2 3 standard 1 2 3 standard 1 2 3 standard 1 2 3 2 0 0 -2 9 0 2 4 3 2 2 0 2 4 0 2 5 ± 1 5 2 5 2 1 2 1 0 ,0 1 7 ± 0 .0 0 2 0 .0 1 8 0 .0 1 9 0 .0 1 7 0 .3 5 ± 0 .0 3 0 .3 5 0 .3 5 0 .3 5 table 4 design parameters of copper wire coated with poin-52 solder wire diameter, mm wire coating thickness, micron standard 1 2 3 standard 1 2 3 0.25±0.010 0.257 0.257 0.250 5.1 0.15.3 + − 3.8 4.5 ˂1.0 (≈0.8) table 5 high humidity / high temperature test conditions exposure in the climate chamber exposure time, hours temperature, °с relative humidity, % frequency of unloading for testing, days exposure conditions 1000 85±2 85±5 7 table 6 test results of volt-ampere characteristics before and after the tests week pmax, watt vpmax, v ipmax, а voc, v isc, а rs, ohm rsh, ohm ff, % eta, % 0 (loading) 317.354 36.33 8.74 43.87 9.25 0.46 687.7 78.20 19.00 6 (discharge) 314.64 36.21 8.69 43.80 9.21 0.46 666.8 77.97 18.84 table 7 test conditions by thermal cycling exposure in the climate chamber number of cycles cycle duration, hours frequency of unloading for tests, cycles 200 6 40 exposure conditions temperature, °с relative humidity, % at the top point at the bottom point at the top point at the bottom point 85±2 –40±1 – – table 8 test results of volt-ampere characteristics before and after the tests series pmax, watt vpmax, v ipmax, а voc, v isc, а rs, ohm rsh, ohm ff, % eta, % 0 (loading) 316.76 36.26 8.74 43.88 9.26 0.461 537.7 77.97 18.97 200 (discharge) 315.47 36.19 8.72 43.89 9.24 0.473 546.2 77.83 18.89 fig. 2 photo of the electroluminescence of the module at the end of the thermal cycling tests 4. conclusions the technological modes of hot tinning of copper wire with the poin-52 alloy considered in this work with the identification of optimal conditions for the tinning temperature, linear velocity and diameter of the diamond drawing allow us to confirm the reliability of the contact electrode with the connecting busbar of solar modules. it is confirmed by the successfully conducted climatic tests of the solar modules by the thermal cycling methods and the method of exposure to high humidity at high temperature. the results of the climatic tests of solar modules comply with the requirements of regulatory and technical documentation and vary within the tolerance ranges. supplementary materials no supplementary data are available. chimica techno acta 2022, vol. 9(2), no. 202292s1 letter 4 of 4 funding the research was carried out by chuvash state university within the implementation of a comprehensive project under the contract no. 2019/0837/1202–19 dated september 19, 2019 with the financial support of the ministry of education and science of russia under the agreement no. 075-112019-047 dated november 25, 2019 and russian foundation for basic research (rfbr, https://www.rfbr.ru/rffi/eng), project no. 20-33-90269. acknowledgments none. author contributions conceptualization: m.s. i., k.yu.i., a.o.p., m.v.k. data curation: m.v.k. formal analysis: k.yu.i., a.o.p. funding acquisition: m.v.k., v.l.s. investigation: m.s. i., k.yu.i., a.o.p. methodology: m.v.k., v.l.s. project administration: m.v.k., v.l.s. resources: m.s. i., k.yu.i., a.o.p. software: m.v.k., v.l.s. supervision: m.v.k., v.l.s. validation: m.v.k., v.l.s. visualization: k.yu.i., a.o.p. writing – original draft: m.s. i., k.yu.i., a.o.p. writing – review & editing: m.v.k., v.l.s. conflict of interest the authors declare no conflict of interest. additional information authors’ ids: illarionova, marina s., scopus id 57203511906; ivanova, kristina yu., scopus id 57222369362; kuzmin, mikhail v., scopus id 55758896300. patianova alice o., scopus id 57202283653 semenov vladislav l., scopus id 57190025583 website of chuvash state university named after i.n. ulyanova https://www.chuvsu.ru. references 1. maronchuk ii, sanikovich dd, mironchuk vi. solnechnye elementy: sovremennoe sostoyanie i perspektivy razvitiya. energetika [solar cells: current state and development prospects. energy] izvestiya vysshih uchebnyh zavedenij i energeticheskih ob"edinenij sng. 2019;62(2):105–123. russian. doi:10.21122/1029-7448-2019-62-2-105-123 2. prospects for energy technologies 2008. scenarios and strategies until 2050 [internet]. international energy agency. oecd / iea, 2008. p. 10–15 [cited 29.07.2021]. available from: https://iea.blob.core.windows.net/assets/0e190efbdaec-41169ff7-ea097f649a77/etp2008.pdf 3. larionov vr, malevskij da, pokrovskij pv et al. izmeritel'nyj kompleks dlya izucheniya kaskadnyh solnechnyh fotoelektricheskih elementov i koncentratornyh modulej na ih osnove [measuring complex for the study of cascade solar photovoltaic cells and concentrator modules based on them] tekh fiz. 2015;60:891– 896. russian. doi:10.1134/s1063784215060158 4. semenov vl, aleksandrov, ri, kuzmin mv, rogozhina lg, ivanova ky, patianova ao, inventors; chuvash state university named after i. n. ulyanov, assignee. method for producing copper wire coated on the basis of an alloy of tin-indium. russian federation patent ru 2764277 c1. 2022. russian. 5. vinokurov eg, margolin ln, farafonov vv. elektroosazhdenie kompozitsionnykh pokrytiy [electrodeposition of composite coatings]. izvestiya vysshikh uchebnykh zavedeniy. seriya: khimiya i khimicheskaya tekhnologiya. 2020;63(8):4–38. russian. 6. ivanova kyu et al. synthesis and research of polyfunctional silylureas used in electric deposition of tin-indium alloy. chim techno acta. 2021;8(3):20210305. doi:10.15826/chimtech.2021.8.3.05 7. socolowski n. lead free alloys and limitations for surface mount . proc surf mount int. 1995;477–480. doi:10.1134/s0031918x09090105 8. csincse j, janjun s, uisang q, stewart v, graham a, inventors; wuxi suntech power co, assignee. a method of producing electrode of solar cell and device for electrochemical deposition. russian federation patent ru 2399119 c2. 2010. russian. 9. semenov vl, aleksandrov, ri, kuzmin mv, rogozhina lg, ivanova ky, patianova ao, inventors; chuvash state university named after i. n. ulyanov, assignee. flux for soldering and tinning of copper wire. russian federation patent ru 2741607 c1. 2021. russian. 10. patianova ao, ivanova kyu, rogozhina lg, kuzmin mv, semenov vl. improving the environmental production of electrodes for solar panels. chim techno acta. 2020;7(4):186–191. doi:10.15826/chimtech.2020.7.4.09 https://www.rfbr.ru/rffi/eng https://www.chuvsu.ru/ https://doi.org/10.21122/1029-7448-2019-62-2-105-123 https://iea.blob.core.windows.net/assets/0e190efbdaec-4116-9ff7-ea097f649a77/etp2008.pdf https://iea.blob.core.windows.net/assets/0e190efbdaec-4116-9ff7-ea097f649a77/etp2008.pdf https://doi.org/10.1134/s1063784215060158 https://doi.org/10.15826/chimtech.2021.8.3.05 https://doi.org/10.1134/s0031918x09090105 https://doi.org/10.15826/chimtech.2020.7.4.09 using a microheterogeneous model to assess the applicability of ion-exchange membranes in the process of reverse electrodialysis chimica techno acta article published by ural federal university 2021, vol. 8(2), № 20218205 eissn 2411-1414; chimicatechnoacta.ru doi: 10.15826/chimtech.2021.8.2.05 1 of 9 using a microheterogeneous model to assess the applicability of ion-exchange membranes in the process of reverse electrodialysis d.v. davidov, e.n. nosova, s.a. loza, a.r. achoh, a.n. korzhov, s.s. melnikov * kuban state university, stavropolskaya st. 149, krasnodar, 350040, russia * corresponding author: melnikov.stanislav@gmail.com this article belongs to the regular issue. © 2021, the authors. this article is published in open access form under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). abstract this paper shows the possibility of using a microheterogeneous model to describe the properties of ion-exchange membranes and calculate the characteristics of a reverse electrodialyzer from the data obtained. we studied the properties of eight samples of heterogeneous cation exchange membranes (two samples of each type of membrane). the samples differed in the year of issue and storage conditions. it is shown that for heterogeneous ion-exchange membranes mk-40 and ma-41, the samples' properties can differ significantly. the counterions transport numbers calculated within the framework of the microheterogeneous model for ralex membranes differ insignificantly. the counterion transport number in 1 mol/l sodium chloride solution is 0.96 for ralex cm and 0.98 ± 0.01 for ralex amh. for the mk-40 membrane, the transport number in the same solution is 0.94 ± 0.04, and for the ma-41 membrane, it is 0.85 ± 0.1. the possibility of calculating the transport numbers and predicting the open-circuit voltage based on simple physicochemical measurements allows selecting the best membrane pairs for the reverse electrodialysis process. comparison of the open-circuit potential value calculated using the obtained transfer numbers with experimental data showed that in the case of using ralex membranes, the difference between the experimental and calculated values is 2%. the calculated value of the open circuit potential was 0.19 v/membrane pair or 1.69 v for the investigated reverse electrodialyzer with nine pair chambers. keywords reverse electrodialysis ion-exchange membrane conductivity diffusion permeability microheterogeneous model received: 30.03.2021 revised: 28.04.2021 accepted: 30.04.2021 available online: 30.04.2021 1. introduction electrodialysis is an electromembrane process designed to remove ionic impurities from aqueous solutions. in electrodialysis, ion-exchange membranes of two types are used: cation-exchange membranes permeable only for cations and anion-exchange membranes permeable only for anions. when an electric current is applied to the electrodialysis apparatus, which consists of a plurality of alternating cation-exchange and anion-exchange membranes, migration of cations occurs through the cation-exchange membranes and the migration of anions through the anion-exchange membranes. during the operation of the electrodialyzer, the concentration of ionic components in one chamber, called the desalination chamber, decreases, and in the other, called the concentration chamber, increases. the two membranes (cation exchange and anion exchange) and the desalination chamber and the concentration chamber are collectively called a membrane pair. the collection of all membrane pairs in an electrodialyzer is called a membrane stack. electrodialysis can be used in several industrial processes associated with the transfer of ions: desalination of aqueous solutions [1,2], electromembrane synthesis [3], concentration of salts and acids [4,5], processing solutions in the agro-food industry [6], processing highly concentrated effluents from installations for obtaining drinking water from the sea [7,8]. in the latter case, the generated http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2021.8.2.05 http://creativecommons.org/licenses/by/4.0/ https://orcid.org/0000-0001-6720-1497 chimica techno acta 2021, vol. 8(2), № 20218205 article 2 of 9 highly concentrated effluents can also be used as a source of “blue” electricity using a process called reverse electrodialysis [9]. reverse electrodialysis is a process of generating electricity based on the utilization of energy released when two solutions with different concentrations are mixed. when using an ion-exchange membrane, which separates concentrated and dilute electrolyte solutions, due to the diffusion of a substance through the membrane, an ion flux (electric current) occurs. at the interfaces between a dilute solution/membrane and a membrane/concentrated solution, a potential difference occurs called the donnan potential. the sum of the two potential drops at the left and right sides of the membrane is called the membrane potential (em). its value is determined by the ratio of ions' activities in solutions to the right and left of the membrane. since each of the two membranes (cation-exchange (cem) and anion-exchange (aem)) has its own membrane potential, the total potential drop on the membrane pair will be the sum of two membrane potentials: 𝐸red = 𝑁(𝐸𝑚 cem + 𝐸𝑚 aem) 𝐸𝑚 cem = 𝛼cem 𝑅𝑇 𝑛𝐹 ln 𝑎𝑏 + 𝑎𝑑 + = 𝑅𝑇 𝑛𝐹 ln 𝑐𝑏 +𝛾𝑏 + 𝑐𝑑 +𝛾𝑑 + 𝐸𝑚 aem = 𝛼aem 𝑅𝑇 𝑛𝐹 ln 𝑎𝑏 − 𝑎𝑑 − = 𝑅𝑇 𝑛𝐹 ln 𝑐𝑏 −𝛾𝑏 − 𝑐𝑑 −𝛾𝑑 − , (1) where n is the number of membrane pairs; α is the permselectivity of ion-exchange membrane; c is the electrolyte concentration, mol/l; γ is the ion activity coefficient; lower indexes “b” and “d” denote high concentration solution (brine) and low concentration solution (diluate); n is the number of electrons; r, t, f are universal gas constant, absolute temperature, and faraday constant. in recent years, interest in reverse electrodialysis has grown significantly, as evidenced by many reviews devoted to this topic. tian et al. [10] considered the effect of the electrode material and the redox pair used, the most important operating parameters (solution pumping rate, concentration of brine and dilute solutions, membrane channel geometry, etc.) were considered by mei and tang [11], current achievements and existing problems are disclosed by pawlowski et al. [12]. for the first time, the possibility of transforming the concentration gradient in natural conditions (for example, at the mouth of a river flowing into the sea) was shown by pattle in 1954 [13]. the energy density obtained in work was 0.2 w/m 2 at 39 °c using a hydroelectric pile composed of alternate 47 cems and 47 aems. further development of the technology made it possible to increase the energy density. nowadays, the average value of the energy density is 0.94 ± 0.4 w/m 2 when using a concentrated solution, either solution from solar ponds or effluents from desalination plants (data from review [14] were taken to calculate the average value). the increase in power density is achieved in various ways. researchers pay special attention to the ionexchange membranes used and their properties [14–16]. one of the key properties of membranes is their selectivity, i.e., cation-exchange membranes' ability to transfer only cations, and of anion-exchange membranes only anions. considering the imperfect selectivity of ion-exchange membranes, the equation for the open-circuit voltage (ocv) of the reverse electrodialyzer takes the form: 𝐸ocv = 𝑁 𝑅𝑇 𝑛𝐹 ln ( 𝑐𝑏 𝛾𝑏 ± 𝑐𝑑 𝛾𝑑 ± ) ( 𝑇cem + − 𝑡 + 1 − 𝑡 + + 𝑇cem − − 𝑡 − 1 − 𝑡 − ) , (2) where 𝑇cem + , 𝑇aem − are the counterion transfer numbers in the cationand anion-exchange membrane; 𝑡 +, 𝑡 − are the counterion transfer numbers for a given membrane in solution. the open circuit voltage is the driving force of the red process and represents the sum of potential differences over each membrane [17]. the terms in the last parenthesis in eq. (2) represent the selectivity of the cation-exchange and anion-exchange membranes (the first term in parentheses is 𝛼cem, and the second is 𝛼aem). the membranes' selectivity can be determined knowing the values of the counterion transport number in the membrane, for which the membrane potential method can be used [18]. however, the transport numbers determined by this method will be “apparent” since they do not consider the transfer of water molecules within the hydration shells of ions. to obtain the “true” value of the transport number, one can use the skachard equation [19]. however, its use requires the water transport number's values, which are also difficult to determine experimentally. one can calculate the “true” transport numbers across an ion-exchange membrane from the concentration dependences of electrical conductivity and diffusion permeability using the microheterogeneous model [20]. in view of the microheterogeneous model, the ion-exchange membrane is represented as a combination of two phases called “gel” and “intergel solution”. integral properties of the membrane, such as electrical conductivity and diffusion permeability, are determined as the geometric mean of some electrotransport coefficients different for the gel and intergel phases. the aim of this work is to test the possibility of using a microheterogeneous model and data on the concentration dependence of the transfer numbers of ions for various ion-exchange membranes to calculate the open-circuit potential and select the best membrane pair for carrying out the reverse electrodialysis process. 2. experimental 2.1. membranes the objects of the study were heterogeneous ion-exchange membranes mk-40, ma-41 (shchekinoazot, russia), and ralex cm, ralex amh (mega a.s., czech republic). two samples of each membrane were studied representing membranes of different batches and years of production (named batch 1 and batch 2 later in the text). chimica techno acta 2021, vol. 8(2), № 20218205 article 3 of 9 the properties of membranes can change during storage because of material degradation due to uv radiation, exposure to atmospheric oxygen, changes in temperature and humidity. in addition, the batches of ion-exchange membranes themselves may differ in their properties, which depend on the conditions for obtaining each specific batch. table 1 shows the years of production of the tested membranes. all studied heterogeneous membranes were produced by hot pressing (mk-40, ma-41) or rolling (ralex cm, ralex amh) of the thermoplastic mixture consisting of the fine powder of the ion-exchanger and polyethylene, in the approximate ratio of 2:1. the ion-exchanger used in the production of membranes mk-40, ma-41, ralex cm and ralex amh can be classified as polymer obtained by copolymerization of polystyrene with divinylbenzene. by type of the ionogenic groups, the membranes mk-40 and ralex cm are strong-acid cation-exchange with sulfonic acid ionogenic groups, ma-41, ralex amh are strong-basic anion-exchange with quaternary ammonium bases. physicochemical properties of the membranes provided by the manufacturers are given in table 2. all membranes were subjected to the following pretreatment procedure prior to the study: a. surface treatment with carbon tetrachloride for degreasing; b. soaking in ethanol for 6 hours to remove residues of monomers and oligomers from the ion-exchange resin; c. soaking of the membrane in excess volume (≈20 volumes of the membrane) of 1 m nacl solution for 24 hours; d. washing of the obtained membranes with deionized water to a constant value of the electrical conductivity of the wash water. the membranes prepared by this method were equilibrated with the working solution in which they were stored before the testing. 2.2. study of the electrical conductivity a mercury-contact method [22] was used for the study of the electrical conductivity of membranes. in this method, the membrane is placed between two mercury electrodes, so that a perfect adjoining of the electrode surface to the membrane is achieved. the internal resistance of mercury is insignificant in comparison with membrane resistance, which allows attributing the whole measured value to the membrane resistance only. the membranes were “airdry”; thus, the formation of electrode/solution and solution/membrane non-ohmic boundaries is excluded. to obtain “air-dry” membranes the excess electrolyte solution was removed from the membrane surface prior to the measurement. presence of the solution on the membrane surface may lead to an apparent low conductivity of the membrane as shown in [23]. a mercury-contact cell with a membrane was connected to the parstat 4000 impedance meter (fig. 1a). the connection was made using a two-electrode circuit. the spectrum of the electrochemical impedance of the membrane (fig. 1b) was recorded in the frequency range from 500 khz to 10 hz with a zero constant current component and an amplitude of the alternating current signal of 100 μa. extrapolation of the spectrum’s linear section in the high-frequency area allows obtaining a value of the active (ohmic) membrane resistance (r) (fig. 1b). the obtained value is converted into electrical conductivity according to the equation: 𝜅𝑚 ac = 𝑙 𝑅𝑆 . (3) the obtained value of electrical conductivity is called electrical conductivity in alternating current, it is related to electrical conductivity in direct current by the following relationship: 𝜅𝑚 dc = 𝜅𝑚 ac𝑡+ 𝑓2 , (4) where 𝜅𝑚 ac is the experimentally determined electrical table 1 year of production of membranes studied membrane* mk-40 1 mk-40 2 ralex cm 1 ralex cm 2 ma-41 1 ma-41 2 ralex amh 1 ralex amh 2 year of production 2002 2015 2008 2017 2010 2015 2008 2017 * the number near the membrane name indicates the batch table 2 physicochemical properties of the membranes studied membrane ralex cm ralex amh mk-40 ma-41 functional groups -so3 -n + (ch3)3 -so3 -n + (ch3)3 ion-exchange resin lewatit s100 lewatit m500 ku-2-8 av-17-8 inert binder ldpe reinforcing mesh ulester 32s nylon ion-exchange capacity, mmol/g-wet 1.12 0.86 1.08 0.91 water content, % 44 45 33 36 wet thickness, μm 720 750 540 530 radii of the ion-exchanger on the membrane surface [21], μm 1-14 2-26 chimica techno acta 2021, vol. 8(2), № 20218205 article 4 of 9 a b fig. 1 the scheme of the mercury-contact cell (а) and a frequency spectrum example of the electrochemical impedance (b). 1 – mercury-contact cell, 2 – studied membrane, 3 – platinum electrodes, 4 – mercury, 5 – impedance meter. conductivity of the membrane on alternating current, s/cm; t+ is the counterion transport number in the solution; f2 is the portion of intergel solution in the membrane [20]. 2.3. study of the diffusion permeability a non-flow two-chamber cell was used for the study of the diffusion permeability. one half of the cell contained a salt solution, and the second half contained distilled water (fig. 2). the half-cells were separated from each other by the studied membrane. a flow water jacket with constant temperature due to the thermostat was used outside the fig. 2 diffusion cell diagram. 1 diffusion cell, 2 studied membrane, 3 mechanical mixers, 4 platinum electrodes, 5 semicell containing salt solution, 6 semi-cell containing distilled water, 7 water cooling jacket, 8 computer, 9 e7-21 immittance meter non-flow semi-cells. the solutions in the non-flow cells were vigorously mixed using vertical mechanical mixers. this mixing is necessary to minimize the concentration polarization in the chamber and to eliminate the effect of the diffusion layer on the transport of ions through the membrane. it was experimentally determined that to remove the effect of concentration polarization on the parameters of diffusion transport through the membrane, a rotational mixers speed of 800 rpm is necessary. the resistance of distilled water was measured during the experiment at a frequency of 1/20 s using pt/pt electrodes connected to the e7-21 immittance meter. based on the calibration dependence of the solution concentration on its resistance, the initial experimental data were recalculated into the concentration change rate of time 𝑑𝑐 𝑑𝜏⁄ . based on the obtained data, it is possible to calculate the salt flow through the membrane (jm) and the integral coefficient of diffusion permeability (pm): 𝑗𝑚 = 𝑉 𝑆 𝑑𝑐 𝑑𝜏 , (5) 𝑃𝑚 = 𝑗𝑚 𝑙 𝑐 . (6) 2.4. electromigration transport numbers of salt ions electromigration transport numbers of counter and coions can be calculated based on the data on the diffusion permeability and electrical conductivity of an ionexchange membrane [20]. for a 1:1 electrolyte, the counterion transport number (𝑡𝑔 ∗) is defined as 𝑡𝑔 ∗ = 𝐿𝑔 𝐿𝑔 + 𝐿𝑐𝑜 , (7) where 𝐿𝑔 and 𝐿𝑐𝑜 are the electrodiffusion coefficients of ion transport. their values are found using the following relations: 0 20 40 60 80 100 0 20 40 60 80 100 -i m z , o h m rez, ohm rez chimica techno acta 2021, vol. 8(2), № 20218205 article 5 of 9 𝐿𝑔 = 𝜅𝑚 dc 2𝐹2 (1 + √1 − 2𝐹2 𝑅𝑇 𝑃∗𝑐 𝜅𝑚 dc𝜋± ) 𝐿𝑐𝑜 = 𝜅𝑚 dc 2𝐹2 (1 − √1 − 2𝐹2 𝑅𝑇 𝑃∗𝑐 𝜅𝑚 dc𝜋± ) , (8) where 𝑃∗ is the differential diffusion permeability coefficient at concentration c, m 2 /s, c is the concentration of the external solution, mol/m 3 ; 𝜋± is the correction factor for the nonideality of the solution; f, r, t are the faraday constant, the universal gas constant and the absolute temperature. the differential diffusion permeability coefficient is calculated from the integral diffusion permeability coefficient (𝑃𝑚): 𝑃∗ = 𝑃𝑚 + 𝑐 𝑑𝑃𝑚 𝑑𝑐 . (9) the correction factor for the nonideality of the solution: 𝜋± = 1 + 𝑐 𝑑 ln 𝛾± 𝑑𝑐 , (10) where 𝛾± is the average ionic activity ratio of the electrolyte. 3. results and discussion 3.1. conductivity measurements the results of measuring the electrical conductivity of ionexchange membranes of two batches in a wide range of concentrations are shown in fig. 3. within the microheterogeneous model, the conductivity of a heterogeneous ion-exchange membrane is the geometric mean of the conductivities of the phase of the ionexchange material itself (the so-called “gel”) and the phase of an electrically neutral solution (also called intergel solution). the gel phase includes the polymer matrix of the ion exchanger, the condensed ion pairs counterionfixed group, the solution inside the electric double layer, the reinforcing fabric, and the inert binder. the intergel phase includes a solution that predominantly occupies macropores in the ion-exchange membrane phase. it is generally accepted that such a solution's physicochemical properties do not differ from the properties of an equilibrium external solution. in view of the above, the conductivity of the membrane is expressed as follows: 𝜅𝑚 = (𝑓1 𝜅𝑖𝑠𝑜 𝛼 + 𝑓2𝜅𝑠 𝛼 ) 1 𝛼⁄ , (11) where 𝑓1 and 𝑓2 are the fractions of gel and intergel solutions and 𝑓1 + 𝑓2 = 1; 𝜅𝑚, 𝜅𝑖𝑠𝑜 and 𝜅𝑠 are the electrical conductivities of the membrane, gel and external solution, s/cm; α is the characteristic parameter which describes the spatial distribution of conducting phases in the membrane (α = +1 for parallel and α = –1 for series-connected phases – in real samples the α parameter takes values in range 0.1-0.3). in dilute solutions near the point of isoelectric conductivity (such a value of electrical conductivity when 𝜅𝑚 = 𝜅𝑠 = 𝜅𝑖𝑠𝑜), eq. (11) is simplified: 𝜅𝑚 = 𝜅𝑖𝑠𝑜 𝑓1 𝜅𝑠 𝑓2 . (12) it can be seen that the linearization of the equation in logarithmic coordinates lg 𝜅𝑚 = 𝑓(lg 𝜅𝑠) . makes it possible to determine the value of the parameter 𝑓2. the found values of the parameter 𝑓2 and the coordinates of the isoelectric conductivity point for the membranes under study are given in table 3. table 3 values of coordinates of the point of isoelectric conductivity and transport-structural parameter 𝑓2 for the studied ionexchange membranes membrane* 𝑓2 𝜅𝑖𝑠𝑜, ms/cm 𝑐𝑖𝑠𝑜, mol/l mk-40 1 0.10 5.0 0.046 mk-40 2 0.12 6.0 0.056 ralex cm 1 0.06 3.6 0.032 ralex cm 2 0.03 4.0 0.037 ma-41 1 0.12 1.9 0.017 ma-41 2 0.14 2.8 0.025 ralex amh 1 0.04 4.3 0.039 ralex amh 2 0.07 4.6 0.042 * the number near the membrane name indicates the batch a b fig. 3 concentration dependence of the electrical conductivity of the ion-exchange membranes batch 1 (a) and batch 2 (b). membranes: 1 – mk-40, 2 – ma-41, 3 – ralex cm, 4 – ralex amh 0 1 2 3 4 5 6 7 8 9 10 0 0.2 0.4 0.6 0.8 1 1.2 κ , m s /c m nacl concentration c, mol/l 1 2 3 4 0 1 2 3 4 5 6 7 8 9 10 0 0.2 0.4 0.6 0.8 1 1.2 κ , m s /c m nacl concentration c, mol/l 1 2 3 4 chimica techno acta 2021, vol. 8(2), № 20218205 article 6 of 9 it can be seen that for heterogeneous ralex membranes, the value of the 𝑓2 parameter is comparable to the value of this parameter for homogeneous membranes. such values of this parameter were obtained in other works [24–26]. in [24], the authors suggested that such a value of the fraction of the intergel solution for these membranes is a consequence of the fact that the particles of the ion exchanger in these membranes are small enough and, at the same time, there are no macroscopic cavities inside the membrane, which electrically neutral solutions can occupy. these structural features of ralex membranes were demonstrated by akberova et al. [27] and slouka et al. [28]. from the point of view of the influence on reverse electrodialysis, a large value of the parameter 𝑓2 (characteristic of heterogeneous membranes mk-40, ma-41), on the one hand, provides high electrical conductivity. this difference is especially large in dilute solutions (fig. 3). on the other hand, the electrically neutral solution in the membrane’s pores causes the decrease in selectivity. another factor that attracts attention is large scatter of electrical conductivity values among the samples under study (fig. 3). according to veerman, commercial membranes are not chemical compounds with unchanging properties; different lot numbers, years of production, and storage conditions can influence their properties [29]. 3.2. diffusion permeability as already mentioned in the introduction, the membrane potential is significantly influenced by the selectivity of the membranes. diffusion permeability is a value that characterizes the non-selective flux of electrolyte through an ion-exchange membrane. the results of measuring the diffusion permeability of the studied ion-exchange membranes are shown in fig. 4. the results obtained for diffusion permeability also differ significantly for all studied membranes. for some samples, the results obtained when measuring the diffusion permeability correlate well with the results obtained when studying the electrical conductivity. for ralex membranes, low values of the 𝑓2 parameter are characteristic, which is reflected in the low dependence of the integral coefficient of diffusion permeability on the concentration of the external solution. at the same time, for the second batch, despite the same low value of the 𝑓2 parameter, the diffusion permeability is comparable to the diffusion permeability of mk-40 and ma-41 membranes. meanwhile, no such dependence was revealed for mk-40 and ma-41 membranes. despite the different values of the integral coefficients of diffusion permeability obtained for different samples, the nature of the relationship between them does not change significantly. to calculate the transport numbers according to eq. (8), the differential (also sometimes called “local” [26]) diffusion permeability coefficient is used. in contrast to the experimentally determined integral coefficient of diffusion permeability, which is the average value over the entire thickness of the ion-exchange membrane, the differential coefficient corresponds to the diffusion permeability of a thin ion-exchange film in equilibrium with a “virtual solution” with a certain concentration c at a point in space x. to move from one coefficient to another, the following transformation is usually employed: 𝑃∗ = 𝑃𝑚 + 𝑐 𝑑𝑃𝑚 𝑑𝑐 = 𝑃𝑚 𝛽𝑗 , (13) where 𝛽𝑗 = 𝑑 lg 𝑗𝑚 𝑑 lg 𝑐⁄ is the parameter which characterizes the concentration profile in the ion-exchange membrane [30] (linear at 𝛽𝑗 = 1, convex at 𝛽𝑗 > 1 or concave at 𝛽𝑗 < 1). the parameter values found on the basis of experimental data are shown in table 4. a b fig. 4 concentration dependence of the diffusion permeability of the ion-exchange membranes batch 1 (a) and batch 2 (b). membranes: 1 – mk-40, 2 – ma-41, 3 – ralex cm, 4 – ralex amh 0 5 10 15 20 25 0 0.2 0.4 0.6 0.8 1 1.2 p m ·1 0 8 , c m 2 /s nacl concentration c, mol/l 1 2 3 4 0 5 10 15 20 25 0 0.2 0.4 0.6 0.8 1 1.2 p m ·1 0 8 , c m 2 /s nacl concentration c, mol/l 1 2, 3, 4 chimica techno acta 2021, vol. 8(2), № 20218205 article 7 of 9 table 4 parameter 𝛽𝑗 values found for the studied ion-exchange membranes membrane mk-40 1 mk-40 2 ma-41 1 ma-41 2 ralex cm 1 ralex cm 2 ralex amh 1 ralex amh 2 𝛽𝑗 1.39 1.35 1.36 1.26 1.22 1.43 1.02 1.39 3.3. transport numbers and ocv according to the microheterogeneous model, the transport numbers are determined by the combined action of two factors – the electrical conductivity of the membrane (which is mainly determined by the counterion transport) and its diffusion permeability (which is determined by the co-ion transport). moreover, both of these parameters depend on each other [30]. thus, membranes with high diffusion permeability are characterized by high electrical conductivity in concentrated solutions. the counterion transfer number for membranes with higher diffusion permeability will be lower, since high diffusion permeability means more co-ions are present in the membrane phase. high electrical conductivity, especially in dilute solutions, is a very important characteristic for the reverse electrodialyzer process, since it allows to reduce the internal resistance losses of the electromembrane stack. counterion transport numbers were calculated using eq. (7). the results are presented in fig. 5. it can be seen that for different samples of ralex membranes, despite the detected differences in electrical conductivity and diffusion permeability, the transport numbers differ insignificantly, both for cation-exchange and anion-exchange membranes. the maximum difference in concentrated (1 mol/l) solutions is negligible for ralex cm and ±0.01 for ralex amh. for mk-40 and ma-41 membranes, the situation is drastically different. for mk-40 membrane, the difference in transfer numbers reaches ±0.05. the largest scatter was obtained for the ma-41 membrane, where, depending on the sample, the difference is ±0.1. the low selectivity of the mk-40 and ma-41 membranes negatively affects the open circuit potential (ocv) and the power density of the reverse electrodialysis process. we used eq. (2) and the results obtained to calculate the ocv. let us assume that black sea water (brine solution) is used as working solution, the concentration of which in terms of sodium chloride is 20 g/l, and “river water” (dilute solution) with a concentration of 0.2– 0.5 g/l nacl. the number of membranes of each type is n = 9. table 5 shows the results of calculating the ocv for the “best” (denoted by “+”) and “worst” (denoted by “-”) membrane pairs among ralex and mk-40 and ma-41 membranes. a b fig. 5 concentration dependence of the counterion transport number for cation-exchange (a) and anion-exchange (b) membranes. batch 1 (a) and batch 2 (b). membranes: 1, 1’ – mk-40, 2, 2’ – ma-41, 3, 3’ – ralex cm, 4, 4’ – ralex amh. membranes from batch 1 (1, 2, 3, 4) and membranes from batch 2 (1’, 2’, 3’, 4’). table 5 the magnitude of the open circuit potential for various membrane pairs investigated in this work membrane pair mk-40 (batch 2) ma-41 (batch 2) mk-40 (batch 1) ma-41 (batch 1) ralex cm (batch 1) ralex amh (batch 1) ralex cm (batch 1) ralex amh (batch 2) ideal selectivity** experimental*** ocv, v 1.65 1.56 1.66 1.65 1.70 1.69 quality* + – + – n/a n/a * “+” sign means the best possible membrane pair, a “-” sign means the worst possible membrane pair ** calculated using eq. (2) with 𝑇cem + = 𝑇aem − = 1 *** experimental value obtained for membrane pair ralex cm/ralex amh 0.9 0.92 0.94 0.96 0.98 1 0 0.2 0.4 0.6 0.8 1 1.2 c o u n te ri o n t ra n s p o rt n u m b e r t g * nacl concentration c, mol/l 1 1' 3, 3' 0.7 0.75 0.8 0.85 0.9 0.95 1 0 0.2 0.4 0.6 0.8 1 1.2 c o u n te ri o n t ra n s p o rt n u m b e r t g * nacl concentration c, mol/l 2 2' 4' 4 chimica techno acta 2021, vol. 8(2), № 20218205 article 8 of 9 as one can see from table 5, the “best” pair mk-40 (batch 2)/ma-41 (batch 2) shows results comparable to ralex membranes. however, in the case of the “worst” set of characteristics, the ocv potential is significantly lower both for all studied membranes and for the case of “ideal selectivity”. among the ralex membranes, there is no significant difference between the “best” and “worst” results. in addition, the experimental results obtained exceed those calculated for a given membrane pair, which may be because nine cation-exchange and nine anion-exchange membranes are used in the electrodialyzer; thus, the obtained characteristics are averaged over the properties of these membranes. 4. conclusions this work shows the possibility of using a microheterogeneous model for describing the properties of ion-exchange membranes and calculating the characteristics of a reverse electrodialyzer using the data obtained. we studied the properties of eight samples of heterogeneous cationexchange membranes (two samples of each type of membrane). the samples differed in the year of issue and storage conditions. it has been shown that for heterogeneous ion-exchange membranes mk-40 and ma-41, the properties of the samples can differ significantly. both the electrical conductivity (higher for batch 2) and diffusion permeability (lower for batch 2) differ, which ultimately leads to a wide scatter of the obtained values of the transfer numbers of counterions. for ralex membranes, such significant differences were not observed between different samples, with the exception of the extremely low diffusion permeability of the ralex amh membrane (batch 1). the possibility of calculating the transfer numbers and predicting the open-circuit potential on this basis will allow in the future selecting the best membrane pairs for the reverse electrodialysis process based on measuring their physicochemical characteristics. the data obtained from these measurements on the electrical conductivity of ion-exchange membranes can also be used to calculate the ohmic components of the internal resistance of the electrodialyzer. the latter characteristic, in turn, will allow calculating not only the open circuit potential, but also the theoretical power. acknowledgements the research was carried out with the financial support of the kuban science foundation in the framework of the scientific project № ifr-20.1/110. references 1. strathmann h. electrodialysis, a mature technology with a multitude of new applications. desalination. 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ekaterinburg 620990, russia. * corresponding author: natalia.tarasova@urfu.ru this paper belongs to a regular issue. © 2022, the authors. this article is published in open access under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). abstract the creation of highly efficient and eco-friendly energy sources such as hydrogen energy systems is one of main vectors for the sustainable development of human society. proton-conducting ceramic materials can be applied as one of the main components of such hydrogen fueled electrochemical devices, including protonic ceramic fuel cells. the oxyanion doping strategy is a promising approach for improving transport properties of proton-conducting complex oxides. in this paper, this strategy was applied to proton-conducting layered perovskites for the first time. the phosphorus-doped protonic conductors based on balaninno3n+1 (n = 1, 2) were obtained, and their electrical conductivity was thoroughly investigated. it was found that the phosphorous doping leads to an increase in the electrical conductivity values by ~0.7 orders of magnitude. keywords layered perovskite oxyanion doping phosphorus doping proton conductivity balaino4 bala2in2o7 received: 20.06.22 revised: 05.07.22 accepted: 05.07.22 available online: 12.07.22 key findings ● the oxyanion doping strategy is a promising method for improving transport properties of protonconducting layered perovskites. ● the phosphorous-doping leads to a considerable increase of electrical conductivity of the balain0.9p0.1o4.1 and bala2in1.9p0.1o7.1 compared to the p-free materials. 1. introduction the creation of high-efficiency and eco-friendly energy source is one of main objectives for the sustainable global development of human society [1−8]. hydrogen energy belongs to the renewable energy industry and includes the systems for storage, transport and using of hydrogen for power generation [9−12]. proton-conducting ceramic materials can be applied as the one of main component of such hydrogen-based electrochemical devices for various purposes, including electricity generation in protonic ceramic fuel cells, pcfcs [13−25]. the most studied protonic conductors have perovskite or perovskite-related structures [26−30]. doping of cationic sublattices is a common way for improving their transport properties. however, the anion [31−35] and oxyanion [36, 37] doping methods can increase proton conductivity in the complex oxides as well. the oxyanion doping strategy is based on the displacement of the [bo6] octahedra to the [b'o4] tetrahedra such as phosphate, sulphate and silicate (figure 1). slater et al. proved the validity of this strategy for the protonconducting materials, studying barium indate, ba2in2o5, as an example [36]. this confirms that substitution [po4] → [ino6] is fundamentally possible, and the proton conductivity in such compositions can be improved by phosphorus doping. figure 1 the scheme of oxyanion doping strategy of layered perovskites. http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2022.9.4.05 mailto:natalia.tarasova@urfu.ru http://creativecommons.org/licenses/by/4.0/ https://orcid.org/0000-0001-7800-0172 https://orcid.org/0000-0003-4346-5644 https://crossmark.crossref.org/dialog/?doi=https://doi.org/10.15826/chimtech.2022.9.4.05&domain=pdf&date_stamp=2022-7-12 chimica techno acta 2022, vol. 9(4), no. 20229405 letter 2 of 6 barium lanthanum indates, balaino4 and bala2in2o7, have a layered perovskite structure and can be written using a general formula, balaninno3n+1 (n = 1, 2). they belong to the newly opened class of proton-conducting solid oxide materials [38−49]. it was proved that they are nearly pure (~95–98 %) protonic conductors under wet air below 350–400 °c [50]. different ways of cationic (isoand heterovalent) doping lead to increasing the protonic conductivity up to ~1.5 orders of magnitude (from 2∙10–7 s cm–1 for balaino4 to 8∙10–6 s cm–1 for ba1.1laino3.95 at 400 °c) [51−56]. based on this fact, the other doping strategies, such as oxyanion (phosphorus) doping, can be applied to these materials. the reason of this materials search is necessity to create highconductive proton conductors with the layered perovskite structure because the promising cathode materials based on nickelates lanthanides [57−60] belong to the layered perovskites as well. in the present study, the oxyanion doping strategy was applied to the proton-conducting layered perovskites for the first time. the phosphorus-doped protonic conductors based on balaninno3n+1 (n = 1, 2) were obtained, and electrical conductivity of ceramic samples was investigated. 2. experimental the complex oxides of balain0.9p0.1o4.1 and bala2in1.9p0.1o7.1 were obtained by a solid state method. firstly, high-purity starting powder materials were dried and the stoichiometric amounts of the reagents were weighed on a sartorius analytical balances (goettingen, germany). the chemical reactions can be presented in as: baco3 + 0.5la2o3 + 0.45in2o3 + 0.1nh4h2po4 → balain0.9p0.1o4.1 + 0.1nh3 + 0.15h2o + co2 (1) baco3 + la2o3 + 0.95in2o3 + 0.1nh4h2po4 → bala2in1.9p0.1o7.1 + 0.1nh3 + 0.15h2o + co2 (2) further, the milling of all reagents in an agate mortar followed by calcination of the obtained mixtures was made. the calcination was performed in a temperature range from 800 to 1300 °с with a step of 100 °с and 24 h of time treatments. the x-ray diffraction (xrd) studies were performed by a bruker advance d8 diffractometer (rheinstetten, germany) with a cu kα radiation with a step of 0.01o and at a scanning rate of 0.5o min–1. the morphology and chemical composition of the samples were studied using a phenom prox desktop scanning electron microscope (waltham, ma, usa) (sem) integrated with an energy-dispersive xray diffraction (eds) detector. for the investigations of the electrical properties, the pressed cylindrical pellets (1300 °c, 24 h, dry air) were obtained. the samples had a relative density of ~90% (density of the sintered samples was determined by the archimedes method). the ac conductivity measurements were performed by a z-1000p (elins, rf) impedance spectrometer within a frequency range of 1–106 hz. electrical measurements were performed using pt paste electrodes (sintering at 1000 °c for 2 h). the temperature dependencies of electrical conductivity were obtained in a temperature range 200–1000 °c (step 10–20 °c, 1 °c min–1 cooling rate). these investigations were performed under “dry” and “wet” air atmospheres. the dry air was produced by circulating the gas through p2o5 (ph2o = 3.5·10−5 atm). the wet air was obtained by bubbling the gas at room temperature first through distilled water and then through a saturated solution of kbr (ph2o = 2·10−2 atm). the humidity of the gas was controlled by a honeywell hih-3610 h2o-sensor (freeport, usa). 3. results and discussions the xrd analysis of the powder samples balain0.9p0.1o4.1 and bala2in1.9p0.1o7.1 confirmed the single phase for both compositions. the xrd-patterns for the compositions of balain0.9p0.1o4.1 and bala2in1.9p0.1o7.1 are presented in the figure 2 and 3 correspondingly. phosphorous-doped balain0.9p0.1o4.1 and bala2in1.9p0.1o7.1 samples are isostructural to theirs matrix compositions, balaino4 and bala2in2o7, correspondingly. the monolayer balain0.9p0.1o4.1 composition belongs to the pbca space group (orthorhombic symmetry), and the twolayered composition of bala2in1.9p0.1o7.1 crystallizes in the p42/mnm space group (tetragonal symmetry). the values of lattice parameters and unit cell volume are presented in table 1. figure 2 the xrd-results for balain0.9p0.1o4.1 composition. the sem-image is presented in the inset. chimica techno acta 2022, vol. 9(4), no. 20229405 letter 3 of 6 figure 3 the xrd-results for bala2in1.9p0.1o7.1 composition. the sem-image is presented in the inset. table 1 the lattice parameters and unit cell volume of investigated compositions. composition a, å b, å c, å v, å3 balaino4 [50] 12.932 5.906 5.894 450.19 balain0.9p0.1o4.1 12.803 5.939 5.906 449.04 bala2in2o7 [50] 5.891 5.891 20.469 710.520 bala2in1.9p0.1o7.1 5.909 5.909 20.868 728.605 as can be seen, phosphorous-doping leads to a change in these characteristics for both doped compositions compared with undoped. the oxyanion doping for the monolayer composition of balaino4 leads to a decrease in the a parameter and to an increase in the b and c parameters. the applying of this doping strategy to the two-layered compositions of bala2in2o7 leads to an increase of all (a, b and c) lattice parameters. as it is known [61], the ionic radius of phosphorous is smaller than ionic radius of indium (r(p5+) = 0.38 å, r(in3+) = 0.8 å). however, the displacement of [ino6] octahedra to the [po4] tetrahedra should inevitably lead to the appearance of local distortions and to a redistribution of bond lengths in the crystal structure. the microphotography (sem-image) of the bala2in1.9p0.1o7.1 powder sample is presented in the inset of figure 3. this composition consists of grains ~5 μm, forming agglomerates of ~15−30 μm. the electrical conductivity was measured by the impedance spectroscopy method. the nyquist-plots for balain0.9p0.1o4.1 composition obtained under dry air are presented in the figure 4a, b. the fitting of the spectra was made using zview software, and the obtained results are presented in the table 2. according to the fitting of the spectra (red line) with using the equivalent circuit presented in the figure 4c, three different electrochemical processes can be defined. as it was shown earlier [51], the nyquist-plots for undoped balaino4 composition were represented by one visible semicircle with a capacitance of around 10–11 f. for the calculation of electrical conductivity, the bulk resistance values (r1) were used and discussed below. it can be noted, that due to a small depression of the semicircles, the constant phase element (cpe) was used during the analysis of nyquist plots. the results of the electrical conductivity investigations are presented in the figure 5. as can be seen, phosphorous-doping leads to an increase in the conductivity values for both monolayer (balaino4) and two-layered (bala2in2o7) compositions and. the conductivity growth is about 0.7 orders of magnitude for both compositions. we can assume that such increasing electrical conductivity is due to two factors. firstly, an increase in the lattice parameters for the layered perovskites of balaninno3n+1 results in a higher conductivity due to facilitating ionic transport [50]. secondly, the phosphorous-doping can be considered as a donor doping (p5+ → in3+) that causes the appearance of interstitial (“additional”) oxygen in the structure. it is obvious that an increase in the concentration of charge carriers (oxygen ions) should lead to the corresponding increase in the conductivity as well. the change in atmospheric humidity also affects the electrical conductivity values (figure 5). the air humudification leads to an increase in the conductivity values at low temperatures (450 °c). figure 4 the nyquist-plots obtained at the different temperatures under dry air for the composition balain0.9p0.1o4.1: 600 °с (a), 500 °с (b), and the equivalent circuit of fitting (red line) (c). chimica techno acta 2022, vol. 9(4), no. 20229405 letter 4 of 6 table 2 results of nyquist-plots fitting, where cpe is the constant phase element (f) and the r is the resistance (kω). element value (600 °с) value (500 °с) cpe1 2.1∙10−12 3.6∙10−12 r1 11 280 cpe2 4.5∙10−10 4.8∙10−10 r2 4.5 40 cpe3 3.4∙10−7 5.1∙10−7 r3 2 70 0.8 1.0 1.2 1.4 1.6 1.8 -9 -8 -7 -6 -5 -4 -3 -2 (a) 10 3 /т, к -1 lo g  ( s /c m ) balaino 4 balain 0.9 p 0.1 o 4.1 0.8 1.0 1.2 1.4 1.6 1.8 -9 -8 -7 -6 -5 -4 -3 -2 (b) balain 0.9 p 0.1 o 4.1 bala 2 in 2 o 7 lo g  ( s /c m ) 10 3 /т, к -1 figure 5 the temperatures dependencies of conductivity for the compositions balain0.9p0.1o4.1 (a) and bala2in1.9p0.1o7.1 (b) under dry (filled symbols) and wet (open symbols) air. because layered perovskites balaino4 and bala2in2o7 are capable for the dissociative absorption of water from the gas phase [50], the reason of better conductivity is the appearance of proton contribution of conductivity. it can be concluded that the oxyanion doping strategy can be applied for layered perovskites for improving their transport properties. 4. conclusions in this paper, the oxyanion doping strategy was purposefully applied to the proton-conducting layered perovskites for the first time. the phosphorus-doped protonic conductors based on balaninno3n+1 (n = 1, 2) were obtained, and their electrical properties were investigated. the balain0.9p0.1o4.1 and bala2in1.9p0.1o7.1 oxides were obtained for the first time. it was found that the phosphorousdoping leads to an increase in the electrical conductivity values by ~0.7 orders of magnitude. the oxyanion doping strategy is a promising method for improving transport properties of proton-conducting layered perovskites. supplementary materials no supplementary materials are available. funding this research was performed according to the budgetary plan of the institute of high temperature electrochemistry and funded by the budget of russian federation. acknowledgments none. author contributions conceptualization: n.t. data curation: a.g., n.t. methodology: n.t. validation: a.g., n.t. visualization: a.g., n.t. writing – original draft: n.t. writing – review & editing: n.t. conflict of interest the authors declare no conflict of interest. additional information author ids: natalia tarasova, scopus id 37047923700; anzhelika galisheva, scopus id 57195274932. https://www.scopus.com/authid/detail.uri?authorid=37047923700 https://www.scopus.com/authid/detail.uri?authorid=57195274932 chimica techno acta 2022, vol. 9(4), no. 20229405 letter 5 of 6 website: institute of high temperature 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tusseyev*, aktolkyn k. danlybaeva, saltanat s. raimkul, aizhan a. kiykabaeva, ospan m. doszhanov al-farabi kazakh national university, 050040 al-farabi ave., 71, almaty, kazakhstan * corresponding author: turgaratus@mail.ru this article belongs to the regular issue. © 2021, the authors. this article is published in open access form under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). abstract the paper presents the study results of photo and gamma radiation effect on the beryllium oxide (beo) surface properties. photoadsorption studies of о2 on beo by the methods of infrared (ir) spectroscopy and manometry with a change in the temperature of preliminary annealing from 473 to 1073 k show that samples subjected to preliminary training at 473 k are most active. the maximum of adsorption activity on -irradiated beryllium oxide is observed on the samples annealed at 673 k before the irradiation. the maximum of paramagnetic centers (pmcs) is also observed on samples annealed at this temperature. comparison of electron paramagnetic resonance (epr) and adsorption studies shows that absorption of h2 and o2 leads to the destruction of paramagnetic centers. it is assumed that, upon irradiation, adsorption centers with electron and hole modes are formed on the surface of beo. keywords adsorption irradiation beryllium oxide surface defects spectra temperature received: 19.11.2021 revised: 18.01.2022 accepted: 27.01.2022 available online: 28.01.2022 1. introduction beryllium oxides (beo) [1] are widely used molecules in the nuclear and chemical industries [2, 3]. recently, it was found that beo functions as a catalyst with a developed surface, and its properties (catalytic) are influenced by external factors (e.g., temperature, radiation, etc.) [4]. it is now acceptable that nuclear radiation causes fundamental changes in the physical and chemical properties of materials. the above is largely true for the surface properties of oxide materials [5–11]. the changes in the adsorption properties of a solid body often occur due to radiation defects; thus, the interactions between adsorbates and adsorbents may be studied to determine the nature of these defects. by studying adsorption kinetics, the rate of radiation accumulation on the surface of irradiated materials can be traced to determine energy characteristics, e.g., depth of radiation level in the area and interaction energy with the adsorbate molecule. thus, we can determine the mechanism for transferring energy from the irradiated solid to the adsorbed molecule, and so on [12, 13]. using physical and chemical research methods (electron paramagnetic resonance (epr), infrared (ir), and mass spectrometry), it is possible to investigate the nature of surface radiation defects, their adsorption activities, lifetime, and annealing activation energies. adsorbates with pronounced acceptor (e.g.oxygen) and donor (e.g.hydrogen) properties may act as a "probe" as there will be an electron transfer between donor and acceptor. thus, the effects of radiation on solids with a developed surface and the impact of adsorption processes on irradiated materials are new research fields in electronic and structural factors. the present research makes it possible to understand the role of free and localized charge carriers in elementary acts of catalysis and chemisorption and the ability of adsorbed molecules to serve as traps for electrons and holes, as compared with other trappings of structural defects or impurity atoms located on the surface [14–17]. with sufficient information on these factors, it is possible to generate effective systems with predicted physical and technological properties [18]. therefore, the aim of this work is to study the impact of irradiation on beryllium oxide properties. 2. experimental methods 2.1. preparation of beo surface in this research, beryllium oxide, the grade “for luminophores”, was used to conduct the experiments the irradiation impact. this material had a form of white powder http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2022.9.1.06 http://creativecommons.org/licenses/by/4.0/ chimica techno acta 2022, vol. 9(1), № 20229106 article 2 of 5 with a surface area of 60 m2/g and had impurities of other elements (al, fe, mn, ca, si) from 10–2 to 10–4 weight %. it is well-known that beo is very hygroscopic [19], the weight loss during calcination at 900 °c may be up to 20% of the initial weight; thus, we tried not to overheat beryllium oxide samples. 2.2. characterization the surface properties were characterized using manometeric, infrared spectroscopic and radio spectroscopic methods. the apparatus, on which vacuum-temperature training of samples was carried out and gamma adsorption was studied, has two parallel pumping branches consisting of zeolite-coal adsorption pumps, diffusion pump type, and cooled traps with a heated oil-free high-vacuum valve. preliminary studies had shown that there was no noticeable difference in the measurement results between the two pumping methods. therefore, due to the advantage of the first pumping method consisting in the freedom from contamination by foreline pump oil vapors, we preferred to use it in the experiments. pressure measurements in the adsorbent-gas system in the gamma adsorption experiments were performed using a manometer pre-gauged for the gas used as adsorbate. the temperature in the system was measured using chromel-alumel, chromel-copper, and platinum-platinumrhodium thermocouples. the investigated gases were mainly hydrogen and oxygen. oxygen was obtained by decomposition of potassium permanganate at temperatures above 230 °c and further purified by passing it through a trap cooled with liquid nitrogen. before obtaining the gas, the initial product was held for several hours at a temperature slightly lower than the starting reaction temperature. the electrolysis of distilled water produced hydrogen, which was purified further by diffusion through heated palladium capillary walls and then passed through a trap cooled with liquid nitrogen. the resulting gas was stored in the gas production system for 3–4 h before being pumped out and produced again to avoid contamination. although the gases were thoroughly purified, there were still impurities in their composition. mass spectrometric analysis showed that oxygen contains carbon dioxide and hydrogen has water vapor. the gamma unit with a dose rate in the central channel of 200 rad/s was used as a source of -quanta, with the radiation source being the preparation of the radioactive isotope 60co. the dose was determined using a ferrous sulfate dosimeter. the radiation dose was calculated according to the formula: 𝐷 = 𝑘𝛾𝑀 𝑡 𝑅 2⁄ , (1) where r is the distance in meter; t is time in h; m is isotope activity in millicuries; kγ is the gamma constant, indicating the dose rate of a point source. the following formula was used to calculate the amount of gammaadsorbed gas: n= 3.3∙1016 δpv, (2) where n is the amount of adsorbed gas in mol/g; δp is the pressure drop in mmhg; v is the volume in mm3. pressure measurements and recordings during the adsorbentadsorbent coexposure were remotely made while irradiating samples in the central channel of the gamma unit. the error in the pressure measurement was ~5%. the method of infrared (ir) spectroscopy is one of the most effective methods for the investigation of solid surfaces. this method is widely used as a solution of research and many other problems in physics, chemistry and other sciences [20–22]. an infrared spectrometer (karlzeiss jena type ur-20) was used with an operating frequency range of 5000400 cm–1. to reduce ir scattering, beryllium oxide powder particles were repeatedly sieved and pressed into thin pellets at a pressure of 812 kg/mm. dimensions of the tablets pressed in a special collapsible mould were 30 x 10 mm2 or 35 x 15 mm2, depending on irradiation and examination of the samples. the beryllium oxide tablets were 0.2 mm thick. in case of significant light scattering in the short wavelength range, an aperture was placed in the comparison beam. radiation defects in beryllium oxide irradiated by gamma-rays depending on irradiation dose rate and pretreatment temperature were investigated using an electron paramagnetic resonance (epr) method widely used to study free radicals in various paramagnetic centers formed in the material during the action of ionizing radiation [23, 24]. before irradiation, beryllium oxide was subjected to several hours of thermal-vacuum treatment. for one series of experiments, the samples were soldered at a pressure ~10–6 mmhg, and in experiments on co-irradiation of samples with gas, the pressure in ampoules was 10–2 mmhg. after that, the samples were irradiated either in dewars with liquid nitrogen or at room temperature. the adsorption and epr spectra were studied in the same ampoules made of molybdenum glass, giving an intense epr signal when irradiated. before the measurements, the ampoules were annealed in a soft flame of a gas burner, and the sample was transferred to the other end of the ampoule and kept either in liquid nitrogen or at room temperature. before irradiation, the beo samples were transferred back into the annealed end of the ampoule. the annealing operation is superfluous when working with luch glass ampoules, as it is practically not activated under radiation. in this work, radio spectrometers of centimeter (λ = 3.2 cm) and decimeter ranges (λ = 30 cm) were used to capture epr spectra. the sensitivity of the spectrometer is ~1013 unpaired spins in the sample by diphenylpicrylhydrosyl (dpph). the resolution of the device was 0.2 oe. the width of the epr position spectrum lines and the value of the splitting between the components of the superfine structure were calculated chimica techno acta 2022, vol. 9(1), № 20229106 article 3 of 5 from the chart tape of the recorder. the epr spectra were recorded at room temperature or liquid nitrogen temperature at constant microwave power and instrument sensitivity. dpph and mn+2 samples in magnesium oxide, whose positions relative to the sample are strictly fixed, and cucl2∙5h2o containing a known amount of paramagnetic particles were used as reference sources in these studies. the g-factors of irradiated beo were calculated by the standard method. the reference sources were located either in the dewar or directly in the resonator of the spectrometer. before irradiation, samples were annealed for 68 h in air; the same amounts were annealed in a vacuum at 400 °c. irradiation with 60co γ-rays was carried out at dose rate j = 14.4 r/s. experiments on radiation adsorption kinetics were done at an initial pressure of oxygen and hydrogen of ro = 8.510–15.10–2 torr. ir spectroscopic studies were carried out in the absorption spectrum range of υ = 30004000 cm–1. epr studies were performed in both centimeter and decimeter ranges at both room temperature and liquid nitrogen temperature. 3. results and discussion above we described the experiments carried out in this research. detailed studies of the radiation adsorption regularities of hydrogen and oxygen were presented on beo samples trained at 473–1023 k in a radiation field. fig. 1 demonstrates ir absorption spectra of irradiated beo obtained during the experiments. the inlet of o2 and exposure to beo at 673–773 k decreased the intensity of absorption bands of isolated oh-groups of type 1 (3750 cm–1), resulting in the appearance of weak peaks of 3680–3720 cm–1 and constant growth of the band of isolated oh-groups (3630 cm–1). fig. 1 ir absorption spectra of -irradiated beo: 1 – initial spectrum before irradiation; 2 – spectrum after irradiation, d = 0.024 mgy; 3 – puffing of h2; 4 – in 2.5 h after puffing; 5 – in 5 h after puffing with tpr = 873 k it was assumed that the decrease in the intensity of the 3750 cm–1 band and the appearance of peaks at 3680–3720 cm–1 are due to the participation of type 1 oh-groups, which play the role of protons in the hydrogen bonding in the oxygen adsorption. in the ir spectrum, along with a decrease in the intensity of hydroxyl groups (primarily the 3740 cm–1 band), bands at 3580 and 3680 cm–1 appear, corresponding to adsorbed water and hydrogen-bonded oh groups (fig. 1). as can be seen from fig. 2, due to preliminary annealing of samples at 1073 k, oxygen puffing did not cause any changes in the infrared spectrum of beo, suggesting sintered surfaces. fig. 2 represents dose dependence of radiation adsorption of gases on beryllium oxide. this figure shows that the amount of adsorbed gas changed symbatically with the initial pressure and radiation dose while the initial adsorption rate of hydrogen was greater than oxygen. however, at the same initial pressure, for hydrogen adsorption, lower doses were required for saturation compared with oxygen. fig. 2 dose dependence of radiation adsorption of gases on beryllium oxide: 1 – hydrogen adsorption, 2 – oxygen adsorption (p = 113 pa) fig. 3 presents a graphical representation of the kinetics of radiation adsorption of o2 on the beo surface. fig. 3 kinetics of radiation adsorption of o2 by beo: 1 – ро=110 –1, 2 – 1.210–1, 3 – 0.510–1, 4 – 8.510–1 mmhg chimica techno acta 2022, vol. 9(1), № 20229106 article 4 of 5 the result shows that radiation adsorption of oxygen depends on the initial oxygen pressure, i.e., the surface coverage. however, the maximum adsorption activity was observed on samples heated before exposure at 673 k on -irradiated beo, as shown in fig. 4 demonstrating temperature dependence of gamma-adsorption of o2 on beryllium oxide. fig. 4 distribution in temperature dependence of -adsorption of o2 on beo (ро = 910 –2 mmhg) d: 1 – 0.4; 2 – 1.2; 3 – 2.4; 4 – 4.8; 5 – 18.6 mrad the maximum number of paramagnetic centers was also observed at a temperature around 400 c, i.e., 673 k, as shown in fig. 5 demonstrating dose dependence of paramagnetic centers on beo samples that were calcined before irradiation at different temperatures (tc). fig. 5 dose dependence of paramagnetic centers on beo: 1 – tpr = 200 °с; 2, 4 – 400 °с; 3 – 600 °с; 4 – leak-in of o2 (λ = 30 cm) besides, the adsorption of hydrogen caused a decrease in pmc numbers (fig. 6), indicating adsorption of hydrogen on hole centers and the resulting destruction of such centers. moreover, during the oxygen adsorption, an increase in the epr signal is observed, possibly due to the adsorption of oxygen in the paramagnetic form o2. thermal desorption of adsorbed h2 and o2 occurred at temperatures >423 k. besides, oxygen had two peaks of excitation within 453–533 k and 573–673 k, corresponding to characteristic ranges of hydrogen-bonded and coordination-bonded molecular release, respectively. fig. 7 shows dose dependence of pmc in beo (1) containing adsorbed o2 (2) and adsorbed h2 (3). fig. 6 epr spectra of gamma-irradiated beo (a) with absorbed o2 (b), with adsorbed h2 (d = 60 mrad) (c). the irradiation and measurement temperature are ambient fig. 7 dose dependence of pmc on beo (1) containing adsorbed o2 (2) and adsorbed h2 (3) fig. 8 presents the annealing of paramagnetic centers on -irradiated beo (dose of radiation, d = 18.6 mrad). the annealing of adsorption and paramagnetic centers ended at different temperatures as the adsorption centers were annealed completely at 673 k, while the pmcs are retained at high temperatures, as described in fig. 8. it is possible that paramagnetic centers, in contrast to adsorption centers, are also formed in the amount of the sample and, therefore, have higher temperature resistance. a comparison of infrared spectroscopy, epr, and manometric data indicated that the -adsorption centers for oxygen and hydrogen are paramagnetic centers with electron and hole regimes. thus, secondary processes involving surface hydroxyl groups and adsorbed molecules are possible. further, the possibility of oxidation of organics in the presence of organic matter can not be excluded in this research. fig. 8 annealing of paramagnetic centers on gamma-irradiated beo. (dn = 18.6 mrad). a – t = 20, b – 60, c – 120, d – 170, e – 240, f – 360, g – 460, 3 – 480 °c 0 200 400 600 800 0 2 4 6 8 10 12 14 t, o c x10 17 n, mol / g 1 2 3 5 4 0 20 40 60 80 100 120 0 10 20 30 y, otn.yed. d, mrad 1 2 3 chimica techno acta 2022, vol. 9(1), № 20229106 article 5 of 5 4. conclusions in summary, a comparison of electron paramagnetic resonance and adsorption studies indicates that absorption of h2 and o2 leads to the destruction of paramagnetic centers, which provides the evidence of formation of adsorption centers with electron and hole regimes on the beo surface. at the same time, the discrepancy between the absorption dose ranges (up to 0.3 mgy for adsorption and 0.6 mgy and more for epr centers) and the annealing temperature (573–673 k and below are adsorption centers, 723 k and above are paramagnetic centers) indicates that these types of centers are not identical. it can be assumed that both surface and bulk paramagnetic centers are formed upon irradiation. the 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https://doi.org/10.1088/1757-899x/1047/1/012187 https://doi.org/10.1016/j.jallcom.2021.160105 https://doi.org/10.1088/1757-899x/919/2/022049 https://doi.org/10.1016/0272-8842(90)90045-h https://doi.org/10.1016/j.jmmm.2018.11.081 morphological and structural features of the cdxpb1−xs films obtained by cbd from ethylenediamine-citrate bath chimica techno acta article published by ural federal university 2021, vol. 8(2), № 20218210 eissn 2411-1414; chimicatechnoacta.ru doi: 10.15826/chimtech.2021.8.2.10 1 of 8 morphological and structural features of the cdxpb1−xs films obtained by cbd from ethylenediamine-citrate bath a.d. kutyavina a,* , l.n. maskaeva a,b , v.i. voronin c , i.а. anokhina d , v.f. markov a,b a: ural federal university named after the first president of russia b.n. yeltsin, 620002, 19 mira st., yekaterinburg, russia b: ural institute of the state fire service of the emercom of russia, 620062, 22 mira st., yekaterinburg, russia c: m.n. miheev institute of metal physics, ural branch of russian academy of sciences, 620108, 18 s. kovalevskaya st., yekaterinburg, russia d: institute of high temperature electrochemistry, ural branch of the russian academy of sciences, 620990, 20 akademicheskaya st., yekaterinburg, russia * corresponding author: n-kutyavina@mail.ru this article belongs to the regular issue. © 2021, the authors. this article is published in open access form under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). abstract the calculating of ionic equilibria in the system «pb(ch3coo)2  cdcl2  na3c6h5o7  ‎(nh3)2(ch2)2  n2h4cs» allowed us to find conditions and concentration regions of pbs and cds co-deposition. the determined conditions provided the cbd obtaining of cdxpb1−xs (0 ≤ x ≤ 0.033) substitutional solid solutions films with a cubic structure b1 (space group fm3̅𝑚) with the grains preferred orientation (200). we established the evolution of the surface morphology of the synthesized films from cubic crystallites to hierarchical structure of globular aggregates by scanning electron microscopy. a quantitative analysis of diffraction patterns showed a decrease of microstrains in cdxpb1−xs films by a about factor of 3 with an increase of the cadmium chloride concentration in the reaction mixture from 0.005 to 0.14 mol/l. the excess of the cadmium content, established by edx analysis, in the studied films as compared to its content in the solid solution is associated with the additional formation of the amorphous cds phase up to 72 mol %. keywords ethylenediamine-citrate bath boundary conditions chemical bath deposition thin films cdxpb1−xs solid solutions received: 22.03.2021 revised: 01.06.2021 accepted: 08.06.2021 available online: 10.06.2021 1. introduction ternary compounds in the cds-pbs system, f.e. the cdxpb1−xs substitutional solid solutions, have been attracting interest among the researchers of semiconductor structures for half a century. the possibility of regulating the band gap from small of pbs (0.4 ev) to rather big of cds (2.42 ev) value finds application in the production of heterojunctions and solar cells based on these substances [1-2]. the cdxpb1−xs photosensitivity in the range of 0.43.1 μm is used to create ir detectors [3-4]. the developed morphology of the layer surface facilitates using these thin-film compounds as sensitive elements for the determination of toxic compounds in gas and liquid media [5]. various nanoscale structures are constructed on the basis of cdxpb1−xs solid solutions, in particular, quantum dots, nanocrystals, and nanowires [6-8]. the thin-film cdxpb1−xs solid solutions have the unique functional physical and chemical properties. semiconductor or ionic conductivity, mechanical, thermal, and radiation resistance of these compounds can be controlled by changing the cadmium content or particle sizes making up the film. also, we can note relative simplicity of their preparation. many researchers prefer chemical deposition from aqueous solutions (chemical bath deposition, cbd) [1-5,8-20]. this method allows obtaining cdxpb1−xs solid solutions both in powder and thin-film states on substrates of any nature and configuration without complex technological equipment. the chemical bath deposition essence of semiconductor compounds is the interaction of metal cations and s 2– anions in solution. the sources of those ions are the metal salt and chalcogenizer, respectively. ligands allow regulating the amount of free metal ions in the reactor due to http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2021.8.2.10 http://creativecommons.org/licenses/by/4.0/ https://orcid.org/0000-0002-1489-1137 chimica techno acta 2021, vol. 8(2), № 20218210 article 2 of 8 the gradual dissociation of complex compounds. consequently, the rate of solid phase formation reduces leading to form a film structure. in situ control the morphology, composition, structure, and semiconducting properties of cdxpb1−xs is possible by varying the components concentrations in the reaction mixture and the deposition conditions (ph of the medium, temperature and duration of synthesis) [9-11], as well as by using different substrates [12]. a typical reaction mixture for the cdxpb1xs solid solutions production by cbd includes lead and cadmium salts, mainly pb(ch3coo)2, pb(no3)2 and cdcl2; thiourea (nh2)2cs and various alkaline agents: sodium hydroxide naoh, aqueous ammonia solution nh4oh, ethylenediamine (nh2)2(ch2)2. as for the ligand, different research groups use various substances as complexing agents: triethanolamine (c6h15no3), aqueous ammonia (nh4oh), ethylenediamine (c2h8n2), sodium citrate (na3c6h5o7), or a combination thereof. it should be noted that ligands play a key role in the nucleation and growth of a new phase and directly affect the properties of the resulting layers. in a number of works it is quite popular to use either triethanolamine together with an alkaline agent naoh [13] or an aqueous solution of ammonia [1,17-19], or their combination [10,17,19]. however, the instability of triethanolamine complexes with both lead and cadmium promotes the rapid transformation of these metal ions into sulfide and the aggregation of sulfide particles in the bulk of the solution. solid phase precipitates at the reactor bottom in the powder form, reducing the thickness of the cdxpb1−xs layer. the use of an ammonia aqueous solution as a complex agent [14] leads to formation of a film surface consisting of spherical particles of ~50 nm. their shape is further transformed into a plate-like one with increase in the cadmium salt content in the bath. since ammonia forms stable complexes only with cadmium, in the system under consideration oh – ions act as ligand for pb 2+ ions. the instability constant of the pb(oh)4 2− tetradentate complex (рk1–4,in = 16.3 [19]) significantly exceeds the values of the cd(nh3)n 2− complexes instability constants (рk1-4,in = 6.56 [19]). as a result, free cadmium ions prevail in the solution, which leads to the enrichment of the synthesized layers with cd. thin-film cdxpb1xs structures (x = 0.35; 0.42; 0.49) synthesized by the authors of [2] had a crystal lattice period of 6.0295–6.0227 å. that value is more typical of the wurtzite type cds hexagonal modification (b4, space group p63mc). attempts to obtain the compositions cd0.2pb0.8s and cd0.4pb0.6s in [15] and [16] led to the formation of cds films with pbs inclusions. similar structures consisting of spherical nanoaggregates up to 10 nm were obtained from reaction mixtures containing a mixture of triethanolamine and ammonia as ligands [17, 18]. note that in these publications the authors did not give the true composition of the solid solution, indicating only the elemental composition of the compound. however, the thermodynamic assessment of the solid phases pbs and cds formation [12] showed the possibility of the cadmium cyanamide producing at ph > 10. impurity phases can negatively affect the properties of the obtained semiconductor layers. to reduce the rate of metal ions release into the solution, pentia et al. [4] used the disodium salt of ethylenediaminetetraacetic acid c10h14n2na2o8 (edta) in an ammonia alkaline medium. this ligand provides the strong complexes formation of both lead (pb(edta) 2– рk1,in = 18.04 [19]) and cadmium (cd(edta) 2− рk1,in = 16.46 [19]). as a result, films were obtained consisting of a mixture of cubic and tetrahedral crystallites. the films size particles decreased with an increase in the content of cadmium ions in the reaction bath. despite the fact that in this work a decrease the studied cdxpb1−xs films lattice constant was observed, the authors unreasonably assert that the cadmium content x in the composition of the solid solution can vary in a wide range from 0 to 1 by fitting of the concentration ratio of lead and cadmium salts in a reaction bath. researchers [3,7,11,12,20] used a reaction mixture containing simultaneously two complexing agents: an aqueous solution of ammonia and sodium citrate. it was found that the cdxpb1−xs solid solutions films deposited from this reaction bath mainly consist of faceted particles whose shape and size depend on the composition [20] and the type of substrate [12]. nevertheless, in this system there is a possibility of the formation of individual cds phase [9,12]. the cds deposition may be associated with the formation of insufficiently stable ammonia complexes of cadmium (the biggest instability constant for the cd(nh3)4 2− complex рk1-4,in = 6.56 [19]) hence, the active cd 2+ ions can arrive intensively into the reaction medium. ethylenediamine (nh3)2(ch2)2 (en) can be an alternative to aqueous ammonia, because it has weak basic properties for providing an alkaline medium necessary for the hydrolytic thiourea decomposition. another important advantage of ethylenediamine is its low volatility, which contributes to a constant ph of the reaction mixture. bearing in mind the disadvantage of using the same ligand for lead and cadmium due to their competition, we have decided to supplement the formulation by ethylenediamine in addition citrate ions, which are effective for creating stable complexes. ethylenediamine forms strong complexes with both lead (pb(en) 2+ (рk1,in = 7.00); pb(en)2 2+ (рk1−2,in = 8.45) [21]), and with cadmium (cd(en) 2+ (рk1,in = 5.63), cd(en)2 2+ (рk1−2,in = 10.22), cd(en)3 2+ (рk1−3,in = 12.29) [21]). the ethylenediamine-citrate mixture has proven well in the preparation of cdxpb1−xs solid solutions [9]. however, the authors of the publication used a rather small range of cadmium salt concentrations (up to 0.025 mol/l). it should be noted that intuitive approaches prevail in the overwhelming majority of publications devoted to the synthesis of cdxpb1−xs solid solutions by cbd. an experimental search of the process conditions and of the reacchimica techno acta 2021, vol. 8(2), № 20218210 article 3 of 8 tion baths compositions is also often encountered accompanied formal reactions of interaction between precursors. calculation of the concentration range of the lead and cadmium sulfides formation allows predicting the formation of a solid solution before the start of synthesis. determination of deposition conditions with the least labor input is one of the important aims of a researcher using cbd. in this regard, this work is devoted to the ionic equilibria analysis with the determination of the potential area of the cdxpb1xs solid solutions formation in the system «pb(ch3coo)2  cdcl2  na3c6h5o7  ‎(nh3)2(ch2)2  n2h4cs». the goal of this research is deposition of cdxpb1xs thin films using found formation boundary conditions, the study of morphology, composition and crystal structure of these compounds. 2. experimental the reaction mixture for the chemical bath deposition of cdxpb1−xs solid solutions films included the following components. the precursors were lead acetate pb(ch3coo)2 0.04 mol/l and cadmium chloride cdcl2. the cadmium salt concentration was varied in the range 0.005–0.14 mol/l. ethylenediamine ‎(nh3)2(ch2)2 (en) 0.6 mol/l and sodium citrate na3c6h5o7 (na3cit) 0.33 mol/l provided ligands for lead and cadmium ions. ethylenediamine also served as an alkaline agent, and thiourea (nh2)2cs was used as a chalcogenizer. lead sulfide films were obtained under the same conditions without the cadmium salt in the reaction bath. the films synthesis was carried out on pre-degreased st-50 sitall substrates in sealed glass reactors (100 ml), which were placed in the ts-tb-10 liquid thermostat heated to 353 k. the process duration was 120 minutes. the thickness of the films was determined using an interference microscope (linnik microinterferometer) mii4m with a measurement error of 20%. the microstructure and elemental composition of the films were studied using mira 3 lmu scanning electron microscope at the electron beam accelerating voltage of 10 kv and a jeol jsm-5900 lv scanning electron microscope with an eds inca energy 250 energy-dispersive x-ray (edx) analyzer. x-ray studies of the deposited films were carried out by a panalytical empyrean series 2 diffractometer in cu kα radiation in the parallel beam geometry with a positionsensitive pixel3d detector providing a resolution on 2θ scale of at least 0.0016°. the diffraction patterns were recorded in 20–100 degrees (2θ) range with the step of 0.02°, the scanning time was 10 s at a point. the structural parameters of the cdxpb1−xs films were refined by the full-profile rietveld analysis [22, 23] using the fullprof software [24]. to separate the contributions of grain size and deformations in the studied films into the width of the diffraction peaks, the conventional williamson – hall plot equation was used [25]: β∙cosθ= 0.9λ/d + 4ε∙sinθ (1) where d is the average size of the coherent scattering regions, taken as the average particle size, β is the halfwidth of the peak in radians, λ is the wavelength of the xray radiation used, ε = δd/d is the deformation, d is the interplanar distance. 3. thermodynamic assessment of the formation boundary conditions of pbs, cds, cd(oh)2 and pb(oh)2 to determine the cbd optimal conditions, analysis of ionic equilibria was carried out in the system «pb(ch3coo)2  cdcl2  na3c6h5o7  ‎(nh3)2(ch2)2 n2h4cs» according to the method proposed in [26]. these calculations allowed estimating the formation regions of the main phases (pbs and cds) and impurities (cd(oh)2, pb(oh)2). the prerequisite for obtaining thin-film metal sulfide is to slow down the rate of the metal salt transformation into sulfide. the rate decreasing is achieved by reducing its active concentration due to the metal ions binding into complex compounds. in the studied system lead ions form complexes with citrate ions pb(cit) − (instability constant, рk1,in = 4.34), pb(cit)2 4− (рk1−2,in = 6.08), pb(cit)3 7− (рk1−3,in = 6.97) [19], pb(oh)(cit) 2− (рk1,in = 13.72) [21]; with hydroxide ions pb(oh) + (рk1,in = 7.52), pb(oh)2 (рk1−2,in = 10.54), pb(oh)3 − (рk1−3,in = 13.95), pb(oh)4 2− (рk1−4,in = 16.3) [19], and also with ethylenediamine pb(en) 2+ (рk1,in = 7.00); pb(en)2 2+ (рk1−2,in = 8.45) [21]. for cadmium, the ligands were ethylenediamine cd(en) 2+ (рk1,in = 5.63), cd(en)2 2+ (рk1−2,in = 10.22), cd(en)3 2+ (рk1−3,in = 12.29) [19], citrate ions cd(cit) − (рk1,in = 5.36) [19], cd(oh)(cit) 2− (рk1,in = 9.3) [21] and hydroxide ions cd(oh) + (рk1,in = 3.92), cd(oh)2 (рk1−2,in = 7.65), cd(oh)3 − (рk1−3,in = 8.70), cd(oh)4 2− (рk1−4,in = 8.65) [19]. the regions of individual lead and cadmium sulfides formation, as well as their co-deposition region, were found as a graphical solution of the equilibrium conditions equation in the coordinates “the of the initial metal salt concentration power pcin – the ligand concentration [na3cit(en)] – ph” at 298 k [26]: p𝐶in = pspms – pαm2+ − (p𝑘h2s 1,2 + 1 2 p𝐾ss − 2ph + 1 2 p[cs(nh2 )2]in + 1 2 p 𝛽c 𝛽s ) − 0.86 ∙ 𝜎 ∙ 𝑉𝑀 𝑅 ∙ 𝑇 ∙ 𝑟𝑐𝑟 , (2) p𝐶in = spm(oh)2 – pαm2+ – 2p𝐾w + 2ph, (3) where р is the power (negative logarithm); 𝐶in is the lead or cadmium salt initial concentration; pspms, pspm(oh)2 are the solubility products’ powers of sulfides cds (pspcds = 26.6) and pbs (psppbs = 27.8) and hydroxides cd(oh)2 (pspcd(oh)2 = 15.8) and pb(oh)2 (psppb(oh)2 = 13.66) [19], respectively; [cs(nh2)2]in is the thiocarbamide initial concentration in solution, equal to 0.6 mol/l; σ is the specific chimica techno acta 2021, vol. 8(2), № 20218210 article 4 of 8 surface energy of metal sulfide (σpbs = 1.2 j/m 2 and σсds = 0.9 j/m 2 ); vm is the molar volume of the synthesized phase vm(pbs) = 31.9∙10 -6 m 3 /mol and vm(cds) = 29.97∙10 -6 m 3 /mol; rcr is the critical nucleus radius (3.5∙10 −9 m) [26]; r is the ideal gas constant, j/(mol∙k); т is the temperature of the process, 298 k; p𝑘h2s 1,2 is the hydrogen sulfide dissociation constant, 1.3∙10 20 [19]; 𝐾ss is the thiourea hydrolytic decomposition constant, 3.2∙10 23 [27]; βs and βc are the values that include the dissociation constants of hydrogen sulfide h2s and cyanamide h2cn2, calculated by the expressions 𝛽s = [h3 o + ]2 + 𝑘hs− 1 [h3o +] + 𝑘h2s 1,2 , 𝛽c = [h3 o +]2 + 𝑘hcn2− 1 [h3o +] + 𝑘h2cn2 1,2 , where 𝑘hs− 1 , 𝑘hcn2− 1 and 𝑘h2s 1,2 , 𝑘h2cn2 1,2 are the first stage dissociation constants of hydrogen sulfide and cyanamide (𝑘hs− 1 = 6.99 [19], 𝑘hcn2− 1 = 10.33 [27]) and their cumulative ones (𝑘h2s 1,2 = 19.59 [19], 𝑘h2cn2 1,2 = 21.51 [27]); pαm2+ is the power of the fraction of free lead or cadmium ions in uncomplexed forms. the calculation was carried out considering all possible lead and cadmium forms according to the method proposed in [26]. the last term in eq. (2) is the derivative of the thomson ostwald relation. this expression determines the supersaturation contribution of lead or cadmium sulfide in the system, taking into account the formation of critical size nuclei. sulfide ions formed during the decomposition of thiourea are distributed between the ions of two metals. hence the cdxpb1xs solid solution formation will occur by way of competing reactions of the cds and pbs formation. to exclude the limiting effect of the chalcogenizer, the deposition of cdxpb1xs solid solutions was carried out with an excess of thiourea concentration by about 3–13 times compared with the metal concentrations in the reaction mixture. thermodynamic assessment of potential regions of the sparingly soluble phases formation in the studying system was performed at a temperature of 298 k under varying the concentration of ethylenediamine (en) from 0.1 to 1.0 mol/l (a) and sodium citrate (na3cit) from 0.1 to 0.6 mol/l (b) considering the crystallization factor (fig. 1). the predicted simultaneous deposition area of cds and pbs solid phases corresponds to the space lying between the surfaces characterizing the initial conditions for the deposition of sulfides (upper surfaces) and hydroxides (lower surfaces) of these metals. in three-dimensional coordinates pcin = f(ph, [l]) the plotted dependences reveal that the cdpbs ternary compound formation without hydroxides admixtures begins with the cadmium sulfide precipitation at ph = 10–14 (a) and 10–12 (b). in the less alkaline region (ph = 8-10) the process begins with the pbs formation. the simultaneous deposition area of solid phases of both pbs, cds sulfides and hydroxides pb(oh)2 and cd(oh)2 is situated under the concentration planes of the lead and cadmium hydroxides (lower surfaces) formation at ph 11.7–14.0 (a) and 11.2–14.0 (b). it should be noted that, in the system under discussion, the sulfides formation occurs according to a heterogeneous mechanism by sulfidization of lead and cadmium hydroxides at ph > 11. the reaction mixture composition was formed from calculations and preliminary experiments. mirror films with good adhesion to the substrate were obtained with varying the concentration of cadmium salt (0.005–0.14 mol/l). the synthesized films were 400 to 650 nm thick. a change in the gray color (characteristic of pbs) to a dark blue and light green hue (imparted by the content cadmium) indicated the cdpbs three-component compound formation. 4. results and discussion the morphology of pbs films (a) and cdpbs thin-film ternary compounds obtained from reaction baths containing 0.01 (b) and 0.1 mol/l (c) cdcl2 is shown in fig. 2. fig. 1 boundary conditions of the pbs, cds, pb(oh)2 and cd(oh)2 sparingly soluble phases formation depending on the ph of the medium and the concentration of ethylenediamine (en) (a) and sodium citrate na3cit (b). calculations were performed at [na3cit] = 0.3 mol/l (a) and [en] = 0.6 mol/l (b), т = 298 k a b chimica techno acta 2021, vol. 8(2), № 20218210 article 5 of 8 fig. 2 sem images of pbs (a) and cdpbs films obtained from reaction baths containing (b) 0.01 and (c) 0.1 mol/l cdcl2 the lead sulfide film analysis revealed that the average observed crystallite size was ~150–200 nm, and the film continuity degree did not exceed ~80% (fig. 2a). the minimum cadmium salt amount introduction (0.01 mol/l) into reactor led to a slowdown in the rate of formation of lead sulfide, which was also noted by the authors in [28], and the formation of a uniform film consisting of cubic crystallites with an edge of ~150 nm. the particles did not completely cover the substrate surface (fig. 2b). the cubic grains shape is due to the presence in the system of sufficiently stable ethylenediamine complexes of lead. the destruction of these complexes requires additional energy, which increases the energy barrier of interaction between lead and thiourea ions. according to [29], the process proceeds in a thermodynamic regime, the crystallites grows along the <111> directions. the radical change in the cdpbs films morphology has occurred with the 0.1 mol/l cadmium chloride introduction into the reaction mixture. the obtained films grains composed of the spherical globules ~300–400 nm in size, representing clusters of nanoparticles 50–70 nm in size (fig. 2c). the presence of the hierarchical structure characteristic of cds [30] is a consequence of the block deposition mechanism implementation. in the bulk of the reaction mixture, solid phase clusters form followed by deposition on the substrate surface [31]. the crystal structure of solid solution films deposited from solutions with 0.005, 0.01, 0.1, 0.12, and 0.14 mol/l concentrations of cadmium chloride was studied by x-ray diffraction. xrd patterns of the synthesized pbs and ternary cdpbs compounds are shown in fig. 3. the observed peaks corresponded to the pbs cubic structure b1 (space group fm3̅m) and to the sitall substrate (tio2 and cordierite). the gradual shift of all reflections to the region of greater angles 2θ evidences solid solutions formation (fig. 3, inset). as a result, a slight decrease of the period cubic lattice b1 is observed from 0.5933(8) to 0.5929(2), 0.5923(6), 0.5918(0), 0.5920(7), and 0.5918(0) nm (table 1). fig.3 x-ray diffraction patterns of pbs film and cdxpb1−xs solid solution films obtained at different cdcl2 contents in the reaction bath. the inset shows the (311) b1 peak shift of the cdxpb1−xs films to 2θ high-angle region. a b c chimica techno acta 2021, vol. 8(2), № 20218210 article 6 of 8 the observed crystal lattice period decrease is due to the replacement of lead (ii) ions (r = 0.120 nm [32]) by cadmium ions with smaller radius (r = 0.097 nm [32]) in the pbs structure. to estimate the relative content of cadmium and lead, we used the cdxpb1−xs (ass) solid solutions lattice period decreasing (ass), the experimental value for pbs apbs = 0.5933(8) nm, and the lattice period for the pseudocubic в1 structure acds=0.546 nm given in [33–36]. vegard's rule was used [37-38] to determine the (х) cadmium relative content in cdxpb1−xs solid solutions. according to vegard's rule, the molar fraction of cadmium is defined as x = (apbs –ass)/(apbs− acds). the performed calculation allowed us to establish the relative content of cadmium x in the lead metal sublattice with an accuracy of ± 0.001 (table 1). comparison of the established solid solutions compositions (table 1) with the pbs cds system equilibrium phase diagram [39] indicates a significant supersaturation of the lead sulfide lattice by cadmium for all synthesized cdxpb1−xs solid solutions (0 <x ≤ 0.033) at 353 k. a quantitative analysis of x-ray diffraction patterns was performed by the full-profile analysis method using fullprof software. the synthesized pbs layers were formed from grains with a predominant orientation (111) with a texture degree t111 equal to 35.6% (table 1). the presence of 0.005 mol/l cadmium salt in the reactor leads to a change in the dominant crystallite growth direction from [111] to [200] (table 1). the grains reorientation is consistent with the results of scanning electron microscopy (fig. 2b). the insignificant structure ordering is observed with the cdcl2 concentration rise: the texture coefficient t(200) increases from 22.4 to 28.2%. the diffraction reflections on the studying films xrd patterns (fig. 3) were broadened due to the small particle size and the microstrains presence. the separation of the size and deformation contributions to the reflections broadening and the estimation of coherent scattering regions average size, taken in the first approximation as the average grains size (d), was performed using the williamson-hall extrapolation method. the estimated microstresses δd/d in cdxpb1xs solid solutions films indicated microstrains decreasing from 11.5∙10 4 to 3.5∙10 4 with the growth of the cadmium salt concentration in the reaction mixture up to 0.14 mol/l. the coherent scattering regions size (d) of cdxpb1xs (x ≤ 0.028) solid solutions films increased from 110 to 123-139 nm with increase in the cadmium chloride content to 0.12 mol/l in comparison with the individual pbs layer, and decreased to 77 nm at 0.14 mol/l of cdcl2. local energy-dispersive x-ray spectroscopy (edx) was carried out to establish the elemental composition of the synthesized films over the entire films surface area in at least 10 points. the results of edx analysis are given in table 2. according to the data, the individual pbs film contained (49.7 ± 0.4 at %) lead and (50.3 ± 0.4 at %) sulfur, i.e. there was an excess of chalcogen. in the ternary cdpbs compounds the cadmium content increased from 9.54 to 37.39 at % with an increasing of the cadmium salt concentration in the reaction bath. the ratio between the total content of metals (cd + pb) and sulfur s was within 1.01.05. according to the results of edx analysis, the cadmium content in the synthesized films exceeds the value calculated from the data of x-ray diffraction in the сdxpb1−xs solid solution (table 2). this means that the synthesized table 1 the lattice parameter (a), the cadmium content (x) in cdxpb1xs solid solution, portion of the grains with predominant orientation (200) or (111) along substrate plane (t200 or t111), the averaged values of microdeformation in the film volume <δd/d>, sizes of coherent scattering regions d given for cdxpb1xs thin films obtained with different concentrations of [cdcl2] cadmium chloride in the reaction bath. content of the cadmium salt in the reaction bath, [cdcl2], mol/l 0 0.005 0.01 0.1 0.12 0.14 ав1 (nm) 0.00001 0.5933(8) 0.5933(1) 0.5929(2) 0.5923(6) 0.5920(7) 0.5918(0) x in cdxpb1xs − 0.001 0.010 0.022 0.028 0.033 t200 (%) t111 (%) − 35.6 22.5 − 24.2 − 24.5 − 21.8 − 28.2 − <d/d>, ∙10 4 4.8 11.5 6.0 6.2 5.7 3.5 d, nm 110 138 123 139 130 77 table 2 effect of the concentration of cadmium chloride on the composition of сdxpb1-xs solid solutions. composition of the reaction mixture, mol/l: [pbac2] = 0.4, [en] = 0.6, [tm] = 0.6, [na3cit] = 0.3. the temperature of synthesis was 353 k. [cdcl2], mol/l content of elements in the film, at % formula composition of the film (without separation into crystalline and amorphous phases) formula composition of the cdхpb1−хs solid solution, estimation by the lattice parameter, ±0.004 phase composition of the film, mol % cd ±0.07 pb ±0.05 s ±0.08 cdхpb1−хs solid solution сds amorphous sulfide 0.005 9.54 40.45 50.01 cd0.19pb0.81s0.99 cd0.001pb0.999s ~81 19 0.01 16.35 34.09 49.56 cd0.32pb0.68s1.02 cd0.010pb0.990s 69 31 0.10 34.14 16.77 49.09 cd0.67pb0.33s1.04 cd0.022pb0.978s 34 66 0.12 36,79 13,84 49,36 cd0.73pb0.27s1.03 cd0.028pb0.972s 28 72 0.14 37.39 13.87 48.74 cd0.73pb0.27s1.05 cd0.033pb0.967s 28 72 chimica techno acta 2021, vol. 8(2), № 20218210 article 7 of 8 films contain, in addition to 28–81 mol.% crystalline сdxpb1−xs, 19–72 mol.% the cadmium sulfide amorphous phase. the high content of the cds amorphous phase in the synthesized films was due to the more favorable conditions for cds formation at the ph of thiourea hydrolytic decomposition (ph = 11-12). that assumption is consistent with the potential thermodynamic area assessment of cds and pbs sulfides co-precipitation in the system under discussion. 5. conclusions the concentration regions of the isovalent lead sulfides pbs and cadmium cds co-precipitation were determined based on the ionic equilibria analysis in the system «pb(ch3coo)2  cdcl2  na3c6h5o7  ‎(nh3)2(ch2)2  n2h4cs». for the studied system, these calculations allowed defining the deposition parameters of the cdxpb1xs substitutional solid solutions. films of supersaturated cdxpb1xs solid solutions with the cadmium content up to x = 0.033 were obtained by chemical bath deposition at 353 k on sitall substrates. the crystalline structure of the films was b1 cubic (space group fm3̅m). sem analysis of cdpbs films demonstrated the evolution of the morphology layers. the polycrystalline structure has replaced by globular aggregates with increasing of the cadmium chloride concentration up to 0.14 mol/l in the reaction bath. the higher cadmium content in the cdpbs films found by edx analysis in comparison with its amount estimated from the xrd data is associated with the formation of the cds amorphous phase. acknowledgements the research was financially supported by 211 program of the government of the russian federation (no. 02.a03.21.0006), was carried out within the state assignment of ministry of science and higher education of the russian federation (theme no. н687.42б.223/20) and supported by rfbr (projects no. 20-48-660041). references 1. suryavanshi ke, dhake rb, patil am, sonawane mr. growth mechanism and transport properties of chemically deposited pb cd s thin film’s photoelectrochemical (pec) solar cell. optik. 2020;165008. doi:10.1016/j.ijleo.2020.165008 2. ounissi a, ouddai n, achour s. optical characterisation of chemically deposited pb(1−x)cdxs films and a pb1−xcdxs(n)/si(p) heterojunction. eur phys j appl phys. 2007;37(3):241−5. doi:10.1051/epjap:2007034 3. maskaeva ln, markov vf, porkhachev myu, mokrousova ао. thermal and radiation stability ir-detectors based on films of solid solutions cdxpb1−xs. pozharovzryvobezopasnost [fire and explosion safety]. 2015;24(9):67-73. russian. doi:10.18322/pvb.2015.24.09.67-73 4. pentia e, draghici v, sarau g, et al. structural, electrical, and photoelectrical properties of cdxpb1−xs  thin films prepared by chemical bath deposition. j electrochem soc. 2004;151(11):g729−33. doi:10.1149/1.1800673 5. bezdetnova ae, markov vf, maskaeva ln, et al. determination of nitrogen dioxide by thin-film chemical sensors based on cdxpb1–xs. j anal chem. 2019;74(12):1256−62. doi:10.1134/s1061934819120025 6. au ght, shih wy, tseng sj, shih wh. aqueous cdpbs quantum dots for near-infrared imaging. nanotechnology. 2012;23(27):275601(1-9). doi:10.1088/0957-4484/23/27/275601 7. tan gl, liu l, wu w. mid-ir band gap engineering of cdxpb1−xs nanocrystals by mechanochemical reaction. aip advances. 2014;4(6):067107(1-11). doi:10.1063/1.4881878 8. nichols pl, liu z, yin l, et al. cdxpb1–xs alloy nanowires and heterostructures with simultaneous emission in mid-infrared and visible wavelengths. nano lett. 2015;15(2):909−16. doi:10.1021/nl503640x 9. rabinovich e, wachtel e, hodes g. chemical bath deposition of single-phase (pb,cd)s solid solutions. thin solid films. 2008;517(2):737−44. doi:10.1016/j.tsf.2008.08.162 10. barote m, yadav a, masumdar e. effect of deposition parameters on growth and characterization of chemically deposited cd1-xpbxs thin films. chalcogenide lett. 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russian. https://doi.org/10.1016/j.tsf.2020.138468 https://doi.org/10.1107/s0021889869006558 https://doi.org/10.1180/claymin.1990.025.4.12 https://doi.org/10.1016/0921-4526(93)90108-i https://doi.org/10.1016/0001-6160(53)90006-6 https://doi.org/10.1134/s1070427217050044 https://doi.org/10.1134/s1070363210110198 https://doi.org/10.1134/s1070363216100054 https://doi.org/10.1002/adma.200390102 https://doi.org/10.1134/s1070363215110031 https://doi.org/10.1007/s11172-014-0630-7 https://doi.org/10.3103/s0027131408060011 https://doi.org/10.1016/0022-3697(79)90160-4 https://doi.org/10.1063/1.1713151 https://doi.org/10.1016/0031-9163(63)90356-1 https://doi.org/10.1016/0022-4596(80)90120-6 https://doi.org/10.1007/bf01349680 https://doi.org/10.1103/physreva.43.3161 novel synthesis of 3-(phenyl) (ethylamino) methyl)-4-hydroxy-2h-chromen-2-one derivatives using biogenic zno nanoparticles and their applications chimica techno acta article published by ural federal university 2022, vol. 9(1), no. 20229104 eissn 2411-1414; chimicatechnoacta.ru doi: 10.15826/chimtech.2022.9.1.04 1 of 16 novel synthesis of 3-(phenyl) (ethylamino) methyl)-4hydroxy-2h-chromen-2-one derivatives using biogenic zno nanoparticles and their applications g.c. anjan kumar a, yadav d. bodke a*, b. manjunatha a, n.d. satyanarayan b, b.n. nippu b, muthipeedika nibin joy c a: department of pg studies and research in chemistry, school of chemical sciences, kuvempu university, 577451 jnana sahyadri, shankaraghatta, karnataka, india b: department of pharmaceutical chemistry, p.g. centre, kuvempu university, 577548 kadur, karnataka, india c: innovation centre for chemical and pharmaceutical technologies, institute of chemical technology, ural federal university, 620002 mira st., 19, yekaterinburg, russia * corresponding author: ydbodke@gmail.com this article belongs to the regular issue. © 2021, the authors. this article is published in open access form under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). abstract the present work describes the novel synthesis of 3, 3-((phenyl) (ethylamino) methyl)-4-hydroxy-2h-chromen-2-one derivatives catalyzed by biogenic zno nanoparticles. the synthesized heterocyclic compounds were characterized by fourier-transform infrared spectroscopy (ft-ir), nuclear magnetic resonance (nmr) and mass spectrometric techniques. absorption, distribution, metabolism and excretion properties and various toxicities (admet) studies and in silico molecular docking studies were carried out for the synthesized compounds. the synthesized compounds were screened for their efficacy towards the antioxidant activity and were subjected to corrosion inhibition study towards the mild steel in acidic medium by weight loss method. additionally, the recyclability of the employed catalyst was studied. keywords mcrs biogenic zno benzylamino coumarins antioxidant corrosion inhibition received: 29.11.2021 revised: 15.01.2022 accepted: 15.01.2022 available online: 21.01.2022 1. introduction in the past decades, the aqueous environment has elicited much consideration in organic synthesis. water demonstrated unique reactivity and selectivity, which cannot be attained in conventional organic solvents [1]. multicomponent reactions (mcrs) provide the most effective advance in the field of green chemistry and are vital tools in material, medical and modern synthetic organic chemistry; in particular, for the building of heterocyclic scaffolds. the last two decades were exclusively devoted to mcrs involving three or more precursors to synthesize structurally diverse bioactive heterocyclic compounds [2, 3]. the supremacy of mcrs are high atom-economy, convergence and structural diversity, operational simplicity of the resulting products makes this sustainable approach a potent tool for the synthesis of biologically active molecules and optimization processes in the medicinal industry [4–6]. coumarin heterocyclic moiety is well regarded as a privileged structural motif in abundant natural products and synthetic organic compounds of various pharmacological properties. the 4h-pyran core is a rich source of biologically vital molecules possessing a broad spectrum of biological and pharmacological activities [7]. pharmacological activities includes neuroprotective agents [8], antimicrobial agents [9, 10], cardio preventive agents [11], antioxidant [12–14], anti-inflammatory agents [15] and antituberculating agents [16]. further, the presence of n and o made them good corrosive inhibitors [17, 18]. therefore, we tried to synthesize benzyl substituted coumarins via the mannich type reaction. the mannich reaction is one of the most powerful synthetic methods for carbon-carbon bond forming reactions for the synthesis of novel nitrogen-containing organic molecules. currently, mild steel (ms) finds extensive applications in the industrial handling of alkali, acids, and salt solutions. the aggressiveness of these solutions causes brutal corrosion to engineered structures made of ms, which leads to immense economical and material losses. hence, the study of ms corrosion and its inhibition has attracted http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2022.9.1.04 http://creativecommons.org/licenses/by/4.0/ chimica techno acta 2022, vol. 9(1), no. 20229104 article 2 of 16 the attention of scientists and authorities to think up ways of overcoming the corrosion. among the variety of corrosion control measures, utilization of corrosion inhibitors is a known method. it is identified that corrosion inhibitors act by adsorbing on the metal surface. compounds having aromatic systems incorporated with n, s, and o heteroatoms have been found to possess exceptionally potent anticorrosion properties. in recent years, due to environmental issues, researchers have been functioning on the concept of diminished destructive effects to the environment to avoid the toxic effect of synthetic corrosion inhibitors [19–21]. in this regard, several methods have been employed for the synthesis of different corrosion inhibitors for the ms. earlier methods employed for these types of synthesis suffered from many drawbacks such as poor yield, longer reaction time, use of expensive reagents, etc. one of the methods of overcoming these drawbacks is using the metal oxide nanoparticles as catalysts due to their higher surface-to-volume ratio of nanoparticles (nps) which is predominantly responsible for their catalytic properties. in addition, they actas paramount adsorbents for the multitude of organic compounds, amplifying the reactivity of the reacting molecules [22, 23]. synthesis of metal and oxide nanoparticles using plants and their parts is a sustainable method because of its environmental compatibility for pharmaceutical and other biomedical applications. plants and their parts have emerged as a substitute to chemical synthetic procedures because no complex processes such as intracellular synthesis, no several purification steps are involved and no toxic chemicals are used in the synthesis. from the literature survey, among others, zno nps have gained more attention because of their versatile characters like low toxicity, large surface area, high pore volume, low cost, lewis acidic nature, ecofriendliness, heterogeneous nanocatalytic properties and reusability [24–26]. in the present study, we discussed the synthesis of 3((phenyl) (ethylamino) methyl)-4-hydroxy-2h-chromen-2one derivatives catalyzed by biogenic zno nps by the reaction of 4-hydroxy coumarin with aromatic aldehydes and especially with ethylamine as an amine source. the schematic pathway is given in scheme 1. 2. experimental 2.1. materials and methods all the chemicals were purchased from sigma aldrich, merck and used as received with no further purifications. areca nuts were collected from local suppliers near channagiri, davanagere and used after washing with double distilled water. uv-visible spectra were recorded using hr 4000 uv-vis spectrophotometer and ft-ir spectra by alpha t brucker instrument. the nmr spectra were recorded in dmso with tms as an internal standard on a brucker avance drx 400 mhz spectrometer and chemical shift (δ) values were expressed in parts per million (ppm) units. high-resolution liquid chromatography-mass spectra (hrms) were recorded using water’s synapt g2 qtof lcms instrument, and the crystalline structure of zno was obtained by x-ray diffractometer (xrd) (rigaku). the surface morphology and crystallinity were obtained by scanning electron microscopy (sem), (ciirc) and the elemental analysis of zno nanoparticles was conducted by energy dispersive analyzer using x-rays (edx) (thermo scientific noran 7). molinspiration cheminformatics webbased server [27] was used to evaluate drug likeliness; absorption, distribution, metabolism and excretion properties and various toxicities (admet) prediction for all the designed compounds was evaluated using the admet descriptor module of the admet lab web-based server [28]. protein used: cyclooxygenase cox-2, classification: oxidoreductase and organism(s): mus musculus, pdb id: 1pxx. in silico molecular docking study was also carried out by (chembiooffice ultra 14.0 suite). 2.2. preparation 2.2.1. preparation of areca nut extract mediated zno nps freshly collected areca nuts were stripped off their outer layer, washed with double distilled water, dried, and ground well to get a fine powder. to prepare the areca nut extract, 5 g of areca nut powder was boiled in water for about 30 min at 80 °c to get the reddish colour solution. then the extract was filtered and dried under vacuum using a rotary evaporator. o oh o o h o nhoh o + + nh2 1 2(a-h) 3 4(a-h) where : r = 4-cl, 4-no 2 , 3-no 2 , h, 4-oh, 3-oh, 4-oh 3-och 3 , 4-oh 3-och 2 ch 3 . r r biogenic nano zno r t, 10 -15 min scheme 1 the schematic pathway of synthesis of 3-((phenyl) (ethylamino) methyl)-4-hydroxy-2h-chromen-2-one derivatives chimica techno acta 2022, vol. 9(1), no. 20229104 article 3 of 16 the zno nps were prepared by solution combustion method. in brief, 10 ml of areca nut extract and 0.5 g of zinc nitrate hexahydrate zn(no3)26h2o were weighed in a silica crucible and placed in a preheated muffle furnace maintained at 500 °c. an exothermic vigorous reaction leads to the formation of fine, white zno nps. the obtained product was kept in a sealed container for further analysis [29]. 2.3. characterization of prepared nanomaterials 2.3.1. uv-vis spectroscopy the uv-vis absorption spectrum of zno nanoparticles was recorded between the wavelength of 200 and 800 nm and is presented in fig. 1. the spectrum showed the absorbance peak at 293 nm corresponding to the characteristic band of zinc oxide nanoparticles. the bandgap energy (e) is calculated using the following equation: 𝐸 = ℎ𝐶  , (1) where ℎ is the planks constant, 6.62610−34 js, c is the velocity of light, 3.0108 m/s, and 𝜆 is the wavelength (nm). the bandgap of zno nps was found to be 3.15 ev. fig. 1 uv-vis spectrum of zno nps 2.3.2. ft-ir spectroscopy the ft-ir spectrum of zno was recorded in the range of 400–4000 cm−1 and is presented in fig. 2. the peaks at 3450.46 cm−1 and 1636.48 cm−1 are due to the stretching and bending vibration of the oh functionality. the peak at 1382.97 cm−1 is due to stretching vibrations of zn–o–zno, and the peak between 700–400 cm−1 is due to stretching vibration of zn–o. 2.3.3. x-ray diffraction studies the powder x-ray diffraction (p-xrd) pattern of prepared zno nps is presented in fig. 3. it indicates the phase purity and structural parameters of zno. the xrd peaks are observed in the wide-angle range of 2θ (10°<2θ<80°). fig. 2 ft-ir spectrum of zno nps the reflections from (100), (002), (101) and (110) planes suggested that the synthesized nanoparticle s possess hexagonal symmetry, which was further confirmed from the jcpds no.: 01-089-0510. the crystallite size (d) can be determined by scherrer’s formula: 𝐷 = 𝐾 c𝑜𝑠 (2) where 𝜆 is the wavelength of x-ray radiation (cu k𝛼 = 0.15406 nm), k is a constant taken as 0.90, β is the line width at half-maximum height (fwhm) of the peak and θ is the diffracting angle. the (100) plane is chosen to calculate the crystallite size. the average crystallite size for the synthesized zno nps was found approximately 12 nm from this debye-sherrer equation 2. fig. 3 xrd pattern of synthesized zno 2.3.4. sem and edx the surface morphology of the prepared zno nps was studied using scanning electron microscopic (sem) technique; it showed that the particles were in spherical shape, as shown in fig. 4. the energy-dispersive x-ray spectroscopic (edx) study was carried out for the prepared zno nps to identify the elemental composition. edx confirms the existence of zinc and oxygen signals of zno nps as shown in fig. 5. chimica techno acta 2022, vol. 9(1), no. 20229104 article 4 of 16 fig. 4 sem image of synthesized zno fig. 5 edx analysis of synthesized zno the elemental analysis of the nanoparticle yielded 50.54% of zinc and 49.46% of oxygen, as shownin table 1. table 1 the elemental analysis of synthesized nanoparticle element line weight % weight % error atom % atom % error o 20.00 ±1.43 50.54 ±3.61 zn – – – – zn 80.00 ±3.36 49.46 ±2.08 total 100.00 100.00 2.4. synthetic procedure for 3-((phenyl) (ethylamino) methyl)-4-hydroxy-2h-chromen-2-one derivatives a mixture of 4-hydroxy coumarin (1 mmol) 1, aromatic aldehydes (1 mmol) 2, ethylamine (1 mmol) 3, and biogenic zno nanoparticles (5 mol.%) was taken in a round-bottom flask containing 10 ml water and stirred at room temperature. after the completion of the reaction (checked by thin-layer chromatography (tlc)), the reaction mixture was quenched in water, the solid compound obtained was filtered off, and the crude product was purified by recrystallization from etoh. 2.4.1. 3-[(4-chlorophenyl) (ethylamino) methyl]-4hydroxy-2h-chromen-2-one: 4a white solid, yield: 98%. m.p. 189–191 °c; ft-ir (kbr) in cm–1: 3431 (o–h), 3137 (n–h), 2983 (ar–h), 2708 (aliphatic c–h) 1706 (c=o), 1604, 1518 (c–n), 756 (c–cl). 1h nmr (400 mhz, dmso-d6): δ: 10.20 (s, 1h, oh), 9.30 (s, 1h, nh), 8.54 (s, 1h, ar–h), 8.22–8.20 (d, 1h, j = 8.0 hz, ar–h), 8.15–8.13 (d, 1h, j = 8.0 hz, ar–h) 8.01–7.99 (t, 1h, j = 8.0 hz, ar–h) 7.87–7.79 (m, 3h, ar–h), 7.65–7.61 (t, 1h, j = 8.0 hz, ar–h),7.55 (s, 1h, ar–h), 7.51–7.40 (m, 1h, ar–h), 5.52 (s, 1h, aliphatic h), 2.95–2.65 (q, 2h, j = 12.0 hz, ch2), 1.19 (t, 3h, j = 8.0 hz, ch3) ppm. 13c nmr (100 mhz, dmso-d6): 173.92 (c=o), 163.79, 154.23, 148.07, 147.33, 146.58, 141.39, 134.69, 131.44, 130.32, 128.83, 124.84, 123.25, 122.96, 116.37, 91.56, 58.35, 11.52 ppm. hrms (esi) m/z = 330.06 [m]+; mol. formula: c18h16clno3. calcd: for c 65.56, h 4.89 and n 4.25. found: c 65.60, h 4.90 and 4.20. 2.4.2. 3-[(ethylamino) (4-nitrophenyl) methyl]-4hydroxy-2h-chromen-2-one: 4b yellow solid, 95%. m.p. 315–317 °c; ft-ir (kbr) in cm–1: 3418 (o–h), 3063 (n–h), 2986 (ar–h), 2803 (aliphatic c–h) 1634 (c=o), 1602, 1519 (c–n), 1348 (n–o). 1h nmr (400 mhz, dmso-d6): δ: 10.06 (s, 1h, oh), 9.98 (s, 1h, nh), 8.90 (s, 1h, ar–h),7.84 (d, 1h, 8.0 hz, ar–h), 7.62 (d, 2h, j = 8.0 hz, ar–h), 7.43–7.39 (t, 3h, ar–h), 7.17–7.12 (q, 2h, j = 8.0 hz, ar–h), 5.34 (s, 1h, aliphatic h) 2.92 (q, 2h, j = 8.0 hz), 1.12 (t, 3h, j = 7.9 hz, ch3), ppm. 13c nmr (100 mhz, dmso-d6): 173.83 (c=o), 163.75, 154.19, 138.29, 132.99, 131.31, 129.91, 128.70, 124.78, 123.93, 122.84, 122.57, 116.37, 91.96, 58.70, 11.53 ppm. hrms (esi) m/z = 342.16 [m+1]; mol. formula: c18h16n2o5. calcd: for c 63.52, h 4.74 and n 8.23. found: c 63.90, h 4.67 and 8.20. 2.4.3. 3-[(ethylamino) (3-nitrophenyl) methyl]-4hydroxy-2h-chromen-2-one: 4c light yellow solid, yield: 94%. m.p. 310–312 °c; ft-ir (kbr) in cm–1: 3421 (o–h), 3067 (n–h), 2985, (ar–h), 2808 (aliphatic c–h) 1630 (c=o), 1606, 1524 (c–n), 1348 (n–o). 1h nmr (400 mhz, dmso-d6):): δ: 9.91 (s, 1h, oh), 9.06 (s, 1h, nh), 8.53 (s, 1h, ar–h), 8.12 (d, 1h, j = 12.0 hz, ar–h), 7.99 (d, 1h, j = 8.0 hz, ar–h), 7.83–7.81 (t, 1h, j = 7.9 hz, ar–h), 7.62 (s, 1h, ar–h), 7.40 (s, 1h, ar–h), 7.13 (t, 2h, j = 8.0 hz, ar–h), 5.52 (s, 1h, aliphatic ch), 2.95 (q, 2h, j = 8.0 hz, ch2), 1.19 (t, 3h, j = 8.0 hz, ch3) ppm. 13c nmr (100 mhz, dmso-d6): 173.99 (c=o), 163.87, 154.32 148.15 141.49 134.80, 131.56, 130.44, 124.94, 123.37, 123.07, 122.66, 122.58, 116.49, 91.65, 58.38, 11.62, 1.70 ppm. hrms (esi) m/z =341.16 [m]+; mol. formula: c18h16n2o5. calcd: for c 63.49, h 4.70, and n 8.23. found: c 63.90, h 4.64 and 8.12. 2.4.4. 3-[(ethylamino) (phenyl) methyl]-4-hydroxy-2hchromen-2-one: 4d white solid, 93%. m.p. 274–276 °c; ft-ir (kbr) in cm–1: 3419 (o–h), 3158, (n–h), 2981 (ar–ch), 1634 (c=o), 1608, 1497 (c–n). 1h nmr(400 mhz, dmso-d6): δ: 10.59 (s, 1h, oh), 9.42 (s, 1h, nh), 7.82–7.79 (q, 1h, j = 8.0 hz, ar–h), 7.59–7.56 (t, 2h, ar–h), 7.31–7.25(q, 3h, j = 8.0 hz, ar–h), 7.13–7.09 (m, 2h, j = 8.0 hz, ar– h), 5.28 (s, 1h, aliphatic ch), 2.90 (q, 2h, j = 7.2 hz, ch2), 1.15 (t, 3h, j = 8.0 hz, ch3) ppm. 13c nmr (100 mhz, chimica techno acta 2022, vol. 9(1), no. 20229104 article 5 of 16 dmso-d6): 173.88 (c=o), 163.84, 154.26, 139.53, 131.36, 128.88, 128.48, 128.11, 124.84, 122.97, 122.68, 116.39, 92.28, 59.49, 11.63 ppm. hrms (esi) m/z = 296.11 [m]+; mol. formula: c18h17no3. c 73.20, h 5.80 and n 4.74. found: c 75.40, h 5.90 and 4.70. 2.4.5. 3-[(ethylamino) (4-hydroxyphenyl) methyl]-4hydroxy-2h-chromen-2-one: 4e white solid, 90% m.p. 245–247 °c; ft-ir (kbr) in cm–1: 3409 (o–h), 3081 (n–h), 2987 (ar–ch), 1638 (c=o), 1602, 1510 (c–n), 756. 1h nmr (400 mhz, dmso-d6): δ: 9.74 (s, 1h, oh), 9.46 (s, 1h, nh), 8.92 (s, 1h, ar–h), 7.82 (m, 1h, j = 12.0 hz, ar–h), 7.37–7.35 (d, 3h, j = 8.0 hz, ar–h), 7.12–7.10 (d, 2h, ar–h), 6.69 (d, 2h, j = 8.4 hz) 5.15 (s, 1h, aliphatic ch), 2.88 (q, 2h, j = 8.0 hz, ch2), 1.14 (t, 3h, j = 12.0 hz, ch3) ppm. 13c nmr (100 mhz, dmso-d6): 173.89 (c=o), 163.84, 157.85, 154.24, 140.75, 131.36, 129.87, 124.83, 122.98, 118.73, 116.39, 115.46, 115.04, 92.21, 59.58, 11.64 ppm. hrms (esi) m/z = 311.09 [m]+; mol. formula: c18h17no4. calcd. for c 69.44, h 5.50 and n 4.50. found: c 69.49, h 5.44 and 4.46. 2.4.6. 3-[(ethylamino)(3-hydroxyphenyl) methyl]-4hydroxy-2h-chromen-2-one: 4f white solid, 91%. m.p. 237–239 °c; ft-ir (kbr) in cm–1: 3452 (o–h), 3108 (n–h), 2875 (ar–ch), 1649 (c=o), 1616, 1516 (c–n). 1h nmr (400 mhz, dmso-d6): δ: 10.31 (s, 1h, oh), 9.47 (s, 1h, nh), 8.83 (s, 1h, j = 7.6 hz, ar–h), 7.88 (d, 1h, j = 8.0 hz, ar–h),7.48 (m, 1h, ar–h), 7.22–7.14 (m, 3h, j = 8.0 hz, ar–h), 7.07 (q, 2h, j = 7.9 hz), 6.72–6.70 (t, 1h, ar–h), 5.25 (s, 1h, aliphatic h), 2.96–2.91 (q, 2h, j = 7.2 hz, ch2), 1.22 (t, 3h, j = 7.2 hz, ch3) ppm. 13c nmr (100 mhz, dmso-d6): 173.34 (c=o) 163.27 157.30, 153.69, 140.18, 130.77, 129.29, 124.26, 122.39, 118.19, 115.82, 115.41, 114.92, 114.50, 91.64, 59.12, 11.09 ppm. hrms (esi) m/z = 311.97 [m]+; mol. formula: c18h17no4. calcd. for c 69.44, h 5.50, and n 4.50. found: c 69.40, h 5.54 and 4.43. 2.4.7. 3-[(ethylamino) (4-hydroxy-3-methoxyphenyl) methyl]-4-hydroxy-2h-chromen-2-one: 4g white solid, 90%. m.p. 235–237 °c; ft-ir (kbr) in cm–1: 3435 (o–h), 3098 (n–h), 2856 (ar–ch),1649 (c=o), 1606, 1539 (c–n). 1h nmr (400 mhz, dmso-d6): δ: 10.07 (s, 1h, oh), 9.05 (s, 1h, nh), 8.72 (s, 1h, ar–h), 7.88 (d, 1h, j = 8.0 hz, ar–h), 7.48–7.44 (m, 1h, ar–h), 7.27 (d, 1h, j = 2.0 hz, ar–h), 7.21–7.15 (m, 2h, j = 7.8 hz, ar–h), 7.00 (d, 1h, j = 8.0 hz, ar–h), 6.71 (d, 1h, ar–h), 5.22 (s, 1h, aliphatic ch), 3.76 (s, 3h, ch3), 2.92–2.87 (q, 2h, j = 7.8 hz, ch2), 1.21 (t, 3h, j = 12.0 hz, ch3) ppm. 13c nmr (100 mhz, dmso-d6): 173.29 (c=o), 163.31, 153.67, 152.84, 147.25, 146.55, 130.68, 129.63, 124.28, 122.34, 120.57, 115.78, 115.08, 112.40, 92.00, 59.13, 55.69, 11.10 ppm. hrms (esi) m/z = 341.09 [m]+; mol. formula: c19h19no5. calcd: for c 66.85, h 5.61 and n 4.10. found: c 66.80, h 5.56 and 4.06. 2.4.8. 3-[(3-ethoxy-4-hydroxyphenyl) (ethylamino) methyl]-4-hydroxy-2h-chromen-2-one: 4h white solid, 90%. m.p. 288–290 °c; ft-ir (kbr) in cm–1: 3452 (o–h), 3111 (n–h), 2856 (ar–ch), 1649 (c=o), 1632, 1513 (c–n). 1h nmr (400 mhz, dmso-d6): δ: 10.04 (s, 1h, oh), 8.99 (s, 1h, nh), 8.77 (s, 1h, ar–h), 7.89 (d, 1h, j = 8.0 hz, ar–h), 7.48 (t, 1h, j = 7.90 hz, ar– h), 7.27 (s, 1h, ar–h), 7.21–7.15 (q, 2h, j = 8.0 hz, ar–h), 7.00 (d, 1h, j = 8.0 hz, ar–h), 6.76 (s, 1h, j = 8.0 hz, ar– h), 5.22 (s, 1h, aliphatic ch), 4.03–3.97 (q, 2h, j = 8.0 hz, ch2),2.93–2.87 (q, 2h, j = 8.0 hz, ch2), 1.35–1.31 (t, 3h, j = 8.0 hz, ch3), 1.22 (t, 3h, j = 8.0 hz, ch3), ppm. 13c nmr (100 mhz, dmso-d6): 173.28 (c=o), 163.33, 153.67, 152.45, 146.89, 146.38, 130.69, 129.63, 124.29, 122.36, 120.65, 115.79, 115.18, 113.81, 92.07, 64.08, 59.06, 14.76, 11.10 ppm. hrms (esi) m/z = 340.09 [m]+; mol. formula: c20h21no5. calcd: for c 67.59, h 5.96 and n 3.94. found: c 67.53, h 5.90 and 3.92. 3. results and discussion 3.1. chemistry the structure of synthesized compounds was characterized by using different spectroscopic techniques such as uv-vis, ft-ir, 1h nmr, 13c nmr and hrms. the ft-ir spectrum of the compound 4a showed strong absorption bands at 756 cm–1 due to the chlorine atom attached to the benzene ring, 1529 cm–1 and 1518 cm–1 due to c–n, 1706 cm–1 due to c=o functionality of coumarin ring, 2708 cm–1 due to aliphatic –ch, 2983 cm–1 due to aromatic ch, 3137 cm–1 due to n–h and 3431 cm–1 due to –oh functionality. the 1h nmr spectrum of the compound 4a showed a singlet at δ 10.20 due to the oh proton and another singlet at δ 9.30 ppm due to the nh proton. the multiplet appeared between δ 7.12–8.50 ppm is due to the presence of aromatic protons. it also displayed a singlet at δ 5.50 ppm due to the –ch proton. in the hrms spectrum of the compound 4a, it showed a molecular ion peak m+ at m/z 330.0664, which is close to its molecular weight. the reaction of 4-hydroxy coumarin (1), aromatic aldehyde (2(a–h)), and ethylamine (3) achieved the desired product 3-((phenyl) (ethylamino) methyl)-4-hydroxy-2hchromen-2-one (4(a–h)) by using biogenic zno nps in green solvent (scheme 1). initially, to come across the finest conditions, screening was performed with solvent-free and a variety of polar and nonpolar solvents like dmso, dmf, ethanol, methanol, toluene, tetrahydrofuran, acetonitrile, ethanol, methanol, polyethylene glycol and water, as shown in table 2. we observed that the polar protic solvents afforded better yield than other solvents, and in water (table 2, entry 11) the supreme catalytic activity of biogenic nano zno was observed. further, we were concentrated on the efficient assessment of various catalysts for the model reaction in an aqueous medium at room temperature. chimica techno acta 2022, vol. 9(1), no. 20229104 article 6 of 16 table 2 effect of solvents on the three-component synthesis of benzylamino coumarin derivative 4a entry solvents yield a (%) 1 no solvent – 2 toluene 43 3 tetrahydrofuran 46 4 acetonitrile 54 5 dmso 63 6 dcm 61 7 dmf 56 8 ethanol 79 9 methanol 75 10 polyethylene glycol (peg) 80 11 h2o 98 a isolated yield a wide variety of catalysts, including l-proline, alum, tetrabutylammonium bromide, nano aluminum oxide (al2o3), zeolites, bulk zno and biogenic zno nps, were employed to study their efficacy for the synthesis of benzyl amino coumarins. 68% yield of product was obtained in 4 h by using bulk zno and the results are presented in table 3 which illustrats that the presence of biogenic nano zno has given the products with 98% yield within 10–15 min. therefore, this catalyst appeared to be of better quality than any of the other catalysts. table 3 influence of different catalysts on the synthesis of benzylamino coumarin derivative 4a entry catalysts time (h) yield a (%) 1 l-proline 6.0 45 2 alum 8.0 30 3 acetic acid 4.5 60 4 bi(no3)35h2o 1.45 94 5 tetrabutylammonium bromide 6.0 25 6 nano aluminium oxide (al2o3) 8.0 26 7 zeolites 7.0 35 8 bulk zno 4.0 68 9 biogenic zno nps 10–15 min 98 a isolated yield after the selection of catalyst, we have concentrated on the amount of the catalyst to be used by varying the mole ratio of the biogenic zno nps.table 4 displays the different mole ratios of catalyst employed on the model reaction. it shows unambiguously that the enhancement of catalyst load from 3 to 15 mol.%, amplified the yield of the desired product to a large extent (38–98%). table 4 optimization of catalyst loading on model reaction entry catalysts yield a (%) 1 nano-zno (3 mol.%) 38 2 nano-zno (5 mol.%) 98 3 nano-zno (7 mol.%) 92 4 nano-zno (10 mol.%) 90 5 nano-zno (15 mol.%) 85 6 nano-zno (5 mol.%) + l-proline 65 7 nano-zno (5 mol.%) + p-toluenesulphonic acid (5 mol.%) 15 8 nano-zno (5 mol.%) + methanesulphonic acid (5 mol.%) 29 9 nano-zno (5 mol.%) + boric acid (5mol.%) 25 10 nano-zno (5 mol.%) + tetrabutylammonium bromide (5 mol.%) 30 a isolated yield of the pure product again, it also observed that no other additive combinations like protic or lewis acids are at all beneficial in this method. these groundwork results encouraged us to advance the applicability of the catalyst for the synthesis of coumarin derivatives. to study the possibility and limitations of this protocol, we engaged a series of aromatic aldehydes with ethylamine to get the resultant bac. in view of these results, we propose a mechanistic interpretation for the high catalytic activity of biogenic nanocrystalline zno, especially in aqueous media. the nano zno catalyst-water colloidal combination plays vital accountability for the swift formation and stabilization of the imine intermediate. the catalyst may encourage 4-hydroxy coumarin to act as the mannich donor for the rapid formation of benzylamino coumarin derivatives. the swift imine generation and subsequent c–c bond development within a very little instant catalyzed by amphoteric nano zno (colloidal composite) are the striking features of this protocol. to generalize this method, the reaction was studied using different aromatic aldehydes and the results are appended in table 5. aromatic aldehydes with different substitutions underwent smooth reactions with ethylamine and 4-hydroxycoumarin, furnishing the respective products in good yields and considerably shortened reaction time in comparison with the previously reported methods. however, under the same conditions, when the aliphatic aldehydes were used as starting materials, for up to 12 h we could not observe any products, but after 14 h, traces of biscoumarin were observed. table 5 optimization of the model reaction entry aldhyde amine product time (min) yield a % m.p. (°c) 1 4cl ch3ch2nh2 4a 15 98 189–191 2 4–no2 ch3ch2nh2 4b 10 95 315–317 3 3–no2 ch3ch2nh2 4c 10 94 310–312 4 h ch3ch2nh2 4d 15 93 274-276 5 4–oh ch3ch2nh2 4e 15 90 245–247 6 3–oh ch3ch2nh2 4f 10 91 237–239 7 4–och3 ch3ch2nh2 4g 10 90 235–237 8 4–oh, 3–och3 ch3ch2nh2 4h 15 90 288–290 chimica techno acta 2022, vol. 9(1), no. 20229104 article 7 of 16 fig. 6 electronic spectra of synthesized compounds in different solvents chimica techno acta 2022, vol. 9(1), no. 20229104 article 8 of 16 further, the same reaction was performed using aromatic amines, but no detectable products were obtained and this may be due to the low solubility of aromatic amines in water. 3.2. absorption studies the uv–vis absorption spectra of compounds 4(a–h) were recorded in various solvents and the effect of solvent polarity and the electronic substitution were studied at a concentration of 10–5 m at room temperature. the typical absorption spectra are displayed in fig. 6. the absorption maxima (λmax) and its corresponding logarithmic molar extinction coefficient (intensity of the absorption) for all the compounds in studied solvents were obtained from the plot and summarized in table 6 and table 7, respectively. the electronic spectra of the synthesized compounds 4(a–h) showed broad peaks in the region 300–325 nm due to π→π* transitions respectively and additional peaks from 420–510 nm appeared in these compounds were owing to the interaction of attached electron-donating groups (4–oh, 3–oh, och3, and 4–oh och3) with polar solvent due to n→π*. from the close examination of the spectral data (table 6), it can be noted that as the solvent polarity increases, the absorption maxima shift towards a longer wavelength so that the bathochromic shift is observed in all the compounds. this may be due to the effective interaction between the solvent molecules and the lone pair of electrons present on the electron-donating sites of synthesized compounds. the presence of electron-donating substituents on the aromatic ring group also contributes to the bathochromic shift. this study concludes that solvent polarity and electronic substitution played a very important role in the shift of λmax for all the studied compounds. table 6 the electronic spectral data of the compounds (4(a–h)) in different solvents compounds max (nm) chcl3 dcm dmf dmso acn meoh 4a 312 317 306 310 312 314 4b 309 317 314 321 312 316 4c 308 315 316 316 311 315 4d 306 317 311 314 311 316 4e 310 311 311 311 308 315 4f 308 310 311 319 308 315 4g 308 314 312 320 312 315 4h 306 315 314 312 312 317 3.3. in silico molecular docking studies 3.3.1. drug likeness (molinspiration physicochemical parameters) molinspiration software was used to predict the physicochemical parameters of synthesized compounds 4(a–h) like drug-likeliness activities and it is used to make sure whether the synthesized compounds are alike to existing drugs. drug-likeliness measurements were governed by the famous rule called lipinski’s rule of five and druglikeliness data were useful to study the pharmacokinetic parameters like absorption, distribution, metabolism, and excretion from the living body [30, 31]. the computed values are tabulated in table 8. all the compounds exhibited fine physicochemical parameters: enough number of rotational bonds, which would illustrate good flexibility. further, the ample number of h-donors and h-bond acceptors of the synthesized compounds exhibited strong binding with target molecules. the good absorption values from computed data uncovered by all the synthesized compounds and so can easily be absorbed by the living systems. the % abs was calculated by using the formula % abs = 109–(0.345 x tpsa). all the synthesized compounds showed good absorption, i.e., % abs = 60.5482–76.3561 which ranges from considerable to good range. also, we calculated the hydrophilicity values of the octanol-water partition coefficient (milogp), which indicates toxicity, absorption, and drug-receptor interactions. the data range of milogp for the synthesized compounds is from 1.05 to 2.19. this range is less than 5.0 and showed good concurrence as per lipinski’s rule. also, the number of h-bond acceptors ranges from 2–5 for synthesized compounds that are less than 10, and the number of h-bond donors for all synthesized compounds is 2 and thus, less than 5 as per the rule. according to the lipinski (pfizer's rule) of five for any chemical compound, as an oral drug would be biologically active if it does not violate more than one rule out of the proposed rules wherein, the first rule said, the octanol-water partition coefficient (milogp) must be ≤5; the second rule said, the molecular weight of the probable drug must be <500 daltons; the third rule said, taking into consideration of the number of h-bond acceptors in the molecule under consideration must be ≤10 and the last rule said, the number of h-bond donors must be ≤5 [32, 33]. table 9 disclosed bioactivity results, showing that the parameters of all the synthesized compounds were within limits of lipinski’s rule of five with no violation of rules. thus, all the synthesized molecules 4(a–h) possessed good drug-like properties. 3.3.1.1. admet studies admet prediction for all the designed compounds was evaluated using the admet descriptor module of the admet lab web-based server [34]. various adme descriptors like logs, logp, intestinal absorption, caco-2 permeability, plasma protein binding percentage, cns blood-brain barrier, cytochrome p450 models, and toxicity descriptors like hepatotoxicity, mutagenicity, ld50 value, half-life and clearance of the drug were used to predict properties related to pharmacokinetics. the synthesized compounds were subjected to study their toxicity before their application. all of them moderately toxic, having a lower value of ld50 compared to the standard (ld50  500 mg/kg indicate high toxicity, ld50 500 to 1000 mg/kg indicates reasonable toxicity. ld50 1000 to 2000 mg/kg shows low toxicity). the ld50 values are listed in table 10. chimica techno acta 2022, vol. 9(1), no. 20229104 article 9 of 16 table 7 logarithmic molar extinction coefficient of studied compounds 4(a–h) compounds logarithmic molar extinction coefficient (l m–1 cm) chcl3 dcm dmf dmso acn meoh 4a 6.1373 6.1781 6.0047 6.1401 6.0955 6.0812 4b 6.1586 6.1522 6.1078 6.2848 6.1251 6.1303 4c 6.1565 6.0820 6.1945 6.2219 6.1115 6.1414 4d 6.0996 6.1473 5.8356 6.2151 6.1878 6.1559 4e 6.1705 5.9934 6.0224 6.1338 5.8509 6.1489 4f 6. 1728 6.1489 5.9925 6.2798 6.1065 6.0989 4g 5.9929 5.9929 5.9661 6.2846 6.1061 6.1075 4h 6.1051 6.1051 6.1287 6.1120 6.1146 6.1146 table 8 drug-likeliness results of the synthesized compounds 4(a–h) compound mw g/mol logp nha nhd tpsa nviolations 4a 329.080 3.465 4 2 62.470 0 4b 340.110 2.634 7 2 105.610 0 4c 340.110 2.617 7 2 105.610 0 4d 295.120 2.633 4 2 62.470 0 4e 311.120 2.903 5 3 82.364 0 4f 311.337 2.903 5 3 82.723 0 4g 341.363 2.912 6 3 91.931 0 4h 355.391 3.302 6 3 91.931 0 table 9 admet results of the synthesized compounds 4(a–h) ligands a logs (log mol/l) b pcaco (cm/s) c intetstinal absorption(hia) in % d logpgi (inhibitor) e logpgi substrate f logbb probability g plasma protein binding in % h cyp450 2d6 inhibitor i p450 cyp2d6 substrate 4a –3.469 –4.930 63.1 ni ns 0.896 95.668 ni ns 4b –3.370 –4.953 45.8 ni ns 0.773 95.378 ni ns 4c –3.198 –4.975 45.8 ni ns 0.696 93.374 ni ns 4d –2.881 –4.930 60.0 ni ns 0.888 91.289 i ns 4e –2.781 –5.004 40.5 ni ns 0.735 93.256 ni ns 4f –2.624 –5.079 44.5 ni ns 0.656 85.096 ni ns 4g –2.800 –5.036 34.9 ni ns 0.676 87.738 i ns 4h –3.083 –4.949 29.2 ni ns 0.593 91.268 ni ns ibuprofen –3.736 –4.379 85.7 ni ns 0.991 87.592 ni ns a predicted aqueous solubility (optimal level – higher than – 4 log mol/l); b predicted caco-2 cell permeability (cm/s) (optimal level higher than –5.15); c predicted human intestinal absorption in % ( acceptable level ≥30%); d predicted p-glycoprotein inhibitor (i – inhibitor, ni – non inhibitor); e predicted p-glycoprotein substrate (s – substrate, ns – non-substrate); f blood/brain barrier probability (acceptable value >=0.1 is acceptable, <0.1 is poor ); g plasma protein binding (optimal level greater than 90% drugs that are highly protein-bound and have a low therapeutic index); h cyp450 2d6 inhibitor (i-inhibitor, ni-non-inhibitor); i p450 cyp2d6 substrate (s – substrate, ns – non-substrate). table 10 toxicity evaluation designed molecules 4(a–h) ligands a t ½ half life (h) b clearance (l/min/kg) c ld50 (mg/kg) d human hepatotoxicity e ames toxicity 4a 1.910 1.690 811.387 yes no 4b 1.625 1.753 911.815 yes yes 4c 1.564 1.754 790.509 yes yes 4d 2.070 2.078 708.467 yes no 4e 1.760 2.348 692.199 yes no 4f 2.249 2.324 658.007 yes no 4g 1.578 2.086 616.902 yes no 4h 1.690 2.140 577.704 yes no ibuprofen 0.801 0.536 2555.452 yes no a half life in hour (optimal level >0.5 h, >8 h – high, < 3h – low); b clearance of drug in ml/min/kg (>15 ml/min/kg – high; 5ml/min/kg<cl<15ml/min/kg – moderate; <5 ml/min/kg – low); c ld50 oral rat acute toxicity in mol/kg; d human hepatotoxicity (yes – heptatoxic, no – nonheptatoxic); e ames mutagenicity (yes – mutagenic, no – non-mutagenic). chimica techno acta 2022, vol. 9(1), no. 20229104 article 10 of 16 after the determination of cytotoxicity and an in silico molecular docking, the study was carried out with cyclooxygenase cox-2 to learn the interaction and binding mode with different amino acids, the binding energy, number of hydrogen bonds, and hydrophobic interactions, docking scores (affinity) were compared with the diclofenac. the molecular docking results of synthesized compounds are given in table 11. from the in silico studies, it was confirmed that all the studied compounds 4(a–h) have the most similar binding energy compared to diclofenac the most potent cytotoxic compound 4f has a strong binding affinity (–9.3 kcal/mol) which is equal to the binding energy of diclofenac sodium by forming one hydrogen bond with ser530. fig. 7–9 shows the 2d and 3d representation of the interaction of synthesized compounds 4(a–h) and standard diclofenac drug. 3.3.1.2. preparation of ligand the structure of ligands was drawn using chemdraw software and the build of 3d structure and energy of each ligand was minimized using the uscf chimera tool by applying the amber force field and then ligands were converted into pdb format. 3.3.1.3. preparation of the receptor the crystal structure of diclofenac bound to the cyclooxygenase active site of cox-2 pdb id: 1pxx [35] was accessed through a protein data bank [36]. the co-crystal structures of proteins and water molecules are removed from proteins. with the addition of hydrogen, merging of nonpolar hydrogen, adding charges, and energy minimization of proteins by an amber force field carried out by using the uscf chimera tool, prepared proteins were transformed into pdb format. 3.3.1.4. grid box selection based on the active site and binding site tyr385, his07, tyr55 and arg120 grid boxes were arranged. 3.3.1.5. docking and visualization the setting of a grid box around the active sites of proteins, designed ligands were docked against the receptor using autodock vina in the pyrx workstation. the autodock vina docking algorithm has been used to search for the best-docked ligand and target conformation. ligands with the lowest binding affinity were considered as the best conformation, docked protein and target were converted into pdb format by schrodinger pymol, and interactions – visualized biovia discovery studios [37–40]. the structure of the protein used is given in fig. 10. all the docking results of ligand molecules showed potential ligand affinity. amongst the docked molecules in complex with cyclooxygenase cox-2, the compounds 4b, 4h and 4g were found to have the best dock confirmation with a maximum binding affinity (–8.0, –8.0 and –8.1 kcal/mol); the compound 4b establishes four hydrogen bonds and the compound 4h exhibits two hydrogen bond with the active enzymatic sites. also, the compounds 4a and 4h showed a more hydrophobic interaction with the tested protein compared to the standard. the compounds 4d, 4g and 4h have electrostatic interactions. concerning in silico, all eight compounds showed good hydrophobic interactions with the bindin g affinity values ranging between 8.0 –9.3 kcal/mol against the amino acid molecules regarding the cyclooxygenase cox-2 synthase protein. table 11 docking results of ligands with cyclooxygenase cox-2 ligand binding affinity (kcal/mol) hydrogen bond interaction hydrogen bond length in å electrostatic interaction hydrophobic and other interactions 4a –8.7 ser530, gly526 2.06, 3.64 – val349,ala526, val116, tyr385, val523, leu352, trp387, phe518, leu359, ser532, tyr348, tyr355, met13 4b –8.0 his90, phe518, ser353, ser530 2.66, 2.69, 2.84, 3.31 – val523, tyr355, leu359, val349,leu352, ala527, arg513, phe381, tyr385, arg120, gly526 4c –8.6 tyr355 2.14 – val523,leu531, val349, ser530, arg513, ala527, his90, phe518, tyr385 4d –8.8 ser530, ser353 2.39 met522 trp387, ala527, leu357, tyr348, val344, leu352, arg120, gly526, tyr385 4e –8.8 ser530 2.22 – val349, trp387, ala527, leu357, tyr348, val344, leu351, val523 4f –9.3 ser530 2.32 – val349, trp387, ala527, leu357, tyr348, val344, leu351, val523 4g –8.1 ser530, val523, met522 2.61, 3.1, 3.33 met113 leu359, ala527, val116, leu531, leu532, tyr385, trp387, phe518. tyr355, arg120 4h –8.0 ser530, val523 2.69, 3.20 met113 leu359, ala527, val116, leu531, leu532, tyr385, trp387, phe518. tyr355, arg120, gly526, phe381 diclofenac –9.3 tyr385, ser530 2.73, 2.65 – ala527,val349, tyr348, val523, leu351, phe381, trp387, gly526 chimica techno acta 2022, vol. 9(1), no. 20229104 article 11 of 16 2d 3d bonding interactions fig. 7 binding mode and visual interaction of designed ligands with 1pxx (4(a–d)) 4a 4b 4c 4d chimica techno acta 2022, vol. 9(1), no. 20229104 article 12 of 16 2d 3d bonding interactions fig. 8 binding mode and visual interaction of designed ligands with 1pxx (4(e–h)) 4e 4g 4h 4f chimica techno acta 2022, vol. 9(1), no. 20229104 article 13 of 16 4. applications 4.1. biological studies 4.1.1. antioxidant study the dpph free radical scavenging activity of synthesized compounds 4(a–h) was investigated according to the reported method with suitable modification [41–43]. dpph (0.004%) in 95% of methanol was used for the preparation of a stock solution of synthesized compounds (1 mg/ml). the freshly prepared methanolic solution of dpph was taken in the test tube and the stock solution was added (100 μg) to each test tube so that the ultimate volume will be 3ml. after 10 min, the absorbance was recorded using a spectrophotometer at 517 nm. ascorbic acid (aa) was used as a reference standard and control sample having the same volume with no stock solution. the experiment was performed thrice and the ic50 values are exhibited in table 12. fig. 11 represents the plot of ic50 values of synthesized compounds. the dpph radical scavenging activity (%) has been calculated and expressed as: % inhibition (i) = (ab – aa/aa)·100, (3) where ab – absorbance of blank (dpph solution with no test sample), and aa – absorbance due to sample (dpph solution with test sample). from the results, it was revealed that compounds 4h, 4g and 4f with the lowest ic50 value of 78, 81 and 89 μg/ml showed excellent scavenging activity, followed by the compounds 4d and 4e that exhibited noteworthy action with ic50 values 96 and 112 μg/ml, respectively. fig. 10 structure of cyclooxygenase cox-2 table 12 antioxidant activity results of the synthesized compounds 4(a–h) compounds ic50values (μg/ml) 4a 141 4b 137 4c 198 4d 96 4e 112 4f 89 4g 81 4h 78 ascorbic acid 118.29 fig. 11 antioxidant activity results of the synthesized compounds 4(a–h) the compounds 4a, 4b and 4c, showed comparably less stress-reducing activity with the ic50 values 137 and 141 respectively. the compound 4c showed the least scavenging activity with an ic 50 value of 198 μg/ml. the compounds 4d, 4e, 4f, 4g and 4h exhibited more scavenging activity than the standard ascorbic acid. from table 12, it can be concluded that compounds with an electron-donating group possess greater scavenging activity with less ic 50 values than compounds with an electron-withdrawing group of high ic50 values. 2d 3d bonding interactions fig. 9 binding mode and visual interaction of designed ligands with 1pxx (diclofenac) diclofenac chimica techno acta 2022, vol. 9(1), no. 20229104 article 14 of 16 4.2. corrosion studies 4.2.1. weight loss technique the mild steel specimens (sheet) of compositions of 0.41% c, 0.46% mn, 0.24% s, 0.22% si, 0.17% al and remaining is of fe were used. the steel coupons of dimensions 5 cm×2 cm×0.2 cm were chosen for the weight loss experiment. the test solution (1 m hcl) was prepared and a bac (1 mm) was prepared using 1:50 (v/v) of dmso/millipore water. different concentrations of bac solutions (0.0, 0.001, 0.005, 0.01, 0.05, 0.1, and 1 mm) were prepared using 1 m hcl 4.2.2. effect of concentration weight loss measurements were carried out by weighing ms specimens before and after their immersion in 100 ml of pure 1 m hcl and also having different amounts of bac in 1 m hcl. all experiments were conducted at atmospheric ambient pressure and in the temperature range of 303– 333 k. the corrosion rate (𝜐corr) and inhibition efficiency (ie) ( %) were calculated using the following equations 4 and 5, respectively. 𝜐corr = 𝑊0 − 𝑊1 𝑆𝑡 , (4) where w0 is the weight loss value in the absence of bac, w1 is the weight loss value in the presence of bac, s is the surface area of the ms specimen, t is the temperature. the corrosion rates (cr) were determined by using equation 5. % = 𝑊0 − 𝑊1 𝑊0 · 100 (5) among all the synthesized compounds 4e, 4f and 4h exhibited superior ie, compounds 4d and 4g showed reasonable ie, and compounds 4c, 4b, and 4a exhibited the least ie against 1m hcl solution. from table 13 it was concluded that among all the synthesized compounds, those with electron-donating groups on the aromatic ring show the exceedingly superior corrosion inhibition property than compounds with electronwithdrawing groups on the aromatic ring [44], which is depicted in fig. 12. 4.2.3. effect of temperature a study of the corrosion ie of synthesized compounds on ms in acid solutions of the synthesized compounds at different temperatures (303, 313, and 323 k) indicated that ie is better at lower temperature and decreases with temperature, as shown in fig. 13. the decrease in ie with a rise in temperature is indicative of physisorption, which could be attributed to the gradual desorption of the adsorbed synthesized compounds from the surface of the metal [45, 46]. fig. 12 corrosion inhibition efficiency of the synthesized compounds fig. 13 influences of temperatures on corrosion efficiencies of bac at fixed time table 13 corrosion inhibition efficiency of the synthesized compounds 4(a–h) compounds weight in gram corrosion rate gram/day inhibition efficiency (ie) initial w1 final w2 difference w 4a 3.9750 3.3782 0.4968 0.0001295 11.12 4b 3.7793 3.3060 0.4733 0.0017854 15.33 4c 3.7858 3.4200 0.3658 0.004025 34.56 4d 3.6377 3.3550 0.2827 0.005756 49.42 4e 3.8048 3.3891 0.4157 0.0086604 74.36 4f 3.7195 3.2383 0.4812 0.0100250 86.08 4g 3.8651 3.3954 0.4697 0.0097854 84.02 4h 3.8738 3.4073 0.4665 0.0097187 83.45 blank 3.9000 3.3410 0.5590 – – chimica techno acta 2022, vol. 9(1), no. 20229104 article 15 of 16 5. recyclability of the catalyst the recyclability of the catalyst tests was performed to ensure the principle of green chemistry. the recycled catalyst used 6 times without any treatment and no appreciable loss in its catalytic activity was observed up to the sixth run (92%), which is demonstrated in fig. 14. fig. 14 recyclability of the catalyst 6. conclusions we reported the novel synthesis of 3-[(ethylamino) (phenyl) methyl]-4-hydroxy-2h-chromen-2-one derivatives using biogenic zno nps as a catalyst. further, the structures of synthesized compounds were elucidated by different spectroscopic techniques. absorption studies revealed that a bathochromic shift was observed in all the studied compounds. the admet studies revealed that all the compounds have drug likeliness properties, and in silico molecular docking studies revealed a good docking score of studied compounds with respect to cyclooxygenase cox-2. all the studied compounds exhibited superior antioxidant activity against ascorbic acid as standard. the corrosion study revealed that the new bac functioned as a good corrosion inhibitor for ms in 1 m hcl solution. furthermore, the recycled catalyst exhibited better catalytic activity up to the sixth run. acknowledgment the authors are thankful to the chairman, department of chemistry, kuvempu university shankaraghatta for providing the laboratory facilities and to the university of mysore and saif karnatak university, dharwad for 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pt(0.1%)-fe(5%)/al2o3 catalysts promoted with various additives published by ural federal university eissn 2411-1414; chimicatechnoacta.ru letter 2022, vol. 9(3), no. 20229308 doi: 10.15826/chimtech.2022.9.3.08 1 of 5 conversion of model c6–c9 alkanes and straight-run gasoline over pt(0.1%)-fe(5%)/al2o3 catalysts promoted with various additives arai k. zhumabekova a , lyazzat k. tastanova b* , raigul o. orynbassar c , yermek a. aubakirov c , elvira b. zhunusova a a: chemistry, chemical technology and ecology department, kazakh university of technology and business, nur-sultan 010000, kazakhstan b: chemistry and chemical technology department, k. zhubanov aktobe regional university, aktobe 030000, kazakhstan c: department of physical chemistry, catalysis and petrochemistry, al-farabi kazakh national university, almaty 050040, kazakhstan * corresponding author: lyazzatt@mail.ru this paper belongs to the ctfm'22 special issue: https://www.kaznu.kz/en/25415/page. guest editors: prof. n. uvarov and prof. e. aubakirov. © 2022, the authors. this article is published in open access under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). abstract growing demand for hydrogen promotes the research devoted to the development of new catalysts for hydrocarbons processing in absence of h2 or at its low concentration. in the present work, it was shown that during the conversion of straight-run gasoline on a zeolite-containing polyfunctional catalyst in a hydrogen-free environment cracking, dehydrogenation, isomerization and alkylation take place due to the redistribution of h2 between initial and formed products directly on the catalyst surface. fine particles (≤50 å) localize in zeolite cavities and pores of aluminum oxide, while larger ones are on their outer surface. keywords c6–c9 n-alkanes straight-run gasoline zeolite-containing catalyst modification additives received: 25.06.22 revised: 18.07.22 accepted: 18.07.22 available online: 26.07.22 key findings ● high-octane gasoline containing 62.4% isoalkanes and 2.3% aromatic hydrocarbons is obtained on zeolite-containing catalyst at 350 °c with h2:feedstock ratio = 200:1. ● decrease in h2:feedstock ratio to 50 leads to increase of hydrocracking direction, formation of aromatic hydrocarbons and olefins as well as c10–c13 isoalkanes obtained as a result of a disproportionation reaction. ● decrease in h2:feedstock ratio leads to essential change in the composition of straight-run gasoline. the presence of aromatic hydrocarbons and olefins, which are octane-forming components, increases the motor properties of gasoline. c10–c13 isoalkanes are the components of diesel fuel. 1. introduction many processes at petrochemical and chemical plants are based on the use of hydrogen or hydrogen-containing gas (hcg) [1–3]. due to the rapid growth of hydrogen energy application, the shortage and cost of hydrogen are increasing [4–8]; therefore, reducing the consumption of hcg by developing new catalysts and technologies is urgently needed [9–11]. in the literature [12–16] there are data on transformation of model n-alkanes over pt/zeolite catalysts. during n-octane conversion on pt/hy catalysts (t = 300 °с, p = 0.18 mpa, h2/octane ratio is 16 mol.%), selectivity of isomers formation rises from 16.0% (0.02% pt) up to 80.6% (10% pt) with increasing platinum concentration. under these conditions cracking direction decreases from 82.2 to 20.6% [17]. it was shown, that conversion of n-hexane over 0.3% pt-containing zeolites of l and eryonite (e) type is influenced by the degree of ion exchange of k+. under the same conditions (t = 400 °c), the conversion of n-hexane increases from 26.1 to 47.0% with an increase in the degree of ion exchange from 17.0% to 82.0% in l zeolite. according to nh3 adsorption, three types of acid centers with binding energy (q) equal to 100, 110 and 120 kj/mol were determined in the catalyst. the highest activity in the nhexane isomerization reaction is typical for the centers with q = 120 kj/mol, while the acid centers with lower http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2022.9.3.08 mailto:lyazzatt@mail.ru http://creativecommons.org/licenses/by/4.0/ https://orcid.org/0000-0001-6743-8953 https://orcid.org/0000-0002-9236-5909 https://orcid.org/0000-0002-6198-3018 https://orcid.org/0000-0001-5405-4125 https://crossmark.crossref.org/dialog/?doi=https://doi.org/10.15826/chimtech.2022.9.3.08&domain=pdf&date_stamp=2022-7-26 chimica techno acta 2022, vol. 9(3), no. 20229308 letter 2 of 5 binding energy also participate in hydro isomerization but with low efficiency [18]. molecular sieve effect was shown when comparing the properties of catalysts containing l and e zeolites. on l-zeolite with wide pores (0.71 nm) isomer yield is greater than on e-zeolite with narrowpores (0.36x0.52 nm). in the latter case, the pores are not accessible to branched isomers. in the present work, conversion of c6–c9 n-alkanes on pt-fe/al2o3+hzsm catalyst modified with additives of cerium, molybdenum and phosphorus in the presence of h2 was studied. processing of straight-run gasoline was carried out with varying content of hydrogen and in its absence. 2. experimental the catalyst was prepared by impregnation of the al2o3+hzsm mixture with water solutions of fe(no3)3∙9h2o, (nh4)6mo7o24∙4h2o, ce(no3)3∙6h2o, h2ptcl6 and other salts. the wet catalyst sample was formed into granules, dried at 100–250 °c for 5 hours with a heating rate of 20–30 °c/min and calcined at 500 °c for 5 hours. the tatalyst was studied in the reaction of transformation of c6–c9 n-alkanes and straight-run gasoline on the laboratory flow-through unit at the temperatures varying from 280 °c up to 400 °c, the hydrogen pressure of 2mpa, the h2/feed ratio of 200/1, 50/1 and 0/1, and the volume feed rate of 5 h–1. hydrocarbon composition of the reaction products was analyzed on a "chrom-4" chromatograph with a stainless steel column filled with γaluminum oxide by "supelco". argon was used as a carrier gas. 3. results and discussion the conversion and direction of c6–c9 n-alkanes transformation on the pt(0.1%)-fe(5%)/al2o3+hzsm catalyst modified with various additives is affected by the process temperature under otherwise equal conditions (ph2 = 2mpa, v = 5 h–1, h2/feedstock ratio = 200/1). table 1 shows the results obtained at n-nonane processing. as the temperature rises from 300 to 400 °c, the conversion of n-nonane increases from 51.2 to 93.6%. as shown in table 1, the olefins formed during dehydrogenation of intermediate activated surface complexes are rapidly isomerized through the carbonium ion formation and hydrogenated to isoalkanes. due to this, only tracess of olefins are present in the products mixture. other directions of olefins transformation probably include formation of aromatic hydrocarbons (0.1–2.7%) at temperatures of 350–400 °с. the maximum yield of c4–c8 isoalkanes (35.7%) is determined at 350 °c. the assumed mechanism of alkane conversion is possible on the active catalyst sites containing both metal and acid centers. figure 1 presents the data on c6–c8 n-alkanes conversion on the pt-fe/al2o3+hzsm catalyst promoted by different additives and the yield of isomers at different temperatures. with the increase in temperature, conversion of nalkanes grows, and at 400 °c it reaches 96.7–97.9%. the temperature dependence of maximum yield of isomers is observed at close conversion degrees of c6–c8 n-alkanes. the curves pass through the extrema at 350–380 °c. the maximum yield (%) decreases in the following series: hexane (32.0%) > heptane (30.6%) > octane (30.3%). in the high temperature area (>350 °c) the formation of aromatic hydrocarbons (0.1–2.8%) and olefins (tracess) is observed. physical and chemical properties of the polyfunctional, promoted with additives, pt (0.1%)-fe(5%)/al2o3+hzsm catalyst were studied by bet, xrd and electron microscopy (em) methods. the specific surface area and total pore volume of the catalyst are 179.2 m2/g and 0.40 cm3/g, respectively. the xrd results show that the catalyst is dispersed. hzsm structural elements (reflexes 12.5; 10.9; 9.8; 3.83; 3.70; 3.64; 2.96 å), се (reflex 2.76 å) (astm 38-763), pt (superimposed with γ-al2o3, reflex 2.27 å) (astm 4-802), ε-fe2o3 (1.46 å) (astm 16-895), γ-al2o3 (reflexes 2.40; 1.98; 1.40) are present. table 1 influence of temperature on n-nonane conversion on zeolite-containing pt-fe/al2o3 catalyst (p = 2 mpa, v = 5 h –1, h2/feedstock ratio = 200). products composition, % temperature, 0с 300 320 350 380 400 с1–с3 hydrocarbons 1.8 10.9 20.7 34.3 36.5 с4–с9 isoalkanes 20.2 30.9 35.7 33.2 31.5 с4–с8 n-alkanes 29.2 29.4 26.1 23.8 22.9 olefins traces traces traces traces traces aromatic hydrocarbons – traces 0.1 0.2 2.7 feedstock 48.8 28.8 17.4 8.5 6.4 n-nonane conversion, % 51.2 71.2 82.6 91.5 93.6 figure 1 influence of temperature on c6–c8 n-alkanes conversion and yield of isomers (p = 2 mpa, v = 5 h–1, h2:feed = 200:1). 1, 4 – isoalkanes yield and conversion of n-hexane. 2, 5 – isoalkanes yield and conversion of n-heptane. 3, 6 – isoalkanes yield and conversion of n-octane. chimica techno acta 2022, vol. 9(3), no. 20229308 letter 3 of 5 the em study (120000 magnification) showed the presence of an aggregate in the pt-fe/al2o3 catalyst modified with cerium, molybdenum and phosphorus, which consists of dense particles of ~200 å size. the micro diffraction pattern is represented by two rings and can be attributed to fe2o3 hematite (јcpds, 35-664). at low magnification, large elastic lamellar crystals with basal reflections on their bends were detected. the micro diffraction pattern can be attributed to feooh (jcpds, 26792). small loose clusters of dispersed particles with sizes of 20 ǻ were found in the sample; according to the micro diffraction pattern, they represent ceo2 (jcpds, 34-394). small loose clusters of ~100 å particles give a diffraction pattern which can be attributed to a mixture of pt3o4, mo9o26 (јcpds, 21-1284) and cealo3 (јcpds, 28-260). characteristic extensive clusters of 30–40 å particles of ce6o11 were detected. an aggregate of loose small particles 30–50 å in size was found, which is a mixture of се(moo4)2, се2mo3o12 and pto2 (јcpds, 57-330). the sample also contains individual large dense crystals with cut features represented by the reflections with hexagonal arrangement, and they are related to femoo4, cep, β-moo3 (јcpds, 37-1445), and pto2 (јcpds, 23-1306). nanosized (20–100 å) homoand heteroatomic clusters were found in the zeolite-containing pt(0.1%)fe(5%)/al2o3 catalyst modified with phosphorus, molybdenum, and cerium additives. in the calcined catalyst (t = 500 °с), platinum (d = 30–100 å) and iron (d = 200 å) are in the form of oxides. iron and cerium (d = 20–50 å) interact with molybdenum, forming precursors (femoo4, cemoo4, ce2mo3o12), which transform into heteroatomic fe–mo and ce–mo nanoclusters in reducing medium. analysis of the obtained data on dimensionality and structure of metal particles of the catalyst active phase allows us to conclude that it is possible to synthesize nanocatalysts with given composition and properties by directed selection of precursors. presence of phosphorus in the catalyst prevents the formation of heteroatomic pt–fe, pt–mo clusters, whereas the introduction of molybdenum into the catalyst composition in the absence of phosphorus increases the dispersion of metal particles and promotes the formation of heteroatomic highly dispersed clusters at calcination. however, it cannot be excluded that such heteroatomic clusters may be formed during the hydrogen treatment of the catalyst (350–400 °c). metal nanoparticles are localized in the cavity and mouths of zeolite and pores of aluminum oxide. in addition, larger 100–200 å crystals were detected by electron microscopy method on the smooth surface of zeolite. it is known from the literature [19, 20] that reduction of iron (iii) into iron (ii) and iron (0) is observed under hydrogen treatment of air calcined pt–fe/al2o3 – systems [19]. the formation of pt–fe clusters, which facilitates and accelerates the reduction of iron, was detected by ngrs method [20]. zeolite-containing pt(0.1%)-fe(5%)/al2o3-catalyst a modified with additives (mo, ce, p) were studied in the process of straight-run gasoline hydro refining at varying temperatures (280–400 °с), and h2:feed ratio (pressure – 2 mpa, v = 5 h–1). at temperature rise from 280 up to 400 °с (рн2 = 2 мpa, v = 5 h–1, н2:feed=200:1), it was shown, that hydrocracking, hydro isomerization and dehydrocyclizationare occur on the catalyst at hydro refining of straight-run gasoline. the formation of light c1–c3– hydrocarbons occurs at t≥350 °c, and at 400 °c their yield is 17.6% (table 2). the optimum yield of c4–c9 isoalkanes, 62.4%, was determined at 350 °c. at lower and at higher temperatures the yield of c4–c9 isoalkanes decreases to 50.5 and 51.3%. c10–c13 isoalkanes – 15.6%, c4–c9 n-alkanes – 15.3%, c10–c13 n-alkanes – 0.5% and aromatic hydrocarbons – 2.3% are also present in the product mixture. olefins appear (0.3–0.4%) at temperatures ≥380 °c. at straight-run gasoline hydro refining, attention was paid to the influence of h2:crude ratio on the direction of the process. the data on straight-run gasoline conversion on the pt-fe/al2o3 zeolite-containing catalyst at h2:feed=50:1 are presented in table 3. in this case, the process was carried out in the temperature range of 350– 400 °c. the maximum hydro refining of straight-run gasoline occurs in these conditions. it follows from table 3, that with h2:feed ratio decreasing to 50/1 the isomerizing activity of the catalyst decreases from 62.4 to 54.3%. table 2 conversion of straight-run gasoline on zeolite-containing pt-fe/al2o3 catalyst (p = 2 mpa, v = 5 h –1, h2:feed=200:1). products composition, % process temperature, 0с 280 300 320 350 380 с1–с3– hydrocarbons – – traces 3.9 10.9 с4–с9 isoalkanes 50.5 54.7 56.7 62.4 54.2 с10–с13 isoalkanes 20.4 19.5 19.7 15.6 13.8 с4–с9 n-alkanes 26.9 23.3 21.1 15.3 18.7 с10–с13 n-alkanes 0.3 0.6 0.7 0.5 traces aromatic hydrocarbons 1.9 1.9 2.0 2.3 2.1 olefins – – traces traces 0.3 liquid phase yield 100 100 100 96.1 89.1 table 3 conversion of straight-run gasoline on zeolite-containing pt-fe/al2o3 catalyst (p = 2 mpa, v = 5 h –1, h2:feed=200:1). products composition, % process temperature, 0с 350 380 400 с1–с3– hydrocarbons 6.3 12.4 21.8 с4–с9 isoalkanes 54.3 49.9 42.5 с10–с13 isoalkanes 23.5 20.5 16.9 с4–с9 n-alkanes 8.1 9.9 11.6 aromatic hydrocarbons 7.5 6.9 6.7 olefins 0.3 0.4 0.5 liquid phase yield 93.7 87.6 78.2 chimica techno acta 2022, vol. 9(3), no. 20229308 letter 4 of 5 hydrocracking with formation of c1–c3 hydrocarbons increases from 3.9 to 6.3% at 350 °c. however, at a reduced h2:feed ratio the yield of c10–c13 isoalkanes rises from 15.6 to 23.5% (350 °c). in all studied temperature range the yield of c10–c13 isoalkanes is higher than at h2:feed ratio = 200:1. the detected effect of a significant increase in the yield of aromatic hydrocarbons from 2.3 to 7.5% (tables 2 and 3) is of particular interest. 0.3–0.5% of olefins were found in the products. in order to elucidate more fully the role of hbg, the study of the catalyst activity in processing of straight-run gasoline in the absence of hydrogen was carried out. it was shown that the yield of с4–с9 isoalkanes at 350 °с is 62.6%, and with the rise of temperature up to 400 °с the content of isoalkanes in the product mixture falls to 39.0%. at the same time, there is a disproportionation reaction, which leads to c10–c14 isoalkanes and c10–c13 nalkanes appearance. their yields are maximal at 350 °c (14.3% and 4.0% respectively). the most important is the formation of high-octane aromatic hydrocarbons – 5.4% (350 °c) and olefins (6.7%). 4. conclusions thus, in the absence of hydrogen the yield of c4–c9 isoalkanes is 62.6%, and heavier isoalkanes, aromatic hydrocarbons and olefins appear. hydrocracking to c1–c3– hydrocarbons increases at high temperatures (380– 400 °c). at 350 °c the yield of the liquid phase, i.e. gasoline with a sufficiently high octane number is close to 100%. the analysis of the particle size of metals included in the catalyst shows that their dispersion varies within a wide range, from 20 to 200 å. fine particles (≤50 å) can localize in zeolite cavities and pores of aluminum oxide, and large ones-on their outer surface. when the catalyst contacts with n-alkanes, the whole surface participates in the process, but formation of branched isomers of c6+ alkanes is possible only on the outer surface, whereas c1– c4 hydrocarbons of different structure probably appear in zeolite cavities during cracking transformation of nalkanes capable of diffusing deep into the matrix structure. diffusion of molecules and their transformation increase with temperature, which is confirmed by the increase in cracking of n-alkanes. supplementary materials no supplementary materials are available. funding this research had no external funding. acknowledgments none. conflict of interest the authors declare no conflict of interest. author contributions conceptualization: a.k.z., l.k.t. data curation: a.k.z. formal analysis: l.k.t., y.a.a. investigation: a.k.z., l.k.t. methodology: r.o.o., y.a.a. resources: r.o.o. supervision: y.a.a. validation: a.k.z., l.k.t. visualization: e.b.z. writing – original draft: a.k.z., e.b.z. writing – review & editing: l.k.t. additional information author ids: lyazzat k. tastanova, scopus id 57202578243; raigul o. orynbassar, scopus id 57223975563; yermek a. aubakirov, scopus id 55447002200. websites: kazakh university of technology and business, https://kaztbu.edu.kz/; k. zhubanov aktobe regional university, http://zhubanov.edu.kz/en/; al-farabi kazakh national university, https://www.kaznu.kz/en. references 1. wu l, liang xq, kang lx, liu yz. integration 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state of the art chimica techno acta focus review published by ural federal university 2022, vol. 9(2), no. 202292s10 eissn 2411-1414; chimicatechnoacta.ru doi: 10.15826/chimtech.2022.9.2.s10 1 of 8 slow-release agricultural pesticide formulations: state of the art anatoly n. boyandin ab * , anna a. sukhanova a , natalya l. ertiletskaya ab a: scientific laboratory “intelligent materials and structures”, reshetnev siberian state university of science and technology, krasnoyarsk 660037, russia b: institute of biophysics sb ras, federal research center “krasnoyarsk science center of the siberian branch of the russian academy of sciences”, krasnoyarsk 660036, russia * corresponding author: araneus@mail.ru this paper belongs to the mosm2021 special issue. © 2022, the authors. this article is published open access under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). abstract the need for a long-term sustaining of optimal concentrations of applied pesticides in the soil in agriculture resulted in the development of systems for controlled release of active substances. such systems are based on the use of eco-friendly carrier materials that are harmless to plants, humans and environment. inorganic substances (e.g., clays or alike substances), biodegradable polymers of natural or synthetic origin, blends of such polymers and their composites with inorganic fillers can be used as carriers. the deposited pesticides are released by diffusion or, in the case of systems based on biodegradable polymers, by degradation of the carrier. inorganic carriers are usually impregnated with a pesticide. as for polymers, there is a wide range of methods for obtaining forms. namely, these are the microsphere and nanoparticle formation, film casting, tablet pressing, form gelatinizing, and coprecipitation of a pesticide and a polymer from a solution. co-extrusion of pesticides with polymers or their composites at temperatures below the degradation temperature of the components is another promising method for obtaining pesticide carriers. keywords plant protection pesticide long-term release organomodified clay biodegradable polymer composite received: 05.05.22 revised: 17.06.22 accepted: 17.06.22 available online: 27.06.22 key findings ● the application of soil pesticides often requires maintaining their concentrations at optimal levels during the growing season. ● this is complicated by the gradual degradation of the active components due to chemical and biological processes. ● the use of pesticides deposited in different carriers ensures long-term maintenance of optimal bioavailable concentrations in the soil. ● clays, biodegradable polymers, their blends and composites are widely used as carriers of active components. 1. introduction one of the problems related to the use of biologically active preparations (primarily various groups of pesticides) in agriculture is the need to maintain their concentrations at the required level for a long time within the growing season. thus, the germination time of the seeds of many weeds is spread over time; a one-time application of an active but unstable herbicide in the soil may not be sufficient to suppress later seedlings. the application of increased doses of the pesticide poses a risk of an increase in the negative impact on the environment in the initial period. the development of preparations with slow release of active ingredients into the environment can be part of the solution to the problem in relation to the use of soil-based pesticides. in recent years, this area has attracted great interest. many research teams have been investigating the possibility of depositing pesticides of various groups in various carriers, including that of combined composition. since herbicides comprise the largest segment of the pesticide preparations http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2022.9.2.s10 https://orcid.org/0000-0002-9190-2792 https://orcid.org/0000-0002-5830-1450 https://orcid.org/0000-0003-2626-893x mailto:araneus@mail.ru http://creativecommons.org/licenses/by/4.0/ https://crossmark.crossref.org/dialog/?doi=https://doi.org/10.15826/chimtech.2022.9.2.s10&domain=pdf&date_stamp=2022-6-27 chimica techno acta 2022, vol. 9(2), no. 202292s10 focus review 2 of 8 market [1], it is this group of compounds that is most widely studied in the context of development of prolonged forms. there are two main groups of carriers for active ingredients. the first group includes clays and clay-like materials (silicates) of natural origin, or their synthetic analogues. in the soil, the active substances are released from these materials by simple diffusion; the residual carrier material remains as a part of the soil substrate. the second important group of carriers consists of chemically or biologically degradable polymers of different nature. in this case, the active substances are released as the carrier polymer degrades in the soil, although their diffusion from the polymer matrix may also be observed as an additional release mechanism. 2. formulations based on inorganic carriers usually, silicates, natural or modified clay, metal oxides or even clay soil are used as inorganic carriers. the formulations are mainly obtained by impregnation of carrier materials with pesticide solutions [2, 3], as well as by fixation of the preparation on the surface of mineral nanoparticles [4]. in the study [3], diuron and 2,4-dichlorophenoxyacetic acid (2,4-d) herbicides were encapsulated in a layered synthetic silicate magadiite. the inclusion of the herbicides was confirmed by fourier transform infrared analysis (ftir) and x-ray diffraction analysis (xrda). the maximum adsorption numbers of the herbicides were approximately 900 mmol/g for 2,4-d and 1.4 mmol/g for diuron. these values were observed in a highly acidic medium at ph 1.5. the release of herbicides into water was relatively slow and also was affected by ph. specifically, in 42 days, 13.3% and 34.5% of absorbed 2,4-d was released at ph 4.6 and 9, respectively. the respective values for diuron were 17% and 23.5%. the maximum release (14–17% from the total amount of the released herbicides) was observed on the first day of the exposure. in another study [5], glyphosate and 2,4-d herbicides were deposited in the interlayer regions of layered zn/al hydroxides. the depositing was confirmed by xrda and scanning electron microscopy (sem). the 48-hours release of the preparations in distilled water and in 5 and 10 mm solutions of carbonates and chlorides was determined. half of the preparations were released into distilled water in approximately 12 hours. carbonates accelerated the yield of the preparations, whereas chlorides slowed it down. clay-like carriers are often modified with ionic additives. for example, for depositing the anionic herbicide imazapyr, a montmorillonite composite obtained from an aqueous suspension with polydiallyldimethylammonium chloride (pdadmac) was used. the latter constitutes a cation-containing polymer that provides the composite a positive charge and interacts with the herbicide as an antiion [6]. ftir showed the presence of a new peak at 2084 cm–1 in the herbicide-loaded composite, which confirms the formation of electrostatic interactions between the polyamine and the herbicide. the formulations with active ingredient contents of 13, 21 and 40% were obtained. in soil tests, the release of the herbicide from more loaded (40%) formulations was slower than its release from those with a minimum load. specifically, after two waterings, 100% of pesticide in the commercial preparation, 45% of the pesticide at 13% load, and 25% at 45% load of the formulations passed through a thin layer of soil. similarly [7], long-term release formulations of metribuzin were designed by encapsulating the active ingredient in phosphatidylcholine (pc) vesicles and adsorbing the vesicles onto montmorillonite. the maximum active ingredient content in the long-term release formulations was 246 g/kg. infrared spectroscopy results revealed that the hydrophobic interactions between metribuzin and the alkyl chains on pc were necessary for encapsulation. in addition, water bridges connecting the herbicide and the pc headgroup enhanced the solubility of metribuzin in pc. experiments in a sandy soil revealed that the herbicide was not irreversibly retained in the formulation matrix. in soil column experiments, pc–clay formulations enhanced herbicide accumulation and biological activity in the top soil layer relative to a commercial formulation after six irrigations. to impart a positive charge, the addition of trimethylammonium groups to mesoporous silicon oxide nanoparticles was performed, which made it possible to increase their efficiency as a carrier of 2,4-d [4]. as a result, the load of 2,4-d increased from 1.5% to 21.7% compared with pure silicon oxide nanoparticles. an increase in ph and temperature, and, especially, the addition of sodium chloride increased the rate of release of 2,4-d into the water. particularly, in 100 hours approximately 12% of the active ingredient was released at ph 3, about 25% at ph 7, and about 35% at ph 10. the addition of 0.1 m sodium chloride resulted in the release of approximately 60% of the herbicide in 100 hours. in the experiment with soil columns, 15% and 30% of the herbicide were released in 30 and 60 days, respectively. however, later on the release was significantly slowed down to 40% release of the herbicide in 100 days and about 45% – in 350. a substantial advantage of using inorganic carriers is the relatively low cost of both the materials and obtaining methods (impregnation), which is one of the most important factors favoring the use of such preparations. at the same time, diffusion is the only mechanism for the release of biologically active substances from the matrices of this kind, which limits the control of this process. 3. formulations based on biodegradable polymers in the case of biodegradable carriers, the rate of outflow of pesticides, along with simple diffusion, is significantly affected by the rate of degradation of the polymer matrix in the soil. in addition, the range of methods for manufacturing polymer molds is wider than when inorganic carrichimica techno acta 2022, vol. 9(2), no. 202292s10 focus review 3 of 8 ers are used, which can be another way to control the release of active ingredients. the most widely used approach is to obtain a variety of microand nanostructures, primarily polymer microspheres, microcapsules, microand nanoparticles. thus, pcl nanocapsules with triazine herbicides ametrin and atrazine were obtained by the emulsion method [8]. compared with a pure herbicide, the encapsulated formulation was less toxic to pseudokirchneriella subcapitata algae in a 96-hour experiment, and more toxic to daphnia similis in 24-hour and 48-hour experiments. cytogenetic tests on human lymphocyte culture (mitotic index evaluation) showed lower toxicity of the encapsulated herbicide compared to the pure one. study of the effect of atrazineloaded pcl nanocapsules on biomass growth, photosystem state, gas exchange, and oxidative stress parameters of mustard showed an increase in their herbicidal activity compared to a commercial preparation [9]. another degradable polyester, poly(lactide-coglycolide) (plga), was used in combination with the "lipid-peg" hybrid (plga:hybrid ratio was 75:25) for the obtaining of atrazine-loaded nanoparticles by precipitation [10]. the average particle size was 110±10 nm. the structure of the particles corresponded to the "core–shell" model. specifically, plga with atrazine were arranged in the core, and "lipid-peg" molecules – in the shell. the encapsulation efficiency was 50%. the inclusion of atrazine was confirmed by transmission electron microscopy (tem) and ftir, and the half-release time (t50) was 72 hours. the effect of pure atrazine and the deposited formulation on potatoes led to a slowdown in the growth of stems and roots, to a decrease in the number of leaves and in the weight of raw and dry masses. in the case of the root length, the encapsulated formulation had a more significant effect than the pure one. biodegradable polymers, polyhydroxyalkanoates of microbial origin, in particular, are also used for depositing herbicides. in a series of papers [11, 12], microparticles based on poly-3-hydroxybutyrate (phb) and phb copolymers with 3-hydroxyvalerate (phbv) loaded with atrazine and ametrin herbicides were obtained. the yield of atrazine into water from the polymer matrix was significantly reduced compared to the yield of pure herbicide. other authors [13] also used phbv to obtain microspheres loaded with atrazine. specifically, it was shown that, depending on the conditions of microspheres formation, the rate of release of the herbicide into water slowed down compared to the pure herbicide. it should be noted that microspheres, due to their small size and large total surface area, are subject to fairly rapid degradation when they come in contact with the environment. therefore, the release of deposited preparations from microparticles occurs quickly enough, which does not allow a long-term use (tens of days or more). that is why other methods of formulations obtaining are also being actively studied. for example, poly-3-hydroxybutyrate and metribuzin herbicide formulations with a 25% load of metribuzin were obtained in the form of granules, tablets, microparticles and solution-cast films [14]. sem, xrda and differential scanning microscopy (dsc) showed that the formulations were stable in the sterile water for up to 49 days. the highest rate of release (approximately 50% in 5 days and 95% in 49 days) was observed for the microparticles, and the the lowest rate of release (about 40% in 49 days) was shown for the granules. in 49 days about 50% of the deposited herbicide was released out of the tablets and the films. in another paper of the same authors [15], the metribuzin release rate into the soil out of similar formulations at different loads was analyzed. the maximum value of t50 (60 days) was obtained for the pressed tablets, regardless of the initial content of metibuzine, and for the microgranules with a 10% load of the preparation. the lowest values (10 days) were observed for the microparticles and the films with a 50% content of the herbicide. in addition to thermoplastic biodegradable carriers, application of materials of plant origin for this purpose is also known. specifically, an herbal extruded mix of alfalfa and sunflower meals (1:1) with addition of glycerol and a feed supplement was used to prepare granules with insecticide avermectins against locust nymphs [16] and mosquitoes [17]. laboratory experiments with granules containing 0.15% of avermectins fed to locust nymphs resulted in 100% death within 5 d. after the deposition in granules, resistance of the insecticide to uv radiation increased significantly, which is highly preferable in the conditions of its intended use (dry areas with a high level of solar radiation). the efficiency of avermectin-impregnated fine plant powder was also shown on mosquito larvae in water, where flotation properties of such particles can contribute to the probability of being eaten by the target pest, while non-target organisms were more resistant to the drug. for more cost-effective obtaining of polymer preparations, it seems promising to use co-extrusion of polymer and pesticide at a temperature exceeding the melting point of both the components, but below their degradation temperature. so, a simple and low-cost method to obtain longterm release formulations by co-extrusion of a metribuzin herbicide with low-melting polyester poly-ε-caprolactone was proposed [18]. the formulations containing 10%, 20%, and 40% of herbicide were prepared. after 7 days of their water exposure, from 81% to 96% of loaded metribuzin was released; the highest release rate was observed for 40%-loaded formulations. afterwards, biodegradation and pesticide release of the formulations were further explored. degradation rates of the specimens increased with an increase in the pesticide content, from 9% to 20% over 14 weeks for the 10%/20%-loaded and the 40%-loaded specimens, respectively. at the same time, the release of metribuzin reached 37–38% and 55%, respectively. the content of the herbicide in the soil was lower due to its partial degradation. it reached 23–25% and 33% from chimica techno acta 2022, vol. 9(2), no. 202292s10 focus review 4 of 8 initially loaded in the polymer matrix, respectively. release kinetics of metribuzin in water as in soil best fitted the first-order model. the used approach is promising for obtaining slow-release formulations for soil applications. 4. the use of polymer composite systems with inorganic fillers as a matrix for agrochemicals load in many studies related to obtaining formulations with a long-term release of pesticides, polymeric composites or blends with an inorganic filler are used. in most of these studies various gelatinizing agents (alginate, chitosan, carboxymethylcellulose, gelatin) are applied as one of the composite components. clay-like compounds and other carriers with high sorption capacity (e.g. activated carbon) are usually used as additional components. thus, aqueous systems with sodium alginate (gelatinizing agent) (1.4–1.5%), bentonite (0–5%) and/or activated carbon (0.5%) were used for depositing isoproturon, imidacloprid and cyromazine (0.3–1.22% in the aqueous phase). the final obtained loads in formulations with activated carbon were 9–14% for isoproturon, 6–14% for imidacloprid and 1.5–12% for cyromazine, with maximum encapsulation efficiency reaching 90-100%. as the release of isoproturon from the forms was estimated in days and tens of days, the same parameter for the more soluble imidacloprid and most of the forms was estimated in tens of hours and days. at the same time, the most severe slowdown of the pesticide release was observed for the forms with activated carbon. particularly, for alginate forms t50 was approximately 4 days for isoproturone and less than 10 hours for imidacloprid, whereas for the forms with 65% of activated carbon less than 10% of the isoproturone and imidacloprid were released in 48 days and 96 hours, respectively [19]. similar formulations based on sodium alginate with bentonite and anthracite, obtained by mixing with pesticides in an aqueous solution, were used to deposit the herbicides metribuzin and chloridazon [20]. the lowest release-rate (t50 14.37 days for chloridazon-loaded and 3.31 for metribuzin-loaded formulations) was observed for anthracite-based composites. to deposit metribuzin, carboxy methyl cellulose (cmc) and carboxy methyl cellulose – kaolinite (cmc-kao) based formulations with a component ratio of 3.83:100 and 3.83:50:50 g/g, respectively, were used. the formulations were obtained by mixing all the components in the presence of water and aluminum phosphate with subsequent thorough mixing, drying, grinding and sieving [21]. pesticide release study showed that the period of optimal availability of metribuzin when released into water increased from 5.03 days for the pure preparation to 15.09 days for the carboxymethylcellulose-based formulations and up to 27.13 days for the composite formulations. in the soil experiment, the corresponding values were 8.80, 17.99 and 25.16 days, respectively. the theoretically calculated t50 values were 3.25, 12.98 and 20.12 for water, and 4.66, 16.90 and 36.67 for soil, respectively. further studies [22] demonstrated the greater effectiveness of the resulting composite preparation against weeds, compared with both pure herbicide and the formulations based on carboxymethylcellulose only. other authors [23] applied carboxymethylcellulose (cmc) in combination with bentonite to encapsulate 2,4-d herbicide. both pure na-bentonite and bentonite treated with aluminum, iron or cetyltrimethylammonium cations were used. the forms were obtained by successive addition of bentonite, 2,4-d and cmc in water with subsequent injecting of the resulting suspension into a 0.03 m solution of al2(so4)3 and drying the resulting granules. ftir showed the presence of complex interactions between all the components in the formulation. the greatest efficiency of pesticide encapsulation (90%) was shown for aluminum-modified bentonite-cmc with its maximum concentration of 4%. in the other cases, this value varied from 55.5% to 85.3%. the values of the rates of pesticide release into water for the formulations with bentonite were reasonably comparable and differed slightly from the pure cmc formulations. 50% release of the preparation was achieved in 15 hours for the pure cmc formulations and in 15-20 hours for the formulations with different forms of bentonite. 50% of the deposited preparation was released into the soil after five and six waterings when deposited in the pure cmc matrix and in the matrix with the addition of iron-containing bentonite, respectively. in a similar study [24], gel granules loaded with the metolachlor herbicide were obtained from cmc with nabentonite and h-bentonite (the latter was obtained by treating na-bentonite with sulfuric acid). 0.08 m iron nitrate solution was used as a cross-linking agent. the resulting changes in the ir spectrum suggest an interaction between cmc and bentonite. the dried composite granules featured lower water sorption (50–85 wt.%) compared with the granules from the pure cmc (110–120 wt.%). in this study, the addition of bentonite significantly slowed down the release of the pesticide into water, especially in the formulations with h-bentonite. t50 of metolachlor into water from the composites with h-bentonite was 158 hours, compared to 61.1 hours for the composites with pure cmc. in another study [25], the herbicide imazethapyr was encapsulated in a composite hydrogel of guar gum, polyacrylate and bentonite clay for the pre-emergence application and in a nanohydrogel of guar resin and nisopropylacrylamide for the post-emergence application. the herbicide introduced into the nanohydrogel amounted to up to 53.94 wt.% of the initial gel. the encapsulation efficiency (concentration of imazethapyr extracted from the formulation over the initial concentration of imazethapyr added to make the formulation) ranged from 68% to 99%. the amount of the pesticide introduced into chimica techno acta 2022, vol. 9(2), no. 202292s10 focus review 5 of 8 the hydrogel was 3–4 wt.%. on the first day, from 16 to 34% of the deposited herbicide was released from the hydrogel into water. after the fifth day, the release stopped. on the first day, from 14 to 57% of the herbicide was released from the nanohydrogel. predictably, the release decreased with an increase in the content of the crosslinking agent. the effectiveness of the encapsulated forms in weed control in field experiments was higher than that of a pure preparation, although it was inferior to the treatment with a mixed "imazethapyr + pendimethalin" preparation. one of the approaches involved obtaining a polymer matrix directly in a solution [26]. in particular, metribuzin (2–7 wt.%) was introduced in a composite consisting of bentonite (8–12 wt.%) and a mesh copolymer of acrylic acid and acrylamide. polymerization was carried out in an aqueous solution after the introduction of bentonite and a pesticide, followed by the desiccation of the resulting formulations. an increase in the content of the clay component from 8% to 12% led to a significant slowdown in the release of metribuzin into water (between 30 and 40% in 27 days at different pesticide loads). at the same time, an increase in the content of metribuzin had little effect on the patterns of its release. in general, such systems, possessing adequate efficiency, feature a relatively high complexity of manufacture and, consequently, a high cost, which limits their commercial availability. 5. application of blended polymer systems alongside composite systems with introduced inorganic fillers (including organically modified), polymer blends are also widely used for the slow release of pesticides. systems that differ both in composition and ratio of components, as well as in size, manufacturing methods, active substances load and methods of their deposition are widely used as controlled release systems. such differences significantly affect the rate of release of deposited biologically active ingredients due to both different diffusion characteristics and biodegradation rates. specifically, the applied promising polymer components include polysaccharides (starch), a number of well-known polyesters that have proven themselves as biodegradable materials (pha, pla, pga, pcl), some conventional polyesters (polyethylene glycol), and wood processing products (e.g., sawdust, lignin). polymers of this group are also often compounded with gelatinizing agents. thus, chitosan-alginate and chitosantripolyphosphate composite nanoparticles with an average size of approximately 400 nm loaded with herbicides imazapic and imazapyr were obtained [27]. the release of the herbicides was estimated in a two-chamber system with a dialysis membrane of 1000 da. the release of free pure herbicides was 55% and 97% after 300 minutes, whereas for the chitosan-alginate deposited formulations it was by 30% and 20% lower, respectively. for the chitosantripolyphosphate formulations, the corresponding values were 59% and 9%, respectively. the deposited forms had a less pronounced cytotoxic effect on onion seedlings and less influence on the composition of the microbial community. in experiments with burr marigolds, deposited forms had a more significant herbicidal effect than the pure preparation. chitosan and alginate were also used to obtain composite nanoparticles (635±12 nm in size) loaded with paraquat herbicide [28]. dsc showed the absence of the endothermic peak characteristic for paraquat in microparticles compared to the mechanical mixture of components where it was present. the authors explained it by the interaction of the pesticide with the alginate-chitosan matrix with good mixing of the components. ftir showed the presence of complex interactions between alginate and chitosan, as well as the absence of a number of peaks characteristic for paraquat, which was also explained by the interaction of positively charged paraquat groups with polymer chains with a change in the vibrational frequencies of herbicide molecules. a significant slowdown in the release of paraquat into water in a two-compartment membrane system was observed. the release profile was significantly altered for herbicide loaded in the nanoparticles, with near 100% release after 8 h, 2 h longer than the time required for complete release of free herbicide. particularly, the t50 into water was approximately 90 hours. a decrease in its sorption in the soil when using long-term release formulations was also observed. in another study [29], picloram herbicide in the form of microcrystals was coated with a layered composite based on an inner layer of a positively charged chitosan (cs) and an outer layer of positively charged sodium lignosulfonate (sl). ftir showed the presence of strong electrostatic interactions between chitosan and lignosulfonate, but the absence of any changes in the characteristics of the pesticide. the coating significantly increased the photostability of the pesticide and slowed down its release into water, which depended on the number of applied coating layers. whereas the uncoated picloram herbicide completely dissolved after 4 hours, with a 12-layers coating (6 cs layers consecutively alternating with 6 sl layers), approximately 90% of the herbicide came out after 9 hours of exposure. the t50 was 0.05 h, 0.43 h, 1.02 h and 2.26 h for the uncoated forms and the forms coated with 4, 8 and 12 layers of composite, respectively. it is also possible to use such systems for depositing biopesticides. thus, a water-insoluble polyelectrolyte complex of chitosan and polyacrylate-maleate was used to coat chitosan matrices with deposited trichoderma [30]. the matrixes were coated by dipping chitosan granules with trichoderma into an aqueous solution with polyacrylate-maleate and exposing them for two days at ph 4.8. no negative effect of the coating on both the growth of chimica techno acta 2022, vol. 9(2), no. 202292s10 focus review 6 of 8 trichoderma and its ability to inhibit the pathogens of alternaria and fusarium genus has been observed. polysaccharides are not always used directly to obtain hydrogels. in the study [31], beads were obtained from a mixture of cassava starch (cs), sodium alginate (sa) and 2,4-d at a different ratio of cs and sa, and coated with natural rubber. as the cs/sa ratio increased from 0/1 to 1/1, the size of the beads increased from 0.9 mm to 1.8 mm, and the encapsulation efficiency also increased from 65% up to 100%. the three-layer rubber coating made it possible to increase the t50 from several hours to 700 hours. oneand two-layer coatings exhibited intermediate values. along with gelatinizing, thermoplastic biodegradable polymers were also used in a number of studies in the forms of pressed molds or microspheres. thus, composite systems "poly-3-hydroxybutyrate – the second component – metribuzin" in combination with sawdust, peg or pcl as the second component, and with a 25% load of herbicide, were obtained by cold pressing [32]. the most active release of metribuzin into water (38.7% in 35 days) was observed for a composite with peg, and the least active release of the pesticide (16.8% in 35 days) was observed for a composite with pcl. in an experiment with model soils (field and garden), a rapid release of the preparation was shown (approximately 60% in 14 days) for a composite with peg, and comparable values (about 20–30%, depending on the type of soil) were obtained for the remaining types of the studied forms. by the end of the experiment, from 35% to 72% of metribuzin initially introduced in the forms was found in the soil, which the authors explain by the difference in release rates as well as by its partial degradation in the soil. in some studies, polymer mixtures were also used to obtain microspheres. for instance, microspheres loaded with malathion insecticide based on both pure phb and pcl and their mixtures in the ratios 70/30, 80/20, 90/10, 95/5 and 97/3 were obtained by emulsion evaporation [33]. malathion (about 30% of the total weight of the components) was added to chloroform solutions of polymers, and the resulting solution was emulsified in an aqueous solution of gelatin and tween 80. loading with malathion led to a reduction in the size of microspheres of the same polymer composition up to two times compared to the unloaded phb/pcl microspheres. the surface of the microspheres made of pristine polymers was relatively smooth, while mixed particles with greater inclusion of pcl (more than 10%) demonstrated a mesh structure. the introduction of malathion, according to the dsc data, led to a shift in the melting peak of pcl that depends on the content of pcl, which indicates some interaction of the pesticide with the polymer base. the same conclusion was drawn from a slight change in peaks in the ftir spectra, although no new peaks were observed. release of malathion into water tests showed that the release rate was at maximum at a 30% pcl content, somewhat lower at a 20% pcl and minimal for a 5% pcl and pure phb. however, in 5 hours of exposure, 50% of the pesticide was released from all the obtained forms. the obtained data was used for designing a mathematical model. the authors concluded that it is possible to control the release of the preparation by varying the composition of the polymer matrix. a spanish research team has developed and applied extrusion as a method of obtaining controlled-release forms. in one of their studies [34], preparations of the herbicide chloridazon were obtained by introducing all the components in a lignin-peg blend at 206 °c, followed by coating the resulting mixture with ethyl cellulose (ec) or ec with the addition of dibutylsebacinate (dbs) plasticizer. the greatest delay in the release of the herbicide into water (approximately 50% in 65 hours) was observed for the forms coated with ec with dbs. in another study by the same authors [35], metribuzin preparations were obtained in a similar way by melting the active substance with a lignin-peg blend at 126 °c, followed by covering the resulting mixture with ec or ec-dbs. based on dsc and ftir results, the authors assumed the dispersion of pesticide molecules into the polymer matrix and the formation of hydrogen bonds between lignin and peg. in this case, the greatest delay in the release of the preparation into water (about 50% in 20 hours) was observed for eccoated forms. a similar approach with the same components was used to deposit imidacloprid [36]. the maximum t50 for deposited imidacloprid was 168.6 hours. tgdsc showed a significant mass loss for ec-coated samples at temperatures below 360 °c at the first stage of heating compared to the uncoated samples. according to results of ftir, the formation of new hydrogen bonds between the ester groups of peg and lignin was observed. similarly, formulations of metribuzin and chloridazon were obtained by co-melting of a pesticide, lignin and peg (at a 65:20:15 ratio) at melting temperatures of the pesticides (126 °c and 206 °c, respectively), followed by covering the forms with a mixture of ec or ec-dbs (90:10) [37]. compared to the uncoated forms, an increase in t50 was achieved from 1.74 h to 65.39 h for the forms with chloridazon and from 1.01 h to 20.44 h for the forms with metribuzin. the release into the soil also slowed down. particularly, from 70 to 90% of free pure pesticides were washed out by three waterings in soil columns, whereas only 50–60% of metribuzin from the uncoated matrices, 20–40% from the coated forms on sandy-clay soil and 10– 30% on sandy soils, depending on the thickness and composition of the coating, were washed out. for chloridazon, the corresponding values were 40% for sandy-clay soils for the uncoated forms and 5–18% for the coated ones. on sandy soils, the release of chloridazone was much slower. however, in this case, the application of coated forms slowed it down. after ten waterings, more than 90% of free pure metribuzin, 70% of metribuzin from the uncoated forms, and 60–65% of metribuzin from the coated chimica techno acta 2022, vol. 9(2), no. 202292s10 focus review 7 of 8 forms were washed out on sandy-clay soils. on sandy soils, similar values were more than 90%, 70% and 50–60%, respectively. as for chloridazon, these indicators were more than 90%, 70%, 50–60% for sandy-clay soils and 85–95%, 70% and 32–58% for sandy soils. the efficiency of the use of such forms, along with their relatively low cost, allows suggesting further studies and the expansion of the practical applications. 6. conclusions considering the prospects for the development and application of long-term release pesticide formulations, a large number of various possible and sufficiently effective solutions must be noted. however, the commercialization of such solutions requires a cost-cutting of both carrier materials and preparation manufacturing technologies. either natural materials of wide availability (clay, chitosan, alginate) or synthetic polymers (e.g., pcl) can be considered promising carriers. extrusion can be noted as a promising technology for obtaining preparation carriers. although its use limits the range of materials possible for application, it does not require any solvents or other reagents at the processing stage and is a relatively easy and cheap process itself. supplementary materials no supplementary materials are available. funding this research was funded by the grant of the president of the russian federation for state support of young russian scientists – candidates of science, provided by the ministry of science and higher education of the russian federation, “ecological products with prolonged release of biologically active substances for potato nematode control” mk-4374.2021.5 no. 075-15-2021-059 dated 16.04.2021, https://grants.extech.ru. acknowledgments none. author contributions conceptualization: a.n.b. formal analysis: a.n.b, a.a.s. funding acquisition: a.a.s. methodology: a.n.b., a.a.s., n.l.e. resources: a.a.s. writing – original draft: a.n.b., a.a.s., n.l.e. writing – review & editing: a.n.b. conflict of interest the authors declare no conflict of interest. additional information author ids: boyandin anatoly n., scopus id 6507584996; sukhanova anna a., scopus id 55916360000. websites: reshetnev siberian 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https://doi.org/10.1021/jf4004658 https://doi.org/10.1177/0883911512436899 https://doi.org/10.1007/s10924-017-1084-4 https://doi.org/10.1021/acs.jafc.5b05896 https://doi.org/10.1002/app.32082 https://doi.org/10.1016/j.carbpol.2010.10.024 https://doi.org/10.1002/app.41422 https://doi.org/10.1021/jf2037483 https://doi.org/10.1016/j.jhazmat.2017.09.012 effect of chemical treatment of multi-walled carbon nanotubes on the specific capacitance of supercapacitors published by ural federal university eissn 2411-1414; chimicatechnoacta.ru letter 2022, vol. 9(3), no. 20229312 doi: 10.15826/chimtech.2022.9.3.12 1 of 5 effect of chemical treatment of multi-walled carbon nanotubes on the specific capacitance of supercapacitors valeriy v. golovakhin a, ekaterina yu. kim a, oksana n. novgorodtseva ab, alexander g. bannov a* a: chemistry and chemical engineering, novosibirsk state technical university, novosibirsk 630073, russia b: institute of solid state chemistry and mechanochemistry, novosibirsk 630073, russia * corresponding author: bannov.alexander@gmail.com this paper belongs to the ctfm'22 special issue: https://www.kaznu.kz/en/25415/page. guest editors: prof. n. uvarov and prof. e. aubakirov. © 2022, the authors. this article is published in open access under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). abstract to date, the research on carbon nanomaterials has progressed rapidly. more than 400 papers were written in 2021 on the application of carbon nanomaterials in various fields. the high demand for the use of such materials has increased due to a sharp increase in the demand for semiconductor materials and materials for supercapacitor electrodes and other electrical devices. despite the unique physical properties of carbon nanomaterials, there are limitations to their use. to solve this problem, various methods of modifying the surface, both through chemical interactions and physical adsorption, were proposed. one of these methods is chemical modification. the evaluation of effect of chemical treatment parameters on the properties of carbon nanomaterials is an urgent task due to the fact that the chemistry of the processes is poorly understood. in this work, the effect of concentrated sulfuric and nitric acids on the change of specific surface area, elemental composition, composition of functional groups, and also on the change of specific capacitance was considered. it is believed that both the porosity and the functional groups formed during oxidation contribute to the change in specific capacitance. the specific surface area of all samples decreased on average by a factor of 1.5–3 after the chemical treatment. different oxygen and sulfurcontaining functional groups are observed after the chemical treatment. the highest specific capacitance of the treated carbon nanofibers was 114 f/g. keywords multi-walled carbon nanotubes chemical treatment functionalization supercapacitors cyclic voltammetry received: 24.06.22 revised: 26.07.22 accepted: 27.07.22 available online: 08.08.22 1. introduction the necessity of application of carbon nanomaterials (cnms) is related to the possibility of obtaining them by means of decomposition of c1–c4 hydrocarbons over various catalysts. thus, in [1] carbon nanofibers were produced from methane using ni/al2o3 catalyst in a fluidized bed reactor. similarly, carbon nanotubes with different morphologies (single-walled and multi-walled carbon nanotubes (mwnts)) can be produced by varying different catalysts and process parameters. there are several types of surface modification of carbon nanomaterials: plasma treatment [2–4], electrochemical modification [5–7], chemical modification [8– 10], etc. 2. theory plasma treatment consists in the oxidation of cnms in non-equilibrium plasma. the functionalization degree of these materials is low, e.g., up to 6.6 wt.%. barrier discharge plasma is also used to oxidize cnms while maintaining the morphology of the material [13]. these two high-energy methods do not require preheating, and the processing time takes no more than a few seconds. microwave functionalization techniques can also be used [14] but the difficulty lies in the limitation of the materials (vertically oriented cnms). the authors [15] used inductive coupled plasma for oxidation, but the degree of functionalization and product yield were extremely low and lead to the formation of ester and carboxylic groups. http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2022.9.3.12 mailto:bannov.alexander@gmail.com https://www.kaznu.kz/en/25415/page http://creativecommons.org/licenses/by/4.0/ https://orcid.org/0000-0001-5868-9013 https://crossmark.crossref.org/dialog/?doi=https://doi.org/10.15826/chimtech.2022.9.3.12&domain=pdf&date_stamp=2022-8-8 chimica techno acta 2022, vol. 9(3), no. 20229312 letter 2 of 5 electrochemical methods of oxidation consist of passing electric current through dilute solutions of strong acids. in [16] surface modification methods using electric current of different strength were described. there was an increase in oxygen up to 5 at.%, but this method was not safe because of a rattlesnake mixture emission and the necessity of observance of certain safety rules. it is also possible to modify the surface by grafting different polymers. polyaniline [17] and polyacetylene [18] were among the first polymers used. composites with these polymers can be employed in electrochemical current sources, sensors, etc. however, this technology has not found industrial application yet. chemical methods include a wider range of possibilities due to the large number of different oxidizing agents which can influence cnm morphology and functional group composition differently after processing. chemical methods include alkaline activation [19] and acid etching. alkaline activation has a number of limitations: only highly concentrated alkaline solutions are used. this treatment allows the pores to be reduced to a single size, most commonly, mesoporous. the advantages of the acid method include the possibility of varying solution concentrations and using different acid solutions. as oxidizing reagents, oxygen-containing acids and their mixtures are most commonly used: hno3, h2so4, hclo4, hno3 + h2so4, etc. [20]. in studies on the effect of mixtures of concentrated sulfuric and nitric acids in different ratios [19, 21], the authors claimed that applying a mixture of hno3:h2so4 in a ratio of 3:1 to the surface of the carbon material led to the formation of sulfur-containing functional groups, mainly (–so3h). this is an interesting effect, as in the oxidation of tube-like compounds, polyaromatic hydrocarbons, such a mixture is used for nitration. for example, in [22] the effect of heating time of mixture on the formation of functional groups when treated with concentrated nitric acid was investigated. chemical modification of surface does not end with the oxygen-containing acid treatment. another method of functionalization is the use of oxygen-free acids, e.g., hcl, hf and their mixtures with hydrogen peroxide [23]. in addition, solutions of acidic oxides are also used [24], etc. also, various persulphates and hypochlorites have found their application in this area. there is a possibility of chemical modification by mixtures of hydrogen peroxide with different salts, such as the fenton's reagent (h2o2/feso4). prolonged treatment with such a mixture leads to the formation of hydroxyl groups only [25]. chemical methods of surface functionalization of cnms are long processes (up to 24 h or more) carried out by heating the reaction mixture. after this functionalization, various functional oxygen-containing groups are observed: carboxylic, carbonyl, alcohol/phenolic [26]. in [27] the effect of chemical treatment on the specific capacity of nanofibrous carbon was investigated, and the data were obtained that the use of concentrated sulfuric acid was inexpedient, as the specific capacity of the material increased to 0.2 f/g. however, the treatment with nitric acid increased the specific capacitance to 10 f/g. there are also many works which aim at secondary modification of the material. in [28] the synthesis of carboxyl carbon nanotubes with conducting amines was investigated, and material capacity of 200 f/g was obtained. this article is devoted to studying the effect of chemical treatment of multi-walled carbon nanotubes in nitric and sulfuric acids for their further use in supercapacitors. 3. experimental commercial multi-walled carbon nanotubes labeled as lmwnt-1020 and l-mwnt-4060 (hereinafter mwnt1020, mwnt-4060) were chosen as the objects under study. the difference between mwnt-1020 and mwnt4060 is that mwnt-1020 were purified from the catalyst by the manufacturer (it is seen from the tem images). also, the difference is in the diameter of the nanotubes. for mwnt-1020, the diameter of the nanotubes ranges within 10–20 nm, for mwnt-4060 – from 40 to 60 nm. the experimental procedure was as follows: a sample of nanomaterial weighing 0.15 g was poured into 100 ml of concentrated acid, after which the reaction mixture was kept for 6 h, heated at 80 °c and stirred constantly. after that the samples were filtered off, washed several times with distilled water, dried and prepared for their further analysis. the following acids were chosen as oxidizing agents: hno3 (concentrated, pure for analysis grade, gost 11112584 (mod.1), 64%), h2so4 (concentrated, chemically pure grade, gost 4204-77, 97%). change of specific surface area was measured by low-temperature nitrogen adsorption using the bet method using a quantachrome nova 1000e, the adsorbate gas partial pressure range was 0.005–0.9995 p/p0. the measurement error was no higher than 5%. the composition of elements in the powdered samples was determined using scanning electron microscopy (sem) (the beam energy was 10 kev). instrumentation, s3400n (hitachi), was equipped with an energy dispersive x-ray analysis (edx) unit from oxford instruments. the error of the device does not exceed 0.1%. qualitative composition of functional groups was measured by fourier transform infrared spectroscopy (ftir spectroscopy). instrumentation: ft-ir spectrometer ft-801 (tu-4434-805-59962935-2019) with reflection attachment for examination of powdery samples po-45n with angle of incidence of 45°, bottom sample position and a built-in visualization system. specific capacitance of the samples was measured by cyclic voltammetry at a sweep rate of 2–10 mv/s. instrumentachimica techno acta 2022, vol. 9(3), no. 20229312 letter 3 of 5 tion: an ipc-compact potentiometer (russia). a threeelectrode circuit was used for the measurements: auxiliary electrode – pt, reference electrode – ag/agcl (saturated kcl). the potentials in the work are given relative to the ag/agcl electrode. the carbon nanomaterials were deposited on the surface of the glassy carbon electrode. the specific capacitance of the studied carbon materials was determined by the formula [29, 30]: 𝐶𝑠𝑝 = 𝐽 𝑉 · 𝑚 , (1) where csp is the specific capacitance, f/g; j is the sum of cathode and anode currents (j = jk + ja) at 500 mv, ma; m is the mass of material, g; v is the sweep rate, mv/s. then the electrodes were dipped into 3.5 m sulfuric acid solution, and cyclic voltammetry curves were recorded by direct voltammetry when the electric potential varied from 0 to 1 v at the working electrode. the error of the sweep rate was 1.0% and the error of the potential setter was 0.03 mv. a modified mwnt sample was used as the indicator electrode. the electrode was prepared in the following way: mwnt was mixed with 10–15% acetylene soot (alfa aesar, russia); 0.01 g of the resulting composite was taken and mixed with 10% mineral oil (russia) to obtain a paste-like material. the paste was uniformly applied to a graphite electrode (s = 1 cm2). then the electrodes were immersed into 3.5 m sulfuric acid, and cyclic voltammetry curves were measured by direct voltammetry, with the electrical potential of the working electrode being varied from 0 to 1 v. the average sample mass was about 0.0015 g. 4. results and discussions the edx and low-temperature nitrogen adsorption results are shown in table 1. from the data presented in table 1, it is clear that the acid treatment results in a low degree of functionalization (c:o ratio) for mwnt-1020. at the same time, the catalyst content after treatment was close to zero. this is due to the fact that mwnt-1020 were previously purified from the catalyst by the manufacturer. a reduction in specific surface area of 1.5–3 times was observed. this is caused by the oxidation of mwcnts with the formation of co/co2. table 1 the edx and bet results. sample acid concentration of elements at.% specific surface area m2/g c o s c:o oth. mwnt1020 – 99.9 – – – 0.1 128 h2so4 96.6 2.8 0.2 35 0 48 hno3 97 3 – 32 0 76 mwnt4060 – 99.7 – – – 0.3 68 h2so4 91.4 6.9 1.4 13 0.1 46 hno3 95.1 4.2 – 23 0.1 56 for mwnt-4060 the degree of functionalization of the obtained materials was much higher. there was a presence of sulfur in the composition of the material that may be due to the formation of some sulfur-containing functional groups. a decrease in specific surface area, similarly associated with the oxidation of carbon nanotubes, was also observed. figure 1a shows ftir spectra of mwnt-1020 sample, representing the bands at 1125 cm–1 attributed to valence vibrations of the s=o bonds of sulfonic acids; this indirectly confirms the presence of sulfur detected by edx spectroscopy. valence vibrations of the c–o and c=o bonds at 1610, 1695, 1820 cm–1 were also observed. these vibrations refer to both carboxylic groups (1610, 1695 cm–1) and anhydride groups (1820 cm–1). the presence of carboxylic groups was confirmed by valence vibrations of o–h bonds in the carboxyls at 3231 cm–1. for mwnt-4060 (figure 1b) in the case of anhydride groups all is identical, but the vibrations of valence bonds at 1448 cm–1 related to sulfoxides were observed. obtaining sulfur-containing groups will make it possible to use such materials not only as electrodes for supercapacitors, but also in a variety of sensors and membranes. our data partially correlate with the data reported in [31]. figure 1 ftir spectra of the treated samples: l-mwnt-1020 (a); l-mwnt-4060 (b). chimica techno acta 2022, vol. 9(3), no. 20229312 letter 4 of 5 for mwnt-1020 an increase in specific capacitance up to 114 f/g was observed. in spite of the fact that the degree of functionalization of the samples was much lower, the specific capacitance was much higher. this is most likely due to the formation of functional groups, which participate in the electron transfer at the oxygen atom c – o↔c=o [32]. although the degree of functionalization was higher for the mwnt-4060 samples, in particular, for the sample treated in nitric acid, its specific capacity is lower than that of the original sample. this can be explained by the fact that the formed groups are mostly anhydride, or ester groups, which cannot participate in the redox processes. figure 2a and 2b also show the cyclic voltammetry curves of the samples with the highest capacity at a sweep rate of 2mv/s. table 2 cyclic voltammetry results. sample acid specific capacitance, f/g 10 mv/s 5 mv/s 2 mv/s mwnt1020 – 0.2 0.3 0.6 h2so4 36 49 67 hno3 72 89 114 mwnt4060 – 0.3 0.4 0.5 h2so4 32 49 96 hno3 0.085 0.09 0.13 figure 2 cyclic voltammetry curves of the treated samples: lmwnt-1020 (a); l-mwnt-4060 (b). 5. conclusions the study of the effect of different oxidizing agents on the functionalization and application of the obtained carbon nanomaterials is important. it should also be noted that there are practically no mathematical models describing the oxidation process of cnms, which does not allow us to talk about the optimality of the various treatment parameters used. in the multi-walled carbon nanotubes, an increase in the quantity of the oxygen-containing groups was observed, especially in case of sulfuric acid treatment, where the formation of sulfur-containing groups occurred. the electrical capacitance of the chemically treated cnts reached 114 f/g. however, in spite of high oxygen content on the catalyst-free cnts (mwnt-1020), after the treatment in nitric acid, the capacitance of the material decreases. the electrical properties of multi-walled carbon nanotubes as well as the influence of sulfur-containing groups on sensor properties will be investigated. even with a sufficiently high degree of functionalization, acidic treatment leads to bond destruction. in addition, the treatment in nitric acid could lead to a destruction of the conductive channels instead of functionalization (for mwnt-4060). supplementary materials no supplementary materials are available. funding this work was supported by the ministry of science and higher education (grant no. fsun-2020-0008). acknowledgments none. author contributions investigation: v.v.g. methodology: e.yu.k., v.v.g. supervision: a.g.b. writing – original draft: v.v.g., a.g.b. writing – review & editing: v.v.g., a.g.b. conflict of interest the authors declare no conflict of interest. additional information author ids: valeriy v. golovakhin, scopus id 57557002400; oksana n. novgorodtseva, scopus id 57215185765; alexander g. bannov, scopus id 54788777600; https://www.scopus.com/authid/detail.uri?authorid=57557002400 https://www.scopus.com/authid/detail.uri?authorid=57215185765 https://www.scopus.com/authid/detail.uri?authorid=54788777600 chimica techno acta 2022, vol. 9(3), no. 20229312 letter 5 of 5 websites: novosibirsk state technical university, https://en.nstu.ru; institute of solid state chemistry and mechanochemistry, http://www.solid.nsc.ru/en. references 1. kuvshinov dg, kurmashov pb, bannov ag, popov mv, kuvshinov gg. synthesis of ni-based catalysts by 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, nataliya p. belskaya * ural federal university, 19 mira st., yekaterinburg 620002, russia * corresponding author: n.p.belskaya@urfu.ru this article belongs to the regular issue. © 2021, the authors. this article is published in open access form under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). abstract herein we report the research on the sensitivity of six hydroxy derivatives of dihydrotriazolopyrimidines (ho-dtp) to acids and bases. the uv/vis and fluorescence spectra of these compounds were investigated with the addition of the acids and bases. spectral data revealed the strong red shifts for emission and absorption maxima in the presence of koh and naoh. moreover, two dtps demonstrated strengthening of the emission intensity. the obtained results and data published in our previous paper demonstrated the strong and selective sensory response of dtps to the acids and bases and elucidated relationships between the structure and sensitivity to the environment. this finding allowed us to manage these properties by introducing the combination of substituents and functionalities into the heterocyclic core. thus, investigations demonstrated the potential of the application of dtps as chemoand fluorosensors for selective detection of acids and bases. keywords dihydrotriazolopyrimidines acids bases fluorescence response chemosensor received: 27.07.2021 revised: 11.08.2021 accepted: 16.08.2021 available online: 17.08.2021 1. introduction fluorophores sensitive to external stimuli are attractive compounds owing to their application in contaminant analysis environment, electrochemical sensors, biosensing, and detection of toxins [1]. extensive studies have been directed for development of new fluorescent sensory organic materials which are able to respond on the external stimuli via changes of their absorption or fluorescence characteristics. these stimuli may include temperature, scattered light, ph, and even nature of solvent [2]. monitoring the ph levels in high alkaline media is of wide importance for many industrial processes, in gas scrubbers, wastewater monitoring, treatment of the plants and concrete structures [3, 4]. the sensing materials suitable for measurement of high alkali media are very limited. in recent years, a few fluorescent sensors in an alkaline ph region have been reported [5-7]. recently we reported the synthesis and photophysical properties of new blue and blue-green fluorophores derived on dihydro-1,2,3-triazolopyrimidine core (dtp) [8]. these fluorophores exhibited multifunctional properties and showed good fluorescence in solutions (with qy up to 88%, stokes shift (ss) ~151 nm and λem up to 534 nm). we suggested and developed synthetic procedure providing various dtps with different electronic structures (a-π-d and d-π-a). these compounds showed selective reversible acidochromism in solution and in a solid state in the presence of hcl vapor. 1 h nmr investigation showed that the pyrimidine and n-tert-cycloalkylamine moieties are the binding sites responsible for specific sensory response to the acids. current research is focused on the investigation of the photophysical characteristics of the phenoxyderivatives of triazolopyrimidines (oh-dtps) bearing oh-functionality in the different positions of the molecule and studies of their response to the different acids and bases as external stimuli. hydroxy group is very attractive from a biological point of view. numerous biocompounds include ohfunctionalities in their structure (alkaloids, flavonoids, isoflavonoids, terpenoids, lipids, fatty acids, amino acids etc.) [9, 10]. bioluminescent molecule (luciferin) and different synthetic fluorophores bearing this substituent are well known [11-19]. introduction of hydroxy groups usually causes the changes in electronic properties owing to its strong electron-donating nature and increases the intramolecular charge transfer (ict) effect. moreover, hydroxy http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2021.8.3.03 http://creativecommons.org/licenses/by/4.0/ https://orcid.org/0000-0002-0157-7130 https://orcid.org/0000-0002-2509-7916 chimica techno acta 2021, vol. 8(3), № 20218303 article 2 of 5 group can strengthen the fluorophore participation in intraand intermolecular noncovalent bonding to enhance the molecule rigidity and take part in self-organization. finally, hydroxy groups [20] can be transformed into the salts, which are more soluble in water. deprotonation of hydroxy group may influence the optical properties of the resulted salts. 2. experimental uv-vis absorption spectra were recorded on a perkinelmer lambda 35 uv-vis spectrophotometer (shelton, ct usa). fluorescence of the sample solutions was measured using a hitachi f-7000 spectrophotometer (tokyo, japan). the excitation wavelength was at the absorption maxima. atmospheric oxygen contained in solutions was not removed. concentration of the compounds in the solution was 5.0·10 -5 m and 5.0·10 -6 m for absorption and fluorescence measurements, respectively. the relative fluorescence quantum yields (qy) were determined using quinine sulfate in 0.1 m h2so4 as a standard (qy = 0.546). absolute quantum yield study was performed on horiba flouromax 4 spectrofluorometer (kyoto, japan) with quanta-φ integrating sphere using fluoressence 3.5 software. dtps 1a-e, 2a-c and 3a-b were prepared according to procedures reported in the literature and their spectral characteristics were identical to the published data [8, 21]. 3. results and discussion 2-(hydroxyphenyl)-4-(4-trifluoromethylphenyl)-2,4-5h[1,2,3]triazolo[4,5-d]pyrimidines (ho-dtps) 2a-c and 3a-b were prepared via the demethylation of their methoxycongeners by using bbr3 solution in dichloromethane with special temperature profile regime (scheme 1). the spectral and analytical data of dtps 2a-d and 3a, b were consistent with the published data [21]. absorption and emission spectra recorded earlier showed insignificant difference in long wavelength maxima positions compared to the corresponding meo-dtps derivatives. at the same time ho-dtps quantum yields (qy) of were in 6-40fold lower. only ho-dtp 2a demonstrated good qy compared to qy of dtp 1a in dmso (40.1% and 39.4%, respectively) (table 1). however, in the other solvents qys of ho-dtp 2a decreased significantly. the preliminary investigation of the influence of the different acids and bases on the optical properties of the ho-dtp solutions in dmso showed the absence of any effect. therefore, we included only trifluoroacetic acid (tfa) into further consideration. absorption and emission spectral data of the ho-dtps 2a-d and 3a,b in the presence of different organic bases, alkalis and tfa are collected in table 1. analysis of the table 1 data showed that addition of the koh (5% water solution) caused red shift of the absorption and emission maxima by 20-121 and 22169 nm, respectively, and for the most ho-dtp qys were decreased. addition of tfa did not affect the photophysical properties for the most compounds, except the dtp 2b. in this case, the maxima of absorption and emission bands were redshifted for 30 nm and 11 nm accordingly. unlike most acids, the addition of koh solution caused dramatic changes in the photophysical properties of dtps 2a-d, 3a,b. thus, in fluorescence spectra a strong bathochromic shift of the emission maxima of 57-169 nm was observed scheme 1 synthesis of oh-dtps 2a-d and 3a,b chimica techno acta 2021, vol. 8(3), № 20218303 article 3 of 5 table 1 absorption and emission data for dtps 2a-d, 3a,b solution (c = 5·10 -6 m) in dmso before and after the addition of 500 eq. of tfa or koh (5% solution in water) entry compound acid/base λabs, nm λem, nm ss, nm/cm -1 qy, % 1 2a 347 441 94/6143 40.1 2 tfa 347 441 94/6143 18.2 3 koh 375 498 123/6586 19.8 4 2b 296 419 123/9917 0.4 5 tfa 326 408 82/6165 0.6 6 koh 364 503 139/7592 7.5 7 2c 340 416 76/6903 0.5 8 tfa 331 414 83/6057 0.8 9 koh 360 500 140/7778 5.9 10 2d 356 472 116/6903 1.1 11 tfa 360 450 90/5556 0.6 12 koh 418 530 110/5056 0.6 13 3a 347 432 85/5670 0.6 14 tfa 347 420 74/5092 0.6 15 koh 423 500 77/3641 16 3b 341 416 75/5287 0.3 17 tfa 339 404 65/4746 0.2 18 koh 492 585 93/3231 along with the qy decrease for the most dtps, with the exception for 2b and 2c. dtps 2b and 2c, bearing hydroxy group at orthoand meta-position of aromatic ring a showed the large increase of their qys from 0.4 and 0.5% (in pure dmso) to 7.5 and 5.9%, respectively. thus, hydroxyl dtp derivatives display different sensitivity to the alkali media depending on their structure. these results inspired us to check the influence of the set of bases on the photophysical properties of dtp 2b (fig. 1) under the same conditions. these data indicated a significant effect of bases on both the absorption and the emission of dtp 2b. in all the cases, the absorption and emission maxima were redshifted in range 68-110 nm and 19-62 nm, respectively. the effect of tea stimulus deviates from common trend and consists in slight blue shifting (4 nm) (fig. 1). the most effective were alkalis (naoh and кoh), whose addition to the ho-dtps 2b solution in dmso led to large redshifts (61-62 nm) and substantial (in 9-10 folds) increasing of emission intensity. visual emission change from colorless to green was observed for the dtps 2b solution after the addition of 50 eq of naoh solution, which further developed to bright green-yellow emission (fig. 2). further, we studied changes in absorption and emission spectra of ho-dtp 2c induced by naoh (fig. 3). ho-dtp 2c was almost non-fluorescent in dmso solution (c = 5·10 -6 m), while the addition of naoh caused an appearance of a new fluorescence maximum at 504 nm (fig. 3b). the intensity of this new maximum was enhanced drastically upon the increasing amounts of naoh and reached the saturation at 300 eq. changes in absorption were also registered. in this case new maximum was located at 395 nm when 25 eq. of naoh solution were added, and further naoh addition led to increasing of this fig. 1 uv-vis absorption (left) and emission (right) spectra of dtp 2b after addition of different bases (for absorption and emission c = 5·10 -6 m) chimica techno acta 2021, vol. 8(3), № 20218303 article 4 of 5 fig. 2 the titration of ho-dtp 2b solution in dmso with the 5% naoh solution under sunlight (left) and uv-irradiation (right) c a b d fig. 3 absorption (a) and emission (b) of dtp 2c solution in dmso with addition of different eq. of naoh. photos of the solutions of 2c in dmso with increasing amount of naoh under sunlight (c) and uv-irradiation (d). maximum intensity and simultaneous appearance of the new maximum at 368 nm. isosbestic points in absorption spectra emerged at 325 and 425 nm and this suggests a reactive equilibrium between these two components. 4. conclusions in conclusion, we reported the results of the investigation of the optical properties of hydroxy substituted dtps in the presence of different acids or bases. hydroxy-dtps demonstrated a pronounced fluorescence response in alkaline environment, which resulted in strong bathochromic shift of the absorption and emission maxima along with enhancement of the intensity of the fluorescence. however, they did not display any noticeable perceptible response to organic or mineral acids. thus, introducing of the oh group onto the dihydro-1,2,3-triazole structure led to the sharp change in response of these compounds to basic/alkali stimuli. these results together with our recent ones demonstrated that acid/base sensitivity of the dtps can be adjusted by varying the substituents and functionalities attached to the dihydropyrimidine core. acknowledgments the work was carried out with the financial support of the russian foundation for basic research (grant 19-3390184). references 1. qian j, zhang y, liu x, xia j. carbazole and fluorene 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federal university, ekaterinburg 620002, russia * corresponding author: zuev@ihim.uran.ru this paper belongs to the mosm2021 special issue. © 2022, the authors. this article is published in open access under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). abstract nanoparticles of silicates and germanates with a general formula sr2r8–x–yerxybym6o26 (r = y, la; m = si, ge) were produced in vacuum by the method of pulse electron beam evaporation. an upconversion photoluminescence of the nanoparticles was detected during the excitation by a laser with a wavelength of 980 nm with a predominance of lines in the red and near infrared regions of the spectrum. due to their optical properties, the nanoparticles can be excited directly through the biotissues to visualize various pathologies. the obtained nanosamples have k-jumps of x-ray radiation absorption in the 10−100 kev energy region. this opens up prospects for the use of the nanoparticles as x-ray contrast agents. thus, the nanoparticles have both optical and x-ray contrast characteristics, and therefore have the potential necessary for imaging and diagnosing pathologies in biological tissues. keywords er3+ yb3+ upconversion nanoluminofor biotissues bimodal substances received: 19.01.22 revised: 14.07.22 accepted: 14.07.22 available online: 19.07.22 key findings ● silicates and germanates of rare earth elements are promising for visualization of biological tissues. ● upconversion silicate and germanate nanoluminophores containing er and yb ions can be used for optical and x-ray bioimaging. 1. introduction single-mode nanoparticles (np) with optical or magnetic characteristics are widely used in biosensing and biovisualization [1]. however, they do not provide all the necessary information about biological objects. the requirements of modern biomedical technology suggest the development of new, multimodal bioprobes. multimodal bioprobes combining two or more functions are emerging advances in biology and medicine. a number of nanomaterials with such interesting properties have found various biomedical applications, including imaging, separation, and drug delivery [2]. inorganic nanoparticles doped with ln3+ ions are considered good candidates for multimodal bioapplications, since they have unusual optical and magnetic properties [3]. narrow width of f-f emission lines, long lifetime of photoluminescence (pl), ir excitation in the field of transparency of biological tissues (700– 1000 nm), large antistox shifts for separation of upconversion photoluminescence (ucpl) from excitation, weak background of intrinsic luminescence of biotissues, low cytotoxicity, high chemical resistance and resistance to photobleaching make them extremely suitable for use in various bio-applications [4–7]. the increased intensity of red radiation could be useful for various ucpl applications, especially for deep tissue imaging [4]. currently, magnetic resonance imaging (mri), computed tomography (ct) positron emission tomography (pet), optical imaging, and other methods provide vivid tissue imaging; however, they cannot provide comprehensive information in clinical practice. therefore, various multimodal imaging technologies have attracted considerable attention [8–11]. in this work, ucpl was studied and the dependencies of mass coefficients of weakening of x-ray radiation on the radiation energy for the nanopowders (nps) produced by http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2022.9.2.s12 mailto:zuev@ihim.uran.ru http://creativecommons.org/licenses/by/4.0/ https://orcid.org/0000-0002-8491-8980 https://crossmark.crossref.org/dialog/?doi=https://doi.org/10.15826/chimtech.2022.9.2.s12&domain=pdf&date_stamp=2022-7-19 chimica techno acta2022, vol. 9(2), no. 202292s12 letter 2 of 4 electronic evaporation of solid solutions with a general formula sr2r8–x–yerxybym6o26 (r = y, la; m = si, ge) were considered. nps can be promising as bioprobes for various biomedical applications, including photoluminescent and x-ray contrast images of body tissues [12]. currently, iodinated x-ray contrast agents are widely used to contrast organs and systems of the body. however, these means have a number of drawbacks. they have toxic effects on the blood system, liver, kidneys, pancreas, central nervous and endocrine systems. they also have a local irritating effect on the mucous membranes, including the epithelium of the hepatic and pancreatic ducts, the endothelium of the arterial, venous, lymphatic vessels and the heart, and the cerebral membranes. they cause various types of allergic reactions. therefore, there is a search for new effective x-ray contrast agents that do not have the noted drawbacks. the compounds discussed here can be characterized as twomodal substances promising for simultaneous use in optical and x-ray biovisualization. 2. experimental samples of the above compositions were selected to produce nps. the choice of the compositions is due to two factors. firstly, they should have a ucpl and, secondly, they should have a sufficiently high x-ray attenuation covering the entire range of x-ray energies (10-100 kev) used in medical x-ray diagnostics. the samples were synthesized by conventional ceramic technology. the high-purity reactants srco3, y2o3, la2o3, er2o3, yb2o3, sio2, geo2 were used (the content of the main substance not less than 99.99%). the initial components taken in stoichiometric ratio were thoroughly ground. the obtained mixes were pressed in tablets and burned in air at a temperature of 1350–1400 °c for ~50 h. the x-ray difraction analysis was carried out by means of the shimadzu xrd-7000 diffractometer (cu kα-radiation, counter monochromator cm-3121, detector – scintillation counter) with use of an icdd card file. the diffractograms of the samples were processed using the ritveld full-profile analysis method with the use of an icdd card-file. the nps were produced by evaporating the tablets in vacuum by a pulsed electron beam (pebe) in the nanobim-2 unit [13]. the electron energy was 40 kev, electron beam pulse energy 1.8 j, pulse duration 100 μs, repetition rate 100–200 pps. the time of evaporation of the targets was 40–60 minutes. the speed of rotation of the targets was ~8.3 revolutions/min. the specific surface area of the powders was determined by the known bet method in micromeritics tristar 3000. the microscopic analysis of the hp was performed on a jeol jem 2100 transmission electron microscope. the microscopic analysis of the np was performed on a jeol jem 2100 transmission electron microscope. the pl spectra were recorded on a mdr-204 spectrometer (laser klm-h980-200-5, λ = 980 nm, rated power 221 mw; photoelectronic multiplier r928 from hamamatsu). 3. results and discussion figure 1 shows the results of nps microscopy based on solid solutions of sr2la7.85er0.075yb0.075ge6o26 (i) and sr2y6.8yber0.2si6o26 (ii). according to tem hr microscopy and electronography, it can be seen that the nanoparticles are prone to agglomeration, have irregular shapes and amorphous character (insert) (figures 1, 2). according to bet, the nanoparticles sized ~23 nm (sample based on i) and ~4 nm (based on ii) were found. it is known that nanopowders together with an organic additive obtained by evaporation of solid solutions of the composition sr2y8–x–yerxybysi6o26 were proposed for diagnostics of pathologies in biological tissues [14]. 3.1. upconversion photoluminescence figure 2 shows the spectra of ucpl nanopowders produced based on sr2la8–x–yerxybyge6o26 (x = y = 0.075) and sr2y8–x–yerxybysi6o26 (x = 0.2, y = 1). the excitement of ucpl of er3+ions occurs in the presence of yb3+ because of the absorption of the 980 nanometer laser radiation upon 2f7/2→2f5/2 transition of yb3+ ions with the subsequent transmission of energy in er3+ in a state 4i11/2. in addition, there is a 4i11/2→4f7/2 transition at the excitement by the second photon from a state 2f5/2 of yb3+ ion. besides, the excitation of the state of the 4f9/2 ion er3+ occurs directly by two laser photons with the participation of the photons of the matrix. figure 1 temhr snapshots and electronograms (inserts) np based on sr2y6.8yber0.2si6o26 (a) and sr2la7.85er0.075yb0.075ge6o26 (b). chimica techno acta2022, vol. 9(2), no. 202292s12 letter 3 of 4 500 600 700 800 900 0 10000 20000 4 i 9/2 → 4 i 15/2 4 f 9/2 → 4 i 15/2 4 s 3/2 → 4 i 15/2 2 h 1 1 /2 → 4 i 1 5 /2 i, a . u . , nm a 500 600 700 800 900 0 200000 400000 600000 800000 4 s3/2→ 4 i15/2 4f 9/2 → 4i 15/2 , nm b figure 2 pl spectra of np based on samples i (a) and ii (b). as is known, the primary importance of ucpl in the nir-to-red or nir-to-nir [15, 16] radiation transformations regions of the spectrum are at the excitation radiation with a wavelength of typically about 980 nm. this is particularly important for biomedical purposes. excitation in the nir region of the spectrum in combination with ucnp in the nir or red is possible due to the high transparency of biological fluids and low tissue damage. two intense peaks in nir at 836 and red at 670 nm (figure 2a), and a very intense red peak at ~665 nm (figure 2b) were detected. this luminescence can be used in photodynamic therapy (pdt) to excite a photosensitizer (ps) localized in the diseased region. photodynamic therapy (pdt) uses special drugs called photosensitizing agents that respond to a certain wavelength of light to kill cancer cells [17]. currently, a new generation of photosensitizers is actively developing, which have a stronger absorption in the near infrared region of the spectrum (nir), corresponding to the optimal "transparency region" of the biotissue (700–1000 nm) [18]. high red line intensities at λαmax = 670 nm and near ir line at λαmax = 836 nm (figure 2a) as well as λαmax = 664 nm (figure 2b) indicate the nanoparticles’ promise for deep tissue imaging [19]. 3.2. x-ray attenuation mass coefficients let us consider the dependencies of mass attenuation coefficients (μ) on x-ray energy for the samples sr2y6.8yber0.2si6o26 and sr2la7.75er0.075yb0.075ge6o26 (figures 3, 4). figure 3 dependence of mass coefficient of sr2y6.8yber0.2si6o26 attenuation on x-ray energy. figure 4 dependence of mass coefficient of sr2la7.85er0.075yb0.075ge6o26 attenuation on x-ray energy. the schedules are constructed according to the previous work [20] (ρ – x-ray density). k absorption jumps of the elements sr, y, yb, la are indicated. the absorption of radiation by the nanoparticles in almost the entire range of quantum energies used in x-ray diagnostics is ensured by the fact that the np includes sr, y, yb and la elements, the k absorption jumps of which lie in different parts of this range. strontium has a kjump at 16.10 kev, yttrium – at 17.038 kev, ytterbium – at 61.30 kev and lanthanum at 39 kev. it should be noted that due to the low content of er and yb in the solid solutions, the k-jumps of these atoms practically do not affect the mass attenuation coefficients of the samples. 4. conclusions bimodal nanoparticles were produced by pebe in vacuum. ucpl of nps was detected during excitation by a laser with a wavelength of 980 nm with a predominance of red and nir lines. due to their optical properties, nanoparticles can be excited directly through the biotissue to visualize various pathologies. in addition, k-jumps of x-ray absorption in the energy region of 10–90 ev make it promising to use nps as x-ray contrast agents. supplementary materials no supplementary materials are available. funding this work was carried out in accordance with the state assignment of the institute of solid state chemistry, ural branch of the russian academy of sciences. chimica techno acta2022, vol. 9(2), no. 202292s12 letter 4 of 4 acknowledgments none. author contributions conceptualization: m.g.z. data curation: s.y.s. investigation: 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https://doi.org/10.1002/adfm.201304270 https://doi.org/10.1016/j.ccr.2017.09.006 https://doi.org/10.1002/anie.201104192 https://doi.org/10.1016/j.jlumin.2019.02.008 https://doi.org/10.1021/nn405082y https://doi.org/10.1016/j.biomaterials.2012.05.036 https://doi.org/10.1021/nn200298 https://doi.org/10.7150/thno.15914 https://doi.org/10.15764/pche.2014.02005 https://doi.org/10.1016/b978-0-323-41532-3.00002-6 https://doi.org/10.1002/adfm.20130427 https://doi.org/10.1016/j.dyepig.2018.09.052 https://doi.org/10.1177/153303460800700405 https://doi.org/10.1016/j.bmcl.2013.04.093 https://doi.org/10.1016/j.biomaterials.2010.01.040 https://dx.doi.org/10.18434/t4hs32 polymer-metal complex based on copper(ii) acetate and polyvinyl alcohol: thermodynamic and catalytic properties published by ural federal university eissn 2411-1414; chimicatechnoacta.ru article 2022, vol. 9(3), no. 20229304 doi: 10.15826/chimtech.2022.9.3.04 1 of 7 polymer-metal complex based on copper(ii) acetate and polyvinyl alcohol: thermodynamic and catalytic properties kuralay s. maksotova a* , dariya т. kalikh a, arnur t. omirzakova b, botagoz s. bakirova a, dina n. akbayeva a a: al-farabi kazakh national university, almaty 050040, kazakhstan b: nazarbayev university, nur-sultan 010000, kazakhstan * corresponding author: maksotovak@yandex.kz this paper belongs to the ctfm'22 special issue: https://www.kaznu.kz/en/25415/page. guest editors: prof. n. uvarov and prof. e. aubakirov. © 2022, the authors. this article is published in open access under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). abstract in this work we obtained a polymer-metal complex by mixing aqueous solution of copper(ii) acetate with pva at a certain ratio, ph of the solution and temperature. the composition of the complex compound was determined by potentiometric and conductometric titration. the possibility of a complex formation was proved by calculating thermodynamic characteristics. the stability constant of the polymer-metal complex was calculated on the basis of the modified bjerrum’s method. the metal-polymer complex was synthesized in the ratio 1:2. ir spectroscopy and scanning electron microscopy (sem) confirmed the coordination of polymeric pva ligand to copper and allowed evaluating the morphology and features of the complex surface. the catalytic activity of the synthesized compound was evaluated in the oxidation reaction of elemental phosphorus (p4) by oxygen in aqueous-organic media under mild conditions. quantitative analysis of phosphoric acid was made by photocolorimetric method. we found that the oxidation process of p4 in the presence of the complex cu(pva)2(oac)2 in aqueous-organic media is characterized with the maximum absorption rate, in comparison with cu(oac)2·h2o oxidation process with p4, and yields up to 97% of the products. the process of oxidation of yellow phosphorus by oxygen in the presence of the copper(ii)-pva complex proceeds through key reactions of two-electron reduction of the catalyst p4 with the formation of intermediate phosphorus-containing products p3+ and the stages of catalyst regeneration by oxygen. twenty-electron oxidation of p4 to the phosphorus-containing p5+ products involves 10 two-electron redox reactions and a number of complexation or hydrolysis stages. keywords copper(ii) acetate polyvinyl alcohol polymer-metal complex thermodynamic characteristics catalysis oxidation white phosphorus received: 25.06.22 revised: 08.07.22 accepted: 08.07.22 available online: 26.07.22 1. introduction the development of oxidation processes is essential in today’s chemistry and industry [1–4]. many oxidative techniques have been known to exist in natural life, and a lot of them have been used in various applications the industry, from wastewater treatment to cellulose or lignin bleaching [5–8]. among these applications, oxidizing processes in the detergent industry, called bleaching, are particularly preferred for removing dyes [9–11]. in general, the stability and selectivity of homogeneous catalysts are strongly related to their molecular structure. given the steric, electronic and conformational properties, suitable ligands must be designed for metal complexes that function as effective catalysts. these ligands must also be flexible against oxidation and be electron donors in order to achieve high oxidation states of the active metal. most of them are heat-sensitive substances and generally deteriorate above 150 °c [12–14]. furthermore, the consideration of steric, electronic and conformational properties is necessary for the design of suitable ligands for metal complexes that will serve as effective catalysts. under heat treatment, polymers such as polyvinyl alcohol (pva), polyvinyl chloride (pvc), polystyrene (ps), etc., which have saturated main molecular chains and side http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2022.9.3.04 mailto:maksotovak@yandex.kz https://www.kaznu.kz/en/25415/page http://creativecommons.org/licenses/by/4.0/ https://orcid.org/0000-0001-8606-5005 https://orcid.org/0000-0001-9101-2418 https://crossmark.crossref.org/dialog/?doi=https://doi.org/10.15826/chimtech.2022.9.3.04&domain=pdf&date_stamp=2022-7-26 chimica techno acta 2022, vol. 9(3), no. 20229304 article 2 of 7 groups, can form conjugated structures by removing the side groups from the main one. thermal degradation of polymers creates systems with delocalized π-electrons, which can lead to optical and electronic improvements. then, polymer ligand synthesis and selective chelation of specific metal ions is an active research area [15]. metal ions from polymer complexes have potential applications in electrolytes [16], sensors [17], stabilizers [18] and semiconductors [19]. polyvinyl alcohol is an important material, given its large-scale applications, such as biomaterials, biosensors, electrochemical sensors, membranes with selective permittivity, viscous media to control the crystallization process of salts, controlled monitoring of drugs or catalytic systems, etc. polyvinyl alcohol (pva) is a non-toxic, non-carcinogenic, biodegradable, biocompatible, water-soluble and inexpensive polymer. it could also be used for metal ions or salts in ecological composites [20]. pva is a potential material that has a high dielectric strength, a good charge storage capacity and dopant-dependent electrical properties. it has a carbon-chain dorsal bone with hydroxyl groups attached to the methane carbons. oh groups can be a source of hydrogen bonds and can, therefore, help in the formation of polymer complexes. pva has unique mechanical properties and exhibits both ionic and electronic conduction [21]. despite certain achievements in the chemistry of elemental phosphorus (p4), insufficient attention has been paid to the oxidative reactions involving p4 in the catalytic regime, the description of their kinetics and mechanics, the identification of the nature of catalytically active intermediates. therefore, in this work, the optimal molar ratio of a complex compound based on copper(ii) acetate and polyvinyl alcohol was studied. the possibility of a reaction of polymer-metal complex formation was studied by calculating thermodynamic characteristics. the complex was tested as catalyst in yellow phosphorus oxidation in aqueous-organic media under mild conditions. 2. experimental copper(ii) acetate cu(oac)2h2o, polyvinyl alcohol (molecular mass 30 000, sigma aldrich), hydrochloric acid, sodium hydroxide, sodium chloride, toluene, distilled water were used without purification. yellow phosphorus of the shymkent production association “phosphorus” (kazakhstan) was used, which was previously mechanically cleaned from the oxide film under water. the concentration of p4 in the obtained toluene solution (p4, mol/l) was determined by iodometric titration [22]. 2.1. synthesis of cu(ch3coo)2 – pva a solution of 2.0 g (0.01 mol) of cu(oac)2·h2o in 15 ml of distilled water was added to 15 ml of an aqueous solution of 0.88 g of pva (0.02 mol). the resulting mixture was stirred by magnetic stirrer for 1 hour at ambient temperature until the polymer was completely dissolved and bound to cu(ii) ions. the synthesized light-green complex was dried and stored in air at room temperature. yield: 3.15 g (98%). the process of complex formation between copper(ii) ion and pva was investigated by potentiometric and conductometric methods with several ionic strengths and temperatures. potentiometric studies were carried out in thermostated conditions on an ionomer px-150mi using silver chloride and glass electrodes. the accuracy of the ph measurement was 0.02 ph units. conductometric studies were performed on a conductivitymeter 13701/93 device (phywe) under thermostatically controlled conditions. the polymer-metal complex was obtained by mixing aqueous solution of copper(ii) acetate with pva at certain ratio, ph of the solution and temperature. the stability constant of the polymer-metal complex was calculated on the basis of the modified bjerrum’s method. ir spectra of pvp and cu(ii)-pva complex were recorded on a ft ir-4100 type a jasco instrument in the range of 4000–450 cm–1. sem images were taken on a jsm-6490la jeol instrument equipped with an x-ray dispersive energy detector (edx) for elementary analysis (jeol, japan). ir spectra and sem images were obtained in analytical laboratories at the technical university of kaiserslautern (tuk, germany). quantitative analysis of phosphoric acid was performed by photocolorimetric method on a spectrophotometer spekol 1300 (analytik jena, germany). 2.2. typical reaction procedure oxidation of yellow phosphorus by oxygen was carried out on a temperature-controlled laboratory setup with intensively stirred up glass temperature-controlled reactor with negligible temperature gradient ‘‘a catalytic duck”, supplied by the potentiometric device and connected to the gas burette filled with oxygen. the laboratory experiments were made as follows. the reactor with a total volume of 150 ml was charged with the catalyst (1.07 mmol) under an oxygen atmosphere. the reactor and the gas burette were preheated to 60 °c. the temperature was maintained by the water circulating between the glass reactor and the heating devices. then, in oxygen flow, a solution of p4 in toluene (1.07 mmol) was added to water (9 ml, 9:1 by volume), and an electric motor was switched on. during the catalytic reaction the rates of oxygen absorption were recorded in certain intervals. the temperature was maintained with an accuracy of ±0.5 °c by means of the thermostat. after the experimental runs, the reaction solutions were mixed together and analyzed on a spectrophotometer. 3. results and discussion 3.1. potentiometric titration figure 1 shows the potentiometric titration curve of cu(oac)2 – pva complex. the mixing of solutions of polymer with salt is accompanied by a ph decrease, which is explained by the deprotonation of initially protonated pva during the complexation. chimica techno acta 2022, vol. 9(3), no. 20229304 article 3 of 7 from the titration curve (figure 1), the optimal molar ratio of the reacting components k (k=[cu2+]/[pva]=0.50) was found. it means that one central metal atom bonds with two mono-links of polymer ligands. 3.2. conductometric titration in order to confirm the composition of the formed pva-cu2+ complex, the dependence of the conductivity corrected for the viscosity on the ratio of the initial component of the system was studied (figure 2). the increase in electrical conductivity is due to the released h+ ions during the reaction between pva and copper(ii) ions. as can be seen from figure 2, the electrical conductivity of the solution with an increase in the molar content of metal ions passes through the inflection point. based on the data obtained as a result of conducted conductometric studies, it can be argued that the complexation process is accompanied by an increase in the electrical conductivity of the system at the ratios pva-cu2+=2:1. in the process of complexation of the pva polymer ligand, their hydrodynamic dimensions decrease (chelate effect); protons are released, as evidenced by the experimental results. thus, it can be assumed that the complex of the composition is formed in the pva–cu2+ system. figure 1 сurve of potentiometric titration of pva (10–2 m) with copper salt cu(oac)2 (10 –2 m) (where v – titrant volume in ml, ph – рн of solution). figure 2 сurve of conductometric titration of pva (10–2 m) with copper salt cu(oac)2 (10 –2 m) (where v – titrant volume in ml,  – specific electrical conductivity of solution in sm/cm). 3.3. modified bjerrum’s method calculations the stability constant of the resulting polymer complex and the coordination number of copper(ii) were calculated using the modified bjerrum’s method. in accordance with the known method, the potentiometric study was carried out at three values of the ionic strength of the solution: 0.01, 0.05, and 0.1 mol/l, and the polymer ligand solution was titrated with hydrochloric acid (hcl), depending on the nature of the complexing metal salt, with a change in the ph of the medium in the absence and presence of metal ion, as well as at several temperatures (25, 45, 70 °c). figure 3 shows the ph value change in the absence and presence of metal ions during the experiment. it is clearly seen that the ph value in the presence of metal ions is higher than in experiment without metal ions. it signifies the formation of the complex and means that the system reacts in the acidic medium. table 1 shows the values of the bjerrum’s formation functions (n) corresponding to the coordination number of the metal complexing agent at three ionic strengths and at 70 °c. the data obtained indicate the formation of a copper polymer complex in which the coordination number of the metal is equal to two. 3.4. thermodynamic parameters of the process the knowledge of the thermodynamic parameters (changes in gibbs’ energy (∆rg0), enthalpy (∆rh0) and entropy (∆rs0)) of the studied process is necessary for the scientifically based choice of the optimal conditions for its implementation in practice. moreover, many researchers admit that the fundamental laws of thermodynamics, which were established for the systems consisting of low molecular weight compounds, can be applied to the systems involving macromolecules [23]. the pva-cu(oac)2 system is characterized with the negative gibbs’ energy, which indicates the spontaneous occurrence of the studied process in the direction of the compound formation (table 2). figure 3 curves of potentiometric titration of aqueous solutions of polyelectrolyte of pva (10–2 m) (1) and pva – cu2+ (10–2 m) (2) by hydrochloric acid (10–2 m) and lf=0.01, t = 25 °c. chimica techno acta 2022, vol. 9(3), no. 20229304 article 4 of 7 in the temperature range of 25–70 °c, the complexation process of pva with cu2+ ion is accompanied by the release of heat (exothermic process), as a result of which the strength and stability of the polymer-metal complex decreases with temperature increasing. thus, based on analysis of the results of potentiometric and conductometric analysis, the formation of copper(ii)pva polymer complex and its composition were established. 3.5. ir spectroscopy and sem studies the process of the formation of the copper(ii)-pva complex is characterized by the negative value of the change in entropy, which is caused by the existence of donor-acceptor bond in the studied complex. this also indicates that the ratio between copper(ii) ion and pva is 1:2. to study the surface of the pure polymer and the polymer-metal complex, the scanning electron microscopy (sem) method was used; the results of the study are presented in figures 4 and 5. a comparison of microscopic images of the pure polymer and the resulting complex indicates the formation of porous spherulites of different sizes. the infrared spectrum was acquired for polyvinyl alcohol and the complex copper(ii) acetate – pva (figure 6). table 1 values of bjerrum’s formation functions of the cu(oac)2 – pva complex at 70 °c and i =0.01 mol/l. [lh+]104 (mol l–1)a plb l106 (mol l-1)c lc 10 3 (mol l-1)d ne 3.33 5.39 4.12 3.00 2.00 6.66 6.04 0.922 2.67 1.78 9.99 6.33 0.462 2.33 1.56 13.30 6.69 0.206 2.00 1.33 16.60 6.83 0.149 1.67 1.11 20.00 7.22 0.0597 1.34 0.89 23.30 9.42 0.000381 1.00 0.67 26.60 10.67 0.0000213 0.67 0.45 30.00 12.29 0.000000517 0.34 0.23 33.3 13.91 0.0000000124 0.014 0.01 a [lh+] – concentration of the protonated ligand groups; b pl or –lg[l] – concentration of the free ligands calculated on henserson-hasselbach equation ph = pkα + mlg[l]/[lh+], where m – the empirical coefficient considering interlink interaction of a polymeric chain; c [l] – concentration of the free ligands which are not involved in a complexing process; d [l]с – concentration of the ligand groups connected in a complex; e n – bjerrum’s formation functions or average coordination number of a metal ion. table 2 thermodynamic characteristics of the complexation. t, oc -∆rg o, kj/mmola -∆rh o, kj/mmolb -∆rs 0, kj/mmolkc 25 0.32 1.6328 0.004405 45 0.23 1.0900 0.002704 70 0.16 1.3502 0.003470 a ∆rg o – gibbs’s energy change of reaction; b ∆rh o – enthalpy change of reaction (heat effect); c ∆rs 0 – entropy change of reaction. by comparing these two ir spectra, a displacement of the band position νo–h is clearly seen. in the polyvinyl alcohol infrared spectrum, the position of νo–h changes from 2390 to 2410 upon complexation with cu(ii), which can be seen in the infrared spectrum of the complex based on copper(ii) acetate – polyvinyl alcohol, indicating its participation in the formation of copper – polymer complex [20]. it gives strong indication of specific interactions between the ligand and metal ion. 3.6. oxidation of yellow phosphorus (p4) catalyzed by cu(pva)2(oac)2 complex under mild conditions the synthesized catalyst was used in the process of oxidation of phosphorus at room temperature in the presence of oxygen at atmospheric pressure: a) b) c) figure 4 sem micrographs of polyvinyl alcohol. chimica techno acta 2022, vol. 9(3), no. 20229304 article 5 of 7 a) b) c) figure 5 sem micrographs of copper(ii) acetate-pva complex. figure 6 ir – spectra of pva and pva – cu(oac)2h2o. p4 + 12h2o + 5o2 → 4p(o)(oh)3 + 6h2o (1) the results of the oxidation reaction studies at 60 °c were presented in the mole ratio of the reagents [cu(pva)2(oac)2]:[p4] = 1:1; 3:1; 6:1. during the interaction of yellow phosphorus with aqueous alkali solutions at 50oc due to poor solubility of phosphorus (s500 °c = ~3·10–3 g/l) a slow disproportionation reaction takes place with the formation of hypophosphite and ph3 [24]. figure 7 shows the typical kinetic curves of p4 oxidation process in the solution of cu(pva)2(oac)2–с7н8–h2o. the reaction proceeds in an unsteady mode. both the kinetic (w–) and the conversion (w–q) curves go through maximum as in the case of non-modified cu(oac)2. the average duration of experiments was 130 minutes. the maximum oxygen absorption rate was observed for the molar ratio of [cu(oac)2]:[р4] and [cu(pva)2(oac)2]:[р4] of 6:1. the experiment of the oxidation process with p4 in the presence of the complex cu(pva)2(oac)2 was characterized with the maximum absorption rate, in comparison with cu(oac)2·h2o. the reaction conditions and product yield of p4 oxidation by o2 with cu(oac)2·h2o and cu(pva)2(oac)2 in aqueous-organic solutions are presented in table 3. 0 20 40 60 80 100 0,0 0,5 1,0 1,5 2,0 a) , min w o 2 x 1 0 2 , m o l/ (l ·m in ) 1:1 1:3 1:6 0 40 80 120 160 0,0 0,4 0,8 1,2 , min w o 2 x 1 0 2 , m o l/ (l ·m in ) b) 1:1 1:3 1:6 figure 7 the kinetic curves (w–) of the oxidation process of p4 with oxygen in aqueous-organic medium in the presence of cu(oac)2·h2o (a) and cu(pva)2(oac)2 (b) complex. reaction conditions, mol/l: [p4] 1.07; [н2о] 50; [c7h8] 0.94; 60 °c; [cat]: 1 – 0.01; 2 – 0.03; 3 – 0.06. chimica techno acta 2022, vol. 9(3), no. 20229304 article 6 of 7 table 3 oxidative hydrolysis of yellow phosphorus with copper(ii) acetate and copper(ii) acetate – pva at 60 °c. runs composition of solution, mol/l t, °c time, min yield of products, % cat р4 h2o с7н8 i ii cat cu(oac)2·h2o 1 1.07 1.07 50 0.94 60 120 21 40 2 3.21 1.07 50 0.94 60 120 27 47 3 6.42 1.07 50 0.94 60 120 33 55 cat cu(pva)2(oac)2 1 1.07 1.07 50 0.94 60 120 27 47 2 3.21 1.07 50 0.94 60 120 37 53 3 6.42 1.07 50 0.94 60 120 40 57 note: i – (ho)2hpo; ii – (ho)3po. the р4 molecule, its inorganic and organic derivatives are prone to two-electron oxidation in aqueous solutions: р4→4р+; р+→р3+; р3+→р5+. it is known that the products of two-electron oxidation of р4 are stable compounds р4(or)2, р4(or)4, р2(or)4, р(or)3, р(or)5, while the products of oneelectron oxidation of р4 are unstable radicals [25]. they are strong two-electron reducing agents and impose the role of a two-electron oxidizer on cu(ii) complexes [26]. the standard reduction potentials of cu(ii) indicate that, depending on the redox partner, cu(ii) can be reduced to cu(i) or cu. the cu(ii) ion is prone to both single-electron (еcu(ii)/cu(i) = 0,538 v) and two-electron reduction (еcu(ii)/cu(0) = 0,337 v). 4. conclusions in this study, the ratio of components in a complex compound based on copper(ii) acetate and polyvinyl alcohol was determined by the potentiometric method. two monolinks of polymers connect to one complex – forming metal ion. in addition, the results of the conducted conductometric work also proved that the metal-ligand ratio is 1:2. microphotographs taken with sem showed the formation of porous spherolites of various sizes. as a result of ir spectroscopy, it was shown that the peak corresponding to the νo–h subgroup in the polymer-ligand shifted in a complex compound from 2390 to 2410 cm–1. the thermodynamic characteristics of the complex compound based on copper(ii) acetate and polyvinyl alcohol were calculated, and it was found that the gibbs’ energy value is a negative. the process of complex formation occurs spontaneously. the value of the enthalpy is also negative, and with an increase in temperature, it is assumed that the reaction will shift in the opposite direction. the maximum oxygen absorption rate was observed in the case of the molar ratio [cu(pva)2(oac)2]:[р4] = 6:1 with yield of final products up to 97%. supplementary materials no supplementary materials are available. funding this research had no external funding. acknowledgments none. author contributions conceptualization: d.n.a., b.s.b. data curation: d.t.k., a.t.o. investigation: k.s.m., d.t.k., a.t.o. project administration: d.n.a. writing – original draft: d.t.k., b.s.b. writing – review & editing: k.s.m., d.n.a. conflict of interest the authors declare no conflict of interest. additional information author ids: botagoz s. bakirova, scopus id 57204585748; dina n. akbayeva, scopus id 6505789588. websites: al-farabi kazakh national university, https://www.kaznu.kz/en; nazarbayev university, https://nu.edu.kz. references 1. sorokin ab, kudrik ev. phthalocyanine metal 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https://www.allsubjectjournal.com/archives/2019/vol6/issue12/6-11-37 https://www.allsubjectjournal.com/archives/2019/vol6/issue12/6-11-37 https://doi.org/10.1007/bf02373585 https://doi.org/10.9767/bcrec.13.3.1980.560-572 https://doi.org/10.1016/s0277-5387(97)00480-4 https://doi.org/10.1016/s0010-8545(97)00014-3 benzo[de]naphtho[1,8-gh]quinolines: synthesis, photophysical studies and nitro explosives detection chimica techno acta article published by ural federal university 2021, vol. 8(4), № 20218415 eissn 2411-1414; chimicatechnoacta.ru doi: 10.15826/chimtech.2021.8.4.15 1 of 5 benzo[de]naphtho[1,8-gh]quinolines: synthesis, photophysical studies and nitro explosives detection igor l. nikonov ab* , igor а. khalymbadzha a, leila к. sadieva a, maria i. savchuk ab, ekaterina s. starnovskaya аb, dmitry s. kopchuk ab , igor s. коvalev a, grigory а. kim b, oleg n. chupakhin ab a: ural federal university, 620002 mira st., 19, yekaterinburg, russia b: i.ya. postovsky institute of organic synthesis of the ural branch of the ras, 620990 kovalevskoy/akademicheskaya st., 22/20, yekaterinburg, russia * corresponding author: igor.nikonov.ekb@gmail.com this article belongs to the regular issue. © 2021, the authors. this article is published in open access form under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). abstract a rational synthetic approach to substituted naphtho[1,8gh]quinolines based on intramolecular cyclization in the presence of potassium in the series of (naphthalen-1-yl)isoquinolines is described. the photophysical properties of the obtained compounds were studied; in particular, fluorescence emission was detected in the range 454–482 nm with a quantum yield of up to 54%. we also calculated the homo-lumo energies and optimized molecular structures for the resulting fluorophores. based on the results of fluorescence titration, the stern-volmer constants (up to 21587 m–1) and the detection limits of nitroanalytes (up to 1.4 ppm) were calculated, confirming the possibility of their use as potential chemosensors for the visual detection of nitro-containing explosives. keywords benzo[de]naphtha [1,8-gh]quinolones fluorescence sensor explosives received:15.12.2021 revised: 20.12.2021 accepted: 20.12.2021 available online: 23.12.2021 1. introduction annelated polyaromatic compounds represent a wide class of organic substances that are widely used as chemosensors, including ones for the detection of nitro explosives. naphthalene and its aryl-annelated derivatives, such as phenanthrene, triphenylene, pyrene, dibenzoanthracene, gelcenes, etc. are typical chemosensors for nitroanalytes [1]. perylene deserves special attention in this series due to the interesting photophysical properties, as well as a sensory response to some nitroaromatic compounds, for example, picric acid [2–5]. meanwhile, the introduction of a pyridine nitrogen atom into the structure of polycyclic aromatic hydrocarbons can be useful for creating more efficient chemosensors by combining π-excess receptor and fluorophore fragments into one molecule and enhancing the receptor properties, for example, in relation to nitro-analytes, by creating π-conjugated donor-acceptor ensembles [1]. it should be noted that aza analogs of perylene often have promising fluorescent characteristics, as well as higher lumo energies values, which may determine the greater ability of azaperylenes to detect nitro explosives, including aliphatic ones [6, 7]. however, a more detailed study of the photophysical and chemosensory properties of these fluorophores has not been found in the literature. in this regard, we would like to present a method for obtaining new fluorophores of the benzo[de]naphtho[1,8-gh]quinoline series and an investigation of their sensory response to some nitroanalytes. 2. experimental 1h nmr spectra were recorded on a bruker avance-400 spectrometer (400 mhz), the internal standard was sime4. mass-spectra (ionization type — electrospray) were recorded on a microtof-q ii instrument from bruker daltonics (bremen, germany). elemental analysis was performed on a perkin elmer pe 2400 ii chn analyzer. homo-lumo and optimized molecular structures calculations of compounds were carried out in the orca 4.0.1 software package using the dft b3lyp, 6-311g* method [8]. uv–visible absorption spectra were recorded on a perkin elmer lambda 45. luminescence spectra were obtained using a horiba scientific fluoromax-4 spectrofluorometer. the starting 2-(methoxyphenyl)ethanamines 4, 1-naphthoyl chloride, and all reagents were obtained from commercial sources. http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2021.8.4.15 https://orcid.org/0000-0002-2493-0056 https://orcid.org/0000-0002-0397-4033 http://creativecommons.org/licenses/by/4.0/ chimica techno acta 2021, vol. 8(4), № 20218415 article 2 of 5 2.1. general procedure for the synthesis of n-(methoxyphenethyl)-1-naphthamides 2 to an ice cooled solution of the corresponding 2-(methoxyphenyl)ethanamine 4 (10.0 mmol) (in case of compound 4b oxalate was used) and 1-naphthoyl chloride (2.09 g, 11.0 mmol) in dichloromethane (20 ml) was added diisopropylethylamine (2.84 g, 22.0 mmol). the mixture was stirred for 12 h, poured in ice and the product was extracted with dichloromethane. the organic layer was washed with water, dried with anhydrous na2so4 and evaporated to obtain n-(4-dimethoxyphenethyl)-1naphthamide as white solid. n-(4-methoxyphenethyl)-1-naphthamide (2a). yield 2.47 g (81%). 1h nmr (400 mhz, dmso-d6, δ, ppm): 8.36 (br s, 1h), 8.09 (d, j = 7.9 hz, 1h), 7.88–7.93 (m, 2h), 7.46–7.50 (m, 4h), 7.19 (d, j = 8.1 hz, 1h), 6.83 (d, j = 8.1 hz, 1h), 3.77 (s, 3h), 3.52–3.57 (m, 2h), 2.84–2.89 (m, 2h). esi–ms, m/z: 306.14 [m+h]+. found, %: c 78.58, h 6.24, n 4.64. c20h19no2. calculated, %: c 78.66, h 6.27, n 4.59. n-(3,4-dimethoxyphenethyl)-1-naphthamide (2b). yield 2.71 g (77%). 1h nmr (400 mhz, cdcl3, δ, ppm): 8.20–8.22 (m, 1h), 7.84–7.90 (m, 2h), 7.50–7.53 (m, 3h), 7.40–7.44 (m, 1h), 6.79–6.83 (m, 3h), 5.98 (br s, 1h), 3.86 (s, 3h), 3.82–3.78 (m, 5h), 2.94–2.97 (m, 2h). 1h nmr in dmso is in accordance with published data [9]. esi–ms, m/z: 336.15 [m+h]+. found, %: c 75.24, h 6.37, n 4.14. c21h21no3. calculated, %: c 75.20, h 6.31, n 4.18. 2.2. general procedure for the synthesis of 1-(naphthalen-1-yl)-3,4-dihydroisoquinolines (3a,b) to a solution of the corresponding n-(4methoxyphenethyl)-1-naphthamide 2 (6.56 mmol) in dry toluene (30 ml) was added freshly distilled pocl3 (5.03 g, 32.8 mmol). the mixture was stirred at 110 °c for 8 h, poured into ice. water solution of naoh was added until ph>10 was adjusted. the product was extracted with dichloromethane (330 ml). the organic layers were combined, dried and evaporated yielding crude 3,4dihydroisoquinoline. 7-methoxy-1-(naphthalen-1-yl)-3,4-dihydroisoquinoline (3a). off-white solid. yield 1.11 g, (59%). 1h nmr (600 mhz, cdcl3, δ, ppm): 7.91 (dd, j = 5.6 hz, j = 4.0 hz, 1h), 7.88 (d, 7.9 hz, 1h), 7.73 (ddd, j = 8.5 hz, j = 1.0 hz, j = 1.0 hz, 1h), 7.53 (d, j = 2.0 hz, 1h), 7.53 (s, 1h), 7.46 (ddd, j = 8.1 hz, j = 6.8 hz, j = 1.2 hz, 1h), 7.37 (ddd, j = 8.2 hz, j = 6.8 hz, j = 1.3 hz, 1h), 7.22 (d, j = 8.3 hz, 1h), 6.91 (dd, j = 8.3 hz, j = 2.8 hz, 1h), 6.42 (d, j = 2.6 hz, 1н), 4.02 (br s, 2h), 3.55 (s, 3h), 2.90 (m, 2h). esi-ms, m/z: 288.13 [m+h]+. found, %: c 83.67, h 6.02, n 4.78. c20h17no. calculated, %: c 83.59, h 5.96, n 4.87. 6,7-dimethoxy-1-(naphthalen-1-yl)-3,4dihydroisoquinoline (3b). white solid. yield 1.41 g, (68%). 1h nmr in dmso-d6 is in accordance with published data [10]. esi-ms, m/z: 318.14 [m+h]+. found, %: c 79.43, h 6.12, n 4.34. c21h19no2. calculated, %: c 79.47, h 6.03, n 4.41. 2.3. general procedure for the synthesis of 1-(naphthalen-1-yl)isoquinolines (1a,b) to a solution of the corresponding 1-(naphthalen-1-yl)-3,4dihydroisoquinoline 3 (2.48 mmol) in benzene was added mno2 (2.24 g, 25.8 mmol) and the mixture was stirred under reflux for 24 hours. then mixture was cooled and mno2 was filtered off, and benzene was evaporated to obtain isoquinoline. 7-methoxy-1-(naphthalen-1-yl)isoquinoline (1a). yield 0.60 g (85%). 1h nmr (400 mhz, cdcl3, δ, ppm): 8.60 (d, j = 5.6 hz, 1h), 7.99 (dd, j = 6.2 hz, j = 3.5 hz, 1h), 7.95 (d, j = 8.3 hz, 1h), 7.84 (d, j = 8.9 hz, 1h), 7.69 (d, j = 5.6 hz, 1h), 7.62–7.75 (m, 2h), 7.49 (dd, j = 7.8 hz, j = 7.8 hz, 1h), 7.45 (d, j = 8.2 hz, 1h), 7.32–7.37 (m, 2h), 6.88 (d, j = 2.6 hz, 1h), 3.56 (s, 3h). esi-ms, m/z: 286.12 [m+h]+. found, %: c 84.15, h 5.32, n 4.94. c20h15no. calculated, %: c 84.19, h 5.30, n 4.91. 6,7-dimethoxy-1-(naphthalen-1-yl)isoquinoline (1b). yield 731 mg (90%). 1h nmr (400 mhz, cdcl3, δ, ppm): 8.56–8.57 (m, 1h), 7.93–8.00 (m, 2h), 7.60–7.64 (m, 3h), 7.45–7.50 (m, 2h), 7.32–7.36 (m, 1h), 7.17 (s, 1h), 6.85 (s, 1h), 4.06 (s, 3h), 3.59 (s, 3h). esi-ms, m/z: 316.13 [m+h]+. found, %: c 80.06, h 5.39, n 4.47. c21h17no2. calculated, %: c 79.98, h 5.43, n 4.44. 2.4. general procedure for the synthesis of azaperylenes (5a,b) the corresponding 1-(naphthalen-1-yl)-isoquinoline 1 (1.05 mmol) was dissolved in dry toluene (25 ml); subsequently, potassium (10.5 mmol) was added under argon atmosphere. the resulting mixture was stirred at 95 °c for 6 h, quenched with i-proh, filtered through silica gel, and the solvents were removed under reduced pressure. the residue was solved in ethyl acetate (20 ml). the solution was washed with water (3 x 20 ml), the organic layer was dried over anhydrous na2so4 and evaporated under reduced pressure. the residue was purified by column chromatography (corresponding eluent). the crystallization (ch2cl2/hexane) afforded pure product. 6-methoxybenzo[de]naphtho[1,8-gh]quinoline (5a). eluent: hexane:i-proh=20:1, rf = 0.9. yellow-green solids. yield 99 mg (33%). 1h nmr (400 mhz, cdcl3, δ, ppm): 3.56 (s, 3h), 7.35 (d, j = 7.2 hz, 1h), 7.46–7.49 (m, 2h), 7.63 (d, j = 5.6 hz, 1h), 7.85 (d, j = 8.9 hz, 1h), 7.94–8.02 (m, 2h), 8.53 (d, j = 6.8 hz, 1h), 8.60 (d, j = 6.5 hz, 1h). esi-ms, m/z: 284,10 [m+h]+. found, %: c 84.82, h 4.66, n 4.84. c20h13no. calculated, %: c 84.78, h 4.62, n 4.94. 5,6-dimethoxybenzo[de]naphtho[1,8-gh]quinoline (5b). eluent: dcm:meoh=100:1, rf = 0.8. yellow-green chimica techno acta 2021, vol. 8(4), № 20218415 article 3 of 5 solids. yield 33 mg (11%). 1h nmr (400 mhz, cdcl3, δ, ppm): 4.22 (s, 6h), 7.30 (s, 1h), 7.43 (d, j = 7.8 hz, 1h), 7.59–7.62 (t, j = 8.0 hz, 1h), 7.69 (d, j = 5.6 hz, 1h), 7.84 (d, j = 8.9 hz, 1h), 7.93–7.99 (m. 2h), 8.53 (d, j = 8.0 hz, 1h), 8.58 (d, j = 7.5 hz, 1h). esi-ms, m/z: 314,11 [m+h]+. found, %: c 80.56, h 4.74, n 4.50. c21h15no2. calculated, %: c 80.49, h 4.83, n 4.47. 3. results and discussion the synthesis of the precursors of azaperylenes, methoxysubstituted (naphthalen-1-yl)isoquinolines 1, was carried out according to the previously described procedure [9] by cyclization of naphthamides 2 according to the bischlernaperalsky procedure followed by oxidative dehydrogenation of intermediate 3. while, precursor 2 was synthesized by amidation of 1-naphthoyl chloride with methoxysubstituted phenylethanamines 4. further, to obtain the target benzonaphthoquinolines 5, an attempt was made to use lewis acid (fecl3) as an activator of the formation of a charge transfer complex, but this interaction did not allowed to obtain the target compounds 5. the use of cyclization in the presence of potassium [11] was more successfull. thus, the starting isoquinoline 1 was kept in a solution of dry toluene at 95 °c in the presence of metallic potassium for 6 h (scheme 1). the yields of monoand dimethoxy-substituted azaperylenes 5 were 33% and 11%, respectively, which is acceptable for reactions of this type [6, 11]. the obtained azaperylenes 5 demonstrated promising photophysical properties. the results are presented in table 1. thus, the absorption maximum for both fluorophores lies in the visible spectral region (441 nm), and the emission spectra contain two maxima lying in the green region (454–482 nm), which is probably associated with the effect of intramolecular charge transfer (ict). in addition, monoand dimethoxy-substituted azaperylenes 5 demonstrated high luminescence quantum yields (54% and 46%). table 1 photophysical properties of the obtained fluorophores 5 compound λabs, nm λem, nm quantum yield [12], % 5a 226, 417, 441 457, 482 54.0 5b 417, 441 454, 482 46.1 the absorption and emission spectra of azaperylenes 5 in normalized form are presented in fig. 1. for all compounds, the absorption/emission plots have a similar profile and represent a distorted specular reflection of each other. scheme 1 synthesis of benzo[de]naphtho[1,8-gh]quinolones a) b) fig. 1 normalized absorption/emission spectra of compounds 5a (a) and 5b (b) chimica techno acta 2021, vol. 8(4), № 20218415 article 4 of 5 the above results of photophysical studies for azaperylenes 5 allowed predicting their use as potential fluorescent chemosensors for various nitro explosives. for the primary assessment of the efficiency of quenching the fluorescence of sensors under the action of nitroanalytes, the lumo energy differences for the sensor and quencher corresponding to the thermodynamic driving force of this process were calculated [1, 7]. using the basic set dft b3lyp, 6-311g*, the homo-lumo energies were calculated and their optimized molecular structures [13–16] were obtained. the calculation results are shown in table 2. compared to the previously calculated model of the homo/lumo electronic configuration for unsubstituted perylene [17], the electron clouds of the obtained fluorophores are shifted to one degree or another relative to the nitrogen atoms of the azaperylene ring and methoxy groups, which indicates a high probability of intramolecular charge transfer processes. calculations of lumo values for three nitroanalytes, namely, rdx, dnt, and petn, show that, in comparison with perylene, the obtained azaperylenes 5a,b are more capable of transferring an electron from the lumo of azaperylene to the lumo of these nitro compounds, which is expressed in the energy gap lumo(sensor)-lumo(quencher) from 0.3985 to 1.2409 ev, which should cause a “turn-off” fluorescent response. a series of fluorescence quenching experiments were then performed by titrating the chemosensors 5 and perylene in acetonitrile solutions (510–5 m) with solutions of rdx, dnt and petn in acetonitrile (510–3 m), as well as a solution of 2,4,6-trinitrophenol (picric acid) (510–4 m) to confirm the results. it was found that an increasing petn concentration does not cause fluorescence quenching for all of the considered sensors. in all likelihood, this can be caused by the low stability of the donor – acceptor complex between these compounds and petn. as for the other nitroanalytes, (rdx and dnt) in the case of dimethoxy-substituted azaperylene 5b and unsubstituted perylene fluorescence quenching was also practically not observed, and when these compounds were titrated with a solution of picric acid, the obtained stern-volmer constants do not exceed 4400 m–1, which is an extremely low value in comparison with the literature data for other known chemosensors [1]. opposite results were obtained when titrating monomethoxy-substituted sensor 5a with solutions of rdx, dnt and picric acid. in this case, an increase in the concentration of nitroanalyte causes intense quenching of fluorescence. thus, as a result of titration of 6methoxybenzo[de]naphtho[1,8-gh]quinoline 5a with a solution of picric acid, the obtained stern-volmer plot is linear, and the emission spectra of solutions before and after the addition of the analyte indicate almost complete quenching of the sensor fluorescence (fig. 2). the obtained stern-volmer constants (853 m–1 (rdx), 1773 m–1 (2,4-dnt), 21587 m–1 (picric acid)) agree with the values described in the literature for most chemosensors for nitrous explosives [1]. in addition, based on the fluorescence titration data for azaperylene 5a, the values of the limits of detection (lod) of the nitroanalytes under consideration were calculated according to the described method [18]. the obtained lod values are 22.4 ppm (rdx), 12.5 ppm (dnt), 1.4 ppm (pa), which also corresponds to the literature data [1]. table 2 results of calculating the homo-lumo energies and the driving force of fluorescence quenching of compounds 5 upon interaction with nitroanalytes structure homo, ev lumo, ev lumosensor-lumoquencher, ev rdx dnt petn 5a –5.0693 –2.1015 0.3985 1.0985 1.1985 5b –5.2062 –2.0591 0.4409 1.1409 1.2409 [17] –4.201 –2.302 0.198 0.898 0.998 chimica techno acta 2021, vol. 8(4), № 20218415 article 5 of 5 a) b) fig. 2 fluorescence quenching of sensor 5a with picric acid solution: emission spectra (a) and stern-volmer plot (b) 4. conclusions thus, we demonstrated a rational approach to obtaining new 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chronicles young sci. 2011;2:21. doi:10.4103/2229-5186.79345 https://doi.org/10.1070/rc2014v083n09abeh004467 https://doi.org/10.1039/b206367k https://doi.org/10.1002/anie.202108519 https://doi.org/10.1039/c3cc45843a https://doi.org/10.1002/asia.201801410 https://doi.org/10.1063/5.0011229 https://doi.org/10.1002/wcms.81 https://doi.org/10.1016/j.tet.2006.03.088 https://doi.org/10.1021/acs.orglett.9b00534 https://doi.org/10.1021/jo902443s https://doi.org/10.1007/s10895-005-0054-8 https://doi.org/10.1063/1.438955 https://doi.org/10.1063/1.438980 https://doi.org/10.1002/jcc.540040303 https://doi.org/10.1063/1.447079 https://doi.org/10.1186/s13065-017-0352-7 https://doi.org/10.4103/2229-5186.79345 silica gel functionalized with imidazolium group via click chemistry –new stationary phase for ion chromatography chimica techno acta article published by ural federal university 2021, vol. 8(4), № 20218409 eissn 2411-1414; chimicatechnoacta.ru doi: 10.15826/chimtech.2021.8.4.09 1 of 6 silica gel functionalized with imidazolium group via click chemistry – new stationary phase for ion chromatography d.a. chuprynina, i.a. lupanova, v.v. konshin , dzh.n. konshina * kuban state university, department of chemistry and high technologies, 350040 stavropolskaya st., 149, krasnodar, russia * corresponding author: jfox@list.ru this article belongs to the regular issue. © 2021, the authors. this article is published in open access form under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). abstract this manuscript describes the preparation of a simple effective ionexchange material based on silica gel, on the surface of which methylimidazolium bromide is fixed using a click reaction. the resulting material was used as a stationary phase for the separation and determination of cl–, no2–, no3–, i–, and so42– using ion exchange chromatography. the separation efficiency and retention factors for the selected anions were studied in the ph range 3.5–6.5. the proposed material was used for the determination of cl–, so42– in water and can be suggested for successful use in real water samples. keywords click reaction ion exchange modified silica received: 06.08.2021 revised: 16.11.2021 accepted: 09.12.2021 available online: 11.12.2021 1. introduction the development of new anion-exchange phases with improved efficiency and selectivity is one of the topical problems of modern ion chromatography [1]. the selectivity of an anion exchanger is largely governed by the nature and structure of functional layer and the method of its attachment to the matrix surface. the efficiency of an anion exchanger depends on the type of material, as well as on the morphology and the packing mode of particles. organic polymers can be considered as the most convenient and common matrices for the design of anion exchangers. nevertheless, such materials as zirconia, alumina, and, especially, silica gel are quite often used for the preparation of organomineral materials, stationary phases in chromatography and adsorbents for solid-phase extraction. the disadvantage of silica materials is their limited stability at lower and higher ph values, especially in alkaline solutions. silica-based anion exchangers are often used in the ph range 2.0–9.5. however, compared to organic polymers, silicabased ion exchangers have the advantages of higher chromatographic efficiency and greater mechanical stability. in addition, such materials are preferable for operation in the nonsuppressive version of ion chromatography with conductometric detection, since in this case it is necessary to use dilute eluents, which is possible with materials of low exchange capacity. silica gel-based sorbents are synthesized using a conventional approach, which consists in the surface modification with different functional groups. functionalization through covalent attachment of a modifier to the matrix surface has a number of advantages. first, the required amount of sorption and ion-exchange centers is governed by the structure and amount of a modifier. second, variation in the structure of a modifier can influence the capacity, efficiency, and separation selectivity of an ion. third, there are cross linking agents which enable extending the working ph range to 9.2 without affecting the efficiency over the entire life cycle of a column [2]. such surface-grafted anion exchangers have the advantage of a small thickness of the ion-exchange layer that favors an increase in the rate of mass transfer upon ion exchange and thereby makes it possible to separate ions with high performance and high selectivity [3]. various classes of organic compounds are used as the surface modifiers of stationary phase matrices [4]. in recent years, there is a growing interest in the use of ionic liquids that enable a wide variation in the nature of a cationic moiety, which influences the properties of obtained materials [5–7]. among ionic liquids, imidazolium salts gained widespread acceptance as modifiers. examples of their use as efficient extractants capable of forming ion-associative complexes with simple and complex anions have been described. such complexes are readily produced and quite stable and variation of functional groups in the cationic moiety of ionic liquids offer manifold possibilities to apply salts in different version of sample preparation: http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2021.8.4.09 https://orcid.org/0000-0003-1864-531x https://orcid.org/0000-0002-9239-5470 http://creativecommons.org/licenses/by/4.0/ chimica techno acta 2021, vol. 8(4), № 20218409 article 2 of 6 sorption concentration, liquid-liquid microextraction, and modification of stationary phases in gas and liquid chromatography [7, 8]. materials with attached imidazolium salts have been used successfully as stationary phases in liquid chromatography for separation of caffeine, theophylline, theobromine [9], xylose, glucose [10], ephedrine [11], and vitamins [12], as well as for separation of organic and inorganic anions [13–15]. due to the variety of available starting reagents, not only materials for supernatant columns, but also solid columns with attached ionic liquids have been synthesized [16, 17]. the aim of the present work was to obtain ion-exchange materials based on silica gel having a particle size of 8–12 m with imidazolium salt covalently immobilized by click reaction and to study whether they can be used as a stationary phase for ion-exchange chromatography. 2. experimental 2.1. reagents and instrumentation the sorbent was prepared using silica gel “sorbfil” with a particle size of 8–12 m. ir spectra were recorded on a shimadzu ir prestige spectrometer in a range of 400–4200 cm–1. 13с nmr spectra were measured using a 400 mhz bruker wb avance iii spectrometer operating at 9.39 tesla equipped with a bruker h-f/x 4 mm pencil cp/mas probehead. 13с chemical shifts were referenced to external solid tsp ((trimethylsilyl)propionic acid sodium salt) standard. crosspolarization technique from 1h with spinning sideband suppression (cp toss), contact pulse durations of 2–4 ms at a mas rate of 10 khz was used. the thermal stabilities of modified silica gel samples were studied on an sta 409 pc luxx synchronous thermal analyzer (netzsch, gemrany) in a temperature range from 30 to 1000 °c at a heating rate of 10 оc/min in the air atmosphere in al2o3 ceramic crucibles. the ph value of working buffers was verified on an expert-001 ionomer using a calibrated esc-10608 combined glass electrode. chromatographic properties of the column packed with modified silica gel were studied using a modular highperformance liquid chromatograph from shimadzu (kyoto, japan) including a cto-20a column thermostat, an lc-20ad sp mobile phase feed module, and cdd-10a vp. conductometric detector. the volume of injection loop was 20 l. data were collected and processed using the lcsolution program. 2.2. column packing 316 stainless steel hplc columns (150×2 mm) (phenomenex) were used. the chromatographic column was packed by the suspension method under a pressure of 13 mpa. a test portion of the modified silica gel was added to a c2h5oh–chcl3 solution (1:1, v/v). the column was packed and the sorbent was compacted on exposure to ultrasound. after packing, the column was conditioned by passing iso-propanol in a volume equal to the 20-fold volume of the packed column, next – bidistilled water, and then – a working mobile phase until the background signal has become constant. 2.3. synthesis of imidazolium-modified silica gel acetonitrile (70 ml), 3-azidopropyl silica gel (5 g), 1-methyl-3-prop-2-yn-1-yl-1h-imidazolium (1 g), cui (0.095 g), and n,n,n`,n`-(tetramethylethylenediamine) (750 l) were placed in a pressure flask with fluoroplastic screw cap and magnetic bar in the argon atmosphere. the resulting suspension was kept with vigorous stirring at 70 °c for 4 h. silica gel was separated on a schott filter, washed with acetone, water, 2 m hydrochloric acid, and again acetone and dried at 55 °c for 12 h under a residual pressure of 5 mm hg. a portion of the resulting modified silica gel was further treated with a solution of hexamethyldisilazane in toluene for 8 h at 80 °c. 2.4. determination of the total exchange capacity of the modified silica gel the maximum exchange capacity of the material was determined by titrimetry. the modified silica gel (0.5 g) was agitated with 0.1 m nitric acid (20 ml) for 1 h [18]. silica gel was filtered off and the amount of chloride ion released after the ion exchange reaction with 0.1 m hno3 was determined by titrimetry in an aliquot portion of the filtrate. to the aliquot portion of filtrate (5 ml), 0.05 m agno3 (5 ml) was added and the excess of unreacted agno3 was titrated with 0.05 m kscn using a saturated solution of fe(nh4)(so4)2 (0.2 ml) as an indicator. titration was terminated after a sorrel color of the solution appeared due to the formation of iron rhodanate complex. the calculated total exchange capacity was 0.26±0.02 mm/g. the capacity of the silanized material remained unchanged. 3. results and discussion the test object was an organomineral material based on silica gel with acovalently attached imidazolium group obtained by the azide-alkyne cycloaddition click reaction (scheme 1). in 13с nmr spectrum for the modified silica gel with imidazolium salt two groups of spectral signals are seen. one group contains two signals at δ 124.4 and 137.4 corresponding to the carbon nuclei in nitrogen-containing ring. another group consists of spectral signals at δ 52, 44.6, 36.8, 24.1, and 17, which corresponds to the carbon atoms of aliphatic –ch2– fragments. the signal at δ 9.7 corresponds to the –ch3 group. fig. 1 shows the ir spectra for the starting silica gel with covalently attached azide group and the imidazoliumbearing material obtained according to scheme 1. chimica techno acta 2021, vol. 8(4), № 20218409 article 3 of 6 sil-im scheme 1 synthesis of the modified silica gel both spectra display a broad intense band at about 1300–1290 cm–1 corresponding to stretching vibrations of the siloxane (si–o–si) bond in silica. the intense absorption band at 1627 cm–1 is due to bending vibrations of water absorbed on the silica gel surface. the broad intense band at 3200–3500 cm−1 corresponds to the stretching vibrations of о–h adsorbed on the water surface and silanol groups. the intense absorption band at 2106 cm–1 corresponds to stretching vibrations of the azido group grafted to the silica gel surface. in the spectrum of the silica gel sample obtained after the click reaction, the stretching vibration band of the azide group disappears, which suggests a successful click reaction on the silica gel surface. the obtained batch of silica gel with a covalently immobilized group was divided into two portions. one portion was treated with a silanization reagent, hexamethyldisilazane (scheme 2), in order to inactivate residual silanol groups, which are additional sorption centers. the second portion of the material was used without additional treatment. the heat stability is one of the key characteristics of sorption materials, since it governs the temperature range of their possible application (table 1). similar temperature regions of weight loss and the presence of exothermic effect at about 350 °c can be distinguished for both samples of the modified silica gel. table 1 thermal analysis data of silica gel samples sil-im (h) sil-im temperature range, oс weight loss,% temperature range, oс weight loss,% 30–154 4.7 30–165 2.8 154–85 6.1 165–325 4.4 285–566 10.7 325–460 3.6 566–950 0.2 460–900 4.1 fig. 1 ir spectra of the modified silica gel samples chimica techno acta 2021, vol. 8(4), № 20218409 article 4 of 6 sil-im (h) scheme 2 synthesis of the modified silica gel according to the literature data [19], the first section on the tg curve in a range from 80 to 170 °c is due to the evaporation of water adsorbed on the silica gel surface. further decrease in the sample weight in a range from 170 to 900 °c corresponds to destruction of the functional organic layer. the total weight loss of modified silica gel samples at 950 °c was about 16.0–21.7%. chromatographic conditions of the modified silica gels were studied in a single-column version of ion chromatography with non-suppressed conductivity detection. in such cases, for determination of anions on stationary phases possessing relatively low capacity values, diluted eluents based on aromatic acids, such as benzoic and phthalic acids, are preferred. the choice of the nature and composition of a buffer solution was caused by the fact that solutions based on phthalic acid possess high buffer capacity in the ph range recommended for stationary phases based on silica [20, 21]. a mixture of cl–, no2–, no3–, i–, and so42– anions was chosen as the model. the working parameters for chromatographic separation were chosen as follows: the eluent was hoocc6h4cook with c = 2.5 mm and ph = 4 [22]. the comparison of the efficiency of separation of the standard anion mixture by the studied materials under identical conditions demonstrates a considerable decrease in the plate numbers per meter (n/m) for sil-im(h) (table 2). table 2 efficiency of anion separation (n/m) and retention time (tr, min) on the sil-im and sil-im (h) sorbents anion sil-im sil-im (h) n tr n tr cl– 3126 5.0 2720 11.8 no2 – 10093 5.9 4045 14.2 no3 – 8686 6.5 3546 17.8 i– 6273 8.7 2808 29.6 the addition of naoh to the stationary phase results in an increase in the efficiency and higher rapidity of separation of some anions due to an increase in the eluting power of the mobile phase. upon ph change from 4 to 6, the concentration of hydrogen phthalate, an average-strength eluting ion, increases and, upon ph above 6, divalent phthalate with high eluting ability becomes the main anionic form of the eluent. in addition, at ph close to 7, the residual silanol groups on the surface of the anion exchanger, which can enter into ion exchange interactions, undergo almost complete ionization resulting in an increase in the separation efficiency (fig. 2). the most efficient separation was observed at рн = 6.5; one can note a multiple decrease in the retention, which leads to a possibility of determining anions in lower amounts. no change in the elution order was observed, which indirectly suggests a predominant ion-exchange mechanism of anion separation on the proposed stationary phase. a b fig. 2 the effect of naoh content in the mobile phase on the separation efficiency n (n/m) (a) and the retention k of anions on the sil-im(h) sorbent (b) chimica techno acta 2021, vol. 8(4), № 20218409 article 5 of 6 the linearity of the method was tested using a series of inorganic anions standard solutions. each point of the calibration plot was the average of three peak height measurements, because the baseline resolution of some anions couldn’t be achieved without further dilution of the mobile phase and significant decrease of efficiency, which could cause a problem in the analysis of the samples with complex matrices. an example of a typical chromatogram is shown in the fig. 3. the coefficient for calibration curves, the linear range and detection limits (defined as a signal three times the height of the noise level) as well as the quantification limits are presented in table 3. the comparison of the quantitative characteristics by the example of univalent inorganic anions demonstrates narrowing of the working concentration range on going from sil-im to sil-im(h) and, as a consequence, an increase in the limit of detection of an analyte. fig. 3 chromatogram obtained with the sil-im stationary phase using anion-exchange conditions. test mixture: 1) f–; 2) ch3coo –; 3) io3 –; 4) cl–; 5) no2 –+br–; 6) no3 –; 7) i–; 8) scn–; 9) so4 2–. chromatographic conditions: mobile phase: 2.5 mmol/l hoocc6h4cook with ph = 4, flow-rate: 0.3 ml/min, injection volume: 20 l and detection: non-suppressed conductivity however, the sensitivity of determination in this case increases, which is evidenced by an increase in the slope of the calibration curve. the error in the determination of standard solutions of the analyzed group of anions as estimated by the added-found method differs in a regular manner: no more than 6.2% for sil-im and no more than 4% for sil-im(h) (table 4). the applicability of the obtained ion-exchange material as a stationary phase in the ion-exchange chromatography was estimated by the example of sil-im upon determination of inorganic anions in mineral water. since the single-column non-suppressed ion chromatography used in this study does not possess a high sensitivity compared to two-column with suppressed conductivity detection, although it allows one to determine simultaneously in the isocratic mode weakly and strongly retained anions, it seems interesting to analyze real objects with a high content of anions. a “lysogorskaya” bottled mineral drinking water relating to a group of chloride-sulfate ones was chosen as the test object (table 5). the content of main macrocomponents was estimated by the calibration curve. to verify the determination accuracy of cl– and so42–, their contents in the sample were estimated using a commercial column on a dionex ics-300 chromatographic system with a possibility of eluent generation and suppressed conductivity detection. the confidence intervals of ion determination obtained for different chromatographic determination systems overlap, which suggests the accuracy of the obtained data. table 3 sensitivity factors and linear ranges of calibration curves for the studied anions anion sil-im(h) sil-im linear range, mg/l a* r2 lod**, mg/l linear range, mg/l a* r2 lod**, mg/l cl– 40–160 6227 0.9986 5.6 25–400 3494 0.9985 1.9 no2 – 20–160 2210 0.9983 4.9 25–400 2914 0.9990 1.6 no3 – 40–160 3859 0.9978 12.1 25–200 484 0.9982 3.8 i– 40–160 6325 0.9984 11.0 25–300 685 0.9925 11.2 *a – coefficient for calibration curves (y = ax + b) **lod limits of detection = s∙3.3, s – standard deviation of ten independent measurements of a blank sample table 4 errors in the determination of the studied anions using the studied anion exchangers (n = 3, p = 0.95) anion sil-im(h) sil-im added, mg/l found, mg/l δ, % added, mg/l found, mg/l δ, % cl– 80 77.3±9.9 –3.4 100 94.5±14.1 –5.5 no2 – 78.3±10.2 –2.1 94.0±14.1 –6.0 no3 – 80.8±10.4 1.0 97.5±14.3 2.5 i– 81.5±10.6 1.9 106.2±16.2 6.2 table 5 assessment of the anion content in the real sample using different chromatographic systems (n = 5, p = 0.95) anion cl– so4 2– stationary phase c, mg/l cclaimed, mg/l sr, % c, mg/l cclaimed, mg/l sr, % sil-im 2227±387 2200–7700 1.93 7321±425 5500–9000 0.17 seporus a-uni (hc-1) 2845±345 4.13 7691±880 3.87 chimica techno acta 2021, vol. 8(4), № 20218409 article 6 of 6 4. conclusions in this work, the possibility 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https://doi.org/10.1016/0021-9797(89)90426-8 https://doi.org/10.1007/s10973-015-4623-z https://doi.org/10.1002/jssc.201400176 https://doi.org/10.1063/5.0018424 synthesis and analgesic activity evaluation of derivatives of 2-[(1,4-dioxo-1-amino-4-arylbutyl-2-en-2-yl)amino]-4,5,6,7-tetrahydrobenzo[b]thiophene-3-carboxylic acid chimica techno acta article published by ural federal university 2021, vol. 8(4), № 20218404 eissn 2411-1414; chimicatechnoacta.ru doi: 10.15826/chimtech.2021.8.4.04 1 of 5 synthesis and analgesic activity evaluation of derivatives of 2-[(1,4-dioxo-1-amino-4-arylbutyl-2-en-2-yl)amino]-4,5,6,7tetrahydrobenzo[b]thiophene-3-carboxylic acid alena i. siutkina ab , ramiz r. makhmudov ac, daria a. shipilovskikh d a: perm state university, 614068 bukireva st., 15, perm, russia b: perm state pharmaceutical academy, 614990 ekaterininskaya st., 101, perm, russia c: federal scientific center for medical and preventive health risk management technologies, 614045 monastyrskaya st., 82, perm, russia d: perm national research polytechnic university, 614077 komsomolsky prospekt, 29, perm, russia * corresponding author: syutkina.alyona@yandex.ru this article belongs to the mosm2021 special issue. © 2021, the authors. this article is published in open access form under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). abstract the synthesis of new derivatives of 2-[(1,4-dioxo-1-amino-4arylbutyl-2-en-2-yl)amino]-4,5,6,7-tetrahydrobenzo[b]thiophene-3carboxylic acid is described. starting 2-{[5-aryl-2-oxofuran-3(2h)ylidene]amino}thiophene-3-carboxylic acids were obtained by intramolecular cyclisation of substituted 4-aryl-4-oxo-2thienylaminobut-2-enoic acids in acetic anhydride. new derivatives of 2-[(1,4-dioxo-1-amino-4-arylbutyl-2-en-2-yl)amino]-4,5,6,7tetrahydrobenzo[b]thiophene-3-carboxylic acids were obtained via decyclization reaction of 2-{[5-aryl-2-oxofuran-3(2h)ylidene]amino}thiophene-3-carboxylic acids. the structure of the compounds obtained was confirmed by the 1h and 13c nmr spectroscopy, ir spectrometry and elemental analysis methods. analgesic activity of new compounds has been studied by the “hot plate” method on outbred white mice of both sexes with intraperitoneal injection. it was found that derivatives of 2-[(1,4-dioxo-1-amino-4-arylbutyl-2en-2-yl)amino]-4,5,6,7-tetrahydrobenzo[b]thiophene-3-carboxylic acid possess analgesic effect exceeding the effect of the comparison drug metamizole. keywords analgesic activity gewald reaction 2,4-dioxobutanoic acids 3-(thiophen-2-yl)iminofuran 2(3h)-one received: 01.11.2021 revised: 19.11.2021 accepted: 19.11.2021 available online: 22.11.2021 1. introduction the gewald aminothiophene fragment is a promising pharmacophore group, since it was found in both natural and synthetic physiologically active compounds [1–6]. the synthesis of substituted gewald aminothiophenes can be carried out using the gewald reaction [7–9]. in turn, 3imino(hydrazono)-3h-furan-2-ones have high reactivity, leading to the production of compounds of various structures [10–17]. decyclization reactions of 3-imino-3hfuran-2-ones lead to the production of 2,4-dioxobutanoic acid derivatives, for which antiviral [18–22], analgesic [23], anti-inflammatory [24], antimicrobial [25] activity was determined. it was previously shown that 3-imino(hydrazono)-3hfuran-2-ones can be decyclized under the action of aliphatic, aromatic, and heterocyclic amines to form amides of 4aryl(tert-butyl)-4-oxo-2-amino(hydrazono)-2-eno acids [26, 27]. in this paper, synthesis and analgesic activity of new 2-[(1,4-dioxo-1-amino-4-arylbutyl-2-en-2-yl)amino]4,5,6,7-tetrahydrobenzo[b]thiophene-3-carboxylic acid derivatives is discussed. 2. experimental ir spectra were recorded on an fsm-1202 instrument from liquid paraffin. 1h and 13c nmr spectra were recorded on a bruker avance iii instrument (400 and 100 mhz) from cdcl3 and dmso-d6 solutions relative to residual signals of the non-deuterated solvent. elemental analysis was performed on a leco chns-932 instrument. reaction progress and individuality of obtained compounds was monitored by tlc on sorbfil plates, eluting with a diethyl ether–benzene–acetone system (10:9:1); detecting in uv light and iodine vapor. melting points were determined on an smp40 instrument. http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2021.8.4.04 http://creativecommons.org/licenses/by/4.0/ https://orcid.org/0000-0001-6702-7716 chimica techno acta 2021, vol. 8(4), № 20218404 article 2 of 5 starting substituted 4-aryl-4-oxo-2-thienylaminobut-2enoic acids 1a,b and substituted 3-thienylimino-3h-furan2-ones 2a,b were obtained according to the procedure described in [28–30]. all data correspond to the previously obtained ones. 2.1. general procedure for the synthesis of nsubstituted amides of 4-aryl-4-oxo-2-[(3-thiophen-2yl)amino]-but-2-enoic acids 3a–e a mixture of 0.001 mol of compound 2a–e and 0.001 mol of the corresponding amine in anhydrous toluene (20 ml) was stirred at 50 °с for 2 h. after cooling, the precipitate was filtered off and recrystallized. 2.2. ethyl 2-((1-((4-methylpyrimidin-2-yl)amino)-1,4dioxo-4-phenylbut-2-en-2-yl)amino)-4,5,6,7tetrahydrobenzo[b]thiophene-3-carboxylate (3a) yield 0.36 g (74%), orange crystals, mp 172–173 °с (isopropanol). ir spectrum, ν, cm–1: 1671 (conh), 1738, (cooet), 3186, 3351 (nh). 1н nmr spectrum (cdcl3), , ppm: 1.31 t (3h, ch3ch2o, jнн = 7.2 hz), 1.76 m (4h, 2ch2), 2.40 s (3h, ch3), 2.57 m (2h, ch2), 2.80 m (2h, ch2), 4.37 q (2h, ch3ch2o, jнн = 7.1 hz), 6.19 s (1н, с=ch), 6.83 m (2h, harom), 7.22 m (3h, harom), 7.45 m (2h, harom), 8.43 s (1н, nн), 10.21 s (1н, nh). found, %: с 63.60; н 5.37; n 11.43; s 6.52. c26h26n4o4s. calculated, %: с 63.66; н 5.34; n 11.42; s 6.54. 2.3. ethyl 2-((1-((5-bromopyridin-2-yl)amino)-1,4dioxo-4-phenylbut-2-en-2-yl)amino)-4,5,6,7tetrahydrobenzo[b]thiophene-3-carboxylate (3b) yield 0.40 g (73%), orange crystals, mp 188–189 °с (isopropanol). ir spectrum, ν, cm–1: 1667 (conh), 1708, (cooet), 3323, 3416 (nh). 1н nmr spectrum (cdcl3), , ppm: 1.40 t (3h, ch3ch2o, jнн = 6.9 hz), 1.76 m (4h, 2ch2), 2.58 m (2h, ch2), 2.77 m (2h, ch2), 4.36 q (2h, ch3ch2o, jнн = 6.9 hz), 6.17 s (1н, с=ch), 6.71 s (1н, nн), 7.27 m (3h, harom), 7.38 m (2h, harom), 7.83 m (1h, harom), 8.13 m (1h, harom), 8.37 m (1h, harom), 10.49 s (1н, nh). found, %: с 56.37; н 4.33; n 7.56; s 5.74. c26h24brn3o4s. calculated, %: с 56.32; н 4.36; n 7.58; s 5.78. 2.4. ethyl 2-((1,4-dioxo-4-phenyl-1-(thiazol-2ylamino)but-2-en-2-yl)amino)-4,5,6,7tetrahydrobenzo[b]thiophene-3-carboxylate (3c) yield 0.41 g (85%), yellow crystals, mp 200–201 °с (isopropanol). ir spectrum, ν, cm–1: 1663 (conh), 1718, (cooet), 3234, 3439 (nh). 1н nmr spectrum (dmso-d6), , ppm: 1.38 t (3h, ch3ch2o, jнн = 7.2 hz), 1.74 m (4h, 2ch2), 2.63 m (2h, ch2), 2.75 m (2h, ch2), 4.35 q (2h, ch3ch2o, jнн = j 7.2 hz), 6.25 s (1н, с=ch), 7.38 m (5h, harom), 7.62 m (2h, harom), 8.12 s (1н, nh), 10.44 s (1н, nh). found, %: с 59.83; н 4.85; n 8.72; s 13.36. c24h23n3o4s2. calculated, %: с 59.86; н 4.81; n 8.73; s 13.31. 2.5. 2-((1-((4-bromophenyl)amino)-4-(4methoxyphenyl)-1,4-dioxobut-2-en-2-yl)amino)4,5,6,7-tetrahydrobenzo[b]thiophene-3-carboxamide (3d) yield 0.47 g (84%), orange crystals, mp 193–195 °с (isopropanol). ir spectrum, ν, cm–1: 1666, 1686 (conh, conh2), 3294 (nh, nh2). 1н nmr spectrum (dmso-d6), , ppm: 1.69 m (4н, сн2), m 2.50 (2h, ch2), 2.58 m (2h, ch2), 3.84 s (3h, och3), 6.37 s (1н, с=ch), 7.04 m (2h, harom), 7.47 m (2h, nh2; 4h, harom), 8.02 m (2h, harom), 11.17 s (1н, nh), 12.67 s (1н, nh). found, %: с 56.30, н 4.35, n 7.53, s 5.77. c26h24brn3o4s. calculated, %: с 56.32, н 4.36, n 7.58, s 5.78. 2.6. 2-((4-(4-methoxyphenyl)-1-morpholino-1,4dioxobut-2-en-2-yl)amino)-4,5,6,7tetrahydrobenzo[b]thiophene-3-carboxamide (3e) yield 0.41 g (87%), yellow crystals, mp 146–148 °с (isopropanol). ir spectrum, ν, cm–1: 1658 (con, conh2), 3169, 3344 (nh, nh2). 1н nmr spectrum (dmso-d6), , ppm: 1.73 m (4н, 2сн2), 2.62 m (4h, 2ch2), 3.48 m (8h, 4ch2), 3.83 s (3h, och3), 6.14 s (1н, с=ch), 7.00 m (2h, harom), 7.40 br s (1h, nh2), 7.49 br s (1h, nh2), 7.97 m (2h, harom), 12.94 s (1н, nh). found, %: с 61.35, н 5.82, n 8.96, s 6.80. c24h27n3o5s. calculated, %: с 61.39, н 5.80, n 8.95, s 6.83. evaluation of analgesic activity was carried out in the perm state national research university, the research laboratory of biologically active substances. analgesic activity was determined on outbred white mice of both sexes weighing 18–22 g using the “hot plate” method [31]. the studied compounds were administered intraperitoneally in the form of a suspension in a 2% starch solution at a dose of 50 mg/kg 30 min before the animals were placed on a metal plate heated to 53.5 °c [32]. studies were performed 30, 60, 90, 120 min after administration of the compound. the indicator of the change in pain sensitivity was the length of time the animals stay on the hot plate until a defensive pain reflex occurs — licking the hind legs or trying to tear off all four paws from the surface of the plate. the time of onset of this reflex from the beginning of the placement of the animal on the plate was measured in seconds (latent period). the maximum duration of the latent period is the interval of 40 s. in the experiment we used animals with the initial time of the onset of the defensive reflex of no more than 15 s. each compound was tested on 6 animals. the results were evaluated by increasing the time of the onset of the defensive reflex compared with the initial data. the control group of animals was injected with 2% starch mucus. metamizole sodium (farmkhimkomplekt llc) at a dose of 93 mg/kg (ed50) was used as a comparison compound. statistical processing of experimental data was carried out using student's confidence criteria. the effect was chimica techno acta 2021, vol. 8(4), № 20218404 article 3 of 5 considered significant at p<0.05 [33]. the studies were carried out in accordance with all applicable international, national and institutional guidelines for the care and use of animals. 3. results and discussion starting furanones 2a,b were obtained by known literature method via intramolecular cyclization of 4-aryl-4-oxo-2tienylaminobut-2-enoic acids 1a,b in acetic anhydride. the reaction of 3-thienylimino-3h-furan-2-ones 2a,b with alkyl-, aryl-, hetarylamines in inert aprotic solvent proceeded with the formation of n-substituted amides of but-2enic acids 3a-e (scheme 1). as a result, it was found that the attack of the amino group was directed at the carbon atom of the lactone carbonyl moiety of compounds 2a,b and led to the products of the furanone cycle decyclization. the ester and amide groups under the conditions of the reaction did not participate in interaction with amines, which does not contradict the literature data. the mechanism of the decyclization reaction of 5-aryl2,3-dihydro-2,3-furandiones under the action of nucleophilic reagents was published based on the detailed largescale study of kinetic data [34–36] as well as quantum chemical calculations [37]. assuming the similarity of these structures with the iminofuranones discussed in the current paper, we can assume the validity of this mechanism for the transformations 3-thienylimino-3h-furan-2ones 2a,b under the action of amines as nucleophiles (nuh) described here (scheme 2). if the solvent cannot be a donor or acceptor of an electron pair (aprotic nonpolar or weakly polar solvents), a non-catalytic reaction occurs. the use of a nonpolar solvent contributes to the displacement of the equilibrium from the transition state ts1 to the intermediate i that leads to the limiting stage of the process with the formation of the transition state ts2. compounds 3a-e are crystalline substances of orange or yellow color, obtained with yields up to 87%. we have studied the 1h nmr spectra of compounds 3a,b in dmso-d6 and 3c-e cdcl3. it was established that compounds 3a-e are characterized by a proton singlet of the nh group involved in a strong intramolecular hydrogen bond at 10.44–12.94 ppm, proton signals of the nhco group at 6.71, 8.12–11.17 ppm and a proton singlet of the ch group at 6.14–6.37 ppm. some of the compounds obtained were examined for analgesic activity. it is shown in table 1 that all the studied compounds have a pronounced analgesic effect, surpassing the effect of the comparison drug metamizole. table 1 analgesic activity of amides 3a-c compound dosage, mg/kg the latent period of the defensive reflex (120 min), s 3a 50 21.20±1.24 3b 50 22.40±1.83 3c 50 21.00±1.46 metamizole 93 (ed50) 16.60±1.00 control – 10.30±0.60 4. conclusions new derivatives of 2-[(1,4-dioxo-1-amino-4-arylbutyl-2en-2-yl)amino]-4,5,6,7-tetrahydrobenzo[b]thiophene-3carboxylic acid were obtained with 73-87% yields by the decyclization reaction of 2-{[5-aryl-2-oxofuran-3(2h)ylidene]amino}thiophene-3-carboxylic acids under the action of aliphatic, aromatic and heterocyclic amines. it was found that the obtained compounds exhibited significant analgesic activity, reliably exceeding the effect of a referral drug. scheme 1 the reaction of 3-thienylimino-3h-furan-2-ones 2a,b with alkyl-, aryl-, hetarylamines in inert aprotic solvent chimica techno acta 2021, vol. 8(4), № 20218404 article 4 of 5 scheme 2 the transformations 3-thienylimino-3h-furan-2-ones 2a,b under the action of amines as nucleophiles (nuh) acknowledgements the research was supported by the perm research and education centre for rational use of subsoil, 2021. references 1. thomas j, jecic a,vanstreels e, van berckelaer l, romagnoli r, dehaen w, liekens s, balzarini j. pronounced antiproliferative 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https://doi.org/10.1007/s11172-014-0722-4 https://doi.org/10.1134/s1070428014020286v https://doi.org/10.1021/cb200439z https://doi.org/10.1021/ci300039a https://doi.org/10.2174/092986712798918833 https://doi.org/10.1371/journal.ppat.1002831 https://doi.org/10.1016/j.bmcl.2013.09.009 https://doi.org/10.1063/5.0018515 https://doi.org/10.1134/s107036321912003x https://doi.org/10.1063/5.0018494 https://doi.org/10.1134/s1070363219070065 https://doi.org/10.1134/s1070428017010274 https://doi.org/10.1007/s10593-009-0334-3 https://doi.org/10.1007/s11094-013-0960-z https://doi.org/10.1063/5.0018486 impact of herbal supplements nowadays: an overview chimica techno acta focus review published by ural federal university 2022, vol. 9(2), no. 202292s4 eissn 2411-1414; chimicatechnoacta.ru doi: 10.15826/chimtech.2022.9.2.s4 1 of 7 impact of herbal supplements nowadays: an overview l.i. ramirez *, o.n. kanwugu * , m.n. ivantsova * institute of chemical engineering, ural federal university, ekaterinburg 620002, russia * corresponding author: liz170496@gmail.com, nabayire@gmail.com, mivantsova@mail.ru this paper belongs to the mosm2021 special issue. © 2021, the authors. this article is published open access under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). abstract at present, people around the world are looking for more natural alternatives for treating all kinds of health conditions as well as improving the general wellbeing. as such, the consumption of herbal supplements has increased globally, generating billions in revenue. the use of these herbal products is firmly rooted in the traditional use of medicinal plants for disease prevention and treatment, practiced in several cultures. although herbal products are recognized by the who as an essential component of the healthcare system, there have been increasing concerns regarding their quality and safety. generally, herbal products are not strictly regulated as they are largely categorized under dietary supplements, thus escaping the rigorous scrutiny meted out to pharmaceuticals. notwithstanding that many consumers generally perceive herbal products as benign and inherently safe, several reports have shown that herbal products can induce mild to acute adverse effects of clinical significance. moreover, some herbal products on the market have been reported to be contaminated with microorganisms, environmental toxins, and adulterants. furthermore, evidence regarding the efficacy of herbal supplements is extremely discrepant. keywords herbal supplements drug herbal interactions herbal medicine traditional medicine phytomedicine received: 02.11.21 revised: 11.04.22 accepted: 20.04.22 available online: 22.04.22 key findings ● herbal medicine remains an integral health resource globally, patronized in developed as well as developing countries. ● regulation of herbal products has intensified over the years, but their classification is still inconsistent. ● herbal products can cause adverse effects particularly if they are contaminated and should be taken with caution. 1. introduction with a resurgence of interest in a change in lifestyle trend towards a “return to nature”, complementary and alternative medicine (cam) has grown steadily over the past decades to become a part of everyday life for the general population aimed at maintaining health and preventing diseases. the world health organization (who) recognizes cam as an integral but often undervalued health resource, particularly in the prevention and management of chronic lifestyle-related diseases that require lifelong pharmaceutical medication [1]. dietary supplements including botanicals and nutritional products are probably the most prevalent and commonly used cam. the use of herbal supplements, also called herbal/botanical products or phytomedicines, dates back millennia. their usage is grounded in the traditional use of medicinal plants to prevent, alleviate, or cure various ailment in several cultures such as traditional chinese medicine in china, ayurvedic medicine in india, kampo medicine in japan, aboriginal medicine in australia, terongoā in new zealand, unani medicine in muslim culture in south asia and modern-day central asia, african and native american ethnomedicines [2, 3]. medicinal plants are endowed with a rich ensemble of biologically and pharmahttp://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2022.9.2.s4 https://orcid.org/0000-0003-3887-1058 https://orcid.org/0000-0002-2389-0523 mailto:liz170496@gmail.com mailto:nabayire@gmail.com mailto:mivantsova@mail.ru http://creativecommons.org/licenses/by/4.0/ https://crossmark.crossref.org/dialog/?doi=https://doi.org/10.15826/chimtech.2022.9.2.s4&domain=pdf&date_stamp=2022-4-22 chimica techno acta 2022, vol. 9(2), no. 202292s4 focus review 2 of 7 cologically active compounds, which are responsible for their renowned health benefits. in fact, a large part of existing prescription medications is derived from plants used in traditional medicine, with yet another significant portion being synthetic analogs of phytocompounds [3]. although there is no internationally recognized definition, herbal supplements are generally products made from botanical elements and in some cases algae or fungi intended for internal use to enhance health [4]. the rising cost of conventional pharmaceuticals as well the increasing awareness of consumers of their unwanted side effects, in part, drives the growing interests in herbal product. in addition, herbal products are perceived by many to be inherently safe as they are made from natural ingredients; moreover, they are readily available, cheap and culturally acceptable [5]. at present, there are about 30000 herbal products, if not more, available on the global market, representing the second largest dietary supplement segment after vitamins and minerals [6]. they are available as capsules, tablets, elixirs, teas, liquid extracts, oils as well as powdered and chopped “free-standing” dried material [7]. however, unlike vitamins and minerals, the evidence for the effectiveness of these plant-based products is extremely discrepant and in most cases is not supported by hard data [8]. in addition, compared to conventional drugs as well as vitamins and minerals, the regulatory requirements of herbal products are less stringent. depending on the legislation of the country they are being marketed in, herbal products are presented under several description, including traditional medicines, herbal medicines, natural health products, dietary supplements, plant food supplements, nutraceuticals, food supplements, etc., contributing to the poor regulation of these products on the global market [2]. as the uses of herbal products are increasingly becoming prevalent around the world, several issues are raised concerning their quality, safety and efficacy. the preparation of these products is not standardized, and they may vary in consistency, constituents, quality and efficacy between batches and among manufacturers. besides, its known that the composition as well as the concentration of phytochemicals in the same plant species is greatly influenced by the cultivation conditions, geographical location, part and age of plant [3]. beyond these, while most of the phytocompounds in medical plants used in herbal products have therapeutic properties, some are inherently toxic, exhibiting hepatotoxic and nephrotoxic effects among others. some herbal products may as well be contaminated with environmental toxins and microorganisms. in addition, some have been found to be adulterated with banned ingredients [9]. thus, notwithstanding that these products are generally promoted as natural and assumed by many consumers to be always safe, several reports have shown that herbal products can induce mild to clinically significant adverse effects including gastrointestinal discomfort, allergic reactions, nausea, vomiting, diarrhea, chronic toxicity and, most importantly, interaction with drugs [10]. it was reported that about quarter of patients use herbal products and conventional drugs simultaneously [11]. like prescription medications, herbal products contain chemically and biologically active substances; thus, there is a possibility of herb-drug interaction when they are present concurrently in the body. these interactions affect the pharmacological and toxicological effects of these substances and could be potentially deleterious [6]. this article discusses the usage of herbal supplements, their regulation as well as the associated safety issues. 2. global usage and market for thousands of years, several cultures have developed and used herbal medicine for the maintenance of health and in prevention and treatment of diseases, as part of the traditional medical systems, particularly in eastern countries and the african continent [2]. however, the western world, until recently, has used herbal products only for the treatment of minor medical symptoms like cold and stomach upset [12]. in recent times, the general increase in wealth and improvements in living standards have resulted in a greater investment in health care and healthcare products [13]. with hopes of preventing chronic diseases, particularly those related to lifestyle, the use of herbal products is, nowadays, globally widespread but recognized in varying degrees in different countries. in asia and africa, for instance, traditional medicine, particularly herbal medicine, generally coexists with modern medicine in the healthcare sector as a complementary or alternative therapy; however, there is tension and collision between these two in europe and particularly the us [2, 14]. all the same, complementary/alternative therapies are progressively being integrated into the healthcare system of the west, as the number of patients demanding herbal therapy keeps growing [15]. it is estimated that about 80% of the global population and as much as 95% of the population in developing countries to some extent rely on herbal medicine for their primary healthcare needs [3]. in the us, it is estimated that about 50% of the population use herbal products [16]. on the other hand, more than two thirds of the population in canada and germany have used herbal medicine at least once [3]. likewise, in other developed countries such as france, australia, and belgium at least one-third of the population is estimated to have used cam at least once for healthcare [10], with herbal medicine likely constituting a core of it. in china, herbal medicines are projected to account for between 30% to as much as 50% of total drug consumption. similarly, about 30% of malaysians use traditional herbal medicine for their health needs [9]. in most african countries like ghana, nigeria, mali and zambia, however, herbal medicine is the major treatment option at homes, representing up to 60% or perhaps more of home remedies [3]. in the western world where herbal medicine is used not as a primary therapy but more of a chimica techno acta 2022, vol. 9(2), no. 202292s4 focus review 3 of 7 health-conscious lifestyle habit, its use is prevalent among females, the young and the middle aged, the affluent and the erudite [13, 15]. unsurprisingly, there is a rise in herbal products and cam usage among children as a result of increased parental awareness of cam therapies and a conscious desire by parents to limit the amount of drugs consumed by children [13]. the use of herbal products is also common among cancer patients and people living with hiv/aids; it is reported that 32–70% of cancer patients and 75% of hiv/aids patients use herbal formulations [3, 13]. the size of international market for herbal products and dietary supplements as a whole is massive and continues to increase, with a current global market value of roughly over us$ 60 billion [16]. as far back as 2000 a bbc survey reported that uk users spend on average £13.6 per month on cam including, but not limited to, herbal products, resulting in a projected annual expenditure of £1.6 billion nationwide [17]. between 2007 to 2009 the market of complementary medicines (such as herbal products, essential oils etc.) is estimated to have grown by 18% in the uk [4]. as of 1997, the sales of herbal products in france and germany amounted to us$ 1.1 billion and us$ 1.8 billion respectively [4]; it thus reasonable to project that the current market value of herbal products in these countries exceeds the aforementioned values. in the us, consumers spent an estimated us$ 8 billion in 2018 and 9.6 billion in 2019 on herbal supplements [18]. similarly, in china, trade volume of herbal medicine products was pegged at around us$ 6.2 billion in 2019, a significant increase from that of 2018 [19]. in malaysia, the market value of the herbal industry is estimated to grow by 8–15% annually and was projected to hit myr 32 billion in 2020 [9]. some of the commonly used herbal supplements are presented in table 1. table 1 commonly used herbal products. common name (scientific name) applications references aloe vera (aloe vera) used topically for burns, psoriasis and osteoarthritis. it also used in the oral form for digestive issues such as gastritis or constipation. [20] black cohosh (actaea racemosa) used to treat hot flashes, night sweats, vaginal dryness, menopausal symptoms, dysmenorrhea and vaginitis. [21, 22] chamomile (matricaria recutita) used topically for skin conditions. also used to treat anxiety, stomach upset, gas and diarrhea. [23] echinacea (echinacea purpurea) it is colds, bronchitis, flu, and respiratory infections. additionally, it is used as an immune booster. [21] flaxseed (linum usitatissimum) it has long been used for cardiovascular protection and as a laxative. it is also used for managing hyperlipidemia, atherosclerosis, diabetes mellitus, obesity, menopausal symptoms and premature labor. it is a good source of fiber and omega-3s. [23] gingko (ginkgo biloba) used to treat memory and cognitive problems particularly those associated with aging. it is also an effective adjuvant therapy for schizophrenia. additionally, it is used in asthma, autism spectrum disorder, chronic obstructive pulmonary disease and depression. [21, 23] peppermint oil (mentha piperita) used to treat digestion problems such as nausea, indigestion, stomach problems and bowel conditions. [24] soy (glycine max) used to treat menopausal symptoms, memory problems and high cholesterol levels. [25] st. john’s wort (hypericum perforatum) used to treat depression and anxiety. it is also reported to be effective in the treatment of menopausal symptoms, somatoform disorders, attention-deficit hyperactivity disorder, (adhd), angioplasty, glioma, migraine headaches, obsessive-compulsive disorder, polycystic ovary syndrome, and premenstrual syndrome. [23] tea tree oil used topically to treat several conditions including, acne, athlete's foot, nail fungus, wounds, infections, lice, oral yeast infection (thrush), cold sores and dandruff. [26] evening primrose (oenothera biennis) it is used to treat adhd, asthma, atopic dermatitis, chronic fatigue syndrome, dry eye syndrome, dyslexia, hyperlipidemia, obesity, premenstrual syndrome, diabetes mellitus, rheumatoid arthritis, and ulcerative colitis. [23] feverfew (tanacetum parthenium) it is commonly used for treating migraine headaches and menstrual cramps. it has also been used to treat allergies, arthritis, psoriasis, fever, headache, tinnitus, vertigo, menstrual irregularities. [23] garlic (allium sativum) garlic is generally used for cardiovascular conditions, including high cholesterol and triglyceride levels associated with the risk of atherosclerosis. [27] ginseng (panax quinquefolius l. panax ginseng, and panax japonicus) used as a general tonic to increase overall body tone. it is considered helpful in elevating energy levels, enhancing physical and mental performance as well as improving resistance to stress. it also used to treat erectile dysfunction, and strengthen the immune response. [21, 22] goldenseal (hydrastis canadensis) it is famous for its healing and antiseptic properties and used commonly for colds and flu. it is also popular for soothing the nose lining when it is inflamed or sore. in addition, treat skin and eye infections and gastrointestinal irritation. [21, 22] hawthorn (crataegus monogyna) it is used mostly for managing heart-related conditions such as treatment of angina, atherosclerosis, heart failure, and high blood pressure. [21] saw palmetto (serenoa repens) it is currently being used to treat enlarged prostate. it has also been used to treat genitourinary symptoms, relieve inflamed mucous membranes, increase testicular function and increase breast size. [21] chimica techno acta 2022, vol. 9(2), no. 202292s4 focus review 4 of 7 3. regulation of herbal products in general, the classification and, consequently, regulation and legislation regarding herbal products varies among countries, even among those within the same political and economic region such as the eu [16, 28]. they are generally classified as either dietary supplements or over-thecounter drugs; nevertheless, their regulations are largely different from those governing pharmaceutical drugs – they are less stringent [9, 23]. compared to germany, japan and china, herbal supplements are less strictly regulated in the us. the fda considers herbal supplements as foods and not drugs; for this reason, they are not subject to the same regulations and standards of testing, manufacturing and labeling as conventional drugs. according to the fda, “dietary supplements are not intended to diagnose, treat, cure, or prevent disease” [23]. as a result manufacturers of herbal products are currently at liberty to make structurefunction claims that explain how the product can influence different actions in the body without pre-approval of the fda. the fda, however, prohibits disease treatment claims by herbal products since they have not been subjected to rigorous clinical trials. unlike pharmaceuticals, new herbal products do not require premarket approval by the fda before they hit the market; they only need to conform with the dietary supplement health education act of 1994 [16, 23]. although, currently, the fda mandates manufacturers to adhere to the good manufacturing practices (gmps) established in 2007, evaluation of product safety and accurate labeling before products are sold on the market remain the responsible of the manufacturers. the fda only has the authority to evaluate and recall these products in case of violations after they appear on the market [23]. under the umbrella of the eu, herbal products considered as medicine fall with in the jurisdiction of the european medicines agency and are governed according to the european guideline 65/65/eec. however, with regards to other herbal products except for spices and flavouring agents, there is no unified eu legislation and thus herbal products are largely regulated according to national laws. in general, at the national level, products that makehealth/therapeutic claims or are deemed to have therapeutic activity by the regulatory body are classified as medicine and, as such, full registration, including the information about quality, safety and efficacy, is required, according to national legislations [28, 29]. this notwithstanding, legislation and regulation of herbals vary greatly from country to country, with each having its own list of exemptions. some countries, such as germany and the uk, make extra provisions to recognizing and regulate other herbals, which do not fit the above category as dietary supplements; countries like france and ireland, on the other hand, treat all herbals equally as medicinal products [28]. as a result of this, some herbals are marketed as dietary supplement in some eu-member countries and as drugs in others [29]. 4. quality and safety concerns in general, it is expected that any pharmacologically active agent has the potential to elicit adverse reactions due to the functional or structural connection with or because of the similarity in sensitivity to off-target processes [30]. given that herbal products are not strictly regulated by the authorities and scientific information on their dosage and toxicity is scanty, usage of herbals is associated with an increased risk of side effects. in fact, it has been reported in medical literature that commonly used herbals such as ginkgo, garlic and st. john’s wort can cause mild to severe adverse effects [23]. the uppsala monitoring centre of the who reported that over a period of 20 years (1968–1997) a total of 7874 cases of adverse health effects involving herbal medicines were recorded in 55 countries, with anaphylactic reactions being the major recorded adverse effect. however, 21 deaths were reported to be associated with these adverse effects during this period. the other reported adverse health effects associated with herbal medicines included face oedema, bronchospasm, circulatory failure, hypertension and intestinal obstruction. most of the reported adverse effects were associated with opium alkaloids total, evening primrose oil, peppermint oil, psyllium hydrophilic mucilloid and senna [31]. also, in a 5year toxicity study of traditional remedies and food supplements, shaw et al. reported 12 confirmed cases of adverse effects, 10 of which were related to chinese and indian herbal products [32]. furthermore, out of 491 patients who admitted to taking at least one herbal component in a 5-month survey at an urban university general hospital in italy, 9.6% reported adverse effects related to gastrointestinal (associated with dandelion, propolis, and fennel), cardiovascular (associated with liquorice, ginseng, and green tea), dermatological (in connection with propolis, thyme, arnica, and passion-flower) as well as neurological problems (linked with guarana and liquorice) [33]. these adverse effect arising from the use of herbal products are attributed to two factors: intrinsic and extrinsic toxicities [10]. herbal products generally consist of a plethora of phytochemicals, responsible for their often-remarked multi-target effects, any of which could interfere with off-target pathways leading to undesirable effects [4, 6]. also, metabolism of these compounds in herbals could lead to long-term organ (i.e. liver, kidney) damage. these side effects are the results of the inherent components of the herbals, which can be exacerbated by overdosing, considering that there is generally no clinically-backed evidence for the dose of these herbal products [10]. besides, extrinsic factors particularly related to product quality such as misidentification of starting chimica techno acta 2022, vol. 9(2), no. 202292s4 focus review 5 of 7 herbal materials, contamination and adulteration could lead to major adverse health effects [34]. it is interesting to note that most of the severe adverse effects related to the use of herbals have to do with the product quality [30]. although manufacturers are expected to abide by the gmp, poor handling and storage as well as unhygienic production processes result in herbal products being contaminated with microorganisms, particularly fungi and bacteria, as well as mycotoxins [10]. the issue of microbial contamination is an age-old problem of the food industry, and herbal preparations are no exception. for instance, hong kong's department of health at one point had to recall 17 proprietary chinese medicines because they had been found to contain total bacterial count more than the maximum permitted limit, while in croatia, fungal contamination was found to be high in the samples of medicinal plant materials and herbal teas [4]. also, since herbal materials are cultivated on land, they can be contaminated with pesticides and heavy metals. several studies have shown that a considerable number of commercially available herbal products are contaminated with heavy metals of special public health concern such as lead, arsenic and mercury beyond permissible recommended limits [4]. additionally, pesticide residues have been reported in medicinal plants [35]. adulteration of herbal products is likewise a serious quality and safety concern globally. indeed, there have been reports of adulteration in almost every country. in a recent review by ichim et al., the authors observed that over a quarter of 2386 commercial herbal products sold in 37 countries were reported to be adulterated [36]. the adulterants in these cases included fillers, banned substances, and substituted species, with some products completely lacking labeled botanical ingredients. many herbal products have been reported be adulterated with active pharmaceuticals such as corticosteroids, non-steroidal anti-inflammatory drugs, analgesics, benzodiazepines, and many others [30]. in taiwan, for instance, it was reported that around 23.7% of commercially sold traditional chinese medicines are adulterated with drugs [10]. because the adulterants are always not declared, there is a high possibility of overdose. considering that herbal products are often used in conjunction with conventional prescription medicines, one of the major clinically significant safety concerns that has been in the limelight is the issue of potential adverse drug-herbal interaction. the evidence to this effect is, however, still limited, with majority of information coming from only the case reports. this notwithstanding, possible drug-herbal interactions based on these clinical reports and theoretical knowledge of the interaction between specific classes of compounds are available (figure 1). figure 1 the drug-herbal interactions. 5. pharmacokinetic and pharmacodynamic drug-herbal interactions herb-drug interactions may manifest in either pharmacodynamic or pharmacokinetic manner. pharmacodynamic interactions, in general, occur less frequently and involve direct pharmacologic actions of the interacting agents that are unrelated to changes in blood concentrations of the herb or drug. risk of a pharmacodynamics interaction occurs when an herbal supplement has a direct effect on the mechanism of action of a co-administered drug by manipulating molecular targets involved in the physiological responses of the drug. this may antagonize or exacerbate the drug's clinical effects without changing its concentration. in most cases, a change in drug dosage does not counter a pharmacodynamics herb-drug interaction [6, 10, 37]. clinically important herb-drug interactions typically manifest as pharmacokinetic interactions, which affect both the drug's concentration in the blood and the pharmacologic action. this type of interaction involves movement of the drug through the body from absorption to excretion [23]. risk of a pharmacokinetic interaction occurs when the herbal supplement shares the same mechanism of absorption, distribution, metabolism, or excretion as a co-administered drug [38]. competition between the herbal supplement and the drug for a shared adme mechanism may result in a change in the drug's concentration at the site of action [39]. in many cases, pharmacokinetic interactions can be safely countered by adjusting the drug's dosage. 6. conclusions herbal supplements are used extensively worldwide for the treatment and management of many diseases. many consumers consider them safe and good for them due to their natural ingredients; this, however, is not necessarily true. there have been several reported adverse effects of herbals, ranging from mild side effects to clinically significant conditions, resulting from acute toxicity or chronic/cumulative toxicity. these toxicities could be intrinsic, related to the inherent components of herbal or extrinsic, related to microbial/chemical contamination and adulterachimica techno acta 2022, vol. 9(2), no. 202292s4 focus review 6 of 7 tion. the most significant adverse effects usually occur due to pharmacokinetic/pharmacodynamic herbal-drug interactions. aside from this, herbs products do not go through the same rigorous control and testing as conventional medicines. thus, although herbal supplements are, at present, an essential part of our everyday life, care should be taken about their consumption. in addition, governing bodies should step-up the regulation of these products. supplementary materials no supplementary materials are available. funding this research had no external funding. acknowledgment none. author contributions conceptualization: l.i.r., o.n.k., m.n.i. data curation: m.n.i. formal analysis: l.i.r., o.n.k., m.n.i. funding acquisition: l.i.r., o.n.k., m.n.i. investigation: l.i.r. methodology: l.i.r., o.n.k., m.n.i. project administration: o.n.k., m.n.i. resources: l.i.r., o.n.k., m.n.i. software: l.i.r., o.n.k., m.n.i. supervision: m.n.i. validation: l.i.r., o.n.k., m.n.i. visualization: l.i.r., m.n.i. writing – original draft: l.i.r., o.n.k. writing – review & editing: o.n.k., m.n.i. conflict of interest the authors declare no conflict of interest. additional information authors’ ids: kanwugu, osman n., scopus id 57195573903; ivantsova, maria n., scopus id 6507519617. website of ural federal university: https://urfu.ru/en. references 1. who. who global report on traditional and complementary medicine 2019: world health organization; 2019. available from: https://www.who.int/publications-detailredirect/978924151536 2. zhang j, hu k, di l, wang p, liu z, zhang j, et al. traditional herbal medicine and nanomedicine: converging disciplines to improve therapeutic efficacy and human health. adv drug deliv rev. 2021;178:113964. doi:10.1016/j.addr.2021.113964 3. ahmad khan ms, 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https://scielo.isciii.es/scielo.php?script=sci_abstract&pid=s1137-66272006000300007&lng=es&nrm=iso https://scielo.isciii.es/scielo.php?script=sci_abstract&pid=s1137-66272006000300007&lng=es&nrm=iso peg4000 increases solubility and dissolution rate of vinpocetin in solid dispersion system chimica techno acta article published by ural federal university 2022, vol. 9(2), no. 202292s11 eissn 2411-1414; chimicatechnoacta.ru doi: 10.15826/chimtech.2022.9.2.s11 1 of 6 peg-4000 increases solubility and dissolution rate of vinpocetin in solid dispersion system yulia a. polkovnikova а* i̇d , tamara n. glizhova b i̇d , naira v. arutyunova b i̇d , natalya n. sokulskaya b i̇d a: faculty of pharmacy, voronezh state university, voronezh 394018, russia b: faculty of pharmacy, north-caucasus federal university, stavropol 355029, russia * corresponding author: polkovnikova@pharm.vsu.ru this paper belongs to the mosm2021 special issue. © 2022, the authors. this article is published open access under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). abstract in the present work, we determined the optimal ratio of vinpocetine and polyethylene glycol within a solid dispersion (1:2 or 1:5) according to the simulation results in the framework of molecular dynamics associated with the release of the reactant into aqueous medium. for the simulation of vinpocetine release from its alloy with polyethylene glycol, a technique of coarse-grained molecular dynamics in the force field of martini 2.2 was applied using the gromacs 2018 computer program. the results of the simulation demonstrated that at ph 6.8 polyethylene glycol facilitated vinpocetine solubilization and thus considerably enhanced its solubility in water. the data obtained show that the values of the energies of van der waals interaction between vinpocetine and the polymer are similar to those vinpocetine and water, both at a ratio of 1:2 and at a ratio of 1:5. keywords vinpocetin solid dispersion system peg4000 dissolution rate molecular dynamics received: 05.04.22 revised: 26.06.22 accepted: 27.06.22 available online: 30.06.22 1. introduction vinpocetine is a vasoactive and nootropic preparation that is a semisynthetic derivative of the common periwinkle plant alkaloid. vinpocetine is practically insoluble in water [1, 2]. it provides certain problems in provision of the bioavailability, particularly, the rate of attaining its therapeutic concentration in blood. recently, keeping in mind an increase of bioavailability of poorly soluble pharmaceutical preparations, solid dispersed systems have attracted more and more attention as a new basis for the elaboration of new rational drug formulations [3]. solid dispersions are bior multicomponent systems composed of the pharmaceutical substances and a carrier, representing a highly-dispersed solid phases of the pharmaceutical substances or alloys with a partial formation of the complexes of variable composition with a carrier material [4–6]. fabrication of the solid dispersions is considered as one of the most efficient ways for decreasing the particle sizes to the colloid and/or molecular level values. under the effect of environment, the soluble matrix of a polymer is dissolved and colloid particles or molecules of the pharmaceutical substances are immediately released into the solution medium, resulting in a rapid solubilization of the pharmaceutical substance [7–9]. solid dispersions are of a great importance when establishing peroral solid drug formulations with enhanced dissolution rate for the pharmaceutical substances that are weakly dissolved in water. thus the application of solid dispersions facilitates bioavailability under peroral medication [10–12].various soluble polymer matrices on the basis of polyvinylpyrrolidone, polyethylene glycols, methyl cellulose, as well as rather simple sub-stances, for example, urea, lactose, were proposed as carriers for soluble dispersions [13]. in the present work , we investigated the optimal ratio between vinpocetine and peg-4000 in the drug formulation (1:2 or 1:5) using the simulation employed for the molecular dynamics release of the reactant into aqueous medium. 2. experimental in order to simulate vinpocetine release from its alloy with polyethylene glycol, the method of coarse-grain molecular dynamics in a force field of martini 2.2 was applied using the gromacs 2018 software suite [14]. the method of coarse-grain molecular dynamics consists in representing the groups of atoms (consisting of 2–6 atoms) in the molehttp://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2022.9.2.s11 https://orcid.org/0000-0003-0123-9526 https://orcid.org/0000-0002-9477-7851 https://orcid.org/0000-0002-2111-4299 https://orcid.org/0000-0002-5269-6471 mailto:polkovnikova@pharm.vsu.ru http://creativecommons.org/licenses/by/4.0/ https://crossmark.crossref.org/dialog/?doi=https://doi.org/10.15826/chimtech.2022.9.2.s11&domain=pdf&date_stamp=2022-6-30 chimica techno acta 2022, vol. 9(2), no. 202292s11 article 2 of 6 cule by the particles of different types. in the same way, a group of molecules can be represented by a single particle. an assembly of the simulated systems, alloys of vinpocetine with polyethylene glycol, was performed with gromacs 2018 program. to simulate vinpocetine diffusion process using the coarse-grain molecular dynamics method, the model of the vinpocetine molecule was designed in the hyperchem program; after that geometry of the molecule was optimized by mm+ method [15, 16]. the vinpocetine molecule was nominally divided into the fragments corresponding to the cycles and functional groups. the compositions of the simulated systems are presented in table 1. table 1 the number of molecules of the components of the simulated alloys. substance vinpocetine-peg 1:2 vinpocetine-peg 1:5 vinpocetine cationpeg 1:2 vinpocetine cationpeg 1:5 vinpocetine 119 48 – – vinpocetine-cation – – 119 48 clion – – 119 48 peg-4000 21 21 21 21 water 10968 7228 11860 9484 3. results and discussion the modeled system included molecules of polyethylene glycol (figure 1) with a length of 90 monomers with the atomic mass of 3.978 kda, as well as molecules of vinpocetine base or its cations and clions (figure 2). during the simulation, the diffusion of peg-4000 into water was observed. when the ratio of vinpocetine and peg-4000 is 1:2, some of the vinpocetine molecules lose their bond with the polymer and combine into clusters (figure 3). the energies of van der waals interaction of vinpocetine with the polymer and with the solvent are stabilized after the 40th nanosecond of simulation. an increased proportion of vinpocetine molecules unbound with peg-4000 is due to the formation of clusters of substance molecules (figures 4, 5). figure 1 the structure of the polyethylene glycol molecule and its representation in the martini force field 2.2. sna–sн2–…–sн2– sna; sna – terminal oh group; sн2 is a polyethylene glycol monomer. figure 2 chemical structure and spatial structure of vinpocetine and vinpocetine cation and their representation in the martini 2.2 force field. figure 3 simulation of the molecular dynamics of the release of vinpocetine from an alloy with peg-4000 1:2 by weight into water. time is 0 ns (a), 40 ns (b), 100 ns (c). p5 vinpocetine vinpocetinecation chimica techno acta 2022, vol. 9(2), no. 202292s11 article 3 of 6 when modeling the release of vinpocetine from peg4000 into water at a substance-to-carrier ratio of 1:5, the formation of clusters is also observed, but their size is much smaller (figure 6). the energy of van der waals interaction of vinpocetine with peg-4000 at a ratio of 1:5 stabilizes faster – at the 20th nanosecond of simulation (figures 7, 8). this is due to the smaller number of vinpocetine molecules in the system. figure 4 van der waals interaction energy of vinpocetine with peg-4000 and solvent in terms of one molecule of vinpocetine at a ratio of vinpocetine and peg-4000 1:2 by weight. figure 5 estimation of the proportion of vinpocetine molecules not bound to peg-4000 in water at a ratio of vinpocetine to peg4000 1: 2 by weight. when simulating the release of vinpocetine from peg4000 in an acidic medium, no significant formation of clusters of substance molecules is observed, but a uniform distribution of vinpocetine molecules over the volume of the simulated system occurs (figure 9). -200 -180 -160 -140 -120 -100 -80 -60 -40 -20 0 0 20 40 60 80 100 v a n d e r w a a s in te ra ct io n e n e rg y, k j/ m o l ti me , ns van der waas inter action energy peg-4000vinpocetine, kj/mol figure 7 van der waals interaction energy of vinpocetine with peg-4000 and solvent in terms of one molecule of vinpocetine at a ratio of vinpocetine and peg-4000 1:5 by weight. figure 8 estimation of the proportion of vinpocetine molecules not bound to peg-4000 in water at a ratio of vinpocetine to peg4000 1:5 by weight. figure 6 simulation of the molecular dynamics of the release of vinpocetine from an alloy with polyethylene glycol-4000 1:5 by weight into water. time is 0 ns (a), 40 ns (b), 100 ns (c). chimica techno acta 2022, vol. 9(2), no. 202292s11 article 4 of 6 figure 9 modeling of the molecular dynamics of the release of vinpocetine from an alloy with peg-4000 1:2 by weight into water with ph 2.0. time is 0 ns (a), 40 ns (b), 100 ns (c). the energy of van der waals interaction of vinpocetine with peg-4000 when released in an acidic medium is stabilized after 40 ns of simulation at a ratio of 1:2 (figures 10, 11). figure 10 van der waals interaction energy of vinpocetine with peg4000 and with a solvent (water at ph 2.0) in terms of one molecule of vinpocetine at a ratio of vinpocetine and peg-4000 1:2 by weight. when the ratio of vinpocetine and peg-4000 is 1:5 in an acidic medium, vinpocetine is also evenly distributed in the volume of the modeled system without the formation of large clusters (figure 12). van der waals interaction energy between vinpocetine and peg-4000 stabilizes after 30 ns of simulation (figures 13, 14). based on the results of the computational experiments, the average values of the van der waals binding energies of vinpocetine with carriers and with the solvent, as well as the average fraction of vinpocetine molecules not bound to the carrier, were calculated (table 2). figure 11 estimation of the proportion of vinpocetine molecules not bound to peg-4000 in water at ph 2.0 at a ratio of vinpocetine to peg-4000 1: 2 by weight. figure 12 simulation of the molecular dynamics of the release of vinpocetine from an alloy with peg-4000 1:5 by weight into water with a ph of 2.0. time is 0 ns (a), 40 ns (b), 100 ns (c). chimica techno acta 2022, vol. 9(2), no. 202292s11 article 5 of 6 figure 13 van der waals interaction energy of vinpocetine with peg-4000 and with a solvent (water at ph 2.0) in terms of one molecule of vinpocetine at a ratio of vinpocetine and peg-4000 1:5 by weight. figure 14 estimation of the proportion of vinpocetine molecules not bound to peg-4000 in water at ph 2.0 at a ratio of vinpocetine to peg-4000 1: 5 by weight. table 2 average values of vinpocetine release parameters from the studied complexes with polymers. system average energy of van der waals interaction vinpocetine with polymer, kj/mol average energy of van der waals interaction of vinpocetine with a solvent, kj/mol the average proportion of vinpocetine molecules not associated with the carrier, % vinpocetinepeg-4000 1:2 –57.88±3.80 –106.25±4.75 15.274±3.44 vinpocetinepeg-4000 1:5 –97.74±6.93 –116.21±7.64 2.060±2.24 vinpocetinepeg-4000 1:2 ph 2.0 –88.58±4.18 –173.95±5.60 5.893±1.00 vinpocetinepeg-4000 1:5 ph 2.0 –120.51±8.41 –165.37±6.10 1.898±2.06 4. conclusions the data obtained show similar values of the energies of van der waals interaction between vinpocetine and the polymer, as well as vinpocetine and water, both at a ratio of 1:2 and at a ratio of 1:5. in a neutral medium, when released from peg-4000, clusters of vinpocetine molecules are formed. there is an increased release of vinpocetine molecules in an acidic medium and with an increase in the ratio in the alloy towards vinpocetine. supplementary materials no supplementary materials are available. funding this research had no external funding. acknowledgments none. author contributions conceptualization: y.a.p., t.n.g., n.n.s. data curation: y.a.p. formal analysis: y.a.p., n.n.s. methodology: y.a.p., t.n.g. resources: y.a.p., t.n.g., n.v.a. supervision: y.a.p. visualization: y.a.p., t.n.g. writing –original draft: y.a.p., n.v.a. writing –review & editing: y.a.p. conflict of interest the authors declare no conflict of interest. additional information author ids: yulia a. polkovnikova, scopus id 57060554300; tamara n. glizhova, scopus id 57209733391. websites: voronezh state university, 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https://doi.org/10.12991/mpj.2018.63 https://doi.org/10.1016/j.chemphys.2006.04.018 https://doi.org/10.1021/jp071097f https://doi.org/10.1063/1.448118 solution combustion synthesis of i-type heterojunction photocatalyst based on o-ybfeo3/h-ybfeo3/ceo2 toward efficient photo-fenton degradation of methyl violet chimica techno acta article published by ural federal university 2021, vol. 8(4), № 20218407 eissn 2411-1414; chimicatechnoacta.ru doi: 10.15826/chimtech.2021.8.4.07 1 of 11 synthesis, structure, and visible-light-driven activity of o-ybfeo3/h-ybfeo3/ceo2 photocatalysts sofia m. tikhanova ab* , lev a. lebedev a , svetlana a. kirillova c , maria v. tomkovich a , vadim i. popkov a a: ioffe institute, 194021, saint petersburg, russia b: saint-petersburg state institute of technology, 190013, saint petersburg, russia c: saint petersburg electrotechnical university "leti", 197376, saint petersburg, russia * corresponding author: tihanova.sof@gmail.com this article belongs to the regular issue. © 2021, the authors. this article is published in open access form under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). abstract photo-fenton-like oxidation of organic substances is one of the key advanced oxidation processes based on the reversible fe2+↔fe3+ transition and the generation of a strong oxidant ·oh in the presence of h2o2 and is currently considered as a promising method for the purification of polluted aqueous media. however, the absence of effective and stable photocatalysts of this process, operating under the action of visible light, necessitates the exploratory studies, mainly among iron oxides and ferrites of various compositions and structures. in this work, using the method of solution combustion followed by heat treatment in air the heterojunction nanocomposites based on ytterbium orthoferrite and cerium dioxide of the composition o-ybfeo3/h-ybfeo3/ceo2 (0–20 mol.%) with high absorption in the visible region and advanced photo-fentonlike activity were obtained. the nanocomposites were studied by eds, sem, xrd, bet, and drs methods. the photo-fenton-like activity of the nanocomposites was investigated during the degradation of methyl violet under the action of visible (λmax = 410 nm) radiation. as a result, the formation of i-type heterojunction based on stable rhombic (55.4–79.0 nm) and metastable hexagonal (19.5–24.0 nm) modifications of ytterbium orthoferrite (o-ybfeo3 and h-ybfeo3, respectively) and cubic cerium dioxide ceo2 (13.2–19.2 nm) nanocrystals was established. it was shown that the obtained nanocomposites had foamy morphology and were characterized by a specific surface in the range of 9.1–25.0 m2/g, depending on the ceo2 content. it was found that nanocrystalline components were chemically and phase-pure, uniformly spatially distributed over the nanocomposite, and had multiple contacts with each other. based on this fact and the established electronic structure of the nanocomposite components, the formation of i-type heterojunction with the participation of o-ybfeo3 (eg = 2.15 ev), h-ybfeo3 (eg = 2.08 ev), and ceo2 (eg = 2.38 ev) was shown, the presence of which increased photocatalytic activity of the resulting nanocomposite. the optimal content of ceo2 in the nanocomposite was 5%, and the o-ybfeo3/h-ybfeo3/ceo2–5% sample was characterized by the highest rate constant of photo-fenton-like degradation of methyl violet under the action of visible light equal to k = 0.138 min–1, which was 2.5 to 5 times higher than for nanocomposites based on ytterbium orthoferrite. the obtained results obtained indicate that the developed nanocomposites can be considered as a promising basis for the advanced oxidation processes for the purification of aqueous media from organic pollutants. keywords ytterbium orthoferrite cerium dioxide solution combustion synthesis heterojunction photocatalysts fenton-like process received: 29.09.2021 revised: 27.11.2021 accepted: 30.11.2021 available online: 02.12.2021 http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2021.8.4.07 http://creativecommons.org/licenses/by/4.0/ https://orcid.org/0000-0002-9239-5470 https://orcid.org/0000-0001-9449-9487 https://orcid.org/0000-0001-7912-6033 https://orcid.org/0000-0002-1537-4107 https://orcid.org/0000-0002-8450-4278 chimica techno acta 2021, vol. 8(4), № 20218407 article 2 of 11 1. introduction currently, the problem of water purification from organic pollutants is attracting more and more attention. the advanced oxidation processes or aops [1] have been actively studied as the basis for promising and effective methods for eliminating pollution from wastewater. these methods are based on the catalytic production and action of hydroxyl radicals (oh·) having the strong oxidizing ability, due to which complex organic molecules can be oxidized partially to simpler molecules or completely to co2 and h2o. one of the most promising aops is the fenton process, in which fe2+ is used as a catalyst for the formation of hydroxyl radicals, and hydrogen peroxide h2o2 is used as their main source [2]. the mechanism of this process can be represented by two main stages following the reaction equations: fe2+ + h2o2 → fe3+ + oh + oh− (1) fe3+ + h2o2 → fe2+ +·o2h + h+ (2) the main advantages of this process are its relatively high efficiency and ease of implementation. since the final products of the decomposition of hydrogen peroxide are oxygen (o2) and water (h2o), this process is safe and environmentally friendly, which is important for the purification of aqueous media from organic pollutants [3]. however, the classical homogeneous fenton process has significant disadvantages, such as high specific cost, limited operating ph range, the formation of a large volume of iron sludge (which has a detrimental effect on the environment and leads to the loss of a large amount of catalytic metals), as well as difficulties in catalyst regeneration (fe2+). to overcome these disadvantages the improved approaches based on the fenton process are currently being developed and, in particular, a photoinduced fenton-like heterogeneous process, which eliminates the known limitations. thus, the development and production of new highly efficient heterogeneous photocatalysts for photoinduced fenton-like oxidative processes seem to be an urgent task. nanostructured ferrites, in particular ree orthoferrites (rfeo3, where r = sc, y, ln), can be used as the basis for such materials. these compounds have been actively studied due to their practically significant structural [4], magnetic [5–8], electrical [8–10], conducting [11] and photocatalytic properties [12–14]. in particular, ytterbium orthoferrite ybfeo3 has important for practical applications electrical and magnetic properties that change depending on its crystal structure [15]. although ybfeo3 has a thermodynamically stable orthorhombic perovskite structure (pbnm/pnma), some studies have shown that nanostructured ybfeo3 (mainly in the form of thin films) can have more two more metastable hexagonal phases: nonpolar p63/mmc and polar p63cm, depending on the partial pressure of oxygen [4, 16]. in addition, ybfeo3 nanoparticles, being in a magnetically ordered state, can be used in catalytic processes [13] and then removed from the reaction solution by applying of an external field, which makes it promising to use them as the basis for effective magnetically controlled photocatalysts for the purification of polluted waters, including using photo-fentonlike processes. however, the use of ree orthoferrites in fenton-like processes is limited by a high tendency to reverse recombination of electron-hole pairs formed during light absorption, as well as by a limited region of radiation absorption (visible region from 500 nm and above). in the previous work, it was shown that the nanocomposite based on h-ybfeo3/o-ybfeo3 exhibits greater photocatalytic activity compared to single-phase o-ybfeo3 at similar specific surface areas. the formation of a heterojunction prevents the recombination of electron-hole pairs and thereby increases the overall photocatalytic efficiency of the nanocomposite material [15, 17], but does not significantly affect the characteristic region of radiation absorption. to solve this problem, this work proposes the development of nanocomposite photocatalysts based on ytterbium orthoferrite and a co-catalyst, cubic cerium oxide (ceo2). the use of ceo2 as a co-catalyst shifts the absorption edge to the ultraviolet region of the spectrum [16], which should lead to an increase in the efficiency of the photocatalytic system in the photo-fenton-like process due to the more efficient absorption of photons with different energies. the main methods for obtaining single-phase ree orthoferrites are hydrothermal [4, 18], sol-gel [19] and microwave [20]. however, the preparation of nanocomposites of the above composition presents a certain difficulty, since the chemical properties of the corresponding components differ significantly and such systems cannot always be obtained by known approaches and synthetic methods. in this work, we propose the preparation of the o-ybfeo3/h-ybfeo3/ceo2 nanocomposite by the method of solution combustion, carried out in a soft glow mode, followed by a heat treatment of amorphous products at moderate temperatures in air. 2. experimental nanocomposites based on ytterbium orthoferrite and cerium dioxide were obtained by solution combustion followed by heat treatment. a schematic representation of the synthesis procedure is shown in fig. 1. glycine (c2h5no2, 98.5%) was added to a solution of oxidizing salts yb(no3)3·6h2o (99.5%), fe(no3)3·9h2o (98.0%) and ce(no3)3·6h2o (99.5%), and ratio g/n = 0.2, provided a glowing combustion mode and the formation of amorphous products [21]. ytterbium, iron, and cerium nitrates were taken in the ratios required to obtain o-ybfeo3/h-ybfeo3/ceo2 samples with a molar fraction chimica techno acta 2021, vol. 8(4), № 20218407 article 3 of 11 of cerium dioxide of 0, 2.5, 5, 7.5, 10, and 20%. the reagents were dissolved in 10 ml of distilled water with constant stirring for 15–20 minutes, after which the reaction mixture was heated until almost complete removal of water, transformation into a gel-like mass, and autoignition. a dark brown foamy solid was formed, which was then heat-treated in the air for 24 hours at 800 °c to completely remove organic residues and form crystalline products. the elemental composition of the synthesized samples was studied using energy-dispersive x-ray spectroscopy (eds) on a tescan vega 3 sbh scanning electron microscope equipped with oxford inca x-act x-ray microanalysis. x-ray phase analysis was performed on rigaku smartlab 3 powder x-ray diffractometer using cu kα (λ = 1.540598 å). powder x-ray diffraction data were obtained with a step of 0.01° and a rate of 4.5°/s in the 2θ range from 20° to 60°. qualitative x-ray phase analysis was performed using the icsd powder diffraction database. the average crystallite size was calculated from the broadening of x-ray diffraction lines using the method of fundamental parameters, implemented in the smartlab studio ii software package. quantitative x-ray phase analysis was carried out using the rietveld method and structural data of crystalline phases. diffuse reflectance spectra in the uv-visible region (drs) were measured using an avaspec-uls2048 spectrometer equipped with an avasphere-30-refl integrating sphere. the photocatalytic activity of the obtained catalysts was studied using the example of the photodegradation of methyl violet (mv) in the presence of hydrogen peroxide h2o2. the process was carried out in a transparent glass beaker, under a light source λmax = 410 nm with constant stirring. in the course of the experiment, 1.5 mg of the catalyst were suspended in 1 ml of distilled water and added to 1 ml of mv solution (3 mmol/l), after which 10 ml of an h2o2 solution with a concentration of 20 mmol/l were added to start the reaction. in photocatalytic experiments, the concentration of the dye was determined spectrophotometrically. avalight-xe light source and avaspec-uls2048 spectrometer were used to measure the absorption spectra. decolorization mv measurements were taken every 10 minutes. fig. 1 procedure for the preparation of o-ybfeo3/h-ybfeo3/ceo2 nanocomposite chimica techno acta 2021, vol. 8(4), № 20218407 article 4 of 11 3. results and discussion according to the results of the eds analysis, in the samples obtained by the method described above, in the general case, the presence of four main elements is observed – ytterbium (yb), cerium (ce), iron (fe), and oxygen (o) (fig. 2a). no impurity elements were found, which indicates a high chemical purity of the obtained compositions. the result of the quantitative analysis of a series of samples is presented in fig. 2b. the error of the determination method for heavy elements is about 0.5 wt.%, it was stated that the compositions of the composites for the main elements (yb, ce, fe) were in good agreement with the composition specified during their synthesis. the stoichiometric relationship is also confirmed by x-ray diffraction data since no reflections of ytterbium oxide or any of the iron oxides are observed. these facts confirm the successful synthesis of samples with a molar content of cerium of 0, 2.5, 5, 7.5, 10, and 20%. to determine the uniformity of distribution of key chemical elements over the volume of o-ybfeo3/h-ybfeo3/ceo2–5% composition, sem study, combined with eds mapping, was carried out; its results are presented in fig. 3. fig. 2 typical eds spectrum of the o-ybfeo3/h-ybfeo3/ceo2–5% nanocomposite (a) and the composition of the obtained samples concerning the main elements (in wt.%) (b) fig. 3 sem images (a, b), multi-element (c) and single-element (d–f) eds mappings of the o-ybfeo3/h-ybfeo3/ceo2–5% sample chimica techno acta 2021, vol. 8(4), № 20218407 article 5 of 11 the area selected based on the sem results for mapping (fig. 3a, b) reflects the typical foam-like morphology of powders – products of solution combustion. at the same time, a comparison of the results of multi-element and single-element mapping indicates a high uniformity of the distribution of all the main elements – yb, ce, and fe. no areas with enrichment in one of the elements were found in the results of the eds mapping. this also indirectly confirms the presence of a large number of contacts between yb, ce, and fe-containing phases in the composition of the obtained composites. fig. 4a shows the diffraction patterns of the samples with different ceo2 contents subjected to heat treatment at 800 °с for 24 hours. according to the qualitative x-ray phase analysis, the ybfeo3 sample, which does not contain cerium oxide, is a single-phase orthorhombic o-ybfeo3. the samples composed of ceo2 contain two phases of ytterbium orthoferrite – metastable hexagonal h-ybfeo3 and stable orthorhombic o-ybfeo3. as the mole fraction of ceo2 increases, a broadening and an increase in the intensity of the peaks corresponding to cerium oxide are observed, while the relative intensity of the peaks corresponding to o-ybfeo3 does not change. it is known that cerium is capable of forming perovskite-like compounds of the o-cefeo3 type [22]; however, due to the relatively large ionic radius of ce3+ and its low stability in the air, such compounds are oxidized at elevated temperatures with decomposition to more stable ceo2 and iron oxides. for this reason, the cerium orthoferrite phase was not detected in the composition of the samples, and the presence of cerium was observed exclusively in the form of cerium (iv) dioxide. in addition, for the samples containing ceo2, the formation of the h-ybfeo3 phase is observed, which was not previously seen in this system under similar conditions without the addition of cerium [23]. the formation of the hexagonal phase of ytterbium orthoferrite in this case can be caused by the influence of the formed cerium (iv) dioxide, which creates spatial restrictions during crystallization and restricts mass transfer. the combination of these factors creates the conditions for the formation of metastable h-ybfeo3, which, like the hexagonal orthoferrites of other rees, are stable only for small nanocrystals (usually less than 15 nm) [24]. the concentration dependencies in fig. 4b were obtained with the rietveld method by using rigaku smartlab studio ii software. the parameters of refinement and criteria of obtained refinement are presented in fig. 5 and table 1. the rwp, rp, and re parameters show that the calculated xrd pattern is in good correspondence with measured data. fig. 4 x-ray diffraction results of o-ybfeo3/h-ybfeo3/ceo2 (a), molar fraction (mol.%) (b) and average crystallite sizes (c) versus ceo2 content (mol.%) chimica techno acta 2021, vol. 8(4), № 20218407 article 6 of 11 fig. 5 rietveld refinement result for the x-ray diffraction of o-ybfeo3/h-ybfeo3/ceo2 table 1 the parameters of refinement by the rietveld method and criteria of obtained refinement the change in the degree of conversion for crystalline phases, calculated from the data of x-ray diffraction, is presented in fig. 4b. with an increase in the cerium content in the composite, the molar fraction of o-ybfeo3 steadily decreases, while the molar fraction of ceo2 increases. in addition, in the presence of cerium in the composition, the appearance of the h-ybfeo3 phase is observed, the fraction of which remains practically the same with a change in the cerium content. in addition to the change in the molar fraction of crystalline phases the gradual broadening of the diffraction peaks also occurs, based on which it is possible to estimate the change in the average size of the corresponding crystallites depending on the cerium content (fig. 4c). it was found that the crystallite sizes varied in the range 55.4–79.0 nm for oybfeo3, 19.5–24.0 nm, and 13.2–19.2 nm for h-ybfeo3 and ceo2, respectively. the absence of a noticeable change in the average crystallite size of the h-ybfeo3 and ceo2 phases is explained by their relatively small fractions in the composition of the composites, which does not allow them to increase their size due to recrystallization processes – the dominant o-ybfeo3 phase prevents such mass transfer. earlier, using a similar system as an example, it has been demonstrated that for the structural transition hexagonal → orthorhombic ree orthoferrite nanocrystals of the hexagonal phase should reach the critical size [25]. therefore, due to the limited mass transfer, h-ybfeo3 nanocrystals do not acquire the critical size and remain in a metastable state. such mutual influence of the components in the o-ybfeo3/h-ybfeo3/ceo2 system suggests the presence of multiple contacts of individual phases and confirms the heterojunction structure of the resulting composite. the results of scanning electron microscopy (fig. 6) indicate that the obtained samples have a highly porous, foamy structure, which is a consequence of the used synthetic method used, characterized by the violent release of gaseous reaction products and foaming of solid-phase products [23]. in this case, even after heat treatment, the foamy morphology is retained at the microlevel, while at the level of individual nanoparticles there are visible morphological changes. thus, in the case of pure ybfeo3 without added cerium (fig. 6a), the distinguishable nanoparticles are weakly agglomerated, have a spherical morphology, and are aggregated into foam-like structures of micron sizes. as shown earlier, the products of solution combustion have foam-like morphology and orthoferrite nanocrystals are formed upon heat treatment of the initial amorphous product from the pore walls while maintaining the foam microstructure [24]. alternatively, in the case of samples obtained with the addition of cerium (fig. 6b–f), there is a more monolithic aggregation of individual particles, which are less distinguishable. this may point to the presence of more finely dispersed h-ybfeo3 and ceo2 phases in the space between the main coarse-crystalline o-ybfeo3 phase. it is worth noting that the size of o-ybfeo3 nanoparticles regularly decreases with the addition of cerium, which is also confirmed by the xrd results (fig. 4c). the results of determining the specific surface area of the samples by the bet method are presented in fig. 7. according to these data, when cerium is added to the system based on ybfeo3 up to a content of 5.0 mol.%, a 2.5-fold increase in the specific surface area is observed. however, with a further increase in the cerium content, this escalation is replaced by a reduction, and at 20 mol.% cerium, the specific surface area becomes almost the same as that of the pure ybfeo3 sample. the observed pattern is in good agreement with the results of scanning electron microscopy (fig. 6) and the increase in the specific surface area in the first range is explained by the appearance of hybfeo3 and ceo2 nanocrystals with a larger specific surface area than o-ybfeo3 due to smaller crystallite sizes. parameters o-ybfeo3 h-ybfeo3 ceo2 initial cif icsd#189735 isostructural to icsd#73361 icsd#20194 crystal system orthorhombic hexagonal cubic space group 62: pbnm 194: p63/mmc 225: 𝐹𝑚3𝑚 fraction, mol.% 43.58 13.67 42.75 average crystal size, nm 47.2 27.8 25.0 a, å 5.2395 3.50703 5.39149 b, å 5.5628 3.50703 5.39149 c, å 7.5788 11.65325 5.39149 α, ° 90 90 90 β, ° 90 90 90 γ, ° 90 120 90 rwp, % 4.26 4.25 4.25 rp, % 3.35 3.35 3.35 re, % 4.31 4.31 4.31 s 0.9867 0.9853 0.9854 chimica techno acta 2021, vol. 8(4), № 20218407 article 7 of 11 fig. 6 sem images of o-ybfeo3/h-ybfeo3/ceo2 samples with different cerium content: 0% (a), 2.5% (b), 5% (c), 7.5% (d), 10% (e) and 20% (f) the decrease in the specific surface area in the second composition range is associated with the intensification of aggregation processes due to the increased cerium content, as a result of which the part of the nanocrystal surface is inaccessible for contact. thus, the o-ybfeo3/h-ybfeo3/ceo2 sample has the largest specific surface area and it is 25.0 m2/g, which is noticeably higher than for samples based on pure o-ybfeo3 and o-ybfeo3/h-ybfeo3 composite [23]. the diffuse reflectance spectra of the obtained samples (fig. 8a) reveal that they intensively absorb the radiation of the visible spectrum. several inflections in these dependences confirm the presence of several phases with different optical absorption edges in the samples. to determine the band gap of these phases, the experimental data were recalculated into the tauc coordinates (fig. 8b), and the calculation results for o-ybfeo3, h-ybfeo3, and ceo2 are shown in fig. 8c. according to the calculations, the band gaps for all phases do not depend on the cerium content in the samples, as evidenced by their nonsystematic variation within the error of the determination method. the average values of the band gaps were 2.15 ev for o-ybfeo3, 2.08 ev for h-ybfeo3, and 2.38 ev for ceo2, which is in good agreement with the literature data [4, 16, 18–20]. thus, the synthesis of a nanocomposite based on the separate o-ybfeo3, h-ybfeo3, and ceo2 phases with the absence of incorporation of cerium into the structure of ytterbium orthoferrite and ytterbium into the structure of cerium (iv) dioxide is confirmed. based on the data on the average values of the band gap, the boundaries of the valence and conduction bands for all phases were determined using the empirical formulas [26]. the transition energies of orthorhombic and hexagonal ytterbium ferrites are close to each other, but their difference affects the electronic structure. fig. 7 bet surface area of the o-ybfeo3/h-ybfeo3/ceo2 samples versus ceo2 content chimica techno acta 2021, vol. 8(4), № 20218407 article 8 of 11 fig. 8 drs spectra (a), tauc plots (b) and band gap energies (c) of the o-ybfeo3/h-ybfeo3/ceo2 samples the calculation results are presented in table 2 and their comparison allows us to conclude that a type i heterojunction structure is formed within the obtained composites, which is suitable for suppressing the processes of reverse recombination of electron-hole pairs in photocatalytic processes. table 2 parameters of the electronic structure of o-ybfeo3/h-ybfeo3/ceo2 composite eg, ev χ, ev ecb, ev evb, ev o-ybfeo3 2.15 5.574 0.00 2.15 h-ybfeo3 2.08 5.574 0.03 2.11 ceo2 2.38 5.56 –0.10 2.28 the photocatalytic activity of the obtained samples was studied in the process of photo-fenton-like decomposition of methyl violet in the presence of hydrogen peroxide under the action of visible light. fig. 9a shows the mv spectra of the reaction solution obtained at different times after the start of the photocatalytic experiment. from these data, it follows that in the presence of o-ybfeo3/h-ybfeo3/ceo2–5% composite, almost complete decolorization of the solution occurs within 90 minutes, which characterizes the composite as an effective catalyst for fenton-like processes [27]. to assess the effectiveness of the nanocomposites obtained in this work thekinetic studies were carried out, the results of which are presented in fig. 9b. before the start of photocatalytic experiments, the reaction solution with the particles of the composite distributed in it was continuously mixed and kept in the dark until the adsorption-desorption equilibrium was established. at the same time, the drop in the concentration of the dye in the solution for the samples differed and correlated with the values of their specific surface area – the higher the specific surface area of the sample, the more mv was adsorbed on its surface (see the initial interval in fig. 9b). after the equilibrium was established the series of photocatalytic experiments were carried out and the obtained kinetic dependences indicated a different methyl violet photodegradation rate in the presence of the obtained nanocomposites and pure ytterbium orthoferrite. by the end of the experiment, the highest photodegradation efficiency was observed for samples with a cerium dioxide molar concentration of 2.5 and 5.0% and amounted to 94.0% and 96.4%, respectively. thus, the nanocomposites exhibit almost 1.5 times higher efficiency of photodegradation than a sample of pure ytterbium orthoferrite, which is explained by the heterojunction structure of nanocomposites increasing the generation of electron-hole pairs and reducing their recombination. the activity of pure cerium dioxide in this process is very low, which is explained by the absence of photons in the visible radiation spectrum with energy, sufficient for the transition of an electron from the valence band to the conduction band. for a quantitative comparison of the photocatalytic performance of nanocomposites and pure ytterbium orthoferrite, the obtained kinetic dependences were rearranged into logarithmic coordinates, –ln(c/c0) = f(t). the linearization of all kinetic dependences in these coordinates confirms the occurrence of photodegradation of methyl violet accompanied by nanocomposites in the pseudo-first-order characteristic of fenton-like processes [3]. from the slope of the obtained dependences, the rate constants of the photodegradation reaction were determined. these and the other characteristics of the photocatalysts are summarized in table 3 and a visual comparison of the obtained reaction rate values is shown in fig 9d. according to the results obtained, with an increase in the ceo2 content, the rate constant values first increase up to 5% ceo2 and then decrease. the initial trend is associated with promoting charge separation/transfer and reducing overpotential for oxidation, and its change into a downward trend is explained by covering active sites on photocatalyst, shielding the light absorption, decreasing the surface area and activity, increasing the charge recombination. chimica techno acta 2021, vol. 8(4), № 20218407 article 9 of 11 fig. 9 photo-fenton-like degradation of mv over o-ybfeo3/h-ybfeo3/ceo2–5% catalyst under visible light (a) kinetic curves (b) and logarithmic kinetic curves of the pseudo-first-order process (c) and photodecomposition rate constant (d) versus cerium dioxide content table 3 kinetic parameters of fenton-like degradation of methyl violet in the presence of photocatalysts based on ybfeo3 under visible light irradiation thus, the content of cerium dioxide in the nanocomposite equal to 5% is optimal for the given system and the method of its preparation. the corresponding value of the constant k = 0.138 min–1 is 2.5–5 times higher than that for the similar systems based on ytterbium orthoferrite (table 3). based on the results of this work, the information obtained on the electronic structure of nanocomposites and their photocatalytic properties, as well as the literature data, a schematic representation of the mechanism of photo-fenton-like degradation of methyl violet in the presx(ceo2), mol.% organic compound half-life time, min degradation efficiency, % the reaction rate constant, min–1 r ref. 0 mv 35 68.90 0.0067 0.929 this work 2.50 mv 20 96.40 0.0127 0.957 5 mv 30 94.00 0.0138 0.990 7.5 mv 60 69.43 0.0054 0.985 10 mv 45 73.80 0.0064 0.986 20 mv 40 74.70 0.0069 0.986 100 mv 65 57.60 0.0045 0.985 ybfo–700 mv – 66.20 0.0048 0.991 [23] ybfo–800 mv – 47.40 0.0031 0.988 [23] lafeo3 acid orange 7 – 40.70 0.0097 0.952 [28] lafeo3/ceo2 acid orange 7 – 28.40 0.0070 0.971 [28] bifeo3 br46 – 95.00 0.0292 0.970 [29] cofe2o4 br46 – 44.00 0.0054 0.9663 [30] chimica techno acta 2021, vol. 8(4), № 20218407 article 10 of 11 ence of ybfeo3/ceo2 nanocomposite under the action of visible light was proposed (fig. 10). under the action of visible radiation the electron-hole pairs are formed in the components of the composite based on ytterbium orthoferrite, which absorbs in the visible region. since the energy of the conduction band for ceo2 is higher than that for o-ybfeo3 and h-ybfeo3, and the energy of the valence band, on the contrary, is lower, the resulting nanocomposite has a combination of type i heterojunctions cascaded into each other. this arrangement allows the holes to migrate from ceo2 to o-ybfeo3 and from there to h-ybfeo3, oxidizing oh– to ·oh, which is the strongest oxidizing agent. in addition, electrons can also cascade from ceo2 to o-ybfeo3, and then to h-ybfeo3, initiating the fe3+ → fe2+ reduction. the presence of h2o2 makes it possible for the fenton-like process to arise. as shown earlier in [23], fe2+ is formed on the surface of h-ybfeo3 during the reduction of fe3+ by electrons transferred from the o-ybfeo3 conduction band. during the reaction, fe2+ is oxidized by h2o2 to fe3+ and ·oh radicals are formed. due to the addition of ceo2 to the system, a similar process can occur on the o-ybfeo3 surface through electrons supplied from the conduction band of cerium oxide. the interaction of ·oh with methyl violet leads to its oxidation to the most stable products – co2 and h2o. since the fenton-like process of the formation of ·oh radicals is activated both on the surface of h-ybfeo3 and o-ybfeo3, the heterojunction h-ybfeo3/o-ybfeo3/ceo2 nanocomposite exhibits greater photocatalytic activity than the previously obtained h-ybfeo3/o-ybfeo3, pure o-ybfeo3, and pure ceo2. 4. conclusions as a result of the work, new i-type heterojunction nanocomposites were successfully developed based on various structural forms of ytterbium orthoferrite and cerium dioxide, which were obtained using the method of solution combustion and heat treatment. a detailed analysis of the composition and structure of o-ybfeo3/h-ybfeo3/ceo2 nanocomposites made it possible to determine the features of the formation of this polycrystalline system and the mutual influence of the components on the growth and transformation of the corresponding nanocrystals. the study of the morphological features of nanocomposites and their specific surface area established a positive effect of the foamy microstructure and developed surface on the photocatalytic activity of the samples. the formation of i-type heterojunction had a positive effect on the resulting efficiency of photocatalysts in the fenton-like process of methyl violet degradation, and the presence of an optimum cerium dioxide content of 5% indicated a complex mutual influence of the components associated with covering active sites on the photocatalyst, shielding the light absorption, decreasing the surface area and activity, increasing the charge recombination. the nanocomposite photocatalysts developed as a result of this work may be of interest for potential use in photo fenton-like processes of oxidation of organic pollutants and other advanced oxidation processes. fig. 10 schematic mechanism of fenton-like photodegradation 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no. 20229315 doi: 10.15826/chimtech.2022.9.3.15 1 of 7 thermal transformations of bismuth (iii) tartrates liubov i. afonina ab* , tatiana e. timakova a , evgeniya v. timakova ab, konstantin b. gerasimov b, yuri m. yukhin b a: department of chemistry and chemical technology, novosibirsk state technical university, novosibirsk 630073, russia b: institute of solid state chemistry and mechanochemistry, siberian branch of the ras, novosibirsk 630090, russia * corresponding author: aflu@ngs.ru this paper belongs to the ctfm'22 special issue: https://www.kaznu.kz/en/25415/page. guest editors: prof. n. uvarov and prof. e. aubakirov. © 2022, the authors. this article is published in open access under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). abstract the processes of oxidative thermolysis of bismuth tartrates [bi(no3)(c4h4o6)]·3h2o and bic4h3o6·h2o precipitated from bismuth nitrate solutions was studied by the methods of x-ray diffraction, thermal analysis, ir spectroscopy and chemical analysis. the staging of thermal transformation processes was determined. morphological studies of initial precursors and the final products of their thermal transformations were carried out. the expediency of obtaining finecrystal powders of the tetragonal bismuth oxide modification β-bi2o3 with uniform sized particles by oxidative thermolysis of bic4h3o6·h2o was shown. keywords bismuth tartrates thermal transformations x-ray diffraction tetragonal bismuth (iii) oxide bismuth (iii) oxocarbonate ir spectroscopy fine-crystal powders received: 28.06.22 revised: 12.08.22 accepted: 12.08.22 available online: 25.08.22 1. introduction tartaric acid salts are used as compounds showing antimicrobial activity [1–3] and precursors for the synthesis of metal nanoparticles [4, 5], oxides [6, 7] and complex oxide materials [8, 9]. bismuth compounds with tartaric acid also find applications in these areas. bismuth tartrates have a long history of medical use against various kinds of bacterial infections [10, 11] and are promising as substances for the treatment of infections caused by protozoan parasites [12]. however, the use of bismuth tartrate as a precursor for the synthesis of oxide materials has not yet been sufficiently reported in the literature. a method for obtaining bismuth oxide used in the production of enamels and ceramic paints from bismuth tartrate synthesized by treatment of metallic bismuth with tartaric acid while grinding in a mortar followed by heating the resulting mixture in the presence of water at 50–60 °c was proposed [13]. the composition of bismuth tartrate was not indicated, nor was the polymorphic modification of the resulting oxide. analysis of the literature data allows assuming that at bismuth tartrate heat treatment temperatures of 270–300 °c, the target product is the tetragonal modification β-bi2o3. in order to obtain nanoparticles of the monoclinic α-bi2o3 modification, a synthesis using polyethylene glycol 2000 and the initial bismuth-containing compound of two-dimensional coordination polymer composition {[bi(μ-c4h4o6)(no3)(h2o)]–4h2o}∞ [14] was proposed. the above mixture was heated at 500 °c for 3 h. for the synthesis of a bismuth-containing compound, an expensive medium, bismuth nitrate, was used, which was treated at a temperature of 25 °c in stages with tartaric acid solution at a molar ratio of tartrate ions to bismuth of 0.5. the resulting precipitate was filtered off, and the mother liquor was kept at 4 °c until colorless crystals of the desired composition were obtained. bi2o3, an important metal oxide semiconductor, has attracted particular attention because of its excellent optical and electrical properties, such as wide bandwidth, high refractive index, high dielectric constant and good photoconductivity. due to these unique characteristics, bismuth oxides can be used in various fields such as fuel cells, sensor technology, oxide varistors, ionic conductors, photovoltaic materials, high temperature superconductors and functional ceramics. bi2o3 is also an important component in the production of transparent ceramic glass, optical coatings and catalysts [15]. bismuth oxide (iii) is included as a radiopaque agent in dental materials, including hydraulic silicate cements; it is a preferred material for some endodontic procedures [16]. http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2022.9.3.15 mailto:aflu@ngs.ru https://www.kaznu.kz/en/25415/page http://creativecommons.org/licenses/by/4.0/ https://orcid.org/0000-0002-5606-3022 https://orcid.org/0000-0002-7015-9231 https://crossmark.crossref.org/dialog/?doi=https://doi.org/10.15826/chimtech.2022.9.3.15&domain=pdf&date_stamp=2022-8-25 chimica techno acta 2022, vol. 9(3), no. 20229315 article 2 of 7 recently, a large number of studies have been devoted to the photocatalytic activity of bismuth oxides, with a higher activity of the tetragonal modification β-bi2o3 compared to the monoclinic α-bi2o3 being noted [17]. tetragonal bismuth oxide is also used in the synthesis of pigments for the production of coatings, enamels and ceramic paints [18, 19]. the process of obtaining bismuth compounds for engineering and medicine is associated with the hydrolytic processing of bismuth nitrate solutions, as hno3 is the best solvent for metallic bismuth and its alloys [20]. precipitation of the compounds is carried out by diluting bismuthcontaining solutions with water or by adding carboxylic acids and their salts to them. the purpose of this work was to investigate the oxidative thermolysis of bismuth tartrate obtained as a result of processing nitric acid solutions to produce β-bi2o3. two objects of study were chosen: the medium bismuth tartrate of the composition bic4h3o6·h2o, which contains a minimum amount of tartrate ions and is used in medicine as an antibacterial substance, and the bismuth nitrate-tartrate of the composition [bi(no3)(c4h4o6)]·3h2o; the latter was selected to determine the role of nitrate ions in the process of oxidative thermolysis [21]. 2. experimental all reagents in this work were of analytical grade and were used without further purification. bismuth stock solution in nitric acid (420 g·l–1 bi3+, 100 g·l–1 free hno3) was prepared by dissolving pure grade bismuth oxide in 7 m nitric acid. precipitation of bismuth nitrate-tartrate [bi(no3)(c4h4o6)]·3h2o and bismuth tartrate bic4h3o6·h2o was carried out in teflon or glass vessels equipped with stirrers and temperature-controlled using water baths by adding bismuth-containing solutions to aqueous solutions of l(+)-tartaric acid c4h6o4 and sodium tartrate na2c4h4o6, respectively, with a molar ratio of tartrate ions to bismuth equal to 1.1. the mixtures were stirred for 1 h at 25 °c. the precipitates were filtered off and dried in air. chemical determination of macro quantities of bi (iii) in solutions was carried out by titration with a complexon iii solution in the presence of the xylenol orange indicator. micro quantities of bi (iii) were determined photocolorimetrically using potassium iodide. carbon, nitrogen and hydrogen contents in the obtained samples were determined by the modified pregle method with gravimetric termination. the phase compositions of the samples were analyzed using x-ray diffraction technique (xrd) on a diffractometer (bruker d8 advance, germany) using cu kα radiation (λ = 1.5418 å). x-ray diffraction data were collected in scanning mode at a scanning speed of 0.5° min–1 in the range of 4°<2θ<70°. phase analysis was performed using the icdd pdf-4 database (2011). the infrared absorption spectra were recorded with the ir-fourier spectrometer scimitar fts 2000 (digilab) in the range of 400–4000 cm–1. the samples were prepared as tablets with calcined kbr. microstructure of the samples was studied by scanning electron microscopy (sem) using a hitachi tm 1000 scanning electron microscope. thermal analysis of the samples was carried out on a synchronous thermoanalytical complex sta 449 f1 jupiter (netzsch) dynamically under heating in an ar/o2 atmosphere (80/20; o2 10 ml·min−1; ar 40 ml·min−1). samples weighing 180–200 mg were placed in crucibles of pt-10% rh alloy and heated at a rate of 10 °·min–1 to 350–500 °c. the mass spectra of the gaseous products formed in the course of the heat treatment were recorded in the multi-ion detection mode at m/z of 18, 28, 30 and 44 with a qms 403d quadrupole mass spectrometer (netzsch). 3. results and discussion 3.1. synthesis and characterization of bismuth tartrate according to the data of chemical analysis, when a nitric acid bismuth-containing solution is added to a solution of l(+)-tartaric acid at a molar ratio of tartrate ions to bismuth n equal to 1.1 and temperatures of 25 and 60 °c, the samples contain (%): bi – 45.0, c – 10.71, h – 1.59 and n – 2.98, and the molar ratio of bismuth (iii) to tartrate and nitrate ions in the precipitate is 1:1:1. a comparison of the diffractograms of precipitation products with a reference xrd pattern plotted according to [14] (figure 1, 1 and 2) shows significant differences in the structures of the studied nitrate-tartrate. this suggests that, under these conditions, the compound [bi(no3)(c4h4o6)]·3h2o, the formation of which was reported earlier in [21], is precipitated. studies have shown that this compound is also formed after the treatment of medium bismuth nitrate of the composition bi(no3)3·5h2o by tartaric acid solution at a molar ratio of tartrate ions to bismuth in the system of 1–1.1 at 25 °c. the compound [bi(no3)(c4h4o6)]·3h2o becomes x-ray amorphous as a result of multiple washings with water (figure 1, 3). amorphization of the product is already observed after a single washing with water. for a complete purification from nitrate ions 5–7 washes at room temperature are necessary. the content of nitrate ions in the obtained samples does not exceed 0.02%. according to chemical analysis the samples contain (%): bi – 55.9, c – 12.7, h – 1.34, which corresponds to the molar ratio of bismuth (iii) to tartrate ions of 1:1 and indicates that the obtained precipitates, as will be shown below, are bismuth tartrate of the composition bic4h3o6·h2o. further conclusions about the composition of the compound are based on the analysis of its ir spectra in comparison with those of tartaric acid, bismuth nitrate-tartrate and tartrates of other metals. in the ir spectrum of tartaric acid (figure 2, 1), the presence of a carboxyl group appears as weak absorption bands at 3206 and 3112 cm–1, corresponding to the valence vibrations of the o–h bond bound in carboxyl group dimers [22]. chimica techno acta 2022, vol. 9(3), no. 20229315 article 3 of 7 the complex band with maxima at 1740 and 1720 cm–1 corresponds to the valence vibrations of the c=o bond of the unsubstituted carboxyl group [23]. these bands are absent in the spectra of carboxylic acid salts, but there are bands in the region of ~1550–1610 and ~1300–1400 cm–1, respectively, related to asymmetric and symmetrical valence vibrations of ionized groups of coo– [24]. if in the examined compounds the tartrate anion associated with the bismuth cation has at least one non-dissociated group — cooh, bands in the ~1700 cm–1 region should be present in the ir absorption spectra of salt [25]. for the ir spectrum of the bismuth nitrate-tartrate [bi(no3)(c4h4o6)]∙3h2o (figure 2, 2), along with the absorption bands of the carboxylate group (1590 and 1390 cm–1) [26], we observed band broadening in the region of 1400–1280 cm–1 and the appearance of a significant shoulder at 1310 cm–1, which appears to be due to the absorption of nitrate ions [27]. a broad band with a maximum at 3400 cm–1 relates to the valence vibrations of the о–н bond of water molecules and oxogroups of tartrate ions involved in the formation of hydrogen bonds [28]. in the ir spectrum of the bismuth tartrate with the composition bic4h3o6·h2o (figure 2, 3), a number of characteristic features are observed in comparison with the spectra of tartaric acid. in the spectra of the compound there are no valence vibration bands ν(c=o) and ν(c–o) of carboxylic tartaric acid groups indicating the presence of a twice deprotonated tartaric acid anion. bands of valence vibrations of carboxylate groups of asymmetric νas(coo–) with a maximum at 1570 cm–1 and symmetrical vs(coo–) at 1385 and 1360 cm–1 appear, which indicates the substitution of protons in carboxyl groups of carboxylic acid for the bi cation [29]. a wide absorption band with a maximum at 1070 cm–1 indicates the presence of dissociated oxogroups in the compound under study [25, 26]. in the spectrum of the nitrate-tartrate complex two bands are observed in this region, indicating the presence of unsubstituted protons of alcohol groups. weak wide bands with maxima at 470 and 140 cm–1 are related to the valence and deformation vibrations of the bi–o bond, respectively [27]. the presence of water in the compound is indicated by a wide diffuse band in the area of 3650–2800 cm–1, corresponding to valence ν(oh) vibrations of water, as well as a band of plane deformation δ(oh) vibrations of water at 1700–1640 cm–1, which show as a shoulder with a maximum at 1638 cm–1 [29]. thus, as a result of repeated washings of [bi(no3)(c4h4o6)]·3h2o with water, bismuth tartrate monohydrate bic4h3o6·h2o is formed, the composition of which is in good agreement with the physico-chemical investigations and the results of ir spectroscopy. by adding a bismuth nitrate solution to a sodium tartrate solution, x-ray amorphic samples were obtained, the ir spectra of which coincided with those of bic4h3o6·h2o. it should be noted that in this case there is no effective purification of the product from nitrate ions, which is apparently associated with the coprecipitation of bismuth oxonitrates at the stage of adding a bismuth solution to the alkaline salt solution. 3.2. thermal analysis of bismuth tartrate according to thermal analysis data, the process of oxidative thermolysis of [bi(no3)(c4h4o6)]∙3h2o has a complex nature with a predominance of exothermic stages (figure 3) and, as follows from analysis of the obtained mass spectra of gaseous products, involves internal oxidation of tartrate ions by nitrate ions, as a result of which nitrate nitrogen is reduced to n2 (table 1). this is confirmed by the registered amount of no (m/z = 30), which is 20 times less than the amount of co2 (m/z = 44). based on the ratio of the amount of nitrogen and carbon in the initial compound, in the absence of the oxidation process the ionic current integral of no would be about 4 times smaller than for co2. also, the ionic current integral for m/z = 28 (n2 or co) is too large to be related only to the ionization fragment of co2 (for co about 10% of the integral for m/z = 44). figure 1 reference xrd pattern of {[bi(μc4h4o6)(no3)(h2o)]·4h2o}∞ (1) modeled on the basis of the literature data [14] and x-ray powder diffraction patterns of [bi(no3)(c4h4o6)]·3h2o (2) and the product of its washing with water (3). figure 2 ir absorption spectra of tartaric acid c4h6o6 (1) and bismuth tartrates [bi(no3)(c4h4o6)]·3h2o (2) and bic4h3o6 .h2o (3). chimica techno acta 2022, vol. 9(3), no. 20229315 article 4 of 7 table 1 results of mass spectra analysis of gaseous products. m/z ionic current integral, а·s 18 81.83·10–9 28 24.30·10–9 30 5.19·10–9 44 109.27·10–9 based on the dsc data, the temperatures corresponding to the most pronounced thermal effects were determined, at which the [bi(no3)(c4h4o6)]∙3h2o samples were kept consecutively for 3 h and analyzed by x-ray diffraction (figure 4). according to the xrd data (figure 4), when [bi(no3)(c4h4o6)]∙3h2o is kept at 100 °c for 3 h, the diffraction pattern changes significantly (figure 4, 1 and 2) and corresponds to a partially dehydrated initial compound. this process is reversible, since when the samples heated at 100 °c are kept in air for several days, the main reflections of nitrate-tartrate reappear on the diffraction patterns (figure 4, 3). the samples obtained at temperatures of 150, 200, and 250 °c are x-ray amorphous. the diffraction pattern of the sample aged at 300 °c clearly shows reflexes of the tetragonal modification of β-bi2o3 (icdd 01077-5341) and bismuth oxocarbonate (bio)2co3 (icdd 00041-1488) (figure 4, 4). the increase of curing time at 300 °с up to 6 h also yields the β-bi2o3/(bio)2co3 composite. further increase in temperature leads to the β→α phase transition, the product is the monoclinic modification α-bi2o3 (icdd 040-03-2034) (figure 4, 5). the results of the thermal analysis of bic4h3o6·h2o are presented in figure 5. the tg curve shows several different stages of weight loss. the process of oxidative thermolysis of bismuth tartrate monohydrate begins with the removal of one molecule of crystallization water (the endothermic effect at 100 °c). the weight loss at this stage of decomposition is 4.8%, which corresponds to the expected composition of bic4h3o6·h2o. according to mass spectrometry data, two successive exothermic effects at 250 and 270 °c are associated with the release of h2o and co2 due to the decomposition of tartrate ions. thus, a rather low decomposition temperature of the compound in the reaction range 240–280 °c and the absence of nitrate ions in the composition make the medium bismuth tartrate a more preferable precursor for the production of β-bi2o3, compared with tartrates containing nitrate ions. based on the data obtained, the temperature regime and duration of annealing of the bic4h3o6·h2o samples were chosen. according to the xrd data, in the diffractogram of the initial sample bic4h3o6∙h2o (figure 6, 1), kept at a temperature of 240 °c, reflections of bismuth oxocarbonate (bio)2co3 clearly appear in the region of the x-ray amorphous halo (figure 6, 2), and the product of annealing at 270 °c is a mixture of β-bi2o3 and (bio)2co3 (figure 6, 3); upon further heating of the sample at 280 °c, the main reflections of bismuth oxocarbonate disappear (figure 6, 4). powders of single-phase βbi2o3 were obtained by keeping bic4h3o6·h2o for 6 h at 280 °c. figure 3 dsc (1) and mass spectra curves (2–5) of decomposition of [bi(no3)(c4h4o6)]·3h2o. m/z: 18 (2), 28 (3), 30 (4), 44 (5). figure 4 x-ray powder diffraction patterns of [bi(no3)(c4h4o6)]·3h2o (1) and the products of its oxidative thermolysis for 3 h at 100 (2), 300 (4), 320 °c (5) and the product of thermolysis at 100 °c kept in air (3). figure 5 tg (1), dsc (2) and mass spectra curves (3, 4) of decomposition of bic4h3o6 .h2o. m/z: 18 (3), 44 (4). chimica techno acta 2022, vol. 9(3), no. 20229315 article 5 of 7 researching the mechanisms of thermal decomposition of tartrates has been mainly limited to the processes occurring in an inert atmosphere [30, 31]. thus, in the thermal decomposition of tartrates of alkaline-earth [30] and rareearth elements [31] the formation of metal oxalates as intermediate products with their subsequent transformation into carbonates and corresponding oxides was indicated. in our study of oxidative thermolysis process of the bismuth tartrate, based on the xrd data, the formation of bismuth oxalate with the proposed composition bic2o4(oh) [32] as an intermediate product was not established. however, the stage of bismuth oxocarbonate formation was confirmed. sem images indicate that the samples of the βbi2o3/(bio)2co3 composite and β-bi2o3 obtained by oxidative thermolysis of [bi(no3)(c4h4o6)]∙3h2o and bic4h3o6·h2o, respectively, retain the morphology of the original precursors (figure 7). a sample of the βbi2o3/(bio)2co3 composite obtained from [bi(no3)(c4h4o6)]∙3h2o is a large aggregate of plate crystals with signs of a block structure, just like the original [bi(no3)(c4h4o6)]∙3h2o ( figure 7, a and b). the samples of β-bi2o3 synthesized from bic4h3o6∙h2o are aggregates consisting of uniformly sized (1–2 m) amorphous particles (figure 7, c and d). 4. conclusions the final product of the oxidative thermolysis of bismuth tartrates of the compositions [bi(no3)(c4h4o6)]∙3h2o and bic4h3o6∙h2o is bismuth oxide, whose samples retain the morphology of the initial precursors. oxidative thermolysis processes of the precursor compounds include a bismuth oxocarbonate (bio)2co3 formation stage as an intermediate product, and in the case of the bismuth nitratetartrate – also redox reactions involving tartrate and nitrate ions. thus, fine-crystalline powders of tetragonal bismuth oxide β-bi2o3 with uniformly sized particles are expediently obtained by oxidative thermolysis of bic4h3o6·h2o at 280 °c for 6 h. supplementary materials no supplementary materials are available. funding this work was performed in accordance with the thematic plans of novosibirsk state technical university (tpkhkht-1_22) and institute of solid state chemistry and mechanochemistry, siberian branch of the ras (121032500064-8). acknowledgments none. figure 6 x-ray powder diffraction patterns of bic4h3o6 .h2o (1) and the products of its oxidative thermolysis for 3 h at 240 (2), 270 (3) and 280 °с (4). figure 7 sem images of [bi(no3)(c4h4o6)]·3h2o (а), bic4h3o6·h2o (c) and the products of its oxidative thermolysis: β-bi2o3/(bio)2co3 (b) and β-bi2o3 (d). author contributions conceptualization: e.v.t. data curation: l.i.a., e.v.t. formal analysis: k.b.g., l.i.a. funding acquisition: e.v.t., yu.m.y. investigation: t.e.t., k.b.g., l.i.a. methodology: e.v.t., yu.m.y. project administration: e.v.t. resources: yu.m.y., k.b.g. supervision: e.v.t., yu.m.y. validation: l.i.a., t.e.t. visualization: e.v.t., l.i.a. writing – original draft: e.v.t. writing – review & editing: l.i.a., e.v.t., yu.m.y. conflict of interest the authors declare no conflict of interest. chimica techno acta 2022, vol. 9(3), no. 20229315 article 6 of 7 additional information author ids: liubov i. afonina, scopus id 7006080705; 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2012;107(3):1031–1037. doi:10.1007/s10973-011-1599-1 32. timakova ev, afonina li, bulina nv, shatskaya ss, yukhin yum, volodin va. synthesis of basic bismuth (iii) oxalate by precipitation from nitrate solutions. russ j appl chem. 2017;90(7):1040–1046. doi:10.1134/s1070427217070035 https://doi.org/10.1002/jrs.2173 https://doi.org/10.1107/s2052520614027516 https://doi.org/10.1021/jp2092169 https://doi.org/10.1007/s10973-011-1599-1 https://doi.org/10.1134/s1070427217070035 sorption analysis of composites based on zinc oxide for catalysis and medical materials science published by ural federal university eissn 2411-1414; chimicatechnoacta.ru letter 2022, vol. 9(4), no. 20229422 doi: 10.15826/chimtech.2022.9.4.22 1 of 6 sorption analysis of composites based on zinc oxide for catalysis and medical materials science evgeniya maraeva a * , dmitriy radaykin a, anton bobkov a , nikita permiakov a, vasily matveev b , alexander maximov a, vyacheslav moshnikov a a: department of microand nanoelectronics, saint-petersburg electrotechnical university «leti», saint-petersburg 197022, russia b: petersburg nuclear physics institute named by b.p. konstantinov, nrc «kurchatov institute», gatchina 188300, russia * corresponding author: jenvmar@mail.ru this paper belongs to a regular issue. © 2022, the authors. this article is published in open access under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). abstract modified structures based on zinc oxide are of special interest in catalysis and medicine. the work discusses the composite structures based on zinc oxide and hydroxyapatite, as well as silver-modified zinc oxide nanostructures obtained by chemical deposition. the obtained materials were studied using a rigaku smartlab diffractometric complex and a sorbi ms sorption analyzer. the specific surface area was studied and the average size of nanoparticles in the samples is determined. the application scope of the considered materials was catalysis and medicine, including the use in bone engineering as bioactive coatings deposited on the surface of a metal bioimplant. keywords zinc oxide hydroxyapatite adsorption specific surface area catalysis received: 19.10.22 revised: 10.11.22 accepted: 12.11.22 available online: 22.11.22 key findings ● silver-modified zinc oxide nanostructures and nanocomposites based on zinc oxide and hydroxyapatite were obtained via chemical deposition method. ● the specific surface area was 5–20 m2/g, the nanoparticle sizes were 60–260 nm, depending on the synthesis features. ● the use of silver nanoparticles leads to a decrease in the specific surface area of zinc oxide modified with silver and increases the rate of photocatalytic decomposition. 1. introduction zinc oxide is considered to be one of the most important semiconductor photocatalysts due to its high photosensitivity and good chemical stability [1]. the synthesis of this material can be carried out using the hydrothermal method, the homogeneous precipitation, the sol-gel method and other known methods. one of the disadvantages of zinc oxide is a wide band gap (3.2–3.3 ev), due to which the material absorbs light only in the near uv region. unfortunately, metal oxide semiconductors use only 5% of the solar spectrum range [2, 3]. thus, the efficient use of solar energy remains a challenge in photocatalytic applications of zinc oxide. the main mechanism of photocatalysis includes the excitation of the zno band gap by photons, resulting in the generation of exciton pairs with holes in the valence band and electrons in the conduction band. these charge carriers may recombine, dissipating energy as heat, or may interact with pre-adsorbed electron donors/acceptors on the catalyst surface. further, donors/acceptors initiate redox reactions with organic pollutants and destroy them. it should be noted that the intensity of the photocatalysis process is affected by the size of the zno crystallite. small particle size leads to a high specific surface area, which improves the ability to absorb photons and increases the probability of adsorption of dye molecules on the surface, and also leads to the suppression of exciton binding [4]. to improve the photocatalytic efficiency of zinc oxide, colloidal quantum dots of semiconductor materials are deposited on its surface, which inject charge carriers upon irradiation in the visible spectral range [5]; plasmonic nanoparticles [6] (including in the form of dendrites [7]) can also be deposited. the other ways are to change the morhttp://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2022.9.4.22 mailto:jenvmar@mail.ru http://creativecommons.org/licenses/by/4.0/ https://orcid.org/0000-0002-0000-7953 https://orcid.org/0000-0002-0209-9273 https://orcid.org/0000-0001-9079-3363 https://orcid.org/0000-0001-6500-5492 https://crossmark.crossref.org/dialog/?doi=https://doi.org/10.15826/chimtech.2022.9.4.22&domain=pdf&date_stamp=2022-11-22 chimica techno acta 2022, vol. 9(4), no. 20229422 letter 2 of 6 phology [8] or to change the concentration of intrinsic defects on the surface by special alloying [9]. high-energy electron beams [10], plasma chemistry [11], mechanical activation [12, 13], and other energy effects are used as modifying techniques. a special technological direction is the creation of nanocomposites with desired properties of heterojunctions and energy levels at interfaces [14]. in addition, the lspr (local surface plasmonic resonance) effect is worth mentioning. this effect occurs as a result of the modification by nanoparticles (nps) of noble metals (ag and au) [15, 16]. lspr affects the mechanism of charge separation at the metal-semiconductor interface. as a result, an increase in the lifetime of photoinduced electron-hole pairs is observed. reducing the probability of recombination has a positive effect on the generation of highly active radicals on the catalyst surface. this feature attracts the attention of researchers to the development of plasmonic photocatalysts [17]. another important area of zinc oxide application – developments in the field of medical materials science – is also associated with heterosystems [18, 19]. in dental applications, the leading positions are occupied by hydroxyapatite (ha) and composite materials based on it. while the properties of hydroxyapatite as a biocompatible material that is an analogue of bone tissue are widely known and have been studied in detail, the problem of bacterial and microbial effects when using such structures in practice remains unresolved. to improve the antibacterial properties of hydroxyapatite, its combinations with zinc and its oxide are used. thus, in [20], the results of the studies of the biocompatibility and antibacterial properties of multiphase nanocomposite materials based on ha:zno, which were synthesized using calcium nitrate tetrahydrate, ammonium hydrogen phosphate, aqueous ammonia, zinc nitrate hexahydrate, and calcium chloride, are presented. the antimicrobial activity of the samples was assessed on test cultures of gram-negative bacteria (e. coli, p. aeruginosa) and grampositive bacteria (s. aureus and s. epidermidis). mouse fibroblast cells were used for biocompatibility testing and cytotoxicity evaluation. it was shown that the synthesized nanocomposite material has a multiphase nanoscale architecture, where zno nanocrystals are represented by two lattices: cubic and hexagonal. the studied composite demonstrates a high antibacterial activity due to the inclusion of zno particles in the hydroxyapatite powder. in [21], composites based on polycaprolactone, hydroxyapatite and zinc oxide were studied at various mass fractions of zinc oxide. the antimicrobial activity of the obtained scaffolds was shown with a gradual increase in antimicrobial efficiency with increasing zno concentration (optimally at 15 and 30% zno in the composition). such composites may be ideal for achieving optimal biocompatibility (cell proliferation, biomineralization and antimicrobial capacity) and mechanical stability, making them a promising biomaterial for bone tissue regeneration. in [22], ha/zno nanorod composite coatings were fabricated on si substrates. zno nanorods were first grown on a substrate by a hydrothermal method, and then a solution of ca and p precursors was deposited on the surface by centrifugation and fired to form composite coatings of the ha/zno nanorods. the wettability of the surface of such a coating can be controlled by ultraviolet treatment, changing from rather hydrophobic to hydrophilic. such coatings showed a different adsorption capacity of the protein for both the zno nanorod coating and the ha coating. the desired ability to release zn ions was also observed. such coatings can potentially be applied as bioactive coatings to the surface of a metal bioimplant. the aim of [23] was to create a platform with optimal physicochemical properties and photocatalytic activity for the delivery of the standard chemotherapeutic drug doxorubicin. in [24], a highly sensitive and selective sensor with a carbon-modified electrode based on the “hydroxyapatite-zno-pd” composite was made for the simultaneous determination of arbutin and vitamin c. let us consider in more detail the reason for the increased interest in zinc oxide as an antibacterial component of composite structures. the work [25] describes the antibacterial properties of zinc and its oxide. zinc is one of the most widespread mineral elements in hard tissues; this element plays various physiological roles in the immune system, and is also involved in cell division and growth. zinc oxide (zno) has unique optical-electrical and chemical properties. zno promotes bone tissue regeneration, and also has antimicrobial activity with enhanced mechanical properties. zno nanoparticles have three characteristic mechanisms of antimicrobial action, mainly through the generation of reactive oxygen species, attack on the nucleus and protein, and destruction of the cell wall. these modes of action differ from the mechanism of microbial resistance formation, i.e. isolation, drug modification, target modification, and enzyme deactivation. therefore, zinc oxide nanoparticles are considered to be the most suitable nanoantibiotics for bacteria resistant to other antibiotics. it is important to note that the antimicrobial activity of zno depends on the particle size, which in turn regulates the internalization of zn2+. at present, sorption methods of analysis, including the method of thermal nitrogen desorption (ntd), are widely used to characterize the porous structure parameters of nanomaterials for a wide range of functional purposes. ntd belongs to the group of non-destructive techniques that provide express analysis of such parameters of nanomaterials as specific surface area, average particle size, mesopore size distribution, and presence or absence of micropores in the system [26]. the aim of this work was to obtain composite structures based on zinc oxide and hydroxyapatite, as well as zinc oxide with silver additives, to study their phase composition, specific surface area and nanoparticle size. chimica techno acta 2022, vol. 9(4), no. 20229422 letter 3 of 6 2. experimental in this work, the samples of zinc oxide obtained by chemical deposition with the addition of silver nanoparticles, as well as a series of samples of "zinc oxide – hydroxyapatite" (ha:zno) composites were chosen as the objects under study. for the tasks of photocatalysis, zinc oxide powders were synthesized with and without the participation of a surface-active agent (saa) sodium dodecyl sulfate. 2.1. synthesis without saa zinc acetate was dissolved in an aqueous medium with a volume of 25 ml to obtain the aqueous solution of 0.1 m. then a sodium hydroxide solution of 0.2 m was prepared (25 ml). the solution with zinc acetate was stirred at 950 rpm, and the solution with naoh was poured into it. as a result, the solution became turbid. next, the final solution with a volume of 50 ml was heated to 100 °c and kept at this temperature for 1 hour. the finished product (precipitate) was separated from the solution by centrifugation and used in photocatalysis. 2.2. synthesis with saa the technique is similar to the previous one, the differences are as follows: together with a portion of zinc acetate, a portion of surfactant 0.01 m was added; after centrifugation, the powder was washed 7 times before being examined in photocatalysis. using the sodium hydroxide precipitation method, the following samples were synthesized: 1) zno without the addition of saa and ag nps (pure zinc oxide); 2) zno without saa, but with the addition of ag nps; 3) zno with the addition of saa, without ag nps; 4) zno with the addition of saa and ag nps: 5) zno with the addition of saa and ag nps with agglomeration of silver nanoparticles. the difference between samples 4 and 5 is a result of heating the solution with zinc acetate and surfactant during the addition of ag nps. upon heating and adding the particles, the color of the solution changed from yellow to red, and the nanoparticles underwent agglomeration. in order to exclude this process in the future, the nanoparticles were added to the solution at room temperature. the silver nanoparticles were synthesized by the citrate method using silver nitrate (agno3); sodium citrate (na3c6h5o7) and deionized water as a solvent. 2.3. preparation of ha:zno composites the initial powders of hydroxyapatite for the composites were obtained by chemical deposition with the use of microwave radiation. the details of the synthesis are reported in [27]. to obtain zinc oxide, the technology described in [28] was taken, where to synthesize zinc oxide 0.5 ml of 0.5 m zinc nitrate solution (zn(no3)2·6h2o was mixed with 30 ml distilled water containing 0.5 g of cetyltrimethyl-ammoniumbromide (ctab), followed by adding 5 ml of naoh solution. the concentration of the naoh solution was estimated on the assumption of [zn2+]:[oh–]=1:10 ratio. the solution was mixed in an ultrasonic bath (100 w), vigorously stirred for 5 minutes and transferred to the thermostat (90 °c) for 2 hours. the products were collected by centrifugation and washed 3 times in distilled water. zno powder was then dried at 80 °c and annealed at 350 °c for 20 minutes. the initial powders of hydroxyapatite and zinc oxide were mechanically mixed and subjected to manual pressing using a mold with a diameter of 7 mm. as a result of pressing, a series of tablets with a height of about 1100 μm was obtained. 2.4. research methods the phase composition was studied using a rigaku smartlab (cu kα) diffractometric complex. the x-ray diffraction patterns were taken in the quasi-parallel beam mode in the angle range 2θ = 10–80° with a step δ(2θ) = 0.02°. the sorption characteristics of the composites were studied using a sorbi ms device (russia, novosibirsk). the output signal is a desorption peak, the area of which is proportional to the volume of adsorbed/desorbed gas. to recalculate the peak area into the volume of adsorbed gas, preselected coefficients were used. the calibration coefficients were obtained in the study of standard samples with known specific surface area. in this work, the standard sample with a specific surface area sbet = 106 m2/g was used to calibrate the device. the data analysis was carried out according to the results of processing the desorption peaks, taking into account the selected calibration coefficients. as part of the work, a series of adsorption isotherms was studied in the range of relative partial pressures of adsorbate gas (nitrogen) p/po 0–20%, the specific surface area of each composite was determined by the standard brunauer-emmett-teller (bet) method, and the average particle size in the sample was estimated. the average particle size was estimated using the data on the specific surface area and density according to the method described in [26]. 3. results and discussion figure s1 shows the x-ray diffraction pattern of the zinc oxide powder used to create the ha:zno composites. figure s2 shows the x-ray diffraction pattern of the ha:zno (1:1) composite. when studying the composition of the the ha:zno structures, the presence of lines related to the phases ha (iccd: 01-074-0565), zno (iccd: 01-076-0704) and, in some cases, calcium carbonate caco3 (iccd: 01086-2339) was found. the x-ray diffraction patterns obtained when examining the tablets from different angles differ in the intensity ratio of the zno and ha+caco3 peaks. we assume that calcium carbonate caco3 could be formed as a result of the interaction of hydroxyapatite and the unreacted residue of hexamethylenetetramine c6h12n4 or polchimica techno acta 2022, vol. 9(4), no. 20229422 letter 4 of 6 yvinylpyrrolidone, which were used to synthesize zinc oxide by the method [28]. figure 1 shows parts of adsorption isotherms obtained by studying the processes of nitrogen thermal desorption on the initial powders of hydroxyapatite and zinc oxide, and on one of the composites after pressing (in this example, the mixing of the initial components occurred in equal proportions). as it can be seen from figure 1, the values of the volume of adsorbed gas recorded in the study of the composite after pressing are several times lower than those for the initial powders. accordingly, the registered specific surface area sbet of the composites of the entire series turned out to be expectedly lower than the specific surface area of the initial hydroxyapatite and zinc oxide used for mixing (table 1). figure 2 shows a scanning electron microscopy (sem) image of the hydroxyapatite surface before pressing (sample 1). as it can be seen from the figure 2, the surface of the powder is represented by agglomerates about 2 μm in size, consisting of a set of nanorods. we believe that the presence of large agglomerates determines the low specific surface area shown in table 1. table 1 shows that, after pressing the specific surface area of all the composites expectedly decreases, and the size of the particles in the composites in tablets increases. it should be noted that when mixing and pressing a material of lower mass, the specific surface area is 2 times higher (sample ha:zno (1:1)). table 2 presents the results of studying the specific surface area (sbet) and the dye photodegradation rate related to the specific surface area (v) of a series of zinc oxide samples synthesized for catalysis. figure 1 plots of adsorption isotherms of the initial powders and the hap:zno (1:1) composite. table 1 the specific surface area of the initial powders and the composites after pressing. sample sbet, m2/g d, nm ha 9 191 zno 16 66 ha:zno (1:1) 5.3 258 ha:zno (1:3) 5.7 212 ha:zno (1:1) (lower mass) 9.9 138 the specific surface area of pure zinc oxide, sbet, exceeds the specific surface area of the sample modified with silver nanoparticles by a factor of 3 (samples 1 and 2), but, at the same time, the dye photodegradation rate related to the specific surface area (v) for sample 1 is 3.8 times lower than that for sample 2. for the samples obtained in the presence of saa, the specific surface area turned out to be somewhat lower than expected, most likely due to the presence of residual molecules of sodium dodecyl sulfate on the surface. these molecules cover the surface, and the gas (n2) cannot be adsorbed by the entire surface area, so the data are underestimated. to remove surfactants from the surface, drying was undertaken at a temperature of 250 °c for an hour, which led to an increase in the specific surface area by 2–3 m2/g. to obtain more reliable values of the specific surface of photocatalysts synthesized in the presence of surfactants, it was necessary to anneal the powder at 250 °c for 2–3 hours. analyzing the decomposition rates for the samples synthesized in the presence of ssa, we noted a positive effect of precipitated ag nps on the activity of the catalysts: the dye photodegradation rate for sample 5 increased by a factor of 2.75 compared to this parameter for sample 3. it is known [4] that the intensity of the process of photocatalytic decomposition is affected by the size of the zno crystallite. therefore, one of the objectives of the study was to determine the average sizes of nanoparticles in powder catalysts. figure 2 sem image of the initial powder of hap. table 2 the results of the study of the specific surface area and activity of the zno powder catalysts. sample sbet, m2/g v, μmol/h 1 12 0.046 2 4 0.173 3 9.5 0.113 4 10 0.213 5 19 0.311 chimica techno acta 2022, vol. 9(4), no. 20229422 letter 5 of 6 using the specific surface area values obtained from the sorbi device and the density of the test material, an approximate calculation of the size of the catalyst particles can be made. the average size of the particles for sample 1 is 88 nm, for sample 2 – 272 nm, for sample 3 – 107 nm, for sample 4 – 108 nm, and for sample 5 – 59 nm. analyzing samples 4 and 5, it can be noted that the coarsening of silver nanoparticles during synthesis leads to the coarsening of zno aggregates. the band gap value of a series of samples for catalysis was determined from the estimates of the absorption spectra. for pure zinc oxide it was 3.37 ev; for the sample modified only with silver – 3.33 ev. the sample synthesized with the participation of surfactants and modified with silver nanoparticles showed a band gap value of 3.35 ev. 4. conclusions the results of studying the specific surface area of zinc oxide modified with silver nanoparticles in the presence and absence of a surfactant made it possible to select the conditions necessary for the removal of surfactants and evaluate the efficiency of using ag nanoparticles to increase the activity of the zinc oxide surface during catalytic decomposition. for the composites based on zinc oxide and hydroxyapatite, sorption analysis methods made it possible to evaluate the changes that occurred in the powders after pressing in terms of nanoparticle sizes and specific surface area. according to the literature sources analysis, the considered composite structures demonstrate a high antibacterial activity and can be a promising biomaterial with improved mechanical and antibacterial properties. it should be noted that the size estimate will be valid for cases when the particles that make up the composite are the same in size and do not have pores. if the particles in the initial powder are in the form of nanorods, the size analysis should be carried out taking into account the data on the aspect ratio of the nanorods. supplementary materials supplementary materials are available. funding this work was supported by the russian science foundation (grant no. 22-29-20162), https://rscf.ru/project/2229-20162/ with the st. petersburg science foundation (agreement no. 19/2022 dated april 14 2022). acknowledgments the authors are grateful to khalugarova kamilya for assistance in obtaining composites based on hydroxyapatite and zinc oxide by pressing and to arina zaikina (tescan) for sem data. author contributions conceptualization: e.m, v.m1. data curation: n.p. funding acquisition: n.p, e.m, a.b. investigation: e.m, v.m2, d.r. project administration: n.p. supervision: v.m1. validation: a.b, n.p, a.m, v.m2. writing – original draft: e.m, n.p, d.r. writing – review & editing: a.m, v.m1. conflict of interest the authors declare no conflict of interest. additional information author ids: evgeniya maraeva, scopus id 36131990800; anton bobkov, scopus id 56898688900; nikita permiakov, scopus id 56499046400; vasily matveev, scopus id 57211220372; alexander maximov, scopus id 54797495700; vyacheslav moshnikov, scopus id 6701582758. websites: saint-petersburg 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https://doi.org/10.15826/chimtech.2020.7.4.03 https://doi.org/10.1088/1742-6596/1697/1/012050 https://doi.org/10.1088/1742-6596/993/1/012009 new 2,5-bis(2-ethylhexyl)pyrrolo[3,4-c]pyrrole-1,4(2h,5h)-dione-2,2’-bipyridine-based co-polymer, synthesis, photophysical properties and response to metal cations chimica techno acta letter published by ural federal university 2022, vol. 9(1), no. 20229103 eissn 2411-1414; chimicatechnoacta.ru doi: 10.15826/chimtech.2022.9.1.03 1 of 3 features of –c–c– coupling of quinoxaline-2-one with ethyl acetoacetate under acid catalysis yu.a. azev *, o.s. koptyaeva, a.a. mkrtchyan, t.a. pospelova ural federal university, 620002 mira st., 19, ekaterinburg, russia * corresponding author: azural@yandex.ru this short communication (letter) belongs to the regular issue. © 2021, the authors. this article is published in open access form under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). abstract quinoxalin-2-one (1) reacts with ethyl acetoacetate in trifluoroacetic acid (tfa) to form 3-(2-oxopropylideno)-3,4-dihydroquinoxaline-2one (2) and 3-(3-oxo-3,4dihydroquinoxaline-2-(1h)ylidene)methylquinoxaline-2-(1h)-one (3). the reaction product 3 was also obtained by heating the compound 1 with acetone in the presence of tfa. keywords quinoxaline-2-one ethyl acetoacetate nucleophilic substitution of hydrogen vicarious substitution acid catalysis received: 16.11.2021 revised: 11.01.2022 accepted: 11.01.2022 available online: 14.01.2022 key findings ● the replacement of hydrogen led to the formation of water, which activated the process of cleavage of the dicarbonyl group of 3-(2-oxopropylideno)-3,4-dihydroquinoxaline-2-one. the acyl group of com pound 3-(2-oxopropylideno)-3,4-dihydroquinoxaline-2-one was "vicarious" in this reaction. ● the formation of 3-(3-oxo-3,4-dihydroquinoxaline-2-(1h)-ylidene) methylquinoxaline-2-(1h)-one was the result of c,c-coupling of compounds quinoxaline-2-one and 3-(2-oxopropylideno)-3,4 dihydroquinoxaline-2-one, similarly to the reaction of quinoxaline-2-one 1 with acetone. 1. introduction compounds with various types of biological activity were found among quinoxaline derivatives. [1, 2] quinoxidine and dioxidine were used as antimicrobial agents [3]. the features of the synthesis and biological activity of quinoxaline derivatives are described in the review [4]. it was previously reported that quinoxaline salts interact with acetylacetone or ethyl acetoacetate in the presence of base catalysis (diethyl and triethylamines) to form 3a,4,9,9a-tetrahydro-endo-furo[2,3-b]quinoxalines [5]. the authors of the article [6] described the cyclization of 1,3-bis(silyl-enol-ethers) and quinoxaline with the formation of 6-alkylidene-2,3-benzo-1,4-diaza-7oxobicyclo[4,3,0]non-2-yenes. there were known examples of hydrogen substitution in the heterocyclic nucleus of quinoxaline when the reactions with various c-nucleophiles were carried out in the presence of acid. as a result, –c–c-coupling products were obtained [7]. recently [8] it was found that quinoxaline-2-one reacted with acetylacetone, benzylacetone, and heptane-3,5dione when heated in tfa to form derivatives 6а,7dihydropyrido[1,2-a]quinoxaline-6,8-dione. examples of reactions of aliphatic aldehydes with quinoxalin-2-one in the presence of acid with the formation of 6-oxidopyrido[1,2-a]quinoxalinium zwitter ions were published [9]. it was also previously found that when quinoxalin-2one and phenylhydrazine hydrazones are heated in butanol in the presence of tfa, hydrogen substitution products are formed [10]. it should be noted that there have been no data on –c–c– coupling of quinoxaline-2-one with esters of β-dicarbonyl acids in the literature. 2. experimental unless otherwise indicated, all common reagents and solvents were used from commercial suppliers without further purification. the reaction progress and purity of the obtained compounds were controlled by thin layer chromatography http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2022.9.1.03 https://orcid.org/0000-0002-4414-559x http://creativecommons.org/licenses/by/4.0/ chimica techno acta 2022, vol. 9(1), no. 20229103 letter 2 of 3 (tlc) method on sorbfil uv-254 plates, using visualization under uv light. melting points were determined on a stuart smp10 melting point apparatus. 1h, 13c and 19f nmr spectra were acquired on bruker avance-400 and bruker avance neo–600 spectrometers in dmso-d6 solutions, using tms as internal reference for 1h and 13c nmr or cfcl3 for 19f nmr. mass-spectra (ei, 70 ev) were recorded on microtof-q instrument (bruker daltonics) at 250 °c. elemental analysis was performed using a perkinelmer 2400 series ii chns/o analyzer. 2.1. reaction of quinoxaline-2-one 1 with ethyl acetoacetate a mixture of quinoxaline-2-one (1) (0.2 mmol) and ethyl acetoacetate (0.6 mmol) was refluxed in 2.0 ml of tfa at 110 ℃ in a sealed vessel for 50 hours. the solvent was removed in vacuo. the precipitate was dissolved in ethanol (3.0 ml). the alcoholic solution was treated with water (2.0 ml) followed by treatment with 15% nh4oh solution to ph 7–8 with the formation of a precipitate. the precipitate of the mixture of reaction products was filtered off. 3-(2-oxopropylidene)-3,4-dihydroquinoxaline-2-one (2) was isolated using preparative chromatography (rf = 0.156, silica gel kiselgel 60 pf 254, chloroform). yield 35%, m.p. 267–268 °с ([11] 267 °с). 1h nmr (400 mhz, dmso-d6) δ 2.19 (s, 3h), 6.06 (s, 1h), 7.08–7.13 (m, 3h), 7.37–7.40 (m, 1h), 11.86 (s, 1h), 12.96 (s, 1h). ms (ir, 70 эв), m/z (iотн, %): 202 (m+, 100), 187 (м-15, 98), 159 (м-43, 60). found, %: с 65.28; н 4.99; n 13.88. c11h10n2o2. calculated, %: с 65.34; н 4.98; n 13.85. 3 ( 3 o x o 3 , 4 d i h y d r o q u i n o x a l i n e 2 ( 1 h ) ylidene)methylquinoxaline-2-(1h)-one (3) was isolated by preparative chromatography (rf = 0). yield 5%, m.p. >300 °с. 1h nmr (400 mhz, dmso-d6) δ 6.87 (s, 1h), 7.16–7.21 (m, 6h), 7.71–7.73 (m, 2h), 11.93 (s, 2h), 13.62 (s, 1h). 13с nmr (101 mhz, dmso-d6) δ 88.91, 99.49, 115.16, 121.09, 123.29, 125.18, 128.28, 128.54, 147.03, 155.71. ms (ei, 70 ev), m/z (iотн, %): 304 (m+, 100), 276 (18), 248 (27). found, %: с 67.13; н 3.99; n 18.38. c17h12n4o2. calculated, %: с 67.10; н 3.97; n 18.41. 2.2. reaction of quinoxaline-2-one 1 with acetone 0.5 mmol of quinoxaline-2-one (1) was heated with 0.6 mmol of acetone in a mixture of butanol (2 ml) and tfa (0.5 ml) at 110 °c in a sealed vessel for 25 hours. the solvent was removed in vacuo. the precipitate was suspended in ethanol (3 ml) and filtered off. the resulting precipitate of 3-(3-oxo-3,4-dihydroquinoxaline-2(1h)ylidene) methylquinoxaline-2-(1h)-one (3) was recrystallized from dmso and dried. yield 30%. the melting point and spectral characteristics of the reaction product were similar to those obtained in the product of the interaction of quinoxaline-2-one (1) with ethyl acetoacetate. 3. results and discussion while developing effective methods for the functionalization of quinoxaline-2-one, we investigated the interactions of quinoxaline-2-one with ethyl acetoacetate under acid catalysis. we found that heating the reagents in tfa resulted in the formation of 3-(2-oxopropylideno)-3,4dihydroquinoxaline-2-one 2 (scheme 1). the mass spectrum of compound 2, in addition to the molecular ion peak, contained intense peaks of ions with molecular weights of 187 (м–сн3) and 159 (м–сосн3). these peaks were formed during the decomposition of ketones, which were characteristic of these compounds in common (scheme 2). the singlet of the protons of the methyl group in the nmr spectrum of compound 2 in dmso-d6 was observed at 2.3 ppm. the signal of the proton of the methine group of the enamine fragment was observed at 6.2 ppm. scheme 1 the formation of 3-(2-oxopropylideno)-3,4-dihydroquinoxaline-2-one 2 chimica techno acta 2022, vol. 9(1), no. 20229103 letter 3 of 3 scheme 2 the decomposition of ketones to form molecular ions it could be assumed that the formation of the reaction product 2 proceeded through a number of stages: nucleophilic substitution of hydrogen, hydrolysis of the ester group, and decarboxylation with the formation of the final product. obviously, the replacement of hydrogen led to the formation of water, which activated the process of cleavage of the dicarbonyl group of compound 2. in addition to the compound 2, 3-(3-oxo-3,4dihydroquinoxaline-2-(1h)-ylidene) methylquinoxaline-2(1h)-one 3 was found in the reaction products. in the mass spectrum of compound 3, an intense peak with m/z 304 was observed. it corresponded to the proposed structure. the 1h nmr spectrum of compound 3 contained the characteristic signal of the proton of the enamine fragment at 6.9 ppm. a two-proton singlet of two amide nh-groups was observed at 11.9 ppm. the singlet of the nh group of the quinazoline nucleus appeared in a weak field at 13.7 ppm. the shift of this signal was apparently due to the presence of a hydrogen bond between the nh group of quinazoline and the n-atom of another quinoxaline nucleus. the formation of compound 3 was the result of –c–c– coupling of quinoxaline-2-one 1 with a new c-nucleophilic agent, which was formed during the reaction, compound 2. apparently, the acyl group of compound 2 was "vicarious" in this process. the ompound 3 was also obtained by heating the compound 1 in acetone in the presence of tfa. obviously, the formation of 3 was the result of c,c-coupling of the compounds 1 and 2, similarly to the reaction of quinoxaline-2-one 1 with acetone. 4. conclusions in conclusion, it should be noted that the synthesis of alkylated derivatives of quinoxaline-2-one was carried out earlier [11] by the interaction of 1,2-dihydroquinoxaline 4-oxide with active methylene compounds in the presence of piperidine. nevertheless, direct alkylation of quinoxaline-2-one with ethyl acetoacetate under conditions of acid catalysis was described by us for the first time. declaration of competing interest the authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported 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with quinoxalines. tetr let. 2007;48:2067–2069. doi:10.1016/j.tetlet.2007.01.147 7. azev yua, kodess mi, ezhikova ma, gibor am, baranov vi, ermakova os, bakulev va. new opportunities for the synthesis of quinoxaline-substituted heterocyclic and aryl moieties. pharm chem j. 2013;9:498–502. doi:10.1007/s11094-013-0989-z 8. azev yua, kodess mi, ezhikova ma, ermakova os, berseneva vs, bakulev va. reactions of quinoxaline-2-one with βdiketones: a new approach to 6a,7-dihydro-5h-pyrido[1,2a]quinoxaline-6,8-diones. mend comm. 2017;1:97–98. doi:10.1016/j.mencom.2017.01.032 9. azev yua, ermakova os, berseneva vs, kodess mi, ezhikova ma, ganebnykh in. synthesis of the 6-oxidopyrido[1,2a]quinoxalinium derivatives from quinoxaline-2-one and aldehydes – new examples of domino reactions. mend comm. 2017;27:637–639. doi:10.1016/j.mencom.2017.11.034 10. azev yua, koptyaeva os, tsmokalyuk an, pospelova ta, bakulev va. benzaldehyde phenylhydrazones as c-nucleophiles for functionalization of quinoxaline-2-one. unusual transformations of indole-3-carbaldehyde phenylhydrazones. aip conf proc. 2020;2280:0018799. doi:10.1063/5.0018799 11. tennant g. heterocyclic n-oxides. part ii. nucleophilic reactions of 1,2-dihydro-2-oxoquinoxaline 4-oxide. j chem soc. 1964;1982–1986. https://doi.org/10.1002/9780470187173 https://doi.org/10.3987/rev-88-397 https://doi.org/10.1007/bf00503539 https://doi.org/10.1016/j.tetlet.2007.01.147 https://doi.org/10.1007/s11094-013-0989-z https://doi.org/10.1016/j.mencom.2017.01.032 https://doi.org/10.1016/j.mencom.2017.11.034 https://doi.org/10.1063/5.0018799 effect of gas-chromatography column regeneration during the chn/s analysis of copper-chromium disulfide published by ural federal university eissn2411-1414; chimicatechnoacta.ru letter 2022, vol. 9(4), no. 20229423 doi: 10.15826/chimtech.2022.9.4.23 1 of 4 effect of gas-chromatography column regeneration during the chn/s analysis of copper-chromium disulfide irina b. troitskaia * , mikhail m. syrokvashin , evgeny v. korotaev , anatoly i. saprykin nikolaev institute of inorganic chemistry, novosibirsk 630090, russia * corresponding author: troitskaia@niic.nsc.ru this paper belongs to a regular issue. © 2022, the authors. this article is published in open access under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). abstract the effect of gas-chromatography column (gcc) regeneration during the chn/s analysis of copper-chromium disulfide cucrs2 (ccds) samples on the euro ea 3000 analyzer was identified. the effect results in a perfect straight baseline on the chromatograms of both cucrs2 and standard samples. the obtained straight baseline causes high-quality peaks separation. in addition, the reported regeneration procedure reduces significantly the gcc regeneration duration that usually takes up to several days. keywords chn/s analysis chromatography column regeneration copper-chromium disulfide received: 01.11.22 revised: 15.11.22 accepted: 16.11.22 available online: 22.11.22 key findings ● regeneration of gas-chromatography column during chn/s analysis of cucrs2 samples on the euro ea 3000 analyzer was detected. ● the effect results in a perfect straight baseline on the chromatograms. ● the described effect is important for chn/s analysis of samples with low sulfur content. 1. introduction nowadays the analysis for c, h, n, s contents is required for the study not only of organic compounds but also of various metal-organic complexes and sulfur-containing compounds [1–10]. due to a wide range of promising physicochemical properties, these compounds are used as advanced energy [2, 6], thermoelectric [11, 12] and magnetic [13, 16] materials. from among the above mentioned compounds, the cucrs2-matrix and solid solutions were chosen for the chn/s analysis of the sulfur content due to the fact that electrical properties of these materials depend strongly on the sulfur content [12, 15, 16]. moreover, this method was used to control the content of c, h, and n admixtures in these materials because the synthetic procedure of cucrs2 involves the thermal sulfidation of the initial cr2o3 and cuo oxides by the thermolysis products of nh4scn [11, 14–17]. as it is known, gas-chromatography column (gcc) regeneration is required during the operation of chn/s analyzers. to this aim, the gcc is usually purged with highpurity helium at high temperatures for a day or two. this article describes the effect of gcc regeneration observed after the chn/s analysis of copper-chromium disulfide cucrs2 samples. the effect results in a perfect straight baseline on the chromatograms of both cucrs2 and standard samples. the mechanism of this effect was studied by the differential scanning calorimetry (dsc) method. 2. experimental 2.1. instrumentation a euro ea 3000 chn/s analyser (eurovector, italy) with a gcc “separation column sulphur 0.8m ptfe 26007800 e3002 bn203557” (elemental microanalysis, uk) was used for the chn/s analysis. the procedure was carried out using the optimized technique [18]. the dsc analysis was performed using an sta 449 f1 jupiter thermoanalyzer (netzsch, germany). the experiment was run in an open al2o3 crucible in synthetic air flow at a heating rate of 10 k/min. the sample weight was ~ 10 mg. 2.2. reagents and materials tungsten oxide (vi) (elementar, germany) was used in the reactor oxidation zone and “copper wires reduced 6x0.65 mm” (elemental microanalysis, uk) were used in the reduction zone. sulfanilamide (sam) and atropine sulfate (atrs) (elemental microanalysis, uk) were used as the standards. high purity helium n5.0 was used as a carrier gas. http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2022.9.4.23 mailto:troitskaia@niic.nsc.ru http://creativecommons.org/licenses/by/4.0/ https://orcid.org/0000-0001-5438-6007 https://orcid.org/0000-0001-5808-0232 https://orcid.org/0000-0001-7735-0285 https://crossmark.crossref.org/dialog/?doi=https://doi.org/10.15826/chimtech.2022.9.4.23&domain=pdf&date_stamp=2022-11-22 chimica techno acta 2022, vol. 9(4), no. 20229423 letter 2 of 4 the studied effect was noticed during the analysis of cucrs2 samples. the samples had the following element content: copper (35 wt.%), chromium (29 wt.%), and sulfur (36 wt.%). sulfur content was determined by analyzing fourteen 0.6–0.7 mg samples. the content of c, h, and n admixtures was determined by analyzing fourteen 3.5–4.0 mg samples. the analysis time for each sample was 960 seconds. thus, the total analysis time was ~8 h. 3. results and discussion the chn/s analysis was carried out in a high-temperature quartz reactor shown schematically in figure 1. to be analyzed, the ccds sample was placed in a tin capsule introduced into the pyrolysis zone at 1020 °c (point 1 in figure 1) and burnt with oxygen dose in helium atmosphere. then the gaseous products (so2, so3, co, co2, h2o, no, no2) were passed through the oxidation zone filled with wo3 catalyst grains (point 3 in figure 1) for complete conversion of co to co2. after that, sulfur and nitrogen oxides were reduced to so2 and n2, respectively, in the reduction zone filled with copper wires (point 4 in figure 1). finally, the mixture of so2, n2, co2, and h2o gases passed into the gcc for separation. the resulting chromatographic signal was recorded using a thermal conductivity detector. it was observed during the experiment that the baselines of a number of cucrs2 samples became perfectly straight after the chn/s analysis. this effect was studied by comparison of the chromatograms of sam and atrs standards, which were recorded after the standard procedure of gcc regeneration and after the cucrs2 analysis. as it can be seen in figure 2, the baselines of sam and atrs standards became perfectly straight after the analysis of all cucrs2 samples. figure 1 scheme of reactor for sample decomposition: pyrolysis zone (1); separation zone (quartz wool) (2); oxidation zone (3); reduction zone (4); halogen capture zone with silver wire (5). usually baseline flattening is a result of long-lasting column regeneration in helium. note that a straight baseline is necessary for qualitative separation of n2, co2, h2o, and so2 peaks. baseline flattening may be important for the analysis of the samples with a low content of elements in various metal-organic complexes and sulfur-containing compounds. in this case the straight baseline diminishes the absolute error of determination. as it can be seen in figure 2, h2o and so2 peaks are shifted slightly towards the increased retention time on the sam and atrs chromatograms after the cucrs2 analysis. this effect can be explained by the fact that free adsorption centers appear in the column filler, thereby increasing the retention of incoming pyrolysis products. the mechanism responsible for the effect of cucrs2 regeneration was investigated by the dsc method (curve 1 in figure 3) as seen, the sample undergoes no significant weight changes until 400 °c (curve 2 in figure 3). between 400 and 600 °c the weight of the sample increases due to the oxidation of elements (cu, cr, s) in its composition. the dsc curve shows a sustained smooth exothermic effect up to 600 °c, apparently, due to sulfur oxidation. at ~600 °c the dsc curve has an intense double-split peak associated with an exothermic effect, possibly, due to copper and chromium oxidation. then at the temperature of ~600 °c a little weight loss peak is observed. this could be due to partial evaporation of sulfur oxides under a strong temperature increase. then the weight of the sample continues to increase until 670 °c and drops significantly after 700 °c due to evaporation of sulfur oxides. between 750 and 800 °c the dsc curve (curve 1 in figure 3) shows two endothermic effects that are probably caused by hightemperature phase transitions of the formed copper and chromium oxides. thus, it was established by the dsc data that oxidizing cucrs2 causes an intense heat release. as a result, so2 is overheated (compared to normal conditions of the chn/s analysis) when reaching the gcc. since so2 is a reducing agent, this process can be accompanied by the reduction and removal of adsorbed pyrolysis products that were left from other samples in the course of numerous preceding chn/s analysis procedures. the baseline shape influence on the measured c, h, n, s contents was estimated by analyzing the sam and atrs standards after gcc regeneration using the above procedure. table 1 summarizes the determined c, h, n and s contents in the sam and atrs samples. the confidence interval was calculated from the data of five parallel measurements. as can be seen from table 1, the determined composition of sam and atrs standards is very close to the theoretical values. note that the c, h, n, s contents were measured immediately after the cucrs2 analysis without preliminary gcc regeneration using a standard procedure. chimica techno acta 2022, vol. 9(4), no. 20229423 letter 3 of 4 figure 2 chromatograms: sam (green solid line) after standard procedure of gcc regeneration and after cucrs2 analysis (a); atrs (blue solid line) after standard procedure of gcc regeneration and after cucrs2 analysis (b). baselines are shown as dotted red line. in the top right-hand corners, there are the insets showing the nitrogen and carbon dioxide peaks separation at a larger scale. figure 3 dsc (curve 1) and tg (curve 2) for the cucrs2 sample. table 1 chn/s analysis data for sam and atrs samples. element n c h s sa standard theoretical value, wt.% 16.267 41.848 4.683 18.621 found, wt.% 16.270.04 41.870.11 4.70.06 18.620.08 atrs standard theoretical value, wt.% 4.032 58.772 7.253 4.615 found, wt.% 4.030.06 58.770.09 7.250.05 4.620.12 4. conclusions the gcc regeneration effect when determining c, h, n, s contents in the composition of cucrs2 was described. the effect results in a perfectly straight chromatogram baseline for standard samples. such baseline shape provides good separation of chromatographic peaks and a highly accurate determination of c, h, n, s contents in the subsequent measurements. the observed effect allows one to diminish the gcc regeneration time from one or two days to 8 hours. supplementary materials no supplementary materials are available. funding m.m.s and e.v.k. thank to the russian science foundation (project no. 19-73-10073). acknowledgments i.b.t. and a.i.s. thank to the ministry of science and higher education of the russian federation (project no. 121031700315-2, no. 121031700313-8). author contributions conceptualization: m.m.s, i.b.t. data curation: a.i.s. formal analysis: e.v.k., m.m.s, i.b.t. funding acquisition: e.v.k. investigation: m.m.s, i.b.t. methodology: m.m.s, i.b.t. project administration: a.i.s. resources: e.v.k., m.m.s, i.b.t. software: a.i.s., e.v.k. supervision: a.i.s., e.v.k. validation: a.i.s., e.v.k. visualization: e.v.k. writing – original draft: m.m.s, i.b.t. writing – review & editing: a.i.s. conflict of interest the authors declare no conflict of interest. chimica techno acta 2022, vol. 9(4), no. 20229423 letter 4 of 4 additional information author ids: irina b. troitskaia, scopus id 24339314400; mikhail m. syrokvashin, scopus id 56747996900; evgeny v. korotaev, scopus id 55579731100; anatoly i. saprykin, scopus id 7003667465. website: nikolaev institute of inorganic chemistry, http://www.niic.nsc.ru. references 1. krasilnikova aa, shestopalov ma, brylev ka, kirilova ia, khripko op, zubareva ke, khripko yi, podorognaya vt, shestopalova lv, fedorov ve, mironov yv. prospects of molybdenum and rhenium octahedral cluster complexes as x-ray contrast agents. j inorg biochem. 2015;144:13–17. doi:10.1016/j.jinorgbio.2014.12.016 2. arif m, li y, el-dalatony mm, zhang c, li x, salama e-s. a complete characterization of microalgal biomass through ftir/tga/chns analysis: an approach for biofuel generation and 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syrokvashin mm, filatova iy, zvereva vv. vanadium doped layered copper-chromium sulfides: the correlation between the magnetic properties and xes data. vacuum. 2020;179:109390. doi:10.1016/j.vacuum.2020.109390 17. ohta m, hirai s, kato h, sokolov vv, bakovets vv. thermal decomposition of nh4scn for preparation of ln2s3 (ln=la and gd) by sulfurization. mater trans. 2009;50:1885–1889. doi:10.2320/matertrans.m2009060 18. koshcheeva os, zubareva ap, saprykin ai. chn analysis of functional materials and their precursors. j struct chem. 2010;51:175–178. doi:10.1007/s10947-010-0209-6 https://www.scopus.com/authid/detail.uri?authorid=24339314400 https://www.scopus.com/authid/detail.uri?authorid=56747996900 https://www.scopus.com/authid/detail.uri?authorid=55579731100 https://www.scopus.com/authid/detail.uri?authorid=7003667465 http://www.niic.nsc.ru/ https://doi.org/10.1016/j.jinorgbio.2014.12.016 https://doi.org/10.1016/j.renene.2020.10.066 https://doi.org/10.1007/s12039-015-0822-1 https://doi.org/10.1134/s0022476615060359 https://doi.org/10.1016/j.chemosphere.2019.06.010 https://doi.org/10.1016/j.jcrysgro.2017.01.019 https://doi.org/10.15826/chimtech.2021.8.4.04 https://doi.org/10.1007/s12039-015-0972-1 https://doi.org/10.1016/j.chemosphere.2019.06.010 https://doi.org/10.1016/j.carres.2009.08.030 https://doi.org/10.1007/s11664-018-6230-9 https://doi.org/10.3390/ma14112729 https://doi.org/10.1063/1.4863937 https://doi.org/10.1016/s0925-8388(96)02418-8 https://doi.org/10.1016/j.jssc.2011.11.040 https://doi.org/10.1016/j.vacuum.2020.109390 https://doi.org/10.2320/matertrans.m2009060 https://doi.org/10.1007/s10947-010-0209-6 synthesis of polycalciumphenylsiloxane and composites based on the skeleton of a sea urchin with the resulting polymer chimica techno acta article published by ural federal university 2022, vol. 9(2), no. 202292s6 eissn 2411-1414; chimicatechnoacta.ru doi: 10.15826/chimtech.2022.9.2.s6 1 of 7 synthesis of polycalciumphenylsiloxane and composites based on the skeleton of a sea urchin with the resulting polymer nikolai p. shapkin * , irina g. khalchenko , kvan h. kim, evgeniy k. papynov , alexander n. fedorets, natalia v. maslova, michael i. balanov far eastern federal university, russky island, vladivostok 690922, russia * corresponding author: shapkin.np@dvfu.ru this paper belongs to the mosm2021 special issue. © 2022, the authors. this article is published in open access form under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). abstract in this work, we obtained polycalciumphenylsiloxane (pcps) by the interaction of calcium bis (acetylacetonate) with polyphenylsiloxane. the first method consisted in boiling the starting reagents in toluene for several hours; the second was as follows: the mixture of the starting reagents was preliminarily treated mechanically in a ball mill, followed by boiling in toluene for several hours. two fractions, soluble and insoluble, were isolated in both syntheses. they were investigated using ir, nmr spectroscopy, thermogravimetric analysis, and gel permeation chromatography. it was shown that the insoluble fraction is a mixture of calcium acetylacetonate and polyphenylsiloxane with a small calcium ion content. the soluble fraction is polycalciumphenylsiloxane. the yield of the soluble fraction is higher in the second synthesis method. the polymers obtained in the first and second synthesis methods are similar in composition and structure, which was confirmed by physicochemical methods. next, the skeleton of the sea urchin strongylocentrotus intermedius was treated with a soluble fraction in toluene. in this case, a composite was obtained, which was treated with 2–3% hydrochloric acid and then calcined at a temperature of 600 °c. at each stage, the composition of the composites was investigated using elemental analysis and ir spectroscopy. the morphology was investigated using scanning electron microscopy. keywords polyphenylsiloxane calcium acetylacetonate sea urchin skeleton mechanochemical activation received: 18.02.22 revised: 13.05.22 accepted: 01.06.22 available online: 14.06.22 1. introduction biomimetic systems, such as shells of mollusks, sea urchins, and sponges, are potentially attractive as templates containing calcium and magnesium for the production of nanobioceramics [1, 2]. significant interest has been drawn towards the combination of calcium-containing templates with polyorganosiloxanes based on trifunctional organosilicon fragments with high thermal and hydrolytic stability and a uniformly organized structure [3, 4]. at the same time, as was shown recently, biological objects containing calcium and magnesium are most promising for obtaining bioceramics based on the resulting wollastonite, forsterite [5]. organosiloxane oligomers upon hightemperature condensation gradually transform into inorganic silicates, retaining the original structure [6]. it is known [7, 8] that natural biominerals are organoinorganic composites with a well-developed calciumcontaining skeleton. the interpenetrating mineral composites of strongylocentrotus intermedius form the skeleton of structured calcium nanocrystals. taking into account the possibility of biomimetic application of the sea urchin skeleton for obtaining nanomaterials of a certain structure, the aim of this work was to synthesize policalciumphenylsiloxane based on calcium acetylacetonate and to obtain composites by the interaction of a soluble polymer with the skeleton of the sea urchin strongylocentrotus intermedius. 2. experimental toluene was distilled before synthesis. calcium chloride used was of reagent grade. acetylacetone was distilled in vacuum before synthesis. calcium bis-acetylacetonate was obtained by the method described elsewhere [9]. http://chimicatechnoacta.ru/ https://dx.doi.org/10.15826/chimtech.2022.9.2.s6 mailto:shapkin.np@dvfu.ru http://creativecommons.org/licenses/by/4.0/ https://orcid.org/0000-0002-4287-8917 https://orcid.org/0000-0002-5541-2200 https://orcid.org/0000-0002-1185-7718 https://crossmark.crossref.org/dialog/?doi=https://dx.doi.org/10.15826/chimtech.2022.9.2.s6&domain=pdf&date_stamp=2022-6-14 chimica techno acta 2022, vol. 9(2), no. 202292s6 article 2 of 7 2.1. synthesis of polyphenylsiloxane (pps) a solution of 100.75 g (0.5 mol) of phenyltrichlorosilane in 150 ml of sulfuric ether was added dropwise to a mixture of 150 ml of sulfuric ether and 250 ml of distilled water placed in a 1 l flask equipped with a mechanical stirrer and a reflux condenser. the synthesis was carried out with constant cooling of the flask to –20 °c and vigorous stirring for one hour. the organic ether layer was separated on a separating funnel, washed with distilled water until neutral, and dried over anhydrous sodium sulfate (20 g na2so4) for a day. ether was distilled off while heating the mixture in a water bath, and at the final stage, a rotary evaporator was used. the product was dried in a vacuum oven at 80 °c. a substance of the composition [с6н5sio1.5∙0.17н2о] n was obtained with a yield of 93.7%. found: si – 21.2%, c – 54.5%. 2.2. synthesis of polycalciumphenylsiloxane (method 1) a mixture of 2.58 g (0.1 mol) (с6н5siо1.5)n, calcium bisacetylacetonate and 100 ml of toluene was placed in a oneneck flask equipped with a reflux condenser and boiled for 12 h. a soluble fraction was isolated by filtration. 2.3. synthesis of polycalciumphenylsiloxane (method 2) the mechanochemical activation of the reagents was carried out in a planetary ball mill "рulverisette 6" at a frequency of 600 rpm for three minutes. the ratio of the packing weight to the payload weight was 1.8. pps weighing 2.58 g (0.01 mol) and (acac)2са) with a weight of 1.0 g (0.01 mol) were added to the activator. after mechanochemical activation, the entire reaction mixture was dissolved in dry toluene (100 ml) and boiled for 12 hours. the soluble fraction was precipitated with hexane (100 ml) from a solution in toluene. received a soluble fraction – pca(acac)ps (relative mass fraction 65.4%). elemental analysis data are presented in table 1. 2.4. synthesis of composites no. 1–3 composites 1–3 were obtained using the skeleton of the sea urchin strongylocentrotus intermedius. the composite no. 1 was obtained by interaction of the sea urchin skeleton with a soluble fraction of polymer 1.1 (method 1) by boiling for an hour in a toluene solution with the mass of the sea urchin skeleton to the mass of the polymer ratio of 1.0:0.1, followed by distilling off the solvent to 1/5 of the initial volume of the solution. solution was dried on a rotary evaporator at 80 °c and 100 torr. the solid fraction was filtered off and dried in air. the composite no. 2 was obtained by processing composite no. 1 in 2–3% hydrochloric acid until the emission of carbon dioxide stopped. the resulting product was washed with distilled water and dried in air to a constant weight. the composite no. 3 was obtained by calcining the composite no. 2 at a temperature of 600 °c for 30 min. infrared spectra of polymer samples were recorded on a spectrum-1000 spectrometer (perkin elmer) in kbr tablets. diffraction patterns were recorded on an advance-d8 device (bruker) using cu kα radiation in the angle range 20<2ө<900 in the point-by-point scanning mode. the maximum deviation of the reflection position, determined according to nist srm 1976, is less than 0.0102ө. gel chromatography was performed on a column with a diameter of d = 12 mm and a length of l = 1200 mm; gel carrier: cross-linked polystyrene 4% divinylbenzene, grain diameter 0.10–0.08 nm, free volume (v0) equal to 30 ml, fractions of the toluene solution were taken in 3 ml, determination of the polymer content was carried out by the gravimetric method with an accuracy of 0.1 mg. the column was calibrated using the following organosilicon compounds: octaphenylcyclosilsesquioxane, trimethyltriphenylcyclosiloxane, calcium acetylacetonate. nuclear magnetic resonance (nmr) spectra were recorded on an advance ii-400mhz high-resolution spectrometer (bruker, germany). solvents: deuterochloroform, dimethylsulfoxide. nmr spectra of solid samples were recorded on advance av-300 (mas ∙ nmr) "bruker" germany. scanning electron microscopy was performed using a tm3000 hitachi electron microscope (japan). sem images of the samples were obtained using a s-3400n hitachi scanning electron microscope (japan) and a carl zeiss crossbeam 1540xb with an oxford instruments x-max 80 energy dispersive detector (carl zeiss, germany). thermogravimetric analysis was performed on a dtg-60 h differential thermogravimetric analyzer. 3. results and discussion the interaction of calcium bis (acetylacetonate) with polyphenylsiloxane was carried out in two different ways. method 2 differed from method 1 by the use, in addition to boiling in toluene, of the preliminary mechanochemical treatment [10]. the interaction proceeded according to the equation: in both syntheses (1 and 2), two fractions were isolated – soluble (1.1 and 2.1) and insoluble (1.2 and 2.2). the elemental analysis of the fractions is shown in table 1. table 1 elemental analysis of soluble and insoluble fractions of syntheses 1 and 2. no. faction found, % calculated for gross formula, % с si ca c si ca gross formula 1.1 36.7 22.8 13.8 34.0 22.6 13.5 [(phsio1.5)1.4(sio2)1.0(cao)1.0]n 1.2 48.0 0.4 19.9 47.0 0.4 19.2 {[ca(o)0.5(acac)1.6]3.3(phsio1.5)}n 2.1 37.5 21.8 16.2 34.2 21.0 15.8 [(phsio1.5)1.2(sio2)0.7(cao)1.0]n 2.2 47.4 1.5 19.1 46.9 1.5 19.1 {[ca(o)0.5(acac)1.5]9(phsio1.5)}n chimica techno acta 2022, vol. 9(2), no. 202292s6 article 3 of 7 gel chromatography of soluble fractions 1.1 and 2.1 was carried out; the results were identical. it was shown that both fractions are high molecular weight compounds (figure 1). figure 1 gel permeation chromatography data for fraction 1.1. ir spectra were recorded for all fractions (figure 2). in the ir spectra of soluble fractions of syntheses 1 and 2, absorption bands of medium intensity are observed at 3627 cm–1, corresponding to stretching vibrations of the o – h bond at the silicon atom; a weak band at 3402 cm–1 corresponds to the vibrations of the o – h bond in coordinated molecules water. several bands at 3095, 3074, 3030, 3016, and 3006 cm–1 correspond to the vibrations of c–h bonds in aromatic radicals as well as the c–h bonds at the γ-carbon of chelate groups. the absorption bands at 1570 and 1631 cm–1 correspond to the stretching vibrations of the c=c and c=o bonds in the acetylacetonate ring; the absorption bands at 1431 and 1384 cm–1 correspond to the stretching vibrations of the c–c bond in the aromatic radical and in the chelate ring. intense bands were also observed at 1134, 1029, 999 cm–1, corresponding to stretching vibrations of ≡si–ph, ≡si–o–si≡ bonds, respectively; absorption bands at 495, 455 and 447 cm–1 correspond to deformation vibrations of bonds si–o and ca–o, respectively. such a set of absorption bands corresponds to the vibrations of bond groups found in typical polymetalorganylsiloxanes [10]. ir spectra of insoluble fractions of syntheses 1 and 2 are similar and contain the following absorption bands: at 3467, 3371, 3230 cm–1 – correspond to stretching vibrations of о–н bonds in coordinated water molecules; at 3074 and 2989, 2920 cm–1 – correspond to stretching vibrations of с–н bonds in the phenyl and chelate rings, respectively; at 1637, 1608 and 1519 cm–1 – correspond to stretching vibrations of c=o, c=c bonds in the acetylacetonate ring; at 1460 cm–1 and 1398 cm–1 – correspond to stretching vibrations of the c–c bond, respectively, in the phenyl and chelate rings; at 1016.918 cm–1 – correspond to vibrations of si–o bonds; at 445 and 424 cm–1 – correspond to vibrations of ca–o bonds in metallsiloxane [5] and in the chelate ring [11]. to establish the main structural fragments constituting the empirical formula of the polymers, 1h, 13c, 29si nmr spectra were recorded for all fractions and calcium bis (acetylacetonate) as a control sample. figure 2 ir spectra of fractions: 1.1(a), 1.2(b), 2.1(c), 2.2(d). chimica techno acta 2022, vol. 9(2), no. 202292s6 article 4 of 7 the 1h nmr spectrum of calcium bis (acetyacetonate) (figure 3a) contains a signal at 1.66 ppm, which corresponds to the chemical shift of the proton in the ch3 group, and a signal at 5.05 ppm, which corresponds to the chemical shift of the methine proton. the 13c nmr spectrum (figure 3b) contains signals at 28.38 ppm, 99.40 ppm, and 188.33 ppm, corresponding to carbon in the ch3 and γ-ch group, respectively. figure 3 nmr spectra of 1h (a), 13c (b) calcium bis-(acetylacetonate), solvent – dimethylsulfoxide. in the 1h nmr spectra of soluble fractions of syntheses 1 and 2 (figures 4a, 5a), there are signals in the region from 6 to 8 ppm, corresponding to the proton shift of the phenyl group located at the silicon atom, and signals of low intensity at 1.79 ppm and 5.1 ppm, corresponding to the protons of ch3 and ch groups. the region 2.29–2.5 ppm corresponds to protons of associated water and dmso. the 13c nmr spectrum of soluble fractions (figures 3b, 4b) of syntheses 1 and 2 contains signals in the range of 125.6–134 ppm, corresponding to the resonance of the carbon atoms of the phenyl group. the difference in the 13c spectra is observed for the soluble fraction of synthesis 2, where there are low-intensity signals of the carbon atoms of the acetylacetonate groups, which is associated with the high calcium content in this fraction (table 1), and, accordingly, a small part of the calcium atoms has chelating groups. to confirm the composition and structure of the soluble and insoluble fractions of the first synthesis, thermal destruction was investigated. the nature of the thermal destruction of ladder polyorganosiloxanes [2, 3] can determine the yield and composition of the products of the interaction of siloxanes with metal complexes. earlier in [12] it was shown that heating the products of the interaction of vanadium bis (acetylacetonate) with polyphenylsiloxane to 300 °c sharply increased the yield of the target product due to the removal of acetylacetonate groups and the formation of the –m–o–si≡ bond. the tg-dta curve of insoluble fraction 1.2 (figure 6) shows three exothermic effects at 290, 380, and 460 °c, the weight loss at which is 43%, while the mass of acetylacetonate groups in the gross formula (table 1) corresponds to 40%. the exo effect and loss of mass of the sample at a temperature of ~600 °c corresponds to the oxidation of phenyl groups. in this case, the sum of oxides by tga is 28%, which is close to the calculated sum of oxides according to the gross formula, 27.6%. figure 4 nmr spectra of 1h (a), 13c (b), 29si (c) fractions 1.1. chimica techno acta 2022, vol. 9(2), no. 202292s6 article 5 of 7 figure 5 nmr spectra of 1h (a), 13c (b), 29si (c) fractions 2.1. figure 6 tg and dta curves for the fraction 1.2. the dta plot of the soluble fraction (1.1) (figure 7) shows an exothermic effect at 625 °c, which corresponds to the abstraction and oxidation of phenyl groups in polycalcium-phenylsiloxane. it is known [13] that the siliconphenyl bond is destroyed at a temperature of 550–600 °c. the sum of oxides after 800 ° according to tga data for the soluble fraction 1.1 is 66.9%. according to the proposed empirical formula (table 1) the amount of oxides is 68.2%. the soluble fractions of both syntheses have an amorphous structure (figure 8a, b). the difference lies in the presence of an admixture of calcium acetylacetonate in the soluble fraction 1.1 of the first synthesis (figure 8a). figure 7 tg and dta curves for the fraction 1.1. figure 8 diffraction patterns of soluble fractions: 1.1 (a), 2.1 (b). chimica techno acta 2022, vol. 9(2), no. 202292s6 article 6 of 7 the composites 1–3 were obtained using the skeleton of the sea gray urchin strongylocentrotus intermedius and the soluble fractions 1.1 and 2.1. the ir spectrum of the composite no. 1 (figure 9a) shows absorption bands at 1410–1460 cm–1, which belong to the vibrations of the c=o bond in carbonate. these bands are absent in the starting polymer. the rest of the absorption bands are similar to the bands in the ir spectrum of the soluble fraction 2.1 (figure 2c). the composite no. 2 was obtained by treating composite no. 1 with 2–3% hydrochloric acid until the emission of carbon dioxide ceased. the ir spectrum of the composite no. 2 is similar to the ir spectrum of the soluble fraction 2.1 (figure 2c). the composite no. 3 was obtained by calcining the composite no. 2 at a temperature of 600 °c for 30 min. in the ir spectrum of the composite no. 3, absorption bands corresponding to the vibrations of c–h, c–c, c=o bonds disappear, and absorption bands remain at 1100–900 cm–1, 590 cm–1, 495 cm–1 (figure 9c). using scanning electron microscopy, the surface of the composites no. 1–3 was examined (figure 10). for the composite no. 1, a continuous polymer-coated surface is observed (figure 10a). after treatment with hydrochloric acid (figure 10b), the manifestation of an inverted structure is observed, which completely repeats the internal structure of the gray hedgehog [15]. after heating the composite no. 2 at 500–600 °c, the morphology changed dramatically and the structure of the skeleton, which was not completely dissolved by acid, appeared (figure 10c). figure 9 ir spectra of composites: no. 1 (a); no. 3 (b). figure 10 surface morphology of composites: no. 1 (a), no. 2 (b), no. 3 (c). the chemical composition of the surface film of the composites no. 1–3 was investigated using edx spectroscopy (table 2). in the composite no. 1, polycalciumphenylsiloxane formed a film on the surface of the hedgehog's skeleton, as evidenced by the disturbed ratio of silicon to calcium. thus, the skeleton “shines” through the film on the surface. after treatment with acid, an internal structure formed by polyalciumphenylsiloxane was opened (figure 10b), while calcium was also extracted from policalciumphenylsiloxane; that is, this structure consists mainly of polyphenylsiloxane with a small calcium content. after heating, the degradation of the organosilicon component chimica techno acta 2022, vol. 9(2), no. 202292s6 article 7 of 7 on the surface took place, and the remaining calcite skeleton of the hedgehog appeared, since the calcium content on the surface increased sharply. in this case, a calcium silicate film was formed. table 2 the chemical composition of the surface film of composites no. 1–3. no. composite the chemical composition of the surface film, % с si ca si/са 1 55.20 5.68 6.12 1.33 2 59.10 14.10 0.65 31.0 3 14.96 4.01 22.98 0.25 4. conclusion the reaction of calcium bis (acetylacetonate) with polyphenylsiloxane yielded soluble polycalciumphenylsiloxane, the composition and structure of which was confirmed by ir, nmr, gpc data, which does not differ from those for the known metallosiloxanes obtained under similar conditions. the skeleton of the sea urchin was treated with a soluble fraction of polycalciumphenylsiloxane and the composite no. 1 was obtained, which had a filled skeleton space on the surface and inside. after the treatment with hydrochloric acid of the composite no. 1, a threedimensional polymer structure was obtained, which is an inverted internal structure of a hedgehog stereome. after calcination, the three-dimensional polymer structure is destroyed, forming calcium silicate on the surface. supplementary materials no supplementary materials are available. funding this research had no external funding. acknowledgments none. author contributions conceptualization: n.p.s. data curation: e.k.p. investigation: n.p.s., k.h.k., a.n.f. project administration: m.i.b. writing – original draft: n.v.m. writing – review & editing: i.g.k. conflict of interest the authors declare no conflict of interest. additional information author ids: nikolay p. shapkin, scopus id 6603925928; irina g. khalchenko, scopus id 57193719438; evgeniy k. papynov, scopus id 35096586600; alexander n. fedorets, scopus id 55513334500; natalia v. maslova, scopus id 57218705146; michael i. balanov, scopus id 24331073600. website: far eastern federal university, https://www.dvfu.ru/en/. references 1. coradin t, lopes pj. biogenic silica patterning: simple chemistry or subtle biology? chembiochem. 2003;3:1–9. doi:10.1002/cbic.200390044 2. sanchez c, arribart h, madeleine gg. biomimetism and bioinspiration as tools for the design of innovative materials and systems. nature mater. 2005;4:277–288. doi:10.1038/nmat1339 3. michalczyk mj, farneth we, vega аj. high temperature stabilization of crosslinked siloxanes glasses. chem mater. 1993;5(12):1687–1689. doi:10.1021/cm00036a001 4. eguchi k, zank ga. silicon oxycarbide glasses derived from polymer precursors. j sol-gel sci technol. 1998;13:945–949. doi:10.1023/a:1008639727164 5. choudhary r, kumar venkatraman s, bulygina i, senatov f, kaloshkin s, anisimova n, kisilevskiy m, knyazeva m, kukui d, walther f, swamiappan s. biomineralization, dissolution and cellular studies of silicate bioceramics prepared from eggshell and rice husk. mater sci eng c. 2021;118:111456. doi:10.1016/j.msec.2020.111456 6. levitsky mm, zavin bg, bilyachenko an. chemistry of metallasiloxanes. current trends and new concepts. russ chem rev. 2007;76(9):907–926. doi:10.1070/rc2007v076n09abeh003691 7. prockop dj, fertala a. the collagen fibril: the almost crystalline structure. j struct biol. 1998;122:111–118. doi:10.1006/jsbi.1998.3976 8. erlich h, brunner е, simon р et al. calcite reinforced silica– silica joints in the biocomposite skeleton of deep-sea glass sponges. adv funсt mater. 2011;21:3473–3481. doi:10.1002/adfm.201100749 9. kuzmina np, chechernikova mv, martynenko li. calcium acetylacetonates. j inorg chem. 1990;35(11):2776–2780. 10. shapkin np, kapustina aa, dombai nv, libanov vv, khalchenko ig, gardionov sv, gribova vv. synthesis and physicochemical characteristics of polymolybdenum(vi) phenylsiloxanes by means of different methods. polym bull. 2020;77(3):1177–1190. doi:10.1007/s00289-019-02790-3 11. morozova nb, zharkova gi et al. synthesis and physicalchemical study of β-diketonates of alkaline earth metals. novosibirsk; 1989. 28 p. 12. shapkin np, kapustina aa, gardionov sv, khalchenko ig, libanov vv, tokar ea. studies of interaction of polyphenylsiloxane with vanadyl bis-acetylacetonate. silicon. 2019;11(5):2261–2266. doi:10.1007/s12633-017-9551-z 13. berman a, addadi l, kvick å, leiserowitz l, nelson m, weiner s. intercalation of sea urchin proteins in calcite: study of a crystalline composite material. sci. 1990;250:664–667. doi:10.1126/science.250.4981.664 14. seto j, ma y, davis s et al. structure-property relationships of a biological mesocrystal in the adult sea urchin spine. proc nat acad sci. 2012;109:3699–3704. doi:10.1073/pnas.1109243109 15. shapkin np, papynov ek, panasenko ae, khalchenko ig, mayorov vyu, drozdov al, maslova nv, buravlev iyu. synthesis of porous biomimetic composites: a sea urchin skeleton used as a template. appl sci. 2021;11;19:8897. doi:10.3390/app11198897 https://www.scopus.com/authid/detail.uri?authorid=6603925928 https://www.scopus.com/authid/detail.uri?authorid=57193719438 https://www.scopus.com/authid/detail.uri?authorid=35096586600 https://www.scopus.com/authid/detail.uri?authorid=55513334500 https://www.scopus.com/authid/detail.uri?authorid=57218705146 https://www.scopus.com/authid/detail.uri?authorid=24331073600 https://www.dvfu.ru/en/ http://dx.doi.org/10.1002/cbic.200390044 https://doi.org/10.1038/nmat1339 http://dx.doi.org/10.1021/cm00036a001 https://doi.org/10.1023/a:1008639727164 https://doi.org/10.1016/j.msec.2020.111456 https://doi.org/10.1070/rc2007v076n09abeh003691 https://doi.org/10.1006/jsbi.1998.3976 https://doi.org/10.1002/adfm.201100749 https://doi.org/10.1007/s00289-019-02790-3 https://doi.org/10.1007/s12633-017-9551-z https://doi.org/10.1126/science.250.4981.664 https://doi.org/10.1073/pnas.1109243109 https://doi.org/10.3390/app11198897 obtaining cyclopentanone in the presence of metal oxides chimica techno acta letter published by ural federal university 2021, vol. 8(4), № 20218410 eissn 2411-1414; chimicatechnoacta.ru doi: 10.15826/chimtech.2021.8.4.10 1 of 4 obtaining cyclopentanone in the presence of metal oxides i.v. tsvetkova * , a.a. golovanov, a.a. kondrateva, n.v. chirkunova togliatti state university, 445020 belorusskaya st., 14b, togliatti, russia * corresponding author: irina.cvetkova.56@mail.ru this short communication (letter) belongs to the mosm2021 special issue. © 2021, the authors. this article is published in open access form under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). abstract the possibility of obtaining cyclopentanone by pyrolysis of calcium adipate at different temperatures was considered. the pyrolysis proceeded with the formation of cyclopentanone and cyclopentene. the use of metal salts and metal oxide catalysts for the dehydrogenation of lower alkanes makes it possible to increase the yields of the target products. the best results were achieved in the presence of a «k-16u» catalyst. keywords adipic acid pyrolysis cyclopentanone cyclopentene catalysts metal oxides received: 01.12.2021 revised: 13.12.2021 accepted: 14.12.2021 available online: 15.12.2021 1. introduction in the period of development of the chemical and petrochemical industry, the main tasks are deep conversion, maximum use of feedstocks, and waste disposal. the problem of the impact of the chemical industry byproducts on the environment is being solved by the development of new technologies and advanced waste processing. water-acid effluents are formed in the process of obtaining caprolactam after isolation of the target product by washing the reaction mixture with water. generally, incineration is used for the disposal of these effluents. however, they contain large amounts of oxygencontaining by-products. one of these compounds is adipic acid – a promising raw material for the production of cyclopentanone and other valuable monomers [1]. the content of adipic acid in water-acid effluents is significant. theoretically, with a capacity of 100 thousand tons per year, 200–300 tons of adipic acid can be obtained. earlier, the possibility of obtaining cyclopentanone from byproducts of caprolactam production by pyrolysis of calcium salts of adipic acid was shown. the thermal stability study of calcium adipate using a shimadzu dtg60/60h derivatograph was carried out. its decomposition temperature was 400 °c [2]. in this work, we study the thermal decomposition of adipic acid salts in the presence of metal oxides. the raw material is adipic acid, isolated from the water-acid effluent of the caprolactam production. this work is aimed at improving the method for cyclopentanone production on the basis of water-acid effluents, studying the dependence of the yield of cyclopentanone on the process conditions, and investigating the possibility of using metal oxides as process catalysts. 2. experimental the pyrolysis was carried out in an electric furnace using a quartz reactor at different temperatures (from 400 to 600 °c) and a contact time of 2 hours. the masses calcium adipate samples were from 1.5 to 3.0 g. a refrigerator was attached to a quartz test tube, distillation adapter. a conical flask was used to collect the resulting product. over time, a liquid product with a characteristic odor formed in the flask; the color of the liquid changed from light yellow to light brown, depending on the pyrolysis temperature. the analysis of the obtained liquids composition was carried out using a kristallux 4000m chromatograph with a flame ionization detector (capillary column, helium carrier gas, quartz, db-wax (peg), 30 m/0.32 mm/0.5 m). calcium adipate pyrolysis can proceed in two directions – with the formation of cyclopentanone and cyclopentene (fig. 1). the composition of the resulting product included these compounds [3]. fig. 1 two directions of pyrolysis of calcium adipate http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2021.8.4.10 https://orcid.org/0000-0002-5945-2015 http://creativecommons.org/licenses/by/4.0/ chimica techno acta 2021, vol. 8(4), № 20218410 letter 2 of 4 for the identification of retention times, pure substances were introduced into the chromatograph. cyclopentene was synthesized by acid dehydration of cyclopentanol. cyclopentanol was obtained by reduction of cyclopentanone with sodium borohydride (fig. 2) [4]. fig. 2 cyclopentene synthesis the quantitative chemical analysis of calcium adipate was carried out using an edx-8000 energy dispersive xray fluorescence spectrometer (x-ray tube – rh anode, silicon drift detector); the results are presented in table 1. table 1 the results of x-ray fluorescence analysis of calcium adipate analyte ca na mg k s zn cu cl result, wt.% 46.60 8.10 0.20 0.10 0.10 0.05 0.02 0.01 3. results and discussion the chromatograms of the samples obtained at 500 and 600 °c are shown in fig. 3. the chromatograms of cyclopentanone and cyclopentene are shown in fig. 4. the difference between the retention times of pure substances and the obtained samples is due to the presence of impurities in the technical products. fig. 3 chromatograms of a liquid product obtained at 500 and 600 °c fig. 4 chromatograms of pure cyclopentanone and cyclopentene based on the results of x-ray fluorescence analysis, calcium phosphate and zinc chloride were chosen to study the possibility of using metal salts as catalysts for the process. the chromatograms of the products obtained during pyrolysis are shown in fig. 5 and fig. 6. the results obtained in the presence of zinc chloride suggest that it is possible to use dehydrogenation catalysts (twoand three-component mixtures of metal oxides). the «k-16u» and «im-2201» catalysts were tested. the «k-16u» catalyst can be represented by the formula fe2o3cr2o3zno2. it is used in the dehydrogenation of butylenes and isoamylenes [5]. the chromatograms of liquid products obtained using the «k-16u» catalyst at temperatures of 500 and 600 °c are shown in fig. 7. fig. 5 chromatogram of the product obtained at 500 °c in the presence of calcium phosphate chimica techno acta 2021, vol. 8(4), № 20218410 letter 3 of 4 fig. 6 chromatograms of the product obtained at 500 and 600 °c in the presence of zinc chloride fig. 7 chromatograms of the product obtained at 500 and 600 °c in the presence of «k-16u» catalyst the «im-2201» catalyst is a chromium-alumina catalyst (al2o3cr2o3), using for the dehydrogenation of butane, isopentane and isobutane. the chromatograms of liquid products obtained using the «im-2201» catalyst at temperatures of 500 and 600 °c are shown in fig. 8. fig. 8 chromatograms of the product obtained at 500 and 600 °c in the presence of the «im-2201» catalyst a comparison of the results of pyrolysis of calcium adipate in the presence of catalysts is shown in table 2. the dependence of the cyclopentanone yield on the catalyst is shown in fig. 9. table 2 comparison of the results of pyrolysis of calcium adipate in the presence of catalysts catalyst № process conditions cyclopentanone yield, wt.% t, h t, °c without catalyst 1 2 600 16.81 «к-16u» (fe2o3cr2o3zno2) 2 2 500 34.14 3 2 600 51.62 4 2 700 42.05 zncl2 5 2 500 23.70 6 2 600 29.27 «im-2201» (al2o3cr2o3) 7 2 500 4.99 8 2 600 24.56 ca3(po4)2 9 2 500 17.88 fig. 9 the dependence of the cyclopentanone yield on the catalyst see table 2 chimica techno acta 2021, vol. 8(4), № 20218410 letter 4 of 4 4. conclusion according to the results of pyrolysis of calcium adipate in the presence of oxides and metal salts, it was found that the highest product yield is achieved using the «k-16u» catalyst for the dehydrogenation process. in addition to cyclopentanone, cyclopentene is formed. its maximum yield is reached at 500 ℃. the developed method of pyrolysis of calcium adipate can be used to obtain valuable substances for organic synthesis – cyclopentanone and cyclopentene. references 1. kisil im, preobrazhensky va, zolin vs, gorodetskaya ni, davydov yui, polikarpov av, salomykov vi. method of utilization of acidic wastewater of caprolactam production: pat. 2039740 rus. federation. 93009600/04; declared 02.24.1993; publ. 07.20.1995 2. tsvetkova iv, golovanov aa, reznikova ns, chirkunova nv. obtaining cyclopentanone from acidic wastewater of caprolactam production. chimica techno acta. 2020;7(4):177–179. doi:10.15826/chimtech.2020.7.4.07 3. sokolova aa, glazko il, martynenko ea. isolation of adipic acid from aqueous acid effluents of caprolactam production. bulletin of mitht of m.v. lomonosov. 2013;6:78–71 4. kogay ti, vasileva nu. synthesis, purification and identification of organic compounds: guidelines. krasnoyarsk: krasnoyarsk state university, 2005. 90p. russian. 5. kirpichnikov pa, liakumovich ag, pobedimskiy dg, popova lm. chemistry and technology of monomers for synthetic rubbers. leningrad: chimiya, 1981. 264 p. russian. https://doi.org/10.15826/chimtech.2020.7.4.07 borated graphite cathodes for low-temperature aluminum electrolysis chimica techno acta article published by ural federal university 2022, vol. 9(2), no. 20229208 eissn 2411-1414; chimicatechnoacta.ru doi: 10.15826/chimtech.2022.9.2.08 1 of 9 borated graphite cathodes for low-temperature aluminum electrolysis rudenko a.v. a* , kataev a.a. a , neupokoeva m.m. ab, tkacheva o.yu. ab a: institute of high temperature electrochemistry, ural brunch of russian academy of sciences, ekaterinburg 620137, russia b: ural federal university named after the first president of russia b.n. yeltsin, ekaterinburg 620002, russia * corresponding author: a.rudenko@ihte.uran.ru this paper belongs to a regular issue. © 2022, the authors. this article is published in open access form under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). abstract electrochemical boriding of the graphite plates in the potassium cryolite based electrolytes was studied. the boriding were carried out in a cell with vertical electrodes. the procedure included 2 stages: 1) electrolysis in the kf–alf3–kbf4 melt (cr=1.3) at low current density (0.01–0.02 a/cm2), required for the boron reduction, at 700 and 750 °c; 2) electrolysis in the kf–alf3–al2o3 melt at higher current density (0.2 a/cm2), required for the aluminum reduction. the optimal conditions of electrodeposition for obtaining the borated wettable cathodes were determined. according to the sem data, a continuous alb2 layer with a thickness of 7–10 μm was formed on the graphite surface. the borated graphite was tested as a wetted cathode during the low-temperature aluminum electrolysis. prolonged electrolysis in a vertical cell with the graphite anode and the borated graphite cathode was carried out in the kf–naf(10 wt.%)–alf3–al2o3 electrolyte (cr=1.5) at 830 °c. after 100 h of electrolysis, the thickness of the alb2 layer on the graphite surface was 5 μm, while the cathode surface was completely wetted with aluminum. thus, we demonstrated the feasibility of using the borated graphite cathode as a wettable dripping cathode in the low-temperature aluminum electrolysis in the vertical cell. keywords graphite cathode boriding cryolite electrolysis received: 04.04.22 revised: 17.05.22 accepted: 17.05.22 available online: 26.05.22 1. introduction nowadays, almost all primary aluminum is obtained by the heroult-hall process, which has not undergone any fundamental changes during more than 100 years [1]. the technology consists in the electrolytic decomposition of alumina dissolved in sodium cryolite (na3alf6 with additions of alf3, caf2, etc.) at 940–970 °c. it is worth noting that aluminum production is an extremely energy-consumption process: the cost of electricity is more than 30%. the process is accompanied by the consumping of carbon anodes and the emission of a significant amount of harmful gases (co, co2 and freons) that create a greenhouse effect [2, 3]. a radical modification of the heroult-hall process is possible by replacing consumable carbon anodes with non-consumable inert anodes [4]. however, as of now, there is no information regarding the successful application of inert anodes in conventional technology. the main reason for this is the aggressiveness of the cryolite-alumina melt at high temperatures. to prevent fast corrosive destruction of structural materials, it is necessary to reduce the operating temperature of the process. in this regard, it becomes necessary to create and develop a new technology for low-temperature aluminum electrolysis. its main advantages would be energy saving, a significant reduction in greenhouse gas emissions and an increase of the cell life. in addition, the solubility of metallic aluminum in the molten electrolyte decreases with reducing temperature [5], which will lead to an increase in the current efficiency. attempts to develop a low-temperature process for producing aluminum were focused on modifying the conventional electrolyte based on sodium cryolite: lowering the temperature was achieved mainly by increasing the aluminum fluoride content. however, due to the low solubility of alumina in such melts, they have not found application in the industry. http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2022.9.2.08 mailto:a.rudenko@ihte.uran.ru http://creativecommons.org/licenses/by/4.0/ https://orcid.org/0000-0003-0439-5516 https://orcid.org/0000-0002-2157-2484 https://orcid.org/0000-0001-5451-2915 https://crossmark.crossref.org/dialog/?doi=https://doi.org/10.15826/chimtech.2022.9.2.08&domain=pdf&date_stamp=2022-5-26 chimica techno acta 2022, vol. 9(2), no. 20229208 article 2 of 9 another way of solving the problem is using an electrolyte based on potassium cryolite. the physicochemical properties of such melts are well studied [6–8]. the kf–alf3 mixtures with cryolite (molar) ratio (cr) (cr=x(kf)/x(alf3)) from 1.3 to 1.5 have a liquidus temperature below 800 °c and the solubility of alumina that is higher than in the sodium system. the low-temperature electrolysis in electrolytes, the main component of which is potassium cryolite, was demonstrated by several researchers [9–13]. in the low-temperature aluminum electrolysis inert anodes are used instead of graphite anodes. the inert anodes must meet certain requirements: low solubility in cryolite melts, high electrical conductivity, easy machining, and low cost. the metal anodes fulfill all requirements and are, therefore, the subject of special attention. as a rule, the composition of the material for inert metal anodes is based on the cu–al or cu–fe–ni alloys [14–17]. the low-temperature electrolysis with inert anodes requires a new operation system of the electrolytic process and a new cell design, specifically, the use of cells with vertically arranged electrodes. such design, according to preliminary calculations, will reduce energy consumption by 25%, increase the current efficiency, while maintaining a high density current, and reduce the cell size [17, 18]. beck [9, 18] carried out the long-term (300 h) electrolysis in the kf–alf3 molten eutectic and the kf–alf3 and naf–alf3; the temperature varied from 700 to 850 °c. although al2o3 was added in an amount of 10 wt.%, the actual concentration of dissolved alumina was about 4 wt.% (as follows from the figures of report [18]). the 10, 200 and 300 a cells were equipped with the cu–ni–fe anodes and the tib2 cathodes. it was reported that current efficiency reached 95%, and the purity of aluminum was 99.5% in 200-ampere cell. the electrolysis in the (45wt%)kf–alf3–(5wt%)al2o3 melt with cr=1.3 was successfully performed at 700 and 750 °с in the 10, 20 and 100 and 1000 a vertical cells [10, 11]. aluminum bronze was served as the anode, and the tib2–c composite was used as the cathode. the same electrolyte composition was used in electrolysis tests in a cell with the cu–ni–fe inert anodes at 700 °c [15]. however, in addition to the issues concerning corrosion-resistant material for inert anodes, the composition of low-melting electrolyte, etc., the necessity in the material of vertical cathodes with good wettability and corrosion resistance in fluoride melts arises. in addition, several researchers have noted the problem of cathode passivation during low-temperature electrolysis [19–21]. the cathode material should be thermally and chemically stable under electrolysis conditions, but, perhaps, the most important requirement is a good wettability of the cathode surface by the liquid aluminum [22]. it is known that the titanium diboride is the best material for a wetted cathode. cathodes made of tib2 or tib2–c composite are well suited for a vertical cell design. brown [23] investigated materials tib2–b4c, tib2–bn, tib2–tic under electrolysis conditions. the cathodes were prepared using different techniques. the performance of the cathode material was evaluated by the values of current efficiency compared to commercial hp tib2. it was found that no one material has performed better than tib2. however, it should be noted that the tib2 is very difficult to machine, and its cost is also high. therefore, the search for new materials for wettable cathodes for the lowtemperature aluminum electrolysis remains an urgent task. the electrolytic methods of applying a boride coating on cathodes for the electrolytic aluminum production, including the electrodeposition of boron and titanium in the form of titanium diboride on graphite and other materials, were described in [24, 25]. the electrodeposition was performed in fluoride and chloride-fluoride melts at 650–710 °с, using the k2tif6 and kbf4 salts as sources of titanium and boron. the resulting coatings were characterized by a good adhesion to the cathode and relatively high erosion and chemical resistance in molten salts. the electrochemical boriding of steel in a borax-based molten electrolyte at 950 °c was considered in works [26, 27]. it was described that this process yielded a very dense, uniform, and hard boride layer. the authors [28] studied the electrochemical behavior of boron in a melt kbf4–lif–naf–kf at 700 °c and found that boron interacts with the surface of the working electrode, which was glassy carbon, platinum, or silver. ray [29] discovered that small additions of tio2 and b2o3 to the cryolite-based melt (na3alf6–al2o3–caf2) at about 1000 °с increase the wettability of the graphite electrode by molten aluminum due to formation of al–ti or al–b alloys on the graphite surface. moreover, the al–b alloy improves the wettability of graphite more efficiently. the authors [30] compared the wettability of borated steel and hot pressed tib2 in terms of the wetting angle. a sample of borated steel was obtained in two stages: first, by boriding steel in a borax melt; then aluminizing was carried out by the thermal diffusion saturation. they found that the borated steel was wetted better by the liquid al than the tib2. however, it was noticed that the properties of tib2 largely depend on the preparation technique. kataev [31] found that during electrolysis in the kf– alf3–b2o3 melt at 700 °c in cells with graphite electrodes a layer of the alb2 intermetallic compound was formed on the surface of graphite cathode, which significantly improved the wettability of c-cathode with liquid aluminum. thus, it can be concluded that borated graphite, probably, surpasses even titanium diboride in wettability with the liquid aluminum, and the boron coatings on graphite can be obtained by electrolysis of molten salts. the objectives of this work were: (i) to determine the operating parameters for obtaining a boride coating on graphite cathode by electrolysis in the kf–alf3–kbf4 melt; (ii) to test a wetted cathode in a cell with vertically arranged electrodes during the low-temperature aluminum electrolysis. chimica techno acta 2022, vol. 9(2), no. 20229208 article 3 of 9 2. experimental 2.1. chemicals the melts were prepared from the reagent-grade naf, kf·hf, alf3(99%), kbf4 (99%), al2o3 supplied by vekton ltd (russia). the kf–alf3–kbf4 melt was used as a medium for the electrochemical boriding. the kf–alf3 electrolyte with a cryolite ratio (cr=x(kf)/x(alf3)) of 1.3 was obtained by mixing the kf·hf and alf3 salts (in a glassy carbon container). the mixture was exposed to 750 °c over 4 h in order to remove the hf from the melt due to the thermal decomposition of the kf·hf. the electrolyte preparation process is described in detail elsewhere [8]. the amount of “o” in the prepared electrolyte was determined by the carbothermal reduction technique using an oxygen analyzer leco tc836. it was found that the original electrolyte contained 0.6 wt.% “o”, which corresponds to 1.25 wt.% al2o3. the molten mixture kf–naf(10 wt.%)–alf3 with cr=1.5 (cr=(xkf + xnaf)/xalf3) was used for prolonged 100 h electrolysis in order to test efficiency of the borated graphite cathode. the kf–alf3–kbf4 electrolyte was chosen for boriding because it has a significantly lower liquidus temperature than the kf–naf(10 wt.%) –alf3 molten mixture [7]. this provided a low operating temperature and, consequently, a lower degree of the thermal decomposition of kbf4 with the release of gaseous bf3. in addition, it is known [32, 33] that nabf4 is more susceptible to the thermal decomposition than kbf4; that is, the presence of naf in the electrolyte is undesirable. on the other hand, the electrolyte kf–naf(10 wt.%)– alf3 was recommended for the low-temperature electrolysis because it has a higher alumina solubility [7]. it should be noted that the operating temperature of electrolysis in this electrolyte is higher than 800 °c; however there is no so-called “sodium problem” associated with the accumulation of naf, which enters the electrolyte as an alumina impurity, and is accompanied by a significant increase in the operating temperature [7]. 2.2. electrochemical cell boriding the graphite cathode as well as testing a wettable cathode under electrolysis conditions was carried out in the vertical cell. the procedures for these processes have some differences, as will be indicated below. however, the design of the cell remained the same. a schematic diagram of the electrochemical cell is presented in figure 1. dense graphite served as the anode. graphite or borated graphite was used as the cathode. the anode-cathode distance was 20 mm. the dimensions of the electrodes were 20x70x8 mm. the electrodes were not completely immersed in the melt, but to a depth of 75 mm. the current density was calculated on the surface area facing the anode. for reliable electrical contact the current leads (steel) were screwed into the threaded electrodes. the current leads were protected from interaction with the atmosphere by alumina cases. the salt mixture (about 400 g) was placed into the alumina crucible (v=600 ml). the alumina powder was filled between the crucible and the container. the experiments were carried out in an open cell in ambient air. figure 1 schematic diagram of an electrochemical cell: 1 – protective alumina container; 2 – alumina backfill; 3 – alumina crucible; 4 – cathode;5 – electrolyte; 6 – liquid aluminum; 7 – pt/pt–rh thermocouple; 8 – carbon anode; 9 – two tungsten quasireference electrodes in alumina case. the temperature of the cell was measured by pt–pt/rh thermocouple using an appa 109n multimeter. the potential between the anode, the cathode and w quasi-reference electrodes was measured and recorded using an appa 109n multimeter. the electrolysis was performed with the help of an autolab pgstat 302 with a bstr20a booster. 2.3. boriding a boride coating on a graphite cathode was obtained by electrolysis in the kf–alf3–kbf4 melt. it was evaluated in [33] that in the potassium cryolite melt with the addition of 15 mol.% kbf4 the loss of boron due to the thermal decomposition does not exceed 3% in the temperature range of 400–800 °c. however, taking into account the possible low boron current efficiency, the addition of kbf4 was made in excess. the kbf4 component was added to the kf–alf3 electrolyte in amount of 0.5 wt.%, that ten times exceeded the calculated value for the formation of alb2 layer (10 m) at the boron current efficiency of 100%. it should be noted that the boron concentration in the electrolyte during boriding was not analyzed. the current density was 0.01 and 0.02 a/cm2, and temperature was varied from 700 to 750 °c. the choice of such a low current density was based on the results of the work [31]. the authors determined the operating paramechimica techno acta 2022, vol. 9(2), no. 20229208 article 4 of 9 ters for the production of al–b alloy by electrolytic reduction of b2o3 in the kf–alf3–al2o3 melt: the initial current density was 0.02 a/cm2 at 700 °c. in order to identify the boride layer by scanning electron microscope (sem) the electrolysis process was continued at a higher current density. the alumina in amount of 3 wt.% was added to the electrolyte. an aluminum layer on top of the boron facilitated the determination of the presence and thickness of the boron on graphite against the background of aluminum. cross-section of the borated cathode was analyzed using the sem with nitrogen-free energy dispersive detector x-act add+jsm5900lv supplied with a wave dispersive micro analyzer, sluice chamber and a device for suppression of electromagnetic interference inca energy 250 and inca wave 500. 2.4. electrolysis test the borated cathodes were tested under the conditions of the low-temperature aluminum electrolysis in the kf–naf(10 wt.%)–alf3–al2o3 melt with cr = 1.5. the anode was graphite. as it was consumed, the anode was replaced with a new one. electrolysis parameters were as follows: current density i = 0.2 a/cm2, temperature 830 °c. the current density was chosen based on the results of work [34], in which it was recommended not to increase the cathode current density above 0.35–0.5 a/cm2 in order to avoid the formation of solid deposits on the cathode. as indicated by the authors, at the current density of 0.2 a/cm2, the current efficiency in the vertical cell was about 67%. thus, in the present work the amount of added al2o3 during electrolysis was calculated assuming 60% current efficiency in order to maintain the al2o3 concentration in the electrolyte at 2–3 wt.%. during electrolysis, liquid aluminum drips from the cathode and forms a pool at the bottom of the cell (figure 1). the potential differences between the cathode and the w quasireference electrode and between the anode and the w quasi-reference electrode were measured during electrolysis. they were used only to identify possible malfunctions of either the anode or the cathode. 3. results and discussion 3.1. boriding the graphite cathode a wettable coating on the graphite cathode was obtained by electrolysis in the kf–alf3–kbf4 melt. the current density and operating temperature were varied. according to the data [35], the boron may be electrochemically deposited from the cryolite-based electrolyte (na3alf6 + 1 wt.% al2o3 + 0.2 wt.% b2o3, 1050 °c) at lower voltage that that required for the aluminum reduction. the difference between the reduction potentials is reported to be about 0.6 v. the authors [36] recommend performing the boron electrodeposition in the kf–alf3–al2o3– b2o3 (cr=1.3) melt at potentials 0.6 v more positive than the aluminum reduction potential (at 750 °с). since there is a small amount of oxygen ions in the original electrolyte (as stated above), the oxidation process of the oxygen-containing ions occurs at the graphite anode with the formation of co2. considering that boron is in the ionic melt in the form of a complex anion bf4– [37], the cathode process can be described by the following equation: bf4– + 3e = b + 4f–– (1) during the deposition of aluminum, the interaction of al and b with the formation of intermetallic compounds (alb2, alb12) can occur [38]. according to the al–b phase diagram, at a temperature of about 750 °с, it is possible to obtain al–b alloys containing at least 0.09% boron. thus, the process of obtaining a wettable cathode took place in 2 stages. stage 1: the objective of the first stage was to obtain a boron coating on the graphite cathode. the electrolysis in the kf–alf3–kbf4 melt with cr=1.3 was carried out in a galvanostatic mode at low current densities required for boron reduction at 700 and 750 °с. the electrolysis time was varied, while the charge in all experiments remained constant and equal to 0.6 c. stage 2: the goal of the second stage was to deposit the aluminum at the cathode in order to obtain an aluminumboron coating. the electrolysis in the kf–alf3–al2o3 cr=1.3 melt was carried out in a galvanostatic mode at higher current densities required for the production of aluminum. the duration and current density in all experiments were the same. the parameters of two-staged electrolysis are summarized in table 1. four series of experiments were carried out. in each series, the electrolysis proceeded stably, the voltage was constant both at the first and at the second stages of electrolysis (figure 2). the images of the coating obtained on graphite in exp.1 with i = 0.02 a/cm2 at 700 °с and the boron distribution map in the aluminum matrix are given in figure 3. the boron is represented in red. the thickness of the al layer was 800 μm. a continuous boron layer, 7–10 μm thick, was formed on the graphite surface. the enlarged spectrum shown in figure 3b indicates that in the dark areas (spectrum 1, 3, 7, 9) the b content was about 63 at.% and the al content was about 33 at.%, which corresponds to alb2. the grain size of alb2 was 3–5 μm. table 1 parameters of two-stage electrolysis for obtaining boride coating on graphite. parameters stage 1 stage 2 exp.1 exp.2 exp. 3 exp.4 electrolyte kf–alf3–kbf4, cr=1.3 kf–alf3–al2o3, cr=1.3 addition kbf4 0.5 wt.% al2o3 3 wt.% temperature, °c 700 700 750 750 700–750 current density, a/cm2 0.02 0.01 0.02 0.01 0.2 duration, h 3 6 3 6 3 chimica techno acta 2022, vol. 9(2), no. 20229208 article 5 of 9 figure 2 voltage in two-stage electrolysis: 1 – exp.1; 2 – exp.2; 3 – exp.3; 4 – exp. 4 (table 1). figure 3 image of the aluminum layer and the boron distribution map obtained in exp. 1 (a); enlarged area of the image (a) (yellow square). in exp.2 under the same conditions, but with a decrease in current density and an increase in duration by a factor of 2, the boron distribution changed (figure 4), while the thickness of the al layer remained the same (800 µm). the boron was distributed uniformly over the thickness of the aluminum layer; however, no continuous uniform boron layer covering the graphite surface was found. with an increase in the electrolysis temperature to 750 °c and at i = 0.02 and 0.01 a/cm2 (exps. 3 and 4), the boron is almost absent from the aluminum layer (figure 5). the thickness of the aluminum layer on graphite is 600 and 370 μm, respectively. for testing the coating cathodes under conditions of prolonged electrolysis, the cathode obtained in exp. 1 was chosen. it had the thickest aluminum layer and uniform boride coating on the graphite surface. figure 4 image of the aluminum layer and the boron distribution map obtained in exp. 2. figure 5 images of the aluminum layer and the boron distribution map obtained at 750 °c at the current density of 0.02 (a) and 0.01 (b) a/cm2. thus, a twofold decrease in the current density at the same temperature leads to a more uniform distribution of the intermetallic compound alb2 over the thickness of the aluminum coating. an increase in temperature by 50 °c under the given electrolysis conditions prevents the formation of boride coatings on the graphite surface. it should be noted that for all the parameters of the two-stage electrolysis, the aluminum formed in the second stage wetted well and was evenly distributed over the surface of the graphite cathode. the only differences were that, depending on the electrolysis parameters applied, the thickness of the aluminum layer, the uniformity of the boron distribution in the aluminum layer and its amount changed. for comparison, uncoated graphite was used as the cathode in the vertical cell. the electrolysis was carried out for 50 h. the photos of the graphite cathode before and after electrolysis are shown in figure 6. the cathode was covered with aluminum droplets, indicating that the graphite surface was not wetted by the al metal. 0.0 0.5 1.0 1.5 2.0 2.5 3.0 0 2 4 6 8 10 v o lt a g e , v duration, h 21 43 (a) (b) (a) (b) chimica techno acta 2022, vol. 9(2), no. 20229208 article 6 of 9 figure 6 uncoated graphite cathode before and after aluminum electrolysis in vertical cell. 3.2. test of wettable cathode during the aluminum electrolysis the test of the borated graphite cathode were carried out in the kf–naf(10 wt.%)–alf3–al2o3 melt with cr=1.5 at 830 °c for 100 h (in total). the electrolysis with the same cathode was carried out in two steps: the duration of the first step was 75 h and the second step lasted for 25 h. the voltage and potentials of the cathode and the anode during electrolysis are given in figure 7. the electrolysis was sustained, the voltage at step 1 was ~2.1 v. the cathode potential was stable. the increase in the anode potential by 38th, 49th, and 62nd h of electrolysis is associated with the consumption and replacement of the graphite anodes. at the second step, the voltage systematically increased from 2.1 to 2.3 v. it appears from the symbatic nature of curves trend of the voltage and the anode potential that the increase in voltage is associated precisely with the operation of the inert anode. the increase in voltage after 21st h of electrolysis is explained by the breakdown in the contact of the current lead with the anode. after each step of electrolysis, the lower part of the cathode was cut off and a cross-section was prepared for a metallographic examination. an image of the cathode section after 75 h of electrolysis is shown in figure 8a. the dark gray areas in the image are alb2, the lighter areas contain less boron. the boride coating layer alb2 is preserved, its thickness is 7 μm. the grains are distributed uniformly over the thickness of the al layer. an image of the cathode cross-section after 100 h of electrolysis is presented in figure 8b. the thickness of the alb2 coating on the graphite surface after 100 h (figure 8b) is about 5 μm. it can be assumed that boron dissolves in molten aluminum. based on the sem data, it was calculated that about 0.0028 g of boron was transferred from the cathode surface to the volume of molten aluminum during 25 h of electrolysis (figure 8b). an external examination of the cathode after the experiment did not reveal any damage. an image of the crosssection of the graphite cathode with the diboride coating after electrolysis is shown in figure 9. the cathode surface was completely wetted with aluminum. the thickness of the aluminum layer was 2 mm. detachment of the aluminum from the cathode surface is not observed, which indicates good wetting of the graphite surface with aluminum. the current efficiency was 62 %. thus, the prolonged 100-h electrolysis tests of the graphite cathode, previously coated with the aluminum diboride, in the vertical cell proved its efficiency. undoubtedly, tests of wetted cathodes should be continued under conditions of longer electrolysis duration. however, it should be noted that, if necessary, an additional boriding of the cathode can be carried out during low-temperature aluminum electrolysis without changing its parameters. figure 7 voltage during electrolysis in the vertical cell with wetted borated graphite cathode. chimica techno acta 2022, vol. 9(2), no. 20229208 article 7 of 9 figure 8 images of the borated cathode after 75 h (a) and 100 h (b) of electrolysis. a b figure 9 image of cross-section (a) and general view of the hot wetted cathode after 100h electrolysis (b). 4. conclusions boriding the graphite plates was accomplished by electrolysis in the kf–alf3–kbf4 melt (cr=1.3) in two stages. at the first stage, the boron was reduced at the graphite cathode at the current density of 0.01 and 0.02 a/cm2 and temperature 700 and 750 °c, and at the second, the aluminum was deposited at the current density of 0.2 a/cm2. the second stage was necessary in order to improve the identification of boron against the background of the aluminum by sem. the operating parameters for the electrochemical deposition of continuous boride coatings on the graphite surface were found. nevertheless, despite the different values of the parameters of two-stage electrolysis, in all cases, aluminum, being reduced in the second stage of the process, wetted the graphite surface well. the difference was found only in the thickness of the aluminum layer and the amount and distribution of boron in the aluminum layer. the test of the borated graphite cathode under conditions of the low-temperature electrolysis in the kf– naf(10 wt.%)–alf3–al2o3 (cr=1.5) melt at 0.2 a/cm2 and 830 °c for 100 h confirmed the possibility of its use as a wetted dripping cathode in the electrolytic production of aluminum in low-melting cryolite. supplementary materials no supplementary materials are available. funding this research had no external funding. acknowledgment the authors are grateful to the staff of the shared access centre “composition of compounds” of the institute of high temperature electrochemistry for their help in metallographic studies. author contributions conceptualization: k.a.a., t.o.yu. data curation: t.o.yu. formal analysis: r.a.v., k.a.a., t.o.yu. funding acquisition: r.a.v., t.o.yu. investigation: r.a.v., k.a.a., n.m.m. methodology: r.a.v., k.a.a. project administration: r.a.v. resources: r.a.v., k.a.a. software: r.a.v., k.a.a. supervision: t.o.yu. validation: r.a.v., t.o.yu. visualization: r.a.v. writing – original draft: r.a.v., t.o.yu. writing – review & editing: r.a.v., t.o.yu. conflict of interest the authors declare no conflict of interest. additional information author id’s: rudenko a.v., scopus id 57197500558; kataev a.a., scopus id 12241606800; tkacheva o.yu., scopus id 6602941818. 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https://doi.org/10.1007/s11837-001-0209-2 https://doi.org/10.31857/s0235010622010030 https://doi.org/10.3103/s1067821219040059 https://doi.org/10.1016/j.jallcom.2017.06.107 chimica techno acta 2022, vol. 9(2), no. 20229208 article 9 of 9 peculiarities of electrophoretic deposition and morphology of deposited films in non-aqueous suspensions of al2o3–al nanopowder chimica techno acta article published by ural federal university 2022, vol. 9(2), no. 20229207 eissn 2411-1414; chimicatechnoacta.ru doi: 10.15826/chimtech.2022.9.2.07 1 of 8 peculiarities of electrophoretic deposition and morphology of deposited films in non-aqueous suspensions of al2o3–al nanopowder elena g. kalinina ab* , darya s. rusakova ab, elena yu. pikalova bc a: institute of electrophysics, ural brunch of russian academy of sciences, ekaterinburg 620016, russia b: ural federal university named after the first president of russia b.n. yeltsin, ekaterinburg 620002, russia c: institute of high temperature electrochemistry, ural brunch of russian academy of sciences, ekaterinburg 620137, russia * corresponding author: kalinina@iep.uran.ru, jelen456@yandex.ru this paper belongs to a regular issue. © 2022, the authors. this article is published open access under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). abstract the paper presents the results of a comprehensive study of the electrokinetic properties of non-aqueous suspensions of the al2o3–al nanopowder obtained by the method of electric explosion of wires with 0.3 wt.% of metallic aluminum in its composition. the dependence of zeta potential on the concentration of the al2o3–al suspension is revealed. the nature of long-term changes in zeta potential and ph in suspensions is established. appearance of bubbles in the deposited coatings due to the interaction of metallic aluminum particles with the liquid suspension medium during electrochemical reactions on the electrodes is defined as the main feature of the electrophoretic deposition process in the al2o3–al suspensions. the influence of the suspension preparation method on the deposited coatings’ morphology is demonstrated. keywords electrophoretic deposition electric explosion of wire alumina weakly aggregated nanopowder non-aqueous suspension zeta potential received: 28.04.22 revised: 09.05.22 accepted: 09.05.22 available online: 12.05.22 1. introduction formation of al2o3-based ceramic coatings is of interest in diverse fields of mechanical engineering, electrical industry [1], as well as in the field of creating composite materials for electrochemical devices [2, 3]. al2o3-based ceramics is of interest in the field of luminophore production [4]. well-known methods for developing thin-film coatings such as pulsed laser deposition [5] or chemical vapor deposition [6] require the use of complex and expensive equipment and limit the scalability of the technology. electrophoretic deposition (epd) from suspensions is an instrumentally simple method, which allows coatings’ formation on the surface of substrates of various shapes and sizes at high rates, easily controlled by the strength of the applied electric field [7–10]. the epd process in a liquid dispersion medium is caused by the motion of particles in the suspension under the action of an external electric field and their deposition on the electrode [9]. one of the possible deposition mechanisms is electrochemical coagulation of the suspension in the near-electrode region [11]. the movement of particles in suspension or electrophoresis proceeds due to the formation of an excess electric charge on the particles and the formation of an electric double layer (edl) due to the specific adsorption of potential-determining ions, for example, protons, on the particle surface [12, 13]. the stability of the colloidal system [14, 15] and the electrokinetic properties of the suspension depend on the zeta potential value, which directly determines the electrophoretic mobility of particles in the suspension and the deposition rate [16, 17]. the epd method was used to obtain coatings based on aluminum oxide using commercial powders [18, 19]. however, the properties of suspensions and obtained epd coatings were shown to depend significantly on the type and size of particles of the powders used, which is probably related to the specific technologies for their production, used by the manufacturer. the method of electric explosion of wires (eew) [20–23] allows obtaining weakly aggregated nanoparticles of nearly spherical shape. suspensions based on such powders are characterized by the appearance of a self-stabilization effect [24] and high values of zeta potential, which makes it possible to use suspensions of the eew nanopowders without the addition of http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2022.9.2.07 mailto:kalinina@iep.uran.ru mailto:jelen456@yandex.ru http://creativecommons.org/licenses/by/4.0/ https://orcid.org/0000-0002-5637-7451 https://orcid.org/0000-0001-8176-9417 https://crossmark.crossref.org/dialog/?doi=https://doi.org/10.15826/chimtech.2022.9.2.07&domain=pdf&date_stamp=2022-5-12 chimica techno acta 2022, vol. 9(2), no. 20229207 article 2 of 8 dispersants and charging agents. in our recent work, we demonstrated the efficiency of using al2o3-based nanoparticles for the formation of bulk ceramics by the epd method [25, 26]. when using the eew mg-doped al2o3 nanopowder containing 0.3 wt.% of metallic aluminum, an improvement in the sintering properties of the ceramics was demonstrated, which confirms the relevance of the development of colloidal technologies based on ceramic nanopowders containing metal particles. the study of the features of the epd kinetics during the formation of a ysz (yttria-stabilized zirconium dioxide)/al2o3 composite coating was carried out in [27], where the sintering additive containing al particles was introduced to decrease the sintering temperature down to 1150 °c. structural features of ysz/al2o3 composite coatings obtained by epd from the suspensions containing metallic al particles were studied in [28]. the study of the sintering behavior of individual (ysz) and composite coatings (ysz/al2o3) was carried out in [29] with the use of the ysz and al2o3 nanopowders obtained by the laser condensation-evaporation and eew methods. the influence of the epd modes under the deposition process in dilute suspensions (1 g/l) of cuox with the addition of al nanoparticles on the weight of the obtained coatings is discussed in [30]. the purpose of this work was to study the electrokinetic properties of the suspensions based on the eew al2o3 nanopowder containing metallic al (al2o3–al) and to determine the effect of the metal component in the composition of the nanopowder on the morphology of the epd coatings. the regularities of aging of suspensions based on ceramic nanopowders with a metal component are not currently covered in the literature. thus, as a separate task of the study, the issue of changing the properties of suspensions during their long-term storage and resulting aging effects were singled out. this can be important from the point of view of the practical application of the epd technology, since the prepared suspensions are commonly stored for a long time to be reused for the deposition. 2. experimental part the al2o3 and al2o3–al nanopowders were obtained by the eew method using the wires made of metallic al and almg alloy with a mg content of 1.3 wt.%, respectively [20– 22]. the specific surface area (sbet) of al2o3 and al2o3–al nanopowders was 42 and 40 m2/g, respectively; it was determined by the brunauer-emmett-teller (bet) method using a tristar 3000 vacuum sorption unit (germany). x-ray phase analysis of nanopowders was carried out using a d8 discover diffractometer (bruker axs, germany). processing of the xrd data was performed using the topas-3 program. according to the xrd data (table 1), the initial al2o3–al nanopowder did not contain magnesium as a separate crystalline phase. probably, magnesium is present in the form of interstitial or substitutional ions in the aluminum oxide crystal lattice. we have calculated the amount of mg in the composition of the nanopowder with respect to al2o3. taking into account the proportion of mg in the al-mg alloy, equal to 1.3 wt.%, the calculated content of mg in the composition of al2o3 is 0.67 wt.%. table 1 xrd data for the al2o3 and al2o3–al nanopowders. crystalline phase (content, wt.%) lattice type (space group) lattice parameters, å csr, nm al2o3 powder γ-al2o3 (15) cubic (fd–3m) а = 7.919(8) 18(1) δ-al2o3 (85) orthorhombic (p222) а = 7.934(8) b = 7.956(8) c = 11.711(8) 18(2) al2o3–al powder γ-al2o3 (31) cubic (fd–3m) а = 7.950(10) 26(2) metallic al (0.3) cubic (fm–3m) a = 4.054(4) 150(15) α-al2o3 (0.4) rhombohedral (r–3c) a = 4.764(4) c = 12.990(20) 180(16) δ-al2o3 (69) orthorhombic (p222) а = 7.934(8) b = 7.956(8) c = 11.711(8) 18(2) according to the transmission electron microscopy study performed using a jem 2100 transmission electron microscope (jeol, japan), the nanopowders’ particles were weakly aggregated and had a spherical shape (figure 1). lognormal particle size distributions for al2o3 and al2o3–al powders were obtained using graphical analysis of tem images. the distribution function was as follows: 2 2 (ln ln ) 2 1 ( ) 2 d f d e d     − − = , (1) where d is the diameter of particles, nm; μ is the distribution average value, nm; σ is dispersion of the lnd distribution. the values of the parameters were μ = 14.8 nm, σ = 0.608 for the al2o3 nanopowder and μ = 19.0 nm, σ = 0.632 for the al2o3–al nanopowder, respectively. the al2o3 and al2o3–al nanopowders were used to prepare suspensions in an isopropyl alcohol medium without introducing dispersants or other additives. a suspension of the al2o3 nanopowder was prepared with a concentration of 10 g/l. initial suspensions of the al2o3–al nanopowder were prepared with concentrations of 25, 50, 100, 150 and 250 g/l. all the suspensions were sonicated using an ultrasonic bath uzv-13/150-tn (reltek, russia) for 125 min. in freshly prepared suspensions with different concentrations, zeta potential and ph were measured. the al2o3–al suspensions were stored for a period of time up to 250 days with following measurements of zeta potential and ph. separately, a series of experiments was carried out for the al2o3–al suspensions with a fixed concentration of 100 g/l, both freshly prepared and aged for 100 days. chimica techno acta 2022, vol. 9(2), no. 20229207 article 3 of 8 figure 1 morphology of nanoparticles and numerical size distributions for al2o3 (a) and al2o3–al (b) nanopowders. large aggregates remained in the suspensions after the ultrasonic treatment were removed by centrifugation using a z383 centrifuge (hermle labortechnik, germany) at a speed of 6000 rpm for 3 min. measurements of the electrokinetic zeta potential and ph in suspensions were carried out by the electroacoustic method using a dt-300 analyzer (dispersion technology, usa). all measurements for the suspensions were carried out under isothermal conditions in air at 25 °c. electrophoretic deposition was performed using a specialized computerized setup providing constant voltage modes, which was developed and manufactured at the iep, ural branch, russian academy of sciences. epd was performed with a vertical arrangement of the electrodes. the deposition was carried out in a cell with ni-foil electrodes, the distance between them was 10 mm. during the epd process, the voltage ranged from 5 to 50 v, while the deposition time was varied from 20 s to 15 min. the deposited coatings were dried on the electrode for a day at room temperature in a petri dish. the thickness of the coatings was estimated by measuring their weight and taking into account the area and density of the coatings. morphology of thin-film coatings obtained by the epd method was studied using an optical microscope st-vs-520 (russia). the value of the current during epd was measured using a ut71e digital multimeter (uni-trend technology, china). 3. results and discussion 3.1. influence of the concentration and exposure time of the al2o3–al suspension on the zeta potential and ph values the results of measurements of zeta potential (ζ-potential) of the freshly prepared suspensions of the al2o3–al nanopowder with various concentrations (25, 50, 100, 150, 250 g/l) after ultrasonic treatment for 5 min are shown in figure 2a. it can be seen that with increasing concentration of the powder in the suspension the value of ζ-potential decreases. this dependence is probably associated with an increase in the interparticle interaction of nanoparticles with an increase in their concentration in the suspension due to overlapping electrical double layers [31]. ζ-potential and ph time changes in the al2o3–al suspensions were studied for 250 days to determine the suitability of the suspensions commonly used in the technology of epd coatings for an extended period of time. from dependences presented in figure 2b, it can be seen that in the initial period of time up to 66 days the value of ζ-potential increased for all the studied suspensions of various concentrations. with a further increase in the storage time (more than 66 days), changes in ζ-potential became sign-alternating and chaotic. the most significant time changes in ζ-potential were noted for a suspension with a concentration of 100 g/l. significant changes in ph of the suspensions were observed during the first 150 days of the (figure 2c) followed by a return to the initial values, and then the ph values stabilized. the change in ph over time had a similar character at different concentrations of the suspensions. the noted peculiarities of the dynamics of ph and ζ-potential may be associated with the hydrolysis of aluminum cations with the formation of hydrated complexes (al2(oh)2(h2o)8)4+, (al3(oh)4(h2o)9)5+, as well as (al13o4(oh)24(h2o)12)7+, as shown in [32]. the suspensions of various concentrations are characterized by a high initial value of ζ-potential (fresh, not aged suspensions), which may be associated with the effect of self-stabilization due to the formation of aluminum cations in the dispersion medium as a result of the hydrolysis of trace amounts of nitrates, which inevitably appear on the surface of al2o3 nanoparticles during their production by the eew method [24]. according to the xrd data, the al2o3–al nanopowder used for the suspensions’ preparation contains 0.3 wt.% of metallic aluminum (table 1), and, despite its small proportion, aluminum particles can actively react with a trace amount of water in the suspension. this can radically affect the electrokinetic properties of the suspensions and morphology of the deposited coatings, as well as cause slow changes in ζpotential and ph over time. chimica techno acta 2022, vol. 9(2), no. 20229207 article 4 of 8 (a) (b) (c) figure 2 dependences obtained for the suspensions based on the al2o3–al nanopowders: influence of concentration on the ζpotential value for the freshly prepared suspensions (а); influence of exposure time of the suspensions of various concentrations (25, 50, 100, 150 g/l) on the ζ-potential value (b); influence of exposure time of the suspensions of various concentrations (25, 50, 100, 150 g/l) on ph (c). 3.2. influence of the method of the suspension preparation on the morphology of the epd coatings the studies in this section were carried out using the suspension with a concentration of 100 g/l of the al2o3–al nanopowder. as noted in the previous section, this suspension had the most significant changes in ζ-potential with time. in this regard, a study was made into the effect of processing this suspension (centrifugation, dilution) on the epd coatings’ morphology. the scheme of the experiment is shown in figure 3. the results of experiments are summarized in table 2. ultrasonic treatment of the freshly prepared suspension with a concentration of 100 g/l of the al2o3–al nanopowder was carried out for 125 min followed by the measurement of ζ-potential and ph, the values of which were +42 mv and 5.7 mv, respectively. the resulting suspension was used to conduct epd on a model electrode (ni-foil) in a constant voltage mode, varying the applied voltage in the range from 5 to 20 v and deposition time from 20 s to 1 min. the selection of the deposition mode in each case was carried out based on the necessity to obtain a continuous coating. therefore, for each suspension, the lowest possible epd voltage was selected at which it was possible to form such a coating (table 2). after the epd process conducted in the freshly prepared suspension at a voltage of 20 v and a time of 1 min, the resulting coating with a thickness of 20 μm was continuous, but contained cracks and a large number of bubbles. it should be noted that the appearance of bubbles in coatings during epd is not characteristic of the deposition of ceramic powder materials from non-aqueous suspensions, and, usually, it is observed mainly for water-based suspensions [8, 33]. in order to determine the possible effect of the suspension concentration on the morphology of the deposited coatings and nature of the bubbles’ formation, the freshly prepared suspension of 100 g/l was diluted to a concentration of 10 g/l followed by epd on the ni-foil (table 2). the diluted suspension was characterized by a higher positive ζ-potential of +88 mv and ph=6.4. epd from the diluted freshly prepared suspension showed that bubbles also formed in the coating, but in a smaller amount than under the deposition in the initial concentrated suspension (100 g/l). however, to obtain a continuous coating with a thickness of ~5 µm for 1 min, it was necessary to increase the voltage up to 35 v. at the next stage, the freshly prepared concentrated suspension (100 g/l) was centrifuged at 6000 rpm for 3 min. after the treatment, the resulting suspension had a concentration of 77 g/l, and the measured ζ-potential and ph values were +50 mv and 4.8, respectively. a continuous coating 8.2μm thick was obtained at a voltage of 10 v and a deposition time of 1 min. the coating contained a large number of bubbles; therefore, centrifugation did not make it possible to exclude their formation. however, the number of bubbles became less in comparison with those formed during epd from the initial suspension (concentration of 100 g/l). figure 3 experimental scheme: effect of centrifugation and dilution of the suspensions on the morphology of the deposited al2o3– al coatings. chimica techno acta 2022, vol. 9(2), no. 20229207 article 5 of 8 considering the previously established tendency for the number of bubbles to decrease with decreasing the suspension concentration, a dilution of the centrifuged freshly prepared suspension (77 g/l) to a concentration of 10 g/l was performed. epd was carried out at 40 v. the resulting coating with a thickness of approximately 4 μm, formed after 1 min of the deposition time, contained single bubbles, but their number was minimal compared to all previous experiments (table 2). the effect of centrifugation on the nature of bubble formation in epd coatings was studied using the al2o3–al suspension with a concentration of 100 g/l aged for 100 days (figure 3, table 2). the ζ-potential and ph values, measured in the suspension treated with ust for 125 min, were +50 mv and 4.1, respectively. the resulting suspension was used to conduct epd on an electrode (ni-foil) in a constant voltage mode of 20 v and a deposition time of 1 min. the resulting film of 26 μm in thickness contained a network of cracks and a large number of bubbles. the centrifugation of the suspension aged for 100 days resulted in the formation of a continuous coating with a thickness of 15 μm during epd, which was characterized by the presence of cracks and a reduced number of bubbles compared to the non-centrifuged aged suspension. it is of interest to study the kinetics of current change during the epd process in order to establish the nature of the charge transfer in the al2o3–al suspension during the formation of the epd coating. this study was performed during the epd process at a constant voltage of 20 v and a deposition time of 15 min from various types of suspensions (with concentration of 100 g/l – freshly prepared and aged for 100 days; with concentration of 77 g/l – centrifuged, freshly prepared and aged for 100 days), and also for pure isopropanol. the results are shown in figure 4. it is seen that for pure isopropanol the current value does not depend on time and has a value of about 0.01 ma, which is lower than the current values in suspensions (~0.02–0.05 ma). the charge transfer mainly proceeds with the participation of particles in suspensions, and a decrease in current is due to the depletion of the suspension during epd, as well as because of an increase in the resistance of the deposited film [9]. with the use of the aged (100 days) suspension with a concentration of 100 g/l, the drop in current became sharper. centrifugation of the aged suspension (77 g/l) led to the return of the current kinetics to the values of a freshly prepared suspension. in a freshly prepared suspension, centrifugation does not change the current kinetics. 3.3. possible mechanisms of the bubble formation in the epd coatings with the participation of a metal component in the al2o3–al nanopowder composition figure 5 represents optical micrographs of the epd coatings obtained from the aged suspension of the al2o3–al nanopowder with a concentration of 100 g/l (figure 5a), as well as the coatings obtained from the freshly prepared al2o3–al suspension: with a concentration of 100 g/l (figure 5b); from the centrifuged suspension of 77 g/l (figure 5c); from the centrifuged suspension diluted to 10 g/l (figure 5d). analysis of the images shows that there is a tendency for a decrease in the number of bubbles when using centrifugation of the freshly prepared suspension, especially when it is subsequently diluted to 10 g/l. in order to confirm the effect of the metal component in the composition of al2o3–al nanopowder on the formation of bubbles in the epd coating, the deposition was carried out from the suspension with a concentration of 10 g/l based on the al2o3 nanopowder on the ni-foil at a constant voltage of 50 v and deposition time of 1 min. the obtained continuous coating with a thickness of 10 μm did not contain bubbles, which confirmed the earlier assumption about the key role of metallic aluminum in the al2o3–al nanopowder composition in the formation of bubbles in the structure of the epd coatings. metallic al (0.3 wt.%) in the composition of the initial al2o3–al nanopowder can interact with a trace amount of water contained in isopropyl alcohol to form gaseous hydrogen and aluminum hydroxide. table 2 influence of the al2o3–al nanopowder suspension preparation method on the ζ-potential value and morphology of the epd coatings obtained under the selected epd modes. method of the suspension preparation (concentration, g/l) ζ-potential, mv (рн) epd mode (voltage, deposition time) thickness and morphology of the resulting epd coating freshly prepared (100 g/l) +42 (5.7) 20 v, 1 min 20 μm; a significant amount of bubbles diluted from freshly prepared (10 g/l) +88 (6.4) 35 v, 1 min 5.6 μm; numerous bubbles centrifuged freshly prepared (77 g/l) +50 (4.8) 10 v, 1 min 8.2 μm; numerous bubbles diluted from centrifuged freshly prepared (10 g/l) +80 (6.1) 40 v, 1 min 3.9 μm; single bubbles aged for 100 days (100 g/l) +50 (4.1) 20 v, 1 min 26 μm; the largest number of bubbles centrifuged and aged (77 g/l) +53 (5.2) 20 v, 1 min 15 μm; numerous bubbles chimica techno acta 2022, vol. 9(2), no. 20229207 article 6 of 8 figure 4 time dependences of current intensity during epd performed at an applied constant voltage of 20 v in freshly prepared and aged al2o3–al suspensions with different concentrations of 100 g/l and 77 g/l and for pure isopropanol. figure 5 optical micrographs of the al2o3–al coatings deposited from the suspensions obtained using different methods: from the aged suspension (100 days) with a concentration of 100 g/l (а); from the freshly prepared suspension with a concentration of 100 g/l (b); from the freshly prepared centrifuged suspension with a concentration of 77 g/l (c); from the freshly prepared centrifuged suspension diluted to 10 g/l (d). electrochemical reactions on the electrodes may enhance the interaction of the liquid medium with metallic aluminum due to the reaction occurring at the anode with the formation of water as a result of the oxidation of hydroxide ions: 4oh– – 4e– = o2↑ + 2h2o. at the same time, water decomposes at the cathode with formation of the molecular hydrogen: 2h2o + 2e– = h2↑+ 2oh, and the reduction of h+ protons with the formation of the molecular hydrogen н2 is also possible [33, 34] as it was shown above (figure 4), pure isopropanol is characterized by the time-independent current intensity, which indicates the absence of significant electrochemical reactions involving a trace amount of water in pure alcohol, since the conductivity of the liquid medium does not change for a long time (15 min). therefore, it can be concluded that the main contribution to the electrochemical electrode reactions during epd is made by ions present in the edl of solvated particles in the suspension. water can be introduced into the suspension during the process of the powder dispergation, as well as during the oxidation reaction of hydroxide ions at the anode. exposure of the suspension over time has a negative effect on the formation of bubbles in the coating, which may be due to an uncontrolled change in the ionic composition in the suspension. the experiments performed show that the use of centrifugation of the al2o3–al suspension allows the formation of bubbles in the coatings to be significantly reduced, possibly due to the partial removal of aluminum metal particles during centrifugation. the particularities revealed in the use of the eew al2o3–al nanopowder can be considered when using other ceramic powdered materials containing metal particles in the epd technology of functional coating. 4. conclusions in the present work, a comprehensive study of the electrokinetic properties of the suspensions based on the al2o3–al nanopowder, obtained by the method of electric explosion of wires and containing a small fraction (0.3 wt.%) of metallic aluminum, was carried out with variation in their concentration and aging time. a decrease in zeta potential with an increase in the concentration of the al2o3–al suspension was shown, which is due to the influence of interparticle interaction in a concentrated suspension. the appearance of bubbles in the coatings obtained by epd from suspensions of the al2o3–al nanopowder in isopropyl alcohol was found, while no bubbles were formed in the suspension of the al2o3 nanopowder. thus, the presence of metallic aluminum particles in the composition of the eew nanopowder was revealed as the most possible reason for the appearance of bubbles in the structure of the al2o3–al deposited coatings, which, in turn, is enhanced by the electrochemical reactions on the electrodes. it was shown that the long-term storage of the suspensions of the al2o3–al nanopowder for their following usage for epd to obtain coatings of the satisfactory quality should not exceed approximately two months (66 days). supplementary materials no supplementary materials are available. funding the work was performed within the framework of the government task (project no. 122011200363-9) using the equipment of the shared access center of iep ub ras. chimica techno acta 2022, vol. 9(2), no. 20229207 article 7 of 8 acknowledgments the authors are grateful to the head of the laboratory of pulsed processes, ph.d., i.v. beketov and junior researcher a.v. bagazeev for providing al2o3-based nanopowders obtained by the eew method. author contributions conceptualization: e.g.k. data curation: d.s.r. formal analysis: e.g.k., d.s.r. funding acquisition: e.g.k. investigation: e.g.k., d.s.r. methodology: e.g.k., e.yu.p., d.s.r. project administration: e.g.k. resources: e.g.k. software: d.s.r. supervision: e.g.k. validation: d.s.r. visualization: d.s.r. writing – original draft: e.g.k. writing – review & editing: e.yu.p. conflict of interest the authors declare no conflict of interest. additional information author id’s: elena g. kalinina, scopus id 36697946700; darya s. rusakova, scopus id 57223935087; elena yu. pikalova, scopus id 16242376500. institute websites: institute of electrophysics, ub ras, http://eng.iep.uran.ru; ural federal university, https://urfu.ru/en; institute of high temperature electrochemistry, ub ras, 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under modulated electric fields: a review. rsc adv. 2012;2:7633–7646. doi:10.1039/c2ra01342h https://doi.org/10.1134/s0036024421080148 https://doi.org/10.15826/chimtech.2021.8.2.06 https://doi.org/10.2298/pac2101001m https://doi.org/10.1016/j.ceramint.2017.12.185 https://doi.org/10.1134/s0020168516110054 https://doi.org/10.1051/e3sconf/202123900015 https://doi.org/10.1021/jp027148k https://doi.org/10.1016/0921-5093(95)09955-7 https://doi.org/10.1016/j.jeurceramsoc.2009.07.004 https://doi.org/10.1039/c2ra01342h the effect of processing conditions on the dielectric properties of doped calcium lanthanum nickelate published by ural federal university eissn 2411-1414; chimicatechnoacta.ru article 2022, vol. 9(4), no. 20229410 doi: 10.15826/chimtech.2022.9.4.10 1 of 11 the effect of processing conditions on the dielectric properties of doped calcium lanthanum nickelate yulia a. deeva a* , abdullo a. mirzorakhimov a , alexey yu. suntsov b , nadezhda i. kadyrova b , nina v. melnikova a, tatyana i. chupakhina b a: institute of new materials and technologies, ural federal university, ekaterinburg 620009, russia b: institute of solid state chemistry ub ras, ekaterinburg 620990, russia * corresponding author: juliahik@mail.ru this paper belongs to a regular issue. © 2022, the authors. this article is published in open access under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). abstract the influence of thermal and thermobaric (tbt) effects on the structure, microstructure, and dielectric properties of ceramics based on solid solutions of the la1.8ca0.2ni0.8m0.2o4+δ (m = co, cu) composition was studied. tbt treatment of the samples leads to a change in the grain morphology of ceramics and an increase in the dielectric constant compared to its value only after heat treatment. the change in the anisotropy of the coordination (la,ca)o9 and (ni,m)o6 polyhedra after tbt contributed to interlayer polarization in the crystal structure of la1.8ca0.2ni0.8m0.2o4+δ. keywords ceramics solution combustion thermobaric treatment impedance spectroscopy dielectric response received: 22.07.22 revised: 10.08.22 accepted: 11.08.22 available online: 23.08.22 1. introduction the search for materials with a high dielectric constant and low dielectric losses is one of the main tasks of modern materials science. however, this problem does not have a simple solution since an increase in the dielectric constant (ε) is accompanied by an increase in dielectric losses (tan δ) and the dependence of dielectric parameters on temperature. for the first time, a very high value of the permittivity was found in single crystals of layered perovskite-like oxides, such as cacu3ti4o12, la15/8sr1/8nio4 (structural type k2nif4, for oxides – a2bo4) and solid solutions based on them; the value was ε is very large [1, 2]. in the lanthanum-strontium nickelate, this characteristic is frequencyand temperature independent, which makes this material promising for practical applications (ε ~ 105–106) [3, 4]. in ceramic samples and thin films of cacu3ti4o12 and la15/8sr1/8nio4, the dielectric constant has a lower value and decreases with an increase in the frequency of the electric field [3, 5]. it was found that the ceramics obtained by the thermobaric method have better dielectric characteristics in comparison with those of the samples obtained by the ceramic technology at atmospheric pressure [6, 7]. at a low frequency (102 hz), the dielectric constant and dielectric losses of cacu3ti4o12 (ccto) increase with an increase in the calcination temperature and an increase in the grain size [8]. thus, ccto had the highest dielectric constant and tan δ values. at the middle frequency (103–105 hz), ccto was found to exhibit the lowest tan δ value (0.091). among ceramics based on complex oxides with a structure of the type k2nif4 (for oxides, the formula is written as а2во4), which have been extensively researched over the past decade, the compounds with both temperatureand frequency-independent giant dielectric constant (ln2−xsrxni1−ymyo4 (ln – rare earth element (ree), m = co, cu; ε ~ 103–106, tan δ>1.0), and with a low tangent of the dielectric loss angle (а2−xlnxti1−ymyo4 (a = ca, sr); ε ~ 10– 30, tan δ<10−3) were found [9]. it is known that a high dielectric constant in reestrontium layered nickelates is realized due to interlayer charge polarization, which is influenced by structural anisotropy. structural distortions of the ao9 and bo6 coordination polyhedra can be regulated by partial or complete substitution of cations in the position a. the dielectric response suddenly changes with changing the rare earth ion, when the crystal symmetry changes, so there should be a link between the dielectric response and crystal symmetry [6, 10]. of the unsubstituted nickelates, the sm1.5sr0.5nio4 compound has the best characteristics (ε = 106, tan δ<0.1), but these parameters are unstable and depend on the temperature and frequency of the electric field [11]. it should be noted that the difference between the radii of sm and sr (coordination number of which is ix) leads to the formation of an oxide with orthorhombic symmetry [12], in contrast with the analogous compounds, la-, pr-, nd-containing http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2022.9.4.10 mailto:juliahik@mail.ru http://creativecommons.org/licenses/by/4.0/ https://orcid.org/0000-0003-1207-7331 https://orcid.org/0000-0002-9844-1570 https://orcid.org/0000-0002-3488-1454 https://orcid.org/0000-0001-5832-7688 https://orcid.org/0000-0002-1317-3803 https://crossmark.crossref.org/dialog/?doi=https://doi.org/10.15826/chimtech.2022.9.4.10&domain=pdf&date_stamp=2022-8-23 chimica techno acta 2022, vol. 9(4), no. 20229410 article 2 of 11 ones, crystallizing in the tetragonal modification [13–15]. in solid solutions (sm1−xndx)1.5sr0.5nio4 the orthorhombic phase exists for x<0.6, while for 0.6<x<1.4 the structure becomes tetragonal [16], and after this transition ε falls and tan δ increases. the relationship between dielectric characteristics and structural anisotropy due to the replacement of la (r = 1.31 å) by ca cation (r = 1.01 å) was described in [17] using the la2−xcaxnio4 solid solution as an example. it was shown that the distortions of the ao9 and bo6 polyhedra change at different x, which allowed the authors to obtain a compound with a high ε ~ 104 (x = 0.2), but a rather high value of tan δ ~ 100 (x = 0.3). in the resulting oxides, the dielectric constant strongly depends on frequency and temperature, which is unusual for compounds of this class. there are no other data on the dielectric properties of casubstituted nickelates of lanthanum and other rare-earth elements in the literature. on the other hand, the parameters of the а2во4 structure change upon partial substitution of elements located not only in the a position, but also in the b position, especially if the substitution is heterovalent. in this case, the interlayer polarization is affected not only by structural distortions, but also by the charge state of the cations that make up the oxide [18]. investigation of the dielectric characteristics of (la,ca)(ni,m)o4 (m = cu, co) ceramics, the results of which we present in this work, was aimed at studying the nature of high dielectric permittivity in layered perovskitetype oxides with a k2nif4 type structure. the choice of co and cu as substitute elements is due to the jahn-teller nature of the cu2+ cation and the preferred oxidation state of co3+ at high temperatures, which should have a significant effect on the structural anisotropy. elongations of bo6 octahedra along the c axis in the presence of cu2+ in position b, as shown in [19], stabilizes the frequency-independent behavior of the dielectric constant in lanthanum-strontium nickelates, and the presence of co3+ increases the dielectric constant [6]. another, no less important task of this study was to investigate the influence of the sample morphology on the dielectric characteristics. thermobaric treatment changes the microstructure of the samples, which has a noticeable effect on the dielectric properties of ceramics based on oxide compounds. strong influence on the dielectric parameters is exerted by the maxwell-wagner polarization at grain boundaries and inhomogeneities. this effect refers to external factors that affect the dielectrics parameters value. in this paper, ceramic samples of k2nif4 structural type, which have a composition la1.8ca0.2ni0.8m0.2o4+δ (m = co, cu) were investigated. to improve the dielectric properties of ceramics based on the complex oxides, the anisotropy of coordination polyhedra was controlled by conjugated substitution of the cationic positions of ln and 3d-metals, the shape and particle size distribution of crystallites were formed using the precursor method for the synthesis of ultrafine powders and subsequent thermobaric treatment. 2. experimental for the formation of single-phase solid solutions of the composition la1.8ca0.2ni0.8m0.2o4+δ (m = co, cu), we employed the precursor synthesis method described in detail in [6] using 2-substituted ammonium citrate (c6h14n2o7). la(no3)3∙6h2o, caco3, nio, coo and cuo of the “extra pure” qualification were used as starting reagents. the oxides and carbonates were dissolved in concentrated nitric acid, and the nitrates – in distilled water. the solutions were mixed, and a 1.5-fold excess of the organic component was added. the resulting homogeneous solution was evaporated at 673 k until the reaction mixture ignited. thermal treatment of the obtained pyrolysis product was carried out in two stages: at 873 k for 5 h to remove the residual organic products and at 1323 k for 16 h to complete the phase formation process. the phase analysis of the reaction products was performed using the crystallographic database “database of powder standard – pdf2” (icdd, usa, release 2009 [card 00-024-1326]). to form ceramic samples, the obtained single-phase finely dispersed black powder was pressed at a pressure of 9.5 mpa into tablets 10 mm in diameter and sintered at 1523 k for 8 h. the composition of the obtained samples was controlled using a shimadzu xrd-7000 s automatic diffractometer with 0.03° step in the 10–120° range with 3–5 s exposure per point. x-ray pattern processing was performed with a fullprof-2019 program. the shape and average size of particles of the samples under investigation were determined by scanning electron microscopy on a jeol jsm 6390 scanning electron microscope with an attachment for energy dispersive analysis of jed 2300 in the bes mode at a x3000 magnification. the determination of the thermal expansion coefficient of the samples under study was carried out on a netsch dil 402 c dilatometer in an argon atmosphere. the maximum temperature was 1720 k. the measurements of oxygen content in the obtained specimens were carried out by thermogravimetry (tg) technique with the use of a tg-92 setaram analyzer. for the thermal analysis, about 0.2 g of the pulverized material was placed in the corundum pan, heated, and kept in air at 1223 k for 2 h. then the sample was slowly cooled down to 423 k with the rate of 1°/min. such preliminary procedure is believed to provide a total removal of surface adsorbates and to achieve equilibrium values of oxygen content in oxides in the cooling mode. then the atmosphere was switched to ar diluted by 5 vol.% h2 and the samples were heated up to 1223 k until an exhaustive oxygen loss was achieved. such procedure resulted in the reduction of the sample to the powder mixture of la2o3, cao, co and cu. the respective weight loss was used for calculations of the total oxygen content (4±δ) in the as-synthesized samples. chimica techno acta 2022, vol. 9(4), no. 20229410 article 3 of 11 thermobaric treatment of ceramic samples was carried out in a “toroid” high-pressure chamber on a do-137a press at a pressure of 2.5 and 4 gpa for 5 minutes at 1173 k. to prevent carbon contamination of the sample, the internal walls of the heater were covered with platinum foil. dielectric characteristics were measured using a universal analyzer of the frequency response of an impedance meter/dielectric spectrometer solartron 1260a functioning in the frequency range 1 mhz–30 mhz. the frequency dependence of the dielectric constant was estimated in the frequency range from 1 khz to 1 mhz. temperature examinations of electrical characteristics of samples in the range 10–300 k were carried out in pure helium atmosphere in an autonomous closed cycle cryostat with the de-204sl two-stage cryorefrigerator, based on giffordmacmagon cycle using a helium water-cooled compressor. the accuracy of cryogenic temperature measurements was 0.2 k. 3. results and discussion 3.1. synthesis and structural characteristics of complex oxide la1.8ca0.2ni0.8m0.2o4+δ (m = co, cu). microstructural analysis of the obtained ceramic samples for the synthesis of powdered oxides of the la1.8ca0.2ni0.8m0.2o4+δ (m = co, cu) composition, the "solution combustion" method was used [20–22]. the choice of diammonium citrate as an organic component ensures the formation of citrates of the corresponding metals and the release of nh4no3 into the reaction zone [19]. the interaction of ammonium nitrate with organic components of the reaction mixture provides the ignition of the solution, accompanied by decarboxylation. pyrolysis of a reaction mass containing nitrogen in a reduced form proceeds with the formation of nanodispersed powders with a developed surface and high reactivity [23]. the high dispersion of the studied powders contributes to better sintering of ceramics and the absence of through and closed pores. figure 1 illustrates the results of thermogravimetry experiments. as can be seen, the studied oxides start to lose oxygen at 550 k and 650 k for the copperand cobalt-doped samples, respectively. earlier, a mechanism for the reduction of the copper-containing nickelate was considered in the literature [24–26] where two steps were also observed. the first one is related to the formation of the stoichiometric phase. at higher temperatures, deeper decomposition takes place, resulting in the formation of metals and simple oxides. xrd analysis of the reduced mixtures fully supports this point of view. it is important that the studied oxides remain stable in air media where negligible changes in oxygen content are observed. at the same time, the cobalt-containing sample is characterized by elevated oxygen content compared with copper doped one which may indicate the formation of more oxidized forms such as co3+. to determine the effect of particle morphology on dielectric properties, the formation of ceramics was carried out in two ways: heat treatment of the precursor in the air and thermobaric treatment (tbt) of the precursor. 3.1.1. heat treatment of the precursor in the air figure 2 shows the dilatometric measurement data for the obtained powder samples. it can be seen from the plots that the sintering process of both samples begins at a temperature in the range from 1155 k to 1280 k. figure 3 shows sem images of ceramics obtained after heat treatment at 1523 k. the countable size distribution of crystallites is presented in the form of a histogram (figure 3 (inset)) expressing the percentage of grains with sizes lying in these intervals. the surface of ceramic samples (figures 3a and 3b) is densely sintered i.e. has no through pores. crystallites of ceramic samples in both cases have a poorly crystallized shape with a not clearly pronounced growth zone. however, the sample containing co has a more faceted lamellar shape compared to the sample containing cu. the average crystallite size for both samples is about 3 μm. nevertheless, it should be noted that in the ceramics with co the particles are more dispersed than in the sample containing cu. figure 1 variations of oxygen content in la1.8ca0.2ni0.8m0.2o4±δ (m = cu, co) measured in air flow and ar diluted by 5 vol.% h2. the represented data were collected in cooling and heating modes, respectively. figure 2 kinetic curves of sintering complex oxides of la1.8ca0.2ni0.8m0.2o4±δ (m = cu, co) composition. chimica techno acta 2022, vol. 9(4), no. 20229410 article 4 of 11 figure 3 sem micrographs of the la1.8ca0.2ni0.8m0.2o4+δ (m = co (a), cu (b)) ceramics surface obtained after heat treatment (sintering) (the inset shows the crystallite size distribution). 3.1.2. thermobaric treatment (tbt) of the precursor significant changes in the morphology of ceramics are observed after treatment of precursors simultaneously with temperature and pressure (tbt) (figure 4). the morphology of crystallites changes significantly, acquiring a more faceted shape, and the particle size decreases for both samples by approximately a factor of 2 (figure 4 (insets)). the influence of the morphology of ceramics after tbt on the dielectric properties and the regularities of changes in the shape of crystallites are poorly studied. in [27] the effect of tbt on ceramics with the composition cacu3ti4o12 leads to an increase in the particle size and to the absence of a visible change in grain morphology. in contrast, after tbt in the la1.8ca0.2ni0.8m0.2o4+δ (m = co, cu) compounds the ceramic grain morphology changes rather strongly (figure 4 (a) and (b)). it can be assumed that the shape and size of crystallites after tbt depend on the type of crystal lattice of the compound under study. the phase composition of the obtained ceramic samples was determined based on the results of x-ray phase analysis (figure 5). figure 4 sem micrographs of the la1.8ca0.2ni0.8m0.2o4+δ (m = co (a), cu (b)) ceramics surface obtained after tbt (the inset shows the crystallite size distribution). the results of phase analysis of the obtained ceramic indicate the absence of foreign phases; this is proven by the correspondence of the x-ray diffraction reflections with the miller indices (hkl) of the structure of the ruddlesden–popper phase. since, in oxides with a structure of the k2nif4 type, there is a correlation between the dielectric properties and distortion of the antiprisms of ao9 and octahedra bo6 [17, 28, 29], the crystal chemical parameters of all the samples under study were determined. table 1 shows the crystallochemical parameters of the test compounds before and after tbt. to analyze the structural distortions of the compounds under study before and after tbt, figure 6 shows a graph of normalized bond lengths, i.e., the ratio of the experimental interatomic distances to the theoretical sum of ion radii (according to shannon [30]) in the corresponding coordination (lexp/ltheor). the coordination polyhedra (la,ca)o9 and (ni,m)o6 are shown in the crystal structure (figure 7). according to the literature date [27, 31], thermobaric treatment at temperatures up to 1200 k does not lead to a change in the space group of crystalline substances. however, structural deformation can occur, which can have a significant effect on material properties, such as magnetic or electrical. chimica techno acta 2022, vol. 9(4), no. 20229410 article 5 of 11 figure 5 theoretical and experimental diffraction patterns of the la1.8ca0.2ni0.8m0.2o4+δ (m = cu (a), co (b)) ceramics obtained before and after thermobaric treatment. the bragg reflections positions are marked with dashes. according to the data obtained (figure 6), the strongest structural change after tbt is manifested along the c axis (the la (ca)–o2b bond in the ao9 coordination polyhedron and the ni(m)–o2b bond in bo6) for both samples. however, it is important to note that in the case of the sample containing cu in position b (sample ii'), the bo6 octahedron becomes more distorted, while the sample containing co, on the contrary, after tbt, approaches the ideal lattice state. according to [32] the presence of jahn-teller ions in the composition of perovskite-type oxides provides the greatest response of structural distortions to thermobaric action. 3.2. temperature dependences of the electrical properties of materials at different frequencies the impedance hodographs (figure 8) are the arcs of semicircles whose rez intercepts correspond to the resistance of grain boundaries. the impedance hodographs for samples in all temperature range are arcs of semicircles, the radii of which monotonously decrease with increasing temperature, which indicates a decrease in electrical resistance of the grain boundaries. figure 6 normalized bond lengths values in coordination polyhedra (la,ca)o9 and (ni,m)o6 of the composition la1.8ca0.2ni0.8m0.2o4+δ (m = co (i), cu (ii)) compounds, where i’ and ii’ – samples after tbt at p = 2.5 gpa. figure 7 crystallographic structure of la1.8ca0.2ni0.8co0.2o4+δ. the la and ca atoms are represented by purple, ni and m – by dark blue, oxygen – by red spheres. the presence of one arc on the impedance hodographs of the studied materials indicates that the processes occurring in an alternating field can be characterized by a single relaxation time or that the relaxation times of carriers and polarization relaxation processes are distributed in a certain narrow interval. the frequency dependences of the imaginary part of the electric modulus for the studied samples at some temperatures are shown in figure 9 (for la1.8ca0.2ni0.8cu0.2o4+δ samples) and figure 10 (for la1.8ca0.2ni0.8co0.2o4+δ samples). the polarization relaxation time (τ) was determined using the frequency values fmax corresponding to the maximum point of the graph imm(f) plot using the equation: τ = 1/2π𝑓𝑚𝑎𝑥. (1) chimica techno acta 2022, vol. 9(4), no. 20229410 article 6 of 11 table 1 crystallo chemical parameters of la1.8ca0.2ni0.8m0.2o4+δ (m = co (i), cu (ii)) samples (space group i4/mmm, la/ca (0, 0, z), ni/m (0, 0, 0), o(1) (0, 0.5, 0); o(2) (0, 0, z)). samples i i’ (2.5 gpa) ii ii’ (2.5 gpa) unit cell parameters a = b, å 3.8552(2) 3.8580(2) 3.8257(4) 3.8328(1) c, å 12.5546(3) 12.5208(7) 12.7156(1) 12.7212(3) v, å3 186.591(4) 186.363(8) 186.110(7) 186.881(2) atom coordinates la (ca) z 0.3611(8) 0.3631(5) 0.3621(4) 0.3619(2) o1 occupancy 0.929(3) 0.902(8) 0.993(8) 0.889(6) о2 z 0.1740(7) 0.1715(9) 0.1757(8) 0.1788(1) occupancy 0.946(4) 1.086(7) 1.018(6) 1.090(3) χ2 0.781 0.937 0.785 0.892 interatomic distances, å ni/m–o1(x4) 1.9276(8) 1.9290(6) 1.9128(6) 1.9164(2) ni/m–o2b(x2) 2.186(7) 2.147(3) 2.234(4) 2.276(1) la/ca–o1(x4) 2.5988(7) 2.5806(12) 2.5946(12) 2.5990(17) la/ca –o2a(x4) 2.7617(3) 2.7622(6) 2.7481(2) 2.7573(3) la/ca –o2b(x1) 2.348(6) 2.399(3) 2.371(4) 2.379(7) rf-factor 3.98 4.32 3.40 2.65 gii 0.3909 0.8723 0.5561 0.6720 figure 8 impedance spectra of cells with samples la1.8ca0.2ni0.8m0.2o4+δ (m = co, cu) (a, c) compounds before and after tbt at p = 2.5 gpa (b, d). chimica techno acta 2022, vol. 9(4), no. 20229410 article 7 of 11 figure 9 the frequency dependences of the imaginary part of the electric modulus for the la1.8ca0.2ni0.8cu0.2o4+δ samples (before (a, c) and after tbt (b, d)) at some temperatures and frequency dependences of the imaginary part of the impedance at t = 100 k. the relaxation times of charge carriers from –imz(f) at t = 100 k (figure 9) are  = 5.010–6 s and = 1.110–5 s (for before and after tbt, respectively). for the material with copper, the relaxation times τ = 1/2π𝑓𝑚𝑎𝑥 after tbt slightly increase, but for the material with co, the values  decrease by an order of magnitude and even by two at 𝑇 ≤ 100 k. an increase in the relaxation time after tbt can be associated with an increase in polarization in the regions of grain boundaries, the surface of which increases with a decrease in the particle size during such treatment. that is, the external causes described in the iblc model and associated with the maxwell-wagner polarization mechanism play a large role in increasing the dielectric constant. 3.3. dielectric properties of la1.8ca0.2ni0.8m0.2o4+δ (m = co, cu) ceramics the relative complex permittivity, admittance and loss tangent were estimated by measuring the impedance z = re z + i imz with the equation: ∗(𝜔) = 𝑙 𝑆 1 𝑖𝜔 0𝑍 ∗(𝜔) , (2) 𝑌∗(𝜔) = 1 𝑍∗(𝜔) , (3) tan 𝛿(𝜔) = im re , (4) where  is the circular frequency (ω = 2π𝑓, and 𝑓 is the linear frequency of electric field), 0 is the dielectric constant of vacuum, and 𝑙 and s are the sample thickness and the surface area contacting with one electrode, respectively. 3.3.1. dielectric characteristics of the test samples obtained after heat treatment in air the plots of the dependence of the dielectric constant and the dielectric loss angle tangent of the la1.8ca0.2ni0.8m0.2o4+δ (m = co, cu) ceramics on the frequency at different temperatures are shown in figure 11. the dielectric constant for both samples have high values of the order of 103 (m = co) and 8∙102 (m = cu) and is frequency independent in the temperature range from 100 to 260 k. however, low values of the dielectric loss tangent are observed only in the temperature range of 100–120 k. chimica techno acta 2022, vol. 9(4), no. 20229410 article 8 of 11 figure 10 the frequency dependences of the imaginary part of the electric modulus for the la1.8ca0.2ni0.8co0.2o4+δ samples (before (a, c) and after tbt (b, d)) at some temperatures and frequency dependences of the imaginary part of the impedance at t = 160 k. the appearance of sufficiently high values of the dielectric constant can be due to both external factors (near-electrode polarization effects, maxwell-wagner effects on grain boundaries, the influence of shape and size of grains) and internal reasons (properties of the material itself – features of the crystalline layered structure, type of charge carriers and related polarization processes). 3.3.2. dielectric characteristics of the ceramics obtained after thermobaric treatment the resulting dielectric data for the ceramics after tbt are shown in figure 12. both samples are characterized by an increase in re ε and retention of frequency and temperature independence (in comparison with the ε value after the ceramics heat treatment). for the sample containing cu in position b, the value of the dielectric constant increases by 200, and for m = co – increases by 100. the dielectric constant of the la1.8ca0.2ni0.8cu0.2o4+δ ceramic increases significantly after thermobaric treatment from 600 to 2000. for the la1.8ca0.2ni0.8co0.2o4+δ sample, the change in the dielectric constant increases from 1000 to 2000). the difference is due to a stronger distortion of the bo6 tetrahedron in the copper-containing sample, which due to the influence of the jahn-teller effect. also , an increase increasing in the dielectric constant of la1.8ca0.2ni0.8m0.2o4+δ (m = co, cu) ceramic after tbt can be associated with a change in the morphology of crystallites that acquire regular geometric flat surfaces after tbt (figure 4), with a decrease in the average grain size (from ~3 μm to ~1.7 μm). as a consequence, this leads to more pronounced polarization effect in the region of grain boundaries with an increased total area of grain boundaries (iblc model) [33, 34], and with an increase in the number of barriers for charge carriers in the form of surfaces of inhomogeneities, the number of which increases in the course of tbt. thus, the increase in the values of the dielectric constant observed in the materials after tbt is mainly associated with the maxwell-wagner mechanism of polarization at grain boundaries and inhomogeneities. 4. conclusions new complex oxides of the k2nif4 type with the la1.8ca0.2ni0.8m0.2o4+δ (m = co, cu) composition were synthesized by pyrolysis of nitrate-organic compositions with 2-substituted ammonium citrate as an organic component, proceeding in the "solution combustion" mode. chimica techno acta 2022, vol. 9(4), no. 20229410 article 9 of 11 figure 11 the frequency dependence of dielectric constant and dielectric loss tangent on temperature for la1.8ca0.2ni0.8m0.2o4+δ (m = cu (a), co (b)) ceramics obtained after heat treatment in air. the transformation of the resulting precursors into the final product takes place at lower temperatures (1223 k) compared to the solid-phase method (1473 k), which solves the problem of obtaining nanodispersed single-phase samples for the manufacture of gas-tight ceramics. to obtain ceramic samples based on these precursors, two methods were used: thermal treatment in air and thermobaric treatment (tbt). during the formation of ceramic samples, the stage of obtaining nanodispersed single-phase powders of the required composition makes it possible to separate two processes that run in parallel during the solidphase synthesis – phase formation and sintering. the nanodispersion of the powder of an already prepared composition ensures the production of dense ceramic samples, the sintering of which requires much less time than the sintering of the samples produced by the solid-phase synthesis. a study of the influence of methods for obtaining ceramics on the morphology of the obtained samples was carried out. a decrease in the average grain size after tbt was found to be almost twofold in comparison with ceramics obtained by sintering in an air atmosphere. the geometric shape of the grains also undergoes significant changes, becoming more faceted. figure 12 the frequency dependence of dielectric constant and dielectric loss tangent on temperature for la1.8ca0.2ni0.8m0.2o4+δ (m = cu (a), co (b)) ceramics obtained after tbt. two reasons for the increase in the dielectric constant of ceramic samples after tbt were identified. the first one is the distortion of the ao9 and bo6 coordination polyhedra, which is most pronounced along the с axis. a significant increase in the ni(m)–o2b bond length, for example, in the case of the sample containing cu leads to a noticeable increase in reε from 600 to 2000. the second reason lies in the increasing the permittivity with decreasing crystallite size, due to the influence of grain boundary effects resulting from the maxwell-wagner polarization mechanism. supplementary materials no supplementary materials are available. funding this work was supported by the russian foundation for basic research (rfbr) (grant no. 20-33-90239), https://www.rfbr.ru/rffi/eng. https://www.rfbr.ru/rffi/eng chimica techno acta 2022, vol. 9(4), no. 20229410 article 10 of 11 acknowledgments the authors are grateful to the leading researcher of the laboratory of oxide systems of the institute of solid state chemistry ub ras leonidov ilia arkadievich for the discussion of the results. author contributions conceptualization: d.y.a., c.t.i. data curation: m.n.v. formal analysis: d.y.a, m.n.v. funding acquisition: d.y.a. investigation: d.y.a., m.a.a., methodology: d.y.a., m.a.a., s.a.y., k.n.i. project administration: d.y.a. resources: d.y.a., c.t.i. software: d.y.a., m.a.a. supervision: c.t.i., l.i.a. validation: d.y.a., c.t.i., m.n.v. visualization: d.y.a. writing – original draft: d.y.a. writing – review & editing: c.t.i., m.n.v., l.i.a. conflict of interest the authors declare no conflict of interest. additional information author ids: yulia a. deeva, scopus id 57208866603; abdullo a. mirzorakhimov, scopus id 57133042800; alexey yu. suntsov, scopus id 26536695400; nadezhda i. kadyrova, scopus id 6701574610; nina v. melnikova, scopus id 7003907528; tatyana i. chupakhina, scopus id 6602115793. websites: ural federal university, https://urfu.ru/en; institute of solid state chemistry ub ras, https://www.ihim.uran.ru. references 1. ramirez ap, subramanian ma, et al. giant dielectric constant response in a 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furyland benzofuryl-containing building blocks for organic materials diana a. eshmemet’eva i̇d , danil k. vshivkov i̇d , yury a. vasev i̇d , danil a. myasnikov* i̇d perm state university, perm 614990, russia * corresponding author: mda@psu.ru this paper belongs to a regular issue. © 2022, the authors. this article is published in open access under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). abstract a synthetic approach to furyland benzofuryl-containing building blocks utilizing easily accessible substrates is reported. cascade acidcatalyzed reactions of 2-methylfuran with α,β-unsaturated carbonyl compounds or salicyl alcohols followed by oxidation afford functionalized furans and benzofurans, respectively. synthetic potential of the obtained products was demonstrated by synthesizing hetarylsubstituted heterocycles, which may find an application in materials chemistry. keywords furan benzofuran heterocycle methodology building block received: 17.05.22 revised: 23.06.22 accepted: 25.06.22 available online: 12.07.22 1. introduction organic molecules have an opportunity for replacing the traditional inorganic compounds in functional materials due to their low cost, flexibility in designing physical and chemical properties, and simplicity of the manufacturing processes [1, 2]. the possibility for the organic compounds to act as active components of solar cells [3], optoelectronic devices [4], sensors [5, 6] and other materials [7, 8] has been the focus of extensive research. the functional properties of heterocyclic architectures, which have certain advantages over carbocyclic counterparts [9], have been intensively studied [10, 11]. historically, thiophene derivatives were among the first to be used as substrates to obtain functional materials for organic electronics [12]. in turn, furans, being oxygencontaining analogs with better solubility as well as with other suitable physicochemical features [13] could compete with thiophenes; however, their use as integral parts of functional materials started to be investigated just recently. thus, the potential applications of furans and benzofurans in photovoltaics [14–16] and optoelectronics [17, 18] are being evaluated currently with a specific focus on hetaryl-substituted systems (figure 1). to date, there are few general synthetic strategies toward furyland benzofuryl-containing heterocycles. usually, benzofurans are accessed via transition metal-catalyzed interor intramolecular cyclizations of phenols or their oprotected derivatives with alkenes and alkynes [19]. suzukimiyaura cross-coupling is used to obtain target heterocyclic motifs possessing both benzofuran [20] and furan [21, 22] moieties. the conjugate addition/cyclization has also been successfully utilized for the synthesis of substituted furanindol conjugates [23]. heterogeneous catalysis with cu@imine/fe3o4 nanoparticles [24], graphene oxide with cascade addition/cyclization [25] was applied to obtain complex heterocyclic molecules with furyl substituents. acid-catalyzed domino reaction of accessible alkylfurans [26] with ambiphilic compounds, comprehensively explored by butin et al., serves as a convenient tool for constructing functionalized heterocyclic compounds [27]. the butin reaction yields a wide range of heterocycles that possess alkanone fragments, including furans and benzofurans. in the present work, we propose a way for the utilization of the butin reaction products as building blocks for construction hetaryl-substituted furans [28] and benzofurans [29] as potential functional molecules. the synthetic design relies on the possibility for the oxidation of the alkanone side chain followed by chemical engagement of the formed α,β-unsaturated ketone fragment into chemical transformations to obtain novel heterocyclic systems [30, 31, 32] (scheme 1). http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2022.9.4.03 https://orcid.org/0000-0001-5066-4903 https://orcid.org/0000-0003-0952-7215 https://orcid.org/0000-0003-3434-5712 https://orcid.org/0000-0001-8889-9580 mailto:xx@yy.zz http://creativecommons.org/licenses/by/4.0/ https://crossmark.crossref.org/dialog/?doi=https://doi.org/10.15826/chimtech.2022.9.4.03&domain=pdf&date_stamp=2022-7-12 chimica techno acta 2022, vol. 9(4), no. 20229403 article 2 of 6 figure 1 furan-based molecules for material chemistry. scheme 1 known synthetic strategies toward hetaryl-substituted furans and benzofurans and our protocol. 2. experimental 1h and 13c nmr spectra were recorded with a «bruker avance iii hd 400» (400 mhz for 1h and 101 mhz for 13c nmr) spectrometer at room temperature; the chemical shifts (δ) were measured in ppm with respect to the solvent (cdcl3, 1н: δ = 7.26 ppm, 13c: δ = 77.16 ppm). coupling constants (j) are given in hertz. splitting patterns of apparent multiplets associated with an averaged coupling constants were designated as s (singlet), d (doublet), t (triplet), m (multiplet), and br (broadened). gc/ms analysis was performed on an «agilent 7890в» interfaced to an «agilent 5977а» mass selective detector. melting points were determined with a «stuart smp 30». column chromatography was performed on silica gel macherey nagel (40–63 μm). reaction progress was monitored by gc/ms analysis and thin layer chromatography (tlc) on aluminum backed plates with merck kiesel 60 f254 silica gel. the tlc plates were visualized either by uv radiation at a wavelength of 254 nm. all the reactions were carried out using dried and freshly distilled solvent. 2.1. general method for synthesis of furans a 5 ml microreaction vial equipped with a stirring bar and a teflon cap was charged with unsaturated ketone 1 (1 mmol), 2-methylfuran (2) (1.5 mmol, 123 mg, 1.5 equiv), acoh (5 ml), and 48% aq. hbr (8.4 mg, 5.6 μl, 5% mol). the vial was closed and placed into an aluminum heating block preheated to 80 °c, and the mixture was stirred for 12 h (tlc control). upon completion, the reaction mixture was filtered through a thin layer of silica gel. the solvent chimica techno acta 2022, vol. 9(4), no. 20229403 article 3 of 6 was evaporated, and the residue was dissolved in dichloromethane (2 ml) and ddq (1.2 mmol, 272 mg, 1.2 equiv.) was added. the mixture was stirred at room temperature until full consumption of the starting material (tlc control). upon completion, the reaction mixture was subjected to column chromatography on silica gel (eluent: dichloromethane/petroleum ether, 1:1). 2.1.1. (e)-4-(3,5-diphenylfuran-2-yl)but-3-en-2-one (3a) yellow needles. yield 265 mg (92%); mp = 112–113 °c (ethanol). rf = 0.45 (petroleum ether/ethyl acetate, 3:1). 1h nmr (400 mhz, cdcl3): δ 7.82–7.75 (m, 2h), 7.51–7.32 (m, 9h), 6.90 (s, 1h), 6.84 (d, j = 15.6 hz, 1h), 2.34 (s, 3h) ppm. 13c nmr (101 mhz, cdcl3): δ 197.6, 155.7, 146.1, 134.3, 132.5, 129.7, 129.1 (2c), 129.0 (2c), 128.9, 128.5 (2c), 128.3, 128.1, 124.6 (2c), 124.3, 108.8, 28.1 ppm. gclrms (ei, m/z): 288 (m+, 100%), 273 ([m–ch3]+), 245 ([m–ch3co]+). 2.1.2. (e)-4-(5-(4-methoxyphenyl)-3-phenylfuran-2-yl)but3-en-2-one (3b) orange solid. yield 264 mg (83%); mp = 142–143 °c (ethanol). rf = 0.40 (petroleum ether/ethyl acetate, 3:1). 1h nmr (400 mhz, cdcl3): δ 7.73–7.68 (m, 2h), 7.50–7.37 (m, 6h), 6.98–6.94 (m, 2h), 6.79 (d, j = 15.8 hz, 1h), 6.76 (s, 1h), 3.85 (s, 3h), 2.33 (s, 3h) ppm. 13c nmr (101 mhz, cdcl3): δ 197.7, 160.4, 155.9, 145.4, 134.6, 132.6, 129.1 (2c), 128.5 (2c), 128.3, 128.3, 126.2 (2c), 123.7, 122.6, 114.5 (2c), 107.4, 55.5, 28.1 ppm. gc-lrms (ei, m/z): 318 (m+, 100%), 303 ([m–ch3]+), 275 ([m–ch3co]+). 2.1.3. (e)-4-(3,5-bis(4-methoxyphenyl)furan-2-yl)but-3-en2-one (3c) brown solid. yield 261 mg (75%); mp = 137–139 °c (ethanol). rf = 0.28 (petroleum ether/ethyl acetate, 4:1). 1h nmr (400 mhz, cdcl3) δ 7.73–7.68 (m, 2h), 7.44 (d, j = 15.6 hz, 1h), 7.41–7.37 (m, 2h), 7.02–6.93 (m, 4h), 6.77 (d, j = 15.6 hz, 1h), 6.73 (s, 1h), 3.86 (s, 3h), 3.858 (s, 3h), 2.32 (s, 3h) ppm. 13c nmr (101 mhz, cdcl3) δ 197.6, 160.4, 159.9, 155.9, 145.2, 134.5, 129.8 (2c), 128.4, 126.27 (2c), 125.1, 123.3, 122.8, 114.7 (2c), 114.6 (2c), 107.5, 55.5 (2c), 28.1 ppm. gc-lrms (ei, m/z): 348 (m+, 100%), 333 ([m–ch3]+), 305 ([m–ch3co]+). 2.2. general method for synthesis of benzofurans to a solution of salicyl alcohol 4 (0.5 mmol) in dichloroethane (2 ml) was added 2-methylfuran (2) (0.75 mmol, 61.5 mg, 1.5 equiv.) and trifluoromethanesulfonic acid (0.05 mmol, 7.5 mg, 0.1 equiv.). the resulting mixture was stirred at 80 °c until full consumption of the starting material (tlc control, ca. 1 h). upon completion, the reaction mixture was filtered through a thin layer of silica gel, and ddq (0.6 mmol, 136 mg, 1.2 equiv.) was added. the mixture was stirred at room temperature until full consumption of the starting material (tlc control). upon completion, the reaction mixture was subjected to column chromatography on silica gel (eluent: ethyl acetate/petroleum ether, 1:20). 2.2.1. (e)-4-(3-phenylbenzofuran-2-yl)but-3-en-2-one (5a) orange solid. yield 127 mg (97%); mp = 102–104 °c (ethanol). rf = 0.56 (petroleum ether/ethyl acetate, 1:1). 1h nmr (400 mhz, cdcl3) δ 7.67–7.63 (m, 1h), 7.56–7.40 (m, 8h), 7.31–7.26 (m, 1h), 6.98 (d, j = 15.7 hz, 1h), 2.35 (s, 3h) ppm. 13c nmr (101 mhz, cdcl3) δ 197.6, 155.2, 148.5, 131.3, 129.7 (2c), 129.3 (2c), 128.6, 128.6, 128.5, 127.3, 127.2, 126.9, 123.7, 121.1, 111.7, 28.6 ppm. gc-lrms (ei, m/z): 262 (m+), 247 ([m–ch3]+), 219 ([m–ch3co]+, 100%) [33]. 2.2.2. (e)-4-(4,7-dimethoxy-3-phenylbenzofuran-2-yl)but-3en-2-one (5b) yellow solid. yield 135 mg (84%); mp = 166–167 °c (ethanol). rf = 0.49 (petroleum ether/ethyl acetate, 1:1). 1h nmr (400 mhz, cdcl3) δ 7.42–7.33 (m, 5h), 7.26 (d, j = 15.7 hz, 1h), 6.91 (d, j = 15.7 hz, 1h), 6.76 (d, j = 8.6 hz, 1h), 6.47 (d, j = 8.6 hz, 1h), 3.94 (s, 3h), 3.60 (s, 3h), 2.22 (s, 3h) ppm. 13c nmr (101 mhz, cdcl3) δ 197.7, 149.3, 148.4, 145.6, 140.2, 131.4, 130.9 (2c), 128.4, 128.2, 127.9 (2c), 127.5, 126.7, 119.9, 110.0, 104.1, 57.1, 56.0, 28.7 ppm. gc-lrms (ei, m/z): 322 (m+, 100%), 307 ([m–ch3]+), 279 ([m–ch3co]+). 2.2.3. (e)-4-(5-methoxy-7-methyl-3-phenylbenzofuran-2yl)but-3-en-2-one (5c) brown solid. yield 133 mg (87%); mp = 135–136 °c (ethanol). rf = 0.55 (petroleum ether/ethyl acetate, 1:1). 1h nmr (400 mhz, cdcl3) δ 7.57–7.44 (m, 6h), 6.96 (d, j = 15.7 hz, 1h), 6.88–6.85 (m, 2h), 3.80 (s, 3h), 2.55 (s, 3h), 2.35 (s, 3h) ppm. 13c nmr (101 mhz, cdcl3) δ 197.7, 156.8, 149.4, 148.9, 131.7, 129.6 (2c), 129.3 (2c), 128.8, 128.5, 128.4, 127.4, 126.8, 122.9, 117.6, 100.2, 56.1, 28.3, 15.2 ppm. gc-lrms (ei, m/z): 306 (m+), 291 ([m–ch3]+), 263 ([m–ch3co]+, 100%). 2.3. general method for synthesis of pyrroles to a solution of furan 3a or benzofuran 5a (0.4 mmol) in dioxane (3 ml) was added tosmic (0.8 mmol, 156 mg, 2 equiv.) and cs2co3 (0.8 mmol, 260 mg, 2 equiv.). the resulting suspension was stirred at 60 °c until full consumption of the starting material (tlc control, ca. 24 h). upon completion, the reaction mixture was poured into water (200 ml) and extracted with ethyl acetate (3×20 ml). combined organic phase was dried over anhydrous na2so4, filtered and concentrated under reduced pressure. crude concentrated extract was subjected to column chromatography on silica gel (eluent: ethyl acetate/petroleum ether, graduate elution from 1:5 to 1:2). 2.3.1. 1-(4-(3,5-diphenylfuran-2-yl)-1h-pyrrol-3-yl)ethan-1one (6) colorless oil. yield 116 mg (89%). rf = 0.41 (petroleum ether/ethyl acetate, 1:1). 1h nmr (400 mhz, cdcl3) δ 9.57 (br. s, 1h), 7.77–7.70 (m, 2h), 7.45–7.36 (m, 5h), 7.31–7.25 (m, 3h), 7.24–7.19 (m, 1h), 6.96 (s, 1h), 6.79 (t, j = 2.3 hz, 1h), 2.23 (s, 3h) ppm. 13c nmr (101 mhz, cdcl3) δ 194.7, 153.0, 143.5, 133.9, 130.8, 128.8 (2c), chimica techno acta 2022, vol. 9(4), no. 20229403 article 4 of 6 128.5 (2c), 127.5, 127.3 (2c), 126.7, 125.3, 125.3, 124.9, 123.8 (2c), 121.8, 114.0, 106.8, 28.1 ppm. gc-lrms (ei, m/z): 327 (m+, 100%), 312 ([m–ch3]+), 284 ([m– ch3co]+). 2.3.2. 1-(4-(3-phenylbenzofuran-2-yl)-1h-pyrrol-3-yl)ethan1-one (7) colorless oil. yield 114 mg (95%). rf = 0.33 (petroleum ether/ethyl acetate, 1:1). 1h nmr (400 mhz, cdcl3) δ 9.42 (br. s, 1h), 7.56–7.50 (m, 1h), 7.38–7.33 (m, 1h), 7.33–7.27 (m, 2h), 7.25–7.09 (m, 6h), 6.58–6.51 (m, 1h), 2.10 (s, 3h) ppm. 13c nmr (101 mhz, cdcl3) δ 193.9, 154.7, 146.9, 133.1, 129.2 (2c), 128.9, 128.7 (2c), 127.1, 125.8, 124.6, 124.5, 122.9, 122.0, 120.1, 119.0, 113.7, 111.4, 28.3 ppm. gc-lrms (ei, m/z): 301 (m+, 100%), 286 ([m– ch3]+), 258 ([m–ch3co]+). 3. results and discussion we began our research with evaluating the possibility of synthesizing the target α,β-unsaturated carbonyl compounds with furyl substituent at β-position. to this end, we utilized a recently reported acid-catalyzed domino reaction of 2-methylfuran (2) with unsaturated ketones 1 that led to the formation of furylalkanones a (scheme 2). we screened various oxidants in order to obtain respective unsaturated products 3 from alkanones a [34–36] and found that ddq in the amount of 1.2 equiv. effectively induced the desired transformation affording compounds 3 with high yields. the oxidation step could be coupled with the acid-catalyzed domino reaction with the only requirement to change the solvent after passing the initial reaction mixture through a pad of silica gel. the developed method was evaluated by synthesizing three examples of the target molecular architecture. in order to obtain the target benzofuryl-containing unsaturated ketones 5, we employed another acid-catalyzed domino reaction, namely, a reaction of salicyl alcohols 4 with 2-methylfuran (2) [29] (scheme 3). the oxidative conditions found for the synthesis of compounds 3 from alkanone intermediates appeared to be suitable for obtaining the benzofuran counterparts 5. the oxidation step was also integrated into the process without the need to switch the solvent, and the resulting products 5a-c were obtained with high yields. the presence of a highly reactive α,β-unsaturated ketone fragment in the structure of the synthesized compounds opens prospect for applying the products 3 and 5 as building blocks for obtaining the furyland benzofurylcontaining heterocycles. to demonstrate this possibility, we performed the reaction of the compounds 3a and 5a with tosmic upon activation with a base [37–40]. the reaction afforded respective pyrroles 6 and 7 with high yields (scheme 4). the structure of the compounds 6 and 7 represents a general furyl/benzofuryl-substituted heterocyclic motif. importantly, well-explored chemical behaviour of the acetyl group and free pyrrolic nitrogen possessed by the final compounds could be utilized for further structural modifications. scheme 4 synthesis of pyrroles 6 and 7. scheme 2 synthesis of furans 3. scheme 3 synthesis of benzofurans 5. chimica techno acta 2022, vol. 9(4), no. 20229403 article 5 of 6 4. conclusions we developed a protocol for the synthesis of functionalized furans and benzofurans starting from easily available precursors. the obtained products could serve as building blocks for designing potential furanand benzofuran-based heterocyclic functional molecules for organic electronics. supplementary materials no supplementary materials are available. funding the research was supported by the perm research and education centre for rational use subsoil, 2022. acknowledgments none. author contributions conceptualization: d.a.m. data curation: y.a.v. formal analysis: d.a.m., y.a.v. funding acquisition: y.a.v. investigation: d.a.e., d.k.v. methodology: d.a.e., d.k.v. project administration: d.a.m. resources: d.k.v., y.a.v. software: d.a.m., y.a.v. supervision: d.a.m. validation: d.a.m., y.a.v. visualization: y.a.v., d.a.m writing – original draft: y.a.v., d.k.v., d.a.e., d.a.m. writing – review & editing: y.a.v., d.a.m. conflict of interest the authors declare no conflict of interest. additional information author ids: diana a. eshmemet’eva, scopus id 57223841093; danil k. vshivkov, scopus id 57248107200; danil a. myasnikov, scopus id 57487382800. website: perm state university, 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https://doi.org/10.1021/jo402132p https://doi.org/10.1016/j.tet.2017.09.043 https://doi.org/10.1002/adsc.202000454 https://doi.org/10.1039/d1ra04575j https://doi.org/10.1021/cr60246a002 https://doi.org/10.1039/c9ob00847k https://doi.org/10.3390/molecules23102666 https://doi.org/10.1039/c5ra07876h https://doi.org/10.1002/slct.202001344 titanium dioxide activated carbon composite for photoelectrochemical degradation of phenol published by ural federal university eissn 2411-1414; chimicatechnoacta.ru article 2022, vol. 9(4), no. 20229416 doi: 10.15826/chimtech.2022.9.4.16 1 of 11 titanium dioxide activated carbon composite for photoelectrochemical degradation of phenol l. h. q. anh a , uyen p. n. tran b , p. v. g. nghi c, h. t. le c, n. t. b. khuyen d*, t. d. hai e* a: faculty of general sciences, ho chi minh city university of natural resources and environment, ho chi minh city 70000, vietnam b: faculty of engineering and technology, van hien university, ho chi minh city 70000, vietnam c: faculty of applied science, ton duc thang university, ho chi minh city 70000, vietnam d: office of r&d and external relations, ho chi minh city university of natural resources and environment, ho chi minh city 70000, vietnam e: faculty of environment, ho chi minh city university of natural resources and environment, ho chi minh city 70000, vietnam * corresponding author: ntbkhuyen@hcmunre.edu.vn, tdhai@hcmunre.edu.vn this paper belongs to a regular issue. © 2022, the authors. this article is published in open access under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). abstract in this study, titanium dioxide (tio2) and titanium dioxide – activated carbon composite (tio2–ac) were prepared by sol-gel method for photoelectrochemical (pec) applications. characterization of the materials was performed by scanning electron microscope, energy dispersive x-ray analysis, fourier transform infrared spectroscopy, x-ray diffraction, and diffuse reflectance spectroscopy. the results show that tio2 was successfully loaded on activated carbon (ac), producing tio2–ac with 2.61 ev of bandgap energy, lower than that of tio2 (3.15 ev). photoanodes based on tio2 and tio2–ac were fabricated and applied to pec experiments for phenol degradation. in comparison with the tio2 photoanode, the tio2–ac one exhibited superior photocatalytic activity, which was indicated by a high current density and effective phenol removal. a mechanism of phenol pec degradation on the tio2–ac photoanode was proposed, which includes interaction between protonated phenol and active sites bearing oxygen on the photoanode surface. a kinetic model according to this mechanism was also established and fitted to experimental findings, resulting in rate constants of elementary reactions. keywords photoelectrochemical titanium dioxide phenol degradation photocatalyst kinetic model received: 17.09.22 revised: 15.10.22 accepted: 16.10.22 available online: 25.10.22 1. introduction phenol and phenolic compounds are commonly used in pharmaceuticals, insecticides, cosmetics, and other industrial substances [1]. phenol is known as a hazardous pollutant due to its toxicity and high stability for a long period of time in the environment [2, 3]. phenol exposure may cause acute and/or chronic diseases on the skin, eye, respiratory and nervous systems [4, 5]. there are some techniques for phenol removal from wastewater, as summarized in [6]. among advanced oxidation processes, photocatalysis is described as an effective choice for phenol degradation. based on tio2 photocatalyst synthesized by the solgel method, phenol degradation was attained at 58.8% after 240 minutes of uv illumination [7]. in the presence of carbon, photogenerated charge recombination of tio2 was delayed [8], suggesting an improvement in phenol degradation. synergy effect between tio2 and carbon-based materials was explored in the previous reports on multi-walled carbon nanotubes – tio2 [9], activated carbon – tio2 [10], graphene – tio2 [11], and carbon fiber – tio2 [12]. difficult recovery and fast photoexcited electron-hole pairs recombination of catalysts are two considerable drawbacks of photocatalysis, which can be minimized with the photoelectrochemical (pec) method [13, 14]. according to the pec principle, a photocatalyst is coated onto a photoelectrode, to which a bias voltage is applied to improve photogenerated charge carrier separation, thus enhancing the activity of the photocatalyst [15, 16]. therefore, the pec method has attracted considerable interest in water splitting [17] as well as organic pollutants degradation [13]. ushttp://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2022.9.4.16 mailto:ntbkhuyen@hcmunre.edu.vn http://creativecommons.org/licenses/by/4.0/ https://doi.org/10.1039/d0fo02324h http://dx.doi.org/10.1088/1674-0068/22/04/423-428 https://doi.org/10.1016/j.apsusc.2009.12.113 https://doi.org/10.1021/ie501673v https://doi.org/10.1016/j.partic.2010.03.013 https://doi.org/10.1021/acsaem.1c02548 https://orcid.org/0000-0001-7855-1337 https://orcid.org/0000-0001-6038-3873 https://orcid.org/0000-0002-0103-8866 https://crossmark.crossref.org/dialog/?doi=https://doi.org/10.15826/chimtech.2022.9.4.16&domain=pdf&date_stamp=2022-10-25 chimica techno acta 2022, vol. 9(4), no. 20229416 article 2 of 11 ing a tio2-based photoanode for the pec experiment, phenol degradation achieved 73.76% after 120 minutes of uv illumination under 0.8 v of applied voltage [18]. by adding peroxymonosulfate into the pec system, a photoelectrode based on co3o4-loaded carbon fiber demonstrated 100% phenol degradation within 90 minutes under uv radiation at 1.5 v of applied voltage [19]. the contribution of carbon to pec behavior of the c/tio2 composite was explored by haro et al. [20]. it was found out that carbon promoted charge transfer reactions on c/tio2 photoelectrode surface through enhancement of charge carrier generation and separation. however, the application of c/tio2 in pec degradation of organic compounds has not been reported in the literature. in this study, tio2 and tio2-activated carbon (tio2–ac) composites were synthesized by a sol-gel method for pec degradation of phenol. effects of ac on pec properties of the tio2/ac photoanode for phenol were determined. moreover, a mechanism of phenol pec degradation was proposed, revealing a kinetic model describing the surface responses of the tio2/ac photocatalyst. 2. experiment 2.1. materials, chemicals and apparatus pure titanium tetrachloride (ticl4) (99.99%) was purchased from shanghai aladdin bio-chem technology co., ltd (china). commercial activated carbon (ac), ethanol (99%), phenol (>99%), and hexane (>96%) were obtained from xilong scientific co., ltd (china). hydrochloric acid (hcl, 36.5% w/w), sodium hydroxide (naoh, >99%) were bought from merck (germany). liquid polyester resin was collected from en chuan chemical industries co., ltd (taiwan). 1-butyl-1-methylpyrrolidinium hexafluorophosphate (bmim fp6, 97.5%) was supplied by indianmart. tap water was used to prepare all solutions. characterization of materials was conducted with analytic methods such as scanning electron microscopy (sem) and energy dispersive x-ray (edx) using prisma e sem, xray diffraction (xrd) recording by d2 phaser, diffuse reflectance spectra carried out by fl-1039 (horiba), fourier-transform infrared spectroscopy (ft-ir) with nicolet is5, current − voltage (j–v) curve and electrochemical impedance spectroscopy (eis) using mpg2 biologic system. 2.2. preparation of tio2, tio2–ac composite, and photoanodes 10 ml of ticl4 and 10 g of ac were added into an erlenmeyer flask containing 200 ml of hexane under n2 atmosphere in a glovebox. the erlenmeyer flask was then covered and moved to an ultrasonic tank. the mixture was dispersed under 40 khz of sonication for 15 minutes before adding 500 ml of distilled water. after 30 minutes of sonication, the solid phase was separated and washed with distilled water in a vacuum filtration system until the filtrate reached neutral ph. the obtained solid was thermally treated at 550 °c for 30 minutes to produce the tio2–ac photocatalytic composite. to prepare the tio2 photocatalyst, the above procedure was applied without ac. a coating mixture (consisting of 80% w/w of polyester, 19% w/w of ethanol, and 1% w/w of bmim pf6) was deposited onto a sus 304 stainless sheet (0.8 mm of thickness, 100100 mm of dimension) as a photoanode substrate by the dip-coating method. then, an abundant amount of photocatalyst was spread on the photoanode surface and pressed under 3 n/cm2 of pressure to create contact between the photocatalyst and the photoanode substrate. the obtained photoanodes based on tio2 and tio2–ac photocatalysts were stored at room temperature for one week before being utilized in the pec system. 2.3. photoelectrochemical measurements a three-electrode cell was used for pec measurements with a pt grid as a counter electrode, an ag/agcl as a reference electrode, the photoanode as a working electrode, and a uvc mercury lamp (9 w) vertically soaked in a solution. all pec measurements were conducted under fluorescent light (400−600 lux of illumination) in a 10 mg/l of phenol solution, ph = 5 with uv and non-uv radiation. the j–v curves were recorded according to the linear sweep voltammetry technique in a potential range of 0 v to +1.5 v at a scan rate of 50 mv/s. the eis characteristics were obtained over a frequency range of 10 mhz to 10 khz with 10 mv amplitude. 2.4. photoelectrochemical degradation of phenol bath experiments for pec degradation of phenol under uv and non-uv illumination were performed in a stirred pec reactor containing 1 liter of phenol solution. the pt grid and photoanode were vertically dipped into phenol solution and connected to a controllable dc voltage source. between the pt grid and the photoanode, the uv-c lamp was also immersed in the solution. phenol concentration was determined by the colorimetric method using hi 3864 phenol test kit with the instrumental error up to 0.1 mg·l−1. the efficiency of phenol removal was calculated by equation (1). ( )   −    t 0 c phenol removal % = 1 ×100 c (1) where ct, c0 are the concentrations of phenol after contact time t and at the start (initial concentration) in mg·l−1, respectively. 3. results and discussion 3.1. characterization of materials the morphology of tio2, ac and tio2–ac can be observed in sem images. as shown in figure 1a, tio2 particles are irregular polygonal shapes that are less than 25 m in size. porous structure with cavities and pits of ac is disclosed in figure 1b. https://doi.org/10.1016/j.dib.2019.103949 chimica techno acta 2022, vol. 9(4), no. 20229416 article 3 of 11 figure 1 sem images of tio2 (a), ac (b), tio2–ac (c), and edx spectrum of tio2–ac (d). for tio2–ac, a large number of tio2 particles was loaded on ac structure by filling into the pits instead of the surface of cavities, as shown in figure 1c. similar observation was also reported in a previous publication [21]. located in pits, tio2 particles could avoid being washed out from ac in photoanode preparation and utilization. as expected, c, o, and ti elements in tio2–ac were indicated in the edx results, as shown in figure 1d. crystal phase characteristics of tio2, ac, and tio2–ac were explored with x-ray diffraction analysis as shown in figure 2. the reflections from the (002) and (100) planes of aromatic rings of amorphous carbon structure caused the diffraction peaks at 26.2° and 43.5° [22]. for the xrd pattern of tio2, peaks appearing at 27.7°, 36.1°, 41.2°, 54.2°, and 56.7° were indexed as (110), (101), (111), (211), and (220) planes of rutile phase, whereas the presence of anatase phase was identified by the peaks at 25.3° and 48.3°, according to (101) and (200) planes [23]. however, only characteristic peaks of rutile tio2 exist in tio2–ac material, as shown in the xrd pattern of tio2–ac. this may be due to the effect of carbon on anatase to rutile transformation of tio2 through the formation of oxygen vacancies, as mentioned in [24–26]. this is a disadvantage of our tio2–ac because rutile tio2 exhibits lower photocatalytic activity than anatase tio2 [27]. chemical bonds in tio2, ac, and tio2–ac were identified by ftir analysis (figure 3). as shown in the ftir spectrum of tio2, a strong absorption band at about 500 cm−1 reflects the vibration of ti−o bond, and a band at 1653 cm−1 corresponds to o−h bending in absorbed water molecules [28]. stretching vibrations of c−o and c=c bonds in ac structure were identified by bands at 1097 cm−1 and 1554 cm−1, respectively [29]. a band appearing at 3469 cm−1 is associated with the stretching vibration of o−h bond and free water [28]. it can be observed in the ftir spectrum of tio2–ac that characteristic bands of the bonds in tio2 and ac appeared again without a new band, indicating tio2 did not conjugate to ac in tio2–ac by a chemical bond. a similar result could be found in [21, 30]. figure 2 xrd patterns of materials. http://dx.doi.org/10.1155/2016/8393648 http://dx.doi.org/10.1155/2012/702503 http://dx.doi.org/10.1039/c8ra06681g http://dx.doi.org/10.1155/2012/702503 chimica techno acta 2022, vol. 9(4), no. 20229416 article 4 of 11 as presented in figure 4a, uv-v is diffuse reflectance spectra of tio2 and tio2–ac shows the absorption edge of the tio2 and tio2–ac at about 370 nm and 420 nm, respectively. it indicates the red-shift of the tio2–ac towards the visible region in comparison with tio2. tauc plots, relationships of h vs (h)1/2 of materials, are illustrated in figure 4b, revealing band gap energies of 3.15 ev and 2.61 ev for tio2 and tio2–ac, respectively. carbon not only promotes the 4p → 4s electronic transition at defect points in the titanium atoms [31], but also improves the electron transfer due to the high electronic conductivity of carbon, thereby resulting in the lower band gap energy of tio2–ac compared to tio2. this result indicates that tio2–ac can effectively separate electron-hole pairs in the visible region, which promotes photocatalytic activity under the solar illumination. 3.2. characterization of photoanodes a tio2–ac photoanode was selected for morphological analysis by the sem technique. it can be observed in figure 5a that tio2–ac particles in random shapes were widely spread on the photoanode surface generating a rough structure. the original morphology of tio2–ac (figure 1c) exposed on the photoanode surface (as shown in figure 5b) indicated that tio2–ac particles were not immersed completely in the coating mixture. it proves that photoactive sites in tio2–ac were disclosed on the photoanode surface, enabling photoexcitation of the tio2–ac photoanode in the photoelectrochemical system. the mean thickness of a coated layer on the photoanode was determined to be 136 m. photoelectrochemical properties of the tio2 and tio2– ac photoanodes were examined using a three-electrode cell in phenol solution at ph = 5. figure 6 demonstrates the current density of the tio2 and tio2–ac photoanodes under non-uv and uv illumination applying linear sweep voltammetry. in the absence of uv (non-uv), photoanodes present low current density. under uv radiation, photocurrent densities of photoanodes significantly increase. the tio2–ac photoanodes generated a current density of 283 a/cm2 (at 1.45 v vs. ag/agcl), which is approximately 2.2 times higher than that of the tio2 photoanode. this result may be due to the decrease of tio2 band gap in the presence of ac. photocatalytic activity of a photoanode driving a reaction can be evaluated through an onset potential, which is a potential at the intersection point between j-v curve in nonuv radiation and the tangent line with a maximum slope of j-v curve in uv radiation [32, 33]. the onset potential of the tio2 photoanode driving phenol oxidation (~1.0 v vs ag/agcl) is about 350 mv higher than that of the tio2–ac photoanode (~0.66 v vs ag/agcl), indicating heterojunction formation of tio2/ac in the tio2–ac material [34]. the low onset potential of the tio2–ac photoanode demonstrated an effective charge separation and transfer, manifesting a favorable application of the tio2–ac photoanode for pec degradation of phenol. figure 3 ftir spectra of materials. 350 400 450 500 0 1 2 a b s o r b a n c e wavelength, nm (a) tio2 tio2-ac 2,5 3,0 3,5 0 1 2 3 2.6 3.15 ( h  )1 / 2 , e v 1 / 2 h, ev (b) tio2tio2-ac figure 4 curves of uv-vis diffuse reflectance spectra (a) and tauc plots of tio2 and tio2–ac materials (b). https://doi.org/10.1021/acsaem.9b01101 chimica techno acta 2022, vol. 9(4), no. 20229416 article 5 of 11 figure 5 sem images of tio2-ac photoanode surface in 80x (a) and 1200x (b). figure 6 current – voltage (j–v) curves of photoanodes in 10 mg/l of phenol solution (ph = 5). figure 7 presents nyquist plots of tio2 and tio2–ac photoanodes under uv and non-uv illumination. there is only one semicircle for each nyquist plot, indicating that pec process on the photoanodes for phenol was controlled by trap electron transfer [35]. smaller diameter semicircle demonstrates lower charge transfer resistance [36]. it can be observed clearly from figure 7 that the semicircle in the nyquist plot of the tio2 and tio2–ac photoanodes under uv radiation is smaller than that under the non-uv excitation. this finding proves that the charge transfer of photoanodes was improved under uv illumination. the tio2–ac photoanode exhibited a better charge transfer in comparison to tio2 one because nyquist plots of the tio2–ac photoanode show smaller semicircles in both uv and non-uv excitation. this result indicates that the presence of ac not only did not reduce the photocatalytic properties of tio2, but also improved the electrical conductivity of tio2–ac, advancing the applicability of the tio2–ac photoanode in pec process. 3.3. photoelectrochemical degradation of phenol applied external voltage (vapp) can improve pec performance of tio2 by enhancing the generation and separation of charge carriers [37]. after 30 minutes of pec treatment under different vapp in the range of 0−0.7 v, phenol and cod removal at the tio2–ac photoanode were recorded and shown in figure 8a. phenol and cod removal exhibit similar trends under vapp variation. phenol can be converted to organic intermediates during the photocatalysis process before it is completely oxidized to co2 [38]. if cod removal equates to phenol removal, the total removed phenol is oxidized to co2 without the formation of intermediates. as illustrated in figure 8a, the ratio of phenol and cod removal decreases to approximately 1 with the increase of vapp, corresponding to 15.50, 13.67, 7.45, 2.58, 1.04, and 1.04 for 0, 0.2, 0.4, 0.5, 0.6, and 0.7 v of vapp, respectively. dependences of phenol and cod removal as a function of vapp present a break-like point at 0.4 v and an exhaustion-like point at 0.6 v (figure 8a), which is close to the onset potential of the tio2–ac photoanode, suggesting a decisive contribution of the applied external voltage to the pec degradation of phenol. significant improvement of phenol degradation with pec process as compared to photocatalysis is shown in figure 8b. under uv illumination, electrons and holes were photogenerated on tio2, enhancing charge transfer between phenyl ring and photoanodes [39] and promoting phenol degradation. however, fast recombination of these electron-hole pairs causes a low limit of phenol removal, as seen in the tio2/uv and tio2–ac/uv curves. the recombination time of electron-hole pairs can be longer than charge transfer time in the redox reaction under appropriate vapp. as expected, at vapp = 0.7 v, tio2/pec and tio2– ac/pec curves in figure 8b exhibit an increase in phenol removal. moreover, the tio2–ac photoanode presents a higher efficiency of pec degradation of phenol than the tio2 photoanode owing to the contribution of electric conductivity of ac. after 60 min of contact time, phenol pec degradation achieved 75.9% on tio2–ac, which is lower than that on tio2 nanotubes [40], but significantly higher than on tio2 [18]. http://dx.doi.org/10.1134/s1023193515110130 chimica techno acta 2022, vol. 9(4), no. 20229416 article 6 of 11 figure 7 nyquist plots from electrochemical impedance measurements on photoanodes in 10 mg/l of phenol solution (ph = 5). 18,6 20,5 24,6 63,4 71,4 73,2 1,2 1,5 3,3 24,6 68,2 70,4 0,0 0,2 0,4 0,6 0,8 0 25 50 75 p h e n o l r e m o v a l, % applied voltage, v (a) c0 = 10 mg/l ph0 = 5 0 50 100 c o d r e m o v a l, % 0 40 80 120 0 20 40 60 80 tio2-ac/pec tio2/pec tio2-ac/uvp h e n o l r e m o v a l, % contact time, min (b) tio2/uv c0 = 10 mg/l ph0 = 5 vapp = 2 v figure 8 effects of a) applied external voltage and b) pec degradation of phenol on tio2–ac photoanode. as discussed above, the following experiments for the kinetic study of phenol pec degradation were conducted at the tio2–ac photoanode under vapp = 0.7 v and uv illumination. 4. kinetic of photoelectrochemical degradation of phenol in acidic solution photocatalytic degradation of phenol can be described by the following langmuir – hinshelwood (l-h) kinetic mechanism [41–42], in which phenol is first adsorbed onto the photocatalyst surface and then decomposed. therefore, this l-h model (2) was used to fit our experimental data, revealing negative values of kb (as shown in table 1). however, this is unreasonable because the adsorption equilibrium constant kb must be positive. • l-h model: − a b dc k c r = = dt 1+k c (2) • first-order model: − 1 dc r = = k c dt (3) in the case of chemical reaction control, a first-order kinetic model (3) well described the photodegradation of phenol on tio2/ac [43] as well as zno, tio2 and zno–tio2 photocatalysts [44]. photoelectrochemical degradation rate following the first-order model was identified for acidic red 17 dye on ammonium persulphate [45], and phenol on pbo2 anode [46]. however, the determination coefficients (r2) obtained from fitting our experimental data with this model were not close to 1 (as shown in table 1). it signifies that the pec degradation of phenol occurred in a complex mechanism and was not controlled exclusively by a chemical reaction process. we proposed a mechanism of pec degradation of phenol through reactions (4)–(6) based on the previous reports. spallart et al. [47] proved that water competed with aromatic compounds in pec oxidation. moreover, oxygen atoms from water molecules can form o2 •− radicals at photoexcited points [39]. hence, the active site on the photoanode surface (∗𝑛+) was suggested to interact with a water molecule under the applied external potential and form an active site bearing oxygen (∗𝑛+ o2−) following reaction (4). in other consideration, phenol (ph) can be protonated into h+ph form [48] in acid solution, promoting the transfer of electron pair of oxygen in −oh group into the aromatic ring [49] and resulting in polar structure h+ph− according to reaction (5). we suppose that h+ph− contacted with ∗𝑛+ o2− and then oxidized according to reaction (6), yielding the decomposition products and regenerating the active site. − − + + w w kn+ n+ 2 + 2 k h o + * * o 2h (4)  + − + + − + p p k k ph h h ph (5)  − − + − ⎯⎯→ +d k+ n+ 2 n+h ph * o ze products * (6) https://doi.org/10.1016/j.mssp.2014.05.031 http://dx.doi.org/10.1016/j.arabjc.2011.03.001 https://doi.org/10.1016/j.electacta.2013.08.080 https://doi.org/10.1021/acs.jpca.8b04446 chimica techno acta 2022, vol. 9(4), no. 20229416 article 7 of 11 table 1 calculated parameters of kinetic models at different initial concentrations and ph values. kinetic model parameters initial concentrations, mg/l (ph = 5) ph values (c0 = 20 mg/l) 5 10 15 20 3 4 6 l-h ka 0.011 0.012 0.014 0.016 0.033 0.026 0.003 kb −18.62 −9.22 −5.05 −2.78 −3.073 −3.143 −4.595 r2 0.944 0.978 0.995 0.994 0.984 0.998 0.986 first-order k1 0.021 0.021 0.022 0.022 0.034 0.031 0.009 r2 0.054 0.610 0.884 0.959 0.832 0.901 0.704 this study 𝑘𝑤 + 0.131 0.070 0.204 0.122 0.013 0.241 0.231 𝑘𝑤 − ∙ 103 5.608 5.321 6.463 6.339 5.792 6.279 6.325 𝑘𝑝 + 0.099 0.071 0.045 0.034 0.070 0.061 0.023 𝑘𝑝 − 0.032 0.024 0.022 0.013 0.009 0.027 0.028 𝑘𝑑 ∙ 10 3 0.164 0.158 0.156 0.142 0.168 0.192 0.152 [∗𝑛+]𝑒𝑥 452 435 438 392 464 589 471 r2 0.999 0.998 0.994 0.994 0.994 0.998 0.990 k1 [min–1]; ka [min–1]; kb [l·mmol–1]; 𝑘𝑤 + , 𝑘𝑤 − , 𝑘𝑝 +, 𝑘𝑝 − [min–1]; kd [l·mmol–1·min–1], [∗𝑛+]𝑒𝑥 in mmol·l –1 we assume that reactions (4)–(6) occurred in the presence of large amounts of h+ ions and h2o. therefore, the rates of these reactions depend on the concentration of phenol (x1),  −+h ph (x2), and −n+ 2* o (x3), as shown in equations (7), (8), (9). d𝑥1 d𝑡 = −𝑘p +𝑥1 + 𝑘p −𝑥2, (7) d𝑥2 d𝑡 = 𝑘p +𝑥1 − 𝑘p −𝑥2 − 𝑘d 𝑥2𝑥3, (8) d𝑥3 d𝑡 = 𝑘w + [∗𝑛+] − 𝑘w − 𝑥3 − 𝑘d 𝑥2𝑥3, (9) where x1, x2, x3 are in mmol·l−1, and [∗𝑛+] is an apparent concentration of active sites in mmol·l−1. under uv illumination, tio2–ac particles on the photoanode surface were excited to create photoexcited sites (∗). then, under the applied external potential, the photoexcited site lost n electrons and became an active site (∗𝑛+). supposing that the total number of ∗𝑛+ does not change with an apparent concentration [∗𝑛+]𝑒𝑥, equation (10) is obtained: [∗𝑛+]𝑒𝑥 = 𝑥3 + [∗ 𝑛+]. (10) the value of [∗𝑛+] can be determined from (10) and substituted in to (9) to result in (11): d𝑥3 d𝑡 = 𝑘w + [∗𝑛+]ex − (𝑘w + + 𝑘w − + 𝑘d 𝑥2)𝑥3. (11) the parameters in the proposed model (𝑘𝑤 + , 𝑘w − , 𝑘p +, 𝑘p −, kd, and [∗𝑛+]ex) were determined by fitting experimental data with the model using the least-square method for x1 objective: ∑(𝑥1,𝑖 − 𝑥1,�̂�) 2 → min 𝑛 𝑖=1 (12) where, 𝑥1̂ is the phenol concentration predicted by the model, i = 1, 2, …, n denotes ith value, and n = 12 is the number of experimental data points. the determination coefficient (r2) is used to evaluate the goodness of fit of the model as presented in formula (13). 𝑅2 = 1 − ssr sst = 1 − (𝑥1−𝑥1̂) 2 (𝑥1−𝑥1̅̅ ̅) 2 (13) where sss = ∑(𝑥1 − 𝑥1̂) 2 is the residual sum of squares, tss = ∑(𝑥1 − 𝑥1̅̅ ̅) 2 is the total sum of squares, 𝑥1̅̅ ̅ = 1 𝑛 ∑ 𝑥1 𝑛 𝑖=1 is the mean value of x1. numerical solutions of ordinary differential equations (7), (8), and (11) were carried out using runge – kutta 4th order method with initial conditions: 𝑥1(0) = [ph]0 = 𝐶0 94.11 , 𝑥2(0) = 𝑥3(0) = 0 (94.11 is molecule weight of phenol). the minimization problem (12) was solved with the help of the excel solver tool (ver. 2016) with a grg non-linear option. figure 9 shows the effects of initial phenol concentration (c0) and initial ph (ph0) on phenol removal under both observations of the experiment and simulation. the proposed model exhibited a good description of the experimental data due to the closeness of r2 to 1, obtaining kinetic parameters as summarized in table 1. experiments of pec degradation of phenol were performed at different c0 from 5 to 20 mg·l−1 at ph0 = 5, revealing kinetic behavior as presented in figure 9a. phenol exhibits a property of uv light interception [39, 50], causing a decrease in the active site quantity (*n+) and oxidation rate constant (kd) while increasing c0 as shown in table 1. consequently, the rate of phenol removal is lower with higher c0. moreover, contact time for 99.95% phenol removal was predicted to be 1110, 725, 490, and 450 minutes at c0 = 5, 10, 15, and 20 mg·l−1, respectively, according to the proposed model. it proves that the pec degradation of phenol on tio2–ac photoanode did not reach equilibrium and tended to complete phenol removal. ph0 of the solution is an important parameter in the photodegradation of phenol because of the variation of charge properties of phenol at different ph values [51]. in this study, pec degradation of phenol was studied at various ph0 values of solution (3, 4, 5, and 6) with c0 = 20 mg·l−1. phenol is protonated to h+ph− in the presence of ion h+ according to reaction (4). therefore, the lower ph0 value was, the more h+ph− was produced, resulting in an improvement in phenol degradation (as shown in figure 9b). chimica techno acta 2022, vol. 9(4), no. 20229416 article 8 of 11 0 40 80 120 0 20 40 60 80 100 5 mg*l−1 10 mg*l−1 15 mg*l−1 20 mg*l−1 p h e n o l r e m o v a l, % contact time, min (a) conditions: ph0 = 5 vapp = 2v 0 40 80 120 0 20 40 60 80 100 ph0 = 3 ph0 = 4 ph0 = 5 ph0 = 6 p h e n o l r e m o v a l, % contact time, min (b) conditions: c0 = 20 mg*l -1 vapp = 2v figure 9 simulation (continuous line) and experimental results (discrete points) for pec degradation kinetic of phenol on tio2–ac photocathode at different c0 (a) and ph0 (b). variation of [h+ph−]/[ph]0 and [∗𝑛+ o2−] as a function of contact time at different c0 was simulated and presented in figure 10. as shown in figure 10a, [h+ph−]/[ph]0 increased in the first stage, then decreased, reaching the maxima around 25 minutes of contact time. a similar trend is also observed in the inset in figure 10a, which shows the dependence of [h+ph−] on t. the higher c0, the higher maximum value of [h+ph−] would be, contrary to the [h+ph−]/[ph]0 relation. moreover, the rate constant 𝑘p + was found to be 0.099, 0.071, 0.045, and 0.034 min−1 (table 1) at 5, 10, 15, and 20 mg·l−1 of c0, respectively, which proves that high c0 is a disadvantage to protonation of phenol. the curves in figure 10b present the relationships between the amount of *n+o2− and the contact time. in all studied c0, [*n+o2−] quickly increases to reach the equilibrium concentration ([*n+o2−]eq). the ratios of [*n+o2−]eq and [*n+]ex are larger than 0.9, as shown in the inset in figure 10b. it means that most photoexcited sites changed to form active sites bearing oxygen, which acts as a reactant in pec degradation of phenol. although [*n+o2−]eq decreased with the increase of c0, the high value (>350 mmol·l−1) was enough to interact entirely with protonated phenol molecules. the relationship of [h+ph−]/[ph]0 vs contact time at different ph0 (3, 4, 5, and 6) exhibited maxima as shown in figure 11a. the maximum value of [h+ph−]/[ph]0 at ph0 = 3 was the highest. at ph0 = 4, 5, and 6, the maximum values of [h+ph−]/[ph]0 were similar; however, the maximum peaks shifted to longer contact time with the increase of ph0. in other consideration from table 1, the ratio of 𝑘p +/ 𝑘𝑝 − generally decreased with the rise in ph0 (7.8, 2.3, 2.6, and 0.82 at ph0 = 3, 4, 5, and 6, respectively). these results prove that phenol protonation was promoted in low ph0. moreover, ph0 also affected the amount of *n+o2− on tio2–ac photocathode, as shown in figure 11b. for ph0 = 4, 5, and 6, [∗𝑛+ o2−] tended to reach [*n+o2−]eq after around 30 minutes of contact time; and [*n+o2−]eq at ph0 = 4 was the highest. because the point of zero charge of the prepared tio2–ac was determined at ph = 5.4, tio2–ac was positively charged under acidic conditions, advancing to generate *n+o2−. however, the amount of h+ ion was too high at ph0 = 3, causing a strong electrostatic force between h+ and oxygen in ∗𝑛+ o2−, which dissociated oxygen and active site. consequently, [*n+o2−] cannot reach equilibrium concentration after 120 minutes of contact time at ph0 = 3, as shown in figure 11b. 0 40 80 120 0,0 0,2 0,4 0,6 0,8 1,0 20 mg*l−1 c0 = 5 mg*l −1 20 mg*l−1 [h + p h  − ]/ [p h ] 0 contact time, min c0 = 5 mg*l −1 (a) 0 50 100 0,00 0,04 0,08 [h + p h  − ], m m o l* l − 1 contact time, min 0 40 80 120 0 100 200 300 400 500 c0 = 20 mg.l −1 [* n + o 2 − ], m m o l* l − 1 contact time, min (b) 5 0 5 10 15 20 0,00 0,25 0,50 0,75 1,00 [* n + o 2 − ] e q / [* n + ] e x c0, mg*l −1 figure 10 simulation of h+ph− (a) and *n+o2− (b) variations in pec degradation of phenol on tio2–ac photoanode at different c0 (ph0 = 5, vapp = 0.7 v). chimica techno acta 2022, vol. 9(4), no. 20229416 article 9 of 11 0 40 80 120 0,0 0,2 0,4 0,6 0,8 1,0 ph0 = 6 ph0 = 5 ph0 = 4 [h + p h  − ] / [ p h ] 0 contact time, min ph0 = 3 (a) 0 40 80 120 0 100 200 300 400 500 ph0 = 6 ph0 = 5 ph0 = 4 [* n + o 2 − ], m m o l* l − 1 contact time, min ph0 = 3 (b) 3 4 5 6 0,00 0,25 0,50 0,75 1,00 [* n + o 2 − ] e q / [* n + ] ph0 figure 11 simulation of a) h+ph− and b) [∗𝑛+ o2−] variations in pec degradation of phenol on tio2–ac photoanode at different ph0 (c0 = 20 mg·l−1, vapp = 0.7 v). the inset in figure 11b presents the effect of ph0 on the ratio of [∗𝑛+ o2−]/[∗𝑛+] ex. it can be seen that this ratio at ph0 = 5 is the highest (close to 1). it means that more separation between the point of zero charge and ph0 caused lower [∗𝑛+ o2−]/[∗𝑛+] ex. 5. conclusions in this work, tio2 and tio2–ac photocatalysts were successfully synthesized by the sol-gel method to apply to the pec degradation of phenol. the tio2–ac photoanode exhibits higher photoactivity for degrading phenol under uv-c illumination than tio2. effects of applied external voltage, ph, and initial concentration of phenol on the kinetics of phenol pec degradation were also experimentally investigated in this study. the interaction mechanism between protonated phenol and the active site bearing oxygen was well-demonstrated for the phenol pec degradation. the kinetic constants and the concentration variations of protonated phenol and the active site bearing oxygen were determined by fitting the established kinetic model to the experimental data. supplementary materials no supplementary materials are available. funding this research had no external funding. acknowledgments this work was supported by the vietnam’s ministry of natural resources and environment through project coded cs.2022.12. author contributions conceptualization: l.h.q.a, t.d.h formal analysis: p.v.g.n, h.t.l investigation: p.v.g.n, h.t.l methodology: l.h.q.a., n.t.b.k, t.d.h validation: l.h.q.a, u.p.n.t, n.t.b.k visualization: t.d.h writing – original draft: l.h.q.a, t.d.h writing – review & editing: n.t.b.k, u.p.n.t conflict of interest the authors declare no conflict of interest. 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derived from coal fly ash cenospheres published by ural federal university eissn 2411-1414; chimicatechnoacta.ru article 2022, vol. 9(4), no. 20229418 doi: 10.15826/chimtech.2022.9.4.18 1 of 9 hydrothermal synthesis and sorption performance to cs(i) and sr(ii) of zirconia-analcime composites derived from coal fly ash cenospheres tatiana a. vereshchagina a* , ekaterina a. kutikhina a , olga v. buyko b , alexander g. anshits a,с a: institute of chemistry and chemical technology, federal research center “krasnoyarsk science center of siberian branch of the russian academy of sciences”, krasnoyarsk 660036, russia b: research department, siberian federal university, krasnoyarsk 660041, russia c: department of chemistry, siberian federal university, krasnoyarsk 660041, russia * corresponding author: vereschagina.ta@icct.krasn.ru this paper belongs to a regular issue. © 2022, the authors. this article is published in open access under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). abstract the paper is concerned with (i) the hydrothermal synthesis of hydrous zirconium dioxide (hzd) bearing analcime (hzd–ana, zirconia-analcime) and (ii) its sorption properties with respect to cs+ and sr2+. the hzd–ana particles were synthesized from coal fly ash cenospheres composed of aluminosilicate glass with (sio2/al2o3)wt.=3.1 and characterized by pxrd, sem-eds, sta, and low-temperature n2 adsorption. the non-radioactive simulant solutions of different acidity (ph = 2–10) and cs+/sr2+ content (0.5–50.0 mg/l) were used in the work. the effect of synthesis conditions on the hzd–ana particle size, zirconia content and localization as well as the sorption behavior with respect to cs+ and sr2+ (capacity, kd) were clarified. it was found that the small-sized hzd–ana composites surpasses the zr-free analcime and large-sized hzd–ana material in the cs+ and sr2+ sorption parameters (kd ~ 104–106 ml/g). the conditions to synthesize the zirconiaanalcime composite of the highly enhanced sorption ability with respect to sr2+ (kd ~ 106 ml/g) were determined. the high-temperature solid-phase re-crystallization of cs+/sr2+-exchanged hzd–ana composites was shown to occur at 1000 °c, resulting in a polyphase system based on nepheline, tetragonal zro2, and glass phase. keywords cenospheres hydrothermal synthesis zirconia-analcime composite cs(i) and sr(ii) sorption radioactive waste received: 10.10.22 revised: 04.11.22 accepted: 05.11.22 available online: 10.11.22 1. introduction the increased role of inorganic ion exchangers for treatment of radioactive waste solutions, both in nuclear power production and fuel reprocessing plants, is widely recognized [1, 2]. the sorption technologies being developed are aimed, first of all, at separation of heat-emitting fission products, such as 137cs (t1/2 ~ 30 years) and 90sr (t1/2 ~ 29 years) [3, 4], and long-lived actinides, e.g., am (iii), cm (iii), u (iv), pu (iv) [5, 6]. in the context of the ultimate disposal of radioactive waste, the thermally treated inorganic ion exchangers loaded with radionuclides can function as primary mineral-like containment media in a multibarrier geological disposal system [1, 7]. from the point of view of radioactive waste minimization and reduction of a number of separation stages utilized, sorption technologies that simultaneously separate two or more radionuclides are of the greatest interest as compared with technologies that separate only one element. the management of different radionuclides together results in a single product, in which sorbed cations can accommodate in the only phase [8, 9] or be partitioned between several phases [10]. the last immobilization option can be implemented using composite sorbents based on the components differentiated by the affinity to certain radionuclides. some composite sorbents for co-sorption of different cations, for example, alginate-encapsulated graphene oxide-layered double hydroxide beads [11], al2o3–zro2–ceo2 composite material [12], poly-condensed feldspar and perlite-based sorbents [13], nickel-potassium ferrocyanide supported by hydrated titanium and zirconium dioxides [14], silica/ferrocyanide composite [15], synthetic nanocopper ferrocyanide-sio2 materials [16], nano composite materials from biomass waste [17] were reported. http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2022.9.4.18 mailto:vereschagina.ta@icct.krasn.ru http://creativecommons.org/licenses/by/4.0/ https://orcid.org/0000-0003-4538-8902 https://orcid.org/0000-0002-8730-129x https://orcid.org/0000-0003-4671-4909 https://orcid.org/0000-0002-5259-0319 https://crossmark.crossref.org/dialog/?doi=https://doi.org/10.15826/chimtech.2022.9.4.18&domain=pdf&date_stamp=2022-11-10 chimica techno acta 2022, vol. 9(4), no. 20229418 article 2 of 9 great capabilities for selective separation of metal cations are inherent to zeolites, which are framework aluminosilicates with an open microporosity [18, 19]. the size of pore entrances imparts a molecular/ion sieve property to zeolites. in particular, analcime (ana) having the minimal pore entrances (d = 2.6 å) compared to other zeolites displays an affinity towards well-proportioned cations of actinides, lanthanides, and heavy metals [20–22]. at the same time, due to the ion sieving effect, analcime has a poor cs+ and sr2+ sorption capacity at 25 °c [23] but is capable to trap these cations under hydrothermal conditions at 250–300 °c [24]. the prospective single-phase ceramics proposed for ‘‘minor’’ actinide isolation are based on zr-bearing minerallike host phases including zircon, zirconia, zirconates, etc. [25, 26]. to implement the sorption approach to actinide immobilization, the zr-based ion exchangers as precursors of zr-bearing phases are to be used. the sorbent-precursor must be thermodynamically metastable to undergo the phase transformation in relatively mild conditions. high sorption ability and a developed porosity also facilitate crystallization of the sorbent due to the homogeneous distribution of target radionuclides in the sorbent structure. these properties are inherent to the microporous/layered ion exchange materials synthesized under mild hydrothermal treatment at 100–200 °c and autogenic pressure [27, 28]. the methods to synthesize hydrothermally nano-zirconia, zirconium incorporated micro/mesoporous silica, and zirconia-based nanocomposites were also reported [29−31]. recently, the analcime based composite materials with hydrous zirconium dioxide (hzd) species embedded in a zeolite analcime body (hzd-ana) were synthesized hydrothermally in an alkaline media using coal fly ash cenospheres as a si and al source and zirconium citrate, ammonium complex, as a zr source [22, 32]. variation of the synthesis conditions enables producing small-sized and large-sized zro2analcime crystals of narrow size distributions with maxima at about 6 μm [22] and 40 μm [32], respectively. the thermal treatment of zro2-bearing analcime up to 1000 °c resulted in a powdered zirconia/nepheline/glass composite material [32] having a potential as a precursor of the chemically – mechanically –, and radiation – resistant nuclear waste form, in which sorbed actinides can accommodate in a tetragonal zirconia-based phase, and retained cs+ and sr2+ can be hosted by aluminosilicatebased or vitreous phases [33, 34]. evaluation of sorption properties of the small-sized hzd–ana particles with respect to nd3+, taken as an imitator of actinides (iii), demonstrated that the material traps nd3+ cations from diluted solutions with a distribution coefficient of about 105 ml/g and efficiency of up to 99.6% [22]. the nd3+ sorption parameters obtained for hzd–ana are comparable with ones determined for pure analcime. this fact testifies that, for the most part, analcime but not zirconia is responsible for nd3+ sorption on the hzd– ana composite. as for the zr-bearing component, zirconia in a hydrous form is an effective ion exchanger with respect to both anions and cations, including cesium and strontium [2, 35–37]. so, the hzd–ana material is expected to display the sorption properties also towards the cs+ and sr2+ cations. the present paper is aimed at (i) the hydrothermal synthesis of hydrous zirconia bearing analcime under varied conditions, (ii) the evaluation of its sorption properties with respect to cs+ and sr2+ as imitators of radionuclides 137cs and 90sr, and (iii) the demonstration of possibility to immobilize the sorbed cations of different nature in a single solid. the non-radioactive simulant solutions of different acidity (ph = 2–10) and cs+/sr2+ contents being close to the compositions of the actual radioactive wastewater were used in the work. 2. experimental 2.1 chemicals and materials the chemicals (sodium hydroxide; zirconium citrate, ammonium complex) used in this work were of reagent grade quality. they were obtained from the commercial supplier (ooo “reactiv”, russia) and used without further purification. the cenosphere material (marked further as (sio2–al2o3)glass) was a product of separation of a coal fly ash cenosphere concentrate resulted from combustion of kuznetsk coal (russia) [38, 39]. the chemical and phase compositions (wt.%) of the initial cenosphere fraction were as follows: sio2 – 67.6, al2o3 – 21.0, fe2o3 – 3.2, cao+mgo+na2o+k2o – 7.7; quartz – 3.4, mullite – 0.8, calcite – 0.5, glass phase – 95.4; (sio2/al2o3)glass – 3.1. the micrographs of the cenosphere globules are given in figure 1. 2.2 synthetic procedures the small-sized zirconia bearing analcime was synthesized in the zrc6h7o7nh4–naoh–h2o–(sio2–al2o3)glass system of the 1.0 sio2/0.18 al2o3/0.89 na2o/0.15 zro2/65 h2o molar composition using zirconium-ammonium citrate as a zr source and cenospheres as a si and al source. the reaction mixture was hydrothermally treated in a teflon-lined stainless-steel autoclave (“beluga”, premex ag switzerland) at 150 °c and autogenoius pressure for 48–96 h applying two stirring modes. the first one is based on the permanent stirring of the reaction mixture in the horizontal plane at a rate of 50 rpm for 48 h (the sample is denoted as ss-hzd-ana50). another option is the alternate stirring in the horizontal plane at a rate of 30 rpm, under which the agitation for 30 min alternated with the two-hour non-stirring regime for 96 h (the sample is denoted as ss–hzd–ana–30). the solid products were separated by filtration and washed with distilled water, followed by centrifuging the suspension, separation of a sediment, and drying at 65 °c. the subsequent separation of the sediment by particle sizes was done using a sieve with an aperture of 36 μm. to remove free zirconium dioxide, the product fractions <36 μm were put into water and treated by an ultrasonic source (cole-parmer instruments cpx-750, usa) for 30 min. the sediments were separated by decantation and dried at 65 °c. chimica techno acta 2022, vol. 9(4), no. 20229418 article 3 of 9 figure 1 sem images of initial cenospheres: total view (a); broken globule (b). the large-sized (~40 µm) zirconia bearing analcime was prepared as described in [32] applying the agitation procedure based on rotation of the autoclave in a vertical plane at a rate of 30 rpm (the sample is denoted as ls–hzd–ana–30). small-sized zr free analcime was synthesized in the naoh–h2o–(sio2–al2o3)glass system of the 1.0 sio2/0.18 al2o3/0.89 na2o/65 molar composition under the same hydrothermal conditions (150 °c, 48 h) applying the permanent stirring of the reaction mixture in the horizontal plane at a rate of 50 rpm as described in [40] (the sample is denoted as ss–ana–50). the solid product was washed with distilled water followed by filtration and drying at 80 °c. 2.3 sorption experiments batch sorption experiments were performed upon contacting the specimen (0.0500±0.0005 g) with csno3 or sr(no3)2 solution of 0.5–50.0 mg/l cs+/sr2+ at agitation and ambient temperature (v = 40 ml; τ = 24 h). then the solid and liquid phases were separated by filtration and cs+/sr2+ equilibrium concentrations in the filtrate solutions were measured by flame atomic absorption spectroscopy (aas) (aas-30, carl zeiss, germany) and, in the case of the metal content being below an aas detection limit, inductively coupled plasma mass spectrometry (icp-ms) (xseries ii, thermo scientific, usa). the equilibrium cs+/sr2+ concentrations in the solid phase (qe, mg/g) were determined as qe = (co–ce)∙v/m, where co is the initial metal concentration in the liquid phase, mg/l; ce is the equilibrium cs+/sr2+ concentration in the liquid phase, mg/l; v is the volume of solution, l; m is the mass of the sample, g. the experimental sorption data were plotted as qe = f(сe) and fitted by the langmuir equation: 𝑄𝑒 = 𝑎𝑚 ∙ 𝑏 ∙ 𝐶𝑒 (1 + 𝐶𝑒) , (1) where am is the maximum sorption capacity of the solid, mg/g; b is the langmuir constant, l/mg; ce is the cs+/sr2+ equilibrium solution concentration, mg/l. the distribution coefficient values (kd = qe/ce, ml/g) were determined for the region of low equilibrium concentrations (ce < 1 mg/l). 2.4 characterization techniques chemical composition of the cenosphere fraction was determined according to state standard (gost) no. 5382-2019 [41]. powder x-ray diffraction (pxrd) data were collected on a dron-3 (russia) and a panalytical x’pert pro (netherlands) diffractometers using the cu kα radiation over the 2θ range of 12–120 °. the samples were prepared by grinding with octane in an agate mortar and packed into a flat sample holder for the pxrd measurements in the braggbrentano geometry. the crystallographic data base jcpdsicdd pdf-2 release 2004 and the software phasanx 2.0 were used to process the pxrd patterns. the morphologies of materials under study were identified by the scanning electron microscopy (sem) using a тм3000 and a tm-4000 (hitachi, japan) instruments. to identify the elemental composition of sample materials, energy dispersive x-ray spectroscopy (eds or edx) analysis was performed using the tm-3000 microscope equipped with the bruker microanalysis system including an energy-dispersive x-ray spectrometer with an xflash 430 h detector and quantax 70 software. the analysis was carried out at an accelerating voltage of 15 kv in a mapping mode. the data accumulation time was 10 min. the synchronic thermal analysis (sta) was performed on a sta jupiter 449c device (netzsch, germany) under a dynamic argon-oxygen atmosphere (20% o2, 50 ml/min total flow rate). platinum crucibles with perforated lids were used. the measurement procedure consisted of a temperature stabilization segment (30 min at 40 oc) and a dynamic segment at a heating rate of 10 o/min. qualitative composition of a gas phase was evaluated on the basis of the ion intensity change with m/z = 18 (h2o). the specific surface area (ssa, m2/g) of the ana-based materials was evaluated by the brunauer-emmett-teller (bet) method [42] on the basis of nitrogen adsorption isotherm measurements at 77 k using a nova 3200e analyzer (quantachrome instruments, usa) and novawin software. chimica techno acta 2022, vol. 9(4), no. 20229418 article 4 of 9 3. results and discussion 3.1 morphology and composition of solid products as it follows from table 1, the single crystal phase identified by pxrd in all the solid products is cubic analcime (ana), naalsi2o6∙h2o (icdd #01–070–1575). the pxrd peaks of zirconium phases were not observed for the zr bearing systems. this fact gives reason to assume that zr-containing matter is essentially amorphous in the sample. by the sem data (figure 2–6), crystals of an icositetrahedron habit typical of analcime [43] are visualized on all images. however, some differences in the particle morphology and analcime crystal sizes are clearly evident for solids resulted from the zr-free and zr-containing reaction mixtures. so, in the na2o–h2o–(sio2–al2o3)glass system the analcime crystals of 3–10 µm in size are attached to an unconverted glass support, forming the hollow polycrystalline analcime microspheres (figure 2). in the presence of zirconium, the loose analcime crystals of a narrow size distribution (5–10 µm) are formed (figure 3, 4), the analcime-like particles being the only product in the reaction mixtures. the effect of the synthesis operation (autoclave type, agitation mode) was manifested to the greatest extent in the size of the formed particles. figure 3 shows the large-sized zirconium-bearing analcime crystals with the size distribution maximum of about 40 µm (figure 3a, table 1), which were produced under rotation of the autoclave in a vertical plane and described in detail in the earlier work [32]. the zirconia inclusions in the bulk of analcime crystals with an average zr content of 4.8 wt.% was supported in [32] by the sem-eds measurements over analcime crystal cross-sections and x-ray photoelectron spectroscopy. zirconia species are also visible as contrast white spots on facets of analcime icositetrahedra (figure 3b, 3c) giving the zr content of about 5 wt.% (figure 3d). the most probable state of zirconium occurred in zr-bearing analcime is amorphous zirconia. there is no free zirconia matter on the crystal surfaces and between analcime particles (figure 3a). the absence of an unbound porous material mixed with analcime is supported by the measurements of the low-temperature n2 adsorption, which was extremely small due to the inaccessibility of the analcime microporous structure (d = 0.26 nm) for penetration of nitrogen molecules with a kinetic diameter of 0.37 nm [18]. as for the small-sized zr-analcimes synthesized in the autoclave applying the stirring in a horizontal plane, the aggregated zirconia species cover the crystal surfaces as a free porous matter (figure 4) providing the rather high specific surface area – 30–40 m2∙g–1 (table 1). the enhanced ssa of the zr-free ss-ana-50 is likely to be due to the porosity of residual leached glass and micro/meso-sized voids between analcime crystals fixed on glass. the main difference between two small-sized zranalcimes is revealed in the zr content on the crystal surface (figure 4e, 4f). the analcime particles synthesized at the alternate stirring are characterized by the greater zr content than zirconia-analcime resulted from the synthesis at the permanent agitation. one can see in figure 5 that the analcime particles entering the ss–hzd–ana–30 display the inhomogenious zirconia covering with variation of the zr content in the range of 8–14 wt.%. additional agglomerates of an irregular form containing zr species together with glass residues are also a part of this solid product. table 1 composition, specific surface area and crystal size of the solid products. sample main crystal phase ssa, m2g–1 zr content, wt.% crystal size, µm ss–ana– 50* cubic (ia–3d) analcime naalsi2o6∙h2o 36 – 2−7 ss–hzd– ana–50 30 4−5 5−10 ss–hzd– ana–30 39 8−13 7−10 ls–hzd– ana–30 n.d.** 5−7 20−50/41 *** *glass-supported analcime; ** not determined; *** crystal size distribution maximum. figure 2 sem images of zr-free devitrified cenospheres resulted from the naoh–h2o–(sio2–al2o3)glass system: total view of the microsphere product (a); glass-supported analcime (b). chimica techno acta 2022, vol. 9(4), no. 20229418 article 5 of 9 in turn, the synthesis carried out at the permanent agitation resulted in predominantly pure zirconia-analcime with the lower content of zirconia deposition (4–7 wt.% zr) (figure 6). the ssa value for ss–hzd–ana–50 is, reasonably, by one and a half time lower than the ssa for the ss– hzd–ana–30 sample (table 1). thus, the revealed features of particle morphology, zirconia occurrence form and content in the solid products are expected to affect their retention ability with respect to cs+ and sr2+. 3.2 sorption behavior to cs(i) and sr(ii) of the zirconia-analcime composites the sorption ability of the zirconia-analcime composites with respect to cs+ and sr2+ was evaluated by measuring the equilibrium sorption capacity at different concentrations of metal cations in solutions and ph. figure 7 show the experimental values of cs+ and sr2+ sorption at ph = 6 as well as the cs+ and sr2+ sorption isotherms based on the langmuir model for ss–ana–50 (figure 7a) and ls–hzd– ana–30 (figure 7b). it was revealed that the zr-free analcime bearing solid exhibits the expected poor cs+ and sr2+ sorption capacities (figure 7a, table 2) because of the ion-sieve effect [18]. figure 3 sem (a) and bse (b, c) images of ls-hzd-ana-30 particles; edx spectrum (d) of the marked crystal part (b) and associated zr distribution map (c). figure 4 sem images of small-sized hzd-analcime crystals prepared at different agitation regimes: ss–hzd–ana–30 (a, c, e); ss– hzd–ana–50 (b, d, f). figure 5 the zr distribution map for ss–hzd–ana–30 particles of the following zr content (wt.%): 1 – 8.8; 2 – 8.5; 3 – 13.0; 4 – 8.8; 5 – 13.6; 6 – 11.2; 7 – 12.2. figure 6 bse images of a ss–hzd–ana–50 crystal (a, b); edx spectrum (c) of the marked crystal part (a) and associated zr distribution map (b). chimica techno acta 2022, vol. 9(4), no. 20229418 article 6 of 9 the sorption behavior of the large-sized zirconia-analcime composite is slightly better (figure 7 b, table 2), which is most likely due to embedded zirconia being partially available on the particle surface. it is notable that the qe = f(сe) dependences for sr2+ sorption on ss–hzd–ana–30 are linear in the whole region of applied sr2+ concentrations and ph, giving the kd of up to 106 ml/g (figure 8a–c). such high sr2+ sorption parameters of the small-sized zirconia-analcime composites are comparable with those for the known specific sr2+ sorbents, such as hydrated antimony pentoxide [44, 45], titanoand zirconosilicates [46, 47]. a number of distribution coefficients for cs+ and sr2+ sorption for different inorganic sorbents produced in russia [48] are given in table 3. it can be seen that in near neutral solutions hydrated zirconium dioxide (termoxide 3k) displays the higher kd value (3.5104 ml/g) for the sr2+ sorption than kd for the cs+ sorption. the lower kd for the cs+ sorption is observed also in the case of ss–hzd–ana–30 (tables 2, 3). the enhanced kd at ph ≥ 6 is the characteristic feature of amphoteric oxides, such as hydrated zirconia, operating as a cation exchanger in alkaline and neutral solutions [49]. this is also in good agreement with the zirconia content and accessibility on the analcime surface in both samples, supporting the determining role of hydrated zirconia in the cs+ and sr2+ sorption behavior of the zirconia-analcime composites. at the same time, due to the dissolution of cenosphere’s aluminosilicate glass in the alkaline reaction medium, the formation of zirconium silicate cannot be excluded. therefore, the marked cs+ and sr2+ sorption in acid media (figure 8a, d) can be associated with the existence of additional binding centers, such as zirconium silicate reported as a cation exchanger [50]. table 2 parameters of the langmuir equation and distribution coefficients for cs+ and sr2+ sorption on zr-free and zr-bearing analcime solids. sample ph cation am, mg/g b, l/mg kd, ml/g ss–ana–50 6 cs+ 24.3 0.03 9.0∙103 sr2+ 15.7 0.17 4.7∙103 ls–hzd– ana–30 6 cs+ 30.5 0.06 7.0∙103 sr2+ 15.9 0.77 5.0∙104 ss–hzd– ana–30 2 cs+ 66.5 0.05 4.8∙103 sr2+ n.d. n.d. 2.8∙103 6 cs+ 39.7 0.69 8.1∙104 sr2+ n.d. n.d. 1.3∙106 10 cs+ 36.0 0.48 5.2∙104 sr2+ n.d. n.d. 2.5∙106 ss–hzd– ana–50 2 cs+ 26.9 0.11 2.5∙103 sr2+ n.d. n.d. 3.0∙103 6 cs+ 12.9 0.28 3.6∙104 sr2+ 9.3 4.2 6.0∙104 10 cs+ 31.5 0.43 2.7∙104 sr2+ 36.4 0.75 2.7∙105 figure 7 the cs+ and sr2+ sorption isotherms for ss–ana–50 (a) and ls–hzd–ana–30 (b) at ph = 6: (points – experiment, lines – langmuir model). figure 8 the cs+ and sr2+ sorption isotherms for zro2-analcime composites at different ph: ss–hzd–ana–30 (a–c), ss–hzd–ana– 50 (d–f): (points – experiment, solid lines – langmuir model, dashed lines – linear approximations of experimental points as a guide toeyes). table 3 distribution coefficients (kd) for cs + and sr2+ sorption on different inorganic sorbents in 0.1 mol/l nano3, ph = 5−6 [48]. sorbent kd, ml/g cs+ sr2+ natural zeolite clinoptilolite 1800 310 bentonite clay 1.9104 110 synthetic zeolite naa 8900 8.5104 synthetic zeolite nax 1800 7900 hydrated zirconium dioxide (termoxide 3k) 150 3.5104 zirconium phosphate (termoxide 3a) 1800 326 sodium titanosilicate (tisi) 1.9105 3.0104 nickel ferrocyanide/hydrated zirconium dioxide (termoxide 35) 1.2105 – nickel ferrocyanide/silica gel 8.4104 – hydrated zirconium dioxide/analcime (ss–hzd–ana–30) (this work)* 8.1∙104 1.3∙106 * ph = 6, no added nano3 0 10 20 30 40 0 10 20 30 40 50 a cs+ sr2+ q e , m g /g ce, mg/l 0 10 20 30 40 0 10 20 30 40 50 b q e , m g /g ce, mg/l cs+ sr2+ chimica techno acta 2022, vol. 9(4), no. 20229418 article 7 of 9 3.3 thermochemical conversion of zirconia-analcime composites loaded with cs(i) and sr(ii) the thermochemical conversion of the zirconia-analcime composites studied by example of the ss–hzd–ana–30 sample loaded with cs+ and sr2+ includes two stages (figure 9). the first broad endothermic dsc peak with the substantial mass loss is situated at 100–400 °c and is accompanied by the simultaneous increase of intensity of m/z=18 (h2o) ion due to the elimination of structural water from the analcime structure [32]. there are two pronounced exothermic peaks at 800–950 °c. the absence of mass change in this temperature interval suggests that the exo-effects are caused by the solid-state transformation (re-crystallization) of analcime and amorphous zirconia [51, 52]. the pxrd analysis of the zirconia-analcime composite calcined at 1000 °c revealed tetragonal zirconia (icdd #04-005-4479) and hexagonal nepheline (icdd #01-079992) phases in the calcination product (figure 1b, c), so the observed broad double peak at 800–950 °c can be assigned to the hzd and analcime (figure 10a) phase transformation. figure 9 the tg and dsc curves for thermal conversion of the ss– hzd–ana–30 material loaded with cs+ (a) and sr2+ (b). figure 10 powder x-ray diffraction patterns for the ss–hzd–ana– 30 (a) and solids resulted from calcination of the ss–hzd–ana–30 loaded with sorbed cs+ (b) and sr2+ (c) at 1000 °c: a – c-analcime (icdd #01-070-1575), n – h-nepheline (icdd #01079-992), z – t-zirconia (icdd #04-005-4479). the formation of tetragonal zirconia under heating is an additional evidence of the fact that amorphous zirconia that resulted from the hydrothermal synthesis is the dominant zr-bearing matter covering the analcime surface. thus, the obtained data for the small-sized hzd-analcime composites loaded with cs+ and sr2+ are in agreement with the previous sta results [32], making it possible to consider this material as the efficient cs+ and sr2+ sorbent with a potential to be a precursor of a zr-aluminosilicate mineral-like matrix hosting the trapped cations. 4. conclusions for the first time, the hydrous zirconia bearing analcime composite which demonstrated the high sorption ability to trap cs+ and sr2+ from diluted csno3 and sr(no3)2 solutions of ph = 2–10, in terms of retention capacity and distribution coefficient, was prepared under selected hydrothermal conditions starting from coal fly ash cenospheres with the (sio2/al2o3)glass = 3.1. it was established that the defining role in the sorption performance to cs+ and sr2+ belongs to the parameters such as the zirconia occurrence form, its content and the localization in the hzd–ana particle as well as the particle size. the conditions for the synthesis of the zirconia-analcime with a highly enhanced sorption ability regarding sr2+ (kd ~106 ml/g) were determined. based on the previous knowledge together with the data obtained, the hzd-analcime composite can be considered as a sorbent targeted at both cs+/sr2+ (due to hzd) and ln3+ (due to analcime), which can simultaneously immobilize two or more radionuclides in the single product under heating with partitioning the sorbed cations between several phases – cs+/sr2+ in the aluminosilicate phases (e.g., nepheline) and ln3+/an3+ in the zr-phases (in this case, zirconia). the further testing of the sorbent on simulant waste solutions and real radioactive waste is a necessary step to confirm its effectiveness. supplementary materials no supplementary materials are available. funding this research was funded by ministry of science and higher education of the russian federation (budget project no. 0287-2021-0013 for the institute of chemistry and chemical technology sb ras). the reported study was conducted by using the equipment of krasnoyarsk regional research equipment centre of sb ras for sem-eds, pxrd and aas analyses and siberian federal university for sta, pxrd and icp-ms analyses. acknowledgments the authors acknowledge g.n. bondarenko and l.a. solovyov for performing the pxrd, s.n. vereshchagin for the 0 10 20 30 40 50 60 70 0 200 400 600 800 1000 1200 1400 1600 1800 a b c zzz n z nnn n 1 .5 8 1 .8 2 2 .3 4 2 .5 9 2 .9 6 3 .2 6 3 .8 4 4 .1 7 8 .5 9 in te n s it y 1 /2 ( a rb . u n it s ) 2 theta (degrees) aa a a a a 1 .7 4 6 2 .6 9 8 2 .9 3 7 3 .4 4 3 4 ,8 8 5 .6 3 chimica techno acta 2022, vol. 9(4), no. 20229418 article 8 of 9 sta, e.v. mazurova for the sem-eds, o.a. levitskaya and v.r. kuzik for the aas analysis. author contributions conceptualization: v.t.a., a.a.g. data curation: k.e.a. formal analysis: k.e.a., b.o.v. funding acquisition: v.t.a., a.a.g. investigation: k.e.a., b.o.v. methodology: v.t.a., a.a.g. project administration: a.a.g. resources: k.e.a., b.o.v. software: k.e.a., b.o.v. supervision: a.a.g. writing – original draft: v.t.a. writing – review & editing: v.t.a. conflict of interest the authors declare no conflict of interest. additional information author ids: tatiana 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https://doi.org/10.1016/j.jnucmat.2018.08.015 https://doi.org/10.1039/c4ra13992e https://doi.org/10.1016/j.desal.2012.02.027 https://doi.org/10.1021/cm9701419 https://doi.org/10%2025283/2587-9707-2020-4-80-89 https://doi.org/10.1016/0001-8686(94)80034-0 influence of alloying (cr, fe, ni) on the corrosion resistance of layers formed by electron-beam processing published by ural federal university eissn 2411-1414; chimicatechnoacta.ru letter 2022, vol. 9(3), no. 20229314 doi: 10.15826/chimtech.2022.9.3.14 1 of 4 influence of alloying (cr, fe, ni) on the corrosion resistance of layers formed by electron-beam processing evdokiya bushueva a* , evgeniy turlo a, evgeniya kladieva a, veronica sulyaeva b , elizaveta pukhova a a: faculty of mechanical engineering and technologies, novosibirsk state technical university, novosibirsk 630073, russia b: nikolaev institute of inorganic chemistry sb ras, novosibirsk 630090, russia * corresponding author: bushueva@corp.nstu.ru this paper belongs to the ctfm'22 special issue: https://www.kaznu.kz/en/25415/page. guest editors: prof. n. uvarov and prof. e. aubakirov. © 2022, the authors. this article is published in open access under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). abstract the paper presents the results of comparative analysis of the properties of coatings based on chromium, nickel and iron borides. the alloy obtained in the process of electron-beam surfacing of the powder mixture “amorphous boron – 10 wt.% chromium” has the best properties. this is explained by the structures, fine chromium borides cr2b and complex iron borides (fe, cr)2b, distributed in the austenitic matrix. the material modified in this way in a nitric acid solution corrodes at a rate of 0.02 mm/year. in sulfuric acid, its corrosion rate is 0.81 mm/year. key words stainless steel corrosion resistance surface modification electron beam metal borides received: 27.06.22 revised: 21.07.22 accepted: 01.08.22 available online: 12.08.22 key findings ● the greatest positive effect was obtained in the process of electron-beam surfacing of the powder mixture of "amorphous” boron and 10 wt.% chromium. ● the corrosion resistance of chromium-modified layers is related to the morphology of the chromium borides cr2b formed during surfacing. ● this result is novel, and the developed material can be recommended as a protective corrosionresistant layer for products made of structural chromium-nickel steels. 1. introduction chemical, oil and gas, power industries and mechanical engineering are among the strategically important industries in modern russia. chromium-nickel austenitic steels are widely used due to their high corrosion resistance and machinability for manufacture of critical structures in these industries [1, 2]. however, one of the problems limiting the use of chromium-nickel austenitic steels as materials for tribological applications is their low resistance to abrasive wear [3–5]. a rational solution that makes it possible to significantly improve these characteristics is the application of wear-resistant protective layers to wear surfaces by high-energy methods, for example, non-vacuum electron beam surfacing (eb) of powder mixtures [6–8]. however, increasing the strength of the surface layers can lead to a loss of the corrosion resistance of the material [9, 10]. therefore, the determination of the influence of alloying elements on the oxidation resistance during surface hardening of stainless steels is an urgent task of modern industry [11–13]. 2. materials and methods surfacing of powder mixtures was carried out at budker institute of nuclear physics of siberian branch russian academy of sciences (binp sb ras) at the industrial electron accelerator elv-6. processing was carried out in the scanning mode according to the following parameters: electron beam energy – 1.4 mev; maximum power – 100 kw; scan rate – 5 hz; speed of sample movement relative to the beam – 10 mm/s; beam current – 23 ma [14–16]. amorphous boron (40 wt.%), fe, ni, cr (10 wt.%), mgf2 (wt.50%) were used as a deposited powder mixture [17– 19]. the tests to determine the corrosion resistance of materials were carried out by anodic etching in inhibited sulfuric acid and in an oxidizing environment with weight http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2022.9.3.14 https://orcid.org/0000-0001-7608-734x https://orcid.org/0000-0001-6940-057x https://en.nstu.ru/education/faculty-of-mechanical-engineering-and-technologies/ mailto:pukliza@yandex.ru https://www.kaznu.kz/en/25415/page http://creativecommons.org/licenses/by/4.0/ https://crossmark.crossref.org/dialog/?doi=https://doi.org/10.15826/chimtech.2022.9.3.14&domain=pdf&date_stamp=2022-8-12 chimica techno acta2022, vol. 9(3), no. 20229314 letter 2 of 4 loss control [20–22]. unmodified steel 12x18h9t was chosen as a standard [8]. 3. results and discussion corrosion resistance was evaluated by the gravimetric method by measuring the mass loss of samples during chemical reactions. the corrosion rate of materials was calculated according to the standard method iso 11845:1995 "corrosion of metals – general principles for corrosion testing". it was established that the samples obtained using chromium as a wetting component have oxidation resistance 1.75 times higher than the reference material (steel 12kh18n9t) [23–25]. the resistance of the nickel-modified materials is 1.4 times higher than that of the standard. the corrosion rate increased 1.3 times when using iron as a wetting component. the results of the corrosion resistance analysis are shown in figure 1. the increase in the corrosion resistance of the analyzed materials is explained by the favorable effect of chromium and nickel, as well as the formation of chemically resistant chromium and iron borides in the surface layers [8, 26]. structural features of the surface of the samples after corrosion tests were analyzed using the method of scanning electron microscopy. the resulting images reflect the nature of the impact of acids on materials deposited by an electron beam [26]. one of the characteristic features recorded by scanning electron microscopy is etching of the interboride space (figure 2). one of the reasons for corrosion resistance of chromiummodified layers is related to the morphology of the chromium borides cr2b formed during the surfacing. it is assumed that elongated borides contribute to the development of corrosion processes in the alloy to a lesser extent. figure 3 shows the data characterizing the mass loss of the samples obtained in the process of surfacing amorphous boron with different wetting components (cr, fe, ni). 4. conclusions the creation of boron-containing layers on workpieces made of chromium-nickel steel by the eb method makes it possible to maintain or increase the level of corrosion resistance in boiling concentrated nitric acid and inhibited sulfuric acid. the greatest positive effect was recorded in the study of the samples obtained in the process of electronbeam surfacing of the powder mixture of "amorphous boron – 10 wt.% chromium”. the layer modified in this way in a nitric acid solution corrodes at a rate of 0.02 mm/year (the corrosion rate of steel 12x18h9t is 0.05 mm/year). in sulfuric acid, the corrosion rate of the deposited material was 0.81 mm/year, which is 1.7 times lower compared to 12kh18n9t steel (1.4 mm/year). the developed material can be recommended as a protective corrosion-resistant layer for products made of structural chromium-nickel steels. supplementary materials no supplementary materials are available. figure 1 relative corrosion resistance of 12kh18n9t steel and samples obtained by surfacing amorphous boron and 10 wt.% wetting components (fe, cr, ni). figure 2 surface morphology of alloyed layers (surfacing of amorphous boron and 10 wt.% chromium, i = 23 ma) after corrosion tests in inhibited sulfuric acid (a) and (b) nitric acid. figure 3 the nature of the change in the relative mass loss of samples obtained by non-vacuum electron beam surfacing of amorphous boron with various wetting components, from the time of exposure to nitric acid. surfacing current is 23 ma. funding the work on microscopic characterization of samples was supported by the ministry of science and higher education of the russian federation, project no. 121031700314-5. the work is done in accordance t0 tp_xxt 1-22. acknowledgments the studies were carried out on the equipment of the central collective use center "structure, mechanical and physical properties of materials" of nstu (no. 13.tskp.21.0034, 075-15-2021-698). chimica techno acta2022, vol. 9(3), no. 20229314 letter 3 of 4 author contributions conceptualization: e.b., e.t. data curation: e.b., e.t. formal analysis: e.b., e.t., e.k., e.p., v.s. funding acquisition: e.b. investigation: e.b., e.t., e.k., e.p. methodology: e.b., e.t. project administration: e.t. resources: e.t. software: e.b. supervision: e.t. validation: e.b., e.t. visualization: v.s. writing – original draft: e.b., e.t. writing – review & editing: e.b., e.t. conflict of interest the authors declare no conflict of interest. additional information author ids: evdokiya bushueva, scopus id 25627090600; evgeniy turlo, scopus id 57220026913; veronica sulyaeva, scopus id 12141245300. websites: novosibirsk state technical university, https://en.nstu.ru; nikolaev institute of inorganic chemistry sb ras, http://www.niic.nsc.ru. references 1. paschke h, stueber m, ziebert c, bistron m, mayrhofer p. composition, microstructure and mechanical properties of boron containing multilayer coatings for hot forming tools. surf coatings technol. 2011;205:s24–s28. doi:10.1016/j.surfcoat.2011.04.097 2. takai t, furukawa t, yamano h. thermophysical properties of austenitic stainless steel containing boron carbide in a solid state. mech eng j. 2021;8(4):20-00540. 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steel. j mater res technol. 2021;10:594–604. doi:10.1016/j.jmrt.2021.05.004 22. wei x. first-principles investigation of cr-doped fe2b: structural, mechanical, electronic and magnetic properties. j magn magn mater. – 2018;456:150–159. doi:10.1016/j.jmmm.2018.02.004 23. koga g, otani l, silva a, roche v. characterization and corrosion resistance of boron-containing-austenitic stainless steels produced by rapid solidification techniques. mater. 2018;11(11):2189. doi:10.3390/ma11112189 24. krylova t, ivanov k, chumakov yu, trotsenko r. corrosion and wear resistance of coatings produced by nonvacuum electron beam cladding of refractory carbides on low-carbon steel. inorg mater. 2020;56(3):328–332. doi:10.1134/s0020168520030097 25. krylova t, chumakov y. fabrication of cr-ti-c composite coating by non-vacuum electron beam cladding. mater lett. 2020;274:128022. doi:10.1016/j.matlet.2020.128022 26. baranova a, konstantinova m, guseva e, grechneva m. intergranular corrosion of austenitic steels. sistem metod tehnol. https://www.scopus.com/authid/detail.uri?authorid=25627090600 https://www.scopus.com/authid/detail.uri?authorid=57220026913 https://www.scopus.com/authid/detail.uri?authorid=12141245300 https://en.nstu.ru/ http://www.niic.nsc.ru/ https://doi.org/10.1016/j.surfcoat.2011.04.097 https://doi.org/10.1299/mej.20-00540 https://doi.org/10.4028/www.scientific.net/amm.698.419 https://doi.org/10.30657/pea.2017.14.04 https://doi.org/10.1007/s12613-018-1610-y https://doi.org/10.3390/met11010137 https://doi.org/10.1051/matecconf/202134001022 https://doi.org/10.3103/s1063457614040066 https://doi.org/10.18698/2308-6033-2012-6-227 https://doi.org/10.30906/mitom.2019.12.13-20 https://doi.org/10.15330/pcss.18.1.58-63 https://doi.org/10.1016/j.promfg.2016.12.096 https://doi.org/10.30906/mitom.2021.12.48-53 https://doi.org/10.1007/s11041-019-00331-3 https://doi.org/10.52351/00260827_2021_11_62 https://doi.org/10.1134/s0012500819070061 https://doi.org/10.17073/1997-308x-2020-55-64 https://doi.org/10.1557/jmr.2016.323 https://doi.org/10.1007/s11661-018-4785-y https://doi.org/10.1016/j.jmrt.2021.05.004 https://doi.org/10.1016/j.jmmm.2018.02.004 https://doi.org/10.3390/ma11112189 https://doi.org/10.1134/s0020168520030097 https://doi.org/10.1016/j.matlet.2020.128022 chimica techno acta2022, vol. 9(3), no. 20229314 letter 4 of 4 2015;2:142–147. russian. available from: https://www.elibrary.ru/item.asp?id=23599020&ysclid=l4tjis 19og57936900, accessed on 1 june 2022. https://www.elibrary.ru/item.asp?id=23599020&ysclid=l4tjis19og57936900 https://www.elibrary.ru/item.asp?id=23599020&ysclid=l4tjis19og57936900 ceramic materials based on lanthanum zirconate for the bone augmentation purposes: materials science approach chimica techno acta letter published by ural federal university 2022, vol. 9(2), no. 20229209 eissn 2411-1414; chimicatechnoacta.ru doi: 10.15826/chimtech.2022.9.2.09 1 of 4 ceramic materials based on lanthanum zirconate for the bone augmentation purposes: materials science approach natalia tarasova * , anzhelika galisheva , ksenia belova , anastasia mushnikova, elena volokitina institute of high temperature electrochemistry, ural brunch of russian academy of sciences, ekaterinburg 620137, russia * corresponding author: natalia.tarasova@urfu.ru this paper belongs to a regular issue. © 2022, the authors. this article is published open access under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). abstract the creation of new non-toxic materials that combines high osteointegration and strength characteristics is an urgent contemporary challenge. the use of complex oxides, such as lanthanum zirconate (la2zr2o7), as non-reservable alloplastic implant materials is a novel and promising way of fulfilling this challenge. in this work, the ceramic materials based on undoped and alkali-earth (ca, sr) doped la2zr2o7 were obtained. the main physical and chemical characteristics of the ceramic materials were determined. the effects of synthesis method and dopant nature on the target characteristics of potential allografts were established. keywords la2zr2o7 bioceramics augmentation implant osteoreplacement material received: 12.05.22 revised: 23.05.22 accepted: 23.05.22 available online: 30.05.22 key findings ● the sol-gel method is more preferable, requiring less time to obtain a single-phase composition. ● the density of the prepared ceramic samples was 3.56–4.16 g/cm3. ● the porosity of the prepared ceramic samples was 30–42%. 1. introduction a wide range of tasks related to the field of biomedical materials science includes the unresolved problem of effective implant osseointegration [1–8]. currently known materials which can potentially be used as bone allografts have a number of disadvantages, such as reduced biocompatibility, allergic and toxic reactions [9–20]. this suggests that the creation of new non-toxic materials that combines high osteointegration and strength characteristics is an urgent task. the solution of it will provide conditions for adequate compensation of bone defects with subsequent remodeling of the adjacent bone tissue. as it was shown in the literature, the use of calciumdoped lanthanum zirconate as a non-reservable alloplastic implant is possible and demonstrates positive results in the process of bone remodeling [21]. the choice of this material was due to the fact that the crystal structure of lanthanum zirconate (figure 1) is tolerant to various substitutions, including calcium and strontium ions. moreover, it was shown that strontium incorporation into calcium phosphate ceramics results in improved biocompatibility, osteoconductivity and strength [22]. however, despite promising preliminary results, this approach requires comprehensive development both in terms of traumatology, physiology, and chemical materials science. to date, the influence of metal nature on the processes of osseointegration remains unclear. in particular, the possibility of ion exchange of augment and bone tissue has not been studied. there are no data on bone remodeling markers in the experiment. the degree of biomechanical correspondence of the augment based on lanthanum zirconate and bone tissue has not been established. in the present study, the ceramic materials based on undoped and alkali-earth (ca, sr) doped lanthanum zirconate were successfully obtained. the main physical and chemical characteristics of the prepared ceramic materials were determined, and the effects of the synthesis method and dopant modification on the target characteristics of potential allografts were established. 2. experimental the complex oxides la2zr2o7, la0.9ca0.1zr2o6.95 and la0.9sr0.1zr2o6.95 were obtained by three different ways. the sol-gel synthesis method (figure 1d) was taken from http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2022.9.2.09 mailto:natalia.tarasova@urfu.ru http://creativecommons.org/licenses/by/4.0/ http://orcid.org/0000-0001-7800-0172 https://orcid.org/0000-0003-4346-5644 https://orcid.org/0000-0003-0768-7039 https://crossmark.crossref.org/dialog/?doi=https://doi.org/10.15826/chimtech.2022.9.2.09&domain=pdf&date_stamp=2022-5-30 chimica techno acta 2022, vol. 9(2), no. 20229209 letter 2 of 4 [23]. the solid-state method was performed by mill and using agate mortar (figure 1c). the powders of initial materials, la2о3, zrо2, cacо3, srcо3, were previously dried, weighed and mixed in stoichiometric quantities. the calcination was performed in the temperature range from 800 to 1300 °с with a step of 100 °с and 24 h dwells. the milling of powders was made after each calcination step. the x-ray diffraction (xrd) studies were performed by a bruker advance d8 cu kα diffractometer with a scanning step of 0.01° and at a scanning rate of 0.5°/min. the morphology and chemical composition of the samples were studied using a scanning electron microscope phenom prox desktop (sem) equipped with an energydispersive x-ray diffraction (eds) detector. 3. results and discussions in the experiment, nine powder samples were obtained. each la2zr2o7, la0.9ca0.1zr2o6.95 and la0.9sr0.1zr2o6.95 composition was produced by three different methods: sol-gel (sg) method, solid state (ss) method using a mortar for grinding and solid state method using a ball mill. first, the xrd-check for the phase formation process was performed after 1100 °c heat treatment. for the compositions obtained by the sg method, all peaks were indexed in the fd3m space group. however, they were broad, so the increase in the sintering temperature was required. after the same synthesis step (1100 °c), the compositions obtained by both variations of solid state method were not single phase. the peaks belonging to the metal oxides were detected together with the peaks of the target complex oxide phase. the second xrd-check was performed after the next stage of treatment (1200 °c, 24 h). the peak broadening for the sg-compositions were observed. however, they were less pronounced in comparison with the previous stage. the intensity of metal oxide peaks in the xrd-data for the ss-compositions was lower than it was after the previous stage, but all compositions were not single phase yet. the third xrd-check was made after 1300 °c treatment for 24 h. the sg-compositions were single-phase, the peaks were not broadened. the ss-compositions obtained using the mill were single phase as well. as an example, figure 1e presents the photo of the powder sample of la2zr2o7, and the corresponding xrd-data is shown in figure 1a. the ss-compositions obtained using the mortar contained both complex oxide and initial reagents. the single-phase compositions were obtained only after 1600 °c treatment for 24 h. it should be noted that doping leads to a slight decrease in the unit cell parameters (10.810 å for la2zr2o7, 10.797 å for la0.9ca0.1zr2o6.95, 10.805 å for la0.9sr0.1zr2o6.95). thus, we can conclude that the presence of alkali-earth dopants in the structure of lanthanum zirconate does not affect the final annealing temperature that is necessary for obtaining a single-phase composition. the use of sg and ss-mill synthesis methods allow single phase compositions at the lower temperatures to be obtained. at the same time, the sg-method is more preferable due to less time it takes to obtain single-phase compositions. figure 1 the xrd-pattern (a), crystal structure (b), photo of powder sample, image of surface of ceramic sample (f) of composition la2zr2o7; schemes of solid state (c) and sol-gel (d) synthesis methods; image of ceramic pellets (g) and of bone with augmentation. chimica techno acta 2022, vol. 9(2), no. 20229209 letter 3 of 4 table 1 the density (g/cm3) and porosity (%) of the fabricated ceramic samples. composition density porosity la2zr2o7 (sg) 4.02 33 la0.9ca0.1zr2o6.95 (sg) 3.94 36 la0.9sr0.1zr2o6.95 (sg) 4.16 30 la2zr2o7 (ss-mill) 3.89 35 la0.9ca0.1zr2o6.95 (ss-mill) 3.41 42 la0.9sr0.1zr2o6.95 (ss-mill) 3.56 40 the morphology of the powder samples was studied using the scanning electron microscopy (sem). the doping did not significantly affect the dispersity of the samples. the sg-compositions consisted of irregular round-shaped grains with a size of 30−50 μm, forming agglomerates of up to 100 μm. the ss-compositions were represented by the grains with ~3−5 μm, forming agglomerates of ~10–15 μm. the grain boundaries for all samples were clean. the chemical composition and the elements distribution were determined by energy-dispersive spectroscopy (eds) analysis performed on polished cleavage of the ceramic samples. the ceramic samples were prepared by pressing of cylindrical pellets (pressure ~7 mpa) (figure 1g) and sintering them at 1400 °c for 24 h. the image of the surface of ceramic la2zr2o7 sample is shown in figure 1f. homogeneous distribution of the elements was observed; the concentration of dopant at the grain boundaries and in the bulk of the grain was comparable. the relative density and porosity of ceramic samples are presented in table 1. as we can see, the density of sgcompositions is higher as compared with the density of ss-compositions. the porosity of the sg-compositions is lower; however, it is high enough. it is obvious that to increase the ceramic density, it is necessary either to use sintering additives or to modify the method of synthesis. however, the requirements for bone augmentation ceramics (figure 1h) are different and they depend on many factors including the type and condition of the bone and the size of the implant. 4. conclusions in this paper, the materials science approach to the problem of obtaining novel ceramic materials for the bone augmentation purposes was implemented. the ceramics based on undoped and alkali-earth (ca, sr) doped lanthanum zirconate were obtained by three different methods: sol-gel method, solid state method in the mortar and solid state method in the mill. it was shown that the presence of an alkali-earth dopant in the structure of lanthanum zirconate does not affect the final annealing temperature required for obtaining single-phase compositions in less time. however, the sol-gel method is more preferable it allows synthesizing a single-phase composition. the density of ceramic samples obtained using the solid state method (3.56–3.89 g/cm3) was lower in comparison with the samples obtained by the sol-gel method (3.94–4.16 g/cm3). the porosity was lower for the latter. we can conclude that effects of the synthesis method and the presence of a dopant in the structure on the basic properties of ceramic samples were established. however, this work is only a first step to obtaining novel highly effective ceramic materials for the bone augmentation. supplementary materials no supplementary materials are available. funding this work was supported by the russian science foundation (grant no. 22-25-20037), https://www.rscf.ru/en. acknowledgments none. author contributions conceptualization: n.t. data curation: a.g., k.b., a.m. funding acquisition: e.v. investigation: a.g., k.b. methodology: n.t. validation: a.g., k.b., n.t. visualization: n.t. writing – original draft: n.t. writing – review & editing: n.t. conflict of interest the authors declare no conflict of interest. additional information author ids: natalia tarasova, scopus id 37047923700; anzhelika galisheva, scopus id 57195274932; ksenia belova, scopus id 56509536000. website: institute of high temperature electrochemistry ub ras, http://www.ihte.uran.ru/. references 1. winkler t, sass fa, duda gn, schmidt-bleek k. a review of biomaterials in bone defect healing, remaining shortcomings https://www.rscf.ru/en https://www.scopus.com/authid/detail.uri?authorid=37047923700 https://www.scopus.com/authid/detail.uri?authorid=57195274932 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https://doi.org/10.1080/15476278.2020.1808428 https://doi.org/10.1016/j.bioactmat.2017.05.007 https://doi.org/10.1111/jcpe.13058 https://doi.org/10.1007/s10856-020-06486-3 https://doi.org/10.1038/s41413-021-00180-y https://doi.org/10.1038/boneres.2014.17 https://doi.org/10.1038/s41413-018-0032-9 https://doi.org/10.3390/ijms19010017 https://doi.org/10.3390/ijms22020903 https://doi.org/10.1016/j.bioactmat.2021.10.034 https://doi.org/10.1016/j.ceramint.2021.12.126 https://doi.org/10.1016/j.bioactmat.2021.03.043 https://doi.org/%2010.1021/jp808713m https://doi.org/10.12307/2022.209 https://doi.org/10.1177/17585732211008474 https://doi.org/10.3390/ijms23063352 https://doi.org/10.3390/jfb13010001 https://doi.org/10.21823/2311-2905-2020-26-3-130-140 https://doi.org/10.1007/s41779-019-00360-4 https://doi.org/10.1134/s1063782614100182 dilatometric characteristics of weakly sintered ceramics published by ural federal university eissn 2411-1414; chimicatechnoacta.ru article 2022, vol. 9(4), no. 20229412 doi: 10.15826/chimtech.2022.9.4.12 1 of 6 dilatometric characteristics of weakly sintered ceramics yury i. komolikov a, larisa v. ermakova b* , vladimir r. khrustov c, victor d. zhuravlev b a: m.n. mikheev institute of metal physics, ural branch of the russian academy of sciences, ekaterinburg 620108, russia b: institute of solid state chemistry, ural branch of the russian academy of sciences, ekaterinburg 620990, russia c: institute of electrophysics, ural branch of the russian academy of sciences, ekaterinburg 620016, russia * corresponding author: larisaer@ihim.uran.ru this paper belongs to a regular issue. © 2022, the authors. this article is published in open access under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). abstract thermal expansion of refractory ceramics cazro3, mgal2o4, la2zr2o7 and ysz-12 was studied. the samples of the complex oxides were synthesized by solution combustion synthesis with glycine; the fuel:oxidant ratio was varied depending on the character of redox reaction. the linear thermal expansion coefficient (ltec) of ceramics was measured on the samples with an initial density 23–52%. the maximal sinterability of 89–92% after 6 h annealing at 1550 °с was demonstrated by la2zr2o7 and ysz-12, and the minimal values (78–82%) – by cazro3 and mgal2o4. all materials have close ltec values, from 9.0 to 9.6·10–6 k–1. keywords refractory oxide weakly sintered ceramics linear thermal expansion coefficient thermal expansion ceramic density received: 29.06.22 revised: 25.08.22 accepted: 01.09.22 available online: 13.09.22 1. introduction thermal stability of ceramic materials based on zirconium and/or aluminum oxides makes it possible to use them as functional ceramics and thermal barrier coatings at high temperatures [1–5]. however, under the action of high temperatures, especially during abrupt heating or cooling, internal stresses appear in the material – usually compression stresses, tensile stresses of cut, and more rarely bending stresses. as a result, cracks are formed in ceramics or coatings leading to their destruction. the number and the value of stresses depend on the elastic properties and thermal expansion of anisotropic phases and/or crystals in ceramics [6, 7]. for thermal barrier coatings (tbc) it is particularly important to determine the linear thermal-expansion coefficient (ltec), since for providing good contact between layers of gradient coating it is necessary to select compositions with close, gradually varying ltec values. this prevents cracking or exfoliation of coating from the substrate in the process of thermal cycling [8–10]. the most widespread methods of tbc application are: 1) kinds of plasma spraying: atmospheric plasma spraying (aps), low-pressure plasma spray (lpps), solution precursor plasma sprayed (spps); 2) chemical vapor deposition (cvd); 3) chemical gas-dynamic spraying (cgds) [11–15]. of much interest is the sol-gel procedure allowing one to apply coatings on complex-shaped articles (as distinct from aps and electron beam vacuum plasma deposition (ebpvd)), as well as multilayer coatings. besides, its cost is comparable with the cost of production of coatings by the aps method [16, 17]. the principle of this method consists in the formation of a coating from a deposit as a result of hydrolysis (pyrolysis, thermolysis, combustion of polymer-salt composition, xerogel). the temperature of coating formation from oxide powder depends on the temperature at which initial salts and components decompose in this technique. then the coating is heat treated and sintered at chosen temperatures. the key controlled parameter affecting the characteristics (porosity, homogeneity, thickness) and quality of coating is the rate of oxide coating formation from gel (xerogel). however, the initial density of coating in these technologies is much lower than that for materials produced with the use of plasma methods. as a result, such processes as formation of crystal phases, coarsening and sintering of crystallites, inevitable emergence of structural defects, cracking, etc., take place in coatings during the high-temperature treatment. for successful development of this coating method it is necessary to study the behavior of lowdensity and porous ceramics during sintering. therefore, the aim of this work is to perform dilatometric studies of weakly sintered refractory materials cazro3, mgal2o4, http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2022.9.4.12 mailto:larisaer@ihim.uran.ru http://creativecommons.org/licenses/by/4.0/ https://orcid.org/0000-0001-7839-1441 http://orcid.org/0000-0001-5933-4310 https://crossmark.crossref.org/dialog/?doi=https://doi.org/10.15826/chimtech.2022.9.4.12&domain=pdf&date_stamp=2022-9-13 chimica techno acta 2022, vol. 9(4), no. 20229412 article 2 of 6 la2zr2o7 and zro2-12 produced by solution combustion synthesis (scs) [18–21]. 2. experimental 2.1. starting materials zirconium and calcium carbonates, magnesium, lanthanum and yttrium oxides, aluminum nitrate nonahydrate, nitric acid, glycine were used as initial reagents. metal carbonates and oxides were preliminarily dissolved in nitric acid. the resulting solutions were mixed in the required stoichiometric amount, and powders of cazro3, mgal2o4, la2zr2o7 and zro2-12 mol.% y2o3 were produced by solution combustion synthesis. the powders were prepared in a wide aluminum reactor with a capacity of 3 dm3. to reduce heat removal, the reactor had asbestos sheet insulation. other conditions for the production of samples are given below. the sample of cazro3 prepared at the donetsk plant of chemical reagents (dpcr) was used as a reference. 2.2. preparation of cazro3 cazro3 was synthesized at  = 1.0 in accordance with equation 1, i.e. stoichiometric ratio of fuel and oxidizer, which ensures the maximum speed and temperature of the scs process [22]: zro(no3)2 + ca(no3)2 + 2.22nh2ch2cooh → cazro3 + 3.59n2 + 4.44co2 + 7.97h2o (1) scs reaction under stoichiometric conditions ( = 1.0) leads to complete oxidation of organic fuel (glycine), the precursors are white in color (figure 1а). the produced cazro3 powders were mixed, placed in corundum crucibles and annealed in a muffle furnace at a temperature of 1100 ос for 5 h to complete the crystallization. upon annealing, the product decreased in volume by 5–10%. 2.3. preparation of la2zr2o7 synthesis was performed from a solution of lanthanum and zirconyl nitrates containing 160 g/dm3 of precursors expressed as la2zr2o7 with glycine ( = 1.0) according to equation 2: 2la(no3)3 + 2zro(no3)2 + 5.55nh2ch2cooh → la2zr2o7 + 11.11co2 + 13.875h2o + 7.775n2 (2) due to a large amount of gases evolved during the reaction, the precursor takes the shape of foam or whipped cream, which decreases the degree of particle sintering. the precursor was mixed and annealed in corundum crucibles for 5 h at 900 °c. the annealed product was averaged by way of short-term agitation. 2.4. preparation of mgal2o4 aluminum-magnesium spinel was synthesized by equation 3 in oxidative regime ( = 0.6) [22] from a solution of magnesium and aluminum nitrates containing 67 g/dm3 or precursors expressed as mgal2o4. figure 1 appearance of cazro3 (а) and la2zr2o7 (b) powders after scs ( = 1.0). mg(no3)2 + 2al(no3)3 + 2.67nh2ch2cooh → mgal2o4 + 3.2n2 + 3.27no2 + 6.675h2o (3) this synthesis regime was chosen to reduce the rate of combustion and prevent the removal of the material outside the reactor. upon completion of combustion, a downy powder of light brown color was formed. the precursor was annealed at 850 °с for 5 h. the product annealed at 850 ос was ground and additionally annealed at 900 °с for 5 h. 2.5. preparation of ysz-12 the powder was synthesized by reaction 4 with a considerable excess of glycine ( = 1.52) by calcining the solution of yttrium and zirconyl nitrates containing 128.5 g/dm3 of precursors expressed as ysz-12. 0.88zro(no3)2 + 0.24y(no3)3 + 2.07nh2ch2cooh → (zro2)0.88(y2o3)0.12 + 2.275n2 + 10.35h2o + (4.14–x–y)сo2 + xco + yc (4) since the scs reaction occurs in the reduction combustion regime, the produced downy and voluminous powder has a gray-brown color due to carbon impurity remaining in the synthesis product as a result of incomplete oxidation of carbon atoms in glycine. the content of unburnt carbon was not estimated; that is why the quantities of the carboncontaining components in equation 4 are given as variables x and y. upon annealing in air at 900 °с, the powder became white. in order to complete the reaction of synthesis, the material was ground and annealed for 5 h at 1100 °с with subsequent grinding. chimica techno acta 2022, vol. 9(4), no. 20229412 article 3 of 6 2.6. sample preparation procedure for measurement of ltec for the preparation of molding material, each produced powder with a preassigned composition was further mechanically activated with addition of pvc as a binder [23]. the samples for measurements were molded by semidry uniaxial static pressing under a pressure of 160 mpa and preliminarily sintered at 1000 °c. the ceramics for investigation was represented by cylinders of d = 4.5±0.2 mm in diameter and l = 10.0±0.2 mm in length. the opposite faces of the cylinders were made plane-parallel, the distance between faces (l0) was fixed before the experiment. 2.7. research methods the x-ray diffraction studied were performed on a shimadzu xrd-7000 x-ray diffractometer in cu kα radiation (λ = 1.5456 å) in the 2θ angle interval from 10 to 70° in stepwise scanning mode with ∆(2θ) = 0.03° and exposition of 3 s. the determination of the phase composition, structure refinement and coherent scattering region (csr) definition were carried out using the icdd and icsd files and winxpow and powder cell 2.4 programs. the structural and morphological characteristics were studied on a jeol jsm 6390 la scanning electron microscope. the specific surface of the powders was determined by the bet method (tri star 3000v6.03a) from thermal desorption of nitrogen. the density of the sintered ceramics was determined by hydrostatic weighing in alcohol on a shumadzu auw–220 d balance equipped with a special attachment. the linear thermal expansion of ceramic samples was studied on a dilatometer dil 402 c (netzsch, germany). heating to 1550 °c was carried out with a constant rate of 5 °c/min; simultaneously, air blowing at a rate of 100 cm3/h provided constant atmosphere and a uniform temperature field. the samples were cooled with the furnace to room temperature. the results of dilatometric studies were used to calculate the integral (average) ltec (αav) in the temperature interval (t1–t0) (equation 5): 𝛼𝑎𝑣 = 1 𝐿0 ∙ (𝐿1 − 𝐿0) (𝑇1 − 𝑇0) , (5) where l0, l1 are initial and final length of the sample; t0, t1 are initial and final temperature, respectively. the dimensional accuracy (δl) was 0.133%; it was determined by the nonlinearity of the dilatometer displacement meter transfer function. 3. results and discussion in combustion reactions, fine-dispersed oxide precursor is formed as a result of decomposition of metalorganic complexes [23]. generous and rapid gas liberation promotes the formation of high-porous, chemically non-equilibrium powders with a small bulk weight and low density. usually, these are bulk powders composed of aggregates of nano and microparticles (figures 2, 3). aggregates of powders, for example cazro3, practically do not sinter at temperatures up to 900–1000 °c without preliminary grinding. after mechanical activation (long-term grinding), the original cazro3 aggregates are partially destroyed and form more dense, albeit more fine, in comparison with the powders obtained by the solid-phase method (figure 2). the morphology of aluminum-magnesium spinel upon annealing at 900 oc differs from other materials and is represented by denser particle aggregates, although less dense than for cazro3 produced by the solid-phase method (figure 4). all samples after scs are mixed-phase materials, and the morphological features of the powders allow their active sintering to be carried out at lower temperatures. in the process of high-temperature annealing, the samples become single-phase. the crystal-chemical characteristics of the examined materials are listed in table 1. the densities of the samples after sintering at 1550 °c for 2 h (dilatometer) and 6 h (muffle furnace) are shown in table 2. in the former case, sintering was performed in a dilatometer with measurement of the sample length variation, in the latter case – in a chamber furnace; the heating in all cases was carried out at a rate of 5 °с/min. the obtained results indicate that the density of the samples is practically independent of the holding time of ceramics at 1550 °c. figure 2 morphology of cazro3 powder produced by scs method (а) and at dpcr (b). chimica techno acta 2022, vol. 9(4), no. 20229412 article 4 of 6 figure 3 morphology of la2zr2o7 (а) and ysz-12 powders (b). table 1 physicochemical characteristics of powders. sample structure phase composition unit cell parameters, å csr, nm cazro3 pbnm traces of zro2 cub. 5.753±0.001 8.011±0.001 5.589±0.001 114±1 cazro3 (dpcr) pbnm cazro3 68.9% zro2 cub. 5.1% caco3 26.0% – – mgal2o4 fd–3m 100% 8.083±0.001 18±1 la2zr2o7 fd–3m 100% 10.763±0.001 21±1 ysz-12 fm–3m 100% 5.145±0.001 90±1 note that the initial density of mgal2o4 and la2zr2o7 samples did not exceed 30% of the theoretical one. upon 2 h annealing at 1550 °с both cazro3 samples exhibited moderately high density values, 76–77%; approximately the same density values were observed for the mgal2o4 sample (table 2). the sample of la2zr2o7 ceramic had the maximal value of density, 98%. three-fold enhancement of the annealing time, from two to six hours, did not lead to any considerable increase in density (table 2). this effect is likely to be due to stronger sintering inside powder aggregates of these materials and the absence of diffusion processes between particle aggregates [24]. dilatometric analysis of thermal shrinkage makes it possible to trace the regularities and specific features of the examined compacts. figure 5 displays the temperature dependences of shrinkage during heating to 1550 °с at a rate of 5 °с/min, and figure 6 – the time dependences allowing one to estimate the effect of isothermal exposure on shrinkage at 1550 °с. from figure 5 it is seen that all materials begin to sinter actively at a temperature slightly above 1100 °с. the exception is provided by cazro3 samples of both types (curves 1 and 2). they are characterized by a higher initial sintering temperature, about 1200 °с. probably, in this way the effect of preliminary annealing of powders performed at elevated temperature manifests itself, leading to coarsening and densification of agglomerates. the maximal shrinkage rate is typical of lanthanum zirconate and magnesium aluminate. the degree of shrinkage of these materials exceeds the limits of the instrument operating range (50%). therefore, the above-mentioned curves are extrapolated up to the maximal temperature of the experiment. figure 4 morphology of mgal2o4 powder upon annealing at 900 °с. figure 5 dilatometric curves during heating at a constant rate of 5 °с/min with isothermal exposure of 2 h at 1550 °с. 1 – cazro3 (scs); 2 – cazro3 (dpcr); 3 – ysz-12; 4 – mgal2o4; 5 – la2zr2o7. chimica techno acta 2022, vol. 9(4), no. 20229412 article 5 of 6 table 2 theoretical, ρ(theor), initial, ρ(init), densities of samples after pressing and preliminary sintering at 1000 °с, and final, ρ(1550), density of samples after annealing at 1550 °с and ltec values. sample material ρ(theor), g/сm 3 ρ(init), g/сm 3 / (%) ρ(1550), g/сm 3 / (%) ltec, 10–6 k–1 2 h 6 h 1 cazro3 cs 4.78 2.495/(52) 3.626/(76) 3.713/(78) 9.2 2 cazro3, dpcr 4.78 2.418/(51) 3.693/(77) 3.781/(81) 9.2 3 ysz-12 5.90 2.585/(44) 5.378/(91) 5.24/(89) 9.0 4 mgal2o4 4.10 0.987/(29) 2.785/(80) 2.833/(82) 9.6 5 la2zr2o7 6.06 1.397/(23) 5.915/(98) 5.924/(98) 9.3 figure 6 a time dependences of the relative linear shrinkage (l–l0)/l0 in the heating mode at a rate of 5 °c/min to a temperature of 1550 °c, followed by holding for 2 hours: 1 – cazro3 (scs); 2 – cazro3 (dpcr); 3 – ysz-12; 4 – mgal2o4; 5 – la2zr2o7. the change in the shrinkage of materials with the time of isothermal holding at 1550 °c can be traced from the curves in figure 6. the nonzero slope of the dilatometric curves during isothermal exposure in the range of 304– 424 min indicates that the sintering process of the three materials cazro3 (cs), cazro3 (dpcr), and ysz-12 is far from completion. an increase in the annealing time did not give a noticeable result: the final density of the three materials was less than 80%, and the density of the ysz-12 sample even decreased (table 2). this effect can be associated with significant agglomeration of powders and their internal sintering, since in this case closed pores are formed that prevent compaction [24]. based on the fact that very loose aggregates of materials with a low initial density were obtained in combustion reactions, the reasons for differences in density after sintering can be (in descending order of probability): 1) the formation of closed porosity; 2) the strength of the formed aggregates of complex oxides; 3) different melting points of the compounds. possible ways to solve the problem of obtaining denser ceramics may include: 1) lowering the scs temperature; 2) lowering the degree of agglomeration of powders after synthesis; 3) annealing at a temperature below 1000 °c to avoid reaching chemical equilibrium so as to obtain multiple-phase powders. 4. conclusions the effect of weak preliminary sintering (to 23–52% density) on the production and subsequent sintering of dense oxide ceramics cazro3, ysz-12, mgal2o4 and la2zr2o7 was studied. it was established that weakly sintered ceramics mgal2o4 and la2zr2o7 demonstrate continuous shrinkage during annealing in the region of 1100–1550 °с reaching 98% of the theoretical density of ceramics. preliminary annealing at 1100 °с adversely affects the degree of shrinkage of cazro3 and ysz-12 compacts leading to coarsening and densification of particle agglomerates. supplementary materials no supplementary materials are available. funding this study was carried out in the framework of the state assignment for the institute of solid state chemistry ub ras (no. аааа-а19-119031890026-6), mikheev institute of metal physics ub ras (no. аааа-а18-118020690196-3) and the institute of electrophysics ub ras (no. 122011200363-9). acknowledgments none. author contributions conceptualization: yu.i.k., v.d.zh. data curation: v.d.zh. formal analysis: yu.i.k, v.r.kh., l.v.e. funding acquisition: v.d.zh. investigation: v.r.kh., l.v.e. methodology: yu.i.k., v.r.kh., l.v.e. project administration: v.d.zh. resources: yu.i.k, v.r.kh., l.v.e., v.d.zh. software: l.v.e. supervision: v.d.zh. validation: yu.i.k., v.d.zh. visualization: v.r.kh., yu.i.k. writing – original draft: yu.i.k., v.d.zh. writing – review & editing: v.d.zh., l.v.e. chimica techno acta 2022, vol. 9(4), no. 20229412 article 6 of 6 conflict of interest the authors declare no conflict of interest. additional information author ids: yury i. komolikov, scopus id 6602000371; larisa v. ermakova, scopus id 35886395200; vladimir r. khrustov, scopus id 6602908178; victor d. zhuravlev, scopus id 7202032601. websites: m.n. mikheev institute of metal physics, https://www.imp.uran.ru; institute of solid state chemistry, http://www.solid.nsc.ru; institute of electrophysics, http://eng.iep.uran.ru. references 1. zhu d, miller ra. development of advanced low conductivity thermal barrier coatings. int j appl ceram technol. 2004;1(1):86–94. doi:10.1111/j.1744-7402.2004.tb00158.x 2. yang f, zhao x, xiao p. thermal conductivities of ysz/al2o3 composites. j eur ceram 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https://www.scopus.com/authid/detail.uri?authorid=6602000371 https://www.scopus.com/authid/detail.uri?authorid=35886395200 https://www.scopus.com/authid/detail.uri?authorid=6602908178 https://www.scopus.com/authid/detail.uri?authorid=7202032601 https://www.imp.uran.ru/ http://www.solid.nsc.ru/ http://eng.iep.uran.ru/ https://doi.org/10.1111/j.1744-7402.2004.tb00158.x https://doi.org/10.1016/j.jeurceramsoc.2010.07.007 https://doi.org/10.1016/j.surfcoat.2018.10.045 https://doi.org/10.1134/s1063782614100182 https://doi.org/10.1016/j.ceramint.2019.01.196 https://doi.org/10.1134/s1063783415020250 https://doi.org/10.1016/j.matpr.2021.01.756 https://doi.org/10.1016/j.ceramint.2008.08.017 https://doi.org/10.1016/j.ceramint.2016.11.119 https://doi.org/10.1016/j.ceramint.2021.10.087 https://doi.org/10.1016/j.ceramint.2022.01.001 https://doi.org/10.1016/j.jmrt.2020.11.102 https://doi.org/10.1016/j.surfcoat.2020.125875 https://doi.org/10.1016/j.wear.2020.203276 https://doi.org/10.1016/j.vacuum.2020.109609 https://doi.org/10.1016/j.tsf.2022.139125 https://doi.org/10.1016/j.matpr.2018.12.145 https://doi.org/10.1016/j.pcrysgrow.2018.03.001 https://doi.org/10.1016/j.crci.2018.10.004 https://doi.org/10.1016/j.ceramint.2017.03.006 https://doi.org/10.3103/s1061386217020078 https://doi.org/10.1016/s1383-5866(01)00096-x http://dx.doi.org/10.1016/j.ceramint.2016.01.204 https://doi.org/10.1111/j.1151-2916.1981.tb09552.x 2-(4-oxo-1,3-thiazolidin-2-ylidene)acetamid as promising scaffold for designing new antifungal compounds published by ural federal university eissn 2411-1414 chimicatechnoacta.ru letter 2023, vol. 10(1), no. 202310106 doi: 10.15826/chimtech.2023.10.1.06 1 of 5 2-(4-oxo-1,3-thiazolidin-2-ylidene)acetamid as promising scaffold for designing new antifungal compounds konstantin l. obydennov * , tatiana a. kalinina , daria v. ryabova, maria f. kosterina, tatiana v. glukhareva institute of chemical engineering, ural federal university, ekaterinburg 620009, russia * corresponding author: k.l.obydennov@urfu.ru this paper belongs to the mosm2022 special issue. abstract 1,3-thiazolidin-4-one derivatives with an exocyclic c=c double bond in position 2 of the hetero ring have a wide spectrum of biological activity, but their fungicidal activity has not been studied as much as it should be. this paper presents a simple and convenient approach for obtaining potential antifungal agents based on 2-(4-oxo-1,3-thiazolidin-2-ylidene)acetamides. the first examples of evaluating the fungicidal activity of 8 obtained compounds on 8 strains of phytopathogenic fungi are presented. a highly active compound 4e with ec50 of 0.85 and 2.29 µg/ml against a. solani and p. lingam, respectively, was found to be promising for further study. keywords 1,3-thiazolidine cyanoacetamide exocyclic double bond fungicide biological activity received: 08.12.22 revised: 21.12.22 accepted: 22.12.22 available online: 29.12.22 © 2022, the authors. this article is published in open access under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). 1. introduction derivatives of 1,3-thiazolidin-4-one with a double c=o, c=n, c=s, c=c exocyclic bond in position 2 of the hetero ring have a wide range of biological activity: antituberculosis [1], antioxidant [2], anticancer [3, 4], antiinflammatory [5], anticonvulsant [6], antiviral [7, 8], trypanocidal [9], antiarrhythmic [10], antibacterial [11, 12] and fungicidal [12, 13]. although 1,3-thiazolidines and 1,3-thiazolines have centers for polar interactions and hydrogen bonds [14], these heterocycles often act as a scaffold for substituents interacting with biotargets. thus, the analysis of the crystal structure of the complex of succinate dehydrogenase with the inhibitor thiapronil i (pdb id: 6myr) showed that thiapronil i does not form strong non-covalent interactions (hydrogen bonds and π–π interactions) with the enzyme due to the 1,3-thiazol-2-ylidene fragment [15]. anticancer compounds ii [16] and iii [17] containing a 3,4,5-trimethoxyphenyl substituent are prominent examples as well. due to this substituting group, compounds ii and iii bind to the bioreceptor tubulin (scheme 1) [18]. it is known that 1,3-thiazolidine derivatives with c=o [2, 19], c=n [20–22], c=s [23] exocyclic bonds in position 2 of the hetero ring show fungicidal properties. however, information on the study of the antifungal properties of 1,3thiazolidine with a c=c double bond in position 2 of the ring is limited [12]. for example, 1,3-thiazolindin-2-ylidene iv is known to exhibit antifungal activity against human pathogens c. albicans and c. neoformans [24]. one of the convenient methods for the synthesis of 1,3thiazolidin-2-ylidene derivatives is the condensation of cyanoacetamides 1 with thioglycolic acid 2 (scheme 2) [25]. in this case, 1,3-thiazolidin-2-ylidenes 3 can be modified both at the nh and ch2 groups of the hetero ring. scheme 1 examples of active 1,3-thiazol-2-ylidene and 1,3-thiazolidin-2-ylidene derivatives. http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2023.10.1.06 http://creativecommons.org/licenses/by/4.0/ https://orcid.org/0000-0002-5884-4105 https://orcid.org/0000-0002-7549-686x https://orcid.org/0000-0002-5231-9879 https://crossmark.crossref.org/dialog/?doi=https://doi.org/10.15826/chimtech.2023.10.1.06&domain=pdf&date_stamp=2022-12-29 https://journals.urfu.ru/index.php/chimtech/rt/suppfiles/6411/0 chimica techno acta 2023, vol. 10(1), no. 202310106 letter 2 of 5 doi: 10.15826/chimtech.2023.10.1.06 scheme 2 synthesis of 1,3-thiazolidin-2-ylidenes. as a result of varying the substituents in the acetamide fragment and the hetero ring, a wide range of 1,3-thiazolidin-2-ylidenes can be obtained for the search for biologically active compounds. in this paper, we present the first results of using this approach to search for antifungal compounds. 2. experimental 2.1. synthesis of target compounds 1h and 13c nmr spectra were recorded with a bruker avance ii (karlsruhe, germany) spectrometer (400 mhz for 1h, 100 mhz for 13c) using me4si as an internal standard. the nmr spectra of all compounds are demonstrated in the supporting information (figures s1–s10). mass spectra were recorded with a shimadzu gcms-qp 2010 “ultra” (kyoto, japan) in electron ionization (ei) mode (electron energy 70 ev). the fourier transform infrared (ft-ir) spectra were obtained using a bruker alpha (atr, znse) spectrometer (ettlingen, germany). elemental analyses were performed with a perkin-elmer 2400 series ii chns/o analyzer (shelton, ct usa). melting points were determined using a stuart smp 3 apparatus (staffordshire, st15 osa, uk). the progress of the reactions and the purity of the compounds were monitored by thin-layer chromatography (tlc, merck kgaa) in an ethyl acetate-hexane system. the synthesis of compounds 3a–c was carried out according to the published method [25]. alkylation reaction of thiazolidines 3a–c with the formation of products 4a–e was carried out according to the published method [26]. (2z)-n-benzyl-2-(4-oxo-1,3-thiazolidin-2-ylidene)acetamide (3a). yield 0.37 g (72%), white powder, mp 207– 209 °с (lit. 208–209 °с [25]). (2z)-2-(4-oxo-1,3-thiazolidin-2-ylidene)-n-phenylacetamide (3b). yield 0.44 g (67%), white powder, mp 290– 293 °с (decomp.) (lit. 282–285 °c [25]). (2z)-n-(2-methylphenyl)-2-(4-oxo-1,3-thiazolidin-2ylidene)acetamide (3c). yield 0.23 g (75%), white powder, mp 235–236 °с. ir spectrum, ν, cm–1: 3205 (nh), 2969, 2594, 1702 (c=o), 1623 (c=o), 1600, 1576, 1549, 1492, 1456, 1427, 1399, 1367, 1319. 1h nmr spectrum (400 mhz, dmso-d6), δ, ppm, (j, hz): 2.19 (3h, s, ch3); 3.67 (2h, s, ch2); 5.91 (1h, s, ch=); 7.02 (1h, t, j = 7.2, ar h); 7.00 (1h, t, j = 7.3, ph p-h); 7.08–7.24 (2h, m, ph h); 7.49 (1h, d, j = 7.4, ph h); 9.08 (1h, s, nh); 11.46 (1h, s, nh). 13с nmr spectrum (100 mhz, dmso-d6, δ, ppm: 17.99 (ch3); 32.00 (ch2); 92.37 (с-2’); 124.36 (2c ar); 125.78 (c ar); 130.18 (c ar); 130.77 (c ar); 136.79 (c ar), 153.92 (с-2); 165.40 (c=o), 174.18 (c=o). found, %: c 58.05; h 4.87; n 11.28. c12h12n2o2s. calculated, %: c 57.96; h 4.66; n 11.36. (2z)-n-benzyl-2-(3-methyl-4-oxo-1,3-thiazolidin-2ylidene)acetamide (4a). yield 0.50 g (64%), white powder, mp 183–186 °с. ir spectrum, ν, cm–1: 3295 (nh), 1705 (c=o), 1635 (c=o), 1623, 1553, 1534, 1495, 1453, 1431, 1411, 1386, 1334. 1h nmr spectrum (400 mhz, dmso-d6), δ, ppm, (j, hz): 3.04 (3h, s, ch3); 3.72 (2h, s, ch2); 4.32 (2h, d, j = 5.4, ch2n); 5.67 (1h, s, ch=); 7.22–7.34 (5h, m, ph h); 8.22 (1h, t, j = 5.1, nh). 13с nmr spectrum (100 mhz, dmso-d6, δ, ppm: 29.47 (ch2); 31.10 (ch3); 93.13 (с2’); 126.70 (c ar); 127.24 (c ar); 128.25 (c ar); 139.81 (c ar); 153.08 (c-2), 166.19 (c=o), 172.12 (c=o). ei-ms m/z (%): 262 [м]+ (90). found, %: c 59.52; h 5.38; n 10.68. c13h14n2o2s. calculated, %: c 59.32; h 5.37; n 10.56. (2z)-n-benzyl-2-(3-benzyl-4-oxo-1,3-thiazolidin-2ylidene)acetamide (4b). yield 0.31 g (76%), white powder, mp 144-147 °с. ir spectrum, ν, cm–1: 3307 (nh), 1720 (c=o), 1649 (c=o), 1631, 1572, 1546, 1495, 1454, 1430, 1389, 1364, 1321. 1h nmr spectrum (400 mhz, dmso-d6), δ, ppm, (j, hz): 3.86 (2h, s, ch2); 4.25 (2h, d, j = 5.5, ch2n); 4.79 (2h, s, ch2n); 5.65 (1h, s, ch=); 7.21– 7.37 (10h, m, ph h); 8.17 (1h, t, j = 5.2, nh). 13с nmr spectrum (100 mhz, dmso-d6, δ, ppm: 31.45 (ch2); 42.49 (ch2n); 46.38 (ch2n); 94.32 (с-2’); 127.26 (c ar); 127.90 (c ar); 127.97 (c ar); 128.75 (c ar); 129.11 (c ar); 135.56 (c ar); 140.15 (c ar); 152.47 (c-2), 166.53 (c=o), 173.21 (c=o). ei-ms m/z (%): 338 [м]+ (23.79). found, %: c 67.43; h 5.36; n 8.28. c19h18n2o2s. calculated, %: c 67.38; h 5.35; n 8.41. (2z)-2-(3-methyl-4-oxo-1,3-thiazolidin-2-ylidene)-nphenylacetamide (4c). yield 0.22 g (79%), white powder, mp 209–211 °c (lit. 205–208 °c [26,27]). ir spectrum, ν, cm–1: 3447 (nh), 1714 (c=o), 1650 (c=o), 1617, 1608, 1596, 1567, 1494, 1443, 1421, 1405, 1346, 13.11. 1h nmr spectrum (400 mhz, dmso-d6), δ, ppm, (j, hz): 3.09 (3h, s, ch3); 3.78 (2h, s, ch2); 5.80 (1h, s, ch=); 7.00 (1h, t, j = 7.3, ph p-h); 7.28 (2h, t, j = 7.7, ph h); 7.60 (2h, t, j = 7.9, ph h); 9.87 (1h, s, nh). 13с nmr spectrum (100 mhz, dmso-d6), δ, ppm: 29.43 (ch3); 31.00 (ch3); 93.37 (с-2’); 118.50 (c ar); 122.38 (c ar); 128.45 (c ar); 139.49 (c ar); 154.76 (c2), 164.79 (c=o), 171.95 (c=o). ei-ms m/z (%): 248 [м]+ (31). found, %: c 58.05; h 4.87; n 11.28. c12h12n2o2s. calculated, %: c 58.27; h 5.07; n 11.45. (2z)-2-(3-benzyl-4-oxo-1,3-thiazolidin-2-ylidene)-nphenylacetamide (4d). yield 0.54 g (80%), white powder, mp 214–217 °c (lit. 216–218 °c [27]). (2z)-2-(3-benzyl-4-oxo-1,3-thiazolidin-2-ylidene)-n(2-methylphenyl)acetamide (4e). yield 0.37 g (76%), white powder, mp 166–169 °c. ir spectrum, ν, cm–1: 3274.81, 3062.51, 1713.51 (c=o), 1653.91 (c=o), 1639.00, 1578.96, 1566.82, 1535.97, 1494.73, 1455.75, 1397.69, 1364.59, 1316.31. 1h nmr spectrum (400 mhz, dmso-d6), δ, ppm, (j, hz): 2.16 (3h, s, ch3); 3.90 (2h, s, ch2); 4.85 (2h, s, ch2n); 5.96 (1h, s, ch=); 7.02–7.48 (9h, m, ar h); 9.06 (1h, s, nh). 13с nmr spectrum (100 mhz, dmso-d6), δ, ppm: 17.93 (ch3); https://doi.org/10.15826/chimtech.2023.10.1.06 https://doi.org/10.15826/chimtech.2023.10.1.06 chimica techno acta 2023, vol. 10(1), no. 202310106 letter 3 of 5 doi: 10.15826/chimtech.2023.10.1.06 31.02 (ch2); 45.98 (ch2n); 93.81 (с-2’); 124.08 (c ar); 124.42 (c ar); 125.84 (c ar); 126.72 (c ar); 127.51 (c ar); 128.66 (c ar); 130.22 (c ar); 130.41 (c ar); 135.04 (c ar); 136.53 (c ar); 153.86 (c-2); 165.00 (c=o); 172.78 (c=o). ei-ms m/z (%): 338 [м]+ (8.83). found, %: с 67.43; h 5.36; n 8.28. c19h18n2o2s. calculated, %: c 67.58; h 5.20; n 8.19. 2.2. study of fungicidal activity the fungicidal activity of compounds 3a–c and 4a–e was tested in vitro on alternaria solani sorauer mfp601021, botrytis cinerea pers. mfg 60449, colletotrichum coccodes js 161-1, fusarium solani (mart.) sacc. mfg 70523, phytophthora infestans (mont.) de bary, plenodomus lingam (tode:fr.) höhn. mf br17-044, rhizoctonia solani rcam01785 and sclerotinia sclerotiorum using the agar block method. p. infestans was isolated at nankai university (tianjin, china). c. coccodes was purchased from the all-russian collection of industrial microorganisms (moscow, russia). the remaining strains of fungi were purchased from the russian collection of agricultural microorganisms (st. petersburg, russia). solutions of the tested compounds were prepared at a concentration of 0.5 mg/ml by dissolving 5 mg of the compound in 1 ml of dmso with the addition of 9 ml of water. a total 1 ml of the test solutions was added to sterile petri dishes containing 9 ml of heated (60 °c) nutrient medium and then mixed in a laminar flow cabinet. fungal discs (4 mm in diameter) were cup under aseptic conditions from a 7-day-old culture of the test fungus using a sterile cork borer. the mycelium discs were placed in the center of petri dishes containing the culture medium at room temperature. a negative control was prepared with the culture medium and dmso. the fungi were incubated at 25 °с (48 h for r. solani, 120 h for a. solani, p. lingam, 72 h for other fungi). after incubation, the diameter of fungal colonies was measured. the percentage of fungus growth inhibition was determined by the formula [28]: i (%) = [(c – t)/(c – 4 mm)]·100, (1) where i (%) – the degree of inhibition of mycelial growth, т (mm) – the mean value of the diameter of the colonies in the presence of a given concentration of each compound, and с (mm) – the mean diameter of the colonies in the absence of the compound under the same conditions. all the experiments were carried out in triplicate. the standard deviation was calculated. the half maximal effective concentration for compound 4e was determined by linear regression of the probability of the corresponding percentage of fungus radial growth from the logarithm of the concentration [29] in the graphpad prism 9.4.1 program. the commercial fungicide carbendazim, which is highly active against p. lingam, was used as a comparator agent. 3. results and discussion compounds 3а–с were obtained by reacting the corresponding cyanoacetamides 1a–c with thioglycolic acid 2 in pyridine with the addition of dimethylaminopyridine as a catalyst according to a previously published procedure (scheme 3 [25]. further alkylation with methyl iodide or benzyl chloride in dimethylformamide in the presence of k2co3 gave products 4a–e in 64–80% yields. the fungicidal activity of obtained compounds 3a–c and 4a–e was studied against 8 strains of phytopathogenic fungi that are widespread and cause significant damage to agriculture, such as a. solani, b. cinerea, c. coccodes, f. solani, p. infestans, p. lingam, r. solani and s. sclerotiorum. an in vitro study of antifungal activity showed that most of the obtained compounds exhibit low (i  50%) or moderate (50%  i  70%) activity against phytopathogenic fungi, inhibiting the growth of mycelium by 65% or less (table 1). however, compound 4e, containing 2-methylphenyl at the nitrogen atom of the acetamide fragment and benzyl at the nitrogen atom of the thiazolidine ring, showed high activity against a. solani (causative agent of early blight of nightshade crops) and p. lingam (causative agent of cruciferous plants phomosis) with the inhibition degree of the fungi radial growth 75.77 and 85.94%, respectively. scheme 3 synthesis of compounds 3а–с and 4a–e. table 1 results of antifungal activity study in vitro for compounds 3a–c and 4a–e at a concentration of 50 μg/ml*. compounds degree of inhibition of mycelial growth (i±sd, %) a. solani b. cinerea c. coccodes f. solani r. solani p. infestans p. lingam s. sclerotiorum 3a 29.60±0.53 29.95±0.96 9.34±0.65 7.28±1.17 13.38±0.72 8.77±0.35 28.95±2.26 31.58±0.31 3b 37.80±0.60 32.50±1.21 4.20±0.77 9.63±0.99 9.75±0.68 5.48±0.60 1.95±0.16 6.06±0.94 3c 54.95±2.02 6.70±0.23 39.21±0.22 4.86±0.63 2.40±0.79 6.33±0.50 26.12±3.30 10.98±3.11 4a 37.22±2.63 12.25±0.67 58.65±0.18 1.08±1.12 9.76±0.77 10.25±0.21 43.45±2.48 17.01±1.04 4b 54.11±0.61 10.84±2.19 36.18±1.04 5.09±0.28 9.59±0.18 9.90±0.88 31.83±0.63 25.63±0.34 4c 51.73±1.56 8.21±0.76 47.04±0.52 3.42±0.38 0 12.33±1.12 30.59±1.15 64.45±2.10 4d 47.37±0.47 7.92±0.61 19.43±0.57 6.83±0.66 9.84±0.81 8.62±0.91 11.83±0.34 7.58±1.71 4e 75.77±0.39 22.89±1.00 54.47±0.11 8.74±0.96 3.27±0.32 10.23±1.38 85.94±0.06 34.09±0.91 *sd – standard deviation, i = 100 – active compound, i = 0 – in active compound. https://doi.org/10.15826/chimtech.2023.10.1.06 https://doi.org/10.15826/chimtech.2023.10.1.06 chimica techno acta 2023, vol. 10(1), no. 202310106 letter 4 of 5 doi: 10.15826/chimtech.2023.10.1.06 half maximal effective concentration values of 1,3-thiazolidin-2-ylidene 4e for a. solani and p. lingam were determined (table 2). thus, promising results were obtained. compound 4e was found to have low ec50 values at the level of 1–2 μg/ml, comparable with commercial fungicides [30]. 4. limitations in this paper, we present the first data on the antifungal activity of 2-(4-oxo-1,3-thiazolidin-2-ylidene)acetamide derivatives. the proposed approach for the preparation of potential fungicides is a one-step method for the synthesis of 2-(4-oxo-1,3-thiazolidin-2-ylidene)acetamide scaffold. this approachmakes it easy to modify the resulting compounds. using this strategy makes it possible to obtain a wide range of compounds. thus, this direction in the future will be followed so as to discover new compounds that are highly active against fungi. for targeted design of the potential fungicide structures based on the 2-(4-oxo-1,3-thiazolidin-2ylidene)acetamides, additional studies of the mode of their biological action and identification of biological targets are required. also, it is necessary to perform further biological studies in vivo of the highly active compounds to evaluate their selectivity, toxicity to humans, animals and beneficial microorganisms, etc. 5. conclusions thus, as a result of the work, we synthesized 8 derivatives of 2-(4-oxo-1,3-thiazolidin-2-ylidene)acetamide and studied their fungicidal activity in vitro. compound 4e was highly active against a. solani and p. lingam. it was shown that 2-(4oxo-1,3-thiazolidin-2-ylidene)acetamides are promising base compounds for designing new fungicides. ● supplementary materials this article contains supplementary materials with copies of 1h, and 13c spectra, which are available on the corresponding online page. ● funding this research was supported by the russian science foundation and government of sverdlovsk region, joint grant no 22-26-20124, https://rscf.ru/en/project/22-26-20124. ● acknowledgments the authors are grateful to the laboratory of integrated research and expert evaluation of organic materials of ural federal university for the registration of nmr spectra of compounds. table 2 antifungal ec50 values of compound 4e. fungi compounds regression equation r2 ec50, μg/ml a. solani 4e y = 1.4767x+9.5355 0.9654 0.85 cz* y = 0.5110x+2.3270 0.9794 >10000 p. lingam 4e y = 2.3053x+11.0900 0.9881 2.29 cz y = 3.649x+15.7200 0.9880 1.15 *cz – commercial fungicide carbendazim. ● author contributions conceptualization: к.l.o., t.v.g. data curation: k.l.o., t.a.k. formal analysis: t.a.k. funding acquisition: t.a.k. investigation: t.a.k., d.v.r., m.f.k. methodology: t.v.g., k.l.o. project administration: t.a.k. resources: t.a.k., t.v.g. supervision: t.v.g. validation: t.a.k., t.v.g. visualization: k.l.o. writing – original draft: k.l.o., t.a.k. writing – review & editing: t.v.g. ● conflict of interest the authors 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https://doi.org/10.1021/acs.jafc.1c03325 https://doi.org/10.1021/acs.jafc.8b02151 https://doi.org/10.1016/j.fitote.2018.03.013 influence of process parameters on the patterns of catalytic published by ural federal university eissn 2411-1414; chimicatechnoacta.ru article 2022, vol. 9(3), no. 20229301 doi: 10.15826/chimtech.2022.9.3.01 1 of 8 catalytic cracking of m-100 fuel oil: relationships between origin process parameters and conversion products tatyana v. shakiyeva a , larissa r. sassykova a* , anastassiya a. khamlenko a , ulzhan n. dzhatkambayeva a , albina r. sassykova b , aigul a. batyrbayeva a , zhanar m. zhaxibayeva c , akmaral g. ismailova a , subramanian sendilvelan d a: al-farabi kazakh national university, almaty 050040, kazakhstan b: almaty college of economics and law, almaty 050004, kazakhstan c: abai kazakh national pedagogical university, almaty 050010, kazakhstan d: department of mechanical engineering, dr. m.g.r. educational and research institute, tamilnadu 600095, india * corresponding author: larissa.rav@mail.ru this paper belongs to the ctfm'22 special issue: https://www.kaznu.kz/en/25415/page. guest editors: prof. n. uvarov and prof. e. aubakirov. © 2022, the authors. this article is published in open access under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). abstract the development of technologies for processing oil residues is relevant and promising for kazakhstan, since the main oil reserves of hydrocarbons in the country are in heavy oils. this paper describes the study of the influence of technological modes on the yield and hydrocarbon composition of products formed because of cracking of commercial fuel oil and fuel oil m-100 in the presence of air in the reactor. for catalysts preparation, natural taizhuzgen zeolite and narynkol clay were used. it was found that the introduction of air into the reaction zone, in which oxygen is the initiator of the cracking process, significantly increases the yield of the middle distillate fractions. in the presence of air, the yield of diene and cyclodiene hydrocarbons significantly increases compared to cracking in an inert atmosphere. according to the data of ir spectral analysis of m-100 grade oil fractions, in addition to normal alkanes, the final sample contains a significant amount of olefinic and aromatic hydrocarbons. on the optimal catalyst, owing to oxidative cracking of fuel oil, the following product compositions (in %) were established: fuel oil m100: gas – 0.8, gasoline – 1.1, light gas oil – 85.7, heavy residue – 11.9, loss – 0.5 and total – 100.0%; commodity fuel oil (m-100): gas – 3.3, gasoline – 8.4, light gas oil – 84.3, heavy residue – 4.0, loss – 0 and total – 100.0%. keywords catalytic cracking oxidative cracking natural zeolite taizhuzgen zeolite narynkol clay amangeldy gpp fuel oil m-100 received: 12.06.22 revised: 27.06.22 accepted: 27.06.22 available online: 04.07.22 1. introduction recently, there has been an increased interest in technologies for processing oil residues due to the growing difference in prices for light and heavy grades of oil. at present, the development of technologies for processing oil residues is relevant and promising, which is associated with an increase in the share of hard-to-recover oil reserves: heavy and high-viscosity oils in the world. this, in turn, forces refineries to select carefully the available technologies for processing oil residues and increase the share of heavy oil raw materials in the total volume of oilprocessing feedstock [1–20]. 40–45% of all high-octane gasoline is produced at catalytic cracking plants with a steamer. in the classical version, the cracking process of heavy hydrocarbons occurs in the vapor phase due to contact with a circulating fluidized catalyst consisting of particles ranging in size from 50 to 100 microns [4, 21–36]. over the past decades, the world’s leading companies have developed a number of new catalytic cracking technologies to maximize the yield of light olefins, for example: the use of promoted catalysts or increased rigidity of the technological mode; the addition of light hydrocarbon fractions to raw materials; reducing the contact time of raw materihttp://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2022.9.3.01 mailto:larissa.rav@mail.ru https://www.kaznu.kz/en/25415/page http://creativecommons.org/licenses/by/4.0/ https://orcid.org/0000-0002-9664-442x https://orcid.org/0000-0003-4721-9758 http://orcid.org/0000-0003-0978-510x http://orcid.org/0000-0001-8216-3206 https://orcid.org/0000-0002-1806-522x https://orcid.org/0000-0003-2280-4846 https://orcid.org/0000-0002-5751-6791 https://orcid.org/0000-0002-5555-2705 https://orcid.org/0000-0003-1743-4246 https://crossmark.crossref.org/dialog/?doi=https://doi.org/10.15826/chimtech.2022.9.3.01&domain=pdf&date_stamp=2022-7-4 chimica techno acta 2022, vol. 9(3), no. 20229301 article 2 of 8 als with the catalyst and, finally, the use of heavy fractions to ensure the thermal balance of the installation [33–49]. fuel oil is a residual substance after a simple distillation of oil, which contains mainly hydrocarbons and oil resins of large molecular weight. fuel oil m-100 belongs to the furnace types of fuel oil and can be used as a liquid fuel for combustion in boiler furnaces of thermal power plants. the fuel oil can be further processed to produce gas oil by vacuum distillation [54, 55]. most scientists in the field recognize that the specific properties and complex composition of heavy oils and oil residues do not allow the use of classical processing methods for light oils; such schemes are ineffective or not suitable at all [1, 2, 4, 14–16]. one of the actual methods of intensification of thermal processes of refining of high-viscosity oils is wave action (ultrasonic, acoustic, ultra-frequency) [56–65]. oxidative cracking is a process of cracking petroleum fractions carried out at atmospheric pressure in the vapor phase. a soviet petroleum engineer, doctor of technical sciences, a specialist in the field of oil production and oil refining, one of the founders of thermal methods of oil production, a. b. sheinman (1898–1979) with his colleagues (among them, in particular, a famous soviet and hungarian scientist of hungarian origin carl dubrovay (1888–1957)) created the scientific and technical foundations of oxidative cracking [66, 67]. the efficiency of processing raw materials with ozone to the depth of conversion of fuel oil under the conditions of its cracking process and the possibility of lowering the temperature to 425–450 °с are described [1, 2, 4, 58–75]. in the literature, studies are known of the processes of cracking vacuum distillates on a zeolite-containing catalyst and the reforming of gasoline fractions on a modified catalyst in the presence of atmospheric oxygen. the authors found that the presence of oxygen contributes to an increase in the yield of light fractions, but causes an increase in the yield of hydrocarbon gases and the formation of coke on the catalyst. the octane number of the obtained gasoline fraction in the presence of oxygen was higher (the increase in the number was within 1.5–2.3 units) than the octane number of the same fraction obtained in the absence of oxygen. this phenomenon can be explained by the presence of oxygen-containing hydrocarbon compounds in it, which was confirmed by ir spectroscopy. these results, obtained by various authors, indicate the feasibility of processing heavy oil fractions by oxidative cracking. an analysis of the data of various scientific schools allows us to conclude that one of the most promising ways to increase the depth of processing of heavy oil fractions is to carry out catalytic cracking in an oxidizing medium, for example, with controlled air supply to the reactor [58–75]. in this work, the influence of technological modes on the yield and hydrocarbon composition of products formed as a result of catalytic cracking of commercial fuel oil and fuel oil m-100 in the presence of air in the reactor on catalysts synthesized on the basis of natural raw materials of kazakhstan fields was investigated. 2. experimental commercial fuel oil and fuel oil grade m-100 from the amangeldy gpp (kazakhstan) were used as initial products for studying cracking. sulfur content is 0.7% in fuel oil m-100, and 2.1% – in commercial fuel oil. for the preparation of catalytic composites, the fractions of 60–80 μm of natural zeolite from the taizhuzgen deposit (kazakhstan) and clay from the narynkol deposit (kazakhstan) were taken (figure 1, table 1). figure 1 study of physico-chemical properties of natural zeolite from the taizhuzgen deposit (kazakhstan): x-ray diffraction analysis (a), ir spectroscopy (b). the chemical composition of the original narynkol clay is (in %): sio2 – 38.05; cao – 20.40; al2o3 – 8.49; mgo – 6.15; fe2o3 – 6.15; k2o – 1.80; na2o – 1.10; tio2 – 0.44; p2o5 – 0.11; mno – 0.10. the zeolite was activated by ionic exchange of zeolite framework sodium cations for lanthanum and ammonium cations. then, the zeolite suspension was stirred for two minutes with a suspension containing a certain amount of clay in distilled water, which was changed in each experiment in order to prepare composites with different concentrations of components. (a) (b) chimica techno acta 2022, vol. 9(3), no. 20229301 article 3 of 8 table 1 composition of natural zeolite from the taizhuzgen deposit (kazakhstan) according to x-ray diffraction analysis. no. chemical element concentration, % intensity 1 fe 49.94 739.15 2 ca 1.71 9.16 3 sr 0.270 1.98 4 mn 0.130 1.82 5 al 21.955 0.30 6 si 23.115 0.98 7 ti 1.902 20.86 8 k 0.975 1.97 after that, the mixture was evaporated and molded to form a 0.05–0.25 mm fraction. the resulting microspherical catalyst was dried at 100 °c for 10 hours and hardened at 550 °c for 5 hours. ion exchange for nh4+ and la3+ cations was carried out at 80 °c for 3 hours in a solution of ammonium sulfate and lanthanum nitrate at a ratio of 5 g-eq. (nh4)2so4 to 1 g-eq. na2o and 2 wt.% lanthanum. then the samples were heat-treated and ion exchange was repeated in a solution of a mixture of ammonium sulfate and lanthanum nitrate. the final residual sodium oxide content in the zeolite was about 0.5 wt.%. figure 2 shows the methodology for the catalyst preparation used in our study. figure 2 the scheme of preparation of the catalyst. the procedures for selection and adjustment of process conditions were also described in more detail in our previous works [21, 30, 32, 58, 59]. the process was carried out in four versions: in an inert atmosphere in the absence of a catalyst (thermal cracking), with air supplied to the reactor (oxidative thermal cracking), in an inert atmosphere in a 0.2 wt.% suspension of a fine catalyst (catalytic cracking), and, finally, with the simultaneous supply of a catalyst suspension in fuel oil and air to the reactor (oxidative catalytic cracking). figure 3 shows a principal scheme for implementing the process under study. figure 3 schematic diagram for the implementation of catalytic processing of commercial fuel oil and fuel oil grade m-100 from the amangeldy gpp (kazakhstan): i – catalyst preparation section: 1 – section for mixing; 2 – sieves; 3 – temperature-controlled container with a stirrer; 4 – kiln for drying and calcining; 5 – electromagnetic homogenizer. ii – section for preparation of a catalyst suspension in the feedstock (fuel oil): 1 – a thermostatically controlled vessel with a stirrer; 2 –reactor for electromagnetic activation of the feedstock-fuel oil. iii – section for the implementation of the oxidative cracking process: 1 – thermostatically controlled flow reactor, equipped with devices and valves for dosed supply of inert gas, air, as well as a composite catalyst in the feedstock – fuel oil, 2 – flow tank with cooling for condensing liquid cracking products; 3 – output of the tar residue mixed with the spent catalyst; 4 – system for discharge and combustion of gaseous products formed as a result of cracking. iv – section of rectification of cracking products: 1 – evaporation column; 2 – rectification of cracking products. the analysis of gaseous cracking products was carried out on a chromatograph with a flame ionization detector: on a 2-meter column with an inner diameter of 2 mm, filled with poralac sorbent (fraction 8.2–8.3 mm) – for the analysis of hydrocarbon gases; on a 1-meter packed column filled with nax zeolite (fraction 0.25–0.5 mm) – for the analysis of non-hydrocarbon gases. argon was used as the carrier gas. the programmed temperature sweep was carried out for hydrocarbon gas in the range of 25–165 °c with exposure at 25 °c for 7 minutes; and for non-hydrocarbon – 40–100 °c, at a speed of 8°/min. determination of the hydrocarbon composition of gasoline fractions was carried out by gas chromatography on a chromatograph with a flame ionization detector on a 50 m stainless steel capillary column (internal diameter 0.2 mm) filled with squalane sorbent. the carrier gas was argon. the programmed temperature sweep was carried out in the range of 40–110 °c at a speed of 2°/min. 3. results and discussion the content of components in catalysts affects the activity of catalytic composites. the chemical composition of the starting materials and catalysts based on them was determined. two samples of catalysts were taken for comparison; in the 1st sample the content of zeolites was less than 15%, and in the 2nd – above 15% (table 2). the sio2/al2o3 ratio in the natural zeolite from the taizhuzgen deposit is 4.5, and in the synthesized catalysts it is about 4. it should be noted that the content and ratio of silicon and aluminum oxides in the catalysts varies in proportion to their chimica techno acta 2022, vol. 9(3), no. 20229301 article 4 of 8 concentration in the initial components and their content in the catalysts under study. when narynkol clay is activated by the ion exchange method, the sodium cations are completely replaced by lanthanum cations. the natural zeolite of the taizhuzgen deposit has a higher ion exchange activity compared to the used narynkol clay. for this reason, the content of lanthanum varies. table 2 chemical composition of initial materials-taizhuzgen zeolite and narynkol clay and samples of catalysts based on them . chemical component activated taizhuzgen zeolite initial narynkol clay zeolite-containing composite catalysts 1 2 sio2 67.93 38.05 40.00 47.07 cao 1.97 20.40 19.77 15.14 al2o3 14.28 8.49 9.97 11.51 mgo 1.39 6.15 6.27 4.72 fe2o3 1.79 6.15 3.75 4.01 k2o 4.47 1.80 2.29 3.02 na2o 1.11 1.10 0.30 0.55 tio2 0.29 0.44 0.23 0.41 p2o5 0.01 0.11 0.15 0.14 mno 0.01 0.10 0.15 0.11 calcination losses 7.04 19.47 17.43 0.20 la 0.24 0.0 13.52 0.20 the effect of the catalyst and air on the process of cracking commercial fuel oil was studied at wsuspension = 0.1 h–1 and reaction temperature of the process is 450 °c; in the presence of 0.2 wt.% – catalyst based on taizhuzgen zeolite and more than 80 wt.% of narynkol clay. the ratio of the catalytic cracking products is shown in figure 4. figure 4 catalytic cracking product ratio at different cracking conditions. according to the results of chromatographic analysis, the quantitative composition of the gaseous products of thermal and oxidative thermal cracking is almost identical (table 3, figure 5). table 3 composition of gaseous products (%) of m-100 fuel oil cracking (wsuspension = 1.0 h –1, t = 470 °c) composition of gases cracking conditions without catalyst and air without catalyst, wair=0.15 h –1 0.2 wt.% zeolitecontaining catalyst, without air 0.2 wt.% zeolitecontaining catalyst, wair=0.15 h –1 hydrogen 2.8 3.4 10.7 4.3 methane/ ethane 16.2/15.5 20.1/18.4 68.0/4.9 21.8/20.1 ethylene/ butylene 25.4/9.2 25.7/6.1 11.7/0.2 29.3/2.8 propane/ propylene 5.6/17.6 5.6/14.0 0.1/0.1 5.6/12.2 carbon monoxide/ carbon dioxide 6.3/1.4 6.7/0 4.9/0 3.8/0.1 figure 5 composition of gaseous products of m-100 fuel oil cracking. the only difference is that in the presence of air slightly more methane is formed, and the content of propylene and butylene is reduced, i.e. the depth of destruction of gaseous hydrocarbons increases. during catalytic cracking, the yield of methane is maximum, the resulting ethane is dehydrogenated to ethylene, and there are practically no c3–c4 hydrocarbons. consequently, the reactions of destruction and dehydrogenation of hydrocarbons proceed on the catalyst. the presence of the latter reaction is confirmed by the maximum hydrogen concentration in the gaseous products compared to the other cracking conditions. in the presence of air additives, the yield of diene and cyclodiene hydrocarbons significantly increases compared to cracking in an inert atmosphere if the process is carried out at low volumetric feed rates to the reactor. the conclusions obtained agree with the data that the yield of the reaction of oxidative dehydrogenation of olefins increases in the presence of air [5, 12, 22, 26]. the hydrocarbon composition of cracking gasolines depends on the conditions of cracking in a similar way (table 4). chimica techno acta 2022, vol. 9(3), no. 20229301 article 5 of 8 table 4 influence of process conditions on the hydrocarbon composition of gasoline cracking fuel oil m-100 (wsuspension=1.0 h –1, t = 470 °c). composition of hydrocarbons, % cracking conditions without catalyst and air without catalyst, wair=0.15 h –1 0.2 wt.% zeolitecontaining catalyst, without air 0.2 wt.% zeolitecontaining catalyst, wair=0.15 h –1 n-paraffins/ isoparaffins 23.6/46.2 24.9/45.6 7.15/5.8 17.8/40.2 naphthenes 14.8 15.8 15.8 22.8 olefins/ cycloolefins 4.9/0 5.2/0 6.3/1.1 3.9/0 arenes/ dienes 10.1/0 8.2/0 12.7/0.9 15.1/0 octane number (rm) 71.3 70.5 76.6 76.2 in the absence of a catalyst, the ratio of hydrocarbons of different classes does not change when moving from an inert to an oxidizing atmosphere. in the presence of a catalyst, the process of isomerization of n-alkanes sharply intensifies and, to a much lesser extent, so does the dehydrogenation of the formed light hydrocarbons. the oxygen from air changes the course of catalytic cracking reactions: the proportion of naphthene and arene cyclization reactions increases and the isomerization process decreases. however, the isomerization of hydrocarbons that make up gasoline under all the conditions studied prevails over other reactions occurring during cracking. according to the data of the individual hydrocarbon composition of the obtained gasolines, their formation is most likely by the carbocation mechanism. this is evidenced by the presence of a large number of isomeric hydrocarbons with a substituent at the tertiary carbon atom. the results obtained suggest the mechanism of oxidative cracking of fuel oil on a low-percentage suspension of an activated catalyst synthesized from natural zeolites. the catalytic destruction of hydrocarbon molecules proceeds through the formation of free radicals, so the introduction of air into the reaction zone, in which oxygen is the initiator of this process, significantly increases the yield of the middle distillate fraction. since the symmetrical decomposition of heavy fraction hydrocarbon molecules occurs during cracking, the main product is light gas oil. the resulting less reactive light hydrocarbons are practically not cracked on the relatively weak acid sites of the natural catalyst, so the total yield of gas and gasoline fraction does not exceed 4 wt.%. according to the ir spectral analysis of m-100 fuel oil fractions, in their composition, along with normal alkanes, a significant amount of olefinic and aromatic hydrocarbons was also noticed. the composition of the products according to the optimal composition of catalysts for oxidative cracking of fuel oil (in %) was as follows: fuel oil m-100: gas – 0.8; gasoline – 1.1; light gas oil – 85.7; heavy residue – 11.9; loss – 0.5; total – 100.0%. commodity fuel oil (m-100): gas – 3.3; gasoline – 8.4; light gas oil – 84.3; heavy residue – 4.0; loss – 0; total – 100.0%. 4. conclusions this study showed that the introduction of air into the reactor during the catalytic cracking of m-100 fuel oil on natural zeolites increases the yield of the middle distillate fractions. since cracking involves symmetrical decomposition of heavy fraction hydrocarbon molecules, the main product is light gas oil. the resulting light hydrocarbons are almost not cracked on the relatively weak acid centers of the natural catalysts. the identical catalysts based on natural zeolites were used in this work. it is obvious that the differences found in the rates of catalytic cracking can only be associated with a change in the process conditions (without air additions or in the presence of air). supplementary materials no supplementary materials are available. funding this research was funded by the grant provided by the ministry of education and science of the republic of kazakhstan under the program: “no. ap09260687 technology for the recovery and disposal of toxic compounds from industrial wastewater”. acknowledgments none. author contributions conceptualization: t.v.s., l.r.s. data curation: l.r.s., a.a.b. formal analysis: l.r.s., a.a.b., a.r.s. funding acquisition: t.v.s. investigation: u.n.d., a.a.k., z.m.z. methodology: t.v.s., l.r.s., s. s. project administration: t.v.s. resources: t.v.s., l.r.s. software: l.r.s., a. r. s., a.g. i. supervision: t.v.s. validation: t.v.s., l.r.s., s.s. visualization: a.r.s., z.m. z., a.g.i. writing – original draft: l.r.s., a.a.k. writing – review & editing: l.r.s. conflict of interest the authors declare no conflict of interest. additional information author ids: tatyana v. shakiyeva, scopus id 55911739700; larissa r. sassykova, scopus id 56178673800; anastassiya a. khamlenko, scopus id 57224856359; https://www.scopus.com/authid/detail.uri?authorid=55911739700 https://www.scopus.com/authid/detail.uri?authorid=56178673800 https://www.scopus.com/authid/detail.uri?authorid=57224856359 chimica techno acta 2022, vol. 9(3), no. 20229301 article 6 of 8 ulzhan n. dzhatkambayeva, scopus id 57220106876; albina r. sassykova, scopus id 57220005479; aigul a. batyrbayeva, scopus id 57195066284; zhanar m. zhaxibayeva, scopus id 57224865951; akmaral g. ismailova, scopus id 57193336562; sendilvelan subramanian, scopus id 57207790071. websites of al-farabi kazakh national university, https://www.kaznu.kz/en; almaty college of economics and law, https://www.alem-edu.kz/en; abai kazakh national pedagogical university, https://www.kaznpu.kz/en; dr. m.g.r. educational and research institute, https://www.drmgrdu.ac.in. references 1. pleshakova na, tyshchenko va, tomina nn, pimerzin a. hydrofining of oil fractions of naphthenoaromatic crude. pet chem. 2008;48(5):346–354. doi:10.1134/s0965544108050034 2. yunusov mp, djalаlova shb, nasullaev kha, gulyamov sht, isaeva nf, mirzaeva ei. new catalytic systems for hydrofining and 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of liquid hydrocarbons for thermal management of high-speed flight vehicles. sustain energy fuels. 2022;6(7):1664–1686. doi:10.1039/d1se01999f 75. thangadurai t, tye chth. acidity and basicity of metal oxidebased catalysts in catalytic cracking of vegetable oil. braz j chem eng. 2021;38:1–20. doi:10.1007/s43153-020-00085-z https://doi.org/10.1016/j.radphyschem.2004.04.075 https://doi.org/10.1023/b:cafo.0000041223.91179.af https://doi.org/10.1016/j.fuproc.2004.01.002 https://doi.org/10.1039/d1se01999f https://doi.org/10.1007/s43153-020-00085-z portable potentiometric device for determining the antioxidants capacity published by ural federal university eissn 2411-1414 chimicatechnoacta.ru article 2023, vol. 10(1), no. 202310104 doi: 10.15826/chimtech.2023.10.1.04 1 of 8 portable potentiometric device for determining the antioxidant capacity elena r. salimgareeva a* , dinara i. igdisanova a , daria s. gordeeva b, anatoly i. matern a, elena. a. yarkova a, elena l. gerasimova a , alla v. ivanova a a: institute of chemical engineering, ural federal university, ekaterinburg 620009, russia b: llc “ank-service”, novouralsk 624130, russia * corresponding author: e.r.gazizullina@urfu.ru this paper belongs to the mosm2022 special issue. abstract at present, the development of portable devices for the express assessment of the content of biologically active objects, such as antioxidants, is one of the relevant technological problems of modern chemistry, medicine, and engineering. the main advantages of such devices are the simplicity and rapidity of analysis, small volumes of analyte, as well as miniaturization of equipment, making it possible to carry out the on-site analysis and, thus, to take a step towards the personalized medicine. the potentiometric method using the k3[fe(cn)6]/k4[fe(cn)6] system, which in the laboratory-scale version proved to be the most accurate, reproducible, and express, was the basis for the developed prototypes of portable devices. in this study, two versions of prototypes of the portable device are proposed, namely, the open microcell with the 0.2 ml volume and the microfluidic device with flow control. the correctness of the antioxidant capacity (aoc) determination in both systems was confirmed by comparing the results of the "introduced-found" method on model solutions of antioxidants and their mixtures with the aoc results obtained in a standard laboratory electrochemical cell. the relative standard deviation did not exceed 10%. the aoc of some beverage industry was determined using the microfluidic device. the correlation coefficient of the results, obtained in the microfluidic device and the laboratory cell, was 0.90, which indicates good data convergence and the possibility of using the potentiometric method implemented in the microfluidic device to assess the aoc of multicomponent objects. keywords portable device antioxidant potentiometry microcell microfluidic device received: 25.11.22 revised: 12.12.22 accepted: 12.12.22 available online: 21.12.22 key findings ● the open microcell and the microfluidic device were developed for the determination of the antioxidants capacity of various objects. ● the potentiometric method implemented in the devices allows estimating the aoc of model and multicomponent objects. ● the relative standard deviation of the aoc in the devices did not exceed 10%. © 2022, the authors. this article is published in open access under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). 1. introduction it is known that the oxidative stress is one of the factors causing the occurrence of many pathological conditions in the human body, on the one hand, and accompanying the course of diseases and causing complications in a large number of diseases, on the other. the risk of the oxidative stress increases in the conditions of the technogenic development of society, the environmental degradation, the growth of pathological conditions of the population. as a consequence the assessment of the antioxidants content in various objects, such as food, pharmacy, biological objects, is becoming more and more demanded [1–3]. one of the relevant technological tasks of modern chemistry, engineering and medicine is the transition to the miniaturization of equipment and the creation of portable devices for personal use. their undoubted advantages are the simplicity and rapidity of analysis, and small volumes of the analyte, which will make it possible to take a http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2023.10.1.04 mailto:e.r.gazizullina@urfu.ru http://creativecommons.org/licenses/by/4.0/ https://orcid.org/0000-0003-1304-0346 http://orcid.org/0000-0003-2203-4546 https://orcid.org/0000-0001-9514-0070 https://orcid.org/0000-0001-7515-3712 https://crossmark.crossref.org/dialog/?doi=https://doi.org/10.15826/chimtech.2023.10.1.04&domain=pdf&date_stamp=2022-12-21 chimica techno acta 2023, vol. 10(1), no. 202310104 article 2 of 8 doi: 10.15826/chimtech.2023.10.1.04 step towards personalized medicine. from this point of view, the purpose of this work was the creation of a portable device for the express determination of the antioxidants content in various objects. currently, a large number of methods have been developed for determining the antioxidant content. based on the three main mechanisms of antioxidant action in the human body, the existing methods can be classified into the methods based on the reaction of electron transfer from an antioxidant to a reagent (et-mechanism), the reaction of a hydrogen atom transfer from an antioxidant to a reagent (hat-mechanism), and the complex formation reactions of an antioxidant with metal ions of variable valence [4]. the developed methods for determining the antioxidant content are quite accurate and informative, but they have disadvantages and limitations, which mainly include the complexity of the methodology and equipment, and the high cost of instruments and reagents. the main disadvantage of optical methods for determining the antioxidant content, which include such well-known approaches as teac (trolox equivalent antioxidant capacity) [5, 6], trap (total radical trapping parameter) [7, 8], orac (oxygen radical absorbance capacity) [9], frap (ferric reducing antioxidant power) [10], cuprac (cupric reducing antioxidant capacity) [11], is the difficulty in studying turbid and colored samples. many methods for assessing antioxidant properties use strong oxidizing agents, or the analysis is carried out in an acidic solution, which, again, makes it difficult to use them for the analysis of objects containing proteins and amino acids. the literature describes works on the creation of devices for the transition to miniaturization for some of the methods for determining the antioxidants content: frap and cuprac, implemented in the form of test strips [12– 14], sensors based on nanoparticles of transition metal oxides (ceo2, fe2o3, sio2, etc.) [15–17]. despite the high reproducibility and accuracy of the analysis results, the devices have disadvantages associated with the difficulty in manufacturing and using them on-site, as well as the use of expensive materials and reagents. for more objective information about the antioxidant properties of objects, it is advisable to use the integrated approach that allows one to evaluate the antioxidant effect by three main oxidation mechanisms [18]. numerous studies [3, 19] show that, despite the variety of mechanisms of antioxidant action in the human body, the determination of antioxidant content using the et-mechanism is quite informative and has a high correlation degree with known methods of analysis [18]. in addition, methods based on the et-mechanism are simple to implement, which has been confirmed by numerous works. electrochemical methods are among the most promising methods of analysis, characterized by the simplicity of techniques and equipment, and the low cost of devices. the potentiometric method, in contrast with the other electrochemical methods, is more rapid and sensitive, allows studying turbid and colored samples, and the instrumentation can be implemented in a portable format [20–23]. in this work, the potentiometric method using the k3[fe(cn)6]/k4[fe(cn)6] system, which in the laboratoryscale version proved to be the most accurate, reproducible, and express, was the basis for the developed prototypes of portable devices [24]. our proposed approach for creating the analytical platform for determining the antioxidant content includes the transition from a standard laboratory electrochemical cell to a microcell for the purpose of conducting studies in small volumes, and then creating a prototype of a microfluidic device. 2. experimental 2.1. reagents and objects the following reagents were used in this work: potassium hexacyanoferrate (iii) к3[fe(cn)6] (sigma-aldrich, usa), puriss. grade; potassium hexacyanoferrate (ii) к4[fe(cn)6] (reachim, russia), puriss. grade; kcl (sigmaaldrich), puriss. grade; lascorbic acid (panreac), puriss. grade; l-cysteine (panreac), puriss. grade.; glutathione (panreac), puriss. grade.; pyrogallol (panreac), puriss. grade.; caffeic acid (panreac), puriss. grade.; rutin (panreac), puriss. grade.; quercetin (panreac), puriss. grade.; luteolin (panreac), puriss. grade.; dihydromyricetin (panreac), puriss. grade.; phloroglucinol (panreac), puriss. grade.; catechol (panreac), puriss. grade. as objects, mass-produced drinks were investigated: rich orange, sady pridonia apple-cherry, lyubimiy peach, dobry cherry, lyubimiy multifruit, dobry apple-pear, lipton green iced tea, and coca-cola lime. 2.2. apparatus potentiometric measurements were carried out using the ph-meter expert-рн (ooo econics-expert, moscow). epv-1 redox platinum electrode (gomelsky zip, gomel, belarus) and evl-1m silver-silver chloride electrode (ag/agcl/3m kcl) (gomelsky zip, gomel, belarus) were used as electrodes when working with the standard laboratory electrochemical cell, and platinum wire and silver wire coated with an insoluble silver salt – for operation in the microcell and microfluidic device. the design of the microcell and microfluidic device was carried out in tinkercad for 3d modeling. the devices were printed on the longer orange 10 3d printer (longer, china) using sla technology, which is characterized by high accuracy, good surface quality, no visible polymer layers, and a wide selection of consumables. the photopolymer with increased strength characteristics was used as a material. the selection criteria for this polymer resin were: – high speed, accuracy and reproducibility of printing; – the ability to create complex models (including systems of microchannels with thin walls); https://doi.org/10.15826/chimtech.2023.10.1.04 chimica techno acta 2023, vol. 10(1), no. 202310104 article 3 of 8 doi: 10.15826/chimtech.2023.10.1.04 – high level of detail; – resistance to reagents of the system; – easy post-processing. the reagents and samples were introduced into the microfluidic device using the syringe pump model no 1000 (syringe pump, ny, usa). 2.3. the potentiometric method of determining aoc the potentiometric method of determining the antioxidant capacity was used with the k3[fe(cn)6]/k4[fe(cn)6] oxidizing agent to measure the potential of the platinum electrode of the k3[fe(cn)6]/k4[fe(cn)6] system and after the chemical reaction between the sample antioxidants and the oxidizing agent [24]. the potential change occurs as a result of a chemical reaction in solution (1): 𝑛[fe(cn)6] 3− + ao = 𝑛[fe(cn)6] 4− + aoox, (1) where ao – an antioxidant, аоox – an oxidation product of antioxidant. the dependence of the potential change on time is shown in figure 1. antioxidant capacity (aoc) is calculated as (2–3): aoc = 𝐶ox − 𝛼 ∙ 𝐶red 1 − 𝛼 ∙ 𝑛, (2) 𝛼 = ( 𝐶ox 𝐶red ⁄ ) ∙ 10 (𝐸2−𝐸1)∙ 2.3∙𝑅∙𝑇 𝑛∙𝐹 , (3) where cox is the k3[fe(cn)6] concentration, mol/dm3; cred is the k4[fe(cn)6] concentration, mol/dm3; e1 is the potential measured before the introduction of a test sample, v; e2 is the potential measured after the addition of the test sample, v, n is the dilution degree. since potassium hexacyanoferrate (iii) satisfies the requirements for oxidizing agents that can be used to determine antioxidant properties [25], as previously established, aoc is an integral parameter equal to the total effective equivalent concentration of potassium hexacyanoferrate (iii) that entered in reaction with antioxidants of the analyzed sample. the half-life period (t1/2, s) of the interaction of the studied compound with potassium hexacyanoferrate (iii) was calculated from the kinetic curves of the concentration change of the reduced form of iron on time during reaction (1). the half-life period corresponds to the time at which 50% aoc is recorded (aoc1/2 = aoc/2 mol/l) (figure 2). the experimentally obtained stoichiometric coefficient is calculated as the ratio of aoc to the introduced antioxidant concentration (n = aoc/cao). 2.4. data treatment the measurements were replicated five times. statistical evaluation was performed at the significance level of 5%. all data were expressed as x±∆x, where x is the average value and ∆x is the expanded standard uncertainty. the relationship between the results obtained in the microcells and in the standard laboratory cell was calculated using the pearson correlation. the convergence of the analysis results in microand macrocells was assessed using the t-test to compare mean values and the f-test to compare dispersions. 2.5. quantitation limit the quantitation limit clim was calculated by a probabilistic method [26]. the dependence of the relative standard deviation σ on the average values, in this case, the antioxidant capacity (aoc), determined by the potentiometric method in the microfluidic device, for the entire concentration range, was built for this purpose. the quantitation limit was estimated from the plot of σ = f(сi) dependence. the clim value corresponded to the minimum content of the sample component determined by this approach with the relative standard deviation σ = 0.33. 3. results and discussion in this work, the determination of the antioxidant capacity in the standard laboratory electrochemical cell and the microsystems was carried out by the potentiometric method using the k3[fe(cn)6]/k4[fe(cn)6] system. the following requirements guided the choice of the oxidizer model [25]: – the reaction of electron transfer from ao to the oxidant molecule must be thermodynamically possible; figure 1 time-dependent potential change when the pyrogallol (с = 0.1 mm) is introduced into the solution of the k3[fe(cn)6] (0.01 m)/k4[fe(cn)6] (0.1 mm) system. figure 2 aoc change with time during the interaction of the pyrogallol with the k3[fe(cn)6] (k3[fe(cn)6] (0.01 m)/ k4[fe(cn)6] (0.1 mm)). https://doi.org/10.15826/chimtech.2023.10.1.04 chimica techno acta 2023, vol. 10(1), no. 202310104 article 4 of 8 doi: 10.15826/chimtech.2023.10.1.04 – the redox potential of the oxidizing agent under the analysis conditions should be between the potentials of active oxygen metabolites and ao, but there should be a certain difference between them; – the reaction rate between the oxidizing agent and the antioxidant must be sufficiently high. in this case, the choice of k3[fe(cn)6] as a model of an oxidizing agent is substantiated theoretically and experimentally as an optimal model for studying the antioxidant properties of compounds according to the electron transfer mechanism [27–28]. this method makes it possible to evaluate the redox characteristics of the studied compounds and the thermodynamic possibility of their interaction with active oxygen metabolites, which is a rather important parameter in the study of antioxidant properties. the method for evaluating antioxidant properties using potassium hexacyanoferrate (iii) as a model of an oxidizing agent was tested on a large number of objects and proved to be accurate, informative, simple, and express [24, 25, 28]. at the first stage, to move towards microvolumes, the open microcell with the 0.2 ml volume, structurally repeating the form of a standard laboratory electrochemical cell (figure 3), was developed. the volume and form of the microcell were selected empirically. the potential was recorded using the electrode pair – the platinum wire and the silver wire, electrochemically coated with an insoluble silver salt. the background electrolyte was the 0.1 m kcl solution. the platinum wire was used as a working electrode. the potentials of platinum wire relative to silver wire and silver wire with electrochemically deposited silver chloride were recorded at different ratios of the components of the oxidized and reduced forms of the k3[fe(cn)6]/k4[fe(cn)6] system in the 0.1 m kcl solution to select the reference electrode. high reproducibility, as well as potential stability, was achieved using silver wire coated with electrochemically deposited silver chloride. thus, all further studies were carried out with respect to this reference electrode. the slope of the dependence of the potential on the logarithm of the k3[fe(cn)6]/k4[fe(cn)6] concentration ratio in the microcell relative to the silver wire coated with electrochemically deposited silver chloride was 57±1 mv/decade (figure 4). figure 3 prototype of the open microcell. model solutions of antioxidants and their mixtures with known mechanisms of oxidation by the electron transfer mechanism were chosen as analysis objects [29– 33]. it is known that one of the mechanisms of oxidation of ascorbic acid and pyrogallol consists in the transfer of two electrons and two hydrogen atoms (scheme 1–2). thiol compounds such as the cysteine and glutathione are oxidized to form dimers. in this case, one electron and one hydrogen atom are transferred from one antioxidant molecule (scheme 3–4). table 1 presents the aoc values of model solutions of antioxidants and their mixtures in different ratios obtained in the microcell. the correctness of the aoc determination was confirmed by the "introduced-found" method, taking into account stoichiometric coefficients, as well as in comparison with the data obtained in the standard laboratory electrochemical cell (in macrocell). it follows from the data in the table 1 that the interaction of ascorbic acid (aa) and cysteine (cys) occurs according to equations (4–5), which correspond to the mechanisms of oxidation of these aos described in the literature. figure 4 dependence of the potential on the logarithm of the k3[fe(cn)6]/k4[fe(cn)6] ratio, obtained using a microcell. scheme 1 ascorbic acid oxidation scheme. scheme 2 pyrogallol oxidation scheme. scheme 3 glutathione oxidation scheme. scheme 4 cysteine oxidation scheme. https://doi.org/10.15826/chimtech.2023.10.1.04 chimica techno acta 2023, vol. 10(1), no. 202310104 article 5 of 8 doi: 10.15826/chimtech.2023.10.1.04 (4) (5) in case of pyrogallol, rather high values of stoichiometric coefficients were obtained in the reaction with potassium hexacyanoferrate (iii). such values are associated not only with the electron transfer mechanism, but also with the possible mechanism of complex formation with iron ions [34–35] as a result of a competing reaction. it is known that polyphenolic compounds having gallic structures are able to form fairly stable complexes with metals of variable valence and inhibit radical processes at the stage of chain branching (scheme 5). thus, the aoс values of the model solutions of antioxidants obtained in the microcell are confirmed by the "introduced-found" method, taking into account stoichiometric coefficients, and these values are similar to those obtained in the standard electrochemical cell. the calculated t-test and f-test these values are range from 0.5 to 1.7 and 0.4 to 1.1, respectively, which are significantly below the critical values at a 95% confidence level (tkrit = 2.57, fkrit = 5.05). this shows that the variances of the two populations are homogeneous. the relative standard deviation does not exceed 8%. since the aoс data obtained using the microсell are quite reproducible and similar to the results obtained in the laboratory cell, the microсell design can be used to determine the content of antioxidants. however, the open design of the microсell is difficult to use on-site. the design of the second model in the form of the microfluidic device was developed to eliminate this drawback. figure 5 shows the scheme of preparation and analysis on the microfluidic device. the scheme of the microfluidic device is shown in figure 6. for analysis, the purified platinum wire and the silver wire coated with an insoluble silver salt are placed in the electrode holes of the microfluidic device (stage i). the next step is to wash the microfluidic device with water and the solution of the k3[fe(cn)6]/k4[fe(cn)6] system (stage ii). the systems of potassium hexacyanoferrates (1) and analyte (2) are injected using the syringe pump. in this case, the k3[fe(cn)6]/k4[fe(cn)6] system is pumped continuously at a constant flow rate (stage iii). the antioxidant solution is injected after equilibrium is established on the platinum electrode (stage iv). the system solution, flowing through the microfluidic channels (3) to the near-electrode space (4), is mixed with the antioxidant. then, the potential change is recorded. all studies were carried out in 0.1 m kcl. the kinetic characteristics, namely, the half-reaction period of the interaction of the antioxidant with k3[fe(cn)6], for a number of natural antioxidants, which are most often found in food and pharmaceutical objects, were analyzed to select the length and shape of microfluidic channels (table 2). table 1 аоc of model solutions of antioxidants (сао=0.1 mmol/dm 3, n = 5, p = 0.95) and their mixtures. name cao, 10 –4 mol/dm3 аоc, 10–4 mol-eq/dm3 (in microcell) аоc, 10–4 mol-eq/dm3 (in macrocell) n ascorbic acid 1 1.83±0.05 1.98±0.02 1.83 cysteine 1 1.10±0.04 1.01±0.01 1.10 pyrogallol 1 5.43±0.11 5.17±0.06 5.43 mixtures of antioxidant solutions ascorbic acid : cysteine 1:1 3.05±0.09 2.94±0.03 2:1 5.01±0.05 4.96±0.06 1:2 4.13±0.17 4.05±0.04 scheme 5 scheme of the formation of pyrogallol complexes with iron ions. figure 5 scheme of analysis using the microfluidic device. https://doi.org/10.15826/chimtech.2023.10.1.04 chimica techno acta 2023, vol. 10(1), no. 202310104 article 6 of 8 doi: 10.15826/chimtech.2023.10.1.04 figure 6 the scheme of the microfluidic device. table 2 half-reaction periods of the interaction of antioxidants with k3[fe(cn)6] (сао = 0.1 mmol/dm 3, n = 5, p = 0.95). name τ1/2, sec rsd (%) ascorbic acid 3 5 cysteine 7 5 pyrogallol 5 3 caffeic acid 3 5 rutin 3 5 quercetin 10 4 luteolin 4 3 dihydromyricetin 6 1 phloroglucinol 133 3 glutathione 155 6 catechol 376 5 the optimal reaction time was chosen based on the data in table 2, which was 10 minutes. the overall dimensions of the microfluidic device were 60×30 mm, the channel diameter was d = 1 mm, the channel length was l = 100 mm, the flow rate was v = 50 ml/hour. the antioxidant capacity of some solutions of model antioxidants and their mixtures was determined using the microfluidic device (table 3). the correctness of the obtained results, similarly to the aoc obtained in the microcell, was determined by the "introduced-found" method, taking into account stoichiometric coefficients. the data obtained in the microfluidic device and in the standard laboratory electrochemical cell agree with each other (calculated t-test and f-test range from 0.3 to 1.5 and 0.2 to 1.3, respectively), and are consistent with the literature data. the relative standard deviation does not exceed 10%. the quantitation limit of aoc by the potentiometric method using the microfluidic device was calculated. the dependence of the calculated values of the relative standard deviation from the average values of aoc at different concentrations of ascorbic acid was plotted to determine the quantitation limit (figure 7). according to the 3σ criterion, it was 5.20·10–6 mol-eq/dm3, which is sufficient for studying objects with a low content of antioxidants. thus, working range of the developed device was (5.2·10–6– 9.9·10–3) mol-eq/dm3. according to iupac, the response time of electrodes is defined as the time required to reach 95% of the equilibrium potential for each tenfold change in concentration [36]. table 3 аоc of model solutions of antioxidants (сао = 0.1 mmol/dm 3, n = 5, p = 0.95) and their mixtures. name cao, 10 –4 mol/dm3 аоc, 10–4 mol-eq/dm3 (in microcell) аоc, 10–4 mol-eq/dm3 (in macrocell) n ascorbic acid 1 2.16±0.07 1.98±0.02 2.16 cysteine 1 1.28±0.06 1.01±0.01 1.28 glutathione 1 1.22±0.09 0.98±0.01 1.22 pyrogallol 1 4.48±0.27 5.17±0.06 4.48 mixtures of antioxidant solutions ascorbic acid : cysteine 1:1 3.32±0.17 2.94±0.03 ascorbic acid : glutathione 1:1 3.41±0,16 3.12±0.09 figure 7 dependence of relative standard deviation on aoc at different concentrations of ascorbic acid. in this study, the response time was investigated in the concentration range of the k3[fe(cn)6]/k4[fe(cn)6] system from 0.01 m/0.1 mm to 0.01 m/1 mm. as a result, the response time of the developed device was found to be 60 s. aoc of multicomponent objects, which are massproduced drinks (table 4), is determined. the composition of mass-produced drinks includes freshly squeezed juice and pulp of fruits and berries containing polyphenolic compounds, vitamins a, c and e – natural antioxidants [29]. the selected objects of analysis were not subjected to additional sample preparation. thus, beverages such as lyubimiy peach and dobry cherry juices, as well as coca-cola lime, did not show antioxidant properties. perhaps, this is due to the quality and storage conditions of raw materials and finished products. rich orange, sady pridonya apple-cherry, lyubimiy multifruit, dobry apple-pear, and lipton green iced tea exhibit antioxidant properties. the relative standard deviation of the aoc results obtained in the microfluidic device did not exceed 10%. the highest content of antioxidants was found in rich orange juice. the correlation coefficient of the aoc results obtained in the microfluidic device and in the laboratory cell was 0.90 (rkrit = 0.80), which indicates a good convergence of the data and the possibility of using the potentiometric method implemented in the microfluidic device to assess the antioxidant capacity of multicomponent objects. × https://doi.org/10.15826/chimtech.2023.10.1.04 chimica techno acta 2023, vol. 10(1), no. 202310104 article 7 of 8 doi: 10.15826/chimtech.2023.10.1.04 table 4 аоc of industrial drinks (n = 5, p = 0.95). name аоc, 10–2 moleq/dm3 (in microcell) аоc, 10–2 moleq/dm3 (in macrocell) rich orange 5.60±0.29 6.20±0.07 sady pridonia applecherry 0.09±0.02 0.19±0.01 lipton green iced tea 2.14±0.11 2.62±0.04 lyubimiy multifruit 3.24±0.94 2.57±0.02 dobry apple-pear 0.43±0.06 0.75±0.04 4. limitations in this work, the silver wire, coated with an insoluble silver salt, was used as a reference electrode. this electrode is quite common. however, the use of silver wire has some limitations associated with damage to the upper layer of silver chloride during repeated use and the need for its redeposition. in order to increase the capability of using these devices multiple times, it will be necessary to conduct a study on the choice of material and design of the reference electrode. 5. conclusions in this work, two prototypes of portable devices were developed – the open microcell and the flow microfluidic device, based on the potentiometric method using the k3[fe(cn)6]/k4[fe(cn)6] system. the high reproducibility of the aoc results and the similarity with the data obtained in the standard laboratory electrochemical cell suggest the possibility of using the developed designs of portable devices for the express assessment of the antioxidant content in complex multicomponent objects. thus, the potentiometric method for determining the antioxidant content, due to the simplicity of hardware design, the possibility of miniaturization of the measurement cell and express analysis, is quite promising from the point of view of implementation in the portable device. further research will be aimed at improving the design of the prototypes in order to develop the analytical platform for the determination of antioxidants in various objects. ● supplementary materials no supplementary materials are available. ● funding the research funding from the ministry of science and higher education of the russian federation (ural federal university program of development within the priority2030 program) is gratefully acknowledged. ● acknowledgments none. ● author contributions conceptualization: a.v.i., e.r.s., a.i.m. data curation: e.r.s., e.l.g. formal analysis: e.r.s., d.i.i. funding acquisition: a.v.i., e.l.g., d.i.i. investigation: d.s.g., e.a.y. methodology: a.v.i., e.r.s., e.l.g. project administration: e.r.s. resources: d.s.g., e.a.y., d.i.i. software: d.s.g., e.a.y. supervision: a.v.i., a.i.m. validation: a.v.i., e.r.s., e.l.g. visualization: e.r.s. writing – original draft: e.r.s. writing – review & editing: a.v.i., e.r.s., e.l.g. ● conflict of interest the authors declare no conflict of interest. ● additional information author ids: elena r. salimgareeva, scopus id 57193423139; dinara i. igdisanova, scopus id 57364641300; daria s. gordeeva, scopus id 57212411112; elena a. yarkova, scopus id 57204419700; anatoly i. matern, scopus id 12142454900; elena l. gerasimova, scopus id 8343024000; alla v. ivanova, scopus id 8233431000. website: ural federal university, https://urfu.ru/en. references 1. neha k, haider mr, pathak a, yar ms. medicinal prospects of antioxidants: a review. eur j med chem. 2019;178:687–704. doi:10.1016/j.ejmech.2019.06.010 2. pisoschi am, 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https://doi.org/10.1007/s12034-022-02696-3 https://doi.org/10.1080/10408347.2014.910443 https://doi.org/10.1016/j.aca.2020.03.041 https://doi.org/10.1134/s1061934810030020 https://doi.org/10.1016/j.aca.2006.03.094 https://doi.org/10.1002/elan.200804458 https://doi.org/10.1080/07315724.2003.10719272 https://doi.org/10.1016/j.jenvman.2007.12.007 https://doi.org/10.1007/s11172-018-2129-0 https://doi.org/10.1016/s1054-3589(08)60979-5 https://doi.org/10.1007/s12013-009-9043-х https://doi.org/10.3390/molecules25184251 https://doi.org/10.1351/pac199466122527 synthesis and characterization of znbtc-based mofs: effect of solvents and salt published by ural federal university eissn 2411-1414 chimicatechnoacta.ru article 2023, vol. 10(1), no. 202310105 doi: 10.15826/chimtech.2023.10.1.05 1 of 7 synthesis and characterization of znbtc-based mofs: effect of solvents and salts maria v. timofeeva * , andrey n. yankin school of physics and engineering, itmo university, st. petersburg 197101, russia * corresponding author: maria.timofeeva@metalab.ifmo.ru this paper belongs to the mosm2022 special issue. abstract in this work, we studied the optimization of synthetic approaches to creating structurally modified metal-organic frameworks under various synthesis conditions. we investigated the influence of the various solvents and zinc salts on the structural characteristics of the metal-organic framework based on benzene-1,3,5-tricarboxylic acid (h3btc). the results indicate that the variation of the types of both solvent and salt is a parameter affecting the crystallinity, phase purity, and morphology of the metal-organic framework. this was confirmed by comprehensive structural characterization (sem, edx, pxrd). keywords metal-organic frameworks solvothermal synthesis trimesic acid mof synthesis received: 11.11.22 revised: 13.12.22 accepted: 13.12.22 available online: 22.12.22 key findings ● the synthesis method for obtaining znbtc. ● new morphology of znbtc not previously described in the literature was obtained. ● it was found that the type of solvents and the type of salts used in the synthesis of the znbtc affect the morphology of the compounds. © 2022, the authors. this article is published in open access under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). 1. introduction materials have always played an important role in the development of humanity. the past 20 years have been marked by major achievements in the theoretical and applied materials science, which continues to develop rapidly. the main directions of modern materials science are as follows: a) polyfunctionality – giving the material the maximum number of different useful properties; b) the use of nano-sized materials; c) creation of smart materials capable of changing their characteristics under the effect of various external factors (light, temperature, electromagnetic field, etc.). currently, various materials have been intensively studied in materials science, such as inorganic nanoparticles [1– 3], molecular crystals [4–6], cof (covalent organic framework) [7, 8]. applications for these materials include electronics [9], cancer treatment [10], catalysis [11], etc. porous materials attract special attention in materials science. porous materials are solids with voids filled with air or other gases. porous materials can be ordered (crystalline, with a regular pore system) and disordered (irregular pores system). inorganic materials often have a highly ordered structure, whilst plastics, for example, are amorphous or partially ordered. amorphous materials have certain advantages: they are inexpensive and easy to process. their disadvantage is the uncertainty of the structure (due to the difficulties in x-ray diffraction analysis). their synthesis is most often unpredictable; they exist in the form of several modifications and have low mechanical strength. more interesting are the highly ordered materials, the structure of which can be studied by x-ray diffraction methods. these are, for example, crystalline zeolites [12, 13]. they have a regular structure, are strong, and possess the ion exchange capability. their main applications are is molecular sieves and catalysts [14–16]. the development of a new class of highly ordered hybrid structures – metalorganic frameworks – is the next stage in the development of zeolite-like materials. metal-organic framework (mof) are a class of crystalline porous coordination compounds with a 1-, 2-, 3-dimensional structure consisting of metal ions or clusters linked by organic linkers [17–21]. different functionality, adjustable porosity, mechanical strength and thermal stability can be http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2023.10.1.05 mailto:maria.timofeeva@metalab.ifmo.ru http://creativecommons.org/licenses/by/4.0/ https://orcid.org/0000-0002-8156-5411 https://orcid.org/0000-0003-4221-5619 https://crossmark.crossref.org/dialog/?doi=https://doi.org/10.15826/chimtech.2023.10.1.05&domain=pdf&date_stamp=2022-12-22 chimica techno acta 2023, vol. 10(1), no. 202310105 article 2 of 7 doi: 10.15826/chimtech.2023.10.1.05 imparted to the framework by changing its constituent parts [22]. due to these properties mof appear as promising materials that can be used for the adsorption/storage and separation of gases, in catalysis, biomedicine, and also for the creation of sensor devices [23–26]. of particular interest is the further modification of the structure of mofs, including their intracrystalline space, to create new properties or optimize existing structural/chemical characteristics [27,28]. however, there are just a few studies that demonstrate the conditions for the mofs synthesis effect on the structure and properties of the framework. the comprehensive understanding of the framework’s synthesis and formation and its effect on the final structure are still missing [29–31]. among the ligands for the synthesis of mofs, trimesic acid has a leading position. thus, the most famous and one of the first mofs, hkust-1, is based on trimesic acid and copper salt [32, 33]. trimesic acid and its derivatives are available and ecofriendly substances that can be used as intermediate pharmaceutical products and as drug delivery agents as parts of mof [34, 35]. there are many publications on mofs based on ni [36], fe [37], co [38, 39] and other metals [40], where trimesic acid played the role of a ligand [41–43]. basically, these publications investigated the possible applications mof: catalysis [44–46], medicine [47, 48], adsorption [49–51], sensors [52–53]. however, to the best of our knowledge, there is no research on the development of a synthesis strategy and design of btc-based mofs. nowadays, there are different methods for mofs production: solvothermal (synthesis under high pressure, in a boiling solvent), microwave (synthesis by radiation of a microwave explosion), sonochemical (synthesis under the action of ultrasound), microfluidic (control of liquid flows at microand nanoscales), mechanochemical, electrochemical and slow evaporation method (does not require any traces, electricity or mechanical action). consequently, there is often a discrepancy in the structural data between different reports on the same mof, which usually arises from using different methods and parameters of synthesis. znbtc is a well-known mof in which infinite zinc chains are connected by organic ligand into a three-dimensional microporous framework [54]. despite only one synthesis method, there are various znbtc morphologies known, which can be explained by different conditions of the solvothermal reaction. among existing morphologies, nonuniform rod-like [55], large crumps with irregular shapes [56], and spherical nanoparticle [57, 58] structures of znbtc can be distinguished. it is important to mention that all known methods for the synthesis of znbtc take place at high temperatures ( >120 °c). here we report the optimization of the mofs synthesis based on zinc salt and trimesic acid. we studied the critical role of the solvent type variation on the morphology and crystallinity of the synthesized mof based on zinc salt. we report the soft synthesis conditions (80 °c temperature). in this regard, the following adjustments to the synthesis technique were attempted: a) variation of the solvent mixture; b) precursor (zinc salt type) variation. 2. experimental all the chemical reagents were obtained from commercial sources and used without further purification unless otherwise specified: zn(no3)2·6h2o (sigma-aldrich, ≥98.0%), znso4·7h2o (sigma-aldrich, ≥98.0%), zn(ch3co2)2·2h2o (sigma-aldrich, ≥98.0%), 1,3,5-benzenetricarboxylic acid (sigma-aldrich, trimesic acid (h3btc), 95%), dimethylformamide (acs reagent, ≥99.8%), ethanol (acs reagent, ≥99,5%), 1,4-dioxane (dioxane, acs reagent, ≥99,5%), ethanol (etoh, acs reagent, ≥ 99,5%), toluene (tol, acs reagent, ≥99,5%), chlorobenzene (phcl, acs reagent, ≥99,5%), and dimethyl sulfoxide (dmso, acs reagent, ≥99,5%) were used in all syntheses. the chemical composition and homogeneity of obtained compounds were controlled with a scanning electron microscope (sem, quanta 200, fei, netherlands) with an accelerating voltage of 10 kv. dry samples were coated with a gold thin film and imaged with sem. diffraction patterns of the samples were recorded on a shimadzu 7000-maxima x-ray diffractometer with a 2 kw characteristic cu kα (kα1 λ = 1.54059 å, angular range 2θ = 5° – 80°) x-ray radiation source and a bragg-brentano goniometer geometry. the angular resolution during the analysis was 0.05 degree at a scanning speed of 1 degree/min. energy-dispersive elemental analysis was performed using sem supra 55 vp at an accelerating voltage of 10 kv. before imaging, samples were coated with gold. 2.1. general synthesis of znbtc fifteen different znbtc samples were each prepared as follows. two precursors, a zinc salt and 1,3,5-benzenetricarboxylic acid, were taken in the quantities listed in table 1 and dissolved under ultrasound in a mixture of three solvents, 1 ml each (see table 1). after that, the solution mixture was hermetically sealed with a lid with a rubber septum in a 4 ml vial to exclude the interaction with the external environment and create excess pressure in the vial. the solution mixture was heated up to 80 °c and kept for 48 h, after which the reaction mixture was cooled down to room temperature. the formed powder was separated from the mother liquid by filtration, and then it was repeatedly washed 5 times with the same mixture of solvents as the one used for its synthesis (see table 1). the washed powder was dried in the air. 3. results and discussion the synthesis of mofs was performed under solvothermal reaction conditions (scheme 1). along with the study of the synthesis conditions effect on znbtc structure, we analyzed the solvent composition https://doi.org/10.15826/chimtech.2023.10.1.05 chimica techno acta 2023, vol. 10(1), no. 202310105 article 3 of 7 doi: 10.15826/chimtech.2023.10.1.05 (polarity of the mixed aqueous-organic solvent) and the counterion in the zn salt composition. the mof synthesis process can be affected by the reaction medium due to the polarity of the solvent used. to explore this aspect, several znbtc were prepared by solvothermal reactions of the zn2+ ion with the h3btc ligand in various solvent systems dmf/h2o/dioxane, dmf/h2o/etoh, dmf/h2o/toluene, dmf/h2o/phcl, dmf/h2o/dmso, respectively (table 1). it is known that the medium polarity (the solvent nature) has a great influence on the course of a chemical reaction. the polarity of the medium during the synthesis of znbtc-1– 15 was calculated according to the literature data. the solvent mixture of dmso/dmf/h2o had the highest polarity (corresponds to samples znbtc-5, znbtc-10, znbtc-15), whilst the solvents mixture of toluene/dmf/h2o (corresponds to samples znbtc-3, znbtc-8, znbtc-13) was the least polar of the solvent mixtures presented in table 2. in the sem images (figure 1a–e), all obtained compounds of znbtc-1–5 are mainly needle-shaped agglomerates of crystals in the form of "blowball". this form of znbtc crystals was obtained for the first time. according to the literature, znbtc is usually characterized by a single rectangular crystal [55–58]. however, sem failed to detect a fragment with a rectangular topology. compounds of znbtc-3 and znbtc-4 (figure 1c and d), synthesized in the solvent mixtures dmf/h2o/tol and dmf/h2o/phcl, respectively, did not assemble into a whole "blowball". such small differences in the crystalline form of the compounds at the same temperature, synthesis time and type of salt could be explained by use of the different types of synthesis medium. the qualitative and quantitative composition of the compounds was analyzed by energy dispersive x-ray (edx) spectroscopy (figure 2a–e). the sem images of compounds znbtc-6–10 can also be described as needle-shaped crystals (figure 3a–e), but their «blowball» shape is less pronounced than that of substances znbtc-1–5. the morphologies of znbtc-1 and znbtc-6 are different. the synthesis parameters differed only in the type of salt (zn(no3)2·2h2o and znso4·7h2o), and the solvent medium was the same (dioxane/dmf/h2o). therefore, it can be assumed that the type of salt (counterion) affects the growth of crystals. this assumption is confirmed by the third znbtc-mof series. znbtc-11–15, obtained by the interaction of h3btc and zn(ch3coo2)2·2h2o, did not form the "blowball" crystalline agglomerates (figure 4a–e). all compounds znbtc11–15 are crystalline powders. the nature of the crystalline phase was studied using pxrd analysis [64]. all diffraction patterns of znbtc-1–15 (figure 1f, 3f and 4f) show an intense diffraction peak at 2θ = 10°, which corresponds to the literature data [65], confirming the formation of znbtc. the diffraction patterns show no background noise over the entire 2θ range. this confirms the presence of a crystalline phase in the studied compositions. scheme 1 general synthesis of znbtc. table 2 polarity of solvents mixture. solvent mixture polarity dioxane/dmf/h2o 21.4 etoh/dmf/h2o 21.8 toluene/dmf/h2o 19 phcl/dmf/h2o 19.3 dmso/dmf/h2o 23.8 table 1 optimization of the synthesis of znbtc (ligand: h3btc). sample no. zn salt mixture of solvents (1 ml each) ligand/salt quantities (mmol) 1 zn(no3)2·6h2o dioxane/dmf/h2o 0.067/0.036 2 zn(no3)2·6h2o etoh/dmf/h2o 0.067/0.036 3 zn(no3)2·6h2o toluene/dmf/h2o 0.067/0.036 4 zn(no3)2·6h2o phcl/dmf/h2o 0.067/0.036 5 zn(no3)2·6h2o dmso/dmf/h2o 0.067/0.036 6 znso4·7h2o dioxane/dmf/h2o 0.070/0.035 7 znso4·7h2o etoh/dmf/h2o 0.070/0.035 8 znso4·7h2o znso4·7h2o toluene/dmf/h2o 0.070/0.035 9 znso4·7h2o znso4·7h2o phcl/dmf/h2o 0.070/0.035 10 znso4·7h2o znso4·7h2o dmso/dmf/h2o 0.070/0.035 11 zn(ch3co2)2·2h2o dioxane/dmf/h2o 0.091/0.046 12 zn(ch3co2)2·2h2o etoh/dmf/h2o 0.091/0.046 13 zn(ch3co2)2·2h2o toluene/dmf/h2o 0.091/0.046 14 zn(ch3co2)2·2h2o phcl/dmf/h2o 0.091/0.046 15 zn(ch3co2)2·2h2o dmso/dmf/h2o 0.091/0.046 https://doi.org/10.15826/chimtech.2023.10.1.05 chimica techno acta 2023, vol. 10(1), no. 202310105 article 4 of 7 doi: 10.15826/chimtech.2023.10.1.05 figure 1 sem images of znbtc-1–5 (a–e, respectively), comparative diffraction pattern of samples znbtc-1–5 (f). figure 2 edx of znbtc-1–15 (a–0, respectively). the appearance of sharp reflections in pxrd patterns indicates a good degree of crystallinity of the synthesized products. the presence of reflections in the region of small angles confirms that the synthesized samples are mofs. the positions of the main diffraction peaks of all substances znbtc-1–15, namely, 10°, 15–20°, 25–30° and 35–40° 2θ (theta) are identical, which indicates that they possess the same crystal structure. figure 3 sem images of znbtc-6–10 (a–e, respectively), comparative diffraction pattern of samples znbtc-6–10 (f). figure 4 sem images of znbtc-11–15 (a–e, respectively), comparative diffraction pattern of samples znbtc-11–15 (f). but compounds znbtc-1–5 also have a diffraction peak at 52° 2θ (theta) in their pxrd patterns and, in addition, the intensities of the main diffraction peaks of samples znbtc1–5 are greater than those of the other samples. it can be assumed that this is due to the increased crystallinity of the samples znbtc-1–5 and the effect of zn(no3)2·6h2o on the f) https://doi.org/10.15826/chimtech.2023.10.1.05 chimica techno acta 2023, vol. 10(1), no. 202310105 article 5 of 7 doi: 10.15826/chimtech.2023.10.1.05 crystal growth during synthesis. the diffraction patterns of samples znbtc-5 and znbtc-10 synthesized in dmso have additional reflections. it can be assumed that znbtc-5 is characterized by a crystal structure different from that of the other znbtc. comparative analysis of powder diffraction patterns of znbtc-1–15 showed that the replacement of the counterion in the composition of the precursor does not affect the elemental composition of mof and is not included in the structure of the final mof (figure 1–4), but the crystallinity and morphology of obtained structures are strongly dependent on the type of salt (zn(no3)2·6h2o facilitates the formation of more crystalline materials, while zn(ch3co2)2·2h2o – of more amorphous, and zinc acetate does not form into "blowball" during the solvothermal synthesis). the reason for this could be that zn(no3)2·6h2o and znso4·7h2o are more acidic (ph<7) than zn(ch3co2)2·2h2o (ph = 7). polarity of the solvent also affects the crystallinity and structure of the obtained compounds. the mixture of dmso/dmf/h2o solvents that has the highest polarity among the other ones (table 2) yields an additional diffraction peak in the region of 10–15° 2θ (theta) in the pxrd pattern of the synthesized znbtc. 4. limitations we obtained a new morphology of znbtc; therefore, we needed to confirm its structure by single-crystal x-ray crystallography. however, the particles of znbtc were agglomerates. the possible solution of this challenge is a recrystallization of a synthesized compound to obtain a single crystal. 5. conclusions the results of the study show that the type of solvent and salt does not affect the elemental composition and crystallinity of a znbtc-based mof. however, these critical parameters affect the morphology of the mof. according to the sem images, znbtc crystals in the form of "blowball" were obtained for the first time. such sample surface can potentially be used for the sorption of organic molecules. ● supplementary materials no supplementary materials are available. ● funding this work was supported by the russian science foundation (grant no. 22-23-00738), https://www.rscf.ru/en. ● acknowledgments this research would not have been possible without the help of the following organizations: – saint petersburg state institute of technology; – the faculty of physics of itmo; ● author 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2411-1414; chimicatechnoacta.ru doi: 10.15826/chimtech.2022.9.1.02 1 of 7 influence of preparative form on the target efficiency and toxicity of the solid insecticide based on pyrethroid and neonicatinoid andrey v. tretiakov ab * , sergey b. yaroshuk b , vyacheslav f. markov ac , lyudmila g. budnik b a: institute of chemical engineering, ural federal university, 620002 mira st., 19, yekaterinburg, russia b: "get biotechnology" ltd, 620072 constructors st., 5, yekaterinburg, russia c: department of scientific research, ural institute of state fire service of emercom, 620022 mira st., 22, yekaterinburg, russia * corresponding author: tretyakoff_93@mail.ru this article belongs to the regular issue. © 2021, the authors. this article is published in open access form under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). abstract the influence of solid preparative form was studied on the «get dry» insecticide based on alpha-cypermethrin and imidacloprid. the target efficiency as acute and residual impact was studied when agent was applied against the bedbugs (cimex hemipterus), german cockroach (blatella germanica), common house flies (musca domestica) and larvae of the leather beetles (attagenus smirnovi). the agent demonstrated strong acute effect (about 100%) when applied against the cockroaches, bugs, and flies. moreover, the agent demonstrates the residual impact on the cockroaches, flies, fleas for 45 days, and on the bugs for 30 days. the slight insecticidal activity was observed when the agent was applied against the larvae. we studied toxicity of the agent, ld50, when swallowed (moderately hazardous substances, class iii) and when applied to the skin (low-hazard substance, class iv) as well as studied its inhalation hazard according to its volatility с 20 °c, irritant action when applied to the skin (slight) and eye irritation (moderate). sensibilizing action was not observed. keywords solid form insecticide pyrethroid neonicatinoid target efficacy toxicity received: 24.11.2021 revised: 11.01.2022 accepted: 11.01.2022 available online: 13.01.2022 1. introduction in the world practice of disinsection, there is a shortage of effective and at the same time ready-to-use formulations. in the control of household crawling pests, the priority is given to the contact type of agents, which are blockers or inhibitors of acetylcholinesterase. if the formulation of the insecticide is ready for use, there is a possibility of low efficacy or high toxicity of the drug. existing ready-made insecticides often have an intestinal (calcium, magnesium, barium arsenates, etc.) or fumigation (katfos, dichlorvos, etc.) principle of action; as a result, the disinsector is exposed to an additional risk of drug poisoning. in the case of domestic use, when the products are used by nonprofessionals, insecticides of these types of action can cause undesirable consequences due to the poisoning. taking this into account, specialists of "get biotechnology" ltd (yekaterinburg, russia) have developed a readymade insecticide with a contact type of action for use in everyday life [1]. the agent contains the active ingredients alpha-cypermethrin with a mass fraction of 3% and imidacloprid with a mass fraction of 0.4%. these active ingredients have relatively low toxicity and resistance in most insects [2–4]. alpha-cypermethrin (concord, renegade, fastak, fendon) – is an (s)-α-cyano-3-phenoxybenzyl ester of (1r, 1s)-cis-3(2,2-dichlorovinyl)-2,2-dimethylcyclopropanecarboxylic acid (fig. 1). a similar solid insecticidal agent with contact action principle is known [5]. the use of an insecticide based on pyrethroids for the control of household pests was described in the patents [6–7]. toxicological tests and monitoring of insecticide degradation were discussed in the article [8]. alpha-cypermethrin is a contact-intestinal pyrethroid with repellent properties, effective in combating all stages of insect development. http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2022.9.1.02 https://orcid.org/0000-0002-0742-7977 https://orcid.org/0000-0003-0758-2958 https://orcid.org/0000-0002-1425-4170 https://orcid.org/0000-0002-3374-110x http://creativecommons.org/licenses/by/4.0/ chimica techno acta 2022, vol. 9(1), no. 20229102 article 2 of 7 fig. 1 structural formula of alpha-cypermethrin for a long time, it retains its insecticidal and acaricidal properties, and it is resistant to being washed out by rain. it is safe for bees, as it has a repellent effect on them – bees leave the site immediately after processing. alphacypermethrin does not pose danger to mammals and birds [9]. resistance to alpha-cypermethrin may be due to mutations in voltage-sensitive sodium channels (vsscs) and enhanced detoxification by p450 monooxygenase. the authors of [10] included both components in insects to determine the effects of pyrethroids. pyrethroid hydrolase in bacteria and p450 in insects are potential targets. pyrethroid hydrolase was aimed at increasing the biodegradation of bacteria, and p450 was aimed at increasing insect sensitivity/resistance. similarly, the chimeric p450 enzyme has been reported to be involved in pyrethroid resistance in helicoverpa armigera (hubner). a study [11] reports on the effect of the presence of pyrethortroids in combination with other environmental pollutants (microplastics) on the vital activity of chironomus riparius. combined and single exposure to pyrethroids and microplastics affects vital traits and microbiomes, therefore, it is necessary to focus on effects at limited food levels because they can simulate realistic nutritional conditions in nature and indicate competition for food in the host microbiota. the results of a study [12] show that ecologically significant concentrations of pyrethroids can disrupt the behavior of delta smelt larvae even at the lowest concentrations (<1 ng/l) and that salinity can alter the dynamics of pyrethroid toxicity in terms of behavioral effects, especially for bifenthrin, where salinity was positively correlated with antithigmotaxis at each concentration. the aim of the study [13] was to investigate the enantiomerically specific acute toxicity for the earthworm eisenia fetida and a potential mechanism through a multilevel response. gut damage, changes in body weight, and dna damage caused by oxidative stress may be the main mechanisms of tefluthrin toxicity to earthworms. the authors of [14] report a strong correlation between surface area/volume and toxicokinetic (tk) parameters (rate constants of sorption and absorption and the resulting bioconcentration factors (bcf)), but none of the tk parameters correlated with sensitivity. the only parameter consistently correlating with sensitivity for all species was the death rate constant of the guts-red-sd model (models with a reduced overall unified survival threshold, suggesting stochastic death), indicating that sensitivity to cypermethrin is more related to toxicodynamic (td) parameters than the parameters of the tk. research [15] reports that due to its regulatory role at the initial stage of hydrolysis of the ester bond, esterase acts as a regulatory enzyme in all organisms in the case of pyrethroid metabolism. this family of enzymes exists in almost all life forms (bacteria, fungi, plants, animals), and pyrethroid degradation functions have been reported in all organisms. in insects, these enzymes play a role in pest resistance and have also been reported to have a detoxifying role in animals. pesticides are not toxic to animals in low doses due to the presence of pyrethroid hydrolase isoenzymes. bacteria and fungi produce pyrethroid hydrolase to degrade pyrethroid insecticides. based on the evidence that dopamine regulates behavior and studies showing that other pyrethroids affect the dopamine system, transcripts involved in dopaminergic signaling were measured. researchers [16] found that the active dopamine transporter was inhibited with 0.2 mg/l of a similar pyrethroid insecticide, esfenvalerate. the results of the study [17] showed that the administration of deltamethrin is associated with a significant decrease in reproductive hormones, especially fsh, lh, and a significant increase in the levels of interleukin 2 (il2), interleukin 6 (il6), histamine and cortisol. they also noted the importance of suppressing sperm motility and viability, reducing testicular weight, sperm count and fructose in sperm. these results clarify the deleterious effects of deltamethrin on the male reproductive system, causing significant changes in reproductive hormones, markers of inflammation, and testicular function. the structure-activity relationships showed that substituents at the position of the chiral atom in the oxadiazine ring are very important for the biological activity of the oxadiazine insecticide. zhang et al. [18] synthesized a series of derivatives of tricyclic oxadiazine 4a-methyl ester. the authors of [19] created a navms-based cockroach sodium channel model in which pyrethrin ii docked with the pyrethroid receptor 1 (pyr1) site and proposed a rationale for the observed structure-activity relationship of six pyrethrins. our study shed light on the molecular mechanism of action of pyrethrum on sodium channels and revealed differences in the modes of action of the six biologically active components of pyrethrum. ld50 of pyrethrum when introduced into the stomach, depending on the solvent and the species of animals, varies for mice 762.0 mg/kg (in corn oil), 35 mg/kg – in dmso and 168 mg/kg – in 2% starch gel; for rats in the range of 80–368 mg/kg in corn oil, 75 mg/kg – in ethyl chimica techno acta 2022, vol. 9(1), no. 20229102 article 3 of 7 alcohol, 208 mg/kg – in 2% starch gel and according to state all-union standard 12.1.007-76 it belongs to 2–3 hazard classes. ld50 when applied to the skin of rats is 500 mg/kg, on the skin of rabbits >2000 mg/kg. cl50 for rats with 4-hour inhalation exposure in the form of dust >1300 mg/m3 (according to the active substance >400 mg/m3). the clinical picture of acute poisoning is characterized by a neurotoxic type of action with impaired coordination of movements and the appearance of seizures, tremors, salivation, etc. the most affected organs are the nervous system, liver, and kidneys. in case of contact with eyes, it causes moderate irritation of the mucous membranes. has a mild irritant effect on the skin of rabbits. cumulative activity of alpha-cypermethrin using the method of yu.s. kagan et al. is moderate (сcum = 4.6). the skin-resorptive effect is poorly expressed. a weak sensitizing effect of the substance was established (the magnusson-kligman method on guinea pigs). mutagenic activity, studied in various test systems in vivo and in vitro, has not been identified. carcinogenic, embryotoxic and teratogenic effects have not been established. srli (safe reference level of impact) of alpha-cypermethrin in the air of the working area – 0.1 mg/m3; srli in atmospheric air 0.002 mg/m3. imidacloprid (admir, gauchko, copfidor, prime) is a 4,5-dihydro-n-nitro-1-[(6-[chloro-3-pyridyl)-methyl]imidazolidin-2-ylen-amine (fig. 2). imidacloprid is a synthetic insecticide from the group of neonicatinoids, which, when ingested by an insect, suppresses the activity of acetylcholinesterase. this leads to prolonged opening of sodium channels, because of which the nervous system is overexcited, and the insect is paralyzed for a long time, which leads to death. low concentrations of imidacloprid can lead to reversibility of paralyzed insects. the authors of [20] report the zero efficacy of confidor with the active ingredient imidacloprid against female n. californicus ticks. according to the ld50 value, the substance for rats belongs to the 3rd class of moderately hazardous substances (ld50 410–475 mg/kg), for mice – to the 2nd class of highly hazardous substances (ld50 98 mg/kg) according to state all-union standard 12.1.007-76. fig. 2 structural formula of imidacloprid clinical signs of poisoning: tremor, staggering gait, narrowing of the eye slits, apathy, shortness of breath, inhibited movements. with a single application to the skin, imidacloprid is classified as low-hazard – ld50 for rabbits is more than 5000 mg/kg. the irritant effect on the skin of rabbits at a dose of 5000 mg/kg (exposure 4 hours) has not been established. no irritating effect was found on the mucous membranes of the eyes of rabbits, which were injected into the conjunctival sac of the eye with a substance in the form of a 20% aqueous solution. the sensitizing effect has also not been identified [21]. as a result of numerous studies, the following longterm effects of imidacloprid have not been identified: embryotoxic, teratogenic, gonadotoxic, mutagenic, carcinogenic. mcl (maximum concentration limit) in the air of the working area is 0.5 mgm3 (aerosol), srli in the atmospheric air of populated areas is 0.002 mg/m3. synthetic pyrethroids in composition with neonicatinoids enhance each other's action, creating a synergistic effect. such compositions make it possible to control populations resistant to pyrethroids. in connection with the above, the aim of the work was to study the effectiveness against cockroaches, bedbugs, house flies, and leather beetle, as well as the toxicity of a solid insecticidal agent based on alpha-cypermethrin and imidacloprid. 2. experimental 2.1. target effectiveness of the product 2.1.1. characteristics of test conditions target effectiveness tests were carried out according to the methods described in guidelines p 4.2.2643-10 issued by the federal service for surveillance on consumer rights protection and human wellbeing (rospotrebnadzor) of the russian federation. the results were evaluated in accordance with the criteria set out in p 4.2.2643-10 "methods of laboratory research and testing of disinfectants to assess their effectiveness and safety". 2.1.2. applicable test objects german cockroaches (blatella germanica l.), bedbugs (cimex hemipterus), house flies (musca domestica), and larvae of leather beetle (attagenus smirnovi) of a sensitive laboratory race were used as test objects for testing the agent. to determine the acute action of the agent, the experiment was carried out according to the standard technique adopted for testing agents in the form of insecticidal crayons and bars against flightless insects and imago of houseflies. the study of the acute action of the agent was carried out at a temperature of 22–24 °c and a relative humidity of 60–70%. plywood plates 10×10 cm in size, which were previously weighed, were used as test surfaces. the chimica techno acta 2022, vol. 9(1), no. 20229102 article 4 of 7 consumption rate for the test agent is calculated for an area of 100 cm2. the optimal consumption rate was chosen to be 0.4 g per 100 cm2. the agent was applied to the entire area of the test surface; after application, the weight of the plate was fixed to control the consumption rate. when determining the acute effect, insect replanting was carried out immediately after the application of the agent, the experiment time was 30 s (for larvae of leather beetle the exposure was 15 min), then the insects were transferred to clean glasses. the deaths were recorded for 24 hours. to determine the residual effect, the treated surfaces were stored upright at room temperature. to determine the duration of the insecticidal action, insects were planted on previously treated surfaces (on days 7, 30, 45 and 60), the exposure time was 30 s (for larvae of leather beetle the exposure was 15 min). after contact with the treated plates, the insects were transferred to clean vessels and their condition was recorded 24 hours later. the residual action was considered complete when the insect mortality was less than 50%. when determining the acute and residual effects, each experiment was performed 3 times, using 10 insects for each iteration. 2.1.3. criteria for evaluating results in accordance with the manual, “methods of laboratory research and testing of disinfectants to assess their effectiveness and safety. 2011" р 4.2.2643-10, the criteria for evaluating insecticidal agents are: 1. acute effect on flightless insects: death in 24 hours – not less than 100%; 2. residual action – 7–60 days. 2.2. assessment of toxicity and hazard of the agent studies to assess the toxicity and hazard of the product were carried out in accordance with the manual "methods of laboratory research and testing of disinfectants to assess their effectiveness and safety 2011" р 4.2.2643-10, methodical guidelines "requirements for experimental studies to justify the mpc of industrial allergens in the air zones and atmosphere”, as well as measures for the protection of animals used for scientific and educational purposes in ltd get biotechnology. the studies were carried out on white outbred mice weighing 18–27 g and rabbits of the "soviet chinchilla" breed weighing 2.5–3.5 kg. groups of animals were formed according to their weight and age. the animals were kept in the vivarium, their food ration included all the necessary components for their normal life in the form of briquetted feed and vegetables. average lethal doses were determined by intragastric administration and application to the skin in white mice. the duration of observation after exposure was 14 days. the local irritant effect was assessed with a single application of 500 mg of the substance on a cut-out area of the skin of the lateral surface of the back of rabbits with an area of 56 cm, followed by removal of the substance after 4 hours. also, to determine the local irritant effect, 50 mg of the substance was added once to the conjunctival sac of the rabbit's eye and the condition of the animals was monitored for 2 weeks. the sensitizing effect of the substance was studied in accordance with the methodological guidelines in mice (delayed-type hypersensitivity reaction – dthr). sensitization of mice was carried out by intradermal injection into the base of the tail of 60 μl of a mixture of the test drug (100 μg) with complete freund's adjuvant in a ratio of 1:1. the degree of sensitization was assessed after 5 days by introducing a substance in a dose of 100 μg in hanks solution into the hind paw pad of mice, followed by measuring the thickness of the hind paws after 24 hours. the dthr indicator was assessed by the amount of edema measured by the difference between the experimental and control groups. methods for studying the functions of organs and systems in experimental animals were chosen considering the data on the biological effect of the studied drug. to register the manifestations of intoxication, both integral indicators and indicators of the functional state of organs and systems were used. the integral indicators of the organism's vital activity were the survival rate of animals and the clinical picture of poisoning. the function of the respiratory system was studied by recording the respiratory rate using a complex for assessing the cardiorespiratory system of small laboratory animals. the state of the nervous system was assessed by changes in behavioral reactions in the open field test. statistical processing of the data obtained was carried out using the student-fisher test. the level of reliability was taken as statistically significant changes at p≤0.05. 3. results and discussion 3.1. target effectiveness of the product the results of the acute and residual insecticidal action of the agent against insects are listed in tables 1–4. from the data presented, a solid insecticidal agent has maximum acute efficacy as well as a long residual effect (up to 30 days) against red cockroaches, bedbugs, and house flies. however, the agent showed low efficacy both in the acute and in the residual phase against the larvae of leather beetle. the low insecticidal effect on larvae of leather beetle may be due to the phase of insect development. so, the presence of villi in the larvae of the leather beetle can prevent the insecticide from getting on the chitinous cover of the insect, resulting in a low penetration of the active substance into the insect's body. chimica techno acta 2022, vol. 9(1), no. 20229102 article 5 of 7 table 1 efficiency of the agent applied against the cockroaches blatella germanica identifiable indicators amount of the agent per 100 cm2 test results, units norm, units regulatory documents for the test methods death of insects 24 hours later acute impact 0.4 g 100% 100% p 4.2.2643-10 sec. 6.3.1 residual impact as on the 7th day 0.4 g 100% 7–90 days, minimum 50% of insects died residual impact as on the 30th day 0.4 g 100% residual impact as on the 45th day 0.4 g 60% residual impact as on the 60th day 0.4 g 6% table 2 efficiency of the agent applied against the bedbugs cimex hemipterus identifiable indicators amount of the agent per 100 cm2 test results, units norm, units regulatory documents for the test methods death of insects 24 hours later acute impact 0.4 g 100% 100% р 4.2.2643-10 sec. 6.3.1 residual impact as on the 7th day 0.4 g 93% 7–90 days, minimum 50% of insects died residual impact as on the 30th day 0.4 g 85% table 3 efficiency of the agent applied against the false stable flies musca domestica identifiable indicators amount of the agent per 100 cm2 test results, units norm, units regulatory documents for the test methods death of insects 24 hours later acute impact 0.4 g 100% 100% р 4.2.2643-10 sec. 6.3.1 residual impact as on the 7th day 0.4 g 100% 7–90 days, minimum 50% of insects died residual impact as on the 30th day 0.4 g 100% table 4 efficiency of the agent applied against the beetle larvae attagenus smirnovi identifiable indicators amount of the agent per 100 cm2 test results, units norm, units regulatory documents for the test methods death of insects 24, 48 and 72 hours later acute impact 0.4 g 24 hours 48 hours 72 hours 100% after 72 hours р 4.2.2643-10 sec. 6.3.1 16% 27% 47% residual impact as on the 7th day 0.4 g 10% 30% 43% 7–90 days, minimum 50% of insects died 3.2. assessment of toxicity and hazard of the agent 3.2.1. determination of acute toxicity when administered to the stomach and applied to the skin to determine the ld50 when administered to the stomach of white rats, the agent was administered in doses ranging from 500 to 5000 mg/kg. the ld50 value was 2000±450 mg/kg. the clinical picture of acute poisoning in animals was characterized by excitement, lethargy, adynamy, refusal to feed, as well as the presence of tremors and tail rigidity. the death of animals occurred in 1–2 days after exposure. with a single application of the test agent to the skin of sexually mature rats at a dose of 2500 mg/kg, no clinical manifestations of poisoning and death of animals were observed during the next 14 days. ld50>2500 mg/kg. thus, when injected into the stomach, the agent belongs to the 3rd class of moderately hazardous substances, when applied to the skin, it belongs to the 4th class of low-hazard substances according to the classification of state all-union standard 12.1.007-76. 3.2.2. inhalation hazard according to the degree of volatility the inhalation hazard of the volatile components of the agent was determined by preliminary saturation of the desiccator for 24 hours at room temperature (21 °c), followed by placing the experimental animals (white mice) in the desiccator. the exposition time was 2 hours. during the observation of the animals exposed to the vapors of the agent, the animals showed no clinical signs of poisoning. in appearance, and in response to painf and sound stimuli, the animals belonging to the experimental group did not differ from those in the control one. after the termination of the exposure, the animals were examined according to a number of indicators reflecting the functional state of the respiratory and nervous systems. the results of the experiment are presented in table 5. as follows from the data presented, when exposed to vapors of the agent in animals, no changes were revealed in the recorded indicators of intoxication. chimica techno acta 2022, vol. 9(1), no. 20229102 article 6 of 7 table 5 indicators of the functional state of the mice after the impact of the agent parameters control test respiration rate per min 212.0±2.9 215.5±3.5 horizontal activity 97.2±6.7 91.8±10.5 vertical activity 5.8±1.7 10.3±2.7 hole exploratory behavior 3.7±0.4 4.3±0.3 thus, with inhalation exposure to a vapor, agents in saturating concentrations belong to the 4th class of lowhazard substances according to the criteria for the selection of insecticidal preparations. 3.2.3. local irritant effect on mucous membranes of eyes and skin with a single contact of the composition with the mucous membranes of eyes of rabbit, signs of moderate irritant action were observed: hyperemia (2 points); edema (1 point), discharge (1 point), total points – 4. the revealed changes disappeared on their own after 3–4 days. with a single contact of the agent with the skin in rabbits, no changes were detected at the application site: there was no erythema (0 points), the thickness of the skin fold of the experimental animals did not differ from that of the control group of animals (control: 3.0±0.3; experiment: 3.1±0.2 mm, p>0.005). on visual examination, the experimental animals' skin was clean, without features. thus, the agent has a moderate irritant effect on the mucous membranes of the eyes and a weak irritant effect on the skin with repeated applications. 3.2.4. sensitizing effect of the agent the sensitizing effect of the investigated substances was studied in accordance with the methodological guidelines on white mice (dthr). the effect on mice of the agent did not lead to statistically significant differences in the response between the experimental and control groups of animals. the data obtained indicate the absence of sensitizing activity in the agent. the data are presented in table 6. table 6 the results of the delayed hypersensitivity reaction of mice parameters difference between the thickness of paws of the test group and control group (mm) variation range average within the group test 0.05–0.15 0.070±0.008 hole exploratory behavior 0.05–0.10 0.080±0.008 4. conclusions the solid insecticidal agent containing the active substances alpha-cypermethrin 3% and imidacloprid 0.4% has insecticidal activity against cockroaches, bedbugs, flies, fleas. the agent also has a residual effect: against cockroaches, flies, fleas for 45 days , and towardsbedbugs within 30 days. the recommended application rate is 0.4 g of the product per 1 dm2 of the treated surface. according to the parameters of acute toxicity when administered into the stomach, the agent belongs to the 3rd class of moderately hazardous substances, when applied to the skin – to the 4th class of low-hazard substances in accordance with state all-union standard gost 12.1.007-76 "occupational safety standards system. noxious substances. classification and general safety requirements". vapors of the agent in saturating concentrations belong to the 4th hazard class according to the criteria for the selection of insecticidal preparations. the irritating effect of the agent after a single contact with the skin was not revealed. when the agent comes into contact with the mucous membranes of the eyes, a moderate irritant effect was found. the product does not have a sensitizing effect. declaration of competing interest the authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. references 1. yaroshuk sb, tretiakov av; obshchestvo s ogranichennoi otvetstvennostiu get. solid insecticide. russian federation patent ru 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https://doi.org/10.1021/acs.jafc.9b00826 https://doi.org/10.1016/j.pestbp.2018.05.002 https://doi.org/10.1088/1755-1315/901/1/012068 solvent effect on the no2 sensing properties of multi-walled carbon nanotubes published by ural federal university eissn 2411-1414; chimicatechnoacta.ru article 2022, vol. 9(3), no. 20229311 doi: 10.15826/chimtech.2022.9.3.11 1 of 6 solvent effect on the no2 sensing properties of multi-walled carbon nanotubes nikita i. lapekin a , tatyana v. anufrieva a, arina v. ukhina b, artem a. shestakov a, alexander g. bannov a* a: department of chemistry and chemical technology, novosibirsk state technical university, novosibirsk 630073, russia b: institute of solid state chemistry sb ras, novosibirsk 630090, russia * corresponding author: bannov.alexander@gmail.com this paper belongs to the ctfm'22 special issue: https://www.kaznu.kz/en/25415/page. guest editors: prof. n. uvarov and prof. e. aubakirov. © 2022, the authors. this article is published in open access under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). abstract this article is devoted to the investigation of the influence of the solvent on sensing properties, such as response and recovery rate, of chemiresistive gas sensors. multi-walled carbon nanotubes were used as an active material for the sensors. the initial material was investigated by scanning electron spectroscopy and transmission electron microscopy, low-temperature nitrogen adsorption, raman spectroscopy, and x-ray diffraction. the active material was produced by drop casting. different polar solvents (acetone and ethanol) were used for suspension preparation. textolite with copper contacts on the edges of one side was used as a sensor substrate. the gas sensing properties (the response and the recovery time) were investigated in the range of 100–500 ppm no2 at room temperature. the films made using different solvent suspensions showed high sensitivity and rapid recovery rate to nitrogen dioxide. it was found that the method of film preparation has an effect on the measured sensing properties. the films prepared using different suspensions possessed different properties: the film made from the acetone suspension had the response values from 8.49% to 20.26%, and the recovery values from 0.06%/min to 0.16%/min. the response of the film made from the ethanol suspension increased , being from 12.25% to 23.63%; the recovery rate were also increased (from 0.19%/min to 0.39%/min). keywords carbon nanomaterials mwnts films gas sensors no2 detection ultrasonic dispersion polar solvent received:25.06.22 revised: 22.07.22 accepted: 22.07.22 available online: 08.08.22 1. introduction the detection of hazardous and toxic gases in industry and everyday life is of interest from environmental and occupational health and safety points of view. this is because exposure to such gases, even at low concentrations, can cause visual disturbances, respiratory diseases and even death [1–4]. that is why the development of effective techniques with rapid, sensitive and selective real-time monitoring capabilities is an urgent task. there are several ways of detecting gases in the air. one of the most commonly used methods of analysis is gas chromatography-mass spectrometry due to its reliability and accuracy [5, 6]. however, this method has a number of disadvantages, such as high cost and complex equipment, as well as time-consuming preconcentration of samples [7–9], which prevents real-time monitoring and analysis of gas content in the air. because of the problems described above, this method of analysis is not suitable for the real-time detection of hazardous gases. chemiresistive gas sensors are preferable for gas detection due to the obvious advantages. in addition, with the development of mems (microelectromechanical systems), chemiresistive gas sensors can be integrated into smart devices such as smartphones, smartwatches, and hand-held medical instruments [10, 11]. thus, the use of chemiresistive gas sensors will enable reliable real-time monitoring of hazardous gases. compared to traditional semiconductor-based sensors which consume high power and operate at high temperatures, sensors operating at room temperature have many challenges to overcome: improving sensor response, increasing sensor recovery rate, and finding ways to improve sensitivity. typically, gas sensors are implemented http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2022.9.3.11 mailto:bannov.alexander@gmail.com https://www.kaznu.kz/en/25415/page http://creativecommons.org/licenses/by/4.0/ https://orcid.org/0000-0001-6101-9707 https://orcid.org/0000-0001-5868-9013 https://crossmark.crossref.org/dialog/?doi=https://doi.org/10.15826/chimtech.2022.9.3.11&domain=pdf&date_stamp=2022-8-8 chimica techno acta 2022, vol. 9(3), no. 20229311 article 2 of 6 in the form of metal oxide semiconductor sensors, but they operate at relatively high temperatures (200–350 °c), which requires high energy input [12]. this is another problem that can be solved by using new active materials. in view of this, the development of sensors operating at room temperature (25±2 °c) is an urgent task that needs to be done. a wide range of nanomaterials, including materials based on carbon, noble metals, metal oxides or sulphides, and organic semiconductors, opens up opportunities for the development of functional gas sensors. recently, carbon nanomaterials (cnms) have received much attention in this field and have found wide application as the materials of catalysts, biosensors and chemoresistive gas sensors [13, 14]. this is due to their unique physical structure and excellent electronic properties. multi-walled carbon nanotubes (mwnts) are a special type of material that can be used for hazardous gas detection [15–17]. the use of mwnts as an active material for chemiresistive gas sensors is preferable due to the low cost, high sensitivity, and the possibility of incorporation into portable devices. carbon nanomaterials can be implemented in sensors both in the form of films and compacts (pellets). the method of implementation has a significant impact on the properties of the sensors. despite of the traditional method of sensors preparations, called drop casting, is well investigated, there are no data on the ultrasonic parameters influencing the sensory properties of films. the choice of a solvent used for the ultrasonic suspension preparation is necessary to drop casting method. it is well known [18, 19], that the nature of a solvent affects the dispersion, stability and electrical properties of mwnts. so, it is important to evaluate the solvents’ effect on the sensing properties of mwnts. this work is devoted to the study of the solvent’s effect on the sensing properties of multi-walled carbon nanotubes for chemiresistive gas sensors of nitrogen dioxide. 2. experimental commercial multi-walled carbon nanotubes (mwnts) were used as an active material for chemoresistive gas sensors for no2 detection. the mwnts were manufactured by shenzhen nanotech port co. (china). the mwnts were studied by transmission electron microscopy (tem) on a jem-2010 electron microscope (jeol, japan) with a resolution of 0.14 nm at an accelerating voltage of 200 kv. the morphology of the mwnt surface was investigated by a s-3400n scanning electron microscope (sem) (hitachi, japan). the structure characteristics of mwnts were determined by raman spectroscopy (raman spectroscopy) on a horiba jobin yvon t64000 (λ = 514 nm). the degree of degree was estimated by the ratio of intensities of peaks d and g. the surface area of mwnts was investigated by lowtemperature nitrogen adsorption at 77 k on a quantochrome nova 1000 e. in addition to raman spectroscopy, the structural features of mwnts were also determined by x-ray diffraction (xrd). the degree of graphitization was calculated from the interlayer spacing using the following equation: 𝑦 = 0,688 − 2𝑑002 0,688 − 0,6708 ∙ 100 %, (1) where d002 is the interlayer spacing, nm. the chemiresistive gas sensor was made in the form of a film of active material deposited by drop casting onto a textolite substrate. mwnt films were obtained from acetone and ethanol suspensions. the mass of mwnts, the duration of ultrasonication and the volume of polar solvent are presented in table 1. the preparation of films included dispersion of an initial sample of polar solvent in an ultrasonic bath (150 w, 22 khz) for 20 min followed by the deposition of suspension on a heated substrate. slurry deposition was carried out on the substrate heated to 70 °c. the sample formed a square film that partially covered the copper contacts. a scheme of the sensor is shown in figure 1. the sensing properties were studied in a custom dynamic type station shown in figure 2. the station consists of the lines of analytes and carrier gas. in the study synthetic air (79% n2, 21% o2, a verified gas mixture) was used as a carrier gas, nitrogen dioxide mixture in the air (5000 ppm no2 in air, calibrated mixture) of constant composition was used as the analyte. table 1 parameters for the preparation of mwnt films. sample solvent mass, g duration of ultrasonication, min volume of solvent, ml mwnts acetone 0.01 20 5 ethanol figure 1 obtained sensor (a): copper contacts (1), film of cnms (2), dielectric substrate (3) and its scheme (b). chimica techno acta 2022, vol. 9(3), no. 20229311 article 3 of 6 the response and recovery time of the sensors were studied. the response (%) of chemoresistive gas sensors was calculated according to equation 2: ∆𝑅 𝑅0 = 𝑅 − 𝑅0 𝑅0 ∙ 100 %, (2) where r is the sensor resistance during the contact with the analyte, ω; r0 is the sensor resistance during the carrier gas flowing, ω. the rate of recovery of sensors (%/min) was calculated according to equation 3: 𝑈 = 𝑅𝑟 − 𝑅 𝑅0(𝑡𝑟 − 𝑡) ∙ 100 %. (3) where rr – the sensor resistance after regeneration in air flow, ω; tr – the time of measurement when the sensor resistance was rr, min; t – the time of measurement when the sensor resistance was r, min. the sensors were placed in a measurement cell (figure 3) on a heater. the sensor resistance was measured using the two-point method between the two electrodes using a keithley 2401 source meter at a bias voltage of 0.1 v at room temperature (25±2 °c). the total flow rate of the gas mixture fed into the measuring chamber for contact with the sensor was 100 ml/min. the concentration of the analyzed gas in the system was controlled by the flow of the air-analyte mixture coming from the cylinder. the carrier gas flow was varied so that the resulting mixture had a certain gas concentration. all sensor measurements were taken according to the following procedure: firstly, before the experiment, empty cell was blown by 100 ml/min of synthetic air for 10 min to clean the system after the last measurement. after cleaning, the sample was placed in the cell and was heated by 70 °c by the same carrier gas flow for the same time for desorption of moisture and adsorbed compounds. the last preparation part included the cooling of the cell and the sensor inside by the same flow rate for 10 min. after the preparation, the humidity inside the cell was 18–19% and the temperature of the sensor was 25±2 °c. the measurement was started with baseline recording for 60 min in the 100 ml/min of carrier gas flow followed by three 10 min cycles of analyte flow (for 100 ppm, 250 ppm, 500 ppm of no2) alternated with three 10 min cycles in synthetic air flow. 3. results and discussion the sem and tem microphotographs are shown in figure 4. the mwnts sample consisted of relatively thick carbon nanotubes and chain like carbon nanofibers with a diameter of 60–80 nm and a narrow hollow channel of 10–20 nm. figure 2 scheme of a station for gas sensor testing. figure 3 model of measurement cell for the characterization of gas sensors (a) and its scheme (b): housing (1), cover (2), common contact (3), gas inlet connection (4), gas outlet connection (5), clamping contacts (6), leds (7), heater (8), sealing (9), humidity-temperature sensor (10), pressure sensor (11). figure 4 tem-micrographs (a, b) and sem-micrographs (c, d) of mwnts. chimica techno acta 2022, vol. 9(3), no. 20229311 article 4 of 6 the mwnts were relatively defective, which was confirmed by raman spectroscopy, namely, by a high value of the i(d)/i(g) peaks ratio (i(d)/i(g) = 0.99), which, in turn, corresponds to the disordered structure of the carbon material and the ordered structure of carbon in the sp2-hybridized state, respectively (figure 5). mwnts had a 128 m2/g surface area, as measured by low-temperature nitrogen adsorption. the data of raman spectroscopy is consistent with the graphitization degree data obtained from xrd (figure 6). table 2 summarizes the data obtained for the mwnts. the mwnt samples showed a high response to no2 in the concentration range of 100–500 ppm at room temperature (figure 7). for both sensors an increase in the response value with increasing analyte concentration was observed. however, the sample obtained in ethanol showed outstanding results of response and recovery, more than 1.5– 2 times compared to that synthesized from the acetone dispersion. figure 5 raman spectrum of mwnts. figure 6 x-ray diffraction pattern of mwnts. table 2 properties of the pristine mwnts. sample mwnts diameter, nm 60–80 i(d)/i(g) 0.99 surface area, m2/g 128 interlayer spacing, nm 0.34 degree of graphitization, % 46.51 the response values of the mwnts obtained in acetone ranged from 8.49% to 20.26%; the recovery rate values ranged from 0.06%/min to 0.16%/min. the response values of the mwnts obtained in ethanol increased from 12.25% to 23.63%, the recovery values also increased (from 0.19%/min to 0.39%/min). for clarity, the response values and recovery rates are shown in table 3. the differences in sensing properties are based on the nature of the solvent or, to be more precise, on the value of dielectric permittivity. for ethanol, the permittivity is higher than for acetone: 25 and 21, respectively [20]. probably, the higher the permittivity of a polar solvent, the better the dispersion during ultrasonication, the better the adsorption of no2 on a surface of an mwnt. due to the high degree of disorder (according to the raman spectroscopy), good recovery without heating and uv irradiation, it can be concluded that the physisorption is a dominate mechanism of the gas detection. figure 7 response of mwnt films obtained in ethanol (a) and in acetone (b) to 100–500 ppm no2 at room temperature. table 3 response and recovery rate (values module) of mwnts obtained in ethanol and acetone. solvent r, ω response, % recovery rate, %/min 100 ppm 250 ppm 500 ppm after 100 ppm after 250 ppm after 500 ppm acetone 329 8.49 16.93 20.26 0.06 0.15 0.16 ethanol 979 12.25 20.65 23.63 0.19 0.34 0.39 chimica techno acta 2022, vol. 9(3), no. 20229311 article 5 of 6 it should be noted that sensing properties of the prepared sensors are better compared to the other sensors [21–23]. the detailed comparison is shown in table 4. also, the sensing properties of the mwnt films were compared with the sensing properties of the mwnt pellets. in work [24] the pellets were made of the same mwnts under the pressure of 9–13 mpa. the graphs of the response of the mwnt pellets compacted under 9 mpa and 13 mpa are shown in figure 8. table 4 comparison of sensing properties of proposed no2 sensor with other published no2 sensors. material concentration, ppm operating temperature, °c response, % reference rgocntssno2 100 rt 5,3 [21] sno2rgo 100 45 1,08 [22] znoswcnt 500 150 9 [23] mwnt obtained in ethanol 100 rt 12,25 this work figure 8 response of mwnt pellets compacted under 9 mpa (a) and 13 mpa (b) pressure to 100–500 ppm no2 at room temperature. according to the data shown in figure 7 and figure 8, it was established that the films are better as active materials for chemoresistive gas sensors as compared to thepellets, made of compacted powder of mwnts. for the pellets of mwnts the recovery was not observed, because of the pores blocked and the plastic deformation of mwnts during pressure. also, according to the xrd, the degree of graphitization of the initial mwnts was 46.51%, and the degree of graphitization of the mwnt compacts pressed under 11 mpa was only 26.82%. the response of the mwnt compacts, pressed under 9 mpa and 13 mpa, increased in range of 2.94–16.65 % and 2.35–14.33%, respectively. a comparison of films and compacts of mwnts showed the better response of the former. the differences in gas-sensing properties between films and pellets are in the thickness. for gas sensors based on carbon nanomaterials, the thinner the active layer, the better the properties. because of the bigger response and the better recovery rate, films are more appropriate for active materials of gas sensors despite their higher cost. 4. conclusions chemoresistive gas sensors based on mwnt films have a relatively high response toward no2 and a rapid recovery rate compared to mwnt pellets. the method of film preparation also has an effect on the sensing properties. the films made using different suspensions have different properties. the film made using the acetone suspension has the response values from 8.5% to 20.3%, and the recovery values from 0.06%/min to 0.16%/min. the response of the film made from the ethanol suspension increased, being from 12.3% to 23.6%; the recovery values also increased (from 0.19%/min to 0.39%/min). because of the lack of the data on the solvent influence on sensing properties reported in the literature, we suppose that the differences in sensing properties are based on the nature of the solvent, namely, the value of permittivity, the surface tension, the dipole moment, etc. supplementary materials no supplementary materials are available. funding the work was carried out within the scope of the state task of the ministry of science and higher education of russia (project no. fsun-2020-0008). acknowledgments none. chimica techno acta 2022, vol. 9(3), no. 20229311 article 6 of 6 author contributions data curation: n.i.l., a.g.b. resources: a.v.u. supervision: a.g.b. validation: a.a.s., t.v.a. writing – original draft: n.i.l., a.g.b. conflict of interest the authors declare no conflict of interest. additional information author ids: nikita lapekin, scopus id 57220028358; arina ukhina, scopus id 54382315900; artem shestakov, scopus id 57220033659; alexander bannov, scopus id 54788777600. websites: novosibirsk state technical university, https://en.nstu.ru; institute of solid state chemistry sb ras, http://www.solid.nsc.ru/en. references 1. li h-y, zhao s-n, zang s-q, li j. functional metal–organic frameworks as effective sensors of gases and volatile compounds. chem soc rev. 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the ras, 620990 kovalevskoy/akademicheskaya st., 22/20, yekaterinburg, russia * corresponding author: igor.nikonov.ekb@gmail.com this article belongs to the regular issue. © 2021, the authors. this article is published in open access form under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). abstract a rational approach to the synthesis of substituted naphtho[1,8ef]perimidines based on snh methodology and cyclization reaction in the series of condensed azines with naphthalene substituents was presented. photophysical properties of the obtained fluorophores were studied, in particular, green fluorescence in the 485–536 nm range with quantum yield up to 32.4% was detected. homo-lumo energy values and distributions for the new compounds were calculated by the dft method in comparison with nitroanalytes and perylene. based on the data obtained, as well as on the results of fluorescence titration, the possibility of using the new diazaperylenes as potential chemosensors for the visual detection of nitrocontaining explosives was shown. keywords naphtho[1,8-ef]perimidines fluorescence sensor explosives received: 15.12.2021 revised: 20.12.2021 accepted: 20.12.2021 available online: 24.12.2021 1. introduction polyaromatic compounds are widely used as various types of chemosensors, including ones for the detection of nitrocontaining explosives. this is achieved by preferential formation of π-complexes between the sensor and quencher due to high π-deficiency of the latter, as well as hydrogen bonding due to participation in interaction with nitroaromatic analytes of functional groups on the periphery of the chemosensor and formation of inclusion complexes. triphenylene and its aryl-condensed analogues such as naphthalene, phenanthrene, pyrene, dibenzanthracene, helicenes etc. are the typical chemosensors of this group [1]. perylene and its derivatives deserves special attention in this series due to promising photophysical properties and sensor response to some nitroanalytes [2–5]. it is known that the presence of pyridine nitrogen atom in the structure of polycyclic aromatic hydrocarbons can significantly enhance the susceptibility of such structures to the action of nucleophilic agents, thereby opening the possibility of using the snh methodology for its functionalization [6, 7]. the aza-heterocycles obtained by this approach can serve as a basis for synthesis of more efficient chemosensors by combining π-conjugated and fluorophore fragments into one molecule for the enhancement of its sensory properties, e.g. towards nitroanalytes, by the creation of π-conjugated donor-acceptor systems [1]. among currently known poly(hetero)aromatic fluorophores, di-, tri and tetraazaperylenes possess the most promising photophysical properties. at the same time, they have higher lumo energies values, which in turn may provide better detection capability, for example, for aliphatic nitrocontaining explosives [8, 9]. however, no examples of using azaperylenes as chemosensors for such nitro analytes have been described in the literature so far. therefore, in this work we propose a methodology for the synthesis of new fluorophores based on naphtho[1,8ef]perimidine and studying their ability to use for visual detection of nitro-containing analytes. 2. experimental 1h nmr spectra were recorded on a bruker avance-400 spectrometer (400 mhz), the internal standard was sime4. mass-spectra (ionization type – electrospray) were recorded on a microtof-q ii instrument from bruker daltonics (bremen, germany). elemental analysis was performed on a perkin elmer pe 2400 ii chn analyzer. homo-lumo and optimized molecular structure calculations of comhttp://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2021.8.4.16 https://orcid.org/0000-0002-2493-0056 https://orcid.org/0000-0002-0397-4033 http://creativecommons.org/licenses/by/4.0/ chimica techno acta 2021, vol. 8(4), № 20218416 article 2 of 5 pounds were carried out in the orca 4.0.1 software package using the dft b3lyp, 6-311g* method [10]. uv–visible absorption spectra were recorded on a perkin elmer lambda 45. luminescence spectra were obtained using a horiba scientific fluoromax-4 spectrofluorometer [11]. the starting quinazoline 2, 2-naphthol and all reagents were obtained from commercial sources. 2.1. 4-(2-hydroxynaphthalen-1-yl)quinazoline (1) trifluoromethanesulfonic acid (1.3 g, 8.77 mmol) was added to the solution of 1.0 g (7.6 mmol) quinazoline 2 in dcm (35 ml). then 2-naphthol (1.1 g, 7.6 mmol) was added and the resulting mixture was stirring for 1 h at room temperature. then solvent was removed under reduced pressure. the residue was suspended in thf (35 ml) and solution of k3[fe(cn)6] (4.6 g, 14.0 mmol) and naoh (1.1 g, 28.0 mmol) in water (35 ml) was added. a formed suspension was stirred for 8 h at room temperature. after thf was removed under reduced pressure. the product was extracted from the remaining suspension with ethyl acetate (3×90 ml). organic layer was collected and dried over anhydrous na2so4. then solvent was evaporated under reduced pressure. the residue was purified by column chromatography (hexane:ethyl acetate = 2:1, rf = 0.1). white solid. yield 1.5 g (71%). 1h nmr spectra is in accordance with published data [12]. 2.2. 4-(2-methoxynaphthalen-1-yl)quinazoline (3) 4-(2-hydroxynaphthalen-1-yl)quinazoline 1 (0.2 g, 0.7 mmol) was dissolved in dry dmf (5 ml). k2co3 (0.15 g, 1.1 mmol) was added to the resulting solution. methyl iodide (1.5 g, 1.1 mmol) was added dropwise and the resulting mixture was stirred in an argon atmosphere for 16 h at room temperature. then dmf was evaporated under reduced pressure, the residue was suspended in distilled water (10 ml). the reaction product was extracted withethyl acetate (3×10 ml), the organic layer was dried over anhydrous na2so4. the solvent was evaporated under reduced pressure, the residue was purified by column chromatography (ethyl acetate, rf = 0.9). light yellow crystals. yield 1.4 g (66%). 1h nmr (400 mhz, cdcl3, δ, ppm): 3.79 (s, 3h), 7.08 (d, j = 8.5 hz, 1h), 7.28–7.38 (m, 2h), 7.44–7.47 (m, 2h), 7.53 (d, j = 8.0 hz, 1h), 7.88–7.92 (m, 2h), 8.06 (d, j = 9.2 hz, 1h), 8.16 (d, j = 8.4 hz, 1h), 9.52 (s, 1h). esi-ms, m/z: 287.11 [m+h]+. found, %: c 79.64, h 5.07, n 9.83. c19h14n2o. calculated, %: c 79.70, h 4.93, n 9.78. 2.3. general procedure for the synthesis of diazaperylenes (4,5) the corresponding (naphthalen-1-yl)quinazoline 1,3 (1.05 mmol) was dissolved in dry toluene (25 ml); subsequently, potassium (0.41 g, 10.5 mmol) was added under argon atmosphere. the reaction was stirred at 95 °c for 6 h, quenched with i-proh, filtered through silica gel. the solvents were removed under reduced pressure. the residue was solved in ethyl acetate (20 ml). the solution was washed with water (3×20 ml). the organic layer was dried over anhydrous na2so4. the solvent was removed under reduced pressure. the residue is purified by column chromatography (corresponding eluent). the crystallization (ch2cl2/hexane) afforded pure product. 2.4. 12-methoxynaphtho[1,8-ef]perimidine (4) eluent: dcm:meoh=20:1, rf = 0.8. yellow-green solids. yield 38 mg (16%). 1h nmr (400 mhz, cdcl3, δ, ppm): 3.79 (s, 3h), 7.51–7.54 (m, 3h), 7.86–7.90 (m, 2h), 8.24 (d, j = 8.4 hz, 1h), 8.33 (d, j = 8.0 hz, 1h), 9.02 (d, j = 8.0 hz, 1h), 9.57 (s, 1h). esi-ms, m/z: 285.09 [m+h]+. found, %: c 80.29, h 4.21, n 9.79. c19h12n2o. calculated, %: c 80.27, h 4.25, n 9.85. 2.5. benzo[de]naphtho[1,8-gh]quinolin-12-ol (5) eluent: toluene: meoh = 7:1, rf = 0.5. brown solids. yield 55 mg (18%). 1h nmr (400 mhz, cdcl3, δ, ppm): 6.95 (d, j = 8.4 hz, 1h), 7.43–7.47 (t, j = 7.6 hz, 1h), 7.74–7.81 (m, 3h), 8.08–8.13 (m, 2h), 8.38 (d, j =7.7 hz, 1h), 8.48 (d, j = 8.7 hz, 1h), 9.36 (s, 1h), 9.42 (s, 1h). esi-ms, m/z: 270.08 [m+h]+. found, %: c 84.80, h 4.15, n 5.14. c19h11no. calculated, %: c 84.74, h 4.12, n 5.20. 3. results and discussion synthesis of diazaperylenes precursor, 4-(2hydroxynaphthalen-1-yl)quinosaline 1, was performed according to the described method by direct introduction of 2-hydroxynaphthalene residue into c2 position of quinazoline 2 by snh method with using trifluoromethanesulfonic acid as an adduct formation activator [12]. further alkylation of the hydroxyl group of compound 1 with methyl iodide resulted in the formation of 4-(2-methoxynaphthalene-1-yl)quinazoline 3 (scheme 1). further, to realize the cyclization of compound 3 with obtaining the corresponding diazaperylene, an attempt was made to use excess of trifluoromethanesulfonic acid as an activator for the formation of charge transfer complex. however, in this case only the starting compounds were isolated from the reaction mass. the method of intramolecular cyclization [13], according to which the quinazoline 3 was kept in a solution of dry toluene at 95 °c in the presence of potassium for 6 h, was more successful. the yield of12-methoxynaphtho[1,8-ef]perimidine 4 after purification by column chromatography was 16%, which is acceptable for reactions of this type [8,13]. in addition, 12-oxonaphto[1,8-ef]pyrimidine 5 was similarly obtained from quinazoline 1 in 18% yield. further, the photophysical properties of the obtained fluorophores 4 and 5 were studied. the results obtained are collected in table 1. thus, the absorption maxima are located in the visible light region (495 nm) and the emission maxima lie in the green region (485–536 nm). the spectra contain two maxima, which is probably due to the effect of intramolecular charge transfer (ict). in addition, chimica techno acta 2021, vol. 8(4), № 20218416 article 3 of 5 compound 4 shows a high value of luminescence quantum yield (32.4%), apparently due to a significant influence of the electron-donating methoxy group on the heteroaromatic chromophore system. this is confirmed by the fact that diazaperylene 5, containing a hydroxy group, exhibits a value of φ = 4.5%, which is 7 times lower than that of the methoxy-containing analogue 4. table 1 photophysical characteristics of the obtained fluorophores 4 and 5 compound λabs, nm λem, nm φ [11], % 4 225, 285, 307, 329, 395, 429 485 (sh), 510 32.4 5 226, 433, 464, 495 501, 536 4.5 fig. 1 shows the absorption and emission spectra of diazaperylenes 4,5 in normalised form. for both compounds the absorption/emission spectra profiles are similar and represent distorted mirror images of each other. the photophysical properties for the naphthoperimidines 4,5 allow predicting their use as potential fluorescent chemosensors for various nitro-containing explosives. for an initial estimation of sensors fluorescence quenching efficiency by nitroanalytes, the lumo energy difference for the sensor and quencher corresponding to the thermodynamic driving force of this process was calculated [1, 9]. using the dft basis set b3lyp, 6-311g* values of homo-lumo energies were calculated for the compounds, and their optimized molecular structures were obtained [14–17]. the results are given in table 2. in comparison with the previously calculated model of the electronic configuration of homo/lumo for unsubstituted perylene [18], the electronic clouds of the obtained fluorophores are shifted in a certain degree relative to the nitrogen atoms of diazaperylene cycle and methoxy groups, which indicates a high probability of intramolecular charge transfer processes. calculations of the lumo energy values for the three nitroanalytes, namely rdx, dnt and petn, show that in the case of methoxy-substituted diazaperylene 4, the lumo(sensor)-lumo(quencher) energy gap values are from 0.1620 to 0.9620 ev, which is comparable with the values for unsubstituted perylene. whereas for the hydroxysubstituted diazaperylene 5 the energy gap with respect to rdx is –0.0277 ev, which characterises the energy ban on fluorescence quenching. for the other nitro analytes the energy gap values are also significantly inferior to the obtained fluorophore 4 and are 0.6723 ev (dnt) and 0.7723 ev (petn). scheme 1 synthesis of diazaperylenes precursor, 4-(2-hydroxynaphthalen-1-yl)quinosaline 1 a) b) fig. 1 normalised absorption/emission spectra of compounds 4 (a) and 5 (b) chimica techno acta 2021, vol. 8(4), № 20218416 article 4 of 5 a series of fluorescence quenching experiments were then performed by titrating the chemosensors 4,5 and perylene in acetonitrile solutions (5·10–5 м) with rdx, dnt and petn solutions in acetonitrile (5·10–3 m) and with 2,4,6-trinitrophenol (picric acid) solution (5·10–4 m) to confirm the results. it was found that increasing the petn concentration does not cause fluorescence quenching for all the sensors considered. in all likelihood this could be due to the low stability of the donor-acceptor complex between these azaheterocycles and petn. as for the other nitroanalytes, for rdx and dnt in the case of diazaperylene 5 and unsubstituted perylene fluorescence quenching is also practically not observed, and when titrated with picric acid solution these compounds demonstrated stern-volmer constants values less than 4400 м–1, which is an extremely low values compared to the literature data for other known chemosensors [1]. the opposite results were obtained when titrating naphtho[1,8ef]perimidine 4 with rdx, dnt and picric acid solutions. here, increasing the concentration of nitroanalytes causes intense quenching of the fluorescence. thus, as a result of titration of compound 4 solution with picric acid, the resulting stern-volmer plot is linear, and the emission spectra of the solutions before and after the addition of the analyte show significant quenching of the fluorescence sensor (fig. 2). table 2 results of calculations of homo-lumo energies and driving force quenching of fluorescence of compounds 8,9 in interaction with nitroanalytes structure homo, ev lumo, ev lumosensor – lumoquencher, ev rdx dnt petn 4 –5.3973 –2.3380 0.1620 0.8620 0.9620 5 –5.6322 –2.5277 –0.0277 0.6723 0.7723 [18] –4.201 –2.302 0.198 0.898 0.998 a) b) fig. 2 fluorescence quenching plots of sensor 4 with picric acid solution chimica techno acta 2021, vol. 8(4), № 20218416 article 5 of 5 the obtained stern-volmer constants (636 m–1 (rdx), 1187 m–1 (2,4-dnt), 25279 м–1 (picric acid)) are in agreement with values described in the literature for most chemosensors for nitro-containing explosives [1]. in addition, based on the fluorescence titration data for naphthoperimidine 4, the values of the limits of detection (lod) of the nitroanalytes were calculated according to the described method [19]. the obtained lod values are 6.6 ppm (rdx), 13.9 ppm (dnt), 1.9 ppm (pa), which also corresponds to the literature data [1]. 4. conclusions in conclusion, we have proposed a synthetic approach to the preparation of new fluorophores of the naphtho[1,8ef]perimidines series based on the snh methodology and further intramolecular cyclization of 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https://doi.org/10.1186/s13065-017-0352-7 https://doi.org/10.4103/2229-5186.79345 bright blue emissions on uv-excitation of labo3 (b=in, ga, al) pervoskite structured phosphors for commercial solid-state lighting applications chimica techno acta article published by ural federal university 2022, vol. 9(1), no. 20229108 eissn 2411-1414; chimicatechnoacta.ru doi: 10.15826/chimtech.2022.9.1.08 1 of 7 on the possibility of obtaining the elastic and biocompatible film materials based on chitosan and n-succinyl chitosan marina v. bazunova a* , roman yu. lazdin a , mariya r. elinson a, lucia a. sharafutdinova b, robert a. mustakimov a , elena i. kulish a a: bashkir state university, 450076 zaki validi st., 32, ufa, russia b: bashkir state medical university, ground floor, 450000 teatralnaya st., 2a, ufa, russia * corresponding author: mbazunova@mail.ru this article belongs to the regular issue. © 2022, the authors. this article is published in open access form under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). abstract for the first time, the studies of polyhydric alcohols (glycerol, ethylene glycol and propylene glycol) impact on the structure, deformation–strength characteristics and hemocompatibility of the film materials based on chitosan and n-succinyl chitosan were carried out. it was shown that the introduction of polyhydric alcohols into molding solutions during the creation of the films based on chitosan and succinyl chitosan in the amount up to 0.05 mol/l is accompanied by the tensile elongation value increase by 2–2.5 times. the value of the breaking stress in this case decreases by 3–4 times. there is also a decrease in the overall surface roughness and a sharp drop in the elastic modulus of the films. the stabilizing impact of the systems based on chitosan and succinyl chitosan in the presence of glycerol and propylene glycol upon the cell membranes in physiological conditions allows inferring their high hemocompatibility. keywords chitosan sodium salt of n-succinyl chitosan polyhydric alcohols plasticization deformation–strength properties received: 22.01.2022 revised: 11.03.2022 accepted: 11.03.2022 available online: 16.03.2022 1. introduction the problem of wound healing and wound infection remains actual nowadays as the number of patients with various kinds of wounds does not decrease and makes up more than 50% of the total number of patients [1]. the use of traditional dressing materials is not efficient enough. that is why the development of new modern wound healing coatings possessing a complex of properties meeting the necessary demands is underway. these coatings should effectively remove the excess of the wound exudate and its toxic components, provide an adequate gas exchange between the wound and the atmosphere, prevent the secondary wound infection, promote the creation of the optimal humidity of the wound surface, possess anti-adhesive properties and have sufficient mechanical strength [2]. proceeding from these demands, a proper base for the creation of effective wound coatings is the film materials based on bioand hemocompatible biopolymers, e.g. polysaccharides. thus, a promising one is polysaccharide chitosan (cht) and its derivatives, e.g. n-succinyl chitosan (scht). the advantages of chitosan and its derivatives in the creation of the medical purpose materials are the biocompatibility with living tissues, the proximity to the derma components in vivo by their functional qualities, bacteriostaticity, the ability to bio-degradation and others [3–6]. however, cht and the part of its described derivatives are polymers with a high degree of crystallinity and the materials based on them are characterized by the brittleness and the absence of elasticity [7, 8]. this limits the use of the film materials based on the unmodified cht and its derivatives as the wound healing coatings. at the same time, it is known that the structure and, consequently, both physico-chemical and physico-mechanical properties (the plasticity being among them) of cht films are defined by the way of their forming and modification [8–10]. the most widespread way of obtaining cht and scht based films is the method of polymer solution irrigation on the solid base. that is why the most simple and the most accessible way of regulating plastic properties of the films is the introduction of a modifying additive into the forming solutions, which may behave as the polymers’ plasticizers. in the present work, polyhydric alcohols, such as glycerol, ethylene glycol and propylene glycol, were chosen as the plasticizing additives based on cht and scht. the http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2022.9.1.08 http://creativecommons.org/licenses/by/4.0/ https://orcid.org/0000-0003-3160-3958 https://orcid.org/0000-0003-4774-9994 https://orcid.org/0000-0002-2342-7213 https://orcid.org/0000-0002-6240-0718 https://crossmark.crossref.org/dialog/?doi=https://doi.org/10.15826/chimtech.2022.9.1.08&domain=pdf&date_stamp=2022-3-16 chimica techno acta 2022, vol. 9(1), no. 20229108 article 2 of 7 choice of polyhydric alcohols was due to the following reasons. on the one hand, they mix with water in any ratio and may be introduced into the system at the stage of polymer dissolution. on the other hand, glycerol, ethylene glycol and propylene glycol have a high boiling temperature and are not removed from the film being dried. in the creation of medical purpose materials it is necessary to take into account that the substances contacting with the organism may enter the blood, the lymph and the tissues in a diluted form. therefore, it is reasonable to study the blood indices’ changes under the impact of cht (scht) – polyhydric alcohol systems being studied, which may prove their hemocompatibility. thus, the present paper aims to study the polyhydric alcohols’ impact (glycerol, ethylene glycol and propylene glycol) on the deformation-strength characteristics and hemocompatibility of cht and scht-based film materials. 2. experimental 2.1. materials chitosan with molecular weight 113 kda (deacetylation degree 82%) and sodium salt of n-succinyl chitosan with molecular weight 207 kda (substitution degree of cht by amino groups 75%) [11] were obtained from “bioprogress” company (russia). propylene glycol, ethylene glycol and glycerol were used as film plasticizers and were supplied by sigma-aldrich (usa). glacial acetic acid and sodium chloride were supplied by sigma-aldrich (usa). 2.2. film preparation the cht and scht based films were prepared by conventional solution-casting technique. propylene glycol, ethylene glycol and glycerol at 0.03–0.3 mol/l were used as plasticizers to investigate the effect of each individual plasticizer on the developed films. as solvents in the preparation of the film forming solutions were used 1% acetic acid for cht and milli-q quality ultrapure water for scht. the film preparation procedures are described as follows. initially, 1 g/dl dispersions of chitosan and succinyl chitosan in appropriate solvents with different plasticizers were dissolved using a magnetic stirring plate at room temperature for 24 h. after dissolving, the film forming solutions were casted on a preliminary degreased surface of the glass petri dishes. after 144 h of drying, the films were peeled from the petri dish surfaces and stored in desiccators. in the preparation of cht solutions, a 1% aqueous solution of acetic acid was used as a solvent. therefore, chitosan in films is in the form of an acetate salt. 2.3. thickness thickness of the films was determined using a micrometer mk 0.25 to the nearest 0.1 mm. the selected values are the averages of at least ten random locations of the film sheets. the means were calculated and used in the determination of mechanical and physical properties. 2.4. dimensions of the aggregates the size of the aggregates was determined on a zeta sizer nano photon correlation dynamic light scattering spectrometer (malvern, uk). the light scattering angle is –1730°. the source of laser radiation is a he-ne gas laser. the wavelength is 633 nm. power – 10 mw. the analysis of the signals was carried out by a single-board multichannel correlator coupled with an ibm pc compatible computer. the pulse accumulation time is 5–7 min. the effective radius of the structures r was calculated by the stokes-einstein equation for spherical particles: 𝑟 = 𝑘𝑇 6𝜋𝜂𝐷⁄ (1) where k – the boltzmann constant, t – the temperature,  – the viscosity of the solvent. 2.5. morphology and topography the morphology and topography of the polymer films were studied using the agilent 5500 afm atomic force microscope (usa). the samples were scanned in air in semi-contact mode using silicon probes ppp-ncl (nanosensors) with a hardness of 34 nm and a resonant frequency of 172 khz. image processing and statistical processing of the results were carried out in the gwyddion program. to visualize the scanned objects the picoview 1.20 program was used. 2.6. temperatures of relaxation transitions the temperatures of relaxation transitions of polymer films based on cht and scht were determined by differential scanning calorimetry (dsc) on the dsc-1 device (netzsch) under the following conditions: temperature range 40–200 °c; dynamic mode – heating/cooling speed of 10°/min; medium – nitrogen. 2.7. elastic properties the elastic properties of the surface of the films were studied in the mode of force spectroscopy. to do this, when the probe was brought to the surface, the dependences of force on distance, the so-called "force curves", were recorded. the elastic properties (determination of the effective young's modulus) of the films were evaluated based on the analysis of the obtained dependence within the framework of the accepted hertz contact mechanics model by the expression for the dependence of the indentation depth (h) on the force (f): ℎ = ( 𝐹2 𝑅𝐸𝑒𝑓𝑓 2 ) 1/3, (2) where r – probe tip radius, eeff – effective young's module. 2.8. tensile properties the mechanical properties of the films were tested using a tensile testing machine autograph ags-10 kng equipped with the software “trapezium” (shimadzu, japan). the length of the sample base was 20 mm, the width was 20 chimica techno acta 2022, vol. 9(1), no. 20229108 article 3 of 7 mm and the thickness was 0.1 mm. the films were pulled using a crosshead speed of 2 mm/min. the tensile stress (σ) was determined considering the cross-sectional area of the analyzed sample and was expressed in mpa. the relative elongation at the rupture (ε) was calculated taking into account the initial film sample length taken for the testing and was expressed in percents. the values of the relative elongation at the rupture and the tensile stress were calculated as arithmetic averages of five parallel measurements. 2.9. hemocompatibility hemocompatibility of the cht (scht)-polyhydric alcohol systems was evaluated by determining the osmotic resistance of red blood cells by the degree of their hemolysis in hypotonic sodium chloride solutions. the expediency of using solutions for determining the osmotic resistance of erythrocytes is due to the fact that the components of film materials based on cht and scht, upon contact with body tissues, can enter the blood only in a dissolved form. blood was produced by decapitation of rats and collected in test tubes with an anticoagulant – heparin at a concentration of 150 u/ml of blood. the decapitation of animals was carried out in accordance with the "rules for the work using experimental animals", under chloral hydrate anesthesia intraperitoneally (2.5% solution, 1 ml per 100 g of animal body weight). after pouring 5 ml of the working solutions’ mixture of nacl with the concentration of 0.1 to 0.9% into several centrifugal tubes, 0.02 ml of the heparinized blood was added into the sodium chloride solutions. the samples were incubated for an hour at a room temperature and centrifuged at 1500 rpm for 10 min. the degree of erythrocytes’ lysis was evaluated photometrically for the absorbance of released hemoglobin at the wavelength of =530 nm against the distilled water with the layer thickness of 1 cm. in the experiments in vitro we added 0.2 ml of scht or cht solutions with a concentration of 1 mmol/l and their mixtures with polyhydric alcohols to the sodium chloride solutions. then 0.02 ml of the intact rats’ blood was added into the hypotonic solutions. with the values obtained, we plotted the lysis kinetics depending on the type of the system under study. the percentage of hemolysis was calculated using the following equation [12]: hemolysis (%) = 𝐷sample − 𝐷negative control 𝐷𝑚𝑎𝑥 − 𝐷negative control ∙ 100 (3) where dsample – the value of the optical density of the experimental sample; dmax – the value of optical density at complete (100%) hemolysis in a test tube with 0.1% sodium chloride solution; dnegative control – the value of the optical density of the control sample (a characteristic of spontaneous hemolysis of erythrocytes under experimental conditions). 3. results and discussion the process of obtaining materials from polymer solutions is carried out by processing semi-diluted solutions in which macromolecules aggregate with each other. thus, even in the solutions of cht and scht with a concentration of about 0.1 g/dl already contain aggregates of macromolecules [12, 13] as determined by the method of dynamic light scattering (table 1). naturally, the higher the concentration of the polymer in the solution, the larger the size of the aggregates formed. table 1 diameter (d, nm) of aggregates in solutions of cht and scht in the presence of glycerol polymer polymer concentration, g/dl glycerol concentration, mol/l d, nm cht 0.1 – 142±7 1.0 250±13 3.0 327±16 0.5 – 163±8 1.0 271±14 3.0 358±18 1.0 – 178±9 1.0 328±16 3.0 445±22 scht 0.1 – 164±8 1.0 197±10 3.0 266±13 0.5 – 194±10 1.0 250±13 3.0 342±17 1.0 – 221±11 1.0 387±19 528±26 the use of polyatomic alcohols, for example, glycerol, leads to changes in the size of aggregates: so, as can be seen from the data in table 1, in the presence of glycerol, the size of the resulting aggregates is significantly larger than in its absence. it can be assumed that the composition of polysaccharide aggregates when using polyatomic alcohols includes solvent molecules, i.e. the aggregates are intermolecular in nature due to the ability of polyatomic alcohols to "cross-link" macro chains. the features of the supramolecular state of polymers in the solution in the presence of polyatomic alcohols are preserved during the transition to films. for example, as can be seen from atomic force microscopy data (fig. 1), in film samples (as well as in solution) the size of supramolecular formations in the presence of polyatomic alcohols is larger than in their absence. at the same time, the addition of polyhydric alcohols to films based on cht and scht leads to a sharp drop in the elasticity modulus of the films (table 2), which may indicate their plasticizing effect. chimica techno acta 2022, vol. 9(1), no. 20229108 article 4 of 7 fig. 1 phase contrast afs images of the surface of cht films obtained from initial solutions in the absence of glycerol (a) and in the presence of glycerol with a concentration of 2 mol/l (b) table 2 the modulus of elasticity of films of scht films with a thickness of 0.1 mm with the addition of glycerol glycerol content in the initial solution, mol/l еeff, mpa 0 2300 0.03 1.51 0.05 0.57 the physico-mechanical properties of films in the presence of polyatomic alcohols undergo the most serious changes. the general character of the physico-mechanical behavior of the polymer body is determined by its phase state: amorphous and crystalline. cht and many of its derivatives are the typical polymers being in the crystalline state and undergoing brittle damage [14]. however, as it follows from fig. 2 data, scht in contrast with cht can reveal forced-elastic deformation. such changes of the properties may be connected with some change in the molecule package density of scht film stipulated by the presence of the comparatively voluminous salt groups in its structure; they also may cause a plasticizing effect as a result of intermolecular interaction weakening and the segmental macromolecules mobility increase. but, in spite of this, the level of the forced-elastic deformation in scht films is not enough for the use of unmodified films based on it as the wound healing coatings. for example, the value of the tensile stress of the human skin is in the range of 20–30 mpa and the value of the tensile elongation makes up 40–80% (depending on the age, sex and the section from which the skin for the study was taken). thus, the problem of obtaining elastic film materials based on cht and scht has not been solved, which limits its use in the medical practice. one of the ways of regulating the elastic properties of the films based on cht is the plasticizer use. it is well known that the polymer plasticizers are the substances able to shift the glass transition temperature to the area of lower temperatures [10]. the fact that polyatomic alcohols play the role of plasticizers is evidenced by the dsc data presented in fig. 3. it can be seen that the values of relaxation transition temperatures in films formed in the presence of polyatomic alcohols decrease. very often plasticizers are introduced not only for the purpose of glass transition temperature reduction, but also for the reduction of the elasticity module, the elasticity increase, namely, the material deformation at the mechanical force impact in all the three physical states. as the performed studies demonstrated, the introduction of polyhydric alcohols in the film forming process leads to a significant improvement of their physical and mechanical characteristics. fig. 2 stress-strain relationship for cht (1) and scht (2) films (a) (b) chimica techno acta 2022, vol. 9(1), no. 20229108 article 5 of 7 fig.3 dsc curves of cht films obtained from initial solutions in the presence of glycerol with a concentration of 0, 0.05 and 0.15 mol/l (from top to bottom) thus, it is clearly seen from fig. 4 that an increase in the content of glycerin and propylene glycol in the initial solutions during the production of films based on cht and scht to 0.05 mol/l is accompanied by a significant increase in discontinuous elongation. in this case, the values of the breaking voltage naturally decrease. but, since the values of the breaking stress in any case remain at the required level, the observed drop in strength indicators is not of a fundamental nature. similar results were obtained for films in the presence of ethylene glycol. an increase in the content of polyatomic alcohol in the initial solutions on the basis of which the films were obtained, more than 0.05 mol/l, is accompanied by a sharp loss of strength and it is not possible to remove deformation and strength indicators for them. the fact of the elasticity increase of the films based on cht and scht in the presence of polyhydric alcohols may have the following explanation. the films were prepared from solutions of polyelectrolytes–chitosan n-succinyl sodium salt (polyanion) and chitosan acetate (polycation). the dissolution of polyelectrolytes is accompanied by dissociation. thus, the charged macromolecules become solvated molecules of the solvent that leads to the decrease of the interactions among the macromolecules. but in the film formation, the solvent evaporates and the intermolecular interaction among the chains increases. if in the process of dissolution polyhydric alcohols are added to scht (cht)-water system, the situation changes. taking into account a high boiling temperature of the alcohol, it remains in the film even after removing the solvent. as a result, it is the decrease of polymer-polymer intermolecular interaction in comparison with the initial unmodified film that leads to the increase of the molecular mobility of the whole system. this causes the change of the whole complex of physical, chemical and physico-mechanical properties of cht and scht-based films. the construction of generalizing dependencies (fig. 5) of the values of breaking stress and breaking elongation on the content of the modifying additive in the initial solution showed that for both studied polymers their introduction into the molding solution leads to a natural decrease in the values of breaking stress and an increase in the values of breaking elongation. in fact, it is not possible to obtain a film with satisfactory strength from a solution containing polyatomic alcohol at a concentration above 0.05 mol/l. undoubtedly, the materials recommended for the medical purpose must undergo a complex study of the living organism's response to their use. since the components of film materials based on cht and scht in contact with body tissues can enter into the bloodstream in dissolved form, it is advisable to study changes in blood parameters under their action. the functional state of the erythrocytes’ membranes is the most successful model for the analysis of the dynamics of many destructive changes taking place in the organism at the impact of exogenous and endogenous factors. (a) (b) (c) fig. 4 tensile stress-strain curves for films obtained from initial solutions in the presence of polyhydric alcohols. the films based on scht (1) and scht in the presence of glycerol with a concentration of 0.03 (2), 0.04 (3), 0.05 (4) mol/l (а). the films based on cht (1) and cht in the presence of glycerol with a concentration of 0.03 (2), 0.04 (3), 0.05 (4), 0.075 (5) и 0.1 mol/l (6) (b). the films based on cht (1) and cht in the presence of propylene glycol with a concentration of 0.03 (2), 0.04 (3), 0.05 (4) mol/l (с). chimica techno acta 2022, vol. 9(1), no. 20229108 article 6 of 7 fig. 5 dependence of the breaking stress and breaking elongation of films based on the chtglycerol (1) and cht-propylene glycol (2) systems on the concentration of the modifying additive in the initial solution physiological properties, such as deformity, osmotic resistance and the ability to aggregate, providing the movement of erythrocytes through the bloodstream and, as a consequence, the oxygen transport to organs and tissues, are determined by the lability of the erythrocyte membrane. besides, metabolic processes, taking place in erythrocytes at the stress in the clinical pathology, are an integral reflection of the cells’ reaction to the level of the whole organism. in the clinical practice, the most frequently used test for the qualitative characteristics of erythrocytes is the determination of the osmotic resistance of erythrocytes by the osmotic lysis model. the osmotic resistance of erythrocytes is an important integral physiological cell function, the changes of which are widely used as a marker reflecting the cell membrane state. thus, the influence of the systems cht and scht with polyhydric alcohols on the resistance of erythrocyte membranes to osmotic lysis was studied in vitro. our study showed that in the control series of sodium chloride solutions, lysis of erythrocytes occurred in the range of 0.4–0.5% nacl, which corresponds to the literature data. a comparison of the studied samples based on scht showed that, in combination with ethylene glycol and propylene glycol, scht does not affect the stability of the erythrocyte membrane (it does not change the degree of hemolysis) over the entire range of nacl concentrations. the minimum limit of osmotic resistance of erythrocytes, as in the control sample, is observed in physiological saline with a concentration of 0.45–0.50% (table 3). in the range of low and high nacl concentrations, the intensity of hemoglobin release from erythrocytes does not statistically significantly differ from the control values. scht in combination with glycerol has a pronounced membrane-stabilizing effect both in the zone of hypotonic and physiological concentrations of nacl solutions. moreover, the initial signs of hemolysis appear at higher concentrations of nacl (about 0.5–0.6%) than in the control. at the same time, there is a two-fold decrease in the intensity of hemolysis relative to the control values at physiological nacl concentrations of 0.7–0.8%. of particular note is the fact that unmodified scht causes a slight destabilizing of erythrocyte membranes. when studying the effect of cht (table 3), it was shown that both cht itself and all cht solutions in the presence of modifiers have a pronounced positive effect (especially when glycerol is used as a modifier). a decrease in the degree of erythrocyte hemolysis was observed both in hypotonic nacl solutions and at physiological nacl concentrations. table 3 the values of the hemolysis degree (x) under the action of a 1% polymer solution containing polyhydric alcohols with a concentration of 3 mol/l polymer nacl, % х (%) negative control – ethylene glycol propylene glycol glycerol scht 0.1 99 98 98 98 97 0.2 97 98 97 98 95 0.3 96 98 96 97 90 0.4 65 78 67 70 78 0.5 21 31 25 28 75 0.6 10 12 8 10 34 0.7 7 8 6 7 3 0.8 5 7 5 6 2 cht 0.1 99 98 98 98 96 0.2 97 96 96 96 95 0.3 96 94 94 94 93 0.4 65 64 65 65 58 0.5 21 19 20 20 18 0.6 10 9 10 10 8 0.7 7 6 7 5 3 0.8 5 5 5 3 2 chimica techno acta 2022, vol. 9(1), no. 20229108 article 7 of 7 according to the present opinion, the erythrocytes’ stability to the osmotic lysis is determined to a high extent by the permeability of the membrane for water being regulated by the presence of aquaporins, the specific integral albumen of erythrocyte membranes. we may assume that polyhydric alcohols in combination with cht and scht block the action of aquaporins, reducing the water inlet into the cell and, at the same time, increasing the cell membrane resistance. thus, the stabilizing impact of scht (cht) – polyhydric alcohol systems upon the cell membranes in the physiological conditions allows inferring their high hemocompatibility. 4. conclusions it was stated that succinyl chitosan, in contrast with chitosan, can reveal a slight forced – elastic deformation, but this is not enough for the use of unmodified film based on it as the wound healing coatings. the presence of polyhydric alcohols (glycerol, ethylene glycol and propylene glycol) in molding solutions of n-succinyl chitosan and chitosan leads to an increase in the size of aggregates of macromolecules both in solution and in films based on them, as well as to a decrease in the overall surface roughness and to a sharp drop in the elastic modulus of films. the use of polyhydric alcohols for molding solutions in the production of films based on chitosan and chitosan n-succinyl in an amount of up to 0.05 mol/l is accompanied by an increase in the value of tensile elongation by almost 2–2.5 times. the value of the breaking voltage is reduced by 3–4 times. the optimal content of polyatomic alcohols as plasticizers is 0.03–0.04 mol/l. the stabilizing effect of systems based on chitosan and succinyl chitosan in the presence of polyhydric alcohols on the cell membranes in the physiological conditions indicates their high hemocompatibility. conflict of interest the authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. references 1. vinnik yus, markelova nm, solov'yeva ns, shishatskaya yei, kuznetsov mn, zuyev ap. sovremennyye ranevyye pokrytiya v lechenii gnoynykh ran [modern wound coatings in the treatment of purulent wans]. novosti khirurgii. 2015;23(5):552–558. doi:10.18484/2305-0047.2015.5.552 2. slivkin ai, lapenko vl, arzamastsev ap, bolgov aa. aminoglyukany v kachestve biologicheski aktivnykh komponentov lekarstvennykh sredstv (obzor za period 2000–2004). vestnik voronezhskogo gosudarstvennogo universiteta. seriya: khimiya. biologiya. farmatsiya. 2005;(2):73–87. 3. alekseeva tp, bogoslovskaya oa, olkhovskaya ip, glushchenko nn, rakhmetova aa, ilina av, varlamov vp, baitukalov ta, levov an. wound healing potential of chitosan and nsulfosuccinoyl chitosan derivatives. biol bul. 2010;37(4):339–345. doi:10.1134/s1062359010040023 4. buzinova da, abramov ayu, shipovskaya ab. svoystva 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produced from aqueous solutions. polym sci ser a. 2020;62(4):422– 429. doi:10.1134/s0965545x20040100 9. rogovina sz, akopova ta, zelenetskii an, vikhoreva ga, gorbacheva in, zharov aa. а study of cellulose-chitosan blends obtained under shear strain. polym sci ser a. 2000;42(1):5–9. 10. komarov ba, albulov ai, belov myu, samuylenko aya, fomenko as, shinkarev sm, trunov am. method for producing sodium salt of chitosan succinate. russian federation patent ru 2144040. 1998 apr 07. russian. 11. zhou y, li j, lu f, deng j, zhang j, fang p, et. al. a study on the hemocompatibility of dendronized chitosan derivatives in red blood cells. drug design develop therapy. 2015;9:2635– 2645. doi:10.2147/dddt. s77105 12. lazdin ry, chernova vv, bazunova mv, zakharov vp. rheological properties of chitosan succinimide in water-glycerol mixed solvent. russ j appl chem. 2019;92(1):50–56. doi:10.1134/s1070427219010075 13. bazunova mv, chernova vv, lazdin ry, zakharov vp, kulish ei. a study of the viscosity characteristics of chitosan solutions in the presence of organic cosolvents. russ j phys chem b. 2018;12(6):1039–1044. doi:10.1134/s1990793118060143 14. tager aa. fiziko-khimiya polimerov [physicochemistry of polymers]. moscow: nauchnyy mir; 2007. 574 p. russian. https://doi.org/10.18484/2305-0047.2015.5.552 https://doi.org/10.1134/s1062359010040023 https://doi.org/10.1134/s0003683818050058 https://doi.org/10.1134/s0965545x20040100 https://doi.org/10.2147/dddt.%20s77105 https://doi.org/10.1134/s1070427219010075 https://doi.org/10.1134/s1990793118060143 effect of cooling rate on the structure and electrochemical properties of mn-based fluoride oxides with cation-disordered rock-salt structure published by ural federal university eissn 2411-1414; chimicatechnoacta.ru article 2022, vol. 9(3), no. 20229310 doi: 10.15826/chimtech.2022.9.3.10 1 of 9 effect of cooling rate on the structure and electrochemical properties of mn-based oxyfluorides with cation-disordered rock-salt structure kseniya v. mishchenko a , maria a. kirsanova b , arseny b. slobodyuk ac , anna a. krinitsyna a, nina v. kosova a* a: institute of solid state chemistry and mechanochemistry sb ras, novosibirsk 630128, russia b: skolkovo institute of science and technology, moscow 121205, russia c: institute of chemistry feb ras, vladivostok 690022, russia * corresponding author: kosova@solid.nsc.ru this paper belongs to the ctfm'22 special issue: https://www.kaznu.kz/en/25415/page. guest editors: prof. n. uvarov and prof. e. aubakirov. © 2022, the authors. this article is published in open access under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). abstract according to the extensive studies in the field of high-energy cathode materials for lithium-ion batteries (libs), mn-based oxyfluorides li1.2mn0.6+0.5ynb0.2–0.5yo2–yfy with li-excess and cation-disordered rock-salt structure capable of reversible cationic and anionic redox reactions are among the most promising candidates. in this work, a series of mn-based oxyfluorides with y = 0.05, 0.10, 0.15 were obtained using mechanochemically assisted solid-state synthesis with different cooling rates. transmission electron microscopy, electron paramagnetic spectroscopy (epr) and nuclear magnetic resonance spectroscopy (nmr) show that increasing the amount of fluorine promotes local ordering in crystals with the formation of isolated clusters of mn3+–o2––mn4+ that interrupt lithium diffusion. the occurrence of local ordering depends on the conditions of synthesis and affects electrochemistry. it was found that more clusters are formed in slowly cooled samples than in quenched ones. the best electrochemical characteristics with reversible capacity of 150 mah·g–1 at room temperature were demonstrated by the li1.2mn0.65nb0.15o0.90f0.10 sample obtained by quenching. keywords lithium-ion batteries oxyfluorides disordered rock-salt structure local ordering oxygen redox mn3+/mn4+ redox cyclability received: 24.06.22 revised: 21.07.22 accepted: 22.07.22 available online: 04.08.22 1. introduction over the past two decades, electrochemical energy storage systems have been actively introduced in a variety of fields, from portable equipment to electric vehicles and energy storage devices. with the development of new technologies, the requirements for lithium-ion batteries (lib) are increasing, which primarily concerns specific energy. the efforts of researchers are focused on optimizing the properties of cathode materials. in the last few years, a new class of cathode materials for libs has been proposed based on oxides with the disordered rock-salt structure (drx), in which li and transition metal (tm) ions randomly occupy octahedral sites. until recently, these structures were excluded as possible cathode materials, since it was believed that they have a small electrochemical activity due to limited diffusion of li+. in disordered rock-salt structures, li diffusion proceeds by hopping from one octahedral site to another octahedral site via an intermediate tetrahedral void (o-t-o diffusion), where o is an octahedron and t is a tetrahedron. a tetrahedral void shares faces with octahedra: one, in which there is no transition metal (0tm), another has one transition metal (1tm), or two transition metals (2tm). further studies have shown that the excess of li forms a percolation network consisting of 0tm tetrahedral voids, which are surrounded only by li+ ions and provide sufficient li+ mobility [1]. highly valent transition metal ions, such as 3d ti4+, 4d nb5+ or 4d mo6+, are used to increase the li+ content in the structure and, as a result, specific capacity [2–4]. on the other hand, the authors [5] showed that highly valent tm are more prone to repel each other and intimately mix with li+ to maintain local electrоneutrality; thus, significant li segregation can be suppressed, which may hinder the macrodiffusion of lithium. however, it has been shown that short-range ordering (sro) of metal ions occurs to some extent in almost all http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2022.9.3.10 mailto:xx@yy.zz http://creativecommons.org/licenses/by/4.0/ http://orcid.org/0000-0002-4774-2189 http://orcid.org/0000-0001-7476-6293 http://orcid.org/0000-0002-1363-493x http://orcid.org/0000-0003-3909-7068 https://crossmark.crossref.org/dialog/?doi=https://doi.org/10.15826/chimtech.2022.9.3.10&domain=pdf&date_stamp=2022-8-4 chimica techno acta 2022, vol. 9(3), no. 20229310 article 2 of 9 such materials. the presence of a small number of different types of tm cations in the structure leads to the formation of sro and, as a consequence, to a decrease in li percolation compared to the random arrangement of metal ions [5–7]. previously, the formation of onb6 and omn1nb5 octahedra, more stable than mn-rich ones, was confirmed in drx oxide li1.3nb0.3mn0.4o2 by computational methods [8]. on the other hand, using geometricaltopological method (bond-valence site energy modeling, bvse), and density functional theory (dft) calculations, we demonstrated that mn ions form mno6 clusters, which are preferably linked in dense layers in li1.3nb0.3mn0.4o2, and negatively affects lithium diffusion [9]. the formation of mn clusters was also confirmed by epr and nmr spectroscopy [9–11]. the extra capacity of these li-excess materials, which cannot be provided only by the redox activity of tm, is explained by the oxidation of o2– at high voltage [12, 13]. as a disadvantage, we can note the release of oxygen from the lattice, which is typical almost for all drx oxides. in general, the structure of drx oxides is stable to modifications in both the cationic and anionic sublattices. partial substitution of oxygen with fluorine reduces irreversible o losses and improves the cyclability [2]. however, fluorine ions are more easily introduced into the anionic sublattice due to the local chemical heterogeneity caused by the presence of li excess in the drx structure. in this case, the degree of f doping significantly exceeds the level of surface doping, achieved in ordered layered cathode materials [13]. fluorination of the anionic sublattice using lif as a precursor of f– can reach ~10 at.% (li1.2mn0.625nb0.175o1.95f0.05, li1.2mn0.65nb0.15o1.9f0.1, li1.2mn0.7nb0.1o1.8f0.2) [12] when using the equilibrium solid-state method, and ~33 at.% (li2mn2/3nb1/3o2f) when using non-equilibrium mechanochemical synthesis [4, 14, 15]. when using a fluoropolymer precursor – poly(tetrafluoroethylene), up to 12.5 at.% of fluorine can be introduced into the structure of li–nb–mn–o using conventional solid-state synthesis [16]. fluorine doping reduces the valence of the cation, which leads to an increase in the redox reservoir due to the redox processes of transition metals [4, 12]. an increase in the f content improves connectivity between li-rich tetrahedral voids, which leads to an increase in the li percolation. so, an important step towards sustainable cycling is to use the strategy of replacing o2– with f–. in this case, it is possible to increase electrochemical capacity, improve the stability of cathode materials, and avoid irreversible anionic oxidation. in addition, the release of oxygen from the lattice of oxyfluorides, observed in the differential electrochemical mass spectra, is insignificant [12, 17]. at high voltage, the release of co2 was also observed, which is assigned to interaction of carbonate solvent with highly reactive oxygen species [19]. these parasitic reactions lead to irreversible degradation of cathode material and rapid capacity loss. in this manuscript, we study in detail the relationship between the synthesis conditions (using various cooling rates), the local structure and the electrochemical performance of the li-rich mn-based oxyfluoride cathode materials with the general formula li1.2mn0.6+0.5ynb0.2–0.5yo2–yfy (y = 0.05, 0.10, 0.15) and cation-disordered rock-salt structure. 2. experimental 2.1. material synthesis cathode materials with the general formula li1.2mn0.6+0.5ynb0.2–0.5yo2–yfy (y = 0.05, 0.10, and 0.15) were prepared by the mechanochemically assisted solidstate synthesis from stoichiometric reagent mixtures of lif, nb2o5, mn2o3, and li2co3. mechanical activation (ma) of the reagent mixtures was performed using a highenergy ago-2 planetary mill at 600 rpm for 10 min using stainless steel jars and balls in an ar atmosphere. the diameter of the balls was 5 mm, the volume of the jars was 125 ml, the mass ratio of the sample to the balls was 1:40. the activated mixtures were then pressed into pellets at 50 bar and annealed at 950 °c in an ar atmosphere for 4 h, followed by natural cooling in a furnace (hereafter, f0.05, f0.10, f0.15) or quenching (hereafter, f0.05q, f0.10q, f0.15q). 2.2. characterization detailed information about the crystal and local structure, particle size and morphology were obtained using a complex of physicochemical methods. phase composition and lattice parameters of the samples were characterized by x-ray powder diffraction (xrd) using a bruker d8 advance diffractometer, cu kα irradiation (λ = 1.54181 å). the xrd patterns were collected over the range of 20–80° with a step of 0.02°·s−1 and uptake time of 0.3–0.5 s. structural refinement of the xrd data was carried out by the rietveld method using the gsas software package. particle size and morphology were investigated by transmission electron microscopy (tem). the samples were prepared in air by grinding the powders in an agate mortar in acetone and depositing drops of suspension onto holey tem grids with lacey/carbon support layers. bright-field tem (bf-tem) images, selected area electron diffraction patterns (saed), high angle annular dark field scanning transmission electron microscopy (haadf-stem) images and energy dispersive x-ray (edx) spectra and maps were registered on an aberration-corrected titan themis z transmission electron microscope equipped with a super-x detection system and operated at 200 kv. electron energy loss spectra (eels) were recorded in a stem mode with energy dispersion of 0.05 ev per channel and energy resolution of zero-loss peak of 0.85 ev using a gatan quantum ers/966 p spectrometer. oxidation state of mn chimica techno acta 2022, vol. 9(3), no. 20229310 article 3 of 9 was calculated from liii/lii line ratio according to the algorithm described by tan et al. [20]. electron paramagnetic resonance (epr) spectroscopy (adani spinscan x, belarus) was used to determine the presence of possible paramagnetic interactions in the samples. the epr spectra were registered as the first derivative of the absorption signal within the center field of 336 mt, microwave frequency of 9415 mhz, power of 0.240 mw, and modulation frequency of 100 khz at room temperature (25 °c) and in liquid nitrogen (–196 °c). the g-factor was established with respect to the cucl2·2h2o standard. signal intensities were normalized based on the mass of the sample. 7li mas nmr spectra were obtained by means of an avance av-300 solid state bruker spectrometer (b0 = 7.05t) with a rotor synchronized hahn echo pulse sequence using a 4 mm mas probe at 300 k. a sample rotation frequency of 14 khz was used for the final spectra; the separation of the sidebands from the main signal was performed using a 12 khz frequency. the li chemical shifts were referenced to 1 m licl water solution (0 ppm). 19f nmr spectra were recorded using a direct 90° pulse method of registration. the chemical shifts of 19f were referenced to cfcl3 (0 ppm). 2.3. electrochemical measurements for the electrochemical testing, the as-prepared samples were mixed with 5 wt.% carbon black “p 277” from the center of new chemical technologies of the institute of catalysis sb ras, omsk branch by ball milling at 400 rpm for 2.5 minutes. to obtain working electrodes, the slurry consisting of 75 wt.% active material, 20 wt.% carbon black (in total), and 5 wt.% polyvinylidene fluoride dissolved in n-methyl-2-pyrrolidone was spread on an al foil using a doctor blade technique and dried at 90 °c for 2 h in vacuum and then laminated. then, discs with a diameter of 11 mm were cut out with a loading density of the active material of 2–3 mg cm−2. the swagelok-type cells were assembled in an argon-filled glove box (vboxss 950, vilitek, russia) with li metal foil as an anode. 1 m lipf6 (sigma aldrich, 98%) solution mixed with ethylene carbonate and dimethyl carbonate (alfa aesar, 99%) 1:1 by weight was used as an electrolyte, and a glass fiber filter (whatman, grade gf/c) was used as a separator. cycling was performed in a galvanostatic mode at a c/40 charge/discharge rate within the voltage range of 1.5–4.8 v vs li/li+ at room temperature using a biologic bcs 805 battery testing system. 3. results and discussion 3.1. phase composition, morphology and homogeneity as it was previously shown [14], anionic substitution in drx without the formation of a secondary lif phase is possible only with a fluorine content of less than 7.5 at.%. the xrd patterns of the f0.05, f0.05q, f0.10q samples obtained at different cooling rates with different amounts of f– do not contain any impurity phases (figure 1a), while the samples with a high fluorine content (y= 0.15) have a very broad reflections at 23.9 (2θ), which were earlier interpreted as (101) planes of a body centered tetragonal supercell with the space group (s.g.) i41/amd [7]. the xrd patterns of the phase pure materials were refined by the rietveld method in the cubic s.g. fm−3m (figure 1b) with unit cell parameters given in table 1. as can be seen, with an increase in the f content, the lattice parameters have a tendency to decrease due to the differences in ionic radii of oxygen and fluorine (ro2– = 1.4 å, rf– = 1.33 å). the average crystallite sizes (cs), determined by the xrd analysis using the scherrer equation with the lorentzian component of the reflection broadening (table 1) are close to each other and are larger for the naturally cooled samples, which indicates a higher degree of crystallinity of these samples. since all samples were synthesized at the same temperature, we do not expect any noticeable difference in the particle sizes, which is clearly confirmed by the haadfstem images (figures 2 and s1). the particles of f0.05, f0.05q, f0.10q, and f0.15q have an irregular form and an average size from 0.5 to 3–5 μm (figure s1). individual and mixed elemental stem-edx maps in figure 2 illustrate the homogeneous distribution of tm cations, which lies on the same level for all samples (figure s2). figure 1 powder xrd patterns of the f0.05, f0.10, f0.15 samples obtained by natural cooling and quenching (a). rietveld refined xrd pattern of the f0.10q sample based on the cubic structure with fm–3m space group (b). chimica techno acta 2022, vol. 9(3), no. 20229310 article 4 of 9 table 1 rietveld refined lattice parameters and the average crystallite size (cs) of the samples obtained with natural cooling and quenching in ar. sample f0.05 f0.10 f0.15 f0.05q f0.10q f0.15q a, å 4.1907(5) 4.1870(5) 4.1829(6) 4.1843(7) 4.1883(6) 4.1778(8) v, å3 73.60 73.40 73.19 73.26 73.47 72.92 rwp, % 4.28 4.83 4.59 5.37 4.73 5.21 gof 1.33 2.05 1.71 2.17 1.10 1.25 cs, nm 34 28 25 26 24 29 as can be seen from the edx spectra in figure s3, the mn:nb atomic ratio increases from f0.05 to f0.15q as expected from the nominal composition. 3.2. local ordering the [001] and [011] saed patterns of f0.05 (figure 3a, b) demonstrate diffuse scattering patterns typical of the f-centered cubic structure with sro, and are very similar to those of li–nb–mn–o materials [5–7]. high-resolution haadf-stem images show the variable intensity of atomic columns, which means that brighter columns are enriched with heavier nb, while less intense columns contain more mn (figures 3c, d). the saed patterns and haadf-stem images of f0.05q and f0.10q look similar to those of f0.05 (figure s4) and correspond to the disordered rock-salt structure with the sro of tm cations. in the f0.15q sample, a higher degree of local ordering was found for all the crystals studied. the [001] and [011] saed patterns of f0.15q in figures 4a, b show a dashed scattering pattern instead of a circular one, while the [001] and [011] saed patterns registered from another f0.15q crystal (figures 4c, d) have point reflections corresponding to superstructure cubic lattices with asuper = 2abasic or asuper = 4abasic or their superposition. at the same time, the haadf-stem image taken from more ordered f0.15q crystals (figure s4) is not distinguishable from haadf-stem images of other samples. thus, we suppose that partially ordered and fully ordered domains can coexist in one crystal . such a change in the ordering of tm in f0.15q in comparison with the other samples correlates with the mn:nb atomic ratio (table 2) and the absolute amount of mn in the crystal structure. as described in ref. [7], slow cooling during the synthesis of the li1.25nb0.25mn0.5o2 oxide leads to the formation of a thermodynamically stable phase, but the short correlation length of ordering is realized in the quenched drx oxide. with an increase in the f at.%, the mn content also increases for charge compensation, which, in turn, can lead to the formation of mn-enriched arrangement similar to that described in ref. [7]. in a “high entropy” concept, the term –t∆smix in equation 1 is insufficient to overcome ∆hmix, and the structures with more favorable enthalpies are formed [21]: ∆gmix = ∆hmix – t∆smix. (1) figure 2 haadf-stem image, individual edx maps of o, f, mn, nb and mixed mn/nb compositional edx map of the f0.05 sample. figure 3 [001] and [011] saed patterns of f0.05 (a, b) indexed in the f-centered cubic cell and fourier-filtered high-resolution [001] and [011] haadf-stem images (c, d). chimica techno acta 2022, vol. 9(3), no. 20229310 article 5 of 9 figure 4 [001] and [011] saed patterns taken from two different crystals of f0.15q (a, b and c, d). if we assume that the contribution of anionic sites has a negligible effect on the configuration entropy sconf, then sconf as a function of a molar fraction in equation 2 decreases and is equal to 0.88r (r is the ideal gas constant), 0.86r, and 0.85r for f0.05, f0.10, and f0.15, respectively: sconf = – r/2[(∑xilnxi )cation + (∑xilnxi )anion]. (2) thus, we should expect a more uniform distribution of cations for the f0.05 composition. the average oxidation state of mn in the crystals synthesized by quenching, measured by the eels method, is close to +3 and is slightly below +3 for the f0.05 sample (table 2). the decrease in the state of charge can be explained by a partial reduction of mn ions during synthesis. no noticeable disproportion between reduced and oxidized mn states was found for these four samples. thus, the average oxidation state of mn is +2.90(3), +3.06(4), +2.95(6), and +3.05(3) for the f0.05, f0.05q, f0.10q, f0.15q samples, respectively. earlier, it was found that the li1.3nb0.3mn0.4o2 oxide has a tendency to form the mn3+–o–mn4+ clusters [9]. on the other hand, the authors [10] revealed ferromagnetic interactions in li1.2ti0.4mn0.4o2 oxide during cycling. to determine whether the ferromagnetic interactions occur in our samples or not, epr spectra were taken both at room temperature (25 °c) and in liquid nitrogen (–196 °c). it is known that mn3+ in a high spin state (electronic configuration 3d4, s = 2) has a silent epr spectrum [10]. for all samples, the epr signal exhibits the lorentzian line shape with a significant broadening (figure 5a). the line width from peak to peak is 360, 280, 269 mt for the f0.05, f0.10, f0.15 samples and 299, 293, 246 mt for the f0.05q, f0.10q, f0.15q samples, respectively (figure s5). the reason for the broadening may be related to the presence of local paramagnetic clusters that are magnetically isolated from the rest of the framework by diamagnetic surroundings of li+ and nb5+ [11,22]. with an increase in the f– content, the estimated number of paramagnetic centers (p.c.) decreases and corresponds to 0.26, 0.14, 0.08 at.% of the initial mn content for the f0.05, f0.10, f0.15 samples, respectively. obviously, the decrease in signal intensity is associated with an increase in f–mn– f bonds (more ionic), where mn ions are more difficult to oxidize, in contrast to mn ions with oxygen coordination [4]. the wide paramagnetic signal for f0.10, taken a t –196 °c, disappears, indicating that the super-exchange interaction is not ferromagnetic (figure 5a) [10, 23]. table 2 average oxidation state of mn calculated from eels data and mn:nb atomic for the li1.2mn0.6+0.5ynb0.2–0.5yo2–yfy samples. sample f0.05 f0.05q f0.10q f0.15q average oxidation state of mn +2.90(3) +3.06(4) +2.95(6) +3.05(3) edx mn:nb atomic ratio 0.79:0.21(1) 0.81:0.19(1) 0.83:0.17(1) 0.86:0.14(1) theoretical mn:nb atomic ratio 0.78:0.22 0.78:0.22 0.81:0.19 0.84:0.16 figure 5 epr spectra of the f0.10 sample, recorded at 25 °c and –196 °c (a). dotted line corresponds to the simulated spectrum. 19f nmr spectra of the f0.05, f0.10, f0.10q, f0.15, and f0.15q samples recorded using direct 90° pulse registration method (b). chimica techno acta 2022, vol. 9(3), no. 20229310 article 6 of 9 the number of p.c. in quenched samples increases with increasing mn content. there is a superposition of two mn states (a narrow shoulder in a wide signal) with a g-factor close to 2 (figure s5). the amount of mn4+ in a diamagnetic environment (li+ or nb5+), calculated from the integral intensity, is less than the amount of mn4+ in clusters and correlates as 0.001:0.02; 0.002:0.02; 0.006:0.06 at.% for the f0.05q, f0.10q, f0.15q samples, respectively. summarizing, we can say that the amount of p.c. and mn3+ ions in clusters is significantly less in quenched samples due to the possible formation of oxygen vacancies [24]. with an increase in the mn or f content, the formation of more mn3+–o–mn4+ clusters and mn4+ ions in a diamagnetic environment is observed, which indicates that the more li+ accumulates around f– with formation of sublattice populated with li-rich medium, which also corresponds to the xrd data for the f0.10q and f0.15q samples (figure 1). to get more information about the local lithium environment, mas nmr studies were conducted. 7li mas nmr spectra of the f0.05, f0.10, f0.15, f0.10q, f0.15q samples in figure s6 consist of a wide asymmetric background (p1) and an asymmetric narrow line due to magic angle spinning along with its spinning sidebands, which can be deconvoluted into the peaks p2 and p3 (table 3). lithium, being in a paramagnetic mn3+ environment, experiences a strong dipole-dipole interaction, which leads to the appearance of a number of signals shifted to a weaker and stronger magnetic field. this also leads to a broadening of the nmr signal [10]. as can be seen from table 3, the position of the wide component (δ1) and its intensity are associated with the mn content. with an increase in the mn content, the average shift of δ1 and the gravity center position m1 are directed toward a weak magnetic field. these averaged shifts lie far beyond the range of lithium chemical shift for diamagnetic compounds and are the result of contact fermi interaction with mn3+ centers. it can be noted, that the differences in m1 between the samples prepared with and without quenching are quite small. the large value of m1 observed for the f0.15q sample may be due to increased 90° li–o– mn interaction [25]. taking into account the view of the saed patterns for various crystals (figure 4), the lowfield shift can be related to the mn clusterization taking place for the quenched f0.15q sample. on the enlarged fragment of the mas component (figure s6), it is possible to notice the asymmetry of the signal, which can be explained by the interaction of the quadrupolar 7li nuclei with the electric field gradient. the small quadrupolar moment of the nucleus and the cubic symmetry of the structure lead us to the conclusion that the mas peaks should be divided into two overlapping lines. the lines narrowed with mas correspond to lithium sites adjacent only to the diamagnetic (nb5+) nearest neighbors. the positions and intensities of the components, which for the mas lines include the intensities of 12 corresponding spinning sidebands, are shown in table 3. there is some variation in the positions of the mas components that could be related to the volumetric susceptibility of the samples. 19f nmr data confirm the presence of the interaction between oxides and lif (figure 5b). all studied samples have similar spectra with the shape and shift of the dominant signal differing from those of lif. the halfwidth of the spectra for the studied samples is ~20 khz, and the shift is about –180 ppm, while for lif, these values are 64 khz and –204 ppm, respectively. the spectra of the studied materials also contain a wide low-intensity signal of about –1040 ppm. in the case of fluorine coordinated by mn3+ ion, a strong dipole-dipole interaction of order of megahertz exists between unpaired electrons of the mn3+ ion and 19f nucleus. therefore, only fluorine in a diamagnetic environment is expected to give rise to an nmr signal. the shift of –180 ppm falls within a diamagnetic chemical shift range and may correspond to bridged axial fluorine in coordination of nb [26]. the non-bridged equatorial fluorine resonating in the positive region of chemical shifts is not visible in the spectra. the shape and the halfwidth of the spectra are determined by the interaction with lithium ions, while the main contribution of lif is due to dipole-dipole interactions between fluorine nuclei. the signal at –1040 ppm probably comes from the similar environment, where the next nearest neighbor of fluorine is the mn3+ ion and the unpaired electron density is transferred to the 2s orbitals of fluorine, which leads to a contact shift. 3.3. electrochemistry the electrochemical properties of the samples were studied by galvanostatic cycling (figures 6a and s7). theoretical capacities based on the li content are 353, 356, and 359 mah·g–1 for f0.05, f0.10, and f0.15, respectively, of which 184, 193, and 202 mah·g–1 comes from the mn3+/mn4+ redox couple. the value of the experimental specific capacity for the first charge for all samples exceeds the capacity calculated for the mn3+/mn4+ redox couple, which indicates the participation of the o2– /o– couple in the cycling process. for all samples, an irreversible drop of the specific capacity is observed during the first cycle. table 3 7li nmr peak shifts and intensities. sample δ1 a, ppm i1 a, % δ2, ppm i2, % δ3, ppm i3, % err., % m1 b f0.05 245 94 9 2 –2 3 3.0 241 f0.10 268 96 9 1 –1 3 3.3 266 f0.10q 263 96 8 1 –1 3 2.8 239 f0.15 308 95 6 1 –2 3 3.1 294 f0.15q 321 96 8 1 –2 3 2.7 309 a δn, in: position and integrated intensity of the component pn. b m1: center of gravity of the spectrum. chimica techno acta 2022, vol. 9(3), no. 20229310 article 7 of 9 the difference in charge and discharge capacity values is usually associated with the formation of a cathodeelectrolyte interface (cei) on the surface of electrode along with li+ deintercalation. the differential curves dq/dv of the first charge show three oxidation peaks at 3.6, 4.4, and 4.6 v, which are related to the oxidation reaction of mn3+ and o2– ions (figures 6b and s7). the third oxidation peak on the differential curves is observed at ~4.8 v (figures 6b and s7), which is similar to that observed in li–nb(ti)–mn–o(f) systems [27, 28]. this may be a result of parasitic side reactions of highly reactive oxidized oxygen species with the electrolyte or irreversible release of o2 gas from the lattice at high voltage [12, 16, 18]. on the other hand, as mentioned in ref. [28], the presence of highly valent transition metal ions (such as mn4+) has a catalytic effect on the position of the peak of side reactions during the first charge. among all prepared oxyfluorides, the most intense oxidation peak is observed for the f0.05 sample, where the number of p.c. (mn4+) is maximal. comparing the electrochemical behavior of all the samples, the highest contribution of the o2–/o– redox couple in specific capacity on the second cycle is observed for the f0.10 and f0.10q (figures 6 and s7). this can be explained by the optimal content of f, which stabilizes the o2–/o– redox reaction [3, 12, 16]. moreover, the figure 6 charge-discharge curves of the f0.10 and f0.10q samples, cycled at the c/40 charge/discharge rate within the voltage range of 1.5–4.8 v at rt (a) and corresponding dq/dv curves (b). quenched f0.10q sample demonstrates contribution of both mn3+/mn4+ and o2–/o– redox couples with discharge capacity of about 150 mah·g–1 after 10 cycles (figure 7). on the other hand, the best capacity retention after 10 cycles is observed for the f0.15 and f0.15q samples, which can be explained by the maximum mn content along with the less contribution of o2–/o– redox couple. the existence of large amount of nb in the drx structure contributes to an increase in the number of 180° li–o–li bonds [29, 30] necessary for the activation of the o2–/o– redox couple. this leads to oxidation of oxygen o– ions that are inherently unstable and release in the form of o2 from the lattice. therefore, the reason of the capacity loss is the tm migration and densification of the crystal lattice as a result of o2 loss [10, 16]. the second reason for the capacity loss is the formation of isolated 0tm tetrahedra due to the accumulation of li+ around the f– ion. these processes are irreversible and interrupt lithium diffusion. thus, the optimal electrochemical properties can be achieved by combining the required amount of d0 tm and f– ions. 4. conclusions we described for the first time the effect of the cooling rate on the crystal and local structure of li1.2mn0.6+0.5ynb0.2– 0.5yo2–yfy (y = 0.05, 0.10, 0.15) oxyfluorides. it was shown that increasing the cooling rate can stabilize the disorder, thereby suppressing local ordering and superstructure formation. this was also confirmed by epr and nmr spectroscopy, which show a smaller number of mn3+–o2–– mn4+ clusters in the quenched samples. the minimum amount of the paramagnetic clusters was observed for the li1.2mn0.625nb0.175o0.95f0.05 sample. the fluorine content influences the local ordering of mn3+ ions: with an increase in the f content, the amount of paramagnetic centers decreases, and the minimum amount of them is observed for the li1.2mn0.675nb0.125o0.85f0.15 sample. this effect may be associated with the interruption of magnetic exchange interactions in mn clusters by replacing o2– ions with f–. figure 7 the loss of discharge capacity after 10 cycles for all samples. the dotted lines indicate the total theoretical capacity. chimica techno acta 2022, vol. 9(3), no. 20229310 article 8 of 9 it was established that the cooling rate influences the electrochemical properties of the samples: the capacity retention is higher for the samples obtained by quenching. in addition, the fluorine content affects the stability of the o2–/o– redox couple and its contribution to the specific capacity. despite the greater contribution of the o2–/o– redox couple to the capacity of the li1.2mn0.625nb0.175o0.95f0.05 sample, this sample suffers from irreversible oxygen loss. stable contribution of both mn3+/mn4+ and o2–/o– redox couples in specific capacity is characteristic of the li1.2mn0.65nb0.15o0.90f0.10 sample. thus, the selection of the optimal fluorine content and cooling rate leads to the production of cathode materials with the best electrochemical properties. supplementary materials this manuscript contains supplementary materials, which are available online. funding this work was supported by the russian science foundation (grant no. 21-73-20064), https://www.rscf.ru/en. acknowledgments the authors would like to acknowledge dr. anna matveeva at the institute of solid state chemistry and mechanochemistry sb ras for the assistance in registering the epr spectra. author contributions conceptualization: n.v.k. data curation: k.v.m., m.a.k., a.b.s., a.a.k. formal analysis: k.v.m. investigation: k.v.m., m.a.k., a.b.s. methodology: k.v.m., n.v.k. project administration: n.v.k. supervision: n.v.k. validation: n.v.k. visualization: k.v.m. writing – original draft: k.v.m. writing – review & editing: n.v.k. funding acquisition: n.v.k. conflict of interest the authors declare no conflict of interest. additional information author ids: kseniya v. mishchenko, scopus id 55226355900; maria a. kirsanova, scopus id 57189519143; arseny b. slobodyuk, scopus id 9632643200; nina v. kosova, scopus id 7003555655. websites: institute of solid state chemistry and mechanochemistry sb ras, http://www.solid.nsc.ru/; skolkovo institute of science and technology, https://www.skoltech.ru/en; institute of chemistry feb ras, http://www.ich.dvo.ru/. references 1. lee j, urban a, li x, su d, hautier g, ceder g. unlocking the potential of cation-disordered oxides for 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https://doi.org/10.1149/1.3080659 https://doi.org/10.1016/j.chempr.2019.10.001 https://doi.org/10.1039/c8ee00816g https://doi.org/10.1002/aenm.202001671 https://doi.org/10.1002/aenm.202001500 https://doi.org/10.1021/jacs.7b08461 https://doi.org/10.1021/ja2021747 https://doi.org/10.1016/j.ultramic.2012.03.002 https://doi.org/10.1007/s10853-020-05183-4 https://doi.org/10.1039/a909066e https://doi.org/10.1557/proc-548-187 https://doi.org/10.3103/s0027131411030060 https://doi.org/10.1021/ja9817794 https://doi.org/10.1021/jp020457q https://doi.org/10.1016/j.ensm.2020.07.012. https://doi.org/10.1021/acs.chemmater.7b05036 https://doi.org/10.1002/smll.202000656 https://doi.org/10.1039/c9ee02803j testing the antigenotoxicity and anticytotoxicity properties of prunella grandiflora l. extract using the example of drosophila melanogaster published by ural federal university eissn 2411-1414; chimicatechnoacta.ru article 2022, vol. 9(2), no. 202292s14 doi: 10.15826/chimtech.2022.9.2.s14 1 of 5 testing the antigenotoxicity and anticytotoxicity properties of prunella grandiflora l. extract using the example of drosophila melanogaster ngonidzaishe magombe a*, viktoria v. kostenko b, olga n. antosyuk a , elizaveta v. bolotnik c a: institute of natural sciences and mathematics, ural federal university, ekaterinburg 620026, russia b: department of genetics, kazan federal university, kazan 420008, russia c: botanical garden of the ural branch of the russian academy of sciences, ekaterinburg 620144, russia * corresponding author: magombengonidzaishe@gmail.com this paper belongs to the mosm2021 special issue. © 2022, the authors. this article is published in open access form under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). abstract using the drosophila melanogaster model object, the presence of protective properties in 10% of prunella grandiflora l. (lamiaceae) extract was determined in relation to the toxic and cytotoxic effects of the antitumor drug etoposide in two concentrations of 800 and 8000 µg/kg of nutrient medium. the grass p. grandiflora was collected in the flowering phase in sverdlovsk region (n 56°09'22.0'', e 058°32'19.6'') in 2021. no genotoxic manifestations of the extract were found. comparative characteristics of wing parameters under the influence of etoposide at a dose of 800 and 8000 g showed significant differences in linear and two-dimensional parameters of the wing. keywords extract prunella etoposide morphometry antigenotoxic received: 05.04.22 revised: 21.07.22 accepted: 25.07.22 available online: 08.08.22 1. introduction cancer is a disease that causes great harm to human society. there are accepted approaches to the treatment of this disease, but the side effects that occur force us to look for alternative ways to recover or improve the quality of life of each patient. more and more often in scientific circles we hear about personalized medicine, on the threshold of which we are standing. this means that the search for new pharmaceuticals that will be preventive or complementary to existing treatment methods is an important problem in the applied aspect. one of the promising species in the treatment of cancer is the common blackhead prunella vulgaris l. family lamiaceae. using this plant extract, clinical trials were conducted to inhibit cancer cells of the human esophagus, stomach, colon, cervix, liver, which showed positive results [1]. in addition, its chemical composition was studied in the most detail, according to which its high therapeutic effect in the treatment of cancer is explained. thus, several phytochemicals from p. vulgaris, including rosemary acid [2] and caffeic acid [3] cause or promote apoptosis of cancer cells. in the literature, there is mainly information about the medicinal properties of p. vulgaris [4], while data on the pharmacological features of the closely related species p. grandiflora are extremely scarce. previously, we conducted a comparative study on some phenol carboxylic acids of these types. as the research results showed, the content of most phenol-carboxylic acids, including those having antitumor properties, in the leaves of p. grandiflora was higher than that in the leaves of p. vulgaris. we noted a higher content of rosemary acid in p. grandiflora (41.77–52.39 mg/g) than in p. vulgaris (17.88–31.17 mg/g). in p. grandiflora and p. vulgaris, caffeic acid contains 1.13– 1.60 mg/g and 0.40–0.64 mg/g, respectively. in this regard, the species p. grandiflora was chosen as a protector. one of the tasks in testing protective substances that presumably have antigenotoxic properties is to identify various types of side effects when using a protector and an antitumor preparation together. the protective properties of prunella grandiflora l. extract were studied in 10% concentration relative to the etoposide drug used at a dose of 800µg/kg and 8000µg/kg of nutrient medium. 2. materials and methods the grass of the large-flowered blackhead in an amount of 0.8 g was extracted in 10 ml of 70% alcohol for 24 hours. 2.4 ml of 10% extract was added to a nutrient medium weighing 17.6 ml (figure 1). the drug etoposide 20 mg /ml (vero-pharm ebave) was used at a concentration of http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2022.9.2.s14 mailto:magombengonidzaishe@gmail.com http://creativecommons.org/licenses/by/4.0/ http://orcid.org/0000-0003-3902-298x http://orcid.org/0000-0001-5774-3866 https://crossmark.crossref.org/dialog/?doi=https://doi.org/10.15826/chimtech.2022.9.2.s14&domain=pdf&date_stamp=2022-8-8 chimica techno acta 2022, vol. 9(2), no. 202292s14 article 2 of 5 800 µg/kg and 8000 µg/kg of nutrient medium. the oregon – r laboratory line was used to assess viability and morphometric analysis. to account for fertility, 25 individual pairs were placed in 25 tubes with a hollow lid filled with agar medium and lubricated with yeast, from which laid eggs (f1) were collected daily and placed on petri dishes. the percentage of undeveloped eggs at an early stage of development (<6 hours, white color, eel [early embryonic lethality]), at a late stage of development (>6 hours, brown color, lel [late embryonic lethality]) was calculated from the total number of eggs laid per day. the genotoxic effect was determined using the smart (somatic mutation and recombination test) technique. to do this, females from the mutant yellow line (yellow body color, the yellow gene is localized on the x chromosome) were crossed with males from the mutant white singed 3 line (white eyes and singed bristles on the body, the genes are also localized on the x chromosome), placing them on the test medium for 72 hours. hybrid females of the wild f1 phenotype (brown-gray body, straight bristles, red eyes) were used for analysis. in females, the bristles on the body were examined, and the number of bristles not typical for the normal phenotype in color and shape was noted. the area containing a similar bristle was recorded in the table as a single spot y (yellow) or sn (singed) or double y sn. the dna damage in fly enterocyte cells of the control and experimental groups was evaluated using the alkaline dna comet method, which allows determining singlestrand breaks. the dna damage analysis was performed as described in [5] with modifications. to do this, 5 flies of all the studied variants were selected and washed three times in pbs. then the intestine was isolated in the poel's saline solution (15 mm nacl, 6.4 mm nah2po4, 42 mm kcl, 7.9 mm cacl2, 1.8 mm khco3, 20.8 mm mgso4; ph 6.95). further, the samples were centrifuged for 5 min (5000 rpm) at 4 °c, a supernatant was selected and applied to 80 µl 0.65% low-melting agarose. after that, the obtained samples were applied to prepared slides coated with 1% agarose. then, for 1 hour in the dark, the glasses were treated with a lysing buffer (2.5 m nacl, 100 mm edta, 10 mm tris, 1% triton x-100; ph 10). before electrophoresis (15 v/300 ma, 30 min), the samples were incubated in an electrophoresis buffer (0.3 m naoh, 1 mm edta, ph 13) for 15 minutes, after which the glasses were washed 3 times with 20 mm tris, ph 7.5 and 3 times with distilled water. further, the samples were treated with an etbr solution for 20 minutes. the analysis of the finished preparations was performed using a fluorescence microscope carl zeiss axio imager m2. for each variant of the experiment, three glasses were prepared and 50 cells were counted (150 cells per 1 variant), the dna comet index (idc) was determined [6]. the change in the morphology of the wing was determined using morphometric analysis of the wing by 24 indicators (18 linear and 6 two-dimensional (areas of individual wing cells) (figure 2). the wings of the individuals were fixed in 70% alcohol on a slide in the form of a temporary preparation, photographed and processed using the universal dekstop ruler program. statistical analysis was performed using the statistica ultimate academic for windows program. during comparison and analysis of samples, the student's criterion, the chi-square criterion together with the yates correction and discriminant analysis were used. 3. results and discussion 3.1. the average individual fecundity (aif) the frequency of early and late mortality of offspring at the embryonic stage (up to 6 hours of development – eel, after – lel) were evaluated to analyze the viability of each group of d. melanogaster. figure 3 shows an improvement in fertility indicators with the combined use of etoposide at a dose of 800 µg/kg and extract. this indicator increases almost twofold: when using etoposide together with an extract aif is 16.50; when using a single cytostatic agent, it is 9.03. an increase in the applied dose of etoposide to 8000 µg/kg significantly reduces the fertility rate compared to the control sample. however, the use of the extract together with etoposide at a dose of 8000 µg/kg restores the cpi index to the values of the control sample. accordingly, the extract has a positive effect on leveling the toxic effect on the fertility potential, increasing the average value of the aif index twice, regardless of the dose of cytostatic. figure 1 prunella grandiflora l. before the drying. figure 2 linear parameters of the wing plate of drosophila melanogaster. chimica techno acta 2022, vol. 9(2), no. 202292s14 article 3 of 5 according to the indicators of eel and lel, a similar pattern can be noted. the range of lel, lel and the average value of eel, eel decreases with the use of the extract and etoposide at a dose of 800 µg/kg. the reverse pattern was obtained when using a high dose of etoposide 8000 µg/kg. the maximum mortality value was noted in the early embryonic stage when etoposide was administered at a dose of 8000 µg/kg and is 60. it can be noted that in all groups, mortality is higher in the early embryonic stage. 3.2. somatic mutation and recombination tests (smart) the genotoxic effect of etoposide was also analyzed at a dose of 800 µg/kg and 8000 µg/kg using smart lines. table 1 shows that the extract, when used in combination with etoposide at a dose of 800 µg/kg, reduces the frequency of aberrant phenotypes by 3 times in relation to the action of a single cytostatic agent, but does not affect the frequency of occurrence of certain types of spots. thus, among 873 flies, 14 spots of different types and 3 aberrant phenotypes were found, whereas when exposed to etoposide, 13 spots and 9 aberrant forms were found among 669 individuals. yellow spots were found in one individual in the control and experimental samples with etoposide at a dose of 800 µg/kg. according to preliminary data, etoposide in both doses mainly caused singed-type spots. in the case of exposure to 8000 µg/kg of etoposide, the use of 10% p. grandiflora extract is also effective in reducing the frequency of aberrant types in hybrid females. 3.3. comet assay dna comet analysis is a fast and sensitive method for detecting dna damage in individual cells. the size, shape and amount of dna inside the "comet" determine the severity of dna damage. this analysis is used to test dna damage by various chemicals and infectious agents using drosophila as a model system. in drosophila, brain ganglia, midgut cells (enterocytes), and imaginal disc cells are targeted for genotoxicity testing in vivo [7]. in the case of invertebrates, enterocytes are used instead of human lymphocytes [8]. enterocytes are very sensitive to the effects of genotoxic agents, and the treatment methodology is very simple, since the cells come into direct contact with toxic materials that enter the intestines of flies [9]. the data obtained by us showed the absence of genotoxic manifestations in p. grandiflora extract in 10% concentration relative to the nutrient substrate (f = 58.3; p<0.05) (figure 4). when exposed to 800 µg/kg of etoposide 10% extract, the dna comet index increased by 18% compared to the standard nutrient substrate (f = 64.1; p<0.05). in highly replicating cells, such as hematopoietic stem cells and epithelial cells, dna mutations resulting from non-repaired dna damage play a crucial role in malignant transformation and cancer progression [10]. endogenous agents capable of damaging dna, such as reactive oxygen species (ros), lipid peroxidation products, and reactive nitrogen species (rns) are naturally released during cellular metabolic activity or hydrolytic processes [11]. figure 3 the average individual fertility of flies of individual experimental groups of d. melanogaster. table 2 idc indicators in different experimental groups of d. melanogaster. experiment variant idc one way anova control 0.86±0.02 – 10% p. grandiflora extract 0.89±0.06 f = 58.3; p<0.05 10% p. grandiflora extract + etoposide 1.05±0.04 f = 64.1; p<0.05 figure 4 the main types of dna damage: (a) control, (b) etoposide + extract. table 1 the examination of somatic mosaicism in various experimental groups of d. melanogaster. experimental groups number of individuals with mutant spots other mutant phenotypes % fraction of the sample (χ2) (p) samples y sn y sn control 669 1 2 0 0 0.44843 – – etoposide (800 μg/kg) 833 1 12 0 9 2.641056 9.6 0.002 extract p. grandiflora 10%+ etoposide (800 μg/kg) 873 1 12 1 3 1.901141 5.5 0.019 extract p. grandiflora 10%+ etoposide (8000 μg/kg) 591 0 1 0 2 0.507614 0.1 0.797 etoposide (8000 μg/kg) 263 0 4 0 1 1.901141 3.1 0.077 chimica techno acta 2022, vol. 9(2), no. 202292s14 article 4 of 5 in addition, activation of the response in dna damage can be caused by thousands of exogenous agents, including ionizing radiation, chemotherapy, viral infections and chronic inflammation [12]. 3.4. morphometry analysis of wings when comparing the wing shape according to the linear parameters of the experimental groups: control, etoposide 800 and etoposide 8000, several discriminating parameters were found (figure 5). according to discriminant analysis, it was revealed that the wing plate undergoes extensive changes affecting almost all areas of the wing, both its central part and lateral areas. according to the graph of canonical variables, it can be assumed that when exposed to different concentrations of etoposide, the shape of the wing changes significantly. the samples of control and after exposure to etoposide do not overlap. in etoposide samples 800 and etoposide 8000, there was also a small similarity of the samples in the linear parameters of the wing plate (figure 6). this suggests that it is possible that with a higher dose of etoposide, changes in the wing occur in a different form than changes at a concentration of 800, at least the rcd (regulated cell death) processes occur more intensively in all 4 compartments [13]. according to the data of discriminant analysis for twodimensional parameters of the wing, it was found that two of the 6 areas of the wing shown in figure 7 do not change in area. these cells are located in the central part of the wing plate respectively, the lateral parts of the wing are more affected by etoposide. 4. conclusions according to the preliminary data, etoposide in both tested concentrations have an effect on both generative and somatic cells of individuals of the oregon-r drosophila melanogaster line. according to the results of smart analysis, 10% prunella grandiflora l extract does not have genotoxic properties. the use of the extract together with etoposide increases the fertility of individuals. the cytotoxic properties of etoposide of both concentrations are manifested in a change in the shape of the wing plate, both with respect to linear parameters and the size and shape of individual wing cells. supplementary materials no supplementary materials are available. funding this work was financially supported by decree no. 211 of the government of the russian federation, contract no. 02.a03.21.0006. figure 5 the discriminating parameters of the wing plate of d. melanogaster experimental groups: control, etoposide 800 µg/kg and etoposide 8000 µg/kg. figure 6 canonical analysis of morphometric parameters of the wing of experimental groups of d. melanogaster. figure 7 non-discriminating two-dimensional wing parameters of d. melanogaster experimental groups: control, etoposide 800 µg/kg and etoposide 8000 µg/kg. acknowledgments we are grateful to marvin n.a. and all the laboratory teammates for their continued support. author contributions investigation: n.m. methodology: o.n.a., e.v.b., v.v.k. project administration: n.m. supervision: o.n.a. chimica techno acta 2022, vol. 9(2), no. 202292s14 article 5 of 5 writing – original draft: n.m. writing – review & editing: o.n.a., e.v.b., v.v.k. conflict of interest the authors declare no conflict of interest. additional information author ids: olga n. antosyuk, scopus id 57191491478; elizaveta v. bolotnik, scopus id 57219989897. websites: ural federal university, https://urfu.ru/en; kazan federal university, https://eng.kpfu.ru; botanical garden of the ub ras, http://botgard.uran.ru. references 1. huang m, wang y, you m. anti-tumor properties of prunella vulgaris. springer international publishing, ag; 2015, 401– 419 p. 2. xavier cp, lima cf, fernandes-ferreira m, pereira-wilson c. salvia fruticosa, salvia officinalis, and rosmarinic acid induce apoptosis and inhibit proliferation of human colorectal cell lines: the role in mapk/erk pathway. nutr cancer. 2009;61(4):564–571. doi:10.1080/01635580802710733 3. rajendra np, karthikeyan a, karthikeyan s, reddy bv. inhibitory effect of caffeic acid on cancer cell proliferation by oxidative mechanism in human ht-1080 fibrosarcoma cell line. mol cell biochem. 2011;349(1–2):11–19. doi:10.1007/s11010-010-0655-7 4. budantsev al. plant resources of russia: wild flowering plants, their component composition and biological activity: botanical institute named after v. l. komarova. st. petersburg; 2008). 236–239 p. 5. mukhopadhyay a, vij shubha s, tyagi a. overexpression of a zinc-finger protein gene from rice confers tolerance to cold, dehydration, and salt stress in transgenic tobacco. proc nat acad sci usa. 2004;101:6309–6314. doi:10.1073/pnas.0401572101 6. plyusnina e, shaposhnikov m, moskalev a. increase of drosophila melanogaster lifespan due to d-gadd45 overexpression in the nervous system. biogerontol. 2010;12(3):211–226. doi:10.1007/s10522-010-9311-6 7. carmona er, guecheva tn, creus a, marcos r. proposal of an in vivo comet assay using haemocytes of drosophila melanogaster. environ mol mutagen. 2011;52(2):165–169. doi:10.1002/em.20604 8. irving p, ubeda j, doucet d, troxler l, lagueux m, zachary d, hoffmann j, hetru c, meister m. new insights into drosophila larval haemocyte functions through genome-wide analysis. cell microbiol. 2005;7:335–350. doi:10.1111/j.1462-5822.2004.00462.x 9. sharma a, mishra m, ram kr, kumar r, abdin mz, chowdhuri dk. transcriptome analysis provides insights for understanding the adverse effects of endosulfan in drosophila melanogaster. chemosphere. 2011;82(3):370–376. doi:10.1016/j.chemosphere.2010.10.002 10. delia d, mizutani s. the dna damage response pathway in normal hematopoiesis and malignancies. int j hematol. 2017;106(3):328–334. doi:10.1007/s12185-017-2300-7 11. roos wp, kaina b. dna damage-induced cell death: from specific dna lesions to the dna damage response and apoptosis. cancer lett. 2013;332(2):237–248. doi:10.1016/j.canlet.2012.01.007 12. goldstein m, kastan mb. the dna damage response: implications for tumor responses to radiation and chemotherapy. annu rev med. 2015;66:129–143. doi:10.1146/annurev-med-081313-121208 13. magombe n, antosyuk on, bolotnik ev. izuchenie protektornyh svojstv ekstrakta prunella grandiflora l. otnositel'no vozdejstviya protivoopuholevogo preparata etopozid na primere drosophila melanogaster. in: abstracts of the openbio viii mezhdunarodnaya nauchno-prakticheskaya konferenciya molodyh uchenyh: biofizikov, biotekhnologov, molekulyarnyh biologov i virusologov, 2021 oct 5-8, novosibirsk, russia. p. 35–36. http://www.scopus.com/inward/authordetails.url?authorid=57191491478 http://www.scopus.com/inward/authordetails.url?authorid=57219989897 https://urfu.ru/en https://eng.kpfu.ru/ http://botgard.uran.ru/ https://doi.org/10.1080/01635580802710733 https://doi.org/10.1007/s11010-010-0655-7 https://doi.org/10.1073/pnas.0401572101 https://doi.org/10.1007/s10522-010-9311-6 https://doi.org/10.1002/em.20604 https://doi.org/10.1111/j.1462-5822.2004.00462.x https://doi.org/10.1016/j.chemosphere.2010.10.002 https://doi.org/10.1007/s12185-017-2300-7 https://doi.org/10.1016/j.canlet.2012.01.007 https://doi.org/10.1146/annurev-med-081313-121208 expedient synthesis of 1,2,4-triazinyl substituted benzo[c]coumarins via double oxidation strategy published by ural federal university eissn 2411-1414 chimicatechnoacta.ru article 2023, vol. 10(2), no. 202310205 doi: 10.15826/chimtech.2023.10.2.05 1 of 7 expedient synthesis of 1,2,4-triazinyl substituted benzo[c]coumarins via double oxidation strategy ramil f. fatykhov a * , igor a. khalymbadzha a , ainur d. sharapov a, anastasia p. potapova a, ekaterina s. starnovskaya ab , dmitry s. kopchuk ab , oleg n. chupakhin ab a: institute of chemical engineering, ural federal university, ekaterinburg 620002, russia b: institute of organic synthesis, ural branch of the russian academy of sciences, ekaterinburg 620219, russia * corresponding author: rf.fatykhov@urfu.ru this paper belongs to a regular issue. abstract herein, we report a convenient one-pot synthesis of 1,2,4-triazinyl derivatives of benzocoumarins. the proposed approach consists of the nucleophilic addition of tetrahydrobenzo annulated dimethoxycoumarin to 1,2,4triazines followed by double oxidation of both dihydrotriazine and tetrahydrobenzo groups with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (ddq). the nucleophilic addition of the dimethoxycoumarin to 1,2,4-triazines was carried out in the presence of three-fold excess of methanesulfonic acid in dcm at room temperature. it takes place between positions 8 and 5 of coumarin and 1,2,4-triazine, respectively. the double oxidation step was carried out with 3.6 equivalent of ddq. selective oxidation of dihydrotriazine moiety, without affecting the tetrahydrobenzo fragment, was achieved using 1.2 equivalent of tetrachlorobenzoquinone (tcq). the differences in the oxidation with tcq and ddq appear to be related to the higher oxidative potential of ddq in contrast to tcq. the advantages of the method are the elimination of the use of transition metals, the availability of starting materials, and the simplicity of the procedure. the proposed approach provides a two-step one-pot protocol for the synthesis of triazinyl benzocoumarins, precursors for the preparation of push-pull pyridinyl chromophore. keywords coumarin 1,2,4-triazine nucleophilic substitution of hydrogen quinone oxidation push-pull chromophore received: 06.03.23 revised: 27.03.23 accepted: 04.04.23 available online: 11.04.23 key findings ● one-pot synthesis of triazinyl-benzo[c]coumarin conjugate was developed. ● oxidation of adduct with ddq leads to double oxidation of both dihydrotriazine and tetrahydrobenzo groups. ● oxidation of adduct with tcq leads to chemoselective oxidation of dihydrotriazine. © 2023, the authors. this article is published in open access under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). 1. introduction azaheterocyclic coumarin derivatives provide one of most important photophysical-active compounds [1–3]. due to good photophysical properties, such as high quantum yields and long-wavelength absorption/emission, various push-pull coumarins, containing azaheterocyclic fragment, have been studied as sensors [3–5] and fluorescent probes [6–8], components of organic light-emitting diodes (oled) [9, 10] and solar cells [11, 12]. for example, coumarin-based terpyridine–zinc complex (figure 1) demonstrated sensing ability for pyrophosphate (ppi) in aqueous media and was successfully applied to fluorescence imaging for ppi in hi-5 cells and caenorhabditis elegans [13]. coumarin-based cyclometalated ir(iii) complex (figure 1) was studied as an emitter in oled, and the device based on this derivative displayed impressive electroluminescence performance [14]. coumarin–benzothiazole–chlorambucil conjugate (figure 1) was developed as a ph-sensitive photoresponsive drug delivery system [15]. in the literature, the synthesis of azinyl-coumarin or benzocoumarin derivatives is reported by multistep reactions sequences, involving construction of azaheterocyclic ring (scheme 1, a) [16] or pyrone core (scheme 1, b) [17] from corresponding precursors or transition metal (tm)-catalyzed cross-coupling reactions between prefunctionalized precursors (scheme 1, c) [14]. http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2023.10.2.05 mailto:rf.fatykhov@urfu.ru http://creativecommons.org/licenses/by/4.0/ https://orcid.org/0000-0003-3129-8658 https://orcid.org/0000-0002-8043-8023 https://orcid.org/0000-0002-9679-8269 https://orcid.org/0000-0002-0397-4033 https://orcid.org/0000-0002-1672-2476 https://crossmark.crossref.org/dialog/?doi=https://doi.org/10.15826/chimtech.2023.10.2.05&domain=pdf&date_stamp=2023-04-11 https://journals.urfu.ru/index.php/chimtech/rt/suppfiles/6627/0 chimica techno acta 2023, vol. 10(2), no. 202310205 article 2 of 7 doi: 10.15826/chimtech.2023.10.2.05 figure 1 some important azaheterocyclic coumarin derivatives. scheme 1 approaches to azinyl-coumarin. nucleophilic substitution of hydrogen (snh) [18] in nitrogen-containing heterocycles represents a powerful tool for the construction of a novel c–c bond, conforming to the requirements of “green” chemistry and pase (pot, atom, step economy) approaches. the advantages of this approach are the avoidance of tm catalysts and the so-called “chlorine technologies”, mild reaction conditions, which, in turn, leads to a decrease in the number of steps and an increase in the overall yield of the desired product. snh reactions often proceed as the addition of a nucleophile to an electrophilic azine with the formation of a σн-adduct, which can subsequently be oxidized in the presence of an external oxidizing agent (air oxygen [19], 2,3-dichloro-5,6-dicyano1,4-benzoquinone (ddq) [20–23], k3[fe(cn)6] [24–26], mno2 [22, 27]) to a product of nucleophilic substitution of hydrogen. earlier, we proposed a convenient synthetic approach to push-pull 8-pyridinylcoumarin chromophores (scheme 1, d) by using a sequence of reactions of nucleophilic substitution of hydrogen and boger pyridine synthesis in the series of 3,6-diaryl-substituted 1,2,4-triazines and 5,7-dimethoxycoumarins [20, 28]. thus, at the first step, coumarin was added to the triazine core with the formation of a 1,4-dihydrotriazine derivative, which then easily underwent aromatization under the action of the external oxidant such as ddq with the formation of snh product in high yield, which then transformed to pyridine derivative with 2,5-norbornadiene. in order to study the scope and limitations of this snh approach, we adopted synthetic protocol of the oxidative cross-coupling of 1,3-dimethoxy-7,8,9,10-tetrahydro-6h-benzo[c]coumarin 1 with 3,6-substituted triazines 2. in the present work, we report the double aromatization of both the dihydrotriazine and tetrahydrobenzene moieties (scheme 1, e). this double aromatization strategy allowed us to extend the opportunities of snh reactions in triazines providing stringboard access to 1,2,4-triazinyl substituted benzo[c]coumarins. 2. experimental 1h nmr (400 mhz) and 13c nmr (101 mhz) spectra were recorded on a bruker drx-400 avance spectrometer with dmso-d6 or cdcl3 as a solvent at ambient temperature. chemical shifts are reported in ppm and coupling constants are given in hz. data for 1h nmr are recorded as follows: chemical shift (ppm), multiplicity (s, singlet; d, doublet; t, triplet; m, multiplet; br s, broad signal), coupling constant (hz), integration. high resolution mass spectra were recorded on an agilent uhplc/ms accurate-mass q-tof 1290/6545. thin layer chromatography (tlc) was performed on silica gel coated glass slide (merck, silica gel g for tlc). aluminium oxide 90 (70–230 mesh, merck) was used for column chromatography. all solvents were dried and distilled before use. commercially available substrates were freshly distilled before the reaction. solvents, reagents and chemicals were purchased from aldrich, fluka, merck, srl, spectrochem and process chemicals. all reactions involving moisture sensitive reactants were carried out using oven dried glassware. 2.1. 4-(3,6-diphenyl-2,5-dihydro-1,2,4-triazin-5yl)-1,3-dimethoxy-7,8,9,10-tetrahydro-6hbenzo[c]chromen-6-one 3a to a solution of coumarin 1 (260 mg, 1 mmol) and triazine 2a (233 mg, 1 mmol) in dichloromethane (dcm,6 ml) was added meso3h (288 mg, 3 mmol). the resulting solution was left for 3 h; the progress of the reaction was monitored by tlc. after completion of the reaction, the reaction mixture was washed with a saturated na2co3 solution. the organic layer was separated, dried with anhydrous sodium sulfate, and the solvent was removed under reduced pressure. the residue was recrystallized from benzene to give pure adduct 3a. white precipitate. yield 449 mg (91%). 1h nmr (400 mhz, dmso-d6) δ 11.14–10.93 (br s, 1h), 7.86– 7.77 (m, 2h), 7.67–7.58 (m, 2h), 7.47–7.35 (m, 3h), 7.30– 7.20 (m, 3h), 6.57 (s, 1h), 6.41 (s, 1h), 3.92 (s, 3h), https://doi.org/10.15826/chimtech.2023.10.2.05 https://doi.org/10.15826/chimtech.2023.10.2.05 chimica techno acta 2023, vol. 10(2), no. 202310205 article 3 of 7 doi: 10.15826/chimtech.2023.10.2.05 3.85 (s, 3h), 2.97–2.85 (m, 2h), 2.42–2.29 (m, 2h), 1.67– 1.54 (m, 4h). 13c nmr (101 mhz, dmso-d6) δ 159.8, 159.2, 158.1, 151.7, 149.3, 149.2, 139.3, 136.0, 133.4, 130.1, 128.6, 128.2, 128.1, 126.2, 124.9, 118.0, 111.2, 103.9, 92.7, 56.3, 56.1, 45.8, 29.4, 24.2, 21.7, 20.6. hrms (esi): c30h28n3o4+ [(m+h)+]: calcd.: 494.2074; found: 494.2069. 2.2. 4-(3,6-diphenyl-1,2,4-triazin-5-yl)-1,3-dimethoxy-7,8,9,10-tetrahydro-6hbenzo[c]chromen-6-one 4a dihydrotriazine 3a (493 mg, 1 mmol) was dissolved in 1,2dichloroethane (dce, 10 ml), tetrachloro-1,4-benzoquinone (tcq) (340 mg, 1.2 mmol) was added, and the mixture was refluxed for 6 h. the solvent was removed under reduced pressure, and the residue was recrystallized from butanol-1 to give pure 4a. pale yellow precipitate. yield 417 mg, 85%. 1h nmr (400 mhz, cdcl3) δ 8.60–8.54 (m, 2н), 7.58–7.49 (m, 5н), 7.35–7.27 (m, 3н), 6.21 (s, 1h), 3.90 (s, 3н), 3.51 (s, 3н), 3.11–3.10 (m, 2н), 2.57–2.46 (m, 2н), 1.80–1.69 (m, 4н). 13c nmr (101 mhz, cdcl3) δ 162.3, 160.8, 160.3, 158.4, 152.4, 152.3, 149.3, 135.9, 135.3, 131.4, 129.3, 128.8, 128.6, 128.5, 128.2, 120.2, 107.2, 105.5, 91.2, 66.0, 55.8, 30.1, 24.8, 22.5, 21.4. hrms (esi): c30h26n3o4+ [(m+h)+]: calcd.: 492.1918; found: 492.1923. 2.3. general method for synthesis of compounds 5 to a solution of coumarin 1 (260 mg, 1 mmol) and corresponding triazine 2a–i (1 mmol) in dcm (6 ml) was added meso3h (288 mg, 3 mmol). the resulting solution was left for 3 h. after completion of the reaction, the reaction mixture was washed with a saturated na2co3 solution. the organic layer was separated, dried with anhydrous sodium sulfate, and the solvent was removed under reduced pressure to give adduct 3, which then was dissolved in dce (10 ml). then, ddq (3.6 mmol, 817 mg) was added, and the mixture was refluxed for 6 h. the resulting mixture was purified using flash chromatography (al2o3/ethyl acetate). the solvent was removed under reduced pressure, and the residue was recrystallized from butanol-1 to give pure 5. 2.3.1. 4-(3,6-diphenyl-1,2,4-triazin-5-yl)-1,3-dimethoxy6h-benzo[c]chromen-6-one 5a yellow powder. yield 429 mg, 88%; 1h nmr (400 mhz, cdcl3) δ 8.89 (d, j = 8.4 hz, 1h), 8.64–8.57 (m, 2h), 8.34 (d, j = 7.9 hz, 1h), 7.76 (t, j = 7.6 hz, 1h), 7.61– 7.56 (m, 2h), 7.55–7.46 (m, 4h), 7.34–7.27 (m, 3h), 4.08 (s, 3h), 3.60 (s, 3h). 13c nmr (101 mhz, cdcl3) δ 162.3, 160.7, 160.4, 158.4, 158.3, 152.4, 151.2, 135.9, 135.3, 135.0, 134.6, 131.4, 130.4, 129.3, 128.9, 128.6, 128.5, 128.2, 127.6, 126.7, 119.9, 108.0, 102.5, 91.8, 56.2, 56.0. hrms (esi): c30h22n3o4+ [(m+h)+]: calcd.: 488.1605; found: 488.1609. 2.3.2. 4-(3,6-bis(4-methoxyphenyl)-1,2,4-triazin-5-yl)1,3-dimethoxy-6h-benzo[c]chromen-6-one 5b yellow powder. yield 421 mg, 77%. 1h nmr (400 mhz, cdcl3) δ 8.88 (d, j = 8.5 hz, 1h), 8.58–8.51 (m, 2h), 8.33 (dd, j = 7.5, 1.6 hz, 1h), 7.75 (ddd, j = 8.5, 7.5, 1.6 hz, 1h), 7.56–7.43 (m, 3h), 7.06–6.98 (m, 2h), 6.85–6.75 (m, 2h), 6.41 (s, 1h), 4.08 (s, 3h), 3.87 (s, 3h), 3.75 (s, 3h), 3.63 (s, 3h). 13c nmr (101 mhz, cdcl3) δ 162.4, 161.6, 160.6, 160.5 (2c), 158.3, 157.3, 152.0, 151.1, 135.0, 134.6, 130.4, 130.2, 129.8, 128.4, 128.0, 127.5, 126.7, 119.9, 114.2, 113.7, 108.3, 102.4, 91.9, 56.2, 56.1, 55.5, 55.3. hrms (esi): c32h26n3o6+ [(m+h)+]: calcd.: 548.1816; found: 548.1820. 2.3.3. 1,3-dimethoxy-4-(6-(4-methoxyphenyl)-3-(p-tolyl)1,2,4-triazin-5-yl)-6h-benzo[c]chromen-6-one 5c yellow powder. yield 405 mg, 74%. 1h nmr (400 mhz, cdcl3) δ 8.87 (d, j = 8.4 hz, 1h), 8.48 (d, j = 7.9 hz, 2h), 8.32 (d, j = 7.9 hz, 1h), 7.74 (t, j = 7.9 hz, 1h), 7.53 (d, j = 8.4 hz, 2h), 7.47 (t, j = 7.9 hz, 1h), 7.31 (d, j = 7.9 hz, 2h), 6.78 (d, j = 8.4 hz, 2h), 6.41 (s, 1h), 4.07 (s, 3h), 3.74 (s, 3h), 3.62 (s, 3h), 2.42 (s, 3h). 13c nmr (101 mhz, cdcl3) δ 161.9, 160.6, 160.5, 160.4, 158.3, 157.7, 152.1, 151.1, 141.6, 134.9, 134.6, 132.6, 130.3, 129.8, 129.6, 128.4, 128.3, 127.5, 126.7, 119.8, 113.7, 108.2, 102.4, 91.9, 56.2, 56.0, 55.3, 21.7. hrms (esi): c32h26n3o5+ [(m+h)+]: calcd.: 532.1867; found: 532.1871. 2.3.4. 1,3-dimethoxy-4-(3-phenyl-6-(p-tolyl)-1,2,4-triazin-5-yl)-6h-benzo[c]chromen-6-one 5d yellow powder. yield 296 mg, 59%. 1h nmr (400 mhz, cdcl3) δ 8.88 (d, j = 8.5 hz, 1h), 8.64–8.55 (m, 2h), 8.34 (dd, j = 7.9, 1.6 hz, 1h), 7.76 (ddd, j = 8.5, 7.9, 1.6 hz, 1h), 7.56–7.44 (m, 6h), 7.11–7.04 (m, 2h), 6.41 (s, 1h), 4.08 (s, 3h), 3.61 (s, 3h), 2.28 (s, 3h). 13c nmr (101 mhz, cdcl3) δ 162.0, 160.7, 160.4, 158.3, 152.3, 151.2, 134.9, 135.4, 135.0, 134.6, 132.9, 131.3, 130.4, 129.0, 128.8, 128.6, 128.4, 128.4, 127.5, 126.7, 119.9, 108.2, 102.4, 91.9, 56.2, 56.0, 21.5. hrms (esi): c32h26n3o5: calcd.: 532.1867; found: 532.1871. 2.3.5. 1,3-dimethoxy-4-(6-(naphthalen-2-yl)-3-phenyl1,2,4-triazin-5-yl)-6h-benzo[c]chromen-6-one 5e yellow powder. yield 381 mg, 71%. 1h nmr (400 mhz, cdcl3) δ 8.86 (d, j = 8.5 hz, 1h), 8.69–8.60 (m, 2h), 8.33 (dd, j = 7.9, 1.6 hz, 1h), 8.15 (s, 1h), 7.80–7.71 (m, 4h), 7.67 (dd, j = 8.5, 1.6 hz, 1h), 7.60–7.50 (m, 3h), 7.51–7.38 (m, 3h), 6.34 (s, 1h), 4.03 (s, 3h), 3.54 (s, 3h). 13c nmr (101 mhz, cdcl3) δ 162.2, 160.7, 160.5, 158.4, 158.3, 152.6, 151.3, 135.3, 135.0, 134.6, 133.6, 133.3, 133.0, 131.4, 130.4, 128.9, 128.8, 128.6, 128.5, 127.9, 127.7, 127.6, 126.9, 126.7, 126.3, 125.6, 119.8, 108.0, 102.5, 91.8, 56.2, 56.0. hrms (esi): c34h24n3o4+ [(m+h)+]: calcd.: 538.1761; found: 538.1757. 2.3.6. 4-(6-(4-bromophenyl)-3-phenyl-1,2,4-triazin-5yl)-1,3-dimethoxy-6h-benzo[c]chromen-6-one 5f yellow powder. yield 441 mg, 78%. 1h nmr (400 mhz, cdcl3) δ 8.89 (d, j = 8.5 hz, 1h), 8.63–8.56 (m, 2h), 8.34 (dd, j = 7.5, 1.6 hz, 1h), 7.77 (ddd, j = 8.5, 7.5, 1.6 hz, 1h), 7.61–7.44 (m, 6h), 7.44–7.37 (m, 2h), 6.41 (s, 1h), 4.10 (s, 3h), 3.64 (s, 3h). 13c nmr (101 mhz, cdcl3) δ 162.5, 160.9, 160.3, 158.2, 157.5, 152.3, 151.1, 135.1, 135.1, 134.9, 134.5, 131.6, 131.5, 130.4, 130.0, 128.9, 128.7, 127.7, 126.7, https://doi.org/10.15826/chimtech.2023.10.2.05 https://doi.org/10.15826/chimtech.2023.10.2.05 chimica techno acta 2023, vol. 10(2), no. 202310205 article 4 of 7 doi: 10.15826/chimtech.2023.10.2.05 124.0, 119.8, 107.5, 102.5, 91.8, 56.3, 56.0. hrms (esi): c30h21brn3o4+ [(m+h)+]: calcd.: 566.0710; found: 566.0715. 2.3.7. 4-(6-(4-bromophenyl)-3-(4-methoxyphenyl)1,2,4-triazin-5-yl)-1,3-dimethoxy-6hbenzo[c]chromen-6-one 5g yellow powder. yield 446 mg, 75%. 1h nmr (400 mhz, cdcl3) δ 8.89 (d, j = 8.5 hz, 1h), 8.59–8.51 (m, 2h), 8.34 (dd, j = 7.5, 1.6 hz, 1h), 7.77 (ddd, j = 8.5, 7.5, 1.6 hz, 1h), 7.54–7.38 (m, 4h), 7.07–6.98 (m, 2h), 6.41 (s, 1h), 4.10 (s, 3h), 3.88 (s, 3h), 3.63 (s, 3h). 13c nmr (101 mhz, cdcl3) δ 162.6, 162.2, 160.8, 160.4, 158.2, 156.8, 152.1, 151.2, 135.1, 134.5, 131.5, 130.4, 130.4, 130.0, 127.7, 127.7, 126.7, 123.8, 119.8, 114.3 (2c), 107.7, 102.5, 91.8, 56.3, 56.0, 55.5. hrms (esi): c31h23brn3o5+ [(m+h)+]: calcd.: 596.0816; found: 596.0822. 2.3.8. 4-(6-(4-bromophenyl)-3-(p-tolyl)-1,2,4-triazin-5yl)-1,3-dimethoxy-6h-benzo[c]chromen-6-one 5h yellow powder. yield 428 mg, 74%. 1h nmr (400 mhz, cdcl3) δ 8.89 (d, j = 8.5 hz, 1h), 8.49 (d, j = 8.0 hz, 2h), 8.34 (dd, j = 7.9, 1.6 hz, 1h), 7.77 (ddd, j = 8.5, 7.9, 1.6 hz, 1h), 7.54–7.38 (m, 5h), 7.33 (d, j = 8.0 hz, 2h), 6.41 (s, 1h), 4.10 (s, 3h), 3.64 (s, 3h), 2.44 (s, 3h). 13c nmr (101 mhz, cdcl3) δ 162.5, 160.8, 160.3, 158.2, 157.3, 152.2, 151.1, 142.0, 135.1, 135.0, 134.5, 132.4, 131.5, 130.4, 130.0, 129.7, 128.6, 127.7, 126.7, 123.9, 119.8, 107.6, 102.5, 91.8, 56.2, 56.0, 21.7. hrms (esi): c31h23brn3o4+ [(m+h)+]: calcd.: 580.0866; found: 580.0870. 2.3.9. 1,3-dimethoxy-4-(3-phenyl-1,2,4-triazin-5-yl)-6hbenzo[c]chromen-6-one 5i yellow powder. yield 275 mg, 67%. 1h nmr (400 mhz, dmso-d6) δ 9.53 (s, 1h), 8.96–8.90 (m, 1h), 8.50–8.43 (m, 2h), 8.26–8.19 (m, 1h), 7.93–7.88 (m, 1h), 7.68–7.56 (m, 4h), 6.92 (s, 1h), 4.19 (s, 3h), 3.96 (s, 3h). 13c nmr (101 mhz, dmso-d6) δ 162.8, 160.9, 159.5, 158.9, 153.7, 150.5, 150.3, 135.4, 134.8, 133.9, 131.8, 129.6, 129.1, 127.9, 127.8, 126.4, 119.0, 104.9, 101.1, 93.2, 56.8, 56.7. hrms (esi): c24h18brn3o4+ [(m+h)+]: calcd.: 412.1292; found: 412.1297. 3. results and discussion we started our research with the reaction of dimethoxycoumarin 1 with 3,6-diphenyl-1,2,4-triazine 2a, which was carried out in the presence of three-fold excess of methanesulfonic acid (msoh) in dcm at room temperature, yielding dihydrotriazine 3a in high yield (scheme 2), in accordance with the previously described procedure [2o]. aromatization of the adduct 3a with 1.5 equivalent of ddq (table 1, entry 1) [20] provided a complex mixture of products. we hypothesized that, in contrast to our previous work [20, 28], ddq not only oxidizes 1,4-dihydrotriazine core to give expected product of the nucleophilic substitution of hydrogen 4a, but also aromatizes tetrahydrobenzene moiety yielding 5a and 6a, which is confirmed by the literature data [29, 30]. however, it was found that increasing amount of oxidant up to 3.6 equivalents (1.2 equiv. per σ-bond) in 1,2dichloroethane (dce) at 70 °c allows producing 4-triazinyl-benzo[c]coumarin derivative 5a in 90% yield (scheme 4). further increasing of ddq amount up to 5 equivalents did not improve the yield (table 1, entry 3). in addition, we also demonstrated that using even fourfold excess of tcq (table 1, entry 4) instead of ddq as the oxidizing agent in the same oxidation process led to aromatization of dihydrotriazine moiety with excellent chemoselectivity to give snh product (scheme 5). after quick reoptimization of the reaction conditions, we found that the use of 1.2 eq. tcq in dce at 70 °c (table 1, entry 5) could allow the formation of 4a in best yield. one can assume that the differences in the oxidation with tcq and ddq are related to the higher oxidative potential of ddq in contrast to tcq (0.51 vs. 0.01 volts [31]). scheme 2 synthesis of adduct 3a. scheme 3 formation of the complex mixture of products during the oxidation of adduct 3a with 1.5 equivalents of ddq. table 1 optimization of the oxidation reaction conditions a. entry oxidant (equivalents) product yield b 1 ddq (1.5 eq.) – c 2 ddq (3.6 eq.) 5a 90 3 ddq (5.0 eq.) 5a 88 4 tcq (4.0 eq.) 4a 84 5 tcq (1.2 eq.) 4a 85 6 air (bubbling) – d 7 oxygen (bubbling) – d 8 mno2 (10 eq.) 4a 51 a conditions: 3a (1 mmol), dce (10 ml), 70°c; b isolated yield; c hard-to-separate mixture; d starting material was isolated. https://doi.org/10.15826/chimtech.2023.10.2.05 https://doi.org/10.15826/chimtech.2023.10.2.05 chimica techno acta 2023, vol. 10(2), no. 202310205 article 5 of 7 doi: 10.15826/chimtech.2023.10.2.05 scheme 4 oxidation of adduct 3a with 3.6 equivalents of ddq. scheme 5 oxidation of adduct 3a with tcq. air or oxygen bubbling through the reaction mixture did not produce desired products (table 1, entries 6 and 7, respectively), and only the starting material was isolated from the reaction mixture. manganese oxide (iv) is another oxidizing agent that can oxidize dihydrotriazines to aromatic triazines [27]. when dihydrotriazine 3a was refluxed with 10 equivalents of mno2 in dichloroethane, product 4a was formed in 51% yield (table 1, entry 8). formation of compound 5a was proven by 1h and 13c nmr spectroscopy data. in particular, multipletes of protons of the methylene groups were not observed in the 3.5– 1.5 ppm region. in addition, signals of sp3-hybridized carbons of the tetrahydrobenzene ring were also absent in the high field of 13c nmr spectrum. after optimizing the reaction conditions, we examined the applicability and scope of this reaction sequence with respect to 3,6-diaryl-substituted 1,2,4-triazines 2a–h. the results are summarized in scheme 6. 1,2,4-triazines 2 bearing p-tolyl, 4-methoxyphenyl (pmp), 4-bromophenyl and even bulky naphthalenyl group at the c6 position were tolerated, and corresponding products 5a–h were isolated in 59–88% yields after recrystallization. the reduced yield for compound 5d may be due to oxidation of the p-tolyl group with ddq [32]. on the other hand, all attempts to involve 3-pyridin-2-yl substituted 1,2,4-triazines in this reaction sequence were unsuccessful. in addition, using 3-phenyl-1,2,4-triaizine 2i also provided desired product 5i in good yield. it is well known that 1,2,4-triazines are readily accessible and cheap building block for construction of pyridine derivatives, which are used as functional materials [33]. at the same time, the annulation of an additional benzene cycle to the coumarin framework often improves the photophysical characteristics: it leads to a bathochromic shift of the absorption and emission maxima and can also increase the fluorescence quantum yield [34, 35]. scheme 6 synthesis of benzo[c]coumarin 5. thus, the obtained products may be considered as precursors for pyridyl-coumarin conjugate chromophores. further transformations and detailed photophysical studies are in progress and will be published later. 4. limitations we proposed the method of synthesis of 1,2,4-triazinyl substituted benzo[c]coumarins via double aromatization strategy. various 3,6-biaryl-1,2,4-triazines were involved in this transformation. however, in the case of 3-pyridinyl substituted 1,2,4-triaines, desired benzo[c]coumarin derivatives were not observed. in the course of our further research, we will attempt to overcome those limitations and develop a method of the oxidative cross-coupling 3-pyridin-2-yl 1,2,4-triazines with coumarins. 5. conclusion we proposed a new protocol of the synthesis of triazinylbenzo[c]coumarin derivatives by means of simultaneous oxidation dihydrotriazine and tetrahydrobenzene frameworks under the action of ddq as an oxidant. in contrast to ddq, oxidation in the presence of tcq exclusively provided the snh products. the obtained products could serve as precursors for push-pull pyridyl-coumarin conjugate chromophores for potential applications in material science. ● supplementary materials this manuscript contains supplementary materials, which are available on the corresponding online page. https://doi.org/10.15826/chimtech.2023.10.2.05 https://doi.org/10.15826/chimtech.2023.10.2.05 chimica techno acta 2023, vol. 10(2), no. 202310205 article 6 of 7 doi: 10.15826/chimtech.2023.10.2.05 ● funding this work was supported by the russian science foundation (grant no. 21-73-00214). ● acknowledgments none. ● author contributions conceptualization: r.f.f., i.a.k. data curation: r.f.f. formal analysis: a.d.s, e.s.s., a.p.p. funding acquisition: r.f.f. investigation: e.s.s., a.p.p. methodology: a.d.s, e.s.s., d.s.k. project administration: r.f.f. resources: a.d.s., a.p.p., d.s.k. software: r.f.f. supervision: o.n.c. validation: r.f.f., d.s.k. visualization: i.a.k. writing – original draft: r.f.f., i.a.k. writing – review & editing: r.f.f., i.a.k. ● conflict of interest the authors declare no conflict of interest. ● additional information author ids: ramil f. fatykhov, scopus id 57190761230; igor a. khalymbadzha, scopus id 18434200300; ainur d. sharapov, scopus id 57201740165; 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nio–ysz artem v. solovev a* , george n. starostin ab , inna a. zvonareva ab , stanislav s. tulenin a , vyacheslav f. markov ac a: ural federal university named after the first president of russia b. n. yeltsin, ekaterinburg 620002, russia b: institute of high temperature electrochemistry, ekaterinburg 620660, russia c: ural institute of the state fire service of the ministry of emergency situations of russia, ekaterinburg 620062, russia * corresponding author: tom1799@yandex.ru this paper belongs to a regular issue. © 2022, the authors. this article is published in open access under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). 1. introduction currently, there is an increased interest in the development of novel electrical energy storage and production facilities, in particular, power plants based on solid oxide fuel cells (sofc) [1, 2]. the advantages of such devices are the absence of harmful emissions and thermal pollution, higher efficiency, scalability, noiselessness in operation, and low energy consumption [3–5]. however, the mass production and use of solid oxide fuel cells are constrained by their high operating temperatures (1073–1273 к), at which the conductivity of the main component of the sofc – the oxygen–ion electrolyte – reaches a sufficient level. at high temperatures, degradation processes and chemical interactions among components in the membrane-electrode block of fuel cells are accelerated [6]. all this imposes strict requirements on the materials used, causes a high cost of sofcs, and significantly limits their further production [7]. application of a thin-film electrolyte based on zirconium dioxide stabilized with 3 to 10 mol.% of yttrium oxide is an effective solution to the problem of reducing the operating temperature of the sofc since decreasing the thickness of the electrolyte leads to a decrease in the internal resistance of the element and an increase in its power [8, 9]. one of the most rapidly expanding fields in electrochemistry right now is the development of fuel cells using a thin-film solid oxide electrolyte [10, 11]. the electrophoretic deposition (epd) of a solid electrolyte on the surface of the anode or cathode appears to be the most appealing among the potential techniques for producing such films because it is cost-effective and does not require complicated hardware design [12–14]. the cost of obtaining ceramic layers of ysz will be significantly reduced by using precursors from abstract solid oxide fuel cells are promising hydrogen energy devices. the goal of this research was to create ceramic layers for sofcs based on yttriastabilized zirconia (ysz) and to investigate their parameters. ysz ceramic layers with a thickness of 5.14 μm on a porous nio–ysz substrate and 7 μm on pyrolytic graphite were obtained by electrophoretic deposition. x-ray diffraction and electron microscopy were used to determine the composition, structure, and morphological features of ceramic layers. the effects of the substrate's nature, the degree of dispersion of the initial ysz powder, and the heat treatment conditions on the properties of the ceramic layer ysz were considered. keywords zirconium dioxide yttrium oxide hydrogen energy solid oxide fuel cell electrophoretic deposition ysz received: 05.11.22 revised: 01.12.22 accepted: 02.12.22 available online: 09.12.22 key findings ● ceramic layers based on zirconium dioxide stabilized with yttrium oxide were obtained by electrophoretic deposition. ● the thickness of the obtained ceramic layers was 5.14 μm on a porous nio–ysz anode substrate and 7 μm on pyrolytic graphite. ● the dependence of the epd process efficiency on the precursor dispersion degree was established. http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2022.9.4.25 mailto:tom1799@yandex.ru http://creativecommons.org/licenses/by/4.0/ https://orcid.org/0000-0003-0269-1119 https://orcid.org/0000-0001-9836-0896 https://orcid.org/0000-0002-9793-1375 https://orcid.org/0000-0003-3941-4748 https://orcid.org/0000-0003-0758-2958 https://crossmark.crossref.org/dialog/?doi=https://doi.org/10.15826/chimtech.2022.9.4.25&domain=pdf&date_stamp=2022-12-09 chimica techno acta 2022, vol. 9(4), no. 20229425 letter 2 of 6 domestic production, such as high-quality powder of the dci-1 brand with an affordable price and large volumes of industrial production. the epd method allows controlling the morphology and output parameters of the resulting ceramic coatings and obtaining layers with good adhesive properties and with a higher density compared to coatings obtained by other methods [15, 16]. the purpose of this research was to obtain ceramic layers of ysz and analyze their morphology and crystal structure. electrophoretic deposition was carried out on pyrolytic graphite and a porous nio–ysz anode substrate. 2. experimental the epd process includes three main stages. the first stage is the preparation of a stable suspension of the applied oxide material in a suitable liquid dispersion medium. the second one is the application of an electric field to the suspension, causing the movement of the particles to the electrode and their deposition on it. the last one is the drying and sintering of the resulting coating. 2.1. preparation of the suspension a 1:1 mixture of acetylacetone сн₃сосн₂сосн₃ (p.a.) and isopropanol ch₃ch(oh)ch₃ (puriss) was used as the starting reagent for the preparation of a stable suspension. as a polymer binder that prevents cracking, a bma-5 (butyl methacrylate-methacrylic acid copolymer, sri polymers, russia) copolymer was added to the prepared mixture, which was dissolved in the mixture for 48 h. commercial zirconium dioxide powder stabilized with yttrium oxide (zr0.97y0.03o2–δ) grade dci-1, (jsc chmp, russia), with an average particle size of 75 μm, was milled in a planetary mill, fritsch pulverisette 7, for 4 h at 500 rpm. grinding with zirconium dioxide balls was carried out in an acetone environment. during the grinding process, 4 samples of ysz powder were taken at an interval of 1 h. figure s1 shows the x-ray diffraction pattern of the commercial powder dci-1. then, a portion of the milled powder in the amount of 65 g·l–1 was added to the prepared dispersion medium and dispersed on a submersible ultrasonic disperser uzdn-a at an emitter frequency of 22 khz for 15 min. 2.2. used substrate material pyrolytic graphite and porous anode substrates based on nio–ysz with a nickel foil sublayer were used as substrate materials for electrophoretic deposition. a nickel substrate in the form of a foil with a thickness of 100 μm provided the conductive paths, since nio–ysz is a non-conductive substrate [17] (figure 1a). pyrolytic graphite substrates were obtained by chemical vapor deposition (cvd). the thickness of the substrates was 1 mm. the ohmic resistance of the material was 2±0.4 ω. graphite substrates were used to study the influence of the nature of the substrate material on the morphology of the ceramic coating. the multilayer joint rolling of films method was used to create porous anodic nio–ysz substrates (mass ratio of precursors nio:ysz:starch = 60:40:20). the thickness of nio–ysz was 0.87 mm. 2.3. electrophoretic deposition of ysz electrophoretic deposition was carried out at 298 k with a voltage of 60 v applied between the electrodes in two cycles of 10 minutes. the cathode and anode were fixed in a specially designed holder at a distance of 10 mm from each other and immersed in a reactor with a prepared suspension (figure 1b). pyrolytic graphite was used as a counter electrode. the resulting coatings underwent heat treatments at 973 k, 1173 k, and 1573 k for 2 h. x-ray phase analysis was performed on a rigaku d/max-2200vl diffractometer. the survey was conducted in cu kα radiation at 10° ≤ 2θ ≤ 90°. on a jeol jsm-5900 lv microscope, morphological characteristics of the obtained ysz layers were examined using scanning electron microscopy (sem). the measurer software was used to process the obtained sem data in order to establish the average particle size. figure 1 electric field distribution scheme on the nio–ysz surface (a), where 1 – nickel foil, 2 – porous anode substrate based on nio– ysz, 3 – electric field lines, 4 – charged ceramic ysz particles. schematic diagram of an installation for electrophoretic deposition (b), where 1 – reactor, 2 – counter electrode, 3 – porous anode substrate based on nio–ysz, 4 – suspension, 5 – electric current source. chimica techno acta 2022, vol. 9(4), no. 20229425 letter 3 of 6 3. results and discussion one of the main aspects of obtaining a high-quality coating in the epd process is the presence of a stable dispersion of ysz. the formation of a dense, well-anchored coating is possible only if the epd proceeds in sedimentationally and aggregatively stable suspensions [18–20]. the stability of the suspension is influenced by the choice of the dispersion medium and the ratio of the initial components. according to [21–24], it is preferable to carry out electrophoretic deposition in non-aqueous organic media, as alcohols, ketones, and their mixtures are most often used. when conducting epd in aqueous media, electrochemical reactions occur that are accompanied by the release of gasses that significantly affect the process [25]. for this reason, an anhydrous dispersion medium consisting of acetylacetone and isopropanol has proven itself in the best way. this is due to the fact that isopropanol is less hygroscopic than ethanol, which ensures the stability of the physicochemical characteristics of the suspension. acetylacetone contains the carbonyl group, which is capable of donor-acceptor interaction with the surface of the oxides [26]. indeed, the stability of such suspensions, according to light transmission data at wavelengths of 540, 800, and 1000 nm, was at least 50 h. the spectral methods, in particular, spectrophotometry, quite accurately indicate the beginning of the sedimentation process in the suspension volume, which is caused by the aggregation and coagulation of particles over time. the gradual removal of small particles from the suspension leads to an increase in transmission at the beginning at small wavelengths, with the gradual settling of large particles at large wavelengths. figure 2a shows a plot of the stability of the suspension over time. an important condition for successful epd is the size of the ysz particles in the suspension and the absence of aggregation of these particles in the dispersion medium. it is worth noting that with a size of less than 1 μm, particles can remain in suspension for a long time due to brownian motion [27]. also, for a positive result in conducting epd, it is necessary that the ysz powder has a narrow particle size distribution. to achieve this, grinding in planetary mills and ultrasonic dispersion are used. according to the results, an increase in the powder grinding time leads to a decrease in the average particle size from 4 μm to 0.9 μm with a single-modal distribution (figure 2b). the percentage of particles with a size of from 2.5 to 7.5 μm after 1 h of grinding was 84%, but after 4 h of grinding, 90% of particles were from 0.5 to 2 μm (figure 2c). after dispersing the ground ceramic particles from their suspensions by the epd method, ysz-based layers with a thickness of up to 7 μm on pyrolytic graphite were successfully obtained. however, the high-quality coatings without cracks and with a small particle size distribution were obtained from suspensions containing powder ground in a planetary mill for 4 h on nio–ysz substrates up to 5.14 μm thick. the x-ray phase analysis showed that the formed ceramic coating consists of two phases: zirconium dioxide stabilized with yttrium oxide in an amount of 3 mol.% (95.68%) and zirconium dioxide in an amount of 4.32%, which is apparently due to the presence of residual zro2 in the initial commercial powder dci-1. figure 3 shows the x-ray diffraction pattern of the ysz sample deposited on a porous nio-ysz anode substrate. according to the xrd data, zirconium dioxide, stabilized by 3 mol.% yttrium oxide, has a tetragonal structure with crystal lattice parameters a = 3.6249(3) å, c = 5.1275(1) å with a predominant growth direction (101). the phase of individual zirconium dioxide has a cubic lattice with a parameter a = 5.1522(1) å and a predominant growth direction (111). figure 2 dependence of the light transmission of the suspension on time, at wavelength (a), nm: 540 (1), 800 (2), 1000 (3). average ysz particle sizes with grinding time (b), in h: 1, 2, 3, 4. a histogram of the distribution of ysz particles by size. the grinding time of the precursor was 4 h (c). chimica techno acta 2022, vol. 9(4), no. 20229425 letter 4 of 6 pyrolytic graphite and a porous anode substrate nio– ysz with a nickel foil sublayer were used as the substrates for the deposition of ysz in order to study the impact of the substrate material on the coating structure. it was possible to create a uniform coating made of zirconium dioxide with a thickness of up to 7 μm thanks to the higher conductivity of graphite substrates. after drying for 24 h at room temperature, the ceramic layer was fixed and free of visible cracks. however, following heat treatment at temperatures between 973 and 1173 k, the ysz layer peeled off the substrate material and microcracks as large as 3 μm in width appeared. this phenomenon can be attributed to significant variations in the thermal expansion coefficients of graphite and ysz [28]. in addition, thin layers of graphite deform at high temperatures, and the graphite substrate collapses, which leads to direct deformation and cracking of the deposited layer of zirconium dioxide stabilized with yttrium oxide on this substrate material. deposition of ysz on porous anode substrates based on nio–ysz gave different results. the high porosity of the material allowed ysz particles to penetrate into the nearsurface layer during electrophoretic deposition and fix themselves on the substrate. the surface of the ceramic ysz layer that was deposited on a non-conductive nio–ysz coating is depicted in the sem image in figure 4a. since in the course of thermal studies it was found that the temperature of 1173 k is not sufficient for sintering the deposited layer consisting mainly of irregularly shaped particles, due to the higher melting point of the nio–ysz anode substrate [29], the ysz functional layers were annealed at a temperature of 1573 k for 2 h. figures 4b and 4c show sem images of the surface of the ceramic layer and the end part of the ysz layer on the nio–ysz substrate after heat treatment. the resulting layer had a thickness of 5.14 μm. the ysz particles can be seen to have started to sinter with one another, losing the distinct grain boundaries, and there is also no evidence of the particle aggregation that was seen during the deposition on graphite. 4. conclusions in this work, ysz suspensions based on an isopropanol, acetylacetone, and bma-5 copolymer mixture were successfully produced. it was discovered that as the initial ysz powder was ground for longer periods of time, the suspensions became more stable as the average particle size decreased from 4 to 0.9 μm and the quality of the ceramic coatings that were deposited improved. the prepared suspension's stability time exceeded 50 h. by using the epd method, ceramic layers on nio–ysz and pyrolytic graphite substrates were successfully produced. the obtained ysz layers have the crystal lattice parameters a = 3.6249(3) å, c = 5.1275(1) å and are composed of tetragonal zirconium dioxide stabilized by 3 mol.% yttrium oxide. figure 3 x-ray diffraction pattern of the ysz layer deposited on a porous nio–ysz anode substrate. figure 4 sem images of the obtained ysz layer on a ni–ysz substrate before (a) and after heat treatment at 1573 k (b). sem image of the end of the ysz layer; the heat treatment temperature was 1573 k (c). chimica techno acta 2022, vol. 9(4), no. 20229425 letter 5 of 6 it was determined that the epd of ysz undergoes successfully on a porous nio–ysz anode substrate with a nickel foil sublayer, ensuring that the deposited layers of ysz are up to 5.14 μm thick. the thickness of the ysz layers obtained on graphite was 7 μm. the epd method can be used to apply ceramic layers on non-conductive substrates by using a nickel plate as a sublayer of nio–ysz. the use of epd and inexpensive commercial powders greatly simplifies and reduces the cost of the process of obtaining ceramic coatings, which allows better integration into the green energy agenda. supplementary materials this manuscript contains supplementary materials, which are available on a corresponding online page. funding the research funding from the ministry of science and higher education of the russian federation (ural federal university project within the priority-2030 program) is gratefully acknowledged. acknowledgments none. author contributions conceptualization: v.f.m. data curation: a.v.s., s.s.t. formal analysis: a.v.s., s.s.t. funding acquisition: a.v.s. investigation: g.n.s., i.a.z. methodology: a.v.s., s.s.t. project administration: v.f.m. resources: a.v.s. software: a.v.s., g.n.s., i.a.z. supervision: s.s.t., v.f.m. validation: s.s.t. visualization: a.v.s. writing – original draft: a.v.s. writing – review & editing: s.s.t., v.f.m. conflict of interest the authors declare no conflict of interest. additional information author ids: george n. starostin, scopus id 57882347600; inna a. zvonareva, scopus id 57209229327; stanislav s. tulenin, scopus id 55189942200; vyacheslav f. markov, scopus id 7201577312. websites: ural federal university, https://urfu.ru/ru; institute of high temperature electrochemistry, http://www.ihte.uran.ru ural institute of the state fire service of the ministry of 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мира, 19. e-mail: tasika06@mail.ru. 2нанкайский университет, 94 вейджин роуд, 300071 тяньцзинь, китай синтез и исследование цис-транс-изомерии 5-(4-метоксибензоил)-6-(4-метоксифенил)6,7-дигидро-5h-[1,2,3]триазоло[5,1-b][1,3,4] тиадиазина* показано, что при взаимодействии 1,2,3-тиадиазолилгидразона 4-метоксибензальдегида с α-бром-4-метоксиацетофеноном в присутствии триэтиламина образуется 5-(4-метоксибензоил)-6-(4-метоксифенил)-6,7-дигидро-5h-[1,2,3]триазоло[5,1-b][1,3,4]тиадиазин в виде смеси циси транс-стереоизомеров. первой стадией процесса явлется перегруппировка димрота. строение продуктов реакции доказано спектроскопией ямр. в спектрах ямр 1н, снятых в разных растворителях (c 6 d 6 , cdcl 3 , cd 3 соcd 3 , dmso-d6), наблюдались два набора сигналов, соответствующие транси цис-стереоизомерам. во всех растворителях преобладал транс-стереоизомер. исследовано влияние на соотношение изомеров природы растворителя и температуры. выявлено увеличение относительного количества трансстереоизомера с увеличением полярности растворителя. показано, что температура слабо влияет на соотношение изомеров. у д к 6 61 .7 7+ 54 7. 79 © калинина т. а., быстрых о. а., шахмина ю. с., глухарева т. в., fan zh. j., моржерин ю. ю., 2014 46 cta | № 2 | 2014 результаты и обсуждение в продолжении наших исследований по изучению перегруппировок и трансформаций производных 5-гидразино1,2,3-тиадиазолов нами была проведена реация 1,2,3-тиадиазолилгидразона 4-метокси-бензальдегида с α-бром-4метоксиацетофеноном в присутствии триэтиламина при нагревании в этаноле. в результате реакции мы ожидали получить 3-меркапто-1,2,3-триазол 2 [4], продукт перегруппировки димрота и реакции алкилирования α-бромацетофеноном исходного тиадиазола 1, либо 5h-[1,2,3]триазоло[5,1-b] [1,3,4]тиадиазин 3, образующийся в результате последующей внутримолекулярной циклоконденсации соединения 2 [5]. при анализе спектральных данных было установлено, что в данных условиях реакции образуется [1,2,3] триазоло[5,1-b][1,3,4]тиадиазин 3. в спектрах ямр 1н, снятых в разных растворителях (c6d6,cdcl3, cd3соcd3, dmso-d6), наблюдались два набора сигналов, соответствующие транси цис-стереоизомерам. во всех растворителях преобладал транс-стереоизомер (табл. 1). при этом в более полярных растворителях его относительное количество увеличивалось. было также показано, что температура практически не влияет на соотношение изомеров. следует отметить, что при попытке провести данную реакцию в сухом ацетонитриле в присутствии k2co3 была получена трудноразделимая смесь продуктов. экспериментальная часть cпектры ямр 1h и 13с получены на приборе bruker drx-400 (400 мгц для 1h, 100 мгц для 13с), внутренний стандарт – тмс. общая методика получения этилового эфира (3): 0,2 г (1 ммоль) гидразона 1 и 0,25 мл (1,8 ммоль) триэтиламина в абсолютном спирте (10 мл) нагревают 30 минут до полного растворения. затем добавляют α-бром-4метоксиацетофенон 0,230 г (1 ммоль). реакцию проводят при интенсивном перемешивании и нагревании до 45– 50 °с в течение 6 ч. растворитель отгоняют под вакуумом. остаток чистят колоночной хроматографией, элюент этилацетат-гексан 1:1. выход 0,103 г (62 %), тпл = 190 °с. найдено (%): c, 58.16; h, 4.85; n, 12.34; s, 7.07. c22h22n4o5s. вычислено (%): с, 58.14; h, 4.88; n, 12.33; s, 7.05. 1) растворитель cdcl3. соотношение транс-изомера к цис-изомеру – 3.3:1. спектр ямр 1н (400 гц, cdcl3), δ, м.д. (j, гц): транс-изомер: 7.87 (2h, д, j = 8.9, arh); 7.24 (2h, д, j = 8.7, arh); 7.03 (1h, д, j = 3.5, nh); 6.91 (2h, д, j = = 8.9, arh); 6.75 (2h, д, j = 8.7, arh); 5.21 (1h, дд, j = 3.4, j = 3.5, c-(6) т. а. калинина, о. а. быстрых, ю. с. шахмина, т. в. глухарева, zh. j. fan, ю. ю. моржерин 47 2014 | № 2 | cta синтез и исследование цис-транс-изомерии 5-(4-метоксибензоил)-6 (4-метоксифенил)-6,7-дигидро-5h-[1,2,3]триазоло[5,1-b][1,3,4]тиадиазина таблица 1 соотношение изомеров в спектрах ямр 1н, снятых в разных растворителях при разных температурах растворитель температура, °с отн. полярность растворителя, еt отн. кол-во, цис-изомера отн. кол-во, транс-изомера c6d6 25 0,111 1.0 1.6 cdcl3 25 0,259 1.0 3.3 cdcl3 50 0,259 1.0 3.3 cd3соcd3 25 0,355 1.0 2.9 dmso-d6 27 0,444 1.0 3.8 dmso-d6 50 0,444 1.0 3.7 dmso-d6 90 0,444 1.0 3.8 h); 5.08 (1h, д, j = 3.4, c-(5)h); 4.24 (2h, к, j = 8.0, och2ch3); 3.83 (3н, с, och3); 3.69 (3н, с, och3); 1.27 (3h, т, j= 8.0, och2ch3). цис-изомер: 7.70 (2h, д, j = 8.9, arh); 7.20 (2h, д, j = 11.9, nh); 7.18 (2h, д, j = 8.72, arh); 6.84 (2h, д, j = 8.9, arh); 6.76 (2h, д, j = 8.7, arh); 4.91 (1h, д, j = 2.3, c-(5)h); 4.65 (1h, дд, j = 11.9, j = 2.3, c-(6)h); 4.37-4.31 (2h, к, j = 7.1, och2ch3); 3.80 (3н, с, och3); 3.69 (3н, с, och3); 1.32 (3h, т, j = 7.1, och2ch3). спектр ямр 13с (100 гц, cdcl3): 193.78; 164.84; 159.71; 131.07; 130.78; 127.82; 127.68; 127.38; 126.91; 114.44; 114.33; 61.03; 56.78; 55.53; 55.11; 38.80; 35.07; 14.25; 14.19. 2) растворитель dmso-d6. соотношение транс-изомера к цис-изомеру – 3.8:1. рис. 1. спектры ямр 1н соединения 4, снятые в различных растворителях и при различных температурах: а – cdcl3 при 50 °с; б – c6d6; в – cd3cocd 3; г – dmso-d6 при 28 °с 48 cta | № 2 | 2014 спектр ямр 1н (400 гц, dmsod6), δ, м.д. (j, гц): транс-изомер: 8.00 (2h, д, j = 8.9, arh); 7.89 (1h, д, j = 6.5, nh); 7.37 (2h, д, j = 8.7, arh); 7.01 (2h, д, j = 8.9, arh); 6.82 (2h, д, j = 8.7, arh); 5.53 (1h, д, j = 6.2, c-(5)h); 4.88 (1h, д, j = 6.2, j = 6.5, c-(5)h); 4.28 (2h, к, j = 7.1, och2ch3); 3.89 (3н, с, och3); 3.73 (3н, с, och3); 1.34 (3h, т, j = 7.1, och2ch3). цис-изомер: 7,91 (1h, д, j = 10.0, nh); 7.88 (1h, д, j = 9.0, arh); 7.23 (2h, д, j = 8.8, arh); 6.94 (2h, д, j = 9.0, arh); 6.76 (2h, д, j = 8.8, arh); 5.60 (1h, д, j = 2.6, c-(5)h); 4.99 (1h, д, j = 2.6, j = 10.0, c-(6)h); 4.37-4.30 (2h, дк, j = 7.1, j = 3.7, och2ch3); 3.86 (3н, с, och3); 3.71 (3н, с, och3); 1.38 (3h, т, j = 7.1, och2ch3). 3) растворитель сd3сoсd3. соотношение транс-изомера к цис-изомеру – 2.9:1. спектр ямр 1н (400 гц, сd3сoсd3), δ, м.д. (j, гц): транс-изомер: 8.14 (2h, д, j = 9.0, arh); 7.56 (1h, д, j = 5.20, nh); 7.48 (2h, д, j = 8.8, arh); 7.10 (2h, д, j = 9.0, arh); 6.88 (2h, д, j = 8.8, arh); 5.65 (1h, д, j = 4.5, c-(5)h); 5.29 (1h, дд, j = 4.5, j = 5.2, c-(6)h); 4.27 (2h, к, j = 7.1, och2ch3); 3.83 (3н, с, och3); 3.93 (3н, с, och3); 3.75 (3н, с, och3); 1.28 (3h, т, j = 7.1, och2ch3). цис-изомер: 7.95 (2h, д, j = 9.0, arh); 7.52 (1h, д, j = 10.3, nh); 7.43 (2h, д, j = 8.6, arh); 7.01 (2h, д, j = 9.0, arh); 6.88 (2h, д, j = 8.6, arh); 5.06 (1h, д, j = 2.5, c-(5)h); 4.99 (1h, дд, j = 2.5, j = 10.3, c-(6)h); 4.37-4.30 (2h, дк, j = 7.1, j = 3.7, och2ch3); 3.89 (3н, с, och3); 3.74 (3н, с, och3); 1.33 (3h, т, j = 7.1, och2ch3). 4) растворитель с6d6. соотношение транс-изомера к цис-изомеру – 1.6:1. спектр ямр 1н (400 гц, с6d6), δ, м.д. (j, гц): транс-изомер: 7.72 (2h, д, j = 9.0, arh); 6.70 (1h, д, j = 4.6, nh); 6.62 (2h, д, j = 8.8, arh); 6.58 (2h, д, j = 9.0, arh); 6.56 (2h, д, j = 8.8, arh); 5.67 (1h, т, j = 4.6, c-(5)h); 5.31 (1h, дд, j = 4.6, j = 4.6, c-(6)h); 4.07-4.14 (2h, дк, j = 7.1, j = 1.4, och2ch3); 3.19 (3н, с, och3); 3.18 (3н, с, och3); 0.95 (3h, т, j = 7.1, och2ch3). цис-изомер: 7.46 (2h, д, j = 9.0, arh); 7.29 (1h, д, j = 11.7, nh); 7.17 (2h, д, j = 8.6, arh); 6.99 (2h, д, j = 8.6, arh); 6.46 (2h, д, j = 9.0, arh); 5.62 (1h, д, j = 2.5, c-(5)h); 5.01 (1h, дд, j = 2.5, j = 11.64,c-(6)h); 4.18-4.13 (2h, дк, j = 7.1, j = 2.6, och2ch3); 3.16 (3н, с, och3); 3.11 (3н, с, och3); 1.05 (3h, т, j = 7.1, och2ch3). 1. l’abbe. g., vanderstede, e. j. het. chem., 1989, 26, 1811. 2. kalinina t. a., prokhorova p. e., glukhareva t. v., morzherin yu. yu. russ. chem. bull. 2011, 60, 981. 3. morzherin yu. yu., glukhareva t. v., slepukhina i. n., mokrushin v. s., tkachev a. v., bakulev v. a. mend. comm., 2000, 10, 19. 4. morzherin yu. yu., glukhareva t. v., bakulev v. a. chem. heterocycl. compds, 2003, 39, 679. 5. al-etaibi a., john e., ibrahim m. r., al-awadi n. a., ibrahim y. a. tetrahedron, 2011, 67, 6259. т. а. калинина, о. а. быстрых, ю. с. шахмина, т. в. глухарева, zh. j. fan, ю. ю. моржерин 49 2014 | № 2 | cta синтез и исследование цис-транс-изомерии 5-(4-метоксибензоил)-6 (4-метоксифенил)-6,7-дигидро-5h-[1,2,3]триазоло[5,1-b][1,3,4]тиадиазина t. a. kalinina1, o. a. bystrykh1, ju. s. shakhmina1, t. v. glukhareva1, zh.-j. fan2, yu. yu. morzherin1 1 ural federal university, 19, mira street, 620002, ekaterinburg. e-mail: tasika06@mail.ru. 2nankai university, 94 weijin road, 300071, tianjin, china synthesis and research of cis-trans isomerism for 5-(4-methoxybenzoyl)-6-(4-metoxyphenyl)-6,7-dihydro5h-[1,2,3]triazolo[5,1-b][1,3,4]thiadiazine it was shown that the reaction of 1,2,3-4-methoxybenzaldehyde thiadiazolyl hydrazone and α-bromo-4-methoxyacetophenone in the presence of triethylamine allowes 5-(4-methoxybenzoyl)-6-(4-methoxyphenyl)-6,7-dihydro-5h-[1,2,3]triazolo[5,1-b] [1,3,4]thiadiazine as a mixture of cisand trans-stereoisomers. the influence of nature of the solvent and temperature on the ratio of isomers was studied. an increase of the relative amount of the trans-stereoisomer with increasing polarity of the solvent is disclosed. it is noted that the temperature does not affect the ratio of isomers. the first step of the process is the dimroth rearrangement. revealed an increase in the relative amounts of trans stereoisomer with increasing polarity of the solvent. it is shown that the temperature has little effect on the ratio of the isomers. страница 1 synthesis, computational study, solvatochromism and biological studies of thiazoles-hydrazones derivatives published by ural federal university eissn 2411-1414 chimicatechnoacta.ru article 2023, vol. 10(1), no. 202310110 doi: 10.15826/chimtech.2023.10.1.10 1 of 13 synthesis, computational study, solvatochromism and biological studies of thiazole-owing hydrazone derivatives c. kiran yadav a, b.p. nandeshwarappa a * , k.m. mussuvir pasha b a: department of studies in chemistry, shivagangotri, davangere university, davanagere, karnataka 577007, india b: department of p.g. studies and research in chemistry/industrial chemistry, vijayanagara sri krishnadevaraya university, ballari 583105, karnataka, india * corresponding author: belakatte@gmail.com this paper belongs to a regular issue. abstract in the present work, we have synthesized thiazole-hydrazone conjugates 5(a–h) and characterized them using various analytical techniques such as uv, ir, nmr, and mass spectrometry. solvatochromic properties were evaluated in ten solvents with different polarity and quantum chemical parameters using a dft study. the antibacterial activity results revealed that compounds 5c, 5d and 5g exhibited good efficacy and that the remaining compounds displayed significant activity. the synthesized compounds were screened for their cytotoxic activity against hepg2 and mcf-7 cell lines, and all the synthesized compounds exhibited significant potency towards the screened cancer cell lines. the anti-inflammatory efficacy of the synthesized thiazole derivatives was determined against mmp-2 and mmp-9, and some of the compounds showed significant activity. furthermore, the in silico molecular docking was performed with the cox-2 receptor. keywords biological activity dft solvatochromic study thiazole-hydrazone conjugates received: 18.01.23 revised: 05.02.23 accepted: 10.02.23 available online: 20.02.23 key findings ● thiazole-hydrazone conjugates were synthesized. biological efficacy of the synthesized compounds was determined. ● solvatochromic properties were evaluated in ten different solvents. structures were characterized by using various analytical techniques. ● quantum chemical parameters were evaluated using a dft study. © 2023, the authors. this article is published in open access under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). 1. introduction heterocyclic compounds are important for medicinal chemistry because they serve as key building blocks for active pharmaceutical ingredients. compounds with heterocyclic ring systems are extremely useful in both medicine and material science [1–5]. thiazoles, for example, are five-membered ring heterocycles with three carbon atoms, one nitrogen atom, and one sulfur atom. these heterocycles are of great interest in medicinal and pesticide chemistry, as well as polymer and material science [6]. thiazoles are one of the most important classes of heterocyclic moieties which possess a wide range of therapeutic and pharmacological applications. compounds containing thiazole ring have chemotherapeutic, fungicidal, and pesticidal properties [7– 11]. thiazole derivatives have broad biological activities such as antimicrobial [12], anti-inflammatory [13], antitubercular [14], antihypertensive [15], anticancer [16], and analgesic [17]. natural compounds such as thiamine, thiamine pyrophosphate, bacitracin, penicillin antibiotics, and most of the drugs contain thiazole moiety. from the recent literature survey, thiazole and its derivatives were used as antimicrobial additives in polyurethane coating, and their corrosion behavior was also investigated [18, 19]. an asymmetric thiazole core exhibits fascinating behavior such as nonlinear optical properties and ferroelectricity with a lateral π-conjugated system [20]. thiazole-based fluorophores are used as blue light-emitting polymers in organic light-emitting diodes (oleds); thiazoles are also used in dye synthesized solar cells [21]. hydrazones and their derivatives are organic compounds with a wide range of applications. the biological properties of these compounds are intriguing. hydrazones are useful as potential ligands for metal complexes, organocatalysis, and the synthesis of heterocyclic http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2023.10.1.10 mailto:belakatte@gmail.com http://creativecommons.org/licenses/by/4.0/ https://orcid.org/0000-0003-0559-7240 https://crossmark.crossref.org/dialog/?doi=https://doi.org/10.15826/chimtech.2023.10.1.10&domain=pdf&date_stamp=2023-02-20 https://journals.urfu.ru/index.php/chimtech/rt/suppfiles/6537/0 chimica techno acta 2023, vol. 10(1), no. 202310110 article 2 of 13 doi: 10.15826/chimtech.2023.10.1.10 compounds [22–25]. the complex study of hydrazones has piqued interest due to their biological activity and potential as enzyme inhibitors. hydrazones' rings are crucial in determining the magnitude of their pharmacological properties [26, 27]. hydrazones can act as neutral or anionic ligands for metal ions, resulting in stable metal complexes. these hydrazones have revealed themselves to be important optical phenomena materials [28]. 2. experimental details 2.1. materials and methods all the chemicals and solvents were purchased from sigmaaldrich and spectrochem. the ft-ir spectra were recorded on a perkin elmer spectrometer (spectrum 100). the electronic absorption spectra were recorded on a shimadzu spectrophotometer (uv-1800). the 1h nmr and 13c nmr spectra were recorded with the aid of an agilent nmr at 400 mhz and 100 mhz, respectively. the hr-ms spectra were recorded on a sciex api 3200 mass spectrometer. melting points were determined in open capillary and are uncorrected. silica-gel gf-254 was used for thin-layer chromatography (tlc). purity of the compounds was checked by tlc on silica gel. all extracted solvents were dried with anhydrous na2so4 and evaporated with a buchi rotary evaporator. 2.2. computational studies all computational calculations were performed using the gaussian 09 software [29], and b3lyp was used for the dft calculations with a 6-31g (d, p) basis set [30, 31]. output files of the gaussian software were visualized by using gaussview 05 [32]. mep and rdg calculations were done using multiwfn 3.7 [32] and visualized using visual molecular dynamics (vmd) software [33]. 2.3. general procedure for the synthesis of thiazole hydrazones 5(a–h) 2.3.1. step 1: synthesis of thiosemicarbazones 3(a–h) 2 mmol of various carbonyl compounds 1(a–h) and 2 mmol of thiosemicarbazide 2 were taken in 10 ml of ethanol and stirred with reflux at 70–80 °c in oil bath for about 1–2 hrs, employing 2–3 drops of acoh catalyst. after the complete formation of the product identified by tlc (mobile phase: n-hexane:ethyl acetate 8:2), the obtained solid was filtered, washed with ethanol, dried and recrystallised using ethanol solvent. 2.3.2. step 2: synthesis of thiazole hydrazones 5(a–h) 1 mmol of the obtained thiosemicarbazones 3(a–h) from step 1, and phenacyl bromide(1 mmol) were taken together in 50 ml rb; to that, 10–15 ml of isopropanol was added, and the mixture was stirred at room temperature for about 2–3 hrs. the formation of the product was monitored by tlc (mobile phase: n-hexane:ethyl acetate 8:2). after the completion of the reaction, the obtained colorant was filtered, dried, and recrystallized using ethanol. 2.3.3. 2-{(2e)-2-[4-fluoro-3-(trifluoromethyl)benzylidene]hydrazinyl}-4-phenyl-1,3-thiazole (5a) c17h11f4n3s, m.p: 187–189 °c. ft-ir (kbr) νmax: 3066 (n– h), 1582 (c=n), 1484 (c=n), 1278 (c–f), 709 (c–s). 1h nmr (400 mhz, dmso-d6) δ in ppm 7.31 (t, 1h, arh, j = 7.6 hz), 7.36 (s, 1h, arh), 7.41 (d, 2h, arh, j = 8 hz), 7.58 (t, 1h, arh, j = 8 hz), 7.85 (d, 2h, arh, j = 8 hz), 8.04 (t, 2h, arh, j = 8 hz), 8.11 (s, 1h, arh), 12.40 (s, 1h, n–nh). 13c nmr (100 mhz, dmso-d6): δ 103.97, 117.81, 121.10, 123.80, 124.65, 125.51, 127.56, 128.59, 131.77, 132.29, 134.57, 138.43, 150.61, 157.60, 160.14, 168.01. hrms: m/z = 365.8 [m+]. anal. calcd (%): c (55.89%), h (3.03%), n (11.50%), found: c (55.35), h (2.98), n (11.12). 2.3.4. 2-[(2e)-2-(2,6-dibromobenzylidene)hydrazinyl]4-phenyl-1,3-thiazole (5b) c16h11br2n3s, m.p: 192–193 °c. ft-ir (kbr) νmax: 3317 (n–h), 1633 (c=n), 1546 (c=n), 725 (c–s), 608 (c– br). 1h nmr (400mhz, dmso-d6) δ in ppm 7.23 (t, 1h, arh, j = 8 hz), 7.33 (t, 2h, arh, j = 7.2hz), 7.41 (t, 2h, arh, j = 8 hz), 7.81 (d, 2h, arh, j = 8 hz), 7.86 (t, 2h, arh, j = 7.6 hz), 8.15 (s, 1h, arh), 12.30 (s, 1h, n–nh). 13c nmr (100 mhz, dmso-d6): δ 104.31, 123.20, 125.65, 127.76, 127.91, 128.37, 128.62, 131.33, 132.74, 133.09, 134.16, 139.70, 149.83, 168.16. hrms: m/z = 436.0 [m-1]. anal. calcd (%): c (43.96%), h (2.54%), n (9.61%), found: c (43.45), h (2.24), n (9.27). 2.3.5. 4-{(e)-[2-(4-phenyl-1,3-thiazol-2-yl)hydrazinylidene]methyl}benzaldehyde (5c) c17h13n3os, m.p: 171–173 °c. ft-ir (kbr) νmax: 3299 (n– h), 1689 (c=n), 1569 (c=n), 712 (c–s). 1h nmr (400mhz, dmso-d6) δ in ppm 7.1 (s, 1h, arh), 7.26 (m, 2h arh, j = 7.2 hz), 7.38 (m, 2h, arh, j = 8 hz), 7.72 (s, 1h, arh), 7.75 (m, 1h, arh, j = 8 hz), 7.83 (m, 3h, arh, j = 4 hz), 8.03 (s, 1h, arh), 9.94 (s, 1h, –cho). 13c nmr (100 mhz, dmso-d6): δ 38.87, 40.12, 104.11, 125.68, 126.77, 128.03, 128.79, 130.20, 134.78, 135.22, 139.44, 140.83, 150.72, 168.42, 192.63. hrms: m/z = 308.1 [m+1]. anal. calcd (%): c (66.43%), h (4.26%), n (13.67%), found: c (66.12), h (4.06), n (13.16). 2.3.6. 2-{(2e)-2-[4-(methylsulfanyl)benzylidene]hydrazinyl}-4-phenyl-1,3-thiazole (5d) c17h15n3s2, m.p: 189–191 °c. ft-ir (kbr) νmax: 3054 (n– h), 1595 (c=n), 1494 (c=n), 712 (c–s). 1h nmr (400mhz, dmso-d6) δ in ppm: 2.50 (t, 3h,–ch3), 7.30 (t, 4h, arh, j = 1.2 hz), 7.41 (t, 2h, arh, j = 8 hz), 7.60 (d, 2h, arh, j = 4.4 hz), 7.86 (d, 2h, arh, j = 7.2 hz), 7.99 (s, 1h, arh), 12.01 (s, 1h, n–nh). 13c nmr (100 mhz, dmso-d6): δ 14.35, 40.12, 103.54, 125.48, 126.64, 127.46, 128.56, 130.90, 134.62, 139.82, 140.89, 150.43, 168.16. hrms: m/z =anal. calcd (%): c (62.74%), h (4.65%), n (12.91%), found: c (62.41), h (4.35), n (12.62). https://doi.org/10.15826/chimtech.2023.10.1.10 chimica techno acta 2023, vol. 10(1), no. 202310110 article 3 of 13 doi: 10.15826/chimtech.2023.10.1.10 2.3.7. 2-{2-[1-(furan-2-yl)ethylidene]hydrazinyl}-4phenyl-1,3-thiazole (5e) c15h13n3os, m.p: 135–136 °c. ft-ir (kbr) νmax: 3088 (n– h), 1612 (c=n), 1496 (c=n), 719(c–s). 1h nmr (400 mhz, dmso-d6) δ in ppm 2.25 (s, 3h, –ch3), 6.58 (m, 2h, arh, j = 1.6 hz), 6.84 (d, 1h, arh, j = 3.2 hz), 7.31 (d, 2h, arh, j = 5.6 hz), 7.41 (t, 2h, arh, j = 8 hz), 7.77 (d, 1h, arh, j = 1.2 hz), 7.88 (t, 2h, arh, j = 7.2 hz), 11.30 (s, 1h, n–nh). 13c nmr (100 mhz, dmso-d6): δ 13.85, 40.12, 104.17, 110.17, 111.89, 125.59, 127.68, 128.06, 128.64, 134.18, 139.66, 144.13, 151.66, 169.41. hrms: m/z = 283.80 [m+]. anal. calcd (%): c (63.58%), h (4.62%), n (14.83%), found: c (63.37), h (4.28), n (14.57). 2.3.8. 4-phenyl-2-[(2e)-2-(1-phenylpropylidene)hydrazinyl]-1,3-thiazole (5f) c18h17n3s, m.p: 159–160 °c. ft-ir (kbr) νmax: 3062 (n– h), 1617 (c=n), 1494 (c=n), 769 (c–s). 1h nmr (400 mhz, dmso-d6) δ in ppm 1.09 (t, 3h, –ch3), 2.88 (m, 2h, –ch2), 7.32 (d, 2h, arh, j = 7.2 hz), 7.42 (m, 5h, arh, j = 7.6 hz), 7.80 (d, 2h, arh, j = 7.2 hz), 7.89 (d, 2h, arh, j = 7.2 hz), 11.30 (s, 1h, n– nh). 13c nmr (100 mhz, dmso-d6): δ 8.08, 19.74, 31.20, 104.15, 125.59, 127.48, 128.11, 128.53, 128.65, 128.73, 129.03, 130.54, 132.96, 133.62, 136.35, 136.59, 168.63, 169.83. hrms: m/z = 309.10 [m+2]. anal. calcd (%): c (70.33%), h (5.57%), n (13.67%), found: c (70.10), h (5.38), n (13.52). 2.3.9. 2-{(2e)-2-[1-(4-ethylphenyl)ethylidene]hydrazinyl}-4-phenyl-1,3-thiazole (5g) c19h19n3s, m.p: 201–203 °c. ft-ir (kbr) νmax: 3061 (n– h), 1614 (c=n), 1508 (c=n), 717 (c–s). 1h nmr (400 mhz, dmso-d6) δ in ppm 1.19 (m, 3h, –ch3), 2.32 (s, 3h, –ch3), 2.65 (m, 2h, –ch2), 7.27 (t, 2h, arh, j = 8 hz), 7.32 (m, 2h, arh, j = 5.2 hz), 7.42 (t, 2h, arh, j = 8 hz), 7.70 (m, 2h, arh, j = 6 hz), 7.89 (d, 2h, arh, j = 7.2 hz), 11.10 (s, 1h, n–nh). 13c nmr (100 mhz, dmso-d6): δ 14.61, 15.87, 39.30, 104.57, 126.27, 128.23, 128.77, 129.06, 134.44, 135.67, 145.16, 157.98, 170.28, 189.43, 215.73. hrms: m/z = 321.80 [m+]. anal. calcd (%): c (70.99%), h (5.96%), n (13.07%), found: c (70.84), h (5.81), n (12.96). 2.3.10. 2-{(2e)-2-[1-(1,3-benzodioxol-5-yl)ethylidene]hydrazinyl}-4-phenyl-1,3-thiazole (5h) c18h15n3o2s, m.p: 123–124 °c. ft-ir (kbr) νmax: 3022 (n– h), 1599 (n–h), 1489 (n–h), 706 (c–s). 1h nmr (400 mhz, dmso-d6) δ in ppm 2.82 (s, 3h, –ch3), 6.06 (s, 2h, –ch2), 6.96 (d, 1h, arh, j = 8.4 hz), 7.27 (m, 1h, arh, j = 1.6 hz), 7.31 (d, 2h, arh, j = 7.6 hz), 7.35 (d, 2h, arh, j = 1.6 hz), 7.40 (m, 2h, arh, j = 8 hz), 7.88 (d, 2h, arh, j = 7.2 hz), 11.15 (s, 1h, n–nh). 13c nmr (100 mhz, dmso-d6): δ 14.53, 39.30, 101.73, 104.33, 105.84, 108.35, 120.59, 125.94, 127.89, 129.01, 132.71, 135.16, 146.66, 148.37, 170.32, 223.72. hrms: m/z =338.10 [m+1]. anal. calcd (%):c (64.08%), h (4.48%), n (12.45%), found: c (59.97), h (4.36), n (12.32). 2.4. biological activity 2.4.1. antimicrobial activity the antibacterial activity screening for synthesized compounds 5(a–h) was done by the disc diffusion method [34–36]. the tubes were inoculated with 1ml lag phase culture of gram-negative bacteria such as escherichia coli, pseudomonas aeruginosa, and gram-positive bacteria such as staphylococcus aureus and bacillus subtilis. fungal strains such as candida albicans and aspergillus flavus were used. the sterile nutrient agar media was used for bacteria growth, and potato dextrose agar media was used for fungi. in the respective labeled discs, different concentrations (10–100 mg) of synthesized conjugates 5(a–h) were added and mixed with dmso. then the bacterial plate was incubated at 37 °c for 24 hours and the fungal plate – at 27 °c for 48 hours. the zone of inhibition was measured for each compound. 2.4.2. cytotoxic activity gibco dulbecco's modified eagle medium (dmem) with 10% fetal bovine serum was used to culture the cell line. the cytotoxic activity of the synthesized compounds was evaluated against mcf-7 and hepg2 cell lines using a modified micro-titration colorimetric mtt reduction method [37]. for 24 hours, cells were seeded at a density of 1·104 cells per well in 96-well plates. the cells were then exposed to various concentrations of synthesized compounds 5(a–h) for 24 hours, ranging from 15.625 m to 1000 m. 10 μl of mtt solution (5 mg/ml) was pipetted into each well and incubated for another 4h. the medium was discarded after the formazan precipitate was formed and dissolved in dmso. the absorbance of the mixtures was measured at 570 nm with a microfilter plate reader, and cell viability was calculated. % inhibition = [atest / acontrol · 100], (1) where atest is the absorbance of the test sample, acontrol is the absorbance of control. the ic50 value of the synthesized compounds was calculated using linear aggression equation, viz., y = mx+c. here y = 50 and m and c values were derived from the viability graph. 2.4.3. anti-inflammatory activity gel electrophoresis was used to determine the anti-inflammatory efficacy of the prepared compounds against two matrix metalloproteinases, mmp-2 and mmp-9, as described in the published methodology [38]. electrophoresis gels were prepared, and 50 liters of test compounds and 50 liters of mmp sample were thoroughly mixed before being incubated for one hour. furthermore, the non-reducing buffer was thoroughly mixed in an equal-volume tank with the positive control (mmp) and negative control (tetracycline hydrochloride) (mmp). the tank was then closed and https://doi.org/10.15826/chimtech.2023.10.1.10 chimica techno acta 2023, vol. 10(1), no. 202310110 article 4 of 13 doi: 10.15826/chimtech.2023.10.1.10 plugged into a 50 v power supply for 15 minutes before increasing the voltage to 100 v until bromophenol blue reached the plate's bottom. the instrument was disconnected after completion, and the gel was gently removed, washed with a zymogram renaturing buffer solution for about 1 hour to remove sds (sodium dodecyl sulfate), and allowed the proteins to denature. the zymogram renaturing buffer was decanted, and the gel was incubated overnight at 37 °c in the zymogram incubation buffer. furthermore, the background stains blue with coomassie stain where the gelatin is degraded, and the gels are stained with coomassie blue r-250. the presence of gelatinases is indicated by the development of white bands, with the lower bands being gelatinases-a (mmp-2) at 72 kd and the upper bands being gelatinases-b (mmp-9) at 95 kd. 2.4.4. in silico molecular docking the 2d structures of synthesized derivatives were drawn using chemdraw. the energy was minimized using the dundee prodrug server and then converted into pdbqt using the graphical interface program ‘mgl tools’ [39]. 3kcy is a crystal structure of factor inhibiting hif-1 (fih-1) with quinol family inhibitors at a resolution of 2.59 å [40]. ‘mgl tools’ were used to adjust the grid box for docking simulations. the grid was adjusted so that it encompasses the region of the active site of the protein which comprised of ile 281, phe 207, his 279, asp 201, trp 296, his 199, leu 186, leu 188, gln 147. the docking algorithm provided with autodockvina was used to search for the best-docked conformation between ligand and protein, and the binding energy was determined. ligplot and pymol were used to infer the pictorial depiction of the interaction between the ligands and the target protein [41]. 3. results and discussion 3.1. chemistry and characterization the main aim of this work was to synthesize the novel thiazole hydrazones and explore their biological potency. herein, we prepared a novel thiazole hydrazones 5(a–h) except 5e [42, 43], by a simple two-step reaction. the synthetic route is shown in scheme 1, and the physical data summarized in table 1 were obtained using various analytical techniques. the compounds' efficacy towards cytotoxicity and anti-inflammatory activity were determined. in the ir spectrum of compound 5a, the signal at 3066 cm–1 was observed due to the presence of –nh functionality, the ar–ch stretching occurs at 2939 cm–1, the –c=n of hydrazone and thiazole resonated respectively at 1529 cm–1 and 1484 cm–1, the peak at 1278 cm–1 is related to c–f stretching, and the c–s group resonated at 709 cm–1. in the 1h nmr spectra of conjugate 5a, the –nh proton resonated at δ 12.40 ppm as a broad singlet, the aromatic proton of –ch–n= functionality appeared at δ 8.01 ppm as a singlet, the signal at δ 7.36 ppm is related to the proton of thiazole ring and the aromatic protons were observed in the region 7.29–8.06 ppm as a multiplet. in the proton decoupled 13c nmr spectra, the thiazole ring carbon resonated at δ 168.01 ppm, the aromatic carbons resonated in the region 117–160 ppm, and the azomethine carbon resonated at δ 105 ppm. the mass spectra of compound 5a confirmed the formation of the product by demonstrating a m+ signal at m/z 365.8, which corresponds to a calculated molecular weight of the compound. the ir, 1h nmr, 13c nmr and mass spectra of all the synthesized thiazole derivatives 5(a–h) are shown in the supplementary material (figure s1–figure s32). 3.2. solvatochromic uv-vis absorption figure 1 and figure 2 show the uv-vis absorption spectra of the synthesized conjugates, and table 2 lists the specific spectral data. the maximum absorption of these compounds was found in the range of 326–366 nm in the uvvisible spectra. the π–π* transition of electrons in aromatic rings present in all derivatives may account for this absorption [44]. on conjugation with aromatic rings, there is an abundance of electrons, resulting in a bathochromic shift. the compounds 5a and 5d exhibited bathochromic shift, as compared to the other synthesized compounds, and the compounds 5f and 5g showed a blue shift related to the other synthesized conjugates. scheme 1 synthesis of thiazole hydrazone conjugates 5(a–h). https://doi.org/10.15826/chimtech.2023.10.1.10 chimica techno acta 2023, vol. 10(1), no. 202310110 article 5 of 13 doi: 10.15826/chimtech.2023.10.1.10 table 1 analytical data of the synthesized thiazole derivatives 5(a–h). compound structure molecular formula molecular weight yield (%) m.p. (°c) 5a f n n n s h ff f c17h11f4n3s 365.3479 88 187–189 5b n n n s hbr br c16h11br2n3s 437.1516 90 192–193 5c n n n s h o c17h13n3os 307.3692 86 171–173 5d n nh n s s ch3 c17h15n3s2 325.4511 92 189–191 5e n n n s hch3 o c15h13n3os 283.3482 89 135–136 5f n n n s h ch3 c18h17n3s 307.4126 91 159–160 5g n n n s hch3 ch3 c19h19n3s 321.4392 88 201–203 5h n n n s hch3 o o c18h15n3o2s 337.3956 92 123–124 the values of λmax for the synthesized thiazole compounds vary depending on the nature of the solvents and change with changing solvent polarity; among the ten solvents, the largest λmax was observed for any given compound in dmf and dmso solvents with high polarity. this demonstrates that synthesized compounds are exhibiting solvatochromic behavior, which is attributed to the interaction of the solvent and lone pair electrons of azo dyes. 3.3. computational studies the optimized structures of the synthesized thiazole-conjugates are shown in the supplementary material (figure s33–figure s40). figure 3 and figure 4 display the energy gap and electronic distribution of homo-lumo of the synthesized thiazole hydrazones 5(a–h). as can be seen from the figures, compound 5a has less energy gap, viz., 3.512 ev; soft molecule and the compound 5g was found to have a large energy gap, viz., 4.38 ev. with the help of the energy of frontier molecular orbitals, some of the quantum chemical parameters were calculated using the following equations, and the values are listed in table 3. electronegativity (χ) = –1/2(elumo + ehomo). chemical potential (μ) = –χ = 1/2(elumo + ehomo). global hardness (η) =1/2 (elumo – ehomo). global softness (s) = 1/2η. electrophilicity index (ω) = μ2/2η. https://doi.org/10.15826/chimtech.2023.10.1.10 chimica techno acta 2023, vol. 10(1), no. 202310110 article 6 of 13 doi: 10.15826/chimtech.2023.10.1.10 figure 1 solvatochromic absorption spectra of compounds 5(a–d). figure 2 solvatochromic absorption spectra of compounds 5(e–h). https://doi.org/10.15826/chimtech.2023.10.1.10 chimica techno acta 2023, vol. 10(1), no. 202310110 article 7 of 13 doi: 10.15826/chimtech.2023.10.1.10 table 2 uv-visible data of the synthesized compounds 5(a–h). compounds λmax, nm dmf dmso acn n-hexane meoh benzene ethyl acetate toluene etoh 1,4dioxane 5a 353.63 355.29 342.83 348.63 346.42 349.75 348.09 348.92 349.18 353.63 5b 349.75 352.51 346.97 347.25 338.96 346.13 342.00 345.59 346.42 336.17 5c 350.59 356.96 343.92 343.09 346.97 347.25 344.75 346.42 346.97 348.92 5d 358.34 366.38 353.08 350.84 351.67 355.84 355.29 354.46 349.18 357.22 5e 341.23 346.90 334.49 332.75 336.00 339.70 337.31 338.19 337.31 339.04 5f 338.58 341.37 326.31 336.97 335.42 334.23 330.66 334.23 331.85 331.07 5g 338.71 340.50 330.41 333.08 328.35 334.29 331.88 334.56 330.72 334.29 5h 345.04 344.47 334.76 330.08 335.05 338.96 337.29 337.00 337.55 338.67 compounds logε dmf dmso acn n-hexane meoh benzene ethyl acetate toluene etoh 1,4dioxane 5a 3.58 3.72 4.17 3.36 3.98 4.10 4.24 3.89 3.85 3.39 5b 4.36 3.74 2.93 3.15 4.23 3.83 3.36 3.45 3.57 3.91 5c 3.32 3.36 3.77 2.80 3.43 3.67 4.15 4.22 3.99 3.83 5d 3.14 3.18 3.11 3.20 3.53 3.97 3.53 3.77 4.17 3.86 5e 3.96 3.46 3.73 4.18 3.89 4.19 3.77 4.03 4.07 3.47 5f 3.36 3.78 3.57 3.58 2.97 3.99 3.24 3.62 3.77 3.99 5g 3.81 3.84 3.82 3.41 4.34 3.78 3.97 4.10 4.03 4.26 5h 3.72 4.13 3.79 3.30 4.07 3.35 3.77 3.57 3.58 3.87 figure 3 calculated fmo orbitals plot of the synthesized compounds 5(a–d). figure 4 calculated fmo orbitals plot of the synthesized compounds 5(e–h). 5a 5b 5c 5d lumo homo 3.512 ev 3.960 ev 3.776 ev 3.674 ev lumo homo 5e 5f 5g 5h 3.776 ev 3.823 ev 4.388 ev 3.860 ev https://doi.org/10.15826/chimtech.2023.10.1.10 chimica techno acta 2023, vol. 10(1), no. 202310110 article 8 of 13 doi: 10.15826/chimtech.2023.10.1.10 table 3 quantum chemical parameters calculated for synthesized compounds 5(a–h). parameters 5a 5b 5c 5d 5e 5f 5g 5h ehomo (ev) –5.918 –5.680 –5.839 –5.623 –5.418 –5.517 –5.552 –5.429 elumo (ev) –2.406 –1.720 –2.063 –1.984 –1.642 –1.693 –1.163 –1.568 energy gap (δ) (ev) 3.512 3.960 3.776 3.674 3.776 3.823 4.388 3.860 ionization energy (i) (ev) 5.918 5.680 5.839 5.623 5.418 5.517 5.552 5.429 electron affinity (a) (ev) 2.406 1.720 2.063 1.984 1.642 1.693 1.163 1.568 electronegativity (χ) (ev) 4.162 3.70 3.951 3.803 3.530 2.758 3.357 3.498 chemical potential (μ) (ev) –4.162 –3.70 –3.951 –3.803 –3.530 –2.758 –3.357 –3.498 global hardness (η) (ev) 1.756 1.98 1.888 1.819 1.888 1.065 2.194 1.930 global softness (s) (ev–1) 0.284 0.252 0.264 0.274 0.264 0.469 0.227 0.259 electrophilicity index (ω) (ev) 4.932 3.457 4.134 3.974 3.30 3.571 2.567 3.169 molecular electrostatic potential map (mep) helps to predict the charge distribution in the molecule. in the mep, the electrophilic nature of the molecule is represented by the positive regions (blue), and the nucleophilic nature of the molecule is represented by the negative regions (red). the mep map was displayed in figure 5, which reveals that the blue region was found at –nh of the hydrazone in the synthesized compounds 5(a–h), and the red region was observed in compounds 5(c–f). 3.4. biological activity 3.4.1. antimicrobial activity the inhibition efficacy of the synthesized compounds 5(a–h) towards both gram-positive and gram-negative bacterial strains was determined by the disc diffusion method using dmso, even though dmso is toxic to antimicrobial strains, but to a lesser extent [44], and the results were appended in table 4. the compounds 5c, 5d, and 5g showed excellent activity compared to escherichia coli, pseudomonas aeruginosa, staphylococcus aureus, and bacillus subtilis compared to streptomycin, and the remaining compounds showed moderate to good activity. the antifungal activities of the titled compounds 5(a–h) towards fungal strains such as aspergillus flavus, candida albicans and aspergillussterreus are shown in table 4. from the results, it was found that compounds 5a and 5c display a good activity against aspergillus flavus and candida albicans. furthermore, the remaining derivatives also show significant activity. 3.4.2. cytotoxic activity all the synthesized thiazole derivatives were screened for their cytotoxic activity against mcf-7 and hepg2 cell lines. the ic50 values for cytotoxic activity of the synthesized compounds are listed in table 5, and the % cell viability against the treated compounds is shown in figure 6 and figure 7. compounds 5c and 5f inhibited mcf-7 cell lines to a good extent with ic50 values 58.13 µg/ml and 60.88 µg/ml, respectively; compounds 5h and 5d displayed excellent activity against hepg2 cells with ic50 values 55.8 µg/ml and 57.47 µg/ml, respectively, and the remaining compounds exhibited moderate activity against both mcf-7 and hepg2 cells with the ic50 values ranging from 61.80 to 70.08 µg/ml. 3.4.3. anti-inflammatory activity the anti-inflammatory efficacy of the synthesized derivatives 5(a–h) was determined against mmp-2 and mmp-9, and results were interpreted in terms of % inhibition. the % inhibition of the synthesized compounds is shown in table 6. gelatin zymography image is shown in figure 8. from table 6, it can be noticed that compound 5c indicates very good efficacy, viz., inhibited mmp-2 and mmp-9 to 70% and 55% respectively. compound 5f exhibits lower activity against both mmp-2 and mmp-9 compared to the other compounds. the remaining compounds exhibit moderate activity. figure 5 mep map of the synthesized compounds 5(a–h). figure 6 mcf-7 cell viability % against the synthesized thiazole conjugates 5(a–h). https://doi.org/10.15826/chimtech.2023.10.1.10 chimica techno acta 2023, vol. 10(1), no. 202310110 article 9 of 13 doi: 10.15826/chimtech.2023.10.1.10 table 4 antimicrobial activity results of synthesized compounds 5(a–h). compounds concentration, mg/ml zone of inhibition in mm (mean ± s.d.) bacterial strains fungal strains p. a. b. s. s. t. e. c. a. f. c. a. m. g. a.t. 5a 1 18±0.4 19±0.3 15±0.2 17±0.4 20±0.45 16±0.7 19±0.2 21±0.53 0.5 12±0.2 11±0.4 16±0.5 14±0.6 15±0.2 15±0.9 16±0.2 17±0.3 5b 1 16±0.36 17±0.25 20±0.4 19±0.2 19±0.43 20±0.4 21±0.4 18±0.5 0.5 14±0.23 13±0.5 17±0.34 16±0.24 15±0.32 14±0.5 16±0.3 13±0.53 5c 1 23±0.4 21±0.3 19±0.6 20±0.5 21±0.3 17±0.4 19±0.6 18±0.4 0.5 14±0.52 13±0.3 11±0.5 12±0.6 11±0.32 13±0.4 11±0.6 12±0.6 5d 1 20±0.4 19±0.6 17±0.4 18±0.4 19±0.25 18±0.36 17±0.4 18±0.6 0.5 13±0.1 16±0.54 14±0.24 15±0.45 12±0.5 11±0.23 15±0.4 14±0.3 5e 1 17±0.5 15±0.4 14±0.4 19±0.7 18±0.5 15±0.23 19±06 18±0.4 0.5 12±0.3 13±0.1 12±0.4 11±0.7 14±0.35 11±0.5 13±0.1 12±0.5 5f 1 12±0.4 11±0.31 13±0.5 11±0.6 13±0.32 10±0.3 15±0.6 14±0.4 0.5 09±0.6 10±0.3 12±0.4 10±0.4 10±0.5 12±0.3 08±0.25 12±0.6 5g 1 20±0.25 21±0.16 19±0.44 20±0.6 17±0.5 20±0.1 19±0.25 20±0.26 0.5 14±0.36 17±0.3 11±0.5 23±0.4 12±0.4 20±0.2 15±0.4 16±0.22 5h 1 16±0.4 17±0.5 19±0.4 15±0.41 16±0.4 21±0.46 19±0.51 17±0.3 0.5 10±0.1 15±0.21 13±0.5 10±0.24 12±0.4 15±0.4 12±0.6 13±0.5 standarda 23±0.6 22±0.3 21±0.4 20±0.3 – – – – standardb – – – – 22±0.3 21±0.5 20±0.4 22±0.2 p.a – pseudomonas aeruginosa, b.s – bacillus subtilis, e.s – escherichia coli, s.a – staphylococcus aureus, a.f – aspergillus flavus, c.a – candida albicans, a.s – aspergillusterreus, a.t – aspergillus terreus. standarda – streptomycin, standardb – fluconazole. table 5 ic50 values of the synthesized compounds against mcf-7 and hepg2 cell lines. compounds ic50 in µg/ml against mcf-7 cells ic50 in µg/ml against hepg2 cells 5a 62.35 61.02 5b 65.43 70.02 5c 58.13 62.6 5d 63.36 57.47 5e 64.48 67.31 5f 60.88 64.57 5g 64.54 61.8 5h 63.03 55.8 table 6 anti-inflammatory activity of the synthesized compounds 5(a–h). s.no. name of the compound mmp-2 (% inhibition) mmp-9 (% inhibition) 1 5a 55 15 2 5b 50 30 3 5c 70 55 4 5d 60 20 5 5e 65 15 6 5f 20 15 7 5g 70 30 8 5h 30 10 9 pc (positive control) 100 95 10 nc (negative control) 0(nil) 0(nil) figure 7 hepg2 cell viability % against the synthesized thiazole conjugates 5(a–h). figure 8 gelatin zymography showing mmp-2 and mmp-9 treated with synthesized derivatives 5(a–h). https://doi.org/10.15826/chimtech.2023.10.1.10 chimica techno acta 2023, vol. 10(1), no. 202310110 article 10 of 13 doi: 10.15826/chimtech.2023.10.1.10 3.4.4. in silico molecular docking study to support the in vitro biological activity of the synthesized thiazole-hydrazone conjugates, in silico molecular docking study was carried out with cox-2 receptor (pdb:1pxx). the binding energy, number of hydrogen bonds and the hydrophobic interaction of the compounds with receptors are tabulated in table 7. the 2d and 3d view of the interaction of synthesized compounds with cox-2 is given in figure 9. from the in silico study results, it was found that all the compounds showed excellent binding affinity in the range of –6.9 to –8.4 kcal/mol compared to standard drug diclofenac (–8.4 kcal/mol). compounds 5d, 5f, and 5g exhibited hydrogen bonds, but the remaining compounds did not show hydrogen bond. all compounds displayed hydrophobic interactions with the cox-2 receptor. 4. limitations the authors did not find any difficulties and limitations during this research work. 5. conclusions herein we reported the synthesis of thiazole-hydrazone conjugates 5(a–h), and their structure was identified with the help of analytical techniques such as uv, ir nmr and mass spectrometry. in addition, global and reactive parameters were calculated via the computational study. all the synthesized compounds exhibit positive solvatochromic behaviour, significant potency towards antibacterial activity, excellent efficacy toward cytotoxins and anti-inflammatory activity. furthermore, the synthesized compounds showed a good docking score with the cox-2 receptor. ● supplementary materials this manuscript contains supplementary materials, which are available on the corresponding online page. ● funding this research had no external funding. table 7 molecular docking results of synthesized thiazole-conjugates 5(a–h) and diclofenac with cox-2 receptor. ligand hydrogen bonds bond length (å) h-bond with hydrophobic interactions binding energy (kcal/mol) 5a 0 met 113, arg 120, ile 345, leu 531, phe 518, val 349, met 522, leu 352, val 523, gly 526, tyr 385, phe 381, leu 384, trp 387, tyr 355, ser 353, leu 359, val 116, met 113 –8.4 5b 0 leu 359, val 116, met 113, val 349, ser 353, val 523, phe 381, gly 526, tyr 385, met 522, leu 384, trp 387, ala 527, leu 531, ile 345 –8.0 5c 0 phe 518, val 253, gln 192, ala 516, ala 527, ser 253, his 90, val 116, val 349, arg 120, leu 531, ser 530, leu 352 –6.9 5d 1 3.1 drg:n2:tyr 355ob ala 516, ser 353, his 90, arg 513, leu 352, val 523, phe 518, ser 530, tyr 385, tyr 348, gly 526, ala 527, val 349, leu 531 –7.5 5e 0 tyr 385, leu 384, trp 387, gly 526, val 523, ala 527, leu 531, met 113, leu 359, tyr 385, val 349, tyr 355, val 116, ser 353, phe 518, leu 352, trp 387, met 522 –7.9 5f 2 3.12 drg:e:tyr 355ob phe 518, leu 352, trp 387, gly 526, val 523, ala 527, phe 381, leu 384, tyr 385, met 522, ile 345, met 113, val 349, leu 531, leu 359, ser 353 –7.6 2.91 drg:e:arg 120 nb1 5g 1 2.88 drg:n1:tyr 385 oh val 349, leu 352, tyr 348, ser 530, leu 534, phe 205, ile 377, val 228, phe 381, phe 381, phe 209, gly 533, val 344, ala 527, leu 531 –6.9 5h 0 phe 369, trp 194, leu 209, tyr 489 –7.9 diclofenac 2 2.87 drg:n1:tyr 385 oh leu 384, gly 526, phe 518, trp 387, ser 353,val 523, met 522, tyr 355, ala 527, leu 352, val 349, tyr 348, –8.4 2.82 drg:n1:tyr 385 oh https://doi.org/10.15826/chimtech.2023.10.1.10 chimica techno acta 2023, vol. 10(1), no. 202310110 article 11 of 13 doi: 10.15826/chimtech.2023.10.1.10 figure 9 2d and 3d docked view of compounds 5(a–h) and diclofenac with cox-2 receptor. https://doi.org/10.15826/chimtech.2023.10.1.10 chimica techno acta 2023, vol. 10(1), no. 202310110 article 12 of 13 doi: 10.15826/chimtech.2023.10.1.10 ● author contributions conceptualization: n.b.p. data curation: k.y.c. formal analysis: k.y.c., n.b.p., m.p.k. funding acquisition: n.b.p., m.p.k. investigation: k.y.c., m.p.k. methodology: k.y.c., n.b.p., m.p.k. project administration: m.p.k. resources: k. k.y.c., y.c., n.b.p. software: k.y.c., m.p.k. supervision: m.p.k. validation: k.y.c., m.p.k. visualization: m.p.k. writing – original draft: k.y.c., n.b.p. writing – review & editing: m.p.k. ● conflict of interest the authors declare no conflict of interest. ● additional information author ids: bp nandeshwarappa, scopus id 11839628200; km mussuvir pasha, scopus id 57416747400. websites: davangere university, https://vskub.ac.in; vijayanagara sri krishnadevaraya university, https://davangereuniversity.ac.in. references 1. mallikarjuna sm, padmashali msmb, chandrashekharappa s, sandeep c. synthesis, anticancer and antituberculosis studies for [1-(4-chlorophenyl) cyclopropyl](piperazine-yl) methanone derivates. int j pharm sci res. 2014;6(7):423–427. 2. nagesh hk, padmashali b, sandeep c, musturappa te, lokesh m. synthesis and 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https://doi.org/10.1107/s0907444904011679 https://doi.org/10.1016/j.molstruc.2021.131642 https://doi.org/10.1016/j.molstruc.2021.131170 https://doi.org/10.1002/ardp.201300099 https://doi.org/10.1016/j.bioorg.2020.104615 https://doi.org/10.4103/ijmy.ijmy_35_18 https://doi.org/10.1016/j.optmat.2019.02.041 corrosion of diffusion zinc coatings in sodium chloride solutions published by ural federal university eissn 2411-1414; chimicatechnoacta.ru article 2022, vol. 9(4), no. 20229421 doi: 10.15826/chimtech.2022.9.4.21 1 of 6 corrosion of diffusion zinc coatings in sodium chloride solutions alexander i. biryukov a, dmitry a. zakharyevich a, tatyana v. batmanova a * , rashit g. galin b, maksim n. ulyanov a, vladimir e. zhivulin c a: chelyabinsk state university, chelyabinsk 454001, russia b: vika-gal ltd, chelyabinsk 454087, russia c: south ural state university, chelyabinsk 454080, russia * corresponding author: batmanovatt@gmail.com this paper belongs to a regular issue. © 2022, the authors. this article is published in open access under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). abstract diffusion galvanizing is widely used in the pipe industry for coating the threaded surface of pipe couplings and protecting water pipelines, gas pipelines, and other metal products. diffusion coatings have a number of advantages over other types of zinc coatings. in this work, electrochemical and gravimetric methods were used to study the corrosion behavior of diffusion zinc coatings in sodium chloride solutions. the corrosion rate depends non-linearly on the thickness of the coating. at the initial stages, the corrosion rate of coatings depends on the structure of the phases on the surface, and with an increase in the holding time, the corrosion rate depends to a greater extent on the properties of the products formed during the corrosion process. the films of corrosion products of diffusion zinc coatings consist of zinc oxide/hydroxide and basic zinc salts, while the composition of the filmf changes with increasing coating thickness. keywords corrosion sherardizing zinc coatings received: 05.10.22 revised: 10.11.22 accepted: 11.11.22 available online: 18.11.22 1. introduction zinc coating is one of the most popular methods of protecting steel products from corrosion. galvanic zinc coatings and the so-called "hot" zinc coatings are widely used in industry. these coatings are obtained by immersing steel products in a zinc melt. they differ in the chemical and phase composition, besides the method of application. galvanic zinc coatings are practically pure zinc and are uniform in thickness. the coatings obtained from the melt consist of iron-zinc phases, which are distributed layer by layer, in accordance with the phase diagram of zn-fe [1]. according to the diagram, zinc and iron can form the following phases: α-; г-; δ-; ζand η-phase, in the order of increasing zinc concentration [1]. the composition of "hot" zinc coatings includes ηand ζ-phases with a zinc concentration of 95.0–96.0 wt.% [1, 2]. the corrosion behavior of such coatings has been studied by various authors [3–6] and is often interpreted on the basis of the corrosion mechanism of pure zinc [7–11]. the sherardizing method involves heating the steel products in mixtures based on zinc powders. the advantages of this approach are the possibility of obtaining coatings with desired properties, high productivity, minimal production waste and a low load on the environment. diffusion zinc coatings consist of iron-zinc phases, but their structure is dominated by a phase with a lower zinc content, the δ-phase (88.5–93.0 wt.%). a few works were devoted to the study of corrosion of diffusion zinc coatings [12–14]. galin [15] developed a sherardizing technology using saturating powder mixtures with nanostructured zinc oxide. this technology is used now at the enterprises of jsc "pntz" and pjsc "sintz" for applying diffusion zinc coating on the threaded surface of tubing couplings and at other enterprises for galvanizing metal products. the technology makes it possible to obtain coatings consisting of predominantly single-phase layers of iron-zinc phases of relatively large thickness. the work [16] provides the data on the mechanical properties of the coatings, their hardness and corrosion under operating conditions. the purpose of this work is to study the corrosion behavior of diffusion zinc coatings using various laboratory corrosion test methods. 2. materials and methods diffusion zinc coatings were applied to steel discs (steel 45) with a diameter of 32.0 mm and a thickness of 2.5 mm. the galvanizing temperature was 450 °c, the duration was from 1 to 4 hours. the saturating mixture contained http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2022.9.4.21 mailto:batmanovatt@gmail.com http://creativecommons.org/licenses/by/4.0/ https://orcid.org/0000-0001-8049-0940 https://orcid.org/0000-0002-4389-8936 https://crossmark.crossref.org/dialog/?doi=https://doi.org/10.15826/chimtech.2022.9.4.21&domain=pdf&date_stamp=2022-11-18 chimica techno acta 2022, vol. 9(4), no. 20229421 article 2 of 6 zinc particles with nanostructured oxide on the surface [15–18], which is a feature of the proprietary technology. the galvanizing technique is described in [15–18]. the resulting coatings have a dark gray color and a uniform appearance. the thickness of the coatings was determined with a magnetic thickness gauge. the samples with a thickness of 20 to 80 μm were used. the corrosive medium in all studies was a 3 wt.% sodium chloride solution. it was prepared by dissolving weighed portions of a chemically pure grade reagent in distilled water. the determination of the corrosion rate of the samples by the gravimetric method was carried out at room temperature, and the exposure time was 30 days. the geometric parameters of the samples were measured with an accuracy of 0.1 cm and weighed before and after testing with an accuracy of 0.0001 g. the corrosion products were removed mechanically after exposure. based on the results of determining the area and weight loss, the corrosion rate was calculated as g∙m–2∙hour-1. a flat corrosion cell was used to measure electrode potentials and polarization curves. a silver chloride electrode was used as a reference electrode (the potentials were recalculated to a standard hydrogen scale), and a graphite electrode served as an auxiliary one. the polarization curves were recorded after measuring the stationary potential, after 1 hour exposure in a corrosive environment. the polarization curves were obtained in the potential range from (–1.3) to (+0.2) v (she) with a sweep rate of 5 mv∙s–1. the curves were used to estimate the corrosion current density. the corrosion current density of the coatings under study was estimated from the point of intersection of the linear sections of the anodic and cathodic curves. the time dependences of the potential were obtained in the same clamping cell using a silver chloride reference electrode. the measurements were carried out for 60 minutes, until stationary values were established. corrosion products of diffusion zinc coatings were characterized using by x-ray phase analysis (dron-3, cu kα) and scanning electron microscopy (jeol jsm7001f microscope with an oxford inca x-max 80 energy dispersive spectrometer for x-ray spectral microanalysis). 3. results and discussion in the previous works [17–19], the relationship between the coating thickness, phase and chemical composition of the surface layers is described in detail. the δ-phase (fezn7–10) is present on the surface of the coatings with a thickness of 10 to 40 μm, and for the coatings with a thickness of 50 to 80 μm the ζ-phase (fezn13) appears on the surface. the proportion of ζ-phase increases with the thickness of the coating. the corrosion behavior of diffusion zinc coatings was compared with samples of pure zinc, imitating galvanic zinc coatings and samples of a substrate made of steel 45. 3.1. stationary potentials figure 1 shows a time dependence of the electrode potential of a coating. the potential shifts over time to the negative region by 90 mv. this is apparently due to the corrosion of the coating and the formation of a film of corrosion products. at the initial stage of the corrosion process, the film is inhomogeneous and does not protect the coating, since otherwise the electrode potential would be refined. stationary potentials of different samples were compared (table 1). steel has the most positive potential, and zinc has the most negative potential. their potentials differ by 300 mv, which with a small error corresponds to the difference between the standard electrode potentials of zinc and iron. the stationary potentials of the coatings are in the range of –0.6 to–0.8 v (she). as the thickness increases, the electrode potential of the coating shifts to the negative region. this is due to the fact that with increasing thickness the concentration of zinc in the surface layer increases. zinc has a more negative potential and, consequently, the coating potential also becomes more negative. no extremum is observed in the series of potentials. 3.2. polarization curves figure 2 shows the polarization curves of the diffusion zinc coatings of various thicknesses. it can be seen that the coating with a minimum thickness of 10 μm has a more positive stationary potential, which can be explained by a relatively high concentration of iron. the electrode potentials of other coatings are in the range from –0.6 to –0.8 v (she), which corresponds to the distribution of stationary potentials of the coatings. figure 1 dependence of e on τ for a zinc coating (50 μm). table 1 stationary potentials of the samples. sample / thickness, μm е, mv (she) steel 45 – 403 zinc coating /10 μm – 600 zinc coating /20 μm – 700 zinc coating /40 μm – 738 zinc coating /80 μm – 758 zinc – 803 chimica techno acta 2022, vol. 9(4), no. 20229421 article 3 of 6 figure 2 polarization curves of diffusion zinc coatings of various thicknesses. however, in this case, no strict dependence of the potential values is observed on the coating thickness. the anodic polarization curves do not have any inflection points, and the oxidation current increases uniformly as the potential is shifted. on the cathodic polarization curve of the 10 μm thick sample, a small current area is observed between the potentials –0.6 v and –1.0 v (she). this shape of the cathode curve corresponds to a slow diffusion of oxygen to the electrode surface. on the cathode curves of the remaining coatings, this section is not pronounced. a nonlinear dependence of the corrosion current on the thickness is observed for the diffusion zinc coatings (table 2). the samples of diffusion zinc coatings with a thickness of 30–40 μm have the minimum value of the corrosion current. in the previous works [19, 20], a minimum of the corrosion rate was also observed for the coatings on the surface of which the δ-phase was present, the composition of which approximately corresponds to the middle of the region of its existence in the fe-zn phase diagram. the authors [19, 20] explained this by the structural features of the δ-phase, in particular, by the minimum number of relatively isolated zinc atoms in the structure, with the composition of the δ-phase corresponding to the observed minimum of the corrosion current. with an increase in thickness over 40 μm, which corresponds to the transition from the δ-phase to the ζ-phase, the corrosion current doubles compared to the coatings predominantly consisting of the δ-phase. the corrosion current increases to a lesser extent with a decrease in the thickness of the coatings, which can be associated with an increase in the concentration of iron in the surface layers. 3.3. gravimetric tests figure 3 shows the dependence of the gravimetric corrosion rate of coatings on their thickness. the corrosion rate of steel 45 (the reference data according to [21]) is two times higher than the corrosion rate of zinc, and the corrosion rate of the coatings is in the range of 0.02–0.03 g∙m–2∙h–1 regardless of the thickness. when passing from coatings with the δ-phase on the surface to coatings with the ζ-phase, a slight increase is observed in the corrosion rate, which may be associated with disturbances in the phase composition of the surface layers. the gravimetric method also gives a nonlinear dependence of the corrosion rate on thickness, although the spread is less than that observed for the initial corrosion stage. the coatings that are in the middle of the studied thickness range have the maximum corrosion rate. this dependence differs from that obtained when assessing the corrosion current, where the coatings with a thickness of 30–40 μm had a minimum corrosion rate. it should be noted that when recording the polarization curves, the exposure of the coatings in a corrosive environment did not exceed 1 hour, while, in the gravimetric studies, the exposure was 720 hours. corrosion formed on the coatings during the long exposure. 3.4. corrosion products figure 4 shows the diffraction patterns of the diffusion zinc coatings of different thicknesses after exposure for 720 hours in a 3% nacl solution. the compositions of the corrosion products are similar, the films contain zinc oxide/hydroxide zno/zn(oh)2 as well basic zinc salts. these include basic zinc chloride (simoncolleite) zn5cl2(oh)8∙h2o and basic zinc carbonate (hydrozincite) zn5(oh)6(co3)2. thus, the films of corrosion products are mixtures of zinc compounds with different ability to protect the metal from corrosion. with an increase in the thickness of the coating, the intensity of the peaks corresponding to zinc oxide/hydroxide increases, while the intensity of the peaks of simoncolleite and hydrozincite decreases. table 2 corrosion currents of the investigated coatings in 3% nacl solution. figure 3 corrosion rate of coatings, steel and zinc. thickness, μm icorr·10 –3, ma/cm2 10 2,5 20 3,1 30 1,3 40 1,4 55 3,4 80 3,4 chimica techno acta 2022, vol. 9(4), no. 20229421 article 4 of 6 figure 5 shows electron microscopic images of a transverse section of a coating (thickness 50 μm) after 720 hours exposition in 3% sodium chloride. the corrosion products (dark-gray area at the top part of figure 5) uniformly cover the remaining coating and fill cracks and defects. thus, the products of corrosion prevent further contact of the corrosive medium with the coating. according to the x-ray microanalysis data, the corrosion products in cracks have the following chemical composition (at.%): o – 41.75; cl – 9.55; fe – 3.65; zn – 45.05. the concentration of chemical elements satisfactorily corresponds to simonkolleite, which is confirmed by the x-ray phase analysis. 3.5. discussion zinc corrosion is usually represented as the work of localized anode and cathode sites. oxidation occurs at the anode sites: zn – 2e → zn2+, (1) and oxygen reduction – at the cathode sites: 1/2o2 + h2o + 2e– → 2oh–. (2) the accumulation of zn2+ and oh– leads to the formation of amorphous zinc hydroxide: zn2+ + 2oh– → zn(oh)2, (3) which, in turn, can be converted depending on ph to zinc oxide zno or crystalline forms of zinc hydroxide zn(oh)2. these compounds exhibit semiconductor properties and poorly protect the metal from corrosion. if carbonate ions co32– or hydrocarbonate ions hco3– are present in the solution, basic zinc carbonate zn(co3)2(oh)6 can be formed, for example, by the reaction [22,23]: 5zn(oh)2(s)+2hco32–+2h+→zn5(oh)6(co3)2+4h2o. (4) in solutions with a high content of chloride ions cl–, basic zinc chloride is formed zn5cl2(oh)8∙h2o [22, 23]: 5zn(oh)2 + 2cl– + h2o → zn5(oh)8cl2∙h2o + 2oh–. (5) the literature describes various mechanisms for the formation of basic salts during the zinc corrosion. these compounds are known to form insoluble, poorly conductive films that are capable of slowing down the corrosion of zinc. however, the formation of such compounds takes some time [22, 23]. a feature of the corrosion of iron-zinc coatings fezn and zinc alloys in general is the selective dissolution of zinc as a more electronegative metal. in a number of works [24, 25], it is noted that selective dissolution can have a positive effect on the anticorrosion properties of a film of corrosion products, in particular, due to the formation of a microheterogeneous rough surface, which is convenient for the nucleation of numerous crystallization centers, or due to the enrichment of the film with a more noble metal. thus, at the beginning of corrosion, with minimal exposure to the environment, the corrosion characteristics of coatings are affected by the structure and phase composition of the surface layers. at this moment, there are no films of corrosion products on the surface of the coatings. the dependences of the corrosion current on the coating thickness at this stage can be explained by the structural and phase inhomogeneity of surface coatings of various thicknesses [19, 20]. with an increase in the exposure time, films of corrosion products have a greater effect on the corrosion rate. so, a loose layer of iron hydroxides is formed on the steel, which has low adhesion to the metal base. such a layer of corrosion products poorly protects the sample from contact with an aggressive environment, so the corrosion rate of steel is the highest. as shown by the authors of [26], in the presence of chloride ions on the surface of iron-zinc coatings, the formation of basic zinc salts occurs faster than on the surface of pure zinc. this explains the lower gravimetric corrosion rate of diffusion zinc coatings compared to pure zinc. at the same time, when analyzing films of corrosion products, it can be seen that they are mixtures of various zinc compounds, both zinc oxide and basic salts. these compounds have different ability to inhibit the corrosion process. increasing the concentration of zinc oxide/hydroxide in the film leads to an increase in the corrosion rate of the coatings. figure 4 diffraction patterns of corrosion products. figure 5 cross section of coating after corrosion in 3% nacl. chimica techno acta 2022, vol. 9(4), no. 20229421 article 5 of 6 the question of the chemical or structural state of iron in corrosion products that provide the best long-term protection in a corrosive environment requires separate consideration. some authors made assumptions about the reasons for the positive effect of iron on the protective ability of zinc corrosion products. in [24], the authors point to the formation of a dense deposit, which slows down the ionic conductivity. it was shown in [25] that a film of corrosion products with 7 wt.% fe suppresses the oxygen reduction reaction due to its low electrical conductivity. in addition, in [27, 28], it was assumed that the effect of iron is reduced to the amorphization of the deposit of corrosion products, an increase in its compactness and a decrease in porosity. 4. conclusions the corrosion rate of diffusion zinc coatings depends nonlinearly on the thickness, while on average it is two times less than the corrosion rate of steel and one and a half times less than the corrosion rate of zinc. at the initial stages, the corrosion rate of the coatings is influenced by the structure and phase composition of the surface layers of the coating. with an increase in the exposure time, the corrosion rate of the coating depends to a greater extent on the properties and composition of the film of corrosion products. the films of corrosion products of the diffusion zinc coatings consist of zinc oxide and basic zinc salts, while the composition of the films changes with increasing coating thickness. supplementary materials no supplementary materials are available. funding the research was funded by russian foundation for basic research and chelyabinsk region (project no. 20-43740026), https://kias.rfbr.ru/. acknowledgments none. author contributions conceptualization: b.a.i., b.t.v., z.d.a., r.g.g. data curation: b.a.i. formal analysis: b.a.i, z.d.a., b.t.v. funding acquisition: b.a.i., z.d.a., r.g.g. investigation: b.a.i., z.d.a., b.t.v., m.n.u., v.e.z. methodology: b.a.i., b.t.v., r.g.g. project administration: b.a.i., z.d.a. resources: b.a.i., z.d.a., b.t.v., r.g.g., m.n.u., v.e.z. software: z.d.a., b.t.v. supervision: b.t.v. validation: b.a.i., b.t.v. visualization: b.a.i., z.d.a., b.t.v., v.e.z. writing –original draft: b.a.i, b.t.v. writing –review & editing: b.a.i., z.d.a. conflict of interest the authors declare no conflict of interest. additional information author ids: alexander i. biryukov, scopus id 57190129477; tatyana v. batmanova, scopus id 57208816951; dmitry a. 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2411-1414; chimicatechnoacta.ru letter 2022, vol. 9(3), no. 20229303 doi: 10.15826/chimtech.2022.9.3.03 1 of 5 proton-conducting membranes based on csh2po4 and copolymer of tetrafluoroethylene with vinylidene fluoride irina n. bagryantseva a , yuri e. kungurtsev ab, valentina g. ponomareva a* a: institute of solid state chemistry and mechanochemistry sb ras, novosibirsk 630090, russia b: novosibirsk state university, novosibirsk 630090, russia * corresponding author: ponomareva@solid.nsc.ru this paper belongs to the ctfm'22 special issue: https://www.kaznu.kz/en/25415/page. guest editors: prof. n. uvarov and prof. e. aubakirov. © 2022, the authors. this article is published open access under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). abstract in this work, proton conductivity, morphology and mechanical properties of (1–x)csh2po4–xf-42 (x=0.05–0.3, weight ratio) membranes were investigated for the first time. thin flexible membranes for x≥0.15 with the uniform distribution of the components were obtained by a tape casting method. mechanical properties of the membranes were measured by vickers microhardness tests for a low polymer content (x˂0.15), also the tensile strength for membranes with high polymer content x=0.2–0.3 were evaluated. proton conductivity of the (1–x)csh2po4–xpf-42 composite polymer electrolytes decreases monotonically with increasing x due to the effect of a «conductorinsulator» percolation. the combination of conductivity, mechanical strength and hydrophobic properties of (1–x)csh2po4–xf-42 makes certain compositions of proton-conducting membranes (x~0.2–0.25) promising for their use in intermediate-temperature fuel cells, despite decreased conductivity. keywords proton conductivity cesium dihydrogen phosphate fluoropolymer p(vdf/tfe) tape casting received: 27.06.22 revised: 15.07.22 accepted: 15.07.22 available online: 19.07.22 1. introduction solid acid fuel cell (safc) is a promising new type of fuel cells with a csh2po4 acid salt as a membrane [1, 2]. interest in solid acid compounds, such as alkali metal dihydrogenphosphates and dihydrogensulfates, is constantly growing, a number of salts of this family is increasing; as a result, new compounds with cs3(h1.5po4)2 [3–5] and cs7(h4po4)(h2po4)8 [6] compositions have been recently discovered. however, csh2po4 remains the salt with the highest value of proton conductivity. the csh2po4 phase at room temperature is characterized by a low conductivity, while at 230 °c there exists its sharp increase by several orders of magnitude due to the phase transition to a pm3m superionic phase, which is characterized by a high degree of structural disorder and high proton conductivity, 6·10–2 s/cm [7]. to achieve a more efficient and stable operation of h2/o2 fcs based on csh2po4 in a wider temperature range, it is necessary to maintain humidity level of ph2o ~0.3 atm. to prevent salt dehydration [8, 9]. the disadvantages of the csh2po4 membranes (such as a narrow temperature range of the existence of a highly conductive state, time-dependent plasticity of acid salt in superionic phase, solubility in water, low mechanical strength) can be significantly improved by methods of homogeneous and heterogeneous doping. the search for polymer additives for the synthesis of thin membranes, which combine the flexibility and hydrophobicity of a polymer additive with a high proton conductivity of the acid salt, is being intensively developed. a number of composite membranes based on csh2po4 and different polymers such as pvdf, speek, epoxy resin, uptfe, butvar b98, p(vdf/hfp) have been investigated [10–16]. at a high concentration of polymer in such systems, the mechanical properties of the membranes are improved, while the high content of the non-conductive component results in a decrease in conductivity due to the effect of the «conductorinsulator» percolation. the «csh2po4 – polymer» composites can combine the required mechanical, conductive, and hydrophobic properties. in addition, the solubility of polymer additives in various solvents makes it possible to switch from the solid-phase methods of membrane’s synthesis to the production of thin and flexible films by tape casting technique. fluoropolymers are considered as a chemically inert, thermally stable, effective additive to the acid salt csh2po4. the previous studies have included pvdf [10], ultrafine ptfe [14], and a vdf/hfp copolymer [15]. fluoroplast 42 (f-42, similar to kynar 7200) copolymer of vinylidene fluoride (vdf) with tetrafluoroethylene (tfe) http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2022.9.3.03 mailto:ponomareva@solid.nsc.ru http://creativecommons.org/licenses/by/4.0/ http://orcid.org/0000-0003-1800-3421 http://orcid.org/0000-0002-8661-5799 https://crossmark.crossref.org/dialog/?doi=https://doi.org/10.15826/chimtech.2022.9.3.03&domain=pdf&date_stamp=2022-7-19 chimica techno acta 2022, vol. 9(3), no. 20229303 article 2 of 5 is a promising polymer matrix for csh2po4. tfe and vdf can be polymerized in any ratio giving rise to a broad variety of copolymers. a composition of f-42 corresponds to the approximate tfe:vdf component ratio of 29:71. the polymer has a high hydrophobicity due to the high content of fluorine atoms 65.8 (wt.%). f-42 is a robust polymer with a high tensile strength (~14.6 mpa), high specific surface resistance (~1010 ohm/m). it is chemically resistant in acidic and basic media, and soluble in esters, ketones and n,n-dimethylformamide (dmf) [17–19]. f-42 polymer has high thermal stability with decomposition temperatures above 360 °c. melting of f-42 at temperatures of 150–160 °c corresponds to the crystallites, but the polymer does not pass into a viscous state. in present work, morphology, mechanical characteristics, transport and structural properties of (1–x)csh2po4–xf42 polymer composite electrolytes have been studied. 2. materials and methods the csh2po4 salt was obtained by a slow solvent evaporation of an aqueous solution of cs2co3 and h3po4 in a ratio of 1:2. composite electrolytes with a polymer weight ratio of x=0.05–0.15 were synthesized by a thorough homogenization of a suspension of csh2po4 particles in a solution of p(vdf/tfe) in dmf with a mortar and a pestle with a further drying and uniaxial pressing of formed powder at 300 mpa. for the x=0.2–0.3, a viscous suspension of csh2po4 particles in polymer solution was spread on a fluoroplastic substrate using a tob-vfc-150 tape casting machine and dried to form the film. proton conductivity measurements were carried out on the thin films ~150 μm for x=0.2 or pellet (x=0.05–0.15) with silver or platinum paste or pressed electrodes. membranes were subjected to repetitive heating-cooling cycles in the temperature range from 50 to 245 °c. humid conditions (ph2o ~0.3 atm) were used at temperatures higher 180 °c to prevent the csh2po4 dehydration. the conductivity was measured by electrochemical impedance spectroscopy using an p-5x impedance meter (frequency range of 1 mhz to 0.5 mhz) and instek (12 hz-200 khz) in a cooling regime. scanning electron microscopy (sem) images of composites were obtained on the gold sputter-coated membranes using a hitachi tm 1000 microscope. x9ray diffraction (xrd) analysis was performed on a bruker d8 advance diffractometer (λ cu kα1 = 1.5406 å) with a onedimensional lynx-eye detector and kβ filter. vickers hardness for (1–x)csh2po4–xf42 (x≤0.15) was determined using a durascan 50 microhardness tester emco-test with an application time of load (0.5 kgf (4.9 n)) for 10 seconds. the measurements were repeated at least ten times for each sample. dense tablets (5 mm in diameter and 1 mm in thick) were obtained by uniaxial pressing at 300 mpa. the tensile strength of thin-film polymer composite electrolytes with x >0.15 was measured using an instron 5944 mechanical testing machine. for the preparation of samples, a punching die of certain sizes was used to obtain the samples with a form of a double blade with a 5 mm wide and 20 mm high working area. the thin-film membrane was stretched at a constant rate of 5 mm/min under atmospheric conditions and the applied load and elongation was recorded. for each x at least six measurements were made, and average value was calculated. 3. results and discussion for the synthesis of composites, the x<0.38 composition range was chosen, since the proton conductivity drops sharply with an increase in the ratio of the polymer additive due to the predominance of the nonconductive component in the membrane volume. composites with a low content of f-42 x=0.05–0.15 were obtained in the form of pellets. for higher polymer content (x>0.15) it was possible to produce thin flexible films with a thickness ~150 µm by tape casting method. the search for optimal conditions for tape casting process such as solvent used, application speed, the height of the gap, number of layers and the temperature regime of drying has been carried out. dmf was used as a solvent with a high boiling point (t=153 °c) that provides high quality of films obtained. according to x-ray diffraction data, a monoclinic csh2po4 (p21/m) phase is retained in composite electrolytes over the entire range of compositions. figure 1 xrd data for the (1–x)csh2po4–xf42 membranes of various composition. chimica techno acta 2022, vol. 9(3), no. 20229303 article 3 of 5 figure 2 sem images of (1–х)csh2po4–xf-42 for х=0.05 (a, c), x=0.1 (b), x=0.15 (d), x=0.25(e), cross-section of x=0.25 (f). with an increase in the weight ratio of a polymer additive, the intensity of the csh2po4 reflexes decreases in accordance with the change in the mass fraction of the salt (figure 1). the f-42 fluoropolymer has a sufficiently high degree of crystallinity; the xrd pattern has reflections in a region of 2θ~19 and 40º. the structure of the β-phase of pvdf is realized in the f-42 polymer [20]. for composite electrolytes with x≥0.1, the most intense f-42 reflex appears in vicinity of 19°. the distribution of components in the volume significantly affects the proton conductivity and mechanical properties of membranes. csh2po4 is practically insoluble in most known organic solvents, and composite membranes present a polymer matrix with salt particles dispersed in its volume. the study of membrane morphology and determination of the size of salt particles in the polymer matrix was performed using sem. the resulting membranes exhibit a uniform distribution of components with the salt particles size less than 5 μm (figure 2). the nature of the temperature dependences of the composites is close to that of pure salt. the conductivity of the high-temperature phase decreases by less than an order of magnitude for compositions with x≤0.15 (figure 3). compared to the initial salt of csh2po4, the proton conductivity of the composites decreases even at a low volume fraction of the polymer (7.87 vol.% for x=0.05) due to its dielectric nature. a further increase in the polymer content (x>0.2) results in a close-to-linear decrease of conductivity. to assess the mechanical properties of the membranes, the vickers microhardness was determined for the acid salt csh2po4 and hybrid polymer compounds with f-42. figure 3 temperature dependences of conductivity for the (1–x)csh2po4–xf-42 composites. csh2po4 x=0.05 (7.87 vol.%) x=0.1 (15.3 vol.%) x=0.15 (22.3 vol.%) figure 4 microscopic images of the indenter's imprint on the surface of (1–x)csh2po4–xf42 membranes. the vickers microhardness test evaluates the mechanical properties of composite polymer electrolytes in the form of tablets with a low polymer content (x≤0.15) in comparison with initial csh2po4 salt. the relative density of the obtained tablets "csh2po4-polymer" was close to 95%. vickers hardness (hv) was determined by division of the load by the area of the sloping surface of the indentation. with an increase in the content of the polymer additive, the diagonals of the indentation from the diamond pyramid increase (figure 4). thus, the vickers numbers, hv, for the initial salt had the values hv~34, which corresponds to 333.4 mpa, for hybrid membranes containing chimica techno acta 2022, vol. 9(3), no. 20229303 article 4 of 5 f-42 polymer x=0.15, the microhardness decreases by more than two times reaching value ~13 hv. for hybrid compounds, it was shown that with an increase in the mass fraction of the polymer, the ability to resist plastic deformation and, as a result, the mechanical strength increase. for thin-film membranes with x>0.15, the tensile strength was measured as the load at which the sample failed, referred to the initial cross-sectional area of the sample. films with x=0.2–0.3 and thickness of ~150 μm were obtained by applying a two layer of suspension and drying until the solvent evaporation. the magnitude of the breaking stress increased with the increase in the mass fraction of f-42. the maximum value of the breaking stress of a thin-film polymer-composite membrane with x=0.3 was 0.7 mpa. 4. conclusions the synthesis method of the (1–x)csh2po4–xf-42 composite electrolytes by tape casting technique was developed. a study of the proton conductivity, structural properties, mechanical characteristics, and morphology of the system was carried out for the first time. according to xrd, f-42 is the chemically inert polymer matrix for csh2po4. composite electrolytes in the form of thin flexible films with the thickness 100–150 μm can be obtained for high polymer content. the (1–x)csh2po4–x-42 composites are characterized by a decrease in superionic conductivity in comparison with the initial salt within 1 order of magnitude for x=0.15. a further increase in the polymer content (x>0.2) results in a conductivity decrease close to linear. polymer content x˂0.15 results in the low hv values corresponding to the high robustness of the membranes to plastic deformation. the improvement of mechanical properties and hydrolytic stability makes the investigated composite polymer electrolytes promising for use as protonconducting membranes in the medium-temperature range fuel cells. supplementary materials no supplementary materials are available. funding this work was supported by the russian science foundation (grant no. 21-73-00298), https://www.rscf.ru/en. acknowledgments none. author contributions conceptualization: i.n.b, v.g.p. data curation: i.n.b, y.e.k. formal analysis: i.n.b, v.g.p., y.e.k. funding acquisition: i.n.b. investigation: y.e.k., i.n.b. methodology: v.g.p., i.n.b. project administration: i.n.b. resources: v.g.p., i.n.b. software: v.g.p., i.n.b. supervision: i.n.b. validation: i.n.b, v.g.p. visualization: i.n.b, y.e.k. writing – original draft: i.n.b. writing – review & editing: v.g.p. conflict of interest the authors declare no conflict of interest. additional information author ids: bagryantseva i.n., scopus id 41461057600; ponomareva v.g., scopus id 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https://doi.org/10.1007/s10853-021-06137-0 https://doi.org/10.3390/membranes11030196 https://doi.org/10.1021/cr800187m https://doi.org/10.1021/ma00179a017 influence of the micromycete fusarium culmorum and its antagonists on the state of the antioxidant system of melissa officinalis l. chimica techno acta letter published by ural federal university 2022, vol. 9(2), no. 202292s5 eissn 2411-1414; chimicatechnoacta.ru doi: 10.15826/chimtech.2022.9.2.s5 1 of 5 influence of the micromycete fusarium culmorum and its antagonists on the state of the antioxidant system of melissa officinalis l. svetlana skugoreva a* , polina gushchina b, yana sharipova b, larisa darovskikh b a: biomonitoring laboratory, institute of biology of komi science centre, ural branch of the russian academy of sciences, syktyvkar 167982, russia b: institute of chemistry and ecology, vyatka state university, kirov 610000, russia * corresponding author: skugoreva@mail.ru this paper belongs to the mosm2021 special issue. © 2022, the authors. this article is published in open access form under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). abstract in recent years, the popularity of herbal medicine has increased. lemon balm (melissa officinalis l.) is a perennial essential oil herb that has been used as a medicinal plant for more than 2 thousand years. it is known that the productivity of plants is directly related to their resistance to phytopathogens, in particular, micromycetes of the genus fusarium. one of the main mechanisms of plant damage by phytopathogens is oxidative stress. micromycetes of the genus trichoderma and soil cyanobacteria (cb) occupy an important place among the natural antagonists of fungi of the genus fusarium. the aim of the work was to study the state of the antioxidant system of melissa officinalis l. plants when grown on substrates contaminated with the micromycete fusarium culmorum and its antagonists – the cyanobacterium fischerella muscicola and the micromycete trichodеrma viride. it was found that the presence of the pathogenic micromycete f. culmorum in the soils for growing lemon balm for two months has a stressful effect on lemon balm plants: the intensity of lipid peroxidation, the content of phenolic compounds and the amount of antioxidants in the in plant leaves were significantly higher than in the control. at the same time, at elevated temperatures, the content of phenolic compounds increased, which may be due to increased metabolism and the level of oxidative stress. the introduction of microorganisms-antagonists f. muscicole and t. viride into the soil makes it possible to activate the work of the antioxidant system of plants and reduce the effects of oxidative stress almost to the level of control. the studied antagonists can be recommended as promising for the development of biological products on their basis in order to protect medicinal plants from fusarium diseases. keywords lemon balm oxidative stress antioxidant system phytopathogens micromycetes antagonists received: 29.04.22 revised: 06.05.22 accepted: 24.05.22 available online: 30.05.22 key findings ● the presence of the pathogenic micromycete fusarium culmorum in the soil has a strong effect on lemon balm plants: it enhances lipid peroxidation, leads to the accumulation of phenolic compounds and antioxidants. ● the introduction of fischerella muscicola and trichodеrma viride antagonist microbes into the soil makes it possible to activate the antioxidant system of plants and reduce the consequences of oxidative stress almost to the level of control. http://chimicatechnoacta.ru/ https://dx.doi.org/10.15826/chimtech.2022.9.2.s5 http://creativecommons.org/licenses/by/4.0/ https://orcid.org/0000-0002-5902-5187 https://crossmark.crossref.org/dialog/?doi=https://doi.org/10.15826/chimtech.2022.9.2.s5&domain=pdf&date_stamp=2022-5-30 chimica techno acta 2022, vol. 9(2), no. 202292s5 letter 2 of 5 1. introduction in recent years, despite the great success in the creation of synthetic medicinal substances, the popularity of herbal medicine is growing. interest in medicinal herbs and preparations based on them is increasing due to the unique properties of herbal preparations and rapidly developing research technologies [1]. about 300 plant species are used by modern domestic scientific medicine [2]. the volume of cultivated medicinal plants is growing every year [3]. lemon balm (melissa officinalis l.) is a perennial essential oil herb that has been used as a medicinal plant for more than 2 thousand years. it grows in the regions of western asia and the eastern mediterranean, and is also cultivated in central europe. oils obtained from lemon balm plants exhibit antibacterial, antidepressant, antiviral and antispasmodic activity. the growth and development of plants is influenced by many factors. higher plants are in direct contact with the microflora of the rhizosphere. it is known that the productivity of plants is directly related to their resistance to phytopathogens. phytopathogenic microorganisms (mo) synthesize toxins that can inhibit and retard plant growth. these mo include micromycetes of the genus fusarium, which are widespread in soils and produce more than 150 toxins. one of the main mechanisms of plant damage by phytopathogens is oxidative stress, which is based on a sharp increase in oxidative processes in the body with insufficient functioning of the antioxidant system [4]. as a result of stress, the formation of free radicals increases, which induces the processes of lipid peroxidation (lpo) and causes the development of destructive processes both at the level of the cell, organ, and the whole organism [5]. unsaturated lipids or free fatty acids, which are part of the phospholipids of biological membranes, are most easily oxidized. the primary products of lpo are diene conjugates and hydroperoxides; the secondary products are alcohols, ketones, aldehydes, dialdehydes, etc. among the dialdehydes, malondialdehyde (mda) is of particular interest, serving as a marker of the degree of endogenous intoxication. by the content of mda in cells, one can judge the intensity of lpo. in the plant kingdom, phenolic compounds (pc) are among the most powerful natural antioxidants. the antioxidant properties of pс – reducing agents are due to their ability to serve as “traps” for free radicals [6]. pс are able to interact with hydroxyl (lo•) and peroxyl (loo•) lipid radicals due to their ability to donate an electron (or hydrogen atom). as a result, phenol radicals are formed – phenoxyls, which do not participate in the propagation of the oxidative process. in general, stress reactions initiate the formation or mobilization of specialized adaptation mechanisms, and also perform operational protection of the plant organism from death under unfavorable conditions [7]. micromycetes of the genus trichoderma [8] and soil cyanobacteria (cb) [9] occupy an important place among the natural antagonists of many phytopathogenic mo, in particular, fungi of the genus fusarium. antimicrobial compounds of cb can suppress phytopathogens through the destruction of the cytoplasmic membrane, inhibition of protein synthesis, the activity of hydrolytic enzymes, etc. [10]. the aim of the work was to study the state of the antioxidant system of melissa officinalis l. plants when grown on substrates contaminated with the micromycete fusarium culmorum and its antagonists – the cyanobacterium fischerella muscicola and the micromycete trichodеrma viride. 2. materials and methods 2.1. materials the cultures of mo were taken from the collection of the vyatka state agricultural academy (kirov, russia): micromycetes fusarium culmorum and trichodеrma viride, cyanobacterium fischerella muscicola. sterile nutrient soil for growing plants possessed the following agrochemical characteristics: ph=5.5–6.5; n – 50–150 mg/100 g; p (p2o5) – 100–250 mg/100 g; k (k2o) – 150–300 mg/100 g of soil (tver, russia). the instruments used include the spectrophotometer pe-5300vi, (llc “ekroskhim”, st. petersburg, russia) and the coulometer “expert-006” (econix-expert, moscow, russia). the key reagents are tris(hydroxymethyl)aminomethane, thiobarbituric acid, trichloroacetic acid (determination of mda content in lemon balm plants); folin-chocalteu reagent (content of phenolic compounds in alcohol extracts from lemon balm); potassium iodide (the total content of antioxidants in alcoholic extracts from lemon balm). 2.2. experiment preparation and conduct lemon balm seeds were washed with 1% potassium permanganate solution. the seeds were germinated under sterile conditions in petri dishes on filter paper moistened with distilled water for seven days. then the plants were transplanted into the soil. before planting the plants, suspensions of micromycetes f. culmorum (т = (5.0±0.1)·109 cells/cm3, 1 cm3 per 60 g of soil), t. viride (т = (5.0±0.1)·109 cells/cm3, 5 cm3 per 60 g soil), as well as cb f. muscicola (т = (3.0±0.1)·109 cells/cm3, 5 cm3 per 60 g soil) [11]. experiment scheme: 1) control (without mo additives); 2) f. culmorum; 3) f. culmorum + f. muscicola; 4) f. culmorum + t. viride; 5) f. culmorum + f. muscicola + t. viride. the studies were carried out in two series of experiments, differing from each other in temperature conditions: series no. 1 – 21±1 °c, series no. 2 – 29±3 °c. in both series of experiments, the change of day and night was controlled (12 h/12 h). two months after transplanting the plants into the soil, the content of pс chimica techno acta 2022, vol. 9(2), no. 202292s5 letter 3 of 5 in the leaves of lemon balm was determined by the spectrophotometric method with the folin-ciocalteu reagent (70% ethyl alcohol was used to prepare the aqueousalcoholic extract of lemon balm; the weighed portion of the plant was boiled with alcohol for two hours in a water bath). the mda content was determined by spectrophotometry with thiobarbituric acid, the аа of alcohol extracts was determined by coulometric titration in extracts prepared in the same way as for the determination of pс. 2.3. formulas for calculations the concentration of mda in lemon balm leaves was calculated by the formula [12]: 𝐶 = 𝐷 𝜀 ∙ 𝑙 ∙ 𝑚 , (1) where c is the concentration of mda, μmol/g fresh weight; d is the optical density; ԑ – the coefficient of molar extinction mda (1.56 · 105 cm-1 · m-1); l – the thickness of the solution layer in the cuvette, cm; m – the mass of the sample of plant material, g. the content of intracellular pс in plant samples was calculated using the formula: 𝑃𝐶 = 𝐶 ∙ 𝑉extr. 𝑚 ∙ 1000 , (2) where pс is the total content of intracellular pс, mg gallic acid/g dry weight; c is the concentration of pс obtained from the calibration curve based on the optical density of the samples, mg of gallic acid/dm3; vextr. – the total volume of the extract, cm3; m is the weight of the sample, g; 1000 – the conversion factor dm3 to cm3 (extract volume). the total antioxidant content was determined by the formula: 𝐴𝑂 = 𝑀 ∙ 𝑉extr. 𝑉al. ∙ 𝑚 , (3) where aо is the total antioxidant content, mg rutin/g dry weight; m is the concentration of phenolic compounds obtained in an aliquot of the extract, mg; vextr. – the total volume of the extract, cm3; val. – the volume of the aliquot, cm3; m is the mass of the sample, g. 2.4. statistical analysis the experiment was repeated four times when growing plants, the analyses – three (for determining the content of mda and aо) and two times (for fс). the results were statistically processed in excel. the significance of differences with the control was assessed by the student's test. 3. results and discussion medicinal plants can have a fungicidal effect due to the release of substances with allelopathic phytopathogenic properties, the so-called root rhizodeposites (essential oils, phenols, etc.) [13, 14], which reduce the effect of pathogenic mo. the study showed that the antimicrobial activity of lemon balm was not enough to neutralize the effect of the phytopathogen. the addition of f. culmorum mycelium suspension to the soil initiated the development of oxidative processes in lemon balm cells (figure 1). at a temperature of 29 °c, the concentration of mda in lemon balm leaves in variant 2 (only with the introduction of f. culmorum) was 1.8 higher than in the control. in the variants with the introduction of mo antagonists into the soil, the accumulation of mda was noted in the plants decreased almost down to the control values. to a lesser extent, this effect was manifested in the variant no. 4 with the introduction of t. viride, which is probably due to the relatively low antagonistic activity of this mo in relation to f. culmorum. to a greater extent, a decrease in the intensity of lipid peroxidation in plants caused by micromycetes was observed when f. muscicole was introduced into the soil (variants no. 3 and no. 5). earlier [11] it was found that at a temperature of 21 °c the mda content in lemon balm plants in the variant with fusarium (no. 2) was 5.9 times higher than that in the control. the use of mo antagonists reduced the accumulation of mda in plants. figure 1 the content of malondialdehyde in the leaves of lemon balm plants when f. culmorum and its antagonists are introduced into the soil (t = 29 °c). note: differences with control are significant at ** – p<0.01; *** – p<0.001. in response to the action of a stress factor, the work of the body's defense system is activated, which manifests itself in the synthesis of antioxidants. the total content of antioxidants in lemon balm leaves when the suspension of f. culmorum mycelium (variant no. 2) was added to the soil was 1.6 times higher than that in the control (figure 2). the use of mo antagonists significantly reduced this indicator. in the variants no. 4 and no. 5, the aa of plants slightly exceeded the control. when f. muscicole was added to the soil (option no. 3), the value of the total antioxidant content was 1.6 times lower than the one in the control. 0 1 2 3 4 5 6 7 8 control f. culmorum f. culmorum + f. muscicola f. culmorum + t. viride f. culmorum + f. muscicola + t. viride t h e c o n te n t o f m a lo n d ia ld e h y d e , μ m o l/ g experience options *** ** chimica techno acta 2022, vol. 9(2), no. 202292s5 letter 4 of 5 figure 2 the total content of antioxidants in the leaves of lemon balm plants when f. culmorum and its antagonists are introduced into the soil (t = 29 ºc). note: differences with control are significant at ** – p < 0.01; *** – p < 0.001. the activation of lpo processes in plant cells led to the accumulation of ps. with an increase in temperature, plant metabolism intensified, which led to an increase in the ps content. thus, at a temperature of 29 °с, the values of the pс concentration in lemon balm plants were 3.8–9.0 times higher than at a temperature of 21 °с (figure 3). with an increase in temperature, an increase in the concentration of mda in lemon balm plants was also noted [11]. there is evidence in the literature that temperature stress affects the antioxidant system of plants. it was found that under the action of elevated temperatures there is an increase in activity and the appearance of multiple forms of enzymes in plants [15], which is explained by an increase in metabolism. in the variants with mo addition, a greater accumulation of pс was noted than in the control (by 1.3–3.4 times), which indicates a more active work of the plant defense system in response to the stress factor. the maximum content of these compounds was determined in the option no. 2 with the addition of a suspension of the mycelium of the phytopathogenic micromycete f. culmorum. in the other variants, lower values of this indicator were noted, which may be due to the antagonistic effect of f. muscicola and t. viride. there is a direct correlation between the content of pс and mda (r=0.69), pс and aо (r=0.84), mda and aо (r=0.69), which indicates the activation of the plant antioxidant system (accumulation of antioxidants and pс) under conditions of oxidative stress. figure 3 the content of phenolic compounds in the leaves of lemon balm plants when f. culmorum and its antagonists are introduced into the soil. note: differences with control are significant at * – р < 0.05; ** – p < 0.01; *** – p < 0.001. 4. conclusion the presence of the pathogenic micromycete f. culmorum in the cultivation grounds has a stressful effect on lemon balm plants: the lpo intensity, the content of pс and aо in the leaves were significantly higher than those in the control. at the same time, at elevated temperatures, the pс content increased, which may be due to the increase in the metabolism and the level of oxidative stress. the introduction of microorganisms-antagonists f. muscicole and t. viride into the soil makes it possible to activate the work of the antioxidant system of plants and reduce the effects of oxidative stress almost to the level of control. the studied antagonists can be recommended as promising for the development of biological products on their basis in order to protect medicinal plants from fusarium diseases. supplementary materials no supplementary materials are available. funding the work was carried out within the framework of the state task of the ib of the komi national research center of the ural branch of the russian academy of sciences on the topic “structure and state of components of man-made ecosystems of the southern taiga subzoneˮ, the state registration number in the unified state register no. 122040100032-5. 0 10 20 30 40 50 60 70 80 90 control f. culmorum f. culmorum + f. muscicola f. culmorum + t. viride f. culmorum + f. muscicola + t. viride t o ta l a n ti o x id a n t c o n te n t, m g r u ti n /g d ry w e ig h t experience options *** ** *** 0 20 40 60 80 100 control f. culmorum f. culmorum + f. muscicola f. culmorum + t. viride f. culmorum + f. muscicola + t. viride p h e n o li c c o m p o u n d s , m g g a ll ic a c id /g d ry w e ig h t experience options t = 21 °с t = 29 °с * ** *** ** ** * *** *** chimica techno acta 2022, vol. 9(2), no. 202292s5 letter 5 of 5 acknowledgments none. author contributions conceptualization: s.s. data curation: l.d. formal analysis: p.g., ya.b. funding acquisition: s.s. investigation: ya.b., s.s. methodology: l.d. project administration: s.s. resources: l.d. software: p.g. supervision: s.s. validation: l.d. visualization: p.g. writing – original draft: s.s., p.g. writing – review & editing: s.s., p.g. conflict of interest the authors declare no conflict of interest. additional information author ids: svetlana skugoreva, scopus id 57195525210; larisa darovskikh, scopus id 57201724246. websites: institute of biology of komi science centre, ub ras, https://ib.komisc.ru/rus; vyatka state university, https://www.vyatsu.ru. references 1. sambukova tv, ovchinnikov bv, ganapolsky vp, yatmanov an, shabanov pd. prospects for phytopreparations (botanicals) use in modern pharmacology. rev clin pharmacol drug ther. 2017;15(2);56–63. doi:10.17816/rcf15256-63 2. vishnyakova sv, zhukova mv. medicinal and essential oil plants ekaterinburg: ural state forestry engineering university, 2017. 41 p. 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http://dspace.bsu.edu.ru/bitstream/123456789/34109/1/svistova_lekarstvennye.pdf https://elibrary.ru/download/elibrary_25135527_71369302.pdf https://elibrary.ru/download/elibrary_37276206_29674813.pdf electroreduction of silicon from the nai-ki-k2sif6 melt for lithium-ion power published by ural federal university eissn2411-1414; chimicatechnoacta.ru article 2022, vol. 9(4), no. 20229424 doi: 10.15826/chimtech.2022.9.4.24 1 of 6 electroreduction of silicon from the nai–ki–k2sif6 melt for lithium-ion power sources rayana k. abdurakhimova ab *, michail v. laptev b , natalia m. leonova a , anastasia m. leonova a , alexander s. schmygalev ab , andrey v. suzdaltsev ab a: institute of hydrogen energy, ural federal university, ekaterinburg 620075, russia b: institute of high-temperature electrochemistry ub ras, ekaterinburg 620137, russia * corresponding author: arianaboimuradova@yandex.ru this paper belongs to a regular issue. © 2022, the authors. this article is published in open access under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). abstract silicon and silicon-based materials are increasingly used in microelectronics, metallurgy and power generation. to date, the active study aimed at the development of silicon materials to be used in devices for solar energy conversion, accumulation and storage is underway. in addition, silicon is a promising anode material for lithium-ion fuel cells. in the present paper, a possibility of silicon electroreduction from the nai–ki–k2sif6 melt in the argon atmosphere was studied. with this aim in view, the electrolysis of the nai-ki-k2sif6 melt with glassy carbon cathode was performed under galvanostatic and potentiostatic regimes at the temperatures from 650 to 750 °с. the morphology, phase and elemental analyses of the obtained silicon deposits were performed after their separation from the electrolytes by the icp, sem-edx, xrd and raman spectroscopy methods. fiber and thread-like silicon samples of 60 to 320 nm in dimeter with admixture concentrations (mainly oxygen) from 1.2 to 4.6 wt.% were synthesized. the obtained samples were tested as possible si/c composite anodes for lithium-ion power sources. the discharge capacity of such power sources after 30 cycles of lithiation-delithiation ranged from 440 to 565 mah·g–1, and the coloumbic efficiency ranged from 89 to 91%. keywords silicon nanofibers electroreduction melt lithium-ion power source cycling received: 21.10.22 revised: 01.12.22 accepted: 01.12.22 available online: 06.12.22 key findings ● the possibility of electrodeposition of silicon deposits with a developed surface from the nai–ki–k2sif6 melt at a temperature from 650 to 750 °с was shown for the first time. ● the energy characteristics of the obtained silicon in the anode material of a lithium-ion current source during cycling were determined. 1. introduction silicon and silicon-based materials are becoming widely used in microelectronics, metallurgy and power generation [1]. silicon materials to be used in devices for solar energy conversion, accumulation and storage are being actively developed [2–4]. silicon is a promising anode material for lithium-ion power sources because its specific lithium-adsorption capacity (4200 mah·g–1) is by an order of magnitude higher than those of graphite-containing anode materials (372 mah·g–1) [5–7]. however, high silicon anode lithium-adsorption capacity implies a significant volume expansion (up to 300%) that may result either in destruction of the power source or in the contact fault between the anode material and the substrate (current collector). application of composite materials based on nano-size or submicron silicon particles is one of the possible ways to solve this problem [8, 9]. the methods of carbothermal reduction of quartz followed by refining the obtained silicon from admixtures via chlorination and hydration [10] were implemented in the industrial scale, but thus-obtained silicon has a form of crystals of several tens of µm is size. to obtain nano-size silicon crystals, relatively complex and expensive methods of laser ablation, plasma chemical synthesis, laser-induced dissociation, etc. [11], are known. these methods are unsuitable for industrial silicon production. methods of silicon electroreduction from molten salts for producing the nanoand micro-sized silicon with http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2022.9.4.24 mailto:arianaboimuradova@yandex.ru http://creativecommons.org/licenses/by/4.0/ https://orcid.org/0000-0003-3338-0057 https://orcid.org/0000-0003-1016-8977 https://orcid.org/0000-0001-5900-7045 https://orcid.org/0000-0001-9783-309x https://orcid.org/0000-0003-3004-7611 https://crossmark.crossref.org/dialog/?doi=https://doi.org/10.15826/chimtech.2022.9.4.24&domain=pdf&date_stamp=2022-12-06 chimica techno acta 2022, vol. 9(4), no. 20229424 article 2 of 6 controlled morphology are industrially promising, relatively simple and inexpensive. fluoride mixtures of kf–naf–lif, lif–naf, lif–caf2 and similar compositions were suggested as first possible electrolytes for silicon production at the process temperatures ranging from 500 to 1500 °с [12–14]. however, their main drawback was the difficulty of separating the fluoride residues from the cathode deposits because of their low solubility in water and high boiling temperatures. high chemical aggressiveness to the reactor materials is the main disadvantage of fluoride melts, which limits the possible range of their application and leads to the complication of the reactor construction as well as to the silicon contamination by the corrosion products. the kcl–kf system with kf concentration up to 66 mol.% was suggested as a water-soluble electrolyte that is a good solvent for both k2sif6 and sio2 [15–17]. a relative aggressiveness of kf to the reactor materials and a required decontamination of kf from h2o and hf during the molten kcl–kf mixture preparation are the disadvantages of the method of electrolytic silicon production. all mentioned factors may cause the melt composition instability and appearance of the admixtures in the obtained silicon. molten electrolytes based on cacl2–cao, where sio2 is a source of silicon, were extensively studied for the electrolytic silicon production [18–20]. the advantages of these electrolytes include high cacl2 solubility in water that allows separating deposits from the electrolyte residues after the electrolysis and lower chemical aggressiveness, as compared with fluorite salts, to the reactor materials. among the disadvantages of this method, we should mention a relatively high temperature, unstable composition of electroactive ions in the molten electrolyte and presence of oxide admixtures, which causes inevitable appearance of oxygen in the silicon deposit bulk. to decrease the electrolysis temperature, stabilize the composition of the silicon-containing electroactive particles and to control the morphology of silicon deposits, the melts containing iodides may be used. in particular, the kcl–kf–ki–k2sif6 system containing ki up to 75 mol.% [21] is assumed to eliminate the presence of water traces in the reactor and, therefore, the requirements to the preparation of the molten electrolytes and equipment used increase. electrodeposition of silicon and silicon-based materials from low-temperature ionic liquids and organic electrolytes is also a promising direction [22–26]. however, the productivity of such methods seems to be relatively low, and the organization of feeding the electrolyzer with sicl4 is more complex and requires additional equipment. in this work, we studied the possibility of electrodeposition of fibrous silicon deposits from the nai-ki-k2sif6 melt as well as the cycle ability of the obtained silicon deposits in the lithium-ion current sources with silicon-based anodes. the selected melt is promising for silicon electrodeposition, since it has a relatively wide range of compositions with a liquidus temperature below 700 °c [27]. 2. experimental 2.1. electrolyte preparation electrolytes for silicon electroreduction were prepared in a glassy carbon crucible from commercial chemically pure individual nai and ki salts (reakhim, russia) and commercial reagent grade k2sif6 (reakhim, russia), which was preliminary subjected to hydrofluoration by stepwise heating to 450 °с in the mixture with nh4f [28]. the salt mixture of (wt.%) 56nai–44ki was purified from oxygen and other admixtures immediately prior to the experiments. the salts were mixed with elemental iodine, heated stepwise to 400 °с and exposed for 3–4 h. the evaporating iodine interacted with oxides according to reaction (1) [21]: 2m2o + i2 = 4mi + o2 (m = k, na) (1) after this, the mixture was heated to the working temperature, and the obtained melt was additionally subjected to the galvanostatic electrolysis at the cathode current density of 0.02 a·cm–2 during 2–4 h. a graphite cathode and an insoluble glassy-carbon anode (crucible) were used. the electrolysis durability was determined empirically by the moment of shifting the electrode potential to the potential of alkali metal electroreduction. during the electrolysis, electropositive admixtures (fe, ni and etc.) were deposited on the cathode and removed from the reactor with a cathode. 2.2. reactor for the silicon synthesis the experiments on the silicon electroreduction were performed at the temperatures from 650 to 750 °с in a hermetically sealed quartz reactor with the pure argon atmosphere. a glassy carbon container with a molten electrolyte was located at the bottom of the reactor. the walls of the reactor were screened with nickel foil to protect them from possible salt vapors. the electrodes and the control thermocouple were assembled to the fluoroplastic cover of the reactor. cylindrical graphite bars of the mpg8 grade (technocarb company, chelyabinsk, russia) were preliminary rinsed in acidic water solution and dried under vacuum. there bars served as working electrodes. monocrystalline silicon (99.9999 wt.%) was used as a counter electrode and a quasi-reference electrode. the silicon electroreduction from the nai-ki melt with the addition of 7 wt.% of k2sif6 was performed under the potentiostatic regime at the cathode overpotential of 0.2 v and under galvanostatic regime at the cathode current density ranging from 1 to 5 ma·cm–2. the parameters of the electrolysis were determined during the process of silicon electroreduction in halide melts in the temperature range of 700–750 °с [15–17, 29]. the electrolysis was performed using a pgstat autolab device with the nova 1.12 software (metrohm, netherlands). when the electrolysis was terminated, the deposits were lifted from the melt, cooled down to room temperature and then removed from the reactor. chimica techno acta 2022, vol. 9(4), no. 20229424 article 3 of 6 the electrolyte residues were removed from the deposits by the high-temperature distillation under the argon flow at 950 °с for 6–8 h. during this procedure, cathode sediments with the salt residues were heated in argon to a temperature of 950 °c. in these conditions, the component with the highest vapor pressure (salts) evaporated and crystallized in the cold part of the distillation device [30]. the conventional method (washing out electrolyte residues in water-acid solutions) is less effective in the case of fibrous deposits, since it leads to silicon oxidation and its significant losses. 2.3. analysis of the melts and deposits the concentration of silicon in the melt before and after the electrochemical measurements and electrolysis was determined using the atomic-emission method by an icap 6300 duo spectrometer (thermo scientific, usa). the morphology of the obtained deposits was studied using a scanning electron microscope tescan vega 4 (tescan, czech republic) with an xplore 30 eds attachment (oxford, great britain). the phase composition and the presence of si–si and si–o bounds were determined by the xrd and raman spectroscopy methods using a “leica dmlm” microscope and “renishaw u1000” spectroscope (great britain) equipped with a notch-filter and ccd camera (solid state laser produced by cobolt samba company (sweden) of the 50 mw capacity). 2.4. electrochemical characteristics of silicon the electrochemical characteristics of the obtained silicon powders at lithiation/delithiation were tested in the composition of the composite anode of the lithium-ion power source containing (wt.%): 80 – silicon, 10 – carbon, 10 – bounding polyvinylidene difluoride dissolved in n-methyl2-pyrollidone. the samples of lithium-ion power sources were assembled in a hermetically sealed argon box with the concentration of admixtures (o2, h2o) not exceeding 0.1 ppm. the anode material was spreaded on the steel net, a lithium foil served both as a counter electrode and as a reference electrode. all electrodes were separated from each other by two separator layers. a solution of lipf6 in the mixture of ethylene carbonate/dimethyl carbonate/diethyl carbonate was used as the electrolyte. the purity of all elements used was 99.99 wt.% (sigma-aldrich, germany). the measurements were performed by the galvanostatic cycling using a multichannel potentiostat wonatech wbcs-3000 m2 (wonatech co., ltd., korea). 3. results ana discussion 3.1. silicon electroreduction the parameters and results of the silicon electroreduction are illustrated in table 1. depending on temperature, electrolysis regime and parameters, fiber and thread-like silicon deposits of 50 to 320 nm in diameter and up 20 µm in length were primarily obtained on the graphite cathode. the microphotographs of the typical deposits are presented in figures 1 and 2. according to the eds analysis, the concentration of admixtures in the obtained silicon varied from 1.2 to 4.6 wt.%. oxygen was the main admixture. we have not been able yet to determine whether it is a surface oxide or a bulk one. however, we assume that this is surface oxygen and oxidated si, since the methods and devices used allow the electrodeposition to be carried out as cleanly as possible. figures 3 and 4 provide the x-ray diffraction pattern and raman spectra of the obtained silicon deposit. it is seen that the sample has the form of polycrystalline silicon with sio2 admixtures. only a si–si bond is observed, which testifies that there is no interaction between the deposited silicon and the carbon substrate under the experiment conditions. 3.2. electrochemical characteristics of silicon figure 5 provides potential dependencies of si/c composite anodes, fabricated from the fiber (sample 1) and thread-like (sample 2) silicon deposits, in the composition of the experimental lithium-ion power sources, during their first lithiation/delithiation cycle (forming cycling). it is seen that the anode is subjected to charging and discharging, which proves the possibility of application of such anodes in lithium-ion power sources. table 1 parameters and results of silicon electroreduction from the nai-ki melt with addition of 7 wt.% of k2sif6. no. t, °c i, ma cm–2 overpotential, v time, min deposit 1 650 1 – 60 fibers, ø 60–160 nm 2 700 – 0.2 40 threads, ø 130–200 nm 3 750 5 – 25 fibers, ø 90–320 nm figure 1 microphotographs of a typical fiber silicon deposit obtained by the electrolysis of the nai-ki-k2sif6 melt at a cathode current density of 5 ma cm–2 and 750 °c before (a) and after (b) the electrolyte residues removal. chimica techno acta 2022, vol. 9(4), no. 20229424 article 4 of 6 figure 2 microphotographs of a typical thread-like silicon deposit obtained by the electrolysis of the nai–ki–k2sif6 melt at 700 °c and cathode overpotential of 0.2 v after the electrolyte residues removal. figure 3 x-ray diffraction of the silicon deposit, obtained by the electrolysis of the nai–ki–k2sif6 melt at a cathode current density of 5 ma cm–2 and 750 °c after the electrolyte residues removal. figure 4 raman spectra of the silicon deposit, obtained by the electrolysis of the nai–ki–k2sif6 melt at a cathode current density of 5 ma cm–2 and 750 °c after the electrolyte residues removal. the inclined regions at the potentials of 0.2–1.25 v for the sample 2 and at the potentials of 0.2 and 1.2 v for the sample 1 correspond to the process of electrode/electrolyte interphase boundary formation (sei). on the charge curves (left part) there is a region where the potential stabilizes at 0.18 v. the characteristic plateau in the region of 0.1-0.2 v corresponds to the process of lithium intercalation into silicon according to reaction [31]: siy + xli+ xe →lixsiy. (2) the discharge (right part) curves illustrate an abrupt potential jump up to 1.4 v, which corresponds to the process of silicon deintercalation. during the first (forming) cycling the coulombic efficiency of the charge/discharge process was 60%. to estimate the reversibility of the anode material, cvs of samples 1 and 2 were also obtained after its cycling (see figure 6). from them, we can draw a preliminary conclusion about the presence of reversibility (the presence of peaks in the cathode and anode regions) of the samples, as well as the closeness of the lithium reduction/oxidation potentials to the charge/discharge potentials from the dependences shown in figure 5. to determine the discharge capacity and coulombic efficiency (the ratio of the charge capacity to the discharge one) a galvanostatic cycling of the experimentally obtained samples was charged at the current of 200 ma·g–1. we performed 30 cycles. figure 7 presents the dependencies of discharge capacity and coulombic efficiency of the samples during cycling. after 30 charge/discharge cycles, the discharge capacity of the anode samples composed of fiber and thread-like silicon decreased from 1390 and 1610 to 440 and 565 mah·g–1, and the coulombic efficiency was 89 and 91%, respectively. an irreversible capacity may be explained by the presence of sio2 admixture that transforms into lithium silicate during the lithiation, by the interaction of the substrate components with silicon and lithium, and by the destruction of silicon fibers and the contact fault with the substrate [32]. further research is needed to determine the reasons for such behavior. figure 5 first charge/discharge cycle of half-elements with silicon-based composite anodes. 0 10 20 30 40 50 60 70 80 2theta / in te n si ty / c p s 1 si 2 sio2 1 1 1 1 12 98.4 1.5 si sio2 0 100 200 300 400 500 600 700 800 900 raman shift / cm-1 in te n si ty 510 cm-1 si-si bond 0.0 0.4 0.8 1.2 1.6 0 10 20 30 40 50 60 70 80 90 е (v s e l i/ l i+ ), v time, h sample 1 sample 2 chimica techno acta 2022, vol. 9(4), no. 20229424 article 5 of 6 figure 6 cvs for samples of silicon-based composite anodes after cycling. sweep rate of 0.1 mv s–1. figure 7 change in the discharge capacity and coloumbic efficiency of the charge/discharge process of the samples during cycling. 4. conclusions the possibility of using silicon fibers electrolytically produced from the nai–ki–k2sif6 melt at 650–750 °c in composite si/c anodes of lithium-ion power sources was studied. the silicon electroreduction was performed under the galvanostatic regime at the cathode current density ranging from 1 to 5 ma cm–2, as well as under the potentiostatic regime and the cathode overpotential of 0.2 v. the electrolysis was found to result in the formation of fiber and threadlike silicon deposits with the average diameter from 60 to 320 nm and length up to 20 µm. according to the analyses, the concentration of admixtures, primarily oxygen, in the obtained deposits varied from 1.2 to 4.6 wt.%. the energy characteristics of the obtained silicon samples were determined during their lithiation-delithiation in the composition of the lithium-ion power source. after 30 cycles, the discharge capacity of the anode samples of fiber and thread-like silicon decreased from 1390 and 1610 to 440 and 565 mah·g–1, and the coloumbic efficiency was 89% and 91%, respectively. we assume that the irreversible capacity of the samples may be associated with the presence of sio2 admixture; it also may be caused by the interaction of the substrate components with silicon and lithium as well as by the destruction of silicon fibers and contact fault between silicon and the substrate. supplementary materials no supplementary materials are available. funding the work was performed within the agreement no. 075-032022-011 dated 14.01.2022 (theme number feuz-20200037). acknowledgments the facilities of the composition of compounds the shared access center of institute of high-temperature electrochemistry ub ras were used in this work. author contributions conceptualization: a.v.s. data curation: r.k.a., a.v.s. formal analysis: r.k.a., n.m.l., a.m.l. funding acquisition: a.v.s. investigation: r.k.a., m.v.l., n.m.l., a.m.l. methodology: r.k.a., a.s.s., n.m.l., a.m.l. project administration: a.v.s. resources: r.k.a., m.v.l., n.m.l., a.m.l. supervision: a.s.s., a.v.s. validation: n.m.l., a.m.l., a.v.s. visualization: r.k.a., a.v.s. writing – original draft: r.k.a., n.m.l., a.m.l. writing – review & editing: a.v.s. conflict of interest the authors declare no conflict of interest. additional information author ids: michail v. laptev, scopus id 57203958198; natalia m. leonova, scopus id 57352201500; anastasia m. leonova, scopus id 57352053900; alexander s. schmygalev, scopus id 56458886600; andrey v. suzdaltsev, scopus id 55218703800. websites: ural federal university, https://urfu.ru/en; institute of high-temperature electrochemistry, 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obtaining nano and microparticles chimica techno acta article published by ural federal university 2021, vol. 8(4), № 20218405 eissn 2411-1414; chimicatechnoacta.ru doi: 10.15826/chimtech.2021.8.4.05 1 of 8 kinetic instability of a chitosan – aspartic acid – water system as a method for obtaining nanoand microparticles t.n. lugovitskaya a* , a.b. shipovskaya b, x.m. shipenok b a: ural federal state university named after the first president of russia b. n. yeltsin, 620002 mira st., 19, yekaterinburg, russia b: saratov national research state university named after n.g. chernyshevsky, 410012 astrakhanskaya st., 83, saratov, russia * corresponding author: tlugovitskaja@mail.ru this article belongs to the regular issue. © 2021, the authors. this article is published in open access form under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). abstract the specific electrical conductivity and dielectric constant of aqueous solutions of ionic aminopolysaccharide chitosan in l-aspartic acid were investigated. an increase of the mobility of charge carriers in these solutions was found in comparison with solutions of an ind ividual acid. the evaluation of the kinetic stability revealed that the viscosity, electrical conductivity and dielectric constant of the ch itosan – l-aspartic acid – water system decrease, while the ph value increases. it was shown that the time variation of physicochemical and electrochemical parameters is due to the effects of counterionic association with the transition of macromolecules to the ionomeric state and is accompanied by phase segregation of the polymer phase in the form of nanoand microparticles. the conducted studies carried out have shown the fundamental possibility of controlling the metastable state of this system in order to obtain nanoand microparticles. keywords chitosan l-aspartic acid counterionic association nanoparticles received: 06.10.2021 revised: 20.11.2021 accepted: 23.11.2021 available online: 26.11.2021 1. introduction chitosan (cts), a product of partial or complete deacetylation of chitin, is an ionic copolymer of aminopolysaccharide. since the temperature of thermal decomposition of cts is lower than its melting point, the processing of this polymer into the final products involves the step of dissolving in organic or inorganic acids. in an aqueous acidic medium at ph below pka, the amino groups of cts are protonated, resulting in the formation of a salt form of the polymer – a positively charged polyelectrolyte (~ − nh3 + ) with ionic conductivity. the main contribution to the transfer of electricity in an aqueous acidic cts solution is made by free counterions, as well as excess of hydronium ions [1–3]. in this case, the nature of the acid-solvent of cts significantly affects the quantitative characteristics of electrical conductivity, which determines the conformation of macromolecules in solution and the phase state of the polymer system after removal of the liquid medium [1]. thus, in strong hcl, a linear decrease in the specific electrical conductivity (æsp) with an increase in the cts concentration (сcts) is observed. the conformation of the expanded helix is realized due to the repulsion of charged macrochains. in weak acids (propionic, acetic and formic), the concentration dependence of the specific electrical conductivity is nonlinear, the æsp values grow increase with an increase in ccts value. there is an attraction and “adhesion” of local sections of macrochains through ionic crosslinking ~ − nh3 + with r − coо− and h-bonds of ohgroups of cts with the carbonyl oxygen of the acid, as a result of which the macromolecules assume the coiled conformation. cts solutions in hcl have a weak film-forming ability and give a loose structure with a pore diameter of more than 10 mm when dried on an inert surface. cts films cast from aqueous solutions of carboxylic acids are characterized by a dense ordered structure. when an electric field is applied in an aqueous acidic cts solution, internal polarization phenomena can occur, i.e., displacement of charges that create a volumedistributed dipole moment. the relaxation processes of the electric polarization of the cts salt form are manifested in dielectric spectra in the frequency range below 1010 hz [4]. like conductometry, dielectric relaxation spectroscopy is highly sensitive to changes in the electrical conductive properties of aqueous acidic cts solutions and makes it possible to reliably control the state of counterions (free, bound) in them. http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2021.8.4.05 http://creativecommons.org/licenses/by/4.0/ https://orcid.org/0000-0002-8286-0711 chimica techno acta 2021, vol. 8(4), № 20218405 article 2 of 8 cts macromolecules are characterized by highly co mplex behavior in solutions. this is primarily due to the polyelectrolyte swelling of charged macromolecular coils and increased chain rigidity. cts solutions are also characterized by instability of viscosity properties over time, which is usually explained by the destruction of macromolecules as a result of acid hydrolysis of glycosidic bonds [5–7]. however, there are studies that make it possible to exclude destruction as the main reason for the decrease in the viscosity of chitosan solutions in time [8, 9] and to explain this effect by conformational rearrangements o f macromolecules [10], changes in the supramolecular structure, including aggregation [9, 11], and also by phase separation of the system as it is stored [11, 12]. cts is widely used due to a complex of valuable properties, as well as an annually renewable resource base [13–15]. chitosan-containing nanomaterials, in particular nanoparticles, deserve special attention [16, 17]. compared to the original cts, they acquire additional valuable properties due to their small size, increased surface area, and quant um size effects. like cts, chitosan-containing nanoparticles are nontoxic, biocompatible, and biodegradable, which predetermines their use in medicine, as well as in the food, textile, and cosmetic industries [18–22]. for obtaining nanoparticles, the most common used are spray drying under special conditions, or methods of ionotropic gelation and emulsion cros slinking with tripolyphosphate, glutaraldehyde, genipin [16]. in some cases, dibasic and tribasic pharmacopoeial acids (malic, tartaric, citric, and succinic) were used, which simultaneously act as a solvent for the polymer and as a cross linking reagent [23–25]. it should be noted that the use of biologically active acids for the formation of cts nanoparticles significantly expands the directions of t heir application in biomedical and pharmacological applications [26–28], veterinary medicine [29], and plant growing [30–33]. the use of l-aspartic acid (aspa), a proteinogenic amino acid that plays an important role in a living organism, seems to be promising [34, 35]. unlike traditional wateracid cts dissolving media based on monobasic carboxylic acids (hcooh, acoh), aspa contains two carbo xylic and one amino groups. therefore, in an aqueous solution, depending on the ph of the medium, its molecules can exist in several ionic forms. at ph = 3.0, the isoelectric point is located, at ph = 4, almost equal proportions of zwitter ions (н2asp) and aspartate anions (нasp−) are realized, whereas in the range of ph = 4.7–8.0, нasp− is the predominant ion [36]. the resulting high concentration of hydrogen ions (hydronium), which are the main carriers of electricity, provides prototropic conductivity of an aqueous solution of aspa [37, 38]. previously, we have found that the solubility of aspa in н2о increases in the presence of cts [39]. the conditions for the preparation of cts solutions in aspа – н2о mixture and some of their properties have also been discussed [40]. thus, in an aqueous medium, the macromolecules of the salt cts form exhibit the properties of a weakly dissociating polyelectrolyte with a partially compensated charge. the calculated huggins constants and temperature viscosity coefficients showed an increased rigidity of their macrochains. however, kinetic stability was not evaluated, although the cts – aspa – h2o system showed all the characteristic features of phase separation. as in the case of synthetic polyelectrolytes [41, 42], not only the dissociation of ionogenic groups of cts aspartate can occur in an aqueous medium, but also the interaction of the polycation with hasp– with the formation of ion pairs, multiplet structures (combination of ion pairs) and the transition of macromolecules to the ionomeric state. at the initial stage of phase separation, these processes should be accompanied by phase segregation of the polymer phase in the form of nanoand microparticles. this assumption served as the basis for this study. the aim of this work is to study the kinetic stability of the cts – aspa – h2o system during storage to obtain nano and microparticles using viscometry, potentiometry, conductometry, and dielectric relaxation spectroscopy as the most informative methods for studying the counterions state (free, bound) in polyelectrolyte solutions [4, 40–42]. 2. materials, objects and methods 2.1. m aterials the starting reagents were powdered cts with a viscosity average molecular weight m̅η = 200 kda, a degree of deacetylation of 82 mol%, and a moisture content of w = 8±1 wt% (zao bioprogress, rf); powdered l-aspа of pharmacopoeial purity, obtained by biocatalytic synthesis using e. coli strain vkpm 7188 (jsc bioamid, rf); distilled water (ph = 6.0); ethyl alcohol (95.6%), and acetone (99.8%). cts and aspa were used without additional purification; all other reagents were of analytical grade. 2. 2. p reparation of objects of study a working aspa solution with a concentration of сaspа = 0.06 mol/l was prepared by dissolving a weighed portion of aspa powder in distilled water at 80 °c, followed by cooling down to room temperature at a rate of 20 °c/h. a series of solutions of lower concentrations were obtained by successive dilution of the working solution with distilled water. the ph values of aspa solutions in н2о with сaspа = 0.003–0.060 mol/l were in the range of 3.1–4.2. freshly prepared acid solutions were used in all experiments. to obtain system cts + aspa + н2о, calculated weighed portions of cts (considering the moisture sample) and aspa were placed into some volume of н2о and stirred on a magnetic stirrer at a rotation speed of 400–500 rpm at 25 °c until visual dissolution of the powders (for 2–3 h). the concentrations of the polymer and acid in the solution were varied in the ranges сcts = 0.002–0.035 monomol/l and сaspа = 0.03–0.06 mol/l, respectively. before experiments, all systems were filtered through a millipore filter with a pore diameter ≤0.45 μm. chimica techno acta 2021, vol. 8(4), № 20218405 article 3 of 8 the cts + aspa + н2о system were stored in a room atmosphere (760 mm hg, 22±2 °c) for 96 h, regularly taking samples to assess their physicochemical parameters. in all experiments, the conditions for the preparation of the system and the time at which the physicochemical characteristics began to be measured were the same. the stability of the systems was assessed by measuring their conductivity, ph, viscosity and permittivity, as well as by sem. 2. 3. obtaining p articles to obtain nanoparticles and microparticles, 0.5 μl of a freshly prepared or stored cts + aspа + н2о system was sprayed onto a degreased (ethyl alcohol, acetone) glass surface using a mechanical syringe-shaped injector and dried for 1–2 h (the technique is similar [43]). the obtained particles obtained were dried at 22±2 °c under atmospheric pressure to an air-dry state, and analyzed using sem. 2.4. м e thods gravimetric measurements were carried out on an ohaus discovery analytical balance (usa), weighing accuracy being ±0.0001 g. ph was measured on a mettler toledo five easy fe20 ph-meter (mtd, singapore). conductivity was measured on a wtw inolab cond 7110 conductometer (germany) at 25 °c. a thermostated cell with a volume of 25 ml was used. specific conductiv ity (æsp, s·m−1) was calculated using the specific conductivity of water by the formula: æsp = 𝐾 𝑅⁄ − æh2o = æcts − æh2o, (1) where к = 0.1213 m−1 is the cell constant evaluated from 0.01 n kcl solution; r is the resistance of the system, s; æcts and æн2о are the specific conductivity of the chitosancontaining system and water, respectively, s·m−1. the viscometric measurements were carried out in an ubbelohde viscometer (rf) with a capillary diameter of 0.56 mm at 25 °c. the relative viscosity (rel) was calculated from: rel = 𝑡 𝑡0 ⁄ , (2) where t is the flow time of the cts + aspа + н2о sistems, s; t0 is that of the aspa aqueous solution, s; сcts is expressed in g/dl; the accuracy of measuring t and t0 was ±0.1 s. the frequency dependences of the real (εʹ) and imaginary (εʹʹ) parts of the complex permittivity were measured on an agilent microwave network analyzer pna-x n5242a vector network analyzer (usa) using an agilent 85070e coaxial probe in the frequency range f = 107–1011 hz at 25 °с. the dielectric loss tangent was calculated from the ratio tgδ = εʹʹ/εʹ. sem images were taken on a mira\\lmu scanning electron microscope (tescan, cz) equipped with an energy dispersive detector (edx) at a voltage of 30 kv and a conducting current of 400 pa. a 5 nm thick gold layer was deposited on each sample using a k450x carbon coater (de). 2. 5. statistical analysis in each experiment on the study of physicochemical properties, at least 3 parallel experiments were carried out; the arithmetic mean and standard deviation were calculated. 3. r esults and discussion we have previously shown that the concentration dependence of the reduced specific viscosity of a freshly prepared aqueous solution of cts aspartate is not linear, has a max or a plateau and a descending branch with a decrease in cts [40]. this hydrodynamic behavior indicates the implementation of a mixed polyelectrolyte-ionomer mode, when some of the hasp– counterions are in an associated (bound) state with −nh3 + groups of the macrochain with the formation of ion pairs (fig. 1a). the revealed features of the counterions state in macromolecular coils of the cts salt form were proved by studying the electrochemical properties of the polymer system. thus, the specific electrical conductivity of a cts solution in aspа – н2о at сcts = const increases with an increase in the acid concentration (fig. 2a, curve 1). a similar dependence is observed for aqueous solutions of individual aspa (curve 2). (a ) (b) (c ) (d) fi g. 1 distribution of free and bound counterions in the cts – aspа – н2о system during storage: (a) polycation with a partially compensated charge, (b) ion pairs, (c) multiplets, (d) phase segregation of the polymer phase in the form of a nanoparticle chimica techno acta 2021, vol. 8(4), № 20218405 article 4 of 8 the revealed features of the counterions state in macromolecular coils of the cts salt form were proved by studying the electrochemical properties of the polymer system. thus, the specific electrical conductivity of a cts solution in aspа – н2о at сcts = const increases with an increase in the acid concentration (fig. 2a, curve 1). a similar dependence is observed for aqueous solutions of individual aspa (curve 2). it is noteworthy that at сaspa < 0.01 mol/l, the increase in æsp values of both aspа – н2о and cts solutions in aspа – н2о is practically proportional to the increase in сaspa. in this case, despite the protonation of the amino groups of the macrochains in an aqueous acidic medium and, as a consequence, the binding of the labile h+ of the carboxyl group to the nh2 moiety of the polymer, the æsp values of aqueous solutions of cts aspartate and aspa are the same. taking into account that the electrical conductivity is determined by the number of charged particles and their mobility [1–3], this character of the dependence æsp = f(сaspa) for a polymer solution can be explained by shifting acid-base equilibrium towards the acid in the presence of cts (base). as a result of ionization of previously undissociated aspa molecules, the concentration of h+ and hasp– ions increases, and the total amount of free ions (electricity carriers) in solutions of cts in aspa – h2o and aspa in h2o remains constant. at сaspa > 0.01 mol/l, the rate of increase in the specific conductivity of the cts solution slightly decreases and the æsp values become lower than that of individual aspa, which may be due to a decrease in the degree of acid dissociation as it is concentrated in the solution. however, an increase in æ sp value with an increase in the acid concentration in this caspa range also indicates the intensification of aspa protolysis in an aqueous acid solution of cts, although to a lesser extent compared to the range of caspa < 0.01 mol/l. the proposed explanation of the associative-dissociative processes is also confirmed by the data in fig. 2b, if we consider the dependence æsp = f(сcts) at сcts = const. in addition, a significant increase in the specific electrical conductivity with an increase in сcts at сaspa = const indicates an increase in the mobility of conductive particles not only in comparison with an aqueous solution of aspa, but also in comparison with н2о. note that a nonlinear increasing dependence æsp = f(ccts) has also been observed in cts solutions in weak propionic, acetic, and formic acids [1]. the evaluation of the dielectric properties also showed an increase in the mobility of the electrically transporting particles in the cts aspartate solution. it is noteworthy that in the frequency range of f < 109 hz, the real part of the complex dielectric constant of cts solutions in aspa–h2o mixture is less than εʹ of an aqueous solution of aspa and water (fig. 3a), and the dielectric loss factor and dielectric loss tangent are larger (fig. 3b, c). the εʹ values decrease, εʹʹ and tgδ values increase with an increase in сcts. consequently, in cts solutions in aspa–н2о mixture there is a larger amount of mobile charge carriers providing ohmic current than in aspa–н2о and aqueous solutions. at f > ~1.6–1.8·109 hz, the εʹ, εʹʹ, and tgδ values of aqueous solutions of cts aspartate, aspа and water are comparable. this character of the dispersion of εʹ, εʹʹ, and tgδ values of a solution of cts aspartate is explained by the fact that at high frequencies a “fast” mechanism of ion polarization is realized, the large sizes of macrocoils prevent the movement of macrodipoles (associations of polar groups of a polymer molecule through dipole-dipole interaction) in an alternating electric field and the electric the induction of the system is determined only by the mobility of low molecular weight ions [4]. as f value decreases, the “slow” mechanism of orientational (dipole) polarization occurs, and the possibility of the macrodipoles motion, accompanied by dissipative losses, appears. the smaller f values, the greater are the dielectric losses (εʹʹ, tgδ), since the macrodipoles have more time to orient themselves along the electric field. fi g. 2 dependence of the electrical conductivity of cts solutions in aspа–н2о mixture with сcts = 0.015 monomol/l (1а) and aspа aqueous solution (2а) on aspа concentration, as well as cts solutions in aspа–н2о mixture with сaspa = 0.030 (1 b), 0.045 (2b) and 0.060 mol/l (3b) on cts concentration; the dotted line shows æsp value for water (b) (a) chimica techno acta 2021, vol. 8(4), № 20218405 article 5 of 8 fi g . 3 dispersion of the real part of the complex dielectric constant (a), dielectric loss factor (b) and dielectric loss tangent (c) of cts solutions in aspa – н2о mixture with сaspa = 0.030 mol/l and сcts = 0.010 (1), 0.018 (2) and 0.035 monomol/l (3), as well as aspa – н2о mixture with сaspa = 0.030 (4) and water (5) the high mobility of charged particles in a solution of cts aspartate was reflected in the kinetic stability of the polymer system. it turned out that exposure at room atmosphere is accompanied by a significant decrease in the relative viscosity of cts solutions in aspa–н2о mixture and an increase in the medium acidity (fig. 4a, curves 1 and 2). these changes are most intense in the first ~ 16–18 hours after preparation of the solution and increase with increasing cts concentration. so, after 24 hours of storage of solutions with ccts = 0.002–0.006 monomol/l, the effect of reducing ηrel was 7–10%, and 23% (fig. 4а, curve 1) for more concentrated solutions, for example, with ccts = 0.035 monomol/l. in addition, during storage for ~16 – 18 hours in a visually homogeneous solution of cts in aspa – н2о mixture, the specific conductivity increases (fig. 4b, curve 3). the dielectric constant in the frequency range of f < 109 hz decreases, and in the range of f > 1.8·109 hz it increases with a local maximum (curves 4 and 5). at t > 24 hours, opalescence appears æsp value begins to decrease with the realization of lower values than in a freshly prepared solution; εʹ value decreases with time over the entire range of f. like ηrel value, in this case, the æsp and εʹ values change to the greater extent, the higher the polymer concentration in the system. after ~66–74 hours the phase separation occurs, which is observed visually as the precipitation of a water-insoluble fine sediment. like relative viscosity, specific electrical conductivity and dielectric constant change with time to the greater extent, the higher the polymer concentration, and ph – vice versa. for example, for a system with сcts = 0.035 monomol/dl, during ~50–60 days of storage the values of these parameters change in the range of æsp = (92–88)·10−5 s·m−1, εʹ = 38–22 (f = 1.2·108 hz), рн = 4.9–5.0, and for a system with сcts = 0.002 monomol/dl − æsp = (60–58)·10−5 s·m−1, εʹ = 72–64 and рн = 3.1–3.2. the shortest time interval before the precipitation of the polymer phase is also observed at a higher сcts. at first glance, a decrease in the viscosity of the system under study with time may be associated with the macromolecules destruction as a result of acid hydrolysis of glycosidic bonds [5–7], and an increase in ph is due to deprotonation of aspa with the transition of some of the acid molecules into the zwitterionic h2asp form. however, upon destruction with a decrease in the molecular weight of cts, the amount of free counterions and hydronium ions should increase, and the ph value should decrease. as a result, the destructive processes should lead to an increase in ionic conductivity, i.e., electrical conductiv ity and dielectric constant should increase monotonically, but not very significantly. since for the cts – aspa – н2о polyelectrolyte system under study a different character of the æsp and εʹ kinetics is observed, it seems that its instability in time is associated with the effects of the association of counterions with protonated amino groups of the polycation and their further transformations. probably, it is thermodynamically not favorable for counterions to be in a free state, and they continue to form ion pairs with –nh3+ groups of polymer chains (ionomers), while losing in entropy, but gaining in electrostatic energy (fig. 1b). (a) (b) (c) chimica techno acta 2021, vol. 8(4), № 20218405 article 6 of 8 fi g . 4 kinetic dependences of the relative viscosity (1a), ph (2a), specific electrical conductivity (3b) and dielectric constant at f = 1.2·108 (4b) and 1010 hz (5b) of the cts – aspa – н2о system with сcts = 0.035 monomol/l, сaspа = 0.030 mol/l the transition of counterions from the aqueous medium to the macrocoil volume leads to screening of electrostatic repulsion between the like-charged links of the macrochain, a decrease in æsp, ηrel, and εʹ values of the system and, accordingly, its transition to the ionomeric mode. the resulting effective attraction between monomer units contributes to the dipole-dipole interaction of ion pairs and their combination into multiplet structures (fig. 1c). most likely, the stabilization of the latter occurs through complex ion-ion-hydrogen contacts of ionogenic groups of the cts aspartate macromolecule and the aspa molecule (the possibility of the formation of such cts– acid contacts has been reported in [1]). multiplets function as physical crosslinks between different polymer chains, which contributes to the compaction of macrocoils and the formation of nanosized nuclei of a new phase (fig. 1d). upon aggregation of the latter to micro and macroparticles, the metastable polymer system is divided into two equilibrium phases: the polymer-rich phase precipitates, the polymer-depleted phase is represented by the supernatant liquid. according to [41], phase separation in a polyelectrolyte solution under conditions of ionic association can occur even in a thermodynamically good solvent. fi g. 5 sem image of particles isolated from the cts–aspa–н2о system with сcts = 0.035 monomol/l, сaspа = 0.030 mol/l after 24 (a) and 36 hours (b) (b) (a) (b) (a) chimica techno acta 2021, vol. 8(4), № 20218405 article 7 of 8 the described associative processes were confirmed and visualized using scanning electron microscopy. for example, in a cts – aspa – н2о sample, spherical nanoparticles with a size of d = 40−90 nm (fig.5a) and ellipsoidal ones with a size of d = 70−260 nm (fig. 5b) were revealed after 24 and 36 hours, respectively. after ~48–70 hours, the average size of chitosan-containing particles was ~1.4–2.0 μm, width was ~0.6–0.8 μm; their aggregation was also observed. elemental analysis data showed that the nanosized polymer phase contains 42.95±1.2% carbon, 21.09±0.9% nitrogen, and 35.96±1.0% oxygen. this suggests that the nanoparticles are represented by the polymer salt form, cts aspartate. 4. conclusions in conclusion, cooperative interactions between fixed charges of the polycation and low-molecular counterions in the cts – aspa – н2о system are accompanied by the formation of ion pairs, multiplet structures, and phase segregation of the polymer substance to form nano and microparticles. the "fixation" of the nuclei of a new phase at the initial stage of phase separation by injection spraying onto a glass support makes it poss ible to visualize the formation of particles by the sem method. further search for ways to stabilize particles in solution, for example, by creating a “shell” that prevents aggregation, will make it possible to develop methods for their preparation in a preparative amount. due to the high biological activity of cts and aspa, chitosan-containing nanoand microparticles can be promising as independent pharmaceutical and veterinary drugs, plant protection products, providing synergy of useful properties of their constituent components, as well as in drug storage and delivery sy stems, and theranostics. acknowledgements this work was financially supported by the foundation for assistance to innovations of the russian federation (grant no. 16317gu/2021). r eferences 1. li q, song b, yang z, fan h. electrolytic conductivity behaviors and solution conformations of chitosan in different acid solutions. carbohydr polym. 2006;63(2):272–282. doi:10.1016/j.carbpol.2005.09.024 2. bobreshova ov, bobylkina 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release chimica techno acta article published by ural federal university 2022, vol. 9(2), no. 20229206 eissn 2411-1414; chimicatechnoacta.ru doi: 10.15826/chimtech.2022.9.2.06 1 of 8 prolonging effects of polyvinyl alcohol on drug release anzhela s. shurshina * , roman yu. lazdin , elena m. zakharova, anastasiya s. titlova, elena i. kulish bashkir state university, ufa 450076, russia * corresponding author: anzhela_murzagil@mail.ru this paper belongs to a regular issue. © 2022, the authors. this article is published open access under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). abstract polymers are currently of interest as drug delivery systems. the use of polymeric forms of medicinal substances will eliminate or reduce the disadvantages of traditional drugs. the purpose of this work was to assess the ability to prolong the action of polyvinyl alcohol in relation to the drug release when going from dilute to more concentrated solutions. it was established that an increase in the viscosity of the polymer in solution caused by an increase in its concentration results not only in a slowdown in the diffusion of drugs from the polymer solution, but also in a significant decrease in the amount of drugs firmly fixed on the polymer matrix. since it is the adduct of the polyvinyl alcohol-drug interaction that provides the slow release of the drug from the polymer solution, a decrease in its amount leads to the fact that no enhancement of the prolonging action is observed. it is claimed that when moving from solutions to polymer films, the rate of drug release is also determined by the structure of the polymer matrix. the lower the density of the polymer film, the greater the diffusion coefficient of the drug release from the film. thus, in the course of evaluating the ability to prolong the action of polyvinyl alcohol, it was shown that using some prolongation techniques, it is possible to achieve targeted regulation of the rate of drug release from polymer dosage forms. keywords polyvinyl alcohol prolongation drug delivery polymer film received: 11.04.22 revised: 04.05.22 accepted: 05.05.22 available online: 11.05.22 1. introduction almost all currently known dosage forms are produced using pharmaceutical aids. until recently, the requirements of pharmacological and chemical inertness have been imposed on pharmaceutical aids [1–3]. however, it turned out that with their help it is possible to significantly influence the pharmacological activity of drugs and regulate the parameters of pharmacokinetics and pharmacodynamics [4–6]. for example, dimethyl sulfoxide added to eye drops accelerates the penetration of antibiotics into the eye tissue [7, 8]. the use of methylcellulose allows the drugs to be retained in tissues for a long time, prolonging their action [9]. pharmaceutical aids affect not only the therapeutic efficacy of drugs, but also the physicochemical characteristics of dosage forms during their manufacture and storage. for example, the introduction of up to 1% polyvinylpyrrolidone into the composition of nitroglycerin tablets significantly reduces their porosity and, as a consequence, reduces the ability of nitroglycerin to evaporate [10]. as a result, the shelf life of the tablets in open packages increases from 2 weeks to several months. pva nanofibers produced by o/w emulsion electrospinning were demonstrated to be suitable solid dispersion systems enabling robust controlled release of poorly water-soluble drugs in work [11]. one of the largest groups of pharmaceutical aids used are polymers, which mainly function as prolongates [12–14]. the use of prolonged dosage forms is caused by negative phenomena arising from the rapid clearance of drugs from the body. in this case, there is a need for frequent administration of drugs, which often leads to a sharp fluctuation in their concentration in the body and, in turn, causes toxicity, allergic reactions, irritation, etc. [6]. rapid clearance of drugs from the body, in addition, causes the appearance of the forms of microorganisms resistant to these substances. http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2022.9.2.06 mailto:anzhela_murzagil@mail.ru http://creativecommons.org/licenses/by/4.0/ https://orcid.org/0000-0001-6737-7265 https://orcid.org/0000-0003-4774-9994 https://orcid.org/0000-0002-6240-0718 https://crossmark.crossref.org/dialog/?doi=https://doi.org/10.15826/chimtech.2022.9.2.06&domain=pdf&date_stamp=2022-5-11 chimica techno acta 2022, vol. 9(2), no. 20229206 article 2 of 8 one of the promising polymers for medicine, in general, and the technology of dosage forms, in particular, is polyvinyl alcohol (pva) [15–17]. pva is a biodegradable semicrystalline synthetic polymer that has been used for biomedical applications for several years [18]. crystalline structures can be controlled by modifying the chemical composition of oh groups [19]. for example, in the pharmaceutical area, pva has been widely used to prepare solid dispersions to improve the solubility of drugs [18, 20]. on the basis of pvs, nanoparticles are also created that provide prolonged release of medicinal substances [21]. the effects of pva on the release behavior of polymer nanoparticles from nanocomposite particles using amino acids were investigated [22]. pva cross-linked microspheres are used in oral precision relief systems [23, 24]. hydrogel composites based on pvs are of interest [25, 26]. in the work [25] lomefloxacin drug was loaded into the hydrogels and its release profile was studied. the two most important factors affect the ability to prolong drug release. first, it is the high viscosity of pva solutions, which provide a slow diffusion of drugs. second, it is the ability of pva functional groups to form complex compounds with drugs through hydrogen bonds [27–29]. in this case, it is a priori assumed that if in dilute solutions pva is capable of interacting with drugs, then this fact will provide a high level of prolongation in the transition from liquid to soft dosage forms. however, an increase in the concentration of polymer in solution is accompanied not only by an increase in viscosity, which could contribute to the prolongation, but also by the structuring of the polymer. in its turn, the structure formation is accompanied by the aggregation of macromolecules and a hereto related decrease in the availability of polymer units for interaction with drugs [30], which makes the prolongation effect not so prominent. in this regard, the purpose of this work was to assess the ability to prolong the action of pva in relation to the drug release when going from dilute to more concentrated solutions. three compounds of different chemical nature and mechanism of action–lidocaine (ld), cefazoline (cfz) and dioxidine (do)–which are presumably capable of forming complex compounds with pva and are promising for creating liquid and soft dosage forms for the treatment of burns, purulent wounds of various etiologies, were taken as drugs. 2. experimental 2.1. materials a sample of pva grade 11/2 and m = 35 kda produced by ooo “reakhim”, sodium salt of cefazolin (cfz) produced by ojsc biosintez (penza, russia), lidocaine hydrochloride (ld) – pjsc biokhimik (saransk, russia), dioxidin (do) – ojsc novosibkhimpharm "(novosibirsk, russia) were taken for the study. the drugs were used without any additional purification. 2.2. equipment uv-spectra were recorded on an uv-2600 shimadzu spectrophotometer in bidistilled water solution at 298 k, wavelengths ranged from 190 to 500 nm (slit width 1.0 nm, medium scanning rate), with a quartz cuvette of 1 cm thickness. irspectra were recorded on an ir affinity-1s shimadzu spectrophotometer with attachments for attenuated total internal reflection (atir). rheological studies were carried out on a haake mars iii modular dynamic rheometer at 298 k in the mode of continuous shear deformation in the range of shear rates from 0.1 to 100 s–1. the physicomechanical properties were investigated on a shimadzu ags-x tensile testing machine (shimadzu, japan). dsc curves were recorded on a netzsch-gerätebau instrument (germany) with a heating rate of 10°c/min. 2.3. study of interaction of polyvinyl alcohol with drugs to study the interaction of pva with drugs, the uv spectra of individual compounds, as well as their mixtures, were investigated on a uv-2600 spectrophotometer. the concentration of pva solutions used in the study was 10–4–10–3 mol/l, cfz and do – 10–4 mol/l, ld – 10–3 mol/l. the composition and the stability constant of the resulting complexes were determined by the method of molar ratios [31, 32]. 2.4. film preparation the films were obtained by pouring a pva solution onto the degreased surface of a petri dish glass. the films were dried in two stages: first, in the open air, until the film was formed, and then in a vacuum cabinet at 30 °c until constant weight was obtained. the pva concentration in the solution varied from 1 to 10%. in the case of preparation of drug-filled films, the drug dissolved in a small amount of water (2 ml) was added with stirring to the pva solution immediately before the formation of the films. the drug content in the film was 0.01–0.1 mol/mol of the polymer. 2.5. rheological investigations rheological investigations of pva solutions, as well as their mixtures with drugs, were carried out on a haake mars iii modular dynamic rheometer. 2.6. in vitro drug release the drug loaded solution of pva was added to dialysis membrane cellophane bags. the bags were immersed in a flask containing 150 ml of pva solution of the same concentration as placed in the cellophane bags with a shaking speed of 100 r/min. the experiment was carried out in a thermostat at a temperature of 298 k. at specific time intervals, 1 ml of the solution was removed from the medichimica techno acta 2022, vol. 9(2), no. 20229206 article 3 of 8 um and replaced with fresh solution. the drug concentration was determined by spectrophotometry in the uv region at a wavelength corresponding to the drug absorption maximum. pva solution was used as a reference solution. the diffusion coefficient of the drug through a semipermeable membrane was determined based on the crank approach [33] by the formula: 𝐺s 𝐺∞ ⁄ = [ 16𝐷s𝑡 π𝐿2 ] 0.5 , (1) where gs is the concentration of the desorbed substance at time t, g∞ is the value of gs at t→∞, l is the semipermeable membrane thickness. the amount of the drug that passed through the membrane by the time t (gs) was estimated from the calibration curve. the moment when a constant drug concentration (g∞) was established in the solution was considered the moment when equilibrium was established. 2.7. in vitro drug release from polymer films the kinetics of the drug release from the films into the aqueous medium at 298 k was studied by uv spectrophotometry of aqueous solutions in the region of the drug absorption maximum. diffusion coefficients were calculated using equation (1). in this case, l was understood to be the thickness of the film. 2.8. determination of density of polymer films the density of pva and pva-drug films was determined by the pycnometric method according to the standard procedure. 3. results and discussion 3.1. characterization of complexes polyvinyl alcohol-drugs the prolonging effect of polymers is, in fact, largely determined by their ability to form strong compounds such as complexes or salts with drugs. uv-spectroscopic study of dilute pva solutions in the presence of the studied medicinal substances confirms the existing interaction between them. thus, absorption maxima in uv spectra of cfz and ld in the aqueous solution are observed at 272 nm (cfz) and 262 nm (ld). there are three absorption maxima in the uv spectra of do – at 235, 266, and 280 nm. when the equivalent amount of pva not absorbed in the uv region at a concentration of 10−4–10−2 mol/l is added to the solution, the intensity of the absorption peak changes, while the absorption maximum shifts by about 3–5 nm bathochromically (figure 1). the phenomena observed indicate the effect of the polymer on the electronic system of the drugs and the formation of the interaction adducts. by the difference in the values of the wavelengths δλ corresponding to the absorption maximum of the complex and the individual drug, it is possible to estimate the binding energy in the complex compound by the planck formula: ∆𝐸 = ℎ𝑐 ∆𝜆 , (2) where δe is the binding energy, h is planck's constant, c is the speed of light. figure 1 uv spectra of drug (1), pva (2), and pva-drug (3) for cfz (a), ld (b) and do (c). the value of the binding energy in the complexes of pva with the drugs studied, estimated from the shift of absorption maxima in uv spectra, is about 10–15 kj/mol. chimica techno acta 2022, vol. 9(2), no. 20229206 article 4 of 8 the small values of the bond energies suggest that complex formation occurs via hydrogen bonds. the composition of the reaction adducts obtained for all studied systems, determined by the method of isomolar series and the method of molar ratios, is equal to 1. the values of the stability constant for pva-drug systems are 5.7·103, 6.5·103 and 5.1·103 l/mol when using do, cfz and ld, respectively. thus, the adducts of the pva-drug interaction in an extremely dilute solution can be characterized as compounds with medium stability. 3.2. in vitro drug release the presence of interaction in the pva-drug system, in principle, is capable of providing a certain level of drug action prolongation due to the attachment to the polymer chain. indeed, as can be seen from curve 1 in figure 2, the release of the drug (in this case, cfz) from a dilute pva solution occurs rather slowly. however, the situation changes when going from extremely dilute solutions to more concentrated ones. the kinetic curves of the release of cfz from pva solutions shown in figure 2 can be divided into two ranges. in the first initial short range, the release of free cfz, not fixed on the polymer chain, occurs through diffusion. in the second range, cfz attached to the macromolecule is released slowly due to the disintegration of the pva-cfz complex. in this case, the kinetic curves reach the limit corresponding to the equilibrium drug yield. from the difference between the optical density value corresponding to the equilibrium drug yield and the optical density corresponding to the amount of cfz introduced into the solution, it is possible to determine the value of equilibrium βequ fixed on the macromolecular chain. generally, the higher the pva concentration in the solution, the lower the value of the amount of the drug βequ fixed on the polymer chain (figure 3). this fact allows us to assume that with an increase in the viscosity of the pva solution, the effect of prolongation can actually be leveled. figure 2 kinetic curves of the release of cfz from a pva solution with a concentration of 4·10–3 (1), 4·10–1 (2), 1 (3) and 4 (4) g/dl. the content of cfz in the solution is 10–4 mol/l. the dotted line shows the optical density value corresponding to the amount of cfz introduced into the solution. figure 3 dependence of the amount of cfz (1), do (2) and ld (3) firmly attached to the polymer chain on the concentration of pva in solution. for all the drugs studied, the nature of the dependence of βequ on the concentration is the same. there is a concentration range within which the amount of drug firmly held by macrochains is maximal and practically does not depend on the concentration of pva. with an increase in the concentration of pva in the solution, the values of βequ begin to decrease up to a minimum value, reaching the limit at a pva concentration of the order of 8–10 g/dl. a decrease in the amount of the drug retained by macromolecules is likely to be associated with a decrease in the availability of polymer units for interaction with drugs due to changes in the supramolecular state of the polymer that occur with an increase in the pva content in the solution. 3.3. rheological investigations of polymer solutions the data of rheological measurements unambiguously indicate that an increase in the concentration of polymer in the solution is accompanied by an increase in viscosity. moreover, this increase in viscosity is not monotonic. figure 4 clearly distinguishes three regions. region i is the so-called region of dilute solutions, in which macromolecules do not interact with each other. the viscosity in this area increases with increasing concentration according to the linear law η~с1 [34–36]. region ii is the region of concentrated solutions with a fully formed fluctuation network of entanglements of macromolecules. in this region, the viscosity increases with an increase in concentration according to the power law η~сn, where n~5. the intermediate region of semi-diluted solutions is characterized by an intensive rearrangement of the supramolecular structure and the formation of a fluctuation network [37, 38]. despite the fact that the addition of drugs at a concentration of up to 0.5 mol/l does not change the viscosity either in dilute or in more concentrated solutions (figure 4), the changes in the structural-physical state of pva in solution are directly reflected in the character of the chimica techno acta 2022, vol. 9(2), no. 20229206 article 5 of 8 interaction of pva with the drugs analyzed in the work (figure 3). and, since from the structural-physical point of view pva solutions are not equivalent, the value of βequ also changes unequally. solutions with a pva concentration of less than 0.5 g/dl are the solutions of noninteracting macromolecules that are maximally available for interaction with a drug. it is in this region that βequ reaches its highest values, which remain constant while the solution is diluted. pva solutions with a concentration of about 10 g/dl and more represent a continuous fluctuation network, in which the availability of pva links for interaction with a drug is minimal. in this region, the values of βequ are the lowest. the intermediate region of semi-diluted solutions is characterized by significant changes in the values of βequ. consequently, an increase in the viscosity of the polymer in the solution caused by an increase in its concentration leads to a decrease in the fraction of the drug that is firmly attached to the polymer chain. in the case when the amount of a strongly attached drug is not large, there is a rapid release of a part of the drug that is not associated with the polymer chain but the remaining part of the drug, which is attached to the chain, is released at a rate corresponding to the rate of decomposition of the pva-drug adduct. as can be seen from the data in table 1, the rate of the drug release increases with an increase in the pva concentration in the solution, since as the content of pva in the solution increases, the amount of the free drug increases. the values of the diffusion coefficient undergo similar changes. if with an increase in the concentration of pva in solution the value of βequ tended to zero, in concentrated solutions the yield of the drug would only be determined by the concentration of the free drug not bound by the polymer chain. in this case, during the transition from liquid to soft dosage forms of protective film coatings the prolongation effect due to the formation of the pva-drug adduct would be virtually absent. however, since the value of βequ goes to the non-zero limit, the drug yield from concentrated solutions is determined by two factors – the amount of the free drug and the stability constant of the pva-drug complex. thus, the effect of prolonging the action of pva does not increase with an increase in its content in the solution. an increase in the viscosity of the polymer in solution, caused by an increase in its concentration, leads not only to a slowdown in the diffusion of the drug from the polymer solution, but also to a significant decrease in the amount of drugs firmly fixed on the polymer matrix. since it is the pva-drug interaction adduct that provides the slow release of the drug from the polymer solution, a decrease in its amount leads to the fact that no enhancement of the prolonging action is observed. table 2 presents the physicochemical and physicomechanical characteristics of the pva films obtained from solutions of various concentrations. figure 4 dependence of the dynamic viscosity of pva on its concentration in solution in logarithmic coordinates in the absence () and in the presence of do (), ld (), cfz () taken at a concentration of 0.1 mol/l. table 1 results of processing the kinetic curves of the drug release from pva solutions. drug pva concentration in solution, g/dl v, %/min da·10 9, cm2/s cfz 4·10–3 0.10 0.04 4·10–1 0.18 0.27 1.0 0.49 1.18 2.0 1.25 3.40 4.0 1.92 5.35 8.0 2.15 6.02 10.0 2.18 6.11 ld 4·10–3 0.13 0.11 4*10–1 0.19 0.30 1.0 0.67 1.70 2.0 1.75 4.86 4.0 1.98 5.53 8.0 2.26 6.35 10.0 2.28 6.40 do 4·10–3 0.14 0.15 4·10–1 0.15 0.18 1.0 0.56 1.38 2.0 1.58 4.36 4.0 1.82 5.06 8.0 2.00 5.59 10.0 2.10 5.88 3.4. in vitro drug release from polymer films when film materials are obtained from pva solutions, from the technological point of view it is much more convenient to obtain them not from diluted but from more concentrated solutions. consequently, the process of film formation will be carried out under conditions when the amount of the drug firmly fixed on the polymer matrix βequ, is small. this means that most of the drug will freely diffuse through the polymer film. so, the rate of this process will be determined not only by the value of βequ and kest but also by the characteristics of the polymer film itself. in this regard, it becomes possible to additionally regulate the rate of the drug release from the polymer film. chimica techno acta 2022, vol. 9(2), no. 20229206 article 6 of 8 table 2 characteristics of pva films obtained from solutions of different concentrations. pva concentration in the film, g/dl tg, 0c t, 0c ∆h, j/g wcr, % αcr, % e, mpa σbreak, mpa lbreak, mpa 1 52 227 86.2 55.0 33.5 2404 57.8 86.3 2 44 226 85.4 54.5 33.0 3965 65.3 146.7 3 42 225 85.5 54.5 32.6 4672 87.4 150.6 5 40 224 84.7 54.0 32.4 5277 90.5 153.8 7 43 224 80.4 51.3 30.0 5513 88.5 110.0 10 45 223 71.8 45.8 28.3 4850 83.3 65.8 20 50 224 70.8 45.1 27.5 4167 73.4 50.1 wcr – from dsc data; αcr – from ir-spectra data. for example, by varying the concentration of the polymer in the initial solution films with different densities can be obtained. from the data shown in table 3, it can be seen that the values of the density of the films obtained from the initial different concentration of the polymer in the solution (in the presence of the drug as well) pass through a minimum corresponding to the concentration value of 5 g/dl. it is important that, according to the change in density, the values of the drug release rate from the film and the diffusion coefficient also change. table 3 summary data on the results of processing the kinetic curves of drug release from the pva films and data on the film density. drug drug concentration, mol/mol pva pva concentration in fillm, g/dl ρ, g/cm3 da·10 9, cm2/s – – 1 1.142 – 2 1.120 – 5 1.050 – 10 1.156 – cfz 0.01 1 – 1.11 2 – 2.72 5 – 3.22 10 – 1.98 0.10 1 1.159 1.14 2 1.134 2.80 5 1.072 3.41 10 1.167 1.92 ld 0.01 1 – 1.54 2 – 2.83 5 – 3.92 10 – 3.46 0.10 1 1.154 1.89 2 1.129 2.90 5 1.063 3.68 10 1.163 3.05 do 0.01 1 – 1.24 2 – 1.98 5 – 2.90 10 – 2.81 0.10 1 1.150 1.27 2 1.125 1.32 5 1.057 1.41 10 1.160 0.98 analysis of the data given in table 3 unambiguously proves the fact that varying the polymer concentration in the initial solution is an additional factor regulating the rate of drug release. previously, this kind of impact of the supramolecular organization of the polymer matrix on diffusion processes was discovered in the works [30, 39, 40] for the films of physiologically active polymers – chitosan polysaccharides, sodium salt of chitosan succinamide and sodium salt of carboxymethylcellulose. it is noteworthy that the diffusion coefficients for the film samples for all considered cases are lower than those for solutions of the corresponding concentrations (table 1). obviously, a sharp increase in viscosity when going from solutions to solid film samples, in this case, has a decisive effect on the value of the diffusion coefficients. thus, the assessment of the ability to prolong the action of one of the physiologically active polymers, polyvinyl alcohol, showed that using some prolongation technological methods, involving the creation of compounds of medicinal and auxiliary substances, as well as an increase in the viscosity of the dispersion medium when the drugs are enclosed in film shells, it is possible to achieve direct regulation of the rate of release of medicinal drugs from polymer dosage forms. 4. conclusions it was shown that mixing aqueous pva solutions with the solutions of cefazolin, lidocaine, and dioxidine is accompanied by the formation of reaction adducts which are complex compounds of medium stability formed by means of hydrogen bonds. it was found that the range of pva concentrations in a solution of 0.5–10 g/dl is characterized by an intense rearrangement of the supramolecular structure, which results in a significant decrease in the amount of the drug which can be firmly fixed on the macromolecular chain under the equilibrium conditions. as a result, no increase in the prolonging effect of pva with an increase in its content in the solution and a corresponding increase in viscosity is observed. it was proven that when going from solutions to polymer films, the yield of drugs is largely determined by the structure of the polymer matrix, in particular, by its density. the lower the density of the polymer film, the greater chimica techno acta 2022, vol. 9(2), no. 20229206 article 7 of 8 the diffusion coefficient of the drug release from the film. the diffusion coefficient values for the film samples for all considered cases are lower than those for the solutions of corresponding concentrations. supplementary materials no supplementary data are available. funding this research had no external funding. acknowledgments none. author contributions conceptualization: k.e.i. data curation: sh.a.s formal analysis: t.a.s., l.r.yu., z.e.m. investigation: sh.a.s., l.r.yu., z.e.m. methodology: k.e.i., sh.a.s. project administration: k.e.i. validation: k.e.i. visualization: l.r.yu writing – original draft: k.e.i., sh.a.s., t.a.s. writing – review & editing: sh.a.s. conflict of interest the authors declare no conflict of interest. additional information authors’ ids: anzhela shurshina, scopus id 56014778000; roman lazdin, scopus id 56926678400; elena zakharova, scopus id 26028213800; elena kulish, scopus id 7003930406. 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chimicatechnoacta.ru article 2022, vol. 9(4), no. 20229407 doi: 10.15826/chimtech.2022.9.4.07 1 of 7 factors for increasing strength of composite materials based on fine high-calcium fly ash olga m. sharonova a* , leonid a. solovyov a , alexander g. anshits ab a: institute of chemistry and chemical technology sb ras, federal research center "krasnoyarsk science center sb ras", krasnoyarsk 660036, russia b: siberian federal university, krasnoyarsk 660041, russia * corresponding author: shar@icct.ru this paper belongs to a regular issue. © 2022, the authors. this article is published in open access under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). abstract industrial high-calcium fly ashes obtained by burning kansk-achinsk coal at a thermal power plant and selected from different fields of electrostatic precipitators of an ash collecting plant were studied as the basis for composite binders (cb). the main factors influencing the properties of such cbs are the particle size, the concentration of superplasticizer at a water:binder (w/b) ratio of 0.25, and the proportion of hcfa in the mixture with cement. in particular, for cementless cbs at w/b 0.4, it was found that a change in the particle size d90 from 30 μm to 10 μm leads to an increase in compressive strength by more than 2 times – from 5.5–14 mpa to 11–36 mpa, accordingly, with a curing age of 3–300 days. the 0.12% additive of melflux 5581f superplasticizer at w/b 0.25 increases the compressive strength – up to 14–32 mpa and up to 24–78 mpa, accordingly. the hcfa-cement blends were investigated in the range of 60–90% hcfa and the maximum compressive strength 77 mpa at 28 days of hardening was found at 80% hcfa. on the basis of 80% hcfa blend with the 0.3% addition of melflux 5581f and 5% silica fume, the specimens of ultra-high strength (108 mpa at 28 days of hardening) were obtained. keywords binder high-calcium fly ash superplasticizer compressive strength phase composition received: 26.05.22 revised: 08.07.22 accepted: 12.07.22 available online: 19.07.22 1. introduction fly ash from coal burning is considered as a technogenic resource of mineral raw materials in various technologies of their processing into valuable products [1–3]. for example, because of the environmental and economic benefits, fly ashes (fas) are used as supplementary cementitious materials (scms) in the production of modern construction composite materials [4–6]. the effect of fly ashes on the properties of composite materials can vary strongly depending on the fly ash composition. in the compositions with cement, all fas exhibit a pozzolanic activity in the reaction between ca(oh)2, which is formed during hydration of the silicate phases of cement, and aluminosilicate glass (a component of the fa) to yield calcium silicate hydrates (c–s–h), calcium aluminosilicate hydrates (c–a–s–h), and calcium aluminate hydrates (c–a–h) [7]. fly ashes with high calcium content (20–40%) contain calcium-bearing phases that independently exhibit binding properties: lime cao, anhydrite caso4, calcium aluminate ca3al2o6, calcium aluminoferrite ca4al2fe2o10, and dicalcium silicate β-ca2sio4 [8–10]. these ashes were also found to contain such crystalline phases as calcite caco3, quartz α-sio2, periclase mgo, hematite α-fe2o3, ferrospinel, and various calcium aluminosilicates [11–13]. the phase composition of hcfas varies greatly for different sources and primarily in terms of glass content: from 23 to 82% [8, 11, 12]. moreover, the phase composition varies greatly for fly ashes sampled from different fields of electrostatic precipitators (ep). according to the data [14], the content of the glass phase increases by 2.2 times in the series of high-calcium fly ashes from the 1st to the 4th field of the ep, but the content of free cao decreases by a factor of 5.6. even more radical differences are observed in the particle size, for example, the maximum size distribution shifts from ~25 to ~3 m for hcfa of 1st and 4th fields, respectively [8]. when the content of fine cementitious components increases in the binder, it becomes more important to use water-reducing admixtures. already the third generation of water-reducing admixtures is used to reduce water demand http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2022.9.4.07 mailto:shar@icct.ru http://creativecommons.org/licenses/by/4.0/ https://orcid.org/0000-0002-5613-3203 https://orcid.org/0000-0002-3905-3252 https://orcid.org/0000-0002-5259-0319 https://crossmark.crossref.org/dialog/?doi=https://doi.org/10.15826/chimtech.2022.9.4.07&domain=pdf&date_stamp=2022-7-19 chimica techno acta 2022, vol. 9(4), no. 20229407 article 2 of 7 − polycarboxylate ether superplasticizers (pce). these agents allow controlling the water-to-cement ratio and properties of fresh concrete mortar, as well as affect the hardening rate and strength of the product with high efficiency. the mechanism of action of pce is based on the fact that carboxyl groups (–cooh) in the polymer backbone ensure adsorption on the surface of cement grains, while side polyester chains cause steric hindrance, thus preventing the coalescence of fine particles [15]. different components of the mineralogical composition of cement are known to vary in terms of their adsorption characteristics with respect to superplasticizers. namely, calcium silicates ca3sio5 and ca2sio4 have a negative -potential (–5 mv), while calcium aluminate ca3al2o6 and calcium aluminoferrite ca4al2fe2o10 are characterized by a positive -potential (~+10 and +5 mv, respectively) [16]. once the superplasticizer is adsorbed, the surface of ca3al2o6 and ca4al2fe2o10 becomes negatively charged, thus contributing to mutual repulsion of cement particles and causing high dispersibility of cement. there are few data on the behavior of dispersed mineral components with respect to superplasticizers in the available literature. so, for example, the study focused on cements with admixtures of aluminosilicate fa, ground limestone powder, and blastfurnace slag with -potentials of +13 mv, +2.5 mv, and –2.7 mv, respectively, showed that the greatest amount of polycarboxylate ether superplasticizer was adsorbed in the case of limestone powder, while this amount was the lowest in the case of slag [17]. therefore, in order to achieve identical rheological parameters, the highest superplasticizer concentration was used in the case of limestone powder, and the lowest superplasticizer concentration, in the case of slag admixture. although the scope of practical application of coal ashes is currently expanding, there is still no clear understanding of the regularities of the influence of the composition, the particle size, as well as the type and concentration of a superplasticizer, on the structure and properties of cementitious materials based on fly ash, in particular, on high-calcium fly ash. this study aimed to investigate the influence of the particle size, the composition of hcfa and hcfa–pc blends, as well as the content of a superplasticizer admixture on the strength properties of cement-free and highly filled (60–90% hcfa) composite cements materials. 2. experimental 2.1. objects high-calcium fly ashes produced during pulverized combustion of grade b2 low-ash (11%) brown coal mined from the kansk–achinsk coal basin were used as the starting material for the composite specimens. the coal was burned at a temperature of 1400–1500 °c in the furnaces of the bkz-420 boiler with liquid slag removal at the krasnoyarsk thermal power plant 2. the fly ashes were sampled from fields 3 and 4 of electrostatic precipitators (fractions 3 and 4, respectively) on a setup characterized by a particle capture efficiency of ≥98%. portland cement pc 42.5 n manufactured at krasnoyarsk cement plant was also used in this study. melflux 5581f polycarboxylate ether superplasticizer (basf construction solutions, trostberg, germany) and silica fume mku-95 (stromex ojsc, moscow, russia) were used as admixtures. 2.2. methods particle size distribution was measured on an analysette 22 microtec laser diffraction particle size analyzer (fritsch, germany) using a dry cell. the macrocomponent composition (sio2, al2o3, fe2o3, cao, mgo, so3, na2o, k2o, and tio2) and loss on ignition (loi) were determined by chemical analysis in compliance with a state standard gost 5382-91. quantitative xrd analysis was performed using the fullprofile rietveld method [18]. the xrd patterns were recorded in reflection geometry using co kα radiation on a panalytical x'pert pro diffractometer equipped with a pixcel detector and a graphite monochromator. the xrd pattern were recorded in the range of diffraction angles 2θ=7–100°. the mass percentages of the crystalline and amorphous components were determined by the external standard method (using corundum). the absorption coefficients of the samples were calculated from the total elemental composition according to the chemical analysis data. this method has been successfully used for quantification of the phase composition of hcfa [8, 10]. the specific surface area (ssa) was determined using a nova 3200e sorption analyzer (quantachrome instruments, usa) in the lowtemperature nitrogen adsorption/desorption mode at – 195.8 °c (77.35 k) in the range of relative pressures p/p0=0.01–0.995. the 20×20×20 mm hardened cube-shaped composite specimens were produced from 100% hcfa (fraction 3 or 4) at a water–binder ratio w/b = 0.4 without the superplasticizer (specimens fa-3 and fa-4, respectively) or at a water–binder ratio w/b = 0.25 with an admixture of 0.12 wt.% melflux 5581f superplasticizer (specimens 100fa-3 and 100fa-4, respectively). superplasticizer concentration was chosen according to the results of the flowability test [10]. the reference specimens were produced from cement pc 42.5 n at a w/b ratio = 0.4 without a superplasticizer (specimen pc_04) and w/b = 0.25 with the admixture of 0.12 wt.% melflux 5581f superplasticizer (specimen pc_025). all the specimens were stored in a moist atmosphere for 1–300 days. the specimens of the composite materials with composition hcfa–pc were prepared (where hcfa is fraction 4, its content in the blend being 60, 70, 80 and 90%) at w/b = 0.25 and concentration of the melflux 5581f superplasticizer being 0.12% (specimens 60fa, 70fa, 80fa, and 90fa, respectively). the composition containing 80% hcfa was used to produce the specimen 80fa-sf at w/b ratio = 0.25 with an admixchimica techno acta 2022, vol. 9(4), no. 20229407 article 3 of 7 ture of 0.3% melflux 5581f superplasticizer and 5% of silica fume to the blend. the strength tests of the specimens were conducted on a 3360 series dual column tabletop universal testing system (instron, usa) at a frame speed of 5 mm/min. compressive strength was measured for four cubes for each curing age, and calculated as the average of three nearest strength values. 3. results and discussion 3.1. characteristics of initial fractions of hcfa and portland cement the particle size distribution data (table 1) show that hcfa fraction 4 has a much smaller particle size compared to that of fraction 3. in particular, d90 is ~10 and 30 µm, while d50 is 4 and 9 µm for fractions 4 and 3, respectively. meanwhile, both these fractions are much smaller than pc particles. for pc 42.5 n, the particle size distribution is shifted towards coarser particles: d90 and d50 are 55 and 20 m, respectively. the total specific surface area (ssa) of powder materials is primarily determined by the particle size, but it is also influenced by other factors such as particle density and porosity. the studied hcfa fractions consist of microspheres of different sizes and morphologies [14]. the microspheres are formed from authigenic minerals (being responsible for their composition) contained in coal in the porous structure of the carbon matrix regulating their size [19]. the analyzed fractions 3 and 4 sampled from fields 3 and 4 of the electrostatic precipitators of the ash collection facility have similar chemical compositions, as can be seen from the content of the five main components of the composition (figure 1). the predominant component is cao (40 and 39.69 wt.%); the content of sio2 is appreciably high (24.26 and 24.60 wt.%), while the content of other macrocomponents is significantly lower (al2o3, 6.71 wt.% and 7.30 wt.%; fe2o3, 13.45 wt.% and 14.29 wt.%; mgo, 9.10 wt.% and 8.24 wt.%, respectively). unlike portland cement pc 42.5 n, these fractions are characterized by a lower (1.6-fold) content of cao, but higher contents of the sio2, al2o3, fe2o3, mgo components. both fractions are characterized by a significantly higher content of total cao compared to most class c fly ashes from pulverized coal combustion [1, 20–22], which causes a higher contribution of ca-containing phases. fractions 3 and 4 contain the same phases, but there are some differences in their contents. the amorphous phase (32.6 and 42.1 wt.%) is the predominant component of both fractions 3 and 4 [14]. table 1 dispersity characteristics of hcfa fractions 3 and 4 and portland cement pc 42.5 n. sample d90, m d50, m ssa, g/cm 3 fraction 3 30 9 1.52 fraction 4 10 4 2.36 pc 42.5 n 55 20 0.30 fraction 4 is characterized by lower contents of the ca3al2o6 and cao phases, while the contents of ca2fexalyo5, caco3, ca(oh)2 and the amorphous phase are increased. in comparison with the fly ash fractions, pc 42.5 n cement has a qualitatively different phase composition [14]. it contains tricalcium silicate ca3sio4 as the predominant component (64.5 wt.%), and clinker phases typical of cement are also present: dicalcium silicate ca2sio4, aluminoferrite ca2fexalyo5, aluminate ca3al2o6, as well as calcium sulfate hydrates caso40.5h2o and caso42h2o, which are commonly added during grinding. 3.2. the effect of particle size of hcfa fractions on strength of composite materials without and with superplasticizer admixture a detailed description of the prepared composite specimens is given in table 2. measuring compressive strength (comp) of the specimens based on 100% hcfa of each fraction 3 and 4 at a water–binder ratio w/b = 0.4 without a superplasticizer (figure 2, specimens fa-3 and fa-4) demonstrated that comp is 2to 2.6-fold higher for fa-4 compared to fa-3 and is equal to 11–36 mpa and 5.5–14 mpa, respectively, at the curing age of 3–300 days. figure 1 the content of the main components in the chemical composition of fractions 3 and 4. table 2 mixture proportion (wt. %) of composite materials (sf – silica fume; w/b – water/binder ratio; sp – superplasticizer). specimen hcfa pc sf w/b sp fr. 3 fr. 4 fa-3 100 – – – 0.4 – fa-4 – 100 – – 0.4 – pc_04 – – 100 – 0.4 – pc_025 – – 100 – 0.25 0.12 100fa-3 100 – – – 0.25 0.12 100fa-4 – 100 – – 0.25 0.12 60fa – 60 40 – 0.25 0.12 70fa – 70 30 – 0.25 0.12 80fa – 80 20 – 0.25 0.12 90fa – 90 10 – 0.25 0.12 80fa-sf – 80 20 5 0.25 0.3 chimica techno acta 2022, vol. 9(4), no. 20229407 article 4 of 7 while the fractions’ compositions differ only slightly, the higher fineness of fraction 4 is the key factor being responsible for the higher strength of the fa-4 specimens compared to those of the fa-3 specimens. the most active phases of these hcfa are ca2fexalyo5, caso4, cao and glass [10] more actively involved in the hydration process with an increase in the dispersion of the ash material, forming more hydrate products that increase strength. the effect of fraction fineness on the strength of composite materials is quite expected when using the melflux 5581 f superplasticizer, which provides better dispersibility of micron and submicron particles in the liquid phase. melflux 5581f is a polycarboxylate ether superplasticizer consisting of the poly(methacrylic acid) backbone and methoxypolyethylene glycol side chains [23]. the mechanism of dispersion ensured by melflux 5581f superplasticizer is considered to be related to electrostatic repulsive forces generated by carboxyl groups (–coo–) of the backbone on the surface of cement grains and to the steric effect of repulsion induced by the hydrophobic side chains of methoxypolyethylene glycol [24]. the effect of superplasticizer admixture was studied for the specimens based on 100% hcfa of each fraction (3 and 4) at melflux 5581f concentration of 0.12% and w/b ratio = 0.25 (figure 3, specimens 100fa-3 and 100fa-4, respectively). figure 2 compressive strength of specimens fa-3 and fa-4 and portland cement pc_04 at a w/b ratio = 0.4 without superplasticizer added. figure 3 compressive strength of specimens 100fa-3 and 100fa-4 at a w/b ratio = 0.25 with an admixture of 0.12% melflux 5581f and pc_04 at a w/b ratio = 0.4 in the absence of superplasticizer. the findings indicate that strength of 100fa-4 specimens increased more than two-fold: up to 24–78 mpa after the curing age of 3–300 days. a similar effect was also observed for 100fa-3 specimens, whose strength increased to 14–32 mpa after the same curing age. the comp value of 100fa-4 specimens was similar to that of the reference specimens based on portland cement pc 42.5 n at w/b ratio = 0.4 without the superplasticizer (pc_04) during the early curing age, while being higher than that of the reference specimen by ~10 mpa during the late curing age (figure 3). more detailed studies were conducted for the specimens based on fraction 4. 3.3. the effect of cement admixtures on strength of composite materials the effect of cement admixtures on activity of the fly ash fraction 4 was studied for the specimens of composite materials based on mixture hcfa–pc (table 2), where the pc content is 10, 20, 30, and 40% and the hcfa is fraction 4 with its content in the blend of 90, 80, 70, and 60 wt.% (specimens 90fa; 80fa; 70fa, and 60fa, respectively). strength values of the specimens containing an admixture of 40 wt.% cement (specimen 60fa) and the without cement admixture (specimen 100fa-4) at the curing age of 28 days are comparable to those of specimen pc_04 based on 100 wt.% cement at w/b ratio = 0.4 in the absence of superplasticizer (figure 4). if the content of cement admixture is 10–30 wt.% (hcfa content is 70–90 wt.%), the compressive strength rises and passes through the maximum at pc content of 20 wt.% (specimen 80fa in figure 4), where comp is 77 and 125 mpa at the curing age 28 and 100 days, respectively. with an increase in curing age to 100 days, the strength of specimens with a high fly ash content (specimens 70fa, 80fa, 90fa, and 100fa4) increases to a greater extent (1.3–1.6 times) compared to specimens with a high cement content (pc_04, 60fa, pc_025), for which the strength increases by 1.1–1.16 times (figure 4). the observed rise in strength is the significant advantage of using fine hcfa as a basis for cementitious composite materials. figure 4 compressive strength of the composite specimens based on pc 42.5 n (pc_04 and pc_025), on fraction 4 (100fa-4), on hcfa–pc blends (60fa, 70fa, 80fa, and 90fa), and sample 80fa-sf containing 0.3% melflux 5581f and 5% of silica fume added to the blend. chimica techno acta 2022, vol. 9(4), no. 20229407 article 5 of 7 figure 5 optical microscope images of the cured specimens at 100 days: portland cement (a); 80% fr4 – 20% pc (b). a similar effect was observed by the authors of [4] when 18% of pc was replaced with class c fly ash (cao 36.56 wt.%) in self-consolidating concretes containing a polycarboxylate ether superplasticizer hrwr (admixture content, 1.28 wt.%). the specimens were obtained with a compressive strength close to that of specimens based 100 wt.% pc at curing age of 7 days and exceeding it by 3–6 mpa at the curing age of 28–90 days. as the ash content increased to 36%, the strength increased even more. unlike high-calcium fly ash, admixtures of fly ash with aluminosilicate composition (class f) usually reduce early strength of cement-based composite materials [4, 25]. for example, the addition of class f fly ash of 10–40% leads to a decrease in strength by 1.5–3 times at the curing age of 3–7 days and, with an increase to 70% fa, the strength decreased by 6–13 times. thus, the factors for improving the strength of cement compositions in the early stages are the higher cao content in fly ash, the decrease in the size of ash particles, and the addition of a superplasticizer, which facilitates their dispersion. it was previously established [14] that the main newly formed phases for the binder based 100% hcfa are ettringite 3caoal2o33caso432h2o, calcium carboaluminate hydrates ca4al2(oh)13(co3)0.54h2o, ca4al2(oh)12co35h2o and cryptocrystalline calcium hydrosilicates. since calcium aluminoferrite ca2fexalyo5 was actively involved in their formation, the ettringite and calcium carboaluminate phases are solid solutions due to the isomorphous replacement of al3+ with fe3+. the main source of silicates is the amorphous phase (glass). the contribution of glass transformation yielding cryptocrystalline calcium hydrosilicates increases with curing time. the microstructure of the hardened sample obtained with the addition of hcfa fraction 4 (figure 5) becomes thinner compared to the hardened portland cement sample and, consequently, finely mixed hydrate phases are formed, providing a higher strength of the composite material. based on a blend of 80% hcfa – 20% pc at w/b = 0.25, the ultra-high strength specimens (80fa-sf) were obtained by increasing the concentration of melflux 5581f to 0.3% and adding silica fume (sf) in an amount of 5%. compressive strength of 80fa-sf specimens is 108 and 150 mpa at curing age 28 and 100 days, respectively (figure 4). adding the silica fume can improve properties of composite materials due to denser packing of particles and the pozzolanic reaction with ca(oh)2 yielding additional calcium hydrosilicates [15]. 4. conclusions the factors of improving the strength of the composite materials based on high-calcium fly ash were investigated in this study. the effect of particle fineness on strength of the cementless composite materials based on microspherical fractions of high-calcium fly ashes (hcfa) with total cao content of ~40 wt.% was studied. it was found that for fly ash fractions having similar chemical and phase compositions, a decrease in the particle size from d90 30 m (fraction 3) to 10 m (fraction 4) increases compressive strength more than twofold: from 5.5–14 mpa to 11–36 mpa at curing age of 3–300 days. the effect of adding a superplasticizer was studied and it was found that the addition of 0.12% melflux 5581f made it possible to reduce the w/b ratio to 0.25 and increase the strength by 2.3–2.5 times for the specimens based on fraction 3 – up to 14-32 mpa and by 2.2 times for the specimens based on fraction 4 – up to 24–78 mpa at the curing age of 3–300 days. the influence of adding pc 42.5 n on the enhancement of strength of the composite materials based on hcfa fraction 4 of in the presence of 0.12% melflux 5581f at w/b ratio = 0.25 was studied in the range of 10–40% pc. it was found that the value of compressive strength has a maximum at 20% pc (80% hcfa), which is 77 and 125 mpa with the curing age of 28 and 100 days, respectively. on the basis of the composition 80%hcfa-20%pc, the ultra-high strength specimens were obtained with the addition of 0.3% melflux 5581f and 5% silica fume, which have a compressive strength of 108 and 150 mpa at the curing age of 28 and 100 days, respectively. chimica techno acta 2022, vol. 9(4), no. 20229407 article 6 of 7 supplementary materials no supplementary data are available. funding this work was conducted within the framework of the budget project no. 121031500198-3 for institute of chemistry and chemical technology sb ras. acknowledgments this work was conducted using the equipment of krasnoyarsk regional research equipment centre of sb ras. the authors are grateful to e.v. mazurova for obtaining sem images. author contributions conceptualization: o.m.s., a.g.a. data curation: o.m.s. formal analysis: o.m.s., l.a.s., a.g.a. funding acquisition: o.m.s., l.a.s., a.g.a. investigation: o.m.s., l.a.s., a.g.a. methodology: o.m.s., l.a.s., a.g.a. project administration: a.g.a. resources: o.m.s., l.a.s., a.g.a. software: o.m.s., l.a.s. supervision: a.g.a. validation: o.m.s., a.g.a. visualization: o.m.s., l.a.s., a.g.a. writing – original draft: o.m.s., a.g.a. writing – review & editing: o.m.s. conflict of interest the authors declare no conflict of interest. additional information author ids: olga m. sharonova, scopus id 6506111906; leonide a. solovyov, scopus id 6701367459; alexander g. anshits, scopus id 57200009289. websites: institute of chemistry and chemical technology sb ras, federal research center "krasnoyarsk science center sb ras", https://ksc.krasn.ru; siberian federal university, https://www.sfu-kras.ru. 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j, winnefeld f, plank j. multi-method approach to study influence of superplasticizers on cement suspensions. cem concr res. 2011;41:1058–1066. doi:10.1016/j.cemconres.2011.06.010 25. yang j, su y, he x, tan h, jiang y, zeng l, strnadel b. pore structure evaluation of cementing composites blended with coal by-products: calcined coal gangue and coal fly ash. fuel process technol. 2018;181:75–90. doi:10.1016/j.fuproc.2018.09.013 https://doi.org/10.1016/j.cemconres.2010.12.001 https://doi.org/10.1016/j.conbuildmat.2017.04.188 https://doi.org/10.1016/j.cemconres.2015.02.008 https://doi.org/10.1061/(asce)mt.1943-5533.0002633 https://doi.org/10.1016/j.cemconres.2011.06.010 https://doi.org/10.1016/j.fuproc.2018.09.013 investigation of physical and chemical parameters of the raw hydrocarbon material base of kaliningrad region for the concept development of an oil refinery published by ural federal university eissn 2411-1414; chimicatechnoacta.ru letter 2022, vol. 9(4), no. 20229413 doi: 10.15826/chimtech.2022.9.4.13 1 of 7 investigation of physical and chemical parameters of the raw hydrocarbon material base of the kaliningrad region for the concept development of an oil refinery pavel shcherban a* , yakov masyutin b , anna vatagina b, margarita belova b, alexander stolyarenko a a: educational and scientific cluster "institute of high technologies", higher school of interdisciplinary investigations and engineering, i. kant baltic federal university, kaliningrad 236041, russia b: educational and scientific сluster "institute of medicine and life sciences", higher school of living systems, i. kant baltic federal university, kaliningrad 236041, russia * corresponding author: ursa-maior@yandex.ru this paper belongs to a regular issue. © 2022, the authors. this article is published in open access under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). abstract the article analyzes the factors that determine the necessity of oil refinery construction in the kaliningrad region of the russian federation. the assessment of the existing and prospective raw material base is performed. the data for the development of the feasibility study for an oil refinery construction are formed and analyzed. taking into account the outdated data on the parameters of hydrocarbon raw materials produced in the region, as well as significant changes in the raw material base due to the tendency to develop offshore, rather than continental, fields the physical and chemical parameters of the oil fields of the kaliningrad region are investigated for the possibility of their further use in oil refining in order to obtain high-quality gasoline and diesel fuel. the laboratory studies of oil samples on viscosity, density, fractional composition, content of sulfur, chloride salts, mechanical impurities, water, and flash point determination are carried out on the basis of the russian state standards. the different variants of the refinery layouts are analyzed, considering the available raw material base. taking into account the initial data obtained, a preliminary predesign study of the technological scheme and the refinery mass balance is carried out and presented in the article. keywords oil quality fractional composition refinery design regional energy security physical and chemical oil analysis received: 03.08.22 revised: 19.08.22 accepted: 01.09.22 available online: 13.09.22 key findings ● according to the results of physical and chemical studies, the oils of the kaliningrad region offshore fields (including new deposit d33) can be classified as the first-class oil with a low sulfur and other impurities content along with high concentrations of light fractions. ● the necessities of the kaliningrad region in gasoline, diesel, fuel oil, and other petroleum products could be fulfilled by local crude oil fields. the volume and quality of this crude oils from local fields correspond technical requirements for classic refinery process. ● the optimal scheme of a refinery plant for the kaliningrad region should use fuel variant of the processing. the final volume of products in this scheme will be around 220 thousand tons of gasoline, 120 thousand tons of kerosene and 250 thousand tons of diesel fuel annually. 1. introduction in 2023–2024, the new offshore field of oil d33 is planned to be put into the operation in the kaliningrad region, with a recoverable reserve volume of about 20 million tons [1]. considering the fields currently in the operation, annual oil production volumes should exceed 2 million tons. besides the d33 oil field, there are prospects for the development of two more offshore structures: d6 yuzhnaya and d29 [2, 3]. http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2022.9.4.13 http://creativecommons.org/licenses/by/4.0/ https://orcid.org/0000-0001-5106-7852 https://orcid.org/0000-0003-4347-3425 https://crossmark.crossref.org/dialog/?doi=https://doi.org/10.15826/chimtech.2022.9.4.13&domain=pdf&date_stamp=2022-9-13 chimica techno acta 2022, vol. 9(4), no. 20229413 letter 2 of 7 thus, annual oil production volumes exceeding 1 million tons will remain the same in the kaliningrad region in the next 15–20 years, which provides the necessary raw material base for the creation of an oil refinery. at the same time, the consumption of gasoline and diesel fuel is constantly growing in the region. for instance, in 2021 the kaliningrad region consumed various brand gasoline in the amount of 243,760 thousand tons, which is 22% more than in 2011. as for diesel fuel, the kaliningrad region consumed 200,300 thousand tons of it in 2021, which is 34% more than in 2011 (figure 1) [4]. as the result, the volume of hydrocarbon consumption is steadily growing in the region, while the existing oil production capacities and the quality of the recoverable raw materials can meet these needs [4]. despite having its own resource base, diesel fuel and gasoline are imported to the region from the main territory of the russian federation due to the lack of specialized petrochemical enterprises [5]. calculations show that the cost of transporting a 60-ton tank from the nizhny novgorod refinery to kaliningrad, provided that it is owned, is 174,276 rubles without vat, to this the fee of 10% is added on the territory of belarus and lithuania, which is 3,972 rubles and 5,659 rubles respectively [6]. as a result, transportation costs for the delivery of gasoline and diesel fuel to the region by rail in 2021 amounted to 1,696,402,584 rubles without vat and freight forwarders' fees [7]. based on the presented geological and economic indicators, as well as the current geopolitical situation, providing the kaliningrad region with its own oil refining products is promising and a priority [6]. as the result, the purpose of this study is to conduct a pre-project assessment of the resource base of the region based on physical and chemical characteristics of hydrocarbon raw materials and the choice of the new oil refinery layout concept. 2. the experimental part to determine physical and chemical characteristics of the hydrocarbon raw material base of the kaliningrad region, a number of technological samples were selected, in terms of the largest deposits of the region on the land ladushkinskoye, krasnoborskoye, and on the shelf – d6 and d33 [2]. the samples were analyzed according to the main physical and chemical parameters for the study and understanding of their properties in terms of further refining and a relevant economic model forecasting of the projected refinery. in order to determine the fractional composition, the tests were carried out according to [8]. according to the experimental data, true boiling point curves were constructed and comparative diagrams were compiled (figure 2a, 2b). as the result, we can assume that the following fractions predominate in the oil samples of the largest deposits of the kaliningrad region: diesel and fuel oil. however, the total share of light petroleum products is more than 45.0% by weight, which makes it possible to attribute these oils to type t1 according to the technological classification of oils and along with a density value – to type 0 (especially light) according to the technical classification of gost r 51858-2002. this creates excellent opportunities for the production of the most valuable commodity petroleum products [9]. the highest content of light fractions is found in the oil of the krasnoborsky continental deposit and the offshore deposit d6. when determining the density, tests were carried out according to gost r 51069-97, while gost 33-2016 was used to determine the kinematic viscosity. as the result, it was found that all the studied oil samples of the kaliningrad region deposits belong to type 0 (especially light) according to gost r 51858-2002. such oils are characterized in general by the predominance of methane hydrocarbons, a low content of resinous-asphaltene components, and in fractional terms – by a high content of gasoline and kerosene fractions [10]. figure 1 volumes of gasoline and diesel fuel consumption in the kaliningrad region in 2000–2030. figure 2 true boiling point curves of the studied deposit samples (a), comparison of percent content by weight (b). chimica techno acta 2022, vol. 9(4), no. 20229413 letter 3 of 7 table 1 shows the values of experimentally determined kinematic viscosity, as well as the values of dynamic viscosity obtained from multiplying by the previously determined density values. refining light oil requires less economic costs; that is why it is considered especially valuable. the constant of the used capillary viscometer type – vpj1 is 0.1068 mm2/s2. according to the data obtained, it can be concluded that all types of tested oils belong to the category with insignificant viscosity (<5 mpa·s) [11]. the flash point and ignition temperature in an open crucible were determined in accordance with gost 4333-2014. to determine the ignition temperature, after performing the flash detection procedure, the sample continued to be heated. the use of the ignition source was repeated at intervals of 2 °c until the sample's vapors ignited and burned steadily for at least 5 seconds [12]. the temperature, which was registered at this moment, was recorded as the observed ignition temperature of the sample. then the final values of temperature were found after the adjustment procedure to the normal atmospheric pressure, according to the following empirical formula, discovered by d. holde and k. lohmann [13]: t760 = tp + 0.00012(760 – р)(273 + tp), (1) where t760 is the flash point at normal pressure of 760 mm hg, р – the observed pressure in units of mm hg, tр – the observed flash point. as a result, it was found that all the studied oil samples of the kaliningrad region deposits can be classified as highly flammable liquids, since their flash point is no more than 66 °c in an open crucible, which is due to their relatively low density. these samples require special precautions, especially for the oil of the krasnoborskoye field, which is classified as a particularly dangerous highly flammable liquid (<28 °c). obtaining data on mechanical impurities in the studied oil samples of the kaliningrad region deposits was carried out by conducting tests according to [14]. the sulfur content was determined according to gost r 51947 by means of energy dispersive x-ray fluorescence spectrometry in the laboratory of geochemistry and reservoir oils of jsc tomsknipineft. based on the results of the mechanical impurities determination, it can be concluded that the oils comply with the requirements of gost r 51858-2002, since the content does not exceed 0.05% [15]. it can be deduced that according to the technical classification of gost r 51858-2002, the studied oils belong to the low-sulfur class (≤0.6% by weight) [16]. according to the technological classification, the studied oils also belong to the 1st class of low-sulfur oils (≤0.5% by weight). the content of chloride salts in the samples was determined according to gost 21534 by method b – nonaqueous potentiometric titration in the laboratory of geochemistry and reservoir oils of jsc tomsknipineft. based on the results of determining the water and chloride salts content, it can be concluded that according to gost r 51858-2002, the studied oils belong to group 1 based on the extent of preparation, since the water content does not exceed 0.5%, while the chloride salt content does not exceed 100 mg/dm3 [17]. the octane numbers of gasoline fractions (initial boiling point – 180 °c) of the studied samples of oil and commercial brands of gasoline of 92 and 95 ron as comparison samples were determined using the quality portable octane meter, type – sim-3b, which belongs to the group of automated analyzers according to gost 16851-71, where sampling is done manually, and the measurement of the octane number occurs automatically [18, 19]. the principle of operation of the analyzer is based on the measurement of the dielectric constant of leaded and unleaded motor gasolines, which is functionally dependent on the octane number, and the transfer of the octane number from standard samples of gasoline to the tested samples of gasoline. as a result of determining the octane numbers, it can be concluded that the straight-run gasoline fractions of the studied oils are a good enough base for further compounding and obtaining commercial automobile gasoline by adding various high-octane components and additives, primarily, reformat [20]. table 1 density (at 15 °c), kinematic and dynamic viscosity (at 60 °c) of oil samples. oilfield density, kg/m3 kinematic viscosity mm2/s (cst) dynamic viscosity mpa·s ladushkinskoye 823.2±0.5 0.497±0.021 0.409±0.021 krasnoborskoye 825.7±0.5 0.472±0.013 0.390±0.013 d6 823.2±0,5 0.505±0.018 0.416±0.018 d33 824.2±0.5 0.428±0.011 0.353±0.011 table 2 density (at 15 °c), kinematic and dynamic viscosity (at 60 °c) of oil samples. oilfield average value of flash temperature, °с flash point adjusted for normal pressure, °с average value of ignition temperature, °с ignition temperature adjusted for pressure, °с ladushkinskoye 54.5±0.5 54.8±0.5 57.0±0.5 57.3±0.5 krasnoborskoye 15.5±0.5 15.8±0.5 17.0±0.5 17.3±0.5 d6 62.0±0.5 62.3±0.5 63.0±0.5 63.3±0.5 d33 45.5±0.5 45.8±0.5 47.5±0.5 47.8±0.5 chimica techno acta 2022, vol. 9(4), no. 20229413 letter 4 of 7 table 3 results of mechanical impurities and sulfur determination in oil samples. oilfield percentage of mechanical impurities, % sulfur mass fraction, % ladushkinskoye 0.032±0.002 0.127±0.011 krasnoborskoye 0.031±0.006 0.11±0.06 d6 0.038±0.006 0.127±0.013 d33 0.031±0.009 0.127±0.006 table 4 the content of chloride salts and water in oil samples. oilfield concentration, mg/l percentage of water, % ladushkinskoye 5.54±0.27 0.056±0.013 krasnoborskoye <5.00 0.176±0.011 d6 5.25±0.25 0.058±0.007 d33 <5.00 0.060±0.006 table 5 octane values according to research and motor methods for the gasoline fraction of the studied oil samples (initial boiling point –180 °c) and commercial brands of gasoline 92 and 95 ron. oilfield mon (5) ron (8) ladushkinskoye 68.0±0.9 77.3±1.0 krasnoborskoye 71.7±0.9 79.2±1.1 d6 69.02±0.18 78.4±0.5 d33 70.6±1.0 78.0±0.6 92 ron 83.0±0.8 92.02±0.28 95 ron 86.20±0.78 95.8±0.5 3. results and discussion summing up all the studies of the physical and chemical properties of oil samples, it can be concluded that according to the technical classification of gost r 51858-2002, the studied oils belong to class 1 (low-sulfur); type 0 (especially light); group 1 (according to the extent of feedstock preparation). the designation of the studied oils according to the standard is "oil 1.0.1 gost r 51858-2002". this makes them very useful, allowing a large number of valuable products from gasoline to diesel fuel and heavier products to be obtained at relatively low cost. according to the technological classification, the studied oils belong to class 1 (low-sulfur) and the first type (t1) in terms of the yield of light fractions. thus, it was found from the conducted physical and chemical studies of oil samples from the kaliningrad region deposits that oils from all major deposits can be used to produce gasoline, kerosene and diesel fuel, since their properties are low viscosity, low content of mechanical impurities and a high proportion of light fractions [21]. at the same time, these characteristics are more apparent in the oil of offshore fields that creates the necessary raw material base, taking into account the tendency to their development. the preliminary material balance to ensure the needs of the kaliningrad region with petroleum products obtained from local oil fields is given according to the average oil indicators of the kaliningrad fields based on the experimental data of the fractional composition in table 6. the balance is based on the distillation (primary) processes and not takes into account the additional separation of fuel oil (secondary processes). from the given table it can be concluded that there is a sufficiently large excess of kerosene, diesel and especially boiler fuel as a result of oil refining based only on the primary processes with further refinement of the resulting products. it is advisable to sell these surplus products to other regions of russia, transporting, for example, by sea, while almost the entire volume of gasoline produced is consumed within the region. taking into account the obtained physical and chemical data on the studied oils, as well as the needs of the region for petroleum products, the following economic concepts of designing an oil refinery were considered, given in order of increasing the oil refining efficiency. the first concept deals with a primary crude oil processing, i.e., oil distillation of the entire volume. a certain amount of crude oil is distilled only for the needs of the region, the rest volume is sent for sale in its original state. the second concept lies within a deep processing of crude oil only for the needs of the region. with this option a certain amount of oil is processed using secondary or destructive processes (cracking, reforming, etc.) for the needs of the region, while the rest of the crude oil volume is sold as a raw material. the third concept lies in a deep processing of some crude oil volume only for the needs of the region, while the rest volume of oil is processed to the form of primary or semi-finished products (straight-run gasoline, etc.) and sent for sale. the fourth concept is a deep processing of the entire volume of crude oil, including for export, i.e., by means of distillation and the above-mentioned secondary or destructive processes. in this variant one part of the products volume is sold within the region, and the other part of products is sold to other regions. the main classical technological pathways of oil refining were also considered: simple fuel, deep fuel, fuel-oil and petrochemical (complex). a rationale for the greatest expediency of the third economic concept, which consists of partially deep oil processing only for the region needs, while other volume of oil is sent in the form of primary products and semi-finished products for sale, was made as a result. it corresponds to a simple fuel variant of oil processing for the projected oil refinery in terms of chemical technology, which implies a small number of technological processes and the production of a small assortment of commodities: 55–60% of which are motor fuels (gasoline, kerosene, diesel fuel), and 30–35% are boiler fuels [22]. that means that vacuum fuel oil separation columns and such processes as catalytic cracking, thermal cracking, hydrocracking, etc. are not provided. chimica techno acta 2022, vol. 9(4), no. 20229413 letter 5 of 7 table 6 the material balance of the fraction output according to the average composition of the kaliningrad region oil. oil fractions average yield by fractions, % by weight total, total production, thousand tons/year annual average demand in thousand tons per year surplus for sale, thousand tons/year gasoline 16.53 371.93 220.00 151.92 kerosene 11.24 252.90 120.00 132.90 diesel 25.81 580.73 250.00 330.73 boiler fuel 36.26 815.85 220.00 595.85 other 10.16 228.60 0.00 228.60 total – 2250.00 810.00 1440.00 as it is known, it is mandatory to take into account the physical and chemical properties of raw materials in a simple distillation variant of oil processing, since there is no additional opportunity to increase the oil refining efficiency due to a number of secondary (destructive) processes [23]. considering the above mentioned facts, the proposed technological scheme for an oil refinery in the kaliningrad region in general may look as, shown in figure 3. at the first stage, the oil is subjected to electric desalination and dehydration at the crude desalter unit installation, then by means of atmospheric tubing (at) it is fractionated into gases, gasoline, kerosene, diesel fractions, and fuel oil. the gases are separated by means of gas fractionation unit with the separation of hydrogen sulfide and fuel gases, which are separated into dry and fatty gases. the gasoline fraction is fed to the secondary distillation, as a result of which two fractions of ibp –85 °c and 85–180 °c are released, being the raw materials for catalytic reforming, producing high-octane components of gasoline for compounding with a low-octane base. kerosene and diesel fractions are subjected to hydrotreatment to obtain components of jet and diesel fuels, respectively, followed by the introduction of appropriate additives to obtain marketable products. fuel oil is removed in a separate stream without secondary separation [23]. in view of the relatively small fuel needs of the region and the high cost of most secondary processes, primarily catalytic cracking and hydrocracking, it seems impractical to design processes to enhance oil refining efficiency by refining fuel oil. the incorporation of the catalytic reforming process to the scheme is sufficient in terms of the production of high-octane components for the gasoline production, which is the most used type of fuel in the region. figure 3 a variant of the kaliningrad refinery basic plan for a "simple" oil refining scheme: 1 – tank farm; 2 – gas fractionation unit; 3 – cleaning and disposal of h2s; 4 – fuel gas preparation unit; 5 – atmospheric distillation (crude desalter unit and at); 6 – secondary distillation; 7 – catalytic reforming; 8 – gasoline cleaning and compounding; 9 – petrol vst; 10 – hydrotreating of kerosene and jet fuel; 11 – jet fuel vst; 12 – hydrotreating and compounding of diesel fuel; 13 – diesel fuel vst; 14 – fuel oil handling equipment; 15 – fuel oil storage; 16 – energy complex; 17 – laboratory and administrative complex. chimica techno acta 2022, vol. 9(4), no. 20229413 letter 6 of 7 4. conclusions the conducted complex of the studies made it possible to establish the physical and chemical characteristics of hydrocarbons, currently being extracted in the kaliningrad region and planned for the production in the next 10 years, and to clarify their parameters in terms of the organization of the crude oil processing into petroleum products. it was determined that the oils of the kaliningrad region, both in old deposits and in new ones, belong to class 1 (low-sulfur) and the first type (t1) in terms of the yield of light fractions according to the technological classification. in case of the technical classification of gost r 518582002, the studied samples of crude oils belong to class 1 (low-sulfur); type 0 (especially light); group 1 (according to the degree of preparation). the volume of its production in the future by 2023–2024 will be at least 2– 2.5 million tons. gasoline consumption in the kaliningrad region by 2025–2027 will be about 220 thousand tons annually, diesel fuel consumption will be about 250 thousand tons annually, kerosene consumption will be about 120 thousand tons. the quality and quantity of crude oil planned for the production in the region are sufficient to organize the production of petroleum products in the kaliningrad region. the volume of oil refining will fully satisfy the regional market for all motor and boiler fuels. excess fuel, refined products, and crude oil unused in production can be sent to the foreign or russian mainland market. based on the results obtained and taking into account the consideration of several conceptual options, it was possible to form a basic optimal option for creating an oil refinery in the region. it seems rational to place an oil refinery on a production site next to the existing izhevsk oil terminal, since there is a suitable transport infrastructure there. taking into account the characteristics of raw materials and the parameters of the resulting petroleum products, it seems optimal to create an oil refinery according to the scheme of fuel variant of the processing. supplementary materials no supplementary materials are available. funding this research had no external funding. acknowledgments authors expressed their gratitude to the head of the laboratory of geochemistry and reservoir oils of jsc tomsknipineft – vadim samoylenko and to the student of immanuel kant baltic federal university alina berdnikova for their assistance in carrying out the experiments. author contributions conceptualization: ya.m., p.s. data curation: ya.m., p.s. formal analysis: a.v, m.b., a.s. investigation: a.v, m.b., a.s. methodology: ya.m., p.s. project administration: ya.m., p.s. supervision: ya.m., p.s. validation: ya.m. visualization: ya.m., p.s. writing – original draft: ya.m., p.s. writing – review & editing: ya.m., p.s. additional information author ids: pavel shcherban, web of science id a-7944-2019; yakov 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moscow, russia * corresponding author: spiridonova-25@mail.ru this article belongs to the regular issue. © 2021, the authors. this article is published in open access form under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). abstract new compounds of the composition na5rb7sc2(xo4)9 (x = mo, w) were obtained via the ceramic technology. the sequences of chemical transformations occurring during the formation of these compounds were established, and their primary characterization was performed. both na5rb7sc2(xo4)9 (x = mo, w) were found to melt incongruently at 857 k (x = mo) and 889 k (x = w). they are isostructural to ag5rb7sc2(xo4)9 (x = mo, w), na5cs7ln2(moo4)9 (ln = tm, yb, lu) and crystallize in the trigonal crystal system (sp. gr. r32). the crystal structures were refined with the rietveld method using the powder x-ray diffraction data. the thermal expansion of na5rb7sc2(wo4)9 was studied by high-temperature powder x-ray diffraction; it was shown that this triple tungstate belongs to high thermal expansion materials. keywords sodium rubidium scandium triple molybdate triple tungstate synthesis crystal structure thermal expansion received: 03.12.2021 revised: 10.12.2021 accepted: 14.12.2021 available online: 16.12.2021 1. introduction the search for new functional inorganic materials based on the development of ideas about the relationships between their structure and properties is one of the high-priority directions of modern solid state chemistry, crystal chemistry and materials science. the greatest attention is paid to the synthesis, study of the structure and properties of complex oxides, among which binary mo (vi) and w (vi) compounds of various compositions occupy a significant place. in the last two decades, triple molybdates have been actively studied, and in recent years, triple tungstates have also attracted much attention as interesting research objects. constant interest in such compounds is maintained due to their wide range of functional properties, such as catalytic, luminescent, laser, nonlinear optical, ferroelectric, ion-conducting, and others. thus, numerous publications are devoted to triple molybdates and tungstates with the band2(moo4)4-type structure, which are represented by two families of compounds: limr2(moo4)4 (m = k, tl, rb; r = bi, ln) and li3ba2ln3(хo4)8 (х = mo, w). the prospects for possible application of these compounds as photoand ir-phosphors, materials for uv radiation dosimeters, laser materials are shown in [1–10]. the latter is also facilitated by the fact that the maximum anisotropy of thermal expansion in several representatives of this family is lower than that in other successfully used laser crystals [11]. the molybdate phosphor nacala(moo4)3: tb3+/yb3+ can be used as a spectral converter [12]. triple molybdates na25cs8r5(moo4)24 (r = in, sc or fe) [13, 14] and na10cs4со5(moo4)12 [15], built on the basis of alluaudite (na,ca)mn(fe,mg)2(po4)3, m1–xa1–xr1+x(moo4)3 [16, 17] with the nasicon-type structure, k5schf(moo4)6 [18] with the k5inhf(moo4)6-type structure, and agrb2in(moo4)3 [19], ag3rb9sc2(wo4)9 [20], ag5rb7sc2(xo4)9 (x = mo, w) [21] that formed their own structural types are considered to be promising solid state electrolytes. in this work, the family of triple molybdates and tungstates represented by formula m′5m″7r2(xo4)9 [21, 22] is extended by two new compounds, na5rb7sc2(xo4)9 (x = mo, w). the primary characterization of these phases was carried out. their crystal structure was refined by the rietveld method from powder x-ray diffraction data. in addition, the thermal expansion of na5rb7sc2(wo4)9 was studied. http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2021.8.4.12 https://orcid.org/0000-0001-7498-5103 https://orcid.org/0000-0002-7108-8535 https://orcid.org/0000-0003-1301-1983 https://orcid.org/0000-0003-2482-9297 http://creativecommons.org/licenses/by/4.0/ chimica techno acta 2021, vol. 8(4), № 20218412 article 2 of 8 2. experimental 2.1. preparation of materials commercially available chemically pure moo3, wo3 (reakhim, ltd, russia), agno3 (khimko, ltd, russia) and high purity sc2o3 (sibmetalltorg, ltd, russia), rb2co3 (sigma-aldrich, china) were used as starting materials for preparing molybdates and tungstates. rb2хo4 (х = mo, w) was prepared by high temperature annealing of a stoichiometric mixture of rb2co3 and хo3 (723–823 k, 80 h). sc2(хo4)3 (х = mo, w) was obtained from sc2o3 and хo3 (х = mo, 773–1023 k, 80 h; х = w, 773–1123 k, 80 h). anhydrous na2xo4 (x = mo, w) used in this work were obtained by calcining the corresponding crystalline hydrates at 823–873 k. the phase purity of the prepared samples was confirmed by powder x-ray diffraction (pxrd). the pxrd patterns of na2хo4, rb2хo4, sc2(хo4)3 (х = mo, w) were in good agreement with the literature data [23]. 2.2. instrumental characterization methods the processes that occur during the solid-state syntheses were monitored with pxrd using a d8 advance bruker diffractometer (vantec detector, cu kα radiation, λ = 1.5418 å, reflection geometry, secondary monochromator). high temperature x-ray measurements of na5rb7sc2(wo4)9 were performed with the same instrument using an anton paar htk 16 high temperature chamber in the temperature range of 303–823 k. the heating rate was 20 k min–1. prior to measurements, the sample was kept at a specified temperature for 25 min. the unit cell parameters of na5rb7sc2(xo4)9 (x = mo, w) were refined by the least-squares method using icdd program package for preparing experimental standards. the smith–snyder f30 criterion was used as a validation criterion for x-ray patterns indexing [24]. the crystal structures refinement of na5rb7sc2(xo4)9 (x = mo, w) at room temperature and the unit cell parameters determination in high-temperature studies were carried out by the rietveld method [25] using the topas 4.2 software [26]. the thermal measurements were carried out using an sta 449 f1 jupiter netzsch thermoanalyser (pt crucible, heating rate of 10 k min–1 in a flow of argon). 3. results and discussion 3.1. synthesis and characterization of na5rb7sc2(хo4)9 (х = mo, w) polycrystalline na5rb7sc2(хo4)9 (х = mo, w) were synthesized by annealing the stoichiometric mixtures of na2хo4, rb2хo4 and sc2(хo4)3 at 773–823 k for 80 h (х = mo), 100 h (х = w). the final powder products are of white color, insoluble in water and common organic solvents, soluble in hcl (na5rb7sc2(moo4)9 at room temperature, na5rb7sc2(wo4)9 – at heating). according to the results of pxrd data, the sequence of chemical transformations in the course of na5rb7sc2(wo4)9 formation from a stoichiometric mixture of simple tungstates can be illustrated by the following scheme: scheme 1 the sequence of chemical transformations in the course of na5rb7sc2(wo4)9 formation in the mo-containing system the formation of na5rb7sc2(moo4)9 started at the stage when narb3(moo4)2 and rbsc(moo4)2 appeared. the corresponding scheme differs from that for ternary tungstate only in shorter synthesis times. both moand w-based na5rb7sc2(хo4)9 melt incongruently at 857 k (x = mo) and 889 k (x = w) (fig. 1). reflections of both nasc(moo4)2 and a phase with an alluouditetype structure together with the initial phase were found in the pxrd pattern of the cooled na5rb7sc2(moo4)9 melt. the cooled melt of na5rb7sc2(wo4)9 contains the double tungstates rbsc(wo4)2 and nasc(wo4)2 and an alluaudite-like phase. the amount of the latter phase was dominant. fig. 1 the dsc curves for polycrystalline na5rb7sc2(хo4)9 (х = w, mo) chimica techno acta 2021, vol. 8(4), № 20218412 article 3 of 8 the pxrd patterns of prepared single-phase compounds na5rb7sc2(хo4)9 (х = mo, w) are similar and show that these complex oxides are isostructural to trigonal na5cs7yb2(moo4)9, ag5rb7sc2(хo4)9 (х = mo, w) (sp. gr. r32, z = 3) [21, 22]. this allows satisfactorily indexing the pxrd patterns of na5rb7sc2(хo4)9 (х = mo, w) (in the case of molybdate f(30) = 141.6 (0.0056; 38), for tungstate f(30) = 287.2 (0.0028; 37)). the obtained crystallographic characteristics are shown in table 1, the results of indexing of na5rb7sc2(wo4)9 are shown in table 2 as an example. table 1 unit cell parameters for na5rb7sc2(хo4)9 (х = mo, w) х a, å c, å v, å3 mo 10.1264(1) 35.6570(7) 3172.80 w 10.1899(2) 35.6096(9) 3202.12 table 2 the pxrd data for na5rb7sc2(wo4)9 h k l 2exp,° i/i0 dexp, å  = 2exp – 2calc,° h k l 2exp,° i/i0 dexp, å  = 2exp – 2calc,° 1 0 1 10.322 1 8.563 –0.003 2 1 13 42.680 3 2.1167 –0.002 0 1 2 11.183 2 7.906 –0.002 0 4 5 42.879 2 2.1074 +0.000 1 0 4 14.117 1l 6.268 +0.003 3 0 12 43.273 2 2.0891 +0.000 0 0 6 14.911 1l 5.936 +0.004 0 1 17 44.418 1l 2.0379 –0.005 0 1 5 15.974 1l 5.544 +0.004 4 0 7 44.739 2 2.0240 –0.001 1 1 0 17.390 20 5.095 +0.001 1 2 14 44.781 2 2.0222 –0.009 1 1 3 18.938 42 4.682 +0.001 3 2 1 44.813 2 2.0208 –0.011 1 0 7 20.131 1 4.407 +0.000 1 3 10 44.914 1 2.0165 –0.013 0 2 1 20.264 1 4.379 –0.001 2 3 2 45.033 1 2.0114 –0.003 2 0 2 20.724 2 4.283 –0.001 0 2 16 45.615 1l 1.9871 +0.000 0 0 9 22.454 13 3.9563 –0.002 0 0 18 45.831 7 1.9783 –0.001 1 1 6 22.987 100 3.8658 +0.000 3 2 4 45.930 1 1.9742 +0.002 2 0 5 23.694 1 3.7520 +0.007 3 1 11 46.475 2 1.9523 +0.000 0 2 7 26.722 2 3.3333 +0.001 2 3 5 46.604 1 1.9472 –0.004 2 1 1 26.824 15 3.3209 +0.000 2 2 12 46.970 2 1.9329 +0.000 1 0 10 26.973 1l 3.3029 +0.005 4 1 0 47.157 3 1.9257 –0.001 1 2 2 27.178 3 3.2784 +0.000 4 1 3 47.813 5 1.9008 –0.002 1 1 9 28.541 59 3.1249 –0.001 2 0 17 48.045 1l 1.8921 –0.004 0 1 11 29.345 2 3.0411 +0.018 3 2 7 48.348 2 1.8810 –0.001 1 2 5 29.546 5 3.0208 +0.002 4 0 10 48.505 1l 1.8753 –0.004 0 0 12 30.094 1 2.9671 –0.004 2 1 16 49.167 1l 1.8516 +0.007 0 3 0 30.362 54 2.9415 –0.001 3 0 15 49.280 1l 1.8476 +0.005 3 0 3 31.304 1 2.8551 –0.001 1 1 18 49.379 5 1.8441 –0.002 2 1 7 32.067 2 2.7889 –0.006 2 3 8 49.422 1 1.8426 –0.008 1 2 8 33.548 3 2.6690 –0.002 4 1 6 49.737 8 1.8317 –0.001 3 0 6 33.989 5 2.6354 –0.002 1 3 13 49.930 1 1.8250 –0.002 2 0 11 34.335 1l 2.6096 –0.006 0 4 11 49.993 2 1.8229 –0.006 1 1 12 34.964 15 2.5641 –0.002 1 2 17 51.478 2 1.7737 –0.005 2 2 0 35.200 5 2.5475 +0.000 3 1 14 51.749 1l 1.7651 +0.045 2 2 3 36.031 1 2.4906 –0.002 0 5 1 51.820 1l 1.7628 +0.001 0 1 14 36.738 1l 2.4443 +0.004 3 2 10 51.916 1 1.7598 –0.006 1 3 1 36.779 2 2.4417 –0.002 2 2 15 52.659 4 1.7367 –0.002 2 1 10 36.898 1l 2.4340 –0.004 4 1 9 52.831 15 1.7314 –0.002 3 1 2 37.057 1l 2.4240 –0.012 0 2 19 53.025 1 1.7256 +0.018 3 0 9 38.091 6 2.3605 –0.002 4 0 13 53.279 1 1.7179 –0.009 2 2 6 38.423 8 2.3409 –0.001 2 3 11 53.336 1 1.7162 –0.009 3 1 5 38.875 2 2.3147 +0.001 3 3 0 53.946 5 1.6983 –0.002 1 3 7 40.884 1 2.2055 –0.001 3 3 3 54.538 2 1.6812 +0.001 4 0 1 40.950 1 2.2021 +0.002 0 5 7 55.016 1l 1.6677 +0.011 0 4 2 41.201 1 2.1892 –0.004 2 4 1 55.077 2 1.6660 +0.005 1 0 16 41.799 1l 2.1593 +0.025 4 2 2 55.268 1l 1.6607 +0.010 1 1 15 41.952 9 2.1518 –0.002 1 3 16 55.766 1l 1.6471 +0.017 2 2 9 42.156 19 2.1418 –0.002 3 0 18 55.969 13 1.6416 –0.001 cu kα1 radiation ( = 1.54056 å) chimica techno acta 2021, vol. 8(4), № 20218412 article 4 of 8 3.2. rietveld refinement of na5rb7sc2(хo4)9 (х = mo, w) structure the positional atomic parameters for the ag5rb7sc2(moo4)9 structure [21] were taken as a starting model for the refinement of the na5rb7sc2(хo4)9 (х = mo, w) structures by the rietveld method. the refinement was carried out by gradually adding the refined parameters with the simultaneous graphical simulation of the background. the pearson vii function was used to describe the shape of peaks. isotropic displacement parameters (biso) for all atoms in na5rb7sc2(moo4)9 were refined separately, while for the o atoms in na5rb7sc2(wo4)9 they were taken as equal. the refinement procedure included corrections for the sample preferred orientation and broadening of peaks due to anisotropy within the model of spherical harmonics [27]. the refinement results for na5rb7sc2(хo4)9 (х = mo, w) are shown in table 3. experimental, theoretical and difference pxrd patterns for na5rb7sc2(хo4)9 (х = mo, w) are shown in fig. 2 and 3. the fractional atomic coordinates, isotropic atomic displacement parameters, cation occupancies and main selected interatomic distances are presented in tables 4–7. the crystal structures of na5rb7sc2(moo4)9 and na5rb7sc2(wo4)9 were deposited in the cambridge crystallographic data centre with cambridge structural database (csd) № 2124713 and № 2124691, respectively [28]. table 3 main structure parameters for na5rb7sc2(хo4)9 (х = mo, w) after the rietveld refinement compound na5rb7sc2(moo4)9 na5rb7sc2(wo4)9 sp. gr. r32 r32 a, å 10.13752(9) 10.19247(9) c, å 35.6615(4) 35.6191(4) v, å3 3173.91(7) 3204.59(7) z 3 3 2θ-interval, º 8–100 8–100 rwp, % 4.15 4.56 rp, % 3.20 3.42 rexp, % 2.04 1.81 χ2 2.04 2.51 rb, % 1.64 2.11 fig. 2 observed, calculated and difference diffractograms of na5rb7sc2(moo4)9 fig. 3 observed, calculated and difference diffractograms of na5rb7sc2(wo4)9 in the structures of na5rb7sc2(хo4)9 (х = mo, w), na1 and na2 atoms are located in threefold special positions with the point symmetry 32; sc, rb1, and rb2 sit at threefold axes; rb3, mo2 (w2), and na3 are settled at twofold axes, and mo1 (w1) and oxygen atoms are in general positions. both mo and w atoms have tetrahedral coordination, while sc, na1 and na3 possess octahedral coordination. it is worth noting that, unlike the octahedron surrounding na1, the octahedron around na3 is distorted. the half-occupied na2 site has a trigonal-prismatic environment. rb1 and rb2 atoms have 9-fold environments, while rb3 exhibits cn = 8. the general view of the structure is illustrated in fig. 4a. the characteristic details of the title compounds are so-called ‘lanterns’ [sc2(xo4)9] (x = mo, w) composed by two sco6 octahedra sharing corners with six terminal and three bridging xo4 tetrahedra (fig. 4b). together with the rb1, rb2 and na3 cations they form two-tiered hexagonal layers parallel to (001) plane, which resemble the motif of the k3na(so4)2 glaserite structure [29]. the layers are folded with a displacement along the b axis and are connected by na3, na1 and rb3 cations (fig. 4c). similar "lanterns" [m2(to4)9] (m is an octahedrally coordinated cation, to4 is a tetrahedral oxoanion), and hexagonal layers formed by them also characterize the structures of previously studied ag5rb7sc2(moo4)9, ag5rb7sc2(wo4)9 and na5cs7yb2(moo4)9 [21]. the relationship between structure of the considered family m′5m″7r2(xo4)9 (x = mo, w) and many rhombohedral triple molybdates and tungstates with а = 9–10 å and large c-periods (more than 20 å) was discussed in [21]. 3.3. thermal expansion of na5rb7sc2(wo4)9 the thermal expansion of na5rb7sc2(wo4)9 was studied by high-temperature x-ray diffraction. the thermal expansion of this compound, which crystallizes in a trigonal symmetry, is defined by two linear thermal expansion coefficients (ltecs) measured along (с) and across (a) the threefold axis. the average ltec can be calculated as follows: av = v/3 = (2a+с)/3. thermal expansion anisotropy is quantitatively defined as |a – с|. chimica techno acta 2021, vol. 8(4), № 20218412 article 5 of 8 a b c fig. 4 the crystal structure of na5rb7sc2(хo4)9 (х = mo, w): a general view (a); [sc2(xo4)9] cluster (b); layers of [sc2(xo4)9] clusters (c) table 4 fractional atomic coordinates and isotropic displacement parameters (å2) for na5rb7sc2(moo4)9 atom x y z biso occ. rb1 0 0 0.2332(1) 1.9 (1) 1 rb2 0 0 0.1074(1) 2.0(1) 1 rb3 0 0.3687(3) 0 4.6(2) 1 na1 0 0 0 1.9(6) 1 na2 0 0 0.3376(8) 2.1(3) 0.5 na3 0.4030(9) 0.4030(9) 0.5 2.1(3) 1 sc2 0 0 0.4253(3) 2.1(2) 1 mo1 0.3429(2) 0.3265(3) 0.39176(4) 1.30(9) 1 mo2 0.7331(2) 0.7331(2) 0.5 0.9(1) 1 o1 0.458(1) 0.269(1) 0.3746(4) 3.2(4) 1 o2 0.362(1) 0.480(1) 0.3662(3) 1.4(4) 1 o3 0.406(1) 0.394(1) 0.4344(3) 0.4(3) 1 o4 0.147(1) 0.180(1) 0.3938(3) 1.8(2) 1 o5 0.566(1) 0.719(1) 0.4937(4) 1.6(4) 1 o6 0.822(1) 0.839(2) 0.5391(3) 1.8(2) 1 table 5 fractional atomic coordinates and isotropic displacement parameters (å2) for na5rb7sc2(wo4)9 atom x y z biso occ. rb1 0 0 0.2331(2) 1.1(2) 1 rb2 0 0 0.1083(2) 1.7(2) 1 rb3 0 0.3671(5) 0 3.1(2) 1 na1 0 0 0 2(1) 1 na2 0 0 0.329(2) 3(1) 0.5 na3 0.418(1) 0.418(1) 0.5 4.3(6) 1 sc2 0 0 0.4241(3) 0.5(3) 1 w1 0.3410(1) 0.3251(1) 0.39174(3) 0.8(1) 1 w2 0.7329 (1) 0.7329(1) 0.5 0.9(1) 1 o1 0.4660(7) 0.2580(8) 0.3785(3) 1.0(2) 1 o2 0.376(1) 0.4839(7) 0.3633(2) 1.0(2) 1 o3 0.4104(8) 0.3974(9) 0.4371(2) 1.0(2) 1 o4 0.1487(9) 0.1765(9) 0.3976(4) 1.0(2) 1 o5 0.5570(8) 0.7196(7) 0.4896(2) 1.0(2) 1 o6 0.823(1) 0.840(1) 0.5412(2) 1.0(2) 1 chimica techno acta 2021, vol. 8(4), № 20218412 article 6 of 8 table 6 main bond lengths (å) in na5rb7sc2(moo4)9 mo1-tetrahedron mo2-tetrahedron sc-octahedron mo1–o1 1.660(9) mo2–o5 1.64(1) (× 2) sc–o4 2.02(1) (× 3) –o2 1.73(1) –o6 1.71(1) (× 2) –o6 2.14(1) (× 3) –o3 1.66(1) <mo2–o> 1.67 <sc–o> 2.08 –o4 1.79(1) <mo1–o> 1.71 na1-octahedron na2-trigonal prism na3-octahedron na1–o1 2.39(1) (× 6) na2–o2 2.45(2) ( 3) na3–o3 2.34(1) (× 2) –o4 2.62(2) (× 3) –o5 2.192(9) (× 2) <na2–o> 2.53 –o5 2.78(1) (× 2) <na3–o> 2.44 rb1-polyhedron rb2-polyhedron rb3-polyhedron rb1–o5 3.04(1) (× 3) rb2–o5 3.18(1) (× 3) rb3–o1 3.05(1) (× 2) –o3 3.20(1) (× 3) –o3 3.00(1) (× 3) –o2 3.00(1) (× 2) –o2 3.16(1) (× 3) –o1 3.01(1) (× 3) –o2 3.11(1) (× 2) <rb1–o> 3.13 <rb2–o> 3.06 –o4 3.18(1) (× 2) <rb3–o> 3.08 table 7 main bond lengths (å) of na5rb7sc2(wo4)9 w1-tetrahedron w2-tetrahedron sc-octahedron w1–o1 1.785(5) w2–o5 1.768(6) (× 2) sc–o4 1.92(1) (× 3) –o2 1.788(7) –o6 1.786(8) (× 2) –o6 2.12(1) (× 3) –o3 1.771(8) <w2–o> 1.777 <sc–o> 2.02 –o4 1.792(7) <w1–o> 1.784 na1-octahedron na2-trigonal prism na3-octahedron na1–o1 2.406(9) (× 6) na2–o2 2.30(2) ( 3) na3–o3 2.247(8) (× 2) –o4 2.96(5) (× 3) –o5 2.76(1) (× 2) <na2–o> 2.63 –o5 2.69(1) (× 2) <na3–o> 2.57 rb1-polyhedron rb2-polyhedron rb3-polyhedron rb1–o5 2.870(8) (× 3) rb2–o5 3.202(9) (× 3) rb3–o1 3.043(9) (× 2) –o3 3.212(8) (× 3) –o3 2.997(7) (× 3) –o2 2.874(9) (× 2) –o2 3.27(1) (× 3) –o1 2.88(1) (× 3) –o2 3.209(9) (× 2) <rb1–o> 3.12 <rb2–o> 3.03 –o4 3.32(1) (× 2) <rb3–o> 3.11 the reflections in the x-ray diffraction patterns of na5rb7sc2(wo4)9 regularly shift with increasing temperature (fig. 5) due to an increase in the unit cell parameters (fig. 6). fig. 5 fragments of na5rb7sc2(wo4)9 diffractograms from 303 k to 823 k the parameter a changes with temperature almost linearly; the temperature variation of the parameter c is described by a polynomial of the second degree (table 8). table 8 also presents the coefficients of thermal linear expansion and thermal expansion anisotropy. the obtained results allowed classifying na5rb7sc2(wo4)9 as belonging to high thermal expansion materials. 4. conclusions two new compounds na5rb7sc2(хo4)9 (х = mo, w) were obtained by a solid-phase synthesis, supplementing the previously discovered family of isostructural triple molybdates and tungstates of the composition m'7m''5r2(xo4)9. the thermal stability of obtained compounds was studied and the thermal expansion of na5rb7sc2(wo4)9 was examined by the high-temperature xrd diffraction method; it was shown that this compound belongs to highly expanding substances. the crystal structure of na5rb7sc2(хo4)9 (х = mo, w) was refined by the rietveld method using the pxrd data. chimica techno acta 2021, vol. 8(4), № 20218412 article 7 of 8 table 8 fitting polynomials for temperature dependent ltecs and average ltecs for na5rb7sc2(wo4)9 in the temperature range 303–823 k composition polynomials for a(t) and c(t), å ltec10–6, k–1 αa αс αav |αa–αc| na5rb7sc2(wo4)9 а = 0.0003т + 10.18 с = 1×10–6т2 + 0.0002т + 35.612 27.8(3) 22.9(2) 26.2(3) 4.9 the obtained compounds crystallize in the chiral sp. gr. r32 and together with their formula and structural analogues ag5rb7sc2(хo4)9 (х = mo, w), na5cs7ln2(moo4)9 (ln = tm, yb, lu) belong to the series of rhombohedral triple molybdates and tungstates with а = 9–10 å and long c-parameter, more than 20 å; many of those have noticeable ionic conductivity at elevated temperatures [19–21]. for two representatives of the m'7m''5r2(xo4)9 family, namely, ag5rb7sc2(хo4)9 (х = mo, w), we confirmed this experimentally earlier [21]. this stimulates our research to find new representatives of this group of phases, as well as to continue the study of the ion-conducting properties of already obtained compounds – (na5rb7sc2(хo4)9 (х = mo, w) and na5cs7ln2(moo4)9 (ln = tm, yb, lu). in addition, it seems expedient to carry out a further study of thermophysical properties for representatives of the considered structural type to reveal the influence of the nature of one-, threeand hexavalent elements on the value of thermal expansion coefficients and anisotropy in these phases. fig. 6 temperature dependences of the a 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https://scripts.iucr.org/cgi-bin/citedin?search_on=name&author_name=rietveld,%20h.m. https://journals.iucr.org/j/issues/1969/02/00/a07067/a07067.pdf https://journals.iucr.org/j/issues/1969/02/00/a07067/a07067.pdf https://journals.iucr.org/j/contents/backissues.html https://doi.org/10.1107/s0021889869006558 https://doi.org/10.1107/s0021889893001219 https://www.ccdc.cam.ac.uk/structures/ https://doi.org/10.1107/s0567740880004852 activity features of catalysts for thermocatalytic hydrogenation processing of polymer waste published by ural federal university eissn 2411-1414; chimicatechnoacta.ru article 2022, vol. 9(3), no. 20229302 doi: 10.15826/chimtech.2022.9.3.02 1 of 6 activity features of catalysts for thermocatalytic hydrogenation processing of polymer waste zheneta kh. tashmukhambetova a , tanakoz o. kalamgali a , yermek a. aubakirov a , larissa r. sassykova a* , firuza zh. akhmetova b , albina s. alpysbay a a: al-farabi kazakh national university, almaty 050040, kazakhstan b: zhangirkhan west-kazakhstan agrarian technical university, uralsk 090009, kazakhstan * corresponding author: larissa.rav@mail.ru this paper belongs to the ctfm'22 special issue: https://www.kaznu.kz/en/25415/page. guest editors: prof. n. uvarov and prof. e. aubakirov. © 2022, the authors. this article is published in open access under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). abstract the aim of this study was to obtain new catalysts for the processing of carbon-containing polymer waste based on polyethylene and polypropylene, represented mostly by lids from beverages bottled in plastic containers, which accumulate in huge quantities in landfills, by the method of thermocatalytic hydrogenation into liquid fuels and other products. the process was carried out in the presence of fuel oil as a binder, a source of hydrogen and additional hydrocarbons. thus, two tasks can be solved simultaneously: recycling the polymer waste and obtaining the alternative raw materials from the polymer waste in order to save resources and improve the environmental situation in general. new catalysts based on activated zeolite modified with mo(vi) and w(vi) salts of various concentrations for the thermocatalytic hydrogenation processing of waste plastics into motor fuels were synthesized. the composition, structure, morphology and adsorption properties of the catalysts were determined by different physicochemical methods. the suitability of the obtained catalysts for use in the thermocatalytic hydrogenation processing of plastic waste into fuels was determined. the catalysts were tested during the processing of a mixture of polyethylene-polypropylene: a paste-forming agent (fuel oil) at t=450 °c and a pressure of 0.6 mpa. the individual and group composition of gasoline, diesel and gas oil fractions was determined by chromatography coupled with mass spectrometry. the maximum yield of the gasoline fraction (16.9 wt.%) and diesel fraction (39.31 wt.%) was obtained on a 2%w(vi)/diatomite catalyst. keywords polymer waste thermocatalysis hydrogenation catalyst fuel diatomite received: 12.06.22 revised: 28.06.22 accepted: 30.06. 22 available online: 05.07.22 1. introduction the problem of environmental pollution with carboncontaining industrial and household waste based on polymer and rubber products needs to be addressed. the main ways of the disposal of such waste are incineration and storage [1–15]. if we consider these carbon-containing wastes as an alternative source of hydrocarbons, then the development of new integrated technologies based on the use of effective catalysts will allow us to fully solve the existing environmental threats in the future. moreover, it will make it possible to saturate the market with the necessary fuels, products and materials [16–23]. in the laboratory of the department of physical chemistry, catalysis and petrochemistry of the al-farabi kazakh national university, tests of new composite catalysts for the thermocatalytic hydrogenation processing of polymer waste were carried out. composites based on mo(vi) and w(vi) salts deposited on a diatomite substrate were studied for the first time as catalysts. as is known, diatomite is a natural aluminosilicate material of a macroporous structure with a large internal surface formed as a result of the vital activity of organisms – diatomies. it has a complex “cemented” composition and contains inclusions of various minerals, such as silica, quartz, kaolin, opal, etc. such a structure http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2022.9.3.02 http://orcid.org/0000-0003-4125-4114 http://orcid.org/0000-0003-0225-0049 http://orcid.org/0000-0001-5405-4125 http://orcid.org/0000-0003-4721-9758 http://orcid.org/0000-0002-8869-3053 http://orcid.org/0000-0001-5717-0842 mailto:larissa.rav@mail.ru https://www.kaznu.kz/en/25415/page http://creativecommons.org/licenses/by/4.0/ https://crossmark.crossref.org/dialog/?doi=https://doi.org/10.15826/chimtech.2022.9.3.02&domain=pdf&date_stamp=2022-7-5 chimica techno acta 2022, vol. 9(3), no. 20229302 article 2 of 6 allows us to consider it as a natural ion exchanger and adsorbent, as well as a substrate for the deposition of active catalysts [24–27]. the aim of this work was to synthesize new catalysts for the processing of carbon-containing polymeric wastes based on polyethylene and polypropylene, mainly represented by lids from drinks poured into plastic containers, which accumulate in large quantities in landfills, by thermal catalytic hydrogenation into liquid fuels and other products. the process was carried out in the presence of fuel oil as a binder, a source of hydrogen and additional hydrocarbons. 2. experimental in this work, diatomite from the aktobe deposit of the republic of kazakhstan was studied. the concentration of the active metal in the composite was varied in the range from 1 to 2 wt.%. the effect of 4 different catalysts on the thermocatalytic hydrogenation processing of plastic waste was studied: diatomite activated by the acid-free method, 2% mo(vi)/diatomite, 2% w(vi)/diatomite, and (1%mo(vi) and 1%w(vi))/diatomaceous earth. as a feedstock, polymeric wastes crushed to the state of crumbs from a waste processing plant in almaty, represented by a mixture of polyethylene and polypropylene lids, were studied. to impart viscous paste-forming properties to the polymer mixture, fuel oil with a boiling point of more than 350 °с, obtained during the distillation processing of oil from the kumkolskoe field, was used. as is known from our previous studies [6, 28–31], fuel oil was used not only as a paste-forming agent, but also as an additional source of hydrocarbons and hydrogen necessary for the hydrogenation reaction to proceed. in order to determine the composition, structure, morphology and adsorption properties of the studied catalysts, such physico-chemical methods of analysis as x-ray fluorescence, ir spectroscopy, scanning electron microscopy (sem), adsorption nitrogen porometry (bet), x-ray diffraction analysis (xrd), thermogravimetric analysis (tga) and differential thermogravimetric analysis (dtga) were used. 3. results and discussion the presence of tungsten immobilized on the surface of diatomite during ion exchange in the composition of catalysts was established by x-ray fluorescence (figure 1). the process of ion exchange was accompanied by a decrease in the structure of diatomite of the concentrations of potassium, chromium, iron, as well as aluminum and silicon, which may indicate a possible destruction of the m–o–si (where “m” is a metal) bond, a slight destruction of the si–o–si bond, and a partial removal of the sixcoordinate aluminum. figure 1 data of x-ray fluorescence analysis: 2% w(vi)/diatomite catalyst (a); the catalyst 1% mo(vi) – 1% w(vi)/ diatomite (b); an activated diatomite (c). (b) (a) (c) chimica techno acta 2022, vol. 9(3), no. 20229302 article 3 of 6 so, for example, in the composition of activated diatomite, the concentration of si was 65.30%, in 2% w(vi)/diatomite – 33.40%; in 2% mo(vi)/diatomite – 45.40% in (1% mo(vi) and 1% w(vi))/diatomite – 49.10%, respectively. the al concentration was 12.22%, in 2% w(vi)/diatomite – 8.74%; in 2% mo (vi)/diatomite – 22.45% in (1% mo(vi) and 1% w(vi))/diatomite – 0%, respectively. the presence of molybdenum in the catalyst samples could not be determined by this method. the study of the morphology of catalysts by sem at different magnifications showed the presence in the images of distinct sections of the cellular structure inherent in diatomite, as well as loose and convex oval inclusions, most likely corresponding to the sites of destruction of diatomite and the introduction of molybdenum and tungsten ions into the substrate structure as a result of exchange with other ions (figure 2). the images clearly show integral fragments of the flaps of various organisms – diatoms with their inherent cellular structure, macropores with the inclusion of mesoand micropores, which indicates the heterogeneity of the surface of the diatomite. the samples of the studied catalysts, regardless of the content of the active metal, have a sufficiently developed specific surface area and are of interest for studying their structure by nitrogen porometry with a view to further use as a carrier of the active phase of the catalyst. according to the data of the bet analysis (table 1), in pure diatomite, the adsorption and desorption indices differ from those in the samples of catalysts with mo and w active centers immobilized on them. this is also apparently due to a change in the structure of the catalyst after ion exchange treatment. the maximum value of the specific surface corresponds to the sample of 2% w(vi)/diatomite – 42.71 m2/g. figure 2 study of the morphology of the catalysts by sem: 2% w(vi)/diatomite (10 μm (a), 20 μm (b), 100 μm (c)); 2% mo(vi)/diatomite (10 μm (d), 20 μm (e), 100 μm (f)); 1% mo(vi) – 1% w(vi)/diatomite (10 μm (g), 20 μm (h), 100 μm (i)). chimica techno acta 2022, vol. 9(3), no. 20229302 article 4 of 6 table 1 determination of the specific surface area of catalysts by the bet method. catalyst sspecific surface area, m²/g 2% w(vi)/diatomite 60.76 2% mo(vi)/diatomite 42.71 1% mo(vi) – 1% w(vi)/diatomite 14.39 activated diatomite 34.41 the study of catalyst samples by ir spectroscopy showed the presence in the spectra, mainly, of absorption bands characteristic of diatomite, since it has a complex composition and contains, in addition to si and al oxides, a number of oxides of various metals, such as mn, fe, ti, cr, k, etc. however, during the processing of mo(vi) and w(vi) diatomite separately and with the total presence, a slight shift of the peak at 1098.94 cm–1 from 0.038 to 0.045 cm–1 is observed, corresponding to strong valence and deformation vibrations of si–o–si silica and quartz, as well as weak vibrations in the region of 460, 550, 804, 951 cm–1, valence fluctuations at 3450–3500 cm-1, corresponding to the oh group; valence fluctuations in the region of 3630–3695 cm–1, characteristic of clay and mica. the activated diatomite and w(vi)/diatomite catalyst samples were analyzed by tga and processed by dtga. as the analyzes showed, the destruction of samples under the influence of temperature occurs intensively up to 130– 135 °с, then it somewhat slows down until reaching 450– 470 °с and then the final destruction occurs up to 898 °с (figure 3 and 4). the tga curves for both catalysts are approximately the same. the greatest mass loss of the sample, therefore, will be achieved already at the temperature of thermodestructive hydrogenation processing, which is 450 °с. however, the percentage of mass loss by the activated diatomite is insignificant and amounts to only 4.553%, and by the w(vi)/diatomite catalyst – 6.323%, respectively, which may indicate their resistance to temperature and the formation of disilicates (600–650 °с) with their further transition to the melt above 700 °с. figure 3 data of tga and dta analysis of activated diatomite. figure 4 data of tga and dtga analysis of the catalyst w(vi)/diatomite. based on the x-ray phase analysis (xrd) of the studied catalysts, it was also found that the main contribution is made by the crystalline and amorphous phases of diatomite and minor fluctuations in intensity may be due to the presence of mo(vi) and w(vi) salts. the obtained catalysts were tested for processing a polyethylene-polypropylene mixture in the presence of a paste-forming agent at t = 450 °с and a pressure of 0.6 mpa. the maximum yield of the gasoline fraction (tboiling point=0–180 °с) was observed on a catalyst of 2%w(vi)/diatomite – 16.90 wt. %. the material balance of the most significant process under given conditions is presented in table 2. table 3 shows the group composition of hydrocarbons of the gasoline fraction obtained on the catalyst 2% w/diatomite. the hydrocarbon composition of distillates obtained on the synthesized catalysts was studied by chromatography– mass spectrometry. the chromatogram of the gasoline fraction boiling in the range of 0–180 °c obtained on a 2% w/diatomite catalyst is shown in figure 5. the main conclusions obtained as a result of the physicochemical studies and experimental tests of catalysts in this work are in agreement with the data mentioned in the scientific literature [2, 5, 32–41]. table 2 material balance of the thermocatalytic hydrogenation processing of polymer waste on a catalyst 2% w(vi)/diatomite (t = 450 °с, p = 0.6 mpa). taken wt.% consumption wt.% catalyst 2.00 gasoline fraction 0–180 °с 16.90 polymer waste 49.02 diesel fraction 180–250 °с 39.31 heavy gas oil fraction 250–320 °с – fuel oil 49.02 losses, water, sediment 30.08 gas 13.68 total 100 total 100 table 3 chemical composition of the gasoline fraction (tboiling point = 0–180 °с) obtained on a 2% w/diatomite catalyst. liquid fraction hydrocarbons, % alkanes isoalkanes alkenes cyclo alkanes cycloalkenes aromatic heterocompounds 0–180 °с 58.65 4.08 7.01 5.48 – 22.83 1.08 chimica techno acta 2022, vol. 9(3), no. 20229302 article 5 of 6 figure 5 chromatogram of the gasoline fraction (tboiling point = 0–180 °c) obtained on a 2% w(vi)/diatomite catalyst. 4. conclusions in this paper, the new composite catalysts based on activated zeolite modified with mo(vi) and w(vi) salts of different concentrations for the thermocatalytic hydrogenation processing of plastic waste into motor fuels were developed. the basic physicochemical properties of the synthesized catalysts: the elemental and phase composition, surface morphology, specific surface area and the optimal destruction temperature were obtained. based on the results of the experiments and the calculation of the material balance of the process, it was found that the catalyst 2% w/diatomite is the most active in the yield of the total liquid product. the effectiveness of the obtained composite catalysts is confirmed by the group hydrocarbon composition of fractions boiling up to 180 °c, from 180 to 250 °c, from 250 to 320 °c, determined by gas-liquid chromatography-mass spectrometry. supplementary materials no supplementary materials are available. funding this research had no external funding. acknowledgments none. author contributions conceptualization: z.k.t. data curation: z.k.t., l.r.s. formal analysis: y.a.a., l.r.s. funding acquisition: y.a.a., z.k.t. investigation: z.k.t., t.o.k., a.s.a., f.z.a. methodology: z.k.t., y.a.a. project administration: y.a.a. resources: z.k.t., y.a.a., t.o.k. software: l.r.s. supervision: l.r.s., z.k.t. validation: z.k.t., l.r.s. visualization: z.k.t., l.r.s., y.a.a. writing – original draft: z.k.t., l.r.s. writing – review & editing: z.k.t., t.o.k., l.r.s. conflict of interest the authors declare no conflict of interest. additional information author 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stability of hydroxyapatites with different types of substitution natalya v. eremina a* , svetlana v. makarova a , denis d. isaev ab , natalia v. bulina a a: institute of solid state chemistry and mechanochemistry, siberian branch of russian academy of sciences, novosibirsk 630090, russia b: novosibirsk state university, novosibirsk 630128, russia * corresponding author: eremina@solid.nsc.ru this paper belongs to the ctfm'22 special issue: https://www.kaznu.kz/en/25415/page. guest editors: prof. n. uvarov and prof. e. aubakirov. © 2022, the authors. this article is published in open access under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). abstract the feasibility of soft mechanochemical synthesis was studied here for hydroxyapatite with various types of substitution. it was shown that this method allows obtaining hydroxyapatites substituted with copper or iron cations and hydroxyapatites cosubstituted with zinc cations and silicate groups. thermal stability of the synthesized samples was evaluated. it was found that to preserve phase homogeneity of the material, the temperature during the preparation of ceramic products and coatings should not exceed 600–800 °c. an exception is the hydroxyapatite where a hydroxyl group is expected to be replaced by a copper cation during the synthesis at a degree of substitution x = 0.5. for this sample, the temperature of the the heat treatment can be increased to 1100–1200 °c because copper cations return to the hydroxyapatite crystal lattice at these temperatures, and the material becomes single-phase. keywords mechanochemical synthesis hydroxyapatite substitution iron cupper zinc silicate thermal stability received: 23.06.22 revised: 18.07.22 accepted: 18.07.22 available online: 26.07.22 1. introduction hydroxyapatite (ha) is an inorganic material of chemical composition ca10(po4)6(oh)2 which crystalizes in hexagonal syngony with a p63/m space group [1]. the ha unit cell contains 10 calcium cations located at two nonequivalent positions: four cations at the ca1 site and six cations at the ca2 site, which are surrounded by nine and seven oxygen ions, respectively. in addition to calcium ions, the ha unit cell contains six phosphate and two hydroxyl groups. the latter are located on the c axis in a hexagonal channel formed by calcium ions and by oxygen ions from phosphate tetrahedrons. ha is widely used in various fields of medicine and is a suitable material for the construction of biocompatible ceramic products, composites, bone defect fillers, medical cements, and implant coatings [2–4]. methods are being developed for 3d printing of custom implants, where ha serves as either an additive or a base material from which a product is created [5, 6]. prospective applications include drug delivery and tissue engineering because has appear to be promising carriers of growth factors, bioactive peptides, and various types of cells [7]. in the crystal lattice of ha, all ions can be substituted with isovalent or heterovalent ions of other chemical elements or their chemical groups [8]. stoichiometric ha has a low resorption rate, which is a disadvantage of bioresorbable materials based on this substance [9]. in addition, stoichiometric ha does not have antibacterial properties. nonetheless, the introduction of substituent ions into this material can substantially improve required characteristics. for example, doping of ha with copper, iron, zinc, or silver ions can give antibacterial properties to ha-based materials and thereby can prevent inflammation and stimulate new bone growth, which is important for surgical applications [10]. silicon ions decrease the crystallinity of the material and increase osseointegration and biocompatibility [11, 12]. ha doped with iron ions has magnetic properties used in biomedicine for heating mediators in cancer hyperthermia therapy and in contrast agents for magnetic resonance imaging [13]. thermal stability of synthetic ha is crucial for the manufacture of ceramics and ha coatings. it is necessary to correctly select the conditions of thermal treatment when a technological process is designed because when substituted has are heated, structural transformations can take place, http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2022.9.3.05 mailto:eremina@solid.nsc.ru http://creativecommons.org/licenses/by/4.0/ https://orcid.org/0000-0002-2692-9745 https://orcid.org/0000-0002-0770-5914 https://orcid.org/0000-0003-2346-9584 https://orcid.org/0000-0003-4751-0705 https://crossmark.crossref.org/dialog/?doi=https://doi.org/10.15826/chimtech.2022.9.3.05&domain=pdf&date_stamp=2022-7-26 chimica techno acta 2022, vol. 9(3), no. 20229305 article 2 of 7 accompanied by the formation of impurity phases [14, 15], which affect not only physical but also biological properties of the resultant product. the purpose of this work was to investigate the feasibility of soft mechanochemical synthesis of ha containing different substituents (fe, cu, or zn simultaneously with si) and to assess thermal stability of the obtained materials. 2. experimental samples of ha with various substituents were prepared via soft mechanochemical synthesis in an ago-2 planetary ball mill (russia). a detailed description of the synthesis conditions is provided in ref. [16]. previously, it was reported that dopants complicate mechanochemical synthesis [17]; as a consequence, the duration of synthesis of substituted has was 40 min, whereas that of unsubstituted ha was 30 min. expected reactions of mechanochemical synthesis are presented in table 1. reagents had purity grade not lower than “chemically pure.” reaction 1 was expected to generate unsubstituted ha. in reactions 2, 3, 5 and 6, some calcium cations are substituted with either copper or iron cations, whereas in reactions 4 and 7, hydroxyl groups are replaced. to obtain cu-substituted ha and fe-substituted ha, the synthesis was carried out using either an oxide form (reactions 3–5) or a phosphate form of the substituent ion (reactions 2, 6, and 7). reactions 8 and 9 imply the cosubstitution of calcium cations by zinc cations and of the phosphate group by the silicate group. sintering of the powders was conducted in a high-temperature electrical furnace pvk-1.4 at different temperatures for 2 h at heating and cooling rates of 5 °c/min in ambient air. powder x-ray diffraction (pxrd) patterns of the samples were recorded on a d8 advance powder diffractometer (bruker, germany) in bragg–brentano geometry with cu kα radiation. for the in situ pxrd analysis, a high-temperature chamber htk 1200n (anton paar, austria) was employed. a sample was heated stepwise in a corundum carrier in ambient air at a heating rate of 12 °c/min. when a required temperature was reached, the heating was stopped, and the pxrd pattern was registered. x-ray phase analysis of the compounds was performed using a database of pxrd patterns, icdd pdf-2. unit cell parameters, crystallite size, and concentrations of crystal phases were determined by the rietveld method implemented in the topas 4.2 software (bruker, germany). the instrumental contribution was taken into account by the fundamental parameter method. fourier transform infrared (ftir) spectra were acquired with the help of an infralum-801 spectrometer (simex, russia). the samples were prepared by the kbr pellet method. 3. results and discussion 3.1. mechanochemical synthesis 3.1.1. cu-substituted ha figure 1a shows that pxrd patterns of ha samples containing copper are identical and match the pattern of unsubstituted ha. the observed reflections belong to the ha phase (card pdf 40-11-9308), indicating that the obtained samples are single-phase. the absence of any reflections of impurity phases suggests that the synthesis procedures produced expected substances in accordance with the expected reactions (table 1). it is obvious that when either the oxide form or the phosphate form of a substituent ion is used, initial reagents are not detectable among the products; therefore, any of the reagents tested here can be utilized for the synthesis of cu-substituted ha. infrared spectra of all synthesized samples (figure 1b) show absorption bands corresponding to the ha structure. there are bands of the phosphate ion (572, 602, 960, 1048, and 1089 cm–1), oh group (630 and 3573 cm–1), and of carbonate group (co3)2– (1420 and 1470 cm–1); the latter came from ambient air during the mechanochemical synthesis. it should be noted that the intensity of the absorption bands of the hydroxyl group is identical between the samples obtained via reactions 3 and 4, although judging by the reactions given in table 1, the concentrations of the hydroxyl group should differ by a factor of 2. therefore, in the sample 0.5cu(о)–oh, copper ions do not replace hydroxyl groups. table 1 expected reactions of mechanochemical synthesis (mcs). number equations for the expected chemical reaction sample name 1 6cahpo4 +4cao mcs → ca10(po4)6(oh)2 +2h2o 0.0ha 2 5.5cahpo4 + 4cao + 0.5сu(hpo4)h2o mcs → ca9.5cu0.5(po4)6(oh)2 +nh2o 0.5cu(p)–ca 3 6cahpo4 +3.5cao+0.5cuo mcs → ca9.5cu0.5(po4)6(oh)2 +nh2o 0.5cu(o)–ca 4 6cahpo4 +4cao+0.5cuo mcs → ca10(po4)6(oh)1cu0.5o+nh2o 0.5cu(o)–oh 5 6cahpo4 +3.5cao+0.25fe2o3 mcs → ca9.5fe0.5(po4)6(oh)1.5o0.5 +nh2o 0.5fe(o)–ca 6 5.334cahpo4 + 3.666cao + 0.333fe3(po4)2 ∙ 8h2o mcs → ca9fe1(po4)6(oh)2 +nh2o 1.0fe(p)–ca 7 5.67cahpo4 + 4.33cao + 0.166fe3(po4)2 ∙ 8h2o mcs → ca10(po4)6(oh)1fe0.5o+nh2o 0.5fe(p)–oh 8 4.4cao+5.4cahpo4 +0.2sio2 ∙ nh2o+0.2zn(h2po4)2 ∙ 2h2o mcs → ca9.8zn0.2(po4)5.8(sio4)0.2(oh)1.8 +nh2o 0.2zn0.2si 9 6cao+3cahpo4 +1sio2 ∙ nh2o+1zn(h2po4)2 ∙ 2h2o mcs → ca9zn1(po4)5(sio4)1(oh)1 +nh2o 1.0zn1.0si chimica techno acta 2022, vol. 9(3), no. 20229305 article 3 of 7 figure 1 pxrd patterns (a) and ftir spectra (b) of as-synthesized samples 0.0на (1), 0.5cu(p)–ca (2), 0.5cu–ca (3), and 0.5cu– oh (4) according to the (1) – (4) reactions. table 2 structural characteristics of the ha phase in the synthesized samples. sample name а (å) с (å) crystallite size (nm) 0.0ha 9.437(1) 6.892(1) 24.9(2) 0.5cu(p)–ca 9.431(2) 6.879(1) 20.4(2) 0.5cu(o)–ca 9.435(1) 6.881(1) 20.2(2) 0.5cu(o)–oh 9.432(2) 6.887(1) 20.2(2) 1.0fe(p)–ca 9.436(2) 6.877(1) 20.3(2) 0.5fe(p)–oh 9.435(2) 6.886(1) 20.7(2) 0.2zn0.2si 9.435(1) 6.889(1) 20.9(2) 1.0zn1.0si 9.434(2) 6.891(1) 16.4(3) note: the estimated standard deviations of the refined values are in parentheses. at the same time, the intensity of absorption bands is much higher in the 0.5cu(о)–oh sample than in the other ones. it can be concluded that in the 0.5cu(о)–oh sample, copper cations occupy positions of calcium cations, and the shortage of phosphate ions is compensated by the carbonate ion, which can occupy the phosphate group’s position. consequently, in the samples 0.5cu(о)–oh and 0.5cu(o)–ca, copper cations replace calcium cations. a possible stoichiometric formula of the resultant cu-substituted ha in the sample 0.5cu(о)–oh can be written as ca10−xсux(po4)6−y(co3)y(oh)2−yоy, where y = х/1.67. crystal lattice parameters of the synthesized cu-substituted has are lower than those of unsubstituted ha (table 2). the smaller ionic radius of copper as compared to calcium should diminish the lattice parameters, as observed in our case. the slight difference in the parameter c between the samples 0.5cu(о)–ca and 0.5cu(о)–oh can be explained by an influence of the carbonate ion. the size of the crystallites decreases with the introduction of the copper cation (table 2), meaning that the substituent ion complicates the formation of the ha crystal lattice. thus, after 30 min of mechanochemical processing of the mixtures in accordance with reactions 2–4, in all cases, the structure of cu-substituted ha forms with localization of copper ions at the positions of calcium ions. therefore, the expected substitution of the hydroxyl group with copper cations does not proceed under our conditions of mechanochemical synthesis. for the synthesis of cu-substituted ha, it is possible to use both copper oxide and copper (ii) hydrogen orthophosphate monohydrate. 3.1.2. fe-substituted ha in the pxrd patterns of the samples synthesized with the introduction of iron (figure 2a), one can see that the 0.5fe(o)–ca sample, which was obtained using iron (iii) oxide, contains reflections of fe2o3, which was employed as the initial reagent, i.e. the source of the iron cation (figure 2a). in the sample 1.0fe(p)–ca, where iron (ii) orthophosphate hydrate was chosen as the initial reagent (the iron source), only reflections of ha were detectable, without additional reflections. therefore, iron (iii) oxide does enter into the mechanochemical reaction forming the fesubstituted ha. the 1.0fe(p)–ca sample turned out to be single-phase even at a dopant concentration two times higher than that in the case of the sample 0.5fe(o)–ca. the sample 0.5fe(p)–oh, where the hydroxyl group was expected to be replaced by iron cations from iron (ii) orthophosphate hydrate, also proved to be single-phase. table 2 indicates that after the introduction of iron cations in the phosphate form, in all cases, parameter a stay almost the same while parameter c declines relative to unsubstituted ha. the ftir spectra of the samples 1.0fe(p)–ca and 0.5fe(p)–oh (figure 2b) are similar to the spectra of unsubstituted ha and of cu-substituted ha. all absorption bands of the ha structure are present. during the mechanochemical synthesis, the substitution of the hydroxyl group during the attempted introduction of iron cations obviously does not proceed either because a more intense absorption band of the carbonate group is visible in the 0.5fe(p)–oh spectrum. according to the literature, high-temperature processing of a material at 1100 °c is performed to place copper and iron cations in the hydroxyl channel [18, 19]. in mechanochemical synthesis, such a temperature is unattainable, which is why it is evidently impossible to synthesize ha containing copper and iron cations in the hydroxyl channel. chimica techno acta 2022, vol. 9(3), no. 20229305 article 4 of 7 figure 2 pxrd patterns (a) and ftir spectra (b) of as-synthesized samples 0.0на (1), 0.5fe(o)–ca (2), 1.0fe(p)–ca (3), and 0.5fe(p)–oh (4) according to the (1), (4) – (6) reactions. 3.1.3. zn-si-substituted ha the analysis of the pxrd patterns revealed that after cosubstitution with zinc and silicate the synthesized samples are single-phase (figure 3a). the lattice parameters of the obtained samples are virtually identical to those of the unsubstituted ha (table 2). this is probably because the substitution of calcium cations by zinc cations should reduce the lattice parameters owing to a decrease in the ionic radius, while the substitution of the phosphate tetrahedron by the silicate tetrahedron should lead to an increase. after the cosubstitution, the contributions of the substituents cancel each other out. in the ftir spectra of the samples 0.2zn0.2si and 1.0zn1.0si (figure 3b), there are all absorption bands characteristic of ha. the intensity of hydroxyl bands in the spectra declines with the increasing concentration of the introduced ions, consistently with the equation of the expected reaction (table 1). in this context, the diminished number of hydroxyl groups is a consequence of compensation of the silicate group’s excess negative charge as compared to the phosphate group, which is being replaced. figure 3 pxrd patterns (a) and ftir spectra (b) of as-synthesized samples 0.0на (1), 0.2znsi (2), and 1.0zn1.0si (3) according to the (1), (7) – (8) reactions. 3.2. thermal stability 3.2.1. cu-substituted ha examination of the synthesized samples by high-temperature in situ diffractometry (figure 4) showed that these samples differ in thermal stability. as illustrated in figure 4a, the unsubstituted ha is stable up to 1200 °c. raising the temperature of the thermal treatment enhances the intensity of the reflections and decreases their half-width, thereby indicating the growth of crystallites during the sample heating. there are no reflections of impurity phases in the patterns. as for the 0.5cu(o)–ca sample, in which the dopant was expected to replace calcium ions, its thermal stability is much lower as compared to the unsubstituted ha. already at 700 ºc, copper (ii) oxide separates, which is present in the sample up to 1000 °c (figure 4b, table 3). a further increase in temperature causes the cuo reflections to disappear from the diffraction pattern. table 3 concentrations of impurity phases in substituted-ha samples in the in situ experiment, as evidenced by diffraction patterns processed by the rietveld method. sample name impurity phase (wt.%) temperature (ºc) 500 600 700 800 900 1000 1100 1200 0.5cu(o)–ca β-ca3(po4)2 – – – 17 26 27 31 34 cuo – – 1 2 2 1 – – 0.5cu(o)–oh cuo – 3 4 4 4 3 – – 1.0fe(p)–ca β-ca3(po4)2 – – – 36 57 71 72 74 fe2o3 – – – 1 4 6 7 7 fe3o4 – – – 2 3 2 2 2 0.5fe(p)–oh fe2o3 – – – – 1 2 2 – fe3o4 – – – 2 2 2 2 1 chimica techno acta 2022, vol. 9(3), no. 20229305 article 5 of 7 therefore, there is a reverse process at 1000 °c, namely, diffusion of copper ions into the hydroxyl channel of ha. additionally, at 800 °c, a large amount of another impurity phase, -ca3(po4)2, emerges, whose concentration goes up with temperature. in the 0.5cu(о)–oh sample, the release of copper oxide starts at a lower temperature – 600 °c. at 1100 and 1200 °c, cuo reflections are absent, and the sample becomes single-phase. it is known that prolonged annealing at 1100 °c of a mixture of reagents containing cuo gives rise to ha containing linear oxocuprate groups in the hydroxyl channel [18, 20]. accordingly, it is likely that at 1100 °c, copper ions of the 0.5сu(о)–ca sample localize to the hydroxide channel, thus yielding the ca10(po4)6(oh)2–2xcuxo2x structure, and the sample goes back to being single-phase (figure 4b, table 3). thus, the sample 0.5cu(o)–ca is thermally stable up to 700 °c. stability of 0.5cu(о)–oh is lower by 200 °c, but at 1100 °c, the newly formed copper (ii) oxide phase disappears making the material single-phase again. figure 4 in situ high-temperature pxrd patterns of samples 0.0ha (a), 0.5cu(o)–ca (b), and 0.5cu(o)–oh (c). 3.2.2. fe-substituted ha in the diffraction pattern of the 1.0fe(p)–ca sample, reflections of ca3(po4)2 and fe2o3 phases are clearly visible. modeling of the diffraction patterns by the rietveld method detected reflections of the fe3o4 phase as well (table 3). judging by these data, thermal stability of the materials containing iron cations (samples 1.0fe(p)–ca (a) and 0.5fe(p)–oh) is equally low. the introduced cation is released in the oxide form starting at a temperature of 800 °c in both cases (table 3). the sum of concentrations of the oxide phases is approximately twofold for the 1.0fe(p)–ca sample than for 0.5fe(p)–oh because the concentration of introduced iron is 2 times higher in the former case than in the latter. the concentration of -ca3(po4)2 seen in the 1.0fe(p)–ca sample increases with temperature, reaching a maximum at 1200 °c (figure 5a, table 3). in contrast to the doping with copper cations, in the samples with iron cations, there is no complete disappearance of the substituent ion during the high-temperature treatment. perhaps the reason is lower solubility of iron in ha. thus, we can assume that the samples 1.0fe(p)–ca and 0.5fe(p)–oh are thermally stable up to 800 °c. 3.2.3. zn-si-substituted ha after the cosubstitution with zinc cations and silicate groups, the material also has lower thermal stability than the unsubstituted ha. in the pxrd patterns of the sample 0.2zn0.2si at 1000 °c, reflections of additional phases come into being, such as zno and β-ca3(po4)2 (figure 6a). in the 1.0zn1.0si sample, zno reflections appear already at 800 °c, but the β-ca3(po4)2 phase still forms at 1000 °c (figure 6b). figure 5 in situ high-temperature pxrd patterns of samples 1.0fe(p)–ca (a) and 0.5fe(p)–oh (b). chimica techno acta 2022, vol. 9(3), no. 20229305 article 6 of 7 figure 6 pxrd patterns of samples 0.2zn0.2si (a) and 1.0zn1.0si (b) after heating. therefore, thermal stability of cosubstituted zn-si-ha depends on concentrations of the substituent ions. the higher their concentrations, the lower is the stability of the material. obviously, during the thermal treatment, zinc cations leaving their positions (previously belonging calcium ions) create vacancies at the former calcium positions. a large number of such vacancies promotes structural transformations, which generate the β-ca3(po4)2 and zno phases. 4. conclusions it was demonstrated that cu-substituted ha and fe-substituted ha can be synthesized mechanochemically via the introduction of the dopants at calcium positions. for the synthesis of such materials, 40 min is sufficient when an appropriate mixture of initial reagents is mechanochemically processed in a planetary ball mill. it was shown that for the synthesis of cu-substituted ha, either copper (ii) oxide or copper (ii) hydrogen orthophosphate monohydrate can be utilized as a reagent providing the substituent ion. as for the synthesis of fe-substituted ha, the stablest oxide of the substituent (fe2o3) is not suitable, but iron (ii) orthophosphate hydrate is suitable. the mechanochemical method also allows to synthesize ha with cosubstitution of calcium cations by zinc and of phosphate tetrahedra by silicate ones. for this synthesis, silicic acid, and zinc (ii) dihydrogen phosphate hydrate can be used. thermal stability of the obtained substituted has is significantly lower than that of the stoichiometric unsubstituted ha. at 600–800 °c, in the substituted-ha samples containing copper, iron, or zinc at the position of calcium ions with a degree of substitution (x) of ≥0.5, a release of the corresponding oxides is observed, pointing to the diffusion of the substituent ions onto the surface of substituted-ha particles. the created vacancies at calcium ions’ positions promote structural transformations, which give rise to the β-ca3(po4)2 phase. it was demonstrated here that in the ha sample where copper cations are expected to replace the hydroxyl group, a cuo phase emerges during the thermal treatment at 600 °c. on the other hand, a further increase in temperature, to 1100 °c, results in a single-phase material in which copper cations redissolve in the crystal lattice of ha, thereby most likely localizing to the hydroxyl channel. the observed changes in phase composition of the synthesized samples can significantly affect the properties of the materials. low thermal stability of the materials imposes limitations on the manufacture of ceramic products or coatings from ha containing such substituents as copper, iron, or zinc ions. supplementary materials no supplementary materials are available. funding the synthesis and analysis of the iron compounds was carried out within a grant from the russian science foundation (no. 21-12-00251). the research on the compounds containing copper, zinc, and silicon was conducted within the framework of a state assignment for the institute of solid state chemistry and mechanochemistry sb ras (project no. 121032500064-8). acknowledgments none. author contributions conceptualization: b.n.v., e.n.v. data curation: m.s.v. funding acquisition: b.n.v. investigation: m.s.v., i.d.d. methodology: b.n.v., e.n.v., m.s.v. project administration: b.n.v. resources: m.s.v., i.d.d. visualization: e.n.v. writing – original draft: e.n.v., m.s.v, i.d.d. writing – review & editing: b.n.v. chimica techno acta 2022, vol. 9(3), no. 20229305 article 7 of 7 conflict of interest the authors declare no conflict of interest. additional information author ids: natalya v. eremina, scopus id 8637401500; svetlana v. makarova, scopus id 57212079249; denis d. isaev, scopus id 57316390200; natalia v. bulina, scopus id 6602885126. websites: institute of solid state chemistry and mechanochemistry, http://www.solid.nsc.ru; novosibirsk state university, https://www.nsu.ru. references 1. hughes m, rakovan j. the crystal structure of apatite, ca5(po4)3(f,oh,cl)2. rev mineral geochem. 2002:48(1):1–12. doi:10.2138/rmg.2002.48.1 2. dorozhkin sv. calcium orthophospates (capo4): occurrence and properties. prog biomater. 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https://www.scopus.com/authid/detail.uri?authorid=57212079249 https://www.scopus.com/authid/detail.uri?authorid=57316390200 https://www.scopus.com/authid/detail.uri?authorid=6602885126 http://www.solid.nsc.ru/ https://www.nsu.ru/ http://dx.doi.org/10.2138/rmg.2002.48.1 https://link.springer.com/article/10.1007/s40204-015-0045-z https://link.springer.com/article/10.1023/a:1026394530192 https://www.frontiersin.org/articles/10.3389/fmats.2019.00313/full https://www.mdpi.com/2073-4352/11/4/353 https://doi.org/10.1002/wnan.1504 https://doi.org/10.1016/j.ceramint.2015.03.316 https://doi.org/10.3390/ma2020399 http://dx.doi.org/10.1155/2014/178123 https://doi.org/10.1023/a:1021114710076 https://doi.org/10.1016/j.ica.2016.07.041 https://doi.org/10.2147/ijn.s147355 https://doi.org/10.1002/ejic.201501486 https://doi.org/10.1016/j.materresbull.2017.09.056 https://doi.org/10.1016/j.ceramint.2019.05.239 http://dx.doi.org/10.1134/s0036023620120116 http://dx.doi.org/10.1039/b906639j http://dx.doi.org/10.1039/c3tb21397h http://dx.doi.org/10.1016/s1293-2558(03)00152-3 synthesis and cytotoxic activity of (2-arylquinazolin-4-yl)hydrazones of 2-hydroxybenzaldehydes as potential casein kinase 2 (ck2) inhibitors published by ural federal university eissn 2411-1414 chimicatechnoacta.ru article 2023, vol. 10(2), no. 202310211 doi: 10.15826/chimtech.2023.10.2.11 1 of 8 synthesis and cytotoxic activity of (2-arylquinazolin 4-yl)hydrazones of 2-hydroxybenzaldehydes emiliya v. nosova ab* , ilya i. butorin a , margarita d. likhacheva a, svetlana k. kotovskaya a a: institute of chemical engineering, ural federal university, ekaterinburg 620009, russia b: i. postovsky institute of organic synthesis, ural division of the russian academy of sciences, ekaterinburg 620219, russia * corresponding author: emilia.nosova@yandex.ru this paper belongs to a regular issue. abstract 2-phenyl-6,7-difluoro and 2-(4-fluorophenyl)quinazoline derivatives bearing salicylidenhydrazino fragments at position 4 were prepared based on 4,5-difluoroantranilic acid or anthranilamide. molecular docking to casein kinase 2 was performed; compounds with high in silico activity to ck2 were revealed. cytotoxic activity of the synthesized compounds was studied on cancer cell line mda-mb-231 and normal cell line wi26 va4. keywords 2-arylquinazolines salicylidenhydrazines in silico activity casein kinase 2 inhibitor cytotoxic activity received: 28.03.23 revised: 26.04.23 accepted: 27.04.23 available online: 04.05.23 key findings ● n-salicylidene-n’-(6,7-difluoro-2-phenylquinazolin-4-yl)-hydrazines were obtained based on 4,5-difluoroantranilic acid. ● n-salicylidene-n’-(2-(4-fluorophenyl)quunazolin-4-yl)-hydrazines were synthesized based on anthranilamide. ● molecular docking towards casein kinase 2 was performed, cytotoxic activity was studied. © 2023, the authors. this article is published in open access under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). 1. introduction fluorine-containing quinazoline derivatives represent a class of anticancer agents. phosphoinositide 3-kinase and idelalisib (zydelig) is used as a medication to treat certain blood cancers; the molecule acts as inhibitor of p110δ, the delta isoform of the enzyme phosphoinositide 3-kinase [1]. gefitinib (iressa) is a selective egfr tyrosine kinase (egfr-tk) inhibitor. this agent retards growth of various human tumor cell lines, metastasis, and angiogenesis, accelerates the apoptosis of tumor cells and enhances the efficiency of chemotherapy, radiation, and hormone therapy [2]. casein kinase 2 is a promising template for designing anticancer drugs. protein kinase ck2 is a ubiquitous, highly conserved, and constitutively active serine/threonine protein kinase; overexpression and hyperactivation of ck2 was observed in a wide variety of cancers, including breast, lung, prostate, colorectal, and renal [3–11]. for this reason, ck2 represents an attractive target for chemotherapy [12– 16]. anilino-substituted 2,6-naphthyridines were found to act as potent ck2 protein kinase inhibitors [17]. the search of antitumor agents inhibiting kinases among biand tricyclic derivatives of six-membered heterocycles with two nitrogen atoms is promising [18–23]. (2-phenylquinazolin-4-yl)hydrazones of 2-hydroxybenzaldehydes 1a–c, 2a–c, 3a,b (figure 1) were reported previously [24]. the aim of the present article is to describe a series of new 2-arylquinazolines 3c,d, 9a,b, bearing salicylidenhydrazino group at position 4, to estimate the interaction of quinazolines 1–3, 9 with important target of anticancer agents (ck2) by using molecular docking method, and to study cytotoxic and ck2 inhibition activity of some salicylidenhydrazino-substituted 2-arylquinazolines. 2. experimental 2.1. general unless otherwise indicated, all common reagents and solvents were used from sigma aldrich without further purification. http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2023.10.2.11 mailto:emilia.nosova@yandex.ru http://creativecommons.org/licenses/by/4.0/ http://orcid.org/0000-0002-0177-1582 https://orcid.org/0000-0003-3403-5079 https://crossmark.crossref.org/dialog/?doi=https://doi.org/10.15826/chimtech.2023.10.2.11&domain=pdf&date_stamp=2023-05-04 https://journals.urfu.ru/index.php/chimtech/rt/suppfiles/6708/0 chimica techno acta 2023, vol. 10(2), no. 202310211 article 2 of 8 doi: 10.15826/chimtech.2023.10.2.11 figure 1 structure of anticancer agents idelalisib, gefitinib and previously prepared salicilidenehydrazono substituted quinazolines (1a–c, 2a–c, 3a,b). 1, 2: r = h (a), 4-oh (b), 3,5-dibr (c); 3: r = h (a), 5-no2 (b). the 1н nmr, 13c nmr and 19f nmr spectra were obtained on a bruker avance ii dmx400 spectrometer using dmsod6 as the solvent. the 1н nmr experiments chemical shifts were referenced to the hydrogen resonances of the solvent (dmso, δ = 2.50 ppm). carbon chemical shifts were referenced to the carbon resonances of the solvent (cdcl3, δ = 77.16 ppm). 19f nmr spectra were recorded with cfcl3 (c6f6 was used as secondary reference, δf –162.9 ppm). mass spectra were recorded on a shimadzu gcms-qp2010 ultra instrument with electron ionization (ei) of the sample. microanalyses (c, h, n) were performed using a perkin–elmer 2400 elemental analyzer. melting points were measured on the instrument boetius. microanalyses (c, h, n) were performed using the perkin–elmer 2400 elemental analyzer. 2.2. preparation of intermediates 2.2.1. (e)-2-(4-fluorophenylydeneamino)benzamide (6) 4-fluorobenzaldehyde (0.67 g, 5.4 mmol) was added to a solution of 2-aminobenzamide 5 (0.74 g, 5.4 mmol) in ethanol (9.62 ml). the mixture was stirred at room temperature for 3 h, and the white precipitate was filtered off and recrystallized from acetonitrile. yield 1.07 g (82 %), mp 194–196 °c (lit. 197–200 °c [25]). 1н nmr, δ, ppm: 7.18 d (1h, ar, 3j 8.1 hz), 7.25–7.40 m (3h, ar), 7.4 br. s (1h, nh), 7.5–7.6 m (2h, ar), 7.95–8.05 m (2h, ar), 8.2 br. s (1h, nh), 8.59 s (1h, ch=n). 19f{h} nmr, δ, ppm: –107.05 s. found, %: c 69.32, н 4.62, n 11.49. c14h11fn2o. calculated, %: c 69.41, н 4.58, n 11.56. 2.2.2. 2-(4-fluorophenyl)quinazolin-4(3н)-one (7) copper(ii) chloride (0.67 g, 4.9 mmol) was added to the suspension of 2-(4-fluorophenylydeneamino)benzamide 6 (0.90 g, 3.7 mmol) in ethanol (14 ml) and the mixture was refluxed for 5 h. after cooling the precipitate was filtered off and recrystallized from dimethyl sulfoxide. yield 0.705 g (79%), mp 282–284 °c (lit. 284–286 °c [36]). 1н nmr, δ, ppm: 7.26–7.31 m (2h, ar), 7.46–7.49 m (1н, ar), 7.68– 7.70 m (1н, ar), 7.77–7.81 m (1н, ar), 8.13–8.15 m (1н, ar), 8.27–8.30 m (2н, ar), 12.4 br. s (1н, nh). 19f{h} nmr, δ, ppm: –108.90 s. found, %: c 70.11, н 3.90, n 11.53. c14h9fn2o. calculated, %: c 69.99, н 3.78, n 11.66. 2.2.3. 2-(4-fluorophenyl)-4-chloroquinazoline (8) phosphorus oxychloride (3.2 ml) was added to quinazolin4-one 7 (0.65 g, 2.7 mmol), and the mixture was refluxed for 2 h. the reaction mixture was cooled to room temperature and poured onto ice. the white precipitate was filtered off, washed with water, dried in air and used without additional purification. yield 0.52 g (75%), mp 148−150 °c. 1н nmr, δ, ppm: 7.41–7.45 m (2h, ar), 7.86–7.88 m (1н, ar), 8.14–8.15 m (2н, ar), 8.29–8.32 m (1н, ar), 8.53–8.57 m (2н, ar). 19f{h} nmr, δ, ppm: –109.38 s. found (%): c 64.89, h 3.03, n 10.92. c14h8clfn2. calculated (%): c 65.00, h 3.12, n 10.83. 2.2.4. 2-(4-fluorophenyl)-4-hydrazinoquinazoline (4b) hydrazine monohydrate (0.72 ml, 9.7 mmol, 65% solution) was added to a solution of 4-chloroquinazoline 8 (0.5 g, 1.94 mmol) in ethanol (10 ml). the mixture was stirred at 70 °c for 3 h, then cooled. the bright yellow precipitate was filtered off and recrystallized from acetonitrile. yield 0.39 g (80%), mp 174–176 °c. 1н nmr, δ, ppm: 4.8 br. s (2h, nh2), 7.19–7.24 m (2h, ar), 7.35–7.45 m (1н, ar), 7.65– 7.72 m (2н, ar), 8.15–8.20 m (1н, ar), 8.60–8.63 m (2н, ar), 9.6 br. s (1h, nh). 19f{h} nmr, δ, ppm: –111.81 s. found (%): c 66.04, h 4.27, n 22.12. c14h11fn4. calculated (%): c 66.13, h 4.36, n 22.03. 2.3. preparation of target hydrazonoquinazolines 3c, d, 9a, b general method. the corresponding salicylic aldehyde (0.897 mmol) was added to a solution of 4-hydrazinoquinazoline 4a or 4b (0.753 mmol) in ethanol (7 ml). the reaction mixture was refluxed for 1.5 h, then cooled; the precipitate formed was filtered off and recrystallized from ethanol. 2.3.1. n-(3,5-di(t-butyl)salicylidene)-n’-(6,7-difluoro-2phenylquinazolin-4-yl)-hydrazine (3c) yield 83%, mp 184−186 °c. nmr, δ, ppm: 1.37 s (9h, 3ch3), 1.55 s (9h, 3ch3), 7.25 s (1н, н4”), 7.33 s (1н, н6”), 7.49– 7.53 m (3н, н3’, н4’, н5’), 7.76 dd (1н, н5, 3jhf 9.2, 4jhf 4.9 hz), 8.42 dd (1н, н8, 3jhf 9.2, 4jhf 4.9 hz), 8.58 s (1h, ch=n), 8.68–8.72 m (2н, н2’, н6’), 12.0 br. s (1н, nh), 13.1 br. s (1h, oh). 19f{h} nmr, , ppm: –136.94 d (1f, 3jff 24.3 hz), –128.62 d (1f, 3jff 24.3 hz). 13c nmr: 29.32 (3ch3), 31.34 (3ch3), 33.89 (s, cme3), 34.76 (s, cme3), 108.87 (s, c-2’’), 110.04 (s, c-3’’, c-5’’), 114.90 (s), 117.40 (s), 125.20 (s), 125.38 (s), 128.05 (s), 128.22 (s), 130.80 (s), 135.76 (s), 137.51 (s), 140.10 (s), 148.01 (dd, c6 or c-7, 1jcf = 249.4, 2jcf = 12.6 hz), 148.56 (s), 148.85 (d, c-5, c-8, 2jcf = 17.1 hz), 153.60 (dd, c-7 or c-6, 1jcf = 254.9, 2jcf = 17.1 hz), 155.11 (s), 155.61 (s), 159.85 (s). ms, m/z (irel (%)): 488 [m]+ (99), 257 [m−di-tbu-isobenzoxazole]+ (100), 154 [m−di-tbu-isobenzoxazole-phcn]+ (14). found, %: c 71.41, н 6.32, n 11.39. c29h30f2n4o. calculated, %: c 71.29, н 6.19, n 11.47. https://doi.org/10.15826/chimtech.2023.10.2.11 chimica techno acta 2023, vol. 10(2), no. 202310211 article 3 of 8 doi: 10.15826/chimtech.2023.10.2.11 2.3.2. n-(5-chlorosalicylidene)-n’-(6,7-difluoro-2-phenylquinazolin-4-yl)-hydrazine (3d) yield 78%, mp 192–194 °c. 1н nmr, δ, ppm: 7.03 d (1н, н3”, 3jhн 7.2 hz), 7.28 d (1н, н4”, 3jhн 7.2 hz), 7.50–7.54 m (3н, н3’, н4’, н5’), 7.63 s (1н, н6”), 7.76 dd (1н, н5, 3jhf 10.1, 4jhf 5.8 hz), 8.50–8.52 m (1н, н8), 8.57 s (1h, ch=n), 8.58–8.62 m (2н, н2’, н6’), 12.0–12.2 br. s (2н, nh, oh). 19f{h} nmr, δ, ppm: –136.75 d (1f, 3jff 24.0 hz), –128.41 d (1f, 3jff 24.0 hz). 13c nmr: 108.92 (s, c-2’’), 114.72 (s), 114.85 (s), 118.41 (s), 120.40 (s), 122.87 (s), 127.86 (s), 128.44 (s), 130.54 (s), 130.74 (s), 137.52 (s), 143.57 (s), 146.97 (s), 149.08 (s), 149.23 (d, c-5, c-8, 2jcf = 17.1 hz), 151.64 (dd, c-6 or c-7, 1jcf = 249.4, 2jcf = 12.6 hz), 153.82 (dd, c-7 or c-6, 1jcf = 249.8, 2jcf = 16.5 hz), 156.32 (s), 159.99 (s), 159.93 (s). ms, m/z (irel (%)): 410 [m]+ (56), 257 [m−chloroisobenzoxazole]+ (100), 154 [m−chloroisobenzoxazole-phcn]+ (29). found, %: c 61.52, н 3.30, n 13.59. c21h13clf2n4o. calculated, %: c 61.40, н 3.19, n 13.64. 2.3.3. n-(3,5-di(t-butyl)salicylidene)-n’-(2-(4-fluorophenyl)quinazolin-4-yl)-hydrazine (9а) yield 76%, mp 152–154 °c. 1н nmr, δ, ppm: 1.36 s (9h, 3ch3), 1.55 s (9h, 3ch3), 7.20–7.24 m (3н, н4”, h3’, h5’), 7.31 s (1н, н6”), 7.59 m (1н, h7), 7.85–7.89 m (2н, н2’, н6’), 8.34–8.36 m (1н, h5), 8.62 s (1h, ch=n), 8.75–8.79 m (2н, h6, h8), 12.1 br. s (1н, nh), 13.3 br. s (1h, oh). 19f{h} nmr, δ, ppm: –111.28 s. 13c nmr: 29.33 (3ch3), 31.34 (3ch3), 33.89 (s, cme3), 34.76 (s, cme3), 112.14 (s, c-2’’), 114.93, 115.14 (both s, c-3’’, c-5’’), 117.53 (s), 122.60 (s), 125.20 (d, c-3’, c-5’, 2jcf = 21.6 hz), 126.09 (s), 127.98 (s), 130.34 (d, c-2’, c-6’, 3jcf = 8.8 hz), 133.50 (s), 134.57 (s), 135.76 (s), 140.08 (s), 148.45 (s), 150.51 (s), 155.10 (s), 156.08 (s), 158.18 (s), 163.85 (d, c-4’, 1jcf = 259.4 hz). ms, m/z (irel (%)): 470 [m]+ (67), 239 [m−di-tbu-isobenzoxazole]+ (100), 118 [m−di-tbu-isobenzoxazole-fc6h4cn]+ (12). found, %: c 74.15, н 6.80, n 11.79. c29h31fn4o. calculated, %: c 74.02, н 6.64, n 11.91. 2.3.4. n-(5-chlorosalicylidene)-n’-(2-(4-fluorophenyl)quinazolin-4-yl)-hydrazine (9b) yield 74%, mp 202–204 °c. 1н nmr, δ, ppm: 7.02 d (1н, н3”, 3jhн 7.1 hz), 7.25–7.35 m (3н, н4”, н3’, н5’), 7.58– 7.62 m (2н, н6’’, н7), 7.85–7.89 m (2н, н2’, н6’), 8.38– 8.42 m (1н, h5), 8.60–8.70 m (3h, ch=n, h6, h8), 12.2 br. s (1н, nh), 12.3 br. s (1h, oh). 19f{h} nmr, δ, ppm: –111.13 s. 13c nmr: 112.18 (s, c-2’’), 115.20 (s), 115.48 (s), 118.28 (s), 118.48 (s), 120.30 (s), 122.78 (s), 126.11 (s), 127.87 (d, c-3’, c-5’, 2jcf = 21.7 hz), 128.77 (s), 130.09 (d, c-2’, c-6’,3jcf = 9.2 hz), 130.39 (s), 133.64 (s), 134.47 (s), 145.43 (s), 150.51 (s), 156.21 (s), 156.45 (s), 157.24 (s), 158.21 (s), 163.84 (d, c-4’, 1jcf = 256.2 hz). ms, m/z (irel (%)): 392 [m]+ (47), 239 [m−chloroisobenzoxazole]+ (100), 118 [m−chloroisobenzoxazole-fc6h4cn]+ (27). found, %: c 64.34, н 3.70, n 14.19. c21h14clfn4o. calculated, %: c 64.21, н 3.59, n 14.26. 2.4. molecular docking studies protein preparation. the ligand protein complex ck2 with the azolopyrimidine derivative chembl2062585 (pdb id: 3u4u) was uploaded from the protein data bank database in .pdb format. further, in the arguslab 4.0.1 software, third-party molecules (water, ions, etc.) were removed from the complex and then hydrogen atoms were added. binding site was determined relative to the position of native ligand with nanomolar activity (ic50 = 3 nm). validation of docking parameters was carried out by redocking the native ligand with the following parameters: gadock (elitism: 3), scoring function: ascore, binding site box size: 18.6×17.5×16.5 å, grid resolution: 0.2 å. a quantitative assessment of the docking protocol was carried out according to the rmsd (root-mean-square deviation). for the native structure rmsd < 2 å, which indicates sufficient calculation accuracy. the parameters used for redocking were then used for docking the studied structures without changes. ligand preparation. ligands were prepared in datawarrior software. 3d coordinates of the ligands (1 conformer per 1 structure) were generated using the self-organized algorithm and the mmff94s+ force field. docking protocol. molecular docking was performed in arguslab 4.0.1 software on a previously prepared protein with established parameters and binding site size. for docking, the lamarckian genetic algorithm gadock and the empirical function ascore were used to calculate the free binding energy; the protein is taken as a rigid structure, and the ligands are flexible. a quantitative assessment of the affinity of ligands to the protein was carried out by analyzing the calculated docking score. for the hit compound 9a with the best (lowest) docking score, refined docking (grid resolution 0.1 å) was carried out with the initial generation of structures in arguslab with geometry optimization on the uff molecular force field. the evaluation of docking results, i.e., the calculation of the 3d position of the hit compound in the target protein and the 2d-map of non-covalent interactions, was carried out in arguslab and the poseview module of the proteins.plus web service, respectively. 2.5. ck2 assay kinase activity was determined using the ck2a1 enzyme system (promega v4482, madison, wi, usa) and the adpglotm kit (promega v9101, madison, usa) in white 96well plates (nunc u96 microwell 267350, denmark). bovine casein was used as the peptide substrate. staurosporine atp-competitive inhibitor (sts, cas 62996-74-1, alfa aesar j62837, 99 +%) was used as a positive control. the assay was carried out using 10 ng/well of n-gst labelled human recombinant ck2a1 expressed in sf9 cells, 0.1 mg/ml casein, 10 mm atp in a 40 mm tris buffer (ph 7.50) containing 20 mm mgcl2, 0.1 mg/ml bsa and 50 mm dtt. compounds were introduced in 1.25% dmso and https://doi.org/10.15826/chimtech.2023.10.2.11 chimica techno acta 2023, vol. 10(2), no. 202310211 article 4 of 8 doi: 10.15826/chimtech.2023.10.2.11 preincubated with kinase at 450 rpm for 10 min. the reaction was carried out for 60 min at 25 °c in pst-60hl shaker (biosan, latvia). atp-dependent luminescence was measured at an integration time of 1000 ms using infinite m200 pro microplate reader (tecan gmbh, grödig, austria). the experiments were run in two replicates. the activity of ck2 in the sample wells was normalized against the control and enzyme-blank wells. 2.6. mtt assay and cell culture mda-mb-231 breast cancer cells and wi-26 va4 lung epithelial-like cells were purchased from the atcc (manassas, va, usa). mda-mb-231 cells were maintained in dulbecco's modified eagle's medium (dmem), supplemented with 1× non-essential amino acids, 25 mm hepes, 1× penicillin/streptomycin, and, where indicated, 10% (v/v) foetal bovine serum (fbs), all obtained through gibco (thermo fisher scientific, inc., waltham, ma, usa) [37]. wi-26 va4 cells were maintained in advanced mem (gibco, loughborough, uk) supplemented with 5% fetal bovine serum (fetal bovine serum, qualified, australia, gibco, uk), penicillin (100 ui ml–1), streptomycin (100 mg ml–1), and glutamax (1.87 mm, gibco, loughborough, uk). all all cell lines were cultivated under a humidified atmosphere of 95% air/5% co2 at 37 °c. subconfluent monolayers, in the log growth phase, were harvested by a brief treatment with tryple express solution (gibco, loughborough, uk) in phosphate buffered saline (pbs, capricorn scientific, germany) and washed three times in serum-free pbs. the number of viable cells was determined by trypan blue exclusion. the effects of the synthesized compounds on cell viability were determined using the mtt colorimetric test [38]. all examined cells were diluted with the growth medium to 3.5·104 cells per ml, and the aliquots (7·103 cells per 200 ml) were placed in individual wells in 96-well plates (eppendorf, hamburg, germany) and incubated for 24 h. the next day, the cells were treated with the synthesized compounds separately in 10 and 100 mm concentrations (or 200.0 mm concentration and diluted at various concentrations for determination of ic50) and incubated for 72 h at 37 °c in 5% co2 atmosphere. each compound was tested in triplicate. after incubation, the cells were treated with 40 ml mtt solution (3-(4,5-dimethylthiazol2-yl)-2,5-diphenyltetrazolium bromide, 5 mg ml–1 in pbs) and incubated for 4 h. after additional 4 h incubation, the medium with mtt was removed and dmso (150 ml) was added to dissolve the formazan crystals. the plates were shaken for 10 min. the optical density of each well was determined at 560 nm using glomax multi+ (promega, madison, wi, usa) microplate reader. each of the tested compounds was evaluated for cytotoxicity in three separate experiments. all stock solutions for biological evaluations were prepared via dissolving synthesized compounds in dmso. 3. results and discussion 3.1. synthesis synthesis of hydrazones 3c,d was realized by the heating of 2-phenyl-4-hydrazino-6,7-difluoroquinazoline 4a [24], with 3,5-di(t-butyl)-2-hydroxybenzaldehyde and 5-chloro2-hydroxybenzaldehyde, respectively (scheme 1). for obtaining 2-(4-fluorophenyl)-derivatives 9a,b we performed the synthesis of 4-hydrazinoquinazoline 4b. the key intermediate 7 was synthesized by condensation of 2aminobenzamide 5 with 4-fluorobenzaldehyde (under stirring in ethanol at room temperature) and subsequent oxidation of azomethine 6 with copper(ii) chloride (scheme 2). earlier, the synthesis of 2-(4-fluorophenyl)quinazolin4-one 7 from aminoamide 5 and 4-fluorobenzaldehyde was achieved in the presence of other oxidants, such as iodine in ionic liquid [bmim+][bf4–] [25], antimony chloride without solvent at microwave irradiation [26], or air in the presence of vanadium bis(acetylacetonate) vo(acac)2 as a catalyst [27]. the formation of intermediate 6 in [bmim+][bf4–] at room temperature was mentioned [25]. notably, that interaction between anthranilamide 5 and aryl carbaldehydes leads to the formation of schiff bases or 2,3-dihydroquinazolin-4(1h)-ones depending on the reaction conditions and the nature of aldehydes [28]. therefore, it is not surprising that at room temperature the interaction of 4-fluorobenzaldehyde and aminoamide 5 resulted in the formation of azomethine 6. the chloro-derivative 8 obtained by refluxing of quinazolinone 7 with phosphorus oxychloride was used for the introduction of the hydrazine group into position 4. the synthesis of hydrazones 9a,b was carried out by heating of 2-(4-fluorophenyl)-4-hydrazinoquinazoline 4b with correspondent aldehyde in ethanol (scheme 2). the structure of target quinazolines 3c, d and 9a,b was determined based on their 1h nmr, 19f nmr and 13c nmr spectroscopy as well as mass spectrometry data (figures s1-s18). scheme 1 synthesis of 2-phenyl-6,7-difluoro-4-salicylidenehydrazino quinazolines 3c,d. reaction conditions: (i) ethanol, reflux, 1.5 h. https://doi.org/10.15826/chimtech.2023.10.2.11 chimica techno acta 2023, vol. 10(2), no. 202310211 article 5 of 8 doi: 10.15826/chimtech.2023.10.2.11 the 1h nmr spectra of salicylidenehydrazones 3c,d, 9a,b (figures s1, s5, s11, s15) characteristically showed signals of aryl fragment protons, benzene or difluorobenzene ring, singlets of –cн=n-groups at 8.57–8.70 ppm, broaden singlets of nh at 12.0–12.2 ppm and oн at 12.0–13.3 ppm. two doublet signals present at 19f{h} nmr spectra of compounds 3c,d, and one singlet in the case of derivatives 9a,b. structures 3c,d and 9a,b are also evidenced by the mass spectra data; the relative intensities of molecular ion peaks are 47–99%. the most abundant ions in the mass spectra of the correspondent 2-aryl-4-aminoquinazolines are m/z 257 for 2-phenyl-6,7-difluoroquinazolines 3c,d and m/z 239 for 2-(4-fluorophenyl)quinazolines 9a,b, which can form due to isobenzoxazole elimination. 3.2. molecular docking molecular docking was performed using arguslab 4.0.1 software [29]. previously, a protein-ligand complex was taken from the protein data bank database [30]: a ck2 complex with the azolopyrimidine derivative chembl2062585 [31] (pdb id: 3u4u) [32]. after preparation (see experimental) validation of the docking protocol was carried out for the protein-ligand complex by redocking the native ligand as a nanomolar inhibitor. according to the results of redocking, the standard deviation (rmsd) of the known position of ck2 protein inhibitor was 1.5 å (figure s19). the results of molecular docking of several studied ligands prepared in datawarrior [33] (see experimental) with the calculated free binding energy (δg) as individual activity indicator are given in table 1. all docking compounds are more active than the comparison compound chembl2062585 (ic50 (ck2) = 3 nm). to deepen the understanding of the action mechanism of probable ck2 inhibitors among the studied quinazoline derivatives, an updated docking refinement was carried out for the leader compound 9a based on in silico activity indicators. the position of the calculated ligand 9a in the active site of the protein with the recalculated values of δg is presented in figure s20a. the profile of non-covalent interactions is defined using the poseview module of the proteins.plus service [34, 35]. molecular docking towards ck2 shows higher in silico activity with partial coincidence of non-covalent interactions for all compounds compared to known nanomolar inhibitor of this protein. in silico experiment revealed two hit compounds with the best affinity for casein kinase 2: the g value for hydrazone 3a is –13.91 kcal/mol, and for derivative 9a g = –14.16 kcal/mol (table 1). the leader compound 9a is characterized by another binding method to the ck2 active site compared to the native ligand (figure s20b). the main contribution to the binding of 9a with the protein is made by several hydrophobic interactions (figures 2, s20c), π-π stacking between the fluorophenyl moiety and the residue phe113, and a hydrogen bond between the hydroxy group of the ligand and the residue his160. at the same time, both native ligand and 9a are characterized by interactions only with residues of asp175 and met163. thus, despite the significant in silico activity of 9a in terms of free binding energy relative to the nanomolar ck2 inhibitor, a different profile of non-covalent interactions can influence negatively the in vitro experiments. scheme 2 synthesis of 2-(4-fluorophenyl)-4-salicylidenehydrazino quinazolines 9a,b. reagents and conditions: (i) ethanol, r.t., 3 h; (ii) cucl2, ethanol, reflux, 5 h; (iii) pocl3, reflux, 2 h, (iv) h2nnh2·h2o, ethanol, 70 °c, 3 h; (v) ethanol, reflux, 1.5 h. figure 2 non-covalent interactions of the docked ligand 9а. table 1 docking results and indicators of in vitro/in silico activity to casein kinase 2. compound δg, kcal/mol compound δg, kcal/mol 1a –12.33 3a –13.91 1b –13.16 3b –12.47 1c –12.20 3c –11.33 2a –11.84 3d –12.69 2b –12.77 9a –14.16 –13.86* 2c –13.10 9b –12.70 chembl 2062585 (ic50 = 3 nm) –10.67 * the docking score obtained after docking refinement https://doi.org/10.15826/chimtech.2023.10.2.11 chimica techno acta 2023, vol. 10(2), no. 202310211 article 6 of 8 doi: 10.15826/chimtech.2023.10.2.11 3.3. ck2 inhibition and cytotoxicity study the target compounds were evaluated against human recombinant ck2 using the luminescent adp-glotm assay. due to the limited solubility of the compounds, only four derivatives 1a, 3c, 9a,b was tested. the ck2 activity was determined after the casein phosphorylation reaction by the value of atp-dependent luminescence. the data obtained and the ck2 activity in the presence of 50 μm of the tested compounds are shown in table 2. initial screening at 50 µm revealed that the compounds are not active towards ck2. all tested compounds showed no inhibitory activity at the level of the reference drug (table 2). even though the compounds 1, 3, 9 did not act as inhibitors of casein kinase 2, their cytostatic activity was investigated, since a different mechanism of cytotoxic action is possible. some hydrazonoquinazolines 1, 3, 9 were evaluated for their anticancer properties against mda-mb-231 cells. additionally, non-cancerous lung fibroblast cells wi-26 va4 were used to control non-specific cytotoxicity (table 3, figure s21). as can be concluded from the table 3, compounds 1b, 3b–d and 9b possess pronounced antiproliferative activities against mda-mb-231 cells with ic50 values ranging between 4.91 and 65.2 m. noteworthy, non-cancerous lung fibroblast wi-26 va4 cell line was less sensitive only to two tested molecules, including the most active nitrosalicylidene derivative 3b. 4. limitations structural modification is required to improve the solubility and bioavailability of the compounds. unfortunately, the possibilities of purchasing reagents for various modifications are limited, and study of expanded range of compounds is hardly achievable. 5. conclusions the novel fluorine-containing 2-aryl-4-salicilidenhydrazino quinazolines 3, 9 were synthesized and characterized by using nmr and ms, and all the data are in accordance with the proposed structures. the results of molecular docking clearly indicate a high potential activity of this series of compounds in terms of free binding energy. on the other hand, other profiles of non-covalent interactions of the leader compounds compared to the nanomolar inhibitor can have various consequences. therefore, an in vitro activity study with an in vitro-in silico correlation assay is expected to be the best direction for further targeted development of ck2 inhibitors for the considered class of compounds. n(6,7-difluoro-2-phenylquinazolin-4-yl)-n’-(5-nitrosalicylidene)hydrazine 3b exhibited enhanced activity against breast cancer (mda-mb-231) cells in combination with moderate selectivity toward normal wi-26 va4 cells. the rest of compounds do not show noticeable selectivity to normal and tumour cells. ● supplementary materials this manuscript contains supplementary materials, which are available on the corresponding online page. ● funding this work was supported by the ministry of science and higher education of the russian federation, state contract no feuz-2023-0021 (n687.42b.325/23). ● acknowledgments authors thank academician alexander a. spasov (department of pharmacology & bioinformatics, scientific center for innovative drugs, volgograd state medical university) for assistance with study of human recombinant ck2 inhibition and the head of medicinal chemistry center alexander s. bunev (togliatti state university) for cytotoxicity data. ● author contributions conceptualization: e.v.n., s.k.k. data curation: e.v.n. investigation: m.d.l. methodology: e.v.n, m.d.l., i.i.b. software: i.i.b. validation: i.i.b. visualization: i.i.b. writing – original draft: e.v.n. writing – review & editing: s.k.k. project administration: s.k.k. table 2 data of ck2 inhibition activity study for some hydrazonoquinazolines. compound ck2 activity (msd), % ck2 inhibition at 50 μm (msd), % 1a 102.1418.22 –2.1418.22 3c 94.514.98 5.514.98 9a 96.0222.88 3.9822.88 9b 108.161.1 –8.161.1 staurosporine 7.871.34* 92.131.34* statistical significance relative to negative control, 1-factor anova; *p <0.05 table 3 mtt assay results for 2-aryl-4-salicylidenehydrazino quinazolines against breast cancer cell line (mda-mb-231). compound ic50, m mda-mb-231 (breast cancer) wi26 va4 (normal cell) 1a >100 46.612.57 1b 65.27.67 69.819.15 3b 4.910.66 6.320.47 3c 41.912.6 17.492.41 3d 7.430.87 4.020.38 9a n.d. 42.44.75 9b 14.51.80 11.271.02 n.d. – no data https://doi.org/10.15826/chimtech.2023.10.2.11 chimica techno acta 2023, vol. 10(2), no. 202310211 article 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https://doi.org/10.1021/ci500588j https://doi.org/10.1093/nar/gkaa235 https://doi.org/10.1093/bioinformatics/btl150 https://doi.org/10.1134/s1070428020080163 https://doi.org/10.1039/d0tb00620c https://doi.org/10.1007/978-1-61779-012-6_9 1. introduction 2. experimental 2.1. general 2.2. preparation of intermediates 2.2.1. (e)-2-(4-fluorophenylydeneamino)benzamide (6) 2.2.2. 2-(4-fluorophenyl)quinazolin-4(3н)-one (7) 2.2.3. 2-(4-fluorophenyl)-4-chloroquinazoline (8) 2.2.4. 2-(4-fluorophenyl)-4-hydrazinoquinazoline (4b) 2.3. preparation of target hydrazonoquinazolines 3c, d, 9a, b 2.3.1. n-(3,5-di(t-butyl)salicylidene)-n’-(6,7-difluoro-2-phenylquinazolin-4-yl)-hydrazine (3c) 2.3.2. n-(5-chlorosalicylidene)-n’-(6,7-difluoro-2-phenylquinazolin-4-yl)-hydrazine (3d) 2.3.3. n-(3,5-di(t-butyl)salicylidene)-n’-(2-(4-fluorophenyl)quinazolin-4-yl)-hydrazine (9а) 2.3.4. n-(5-chlorosalicylidene)-n’-(2-(4-fluorophenyl)quinazolin-4-yl)-hydrazine (9b) 2.4. molecular docking studies 2.5. ck2 assay 2.6. mtt assay and cell culture mda-mb-231 breast cancer cells and wi-26 va4 lung epithelial-like cells were purchased from the atcc (manassas, va, usa). mda-mb-231 cells were maintained in dulbecco's modified eagle's medium (dmem), supplemented with 1× non-essential amino acids, 25... 3. results and discussion 3.1. synthesis 3.2. molecular docking 3.3. ck2 inhibition and cytotoxicity study 4. limitations 5. conclusions ● supplementary materials ● funding ● acknowledgments ● author contributions ● conflict of interest ● additional information references electrochemical creatinine determination with metal-organic framework based on copper and acetylenedicarboxylic acid as catalyst published by ural federal university eissn 2411-1414 chimicatechnoacta.ru letter 2023, vol. 10(2), no. 202310201 doi: 10.15826/chimtech.2023.10.2.01 1 of 6 electrochemical creatinine determination with metalorganic framework catalyst based on copper and acetylenedicarboxylic acid andrei v. okhokhonin * , alsu a. ibatullina , yulia v. izmozherova , marina i. stepanova , anatoly i. matern , alisa n. kozitsina institute of chemical engineering, ural federal university, ekaterinburg 620009, russia * corresponding author: a.v.ohohonin@urfu.ru this paper belongs to a regular issue. abstract fast and accurate determination of creatinine is critical in kidney function diagnostics. this paper discusses the usage of the metal-organic framework based on copper(ii) and acetylenedicarboxylic acid (cuadca) as a catalyst of electrochemical oxidation of creatinine, glucose and urea. cuadca was synthesized by deprotonation with triethylamine for the first time. successful synthesis was confirmed by ftir and eds. the material was characterized by sem, eis, and cv. cuadca forms laminated-like flakes with diameter from 1 µm to 20 µm, which is consistent with the polymer-like structure. cv and eis analyses showed that cuadca immobilized on gce acts as a catalyst in electrooxidation reaction of glucose, urea, and creatinine. the sensitivity of creatinine detection, 1057±99 µa/mm, was higher than the detection sensitivity of glucose and urea by more than 100 times with the limit of detection of 2 µm, so cuadca is a promising material for further development of enzymeless sensors for creatinine. keywords metal-organic framework creatinine voltammetry electrochemical catalyst enzymeless determination received: 03.03.23 revised: 18.03.23 accepted: 19.03.23 available online: 29.03.23 © 2023, the authors. this article is published in open access under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). 1. introduction the determination of creatinine in urine and blood is critical in case of diagnosis of kidney and liver diseases. modern methods for these purposes are chromatography, massspectrometry, and jaffe reaction. chromatography and mass-spectrometry require cumbersome devices highly qualified personnel and high-cost consumables. the jaffe reaction, despite its simplicity and availability, is associated with using poisonous and explosive picric acid and low specificity, causing erroneously high creatinine results in the presence of proteins, glucose, acetoacetate, ascorbic acid, guanidine, acetone, cephalosporins, aminoglycosides, ketone bodies, α-keto acids, and other organic compounds. thereby, the development of new simple, express, safe, and specific methods of creatinine determination is an urgent task in the field of medical diagnosis. a promising approach for solving this problem involves electrochemical methods, especially voltammetry, due to its accuracy, high rate and low-cost of consumables and devices. however, analysis of organic compounds, including creatinine, on traditional electrodes (platinum, glassy carbon, etc.) is difficult because of the absence of inherent electroactivity. there are a few ways of avoiding this drawback. one of them is using an electrochemical catalysts, which can reversibly oxidize or reduce and transfer electrons from non-electroactive molecule to electrode (or vice versa). the most popular electrochemical catalysts used in electrochemical sensors are metal (platinum, gold, palladium, etc.) and carbon nanomaterials, metal–organic complexes. during the past two decades, metal–organic frameworks (mofs), also known as porous coordination polymers (pcps), have experienced explosive growth. mofs exhibit a wide variety of potential applications in catalysis, gas storage and separation, luminescence, and drug delivery, owing to their specific features, such as structural diversity, flexibility and tailorability, high porosity, large surface area, and extraordinary adsorption affinities [1]. in electrochemical biosensing mofs were used for determination of cancer biomarkers [2], heavy metals [3], herbicides [4], h2o2 [5], bisphenol a [6] and other analytes. there are several mofs that are used to absorb creatinine in hemodialysis apparatus [7] and to detect creatinine: in the works [8, 9] the authors report a luminescent sensor http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2023.10.2.01 mailto:a.v.ohohonin@urfu.ru http://creativecommons.org/licenses/by/4.0/ https://orcid.org/0000-0003-2922-7623 https://orcid.org/0009-0003-2562-9606 https://orcid.org/0009-0008-3601-5016 https://orcid.org/0000-0002-1779-1756 https://orcid.org/0009-0000-4645-0961 https://orcid.org/0000-0002-0263-2111 https://crossmark.crossref.org/dialog/?doi=https://doi.org/10.15826/chimtech.2023.10.2.01&domain=pdf&date_stamp=2023-03-29 chimica techno acta 2023, vol. 10(2), no. 202310201 letter 2 of 6 doi: 10.15826/chimtech.2023.10.2.01 for detecting creatinine based on lanthanide–organic frameworks, but such sensors are non-reusable and require expensive equipment. anyway, electrochemical creatinine sensors based on mofs have not been described in the literature. in the past, a lot of mofs with different linkers and metal ions were synthesized and applied as sensing receptors in electrochemical sensors. significant portion of these mofs are based on copper(i) or (ii) ions because of their high catalytic activity and low cost [1, 5, 6, 10–12]; besides, copper ions form a strong coordination bond with creatinine: from 2 to 4 creatinine molecules per one cu2+ ion [13]. a variety of mof forms and their characteristics are available due to using different linkers between metal ions. the main requirements for these molecules are the rigid structure, e.g., imidazole, benzene ring(s), acetylene group, etc., and the presents of two or more functional groups that can attach ions (–cooh, –nh2, pyridines, etc.) [1]. one of the promising linkers for mof synthesis is acetylenedicarboxylic acid (adca), which meets all these requirements [14]. some amount of copper and adca containing cps were synthesized to date[14, 15]. so, the aims of the present work were the synthesis of cu2+-acetylenedicarboxylic acid mof (cuadca) and the investigation of its electrochemical behavior towards creatinine in the presence of glucose and urea. 2. materials and methods 2.1. materials cucl2∙2h2o, ethyl alcohol, dimethylformamide (dmf), acetylenedicarboxylic acid (adca, 95%, sigma-aldrich, usa), triethylamine (tea, sigma, usa), creatinine (millipore, germany), glucose (panreac, spain), urea (sigma-aldrich, usa), na2hpo4 (sigma-aldrich, usa), kh2po4 (sigma-aldrich, usa), kcl (sigma-aldrich, usa), nacl (sigma-aldrich, usa), k4[fe(cn)6] (sigma-aldrich, usa), k3[fe(cn)6] (sigma-aldrich, usa). deionized water (18.2 mω) was produced with barnstead™ pacific tii water purification system (germany) and was used in all experiments. phosphate buffer saline (pbs) ph = 7.4 was prepared by dissolving of 8.00 g of nacl, 0.2 g of kcl, 1.44 g of na2hpo4 and 0.24 g of kh2po4 in 1 liter of water with further adjustment to the desired ph. 2.2. apparatus voltammetric and electrochemical impedance spectroscopy (eis) studies were performed using an autolab pgstat302n potentiostat/galvanostat (metrohm ag, the netherlands). three-electrode electrochemical cell was used: glassy carbon disk working electrode (gce) with s=0.07 cm2, ag/agcl reference electrode and glassy carbon rod counter electrode (all – metrohm ag, the netherlands). cyclic voltammetry (cv) measurements were carried out at room temperature in pbs. the electrode modification process was investigated by electrochemical impedance spectroscopy (eis), which was performed in 5.0 mm fe(cn)63–/4– solution containing 0.1 m kcl. the ir spectra were recorded in kbr tablets on an alpha ftir spectrometer manufactured by brukeroptikgmbh (germany). sem microphotographs and elemental analysis by energy-dispersive x-ray spectroscopy (eds) were obtained with auriga crossbeam (carl zeiss nts, germany). 2.3. synthesis of cuadca and working electrode modification scheme 1 represents the routes of cuadca synthesis and gce modification. briefly, 0.33 ml of distilled water, 0.33 ml of ethyl alcohol, and 0.33 ml of dmf were added to a 1.5 ml eppendorf tube. next, the resulting mixture was divided into two equal parts of 0.5 ml. 0.54 mmol (0.0092 g) of cucl2∙2h2o was dissolved in the first part, 0.02925 mmol (0.0034 g) adca was dissolved in the second part. after the dissolution of both components, the solutions were mixed and stirred for 10 minutes. then 12.5 μl of triethylamine was added to the tube and stirred for 1.5 hours. the precipitated blue crystals were isolated by centrifugation and washed 3 times with water, ethyl alcohol and dmf and dried in air at 60 °c for 3 hours. then the 5 µl of suspension of 1 mg of cuadca per 1 ml of water prepared with ultrasonication was drop casted on gce and dried in air. the modified electrode was named cuadca@gce. 2.4. procedure of electrocatalytic creatinine detection using cuadca@gce as the electrocatalyst the analytical procedure included the following stages: 1. a cyclic voltammogram of cuadca@gce was registered in the working solution (10 ml of pbs), and anodic peak current was denoted as i0. 2. 100 µl of standard creatinine solution in pbs (10 mm) was added to the working solution, and a cyclic voltammogram was registered. anodic peak current was denoted as ist. 3. 100 µl of analyzed creatinine solution in pbs (sample) was added to the working solution, and a cyclic voltammogram was registered. anodic peak current was denoted as is. 4. the concentration of creatinine in the sample (cx) was calculated as in equation 1: 𝑐𝑥 = 𝑐st 𝐼st 𝐼𝑥 (1) 3. results and discussion 3.1. characterization of cuadca the cuadca synthesis methods used in the past involved mixing a cu2+ salt with adca with further slow water evaporation during several days [14]. to avoid long synthesis time, we use tea as a deprotonating agent, so the reaction time reduces by up to 2 hours. the synthesis of the cuadca can be explained by each adca ligand connecting to two cu2+ ions metal nodes, forming the linear polymer-like structure [14]. https://doi.org/10.15826/chimtech.2023.10.2.01 https://doi.org/10.15826/chimtech.2023.10.2.01 chimica techno acta 2023, vol. 10(2), no. 202310201 letter 3 of 6 doi: 10.15826/chimtech.2023.10.2.01 scheme 1 cuadca synthesis and electrode modification. the morphology, composition, and electrochemical properties of cuadca were determined by sem, eds, ftir, eis and cv. figure 1 shows the sem image of cuadca. as can be clearly seen, cuadca particles appear layered, which is consistent with the polymer-like structure. the dimensions of the flakes vary from 1 µm to 20 µm. successful synthesis of cuadca material is confirmed by eds (table 1) and ftir (figure 2): the spectra of cuadca synthesized using triethylamine are identical to the spectra in the literature [16]. the spectra of adca have a characteristic peak at 1698 cm–1 (dimer between two carboxylic groups of the adca) that shifts to 1597 cm–1 in cuadca spectra, which shows the pseudo-monodentate coordination of the anion. nyquist plots for bare gce and cuadca@gce were registered in the solution containing 5 mm k4[fe(cn)6]/k3[fe(cn)6] and 0.1 m kcl at a potential of 0.25 v (figure 3). compared with the small semicircle of gce, the rct of cuadca@gce was increased, indicating the successful modification of cuadca nanoparticles on the gce surface. the increased rct is due to the poor conductivity of cuadca, which hinders, to some extent, the electron transfer through the electrode-solution interface. 3.2. electrochemical behaviour of cuadca in the presence of creatinine figure 4a shows cyclic voltammograms of bare gce and cuadca@gce registered in 0.1 m pbs ph = 7.4 in absence and in presence of different concentrations of creatinine. as seen, a couple of cathodic (at –0.4 v) and anodic (at –0.1 v) peaks in cuadca@gce are observed. to determine the number of electrons involved in the electrochemical reaction, heyrovsky-ilkovic equation (equation 2) was used: 𝐸 = 𝐸1 2⁄ + 𝑅𝑇 𝑛𝐹 ln ( 𝐼d − 𝐼 𝐼 ), (2) where r is the gas constant; t is the absolute temperature, k; f is the faraday constant; n denotes the number of electrons taking part in the electrode reaction; e1/2 is the halfwave potential, v; e is the potential applied, v; i is the current registered when e is applied, a; id is the limiting diffusion current (peak current), a. after rebuilding of voltammograms in the ranges of [(–0.20 v)–0 v] and [(–0.26 v)–(–0.35 v)], the numbers of electrons involved in the electrochemical reaction were calculated as na = 1.3, nc = 0.4. deviations from a whole number can be explained as processes of reduction of cu2+ and cu1+ to cu0 and further oxidation of cu0 to cu1+ occurring simultaneously. the presence of creatinine, urea, or glucose in the working solution leads to the increase in the peaks currents, and the additional current depends linearly on the analyte concentration (figure 4a, for creatinine). this fact can be explained as electrocatalytic processes represented by equations 3–5: cu+2 + e− → cu+1, (3) cu+1 − e− → cu+2, (4) cu+2 + a → cu+1 + oxa. (5) copper in form of cu2+ binds with the analyte molecule (a) and then cu2+ oxidizes the analyte molecule, is converted to cu+1 while oxidizing the analyte to form oxa, so cuadca acts as a catalyst of electrochemical oxidation of analytes. figure 1 sem microphotograph of cuadca. green arrows point to layered structure of microparticles. table 1 elemental composition of cuadca in atomic %, measured with eds. spectrum numbers correspond to points in figure 1. spectrum number c o cl cu spectrum 1 54.3 11.6 2.7 31.3 spectrum 2 57.7 18.4 4.2 19.7 https://doi.org/10.15826/chimtech.2023.10.2.01 https://doi.org/10.15826/chimtech.2023.10.2.01 chimica techno acta 2023, vol. 10(2), no. 202310201 letter 4 of 6 doi: 10.15826/chimtech.2023.10.2.01 figure 2 ftir spectra of cucl2, adca and cuadca. figure 3 nyquist plots at potential of 0.25 v for bare gce and cuadca@gce registered in 5 mm k4[fe(cn)6]/k3[fe(cn)6] + 0.1 m kcl; dots are experimental data and lines are fitted data. inset: equivalent circuit. electrochemical transformations of cuadca are process es that are controlled by diffusion of analyte to electrodesolution interface; the linear plots of the dependence of peak current on the square root of scan rate (figure 4b) indicate this. the analytical characteristics of urea, glucose, and creatinine determination were calculated from i vs. ca dependences and are reflected in table 2. as seen, the most linear dependences were obtained for the anodic peaks, and the highest sensitivity (the slope of i vs. ca dependence) and the lowest limit of detection (lod) were obtained for creatinine, which can be explained by the formation of strong complex between copper ions and creatinine molecules. this fact can be used in the future in the development of enzymeless electrochemical sensor for detection of creatinine in the presence of glucose and urea. the developed creatinine determination system of cuadca@gce was compared with known enzymeless creatinine sensors (table 3). it can be noticed that cuadca@gce is not inferior in sensitivity and lod to the previously developed sensors. figure 4 cyclic voltammograms of bare gce and cuadca@gce in absence and in present of 10 µm, 20 µm, 30 µm and 40 µm of creatinine in 0.1 m pbs ph = 7.4. scan rate: 0.1 v/s (a). the dependence of anodic and cathodic current peaks on square root of scan rate of cuadca@gce in 0.1 m pbs ph = 7.4 with 40 µm of creatinine (b). 4. limitations in this research, creatinine, urea and glucose were determined in model solutions imitating blood serum. in order to develop the enzymeless electrochemical sensor for creatinine, it is necessary to make investigations with real blood serum and whole blood. https://doi.org/10.15826/chimtech.2023.10.2.01 https://doi.org/10.15826/chimtech.2023.10.2.01 chimica techno acta 2023, vol. 10(2), no. 202310201 letter 5 of 6 doi: 10.15826/chimtech.2023.10.2.01 table 2 analytical characteristics of urea, glucose, and creatinine determination with cuadca@gce as electrocatalyst (n = 5, p = 0.95). analyte sensitivity (µa/mm) r2 lod (µm) linear range (mm) anodic peak cathodic peak anodic peak cathodic peak urea 1.0±0.1 5.0±0.4 0.973 0.891 1923 0–10 glucose 13.0±1.1 116±10 0.969 0.874 228 0–0.4 creatinine 1057±99 1756±150 0.966 0.649 2 0–0.1 table 3 comparing of cuadca@gce with previously developed electrochemical enzymeless sensors for creatinine determination systems. system sensitivity, µa/mm lod, µm linear range, µm reference cuadca@gce 1057±99 2 0–0.1 this work fe2o3/pani-1@gce 28.77 0,23 0.442–8840 [17] cuo/il@ergo 1.02 0.2 0.01–2000 [18] cb nanoparticles@spe 16.7 8.6 370–3600 [19] 5. conclusions in this work we report enzymeless electrochemical determination of urea, glucose, and creatinine in pbs ph = 7.4 on the glassy carbon electrode modified with cuadca synthesized with a simple and rapid method and characterized by sem, ftir, eis and cv. sensitivity and lod were calculated. the results show that cuadca immobilized on gce acts as catalyst in electrooxidation reaction of glucose, urea, and creatinine. since the sensitivity and lod for creatinine detection were more than 100 times higher than for glucose and urea detection, cuadca is a promising material for further development of an enzyme-free sensor for creatinine. as compared with the existing enzymeless sensors, cuadca@gce is not inferior in sensitivity and lod. ● supplementary materials no supplementary materials are available. ● funding the research funding from the ministry of science and higher education of the russian federation (ural federal university project within the priority-2030 program) is gratefully acknowledged. ● acknowledgments the equipment of the ural center for shared use “modern nanotechnology” snsm urfu was used. ● author contributions conceptualization: a.v.o. data curation: a.v.o. formal analysis: a.v.o., a.n.k. funding acquisition: m.i.s., a.n.k. investigation: a.a.i., y.v.i. methodology: a.v.o. project administration: a.n.k. 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doi:10.1016/j.talanta.2019.120277 https://doi.org/10.15826/chimtech.2023.10.2.01 https://doi.org/10.15826/chimtech.2023.10.2.01 https://doi.org/10.1016/j.talanta.2022.123612 https://doi.org/10.1016/j.cej.2022.137001 https://doi.org/10.1016/j.memsci.2022.120369 https://doi.org/10.1016/j.micromeso.2022.111989 https://doi.org/10.1021/acs.inorgchem.2c00850 https://doi.org/10.1002/elan.201800890 https://doi.org/10.1002/anie.201411854 https://doi.org/10.1039/c7cs00122c https://doi.org/10.1016/0010-8545(94)01122-r https://doi.org/10.1039/d2cc02665a https://doi.org/10.1080/00958972.2013.862789 https://doi.org/10.1002/masy.201100131 https://doi.org/10.1016/j.aca.2020.09.004 https://doi.org/10.1016/j.aca.2019.07.029 https://doi.org/10.1016/j.talanta.2019.120277 21 © титов а. г., гильванова з. р., инюшкин н. в., аитова а. и., щелчков и. п., токарева н. а., маньков м. г., перфилов с. а., 2014 а. г. титов, з. р. гильванова, н. в. инюшкин, а. и. аитова, и. п. щелчков, н. а. токарева, м. г. маньков, с. а. перфилов уральский федеральный университет, 620002, екатеринбург, ул. мира, 19, кафедра процессов и аппаратов химической технологии. e-mail: paht@yandex.ru расчет гидродинамики потока в электроциклоне* для анализа гидродинамики потока в электроциклоне применен компьютерный расчет с использованием метода конечных элементов (мкэ). геометрия модели соответствует лабораторному электроциклону. для расчетов использована k-ε-модель турбулентности. система уравнений решается с помощью алгоритма simple. результаты расчета дают картину распределения скоростей потока и линий тока в различных сечениях. на основании результатов делается вывод о гидродинамике электроциклона. выявлен факт, что в бункере электроциклона отсутствует вихревое движение, также нет развитого течения в области стенок, а ниже выхлопного отверстия скорость потока близка к 0. это благоприятно сказывается на эффективности очистки, т. к. выходящий чистый газ не увлекает с собой осевшие частицы. выводы: 1) гидродинамика электроциклона может быть описана с помощью математической модели и рассчитана с помощью мкэ; 2) поток в электроциклоне, как и ожидалось, имеет закрученную структуру, угол закрутки зависит от длины активной зоны; 3) конструкция бункера обеспечивает выход очищенного газа без вовлечения в него уловленных частиц. * исследование проведено при финансовой поддержке молодых ученых урфу в рамках реализации программы развития урфу. у д к 6 6. 04 791 введение электроциклон – это аппарат, предназначенный для удаления из газового потока твердых и жидких частиц. принцип работы заключается в осаждении частиц аэрозолей при совместном действии на них кулоновской и центробежной силы [1]. ряд публикаций [2, 3] содержит данные о возможности применения электроциклона в химической тех22 cta | № 1 | 2014 нологии, металлургии и энергетике. процесс осаждения частиц подробно рассмотрен авторами [4] на основании анализа действующих на частицу сил в кольцевом канале электроциклона, но не учтено распределение скоростей в потоке и конструкция других узлов аппарата. в настоящем исследовании авторами предпринята попытка проанализировать гидродинамику электроциклона с помощью метода конечных элементов. математическая модель на рис. 1 показана схема электроциклона. аэрозоль входит в электроциклон через отверстие в улитке, очищенный газ выходит через выхлопную трубу, а уловленный материал удаляется через нижнее отверстие в бункере. в электроциклоне поле потока, электрическое поле и траектории частиц связаны между собой. для решения столь сложной проблемы должны быть сделаны некоторые допущения с целью упростить расчет [5]. поскольку скорость ионов намного больше, чем скорость воздуха в электроциклоне, предполагается, что электрическое поле не влияет на поле потока. объемная доля частиц очень мала, следовательно, ее влиянием на поле потока также можно пренебречь [6]. также исключим движение частиц, поскольку это тема другого большого исследования. для расчетов принимаем k-ε-модель турбулент-ности. уравнение навье – стокса и уравнение неразрывности для трехмерной несжимаемой жидкости записываются следующим образом: где u – скорость газа, ρf – плотность газа, р – давление газа, g – гравитационное ускорение и μeff – эффективная турбулентная вязкость. эти параметры связаны следующими уравнениями: µeff = µf + µt, (3) µt = ρf cµk 2/ε, (4) ( ) eff , f j i i i ji f i i j i p u u x x uup g x x x ∂ ∂ ρ = − + ∂ ∂   ∂∂∂ + µ + +ρ   ∂ ∂ ∂    (2) (1)0,i i u x ∂ = ∂ рис. 1. электроциклон: 1 – царги корпуса, 2 – улитка, 3 – центральный осадительный электрод, 4 – коронирующий электрод, 5 – выхлопная труба, 6 – бункер, 7 – изолятор а. г. титов, з. р. гильванова, н. в. инюшкин, а. и. аитова, и. п. щелчков, н. а. токарева, м. г. маньков, с. а. перфилов 23 2014 | № 1 | ctaрасчет гидродинамики потока в электроциклоне здесь μf – молекулярная динамическая вязкость жидкости и μt – турбулентная вязкость. прочие константы для стандартной k-ε-модели турбулентности устанавливаются по умолчанию для течения воздуха при стандартных условиях. уравнения (1) и (2) решаются с помощью алгоритма simple на тетраэдрической сетке, показанной на рис. 2. общее число элементов сетки – 7574, сетка автоматическая, с регулируемым размером элементов, размер наименьшего тетраэдра – 0,5 мм. граничные условия на входе – скорость потока воздуха 24 м/с при стандартных условиях. стенки каналов жесткие, недеформируемые. давление на выходе определяется в процессе решения. решение задачи потребовало 12 часов процессорного времени при характеристиках системы: процессор amd i5 4 × 2,2 ггц и озу 8 гб. результаты и обсуждение cfd (computational fluid dynamics), т. е. вычислительная гидродинамика позволяет наглядно и красочно визуализировать решение, поэтому еще одна расшифровка термина – colorful fluid dynamics – полностью оправдывает себя. постпроцессорная обработка позволила получить профиль скоростей в вертикальной и горизонтальных плоскостях, а также линии тока (рис. 3–5). на рис. 3 показана 1 плоскость, на рис. 4–15 параллельных плоскостей, цветом показана величина скорости, на рис. 5–40 линий с началом на входе аэрозоля. из рисунков 3–5 видно, что поток входит в электроциклон на высокой скорости (24 м/с), образуя интенсивный вихрь в улитке с углом закручивания окорис. 2. расчетная сетка рис. 3. поле скоростей потока. вертикальное сечение 24 cta | № 1 | 2014 ло 90º относительно оси аппарата. после улитки поток попадает в активную зону, где угол закручивания уменьшается до 60º, а скорость (ее результирующий вектор) падает до 10–15 м/с. пройдя 20 % длины активной зоны, поток имеет угол закручивания 45º при скорости 3–5 м/с. после 50 % длины активной зоны вихрь затухает: угол закручивания всего 10º, скорость – менее 4 м/с. интересным фактом является то, что в бункере электроциклона отсутствует вихревое движение, также нет развитого течения в области стенок, а ниже выхлопного отверстия скорость потока близка к 0. это благоприятно сказывается на эффективности очистки, т. к. выходящий чистый газ не увлекает с собой осевшие частицы. выводы 1) гидродинамика электроциклона может быть описана с помощью математической модели и рассчитана с помощью мкэ. 2) поток в электроциклоне, как и ожидалось, имеет закрученную структуру, угол закрутки зависит от длины активной зоны. 3) конструкция бункера обеспечивает выход очищенного газа без вовлечения в него уловленных частиц. рис. 4. поле скоростей потока. горизонтальные сечения рис. 5. линии тока а. г. титов, з. р. гильванова, н. в. инюшкин, а. и. аитова, и. п. щелчков, н. а. токарева, м. г. маньков, с. а. перфилов 25 2014 | № 1 | ctaрасчет гидродинамики потока в электроциклоне 1. lim k. s., kim h. s., lee k. w. j. aerosol sciences, 2004, № 35, 103. 2. inyushkin n. v., yugay f. s., gilvanova z. r., titov a. g., ermakov s. a. chem. chem.technol. 2012, 55, 104 [инюшкин н. в., югай ф. с., гильванова з. р., титов а. г., ермаков с. а. известия вузов. химия и химическая технология. 2012, 55, 104]. 3. inyushkin n. v., ermakov s. a., titov a. g., gilvanova z. r., novikov k. l., pframonov d. a. inzhenern. vestnik dona, 2011, n 4, 1271 [инюшкин н. в., ермаков с. а.,титов а. г., гильванова з. р., новиков к. л., парамонов д. а. // инжен. вестник дона, 2011, №4, 1271] http://ivdon.ru/magazine/archive/ n4p1y2012/1271. 4. petrov v. a., inyushkin n. v., ermakov s. a. vestnik tgtu, 2010, 16, 44 [петров в. а., инюшкин н. в., ермаков с. а. // вестник тгту. 2010. т. 16, № 1. 44]. 5. tsai r., mills a. f. j. aerosol science, 1995, № 2, 227. 6. xiangrong z., lianze w., keqin z. j. electrostatics, 2005, 1071. a. g. titov, z. r. gilvanova, n. v. inushkin, a. i. aitova, i. p. shhelchkov, n. a. tokareva, m. g. mankov, s. a. perfilov ural federal university, 19 mira street, 620002, ekaterinburg. e-mail: paht@yandex.ru elektrocyclone hydrodynamic flow computation to analyze the elektrocyclone flow hydrodynamic computer calculation using the finite element method (fem) is applied. the geometry of the model corresponds to the laboratory elektrocyclone. the k-ε-turbulence model is used for the computation. the system of equations is solved by the simple algorithm. the calculation results give a pattern of the flow velocity distribution and the flow lines in the different sections. there is conclusion based on the results about the elektrocyclone flow hydrodynamic. is elicited the fact that in the bunker of an electrocyclone there is no whirl, also there is no developed current in the field of walls, and below an exhaust opening the speed of a stream is close to 0. страница 1 chemical mechanical treatment of potato starch for isolation of nanocrystal particles published by ural federal university eissn 2411-1414; chimicatechnoacta.ru letter 2022, vol. 9(3), no. 20229313 doi: 10.15826/chimtech.2022.9.3.13 1 of 5 chemical-mechanical treatment of potato starch for isolation of nanocrystal particles denis e. tryakhov ab*, anatoly a. politov ab a: institute of solid state chemistry and mechanochemistry, novosibirsk 630128, russia b: novosibirsk state university, novosibirsk 630090, russia * corresponding author: tryakhov@solid.nsc.ru this paper belongs to the ctfm'22 special issue: https://www.kaznu.kz/en/25415/page. guest editors: prof. n. uvarov and prof. e. aubakirov. © 2022, the authors. this article is published in open access under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). abstract starch nanocrystals were isolated by a combination of acid hydrolysis and sonication of native potato starch. the obtained samples were examined by xrd, scanning electron microscopy and static light scattering. an increase in hydrolysis time increases the degree of crystallinity from 47 to 66%. by changing the processing conditions, it is possible to isolate particles of a given size. first, submicron flat particles with dimensions of 3000–5000 nm and a thickness of 80–100 nm are obtained. with longer processing, approximately isometric nanoscale particles remain. based on the obtained data, a stepwise topochemical mechanism for the formation of starch nanoparticles was proposed. keywords starch nanocrystals potato starch ultrasonic treatment chemical-mechanical treatment topochemical hydrolysis of starch granule received: 25.06.22 revised: 01.08.22 accepted: 01.08.22 available online: 12.08.22 key findings ● the process of acid hydrolysis of potato starch has a pronounced topochemical nature. ● ultrasonication of crystalline starch nanocrystals results in particle size reduction. 1. introduction among the numerous practical applications of nanoparticles from natural polymers, perhaps, the most known is their use for reinforcement of biodegradable materials [1– 3]. no less interesting is the use of nanosized particles from natural biopolymers as adjuvants. adjuvants are inorganic and organic nanoparticles that are able to adsorb and retain antigens on their surface for a long time, which increases the duration of their effect on the body's immune system [4–7]. inorganic and organic adjuvants based on synthetic and natural polymers have been used. inorganic adjuvants based on oxide and aluminum hydroxide nanoparticles are easy to prepare, and their surface is easy to modify. however, they often show cytotoxicity, have abrasive properties, are unfriendly to living organisms and have a short sedimentation time, which makes their use in vaccination inconvenient. nanoparticles of natural polymers in general and starch nanoparticles in particular are non-toxic, biodegradable; and biocompatible, their surfaces can be easily modified [8]. moreover, the sedimentation time of the snp-based adjuvants is long enough that there is no need to shake continuously the needle vaccinator during vaccination. according to the literature, the following polymer-based nanomaterials are used as adjuvants: starch, cellulose, chitosan or some alginic acid salts – alginates. we chose potato starch, which can most easily be extracted from biomass and which, unlike cereal starches, contains significantly less fat and proteinfacilitating the purification process. 2. materials and methods 2.1. materials for this work, normal potato starch was isolated from rosara breed, and then it was dried at room temperature [10]. the selected breed did not belong to highly starchy or waxy potato, had about 14% starch and the amylose and amylopectin contents were assumed to be approximately 30 and 70%, respectively. the moisture and protein contents of potato starch were 12.4% and 0.07%, respectively. 2.2. preparation of snc starch nanoparticles were isolated according the ‘rapid method’ using diluted sulfuric acid [7–8]. starch (133 g, dry basis) was suspended in 500 ml of h2so4 (3 m) and http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2022.9.3.13 mailto:tryakhov@solid.nsc.ru https://www.kaznu.kz/en/25415/page http://creativecommons.org/licenses/by/4.0/ https://crossmark.crossref.org/dialog/?doi=https://doi.org/10.15826/chimtech.2022.9.3.13&domain=pdf&date_stamp=2022-8-12 chimica techno acta 2022, vol. 9(3), no. 20229313 letter 2 of 5 incubated with 500 rpm mechanical stirring at 37 °c for 1–6 days. the resulting suspension was washed by successive centrifugation (3500 g, 10 min) with distilled water until neutral ph had been reached; then the precipitated residue was washed with ethanol (95%) and dried in air at room temperature. the yield of hydrolysis (y) was calculated as the ratio of the weight of solid starch residues to the dry weight of the initial starch. therefore, the degree of hydrolysis refers to 1–y (%). 𝑌(%) = the weight of solid starch residues(g) weight of initial starch(𝑔) . (1) the resulting snc suspension was subjected to ultrasonic treatment with 400 w power for 20 seconds, 5 times, with cooling in an ice bath. 2.3. morphology observation the morphology of the native and hydrolyzed starches was observed using a field emission scanning electron microscope (hitachi tm 1000, japan) at an acceleration voltage of 15 kv. a drop of suspension was spread onto a carbon tape and dried under vacuum. the samples were then coated with a gold layer by ion sputtering using an auto fine coater jfc-1600 (jeol, japan). 2.4. size distribution analysis particle size distribution (psd) of the samples was carried out at 25 °c with a laser particle size analyzer (sald-7500, shimadzu, japan). the ph of the suspensions was approximately adjusted to 7. a value of 1.40 was considered as the refractive index, and the data were means of three replicates. 2.5. xrd analysis x-ray diffraction patterns of the investigated starches were recorded using сu kα radiation on a d8 advance x-ray diffraction meter (bruker axs, germany) with bragg-brentano geometry equipped with a one– dimensional lynx–eye detector and a kβ filter. pxrd patterns were collected in the interval 5°<2θ<40° with a step size of δ2θ = 0.0195° and a counting time of one second per step. the relative crystallinity was calculated by estimating the percentage of the crystalline area relative to the total diffraction area according to nara and komiya [9]. 3. results and discussion 3.1. size distribution figure 1 shows the size distribution for the native potato starch. the starch is characterized by a bimodal distribution, 5% of all particles have diameters from 1 to 10 µm, and 95% from 10 to 150 µm. hydrolysis for 6 days leads to the disappearance of a fraction >50 µm in size. the volume fraction of particles up to 10 µm in diameter increased from 6% to 65%. the impact of ultrasonic treatment of hydrolyzed starch leads to the appearance of a nanosized fraction of starch 20–350 nm, which constitutes is 57% of the total mass of particles in suspension. this observation shows that acid hydrolysis leads to the destruction of native starch granules. however, to obtain colloidal solutions of starch nanocrystals, mechanical processing is necessary. figure 1 particle size distribution of samples of native potato starch (ps, a), obtained after 6 days of hydrolysis (hps-6, b) and hydrolyzed starch subjected to ultrasonic treatment (hps-6-us, c). the integral form of these distributions (d). chimica techno acta 2022, vol. 9(3), no. 20229313 letter 3 of 5 3.2. crystalline structure of initial and hydrolyzed potato starch figure 2 shows x-ray diffraction patterns of the native and hydrolyzed starch. the native potato starch possesses a distinct b-type crystalline structure with diffraction peaks at 5.6°, 11.4°, 14.4°, 15.0°, 17.2°, 19.7°, 22.2°, and 24.0°. it is well established in the literature that in the acid hydrolysis the amorphous regions of starch granules are the first to react. thus, diffuse scattering from disordered phase supposed to be decreased and the degree of crystallinity – increased during the acid treatment. crystalline indices are presented in table 1. 3.3. peculiarities of acid hydrolysis of potato starch the degree of acid hydrolysis was measured by the weight of the dry residue contained in a daily taken aliquot of the reaction mixture (see 2.2). the hydrolysis of starch grains is typically represented by two processes having different rates. the initial hydrolysis step is slow and involves hydrolysis of the crystalline regions of the outer layer. microscopic observations carried out during the six-day hydrolysis showed that the size and morphology of starch grains remained virtually unchanged. due to the tight packing of the double helices, there is limited penetration of h3o+ ions in the crystalline regions. the second hydrolysis step corresponds to hydrolysis of amorphous regions. it proceeds quickly, leads to a noticeable loss of starch mass and a change in its morphology. in the first 24 hours of slow hydrolysis, the mass loss was about 10%, after 70– 84 hours of hydrolysis the mass loss was 70–80%. microscopic observations show that a significant part of the starch granules is deformed and split into pieces (figure 3b and 3c). table 1 index of crystallinity of native and hydrolyzed starch. type of samples ps hps-3 hps-6 crystallinity, % 47±2 59±2 66±2 figure 2 xrd patterns of native potato starch (ps), starch hydrolyzed for 3 days (hps-3) and for 6 days (hps-6). after three days of hydrolysis, many outer layered shells of granules, "ghost granules", are observed in the samples, which indicates their increased resistance compared to the inner layers. similar observations were made in earlier papers [11]. it is also worth noting that on the third day of hydrolysis, the samples contain particles of varying degrees of destruction, from whole spherical granules (outwardly close to native starch) to submicron particles. therefore, we hypothesize that native starch granules can vary greatly in their resistance to acid hydrolysis depending on their size and the presence of internal defects such as cracks and cavities [12]. the different reactivity of starch granules leads to the need to increase the hydrolysis time, which leads to low yields of nanoparticles [13]. a possible solution to this drawback may be the mechanical activation of starch grains at various stages of hydrolysis. figure 3 initial starch granules before hydrolysis (a), starch granules after 6 days of hydrolysis at different magnifications (b, c). chimica techno acta 2022, vol. 9(3), no. 20229313 letter 4 of 5 3.4. topochemical mechanism of starch granule hydrolysis the data, represented in micrographs in figure 4, help to understand the topochemical mechanism of starch grain hydrolysis. topochemistry is a branch of chemistry that studies solid-phase reactions occurring locally in certain areas of a solid [14]. the local nature of the reaction is due to the increased reactivity of the solid at a given site and to the large free volume, which ensures the mobility of the reactants and reaction products. starch grains consist of alternating amorphous and semi-crystalline layers. in amorphous areas of starch, consisting mainly of amylose, the necessary conditio ns for the topochemical development of reactions are fulfilled, at which the rate of hydrolysis in the center of the grain is so high as to observe empty and semi-empty grains consisting mainly of semi-crystalline shells and an empty core (figure 4b). in figure 4c, taken at a larger magnification, it can be seen that the outer shell, which in turn consists of thin crystalline and thin amorphous layers, is also subjected to hydrolysis by a topochemical mechanism. the outer layer is in turn composed of five to six layers of 100 to 200 nm in thickness and which, apparently, are crystalline lamellae consisting mainly of amylopectin molecules. with further advancement of the reaction zone tangentially to the outer shell, fragmentation of these thin lamellae begins, followed by their disintegration into nanoscale layers. first, these layers have strong anisotropy and are flat nanosized particles with characteristic dimensions of 100–200 nm by 3–8 m. the size of such particles is smaller than the size of blood cells, and they are of interest as adjuvants for vaccines against salmonellosis and mycoplasmosis. the pathogens of these diseases have a size of 0.7–7.0 m and, as experts believe, will be effectively absorbed on the surface of flat starch particles, and used for vaccination of animals and birds. with longer hydrolysis and ultrasonic processing, submicron plates of starch particles are destroyed and more isometric nanoparticles with a characteristic size of 20–200 nm are formed. 4. conclusions this work proposes a chemical-mechanical method for producing potato starch nanoparticles with controlled particle size. the study of the dynamics of hydrolysis of starch grains by electron scanning microscopy and laser granulometry made it possible to propose a topochemical mechanism of staged solid-phase hydrolysis, first to nanoscale plates with a characteristic size of 0.2–7.0 m, and then to more isometric nanoparticles with a characteristic size of 20–200 nm. this method enables obtaining adjuvants consisting of nanoparticles with a predetermined size. figure 4 starch granules after 6 days of hydrolysis at different magnifications (a, b, c). supplementary materials no supplementary materials are available. funding the research was funded within the state assignment to isscm sb ras (project no. 122011700261-3). acknowledgments none. author contributions writing – original draft: d.e.t., a.a.p. writing – review & editing: a.a.p., d.e.t. chimica techno acta 2022, vol. 9(3), no. 20229313 letter 5 of 5 conflict of interest the authors declare no conflict of interest. additional information author id: anatoly a. politov, scopus id 6603400773. websites: novosibirsk state technical university, https://en.nstu.ru; institute of solid state chemistry sb ras, http://www.solid.nsc.ru/en. references 1. yu l, liu x, petinakis e, dean k, bateman s. starch-based blends, composites and nanocomposites. royal soc chem. 2015:439. doi:10.1007/978-3-642-20940-6_4 2. chen g, wei m, chen j, huang j, dufresne a, chang pr. simultaneous reinforcing and toughening: new nanocomposites of waterborne polyurethane filled with low loading level of starch nanocrystals. polym. 2008;49:1860–1870. doi:10.1016/j.polymer.2008.02.020 3. garcıґa nl, ribba l, dufresne a, aranguren m, goyanes s. effect of glycerol on the morphology of nanocomposites made from thermoplastic starch and starch nanocrystals. carbohydr polym. 2011;84:203–210. doi:10.1016/j.carbpol.2010.11.024 4. han j, zhao d, li d, wang x, jin z, han kz. polymer-based nanomaterials and applications for vaccines and drugs. polym. 2018;10:31. doi:10.3390/polym10010031 5. gutjahr a, phelip 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https://doi.org/10.1016/j.polymer.2008.02.020 https://doi.org/10.1016/j.carbpol.2010.11.024 https://doi.org/10.3390/polym10010031 https://doi.org/10.3390/vaccines4040034 https://doi.org/10.1007/978-1-4615-1823-5_19 https://doi.org/10.1016/s1734-1140(12)70901-5 https://doi.org/10.1016/j.reactfunctpolym.2014.09.02 https://doi.org/10.1002/star.19830351202 https://doi.org/10.1016/j.ijbiomac.2020.01.028 https://doi.org/10.1002/masy.200550310 https://doi.org/10.1021/bm049914u https://doi.org/10.1016/0032-5910%2880%2987021-5 optical response of srtio3 thin films grown via a sol-gel-hydrothermal method published by ural federal university eissn 2411-1414 chimicatechnoacta.ru article 2023, vol. 10(1), no. 202310108 doi: 10.15826/chimtech.2023.10.1.08 1 of 6 optical response of srtio3 thin films grown via a sol-gel-hydrothermal method yulia eka putri a * , tio putra wendari a , restu aulia arham a, melvi muharmi a, dedi satria b , rahmayeni rahmayeni a , diana vanda wellia a a: department of chemistry, faculty of mathematics and natural sciences, andalas university, padang 25163, indonesia b: department of pharmacy, muhammadiyah university of sumatera barat, padang 25172, indonesia * corresponding author: yuliaekaputri@sci.unand.ac.id this paper belongs to a regular issue. abstract the polycrystalline srtio3 thin films were prepared by the sol-gel-hydrothermal method on glass substrates. the synthesis pathway was initiated by preparing a clear tio2 solution using the sol-gel method. this clear solution was then deposited on a glass substrate using the dip coating technique, followed by the transformation of a thin layer of tio 2 into srtio3 by the hydrothermal method. the crystal structure, bond interactions, and band gap energy of srtio3 thin layers were characterized using x-ray diffraction (xrd), fourier transform infra-red spectroscopy (ftir), and uv–vis diffuse reflectance spectroscopy (uv-drs). the xrd patterns of all srtio3 thin layers indicated the perovskite structure of the samples. the ftir spectrum showed an interaction of the silanol groups on the surface of the glass substrate with ti–o–ti of srtio3 layers. the characteristics of the uv-drs spectrum were influenced by the thickness of the srtio3 layer formed on the glass substrate. the findings of this work provide insights for producing srtio3 layers with specified thickness and morphology. keywords srtio3 thin film perovskite hydrothermal optical properties received: 18.12.22 revised: 12.01.23 accepted: 16.01.23 available online: 23.01.23 key findings ● srtio3 thin films were synthesized using the sol-gel-hydrothermal method. ● the hydrothermal synthesis time affected the purity of the srtio3 thin film. ● the optical bandgap of srtio3 was influenced by the specified thickness of the samples. © 2022, the authors. this article is published in open access under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). 1. introduction two-dimensional (2-dimensional/2d) nanomaterials in the form of thin layers have attracted significant attention because of the successful isolation of graphene into sheet forms. thin films are currently employed in various fields to develop their capabilities [1]. 2d materials have several advantages, such as having layers with a thin atomic-scale arrangement, large surface area, strong mechanical properties, and good electrical and thermal conductivities [2]. this is the main attraction for preparing 2d nanomaterials with good physical and chemical properties and using them in various applications [3]. metal oxide-based perovskite structures are an important and attractive class because of their wide application range. the strontium titanate (srtio3) semiconductor compound has a typical metal oxide perovskite structure with the pm3m space group of at room temperature. inside the perovskite structure, sr2+ ions are in the corners and ti4+ ions in the centers of the cube, while o2– anions surround ti4+ ions to form a regular octahedron in the cubic symmetry. each sr2+ ion is surrounded by four tio6 octahedra and coordinated by twelve o2– ions, whereas the ti4+ ion is sixfold coordinated by the o2– ion [4]. in the tio6 octahedra, the hybridization of the o-2p state with the ti-3d state results in a pronounced covalent bonding, whereas the sr2+ and o2– ions exhibit ionic bonding characteristics. therefore, srtio3 has mixed ionic-covalent bonding properties [5]. this type of chemical bonding leads to a unique structure, which can be a http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2023.10.1.08 mailto:yuliaekaputri@sci.unand.ac.id http://creativecommons.org/licenses/by/4.0/ http://orcid.org/0000-0003-2610-3780 https://orcid.org/0000-0002-3600-0905 http://orcid.org/0000-0002-5568-8426 http://orcid.org/0000-0003-2569-9914 http://orcid.org/0000-0002-8694-1308 https://crossmark.crossref.org/dialog/?doi=https://doi.org/10.15826/chimtech.2023.10.1.08&domain=pdf&date_stamp=2023-01-23 chimica techno acta 2023, vol. 10(1), no. 202310108 article 2 of 6 doi: 10.15826/chimtech.2023.10.1.08 model for electronic materials. in an ideal srtio 3 perovskite structure, there is a flexible ionic arrangement making it easy to modify. so, the structural instability creates new properties and improves the optical and electrical properties [6]. srtio3 thin films are amongthe perovskite oxides with various advantages, including catalytic activities [7], electrical and dielectric properties [8], ferroelectric properties [9], and a possibility of using them as lattice-matched substrates for high-tc oxide superconductors [10]. one of the strategies to improve its promising properties is the thin film fabrication techniques. several thin film growth technique have been reported, such as sputtering [11], solgel [12], pulsed laser ablation [13], and chemical vapor deposition [14]. on the other hand, substrate selection is crucial because the substrate greatly affects the quality of the film. glass, fluorine-doped tin oxide (fto), indiumdoped tin oxide (ito), silicon, and metal substrates have been used to fabricate srtio3 thin films [15]. this work adopted a two-stage sol-gel-hydrothermal technique to deposit srtio3 thin films on the glass substrate. the first stage was depositing a tio2 layer on a glass substrate. then the second stage was the conversion of the tio2 thin film into srtio3 on the same substrate. synthesis of tio2 was performed by the sol-gel method. tio2 was deposited on the glass substrate by the dip coating method. afterward, the srtio3 layer was formed by the hydrothermal method. in forming srtio3 thin films using the hydrothermal method, the effect of sr(oh)2·8h2o concentration on the structure and the optical response was identified by varying the concentration of sr(oh)2·8h2o precursor solution. then, x-ray diffraction (xrd) was utilized to analyze the structure and crystallinity of the synthesized sample. difuse-reflectance ultra violet visible (drs uv-vis) and fourier transform infra-red (ftir) spectroscopy methods were also employed to determine optical properties by calculating band gap values and the interaction between the synthesized compound and the glass substrate, respectively. 2. materials and method 2.1. chemicals the materials used in this study were titanium tetrachloride (ticl4) (sigma-aldrich 0.09 m in 20% hcl), ammonium hydroxide (nh4oh) (pudac scientific 25%), hydrogen peroxide (h2o2) (merck 30%), distilled water, ethanol (c2h5oh) (merck ≥ 97.5%), silver nitrate (agno3) (sigmaaldrich), strontium hydroxide octahydrate (sr(oh)2·8h2o) (sigma-aldrich), ice cube, and commercially available glass substrates (76.2 mm × 25.4 mm × 1 mm). 2.2. instrumentation the tools used in this study were glassware, analytical scales, pipettes, stirring rods, spatulas, ph paper, ice baths, magnetic stirrer (ika c-mag hs 7), oven, autoclaves, teflon vessel, xrd diffractometer panalytical x'pert pro, drs uvvis spectrometer specord 210 plus analytic jena, and ftir (fourier transform infra-red spectrometer) shimadzu-ir prestige 21. 2.3. synthesis of tio2 gel precursor the tio2 gel precursor solution was synthesized by dropwise addition of 36 ml ticl4 into 300 ml of distilled water in an ice water bath while stirring using a magnetic stirrer for 30 min. then, the 25% nh4oh solution was added dropwise to adjust the ph of the solution to 7 under stirring for 24 h. the solution was then centrifuged to separate the precipitate and filtrate. the resulting precipitate was washed using distilled water until no cl– ions remained. the presence of cl– ions remaining in the solution was detected by adding agno3 solution to the remaining washing water until no white precipitate of agcl was formed. 80 ml of distilled water and 28 ml of h2o2 were added to the white free of cl– precipitate dropwise while stirring using a magnetic stirrer. the mixed solution was then stirred for 4 h until a transparent yellow solution was formed. the color was because of the tio2 gel precursor [16]. 2.4. deposition of tio2 thin films on glass substrate the used glass substrate was commercial glass with the size of 76.2 mm × 25.4 mm × 1 mm. 4 preparatory glass sheets were cleaned using the ultrasonication method in distilled water, acetone, isopropanol, and ethanol, for 15 min in each. the clean glass was dried at room temperature. then, the tio2 layer was deposited on the glass substrate using the dip coating method. the glass substrate was dipped for 30 s into the tio2 gel precursor and then withdrawn with a withdrawal speed of 0.1 cm/s. afterward, it was dried for 5 min at 100 °c. this procedure was repeated 5 times to achieve several nanolayers of tio2. after that, the tio2-coated glass substrate was further dried for 1 h at 120 °c and labeled toft. next, a sheet of toft sample was calcined at 500 °c and cooled by normal cooling for 1 h to ensure the formation of tio2 on the glass substrate. this calcined toft sample was labeled tofk. 2.5. transformation of tio2 thin films into srtio3 thin films the transformation of the tio2 thin layer sample into srtio3 was conducted by preparing a strontium solution, sr(oh)2·8h2o, with varying concentrations of 25 mm, 50 mm, and 75 mm. then, the solution was placed into the autoclave teflon vessel; the glass substrate coated with tio2 thin films was placed in a vertical position. the hydrothermal process was conducted at 150 °c for 3 h. after the hydrothermal process was completed, the thin film on the glass substrate was removed from the autoclave and calcined at 600 °c for 30 min. the synthesized srtio3 thin films were labeled stof-25, stof-50, and stof-75. https://doi.org/10.15826/chimtech.2023.10.1.08 chimica techno acta 2023, vol. 10(1), no. 202310108 article 3 of 6 doi: 10.15826/chimtech.2023.10.1.08 3. results and discussion the srtio3 thin films were synthesized in-situ using two methods. firstly, the tio2 precursors were synthesized using the sol-gel method and then deposited on a glass substrate using the dip-coating method. secondly, the srtio3 thin films were synthesized using the hydrothermal method through the diffusion of sr2+ on the tio2 layer. the resulting srtio3 thin film product is a layer that grows evenly on the substrate with good transparency because the color of the glass substrate coated with srtio3 is not much different from that of the glass substrate. the differences in the physical shapes of the glass substrate, the tio2 thin layer, and the srtio3 thin layer are shown in figure 1. this image shows the changes that occurred in the coating process. it can be seen that the glass substrate coated with the tio2 thin layer still looks transparent (figure 1b). however, after being coated with srtio3, all samples of the srtio3 film appear slightly opaque (translucent) (figure 1d, e, f). the tio2 layer synthesized by the sol-gel method was in an amorphous form. therefore, a sintering process was conducted to ensure the formation of crystalline tio2. tio2 in the amorphous phase can be altered into a crystalline phase by the sintering process. so, the crystalline tio2 was characterized by xrd to determine its crystal structure, as shown in figure 2. the toft xrd pattern shows that this thin layer is amorphous because no specific peaks appear. however, the tofk sample showed diffraction peaks at the 2θ values of 25.2°, 47.8°, and 54.9° indexed as (101), (200), and (105). these diffraction peaks correspond to the anatase tio2 phase based on the icsd standard no. 9855 [17]. this proves that the thin film tio2 synthesized by the solgel method was successfully formed as a tio2 gel. therefore, it can be used as a precursor for synthesizing srtio3. furthermore, the srtio3 thin layer samples synthesized by the hydrothermal method were characterized by xrd. the diffraction patterns are shown in figure 3. the xrd patterns show that the stof-50 and stof-75 samples exhibited srtio3 diffraction peaks. meanwhile, stof-25 samples did not show any srtio3 diffraction peaks with only srco3 diffraction peaks as impurities. figure 1 physical appearance of glass substrate (a), tio2 thin film (b), srtio3 thin film (c), stof-25 (d), stof-50 (e), stof-75 (f). the absence of srtio3 in the stof-25 is due to the lower concentration of sr2+ than the amount sufficient for the stoichiometric formation of srtio3. meanwhile, the presence of diffraction peaks in the plane (110) for the stof-50 and stof-75 samples indicates that srtio3 formed on the surface of the glass substrate. the shift of plane (110) towards smaller 2θ can be caused by several factors, such as (1) lattice strain, (2) sintering process at high temperature, and (3) mismatch of thermal expansion between the srtio3 compound and the used glass substrate [18]. also, the emergence of srco3 diffraction peaks is due to the possible reaction of the dissolved co2 in the autoclave with the sr2+ ions during the synthesis. this is due to the interaction between sr2+ and the dissolved co2 in the aqueous solution. theoretically, hydrated alkaline earth solutions ((sroh)2·8h2o) have a high solubility in the presence of carbonate ions (co32–) because the solution is alkaline. 20 30 40 50 60 (b)(1 0 5 ) (2 0 0 ) in te n si ty ( a .u .) 2 () (1 0 1 ) tio 2 (icsd-9855) (a) 24 26 figure 2 xrd patterns of tio2 thin films before sintering (toft) (a) and tio2 thin films after sintering (tofk) (b). 20 30 40 50 60 30 33 * . . * * * * * * std. srco 3in te n si ty ( a .u .) 2 () (a) (b) (c) std. srtio 3 * . srtio3 srco3 figure 3 xrd pattern of srtio3 thin films: stof-25 (a), stof-50 (b) and stof-75 (c). https://doi.org/10.15826/chimtech.2023.10.1.08 chimica techno acta 2023, vol. 10(1), no. 202310108 article 4 of 6 doi: 10.15826/chimtech.2023.10.1.08 then, water absorption also causes the strontium to become more alkaline. so, the sr2+ ions are likely to combine with oh– ions to form sroh+ and absorb co2 in the autoclave during the hydrothermal process. the absorbed co2 is then converted to co32– and reacts with hydrated strontium to form srco3 impurities [19]. functional group analysis using ftir aims to determine the presence of interactions in the successfully synthesized stof-50 and stof-75 samples. figure 4 shows the ftir spectrum of the glass substrate and the synthesized samples in the wave number range of 400– 1600 cm–1. the obtained spectra for the glass substrate and the stof-50 and stof-75 samples show specific peaks of their functional groups. the ftir spectrum of the glass substrate showed the presence of the si–o stretching vibration of the silanol (si–oh) group at the wave number of 917 cm–1 [20], and the stretching vibration of si–o in the siloxane (si–o–si) group at the wave number of 766 cm–1 [21]. the silanol stretching vibrations were also observed in the spectrum of stof-50 and stof-75 samples; however, these peaks shifted to the wavenumber of 903 cm–1 (stof-50) and 892 cm–1 (stof-75). the shift in the wave number of silanol functional groups is due to the strong interaction between the surface of the glass substrate through the silanol present in the surface glass with ti–o–ti present in the srtio3 compound. the intense interaction results in the formation of new chemical bonds through the terminal groups si–o–h with ti–o–ti to produce si–o–ti along the surface of the glass substrate and srtio3 film. the formation of si– o–ti is further strengthened by changes in the intensity of the ftir spectrum by weakening the silanol peaks in stof50 samples and stof-75, indicating a stronger si–o–ti bond. furthermore, the appearance of a new peak at a wavenumber of 478 cm–1 in the stof-50 and stof-75 spectrum refers to the ti–o stretching vibration of the ti–o–ti of tio6 octahedral in the srtio3 compound [22]. 1600 1400 1200 1000 800 600 400 500 400 t io (b) t r a n sm it ta n c e ( % ) wavenumber (cm -1 ) (a) (c) s io -s i s io t io figure 4 ftir spectrum of glass substrate (a), stof-50 (b) and stof-75 (c). drs uv-vis analysis was performed to analyze the optical properties of the stof-50 and stof-75 samples based on the band gap energy values, as shown in figure 5a. both samples demonstrate a good absorbance in uv light at around 325 nm and a weak absorbance in visible light. the stof-75 sample shows a higher peak intensity than the stof-50 sample. these results show that the absorbance value is directly proportional to the srtio3 concentration on the glass substrate, as the absorbance of the stof-75 is greater than that of stof-50 [23]. the obtained band gap for each sample was calculated using the tauc-mott (mt) method from the uv-drs absorption spectrum, according to the following equation: (𝛼h𝑣)2 = a(h𝑣 − 𝐸𝑔), (1) where a is the side width parameter, 𝛼 is the absorption coefficient, h is plank's constant (j·s), and eg is the bandgap energy (ev). figure 5b shows the optical band gap energy of the samples using tauc plots of the stof-50 and stof-75 thin film samples at 2.50 ev and 3.58 ev, respectively. the difference in these values is due to the presence of impurities in the sample, as confirmed by the xrd pattern, and the thickness of the thin layer, known from the absorption of the uv-drs spectrum. 300 350 400 450 500 0.0 0.2 0.4 0.6 0.8 1.0 1.2 a b so r b a n c e ( a .u .) wavelength (nm) stof-75 stof-50 (a) 1.0 1.5 2.0 2.5 3.0 3.5 4.0 0 10 20 30 40 50 (b) h (ev) ( h  )2 stof-75 stof-50 2.5 ev 3.58 ev figure 5 uv-vis spectrum of srtio3 thin films (a) and optical band gap energy (b). https://doi.org/10.15826/chimtech.2023.10.1.08 chimica techno acta 2023, vol. 10(1), no. 202310108 article 5 of 6 doi: 10.15826/chimtech.2023.10.1.08 according to the xrd pattern and uv-drs spectrum, it is known that the stof-75 sample contains srco3 impurities, and its absorption is greater than that of the stof-50 sample. therefore, the band gap energy value of the stof-75 sample is greater than that of the stof-50 [15]. 4. limitations in this study, srtio3 thin films were not single-phase because srco3 was found as an impurity. so, the crystallinity of the samples remained low. therefore, future research will focus on forming single-phase srtio3 thin films by adjusting several hydrothermal synthesis parameters, such as variations in temperature, time, and the concentration of the starting material. 5. conclusions srtio3 thin films were synthesized using the sol-gel-hydrothermal method. the concentration of sr2+ in the solution affected the growth of srtio3 on a glass substrate, where the stof-50 and stof-75 formed a thin layer of srtio3. however, the presence of srtio3 was not found in the stof-25 because the strontium solution concentration was insufficient. the ftir spectrum showed an interaction between the glass substrate and srtio3 with the appearance of silanol groups. the stof-50 and stof-75 samples had a good absorbance in uv light and a very weak absorbance in visible light with band gap values of 2.50 ev and 3.58 ev, respectively. ● supplementary materials no supplementary materials are available. ● funding the author would like to thank the faculty of mathematics and natural sciences, universitas andalas, through the pnbp fund research grant no.16/un.16.03.d/pp/fmipa/2021. ● acknowledgments none. ● author contributions conceptualization: y.e.p. visualization: t.p.w. investigation: r.a.a., m.m. methodology: y.e.p., d.v.w. supervision: r.r., d.v.w. writing – original draft: y.e.p. writing – review & editing: d.s. ● conflict of interest the authors declare no conflict of interest. ● additional information author ids: yulia eka putri, scopus id 55261197300; tio putra wendari, scopus id 57208920083; dedi satria, scopus id 57200695552; rahmayeni rahmayeni, scopus id 55544632300; diana vanda wellia, scopus id 35363286300. websites: andalas university, https://www.unand.ac.id; muhammadiyah 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jaglarz j, zięba p, kanak j, żukowski w. photocatalytic methylene blue degradation on multilayer transparent tio2 coatings. opt mater (amst). 2019;90:264– 272. doi:10.1016/j.optmat.2019.02.041 https://doi.org/10.15826/chimtech.2023.10.1.08 https://doi.org/10.1007/s00339-022-05805-5 https://doi.org/10.1016/j.apsusc.2017.12.063 https://doi.org/10.1016/j.apsusc.2018.11.200 https://doi.org/10.1002/slct.201904153 https://doi.org/10.1088/2053-1591/aae4d0 https://doi.org/10.1126/sciadv.aao5616 https://doi.org/10.1038/s41598-021-82651-0 https://doi.org/10.1016/j.dental.2019.05.002 https://doi.org/10.1016/j.jnoncrysol.2009.01.010 https://doi.org/10.1007/s10854-016-6018-8 https://doi.org/10.1016/j.optmat.2019.02.041 synthesis and performance evaluation of polymeric surfactant from rice husk and polyethylene glycol for the enhanced oil recovery process published by ural federal university eissn 2411-1414; chimicatechnoacta.ru article 2022, vol. 9(4), no. 20229406 doi: 10.15826/chimtech.2022.9.4.06 1 of 9 synthesis and performance evaluation of polymeric surfactant from rice husk and polyethylene glycol for the enhanced oil recovery process slamet priyanto, ronny w. sudrajat, suherman suherman * , bambang pramudono, teguh riyanto , desty d. setianingrum, alfin a. pratama department of chemical engineering, universitas diponegoro, semarang 50275, indonesia * corresponding author: suherman.mz@che.undip.ac.id this paper belongs to a regular issue. © 2022, the authors. this article is published in open access under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). abstract a tertiary recovery technique is needed to recover the remained oil in the oil field after primary and secondary recoveries, which can only recover approximately 30–50% of the total oil. this study investigated the synthesized polymeric surfactants from rice husk and polyethylene glycol (peg) for the enhanced oil recovery (eor) process as a tertiary recovery technique. the rice husk was used as sodium lignosulfonate (sls) surfactant production feedstock. sls-peg polymer surfactant from rice husk has not been widely studied, especially for the eor process. this study has comprehensively investigated the effect of peg concentration on the polymeric surfactant properties. the surfactants were characterized using fourier transform-infrared (ftir) analysis. several other tests were also conducted, including surfactant compatibility, viscosity, thermal stability, interfacial tension (ift), and phase behavior. it was found that the peg introduction to the sls surfactant could increase the hydrophilic property of the polymeric surfactant due to the presence of the c−o−c group. in addition, the ift value decreased with the increase in the peg concentration due to the increase in the hydrophilic property. however, the ift value decreased when the peg concentration was too high. the lowest ift value was obtained at the sls to peg ratio of 1:0.8. it produced the highest increase in the additional recovered oil after brine flooding. the results showed that the rice husk, which is agricultural waste, could be utilized as a feedstock for the surfactant production. keywords polymeric surfactant rice husk sodium lignosulfonate polyethylene glycol enhanced oil recovery received: 01.07.22 revised: 08.07.22 accepted: 08.07.22 available online: 12.07.22 1. introduction with the increase in the human population energy consumption tends to increase. in addition, the main resource supplying the energy demand in the world is fossil-based fuel. therefore, exploitation of oil fields is going to increase. however, the primary recovery can only recover approximately 10% of the total oil and the secondary recovery can give an additional 20–40% [1]. it means that around 50–70% of the original oil remains in the oil field after both primary and secondary recoveries. therefore, a tertiary recovery technique is required to retrieve the oil left in the oil field. one of the methods that can be used is the enhanced oil recovery (eor) process, including thermal, chemical, gas flooding, and microbial eor [2]. these methods cannot be applied to the same reservoir because of the different processes and the different characteristics of the extracted oil. however, due to the low-cost process, one of the most developed eor processes is the chemical injection or ceor [2, 3]. the injected chemical is a surfactant which can reduce the interfacial tension (ift). ift is the tendency of a liquid to possess a minimum free surface when it is in contact with another immiscible liquid [4]. therefore, the primary requirement for the surfactant in the eor process is the lowest ift [5]. the surfactant injected into the oil reservoir will reduce the ift of the oil water, which will then reduce the capillary pressure so that the oil left after the water-flooding process can be taken up. http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2022.9.4.06 mailto:suherman.mz@che.undip.ac.id http://creativecommons.org/licenses/by/4.0/ https://orcid.org/0000-0002-3055-0295 https://orcid.org/0000-0002-3553-4219 https://crossmark.crossref.org/dialog/?doi=https://doi.org/10.15826/chimtech.2022.9.4.06&domain=pdf&date_stamp=2022-7-12 chimica techno acta 2022, vol. 9(4), no. 20229406 article 2 of 9 an ionic surfactant such as sodium lignosulfonate (sls) is the most developed lignin-based surfactant which can be applied for the eor process. sls molecule has the hydrophobic and hydrophilic parts, which are associated with the aromatic skeleton and sulfonate group, respectively [6]. pramudono and co-workers [3, 7–9] have intensively developed sls surfactants for the eor process from biomassbased lignin. priyanto et al. [9] synthesized sls from black liquor for the eor process. they reported that the sls surfactant could decrease the ift value of oil and water up to 0.0254 dyne/cm at an sls concentration of 0.5%wt in a brine solution of 3000 ppm. previously, priyanto et al. [10] have also studied the hydrodynamic of the eor process using the sls surfactant from black liquor. even though the sls surfactant has a high performance to reduce the ift value of oil-water, some disadvantages, such as intolerance to a high brine solution, easy adsorbance by the stone during the eor process, and high sensitivity to divalent ions, make sls less appropriate for the eor process [3, 11]. therefore, some modifications should be done to improve the characteristics and performance of the sls surfactant. modifications of the sls surfactant can be conducted through the addition of a nonionic polymeric surfactant, such as polyethylene glycol (peg). nonionic surfactants are much more tolerant of high salinity [12]. in addition, the main advantage of a polymeric surfactant is that, in addition to the ift reduction, it also increases the viscosity of the solution, which is very important for enhanced sweep efficiency in enhanced oil recovery [13]. however, if the viscosity of the surfactant is too high, it can block the reservoir; conversely, if the viscosity of the surfactant is too low, mobility is not appropriate [14]. yin and zhao [15] have studied the effect of viscosity and interfacial tension on oil recovery in the heterogeneous reservoir and determined the main controlling factors of the polymer-surfactant (sp) flooding. they reported that a higher polymer concentration could increase the surfactant viscosity. to the best of our knowledge, research on synthesizing sls-peg polymer surfactants from rice husk has not been performed and published. the research that has been done is to produce sls surfactant from rice husk [16]. referring to this fact, it was necessary to conduct a study on the synthesis of the sls-peg polymer surfactant. some characterization tests were carried out to determine the character of the polymer surfactant obtained and a core flooding test to determine the amount of the recovered oil using the sls-peg polymeric surfactant. the effect of peg concentration in the polymeric surfactant on surfactant characteristics was also comprehensively studied. this study discovered the potential of rice husk, which is a waste, as a feedstock for the low-price and highperformance surfactants production for the eor process. 2. materials and methods 2.1. materials the sodium lignosulfonate surfactant was synthesized from rice husk which was obtained from purwokerto, central java, indonesia. the other raw material of the polymeric surfactant was polyethylene glycol with a molecular weight of 400 (peg-400). the other chemicals which were used in this study were brine, hydrogen peroxide (h2o2), sodium bisulfite (nahso3) (merck), sodium hydroxide (naoh) (merck), sulfuric acid (h2so4) (mallinckrodt), methanol, ammonium persulfate, and demineralized water which was obtained from the integrated laboratory of universitas diponegoro, semarang, central java. in order to assess the performance of the surfactant in the eor process, kawengan oil from stem akamigas cepu, indonesia, was used as the raw oil. 2.2. lignin isolation from rice husk the isolation process of lignin from rice husk followed the method by ma’ruf et al. [17], who isolated lignin from rice husk using alkaline hydrogen peroxide solution. about 20 g of dried rice husk (dried at 50 °c for 6 h) was immersed in 120 ml of demineralized water, which contained 1% h2o2 (volume/weight ratio of 1:6). the ph of the suspension was maintained at 10.5 using naoh solution with a concentration of 2 m. furthermore, the suspension was heated to 100 °c and stirred (250 rpm) for 2 h. the suspension was then filtered and the obtained lignin was dried at 45 °c for 24 h. 2.3. synthesis of sodium lignosulfonate and polymeric surfactant the sls surfactant synthesis followed the priyanto et al. method [18]. approximately 3 g of lignin obtained from section 2.2 was immersed in 90 ml of demineralized water. sodium bisulfite (1 ml) was then added to the mixture. the ph was adjusted to 8.3 using naoh 1 m. the sulfonation process was conducted for 2 h at 80 °c. after the sulfonation process, the mixture was then evaporated at 100 °c to obtain a black sludge. the sludge was filtered using a büchner funnel which was equipped with a vacuum pump. the obtained sls surfactant was then used to synthesize sls-peg polymeric surfactants. the sls-peg polymeric surfactants were synthesized using the sls surfactant, peg and ammonium persulfate, following the method by priyanto et al. [3]. the sls to peg ratios were 1:0.5, 1:0.8, and 1:1. afterwards, the synthesized polymeric surfactants were denoted as sls-0.5peg, sls-0.8peg, and sls-1.0peg, respectively. sls was dissolved in 80 ml of demineralized water, peg was dissolved in 10 ml of demineralized water, and ammonium persulfate was dissolved in 10 ml of demineralized water. the sls and peg solutions were put into a three-neck flask and heated to a temperature of 70 °c with a stirring speed of 300 rpm. after the temperature was reached, the ammonium persulfate solution was then put in a three-neck flask to react with the polymeric surfactant. the reaction was carried out for 2 h. the product of this reaction was extracted using acetone and then put into the oven for 12 h before characterization tests. chimica techno acta 2022, vol. 9(4), no. 20229406 article 3 of 9 2.4. characterization methods the obtained surfactants were characterized using fourier transform-infrared (ft-ir) analysis to determine their functional groups. ft-ir spectra were scanned using a perkin-elmer infrared spectrophotometer in the wavenumber range of 4000–400 cm−1. the other characterization tests were also conducted, including surfactant compatibility, viscosity, thermal stability, ift, and phase behavior, before using the surfactants in the eor process performance test. prior to the characterization with the previously mentioned tests, the surfactant, with 0.1%wt concentration, was dissolved in 5000 ppm of brine solution. the compatibility test was conducted for 28 days. in addition, the thermal stability test was also conducted for the same period of time at 70 °c, which is the reservoir temperature. the density of the polymeric surfactant was periodically measured. the viscosity test was conducted using the ostwald viscometer. the ift measurement was conducted using the spinning drop interfacial tensiometer at 70 °c [10]. the phase behavior test was carried out in a tube test which consists of oil and brine solution (injection water) consisting of 0.1 wt.% of surfactants. the volumetric ratio of oil and brine solution was 1:1. the mixture was then shaken and heated to the reservoir temperature (70 °c) for 28 days. 2.5. core flooding test the core flooding test was undertaken according to the previous study [10] using the experimental rig as shown in figure 1. this test requires rock, brine solution, oil, and 0.1%wt polymeric surfactant. this study uses kawengan oil, a heavy crude oil with a density of 0.96 g/cm3, as the oil for the eor process. the brine solution was in a concentration of 5000 ppm. filters are placed at both ends of the core holder to prevent rocks from clogging the pipe from the core holder. the size of the silica sandstone was 100 mesh with a 150-mesh filter. the performance tests were carried out at 70 °c. 3. results and discussion 3.1. fourier transform infrared spectroscopy analysis of surfactants the synthesized surfactants from rice husk and peg were characterized using ft-ir analysis. this analysis was conducted to investigate the functional groups in the synthesized polymeric surfactants. the infrared spectra were recorded at a wavenumber of 4000–400 cm−1. figure 2 shows the infrared spectra of the synthesized surfactants. as shown in figure 2, the broad intense peak between 3600–3200 cm−1 was found in all surfactants. this peak corresponds to the hydroxy group stretches [3]. the hydroxy group stretches could be found in the form of intramolecular and intermolecular hydrogen bonds of o−h, which appear at a wave number of ~3550 cm−1 and ~3400 cm−1, respectively [19]. the peak at ~2925 cm−1 is attributed to the stretching vibration of methyl (−ch3). the peak at ~2850 cm−1 corresponds to the c−h stretching of methylene (−ch2−). the peak at ~2850 cm−1 seems to increase as the peg concentration increases. it is because the peg has more methylene groups than sls. therefore, the addition of peg could increase the methylene group in the synthesized polymeric surfactants. in the sls surfactant, the sulfonate group can be found at wavenumbers of ~1180 cm−1, ~1137 cm−1, ~1042 cm−1, and ~644 cm−1, which are assigned to the symmetric stretch vibration of o=s=o, asymmetric stretch vibration of o=s=o, s−o stretch, and s−o band, respectively [17, 20, 21]. in addition, the aromatic ring from the sls surfactant molecules can also be detected using the ft-ir analysis. the c=c vibration of an aromatic ring is found at a wavenumber of ~1608 cm−1. in addition, the c−h stretch from an aromatic ring is found at ~1512 cm−1 [21, 22]. figure 1 scematic diagram of the experimental rig for the eor process. 1. compressor 5. oil 9. heater 13. thermometer 2. temperature indicator 6. brine 10. input cone 14. core 3. heating indicator 7. output valve 11. manometer 15. output 4. surfactant 8. air valve 12. oven 16. measuring cup chimica techno acta 2022, vol. 9(4), no. 20229406 article 4 of 9 figure 2 ftir analysis of sls (a), sls-0.5peg (b), sls-0.8peg (c) and sls-1.0peg (d). (a) (b) (c) (d) chimica techno acta 2022, vol. 9(4), no. 20229406 article 5 of 9 after the peg introduction, some new peaks are found in the synthesized polymeric surfactants. the scissoring vibration of two o−h from water molecules appears at a wavenumber of ~1632 cm−1, followed by a peak at ~1350 cm−1, which is assigned to the in-plane o−h deformation. the ether group of peg is found, which is pointed by the appearance of intense peaks at ~1210 cm−1 and ~1100 cm−1. these peaks correspond to the asymmetric and symmetric stretching vibration of c−o−c, respectively [21]. the new peak at ~950 cm−1 is assigned to the c−c skeletal stretching vibration [23] or c−h deformation [24]. 3.2. compatibility test of surfactants the compatibility test was conducted to investigate the behavior of the surfactant in the brine solution and whether it can be dissolved or not. in this study, 0.1 wt.% of surfactant was dissolved in a 5000 ppm brine solution. a good surfactant will be dissolved in the brine solution. dasilva et al. [7] reported that a surfactant is compatible or good if it can be completely mixed with the brine solution without any precipitates. therefore, a completely dissolved surfactant in the brine solution is desired because the suspension is not allowed. during the eor process, a suspended surfactant should be because it can clog the pore of the rock during the eor process when it is injected [3, 25]. in this study, the compatibility test was conducted for 28 days. figure 3 shows the appearance of the surfactant in the brine solution on day-0 and day-28. as can be seen, no precipitation was observed during the compatibility test even on day-28. it verifies that the polymeric surfactant of sls from rice husk and peg is highly soluble in the brine solution. it is speculated that the high solubility of the surfactant is caused by the presence of ether group (c−o−c) in the peg structure and the hydrophilic nature of the sls surfactant. the interaction between the ether group with water molecules allows the surfactant to be dissolved in the brine solution. it was reported that the water molecules could bind with oxygen in the ether group through the hydrogen bonding interaction [3, 26]. in addition, the hydrophilic nature of sls also affects the solubility of surfactants in the brine solution. the sls surfactant has a short chain molecular structure, allowing sls to be easily dissolved in the brine solution [27]. figure 3 surfactant appearance on day-0 and day-28 during the compatibility test. table 1 viscosity, density, and ift value of the polymeric surfactants. polymeric surfactant viscosity (centipoise) density (g/cm3) ift (dyne/cm) sls 0.835 0.992 1.012 sls-0.5peg 0.839 0.993 0.427 sls-0.8peg 0.841 0.995 0.386 sls-1.0peg 0.854 0.998 0.622 on the other hand, sls has negative charges on its hydrophilic part. it is known that the hydrophilic part of sls surfactant consists of the sulfonate structure (−so3−) and its salt (naso3) [28, 29]. the presence of the negative charges in the hydrophilic part makes sls an anionic surfactant which is water-soluble [25]. therefore, the presence of ether group (c−o−c) from peg and negative charges from sls makes the polymeric surfactant more soluble. 3.3. viscosity test of surfactants the viscosity of the surfactant is one of the important parameters in the eor process. it was reported that a high surfactant viscosity is needed in the eor process. surfactants with high viscosity can enhance or increase oil recovery due to their ability to reduce oil-water mobility [14, 15]. even though a viscous surfactant can enhance or increase the oil recovery in the eor process, it may block the pore of rock [3]. therefore, the viscosity of the surfactant should be controlled. the viscosity of the surfactants is presented in table 1. as can be seen in table 1, the viscosity of the sls surfactant is 0.835 centipoise. furthermore, it can be observed that the viscosity of the surfactant increases after the addition of peg. it is also shown that the viscosity of the surfactant linearly increases with the peg amount in the polymeric surfactant. therefore, it is reasonable to conclude that the viscosity of the surfactant can be increased and controlled by controlling the peg concentration (ratio of sls to peg) in the polymeric surfactant. the increase in the viscosity of the polymeric surfactant after peg addition can be caused by the fact that peg is a viscous material. therefore, the addition of peg will indeed increase the viscosity of the polymeric surfactant. this finding is in accordance with some previous reports [3, 8]. priyanto et al. [3] and sudrajat et al. [8] reported that the viscosity of the sls surfactant, which was synthesized from black liquor, can be increased by the addition of peg. in addition, alli et al. [30] also reported that the viscosity of the injecting brine could be increased by adding peg as a polymer. 3.4. thermal stability test of surfactants the thermal stability test was conducted for 28 days at 70 °c. the temperature of 70 °c was chosen because it is the temperature of the reservoir. this test was conducted to investigate the effect of heat on the surfactant stability. the desired surfactant is a stable surfactant without any agglomerate being formed. as reported, sulfonate-type surfactants tend to create agglomerate or precipitate at high s l s -1 .0 p e g s l s -0 .8 p e g s l s -0 .5 p e g s l s -1 .0 p e g s l s -0 .8 p e g s l s -0 .5 p e g day-0 day-28 chimica techno acta 2022, vol. 9(4), no. 20229406 article 6 of 9 temperatures because they are sensitive to divalent ions [11]. density is the observed parameter during this thermal stability test. the change in the surfactants' density is presented in figure 4. as can be seen in figure 4, the density of 0.1 wt.% surfactants in 5000 ppm brine at all peg concentrations was stable. after 28 days of observation, the density of all surfactants is relatively unchanged. it can be concluded that the synthesized from rice husk polymeric surfactant is stable in the brine solution. as expected, this thermal stability test found no precipitates or agglomerates in the surfactant solution. it confirms that this polymeric surfactant is stable at 70 °c. moreover, it shows that rice husk can be utilized as a raw material for the stable polymeric surfactant production. as was explained before, the synthesized polymeric surfactants are stable at 70 °c as the densities of the surfactants are constant during the test and as no precipitates or agglomerates were found. it is possibly caused by the fact that the surfactants have a high solubility. this solubility comes from the ether group of peg (c−o−c) and the negative charges in the sls surfactant in the form of sulfonate structure (−so3−) and its salt (naso3). it was reported that interaction between water molecules and oxygen of ether group in peg could be separated at a high temperature through the dehydration process [26]. however, polymeric nonionic surfactants have a high solubility due to their high hydrophilic property [3, 26]. therefore, the synthesized surfactants from rice husk and peg have high stability in the brine solution. figure 4 density of surfactant in brine solution during the stability test for 28 days. 3.5. interfacial tension (ift) test of surfactants the interfacial tension (ift) of the fluids indicates the miscibility of the two fluids. moghadasi et al. [31] explained that the ift determines the mixing potential between two fluids. the lower the ift value, the higher the possibility of two fluids being mixed. in the eor process, the addition of surfactants to the injected brine or water is to reduce the ift value between water and oil and/or to alter wettability; therefore, the amount of the recovered oil from the reservoirs will be increased [32]. thus, the desired surfactant is the one that can reduce the ift value as strongly as possible. the ift values as a function of the surfactant are presented in table 1. as shown in table 1, the ift value of the sls surfactant from rice husk is 1.012 dyne/cm. this value shows the highest value as compared to the other surfactants. interestingly, the ift value can be reduced after the addition of peg. as can be seen, the ift value decreases as the increase in peg concentration. peg is known as a polymeric surfactant. bustamante-rendón et al. [33] reported that the combination of ionic and nonionic surfactants has a good performance in decreasing the ift value between oil and water. in addition, peg is highly hydrophilic due to the presence of ether groups that can bind with water molecules through hydrogen bonding [34, 35]. therefore, the addition of peg to sls increases the hydrophilicity of the surfactant. as a result, the ift value is reduced. priyanto et al. [9] explained that the ift value could be reduced by increasing the hydrophilicity of surfactants. 3.6. phase behaviour test of surfactants the phase behavior test was conducted to investigate the formation of microemulsions of brine and oil in the presence of polymeric surfactants. the test was carried out in a tube test which consists of oil and brine solution (injection water) consisting 0.1 wt.% of surfactants. the volumetric ratio of the oil and brine solution is 1:1. the mixture was then shaken and held at the reservoir temperature (70 °c) for 28 days. the minimum requirement of microemulsion type for the eor process is winsor type i, which can also be mentioned as winsor type ii(−) [36, 37]. as reported by zulkifli et al. [11], winsor type iii microemulsion type is the best microemulsion for eor process, followed by winsor type i and winsor type ii. therefore, the desired surfactant is the one that can produce winsor type iii microemulsion or at least winsor type i. figure 5 shows the appearance of the formation of microemulsion by surfactants. figure 5 the appearance of phase behavior test of polymeric surfactants at day-28 (a) and illustration of winsor type i or ii(−) microemulsion (b). 0 7 14 21 28 0.992 0.993 0.994 0.995 0.996 0.997 0.998 0.999 1.000 d e n s it y ( g / c m 3 ) time (day) sls-1.0peg sls-0.8peg sls-0.5peg chimica techno acta 2022, vol. 9(4), no. 20229406 article 7 of 9 as shown in figure 5, all surfactants produce microemulsions of winsor type i or lower-phase microemulsion (winsor type ii(−)). it means that the surfactants tend to create oil-in-water microemulsion (o/w microemulsion). this type of microemulsion is formed by the presence of hydrophilic or water-based surfactants [3, 38]. it is true since sls was reported as a water-based surfactant [27]. it makes sense since the sls surfactant contains negative charges in the form of sulfonate structures (−so3−) in the hydrophilic part. in addition, the introduction of peg to the sls surfactant increases the surfactant’s hydrophilicity. the increase of the surfactant’s hydrophilicity is caused by the presence of the c−o−c group that can interact with water molecules. the interaction of water molecules with the c−o−c group occurs through hydrogen bonding [3, 26]. this fact is confirmed through the ft-ir analysis, which shows that the concentration of the c−o−c groups of the surfactants has increased after peg addition. therefore, the hydrophilicity of the surfactants increases [39, 40]. being more focused on the microemulsion formation as the effect of peg concentration, it is shown that the sls0.8peg has the darkest microemulsion, followed by sls0.5peg and sls-1.0peg. it means that the amount of oil that dissolved in the brine phase by sls-0.8peg is higher. it can be explained by the fact that the sls-0.8peg surfactant produces the lowest ift value, followed by sls0.5peg and sls-1.0peg. as been explained, the lower the ift value, the higher the possibility of two fluids being mixed [31]. therefore, the sls-0.8peg is expected to give the highest yield in the enhanced oil recovery process. 3.7. performance test of surfactants for eor process the performance test of surfactants was conducted through the eor process using the experimental rig, as shown in figure 1 and described above. as can be seen in figure 6, the brine injection with a concentration of 5000 ppm can recover the oil at around ~82% to ~84%. in addition, the injection of the surfactant can enhance oil recovery. as shown in figure 6, the amount of the recovered oil can be increased by the surfactant injection. the injection of the surfactant increases the total recovered oil by about ~10% to ~12%. in addition, the increase in the total recovered oil percentage is affected by the peg concentration in the sls surfactant. the total recovered oil amount increases by 11.52% from 83.94% to 95.46% by using the sls-0.5peg surfactant (sls to peg ratio of 1:0.5), increases by 12.22% from 84.72% to 96.94% by using the sls-0.8peg surfactant (sls to peg ratio of 1:0.8), and increases by 10% from 81.43% to 91.43% by using the sls1.0peg surfactant (sls to peg ratio of 1:1.0). it shows that the peg as a polymeric surfactant affects the oil recovery process. babu et al. [13] reported that the polymeric surfactant could increase the surfactant viscosity and reduce the ift, which are very important to enhance the sweep efficiency in the eor process. figure 6 eor performance of surfactants. as shown in figure 6, the increase in the total recovered oil percentage after the surfactant injection is affected by the peg concentration in the surfactant. the increase in the total recovered oil amount increases as the peg concentration increases. the total recovered oil percentage increases from 11.52% to 12.22% by increasing the sls to peg ratio from 1:0.5 to 1.08. however, a further increase in peg concentration or sls to peg ratio to 1:1.0 reduces the increase in the total recovered oil amount by 10%. it is caused by the fact that the sls-1.0peg has the highest ift value as compared to sls-0.5peg and sls-0.8peg. therefore, the less oil is recovered with the latter. it shows that the ratio of 1:0.8 (sls-0.8peg surfactant) gives the highest increase in the total recovered oil yield by 12.22%. this increase is caused by the fact that sls-0.8peg has the lowest value of ift (table 1). surfactants can reduce the interface tension between oil and brine solution so that more oil is recovered. bera et al. [41] reported that the residual oil in the core could be emulsified if the ift value is low enough. since the sls-0.8peg has the lowest ift value, it is reasonable that sls-0.8peg gives the highest increase in the total recovered oil amount. 4. conclusions a polymeric surfactant from rice husk and peg was successfully synthesized. the peg introduction to the sls surfactant could increase the hydrophilic property of the polymeric surfactant. the increase in the hydrophilic property was due to the presence of the c−o−c group. the increase in the hydrophilic property positively affected the surfactant because it could reduce the ift value. it was found that the ift value decreased with the increase in the peg concentration. however, the ift value decreased when the peg concentration was too high. the lowest ift value (0.386 dyne/cm) was obtained by the sls-0.8peg surfactant (sls to peg ratio of 1:0.8), which produced the highest (12.22%) increase in the additional recovered oil after brine flooding. the results showed 0 1 2 3 4 5 6 0 10 20 30 40 50 60 70 80 90 100 o il r e c o v e r y ( % ) pore volume sls-1.0peg sls-0.8peg sls-0.5peg surfactant injection 10% 12.22% 11.52% brine injection chimica techno acta 2022, vol. 9(4), no. 20229406 article 8 of 9 that the rice husk, which is agricultural waste, could be utilized as a feedstock for the surfactant production. supplementary materials no supplementary materials are available. funding this work was supported by the ministry of education and culture, indonesia through the research project of penelitian disertasi doktor (grant no. 25843/un7.6.1/pp/2020), https://www.kemdikbud.go.id/. acknowledgments the authors would like to acknowledge integrated laboratory universitas diponegoro for providing the instrumental analysis. author contributions conceptualization: s.p., s.s., b.p. data curation: r.w.s formal analysis: s.s., b.p., t.r. funding acquisition: s.s. investigation: d.d.s., a.a.p. methodology: s.p., r.w.s., s.s., b.p. project administration: s.s. resources: s.p., r.w.s. software: s.p. supervision: s.s. validation: s.p., s.s., b.p. visualization: t.r. writing – original draft: t.r., d.d.s., a.a.p writing – review & editing: s.s., b.p., t.r. conflict of interest the authors declare no conflict of interest. additional information authors ids: s. priyanto, scopus id 6507005325; r.w. sudrajat, scopus id 57213605660; s. suherman, scopus id 57194070495; b. pramudono, scopus id 57190939191; t. riyanto, scopus id 57208816811; ; . website: universitas diponegoro, https://www.undip.ac.id/. references 1. nilsson ma, kulkarni r, gerberich l, hammond r, singh r, baumhoff e, rothstein jp. effect of fluid rheology on enhanced oil recovery in a microfluidic sandstone device. j nonnewton fluid mech. 2013;202:112–119. doi:10.1016/j.jnnfm.2013.09.011 2. nwidee ln, theophilus s, barifcani a, sarmadivaleh m, iglauer s. eor processes, opportunities and technological advancements. in: chemical enhanced oil 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2411-1414; chimicatechnoacta.ru article 2022, vol. 9(4), no. 20229420 doi: 10.15826/chimtech.2022.9.4.20 1 of 8 piezo-, photoand piezophotocatalytic activity of electrospun fibrous pvdf/ctab membrane alina rabadanova a , magomed abdurakhmanov a , rashid gulakhmedov a , abdulatip shuaibov a , daud selimov a , dinara sobola a,b , klára částková c , shikhgasan ramazanov d , farid orudzhev a,d,e * a: smart materials laboratory, dagestan state university, makhachkala 367015, russia b: department of physics, faculty of electrical engineering and communication, brno university of technology, brno 61600, czech republic c: ceitec but – brno university of technology, brno 61200, czech republic d: amirkhanov institute of physics of dagestan federal research center, russian academy of sciences, makhachkala 367003, russia e: rec smart materials and biomedical applications, immanuel kant baltic federal university, kaliningrad 236041, russia * corresponding author: farid-stkha@mail.ru this paper belongs to a regular issue. © 2022, the authors. this article is published in open access under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). abstract a composite material based on polyvinylidene fluoride (pvdf) nanofibers modified with cetyltrimethylammonium bromide (ctab) was synthesized by coaxial electrospinning. the morphology and structure of the material were studied by sem, ftir spectroscopy, x-ray diffraction analysis, xps, and the piezo-, photoand piezophotocatalytic activity during the decomposition of the organic dye methylene blue (mb) was studied. it was shown that the addition of ctab promotes additional polarization of the pvdf structure due to the ion-dipole interaction. it was shown for the first time that the addition of ctab promotes the photosensitivity of the wide-gap dielectric polymer pvdf (the band gap is more than 6 ev). it was demonstrated that the photocatalytic decomposition efficiency is 91% in 60 minutes. the material exhibits piezocatalytic activity – 73% in 60 minutes. the experiments on trapping active oxidizing forms established that oh hydroxyl radicals play the main role in the photocatalytic process. keywords pvdf photocatalysis piezocatalysis piezophotocatalysis nanofibers coaxial electrospinning ctab methylene blue received: 18.10.22 revised: 07.11.22 accepted: 10.11.22 available online: 17.11.22 1. introduction water pollution caused by persistent organic dyes is a serious environmental problem. various effective methods have been developed to eliminate pollution, such as absorption, electrochemical treatment, photocatalysis, piezocatalysis, piezophotocatalysis [1]. however, inappropriate band gap structure, low mobility rate, fast recombination of the generated charge carriers often limit the photocatalytic applications [2]. recently, the internal electric field of piezoelectric materials that can be used to overcome the above limitations in the photocatalytic process has generated a lot of interest [3]. the piezoelectric effect is used to enhance photocatalysis by an internal electric field, which promotes the separation and migration of photogenerated electron-hole pairs, thereby realizing higher piezophotocatalytic efficiency for the simultaneous use of these two types of natural energy. compared to the relatively mature research on photocatalysis, piezocatalysis is seen as a new strategy for tackling environmental pollution and energy shortages [4]. so far, the research on piezocatalytic applications is still in its infancy. however, it is already clear from the available studies that the wide spread practical application of heterogeneous photo-, piezoand piezophotocatalysts in the suspension mode is difficult due to their uneven dispersion and the difficulty of extracting and reusing the catalysts. the solution to these problems can be the immobilization of the catalyst on a polymer matrix. a recent review [5] summarized significant progress in the preparation of various photocatalytic materials based on hybrid polymers. in recent years, polymer composites based on pvdf and semiconductor nanoparticles, the so-called heterophase doping, have been intensively studied for the purposes of piezocatalysis and piezophotocatalysis [6–9]. moreover, poly(vinylidene fluoride) (pvdf) can crystallize into at least four polymorphs (α, β, γ and δ), which leads to different ferroelectric properties. http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2022.9.4.20 mailto:farid-stkha@mail.ru http://creativecommons.org/licenses/by/4.0/ https://orcid.org/0000-0003-2254-2161 https://orcid.org/0000-0002-0805-2089 https://orcid.org/0000-0001-6856-5954 https://orcid.org/0000-0002-5015-8274 https://orcid.org/0000-0002-4911-4282 https://orcid.org/0000-0002-0008-5265 https://orcid.org/0000-0002-6343-6659 https://orcid.org/0000-0003-2190-7704 https://orcid.org/0000-0002-2966-8931 https://crossmark.crossref.org/dialog/?doi=https://doi.org/10.15826/chimtech.2022.9.4.20&domain=pdf&date_stamp=2022-11-17 chimica techno acta 2022, vol. 9(4), no. 20229420 article 2 of 8 compared to the α-phase, the polar βand γ-phases have attracted a lot of attention due to their unique physical properties and potential applications [10]. for example, the polar phases, β and γ, cause pyroelectricity, piezoelectricity, and ferroelectricity. meanwhile, the γ-phase increases transparency, which makes it suitable for optical devices. to obtain the maximum content of the β phase in pvdf membranes, various approaches are used, among which the most effective are the choice of a synthesis method and the addition of various fillers [11]. one of the most effective methods for the synthesis of pvdf with the maximum content of the β phase is considered to be electrospinning, in which high voltages contribute to the repolarization of the structure due to the alignment of electric dipoles. a recent review [12] summarized the generalized approaches to the fabrication of hybrid piezoelectric materials based on pvdf and its copolymer, poly-(vinylidene fluoride)-trifluoroethylene pvdf-trfe with fillers of inorganic and metal nanoparticles, conductive rgo nanosheets and others to improve the piezoelectric characteristics of composites and their practical application as mechanical energy converters. however, for photocatalytic applications, composite polymer-inorganic structures have their own specific requirements [13]. in most studies, composites are synthesized by phase inversion, in which most of the nanoparticles are in the bulk of the polymer membrane, which limits the access of light and solution to the surface of the nanoparticles. proceeding from this, the actual task of materials science is to find a method for homophase doping of pvdf to give it new functional properties. the previous reports have demonstrated that the addition of a low concentration of the cationic surfactant cetyltrimethylammonium bromide (ctab) can effectively induce a pure γ-phase by introducing a strong ion-dipole interaction between the ctab and pvdf dipoles [14, 15]. in [16] the authors reported the piezocatalytic activity of pure pvdf and its copolymer with hexafluoropropylene (hfp) to produce hydrogen under ultrasonic irradiation. in this study, we synthesized a composite pvdf/ctab nanofiber membrane by electrospinning. it was shown that doping with ctab leads to photosensitization of the polymer. it was also shown for the first time that a pvdf polymer membrane exhibits high piezocatalytic and photocatalytic activity towards the decomposition of methylene blue. it was demonstrated for the first time that irradiation with uv-visible light leads to the suppression of piezocatalytic properties during piezophotocatalysis. figure 1 contipro 4spin lab electrospinning device and the image of the resulting sample. 2. methodology 2.1. synthesis of pvdf/ctab nanofibers for electrospinning, pvdf with a molecular weight of 275,000 g mol–1 (sigma aldrich, st. louis, mo, usa) was used. dimethyl sulfoxide (dmso, sigma aldrich, st. louis, mo, usa) and acetone (ac, sigma aldrich, st. louis, mo, usa) were used as solvents. ctab (sigma aldrich, st. louis, mo, usa) was added as a surfactant. pvdf with a concentration of 20 wt.% was dissolved in the binary solvent dimethyl sulfoxide/acetone in a volume ratio of 7/3 at 50 °c for 24 h until a visually homogeneous solution was formed. a pvdf/ctab solution was prepared by modification of the neat pvdf solution with 1 wt.% ctab (by weight of solution). pvdf nanofibers were produced by coaxial electrospinning on a contipro 4spin lab facility (contipro as, dolni dobrouc, czech republic). a coaxial setup included two syringes to feed pvdf and pvdf/ctab solutions independently to a coaxial tip consisting of two concentric needles. the interior needle had an inner diameter of 0.514 mm and was set 0.5 mm longer than the exterior one at the end of the tip. the outer needle had an inner diameter of 1.372 mm. the coaxial electrospinning was performed with feeding rates of 9 μl/min at a constant voltage of 50 kv and a collector rotation speed of 2000 rpm. the distance between the tip of the needle and the collector (a rotating metal drum covered with aluminium foil) was 20 cm. the processing time was 30 minutes. visually, the process is shown in figure 1. 2.2. characterization and analysis of nanofibers the morphology of the samples was studied using a scanning electron microscope (sem) lyra3 (tescan, brno, czech republic). the samples were coated with a 15 nm carbon layer using a leica em ace600 coater (leica microsystems, wetzlar, germany). mean fiber diameters were calculated from the sem images using imagej software. the xrd analysis was performed with an x-ray powder diffractometer rigaku smartlab 3 kw (rigaku corporation, tokyo, japan) in the bragg-brentano configuration. diffraction patterns were obtained between 10 ° and 50 ° (2θ) with cu kα radiation. xps spectra were recorded on an axis supratm x-ray photoelectron spectrometer (kratos analytical ltd., manchester, uk) with an emission current of about 15 ma. the spectra were adjusted using casaxps v.2.3.23 program. the measurement of ft-ir spectroscopy was carried out in transmission mode using a bruker spectrometer (billerica, massachusetts, usa) with a resolution of 1 cm–1 and 512 iterations. 2.3. piezophotocatalytic experiment the piezocatalytic/piezophotocatalytic decomposition test was carried out using uv-visible irradiation. a 250 w highpressure mercury lamp (philips) was used as a source of uv-visible light. the distance from the light source to the chimica techno acta 2022, vol. 9(4), no. 20229420 article 3 of 8 reactor was 10 cm. piezophotocatalytic decomposition was carried out in an ultrasonic (us) bath with a power of 250 w at a frequency of 18 khz. to eliminate the effect of temperature on the decomposition efficiency, the reactor was kept at a constant temperature of 26 °c. before testing, a film (3x1 cm2, thickness 25 μm, weight 0.7 mg) was immersed in a beaker with a solution of methylene blue (mb) (1 mg l–1, 20 ml) and kept in a dark place for 1 h to establish the adsorption–desorption balance. during the test, 3 ml of the sample solution was taken every 15 min and analyzed using a uv-visible spectrometer. the dye concentration was measured from the maximum absorption peak λ = 663 nm. the percentage of degradation was indicated as c/c0 (c and c0 are the measured and initial concentrations of the dye solution, respectively). 3. results and discussions the morphology of the samples was characterized using a scanning electron microscope (sem). figure 2 shows the sem images of the films of pvdf/ctab nanocomposite fibers obtained by electrospinning. to determine the particle size distribution, the sem image was examined using imagej. it can be seen that the surface and structure are smooth, uniform, without visible defects. the pvdf/ctab fibers are formed as elongated nanofibers with different diameters. from the distribution histogram obtained using imagej program, it can be seen that the average diameter of the nanofibers is about 450 nm. to determine the phase composition, the samples were characterized using ftir spectroscopy and xrd. the data are presented in figure 3. the xrd measurements of the pvdf/ctab nanofibers show that the predominant phase is the β-phase. the peaks at 20.6 ° (110/200) and 36.6 ° (101) testify to this [17, 18] (figure 2a). the diffraction bands of the monoclinic α phase peaks are located at 18.4 ° (020) and 41.1 ° (111). since the diffraction bands of the γ and α phases overlap and it is not possible to accurately determine the phase distribution, ftir analysis was used to quantify the phase distribution in pvdf. from the ftir spectra, the relative abundance of all three α-, βand γ-phases in the samples were calculated. first, the fraction of the electroactive phase (fea) was calculated, according to equation 1: 𝐹ea = 𝐼ea ( 𝐾840∗ 𝐾763 ) 𝐼763 + 𝐼ea ∙ 100% (1) where iea and i763 are the absorbances at 840 and 763 cm–1, respectively; k840* and k763 are the absorption coefficients at the respective wave numbers, whose values are 7.7·104 and 6.1·104 cm2 mol–1, respectively. then, using equations 2 and 3, the distribution of βand γ-phases in the electroactive phase was calculated: 𝐹(β) = 𝐹𝐸𝐴 ∆𝐻β′ ∆𝐻β′ + ∆𝐻γ′ ∙ 100% (2) and 𝐹(γ) = 𝐹𝐸𝐴 ∆𝐻𝛾′ ∆𝐻β′ + ∆𝐻γ′ ∙ 100%, (3) where δhβ′ and δhγ′ are the height differences (absorbance differences) between the peak around at 1275 cm–1 and the nearest valley around at 1260 cm–1, and the peak around at 1234 cm–1 and the nearest valley around at 1225 cm–1, respectively [18]. the calculations showed that in pure pvdf the fraction of the α phase was 9.74%, the fraction of the γ phase was 4.71%, and the fraction of the β phase was 85.55%, respectively. after the modification of ctab, the proportion of the β-phase increased to 90.34%, the proportion of the α-phase was 9.51%, and the proportion of the γ-phase was 0.15%. the effect of ctab addition on the formation of pure pvdf γ-phase due to the ion-dipole interaction was previously reported for membranes prepared by thermally induced phase inversion (tips). at the same time, it was reported that in the presence of ctab, the charges in ctab molecules attract the pvdf chains due to ion-dipole interactions, and the pvdf chains tend to form a trans conformation that is favorable for the nucleation of the γ-phase, which leads to the suppression of the growth rate of the α-phase. however, our results show that the addition of ctab leads to suppression of the growth of the γ-phase and an increase in the proportion of the β phase. this discrepancy is apparently explained by the contribution of electric polarization during electrospinning. the chemical state of the surface was examined using xps. the wide spectrum (see figure 4a) shows peaks in the main levels of carbon (c1s), fluorine (f1s) and oxygen (o1s). the f1s ground level spectra can be well decomposed into two peak components associated with cf (686.5 ev) and cf2 (687.4 ev), respectively [19]. figure 2 sem images of pvdf/ctab nanofibers at various magnifications (a, b) and the histogram of the distribution of nanofibers by diameter (c). chimica techno acta 2022, vol. 9(4), no. 20229420 article 4 of 8 figure 3 x-ray diffraction analysis of pvdf/ctab nanofibers (a); ir fourier spectrum of pvdf/ctab nanofibers and pure pvdf (b). these components can be attributed to the presence of covalent and semi-ionic fluorinated bonds. the previous work showed that pure pvdf has a high content of semiionic bonds [20, 21]. as is known, semi-ionic bonds are more oriented than covalent bonds, and a decrease in the proportion of semi-ionic bonds may indicate a decrease in the concentration of the more oriented β-phase. this result confirms the conclusions drawn from the ftir spectra, where it was shown that the addition of ctab leads to a change in the proportion of the β-phase by more than 5%. the changes in the concentration suggest that ctab molecules bind to the pvdf structure and change the orientation of the polymer chain, rather than simply being located between individual fibers. the xps spectra of c1s (figure 4c) show the presence of the standard bands expected for pvdf [22]. deconvolution of the c1s spectrum identifies 6 peaks: c-c/c-h, ch2, c-o, fc-oh, cf2 and cf3, among which the ch2 peak is the most prominent. deconvolution of the o1s peaks shows that the samples prepared with ctab are enriched in oxygen-containing functional groups (figure 4d), associated with residual oxygen from solvents and possible oxidative processes during the synthesis in open air. figure 5 shows the results of catalytic experiments in the decomposition of ms using a pvdf/ctab membrane as a catalyst. two blank experiments were carried out in order to elucidate the contribution of mb self-decomposition under direct light (photolysis) and ultrasonic treatment (sonolysis). blank experiments showed that mb degraded under the action of us treatment and uv-visible light, while the degree of degradation was 51.3% and 62.0% after 60 minutes. the results of the piezocatalytic experiment, where the degree of dye decomposition was 73.0%, clearly indicate the generation of a piezopotential. when a sample is deformed by an external force from ultrasonic treatment, a polarization phenomenon occurs inside it, which generates positive and negative charges present on two relative surfaces. thus, an effective conversion of the external force into electrical energy occurs and a polarization electric field is generated, which contributes to the occurrence of redox chemical reactions, leading to the generation of highly active oxygen species, which oxidize the mb. it can also be seen that the sample exhibits high photocatalytic activity – 93% of the dye decomposed in 60 minutes. the presence of pc activity under uv-visible irradiation in a polymer material whose band gap (bg), according to the literature data, is more than 6 ev, is an unexpected result and requires a deeper study of the electronic structure of the material. for example, in [23] using ultraviolet photoelectron and inverse photoemission spectroscopy, it was demonstrated that a change in the polarization state from positive to negative in the p(vdf-trfe) ferroelectric caused a distinct shift of the valence band towards the fermi level by 2.1 ev and the conduction band by 0.4 ev, as a result of which the bg decreased by 2.5 ev. it is likely that the addition of ctab and the electrical polarization of the material during electrospinning facilitate the rearrangement of the electronic structure of pvdf, leading to a narrowing of the bg. it is well known that photocatalytically active piezoelectric materials are widely used for photocatalytic wastewater treatment from organic pollutants, due to the because they are able to generate more free radicals with stronger oxidizing properties with the synergy of mechanical force and light [24]. taking this into account, we studied the piezophotocatalytic oxidation of mb under the simultaneous action of ultrasonic and uv-visible irradiation. the degree of mb decomposition in this case was 91%, which practically corresponds to the photocatalytic activity. this may probably indicate that, upon photoexcitation of pvdf/ctab, a large number of photogenerated charge carriers suppress the piezoelectric properties. chimica techno acta 2022, vol. 9(4), no. 20229420 article 5 of 8 figure 4 xps spectra of pvdf/ctab nanofibers: wide xps and high-resolution (a) f1s (b); c1s (c) and o1s spectra (d). to the best of our knowledge, this effect has not been previously mentioned in the literature, and the explanation requires additional research. the rate constants (k) were calculated from the kinetic curves according to the pseudo-first order equation and are presented in figure 5b: ln(c0/c) = k t. (4) the k values were 0.011, 0.018, 0.021, 0.043, and 0.046 min–1 for sonolysis, photolysis, piezocatalysis, photocatalysis, and piezophotocatalysis, respectively. during piezocatalysis, the reaction rate increased by a factor of 1.91 compared to sonolysis, indicating the generation of the pvdf/ctab piezopotential under ultrasonic treatment. during photocatalysis, the reaction rate increased by a factor of 2.4 compared with photolysis, indicating the photogeneration of electron-hole pairs upon irradiation with uv-visible light. these data indicate that the as-synthesized pvdf/ctab composite membranes have a certain photocatalytic activity, and the comparable values reported in the literature are shown in table 1. 3.1. mechanism according to the classical concepts, the photocatalytic reaction can be generally divided into three stages: (1) after the absorption of photons by a semiconductor, electron-hole pairs are formed in the volume; figure 5 mb degradation curves (1 mg l–1, 20 ml) (a); time dependence of ln(c/c0) for pvdf/ctab nanofibers (b). (2) the photogenerated electrons and holes, meanwhile, separate and migrate to the surface of the photocatalyst; (3) the photogenerated charge carriers participate in the redox reaction on the surface of the photocatalyst leading to the generation of reactive oxygen species. to find out by what mechanism the photocatalytic reaction proceeds, the experiments were carried out with traps for reactive oxygen species. generally, superoxide radicals (·o2–), holes (h+), electrons (e–) and hydroxyl radicals (·oh) are considered to be the potential dominant active species in the photocatalytic decomposition process. we used isopropanol (ip) for fixing hydroxyl radicals (·oh), ethylenediaminetetraacetic acid (edta) for holes (h+), benzoquinone (bzq) for superoxide radicals (·o2–) and silver nitrate (agno3) for electrons (e–) respectively. the data are presented in figure 6. when irradiated with light, pvdf/ctab is excited, producing electrons and holes. the holes, migrating to the surface, enter into chemical reactions, oxidizing ohwith the formation of ·oh. thus, mb decomposes at the expense of h+ and ·oh in the reaction system. pvdf/ctab + ℎ𝑣 → ℎ+ + 𝑒 − (5) ℎ+ + oh – →∙ oh + h+ (6) chimica techno acta 2022, vol. 9(4), no. 20229420 article 6 of 8 table 1 comparison of photocatalytic contaminant removal rates by immobilized catalyst on pvdf substrates. photocatalyst pollutant light source efficiency ref pvdf/go/zno mb, 60 ml, 10 mg l–1 xenon, 300w 86.8% (100 min) [25] pvdf/zif-8/zno mb, 100 ml, 10 mg l–1 xenon, 300w 95% (4.5 h) [26] pvdf/tio2 rhb, 10 ppm led, 18 w 80% (6 h) [27] pvdf/tio2/g-c3n4 rhb, 50 ml, 5 mg l –1 xenon, 800 w 78% (180 min) [28] sno2/tio2/pvdf rhb, 100 ml, 10 mg l –1 xenon, 250w 92% (270 min) [29] tio2/pvdf mb, 300 ml, 10 ppm high-pressure mercury lamp 95% (60 min) [30] pvdf/go mb, 150 ml, 10 µmol l–1 xenon, 150w 83% (360 min) [31] pvdf-go/nb-tio2 mb, 50 ml, 5 mg l –1 halogen lamp, 500w 39% (30 min) [32] pvdf-b4c mb, 50 ml, 50 mg l –1 uv lamp 96% (20 min) [33] pvdf/zno/ag2o mb, 30 ml, 10 mg l –1 uv light, 6 w 97.2% (210 min) [34] pvdf/ctab mb, 20 ml, 1 mg l–1 high-pressure mercury lamp, 250w 91% (60 min) this work since electrons have little effect on the mb degradation, they will accumulate in the conduction band. probably, the accumulation of excess negative charge acts as an inhibitor for the piezopotential, or as a depolarizer of the piezo field. it should be noted that a clear deactivation of the catalytic activity manifests itself when ip is added to the reaction system, at which the efficiency of mb decomposition decreased from 91% to 12.0%. this indicates the dominant role of hydroxyl radicals ·oh. holes also play an important role in the course of the reaction, because with the addition of edta, the decomposition efficiency was 60%. with the addition of agno3 and benzoquinone, the decomposition efficiency was 86 and 82%, which indicates a small contribution of e– and ·о2– to the reaction. based on this, the proposed mechanism of photocatalytic decomposition of mb is shown in figure 7. 4. conclusions thus, it was shown that the modification of pvdf with the cationic surfactant ctab leads to an increase in the electroactive phase due to the ion-dipole interaction. it was also shown for the first time that the addition of ctab promotes the photosensitivity of the wide-gap dielectric polymer pvdf (the band gap is more than 6 ev). it was demonstrated that the photocatalytic decomposition efficiency is 91% in 60 minutes. the material exhibits piezocatalytic activity – 73% in 60 minutes. the experiments on trapping active oxidizing forms established that ·oh hydroxyl radicals play the main role in the photocatalytic process. supplementary materials no supplementary materials are available. funding this work was supported by the russian science foundation (grant no. 22-73-10091), https://www.rscf.ru/en. figure 6 photocatalytic under uv-vis light performance of pvdf/ctab nanofibers for degradation of mb after adding various scavengers. figure 7 schematic illustration of the photocatalytic mechanism for pvdf/ctab. acknowledgments part of the work was carried out with the support of ceitec nano research infrastructure supported by meys cr (lm2018110) and the grant agency of the czech republic under project no. 19-17457s. https://www.rscf.ru/en chimica techno acta 2022, vol. 9(4), no. 20229420 article 7 of 8 author contributions conceptualization: f.o., d.so. data curation: a.sh., r.g. formal analysis: sh.r., d.so., f.o. funding acquisition: f.o., d.so. investigation: d.se., k.c., a.r., m.a., r.g., a.sh. methodology: d.se., k.c., f.o. project administration: f.o. resources: d.so., k.c., f.o. software: sh.r., supervision: f.o. validation: d.so., sh.r. visualization: d.se. writing – original draft: f.o. writing – review & editing: f.o., d.so. conflict of interest the authors declare no conflict of interest additional information author ids: alina rabadanova, scopus id 57429741000, colab magomed 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https://doi.org/10.3390/polym12071509 https://doi.org/10.1007/s11356-021-12618-1 https://doi.org/10.1002/app.51663 https://doi.org/10.1016/j.ceramint.2022.05.312 synthesis, in vitro and docking studies of 2-substituted 5,6,7,8-tetrahydrobenzo[4,5]thieno[2,3-d]pyrimidine-4(3h)-one derivatives as agents for the treatment of alzheimer's disease chimica techno acta article published by ural federal university 2022, vol. 9(2), no. 20229204 eissn 2411-1414; chimicatechnoacta.ru doi: 10.15826/chimtech.2022.9.2.04 1 of 11 synthesis, in vitro and docking studies of 2-substituted 5,6,7,8-tetrahydrobenzo[4,5]thieno[2,3-d]pyrimidine-4(3h)-one derivatives as agents for the treatment of alzheimer's disease alexey s. chiriapkin * , ivan p. kodonidi , dmitry i. pozdnyakov , alexander a. glushko pyatigorsk medical and pharmaceutical institute, branch of volgograd state medical university, pyatigorsk 357532, russia * corresponding author: prk@pmedpharm.ru this paper belongs to a regular issue. © 2022, the authors. this article is published open access under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). abstract alzheimer's disease is a chronic neurodegenerative disease, which is characterized mainly by a progressive decrease in intellectual abilities, memory impairment and a change in a person's personality. unfortunately, there are practically no medicines that act on the pathogenesis of alzheimer's disease. the development of new highly effective medicines for the treatment of this pathology is one of the crucial areas of pharmaceutical research. the aim of this work is to search among 2-substituted 5,6,7,8-tetrahydrobenzo[4,5]thieno[2,3d]pyrimidine-4(3h)-one effective compounds with anticholinesterase and antiamyloid activities. as a result, it was found that compounds 4d, 4e and 4f have the highest anticholinesterase ability, containing in their structure the residues of hydroxy-methoxyphenyl fragments. structures 4c, 4g, 4h, 4j, 4k, 4m, 4n and 4p showed slightly lower activity, the effect of which did not differ statistically from that of donepezil. compounds 4c, 4e, 4k and 4m have the greatest ability to inhibit the formation of the amyloid, comparable to gv-971. it should be noted that the molecular docking data are consistent with the results of the determination of the anticholinesterase activity of the studied compounds obtained in vitro. thus, the prospects for future studies of these compounds concerning the possibility of creating a pharmaceutical active substance for the treatment of neurodegenerative diseases have been revealed. keywords alzheimer's disease tetrahydrothienopyrimidine synthesis molecular docking ache acetylcholinesterase anticholinesterase action amyloid medicinal chemistry received: 08.03.22 revised: 21.04.22 accepted: 21.04.22 available online: 26.04.22 1. introduction alzheimer's disease (ad) is one of the most common neurodegenerative diseases in humans. currently, there are practically no pathogenetic drugs that can cure the patient. drug therapy is aimed only at eliminating the symptoms of the disease and slowing its progression. the most widely used anticholinesterase (ache) drugs that can neutralize the symptoms of cholinergic insufficiency. recently, the development of antiamyloid drugs that can directly affect the pathogenesis of the disease and thereby significantly improve the patient's well-being has been intensified. thus, the search for new compounds with the above properties is a cutting-edge area of medicinal chemistry and neuropharmacology [1]. research is actively underway to develop the new acetylcholinesterase inhibitors. thus, new thiazolylhydrazone derivatives were designed and synthesized as acetylcholinesterase and butyrylcholinesterase (bche) inhibitors. all compounds showed a weak inhibitory effect on bche; meanwhile, most of the compounds had a certain ache inhibitory activity [2]. research was carried out to study the possibility of designing acetylcholinesterase inhibitors based on isoquinolone and azepanone derivatives. overall, the compounds studied are weak ache inhibitors, but, nonetheless, important insights were obtained on their mode of inhibition so that more potent analogues can be designed, prepared and tested [3]. there are literature data indicating that chalcone can be used as the scaffold for cholinesterase inhibitor [4]. pharmacophore based 3d qsar http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2022.9.2.04 https://orcid.org/0000-0001-8207-2953 https://orcid.org/0000-0003-1333-3472 https://orcid.org/0000-0002-5595-8182 https://orcid.org/0000-0001-7465-5657 mailto:prk@pmedpharm.ru http://creativecommons.org/licenses/by/4.0/ https://crossmark.crossref.org/dialog/?doi=https://doi.org/10.15826/chimtech.2022.9.2.04&domain=pdf&date_stamp=2022-4-26 chimica techno acta 2022, vol. 9(2), no. 20229204 article 2 of 11 models for human acetylcholinesterase inhibitors with good significance, statistical values were generated. virtual screening experiments and subsequent in vitro evaluation of promising hits revealed a novel and selective ache inhibitor [5]. a number of pyrimidine derivatives were synthesized, among which there are compounds that may be considered as leaders for investigations in neurodegenerative diseases [6]. some of diversely functionalized pyrimidine fused thiazolino-2-pyridones have an ability to inhibit the formation of amyloid-β fibrils associated with alzheimer's disease, while others bind to mature amyloid-β and αsynuclein fibrils [7]. a new series of pyrimidine and pyridine diamines was designed as dual binding site inhibitors of cholinesterases, characterized by two small aromatic moieties separated by a diaminoalkyl flexible linker [8]. to obtain a multipotent framework that can target simultaneously cyclooxygenase-2, arachidonate 5-lipoxygenase, acetylcholinesterase, and butyrylcholinesterase to treat neuroinflammation, a series of derivatives containing pyrimidine and pyrrolidine cores were rationally synthesized and evaluated. tacrine–pyrrolidine hybrids and tacrine– pyrimidine hybrid emerged as the most potent ache inhibitors [9]. a series of 2,4-phenylsulfonyl-pyrimidine carboxylate derivatives was designed and synthesized. two compounds among them exhibited promising ache inhibition and significantly inhibited aβ aggregation, that is important for anti-alzheimer's action [10]. 2-arylidene derivatives of thiazolopyrimidine with different linker size and targetanchoring functional groups for the treatment of ad were synthesized. some of them showed excellent to good ache and bche inhibition potential at nanomolar to low micromolar concentration [11]. a series of novel tetrahydropyrimidin-4-yl)pyridine derivatives was designed and synthesized as inhibitors of ache and bche. the in vitro studies showed that all the synthesized derivatives showed significant bche inhibitory activity and were more potent than donepezil as the standard. all the target compounds demonstrated good ache inhibitory effects, comparable with donepezil as the reference drug [12]. 4-(pent-4-yn-1yloxy)phenyl)-2-phenylpyrimidine derivatives were synthesized and screened for monoamine oxidase and ache inhibitory activities [13]. new triazolopyridopyrimidine was easily prepared in good yields showing anticholinesterase inhibition and strong antioxidant power, which allows using new hit-triazolo pyridopyrimidine for ad therapy [14]. previously, we studied the biological activity of azomethine derivatives of 2-amino-4,5,6,7-tetrahydro-1benzothiophene-3-carboxamide, which are acyclic precursors of 2-substituted 5,6,7,8tetrahydrobenzo[4,5]thieno[2,3-d]pyrimidine-4(3h)-one. the results show that some representatives of the studied azomethines have pronounced anticholinesterase and antiamyloid activities [15]. in this study, we decided to continue our research on finding candidates for the treatment of alzheimer's disease. we decided to take 2-substituted 5,6,7,8-tetrahydrobenzo[4,5]thieno[2,3d]pyrimidine-4(3h)-one as the objects of the study, since their azomethine precursors demonstrated the ability to inhibit the acetylcholinesterase enzyme and the formation of the amyloid. the proposed class of organic compounds has various types of biological activity. it was found that 2-(4methoxyphenyl)-5,6,7,8-tetrahydrobenzo[4,5]thieno[2,3d]pyrimidine-4(3h)-one may be an efficacious compound for the treatment of prostate cancer in advanced stages [16, 17]. some thieno[2,3-d]pyrimidine-4(1h)-one-based analogs inhibit the growth of human colon tumor cells [18]. also, this class of organic compounds can suppress the production of inflammatory mediators [19]. studies on thiophenpyrimidine derivatives with various conjugated cyclic systems showed that modification of 5,6,7,8tetrahydrobenzo[4,5]thieno[2,3-d]pyrimidine-4(3h)-one by replacing conjugated cyclohexane with 1-methylpiperidine can increase the ability of such compounds to be used in breast cancer therapy [20]. derivatives of thieno[2,3d]pyrimidine-4-one may have antioxidant properties [21]. some new thieno[2,3-d]pyrimidine-4(3h)-one derivatives showed good analgesic activity by using eddy´s hot plate method [22]. there are data indicating that tetrahydrobenzo[4,5]thieno[2,3-d]pyrimidine scaffolds may serve as models for the development of antimalarial agents [23]. some of the 5-alkoxytetrazolo[1,5-c]thieno[2,3-e]pyrimidine derivatives may exhibit anticonvulsant and antidepressant effects, which makes it possible to design compounds based on them with an effect on the central nervous system [24]. a method was proposed for the synthesis of 2-substituted 5,6,7,8-tetrahydrobenzo[4,5]thieno[2,3-d]pyrimidine-4(3h)one by suspending 2-amino-4,5,6,7-tetrahydro-1benzothiophene-3-carboxamide in a small amount of butanol and the corresponding aldehyde with a catalytic amount of concentrated hydrochloric acid [17]. there is a technique for obtaining compounds of this series using zno-ceo2 nanocomposite as a catalyst. zno-tio2 nanocomposites were added to the mixture of aminoamide and aldehyde [25]. it is possible to carry out the chemical interaction of 2-amino-4,5,6,7tetrahydro-1-benzothiophene-3-carboxamide with aldehydes in a dmf and piperidine medium when heated [26] and in the environment of hydrochloric acid and methanol [18]. a method was proposed for the preparation of 2-substituted 5,6,7,8tetrahydrobenzo[4,5]thieno[2,3-d]pyrimidine-4(3h)-one by adding 2-amino-3-carbethoxythiophene in anhydrous dioxane saturated with hydrogen chloride gas nitrile to a solution of 2-amino-3-carbethoxythiophene in anhydrous dioxane [20]. 2. experimental 2.1. molecular modeling a virtual model of human acetylcholinesterase from the rcsb protein data bank database was taken as an object for molecular docking with the identification number 4ey7 [27]. the three-dimensional structures of the studied compounds were constructed in the hyperchem 8.0.4 prochimica techno acta 2022, vol. 9(2), no. 20229204 article 3 of 11 gram and then geometrically optimized by the mm+ method. the final geometry optimization of the virtual structures was calculated in the orca 4.1 program using the density functional theory (ub3lyp) method and the 6-311g** basis set. the docking study was performed using the autodock4 program. it was set to search for 200 energetically favorable conformations of the ligandenzyme complex formation using the lamarckian ga 4.2 scoring function for calculating the energy of the ligandenzyme interaction. rmsd is 0.44 å for donepezil. molecular docking is presented in more detail in the following work [15]. 2.2. chemistry all chemicals were acquired from sigma-aldrich (sigmaaldrich, st. louis, mo, usa), carl roth (carl roth, karlsruhe, germany) and merck chemicals (merckkgaa, darmstadt, germany). melting points (m.p.) were recorded using the pmp-m1 melting point apparatus (himlaborpribor, klin, russia). all reactions were monitored by thin-layer chromatography (tlc) using silica gel 60 f254 tlc plates (merck, darmstadt, germany). spectroscopic data were registered with the following instruments: ir, ir-fourier fsm 1201 spectrophotometer (spectrum, moscow, russia); uv, sf-2000 device (spectrum, moscow, russia); 1h nmr and 13c nmr, bruker avance iii 400 мhz spectrometer (bruker, germany) in dmso-d6 using tetramethylsilane as the internal standard. coupling constant (j) values are measured in hertz (hz) and spin multiplets are given as follows: s (singlet), d (double), t (triplete), q (quartet), m (multiplet). 2.2.1. general procedure for synthesis of azomethine derivatives of 2-amino-4,5,6,7-tetrahydro-1benzothiophene-3-carboxamide (3a–3s) 0.01 mol (1.92 g) of compound 1 and the equimolar amount of the corresponding aldehyde (2) were dissolved by heating in a minimum amount of ethanol. then the solutions were combined. the reaction was carried out until a precipitate was formed. it took about 30 minutes. the precipitate was filtered and purified by recrystallization from ethanol [15, 28]. 2.2.2. general procedure for synthesis of 2-substituted 5,6,7,8-tetrahydrobenzo[4,5]thieno[2,3d]pyrimidine-4(3h)-one (4a–4s) azomethine 3 (0.08 mol) was refluxed for 30–60 min in the glacial acetic acid. then 1 ml dmso was added and the reaction mixture was refluxed for 60 min. after cooling, the formed precipitate was filtered. in the filtrate the remaining target product was precipitated with a 0.1 м cold water solution of sodium chloride. the precipitates were combined. recrystallization of the obtained compounds was carried out from acetic acid. compounds 4a–4j, 4p, 4q were obtained earlier [29]. 2.3. pharmacological study 2.3.1. evaluation of anti-amyloid activity in vitro the fragments aß 1-42 were obtained from sigma-aldrich (germany). gv-971 was provided by hunan warrant pharm. (china). the aggregation process of amyloid particles was evaluated in the reaction of the interaction of aß with congo red. 25 µl of a solution of the test compounds in dimethyl sulfoxide (the final concentration is 20 mg/ml, gv-971 in a similar concentration was used as a referent compound) was mixed with 225 µl of a 20 mm solution of congo red in phosphate buffer solution. the resulting mixture was incubated at room temperature. then the absorbance of the samples was recorded at wavelengths of 540 nm and 405 nm. after nine days of incubation. the number of aggregates aß was calculated by the following equation on the 3rd, 6th and 9th day of the experiment: (1) where a405bl is the absorbance of the congo red solution at a wavelength of 405 nm; a540 and a405 are the absorbances of the solution containing the test substances at a wavelength of 540 nm and 405 nm, respectively. the difference between the compounds was evaluated by the anova method with the tukey post-test [30]. 2.3.2. evaluation of anticholinesterase activity in vitro the activity of acetylcholinesterase was determined by the modified ellman method. the analyzed medium contained 20 ml of acetylcholinesterase solution (3.2 u/l), 25 ml of a solution of the test compounds in various concentrations (30 mg/ml, 15 mg/ml, 7.5 mg/ml, 3.75 mg/ml and 1.875 mg/ml) and a potassium-phosphate buffer solution in a volume of up to 300 ml. donepezil (krka, slovenia) in similar concentrations was used as a reference substance. the mixture was incubated for 5 minutes. the reaction was started by adding the acetylcholine chloride (25 µl, 0.02 m solution) and 5.5'-dithiobis-2-nitrobenzoic acid (25 µl, 0.02 m solution). the absorbance of the mixture was recorded after 5 minutes at 412 nm using the infinite f50 microplate reader (tecan, austria). the tests were performed in a triplet version. ic50 (mg/ml) was calculated by probit analysis. the data is presented in the form of m±sem (mean ± standard error of the mean). statistical differences were evaluated at a significance level of p<0.05 by the anova method with post-processing by tukey [31]. 3. results and discussion 3.1. synthesis as shown in scheme 1, 2-amino-4,5,6,7-tetrahydro-1benzothiophene-3-carboxamide 1 and aldehydes 2 were refluxed in ethanol to obtain azomethine derivatives 3. the reactions were performed in ethanol as a green solvent. heterocyclization reaction was performed using glacial acetic acid and dmso to afford the 2-substituted chimica techno acta 2022, vol. 9(2), no. 20229204 article 4 of 11 5,6,7,8-tetrahydrobenzo[4,5]thieno[2,3-d]pyrimidine4(3h)-one 4. the products 4a-4s were obtained with the high yields. the compounds were characterized by nuclear magnetic resonance and infrared spectroscopy. 3.1.1. 2-(3,5-di-tert-butyl-4-hydroxy-phenyl)-5,6,7,8tetrahydrobenzo[4,5]thieno[2,3d]pyrimidine-4(3h)one (4k) the beige crystals were obtained. yield: 85%. m.p.: 293–294 °c. uv spectrum (ethanol), λmax, nm: 207, 337. ir spectrum (kbr), ν, cm–1: 3620 (nh), 3447 (oh, stretching), 2951 (csp3–h), 1649 (c=o). 1h nmr spectrum (400 mhz, dmso-d6), δ, ppm: 1.44 (s, 18h, ch3), 1.87–1.71 (m, 4h, ch2), 2.72 (t, j = 6.0 hz, 2h, ch2), 2.90 (t, j = 5.9 hz, 2h, ch2), 7.60 (s, 1h, oh), 7.84 (s, 2h, arh), 12.50 (s, 1h, nh). 13c nmr spectrum (100,6 mhz, dmso-d6), δ, ppm: 22.26, 23.00, 24.96, 25.83, 35.21, 56.49, 120.46, 123.47, 131.14, 131.72, 139.13, 153.64, 157.60, 159.56, 164.00. 3.1.2. 2-(2-hydroxy-5-nitro-phenyl)-5,6,7,8tetrahydrobenzo[4,5]thieno[2,3d]pyrimidine-4(3h)one (4l) the yellow crystals were obtained. yield: 88%. m.p.: 285–286 °c. uv spectrum (ethanol), λmax, nm: 220, 370. ir spectrum (kbr), ν, cm–1: 3466 (oh, stretching), 2939 (csp3-h), 1657 (c=o). 1h nmr spectrum (400 mhz, dmso-d6), δ, ppm: 1.90–1.57 (m, 4h, ch2), 2.78 (t, j = 5.9 hz, 2h, ch2), 2.91 (t, j = 6.0 hz, 2h, ch2), 7.12 (d, j = 9.1 hz, 1h, arh), 8.25 (dd, j = 9.2, 2.9 hz, 1h, arh), 8.92 (d, j = 2.9 hz, 1h, arh), 12.84 (s, 1h, nh). 3.1.3. 2-(5-bromo-2-hydroxy-3-methoxy-phenyl)-5,6,7,8tetrahydrobenzo[4,5]thieno[2,3d]pyrimidine-4(3h)one (4m) the brown crystals were obtained. yield: 95%. m.p.: t>300 °c. uv spectrum (ethanol), λmax, nm: 215, 235, 282. ir spectrum (kbr), ν, cm–1: 3455 (oh, stretching), 2928 (csp3-h), 1657 (c=o). 1h nmr spectrum (400 mhz, dmso-d6), δ, ppm: 1.86–1.72 (m, 4h, ch2), 2.77 (t, j = 6.1 hz, 2h, ch2), 2.89 (t, j = 6.1 hz, 2h, ch2), 3.88 (s, 3h, ch3), 7.30 (s, 1h, arh), 7.84 (s, 1h, arh), 11.84 (s, 1h, oh), 12.27 (s, 1h, nh). 3.1.4. 2-(3-bromo-2-hydroxy-5-methyl-phenyl)-5,6,7,8tetrahydrobenzo[4,5]thieno[2,3d]pyrimidine-4(3h)one (4n) the brown crystals were obtained. yield: 93%. m.p.: 287–288 °c. uv spectrum (ethanol), λmax, nm: 210, 390. ir spectrum (kbr), ν, cm–1: 3458 (oh, stretching), 2928 (csp3-h), 1658 (c=o). 1h nmr spectrum (400 mhz, dmso-d6), δ, ppm: 1.86–1.70 (m, 4h, ch2), 2.28 (s, 3h, ch3), 2.78 (t, j = 5.8 hz, 2h, ch2), 2.91 (t, j = 6.0 hz, 2h, ch2), 7.60 (s, 1h, arh), 8.07 (s, 1h, arh), 12.93 (s, 1h, nh), 13.24 (s, 1h, oh). a (4d) b (4i) ( 3 ) (4n) (4l) ( 1 ) (4k) (4m) ( 2 ) (4g) ( 4 ) (4j) (4o) (4s) (4h) (4r) r1 4= r7 = r1 2 = (4a) r8 = r1 1 = r1 0 = r1 3 = r1 5= r9 = r1 9 = ; ; r1 8=; (4b) ; ; ; ; (4e) ; (4f) r4=r1 = r2 = r3 = r6 = r5 =; ; ; ; (4c) r1 6 = r1 7 = (4p) (4q) ; ; ; ; ; ; scheme 1 reagents and conditions: (a) ethanol, reflux; (b) glacial acetic acid, dmso, reflux. chimica techno acta 2022, vol. 9(2), no. 20229204 article 5 of 11 3.1.5. 2-(3,5-dibromo-2-hydroxy-phenyl)-5,6,7,8tetrahydrobenzo[4,5]thieno[2,3d]pyrimidine-4(3h)one (4o) the brown crystals were obtained. yield: 92%. m.p.: 290–291 °c. uv spectrum (ethanol), λmax, nm: 211, 389. ir spectrum (kbr), ν, cm–1: 3429 (oh, stretching), 2928 (csp3-h), 1653 (c=o). 1h nmr spectrum (400 mhz, dmsod6), δ, ppm: 1.88–1.72 (m, 4h, ch2), 2.78 (t, j = 5.9 hz, 2h, ch2), 2.89 (t, j = 5.8 hz, 2h, ch2), 7.94 (d, j = 2.4 hz, 1h, arh), 8.44 (d, j = 2.3 hz, 1h, arh), 13.04 (s, stretching, 2h, oh, nh). 3.1.6. 2-(5-iodo-2-furyl)-5,6,7,8tetrahydrobenzo[4,5]thieno[2,3d]pyrimidine-4(3h)one (4r) the brown crystals were obtained. yield: 79%. m.p.: 297–298 °c. uv spectrum (ethanol), λmax, nm: 218, 283, 353. ir spectrum (kbr), ν, cm–1: 3436 (nh, stretching), 2928 (csp3-h), 1649 (c=o). 1h nmr spectrum (400 mhz, dmso-d6), δ, ppm: 1.84–1.74 (m, 4h, ch2), 2.75 (t, j = 6.1 hz, 2h, ch2), 2.88 (t, j = 6.2 hz, 2h, ch2), 6.97 (dd, j = 3.5, 1.6 hz, 1h, arh), 7.54–7.47 (m, 1h, arh), 12.51 (s, 1h, nh). 13c nmr spectrum (100,6 mhz, dmso-d6), δ, ppm: 22.20, 22.89, 25.02, 25.76, 98.87, 121.46, 131.53, 133.22, 143.14, 150.73, 158.55. 3.1.7. 2-[5-(4-nitrophenyl)-2-furyl]-5,6,7,8tetrahydrobenzo[4,5]thieno[2,3d]pyrimidine-4(3h)one (4s) the brown crystals were obtained. yield: 78%. m.p.: t>300 °c. uv spectrum (ethanol), λmax, nm: 204, 219, 399. ir spectrum (kbr), ν, cm–1: 3447 (nh, stretching), 2932 (csp3-h), 1645 (c=o). 1h nmr spectrum (400 mhz, dmso-d6), δ, ppm: 1.85–1.71 (m, 4h, ch2), 2.75 (q, j = 3.9, 2.3 hz, 2h, ch2), 2.91 (t, j = 5.6 hz, 2h, ch2), 7.53 (d, j = 3.7 hz, 1h. arh), 7.60 (d, j = 3.8 hz, 1h, arh), 8.35–8.25 (m, 4h, arh), 12.84 (s, 1h, nh). 13c nmr spectrum (100,6 mhz, dmso-d6), δ, ppm: 22.19, 22.88, 25.05, 25.80, 113.03, 116.85, 121.65, 124.70, 125.76, 131.65, 133.27, 135.32, 143.75, 147.07, 147.33, 154.00, 158.65, 162.98. 3.2. docking studies based on the results of computational experiment, molecular complexes were selected, in which the simulated compounds occupy the most energetically advantageous location in the active site of the acetylcholinesterase enzyme. 2-substituted 5,6,7,8-tetrahydrobenzo[4,5]thieno[2,3d]pyrimidine-4(3h)-one mainly formed bonds with the following amino acid residues of the active site of ache: tyr 124, trp 286, val 294, phe 295, arg 296, phe 297, tyr 337, phe 338, tyr 341 and his 447. table 1 shows the minimum energies for the formation of ligand complexes with the active site of ache and the hydrogen bonds. figure 1 and 2 shows locations of 4a–4s according to molecular docking. table 1 results of molecular docking experiments for compounds 4a–4s, donepezil and its hydrogen bonds. compound autodock binding energy (kcal/mol) residue ligand atoms distance (å) 4a –9.05 – – – 4b –10.16 arg 296 oh 1.979 ser 293 oh 2.141 4c –9.23 ser 293 oh 2.041 4d –9.55 phe 295 och3 2.199 4e –10.29 arg 296 oh 1.679 4f –10.29 phe 295 oh 1.895 arg 296 och3 2.146 4g –9.95 ser 293 oh 1.804 arg 296 oh 1.898 arg 296 oh 1.895 4h –9.55 – – – 4i –9.48 – – – 4j –10.86 phe 295 c=o 2.225 4k –10.30 – – – 4l –9.67 phe 295 c=o 2.155 arg 296 oh 2.064 arg 296 oh 2.188 4m –11.64 arg 296 och3 2.211 phe 295 oh 2.153 4n –10.52 phe 295 c=o 2.128 ser 293 oh 1.822 4o –10.84 phe 295 oh 2.104 4p –9.05 arg 296 furo 1.891 4q –8.93 phe 295 c=o 1.700 4r –9.71 phe 295 –s– 2.222 4s –10.67 arg 296 no2 1.903 donepezil –11.89 phe 295 c=o 1.770 the compounds 4b, 4c, 4g and 4n form a hydrogen bond between their hydroxy groups and the amino acid residue ser 293. the structures 4b, 4e, 4g and 4l by the same structural fragment can make a hydrogen bond with arg 296. the compounds 4p and 4s form a hydrogen bond with arg 296 by oxygen atoms of the furan heterocycle and the nitro group, respectively. it is often seen that the simulated compounds can form a hydrogen bond in a ligand-enzyme complex with phe 295. 4j, 4l, 4n and 4q interact with phe 295 with their carbonyl groups, and 4r molecule forms a hydrogen bond between phe 295 and the sulfur atom of the thiophene heterocycle. three compounds among the simulated structures 4f, 4m and 4o with the above amino acid residue interact with the oxygen atom of the hydroxy group of the aryl fragment of the molecule. it follows from the docking results that compounds 4f and 4m can form a hydrogen bond with the arg 296 oxygen atom by the methoxy group, and in the structure of 4d similarly structural fragments interacts with phe 295 by forming a hydrogen bond with a length of 2.199 å. according to the molecular docking data for 4a, 4h, 4i and 4k, the formation of hydrogen bonds is not observed. donepezil makes a hydrogen bond between the oxygen atom of the carboxyl group of the five-membered cycle of the molecule and the amino acid phe 295 of the active site of the enchimica techno acta 2022, vol. 9(2), no. 20229204 article 6 of 11 zyme. many 2-substituted 5,6,7,8tetrahydrobenzo[4,5]thieno[2,3-d]pyrimidine-4(3h)-one form a hydrogen bond with phe 295, as does the donepezil. there is no non-bonding interactions such as van der waals, π–π, π–alkyl according to this docking protocol. 3.3. pharmacological studies the results of the antiamyloid activity evaluation of the test substances are presented in table 3. as can be seen from the data in table 3, the compounds 4c, 4e, 4k and 4m have the highest ability to inhibit the formation of β-amyloid in the model mixture. at the same time, the compounds 4c, 4e significantly suppressed the process of amyloidogenesis after 3 days of incubation. it is worth noting that on the 9th day of the experiment, all the leading compounds showed a comparable level of pharmacological efficacy, which, however, was lower than that of gv-971. 4a 4b 4c 4d 4e 4f 4g 4h figure 1 the location of 4a–4h according to molecular docking. chimica techno acta 2022, vol. 9(2), no. 20229204 article 7 of 11 4i 4j 4k 4l 4m 4n 4o 4p 4q 4r 4s figure 2 the location of 4i–4s according to molecular docking. as can be seen from the data obtained, the highest anticholinesterase activity was established for the compounds 4d, 4e and 4f, surpassing that of the referent. the substances 4c, 4g, 4h, 4j, 4k, 4m, 4n and 4p showed slightly lower activity, the effect of which did not differ statistically from that of donepezil. 3.4. structure-activity relationship of the studied compounds in general, the results of molecular docking of the predicted structures are in a good agreement with the results of the primary pharmacological screening of anticholinesterchimica techno acta 2022, vol. 9(2), no. 20229204 article 8 of 11 ase activity in vitro of 2-substituted 5,6,7,8tetrahydrobenzo[4,5]thieno[2,3-d]pyrimidine-4(3h)-one. the most active compounds inhibiting ache are thienopyrimidines, containing in the second position of the heterocycle pyrimidine-4(3h)-one fragment with hydroxy and methoxyphenyl substituents (4d, 4e and 4f). table 2 the effect of the studied compounds and gv-971 on the aggregation of amyloid particles. compounds % of inhibition 3th day 6th day 9th day 4a 10.2±1.2* 34.5±1.6* 67.5±2.3* 4b 10.7±1.0* 42.5±2.5* 55.1±2.0* 4c 24.5±3.9* 32.2±3.8* 66.4±1.2* 4d 14.2±2.1* 38.6±2.4* 57.9±1.2* 4e 22.2±1.5* 39.1±2.2* 67.2±3.6* 4f 16.8±3.8* 38.1±1.5* 60.8±3.7* 4g 13.9±3.7* 33.7±2* 60.4±2.9* 4h 13.4±3.9* 42.9±3.6* 57.3±3.6* 4i 15.5±1.6* 36.5±3.7* 62.7±1.3* 4j 12.3±1.5* 45±2.9* 50±1.8* 4k 16.4±1.6* 55.3±2.3* 69.4±2.5* 4l 18.7±2.6* 38±2.9* 50±1.2* 4m 21.1±2.7* 49±3.5* 72.8±1.9* 4n 16.9±1.6* 31.2±3.3* 60.4±2.4* 4o 16.2±2.8* 34.9±3.1* 55.9±3.9* 4p 22.2±3.2* 43±1* 54.7±3.4* 4q 18.1±1.6* 32.2±2.8* 58±4* 4r 23.5±2.6* 41.3±3.4* 52.3±1.2* 4s 15.1±2.1* 41.2±3.4* 52.9±1.4* gv-971 33.5±2.4 65.2±3.9 86.3±2.5 * – statistically significant relative gv-971 (anova with the tukey post-test, p<0,05) table 3 the effect of the studied compounds and donepezil on the acetylcholinesterase activity. compounds ic50, mg/ml 4a 6.31±0.091* 4b 5.36±0.087* 4c 3.10±0.031 4d 1.17±0.064* 4e 1.24±0.027* 4f 1.11±0.044* 4g 3.08±0.084 4h 3.75±0.058 4i 5.99±0.021* 4j 4.52±0.034 4k 3.19±0.044 4l 5.42±0.012* 4m 3.22±0.021 4n 3.68±0.092 4o 5.23±0.061* 4p 3.75±0.071 4q 5.82±0.025* 4r 4.92±0.074* 4s 4.57±0.096* donepezil 2.40±0.06 * – statistically significant relative donepezil (anova with the tukey post-test, p<0,05) these compounds are superior in the effectiveness to the drug donezepil. it should be noted that for the acyclic precursors of azomethine derivatives of 2-amino-4,5,6,7tetrahydro-1-benzothiophene-3-carboxamide, substances with similar substituents showed better activity. this fact indicates the significance of these pharmacophores. to a lesser extent, the 4c and 4g substances containing only hydroxyphenyl groups as a pharmacophore fragments exhibit the anticholinesterase activity. among the compounds having a furan heterocycle, the compound 4p has the greatest ability to inhibit ache. the analysis of thecompounds 4j and 4k containing a tert-butyl radical in a hydroxyphenyl fragment allows us to judge its effect on the pharmacological properties of these structures. particularly interesting is the remainder of the sterically hindered phenol contained in the 4k compound. among the halogen-derived target products, 4o containing two bromine atoms in the 3,5 positions of the phenyl substituent showed the least activity. compounds that do not contain hydroxy, methoxy and bromophenyl substituents have weak inhibitory properties of ache, which is in a good agreement with the results of molecular docking and confirms the revealed tendency of the influence of electrondonating substituents in the 2-substituted phenyl fragment of the condensed thiophenpyrimidine system. figure 3 shows the location of donepezil and 4d in the active site of ache. figure 3 the location of donepezil determined by x-ray diffraction analysis (blue color) and the location of 4d according to molecular docking (green color). figure 4 shows the location of the donezepil molecule corresponding to the data of x-ray diffraction analysis in the 4ey7 molecular complex and the positions of 2-substituted 5,6,7,8-tetrahydrobenzo[4,5]thieno[2,3-d]pyrimidine-4(3h)one with hydroxy-methoxyphenyl fragments. figure 4 the location of donepezil determined by x-ray diffraction analysis (a – red color) and the location according to molecular docking: 4d (b – blue color), 4e (c – green color), 4f (d – yellow color). chimica techno acta 2022, vol. 9(2), no. 20229204 article 9 of 11 it can be seen that the aryl fragments 4d, 4e and 4f with methoxy and hydroxy groups occupy a similar position with the same structural element of donezepil. thus, it is possible to assume similar molecular mechanisms of inhibition of ache in the predicted compounds and their prototypes, as well as the importance of the hydroxymethoxyphenyl fragment for the process of inhibition of the enzyme. the study of the ability of synthesized compounds to aggregate amyloid particles allowed us to determine that the most active are tetrahydrothienopyrimidines with 5bromo-2-hydroxy-3-methoxyphenyl (4m) and 3,5-di-tertbutyl-4-hydroxyphenyl (4k) substituents containing ditert-butyl and bromine-substituted hydroxymethoxyphenyl fragments in the second position of the pyrimidine-4(3h)-one heterocycle. of the compounds with hydroxy-methoxyphenyl substituents, the substance 4e containing an isovaniline residue in its structure showed the greatest activity. the compound 4a, which has an unsubstituted phenyl substituent, also inhibits the aggregation of amyloid particles well. the resulting combination of pharmacological properties of the studied objects, namely, the combination of the ability to suppress amyloidogenesis and anticholinestrease activity, opens up certain prospects in terms of the therapeutic use of these compounds. so, it is known that amyloidogenic processes underlie irreversible neurodegenerative diseases, in particular, alzheimer's disease [32]. the development of drugs for the treatment of alzheimer's disease is an extremely difficult task. since 2003, extensive preclinical and clinical studies of promising molecules have been conducted, but none of them has been put into practice. as of 2021, not a single drug has been registered that directly affects the pathogenesis of the disease. but, at the same time, a purposeful search for substances that can prevent a neurodegeneration is ongoing [33]. according to cummings et al., the most promising direction for the development of new therapeutic agents for the treatment of alzheimer's disease is the suppression of the formation of β-amyloid. the most promising in this regard are purposefully obtained monoclonal antibodies, which are at different stages of clinical trials: solanezumab; gantenerumab; crenezumab; aducanumab [34]. but it is impossible to deny the possibility of using small molecules to suppress the formation of amyloid fragments. it should be emphasized that in addition to pathogenetic, symptomatic treatment is also important, which, as a rule, is aimed at eliminating cholinergic deficiency [35]. in this regard, the combination of pharmacological properties of 2substituted 5,6,7,8-tetrahydrobenzo[4,5]thieno[2,3d]pyrimidine-4(3h)-one may be a new vector of therapy for alzheimer's disease, combining both the effect on the pathogenesis of the disease and the elimination of its leading symptoms. 4. conclusions in the course of the research, a method for the synthesis of 2-substituted 5,6,7,8-tetrahydrobenzo[4,5]thieno[2,3d]pyrimidine-4(3h)-one was proposed, according to which new representatives of this class of organic compounds were obtained. among the studied compounds there are substances with the high anticholinesterase activity. the most active are tetrahydrothienopyrimidine derivatives containing hydroxy-methoxyphenyl substituents in their structure. the compounds with fragments of 5-bromo-2hydroxy-3-methoxyphenyl and 3,5-di-tert-butyl-4hydroxyphenyl have the highest antiamyloid activity. as a result of the studies, the expediency of searching for new highly effective compounds for the treatment of neurodegenerative diseases in the series of tetrahydrobenzthienopyrimidine-4(3h)-one was confirmed. supplementary materials no supplementary materials are available. funding the reported study was funded by rfbr, project no. 20-315-90060. acknowledgment none. author contributions conceptualization: i.p.k data curation: i.p.k. formal analysis: a.s.c., i.p.k., d.i.p., a.a.g. funding acquisition: a.s.c., i.p.k. investigation: a.s.c., i.p.k., d.i.p., a.a.g. methodology: a.s.c., i.p.k., d.i.p. project administration: i.p.k. resources: a.s.c., i.p.k., d.i.p. software: d.i.p., a.a.g. supervision: i.p.k. validation: a.s.c., d.i.p. visualization: a.s.c., d.i.p., a.a.g. writing – original draft: a.s.c., i.p.k., d.i.p., a.a.g. writing – review & editing: a.s.c., a.a.g. conflict of interest the authors declare no conflict of interest. chimica techno acta 2022, vol. 9(2), no. 20229204 article 10 of 11 additional information author id’s: a.s. chiriapkin, scopus id 57218134815; i.p. kodonidi, scopus id 10240218600; d.i. pozdnyakov, scopus id 57190954589; a.a. glushko, scopus id 7003386007. institute’s website: pyatigorsk medical and pharmaceutical institute, https://www.pmedpharm.ru/sveden_eng. references 1. weber sa, patel rk, lutsep hl. cerebral amyloid angiopathy: diagnosis and potential therapies. expert rev neurother. 2018;18(6):503–513. doi:10.1080/14737175.2018.1480938 2. sağlık bn, osmaniye d, acar çevik u, levent s, kaya çavuşoğlu b, özkay 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https://doi.org/10.1016/j.ejmech.2012.08.027 https://doi.org/10.1515/mgmc-2017-0038 https://doi.org/10.1002/jhet.5570450243 https://doi.org/10.1021/jm300871x https://doi.org/10.33380/2305-2066-2021-10-2-25-31 https://doi.org/10.33619/2414-2948/73/02 https://doi.org/10.1016/j.jinorgbio.2017.02.021 https://doi.org/10.3390/molecules25112604 https://doi.org/10.1016/j.jagp.2015.12.003 https://doi.org/10.1016/j.jalz.2019.09.075 https://doi.org/10.1016/j.trci.2019.05.008 https://doi.org/10.1093/brain/awy132 kinetics of solid-state oxidation of iron, copper and zinc sulfide mixture published by ural federal university eissn 2411-1414 chimicatechnoacta.ru article 2023, vol. 10(2), no. 202310202 doi: 10.15826/chimtech.2023.10.2.02 1 of 12 kinetics of solid-state oxidation of iron, copper and zinc sulfide mixture alexander m. klyushnikov , sergey m. pikalov , roza i. gulyaeva * laboratory of non-ferrous metals pyrometallurgy, department of non-ferrous metals, institute of metallurgy of the ural branch of the russian academy of sciences, ekaterinburg 620016, russia * corresponding author: amk8@mail.ru this paper belongs to a regular issue. abstract the kinetics of solid-state oxidation by air of iron, copper and zinc sulfide natural mixture, which is typical of the pyritic copper ores, is investigated. using the high-temperature x-ray powder diffraction, thermogravimetry and differential scanning calorimetry, it was found that the process can be represented by five exothermic elementary reactions, corresponding to intensive burning of iron, copper and zinc sulfides, and two endothermic ones, associated with decomposition of copper and iron sulfates. kinetic analysis is performed by kissinger and augis–bennett methods, the model-free function mechanism was determined from y(α) master plots and iterative optimization of the kinetic parameters. the limiting steps of these reactions are nucleation and crystal growth, and the values of activation energy, pre-exponential factor and avrami exponent are in the ranges of 140–459 kj·mol–1, 1.41·104–3.49·1031 s–1, and 1.0–1.7, respectively. crystallization is followed by an increase in the number of nuclei, which may be formed both at the interface and in the bulk of the ore particles, and crystal growth is one-dimensional and controlled by a chemical reaction at the phase boundary or diffusion. the results of the work can contribute to the development of theoretical ideas about the physicochemical transformations of pyritic ores and concentrates during pyrometallurgical operations. keywords iron sulfide copper sulfide zinc sulfide pyritic copper ore oxidation kinetics received: 16.03.23 revised: 18.03.23 accepted: 20.03.23 available online: 30.03.23 key findings ● the formal kinetics of the sulfides, oxidation is attributed to seven elementary reactions. ● the activation energy of the elementary reactions is 140–459 kj·mol–1. ● the limiting steps of the elementary reactions are nucleation and crystal growth. ● nuclei may be formed both at the interface and in the volume of the ore particles. ● crystal growth is one-dimensional and is controlled by a chemical reaction or diffusion. © 2023, the authors. this article is published in open access under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). 1. introduction currently, pyritic copper ores are primarily processed according to the scheme that includes the following operations: comminuting and froth flotation of initial ore with the separation of sulfide concentrate, autogenous matte smelting of the concentrate, converting of the matte into blister copper, and fire refining and electrorefining of the blister copper to cathode copper. the matte smelting and converting slags are depleted by flotation, the resulting concentrates are returned to matte smelting, and the depleted slag is sent to the dump. the off-gases from matte smelting and converting are utilized in the production of sulfuric acid. the final products of the technology are cathode copper, slags, sulfuric acid, and electrolytic slime that concentrates precious and rare metals [1]. massive and disseminated ores of pyritic copper deposits from the urals region (russia) may have an increased (up to 0.2 mass%) content of cobalt [2, 3], and there is a need for its associated extraction in commercial products. the cobalt output channel in the scheme described above is the converter slag; smelting with a carbonaceous reducing http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2023.10.2.02 http://creativecommons.org/licenses/by/4.0/ https://orcid.org/0000-0001-8239-3757 https://orcid.org/0000-0001-6292-0468 https://orcid.org/0000-0003-2860-0377 https://crossmark.crossref.org/dialog/?doi=https://doi.org/10.15826/chimtech.2023.10.2.02&domain=pdf&date_stamp=2023-03-30 chimica techno acta 2023, vol. 10(2), no. 202310202 article 2 of 12 doi: 10.15826/chimtech.2023.10.2.02 agent and a sulfidizer (sulfide concentrate) can be used to extract a cobalt-rich sulfide product suitable for processing by conventional methods. the problem is that the fine intergrowth of ore minerals and high solubility of non-ferrous metals in pyrite are the reasons of transition of up to 95% of cobalt into the waste products during flotation of the ores [4]. processing the entire mass of the ore according to the described scheme is limited for technological and economic reasons. a promising route for the processing of pyritic copper ores from the urals can be their direct partial oxidative roasting in a fluidized bed furnace at 800–900 °c with the transfer of up to 80% of sulfur into the gas phase (in this case, a significant part of the calorific capacity of the ore will be used) and the use of the resulting calcine as a sulfidizing agent in the reduction-sulfiding smelting of oxidized nickel-cobalt ores (laterites) from the deposits of the same region, which are not currently processed [5]. varying the proportions of the roasted pyrite ore and oxidized nickel-cobalt ore in the feed of matte smelting will allow: i) regulating the yields and compositions of the smelting products; ii) controlling sulfur distribution, where most of the sulfur in the form of so2-rich roasting gases will be directed to manufacturing sulfuric acid, and the remainder will be spent for nickel and cobalt sulfiding of oxidized nickel ore during matte smelting; iii) extracting nickel, copper, cobalt and precious metals into the matte containing up to 10 mass% ni+cu+co (at the same time, the presence of copper in the matte will reduce the loss of nickel and cobalt in slag [6]); iv) eliminating or minimizing the need for fluxes by using the fluxing potential of the ores; v) obtaining the final slag in the final step of the scheme [7, 8]. we have conducted research towards the development of the scientific basis and the feasibility study of this method [9– 13]. an important aspect of the technology is the intensity of oxidative roasting of the copper ore, which determines the specific productivity of the fluidized bed furnace and temperature and duration of the process; for its evaluation, information on the chemistry, kinetics, and mechanism of roasting is needed. a lot of publications are devoted to these questions in relation to copper-nickel ores [14], copper [15– 27], zinc [17, 28, 29], nickel [30, 31], and copper-cobalt [32] concentrates, as well as individual sulfide minerals which are part of them: pyrite [33–46], marcasite [47], mackinawite [48], pyrrhotite [34, 36, 39, 49–54], chalcopyrite [36, 47, 55–59], covellite [60], chalcocite [47, 60–62], zinc sulfide [63–69], cobalt sulfide [70], and their mixtures [71, 72]. the purpose of the present work is to study the kinetics and mechanism of solid-state oxidation of iron, copper and zinc sulfide natural mixture, typical of the pyritic copper ores. 2. experimental for the study, a representative sample of a pyritic copper ore from the dergamysh deposit (russia) was taken; the sample was ground in a laboratory mill to a particle size of less than 0.1 mm. the chemical composition of the ore sample was investigated by inductively coupled plasma atomic emission spectrometry (icp aes) on an icap 6300 duo optical emission spectrometer (thermo scientific). preparations for analysis were carried out by dissolving a sample weighing 0.1 g in a mixture of mineral acids. the thermal properties of the ore sample were studied by the method of simultaneous thermogravimetry (tg) and differential scanning calorimetry (dsc) on a sta 449 c jupiter® instrument for synchronous thermal analysis (netzsch). for measurements, about 8.4 mg of the sample was distributed in a thin layer at the bottom of a corundum crucible, after which the crucible was placed into the measurement cell of the instrument and heated from 30 to 1100 °c at a rate of βi = 5, 10, and 20 °c·min–1 (hereinafter, the subscript "i" denotes the i-th temperature program (i = 1, 2, 3)). dynamic oxidizing atmosphere in the reaction space was maintained by blowing the measurement cell with dried synthetic air (21 vol% o2, 79 vol% n2) supplied at a flow rate of 30 cm3·min–1. the empty reference crucible was the same as the sample crucible. the dsc correction parameters were estimated from the enthalpy of fusion of chemically pure (99.99 mass%) indium using the netzsch thermokinetics 3.0 software. the composition of gases evolved during heating was evaluated by mass spectrometry (ms), for which a quadrupole qms 403 c aёolos® mass spectrometer (netzsch) was coupled with the thermal analyzer; ionic current (i, a) of gases (h2o, co2, so2, and so3) released during heating and oxidation of the ore was measured in the mode of given mass numbers. the processing of the measurement results was made using the netzsch proteus® 5.1 software, including the identification of the onset (to, °c), maximum (tp, °c), and endset (te, °c) temperatures, and areas (δh, j·g–1) for dsc peaks, relative mass changes (δm, %), and peak temperatures (tph2o, tpco2, tpso2, and tpso3, °c) of the ionic current curves of h2o, co2, so2, and so3. separation of complex dsc peaks into their constituent overlapping elementary peaks and determination of their onset (toij, °c), maximum (tpij, °c), and endset (teij, °c) temperatures, as well as the values of their full width at the half of maximum (δtpij, °c) were performed using the mathworks software according to the method outlined in [73]. the baseline was characterized by a linear function, and the profile of elementary peaks was approximated by frazer–suzuki (asymmetric gaussian) function. for each temperature, the value of the function describing the complex peak was elaborated as the sum of such values for elementary peaks, and the reliability of approximation (for significance level α = 5%) was controlled by the value of pearson correlation coefficient (r). the measurement error was ±0.01 mg for mass, ±3 °c for temperature, and ±5% for heat. the phase composition of the ore sample was determined by x-ray powder diffraction (xrd) on dron-2.0 xhttps://doi.org/10.15826/chimtech.2023.10.2.02 https://doi.org/10.15826/chimtech.2023.10.2.02 chimica techno acta 2023, vol. 10(2), no. 202310202 article 3 of 12 doi: 10.15826/chimtech.2023.10.2.02 ray diffractometer. experiments on oxidative roasting of the ore combined with evaluation of the phase composition of the products using high-temperature xrd (htxrd) method were performed in the high-temperature uvd– 2000 setup mounted on the above device, equipped with a resistance furnace with a platinum heating element; the design of the setup provided free atmospheric air access to the working chamber. the experiment included heating the initial ore at an average rate of 10 °c·min–1 from 25 °c to a given temperature (100, 200, 300, 400, 500, 600, 700, 800, and 900 °c) and isothermal dwelling at this temperature for 80 min. at the same time, as mentioned above, in situ diffractograms were recorded in the isothermal sections of the cycles. the measurements were conducted in the following mode: bragg–brentano geometry; cu kα radiation (λα = 1.54056 å); graphite monochromator on the output beam; tube voltage and current of 30 kv and 30 ma, respectively; angular range (2θ) and step (2θ) of 10–90° and 0.02°, and point exposure time of 2 s at 25 °c and 1.2 s for high-temperature measurements. the samples for the experiment were prepared by applying 1–3 mg of a powdery (<0.1 mm particle size) material to a substrate made of plexiglas or (zr,y)o2–x. the temperature was measured with a type s thermocouple, the hot junction of which was placed near the sample (the measurement error was ±2 °c). phase identification and semi-quantitative (with an error of ±5 relative %) estimation of the contents in the crystal component of the samples were performed by the reference intensity ratio (rir) method [74, 75] using the qualx 2.0 software [76] and the pow_cod database [76]. based on htxrd data, a possible sequence of chemical reactions taking place at the studied temperatures was established; the values of reaction equilibrium constants (kt) at temperature t (k) were calculated using the hsc chemistry 6.12 package (outotec research oy). the microstructure and local elemental composition of the ore sample were studied by scanning electron microscopy (sem) and energy dispersive spectrometry (eds) using a mira 3 lmu auto emission electron microscope (tescan) equipped with an inca energy 350 x-max 80 energy dispersive x-ray spectrometer (oxford instruments). sem imaging was performed at an accelerating voltage of 20 kv, an electron beam current of 20 na, and an effective beam resolution of 3 μm. during the preparation of the specimen for analysis, a sample was embedded into bakelite, the surface of the cured cylindrical block was polished and coated with a thin carbon layer layer (25 nm). kinetic analysis of the oxidation of the ore was performed by mathematical treating of dsc heating data of its sample for three temperature programs (βi = 5, 10, and 20 °c·min–1) in the boundaries of exothermic and endothermic peaks corresponding to the development of this process. first, the inverse kinetic problem was solved, i.e., the kinetic parameters of oxidation were determined based on the experimental data. for this purpose, each j-th (j = 1, 2, …, n) elementary dsc peak was considered as a trace of the j-th formal irreversible one-step reaction aj → bj, where aj and bj are the initial formal reagent and the final formal product, respectively (both the complex and simple i-th curve peaks obtained by separation were counted as elementary peaks). the completion and intensity of the j-th reaction at the i-th temperature program were quantified through conversion degree (αij) and reaction rate (dαij/dt, s–1) of aj → bj transformation [77, 78] according to the equations: α𝑖𝑗 = ∫ ( d𝐻𝑖𝑗 (𝑡) d𝑡 ) d𝑡 𝑡 𝑡0𝑖𝑗 ∫ ( d𝐻𝑖𝑗 (𝑡) d𝑡 ) 𝑡e𝑖𝑗 𝑡0𝑖𝑗 d𝑡 = ∫ ( d𝐻𝑖𝑗 (𝑇) d𝑇 ) d𝑇 𝑇 𝑇0𝑖𝑗 ∫ ( d𝐻𝑖𝑗 (𝑇) d𝑇 ) 𝑇e𝑖𝑗 𝑇0𝑖𝑗 d𝑇 , (1) dα𝑖𝑗 d𝑡 = 𝑘𝑗 (𝑇) 𝑓𝑗 (α𝑖𝑗 ) = 𝐴𝑗 exp (– 𝐸𝑗 𝑅𝑇 ) 𝑓𝑗 (α𝑖𝑗 ), (2) where toij and teij are the initial and final moments of the reaction (that is, the moments of the beginning and the end of the deviation of the dsc curve from the baseline), respectively, s (toij = 0 s); t is the current reaction time, s (toij < t < teij); toij and teij are the temperatures of the beginning and the end of the reaction, respectively, k; t is the temperature at the current time moments of the reaction, k (toij < t < teij); hij(t) and hij(t) are the functions describing the dependence of reaction enthalpy on temperature and time, respectively, j·g–1; kj(t) is the reaction rate constant invariant with respect to the temperature program, s–1; fj(αij) is the reaction model invariant with respect to the temperature program (i.e. a function reflecting the reaction mechanism); ej is the effective activation energy invariant with respect to the temperature program, j·mol–1; aj is a pre-exponential factor invariant with respect to the temperature program, s–1; r is the gas constant, j·mol–1·k–1. in the calculations it was assumed that the temperature changes over time according to a linear law: 𝑇 = 𝑇0𝑖𝑗 + β𝑖 𝑡, (3) and βi = dt/dt = const. the johnson–mehl–avrami– erofeev–kolmogorov (jmaek) model [78, 79] was used as the reaction model fj(αij) (its choice is due to the reaction model identification results described below): 𝑓(α𝑖𝑗 ) = 𝑛𝑗 (1 – α𝑖𝑗 ) [– ln(1 – α𝑖𝑗 )] (𝑛𝑗 –1)/𝑛𝑗 , (4) which is based on the following equation describing the kinetics of nucleation and crystal growth of the new phase in the parent phase α𝑖𝑗 = 1 – exp (– 𝑘𝑗 𝑡 𝑛𝑗 ) = 1 – exp [– 𝐴𝑗 exp (– 𝐸𝑗 𝑅𝑇 ) ( 𝑇−𝑇o𝑖𝑗 β𝑖 ) 𝑛𝑗 ]; (5) here nj is the avrami exponent invariant with respect to the temperature program, which depends on the mechanism of the process. the initial estimation of the apparent activation energy (ej, j·mol–1) and the pre-exponential factor (aj, s–1) was performed by the kissinger method [78, 80]; the method is based on estimating the slope (–ej/r) and https://doi.org/10.15826/chimtech.2023.10.2.02 https://doi.org/10.15826/chimtech.2023.10.2.02 chimica techno acta 2023, vol. 10(2), no. 202310202 article 4 of 12 doi: 10.15826/chimtech.2023.10.2.02 intercept (ln(ajr/ej)) of a pairwise linear regression for the model ln ( β𝑖 𝑇p𝑖𝑗 2 ) = ln 𝐴𝑗 𝑅 𝐸𝑗 − 𝐸𝑗 𝑅𝑇p𝑖𝑗 , (6) constructed from the pairs of observed values of ln(βi/tpij2)–1/tpij for each βi. the reliability of approximation was controlled by the value of the coefficient of determination (rj2). in order to identify the reaction model for the j-th reaction at the i-th temperature program, numerical values of the reference function yij(αij) were calculated for a given series of values αij varying from 0.1 to 1 in step of 0.1: 𝑦(α𝑖𝑗 ) = ( dα𝑖𝑗 d𝑡 ) α𝑖𝑗 exp ( 𝐸𝑗 𝑅𝑇α𝑖𝑗 ) ; (7) then the pairs of yij(αij)–αij for each βi were plotted on the coordinate plane and the resulting curves were compared with the theoretical plots of the function y(α) for the tabulated forms f(α). the reaction model selection was based on qualitative correspondence between the experimental and theoretical curves. the invariant avrami exponent (nj) of the j-th reaction was determined by the augis–bennett method [81]; the calculation was performed using the formulae: 𝑛𝑗 = 1 3 ∑ 𝑛𝑖𝑗 3 𝑖=1 , (8) 𝑛𝑖𝑗 = 2,5𝑅𝑇p𝑖𝑗 2 𝐸𝑗 δ𝑇𝑖𝑗 , (9) where nij is the avrami exponent of the j-th reaction for the i-th heating rate; the value of ej (j·mol–1) was taken from the kissinger analysis. after that, the following iterations were performed: the values of invariant kinetic parameters of elementary reactions (ej, aj, and nj) were substituted into equation (5), analytical expressions were found to estimate the conversion degree (αij) for each j-th reaction and i-th temperature program, calculated kinetic curves αij–t were reconstructed, and, by varying the parameter aj from its initial value at fixed ej and nj, the obtained model was optimized by approximating experimental curves with the calculated ones (the quality of approximation at this and subsequent iterations was controlled by the value of the pearson correlation coefficient (rij)). the refined value of the invariant pre-exponential factor (arj, s–1) was obtained as the arithmetic mean of the optimal aj values for all temperature programs. then obtained arj value was substituted into equation (5), the parameters arj and nj were fixed, and the model was optimized by varying ej from its initial value to obtain a refined invariant value of the activation energy (erj, j·mol–1). at the final stage of optimization, the fixed values of erj and arj were substituted into equation (5) and the model was optimized by varying nj from its initial value to determine the refined invariant value of the avrami exponent (nrj). the optimum invariant kinetic parameters found were used to solve a direct kinetic problem in relation to the ore oxidation process in the studied range of temperature programs; by substituting erj, arj, and nrj values into equations (5) and (2), analytical expressions were obtained to calculate the conversion degree (αj) and conversion rate (dαj/dt, s–1) at for the elementary reactions. verification of the models for each reaction was carried out by assessing the closeness of the correlation between theoretical and experimental data; for this purpose, refined calculated kinetic curves αij–t were suggested and compared with the experimental ones; the pearson correlation coefficient averaged over all temperature programs (ravj) served as the optimality criterion: 𝑟av𝑗 = 1 3 ∑ 𝑟𝑖𝑗 . 3 𝑖=1 (10) 3. results and discussion according to the icp aes data, the original ore has the following composition, mass%: 0.98 cu, 0.01 ni, 0.10 co, 0.78 zn, 38.5 fe, 30.2 s, 0.03 as, 17.0 sio2, 0.9 cao, 6.7 mgo, and 4.8 others. at the ordinary content of copper (0.98 mass%) and zinc (0.78 mass%) it is characterized by higher (0.10 mass%) content of cobalt. the approximate mass fractions of sulfides and rock-forming components are 63.3% and 36.7%, respectively. according to the xrd data (figure 1) the total content of sulfide phases in the initial ore sample, determined by the rir method, is 42.4 mass%; among the revealed minerals pyrite (fes2), chalcopyrite (cufes2), and wurtzite (zns) can be noted, the fractions of which are 30.7, 3.1, and 8.6 mass%, respectively. there are barren minerals in the rest of the ore (57.6 mass%), such as: tremolite (ca2mg5h2(sio3)8), siderite (feco3), and quartz (sio2), whose fractions are 17.1, 2.6, and 38.0 mass%, respectively. figure 1 xrd patterns of the initial ore at 25 °c (the reflections of zirconium dioxide refer to the substrate). https://doi.org/10.15826/chimtech.2023.10.2.02 https://doi.org/10.15826/chimtech.2023.10.2.02 chimica techno acta 2023, vol. 10(2), no. 202310202 article 5 of 12 doi: 10.15826/chimtech.2023.10.2.02 the sem and eds study showed that the ore has a fullcrystalline porphyry-like fine-grained structure characterized by close germination of sulfide and oxide phases, and has a massive (disordered) texture. in the matrix represented by magnesium silicate, there are hydrated iron (iii) oxide, and iron and calcium carbonates of the compositions mg3si4o10(oh)2 (talc), fe2o3·nh2o (limonite), feco3 (siderite), and caco3 (calcite) respectively. in addition, there are distributed phenocrystals (5–150 μm) of iron sulfide corresponding in composition to pyrite (fes2), and small (up to 5 μm) inclusions with sphalerite (zn1–xfexs) and chalcopyrite (cufes2) formulae. the data on the composition and structure of the ore obtained by xrd, sem, and eds methods complement each other and satisfactorily agree with the data obtained earlier for the ore of the same deposit [3, 4]. summarizing the data obtained in the present work, we can conclude that the main ore minerals of the studied sample may be pyrite, pyrrhotite, chalcopyrite, sphalerite (wurtzite), and limonite, and the barren minerals are tremolite, silica, talc, siderite, calcite, and some iron aluminosilicates. regarding the distribution of non-ferrous metals, it should be noted that, in contrast to copper and zinc, cobalt does not form its own mineral forms, and in the amount up to 0.35 mass% it is isomorphically included in pyrite. it follows from the htxrd data that there were no significant changes in the phase composition of the initial sample before 200 °c; only at 200 °c the appearance of iron (iii) sulfate (fe2(so4)3) was noted, indicating the beginning of pyrite oxidation by the following reaction: 2fes2 + 7o2 = fe2(so4)3 + so2, logk473 = 229. (11) the fact of low-temperature pyrite oxidation agrees with the data [15, 52]. the formation of hexagonal pyrrhotite (fe9s10), poitevinite (feso4·h2o), and copper (ii) sulfate (cuso4) at 300 °c can be associated with the processes described by the following equations: 9fes2 + 8o2 = fe9s10 + 8so2, logk573 = ~18, (12) fes2 + 3o2 = feso4 + so2, logk573 = 80, (13) cufes2 + 4o2 = feso4 + cuso4, logk573 = 100, (14) feso4 + h2o = feso4·h2o, logk573 = –1. (15) in this case, the reason for the appearance of hydrate compounds may be the interaction of oxidation products with water contained in the air, released during the dehydration of rock-forming minerals. at 400 °c, in addition to the phases formed at 300 °c, monoclinic pyrrhotite (fe7s8), cubanite (cufe2s3), magnetite (fe3o4), and hematite (fe2o3) were detected, formed by the reactions listed below [15]: 7fes2 + 6o2 = fe7s8 + 6so2, logk673 = 122, (16) 2fes2 + 5.5o2 = fe2o3 + 4so2, logk673 = 121, (17) 3fes2 + 8o2 = fe3o4 + 6so2, logk673 = 176, (18) 4fe3o4 + o2 = 6fe2o3, logk673 = 23, (19) 2cufes2 + 3.5o2 = 2cus + fe2o3 + 2so2, logk673 = 76, (20) cus + 2fes2 = cufe2s3 + s2. (21) despite the fact that the presence of pyrite in the roasting product at 400 °c was not confirmed, its reflections reappear at 500 °c; the other newly formed phases are hexagonal modifications of iron sulfide with the formulae of fe11s12 and fes, dolerophanite (cuo·cuso4), and tenorite (cuo); in this regard the oxidation chemistry can be supplemented with the following set of equations [15, 50]: 11fes2 + 10o2 = fe11s12 + 10so2, logk773 = ~18, (22) fes2 + o2 = fes + so2, logk773 = 18, (23) fe7s8 + 15o2 = 7feso4 + so2, logk773 = 281, (24) fe7s8 + 13.25o2 = 3.5fe2o3 + 8so2, logk773 = 257, (25) fe9s10 + 16o2 = 3fe3o4 + 10so2, (26) 3fes + 5o2 = fe3o4 + 3so2, logk773 = 97, (27) 2cufes2 + 6.5o2 = 2cuo + fe2o3 + 4so2, logk773 = 109, (28) 2cufes2 + 4.5o2 = cu2s + fe2o3 + 3so2, logk773 = 64, (29) cu2s + 2o2 = 2cuo + so2, logk773 = 17, (30) 2cufes2 + 7o2 = cuo·cuso4 + fe2o3 + 3so2, logk773 = 116, (31) cufe2s3 + 5o2 = cuo + fe2o3 + 3so2. (32) reaching 600 °c is characterized by the complete consumption of iron and copper sulfides with the formation of hematite and magnetite, iron (ii) and (iii) and copper (ii) sulfates according to reactions (13), (14), (24)–(30), and also by the appearance of wustite (fe0.902o), which is formed according to the reaction: fes2 + 2.554o2 = 1.109fe0.902o + 2so2, logk873 = ~40. (33) starting from 700 °c, the products of roasting show the absence of sulfates, which is associated their decomposition [15, 20, 27, 31–33, 50, 52, 82]: 2feso4 = fe2o3 + so3 + so2, logk973 = ~0, (34) fe2(so4)3 = fe2o3 + 3so3, logk973 = –2, (35) https://doi.org/10.15826/chimtech.2023.10.2.02 https://doi.org/10.15826/chimtech.2023.10.2.02 chimica techno acta 2023, vol. 10(2), no. 202310202 article 6 of 12 doi: 10.15826/chimtech.2023.10.2.02 4cuso4 + cu2s = 6cuo + 5so2, logk973 = 7, (36) 4cuso4 + cu2o = 3cuo·cuso4 + so2, logk973 = 0.5 (37) 4cuo·cuso4 + cu2s = 10cuo + 5so2, logk973 = 5, (38) 2cuso4 = cuo·cuso4 + so3, logk973 = –2, (39) cuo·cuso4 = 2cuo + so3, logk973 = –2. (40) the products of sulfide oxidation in this case are wustite, magnetite and hematite, as well as copper (i) ferrite (cufeo2), which appears as a result of the attack of magnetite on copper (ii) oxide: cuo + fe3o4 = 2cufeo2 + fe2o3, logk973 = 2. (41) at the same temperature, one can expect the onset of intensive thermal decomposition of hydrated magnesium silicates, for example, chrysotile (mg3si2o5(oh)4) and talc (mg3si4o10(oh)2), leading to the formation of metasilicates, in particular diopside (cafe0.13mg0.943si1.927o6); these processes can be represented by a general scheme [83]: mg3si2o5(oh)4 = mg2sio4 + mgsio3 + 2h2o, logk973 = 3, (42) mg3si4o10(oh)2 = 3mgsio3 + sio2 + h2o, logk973 = 0.5. (43) the absence of traces of forsterite (mg2sio4) in the corresponding diffractograms may be due to its amorphousness at the initial moments of formation. also, at 700 °c, reflections from zincite (zno) formed according to the following equation were detected [29]: zns + 1.5o2 = zno + so2, logk973 = 20. (44) at 800 and 900 °c, the final products of deep roasting are formed containing hematite (fe2o3), magnetite (fe3o4), and diopside (fe0.015mg0.985sio3 at 800 °c and fe0.15mg1.82si2o6 at 900 °c), which originate in the above reactions. at 800 °c, franklinite (znfe2o4) and copper ferrite of the composition cufe5o8 can additionally be formed, and at 900 °c – zinc silicate (znsio3), tenorite (cuo), and delafossite (cufeo2); the first three of these phases are the products of the following reactions [29, 63, 84]: zno + fe2o3 = znfe2o4, logk1073 = 1, (45) cufeo2 + 2fe2o3 = cufe5o8, (46) zno + sio2 = znsio3, logk1173 = ~0, (47) where the last two are the processes described by equations (28) and (41). the composition of the gas phase in the considered temperature range is determined by the reaction 2so2 + o2 = 2so3, logk1053 = ~0, (48) whose direction changes from direct to reverse at ~780 °c. it should also be noted that the absence of siderite and zinc sulfide reflections in a number of diffractograms in the temperature ranges of their possible existence can be explained by the low sensitivity of the applied analytical method with respect to these phases. the values of the equilibrium constants of most of the listed reactions exceed (or are close to) unity, which confirms the possibility of their proceeding in the forward direction (reactions for which, due to the lack of thermodynamic data for a number of compounds in the hsc chemistry 6.12 package, the kt value is not indicated, are hypothetical or confirmed by literature data). on the whole, the presented reactions can only serve as the simplest explanation for the appearance of phases detected by xrd in the roasting products; it is obvious that the chemistry of the ore oxidation is even more complex. the results of thermal analysis of the ore carried out under heating conditions from 30 to 1100 °c in air flow (30 cm3·min–1) with heating rates of βi = 5, 10, and 20 °c·min–1 is presented in figures 2 and 3, and table 1. there are three primary thermal effects on the dsc curves (figure 2). the first effect is a complex exothermic peak of high intensity formed by a series of partially overlapping (partially resolved at βi = 5 °c·min–1) elementary exothermic peaks. the separation of complex exothermic peaks showed (figure 3 and table 1) that each of them is the result of the superimpostion of five elementary exothermic peaks (hereinafter referred to as ep1, ep2, ep3, ep4, and ep5). the second and third effects are weakly expressed simple (elementary) endothermic peaks (hereinafter referred to as ep6 and ep7). according to the tg data (figure 2), by 1100 °c the total mass loss during oxidation is 28–29%, of which the 30– 318 °c region free of dsc effects accounts for 4–5%, and the series of exothermic (359–570 °c) and two endothermic (561–664 °c and 743–927 °c) anomalies are 7–10, 8–9, and, 4–6% respectively; the remaining losses account for the high-temperature region. figure 2 tg and dsc curves (βi = 5, 10, and 20 °c·min –1) for the pyritic copper ore. https://doi.org/10.15826/chimtech.2023.10.2.02 https://doi.org/10.15826/chimtech.2023.10.2.02 chimica techno acta 2023, vol. 10(2), no. 202310202 article 7 of 12 doi: 10.15826/chimtech.2023.10.2.02 figure 3 separation results for complex exothermic dsc peaks. solid straight lines are baselines, dots are experimental dsc data, dashed curves are calculated dsc curves for elementary peaks, and solid curves are summary calculated dsc curves. the circles with arrows show the numbers of elementary peaks. table 1 parameters of the elementary dsc peaks, and nij values calculated by the augis–bennett method. parameter value βi = 5 °c·min –1 peak ep1 ep2 ep3 ep4 ep5 ep6 ep7 toij/°c 413 397 442 449 451 561 743 tpij/°c 415 417 447 467 484 598 774 teij/°c 418 426 457 486 514 629 834 δtpij/k 3.1 16.3 12.6 23.8 14.0 32.2 43.5 nij 2.5 1.6 1.5 1.2 2.8 1.8 3.4 βi = 10 °c·min –1 peak ep1 ep2 ep3 ep4 ep5 ep6 ep7 toij/°c 416 394 442 478 483 566 760 tpij/°c 420 422 466 496 513 615 814 teij/°c 426 443 494 527 546 645 867 δtpij/k 5.7 28.7 30.8 27.9 37.1 38.3 33.6 nij 1.4 0.9 0.7 1.2 1.2 1.6 4.7 βi = 20 °c·min –1 peak ep1 ep2 ep3 ep4 ep5 ep6 ep7 toij/°c 398 431 440 433 489 596 798 tpij/°c 427 450 462 496 536 630 855 teij/°c 445 488 498 549 562 664 927 δtpij/k 26.8 31.9 33.9 38.1 42.4 31.4 42.5 nij 0.3 0.9 0.6 0.8 1.1 1.8 4.0 theoretical calculations demonstrated that the removal of all volatile components (h2o, co2, and s) into the gas phase should reduce the mass of the sample by ~20%; the experimental estimate exceeds this value, indicating either a possible error in determining the material composition of the ore or a more complex process. the zone of exothermic processes is confined to the traces of intense gas emission noted on the ms curves (figure 4): so2 (tpso2 = 415 and 466 °c at βi = 5 °c·min–1, tpso2 = 420 and 465 °c at βi = 10 °c·min–1, and tpso2 = 427 and 456 °c at βi = 20 °c·min–1), so3 (tpso3 = 415 °c and 464 °c at βi = 5 °c·min–1, tpso3 = 419 and 472 °c at βi = 10 °c·min–1, and tpso3 = 463 °c at βi = 20 °c·min–1), and co2 (tpco2 = 519 °c at βi = 5 °c·min–1, tpco2 = 536 °c at βi = 10 °c·min–1, and tpco2 = 546 °c at βi = 20 °c·min–1). https://doi.org/10.15826/chimtech.2023.10.2.02 https://doi.org/10.15826/chimtech.2023.10.2.02 chimica techno acta 2023, vol. 10(2), no. 202310202 article 8 of 12 doi: 10.15826/chimtech.2023.10.2.02 subsequent endothermic events are associated with peaks in the so2 ion current (tpso2 = 604 and 819 °c at βi = 5 °c·min–1, tpso2 = 632 and 842 °c at βi = 10 °c·min–1, and tpso2 = 647 and 855 °c at βi = 20 °c·min–1). the ms traces also revealed three weak peaks of the ion current of water, the maxima of which (tph2o) vary in the ranges of 120–125, 290–310, and 950–960 °c. analysis of the results of htxrd, dsc, tg, and ms shows that heating (βi = 5–20 °c·min–1) of the pyritic copper ore up to 318 °c is accompanied by the removal of adsorption (capillary) and hygroscopic moisture into the gas phase, which is associated with the initial monotonic mass loss (δm = 4–5%) and the release of the h2o into the gas phase at 120–125 and 290–310 °c. the main oxidation period of pyritic copper ore, associated with the release of the largest (–δh = 1468–2052 j·g–1) amount of heat, begins at 359 °c, culminates at 420–468 °c, and finished at 570 °c; it accounts for up to ~34 relative % total mass loss. numerous interactions of the ore minerals with a gaseous atmosphere can occur within its boundaries, described by equations (12)–(32); some reactions are characterized by a high thermal effect and provide for the release of a large amount of so2 capable of interacting with o2 by reaction (48). the appearance of co2, intensifying at 519–546 °c, can be associated with the oxidative decomposition of siderite: 4feco3 + o2 = 2fe2o3 + 4co2, logk819 = 40. (49) based on the fact of the absence of mass increase revealed by the tg method, the main processes in this temperature range can be associated with ignition and direct oxidation (burning) of sulfides with the formation of oxides [15]; the formation of sulfates is limited, or they are effectively broken by sulfide compounds. the final stage of the oxidation includes two processes accompanied by weak endothermic effects (δh = 49–97 and 51–113 j·g–1, respectively), mass reduction (up to ~31 and ~21 relative %, respectively), and so2 release; apparently, in this case, thermal decomposition of residual sulfates takes place: iron sulfates at 561–664 °c (reactions (34) and (35)) and copper sulfates at 743–927 °c (reactions (39) and (40)). this conclusion is confirmed by the literature data [19, 31, 57, 86, 87]. at 950–960 °c, part of the crystallization water of rock-forming silicate minerals is released. thus, the kinetics of oxidative roasting of the ore can be formally attributed to seven elementary reactions: five exothermic (at 398–445, 394–488, 440–498, 433–549, and 451–562 °c) corresponding to intensive burning of iron, copper and zinc sulfides, and two endothermic (at 561– 664 °c and 743–927 °c) related to the decomposition of residual copper and iron sulfates. the grouped dsc peaks of the same name, which are their traces, are shown in figure 5. the results of kinetic analysis of the dsc data in relation to the temperature ranges of these reactions are presented in figures 6, and 7, and table 2. the shape of the plots of the yij(αij) function (figure 7) for elementary oxidation reactions corresponds to the jmaek (an) kinetic model of nucleation and crystal growth [78]. the refined invariant kinetic parameters of the elementary reactions differ somewhat from the initial estimates (table 2). figure 4 ms curves (βi = 20 °c·min –1) for the pyritic copper ore. figure 5 grouping results for elementary endothermic dsc peaks (results for exothermic elementary dsc peaks have a similar view). figure 6 kissinger plots for elementary dsc peaks. https://doi.org/10.15826/chimtech.2023.10.2.02 https://doi.org/10.15826/chimtech.2023.10.2.02 chimica techno acta 2023, vol. 10(2), no. 202310202 article 9 of 12 doi: 10.15826/chimtech.2023.10.2.02 the kinetic models derived from these parameters have the following form: dα1 d𝑡 = 4.89 ∙ 1031 exp (– 459000 𝑅𝑇 ) (1 – α1) [– ln(1 – α1)] 0.29, (50) dα2 d𝑡 = 4.52 ∙ 108 exp (– 140000 𝑅𝑇 ) (1 – α2) [– ln(1 – α2)] 0.09, (51) dα3 d𝑡 = 4.74 ∙ 1013 exp (– 220000 𝑅𝑇 ) (1 – α3), (52) dα4 d𝑡 = 1.32 ∙ 108 exp (– 160000 𝑅𝑇 ) (1 – α4) [– ln(1 – α4)] 0.09, (53) dα5 d𝑡 = 1.24 ∙ 106 exp (– 155000 𝑅𝑇 ) (1 – α5) [– ln(1 – α5)] 0.41, (54) dα6 d𝑡 = 5.88 ∙ 1015 exp (– 320000 𝑅𝑇 ) (1 – α6) [– ln(1 – α6)] 0.17, (55) dα7 d𝑡 = 1.69 ∙ 104 exp (– 149000 𝑅𝑇 ) (1 – α7) [– ln(1 – α7)] 0.17, (56) verification of the obtained models showed a high (ravj = 0.8580–0.9984) level of correlation between the refined calculated and experimental data (figure 8, and table 2). therefore, these models describe the kinetic patterns of oxidation of the investigated pyritic copper ore under given conditions with sufficient reliability. according to the literature data, the effective activation energy of the processes accompanying the oxidation (when heated in air) of iron, copper, and zinc sulfides, as well as their natural and artificial mixtures of various sizes (from –0.043 to –12 mm), can be of 7–463 kj·mol–1 [11, 14, 19, 26, 27, 40, 41, 53, 60, 67, 69, 72, 82, 85]; the estimates obtained in this work (erj = 124–455 kj·mol–1) do not go beyond this range. the results of determining the reaction model show that the limiting step of all elementary oxidation reactions of the studied ore is nucleation and crystal growth. the examples of the application of the jmaek model to describe the mechanism of oxidation of sulfides (in particular, chalcopyrite and pyrite concentrates) should be mentioned [41, 67, 88]. the values of the avrami exponent (nrj) obtained in this work are in the range from 1 to 1.7, which allows us to draw the following conclusions regarding the details of the mechanism and morphological features of the process: i) crystallization of the products of elementary reactions is accompanied by an increase in the number of nuclei; ii) nuclei of a new phase may be formed both at the interface and in the volume of the ore particles; iii) crystal growth is one-dimensional and controlled by a chemical reaction at the phase boundary or diffusion of reagents [89]. figure 7 master plots y(α) for endothermic elementary reactions (results for exothermic elementary reactions have a similar view). figure 8 experimental (circles) and refined calculated (triangles) kinetic curves for endothermic elementary reactions (results for exothermic elementary reactions have a similar view). table 2 kinetic parameters of elementary reactions. elementary reaction kinetic parameter ej/kj·mol –1 erj/kj·mol –1 logaj/log(s –1) logarj/log(s –1) nj n r j ravj 1 455±22 459 32.5 31.5 1.4 1.4 0.8615 2 142±21 140 8.3 8.6 1.1 1.1 0.8580 3 220±22 220 13.7 13.7 1.0 1.0 0.9464 4 159±21 160 8.7 8.1 1.1 1.1 0.9527 5 124±20 155 5.9 5.9 1.7 1.7 0.9928 6 275±15 320 15.6 15.7 1.7 1.2 0.9984 7 154±14 149 4.4 4.2 4.0 1.2 0.9689 note. the numbers of elementary reactions correspond to the numbers of elementary peaks in table 1. https://doi.org/10.15826/chimtech.2023.10.2.02 https://doi.org/10.15826/chimtech.2023.10.2.02 chimica techno acta 2023, vol. 10(2), no. 202310202 article 10 of 12 doi: 10.15826/chimtech.2023.10.2.02 it should be noted that, compared with copper concentrates, pyritic copper ore is a material that is more technologically complex, and the purpose of its roasting is not only the removal of a certain amount of sulfur into the gas phase, but also the corresponding transformation (decomposition and dehydration) of rock-forming minerals. 4. limitations for deeper understanding of the kinetics of solid-state oxidation of the studied sulfide systems, it is necessary to verify the data obtained in this work with the results of studying the isothermal kinetics of the process and information about the microstructure of the oxidation products. 5. conclusions the formal kinetics of the solid-state oxidation of iron, copper and zinc sulfide natural mixture, typical of the pyritic copper ores, can be attributed to seven elementary reactions: five exothermic (at 398–445, 394–488, 440–498, 433–549, and 451–562 °c), corresponding to intensive burning of iron, copper and zinc sulfides, and two endothermic (at 561–664 and 743–927 °c), related to the decomposition of residual copper and iron sulfates. the limiting steps of these reactions are nucleation and crystal growth, and the values of activation energy, pre-exponential factor and avrami exponent are in the ranges of 140–459 kj·mol–1, 1.41·104–3.49·1031 s–1, and 1.0–1.7, respectively. crystallization of the products of elementary reactions is accompanied by an increase in the number of nuclei; nuclei of a new phase may be formed both at the interface and in the volume of the ore particles, and crystal growth is one-dimensional and controlled by a chemical reaction at the phase boundary or diffusion. the resulting kinetic models make it possible to predict a degree of process completion depending on time and temperature. the results of the work as a whole can contribute to the development of theoretical ideas about the physicochemical transformations of pyrite ores and concentrates during pyrometallurgical operations, and can also be used in the practice of oxidative roasting of these materials. ● supplementary materials no supplementary materials are available. ● funding this research had no external funding. ● acknowledgments the work was carried out according to the state assignment for imet ub ras (no. 122020100404-2) using equipment of the collaborative usage center "ural–m". ● author contributions conceptualization: a.m.k. methodology: a.m.k. formal analysis: a.m.k. investigation: r.i.g. and s.m.p. writing – original draft preparation: a.m.k. writing – review and editing: r.i.g. ● conflict of interest the authors declare no conflict of interest. ● additional information author ids: alexander m. klyushnikov, scopus id 57220987625; sergey m. pikalov, scopus id 6603186623; roza i. gulyaeva, scopus id 6602478183. website: institute of metallurgy of the ural branch of the russian academy of sciences, http://www.imet-uran.ru. references 1. schlesinger me, king mj, sole kc, davenport wg. extractive metallurgy of copper. 5th edition. oxford: elsevier; 2011. 2. selivanov en, gulyaeva ri, klyushnikov am. study of structure and phase composition of copper-cobalt sulfide ores of dergamyshskoe deposit. tsvetnye metally. 2016;3:13–17. doi:10.17580/tsm.2016.03.02 3. melekestseva iyu, maslennikov vv, maslennikova sp. traceelements in sulfides of the dergamysh cobalt-bearing massive sulfide deposit, the southern 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hydrogenation reactions of nitroand acetylene compounds published by ural federal university eissn 2411-1414; chimicatechnoacta.ru letter 2022, vol. 9(3), no. 20229306 doi: 10.15826/chimtech.2022.9.3.06 1 of 6 catalytic activity and selectivity of palladium and nickel catalysts in hydrogenation reactions of nitroand acetylene compounds indira m. jeldybayeva a* , zhaksyntay k. kairbekov a, kazhmukan o. kishibayev b, elmira t. yermoldina a , saltanat m. suimbayeva a a: research institute of new chemical technologies and materials, al-farabi kazakh national university, almaty 050012, kazakhstan b: kazakh national women’s teacher training university, almaty 050026, kazakhstan * corresponding author: indiko_87@mail.ru this paper belongs to the ctfm'22 special issue: https://www.kaznu.kz/en/25415/page. guest editors: prof. n. uvarov and prof. e. aubakirov © 2022, the authors. this article is published in open access under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). abstract this paper presents the results of a study on the catalytic activity and selectivity of nickel and palladium catalysts in hydrogenation reactions of nitroand acetylene compounds. it was shown that the activity and selectivity of nickel catalysts in the hydrogenation of phenylacetylene depend on the nature of modifying additives (cu, zn, ti, cr, bi, ti–cu, mn, fe), and the activity and selectivity of palladium catalysts based on a polymer of metal complexes depends on the method of their preparation. it was found that for certain concentrations of the active phase of palladium (0.8 wt.%) and the polymer of potassium humate (1.0 wt.%.) in the catalyst, where palladium and the polymer were deposited on bauxite-094 together, the catalyst exhibits the greatest activity and selectivity when hydrogenating phenylacetylene and potassium orthonitrophenolate. keywords hydrogenation palladium nickel catalysts catalytic activity selectivity nitro compounds acetylene compounds received: 24.06.22 revised: 18.07.22 accepted: 18.07.22 available online: 26.07.22 key findings ● new highly active and selective catalysts were synthesized based on nickel and palladium fixed to the carrier in various ways. ● it was shown that the activity and selectivity of nickel catalysts depends on the nature of modifying additives. ● it was established that the activity and stability of pmc-based catalysts depend on the method of their preparation. 1. introduction in industry, platinum group metals, pt, ph, ru, and pd, deposited on carriers, are commonly used as catalysts for selective hydrogenation of products of high-temperature pyrolysis. however, such catalysts are sensitive to catalytic poisons and expensive due to the high content of precious metals. in addition, carrying out the hydrogenation process in their presence under relatively harsh conditions (high temperature and partial pressure of h2), caused by the need to obtain a product of acceptable quality, increases the energy intensity of the process, which, in turn, increases the cost of the final product. the search for new cheap, highly active and selective hydrogenation catalysts for individual unsaturated hydrocarbons and their technical mixtures is a problem of great practical importance [1–7]. to increase the efficiency of selective hydrogenation of highly unsaturated impurities in hydrocarbon streams, a focused approach is required to select a catalyst system that must meet a certain set of requirements. these include: high activity of the catalyst in the hydrogenation process, which allows bringing the conversion of impurities to almost 100%, high selectivity of the catalyst for alkyne (not lower than 80%), stability of the http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2022.9.3.06 mailto:indiko_87@mail.ru https://www.kaznu.kz/en/25415/page http://creativecommons.org/licenses/by/4.0/ https://orcid.org/0000-0002-1524-4046 https://orcid.org/0000-0002-8567-1342 https://crossmark.crossref.org/dialog/?doi=https://doi.org/10.15826/chimtech.2022.9.3.06&domain=pdf&date_stamp=2022-7-26 chimica techno acta 2022, vol. 9(3), no. 20229306 letter 2 of 6 catalyst, insensitivity of the catalyst to poisoning by reaction products, ease of production, ease of regeneration and low cost of the catalyst. the most applicable for this purpose are palladium and nickel-based hydrogenation catalysts, which have high activity and relatively low cost compared to noble metal-based catalysts [1–9]. among a large number of diverse catalysts, the deposited metal complex catalysts modified with polymers should be especially noted [10–17]. the advantages of polymer-metallic catalysts (pmc) are activity and stability under mild experimental conditions, which allows excluding undesirable side processes of isomerization or destruction. the main achievement in this area is the creation of new technologies based on multifunctional pmc on carriers and their introduction into industry. humic acids (ha) obtained from rk coals are environmentally safe and economically cheap, which determines the possibility of their use as a natural polymer modifier in applied pmc. the study of the regularity of the composition, nature, structure and properties of ha contributes to the possibility of using them as a natural polymer-modifier in pmc, and to understanding of the dependence of the catalytic properties of these catalysts on the physicochemical properties of the polymer, which leads to an increase in the activity, stability and selectivity of the action of catalysts based on them. in this regard, the development of pmc-based catalysts with high activity and stability during long-term use is an urgent task today. multicomponent skeletal nickel catalysts, which have been successfully used in various hydrogenation processes, have also been found to be very industrially effective. this is due to high activity and selectivity, ease of preparation and regeneration, stability of operation in a long cycle, resistance to poisoning with catalytic poisons. it has been shown that the modification of skeletal nickel with various metals allows to regulate the properties of the catalyst in a wide range. in this paper, we synthesized catalysts based on nickel and palladium, fixed on the carrier bauxite-094 (b-094) by various methods and studied their catalytic properties in the processes of hydrogenation of nitroand acetylene compounds. 2. experimental 2.1. preparation of skeletal nickel catalysts weighed amount (0.8 g) of ground, powdered ni-al-alloy from 0.06–0.20 mm fractions (the compositions of alloys are given in table1) was treated with a 20% koh solution at a temperature of 96 °c in a boiling water bath for 2 hours. the washing of the obtained products from alkali was carried out with distilled water by decanting 4–5 times, until a negative reaction to oh– ions in washing water. the catalyst was then washed with a solvent in which hydrogenation was carried out. 2.2. preparation of applied palladium catalysts a 500 cm3 beaker was filled with 100 cm3 of distilled water, carrier and na2co3 to ph 9–10 and stirred at room temperature on a magnetic stirrer. the suspension was stirred for 10–15 minutes until the carrier was completely wetted. bauxite-094 (b-94) was used as the carrier. the calculated amount of na2pdci4 was adjusted with distilled water to 50 ml and then this solution was transferred by impregnation to a beaker with the stirred carrier suspension. in order to achieve complete palladium precipitation, the slurry is stirred for one hour. the completeness of palladium precipitation was tested by a negative reaction with potassium rhodanide. the catalyst was washed with distilled water until neutral, filtered, dried in a vacuum oven at 363 k for three hours. 2.3. potassium humate-modified (pth) palladium catalysts deposited on bauxite-094 the chemical composition of bauxite-094 was аl2о3 – 35.1%; siо2 – 15.1%; fe2о3 – 23.7%. applied on bauxite-094 modified pth, from the coal of the "oi-karagai" deposit, palladium catalysts were prepared as follows: a weighed amount of bauxite (3g) was added to 150 ml of distilled water, then a solution of pth (0.8 wt.% relative to the weight of the carrier) and an aqueous solution of palladium chloride (1.0 wt.%) were added while stirring. the resulting catalysts were stirred for 3 hours and then washed, filtered and dried at 383 k for two hours. 2.4. methods of experiments. hydrogenation was carried out in a thermostatted catalytic “filling” at atmospheric pressure and temperature of 20 °с. simultaneously, reaction rates (amount of hydrogen absorbed per unit time, cm3/min) and catalyst potential (mv) relative to the calomel reference electrode were recorded. prior to the reaction, the catalyst was treated with hydrogen in a solvent (v = 25 cm3) until a reversible hydrogen potential was established. hydrogenation was carried out in a kinetic mode (700–800 rpm). chromatographic analysis was carried out on a chromos gc-1000 chromatograph with a flame ionization detector in isothermal mode using a vr21 capillary column (ffap) with a polar phase (polyethylene glycol modified with nitro terephthalate) of 50 m in length and an internal diameter of 0.32 mm. the column was maintained at 90 °c, the temperature in the evaporation chamber was 200 °c, the carrier gas was helium, the volume of the injected sample was 0.2 μl. during the experiment, 2–3 samples of the liquid reaction mixture were taken for analysis. 3. results and discussion the obtained results of the study of the process of hydrogenation of phenylacetylene on a modified (cu, zn, ti, cr, bi, ti-cu, mn, fe) skeletal nickel catalyst are shown in table 1. chimica techno acta 2022, vol. 9(3), no. 20229306 letter 3 of 6 table 1 hydrogenation of phenylacetylene on multicomponent skeletal nickel catalysts (patm, qcat = 0.8 g, vн2 = 100 cm 3). no. composition of alloys content of ni–al–me, wt.% phenylacetylene (plant / ethanol) w c≡c w c=c ∆estart ks 1 ni–al 50–50 68 82 330 0.82 2 ni–al–cu 40–55–5 100 210 180 0.89 3 ni–al–zn 43–44–13 117 258 170 0.89 4 ni–al–ti 47–50–3 97 134 350 0.87 5 ni–al–cr 47–50–3 70 84 290 0.84 6 ni–al–bi 45–50–5 69 128 320 0.90 7 ni–al–ti–cu 42–50–3–5 72 83 320 0.81 8 ni–al–mn 40–50–10 34 50 290 0.83 9 ni–al–fe 45–50–5 25 47 260 0.85 * w is the activity of the catalyst, cm3/min‧g ni; ∆estart. is the initial displacement of the catalyst potential, mv; ks is the selectivity factor. the activity of the multicomponent skeletal nickel catalysts (table 1, figures 1 and 2) depends on the nature of the modifying additives. the introduction of ti, cu, zn into the alloy leads to an increase in the activity of skeletal nickel (wc≡c = 97–117 cm3/min·g ni). the mn and fe additives reduce it (wc≡c =25–34 cm3/min·g ni). cr, bi and ti–cu have no significant effect on the catalyst activity (wc≡c = 69–72 cm3/min·g ni). the introduction of most modifying additives is associated with an increase in selectivity with the exception of bi, cr, mn and ti–cu (ks = 0.81–0.90, wc=c/wc≡c = 1.2–1.4). the greatest effect falls on cu, zn, ti (кs = 0.88–0.91, wc=c/wc≡c = 1.5–2.4). the displacement of the potential ∆ес≡с, depending on the nature of the additives, ranges from 170 to 360 mv. on cu and zn modified catalysts, ∆ec≡c is 170–180 mv, while ti increases the adsorption strength (∆e = 350 mv). on nickel catalysts, the addition of the first mole of hydrogen to phenylacetylene is predominantly via a triple bond. the "stepwise" form of kinetic curves and a sharp decrease in the potential shift of catalysts (∆e) in the second half of the processes when hydrogenating phenylacetylene on multicomponent skeletal nickel catalysts (figure 1) show greater adsorbability of alkynes compared to intermediate alkenes on the surface of the catalysts. this is probably due to the high selectivity of alkyne hydrogenation: ksphenylacetylene = 0.81–0.90 depending on the nature of the modifying additive (table 1). figure 1 hydrogenation curves of phenylacetylene (ah2 = 100 cm 3 h2) in ethanol on multicomponent skeletal nickel catalysts from alloys: 1 – ni–al (50–50%), 2 – ni–al–mn (40–50–10%), 3 – ni–al–cu (40–55–5%). weighed amount of alloys 0.8 g. further, we conducted a study of the process of hydrogenation of nitro compounds and phenylacetylene on modified palladium catalysts. the dependence of the activity and selectivity of the pd-humate potassium/b-94 catalyst on the method of its preparation was studied. potassium humate (pth) acts as a natural polymer in the formation of polymer-metal complexes (pmc). the optimal concentration of palladium in the catalyst of 0.8 wt.% was selected experimentally, and that of pth was 1.0 wt.% [12]. preparation of modified pth palladium catalysts deposited on bauxite-094. the chemical composition of bauxite094 is siо2 – 15.1%; аl2о3 – 35.1%; fe2о3 – 23.7%. modified pth palladium catalysts applied to bauxite-094 were prepared in the following 5 ways: 1. potassium bauxite-094 and na2pdcl4 were applied simultaneously. the carrier (3 g) was poured with 150 ml water, then while stirring, the solutions of pth (1.0 wt.%) and na2pdcl4 (0.8 wt.%). the mixture was stirred for 2 h, then washed, filtered and dried at 383 k for 2h. 2. the polymer and na2pdcl4 were applied alternately to the support. bauxite-094 was stirred with pth solution for 2 hours, then palladium chloride solution was added by dripping. the mixture was stirred for 2 hours, after which the catalyst was washed, filtered and dried. 3. bauxite-094 was stirred with na2pdcl4 solution for 2 hours, then added by dropping with htk solution. the mixture was stirred for 2 hours, after which the catalyst was washed, filtered and dried. 4. the catalyst was prepared similarly to the previous one, but after stirring the support with both components, the mixture was left in the mother liquor for 10 hours. figure 2 diagrams of the catalyst composition (a) ni–al–bi (45– 50–5%), (b) ni–al–ti–cu (42–50–3–5%): 1 – phenylacetylene, 2 – styrene, 3 – ethylbenzene. chimica techno acta 2022, vol. 9(3), no. 20229306 letter 4 of 6 5. application of pre-mixed solutions of pth and na2pdcl4 to the carrier. with the calculated concentration, the solutions of pth and pdcl2 were pre-mixed with each other, then this mixture was added by dropping while stirring onto the carrier. the mixture was stirred for 2 hours and then the catalyst was washed, filtered and dried at 383 k. the catalysts prepared by these methods were tested for activity and selectivity in the hydrogenation reactions of ortho-nitrophenolate potassium (onpp) and phenylacetylene. the results are presented in table 2. from table 2, it can be seen that jointly, separately and alternately (with settling) precipitated pd and pth catalysts reduce onpp and phenylacetylene at a rate higher than the 0.8% pd/b-094 catalyst and precipitated alternately and pre-mixed pd and pth catalysts are less active and selective than the initial catalyst. the most active and selective (ks = 0.98) turned out to be the catalyst where pd and pth were applied together, whose activity is also twice higher than the activity of the catalyst 0.8% pd/b-094; the least active and selective (ks = 0.79) turned out to be the catalyst prepared according to method 5. so, the activity of the catalyst based on pmc, developed by us, depends on the method of its preparation. when palladium and potassium humate are deposited on the support in parallel, the stereoregular orientation of the active phase particles acquires an optimal structure and, thereby, the activity of the catalyst prepared in this way is explained. micrographs of the 0.8% pd – pth (1%)/b-094 catalyst samples were taken; the samples differed in the methods of applying palladium and potassium humate to bauxite-094 (figure 3). agglomerates consist of loosely bonded particles, with the sizes of the primary particles and agglomerates depending on the method of preparation. thus, the catalyst obtained by co-deposition of pd and pth (table 2, method 1) is dispersed and has a more conformational structure. presumably, in the catalyst prepared in this way, the polymer (pth) binds to the surface of the support mainly in the form of "loops" and in the form of "tails", and palladium is distributed, binding to the functional groups of the polymer matrix and forming a polymer metal complex, as well as partially adsorbing on the surface of the support itself. this contributes to the formation of dispersed nanoparticles (2–3 nm) of palladium and its uniform distribution on the surface of the carrier (figure 3). in the catalysts prepared by other application methods (methods 2), it is likely that the surface of the support is coated with a thin layer of polymer, and then the palladium is bound to the surface functional groups of the polymer. in the catalyst prepared according to method 5, palladium and pth form a polymer-metallic complex, and then, when applying this complex to the surface of the support, the surface conformational construction of the active phase may turn out to be such that some part of it is a closed polymer layer inaccessible to the reagents. figure 3 micrographs of 0.8 pd– pth (1%)/b–094: pd and pth are applied together (a); pd and pth were applied separately (1 – pth; 2 – pd) (b); pd and pth were applied alternately (1 – pth; 2 – pd) (c); pd and pth were applied alternately (1 – pth; 2 – pd) with settling of in stock solution >10 h (d); preapplied mixed pd and pth (e). table 2 activity of 0.8% pd–pth (1%) /b-094 catalysts in the reduction reactions of onpp in 0.1 n koh at t = 313 k and phenylacetylene in 96% ethanol at 313 k (patm, qcat = 0.1 g, vh2 = 100 cm 3). no. preparation methods recovery rate, cm3 n2/min onpp phenylacetylene w, cm3/min δе, mv c=с c=с δе, mv кs – 0.8% pd/b-094 16.0 290 25.0 31.3 230 0.67 1 pd and pth were coapplied 31.0 340 58.0 62.8 260 0.98 2 pd and pth were applied separately: 1 – pth; 2 – pd 25.2 320 35.3 37.7 250 0.93 3 pd and pth were applied alternately: 1 – pd; 2 – pth; 14.6 270 23.5 22.4 240 0.86 4 pd and pth were applied alternately (1 – pth; 2 – pd) with settling >10 h 17.6 270 28.4 27.2 230 0.85 5 pre-applied mixed pd and pth 11.2 330 20.6 18.5 230 0.79 chimica techno acta 2022, vol. 9(3), no. 20229306 letter 5 of 6 thus, the most active and stable catalyst is characterized by the presence of palladium particles uniformly distributed on the surface of the support, which are fixed to the support through a polymer (pth) to form a complex. potassium humate, binding to palladium by chemical bond, prevents agglomeration of active centers into larger particles, which explains the high activity and selectivity of the 0.8% pd – pth /b-094 catalyst, in which pd and pth are codeposited. 4. conclusions the obtained results allow us to draw the following conclusions: 1. new highly active and selective catalysts on the basis of nickel and palladium attached to the medium by various techniques were synthesized, and the optimal process conditions were determined. it was demonstrated that the synthesized catalysts are especially active (w = 68– 258 cm3/min·g) and selective (кs = 0.90–0.98) in case of hydrogenation of potassium o-nitrophenolate and phenylacetylene. 2. it was shown that the activity and selectivity of multicomponent skeletal nickel catalysts in the hydrogenation of phenylacetylene depends on the nature of the modifying additives. 3. it was established that the activity and stability of pmc-based catalysts depends on the method of their preparation. in the best catalyst, palladium and polymer were applied to bauxite-094 together. the optimal concentrations of the active phase and polymer in the catalyst were determined: palladium – 0.8 wt.%; potassium humate – 1.0 wt.%. supplementary materials no supplementary materials are available. funding this research was funded by the science committee of the ministry of education and science of the republic of kazakhstan (grant no. ap09057905 and ap08051873). https://www.gov.kz/memleket/entities/sc?lang=en. acknowledgments none. author contributions conceptualization: zh.k.k., i.m.j. data curation: zh.k.k. formal analysis: i.m.j., e.t.ye. investigation: i.m.j., zh.k.k., s.m.s. methodology: e.t.ye., k.o.k. project administration: zh.k.k. resources: e.t.ye., s.m.s. software: i.m.j. supervision: zh.k.k., k.o.k. validation: zh.k.k., i.m.j. visualization: zh.k.k., i.m.j., s.m.s. writing – original draft: i.m.j., s.m.s. writing – review & editing: zh.k.k. conflict of interest the authors declare no conflict of interest. additional information author ids: indira m. jeldybayeva, scopus id 56600659100; zhaksyntay k. kairbekov, scopus id 55910705200; kazhmukan o. kishibayev, scopus id 57203985931; elmira t. yermoldina, scopus id 55448118600; saltanat m. suimbayeva, scopus id 57201691853; websites: al-farabi kazakh national university, 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https://doi.org/10.7868/s0028242117060065 https://doi.org/ 10.1134/s0023158410020187 https://doi.org/10.1134/s0023158416030174 https://doi.org/10.12783/dtcse/cmsam2016/3657 https://doi.org/10.1051/matecconf/202134001010 https://doi.org/10.1016/j.micromeso.2004.06.030 https://doi.org/%2010.1039/c2cs35244c http://dx.doi.org/10.3390/catal6080122 https://doi.org/10.1134/s0965544111030091 decomposition of light hydrocarbons on a ni-containing glass fiber catalyst published by ural federal university eissn 2411-1414 chimicatechnoacta.ru article 2023, vol. 10(3), no. 202310306 doi: 10.15826/chimtech.2023.10.3.06 1 of 5 decomposition of light hydrocarbons on a ni-containing glass fiber catalyst m.v. popov a , m.v. chudakova a, p.b. kurmashov b , a.g. bannov b * , a.v. kleimenov c a: gazpromneft – industrial innovations llc, st. petersburg 19735, russia b: novosibirsk state technical university, novosibirsk 630073, russia c: gazprom neft pjsc, st. petersburg 190000, russia * corresponding author: bannov_a@mail.ru this paper belongs to the rkfm'23 special issue: https://chem.conf.nstu.ru/. guest editors: prof. n. uvarov and prof. e. aubakirov. abstract the work is devoted to the study of the novel process of catalytic decomposition of light hydrocarbons on a catalyst at temperatures of 550 °с and 600 °c at various pressures. the cvd process is a new cox-free approach for hydrogen production. a glass fiber fabric was used as a catalyst, which was preliminarily modified by the application of additional outer layers of nio and porous silica. a technical mixture of propane and butane was used as feedstock. the main purpose is to investigate the effects of pressure and temperature on the production of hydrogen and carbon nanofibers over a glass-based catalyst. as a result of the decomposition of the mixture, the yield of hydrogen was 266–848 l/gcat, and that of carbon nanofibers was 3–10 g/gcat. increasing the pressure of propane-butane mixture decomposition led to an increase of the catalyst lifetime. the highest yield of hydrogen and carbon nanofibers was achieved at 1 bar and 600 °c. keywords carbon nanofibers hydrogen glass fiber hydrocarbons synthesis received: 04.07.23 revised: 03.08.23 accepted: 03.08.23 available online: 08.08.23 key findings ● the effect of temperature (550, 600 °c) and pressure (1, 2 atm) on the conversion of a propane-butane mixture was studied. ● novel data on hydrogen synthesis via methane decomposition at pressure higher than 1 atm. ● dynamics of catalyst deactivation was investigated. © 2023, the authors. this article is published in open access under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). 1. introduction due to the constantly increasing demand for energy resources that meet modern environmental standards, the development of alternative and renewable energy sources to replace traditional fuels is an urgent task for the world scientific community [1–2]. the most promising and likely scenario for solving this problem is the formation of a hydrogen economy, where hydrogen is a universal energy carrier commensurate with oil, gas and coal. in many respects, hydrogen is superior to other types of fuels, for example, high efficiency (the efficiency of power plants is 80–90%), high environmental friendliness (exhaust gases when it is used as a fuel consist of water vapor), versatility (the ability to accumulate energy obtained from other alternative and renewable sources). according to various forecasts, this could happen worldwide after 2040, but in some regions, the hydrogen economy is already taking shape today [3]. to use hydrogen as an automotive fuel at compressed natural gas (cng) filling stations, it is necessary to deliver it to the consumer. it is possible to t deliver it in cylinders (at pressures up to 700 atm), but this is an energy-intensive process. a more efficient approach is to transport hydrogen in a bound state, for example, in the form of hydrocarbons and produce hydrogen directly on site [4]. two types of readily available hydrocarboncontaining gases can be used as sources at cng filling stations: natural gas and technical propane-butane mixture (pbm). a methane/pbm catalytic converter is installed directly at the cng filling station to produce hydrogen in the required amount. previously, the authors of [5] showed that a glass fiber-based nickel catalyst is active in the decomposition of methane and light hydrocarbons at a temperature of 450 °c and atmospheric pressure. pbm is a cheap, easily transportable raw material with safe storage, since it does not require high pressures. the second prodhttp://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2023.10.3.06 mailto:bannov_a@mail.ru http://creativecommons.org/licenses/by/4.0/ https://orcid.org/0000-0002-0648-4160 https://orcid.org/0000-0002-6263-3634 https://orcid.org/0000-0001-5868-9013 https://orcid.org/0000-0001-8797-9175 https://crossmark.crossref.org/dialog/?doi=https://doi.org/10.15826/chimtech.2023.10.3.06&domain=pdf&date_stamp=2023-08-08 chimica techno acta 2023, vol. 10(3), no. 202310306 article 2 of 5 doi: 10.15826/chimtech.2023.10.3.06 uct which is formed during methane decomposition is nanofibrous carbon [6–8]. there are a variety of its applications, and the investigation of such a material is of increasing interest [9–14]. therefore, in this work, we studied the effects of temperature (550, 600 °c) and pressure (1–2 atm) on the conversion of a propane-butane mixture. 2. experimental the catalyst support was kt-11-to high-silicon fiberglass fabric (manufactured by stekloplastik, zelenograd, russia) containing ~95 sio2 and 4 al2o3 (wt%). the glass fabric was impregnated with an aqueous solution of silica sol (type k-1, npo irea, moscow, russia) and nickel acetate. after impregnation and drying, the glass fabric was subjected to heat treatment by heating from 25 to 500 °c. the addition of silica was necessary to create an intermediate layer of a secondary porous substrate in order to improve the adhesion strength between the nio surface and the glass fabric, while increasing the availability of gaseous reagents to the active compound nio [15]. using the method of transmission microscopy, it was determined that the distribution of particles is uniform, the average size of nio particles was 15 nm [5]. the experiments were carried out on an autoclave engineers btrs-jn catalytic unit in a metal tubular reactor. the catalyst was coiled and placed in a metal flow reactor (figure 1) in an argon flow at a rate of 1.2 l/h. the reactor was thermally stabilized at t = 550–600 °c. the propanebutane technical mixture according to gost 20448-90 was used as a feedstock. experiments on the decomposition of pbm were carried out at pressures of 0.1–0.2 mpa with a specific consumption of methane at the inlet of 100 l/(h·gcat). the concentration of gaseous products was measured on a chromatek-kristall 5000 gas chromatograph equipped with a thermal conductivity detector, a flame ionization detector, and an hp-al/kcl 50 m × 0.32 mm × 8 µm capillary column (p/n 19091p-k15). the microstructure of carbon nanofiber samples was studied by scanning electron microscopy (sem) with field emission on a hitachi su8000 electron microscope. the images were taken in the secondary electron recording mode at an accelerating voltage of 2 kv and a working distance of 4–5 mm. the textural characteristics of the obtained nanofibrous carbon samples were studied by low-temperature nitrogen adsorption at 77 k on a quantachrome nova 1000e adsorption unit. the specific surface area (abet) was calculated by the bet method. the specific surface of the pores remaining after the adsorbate filled the micropores (at) and the volume of micropores (vt) were calculated by the comparative t-method of de boer and lippens, for which the statistical thickness of the adsorption film for which was calculated using the de boer equation. the method is based on a comparison of the increments of adsorption values on the adsorption isotherm under study and the standard adsorption isotherm obtained on well-characterized non-porous materials. in the field of polymolecular adsorption, after the filling of micropores and other specific centers, these increments of adsorption are proportional to the surface, regardless of its detailed chemical nature. 3. results and discussion previously [5], it was shown that a ni-containing glass fiber-based catalyst is active in the decomposition of methane and light hydrocarbons at a temperature of 450 °c and atmospheric pressure. in this work, the effect of temperature and pressure on the conversion of a propanebutane mixture was studied. figure 2 shows the results of the catalytic decomposition of pbm at a temperature t = 550 °c and a pressure p = 1 atm. the maximum volume concentration of hydrogen was 49.7 vol% after 1 h of catalyst operation. the volume concentration of methane at the beginning of the work was 51.8 vol% and reached 0 vol% after 6.5 h of the process. the catalyst worked under these conditions for 35 h without loss of activity, and the nonlinear change in the volume concentrations of the reaction products after 16 h of operation of the glass-fiber catalyst is associated with the carbon formation at the active centers of the catalysts. figure 1 appearance of glass fiber catalyst layer. figure 2 change in the volume concentrations of the reaction products depending on the reaction time (1 atm, 550 °c). https://doi.org/10.15826/chimtech.2023.10.3.06 chimica techno acta 2023, vol. 10(3), no. 202310306 article 3 of 5 doi: 10.15826/chimtech.2023.10.3.06 the hydrogen yield in this experiment was 636 l/gcat with a nanofiber carbon value of 3 g/gcat. it can be seen from the data in figure 3 that an increase in temperature to 600 °c leads to an increase in the maximum volume concentration of hydrogen to 58 vol% and within 34 h of operation of the catalyst, it decreased to 34 vol%. the conversion of pbm under these conditions was 40.63 vol%. the yield of hydrogen in this experiment reached its maximum value and amounted to 848 l/gcat, the yield of carbon nanofibers was 10.5 g/gcat. an increase in pressure to 2 atm at a process temperature of 550 °c leads to a slight decrease in the hydrogen concentration, which amounted to 25.9 vol%, reaching its maximum value of 44.7 vol% and remains approximately unchanged for 5.5 h. in this case, a slight increase in pressure in the system was observed due to the carbonization of the catalyst. the hydrogen yield in this experiment was 420.3 l/gcat, while the nanofibrous carbon yield was 5 g/gcat. figure 4 shows the change in the volume concentrations of the reaction products depending on the reaction time at a temperature t = 600 °c and a pressure p = 2 atm. figure 4 shows that with an increase in pressure to 2 atm at a process temperature of 600 °c, the hydrogen concentration gradually increases from 43.6 vol% and reaches its maximum value of 62.7 vol% after 3 h of the experiment. figure 3 change in the volume concentrations of the reaction products depending on the reaction time (1 atm, 600 °c). figure 4 change in the volume concentrations of the reaction products depending on the reaction time (2 atm, 600 °c). the yield of hydrogen in this experiment was 266.5 l/gcat, carbon nanofibers was 3 g/gcat. it is important to note that under these conditions, the catalyst surface was rapidly carbonized and the experiment time was reduced to 5 h. table 1 presents data on the integral yields of hydrogen and nanofibrous carbon under various conditions. it can be seen that the yields of hydrogen and nanofibrous carbon reach their maximum values during the catalytic decomposition of a commercial propane-butane mixture at a pressure of one atmosphere, a temperature of 550–600 °c and amount to 636 l/gcat and 848 l/gcat, respectively. it is known that the activity of a reaction catalyst directly depends on the amount of ni in the catalyst [16]. in [17], the influence of the catalyst composition on the conversion of propane with the production of hydrogen 7–108 mol h2/gcat was studied. however, it should be noted that the nickel content was 40–50% with the addition of promoting additives (cu, mo). the authors of [18] decomposed light c1–c4 hydrocarbons and their mixtures on a catalyst of complex composition 15%ni·5%co·5%fe·5%cu·2%mo/vcc, obtaining data comparable to this work. whereas in this work, 12–38 h2/gcat was obtained on low-concentration monometallic systems [19–22]. at the same time, a glass fiber-based catalyst has a number of advantages over a granular catalyst, such as higher mechanical strength and ease of transportation, organization of loading into the reactor virtually eliminates gas leakage through its bed [23]. the conditions for the process of decomposition of the propane-butane mixture do not greatly affect the structure of the resulting carbon. table 2 shows typical textural characteristics of the resulting carbon product. 4. limitations the further issues will be linked with the development of pilot plants for catalytic decomposition of methane or c1c4 hydrocarbons over fiberglass catalysts. the reaching of optimum activity of catalysts will be achieved by creating new nanoparticle-based fiberglass systems with enhanced conversion of c1-c4 hydrocarbons. 5. conclusions thus, the results of the experiments showed that the glass fiber material coated with nickel has prospects for application in the process of catalytic pyrolysis of light hydrocarbons, for example, pbm, and can be used as a catalyst in the utilization of associated petroleum gases. the most efficient process for the catalytic decomposition of light hydrocarbons on a ni-containing glass fiber catalyst is the catalytic decomposition of a technical propane-butane mixture at a temperature of 600 °c and a pressure of 2 atm, but due to the high rate of carbonization of the catalyst surface, research should be continued with optimization of the process: introduce a promoting additive and/or select the experimental conditions. https://doi.org/10.15826/chimtech.2023.10.3.06 chimica techno acta 2023, vol. 10(3), no. 202310306 article 4 of 5 doi: 10.15826/chimtech.2023.10.3.06 table 1 the influence of temperature and pressure of the process on the maximum volume concentration of hydrogen, the yield of hydrogen and carbon during the experiment (the pbm was used as a feedstock). pressure, atm temperature, °c с(h2)max, vol.% η(н2), l/g cat. η(с), g/gcat 1 550 49.7 636.1 3 1 600 58.0 848.0 10.5 2 550 44.7 420.3 5 2 600 62.7 266.5 3 also, a great advantage of carrying out the process of catalytic decomposition of pbm at 600 °c and a pressure of 1 atm is the highest yield of hydrogen η(н2) = 848 l/gcat and carbon nanofibers was η(с) = 10.5 g/gcat. the future studies will be devoted to estimating the effect of higher pressures (above 5 bar) and ways to enhance the hydrogen yield. ● supplementary materials no supplementary materials are available. ● funding this work was financially supported by the state task of ministry of science and higher education of russia (fsun-2023-0008). ● acknowledgments none. ● author contributions conceptualization: a.m.p., m.v.c., a.v.k. data curation: p.b.k. formal analysis: a.m.p., m.v.c., a.v.k. funding acquisition: a.m.p., m.v.c., a.v.k., p.b.k. investigation: a.v.k., p.b.k., a.g.b. writing – original draft: m.v.p., m.v.c. writing – review & editing: a.g.b, m.v.p., m.v.c. ● conflict of interest the authors declare no conflict of interest. ● additional information author ids: m.v. popov, scopus id 55925982600; m.v. chudakova, scopus id 37561000100; p.b. kurmashov, scopus id 57206473427; a.g. bannov, scopus id 54788777600; a.v. kleimenov, scopus id 57193235773. websites: gazpromneft – industrial innovations llc, https://innovations.gazprom-neft.ru/; novosibirsk state technical university, https://en.nstu.ru/; center of physicochemical methods of research and analysis, https://cfhma.kz/cfhma/. gazprom neft pjsc, https://www.gazprom-neft.ru/. references 1. parkinson b, tabatabaei m, upham dc, ballinger b, greig c, smart s, mcfarland e. hydrogen production using methane: techno-economics of decarbonizing fuels and chemicals. int j hydrog energy. 2018;43:2540–2555. doi:10.1016/j.ijhydene.2017.12.081 2. qian jx et al. methane decomposition to produce co -free hydrogen and nano-carbon over metal catalysts: a review. 2020. int j hydrog energy;45:7981–8001. doi:10.1016/j.ijhydene.2020.01.052 3. global hydrogen review 2021. int energy agency. 2021. https://iea.blob.core.windows.net/assets/3a2ed84c-9ea0458c-9421-d166a9510bc0/globalhydrogenreview2021.pdf 4. abbas hf, wan mohd wd. hydrogen production by methane decomposition: a review. int j hydrog energy. 2010;35:1160– 1190. 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doi:10.1016/j.ijhydene.2019.04.179 https://doi.org/10.15826/chimtech.2023.10.3.06 https://doi.org/10.1016/j.apcatb.2008.07.011 https://doi.org/10.1016/j.ijhydene.2019.04.179 development of nanostructured catalysts for catalytic oxidative water purification from organic impurities, including phenolic compounds published by ural federal university eissn 2411-1414 chimicatechnoacta.ru article 2023, vol. 10(3), no. 202310309 doi: 10.15826/chimtech.2023.10.3.09 1 of 8 development of nanostructured catalysts for catalytic oxidative water purification from organic impurities, including phenolic compounds larissa r. sassykova a * , binara t. dossumova a , madina s. ilmuratova a , tatyana v. shakiyeva a , bedelzhan b. baizhomartov a , albina r. sassykova b , zhanar m. zhaxibayeva c , tleutai s. abildin a a: al-farabi kazakh national university, almaty 050040 kazakhstan b: almaty management college, almaty 050000, kazakhstan c: abai kazakh national pedagogical university, almaty 050010, kazakhstan * corresponding author: larissa.rav@mail.ru this paper belongs to the rkfm'23 special issue: https://chem.conf.nstu.ru/. guest editors: prof. n. uvarov and prof. e. aubakirov. abstract the purpose of this work was to create magnetic nanocatalysts that could be used for the oxidation of organic water pollutants – phenol and its derivatives – and to determine the physicochemical characteristics of the catalysts. the development of such active nanocomposite catalysts would solve the environmental problem in the republic of kazakhstan in the field of wastewater treatment from organic impurities, including phenols, and would also contribute to the subsequent creation of domestic production of oxygen-containing compounds, since almost the entire spectrum of oxygen-containing compounds for various industries is imported into the republic. nanosized magnetic composites based on fe and co were obtained by chemical deposition, in some cases, using polyethyleneimine and polyvinylpyrrolidone. it was shown that the interaction between nanoparticles and the polymer takes place in the case of a cofe2o4 catalyst stabilized with polyvinylpyrrolidone or polyethyleneimine, which may indicate the efficient formation of nanocomposites. according to the ir study, for the cofe2o4 nanocomposite stabilized with polyvinylpyrrolidone, the absorption bands at 735, 663, 649, 626 cm –1 are natural vibrations for the composite nanoparticles embedded in a polyvinylpyrrolidone matrix. the synthesized nanocomposites were tested in the oxidation of phenol with oxygen. the results demonstrate that the catalysts are promising both for the purification of industrial wastewater from phenol and for the synthesis of oxygen-containing compounds in the liquid phase under mild conditions. keywords oxidation catalysts nanoscale magnetic composites phenol wastewater aromatic hydrocarbons polyethylenimine polyvinylpyrrolidone received: 02.07.23 revised: 26.07.23 accepted: 16.08.23 available online: 22.08.23 key findings ● nanocomposites of fe3o4, fe-co/al2o3 and cofe2o4 as well as cofe2o4 stabilized with polyethylenimine or polyvinylpyrrolidone were synthesized. ● the prepared nanocomposites were studied by physicochemical research methods and tested in the oxidation reaction of phenol with oxygen. ● the efficiency of using fe3o4, cofe2o4 and cofe2o4 stabilized with polyethylenimine in the oxidation of phenol with oxygen was established. © 2023, the authors. this article is published in open access under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). 1. introduction many reservoirs are polluted by phenolic wastewater from petrochemical and oil refineries, pulp and paper mills, chemical industry enterprises producing phenol or using it for the synthesis of other substances, plants and factories of pharmaceutical and forestry industries, and enterprises producing building materials, rubber, adhesives, plastics, http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2023.10.3.09 mailto:larissa.rav@mail.ru http://creativecommons.org/licenses/by/4.0/ https://orcid.org/0000-0003-4721-9758 https://orcid.org/0000-0003-4126-2907 http://orcid.org/0000-0001-7773-6057 https://orcid.org/0000-0002-9664-442x https://orcid.org/0000-0002-3221-114x https://orcid.org/0000-0002-1806-522x https://orcid.org/0000-0002-5751-6791 https://crossmark.crossref.org/dialog/?doi=https://doi.org/10.15826/chimtech.2023.10.3.09&domain=pdf&date_stamp=2023-08-22 chimica techno acta 2023, vol. 10(3), no. 202310309 article 2 of 8 doi: 10.15826/chimtech.2023.10.3.09 pesticides, phenol-formaldehyde resins [1–6]. catalysts based on various metals, metal oxides, deposited systems, and magnetic composites based on metal oxides show good efficiency in the oxidation of phenol with oxygen [3, 4, 7–14]. the most promising catalysts are nanodisperse catalytic systems for the purification of industrial waters from organic impurities, including phenolic compounds. such catalysts can provide a high rate of oxidation of phenolic pollutants and effective oxidation of organic compounds with various functional groups. a significant number of publications are devoted to the study of the properties and applications of magnetic materials based on iron oxides in their common modifications – hematite, maghemite, and magnetite. this is due to the lower toxicity of nanoparticles and their acceptable magnetic properties when compared with similar compounds of nickel and cobalt [13, 15–19]. the oxidation of phenol with oxygen in the presence of a magnetically controlled ferromagnetic catalyst stabilized by polymers is characterized by higher efficiency, low activation energy and the absence of toxic compounds in aqueous solution. for example, fe3o4 is an active particle of catalysts, and cobalt complexes forms stable π-complexes with aromatic compounds; due to the π-dative transfer of electrons from the central atom to π*-loosening c6h6 orbitals, they activate the multiple bonds of the ring more strongly and loosen the molecule. when the metal complex is bound to the polymer, some of the ligands in the complex are replaced by functional groups of the polymer chain. one of the most promising preparative methods is the synthesis of nanoparticles using polyethyleneimine (pei) or polyvinylpyrrolidone (pvp) as a stabilizer due to their biocompatibility and hypoallergenicity. pei coatings contain many amino groups and form cationic complexes that actively react with negatively charged surfaces and substances. pei is a positively charged polymer. the authors of [20, 21] found the effectiveness of magnetofection in vivo when using iron oxide nanoparticles stabilized with pei. the structural formula of pvp contributes to the fact that pvp acts as a surface stabilizer, dispersant and nanoparticle expansion modifier. pvp also has protective properties due to its unique structure. the pvp molecule contains a highly polar amide group, which provides hydrophilic properties, as well as non-polar methyl groups, both in the skeleton and in the ring, which provide hydrophobic properties [22]. the purpose of this work was to create magnetic nanocatalysts that could be used for the oxidation of organic water pollutants – phenol and its derivatives – and to determine the physicochemical characteristics of the catalysts. 2. experimental the following chemical reagents were used for the synthesis of magnetite and cobalt ferrite stabilized with pei and pvp: iron (ii) sulfate heptahydrate (feso4.7h2o) – “chemically pure”; iron (iii) chloride hexahydrate (fecl3·6h2o) – “chemically pure”; co(no3)2·6h2o – “chemically pure”; 25% aqueous solution of ammonia (nh4oh) – “chemically pure”. co-deposition occurs in two stages: first, the nucleation of crystals (when critical supersaturation is reached); second, the slow crystal growth through the process of diffusion of dissolved substances to the crystal surface. these two stages should be separated in order to avoid the formation of crystals during the growth period [5, 16, 23, 24]. according to a number of works [25–27], the creation of polyethyleneimine coatings on magnetic iron oxide nanoparticles is a difficult task due to the aggregation during the adsorption of this polymer. to increase the efficiency of the catalytic system in the oxidation of organic compounds, the surface of magnetite was treated with cobalt nitrate. in the series of mefe2o4 ferrites, where me is fe2+, co2+, ni2+, cu2+and etc.), cobalt ferrite (cofe2o4) has the highest cubic magnetocrystalline anisotropy, which is why cobalt nitrate was chosen. synthesis of cofe2o4 was carried out through the following stages: 1) mixing of the aqueous solutions of fecl3·6h2o and co(no3)2·6h2o; 2) slow heating of the mixture to 353 k; 3) dripping 25% ammonia solution into the mixture with intense stirring and constant control of the crucial parameters (solution ph, mixture temperature); 4) mixing the resulting composite for another 40 minutes. as a result, a very rapid formation of a dark brown suspension occurred. nanosized magnetic composites stabilized with pvp (mw = 10,000) and based on fe3o4, cofe2o4 were obtained by chemical deposition. nanocrystals of iron magnetite (fe3o4) stabilized with pvp were obtained by chemical coprecipitation of the corresponding salts: ferrous and ferric iron ions in an alkaline solution [16, 28–30]. the synthesis was carried out separately in water in an aqueous solution with pvp (mw = 10,000). the composition and structure of the synthesized catalysts were determined by sem, mossbauer and ir-fourier spectroscopy. a vertex 70v ir fourier spectrometer (bruker, germany) with a computer-based system for recording and processing spectra was used. the reactions of phenol with oxygen on the nanocomposites stabilized with pei were carried out according to a widely used method described in the scientific literature, including our previous works [5, 16, 23, 24], in a duck-type thermostated glass reactor. during and after the experiment, the samples of intermediate and final products were analyzed for the presence of phenol and benzoquinone by uv and ir spectroscopy. https://doi.org/10.15826/chimtech.2023.10.3.09 chimica techno acta 2023, vol. 10(3), no. 202310309 article 3 of 8 doi: 10.15826/chimtech.2023.10.3.09 3. results and discussion 3.1. results of physicochemical studies for the fe-co/al2o3 sample (figure 1), according to the sem analysis, areas with an increased iron content were found, which confirms the results of the elemental analysis (figure 2, table 1). in the diffraction pattern of the fe-co/al2o3 sample (figure 3), the signals related to iron oxide, cobalt in the region of 2θ = 50–55°, and a shoulder corresponding to the unknown phase in the region 2θ = 40–45° are seen. the diffraction peaks for cobalt oxide correspond to co3o4 spinel [28, 29, 31–33] (table 2). detection of hydrocarbon by elemental analysis in the case of a cofe2o4 catalyst stabilized with pvp shows that there is an interaction between nanoparticles and polymer, indicating efficient formation of nanocomposites (figure 4, table 3) [34, 35]. according to an ir study, for the cofe2o4 nanocomposite stabilized with pvp, the absorption bands in the region of 600–800 cm–1 are due to the stretching vibrations of the fe–o bond in oxides. the absorption bands at 735, 663, 649, 626 cm–1 are natural vibrations for composite nanoparticles embedded in a polyvinylpyrrolidone matrix. table 1 elemental analysis of the fe-co /al2o3 sample. spectrum na2о al2о3 cl fe2о3 coо total 1 0.21 71.33 0.00 19.90 8.56 100.00 2 0.34 94.07 0.00 4.20 1.39 100.00 3 0.36 93.36 0.00 4.63 1.66 100.00 4 0.23 95.77 0.00 1.38 2.62 100.00 5 0.36 98.29 0.00 0.09 1.26 100.00 6 0.23 98.30 0.00 0.08 1.38 100.00 average 0.29 91.95 0.00 5.05 2.81 100.00 table 2 the diffraction date of the fe-co /al2o3 and nanocomposite with pei samples. sample reflections, å phase fe-co/al2o3 3.48, 2.37, 2.08, 1.74, 1.60, 1.51, 1.40, 1.37, 1.23, 1.18 al2o3 (astm 711123). 2.71, 2.51, 2.20, 1.84, 1.69, 1.59, 1.48, 1.45, 1.30 hematite α-fe2o3 (astm 13-534). 5.52, 4.28, 2.85, 2.76, 2.71, 2.55, 2.51, 2.37, 2.13, 2.06, 1.43, 1.23 co3o4 (astm 801535). nanocomposite with pei 2.96, 2.53, 2.09, 1.71, 1.61, 1.48, 1.32, 1.27 γ-fe2o3 (astm 5637). 2.70, 2.53, 1.84, 1.48, 1.45, 1.30, 1.18 α -fe2o3 (astm 13-534) 2.98, 2.73, 1.38 ε-fe2o3 (astm 16653) 4.29, 2.87, 2.73, 2.65, 2.38, 2.36, 2.04, 1.43, 1.23 co3o4 (astm 801535) figure 1 results of sem analysis: cofe2o4 (a), fe-co/al2o3 (b). figure 2 x-ray fluorescence analysis of the samples: feco/al2o3 (a); cofe2o4 (b); cofe2o4/pei (c). https://doi.org/10.15826/chimtech.2023.10.3.09 chimica techno acta 2023, vol. 10(3), no. 202310309 article 4 of 8 doi: 10.15826/chimtech.2023.10.3.09 figure 3 the diffraction patterns of: fe-co/al2o3 sample (a); cofe2o4 composite (b); cofe2o4/pei composite (c). table 2 elemental analysis data of the cofe2o4 catalyst stabilized with pvp. element number element symbol element name atomic conc. weight conc. 6 c carbon 24.869 10.600 8 o oxygen 42.794 24.300 26 fe iron 23.157 45.900 27 co cobalt 9.180 19.200 bands characteristic of pvp at 1657 cm–1 (amide raman band), 1498, 1461, 1423, and 1372 cm–1 (deformation vibrations of ch2 groups in the pyrrolidone cycle) and 1287 cm–1 (amide iii–c–h bending vibrations) were found in the polymer matrix with slight shifts compared to pure pvp [36, 37]. this probably indicates that pvp forms a composite together with the ferrite nanocrystals. thus, the inclusion of cofe2o4 nanoparticles in the pvp matrix leads to a shift of some absorption bands in the nanocomposites. https://doi.org/10.15826/chimtech.2023.10.3.09 chimica techno acta 2023, vol. 10(3), no. 202310309 article 5 of 8 doi: 10.15826/chimtech.2023.10.3.09 3.2. testing of the synthesized nanocomposites in the oxidation of phenol the synthesized nanocomposites were tested in the oxidation reaction of phenol with oxygen (figure 5). catalytic activity of the magnetic nanocomposites with composition fe3o4, cofe2o4 and cofe2o4/pei was checked in the process of phenol oxidation (cphenol = 0.003 mol/l). brief interpretation of the ir spectra of phenol and reaction products after oxidation with oxygen in the presence of a cofe2o4/pei nanocomposite (figure 6): for phenol: ir spectrum: valence oscillations oh – in the area 3385–3610 cm–1, 3390–3395 cm–1; valence vibrations of c–o are in the fields of 1220–1232 cm–1 and 1240– 1245 cm–1. figure 4 results of physicochemical studies of the cofe2o4 catalyst stabilized with pvp: sem image (fw: 17 μm, mode: 10 kv – image, detector: bsd full) (a); x-ray fluorescence spectrum (b). figure 5 oxidation of phenol with oxygen: oxidation on systems of different composition (a): fe3o4 (1); cofe2o4 (2); cofe2o4/pei (3); oxidation on cofe2o4/pei at different reaction temperatures (b): 303 k (1), 313 k (2), 323 k (3), 333 k (4) and 343 k (5). figure 6 the results of the analysis of the reaction medium for the oxidation of phenol with oxygen: ir spectrum of the starting material, phenol, before the reaction (a); ir spectrum of the final sample after the phenol oxidation reaction (b); uv spectra: pure phenol (c); after 1 hour of oxidation (d); after 2 hour of oxidation (e). https://doi.org/10.15826/chimtech.2023.10.3.09 chimica techno acta 2023, vol. 10(3), no. 202310309 article 6 of 8 doi: 10.15826/chimtech.2023.10.3.09 uv spectrum data: 210 (ε = 6200 l/mol·cm) and 270 nm (ε = 1450 l/mol·cm). there are absorption bands characteristic of phenol in the region 192–194/210– 2011/265–270 nm (figure 6a). the results of ir and uv spectroscopy indicate the presence of ch in the aromatic ring and c=c double bonds, as well as valence vibrations of c=o groups of carbonyl compounds [16, 38–42]. the absorption band of double bonds c=c was found at 3050–3060 cm–1. the oscillation band of hydroxyl groups of hydroquinone, the intermediate product of phenol oxidation is at 3420–3425 cm–1. the vibrations in the c=o bonds of the carbonyl group of benzoquinones were at 1676 cm–1, 1648 cm–1 (intense band). the vibration bands of the c–h and c–c bonds of the quinone ring are at 1365 cm–1 and 1312 cm–1. the uv spectrum of the sample during the reaction shows bands in the 207–210/213 nm region (figure 6b) and a plateau in the 270–275 nm region [16, 40–42]. thus, according to the uv and ir spectroscopy data, the magnetic composites have good catalytic activity during the oxidation of phenol with oxygen. it was concluded that among the magnetic nanocomposites of the fe3o4, cofe2o4 and cofe2o4/pei compositions, the most efficient oxidation of phenol is observed in the presence of the cofe2o4/pei nanocomposite. 4. limitations the magnetic properties of stabilized magnetic composites are determined by many factors, such as the chemical composition, the type of crystal lattice, the size and shape of particles, and the interaction of particles with the surrounding polymer matrix. by changing the size, shape, composition, and structure of nanoparticles, it is possible, within certain limits, to control the magnetic characteristics of materials based on them. however, it is not always possible to control all these factors during the synthesis of nanoparticles of approximately the same size and chemical composition, which means that the properties of stabilized magnetic composites may differ. during synthesis, magnetite can be oxidized to maghemite, but it tends not to oxidize completely even during prolonged heating. in the process of obtaining nanoparticles, the question of their stabilization always arises, which limits the further growth of the solid phase. therefore, it is difficult to determine the optimal reaction conditions, including the type of reaction, solvent, temperature and surfactants, in particular polymers, which react selectively at the resulting phase boundary. 5. conclusions it is known that good results in the purification of industrial wastewater from phenol can be obtained by using catalysts. among the most promising catalysts are nanodispersed catalytic systems and magnetic composites based on metal oxides. within the framework of this research the nanocomposites of fe3o4, fe-co/al2o3 and cofe2o4 were synthesized. the composites of cofe2o4 stabilized with polyethylenimine or polyvinylpyrrolidone were prepared and used for oxidation of phenol with oxygen. according to ir-spectroscopy, there was the presence of c=o bonds of the carbonyl group of benzoquinone and c–h and c–c bonds of the quinone ring in the products of phenol oxidation with oxygen. based on the results of phenol oxidation, it can be concluded that magnetic composites based on iron and cobalt immobilized by polymers are promising catalysts for wastewater treatment from organic compounds, including phenol, as well as for the targeted synthesis of oxygen-containing compounds. ● supplementary materials no supplementary materials are available. ● funding this research has been funded by the science committee of the ministry of education and science of the republic of kazakhstan, grant no. ap14870308 “development of technology for catalytic petrochemical synthesis of oxygencontaining compounds from aromatic hydrocarbons in the presence of nanoscale magnetic composites”. ● acknowledgments none. ● author contributions conceptualization: b.t.d., l.r. s. data curation: l.r. s., t.v. s. formal analysis: l.r. s., a. r. s. funding acquisition: t.v. s. investigation: b.t.d., m.s.i., z.m. z., b.b.b. methodology: b.t.d., l.r. s., b.b.b. project administration: t.v. s. resources: t.v. s., l.r. s. software: l.r.s., a. r. s., t.s.a. supervision: t.v. s., b.t.d. validation: l.r. s., b.t.d. visualization: a. r. s., z.m. z., m.s.i., t.s.a. writing – original draft: l.r. s., b.t.d. writing – review & editing: l.r. s. ● conflict of interest the authors declare no conflict of interest. ● additional information author ids: larissa r. sassykova, scopus id 56178673800; https://doi.org/10.15826/chimtech.2023.10.3.09 https://www.scopus.com/authid/detail.uri?authorid=56178673800 chimica techno acta 2023, vol. 10(3), no. 202310309 article 7 of 8 doi: 10.15826/chimtech.2023.10.3.09 binara t. dossumova, scopus id 57210592713; madina s. ilmuratova, scopus id 57262368200; tatyana v. shakiyeva, scopus id 55911739700; bedelzhan b. baizhomartov, scopus id 55911858500; albina r. sassykova, scopus id 57220005479; zhanar m. zhaxibayeva, scopus id 57224865951; tleutai s. abildin, scopus id 6506476435. websites: al-farabi kazakh national university, https://www.kaznu.kz/en; almaty management college, https://cmab.kz/index.php/en/; abai kazakh national pedagogical university, https://www.kaznpu.kz/en. references 1. zhang z, malik mz, khan a, ali n, malik s, bilal m. environmental impacts of hazardous waste, and management strategies to reconcile circular economy 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merck llc, moscow 115054, russia c: perm state national research university, perm 614990, russia d: perm national research polytechnic university, perm 614990, russia e: peter the great st. petersburg polytechnic university, st. petersburg 195251, russia * corresponding author: gorbunova@psu.ru (i.a. gorbunova), shipilovskikh@psu.ru (daria a. shipilovskikh). this paper belongs to the mosm2022 special issue. abstract new methyl 5-aryl-1-(furan-2-carbonyl)-1h-pyrazole-3-carboxylates were obtained via decyclization reaction of n'-(5-aryl-2-oxofuran-3(2h)ylidene)furan-2-carbohydrazides under the action of methanol. starting n'(5-aryl-2-oxofuran-3(2h)-ylidene)furan-2-carbohydrazides were obtained by intramolecular cyclization of substituted 4-aryl-2-[2-(furan-2ylcarbonyl)hydrazinylidene]-4-oxobutanoic acids in propionic anhydride. the structure of the compounds obtained was confirmed by the 1h nmr spectroscopy, ir spectrometry and elemental analysis methods. analgesic activity of some obtained compounds was studied by the “hot plate” method on outbred white mice of both sexes with intraperitoneal injection. keywords 2,4-dioxobutanoic acid 2-hydrazono-4-oxobutanoic acids 3-hydrazonofuran-2(3h)-one analgesic activity drugs received: 14.11.22 revised: 21.11.22 accepted: 21.11.22 available online: 01.12.22 key findings ● the synthesis method for obtaining methyl 5-aryl-1-(furan-2-carbonyl)-1h-pyrazole-3-carboxylates developed. ● five new compounds not previously described in the literature were obtained. ● some of the compounds obtained have been found to have significant analgetic effects. © 2022, the authors. this article is published in open access under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). 1. introduction the development and creation of new drug forms with lower toxicity is one of the most important tasks of modern pharmaceutical and medicinal chemistry [1–7], since modern medicine is always in need of new drugs. it is necessary to create a universal basic structure that will allow obtaining a wide diversity of different structures possessing biological activity. such a universal structural fragment can be found among the 3-imino(hydrazinylidene)-furan-2(3h)-one derivatives, which results from their chemical availability due to the scalability of the synthetic methods [8] and the reactivity [9– 15]. for example, the reactions of 3-imino(hydrazinylidene)-furan-2(3h)-ones derivatives with various nucleophilic reagents lead to the attack on the carbonyl group of the lactone fragment and to the formation of acyclic or heterocyclic structures [16–21] that retain the pharmacophore fragment of 2,4-dioxobutanoic acid [22–32]. this fragment was found in the structure of various biologically active and natural compounds [33, 34], which indicates that this idea is worth developing. previously, we proposed a simple method for the preparation of 3-hydrazinylidenefuran-2(3h)-one derivatives by intramolecular cyclization of substituted 2-[2-(4-rbenzoyl)hydrazinylidene]-4-oxobutanoic acids in the presence of acetic or propionic anhydride [35, 36]. furthermore, this method was applied to 3-imino(thiophen2-yl)furan-2(3h)-ones derivatives, which include the pharmacophore fragment, gewald aminothiophene [37– 41]. compounds that contain this pharmacophore fragment exhibit analgesic [42–44], anti-inflammatory [45, 46], antimicrobial [47–49] and photoluminescent properties [50, 51] and other biological activities [52–54]. also, http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2023.10.1.01 mailto:gorbunova@psu.ru mailto:shipilovskikh@psu.ru http://creativecommons.org/licenses/by/4.0/ https://orcid.org/0000-0001-6006-168x http://orcid.org/0000-0003-3028-7914 https://orcid.org/0000-0003-3867-5305 https://orcid.org/0000-0001-6086-4300 https://orcid.org/0000-0002-2840-6809 https://orcid.org/0000-0003-0976-9951 https://crossmark.crossref.org/dialog/?doi=https://doi.org/10.15826/chimtech.2023.10.1.01&domain=pdf&date_stamp=2022-12-1 chimica techno acta 2023, vol. 10(1), no. 202310101 article 2 of 8 doi: 10.15826/chimtech.2023.10.1.01 we showed that n′-[5-aryl-2-oxofuran-3(2н)ylidene]furan-2-carbohydrazides and its precursor 4aryl-2-[2-(furan -2-ylcarbonyl)hydrazinylidene] -4oxobutanoic acids have analgesic activity in the previous studies [55]. the interaction of 3-hydrazinylidenefuran2(3h)-one with alcohols in the presence of triethylamine, which leading to the formation of a mixture of alkyl 2hydrazinylidene-4-oxobutanoates and alkyl 5-hydroxy-4,5dihydro-1h-pyrazole-3-carboxylates, was described earlier [56] (scheme 1). in the this study, the research into the reactivity of 3-hydrazinylidenefuran-2(3h)-one towards alcohols was continued. namely, we considered the interaction of n′-[5-aryl-2-oxofuran-3(2н)-ylidene]furan-2carbohydrazides with methanol in the presence of ptoluenesulfonic acid, which leads to the formation of methyl 1-(furan-2-carbonyl)-1h-pyrazole-3-carboxylates as sole products (scheme 1). in addition, the analgesic activity of the original n′-[5-aryl-2-oxofuran-3(2н)-ylidene]furan-2carbohydrazides and the resulting methyl 5-aryl-1-(furan-2carbonyl)-1h-pyrazole-3-carboxylates was studied. 2. experimental ir spectra were recorded on an fsm-1202 instrument in vaseline oil. the 1h nmr spectra were recorded at 400 mhz at the temperature of 313 k; the chemical shifts (δ) were measured in ppm with respect to the solvent ([d6] dmso, 1h: δ= 2.50 ppm). the coupling constants (jhh) are given in hertz. the splitting patterns of apparent multiplets associated with an averaged coupling constants were designated as s (singlet), d (doublet), t (triplet), q (quartet), m (multiplet), dd (doublet of doublets) and br (broadened). elemental analysis was performed on a leco chns-932 instrument. the chemical purity of the compounds and the reactions progress were monitored by tlc on sorbfil plates in the diethyl ether–benzene–acetone (10:9:1) system, detection in uv light and iodine vapor. melting points were determined on an smp40 apparatus. furan-2-carbohydrazide 1 [57] and 4-aryl-2,4dioxobutanoic acids 2a–e [58, 59] were prepared according to the literature methods. 2.1. general procedure for the synthesis of 4-aryl2-[2-(furan-2-carbonyl)hydrazinylidene]-4oxobutanoic acids 3a–e to a solution of 0.01 mol of furan-2-carboxylic acid hydrazide (1) in 30 ml of acetonitrile was added 0.01 mol of 4-aryl-2,4-dioxobutanoic acid 2a–e. the resulting mixture was heated to 50 °c and kept for 5 min at this temperature. the solution was cooled to 0 °c; the formed precipitate was filtered off and recrystallized from dioxane. 2.1.1. 2-[2-(furan-2-carbonyl)hydrazinylidene]-4-oxo4-phenylbutanoic acid (3a) yield 2.52 g (84%), yellow crystals, mp 165–166 °с (dioxane). ir spectrum, ν, cm–1: 3379, 3299, 3137, 1735, 1645, 1600. 1h nmr spectrum (dmso-d6), δ, ppm: form a (14%): 4.53 s (2н, сн2), 6.71 dd (1н, harom, jhh 3.5, 1.6 hz), 7.24–8.01 m (7н, harom), 11.32 br. s (1н, nh); form b (79%): 3.21 d (1н, с4н2, jhh 20.0 hz), 3.33 d (1н, с4н2, jhh 20.0 hz), 6.68 dd (1н, jhh 3.5, 1.8 hz), 7.24– 8.01 m (7н, harom and он); form c (7%): 4.27 с (2н, сн2), 6.71 dd (1н, harom, jhh 3.5, 1.6 hz), 7.24–8.01 m (7н, harom) 13.72 br. s (1н, nh). found, %: c 60.02; h 4.01; n 9.36. c15h12n2о5. calculated, %: c 60.00; h 4.03; n 9.33. 2.1.2. 2-[2-(furan-2-carbonyl)hydrazinylidene]-4-(4methylphenyl)-4-oxobutanoic acid (3b) yield 2.29 g (73%), yellow crystals, mp 179–180 °с (dioxane). 1н nmr spectrum (dmso-d6), δ, ppm: form a (30%): 2.41 s (3н, ch3), 4.52 s (2н, сн2), 6.73 dd (1н, harom, jhh 3.4, 1.7 hz), 7.14–7.99 m (6н, harom), 11.38 br. s (1н, nh); form b (58%): 2.30 с (3н, ch3), 3.22 d (1н, с4н2, jhh 20.0 hz), 3.32 d (1н, с4н2, jhh 20.0 hz), 6.70 dd (1н, jhh 3.5, 1.7 hz), 7.14–7.98 m (6н, harom and он); form c (12%): 2.40 s (3н, ch3), 4.29 s (2н, сн2), 6.73 dd (1н, harom, jhh 3.4, 1.7 hz), 7.14–7.99 m (6н, harom) 13.47 br. s (1н, nh). found, %: c 61.12; h 4.47; n 8.94. c16h14n2о5. calculated, %: c 61.14; h 4.49; n 8.91. 2.1.3. 2-[2-(furan-2-carbonyl)hydrazinylidene]-4-(4methoxyphenyl)-4-oxobutanoic acid (3c) yield 2.81 g (85%), yellow crystals, mp 159–160 °с (dioxane). 1н nmr spectrum (dmso-d6), δ, ppm: form a (43%): 3.86 s (3н, сн3о), 4.48 s (2н, сн2), 6.71 dd (1н, harom, jhh 3.2, 1.7 hz), 6.87–8.00 m (6н, harom), 11.29 br. s (1н, nh); form b (37%): 3.21 d (1н, с4н2, jhh 20.0 hz), 3.31 d (1н, с4н2, jhh 20.0 hz), 6.68 dd (1н, jhh 3.4, 1.6 hz), 6.87–8.00 m (6н, harom and он); form c (20%): 3.81 s (3н, сн3о), 4.24 s (2н, сн2), 6.71 dd (1н, harom, jhh 3.2, 1.7 hz), 6.87–8.00 m (6н, harom), 13.40 br. s (1н, nh). found, %: c 58.16; h 4.31; n 8.46. c16h14n2о6. calculated, %: c 58.18; h 4.27; n 8.48. 2.1.4. 4-(4-chlorophenyl)-2-[2-(furan-2carbonyl)hydrazinylidene]-4-oxobutanoic acid (3d) yield 2.58 g (77%), yellow crystals, mp 182–183 °с (dioxane). ir spectrum, ν, cm–1: 3237, 3131, 1741, 1683, 1617, 1585. 1н nmr spectrum (dmso-d6), δ, ppm: form a (9%), 4.49 s (2н, сн2), 6.71 m (1н, harom), 7.22‒7.96 m (6н, harom), scheme 1 reaction of 3-hydrazinylidenefuran-2(3h)-one with alcohols in basic and acidic conditions. https://doi.org/10.15826/chimtech.2023.10.1.01 chimica techno acta 2023, vol. 10(1), no. 202310101 article 3 of 8 doi: 10.15826/chimtech.2023.10.1.01 11.43 br. s (1н, nh); form b (86%), 3.21 d (1н, с4н2, jhh 20.0 hz), 3.30 d (1н, с4н2, jhh 20.0 hz), 6.69 m (1н, harom), 7.22‒7.96 m (7н, 6нarom and он); form c (5%), 4.31 s (2н, сн2), 6.84 m (1н, harom), 7.22‒7.96 m (6н, harom), 13.50 br. s (1н, nh). found, %: c 53.85; h 3.29; n 8.39. c15h11cln2о5. calculated, %: c 53.83; h 3.31; n 8.37. 2.1.5. (4-bromophenyl)-2-[2-(furan-2ylcarbonyl)hydrazinylidene]-4-oxobutanoic acid (3e) yield 2.99 g (79%), yellow crystals, mp 179–180 °с (dioxane). ir spectrum, ν, cm–1: 3242, 3148, 1734, 1666, 1614, 1583. 1н nmr spectrum (dmso-d6), δ, ppm: form a (8%), 4.51 s (2н, сн2), 6.66 dd (1н, harom, jhh 3.5, 1.6 hz), 7.37‒7.94 m (6н, harom), 11.29 br. s (1н, nh); form b (87%), 3.25 d (1н, с4н2, jhh 20.0 hz), 3.32 d (1н, с4н2, jhh 20.0 hz), 6.68 dd (1нar, jhh 3.6, 1.7 hz), 7.37‒ 7.94 m (7н, 6нarom and он); form c (5%), 4.25 s (2н, сн2), 6.71 dd (1h, нarom, jhh 3.5, 1.8 hz), 7.37‒7.94 m (6h, нarom), 13.06 br. s (1н, nh). found, %: c 47.55; h 2.88; n 7.41. c15h11brn2о5. calculated, %: c 47.52; h 2.92; n 7.39. 2.2. general method of synthesis of n'-(5-aryl-2oxofuran-3(2h)-ylidene)furan-2carbohydrazides 4a–e propionic anhydride (8 ml) was added to 0.01 mol of acid 3a–е. the resulting mixture was slowly heated with stirring to 150 °c and kept for 5 min. the precipitate formed after cooling was filtered off, washed with anhydrous diethyl ether, and recrystallized from anhydrous toluene or dioxane. 2.2.1. n'-(2-oxo-5-phenylfuran-3(2н)-ylidene)furan-2carbohydrazide (4a) yield 2.20 g (78%), yellow crystals, mp 246–248 °с (dioxane). ir spectrum, ν, cm–1: 3188, 1801, 1698, 1667, 1617. 1н nmr (dmso-d6, 400 mhz) δ (ppm): form a (69%): 6.78 dd (1h, harom, jhh 3.5, 1.8 hz), 7.52 m (5h, harom, 2h, 2ch), 8.04 d (1h, jhh 1.0 hz), 11.90 br. s (1h, nh); form b (31%): 6.80 dd (1h, harom, jhh 3.6, 1.7 hz), 7.25 s (1h, ch), 7.65 m (5h, harom, 1h, ch) 8.07 d (1h, harom, jhh 1.0 hz), 12.55 s (1н, nh). found, %: c 63.80; 3.55; n 9.91. c15h10n2o4. calculated, %: c 63.83; h 3.57; n 9.93. 2.2.2. n'-[5-(4-methylphenyl)-2-oxofuran-3(2h)ylidene]furan-2-carbohydrazide (4b) yield 1.57 g (53%), yellow crystals, mp 258–259 °с (dioxane). ir spectrum, ν, cm–1: 3125, 1799, 1693, 1672, 1622. 1н nmr (dmso-d6, 400 mhz) δ (ppm): 2.41 s (3h, me), 6.72 dd (1h, harom, jhh 3.5, 1.8 hz), 7.51 m (5h, harom, 1h, ch), 7.98 d (1h, jhh 1.0 hz), 11.89 br. s (1h, nh). found, %: c 64.84; 4.11; n 9.48. c16h12n2o4. calculated, %: c 64.86; h 4.08; n 9.46. 2.2.3. n'-[5-(4-methoxyphenyl)-2-oxofuran-3(2h)ylidene]furan-2-carbohydrazide (4c) yield 1.75 g, (56%), yellow crystals, mp 265–266 °с (dioxane). ir spectrum, ν, cm–1: 3137, 1801, 1666, 1622, 1592. 1н nmr (dmso-d6, 400 mhz) δ (ppm): form a (76%): 3.86 s (3h, meo), 6.74 dd (1h, harom, jhh 3.6, 1.7 hz), 7.14 d (2h, harom, jhh 8.0 hz), 7.38 s (1h, ch ), 7.56 dd (1h, harom, jhh 3.6, 0.8 hz), 7.72 d (2h, harom, jhh 8.0 hz), 7.99 dd (1h, jhh 1.6, 0.8 hz), 11.66 br. s (1h, nh); form b (24%): 3.85 s (3h, meo), 6.76 dd (1h, harom, jhh 3.6, 1.7 hz), 7.03 s (1h, ch), 7.11 d (2h, harom, jhh 9.0 hz) , 7.40 d (1h, harom, jhh 1.0 hz), 7.80 d (2h, harom, jhh 9.0 hz), 8.02 d (1h, harom, jhh 1.0 hz), 12.44 s (1h, nh). found, %: c 61.53; 3.85; n 8.99. c16h12n2o5. calculated, %: c 61.54; h 3.87; n 8.97. 2.2.4. n′-[5-(4-chlorophenyl)-2-oxofuran-3(2н)ylidene]furan-2-carbohydrazide (4d) yield 2.35 g, (74%), yellow crystals, mp 268–269 °с (dioxane). ir spectrum, ν, cm–1: 3137, 1776, 1694, 1619. 1н nmr (dmso-d6, 400 mhz) δ (ppm): form a (16%), 6.78 dd (1н, нarom, jhh 3.6, 1.7 hz), 7.50 s (1н, сн), 7.59 m (1н, нarom), 7.63 m (2н, нarom), 7.88 m (2н, нarom), 8.04 m (1н, нarom), 11.75 br. s (1н, nh); form b (84%), 6.80 dd (1н, нarom, jhh 3.6, 1.7 hz), 7.17 s (1н, сн), 7.38 m (2н, нarom), 7.43 dd (1н, нarom, jhh 3.5, 0.6 hz), 7.76 m (2н, нarom), 8.07 dd (1н, нarom, jhh 1.6, 0.6 hz), 12.54 s (1н, nh). found, %: c 56.87; h 2.88; n 8.87. с15h9cln2o4. calculated, %: c 56.89; h 2.86; n 8.85. 2.2.5. n′-[5-(4-bromophenyl)-2-oxofuran-3(2н)ylidene]-furan-2-carbohydrazide (4e) yield 2.35 g, (65%), yellow crystals, mp 267–268 °с (dioxane). ir spectrum, ν, cm–1: 3181, 1803, 1683, 1614. 1н nmr (dmso-d6, 400 mhz) δ (ppm): 6.78 dd (1н, нarom, jhh 3.6, 1.7 hz), 7.27 s (1н, сн), 7.42 dd (1н, нarom, jhh 3.6, 0.6 hz), 7.74 m (4н, нarom), 8.04 m (1н, нarom), 12.37 br. s (1н, nh). found, %: c 49.87; h 2.53; n 7.73. с15h9brn2o4. calculated, %: c 49.89; h 2.51; n 7.76 2.3. general method of synthesis of methyl 5-aryl1-(furan-2-carbonyl)-1h-pyrazole-3carboxylates 5a–e. to a suspension of 0.0025 mol n'-[5-aryl-2-oxofuran3(2h)-ylidene]furan-2-carbohydrazide 4a–e in 20 ml of methanol was added 1.16 mmol (0.2 g) of p-toluenesulfonic acid, stirred at 64 °c for 20–60 min and cooled to 0 °c. the formed precipitate was filtered off, washed with cold methanol and recrystallized from propan-2-ol. 2.3.1. methyl 1-(furan-2-ylcarbonyl)-5-phenyl-1hpyrazole-3-carboxylate (5a) yield 0.43 g, (58%), colorless crystals, mp 122–123 °c (propan-2-ol). ir spectrum, ν, cm–1: 1746, 1706, 1557. 1н nmr (dmso-d6, 400 mhz) δ (ppm): 3.94 s (3h, meo), 6.92 dd (1н, harom, jhh 3.7, 1.7 hz), 7.18 s (1h, ch), 7.87 m (7н, harom). found, %: s, 64.88; h 4.06; h 9.44; c16h12n2o4. calculated, %: c, 64.86; h, 4.08; n, 9.46. 2.3.2. methyl 1-(furan-2-ylcarbonyl)-5-(4methylphenyl)-1h-pyrazole-3-carboxylate (5b) yield (0.53 g, 68%), colorless crystals, mp 223–224 °c (propan-2-ol). ir spectrum, ν, cm–1: 1730, 1618, 1587. 1н https://doi.org/10.15826/chimtech.2023.10.1.01 chimica techno acta 2023, vol. 10(1), no. 202310101 article 4 of 8 doi: 10.15826/chimtech.2023.10.1.01 nmr (dmso-d6, 400 mhz) δ (ppm): 2.34 s (3h, me), 3.89 s (3h, meo), 6.82 dd (1н, harom, jhh 3.7, 1.7 hz), 7.02 s (1h, ch), 7.23 d (2н, harom, jhh 7.9 hz), 7.35 d (2н, harom, jhh 7.9 hz), 7.74 dd (1н, harom, jhh 3.7, 0.7 hz), 8.14 dd (1н, harom, jhh 1.6, 0.6 hz). found, %: c, 65.83; h, 4.48; n, 9.05; c17h14n2o4. calculated, %: c, 65.80; h, 4.55; n, 9.03. 2.3.3. methyl 1-(furan-2-ylcarbonyl)-5-(4methoxyphenyl)-1h-pyrazole-3-carboxylate (5c) yield 0.56 g (69%), colorless crystals, mp 155–156 °c (propan-2-ol). ir spectrum, ν, cm–1: 1730, 1714, 1616, 1560. 1н nmr (dmso-d6, 400 mhz) δ (ppm): 3.80 s (3h, meo), 3.89 s (3h, meo), 6.87 dd (1н, harom, jhh 3.6, 1.8 hz), 6.99 d (2н, harom, jhh 8.0 hz) 7.07 s (1h, ch), 7.43 d (2н, harom, jhh 8.0 hz), 7.77 dd (1н, harom, jhh 3.7, 0.6 hz), 8.21 m (1н, harom). found, %: c, 62.54; h, 4.34; n, 8.62. c17h14n2o5. calculated, %: c, 62.57; h, 4.32; n, 8.59. 2.3.4. methyl 5-(4-chlorophenyl)-1-(furan-2ylcarbonyl)-1h-pyrazole-3-carboxylate (5d) yield 0.54 g (65%), colorless crystals, mp 85–86 °c (propan-2-ol). ir spectrum, ν, cm–1: 1751, 1724, 1600. 1н nmr (dmso-d6, 400 mhz) δ (ppm): 3.91 s (3h, meo), 6.89 dd (1н, harom, jhh 3.7, 1.7 hz), 7.17 s (1н, ch), 7.77 m (6н, harom). found, %: c, 58.09; h, 3.37; n, 8.51. c16h11cln2o4. calculated, %: c, 58.11; h, 3.35; n, 8.47. 2.3.5. methyl 5-(4-bromophenyl)-1-(furan-2ylcarbonyl)-1h-pyrazole-3-carboxylate (5e) yield 0.58 g (62%), colorless crystals mp 183–184 °c (propan-2-ol). ir spectrum, ν, cm–1: 1743, 1685, 1616, 1584. 1н nmr (dmso-d6, 400 mhz) δ (ppm): 3.91 s (3h, meo), 6.89 dd (1н, harom, jhh 3.7, 1.7 hz), 7.15 s (1н, ch), 7.48 d (2н, harom, jhh 8.0 hz) 7.65 d (2н, harom, jhh 8.0 hz), 7.83 dd (1н, harom, jhh 3.7, 0.7 hz), 8.23 dd (1н, harom, jhh 3.7, 0.7 hz, jhh 1.7, 0.8 hz). found, %: c, 51.24; h, 2.93; n, 7.50. c16h11brn2o4. calculated, %: c, 51.22; h, 2.96; n, 7.47. 2.4. evaluation of biological activity of target compounds evaluation of analgesic activity was carried out in the perm state national research university, the research laboratory of biologically active substances. analgesic activity was determined on outbred white mice of both sexes weighing 18–22 g using the “hot plate” method [60]. the studied compounds were administered intraperitoneally in the form of a suspension in a 2% starch solution at a dose of 50 mg/kg 30 min before the animals were placed on a metal plate heated to 53.5 °c [61]. studies were performed 30, 60, 90, 120 min after administration of the compound. the indicator of the change in pain sensitivity was the length of time the animals stay on the hot plate until adefensive pain reflex occurs – licking the hind legs or trying to tear off all four paws from the surface of the plate. the time of onset of this reflex from the beginning of the placement of the animal on the plate was measured in seconds (latent period). the maximum duration of the latent period is the interval of 40 s. in the experiment we used animals with the initial time of the onset of the defensive reflex of no more than 15 s. each compound was tested on 6 animals. the results were evaluated by increasing the time of the onset of the defensive reflex compared with the initial data. the control group of animals was injected with 2% starch mucus. metamizole sodium (farmkhimkomplekt llc) at a dose of 93 mg/kg (ed50) was used as a comparison compound. statistical processing of experimental data was carried out using student's confidence criteria. the effect was considered significant at p<0.05 [62]. the studies were carried out in accordance with all applicable international, national and institutional guidelines for the care and use of animals. 3. results and discussion substituted 2-[2-(furan-2-ylcarbonyl)hydrazinilydene]-4oxobutanoic acids 3a–e were obtained in 73–85% yields by reaction of furan-2-carbohydrazide 1 with corresponding 2,4-dioxobutanoic acids 2a–e in acetonitrile at 50 °c (scheme 2). compounds 3a–e are crystalline yellow substances, readily soluble in chloroform, dmso, and, when heated, in toluene, dioxane, and ethanol, and insoluble in water and alkanes. the ir spectra of compounds 3a–e contains an absorption band at 1734–1741 cm–1, which is characteristic of the stretching vibrations of the carbonyl amide group, and absorption bands at 3131–3148 and 3237–3299 cm–1, which are characteristic of the stretching vibrations of the nh group. the 1h nmr spectra (dmso-d6) of compounds 3a–e in the tautomeric form a are characterized by singlet signals of the nh protons (11.29–11.43 ppm) and ch2 (4.48–4.53 ppm) groups. form b is characterized by the presence in the spectrum of a doublet of protons of the ch2 group at 3.21‒3.25 and 3.30‒3.33 ppm, and for form c, singlets of the nh protons (13.06‒13.72 ppm) and ch2 (4.24‒4.31 ppm). scheme 2 synthesis of 2-[2-(furan-2-ylcarbonyl)hydrazynilidene]-4oxobutanoic acids 3a–e. https://doi.org/10.15826/chimtech.2023.10.1.01 chimica techno acta 2023, vol. 10(1), no. 202310101 article 5 of 8 doi: 10.15826/chimtech.2023.10.1.01 intramolecular cyclization of acids 3a–e occurs upon slow heating to 150 °с in propionic anhydride and leads to the formation of substituted n'-(2-oxofuran-3(2h)ylidene)furan-2-carbohydrazides 4a–e (scheme 3). compounds 4a–е, obtained in 53–78% yields, are yellow crystalline substances, readily soluble in dmso, when heated – in toluene and ethanol, and insoluble in water and alkanes. the ir spectra of compounds 4a–е contain an absorption band in the region 1776–1803 cm–1, which is characteristic of the stretching vibrations of the lactone carbonyl of the furan ring, and an absorption band in the region 3125–3188 cm–1, which is characteristic of the stretching vibrations of the nh group. according to 1н nmr data in dmso-d6, compounds 4a, 4c, 4d are present as two geometric isomers a and b. the spectra of the isomers are characterized by the presence of signals of the nh groups [11.66‒11.90 (e-a) and 12.44‒ 12.55 ppm (z-b)]. compound 4b exists only as the eisomer [δ(nh) 11.89 ppm], but compound 4e exists only as the z-isomer [δ(nh) 12.37 ppm]. it was found that the reaction of n'-(2-oxofuran3(2н)-ylidene)furan-2-carbohydrazides 4a–e with methanol in present of p-toluenesulfonic acid led to the formation of methyl 5-aryl-1-(furan-2-carbonyl)-1hpyrazole-3-carboxylates 5a–e (scheme 3). compounds 5a–e are apparently formed due to the addition of methanol to the lactone carbonyl group of furanones 4a–e, opening of the furanone ring at the o1–c2 bond, and subsequent closing of the pyrazole ring due to the addition nh group to carbonyl group of aroyl fragment followed by dehydration (scheme 4). compounds 5a–е, obtained in 58–69% yields, are colorless crystalline substances. the ir spectra of compounds 5a–е are characterized by the absence of nh group signal, in contrast to the spectra of compounds 4a–e, and the presence of the absorption band of two carbonyl groups in region 1685–1751 cm–1. scheme 3 synthesis of n'-(2-oxofuran-3(2н)-ylidene)furan-2carbohydrazides 4a–e. in 1н nmr spectra, in addition to the signals of the protons of arylic and heterocyclic fragments, there are singlet signals of the methoxycarbonyl groups in the region 3.89–3.94 ppm. some of the compounds obtained were examined for analgesic activity. it is shown in table 1 that all the studied compounds have a pronounced analgesic effect, surpassing the effect of the comparison drug metamizole. 4. limitations we have obtained new methyl 5-aryl-1-(furan-2carbonyl)-1h-pyrazole-3-carboxylates with 58-69% yields, yields are significantly declining after recrystallisation of obtained compounds. therefore, we are going to improve a method of purification for achievement higher product yields in our further studies. 5. conclusions new methyl 5-aryl-1-(furan-2-carbonyl)-1h-pyrazole-3carboxylates were obtained with 58-69% yields by the recyclization of n'-(5-aryl-2-oxofuran-3(2h)-ylidene)furan-2carbohydrazides under the action methanol in the presence of p-toluenesulfonic acid. it was found that n'-(5-aryl-2oxofuran-3(2h)-ylidene)furan-2-carbohydrazides and methyl 5-aryl-1-(furan-2-carbonyl)-1h-pyrazole-3-carboxylates exhibit significant analgesic activity, reliably exceeding the effect of a reference drug. further study of biological activity of the compounds obtained is planned. scheme 4 synthesis and proposed pathway of formation of methyl 5-aryl-1-(furan-2-carbonyl)-1h-pyrazole-3-carboxylates 5a–e. figure 1 the structure of the 4a–e and 5b compounds. https://doi.org/10.15826/chimtech.2023.10.1.01 chimica techno acta 2023, vol. 10(1), no. 202310101 article 6 of 8 doi: 10.15826/chimtech.2023.10.1.01 table 1 analgetic activity of substances 4a–e and 5b. compound dosage, mg/kg the latent period of the defensive reflex (120 min), s 4a 50 24.80±0.97 4b 50 26.60±1.36 4c 50 19.48±0.82 4d 50 21.66±0.46 4e 50 24.64±1.38 5b 50 22.18±0.34 metamizole sodium 93 (ed50) 16.60±1.00 control – 10.30±0.60 ● supplementary materials no supplementary materials are available. ● funding this study was performed under financial support of the “rational use of the earth interior” perm scientific educational center 2023 and ministry of science and higher education of russian federation fseg-2022-0012. ● acknowledgments none. ● author contributions conceptualization: d.a.s., n.m.i. data curation: i.a.g., s.n.i., a.s.r., r.r.m., p.s.s. formal analysis: i.a.g., a.yu.t., d.a.k, a.s.r., p.s.s. funding acquisition: d.a.s., n.m.i investigation: s.n.i., i.a.g., a.s.r., r.r.m. methodology: s.n.i., i.a.g., d.a.k, a.s.r., r.r.m. project administration: d.a.s., n.m.i. resources: d.a.s., n.m.i. supervision: d.a.s., n.m.i. validation: d.a.s., p.s.s., n.m.i. visualization: i.a.g., s.n.i., writing – original draft: d.a.s., p.s.s., n.m.i. writing – review & editing: d.a.s., n.m.i. ● conflict of interest the authors declare no conflict of interest. ● additional information author ids: sergei n. igidov, scopus id 57679291500; irina a. gorbunova, scopus id 57219990135; aleksey yu. turyshev, scopus id 57431693900; daria a. shipilovskikh, scopus id 57193555475; ramiz r. makhmudov, scopus id 57366636900; pavel s. silaichev, scopus id 8521794900; nazim m. igidov, scopus id 6701786062. websites: perm state pharmaceutical academy, http://pfa.ru; perm state national research university, http://en.psu.ru; perm national research polytechnic university, https://pstu.ru/en; peter the great st. petersburg polytechnic university, https://english.spbstu.ru. references 1. jhinjharia d, kaushik ac, sahi s. chemoinformatics and bioinformatics in the pharmaceutical sciences. chapter 3 – advances in structure-based drug design. academic press; 2021. 55–103 p. 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https://doi.org/10.1002/jccs.202000166 https://doi.org/10.1007/s11172-022-3445-y https://doi.org/10.1111/j.1439-0507.2011.02089.x https://doi.org/10.1063/5.0018494 https://doi.org/10.1007/s10593-019-02437-1 https://doi.org/10.1016/j.photonics.2021.100990 https://doi.org/10.15826/chimtech.2021.8.4.11 https://doi.org/10.1002/jhet.3849 https://doi.org/10.7124/bc.000a2c https://doi.org/10.1186/s13065-019-0569-8 https://doi.org/10.1134/s1070363222090067 https://doi.org/10.1134/s1070363220050096 https://doi.org/10.1021/acs.joc.1c00654 https://doi.org/10.1023/a:1012438902959 https://doi.org/10.2298/jsc0712201v determination of reducing carbohydrates in natural honey samples by optical micrometry method published by ural federal university eissn 2411-1414; chimicatechnoacta.ru letter 2022, vol. 9(4), no. 20229417 doi: 10.15826/chimtech.2022.9.4.17 1 of 5 determination of reducing carbohydrates in natural honey samples by optical micrometry method ivan s. shchemelev a *, danil s. khasanov a, maria a. smirnova a, alexander v. ivanov a,b, nikolay b. ferapontov a, mikhail g. tokmachev c a: department of chemistry, lomonosov moscow state university, moscow 119991, russia b: kurnakov institute of general and inorganic chemistry of russian academy of science, moscow 119991, russia c: department of physics, lomonosov moscow state university, moscow 119991, russia * corresponding author: shchemelev_93@mail.ru this paper belongs to a regular issue. © 2022, the author. this article is published in open access under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). abstract the present article deals with the determination of the total amount of glucose and fructose in natural honey samples by the optical micrometry (om) method. (poly)vinyl alcohol spherical granules impregnated with a 0.05 mol/l borax solution were chosen as a sensitive element. it was shown that the formation of chelate esters of boron with polymer and carbohydrates is a ph-dependent process, and that the ph range 8.5–10.0 is the most appropriate for quantifying the total amount of reducing carbohydrates because glucose and fructose are undiscriminated. the impregnated polymer is not sensitive to the sucrose presence in the solution due to the absence of cis-diol fragments in it. subsequently, the om method was tested in the analysis of natural honey samples. the relative standart deviation in the case of om method is less than 6%, and the results are similar to those obtained by the iodometric titration method. this makes the om method suitable for laboratory-scale applications. keywords determination of carbohydrates optical micrometry sensitive polymers chelate esters analysis of honey received: 06.10.22 revised: 31.10.22 accepted: 31.10.22 available online: 07.11.22 key findings ● the om method is based on direct measurements of swelling degree of a sensitive polymer. ● an application of (poly)vinylalcohol spherical grains impregnated with borax solution leads to higher selectivity and sensitivity to carbohydrates. ● weak alkaline medium of solution is appropriate for the determination of total amount of glucose and fructose. 1. introduction the determination of carbohydrates in food samples is an important step in their quality control. nowadays, methods used for this purpose, such as redox titration [1–3], irand raman spectroscopy [4–6], uv-vis-spectrometry [7, 8], liquid chromatography [9–11] and capillary electrophoresis [12, 13], are widely applied in laboratories. their main drawbacks include the complicated sample treatment, the high cost of the equipment and the requirement for a highly qualified operator. these problems can be solved by the application of modern chemical sensors or test-systems. sensors for the determination of sugars are often based on enzymatic reactions [14–16]. however, over the last decades, a new class of carbohydrate sensors based on chelation of sugars with boron has been investigated. the nature of analytical signal coming from them is related to a change in the swelling degree of a sensitive polymer. in the works [17–20], the authors used polymers functionalized with phenylboronic acid or its derivatives for the determination of glucose in blood, tears and serum [21, 22]. nevertheless, the difficulty of synthesis of such materials and a high cost of precursors limit their application for the analysis of natural samples. besides, there is only a small number of works dealing with the determination of other sugars that prevents creating a method for the determination of the sugar content in food samples. http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2022.9.4.17 file:///c:/users/student/downloads/shchemelev_93@mail.ru http://creativecommons.org/licenses/by/4.0/ https://orcid.org/0000-0001-9978-1844 https://crossmark.crossref.org/dialog/?doi=https://doi.org/10.15826/chimtech.2022.9.4.17&domain=pdf&date_stamp=2022-11-07 chimica techno acta 2022, vol. 9(4), no. 20229417 letter 2 of 5 the present article is devoted to the application of the optical micrometry (om) method for the analysis of natural honey samples. the om method is based on direct measurements of the swelling degree of a spherical granule made of a sensitive polymer [23]. the device consists of an optical microscope equipped with a camera connected to a personal computer. special software for obtaining and treatment of granule images makes the quantitative analysis both with the equilibrium swelling degree [24, 25] and the kinetic data [26, 27] possible. this method can be an alternative to the fabrication of photonic crystal matrix, because traditional methods of fabrication of photonic crystals are more expensive and difficult to implement. besides, om method can be simply miniaturized and used out of laboratories, whereas the most important limitation of photonic crystal sensors is a strictly fixed angle angle between the sensitive element and the measurement device. nevertheless, the main limitations of the existing methods for the concentration measurements are low sensitivity and non-selectivity. to improve the proposed method, a cross-linked (poly)vinylalcohol that had been well-studied earlier was impregnated by a borax solution. as it is described in [28], functional groups of pva are able to react with the [b(oh)4]− solution forming chelate esters. the presence of glucose molecules in the analyzed solution causes the desorption of boron, and the volume of the polymer gel decreases due to the formation of additional cross-linking fragments. to apply the polymer for the analysis of natural honey samples it is necessary to have information about changing of the swelling degree of the impregnated pva in glucose, fructose and sucrose solutions. 2. experimental 2.1. materials and methods all necessary reagents and solution preparation methods are described in [29]. an experimental appliance for the determination of the carbohydrate concentration from а 48-well plate for biochemical research is equipped with a cover glass and an optical microscope. for obtaining and treatment of granule images, such programs as “webcam screen video capture” and “image treatment”, which is the improved version of “grain size treatment” created by m.g. tokmachev [30] were used. 2.2. a sample treatment 3.000 g of natural honey was put into a beaker and dissolved in a small amount of an appropriate stock solution. the obtained solution was transferred into a volumetric flask and diluted up to 50.0 ml with the stock solution. 2.5 ml of the resulting solution was transferred into a volumetric flask and diluted with the stock solution up to 25.0 ml. 2.3. a general procedure the determination of sugar concentration in analyzed solutions was carried out according to scheme 1. pva granule, held in the stock solution until an equilibrium state had been reached, was put to the measurement cell of the plate. the cell was filled up with the stock solution and covered with a glass to avoid the appearance of air bubbles inside the cell. then, the granule was captured and measured. the initial volume (v0) of it was calculated. after that, the background solution was replaced with the analyzed solution, the granule was kept for about 30 minutes until the equilibrium had been reached, and then the granule volume (veq) was determined. the data obtained were used for the determination of the concentration of carbohydrate according to the calibration plot (veq/v0 = f(c)). 3. results and discussion 3.1. influence of ph on pva swelling it is known that the chelation of elements with ligands-weak acids is a ph-dependent process. this reaction is usually described with conditional constants of chelation that take into account the protonation of a ligand and the hydrolysis of a complexing element. in the present work, the influence of ph of phosphate buffer on the swelling degree change of investigated pva was studied (figure 1). it was shown that the swelling degree of pva in a weakalkaline solution of glucose and fructose decreases at the ph values from 6.5 to 8.5 and keeps constant from 8.5 to 10.0 of ph. it is important to note that in this ph range glucose and fructose are undiscriminated, whereas at the ph value of 6.5 the analytical signals of glucose and fructose are different. it is supposed to be related to a possible mechanism of the reaction between boron and pva. acidic and alkaline solutions are supposed to facilitate the formation of complexes of compositions 1:2 and 1:1, respectively [31]. however, the presence of both glucose and fructose in the solution leads to the desorption of boron due to the ligand exchange. sucrose is supposed not to react with boron due to the absence of cis-diol fragments; thus, the swelling degree of impregnated pva in the sucrose solution does not change in the whole studied ph range. scheme 1 an algorithm of the determination of carbohydrate in solution by om method with equilibrium swelling degree of pva. chimica techno acta 2022, vol. 9(4), no. 20229417 letter 3 of 5 figure 1 dependense of swelling degree of impregnated pva from ph of buffer solution in presence of fructose (1), glucose (2) and sucrose (3): phosphate buffer solution, cborax = 0.05 mol·l –1, csugar = 0.04 mol·l –1. 3.2. analysis of honey samples since glucose and fructose are undiscriminated at ph value from 8.5 to 10.0, it becomes possible to use the impregnated pva for the determination of the total amount of glucose and fructose that are often called «inverted sugar» in natural honey samples. it is also known that the time for getting an equilibrium swelling degree is about 30 minutes [29]. earlier, for the determination of carbohydrates in real samples by the om method, some ion-exchangers in different forms [32] and non-modified pva [33] were suggested as a sensitive matrix. but limits of detection of carbohydrates were very high, and there was no possibility for the determination of sugar using the equilibrium data. for example, the limits of detection for non-modified pva were about 0.2 mol·l–1 for glucose and 0.1 mol·l–1. m for sucrose. impregnation of pva by borax solution led to the decrease of lod of glucose from 0.2 mol·l–1 to 6.9 mmol·l–1 and made it possible to determine the concentration of glucose and fructose in the presence of sucrose. using the calibration plot that was obtained earlier at ph = 8.5, we analyzed some samples of honey by the method proposed. to confirm the accuracy of this method, all the same samples were analyzed by the iodometric titration method according to [34]. the results obtained are presented in the table 1. as seen, the relative standard deviation in the case of om method is less than 6%, and the results of the analysis of honey samples by both methods are similar. therefore, the om method is appropriate for the analysis of natural honey samples and can be used in laboratories. 4. limitations it is known [35] that the equilibrium swelling degree of polymers depends on their degree of cross-linking. to avoid high standard deviation of the analytical signal and ensure good reproducibility of obtained results, all used polymer granules should have the same degree of cross-linking. the existing method of synthesis of cross-linked pva [29] makes it impossible to follow this requirement. one of possible ways to overcome this drawback is working with one granule during the calibration and the analysis of the sample. another possible way for elimination of error is the application of some hydrophilic cross-linking agent instead of epichlorhydrine. the equilibrium swelling degree does not depend on the granule size, but the granule size has an impact on the kinetics of polymer swelling. if the granule diameter is known, it can be used for calculation of the concentration of solution through the application of kinetic constants [27] in simple systems. however, the heterophase model of polymer swelling degree does not take into account the chemisorption of analytes. thus, it can not be used for the description the swelling of pva of impregnated with borax in carbohydrate solutions. the size fractionation of synthesized grains can help to improve the accuracy of analysis with kinetic data and even to create a method for the simultaneous determination of analytes without the pre-separation stage. another way for the improvement of the om method is the modification of the sensitive polymer by magnetite nanoparticles. this approach was tested in the work [36]. the image of a polymer granule coated with fe3o4 has more contrast in comparison with the uncoated granule, and thus its measurement is more precise. besides, such granule can be simply fixed in a measurement cell with a magnet. this opens the possibility for the more accurate description of the initial part of the kinetic curves. 5. conclusions the om method was used for the first time for the analysis of natural samples. the proposed method is inexpensive, fast and simple; it does not require a large number of reagents. it was demonstrated that the modification of pva with borax increases selectivity and sensitivity of swelling granules to reducing sugars such as glucose and fructose. the study of the ph influence showed that weakly alkaline solutions where the ph ranges from 8.5 to 10.0 are the most appropriate for the determination of the total amount of glucose and fructose. subsequently, the om method was tested out in the analysis of natural honey samples, and the results obtained were highly accurate. in the future, it is planned to investigate the behavior of this polymer at ph 6.5 to study the possibility of using the impregnated pva for the separate determination of glucose and fructose by special mathematical algorithms and to find a way to determine sucrose in honey samples by the om method. moreover, this method can be used for the determination of sugar in other food products and even in pet food, and can replace a number of more complex techniques used in laboratories carrying out veterinary and sanitary analyses. this research demonstrated that modification of a sensitive polymer with appropriate functional groups makes the om method appropriate for the analysis of real samples. 3 4 5 6 7 8 9 10 11 0,7 0,8 0,9 1,0 1,1 1,2 v /v 0 , e q ph 1 2 3 chimica techno acta 2022, vol. 9(4), no. 20229417 letter 4 of 5 table 1 results of analysis of honey samples. sample iodometric titrarion, % om, % sr, % a r, % linden honey 71.8 70.5 2.85 98.2 mixed honey 72.9 68.5 5.69 94.0 honeydew honey 69.0 64.5 2.52 93.5 buckwheat honey 59.4 61.5 1.82 103.5 a n = 3 supplementary materials no supplementary materials are available. funding this work was supported in part by the ministry of science and higher education of the russian federation as part of the state assignment of the kurnakov institute of general and inorganic chemistry of the russian academy of sciences and moscow state university. acknowledgments none. author contributions conceptualization: i.s.sh., a.v.i., n.b.f. data curation: a.v.i., n.b.f. formal analysis: i.s.sh., m.a.s., a.v.i., n.b.f. funding acquisition: i.s.sh., a.v.i., n.b.f. investigation: i.s.sh., m.a.s. methodology: i.s.sh., a.v.i., n.b.f. project administration: a.v.i., n.b.f. resources: a.v.i., n.b.f., m.g.t. software: m.g.t. supervision: a.v.i., n.b.f. validation: i.s.sh., m.a.s., d.s.kh. visualization: i.s.sh. writing – original draft: i.s.sh. writing – review & editing: a.v.i., n.b.f. conflict of interest the authors declare no conflict of interest. additional information shchemelev ivan s. – phd student, the analytical chemistry division, chemistry department, moscow state university, moscow. e-mail: shchemelev_93@mail.ru. smirnova maria a. – student, chemistry department, moscow state university, moscow. e-mail: mariasmirnova_2000@mail.ru. scopus id 57220748075. khasanov danil s. – student, chemistry department, moscow state university, moscow. e-mail: danil36393@gmail.com. ivanov alexander v. – dr. sc. (chemistry), associate professor, analytical chemistry division, chemistry department, moscow state university, head of analytical chemistry laboratory at the institute of general and inorganic chemistry of the russian academy of sciences, moscow. e-mail: sandro-i@yandex.ru. scopus id 57208302195. ferapontov nikolay b. – dr. sc. (chemistry), leading researcher, chemistry department, moscow state university, moscow. e-mail: n.ferapontov@gmail.com. scopus id 6602775110. tokmachev mikhail g. – phd. 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doi:10.1134/s0040579521050067 https://doi.org/10.1016/j.jfca.2020.103730 https://doi.org/10.1016/j.microc.2016.05.017 https://doi.org/10.1016/j.talanta.2012.01.034 https://doi.org/10.1016/j.microc.2021.106075 https://doi.org/10.1021/acsami.9b15123 https://doi.org/10.1016/j.talanta.2021.122364 https://doi.org/10.1002/slct.201900840 https://doi.org/10.1021/acsomega.7b02046 https://doi.org/10.1021/acsnano.8b00829 https://doi.org/10.1134/s1061934819010040 https://doi.org/10.1070/qe2010v040n02abeh014169 https://doi.org/10.1109/caol.2010.5634191 https://doi.org/10.1134/s1061934807100048 https://doi.org/10.1134/s1061934819080033 https://doi.org/10.1039/b901017n https://doi.org/10.31857/s0132344x22100061 https://doi.org/10.1134/s1061933x1801012x https://doi.org/10.1007/s10450-010-9300-8 https://doi.org/10.1007/s00289-014-1178-2 http://dx.doi.org/10.1134/s0040579521050067 increase of solubility and transmembrane permeability of niclosamide from its mechanochemically synthesized solid dispersions published by ural federal university eissn2411-1414 chimicatechnoacta.ru article 2023, vol. 10(3), no. 202310307 doi: 10.15826/chimtech.2023.10.3.07 1 of 9 increase of solubility and transmembrane permeability of niclosamide from its mechanochemically synthesized solid dispersions elizaveta s. meteleva a* , elizaveta a. roenko a, nikolay e. polyakov ab a: institute of solid state chemistry and mechanochemistry, siberian branch of russian academy of sciences, novosibirsk 630128, russia b: voevodsky institute of chemical kinetics and combustion, siberian branch of russian academy of sciences, novosibirsk 630090, russia * corresponding author: mete@ngs.ru this paper belongs to the rkfm'23 special issue: https://chem.conf.nstu.ru/. guest editors: prof. n. uvarov and prof. e. aubakirov. abstract more than 4.5 billion people worldwide are affected by parasitic diseases, with helminth infections accounting for 99% of the total number. niclosamide (ns) is a weakly acidic active pharmaceutical ingredient (api) used to treat helminth infections. however, the pharmaceutical use of pure niclosamide is limited by its low bioavailability due to its poor aqueous solubility. the aim of this work is a mechanochemical preparation of niclosamide solid dispersions with increased solubility. due to the ph dependence of ns water solubility and possible complexes formation, ns solid dispersions (sd) with 2-hydroxypropyl-β-cyclodextrin (hp-β-cd) and alkalizing agents, such as calcium carbonate (caco3) and n-methyl-d-glucamine (mg) are mechanochemically prepared in this study. the physical properties of ns sd in solid state are characterized by differential scanning calorimetry, x-ray diffraction, ft-ir spectroscopy, and scanning electron microscopy studies. the characteristics of the water solutions formed from the obtained sds are analyzed by hplc. it is shown that the solubility increases for all studied compositions. these phenomena are obliged by complexation with hp-β-cd, which was shown by 1h-nmr methods, and enhanced ionization in the cases of using calcium carbonate and mg. results of the parallel artificial membrane permeability assay (pampa) have shown that mechanochemically obtained ns/mg sd (1/1 mass ratio, 8 h milling) significantly enhances permeation of ns across an artificial membrane. thus, the obtained compositions are a promising basis for the development of ns-based preparations for oral administration, with reduced dose and high pharmacological effect. keywords niclosamide solubility enhancement solid dispersions mechanochemical synthesis hydroxypropyl-β-cyclodextrin calcium carbonate n-methyl-d-glucamine received: 28.06.23 revised: 25.07.23 accepted: 09.08.23 available online: 14.08.23 key findings ● niclosamide solid dispersions with increased solubility were prepared using mechanochemical solid state method. ● the enhanced niclosamide solubility is caused by inclusion complex formation with hp-β-cd and by increased ionization when using alkalizing agents. ● the obtained niclosamide/n-methyl-d-glucamine solid dispersion (1/1 mass ratio, 8 h milling) has shown enhanced permeation of niclosamide across an artificial membrane. © 2023, the authors. this article is published in open access under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). 1. introduction according to the statistics of the world health organization, about 5 million deaths occur annually in the world as a result of infectious and parasitic diseases. more than 4.5 billion people wordwide are affected by parasitic diseases, with helminth infections accounting for 99% of the total number of such diseases [1]. niclosamide (5-chloro-n-(2-chloro-4-nitrophenyl)-2hydroxybenzamide, ns, figure 1a) is an active pharmaceutihttp://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2023.10.3.07 mailto:mete@ngs.ru http://creativecommons.org/licenses/by/4.0/ https://orcid.org/0000-0002-6255-5381 https://orcid.org/0000-0002-3666-7750 https://crossmark.crossref.org/dialog/?doi=https://doi.org/10.15826/chimtech.2023.10.3.07&domain=pdf&date_stamp=2023-08-14 chimica techno acta 2023, vol. 10(3), no. 202310307 article 2 of 9 doi: 10.15826/chimtech.2023.10.3.07 cal ingredient (api) used to treat helminth infections [2]. various formulations containing ns have been shown to be highly effective against sheep and mice cestode infections [3, 4], moniezia benedeni [5], and anoplocephalidae [6]. ns has shown preclinical efficacy in the treatment of cancer [7], bacterial infections, type ii diabetes, nafld and nash, endometriosis, systemic sclerosis, rheumatoid arthritis and various viral infections [8]. ns can be potentially used to treat covid-19 [9]. the side effects of ns have been shown to be infrequent, mild and temporary [10]. however, the pharmaceutical use of pure niclosamide is limited by its low bioavailability [11] due to its poor aqueous solubility (5–8 mg/l, 20 °c) [12]. since ns is characterized by low solubility and good permeability, it is classified as a class ii drug in the bcs system [13]. many different approaches have been proposed to improve the solubility of niclosamide. an incomplete list includes: wet grinding to reduce the size of ns crystalline particles to nanoscale [14], emulsification of ns in an oilwater system with a number of copolymers [15], cocrystallization [16], ns nanosuspensions and incorporation of ns into dendrimer-like biopolymers [17], solid lipid nanoparticles production using stearic acid, polysorbate80 and polyethylene glycol [18], complexation with ophosphorylated calixarene or cyclodextrin [19]. unfortunately, these processes are often associated with high solvent consumption, partial api decomposition, and are quite complicated. thus, many aspects of niclosamide formulation dosage need to be further improved. in contrast to the traditional liquid-phase preparation methods of apis for dosage formulations, rather simple operations and equipment are used in mechanochemical approach. the preparation time is significantly reduced, and no solvent is required [20]. as a result of mechanochemical processing, sds can be formed. this process is accompanied by a partial or complete transition to an amorphous state with an increase in the entropy of the system, which contributes to the acceleration of the dissolution process. in addition, mechanical activation allows the combination of substances, regardless of their solubility and, to avoid undesirable side chemical reactions, the reduction of the contribution of rapid aggregation of drug molecules during dissolution [21]. more stable intermolecular complexes can be obtained by mechanical processing, which is indicated by an increase in solubility in comparison with the unprocessed mixtures. therefore, the application of mechanochemical processing to niclosamide in order to increase its solubility and bioavailability is of considerable interest. mechanochemical preparation has already been used to obtain ns dosage formulations. polyvinylpyrrolidone (pvp) [3, 22], sodium salt of glycyrrhizic acid na2ga [4], arabinogalactan (ag), and sio2 [5, 6] were used as excipients. as a result, the solubility of ns/pvp sds was increased from 10 to 25 times compared to pure ns. the anthelminthic activity of all sds mentioned above was shown to be improved. unfortunately, no data have been published on ns the solubility from compositions with na2ga, ag and sio2. therefore, it is not known to what extent these excipients affected the solubility of niclosamide. another possible excipient is mg (figure 1b), an alkalizing agent which is able to form supramolecular adducts with lipophilic organic compounds in water, thereby increasing their solubility [23]. in the case of niclosamide mg could play the role of an alkalizing agent and, potentially, a complexing agent. mechanochemical processing with alkalizing agents is suggested due to the fact that the ns water solubility has been shown to be ph dependent [24], and can be enhanced by 1–2 orders of magnitude by increasing the ph of the solution up to ph = 9. this phenomenon reflects the fact that ns is a weakly acidic api (pka = 7.45 [12]) and is capable of ionization in water solution. this approach has already been used for another apis: valsartan (val) [25] and nimesulide (nim) [26]. val has been mechanically processed with caco3 and mg (5/1 mass ratio). nim has been treated with mgco3 (5/1 mass ratio). the obtained sds showed an increased solubility of about 10 times (val sds) and about 100 times (nim sd) compared to the pure apis. hp-β-cd (figure 1d) is known to form water-soluble complexes due to host-guest interactions. various lipophilic organic apis can enter its cylindrical hydrophobic cavity (figure 1d) [27]. figure 1 structure and ionization scheme of the niclosamide molecule (a), structure of the n-methyl-d-glucamine molecule (b), structure of the hp-β-cd molecule (c, d). https://doi.org/10.15826/chimtech.2023.10.3.07 chimica techno acta 2023, vol. 10(3), no. 202310307 article 3 of 9 doi: 10.15826/chimtech.2023.10.3.07 in addition, hp-β-cd has been shown to be more effective than other β-cyclodextrins in increasing the apis stability, solubility, bioavailability, permeability and duration of action, as well as reducing irritation and toxicity, [28]. its complexes with ns, obtained by freeze-drying [29] and powder extrusion [30] methods have been described previously and shown to have increased solubility. unfortunately, these preparation methods are time consuming, require many preparation steps or expensive equipment. therefore, simpler and less expensive solid-state mechanochemical method might be introduced. this technology has been used earlier [26] to obtain nim sds with a variety of complexing agents, such as hpβ-cd, plant water-soluble polysaccharide arabinogalactan, disodium salt of glycyrrhizic acid (na2ga). all sds were shown to enhance the nim solubility due to complexes formation in water solutions, which was confirmed by 1hnmr methods. the aim of the present study is to increase the aqueous solubility of niclosamide, its membrane permeability and thus to improve its bioavailability. with the ns acidity and possible complex formation taken into consideration, ns sd with an alkali–pharmacopeia grade caco3, mg and hpβ-cd have been obtained by mechanochemical processing. 2. materials and methods 2.1. materials niclosamide (shandong chenxing new material co. ltd., china) of pharmaceutical grade was used without further purification. n-methyl-d-glucamine (mg, purity of mg ~99.5%) was purchased from aladdin industrial co. ltd., shanghai, china. calcium carbonate (caco3, pс-000658, 2013-07-30) was purchased from shanghai nuochen pharmaceutical co. ltd., china. hydroxypropyl-βcyclodextrin (hp-β-cd，purity of hp-β-cd ~98.0%, substitution degree of hp-β-cd – 5.4, content of β-cd ~0.17%) was purchased from zhiyuan bio-technology co. ltd., binzhou, china. 2.2. preparation of mechanochemically treated niclosamide solid dispersions mechanical treatment of ns compositions with caco3, mg and hp-β-cd was carried out in a vm-1 roll mill with a cylindrical vessel which was coated with teflon and possessed 300 ml volume. acceleration of grinding bodies is 1 g (free fall). rotational speed of cylindrical vessel is 156 rpm. steel balls (diameter 22 mm, 675 g load) were used as grinding bodies. the total load of the treated powders mixture was 18 and 20 g. the duration of mechanical processing was from 2 to 16 h – (2, 4, 8, and 16 h). mass ratios of 5/1 and 1/1 were used to prepare ns/mg and ns/caco3 sds to provide the desired ph range (up to ph = 10). molar ratio of 1/1 was used to prepare ns/hp-βcd sd considering the fact of possible complex formation. physical mixtures of the same compositions were prepared by shaking (for about 10 min) the previously noted powdered compounds in closed test tube. 2.3. hplc analyses an agilent 1200 hplc system (agilent technologies, palo alto, ca, usa) was used to determine the concentration of ns. the hplc system was equipped with a reverse phase column (5 µm, 4.6 × 50 mm, zorbax eclipse xdb c18) at 30 °c and diode-array detector. the mobile phase consisted of a 2/3 (v/v) mixture of acetonitrile and acetate buffer (ph = 3.4), the flow rate was 0.8 ml/min, the detection wavelength – 336.8 nm, and the injection volume – 5 µl. 2.4. content test for niclosamide solid dispersions to determine the content of ns in compositions, the weighted samples (10 mg) were dissolved in 50 ml of a mixture solution (ch3cn/c2h5oh/ch2cl2, 10:9:1, v/v/v). in all cases, all components of complexes were completely dissolved.the samples were then suitably diluted and assayed by hplc. 2.5. determination of solubility of niclosamide and its solid dispersions the mechanically treated products, which were picked up from different milling time, were separately added into a 25 ml flat-bottomed flask with 5 ml of distilled water. then they were shaken in the orbital shaker for 24 h with 200 rpm at +37 °c. at last, sample solutions were centrifuged at 12,000 rpm for 10 minutes, filtered using a paper filter (pore diameter of 2–3 µm) and determined by hplc method. 2.6. fourier transform infrared spectrophotometry fourier transform infrared spectrophotometry (ft-ir) spectra of samples were collected from 500 to 4000 cm−1 using fourier spectrophotometer “infralum ft-801” (“simeks”, novosibirsk, russia). all samples were taken in thin tablets with kbr. 2.7. powder x-ray diffraction powder x-ray diffraction analysis of niclosamide and its solid dispersions was carried out on a dron-4 equipment (‘‘byrevestnik’’, st. petersburg, russia) using cu kα radiation, counter speed 2 deg/min, range of intensity measurement ~1000, angle range – from 4° to 65°. 2.8. differential scanning calorimetry thermal analysis of niclosamide and its solid dispersions was carried out by differential scanning calorimetry (dsc) with the dsc-550 instrument (instrument scientific specialists inc., omaha, ne) in ar atmosphere. temperature program: 20–250 °c, the heating rate 10 °c deg/min. 2.9. scanning electron microscopy (sem) electronic images were acquired using a tm-1000 microscope (hitachi, tokyo, japan). coating of samples with https://doi.org/10.15826/chimtech.2023.10.3.07 chimica techno acta 2023, vol. 10(3), no. 202310307 article 4 of 9 doi: 10.15826/chimtech.2023.10.3.07 gold was performed using a jfc-1600 auto fine coater (jeol, tokyo, japan). the coating parameters were as follows: sputtering time 30 s, amperage 30 ma, and film thickness 15 nm. 2.10. 1h-nmr spectra in solution 1h-nmr spectra were recorded on an avance iii 500 mhz spectrometer (bruker, rheinstetten, germany) in d2o (99.8%, aldrich, moscow, russia) solutions. measurement of the spin–spin relaxation time t2 was carried out using the standard carr– purcell–meiboom–gill (cpmg) sequence: p1(90°) – (s – p2(180°) – s) n – registration, where s = 0.5 ms-fixed time delay, and varied from 0 to 2000 ms. selective noesy (selective nuclear overhauser effect correlation spectroscopy) spectra were recorded using a special pulse sequence from the bruker library. measurements were carried out at ph 7.0 and 10.0. 2.11. in vitro parallel artificial membrane permeability assay (pampa) pampa experiments were carried out in 12-well filter plates (polycarbonate membrane, 12 mm diameter inserts, 0.4 µm pore size, 1.12 cm2 area, corning inc., corning, ny, usa). the ability of compounds to diffuse from a donor compartment into an acceptor compartment is evaluated. the artificial membrane was first impregnated by pipetting 60 µl of the 5% (v/v) hexadecane in hexane solution to each of the donor plate wells. the wells were then placed into a fume hood for 1 h to ensure complete evaporation of the hexane. after the hexane had evaporated, 1.5 ml of water was added to each of the wells of the acceptor plate. the hexadecane treated donor plate was then placed on top of the 12-well acceptor plate. then, 0.5 ml of ns or its compositions in water was added to each well of the donor plate, and the resulting pampa device was incubated at 37° and shaken for 3 h with 200 rpm. samples (1 ml) were collected from the acceptor plate at appropriate time points (0.5, 1.0, 1.5, 2.0, 2.5 and 3.0 h) and were analyzed with hplc method. the acceptor compartment was refilled with the same volume of distilled water. 3. results and discussion 3.1. content test the drug contents of ns sds with caco3, (1/1 mass ratio) mg (1/1 mass ratio), mg (5/1 mass ratio) and hp-β-cd (1/1 molar ratio) were determined to be 100.0%, 100.0%, 96.7% and 100.0%, respectively. it suggests the preparation of ns sds by mechanochemichal processing was with high content uniformity. 3.2. physical characterization studies of ns sds 3.2.1. analysis on dsc thermograms the dsc thermograms of free ns, physical mixtures (pms), and ns sds are shown in figure 2a, 2b. significant changes are observed after processing the mixtures ns/mg (1/1 mass ratio) and ns/hp-β-cd (1/1 molar ratio) in the vm-1 mill. the dsc curve of the ns/hp-β-cd pm (1/1 molar ratio) contains an ns endothermic peak (ep, 231 °c, 107.8 j/g) corresponding to the ns intrinsic melting points which is significantly lower in intensity (by 49%) compared to the original substance (235 °c, 212.6 j/g), and disappears completely after the mixture is mechanically processed. the same ns endothermic peak is absent in the dsc curve of the ns/mg pm (1/1). a decrease (by 9%) of mgendothermic peak in the pm (126°, 272.7 j/g) in comparison with the original substance (131°, 302.1 j/g) and in thedsc curve of themechanochemically treated mixture (by 52%, 105°, 144.2 j/g) is observed. another change is the mg melting point shift in comparison with the original mg substance. the disappearance of ns ep indicated the existence of intermolecular interaction or the formation of a new solid phase after the treatment of mechanochemical activation. 3.2.2. analysis on powder x-ray diffraction in this experiment, the powder x-ray pattern of ns in the formation of free molecule and compositions were investigated. powder x-ray diffraction data of some obtained compositions are displayed in figure 3. the intensity of ns diffraction peaks decreased significantly in mechanically treated compositions. the decrease of the ns characteristic peaks demonstrated that the main crystalline particles of ns were destroyed by the mechanical activation treatment . it means that the mechanically treated compositions are in amorphous form, which is in accordance with the results of dsc. 3.2.3. scanning electron microscopy analysis the electron micrographs of the obtained sds are shown in figure 4. figure 2 dsc thermograms of ns (a, 1), mg (a, 2), ns/mg (1/1 mass relation) physical mixture (a, 3) and solid dispersion of ns/mg (1/1 mass ratio) treated in, in roll mill for 8 h (a, 4); ns (b, 1); hp-β-cd (b, 2), ns/hp-β-cd (1/1 molar ratio), physical mixture (b, 3) and solid dispersion of ns/hp-β-cd (1/1 molar ratio) treated in roll mill for 8 h (b, 4). https://doi.org/10.15826/chimtech.2023.10.3.07 chimica techno acta 2023, vol. 10(3), no. 202310307 article 5 of 9 doi: 10.15826/chimtech.2023.10.3.07 figure 3 x-ray diffractograms of ns (a, 1); mg (a, 2) and solid dispersion of ns/mg (1/1 mass relation) treated in roll mill for 8 h (a, 3); ns (b, 1); hp-β-cd (b, 2) and solid dispersion of ns/hp-β-cd (1/1 molar relation) treated in roll mill for 8 h (b, 3). figure 4 electron micrographs of ns/mg (1/1 mass relation) solid dispersion, treated in roll mill for 8 h (a); ns/hp-β-cd (1/1 molar relation) solid dispersion, treated in roll mill for 8 h (b). the initial substances are seen to have characteristic crystalline and intact shape. however, during the mechanochemical milling process, the destruction of the particles occurred followed by the formation of polydisperse particles with irregular shape. the average particle size of the obtained sds was about 0.6–1 μm. 3.2.4. analysis on ft-ir spectroscopy ft-ir spectroscopy was used to investigate possible chemical reactions. the pure ns characteristic peaks did not take any shifts, indicating ns was still in a free acid form after the mechanical treatment. moreover, the spectra of the milled complexes were found to be a simple overlap of their initial components, demonstrating no chemical reaction took place between ns and the auxiliary components during the milling process. 3.3. characteristics of ns sds in solutions 3.3.1. solubility test the solubility data of pure ns, its pms and mechanically treated compositions are shown in table 1. by comparison with the pure api, the solubility of ns was improved to different extents in the formation of pms and sds. for ns/caco3 with mass ratio 1/1 (4 h milling) mechanically treated composition, the maximum solubility is 13.8 mg/l, which is larger than that of pm with the same components. for the ns/mg mechanically treated composition, the largest solubilities are 397.0 mg/l with mass ratio 1/1 (8 h milling) and 145.2 mg/l with mass ratio 5/1 (8 h milling), both of which are larger than those of the same pm components. for ns/hp-β-cd mechanically treated composition, the maximum solubility of complex is 78.1mg/l (molar ratio 1/1, 8 h milling), which is larger than same components physical mixture. from the above results, the solubility of ns was sufficiently improved for all of the compositions, but the most significant results were obtained for ns/hp-β-cd and ns/mg mechanically treated compositions. the observed solubility values for the ns compositions with caco3 and mg are in line with the curve of the solubility of ns vs ph presented in [24]. for ns/hp-β-cd the mechanism of improved solubility refers to the formation of inclusion complex. 3.3.2. 1h-nmr study of ns/mg and ns/hp-β-cd complexes in solution in the present study, selective noesy experiment and nmr relaxation method were applied to prove the intermolecular interactions and confirm ns complexes formation [31]. the spin–spin t2 relaxation time is known to be very sensitive to the intermolecular interaction and diffusion mobility of molecules [32, 33]. when the ‘‘guest’’ molecule moves into a ‘‘host’’ molecule and bounds in complexation, its diffusion and rotational mobility reduce and the proton relaxation times decrease significantly. the relaxation times (t2) of ns protons were measured in the aqueous solution for free ns as well as for its mechanically processed sd, namely ns/mg (1/1 mass ratio, 8 h milling) and ns/hp-β-cd (1/1 molar ratio, 8 h milling). the nmr spectrum of the ns/mg aqueous solution at ph = 7.0 contains only mg signals. the precipitate was analyzed at ph = 10 and its spectrum contains only ns signals. this suggests that when the dry ns/mg dispersion is dissolved at ph = 7.0, the rate of ns self-association is much higher than the rate of complexation. preparation of a 1% aqueous ns/mg solution at ph 10.0 allowed recording a spectrum containing both ns and mg protons. under these experimental conditions, noesy spectra show the presence of cross-peaks between ns and mg protons (figure 5). the observed cross-peaks with mg protons (2– 4 ppm) indicate the presence of the ns/mg complex at ph = 10. however, no difference in chemical shifts is observed for this complex compared to pure ns solution. additional evidence for the formation of the ns/mg complex in aqueous solution at ph = 10 was obtained by nmr relaxation for 1% and 0.1% solutions. the ns protons relaxation times at 8.65, 8.4, and 7.8 ppm are summarized in table 2. for comparison, the table also shows the proton relaxation times of pure ns and its complex with hp-β-cd (1% solution). https://doi.org/10.15826/chimtech.2023.10.3.07 chimica techno acta 2023, vol. 10(3), no. 202310307 article 6 of 9 doi: 10.15826/chimtech.2023.10.3.07 table 1 solubility of ns and its mechanical treated products in water (+37 °c). no. samples, mass or molar ratios mechanical processing duration, h solubility, mg/l increase insolubility, times ph 1 ns without processing 0.29 – 4.01 2 ns/caco3 (1/1 mass ratio) without processing 9.9 34 8.0 3 ns/caco3 (1/1 mass ratio) 4 13.8 48 4 ns/mg (1/1 mass ratio) without processing 253.7 875 9.9 5 ns/mg (1/1 mass ratio) 8 397.0 1369 6 ns/mg (5/1 mass ratio) without processing 46.7 161 9.2 7 ns/mg (5/1 mass ratio) 8 145.2 501 8 ns/hp-β-cd (1/1 molar ratio) without processing 8.4 29 7.2 9 ns/hp-β-cd (1/1 molar ratio) 8 78.1 269 table 2 relaxation times т2 (ms) for ns protons (8.65, 8.4 и 7.8 ppm) for pure ns, ns/mg (1/1 mass ratio) and ns/hp-β-cd (1/1 molar ratio) compositions. the error in the calculation of t2 does not exceed 5%. chem. shift, ppm relaxation times т2, ms ns ns/mg, 0.1% ns/mg, 1% ns/hp-β-cd, 1% 8.65 1900 1100 60 140 8.4 4900 3450 190 190 7.8 4000 2160 145 70 the significant decrease in the t2 relaxation time in the presence of mg is direct evidence for the formation of the complex. this confirms the conclusions drawn from the noesy experiments. however, the absence of changes in the chemical shifts of the ns protons in the presence of mg, as well as a significant increase in the relaxation times when the solution is diluted to 0.1% indicates the low stability of this complex. excitation of all ns aromatic protons (8–9 ppm) was performed to record the selective noesy spectrum for ns/hp-bcd complex (1/1) (figure 6); the cross peaks at 1.1 ppm correspond to methyl protons of hp-β-cd and the cross peaks at 3.8 ppm correspond to intrinsic protons of hp-β-cd. this indicates the formation of the inclusion complex and the localization of ns near the narrow end of hp-β-cd (figure 1c). when the ph of this solution was increased to 10.0 by adding koh, the solution turned yellow, indicating the formation of the deprotonated form of ns. at the same time, intense ns nmr signals appeared in the nmr spectrum (figure 7). selective noesy spectra of ns/hp-β-cd aqueous solution recorded at ph = 7.0 also show the presence of cross-peaks between ns and cd protons. considering that only the cross-peaks of closely spaced protons (less than 5 angstroms) are observed in the noesy experiments, the cross-peaks mentioned above indicate existence of a complex with hp-β-cd. figure 8 shows the nmr relaxation experiment for ns/hp-β-cd complex (molar ratio 1/1), as well as for the free form of ns. these results showed a decrease in the relaxation time of ns protons in the presence of hp-β-cd. this is an independent direct evidence of the intermolecular complex formation in this system. simultaneously, some ns protons showed a significant change of chemical shifts relatively to the free molecule in the 1h-nmr spectrum. figure 5 1h nmr spectra (middle) and selective noesy (bottom) of a 1% aqueous ns/mg solution recorded at 303 k and ph = 10.0. selective excitation of all ns signal was performed. the spectrum of pure ns is shown above for comparison. figure 6 1h nmr (top) and selective noesy (bottom) spectra of ns/hp-β-cd aqueous solution recorded at 303 k and ph = 7.0. figure 7 1h nmr spectra (middle) and selective noesy (bottom) of a 1% aqueous solution of ns/hp-β-cd registered at 303 k and ph = 10.0. selective excitation of all ns signal was performed. the pure ns spectrum is shown at the top for comparison. https://doi.org/10.15826/chimtech.2023.10.3.07 chimica techno acta 2023, vol. 10(3), no. 202310307 article 7 of 9 doi: 10.15826/chimtech.2023.10.3.07 3.4. in vitro permeation study a pampa assay enabled rapid determination of the trends in the ability of the compounds to permeate the membrane by passive diffusion [34–36]. in the plots (figure 9), it can be seen that the amount of ns from mechanochemically treated ns/mg composition permeated is higher than from the pure ns, indicating that the co-grinding compositions have enhanced mass transport of ns across an artificial membrane compared to that of the pure drug. the low ns permeation throw artificial membrane of sd with hp-β-cd seen surprising, considering the facts that it had a high solubility, as well as the known hp-β-cd ability to enhance the drug transport through membrane. the possible explanation is that in this case an increase in solubility is achieved by a strong complexation with hp-βcd, which prevents thens release into the free molecule form in solution, whereas the ns/hp-β-cd complex cannot be accepted by the hydrophobic membrane. figure 8 kinetics of the echo signal decay of ns protons (on a logarithmic scale, protons at 7.7 and 8.3 ppm) for pure ns and its hp-β-cd complex measured for 1% water solution at 30 °c and ph = 10.0. figure 9 permeation profile of niclosamide (a) and compositions: ns/mg (1/1 mass ratio) treated in roll mill for 8 h (b), ns/hp-βcd (1/1 molar ratio) treated in roll mill for 8 h (c). 4. limitations a limitation of the mechanochemical method is the difficulty in adapting the process to industrial scale. depending on the required capacity, the parameters of the equipment used and the mechanochemical treatment process itself must be determined. 5. conclusions in this study, we investigated the possibility of improving the solubility of ns by preparing solid dispersions with caco3, n-methyl-d-glucamine, and hp-β-cd using mechanochemical technology. the physical properties of ns sd in the solid state were characterized by differential scanning calorimetry, x-ray diffraction, ft-ir spectroscopy and sem studies. the properties of the water solutions formed from the obtained solid dispersions were analyzed by hplc for intrinsic solubility and 1h-nmr spectroscopy. an increase in solubility was observed for all compositions studied. in the case of the ns/hp-β-cd composition, this phenomenon is caused by the formation of inclusion complexes, which was confirmed by 1h-nmr relaxation and selective noesy methods. in the cases of caco3 and n-methyl-d-glucamine ionization was proposed. although, the formation of the ns and n-methyl-d-glucamine complex was also confirmed by 1h nmr spectroscopy, this complex did not appear to be stable enough to significantly affect the ns solubility. on the contrary, the solubility of niclosamide from the ns/mg sd is consistent with the previously mentioned ns solubility ph dependence. the pampa assay was used to predict passive intestinal absorption. it was found that the mechanochemically obtained sd with n-methyl-d-glucamine (1/1 mass ratio, 8 h milling) shows enhanced permeation of ns across an artificial membrane compared to that of the pure ns and ns/hp-β-cd sd. we suggest that a strong ns complexation with hp-β-cd prevents the ns release into the free form in solution, whereas the ns/hp-β-cd complex cannot be accepted by the hydrophobic membrane. therefore, the compositions of ns with caco3, nmethyl-d-glucamine, and hp-β-cd obtained by using the mechanochemical manufacturing method are a promising basis for the development of ns-based preparations for oral administration, with reduced dose and high pharmacological effect. ● supplementary materials no supplementary materials are available. ● funding this research was carried out within the state assignment to institute of solid state chemistry and mechanochemistry sb ras (project 0237-2021-0008), russian statefunded project (aaaa-a21-121011490015-1, project 0238https://doi.org/10.15826/chimtech.2023.10.3.07 chimica techno acta 2023, vol. 10(3), no. 202310307 article 8 of 9 doi: 10.15826/chimtech.2023.10.3.07 2021-0001), was supported by the ministry of science and higher education of the russian federation. p.n.e. (voevodsky institute of chemical kinetics and combustion) acknowledge the core funding from the russian federal ministry of science and higher education (fwgf-2021-0003). ● acknowledgments none. ● author contributions conceptualization: m.e.s., p.n.e., r.e.a. data curation: m.e.s., p.n.e., r.e.a. formal analysis: m.e.s., p.n.e., r.e.a. funding acquisition: m.e.s., p.n.e. investigation: m.e.s., p.n.e., r.e.a. methodology: m.e.s., p.n.e., r.e.a. project administration: m.e.s. resources: m.e.s., p.n.e. software: m.e.s., p.n.e. supervision: m.e.s., p.n.e. validation: m.e.s., p.n.e. visualization: p.n.e., r.e.a. writing – original draft: r.e.a., p.n.e. writing – review & editing: m.e.s. ● conflict of interest the authors declare no conflict of interest. ● additional information author ids: elizaveta s. meteleva, scopus id 26321175000; nikolay e. polyakov, scopus id 35511398800. websites: institute of solid state chemistry and mechanochemistry, http://www.solid.nsc.ru/; voevodsky institute 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https://doi.org/10.1002/jps.20075 https://doi.org/10.1021/jm970530e application of the similarity theory to analysis of photocatalytic hydrogen production and photocurrent generation published by ural federal university eissn 2411-1414 chimicatechnoacta.ru review 2023, vol. 10(2), no. 202310203 doi: 10.15826/chimtech.2023.10.2.03 1 of 21 application of the similarity theory to analysis of photocatalytic hydrogen production and photocurrent generation dina v. markovskaya * , ekaterina a. kozlova department of heterogeneous catalysis, boreskov institute of catalysis, novosibirsk 630090, russia * corresponding author: madiva@catalysis.ru this paper belongs to a regular issue. abstract in this research some methods of the similarity theory were quantitatively applied to the description of the relationship between the efficiencies of the photocatalytic hydrogen production and photocurrent generation for the first time. two possible similarity criteria, namely, such as the ratio of the number of electrons involved in the photocatalytic reaction to the generation of photocurrent ones and the ratio of energies transformed in the case of photocatalytic hydrogen evolution to the photocurrent, were obtained by the dimensional analysis. the literature data allow checking the first criterion. the application of the first possible similarity criterion to the samples with different chemical nature, solid solutions, series, in which the synthesis time or the ratio of catalyst components, electrolyte amount or its nature is changed, was analyzed. it was shown that the ratio of electrons may serve as the similarity criterion only under the conditions of geometric and physical similarities. keywords photocatalysis hydrogen evolution photocurrent generation theory of similarity similarity criterion dimension theory received: 13.02.23 revised: 20.03.23 accepted: 26.03.23 available online: 04.04.23 key findings ● photocatalytic hydrogen production and photocurrent generation are the analogous phenomena. ● two possible similarity criteria were proposed. ● ratio of the electron numbers acts as a similarity criterion if the conditions of geometric and physical similarity are fulfilled. © 2023, the authors. this article is published in open access under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). 1. introduction nowadays different processes and phenomena whose realization allows generating energy are of particular importance. the traditional method of burning fuel resources has a significant disadvantage associated with the limited reserves of the corresponding resources. accordingly, the search for alternative fuels is known to be an urgent task of modern science [1]. since the 70s, the idea of using hydrogen as a fuel has gained particular popularity among researchers [1, 2]. hydrogen is known to be one of the most common elements on earth and can be obtained from various compounds. when hydrogen is burned, eco-friendly water is formed, and the large amount of heat is realized. however, in this case the question arises about new methods of hydrogen synthesis, because the main methods either use non-renewable energy sources or are quite energy intensive [1]. one of the promising alternative ways to produce hydrogen is the photocatalytic method, implemented in the presence of photocatalysts based on semiconductors. an important feature of this method is the use of sunlight. thus, in fact, we are talking about the conversion of light energy into the energy of chemical bonds occurring on the semiconductor surface [3]. it should be noted that the energy from light can be generated in the photoelectrochemical cells. these processes are often carried out on electrodes made of semiconductors. it is noteworthy that in the case of photocatalytic hydrogen production and photocurrent generation, the same physicochemical processes such as the formation of exciton, the formation of an electron-hole pair, the spatial separation of charge carriers during their migration to the boundaries of the phase interface, interphase transfer to the components of the reaction medium occur on the semiconductor surface http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2023.10.2.03 mailto:madiva@catalysis.ru http://creativecommons.org/licenses/by/4.0/ http://orcid.org/0000-0001-5915-3851 http://orcid.org/0000-0001-8944-7666 https://crossmark.crossref.org/dialog/?doi=https://doi.org/10.15826/chimtech.2023.10.2.03&domain=pdf&date_stamp=2023-04-04 chimica techno acta 2023, vol. 10(2), no. 202310203 review 2 of 21 doi: 10.15826/chimtech.2023.10.2.03 [4–7]. the main difference lies only in the fact that in the case of photoelectrochemical cells, besides participating in various transformations, electrons are transferred to counter electrodes, and for photocatalytic hydrogen evolution, the reaction occurs directly on the surface of semiconductor particles [7]. the similarity of the principles of functioning of these two phenomena can be useful in the development of various strategies for improving the target characteristics of materials. it should be noted that the development of scientific branches related to photoelectrochemical cells and photocatalytic processes takes place in parallel. however, the scientific results of each of these fields may be useful in another one. for example, some materials such as metal phosphides were originally used for the electrocatalytic hydrogen evolution. however, these compounds are active co-catalysts for photocatalytic hydrogen production [8]. titania may be successfully used both as the material for the photoelectrochemical cell and as the photocatalyst [9]. to take into account the achievements in different branches, it is necessary to have a tool that allows comparing some characteristics of the two phenomena. as such a tool, similarity theory can be used, which makes the transition between quantitative characteristics of phenomena of the same nature. the methods of similarity theory are successfully used to describe physical processes in the field of engineering and mechanical engineering. in hydrodynamics, the phenomena of thermal conductivity, diffusion and electrical conductivity in liquids are studied using the similarity theory [10]. the aim of this paper is to determine the possibility of using similarity theory methods to describe the phenomena of photocatalytic hydrogen evolution and photocurrent generation. with the help of the dimension theory, potential similarity criteria were obtained in this work, after which they were used to analyze the literature data. 2. search of parameters which may be used as similarity criteria in the study of physical phenomena, a system of concepts and a system of units are introduced. the system of concepts includes the quantities characterizing various aspects of the studied processes, while the system of units determines the numerical values of the introduced characteristics. there are a number of correlations between these characteristics. any physical relationship between different quantities can be formulated as a relationship between dimensionless quantities. this postulate underlies the theory of dimension [11]. with the help of dimension theory, the parameters that may serve as similarity criteria can be identified. within the framework of this approach, at the first stage it is necessary to identify the defining system of parameters. at the second stage, linearly independent dimensionless combinations, which are potential similarity criteria, are formed from this system of parameters by analyzing dimensions [11]. at the third stage, the obtained parameters are verified by the experimental data. let us apply the theory of dimension to the discussed processes. in the case of photocatalysis, it is necessary to describe quantitatively the reaction system (concentration and nature of reagents, volume of the reaction mixture, concentration of the catalyst or its mass), the light source and the photocatalytic activity of the catalyst. in the case of generating a photocurrent, we will take into account the characteristics of the light source and the photoelectrochemical cell. the irradiation source can be characterized by a set of independent quantities that determine the number of incident light quanta and their energy: the irradiation power and wavelength, the number of incident photons and the wavelength of radiation, the number of incident photons and the energy of one photon, etc. the parameters describing the target properties of the photocatalyst and the photoelectrochemical cell are of the greatest interest. 2.1. parameters characterizing the photocatalytic activity the photocatalytic activity describes to what extent the studied system is a photocatalyst. in the literature several parameters describing the catalyst productivity are mentioned, including the catalytic activity [12–21], the turnover number [20–22], the quantum yield [12, 19–21], the quantum efficiency [12, 19–21], the sth (solar-to-hydrogen) [14, 22]. the ways of their calculation were summarized in table 1. the catalytic activity, just as in the traditional catalysis, is defined as the rate of the photocatalytic process (w) divided by the catalyst mass (m) [20, 23]. the catalytic activity is often measured in μmol·h–1·g–1. the catalytic properties of the samples can be characterized by the turnover number (ton). table 1 quantities characterizing the photocatalytic activity of samples. quantity symbol formula catalytic activity ca ca = 𝑊/𝑚 (1) turnover number ton ton = 𝑊 𝑁active sites or ton = 𝑊 𝑆catalyst surface (2) quantum yield φ, φ φ = 𝑁disappearing molecules 𝑁absorbed photons · 100% (3) quantum efficiency aqe, qe, pe aqe = 𝑁disappearing molecules ∙ 100% 𝑁incident photons = 𝑊 ∙ ℎ ∙ 𝑐 ∙ 𝑁𝐴 ∙ 100% 𝑃irradiation ∙ 𝑆irradiation ∙ 𝜆 (4) solar-tohydrogen sth 𝑆𝑇𝐻 = ∆𝐺° ∙ 𝑊 ∙ 100% 𝑃irradiation ∙ 𝑆irradiation = = 𝐴𝑄𝐸 ∙ 𝜆 ∙ ∆𝐺° ℎ ∙ 𝑐 ∙ 𝑁𝐴 (5) https://doi.org/10.15826/chimtech.2023.10.2.03 https://doi.org/10.15826/chimtech.2023.10.2.03 chimica techno acta 2023, vol. 10(2), no. 202310203 review 3 of 21 doi: 10.15826/chimtech.2023.10.2.03 the ton is the ratio of the number of photoinduced transformations for a given period of time to the number of active sites (nactive sites) [21]. however, in heterogeneous catalysis it is difficult to determine the number of active sites; it is often unknown. therefore, for certainty, when calculating ton, normalization is carried out on the surface area of the catalyst (scatalyst surface). since the photocatalytic activity of the samples is directly related to the lighting conditions (type and power of illumination, wavelength), the quantum yield is used to evaluate the photocatalyst productivity and their comparison with each other [12, 19–21]. the quantum yield is a number of defined events, occurring per photon absorbed by the system at a specified wavelength [20, 21]. in heterogeneous photocatalysis, determining the number of absorbed photons is quite difficult: photocatalyst particles reflect and scatter light, and the contribution of this effect is difficult to measure. in practice, apparent quantum efficiency is commonly used; it is normalized per photon incident in the system instead of a photon absorbed by the system. table 1 shows the formulas for the quantum yield and quantum efficiency calculation when monochromatic light is used. the photocatalytic reaction is often considered as transformation of the energy of the incident light to the energy of the chemical bonds. from this point of view, the photocatalyst producibility may be estimated using solarto-hydrogen (sth). during the reaction, ∆𝐺° ∙ 𝑊 j transforms to the chemical energy per unit of time, while 𝑃irradiation ∙ 𝑆irradiation j enters the system per unit of time [24]. in general, the ratio between these values is the efficiency of energy conversion during the photocatalytic reaction. note that the quantities characterizing the photocatalytic activity can be expressed in terms of a basic set of the certain parameters. this basis includes the photocatalytic reaction rate, the gibbs energy, the mass and surface area of the catalyst, the irradiation power, and the area of the irradiation surface. table 1 shows the relationship between these basic parameters and the parameters characterizing the photocatalytic activity. for a complete description of the reacting system, it is necessary to add to these parameters the concentration and nature of the reagents, the volume of the reaction mixture, and the geometric characteristics of the reactor. the example of a basic set of parameters is given in table 2. this list may be completed as mentioned in the paper [25]; however, this basic set is sufficient for the tasks in the present work. special attention should be paid to the values of quantum efficiency and solar-to-hydrogen. they are dimensionless; therefore, they can act as similarity criteria if the conditions of geometric and physical similarity of two reaction systems are fulfilled, for example, for the photocatalytic hydrogen production in reactors of different volumes but the same geometry. table 2 parameters describing the photocatalytic hydrogen production. part of the reaction system characterizing parameters the basic set of parameters reagents reagent concentration, volume of the reaction mixture light source irradiation power, surface of irradiation, wavelength working photocatalyst mass, catalyst surface, reaction rate chemical reaction gibbs energy chemical reactor geometric parameters similarity criteria reaction system quantum efficiency, sth 2.2. parameters characterizing the efficiency of the photoelectrochemical cell to describe the efficiency of the photoelectrochemical cells, researchers often use short-circuit current density (jsc) [26–36], open-circuit potential (voc) [26, 27, 30, 31, 33, 35– 37], fill factor (ff) [30, 33, 35, 36, 38], power conversion efficiency (pce, η) [26–31, 33, 35, 37, 38], incident photonto-current efficiency (ipce, external quantum efficiency, eqe) [32, 37–39], solar-to-hydrogen (sth) [26, 28, 31, 39]. let us consider each of the values in more details. the short-circuit current density, open-circuit voltage, fill factor, and power conversion efficiency are calculated from the voltammograms (see figure 1) [40]. the short-circuit current density is known to be the current normalized to the area of illumination that occurs in the cell without any potential [41, 42]. the physical meaning of this value is the highest current density which may be obtained in the photoelectrochemical cell. the short-circuit current density is dependent on the rate of electron-hole pair formation, their diffusion into the semiconductor and in the external circuit [41, 42]. one can say that the jsc indirectly depends on the nature of the semiconductor and electrolyte and the characteristics of the irradiation source. the open-circuit voltage is the voltage occurring in the cell without any current [40–42]. for the discussed cell whose voltammogram is given in figure 1 the open-circuit voltage equals ~0.6 v. the open-circuit voltage shows the highest potential which may be obtained in the cell. figure 1 example of calculation of several characteristics describing the effectivity of the photoelectrochemical cell according to [40]. https://doi.org/10.15826/chimtech.2023.10.2.03 https://doi.org/10.15826/chimtech.2023.10.2.03 chimica techno acta 2023, vol. 10(2), no. 202310203 review 4 of 21 doi: 10.15826/chimtech.2023.10.2.03 the physical meaning of the open-circuit voltage is the efficiency of light energy transformation in one act of photoelectrochemical reaction. this parameter is largely determined by the nature of the chemical processes occurring in the electrolyte solution and at the interface of the electrode/electrolyte [42]. the fill factor is the value reflecting the impact of the resistance of the photoelectrochemical cell and showing the degree of deviation of the produced cell power from the possible one without any resistance. the fill factor is calculated as the ratio of maximum power to the product of the short-circuit current density and the open-circuit voltage: ff = 𝐽mpp ∙ 𝑉mpp 𝐽sc ∙ 𝑉oc ∙ 100%, (6) where ff is the fill factor, jmpp is the current density in which the highest power is generated, vmpp is the potential in which the highest power is generated, jsc is the shortcircuit current density, and voc is the open-circuit potential. as shown in figure 1, the plot of the produced power from potential was constructed, after which the maximum point (mpp) was found. the higher the fill factor, the closer the shape of the current-voltage curve to a rectangular one. the deviation from this shape is caused by resistance in the photoelectrochemical system, recombination of electron-hole pairs [42], and changing resistance at the interface electrode/electrolyte [41]. because the fill factor is a dimensionless quantity, it can be used as the similarity criterion for the photoelectrochemical systems, for example, in case of scaling the photoelectrochemical cells. the power conversion efficiency of the photoelectrochemicall cell shows the ratio of the electrical energy produced in the cell to the energy of the incident light [43]: 𝜂 = 𝐽𝑀𝑃𝑃 ∙ 𝑉𝑀𝑃𝑃 𝑃𝑖𝑟𝑟𝑎𝑑𝑖𝑎𝑡𝑖𝑜𝑛 ∙ 100% = 𝐽𝑆𝐶 ∙ 𝑉𝑂𝐶 ∙ 𝐹𝐹 𝑃𝑖𝑟𝑟𝑎𝑑𝑖𝑎𝑡𝑖𝑜𝑛 ∙ 100%, (7) where η is the power conversion efficiency, jmpp is the current density in which the highest power is generated, vmpp is the potential in which the highest power is generated, рirradiation is the power of the irradiation which incidents on the photoelectrochemical cell, jsc is the short-circuit current density, voc is the open-circuit potential, and ff is the fill factor. the power conversion efficiency shows the efficiency of the energy transformation. pce is a dimensionless quantity and can act as the similarity criterion for the photoelectrochemical systems. the incident photon-to-current efficiency is defined as the number of produced electrons divided by the number of photons incident in the system [43]. by simple transformations, one can obtain equation (8), relating the shortcircuit current density and irradiation power. of practical value is the dependence of ipce on the wavelength, which makes it possible to optimize the irradiation conditions of the photoelectrochemical cell. 𝐼𝑃𝐶𝐸 = 𝑁electrons 𝑁photons ∙ 100% = 𝐽sc ∙ ℎ ∙ 𝑐 𝑃irradiation ∙ 𝑒 ∙ 𝜆 ∙ 100%, (8) where ipce is the incident photon-to-current efficiency, nelectrons is the number of electrons generated in the cell, nphotons is the number of photons incident in the system, jsc is the short-circuit current density, pirradiation is the power of irradiation incident on the photoelectrochemical cell, h is planck's constant, c is the speed of light, e is the electron charge, and λ is the wavelength of the incident irradiation. if additional water decomposition and hydrogen evolution occur in the photoelectrochemical cell, the efficiency of this process can be estimated using solar to hydrogen (sth), which may be calculated according to the following equation: sth = 𝐽sc ∙ 1.23 ∙ 𝜂f 𝑃irradiation ∙ 100%, (9) where jsc is short-circuit current density, ηf is the faraday efficiency factor for hydrogen evolution, and pirradiation is the power of irradiation incident on the photoelectrochemical cell. it should be noted that the sth parameter can also characterize the photocatalytic hydrogen production (see 2.1 and equation 5). in this case, sth shows the relationship between the energy of hydrogen production over the photocatalyst and the energy of incident light. in the case of the photoelectrochemical cell, sth reveals the share of the light energy which was used for the water decomposition and contained the product of the rate of electrochemical hydrogen production (𝐽𝑆𝐶 ∙ 𝜂𝐹) and the gibbs energy of this reaction (1.23 v for water decomposition), as shown in the equation 9. so, these values have the same physical meaning for both different processes. as in the case of the photocatalytic hydrogen evolution, the quantities characterizing the efficiency of the photoelectrochemical cell can be expressed in terms of the basic set of several parameters. the short-circuit current density, the open-circuit potential, the current density at which the cell generates maximum power (in this case, vmpp is determined from the experimental data, the maximum cell power can act as the similarity criterion), the irradiation power, the area of the illuminated part of the photoelectrochemical cell, the irradiation wavelength (for simplicity, we restrict our consideration to monochromatic radiation). to fully characterize the reacting system, it is necessary to add to these parameters the concentration and nature of the electrolyte, the nature of the electrodes, and the geometric design of the cell. among the quantities used by researchers to describe the efficiency of the photoelectrochemical cell, several dimensionless parameters can be selected: the fill factor, the power conversion efficiency, the incident photon-to-current efficiency, and the solar-to-hydrogen. these parameters can act as the similarity criteria provided that the conditions of geometric and physical similarity of two photoelectrochemical cells are met. https://doi.org/10.15826/chimtech.2023.10.2.03 https://doi.org/10.15826/chimtech.2023.10.2.03 chimica techno acta 2023, vol. 10(2), no. 202310203 review 5 of 21 doi: 10.15826/chimtech.2023.10.2.03 2.3. derivation of the similarity criteria that may be used for the description of relation between the efficiencies of the photocatalytic hydrogen production and the photoelectrochemical cell the analysis of the nature of the photocatalytic hydrogen production and the photocurrent generation shows that these phenomena are analogous to each other [7]. therefore, their quantitative description uses analogous values whose combination may be serve as the similarity criteria making the transition between the descriptions of both phenomena. let us consider the list of the analogous quantities (see table 3) in detail. the quantities used for the description of the photocatalytic hydrogen evolution and the photoelectrochemical cell allow defining the change in the number of molecules or the number of the electric charges per unit of time. in both cases, these changes are caused by the change in the number of electrons taking part in the target processes. based on the dimensions, the changing electron amount during the photocatalytic hydrogen production per unit of time per unit of irradiation surface may be calculated as 2 ∙ 𝑊 ∙ 𝑁𝐴 ∙ 𝑆𝑖𝑟𝑟𝑎𝑑𝑖𝑎𝑡𝑖𝑜𝑛 −1 , while the changing electron amount during the photocurrent generation per unit of time per the surface of the photoelectrochemical cell may be defined as 𝐽𝑆𝐶 /𝑒. the ratio of these quantities will be dimensionless and may act as the similarity criterion. the validity of this statement will be verified below by analyzing the literature data. it should be noted that voltammograms are often not presented in the literature, while most articles are accompanied by the data on the change in current density over time generated at the constant potential. this quantity, e.g., at the first cycle, may be used instead of the shortcircuit current density, because it was measured at the constant potential and has the same dimension. in this case, the similarity criterion was labeled as q1’. the photocatalytic hydrogen production and the photocurrent generation are considered as the conversion of light energy into chemical bond or electrical energy. therefore, these phenomena may be characterized by the energy converted per unit of time. as in the previous case, for the photocatalytic reaction, it is necessary to normalize by the area of the illuminated part of the reactor, since such accounting occurs when the efficiency parameters of the photoelectrochemical cell are measured. based on dimensions, we obtain formulas for estimating the amount of energy converted per unit of time per unit of area of the illuminated systems. they will be ∆𝐺°∙𝑊 𝑆𝑖rradiation and jsc·voc for the photocatalytic hydrogen production and the photoelectrochemical cell, respectively. the ratio of these quantities will be dimensionless and may serve as the similarity criterion q2. the studied phenomena occur in the light. from this point of view, the photocatalytic hydrogen evolution may be characterized by the quantum efficiency, while the photocurrent generation is described by icpe. both values are dimensionless, and their ratio is dimensionless too and may serve as a similarity criterion: 𝑄3 = 𝐴𝑄𝐸 𝐼𝑃𝐶𝐸 = 𝑊 ∙ 𝑁𝐴 ∙ 𝑒 𝐽sc ∙ 𝑆irradiation = 𝑄1 2 , (10) 𝑄3 ′ = 𝐴𝑄𝐸 𝐼𝑃𝐶𝐸 = 𝑊 ∙ 𝑁a ∙ 𝑒 𝐽 ∙ 𝑆irradiation = 𝑄1 ′ 2 . (11) note that the criteria q1 and q3 differ a constant multiplier. it is known that multiplying the similarity criterion by a number allows getting another similarity criterion [11]. the efficiencies of the photocatalytic hydrogen production and the photocurrent generation are characterized by the solar-to-hydrogen and the power conversion efficiency, respectively. table 3 quantities describing the similar aspects of the photocatalytic hydrogen production and the photocurrent generation in the photoelectrochemical cell. quantity hydrogen production photocurrent generation in the cell possible similarity criterion change in electron amount per unit of time per irradiation surface 2 ∙ 𝑊 ∙ 𝑁𝐴 𝑆𝑖𝑟𝑟𝑎𝑑𝑖𝑎𝑡𝑖𝑜𝑛 𝐽𝑆𝐶 𝑒 q1 = 2 ∙ 𝑊 ∙ 𝑁𝐴 ∙ 𝑒 𝐽𝑆𝐶 ∙ 𝑆𝑖𝑟𝑟𝑎𝑑𝑖𝑎𝑡𝑖𝑜𝑛 𝐽 𝑒 q1 ′ = 2 ∙ 𝑊 ∙ 𝑁𝐴 ∙ 𝑒 𝐽 ∙ 𝑆irradiation energy converted per unit of time per unit of irradiation surface ∆𝐺° ∙ 𝑊 𝑆𝑖𝑟𝑟𝑎𝑑𝑖𝑎𝑡𝑖𝑜𝑛 𝐽𝑆𝐶 ∙ 𝑉𝑂𝐶 q2 = ∆𝐺° ∙ 𝑊 𝑆irradiation ∙ 𝐽𝑆𝐶 ∙ 𝑉𝑂𝐶 efficiency of using light quantum efficiency ipce q3 = aqe ipce = 𝑊 ∙ 𝑁𝐴 ∙ 𝑒 𝐽sc ∙ 𝑆𝑖rradiation = 𝑄1 2 q 3 ′ = aqe ipce = 𝑊 ∙ 𝑁𝐴 ∙ 𝑒 𝐽 ∙ 𝑆 irradiation = 𝑄 1 ′ 2 efficiency of energy conversion sth η q4 = 𝑆𝑇𝐻 𝜂 https://doi.org/10.15826/chimtech.2023.10.2.03 https://doi.org/10.15826/chimtech.2023.10.2.03 chimica techno acta 2023, vol. 10(2), no. 202310203 review 6 of 21 doi: 10.15826/chimtech.2023.10.2.03 dividing these two parameters by each other yields the similarity criterion q4: 𝑄 4 = 𝑆𝑇𝐻 𝜂 = ∆𝐺° ∙ 𝑊 𝑆irradiation ∙ 𝐽𝑆𝐶 ∙ 𝑉𝑂𝐶 ∙ 𝐹𝐹 . (12) thus, four potential similarity criteria were obtained. since the first and the third, the second and the fourth criteria differ by a constant multiplier, in order to find out whether the proposed values are the similarity criteria, it is enough to verify only the parameters q1 and q2. 3. checking the possibility of applying the criterion q1’ as the similarity criterion to check whether the proposed values are similarity criteria, some literature data was analyzed [45–81]. it should be noted that the data of linear voltammetry either were not given by the authors or differ from the form shown in figure 1. so, the current density in the cell at the constant potential value, measured by chronoamperometry, will be used for comparison instead of the short-circuit current density. from the point of view of dimension theory, such substitution is correct due to the same dimensions of both quantities (ma/cm2). thus, in most of the reviewed data, the possibility of using the parameter q1' as the similarity criterion was verified. in the theory of similarity, a geometric level of similarity and a physical one are often distinguished [44]. the geometric level implies an identical shape of particles and/or elements of the reaction set-up, its characteristic sizes [44]. when moving from the study of photocatalytic hydrogen evolution to measuring photocurrents for two different samples, the similarity at the geometrical level is often preserved. it is due to the comparable particle sizes of the tested samples, the experimental set-ups for studying the photocatalytic hydrogen evolution and the photoelectrochemical properties are the same. special attention should be paid to the morphology of the samples: in case of its change, the conditions of the geometric similarity are violated. if the geometric similarity is observed for the studied systems, then the similarity of phenomena can also be taken place at the physical level. two phenomena are similar if all parameters characterizing them are similar [44]. it means that the samples should be tested under the same conditions, such as power irradiation, its wavelength, the composition of electrochemical cells and electrolyte, the composition of catalysts, etc. if these conditions are fulfilled, the question of similarity of the photocatalytic hydrogen production and the photocurrent generation for the studied samples can be considered. below there are data on catalysts of various chemical nature, solid solutions of different compounds, the series of samples in which the mass ratio of the components is changed; the photocatalytic and photovoltaic characteristics were studied in solutions of different electrolytes. all discussed data are given in tables 4–7. each table contains the experimental conditions; the criterion q1’ was calculated. the error in calculating the parameter was determined taking into account the instrumental errors of the methods. they were either for 10% (if quantitative data were taken from tables or from the text), or for 15% in the case of getting data from the figures. 3.1. solid solutions of different compounds the data on the photocatalytic hydrogen production and photocurrent generation over some solid solutions are given in table 4 [45–52]. the solid solutions of cadmium sulfide and zinc sulfide were described in a number of works. the short-circuit current densities were measured in [45] and [46], and the similarity criterion q1 was calculated from obtained data. the ratio of the number of electrons used for the photocatalytic hydrogen evolution and those to the number of electrons taking part in the photocurrent generation remained constant within experimental errors for all samples, except for zinc sulfide in [45]. probably, zinc sulfide should be considered separately due to low absorbance of visible light and different chemical nature (see section 3.2). the authors of [46] studied a wider range of the solid solution composition; however, in this case, no indication of change in the parameter q1 could be identified. perhaps, it was caused by different composition of the electrolytes used in the experiments. the mixture of na2s and na2so3 was used for the photocatalytic hydrogen production while sodium polysulfide was chosen for the photoelectrochemical experiments. in both cases, chemical transformations occurred between charge carriers and electrolytes. however, various chemical processes were realized, so the changes in the target parameters vs. the photocatalyst composition were different. in this case, it was impossible to apply the similarity theory due to the violation of the condition of physical similarity. s. du et al. studied the solid solutions of cadmium sulfide and cadmium selenides with low se content [47]. the dependences of the photocatalytic hydrogen production rate and the current density on selenium concentration have a bell-shaped form, while the electron ratios expressed by the criterion q1’ stayed the same and were 300–400 within the experimental errors. the solid solutions of cds and mns were described in [48]. the dependences of both target characteristics on the solid solution composition went through a maximum. the q1’ criteria were calculated for the tested samples and given in table 4. one can see that q1’ doubles when cadmium sulfide forms solid solutions with manganese sulfide. it may be associated with the changes in the rate constants of photochemical processes and charge recombination depending on the chemical nature of semiconductor. the ratio between the numbers of electrons used for the photocatalytic hydrogen evolution and those taking part in the photocurrent generation remained constant for all samples, excluding the photocatalyst with x = 0.9. for the mentioned sample, the deviation was due to its chemical nature. this photocatalyst https://doi.org/10.15826/chimtech.2023.10.2.03 https://doi.org/10.15826/chimtech.2023.10.2.03 chimica techno acta 2023, vol. 10(2), no. 202310203 review 7 of 21 doi: 10.15826/chimtech.2023.10.2.03 was a composite consisting of mns and the solid solution of cadmium sulfide and manganese sulfide [48]. so, in this case, we deal with the non-compliance with the conditions of the physical similarity of the systems discussed. the same behavior was found for mnxcd1–xs [49]. for the solid solutions with different ratios of manganese to cadmium, the q1’ criterion remained a constant within the experimental error, while it increased by almost two times in the transition from cds to the solid solution of cadmium and manganese sulfides. the solid solutions of more complex composition such as cd1–xznxs and cd1–xznxmoys1+2y were mentioned in [50]. the introduction of the solid solution in the structure changed its chemical composition, affecting both the change in the target characteristics and their ratios. in this case, the condition of the physical similarity of the samples was violated, and it is incorrect to talk about the application of similarity theory. the znfe2o4 and zngao4 spinels and their solid solutions were described in [51]. the ratio between the numbers of electrons used for the photocatalytic hydrogen evolution and those taking part in the photocurrent generation varied for these samples due to different chemical nature. for the solid solutions based on znfe2o4 and zngao4, ratios of the number of electrons used for the photocatalytic hydrogen evolution to the number of electrons taking part in the photocurrent generation were less than those for individual compounds. however, their differences between each other were more than 10%, which may be due to the formation of oxygen vacancies for the samples with x>1. therefore, four samples demonstrated different physicochemical properties, and the similarity theory is not applicable to this case. in the work [52], the authors studied the photocatalysts consisting of the solid solutions of zinc sulfide, chromium sulfide, indium sulfide with different q1’ values. note that for the samples with adjacent values of metal content (e.g., zn:cr = 85:15 and zn:cr = 75:25) the target criteria are the same within the experimental errors. perhaps, it is connected with a stronger influence on the electronic structure of small changes in the composition of the triple solid solutions, which cause significant changes in the physicochemical properties and do not allow considering the samples similar. in the case of small fluctuations in the chemical composition, we can only talk about partial similarity of the discussed systems. to sum up, for binary solid solutions, the criterion q1’ can serve as the similarity criterion in case of compliance with the conditions of physical and geometric similarity. for triple solid solutions, the change in the photocatalyst composition has a stronger effect on its physicochemical properties, as a result of which we can only talk about partial similarity for the samples similar in composition. for transition from individual compounds to their solid solutions, the q1’ criterion may both retain its value and change. such cases should be considered individually. 3.2. samples whose chemical nature were different the data obtained over the samples whose chemical composition was changed during the preparation were given in table 5 ([53–74]). for compounds with different chemical nature, the transition from the photocatalysts to the photoelectrodes was accompanied by the different ratio of the number of electrons used for photocatalytic hydrogen production to the number of electrons taking part in the photocurrent generation. for instance, in [53] nh2-uio-66 and znin2s4 were studied, and for them the q1’ criterion differed by 7 times, while for cds and zns – by 5 times [45]. this result was not surprising because the number of electrons was largely determined by the balance between the rate of charge generation, their recombination, and consumption in various processes. for samples with different chemical nature, the rate constants of these stages differed, and the ratios also diverged. in terms of the similarity theory, one can say that in this case the conditions of physical similarity were violated. more interesting were the cases in which the chemical composition of the catalyst was changed by loading additional compounds or doping. did the q1’criterion change in this case? a special case of modification of the semiconductor was capping some ligands on the photocatalyst surface. in [54] titanium dioxide with capped quantum dots based on cadmium selenide and the solid solution of cadmium sulfide and zinc sulfide using ammonium thiocyanide and mercaptopropionic acid was described. the scheme for the functioning of these photocatalysts was proposed, in which photogenerated holes were transferred from the valence band of quantum dots to the highest occupied molecular orbital of the ligand [54]. as a result, the target characteristics of the photocatalysts prepared with diverse ligands differed. simultaneously, the q1’ criteria showing the number of electrons used for the photocatalytic hydrogen evolution divided by the number of electrons taking part in the photocurrent generation differed. possibly, it may be assisted with strong differences in the transfer constants of the photogenerated holes, which had an indirect effect on the number of electrons in the discussed systems. the photocatalyst surface was often modified by loading compounds and forming the composite catalysts. the researchers extensively studied the composites with different composition. in [55] cadmium sulfide whose surface was modified with nb2ct was studied. this deposition led to the increase in the reaction rate by 1.7 times, while the photocurrent grew by 1.8 times. the ratio of the number of electrons occurring in the photocatalytic hydrogen production to the number of electrons used for the photocurrent generation was the same for these samples. in [56] copper nanoparticles and their role in the photocatalysis after deposition on the surface of bohrium nitride, polyaniline, and the composite photocatalyst consisting of bohrium nitride and polyaniline were discussed. copper nanoparticles and copper nanoparticles deposited on bn demonstrated the same catalytic activity. https://doi.org/10.15826/chimtech.2023.10.2.03 https://doi.org/10.15826/chimtech.2023.10.2.03 chimica techno acta 2023, vol. 10(2), no. 202310203 review 8 of 21 doi: 10.15826/chimtech.2023.10.2.03 table 4 verifying the possibility of using q1’ as the similarity criterion for the series of different solid solutions. no. sample photocatalyst sacrificial agent w (μmol/min) counter and reference electrodes electrolyte current density (ma/cm2) light source q1’ ref 1 cds solid solutions of cds and zns 0.24 m na2s, 0.35 m na2so3 0.08 pt/c 10 vol.% ethanol, 0.5 m naoh 0.150 xe lamp 0.14±0.02 [45]a cd0.25zn0.75s 0.62 0.767 0.22±0.03 cd0.35zn0.65s 0.48 0.992 0.13±0.02 cd0.65zn0.35s 0.57 0.958 0.16±0.02 zns 0.10 0.975 0.027±0.004 2 cds solid solutions of cds and zns 0.1 m na2s, 0.1 m na2so3 0.12 cu2s/brass 1 m na2sn, 0.1 m nacl 0.881 450-led 0.44±0.06 [46] cd0.9zn0.1s 0.29 0.901 1.0±0.1 cd0.8zn0.2s 0.37 2.21 0.54±0.08 cd0.7zn0.3s 0.47 1.37 1.1±0.2 cd0.6zn0.4s 0.39 0.33 3.8±0.5 cd0.5zn0.5s 0.55 0.067 26±4 cd0.4zn0.6s 0.96 0.139 22±3 cd0.3zn0.7s 2.25 0.984 7±1 cd0.2zn0.8s 0.96 0.259 12±2 cd0.1zn0.9s 0.56 0.128 14±2 zns 0.025 0.024 3.3±0.5 3 cds solid solutions of cadmium sulfide and cadmium selenide 5 vol.% lactic acid 0.35 pt, hg|hg2cl2|cl – 0.5 m na2so4 0.0036 xe lamp 308±43 [47]a cds0.99se0.01 0.55 0.0038 466±66 cds0.975se0.025 0.61 0.0058 335±47 cds0.95se0.05 1.22 0.0100 391±55 cds0.925se0.075 0.61 0.0064 306±43 cds0.9se0.1 0.36 0.0027 425±60 4 x = 0 mnxcd1–xs 10 vol.% lactic acid 0.35 pt, agcl|ag|cl– 0.2 m na2so4 0.015 xe lamp 74±10 [48] x = 0.3 1.02 0.021 155±22 x = 0.5 1.50 0.024 199±28 x = 0.6 1.88 0.032 188±26 x = 0.9 0.59 0.002 939±132 5 cds solid solutions of cadmium sulfide and manganese sulfide 20 vol.% lactic acid 0.055 pt, agcl|ag|cl– 0.1 m na2so4 0.03 xe lamp 5.9±0.8 [49] mcs-1 0.152 0.043 11±2 mcs-2 0.178 0.065 9±1 mcs-3 0.127 0.04 10±1 mcs-4 0.117 0.035 10±2 6 zcs solid solutions of zns, cds, mos2 0.35 m na2s, 0.35 m na2so3 0.0003 pt, agcl|ag|cl– 0.5 m na2so4 0.00014 xe lamp 8±1 [50] zcm5s 0.0038 0.00021 58±8 https://doi.org/10.15826/chimtech.2023.10.2.03 chimica techno acta 2023, vol. 10(2), no. 202310203 review 9 of 21 doi: 10.15826/chimtech.2023.10.2.03 table 4 verifying the possibility of using q1’ as the similarity criterion for the series of different solid solutions (continued). no. sample photocatalyst sacrificial agent w (μmol/min) counter and reference electrodes electrolyte current density (ma/cm2) light source q1’ ref 7 x = 0 znfe2–xgaxo4 10 vol.% triethanolamine 4.63 pt, agcl|ag|cl– 0.5 m na2so4 0.0002 xe lamp (7±1)·104 [51] x = 0.5 5.40 0.00075 (2.3±0.3)·104 x = 1.5 5.85 0.00050 (3.7±0.5)·104 x = 2.0 5.98 0.0017 (11±2)·104 8 zis solid solutions of zinc sulfides, chromium sulfide, indium sulfide 0.25 m na2s, 0.35 m na2so3 0.74 с, hg|hg2cl2|cl – 0.5 m na2so4 0.00007 xe lamp (3.4±0.5)·104 [52] z0.85c0.15is 1.35 0.00015 (2.9±0.4)·10 4 z0.75c0.25is 1.71 0.00022 (2.5±0.4)·10 4 z0.55c0.45is 1.09 0.00008 (4.4±0.6)·10 4 a in this work the short-circuit current densities were presented, q1 was calculated. table 5 verifying the possibility of using q1’ as the similarity criterion for the series of samples with different chemical nature. no. sample photocatalyst sacrificial agent w (μmol/min) counter and reference electrodes electrolyte current density (ma/cm2) light source q1’ ref different chemical compounds 1 nu66d nh2-uio-66 decarboxylated 0.25 m na2s/0.35 m na2so3 0.050 pt, agcl|ag|cl– 0.1 m na2so4 0.0028 xe lamp, λ ≥ 420 nm 57±8 [53] zis znin2s4 0.072 0.0058 395±56 nu66/zis-30 znin2s4 deposited on nh2-uio-66 0.85 0.0078 349±49 nu66-d/zis-30 znin2s4 deposited on decarboxylated nh2-uio-66 1.22 0.0091 428±60 2 cds cds 0.24 m na2s, 0.35 m na2so3 0.08 pt/c 10 vol.% ethanol, 0.5 m naoh 0.150 xe lamp 0.14±0.02 [45] zns zns 0.10 0.975 0.027±0.004 capping ligands on the photocatalyst surface 3 scn tio2 with capping quantum dots using nh4scn 0.1 м ascorbic acid 4755 pt, agcl|ag|cl– 0.1 м ascorbic acid 0.053 am-1.5g (2.9±0.4)·105 [54] mpa tio2 with capping quantum dots using mercaptopropionic acid 470 0.028 (53.7±0.8)·103 deposition of different compounds 4 cds cds 10 vol.% lactic acid 0.52 pt, agcl|ag|cl– 1 m na2so4 0.033 xe lamp, λ ≥ 420 nm 501±71 [55] cds/nb2ct-60 cds with deposited nb2ct (60 mg) 0.90 0.062 465±65 5 cu/bn@pani2.5 wt.% 2.5% cu deposited on bn and polyaniline 14 vol.% lactic acid 0.52 pt 0.1 m koh 49 xe lamp, λ ≥ 420 nm 0.034±0.005 [56] cu-pani/2.5% 2.5% cu deposited on polyaniline 0.25 30 0.027±0.004 cu/bn-2.5% 2.5% cu deposited on bn 0.19 19 0.032±0.005 cu nps cu 0.165 15 0.035±0.005 https://doi.org/10.15826/chimtech.2023.10.2.03 chimica techno acta 2023, vol. 10(2), no. 202310203 review 10 of 21 doi: 10.15826/chimtech.2023.10.2.03 table 5 verifying the possibility of using q1’ as the similarity criterion for the series of samples with different chemical nature (continued). no. sample photocatalyst sacrificial agent w (μmol/min) counter and reference electrodes electrolyte current density (ma/cm2) light source q1’ ref 6 nico-ldh nickel-cobalt double layered hydroxides 0.2 m na2s, 0.2 m na2so3 0.13 pt, agcl|ag|cl– 0.5 m na2so4 0.48 am-1.5g 0.9±0.1 [57] coo coo 0.20 0.88 0.7±0.1 coo/nico-ldh coo deposited on nickel-cobalt double layered hydroxides 1.00 3.15 1.0±0.1 7 zns/pda1 polydopamine deposited on zns 0.35 m na2s, 0.25 m na2so3 0.36 pt, agcl|ag|cl– 0.5 m na2so4 0.002 xe lamp 577±81 [58] zns zns 0.16 0.001 526±74 8 uio-66 uio-66 10 vol.% triethanolamine 0.067 pt, agcl|ag|cl– 0.5 m na2so4 0.02 xe lamp, λ ≥ 420 nm 11±2 [59] uio-66/nis2-5 uio-66 with deposited 5 wt.% nis2 0.30 0.07 14±2 9 cpt-14 pt/g-c3n4 10 vol.% triethanolamine 3.38 pt, agcl|ag|cl– 0.5 m na2so4 0.00014 xe lamp, λ ≥ 400 nm (8±1)·104 [60] cpto-6 pto/g-c3n4 4.46 0.00020 (7±1)·10 4 10 cds cds 0.35 m na2s/0.25 m na2so3 198 pt, agcl|ag|cl– 0.5 m na2so4 0.0024 xe lamp, λ ≥ 420 nm (2.6±0.4)·105 [61] 0.4qd/cds 0.4 wt.% c (quantum dots) deposited on cds 309 0.0048 (2.1±0.3)·105 11 pt/sio2 rp/pt/sio2 – 200.4 pt, agcl|ag|cl– 0.5 m na2so4 0.0030 xe lamp, λ ≥ 420 nm 21±3 [62] cop2-6 rp/cop2(6)/sio2 401.4 0.0032 40±6 12 20 wn/cds 20 wn/cds 10 vol.% lactic acid 4.02 pt, agcl|ag|cl– 0.5 m na2so4 0.0021 xe lamp, λ ≥ 420 nm 6218±877 [63] cds cds 0.43 0.0005 2771±391 13 3domm-tio2 tio2 prepared by the template method 10 vol.% methanol 0.136 pt, agcl|ag|cl– 0.5 m na2so4 0.20 xe lamp, λ ≥ 420 nm 2.2±0.3 [64] 3domm-tio2–x tio2 prepared by the template method and reduced by nabh4 0.173 0.31 1.8±0.3 3domm-tio2– x@pani tio2 prepared by the template method with deposited polyaniline 0.264 0.80 1.1±0.1 ag@3dommtio2–x@pani tio2 prepared by the template method with deposited polyaniline and ag 0.281 1.12 0.8±0.1 14 bcn c3n4 prepared by the thermal polymerization 20 vol.% triethanolamine 0.01 pt, agcl|ag|cl– 0.5 m na2so4 0.0002 xe lamp 160±23 [65] can c3n4 prepared by the template method 0.02 0.0004 173±24 10% co/can 10% co3o4 deposited on c3n4 prepared by the template method 0.04 0.0013 97±13 15 in2s3 in2s3 10 vol.% lactic acid 0.0015 pt, hg|hg2cl2|cl – 0.5 m na2so4 0.00055 xe lamp 9±1 [66] 25mpis 25% mop/in2s3 0.24 0.0016 481±68 16 cds cds 20 vol.% lactic acid 0.44 pt, agcl|ag|cl– 0.1 m na2so4 0.005 xe lamp, λ ≥ 420 nm (2.8±0.4)·102 [67] 11% fe2p/cds 11% fe2p/cds 34.6 0.070 (1.6±0.2)·10 3 https://doi.org/10.15826/chimtech.2023.10.2.03 chimica techno acta 2023, vol. 10(2), no. 202310203 review 11 of 21 doi: 10.15826/chimtech.2023.10.2.03 table 5 verifying the possibility of using q1’ as the similarity criterion for the series of samples with different chemical nature (continued). no. sample photocatalyst sacrificial agent w (μmol/min) counter and reference electrodes electrolyte current density (ma/cm2) light source q1’ ref 17 tio2 tio2 0.5 m na2s/na2so3 0.009 pt, agcl|ag|cl– 0.5 m na2s/na2so3 0.10 xe lamp 0.29±0.04 [68] cbt-0 cds/tio2 0.489 0.52 3.0±0.4 18 lto la2ti2o7 10 vol.% triethanolamine 0.06 pt, agcl|ag|cl– 1 m naoh 0.012 am-1.5g 15±2 [69] rgo/lto 71 wt.% reduced graphene oxide deposited on la2ti2o7 0.29 0.026 36±5 lto/ni-fe la2ti2o7 deposited on nickel-irondouble layered hydroxides 0.36 0.034 33±5 rgo/lto/nife graphene oxide deposited on la2ti2o7 deposited on nickel-irondouble layered hydroxides 0.53 0.068 25±4 doping 19 cds cds 20 vol.% с3н6о3 0.84 pt, hg|hg2cl2|cl – 0.5 m na2so4 0.027 xe lamp, λ ≥ 420 nm 100±14 [70] mo-cds cds:mo (25 mol.%) 4.87 0.116 134±19 20 zno zno doped with al – 0.034 pt, agcl|ag|cl– 0.1 m naoh 0.06 light source simulating solar light / sunlight 1.8±0.3 [71] zno/al/0.5 0.056 0.11 1.6±0.2 zno/al/1 0.122 0.24 1.6±0.2 zno/al/5 0.183 0.38 1.5±0.2 21 bcn carbon nitride 20 vol.% methanol 0.054 pt, agcl|ag|cl– 0.1 m na2so4 0.00036 xe lamp, λ ≥ 420 nm 476±67 [72] ptcn carbon nitride doped by phosphorous 0.092 0.00043 685±97 22 gcn-b carbon nitride 20 vol.% triethanolamine 0.0024 pt, agcl|ag|cl– 0.1 m na2so4 0.18 xe lamp, λ ≥ 420 nm (4.3±0.6)·10–2 [73] gcn-ns carbone nitride, nanosheets 0.0083 0.43 (6±1)·10–2 b,cs cn-b carbon nitride doped with b and cs 0.0027 0.175 (5.0±0.7)·10–2 b,cs cn-ns carbon nitride doped with b and cs, nanosheets 0.0189 0.63 (10±1)·10–2 23 cn carbon nitride 10 vol.% triethanolamine 0.29 pt, agcl|ag|cl– 0.2 m na2so4 0.11 xe lamp, λ ≥ 420 nm 8±1 [74] bqcn carbon nitride with benzoquinone as linker 0.66 0.25 8±1 https://doi.org/10.15826/chimtech.2023.10.2.03 chimica techno acta 2023, vol. 10(2), no. 202310203 review 12 of 21 doi: 10.15826/chimtech.2023.10.2.03 table 6 verifying the possibility of using q1’ as the similarity criterion for the series of samples with different weight ratio of the components or preparation time. no. sample photocatalyst sacrificial agent w (μmol/min) counter and reference electrodes electrolyte current density (ma/cm2) light source q1’ ref 1 cop2-4 rp/cop2(4)/sio2 – 401.4 pt, agcl|ag|cl– 0.5 m na2so4 0.032 xe lamp, λ ≥ 420 nm 40±6 [62] cop2-6 rp/cop2(6)/sio2 707.4 0.052 44±6 cop2-8 rp/cop2(8)/sio2 622.8 0.048 42±6 2 6% mos2/cds 6% mos2/cds 10 vol.% lactic acid 10.62 pt, agcl|ag|cl– 0.5 m na2so4 0.0036 xe lamp, λ ≥ 420 nm (9±1)·103 [75] 20% mos2/cds 20% mos2/cds 5.80 0.0018 (10±2)·10 3 3 0% lavo4 carbon nitride with different wt. content of deposited lavo4 10 vol.% triethanolamine 0.027 pt, agcl|ag|cl– 0.1 m na2so4 0.00045 xe lamp 190±40 [76] 10% lavo4 0.061 0.0010 196±42 15% lavo4 0.093 0.0013 230±49 20% lavo4 0.041 0.00075 176±37 25% lavo4 0.015 0.00034 144±31 4 sis-zis-0.1 composites based on znin2s4 and snin4s8, number shows ½ mmol of added tin chloride during the preparation stage 10 vol.% triethanolamine 0.61 pt, agcl|ag|cl– 0.1 m na2so4 0.0048 xe lamp, λ ≥ 400 nm 404±73 [69] sis-zis-0.2 0.76 0.0080 302±54 sis-zis-0.3 1.00 0.0094 339±61 sis-zis-0.4 0.85 0.0083 329±59 sis-zis-0.5 0.67 0.0072 297±53 5 cds cds with different amount of deposited titanium carbide 20 vol.% methanol 0.25 pt, agcl|ag|cl– 0.5 m na2so4 0.005 xe lamp 0.16±0.03 [77] cds@ti3c2-5 0.48 0.009 0.17±0.02 cds@ti3c2-10 0.67 0.010 0.21±0.03 cds@ti3c2-15 1.07 0.017 0.20±0.03 cds@ti3c2-20 0.90 0.0095 0.30±0.04 cds@ti3c2-25 0.88 0.009 0.31±0.04 cds@ti3c2-50 0.50 0.0046 0.35±0.05 cds@ti3c2-100 0.22 0.0025 0.28±0.04 6 1% cose2 cds0.95se0.05 with different amount of deposited cose2 5 vol.% lactic acid 2.95 pt, hg|hg2cl2|cl – 0.5 m na2so4 0.011 xe lamp (9±1)·102 [47] 2.5% cose2 11.96 0.022 (1.7±0.3)·10 3 5% cose2 23.16 0.057 (1.3±0.2)·10 3 7.5% cose2 19.31 0.047 (1.3±0.2)·10 3 10% cose2 12.60 0.028 (1.4±0.2)·10 3 12.5% cose2 9.96 0.017 (1.9±0.3)·10 3 7 hd-tio2 3 h defected titania prepared during different time of hydrothermal treatment 20 vol.% methanol 11.1 pt, hg|hg2cl2|cl 2 m na2so4 0.00036 xe lamp, λ ≥ 420 nm (10±1)·104 [78] hd-tio2 4 h 12.7 0.00046 (9±1)·10 4 hd-tio2 5 h 15.0 0.00056 (9±1)·10 4 hd-tio2 6 h 10.0 0.00029 (11±2)·10 4 8 ptcn/cn-1 ti3c2/p-doped g-c3n4, obtained for different time of mixturing 20 vol.% methanol 0.19 pt, agcl|ag|cl– 0.1 m na2so4 0.0006 xe lamp, λ ≥ 420 nm 995±140 [72] ptcn/cn-2 0.28 0.0012 753±106 ptcn/cn-3 0.21 0.00077 881±124 9 nis/cds-10 nis/cds, number shows time of mixturing of cds suspension 20 vol.% lactic acid 0.75 pt, hg|hg2cl2|cl – no information 1.0 xe lamp, λ ≥ 420 nm 2.4±0.5 [79] nis/cds-30 1.75 1.5 3.7±0.8 nis/cds-60 3.80 2.8 4.3±0.9 nis/cds-90 6.24 5.9 3.4±0.7 nis/cds-120 4.67 4.0 3.7±0.8 10 cbt-30 cds/tio2,number shows water share in water-alcohol solution put into the autoclave 0.5 m na2s/na2so3 2.07 pt, agcl|ag|cl– 0.5 m na2s/na2so3 3.0 xe lamp 2.2±0.3 [68] cbt-50 3.57 4.3 2.7±0.4 cbt-70 2.67 3.5 2.4±0.3 cbt-100 1.68 2.6 2.1±0.3 https://doi.org/10.15826/chimtech.2023.10.2.03 chimica techno acta 2023, vol. 10(2), no. 202310203 review 13 of 21 doi: 10.15826/chimtech.2023.10.2.03 table 7 verifying the possibility of using q1’ as the similarity criterion for the series of samples with different electrolytes and their concentration. no. photocatalyst sacrificial agent hydrogen production rate (μmol/min) counter and reference electrodes electrolyte current density (ma/cm2) light source q1’ ref 1 cufe1.6mn0.4o4 na2s 3.39 pt, agcl|ag|cl– 0.1 m na2so4 0.090 xe lamp 121±17 [80] cufe1.2mn0.8o4 3.57 0.018 635±90 cufe0.8mn1.2o4 3.62 0.065 178±25 cufe1.6mn0.4o4 na2so3 0.80 0.090 29±4 cufe1.2mn0.8o4 3.57 0.018 635±90 cufe0.8mn1.2o4 1.56 0.065 77±11 cufe1.6mn0.4o4 oxalic acid 0.54 0.090 19±3 cufe1.2mn0.8o4 0.58 0.018 103±15 cufe0.8mn1.2o4 5.8 0.065 286±40 2 cd0.8zn0.2s 20 vol.% c2h5oh, 0.1 m naoh 0.04 cu2s/brass 20 vol.% c2h5oh, 0.1 m naoh 0.008 16±2 [81] 1% cus/ cd0.8zn0.2s 0.01 0.015 2.1±0.3 cd0.8zn0.2s 0.1 m na2s 0.10 0.1 m na2s 0.082 3.9±0.6 1% cus/ cd0.8zn0.2s 0.35 0.1 11±2 cd0.8zn0.2s 0.1 m na2s + 0.1 m na2so3 0.59 0.1 m na2s + 0.1 m na2so3 0.259 7±1 1% cus/ cd0.8zn0.2s 0.79 0.837 3.0±0.4 cd0.8zn0.2s 0.02 m na2s, 0.1 m na2so3 0.18 0.02 m na2s, 0.1 m na2so3 0.033 17±2 0.05 m na2s, 0.1 m na2so3 0.35 0.05 m na2s, 0.1 m na2so3 0.168 7±1 0.2 m na2s, 0.1 m na2so3 0.82 0.2 m na2s, 0.1 m na2so3 0.184 14±2 0.3 m na2s, 0.1 m na2so3 0.97 0.3 m na2s, 0.1 m na2so3 0.297 10±2 0.4 m na2s, 0.1 m na2so3 1.15 0.4 m na2s, 0.1 m na2so3 0.240 15±2 0.1 m na2s, 0.02 m na2so3 0.38 0.1 m na2s, 0.02 m na2so3 0.125 10±1 0.1 m na2s, 0.05 m na2so3 0.54 0.1 m na2s, 0.05 m na2so3 0.183 9±1 0.1 m na2s, 0.2 m na2so3 0.47 0.1 m na2s, 0.2 m na2so3 0.211 7±1 0.1 m na2s, 0.3 m na2so3 0.41 0.1 m na2s, 0.3 m na2so3 0.184 7±1 1% cus/ cd0.8zn0.2s 0.02 m na2s, 0.1 m na2so3 0.36 0.02 m na2s, 0.1 m na2so3 0.219 5.3±0.7 0.05 m na2s, 0.1 m na2so3 0.62 0.05 m na2s, 0.1 m na2so3 0.461 4.3±0.6 0.2 m na2s, 0.1 m na2so3 0.89 0.2 m na2s, 0.1 m na2so3 0.727 3.9±0.6 0.3 m na2s, 0.1 m na2so3 0.83 0.3 m na2s, 0.1 m na2so3 0.624 4.3±0.6 0.4 m na2s, 0.1 m na2so3 0.88 0.4 m na2s, 0.1 m na2so3 0.444 6.3±0.9 0.1 m na2s, 0.02 m na2so3 0.48 0.1 m na2s, 0.02 m na2so3 0.192 8±1 0.1 m na2s, 0.05 m na2so3 0.59 0.1 m na2s, 0.05 m na2so3 0.424 4.5±0.6 0.1 m na2s, 0.2 m na2so3 0.62 0.1 m na2s, 0.2 m na2so3 0.718 2.8±0.4 0.1 m na2s, 0.3 m na2so3 0.44 0.1 m na2s, 0.3 m na2so3 0.605 2.3±0.3 https://doi.org/10.15826/chimtech.2023.10.2.03 chimica techno acta 2023, vol. 10(2), no. 202310203 review 14 of 21 doi: 10.15826/chimtech.2023.10.2.03 copper loaded on polyaniline showed a higher catalytic activity (24% greater than 2.5% cu/bn). the composite photocatalysts based on copper, bohrium nitride, and polyaniline were the most active in this set. figure 2 demonstrates the criteria q1’ and q3’ calculated for all samples. in this particular case, the parameter values are the same and can be considered the similarity criteria. in [57] nickel-cobalt double layered hydroxide photocatalysts were studied. another discussed object was cobalt oxide. because of chemical composition similarities, the ratio between the numbers of electrons used to the photocatalytic hydrogen evolution divided and those taking part in the photocurrent generation was the same and equaled 0.7 and 0.9 for cobalt oxide and double layered hydroxides, respectively. the formation of the composite catalyst from these components allowed enhancing the photocatalytic hydrogen production by 5–8 times and increasing the photocurrent generation by 4–7 times compared with pristine compounds [57]. the q1’ criterion retained the value obtained for nickel-cobalt double layered hydroxides whose surface was modified with coo by the hydrothermal method. the same result was reached for zinc sulfide and one deposited with polydopamine described in [58]. such modification allowed improving the target characteristics of the photocatalysts and photoelectrodes and keeping q1’ within experimental error. the same behavior was demonstrated for metal-organic frameworks discussed in [59]. the deposition of 5% nis led to the increase of the photocatalytic hydrogen production rate from aqueous solution of triethanolamine by 4.5 times, while the generated current density was enhanced by 3.5 times. the ratio of the electrons occurring in these processes remained the same. in [53] znin2s4 was deposited on nh2-uio-66 and decarboxylated nh2-uio-66. the q1’ criteria differed for pristine samples, while q1’ was the same for the composite photocatalysts and znin2s4. finally, the same values of q1’ were calculated for graphitic carbon nitride modified with platinum or platinum oxide [60]. the same behavior was found for cds whose surface was modified with carbon quantum dots. the photocatalytic hydrogen production rate and the photocurrent density doubled in these systems while the q1’ criterion was the same within the experimental errors [61]. the contrary trend was characterized for other systems described earlier. for instance, in [62] the photocatalysts based on silicon dioxide and the co-catalyst modified with red phosphorous were studied. the replacement of platinum co-catalyst with cobalt phosphide led to the growth of the catalytic activity and the ratio of the number of electrons used for the photocatalytic hydrogen evolution to the number of electrons taking part in the photocurrent generation. probably, different co-catalysts significantly changed the rate constants of the corresponding processes, which leads to the observed changes in the system. the same behavior was found in the case of cds whose catalytic properties were improved with deposition of 20 wt.% wn [63]. the co-catalyst addition allowed enhancing the hydrogen production rate by 9.3 times while the photocurrent generation was increased by 4.2 times, the q1’ criterion grew by 2.2 times. in [64] researches discussed titanium dioxide prepared by the template method. the reduction of titania by sodium borohydride led to an increase in the reaction rate of hydrogen photoproduction from aqueous methanol solution by 20%; the studied ratio of the electrons occurring in the photocatalytic and the photovoltaic properties did not change in this case. additionally, the authors improved the target characteristics by the deposition of polyaniline and polyaniline and silver on the photocatalyst surface. such modifications favored the photocatalytic hydrogen production; however, the q1’ criteria were different for the obtained samples as shown in figure 3. the authors of [65] compared the target properties of graphitic carbon nitride prepared by different methods such as thermal polymerization and template synthesis. at whole, the template method allowed getting more active samples; the ratio between the number of electrons used for the photocatalytic hydrogen evolution and the number of electrons taking part in the photocurrent generation was the same within experimental errors. the subsequent modification of carbon nitride with cobalt oxide changed the electronic properties of the semiconductor, improved the target characteristics of the photocatalytic and photovoltaic phenomena; the q1’ parameter was also changed. figure 2 parameters q1’ and q3’ calculated for the cu-containing photocatalysts described in [56]. figure 3 the catalytic activities, current densities, and parameters q1’ calculated for the titania-based photocatalysts discussed in [64]. https://doi.org/10.15826/chimtech.2023.10.2.03 chimica techno acta 2023, vol. 10(2), no. 202310203 review 15 of 21 doi: 10.15826/chimtech.2023.10.2.03 the illustration of the significant change in the parameter q1’ was the work [66] in which molybdenum phosphide (25 wt.%) was deposited on the surface of indium sulfide. it caused the increase in the rate of the photocatalytic hydrogen production from lactic acid, the photocurrent generation, and q1’ value by 160, 2.9, and 53 times, respectively. the same result was found for cds modified with 11 wt.% iron phosphide, where the co-catalyst addition led to the growth of the reaction rate, the photocurrent generation, and q1’ by 79, 14, and 5.7 times, respectively [67]. in [68] titania and the composite samples based on titania and cadmium sulfide were tested in 0.5 m na2s/na2so3. the composite photocatalysts were more active under visible light than pristine titania or cadmium sulfide due to the heterojunction formation. perhaps, the heterojunctions changed the number of electrons taking part in the photocatalytic reaction and photocurrent generation, and its ratio defined by q1’. in [69] reduced graphene oxide deposited on la2ti2o7, la2ti2o7 deposited on nickel-iron-double layered hydroxides, the composite material consisting of graphene oxide, nickel-iron-double layered hydroxides, and la2ti2o7. figure 4 reveals that as for cds/tio2, the reaction rates, the current density, and q1’ differed for the composite photocatalysts. thus, in the case of combining materials of different composition, the parameter q1’ can either preserve the constant value of the pristine material or change. probably, the specific values of the parameter are related to the balance of various rate constants that described the processes of electron-hole generation, their transfer and recombination. generally, the condition of physical similarity is not met for the catalysts having different chemical nature. however, in several cases, we can talk about partial similarity. doping. the authors [70] studied the doping of cadmium sulfide with molybdenum. the introduction of 25 wt.% of mos2 led to an increase in the reaction rate and the photocurrent generation, while the ratio of the number of electrons used for the photocatalytic hydrogen evolution to the number of electrons taking part in the photoelectrochemical processes was the same. the introduction of al to zinc oxide (up to 5 wt.%) improved the target characteristics, while the q1’ criteria were the same within experimental error [71] as shown in figure 5. the researchers studied doped graphitic carbon nitride. in [72] phosphorous was used as the dopant; its introduction in the structure allowed improving the target characteristics; however, the ratio of electrons did not remain constant and grew during the doping. probably, this behavior was related to reaction rate constants of the processes occurring when p was introduced into the electronic structure of carbon nitride. the authors [73] discussed carbon nitride doped by b and cs simultaneously for different forms such as nanoparticles and nanosheets. it should be noted that the introduction of these elements into the structure allowed improving both the photocatalytic and photovoltaic characteristics of the materials. however, figure 6 shows that the ratio of the number of electrons used to the photocatalytic hydrogen evolution to the number of electrons taking part in the photoelectrochemical processes was the same for the nanoparticles and differed for the nanosheets. figure 4 the catalytic activities, current densities, and parameters q1’ calculated for the lto-based samples mentioned in [69]. figure 5 the q1’ parameter calculated for the al-doped zno samples described in [71]. figure 6 the q1’ parameter calculated for the samples based on carbon nitride (gcn) discussed in [73]. ns denotes nanosheets. https://doi.org/10.15826/chimtech.2023.10.2.03 chimica techno acta 2023, vol. 10(2), no. 202310203 review 16 of 21 doi: 10.15826/chimtech.2023.10.2.03 in [74] the effect of benzoquinone on the target characteristics of carbon nitride obtained by crosslinking polymer chains of carbon nitride was described. in this case, the change in the electronic properties was similar to ones occurring during doping because the additional impurity level was formed in the electronic structure, which improved charge separation. the appearance of this level contributed to the increase in the reaction rate and photocurrent generation by a factor of 2.3 while the q1’ was the same and equaled 8 [74]. thus, in the case of doping, the parameter q1' can both keep constant during the transition between samples and change. 3.3. samples in which weight ratios of components were changed table 6 contains the data obtained for the samples during whose preparation the weight ratio of components or reaction time were changed. this case was considered on the example of ten series of samples with different chemical nature. in [62] the composite photocatalysts based on cobalt phosphide deposited on the silica surface for different time periods (the time in hours is written in the sample label in table 6) with subsequent deposition of red phosphorous were studied. the ratio of electron amount used in the target processes was the same and equaled ~40 for all samples. in the case of the samples based on cadmium sulfide and molybdenum sulfide [75], the same result was found; increasing mos2 amount from 6 to 25 wt.% led to the halving of the photocatalytic hydrogen production rate and the photocurrent density, while the q1’ criterion remained constant. the authors [76] discussed the composite photocatalysts consisting of lanthanum vanadate and graphitic carbon nitride; the photocatalytic and photovoltaic properties were studied for samples with w(lavo4) from 0 to 25%. the changes in the target properties had a bell-shaped character, while their ratio was the same within the experimental error. for the sample with 25 wt.% lavo4, a slight decrease in this parameter was observed. possibly, it was related to the change in the geometric structure of the catalyst. the excess (relative to the optimal) content of lanthanum vanadate was associated with the location of particles that block the photocatalyst’s active centers. during the transition between catalysts of different geometric structures, the conditions of geometric and/or physical similarity were violated, as a result of which the potential similarity criteria, as seen in figure 7, will not be preserved. in [69] the composite photocatalysts based on znin2s4 and snin4s8 were described. the dependences of the hydrogen production rate and the photocurrent density on the catalyst composition went through a maximum. the ratio of the electron number used in the target processes remained the same for the transition from one sample to another and was 300–400 within experimental error. another situation was found for cds whose surface was modified with titanium carbide (figure 8) [77]. the dependences of the reaction rate and the current density on the titanium carbide content was domed, the maximum values were observed for 15 wt.% of titanium carbide. however, the q1’ criteria were the same values within experimental error for the samples with 15% ti3c2 (q1’ ~ 0.16) and greater than 15% ti3c2 (q1’ ~ 0.28). such difference may be due to the textural characteristics of the samples or the number of interfacial contacts; the increase in the ti3c2 content led to the growth of the interfacial contacts and the surface area. after achieving the optimal structure of cds@ti3c2-15, the number of contacts between titanium carbide and cadmium sulfide decreased, and the surface area and pore volume also declined. thus, in this case, the appearance of two groups of samples with different similarity criteria was connected with the change in their geometric structure; the theory of similarity within each group was fulfilled. in [47] the photocatalysts based on the solid solution of cadmium sulfide and cadmium selenide with deposited cobalt selenide were studied. as for other deposited photocatalysts, the dependences of the hydrogen production rate and the photocurrent density on the co-catalyst content had a wide peak shape, as shown in figure 9. figure 7 the q1’ parameter calculated for the photocatalysts lavo4/cds with different lavo4 content (based on data described in [76]). figure 8 the dependence of q1’ on the co-catalyst content for the composites cds@ti3c2 discussed in [77]. https://doi.org/10.15826/chimtech.2023.10.2.03 chimica techno acta 2023, vol. 10(2), no. 202310203 review 17 of 21 doi: 10.15826/chimtech.2023.10.2.03 the ratio of the target characteristics denoted as q1’ was the same within experimental error for all samples, excluding one with 1% cose2. unfortunately, it was difficult to determine the reasons for such deviation due to the lack of information about the texture and structure of the mentioned sample. in [78] the defect-containing titania prepared by the hydrothermal treatment at 3–6 h was studied. the hydrothermal treatment allowed obtaining the samples with oxygen vacancies whose amount impacted the hydrogen production and the photocurrent generation. the ratio of the electros taking part in the target processes was the same for all samples. the q1’ criterion may serve as the similarity criterion in case of the composite materials based on graphitic carbon nitride doped by p and titanium carbide; the catalyst components were mixed at different time [72]. in [79] cds with deposited nis was described, and the crystallization time of cds was varied. figure 10 showed that for this set of samples the q1’ value remained constant, excluding the first sample. this was probably due to the low crystallization time and the resulting deviations in the structure of the catalyst in relation to other samples. another way of changing the synthesis conditions, indirectly related to the change in the mass ratios of the catalyst components, was the variation of the solvent composition during the synthesis [68]. the number of electrons occurring in the photocatalytic hydrogen production divided by the number of electrons taking part in the photocurrent generation was the same for transition between the samples in this set. to sum up, if the conditions of geometric and physical similarity are fulfilled, the parameter q1’ revealing the ratio of electrons taking part in the target processes can act as the similarity criterion revealing the relation between the efficiencies of the photocatalytic hydrogen production and the photocurrent generation for different samples. 3.4. studying photocatalytic and photovoltaic properties in different electrolytes table 7 showed the data obtained over samples in different electrolytes [80, 81]. unfortunately, little attention has been paid to the study of this issue in the literature. in [80] the authors described photocatalytic processes of the solid solution of copper oxide, iron oxide, and manganese oxide in aqueous solutions of sodium sulfide, sodium sulfite, and oxalic acid. for comparison, the photocurrent generation was carried out in 0.1 m na2so4 solution. in case of inorganic salts, the dependence of hydrogen production rate on the solid solution composition went through a maximum, while for the photocurrent generation this dependence went through a minimum. in case of oxalic acid, the reaction rate increased for the discussed samples. this behavior of the target characteristics was connected with electrolyte nature and different transformations in various media. so, it was difficult to identify any features for the ratio of electrons taking part in target processes. figure 9 the dependences of target values and q1’ on the cose2 content for the photocatalysts cose2/cds0.95se0.05 described in [47]. figure 10 the dependence of q1’ on the mixturing time of cds suspension obtained for nis/cds samples discussed in [79]. the q1’ criterion did not remain the same for transition between different solutions and catalysts.the solutions of distinct nature or concentration possessed different properties such as dielectric constant, density, viscosity, etc., that impacted the charge transfer and current generation. therefore, the condition of physical similarity of the discussed systems was not fulfilled; the transition between different solutions for the same sample cannot be considered using the similarity theory. the same conclusion may be made based on the results described in [81]. in that paper the photocatalytic and photovoltaic properties were studied in 20 vol.% c2h5oh, 0.1 m naoh, 0.1 m na2s, 0.1 m na2s + 0.1 m na2so3. as in the previous case, the features of the photocatalytic hydrogen production and photocurrent generation were different in various media. figures 11 and 12 reveal that when the ratio of salts in the solution varied, the dependences of the target characteristics on the composition of the electrolyte remained at a qualitative level. however, the q1’ criterion changed from 7 to 17 and from 2 to 8 for cd0.8zn0.2s and 1% cus/cd0.8zn0.2s, respectively. thus, in terms of the similarity theory, consideration of the question of transferring the dependence of photocatalytic hydrogen production on photovoltaic parameters was incorrect. https://doi.org/10.15826/chimtech.2023.10.2.03 chimica techno acta 2023, vol. 10(2), no. 202310203 review 18 of 21 doi: 10.15826/chimtech.2023.10.2.03 figure 11 the dependence of the target characteristics of cd0.8zn0.2s measured in na2s/na2so3 [81]. the electrolyte composition was labeled as a/b, where a is the concentration of na2s, m, b is the concentration of na2so3, m. figure 12 the dependence of the target characteristics of 1% cus/cd0.8zn0.2s measured in na2s/na2so3 [81]. the electrolyte composition was labeled as a/b, where a is the concentration of na2s, m, b is the concentration of na2so3, m. 4. limitations the topic of the transfer from the photocatalytic reaction to the photocurrent generation has some promising research directions such as the calculation and verification q2 and q4, getting more information about rate constants and interpretation of the criterion values, discussing other photocatalytic reactions besides hydrogen production, etc. 5. conclusions the photocatalytic hydrogen production and photocurrent generation in the photoelectrochemical cell are analogous phenomena; so, one can use the similarity theory for their description. using dimension theory, two parameters which could potentially act as the similarity criteria revealing relation between efficiencies of the photocatalytic hydrogen evolution and the photocurrent generation were obtained. the first parameter is the ratio of the number of electrons involved in the photocatalytic hydrogen production to the number of electrons taking part in the photocurrent generation. the latter value takes into account the energy aspects of converting light energy into chemical bond and electrical energy. the analysis of the literature data allowed verifying the first criterion and showed that the ratio of the number of electrons did act as a similarity criterion if the conditions of geometric and physical similarity were fulfilled. in practice, this means that the ratio between the quantitative indicators of the photocatalytic hydrogen production and photocurrent generation remained constant in the case of the same chemical nature of the samples, for example, in the set with different ratios of the catalyst components, with the same morphology and texture, or in the case of the solid solutions formation with a similar composition. generally, if the photocatalyst modification by chemical compounds changes the physicochemical properties of samples, such cases, as well as data analysis in various media, cannot be considered in the similarity theory and should be studied individually. ● supplementary materials no supplementary materials are available. ● funding this work was supported by the ministry of science and higher education of the russian federation within the governmental order for boreskov institute of catalysis, project no. aaaa-a21-121011390009-1. ● acknowledgments none. ● author contributions conceptualization: e.a.k., d.v.m. data curation: d.v.m. formal analysis: d.v.m. funding acquisition: e.a.k. investigation: d.v.m. methodology: d.v.m. project administration: e.a.k. resources: e.a.k. software: e.a.k. supervision: e.a.k.,d.v.m. validation: d.v.m.,e.a.k. visualization: d.v.m. writing – original draft: d.v.m. writing – review & editing: e.a.k.,d.v.m. ● conflict of interest the authors declare no conflict of interest. https://doi.org/10.15826/chimtech.2023.10.2.03 chimica techno acta 2023, vol. 10(2), no. 202310203 review 19 of 21 doi: 10.15826/chimtech.2023.10.2.03 ● additional information author ids: dina v. markovskaya, scopus id 55895307200; ekaterina a. kozlova, scopus id 12244601300. website: boreskov institute of catalysis, https://catalysis.ru. references 1. turner ja. sustainable hydrogen production. sci. 2004;305(5686):972–974. doi:10.1126/science.1103197 2. fujishima a, honda k. electrochemical рhotolysis of water at a semiconductor electrode. nat. 1972;238:37–38. doi:10.1038/238037a0 3. vorontsov av, kozlova ea, besov as, kozlov dv, kiselev sa, safatov as. photocatalysis: light energy conversion for the oxidation, disinfection, and decomposition of water. kin cat. 2010;51(6):801–808. doi:10.1134/s0023158410060042 4. tomboc gm, gadisa bt, joo j, 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published by ural federal university 2022, vol. 9(2), no. 20229212 eissn 2411-1414; chimicatechnoacta.ru doi: 10.15826/chimtech.2022.9.2.12 1 of 12 synthesis and evaluation of cerebroprotective activity of novel 6,7-dimethoxyquinazolin-4(3h)-one derivatives containing residues of amino acids and dipeptides alexey s. chiriapkin * , ivan p. kodonidi , dmitry i. pozdnyakov pyatigorsk medical and pharmaceutical institute, branch of volgograd state medical university, pyatigorsk 357532, russia * corresponding author: prk@pmedpharm.ru this paper belongs to a regular issue. © 2022, the authors. this article is published open access under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). abstract neurodegenerative processes of the central nervous system are an important socially significant problem of modern society. they cause many diseases, such as alzheimer's disease and cerebral ischemia, which significantly reduce the quality of human life and can lead to disability or death. the aim of this study was to synthesize novel 6,7-dimethoxyquinazolin-4(3h)-one derivatives with the remains of neuroactive amino acids and dipeptides in order to investigate their cerebroprotective properties. as a result of the study, 13 novel 6,7-dimethoxyquinazolin-4(3h)-one derivatives were synthesized. cerebral ischemia in rats was reproduced by irreversible right-sided occlusion of the middle cerebral artery using the tamura method, and the area of brain necrosis was evaluated. cognitive functions were evaluated in the y-maze test. among the studied quinazolinone derivatives, compounds 3i, 3j and 3k have the most pronounced cerebrotropic activity, which is not inferior to ethylmethylhydroxypyridine succinate in terms of pharmacological activity, making them promising objects for further research. keywords quinazolinones synthesis medicinal chemistry cerebroprotective activity ischemia amino acid dipeptide received: 15.05.22 revised: 10.06.22 accepted: 13.06.22 available online: 16.06.22 1. introduction disorders of the functioning of the central nervous system are an important socially significant problem of modern society. every year there is an increase in patients with various cognitive impairments, which defines the urgency of developing new methods of their treatment. the main causes of cognitive dysfunctions are vascular pathologies (cerebral ischemia [1]), neurodegenerative processes (such as in the case of alzheimer's disease) [2], traumatic brain injuries [3] and neuroinfections [4]. it is worth noting that disorders of cerebral circulation are the second most common cause of cognitive dysfunction after alzheimer's disease [5]. cerebral ischemia forms insufficient oxygen and glucose delivery for the metabolic processes of neurons, which leads to disruption of cellular homeostasis, oxidative stress, inflammation and death of brain cells [6]. vascular pathologies of the brain can provoke an ischemic stroke, which often leads the patient to disability or death. the cause of a stroke can also be an acute traumatic brain injury or a brain dysfunction. modern methods of treatment of ischemic and other pathological conditions of the human central nervous system include intravenous thrombolysis and the use of neuroprotective and anti-inflammatory drugs. despite this, in most patients with an unfavorable prognosis of the course of the disease, there is a malfunction and rapid death of brain cells [7]. based on this, an important task for pharmacy and medicine is the development of new highly effective and low-toxic drugs for the treatment of neurodegenerative processes. one of the most promising classes of organic compounds is quinazolinone derivatives, which have a diverse spectrum of biological activity. so, series of kojyl thioether conjugated to different quinazolinone derivatives were designed, synthesized, and evaluated for their inhibitory activity against mushroom tyrosinase. all derivatives displayed better potency than kojic acid as the positive control [8]. novel quinazolinone derivatives bear benzenesulfonamide moiety with variable heterocyclic tail. one of them showed antioxidant and hepatoprotective activities in irradiated mice [9]. novel iodinated quinazolinones bearing sulfonamide were synthesized. among them there is a compound that acts as a direct antioxidant by scavenging reactive oxygen species and inhibiting radiation-induced oxidative stress [10]. 3-aryl-8-methylquinazolin-4(3h)-ones have promising properties for drug development against keratitis and brain infection causing free-living amoeba, a. http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2022.9.2.12 mailto:prk@pmedpharm.ru http://creativecommons.org/licenses/by/4.0/ https://doi.org/10.1016/j.bmc.2021.116044 https://doi.org/10.1016/j.ejmech.2020.112333 https://www.sciencedirect.com/topics/chemistry/antioxidant-agent https://www.sciencedirect.com/topics/pharmacology-toxicology-and-pharmaceutical-science/keratitis https://orcid.org/0000-0001-8207-2953 https://orcid.org/0000-0003-1333-3472 https://orcid.org/0000-0002-5595-8182 https://crossmark.crossref.org/dialog/?doi=https://doi.org/10.15826/chimtech.2022.9.2.12&domain=pdf&date_stamp=2022-6-16 chimica techno acta 2022, vol. 9(2), no. 20229212 article 2 of 12 castellanii [11]. antimicrobial activity of substituted-6-methyl-1-thioxo-1,2-dihydro-3h-furo[3,2-g]pyrimido[1,6a]quinazolin-3-ones was evaluated against gram-positive, gram-negative bacteria and fungi. furothiazolo pyrimido quinazolines displayed results excellent for growth inhibition of bacteria and fungi [12]. most of the different substituted quinazolinones exhibited moderate to high anticonvulsant activity in all seizure models with no symptoms of neurotoxicity and hepatotoxicity [13]. there are data indicating the ability of some quinazolinone inhibit activity of the urease [14]. novel quinazolinones conjugated with indole acetamide, ibuprofen or thioacetohydrazide were designed to increase cyclooxygenase-2 (cox-2) selectivity. the three synthesized series exhibited superior cox-2 selectivity compared with the previously reported quinazolinones and their nonsteroidal anti-inflammatory drug analogue and had equipotent cox-2 selectivity as celecoxib [15]. some novel compounds of allyl/benzyl quinazolinone displayed remarkable anti-inflammatory activity as compared to diclofenac sodium [16]. also, different 2,7-disubstituted[1,3,4]-tiadiazolov[2,3b]quinazolin-5(4h)-ones were synthesized, and they showed good anti-inflammatory activity [17]. various 2-(3aryl-1h-pyrazol-1-yl)benzo[d]thiazole incorporated fused thiazolo[2,3-b]quinazolinones exhibited prominent anticancer and antibacterial activities. the potent compounds could serve as templates for further development of anticancer and antibacterial drugs [18]. a series of novel quinazoline derivatives were synthesized and evaluated for their anticonvulsant activity against electrically and chemically induced seizures, compared with that of the standard drugs methaqualone and sodium valproate [19]. a novel series of 4-anilinoquinazoline analogues, dw (1–10), were evaluated for anticancer efficacy in human breast cancer (bt-20) and human colorectal cancer cell lines (hct116, ht29, and sw620). dw8 may represent a suitable lead for developing novel compounds to treat the human colorectal cancer [20]. the preparation and screening of the focused libraries of 4-anilinoquinolines and 4-anilinoquinazolines for antiviral activity allowed identifying three potent compounds. n-(2,5-dimethoxyphenyl)-6(trifluoromethyl)quinolin-4-amine effectively inhibited dengue virus infection, and n-(3,4-dichlorophenyl)-6-(trifluoromethyl)quinolin-4-amine and n-(3-ethynyl-4-fluorophenyl)-6,7-dimethoxyquinazolin-4-amine successfully inhibited venezuelan equine encephalitis virus. these results provide a prospect of developing a clinical compound against these emerging viral threats [21]. a series of novel histone deacetylase inhibitors using a substituted quinazoline was designed and synthesized as the capping group, attaching 3, 5-dimethyl pentyl as a potential metabolic site protector. one of representatives was proposed as an oral histone deacetylase inhibitor with a potential capacity of treating breast cancer [22]. there is evidence indicating that novel 1,2,3-triazole-quinazolines can be used as antiproliferative agents displaying the extracellular signal-regulated kinase inhibitory activity [23]. approximately 150 different 6,7-dimethoxyquinazoline-2,4-diamines were synthesized, and via structure-activity relationship studies. among them 6,7-dimethoxy-n4-(1-phenylethyl)-2-(pyrrolidin-1-yl)quinazo-lin-4-amine exhibits high antimalarial activity as a promising antimalarial drug lead [24]. two new series of synthesized quinazolinone derivatives were investigated as potential future antileishmanial agents, by assessing their activities against the leishmania (l.) donovani and l. major species. the two compounds that were found the most active are the mono quinazolinone and the bisquinazolinone with growth inhibitory efficacies of 35% and 29% for the l. major and l. donovani, respectively [25]. based on quinazolin-4(3h)-one derivatives, a series of new dual-target inhibitors of poly (adp-ribose) polymerase-1 (parp 1) and bromodomain containing protein 4 (brd4) were successfully synthesized. among them are compounds that would be promising for the treatment of breast cancer [26]. as a result of the structural modification of the molecular-targeted agent sorafenib, a series of quinazolinyl-arylurea derivatives were synthesized and evaluated for their anti-proliferative activities against six human cancer cell lines. n-(3,4-dichlorophenyl)-n’-(3((quinazolin-4-ylamino)methyl)phenyl)urea could trigger three different cell death forms including apoptosis, ferroptosis and autophagy. this compound could be a promising lead for molecular-targeted anti-bladder cancer agents discovery [27]. thus, quinazoline derivatives are promising compounds for the search for biologically active substances, including those with neuroprotective properties. the most commonly used amino acid for the treatment of diseases of the central nervous system is glycine, acute ischemic stroke [28]. also, in case of brain disorders, gamma-aminobutyric acid and its cyclic derivatives – racetams are actively used [29]. the scientific literature presents the results of studies that indicate high cerebroprotective properties of a number of low-molecular-weight peptides. so, the novel 14-amino acid peptide, with stressprotein-like sequences exhibiting neuroprotection at unprecedented concentrations was revealed. this peptide prevented neuronal cell death associated with the envelope protein (gp 120) from human immunodeficiency virus, with excitotoxicity (n-methyl d-aspartate), with the beta amyloid peptide (putative cytotoxin in alzheimer's disease), and with tetrodotoxin (electrical blockade) [30]. it was found that lipophilic peptide fragments offer bioavailability and stability, providing lead compounds for drug design against neurodegenerative diseases [31]. cationic arginine-rich peptides (carps) are an expanding and relatively novel class of compounds possessing intrinsic neuroprotective properties [32]. the neuroprotective efficacy of different modifications to the poly-arginine-9 peptide (r9) was examined [33]. the new synthetic peptide, cmx-9236, can function as a neuroprotective agent and an activator of a https://doi.org/10.1016/j.ejmech.2019.111575 https://doi.org/10.1080/00397911.2018.1490433 https://doi.org/10.1080/14756366.2021.1956912 https://doi.org/10.1016/j.jics.2021.100033 https://doi.org/10.1039/c6ra01284a https://doi.org/10.1073/pnas.96.7.4143 https://doi.org/10.3389/fneur.2020.00108 chimica techno acta 2022, vol. 9(2), no. 20229212 article 3 of 12 beneficial signal transduction pathway in in vitro and in vivo models of cerebral ischemia [34]. 2. experimental 2.1. chemistry all chemicals were acquired from sigma-aldrich (sigmaaldrich, st. louis, mo, usa), carl roth (carl roth, karlsruhe, germany) and merck chemicals (merckkgaa, darmstadt, germany). melting points (m.p.) were recorded using the pmp-m1 melting point apparatus (himlaborpribor, klin, russia). all reactions were monitored by thin-layer chromatography (tlc) using silica gel 60 f254 tlc plates (merck, darmstadt, germany). spectroscopic data were registered with the following instruments: ir, ir-fourier fsm 1201 spectrophotometer (spectrum, moscow, russia); uv, sf-2000 device (spectrum, moscow, russia); 1h nmr and 13c nmr, bruker avance iii 400 мhz spectrometer (bruker, germany) in dmso-d6 using tetramethylsilane as the internal standard. coupling constant (j) values were measured in hertz (hz) and spin multiplets are given as follows: s (singlet), d (double), t (triplete), q (quartet), m (multiplet). 2.1.1. general procedure for synthesis of amides of 2amino-4,5-dimethoxybenzoic acid (3, 4) 0.05 mol of the acetyl chloride or benzoyl chloride was slowly added to a solution of 9.85 g (0.05 mol) of 2-amino4,5-dimethoxybenzoic acid (2) in 35 ml of 10% sodium hydroxide with stirring. as a result, a precipitate was formed, which was filtered and washed with water. purification of the obtained substances is carried out by recrystallization from ethyl alcohol. 2.1.2. general procedure for synthesis of 2-alkyl-6,7-dimethoxy-3,1-benzoxazine-4-ones (2a–2e) 5.91 g (0.03 mol) of 2-amino-4,5-dimethoxybenzoic acid was dissolved at boiling in 25 ml of the corresponding anhydride and the reaction was carried out for 5 hours. in the case of 2d-2e compounds, the reaction was carried out in a similar way, and 0.03 mol of amides of 2-amino-4,5-dimethoxybenzoic acid (3 and 4) were used as starting substances. the reaction mixture was kept in the refrigerator for a day; the resulting precipitate was filtered and washed with water. the product was purified by recrystallization from ethyl alcohol. 2.1.3. general procedure for synthesis of 6,7-dimethoxyquinazolin-4(3h)-one derivatives containing residues of amino acids and dipeptides (3a–3m) a mixture of 0.01 mole of the corresponding 2-alkyl-6,7-dimethoxy-3,1-benzoxazine-4-one (2a–2e) and 0.01 mole of amino acid or dipeptide was dissolved at boiling in 10-15 ml of glacial acetic acid. next, 0.5 ml of dmf was added and the reaction was carried out with stirring for 1.5 hours. the reaction mixture was kept in the refrigerator for a day; the resulting precipitate was filtered and washed with water. the product was purified by recrystallization from ethyl alcohol. 2.2. pharmacological study 2.2.1. animals the study was performed on 96 mature male wistar rats. the animals were obtained from the laboratory animal nursery "rappolovo" (leningrad region) and for the duration of the experiment were kept in a vivarium, 6 individuals per cage at an air temperature of 20±2 0c, relative humidity of 60±5% and a twelve-hour daily cycle (12 hours day/12 hours night). until the moment of inclusion in the work, the rats were kept in a quarantine room for 2 weeks. animals received a complete dry food diet (granulated food) and water ad libitum. the design of the study and the manipulations performed with the animals were in accordance with the international ethical principles of working with laboratory animals, as set out in the arrive 2.0 guidelines [35]. 2.2.2. cerebral ischemia model cerebral ischemia in rats was reproduced by irreversible right-sided occlusion of the middle cerebral artery according to a tamura, 1981. animals were anesthetized by intraperitoneal injection of chloral hydrate at a dose of 350 mg/kg, the area below and to the right of the eye was depilated, the skin and soft tissues were dissected. next, a burr hole was made over the intersection of the artery with the olfactory tract, then the artery was coagulated by an electrocoagulator. the soft tissue topography was restored, the wound was sutured. the suture was treated with 10% povidone-iodine [36]. 2.2.3. study design the cerebroprotective activity of the tested substances was evaluated during therapeutic administration. when setting up the study, the following experimental groups were distinguished: so – sham-operated animals, to which all sequential procedures were applied with the exception of the coagulation of the middle cerebral artery; nc – a group of rats with cerebral ischemia, but without pharmacological correction (during the experiment, this group of animals received purified water); a group of rats that were treated by the reference drug and groups of rats that received the test substances. a total of 16 groups of 6 individuals each were formed. ethylmethylhydroxypyridine succinate (emhps, «mexidol», farmasoft, russia) was used as a reference drug at a dose of 100 mg/kg, orally [37]. the test compounds were administered at a screening dose of 40 mg/kg orally. the reference and tested compounds were administered 30 min after ischemia modeling and then for 72 h (one administration per day). on the 4th day of the experiment, the changes of cognitive functions of rats in the y-maze test were evaluated. after that, the animals were decapitated under anesthesia and the brain was removed, in which the change in the volume of necrotic tissue was assessed. chimica techno acta 2022, vol. 9(2), no. 20229212 article 4 of 12 2.2.4. y-maze test the setup consisted of three equal arms connected at an angle of 1200. the animal was placed in the center of the setup, and the number of animal movements between the arms was recorded for 8 minutes. at the same time, spontaneous alternating entries into the arms (1–2–3, 3–1–2, 2–3–1) were recorded. based on the data obtained, the percentage of spontaneous alternation was determined (formula (1)), which reflects the change in the cognitive abilities of animals [38]: percentage of spontaneous alternation = number of alternating entries into the arms total number of movements 100 (1) 2.2.5. brane necrosis zone determination the size of the necrosis zone was determined by the change in the color intensity of triphenyltetrazolium chloride. the course of determination was as follows: after decapitation of the animals, the brain was removed, the cerebellum was cut off and the hemispheres were separated along the central sulcus. both hemispheres were weighed, then individually homogenized and placed in weighing bottles. to the homogenate was added 10 ml of a 1% solution of triphenyltetrazolium chloride in phosphate buffer (ph 7.4). the bottles were incubated in a water bath at 37 °c for 20 min. after that, the samples were centrifuged at 5000 rpm/10 min, and the supernatant was removed. 3 ml of phosphate buffer and 3 ml of cold chloroform were added to the precipitate. the mixture was shaken for 2 min and then incubated for 15 min at 4 °c, shaking every 5 min for 30 s, re-centrifuged in the same mode, and its optical density was measured against pure chloroform at 492 nm. the calculation of the necrosis zone was performed according to the formula (2) and expressed as a percentage of the total mass of the hemispheres: 𝑥 = 100 − 𝜀1𝑀1 + 𝜀2𝑀2 𝜀1(𝑀1 + 𝑀2) ∙ 100, (2) where x is the size of the necrosis zone as a percentage of the total brain mass; ε1 is the optical density of the sample with an undamaged hemisphere; ε2 is the optical density of the sample with the damaged hemisphere; m1 is the mass of the undamaged hemisphere; m2 is the mass of the damaged hemisphere. 2.2.6. statistical analysis statistical processing of the obtained results was carried out using the software package statistica 6.0 (statsoft, usa). the data were expressed as m (mean) ± sem (standard error of mean). the gaussian distribution was tested by the shapiro-wilk test. the homogeneity of the variance was assessed in the levene test. one-way analysis of variance (anova) with post-processing by tukey’s test (in the presence of a gaussian distribution) or kruskal wallis (in the absence of gaussian distribution), carried out by the comparison of groups. the critical level of significance was taken as p<0.05. 3. results and discussion 3.1. synthesis a convenient way to synthesize 6,7-dimethoxyquinazoline4(3h)-one is the replacement of the oxygen heteroatom with nitrogen in the intermediate 2-methyl-6,7-dimethoxy3,1-benzoxazine-4-one (scheme 1), which was previously developed with the staff of the research-scientific institute of physical & organic chemistry of rostov university of southern federal university. a new modification of the synthesis was proposed based on the interaction of nitrohomoveratric acid (1) and polyphosphoric acid – ppa (2) with subsequent treatment of the reaction mixture with a small amount of acetic anhydride, which leads to the formation of 2-methyl-6,7-dimethoxy-3,1-benzoxazine-4-one (2d) through the intermediate 2-acetamido-4,5-dimethoxybenzoic acid (3) [39]. however, the yield of 2-methyl-6,7-dimethoxy-3,1-benzoxazine-4-one products is low, because a redox reaction of disproportionation occurs at the first stage of obtaining 2-acetamido-4,5-dimethoxybenzoic acid. another negative factor in obtaining the intermediate 2-methyl-6,7-dimethoxy-3,1-benzoxazine-4-one is the use of acetic anhydride, which is a controlled substance (narcotic drugs, psychotropic substances and their precursors, controlled in the russian federation), and this complicates the possibility of developing laboratory regulations for the synthesis of an active pharmaceutical substance. ac 2 oac2o 1 2 3 2d ppa scheme 1 synthesis of 2-methyl-6,7-dimethoxy-3,1-benzoxazine-4-one using acetic anhydride. chimica techno acta 2022, vol. 9(2), no. 20229212 article 5 of 12 based on this, for the synthesis of 2-substituted ethyl, propionyl and isopropionyl 6,7-dimethoxy-3,1-benzoxazine-4-one, an acylation process with further heterocyclization should be used (scheme 2). this process proceeds by boiling dimethoxyanthronylic acid in the corresponding anhydride without the release of intermediate amides of dimethoxyanthranylic acid, which leads to the formation of intermediate 2-ethyl, 2-propyl and 2-isopropyl-6,7-dimethoxy-3,1-benzoxazine-4-one. at the first stage of synthesis, 2-amino-4,5-dimethoxybenzoic acid is heated in excess of propionic, butyric and isobutyric anhydride. as a result, 2-ethyl-6,7-dimethoxy-3,1-benzoxazine-4-one (2a), 2-propyl-6,7-dimethoxy-3,1-benzoxazine-4-one (2b) and 2-isopropyl-6,7-dimethoxy-3,1-benzoxazine-4-one (2c) were obtained with yields of 90%, 84% and 75%, respectively. according to the yield of 2-substituted 6,7-dimethoxy3,1-benzoxazine-4-one, the reactivity decreases with the elongation of the carbon chain and even more so with an increase in the branching of anhydrides. next, the heteroatom was replaced with nitrogen by the interaction of the corresponding benzoxazinone with amino acids or dipeptides. compounds 1c-10c were obtained by replacing the oxygen of the heterocycle with nitrogen by the interaction of the corresponding 6,7-dimethoxy-3,1-benzoxazine-4-one derivatives with glycine, glycylglycine, glycylleucine and glycyltryptophan in the medium of glacial acetic acid with the addition of 0.5 ml of dimethylformamide. at the same time, it is advisable to synthesize 2-methyl and 2-phenyl-6,7-dimethoxyquinazoline-4(3h)-ones (3k– 3m) through amides of 2-amino-4,5-dimethoxybenzoic acid (3 and 4), which in turn was synthesized by acylation of dimethoxyanthranilic acid (2) by acetyl chloride or benzoyl chloride (scheme 3). 2a; r 1 = -c 2 h 5 2b; r 1 = -c 3 h 7 2c; r 1 = -ch(ch 3 ) 2 3e; r 1 = -c 3 h 7 , r 2 = -ch 2 -cooh 3f; r 1 = -c 3 h 7 , r 2 = -ch 2 -c(o)-nh-ch 2 -cooh 3i; r 1 = -ch(ch 3 ) 2 , r 2 = -ch 2 -c(o)-nh-ch 2 -cooh 3j; r1 = -ch(ch3)2, r2 = 3a-3j nh 2 -r 2 3g; r 1 = -c 3 h 7 , r 2 = acoh, dmf 3h; r 1 = -c 3 h 7 , r 2 = (r 1 o) 2 o 3a; r 1 = -c 2 h 5 , r 2 = -ch 2 -cooh 3b; r 1 = -c 2 h 5 , r 2 = -ch 2 -c(o)-nh-ch 2 -cooh 3c; r 1 = -c 2 h 5 , r 2 = 3d; r 1 = -c 2 h 5 , r 2 = r 1 r 2 r 1 2 scheme 2 synthesis of 3a–3j. r 1 r 1r1 r 2 nh 2 -r 2 r 1 ocl naoh 10% acoh, dmf (eto) 2 o 3k; r 1 = -ch 3 ; r 2 = -ch 2 cooh 3l; r 1 = ph; r 2 = -ch 2 cooh 3m; r 1 = ph; r 2 = -c 2 h 4 cooh 3; r 1 = -ch 3 4; r 1 = ph 2d; r 1 = -ch 3 2e; r 1 = ph 2 scheme 3 synthesis of 3k–3m. chimica techno acta 2022, vol. 9(2), no. 20229212 article 6 of 12 the 2-methyl-6,7-dimethoxy-3,1-benzoxazine-4-one and 2-phenyl-6,7-dimethoxy-3,1-benzoxazine-4-one were obtained by two-stage synthesis. at the first stage, 2-acetamido-4,5-dimethoxybenzoic acid was obtained by interaction in an alkaline medium by adding the acetyl chloride by drop while stirring. according to the method of the schotten–baumann acylation reaction, the ph of the medium should be controlled so that it remains alkaline. further, the formation of the core of 3,1-benzoxazine-4-one was carried out by boiling 2-acetamido-4,5-dimethoxybenzoic acid in excess of propionic anhydride. the preparation of 2-phenyl-6,7-dimethoxy-3,1-benzoxazine-4-one was carried out in a similar way using benzoyl chloride. the substances 3k–3m were obtained by replacing oxygen with nitrogen in 3,1-benzoxazine-4-one by the interaction of the corresponding benzoxazinones with glycine or β-alanine in the medium of glacial acetic acid in the presence of catalytic amounts of dmf (scheme 3). the mechanism of formation of 6,7-dimethoxyquinazoline-4(3h)-one derivatives can be represented through the formation of an intermediate carbocation (scheme 4). possible ways of protonation of the initial 2-phenylbenzoxazine4-one (i) were previously considered; the most reliable variant of the reaction involves protonation of the oxygen heteroatom (ii), leading to a more stable carbocation (iii). the attack by the carbocation amine reagent leads to the formation of another cation (iv), which further cleaves off the proton (v). deprotonation preceding cyclization allows the formation of an intermediate adduct that cleaves off water molecules with the formation of a heterocycle (vi). 3.1.1. 2-acetamido-4,5-dimethoxy-benzoic acid (3) the grey crystals were obtained. yield: 77%. m.p.: 136– 137 °c. uv spectrum (ethanol), λmax, nm: 231, 261, 324. ir spectrum (kbr), ν, cm–1: 3487 (oh), 3375 (nh), 16567 (c=o), 1624 (c=o), 999 (c–o). 3.1.2. 2-benzamido-4,5-dimethoxy-benzoic acid (4) the grey crystals were obtained. yield: 91%. m.p.: 237– 238 °c. uv spectrum (ethanol), λmax, nm: 202, 242, 308. ir spectrum (kbr), ν, cm–1: 3450 (oh), 3157 (nh), 1676 (c=o), 1649 (c=o), 995 (c–o). 3.1.3. 2-ethyl-6,7-dimethoxy-3,1-benzoxazine-4-one (2a) the white amorphous substance was obtained. yield: 90%. m.p.: 142–143 °c. uv spectrum (ethanol), λmax, nm: 242, 275. ir spectrum (kbr), ν, cm–1: 1736 (c=o), 1026 (c–o). 1h nmr spectrum (400 mhz, dmso-d6), δ, ppm: 1.23 (t, j = 7.5 hz, 3h, ch3), 2.67 (q, j = 7.4 hz, 2h, ch2), 3.87 (s, 3h, ch3), 3.92 (s, 3h, ch3), 7.07 (s, 1h, arh), 7.37 (s, 1h, arh). 3.1.4. 2-propyl-6,7-dimethoxy-3,1-benzoxazine-4-one (2b) the white amorphous substance was obtained. yield: 84%. m.p.: 184–185 °c. uv spectrum (ethanol), λmax, nm: 238, 271. ir spectrum (kbr), ν, cm–1: 1742 (c=o), 1018 (c–o). 1h nmr spectrum (400 mhz, dmso-d6), δ, ppm: 0.93 (t, j = 7.4 hz, 3h, ch3), 1.71–1.57 (m, 2h, ch2), 2.35 (t, j = 7.3 hz, 2h, ch2), 3.76 (s, 3h, ch3), 3.81 (s, 3h. ch3), 7.42 (s, 1h, arh), 8.33 (s, 1h, arh). 13c nmr spectrum (100,6 mhz, dmso-d6), δ, ppm: 14.00, 18.74, 55.96, 55.99, 103.43, 107.59, 113.13, 137.42, 143.74, 153.61, 169.83, 171.46. 3.1.5. 2-isopropyl-6,7-dimethoxy-3,1-benzoxazine-4-one (2c) the white amorphous substance was obtained. yield: 75%. m.p.: 214–215 °c. uv spectrum (ethanol), λmax, nm: 237, 271. ir spectrum (kbr), ν, cm–1: 1740 (c=o), 1012 (c–o). 1h nmr spectrum (400 mhz, dmso-d6), δ, ppm: 1.17 (dd, j = 6.9, 1.0 hz, 6h, ch3), 2.56 (qd, j = 6.9, 1.1 hz, 1h, ch), 3.76 (s, 3h, ch3), 3.81 (s, 3h, ch3), 7.43 (d, j = 1.0 hz, 1h, arh), 8.35 (d, j = 1.1 hz, 1h, arh). 13c nmr spectrum (100,6 mhz, dmso-d6), δ, ppm: 19.74, 36.95, 55.95, 55.99, 103.39, 107.61, 113.13, 137.57, 143.73. 153.64, 169.93, 175.33. 3.1.6. 2-methyl-6,7-dimethoxy-3,1-benzoxazine-4-one (2d) the white amorphous substance was obtained. yield: 86%. m.p.: 226–227 °c. uv spectrum (ethanol), λmax, nm: 236, 271. ir spectrum (kbr), ν, cm–1: 1734 (c=o), 1024 (c–o). 1h nmr spectrum (400 mhz, dmso-d6), δ, ppm: 1.12 (t, j = 7.5 hz, 3h, ch3), 3.78 (d, j = 20.3 hz, 6h, ch3), 7.42 (s, 1h, arh), 8.33 (s, 1h, arh). r 1 r 2 r 1 + nh 2 -r 2 r 1 r 1 r 1 r 2r2r1 -h 2 o + h+ v iii -h+ ivvi i ii scheme 4 mechanism of formation of target 6,7-dimethoxykinazoline-4(3h)-one derivatives. chimica techno acta 2022, vol. 9(2), no. 20229212 article 7 of 12 3.1.7. 2-phenyl-6,7-dimethoxy-3,1-benzoxazine-4-one (2e) the white amorphous substance was obtained. yield: 96%. m.p.: 194–195 °c. uv spectrum (ethanol), λmax, nm: 202, 225, 263, 320. ir spectrum (kbr), ν, cm-1: 1740 (c=o), 1019 (c–o). 1h nmr spectrum (400 mhz, dmso-d6), δ, ppm: 3.90 (s, 3h, ch3), 3.95 (s, 3h, ch3), 7.21 (s, 1h, arh), 7.45 (s, 1h, arh), 7.61 (dq, j = 14.4, 6.6 hz, 3h, arh), 8.15 (d, j = 8.1 hz, 2h, arh). 3.1.8. 2-(6,7-dimethoxy-2-ethyl-4-oxoquinazoline-3-yl)acetic acid (3a) the white amorphous substance was obtained. yield: 75%. m.p.: 263–264 °c. uv spectrum (ethanol), λmax, nm: 242. ir spectrum (kbr), ν, cm–1: 3437 (oh), 1682 (c=o), 1610 (c=o), 1011 (c-o). 1h nmr spectrum (400 mhz, dmso-d6), δ, ppm: 1.25 (t, j = 7.2 hz, 3h, ch3), 2.75 (q, j = 7.3 hz, 2h, ch2), 3.92 (s, 3h, ch3), 3.87 (s, 3h, ch3), 4.83 (s, 2h, ch2), 7.10 (s, 1h, arh), 7.40 (s, 1h, arh), 13.24 (s, 1h, cooh). 3.1.9. 2-[[2-(2-ethyl-6,7-dimethoxy-4-oxoquinazoline-3yl)acetyl]amino]acetic acid (3b) the white amorphous substance was obtained. yield: 70%. m.p.: 266–267 °c. uv spectrum (ethanol), λmax, nm: 242. ir spectrum (kbr), ν, cm–1: 3410 (oh), 3298 (c=o), 1736 (c=o), 1659 (c=o), 1612 (c=o), 1013 (c–o). 1h nmr spectrum (400 mhz, dmso-d6), δ, ppm: 1.24 (t, j = 7.2 hz, 3h, ch3), 2.73 (q, j = 7.0 hz, 2h, ch2), 3.80 (d, j = 5.6 hz, 2h, ch2), 3.86 (s, 3h, ch3), 3.91 (s, 3h, ch3), 4.82 (s, 2h, arh), 7.08 (s, 1h, arh), 7.39 (s, 1h, arh), 8.63 (t, j = 5.7 hz, 1h, nh), 12,72 (s, 1h, cooh). 3.1.10. 2-[[2-(2-ethyl-6,7-dimethoxy-4-oxoquinazoline-3yl)acetyl]amino]-4-methyl-pentanoic acid (3c) the beige amorphous substance was obtained. yield: 89%. m.p.: 225–226 °c. uv spectrum (ethanol), λmax, nm: 241. ir spectrum (kbr), ν, cm–1: 3419 (oh), 3309 (nh), 1732 (c=o), 1661 (c=o), 1612 (c=o), 1008,65 (c–o). 1h nmr spectrum (400 mhz, dmso-d6), δ, ppm: 0.86 (d, j = 6.6 hz, 3h, ch3), 0.92 (d, j = 6.5 hz, 3h, ch3), 1.12 (t, j = 7.5 hz, 1h, ch), 1.24 (t, j = 7.2 hz, 3h, ch3), 1.62 – 1.49 (m, 2h, ch2), 2.70 (q, j = 8.1, 7.0 hz, 2h, ch2), 3.86 (s, 3h, ch3), 3.92 (s, 3h, ch3), 4.24 (td, j = 8.9, 5.8 hz, 1h.ch), 4.95 – 4.69 (m, 2h, ch3), 7.08 (s, 1h, arh), 7.40 (s, 1h, arh), 8.63 (d, j = 7.9 hz, 1h, nh), 12,65 (s, 1h, cooh). 3.1.11. 2-[[2-(2-ethyl-6,7-dimethoxy-4-oxoquinazoline-3yl)acetyl]amino]-3-(1h-indole-3-yl)propanoic acid (3d) the beige amorphous substance was obtained. yield: 73%. m.p.: 265–266 °c. uv spectrum (ethanol), λmax, nm: 228, 239, 271. ir spectrum (kbr), ν, cm–1: 3383 (nh), 1730 (c=o), 1661 (c=o), 1641 (c=o), 1013 (c–o). 1h nmr spectrum (400 mhz, dmso-d6), δ, ppm: 1.14 (t, j = 7.2 hz, 3h, ch3), 3.05 (dd, j = 14.7, 8.7 hz, 2h, ch2), 3.22 (dd, j = 14.6, 4.9 hz, 2h, ch2), 3.85 (s, 3h, ch3), 3.91 (s, 3h, ch3), 4.53 (td, j = 8.3, 4.8 hz, 1h, ch), 4.91–4.61 (m, 2h, ch2), 7.00 (t, j = 7.4 hz, 1h, arh), 7.07 (d, j = 7.6 hz, 2h, arh), 7.19 (d, j = 2.5 hz, 1h, arh), 7.35 (d, j = 8.0 hz, 1h, arh), 7.39 (s, 1h, arh), 7.56 (d, j = 7.7 hz, 1h, arh), 8.68 (d, j = 8.0 hz, 1h, nh), 10.91 (d, j = 2.5 hz, 1h, nh), 12,79 (s, 1h, cooh). 3.1.12. 2-(6,7-dimethoxy-4-oxo-2-propyl-quinazoline-3yl)acetic acid (3e) the white amorphous substance was obtained. yield: 58%. m.p.: 234–235 °c. uv spectrum (ethanol), λmax, nm: 241. ir spectrum (kbr), ν, cm–1: 3431 (oh), 1713 (c=o), 1676 (c=o), 1007 (c–o).1h nmr spectrum (400 mhz, dmso-d6), δ, ppm: 0.99 (t, j = 7.4 hz, 3h, ch3), 1.83–1.69 (m, 2h, ch2), 2.74–2.66 (m, 2h, ch2), 3.87 (s, 3h, ch3), 3.92 (s, 3h, ch3), 4.82 (s, 2h, ch2), 7.09 (s, 1h, arh), 7.40 (s, 1h, arh), 13,25 (s, 1h, cooh). 13c nmr spectrum (100,6 mhz, dmsod6), δ, ppm: 14.12, 19,81, 36.17, 45.17, 56.15, 56.44, 105.57, 108.05, 112.96, 143.62, 148.84, 155.21, 155.74, 160.97, 170.16. 3.1.13. 2-[[2-(2-propyl-6,7-dimethoxy-4-oxo-quinazoline-3yl)acetyl]amino]acetic acid (3f) the white amorphous substance was obtained. yield: 78%. m.p.: 247–248 °c. uv spectrum (ethanol), λmax, nm: 242. ir spectrum (kbr), ν, cm–1: 3439 (oh), 3338 (nh), 1740 (c=o), 1662 (c=o), 1641 (c=o), 1011 (c–o). 1h nmr spectrum (400 mhz, dmso-d6), δ, ppm: 0.99 (t, j = 6.7 hz, 3h, ch3), 1.84–1.71 (m, 2h. ch2), 2.68 (t, j = 7.5 hz, 2h, ch2), 3.83–3.78 (m, 2h, ch2), 3.88 (d, j = 20.3 hz, 6h, ch3), 4.82 (s, 2h, ch2), 7.07 (s, 1h, arh), 7.39 (s, 1h, arh), 8.65 (t, j = 5.8 hz, 1h, nh), 12,80 (s, 1h, cooh). 13c nmr spectrum (100,6 mhz, dmso-d6), δ, ppm: 14.12, 19.65, 35.95, 41.26, 45.28, 56.13, 56.41, 105.72, 108.00, 113.10, 143.63, 148.70, 155.08, 156.09, 161.01, 167.86, 171.54. 3.1.14. 2-[[2-(2-propyl-6,7-dimethoxy-4-oxoquinazoline-3yl)acetyl]amino]-4-methyl-pentanoic acid (3g) the beige amorphous substance was obtained. yield: 69%. m.p.: 236–237 °c. uv spectrum (ethanol), λmax, nm: 242. ir spectrum (kbr), ν, cm–1: 3520 (oh), 3308 (nh), 1678 (c=o), 1655 (c=o), 1614 (c=o), 1007 (c–o). 1h nmr spectrum (400 mhz, dmso-d6), δ, ppm: 0.86 (d, j = 6.5 hz, 3h, ch3), 0.92 (d, j = 6.6 hz, 3h, ch3), 0.98 (t, j = 7.4 hz, 3h, ch3), 1.61–1.49 (m, 2h, ch2), 1.67 (dt, j = 12.9, 8.0 hz, 1h, ch), 1.82–1.72 (m, 2h, ch2), 2.63 (t, j = 7.6 hz, 2h, ch2), 3.86 (s, 3h, ch3), 3.91 (s, 3h, ch3), 4.30–4.20 (m, 1h, ch), 4.82 (q, j = 17.0 hz, 2h, ch2), 7.07 (s, 1h, arh), 7.40 (s, 1h, arh), 8.64 (d, j = 8.0 hz, 1h, nh), 12.72 (s, 1h, cooh). 13c nmr spectrum (100,6 mhz, dmso-d6), δ, ppm: 14.12, 19.64, 21.66, 23.34, 24.80, 36.00, 45.04, 50.91, 56.14, 56.41, 105.74, 108.00, 113.08, 143.62, 148.71, 155.08, 156.04, 160.99, 167.44, 174.31. 3.1.15. 2-[[2-(2-propyl-6,7-dimethoxy-4-oxoquinazoline-3yl)acetyl]amino]-3-(1h-indole-3-yl)propanoic acid (3h) the beige amorphous substance was obtained. yield: 57%. m.p.: 272–273 °c. uv spectrum (ethanol), λmax, nm: 229, 239, 271. ir spectrum (kbr), ν, cm–1: 3381 (nh), 1730 (c=o), 1662 (c=o), 1641 (c=o), 1009 (c–o). 1h nmr spectrum (400 mhz, dmso-d6), δ, ppm: 0.91 (t, j = 7.4 hz, 3h, ch3), 1.76–1.60 (m, 2h, ch2), 2.47 (dd, j = 7.6, 2.7 hz, chimica techno acta 2022, vol. 9(2), no. 20229212 article 8 of 12 2h, ch2), 3.25–3.01 (m, 2h, ch2), 3.86 (s, 3h, ch3), 3.91 (s, 3h, ch3), 4.52 (td, j = 8.2, 5.0 hz, 1h, ch), 4.77 (q, j = 16.9 hz, 2h, ch2), 7.00 (t, j = 6.9 hz, 1h, arh), 7.06 (s, 1h, arh), 7.12–7.07 (m, 1h, arh), 7.20 (d, j = 2.4 hz, 1h, arh), 7.41–7.30 (m, 2h, arh), 7.56 (d, j = 7.8 hz, 1h, arh), 8.70 (d, j = 7.9 hz, 1h, nh), 10.93 (s, 1h, nh), 12.83 (s, 1h, cooh). 13c nmr spectrum (100,6 mhz, dmso-d6), δ, ppm: 14.07, 19.61, 27.58, 35.86, 45.16, 53.71, 56.14, 56.41, 105.72, 107.99, 110.12, 111.85, 113.06, 118.63, 118.86, 121.39, 124.12, 127.67, 136.54, 143.62, 148.69, 155.07, 156.06, 160.98, 167.26, 173.57. 3.1.16. 2-[[2-(2-isopropyl-6,7-dimethoxy-4-oxoquinazoline3-yl)acetyl]amino]acetic acid (3i) the white amorphous substance was obtained. yield: 61%. m.p.: 219–220 °c. uv spectrum (ethanol), λmax, nm: 239. ir spectrum (kbr), ν, cm–1: 3425 (oh), 3298 (nh), 1732 (c=o), 1662 (c=o), 1614 (c=o), 1007 (c–o). 1h nmr spectrum (400 mhz, dmso-d6), δ, ppm: 1.24 (d, j = 6.6 hz, 6h, ch3), 3.06–2.92 (m, 1h, ch), 3.82 (d, j = 5.7 hz, 2h, ch2), 3.86 (s, 3h, ch3), 3.92 (s, 3h, ch3), 4.87 (s, 2h, ch2), 7.07 (s, 1h, arh), 7.40 (s, 1h, arh), 8.66 (t, j = 5.9 hz, 1h, nh), 12.68 (s, 1h, cooh). 13c nmr spectrum (100,6 mhz, dmso-d6), δ, ppm: 21.69, 31.88, 41.26, 45.08, 56.15, 56.43, 105.72, 108.05, 113,10, 143.65, 148.76, 155.16, 160.82, 161.09, 167.93, 171.46. 3.1.17. 2-[[2-(2-isopropyl-6,7-dimethoxy-4-oxoquinazoline3-yl)acetyl]amino]-4-methyl-pentanoic acid (3j) the white amorphous substance was obtained. yield: 50%. m.p.: 220–221 °c. uv spectrum (ethanol), λmax, nm: 241. ir spectrum (kbr), ν, cm–1: 3414 (oh), 3309 (nh), 1736 (c=o), 1678 (c=o), 1657 (c=o), 1007 (c–o). 1h nmr spectrum (400 mhz, dmso-d6), δ, ppm: 0.86 (dd, j = 6.5, 1.9 hz, 3h, ch3), 0.92 (dd, j = 6.6, 1.9 hz, 3h, ch3), 1.17 (dd, j = 6.9, 2.0 hz, 3h, ch3), 1.23 (d, j = 4.5 hz, 3h, ch3), 1.63–1.49 (m, 2h, ch2), 1.73 – 1.65 (m, 1h. ch), 3.02–2.89 (m, 1h, ch), 3.86 (s, 3h, ch3), 3.92 (s, 3h, ch3), 4.31–4.20 (m, 1h, ch), 4.89 (q, j = 14.0 hz, 2h, ch2), 7.07 (d, j = 1.9 hz, 1h, arh), 7.42 (dd, j = 13.1, 1.9 hz, 1h, arh), 8.64 (d, j = 8.0 hz, 1h, nh), 12.72 (s, 1h, cooh). 3.1.18. 2-(6,7-dimethoxy-2-methyl-4-oxoquinazoline-3yl)acetic acid (3k) the white amorphous substance was obtained. yield: 72%. m.p.: 215–216 °c. uv spectrum (ethanol), λmax, nm: 242. ir spectrum (kbr), ν, cm–1: 3431 (oh), 16778 (c=o), 1610 (c=o), 1011 (c–o). 1h nmr spectrum (400 mhz, dmso-d6), δ, ppm: 1.25 (td, j = 7.3, 1.6 hz, 3h, ch3), 3.87 (s, 3h, ch3), 3.92 (s, 3h, ch3), 4.83 (s, 2h, ch2), 7.10 (t, j = 1.5 hz, 1h, arh), 7.40 (q, j = 6.3 hz, 1h, arh), 13.26 (s, 1h, cooh). 3.1.19. 2-(6,7-dimethoxy-4-oxo-2-phenyl-quinazoline-3yl)acetic acid (3l) the white crystals were obtained. yield: 66%. m.p.: 281– 282 °c. uv spectrum (ethanol), λmax, nm: 247, 295. ir spectrum (kbr), ν, cm–1: 3437 (oh), 1716 (c=o), 1676 (c=o), 1005 (c–o). 1h nmr spectrum (400 mhz, dmso-d6), δ, ppm: 3.91 (d, j = 2.1 hz, 6h, ch3), 4.53 (s, 2h, ch2), 7.21 (s, 1h, arh), 7.49 (s, 1h, arh), 7.55 (s, 5h, arh), 13.18 (s, 1h, cooh). 3.1.20. 2-(6,7-dimethoxy-4-oxo-2-phenyl-quinazoline-3yl)propanoic acid (3m) the white crystals were obtained. yield: 62%. m.p.: 202– 203 °c. uv spectrum (ethanol), λmax, nm: 246, 302. ir spectrum (kbr), ν, cm–1: 3419 (oh), 1715 (c=o), 1670 (c=o), 1026 (c–o). 1h nmr spectrum (400 mhz, dmso-d6), δ, ppm: 2.59 (t, j = 7.7 hz, 2h, ch2), 3.90 (d, j = 3.7 hz, 6h, ch3), 4.06 (t, j = 7.6 hz, 2h, ch2), 7.16 (s, 1h, arh), 7.49 (s, 1h, arh), 7.57–7.50 (m, 3h, arh), 7.63 (dd, j = 6.8, 2.9 hz, 2h, arh), 12.34 (s, 1h, cooh). 3.2. pharmacological studies by assessing the change in cognitive deficits in animals, it was found that in the nc group of rats a pronounced cognitive impairment was observed, as evidenced by a decrease in the percentage of spontaneous alternations of the labyrinth arms in this group of rats by 66.9% (p<0.05) in relation to the so animals (figure 1). the use of emhps contributed to a significant decrease in cognitive deficit in rats by 80.1% (p<0.05) in relation to the nc group of animals. the administration of the studied compounds also led to a statistically significant decrease in the symptoms of depression of the higher integrative functions of the brain; however, the indicators of spontaneous movement vector change in the animals that were injected with the studied substances were significantly lower than those in the rats that were treated by emhps, with the exception of compounds 3i and 3j. the use of these substances contributed to the reduction (relative to the nc group of rats) of cognitive deficit in animals by 60.2% (p<0.05) and 57.9% (p<0.05), respectively, which did not statistically significantly differ from those in the rats receiving a reference drug. the size of the brain necrosis zone changed similarly (figure 2). in the nc group of rats, this parameter was 33.6±0.567%, while the use of the reference drug contributed to a decrease in this indicator by 27.7% (p<0.05). among the studied substances, the most pronounced effect on the change in necrotic processes in the brain tissue during ischemia was exerted by the administration of the compounds 3i, 3j and 3k, against the background of which the necrosis zone decreased relative to the nc group of rats by 23.1% (p<0.05), 27.9% (p<0.05) and 24.2% (p<0.05) and did not statistically significantly differ from the similar one in the group of animals that received the reference drug. the rest of the studied substances did not have a significant effect on the change in the area of brain necrosis. currently, cerebrovascular accidents and, in particular, ischemic stroke remain one of the main medical and social health problems. it was established that in 2019 stroke ranked second among the main non-communicable causes of death, second only to coronary heart disease and the terminal stage of this disease – myocardial infarction. chimica techno acta 2022, vol. 9(2), no. 20229212 article 9 of 12 figure 1 influence of the studied compounds and the referent on the change in cognitive deficit in rats under the conditions of cerebral ischemia. note: # – significant relative to so (tukey's test, p<0.05);* – significant relative to nc (tukey's test, p<0.05);δ – significant relative to emhps (tukey's test, p<0.05). figure 2 influence of the studied compounds and the referent on the change of the brain tissue necrosis zone in rats under the conditions of cerebral ischemia. note: in the so group of rats, the brain necrosis zone was zero; * – significant relative to nc (tukey's test, p<0.05); δ – significant relative to emhps (tukey's test, p<0.05). more than 6 million deaths from stroke occur annually, while there is a significant increase in cases of primary disability and disability after an ischemic attack, which is more than 50% of the total number of stroke episodes. according to who statistical reports, cerebral hemodynamic disorders are more often recorded in countries with middle and middle-high income levels, while with an increase in the well-being of the population and the possibility of obtaining qualified and timely medical care, the incidence of stroke is significantly reduced, which is confirmed by data from high-income countries [40]. the high medical and socioeconomic role of ischemic stroke dictates the need to find new ways to treat this pathological condition. one of such relatively new strategies for adjuvant therapy of stroke may be “freezing” the chimica techno acta 2022, vol. 9(2), no. 20229212 article 10 of 12 activity of neurons in the ischemic penumbra, i.e. cerebroprotection. cerebroprotectors include agents of various chemical structures: compounds of natural origin, which are most often represented by polyphenols: quercetin, verbascoside, aurapten, thymol, epigallocatechin gallate, curcumin [41], sex hormones, low molecular weight synthetic compounds such as lactic acid salts, acetyl-l-carnitine, angiotensin ii receptor antagonists. several promising neuroprotectors have been discovered in the last decade: succinic acid derivatives, [42], chomones [43] uric acid, otaplimastat (an inhibitor of metalloproteinases) [44], drotrecogin-α (anticoagulant, par-1 agonist) [45], verapamil, nerinetide (anti-excitotoxic drug) [46]. the study showed that the investigated quinazolinone derivatives with fragments of amino acids and dipeptides also could be promising cerebroprotective agents. in this respect, especially noteworthy are the compounds 3i, 3j and 3k, the use of which not only led to the recovery of the cognitive functions of animals, but also reduced the size of the brain necrosis zone. thus, the obtained results will allow expanding the range of potential cerebroprotective agents by three quinazolinone derivatives. 4. conclusions in the course of the study, a number of novel 6,7-dimethoxyquinazolin-4(3h)-one derivatives with alkyl substituents and residues of neuroactive amino acids and dipeptides were synthesized. among the studied quinazolinone derivatives, compounds 3i, 3j and 3k have the most pronounced cerebrotropic activity and are not inferior to ethylmethylhydroxypyridine succinate in terms of pharmacological activity, which makes them promising objects for further research. supplementary materials no supplementary materials are available. funding the reported study was funded by rfbr, project no. 20-315-90060, https://www.rfbr.ru/rffi/eng. acknowledgment none. author contributions conceptualization: i.p.k. data curation: i.p.k. formal analysis: a.s.c., d.i.p., i.p.k. funding acquisition: a.s.c., i.p.k. investigation: a.s.c., i.p.k., d.i.p. methodology: a.s.c., d.i.p., i.p.k. project administration: i.p.k. resources: a.s.c., i.p.k., d.i.p. software: a.s.c., d.i.p. supervision: i.p.k. validation: d.i.p. visualization: a.s.c., d.i.p. writing – original draft: a.s.c., i.p.k., d.i.p. writing – review & editing: a.s.c., d.i.p. conflict of interest the authors declare no conflict of interest. additional information author ids: a.s. chiriapkin, scopus id 57218134815; i.p. kodonidi, scopus id 10240218600; d.i. pozdnyakov, scopus id 57190954589; website: 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controlled trial. the lancet. 2020;395:878–887. doi:10.1016/s0140-6736(20)30258-0 https://doi.org/10.30906/0869-2092-2021-84-3-3-7 https://doi.org/10.1016/j.physbeh.2019.01.005 https://science-education.ru/ru/article/view?id=23168 https://science-education.ru/ru/article/view?id=23168 https://doi.org/10.1212/con.0000000000000840 https://doi.org/10.3390/ijms20225570 https://doi.org/10.2478/cipms-2021-0008 https://doi.org/10.22038/ijbms.2020.46369.10710 https://doi.org/10.1002/ana.25644 https://doi.org/10.1002/ana.25383 https://doi.org/10.1016/s0140-6736(20)30258-0 short information published by ural federal university eissn 2411-1414; chimicatechnoacta.ru editorial 2022, vol. 9(3), no. 202293e doi: 10.15826/chimtech.2022.9.3.e 1 of 1 the ctfm2022 special issue: chemical technologies of functional materials © 2022, cta. this article is published in open access under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). the special issue of the journal chimica techno acta includes papers presented at 8-th international russiankazakhstan conference “chemical technologies of functional materials” held at al-farabi kazakh national university, almaty, kazakhstan, 28–29 april 2022. the conference was organized by al-farabi kazakh national university (almaty, kazakhstan), novosibirsk state technical university (novosibirsk, russia) and institute of solid state chemistry, siberian branch of the russian academy of sciences (novosibirsk, russia). the conference is traditional and held annually alternately in russia and kazakhstan. in 2022 the conference was hosted by al-farabi kazakh national university (almaty, kazakhstan), professor zh.k. tuymebaev, chairman of the board – rector of al-farabi kazakh national university, was the chairmen of the conference. associate professor kh.s. tassibekov, professors n.f. uvarov and e.a. aubakirov were deputy chairmen of the organizing committee. the conference program included two sections: 1. scientific basis for predicting the processes of synthesis, modification and manufacture of functional materials. investigation of characteristics of new functional materials. environmental aspects of the production of functional materials. 2. processes and apparatuses of chemical technologies. physical and chemical studies of catalytic processes and catalysts of petrochemicals and oil refining. the conference was attended by 390 participants, including 85 young scientists and students, from 12 countries, mainly kazakhstan and russia, which presented 8 plenary lectures, 72 oral reports and 53 electronic posters. the organizing committee has selected the best reports and recommended their submission as papers to this special issue. guest editors: nikolai f. uvarov ermek a. aubakirov http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2022.9.3.e http://creativecommons.org/licenses/by/4.0/ https://doi.org/10.15826/chimtech.2022.9.3.e the electrochemical behavior’s character of a potential antiviral drug 3-nitro-4-hydroxy-7-methylthio-4h-[1,2,4]triazolo[5,1-c][1,2,4]triazinide monohydrate published by ural federal university eissn2411-1414; chimicatechnoacta.ru article 2022, vol. 9(4), no. 20229426 doi: 10.15826/chimtech.2022.9.4.26 1 of 6 the electrochemical behavior’s character of a potential antiviral drug 3-nitro-4-hydroxy-7-methylthio-4h[1,2,4]triazolo[5,1-c][1,2,4]triazinide monohydrate polina n. mozharovskaia a* , alexandra v. ivoilova a, roman a. drokin a , alla v. ivanova a , alisa n. kozitsina a, vladimir l. rusinov ab a: institute of chemical engineering, ural federal university, ekaterinburg 620009, russia b: institute of organic synthesis, ural branch of the russian academy of sciences, ekaterinburg 620137, russia * corresponding author: pnmozharovskaia@urfu.ru this paper belongs to a regular issue. © 2022, the authors. this article is published in open access under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). abstract the results of this study of the electrochemical transformation of 3-r4-hydroxy-1,4-dihydro-7-x-1,2,4-triazolo[5,1-c][1,2,4] obtained by voltammetry are presented. it was found that 3-r-4-hydroxy-1,4-dihydro-7-x-1,2,4-triazolo[5,1-c][1,2,4] derivatives are capable of electrochemical reduction in the potential range of –0.28 to –0.33 v (relative to ag/agcl) in britton–robinson buffer at ph = 2. the electrochemical behavior of the sodium salt of 3-nitro-4-hydroxy-7-methylthio-4h[1,2,4]triazolo[5,1-c][1,2,4]triazinide monohydrate (compound 1), which in silico modeling predicted possible biological activity against various tick-borne encephalitis and coxsackie b3 viruses. at the potentials of the first stage of electroreduction at ph = 2, the main transformation process is the three-electron reduction scheme of the nitro group of compound 1. it was established that compound 1 in an aprotic medium is reduced in ionic form, most likely in the form of an ion pair with the na+ cation, and in an aqueous medium in the form of a protonated particle. based on this, a scheme was proposed for the probable electrochemical transformation of the studied compound. keywords nitroheterocyclic compounds antiviral activity cyclic voltammetry triazolotriazines electrotransformations received: 24.10.22 revised: 06.12.22 accepted: 06.12.22 available online: 13.12.22 1. introduction because of the constant variability of viruses and their increasing resistance to existing drugs it becomes relevant to create original antiviral drugs with low toxicity and high biological activity. medicines whose active ingredients contain a nitro group in their structure are of great interest due to the fact that they exhibit a wide range of biological activity, including against various strains of viruses [1, 2]. wardman [3] associated the biological activity of such drugs with the formation of radial particles, primarily, of the radical anion arno2•–, during the reduction of aromatic nitro compounds in vivo. however, the mechanism of action of many pharmaceutical preparations containing nitroheterocyclic compounds is currently not fully understood. therefore, the development and study of models that can describe the redox transformation of new, original nitro compounds is an urgent task. its solution will help to advance the understanding of the biological effects of drugs in living organisms. currently, there is a rapidly increasing interest in a number of azoloazines, which is primarily due to their biological activity [4, 5]. due to their structural similarity to nucleic bases, they can be effective antiviral agents [6–9]. on the basis of nitro-containing azoloazinium compounds, employees of ural federal university, institute of organic synthesis of the ural branch of the russian academy of sciences, and the research institute of influenza of the ministry of health of russia developed a new class of substances – potential drugs with a wide range of antiviral activity [8]. the main representative of this class of compounds is a drug triazavirin® (riamilovir), which is registered in the russian federation and successfully used in the treatment of influenza, sars, covid-19 [10–13]. the sodium salt of 3nitro-4-hydroxy-7-methylthio-4h-[1,2,4]triazolo[5,1-c][1,2,4]triazinide monohydrate (compound 1) is the closest, in http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2022.9.4.26 mailto:pnmozharovskaia@urfu.ru http://creativecommons.org/licenses/by/4.0/ https://orcid.org/0000-0002-2675-5722 https://orcid.org/0000-0003-2797-7738 https://orcid.org/0000-0001-7515-3712 https://orcid.org/0000-0002-1705-4078 https://crossmark.crossref.org/dialog/?doi=https://doi.org/10.15826/chimtech.2022.9.4.26&domain=pdf&date_stamp=2022-12-13 chimica techno acta 2022, vol. 9(4), no. 20229426 article 2 of 6 structure, compound to the antiviral drug triazavirin® and is currently under development as a drug. it is possible, using electrochemical methods, to study the transformation of the drug in vitro in conditions as close as possible to those of the processes occurring with the drug in vivo [14– 17]. therefore, the obtained data on the study of the electroconversion of compound 1 can provide very important information on the interpretation of the mechanism of antiviral action. previously, we studied the redox transformations of substances of a number of triazolotriazines (triazavirin® and triazide) [18, 19]. the studies demonstrated that the electrochemical behavior of a structural analog may differ due to the difference in the structure and requires an individual approach to the investigation of its redox mechanism. the aim of this work is to study the nature of the electrochemical transformations of the sodium salt of 3-nitro4-hydroxy-7-methylthio-4h-[1,2,4]triazolo[5,1-c][1,2,4]triazinide monohydrate by electrochemical methods. 2. experimental 2.1. materials a 3-nitro-4-hydroxy-7-methylthio-4h-[1,2,4]triazolo[5,1c][1,2,4]triazinide monohydrate sodium salt (1); 3-nitro-4hydroxy-1,4-dihydro-7-ethylthio-[1,2,4]triazolo[5,1c][1,2,4]triazine (2); 3-nitro-4-hydroxy-1,4-dihydro-7-propargylthio-[1,2,4]triazolo[5,1-c][1,2,4]triazine (3); 3-ethoxycarbonyl-4-hydroxy-1,4-dihydro-1,2,4-triazolo[5,1c][1,2,4]triazine (4) were synthesized at the department of organic and biomolecular chemistry, ural federal university. structural formulas of compounds 1–4 are given in figure 1. aqueous buffer solutions of britton-robinson (brb), which were prepared according to the recommendations [20], were used as supporting electrolytes. the choice of this buffer is due to its high buffer capacity in a wide ph range (2–12), which also makes it possible to exclude acidification or alkalization of the medium. to prepare the solutions, deionized water was used, which was obtained on a dvs-m/1na (18)-n unit from mediana-filter, moscow, russia. to carry out the study in aprotic solutions, we used dimethylformamide (dmf) of the extra-pure grade from sigma-aldrich (us) with preliminary distillation in the presence of nanoparticles. we used tetrabutylammonium tetrafluoroborate (extra-pure grade) from sigmaaldrich (us). 2.2. electrochemical devices and methods a μautolab type iii potentiostat/galvanostat (metrohm, switzerland) was used to record cyclic voltammograms (cv curves) and chronoamperograms (ca). the working electrodes were glassy carbon disks (gce s = 7.065 mm2) with a surface diameter of 3 mm for stationary and 5 mm for rotating (gce s = 19.625 mm2) (metrohm, switzerland). to polish the surface of the glassy carbon electrode, kit 6.2802.010 (metrohm, switzerland) was used, which included aluminum oxide with a particle size of 0.3 μm and a fabric substrate. for experiments with a rotating electrode, an ametek model 616a (usa) setup was used. a graphite electrode (metrohm, switzerland) was used as an auxiliary electrode. a silver chloride electrode ag/agcl/kclsat (metrohm, switzerland) used as a reference electrode in aqueous solutions. the potentials of the working electrode in an aprotic dmf solution were measured relative to a silver chloride reference electrode with two ag/agcl/kclsat/dmf membranes (the inner part of the electrode was filled with 0.1 mol·l–1 kcl aqueous solution, the outer part was filled with 0.1 mol·l–1 bu4nbf4in dmf) before each measurement for 10 min, the solutions were purged with argon (purity 99.9%). 3. results and discussion electrochemical reduction (ecr) of 3-r-4-hydroxy-1,4-dihydro-7-x-1,2,4-triazolo[5,1-c][1,2,4]triazines with various substituents was carried out in brb solution by cyclic voltammetry with linear potential sweep. the presented cv curves of compounds 1–4, recorded in an aqueous medium at ph = 2, are shown in figure 2. it is seen that the reduction of these compounds occurs in one stage. the presented voltammograms show that the peaks of ecr in the range of potential values from –0.28 to –0.33 v belong to compounds 1–3 having a nitro group in the structure, while for compound 4 the reduction peaks in this range of potential values are not visible. apparently, the elongation of the thiol bond in the –sme substituent does not noticeably affect the ecr potential of heterocyclic nitro compounds and, probably, the electroconversion mechanism. it is possible that the peak on the cv curves for compounds 1–3 can be attributed to the reduction of the nitro group associated with the heterocyclic system. the effect of proton donors on the ecr process of compound 1 was considered. figure 3a show that an increase in the ph of the solution has little effect on the current value. figure 1 structural formulas of compounds 1–4. chimica techno acta 2022, vol. 9(4), no. 20229426 article 3 of 6 figure 2 cv curves of 1 mm compounds 1–4: in brb ph = 2 using gce at ν = 0.1 v/s. potentials were measured relative to ag/agcl/kclsat. moreover, the value of the cathode current imperceptibly differs from the theoretical current, which is calculated according to the randles-shevchik equation for irreversible systems. it can also be seen from figure 3b that a change in ph significantly affects the potential of the ev and shifts it to the cathode region (by 400 mv). based on the foregoing, it can be assumed that with a decrease in the acidity of the medium, the ecr becomes more difficult due to the lack of protons both for the previous protonization and for the protonation of the intermediate products of the electrochemical reaction [21]. since the current does not depend on ph and the dependence of e on ph is linear, it can be assumed that the electroreduction of compound 1 in this range of ph occurs by a similar mechanism. therefore, we can calculate thermodynamic characteristics in an acidic medium. since the electroreduction of compound 1 under these conditions is irreversible, it is not possible to calculate the number of protons involved in the overall process from the plot of the dependence of the potential on ph. however, the dependence of the potential on ph unambiguously indicates the participation of protons in the electrochemical process both before and simultaneously with electron transfer. it is known that nitroaromatic compounds are characterized by a diffusion process complicated by the preceding chemical reaction of anion protonation. therefore, the experiments were carried out to study the kinetics of the electrochemical process. for this, cvs were recorded at different scanning rates of the potential and chronoamperograms. as can be seen from figure 4a the semerano criterion calculated from the logarithmic dependence of the current magnitude on the rate of potential application (tg = logi/logv) is 0.51. this fact, as well as the linear dependence of the peak current on the square root of the potential application rate (figure 4b) indicates the diffusion control of the electrochemical process [22]. figure 3 values of current (a) and potential (b) of the peak of compound 1 (5 mm) with a change in the ph of the buffer solution at ν = 100 mv/s. figure 4 logarithmic dependence of the peak current on the rate of potential application (a) and dependence of the peak current on the square root of the rate of application of potential compound 1 in the brb ph = 2 on the gce (b). chimica techno acta 2022, vol. 9(4), no. 20229426 article 4 of 6 note that compound 1 is a salt formed by the na+ cation and heterocyclic anions; therefore, its reduction should have proceeded at more negative potential values compared to compounds 2–3. most likely, the difference in the reduction currents of compound 1 from 2 and 3 is also associated with the influence of na+ ions contained in the structure of compound 1. it can be assumed that the similarity of the electrochemical behavior of compounds 1–3 in solutions at ph = 2 indicates the initial protonation of heterocyclic anions of compound 1 and further reduction at the electrode not of the heterocyclic anion, but of the corresponding protonated particle. to confirm the above assumption about the participation of protons in the ecr of compounds 1, a study was carried out in a non-aqueous medium, dmf. the presented cv curves in figure 3 were recorded in an aprotic solvent (dmf). the potential of the first ecr peak of compound 1 is 800 mv more negative than that of compound 2. this can be explained by the negative charge of the reducing particles in the case of compound 1. adding an aqueous solution of sodium hydroxide alkali to a solution of compound 2 in dmf medium leads to a significant change in the cv curves: an increase in the values of cathodic and anodic currents is observed, the oxidation/reduction peaks are shifted to the cathode region, but the system remains irreversible (figure 5). in order to exclude the effect of water added together with alkali to a solution of compound 2 in dmf medium, the cv curve of compound 1 was recorded with the addition of 0.5 mm h2o (figure 5, red dotted line). it can be noted that not only the reduction potentials of compound 1 with the addition of water and those of compound 2 with the addition of aqueous alkali, but also the shapes of their cv curves coincide. the anodic peaks on the reverse part of voltammograms somewhat differ in the potential value, which is probably due to the influence of the additional ch3-group in the thiol substituent. therefore, it can be assumed that compound 1 in an aprotic medium is reduced in an ionic form, most likely in the form of an ion pair with the na+ cation, and in an aqueous medium in the form of a protonated particle. the participation of proton donors in the process of ecr of the nitro group of compound 1 can also be indicated by the shift of the reduction potentials to the cathode region relative to the potentials in aqueous media. the electrochemical behavior of compound 1 is of greatest interest; therefore, it was further studied in acidic aqueous buffer solutions. due to the mixed acidosis of the cells [23], an acidic environment was chosen. this environment occurs with an excessive concentration of active oxygen metabolites, which, in turn, are produced in the process of viral infection [24]. the electrochemical behavior of compound 1 was studied using cyclic voltammetry, chronoamperometry, and a rotating disk electrode (rde). the cv curves of this compound with a change in the sweep direction at the value of the potential of the limiting current of the first stage is similar to the peaks on the ecr curve of nitrobenzene in an acidic medium [18]. to approximately determine the effective number of electrons (ne) involved in the electrochemical reduction of compound 1, the current of the first stage in the voltammogram was compared with the current of the fe(cn)63–/fe(cn)64– model redox pair under similar conditions. for a more accurate calculation of the number of electrons, the ca and rde methods were used. analysis of the chronoamperogram in the time interval from 1 to 2 s at the potential value of the limiting current of the electroreduction of compound 1 (e = –0.35 v) made it possible to calculate the amount of electricity that passed during this time and compare it with the amount of electricity passing under the same conditions at the potential value limiting ecr current (e = 0.2 v) in k3fe(cn)6 solution. the results obtained showed that at the value of the potential of the first ecr stage of compound 1 in an acid medium, the main direction of transformations is the three-electron scheme for the reduction of its nitro group. figure 5 cv curves of 5 mm compounds 1,2 in dmf (0.1 m bu4nbf4), recorded using gce with ν = 0.1 v/s: red – 1, red dotted line – 1 with the addition of 0.5 mm h2o, black – 2, black dotted line – 2 with the addition of 9 mm aqueous naoh. table 1 the values of the observed number of electrons ne participating in the ecr of compound 1 and k3fe(cn)6 (с = 5 mm) in an aqueous buffer solution of brb at ph = 2. compound n1e n 2 е (cc) n 3 е n 4 е (ca) n 5 е (rde) 1 2.98 3.10 3.01 3.07 3.23 k3fe(cn)6 1 1 1 1.02 0.96 n1e – the ratio of current of compound 1 with current of the model redox pair fe(cn)6 3–/fe(cn)6 4– in the same conditions; n2e – the ratio of amount of electricity of compound 1 with amount of electricity of the model redox pair fe(cn)6 3–/fe(cn)6 4– in the same conditions; ne 3 – the effective number of electrons which were calculated using rendls–shevchik equation for irreversible processes [25]; n4e – was calculated from the current value in the chronoamperogram of compound 1 at t = 1 s using the cottrell equation, taking into account that the value of the diffusion coefficient for nitroaromatic compounds in aqueous media is ~10–5 cm2·s–1[26]; n5e – according to levich's equation [27]. chimica techno acta 2022, vol. 9(4), no. 20229426 article 5 of 6 figure 6 probable mechanism of electrochemical reduction of compound 1 in brb ph = 2. on the basis of the obtained data and the literature studied [28], it can be assumed that compound 1 in an aqueous medium at ph = 2 is irreversibly reduced in the form of a protonated particle with the consumption of 3 electrons until the formation of a dimeric product (figure 6). to more accurately establish the mechanism of electroreduction of compound 1, it is necessary to carry out preparative electrolysis followed by detection of products by high performance liquid chromatography (hplc) in tandem with high resolution mass spectrometry. conclusions the results of this study show the electrochemical behavior of compounds 3-r-4-hydroxy-1,4-dihydro-7-x-1,2,4-triazolo[5,1-c][1,2,4] using electrochemical methods. it was established that compounds containing a nitro group undergo an irreversible reduction process in the potential range of – 0.28 to –0.33 v (relative to ag/agcl) in a britton–robinson buffer solution at ph = 2. the sodium salt of 3-nitro-4-hydroxy-7-methylthio-4h-[1,2,4]triazolo[5,1-c][1,2,4]triazinide monohydrate (compound 1) in an aprotic medium is reduced in ionic form, most likely in the form of an ion pair with the na+ cation, and in an aqueous medium in the form of a protonated particle. the main direction of the transformations of compound 1 at the first stage at ph = 2 is the three-electron scheme for the reduction of the nitro group of the compound. then it followed by dimerization of cathodic electrolysis products. the obtained information is very useful for further understanding connection between compound’s structure, electrochemistry transformations and biological activity. supplementary materials no supplementary materials are available. funding the research funding from the ministry of science and higher education of the russian federation (ural federal university program of development within the priority2030 program) is gratefully acknowledged. acknowledgments none. author contributions conceptualization: p.n.m., a.v.i., r.a.d. data curation: p.n.m. formal analysis: p.n.m., a.v.i., r.a.d. funding acquisition: p.n.m. investigation: p.n.m., a.vs.i., r.a.d. methodology: p.n.m., a.vs.i., r.a.d. project administration: a.n.k. resources: p.n.m., a.vs.i., r.a.d. software: p.n.m. supervision: a.n.k., a.vl.i., v.l.r. validation: a.n.k., a.vl.i. visualization: p.n.m. writing – original draft: p.n.m., a.vs.i. writing – review & editing: a.n.k., a.vl.i., v.l.r. conflict of interest the authors declare no conflict of interest. additional information author ids: polina n. mozharovskaia, scopus id 57232723000; alexandra v. ivoilova, scopus id 57211981729; roman a. drokin, scopus id 57053422300; alla v. ivanova, scopus id 8233431000; alisa n. kozitsina, scopus id 16432620500; vladimir l. rusinov, scopus id 7006493788. websites: ural federal university, https://urfu.ru/en; institute of organic synthesis, https://iosuran.ru. references 1. fuchi y, murase h, kai r, kurata k, karasawa s, 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https://doi.org/10.1039/c5ra22581g https://doi.org/10.1039/c5ay01619c https://doi.org/10.1016/j.sbsr.2017.04.004 https://doi.org/10.1007/s11172-021-3190-7 https://doi.org/10.3390/molecules26165087 https://doi.org/10.1039/jr9310001456 https://doi.org/10.2174/1385272053544380 https://doi.org/10.3109/10715769209049163 https://doi.org/10.1016/j.ab.2010.09.027 https://doi.org/10.1016/j.talanta.2003.12.005 crystallization kinetics of gdyscalco high-entropy bulk metallic glass published by ural federal university eissn 2411-1414 chimicatechnoacta.ru article 2023, vol. 10(2), no. 202310207 doi: 10.15826/chimtech.2023.10.2.07 1 of 9 crystallization kinetics of gdyscalco high-entropy bulk metallic glass v.a. bykov a , d.a. kovalenko b * , e.v. sterkhov a, t.v. kulikova a a: institute of metallurgy, ural division of russian academy of sciences, ekaterinburg 620002, russia b: ural federal university, ekaterinburg 620009, russia * corresponding author: darya.k.2000@list.ru this paper belongs to a regular issue. abstract the thermal stability and non-isothermal crystallization of a new bulkamorphous high-entropy (he-bmg) equiatomic gdyscalco alloy were studied by differential scanning calorimetry (dsc). the alloy shows a four-stage crystallization process. the kinetic parameters (activation energy (eα)), the pre-exponential factor (loga) and glass-forming ability indicators (kinetic fragility index, characteristic temperatures) for the gdyscalco alloy were obtained. the eα values obtained by isoconversional methods indicate a nonlinear arrhenian behaviour and a complex process. the avrami equation modification proposed by jeziorny and the multivariate nonlinear regression method were applied on the nonisothermal crystallization. in the case of primary crystallization of the amorphous gdyscalco alloy under nonisothermal conditions, the kinetics of the nucleation process is best described by an autocatalytic reaction. keywords high-entropy bulk metallic glass activation energy glass-forming ability primary crystallization received: 13.03.23 revised: 04.04.23 accepted: 11.04.23 available online: 18.04.23 key findings ● new bulk-amorphous high-entropy equiatomic gdyscalco alloy was produced. ● non-isothermal crystallization kinetics of gdyscalco metallic glass was investigated. ● the multivariate nonlinear regression method suggested a combined auto-catalysis reaction model. © 2023, the authors. this article is published in open access under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). 1. introduction since the first discovery in 1960, interest in metal glasses and other metastable materials has been growing [1]. for more than 60 years of research, several hundred bulk metallic glasses (bmg) were synthesized with dimensions up to tens of centimeters. the majority of the synthesized bmgs are alloys based on one or two basic elements with small additions of elements that increase glass-forming ability and characteristics of materials [2–4]. in addition to high glass-forming ability, such materials have a number of unique properties: high thermal stability, high plasticity and soft magnetic properties. also, amorphous alloys based on sc–al–co have unique strength and corrosion characteristics [5]. additionally, additives of rare-earth metals (rem) affect the glass-forming ability (gfa) of these alloys. for example, rem additives (gd, y) increase the glass-forming ability and improve the mechanical properties of sc–al–co alloys [5]. however, the gfa and thermal stability of gdyscalco alloys, as well as the mechanisms of their crystallization, is not studied. we chose an equiatomic gdyscalco alloy for research because it easily amorphizes under arc melting conditions. to estimate the gfa, we used various experimental indicators of glasses, such as glass transition temperature (tg), on-set crystalline temperature (tx) and liquidus temperature (tl), etc. to obtain given properties of the gdyscalco alloy, as well as to predict the optimal compositions and heat treatment modes, the calculation of kinetic parameters (activation energy ea, pre-exponential factor) using iso-conversion methods of thermal analysis was carried out. http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2023.10.2.07 mailto:darya.k.2000@list.ru http://creativecommons.org/licenses/by/4.0/ https://orcid.org/0000-0003-4851-8223 https://orcid.org/0000-0001-5076-6715 https://orcid.org/0000-0002-0674-1139 https://crossmark.crossref.org/dialog/?doi=https://doi.org/10.15826/chimtech.2023.10.2.07&domain=pdf&date_stamp=2023-04-18 chimica techno acta 2023, vol. 10(2), no. 202310207 article 2 of 9 doi: 10.15826/chimtech.2023.10.2.07 2. experimental procedure 2.1. materials and synthesis the master equiatomic gdyscalco alloy was prepared by arc melting al (99.99% purity), gd (99.9%), y (99.9%), sc (99.9%) and co (99.9%) in a helium atmosphere. further, it is re-melted five times to achieve complete melting and compositional homogeneity. the composition of the samples was controlled by weighing them before and after synthesis, and the mass loss did not exceed 0.1 wt.%. then, amorphous alloy was produced by performing suction casting of the arc-melted metal liquid into a copper mold to produce a 3 mm diameter rod. 2.2. differential scanning calorimetry (dsc) and x-ray diffraction measurements the as-cast rod structure was examined by x-ray diffraction at room temperature in a 2θ angular range of 25°–100° at a step of 0.004° using a shimadzu xrd7000 diffractometer and cu kα radiation; the exposition time was 3 s. thermal reactions in the sample were investigated by differential scanning calorimetry using a netzsch sta 449c device, calibrated with indium, tin zinc, aluminum, silver and gold standards. the selected sample mass was 20.1±0.1·10−6 kg. dsc scans were performed at different heating rates (5, 10, 20, 40 k/min) in the temperature range from 273 to 1100 k at an argon flow of 60 ml/min. to describe the initial crystallization process and to determine the kinetic parameters, netzsch kinetics neo software (netzsch, selb, germany) was applied using model-free and the multivariate nonlinear regression methods. 3. results and discussion 3.1. thermal analysis and gfa indicators figure 1 illustrates an x-ray pattern of the gdyscalco rod that shows an amorphous halo without distinct crystalline peaks, i.e., the resulting sample is x-ray amorphous. the non-isothermal dsc of of gdyscalco he-bmg are shown in figure 2. all the dsc curves exhibit the four exothermic reactions corresponding to the crystallization processes. table 1 shows the thermal characteristics of the gdyscalco alloy: glass transition temperature tg, on-set crystalline temperature tx, melting temperature tm, liquidus temperature tl, as well as indicators of glass-forming ability: supercooled liquid interval δtx = tg – tx, trg = tl/tg and melting interval δtl = tl – tm. gdyscalco alloy shows high values of glass transition temperature tg. gfa is related to physical nature of alloy and reflects how well the alloy forms metallic glass during casting. there are various criteria for evaluating gfa, including γ and δ, which are based on the classical theory of nucleation [6]. these criteria can be easily obtained by thermal analysis and show a strong correlation with gfa in metallic glasses. calculation of γ and δ criteria was carried out according to equations: 𝛿 = 𝑇𝑥 (𝑇𝑙 − 𝑇𝑔 ) , (1) 𝛾 = 𝑇𝑥 (𝑇𝑙 + 𝑇𝑔 ) . (2) in paper [7] for the four-component sc36al24co20y20 alloy the value of the criterion γ = 0.444 was presented, which agrees well with our data for the five-component gdyscalco alloy (γ = 0.407). table 1 shows the criteria γ and δ, which indicate a good glass forming ability of the gdyscalco alloy. the term “fragility” introduced by angel [8], shows the degree of deviation of the temperature dependence of the viscosity from the arrhenius curve and is a gfa indicator. from the physical perspective, it characterizes how well the material transitions to the glass state when cooled. substances with high values of this parameter have a narrow range of glass transition temperatures, while substances with low values have a relatively wide range [8]. figure 1 xrd pattern of the gdyscalco rod. figure 2 experimental dsc curves of gdyscalco amorphous alloy at different heating rates (inset: temperatures tm, tl for heating rate of 10 k/min). https://doi.org/10.15826/chimtech.2023.10.2.07 https://doi.org/10.15826/chimtech.2023.10.2.07 chimica techno acta 2023, vol. 10(2), no. 202310207 article 3 of 9 doi: 10.15826/chimtech.2023.10.2.07 table 1 thermal characteristics for gdyscalco alloy according to dsc measurements obtained at a rate of 10 k/min. alloy tg, к tx, к tm, к tl, к δtx trg δtl γ δ gdyscalco 559 631.5 960 992 32 0.563 32 0.407 1.458 fragility is determined by the slope of the viscosity curve according to the dependence of log (viscosity) on tg/t when approaching tg, which gives the kinetic index of a fragility (m). the kinetic a fragility index can be obtained as follows [9]: 𝑚 = 𝐷𝑇0𝑇𝑔 (𝑇𝑔 − 𝑇𝑜 ) 2ln10 , (3) where d is the strength parameter, t0 is the asymptotic value of tg at an infinitely slow cooling and heating rate, and tg is the glass transition temperature [8]. d and t0 can be determined through the relationship between tg and heating rate (β) by an equation with the vogel-fulcher-tammann form [10]: lnβ = ln(𝐵) − 𝐷𝑇0 𝑇𝑔 − 𝑇0 . (4) fragility index for the sample was calculated at heating rates 5, 10, 20, 40 k/min. the data obtained from equations 3 and 4 are summarized in figure 3. the results show that m is equal to 33. the liquids with the fragility index m close to 17 are usually referred to “strong” glass-formers. the liquids with m much higher than 17 are usually referred to “fragile”. in the case of gdyscalco he-bmg, it can be classified into “fragile” glasses. the parameter f1, introduced by senkov [11], is an indicator of glass-forming ability, which establishes a correlation between the fragility parameter and the critical cooling rate at which the amorphous state is formed. the value f1 = 0 corresponds to an extremely fragile liquid, and f1 ~ 0.8 – extremely strong liquid. the f1 parameter can be defined as: 𝐹1 = (𝑇𝑔 − 𝑇0) 0.5(𝑇𝑙 + 𝑇𝑔 ) − 𝑇0 , (5) where tg is the glass transition temperature, tl is the liquidus temperature, and t0 is the on-set temperature. the calculation results are presented in table 2. compared to other metallic glasses: la55al25ni20 (m = 42, f1 = 0.455), la55al25ni10cu10 (m = 35, f1 = 0.540) [11], the alloy gdyscalco shows rather high values in frazilite and the f1 parameter, which indicates its good glass forming ability. 3.2. primary crystallization kinetics of gdyscalco 3.2.1. activation energy one of the most important kinetic parameters of the crystallization process is the activation energy. it represents the energy barrier that must be overcome by the system to start the nucleation and growth process leading to crystallization. according to figure 2, there are four crystallization peaks on the dsc curves. since the first peak overlaps with the second and third ones, we used a mathematical procedure of peak shape separation to correctly estimate the kinetic parameters of the nucleation and primary crystallization process (figure 4) [12]. in the calculations we used the dsc peaks at different heating rates obtained by deconvolution, so they should be compared. the separated peaks have the same shape at different heating speeds, i.e., they are identical to each other. as can be seen in figure 4, the positions of onset and peak maximum temperatures of the original dsc signal and the separated ones are almost the same. the baseline was a straight line. because the crystallization of amorphous alloy is a multistage process, it requires additional structural studies. here, we limit ourselves to calculating the kinetic parameters only for the first peak and describing the mechanism of nucleation and primary crystallization. thus, the dsc curves (figure 2) show peaks corresponding to the nucleation and crystal growth processes. we calculate the activation energies corresponding to these temperatures to understand the nucleation and crystallization in general. in the methods of non-isothermal kinetics based on the free model, it is assumed that the single-step processes occurring can be described following rate equation [13]: 𝛽 𝑑𝑎 𝑑𝑡 = 𝐴𝑓(𝑎)𝑒 −𝐸𝑎 𝑅𝑇 , (6) where 𝐴 is the pre-exponential factor, 𝛽 – the constant heating rate, eα is the activation energy, and the concentration dependence of the reaction rate (reaction model) is 𝑓(𝑎), where a is the degree of transformation of the substance in the range from 0 to 1. figure 3 fragility index for gdyscalco alloy. table 2 tg, tl, m and f1 parameter for gdyscalco alloy. tg (k) tl (k) m f1 559 992 33 0.463 https://doi.org/10.15826/chimtech.2023.10.2.07 https://doi.org/10.15826/chimtech.2023.10.2.07 chimica techno acta 2023, vol. 10(2), no. 202310207 article 4 of 9 doi: 10.15826/chimtech.2023.10.2.07 additionally, it was assumed that the reaction rate at a constant conversion value depends only on temperature (iso-conversion principle). it should be noted the importance of determining the preexponential factor a in the framework of kinetic analysis without using a model. according to vyazovkin [14] model-free method of estimating the preexponential factor a is suitable for both singleand multi-step kinetics. model-free methods of analysis allow us to determine the activation energy eα of the reaction process without making hypotheses about the kinetic model of the process and without knowing the type of reaction [13]. various model-free methods are used to calculate the activation energy eα of non-isothermal reactions at different heating rates [15–17]. first, we used the most common of them, the kissinger method. the basic equation of the kissinger method is written as ln(β 𝑇2⁄ ) = − 𝐸 𝑅𝑇⁄ + const, (7) where β is the heating rate, r is the gas constant, t is the temperature. figure 5 shows the dependences described by equation (2), which correspond to the following processes: the glass transition at tg(eg); the start of nucleation at tx(ex); the crystal growth at tp1(ep1). the calculation results of the activation energy are shown in figure 5 and table 3. table 4 shows that the highest activation energy is at the beginning of the nucleation process, ex = 314 kj/mol. this suggests that the most energy-consuming process is the beginning of crystallization (the appearance of the first nuclei of the crystalline phase in the amorphous matrix). thus, we determined the activation energy of the primary crystallization process (ep) using the kissinger equation (equation 7). however, from a physical viewpoint, this method cannot be applied directly to amorphous alloys, since the crystallization process in them proceeds through the nucleation and crystal growth processes rather than through the n-order reaction [18, 19]. also, as noted by vyazovkin [13], kissinger's method is not very accurate. the method gives a single activation energy in accordance with the assumption of one-step kinetics, which creates a problem for most applications. figure 4 separated dsc curves for a heating rate of 10 k/min. we performed calculations of eα using other model-free methods (vyazovkin [15], friedman [16] and ozawa [17]) in the netzch kinetics neo software. the calculation results by kissinger, vyazovkin, friedman and ozawa methods are presented in table 4 and figure 5. the analysis of the dependence of eα versus α (conversion) of the crystallization process of the he-bmg gdyscalco alloy obtained from isoconversional methods (ozawa, friedman and vyazovkin) allows us to check the applicability of the one-step kinetics according to equation 7. figure 5 kissinger plots for calculating activation energies in gdyscalco bmg. table 3 activation energy eg, ex, ep1 for temperatures тg, тх, tp1. alloy activation energy, kj/mol eg ex ep1 gdyscalco 160 314 227 https://doi.org/10.15826/chimtech.2023.10.2.07 https://doi.org/10.15826/chimtech.2023.10.2.07 chimica techno acta 2023, vol. 10(2), no. 202310207 article 5 of 9 doi: 10.15826/chimtech.2023.10.2.07 figure 4 presents the dependence of the eα and loga on the degree of conversion calculated using ozawa, friedman and vyazovkin methods. we can see from figure 6 that the values of e(α) change nonlinearly, where as the dependences of e(α) are similar. the eα values indicate a nonlinear arrhenian behaviour and a complex process. the close average e(α) values obtained by the conversional methods differ from those calculated with kissinger's method. therefore, the kissinger method can only be used for preliminary estimation of the activation energy of a one-step process. due to the fact that the values of e(α) change nonlinearly and indicate a complex process, naturally, the kissinger activation energy values cannot be applied when simulating the complex process of crystallization of amorphous materials, where multistage processes are observed. table 4 crystal growth activation energy ep1 and pre-exponential factor log a for gdyscalco alloy. kinetic parameter vyazovkin kissinger method friedman ozawaflynnwall average value ep1, kj/mol 250 227 250 260 247 loga 17.6 13.1 17.6 17.8 16.5 figure 6 аctivation energy and loga values of versus conversion during the crystallization process using the friedman (a), vyazovkin (b), and ozawa (c) methods. 3.2.2. avrami model using jeziorny method one of the most commonly used models for describing the crystallization kinetics of polymers, metals, and glasses is the avrami model (also known as the johnson–mehl–avrami–erofeev–kolmogorov (jmaek) model [20–25]). to isothermal conditions, the avrami equation is typically used in the following form: 𝑎 (𝑇) = 1 − 𝑒 −𝑘(𝑇)∙𝑡 𝑛 , (8) where 𝑎 is the degree of conversion, k(t) represents the rate constant, t is time and n is the local avrami index. for nonisothermal experimental conditions, equation (8) is frequently expressed as the following linear equation: 𝑑𝑎 𝑑𝑡 = 𝑘(𝑇) 𝛽 ∙ 𝑛 ∙ (1 − 𝑎) ∙ [− ln(1 − 𝑎)] ∙ (𝑛 − 1) 𝑛 . (9) the volume fraction of crystals (conversion 𝑎) can be determined by the crystallization heat using the following equation [26]: 𝑎 = ∫ (𝑑𝐻/𝑑𝑇)𝑑𝑇 𝑇 𝑇0 ∫ (𝑑𝐻/𝑑𝑇)𝑑𝑇 𝑇𝑖𝑛𝑓 𝑇0 = 𝐴0 𝐴𝑖𝑛𝑓 , (10) where t0 and tinf are the temperatures of the beginning and end of crystallization, respectively. dh corresponds to the enthalpy of crystallization released during an infinitesimal temperature interval dt. a0 and ainf correspond to the region between the initial and specific temperature and the end of crystallization, respectively. figure 7 shows the relationship between the volume fraction of crystallization and the temperature for primary crystallization. from figure 7 we see that with an increase in the heating rate, the s-curves shift to the region of higher temperatures. many attempts have been made to derive equation 8 under non-isothermal temperature with constant heating or cooling rates [27]. the main difficulty in modifying the jmaek model under non-isothermal conditions is that these experiments are much faster than isothermal experiments. figure 7 сrystallized volume fraction versus temperature plots. https://doi.org/10.15826/chimtech.2023.10.2.07 https://doi.org/10.15826/chimtech.2023.10.2.07 chimica techno acta 2023, vol. 10(2), no. 202310207 article 6 of 9 doi: 10.15826/chimtech.2023.10.2.07 in isothermal experiments, the material under study is heated to a certain temperature in a time much shorter than the transformation time. crystallization of metallic glasses under linear heating conditions is mainly studied using the jmaek method modified by jeziorny [28], who converted the linear avrami equation to linear heating conditions using the following assumption: ln 𝑘𝐴 = ln𝑘(𝑇) 𝛽 , (11) where 𝑘(𝑇) = 𝐴𝑒 −𝐸𝑎 𝑅𝑇 – rate constant, β – heating rate however, as vyazovkin states [29], this transformation contradicts the basic principle of equating physical quantities and also leads to incorrect avrami indices, usually larger than the actual value. it should be noted that the jeziorny’s method is often used to calculate the avrami index of non-isothermal crystallization kinetics of amorphous metallic glasses due to the developed algorithm for the interpretation of the polymer crystallization mechanism. [30]. however, the crystallization processes in amorphous metallic materials and polymers can be radically different. further, the mechanism of primary crystallization for the amorphous gdyscalco alloy under non-isothermal conditions by the jeziorny method will be tested in the multivariate nonlinear regression method. to determine the mechanism of nucleation and its growth, we used the approach of determining the local avrami index n(α) with jeziorny's assumption (equation 11), which was proposed in [31]. according to [31], the local avrami index n(α) can be found from a modification of the jmaek equation, given that t–t0 = (t–t0)/β, where t0 is the temperature at the crystallization onset. therefore, it can be written as: 𝑑ln[−ln (1 − 𝛼)] 𝑑{ln [(𝑇 − 𝑇0)/𝛽]} = 𝑛 {1 + 𝐸 𝑅𝑇 (1 − 𝑇0 𝑇 )}, (12) where t0 is the initial crystallization temperature and 𝐸 is the activation energy of the crystallization process. the values of e in equation 10 were used as e(α) calculated by the vyazovkin method. for non-isothermal dsc curves, the local avrami index (n(α)) can be obtained by plotting the dependence of ln[–ln(1–α)] on ln[(t–t0)/β]. the plots of these dependences are shown in figure 8, where the value of n(α) can be obtained from the slope of these curves. in addition, figure 9 shows the local avrami index indices as a function of the volume fraction of crystallized matter α at different heating rates. the resulting curves are not linear, indicating that n(α) changes during the crystallization process. the n(α) is a basic parameter that is necessary to understand the mechanisms of nucleation and grain growth with increasing α during the transformation phase. the local avrami index is expressed as: 𝑛 = 𝑏 + 𝑝𝑚, (11) where b is the nucleation index, m is the dimensionality of grain growth and p is the type of growth. the germination index contains four conditions: (1) b = 0 suggests a zero germination rate; (2) 0<b<1 indicates a decrease in the germination rate with time; (3) b = 1 represents a constant germination rate; (4) b>1 indicates an increase in the germination rate with time. the grain growth magnitude m is 1, 2, or 3; p = 1 represents surface-controlled growth, and p = 0.5 indicates diffusion-controlled growth. before describing the primary crystallisation mechanism using the n(α) dependence, we present an important remark. since the peak separation procedure performed allows determining the approximate baseline, it must be considered that extreme values of n(α) (both α< and α~1) are unreliable, since they are affected by the baseline. figure 8 shows that at the start of the crystallization process, the n(α) values are 2.2–3.5, indicating that the growth mechanism is surface-controlled. the appearance of these curves clearly shows the course of nucleation and grain growth at different heating rates. all n(α) at different heating rates are greater than unity at x = 0, which corresponds to the nucleation process with increasing nucleation rate; n(α) of the three curves (10, 20, 40 k/min) firstly increases and then decreases at 0.05≲x≲0.91, which indicates that the nucleation rate and growth dimension always change at this stage. the continuous decrease of n(α) values after a certain percentage of crystallization volume fraction (≳ 5% for speeds 10–40 k/min) shows that nucleation rates decrease to about zero and the grain growth process dominates; all n(α) curves increase rapidly at 0.91≲x≲1. in the initial stage of crystallization, nucleation dominates, with a constant or increasing rate and no grain growth process when 1≤n(α)<2; there is one (n(α) = 2), two (2<n(α)<3) or three-dimensional growth (3≤n(α)) with constant, decreasing or increasing rate of nucleation. in our case, in the initial stage of crystallization the threedimensional growth of nuclei with increasing nucleation rate is observed. figure 8 ln[−ln (1 − 𝑥)] versus ln [(𝑇 − 𝑇0)/β] plots at various heating rates (1st dsc peak). https://doi.org/10.15826/chimtech.2023.10.2.07 https://doi.org/10.15826/chimtech.2023.10.2.07 chimica techno acta 2023, vol. 10(2), no. 202310207 article 7 of 9 doi: 10.15826/chimtech.2023.10.2.07 at 5 k/min, n(α) remains constant until 0.5≳x≳0.8, and then increases, indicating that the nucleation process continues at a constant rate. thus, for the initial stage of crystallization of the amorphous gdyscalco alloy, there is a dependence of the nucleation process versus the heating rate. 3.2.3. avrami model using the multivariate nonlinear regression method the multivariate nonlinear regression method was also applied to the dsc data of amorphous gdyscalco alloy using the avrami model. this method constructs a kinetic model of the reaction (consecutive, parallel, branched, etc.) and selects the models describing each step. equations describing kinetic models contain several parameters which are defined by the non-linear regression method from the dsc curves approximation. a comprehensive kinetic analysis using multivariate non-linear regression was performed with netzsch kinetics neo software [32]. we verified the jmaek method modified by jeziorny with respect to all heating curves and the fact that the primary crystallization process is sequential and two-stage (a→b→c). according to the above-described n(α) relationships, the crystallization mechanism of amorphous gdyscalco alloy is largely determined by three-dimensional nucleation growth (a→b (an)) that is surface-controlled (b→c (r3)). the simulation results and equations of the crystallization models are shown in figure 10 and table 5. comparative analysis shows satisfactory results (correlation coefficient r2 = 0.9678); the average values of the avrami index and eα are close to those obtained by equation 12 and vyazovkin (friedman, ozawa). as calculated, the best correlation coefficient (0.9950) between the separated and simulated dsc curves was obtained by the combined auto-catalysis reaction as two parallel reactive paths (a → b, a+b→2b) according to heterogeneous reaction of nth order with m-power autocatalysis by-product kamal-sourour [33]: 𝑑𝛼 𝑑𝑡 = 𝐴𝑒 − 𝐸𝑎1 𝑅𝑇 ∙ (1 − 𝛼)𝑛 + 𝐾cat ∙ 𝐴𝑒 − 𝐸𝑎2 𝑅𝑇 ∙ (1 − 𝛼)𝑛 ∙ 𝑎𝑚, (13) where 𝑘𝑐𝑎𝑡 – auto-catalysis factor, α – conversion, n, m – reaction order, т – temperature. the results of the simulation and equations of the crystallization model, according to the above proposed primary crystallization scheme of the amorphous gdyscalco alloy, are shown in figure 11 and table 6. thus, based on multivariate nonlinear regression method simulation data, the primary crystallization of the amorphous gdyscalco alloy proceeds as a combined autocatalysis reaction in two parallel reactive paths. figure 9 the local avrami index n(α) versus the volume fraction of crystallization (α). figure 10 crystallization model of amorphous gdyscalco alloy described by the three-dimensional nucleation growth (a→b (an)) with surface-controlled (b→c (r3)). figure 11 crystallization model of amorphous gdyscalco alloy described by the combined auto-catalysis reaction as two parallel reactive paths (a → b, a+b→2b). table 5 kinetic parameters and the regression coefficient r2 for the fitting of multivariate nonlinear regression according to two-stage consecutive reactions (three-dimensional nucleation growth (a→b (an)) with surface-controlled (b→c (r3)). na–>b logaa–>b, log(s –1) logab–>c, log(s –1) ea a–>b, kj/mol ea b–>c, kj/mol ca–>b cb–>c r 2 2.1 13.7 25.8 200.1 354.3 0.48 0.52 0.9678 https://doi.org/10.15826/chimtech.2023.10.2.07 https://doi.org/10.15826/chimtech.2023.10.2.07 chimica techno acta 2023, vol. 10(2), no. 202310207 article 8 of 9 doi: 10.15826/chimtech.2023.10.2.07 table 6 kinetic parameters and the regression coefficient r2 for the fitting of multivariate nonlinear regression for combined autocatalysis reaction (heterogeneous reaction with n-th order and mpower autocatalysis). n m loga, log(s –1) ea, kj/mol r 2 1.8 0.8 12.7 216.6 0.9950 4. conclusions the thermal stability and primary crystallization kinetics of the gdyscalco he-bmg alloy were studied using dsc. the main conclusions are presented below. 1. gdyscalco he-bmg exhibited four different crystallization events. the characteristic temperatures (such as tx1, tp1, tg...) increased with increasing heating rate. in terms of m = 33 and angel’s gdyscalco classification, he-bmg belongs to the “fragile” glasses. 2. the activation energy (eα) of the process was calculated using the methods of vyazovkin, ozawa, friedman and kissinger. the kissinger method gives inaccurate activation energy values in comparison to the other methods. the eα values obtained by isoconversional methods indicate a nonlinear arrhenian behaviour and a complex process. 3. analysis of the crystallization kinetics by jeziorny’s modification of the avrami model showed that values of the local avrami index are 1.2<n(α)<3.2 for approximately the entire initial crystallization period. this means that the crystallization mechanism is largely determined by threedimensional nucleation growth controlled by the surface as the nucleation rate decreases. as verified by multivariate non-linear regression, the germ growth mechanism in the amorphous gdyscalco alloy is satisfactorily described by interface-controlled process. 4. the multivariate nonlinear regression method demonstrated that the primary crystallization of amorphous gdyscalco alloy proceeds as a combined auto-catalysis reaction in two parallel reactive paths (a→b, a+b→2b), where the nucleation mechanism is determined by the heterogeneous n-th order reaction (a→b), and grain growth (a+b→2b) by the m-power autocatalysis reaction. ● supplementary materials no supplementary materials are available. ● funding this work was supported by the russian science foundation (grant no. 23-23-00100), https://www.rscf.ru/en. ● acknowledgments none. ● author contributions conceptualization: b.v.a., k.t.v. data curation: b.v.a. formal analysis: k.d.a. funding acquisition: b.v.a., k.t.v., k.d.a., s.e.v. methodology: b.v.a., k.t.v., k.d.a., s.e.v. project administration: k.t.v. resources: s.e.v. software: k.d.a. supervision: b.v.a. validation: k.d.a., s.e.v. visualization: k.d.a. writing – original draft: k.d.a., k.t.v. writing – review & editing: b.v.a. ● conflict of interest the authors declare no conflict of interest. ● additional information authors ids: victor a. bykov, scopus id 55838510460; evgeniy v. sterkhov, scopus id 57205360319; tatyana v. kulikova, scopus id 7003952401. websites: institute of metallurgy, http://www.imet-uran.ru; ural federal university, https://urfu.ru/en. references 1. klement w, willens rh, duwez pol. non-crystalline structure in solidified gold-silicon alloys. nature. 1960;187:869–870. doi:10.1038/187869b0 2. yuan r, yu z, leng h, chou k. thermodynamic evaluation and experimental verification of the glass forming ability of cu–zr-based alloys. j non cryst solids. 2021;564:120835. 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chimicatechnoacta.ru letter 2023, vol. 10(4), no. 202310402 doi: 10.15826/chimtech.2023.10.4.02 1 of 6 ceramic materials based on lanthanum zirconate for the bone augmentation purposes: cytocompatibility in a cell culture model maria ulitko ab , yulia antonets a, irina antropova cd * , albert mullabaev d , elena volokitina cd , anna kasyanova ad , ekaterina loginova e, nataliia tarasova d a: ural federal university, ekaterinburg 620002, russia b: institute of medical cell technologies, ekaterinburg 620026, russia c: ural state medical university, ekaterinburg 620028, russia d: institute of high-temperature electrochemistry, ural branch of the russian academy of sciences, ekaterinburg 620137, russia e: prior-m, ekaterinburg 620027, russia * corresponding author: aip.hemolab@mail.ru this paper belongs to a regular issue. abstract creation of new ceramic materials for the bone augmentation purposes that combine the absence of cytotoxicity, high strength and osseointegration characteristics is an urgent modern task. in this work, the cytocompatibility of ceramic materials based on lanthanum zirconate (la2zr2o7) was determined to assess the prospects for their use as implants and components of human joint endoprostheses. the effect of ceramic materials based on undoped and alkali-earth (ca, sr) doped la2zr2o7 on the viability and proliferative activity of human cells was evaluated. the release of elements into the culture medium was also evaluated. keywords lanthanum zirconate bioceramics osteoreplacement material cytocompatibility cell culture received: 03.08.23 revised: 11.08.23 accepted: 14.08.23 available online: 16.08.23 key findings ● during the interaction with the studied materials, the human cell viability is sufficient to maintain their regenerative potential. ● doping of la2zr2o7 with ca or sr slowing down the adaptation of human fibroblasts to the ceramic material. ● sr, zr and la were found in the culture medium, which did not affect cytocompatibility during the cultivation period. © 2023, the authors. this article is published in open access under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). 1. introduction bone defects caused by injuries or diseases are becoming more common and have a huge impact on the patient life quality [1]. bone grafting and repair with autologous material is the gold standard, because it has a number of advantages: osteoconduction, osteoinduction and stimulation of osteogenesis. but possible complications should be taken into consideration: persistent pain syndrome may occur at the bone collection site (in situ), an infectious and inflammatory process may develop, an aesthetic defect may also occur [2, 3]. in this regard, the search for a new material for bone replacement is actively underway. such materials should be biocompatible, promote cell adhesion, proliferation and differentiation without adverse effects on host tissue [4, 5]. due to good biocompatibility, ceramic osseosubstituting materials have become widely used in practical medicine [6]. the presence of zirconium in ceramics significantly improves mechanical properties of the material [7, 8], without having toxic effect on preosteoblasts and improving the reaction of osteoblasts [9, 10]. addition of lanthanum has a significant effect on corrosion resistance of the material, moreover, it has an inhibitory effect on the formation of osteoclasts [11, 12]. doping ceramic materials can contribute to the process of osteogenesis and rapid bone healing [13, 14]. the doping quality depends on the type of ion used. doping with calcium promotes the synthesis of osteopontin, which is involved in bone formation and promotes cell attachment and proliferation on the implant surface [15]. the calcium-doped lanthanum zirconate demonstrates positive results in the process of bone remodeling and repair [16, 17]. the introduction of strontium into osteogenic materials is also considered promising [18]. it has been http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2023.10.4.02 mailto:aip.hemolab@mail.ru http://creativecommons.org/licenses/by/4.0/ https://orcid.org/0000-0003-3193-2903 https://orcid.org/0000-0002-9957-2505 https://orcid.org/0000-0002-3531-6692 https://orcid.org/0000-0001-5994-8558 https://orcid.org/0000-0002-3662-6051 https://orcid.org/0000-0001-7800-0172 https://crossmark.crossref.org/dialog/?doi=https://doi.org/10.15826/chimtech.2023.10.4.02&domain=pdf&date_stamp=2023-08-16 chimica techno acta 2023, vol. 10(4), no. 202310402 letter 2 of 6 doi: 10.15826/chimtech.2023.10.4.02 shown that the introduction of strontium into calcium phosphate ceramics leads to an improvement in biocompatibility, osteoconductivity and strength [19]. doping ions can contribute to osteogenesis and angiogenesis, induce effective regeneration of bone tissue. on the other hand, excessive accumulation of doping ions can provoke cytotoxicity and inhibition of biological activity [20]. creation of new ceramic materials for the bone augmentation purposes that combine the absence of cytotoxicity, high strength and osseointegration characteristics is an urgent modern task. in this research lanthanum zirconate was used, it was chosen was mainly due to the fact that its crystal structure is resistant to various substitutions, including calcium and strontium ions. earlier basic physical and chemical properties of lanthanum zirconate doped with alkaline earth (ca, sr) were studied, the influence of the synthesis method and modification of doping impurities on the target characteristics of materials was determined [21]. in this work, the cytocompatibility of ceramic materials based on lanthanum zirconate was determined to assess the prospects for their use as implants and components of human joint endoprostheses. the effect of three samples of complex oxides based on lanthanum zirconate: undoped la2zr2o7, calcium-doped la0.9ca0.1zr2o6.95, and strontium-doped la0.9sr0.1zr2o6.95 on the viability and proliferative activity of human cells was evaluated. the release of elements into the culture medium was also evaluated. 2. experimental samples of bioceramics la2zr2o7, la0.9ca0.1zr2o6.95 and la0.9sr0.1zr2o6.95 were obtained as described earlier [21]. to study the cytocompatibility of these materials, a culture of human dermal fibroblasts was used. dermal fibroblasts are a good cell model, since they represent a heterogeneous cellular population of connective tissue cells that play an important role in regeneration and the regulation of homeostasis processes. the use of dermal fibroblasts as test cultures to study the cytotoxicity of various biologically active materials (including bone replacement materials) is a standard research practice [22, 23]. cells were provided by the laboratory of cell cultures of the institute of medical cell technologies in yekaterinburg. the cells were cultured in eagle dmem ("biolot") medium with glutamine (1%), in the presence of 10% embryonic calf serum ("biolot") and gentamicin (50 mg/l) at 37 °c, in a humidified atmosphere of 5% co2. samples of bioceramics: la2zr2o7 (1), la0.9ca0.1zr2o6.95 (2) and la0.9sr0.1zr2o6.95 (3) in the form of round plates with a diameter of 5 mm and a thickness of 2 mm were sterilized for 30 minutes with ultraviolet radiation, washed with saline solution, dried in a sterile laminar flow box and placed into the wells of a 24-well tablet. a suspension of human fibroblasts in the volume of 500 µl was applied to ceramic plates. wells without samples of ceramics served as a control. the cells were cultured without changing the medium for 5 days. the study of cytocompatibility of ceramic materials included the determination of viability and proliferative activity of cells after 24, 72 and 120 hours of cultivation respectively. cell viability was assessed using a hemocytometer for the absorption of trypan blue by dead cells according to the international standard iso 10993-5. the counting of living and dead cells was carried out after their disaggregation with a mixture of trypsin and versene in a ratio of 1:3 and staining with a 0.4% solution of trypan blue. only dead cells were stained. based on the data obtained, the viability index (vi) and the proliferation index of the culture were calculated. the viability index was determined by the equation 1. vi = (viable (living )cells number)/ /(total number of cells) · 100% (1) the proliferation index was defined as the ratio of the number of grown cells to the initial number of cells. to assess the statistical significance of the differences between the control group and each of the experimental groups, the nonparametric mann-whitney criterion was used. at p≤0.05, the differences were considered statistically significant. in order to determine the potential release of ca, sr, zr and la from the ceramic materials la2zr2o7, la0.9ca0.1zr2o6.95 and la0.9sr0.1zr2o6.95, samples of the medium were taken after 24 and 72 hours of human fibroblast cultivation. the control was the culture medium from wells without ceramic samples. the concentration of ca and sr doping elements in dmem medium samples was determined by inductively coupled plasma mass spectrometry on a nexion 2000 device (perkin elmer, usa). the sample of the dmem medium of about 0.5 g was weighed in ptfe beakers on analytical scales with the accuracy of 0.0001 g. 2 cm3 of nitric acid purified by distillation without boiling was added to a beaker with a sample attachment, the beaker was covered with a ptfe lid and heated at a temperature of 150 °c until the release of nitrogen oxides ceased. after that, the contents of the beaker were quantitatively transferred into polypropylene measuring flasks with a capacity of 50 cm3 and brought to the mark with deionized water with the specific electrical resistance of 18.2 mω cm. the initial solution was diluted with 1 wt.% nitric acid solution and analyzed on a mass spectrometer. calibration characteristic of the spectrometer, which expresses the dependence of analytical signal value of 43сa and 88sr isotopes on the mass concentration of elements, was established using three standard calibration samples with concentrations of ca, sr, 10, 50 and 100 ppb and three series of measurements. calibration solutions were prepared from high-purity single-element samples of perkinelmer pure grade aquatic standards. spectral overlays on the 43сa isotope were eliminated by ammonia gas in the mass spectrometer reaction cell. control sample of the dmem medium was used as a blank sample. the arithmetic mean of three parallel measurements was taken as the result of the analysis. https://doi.org/10.15826/chimtech.2023.10.4.02 https://doi.org/10.15826/chimtech.2023.10.4.02 chimica techno acta 2023, vol. 10(4), no. 202310402 letter 3 of 6 doi: 10.15826/chimtech.2023.10.4.02 3. results and discussions in the course of the experiment a change in the viability and proliferative activity of cells was observed when they were cultured on ceramic samples. after 24 hours of cultivation on samples (2) and (3), there is a decrease in the viability of fibroblasts relative to the control by 11.4% and 16.5%, respectively. at the same time, the fibroblast viability index during cultivation on sample (1) did not differ significantly from the control (figure 1). there was no proliferative activity of fibroblasts after 24 hours of cultivation, both in the control and on experimental samples, which corresponds to the lag phase – the period when cells adapt to the new environment (figure 2). after 72 hours of cultivation, a lower level of cell viability is observed relative to the control for all samples, including sample (1). the proliferative activity of fibroblasts on all experimental samples lags behind the control, however, it increases relative to a 1-day period, which indicates the development of compensatory reactions in cell culture in response to the action of ceramic materials. after 120 hours of cultivation, the viability of fibroblasts increases to the control level in wells containing samples (1) and exceeds 60% of the control in wells with samples (2) and (3). the proliferative activity of cells on all ceramic materials is significantly lower than the control level, but increases relative to the previous period. at the same time, it was noted that cell proliferation occurs much more actively when grown on ceramic samples (1). the continued gradual increase in proliferative activity and cell viability index during cultivation on ceramic samples may indicate successful adaptation of human fibroblast cells to the effects of ceramic materials due to extracellular regeneration mechanisms. thus, when human fibroblasts interact with ceramic materials la2zr2o7 (1), la0.9ca0.1zr2o6.95 (2) and la0.9sr0.1zr2o6.95 (3), cell viability varies within acceptable values and is sufficient to maintain their recovery potential. doping of lanthanum zirconate with calcium or strontium slows down the adaptation of human fibroblasts during cultivation on the studied ceramic materials without significant differences between la0.9ca0.1zr2o6.95 and la0.9sr0.1zr2o6.95. it can be assumed that the introduction of additional ions (calcium or strontium) into the structure of the lanthanum zirconate leads to the need for additional time for the adaptation of cells growing in culture on the studied materials. additional studies are needed to elucidate the nature of this phenomenon. the results of determining the concentrations of ca, sr, zr and la in dmem culture medium samples in the dynamics of human fibroblast cultivation are shown in figure 3. the concentration of ca ions in the culture medium with ceramic samples did not exceed the control level, which indicates the absence of this element release from all studied ceramic samples during the study period (figure 3a). figure 1 influence of bioceramic samples on the viability of human fibroblasts. la2zr2o7 (1), la0.9ca0.1zr2o6.95 (2) and la0.9sr0.1zr2o6.95 (3); * ‒ differences with control are statistically significant (p<0.05); # – differences in doped samples with undoped lanthanum zircon are statistically significant (p<0.05). figure 2 human fibroblast culture proliferation index when exposed to ceramic samples: la2zr2o7 (1), la0.9ca0.1zr2o6.95 (2) and la0.9sr0.1zr2o6.95 (3); *‒ differences with control are statistically significant (p<0.05); # – differences in doped samples with undoped lanthanum zircon statistically significant (p<0.05). the analysis revealed the presence of sr ions in the medium with the samples of the material (3), while it was noted that the concentration of these ions increased strating from the first to the third day of cultivation (figure 3b). the level of zr ions in the medium during cell culture on samples (1) did not differ from the control. cultivation on samples (2) resulted in a slight increase in the concentration of zr in the medium by the end of the third day. when using samples (3), an increase in the concentration of zr ions in the medium was detected on the 1st day of cultivation with a slight further increase by the 3rd day (figure 3c). when culturing fibroblasts on samples (1), a slight release of la ions into the medium was observed without a significant increase in the dynamics of the studied period. for samples (2), there was also no increase in the release of la ions from the 1st to the 3rd day, although their release was 2 times higher than on samples (1). the release of la ions from samples (3) into the medium was more active compared to samples (1) and (2), and a significant increase in the concentration of this ion was noted the 1st to the 3rd day (figure 3d). https://doi.org/10.15826/chimtech.2023.10.4.02 https://doi.org/10.15826/chimtech.2023.10.4.02 chimica techno acta 2023, vol. 10(4), no. 202310402 letter 4 of 6 doi: 10.15826/chimtech.2023.10.4.02 figure 3 the concentration of ca (a), sr (b), zr (c) and la (d) in the medium after 1 and 3 days of cultivation of human fibroblasts on ceramic samples: la2zr2o7 (1), la0.9ca0.1zr2o6.95 (2) and la0.9sr0.1zr2o6.95 (3). the study showed that ca is resistant and is not released from the studied samples into the culture medium. sr and zr ions are less stable, they are released into the medium mainly from the material (3). la is the least stable, and these ions are also released into the medium most actively from the material (3). it should be noted that despite the obvious differences in the release of sr, zr and la from the samples of materials (2) and (3), no significant differences in the viability and proliferative activity of fibroblasts during cultivation on these samples within the cultivation period were found. 4. limitations the limitation of this work is the inability to establish the effect of new ceramic materials on the body as a whole in the dynamics of the regenerative process after bone injury, which is the driving impulse for the next stage of preclinical studies using laboratory animals. 5. conclusion this paper presents the results of the first stage of preclinical studies of new complex oxides based on lanthanum zirconate, created for bone augmentation. cytocompatibility of ceramics based on undoped and doped lanthanum zirconate (la2zr2o7, la0.9ca0.1zr2o6.95 and la0.9sr0.1zr2o6.95) was determined. it was established that during the interaction of human fibroblasts with the studied ceramic materials, the viability of cells varies within acceptable values and is sufficient to maintain their regenerative potential. doping of lanthanum zirconate with calcium or strontium affects cytocompatibility by slowing down the adaptation of human fibroblasts to the ceramic material. additional studies are needed to elucidate the nature of this effect. it should also be taken into account that some growth retardation at the initial stages of regeneration may not affect the regeneration process as a whole. to test this assumption, it is necessary to conduct animal experiments. it was found that ca is resistant and is not released from the studied samples into the culture medium. the release of sr, zr and la ions into the culture medium was detected, but this did not significantly affect the proliferative activity and viability of human fibroblasts during the cultivation period. cytocompatibility of new ceramic materials was determined on the culture of human fibroblast cells. however, this work is the first stage of preclinical studies of new complex oxides based on lanthanum zirconate. ● supplementary materials no supplementary materials are available. ● funding this work was supported by the russian science foundation (grant no. 22-25-20037), https://www.rscf.ru/en. ● acknowledgments none. https://doi.org/10.15826/chimtech.2023.10.4.02 https://doi.org/10.15826/chimtech.2023.10.4.02 https://www.rscf.ru/en chimica techno acta 2023, vol. 10(4), no. 202310402 letter 5 of 6 doi: 10.15826/chimtech.2023.10.4.02 ● author contributions conceptualization: m.u., i.a., n.t. data curation: m.u, i.a. funding acquisition: e.v. investigation: y.a., e.l., a.k., a.m. methodology: m.u., a.m. validation: m.u., i.a, a.m., visualization: i.a. writing – original draft: m.u., i.a. writing – review & editing: i.a., n.t. ● conflict of interest the authors declare no conflict of interest. ● additional information author ids: maria ulitko, scopus id 56766009100; irina antropova, scopus id 18338795600; albert mullabaev, scopus id 57156662300; elena volokitina, scopus id 57194755505; anna kasyanova, scopus id 57192873241; natalia tarasova, scopus id 37047923700. websites: ural federal university, https://urfu.ru/en/; ural state medical university, https://usma.ru/en/main/; institute of medical cell technologies, https://celltechnologies.ru/; institute of high temperature electrochemistry ub ras, http://www.ihte.uran.ru/; 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(in russian). doi:10.17816/2311-2905-1704 18. chen y, liu z, jiang t, zou x, lei l, yan w, yang j, li b. strontium-substituted biphasic calcium phosphate microspheres promoted degradation performance and enhanced bone regeneration. j biomed mater res part a. 2020;108:895–905. doi:10.1002/jbm.a.36867 19. silva adr, pallone emja, lobo ao. modification of surfaces of alumina-zirconia porous ceramics with sr2+ after sbf. j aust ceram soc. 2020;56:517–524. doi:10.1007/s41779-019-00360-4 20. pereira p, neto as, rodrigues as, barros i, miranda c, ramalho-santos j, pereira de almeida l, ferreira jmf, coelho jfj, fonseca ac. in vitro evaluation of biphasic calcium phosphate scaffolds derived from cuttlefish bone coated with poly(ester urea) for bone tissue regeneration. polymers (basel). 2023;15(10):2256. doi:10.3390/polym15102256 21. tarasova n, galisheva a, belova k, mushnikova a, volokitina e. ceramic materials based on lanthanum zirconate for the https://doi.org/10.15826/chimtech.2023.10.4.02 https://doi.org/10.15826/chimtech.2023.10.4.02 https://www.scopus.com/authid/detail.uri?authorid=56766009100 https://www.scopus.com/authid/detail.uri?authorid=18338795600 https://www.scopus.com/authid/detail.uri?authorid=57156662300 https://www.scopus.com/authid/detail.uri?authorid=57194755505 https://www.scopus.com/authid/detail.uri?authorid=57192873241 https://www.scopus.com/authid/detail.uri?authorid=37047923700 https://urfu.ru/en/ https://usma.ru/en/main/ https://celltechnologies.ru/ https://celltechnologies.ru/ http://www.ihte.uran.ru/ https://www.prior-m.ru/ https://doi.org/10.1016/j.injury.2020.07.040 https://doi.org/10.1007/s11914-018-0432-1 https://doi.org/10.3390/ma11010014 https://doi.org/10.3390/mi13050780 https://doi.org/10.3389/fcell.2021.665813 https://doi.org/10.1007/978-3-319-76711-6_3 https://doi.org/10.1007/978-3-319-76711-6_3 https://doi.org/10.1111/j.1708-8208.2012.00454.x https://doi.org/10.1016/j.mtbio.2022.100270 https://doi.org/10.1371/journal.pone.0113426 https://doi.org/10.1016/j.ijbiomac.2016.11.052 https://doi.org/10.1007/s10856-021-06626-3 https://doi.org/10.1002/jcp.25065 https://doi.org/10.3390/pharmaceutics14081582 https://doi.org/10.2147/ijn.s193576 https://doi.org/10.1007/s10856-010-4011-y https://doi.org/10.21823/2311-2905-2020-26-3-130-140 https://doi.org/10.17816/2311-2905-1704 https://doi.org/10.1002/jbm.a.36867 https://doi.org/10.1007/s41779-019-00360-4 https://doi.org/10.3390/polym15102256 chimica techno acta 2023, vol. 10(4), no. 202310402 letter 6 of 6 doi: 10.15826/chimtech.2023.10.4.02 bone augmentation purposes: materials science approach chimica techno acta. 2022;2:9. doi:10.15826/chimtech.2022.9.2.09 22. bokov ae, bulkin aa, davydenko dv, orlinskaya ny, egorikhina mn, rubtsova yp, charykova in, kovylin rs, yudin vv, chesnokov sa, morozov ag, mlyavykh sg, aleynik dy. biological response to a novel hybrid polyoligomer: in vitro and in vivo models. sovrem tekhnologii med. 2021;12(6):36– 44. doi:10.17691/stm2020.12.6.05 23. hadzik j, jurczyszyn k, gębarowski t, trytek a, gedrange t, kozakiewicz m, dominiak m, kubasiewicz-ross p, trzcionkaszajna a, szajna e, simka w. an experimental anodized and low-pressure oxygen plasma-treated titanium dental implant surface-preliminary report. int j mol sci. 2023;24(4):3603. doi:10.3390/ijms24043603 https://doi.org/10.15826/chimtech.2023.10.4.02 https://doi.org/10.15826/chimtech.2023.10.4.02 https://doi.org/10.15826/chimtech.2022.9.2.09 https://doi.org/10.17691/stm2020.12.6.05 https://doi.org/10.3390/ijms24043603 50 введение в современных нанотехнологиях одними из перспективных материалов являются наночастицы оксидов металлов. наиболее широко используются оксиды железа, алюминия, титана, цинка, никеля и циркония. эти материалы применяются в различных областях науки, технологии и промышленности. например, оксиды железа и алюминия находят применение в медицине из-за отсутствия токсического действия на организм [1]. помимо медицинского применения, наночастицы оксидов металлов являются основой для получения защитных покрытий, керамики, катализаторов и новых эффективных теплоносителей [2]. р. р. мансуров, а. п. сафронов, н. в. лакиза, д. в. лейман уральский федеральный университет, 620002, екатеринбург, ул. мира, 19. адсорбция tx-100 и sdbs на поверхности нанопорошков al 2 o 3 и γ-fe 2 o 3 из водных растворов* методом уф-спектрофотомерии были исследованы адсорбционные равновесия в водных наносуспензиях оксидов алюминия и железа, стабилизированных sdbs и tx-100. установлено, что неионогенный пав tritonx-100 не адсорбируется из водного раствора на гидрофильной поверхности наночастиц оксидов как алюминия, так и железа. в то же время для анионного пав sdbs адсорбция наблюдалась на наночастицах обоих оксидов. в исследованном диапазоне концентраций изотермы адсорбции sdbs из водного раствора на поверхностях наночастиц al 2 o 3 и γ-fe 2 o 3 не достигают насыщения. долю поверхности частиц, занятых молекулями пав, оценивали на основании величины площади молекулы sdbs в адсорбционном слое, которая была получена из изотерм поверхностного натяжения (0,10 нм2)4. расчеты показали, что при исследованных концентрациях sdbs для al 2 o 3 было занято приблизительно до 30 % площади поверхности наночастиц, а для γ-fe 2 o 3 – до 10 %. * работа выполнена при поддержке проектов фундаментальных исследований, финансируемых уро ран. у д к 6 61 .8 62 +6 61 .8 72 .2 © мансуров р. р., сафронов а. п., лакиза н. в., лейман д. в., 2014 51 2014 | № 2 | cta технологии практического использования наночастиц оксидов металлов основаны на получение из них суспензий. но получаемые наносуспензии, как и любая другая коллоидная система, не являются устойчивыми вследствие агрегации наночастиц дисперсной фазы. это закономерно, так как агрегация является термодинамически выгодным процессом, поскольку при этом уменьшается поверхность раздела фаз и, соответст-венно, снижается поверхностная свободная энергия частиц дисперсной фазы. таким образом, главной проблемой практического использования наночастиц оксидов металлов является стабильность образуемых ими суспензий, так как для практического применения необходимы устойчивые суспензии с узким распределением частиц по размерам. в настоящее время для предотвращения агрегации и/или уменьшения размеров агрегатов наночастиц используют, среди прочего, специальные добавки – дисперсанты. поверхностно-активные вещества (пав) являются одними из самых эффективных дисперсантов. пав, адсорбируясь на границе раздела «жидкость – твердая поверхность», понижают поверхностную энергию диспергированных в жидкой среде частиц, предотвращая тем самым их агрегацию. несмотря на насущную необходимость, в литературе имеется весьма ограниченное число работ, посвященных детальному изучению стабилизации наносуспензий оксидов металлов пав [2, 3]. на современном этапе исследования пока только точно установлено, что стабилизация суспензий идет за счет адсорбции пав на наночастицах. таким образом, становится актуальной задача накопления экспериментальных данных по адсорбции пав на наночастицах суспензий оксидов металлов. целью данной работы является изучение адсорбционных равновесий в водных наносуспензиях оксидов алюминия и железа, стабилизированных sdbs и tx-100. объекты и методы исследования для получения водных наносуспензий использовали нанопорошки al2o3 и γ-fe2o3, электронные микрофотографии которых представлены на рис. 1. нанопорошок al2o3 производ-ства inframat advanced materials (iam, сша) был получен методом плазменного распыления. значение удельной поверхности по данным низкотемпературной сорбции паров азота на установке micromeriticstristar 3000 составило 9 м2/г. эффективный средний диаметр частиц составляет 185 нм. нанопорошок γ-fe2o3 был получен методом электрического взрыва проволоки (эвп) в институте электрофизики уро ран. значение удельной поверхности по данным низкотемпературной сорбции паров азота на установке micromeritics tristar 3000 составило 20 м2/г. эффективный средний диаметр частиц составляет 65 нм. на основе нанопорошков готовили адсорбционные системы следующим образом: 15 мл водного раствора пав с 1 г нанопорошка подвергали обработке на ультразвуковой ванне мощностью 90 вт в течение одного часа при 30 0с. полученные суспензии оставляадсорбция tx-100 и sdbs на поверхности нанопорошков al 2 o 3 и γ-fe 2 o 3 из водных растворов 52 cta | № 2 | 2014 ли в темноте на 5 суток для установления адсорбционного равновесия. для корректного измерения остаточной концентрации пав суспензии перед измерением на спектрофотометре подвергали центрифугированию в течение 15 минут при 9000 об/мин. в качестве дисперсантов использовали поверхностно-активные вещества различной природы. в качестве анионного пав был взят додецилбензосульфонат натрия (sdbs) производства acrosorganics, в качестве неионогенного пав – октилфеноксиполиэтоксиэтанол (tritonx-100) производства merck. ккм водных растворов sdbs и tx-100 составляет 0,6 и 0,2 г/л (1,8 ммоль/л и 0,32 ммоль/л), соответственно [4]. для определения величины адсорбции sdbs и tx-100 из водного раствора на наночастицах al2o3 и γ-fe2o3 был использован метод спектрофотометрии в уф-области. уф-спектры поглощения водных растворов пав были получены на спектрофотометре heliosα. измерения проводились в кварцевой кювете толщиной 1 см на диапазоне длин волн 190–350 нм. результаты и их обсуждение на рис. 2 приведены уф-спектры поглощения водных растворов tx-100 и sdbs концентраций до и после ккм. в качестве характеристических были выбраны полосы, отвечающие пикам поглощения: 224 нм и 276 нм для водных растворов tx-100 концентраций до и после ккм, соответственно; 224 нм и 260 нм для водных растворов sdbs концентраций до и после ккм, соответственно. известно, что поглощение в уф-области определяется наличием в ненасыщенных связях легко возбудимых π-электронов. в случае исследованных пав поглощение в уф-области обусловлено наличием у обоих пав бензольного кольца. по данным молекулярного моделирования в программе cache 7.5 методом zindo в геометрии pm5 было установлено, что полоса поглощения 224 нм соответствует электронному переходу взмо => нсмо+1, а полосы 260 и 276 нм – переходу взмо => нсмо. на основании полученных уф-спектров для ряда концентраций водных растворов tx-100 и sdbs рис. 1. электронные микрофотографии ноночастиц порошков γ-fe2o3: а – (пэм, jeoljem 2100) и al2o3 б – (рэм, karl-zeissleo 982) р. р. мансуров, а. п. сафронов, н. в. лакиза, д. в. лейман 53 2014 | № 2 | cta адсорбция tx-100 и sdbs на поверхности нанопорошков al 2 o 3 и γ-fe 2 o 3 из водных растворов были получены калибровочные графики, по которым, используя закон бугера – ламберта – бера, определяли остаточную концентрацию пав в наносуспензиях оксидов металлов после адсорбции. для количественного определения адсорбции измеряли разность интенсивностей поглощения до и после адсорбции на соответствующих характеристических полосах поглощения. на основании полученных уф-спектров адсорбционных систем было установлено, что tx-100 не адсорбировался из водного раствора на наночастицах γ-fe2o3 и al2o3. это проявлялось в том, что поглощение в уф-области до и после выдерживания наночастиц γ-fe2o3 в течение 5 суток в водном растворе tx-100 было неизменно (рис. 3). интересно отметить тот факт, что в случае наносуспензии оксида алюминия наблюдали даже увеличение концентрации tx-100 в дисперсионной среде (рис. 4), что формально отвечает отрицательной адсорбции. по-видимому, это связано с тем, что не ионогенный пав вытесняется из порис. 4. уф-спектр поглощения водного раствора tx-100 концентрации 0,5 г/л до и после адсорбции на наночастицах al2o3 а б рис. 2. уф-спектры поглощения водных растворов tx-100 (а) и sdbs (б) концентраций до и после ккм рис. 3. уф-спектр поглощения водного раствора tx-100 концентрации 0,1 г/л до и после адсорбции на наночастицах γ-fe2o3 54 cta | № 2 | 2014 верхностных слоев вблизи частиц в объем раствора. в отличие от неионогенного пав tx-100, для адсорбционных систем с sdbs поглощения уменьшалась после адсорбции (рис. 5). на основании полученных уф-спектров адсорбционных систем были построены изотермы адсорбции sdbs из водного раствора на поверхности наночастиц al2o3 и γ-fe2o3 (рис. 6). заключение методом спектрофотометрии были получены уф-спектры водных растворов tritonx-100 и sdbs концентраций до и после ккм. установлено, что неионогенный пав tritonx-100 не адсорбируется из водного раствора на гидрофильной поверхности наночастиц al2o3 и γ-fe2o3. в то же время для анионного пав sdbs адсорбция наблюдалась на наночастицах обоих оксидов. в исследованном диапазоне концентраций изотермы адсорбции sdbs из водного раствора на поверхностях наночастиц al2o3 и γ-fe2o3 не достигают насыщения. долю поверхности частиц, занятых молекулями пав, оценивали на основании величины площади молекулы sdbs в адсорбционном слое, которая была получена из изотерм поверхностного натяжения (0,10 нм2) [4]. расчеты показали, что при исследованных концентрациях sdbs для al2o3 было занято приблизительно до 30 % площади поверхности наночастиц, а для γ-fe2o3 – до 10 %. 1. gao j., gu h., xu b. accounts chem. research, 2009, 42, 1097. 2. zhu d., li x., wang n., wang x., gao j., li h. current applied physics, 2009, 9, 131. 3. li x., zhu d., wang x. j. coll. interface science, 2007, 310, 456. 4. рис. 5. уф-спектр поглощения водного раствора sdbs концентрации 0,1 г/л до и после адсорбции на наночастицах al2o3 рис. 6. изотерма адсорбции sdbs из водного раствора на поверхности наночастиц al2o3 и γ-fe2o3 р. р. мансуров, а. п. сафронов, н. в. лакиза, д. в. лейман 55 2014 | № 2 | cta адсорбция tx-100 и sdbs на поверхности нанопорошков al 2 o 3 и γ-fe 2 o 3 из водных растворов 5. mansurov r. r., leiman d. v. problems of teroretical and experimental chemistry. abs. xxii russian conference, ekaterinburg, russia, 24/04/1228/04/12. 2012, 45. [мансуров р. р., лейман д. в., сафронов а. п. // проблемы теоретической и экспериментальной химии: тез. докл. xxii рос. молодеж. науч. конф., екатеринбург, россия. 24–28 апреля 2012 года. с. 45]. r. r. mansurov, a. p. safronov, n. v. lakiza, d. v. leyman ural federal university, 19, mira street, 620002, ekaterinburg adsorption of tx-100 and sdbs on the surface of alumina and maghemite nanoparticles from aqueous solutions adsorption equilibriums in aqueous aluminum and iron oxides nanosuspensions stabilized by sdbs and tx-100 were investigated using uv spectrophotometry. it was established that the non-ionic surfactant tritonx-100 is not adsorbed from aqueous solution on a hydrophilic surface of both aluminum and iron oxide nanoparticles. at the same time adsorption of the anionic surfactant sdbs was observed in both oxides nanoparticles. in the investigated range of concentrations adsorption isotherms sdbs from aqueous solution on the surfaces of nanoparticles al 2 o 3 and g-fe 2 o 3 not reach saturation. the share of the particles surface occupied by surfactant molecules were estimated based on the value of an area of molecules sdbs in the adsorption layer, which was derived from the isotherm of surface tension (0.10 nm2). the calculations showed that at the investigated concentrations sdbs al 2 o 3 employed approximately 30 % of surface of nanoparticles, and for g-fe 2 o 3 – up to 10%. страница 1 104 введение электролитическое рафинирование меди проводят в ваннах ящичного типа. на электролиз поступают аноды после огневого рафинирования, содержащие примеси различных металлов. все примеси делятся на три группы [1]. первую группу состаляют более электрополо жительные, по сравнению с медью, металлы-примеси (au, ag, pt, pd), которые выпадают в виде е. г. демина, а. б. даринцева, и. б. мурашова уральский федеральный университет, 620002, екатеринбург, ул. мира, 19. e-mail: a.b.darintseva@ustu.ru электрохимическое обезмеживание медно-сульфатного электролита при электролитическом рафинировании меди в растворе электролита накапливаются ионы никеля и меди, которые необходимо периодически извлекать. в промышленности извлечение меди проводят в две стадии, снижая концентрацию меди до 1 г/л. численным моделированием установлена зависимость скорости обезмеживания от отдельных параметров: перемешивания электролита, его объема, площади катодной поверхности. экспериментально исследован процесс обезмеживания в спокойном электролите и при перемешивании раствора. во всех опытах на катоде кристаллизовался гладкий, компактный осадок меди. скорость обезмеживания при организации принудительного перемешивания выше, чем в спокойном электролите. промышленный способ обезмеживания сульфатного электролита приводит к образованию на катоде дендритного осадка меди, ионы которой восстанавливаются в предельных условиях. снижение концентрации меди при i = const вызывает образование дендритного осадка, который легко осыпается на дно электролизера, обогащая медью шлам. гарантией получения гладкого осадка при обезмеживании с получением компактной меди, исключающей к тому же восстановления мышьяка с выделением ядовитого арсина, является организация интенсивного перемешивания или циркуляции электролита, обеспечивающая восстанавление ионов меди в допредельных условиях в виде гладкого осадка. у д к 5 44 .6 23 .0 32 .0 32 .7 3 © демина е. г., даринцева а. б., мурашова и. б., 2014 105 2014 | № 3 | cta шлама. во вторую группу входят более электроотрица тельные примеси (fe, ni), которые накапливаются в растворе. третью группу составляют примеси, которые могут восстанавливаются на катоде. металлы с более электроотрицательным потенциалом накапливаются в растворе электролита, увеличивают его вязкость, снижают электропроводность, поэтому необходимо периодически часть электролита отводить на извлечение этих металлов из раствора. обязательной к извлечению из раствора примесью являются ионы никеля. кроме того, из-за разных выходов по току (катодного и анодного) в электролите накапливаются ионы меди. в связи с этим часть электролита подвергают сначала обезмеживанию, а затем его передают на стадию извлечения никеля в виде никелевого купороса. обезмеживание электролита на стадию обезмеживания посту пает раствор, содержащий 100 г/л h2so4, 30 г/л cu 2+ и 50 г/л ni2+. на первой стадии обезмеживания снижают содержание электролита по ионам меди до 10 г/л. на второй стадии проводят электролиз при токовой нагрузке 3 ка с циркуляцией электролита 17 л/ мин и нерастворимыми свинцовыми анодами. концентрацию по меди снижают до 1 г/л. в ходе электролиза на катодах выделяется медь на предельном токе, восстанавливаются примеси металлов. при этом мышьяк, содержащийся в растворе, может выделяться на катоде с образованием ядовитого газа арсина. в связи с этим необходимо решить следующие задачи: подобрать условия проведения электролиза такие, чтобы на катоде восстанавливалась медь в виде компактного осадка. кристаллизация меди в допредельных условиях протекает при потенциалах, гарантирующих исключение образования арсина. моделирование процесса обезмеживания при плотности тока выше предельной на катоде кристаллизуется дендритный осадок. для получения компактного осадка меди рабочая плотность тока не должна превышать предельную. для определения допустимой границы заданного тока в расчетах примем значение тока i, равное предельному: i zfdc i s zfdc kïð = =δ δ ; , (1) где sk – площадь катода в ванне обезмеживания. по закону фарадея количество осевшего металла определяется по соотношению (2) m a zf i t.= ⋅ (2) приращение меди на катоде определяется, с одной стороны, по закону фарадея (2), а с другой – уменьшением концентрации ее в объеме vς: − = ⋅ = − ⋅ ⋅dm a zf i dt v a dc.ς (3) электрохимическое обезмеживание медно-сульфатного электролита 106 cta | № 3 | 2014 тогда изменение концентрации − = ⋅dc i v zf dt. σ (4) подставляя выражение для тока (1) в уравнение для dc (4), получаем: − = ⋅ ⋅ ⋅ ⋅dc c d s v dt.k σ ´ (5) разделим переменные − = ⋅ ⋅ ⋅ dc c d s v dtk σ δ (6) и проинтегрируем в пределах от начальной концентрации снач до текущей с и по времени от нуля до t: −       = ⋅ ⋅ ⋅ln ä ä íà÷ d s v tk σ δ или ln c ñ íà÷      = ⋅ ⋅ ⋅ d s v t.k σ δ (7) таким образом, концентрация металла в ходе обезмеживания меняется во времени ä ä= ⋅ − ⋅ ⋅      íà÷ exp d s v tk σδ , (8) а общее время электролиза при заданных концентрациях снач и с: t v d sk = ⋅ ⋅ ⋅       σ δ ln c ñ íà÷ . (9) согласно полученному выражению (8) скорость процесса определяется следующими параметрами: начальной концентрацией металла в электролите, объемом раствора, подвергаемого электролизу, площадью катодной поверхности, условиями перемешивания и температурой электролита. в приведенные уравнения входят параметры: коэффициент диффузии и толщина диффузионного слоя δ, которые определяются только экспериментально. численное моделирование процесса обезмеживания при изучении эффективности влияния параметров электролиза на скорость обезмеживания проводили численное моделирование. при этом использовали следующие базовые параметры: объем электролита v = 100 мл, площадь катодной поверхности sk = 72 см 2, толщина диффузионного слоя δ = 1·10–4 м, коэффициент диффузии ионов d = 4 · 10–10 м2/с, начальная концентрация меди в растворе с = 10 г/л. при увеличении объема электролита с 50 до 150 мл (рис. 1), при прочих равных параметрах, увеличивается время электро лиза до достижения заданной концент рации. согласно расчету обезмеживание 50 мл электролита необходимо проводить в течение 1,1 часа, а 150 мл – в течение 3,3 часа. при увеличении площади катодной рис. 1. влияние объема поступающего на обезмеживание электролита на скорость процесса. цифрами на диаграмме показан объем электролита v, мл е. г. демина, а. б. даринцева, и. б. мурашова 107 2014 | № 3 | cta электрохимическое обезмеживание медно-сульфатного электролита поверхности с 52 до 112 см2 продолжительность процесса сокращается (рис. 2). время электролиза с использованием катода площадью 52 см2 составляет 3,1 часа, а с использованием катода площадью 112 см2 – 1,3 часа. перемешивание электролита ускоряет процесс обезмеживания. организация принудительного перемешивания электролита сказывается в первую очередь на значении толщины диффузионного слоя δ. численное моделирование проводили при разных значениях толщины диффузионного слоя, которую изменяли от 2,5 · 10–5 до 1 · 10–4 м (рис. 3). численный эксперимент, конечно, не может отразить реальную картину процесса, но влияние отдельных параметров электролиза на скорость обезмеживания может быть наглядно выявлено. эксперимент по обезмеживанию в лабораторных условиях обезмеживание электролита проводили, используя модельный раствор, который содержал 10 г/л cu2+ и 100 г/л h2so4. при обезмеживании в каче-стве анодов исполь зовали свинцовые пластины, которые предварительно подвергали перманга натной обработке [2], катодом служила гофрированная медная фольга, потенциал катода измеряли относительного медного электрода сравнения. во всех опытах обезмеживанию подвергали 100 мл раствора, при этом использовали катод площадью 72 см2. градуировочный график зависимости предельной плотности тока от концентрации ионов меди в растворе получали экспериментально с помощью поляризационных исследований в трех электродной ячейке в растворах с различным содержанием ионов меди (10, 8, 6, 4, 2 и 1 г/л). с помощью потен циостата ipc-pro при скорости разверки потенциала 1 мв/с электрод поляризовали в отрицательную область на 300 мв. в ходе обезмеживания через равные промежутки времени останавливали процесс, получали поляризационную кривую, по предельной плотности тока рис. 2. влияние площади катодной поверхности на скорость процесса. цифрами на диаграмме показана площадь поверхности sk, см 2 рис. 3. влияние толщины диффузионного слоя на скорость процесса. цифрами на диаграмме показана толщина диффузионного слоя δ · 105, м выявлено. 108 cta | № 3 | 2014 которой определяли концентрацию меди в растворе электролита. режим электролиза подбирали для достижения следующих целей: а) снижение концентрации меди с 10 до 1 г/л; б) получение гладкого осадка меди на катоде. в первой серии опытов исследовали процесс обезмеживания без перемешивания, при этом поддерживали ток i = 0,8 iпр. электролиз проводили по следующей схеме: 15 минут электролиз, затем измерение поляризационной кривой. зависимость предельной плотности тока от концентрации металла без перемеши вания электролита представлена на рис. 4. обезмеживание электролита в спокойном растворе оказалось неэффективным (рис. 5); по истечение 3 часов удалось снизить концентрацию меди в растворе только до 5 г/л; при этом на катоде получили ровный осадок меди. для организации перемешивания электролита использовали мешалку с регулируемым числом оборотов heidolph mr hei standart. опыты проводили при скорости 1000 об/мин. результаты поляри зационных исследований при переме шивании электролита в растворах с различной концентрацией меди представ лены на рис. 6. перемешивание электролита приводит к уменьшению толщины диффузионного слоя δ (1), увеличению предельной плотности тока и, соответственно, токовой нагрузки, при которой проводят обезмеживание. в результате расчета получилось, что первые 15 минут процесс необходимо проводить при i = 6,5 а, что невозможно ввиду ограничения источника тока. в связи с этим обмеживание проводили в следующем режиме: первые 15 минут поддерживали ток i1 = 942 ма; на последующих отрезках времени токовая нагрузка составляла i = 754 ма. обезмеживание электролита с перемешиванием увеличивает скорость процесса (рис. 7). в результате опытов удалось снизить концентрацию меди в растворе до 1 г/л через 2 часа электролиза; на катоде при этом кристаллизовался компактный розовый осадок меди. обезмеживание электролита при постоянной поляризации [3] в допредельных условиях позволяет получать в течение всего электролиза компактный осадок меди, но процесс при этом занимает длительное время. рис. 5. обезмеживание электролита без перемешивания раствора рис. 4. градуировочный график в электролите без перемешивания е. г. демина, а. б. даринцева, и. б. мурашова 109 2014 | № 3 | cta электрохимическое обезмеживание медно-сульфатного электролита обсуждение результатов промышленный способ обезмеживания сульфатного электролита приводит к образованию на катоде дендритного осадка меди, ионы которой восстанав ливаются в предельных условиях. снижение концентрации меди при i = const вызывает образование дендритного осадка, который легко осыпается на дно электролизера, обогащая медью шлам. гарантией получения гладкого осадка при обезмеживании с получением компактной меди, исключающей к тому же восстановлениях мышьяка с выделением ядовитого арсина является организация интенсивного перемешивания или циркуляции электролита, обеспечивающая восстанавление ионов меди в допредельных условиях в виде гладкого осадка. 1. baimanov j. v., zhurin a. i. electrolysis in hydrometallurgy. m: metallurgizdat, 1977. 336 pp. 2. ogorodniychuk v. i. tsvet.mettaly, 1974, 25. 3. demina m. g., sabirov g. yu., darintseva a. b., murashova i. b. / problems theoretical and experimental chemistry: abstracts of xxiii of the russian youth scientifi c conference. yekaterinburg, russia. 23–26.04.2013, 389. рис. 6. градуировочный график в электролите с перемешиванием рис. 7. обезмеживание электролита с перемешиванием раствора 110 cta | № 3 | 2014 е. г. демина, а. б. даринцева, и. б. мурашова e. g. demina, a. b. darintseva, i. b. murashova ural federal university, 19, mira street, 620002, ekaterinburg. e-mail: a.b.darintseva@ustu.ru electrochemical copper extraction from sulphate electrolyte copper and nickel ions are accumulated in the solution during electrolytic refining of copper. these ions need to be extracted from the solution from time to time. in industry copper extraction is carried out in two stages. it results in copper ions concentration reducing to 1 g/l. numerical simulation was used to define dependence of the process of copper extraction from particular parameters: mixing of electrolyte, volume of electrolyte, area of cathodic surface. the process of copper extraction was investigated in still electrolyte and during mixing of the solution. smooth and compact precipitate crystallized on the cathode in all experiments. rate of copper extraction during mixing of electrolyte is higher than in still electrolyte. the industrial method of abuseive sulphate electrolyte results in the formation on the cathode dendritic sediment copper ions which are restored in extreme conditions. the decrease in the concentration of copper at i = const causes the formation of dendritic sludge that is easily crumbles to the bottom of the cell, enriching copper sludge. guarantee smooth sediment when basmajian with obtaining compact copper, excluding besides the recovery of arsenic emitting poisonous arsina cars is the organization of intensive mixing or electrolyte circulation, ensuring the recovery of copper ions in limitless conditions smooth and sediment. 14 © михайловская з. а., буянова е. с., петрова с. а., захаров р. г., 2014 з. а. михайловская1, е. с. буянова2, с. а. петрова2, р. г. захаров2 1уральский федеральный университет, 620083, екатеринбург, пр. ленина, 51. e-mail: zozoikina@mail.ru 2институт металлургии уро ран, 620016, екатеринбург, ул. амундсена, 101. e-mail: danaus@mail.ru замещенные молибдаты висмута на основе bi 13 mo 5 o 34±δ : получение и свойства* работа посвящена исследованию возможности получения, установлению специфики структуры и электропроводящих характеристик замещенных молибдатов висмута bi 13 mo 5 o 34±δ , содержащих в структуре уникальные для твердых оксидов колонки [bi 12 o 14 ] n 8n+ и проявляющих одномерную кислород-ионную проводимость. в качестве допантов были выбраны металлы iia подгруппы (mg, ca, sr, ba) и металлы триады железа (co, fe, ni). для аттестации продуктов синтеза применялись методы рентгенофазового анализа и электронной микроскопии, проводились высокотемпературные исследования порошков и керамики сложных оксидов. электропроводящие свойства были исследованы методом импедансной спектроскопии. * работа выполнена при финансовой поддержке грантов рффи 12-03-00464, 12-03-31119, минобрнауки россии (соглашение № 14.132.21.1455) и поддержке молодых ученых урфу в рамках реализации программы развития урфу. у д к 6 61 .8 77 введение сложные оксиды на основе bi2o3 проявляют кислородно-ионную и смешанную проводимость в средней области температур (300–700 °с), сегнетоэлектрические и магнитные эффекты, каталитическую активность. висмутсодержащие соединения кристаллизуются в различных типах структур, например флюоритоподобных на основе δ-bi2o3 [1], перовскитоподобных слоистых семейства bimevox [2], фаз на основе bi26mo10o69, содержащих колонки [bi12o14]∞ [3] и многих других. колончатый тип особенно интересен, т. к. представляет широкие возможности для целенаправленного допирования, и наименее изучен. структура этих уникальных, не имеющих аналогов среди других сложных оксидов висмута соединений содержит 15 2014 | № 1 | cta колончатые фрагменты [bi12o14]n 8n+, направленные параллельно оси y, тетраэдры moo4, расположенные слоями параллельно плоскостям (100) и (001) и изолированные атомы bi, также находящиеся в слоях между тетраэдрами [4, 5]. было установлено, что она обеспечивает эффективный ионный транспорт вдоль кристаллохимического направления распространения колончатых фрагментов (оси y). данные соединения обладают кислородно-ионной проводимостью, причем по значениям электропроводности они могут конкурировать с bimevox и ysz [6], а значит, являются альтернативным электролитическим материалом для газоразрядных мембран, сепараторов, сенсоров и топливных элементов. настоящая работа посвящена синтезу и изучению проводящих характеристик замещенных в подрешетку молибдена или висмута сложных оксидов с колончатой структурой общей формулы, bi13–y meymo5–хme’хo34–δ, где me, me’ – 2-, 3-зарядные металлы. в данной работе в качестве замещающих металлов были выбраны металлы iia подгруппы (mg, ca, sr, ba) и металлы триады железа (co, fe, ni). экспериментальная часть твердые растворы составов bi13mo5–хmeхo34±δ, и bi13–y meymo5o34±δ, где me = co, ni, fe и металлы iia подгруппы: mg, ca, sr, ba; x ≤ 1, ∆x = 0.2, синтезировали по стандарт-ной керамической технологии в интервале температур 773–1123 к с шагом 50 к. в качестве исходных компонентов использовали оксиды и карбонаты металлов (квалификации ос. ч). исходные вещества смешивались в стехиометрическом соотношении, подвергались гомогенизации и брикетированию. после промежуточных стадий синтеза образцы закаливались, на конечной стадии синтеза были охлаждены вместе с печью. фазовый состав промежуточных и конечных продуктов устанавливали рентгенографически (дифрактометр d8 advance bruker). для расчета параметров элементарной ячейки и уточнения кристаллической структуры использовали программные пакеты: fpeak, celref, fullprof [7]. характеристики порошков определяли при помощи лазерной дифракции (sald-7101 shimadzu), денситометрического анализа, атомно-эмиссионного анализа (спектрометр с индуктивно-связанной плазмой icap 6500 thermo scientific), методом электронной микроскопии (растровый электронный микроскоп jeol jsm 6390la). дифференциальный термический анализ проведен с помощью термоанализатора sta 409 pc luxx netzsch. плотность спекания брикетированных образцов рассчитывали по результатам измерения пикнометрической и объемной плотностей керамики. процесс спекания контролировали путем дилатометрических измерений. дилатометрические исследования керамики проводили на дилатометре dil 402c netzsch. объемную плотность определяли методом гидростатического взвешивания. электропроводность образцов исследовали методом импедансной спектроскопии (импедансметр elins z-3000) в интервале температур 1123– 523 к. замещенные молибдаты висмута на основе bi 13 mo 5 o 34±δ : получение и свойства 16 cta | № 1 | 2014 результаты и обсуждение серии твердых растворов bi13mo5–х meхo34±δ, и bi13–ymeymo5o34±δ, где me = co, ni, fe и металлы iia подгруппы: mg, ca, sr, ba; x ≤ 1, ∆x = 0.2, синтезированы по стандартной керамической технологии. по результатам рфа установлены границы областей гомогенности для всех исследованных серий и различных допантов: для co при x, y ≤ 0.2; для fe y ≤ 0.1, x ≤ 0.4; для ni x < 0.1, y < 0.1; для щелочноземельных металлов x < 0.1, y < 0.6. образование твердых растворов во всех случаях обеспечивается близостью радиусов ионов в соответствующей замещаемому иону координации и устойчивостью указанного координационного окружения. так, эффективное замещение в подрешетке молибдена возможно в случае устойчивого тетраэдрического окружения, а замещение изолированного иона висмута – в случае стабильной координации с координационным числом к. ч. = 8 у допирующего иона. в качестве иллюстрации на рис. 1 приведена структура bi13mo5-хmeхo34±δ. отметим, что при малых концентрациях допанта выявлено триклинное искажение, свойственное матричному соединению. в рамках установленных областей гомогенности наблюдается линейное изменение параметров элементарной ячейки. в качестве примера в табл. 1 приведены данные для образцов, допированных железом. элементный состав твердых растворов, установленный при помощи атомно-эмиссионного анализа, соответствует номинальному соотношению, заложенному при синтезе. денситометрический анализ показал соответствие пикнометрической плотности рентгерис. 1. структура bi13mo5-хmeхo34±δ: проекции по основным плоскостям таблица 1 пример изменения параметров элементарной ячейки для fe-допированных молибдатов висмута сложный оксид а, å b, å c, å β, в градусах bi[bi12o14]mo5o34±δ 11.790 5.801 24.706 102.80 bi[bi12o14]mo4.95fe0.05º20±δ 11.785 5.802 24.731 102.75 bi[bi12o14]mo4.9fe0.1º20±δ 11.780 5.802 24.770 102.98 bi[bi12o14]mo4.8fe0.2º20±δ 11.775 5.802 24.786 102.86 bi[bi12o14]mo4.7fe0.3º20±δ 11.774 5.801 24.805 102.86 bi[bi12o14]mo4.6fe0.4º20±δ 11.772 5.801 24.812 102.67 з. а. михайловская, е. с. буянова, с. а. петрова, р. г. захаров 17 2014 | № 1 | cta нографической в пределах погрешности. размер частиц полученных порошков варьируется в пределах 1–10 мкм. для оценки термической устойчивости образцов проведены высокотемпературные термические исследования (дифференциальная сканирующая калориметрия, совмещенная с термогравиметрией). в диапазоне температур 420–1120 к для всех исследованных составов эффектов не наблюдается, что свидетельствует об отсутствии фазовых переходов и процессов разложения сложных оксидов в исследуемом температурном интервале на воздухе. однако исследования с применением высокотемпературного рентгенофазового анализа показали немонотонное изменение параметров элементарной ячейки в случае молибдатов висмута, замещенных металлами iia группы. поверхность спеченных брикетов исследована методом сканирующей электронной микроскопии. на рис. 2 приведены снимки поверхности брикета и порошка допированного молибдата висмута. из рисунка видно, что в ходе спекания наблюдается рост зерен относительно размеров частиц порошка. в общем случае при использовании однофазных порошков происходит формирование плотных керамических брикетов с пористостью менее 5 %, что доказано гидростатическими измерениями. дилатометрические исследования спеченной керамики позволили оценить ктр, равный 14–16×10–6k–1, что является характерным показателем для электролитической керамики. электропроводность твердых растворов исследована методом импедансной спектроскопии в диапазоне температур 523–1123 к. измерения проводились двухконтактным методом с платиновыми электродами на предварительно подготовленных спеченных брикетах. эквивалентную схему ячейки, соответствующей протеканию процессов в определенном температурном интервале, подбирали с использованием программы zview software (version 2.6b, scribner associates, inc.). установлено, что форма зависимости мнимой части комплексного сопротивления от действительной меняется при изменении температуры. при относительно низких температурах на годографе виден ассиметричный полукруг. далее кривая импеданса через минимум плавно переходит в прямую, наклоненную под углом, близким к 45°. для низкотемпературной области схема ячейки представляет последовательное соединение сопротивлений r1, r2 с параллельно присоединенными элементами cpe1, cpe2, характеризующее материал электролита; и закрытый диффузионный элемента варбурга w1. сопротивление r1 и элемент cpe1 в параллельном соединении при этом отвечает объемной проводимости образца, соединение r2 и cpe2 соответствует зернограничному сопротивлению зерен (а их сумма – общему сопротивлению). таким образом, проводимость поликристаллического образца при низких температурах рассчитывалась, исходя из значения r1+r2. элемент варбурга ws описырис. 2. рэм-изображения порошка и брикета bi13mo5–хmeхo34±δ замещенные молибдаты висмута на основе bi 13 mo 5 o 34±δ : получение и свойства 18 cta | № 1 | 2014 вает протекание диффузии, которая является превалирующим фактором в данном интервале температур. порядки величин «емкостей» cpe2 и cpe1 – 10–7 и 10–11 ф позволяют приписать их к объемной и зернограничной проводимости соответственно [8]. при повышении температуры процессы диффузии и адсорбции кислорода на электродах существенно облегчаются, и из схемы уходит элемент варбурга. как и при низких температурах, общее сопротивление будет характеризоваться суммой r1 и r2. рассчитанные из импедансных измерений величины общей электропроводности представлены в виде графиков температурной зависимости проводимости избранных составов и таблиц с электрофизическими характеристиками (рис. 3. и табл. 2). общий вид температурных зависимостей электропроводности от температуры (рис. 3) для изучаемых сложных оксидов является типичным для ионных проводников. на зависимостях lg(σ)–103/t большинства исследованных соединений отсутствуют явные рис. 3. примеры температурных зависимостей проводимости для твердых растворов bi13mo5–хmeхo34±δ таблица 2 электропроводящие характеристики избранных составов замещенных молибдатов висмута состав сложного оксида lg σ700, см·см –1 lg σ350, см·см –1 eakt, эв bi[bi12o14]mo5o20±δ –2.92 –5.00 0.73 bi0.9ba0.1[bi12o14]]mo5 o20±δ –2.81 –4.88 0.71 bi0.8ba0.2[bi12o14]]mo5o20±δ –2.20 –4.30 0.71 bi0.6ba0.4[bi12o14]mo5oo20±δ –2.25 –4.29 0.71 bi0.4ba0.6[bi12o14]mo5o20±δ –2.35 –4.28 0.67 bi0.2ba0.8[bi12o14]mo5o20±δ –3.13 –6.34 0.89 bi0.8co0.2[bi12o14]mo5o20± δ –2.24 –3.87 0.52 bi[bi12o14]mo4.8co0.2 o20±δ –2.23 –3.74 0.51 bi[bi12o14]fe0,1mo5o20±δ –2.18 –3.50 0.5 bi[bi12o14]fe0,2mo5 o20±δ –2.74 –5.12 0.75 bi[bi12o14]fe0,3mo5 o20±δ –2.42 –5.13 0.7 з. а. михайловская, е. с. буянова, с. а. петрова, р. г. захаров 19 2014 | № 1 | ctaзамещенные молибдаты висмута на основе bi 13 mo 5 o 34±δ : получение и свойства перегибы или существенные изломы прямолинейных участков, что подтверждает отсутствие фазовых переходов и согласуется с высокотемпературными дилатометрическими и термогравиметрическими исследованиями. в общем случае при допировании наблюдается повышение значений удельной электропроводности относительно недопированного bi13mo5o34±δ. для рядов твердых растворов концентрационные зависимости электропроводности имеют немонотонный характер. максимальные значения электропроводности получены для сложных оксидов составов bi[bi12o14] mo4.8co0.2o20±δ, bi[bi12o14]fe0,1mo5o20±δ и bi0.8me0.2[bi12o14]mo5o20±δ (me – металл iia группы) (табл. 2). исходя из достаточно высоких значений электропроводности замещенных молибдатов висмута, можно утверждать, что исследованные соединения проявляют себя как перспективные электролиты в средней области температур. благодаря малой пористости, отсутствию фазовых переходов и средним значениям коэффициента термического расширения данные электролиты могут быть рекомендованы как материалы мембран для электрохимических устройств. 1. boivin j. c. int. j. inorgan. matt., 2001, 3, 1261. 2. abraham f., boivin j. c., mairesse g., nowogrocki g. solid state ionics, 1990, 40–41, 934. 3. fonseca f. c., steil m. c., vannier r. n. solid state ionics, 2001, 140, 161. 4. enjalbert r., hasselmann g., galy j. j. solid state chem., 1997, 131. 236. 5. vannier r. n., mairesse g., abraham f., nowogrocki g. j. solid state chem., 1996, 122, 394. 6. vannier r. n., danzé s., nowogrocki g. solid state ionics, 2000, 136–137, 51. 7. rodriguez-carvajal j. physica b, 1993, 192. 55. 8. irvine j. t. s., sinclair d. c, west a. r. advanc. mater., 1990, 2, 132. z. a. mikhaylovskaya1, e. s. buyanova2, s. a. petrova2, r. g. zaharov2 1 ural federal university, 51 lenin street, 620083, ekaterinburg. e-mail: zozoikina@mail.ru 2institute of metallurgy ub ras, 101 amundsen str., 620016, ekaterinburg. e-mail: danaus@mail.ru substutited molybdates of bismuth on a basis of bi13mo5o34±δ: production and properties the present work is devoted to the investigation of the methods of a synthesis and properties of the one of the most interesting one-dimensional oxygen-ion conductors, 20 cta | № 1 | 2014 the bi 13 mo 5 o 34±δ – based complex oxides. the general compositions of these bismuth molybdates are bi 13 mo 5-х me х o 34-δ , and bi 13-y me y mo 5 o 34-δ , with me = mg, ca, sr, ba (iia group) and co, fe, ni (fe triade). the samples have been synthesized using conventional ceramic technology. the powders and pellets of the bismuth molybdates were studied by x-ray diffraction, scanning electron microscopy, laser dispersion, dilatometry, atom absorption and inductively-coupled plasma atomic emission spectrometry. electrical conductivity has been studied using impedance spectroscopy method. з. а. михайловская, е. с. буянова, с. а. петрова, р. г. захаров страница 1 38 введение при создании наносистем в современной микроэлектронике, катализе, спинтронике и фемтохимии используются релаксационные неравновесные атомно-молекулярные кинетические процессы. эти процессы являются в основном «медленными» и адиабатическими. химическая кинетика в основном зависит от характера движения локализованных неравновесных пакетов колебательных и вращательных степеней свободы атомов и молекул. энергии активации таких процессов, как и энергии локализации пакетов, не м. с. гришко, м. с. жуковский, с. а. безносюк алтайский государственный университет, 626049, барнаул, пр. ленина, 61. e-mail: bsa1953@mail.ru исследование самосборки и самоорганизации атомных наночастиц металлов группы железа методом монте-карло в работе изложено решение задачи исследования самосборки и самоорганизации компактных наночастиц из роя атомных наночастиц группы железа на примере системы fe-co. для выполнения численного эксперимента в условиях заданной температуры среды был использован метод монте-карло. представлен анализ результатов компьютерной имитации синтеза наночастиц в форме кластеров магнитных атомарных наночастиц подгруппы железа в квантово-запутанном (η = 1) и квантово-незапутанном (η = 0) состояниях. расчеты показали зависимость морфологии нанокластера от характера квантового запутывания атомарных наночастиц. показано, что результат наносинтеза зависит не только от внешних термодинамических параметров термостата, но и от самосборки и самоорганизации наносистем за счет активизации внутренних электронных квантовых степеней свободы. принципиальной особенностью квантовой нанокинетики является то, что результат наносинтеза зависит не только от внешних термодинамических параметров термостата, но и от квантовых параметров самосборки и самоорганизации наночастиц в условиях активизации внутренних квантовых степеней свободы. квантовые электронные степени свободы задаются кинематическими переменными: временами жизни τ, длинами корреляции λ, степенью η квантовой запутанности наночастиц. у д к 5 46 .7 2+ 54 1. 6 © гришко м. с., жуковский м. с., безносюк с. а., 2014 39 2014 | № 1 | cta превышают электрон-вольт. в слабонеравновесных процессах конечные продукты атомно-молекулярного синтеза и результаты процессинга зависят лишь от слабого изменения внешних управляющих интенсивных переменных термостата. однако в случае быстро протекающих квантово-кинетических неадиабатических процессов самосборки и самоорганизации наночастиц уже необходимо учитывать квантово-размерные эффекты активации внутренних квантовых степеней свободы наносистем. они описываются временами жизни τ, длинами корреляции λ и степенью η запутанности наночастиц при квантовой релаксации их электронных подсистем [1]. в данной работе на примере системы fe-co задача исследования самосборки и самоорганизации компактных наночастиц из роя атомных наночастиц группы железа решается в приближении адиабатического транспорта атомных наночастиц в конденсированной среде под действием спутывающих обменных трансграничных потенциалов между наночастицами. в этой связи интерес представляет компьютерная имитация синтеза наночастиц в форме кластеров магнитных атомарных наночастиц подгруппы железа (fe, co, ni) в квантово-запутанном (η = 1) и квантово-незапутанном (η = 0) состояниях. в работе для точного описания влияния степени запутанности наночастиц на процессы квантовой кинетики релаксации их систем использован метод монте-карло. потенциалы рассчитаны методом нелокального функционала плотности [2]. решение строится, следуя методике изложенной в [3–5]. применение метода монте-карло в моделировании наночастиц наиболее адекватным в решении проблемы описания транспортной релаксации систем наночастиц при заданной температуре т термостата является метод монте-карло6. в методе учитывается стохастичность движения конфигурационной точки ядер r, изображающей в адиабатическом приближении квантовый процесс транспорта атомных наночастиц по эффективной поверхности потенциальной энергии спутывающих обменных трансграничных потенциалов между ними. в методе монте-карло полностью исключается траектория, и вводятся случайные «прыжки» точки r, статистически подчиняющиеся законам квантового релаксационного движения в условиях квазиравновесных процессов при заданной температуре т. рассмотрим модельное 3в-мерное конфигурационное пространство в ядер изучаемой наносистемы и произведем его дискретизацию путем подразделения на произвольно большое число s равных по объему ячеек. все ячейки в каком-либо порядке пронумеруем. тогда можно говорить, что система находится в i-м состоянии, если ее изображающая точка r находится в i-й ячейке. поверхность потенциальной энергии наночастицы дискретизируется значениями энергии ui, где i = 1, 2, …, s. рассматриваемая совокупность всех s возможных состояний системы с постоянными вероятностями переходов ai → aj носит название реализации цепи маркова. последняя характеризуется матрицей вероятностей переходов за один шаг pij, исследование самосборки и самоорганизации атомных наночастиц металлов группы железа методом монте-карло 40 cta | № 1 | 2014 элементы которой pij ≥ 0 представляют собой условную вероятность перехода системы в состояние j к моменту t + 1 случайного блуждания, если в момент t она находилась в состоянии i. если все ai удовлетворяют условиям эргодичности и стационарности, то существуют предельные вероятности переходов: ( ) li 1, 2, , .m ,nij jn j sp u→∞ = …= (1) для всех j при этом: 1 0, 1. s j j j u u = > =∑ (2) 1 , 1, 2, , . s j i ij i ju su p = = = …∑ (3) в теории цепей маркова доказывается, что величины uj однозначно определяются при соблюдении условия нормировки (2) значениями pij из системы линейных уравнений: pijui = pjiuj. (4) согласно принципу микроскопической обратимости для любых ij имеем: pij exp(–ei/kbt) = pji exp(–eij/kbt). (5) тогда уравнение (3) обращается в тождество. каждая новая конфигурация принимается или отвергается; критерием служит вероятность конфигурации uj , пропорциональная больцмановскому фактору данной конфигурации exp(–ej/kbt). практическая реализация метода заключается в следующем. на первом этапе формируется начальное конфигурационное состояние системы. далее производится пробное изменение в начальной конфигурации и вычисляется изменение энергии δe системы, обусловленное пробным изменением в конфигурации. если δe < 0, переход считается приемлемым, и прежняя конфигурация заменяется новой. это соответствует соотношению вероятностей uj > ui. но если δe > 0, то переход может произойти лишь с вероятностью: w = exp(δe/kbt). (6) в этом случае на эвм генерируется случайное число r в интервале между 0 и 1. если r ≤ w, то новая конфигурация принимается, в противном случае переход отвергается. однако в последнем случае считается, что в цепи маркова имел место один шаг ai → ai с вероятностью перехода pii. таким образом, плотность состояний в конфигурационном пространстве оказывается пропорциональной больцмановскому фактору w. благодаря этому полное среднее по реализациям марковского процесса любой функции при n → ∞ стремится к среднему по каноническому ансамблю. самосборка и самоорганизация систем атомных наночастиц по методу монте-карло рассмотрим исследование задачи квантовой кинетики наносинтеза двух типов кластеров атомарных наночастиц переходных металлов группы железа: в квантово-запутанном (η ~ 1) и квантово-незапутанном (η ~ 0) состоянии. основные кинематические условия и приближения, использованные при решении данной задачи, были нижеследующими. 1. длительность аттосекундных стадий положена равной нулю в силу м. с. гришко, м. с. жуковский, с. а. безносюк 41 2014 | № 1 | cta исследование самосборки и самоорганизации атомных наночастиц металлов группы железа методом монте-карло того, что она мала по сравнению с фемтосекундными стадиями (δτ << τ). 2. направление и вероятность неадиабатического квантового скачка ядер на фемтосекундных стадиях задана в модели стохастического марковского процесса случайной генерацией направления скачка с последующей оценкой вероятности этого скачка по методу монте-карло. 3. для квантово-запутанного состояния (η ~ 1) в каждом акте τi происходит смещение одной атомной наночастицы при фиксированной конфигурации остальных наночастиц. в квантово-незапутанном состоянии (η ~ 0) – стохастически независимо смещаются все наночастицы в системе. 4. для расчета поверхности потенциальной энергии (ппэ) кластера β-связанных наноботов используется парное приближение. энергия парного β-взаимодействия атомов-наноботов м-м рассчитывается методом нелокального функционала плотности [2–5]. 5. для использования в методе монте-карло бралась аналитическая аппроксимация этого взаимодейст-вия потенциалом морзе. 6. наносинтез проведен в нанореакторе кубической формы с длинной ребра 10 нм. объем нанореактора разбивался сеткой элементарных ячеек кубической формы с длинной ребра 0,02 нм. в начальный момент времени в объем нанореактора помещались случайным образом 50 атомных наночастиц. на рис. 1 а, б представлен график квантовой нанокинетики выхода структур систем наночастиц на стационарное неравновесное состояние при температуре 298 к. кинетика представлена энергетической зависимостью от шага цепи маркова при общей длине цепи маркова 105 шагов. с учетом того, что время одного шага составляет порядка 10 фемтосекунд2, длительность эксперимента составляет порядка наносекунды. на рис. 1 в, г представлены структуры конечных стационарных состояний нанокластеров fe25co25. видно, что морфология нанокластера сильно различается в случаях η ~ 1 и η ~ 0. в квантово-запутанном пределе η ~ 1 образовался один компактный кластер 50 атомных наночастиц железа и кобальта, а в квантово-незапутанном пределе слабой корреляции возникли островковые 5 нанокластеров с разной нуклеарностью. из представленных графиков кинетических кривых видно, что энергия нанокластера в модели квантово-запутанного квазистационарного состояния составила около –320 кдж/моль, а в модели квантово-незапутанного квазистационарного состояния – около –220 кдж/моль. тем не менее в состоянии с η ~ 0, имея на 100 кдж/моль выше энергию, кластерная система 50 атомов кинетически устойчива – она сохраняет свою квазистационарность во времени. во всех рассмотренных случаях наночастицы кластеры – энергонасыщенные активные наночастицы, имеющие на своем «борту» запас энергии, который можно оценить, зная энергию основного стационарного состояния кластеров атомов того же состава. вычитая энергию молекулярных кластеров fe25co25 в основном состоянии из энергии наноботов кластеров fe25co25, получаем для квантово-запутанного (η ~ 1) и кванто42 cta | № 1 | 2014 во-незапутанного (η ~ 0) случаев запас энергии составляет около 100 и 200 кдж/моль соответственно. обнаруженные закономерности в изменении морфологии наночастиц в зависимости от характера квантового запутывания атомарных наночастиц могут быть использованы для управления квантовыми процессами формирования наноматериалов с заранее заданными свойствами. это может быть использовано для создания адаптивно перестраивающихся высокоактивных катализаторов химического и биохимического молекулярного синтеза. решение этой задачи также важно для построения искусственных систем магнитных атомных наночастиц группы железа, как аналогов гемоглобина. в заключение отметим, что принципиальной особенностью квантовой нанокинетики является то, что резульа – квантовая кинетика для η ~ 1 б – квантовая кинетика для η ~ 0 в – морфология аттрактора нанокластера для η ~ 1 г – морфология аттрактора нанокластера для η ~ 0 рис. 1. квантовая кинетика наносинтеза и морфология самособранных и самоорганизованных нанокластеров из 50 атомарных наноботов состава fe25co25 в квантово-запутанном (η ~ 1) и квантово-незапутанном (η ~ 0) состояниях м. с. гришко, м. с. жуковский, с. а. безносюк 43 2014 | № 1 | cta исследование самосборки и самоорганизации атомных наночастиц металлов группы железа методом монте-карло тат наносинтеза зависит не только от внешних термодинамических параметров термостата, но и от квантовых параметров самосборки и самоорганизации наночастиц в условиях активизации внутренних квантовых степеней свободы. квантовые электронные степени свободы задаются кинематическими переменными: временами жизни τ, длинами корреляции λ, степенью η квантовой запутанности наночастиц. 1. zhukovsky m. s., beznosyuk s. a., potekaev a. i., starostenkov m. d. theoretical foundations of computer nanoengineering biomimetic nanosystems. ntl, tomsk, 2011, 236 p. [жуковский м. с., безносюк с. а., потекаев а. и., старостенков м. д. теоретические основы компьютерного наноинжиниринга биомиметических наносистем. томск: изд-во нтл, 2011. 236 с.]. 2. beznosyuk s. a., minaev b. f., dajanov r. d., muldachmetov z. m. int. j. quant. chem., 1990, 38, 779. 3. zhukovsky m. s., beznosyuk s. a., grishko m. s. proceedings of symposium i “multifunctional advanced composite materials: manufacturing, structure, properties. fall meeting e-mrs 2009, warsaw, poland. september 14–18, 2009, 29. 4. beznosyuk s. a., grishko m. s. perspektivnye materialy, 2009, 7, 44 [безносюк с. а., гришко м. с. перспективные материалы. 2009, 7, 44]. 5. beznosyuk s. a., zhukovskaya t. m., zhukovsky m. s., grishko m. s. fundamental’nye problemy sovremennogo materialovedenia, 2012, 9, 252 [безносюк с. а., жуковский м. с., жуковская т. м., гришко м. с. // фундаментальные проблемы современного материаловедения. 2012. т. 9. с. 252–256]. m. s. grishko, м. s. zhukovsky, s. a. beznosyuk altai state university, 61, lenin street, 656049, barnaul. e-mail: bsa1953@mail.ru the study of self-assembly and self-organization of atomic metal nanoparticles of iron group by monte carlo method the solution of the study of self-assembly and self-organization of compact nanoparticles from the swarm of atomical nanoparticles by the example of fe-co is set out in the report. to perform the numerical experiment was used monte carlo method. the analysis of synthesis atomic clusters of magnetic nanoparticles of iron subgroup in quantum-entangled (η = 1) and quantumnonentangled (η = 0) states is given. it is shown that the result nanosynthesis depends not only on the outside thermodynamic 44 cta | № 1 | 2014 parameters, but also on the self-assembly and self-organization of nanosystem due to activation of the inner quantum electron degrees of freedom. the principal feature of quantum nanokeramiki is that the result of anointeth depends not only on external thermodynamic parameters of the thermostat, but also from quantum parameters of selfassembly and self-organization of nanoparticles in the activation of the internal quantum degrees of freedom. м. с. гришко, м. с. жуковский, с. а. безносюк страница 1 synthesis, intramolecular cyclization and anti-inflammatory activity of substituted 2-(2-(furan-2-carbonyl)hydrazono)-4-oxobutanoic acids published by ural federal university eissn 2411-1414 chimicatechnoacta.ru article 2023, vol. 10(1), no. 202310102 doi: 10.15826/chimtech.2023.10.1.02 1 of 8 synthesis, intramolecular cyclization and anti-inflammatory activity of substituted 2-(2-(furan-2carbonyl)hydrazono)-4-oxobutanoic acids sergei n. igidov ab , dmitriy v. lipin c* , aleksey yu. turyshev a , svetlana v. chashchina a, daria a. shipilovskikh d* , ol’ga v. zvereva a, ksenia a. mitusova e , pavel s. silaichev c , nazim m. igidov a a: perm state pharmaceutical academy, ministry of health of the russian federation, perm 614990, russia b: merck llc, moscow 115054, russia c: perm state national research university, perm 614990, russia d: perm national research polytechnic university, perm 614990, russia e: peter the great st. petersburg polytechnic university, st. petersburg 195251, russia * corresponding author: lipindima@psu.ru (dmitriy v. lipin), shipilovskikh@psu.ru (daria a. shipilovskikh) this paper belongs to the mosm2022 special issue. abstract a method was proposed for the synthesis of substituted 2-(2-(furan-2-carbonyl)hydrazono)-4-oxobutanoic acids by the reaction of substituted 2,4dioxobut-2-enoic acids with furan-2-carbohydrazide. it was found that substituted 2-(2-(furan-2-carbonyl)hydrazono)-4-oxobutanoic acids undergo intramolecular cyclization in the presence of propionic anhydride to form the corresponding n'-(2-oxofuran-3(2h)-ylidene)furan-2-carbohydrazides. the anti-inflammatory activity of the obtained compounds was studied. it was found that the obtained compounds have pronounced antiinflammatory activity. keywords dioxobutanoic acids 2-hydrazono-4-oxobutanoic acids 3-hydrazonofuran-2(3h)-ones anti-inflammatory activity drugs received: 07.11.22 revised: 08.12.22 accepted: 08.12.22 available online: 16.12.22 key findings ● a synthesis method for obtained to produce methyl-2-(2-(furan-2-carbonyl)hydrazono)-4-oxobutanoic acids and n'(2-oxofuran-3(2h)-ylidene]furan-2-carbohydrazides. ● sixteen new biologically active compounds have been obtained and described. ● it was found that some of the compounds obtained have a significant anti-inflammatory effect. © 2022, the authors. this article is published in open access under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). 1. introduction the priority direction in pharmaceuticals and medical chemistry is the development and creation of new dosage forms with low toxicity [1–7]. the main cause is the chaotic usage of medicines, which leads to a loss of their efficiency. the main problem of drug development now is the choice of suitable frameworks that would make it possible to transform compounds at various stages of synthesis. derivatives of 3-iminoand 3-hydrazonofuran-2(3h)one are excellent for this role because of their chemical availability, scalability of synthetic methods [8–12] and high reactivity [13–17]. derivatives of 3-iminoand 3-hydrazonofuran-2(3h)-ones are capable of interacting with various nucleophilic reagents to form acyclic structures preserving the pharmacophore fragment of 2,4-dioxobutanoic acid [18–27]. previously, we proposed a simple method for the preparation of 3-hydrazinylidenefuran-2(3н)-one derivatives by intramolecular cyclization of substituted 2-(2-(4-r-benzoyl)hydrazono)-4-oxobutanoic acids in the presence of acetic or propionic anhydride [28, 29]. furthermore, this method was applied to the synthesis of 3-(imino(thien-2-yl))furan-2(3h)ones derivatives, which include the pharmacophore fragment, gewald aminothiophene [30] (scheme 1). it was found that 2(2-(4-r-benzoyl)hydrazono)-4-oxobutanoic and 2-(thiophen2-ylamino)-4-oxobut-2-enoic acids and their derivativities exhibit analgesic [31, 32], anti-inflammatory [16] antimicrobial activity [24] and photoluminescent properties [33, 34]. we continue to search for new biologically active compounds with low toxicity [35] and expand the methods for the synthesis of 2,4-dioxobutanoic acid and 3-hydrazonofuran-2(3h)-one derivatives. http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2023.10.1.02 mailto:lipindima@psu.ru mailto:shipilovskikh@psu.ru http://creativecommons.org/licenses/by/4.0/ https://orcid.org/0000-0001-6006-168x https://orcid.org/0000-0003-2746-1395 https://orcid.org/0000-0003-3867-5305 https://orcid.org/0000-0001-6086-4300 https://orcid.org/0000-0002-3820-4899 https://orcid.org/0000-0002-2840-6809 https://orcid.org/0000-0003-0976-9951 https://crossmark.crossref.org/dialog/?doi=https://doi.org/10.15826/chimtech.2022.10.1.02&domain=pdf&date_stamp=2022-12-16 chimica techno acta 2023, vol. 10(1), no. 202310103 article 2 of 8 doi: 10.15826/chimtech.2023.10.1.02 scheme 1 synthesis of 3-hydrazonoand 3-(imino(thien-2-yl))furan-2(3h)-ones. in this paper, synthesis and anti-inflammatory activity of new 2,4-dioxobutanoic acids derivatives are discussed. 2. experimental ir spectra were recorded on an fsm-1202 instrument in vaseline oil. 1н nmr spectra were obtained on a bruker avance iii spectrometer (operating frequency of 400 mhz) in dmso-d6, the internal standard was the residual signal of the deuterium solvent. elemental analysis was performed on a leco chns-932 instrument. the chemical purity of the compounds and the reactions progress were monitored by tlc on sorbfil plates in the diethyl ether–benzene–acetone (10:9:1) system (detection in uv light and iodine vapor). melting points were determined on an smp40 apparatus. 2.1. general procedure for the synthesis of substituted 2-(2-(furan-2-carbonyl)hydrazono)-4oxobutanoic acids (3a–h) to a solution of 0.01 mol of furan-2-carboxylic acid hydrazide 2 in 30 ml of acetonitrile was added 0.01 mol of 2,4dioxobutanoic acid 1a–h. the resulting mixture was heated to 50 °c and kept for 5 min at this temperature. the solution was cooled to 0 °c; the formed precipitate was filtered off and recrystallized from acetonitrile or 1,4-dioxane. 2.1.1. 5,5-dimethyl-4-oxo-2-(2-(furan-2-carbonyl)hydrazono)hexanoic acid (3а) yield 1.96 g (70%), pale yellow crystals, m.p. 144–145 °с (mecn). ir spectrum, ν, cm–1: 3324, 3204 br., 3119, 1717, 1676, 1595. 1н nmr spectrum (dmso-d6), δ, ppm: form a (24%): 1.16 s (3h, t-bu), 4.04 s (2h, ch2), 6.62 dd (1h, harom, jhh 3.5, 1.8 hz), 7.02–7.95 m (2h, harom), 11.09 br. s (1h, nh); form b (61%): 1.12 d (3h, t-bu), 3.21 d (1h, c4h2, jhh 20.0 hz), 3.35 d (1h, c4h2, jhh 20.0 hz) , 6.56 dd (1h, jhh 3.5, 1.8 hz), 7.03–7.95 m (2h, harom, 1h, oh); form c (15%): 1.14 s (3h, t-bu), 3.80 s (2h, ch2), 6.70 dt (1h, harom, jhh 1.7, 0.8 hz), 7.03–7.95 m (2h, harom), 13.48 br. s (1h, nh). found, %: с 55.74; h 5.73; n 10.03. c13h16n2o5. calculated, %: с 55.71; h 5.75; n 10.00. 2.1.2. 4-methylphenyl-2-(2-(furan-2-carbonyl)hydrazono)-4-oxobutanoic acid (3b) yield 2.29 g (73%), yellow crystals, m.p. 179–180 °с (1,4dioxane). 1н nmr spectrum (dmso-d6), δ, ppm: form a (30%): 2.41 s (3н, ch3), 4.52 s (2н, сн2), 6.73 dd (1н, harom, jhh 3.4, 1.7 hz), 7.14–7.99 m (6н, harom), 11.38 br. s (1н, nh); form b (58 %): 2.30 с (3н, ch3), 3.22 d (1н, с4н2, jhh 20.0 hz), 3.32 d (1н, с4н2, jhh 20.0 hz), 6.70 dd (1н, jhh 3.5, 1.7 hz), 7.14–7.98 m (6н, harom; 1н, он); form c (12 %): 2.40 s (3н, ch3), 4.29 s (2н, сн2), 6.73 dd (1н, harom, jhh 3.4, 1.7 hz), 7.14–7.99 m (6н, harom) 13.47 br. s (1н, nh). found, %: c 61.12; h 4.47; n 8.94. c16h14n2о5. calculated, %: c 61.14; h 4.49; n 8.91. 2.1.3. (4-ethylphenyl)-2-(2-(furan-2-carbonyl)hydrazono)-4-oxobutanoic acid (3c) yield 2.10 g (64%), yellow crystals, m.p. 143–144 °с (mecn). ir spectrum, ν, cm–1: 3245, 3126, 1736, 1684, 1641, 1612. 1н nmr spectrum (dmso-d6), δ, ppm: form a (12%), 1.20 m (3н, me), 2.65 m (2h, ch2), 4.51 s (2h, ch2), 6.68 dd (1h, harom, jhh 3.6, 1.8 hz), 7.15–7.94 m (6h, harom), 11.30 br. s (1h, nh); form b (81%), 1.20 m (3н, me), 3.20 d (1н, с4н2, jhh 20.0 hz), 3.33 d (1н, с4н2, jhh 20.0 hz), 2.65 m (2н, ch2), 6.66 dd (1h, harom, jhh 3.5, 1.6 hz), 7.15– 7.94 m (7h, 6harom and oh); form c (7%), 1.20 m (3h, me), 2.64 m (2h, ch2), 4.23 s (2h, ch2), 6.71 dd (1h, harom, jhh 3.6, 1.7 hz), 7.15–7.94 m (6h, harom), 13.83 br. s (1h, nh). found, %: c 62.21; h 4.89; n 8.56. c17h16n2o5. calculated, %: c 62.19; h 4.91; n 8.53. m 328.32. https://doi.org/10.15826/chimtech.2023.10.1.02 chimica techno acta 2023, vol. 10(1), no. 202310103 article 3 of 8 doi: 10.15826/chimtech.2023.10.1.02 2.1.4. (4-ethoxyphenyl)-2-(2-(furan-2-carbonyl)hydrazono)-4-oxobutanoic acid (3d) yield 2.89 g (84%), yellow crystals, m.p. 134–135 °с (mecn). ir spectrum, ν, cm–1: 3232, 3121, 1744, 1652, 1641, 1607. 1н nmr spectrum (dmso-d6), δ, ppm: form a (47%), 1.33 m (3н, me ), 4.13 m (2h, ch2), 4.48 s (2h, ch2), 6.68 dd (1h, harom, jhh 3.5, 1.8 hz), 6.85–7.98 m (6h, harom), 11.29 s (1h, nh); form b (32%), 1.33 m (3н, me), 3.21 d (1н, с4н2, jhh 20.0 hz), 3.30 d (1н, с4н2, jhh 20.0 hz), 4.13 m (2н, ch2), 6.66 dd (1h, harom, jhh 3.5, 1.8 hz), 6.85–7.98 m (7h, 6harom and oh); form c (21%), 1.33 m (3h, me),4.13 m (2h, ch2), 4.24 s (2h, ch2), 6.71 m (1h, harom, jhh 3.5, 1.8 hz), 6.85–7.98 m (6h, harom), 13.35 br. s (1h, nh). found, %: c 59.32; h 4.69; n 8.17. c17h16n2o6. calculated, %: c 59.30; h 4.68; n 8.14. m 344.32. 2.1.5. (4-fluorophenyl)-2-(2-(furan-2-carbonyl)hydrazono)-4-oxobutanoic acid (3e) yield 2.32 g (73%), yellow crystals, m.p. 132–133 °c (mecn). ir spectrum, ν, cm–1: 3237, 3131, 1741, 1683, 1617, 1585. 1н nmr spectrum (dmso-d6), δ, ppm: form a (6%), 4.51 s (2н, сн2), 6.71 m (1н, harom), 7.28–7.92 m (6н, harom), 11.30 br. s (1h, nh); form b (90%), 3.24 d (1н, с4н2, jhh 20.0 hz), 3.30 d (1н, с4н2, jhh 20.0 hz), 6.68 m (1н, harom), 7.28–7.92 m (7н, 6harom and он); form c (4%), 4.13 s (2h, ch2), 6.85 m (1h, harom), 7.28–7.92 m (6h, harom), 13.04 br. s (1h, nh). found, %: c 56.63; h 3.46; n 8.82. c15h11fn2o5. calculated, %: c 56.61; h 3.48; n 8.80. m 318.26. 2.1.6. 4-(4-chlorophenyl)-2-(2-(furan-2-carbonyl)hydrazono)-4-oxobutanoic acid (3f) yield 2.58 g (77%), m.p. 182–183 °с (1,4-dioxane). ir spectrum, ν, cm–1: 3237, 3131, 1741, 1683, 1617, 1585. 1н nmr spectrum (dmso-d6), δ, ppm: form a (9%), 4.49 s (2н, сн2), 6.71 m (1н, harom), 7.22‒7.96 m (6н, harom), 11.43 br. s (1н, nh); form b (86%), 3.21 d (1н, с4н2, jhh 20.0 hz), 3.30 d (1н, с4н2, jhh 20.0 hz), 6.69 m (1н, harom), 7.22‒7.96 m (7н, 6нarom and он); form c (5%), 4.31 s (2н, сн2), 6.84 m (1н, harom), 7.22‒7.96 m (6н, harom), 13.50 br. s (1н, nh). found, %: c 53.85; h 3.29; n 8.39. c15h11cln2о5. calculated, %: c 53.83; h 3.31; n 8.37. 2.1.7. 2-(2-(furan-2-carbonyl)hydrazono)-4-(naphthalen-1-yl)-4-oxobutanoic acid (3g) yield 2.38 g (68%), yellow crystals, m.p. 199–200 °c (mecn). ir spectrum, ν, cm–1: 3247, 3124, 1703, 1675, 1654, 1581. 1н nmr spectrum (dmso-d6), δ, ppm: form a (23%), 4.63 s (2н, сн2), 6.71 m (1н, harom), 7.33–8.57 m (9н, harom), 11.44 br. s (1h, nh); form b (66%), 3.39 d (1н, с4н2, jhh 20.0 hz), 3.44 d (1н, с4н2, jhh 20.0 hz), 6.71 m (1н, harom), 7.33–8.57 m (10н, 9harom and он); form c (11%), 4.38 s (2h, ch2), 6.71 m (1h, harom), 7.33– 8.57 m (9h, harom), 13.52 br. s (1h, nh). found, %: c 65.17; h 4.01; n 8.03. c19h14n2o5. calculated, %: c 65.14; h 4.03; n 8.00. 2.1.8. 2-(2-(furan-2-carbonyl)hydrazono)-4-(naphthalen-2-yl)-4-oxobutanoic acid (3h) yield 2.49 g (71%), m.p. 198–199 °с (mecn). ir spectrum, ν, cm–1: 3251, 3118, 1705, 1681, 1649, 1583. 1н nmr spectrum (dmso-d6), δ, ppm: form a (13%), 4.69 s (2н, сн2), 6.70 m (1н, harom), 7.47‒8.73 m (9н, harom), 11.33 br. s (1н, nh); form b (81%), 3.34 d (1н, с4н2, jhh 20.0 hz), 3.40 d (1н, с4н2, jhh 20.0 hz), 6.70 m (1н, harom), 7.47‒8.73 m (10н, 9нarom and он); form c (6%), 4.42 s (2н, сн2), 6.71 m (1н, harom), 7.33‒8.57 m (9н, harom) 13.77 br. s (1н, nh). found, %: c 65.13; h 4.05; n 8.02. c19h14n2о5. calculated, %: c 65.14; h 4.03; n 8.00. 2.2. general procedure for the synthesis of n′-(2oxofuran-3(2н)-ylidene]furan-2-carbohydrazides 4a–h propionic anhydride (8 ml) was added to 0.01 mol of acid 3a–h. the resulting mixture was slowly heated with stirring to 150 °c and kept for 5 min at this temperature. the precipitate formed after cooling was filtered off, washed with anhydrous diethyl ether, and recrystallized from anhydrous toluene or 1,4-dioxane. 2.2.1. n'-(5-(t-butyl)-2-oxofuran-3(2н)-ylidene)furan2-carbohydrazide (4а) yield 1.36 g (52%), light yellow crystals, m.p. 215–216 °с (1,4-dioxane). ir spectrum, ν, см–1: 3186, 1793, 1699, 1663, 1622, 1592. 1н nmr spectrum (dmso-d6), δ, ppm: form a (88%): 1.22 s (9н, t-bu), 6.73 dd (1н, jhh 3.6, 1.8 hz), 6.83 s (1н, сн), 7.52 dd (1н, jhh 3.6, 0.7 hz), 7.98 dd (1н, jhh 1.8, 0.8 hz), 11.63 br. s (1н, nh): form b (12 %): 1.23 s (9н, t-bu), 6.28 s (1н, сн), 6.76 dd (1н, нarom, jhh 3.6, 1.8 hz), 7.39 d (1н, jhh 3.6, 0.7 hz), 8.02 dd (1н, jhh 1.8, 0.8 hz), 12.36 br. s (1н, nh). found, %: c 59.57; 5.35; n 10.66. c13h14n2о4. calculated, %: c 59.54; h 5.38; n 10.68. 2.2.2. n'-(2-oxo-5-(p-tolyl)furan-3(2h)-ylidene)furan2-carbohydrazide (4b) yield 1.57 g (53%), yellow crystals, m.p. 258–259 °с (1,4dioxane). ir spectrum, ν, cm–1: 3125, 1799, 1693, 1672, 1622. 1h nmr spectrum (dmso-d6), δ, ppm: form a (100%): 2.41 s (3h, ch3), 6.72 dd (1h, har, jhh 3.5, 1.8 hz), 7.36– 7.67 m (5h, harom, 1h, ch), 7.98 d (1h, jhh 1.0 hz), 11.89 br. s (1h, nh). found, %: c 64.84; h 4.11; n 9.48. c16h12n2o4. calculated, %: c 64.86; h 4.08; n 9.46. 2.2.3. n'-(5-(4-ethylphenyl)-2-oxofuran-3(2н)-ylidene)furan-2-carbohydrazide (4c) yield 1.89 g (61%), yellow crystals, m.p. 189–190 °с (toluene). ir spectrum, ν, cm–1: 3132, 1806, 1697, 1666, 1616. 1н nmr spectrum (dmso-d6), δ, ppm: form a (25%), 1.22 m (3н, сн3), 2.70 m (2н, сн2), 6.78 dd (1н, harom, jhh 3.6, 1.8 hz), 7.44 m (2н, harom), 7.45 s (1н, сн), 7.59 d (1н, harom, jhh 3.4 hz), 7.70 m (2н, harom), 8.04 d (1н, нarom, jhh 1.5 hz), 11.83 br. s (1н, nh); form b (75%), 1.22 m (3н, сн3), 2.70 m (2н, сн2), 6.80 dd (1н, harom, jhh 3.6, 1.8 hz), 7.17 s (1н, сн), 7.40 m (2н, harom), 7.70 d (1н, harom, jhh https://doi.org/10.15826/chimtech.2023.10.1.02 chimica techno acta 2023, vol. 10(1), no. 202310103 article 4 of 8 doi: 10.15826/chimtech.2023.10.1.02 8.3 hz), 7.78 d (2н, harom, jhh 8.3 hz), 8.07 d (1н, harom, jhh 1.5 hz), 12.53 br. s (1н, nh). found, %: c 49.87; h 2.53; n 7.73. c17h14n2о4. calculated, %: c 65.80; h 4.55; n 9.03. 2.2.4. n'-(5-(4-ethoxyphenyl)-2-oxofuran-3(2н)-ylidene)furan-2-carbohydrazide (4d) yield 1.89 g (58%), yellow crystals, mp. 259–260 °c (1,4-dioxane). ir spectrum, ν, cm–1: 3123, 3118, 1811, 1694, 1662, 1615. 1н nmr spectrum (dmso-d6), δ, ppm: form a (47%): 1.37 t (3н, сн3 , jhh 7.0 hz), 4.15 m (2h, ch2), 6.77 dd (1h, harom, jhh 3.5, 1.8 hz), 7.40 s (1h, ch), 7.58 d (1h, harom, jhh 3.5 hz), 7.72 m (2h, harom), 7.80 m (2h, harom), 8.03 d (1h, harom, jhh 1.5 hz), 11.75 br. s (1h, nh): form b (75%): 1.37 t (3h, ch3, jhh 7.0 hz), 4.15 m (2h, ch2), 6.79 dd (1h, harom, jhh 3.5, 1.8 hz), 7.06 s (1h, ch), 7.09 m (2h, harom), 7.14 m (2h, harom), 7.42 d (1h, harom, jhh 3.5 hz), 8.06 m (1h, harom), 12.50 br. s (1h, nh). found, %: c 62.55; 4.35; n 8.61. c17h14n2o5. calculated, %: c 62.57; h 4.32; n 8.59. 2.2.5. n'-(5-(4-fluorophenyl)-2-oxofuran-3(2h)-ylidene)furan-2-carbohydrazide (4e) yield 1.89 g (63%), yellow crystals, mp. 287–288 °с (1,4-dioxane). ir spectrum, ν, cm–1: 3116, 1808, 1662, 1615. 1h nmr spectrum (dmso-d6), δ, ppm: form a (16%), 6.75 dd (1h, harom, jhh 3.6, 1.7 hz), 7.42 m (2h, harom), 7.49 s (1h, ch), 7.56 m (1h, harom), 7.82 m (2h, harom), 8.00 m (1h, harom), 11.77 br. s (1h, nh); form b (84%): 6.80 dd (1h, harom, jhh 3.6, 1.7 hz), 7.17 s (1h, ch), 7.38 m (2h, harom), 7.43 dd (1h, harom, jhh 3.5, 0.6 hz) , 7.76 m (2h, harom), 8.07 dd (1h, harom, jhh 1.6, 0.6 hz), 12.54 s (1h, nh). found, %: c 60.04; h3.00; n 9.35. c15h9n2o4. calculated, %: c 60.01; h 3.02; n 9.33. 2.2.6. n'-(5-(4-chlorophenyl)-2-oxofuran-3(2h)-ylidene)furan-2-carbohydrazide (4f) yield 2.34 g (74%), yellow crystals, mp. 268–269 °c (1,4-dioxane). ir spectrum, ν, cm–1: 1619, 1694, 1776, 3137. 1н nmr spectrum (dmso-d6), δ, ppm: form a (16%): 6.78 dd (1н, нarom, jhh 3.6, 1.7 hz), 7.50 s (1h, ch), 7.59 m (1h, harom), 7.63 m (2h, harom), 7.88 m (2h, harom), 8.04 m (1h, harom), 11.75 br. s (1h, nh). form b (84%): 6.80 dd (1h, harom, jhh 3.6, 1.7 hz), 7.17 s (1h, ch), 7.38 m (2h, harom), 7.43 dd (1h, harom, jhh 3.5, 0.6 hz), 7.76 m (2h, harom), 8.07 dd (1h, harom, jhh 1.6, 0.6 hz), 12.54 s (1h, nh). found, %: c 56.87; h 2.88; n 8.87. c15h9n2o4. calculated, %: c 56.89; h 2.86; n 8.85. 2.2.7. n'-(5-(naphthalene-1-yl)-2-oxofuran-3(2н)-ylidene)furan-2-carbohydrazide (4g) yield 2.59 g (78%), yellow crystals, mp. 236–237 °с (1,4dioxane). ir spectrum, ν, cm–1: 3163, 1808, 1660, 1612. 1н nmr spectrum (dmso-d6), δ, ppm: form a (100%): 6.77 dd (1н, нarom, jhh 3.6, 1.8 hz), 7.60 s ( 1h, ch), 7.68 m (3h, harom), 7.97 dd (1h, harom, jhh 7.3, 1.2 hz), 8.02 dd (1h, harom, jhh 1.7, 0.8 hz), 8.08 dd (1h, harom, jhh 3.4 , 1.1 hz), 8.16 m (1h, harom), 8.42 m (1h, harom), 11.96 br. s (1h, nh). found, %: c 68.65; h 3.66; n 8.44. c19h12n2o4. calculated, %: c 68.67; h 3.64; n 8.43. 2.2.8. n'-(5-(naphthalene-2-yl)-2-oxofuran-3(2н)-ylidene)furan-2-carbohydrazide (4h) yield 2.79 g (84%), yellow crystals, mp. 264–265 °с (1,4dioxane). ir spectrum, ν, cm–1: 3137, 1805, 1662, 1617. 1н nmr spectrum (dmso-d6), δ, ppm: form a (100%): 6.79 dd (1н, нarom, jhh 3.6, 1.8 hz), 7.64 m (3h, harom), 7.68 s (1h, ch), 7.79 dd (1h, harom, jhh 3.7, 1.7 hz), 8.01 m (1h, harom), 8.05 m (1h, harom, jhh 1.7, 0.8 hz), 8.12 m (2h, harom), 8.39 d (1h, harom, jhh 0.9 hz), 11.91 br. s (1h, nh). found, %: c 68.69; h 3.67; n 8.42. c19h12n2o4. calculated, %: c 68.67; h 3.64; n 8.43. 2.3. anti-inflammatory activity anti-inflammatory activity tests were carried out at the perm state pharmaceutical academy. the study was performed on rats of both sexes (the group included 6 animals) weighing 210–240 g on a model of acute inflammatory edema caused by subplantar injection of 0.1 ml of 1% aqueous solution of carrageenan into the hind paw of a rat. an increase in the volume of the foot, indicating the development of edema, was assessed oncometrically [36] before and 3 hours after the administration of carrageenan. the test substances were administered orally at a dose of 50 mg/kg 1 hour before the administration of the phlogogenic agent. animals that did not receive the drug served as controls. statistical processing was carried out according to the student's method. the effect of inhibition of inflammation was determined as a percentage of the control level. the presence of anti-inflammatory action was judged by the severity of inhibition of the inflammatory response. scheme 2 synthesis of 4-r-2-(2-(furan-2-ylcarbonyl)hydrazono)-4-oxobutanoic acids 3a–h. https://doi.org/10.15826/chimtech.2023.10.1.02 chimica techno acta 2023, vol. 10(1), no. 202310103 article 5 of 8 doi: 10.15826/chimtech.2023.10.1.02 scheme 3 synthesis of n'-(2-oxofuran-3(2н)-ylidene)furan-2-carbohydrazides 4a–h. all applicable international, national, and/or institutional guidelines for the care and use of animals were followed. 3. results and discussion substituted 2-[2-(furan-2-ylcarbonyl)hydrazono]-4-oxobutanoic acids 3a–h were obtained in 64–84% yields by the reaction of corresponding 2,4-dioxobutanoic acids 1a–h with furan-2-carbohydrazide 2 in acetonitrile at 50 °c (scheme 2). compounds 3a–h are crystalline yellow substances, easily soluble in chloroform, dmso, and when heated, in toluene, dioxane, and ethanol, and insoluble in water and alkanes. the ir spectra of compounds 3a–h contain an absorption band at 1703–1744 cm–1, which is characteristic of the stretching vibrations of the carbonyl amide group, and absorption bands at 3119–3131 and 3204–3251 cm–1, which are characteristic of the stretching vibrations of the amino group. the 1h nmr spectra (dmso-d6) of compounds 3a–h in the tautomeric form a are characterized by singlet signals of the nh protons (11.09–11.44 ppm) and ch2 (4.04– 4.69 ppm) groups. form b is characterized by the presence in the spectrum of a doublet of protons of the ch2 group at 3.30‒3.44 and 3.20‒3.39 ppm, and for form c, singlets of the nh protons (13.04‒13.83 ppm) and ch2 (3.80‒4.42 ppm). the spectral data of compounds 3a–h are in good agreement with the corresponding spectral data of alkyl 4-oxo-4-aryl-2[2-(arylcarbonyl)hydrazinylidene]butanoates, which have a similar structure and also exist in three forms [37]. intramolecular cyclization of acids 3a–h occurs upon slow heating to 150 °с in propionic anhydride and led to the formation of substituted n'-(2-oxofuran-3(2h)-ylidene)furan-2-carbohydrazides 4a–h (scheme 3). compounds 4a–h, obtained in 52–84% yields, are yellow crystalline substances, readily soluble in dmso, when heated – in toluene and ethanol, and insoluble in water and alkanes. the ir spectra of compounds 4a–h contain an absorption band in the region 1776–1811 cm–1, which is characteristic of the stretching vibrations of the lactone carbonyl of the furan2(3h)-one ring, and an absorption band in the region 3116– 3186 cm–1, which is characteristic of the stretching vibrations of the amino group. according to 1н nmr data in dmso-d6, compounds 4a, 4c–f are present as two geometric isomers a and b. the spectra of the isomers are characterized by the presence of signals of the nh groups [11.63‒ 11.83 (e–a) and 12.36‒12.54 ppm (z–b)]. compounds 4b, 4g, 4h exist only as the e-isomer, δ(nh) 11.89‒11.96 ppm. the spectral data of compounds 4a–h are in good agreement with the corresponding spectral data of n-[5-aryl-2oxofuran-3(2h)-ylidene]-4-methylbenzohydrazides, which have a similar structure [28]. some of the obtained compounds were examined for antiinflammatory activity. it is shown in table 1 that compounds 3e, g and 4d, f, g have a pronounced anti-inflammatory effect, surpassing the effect of the comparison drug nimesulide. table 1 anti-inflammatory activity of substances 3a, c–e, g. compound increase in foot volume after 3 hours (%) braking swelling after 3 h, % 3a 57.59±3.54 13.36 3c 44.12±3.22*,** 33.62 3d 55.91±5.82 15.89 3e 26.71±5.47* 59.82 3g 30.49±3.55* 54.13 nimesulide 33.90±6.78* 48.99 control 66.47±10.19 – * – the difference is reduced compared to the decrease at р<0.05; ** – the difference is significant compared with nimesulide at p<0.05. table 2 anti-inflammatory activity of substances 4a, b, d–h. compound increase in foot volume after 3 hours (%) braking swelling after 3 h, % 4a 41.32±3.26* 37.84 4b 39.61±1.73* 40.41 4d 28.96±5.58* 56.43 4e 45.34±3.62*,** 31.79 4f 24.04±5.68* 63.83 4g 24.29±3.73* 63.45 4h 114.76±16.45* –72.64 nimesulide 33.90±6.78* 48.99 control 66.47±10.19 – * – the difference is reduced compared to the decrease at р<0.05; ** – the difference is significant compared with nimesulide at p<0.05. https://doi.org/10.15826/chimtech.2023.10.1.02 chimica techno acta 2023, vol. 10(1), no. 202310103 article 6 of 8 doi: 10.15826/chimtech.2023.10.1.02 figure 1 the structure of the 3a, с–e, g compounds. figure 2 the structure of the 4a, b, d–h compounds. 4. limitations we have received new methyl-2-(2-(furan-2-carbonyl)hydrazono)-4-oxobutanoic acids with yields of 64–84% and n'-(2-oxofuran-3(2h)-ylidene]furan-2-carbohydrazides with yields of 52–84%, after recrystallization of the obtained compounds, yields are significantly reduced. in the course of our further research, we are going to improve the purification method in order to achieve a significantly higher yield of the product. 5. conclusions new derivatives of 2-(2-(furan-2-carbonyl)hydrazono)-4oxobutanoic acids and n'-(2-oxofuran-3(2h)-ylidene)furan-2-carbohydrazides were obtained. it was found that some of the obtained compounds (3e, 4g and 4f) exhibited significant anti-inflammatory activity, reliably exceeding the effect of a referral drug nimesulide. compounds 3 and 4 have ld50 > 1500 mg/kg and, according to the drug toxicity classification [38], belong to the v class (practically non-toxic substances). ● supplementary materials no supplementary materials are available. ● funding this study was performed under financial support by the “rational use of the earth interior” perm scientific educational center 2023 and the ministry of science and higher education of the russian federation fseg-2022-0012. ● acknowledgments none. ● author contributions conceptualization: d.a.s., n.m.i. data curation: s.n.i., d.v.l. a.yu.t. formal analysis: d.v.l., p.s.s. funding acquisition: d.a.s., n.m.i. investigation: s.n.i., d.v.l. a.yu.t. s.v.c. o.v.z. k.m. methodology: s.n.i., a.yu.t. s.v.c. o.v.z. k.m. project administration: d.a.s., n.m.i. resources: d.a.s., n.m.i. supervision: d.a.s., n.m.i. validation: d.v.l., d.a.s., p.s.s., n.m.i. visualization: d.v.l., p.s.s. writing – original draft: d.v.l., d.a.s., p.s.s. writing – review & editing: d.v.l., d.a.s. ● conflict of interest the authors declare no conflict of interest. ● additional information author ids: sergei n. igidov, scopus id 57679291500; dmitriy v. lipin, scopus id 57414727200; aleksey yu. turyshev, scopus id 57431693900; daria a. shipilovskikh, scopus id 57193555475; pavel s. silaichev, scopus id 8521794900; ksenia a. mitusova, scopus id 57203920295; nazim m. igidov, scopus id 6701786062. websites: perm state pharmaceutical academy, http://pfa.ru; perm state national research university, http://en.psu.ru; perm national research polytechnic university, https://pstu.ru/en; peter the great st. petersburg polytechnic university, https://english.spbstu.ru. references 1. bouz g, dolezal m. advances in antifungal drug development: an up-to-date mini review. pharmaceutic. 2021;14(12):1312. doi:10.3390/ph14121312 2. huang l, yang j, wang t, gao j, xu d. engineering of smallmolecule lipidic prodrugs as novel nanomedicines for enhanced drug delivery. nanobiotechnol. 2022;20(1):49. doi:10.1186/s12951-022-01257-4 3. jhinjharia d, kaushik ac, sahi s. chapter 3 – advances in structure-based drug design. bioinform pharm sci. 2021:55. doi:10.1016/b978-0-12-821748-1.00009-9 4. samy ke, 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kizimova ia, igidov nm, kiselev ma, ivanov dv, syutkina ai. reactions of n'-[2-oxo-5-r-furan-3(2h)-ylidene]acylhydrazides with primary and secondary alcohols. russ j gen chem. 2020;90(5):815–821. doi:10.1134/s1070363220050096 38. izmerov nf, sanotskii iv, sidorov kk. parametry toksikometrii promyshlennykh yadov pri odnokratnom vozdeistvii [parameters of toxicometry of industrial poisons at a single exposure]. moscow: meditsina; 1977. 196 p. russian. https://doi.org/10.15826/chimtech.2023.10.1.02 https://doi.org/10.15826/chimtech.2021.8.4.11 https://doi.org/10.1134/s1070428021110105 https://doi.org/10.1134/s1070363220050096 characterization and potential applications of silver nanoparticles: an insight on different mechanisms published by ural federal university eissn 2411-1414; chimicatechnoacta.ru review 2022, vol. 9(4), no. 20229402 doi: 10.15826/chimtech.2022.9.4.02 1 of 20 characterization and potential applications of silver nanoparticles: an insight on different mechanisms anton n. kodintcev * institute of high temperature electrochemistry of the ural branch of the russian academy of sciences, ekaterinburg 620066, russia * corresponding author: antonkodintsev@mail.ru this invited review belongs to a regular issue. © 2022, the authors. this article is published in open access under the terms and conditions of the creative commons attribution (cc by) license (http:creativecommons:licenses/by/4.0/). abstract in the 21st century, a great interest is devoted to biomedical application of various nanoparticles, particularly, as a means of improving the effectiveness of therapy for different diseases. silver nanoparticles (agnps) are among the most studied types of nanoparticles. due to the wide spectrum of their action, silver nanoparticles may be used both to influence pathogenic microorganisms and to improve the treatment of cancer. the basic physicochemical characteristics and stabilizing agents play an important modifying role in the pharmacokinetics and pharmacodynamics of nanoparticles, determining the severity of the caused effect and their potential toxicity. this review summarizes the main physicochemical properties of agnps and their impact on the biological effects. additionally, biochemical and pathophysiological mechanisms of silver nanoparticles activity against various microorganisms and tumor cells are considered. finally, we address the problems associated with determining the optimal characteristics of nanoparticles in order to increase their efficiency and reduce their toxicity for the macroorganism. keywords silver nanoparticles physicochemical properties biological effects toxicity received: 23.06.22 revised: 25.06.22 accepted: 25.06.22 available online: 11.07.22 1. introduction currently, the research on biomedical properties of various nanoparticles, synthesized from gold or silver, attracts a considerable interest. despite the lack of data on the mechanisms of silver toxicity in vivo, the nanoparticles obtained from it are widely used as antibacterial substances in medical, cosmetic, food and textile industries. silver nanoparticles (agnps) have unique binding properties, including internal antimicrobial activity and potentially low toxicity. silver, and, in particular, its ions have the strongest antibacterial effect among metals; agnps may be used in wound dressings, local drug delivery systems, orthopedic and orthodontic materials, antiseptic solutions, catheters, bandages, tissue scaffolds and protective clothing [1–3]. thus, agnps can be an effective alternative to local antibacterial drugs because of special physicochemical properties and wide spectrum of action against various gram-negative (escherichia coli, neisseria gonorrhea, p. aeruginosa) and gram-positive (s. aureus, including mrsa) bacteria, as well as intracellular microorganisms (chlamydia trachomatis) and different viruses [3–5]. agnps may be considered as a means to modernize the treatment regimens for mycobacteria, such as tuberculosis [6]. the systematic review of fakhruddin et al. demonstrates the existence of the evidence of antimicrobial properties of silver nanoparticles against cariogenic flora in vitro and prevention of the dentin destruction [7]. moreover, there is evidence of synergistic action of nanoparticles and various antibiotics. combining agnps with these class of drugs could increase the antibacterial activity of imipenem, tetracycline, aminopenicillins, metronidazole, gentamicin, kanamycin, streptomycin, and vancomycin [8–14]. silver nanoparticles may interact with bacterial membranes and penetrate into the cell with the subsequent initiation of vital malfunction and structural changes leading to destruction and death of pathogenic microorganisms [15]. the key factor is the activation of oxidative stress processes leading to dysfunction of cellular structures such as dna (genotoxic effect). disturbance of protein structure occurs due to the formation of ag–s complexes, which leads to malfunction of membrane pumps and respiratory chain. activation of lipid peroxidation processes is another important factor of cellular dysfunction [16]. http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2022.9.4.02 mailto:antonkodintsev@mail.ru http://creativecommons.org/licenses/by/4.0/ https://orcid.org/0000-0002-3978-8902 https://crossmark.crossref.org/dialog/?doi=https://doi.org/10.15826/chimtech.2022.9.4.02&domain=pdf&date_stamp=2022-7-11 chimica techno acta 2022, vol. 9(4), no. 20229402 review 2 of 20 a comparative analysis of the antibacterial effectiveness of silver ions and silver nanoparticles elucidated that they boost the development of many pores in the cell membrane and, consequently, cause the outside leakage of the cytoplasm and macromolecules. besides, there is a significant damage of the flagella, which impairs the mobility of bacteria [19, 20, 21]. agnps have an antifungal effect (candida albicans, aspergillus niger) when adding material to siliconecontaining linings and resins. in addition, there are data on their effectiveness against penicillium citrinum and trichophyton mentagrophytes [20–22]. beyond antibacterial and antifungal activity, agnps demonstrate antiinflammatory and antitumor properties [2, 3, 21, 22]. it is assumed that agnps are able to enhance the immunogenicity of vaccines, have an antidiabetic effect and also contribute to bone regeneration and wound healing [3]. despite the large number of studies indicating antibacterial properties of silver, there is evidence of the possible phenotypic resistance of bacteria to agnps. during repeated applying of nanoparticles, the increasing aggregation under the influence of flagellin protein was detected. this process leads to subsequent loss of beneficial antibacterial effect. inhibition of flagellin, for example, with pomegranate peel extract, helps to overcome this resistance mechanism [23, 24]. it should be noted that the bactericidal and bacteriostatic functions of agnps could be changed in the bacterial environment. for example, oxidation processes can induce the changes of nanoparticles in oxygen-containing liquids, which distinguishes agnps from the potentially stable gold nanoparticles. however, the synthesis of agnps is much cheaper and more affordable, so it is very important to find new ways to prevent any loss of basic silver characteristics in solutions. for example, the potential instability of agnps could be improved by stabilization with organic, inorganic, synthetic, natural, biotic, and abiotic substrates [15]. silver nanoparticles are zero-dimensional materials with particle sizes ranging from 1 to 100 nm. currently, special synthetic methods have been developed to obtain particles with certain shapes and sizes. for example, chemical (reduction of ions to atoms), physical (mechanical and pear-shaped) and biological (extracts of microorganisms and plants) methods of production are actively used (figure 1). the most common approach is chemical synthesis; however, this method is characterized by high toxicity and pollution. biological methods are cheaper and more ecologically friendly. moreover, the substrates obtained during biological synthesis can be used as stabilizers for the nanoparticles [3]. 2. materials and methods 2.1. data sources a literature review on the properties of silver nanoparticles was performed using the following databases: medline (pubmed interface), scopus, cochrane library, google scholar. the published data on the in vitro and in vivo studies were accessed between january 1990 and december 2021. backward and forward reference searching was applied to find the most relevant articles. 2.2. inclusion and exclusion criteria the current review includes predominantly full-text articles presented in english language and focused on silver nanoparticles chemical/physical/biological properties. the selected articles were original studies (observational and experimental), systematic reviews, narrative reviews and meta-analyses. the studies were excluded if they were not consistent with the research objectives and the actual purposes of the current review. all studies were carried out in vitro (cell lines) or on mice/rats due to ethic issues. 2.3. search strategy search terms included the following: silver nanoparticles, agnp, physical, chemical, biological, biocidal, properties, effects, toxicity, microorganism, virus, bacteria, fungi, protozoa, parasites, cancer and tumor. the main search structures consisted of keywords according to each objective of the review: ((silver nanoparticle*) or agnp*) and synth*; ((silver nanoparticle*) or agnp*) and (chemic* or physic* or bio*); ((silver nanoparticle*) or agnp*) and microorg*; ((silver nanoparticle*) or agnp*) and propert*; ((silver nanoparticle*) or agnp*) and (antibacter* or bacter*); ((silver nanoparticle*) or agnp*) and antivirus*; ((silver nanoparticle*) or agnp*) and (protoz* or parasite*); ((silver nanoparticle*) or agnp*) and (anticancer* or tumor*); ((silver nanoparticle*) or agnp*) and toxic*. grey literature and unpublished information were neither considered nor used. after reference screening the duplicates were excluded. the key research objectives were: 1. studying different chemical and physical properties of agnps, which can change biological effects. 2. uncovering some important biological and biochemical mechanisms of agnps effects and toxicity against bacteria, viruses, fungi, protozoa, and cancer. figure 1 characteristics of silver nanoparticles. different ways of agnps synthesis. adapted from refs [17, 18]. chimica techno acta 2022, vol. 9(4), no. 20229402 review 3 of 20 3. elucidating potential harm and toxicity of agnps for a macroorganism and a host. the current review was prepared according to a scale for the quality assessment of narrative review articles – sanra [25]. 3. results and discussion 3.1. physical and chemical properties of silver nanoparticles 3.1.1. size the antibacterial activity of silver nanoparticles is closely related to their size. agnihotri et al. have investigated antibacterial activity of silver nanoparticles of different size (5, 7, 10, 15, 20, 30, 50, 63, 85, and 100 nm) against escherichia coli mtcc 443 (e. сoli) and staphylococcus aureus ncim 5201. antibacterial activity of agnps was enhanced with decreasing size. the smallest nanoparticles of 5 nm demonstrated the best results and the highest bactericidal activity against all tested strains [26]. baker et al. studied the antibacterial activity of nanoparticles with different sizes ranging from 5 to 70 nm (average size 15 nm) and from 50 nm to more than 100 nm (average size 75 nm), respectively. the results showed that smaller agnps (15 nm) were more effective against e. coli [27]. consequently, the smaller size results in the higher antibacterial activity. this rule is explained by the fact that small agnps have larger specific surface area and more surface-acting centers, resulting in the increase in ag+ release rate and, therefore, toxicity [28, 29]. dobias et al. demonstrated that in natural ponds, the dissolution of 5 nm agnps occurred faster than that of 10 nm silver nanoparticles. smaller nanoparticles released more silver ions than 50 nm agnps [30]. morones et al. showed that only nanoparticles with a diameter of 10 nm or less could penetrate through the bacterial cell membrane [31]. in addition, applying the nanoparticles with the size of 8.3±1.9 nm increases the damage of cellular dna by influencing the nucleotide excision repair [32]. conversely, bélteky et al. noticed that in spite of the fact that nanoparticles with the smallest diameter have the greatest toxicity, an increase in the size of the nanoparticles promotes colloidal stability and also provides greater resistance to environmental conditions and aggregation [33]. 3.1.2. shape another property that determines the antibacterial activity of silver nanoparticles is their shape. there are quasispheres, nanotubes, rods, disks, cubes, prisms, octahedral, and triangular nanoplates [34–37] (figure 2). pal et al. investigated the antibacterial activity of spherical, rodshaped, and triangular silver nanoparticles against e. coli. truncated triangular nanoplates demonstrated the highest bactericidal activity compared to nanospheres and nanorods. the result could be explained by the presence of special active faces that determine their high reactivity. this triangular structure of nanoplates promotes more effective interaction with the bacterial cell, leading to its lysis [38]. on the contrary, in one of the latest studies, triangular nanoplates showed a smaller antibacterial effect compared to nanospheres against e. coli, s. aureus, p. aeruginosa. this can be put down to the fact that the surface area of the nanospheres (1.307±5 cm2) exceeded the surface area of triangular nanoplates (1.028±35 cm2) [39]. in the other studies, the greatest bactericidal activity was also demonstrated by nanoparticles with the largest surface area, which caused the accelerated formation of ions on the nanoparticle surface during their dissolution, therefore, increasing the antibacterial effect [40, 41]. figure 2 different shapes of silver nanoparticles. adapted from ref [42]. 3.1.3. concentration of nanoparticles the dissolution of silver nanoparticles depends on their initial concentration. if this concentration is lower than the solubility of agnps (which depends on the size of the nanoparticles, the presence of ligands forming a complex with silver (i) and the physicochemical properties of the solution), all nanoparticles will eventually dissolve. aggregation also explains why the initial concentration of agnps affects the release kinetics of silver ions. for example, if other parameters are fixed, the higher initial concentration of nanoparticles results in the slower initial release of silver ions. [43]. this is explained by the fact that at the high initial concentration agnps tend to aggregate more rapidly, which decreases the soluble agnps surface area [44]. the initial concentration of agnps ranging from 300 to 600 μg/l increases the aggregation rate for all three sizes of agnps (20, 40 and 80 nm) [45]. the antibacterial activity of agnps is also determined by the concentration of nanoparticles. panáček et al. found that agnps are able to exhibit antibacterial activity at a very low concentration of 1.69 μg/ml [46]. shu et al. demonstrated that the antibacterial activity of agnps of 13.8 nm against e. coli depended on their concentration. the growth inhibition analysis illustrated a complete suppression of the e. coli growth at agnps concentrations above chimica techno acta 2022, vol. 9(4), no. 20229402 review 4 of 20 20.0 μg/ml [47]. ugwoke et al. found that bactericidal activity enhanced as the dose of silver nanoparticles increased from 2 to 8 μg/ml. the smallest agnps (3.4±1.2 nm) demonstrated high sensitivity to bacterial strains (coliform) at lower concentrations (8 μg/ml), compared with 30 μg of gentamicin [48]. in addition, the minimal concentration of agnps for antibacterial properties is mainly determined by their shape. thus, truncated triangular silver nanoparticles showed the inhibition of bacterial growth at the 1 μg concentration, while nanospheres and nanorods induce an inhibiting effect at concentrations of 12.5 μg and 50-100 μg, respectively [31, 38]. but, the shape cannot be considered as a single factor that affects antibacterial activity, because the particle size varies with the form, which influences the overall rate of particles dissolving [34]. 3.1.4. stabilizing agents as a rule, stabilizing agents are used during agnps synthesis to provide an electrostatic repulsion between individual particles and to prevent their aggregation [43]. as opposed to other silver forms, nanoparticles exhibit high surface energy values due to their small size and, therefore, they are more likely to clump and to form agglomerates. choosing a suitable stabilizing agent is an important requirement for the nanoparticles stabilization, because coating agent affects the structural properties of the nanoparticle, including its size, shape, surface charge, and interaction with environment [49]. it is worth noting that coatings probably detach from the surface after interacting with environment [50]. among stabilizing mechanisms of coating agents, there are electrostatic stabilization, steric stabilization, and stabilization by hydration forces, depletion stabilization and stabilization by the van der waals forces [51]. organic coating agents are widely used as stabilizers for silver nanoparticles. in some cases, the stabilizing agent acts simultaneously as a reducing agent of ag+ ion to ag0 [52]. also, organic molecules contribute to the complexation of silver ions, thereby accelerating their dissolution [53]. the most common coating agents for silver nanoparticles are citrate, polyvinyl alcohol (pva), sodium dodecyl sulfate (sds), polyvinylpyrrolidone (pvp), tween 80 [54– 58]. citrate is one of the most commonly used stabilizers and reducing agents used for the agnps synthesis. citratecoated particles are electrostatically stabilized by negatively charged anions. however, as the ph value decreases, the citrate-anion protonates, which causes the loss of stabilization [59]. in vivo agnps capped by citrate or pvp demonstrate the greater antibacterial activity against salmonella, compared to uncapped agnps, which could be explained by minimal interaction with serum proteins. uncapped agnps, by contrast, lose their antibacterial activity due to interaction with bovine serum albumin (bsa) [58]. kvítek et al. proved that any of three mentioned stabilizing agents (twin-80, sodium dodecyl sulfate (sds) or polyvinylpyrrolidone (pvp)) increased the antibacterial activity and excellent stabilization of silver nanoparticles dispersion against aggregation. among all agnps ligands, sds-modified agnps proved to be the most stable due to the electrostatic repulsion and steric effect. sds-modified agnps demonstrated the highest antibacterial activity associated with good silver nanoparticles dispersibility and effective interaction with the cell membrane [60]. ajitha et al. found that pva-coated agnps had the smallest size and demonstrated high stability and antibacterial activity, compared to nanoparticles stabilized by other coatings [49]. currently, the biosynthesis of metals and metal oxide nanoparticles, using biological agents such as bacteria, fungi, yeast, plant and algae extracts, has gained popularity in the field of nanotechnology [61]. thus, agnps, which are synthesized by various microorganisms, provide high stability due to the fact that microbes produce large amounts of protein [62]. agnps, which are synthesized using cyanobacterial extract of oscillatoria limnetic, have high antibacterial activity against multidrugresistant bacteria (escherichia coli and bacillus cereus) as well as cytotoxicity against breast cancer and colon cancer cells at low concentrations of 6.147 μg/ ml and 5.369 μg/ml, respectively [63]. plants contain carbohydrates, fats, proteins, nucleic acids, pigments and several types of secondary metabolites that act as stabilizers and reducing agents in the biosynthesis of silver nanoparticles [64]. caffeine and theophylline are widely used as stabilizing agents and could be found in water-alcohol extracts of coffea arabica and camellia sinensis as well as in extracts of black tea [65, 66]. utilization of fungi as reducing and stabilizing agents in the biogenic synthesis of silver nanoparticles is also attractive because they produce large amounts of protein. during biological synthesis, nanoparticles are coated with biomolecules derived from the fungus, which leads to improved stability and increased biological activity [17, 67]. konappa et al. capped silver nanoparticles with secondary metabolites secreted by the t. harzianum fungus. the obtained agnps had high stability as well as a wide range of antibacterial activity against two gram-positive bacteria (s. aureus and b. subtilis) and two gram-negative bacteria (e. coli and r. solanacearum) [68]. silver nanoparticles also could be stabilized with polymeric carbohydrates such as starch, sodium alginate and chitosan [69–71]. muhammad et al. used sericin (a protein that is a part of silk) as a stabilizing agent. sericin-coated nanoparticles proved to be highly effective against bacteria and maintained stability over a wide range of temperatures and ph concentrations. the authors suggested wide use of sericin in the future because of low cost and high stability [72]. hydroxyl groups of sericin form complexes with silver ions, thus preventing their aggregation and deposition [71]. azócar et al. used diclofenac (d) and ketorolac (k) as stabilizing agents, which are widely used as anti-inflammatory drugs in medicine. the results demonchimica techno acta 2022, vol. 9(4), no. 20229402 review 5 of 20 strated that agnps-k were more stable than the uncoated nanoparticles. under the influence of uv light (wavelength of 365 nm), capped nanoparticles generated anion radicals. this effect is probably associated with capping agents, because bare nanoparticles do not promote the formation of superoxide anion [73]. 3.1.5. surface charge of the nanoparticles gao et al. found that dispersion and stability of agnps are related to their surface charge. the negative surface charge contributes to the electrostatic stabilization of the nanoparticles against aggregation. however, the dispersion charge of particle can change depending on the ph value. the surface charge of agnps becomes more negative at higher ph, as confirmed by the high zeta potential value equal to –32.5 mv, which promotes the stability of the suspension. conversely, lower ph values of 5 and 3 are characterized by a decrease in zeta potential to –22.5 and –18.2 mv, which, therefore, reduces the repulsive forces and stability [59]. moreover, small agnps have lower zeta potentials than large agnps; thus, small particles have less electrostatic repulsion and more rapid aggregation. surface charge is one of the most important factors of agnps toxicity. recently, the antibacterial activity of positively and negatively charged agnps has been studied. some studies demonstrated that positively charged agnps have a higher bactericidal activity against all microorganisms compared with negatively or neutral charged agnps [74, 75]. el badawy et al. found out that positively charged bpei-agnp were more toxic against bacteria, compared with negatively charged citrate-agnp. it could be explained by negative membrane charge of both grampositive and gram-negative bacteria. consequently, there is an electrostatic barrier between negatively charged citrate-agnp and bacterial membranes that limits interaction between the cell and nanoparticles, thus reducing toxicity [76, 77]. qiao et al. synthesized zwitterion-modified agnps, which could change the charge depending on the environmental ph. these agnps demonstrated a phdependent transformation of negative charge into positive charge. therefore agnps were innocuous for healthy tissue cells (ph=7.4), while interacted effectively with negatively charged bacterial surfaces in foci of infection (ph=5.5) [78]. 3.2. influence of biological conditions on the nanoparticles properties such factors as ph, presence of dissolved oxygen, electrolytes and organic substances, in particular, proteins affect significantly the physicochemical properties and antibacterial activity of silver nanoparticles [79, 80]. 3.2.1. oxygen availability the dissolution of the nanoparticles occurs in the presence of dissolved oxygen. the surface of agnps is easily oxidized by o2 and other molecules in ecological and biological systems, resulting in the release of ag+ and defining their toxicity [81]. however, silver nanoparticles do not dissolve completely in the presence of molecular oxygen. a complete dissolution requires a stronger oxidizer such as h2o2. the agnps aggregation in oxygenated water is 3–8 times faster than under anaerobic conditions, indicating that dissolved molecular oxygen can also significantly affect this process [45]. 3.2.2. interaction with proteins it is well known that nanomaterials can interact with various biomolecules of living organisms, primarily with proteins that are able to adsorb on the nanoparticles surface, forming the biomolecular corona [82]. about 300– 500 human plasma proteins could be bound to different nanoparticles. nanomaterials are rapidly coated by proteins in physiological fluids. the formation of the protein corona leads to the change in the physicochemical properties of nanoparticles, including hydrodynamic size, surface charge, and aggregation [84]. the structure of protein corona depends primarily on the nanoparticle material, size and surface properties, as well as on the composition of protein environment and experimental/physiological conditions [84–86]. tai et al. and alarcon et al. demonstrated that the protein corona serves as a kind of biological identity of the nanoparticle. in addition, it contributes to the colloidal stability of the particle, that presents the aggregation of the nanoparticles and protective from aggressive environmental conditions [87, 88]. functionalization of silver nanoparticles surface significantly affects the formation dynamics of protein corona. the presence of a protein coating on the surface of the nanoparticles strongly reduces the binding degree to the protein. on the contrary, the formation of the corona on the uncoated nanoparticles improved significantly their stability in biological environment. the in vitro experiments showed that the physiological stability of agnps caused by the corona formation may be directly associated with their binding to the cell, capture and toxicity [89]. the interaction between nanoparticles and different cells is determined by the composition of protein corona [90]. 3.2.3. ph the solution ph affects significantly the surface charge and oxidative dissolution of agnps. the behavior of nanoparticles differs under acidic and alkaline conditions. agnps are found to destabilize in acid and neutral ph, which results in higher aggregation rate. under alkaline conditions, negatively charged hydroxyl ions promote the stabilization of nanoparticles [91]. bélteky et al. found that agnps are more stable at alkaline and neutral values of ph than under acid conditions. an increase in the ph level leads to higher deprotonation degree of free organic functional groups and increasing negative charge on the nanoparticles surface. it facilitates the increasing electrostatic repulsion between particles and reduces the degree of aggregation [82]. sivera et al. showed that gelatinchimica techno acta 2022, vol. 9(4), no. 20229402 review 6 of 20 stabilized agnps have robust resistance to aggregation in a wide range of ph (2 to 13). moreover, these agnps demonstrated long-term stability against aggregation and maintained high antibacterial activity under environmental conditions for several months [92]. 3.2.4. electrolyte concentration an increase in the electrolyte concentration leads to an increase in the agnps aggregation rate [43]. stebounova et al. concluded that agnps aggregate in solutions with high ionic strength regardless of stabilization [79]. bélteky et al. found that in solutions containing 50 mm of nacl, the aggregation is slow and the size of agnps agglomerates does not change significantly. however, the addition of 150 mm of nacl induces the rapid aggregation of agnps up to micrometer size range. sudden changes in aggregation occur due to an increase in the concentration of na+, because in large quantities these ions can shield negatively charged surface groups, which provide electrostatic stabilization. with reduced repulsion, the particles form larger aggregates during collisions [82]. the presence of chloride ions in solution causes silver chloride deposition [53]. however, sulfide ligands significantly reduce the toxicity of agnps caused by generation of insoluble silver compounds [93]. the nanoparticle aggregation is very prominent in solutions with high concentration of divalent cations, such as mg 2+ and ca2+, due to the stronger neutralization of the surface charge. on the other hand, monovalent cations (k+ and na+) can also enhance the aggregation of agnps, but they are much less effective in the shielding of surface charge than divalent ones [43]. finally, the effect of the ionic strength on the agnps aggregation is more significant for smaller particles [93]. 3.3. mechanisms of agnps biological activity 3.3.1. the main mechanisms of antibacterial activity the main antibacterial properties of silver nanoparticles are provided directly by silver ions; in other words, nanoparticles are a kind of transporters of the main active substance [97]. moreover, agnps obtained by the "green" synthesis are more toxic than agnps obtained by nonbiological approaches [64]. agnps release silver ions that interact with sulfa groups of membrane proteins, which disturb the membrane integrity and thereby increase its permeability. agnps interact with the cytoskeletal protein mreb, which plays an important role in the survival and formation of the bacterial cell [98]. active adhesion of silver ions to the cell membrane leads to the change in its charge (depolarization and desensitization), lysis of cellular components and rupture of organelles. moreover, silver ions participate in transduction processes by dephosphorylation of tyrosine residues, initiating the launch of the bacterial cell apoptosis program [13, 99]. once in the cell, free silver ions interact with respiratory chain enzymes (dehydrogenases) and bind to functional electron donor groups (thiols, phosphates, imidazole, indoles, and hydroxyl groups), disrupting the atp synthesis and k+ transport [14, 98, 100]. in addition, the pathological effect of silver nanoparticles is induced by the formation of reactive oxygen species (ros): superoxide anion radical (o2•−), peroxide (o2•−2), hydroxyl radical (•oh), hydrogen peroxide (h2o2), hydroxyl ions (oh−). different ros have various pathological effects, for instance: oh−, h2o2 and o2•− have the greatest antibacterial activity. oh− interacts with positively charged cell membranes, while h2o2 has the greatest penetrating effect. high concentration of ros leads to a decrease in the concentration of glutathione, an increase in lactate dehydrogenase, dysregulation of calcium channels, matrix metalloproteases and intracellular redox homeostasis [101]. actually, ros interacts with the thioredoxin system of s. aureus, which is one of the most important disulfide reductase systems that counteract the processes of oxidative stress. oligomerization and dysregulation of thiol-redox homeostasis due to the depletion of intracellular thiol leads to disruption of the protective components and to activation of the oxidative stress [102]. moreover, ros interact with dna, thereby triggering the processes of its modification. in addition to the indirect effect through oxidative stress, silver ions interact with sulfur and phosphorus groups of dnas, which leads to the rupture of hydrogen bonds between the chains; the processes of replication and reproduction are disrupted (i.e., genome splitting is observed) [103]. unipolar charge of dna and agnps leads to additional destabilization of the chains. damage to dna molecules occurs due to oxidation and alkylation of its bases, which leads to the formation of various compounds: 8-oxoguanine, 7,8-dihydro8-oxoguanine, 8-oxoadenine, unsubstituted and substituted with an imidazole ring of purines. these compounds are integrated into dna under the influence of hydroxyl radicals [103, 104]. in addition to dna, silver ions also interact with rna and block the subunits of ribosomes (30s), which are necessary for binding trna [105, 106]. being in cytoplasm agnps induce the processes of ribosome denaturation, inhibition of translation, protein synthesis and carbohydrate metabolism [102, 107]. the disturbance of the signal transduction processes is equally important because suppressing the phosphorylation of tyrosine residues results in blocking the cell cycle, the synthesis of exopolysaccharides and capsular polysaccharides, which ultimately leads to the interruption of the bacterial cell division [103]. thus, the antibacterial activity of silver has a complex effect on the microorganism, disrupting various aspects of its vital activity. chimica techno acta 2022, vol. 9(4), no. 20229402 review 7 of 20 gram-negative bacteria are more sensitive to the effects of silver ions than gram-positive bacteria, which is due to a thinner layer of peptidoglycans in the cell wall [108]. for example, s. aureus, a gram-positive coccus with a cell wall width of 30 nm, can effectively prevent the inward penetration of nanoparticles due to the high affinity of the peptidoglycan layer [109, 110]. the antibacterial effect may depend not only on the size of the nanoparticles (nanoparticles smaller than 10 nm have high penetrating power), but also on the physicochemical properties, in particular, surface characteristics. so, positively charged nanoparticles have a greater binding ability with a negatively charged cell membrane due to the electrostatic interaction, in contrast to the negatively charged agnps. the higher positive charge of the ions results in the lower severity of the electrostatic barrier [97, 108, 109, 111]. despite the fact that silver ions play a crucial role in disrupting the basic processes of microorganisms’ activity, nanoparticles also have an antibacterial effect due to the mechanism of the "contact destruction". the antibacterial properties of silver nanoparticles also depend on their shape. for example, spherical and triangular agnps have greater activity against e. coli and s. aureus is than agnps of irregular shape, which may be due to a larger surface and increased release of silver ions [5, 13]. however, pal et al. elucidated that the triangular shape’s agnps have a greater antibacterial effectiveness against e. coli, compared to spherical and rod-shaped particles [38]. moreover e.coli is more sensitive to agnp exposure than s. aureus regardless of agnp size and surface properties [112]. there are published data indicating the ability of silver nanoparticles to suppress the formation of bacterial films on medical instruments without significant accumulation of silver ions in surrounding organs and tissues. the most promising direction is the approbation of this coating for catheters, drains and medical masks [5]. moreover, numerous studies pinpoint the antiinflammatory properties of agnps, which are associated with a decrease in the pro-inflammatory cytokines synthesis (tnf, il-12, il-1, nf-kb) and the induction of apoptosis. in addition, the modulation role of silver in the process of wound and periodontal healing has been discovered [104]. thus, the main antibacterial mechanisms of agnps (figure 3) are as follows: 1. interaction with the membrane, impairment of its permeability and change in charge. 2. disturbance of intracellular processes and organelles dysfunction. 3. inhibition of mitochondrial processes (respiratory chain malfunction), activation of oxidative stress, synthesis of reactive oxygen species and lipid peroxidation. 4. interaction with dna and rna, blocking the replication, transcription, and translation. 5. inhibition of transduction of signals due to dephosphorylation of tyrosine residues. figure 3 antibacterial properties of agnps. general mechanisms of antimicrobial mode of action of silver nanoparticles (a); bactericidal effect of green synthesized agnps on different bacterial strains. dose-dependent activity of agnps synthesized using allophylus cobbe leaves. the bacterial strains were incubated at various agnps concentrations ranging from 0.1 to 1.0 mg/ml and bacterial rate survival was estimated by colony forming unit (cfu) assay at 4 h (b); zone of inhibition of silver nanoparticles against various pathogenic microorganisms compared to banana peel extract (bpe) (c). presented from refs [61, 113]. (a) (b) (c) chimica techno acta 2022, vol. 9(4), no. 20229402 review 8 of 20 3.3.2. the main mechanisms of antiviral activity in vitro agnps could adhere to the virus surface, bind the viral ligand and therefore prevent its spreading in cell cultures (figure 4a, 4b). lv et al. indicate the property of silver nanoparticles to inhibit tgev (transmissible gastroenteritis virus in pigs) induced apoptosis by binding to s glycoprotein. the suppression of the proapoptotic pathway is one of the possible mechanisms because tgev causes an increase in concentration of protein bax [114]. based on the published data, there is assumption that the nanoparticles can also be effective against the novel coronavirus infection (covid-19) because they have a possibility to interact with the spike glycoprotein and to decrease ph of respiratory epithelium, which would effectively prevent intracellular invasion of the virus (figure 4c) [98, 115]. there is a description of agnps possibility to bind the gprotein of the respiratory syncytial virus in the hep-2 cell culture. agnps coated with polyvinylpyrrolidone inhibited the reproduction of rsc virus by 44%, while silver nanoparticles coated with biomolecules and rf-112 did not have a visible effect on the pathogen's life cycle [104, 116]. in addition to the binding to surface proteins, agnps interact with the viruses’ nucleic acids (for instance, of the hepatitis b virus) and disrupt their replication in the host cells [103]. the inhibition of hbv rna/dna synthesis and creation of extracellular virions are observed in the human hepatoma hepad38 cell line [117]. biologically synthesized agnps of small size (<20 nm) have greater effectiveness against herpes simplex virus type 1/2 and human parainfluenza virus type 3 due to a more pronounced blocking effect on the interaction between the virus and a cell of the veroline cell line. nanoparticles are able to interact non-covalently with the thymidine kinase ligand, thereby suppressing the activity of herpesviruses. in addition to inhibition of hpv 1 and type 2, there is an inhibition of oncogenic herpesviruses, for example, epstein-barr virus [13, 120]. moreover, agnps block the interaction of herpesviruses with heparan sulfate proteoglycans of cell membranes, preventing invasion processes. these properties could be enhanced by combining agnps with tannic acid [121, 122]. particles smaller than 10 nm can prevent the spreading of influenza virus in cell culture mdck [123]. in 2017, lin et al. published the data about the activity of combination treatment with zanamivir and agnps against the h1a1 influenza virus in mdck cell line. this combination not only demonstrated high thermodynamic and kinetic stability, but also suppressed effectively the replication of the influenza virus by regulating neuraminidase activity [124]. there are published data about the ability of silver nanoparticles to interact with hiv and inhibit significantly its reproduction by binding to the regions of disulfide bond (sulfur-containing residues of cd4-binding domain) of gp120 [125, 126]. moreover, silver nanoparticles could prevent infection of cervical tissue with hiv type 1 without cytotoxic effect in vitro [127]. figure 4 antiviral properties of agnps. schematic model of a virus infecting an eukaryotic cell and antiviral mechanism of metal nanoparticles. (a); the activity of silver nanoparticles against the prevalent viruses (b); mechanisms of antiviral activity against sars-cov2 (c). adapted from refs [118, 119]. silver nanoparticles have a wide antiviral spectrum of action against different viruses that spread through mosquito bites: dengue fever, west nile fever, zika virus and chikungunya virus. both uncoated agnps and polysacchainfluenza inhibition of new virions formation and their spreading hepatitis b virus inhibition of new virions formation and their spreading herpes virus inhibition of replication and invasion processes in a healthy cell hiv binding to gp120 and preventing virus from entering the cell. inhibition of virus reproduction respiratory syncytial virus binding to g-protein, inhibition of virus reproduction (a) ))k k)) (b) (c) chimica techno acta 2022, vol. 9(4), no. 20229402 review 9 of 20 ridescoated agnps have a suppressing effect on the replication of tacaribe virus and monkeypox virus [13, 128, 129]. 3.3.3. the main mechanisms of antifungal activity the mechanisms of agnps antifungal activity are not fully understood. there is a suggestion that the interaction of nanoparticles with the membrane leads to disruption of its function (the current of transmembrane ions, including protons) and division processes (especially in yeast). also, agnps induce an inhibition of germ tube formation, growth of biofilm and secretion of hydrolytic enzymes [130, 131]. beyond the membranotoxic effect, silver nanoparticles could initiate a cascade of intracellular pathological processes leading to the fungus death: oxidative stress, interaction with thiol groups and phosphoruscontaining molecules, blocking protein synthesis. thus, the fundamental antifungal mechanisms are similar to antibacterial ones (figure 5a) [132]. the majority of the published data was acquired by studying the activity of agnps against plant pathogens and mold fungi [133]. however, agnps have antifungal properties against pathogenic fungi that cause dermatophytosis: candida sp. (including candida albicans) and trichophyton mentagrophytes [134, 135]. even amphotericinb resistant strains of candida glabrate were found to be sensitive to nanoparticles [136]. silver nanoparticles also have a biocidal effect on biofilms that are formed by candida spp. [137]. there are data on the inhibition effect of particles on fungal keratitis pathogens (fusarium spp., aspergillus spp., alternaria alternate) in vitro. at the same time, agnps had a potentially greater antifungal effect than antimycotic drug – natamycin [140]. agnps can enhance the effect of antifungal drugs. there are data about synergy of silver nanoparticles and ketoconazole against the main cause of seborrheic dermatitis malassezia furfur. combination therapy leads to a decrease in the frequency of drug use and the frequency of relapses not only of seborrheic dermatitis, but also of other malasesiosis [141]. also, agnps suppress the growth of different pathogenic aspergillus species (aspergillus niger, aspergillus flavus, aspergillus fumigatus), which can cause a wide range of diseases. due to this effect, silver nanoparticles can play an important role in the treatment of aspergillosis, especially in patients with drug-resistant strains [142]. it is worth mentioning that aspergillus niger can be used to synthesize agnps (one of the directions of biological synthesis). the synthesized nanoparticles have the ability to inhibit the growth and development of allovahlkampfia spelaea, which causes resistant keratitis [143]. thus, silver nanoparticles can play an important role in the treatment of fungal infections, especially due to the scarcity of the antifungal drugs and increasing number of drug-resistant species (figure 5b). the combination of nanoparticles and drugs can boost the effect of the latter and have an independent bactericidal action in the case of multiple resistance of pathogenic fungi. agnps can also be used to prevent the spreading of mold on different surfaces [133]. however, the inhibition of fungal growth by silver nanoparticles is less prominent than that of bacteria, which may be due to the presence of chitin in the wall of the fungus, rather than peptidoglycans [142]. figure 5 antifungal activity of silver nanoparticles. schematic representation for the proposed model for mechanism of action of agnps against candida cells, depicting possible cellular targets and existence of ros-dependent and ros-independent pathways for fungicidal action of agnps (a); antifungal activity of silver nanoparticles against: a.niger (1) and p.chrysogenum (2) at the concentrations of 200, 300, 400 and 500 µg/ml(b); colonies of trichophyton tonsurans (1), microsporum gypseum (2) and trichophyton mentagrophytes (3). on pda and pda supplemented with different concentrations of agnp. the bar charts represent the diameter of the colonies in the function of agnp concentration (b). reproduced from [138, 139]. 3.3.4. mechanisms of antiparasitic activity there are reliable data confirming the antiparasitic properties of silver nanoparticles, in particular, against the causative agent of cutaneous leishmaniasis (leishmania tropica) (figure 6a). agnps bind to the sulfoand phosphorus-containing membrane and dna proteins, blocking dna synthesis and activation of oxidative stress. agnps have an anti-promastigote effect because of blocking the proliferation of promastigotes. in addition, agnps sup(a) (c) (b) chimica techno acta 2022, vol. 9(4), no. 20229402 review 10 of 20 press the vital activity of amastigotes and reduce their survival in infected host cells. anti-amastigote properties are boosted by additional exposure of ultraviolet light. probably, when exposed to ultraviolet light, there is an increase in the concentration of monosulfide radicals, which are formed from complexes. these complexes are formed by interaction of silver ions and cysteine groups of parasitic proteins [144, 145]. figure 6 antiparasitic properties of agnp. agnps leishmanicidal activity. l. amazonensis promastigotes forms were subjected to different concentrations of agnps-bio (0.125, 0.25 and 0.50 μg/ml) and the parasite viability was assessed at 0, 24, 48 and 72 h (a); effect of agnps in toxoplasma gondii morphology as assessed by fluorescence microscopy. in the control sample, intact oocyst, in the presence agnps at 45 min and 60 min (b); scanning electron microscopy (sem) micrograph of protoscolices of e. granulosus. protoscolices without nanoparticles and 1 mg/ml concentrations of ag-nps that covered protoscolex (c). reproduced from [146–148]. apart from leishmania, the antibacterial activity of silver nanoparticlesis was observed against oocysts entamoeba histolytica, cryptosporidium parvum and several other protozoa [131, 149]. for example, in the study of costa et al. biogenic agnps inhibited the replication of toxoplasma gondi (which causes toxoplasmosis) in cell cultures, such as bewo, htr-8/svneo, hela and in villous explants. moreover, the nanoparticles induced secretion of inflammatory cytokines in cells, for example, in the bewo line: il-4 and il-10; in the htr-8/svneo line: il-4 and the macrophage migration inhibitory factor (mif). toxoplasma gondi increased the mif concentration in the bewo cell culture and il-6 in htr-8/svneo line. in villous explants the synthesis of il-4, il-6 and il-8 decreased after infesting. in hela cell line an increase in the no concentration, oxidative stress and reduction of pro-inflammatory cytokines, in particular, il-8 were observed. thus, silver nanoparticles can significantly inhibit the spread of t. gondi without developing dysfunction of the host cells (figure 6b) [150, 151]. in addition to the cell cultures and chorionic villi, agnps suppresses toxoplasma’s replication in liver and spleen tissues [152]. one of the possible antiparasitic mechanisms includes the suppression of mitochondrial function, disturbing mitochondrial membrane potential, redox signaling and destruction of leucine aminopeptidase (lap) [153]. the current data plays an important role in the development of alternative approaches to the treatment of toxoplasmosis, particularly in pregnancy, because standard drugs used for the treatment of this pathology have teratogenic and myelosuppressive properties. moreover, toxoplasmosis is part of the torch complex, which includes a group of intrauterine infections that lead to impaired fetal development and even death. the results of younis et al. demonstrated the effectiveness of agnps against blastocystis hominis, which is the causative agent of blastomycosis. the most prominent antiparasitic effect in vitro was observed with a combination of particles and metronidazole. the concentration of b. hominis decreased by 71.69% in the metronidazole group, by 79.67% in the agnps group and by 62.65% in the combination therapy group (agnps + metronidazole) after 3 hours (p<0.05). the nanoparticles are likely to interact with and modify glycoprotein and lipophosphoglycan molecules on the parasite surface they may induce oxidative stress, and inhibit ros synthesis and dna replication [154]. there are data on the possible sporicidal action of nanoparticles against echinococcus (figure 6c). moreover, agnps have a synergistic effect with albendazole and are able to prevent the development of adverse reactions in the liver associated with this drug. for example, they decrease the severity of necrosis, steatosis, and reduce the level of transaminase and ifn-γ. combination therapy is associated with a greater degree of structural changes in echinococcal cysts (reduction of cyst size and cyst mass) [155, 156]. additionally, silver nanoparticles are used for the development of new directions in the treatment of giardiasis (giardia lamblia). the combination with chitosan and curcumin leads to the complete eradication of giardia in the intestine and feces of rodents without the development of adverse reactions [157]. the study of tropical malaria (plasmodium falciparum) using agnps for the treatment is ongoing [158]. moreover, silver nanoparticles could be used in ophthalmology for prevention of acanthamoeba adhesion on contact lenses (amoebic keratitis prophylaxis) [159]. 3.3.5. main mechanisms of anticancer activity silver nanoparticles are promising for developing and modifying approaches to antitumor therapy. agnps can have a cytotoxic effect on tumor cells with subsequent suppression of the pathological process. the decreased lymphatic outflow in malignant tumors allows nanoparticles to accumulate and act longer [160]. moreover, tumor cells absorb agnps (by endocytosis) to greater than normal cells [2]. chimica techno acta 2022, vol. 9(4), no. 20229402 review 11 of 20 there are main mechanisms of anticancer activity: induction of oxidative stress, changing the structuralcellular morphology and activation of pro-apoptotic processes (caspase 3 and 9, regulation of p53, p38 mapk, hif-1α, increase in bax concentration and decrease in bcl2 concentration) [161]. apart from apoptosis, there are also necrosis and autophagy in cancer cells are activated by stimulation of autophagosomes formation through the ptdins3k signaling pathway. except direct pro-apoptotic effect, there is also an indirect activation of apoptosis through oxidative stress and synthesis of proinflammatory cytokines (il-6). an increase in the concentration of tnf-alpha and "nf-kb" nuclear factor contributes to the activation of pro-inflammatory processes in the tumor cell [162]. the increased concentration of oxygen radicals and significant depletion of glutathione leads to the dysfunction of mitochondria and the nadp/nad system, impaired permeability of the outer mitochondrial membrane, destruction of the respiratory chain, blocking the atp synthesis and release of cytochrome c into cytosol, which are important activating factors of caspase 3 (through apaf-1) and caspase 9 (figure 7) [3, 101, 163–165]. besides inhibiting the mitochondrial activity, agnps affect structural and functional characteristics of dna. agnps provoke the dna methylation, increasing the number of chromosomal aberrations and malfunction of the repair system. for example, they cause the downregulation of proliferating cell nuclear antigen, i.e. the clamp of dna polymerase, which plays an important role in the synthesis and reparation of dna. as in bacterial cells, the released silver ions are able to disrupt the hydrogen bonds between the dna bases, which leads to disorganization [3]. the activation of c-jun nh2 terminal kinase (jnk) is an additional factor in dna fragmentation and the atopic bodies formation [162]. moreover, the action of agnps is characterized by the disturbance of metabolic processes and sensitization of the tumor cell, increasing its sensitivity to antitumor drugs, in particular, to 5-fluorouracil due to the modulating effect on expression of uracil phosphoribosyl transferase, which ultimately leads to active induction of apoptosis [166]. in addition, there are data on the pharmacological synergism of agnps and doxorubicin [167]. in lung fibroblasts and glioblastoma cells agnps induce different processes, such as metallothionein upregulation, downregulation of the actin-binding protein and filamine, cell cycle arrest in phase g (2)/m [2, 168]. biosynthesized agnps can block the cell cycle in g1 phase. one possible mechanism of the cell cycle arrest is the downregulation of cyclin b and cyclin e, whose normal functioning is of the paramount importance for division processes [162]. agnps have antiangiogenic properties. in particular, agnps inhibit growth of blood vessels in tumor, limiting its progression. probably, this effect is associated with vegf (vascular endothelial growth factor) blocking and angiogenic fgf-2 (fibroblast growth factor 2) synthesis, as well as the inhibition of the transduction processes of the signaling pathways through the phosphorylation of kdr tyrosinekinase (vegfr-2) and pi3k/akt [169–171]. another mechanism of inhibiting cancer cell proliferation, vascular growth, and tumor progression implies a disruption of signaling transduction by suppressing the effects of hypoxia-induced factor-1a (hif-1α) and matrix metalloproteases. active growth and progression of the tumor are accompanied by insufficiently active formation of the vascular network, which leads to the cell hypoxia and, consequently, an increase in the concentration of hif-1α. hif-1α regulates the expression of genes responsible for cellular activity: division, growth, and angiogenesis [172]. matrix metalloproteases have similar functions. resistance to the therapy is often accompanied with high activity of these signaling pathways, so their blocking plays a potentially important role in the modification of contemporary treatment approaches [3]. the antitumor effect of nanoparticles can be enhanced by coating with nano transfers, for example, with chitosan. chitosan-coated nanoparticles have a greater inhibitory effect and cause apoptosis at a lower concentration than uncoated agnps [2, 173]. smaller nanoparticles (10, 20 nm) have the strongest antineoplastic effect compared to the large agnps (100 nm), which may be due to the greater penetrating capacity. figure 7 anticancer properties of agnps. agnps have a cytotoxic effect, inhibit the mitochondrial functions and boost the processes of oxidative stress and damage of tumor cell membrane. agnps also contribute to the suppression of the vascular growth factor (vegf), which leads to the inhibition of the new vessels formation. moreover, processes of tumor cells division are disturbed and the phenomenon of autophagy is observed. reproduced from refs [180, 181]. chimica techno acta 2022, vol. 9(4), no. 20229402 review 12 of 20 moreover, charge and electrostatic interaction also affect internalization. for example, positively charged particles penetrate more quickly and have greater cytotoxicity than particles with a neutral or negative charge. a positive charge allows the interaction both with a negatively charged membrane and albumin, which leads to formation of a protein shell. the "protein corona" allows agnps to enter cells through receptor-mediated endocytosis with further implementation of cytotoxic and genotoxic effects [75, 174, 175]. there are published data on the antitumor activity of agnps against a wide spectrum of oncological diseases in vitro: blood cancer (acute myeloid leukemia), breast cancer, hepatocellular carcinoma, osteosarcoma, lung cancer, melanoma of the skin and mucous membranes, squamous cell carcinoma of the skin, colon cancer, osteosarcoma, cervical cancer, prostate cancer, adenocarcinoma of the stomach, bladder cancer and pancreas cancer [1, 3, 13, 176–179]. 3.3.6. potential toxicity of silver nanoparticles despite the data indicating the broad therapeutic potential of agnps, it is important to assess their toxicity, since the main biochemical effects of nanoparticles do not have biological selectivity and can interact with the macroorganism cells. studying of toxic effects allows us to determine the therapeutic properties of drugs contain agnps and to minimize adverse side effects. the toxic properties of agnps depend on their size, shape, surface feature (negatively charged particles are less toxic), stabilizing agent and coating. moreover, local environmental factors have an equally important role in toxicity: the strength of the ion interaction, presence of ligands, macromolecules and bivalent cations, as well as ph parameters [74, 182]. toxic effects of nanoparticles have been studied either in vitro on cell cultures or in vivo on rodents. different methodologies and approaches make it difficult to determine common parameters and characteristics of agnps toxicity. pharmacokinetic features of agnps have wide distribution in organs and tissues (lungs, cns, kidneys, heart, liver, spleen, etc.), independent of the route of administration. the clearance of nanoparticles can differ from 17 days to 4 months. in tissues containing natural physiological barriers, for example, brain, excretion of silver proceeds more slowly (up to 260 days), which creates additional conditions for its accumulation [183, 184]. excessive accumulation of agnps leads to disruption of cells activity in different organs and systems: skin (argyria, contact dermatitis), respiratory system (bronchitis, alveolitis, fibrosis, provocation of bronchial asthma exacerbations) visual system (conjunctivitis, argyrias), gastrointestinal tract (hepatobiliary and intestinal dysfunction), immune system (dysregulation of cytokine synthesis and function of cells), cns (cognitive impairment, alzheimer's disease, epileptic seizures), urinary system (acute tubular necrosis, glomerular dysfunction), cardiovascular system (bradycardia, av block, ventricular arrhythmias) (figure 8) [3, 161, 185]. the possible nanoparticles accumulation in the reproductive system and damage of the germ cells structures were discovered by studying the pathological effects of agnps in mice. apart from the metabolic disturbances in germ cells and reduction of female oocyte fertility, the dysfunction of leydig and sertoli cells in males, which leads to infertility and a decrease in testosterone synthesis, was observed [3]. an embryotoxic effect was detected in mice and zebrafish. this effect depended on the size and coating of agnps nanoparticles. smaller agnps of 20 nm have greater toxicity than large particles of 110 nm, and polypyrimidine-coated particles are more toxic than citrate-coated agnps [186]. agnps also have a genotoxic effect due to chromosome damage, oxidative stress, and interaction with dna [185, 187]. figure 8 main spectrum of agnps toxicity. agnps have a wide spectrum of toxicity, which has been studied in mice. the collected data made it possible to predict the different consequences of nanoparticles accumulation in various organs and systems. reproduced rom ref. [180]. the process of the silver ions permutation and their interaction with oxygen or sulfur, which induce a pathological biochemical cascade in cell, are considered the main mechanism of potential agnps cytotoxicity. it is believed that formation of ag+ plays a key role in activation of lysosomal acid phosphatases, dysfunction of the actin cytoskelet, inhibition of na+/k+-atpase, stimulation of apoptosis (through the protein p53, act, tp38), induction of oxidative stress, depletion of glutathione and diffusion of cellular components [101, 185, 188]. however, according to another hypothesis, independent mechanisms of metallic ions toxicity, which can be found for various nanoparticles, cause the pathological effects [189]. except the direct entering into cell through the membrane (diffusion, endocytosis), it is supposed that agnps may penetrate through ion channels ("flip-flop" mechanism) and by the "trojan horse" approach. the latter method consists of phagocytosis and further induction of petrochemical changes in active cells by silver ionization in the cytosol [101]. it is chimica techno acta 2022, vol. 9(4), no. 20229402 review 13 of 20 worth mentioning that the most prominent morphological changes are observed in the liver, lungs, and kidneys, which may be due to the greatest participation of these organs in the clearance of nanoparticles [190]. agnps were found to induce oxidative stress in rat liver cells due to disturbance of metabolism and mitochondrialal malfunction. these changes resulted in the focal liver necrosis, spleen edema and apoptosis in thymus cortex [185, 191]. exposure to the most effective small nanoparticles (10 nm or less) caused much more prominent pathological shifts [192]. the excretion of silver from the body is mostly carried out by the hepatobiliary system (more than 50%), which may be associated with more severe hepatotoxicity because of the greatest accumulation in hepatocytes, kupffer cells and sinusoidal endotheliocytes [193]. kidneys are the second important excretion system. silver nanoparticles accumulate in all structural components of cortex and medulla in spite of a low urinary excretion fraction (less than 0.01%) [161, 193]. beyond hepatoand nephrotoxicity, silver particles may provokepathological changes in the intestinal wall despite a rather low level of absorption in the intestine ranging from 0.12% to 0.88%, which can be caused by the binding of nanoparticles to undigested food [193]. however, oral administration of silver nanoparticles in mice causes destruction of epithelial villi and glands. the implication of bowel dysfunction causes weight loss [194]. in addition, nanoparticles have toxic effect on hearing and retina due to the activation of oxidative stress in the mitochondria, which leads to the loss of hearing and vision [3, 190]. the accumulation of agnps in the central nervous system leads to disorganization of the cytoskeleton, activation of neuroinflammation and increase in the insoluble beta-amyloid concentration. these processes are important pathophysiological entity of alzheimer's disease. thus, it is possible to conclude that agnps can induce the development of neurodegenerative disorders, particularly due to low clearance and pathological accumulation [195]. positively charged silver nanoparticles are known to have toxic effects on myocardial ina and ik1 channels, which leads to significantly increased risk of severe bradycardia [196]. prolonged inhalation of agnps causes reduction of tidal volume and enhancing of inflammatory processes in bronchopulmonary system [131, 197]. thus, it is necessary to study and compare different agnps in order to determine the possibilities to synthesize less toxic nanoparticles with the strongest therapeutic effect. the study of pharmacodynamics and pharmacokinetics properties of agnps to prevent pathological accumulation is equally important. moreover, it is necessary to conduct further research, devoted to direct comparison of coating agents and to selecting the optimal coating approach, because the coating and stabilization have beenproved to have a huge modifying effect. 4. conclusion given the wide range of biological, physical, and chemical properties of silver nanoparticles, a potential role of this compound in clinical medicine may be suggested. approbation and usage of agnps are highly promising, especially in the era of growing antimicrobial resistance. in addition to activity against pathogenic bacteria, viruses, protozoa and fungi, silver nanoparticles are able to inhibit the activity of tumor cells or play the role of drug carriers in the structures of malignant neoplasms in order to increase the effectiveness of chemotherapy [198]. despite the promising results of the studies, most of them are conducted mainly in cell cultures or mice. therefore, pharmacodynamics and pharmacokinetics of silver nanoparticles in human have not been fully studied due to the reliable data on possible multisystem toxicity, which could restrict performing these kinds of studies. moreover, silver nanoparticles are among the most toxic nanocompounds. therefore, it is of tremendous importance to develop and evaluate potential agnps antidotes, such as sulfides [199]. a careful selection of the minimum toxic and at the same time the most effective dose of agnps is an important aspect of planning the clinical and paraclinical trials. the nanoparticles synthesized by the "green synthesis" methods are likely to have less toxicity and a wider biological spectrum against microorganisms, which makes this approach more preferable than chemical or physical synthesis [200]. further studies of different properties of nanoparticles are needed to determine the most optimal concentration, shape, structure and enveloping substance in vivo. these may be achieved by evaluating the doseresponse parameters via comparison of the equivalent values with the results from animal studies and extrapolated potential effects on humans [188]. thus, it can be concluded that the integration of nanotechnologies, agnps in particular, for various medical purposes is highly promising due to the clear biocidal effects. however, the lack of unified methodological approaches and the inconsistencies in the data leave a wide field for further research and development of unified algorithms to prevent biases, trial heterogeneity, inaccurate data processing and compilation. limitations the type of article is a narrative review. it means a more relaxed literature search strategy, and it is affected by subjective approach (in contrast with prsima and multiple search strategy by two or more authors), which limits the comprehensive data extraction and strict study selection. there is a high probability of heterogeneity among studies due to the lack of strict prespecified criteria (selection bias), which leads to the impossibility of generalizing results and performing the statistical summary effect assessment. all studies are carried out in vitro (cell lines) or chimica techno acta 2022, vol. 9(4), no. 20229402 review 14 of 20 on mice/rats which makes it difficult to extrapolate the obtained results to humans and assess a potential minimal clinical important difference. there is a high demand for systematic reviews and meta-analyses according to the prisma guidelines for every particular topic of the current review, including extensive analysis of the published/unpublished literature and following the evidencebased practice. such approach could improve the accuracy and understanding of the research objective for the medical application of silver nanoparticles. supplementary materials no supplementary materials are available. funding this research had no external funding. acknowledgments the author is grateful to anastasia vlasova for assitance in the preparation of the current review. author contributions there is only one author. conflict of interest the author declares no conflict of interest. additional information kodintcev anton nikolaevich – adult general neurologist at polyclinic of the institute of high temperature electrochemistry of the ural branch of the russian academy of sciences and a young scientist at the same institute. education: (md) at ural state medical university (usmu), faculty of general medicine. postgraduate courses, 2019–2022 at ural state medical university (usmu), department of neurology, neurosurgery and medical genetics neurology residency: 2018–2020 at yekaterinburg medical research center for prophylaxis and health protection in industrial workers is a research institute of the russian agency for consumers rights protection (rospotrebnadzor), department of neurology. scientific interest: researching of new and cheap diagnostic methods of neurodegenerative disorders, in particular, alzheimer’s disease based on different biomarkers of biofluids. website: institute of high temperature electrochemistry, 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doi:10.3109/1040841x.2014.912200 10 most important cited papers 1. yin ix, zhang j, zhao is, mei ml, li q, chu ch. the antibacterial mechanism of silver nanoparticles and its application in dentistry. int j nanomed. 2020;15:2555–2562. doi:10.2147/ijn.s246764 2. bruna t, maldonado-bravo f, jara p, caro n. silver nanoparticles and their antibacterial applications. int j mol sci. 2021;22(13):7202. doi:10.3390/ijms22137202 3. lee sh, jun bh. silver nanoparticles: synthesis and application for nanomedicine. int j mol sci. 2019;20(4):865. doi:10.3390/ijms20040865 4. zhang xf, liu zg, shen w, gurunathan s. silver nanoparticles: synthesis, characterization, properties, applications, and therapeutic approaches. int j mol sci. 2016;17(9):1534. doi:10.3390/ijms17091534 5. xu l, wang y-y, huang j, chen c-y, wang z-x, xie h. silver nanoparticles: synthesis, medical applications and biosafety. theranostics. 2020;10(20):8996–9031. doi:10.7150/thno.45413 6. gherasim o, puiu ra, bîrcă ac, burdușel a-c, grumezescu am. an updated review on silver nanoparticles in biomedicine. nanomater. 2020;10(11):2318. doi:10.3390/nano10112318 7. ahamed m, alsalhi ms, siddiqui mk. silver nanoparticle applications and human health. clin chim acta. 2010;411(23– 24):1841–1848. doi:10.1016/j.cca.2010.08.016 8. siddiqi ks, husen a, rao rak. a review on biosynthesis of silver nanoparticles and their biocidal properties. j nanobiotechnol. 2018;16(1):14. doi:10.1186/s12951-018-0334-5 9. li y, cummins e. hazard characterization of silver nanoparticles for human exposure routes. j environ sci health a tox hazard subst environ eng. 2020;55(6):704–725. doi:10.1080/10934529.2020.1735852 10. zivic f, grujovic n, mitrovic s, ahad iu, brabazon d. characteristics and applications of silver nanoparticles. in: et al. commercialization of nanotechnologies–a case study approach. springer, cham. doi:10.1007/978-3-319-56979-6_10 https://doi.org/10.2174/1871520619666190710121727 https://doi.org/10.7150/thno.45413 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https://doi.org/10.1016/j.cca.2010.08.016 https://doi.org/10.1186/s12951-018-0334-5 https://doi.org/10.1080/10934529.2020.1735852 https://doi.org/10.1007/978-3-319-56979-6_10 87 введение в последнее время резко возрос интерес к получению металлов и сплавов из оксидов при электролизе расплавов на основе cacl2 при температуре 550–900 °с [1, 2]. показана принципиальная возможность получек. в. татаренко1, а. в. суздальцев2, а. п. храмов1,2, ю. п. зайков1,2 1уральский федеральный университет, 620002, екатеринбург; ул. мира, 19. e-mail: cyrilfex@yandex.ru 2институт высокотемпературной электрохимии уро ран, 620990, екатеринбург, ул. академическая, 20. e-mail: suzdaltsev_av@mail.ru анодный процесс на платине в расплаве на основе cacl 2 -cao* методами потенциостатической поляризации и циклической вольтамперометрии получены новые экспериментальные данные о механизме и кинетике анодных процессов на платине в расплаве cacl 2 -kcl-cao при 725–775 °с. приведены термодинамические значения разности потенциалов вероятных суммарных реакций в диапазоне исследуемых температур. при помощи потенциостатической поляризации и циклической вольтамперометрии получены новые экспериментальные данные относительно механизма и кинетики анодного процесса на платине в расплаве cacl 2 -kcl-cao при 725–775 °с. проведены термодинамические оценки вероятности протекания суммарных реакций при электролизе расплава на основе cacl 2 -cao с использованием неуглеродного анода. показано, что при высоких плотностях тока анодный процесс протекает преимущественно в условиях замедленной диффузии электроактивных частиц к аноду, а при низких плотностях (до 10 ма/см2) их разряду до атомарного и молекулярного кислорода предшествует стадия, которая может быть связана с адсорбцией атомов кислорода или с образованием оксидной пленки на поверхности платины. для установления природы этой стадии необходимы дальнейшие исследования. * исследование выполнено при финансовой поддержке российского фонда фундаментальных исследований (проект №12-03-31774 мол-а). у д к 6 61 .1 3: 66 1. 84 2. 32 2 © татаренко к. в., суздальцев а. в., храмова. п., зайков ю. п., 2014 88 cta | № 3 | 2014 ния целевого продукта, однако остаются вопросы, связанные с выбором конструкционных и электродных материалов, которые будут определять стабильность и экологическую безопасность процесса. в настоящее время для электролиза расплавов на основе cacl2 используются графитовые аноды [1], на которых выделяются co и co2. известно [3], что эти газы растворяются в cacl2 с образованием ионов co3 2–, которые могут разряжаться на катоде, понижая катодный выход по току и нарушая процесс в целом. в качестве альтернативного анодного материала могут быть использованы смеси оксидов [4–6]. особенности механизма и кинетики анодного выделения кислорода на таких анодах в стационарном режиме были хорошо исследованы ранее [6]. показано, что анодный процесс лимитируют реакции адсорбционно-десорбционного характера на поверхности анода. но поскольку полупроводниковые свойства оксидных анодов могут оказывать определенный вклад в анодное перенапряжение, механизм исследуемого процесса требует уточнения. для этого необходимы дополнительные исследования, в том числе при помощи нестационарных электрохимических методов анализа. целью данной работы было исследование анодного процесса на платине в расплаве cacl2-kcl-cao при 725– 775 °с методами потенциостатической поляризации и циклической вольтамперометрии. экспериментальная часть эксперименты проводили в кварцевой ячейке (рис. 1), через которую продували очищенный аргон. расплав массой 300 г (масс. %: 80,9cacl219,1kcl) предварительно сушили от влаги постепенным нагреванием в течение суток, затем плавили и подвергали гальваностатическому предэлектролизу. в полученный расплав добавляли cao, очищенный от влаги и co2 вакуумированием при 900 °с. анодом служила pt проволока (ø 1 мм, sa = 0,65 см 2), катодом – mo стержень (sк = 3 см 2), размещенный за алундовой диафрагмой. в качестве электрода сравнения использовали pt проволоку, погруженную в насыщенный по cao расплав того же состава в кварцевом чехле с атмосферой кислорода. изменение разности потенциалов между pt электродами при нулевом токе в течение 4 часов не превышало ±3 мв. температуру в печи задавали и поддерживали при помощи терморегулятора варта тп-703 и ха термопар. потенциостатические поляризационные кривые и вольтамперограммы получали при помощи pgstatautolab 302n (ecochemie, netherlands) с учетом омического падения напряжения в измерительной цепи. для оценки вероятности протекания суммарных анодных реакций были произведены термодинамические расчеты, представленные в таблице. исходя из полученных значений, напряжений разложения можно сделать предположение, что наиболее вероятными реакциями на pt в расплаве cacl2-kcl-cao при 725–775 °с будут выделение кислорода (1), окисление (4) и растворение pt (3). к. в. татаренко, а. в. суздальцев, а. п. храмов, ю. п. зайков 89 2014 | № 3 | ctaанодный процесс на платине в расплаве на основе cacl 2 -cao результаты и обсуждение в ходе измерений была проверена функция используемого электрода сравнения. для этого измеряемые в течение 0,5–4 часов значения э. д. с. разомкнутой цепи при разных температурах сопоставляли с рассчитанными значениями э. д. с. гальванического элемента: ( io2−p ) pt│ i o2− a ║ iio2−a │pt ( ii o2− p ), (5) где io2−p , ii o2− p – парциальное давление кислорода в чехле электрода сравнения и в ячейке (атм), io2−a , ii o2− a – активности кислород-содержащих частиц в расплаве электрода сравнения и ячейки (мол/см3). значения разности потенциалов между pt электродами были близки к значениям, рассчитанным по уравнению: ∆e rt f a p a p i= = − − 0 2 2 4 2 2 2 2 / ln(( ) ) / / (( ) ) o ii o i o i o ii (6) потенциостатические поляризационные кривые, полученные на pt аноде в расплаве cacl2-kcl-cao представлены на рис. 2. предельная плотность тока на потенциостатических поляризационных кривых повышается с увеличением температуры, а также при повышении концентрации cao в расплаве. это указывает на диффузионный характер замедленной стадии исследуемого процесса при высоких плотностях тока. из особенностей поляризационных кривых можно отметить высокое перенапряжение (0,10–0,15 в) анодного процесса на pt уже при низких плотностях тока (до 10 ма/см2). это рис. 1. схема измерительной ячейки: 1 – молибденовый катод; 2 – пробка из вакуумной резины; 3 – защитные отражательные экраны из ni; 4, 11 – газоходы; 5 – термопара в алундовом чехле; 6 – кварцевая ячейка; 7 – алундовый тигель; 8 – расплав; 9 – платиновый анод, экранированный алундовой трубкой; 10 – электрод сравнения рис. 2. потенциостатические поляризационные кривые, полученные на pt аноде в расплаве cacl2-kcl-(1 масс. %) cao 90 cta | № 3 | 2014 может быть связано с адсорбцией атомов кислорода [9] или образованием оксидной пленки на поверхности платины [10, 11], обладающей полупроводниковыми свойствами. циклические вольтамперограммы, полученные на pt аноде в расплаве cacl2-kcl-cao, представлены на рис. 3. смещение пика анодного тока (ip) на вольтамперограммах в положительную сторону при увеличении скорости развертки потенциала (ν) и меньшие значения токов катодных пиков указывают на необратимость процесса [12, 13]. выводы 1. при помощи потенциостатической поляризации и циклической вольтамперометрии получены новые экспериментальные данные относительно механизма и кинетики анодного процесса на платине в расплаве cacl2kcl-cao при 725–775 °с. 2. проведены термодинамические оценки вероятности протекания суммарных реакций при электролизе расплава на основе cacl2-cao с использованием неуглеродного анода. 3. показано, что при высоких плотностях тока анодный процесс протекает преимущественно в условиях замедленной диффузии электроактивных частиц к аноду, а при низких плотностях (до 10 ма/см2) их разряду до атомарного и молекулярного кислорода предшествует стадия, которая может быть связана с адсорбцией атомов кирис. 3. циклические вольтамперограммы, полученные на pt аноде в расплаве cacl2-kcl-(1 масс. %)cao таблица 1 напряжения разложения (δe) возможных суммарных реакций при электролизе расплава cacl2-kcl-cao реакция число электронов δe, в при т, °с [7, 8] 725 750 775 2cao = 2ca + o2 4 2,749 2,735 2,722 (1) cacl2 = ca + cl2 2 3,344 3,325 3,307 (2) pt + cacl2 = ptcl2 + ca 2 2,972 2,956 2,940 (3) 2pt + 3cacl2 = 2ptcl3 + 3ca 6 3,137 3,125 3,114 pt + 2cacl2 = ptcl4 + 2ca 4 3,232 3,221 3,211 pt + cao = pto + ca 2 2,812 2,809 2,805 (4) pt + 2cao = pto2 + 2ca 4 2,831 2,826 2,821 3pt + 4cao = pt3o4 + 4ca 8 2,999 2,996 2,994 к. в. татаренко, а. в. суздальцев, а. п. храмов, ю. п. зайков 91 2014 | № 3 | ctaанодный процесс на платине в расплаве на основе cacl 2 -cao слорода или с образованием оксидной пленки на поверхности платины. для установления природы этой стадии необходимы дальнейшие исследования. 1. chen g. z., fray d. j. lightmetals, 2004, 881. 2. wang d., jin x., chen g. z. annual reports section “c”, 2008, 104, 189. 3. kondo h., asaki z., kondo y. metallurg. and mater. trans. b, 1978, 9, 477. 4. yin h., gao l., zhu h. electrochimica acta, 2011, 56, 3296. 5. jiao sh., fray d. j. metallurg. and mater. trans. b., 2010, 41, 74. 6. dubtsev a. b., zaikov yu. p., batukhtin v. p., ivanovsky l. e. melts, 1992, (1), 35. 7. thermodynamic constants of individual substances: a handbook. vol. 1–4. ed. by v. p. glushko m: nauka, 1978–1982. [термодинамические константы индивидуальных веществ : cправочник. т. 1–4 / под ред. глушко в. п. м.: наука, 1978–1982]. 8. rusinov l. p., gulyanitsky b. s. equilibrium transformations metallurgical reactions. m: metallurgy, 1975, 416 p. [рузинов л.п., гуляницкий б. с. равновесные превращения металлургических реакций. м.: металлургия, 1975, 416 с.]. 9. vatolin n. a., sotnikov a. i., vatolina n. d. redox processes with participation of iron ions and oxygen on the boundary of metal-oxide melt. ekaterinburg.: uro ran, ustu-upi, 2008, 232 p. [ватолин н. а., сотников а. и., ватолина н. д. окислительно-восстановительные процессы с участием ионов железа и кислорода на границе металла с оксидным расплавом. екатеринбург : иметуроран, угту-упи, 2008, 232 с.]. 10. dewing e. w., vander-kouwe e. th. j. electrochem.soc., 1977, 124, 58. 11. seriani n., pompe w., ciacchi l. c. j. phys. chem. b, 2006, 110, 14860. 12. electroanalytical methods, 2nd ed. ed. scholz f., berlin, springer-verlag, 2010, 359 p. 13. bard a. j., faulkner l. r. electrochemical methods: fundamentals and applications, 2nd. ed. n.y.: john wiley & sons inc., 2001, 833 p. 92 cta | № 3 | 2014 k. v. tatarenko1, a. v. suzdaltsev2, a. p. kramov1,2, yu. p. zaikov1,2 1ural federal university, 19, mira street, 620002, ekaterinburg. e-mail: cyrilfex@yandex.ru 2institute of high-temperature electrochemistry ub ras, 20, akademicheskaya street, 620990, ekaterinburg. e-mail: suzdaltsev_av@mail.ru anode process on platinum in cacl 2 -cao-based melt methods potentiostatic polarization and cyclic voltammetry obtained new data on the mechanism and kinetics of anodic processes on platinum in the molten cacl 2 -kcl-cao when 725–775°c. given thermodynamic values of potential difference probable total reactions in the range of the studied temperature. using potentiostatic polarization and cyclic voltammetry obtained new data on the mechanism and kinetics of anodic process on platinum in the molten cacl 2 -kcl-cao when 725–775 °c thermodynamic assessment of the probability of occurrence total reactions during electrolysis melt on the basis of cacl 2 cao using non-carbon anode. it is shown that at high current densities anodic process takes place mainly in the conditions of slow diffusion of electrically active particles to the anode, and at low densities (up to 10 ma/cm2) to their discharge to the atomic and molecular oxygen is preceded by a stage, which can be associated with adsorption of atoms of oxygen or with the formation of an oxide film on the surface of platinum. to detect the nature of this stage, further research is needed. к. в. татаренко, а. в. суздальцев, а. п. храмов, ю. п. зайков published by ural federal university eissn 2411-1414 chimicatechnoacta.ru review 2023, vol. 10(1), no. 202310114 doi: 10.15826/chimtech.2023.10.1.14 1 of 11 an overview of wastewater treatment using combined heterogeneous photocatalysis and membrane distillation sarah a. abdulrahman *, salah s. ibrahim , zainab y. shnain * chemical engineering department, faculty of engineering, university of technology-iraq, baghdad, iraq * corresponding authors: zyousif.1973@gmail.com, zainab.y.shnain@uotechnology.edu.iq this paper belongs to a regular issue. abstract the need for efficient remediation solutions to wastewater has risen due to the concerning prevalence of toxic organic pollutants. it is possible for the linked photocatalysis-membrane separation system to concurrently achieve the photoreaction of pollutants and their removal from wastewater in order to accomplish the goal of completely purifying the wastewater. this investigation's objective is to provide analytical overview of the photocatalytic and membrane coupling process, photocatalytic membrane reactors, and the potential applications of these technologies in the treatment of wastewater for the persistent organic matter removal. in the review, an examination of photocatalytic and membrane processes to remove organic compounds from wastewater is presented. based on the literature analysis, it was observed that the application of photocatalytic membrane reactors is significantly influenced by a wide variety of factors. some of these factors include pollutant concentration, dissolved oxygen, aeration, ph, and hydraulic retention time. light intensity is another factor that has a significant influence. it was also revealed how distillation membranes work when integrated with photocatalytic process. this brief overview will help researchers understand how successful coupled photocatalytic and membrane distillation are in the treatment of wastewater containing organic pollutants. keywords heterogeneous photocatalysis membrane photocatalytic wastewater treatment membrane distillation received: 02.02.23 revised: 14.03.23 accepted: 15.03.23 available online: 22.03.23 key findings ● the application of photocatalytic membrane reactors is significantly influenced by a wide variety of factors. ● integration of distillation membrane with photocatalysis enhances the degradation of pollutant in wastewater. ● the recovery of membrane fluxes in membrane distillation after uv irradiation could be achieved using silver-based photocatalysts. © 2023, the authors. this article is published in open access under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). 1. introduction rapid industrialization and processing of raw materials in to different products has resulted into the introduction of various synthetic chemicals into the aqueous effluents [1– 3]. these anthropogenic activities have contributed to environmental damage [4, 5]. to safeguard both human health and the environment, environmental rules and regulations have been made stricter. this is expected to continue for the foreseeable future. green chemistry principles and clean technologies can be used in manufacturing processes to safeguard the environment according to a variety of directions [6, 7]. as a result of their strong resistance (recalcitrant substances), organic contaminants typically remain in high quantities in treated effluents after conventional chemical (e.g. adsorption, chemical oxidation) and biological treatment methods are used to clean up water [8]. hence, new technologies for the removal of developing hazardous chemicals from water and wastewater are required. to avoid the creation of sludge and its disposal, photocatalytic reactions can be employed to degrade organic http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2023.10.1.14 http://creativecommons.org/licenses/by/4.0/ https://orcid.org/0000-0003-1569-292x https://orcid.org/0000-0002-3953-9623 https://crossmark.crossref.org/dialog/?doi=https://doi.org/10.15826/chimtech.2023.10.1.14&domain=pdf&date_stamp=2023-03-22 chimica techno acta 2023, vol. 10(1), no. 202310114 review 2 of 11 doi: 10.15826/chimtech.2023.10.1.14 contaminants in to tiny, non-toxic compound fragments completely without any chemicals being used at all [9]. titanium dioxide (tio2) is the most common photocatalytic substance. tio2 can be suspended in a solution or anchored to a support [10, 11]. when compared to reactors with an immobilized catalyst, photocatalytic reactors with a suspended catalyst provide significantly greater interaction between the photocatalyst and dissolved contaminants [12]. photocatalytic activity of tio2 is great, but its particles must be separated for practical usage. using photocatalytic processes, a wide range of organic pollutants can be completely degraded (i.e., mineralized) in to very small and harmless substances, thereby minimizing the use of chemicals and avoiding sludge production and its disposal as a result of the highly unselective reactions involved [13, 14]. the active surface accessible for components of the solution is greatly decreased for the photocatalyst placed on a support, which typically leads to a loss of photoactivity [15]. therefore, photocatalyst particles must be removed from the treated water after the detoxification if the catalyst is administered as a suspension. photocatalytic membrane reactors (pmrs) which are hybrid reactors that combine photocatalysis and membrane processes are a possible solution to the challenge of separating the photocatalyst and the products and byproducts of photodecomposition from the reaction mixture [16]. the membrane would serve as both a simple barrier for the light catalyst and a selective barrier for the molecules that would be destroyed by the photocatalyst [17]. in pmrs, the catalyst can be immobilized on a membrane (photocatalytic membranes) or suspended in the reaction mixture, similar to traditional photoreactors [18]. compared to traditional photoreactors, photocatalytic membrane reactors offer the advantages of: using a membrane that could serve as an intermediate in the process of containing the photocatalyst inside the reaction environment; regulating the amount of time that each molecule spends within the reactor; realizing a process that can run continuously while simultaneously isolating the catalyst and products from the reaction environment [16]. in the application of pmrs for wastewater treatment, it is also possible to avoid extra steps like coagulation–flocculation–sedimentation, which are required to remove the photocatalyst from the treated solution [19]. the first advantage of this is that it saves energy and reduces the installation size [20]. in addition, the photocatalyst may be reused in subsequent runs, which is almost impossible with the standard separation approach of coagulation-flocculation-sedimentation. photocatalysis and pressure-driven membrane processes such as microfiltration (mf), ultrafiltration (uf), and nonfiltration are found in nearly all pmrs described in the literature [21]. membrane fouling is observed when the catalyst in suspension is utilized, particularly in the case of mf and uf membranes [17]. furthermore, even in the event of nf, tiny molecules can easily pass through the applied membranes, resulting in a lower permeate level. new forms of photocatalytic membrane reactors that combine photocatalysis with dialysis, pervaporation, and direct contact membrane distillation were reported [22]. the advantage of this setup is that the membrane is not fouled by the photocatalyst. molinari et al. [23], molinari et al. [24] ,and nasrollahi et al. [17] reviewed the hybrid photocatalysis-membrane processes. the authors presented and discussed a comparison of four hybrid photocatalysis-membrane processes, namely: photocatalysis + mf for catalytic recycling of slurry; photocatalysis + uf for recycle of catalyst slurry and (polymer) reactant; immobilized photocatalyst and uf/ro recycling of reactant; photocatalytic freezing uf/ro membrane for membrane self– cleaning. considering the fact that various new pmr arrangements have been described in the literature over the last few years, and that there is a lack of publications outlining current advancements, it is necessary to explore fresh innovations and research development regarding the application of pmrs in wastewater treatment. this review, therefore, focuses on the advances in the application of pmrs for wastewater treatment, and also discusses the membrane photoreactors with immobilized and suspended photocatalysts in various arrangements. 2. heterogeneous photocatalysis heterogeneous photocatalysis refers to the process of boosting or speeding up a photoreaction in the presence of a photocatalyst [25]. the photochemical splitting of water into hydrogen and oxygen by fujishima and honda in the presence of tio2 in 1972 was a hot issue in the history of heterogeneous photocatalysis [26]. in oxidation-reduction processes, a wide range of semiconductor catalyst materials have been employed. recently, research has focused on the use of photocatalytic semiconductor materials to remove organic and inorganic species from aqueous or gas phase systems in environmental clean-up, drinking water treatment and industrial applications [27, 28]. in addition to oxygen and water, tio2 may remove both organic and inorganic chemicals from the atmosphere through redox processes. while tio2 has emerged as one of the most intriguing materials for photocatalysis, it has also managed to grab the attention of physicists, chemists, and engineers in a variety of other domains [29]. chemical inertness and long-term photostability have made tio2 an important material in many practical applications and commercial products, ranging from pharmaceuticals to foods, cosmetics to catalyst, paint to medicines and sunblock or solar cells where tio2 is used as a desiccant, brightener, or reactive mediator [14]. the united states federal drug agency permits the use of up 1% of tio2 as an inactive ingredient in food. no known health effects have been linked to tio2; nonetheless, children aged 3–6 were found to be at the greatest risk from the effects of tio2 particles in their meals. numerous new tio2 https://doi.org/10.15826/chimtech.2023.10.1.14 https://doi.org/10.15826/chimtech.2023.10.1.14 chimica techno acta 2023, vol. 10(1), no. 202310114 review 3 of 11 doi: 10.15826/chimtech.2023.10.1.14 properties have been found in the recent several years. tio2 has been thoroughly examined for its possible application in environmental cleanup and the manufacture of solar fuels [14, 30, 31]. the bandgap excitation of tio2 causes charge separation, and the surface-adsorbed species scavenge electrons and holes. 2.1. mechanism of photocatalytic oxidation when organic contaminants are exposed to a light source and an oxidizing agent like oxygen or air, they are eliminated via a photocatalytic oxidation process that utilizes semiconductor photocatalysts like tio2 and zno. as shown in figure 1, electrons in the valence band (vb) can only be excited by photons with energies larger than the band-gap energy (e) [16]. heat is often dissipated when photons with energy lower than e or longer wavelengths are absorbed. create on of a hole in the valence band (hv+) and an electron in the conduction band (e) occurs when the photocatalytic surface is illuminated with enough energy (cb). water pollutants are oxidized directly, while the electron in conduction band oxidizes any oxygen that was adsorbed on the photocatalyst (tio2). the photocatalytic oxidation process generates hydroxyl radicals as described in the above phases [32]. because oxygen inhibits the recombination of an electron-hole pair during the oxidation of adsorbed water to hydroxyl radicals (oh), the hydroxyl radical is a key oxidant in organic pollutant degradation. there is an increase in the recombination rate of e– and h+ if the reduction of oxygen and the oxidation of pollutants do not proceed at the same time in the photocatalytic degradation of pollutants [33]. thus, it is critical to keep electrons from building up in photocatalytic oxidation processes. tio2 has been widely explored in photocatalysis because of its high activity, good physical and chemical features, low cost, and availability [18, 34, 35]. the anatase and rutile forms of tio2 have been widely studied as photocatalysts. the photocatalytic activity of anatase was shown to be higher than that of rutile. previous studies on the photocatalysis of several pesticide and herbicide derivatives prevalent in storm water and wastewater effluent employed various light sources, such as uv lamps and solar radiation. figure 1 an illustration of the tio2 photocatalysis mechanism ahmed et al. [12]. the photocatalytic oxidation of organic compounds under uv light can be represented by the mechanisms in equations (1) to (12). tio2 + ℎ𝑣 → tio2 (ecb− + ℎvb+ ) (1) tio2(ℎvb+ ) + h2o → tio2 + h + + oh∗ (2) tio2(ℎvb+ ) + oh − → tio2 + oh ∗ (3) tio2(ecb− ) + o2 → tio2 + o2 ∗− (4) o2 ∗− + h+ → ho2 ∗ (5) ho2 ∗ + ho2 ∗ → h2o2 + o2 (6) tio2(ecb− ) + h2o2 → oh ∗ + oh− (7) h2o2 + o2 ∗− → oh∗ + oh− + o2 (8) h2o2 + hv → 2oh ∗ (9) organic compound + oh∗ → degradation products (10) organic compound + tio2(hvb+ ) → oxidation products (11) organic compound + tio2 (ecb− ) → reduction products (12) an electron (e) may be promoted from the valence band (vb) to the conduction band (cb) represented in equation (1) if the photon energy is equal to or greater than the band gap width. this would result in an electron vacancy-hole (h+) being created. as shown in equations (2)–(12), when the electron and hole move to the catalyst surface, they can engage in redox reactions with various adsorbed substances. in equations (2)–(3), there is combinations of holes with surface-bonds of water or hydroxyl to produce hydroxyl radicals (oh•), but in equation (4), electrons can combine with oxygen to produce superoxide radical anions (o2•). hydroxyl radicals can also arise by going down the path shown in equations (5)–(9). hydroxyl radicals oh• are listed as the main oxidizing species in equation (10) for the photocatalytic oxidation processes. an illustration of how holes might oxidize organic molecules is the so-called photo-kolbe reaction, in which holes directly react with carboxylic acids to produce co2. in heterogeneous photocatalysis, the role of the reductive pathways in equation (12) is less important than that of oxidation. when dyes are exposed to visible light, a separate photooxidation pathway is apparent. the process known as photosensitized oxidation (photo-assisted deterioration) occurs in this condition. the dye was in excitation stage when adsorbed visible light on the catalyst surface leads to appropriate singlet or triplet states. the electron is transferred to the conduction band of the semiconductor particles from the excited dye molecule and the dye is changed to the cationic dye radical (dye•+). the dye•+ radical reaction with hydroxyl ions or interaction with o2•−, ho2• or oh• species generates https://doi.org/10.15826/chimtech.2023.10.1.14 https://doi.org/10.15826/chimtech.2023.10.1.14 chimica techno acta 2023, vol. 10(1), no. 202310114 review 4 of 11 doi: 10.15826/chimtech.2023.10.1.14 intermediates. eventually, co2, water and other degeneration products (e.g. nitrates, sulfates, etc.) are formed. 2.2. photocatalysts the surface and structural characteristics of the semiconductor, such as crystal composition, surface area, particle size distribution, porosity, band gap, and surface hydroxyl density, affect the photocatalytic activity of tio2 [36]. because it directly affects catalyst's efficiency by defining its specific surface area, particle size is crucial in heterogeneous catalysis. in aqueous conditions, the photocatalytic degradation of phenolic compounds and dyes has been studied using a variety of commercially available catalysts [37]. consideration must be given to the band gap value while choosing the best photocatalyst. due to their typically low band gap, between 1.4 and 3.8 ev, semiconductors are preferred to serve as photocatalysts [31]. tio2 has a number of advantages that make it one of the best photocatalysts, including affordability, excellent chemical stability, commercial availability, non-toxicity, and environmental friendliness. the broad band gap of tio2 as a photocatalyst is its main flaw. the strategies of doping semiconductor photocatalyst such as tio2 with metal or nonmetal elements and constructing a semiconductor heterojunction by mixing them with another semiconductor have been adopted in recent years to boost photocatalytic efficiency and overcome the obstacles faced by ordinary semiconductors [38]. doping of semiconductors can boost the visible photo-response and the photocatalytic activity. a reduction in the energy required to excite an electron in the bandgap can be achieved using non-metal dopants such as carbon and nitrogen, which can form new electronic states close to the valance band. metal elements such as fe, ag, cu, mg, au, pt, cr, and w were used to control the bandgap and increase the photocatalyst performance by extending the lifespan of the photogenerated electron-hole pairs generated by the photovoltaic process [40, 41]. in order to get the best catalytic characteristics and performance, the procedures utilized to prepare the doped tio2 photocatalysts are critically important to understand and optimize their performance in degrading organic pollutants in wastewater. tio2 doped with a variety of elements may be prepared in different ways, including hydrothermal hydrolysis, co-precipitation, sol-gel impregnation, ligand-assisted reduction, chemical vapor deposition, hydrothermal-solvothermal, photodeposition, selfassembly, high temperature sulphuration, photochemical deposition, adsorption-calcination and so on (table 1). sol-gel method of doping tio2 photocatalyst is a standard technique. preparation of nanomaterials is facilitated by the use of inexpensive materials and a straightforward approach. this technique has been utilized since the mid1800s in a wide range of applications, including membranes and chemical sensors. doped tio2 can also be produced via the hydrothermal technique. the hydrothermal methods help to create crystals of uniform size with a smaller band gap, thereby increasing the photocatalytic activity under visible light irradiation. 2.3. factors affecting the photocatalytic degradation of organic pollutants several factors may have an impact on how organic pollutants are degraded by photocatalysis. the intensity of the light is one of these factors [41]. the intensity of the light source affects how much light of a specific wavelength is absorbed by the photocatalyst. light intensity has a significant impact on photochemical electron-hole production during photocatalysis. the distribution of light intensity within the reactor determines the degree of pollutant conversion and degradation efficiency. the impact of light intensity on pollutant breakdown rates for various organic pollutants has been studied extensively [42]. while some research discovered a linear relationship between reaction time and light intensity, others discovered a square root relationship. according to some studies, the photocatalyst loading in the photoreactor also affects how much organic pollutants are degraded (figure 2) [43]. the photocatalytic rate initially rises with catalyst loading but then starts to fall as the catalyst loading increases [45]. the propensity for agglomeration (particle-particle contact) to grow at high solid concentrations results in a reduction in the surface area accessible for photocatalytic degradation [46]. although, while the number of active sites in solution rises with catalyst loading, it appears that there is a limit beyond which light penetration is hindered by high particle concentration. by balancing these two opposing processes, catalyst loading for photocatalytic reactions can be made more efficient. if the catalyst loading is increased above the optimum, nonuniform light intensity distribution will happen, which will slow down the reaction rate [47]. the initial concentration of the organic pollutant is also a vital factor that influences their photocatalytic degradation [44]. for the photocatalytic oxidation system to work well, it must be determined if the rate of photocatalytic degradation depends on the initial concentration of the substrate. the influence of substrate initial concentration on the mineralization of 4-nitrophenol was studied by parida et al. [46]. the study revealed that, as the initial substrate concentration rises, the amount of degradation decreases from 100 to 40.9%. this is as a result of the substrate absorbing light at high concentrations for the specified catalyst loading. at significant levels, the oh radicals available are insufficient for pollutant breakdown. therefore, when the initial concentration rises, the degradation rate of the pollutant is reduced. as the substrate initial concentration rises, the catalyst's surface may adsorb intermediates that might contaminate the reaction. deactivation of photocatalyst active sites can be slowed by the slow diffusion of intermediates from the catalytic surface. this results in a decrease in the degradation rate. https://doi.org/10.15826/chimtech.2023.10.1.14 https://doi.org/10.15826/chimtech.2023.10.1.14 chimica techno acta 2023, vol. 10(1), no. 202310114 review 5 of 11 doi: 10.15826/chimtech.2023.10.1.14 table 1 summary of selected tio2-based photocatalysts used for photodegradation of organic pollutants. photocatalyst preparation method dosage (mg) references cu-tio2 sol-gel 100 [34] pt-au/tio2 ligand-assisted reduction 10 [47] mos2/tio2 chemical vapor deposition 10 [48] mos2/tio2 hydrothermal 80 [49] pd@n-tio2 hydrothermal-solvothermal 15 [50] ag@ni/tio2 photodeposition 50 [51] cms/ths self-assembly 100 [52] tio2–nicos-pc high temperature sulphuration 20 [53] n-tio2/g-c3n4@nixp photochemical deposition 50 [54] cds@tio2/ni2p impregnation followed by na2h2po2treatment 10 [55] nicop(1 wt.%)/tio2 absorption followed by calcination 20 [56] coox/tio2/pt template-assisted atomic layer deposition 35 [57] ruo2/tio2/pt-b chemical reduction 50 [58] cuo/tio2 hydrothermal 20 [59] cu-tio2 nanowire hydrothermal 50 [60] ti3c2tx/tio2 impregnation 30 [61] ti3c2@tio2@mos2 hydrothermal 10 [62] ni(oh)2/tio2 precipitation 50 [63] pt/black tio2 impregnation 100 [64] pt/black tio2–xhx photodeposition 100 [65] pt/tio2-001 deposition–precipitation 15 [66] pt1/def-tio2 adsorption followed by h2 treatment 20 [67] me-tio2@ru adsorption-calcination 50 [68] ni-a/tio2 molten salt synthesis 50 [69] figure 2 effect of tio2 loading(a) and effect of n-tio2 loading on the degradation of organic pollutant with irradiation time [70] (b). the ph of the substrates is another factor that could affect the photodegradation of organic pollutants [71]. to understand the photocatalytic degradation of organic pollutants, it is important to understand how they interact with photocatalytic materials. if the solution ph is high enough, it can have significant effects on a photocatalyst surface charge and an organic pollutant's ionization or speciation (pka). the ph of the solution has a significant impact on the electrostatic interaction between the semiconductor surface, solvent molecules, substrate, and charged radicals produced during photocatalytic oxidation. the speciation behaviour, water solubility, and hydrophobicity of organic molecules in wastewater vary widely. in natural water and wastewater, certain chemicals are uncharged, whereas other compounds show a wide range of speciation (or charge) and physico-chemical characteristics. an organic compound is a neutral species with a ph lower than its pka value. an organic substance has a negative charge above this pka value. it is possible in aqueous solution for certain chemicals to exist in positive, neutral, and negative forms. the photocatalytic degradation behaviour of these materials can likewise be considerably influenced by this difference. wastewater ph is subject to wide variation. the oxygen content in the solution is also a crucial factor that influences the photodegradation of organic pollutant [72]. in photocatalysis reactions, oxygen dissolved in solution is usually utilised as an electron acceptor to make sure that there are enough electron scavengers available to catch the excited conduction band electron and prevent https://doi.org/10.15826/chimtech.2023.10.1.14 https://doi.org/10.15826/chimtech.2023.10.1.14 mailto:tio2-pd@pt mailto:ag@ni/tio2 mailto:cds@tio2/ni2p mailto:ti3c2@tio2@mos2 chimica techno acta 2023, vol. 10(1), no. 202310114 review 6 of 11 doi: 10.15826/chimtech.2023.10.1.14 recombination. the adsorption on the tio2 catalyst surface is unaffected by oxygen because the reduction and oxidation processes occur at different locations. dissolved oxygen is involved in the stabilisation of radical intermediates, mineralization, and direct photocatalytic reactions. furthermore, it was demonstrated that it can lead to the disintegration of aromatic rings in organic pollutants present in water matrices. 3. membrane distillation the membrane distillation process relies on the presence of the vapour phase in the pores of the membrane for the evaporation of volatile feed components [73]. a liquid mixture's vapour/liquid equilibrium serves as the basis for the separation process. only water vapour is transported across the membrane for solutions containing non-volatile solutes, and the resulting distillate is made up of demineralized water [74]. the unique separation features of the md method remove the colours from the water in textile wastewater treatment, allowing for their reuse [75]. md may also be used to treat salty wastewater, yielding both clean water and a concentrated solution that contains the original solution's constituents [76]. concentration may not be enough in some circumstances, and solutes must be separated in solid form. salt crystallization occurs once solution concentration reaches a supersaturated condition via the md process. in addition to concentration, the md procedure provides for the removal of volatile acids from the acidic waste solutions [77]. using the md technique for liquid low-level radioactive waste treatment, all radionuclides were eliminated. membrane wettability and fouling are the key impediments to the implementation of md. there are a number of components in the wastewater that might precipitate on the membrane surface during md operation. as a result, even with elaborate pretreatment systems, part of the effluent cannot be treated directly using membrane methods. fouling was shown to have a significant impact on the performance of md processes during the treatment of various types of wastewaters [78]. low tortuosity and homogeneous pore size distribution are desirable properties for md membranes [79]. microporous membranes used in md must have low mass transfer resistance and low thermal conductivity in order to prevent heat loss across the membrane. also, md membranes must be able to withstand high temperatures and chemicals (e.g., acids and bases) [80]. pore size must be matched between high permeate flow and effective wetting resistance in order to achieve optimal membrane performance. the performance of high-porosity membranes with limited mechanical strength deteriorates even under modest operating pressures. different md membranes used in high-strength wastewater reclamation have porosity levels ranging from 70–85%, according to the testing. polytetrafluoroethylene (ptfe), polypropylene (pp), and polyvinylidene fluoride (pvdf) are the most often used active layers in commercial hydrophobic md membranes. pp or polyester can also be used as a support layer [81]. 3.1. integrated photocatalytic and membrane distillation process for wastewater treatment in order to completely purify wastewater, the combined photocatalysis-membrane distillation process can be employed to achieve the photoreaction of contaminants and their removal from wastewater at the same time. integrated photocatalytic and membrane distillation process used for wastewater treatment is gradually gaining research interest [82]. photocatalysis-membrane separation hybrid systems have been used to purify wastewater while also removing contaminants from it [82]. these systems have been demonstrated to be effective in recent years. photocatalysis can simultaneously photodegrade organic pollutants using the strong oxidation properties of photogenerated species as well as photoreduce metal ions using photoinduced electrons in this synergistic photocatalysismembrane separation system [83]. both the oxidation and reduction processes can help each other. moreover, the photoreaction could be carried out at a consistent pace and efficiently stimulated by the membrane separation process [84]. previous research demonstrated great efficiency for the removal of organic pollutants and their inorganic products using a photocatalysis-membrane distillation reactor [85]. synergistic effects of organic removal and metal recovery in pmr have not yet been thoroughly explored, notably the influence of recovered metal ions on pollutant removal. several authors reported the application of coupling photocatalytic wastewater treatment with membrane distillation [60, 64, 65]. zou et al. [84] reported the removal of metal ions and organic pollutants from wastewater using a photocatalysis-membrane distillation method. for the purpose of an effective treatment of wastewater, the authors designed a photocatalysis-membrane distillation reactor to concurrently remove aqueous organics and metal ions. through the synergistic action of photocatalysis and direct contact membrane distillation, the simultaneous removal of the probing contaminants 4-chlorophenol (4-cp) and ag+ ion was effectively accomplished. li et al. [87] reported the treatment and reuse of petrochemical effluent via treatment with membrane distillation combined with a unique two-stage pretreatment involving photocatalysis. by combining membrane distillation (md) with a two-stage pretreatment procedure that included oil/water separation and photocatalytic organics degradation, the authors created a unique hybrid system for the treatment and reuse of petrochemical effluent. oil emulsions were separated from water by the oil/water separation method, and dissolved oil and volatile organic contaminants were eliminated by the subsequent photocatalysis procedure. after that, the pretreated water was used in the membrane distillation procedure to create distilled water. for the elimination of oil emulsions, a customized stainless-steel mesh/glass microfiber filter was utilized, and it demonstrated good https://doi.org/10.15826/chimtech.2023.10.1.14 https://doi.org/10.15826/chimtech.2023.10.1.14 chimica techno acta 2023, vol. 10(1), no. 202310114 review 7 of 11 doi: 10.15826/chimtech.2023.10.1.14 performance and durability. tio2 p25 was used as the photocatalyst in the photocatalysis step to efficiently break down the residual organic compounds and render microorganisms inactive when exposed to uv light. the twostage pretreatment achieved a total organic degradation rate of 99.5%. the hybrid system's benefits include preventing membrane fouling and generating high-quality distillate with low total dissolved solids and few volatile organics, which are challenging to extract by a traditional md process. for the removal of ketoprofen from diverse aqueous matrices, a novel submerged photocatalytic membrane reactor based on membrane distillation was developed by [86]. the developed process combines photocatalysis with direct contact membrane distillation applied for the removal of ketoprofen from simulated marine, brackish, and surface water as well as secondary effluent of a municipal wastewater treatment plant. the experiments showed that ketoprofen with starting concentration of 10 mg/l was nearly protoxidized after 5 h. the distillate did not contain any ketoprofen; however, the amount of total organic carbon and total inorganic carbon varied depending on the kind of feed. the distillate with the greatest total organic compound level was found in the secondary effluent. the kind of aqueous matrix had an impact on the amount of dissolved oxygen in feed, which reduced most noticeably in surface water. guo et al. [88], reported a self-cleaning membrane regeneration using a biobr/ag photocatalytic membrane incorporated with visible light during membrane distillation. the authors effectively coated an electrospun membrane with biobr/ag catalyst particles utilizing electrospray technique to obtain better hydrophobicity and repeatable properties. there were three membranes examined for comparison: an biobr/ag membrane, a commercial pvdf membrane, and a ptfe membrane. optical coherence tomography was used to monitor the fouling processes on all three membranes in real time. through the electron holes' significant oxidation ability, the biobr/ag particles on the biobr/ag membrane surface accelerated dye foulant degradation. as a result, the photocatalyst's electron separation and transfer efficiency was increased as well as its ability to reduce electron recombination by using ag nanoparticles coated on it via uv deposition. the findings revealed that biobr/ag photocatalyst membrane showed a considerable improvement in the recovery efficiency of the water contact angle and water flow under uv irradiation compared to the two commercial membranes. as a cocatalyst, the addition of ag to biobr increased the amount of visible light that could be harvested. ning et al. [41] manufactured a membrane in membrane distillation to remove semi-volatile organic molecules from wastewater. the authors developed a new agcl/mil100(fe)/ptfe photocatalytic membrane to remove nitrobenzene from wastewater. the photocatalytic membrane distillation system boosted the nitrobenzene removal when compared to the using standalone membrane distillation method. the authors also revealed that there was a steady performance throughout five nitrobenzene removal cycles. the combination of membrane distillation and photocatalysis may be responsible for the improved removal of the nitrobenzene [89]. 3.2. effect of process parameters on hybrid photocatalytic-membrane distillation process for wastewater treatment several factors, such as photocatalytic loading, reaction temperature, and initial concentration of the pollutant was reported to influence the photodegradation rate of pollutants in hybrid photocatalytic-membrane distillation process. the effect of different loadings of photocatalysts on the photodegradation of ay36 in wastewater using hybrid photocatalytic-membrane distillation process has been reported by mozia et al. [83]. the degradation of an azo dye (ay36) was shown to be highly sensitive to photocatalyst concentration. as the photocatalyst loading was increased from 0.1 to 0.3 g/dm3, the ay36 concentration decreased marginally. a further increase in the photocatalytic loading to 0.5 g/dm3, the concentration of azo dye reduced the most. study have shown that more surface area of the catalyst is available for adsorption and degradation as the catalytic loading rises. however, the photocatalytic degradation rate is reduced as the catalyst loading is increased because of the increased opacity of the solution, which reduces the penetration of the photon flux in the reactor [90]. when considering the photodegradation rate of organic pollutant in wastewater, the reaction temperature is also crucial. the studies revealed that the degradation of ay36 from wastewater is more effective with increasing reaction temperature. in a reaction temperature range of 20 °c to 60 °c, a linear relationship between the rate constant of photodegradation of the dye and the reaction temperature was reported by mozia et al. [83]. according to chen and ray [45], the increased frequency of molecular collisions in solution is what causes the photodegradation rate to increase when temperature increases from 10 to 50 °c. adsorption of the reactant, which is a spontaneous exothermic event, is made more likely by a drop in temperature. the final products of the process, whose desorption tends to hinder it, are likewise more readily absorbed when the temperature is lowered. on the other hand, exothermic adsorption of the reactant becomes unfavourable and tends to limit the reaction when temperature rises over 80 °c and moves to the boiling point of water. the efficacy of a dye's photodegradation is greatly influenced by its concentration, which is a crucial factor. it is frequently stated that a dye's initial rate of degradation increases with an increase in concentration. yet, additional growth over a particular value causes its degradation rate to decline. one explanation for this is the dye ion coating on the catalyst surface, which inhibits the production of https://doi.org/10.15826/chimtech.2023.10.1.14 https://doi.org/10.15826/chimtech.2023.10.1.14 chimica techno acta 2023, vol. 10(1), no. 202310114 review 8 of 11 doi: 10.15826/chimtech.2023.10.1.14 hydroxyl radicals. it is evident that a reduction in the initial azo dye concentration resulted in a notable enhancement of the efficiency in breakdown of the organic pollutant in wastewater. 4. limitations this review presents the advances in the application of photocatalytic membrane reactors for wastewater treatment incorporated with immobilized and suspended photocatalysts in various configurations. even under low operational pressures, highly porous membranes are limited in operating ability in such a way that with weak mechanical properties it functions poorly. according to tests, the porosity levels of several membranes used in high-strength wastewater reclamation range from 70–85%. the most often utilized active layers in commercial hydrophobic membrane distillation are polytetrafluoroethylene (ptfe), polypropylene (pp), and polyvinylidene fluoride (pvdf). as a support layer, pp or polyester can also be employed. 5. conclusion and future perspectives photocatalytic membranes utilized in the membrane distillation process have so far been mostly studied for their ability to self-clean and for direct solar distillation. in situ control strategies for pollutants in membrane distillation treatment procedures are not well studied. although photocatalytic technology may theoretically and realistically be integrated with membrane distillation systems, it is typically disregarded. an effective way to prevent the shading effect is to combine the photocatalytic membrane with membrane distillation heat cycling technology to create an organic waste-removal photocatalytic system that operates in a continuous flow. the recovery of membrane fluxes in membrane distillation after uv irradiation has been achieved using silver-based nanomaterials with high photocatalytic capabilities. also, by utilizing photocatalyst-coated membranes in place of chemical cleaning, it is possible to increase fouling resistance during the membrane distillation process as well as aid in the recovery of fouled membranes. photocatalytic nanomaterials on the membrane surface have recently been presented as a strategy to improve fouling resistance during membrane distillation process used for wastewater treatment. as an advantage of the hybrid photocatalysis–membrane distillation system, tio2 particles in feed did not foul the membrane. even more importantly, the distillate was of the highest quality since only water vapour and other volatile components were allowed to enter the membrane distillation unit. because photo degradation was more successful and the residence periods were longer, the membrane distillation process was thought to be a better choice than pressure-driven membrane approaches. the photocatalytic membrane reactors have various benefits over traditional photoreactors. there is still room for improvement in terms of permeate flow and membrane fouling as well as product (permeate) quality when it comes to the hybrid photocatalysis–membrane processes performance. furthermore, it is critical to look at actual treatment techniques for wastewaters. by taking into account the entire scope of the environmental challenge, optimised treatment settings for tiny amounts of wastewater in hybrid photocatalysis–membrane distillation system reactors are typically unrealistic and inapplicable. the development of engineering-designed reactors and treatment methods are thus identified as being truly competitive alternatives. in that regard, reactor design and techno-economic evaluation pose real challenges to putting research findings into action. to fully use promising photocatalytic treatments of organic pollutants, research efforts should focus on configuring benchmark reactors and contrasting passive treatment systems with active ones. ● supplementary materials no supplementary materials are available. ● funding this research had no external funding. ● acknowledgments the authors acknowledge the support of department of chemical engineering, university of technology-iraq. ● author contributions conceptualization: s.s.a., z.y.s. data curation: s.s.a formal analysis: s.s.a, s.s.i., z.y.s investigation: s.s.a, z. y. s. methodology: s.s.a. project administration: z.y.s. resources: s.s.a., z.y.s. supervision: z.y.s. validation: s.s.a., z.y.s visualization: s.s.i. writing – original draft: s.s.a. writing – review & editing: s.s.i., z.y.s ● conflict of interest the authors declare no conflict of interest. ● additional information sarah a. abdulrahman is a master student at the department of chemical engineering, university of technology, iraq. her research is focus on photocatalytic wastewater treatment. scopus id 58032360400. https://doi.org/10.15826/chimtech.2023.10.1.14 https://doi.org/10.15826/chimtech.2023.10.1.14 https://www.scopus.com/authid/detail.uri?authorid=58032360400 chimica techno acta 2023, vol. 10(1), no. 202310114 review 9 of 11 doi: 10.15826/chimtech.2023.10.1.14 dr. salah s. ibrahim is an assistant professor at the department of chemical engineering, university of technology, iraq where he has been involved in research and teaching. his research interest includes separation processes, membrane distillation, modelling & simulation, and thermodynamics. scopus id 57195263461. dr. zainab yousif shnain is an assistant professor at the department of chemical engineering, university of technology iraq where she has been involved in research and teaching. her research is focus on transport phenomena and material technology. scopus id 57218320762. website: university of technology-iraq, http://www.uotechnology.edu.iq. references 1. sekharan s, samal dr, phuleria hc, chandel mk, gedam s, kumar r, et al. river pollution monitoring over an 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the chimica techno acta journal (cta) celebrates its 10th anniversary. a tenth of a century is a long time, during which about 350 papers have been published. in the beginning, the journal has been edited in two formats (electronic and print) and in two languages (russian and english), but then considerable efforts have been made to ensure the rapid consideration of manuscripts while maintaining high peer-review standards at the same time. cta has become an exclusively english-language and online journal. as a result, authors currently receive a first decision on their manuscripts within 17 days of submission, while the total time from submission to publication of a final version does not exceed 50 days. along with providing good conditions for our authors, the journal seeks all possible ways to improve the quality of its content by considering well-designed manuscripts for their publication. therefore, the rejection rate is increased from 10–20% in 2014– 2015 to almost 50% in 2022. another point consists in the support of the published items by visual facilities that have online journals. to avoid boredom, we changed the layout from grayscale to color and then to different colors for each year. the current (10th) volume is published in an orange-based design, symbolizing sunrise, warm sand, and juicy peach. we believe that visual content has a strong focus on the readers' attention. even though the color perception may not impress someone, we will definitely change the coloristics in next year. the cta editorial board is constantly updated with new scientists to ensure a more accurate review of incoming manuscripts. within the current editorial, we are pleased to welcome a new editor, dr. pavel padnya from kazan federal university (russia). a short interview with him can be found below. brief biography i graduated from chemistry faculty of kazan federal university (kfu, russia) in 2010 and defended my phd thesis at kfu in 2015. after that i worked as an engineer and a researcher at organic chemistry department of kfu. from 2019, i am a senior researcher at the above department. i am an author of 70 publications in peer-review scholar journals (h-index 16, scopus). i am a topical advisory panel member of nanomaterials (mdpi), journal of functional biomaterials (mdpi), and an editor of chimica techno acta; at the same time, i am a reviewer of many well-recognized international journals. my research activities deal with the design and synthesis of novel organic compounds based on macrocyclic synthetic platforms, and the development of nanomaterials based on macrocycles and biomacromolecules for biomedical and electrochemical applications. what reasons determined your choice of a career in chemistry? i was born in 1988 in the small industrial petrochemical city, nizhnekamsk, tatar assr. in the 8th grade, i successfully passed the entrance exams to a prestigious school in our city, technological lyceum 35, which was under the patronage of teachers from the local institute of chemical technology. dr. pavel padnya http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2023.10.2.e http://creativecommons.org/licenses/by/4.0/ https://crossmark.crossref.org/dialog/?doi=https://doi.org/10.15826/chimtech.2023.10.2.e&domain=pdf&date_stamp=2023-05-15 chimica techno acta 2023, vol. 10(2), no. 2023102e editorial 2 of 2 doi: 10.15826/chimtech.2023.10.2.e since my school days, i have been interested in exact and natural sciences, such as mathematics, physics, and chemistry. in high school, i actively participated in the city olympiads in various subjects. my best results were reached in physics and chemistry. however, every year chemistry became more interesting for me, as my high school physics teacher told me cheerlessly and repeatedly. so, in grades 9–11, i reached the stage of the all-russian olympiad in chemistry. in the 11th grade during the preparatory activities i met with teachers and professors of kazan state university, including my future supervisor, stoikov ivan ivanovich (currently, he is a doctor of chemistry and a head of the department of organic and medicinal chemistry). from the first year i decided to try to work in a laboratory, and this process does not let me go for half of my life. as a result, after 17 years, i consider my career to be quite successful at this point. now i am a supervisor of several undergraduate and graduate students who are actively involved in scientific work. i hope to make my own team of young scientists capable of successfully solving scientific problems in the field of organic and supramolecular chemistry in the next 5–10 years. which of your own publications are you most proud of? in fact, this question got me thinking and reviewing my list of publications. i believe that the most interesting part of my works is those results that that are not only useful from a scientific and fundamental point of view, but also have real practical applications. among these, i would like to note the studies devoted to the synthesis and study of the biological activity of new macrocyclic compounds. a list of my key works can be found via the following links: 10.1039/c5ob00548e 10.1016/j.bmc.2020.115905 10.3390/ijms222111901 10.1016/j.bioorg.2019.103455 10.3390/pharmaceutics14122748 10.1039/c5ra25562g why should young people study chemistry? i think that understanding the processes of our world is necessarily connected with the study of natural sciences, such as biology, chemistry, physics, etc. in this case, the object of the study of chemistry is the processes of transformation of some molecules into others. there's a joke – "if you don't learn physics at school, your whole life will be filled with miracles and magic". the same can be said about chemistry, i.e. a "magic" of chemical reactions is going on all the time around us. only by studying these phenomena, young people had better understand how our world works. at the same time, the basic knowledge helps them to make new useful scientific discoveries. what are your five most favorite journals? among the favorite journals in which i have already published and whose policies i like are journal of molecular liquids, beilstein journal of nanotechnology, new journal of chemistry, molecules, international journal of molecular sciences. i also like mdpi's approach with their speed of review and publication, but that's a separate topic for discussion. what are the main differences in the roles of author, reviewer and editor? what do they have in common? authors try to present their research in the most understandable way. however, reviewers may have their own opinions about the authors' results, i.e., constructively recommendations for improving the manuscript or for rejecting it and submitting it to another journal. thus, the goal of authors is to publish in a journal with the largest target audience, and the goal of reviewers is to provide constructive criticism. the role of editors in this case is to select the best articles for their journals as well as to ensure an efficient peer review process. overall, all three roles have a common goal: to share new scientific knowledge with readers in as the most effective way as possible. on behalf of the editorial board of the cta journal, i would like to thank all authors, reviewers, editors, and readers for their interest in our journal. we do (and will) our best to maintain a high quality of published items dr. dmitry medvedev editor-in-chief https://doi.org/10.15826/chimtech.2023.10.2.e https://doi.org/10.15826/chimtech.2023.10.2.e https://doi.org/10.1039/c5ob00548e https://doi.org/10.1016/j.bmc.2020.115905 https://doi.org/10.3390/ijms222111901 https://doi.org/10.1016/j.bioorg.2019.103455 https://doi.org/10.3390/pharmaceutics14122748 https://doi.org/10.1039/c5ra25562g 26 © васин а. а., зуев м. г., 2014 а. а. васин1, 2, м. г. зуев1, 2 1уральский федеральный университет, 620002, екатеринбург, ул. мира, 19. e-mail: contact@urfu.ru 2институт химии твердого тела уро ран, 620219, екатеринбург, ул. первомайская, 91. люминесцентные свойства сложнозамещенных оксидов ме 2 ln 8 (xo 4 ) 6 o 2 (me = sr, ca; ln = la, gd, eu; x = si, p) при проведении данной работы были синтезированы кристаллофосфоры со структурой апатита, имеющие общие формулы ca 2 eu 8 si 6(1–x) p 6x o 26 , sr 2 gd 7.2 eu 0.8 si 6(1–x) p 6x o 26 и ca 2 la 8(1–x) eu 8x si 6 o 26 . были исследованы морфология и размеры частиц этих соединений. также были записаны спектры фотолюминесценции и возбуждения рассматриваемых материалов, а также измерена время разрешенная люминесценция соединений с общей формулой sr 2 gd 7.2 eu 0.8 si 6(1–x) p 6x o 26 . на основании полученных данных были сделаны выводы о влиянии на интегральную интенсивность люминесценции ионов заместителей, внедряемых в анионную и катионную подрешетки. также были построены зависимости среднего размера частиц от концентрации фосфора для соединений ca 2 eu 8 si 6(1–x) p 6x o 26 и sr 2 gd 7.2 eu 0.8 si 6(1–x) p 6x o 26 . было показано, что оптимальная концентрация ионов активатора для люминофоров с данной структурой составляет 0,15. при дальнейшем увеличении концентрации возникает концентрационное тушение. рассчитанное по формуле значение rc составляет 15,37å, что намного больше расстояния энергообмена для eu3+ (5å). у д к 5 46 .7 9 введение апатиты − соединения с общей формулой m10(xo4)6y2, имеющие гексагональную пространственную группу р 63/m. в приведенной формуле м − 2или 3-валентные катионы металлов; xo4 − 3-, 4-валентные анионные группы; y − 2-, 3-валентные анионы, расположенные в междоузлиях кристаллической решетки. матрица кристаллофосфора, имеющая структуру апатит силиката, позволяет создавать люминесцентные материалы, дающие высокую интегральную интенсивность свечения, при использовании ионов рзэ в качестве активаторов. фотолюминофоры, в которых в качестве иона активатора используется eu3+, широко используются как источники красно27 2014 | № 1 | cta го свечения в телевизионной технике, приборах графического отображения информации, а также при производстве светодиодов. имеется большое количество работ [1–3], посвященных соединениям типа ae2re8(sio4)6o2:eu, где re − ионы рзэ, такие как y, lu, la, gd; ae − ионы щелочноземельных элементов, например ca, sr, ba, в которых приводится описание спектрально-люминесцентных свойств этих соединений. однако подавляющая их часть не содержит численных данных по интегральной интенсивности люминесценции материалов. кроме того, изменение свойств и структуры люминофора достигалось изменением концентрации иона активатора на довольно узком отрезке (как правило при 0.05 ≤ n ≤ 0.15) [4]. в данной работе впервые были получены три ряда твердых растворов ca2eu8si6(1–x)p6xo26, sr2gd7.2eu0.8si6(1–x) p6xo26 и ca2la8(1–x)eu8xsi6o26 (0.01 ≤ x ≤ 0.2), а также рассмотрено влияние замещения тетраэдров sio4 4на тетраэдры анионных групп po4 3-. экспериментальная часть получение образцов ca2la8(1-x)eu8xsi6o26 исходные компоненты caco3, eu2o3, la2o3 (степень чистоты ч. д. а.) и sio2 (степень чистоты ос. ч.) были взяты в стехиометрических количест-вах. caco3, eu2o3, la2o3 были растворены в 5 мл концентрированной азотной кислоты. после перетирания в агатовой ступке, к раствору был добавлен мелкодисперсный sio2. после этого раствор перемешивался вручную до образования прозрачного геля. после этого гель был перенесен в чашку и выпарен при температуре примерно 120 °с в течение 2 ч. полученный белый осадок был предварительно обожжен в муфельной печи при температуре 900 °с в течение 22 ч. после этого был произведен окончательный обжиг при температуре 1400 °с в течение 25 ч. получение образцов ca2eu8si6(1–x)p6xo26 в качестве исходных компонентов были взяты caco3, eu2o3, (nh4)2hpo4 (степень чистоты ч. д. а.) и sio2 (степень чистоты ос. ч.). целевые продукты были получены посредством высокотемпературного твердофазного синтеза, процесс которого включает две стадии обжига. предварительный обжиг производился при температуре 1350 °с в течение 24 ч. окончательный обжиг при температуре 1400 °с в течение 40 ч. получение образцов sr2gd7.2eu0.8si6(1–x)p6xo26 данный процесс производился в два этапа: 1. получение промежуточных соединений sr2eu8si6(1–x)p6xo26 и sr2gd8si6(1–x)p6xo26 методом высокотемпературного твердофазного синтеза. 2. синтез целевых продуктов из соединений, полученных на первом этапе. в качестве исходного сырья использовались caco3, eu2o3, (nh4)2hpo4, gd2o3 (степень чистоты ч. д. а.) и sio2 (степень чистоты ос. ч.). исходные компоненты, взятые с учетом стехиометрии, были перетерты в агатовой ступке с добавлением этилового спирта в качестве гомогенизатора и перенесены в алундовые тигли. затем посредством двустадийного обжига (1-я стадия: t = 1350 °c, τ = 21 ч, 2-я стадия t = 1350 °c, τ = 24 ч; люминесцентные свойства сложнозамещенных оксидов ме 2 ln 8 (xo 4 ) 6 o 2 (me = sr, ca; ln = la, gd, eu; x = si, p) 28 cta | № 1 | 2014 перед второй стадией производилось перетирание спекающегося вещества) были получены промежуточные продукты. после того как они подверглись перетиранию и гомогенизации в спирте, был произведен предварительный обжиг при температуре 1350 °с в течение 21 ч, после чего полученный белый порошок был перетерт в ступке. окончательный обжиг образцов производился при температуре 1400 °с в течение 50 ч. результаты и обсуждение фазовый состав полученных соединений исследован при помощи рентгеновского дифрактометра shimadzuxrd-7000. на рис. 1 представлены рентгенограммы всех синтезированных образцов. все соединения образуют чистую фазу апатита, имеющую символ пространственной группы p 63/m. попытка в серии образцов с общей формулой ca2eu8si6(1–x)p6xo26 получить соединение ca2eu8si4.95p1.05o26 оказалась неудачной, т. к. готовый продукт оказался неоднофазным. спектры фотолюминесценции представленных образцов были записаны при помощи монохроматора мдр-204, оснащенного фотоумножителем hamamatsu и диспрозиевой лампой, являющейся источником возбуждающего излучения с максимумом светопропускания, соответствующем длине волны 330 нм (фильтр уфс-5). на рис 2. представлены спектры люрис. 1. рентгенограммы образцов: а – ca2la8(1–x)eu8xsi6o26; б – ca2eu8si6(1–x)p6xo26; в – sr2gd7.2eu0.8si6(1–x)p6xo26 а б в рис. 2. спектры фотолюминесценции образцов: а – ca2la8(1–x)eu8xsi6o26; б – ca2eu8si6(1–x)p6xo26; в – sr2gd7.2eu0.8si6(1–x)p6xo26 а б в а. а. васин, м. г. зуев 29 2014 | № 1 | cta люминесцентные свойства сложнозамещенных оксидов ме 2 ln 8 (xo 4 ) 6 o 2 (me = sr, ca; ln = la, gd, eu; x = si, p) минесценции исследуемых образцов. для соединений а, б и в характерно расщепление перехода 5d0→ 7f0 на 2 пика, соответствующих длинам волн 576 и 579 нм. причем и для основного энергетического уровня 5d0, и для равновесного возбужденного состояния, соответствующего уровню 7f0, расщепление штарка является невозможным. таким образом, наличие этих пиков указывает на присутствие в структуре люминофора двух оптических центров образованных ионами eu3+. первый центр имеет класс симметрии с3 и окружен 9 ионами кислорода, входящими в состав тетраэдров анионных групп [sio4] 4– (образцы а, б, в), либо в состав [po4] 3– (образцы б, в), при возбуждении данного центра уф-излучением, он люминесцирует с испусканием оранжевого свечения, соответствующего переходу 5d0→ 7f1. второй центр имеет класс симметрии cs и образован ионами трехвалентного европия, окруженными 7 ионами o2– (6 из них входят в состав анионных групп и один находится в кислородном канале, образованном ионами рзэ, находящимися в вершинах правильного шестиугольника, которые располагаются вокруг междоузлия). данный оптический центр имеет очень низкую степень симметрии, и поэтому для него разрешен интенсивный переход 5d0→ 7f2. как видно на рис. 3 а, оптимальная концентрация ионов активатора для люминофоров с данной структурой составляет 0,15. при дальнейшем увеличении концентрации возникает концентрационное тушение. расстояние между ионами eu3+ можно оценить по формуле, предложенной блассе 1/3 4 2 3 c c v x n r     π  = , где v – объем элементарной ячейки; xc – критическая концентрация иона активатора, в нашем случае xc = 0,15; n – количество кристаллографических позиций, занимаемых ионами активатора n = z × 1 = 2. рассчитанное по этой формуле значение rc составляет 15,37å, что намного больше расстояния энергообмена для eu3+ (5å). таким образом, механизм тушения люминесценции в данном случае иной. кроме того, для соединений со структурой апатита, содержащих только один вид люминесцирующего иона, не происходит полного перекрывания спектров люминесценции спекрис. 3. зависимости интегральной интенсивности люминесценции образцов от концентрации ионов заместителей (х): а – ca2la8(1–x)eu8xsi6o26; б – ca2eu8si6(1–x)p6xo26; в – sr2gd7.2eu0.8si6(1–x)p6xo26 а б в 30 cta | № 1 | 2014 трами возбуждения, поэтому механизм тушения, предложенный декстером, также не реализуется. из предыдущих рассуждений можно сделать вывод, что в данных структурах реализуется мультиполь-мультипольный тип концентрационного тушения. из данных, изображенных на графиках 3 б, в, следует, что максимальная интенсивность свечения достигается при концентрации фосфора 0.05. спектры возбуждения образцов были сняты с помощью спектро-флюориметра cary eclipse varians, в качестве источника свечения использовалась импульсная газоразрядная ксеноновая лампа мощностью 75 вт (ширина импульса 2 μs). на рис. 4 изображены спектры возбуждения образцов, имеющих наибольшую интегральную интенсивность свечения в сериях ca2eu8si6(1–x) p6xo26 и sr2gd7.2eu0.8si6(1–x)p6xo26. наличие вогнутого участка на полосе с переносом заряда (сtb) для образца 4 а указывает на потерю энергии, происходящую в результате мультипольмультипольного взаимодейст-вия, при концентрации активатора значительно выше оптимальной. в диапазоне длин волн 350–465 нм присутствует ряд узких пиков, обусловленных f-f переходами: 7f0 → 5d4, 5gj, 5l6, 5d3, 5d2. на рис. 4 в показан спектр полосы с переносом заряда образца sr2gd7.2eu0.8si5.7p0.3o26. при разделении пика полосы посредством гауссианы появляются два пика, соответствующих переходам 8s7/2→ 6i13/2, 6p7/2 иона gd 3+. на рис. 3 для образцов, содержащих группы [po4] 3в анионной подрешетке, показан провал в интенсивности свечения, соответствующий концентрации фосфора х = 0,1. предпринята попытка объяснить это явление с точки зрения микроскопии. морфология всех образцов исследована при помощи растрового электронного микроскопа jeoljsm 6390 c приставкой для энергодисперсионного анализа jed 2300. на рис. 5 приведены микрофото-графии образцов с наибольшей интегральной интенсивностью люминесценции. все образцы образуют зерна различной фактуры от шаровидных до вытянутых. фотографии, приведенные на рис. 5, получены в отраженных электронах, что позволило уменьшить заряд на поверхности диэлектрических материалов и определить на глаз наличие пририс. 4. спектры возбуждения образцов, полученные при длине волны люминесценции 614 нм (переход 5d0→ 7f2): а – са2eu8si5.7p0..3o26; б – sr2gd7.2eu0.8si5.7p0.3o26; в – спектр возбуждения в диапазоне длин волн 200–345 нм для образца sr2gd7.2eu0.8si5.7p0.3o26 а б в а. а. васин, м. г. зуев 31 2014 | № 1 | cta люминесцентные свойства сложнозамещенных оксидов ме 2 ln 8 (xo 4 ) 6 o 2 (me = sr, ca; ln = la, gd, eu; x = si, p) месных фаз в образцах, так, например, наличие небольшого количества темных зерен в образце ca2la6.8eu1.2si6o26 указывает на наличие посторонней фазы, возможно, образовавшейся при реакции с материалом тигля. сравнивая графики на рис. 5 и рис. 3 б, в, можно прийти к выводу, что на отрезке концентраций фосфора 0 ≤ х ≤ 0.13 существует прямая зависимость между размером зерен люминесцирующего материала и интегральной интенсивностью свечения этого материала. на рис. 7 представлены кривые затухания люминесценции для образца sr2gd7.2eu0.8si5.7p0.3o26. характер затухания – би-экспоненциальный; это обстоятельство указывает на то, что долгоживущий уровень 5d0 частично перекрывается короткоживущим 5d1. рис. 5. микрофотографии образцов: а – ca2la6.8eu1.2si6o26; б – ca2eu8si5.7p0.3o26; в – sr2gd7.2eu0.8si5.7p0.3o26 а б в а б рис. 6. зависимость среднего размера частиц от концентрации фосфора (х) в образцах а – ca2eu8si6(1–x)p6xo26, б – sr2gd7.2eu0.8si6(1–x)p6xo26 рис. 7. время затухания люминесценции образца sr2gd7.2eu0.8si5.7p0.3o26 32 cta | № 1 | 2014 1. il’ves v. g., sokovnin s. y., uporov s. a., zuev m. g. physics of the solid state, 2013, 55, 1262. 2. park j. y., baek m. j., choi e. s., woo s., kim j. h., kim t. j., jung j. c., chae k. s., chang y., lee g. h. acs nano, 2009, 3, 3663. 3. hedlund a., ahren m., gustafsson h., abrikossova n., warntjes m., jonsson j. i., uvdal k., engstrom m. int. j. nanomed., 2011, 6, 3233. 4. karpov a. m., zuev m. g. glass physics and chemistry, 2012, 38, 431. а. а. vasin,1, 2, m. g. zuev1, 2 1ural federal university, 19, mira street, 620002, ekaterinburg. e-mail: contact@urfu.ru 2institute of solid state chemistry ub ras, 91, pervomaiskaya street, 620990, ekaterinburg luminescent properties of complexly substituted oxides ме2ln 8 (xo 4 ) 6 o 2 (me=sr, ca; ln=la, gd, eu; x= si, p) in the current work it is established that the maximum intensity of a luminescence of crystalline phosphors with structure silicate-apatite of general formulae: ca 2 eu 8 si 6(1–x) p 6x o 26 , sr 2 gd 7.2 eu 0.8 si 6(1–x) p 6x o 26 and ca 2 la 8(1–x) eu 8x si 6 o 26 is reached at concentration of europium equal 0.15. the maximum intensity of a luminescence of these substances, at replacement in an anion sublattice of tetrahedrons [sio 4 ] 4– on tetrahedrons [po 4 ] 3 takes place at concentration of phosphorus 0.05. on the basis of the received data the conclusions were made about the impact on the integral intensity of the luminescence of ions-deputies introduced in the anion and cation sublattice. calculated by the formula rc is 15.37å, far greater distances, the energy exchange for eu3+ (5å). а. а. васин, м. г. зуев страница 1 electrochemical behavior of chloramphenicol on carbon electrodes in a microelectrochemical cell published by ural federal university eissn 2411-1414; chimicatechnoacta.ru article 2022, vol. 9(4), no. 20229409 doi: 10.15826/chimtech.2022.9.4.09 1 of 5 electrochemical behavior of chloramphenicol on carbon electrodes in a microelectrochemical cell tatiana s. svalova, regina a. zaidullina *, margarita v. medvedeva, elizaveta d. vedernikova, alisa n. kozitsina institute of chemical engineering, ural federal university, ekaterinburg 620009, russia * corresponding author: zaidullina.regina@urfu.ru this paper belongs to a regular issue. © 2022, the authors. this article is published in open access under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). abstract express determination of antibiotics is an extremely important task today. portable electrochemical microdevices are a viable alternative to traditional methods of analysis. the development of such devices requires the study of redox processes in detail. this article is devoted to the comparative study of the electrochemical behavior of chloramphenicol in water solvents in standard laboratory and portable microelectrochemical cells. it was found that the electrochemical reduction of chloramphenicol proceeds via a 3-electron mechanism to the formation of a dimer. in the transition from the macrocell to the microcell, a decrease in the electrochemical reduction current and a shift of the peak potential to the cathode region are observed, which is apparently associated mainly with the type of the electrode material. the best characteristics of the direct electrochemical response were obtained in the differential pulse voltammetry mode. under the selected operating parameters, the peak current of the electrochemical reduction of chloramphenicol is linearly dependent on the concentration of the antibiotic in the range of 2∙10–3–1∙10–5 m with a detection limit of 3∙10–5 m. obtained characteristics are sufficient for the quality control of pharmaceuticals and can be improved through the use of organic and hybrid modifiers of the working electrode surface. keywords chloramphenicol express-determination electrochemical behavior voltammetry microcell screen-printed electrode received: 14.07.22 revised: 02.08.22 accepted: 02.08.22 available online: 16.08.22 1. introduction chloramphenicol (cap) is a broad-spectrum antibiotic utilized in veterinary and medicine due to its high efficacy and low cost. however, cap entering the aquatic environment does not decompose and accumulates therein. thus, it contaminats sediments and water systems and induces unhealthy effects, such as aplastic anemia (blood disorder), agranulocytosis, dosage independent suspected carcinogenity in humans, and also contributes to the development of bacteria resistance [1, 2]. therefore, detection of chloramphenicol in food and environmental objects is an important task [3]. to determine the trace amounts of chloramphenicol in laboratory practice, chromatographic [4], spectroscopic [5], enzyme immunoassay [6], and other methods of analysis are used [7]. however, all these approaches require expensive equipment, reagents, and a rather lengthy analysis procedure. of greatest interest is the electrochemical determination of chloramphenicol [8], mainly due to the ultrasensitivity of the determination, the possibility of miniaturization and the transition to portable test systems. electrochemical analytical microdevices have great prospects, as they are suitable for the mass production, representing inexpensive, disposable sensor systems. in the designs of such devices, as a rule, three-electrode systems made by screen printing are used [9]. for example, pakapongpan et al. developed an electrochemical sensor using a magnetic screen-printed electrode (spe), which demonstrated a detection limit of 10 nm for the detection of cap [10]. li et al. invented a laser-enabled flexible electrochemical sensor on finger, which can be used for rapid real-time in-site electrochemical identification of cap in meat (lod 10 μm) [11]. the advantages of such electrochemical systems with printed electrodes are low cost and the possibility of onetime use, which simplifies the analysis procedure and improves analytical performance by eliminating the stage of electrode surface regeneration. transition from standard electrochemical cells to portable microdevices requires additional studies of the http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2022.9.4.09 mailto:zaidullina.regina@urfu.ru http://creativecommons.org/licenses/by/4.0/ https://orcid.org/0000-0002-0263-2111 https://crossmark.crossref.org/dialog/?doi=https://doi.org/10.15826/chimtech.2022.9.4.09&domain=pdf&date_stamp=2022-8-16 chimica techno acta 2022, vol. 9(4), no. 20229409 article 2 of 5 electrode reactions because of the significant differences in geometry of a working electrode and electrochemical cell, parameters of diffusion and charge transfer, etc. [12, 13]. it can also influence the analytical signal parameters [14–17]. the aim of this article is the comparative study of the electrochemical behavior of cap in standard laboratory and portable microelectrochemical cells, and the estimation of the possibility of quantitative electrochemical determination of cap using the direct electrochemical response. 2. experimental 2.1. reagents and chemicals all solutions were prepared with ultrapure water from a branstead pacific tii water purification system. britton– robinson buffer solutions (brb) (ph 2–10) were prepared from 0.04 m orthophosphoric acid, 0.04m acetic acid and 0.04 m boric acid; the ph values were adjusted with sodium hydroxide. the ph was measured with a fiveeasy ph meter (mettler toledo). all chemicals were purchased from sigma aldrich: orthophosphoric acid, acetic acid, boric acid, sodium hydroxide, lithium perchlorate, acetonitrile, potassium chloride, ferrocyanide (k4fe[cn]6), potassium ferricyanide (k3fe[cn]6). 2.2. electrochemical research cyclic voltammograms (cv), differential pulse voltammograms (dpv), square wave voltammograms (swv) and chronoammograms (ca) were recorded on a potentiostat/galvanostat μautolab type iii. the three-electrode standard cell (figure 1a) consisted of a glassy carbon working electrode (gce), an ag/agcl/kcl reference electrode, and a carbon rod as an auxiliary electrode. a micrux aioplatform with a three-electrode system made by screen printing was used as a microelectrochemical cell (figure 1b). 3. results and discussion the study of the electrochemical behavior of chloramphenicol in water solutions was carried out both in the standard three-electrode cell and in the microcell. cyclic voltammograms (figure 2a), registered on the glassy carbon electrode, show a pronounced cathodic peak at a potential of –0.7 v and an anodic peak at a potential of 0.3 v, which increases with further cycling. also, in the second cycle, a peak at a potential of –0.3 v appears, and the current of the cathodic peak at a potential of –0.7 v decreases. it probably indicates a two-stage reduction process. on the cv registered in microcell, the electrochemical behavior of cap is similar (figure 2b). the shift of the cathodic peak potential in the negative region can be associated with the type of the electrode material and the differences in effective surfaces (figure 2c). studies on the effect of ph on the electroreduction (figure 3) in the britton–robinson solution were carried out to estimate the proton influence. with an increase in ph, a shift of the peak to the cathodic region is observed. thus, we can assume a proton-dependent reduction mechanism. in an aqueous medium δe/δph = –43 mv, which indicates an equal number of protons and electrons involved in the reaction. the maximal peak current is observed at ph = 5 (figure 3b). figure 4 shows the dependences of the recovery peak current on the square root of the scan rate (ν1/2) in the potential scan rate range from 1 to 2000 mv/s. the peak current has a linear relationship with the square root of the scan rate over the ph range under study. thus, the electrochemical reduction of chloramphenicol is a diffusion-controlled process. the effective number of electrons, involved in cap electroreduction, was estimated as 3, using the randles-sevcik theory (equation 1) [18]: 𝐼p = (2.69 × 105) 𝑛 3 2⁄ 𝐴𝐷 1 2⁄ 𝑐 𝑣 1 2⁄ , (1) where ip is the peak current, a; n is the number of transferred electrons; a is the area of the electrode, cm2; d is the diffusion coefficient, cm2/s; c is the concentration, m; and ν is the potential scan rate, v/s. it is known that the diffusion coefficient for the nitroaromatic compounds in aqueous media is ~10–5 cm2 [19], the diameter of gce is 2 mm, the concentration of cap is 2∙10–3 m (in brb ph = 5), the scan rate is 2 v/s. figure 1 the standard three-electrode cell (a); ‘micrux’ aio-platform for screen-printed electrodes (spe) (b). chimica techno acta 2022, vol. 9(4), no. 20229409 article 3 of 5 figure 2 cv registered in presence of 2∙10–3 m cap in brb ph = 7 on gce (a), on gce and spe (b), cv registered in presence of redox indicator 10 mm k3[fe(cn)6]/k4[fe(cn)6] on gce and spe, 0.1 kcl, scan rate 0.1 v/s (c). figure 3 cvs registered in presence of 2∙10–3 m cap on gce, brb ph = 2–10, scan rate 0.1 v/s (a); plot i = f(ph) (b) and plot e = f(ph) (c). figure 4 cvs registered in presence of 2∙10–3 m cap on gce, brb ph = 5 (a); plot peak recovery current vs scan rate (b). based on the obtained results, we can assume that the electrochemical behavior of chloramphenicol in microcell accompanied with a pronounced cathodic peak corresponds to the 3-electron and 3-proton electroreduction of the nitro group with the formation of the corresponding dimer (scheme 1). chimica techno acta 2022, vol. 9(4), no. 20229409 article 4 of 5 scheme 1 proposed mechanism of cap electrochemical reduction in microcell. to achieve the best analytical characteristics of the cap determination, we optimized the voltammetric mode both in standard and micro-electrochemical cells using cv, dpv and swv. figure 5 shows that during the changing registration mode from the lv (–0.65 v) to the swv (–0.54 v) and dpv (–0.56 v), the cathodic peak potential shifts to the anodic region and the peak current increases significantly. the best characteristics were obtained using the dpv mode (figure 5). similar tendency was also observed in the micrux cell. when registering the dpv of cap in a microvolume of the sample (the volume of the sample was 50 µl), the cathodic peak current significantly decreased, which is probably associated with a complication of charge transfer and a less developed surface of the screen-printed electrode (figure 6). thus, the process of electrochemical reduction of cap, registered in dpv mode can be used as a direct analytical signal in the portable electrochemical cells for express determination of the antibiotic in microvolumes of samples. under the chosen operating parameters, a calibration plot i = f(c) was obtained in model solutions of cap (figure 7). the regression is linear (r2 = 0.9984) in the wide concentration range of the cap. the detection limit, estimated according with the 3-sigma criterion, was 3∙10–5 m. the obtained characteristics are sufficient for the quality control of pharmaceuticals and can be improved using organic and hybrid modifiers of the working electrode surface. 4. conclusions in this work, the electrochemical behavior of chloramphenicol in aqueous solvents was studied in the standard threeelectrode cell and the portable electrochemical cell with the screen-printed three-electrode system. a similar redox behavior of cap was obtained, accompanied with the pronounced irreversible reduction peak corresponding to the 3-electron and 3-proton electrochemical conversion into the corresponding dimer. the best characteristics of the response were obtained in the differential pulse voltammetry mode. in the transition from the macrocell to the microcell, a decrease in the electroreduction current and a shift of the peak potential to the cathodic region are observed, which is apparently associated with the type of the working electrode. under the experimentally optimized operating parameters, the current of the cap electroreduction peak linearly depends on the antibiotic concentration in the range of 2∙10–3–1∙10–5 m with a detection limit of 3∙10–5 m and figure 5 lv, scan rate 0.1 v/s (1); swv, modulation amplitude 0.2 v, frequency 25 hz (2); dpv, modulation amplitude 0.2 v, modulation time 0.005 s (3). 2∙10–3 m chloramphenicol, glassy carbon electrode, brb ph = 5. figure 6 dpv, 2∙10–3 m chloramphenicol, spe (1), gce (2). brb ph = 5, modulation amplitude 0.2 v, time modulation 0.005 s. figure 7 calibration plot i = f(ccap) obtained in the micrux cell on the spe, dpv modulation amplitude 0.2 v, modulation time 0.005 s, brb ph = 5. can be used as an analytical signal of an electrochemical sensor. an increase in the detection sensitivity can be achieved using organic and hybrid modifiers of the working electrode surface. chimica techno acta 2022, vol. 9(4), no. 20229409 article 5 of 5 supplementary materials no supplementary materials are available. funding this work was supported by the presidential grants fund of the russian federation (grant no. mk-392.2022.1.3). acknowledgments none. author contributions conceptualization: t.s.s., m.v.m. data curation: m.v.m. formal analysis: m.v.m., e.d.v. funding acquisition: t.s.s., m.v.m. investigation: m.v.m., e.d.v. methodology: t.s.s., m.v.m., e.d.v. project administration: t.s.s. resources: m.v.m., e.d.v., r.a.z. software: m.v.m., e.d.v. supervision: a.n.k. validation: t.s.s., a.n.k. visualization: t.s.s., m.v.m., r.a.z. writing – original draft: t.s.s., m.v.m., r.a.z. writing – review & editing: t.s.s., a.n.k. conflict of interest 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https://doi.org/10.1007/s11664-022-09434-9 https://doi.org/10.1016/j.talanta.2021.123184 https://doi.org/10.1016/j.jhazmat.2021.127014 https://doi.org/10.1039/c0an00894j https://doi.org/10.1149/1945-7111/ab64d6 https://doi.org/10.1016/j.snb.2012.02.088 https://doi.org/10.1002/elan.201700555 https://doi.org/10.1109/rsm52397.2021.9511577 https://doi.org/10.1007/s11172-021-3190-7 73 введение в связи с развитием молекулярной электроники в последнее время все большее внимание уделяется синтезу и исследованию свойств d-π-a хромофоров [1–4]. в качестве π-сопряженной системы в подобных соединениях могут выступать и гетероциклы [5–10]. производные тиазола в этом аспекте интересны тем, что могут быть представлены двумя региоизомерами из-за несимметричности самого тиазольного цикла [11]. известно, что тиоацетомиды являются удобными синтетическими блоками для получения различных гетероциклов, в том числе и тиазолов, содержащие двойные экзоциклические связи [12, 13]. несмотря на это, реакция между хлоруксусным эфиром и дитиомалонамидами изучена недостаточно [14]. к. л. обыденнов, н. а. головко, ю. ю. моржерин уральский федеральный университет, 620002, екатеринбург, ул. мира, 19. e-mail: k.l.obydennov@ustu.ru синтез производных 2-(5-арилиден 4-оксо-3-арилтиазолидин-2-илиден) n-фенилэтантиоамида из малондитиоамидов в данной работе были синтезированы производные 2-(5-арилиден-4-оксо-3-арилтиазолидин-2-илиден)-n-фенилэтантиоамида из n,n`-дизамещенных малондитиоамидов в две стадии: последовательное проведение реакции ганча и конденсации кневенагеля. нами было показано, что исходя из n,n`-диарилмалондитиоамидов путем последовательного проведения реакции ганча и кневенагеля можно получать производные 2-(5-арилиден4-оксо-3-арилтиазолидин-2-илиден)-n-фенилэтантиоамида. полученные соединения охарактеризованы методами ямр 1н, ямр 13с, а также уф-спектроскопии. у д к 6 61 .7 7+ 54 7. 78 9 © обыденнов к. л., головко н. а., моржерин ю. ю., 2014 74 cta | № 2 | 2014 схема 1 результаты и обсуждение так реакция между n,n`-диарилмалондитиоамидами 1a,b и хлоруксусным эфиром протекает с образованием продукта гетероциклизации только по одной тиоамидной группе – (z)-2-(4-оксо-3-фенилтиазолидин-2-илиден)-n-фенилэтантиоамида (схема 1). дальнейшая конденсация полученного 4-оксотиазолидина 1a с альдегидами приводит к образованию 2-(5-бензилиден-4-оксо-3-фенилтиазолидин-2-илиден)-nфенилэтантиоамидам 2a,b c выходами 80 % и 85 %, соответсвенно. в спектрах ямр 1н тиазолидинонов 2a,b мы наблюдали уширенный сигнал nh группы в 10.66 и 10.90 м. д., уширенные сигналы атома водорода при двойной экзоциклической связи в 5.97 и 5.95 м. д., а также сигналы ch2 группы в области 5,97 и 5,96 м. д., соответственно. тиазол 2a вступает в конденсацию кневенагеля с бензальдегидами 3a,b с образованием тиазолидин-4-он-2,5-илиденов 4a,b с выходом 80 и 85 %, соответственно. в уф-спектрах тиазолов 4a,b в отличие от 2a мы наблюдали два максимума поглощения: в области 300 и 330 нм (со слабой интенсивностью) и 390 и 410 нм с высокой интенсивностью. таблица 1 данные уф-спектров тиазолов 2a, 4a, 4b соед. растворитель, λ (нм) (ε.10–3 (см2.моль–1.л–1)) 2a ch3cn, 340 (24,92); 4a ch3cn, 305 (14,69); 394 (36,39) 4b ch3cn, 334 (17,66); 403 (32,73) таким образом, в данной работе нами было показано, что исходя из n,n`-диарилмалондитиоамидов путем последовательного проведения реакции ганча и кневенагеля можно получать производные 2-(5-арилиден-4-оксо-3-арилтиазолидин2-илиден)-n-фенилэтантиоамида. полученные соединения охарактеризованы методами ямр 1н, ямр 13с, а также уф-спектроскопии. 1. varanasi p. r., jen a. k.-y. chandrasekhar j. namboothiri, i. n. n., rathna, a. j. amer. chem. soci., 1996, 118, 12443. 2. ellinger s., graham k. r., shi p., farley r. t., steckler t. t., brookins r. n., taranekar p., mei j., padilha l. a., ensley t. r., hu h., webster s., hagan d. j., stryland e. w. v., schanze k. s., reynolds j. r. chem. mater., 2011, 23, 3805. 3. andersson a., diederich f., nielsen m. organic & biomol. chem., 2009, 7, 3474. 4. kivala m., diederich f. accounts chem. res., 2009, 42, 235. к. л. обыденнов, н. а. головко, ю. ю. моржерин 75 2014 | № 2 | cta синтез производных 2-(5-арилиден-4-оксо-3-арилтиазолидин-2-илиден) n-фенилэтантиоамида из малондитиоамидов 5. mahuteau-betzer f., piguel s. tetrahedron lett., 2013, 54, 3188. 6. facchetti a., abbotto a., beverina l., van der boom m. e., dutta p., evmenenko g., marks t. j., pagani g. a. chem. mater., 2002, 14, 4996. 7. insuasty a., ortiz a., tigreros a., solarte e., insuasty b., martín n. dyes pigments, 2011, 88, 385. 8. baranac-stojanovi m., kleinpeter e. j. org. chem., 2011, 76, 3861. 9. baranac-stojanovi m., klaumünzer u., markovi r., kleinpeter e. tetrahedron, 2010, 66, 8958. 10. insuasty b., insuasty a., tigreros a., quiroga j., abonia r., nogueras m., cobo j., derita m., zacchino s. j. heterocyclic chem., 2011, 48, 347. 11. galan e., andreu r., garín j., mosteo l., orduna j., villacampa b., diosdado b.e. tetrahedron, 2012, 68, 6427. 12. danilkina n. a., mikhailov l. e., ivin b. a. russ. j. org. chem., 2006, 42, 783. 13. britsun v. n., esipenko a. n., lozinskii m. o. chem. heterocycl. compd., 2008, 44, 1429. 14. dyachenko v. d., chernega a. n., dyachenko s. v. russ. j. gen. chem., 2012, 82, 720. k. l. obydennov, n. a. golovko, yu. yu. morzherin ural federal university, 19, mira street, 620002, ekaterinburg, e-mail: k.l.obydennov@ustu.ru synthesis of 2-(5-arylidene-4-oxo-3-arylthiazolydine-2) n-phenylethanthiamides derivatives from malondithioamides it is shown that thioacetamide are comfortable synthetic blocks for various heterocycles, including thiazole containing a double exocyclic bonds. this work describes the synthesis of (z)-2-((z)-5-arylidene-4-oxo-3-arylthiazolidin-2-ylidene)n-arylethanethioamide 4 obtained from the knoevenagel condensation of (z)-2-(4oxo-3-arylthiazolidin-2-ylidene)-n-arylylethanethioamide 2. the starting material 2 was synthesized by a hantzsch reaction of n,n`-diarylmalondithioamides 1 and ethyl 2-chloroacetate. the structures of the obtained products were established by nmr and the structural features are discussed. several 4-oxothiazolidin-2-ylidenes were studied by uv-visible spectroscopy technique. страница 1 6 volodina n. s., terziyan t. v., safronov a. p., petrov a. v. ural federal university, 51 lenin street, 620083, ekaterinburg phone :+7(343)261-60-46; e-mail:byakovka@gmail.com thermodynamics of disaggregated polymer composites based on nanosized powders of ni and nio* technique to obtain disaggregated composites with uniform distribution of the ni nanoparticles in a polymer matrix were developed on the example of epoxy resin. disaggregated and aggregated composites based on butyl methacrylate copolymer with 5 wt% methacrylic acid and ni and nio nanoparticles have been obtained. enthalpies of mixing the components compositions in a wide range of compositions were defined using isothermal calorimetry. parameters adhesive interaction at the interface and glassy polymer structure changes have been calculated. the influence of the chemical nature of nanosized filler on interfacial energy has been revealed. *this work was done under financial support from rfbr grant № 12-03-31417. introduction the properties of filled polymer materials are determined by four factors: the chemical nature of the polymer and the filler, filler content, structure of filled polymer composites, and interfacial interaction at the interface ‘polymer – filler’1. mutual arrangement of the filler particles in the polymer matrix is understood to be the structure of filled materials. it is typical of nanosized powder fillers to undergo the process of aggregation, which is accompanied by the reduction of free surface energy. as a result, these particle aggregates can be the structural elements of a polymer material, along with the single filler particles. the process of aggregation leads to a decrease in interface boundaries in a filled polymer material; intermolecular forces which are on interface boundaries manifest themselves to a lessen degree, which in turn can influence the composite bulk property2. do i: 1 0. 15 82 6/ ch im te ch .2 01 5. 2. 1. 00 1 © volodina n. s., t. v. terziyan, a. p. safronov, petrov a. v., 2015 8 № 1 | 2015 chimica techno acta thermodynamics of disaggregated polymer composites based on nanosized powders of ni and nio the aim of this study is to develop a method of synthesis of disaggregated composites on the example of epoxy resin with the ni nanoparticles and to investigate the thermodynamics of interface interraction between butyl methacrylate copolymer with 5 wt% methacrylic acid and ni and nio nanoparticles. experiment in order to develop a method for obtaining disaggregated composites, epoxy resin in plastic state was employed as a polymer component. butyl methacrylate copolymer with 5 wt% methacrylic acid (bmc-5) was used for research into the thermodynamics of filled composites. copolymer bmc-5 is a commercial product; it was supplied by research institute ‘polymer technology’ based in dzerzhinsk. copolymer molecular mass measured by dynamic light scattering using «brookhaven zetaplus» was 3,2·105. nickel ni nanopowders and nickel oxide nio were used as fillers; they were obtained in the laboratory of the institute of pulse processes in electrical physics of ub ras by electric explosion of metal wire in an argon atmosphere for nickel and oxygen for nickel oxide. x-ray diffraction data obtained using brukerd8 advance diffractometer revealed that the nickel oxide consists of 98% of the face-centered cubic phase and of 2% of metallic nickel. figure 1 shows electron micrographs of the nanopowders obtained with a transmission electron microscope jeoljem 2100. it is seen that the particles are spherical and their size does not exceed 100 nm. high resolution images for ni show that the particles have a surface structure which differs from that of the core. presumably, this is due to the presence of the oxide coating on the ni metal particle surface. nanopowders specific surface was determined by bet low temperature adsorption of the nitrogen vapor using an automated adsorption installation micromeritics tristar 3000. for the ni powder, the specific surface area was 8.0 m2/g, and for nio 16.6 m2/g. fig. 1 (а) – electron photograph of nickel oxide particles; (b) – electron photograph of nickel particle 10 № 1 | 2015 chimica techno acta volodina n. s., terziyan t. v., safronov a. p., petrov a. v. results and discussion two methods were used for preparation of polymeric compositions based on nanoparticles and on epoxy resin. the first method led to disaggregated compositions; it composed of the following steps: preparation of nanopowder suspension in ethyl acetate; sonication (rcd) of the suspension in the cpu “cole_palmer cpx 750” for 15 min; adding a calculated amount of epoxy resin; processing nanopowder suspension in the presence of epoxy resin using dissolver “ecros-8100.” polymer compound was prepared by casting onto a glass substrate, followed by removing the solvent. the second method was used to obtain aggregated compositions, where the dry powder of filler and epoxy resin were mixed by using a dissolver. uniformity of particles distribution was monitored in two ways. dynamic light scattering data for compounds obtained with the use of an rcd showed the presence of single particle size of ~20 nm. for compositions obtained without rcd, aggregates of more than 100 nm were detected. these data are confirmed by photographs obtained with an optical microscope, "min-8" and presented in figure 2. for compounds obtained with rcd, more even particle destribution was observed. using the developed methods, nanopowder composition of ni and nio with copolymer bmc-5 was obtained; the polymer was added as a 25% solution in ethyl acetate. for studying the thermodynamics of interfacial interaction in composites, isothermal microcalorimetry method was used. the enthalpies of solution of the polymer (δn1), composite films (δn3) and the enthalpy of wetting powders in chloroform (δn2) were experimentally calculated on the calorimeter dak-1-1 of tian-calvet type in isothermal conditions at 25 °c. energy of interfacial interaction was estimated by the amount of enthalpy of mixing of the components of the polymer composition, which was calculated using thermochemical cycle3, according to equation 1: δhm = ω1δh1 + ω2δh2 – δh3 (1) where ω1, ω2 are the mass fractions of the fig. 2. micrograph of film es-kda/ni with 70% degree of filling; (а) – without rcd; (b) – with rcd 12 № 1 | 2015 chimica techno acta thermodynamics of disaggregated polymer composites based on nanosized powders of ni and nio polymer and the powder in the composite. figure 3 shows the concentration dependence of the enthalpy of dissolution for the aggregated and disaggregated compositions based on bmc-5 from the mass of ni filler. the points of intersection with the ordinate axis at ωnap = 1 corresponds to the enthalpy of wetting of nanosized nickel powder. the left vertical axis shows the enthalpy of dissolution of bmc-5 in chloroform. the graph shows that the dependence of the two systems can be described by a single curve. thus, the aggregation process does not affect the thermodynamics of dissolution of the compositions. to compare influence of the filler nature on the thermodynamics of the interfacial interaction, the concentrations dependence of the enthalpy of dissolution of the compositions bmc-5 with nickel oxide was obtained. using equation 1, the concentration dependence of the enthalpy of mixing, shown in fig. 4, were calculated. it is seen that the dependence δhm for a system with ni has the alternating form: in the area of small filler content, positive values of the enthalpy of mixing are observed; in the area of big content, negative; for a system with nio, the enthalpy of mixing is completely in the negative range. the data of enthalpy of mixing were processed using a theoretical model describing the thermodynamics of interaction in filled composites4. parameters of adhesive interaction at the interface ( ∆hадг ∞ is the enthalpy of adhesion per 1 m2 of interface and k is adsorption constant), and the parameters of the glassy polymer structure changes (γ is the maximum increase in the proportion of metastable positions in the structure of the polymer and l0 is the characteristic thickness of the adhesive glassy layer) were calculated. the calculated parameters are given in table 1. table 1 powder ∆hадг ∞ , ∫ j/m2 k γ × 102 l0, nm nio -0,45 99 1,5 65 ni -1,01 98 1,8 980 the table shows that the ∆hадг ∞ of polymer matrix to the ni surface adopts a value which is more exothermic than that of nio surface, which indicates a fig. 3. the concentration dependence of the enthalpy of dissolution of nanocompositions in chloroform fig. 4. the concentration dependence of the enthalpy of composites′ mixing 14 № 1 | 2015 chimica techno acta strong interaction with the surface of polymer nano-powder metal ni as compared with the surface of nio. given the data of electron microscopy, it can be argued that both powders have the same chemical nature of the surface, and the observed difference is due to the nature of the nanoparticle core. so, in the work5, the effect of increasing the protonation of surface hydroxyl groups of the oxide with electro-saturated metal core of aluminium particles had been established 5. a similar mechanism is possible for the studied systems based on ni and nio with a copolymer of bmc-5 under the assumption of the presence of proton-donor interaction. establishing the detailed mechanism of interfacial interaction requires the use of complex structure techniques. k values for the two studied powders are close, ie speed of reaching the adsorption equilibrium does not depend on the chemical nature of the powder and, apparently, is determined by its dispersion. for compositions based on the metal ni, greater thickness surface of the adhesive layer l0 and increase in the proportion of metastable vacancies γ, compared with nio, are observed. strong interaction in the interphase layer can lead to the fixing of a non-equilibrium conformation of macromolecules of the copolymer, which is manifested in the larger values of the parameters of the glassy structure. thus, studying the thermodynamics of the interaction of nanopwoders of metallic nickel and nickel oxide with bmc-5, it was found that the method of producing composites does not affect the interfacial energy, and nickel metal powder contributes significantly to vitrification of the copolymer compared with a powder of nickel oxide. 1. moczo j., pukanszky b. polymer micro and nanocomposites: structure, interactions, properties (review). journal of industrial and engineering chemistry. 2008 ; 14 (5):535–563. doi: 10.1016/j.jiec.2008.06.011. [google scholar]. 2. mutz m., holley d.w., baskaran d., mays j.w., dadmun m.d. impact of nanoparticle size and shape on selective surface segregation in polymer nanocomposites. polymer. 2012 ; 53 (22):5087–5096. doi: 10.1016/j.polymer.2012.08.029. [google scholar]. 3. yushkova s., tager a., bessonov yu. , guzeev v., ezhev v. effect of the thermodynamic affinity of plasticizers for polyvinyl chloride on the heat of its interaction with fillers. polymer science u.s.s.r. 1982 ; 24 (7):1557–1562. doi: 10.1016/0032-3950(82)90436-1. [google scholar]. 4. safronov a., istomina a., terziyan t., polyakova yu., beketov i. interfacial adhesion and the nonequilibrium glassy structure of a polymer on the enthalpy of mixing of polystyrene-based filled composites. polymer science. series a. 2012 ; 54(3):214. [google scholar]. 5. ezhovsky yu. k. surface nanostructures based on tantalum and aluminum oxides. journal of physical chemistry. journal of phsysical chemistry. 2010 ; 84(2):261. doi: 10.1134/s0036024410020172. [google scholar]. n. s. volodina, t. v. terziyan, a. p. safronov, a. v. petrov 7 у д к 4 58 .8 1: 67 7. 62 5. 31 н. с. володина, т. в. терзиян, а. п. сафронов, а. в. петров уральский федеральный университет, пр. ленина, 51, 620000, екатеринбург тел.: (343) 261-60-46; e-mail:byakovka@gmail.com термодинамика дезагрегированных полимерсодержащих композиций на основе нанодисперсных порошков ni и nio* на примере эпоксидной смолы разработана методика получения дезагрегированных композитов с равномерным распределением наночастиц ni в полимерной матрице. получены дезагрегированные и агрегированные композиты на основе сополимера бутилметакрилата с 5% масс. метакриловой кислотой и наночастиц ni и nio. методом изотермической калориметрии с помощью термохимического цикла определены энтальпии смешения компонентов композиций в широком диапазоне составов. с использованием термодинамического подхода в описании наполненных полимерных композиций на основе данных энтальпии смешения рассчитаны параметры адгезионного взаимодействия на границе раздела фаз и изменения стеклообразной структуры полимера. обнаружено влияние химической природы нанодисперсного наполнителя на энергетику межфазного взаимодействия. *работа выполнена при финансовой поддержке гранта рффи № 12-03-31417. введение свойства наполненных полимерных материалов, определяются четырьмя основными факторами: химической природой полимера и наполнителя, содержанием наполнителя, структурой организации наполненной полимерной композиции и межфазным взаимодействием на границе раздела фаз полимер – наполнитель [1]. под структурой наполненных материалов понимают взаимное расположение частиц наполнителя в полимерной матрице. для нанодисперсных порошков наполнителя характерен процесс агрегирования, сопровождающийся уменьшением свободной поверхностной энергии. в результате структурными элементами наполненного полимерного материала, кроме единичных частиц наполнителя, могут быть агрегаты частиц. процесс агрегирования приводит к уменьшению межфазной © володина н. с., терзиян т. в., сафронов а. п., петров а. в., 2015 9 № 1 | 2015 chimica techno acta границы в наполненном полимерном материале, и в меньшей степени проявляют себя силы межмолекулярного взаимодействия, реализуемые на границе раздела фаз, что в свою очередь может повлиять на объемные свойства композита [2]. в этой связи целью настоящей работы стало: разработка методики получения дезагрегированных композитов на примере эпоксидной смолы с наночастицами ni; изучение термодинамики межфазного взаимодействия композиций сополимера бутилметакрилата с 5 % масс. метакриловой кислоты (бмк-5) и наночастиц ni и nio. экспериментальная часть для разработки методики получения дезагрегированных композиций в качестве полимерного компонента использовали эпоксидную смолу кда в вязкотекучем состоянии. для изучения термодинамики наполненных композитов использовали сополимер бутилметакрилата с 5 масс.% метакриловой кислоты (бмк-5). сополимер бмк-5 является промышленным продуктом, был предоставлен нии «технологии полимеров» г. дзержинска. молекулярная масса сополимера, измеренная методом динамического рассеяния света на приборе brookhaven zetaplus, составила 3,2 · 105. в качестве наполнителей были использованы нанопорошки никеля ni и оксида никеля nio, полученные в лаборатории импульсных процессов института электрофизики уро ран методом электрического взрыва проволоки металла в атмосфере аргона для никеля и кислорода для оксида никеля. из рентгеноструктурных данных, полученных с помощью дифрактометра brukerd8 advance, установлено, что оксид никеля на 98 % состоит из кубической гранецентрированной фазы и на 2 % – из металлического никеля. на рис. 1 приведены электронные микрофотографии нанодисперсных порошков, полученные с помощью просвечивающего электронного микроскопа jeoljem 2100. видно, что частицы имеют сферическую форму и их размер не превышает 100 нм. на фотографии высокого разрешения для ni видно, что частицы имеют структуру поверхности, отличающуюся от ядра. по-видимому, это связано с наличием оксидной оболочки на рис. 1. нанодисперсные порошки: а – электронная фотография частиц оксида никеля; б – электронная фотография частицы никеля термодинамика дезагрегированных полимерсодержащих композиций на основе нанодисперсных порошков ni и nio 11 № 1 | 2015 chimica techno acta поверхности металлических частиц ni. удельная поверхность нанопорошков была определена методом бэт по низкотемпературной сорбции паров азота с помощью автоматической сорбционной установки micromeritics tristar 3000. для порошка ni величина удельной поверхности составила 8,0 м2/г, а для nio 16,6 м2/г. результаты и обсуждение для получения полимерных композиций на основе наночастиц и эпоксидной смолы были использованы две методики. первая методика – получение дезагрегированных композиций – включала стадии: приготовление суспензии нанопорошка в этилацетате; ультразвуковую обработку (узо) суспензии на процессоре cole_palmer cpx 750 в течение 15 мин.; добавление рассчитанного количества эпоксидной смолы; обработку суспензии нанопорошка в присутствии эпоксидной смолы на диссольвере «экрос-8100». полимерную композицию получали методом полива на стеклянную подложку с последующим удалением растворителя. вторая методика использовалась для получения агрегированных композиций, где с помощью диссольвера смешивались сухой порошок наполнителя и эпоксидная смола. однородность распределения частиц контролировали двумя способами. данные динамического рассеяния света для композиций, полученных с применением узо, показали наличие единичных частиц размером ~20 нм. для композиций, полученных без узо, обнаружены агрегаты размером более 100 нм. эти данные подтверждаются фотографиями, полученными с помощью оптического микроскопа «мин-8» и представленными на рис. 2. для композиций, при получении которых использовалась узо, наблюдается более равномерное распределение частиц. используя разработанные методики, были получены композиции нанодисперсных порошков ni и nio с сополимером бмк-5, где полимер добавлялся в виде 25 %-го раствора в этилацетате. для изучения термодинамики межфазного взаимодействия в композитах использовали метод изотермической микрокалориметрии. экспериментально измеряли энтальпии растворения рис. 2. микрофотография пленки эс-кда/ni со степенью наполнения 70 %: а – без применения узо; б – с применением узо володина н. с., терзиян т. в., сафронов а. п., петров а. в. 13 № 1 | 2015 chimica techno acta полимера (δн1), композиционных пленок (δн3), а также энтальпии смачивания порошков в хлороформе (δн2) на калориметре дак-1-1 типа тианакальве в изотермических условиях при 25 °с. энергетику межфазного взаимодействия оценивали величиной энтальпии смешения компонентов полимерной композиции, которую рассчитывали с помощью термохимического цикла [3], по уравнению 1: δhm = ω1δh1 + ω2δh2 – δh3 (1) где ω1, ω2 – массовая доля полимера и порошка в композите. на рис. 3 приведены концентрационные зависимости энтальпии растворения для агрегированных и дезагрегированных композиций на основе бмк-5 от массового содержания наполнителя ni. точки пересечения кривых с осью ординат при ωнап = 1 отвечают величине энтальпии смачивания нанодисперсного порошка никеля. на левой оси ординат приведена величина энтальпии растворения бмк-5 в хлороформе. из графика видно, что зависимости для двух систем могут быть описаны одной кривой. таким образом, процесс агрегации не влияет на термодинамику растворения композиций. для сравнения влияния природы наполнителя на термодинамику межфазного взаимодействия была получена концентрационная зависимость энтальпии растворения для композиций бмк-5 с оксидом никеля. используя уравнение 1, были рассчитаны концетрационные зависимости энтальпии смешения, представленные на рис. 4. видно, что зависимость δhm для системы с ni имеет знакопеременный вид: в области малого содержания наполнителя наблюдается положительные значения энтальпии смешения, в области большего содержания – отрицательные; а для системы с nio энтальпия смешения полностью находятся в области отрицательных значений. данные энтальпии смешения были обработаны с помощью теоретической модели, описывающей термодинамику взаимодействия в наполненных композитах [4]. были рассчитаны параметры адгезионного взаимодействия на границе раздела фаз ( ∆hадг ∞ – энтальпия адгезии в расчете на 1 м2 межфазной поверхности и k – константа адсорбции) и параметры изменения стеклообразной структуры полимера (γ – максимальное увеличение доли метастабильных вакансий в структуре рис. 3. концентрационная зависимость энтальпии растворения нанокомпозиций в хлороформе рис. 4. концентрационная зависимость энтальпии смешения композитов термодинамика дезагрегированных полимерсодержащих композиций на основе нанодисперсных порошков ni и nio 15 № 1 | 2015 chimica techno acta полимера и l0 – характерная толщина адгезионного стеклообразного слоя). рассчитанные параметры приведены в таблице 1. таблица 1 п ор ош ок ∆hадг ∞ , дж/м2 k γ × 102 l0, нм nio –0,45 99 1,5 65 ni –1,01 98 1,8 980 из таблицы видно, что ∆hадг ∞ полимерной матрицы к поверхности ni принимает более экзотермическое значение, чем к поверхности оксида никеля, что свидетельствует о более сильном взаимодействии полимера с поверхностью нанопорошка металлического ni по сравнению с поверхностью nio. учитывая данные электронной микроскопии, можно утверждать, что оба порошка имеют одинаковую химическую природу поверхности, и наблюдаемое различие обусловлено природой ядра наночастицы. так, в работе [5] обнаружен эффект повышения протонизации поверхностных гидроксильных групп оксида за счет электронасыщенного металлического ядра частиц алюминия [5]. аналогичный механизм возможен для исследуемых систем на основе ni и nio с сополимером бмк-5 в предположении наличия протонодонорного взаимодействия. установление детального механизма межфазного взаимодействия требует использования комплекса структурных методов. значения k для двух изученных порошков близки, т. е. скорость достижения адсорбционного равновесия не зависит от химической природы порошка и, по-видимому, определяется его дисперсностью. для композиций на основе металлического ni наблюдается большее значение толщины поверхности адгезионного слоя l0 и увеличения доли метастабильных вакансий γ, по сравнению с nio. сильное взаимодействие в межфазном слое может приводить к фиксированию неравновесной конформации макромолекул сополимера, что проявляется в бóльших значениях параметров стеклообразной структуры. таким образом, на примере изучения термодинамики взаимодействия нанопорошков металлического никеля и оксида никеля с бмк-5 установлено, что методика получения композитов не влияет на энергетику межфазного взаимодействия, а также металлический порошок никеля способствует значительному стеклованию сополимера по сравнению с порошком оксида никеля. 1. moczo j., pukanszky b. journal of industrial and engineering chemistry. 2008. v. 14. p. 535. 2. mutz m., holley d. w., baskaran d., mays j. w., dadmun m. d. // polymer. 2012. v. 53. p. 5087. 3. юшкова с. м., тагер а. а., бессонов ю. с., гузеев в. в., ежев в. с. // высокомолекулярные соединения. а. 1982. т. 24, № 7. с. 1373. 4. сафронов а. п., истомина а. с., терзиян т. в., полякова ю. и., бекетов и. в. // высокомолекулярные соединения. а. 2012. т. 54, № 3. с. 411. 5. ежовский ю. к. // журнал физической химии. 2010. т. 84, № 2. с. 314. володина н. с., терзиян т. в., сафронов а. п., петров а. в. 790-2570-1-pb 790-2571-1-pb 33 а. с. холкина1, п. а. архипов1, 2, ю. п. зайков1, 2 1уральский федеральный университет, 620002, екатеринбург, ул. мира, 19. e-mail: a.kholkina@mail.ru 2ивтэ уро ран, 620219, екатеринбург, ул. академическая, 20. e-mail: arh@ihte.uran.ru активность свинца в его сплаве с сурьмой и висмутом работа посвящена изучению термодинамической активности свинца в его сплавах с сурьмой и висмутом как модели при переработке отходов, образующихся как при производстве металлов (дроссы, съемы, пыли, шламы), так и при выработке готовых изделий (свинцовые аккумуляторы). для этого был использован метод измерения э. д. с. концентрационного гальванического элемента: (–)pb|kcl-pbcl 2 ¦¦kcl-pbcl 2 |pb-(sb-bi)(+). полученные концентрационные зависимости э.д.с. гальванического элемента описываются линейными уравнениями. активность свинца в тройном жидкометаллическом сплаве имеет незначительные отрицательные отклонения от поведения идеального раствора. методом э.д.с. измерены равновесные потенциалы сплавов pb-sb-bi в расплаве kcl-pbcl 2 (50–50 мол. %) для широкой области составов в интервале температур от 450 до 630 °с. рассчитана термодинамическая активность свинца в системе свинец-сурьма-висмут. показано, что свинец проявляет незначительные отрицательные отклонения от поведения идеальных растворов. © холкина а. с., архипов п. а., зайков ю. п., 2014 введение в настоящее время остро стоит вопрос о переработке отходов, образующихся как при производстве металлов (дроссы, съемы, пыли, шламы), так и при выработке готовых изделий (свинцовые аккумуляторы). переработка такого сырья требует разработки новых научно обоснованных технологий. эти технологии должны отвечать ряду требований, предъявляемых к современным разработкам, т. е. снижение энергетических затрат, экологическая безопасность и уменьшение образующихся отходов производства. использование расплавов солей для переработки промпродуктов поможет достичь поставленных требований [1, 2]. 34 cta | № 1 | 2014 в литературе имеются данные о исследовании термодинамических характеристик двойных систем pb-sb [3] и pb-bi [4]. в этих работах методом э. д. с. измерены равновесные потенциалы двойных сплавов pb-sb и pb-bi в широком диапазоне концентраций и температур в хлоридном расплаве. определены термодинамические функции свинца в двойном сплаве. рассчитаны парциальные и интегральные термодинамические характеристики двойных систем. проведен расчет теоретической оценки эффективности разделения двойных сплавов свинца с висмутом и сурьмой. в связи с тем, что вторичное сырье содержит в основном количестве свинец, сурьму и висмут, научный интерес представляет изучение равновесных потенциалов тройных сплавов pb-sb-bi и активности свинца в тройной металлической системе. целью данной работы является получение новых данных о значениях равновесных потенциалов тройной системы pb-sb-bi в расплаве kcl-pbcl2 и расчет термодинамической активности элетроотрицательного компонента в сплаве. экспериментальная часть для исследований использовали концентрационный гальванический элемент (1): (–) pb | kcl-pbcl2 ¦¦ kcl-pbcl2 | pb-(sb-bi) (+) одним из полуэлементов является марочный свинец c1, а другим – тройной сплав pb-(sb-bi). опыты провели с использованием сплавов sb-bi различным соотношением 1:1, 3:1, 1:3 с добавками свинца. состав металлических сплавов и электролита контролировали до и после эксперимента атомно-абсорбционным анализом. в качестве электролита использовали смесь хлоридов свинца и калия в соотношении 50–50 мол. %. электрохимическая ячейка для измерения э. д. с. гальванического элемента представлена на рис. 1. исследования проводили в ячейке из кварца (3), в который помещали алундовый тигель (2). в тигель загружали марочный свинец (9), кварцевую трубку, заполненную исследуемым сплавом pb-(sb-bi) (7), и термопару (1). на поверхность свинца в тигле и сплава в трубках помещали электролит kcl-pbcl2 (8). пространства рабочего электрода и электрода сравнения разделили диафрагмой (6) из асбеста для тиглей гуча. токоподвод к жидкометаллическим рис. 1. схема электролитической ячейки: 1 – термопара ха; 2 – алундовый тигель; 3 – кварцевый стакан; 4 – пластины из ni; 5 – стержни из mo; 6 – диафрагма; 7 – сплав pb-(sb-bi); 8 – kcl-pbcl2; 9 – свинцовый электрод сравнения а. с. холкина, п. а. архипов, ю. п. зайков 35 2014 | № 1 | ctaактивность свинца в его сплаве с сурьмой и висмутом электродам осуществили при помощи стержней из молибдена (5), защищенных от контакта с расплавом алундовыми трубками. после помещения ячейки в печь устанавливали температуру 630 ºс для расплавления свинца и сплавов. заданное значение температуры поддерживали с помощью регулятора температуры трм1 с точностью ± 1 ºc. значение э. д. с. регистрировали мультиметром appa-109 с входным сопротивлением ~ 10 мом. для получения более точных значений э. д. с. были проведены измерения при снижении температуры от 630 ºс до 450 ºс с шагом 30 ºс, а затем при повышении температуры от 450 ºс до 630 ºс. полученные значения э. д. с. и температуры усредняли для расчета коэффициентов активности. результаты и обсуждение в результате измерений э. д. с. тройной системы pb-(sb-bi) были получены температурные зависимости e = f(t), которые представлены на рис. 2–4. политермы э. д. с. сплавов имеют прямолинейный вид. выражения e = f(t) хорошо описываются линейными равнениями. общий вид уравнения можно представить следующим выражением: e = a+ b · t. согласно полученным результатам, при одной и той же температуре с уменьшением мольной доли свинца в тройном сплаве потенциал этого сплава относительно металлического свинца сдвигается в область положительных значений. активность свинца в системе pb-(sb-bi) проявляет незначительные отклонения от закона рауля. рис. 3. зависимости э.д.с. элемента (1) (npb-(1:1)) от температуры и концентрации свинца, мол. % рис. 2. зависимости э. д. с. элемента (1) npb–(1:3) от температуры и концентрации свинца, мол. % рис. 4. зависимости э. д. с. элемента (1) (npb–(3:1)) от температуры и концентрации свинца, мол. % на основании экспериментальных данных рассчитали активность свинца в тройном сплаве (рис. 5–7). 36 cta | № 1 | 2014 на рис. 8 представлены зависимости свинца в двойных системах pb-sb, pb-bi и тройной системе pb-sb-bi. и висмут и сурьма совмест-но снижают активность свинца в тройной системе значительнее, чем в двойных системах свинец-сурьма и свинец-висмут. наибольшее влияние оказывает висмут, поэтому в тройном сплаве с высоким содержанием висмута отклонение от идеальности значительнее. выводы 1. методом э. д. с. измерены равновесные потенциалы сплавов pb-sb-bi в расплаве kcl-pbcl2 (50-50 мол. %) для широкой области составов в интервале температур от 450 до 630 °c. 2. рассчитана термодинамическая активность свинца в системе свинецсурьма-висмут. показано, что свинец проявляет незначительные отрицательные отклонения от поведения идеальных растворов. рис. 8. активность свинца в системах pbbi [30], pb-sb [31], pb-(sb-bi) при температуре 480 °с рис. 5. активность свинца в сплаве npb–(sb:bi) = npb–(1:3) при температуре 510 °с рис. 6. активность свинца в сплаве npb–(sb:bi) = npb–(1:1) при температуре 510 °с рис. 7. активность свинца в сплаве npb–(sb:bi) = npb–(3:1) при температуре 510 °с а. с. холкина, п. а. архипов, ю. п. зайков 37 2014 | № 1 | ctaактивность свинца в его сплаве с сурьмой и висмутом a. s. kholkina1, p. a. arhipov1, 2, yu. p. zaikov1, 2 1ural federal university, 19, mira street, 620002, ekaterinburg. e-mail: a.kholkina@mail.ru 2institute of high-temperature electrochemistry ub ras, 20 akademicheskaya street, 620219, yekaterinburg. e-mail: arh@ihte.uran.ru lead activity in pb-sb-bi alloys the present work is devoted to the study of lead thermodynamic activity in the pbsb-bi alloys. the method for emf measurements of the concentration cell: (–)pb|kclpbcl 2 ¦¦kcl-pbcl 2 |pb-(sb-bi)(+) was used. the obtained concentration dependences of the galvanic cell emf are described by linear equations. the lead activity in the ternary liquidmetal alloy demonstrates insignificant negative deviations from the behavior of ideal solutions. activity lead in ternary liquid metal alloy has a slight negative deviation from ideal behavior of the solution. method of the emf measured potentials of equilibrium alloys pb-sb-bi melt kcl-pbcl 2 50–50 mol. %) for a wide range of compounds in the temperature range from 450 to 630 °c. 1. delimarsky yu. k., zarubitsky o. g. electrolytic refining of heavy metals in ionic melts. metallyrgy, moscow, 1975, 321 p. [делимарский ю. к., зарубицкий о. г. электролитическое рафинирование тяжелых металлов в ионных расплавах. м. : металлургия, 1975. 321 с.]. 2. morchevsky a. g. zhurn. fizhich. khimii, 1999, 72, 89 [морачевский а. г. // журнал физической химии. 1999. т. 72. с. 89–92]. 3. zaikov y. p., arkhipov p. a., plekhanov k. a., ashikhin v. v., khalimullina y. r., chebykin v. v., molchanova n. g. russ. j. non-ferrous metals, 2007, 48, 92 [зайков ю. п., халимуллина ю. р., архипов п. а., ашихин в. в., скопов г. в., молчанова н. г. // известия вузов. цветная металлургия. 2007. № 2. с. 11–17]. 4. khalimullina y. r., zaikov y. p., arkhipov p. a., ashikhin v. v., skopov g. v. kholkina a. s., molchalova n. g. melts, 2010, 34 [халимуллина ю. р., зайков ю. п., архипов п. а., ашихин в. в., скопов г. в., холкина а. с., молчанова н. г. расплавы. 2010. № 5. с. 34–43]. страница 1 111 введение цирконистографитовый материал широко применяется в шлаковом поясе погружных корундографитовых стаканов при непрерывной разливке стали. погружной стакан находится между промежуточным ковшом и кристаллизатором. кристаллизатор заполнен расплавленным металлом, который сверху защищен от окисления шлаком. во время разливки шлак расходуется и постоянно обновляется добавлением шлакообразующей смеси (шос). применение цирконисто-графитового материала обусловлено тем, что он более устойчив к расплаву шлака, чем корундографитовый, периклазо-графитовый и шпинелеграфитовый материалы [1]. цирконистографитовый материал – это композиционный материал, который состоит из зерен диоксида циркония и чешуек природного графита, связанных между собой коксовым остатком от фенолформальдегидной смолы. цирконистографитовый матеа. в. яговцев, н. в. обабков уральский федеральный университет, 620002, екатеринбург, ул. мира, 19. e-mail: obabkovn@gmail.com взаимодействие цирконистографитового материала с расплавленым шлаком и воздушной средой цирконистографитовый материал применяется при непрерывной разливке стали. от устойчивости к шлаку зависит продолжительность разливки. был использован дробный факторный эксперимент 25–1 для определения влияния состава огнеупора (содержание графита, карбида кремния, карбида бора) на окисляемость и взаимодействие с шлакообразующей смесью (c/s = 1, f = 8 %) при 1400 °с. установлено, что карбид бора обладает лучшими антиокислительными свойствами по сравнению с карбидом кремния. добавка карбида бора в количестве 3 масс. % снижает устойчивость цирконистографитового огнеупора к шлаку. значения толщины обезуглероженного слоя находятся в пределах 1–7 мм. добавки карбида бора и карбида кремния снижают толщину окисленного слоя. экспериментально установлено, что карбид бора обладает лучшими антиокислительными свойствами, чем карбид кремния, поэтому в изучаемых цирконистографитовых материалах действие sic менее эффективно, чем b 4 c. у д к 6 61 .8 83 1 © яговцев а. в., обабков н. в., 2014 112 cta | № 3 | 2014 риал, корундографитовый и периклазографитовый материалы очень походят друг на друга наличием графита, присутствием коксового остатка (стеклоуглерода) – разница лишь только в заполнителе. шлаковый пояс погружного стакана во время эксплуатации подвергается следующим воздействиям: окисление кислородом воздуха углеродистой составляющей (графита, стеклоуглерода), растворение оксидной составляющей в шлаке, растворение углеродистой составляющей в металле. для защиты графита от окисления в состав огнеупора вводят различные антиоксиданты, металлы и (или) карбиды, которые окисляются с увеличением объема, закрывая поры для дальнейшего проникновения кислорода. кислород играет важную роль в устойчивости цирконистографитового материала к шлаку. известно что, в инертной среде при температуре 1550 °c взаимодействия цирконистографитового материала со шлаком (шлакообразующей смесью) не наблюдается, а наблюдается в окислительной среде при 1450 °с [2]. состав цирконистографитового оказывает влияние на устойчивость к шлаку. экспериментальная часть был реализован дробный факторный эксперимент типа 25–1 [3]. уровни факторов эксперимента и интервалы их варьирования представлены в табл. 1, 2. пресс-порошок смешивали в лабораторном смесителе. на лабораторном прессе прессовали образцы в виде цилиндров с диаметром 50 мм. с торца в цилиндре формовали углубление. образцы были высушены в сушильном шкафу при 240 °с для отверждения фенолформальдегидной смолы. коксование проводили в колпаковой печи при 980 °с. для тестирования образцов огнеупоров была выбрана коммерческая шлако-образующая смесь с основностью (cao/sio2) = 1 и содержанием фтора 8 масс. %. смесь поместили в углубления цилиндров. цилиндры со таблица 1 уровни факторов и интервалы их варьирование (план 25–1) факторы уровни факторов обозначение наименование –1 +1 x1 содержание zro2-cao (крупность –32 меш), масс.% 40 56 x2 содержание графита, масс. % 10 20 x3 содержание sic, масс. % 0 5 x4 содержание b4c, масс. % 0 3 x5 содержание органического связующего с отвердителем, масс. % 6,5 7,5 содержание zro2-cao (крупность –325 меш), масс. % остальное а. в. яговцев, н. в. обабков 113 2014 | № 3 | cta взаимодействие цирконистографитового материала с расплавленым шлаком и воздушной средой смесью установили в печь сопротивления. выдержка образцов при 1400 °с составила 1,5 часа. далее образцы распилили на две части и сфотографировали (табл. 3). в строке 1 – образцы без антиоксидантов. в строке 2 – образцы с карбидом кремния. в строке 3 –образцы с карбидом бора. в строке 4 – образцы с карбидами кремния и бора. в столбцах а и б – образцы с 10 % графита. в столбцах в и г – образцы с 20 % графита. в столбцах б и г – образцы с повышенным содержанием крупной фракции диоксида циркония. изображения с макрострутурой образцов обработали при помощи программы siams photolab и определили площадь разъеденную шлаком, также определили толщину окисленного слоя (hокисл). оценку шлакоустойчивости (ушг) полученных цирконистографитовых материалов определяли по изменению геометрических размеров: из определенных площадей вычли начальную площадь 510 мм2. результаты и обсуждение результаты измерения площади и толщины окисленного слоя были статистически обработаны. получены следующие уравнения регрессии (значения факторов даны в кодированном виде): ушг = 29 – 2х1 – 8х2 – 5х3 + 2х4 + + 4х5 – 2х1х2 + 2х1х3 – 1х2х3 + 5х2х4 – – 3х3х4 таблица 2 матрица планирования эксперимента 25–1 № состава x0 x1 x2 x3 x4 x5 = x1x2x3x4 1 +1 –1 –1 –1 – 1 +1 2 +1 +1 –1 –1 – 1 – 1 3 +1 –1 +1 – 1 – 1 – 1 4 +1 +1 +1 – 1 – 1 +1 5 +1 –1 –1 +1 – 1 –1 6 +1 +1 –1 +1 – 1 +1 7 +1 –1 +1 +1 – 1 +1 8 +1 +1 +1 +1 – 1 –1 9 +1 –1 –1 – 1 +1 – 1 10 +1 +1 –1 – 1 +1 +1 11 +1 –1 +1 – 1 +1 +1 12 +1 +1 +1 – 1 +1 –1 13 +1 –1 –1 +1 +1 +1 14 +1 +1 –1 +1 +1 – 1 15 +1 –1 +1 +1 +1 – 1 16 +1 +1 +1 +1 +1 +1 114 cta | № 3 | 2014 hокисл = 3,3 – 0,4x2 – 0,4x3 – 2,3x4 + + 0,4x2x4 + 0,4x3x4 результаты измерений и вычислений по уравнениям регрессии представлены в табл. 4. значения толщины обезуглероженного слоя находятся в пределах 1–7 мм. добавки карбида бора и карбида кремния снижают толщину окисленного слоя. экспериментально установлено, что карбид бора обладает лучшими антиокислительными свойствами, чем карбид кремния, поэтому в изучаемых цирконистографитовых материалах действие sic менее эффективно, чем b4c. добавка карбида кремния и графита снижает взаимодействие материала с оксидным расплавом. в то же время введение b4c снижает устойчивость цирконистографитового материала к шлаку. в процессе высокотемпературтаблица 3 макроструктура образцов после испытания в разрезе а б в г 1 состав 1 состав 2 состав 3 состав 4 2 состав 5 состав 6 состав 7 состав 8 3 состав 9 состав 10 состав 11 состав 12 4 состав 13 состав 14 состав 15 состав 16 а. в. яговцев, н. в. обабков 115 2014 | № 3 | cta взаимодействие цирконистографитового материала с расплавленым шлаком и воздушной средой таблица 4 матрица планирования эксперимента 25–1 № опыта ушг толщина окисленного слоя, нокисл, мм среднее расчет по модели среднее расчет по модели 1 47 48 7 7,0 2 38 38 7 7,0 3 16 14 6 5,5 4 13 15 5 5,5 5 30 29 6 5,5 6 42 43 5 5,5 7 16 19 4 4,0 8 12 9 4 4,0 9 40 43 1 1,0 10 48 45 1 1,0 11 47 46 1 1,0 12 23 24 1 1,0 13 30 28 1 1,0 14 18 20 1 1,0 15 21 21 1 1,0 16 24 24 1 1,0 ного окисления карбида бора образуется b2o3, который легко растворяется шлакообразующей смесью, обнажая поверхность для дальнейшего окисления. высокое значение парного эффекта взаимодействия факторов х2 и х4 (содержания графита и карбида бора) можно объяснить тем, что зола, содержащаяся в графите, имеет температуру плавления 1340 °с [4], а образующийся при окислении карбида бора оксид бора снижает эту температуру. также известно, что оксидные расплавы (стекла), содержащие b2o3, хорошо смачивают графит, а смачивание приводит к более интенсивному массообмену. 1. koga s., amano j., morikawa k., asano k. j. techn. assoc. refract., 2006, 26, 184. 2. suvorov s. a., vikhrov e. a. refract. industr. ceram., 2010, 51, 187. 3. adler p., markova e. v., granovsky j. v. planning of experiments in search of optimal conditions. m.: nauka, 1976. 279 p. 4. suvorov s. a., musevich v. a. refract. industr. ceram., 2007, 48, 118. 116 cta | № 3 | 2014 a. v. jagovcev, n. v. obabkov ural federal university, 19, mira street, 620002, ekaterinburg e-mail: obabkovn@gmail.com interaction of zg-refractory with mold flux and ambient air zirconia graphite refractory is used in continuous casting of steel. slag corrosion resistance influence on time of casting. with factorial experiment 25-1 influence mixture of refractory (content of graphite, silicon carbide, boron carbide) on oxidation resistance and interaction with mould powder (c/s = 1, f = 8 %) at 1400 °c. boron carbide is better antioxidant than silicon carbide. boron carbide 3 % mass decrease slag corrosion resistance of zg-refractory. the thicknesses de-carbonized layer are within 1–7 mm additives of boron carbide and silicon carbide reduce the thickness of the oxidized layer. it was established experimentally that the boron carbide has the best antioxidant properties than silicon carbide therefore, in the study circolatorio materials action sic less effective than b 4 c. а. в. яговцев, н. в. обабков 56 введение невысокие температуры плавления бинарных смесей kcl-alcl3 обусловливают привлекательность использования хлоралюминатных расплавов для получения и рафинирования ряда переходных металлов, таких как никель, хром, железо, молибден и т. д. также низкоплавкие хлоралюминатные электролиты представляют интерес для использования в качестве теплоносителя второго контура жидкосолевых ядерно-энергетических установок. однако внедрение новых электрохимических и ядерных технологий сдерживает отсутствие данных о физико-химических свойствах хлоридов переходных металлов, в частности их растворимости в расплавленных хлоралюминатах при различных условиях. целью настоящей работы явилось определение растворимости хлоридов переходных металлов в расплавах на основе в. в. карпов, в. а. волкович, и. б. половов, о. и. ребрин уральский федеральный университет, 620002, екатеринбург, ул. мира, 19. e-mail: polovov@dpt.ustu.ru определение растворимости хлоридов переходных d-элементов в хлоралюминатных расплавах представлены результаты выполненных исследований по определению растворимости в расплавах на основе kcl-alcl 3 хлоридных соединений ряда переходных d-элементов (ni, cr, mo, fe). изучено влияние мольного отношения kcl : alcl 3 и температуры на растворимость хлоридов исследуемых металлов в хлоралюминатных расплавах. показано, что растворимость хлорида молибдена в расплавах kcl-alcl 3 снижается по мере обогащения расплава по alcl 3 (иногда величина растворимости уменьшается на порядок). растворимость хлорида никеля имеет v-образную зависимость от мольного отношения k : al с минимумом в области мольных отношений k : al несколько ниже единицы. разница в растворимости nicl2 в расплавах различного состава может достигать двух порядков. растворимость хлоридов хрома и железа, наоборот, имеет максимум в области эквимолярного состава kcl-alcl 3 , снижаясь как при увеличении, так и при уменьшении мольного отношения k : al. у д к 6 61 .8 65 © карпов в. в., волкович в. а., половов, ребрин о. и., 2014 57 2014 | № 2 | cta кcl-alcl3 в зависимости от состава электролита (мольного отношения k : al) и температуры (350 и 500 ос). были исследованы процессы растворения хлоридов никеля, хрома, молибдена и железа. имеющиеся в литературе сведения о растворимости хлористых соединений переходных элементов и влиянии внешних факторов на данный процесс в хлоралюминатных расплавах весьма ограничены. в отношении никеля [1, 2] отмечена очень низкая растворимость его хлорида в хлоралюминатных щелочных расплавах. так, при строго эквимольном соотношении хлоридов алюминия и калия в интервале температур 175–210 °с растворимость nicl2 составляет 1,14 ∙ 10-2 г/л. однако при невысоком избыточном по отношению к эквимольному составу содержании трихлорида алюминия, равному 0,02 г/л, растворимость nicl2 повышается до 1,3 г/л. также было установлено [2, 3], что введение в эквимолярный расплав kcl-alcl3 избытка хлорида калия в количестве, несколько превышающем стехиометрически необходимое для образования двойного хлорида m2mecl4 (m – щелочной металл, ме – никель), приводит к растворению хлорида переходного металла. к такому же эффекту приводит повышение температуры до 700 ос. в случае никеля [1, 2] эксперименты выполняли в относительно разбавленных расплавах, содержащих около 0,13 г/л nicl2. для более концентрированных по хлориду никеля расплавов его растворимость будет определяться диаграммой состояния хлоридов калия, алюминия и никеля, т. е. температурой и количеством избыточного хлорида калия. растворимость хлорида железа (iii) в naalcl4 изменяется в интервале температур 200–500 °с от 0,2 до 0,4 масс. % [4]. о растворимости хлористых соединений других интересующих элементов в хлоралюминатных расплавов можно судить лишь косвенно, например, по диаграммам плавкости систем [5]. исходя из литературных данных, можно справедливо предположить, что хлориды переходных металлов имеют определенную растворимость в хлоралюминатных расплавах, зависящую от температуры и состава электролита и при изменении этих параметров могут выделяться из расплавов в виде твердой фазы (шламов). методика выполнения экспериментов для приготовления рабочего электролита компоненты смешивали, помещали в пробирку из кварца, которую закрывали пробкой с капиллярами для отбора проб расплава. ячейку вакуумировали, заполняли аргоном и помещали в печь сопротивления, предварительно разогретую до необходимой температуры. после расплавления компонентов расплав перемешивали и выдерживали в течение 4–6 часов, время от времени перемешивая. затем расплаву давали отстояться и отбирали пробу электролита, не содержащего шламовой фракции. пробоотбор осуществляли без нарушения герметичности ячейки. в образцах замороженных плавов далее аналитически определяли содержание алюминия, калия и исследуемого элемента. определение растворимости хлоридов переходных d-элементов в хлоралюминатных расплавах 58 cta | № 2 | 2014 результаты и их обсуждение зависимость растворимости хлорида никеля от состава хлоралюминатного расплава представлена на рис. 1. в целом следует отметить, что хлорид никеля обладает относительно невысокой растворимостью в расплаве. при обеих температурах зависимость растворимости от состава расплава имеет экстремальную зависимость, что согласуется с описанными в литературе тенденциями [1, 2]. минимум растворимости (<0,02 масс. % nicl2) достигается при мольном соотношении k : al около 0,92 (350 °с) и 0,97 (500 °с). в расплавах, богатых по хлориду алюминия, растворимость nicl2 слабо зависит от температуры и составляет 0,1–0,3 масс. % при мольном соотношении k : al = 0,7–0,8, снижаясь до 0,02 масс. % при мольном соотношении k : al = 0,92– 0,97. при дальнейшем увеличении мольного отношения k : al растворимость хлорида никеля возрастает до 1,1 мас. % при 350 °с и до 0,1 масс. % при 500 °с. повышение растворимости при введении хлорида калия, по всей видимости, обусловлено образованием тетрахлороникелат-ионов nicl4 2–. в расплавах, содержащих значительный избыток хлорида алюминия, никель координирован с хлороалюминат-ионами и присутствует в виде шестикоординированных групп nicl6 4– в составе соединения «ni(al2cl7)2», по аналогии с растворами хлорида никеля в расплаве индивидуального хлорида алюминия [6]. в области составов с мольным соотношением k : al < 1 растворимость хлорида никеля несколько возрастает с повышением температуры, а в области составов с мольным соотношением k : al > 1 растворимость хлорида никеля с ростом температуры значительно снижается. результаты измерения растворимости хлорида молибдена от состава электролита представлены на рис. 2. растворимость хлорида молибдена в расплавах при соотношении k : al менее 0,95 невелика (составляет 0,015–0,03 масс. % в расчете на mocl3) и слабо зависит от температуры и состава расплава. с повышением содержания kcl растворимость хлорида молибдена (iii) возрастарис. 1. растворимость хлорида никеля в расплаве kcl-alcl3 при 350 и 500 ос рис. 2. растворимость хлорида молибдена в расплаве kcl-alcl3 при 350 и 500 °с в. в. карпов, в. а. волкович, и. б. половов, о. и. ребрин 59 2014 | № 2 | cta определение растворимости хлоридов переходных d-элементов в хлоралюминатных расплавах ет и при соотношении k : al около 1,1–1,4 достигает 2,1 масс. % при 350 ос и 1,7 масс. % при 500 ос. характер кривых растворимости (рис. 2) указывает, что растворение хлорида молибдена происходит за счет образования комплексных хлоридных ионов. растворимость хлорида железа в хлоралюминатном расплаве определяется растворимостью двойных хлоридов kfecl3 и k2fecl4, имеющих относительно высокие температуры плавления (399–406 и 374–380 °с соответственно). данные, полученные в экспериментах по определению растворимости хлорида железа, представлены на рис. 3. видно, что растворимость хлорида железа довольно велика и имеет экстремальную зависимость от состава электролита. растворимость хлорида хрома (ii) в расплаве kcl-alcl3 имеет сложную зависимость от состава электролита (рис. 4). при мольных отношениях k : al < 0,9 она невелика, довольно слабо зависит от состава расплава и составляет менее 0,01 масс. % (в расчете на crcl2). при дальнейшем увеличении содержания kcl в электролите растворимость хлорида хрома начинает возрастать, достигая максимума при соотношении k : al около единицы, после чего проявляет тенденцию к снижению, особенно ярко выраженную при 500 ос. тем не менее даже максимальная растворимость хлорида хрома незначительна и составляет менее 0,36 масс. % (в расчете на crcl2). выводы при организации процесса получения и рафинирования ряда переходных металлов в хлоралюминатных электролитах следует учитывать то, что некоторые хлористые соединения обладают ограниченной растворимостью в подобных средах. так, например, растворимость хлорида молибдена в расплавах kcl-alcl3 снижается по мере обогащения расплава по alcl3, (иногда величина растворимости уменьшается рис. 3. растворимость хлорида железа в расплаве kcl-alcl3 при 350 и 500 ос рис. 4. растворимость хлорида хрома в расплаве kcl-alcl3 при 350 и 500 ос 60 cta | № 2 | 2014 на порядок). растворимость хлорида никеля имеет v-образную зависимость от мольного отношения k : al с минимумом в области мольных отношений k : al несколько ниже единицы. разница в растворимости nicl2 в расплавах различного состава может достигать двух порядков. растворимость хлоридов хрома и железа, наоборот, имеет максимум в области эквимолярного состава kcl-alcl3, снижаясь как при увеличении, так и при уменьшении мольного отношения k : al. 1. gilbert b., osteryoung r. a. j. am. chem. soc., 1978, 100, 2725. 2. brynestad j., smith g. p. j. am. chem. soc., 1970, 92, 3198. 3. oye h. a., gruen d. m. inorg. chem., 1965, 4, 1173. 4. sandler r. a., larionov a. a. russ. j. appl. chem., 1984, 10, 2375 [сандлер р. а., ларионов а. а. // жпх. 1984. т. 10. с. 2375]. 5. chart fusion salt systems. triple systems. red. posypaiko v. i., alekseeva e. a. chemistry, moscow, 1977, 328 p. [диаграммы плавкости солевых систем. тройные системы. под ред. посыпайко в. и., алексеевой е. а. москва: химия, 1977, 328 с.]. 6. oye h.a., gruen d.m. inorg. chem., 1964, 3, 836. v. v. karpov, v. a. volkovich, i. b. polovov, o. i. rebrin ural federal university, 19, mira street, 620002, ekaterinburg. e-mail: polovov@dpt.ustu.ru determination of solubility of chlorides of d-elements in chloroaluminate melts solubility of several transition metal chlorides (nicl 2 , crcl 2 , mocl 3 , fecl 2 ) was measured in kcl-alcl 3 based melts. it was found that the solubility of studied metal chlorides depends on k : al mole ratio. mocl 3 solubility decreases with increasing alcl 3 content. solubility of crcl 2 and fecl 2 reaches maximum at k : al ratio of 1 and decreases when this ratio either de-creases or increases. the dependence of nicl 2 solubility on k : al mole ratio is v-shaped with the maximum near 0.9–0.95. the effect of temperature on solubility of transition metal chlorides in kcl-alcl 3 melts was also investigated. increasing temperature does not alter the character of «solubility – k : al mole ratio» dependences. в. в. карпов, в. а. волкович, и. б. половов, о. и. ребрин страница 1 сomparison of au, au-pt, and au-ag nanoparticles as markers for immunochromatographic determination of nonylphenol published by ural federal university eissn 2411-1414 chimicatechnoacta.ru letter 2023, vol. 10(1), no. 202310103 doi: 10.15826/chimtech.2023.10.1.03 1 of 5 сomparison of au, au–pt, and au–ag nanoparticles as markers for immunochromatographic determination of nonylphenol anna n. berlina * , maria y. ragozina, nadezhda s. komova , kseniya v. serebrennikova, anatoly v. zherdev , boris b. dzantiev a.n. bach institute of biochemistry, research center of biotechnology of the russian academy of sciences, moscow 119071, russia * corresponding author: anberlina@yandex.ru this paper belongs to the mosm2022 special issue. abstract gold spherical nanoparticles, gold-platinum nanoflowers, and gold-silver nanostars were obtained and compared as labels for immunochromatographic analysis. the nanoparticles were synthesized by chemical reduction from various precursors and then conjugated with staphylococcal protein a to be used in indirect immunochromatographic determination of nonylphenol. the results obtained were evaluated in terms of analytical characteristics and r2 value, as well as the color intensity of the test band. according to the comparison results, it was revealed that the r2 value varied from 0.82 for the gold-silver nanostars to 0.96 for the spherical gold nanoparticles. the working range of determined concentrations was from 2 to 100 μg/ml for unspherical and from 2 to 50 μg/ml – for spherical markers used; the analysis time was 20 min. keywords gold nanoparticles gold-platinum nanoflowers gold-silver nanostars immunochromatographic analysis nonylphenol received: 25.11.22 revised: 07.12.22 accepted: 07.12.22 available online: 19.12.22 © 2022, the authors. this article is published in open access under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). 1. introduction nanoparticles are widely used as labels in the development of analytical test systems [1]. due to their unique properties – plasmon resonance, wide color range, the ability to immobilize proteins and other receptor molecules on their surface – they are used as markers in immunochromatography [2]. synthesized metal particles without a polymer coating on the surface and without functionalization with specific active groups (carboxyl or amino) are able to enter into the process of conjugation by the physical adsorption method [3, 4]. the previous laboratory results have repeatedly confirmed the possibility of using various nanoparticles such as gold [5], magnetic [6], bimetallic [7], semiconductor [8], latex [9] etc., as labels in the analysis. sometimes, when traditionally used gold nanoparticles were replaced, the sensitivity of the analysis increased [10]. however, in most cases, the sensitivity and the detection limit of the analyte were determined by the affinity of the antibodies, and, in case of insufficient sensitivity of the analysis, schemes for amplifying the analytical signal were offered [11, 12]. nonylphenol (np) is a surfactant widely used in everyday life as the main component of detergents. with contaminated wastewater, they enter water bodies and soil and spread through the food chains of ecosystems, which leads to a negative impact on human health [13]. the determination of surfactants in environmental objects is mainly carried out by instrumental chromatographic methods [14], which are characterized by laboriousness, high cost and significant analysis time. an alternative approach is to use immunochemical methods, especially immunochromatographic analysis (ica). it has undoubted advantages compared to other immunochemical methods – ease of analysis, short duration (no more than 20 min), and the possibility of visual detection of the analyte when using test systems in out-of-laboratory conditions [15]. the interest and purpose of this work was to compare three types of nanoparticles for the immunochromatographic determination of nonylphenol as the target analyte. to provide this investigation, conjugate hapten-protein, nanoparticles conjugated with protein a were synthesized and the antibodies previously obtained were used [16, 17]. here, for small molecular weight analyte, a competitive determination scheme is used, in which analytes immobilized and free in the sample compete with each other for antibody binding sites. in this case, in the absence of analyte, the maximal intensity is observed. the increase in its concentration leads to the decrease in staining in the test zone. http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2023.10.1.03 http://creativecommons.org/licenses/by/4.0/ https://orcid.org/0000-0002-3761-7472 https://orcid.org/0000-0002-3229-9073 https://orcid.org/0000-0003-3008-2839 https://orcid.org/0000-0003-4008-4918 https://crossmark.crossref.org/dialog/?doi=https://doi.org/10.15826/chimtech.2023.10.1.03&domain=pdf&date_stamp=2022-12-19 chimica techno acta 2023, vol. 10(1), no. 202310103 letter 2 of 5 doi: 10.15826/chimtech.2023.10.1.03 2. experimental part 2.1. synthesis of a hapten-protein conjugate by the mannich reaction the technique was previously used for the synthesis of hapten-protein conjugates and the production of polyclonal rabbit antibodies [16]. for this purpose, 11.5 mg of nonylphenol (np, hapten) was dissolved in 348 μl of dimethyl sulfoxide (dmso) at a concentration of 33 mg/ml. a 11 mg of soybean trypsin inhibitor (sti, the carrier protein) was dissolved in 1 ml of 0.1 m carbonate buffer (ph = 10). then 58 μl of nonylphenol solution was added to the protein solutions. next, 100 μl of 35–37% formaldehyde was added to each eppendorf tube, followed by incubation under stirring for 30 min at room temperature (rt) and then for 5 days at 37 °c. 2.2. synthesis of spherical gold (au) nanoparticles spherical gold nanoparticles were prepared according to the typical citrate reduction process [18]. briefly, the aqueous solution of haucl4 (0.25 mm, 98.5 ml) was heated to boiling, and sodium citrate (0.03 m, 1.5 ml) was added with stirring. the mixture was allowed to stir for 15 min and was then cooled. 2.3. synthesis of gold-platinum (au–pt) nanoflowers the synthesis of gold-platinum nanoflowers was carried out according to the following procedure [19]. haucl4 (0.13 m, 100 µl) was added to bidistilled water (50 ml) and heated to boiling with stirring. sodium citrate (0.03 m, 800 μl) was then added rapidly, and the color of the reaction mixture changed from pale yellow to golden red within a few minutes. for the growth of gold-platinum nanoflowers, ascorbic acid (0.1 m, 1 ml) and sodium hexachloroplatinate (18 mm, 1.25 ml) were successively added to the resulting boiling solution and left for 25 min. all freshly prepared solutions of gold nanoparticles were stored at 4 °c for 3 months. 2.4. synthesis of gold-silver (au–ag) nanostars gold nanostars were synthesized using seed-mediated growth [20]. at the first stage, sodium citrate (0.03 m, 15 ml) was added to the boiling aqueous solution of haucl4 (0.25 mm, 98.5 ml) to prepare seeds. the reaction mixture was allowed to stir for 15 minutes, after which it was cooled to room temperature. to obtain gold nanostars, hydrochloric acid (1 m, 10 μl), haucl4 (0.25 mm, 10ml) and the seed solution (100 μl) were mixed in a 20 ml flask, followed by stirring at about 700 rpm at room temperature. then, silver nitrate (2 mm, 100 μl) and ascorbic acid (100 mm, 50 µl) were rapidly added to the boiling mixture. the solution was stirred for 30 sec until the color changed to blue. 2.5. conjugation of nanoparticles with staphylococcal protein a protein a was dissolved in deionized water to a concentration of 1 mg/ml. the synthesis was carried out at the rate of 10 μg of protein per 1 ml of nanoparticle sol. then, prepared au nanoparticles were pre-adjusted to ph of 8.0 by 0.2 m k2co3. freshly prepared au–pt nanoparticles (ph 2.5) and au–ag nanoparticles (ph 3.6) were adjusted with 1 m naoh to reach the ph 7.9. for conjugate synthesis, 1 ml of nanoparticles was dropped into the glass vessel containing protein a for 45 min at rt. then, 25 μl of 10% bsa in milliq water was added to stabilize each suspension for 15 min. during the synthesis, conjugates were stirred at shaker intellimixer (elmi, riga, latvia). the obtained conjugate was separated from unbound protein a and excess of bsa by centrifugation at 9,500 g at +4 °c for 15 min with the use of amicon 30 kda centrifuge tubes and then stored in 10 mm borate buffer, ph 8.0. characterization of the conjugates was provided using a shimadzu uv-2450 spectrophotometer (shimadzu, japan) and a jem cx-100 electron microscope (jeol, tokyo, japan). 2.6. assembly of the immunochromatographic test system the lateral flow strip was prepared using the nitrocellulose working membrane, the porous cellulose absorbent membrane, and the glass-fiber membrane for sample adsorbtion. sti-np (2 mg/ml) and goat-anti-rabbit antibody (0.5 mg/ml) were immobilized on the working nitrocellulose cnpc 15 membrane (0.1 μl per 1 mm) to form the test and the control lines, respectively. then the multimembrane composite was assembled, dried overnight at rt and cut onto the test strips with a width of 3.5 mm with the use of a guillotine cutter (indexcutter, usa). 3. results and discussion this work was based on the principle of indirect competitive analysis, which was as follows. rabbit polyclonal antibodies against nonylphenol previously obtained in the laboratory were used as the receptor molecule in ica. [16, 17]. the conjugate of nonylphenol with the carrier protein (sti) was immobilized on the working membrane of the test strip to form a test zone (scheme 1). to determine nonylphenol, the following scheme was used when the stages of interactions were separated: (i) the formation of an antigen-antibody complex in the test zone, and then (ii) the use of a conjugate of nanoparticles with protein a. this was necessary to minimize conjugate consumption and reduce the number of non-specific interactions, since rabbit antiserum contains not only specific antibodies to nonylphenol, but also a host of other immunoglobulins. scheme 1. composition of lateral flow test strip and the main components for analysis. https://doi.org/10.15826/chimtech.2023.10.1.03 chimica techno acta 2023, vol. 10(1), no. 202310103 letter 3 of 5 doi: 10.15826/chimtech.2023.10.1.03 therefore, a washing step in 50 mm phosphate-buffered saline solution with 0.05% tween-20 (pbst) was added to remove excess antiserum and third-party proteins before the interaction with conjugate of nanoparticles. first, 50 µl solutions of nonylphenol with known concentrations were added to the wells of the microplate, then 50 µl rabbit antiserum diluted in phosphate-buffered saline containing 1% tween-20 (pbst*) was added. after the reaction mixture of nonylphenol and rabbit antiserum was incubated for 10 seconds, the test strip was immersed into the solution and initiated the movement of liquid along the pores of the membranes under the action of capillary forces. as soon as the entire liquid front passed over the surface of the working membrane, the test strips were immersed into 100 µl pbst to remove excess amount of antiserum. then, after 20 seconds, the test strips were transferred to the wells of a microplate with solution of developing conjugate of nanoparticles with protein a in 100 µl pbst* for signal accumulation. bonding in the test zone reflects competition. in the absence of nonylphenol in the sample, a colored band formed in the test zone, indicating the formation of a complex with followed composition: (sti-nonylphenol)-antibody(protein a-nanoparticle). with an increase in the concentration of nonylphenol in the sample, the intensity of staining in the test zone decreased. in this work, the series of nanoparticles were obtained by chemical oxidation-reduction of various precursors and used as a label. in total, three preparations of different composition (au, au–pt and au–ag), size and shape (nanospheres, nanoflowers, nanostars) were synthesized. the preparations obtained by the chemical syntheses were characterized by spectrophotometry (figure 1, 1a, 2a, 3a) and transmission electron microscopy (tem) (figure 1, 1b, 2b, 3b). the first method made it possible to characterize the spectra of adsorbtion nanoparticles in the synthesis medium. for analysis of nanoparticles by tem, they were deposited on preliminarily prepared meshes with polyvinylformal precipitated in chloroform. micrographs were obtained using a jem-100c electron microscope (jeol, japan) and analyzed using the image tool program (health science center at the university of texas at san antonio, usa). this software allowed to measure the average size of nanoparticles and calculate the effective diameter with the coefficient of ellipticity. thus, for preparations of au, au– pt, and au–ag nanoparticles, the average diameters were 31.7±4.4, 63.4±5.6, and 53.2±9.4 nm, respectively. the ellipticity coefficient for all preparations did not exceed 1.3. the absorption spectra of the obtained sols showed that various methods of synthesis made it possible to obtain preparations with different optical properties, and their absorption peaks were located in different ranges (figure 1, 1a, 2a, 3a). under the selected interaction conditions, calibration curves for the determination of nonylphenol in a buffer solution were obtained (figure 1, 1c–d, 2c–d, 3c–d). the intensity of staining in the test zone differed depending on the type of nanoparticles used as a label. in all experiments, a 1:4000 dilution of antiserum was used, which allowed obtaining a reliable analytical signal and minimizing non-specific staining in the test zone when nonylphenol was introduced (table 1). table 1 choosing of antiserum dilution for immunochromatographic analysis with the use of spherical au nanoparticles conjugated with protein a. parameter antiserum dilution 1:1000 1:2000 1:4000 1:8000 intensity in the test zone, a.u. 20030 20185 13741 4862 intensity in the test zone in the presence of np, a.u. 12694 11575 4949 2357 figure 1 absorption spectrum (1a, 2a, 3a), tem images (1b, 2b, 3b), calibration curves (1c, 2c, 3c) and digital images of test strips (1d, 2d, 3d) for au–pt nanoflowers (1), au–ag nanostars (2) and au spherical nanoparticles (3). the concentrations of nonylphenol were: for figures 1c–d: 1.6, 3.13, 6.25, 12.5, 25, 50 and 100 µg/ml for test strips 1–7; for figures 2c–d: 6.25, 10, 12.5, 25, 30, 50 and 100 µg/ml for test strips 1–7; for figures 3c–d: 2, 3, 4.8, 10, 12.5, 25, 30 and 50 µg/ml for test strips 1–8, n = 3. https://doi.org/10.15826/chimtech.2023.10.1.03 chimica techno acta 2023, vol. 10(1), no. 202310103 letter 4 of 5 doi: 10.15826/chimtech.2023.10.1.03 4. limitations the presented data demonstrate possibilities to realize immunochromatographic test systems for nonylphenol detection using different nanosized labels. actually, a lot of preparations were stated as possible alternatives to traditionally used spherical gold nanoparticles, but detailed comparisons of several labels using the same analyte and the same antibody preparations are very limited. the obtained data demonstrate similar working ranges for the compared labels, and reasons for their choice are based mainly on linearity and sensitivity. probably, this similarity of working ranges is associated with competitive assay format, where affinity of immune interactions becomes limiting factor (in contrast to sandwich ica of large molecules with strong impact of label's properties on the final analytical parameters). but, overall conclusion about sensitivity, working ranges and linearity for different labels cannot be made only on the basis of the given data and needs additional consideration. however, further application of the given test systems to different kinds of real samples contaminated by nonylphenol could include additional factors. matrices of the tested substances may have influence on the rate of the lateral flow along the test strips and the levels of non-specific binding. due to this, the obtained data of comparative characterization of different labels cannot be simply transferred to real sample testing. additional characterization of these labels will be necessary as a basis for further conclusion about the best tests for introduction into practice. 5. conclusions as part of this work, three types of nanoparticles were obtained and compared – au nanospheres, au–pt nanoflowers, au–ag nanostars for their use as a marker in the immunochromatographic determination of nonylphenol. they were conjugated with staphylococcal protein a and used in the last stage of indirect competitive interaction. by the value of the coefficient r2, it was possible to identify the preferred ones for use as a label. therefore, in the series (au) nanoparticles – (au–pt) nanoflowers – (au–ag) nanostars there is a decrease in the r2 value, as well as the analytical signal and the sensitivity of the nonylphenol determination. ● supplementary materials no supplementary materials are available. ● funding this work was supported by the russian science foundation (grant no. 22-13-00293), https://www.rscf.ru/en. ● acknowledgments the authors are grateful to s.m. pridvorova from a.n. bach institute of biochemistry (research center of biotechnology of the russian academy of sciences, moscow, russia) for the support with tem images. ● author contributions conceptualization: a.n.b., a.v.z. data curation: a.n.b., formal analysis: a.n.b., m.y.r., n.s.k., k.v.s. funding acquisition: a.n.b., b.b.d. investigation: a.n.b., n.s.k., m.y.r. methodology: a.n.b., n.s.k., m.y.r. project administration: a.n.b., a.v.z. resources a.v.z., b.b.d. software: n.s.k., k.v.s. supervision: a.v.z., b.b.d. validation: a.n.b., n.s.k., m.y.r. visualization: a.n.b., n.s.k. writing – original draft: a.n.b., n.s.k. writing – review & editing: a.n.b., n.s.k., a.v.z. ● conflict of interest the authors declare no conflict of interest. ● additional information author ids: anna n. berlina, scopus id 21742180800; maria y. ragozina, scopus id 57965305300; nadezhda s. komova, scopus id 57209730245; kseniya v. serebrennikova, scopus id 57200450296; anatoly v. zherdev, scopus id 35608006700; boris b. dzantiev, scopus id 7006549067. website: a.n. bach institute of biochemistry, research center of biotechnology of the russian academy of sciences, https://www.fbras.ru. references 1. guo j, chen s, 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https://doi.org/10.1080/00032719.2021.1956515 https://doi.org/10.3390/s21155185 https://doi.org/10.1080/03067310410001729024 https://doi.org/10.1016/j.talanta.2004.07.004 https://doi.org/10.1021/jp061667w https://doi.org/10.1007/s00604-019-3464-z https://doi.org/10.3390/nano11102565 the crystallization of thin sb2te films with vacuum annealing and an electron beam published by ural federal university eissn 2411-1414 chimicatechnoacta.ru article 2023, vol. 10(1), no. 202310111 doi: 10.15826/chimtech.2023.10.1.11 1 of 7 the crystallization of thin sb2te films with vacuum annealing and an electron beam anton a. yushkov *, vladimir yu. kolosov institute of natural sciences and mathematics, ural federal university, ekaterinburg 620026, russia * corresponding author: yushkov.anton@urfu.ru this paper belongs to a regular issue. abstract thin sb2te films with a thickness gradient were studied via transmission electron microscopy. the processes of forced crystallization were examined with thermal annealing and an electron beam. the crystallization’s general tendencies, including competitive nucleation and growth crystallization, were revealed. as the thickness of the sample increases, the size of the crystals growing in the film enlarges. as the temperature increases, the number of crystals in the film grows. crystallization under the action of an electron beam occurs mainly by nucleation mechanism. keywords sb2te thin films phase-change materials transmission electron microscopy received: 24.12.22 revised: 17.02.23 accepted: 21.02.23 available online: 03.03.23 key findings ● a thin amorphous sb2te film crystallizes in a phase isomorphic to antimony during vacuum annealing. ● during annealing, the processes of nucleation and growth crystallization proceed competitively in the film. as the temperature rises, nucleation predominates. ● the possibility of controlled creation of crystalline regions in an amorphous sb2te film by exposure to a focused electron beam is shown. © 2022, the authors. this article is published in open access under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). 1. introduction sb–te systems, including sb2te and compositions based on it, are considered as perspective thermoelectric materials [1–4]. characteristic of the amorphous state crystal phase transition in these materials has a critical impact on their properties [5]. the non-linear optical properties of these materials open up prospects for their application in optoelectronics [6–8]. these compositions are also advanced materials for manufacturing non-volatile memory based on the phase transition effect (pcm) [9–15]. the development of multi-level memory cells that are competitive with modern flash memory devices is underway [16, 17]. unlike other phase-change materials, sb–te systems are characterized by a high crystallization rate and thermal stability [13]. the properties of antimony telluride as a topological insulator [18, 19] and a high-temperature superconductor [20] have also been studied. in order to increase the stability and performance of devices, various dopants are used [12, 13, 15, 21–24]. in particular, the use of carbon carbide leads to an increase in the crystallization temperature and an increase in the number of pcm memory rewriting cycles [24]. the addition of scandium and yttrium to antimony telluride leads to a reduction in thermal conductivity and an increase in the energy efficiency of pcm devices [23]. the features of the phase transition in materials based on sb–te as a function of temperature [16, 25] and composition changes [22] are investigated. in the context of these applications, it is of interest to study the processes of crystallization in amorphous sb2te films in the context of temperature and impact of an electron beam. studying the effect of temperature and sample thickness on the crystallization process will allow us to evaluate the thermal and mechanical resistance of finished devices. also, indirectly, one can judge their electrical properties. the proven method of exposure to a beam of a transmission electron microscope (tem) is applicable both to further experiments and to the development of industrial methods. http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2023.10.1.11 mailto:yushkov.anton@urfu.ru http://creativecommons.org/licenses/by/4.0/ https://crossmark.crossref.org/dialog/?doi=https://doi.org/10.15826/chimtech.2023.10.1.11&domain=pdf&date_stamp=2023-03-03 chimica techno acta 2023, vol. 10(1), no. 202310111 article 2 of 7 doi: 10.15826/chimtech.2023.10.1.11 2. materials and experimental methods the samples were synthesized by the group led by professor m. wüttig at rwth aachen university (germany). the samples were gradient films (in the order of hundreds of microns) of sb2te deposited on carbon-coated grids via magnetron sputtering. the thickness gradient in the samples was created using a shading plate. shortly after synthesis, the samples were subjected to vacuum annealing at various temperatures and times. according to the energy-dispersive x-ray spectroscopy, the specimens retain the nominal chemical composition throughout the area. in this work, the following goals were set. firstly, the study seeks to investigate patterns of crystallization in thin films along the thickness gradient, depending on the type of exposure, time and annealing temperature. secondly, the study will determine the features of the formed crystal structures: the phase composition and the main crystallographic orientations. sb2te samples were studied via transmission electron microscopy on jeol jem-2100. according to the analysis of zone-axial patterns (zap) in the samples and the interpretation of the corresponding electron diffraction patterns (examples are shown in figure 1), crystallographic orientations of the antimony phase predominate in the crystallized films (astm 05-0562, trigonal syngony, space group r3̅m). according to the measurements of the secondary diffraction maxima in the dark field mode [26], the thickness of the crystallized film varies along the gradient from about 15– 20 nm to 40–50 nm over several tens of micrometers. 3. results and discussion the sb2te 145c-60s sample was annealed at 145 °c for 60 seconds. in the thinnest area of the thickness gradient, the film is predominantly amorphous (figure 2a). along the thickness gradient, the substance crystallizes into separate island-crystallization centers, often with a hexagonal faceting motif, ranging in size from 0.4 µm at the beginning of the thickness gradient to 2 µm in the thickest region. the initial amorphous film’s strong relief, which is characteristic of magnetron sputtering, is ignored by crystallization. as we move along the thickness gradient, the size and number of such islands increases. they fill an increasing area of the film and merge, forming a continuous crystalline field (figure 2c, d). the tem images do not show a connection between crystallization centers and any defects or features of the film relief. in the film’s thickest region, the crystallites measure 1–2.5 µm. the sb2te 145с-48s sample is similar to the 145с-60s in terms of the morphology, sizes and observed zone-axial patterns of the formed crystallites; therefore, a detailed study was not carried out. the sizes of the crystallites range from 0.2 µm at the beginning of the thickness gradient to 2.8 µm in the thickest region. a small change in the annealing time did not significantly affect the formed crystal structure. figure 1 samples sb2te and (145c-48s (a) and 145c-60s (b, c, d)) zap (left), the corresponding indexed electron diffraction patterns of the selected area (right). a – zap with zone axis orientation [͞111] (a); zap with orientation [001] (b); zap [̅225]; d zap [2 ̅2 1] (c). the sb2te 120c-90m sample was annealed at 120 °c for 1.5 hours. the pattern of crystallization before the formation of a continuous film was similar to sb2te 145c-48s and sb2te 145c-60s – hexagonal crystalline islands of increasing size and density along the thickness gradient (figure 3a–c). in the thinnest area, the crystal sizes ranged from 100 to 700 nm. in the thickest continuous film, the crystallites measured 1– 3 μm. in the sb2te 120с-90m sample, the largest crystals were observed in the thickest region. the sb2te 200c-48s sample was annealed at 200 °c for 48 seconds. in this sample, the crystallization processes along the thickness gradient differ from those in the sb2te 145c-48s, sb2te 145c-60s and sb2te 145c-90m samples. near the phase boundary, the film crystallizes into a homogeneous fine-grained field (figure 4a, b), with crystal sizes ~10–50 nm. as the thickness of the film increases, the sizes of the crystallites grow, and there are no areas of the amorphous phase between them (figure 4c, d). this indicates that nucleation in the film increases as annealing temperature increases. this process is enhanced as the sample thickness decreases. the crystallites in the thickest region measure 0.3– 1.8 μm, smaller than in the previously considered samples. https://doi.org/10.15826/chimtech.2023.10.1.11 chimica techno acta 2023, vol. 10(1), no. 202310111 article 3 of 7 doi: 10.15826/chimtech.2023.10.1.11 figure 2 tem images of the 145с-60s sample at the beginning of the thickness gradient, with a noticeable relief of the initial amorphous film and small crystallites in the amorphous matrix (a, b); image taken from the middle of the gradient, crystalline areas are adjacent to amorphous ones (c); image of a completely crystallized area in the thickest area. figure 1b, d provides the measurements of some crystallites (d). figure 3 tem images of the 120с-90m sample at the beginning of the thickness gradient (successively upwards), with individual small/medium crystals in an amorphous matrix (a, b); image of the sample in the area from the middle of the gradient (c); image of the sample in the thickest region. figure 3b, d show the measurements of the linear dimensions of some crystallites (d). https://doi.org/10.15826/chimtech.2023.10.1.11 chimica techno acta 2023, vol. 10(1), no. 202310111 article 4 of 7 doi: 10.15826/chimtech.2023.10.1.11 figure 4 image of the thinnest area of the 200c-48s sample, individual small crystals are distinguishable (a); images from the gradient’s middle (in the direction of increasing thickness) (b, c); image from the thickest region (crystallites reach their maximum size) (d). in the samples 120с-90m, 145c-60s and 145c-48s, the growth of individual crystals with a hexagonal faceting motif was observed. the general trend of crystallization is an increase in crystal size as the film thickness increases. changing the annealing conditions affected the crystallized films’ morphology. with an increase in annealing time, an increase in the linear dimensions of the crystallites was observed: the largest crystals are observed for the 120c-90m sample annealed for 1.5 hours. an increase in annealing temperature led to the growth of smaller crystals. in the sample annealed at 200 °c, a finely crystalline film was formed in the thinnest region instead of individual crystal nuclei. in the thickest region, the crystallites in this sample were the smallest among all the samples. this indicates an increase in nucleation as annealing temperature increases and film thickness decreases. the authors of [27] indicate an increase in nucleation (the appearance of many crystallization centers in an amorphous matrix) in chalcogenide films based on sb2te and a decrease in thickness (in experiments with simultaneous heating and exposure to a tem beam). they call this effect paradoxical: if nucleation crystallization occurs on the sample film’s surface, then it should not depend on the thickness. if nucleation develops in the bulk of the sample, then a larger number of crystallization centers should appear in a thicker film. higher annealing temperatures were characterized by the growth of smaller crystals throughout the thickness gradient, especially in the thinnest regions. this points to the presence of a nucleation mechanism of crystallization. longer annealing times and lower temperatures were characterized by the growth of larger crystals (growth crystallization). this can be explained by the nucleation of a smaller number of crystallization centers at a lower temperature. a time factor of tens of minutes obviously has little or no effect on crystallization. the morphology of the samples with an annealing time of tens of seconds or tens of minutes differs insignificantly. the crystals probably formed within a few seconds. the general trend for the entire group of samples is an increase in the size of the formed crystallites and their density on the film as the thickness increased. fully crystallized by thermal annealing, the film was paved with crystallites of various sizes and arbitrary shapes. no ordering or separate isolated crystallization centers were observed in the samples. this can be explained by the mutual blocking of the growth of neighboring crystals that arise almost simultaneously from numerous crystallization centers. the sample 48s-200c was also distinguished by the fact that, contrary to the general trend, it had the largest number of crystallization centers on the thinnest part. in the temperature range from 145 °c to 200 °c, there is probably a value at which the effect of temperature begins to prevail over the effect of film thickness on the crystallization of sb2te samples. all the samples were characterized by the same predominant crystallographic orientations, which was determined by electron diffraction data and observed zap – [1̅11], [001], [2̅25], [22̅1], [122]. according to the interpretation of the electron diffraction patterns, the substance crystallized in a phase isomorphic to that of antimony. this phenomenon is characteristic of chalcogenide compounds. in the case of antimony-based materials, this is usually the antimony phase. here, this phase’s lower crystallization temperature https://doi.org/10.15826/chimtech.2023.10.1.11 chimica techno acta 2023, vol. 10(1), no. 202310111 article 5 of 7 doi: 10.15826/chimtech.2023.10.1.11 may have an effect [28]. the percentage of elements can also play a role. such is the case for bi–sb films with a predominance of bismuth, which crystallize in the bismuth phase [29]. this may mean that there is a lower sb–sb binding energy (similar to in–sb [30]), although other factors may be responsible. an amorphous sb2te film was exposed to a focused electron beam in a microscope column (figure 5). the exposure was carried out for 1 min at an accelerating voltage of 200 kv and a beam of maximum intensity (without considering the diaphragms in the tem column). the current density on the sample was about 10 ma/m2. as a result, in the initially amorphous film (figure 5a), a polycrystalline region with a diameter of about 1 μm was formed (figure 5b, c). an increase in the size of crystallites in the radial direction from the center was observed. examination of the obtained ring electron diffraction pattern (figure 6, table 1) revealed crystallization in the antimony phase. a number of weak reflections in the electron diffraction pattern (table 1, nos. 10–13) were not correlated with antimony, tellurium or antimony telluride phases. they correspond to small interplanar distances, no data on which are available for these substances from the databases of astm x-ray diffraction analysis. 4. limitations for further studies, it is necessary to prepare a series of samples with a fixed annealing temperature step. a more accurate assessment of the thermal effect on the sample of the tem electron beam will also be useful. the currently available equipment also allows simultaneous exposure to an electron beam and heating of the sample substrate in situ. figure 6 electron diffraction pattern of the area exposed to an electron beam in the sb2te sample. white arcs with three-digit indices indicate ring reflections associated with the antimony phase; the arcs numbered 10–13 denote unidentified reflections. see table 1 for the measurement and indication results. 5. conclusions due to annealing, the samples crystallized from the amorphous state. in gradient sb2te samples subjected to vacuum annealing, crystallization is observed to depend both on the film thickness and temperature. as the thickness of the sample increases, the size of the crystals growing in the film enlarges. as the temperature increases, the number of crystals in the film grows. also, with increasing temperature, the thickness at which crystallization is possible decreases. during thermal crystallization, the processes of nucleation and crystal growth proceed competitively. no spontaneous crystallization was observed in the graded sb2te samples. figure 5 tem of a section of an amorphous film before exposure to an electron beam (a); tem of the area after exposure to a focused electron beam (b); crystal structure grown in an amorphous matrix under the action of a beam (c); electron diffraction pattern from the structure in figure 5c (d). (a) https://doi.org/10.15826/chimtech.2023.10.1.11 chimica techno acta 2023, vol. 10(1), no. 202310111 article 6 of 7 doi: 10.15826/chimtech.2023.10.1.11 table 1 identification of antimony phase reflections on the ring electron diffraction pattern from a sb2te sample after exposure to an electron beam (figure 6). no. of ring d, 1/nm dmeasured, å observed intensity, % dtheor, å intensity theor., % hkl 1 9.43 2.12 100 2.15 37 110 2 11.3 1.77 5 1.77 19 202 3 14.92 1.34 5 1.37 16 122 4 16.45 1.22 40 1.24 6 300 5 18.9 1.06 30 1.08 4 220 6 19.87 1.01 10 1.02 7 4–12 7 22.07 0.91 10 0.92 3 042 8 24.01 0.83 10 0.82 9 –254 9 24.95 0.8 30 0.8 4 235 10 28.12 0.71 5 11 28.71 0.7 5 12 30.5 0.66 5 13 33.82 0.59 5 crystallization occurred during thermal annealing or exposure to a tem beam. all the samples crystallized in a phase isomorphic to that of antimony. the character of crystallization of a magnetron-sputtered sb2te film via a maximum intensity beam differs significantly from that in thermal crystallization. crystallization under the action of an electron beam is characterized by the formation of polycrystalline regions according to the nucleation mechanism. in contrast to single crystals, a polycrystalline region is formed corresponding to the area of the beam impact. in the center of the region with a diameter of about 300 nm, where the highest intensity of the tem beam was achieved, crystallites up to tens of nanometers in size are observed. this points to the nucleation mechanism of crystallization, i.e., the simultaneous nucleation of many neighboring crystallization centers. outside the central region, much larger crystallites are visible, hundreds of nanometers in size, elongated in the radial direction from the center of the crystallization region. this points to the growth crystallization mechanism, i.e., the growth of the crystalline phase from individual crystallization centers located along the nucleation region’s outer edge. ● supplementary materials no supplementary materials are available. ● funding this work was supported by russian foundation for basic research (grant no. 20-02-00906), www.rfbr.ru/rffi/eng. financial support was provided by the public task of the ministry of science and higher education feuz 2023-0020. ● acknowledgments the authors are grateful to professor m. wüttig for providing the samples for the study. ● author contributions conceptualization: v.yu.k., a.a.y. data curation: a.a.y. formal analysis: a.a.y. funding acquisition: v.yu.k. investigation: a.a.y. methodology: v.yu.k., a.a.y. project administration: v.yu.k. supervision: v.yu.k. validation: v.yu.k. visualization: a.a.y. writing – original draft: a.a.y. writing – review & editing: a.a.y. ● conflict of interest the authors declare no conflict of interest. ● additional information author ids: anton a. yushkov, scopus id 57193951559; vladimir yu. kolosov, scopus id 7005960289. website: ural federal university, https://urfu.ru/en. references 1. xiao z, 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https://www.sciencedirect.com/science/article/abs/pii/s0040609016304072 https://www.sciencedirect.com/science/article/abs/pii/s0040609012011492 https://researchain.net/papers/10z99z1016w99wjz99zceramintz99z2019z99z08z99z116 https://www.sciencedirect.com/science/article/abs/pii/s0169433220327161 https://www.sciencedirect.com/science/article/abs/pii/s0921510718300266 https://doi.org/10.1016/j.jcrysgro.2016.03.012 https://www.sciencedirect.com/science/article/abs/pii/s0169433219324511 https://www.sciencedirect.com/science/article/abs/pii/s0009261415003115 https://www.sciencedirect.com/science/article/abs/pii/s1359646219302921 https://www.sciencedirect.com/science/article/abs/pii/s0169433220324600 https://www.sciencedirect.com/science/article/abs/pii/s0925838819347450 https://www.sciencedirect.com/science/article/abs/pii/s0925838816300366 https://www.sciencedirect.com/science/article/abs/pii/s1359646220306618 https://onlinelibrary.wiley.com/doi/10.1002/pssb.19630030406 https://aip.scitation.org/doi/10.1063/1.1690112 https://www.sciencedirect.com/science/article/abs/pii/s0304399108001757 https://www.sciencedirect.com/science/article/abs/pii/s092150930601608x https://onlinelibrary.wiley.com/doi/abs/10.1002/pssr.201004515 novel co-doped protonic conductors bala1.9sr0.1in1.95m0.05o6.925 with layered perovskite structure published by ural federal university eissn 2411-1414 chimicatechnoacta.ru article 2023, vol. 10(2), no. 202310206 doi: 10.15826/chimtech.2023.10.2.06 1 of 7 novel co-doped protonic conductors bala1.9sr0.1in1.95m0.05o6.925 with layered perovskite structure anzhelika bedarkova * , nataliia tarasova , irina animitsa , ekaterina abakumova, irina fedorova, polina cheremisina, evgenia verinkina institute of hydrogen energy, ural federal university, ekaterinburg 620009, russia * corresponding author: a.o.galisheva@urfu.ru this paper belongs to a regular issue. abstract active development of electrochemical devices such as proton-conducting fuel cells and electrolyzers should ensure sustainable environmental development. an electrolyte material of a hydrogen-powered electrochemical device must satisfy a number of requirements, including high proton conductivity. layered perovskites are a promising class of proton-conducting electrolytes. the cationic co-doping method has been successfully applied to well-known proton conductors with the classical perovskite structure abo3. however, the data on the application of this method to layered perovskites are limited. in this work, the bilayer perovskites bala1.9sr0.1in1.95m0.05o6.925 (m = mg2+, ca2+) were obtained and investigated for the first time. cationic co-doping increases oxygen-ion and proton conductivity values. keywords layered perovskite oxygen-ion conductivity proton conductivity hydrogen energy ruddlesden-popper structure received: 20.03.23 revised: 06.04.23 accepted: 06.04.23 available online: 11.04.23 key findings ● cationic co-doping leads to an increase in proton conductivity of bala2in2o7 values of up to ~0.8 orders of magnitude. ● the cationic co-doping strategy is a promising way to improve the transport properties of bilayer perovskites. © 2023, the authors. this article is published in open access under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). 1. introduction electrochemical devices such as proton-conducting fuel cells [1–3] and electrolyzers [4, 5] are in dire need of highly efficient materials with targeted properties including proton conductivity [6–8]. active development and implementation of these devices as a part of the “hydrogen energy in everyday life” strategy should ensure sustainable environmental development [9–16]. the electrolyte material of a hydrogen-powered electrochemical device must satisfy a number of requirements, including high proton conductivity. one of the known ways to improve the conductivity is by co-doping of cationic sublattices of complex oxides. this method has been successfully applied to well-known proton conductors such as barium cerate-zirconates [17–22] and lanthanum scandates [23–26]. at the same time, the possibility of applying this method to a new class of proton-conducting materials, such as layered perovskites aa′nbno3n+1 [27], is currently under investigation. the possibility of oxygen-ion transport in the monolayer perovskites aa′bo4 was opened about ten years ago by fujii et al. for compositions based on bandino4 [28–32] and by troncoso et al. for compositions based on srlaino4 [33–35]. the realisation of proton transport in the layered structures was demonstrated several years later for compositions based on balaino4 [36]. currently, a large class of materials with the monolayer perovskite structure ba(sr)la(nd)in(sc)o4 [37–41] is described in terms of proton transport. the possibility of proton conductivity in bilayer aa′2b2o7 perovskites such as on bala2in2o7 [42–44], band2in2o7 [45] and srla2sc2o7 [46] and compositions based on them was described last year. it was shown that doping cationic sublattices can improve oxygen-ion and proton conductivity by up to 1.5 orders of magnitude [12]. it can be predicted that codoping can also promote an increase in conductivity. in this work, we performed acceptor sr2+→la3+ and m2+→in3+ (m = mg2+, ca2+) co-doping in the cationic sublattices of the bilayer perovskite bala2in2o7. the doping effect on the proton conductivity was revealed. http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2023.10.2.06 http://creativecommons.org/licenses/by/4.0/ https://orcid.org/0000-0003-4346-5644 https://orcid.org/0000-0001-7800-0172 https://orcid.org/0000-0002-0757-9241 https://crossmark.crossref.org/dialog/?doi=https://doi.org/10.15826/chimtech.2023.10.2.06&domain=pdf&date_stamp=2023-04-11 chimica techno acta 2023, vol. 10(2), no. 202310206 article 2 of 7 doi: 10.15826/chimtech.2023.10.2.06 2. experimental the compositions bala1.9sr0.1in1.95mg0.05o6.925 and bala1.9sr0.1in1.95ca0.05o6.925 were prepared by the solid state method. the powders of the starting reagents baco3, srco3, caco3, mgo, la2o3, in2o3 were dried and used in stoichiometric amounts. the agate mortar was used for grinding. the compositions were heated after each grinding. the annealing was carried out in the temperature range of 800– 1300 °c with 100 °c steps and 24 h dwell time at each step. the phase identification of the obtained compositions was carried out using the bruker advance d8 cu kα diffractometer. the scanning electron microscope vega3 tescan was used to define the morphology of the samples. the thermogravimetric and mass spectrometric investigations were carried out using the netzsch sta 409 pc analyser equipped with the netzsch qms 403c aëolos mass spectrometer. initially hydrated samples were used. the hydrated samples were obtained by slow cooling from 1100 to 150 °c (1 °c /min) under a flow of wet ar. the ceramic samples were prepared for the electrical properties studies. the powders were pressed into pellets and then sintered at 1300 °c for 24 h in dry air. the pellets had a relative density of ~92% (the density of the sintered samples was determined by the archimedes method). the electrical conductivity was measured with an impedance spectrometer z-1000p, elins, rf. the investigations were carried out from 1000 to 200 °c at a cooling rate of 1o/min under dry air or dry ar. the dry gas (air or ar) was prepared by circulating the gas through p2o5 (ph2o = 3.5·10−5 atm). the wet gas (air or ar) was obtained by bubbling the gas at room temperature first through distilled water and then through a saturated solution of kbr (ph2o = 2·10−2 atm). 3. results and discussions the phase attestation of the obtained compositions bala1.9sr0.1in1.95mg0.05o6.925 and bala1.9sr0.1in1.95ca0.05o6.925 was made using the x-ray diffraction method. the results of the le bail analysis of the xrd-data are presented in figure 1. both samples are single phase and have orthorhombic symmetry with p42/mnm space group. the introduction of bigger ions (sr2+) into la3+-sublattice (𝑟la3+ = 1.216 å, rsr2+ = 1.31 å, 𝑟in3+ = 0.8 å, 𝑟ca2+ = 1.0 å, 𝑟mg2+ = 0.72 å [47]) leads to an increase in the lattice parameter (table 1). however, the additional introduction of mg2+ and ca2+ ions into the in3+ sublattice (co-doping) leads to a small decrease in the c lattice parameter and unit cell volume. the most probable reason for this is the local distortion of the crystal lattice due to the presence of several different cations in the cationic sublattices. in addition, the appearance of oxygen vacancies in the crystal lattice during acceptor doping also contributes to the distortion: 2sro la2o3 → 2srla ′ +2oo × +vo •• (1) 2ca(mg)o in2o3 → 2ca(mg)in ′ +2oo × +vo •• (2) morphological analysis of the powder samples was carried out using scanning electron microscopy (sem). the diameter of the grains was about ~2–5 μm (figure 2). the typical eis-plots are presented in figure 3. the conductivity values were calculated using resistance values taken at the intersection of the high-frequency semicircle with the abscissa axis. the capacitance values for these semicircles was ~ 10–12 f/cm, which corresponds to the resistance of the grain volume of the polycrystalline sample. figure 1 the results of xrd investigations for the compositions bala1.9sr0.1in1.95mg0.05o6.925 (a) and bala1.9sr0.1in1.95ca0.05o6.925 (b). 10 20 30 40 50 60 70 80 90 (a) 5 000 bala 1.9 sr 0.1 in 1.95 mg 0.05 o 6.925 15 000 10 000 2  in te n si ty 0 10 20 30 40 50 60 70 80 90 (b) 5 000 bala 1.9 sr 0.1 in 1.95 ca 0.05 o 6.925 15 000 10 000 2  in te n si ty 0 https://doi.org/10.15826/chimtech.2023.10.2.06 https://doi.org/10.15826/chimtech.2023.10.2.06 chimica techno acta 2023, vol. 10(2), no. 202310206 article 3 of 7 doi: 10.15826/chimtech.2023.10.2.06 table 1 lattice parameters, unit cell volume and water uptake for the investigated compositions. composition a, b (å) c (å) vcell (å 3) water uptake (mol) bala2in2o7 5.914(9) 20.846(5) 729.33(6) 0.17 bala1.9sr0.1in2o6.95 [42] 5.916(3) 20.870(4) 730.51(8) 0.18 bala1.9sr0.1in1.95mg0.05o6.925 5.916(3) 20.849(5) 729.78(6) 0.17 bala1.9sr0.1in1.95ca0.05o6.925 5.916(4) 20.852(0) 729.89(9) 0.17 figure 2 sem result for the composition bala1.9sr0.1in1.95ca0.05o6.925 figure 3 the eis plots for the composition bala1.9sr0.1in1.95ca0.05o6.925 obtained at 400 °c, 420 °c and 440 °c in dry air (a), and at 400 °c in dry and wet air (b). the temperature dependences of the conductivity obtained under dry/wet air/ar are presented in figure 4a and figure 4b for the compositions bala1.9sr0.1in1.95mg0.05o6.925 and bala1.9sr0.1in1.95ca0.05o6.925, respectively. as can be seen, the conductivity values under dry ar (po2 ~ 10−5 atm) are lower than under dry air (po2 = 0.21 atm), indicating the hole contribution to the electrical conductivity: vo •• +1 2⁄ o2 ⇔ oo × +2h• (3) the increase in water partial pressure leads to an increase in the conductivity values due to the formation of proton charge carriers: h• +1 2⁄ h2o+oo × ⇔ 1 4⁄ o2 +(oh)o • . (4) vo •• +h2o+oo × ⇔ 2(oh)o • . (5) it should be noted that the conductivity values under wet air and wet ar are very close at low temperatures, indicating the dominance of ion (proton) conductivity. figure 5 represents the comparison of the conductivity values for the co-doped compositions bala1.9sr0.1in1.95mg0.05o6.925 and bala1.9sr0.1in1.95ca0.05o6.925 compositions with undoped bala2in2o7 and only sr-doped bala1.9sr0.1in2o6.95 compositions. as can be seen, co-doping leads to an increase in conductivity of up to one order of magnitude. the conductivity values increase in the bala2in2o7 − bala1.9sr0.1in1.95mg0.05o6.925 − bala1.9sr0.1in1.95ca0.05o6.925 − bala1.9sr0.1in2o6.95 series, which correlates with the increase in the lattice parameter and unit cell volume. the activation energy values for the oxygen-ion and proton conductivities were calculated and are presented in table 2. as can be seen, the activation energy of the oxygenion conductivity of the co-doped compositions bala1.9sr0.1in1.95mg0.05o6.925 and bala1.9sr0.1in1.95ca0.05o6.925 is lower than for undoped bala2in2o7 and only sr-doped bala1.9sr0.1in2o6.95 compositions. a more detailed study of these samples is required to explain this fact. table 2 activation energy values for the oxygen-ion and proton conductivities for the investigated compositions. composition ea for o 2–(ev) ea for h +(ev) bala2in2o7 0.80 0.63 bala1.9sr0.1in2o6.95 [42] 0.80 0.57 bala1.9sr0.1in1.95mg0.05o6.925 0.72 0.75 bala1.9sr0.1in1.95ca0.05o6.925 0.77 0.75 0 5 10 15 20 25 30 0 5 10 15 20 25 30 -z '' , k  z', k (a) bala 1.9 sr 0.1 in 1.95 ca 0.05 o 6.925 1 khz 100 khz1000 khz 440 o c 420 o c 400 o c dry air 0 5 10 15 20 25 30 0 5 10 15 20 25 30 (b) -z '' , k  z', k bala 1.9 sr 0.1 in 1.95 ca 0.05 o 6.925 wet 400 o c dry https://doi.org/10.15826/chimtech.2023.10.2.06 https://doi.org/10.15826/chimtech.2023.10.2.06 chimica techno acta 2023, vol. 10(2), no. 202310206 article 4 of 7 doi: 10.15826/chimtech.2023.10.2.06 figure 4 the temperature dependences for the compositions bala1.9sr0.1in1.95mg0.05o6.925 (a) and bala1.9sr0.1in1.95ca0.05o6.925 (b). figure 5 the temperature dependences of electrical conductivity for the compositions bala2in2o7, bala1.9sr0.1in1.95mg0.05o6.925, bala1.9sr0.1in1.95ca0.05o6.925, bala1.9sr0.1in2o6.95 [42] in dry air (a), dry ar (b), wet air (c), wet ar (d). https://doi.org/10.15826/chimtech.2023.10.2.06 https://doi.org/10.15826/chimtech.2023.10.2.06 chimica techno acta 2023, vol. 10(2), no. 202310206 article 5 of 7 doi: 10.15826/chimtech.2023.10.2.06 it should be noted that the co-doped bala1.9sr0.1in1.95mg0.05o6.925 and bala1.9sr0.1in1.95ca0.05o6.925 compositions contain 50% more oxygen vacancies than the bala1.9sr0.1in2o6.95 composition. we can conclude that the change in the geometric characteristic of the unit cell volume has the most significant effect on the conductivity value than a change in the concentration of oxygen vacancies. the temperature dependences of the proton conductivities, calculated as the difference between the ionic conductivity under wet conditions (wet ar) and dry conditions (dry ar), are presented in figure 6. the values of the activation energy of the proton conductivity calculated from figure 6 are given in table 2. the activation energy decreases from 0.63 ev for the undoped bala2in2o7 composition to 0.57 ev for the bala1.9sr0.1in2o6.95 composition by introducing only strontium as a dopant. interestingly, co-doping leads to a decrease in the values of the activation energy of proton conduction. the same regularity of increase in conductivity values for the doped compositions is observed. the values of the proton concentrations are required for the correct analysis of these dependences. figure 7 shows the results of thermogravimetry (tg), mass spectrometry (ms) and differential scanning calorimetry (dsc) analysis for the bala1.9sr0.1in1.95ca0.05o6.925 composition. mass loss occurs at the temperatures below 700 °c (tg curve) and is solely due to the release of water (ms(h2o) curve). the values of water uptake are close for all doped bala1.9sr0.1in1.95m0.05o6.925 (m = mg, ca), bala1.9sr0.1in2o6.95 and undoped bala2in2o7 compositions and are about ~ 0.17−0.18 mol of water per formula unit (table 1). in other words, the proton concentration (𝑐h+) is close for all compositions. consequently, the increase in proton conductivity (𝜎h+) x is due to the increase in proton mobility (𝜇h+): 𝜎h+ = 𝑧 ∙𝑒 ∙ 𝜇h+ ∙ 𝑐h+. (6) we conclude that co-doping positively affects the ionic conductivity of bala2in2o7. an increase in lattice parameters leads to facilitation of oxygen-ion transport, which, in turn, leads to an increase in oxygen-ion conductivity. at the same time, co-doping also leads to an increase in proton conductivity, probably due to an increase in proton mobility. the proton conductivity values for co-doped compositions are 2.9∙10−6 s/cm and 5.4∙10−6 s/cm at 400 °c for the compositions bala1.9sr0.1in1.95mg0.05o6.925 and bala1.9sr0.1in1.95ca0.05o6.925, respectively. the comparison of the electrical conductivity values obtained in wet air for the undoped bala2in2o7, monodoped bala1.9sr0.1in2o6.95 and co-doped bala1.9sr0.1in1.95m0.05o6.925 (m = mg, ca) compositions with known proton conductors such as doped barium and strontium ceramics is shown in figure 8. the conductivity of the studied compositions under wet conditions is lower than that of doped barium and strontium cerates. nevertheless, acceptor doping can increase conductivity values by up to ⁓1.5 orders of magnitude. figure 6 the temperature dependences of protonic conductivity for the compositions bala2in2o7, bala1.9sr0.1in1.95mg0.05o6.925, bala1.9sr0.1in1.95ca0.05o6.925, bala1.9sr0.1in2o6.95 [42] figure 7 the results of tg, dsc and ms(h2o) investigations for the composition bala1.9sr0.1in1.95ca0.05o6.925. figure 8 the temperature dependences of conductivity obtained in wet air for compositions bala1.9sr0.1in2o6.95 [42], bala1.9sr0.1in1.95mg0.05o6.925, bala1.9sr0.1in1.95ca0.05o6.925, bala2in2o7, baceo3 (10 mol.% y2o3) [48], srceo3(10 mol.% y2o3) [48] https://doi.org/10.15826/chimtech.2023.10.2.06 https://doi.org/10.15826/chimtech.2023.10.2.06 chimica techno acta 2023, vol. 10(2), no. 202310206 article 6 of 7 doi: 10.15826/chimtech.2023.10.2.06 4. limitations firstly, we have some limitations in the measurement of electrical conductivity. the maximum frequency measured with the elins z-1000p impedance spectrometer is 1000 khz. the measurement of the conductivity at higher frequencies will give a more accurate representation of the eis-plots at t > 500 oc. secondly, a full explanation of the activation energy values obtained for co-doped compositions is difficult at this stage of the study. for the bala2in2o7 composition, which is co-doped in the a and b sublattices, a more detailed study of the ion transport mechanisms is required. thirdly, doping the bala2in2o7 composition leads to an increase in electrical conductivity of up to 1.5 orders of magnitude. however, the conductivity of the compositions studied in this article is lower than that of doped barium and strontium ceramics. 5. conclusions in this paper, we performed acceptor sr2+→la3+ and m2+→ in3+ (m = mg2+, ca2+) co-doping in the cationic sublattices of the bilayer perovskite bala2in2o7. the bilayer perovskites bala1.9sr0.1in1.95mg0.05o6.925 and bala1.9sr0.1in1.95ca0.05o6.925 were obtained and investigated for the first time. the phase attestation, morphology, possibility of water uptake and electrical conductivity were investigated and discussed. the doping effect on the oxygenion and proton conductivity was revealed. it was shown that cationic co-doping leads to an increase in proton conductivity values of up to ~0.8 orders of magnitude. ● supplementary materials none. ● funding the research funding from the ministry of science and higher education of the russian federation (ural federal university program of development within the priority2030 program) is gratefully acknowledged. ● acknowledgments none. ● author contributions conceptualization: n.t., i.a. data curation: a.b., n.t. methodology: n.t., i.a. investigation: a.b., e.a., i.f., p.c., e.v. validation: a.b., n.t. visualization: a.b., e.a., n.t. writing – original draft: n.t. writing – review & editing: n.t., a.b., ● conflict of interest the authors declare no conflict of interest. ● additional information author ids: natalia tarasova, scopus id 37047923700; 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https://doi.org/10.1039/d0ta11573h https://doi.org/10.3390/ma15010114 https://doi.org/10.15826/elmattech.2022.1.004 https://doi.org/10.3390/ijms232112813 https://doi.org/10.3390/inorganics10100161 https://doi.org/10.3390/pr10122536 https://doi.org/10.1016/j.ijhydene.2022.11.172 https://doi.org/10.3390/ma15248867 https://doi.org/10.1107/s0567739476001551 https://doi.org/10.1146/annurev.matsci.33.022802.09182 glucose-assisted polyol synthesis of silver nanoplates and nanoprisms in the presence of oxyethylated carboxylic acid published by ural federal university eissn 2411-1414; chimicatechnoacta.ru letter 2022, vol. 9(3), no. 20229309 doi: 10.15826/chimtech.2022.9.3.09 1 of 4 glucose-assisted polyol synthesis of silver nanoplates and nanoprisms in the presence of oxyethylated carboxylic acid alexander a. titkov , tatiana a. borisenko, olga a. logutenko * institute of solid state chemistry and mechanochemistry sb ras, novosibirsk 630128, russia * corresponding author: ologutenko@solid.nsc.ru this paper belongs to the ctfm'22 special issue: https://www.kaznu.kz/en/25415/page. guest editors: prof. n. uvarov and prof. e. aubakirov. © 2022, the authors. this article is published in open access under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). abstract this work reports a simple route to synthesizing silver nanoplates and nanoprisms through a polyol approach in the presence of oxyethylated carboxylic acid and glucose. the resulting particles were characterized by electron microscopy and x-ray diffraction (xrd). the introduction of glucose and naoh into the system substantially increases the yield of nanoplates and reduces their thickness. the optimized reaction conditions can be used to produce, in a one-pot synthesis, silver nanoplates and nanoprisms which may have applications as metallic fillers in ink and paste formulations for 2d and 3d printing to fabricate functional components and devices. keywords silver nanoprisms ethylene glycol glucose reduction received: 24.06.22 revised: 21.07.22 accepted: 21.07.22 available online: 03.08.22 key findings ● glucose promotes the formation of silver nanoplates and nanoprisms at room temperature and increases their yield. ● the silver nanoplates change the shape to nanoprisms with increasing temperature. ● in the presence of naoh, the yield of plate-like structures and their aspect ratios increase. 1. introduction over the last few decades, due to the increasing number of applications, conductive inks, pastes and adhesives for flexible printed electronics have received much attention [1, 2]. the metals most commonly used in the ink formulations are silver, copper, nickel, gold, aluminum and zinc. however, silver is the best choice for electrically conductive inks, pastes and adhesives because of its high electrical and thermal conductivity, chemical stability and the ability of its oxide form to show good conductivity [3]. silver nanoplates and nanoprisms, a new class of nanostructures with two-dimensional anisotropy, have been of special interest for the applications in sensors and diagnostics because of their structure, optical, electronic, and catalytic properties that are generally superior to those of spherical nanoparticles of a comparable size [4, 5]. it was also shown that, after printing the inks based on non-spherical silver particles onto plastic substrates and subsequent annealing, the resultant ag patterns are more uniform and show a lower resistivity and improved mechanical properties as compared to those of similar patterns prepared from spherical particles [6]. different chemical and physical techniques are used to prepare silver particles, including chemical reduction of the silver ions in various media, various types of irradiation and electrochemical processes as well as solvothermal and polyol methods, etc. [7]. one of the most common solution-phase approaches to producing micrometerand nanometer-scale silver particles is the polyol process in which the polyol acts both as the solvent and reducing agent. the advantages of the polyol process are that it is low-cost, easy to use, and scalable. it also allows control of the particles size and shape by varying reaction conditions, such as temperature, reduction time, the reagent concentrations, and type of stabilizer, resulting in the formation of different morphologies [4, 8]. among other ag anisotropic nanoparticles, triangular prisms and plate-like nanostructures are being extensively investigated [9]. the formation of anisotropic shapes is not thermodynamically favored; that is why, in order to promote anisotropic growth of silver nanocrystals, the use of structure-directing agents, which can selectively adsorb on different crystal facets, is required. in most of the reported methods, citrate and poly(vinylpyrrolidone) (pvp) http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2022.9.3.09 https://orcid.org/0000-0003-0835-9985 https://orcid.org/0000-0003-1523-5446 mailto:ologutenko@solid.nsc.ru http://creativecommons.org/licenses/by/4.0/ https://crossmark.crossref.org/dialog/?doi=https://doi.org/10.15826/chimtech.2022.9.3.09&domain=pdf&date_stamp=2022-8-3 chimica techno acta 2022, vol. 9(3), no. 20229309 letter 2 of 4 have been widely used as capping agents to induce the formation of silver anisotropic particles [10]. xue et al. reported [11] that citrate ions both reduced silver ions and helped the formation of plate-structured ag nanoparticles. zhang et al. found that the list of ligands with selective adhesion to ag (111) facets can be expanded from citrate to many other diand tricarboxylate compounds [12]. in contrast to citrate, pvp binds more strongly to the (100) than (111) facet [13] and this selectively leads to the formation of ag nanocubes. in addition to citrate and pvp, several other capping agents used to obtain anisotropic structures of silver have also been reported in the literature. thus, in the presence of br− ions, the formation of silver nanocubes, rectangular nanobars, and octagonal nanorods is induced [14]. silver microplates, with average edge length of about 1.5 µm and a thickness of 100 nm, were synthesized in the presence of n-octanol playing an important role in the formation of the plate-like structure [15]. xiong et al. prepared silver nanoplates with a triangular or hexagonal shape by introducing polyacrylamide (pam) when reducing silver nitrate with ethylene glycol [16]. however, it is worth noting that the number of facet-selective capping agents which could be successfully used to prepare silver structures with different shapes is very limited. herein, we report the results of the study on the reduction of silver ions with ethylene glycol in the presence of 2-[2-(2-methoxyethoxy)ethoxy]acetic acid (meeaa) and glucose aiming to develop a simple method to prepare silver nanoplates. the proposed method has advantages in terms of both cost and ease of implementation; it does not require unique and expensive equipment and can be used for large-scale production of silver powders. 2. experimental 2.1. reagents silver nitrate (agno3), 99.9% purity grade, soyuzkhimprom, russia), 2-[2-(2-methoxyethoxy)ethoxy] acetic acid (c7h14o5, meeaa) of 95% purity grade (sigma aldrich, usa), ethylene glycol (ho(ch2)2oh, eg) of 99.9% purity grade, 95% pure ethanol supplied by khimmed (russia), and sodium hydroxide (naoh, 50% aqueous solution) were used as received without further purification. 2.2. synthesis of silver particles the reduction of of silver nitrate was carried out as follows. an appropriate amount of meeaa was dissolved in 25 ml of ethylene glycol, and then a stoichiometric amount of sodium hydroxide was added to the solution under stirring. silver nitrate was dissolved in ethylene glycol and added to a solution of the sodium salt of meeaa in ethylene glycol under constant stirring. after stirring for 5 min, the mixture was heated to the required temperature, followed by the addition of a solution of glucose in ethylene glycol. after the reaction was complete, the mixture was air-cooled and the supernate was decanted. the resulting precipitate was washed three times with ethanol to remove the impurities and then it was dried in air at room temperature. 2.3. characterization x-ray diffraction (xrd) patterns were recorded on a d8 advance powder x-ray diffractometer equipped with a 1d lynx-eye detector and ni-filtered сu kα radiation (0.02° 2θ step size and an accumulated time per step of 35.4 s). phase identification was carried out using powder diffraction file (pdf) databases (icdd, release 2001). analysis of the samples by transmission electron microscopy (tem) was performed using a jem 2010 electron microscope (jeol, japan) operating at 200 kv and having a resolution of 0.14 nm. study of the samples by high-resolution scanning electron microscopy (sem) was performed using a tescan scanning electron microscope (czech republic). 3. results and discussion our earlier study showed [17] that the reduction of silver ions with ethylene glycol in the presence of the sodium salt of meeaa proceeds extremely slowly and leads to the formation of silver nanoparticles of 2–5 nm in size with a very low yield. an increase in the temperature up to 40 °c resulted in the formation of triangular and hexagonal silver nanoplates with edge lengths ranging from 100 to 200 nm and with a thickness of approximately 30 nm, but their yield was too low. a further increase in the temperature to 60–100 °c produced a sample containing irregularly shaped polyhedrons and a very small fraction of plates. in the present study, we attempted to produce ag nanoplates with controlled shapes in high yields by adding glucose in the polyol synthesis. as shown in this study, the addition of glucose (glu) in the synthesis of silver nanoparticles in a mixture of ethylene glycol and sodium salt of meeaa (nar) affects the yield of silver nanoplates. thus, at an ag+:nar:glu molar ratio of 1:3:2 at a temperature of 30 °c and a synthesis time of 72 h, the yield of plates was 57%, and their size and thickness were 240 and 40 nm, respectively (figure 1a). it should be noted that, under similar conditions but at a lower ag+ to glu molar ratio of 1:1, the final product contained 40% of the plates, with mean sizes of 170 nm in edge length and 25 nm in thickness, while the remaining 60% were polyhedral shaped silver nanoparticles. therefore, a decrease in the glucose content in the system decreases the yield of nanoplates, their length and thickness. at a molar ratio of glucose to silver of 1:4, under the same conditions, the final product contained 60% of plates with an edge length of 130 nm and a thickness of 40 nm, while the remaining 40% of silver nanoparticles were polyhedra (figure 1b). a further increase in the ratio of ag+:glu to 1:6 led to a decrease in the nanoplate yield to 50%. the average thickness of these nanoplates was found to be approximately 30 nm, while their edge length was around 200 nm. chimica techno acta 2022, vol. 9(3), no. 20229309 letter 3 of 4 it is known [18] that, as ph increases, the value of the redox potential of glucose decreasese, which means that, in an alkaline solution, its ability to donate electrons increases. as raveendran et al. reported [19], the reason for this is that the base facilitates the opening of the glucose ring by the abstraction of the α-proton of the sugar ring oxygen and thereby speeds up both the oxidation of glucose to gluconic acid and the reduction of silver ions to silver atoms. gluconic acid, the glucose derivative resulting from its oxidation, was reported to form a dense coating on the surface of nanoparticles, thereby stabilizing them [20]. in the presence of naoh, the reduction reaction can proceed according to equation (1): ch2oh(choh)4cho + 2ag+ + 2oh− → ch2oh(choh)4cooh + 2ag↓ + h2o (1) in order to promote the formation of plate-like structures, it was of interest to investigate the effect of alkali on the reduction of silver ions in ethylene glycol in the presence of glucose. in the synthesis, which was conducted at 30 °c and at an ag+:nar:glu of 1:3:2, with the molar ratio of ag to naoh equal to 1:0.1 in the reaction mixture, an increase in the nanoplate yield to 70% was observed. the average edge length of the nanoplates and their thickness were 159.7±68.2 and 25 nm, respectively (figure 2a). therefore, in the presence of naoh, the yield of plate-like structures and their aspect ratios were higher than that obtained from the reduction in the absence of naoh. it should be noted that an increase in the glucose concentration in the reaction system did not lead to any further increase in the nanoplate yield, and it remained at 60%. the effect of temperature on the morphology of silver particles formed in the presence of glucose wasstudied. it was shown that an increase in temperature from 30 °c to 40 °c led to an increase in the thickness of the silver plates (figure 2b). thus, at an ag+:nar:glu molar ratio of 1:3:2, uniform nanoprisms are formed with an edge size of about 150 nm and a thickness of about 70 nm. the reaction yield of the silver nanoprisms was 90%. under similar conditions but at a lower ag+ to glu molar ratio of 1:1, the yield of the silver nanoplates and their thickness also tend to increase as compared to those formed at 30 °c. thus, as the temperature is increased, the ag nanoplates become thicker and are finally transformed into nanoprisms. the same trend was observed to take place when reducing silver ions with ethylene glycol in the presence of the sodium salt of meeaa alone [22]. the x-ray diffraction (xrd) pattern of the sample prepared under these conditions is shown in figure 3. as seen, it has four diffraction peaks at 2θ = 38.08°, 44.26°, 64.36°, and 77.52° attributed, respectively, to the diffraction from the {111}, {200}, {220}, and {311} planes of the face-centered cubic (fcc) lattice of silver (jcpds, card no. 01-071-4613). 4. conclusions triangular and hexagonal silver nanoplates were synthesized by reduction of silver ions with ethylene glycol in the presence of 2-[2-(2-methoxyethoxy)ethoxy]acetic acid (meeaa) and glucose. compared with meeaa alone, adding glucose promotes the synthesis of silver nanoplates and nanoprisms at room temperature and increases their yield. when the temperature is increased, the silver nanoplates were found to undergo a shape transformation to nanoprisms. the addition of naoh to the reaction mixtures increases the yield of plate-like structures and their aspect ratios. the proposed method does not require unique and expensive equipment; it is low-cost and can be used for large-scale production of silver powders. figure 1 micrographs of the silver nanoparticles prepared in the presence of glucose. ag+:nar = 1:3, т = 30 °с, τ = 72 h; ag+:glu = 1:2 (a) and 1:4 (b). figure 2 micrographs of the silver nanoparticles prepared in the presence of glucose. effect of ph (a) and temperature (b) on the size of silver nanoplates. ag+:nar:glu = 1:3:2, t = 30 °c (a) and 40 °c (b), τ = 72 h; ag:naoh = 1:0.1 (a) and 1:0 (b). figure 3 x-ray diffraction pattern of the silver nanoparticles prepared in the presence of glucose. ag+:nar:glu = 1:3:2, т = 30 °с, τ = 72; ag+:naoh = 1:0.1. chimica techno acta 2022, vol. 9(3), no. 20229309 letter 4 of 4 supplementary materials no supplementary materials are available. funding the research was funded within the state assignment to isscm sb ras (project no. 122032900069-8). acknowledgments none. author contributions conceptualization: a.i.t. data curation: a.i.t., t.a.b., o.a.l. formal analysis: a.i.t., t.a.b., o.a.l. funding acquisition: a.i.t. investigation: t.a.b. methodology: a.i.t., t.a.b., o.a.l. project administration: a.i.t. resources: a.i.t software: a.i.t. supervision: a.i.t., o.a.l. validation: a.i.t., o.a.l visualization: o.a.l. writing – original draft: o.a.l. writing – review & editing: a.i.t. conflict of interest the authors declare no conflict of interest. additional information author ids: alexander a. titkov, scopus id 11941014000; tatiana a. borisenko, scopus id 57217250657; olga a. logutenko, scopus id 6506250321. website: institute of solid state chemistry and mechanochemistry sb ras, http://www.solid.nsc.ru. references 1. singh m, haverinen hm, dhagat p, jabbour ge. inkjet printing-process and its applications. adv mater. 2010;22:673–685. doi:10.1002/adma.200901141 2. tekin e, smith pj, schubert us. inkjet printing as a deposition and patterning tool for polymers and inorganic particles. soft matter. 2008;4:703–713. doi:10.1039/b711984d 3. zhang r, moon ks, lin w, wong cp. preparation of highly conductive polymer nanocomposites by low temperature sintering of silver nanoparticles. j mater chem. 2010;20:2018−2023. 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https://doi.org/10.1021/acsami.5b03571 https://doi.org/10.1002/anie.200604637 https://doi.org/10.1021/ja2080345 https://doi.org/10.1021/nl034312m https://doi.org/10.1021/jp306063p https://doi.org/10.1002/crat.200900332 https://doi.org/10.1039/b705253g https://doi.org/10.15372/khur2020204 https://doi.org/10.1007/s13204-012-0169-6 https://doi.org/10.1039/b512540e https://doi.org/10.1002/adma.19970090712 93 введение при описании свойств любого вещества используют ряд фундаментальных физических величин, таких как агрегатное состояние вещества при нормальных условиях, твердость, модуль упругости, плотность, теплоемкость и т. п. одним из таких параметров является температура плавления. температура плавления – температура, при которой происходит переход вещества из твердого кристаллического состояния в жидкое. описание температуры плавления массивных образцов не составляет особых сложностей, что нельзя сказать о температуре плавления наночастиц. основная проблема описания заключается в сложности проведения натурного эксперимента. в настоящее время существует несколько подходов к описанию изменения температуры плавления наноматериалов от размера частицы. эти подходы можно разделить на две а. е. бандин, м. с. жуковский, с. а. безносюк алтайский государственный университет, 626049, барнаул, пр. ленина, 61. e-mail: bsa1953@mail.ru компьютерное моделирование механизмов плавления наночастиц металлов различной формы в работе приведены основные модели описания температуры плавления наноматериалов, основанные на различных представлениях о строении вещества. указаны недостатки описываемых моделей. методами компьютерного эксперимента показано влияние матрицы и формы наночастицы на ее температуру плавления, предложены механизмы плавления наночастиц металлов различной формы. термодинамические модели дают качественное описание температуры плавления наноматериалов, не учитывая влияния ни формы наночастицы, ни матрицы, в которой эта наночастица находится, тем самым показывая, что температура образца будет уменьшаться с уменьшением размера наночастицы. статистические модели учитывают эти влияния и показывают, что температура плавления наночастиц может как увеличиваться, так и уменьшаться с уменьшением размера наночастицы. у д к 5 44 .2 2: 54 4: 18 +5 44 .7 25 © бандин а. е., жуковский м. с., безносюк с. а., 2014 94 cta | № 3 | 2014 основные группы. первая группа использует представления термодинамики, а вторая использует представления динамики кристаллической решетки. термодинамическая модель переход из твердого состояния в жидкое с увеличением температуры начинается с появления на поверхности наночастицы бесконечно малого жидкого слоя, когда ее ядро еще остается твердым. подобное плавление обусловлено поверхностным натяжением, отражающим взаимодей ствие «жидкое – твердое» и изменяющим энергию системы. в связи с этим для температуры плавления авторы получили: ( ) 4exp 2m m t t r ∞ δ = − δ +  , ( ) ( ) m p v t c l ∞ ∞ σ= , (1) где )(∞mt – температура плавления массивного образца, v – молярный объем, l – толщина первой координационной сферы, cp – молярная теплоемкость при постоянном давлении. выражение (1) по форме совпадает с выражением, полученным в модели дебая. константу толмена можно оценить из условия: δ = 6d. (2) что касается знака константы δ, то в (2) он может быть как положительным, так и отрицательным, в зависимости от того, уменьшается или возрастает температура плавления (или поверхностное натяжение) с уменьшением размера частицы [1]. статистическая модель статистические модели основаны на критерии линдемана. согласно представлениям линдемана, кристалл плавится, когда среднеквадратич ное смещение атомов u в кристалле становится больше доли внутриатомных расстояний. увеличение температуры ведет к возрастанию амплитуды колебаний. при некоторой температуре они становятся достаточно большими, разрушают кристаллическую решетку, и твердое тело начинает плавиться. атомы поверхности связаны слабее, и в реальных условиях это может приводить к большим амплитудам колебаний при той же температуре, чем у атомов, находящихся в объеме частицы. этот эффект можно описать как среднеквадратичное смещение атомов на поверхности частицы 2 su и внутри частицы 2 vu . доля поверхностных атомов в сферических наночастицах размером 3 нм достигает приблизительно 50 %, и их колебания сильно влияют на критерий линдемана. это обстоятельство и было использовано для описания зависимости температуры плавления наночастиц от их размера без применения представлений термодинамики. модель, рассматривающая понижение температуры наночастиц с уменьшением их размера, развита в работах [2, 3]. для описания свойств наночастиц предложено уравнение: 1( ) exp ( 1)( 1) ( ) 3 m m r f d t t −  = − α − − ∞   , (3) где tm(r) и tm(∞) – температуры плавления (k) нанокристалла и компактного металла, соответственно; d – высота а. е. бандин, м. с. жуковский, с. а. безносюк 95 2014 | № 3 | cta компьютерное моделирование механизмов плавления наночастиц металлов различной формы монослоя атомов в кристаллической структуре; f – параметр, учитывающий форму наночастицы; α – отношение среднеквадратичных смещений на поверхности и в объеме наночастицы (значение α в большинстве случаев меняется от 2 до 4). существуют случаи, когда наночастицы одного металла включены в другой. в подобных случаях точка плавления частицы может как понижаться, так и повышаться по сравнению с компактным материалом при изменении размера частицы. важно отметить, что уравнение (3) можно применять для описания процессов, связанных с увеличением температуры плавления при уменьшении размера частицы, если значение параметра α < 1. такое явление наблюдается, когда амплитуды колебаний атомов на поверхности меньше, чем в объеме. такое положение может возникнуть в случае сильного взаимодействия атомов, расположенных на поверхности, с материалом основной матрицы [3]. описание среднеквадратичного смещения атома показано в работе [4]. параметр α имеет следующий вид: ( ) ( ) ( ) ( ) 2 2 e s e v e v e s cht kt cht kt ω  ω    α = ω  ω     h h . (4) анализ результатов расчета температуры плавления наночастиц железа расчет температуры плавления проводился для наночастиц железа. для расчета была выбрана модель, основанная на критерии линдемана, так как термодинамическая модель дает значительную ошибку в случае расчета наночастиц с металлическим типом связи [5], а также не учитывает влияние матрицы и формы на температуру плавления наночастиц железа. для расчета параметра α (отношение среднеквадратичных смещений на поверхности и в объеме наночастицы) использовался программный комплекс [6], позволяющий рассчитать потенциал взаимодействия атомов железа друг с другом и с матрицей. на рис. 1 показано влияние формы наночастицы на величину температуры плавления. для данного расчета параметр α = 2.88. на рис. 2 изображено влияние матрицы титана на температуру плавления наночастиц железа. для данного расчета параметр α = 3.92. из рис. 1 видно, что наиболее устойчивой является форма цилиндра. менее устойчивой является наночастица, рис. 1. зависимость температуры плавления наночастиц железа от формы сфера; куб; конус; цилиндр, r – линейный размер, для сферы – радиус сферы, для куба – ребро куба, для конуса – высота конуса, для цилиндра – длина цилиндра 96 cta | № 3 | 2014 имеющая форму сферы. значительное уменьшение температуры плавления наблюдается, когда радиус сферы равен 8 нм. значительное уменьшение температуры плавления наночастиц, имеющих форму куба, наблюдается с 15 нм. самыми неустойчивыми являются наночастицы, имеющие форму конуса. у конуса начало отклонения температуры плавления наночастиц от массивного образца наблюдается с 120 нм, затем она изменяется незначительно. это объясняется тем, что у атомов, находящихся в вершине и в основании конуса, имеют меньшее количество связей с наночастицей. после разрушения вершины и основания конуса наночастица начинает иметь форму, напоминающую форму цилиндра, и продолжает плавиться по тем же механизмам, что и наночастицы, имеющие форму цилиндра. на рис. 2 показано влияние матрицы титана на температуру плавления наночастиц железа. температура плавления наночастиц, имеющих одинаковые линейные размеры и форму, снизилась в среднем на 100 к. из рис. 3 видно, что с уменьшением размера частицы наблюдается увеличение температуры плавления наночастиц титана. в данном случае наблюдается более сильное взаимодействие атомов титана с матрицей, чем атомов титана друг с другом. полученные результаты доказывают, что одними из важнейших факторов, влияющих на температуру плавления образца, являются форма его наночастиц и матрица, в которой эти наночастицы находятся. заключение в заключение стоит отметить, что термодинамические модели дают качественное описание температуры плавления наноматериалов, не учитывая влияния ни формы наночастицы, ни матрицы, в которой эта наночастица находится, тем самым показывая, что температура образца будет уменьшатьрис. 3. зависимость температуры плавления наночастиц титана в матрице железа от формы сфера; куб; конус; цилиндр, r – линейный размер, для сферы – радиус сферы, для куба – ребро куба, для конса – высота конуса, для цилиндра – длина цилиндра рис. 2. зависимость температуры плавления наночастиц железа от формы в матрице титана: сфера; куб; конус; цилиндр, r – линейный размер, для сферы – радиус сферы, для куба – ребро куба, для конуса – высота конуса, для цилиндра – длина цилиндра а. е. бандин, м. с. жуковский, с. а. безносюк 97 2014 | № 3 | cta компьютерное моделирование механизмов плавления наночастиц металлов различной формы а. е. bandin, м. s. zhukovsky, s. а. beznosyuk altai state university, 61, lenin str., 656049, barnaul. e-mail: bsa1953@mail.ru. computer modeling of the mechanisms of melting metal nanoparticles of different shapes the report presents the basic models describing the melting temperature of nanomaterials based on different concepts of the structure of matter. it takes under consideration some drawbacks described models. methods of computer experiment show the effect of the matrix and forms of nanoparticle on its melting point. some mechanisms of melting metal nanoparticles of different shapes are described. thermodynamic models give a qualitative description of the melting temperature of nanomate-rials, not taking into account any impact form nanoparticles, nor matrix in which the nanoparticle is, thus showing that the sample temperature will decrease with decreasing the size of nanoparticles. statistical models take into account these effects and show that the melting temperature of the nanoparticles can either increase or decrease with decreasing the size of nanoparticles. ся с уменьшением размера наночастицы. статистические модели учитывают эти влияния и показывают, что температура плавления наночастиц может как увеличиваться, так и уменьшаться с уменьшением размера наночастицы. влияние матрицы на температуру плавления наночастиц индия показано в работе [3]. 1. rekhviashvili s. s., kishtikova e. v. techn. phys. lett., 2006, 32, 439. 2. shi f. g. j. mater. res., 1994, 9, 1307. 3. sergeev g. b. nanochemistry, moscow, msu, 2007, 336 p. 4. suzdalev i. p. nanotechnology: physico-chemistry of nano-clusters, nanostructures, nanomaterial minerals. moscow: komkniga, 2006. 592 p. 5. beznyuk s. a., bandin a. e. multifunctional chemical materials and technologies. collection of articles. vol. 1. tomsk 2007. 361 p. 6. beznyuk s. a., zhukovsky m. s. the certificate on the state registration of the computer program № 2010612461 from 07.04.2010. molecular dynamic simulation of the [n(c4h9)4]bf4 / (110) α-al2o3 interface published by ural federal university eissn2411-1414 chimicatechnoacta.ru article 2023, vol. 10(3), no. 202310308 doi: 10.15826/chimtech.2023.10.3.08 1 of 7 molecular dynamic simulation of the [n(c4h9)4]bf4 / (110) α-al2o3 interface igor gainutdinov * , nikolai uvarov institute of solid state chemistry and mechanochemistry sb ras, novosibirsk 630090, russia * corresponding author: ur1742@gmail.com this paper belongs to the rkfm'23 special issue: https://chem.conf.nstu.ru/. guest editors: prof. n. uvarov and prof. e. aubakirov. abstract the structure and transport properties of the pure salt [n4]bf4 and this salt located in the contact with the (110) surface of -al2o3 were studied using a md computer simulation in order to reveal the effect of the salt/oxide interface on the structure and properties of the salt. the radial distribution functions of the ions and their mean square displacements were analyzed as a function of the temperature during the cooling of the salt. it was found that in all the cases anions are more mobile than cations. the molten phase of [n4]bf4 tends to crystallize at temperature 420 k which is close to the experimental melting point. the salt located in the [n4]bf4/(110)al2o3 interface exhibits high values of anion self-diffusion coefficients which are higher by 1.2–2 orders of magnitude than in pure salt. this effect is likely to be caused by the formation of a layered atomic structure located within a characteristic thickness of 5 nm. despite the structuring, the structure of the salt is amorphous, no crystallization-related effect is observed. the results of md simulations agree with the experimental effect of the conductivity enhancement observed previously in [n4]bf4-al2o3 nanocomposites. keywords molecular dynamic simulation tetrabutylammonium borofluorate composite organic salts diffusion structure received: 03.07.23 revised: 10.08.23 accepted: 14.08.23 available online: 16.08.23 key findings ● the structure and transport properties of the pure salt [n4]bf4 and this salt located in the contact with (110) surface of -al2o3 were studied using a md computer simulation. ● the molten phase of [n4]bf4 tends to crystallize at temperature 420 k which is close to the experimental melting point. the salt near the interface does not tend to crystallize and remains to be amorphous. ● the anion self-diffusion coefficients in the salt located in the [n4]bf4/(110)al2o3 interface are higher by 1.2–2 orders of magnitude than that in the pure salt, which is in agreement with the experimental observations. © 2023, the authors. this article is published in open access under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). 1. introduction high-temperature plastic phases of organic salts combine properties of both crystals and ionic liquids. on the one hand, they have crystalline structure characterized by a long-range ordering, but on the other hand, these compounds exhibit a strong reorientation disorder and a high local mobility of molecular fragments [1, 2] typical for ionic liquids. the local motions may facilitate ionic transport. a relatively high ionic conductivity of 10–6–10–3 s/cm has been reported for plastic phases of [3–14], but the mechanism of the ionic transport in such phases remains unknown. tetra-alkylammonium salts [r4n]x (r = individual alkyl groups ch3, c2h5, c3h7, c4h9, etc., or their combinations, x = halide anions; bf4–, clo4–, tfsi-anions, etc.) are typical ionic liquids in a molten state [15]. on cooling, tetrabutylammonium salts (c4h9)4nx (x = cl–, br–, i–, bf4–, clo4–) crystallize with the formation of reorientationally disordered high-temperature plastic phases, which transform into ordered low-temperature modifications under further cooling [12, 13, 14]. the melting entropy of these salts is lower or comparable that of the solid-state transition indicating a high disordering in the plastic phases [16, 17]. tetrabutylammonium tetrafluoroborates [r4n]bf4 are promising materials for low-temperature solid-state electrochemical devices due to the high electrochemical stability of both quaternary ammonium cations (r4n)+ and bf4 http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2023.10.3.08 mailto:ur1742@ http://creativecommons.org/licenses/by/4.0/ https://orcid.org/0000-0001-7740-6031 https://orcid.org/0000-0002-8209-7533 https://crossmark.crossref.org/dialog/?doi=https://doi.org/10.15826/chimtech.2023.10.3.08&domain=pdf&date_stamp=2023-08-16 chimica techno acta 2023, vol. 10(3), no. 202310308 article 2 of 7 doi: 10.15826/chimtech.2023.10.3.08 anions. in particular, tetrabutylammonium tetrafluoroborate [(c4h9)4n]bf4 (hereafter, [n4]bf4) exhibit a conductivity of around 10–6 s/cm in the high-temperature plastic phase at 150 °c [13]. according to 19f nmr data, the dominant charge carriers in this phase are bf4– anions [13]. the salt [n4]bf4 has several polymorphic modifications, differing in the degree of conformational disorder in hydrocarbon chains and reorientation disordering of anions [17]. however, despite of a strong disordering in both cation and anion sub-lattices, the total ionic conductivity of the salt is rather low even in the plastic phase. in order to increase the conductivity of the ionic salts, a heterogeneous doping technique can be used [18, 19], which leads to an increase of conductivity by several orders in magnitude. it is known that the introduction of nanocrystalline chemically inert additives to the salt matrix may result in a strong increase in the conductivity of the salts. there are two reasons for the conductivity enhancement in the obtained composite solid electrolytes: (i) the excess concentration of point defects, which form a double electrical layer near the ionic salt/oxide interface [18] and (ii) the formation of the amorphous layer of the ionic salt near the interface [19]. in micro-composites, excess point defects in the surface double layer seems to be a primary reason for the conductivity increase, whereas the ionic conductivity is caused by the contribution of the amorphous interface-induced phases in nanocomposites. to date, a number of experimental data have been reported for a conductivity enhancement in inorganic nanocomposites. in contrast, the conductivity of nanocomposites based on organic salts remains practically unstudied. recently, it has been experimentally found that the introduction of nanocrystalline alumina into the [n4]bf4 salt leads to a strong increase in the conductivity by several orders of magnitude. in parallel, the amorphization of the salt takes place at a high concentration of the alumina additive [20]. it would be very desirable to understand the mechanism of the effect of the heterogeneous doping on the structural and transport properties of the [n4]bf4 salt. previous studies [17] have shown that due to the branched structure of the tetrabutylammonium cations rotational motions of the fragments of hydrocarbon chains and changes in their conformation occur even at relatively low temperatures (about 200 k). therefore, it is difficult to investigate the structure of the [n4]bf4 salt by diffraction methods. the experimental study of the local structure of the salt near the ionic salt/oxide interface is even more complicated. in this situation, molecular dynamics (md) computer simulation can provide an opportunity to obtain qualitative, and, possibly, quantitative information on the local structure of the salt in both individual form and in the composite. previous md simulations of salt-oxide interfaces have been carried out mainly for ionic liquids contacted with different oxide surfaces [21, 22]. as for composites with solid ionic salts, only lii-al2o3 [23], cscl-al2o3 [24] and рb1–xcdxf2–sio2 [25] interfaces were simulated. no data on md simulations of composite solid electrolytes with quaternary ammonium salts have been reported yet. some efforts have been made to analytically solve the problem of crystallization of twocomponent systems, but they do not answer the question of increasing the ionic conductivity of organic salts in the composite [39–41]. this work is devoted to the md computer modelling of the transport properties of pure [n4]bf4 and this salt in contact with the (110) surface of α-al2o3. 2. methodology the calculations were performed with the lammps software package [26] using the dreiding force field [27]. the charges of the ions were refined by quantum chemical calculations of the molecule using the quantum espresso package [28, 29]. the charges of the ions were determined by the bader method [30]. it should be noted that the dreiding force field is a rather early approach and there are now more advanced force fields available, but it has the advantage of allowing a consistent set of parameters to be defined for the system containing c, f, b, n, and h atoms within the same force field that has been developed and validated on a wide range of compounds. a structure of a pure ionic salt containing 215 anion-cation pairs was simulated with periodic boundary conditions. in the present study only coulomb interactions between atoms of different molecules and the lennard-jones dispersion attraction ~ 1 𝑟6 were considered. the intermolecular repulsion of atoms was also expressed in the lennard–jones form ~ 1 𝑟12 . no specific hydrogen bonds and cation polarization effects were taken in consideration. the boron atom in the bf4– anion ion is positively charged, its charge is equal to +2.4e and surrounded by four negatively charged fluorine ions (–0.84e). in the tetrabutylammonium cation, the nitrogen atom is negatively charged (–0.81e), while the charge of the carbon atoms fluctuates along the alkyl chains, the carbon atoms closest to the nitrogen have a charge of +0.17e, the hydrogen atoms have a small positive charge in the range of 0.02–0.1e. quantum chemical calculations show that under the action of the anionic electric field, the electron density is redistributed over the cation. such a polarization effect was also neglected in the present simulation. nevertheless, as it will be seen further, despite a significant simplification of the computational model, the obtained results in terms of characteristic temperatures, are in good agreement with the experimental data. for simulations of the [n4]bf4/al2o3 interface, the modification α-al2o3 (corundum, the symmetry space group r3c, the lattice parameters a = b = 4.7602 å c = 12.9933 å) was used. the oxygen and aluminum ions were located in positions corresponding to the ideal corundum structure [31]. both oxygen and aluminum positions are fixed and these ions act as rigid charged centers interacting due to https://doi.org/10.15826/chimtech.2023.10.3.08 https://doi.org/10.15826/chimtech.2023.10.3.08 chimica techno acta 2023, vol. 10(3), no. 202310308 article 3 of 7 doi: 10.15826/chimtech.2023.10.3.08 coulomb and lennard-jones repulsive and attractive forces. aluminum and oxygen ion charges were as assumed to be +1.8e and –1.2e, respectively. 3. results and discussion 3.1. pure [n4]bf4 salt first, it was necessary to model the organic ionic salt. its melting point is a thermodynamic parameter which can be easily determined experimentally. if the model shows a melting temperature close to the real one, then the interaction parameters used in the model are valid. for example, if hydrogen bonds between fluorine and hydrogen atoms play a significant role in the intermolecular interaction, then excluding them from the calculation would affect the melting temperature, in this case leading to its decrease. the same reasoning applies to the polarization of the cation. it would be desirable to observe the melting temperature during heating the system. however, it is known that when a perfect crystal without defects is heated, the temperature of transition to a disordered state (the temperature of thermal instability) can be up to 20% higher than the melting temperature observed in the experiment [32]. therefore, another approach was used: to melt the model and investigate the properties of the system in the course of its cooling from the molten state. figure 1 shows the mean square displacement of [n4]+ cations and bf4– anions during a slow cooling of pure [n4]bf4 salt from the molten state 550 k to 150 k with a constant cooling rate. in parallel, volume, energy, and the cell shape were monitored. typically, the cooling process took nearly 10 ns (107 time steps). the mean square displacement of atoms was calculated as the square of the deviation of the atoms from their initial positions (at the starting temperature) averaged over all atoms of the selected type. the mean square deviations of the boron atoms as the centers of the geometric position of the anion and the mean square deviations of all atoms included in the cation were monitored. no drastic change in the volume and energy behavior with the temperature was observed. changes in the state of the model during cooling are observed in the mean square displacement of atoms. the mean square displacement of the atom at a fixed temperature is defined by the self-diffusion coefficient value, d ~ x2/dt, which may be estimated from the slope of the time dependence of the mean square displacement. as seen from figure 1, at high temperatures the diffusion coefficients of both cations and anions are rather high, but anions are more mobile than cations. with a decrease in temperature the dx2/dt slope diminishes, hence the mobility of atoms monotonically decreases. however, at 420 k one can observe a sharp change in the dx2/dt slope corresponding to a significant decrease in the mobility of both anions and cations. interestingly, this temperature is close to the experimental value of the melting temperature of 432 k [17]. thus, the simulated mean square displacement curve reflects the freezing of a system at a temperature close to the crystallization point, but at the same time, the system has not crystallized, no long-range order has appeared, as can be seen from the pair distribution function (pdf) presented in figure 2. in the pdf plots obtained at different moments of the cooling process (i.e. at different temperatures from 500 k to 150 k) one can see a broad first peak and slightly split second peak, which is a fingerprint of the disordered glassy structure. apparently, the process of establishing a long-range order is very slow at the crystallization (melting) temperature and the cooling rate that we can obtain in a computer experiment is too high. as a result, the system transforms to the quenched metastable glassy state. it is not surprising for the case of organic salt, which belongs to the class of plastic phases with a low value of entropy and enthalpy of melting and prone to amorphization for this reason. 3.2. the [n4]bf4/al2o3 interface the [n4]bf4/al2o3 interface was simulated as follows: a plate of α-al2o3 bounded by (110) planes, contacted with a layer of the [n4]bf4 salt, containing 250 molecules (anioncation pairs) placed on the alumina surface. figure 1 mean square displacement of boron atoms as centers of anions (blue) and for cation (brown) for pure [n4] salt in comparison with temperature (green) during cooling run. figure 2 pair distribution function for boron for different temperatures during cooling process for pure [n4]. https://doi.org/10.15826/chimtech.2023.10.3.08 https://doi.org/10.15826/chimtech.2023.10.3.08 chimica techno acta 2023, vol. 10(3), no. 202310308 article 4 of 7 doi: 10.15826/chimtech.2023.10.3.08 the bottom part of the salt layer contacted to the oxide surface, whereas the upper part formed a free surface (i.e., contacted to vacuum). if the z axis is perpendicular to the surface, then periodic boundary conditions were applied along the x and y axes. as in the case of pure [n4]bf4 salt, the model was heated up to 450 k and slowly cooled to 220 k with the same cooling rate. the time dependences of the mean square deviation of boron atoms and cations are shown in figure 3. in contrast to the pure [n4]bf4 salt, the composite cooling from 450 to 220 k reveals no sharp changes in the mobility of atoms at 420 k (figure 3). mobility remains high and gradually decreases on cooling to 300 k. the distinction of the temperature dependence of atom mobilities in pure salt and the composite is apparently caused by a difference in the diffusion mechanism. this suggests the [n4]bf4 salt in the contact with the alumina surface exists in an amorphous state which is different from the amorphous state of the pure salt. figure 4 shows the diffusion coefficients of boron atoms in the composite, as well as boron atoms in an infinite sample of pure salt [n4]bf4. the diffusion data for pure salt agree well with the bulk values of the self-diffusion coefficients, 10– 12–10–10 m2/s, obtained for various ionic liquids [33]. figure 3 mean square displacement of boron atoms as centers of anions (brown) and for cation (blue) in comparison with temperature during cooling run for composite [n4]bf4-al2o3. figure 4 temperature dependences of boron self-diffusion coefficients in pure n4bf4 salt (green triangles) and [n4]bf4-al2o3 composite (blue squares) estimated from md simulations made on a cooling run. in contrast, the diffusion coefficient of boron in the composite is by 1–2 orders of magnitude higher than the corresponding values for pure salt. at 420 k an abrupt decrease in the diffusion coefficient is observed for pure salt, while the d values for the composite monotonically decrease over the entire temperature range from 450 to 220 k. the main factor affecting the structure and properties of the salt in the composite is the contact interaction between the oxide and salt. due to coulomb forces, this interaction is strong enough and leads to the formation of a surface layer in which the anions and cations of the salt are actually fixed on the surface of the oxide. they are practically stationary, and are arranged in such a way that the butyl chains of the cation lie on the surface in some flat conformation. the reason for such a strong difference in the atoms mobility in pure salt and in the composite seems to be the change in the local structure of the salt in the vicinity of the interface. figure 5 shows the distribution of the boron atoms along the z-axis directed in perpendicular to the interface. in contrast to the pure [n4]bf4 salt (figure 2), several smooth single anionic layers can be distinguished in the salt structure near the [n4]bf4 – alumina interface. most likely that such a layered structure contains large two-dimensional cavities (“vacancies”) which act as an additional channel for fast ion transport along the interface. the characteristic thickness of the structured interface layer is nearly 5 nm that agrees with the effective thickness of the amorphous layer around the alumina particles estimated earlier for [n4]bf4-al2o3 nanocomposites using thermal analysis data [14]. the formation of layered structures is typical for the contacts between ionic liquids and oxides, metals, carbon nanotubes, etc. [21, 22, 38]. it has been reported [38] that an interfacial layer structure is formed near ionic liquids/al2o3 interfaces with different ionic liquids, indicating the formation of a double-layer consisting of cations being in contact with the anions repelled from the al2o3 surface and formed a second anion layer on the interfacial cation layer. such a structure is completely different from those of dilute aqueous electrolytes near charged substrates, owing to strong correlations between oppositely charged ions. in most of the publications [21, 22, 38], the authors focused mainly on the structure and its influence on adhesion properties of the ionic liquids. figure 5 the time averaged density of boron atoms along z axis at 290 k. the oxide surface is indicated by a dash line. https://doi.org/10.15826/chimtech.2023.10.3.08 https://doi.org/10.15826/chimtech.2023.10.3.08 chimica techno acta 2023, vol. 10(3), no. 202310308 article 5 of 7 doi: 10.15826/chimtech.2023.10.3.08 the effect of the structuring on ionic conductivity was not studied in detail. in this work such effect was clearly demonstrated for the case of ionic plastic phase/oxide interface. 4. limitations the main difficulty of a fundamental nature is the adequacy of the choice of the model of interatomic interaction. on the one hand, for organic molecules, the method of force fields is well tested and is generally accepted. on the other hand, the approach chosen in this work ignores a number of features of these systems that may be important, in particular the polarization of the cation and anion as a whole, hydrogen bonds. in principle, to take into account the effect of changing charges depending on the environment, various empirical methods for the determination of effective charges during the calculation, qeq, eam, etc. [34–37] can be applied. actually, it is planned to use these approaches in further studies. the second difficulty concerns the size of the system. it is possible that in order to manifest a number of effects related to ion mobility, it is necessary to have a large computational domain. only in this case the volume fluctuations necessary for the ion movements can occur. such fluctuations are possible in the glassy state due to the excess free volume frozen into an amorphous structure, but when considering crystalline salts with a denser packing of molecules a low probability of fluctuations becomes critical when modeling diffusion displacements. finally, an important limitation is the physical observation time. now it is limited by an interval of 10 ns, it is possible to increase this time by 2–3 times, but to move further one can carry out a computational experiment for several days. in any case, for a model of our size, a time of 100 ns seems to be a hard limit. is it critical for the processes we are studying? this question requires careful study. 5. conclusions in the present work, the structure and transport properties of the pure salt [n4]bf4 and this salt located in the contact with α-al2o3 were studied using a md computer simulation in order to reveal the effect of the salt/oxide interface on the properties of the salt. the radial distribution functions of the ions and their mean square displacements were analyzed as a function of the temperature during the cooling the salt. it was found that in the molten salt anions are more mobile than cations. the modelled molten phase of [n4]bf4 tends to crystallize at temperature 420 k which is close to the experimental melting point of the salt (432 k). due to a limited time interval of the calculations, we did not achieve a complete crystallization of the salt, but a strong decrease of the diffusion coefficients suggests that the phase transition takes place. the [n4]bf4/(110)al2o3 interface was simulated and the properties of the salt were analyzed. it was found that in the contact with the oxide surface the salt exhibits high values of anions self-diffusion coefficients by higher 1.2–2 orders of magnitude than those in pure salt, anions being dominant charge carriers. this effect is likely caused by a structuring of the salt near the interface, i.e. the formation of a layered atomic structure located within a characteristic thickness of 5 nm. despite the structuring, the salt remains to be amorphous with no tendency to crystallize over the temperature range from 550 to 300 k. the effect of the conductivity increase agrees with the experimental conductivity behavior of [n4]bf4-al2o3 nanocomposites observed earlier [20]. ● supplementary materials no supplementary materials are available. ● funding the work was supported by the russian science foundation (project 20-13-00302), https://www.rscf.ru/en. ● acknowledgments the siberian branch of the russian academy of sciences (sb ras) siberian supercomputer center is gratefully acknowledged for providing supercomputer facilities. ● author contributions conceptualization: i.g., n.u. data curation: i.g., formal analysis: i.g., funding acquisition: n.u. investigation: i.g. methodology: i.g., n.u. project administration: n.u. resources: n.u. software: i.g. supervision: n.u. validation: i.g., n.u. visualization: i.g. writing – original draft: i.g., n.u. writing – review & editing: i.g., n.u. ● conflict of interest the authors declare no conflict of interest. ● additional information author ids: igor gainutdinov, scopus id 37047923700; https://doi.org/10.15826/chimtech.2023.10.3.08 https://doi.org/10.15826/chimtech.2023.10.3.08 https://www.rscf.ru/en https://www.scopus.com/authid/detail.uri?authorid=37047923700 chimica techno acta 2023, vol. 10(3), no. 202310308 article 6 of 7 doi: 10.15826/chimtech.2023.10.3.08 nikolai uvarov, scopus id 7006949152. website: institute of solid state chemistry and mechanoche-mistry, http://www.solid.nsc.ru/. references 1. timmermans j. plastic crystals: a historical review. j phys chem solids. 1961;18:1–8. doi:10.1016/0022-3697(61)90076-2 2. parsonage ng, staveley lak. disorder in crystals. international series of monographs on chemistry. clarendon university press: oxford 1978. 926 p. 3. macfarlane dr, forsyth m. plastic crystal electrolyte materials: new perspectives on solid state ionics. 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university eissn 2411-1414 chimicatechnoacta.ru article 2023, vol. 10(3), no. 202310304 doi: 10.15826/chimtech.2023.10.3.04 1 of 7 high purity β-bi2o3 preparation by thermal decomposition of tartrates evgeniya v. timakova ab * , tatiana e. timakova ab , liubov i. afonina ab a: department of chemistry and chemical technology, novosibirsk state technical university, novosibirsk 630073, russia b: institute of solid state chemistry and mechanochemistry, siberian branch of the ras, novosibirsk 630090, russia * corresponding author: timakova@solid.nsc.ru this paper belongs to the rkfm'23 special issue: https://chem.conf.nstu.ru/. guest editors: prof. n. uvarov and prof. e. aubakirov. abstract the processes of oxidative thermolysis of bismuth(iii) dl-tartrate bic4h3o6 obtained by the interaction of high-purity basic bismuth(iii) nitrates [bi6o4(oh)4](no3)6·h2o and [bi6o5(oh)3](no3)5·3h2o with dltartaric acid solution have been investigated. the products of precipitation have been studied by methods of x-ray diffraction and thermal analysis, ir and raman spectroscopy and chemical analysis. the staging of thermal transformation processes has been determined. morphological studies and grain size analysis of initial precursors and final products of their thermal transformations have been carried out. the possibility of obtaining fine crystalline powders of tetragonal bismuth(iii) oxide modification β-bi2o3 by oxidative thermolysis of dl-bic4h3o6 has been shown. keywords basic bismuth(iii) nitrate dl-tartaric acid x-ray diffraction thermal transformations β-bismuth(iii) oxide fine-crystal powders received: 28.06.23 revised: 28.07.23 accepted: 31.07.23 available online: 03.08.23 key finding ● fine crystalline powders of high purity tetragonal bismuth(iii) oxide β-bi2o3 were obtained from the decomposition of the precursor dl-bic4h3o6 synthesized from basic bismuth(iii) nitrates. © 2023, the authors. this article is published in open access under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). 1. introduction tartrates are widely used as precursors for the preparation of fine crystalline and nanodispersed powders of metals, their oxides [1–4] and mixed oxide materials [5–8] by thermolysis in inert and oxidizing atmospheres. bismuth tartrate precursors are also used to produce bismuth oxides [9] and bismuth-based materials [10, 11]. we have investigated the thermal decomposition of bismuth tartrate [bi(no3)(c4h4o6)]·3h2o obtained by adding a bismuth solution in nitric acid to a solution of l(+)-tartaric acid [12]. it has been shown that thermolysis of [bi(no3)(c4h4o6)]·3h2o in air atmosphere for 6 h at 300 °c with preliminary holding at lower temperatures produces a mixture of tetragonal bismuth(iii) oxide and bismuth(iii) oxocarbonate β-bi2o3/(bio)2co3. with increasing temperature, a β→α phase transition occurs and the final decomposition product is the monocline modification, α-bi2o3. monophase fine crystalline powders of tetragonal bismuth oxide β-bi2o3 were obtained by oxidative thermolysis of bismuth(iii) tartrate bic4h3o6·h2o for 6 h at 280 °c. bic4h3o6·h2o is an x-ray amorphous compound obtained by multiple washing of [bi(no3)(c4h4o6)]·3h2o with water. direct precipitation of bic4h3o6·h2o from nitric acid solutions does not provide effective purification from nitrate ions, and obtaining this compound by multiple washings with water [bi(no3)(c4h4o6)]·3h2o is a lengthy process. therefore, it is of interest to consider the process of obtaining bic4h3o6·h2o by treating solid bismuth precursors with tartaric acid solution. it is reasonable to consider basic bismuth(iii) nitrates as precursors for obtaining bismuth tartrate. it has been shown [13] that bismuth precipitation in the form of basic nitrates, during the hydrolytic processing of technological nitric acid solutions prepared from metallic bismuth of bi1 grade and containing impurities of accompanying metals, allows high values of bismuth purification coefficients from impurities to be achieved. hydrolysis at elevated temperatures not lower than 60 °c allows obtaining easily filterable precipitate of the composition [bi6o4(oh)4](no3)6·h2o (further basic bismuth(iii) nitrate) and separating it effectively from the mother liquor containing impurity metal ions. washing this compound http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2023.10.3.04 mailto:timakova@solid.nsc.ru http://creativecommons.org/licenses/by/4.0/ https://orcid.org/0000-0002-7015-9231 https://orcid.org/0000-0003-0564-8992 https://orcid.org/0000-0002-5606-3022 https://crossmark.crossref.org/dialog/?doi=https://doi.org/10.15826/chimtech.2023.10.3.04&domain=pdf&date_stamp=2023-08-03 chimica techno acta 2023, vol. 10(3), no. 202310304 article 2 of 7 doi: 10.15826/chimtech.2023.10.3.04 with water results in hydrolytic decomposition to form the [bi6o5(oh)3](no3)5·3h2o. as a result of recrystallization, the final product is effectively purified from metal impurities captured in the volume of microcrystals during the precipitation of the primary hydrolysis product. the use of [bi6o4(oh)4](no3)6·h2o and [bi6o5(oh)3](no3)5·3h2o as precursors for further treatment with carboxylic acids or alkaline reagents makes this process widely applicable for the synthesis of high-purity bismuth compounds for engineering and medicine. the aim of this work was the synthesis of high purity bismuth(iii) tartrate by the reaction "basic bismuth(iii) nitrates – tartaric acid solution" followed by the production of tetragonal β-bi2o3. 2. experimental all reagents (acids, bases and salts) in this work were of analytical grade and were used without further purification. metallic bismuth bi1 (kazzinc, gost (state standard) 10928–90) was used. the metal contents were (wt.%): 99.1 bismuth, 0.71 lead, 1.0·10–3 zinc, 1.0·10–3 antimony, 3.3·10–3 copper, 1.0·10–1 silver, 2.0·10–4 arsenic, 1.0·10–3 iron and 1.0·10–4 tellurium. bismuth stock solution in nitric acid (420 g∙l–1 bismuth and 100 g·l–1 free hno3) was prepared by dissolving technical bismuth oxide, obtained according to ref. [14], in nitric acid with the concentration of 7 mol·l–1. the hydrolytic precipitation of bismuth from nitric acid solution, as well as investigation of "solid precursor – carboxylic acid solution" processes were carried out in fluoroplastic or glass vessels equipped with stirrers and thermostatically controlled in water baths. hydrate tetrahydroxo-tetraoxo-hexabismuth(iii) hexanitrate of [bi6o4(oh)4](no3)6·h2o was prepared by adding 50 ml of distilled water heated to 55–60 °c to 50 ml of bismuth nitrate solution with stirring, then 36 ml of ammonium carbonate solution with a concentration of 2.5 mol·l–1 to ph = 1. the mixture was stirred for 30 min and allowed to stand for 1 h. the mother liquor was separated from the sediment by decantation, the sediment was washed with 150 ml of nitric acid solution with a concentration of 0.1 mol·l–1 for 30 min at 60 °c. trihydrate trihydroxo-pentaoxo-hexabismuth(iii) pentanitrate of the composition [bi6o5(oh)3](no3)5·3h2o was obtained by washing the precipitate twice with 150 ml of distilled water for 30 min at 60 °c. for the synthesis of bismuth(iii) tartrate 10 g of freshly prepared basic bismuth(iii) nitrates [bi6o4(oh)4](no3)6·h2o or [bi6o5(oh)3](no3)5·3h2o was stirred for 10 min in 90 ml distilled water to the resulting mixture was added the required amount of tartaric acid c4h6o6. the molar ratio of tartrate ions to bismuth was 1.1. the resulting mixture was stirred for 1–2 h at 70 °c. the resulting precipitate was filtered off, washed 2 times with distilled water at the synthesis temperature and dried in air. bismuth(iii) oxocarbonate of the composition (bio)2co3 was obtained by treating [bi6o4(oh)4](no3)6·h2o or [bi6o5(oh)3](no3)5·3h2o with ammonium carbonate solution at ph ≥ 8 and 25 °c [13]. chemical determination of macro quantities of bi(iii) in solutions was carried out by titration with complexon iii solution in the presence of xylenol orange indicator. micro quantities of bi(iii) were determined by photocolorimetric method using potassium iodide. carbon, nitrogen and hydrogen contents in the obtained samples were determined by modified pregle method with gravimetric termination. the phase compositions of the samples were analyzed using x-ray diffraction technique (xrd) on a diffractometer (bruker d8 advance, germany) using cu kα radiation (λ = 1.5418 å). x-ray diffraction data were collected in scanning mode at a scanning speed of 0.5°·min–1 in the range of 4° < 2θ < 70°. phase analysis was performed using the icdd pdf-4 database (2011). the ir absorption spectra in the range 400–4000 cm–1 were recorded with a ir-fourier spectrometer tensor 27 (bruker, germany). the samples were prepared as tablets with calcined kbr. raman spectra were taken on a t64000 spectrometer (horiba jobin yvon, japan) with an ar+ laser (wavelength 514.5 nm, z(xy)-z geometry). microstructure of the samples was studied by scanning electron microscopy (sem) using a hitachi tm 1000 scanning electron microscope. thermal analysis of the samples was carried out on a synchronous thermoanalytical complex sta 449 f1 jupiter (netzsch) dynamically under heating in an ar/o2 atmosphere (80/20; o2 10 ml·min−1; ar 40 ml∙min−1). samples weighing 20–50 mg were placed in crucibles of pt – 10% rh alloy and heated at a rate of 10 deg·min–1 to 350– 500 °c. the mass spectra of the gaseous products formed in the course of the heat treatment were recorded in the multi-ion detection mode at m/z of 18 and 44 with a qms 403d quadrupole mass spectrometer (netzsch). particle size analysis of powders was performed using a laser particle size analyzer microsizer 201a (va instalt, russia). 3. results and discussion 3.1. synthesis and characterization of bismuth dl-tartrate according to the xrd analysis, the treatment of freshly precipitated [bi6o4(oh)4](no3)6·h2o (figure 1, curve 1) with a solution of l(+)-tartaric acid at a molar ratio of n(c4h4o62–/bi3+) = 1.1 at 70 °c within 1 h leads to the formation of a mixture of [bi6o4(oh)4](no3)6·h2o [13] and [bi6o5(oh)3](no3)5∙3h2o (icdd 000-48-0575) (figure 1, curve 2). increasing the exposure time to 2 h gives [bi6o5(oh)3](no3)5∙3h2o (figure 1, curve 3). when [bi6o5(oh)3](no3)5∙3h2o is treated with l(+)-tartaric acid solution, the initial precursor remains as a synthesis product. thus, in the system "basic bismuth(iii) nitrates https://doi.org/10.15826/chimtech.2023.10.3.04 chimica techno acta 2023, vol. 10(3), no. 202310304 article 3 of 7 doi: 10.15826/chimtech.2023.10.3.04 solution of l(+)-tartaric acid" under the chosen conditions, bismuth tartrate is not formed. considering the possibility of using the racemic form of tartaric acid for the synthesis of tartrate precursors [15–17], we chose dl-tartaric acid to obtain bismuth tartrate. according to the xrd data, the treatment of basic bismuth(iii) nitrates with dl-tartaric acid solution at n = 1.1 and temperature 70 °c for 1–2 h leads to the formation of bismuth tartrate of a bic4h3o6 composition (figure 1, curve 4), which is confirmed by the data of chemical analysis, content in %: bi – 60.1 (theor. 58.7); c – 12.7 (13.5) and h – 0.75 (0.84). dl-bic4h3o6 has a low degree of crystallinity: an intense reflex is observed on the diffractogram of the compound at d/n = 6.57 å (2θ = 13.46°), other reflexes are broadened and have low intensity. the analysis of ir and raman spectra of dl-tartaric acid and its bismuth salt allowed us to conclude the form of the presence of tartaric acid residues in dl-bic4h3o6 and the way of their connection with metal atoms. the assignment of vibrational bands in the ir and raman spectra of dlbic4h3o6 was carried out in comparison with the spectra of dl-tartaric acid based on literature data [18, 19]. tartaric acid can form complex compounds with metals due to carboxylic and alcohol (oxy) groups, so it is necessary to analyze the characteristic vibrational bands of these functional groups. calculations of the vibrational spectrum of tartaric acid [18] showed that only the stretching vibrations of oh, ch, and c=o groups are specific in shape and wavenumbers, while the other vibrations are strongly mixed. therefore, let us consider in detail the changes observed in the spectrum of the salt as compared to the spectrum of the acid. in the spectra of dl-tartaric acid (figures 2 and 3, curve 1) the presence of oh-groups involved in the formation of intermolecular hydrogen bonding is indicated by a broad band in the range of 3650–3280 cm–1, divided into two components at 3413 (ir), 3408 (raman) and 3365 (ir), 3354 (raman), assigned to the stretching vibrations of ν(o–h) alcohol and carboxyl groups, respectively [18]. stretching vibrations of the c=o bond of dimeric carboxyl groups linked by intermolecular hydrogen bonds correspond to a strong band at 1743 (ir), 1690 (raman) cm–1 and those involved in intramolecular hydrogen bonds at 1635 (ir), 1653 (raman) cm–1. these bands are not recorded in the spectrum of bismuth salt (figures 2 and 3, curve 2). in the above spectra bands related to asymmetric νas(coo–) and symmetric νs(coo–) stretching vibrations of ionized coo– groups at (cm–1): 1595, 1555 (ir ); 1583, 1558 (raman) and 1404, 1362 (ir); 1404, 1363 (raman) respectively are present, which denotes substitution of protons in the carboxyl groups of carboxylic acid by bicontaining cation. presence of several asymmetric and symmetric bands of carboxylate ions indicates different structural functions performed by them. the broad band in the range of 3650-3300 cm–1 in the ir spectrum refers to alcohol groups not substituted by bismuth cation and involved in intermolecular hydrogen bonds. in the range of 1460-1200 cm–1 several bands of inplane bending vibration β(oh) overlapping with in-plane bending β(c–h) are observed in acid spectra (figures 2 and 3, curve 1): the medium and strong bands 1455, 1401 (ir) and 1457, 1391 (raman) refer to in-plane bending vibration of alcohol groups, and weak bands 1327 (ir), 1330 (raman) to carboxyl groups [18]. in the spectra of the acid (figures 2 and 3, curve 1), the bands of stretching vibrations ν(c–h) at 2971, 2912 (ir) and 2972, 2923 (raman) cm–1 are observed. in the spectra of the salt (figures 2 and 3, curve 2) these vibrations correspond to bands at 1289, 1258 (ir) and 1283, 1263 (raman) cm–1. in the ir spectrum of the acid a series of strong and medium bands belonging to in-plane bending vibrations of β(c–c–h) at 1291, 1257, 1238, 1220 cm–1 (figure 2, curve 1) are observed. in the raman spectrum these bands are observed at wavenumbers of 1263, 1245, 1219 cm–1 (figure 3, curve 1), these vibrations also overlap with in-plane bending vibrations of hydroxyl groups [18]. when the protons of oh-groups are substituted by bismuth cation, the disappearance of several bands, decrease of intensity and broadening of bands registered at 1289, 1258 (ir) and 1283, 1263 (raman) cm–1 are observed in the spectra of salt (figures 2 and 3, curve 2). figure 1 x-ray powder diffraction patterns of the initial [bi6o4(oh)4](no3)6·h2o (1) and treated by l(+)(2, 3) and dl (4) c4h6o6. synthesis conditions: 70 °c, n = 1.1, 1 h (2, 4), 2 h (3). figure 2 ir spectra of dl-c4h6o6 (1) and dl-bic4h3o6 (2). https://doi.org/10.15826/chimtech.2023.10.3.04 chimica techno acta 2023, vol. 10(3), no. 202310304 article 4 of 7 doi: 10.15826/chimtech.2023.10.3.04 in the acid spectrum strong bands at 1142 (ir) and 1151 (raman) cm–1 related to the stretching vibrations of ν(c– o) carboxyl groups are observed. for alcohol groups, these vibrations appear as a strong band in the ir spectrum at 1095 cm–1 and a weak band in the raman spectrum at 1089 cm–1 [18]. at replacement of protons of carboxylic and alcohol groups by bismuth cation, these bands in bismuth salt spectra (figures 2 and 3, curve 2) shift to the region of lower wavenumbers and additionally the third band appears, which is connected with c–o–bi bond formation and participation of oxygen of non-dissociated alcohol group in bismuth cation coordination. in the region of 1150-850 cm–1, the stretching vibrations ν(c–c) are recorded as bands of medium intensity at 984, 918, 889, 868, 831 (ir) and 991, 900, 889, 873, 833 (raman) cm–1 (figures 2 and 3, curve 1). these bands are mixed with stretching and deformation vibrations of c–o bonds [18]. therefore, changes are also observed in this region in the salt spectrum, consisting in a decrease in the number of vibration bands and a change in their intensity. thus, in the ir spectrum of salt (figure 2, curve 2) bands are observed: weak at 1003 cm–1 and medium at 925 cm–1; in the raman spectra (figure 3, curve 2) these vibrations appear as medium and weak bands at 1006 and 925 cm–1 respectively. оut-of-plane bending vibrations δ(c–c=o) include bands at 831–482 cm–1 in the spectra of acid (figures 2 and 3, curve 1) [18]. these bands are not registered in the salt spectra. the strong band at 818 cm–1 (figure 2, curve 2) in the ir spectrum of salt and weak bands at 827, 817 cm–1 in the raman spectrum (figure 3, curve 2) are related to scissor vibrations of the carboxylate ion δs(coo–) [19]. the presence of two δs(coo–) bands in the raman spectrum confirms the different structural functions of carboxylate ions. a strong band in the ir spectrum of the salt at 719 cm–1 refers to the torsional vibrations of δτ(coo–) [20]. stretching vibrations ν(bi–o) include an intense band at 486 cm–1 with the shoulder at 476 cm–1 [21] in the infrared spectrum of the salt (figure 2, curve 2). these vibrations are recorded in the raman spectrum (figure 3, curve 2) as a strong band with two maxima at 483 and 475 cm–1, which indicate the unequal formation of metal-oxygen bonds. the absence of in-plane bending vibrations β(oh) bands of water molecules at 1630– 1600 cm–1 indicates the formation of anhydrous salt [22]. thus, the proposed composition of bic4h3o6 for bismuth dl-tartrate is in agreement with the physicochemical studies carried out and also confirmed by ir and raman spectroscopy. 3.2. thermal analysis of bismuth dl-tartrate thermal analysis data in ar/o2 atmosphere also confirm the composition of the synthesized compound (figure 4): it is stable up to 220 °c and does not contain crystallization water. this fact indicates the possibility of drying dlbic4h3o6 samples at a temperature of 100–150 °с during their industrial preparation and the possibility of longterm storage at room temperature. further thermolysis of dl-bic4h3o6 samples proceeds with exothermic effect in the temperature range 230–280 °c. its maximum observed around 275 °c is related to tartrate ions decomposition/oxidation; according to mass spectrometry, it is accompanied by water and carbon dioxide removal. the minimum on the tg curve at 265 °c indicates the formation of metallic bismuth as a result of its reduction by carbon of tartrate ions, a further increase in mass is associated with the oxidation of metallic bismuth to oxide. in parallel, the decomposition of bismuth(iii) oxocarbonate resulting from the thermolysis of bismuth tartrate also proceeds. according to mass spectrometry, these processes are accompanied by the release of carbon dioxide. thus, the process of oxidative thermolysis of dl-bic4h3o6 is rather complicated and the effects on the dsc curve at temperature ≥345 °c corresponding to the phase transition of tetragonal modification β-bi2o3 into monocline αbi2o3 [23], indicate only a mixture of αand β-bi2o3 as a result of non-isothermal linear heating of the sample. the total mass loss of salt decomposition to bi2o3 is 34.5% and agrees with the theoretical value (34.55%). figure 3 raman spectra of dl-c4h6o6 (1) and dl-bic4h3o6 (2). figure 4 the tg-dsc curves of dl-bic4h3o6 and ms signals of h2o and co2. https://doi.org/10.15826/chimtech.2023.10.3.04 chimica techno acta 2023, vol. 10(3), no. 202310304 article 5 of 7 doi: 10.15826/chimtech.2023.10.3.04 according to xrd data (figure 5, curve 1), the samples dl-bic4h3o6 aged in air at 280 °c for 6 h represent a mixture of α-, β-bi2o3 and metallic bismuth. a decrease of annealing temperature to 240–270 °c also leads to the formation of the specified mixture of substances. the dlbic4h3o6 samples were successively keeping at temperatures of 200, 220 and 240 °c. according to xrd data, holding the sample at 200 °c for 3 h does not lead to significant changes. its diffractogram (figure 5, curve 2) coincides with the initial one for dl-bic4h3o6 (figure 1, curve 4). further heating of sample at 220 °c for 3–6 h leads to its amorphization (figure 5, curve 3). in the infrared spectrum of this sample, the vibrational bands of dl-bic4h3o6 (figure 6, curves 1 and 2) are not observed. at the same time, the bands typical for bismuth(iii) oxocarbonate of (bio)2co3 composition appear (figure 6, curve 3). thus, we can assume the formation of x-ray amorphous (bio)2co3 during keeping of dlbic4h3o6 at 220 °c. this assumption is confirmed by further exposure of the sample at 240 °c. on the diffractogram of this sample (figure 5, curve 4) the (bio)2co3 (icdd 000-41-1488) reflexes are observed at the background of x-ray amorphous halo. on the basis of the studies carried out, the following scheme can be proposed for obtaining β-bi2o3. the samples of dl-bic4h3o6 are successively kept at 220 °c for 3–6 h and then at 280 °c for 3–6 h. as a result, the single-phase samples of β-bi2o3 are obtained (icdd 010-77-5341, figure 5, curve 5). according to sem data, [bi6o4(oh)4](no3)6·h2o precipitated from nitric acid solutions by ammonium carbonate is well formed short prismatic crystals with the largest single crystal size in the basic plane of 3–10 µm and 1–3 µm thick (figure 7a). as a result of washing [bi6o4(oh)4](no3)6·h2o with water, the obtained [bi6o5(oh)3](no3)5·3h2o, is an elongated prismatic crystal with a length in the basic plane of 4–20 µm, width of 2–8 µm and thickness of 1–3 µm (figure 7b). in the subsequent step of the treatment of freshly prepared basic bismuth(iii) nitrates with dl-tartaric acid solution, the resulting dl-bic4h3o6 samples are aggregates of 5–30 µm, consisting of needle-like particles of 1-3 µm length and 0.1–0.3 µm thickness, both synthesized from [bi6o4(oh)4](no3)6·h2o (figure 7c) and from [bi6o5(oh)3](no3)5·3h2o (figure 7d). the β-bi2o3 samples obtained by oxidative thermolysis inherit the morphology of dl-bic4h3o6, also presenting aggregates of different sizes (figure 7e, f). for the synthesized powders dl-bic4h3o6 and the βbi2o3 samples obtained from them, their particle size distribution was analyzed, the results of which are shown in figure 8. table 1 shows the values of average particle/aggregate size (di), the values of their standard deviations (σ), the degree of asymmetry of particle distribution (sk) calculated by "geometric" method [24] and the value of 50 wt.% particle/aggregate size (d50). figure 5 x-ray powder diffraction patterns of dl-bic4h3o6 samples aged at different temperatures. exposure temperature: 280 (1), 200 (2), 220 (3), 240 (4), 220 and then 280 °c (5). curing times: 6 h (1), 3 h (2–4), 6 h (5). figure 6 ir spectra of dl-bic4h3o6 (1), dl-bic4h3o6 incubated at 220 °c for 6 h (2) and (bio)2co3 (3). figure 7 sem images of the initial [bi6o4(oh)4](no3)6·h2o (a), [bi6o5(oh)3](no3)5·3h2o (b); samples dl-bic4h3o6 (c, d) synthesized from (a) and (b); samples β-bi2o3 (e, f) obtained from (c) and (d). https://doi.org/10.15826/chimtech.2023.10.3.04 chimica techno acta 2023, vol. 10(3), no. 202310304 article 6 of 7 doi: 10.15826/chimtech.2023.10.3.04 figure 8 grain size frequency histograms of dl-bic4h3o6 (1, 2) synthesized from [bi6o4(oh)4](no3)6∙h2o (1) and [bi6o5(oh)3](no3)5∙3h2o (2) and β-bi2o3 (3, 4) obtained from (1) and (2) samples. table 1 results of grain size analysis for samples of dl-bic4h3o6 and β-bi2o3. samples d50, µm di, µm σ, µm sk precursor 1: dl-bic4h3o6 from bi6o4(oh)4](no3)6·h2o 12.0 10.67 2.24 –0.50 β-bi2o3 from precursor 1 9.80 8.98 2.08 –0.41 precursor 2: dl-bic4h3o6 from bi6o5(oh)3](no3)5∙3h2o 7.78 5.93 2.62 –0.48 β-bi2o3 from precursor 2 6.87 5.93 2.42 –0.41 the obtained values of the standard deviation σ are in a range of 2.00–4.00 μm, indicating a wide particle size distribution [24]. assessment of the symmetry of the distribution curves by the degree of asymmetry (|sk|<0.5) shows that the asymmetry is insignificant for all samples [24]. the analysis of the obtained results shows that the particle size distribution in the studied samples is close to normal. this suggests that the processes of dl-bic4h3o6 synthesis from basic bismuth(iii) nitrates occur in conditions close to equilibrium and are accompanied by recrystallization processes. the results of grain size analysis of dl-bic4h3o6 and βbi2o3 powders are in agreement with the electron microscopy data and indicate smaller particle/aggregate sizes in samples synthesized using [bi6o5(oh)3](no3)5·3h2o. 4. limitations this work continues our previous research on the preparation of bismuth compounds with optically active and inactive isomers of oxyacids [25]. this direction in bismuth chemistry is poorly studied. at the same time, it opens up the possibility of using new synthesized compounds in engineering and medicine. 5. conclusions treatment of high-purity basic bismuth(iii) nitrates with dl-tartaric acid solution at molar ratio of tartrate ions to bismuth equal to 1.1 and temperature of 70 °c resulted in bismuth(iii) tartrate of bic4h3o6 composition. it has been shown that the process of oxidative thermolysis of dl-bic4h3o6 includes a stage of formation of bismuth(iii) oxocarbonate (bio)2co3 and metallic bismuth. after consecutive incubation of dl-bic4h3o6 samples in air atmosphere at 220 °c for 3–6 h and then at 280 °c for 3–6 h, fine crystalline powders of tetragonal β-bi2o3, inheriting the morphology of the initial tartrates, were obtained. ● supplementary materials no supplementary materials are available. ● funding this work was performed in accordance with the thematic plans of novosibirsk state technical university (tpkhkht-1_23) and institute of solid state chemistry and mechanochemistry, siberian branch of the ras (121032500064-8). ● acknowledgments the authors would like to express their gratitude to the core facilities vtan nsu for the equipment provided for the registration of raman spectra and to the chemical research centre of n.d. zelinsky institute of organic chemistry sb ras for the spectral (ir) measurements. ● author contributions conceptualization: e.v.t. data curation: l.i.a., e.v.t. formal analysis: t.e.t., l.i.a. funding acquisition: e.v.t., l.i.a. investigation: t.e.t., e.v.t., l.i.a. methodology: e.v.t., l.i.a. project administration: e.v.t. resources: e.v.t., l.i.a. software: e.v.t., t.e.t. supervision: e.v.t., l.i.a. validation: l.i.a., t.e.t. visualization: e.v.t., l.i.a. writing – original draft: e.v.t. writing – review & editing: e.v.t., l.i.a. ● conflict of interest the authors declare no conflict of interest. https://doi.org/10.15826/chimtech.2023.10.3.04 chimica techno acta 2023, vol. 10(3), no. 202310304 article 7 of 7 doi: 10.15826/chimtech.2023.10.3.04 ● additional information author ids: evgeniya v. timakova, scopus id 25032239000; tatiana e. timakova, scopus id 57929100400; liubov i. afonina, scopus id 7006080705. websites: novosibirsk state technical university, https://www.nstu.ru/; institute of solid state chemistry and mechanochemistry, http://www.solid.nsc.ru/. references 1. amrani ma, alrafai ha, al-nami sy, labhasetwar nk, qasem a. effect of mixing on nickel tartrate and ni/nio core/shell nanoparticles: implications for morphology, magnetic, optical, dielectric and adsorption properties. opt mater. 2022;127:112321. doi:10.1016/j.optmat.2022.112321 2. ye l, duan l, liu w, hu y, ouyang z, yang s, xia z. facile method for preparing a nano lead powder by vacuum decomposition from spent lead-acid battery paste: leaching and desulfuration in tartaric 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li, yukhin yi, bulina nv, volodin va. preparation of bismuth(iii) malates by precipitation from nitrate solutions. chem sustain dev. 2017;25(3):293–300. available from: https://sibran.ru/upload/iblock/3a2/preparation_of_bismut h_iii_malates_by_precipitation_from_nitrate_solutions.pdf. accessed on 28 june 2023 https://doi.org/10.15826/chimtech.2023.10.3.04 https://www.scopus.com/authid/detail.uri?authorid=25032239000 https://www.scopus.com/authid/detail.uri?authorid=57929100400 https://www.scopus.com/authid/detail.uri?authorid=7006080705 https://www.nstu.ru/ http://www.solid.nsc.ru/ https://doi.org/10.1016/j.optmat.2022.112321 https://doi.org/10.1016/j.hydromet.2020.105450 https://doi.org/10.1016/j.matchemphys.2019.122024 https://doi.org/10.1007/s11595-022-2519-x https://doi.org/10.1007/s11244-020-01370-4 https://doi.org/10.1021/acsanm.1c03208 https://doi.org/10.1016/j.jmrt.2020.10.015 https://doi.org/10.1016/j.matpr.2021.07.057 https://doi.org/10.3233/mgc-160216 https://doi.org/10.1039/d0ta06466a https://doi.org/10.1016/j.tca.2020.178511 https://doi.org/10.15826/chimtech.2022.9.3.15 https://doi.org/10.1134/s0040579520050097 https://doi.org/10.1134/s0040579517040303 https://doi.org/10.5539/ijc.v12n1p78 https://doi.org/10.5539/ijc.v13n1p38 https://doi.org/10.1016/j.ceramint.2020.11.006 https://doi.org/10.1016/j.saa.2013.12.045 https://doi.org/10.1002/jrs.2743 https://doi.org/10.1002/jrs.1250190108 https://doi.org/10.1039/c6ra03055f https://doi.org/10.1134/s0036023607120030 https://doi.org/10.1002/esp.261 https://sibran.ru/upload/iblock/3a2/preparation_of_bismuth_iii_malates_by_precipitation_from_nitrate_solutions.pdf https://sibran.ru/upload/iblock/3a2/preparation_of_bismuth_iii_malates_by_precipitation_from_nitrate_solutions.pdf effect of sn doping on sinterability and electrical conductivity of strontium hafnate published by ural federal university eissn 2411-1414 chimicatechnoacta.ru article 2023, vol. 10(1), no. 202310113 doi: 10.15826/chimtech.2023.10.1.13 1 of 8 effect of sn doping on sinterability and electrical conductivity of strontium hafnate adelya s. khaliullina * , anastasia n. meshcherskikh , liliya a. dunyushkina laboratory of electrochemical material science, institute of high temperature electrochemistry, ekaterinburg 620066, russia * corresponding author: adelia01@mail.ru this paper belongs to a regular issue. abstract the effect of isovalent substitution of hafnium by tin in strontium hafnate on sinterability and electrical conductivity was studied for the first time. the ceramic samples srhfxsn1–xo3–δ (x = 0–0.16) were synthesized by solid-state reaction and sintered at 1600 °c for 5 h. the samples were examined using the methods of x-ray diffraction, scanning electron microscopy, impedance spectroscopy, and four-probe direct current technique. it was shown that all samples were phase pure and had the orthorhombic structure of srhfo3 with the pnma space group. sn doping resulted in an increase in grain size, relative density and conductivity; the sample with x = 0.08 demonstrated the highest conductivity, which was ~830 times greater than that of undoped strontium hafnate at 600 °c. the conductivity of srhf0.92sn0.08o3–δ was 4.1∙10–6 s cm–1 at 800 °c in dry air. the possible reasons for the effect of sn on the electrical properties of strontium hafnate were discussed. keywords strontium hafnate perovskite electrical conductivity electrolyte received: 16.02.23 revised: 13.03.23 accepted: 14.03.23 available online: 17.03.23 key findings ● ceramic samples srhfxsn1–xo3–δ (x = 0–0.16) were obtained by the solid-phase method. ● sn doping enhances the sintering ability of ceramics. ● sn doping results in an increase in conductivity by more than 2 orders of magnitude . © 2023, the authors. this article is published in open access under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). 1. introduction complex oxides with the abo3 perovskite structure are of interest as functional elements of electronics, thermal barrier coatings, electrolytes and electrodes for hightemperature electrochemical applications [1–7]. in the 1980s, compounds capable of proton transfer were discovered among perovskites [8–11], and since then, active research has been carried out in the field of developing perovskites with high proton conductivity. among perovskite-like oxides of the a2+b4+o3 type, the materials based on baceo3 and srceo3 exhibit the highest proton conductivity [12–16], but their use in electrochemical cells is hindered by their low chemical resistance to carbon dioxide. zirconates and hafnates of alkaline earth metals are characterized by high chemical stability, which makes them promising for practical applications, and possess oxide-ion and proton conductivity; however, the ionic conductivity of these materials is low [17–21]. it is known that the substitutions in a and b positions affect many characteristics of abo3 perovskites; therefore, this approach is widely used to modify the ionic conductivity. as a rule, the method of acceptor doping is used, which makes it possible to increase the concentration of oxygen vacancies and, accordingly, the ionic conductivity [20–25]. in addition, doping is a common approach to improving the sinterability of solid oxides. solid oxide electrolytes, including those with a perovskite structure, are refractory materials, which are sintered at very high temperatures [28–34]. yamanaka et al. [26] reported on the fabrication of ceramic samples of srhfo3 with the relative density of 94% by the solid state method, followed by the prolonged sintering at 1600 °c for 10 h. qian et al. [29] used alumina as sintering aid to increase the density of ce-doped srhfo3 ceramics. the powders of sr0.995ce0.005hfo3 and sr0.995ce0.005hf0.995al0.005o3 were synthesized by the solid state method, pressed into pellets and sintered at 1800 °c for 20 h in vacuum; it was found that the addition of al rehttp://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2023.10.1.13 mailto:adelia01@mail.ruuz http://creativecommons.org/licenses/by/4.0/ https://orcid.org/0000-0002-9616-029x https://orcid.org/0000-0002-9541-6847 https://orcid.org/0000-0003-3369-5454 https://crossmark.crossref.org/dialog/?doi=https://doi.org/10.15826/chimtech.2023.10.1.13&domain=pdf&date_stamp=2023-03-17 chimica techno acta 2023, vol. 10(1), no. 202310113 article 2 of 8 doi: 10.15826/chimtech.2023.10.1.13 sulted in the increase in density up to 98.9%. the use of spark plasma sintering (sps) method was reported to be effective for fabrication of the high-density ceramics of strontium hafnate [30, 31]. the powder synthesized by the solid state method was poured into a graphite die, placed in a sps chamber, stepwise heated to a high temperature (1600–1900 °c), and kept at this temperature for 45 min; the relative density of the obtained samples was more than 99%. it is obvious that the use of sintering technologies, based on long-term high-temperature annealing, sometimes under vacuum conditions, or on the sps method, leads to a significant increase in the cost of ceramics. consequently, the search for additives that promote better sintering of alkaline earth hafnates is relevant. a positive effect of the partial substitution of hafnium by indium and tin on the sintering of bahf0.9–xinxsn0.1o3–δ (x = 0.05–0.25) ceramics was reported in [22]. it was shown that the introduction of indium alone made it possible to achieve a relative density of ~94%, while the codoping led to an increase in density up to 96.25%. isovalent substitution should also affect the ionic conductivity of oxides, in addition to their sinterability, due to the difference in ionic radii and the electronegativity of the host and dopant cations. it was shown in [35] that the introduction of tin into bazr0.8sc0.2o3–δ led to an increase in conductivity, although it was accompanied by a decrease in the average grain size in bazr0.8–xsnxsc0.2o3–δ ceramics from 0.97 μm for x=0 to 0.39 μm for x=0.2. however, it is difficult to assess the effect of partial substitution of hafnium by tin on the sintering ability of bazr0.8sc0.2o3–δ, since the authors additionally introduced a sintering aid, 0.5 wt.% cuo, and did not analyze the change in density depending on the tin content. to the best of the authors, knowledge, there are no data on the effect of sn-doping on the sintering behavior and electrical properties of strontium hafnate. this research aims to study the effect of isovalent substitution of hafnium by tin in strontium hafnate on sinterability and electrical conductivity. the ceramic samples srhfxsn1–xo3–δ (x = 0–0.16) were obtained by solid state synthesis, their phase composition and microstructure were studied by x-ray diffraction (xrd) and scanning electron microscopy (sem), electrical conductivity was measured by the impedance method and the four-probe direct current (dc) method. 2. experimental part srhfxsn1–xo3–δ (x = 0.04–0.16) compositions were synthesized by the solid state reaction method using hfo2, srco3 and sno2 (all with 99.9% purity) as precursors. the starting materials were preliminary dried at a temperature of 150 °c for 5 hours to remove adsorbed water, and then thoroughly mixed in a planetary mill (retsch pm 100) in a calculated ratio. the synthesis was carried out at 1200 °c for 6 hours with intermediate regrinding. then the powder was pressed into pellets under a pressure of 300 mpa and sintered at a temperature of 1600 °c for 5 hours in air. a schematic diagram of the fabrication of srhfxsn1–xo3–δ samples is presented in figure 1. the apparent density of the samples was determined as the mass to volume ratio, which were determined by weighing and measuring the dimensions of the sample. the relative density was calculated as the ratio of measured to theoretical density. the phase composition and crystal structure of the sintered samples were studied using an x-ray diffractometer d-max 2200 (rigaku, tokyo, japan) in cu kα radiation within 2θ range from 20 to 80° at a scanning speed of 0.02 rpm with a step of 0.1°. the x-ray diffraction (xrd) measurements were performed at room temperature. to study the microstructure of the samples by sem, the surface of the samples was polished using diamond pastes and thermally etched at a temperature of 1200 °c for 4 hours in order to make the granular structure of ceramics visible. the microstructure of the samples was studied using a mira 3 lmu electron microscope (tescan, brno, czech republic). impedance measurements were performed on a biologic sp-200 impedance meter in the frequency range from 0.1 hz to 1 mhz with an amplitude of 30 mv in dry air (ph2o = 40 pa). for these measurements, platinum paste was symmetrically applied to the opposite faces of the srhfxsn1–xo3–δ pellets and sintered at 1000 °c (1 hour); the area of the pt electrodes was 0.6 cm2. dry air was obtained by blowing atmospheric air through a column filled with zeolite beads. the measurements were carried out in the temperature range of 550–800 °c. for the spectra analysis, the methods of equivalent circuits (zview software) and distribution of relaxation times (drt) (drttools software) were applied. to measure the electrical conductivity by the four-probe dc method, a sample in the form of a bar was cut out from the pellet. four pt wires were wound on to the sample to serve as current electrodes and potential probes. the distance between the potential probes was 0.75 cm, and the cross-sectional area of the sample was 0.05 cm2. figure 1 schematic diagram of srhfxsn1–xo3–δ ceramics fabrication. https://doi.org/10.15826/chimtech.2023.10.1.13 chimica techno acta 2023, vol. 10(1), no. 202310113 article 3 of 8 doi: 10.15826/chimtech.2023.10.1.13 electrical conductivity σ was calculated using the following formula: 𝜎 = 𝑈𝑆 𝐼𝐿 , (1) where s and l are the cross-sectional area of the sample and the distance between the potential probes, i is the current, and u is the voltage. the dc measurements were performed at 900 °с in the po2-range of 10–18–0.21 atm using a zirconia-318 regulator which ensured the automatical change and control of the oxygen partial pressure. the schematic view of the dc measurement setup is shown in figure 2. figure 2 schematic view of dc measurement setup: 1 – sample, 2 – platinum wires, 3 – ysz tube, 4 – electrochemical pump, 5 – electrochemical sensor, 6 – gas inlet and outlet tubes, 7 – thermocouple, 8 – zirconia-318 regulator, 9 – valve, 10 – fluoroplastic plug, 11 – bubbler, 12 – gas cylinder or compressor, 13 – sealant. 3. results and discussion 3.1. characterization of the structure and morphology of the srhfxsn1–xo3–δ samples analysis of the xrd patterns of srhfxsn1–xo3–δ sintered samples, which are presented in figure 3a, showed that all the samples are single-phase and have the orthorhombic structure of srhfo3 with the pnma space group (icdd 895605). no impurity phases were found in the samples. figure 3b shows that sn doping results in the peak shifting towards higher 2θ angles. a linear decrease in the unit cell volume with an increase in the tin content in strontium hafnate (figure 3c) is consistent with the assumption that tin incorporates into the srhfo3 crystal lattice, replacing hafnium, since the ionic radius of tin is 0.069 nm, and the ionic radius of hafnium is 0.071 nm. a schematic structure of srhfxsn1–xo3–δ is presented in figure 3d. the morphology of srhfxsn1–xo3–δ ceramic samples was evaluated from the sem images displayed in figure 4. as can be seen, the undoped strontium hafnate has a nanograin structure with an average grain size of ~100 nm, while sn doping results in the grain growth: in the doped samples, the grain size varies from 1 to 5 μm, and the morphology of the ceramics practically does not change with the tin content. figure 3 xrd patterns of srhfxsn1–xo3–δ (a), the magnified fragment of diffractograms showing (002) peak (b), unit cell volume of srhfxsn1–xo3–δ as a function of sn content (c), and schematic structure of srhfxsn1–xo3–δ (d). https://doi.org/10.15826/chimtech.2023.10.1.13 chimica techno acta 2023, vol. 10(1), no. 202310113 article 4 of 8 doi: 10.15826/chimtech.2023.10.1.13 figure 4 sem images of the surface of srhfxsn1–xo3–δ samples: x = 0 (a, b), x = 0.04 (c), x = 0.08 (d), x = 0.12 (e), х = 0.16 (f). the relative densities of the sintered srhfxsn1–xo3–δ samples are presented in table 1. as can be seen, the introduction of 4 at.% sn improves the sintering of ceramics, however, an increase in the tin concentration has practically no effect on their density, which is close to 80% for all sn-doped samples. the relatively low density of the ceramics indicates that further efforts are needed to sinter the high-density strontium hafnate-based ceramics. 3.2. electrical conductivity of srhfxsn1–xo3–δ the impedance measurements of srhfxsn1–xo3–δ (x = 0.04– 0.16) samples were performed in the temperature range of 550–800 °c in dry (ph2o = 40 pa) air. the impedance of the undoped srhfo3 could not be measured because of its very high resistance. for illustration, the hodographs of srhfxsn1–xo3–δ measured in dry air at temperatures of 700–800 °c are shown in figure 5a–d. figure 5e presents the fitting of the spectrum on the basis of the equivalent circuit consisting of three rq elements connected in series (r denotes a resistance, q is a constant phase element), and the results of drt analysis for the sample with x = 0.08 at 700 °c. taking into account the obtained characteristic capacitances, the high-frequency semicircle (c~10–11 f cm–2) can be assigned to the response of grain interior of a sample, the medium-frequency semicircle (c~10–8 f cm–2) is related to grain boundaries, and the low-frequency arc with a high capacitance (c~10–3 f cm–2) is caused by the electrode processes. as can be seen in figure 5a–d, in the most of hodographs the grain boundary response is small compared to that of the bulk, which makes it difficult to reliably separate the grain boundary resistance; therefore, only the total resistance of the srhfxsn1–xo3–δ electrolytes was discussed. the conductivity of the samples was calculated as follows: 𝜎 = ℎ 𝑅el𝑆 , (2) where h is the thickness of a sample, s is the area of electrodes, rel is the electrolyte resistance. the arrhenius dependences of conductivity presented in figure 6 are nearly linear; the activation energy for all compositions is 1.5±0.1 ev. for comparison, the figure shows the conductivities of undoped strontium hafnate and strontium zirconate reported in [26, 36]. it can be seen that the substitution of hafnium by tin leads to an increase in conductivity by more than 2 orders of magnitude, e.g., the most conductive composition with x = 0.08 exhibits a conductivity ~830 times greater than undoped strontium hafnate at 600 °c, despite the fact that the density of the srhfxsn1–xo3–δ samples (~80%) is significantly lower than the density of the srhfo3 sample (95%), which was sintered at a much higher temperature of 1750 °c [36]. figure 7 demonstrates the conductivity dependences of srhfxsn1–xo3–δ on the sn concentration; as can be seen, the sample with x = 0.08 has the highest conductivity, which is equal to 4.1∙10–6 s cm–1 at 800 °c. however, the conductivity of srhf0.92sn0.08o3–δ sample is still lower than that of srzro3 by about an order of magnitude, as can be seen in figure 6. in general, an increase in ionic conductivity upon doping may be due to an increase in the concentration of charge carriers (oxygen vacancies in the case of oxide-ion conductors) and/or an increase in their mobility. the isovalent substitution sn4+→hf4+ should not lead to the formation of additional oxygen vacancies; therefore, it can be assumed that the increase in conductivity upon sn doping is related to the higher mobility of oxygen vacancies. however, the smaller radius of sn4+ ion compared to the hf4+ ion is expected to lower the mobility because of the narrowing of channels for oxide-ions migration, although the size factor should not lead to a noticeable effect at low dopant concentrations. probably, it is the chemical nature of tin, namely, its electron configuration, which influences interatomic bonding and, accordingly, the mobility of charge carriers in srhfxsn1–xo3–δ. table 1 relative density of srhf1–хsnxo3–δ ceramic samples. х 0 0.04 0.08 0.12 0.16 relative density, % 75±2 82±2 79±2 79±2 82±2 https://doi.org/10.15826/chimtech.2023.10.1.13 chimica techno acta 2023, vol. 10(1), no. 202310113 article 5 of 8 doi: 10.15826/chimtech.2023.10.1.13 figure 5 impedance spectra of srhfxsn1–xo3–δ in dry air: x = 0.04 (a), x = 0.08 (b), x = 0.12 (c), x = 0.16 (d), impedance with fitting and drt spectra for srhf0.92sn0.08o3–δ at 700 °c (e). figure 6 arrhenius plots of srhfxsn1–xo3–δ conductivity in dry air. solid lines show the conductivity of srzro3 [26] and srhfo3 [36]. the open triangle is the conductivity of the sample with x = 0.08 measured by the four-probe dc method. figure 7 conductivity of srhfxsn1–xo3–δ as a function of sn-content in dry air. open symbols are the conductivity of srhfo3 reported in [36]. -11 -10 -9 -8 -7 -6 -5 -0.04 0 0.04 0.08 0.12 0.16 x lg σ , s ·c m -1 800 °с 600 °с 700 °с 750 °с 650 °с 550 °с https://doi.org/10.15826/chimtech.2023.10.1.13 chimica techno acta 2023, vol. 10(1), no. 202310113 article 6 of 8 doi: 10.15826/chimtech.2023.10.1.13 in addition, it can be assumed that the very thin film of tin oxide is formed at the grain boundaries of doped strontium hafnate, which is undetectable by the conventional xray diffraction and microscopy methods. the impedance data are consistent with this assumption: the response of grain boundaries is not visible in the most of hodographs, which indicates that the contribution of boundaries to the total resistance of the samples is very small (figure 5 a–d). probably, the existence of the film of tin oxide results in a decrease of the resistance of grain boundaries, which is known to be one of the main reasons for the low conductivity of the related perovskites based on strontium zirconate [26, 37], and, as a result, the total conductivity of the sndoped samples increases. however, further studies are needed to establish the mechanism of the effect of sn doping on the electrical conductivity of strontium hafnate. to determine the type of charge carriers, the conductivity of srhf0.92sn0.08o3–δ sample, which exhibits the highest conductivity, as a function of po2 was studied using the four-probe dc method. due to the high resistance of the sample, the measurements were carried out at a high temperature of 900 °c. as can be seen in figure 8, the conductivity increases with increasing po2 under oxidizing conditions (ро2 > 10–5 atm), while a wide plateau is observed in reducing atmospheres (10–18–10–5 atm). the value of conductivity at the plateau is considered an oxide-ion conductivity, which is independent of ро2. an increase in conductivity at high ро2 is typically related to generation of oxygen holes upon oxygen incorporation into oxide lattice according to the generally accepted mechanism of defect formation. in this mechanism, the equilibrium between gaseous oxygen, oxygen ions, oxygen vacancies and holes in oxide-ion conducting oxides in oxidizing atmospheres can be represented in terms of kröger-vink notation as follows: 1 2 o2 + vo •• = oo 𝑥 + 2ℎ•, (3) the electroneutrality condition for reaction 3 can be written as follows: ℎ• = 2[vo ••]. (4) taking into account the electroneutrality condition (equation 4) and the mass action law for equation 3 one can derive that the hole concentration is proportional to 𝑝o2 1 6⁄ . as long as the hole conductivity is proportional to the hole concentration, the slope of the log σ – log po2 dependence is to be equal to 1/6. however, the slope of the experimentally obtained dependence shown in figure 8 is lower, which can be caused by different reasons. first, in the transition region, in which the oxide-ion and hole conductivities are comparable, the slope may vary from zero to 1/6. second, the tin oxide film, which is supposedly formed on the surface of grains in srhfxsn1–xo3–δ may hinder the oxygen incorporation (reaction 3) and the hole generation. figure 8 conductivity of srhf0.92sn0.08o3–δ as a function of po2 at 900 °c. thus, based on the conductivity dependence on po2, it can be concluded that in sn-doped strontium hafnate oxide-ion conductivity dominates in a wide range of po2, while the hole conductivity appears under oxidizing conditions. the transference number of ions ti can be evaluated from the log σ – log po2 dependence as a ratio of the ionic conductivity, which is the conductivity on the plateau, to the conductivity at any value of po2; e.g., for srhf0.92sn0.08o3–δ at 900 °c, ti = 0.35 in air and gradually increases with decreasing po2, approaching unity at po2 of 10–6 atm. 4. limitations sn doping improves the density of srhfo3-based ceramic samples; however, the resulting ceramic is not sufficiently dense for application in electrochemical cells, such as fuel cells or electrolysis cells, which require the use of a gastight electrolyte. our further research aims at the fabrication of high-density ceramics by using nanopowders and sintering aids, and manufacturing and testing fuel and electrolysis cells. 5. conclusions in the present research, the effect of isovalent substitution of hafnium by tin in strontium hafnate on sinterability and electrical conductivity was considered. srhfxsn1–xo3–δ (x = 0–0.16) ceramic samples were obtained by the solidphase method. all samples were found to be phase pure and have the orthorhombic structure of srhfo3 with pnma space group. the sn doped samples sintered at a temperature of 1600 °c for 5 hours exhibited a higher relative density (80±2%) compared to the undoped sample (75±2%). the grain size increased from ~100 nm to 1–5 μm upon the sn-doping. the study of conductivity revealed that the substitution of hafnium by tin leads to an increase in conductivity, and the highest conductivity (4.1∙10–6 s cm–1 at 800 °c in dry air) is observed for the sample with x = 0.08. the conductivity of -6.0 -5.5 -5.0 -4.5 -20 -15 -10 -5 0 lg po2, atm lg σ , s c m − 1 1/6 https://doi.org/10.15826/chimtech.2023.10.1.13 chimica techno acta 2023, vol. 10(1), no. 202310113 article 7 of 8 doi: 10.15826/chimtech.2023.10.1.13 srhf0.92sn0.08o3–δ is ~830 times greater than that of the undoped strontium hafnate at 600 °c. the activation energy of the conductivity of srhfxsn1–xo3–δ is 1.5±0.1 ev. the dependence of conductivity on the oxygen partial pressure indicates that the oxide-ion conductivity dominates in a wide range of po2, while the hole conductivity appears under oxidizing conditions. for srhf0.92sn0.08o3–δ composition, the transference number of ions in air was 0.35 at 900 °c. it is not clear why the isovalent substitution gives a significant increase in conductivity; further research using the high-resolution electron microscopy and energydispersive x-ray spectroscopy methods is needed for understanding the mechanism of the sn-doping effect on the properties of strontium hafnate. ● supplementary materials no supplementary materials are available. ● funding this research had no external funding. ● acknowledgments sem and xrd experiments were done using the facilities of the shared access centre "composition of compounds” (institute of high-temperature electrochemistry, ural branch of the russian academy of sciences). the authors are grateful to artem tarutin for the help with the measurements of conductivity by the dc 4-probe method. ● author contributions conceptualization: l.a.d. visualization: a.s.k. investigation: a.s.k., a.n.m. methodology: l.a.d., a.s.k, a.n.m. supervision: l.a.d. writing – original draft: a.s.k. writing – review & editing: l.a.d. ● conflict of interest the authors declare no conflict of interest. ● additional information author ids: adelya s. khaliullina, scopus id 57206712878; anastasia n. meshcherskikh, scopus id 56784365300; liliya a. dunyushkina, scopus id 6507914539. website: institute of high temperature electrochemistry ub ras, http://www.ihte.uran.ru. references 1. hwang sc, choi gm. the mixed ionic and electronic conductivity of cazro3 with cation nonstoichiometry and oxygen partial pressure. solid state ionics. 2008;179:1042–1045. doi:10.1016/j.ssi.2007.11.034 2. wang c, xu x, yu h, wen y, zhao k. a study of the solid electrolyte y2o3 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electrochemical devices based on solid oxide proton electrolytes, institute of high temperature electrochemistry, yekaterinburg 620066, russia * corresponding author: wolkov@ihte.uran.ru this paper belongs to a regular issue. abstract solid-state gas sensors composed of complex oxide electrolytes offer great potential for analyzing various atmospheres at high temperatures. while relatively simple gas mixtures (h2o+n2, o2+n2) have been successfully studied by means of zro2-based sensors, the precise detection of more complex compounds represents a challenging task. in this work, we present our findings regarding the analysis of lower alkanes (ch 4, c2h6, and c3h8) mixed with nitrogen as an inert gas, utilizing an amperometric zro2-based sensor. this sensor, serving as an electrochemical cell with a diffusion barrier, was tested at 500–600 °c to measure the limiting current, which depends on the gas composition and can be further used as a basis for calibration curves. in addition, the diffusion coefficients of the specified gas mixtures were successfully found and compared with references, confirming the applicability of the fabricated sensor for studying diffusion processes in wide concentration and temperature ranges. keywords alkanes electrochemical approaches limiting current diffusion amperometric sensors diffusion barrier received: 08.02.23 revised: 13.02.23 accepted: 13.02.23 available online: 14.02.23 © 2023, the authors. this article is published in open access under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). 1. introduction complex oxide electrolytes based on zirconia are widely used in many fields of science and technology. one of the promising fields of zro2-containing materials application is analytical chemistry. for example, potentiometric solidstate sensors have been successfully used to monitor the exhaust gases of various heat units and vehicles [1–4]; moreover, they can be used to measure the oxygen activity in metal melts [5] and to detect some gases in the environments (nh3 [6], no2 [7], h2s [8]). based on the concept of potential reading, such types of sensors operate efficiently for detecting low oxygen contents in gases/melts compared to reference conditions (an electrode in air or oxygen atmospheres). to detect a relatively high concentration of the analyzed components, the so-called amperometric-type sensors can be employed. in detail, the zro2-based amperometric sensors have recently been used for measuring the contents of o2, h2, co2 and h2o in inert gases [9–13]. the reading parameter of such sensors is a limiting current, representing an electrical equivalent of the concentration and diffusion parameters of the analyzed gas media. the amperometric sensors allow the analysis of more complex gases, which may contain lower alkanes (ch4, c2h6, and c3h8), not only in terms of gas composition, but also in terms of diffusion coefficients. at present, there are no reliable methods or appropriate techniques for measuring the diffusion coefficients of gases due to the complexity of the equipment and the methodological difficulties, although these coefficients are widely used in the calculation of combustion processes, in chemical kinetics; in addition, the diffusion coefficients are included in many dimensionless criteria for heat and mass transfer. the knowledge of the binary diffusion coefficients for combustible gases is necessary when calculating the processes of transport and regasification of natural gases. in the present work, we develop a new hightemperature ysz-based sensor for the analysis of ch4+n2, c2h6+n2, and c3h8+n2 gas mixtures and the determination of their binary diffusion coefficients. http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2023.10.1.09 http://creativecommons.org/licenses/by/4.0/ https://orcid.org/0000-0002-8816-4303 https://orcid.org/0000-0002-5184-986x https://crossmark.crossref.org/dialog/?doi=https://doi.org/10.15826/chimtech.2023.10.1.09&domain=pdf&date_stamp=2023-02-14 chimica techno acta 2023, vol. 10(1), no. 202310109 letter 2 of 6 doi: 10.15826/chimtech.2023.10.1.09 2. experimental part 2.1. operation principles the working principle of the fabricated amperometric sensor is shown in figure 1. this sensor consists of two plates made of ysz (0.91zro2 + 0.09y2o3) electrolyte glued together by a high-temperature glass sealant. each plate has a cavity, in which a capillary was placed as a diffusion barrier. the capillary is a ceramic tube with an inner diameter of 265 µm and a length of 20 mm. the cavity has a depth of 0.5 mm and an area of approximately 60 mm2. platinum electrodes with wire current leads were organized on opposite surfaces of one solid electrolyte plate. during all the measurements, the electrochemical cell is in the flow of the analyzed gas, while the latter diffuses through the capillary into its internal cavity. there is no free oxygen in the analyzed gas, and oxygen is formed as a result of the dissociation of moisture present in the analyzed gas: h2o + 2e ′ → h2 + o 2−. (1) the oxygen produced by the dissociation of water vapor must be pumped into the cavity of the cell. to provide such a pumping, it is necessary to apply a minus from a dc source to the outer electrode of the cell, and a plus to the inner electrode, respectively. alkane oxidation then takes place at the inner electrode according to the following overall reactions: 4o2− + ch4 − 8e ′ → co2 + 2h2o, (2) 7o2− + c2h6 − 14e ′ → 2co2 + 3h2o, (3) 10o2− + c3h8 − 20e ′ → 3co2 + 4h2o. (4) when working with mixtures of ch4+n2, c2h6+n2, and c3h8+n2, the oxygen pumping current into the sensor cavity ranged from several microamperes to tens of microamperes. as the voltage applied to the cell increases, the current increases and then stabilizes, reaching a certain value corresponding to the as-called limiting current. its values, as shown by the results of this study, are proportional to the concentration of methane, ethane, or propane in the analyzed gases. the appearance of the limiting current is due to the reaction between the hydrocarbons and oxygen ions on the inner surface of the zirconium electrolyte. it is important to note that the flow of the analyzed combustible gas entering the cavity of the electrochemical cell is limited by the diffusion barrier (capillary), which governs the limiting current value. therefore, the measured limiting current is a function of the concentration of the measured hydrocarbon in the analyzed gaseous medium, temperature and geometrical parameters of the diffusion barrier according to the following equation [13]: 𝐼lim = 𝑛 ∙ 𝐹 ∙ 𝑃 ∙ 𝐷 ∙ 𝑆 𝑅 ∙ 𝑇 ∙ 𝐿 ln(1 − 𝑐c𝑥h𝑦), (5) where n in the electron numbers required for full oxidation of 1 mole of alkane, f is the faraday’s constant, p is the total pressure of the analyzed gas (p = 1 atm), d is the binary diffusion coefficient of n2 and alkane mixture, s and l are the cross-section area and length of the capillary, r is the universal gas constant, t is the absolute temperature, 𝑐c𝑥h𝑦 is the volume concentration of alkane in nitrogen. at the relatively low concentration values, the ln(1 − 𝑐c𝑥h𝑦) term is equal to 𝑐c𝑥h𝑦. in turn, the d values depend on the standard conditions as follows [14]: 𝐷 = 𝐷0 ( 𝑇 𝑇0 ) 𝑛 ( 𝑃 𝑃0 ), (6) where to and po are the standard parameters. considering equations (5) and (6) together, one can see that the standard diffusion coefficients can be found, if the limiting current values are known. 2.2. characterization of the sensor the fabricated sensor was placed in an oven and heated to the desired temperature (500, 550 or 600 °c). then the analyzed gas mixtures (ch4+n2, c2h6+n2, or c3h8+n2) were fed to the sensor followed by equilibration of this system for 1 h. these gas mixtures were prepared by adding a portion of hydrocarbons into the nitrogen flow by f-201c-33-v gas flow meters. the dc voltage (gps-18500 instek) was applied to the electrodes to provide electrochemical pumping of oxygen. 3. results and discussion the as-fabricated sensor was first tested with the ch4+n2 gas mixtures. its typical volt-ampere dependences at different gas compositions are presented in figure 2a. three clearly distinguished regions appear at these dependences with a gradual increase in the applied voltage: current growth (i region), a wide range of constant current values (ii region) followed by further current growth (iii region). in the i region, the applied voltage causes oxygen pumping from the external to inner electrode, where the methane oxidation reaction occurs (equation (1)). figure 1 principle scheme of operating the fabricated gas sensor: 1 is the electrolyte discs, 2 is the high-temperature glass sealant, 3 is the cavity, 4 is the platinum electrodes, and 5 is the capillary. https://doi.org/10.15826/chimtech.2023.10.1.09 chimica techno acta 2023, vol. 10(1), no. 202310109 letter 3 of 6 doi: 10.15826/chimtech.2023.10.1.09 figure 2 electrochemical response of the sensor operated in x vol.% ch4 + (1–x) vol.% n2 gas mixtures: (a) volt-ampere dependences at 550 °c and various methane concentration; (b) voltampere dependences at various temperature and x = 2.47; (c) calibration curve at 550 °c. an amount of methane is sufficiently high compared to the oxygen equivalent flow expressed in the current term; as a result, the current rises with increasing the applied voltage. when all the methane molecules in the sensor’s cavity (including those supplied through the capillary) are electrochemically oxidized, the current values stabilize and do not change with a further increase of the applied voltage, ii region. this region corresponds to the realization of the limiting current. finally, when the applied voltage exceeds a certain value, the current increases again (iii region) due to the possible appearance of electronic conductivity [15]. considering the effects of gas composition, it can be seen that the limiting current region increases with its range and in absolute current values, indicating that more oxygen ions should be pumped to oxidize more methane molecules. figure 2b shows similar volt-ampere dependencies obtained for a given gas composition at various temperatures. the limiting current range is virtually unchanged with heating (~about 0.6 v), but the limiting current value increases at the same time. the latter can be explained by improved diffusion of methane molecules into the sensor’s cavity. therefore, a higher oxygen-ion flux is required to oxidize these molecules. the concentration dependence of the limiting current is close to a linear form (figure 2c), which allows these data to be used for the analysis of real ch4+n2 gas mixtures with unknown concentrations of the components. similar characteristics were obtained for c2h6+n2 and c3h8+n2 mixtures in the temperature range of 500–600 °с (figure 3). in general, the electrochemical characteristics have similar trends discussed for the ch4+n2 gas mixtures, with some distinctive points. first, the limiting current values considerably decrease in a series of ch4–c2h6–c3h8 (at close concentrations and the same temperatures), indicating that heavy molecules diffuse more slowly through the capillary. second, the concentration range of the limiting current narrows as the molecular weight of the alkane increases, which limits the analytical capabilities of the sensor. nevertheless, an important advantage of the fabricated sensor is the ability to determine the binary diffusion coefficients from the measured limiting current values (even if they are not high) according to equations (5) and (6). table 1 lists the experimentally obtained diffusion coefficient values for methane in nitrogen for three temperatures and their comparison with reference data. as can be seen from table 1, the experimentally obtained d values for methane in nitrogen have some discrepancies with the reference data obtained by other methods. this may be due to the fact that the reference data do not take the ch4 concentration into account, since in most cases, the d values were obtained for mixtures with a parity concentration of the components, usually 50% to 50%. in addition, available reference data are often presented for several temperatures, typically 0 and 25 °c, and had to be recalculated for elevated temperatures according to equation (6). the experimental data show that the d values depend not only on the temperature, but also on the component concentrations (especially, methane), and this dependence is quite complex. table 2 presents similar d data measured and compared for the c2h6+n2 gas mixtures. there is an acceptable agreement between the measured d values and reference data. however, the reference d values are somewhat higher than the experimental data for the entire temperature range and the considered ethane concentrations. this may be due to the different features of the experimental techniques used in the literature and in this work. finally, table 3 lists the experimental results for the propane – nitrogen gas mixtures. the comparison of the experimental and reference values shows that they are in the best agreement with each other. https://doi.org/10.15826/chimtech.2023.10.1.09 chimica techno acta 2023, vol. 10(1), no. 202310109 letter 4 of 6 doi: 10.15826/chimtech.2023.10.1.09 figure 3 electrochemical response of the sensor operated in x vol.% c2h6 + (1–x) vol.% n2 gas mixtures (left column) and x vol.% c3h8 + (1–x) vol.% n2 gas mixtures (right column): (a) volt-ampere dependences at 550 °c and various methane concentration; (b) volt-ampere dependences at various temperature and x = 2.47; (c) calibration curve at 550 °c. table 1 measured and reference binary diffusion coefficients (d) for the x vol.% ch4 + (1–x) vol.% n2 gas mixtures. temperature (°с) d (cm2 s–1) x = 0.29 d (cm2 s–1) x = 0.61 d (cm2 s–1) x = 0.98 d (cm2 s–1) x = 1.41 d (cm2 s–1) x = 2.47 d (cm2 s–1) [16] d (cm2 s–1) [17] 500 1.8 1.8 1.78 1.77 1.6 1.22 1.32 550 1.3 1.4 1.8 1.9 1.7 1.35 1.48 600 2.2 2.1 2.05 1.7 1.8 1.50 1.66 table 2 measured and reference binary diffusion coefficients (d) for the x vol.% c2h6 + (1–x) vol.% n2 gas mixtures. temperature (°с) d (cm2 s–1) x = 0.18 d (cm2 s–1) x = 0.36 d (cm2 s–1) x = 0.60 d (cm2 s–1) x = 1.28 d (cm2 s–1) x = 2.18 d (cm2 s–1) [17] 500 0.64 0.65 0.69 0.63 0.55 0.76 550 0.68 0.69 0.74 0.67 0.59 0.85 600 0.72 0.73 0.78 0.71 0.62 0.93 table 3 measured binary diffusion coefficients (d) for the x vol.% c3h8 + (1–x) vol.% n2 gas mixtures. temperature (°с) d (cm2 s–1) x = 0.09 d (cm2 s–1) x = 0.13 d (cm2 s–1) x = 0.20 d (cm2 s–1) x = 0.51 d (cm2 s–1) [17] 500 0.52 0.49 0.59 0.50 0.55 550 0.62 0.61 0.67 0.60 0.61 600 0.72 0.72 0.73 0.71 0.67 https://doi.org/10.15826/chimtech.2023.10.1.09 chimica techno acta 2023, vol. 10(1), no. 202310109 letter 5 of 6 doi: 10.15826/chimtech.2023.10.1.09 4. limitations as can be seen from the experimental data (figures 2 and 3), the fabricated sensor shows good operability at low concentrations of alkanes in nitrogen. the higher hydrocarbon contents will provide the higher limiting current. however, a longer response time is required in this case. at the lower concentrations of hydrocarbons, a limiting current region is expected to be very weak, which does not allow the formation of the calibration curves. 5. conclusions this work reports on the possibility of using an amperometric sensor with a diffusion barrier to determine the concentration and binary diffusion coefficients of some light alkanes in nitrogen at elevated temperatures (500–600 °c). we have experimentally obtained the values of the diffusion coefficients for ch4+n2, c2h6+n2, and c3h8+n2 gas mixtures. our values are in good agreement with those reported in published data. ● supplementary materials no supplementary materials are available. ● funding this research had no external funding. ● acknowledgments none. ● author contributions conceptualization: a.s.k., a.n.v. data curation: a.n.v. formal analysis: a.s.k., a.n.v. investigation: a.s.k., a.n.v. methodology: a.s.k. project administration: a.n.v. resources: a.s.k., a.n.v. software: a.s.k., a.n.v. supervision: a.n.v. validation: a.n.v. visualization: a.s.k. writing – original draft: a.n.v. writing – review & editing: a.n.v. ● conflict of interest the authors declare no conflict of interest. ● additional information author ids: anatoly s. kalyakin, scopus id 8943432300 alexander n. volkov, scopus id 7402103148 website: institute of high temperature 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2023, vol. 10(1), no. 202310109 letter 6 of 6 doi: 10.15826/chimtech.2023.10.1.09 16. mcgivern ws, manion ja. binary diffusion coefficients for methane and fluoromethanes in nitrogen. j chem eng data. 2021;66:3047–3056. doi:10.1021/acs.jced.1c00161 17. wakeham wa, slater dh. diffusion coefficients for n-alkanes in binary gaseous mixtures with nitrogen. j phys b at mol phys. 1973;6:886–896. doi:10.1088/0022-3700/6/5/024 https://doi.org/10.15826/chimtech.2023.10.1.09 https://doi.org/10.1021/acs.jced.1c00161 https://doi.org/10.1088/0022-3700/6/5/024 voltammetric sensor based on molecular imprinted polymer for lincomycin determination published by ural federal university eissn 2411-1414 chimicatechnoacta.ru article 2023, vol. 10(2), no. 202310210 doi: 10.15826/chimtech.2023.10.2.10 1 of 8 voltammetric sensor based on molecular imprinted polymer for lincomycin detection yulia a. yarkaeva * , daria a. dymova , marat i. nazyrov , liana r. zagitova , valery n. maistrenko department of chemistry, ufa university of science and technology, ufa 450076, russia * corresponding author: julijajarkaeva05@gmail.com this paper belongs to a regular issue. abstract for the selective detection of the antibiotic lincomycin, we developed a voltammetric sensor based on a glassy carbon electrode modified with reduced graphene oxide and polyarylenephthalide containing diphenylenethio and diphenyleneoxide fragments in the main chain of the polymer in the 1:1 ratio with lincomycin molecular imprints obtained by phase inversion. using ftir spectroscopy, electrochemical impedance spectroscopy, cyclic and differential-pulse voltammetry, the electrochemical and analytical characteristics of the sensor were studied. the detection of lincomycin was carried out by differential pulse voltammetry. the linear concentration range was 2.5·10–7–5·10–4 m with a limit of detection of 6.8·10– 8 m. it was shown that the presence of molecular imprints increases the sensitivity of the developed sensor in comparisons with a sensor with nonimprinted polymer by a factor of 3.05. keywords molecularly imprinted polymers polyarylenephthalides voltammetry lincomycin reduced graphene oxide phase inversion received: 05.04.23 revised: 26.04.23 accepted: 26.04.23 available online: 28.04.23 key findings ● mip-sensor for the lincomycin determination based on polyarylenephthalides was obtained by phase inversion. ● the presence of molecular imprints increases the sensitivity of the mip-sensor by a factor of 3.05. ● mip-sensor was tested to determine lincomycin in human urine and blood plasma; rsd did not exceed 7.5%, and the recovery was 93–108%. © 2023, the authors. this article is published in open access under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). 1. introduction antibiotics are one of the most important medicines that affect human health. it is difficult to imagine modern medicine without antibiotics. however, their uncontrolled use has led to antibiotic contamination of ecosystems and food [1–4]. this has increased the already high level of resistance of many bacteria to antimicrobial drugs. the control of antibiotic content has become an urgent task for specialists in the field of environmental protection and food quality assessment, analysis of biological objects, and clinical medicine [5, 6]. to date, such analytical methods as hplc [7], capillary electrophoresis [8], ftir spectroscopy [9], raman spectroscopy [10], fluorimetry [11], and microbiological methods [12] are widely used for the detection of antibiotics. recently, electrochemical methods have been used for these purposes, in particular, voltammetry, which makes it possible to quite simply, quickly, and with high sensitivity detect drug compounds, including antibiotics, in various matrices [13]. various voltammetric methods, such as cyclic, differential pulse and square wave voltammetry, have been successfully applied with high selectivity and sensitivity for the analysis of drugs and the determination of antibiotics in pharmaceutical dosage forms (tablets, capsules, injections and suspensions) and biological fluids (urine samples, blood and its serum, etc.) [14–17]. when creating sensors for the detection of antibiotics, the main and most commonly employed approach to modifying electrodes is the use of molecularly imprinted polymers (mips) [18]. this allows solving the main problem of voltammetry, i.e., insufficient selectivity of detections. such an approach is analogous to antibody-antigen or enzyme-substrate interactions (key-lock interactions) in biological systems. it is based on http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2023.10.2.10 http://creativecommons.org/licenses/by/4.0/ https://orcid.org/0000-0002-0085-436x https://orcid.org/0000-0001-5602-8609 https://orcid.org/0000-0002-4081-8726 https://orcid.org/0000-0002-7769-7614 https://orcid.org/0000-0001-7831-0269 https://crossmark.crossref.org/dialog/?doi=https://doi.org/10.15826/chimtech.2023.10.2.10&domain=pdf&date_stamp=2023-04-28 chimica techno acta 2023, vol. 10(2), no. 202310210 article 2 of 8 doi: 10.15826/chimtech.2023.10.2.10 the polymerization of a monomer in the presence of a template molecule, with the resulting polymer containing specific cavities of the analyte after its removal from the polymer [19, 20]. compared to antibodies, mips are cheaper, more stable, and withstand a wider range of ph and temperature [21]. the development of mip for modifying electrodes in voltammetry includes several key steps: polymerization or polymer deposition; removal of the template (usually by a solvent or electrochemical method); instrumental measurements. mips can be obtained using various methods of monomer polymerization in the presence of a template molecule (chemical, electrochemical, photopolymerization). in addition to polymerization, the phase inversion method can be used to create mip-sensors [22]. the method consists in the use of ready-made polymers that are deposited on the surface of the working electrode from a solution in the presence of the analyte. its main advantage is the simplicity and faster manufacturing of the mipsensor. to dissolve the two components, a solvent is chosen that is compatible with both the main polymer and the template. their mixing makes it possible to form a "guest-host" complex in solution. mip can be obtained in two ways: 1) wet phase inversion (wpi) – by adding another solvent, which causes the precipitation of the polymer associated with the template; 2) dry phase inversion (dpi) – the mipmembrane is obtained by evaporating the solvent from the polymer during the heating process [23]. the dpi method is simpler and more convenient to manufacture, since, unlike wpi, it does not require the selection of a second solvent. wpi is also complicated by the fact that the template may not be deposited in the polymer composition or may be deposited in a very small amount, which leads to a low specificity of the resulting mip. dpi is usually carried out with heat. therefore, in this case, polyarylenephthalides (pap) [24–26], which are electrically conductive in thin layers and chemically resistant to heat and aggressive media, are of considerable interest and can be used. paps were previously studied and applied in the manufacture of sensors for the creation of composite materials [15]. the selectivity and sensitivity of mip-sensors are their main and most important characteristics. however, the deposition of a polymer on the electrode surface often leads to a decrease in currents due to an increase in resistance. therefore, components that increase electrical conductivity must be added to the sensor layer. recently, nanomaterials have been used for these purposes, such as au and pt nanoparticles, single-walled and multi-walled carbon nanotubes, reduced graphene oxide (rgo) [13, 17, 27], etc. at the same time, rgo is also used as a convenient matrix for immobilizing various components when creating efficient sensor platforms based on composite materials and increasing the sensitivity and selectivity of voltammetric sensors due to its unique properties, such as high electrical conductivity, large specific surface area, mechanical strength, etc. lincomycin hydrochloride (lin) (figure 1a), derived from streptomyces lincolnensis, is a well-established antibiotic. it is active against most common gram-positive bacteria, inhibits cell growth and microbial protein synthesis, and is used to treat many infectious diseases [28] (staphylococcal, streptococcal, bacteroid infections, pneumonia, anthrax, furunculosis, carbuncles, impetigo, burns and wounds). in this work, to determine lin, a voltammetric sensor based on a glassy carbon electrode (gce) modified with rgo and pap containing diphenylenethioand diphenyleneoxide fragments in the main chain of the polymer in 1:1 ratios (figure 1b) was developed. the characteristics of the sensor were studied using ftir spectroscopy, electrochemical impedance spectroscopy (eis), and cyclic voltammetry (cv). lin was determined by differential pulse voltammetry (dpv). the analytical characteristics of the developed sensors, such as sensitivity, selectivity, linear range of concentrations and limit of detection (lod), were studied. 2. experimental 2.1. materials and reagents lin (≥99.5%), k3fe(cn)6 (≥99.0%) and k4fe(cn)6 (≥99.0%), go powder (15–20 sheets, 4–10% edge oxidation) were purchased from sigma-aldrich (usa). samples of the pap polymer (spectroscopically pure) were provided by the laboratory for the synthesis of functional polymers, ural federal research center, russian academy of sciences (ufa, russia) [24–26]. the supporting electrolyte for lin was a phosphate buffer solution (pbs, kh2po4 + na2hpo4, 0.1 m, ph 6.9). a 0.5 mm lin solution was prepared by dissolving an accurate weighed portion of the reagent in 25 ml of pbs. solutions of lower concentrations were prepared by serial dilution. urine samples were obtained with the written consent of the donor, blood plasma was purchased from the ufa republican blood transfusion station. urine and blood plasma samples, 2.5 ml in volume, were centrifuged for 10 min and diluted 10 times with pbs ph 6.9. known amounts of lin were added to the resulting solutions to obtain solutions with concentrations of 0.35 and 0.04 mm. all solutions were prepared using ultrapure deionized water with a specific electrical conductivity of 0.1 μs cm–1. figure 1 structure of lin (a) and pap polymer (b). https://doi.org/10.15826/chimtech.2023.10.2.10 https://doi.org/10.15826/chimtech.2023.10.2.10 chimica techno acta 2023, vol. 10(2), no. 202310210 article 3 of 8 doi: 10.15826/chimtech.2023.10.2.10 all electrochemical measurements were performed on autolab pgstat 204 potentiostat-galvanostat with an fra32m impedance module (metrohm autolab ins., netherlands) with nova software. a standard three-electrode cell consisted of a modified gce (metrohm autolab ins., netherlands) with a diameter of 3 mm as a working electrode, a platinum plate as an auxiliary electrode, and a silver chloride electrode with a 3.5 m kcl solution as a reference electrode. the ph of solutions was measured using a seven compact ph/ion s220 ph meter (mettler-toledo ag, switzerland). the solutions were stirred using an mr heitec magnetic stirrer (heidolph, germany). ftir spectra of go and rgo were recorded in the range 450–3500 cm–1 on an ftir-8400s spectrometer (shimadzu, japan) at room temperature (resolution 8 cm–1, number of scans 30) with ir solution software. 2.2. modification of the electrode surface to modify the gce, 4 mg of go was added to 1 ml of an aqueous ethanol solution (at a ratio of c2h5oh:h2o 1:1), after which it was sonicated for 1 hour. go dispersed in an aqueous ethanol solution was applied dropwise onto a carefully polished gce surface and dried under an ir lamp. the reduction of go was carried out in a potentiostatic mode at a potential of e = –0.8 v for 3 minutes in a phosphate buffer solution. the conditions of go reduction were chosen experimentally according to the values of lin oxidation currents and rsd. to prepare mixtures of polymers with a template, 10 mg of the polymer and 5 mg of lin were dissolved in 10 ml of n,n-dimethylformamide (dmf). the polymer:template ratio was experimentally found to be optimal according to the ip and relative standard deviation (rsd) values. the resulting polymer solutions with the template were applied to the gce surface modified with rgo, followed by removal of the template in 1 m naoh solution for 120 s with stirring. a sensor with a non-imprinted polymer (nip) was obtained by a similar procedure, but without the addition of a template. 2.3. experimental techniques differential pulse voltammograms (dpv) were recorded in the potential range from 0 to 1.2 v with a scan rate of 20 mv s–1. electrochemical impedance spectra were recorded in the frequency range from 500 khz to 0.1 hz with an amplitude of 10 mv. cyclic voltammograms were recorded in the potential range from 0 to 1.3 v with a scan rate of 0.1 mv s–1. before recording the dpv, the sensor was kept in the analyte solution for 80 s to incubate lin. all measurements were carried out at a temperature of 25±0.1 °c. 3. results and discussion 3.1. ftir and eis results as a rule, rgo is used in electrochemical sensors to remove carboxyl and carbonyl groups and increase the electrical conductivity of the material. the ftir spectrum (figure 2) of go shows characteristic bands at 1025, 1223, 1414, 1715, and 3419 cm–1, which can be attributed to the stretching vibrations c–o, c–o–c, c–oh, c=o and –oh, while on rgo these characteristic bands sharply decrease or disappear, confirming that go is reduced to rgo. the stretching vibrations at 1640 cm–1, observed both in go and rgo, correspond to the c=c bonds present in the graphene sheet. the obtained ftir spectra agree with the literature data [29]. the characteristic bands in the lin spectrum are those at 1657 and 1567 cm–1, corresponding to the c=o stretching vibrations and n–h bending vibrations of the amide group, respectively. stretching of s–ch3 is observed at 1107 cm–1, n–h – at 1041 cm–1, c–o–c (ether bond) – at 1263 cm–1, c–h (aliphatic) – at 2955 cm–1. a wide band of o–h stretching vibrations with a complex contour is observed at 3528– 3289 cm–1, which, moreover, overlaps the n–h stretching vibrations. the characteristic bands in the pap spectrum are 1770 and 1078 cm–1, corresponding to the c=o and c–o–c bonds of the phthalide group, 757 cm–1 corresponds to the ar–s–ar bond, 1244 cm–1 – to the ar–o–ar bonds. the characteristic bands of lin appear in the spectrum of the pap-lin complex. and the band at 1770 cm–1, corresponding to c=o, shifts to 1758 cm–1, which may be due to the participation of this group in the formation of a hydrogen bond. eis with [fe(cn)6]3–/4– showed that each modification stage has a different effect on the currents of the [fe(cn)6]3–/4– redox pair. the lowest resistance to electron transfer ret was observed on gce/rgo (figure 3a, curve 3), while on unreduced go (curve 2) the resistance is higher. when a pap polymer film is deposited on gce/rgo, the resistance increases (curve 4), but it does not significantly exceed the resistance on bare gce, which is due to the electrical conductivity of the pap. after lin is washed out of the polymer, ret decreases (curve 5) and the electron transfer rate increases due to the formation of pores in polymers through which [fe(cn)6]3–/4– ions penetrate. figure 2 ftir spectra of go (1), rgo (2), lin (3), pap (4), pap-lin (5). https://doi.org/10.15826/chimtech.2023.10.2.10 https://doi.org/10.15826/chimtech.2023.10.2.10 chimica techno acta 2023, vol. 10(2), no. 202310210 article 4 of 8 doi: 10.15826/chimtech.2023.10.2.10 figure 3 nyquist diagrams of gce (1), gce/go (2), gce/rgo (3), gce/rgo/pap (4), gce/rgo/mipap (5) in 5 mm [fe (cn)6] 3–/4– (1:1, 0.1 m kcl, 0.1 v s–1) (a); cv of the supporting electrolyte on gce/rgo/mipap before (1) and after (2) washing out of lin from the polymer film in the supporting electrolyte (ph 6.9, 0.1 v s–1) (b). also, figure 3b shows that the cvs obtained in the supporting electrolyte solution before and after lin was washed out from the polymer film differ: curve 1 shows a small peak of lin oxidation due to the presence of lin in the polymer film, which disappears after washing out in a 1 m naoh solution with stirring for 120 s (figure 3b, curve 2), confirming the effectiveness of the chosen technique. 3.2. quantum-chemical modeling of the interaction of lin with the pap polymer based on the structure of lin, hydroxyl groups in the galactopyranose fragment can be identified as possible centers of interaction, which suggests a tendency to form hydrogen bonds. the lactone fragments of the phthalide blocks of the polymer contain oxygen atoms, which can act as hydrogen bond acceptors. to calculate possible interactions, the following simplification was introduced: two blocks consisting of two units were used as a polymer. after the initial optimization of the structures by the am1 semi-empirical method, possible complexes were calculated by the charmm method [30] in the hyperchem program (figure 4). the possibility of hydrogen bonding (2.017 å, 2.668 å and 2.713 å) and the formation of cavities in the polymer for the antibiotic molecule was confirmed. 3.3. lin detection lin electrooxidation is a one-electron one-proton process with the formation of a dimerized product [6]. figure 5 shows the dpv of a lin solution on bare gce, gce/rgo, on gce modified with pap, and on gce modified with molecularly imprinted pap (mipap). the deposition of go on the surface of the gce with subsequent electrochemical reduction leads to an increase in the sensitivity of the sensor to lin, as well as to a shift in the oxidation potential of lin to the cathode region, which, apparently, is due to the facilitation of the process of its oxidation on go. the obtained dpvs of the lin solution on gce/rgo/mipap are consistent with the previously obtained eis data. the linear range of the dependence of lin oxidation current on its content in the solution on gce/rgo/mipap remains in the concentration range from 2.5·10–7 to 5·10–4 m, with a detection limit of 6.8·10–8 m (figure 6). figure 4 possible interactions between pap-polymer (blue) and lin (yellow) optimized by the quantum chemical modeling. figure 5 dpvs of 0.5 mm lin solution on gce (1), gce/rgo (2), gce/rgo/mipap (3), gce/rgo/pap (4) (pbs, 20 mv s–1). https://doi.org/10.15826/chimtech.2023.10.2.10 https://doi.org/10.15826/chimtech.2023.10.2.10 chimica techno acta 2023, vol. 10(2), no. 202310210 article 5 of 8 doi: 10.15826/chimtech.2023.10.2.10 in addition, figure 6b shows the calibration curves obtained at each stage of the gce modification. the corresponding equations are as follows: y = (2.99±0.16)x + (0.27±0.02), r² = 0.9966, (1) y = (6.21x±0.26) + (0.88±0.04), r² = 0.9914, (2) y = (1.63±0.13)x + (0.12±0.03), r² = 0.9971, (3) y = (4.97±0.21)x + (0.37±0.02), r² = 0.9975. (4) it can be seen that in all curves there is a linear dependence of the peak current on the lin concentration. the selectivity coefficients s on the gce are lower than those on the final sensor. it should be noted that the sensitivity on gce/rgo is higher than that on gce/rgo/mipap, which is associated with an increase in resistance when using the pap-polymer, being consistent with the eis data. however, the resulting s and lod on gce/rgo/mipap is sufficient to detect lin in real samples [31–33]. the linear dependences on gce/rgo/pap and gce/rgo/mipap show that the presence of molecular imprints increases the sensitivity of gce/rgo/mipap by a factor of 3.05 (smip/snip). these results illustrate the high sensitivity and selectivity of the gce/rgo/mipap sensor. the obtained results show that the developed sensor for lin detecting is comparable to the electrochemical sensors described in the literature, are not inferior to them in their characteristics, and sometimes even surpass them (table 1). this confirm the good sensitivity of gce/rgo/mipap in lin detection. it should be noted that the sensor fabrication procedure has a simple strategy and lower number of steps for creating mip due to the use of the phase inversion method; as a result, this approach is more express. other methods listed in table 1 such as electrochemiluminescence, surface plasmon resonance, raman spectroscopy, colorimetric, photoelectrochemical methods can detect lin with a lower lod. however, according to [31–33], the concentration of lin and its analogues in biological fluids is 0.25–16 μg ml–1 (i.e. 1.2·10–6– 3.9·10–5 m). thus, the lod of the developed sensor is sufficient to detect lin. to estimate the correctness of the detection of lin, the “spike-recovery” test was used (table 2). the sensor made it possible to detect the lin concentration with high accuracy over the entire linear range; the rsd did not exceed 3.6%, which indicates good reproducibility of the detection, and the values of the relative measurement error not exceeding 3% indicate the accuracy of the results. to assess the analytical capabilities of the proposed sensor, it was used to detect lin in human urine and blood plasma. the rsd did not exceed 7.5%, and the recovery was 93–108%. statistical evaluation of the measurement results by the "spike-recovery" test indicates the absence of a significant systematic error. the repeatability and stability tests of the gce/rgo/mipap were carried out for 5·10–4 mm lin. after 10 successive assays, the response signal of the gce/rgo/mipap still remained up to 97.1% of its initial values with rsd 3.9%. after 10 days of storage at room temperature, the current responses of the gce/rgo/mipap remained up to 95.3% of its initial value with rsd 4.1%. 4. limitations when recording the dpv, the capacitive currents on the gce and the gce modified with rgo differ significantly. in this regard, it is necessary to carry out the baseline correction, as well as the curve smoothing based on the savitzky-golay algorithm. figure 6 dpvs of lin solutions of various concentrations (1 – 0.0025, 2 – 0.01, 3 – 0.03, 4 – 0.05, 5 – 0.1, 6 – 0.2, 7 – 0.3, 8 – 0.4, 9 – 0.5 mm) on gce/rgo/mipap (a); calibration curves of gce (1), gce/rgo (2), gce/rgo/pap (3) and gce/rgo/mipap (4) sensors (pbs, 20 mv s–1, n = 5, p = 0.95) (b). https://doi.org/10.15826/chimtech.2023.10.2.10 https://doi.org/10.15826/chimtech.2023.10.2.10 chimica techno acta 2023, vol. 10(2), no. 202310210 article 6 of 8 doi: 10.15826/chimtech.2023.10.2.10 table 1 figures of merit of proposed sensor gce/rgo/mipap in comparison with the reported electrochemical sensors and other methods used for the lin detection. sensing element technique linear range, m lod, m references electrochemical sensors gce/rgo/mipap dpv 2.5·10–7–5·10–4 6.8·10–8 this work mwnts-dhp/gce cv 4.5·10–7–1.5·10–4 2.0·10–7 [5] au dpv 8.0·10–6–1.0·10–4 1.7·10–7 [6] bdd thin film electrodes cv 5.0·10–7–1.3·10–4 2.0·10–8 [34] dme in kh2po4-na2hpo4-k2s2o8 solution cv 8.5·10 –8–9.0·10–5 4.0·10–8 [35] au-ptnps/nanopan/cs/gce cv 7.4·10–6–2.5·10–4 2.5·10–6 [36] other methods mip-au-go/gce ecl 5.0·10–12–1.0·10–9 1.6·10–13 [37] sno2/chitosan/g-c3n4/gce ecl 2.5·10 –10–2.5·10–7 6.9·10–11 [38] n-doped ti3c2 qds/biobr pec 1.0·10 –14–1.0·10–8 3.6·10–15 [39] pfcs-tio2/ng/itoznpc/mos2/ito pec 1.0·10 –11–1.0·10–5 3.3·10–12 [40] haucl4/naoh solution colorimetry 1.0·10 –6–2.5·10–5 9.7·10–7 [41] au-pt nr-apt/cdna/ptp/eu mof/gce ecl-spr 2.5·10–10–2.5·10–4 6.4·10–11 [42] mab-aunps-dtnb sers 2.5·10–13–2.5·10–9 7.1·10–13 [43] cds qds/c-g-c3n4 ecl 1.2·10 –11–2.5·10–4 4.9·10–11 [44] mwnts – multi-wall carbon nanotubes; dhp – dihexadecylphosphate; bdd – boron-doped diamond; dme – dropping mercury electrode; au-ptnps – au-pt alloy nanoparticles; nanopan – polyaniline nanotube; cs – chitosan; g-c3n4 – graphene-like carbon nitride; qds – quantum dots; tio2/ng – nitrogen-doped graphene-loaded tio2 nanoparticles; pfc – dualphotoelectrode photofuel cell; znpc/mos2 – zinc phthalocyanine nanoparticles sensitized mos2; ito – indium tin oxide; nr – nanorod; apt/cdna – bridge of aptamer and complementary dna; ptp – ptca (perylene tetracarboxylic dianhydride) – pani (polyanilin); eu mof – europium metal–organic framework; aunps – gold nanoparticles; dtnb – 5,5′-dithiobis (2-nitrobenzoic acid); mab – monoclonal antibody; c-g-c3n4 – carboxylated g-c3n4; ecl – electrochemiluminescence; pec – photoelectrochemical; spr – surface plasmon resonance; sers – surface-enhanced raman spectroscopy. table 2 lin determination using dpv on the gce/rgo/mipap (pbs, 20 mv s–1, n = 5, p = 0.95). spiked, µm found, µm rsd, % recovery, % lin solution 350 353±9 1.9 101 40 41±6 2.7 103 lin in urine 350 346±15 6.6 99 40 43±5 5.2 108 lin in blood plasma 350 343±11 7.5 98 40 37±6 5.3 93 5. conclusions thus, to detect the antibiotic lin, we developed the sensor based on gce modified with rgo and molecularly imprinted pap obtained by phase inversion by solvent evaporation. it should be noted that when the phase inversion method is used to obtain the mip, the sensor manufacturing process is greatly simplified. it was shown that the developed sensor has a high selectivity for the detected antibiotic, and the presence of specific binding sites in the polymer film makes it possible to detect lin with a sensitivity that is 3.05 times higher than that of a similar sensor without molecular imprints. the resulting sensor was successfully used to determine lin in biological fluids. ● supplementary materials no supplementary materials are available. ● funding this work was supported by the russian science foundation (grant no. 21-73-00295, https://rscf.ru/en/project/2173-00295/). ● acknowledgments the authors are grateful to the laboratory for the synthesis of functional polymers, ural federal research center, russian academy of sciences, supervised by kraikin v.a. for providing polymer samples. ● author contributions conceptualization: v.n.m., y.a.y. data curation: y.a.y. formal analysis: m.i.n., y.a.y., l.r.z. funding acquisition: y.a.y., d.a.d. investigation: d.a.d., m.i.n. methodology: v.n.m., y.a.y. project administration: y.a.y. resources: y.a.y. supervision: v.n.m. validation: d.a.d., y.a.y. visualization: d.a.d., m.i.n., y.a.y., l.r.z. writing – original draft: y.a.y., m.i.n. writing – review & editing: v.n.m. https://doi.org/10.15826/chimtech.2023.10.2.10 https://doi.org/10.15826/chimtech.2023.10.2.10 https://rscf.ru/en/project/21-73-00295/ https://rscf.ru/en/project/21-73-00295/ chimica techno acta 2023, vol. 10(2), no. 202310210 article 7 of 8 doi: 10.15826/chimtech.2023.10.2.10 ● conflict of interest the authors declare no conflict of interest. ● additional information author ids: yulia a. yarkaeva, scopus id 56872864300; daria a. dymova, scopus id 57899452900; marat i. nazyrov, scopus id 57330245700; liana r. zagitova, scopus id 57201803011; valery n. maistrenko, scopus id 6603789725. website: ufa 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https://doi.org/10.1016/j.microc.2021.105949 https://doi.org/10.29356/jmcs.v58i2.182 https://doi.org/10.1016/j.jpba.2018.02.005 https://doi.org/10.1016/j.scitotenv.2022.154775 https://doi.org/10.1007/s11250-014-0595-4 https://doi.org/10.1016/j.snb.2004.12.087 https://doi.org/10.1016/j.microc.2003.10.001 https://doi.org/10.1016/j.bios.2017.01.038 https://doi.org/10.1016/j.talanta.2021.122546 https://doi.org/10.1016/j.biosx.2022.100266 https://doi.org/10.1016/j.aca.2023.340880 https://doi.org/10.1039/c9ra04095a https://doi.org/10.1021/acsami.1c21528 https://doi.org/10.1007/s00217-022-04038-3 https://doi.org/10.1007/s00604-022-05587-w influence of anionic surfactant on stability of nanoparticles in aqueous solutions published by ural federal university eissn 2411-1414 chimicatechnoacta.ru article 2023, vol. 10(3), no. 202310302 doi: 10.15826/chimtech.2023.10.3.02 1 of 8 influence of anionic surfactant on stability of nanoparticles in aqueous solutions dmitry o. zelentsov a , yuliya yu. petrova a * , alexander v. korobkin a, anastasia a. ivanova b , alexey n. cheremisin b , ivan i. shanenkov c , alexander ya. pak d , yuliya g. mateyshina e a: institute of natural and technical sciences, surgut state university, surgut 628408, russia b: skoltech center for petroleum science and engineering, skoltech, moscow 121205, russia c: institute of environmental and agricultural biology, tyumen state university, tyumen 625003, russia d: school of energy and power engineering, tomsk polytechnic university, tomsk 634050, russia e: institute of solid state chemistry and mechanochemistry, siberian branch of the russian academy of sciences, novosibirsk 630090, russia * corresponding author: petrova_juju@surgu.ru this paper belongs to the rkfm'23 special issue: https://chem.conf.nstu.ru/. guest editors: prof. n. uvarov and prof. e. aubakirov. abstract dispersion and aggregation of nanoparticles in aqueous solutions are important factors for safe and effective application of nanoparticles, for instance, in the oil industry. as conventional oil reserves are depleted, it is necessary to advance chemical enhanced oil recovery (ceor) techniques to develop unconventional oil reservoirs. nanoparticles modified by surfactants can be a promising reagent in ceor. these nanomaterials can reduce interfacial tension and change the wettability of reservoir rock, which leads to an increase in oil recovery. however, the application of nanoparticles is limited by their substantial aggregation in aqueous solutions. the purpose of this work is to select nanoparticles for obtaining stable sols in water in the presence of an anionic surfactant and to optimize the conditions (ph) for further modifying the nanoparticles with the anionic surfactant. sodium dodecyl sulfate (sds) is used as an anionic surfactant. the aggregation of oxide and carbon nanoparticles in water and anionic surfactant solutions was studied by laser diffraction, dynamic and electrophoretic light scattering methods. most of the studied nanoparticles in water form aggregates with bi-, threeand polymodal particle size distributions. tio2 nanoparticles obtained by plasma dynamic synthesis form the most stable sols in anionic surfactant solutions. the range of 5–7 ph is defined as optimal for their modification with surfactants. the stability of carbon nanoparticles in aqueous solutions increases significantly in the presence of a surfactant. the obtained results form the basis for further research on the modification of marked nanoparticles in surfactant solutions. keywords nanoparticles anionic surfactant titan oxide carbon nanoparticles aggregation received: 09.07.23 revised: 24.07.23 accepted: 24.07.23 available online: 27.07.23 key findings ● tio2 nanoparticles form the most stable sols in anionic surfactant solutions. ● 5–7 ph is optimal for modification of tio2 with sodium dodecyl sulfate. ● carbon nanoparticles are significantly more stable in anionic surfactant solutions. © 2023, the authors. this article is published in open access under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). 1. introduction with the increased attention toward nanotechnology and its innovative use for different industries including, but not limited to, food, biomedical, electronics, materials, etc., the application of nanotechnology or nanoparticles in the oil and gas industry is a subject undergoing intensive study by major oil companies, which is reflected in the http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2023.10.3.02 http://creativecommons.org/licenses/by/4.0/ https://orcid.org/0009-0007-6153-8380 https://orcid.org/0000-0003-3702-2249 https://orcid.org/0000-0003-2323-6297 https://orcid.org/0000-0002-3580-9120 https://orcid.org/0000-0001-7499-5846 https://orcid.org/0000-0001-8447-1309 https://crossmark.crossref.org/dialog/?doi=https://doi.org/10.15826/chimtech.2023.10.3.02&domain=pdf&date_stamp=2023-07-27 https://journals.urfu.ru/index.php/chimtech/rt/suppfiles/6960/0 chimica techno acta 2023, vol. 10(3), no. 202310302 article 2 of 8 doi: 10.15826/chimtech.2023.10.3.02 huge amount of funds invested in the research and development of nanotechnology. nanotechnology has been recently investigated extensively for different applications in the oil and gas industry, such as drilling fluids and enhanced oil recovery, in addition to other applications including cementing and well stimulation [1]. as conventional oil reserves are gradually depleted, oil producers are increasingly seeking to develop oil reservoirs that have already been discovered. developing oil reservoirs characterized by high temperatures and ultra-low permeability is becoming a major challenge. this can be handled by using chemical enhanced oil recovery (ceor) techniques. they receive a great deal of attention because they allow controlling the properties at the oil-fluid and oilrock interfaces. nanotechnology applications in ceor are studied by researchers around the world [2–5]. first of all, nanoparticles (npts) can adsorb on reservoir rock and change its wettability from oil-wet to water-wet [6–7]. also, nanoparticles can adsorb at the oil-fluid interface and reduce the interfacial tension, which also leads to an increase in oil displacement [8]. a limitation in the application of npts is their low stability in liquid systems and tendency to aggregation [9]. at high mineralization and high temperatures, aggregation of nanoparticles may increase even more. flooding a reservoir with fluids containing large aggregates of npts may lead to clogging of small reservoir pores, which will have a negative effect on the overall oil recovery [10]. to prevent excessive aggregation of npts, they are modified with surfactants. the modification is carried out by two methods: in-situ (physical adsorption) and ex-situ (chemical grafting) [11]. the obtained nano-surfactant composites acquire greater surface activity, and their stability in aqueous systems is improved [12]. fluids with modified npts were shown to displace oil more effectively [13]. adsorbed surfactant molecules can prevent excessive aggregation of npts, but the opposite effect is also possible [14]. it was noted that dispersions with smaller aggregates of nanoparticles are more effective in reducing the interfacial tension [13, 15], and the efficiency in the wettability alteration of modified npts is higher than that of unmodified ones or surfactant solutions without npts [16– 17]. in the work [18] it was shown that modified sio2 npts reduced the adsorption of surfactants on the rock. modification conditions, such as the type of nanoparticles and a surfactant, the ratio of their concentrations, ph and mineralization, can significantly affect the efficiency of modified nanoparticles in oil displacement [19–23]. in this work, we selected nanoparticles that form the most stable dispersions or sols in water and anionic surfactant solutions. also, for the selected nanoparticles we studied the effect of ph on their aggregation in surfactant solution to choose the optimal conditions for further modifying npts with the surfactant. 2. materials and methods 2.1. materials the following silica and titanium oxide npts (sigma-aldrich) were used in this work: sio2 and tio2-sa; β-bi2o3 npts obtained by thermal decomposition of bic2h4(oh) [24]; graphite-like carbon nanoparticles (c-npts) obtained by plasma treatment of asphaltenes [25]; and npts obtained by plasma dynamic synthesis [26]: titanium oxides (tio2 – particles containing magnelli-phase with a wide size distribution from 1 nm to 50 μm, tio2-bk – fine particles up to 1 μm in size), aluminum oxide and a mixture of iron oxides. sodium dodecyl sulfate (sds, panreac) was used as an anionic surfactant. sodium hydroxide (lenreactiv, >99%), phosphoric acid (component-reaktiv, >99%), and phosphate buffer solutions prepared from disodium hydrogen phosphate (merck, >99.9%) and sodium dihydrogen phosphate 2-hydrate (merck, >99.9%) were used to adjust ph. 2.2. nanoparticle characterization the physical–chemical characterization was done using the x-ray fluorescence (vacuum 8–12 pa, energy-dispersive analyzer edx-8000, shimadzu), ft-ir (atr and transmission mode, spectrum 100 series, perkin elmer) and tga/dsc analysis. the tga/dsc analysis of the nanoparticles was performed with a mettler toledo tga/dsc 3+ star system, at a heating rate of 20 ℃/min, under nitrogen atmosphere with a flow rate of 50 ml/min. 2.3. size distribution of nanoparticle aggregates by laser diffraction the particle size was evaluated with a sald-2300 (shimadzu) analyzer for selection of oxide nanoparticles and study of surfactant influence on carbon nanoparticle aggregation. the oxide nanoparticles (~2 mg) were dispersed in 10 ml of distilled water. before each measurement, the nanofluid sample was sonicated using a probe type sonicator at a frequency of 35 khz for 10 min. 0.5 ml of the dispersion was taken and placed in a sald-2300 (shimadzu) analyzer cuvette filled with 9.5 ml of distilled water or 5, 10, or 50 mmol/l sds solution, a stirrer was turned on, and particle size measurements were performed for 1 h. to study the size distribution of c-npts aggregates, 0.01% dispersions were prepared in water or 5 and 50 mmol/l sds solutions. 2.4. zeta-potential and size distribution of npts by dynamic light scattering zeta-potential (ζ) and size distribution of npts in the nanofluid were measured using a particle size analyser (litesizer 500, anton paar) which works on the principle of dynamic light scattering (dls) to study the influence of ph on the aggregation of β-bi2o3 and tio2 npts in 5 mmol/l sds solutions. the solutions were prepared using a phosphate buffer for ph 4.5–9.0, 3.3∙10–4–3.3 mol/l h3po4 for https://doi.org/10.15826/chimtech.2023.10.3.02 https://doi.org/10.15826/chimtech.2023.10.3.02 chimica techno acta 2023, vol. 10(3), no. 202310302 article 3 of 8 doi: 10.15826/chimtech.2023.10.3.02 ph<4.0, and 0.25–25 mmol/l naoh for ph>9.0. thus, 0.025% dispersion of npts was mixed with a buffer solution (h3po4 or naoh) and 25 mmol/l sds in a volume ratio of 2:2:1. the mixture was stirred, and the dls measurements were performed. 2.5. interfacial tension (ift) measurements ift measurements between n-hexane and different aqueous solutions of nanopaticles were conducted using the spinning drop method (sdt, kruss, germany) as it is more convenient and accurate for measuring ift below 20 mn∙m−1 [27]. here, a drop of liquid with lower density (n-hexane) was placed inside the denser fluid (surfactant or surfactant–nanoparticle solutions) in a horizontal tube. then, the tube was rotated, and the drop deformed into an elongated shape. the samples were assumed to be equilibrated when the measured ift values remained unchanged (2%) for 30 min [28]. at the equilibrium point, the balance between surface tension and centrifugal forces defined the shape of the droplet. at a high angular velocity ω (max.15,000 rpm), the droplet shape becomes very close to a cylinder. in this case, the ift values were calculated using the vonnegut expression (equation 1). 𝜎 = ∆𝜌𝜔2𝑅3 4 , (1) where δρ is the density difference between light and heavy phases (n-hexane and surfactant–nanoparticles formulations, measured with an areometer), and r is the shape radius. to avoid the influence of impurities on the results, before and after each experiment, the tube was cleaned with acetone and water and then dried with air. 3. results and discussion 3.1. nanoparticle characterization tio2 and carbon npts were measured by x-ray fluorescence (xrf), and the results are listed in table 1. tio2 npts obtained by plasma dynamic synthesis contain impurities of iron, silicon, aluminum, calcium, etc., and carbon npts obtained by plasma treatment of asphaltenes contain impurities of sulfur. the ftir spectrum of tio2 npts recorded in attenuated total reflection (atr) mode, shown in figure 1a, provided additional information about the tio2 structure. it can be observed that the strong band in the range of 480 to 660 cm–1 was assigned to ti–o stretching bands [29]. ftir absorption spectra of tio2 npts contain the band (wide peak or shoulder) at approximately around 3500 cm–1 (stretching) which stipulates the presence of hydroxyl groups. the 1635 cm–1 absorption band may be related to hydroxyl (bending) representing the water as moisture in the sample. the transmission ir spectra of c-npts samples synthesized in plasma are presented in figure 1b. the band at 1600 cm–1 is due to c=c stretching of the aromatic ring. the wide band at 3300–3650 cm–1 can be observed in the spectra due to oh groups. the differential thermal analysis of tio2 npts obtained by plasma dynamic synthesis (figure 2) showed that up to 600 °c, the studied sample was thermally stable (tga). upon further increase in temperature above 600 °c in an inert medium, an increase in the sample mass was observed (dta, maxima at 650 and 850 °c), which can be explained by the formation of nitrides of iron and calcium impurities. at the same time, the wide exothermic peak observed at about 400–650 °c was attributed to the phase transformation from anatase to rutile (dsc). 3.2. selection of nanoparticles the next stage of our work was the selection of nanoparticles that form stable sols in sds solutions. at this stage, we studied the aggregation of oxide nanoparticles by laser diffraction. sio2 npts formed large aggregates both in water and in sds solutions (figure s1). thus, the modal size of sio2 aggregates in water in 30 min was ~100 μm. addition of sio2 npts in sds solutions led to the formation of smaller aggregates (60~70 μm), which are still large for use in low-permeability reservoirs. smaller particle sizes were observed for tio2-sa npts (figure s2). in water, the nanoparticles mainly form an aggregate fraction with sizes of ~32 μm in 30 min (figure s2, a). in 10 and 50 mmol/l surfactant solutions tio2-sa aggregation increases, forming aggregates ~127 and ~71 μm (figure s2, c and d), respectively. and only 5 mmol/l sds solution has a stabilizing effect, and the bulk of the aggregates form a fraction with a size of ~4 μm (figure s2, b). this phenomenon can be explained by the fact that in 5 mmol/l solution the surfactant is only partially adsorbed on the surface of npts and thus prevents further aggregation of the particles. in 10 mmol/l solution, sds (or its micelles) is completely adsorbed, or close to it, on the surface of npts, forming a monolayer of surfactant molecules. this leads to a sharp increase in the hydrophobicity of the npts, which, in turn, leads to an increase in aggregation. and in 50 mmol/l solution, sds micelles continue to adsorb, forming a bilayer of surfactant molecules. the surface of npts becomes more hydrophilic, and the size of the aggregates decreases. the following is a discussion of nanoparticles of iron, aluminum and titanium oxides obtained by the plasma dynamic synthesis. it should be understood that these nanoparticles are not homogeneous and are a mixture of different oxides. thus, fe2o3 includes a mixture of magnetite, hematite and ε-fe2o3. al2o3 includes γ-al2o3 and spinel phases. tio2 consists not only of rutile and anatase, but also of magnelli phases – non-stoichiometric titanium oxides. the heterogeneous composition can affect the obtained results of particle size distributions. https://doi.org/10.15826/chimtech.2023.10.3.02 https://doi.org/10.15826/chimtech.2023.10.3.02 chimica techno acta 2023, vol. 10(3), no. 202310302 article 4 of 8 doi: 10.15826/chimtech.2023.10.3.02 table 1 the results of xrf analysis of tio2 and carbon npts. figure 1 ftir spectra of tio2 npts (a) and c-npts (b): atr (a), transmission mode (kbr pellet) (b). figure 2 tga (black), dsc (red) and dta (blue) curves of tio2 npts (n2, 20 °c/min). thus, fe2o3 npts in water, 5 and 50 mmol/l sds solutions have low stability (figure s3). this affects the nonequilibrium particle size distributions and sedimentation in 30 min, which prevents further observations. at the same time, in 10 mmol/l sds solution (figure s3, c), the dispersions had a stable bimodal size distribution with modal diameters of 0.16 and 2.29 μm. al2o3 npts in both water and sds solutions form aggregates with similar wide polymodal size distributions ranging from 20 nm to 160 μm (figure s4). this suggests a weak or absent interaction between the npts and the surfactants. in all cases, al2o3 npts as well as fe2o3 npts showed low stability and precipitated in 30 min of measurements. the system of tio2 particles in water was variable and tended to equilibrium throughout the entire measurement (figure 3). in one hour, two fractions of particles with modal diameters of 0.4 and 24.9 μm were formed. the ift measurements showed (table 2) that tio2 npts effectively reduce the interfacial tension at the n-hexane-water interface by two times. however, in sds solutions, the stabilization of npts was observed during the entire hour of measurements. practically monomodal size distributions with a modal diameter of ~0.4 μm are formed. with increasing sds concentration, the fraction of aggregates with sizes of 1~10 μm slightly increases, which is probably also related to some increase in hydrophobicity of npts due to higher adsorption of surfactant. β-bi2o3 npts in water form large aggregates ~90 µm (figure s5). however, in sds solutions as well as for tio2 the stabilization of npts occurs. the aggregates are formed mainly with bimodal size distributions with fractions of ~0.18 and ~6.94 μm. the aggregation of nanoparticles depends on both their type and method of synthesis. different synthesis methods produce nanoparticles not only with different dispersions, but also with different surface properties. for example, the number of hydroxyl –oh groups on the particle surface may differ, which can have a critical impact on the adsorption of surfactants on npts. apparently, tio2 and β-bi2o3 particles have a higher affinity for sds than other particles. also, these nanoparticles simultaneously showed small aggregates (up to 0.18 μm) in sds solutions and high stability. therefore, tio2 and β-bi2o3 nanoparticles were selected for further studies on the effect of ph on their aggregation. 3.3. influence of surfactant on carbon nanoparticle aggregation carbon nanoparticles are of great interest because they are significantly more hydrophobic than oxide nanoparticles. c-npts are poorly wetted by water, which makes it difficult to disperse them. the obtained values of interfacial tension in the aqueous dispersion of c-npts (table 2) confirm their hydrophobicity. in surfactant solutions, the particles disperse much better, which was proved experimentally (figure 4). size distributions of npts in all cases are polymodal with sizes from 0.18 to ~100 μm. sample element, wt.% ti o fe si p ca al hf c s other tio2 77.7 21.2 0.4 0.2 0.1 0.1 0.1 0.1 – – <0.1 a c-nps – – – – 99.6 0.3 <0.1b a – cr, cu b – ca, si, v, al, fe, p, ti, ni, cu, k https://doi.org/10.15826/chimtech.2023.10.3.02 https://doi.org/10.15826/chimtech.2023.10.3.02 chimica techno acta 2023, vol. 10(3), no. 202310302 article 5 of 8 doi: 10.15826/chimtech.2023.10.3.02 table 2 interfacial tension (ift) measurements (between n-hexane and water dispersion). sample ift, mn/m water 37.77±0.03 tio2 19.31±0.03 c-npts 38.78±0.05 figure 3 size distribution of tio2 npts aggregates: in water (a), in 5 mmol/l sds (b); in 10 mmol/l sds (c); in 50 mmol/l sds (d) (q3 – volume percentage, d – particle diameter). figure 4 size distribution of c-npts aggregates: in water (1), in 5 mmol/l sds (2), in 50 mmol/l sds (3) (q3 – volume percentage, d – particle diameter). however, in water the fraction with the modal diameter of 21.8 μm prevails, while in the sds solutions the content of particles with sizes smaller than 12.0 μm significantly increases. the median particle size in water was 17.9 μm, and in 5 and 50 mmol/l sds solutions – 5.6 and 6.1 μm, respectively. the surfactant solution expectedly stabilizes the c-npts in the aqueous system. the modification of cnpts with surfactant is promising because, unlike oxide npts, surfactant is adsorbed by orienting tails to the particle surface. 3.4. influence of ph on nanoparticle aggregation hydroxyl groups and their amount on the surface of nanoparticles can affect the adsorption of ionogenic surfactants. thus, hydroxyl groups are protonated in acidic medium, which should increase the adsorption of anionic surfactants, while in an alkaline medium, on the contrary, they dissociate, and the adsorption should decrease. therefore, the ph of the system can have a significant influence on the adsorption of surfactants. a study of the influence of ph on the aggregation of tio2 npts showed that the size of the aggregates significantly depended on the ph (figure 5a). the size (median d) of the aggregates of tio2 npts in the water dispersion (without a buffer solution and sds) was 196 nm. in the sds solution (without buffer), the aggregate size increases ~1.6 times, which, as mentioned earlier, can be attributed to an increase in the hydrophobicity of the npts surface due to surfactant adsorption. the smallest aggregates (165~177 nm) are formed in solutions with ph from 5.0 to 6.5. in an acidic medium, there is a sharp increase in tio2 aggregates up to ~900 nm, which seems to be due to the protonation of hydroxyl groups on the surface of npts and a significant increase in surfactant aggregation. at ph>7.0, the aggregate size also increases (up to 650 nm). in this case, in contrast with acidic media, this may be due, to an increase in the negative charge of sds, which leads to an increase in its adsorption on the surface of tio2 npts in an alkaline medium. thus, the ph range of 5.0–6.5 is optimal for obtaining stable tio2 nano-sols. for tio2-bk npts, it can be noted that the aggregate size decreases to 850 nm in the 5 mmol/l sds (without buffer) compared to 1000 nm in the aqueous dispersion (figure 5b). in an acidic medium (ph<2), there is also a sharp enlargement of the aggregates up to 1360 nm. at ph>2, the size of the aggregates is in most cases even smaller (up to 750 nm) than in the solution without the added buffer. however, the minimum size of the aggregates is still 4.6 times larger than that for tio2 npts. β-bi2o3 npts formed very large aggregates >1200 nm (figure 5, c). moreover, in water (without a buffer), the aggregates had the smallest size (1210 nm), but in the sds solution, aggregates of 1690 nm were formed. it is also remarkable that in all ph ranges except ph 3 larger aggregates were formed compared to the aqueous dispersion of β-bi2o3 npts. the obtained results are in agreement with the zeta-potential measurements (figure 6). the zeta-potential of tio2 npts confirms the stability of the nano-sol in the region of 4.5 to 7.5 ph. when the particle size is changed (tio2-bk), the sol stabilizes in an alkaline environment (10–11 ph) in sds solution. βbi2o3 npts form stable sols in sds solution at ph 2 and 10–12, which seems to be related to their ionization in strongly acidic and strongly alkaline media. https://doi.org/10.15826/chimtech.2023.10.3.02 https://doi.org/10.15826/chimtech.2023.10.3.02 chimica techno acta 2023, vol. 10(3), no. 202310302 article 6 of 8 doi: 10.15826/chimtech.2023.10.3.02 figure 5 dependence of the median diameter of nanoparticle aggregates on ph in 5 mmol/l sds: tio2 (a); tio2-bk (b); β-bi2o3 (c) (red line – in sds; blue line – in water). figure 6 zeta-potential measurements of tio2 (1, black), tio2-bk (2, red) and β-bi2o3 (3, blue) npts in ph-controlled solutions: dot lines – in 5 mmol/l sds; dash lines – in water. 4. limitations the stability of nanoparticles in aqueous systems remains extremely critical. even the smallest nanoparticles in water are prone to aggregation. preventing or mitigating this phenomenon would be a big step in research. 5. conclusions in this work, the aggregation of oxide nanoparticles in water and sodium dodecyl sulfate solutions was studied by laser diffraction. tio2 and β-bi2o3, obtained by plasma dynamic synthesis and by thermal decomposition of bic2h4(oh), respectively, stabilized in anionic surfactant solutions better than other nanoparticles and formed the smallest aggregates. therefore, these nanoparticles were chosen for further studies. in the study of aggregation of carbon nanoparticles, it was shown that they are well stabilized in sodium dodecyl sulfate solutions. these nanoparticles are of great interest for further research due to their different nature from oxide nanoparticles and poor study in chemical enhanced oil recovery. the influence of ph on the nanoparticle aggregation was studied by evaluating the aggregate sizes and zeta-potential measured using dynamic light scattering. it was shown that among all the studied nanoparticles tio2 formed aggregates of the smallest size, and for them it was possible to determine the optimal ph range at which the most stable sols are formed (5.0–7.0 ph). tio2 and carbon nanoparticles are the most promising for further research, in particular, for their modification with sodium dodecyl sulfate and further application in chemical enhanced oil recovery. ● supplementary materials this manuscript contains supplementary materials, which are available on the corresponding online page. ● funding the work was carried out within the framework of the state task of the isscm sb ras (project №121032500065-5) and also was supported by the russian science foundation (grant №22-13-20016), https://www.rscf.ru/en. ● acknowledgments the authors are grateful to pavel vadimovich povalyaev (tomsk polytechnic university) for the provided carbon nanoparticles and yurii mikhailovich yukhin (isscm sb ran) for the provided β-bi2o3 nanoparticles. ● author contributions conceptualization: yu.yu.p., d.o.z. formal analysis: d.o.z, a.v.k. funding acquisition: y.g.m., yu.yu.p. investigation: d.o.z, a.v.k. https://doi.org/10.15826/chimtech.2023.10.3.02 https://doi.org/10.15826/chimtech.2023.10.3.02 https://www.rscf.ru/en chimica techno acta 2023, vol. 10(3), no. 202310302 article 7 of 8 doi: 10.15826/chimtech.2023.10.3.02 methodology: d.o.z., yu.yu.p. project administration: yu.yu.p., a.n.ch. resources: yu.yu.p., i.i.sh., a.ya.p. supervision: yu.yu.p. validation: a.v.k. visualization: d.o.z., a.v.k. writing – original draft: d.o.z., yu.yu.p. writing – review & editing: a.a.i., y.g.m. ● conflict of interest the authors declare no conflict of interest. ● additional information authors ids: yuliya yu. petrova, scopus id 6603754153; anastasia a. ivanova, scopus id 57196971233; alexey n. cheremisin, scopus 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заинтересованность в новом и в «зеленом» топливе. в настоящее время действительно возможно получать энергию не из нефти и газа, а от альтернативных источников энергии (биотопливо, энергия солнца, ветра и др.). при этом возникает необходимость эффективного хранения и транспортировки энергии [1, 2]. металлогидридный способ хранения часто рассматривается как один из самых эффективных и безопасных [3, 4]. цель нашего исследования – совершенствование материалов для использования в качестве аккумуляторов водорода. предмет нашего изучения – а. л. габов1, и. с. белослудцев1, н. а. медведева1, н. е. скрябина1, д. фрушар2 1пермский государственный национальный исследовательский университет, 614990, пермь, ул. букирева, 15. e-mail:info@psu.ru 2институт л. нееля, нцни, вр 166, 38042, гренобль, франция влияние микроструктуры сплавов на основе магния на катодное выделение водорода* исследована эволюция зеренной структуры магниевых сплавов в процессе равноканального углового прессования (ркуп) при 200 ºс. объектом исследования служили образцы чистого магния и сплавы на его основе – az31 (96 % mg, 3 % al, 1 % zn, вес. %) и zk60 (94 % mg, 5.5 % zn, 0.5 % zr, вес. %). показано, что ркуп приводит к формированию сильно неоднородной структуры. установлено, что деформация не оказывает влияния на кинетику реакции выделения водорода (рвв), но оказывает воздействие на скорость катодного процесса. сплав az31является более эффективным катодным материалам в щелочных средах по сравнению с магнием и сплавом zk60. показано,что каталитическую активность материалов можно увеличить введением бóльшего количества алюминия или деформацией, реализуемой, например, при помощи равноканального углового прессования. * работа выполнена при финансовой поддержке министерства образования пермского края (соглашение № с-26/2011). у д к © габов а. л., белослудцев и. с., медведева н. а., скрябина н. е., фрушар д., 2014 62 cta | № 2 | 2014 это сплавы магния, которые являются одним из лидеров водородной энергетики [5, 6]. немаловажным фактом является то, что залежи магния находятся в пермском крае: соликамске и березниках. экспериментальная часть объектом исследования служили образцы чистого магния и сплавы на его основе – az31 (96 % mg, 3 % al, 1 % zn, вес. %) и zk60 (94 % mg, 5.5 % zn, 0.5 % zr, вес. %). заготовки для деформации, реализуемой при помощи равноканального углового прессования (ркуп), представляли собой параллелепипеды размерами 11×11×100 мм. деформацию материала осуществляли в установке ркуп (рис. 1) по маршруту вс [7–8] с углом пересечения каналов 105º при температуре 200 °с. шлифы для металлографического исследования готовили по методике, описанной в [9]. электронно-микроскопические исследования (sem) были проведены на сканирующем микроскопе hitachi s3400. для оценки каталитической активности поверхности материала к сорбции водорода проводили электрохимические измерения, методика которых описана в [10, 11]. для электрохимических измерений электроды были армированы в оправу из полимеризованной эпоксидной смолы. поверхность электродов (видимая площадь поверхности составляла ~ 0,15–0,25 см2) последовательно шлифовали абразивными бумагами с уменьшающимся размером частиц абразива (до марки 1000), очищали от загрязнений этиловым спиртом, промывали рабочим раствором. рабочие растворы щелочи (1м) готовили на деионизованной воде из 45 %-го кон марки «о. с. ч». поляризационные измерения проводили в стандартной электрохимической ячейке ясэ-2 с использованием потенциостата р-30i в условиях естественной аэрации. регистрацию катодных поляризационных кривых осуществляли потенциодинамическим методом, скорость развертки потенциала составляла 2 ∙ 10–4 в/с. после установления стационарного потенциала задавали развертку потенциала со смещением его в катодную область. при электрохимических исследованиях электродом сравнения служил хлорид-серебряный электрод, вспомогательным – платиновый. потенциалы электрода приведены относительно н. в. э. результаты и обсуждение на рис. 2 показаны микрофотографии сплава в исходном состоянии и после прохода через каналы ркуп матрицы при температуре деформации 200 °с. рис. 1. схема процесса равноканального углового прессования (ркуп) [7, 8] а. л. габов, и. с. белослудцев, н. а. медведева, н. е. скрябина, д. фрушар 63 2014 | № 2 | cta влияние микроструктуры сплавов на основе магния на катодное выделение водорода рис. 2. микроструктура образцов магния и его сплавов в исходном состоянии: а – mg; б – az31; в – zk60 и после деформации ркуп при 200 °c, 1 проход: г – mg; д – az31; е – zk60 а б в г е д исходный образец магния (рис. 2 а) имеет неоднородную структуру со средним размером зерна, изменяющимся в интервале значений от 200 до 1000 мкм. для большинства зерен характерна неравноосная форма. сплав az31 (рис. 2 б) обладает сравнительно мелкозернистой структурой и имеет равноосные зерна со средним размером ~ 30 мкм. в свою очередь микро64 cta | № 2 | 2014 структура сплава zk60 (рис. 2 в) представлена в основном неравноосными фрагментами величиной ~ 60 мкм, вдоль границ которых явно прослеживаются частицы второй фазы. деформация при 200 ºс приводит к формированию сильно неоднородной зеренной структуры. важной особенностью исследуемых материалов является наличие выделенных направлений внутри зерен, вдоль которых, по-видимому, происходило фрагментирование микроструктуры при деформации (рис. 2 г, е). деформация при данных условиях приводит к измельчению зерна и формированию развитой поверхности, что должно способствовать к улучшению каталитических свойств магния и сплавов на его основе. катодные поляризационные кривые (кпк) представлены на рис. 3. для установления вклада каждого из компонентов сплавов были также получены результаты не только на mg, как основном элементе, но и на алюминии и цинке, которые введены в качестве добавок, например в сплав az31 (al, zn) и zk60 (zn) [12]. экспериментальные кпк описываются уравнением тафеля [13]. обработка кривых позволила получить следующие кинетические параметры (табл. 1). необходимо отметить, что перенапряжение выделения водорода (η) сопоставимо со значениями ak при ik = 1 а/см 2. видно, что скорость катодной реакции (ik, в тексте приведены абсолютные значения катодных токов) выделения водорода (рвв) на сплаве az31 примерно в 5,5 раз больше, чем на mg при сопоставимых потенциалах (рис. 3). анализ полученных результатов позволяет предположить, что на механизм рвв влияет в большей степени магний – основа сплавов, а на скорость – компоненты легирования сплавов. сопоставимые значения ak и bk для магния и сплавов указывает на то, что механизм рвв не изменяется, а меняется лишь кинетика процесса. деформация материалов, также оказывает влияние на катодное поведение исследуемых материалов. так, в качестве примера, каталитическая активность сплава az31 по отношению к таблица 1 параметры катодного процесса на az31 и zk60 до и после ркуп при 200 °c, 1 проход сплавы -ест, в bk, в η, в ik, а/м 2 при е = –1,4 в исходные образцы mg 1,12 0,16 1,24 5,13 az31 1,24 0,15 1,15 2,34 zk60 1,30 0,18 1,35 1,00 после ркуп при 200 °c, 1 проход mg 1,43 0,11 1,19 0,19 az31 1,24 0,16 1,18 4,28 zk60 1,28 0,08 0,91 3,98 а. л. габов, и. с. белослудцев, н. а. медведева, н. е. скрябина, д. фрушар 65 2014 | № 2 | cta водороду возросла ~ в 2 раза после деформации. вероятной причиной того, что после деформации поверхности происходит рост плотности катодного тока является увеличение количества дефектов и истинной площади поверхности электрода вследствие обработки, что подтверждают результаты sem (рис. 2). таким образом, проведенные исследования позволили сделать следующие выводы. во-первых, сплав az31 является более эффективным катодным материалом в щелочных средах по сравнению с магнием и zk31. во-вторых, каталитическую активность материалов можно увеличить введением бóльшего количества алюминия или деформацией, реализуемой, например, при помощи равноканального углового прессования. 1. tarasov b. p., burnasheva v. v., lototsky m. v. yartys v. a. alternative 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микроструктуры сплавов на основе магния на катодное выделение водорода рис. 3. катодные поляризационные кривые в 1 м растворе кон исследуемых материалов: 1 – mg, 2 – zk60, 3 – az31, 4 – zn, 5 – al 66 cta | № 2 | 2014 11. medvedeva n., skryabina n., golovin p. intern. symp.metal-hydrogen systems – fundamentals and applications, kyoto, japan. 21–26 oct. 2012. p. 498. 12. wang y.n., huang j. c. mater. trans. 2003, 44, 22761. 13. conway b. e., tilak b. v. electrochim. acta, 2002. vol. 47 (22–23). p. 3571–3594. а. l. gabov1, i. s. belosludtsev1, n.а. medvedeva1, n. е. skryabina1, d. fruchart2 1perm state university, 15, bukireva street, 614990, perm, e-mail:info@psu.ru 2institut néel, cnrs, 25 rue des martyrs, вр 166, 38042 grenoble, france the influence of the magnesium alloys microstructure on the cathodic hydrogen evolution evolution of grain structure of magnesium az31 and zk60 alloys during equal channel angular pressing (ecap) at the 200 ºc temperatures is researched. it is shown that ecap leads to forming of very inhomogeneous structure. it has been found that deformation affects the rate of the cathodic process. az31 alloy is more effective cathode material in alkaline solution environment in comparison with mg and zk60 alloys. the object of study were samples of pure magnesium and alloys on its basis – az31 (96 % mg, 3% al, 1 % zn weight%) and zk60 (94 % mg, 5.5 % zn, 0.5 % zr, wt.%). it is shown that pressing leads to the formation of strongly inhomogeneous structure. it is established that the deformation does not affect the kinetics of the reaction extract the water-kind (rvv), but affects the speed cathodic process. alloy az31является more effective cathode materials in alkaline environments compared with magnesium and alloy zk60. it is shown that the catalytic activity of the materials can be enhanced by the introduction of larger amounts of aluminum or deformed, implemented, for example, by equal-channel angular pressing а. л. габов, и. с. белослудцев, н. а. медведева, н. е. скрябина, д. фрушар substituted benzocoumarin derivatives: synthesis, characterization, biological activities and molecular docking with adme studies published by ural federal university eissn2411-1414; chimicatechnoacta.ru article 2022, vol. 9(4), no. 20229419 doi: 10.15826/chimtech.2022.9.4.19 1 of 13 substituted benzocoumarin derivatives: synthesis, characterization, biological activities and molecular docking with adme studies megha g.v. a, yadav d. bodke a* , shanavaz h. b, muthipeedika nibin joy c a: department of pg studies and research in chemistry, jnana sahyadri, kuvempu university, shankaraghatta 577451, karnataka, india b: department of chemistry, faculty of engineering and technology, jain university, kankapura 562112, karnataka, india c: innovation center for chemical and pharmaceutical technologies, institute of chemical technology, ural federal university, yekaterinburg 620002, russia * corresponding author: ydbodke@gmail.com this paper belongs to a regular issue. © 2022, the authors. this article is published in open access under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). abstract herein, we report an efficient and convenient method for the synthesis of 4-(substitutedphenyl)-1,2-dihydro-2-oxo-6-(2-oxo-2hbenzo[g]chromen-3-yl)pyridine-3-carbonitrile derivatives using ammonium acetate as a catalyst. the structures of the synthesized compounds were confirmed using ft-ir, 1h, 13c-nmr and lc-ms spectroscopic techniques. the synthesized compounds were evaluated for antibacterial activity against bacterial strains by disc diffusion method at different concentrations. further, all the targeted compounds were screened for anti-oxidant and anti-cancer studies by dpph and mtt assay methods respectively at different concentrations. compound 4b displayed good antioxidant and anticancer (against mcf-7 cell line) activity. the binding capability for the synthesized compounds (4a–j) was analyzed by molecular docking studies using human peroxiredoxin 5 (pdb id: 1hd2) and p38 map kinase (pdb id: 1ouk) protein. the physicochemical properties were analyzed using absorption, distribution, metabolism and excretion (adme) studies. keywords benzo-coumarin anti-bacterial anti-cancer anti-oxidant molecular docking received:11.10.22 revised: 08.11.22 accepted: 09.11.22 available online: 16.11.22 1. introduction coumarin is a well-known naturally occurring organic compound, and it has been utilised in various fields such as pharmaceuticals. around the world, research is being conducted on this compound due to its properties [1]. coumarins are naturally occurring active constituents of various plants such as dipteryxodorata, anthoxanthumodoratum, galiumodoratum, etc, [2]. these are found in higher plants like rutaceaeand umbelliferae and essential oils of cinnamon bark, cassia leaf, and lavender oil [3]. coumarin is an aromatic compound that has a bicyclic structure with lactone carbonyl groups. the presence of an electronegative atom is effective for hydrogen bond formation and for solubility, to some extent, and the aromatic ring is responsible for having hydrophobicity. these phenomena are the cause of better interaction of the molecule with a receptor site. the substitution of coumarins activates their bioactivity. for thousands of years, natural products have been utilized in the traditional medicines, in addition to their use as a promising source of components for discovery and development of new therapies [4]. numerous types of coumarins have been synthesized with different types of substitutions or pharmacophore in their basic nuclei, which are significant in showing effective and diverse classes of biological activity [5]. based on the substitution pattern, coumarins show anticancer [6], antihiv [7], anticoagulant [8], antimicrobial [9], antioxidant [10], antihypertensive [11], antihyperglycemic [12], antituberculosis [13], and anti-inflammatory [14] activities. cancer is a chronic disease that is associated with multiple syndromes and, hence, its treatment requires close attention. world health organization (who) reported in 2013 that a not-contagious illness such as cancer is responsible for 60% deaths worldwide. among them, 80% of deaths (28 million) occur in low and middleincome countries like india [15]. a number of anticancer agents are currently used in clinical practice for treatment of various kinds of cancers. coumarin and its derivatives possess anticancer activity against different types of cancers such as prostate, renal, breast, laryngeal, lung, colon, cns, http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2022.9.4.19 mailto:ydbodke@gmail.com http://creativecommons.org/licenses/by/4.0/ https://orcid.org/0000-0003-2851-3492 https://crossmark.crossref.org/dialog/?doi=https://doi.org/10.15826/chimtech.2022.9.4.19&domain=pdf&date_stamp=2022-11-16 chimica techno acta 2022, vol. 9(4), no. 20229419 article 2 of 13 leukemia, malignant melanoma [16–18]. breast cancer is the most frequent in females, and it is one of the leading causes of cancer death for women. breast cancer can also occur in men, but it is far less common. yet new treatment methods provide more reason for optimism than ever before [19]. coumarin derivatives readily interact with a variety of enzymes and receptors in breast cancer cells. moreover, the coumarin-based irosustat drug is known to interact with sulfatase enzyme, indicating that coumarin derivatives are potential materials for anti-breast cancer agents [20]. in the last 30 years, doctors have made great strides in early diagnosis and treatment of the disease and in reducing breast cancer deaths. there are many chemotherapy agents available for the treatment of breast cancer. still, the current therapeutic options have not fulfilled the desired outcomes for breast cancer therapy [21]; thus, there is an urgent need to develop novel synthetic coumarin derivatives with anti-breast cancer potential. 2. experimental 2.1. materials and method the reagents, solvents and chemicals were purchased from sigma-aldrich and were used without further purification. alumina tlc plates were used to check the progress of the reaction. the spots were identified in a 360 nm uv chamber. the melting points were determined by the electro-thermal apparatus using open capillary tubes and are uncorrected. ftir spectra were recorded on a bruker spectrophotometer using kbr pellets in the region of 400–4000 cm−1. 1h-nmr and 13c-nmr (400 mhz and 100 mhz) spectra were recorded using a jeol instruments and estimated with the delta software in dmso-d6 solvent system; chemical shifts (δ) were recorded in ppm relative to tetramethyl silane as a standard reference. the molecular weight of synthesized compounds was confirmed by a lc-ms 2010, shimadzu, mass analyzer. elemental analysis was performed by using the unique method. the anti-bacterial activity was carried out against two gram-negative and gram-positive bacterial strains using the agar diffusion method and anti-oxidant by dpph scavenging activity at different concentrations. the anti-cancer activity was tested against mcf-7 cell line by the mtt method at different concentrations and compared with a standard drug. 2.2. general procedure for the synthesis of 4(substitutedphenyl)-1,2-dihydro-2-oxo-6-(2oxo-2h-benzo[g]chromen-3-yl)pyridine-3carbonitrile derivatives 4(a–j) in a 100 ml round bottom flask, an equimolar mixture of 3-acetyl benzocoumarin (1, 1 mmol), substituted aromatic aldehydes (2, 1 mmol) and ethylcyanoacetate (3, 1 mmol), was taken in 20 ml of ethanol, and ammonium acetate (8 mmol) was added as catalyst. the reaction mixture was refluxed for about 8 h, and after the completion of the reaction (monitored by tlc using ethyl acetate: petroleum ether in the 1:4 ratio) the solid compound separated was filtered, washed thoroughly and recrystallized from absolute ethanol to get pure compounds. the analytical are given in table 1. table 1 analysis and specification of synthesized compounds (4a–j). entry r1 r2 r3 compound yield, % 4a no2 h h n h o cn o o no2 70 4b br h h o cn br oh o n h 74 4c cl h h o cn o nh no2 cl o 72 4d cn h h nh cn cn o oo 76 4e oh och3 h nh och3 cho cn oo o 71 4f h no2 h nh o cn o o no2 74 4g cl h h nh cl cn oo o 78 4h indole h h n h o cn o n h o 81 4i h h br o cn oh o n h br 76 4j och3 h h o cn oh o n h o 82 chimica techno acta 2022, vol. 9(4), no. 20229419 article 3 of 13 2.2.1. 4-(4-nitrophenyl)-1,2-dihydro-2-oxo-6-(2-oxo-2hbenzo[g]chromen-3-yl)pyridine-3-carbonitrile (4a) orange solid, yield-70%, m.p. > 300 °c; ftir (kbr, υ cm–1): 3459 (nh), 2204 (c=n), 1733 (c=o) ,1610 (c=c), 1307 (c– c); 1h-nmr (400 mhz, dmso-d6, δ ppm): 7.26 (s, 1h, ar– ch), 7.62–7.58 (t, 2h, ar–h), 7.82 (s, 1h, ar–h), 8.04– 8.03 (d, j = 6.8 hz, 2h, ar–h), 8.35–8.32 (d, j = 8 hz, 3h, ar–h) 8.56–8.53 (d, j = 12 hz,1h, ar–h), 9.50 (s, 1h, nh); 13c nmr (100 mhz, dmso–d6, δ ppm): 94.22 (c–c), 116 (c–c≡n), 119.14, 120.17, 123.59, 126.59, 129.75, 129.08, 129.511, 130.46, 130.46, 133.11, 134.52, 139.006, 140.59, (c=c), 170 (c=o), 159 (c=0); lcms: m/z 436.04 [m+h]+. anal. calcd. for c25h13n3o5: c 71.25%; h 3.59%; n 9.97%. found: c 68.25%; h 2.58%; n 9.87%. 2.2.2. 4-(4-bromophenyl)-1,2-dihydro-2-oxo-6-(2-oxo-2hbenzo[g]chromen-3-yl)pyridine-3-carbonitrile (4b) pale orange solid, yield-74%, m.p. > 300 °c; ftir (kbr, υ cm–1): 3426 (nh), 2222.59 (c≡n), 1733 (c=o), 1351 (c– c), 605(c–br). 1h-nmr (400 mhz, dmso-d6, δ ppm): 7.26 (s, 1h, ar–ch), 7.61–7.58 (dd, j = 12 hz, 2h, ar–h), 7.63–7.63 (d, 1h, ar–h), 7.74–7.72 (d, j = 8 hz, 1h, ar–h), 7.83–7.81 (d, j = 8 hz, 1h, ar–h) 8.06–8.02 (t, 2h, ar–h), 8.23–8.21 (d, j = 8 hz 1h, ar–h), 8.34–8.31 (d, j = 12hz, 2h, ar–h), 8.55–8.53 (d, j = 8 hz, 1h, ar–h), 9.499 (s, 1h, nh) ;13c nmr (100 mhz, dmso-d6, δ ppm): 116.92 (c– c≡n), 122.88, 122.90, 123.13, 126.77, 128.63, 129.08, 129.38, 129.51, 129.55, 129.68, 130.53, 130.81, 132.58 148.58 (c=c), 152.95 (c=o), 153.54 (c=o); lcms: m/z 470.98 [m+h]+. anal. calcd. for c25h13brn2o3: c 66.54%; h 3.65%; n 5.97%. found: c 64.25%; h 3.58%; n 4.87%. 2.2.3. 4-(4-chloro-3-nitrophenyl)-1,2-dihydro-2-oxo-6(2-oxo-2h-benzo[g]chromen-3-yl)pyridine-3carbonitrile (4c) yellow solid, yield-72%, m.p. > 300 °c; ftir (kbr, υ cm–1): 3414 (nh), 2206(c≡n), 1637 (c=o), 617(c–cl). 1h-nmr (400 mhz, dmso-d6, δ ppm): 7.22 (s, 1h, ar–ch), 7.67– 7.62 (dd, 2h, ar–h), 7.89–7.79 (d, j = 8 hz, 2h, ar–h), 7.94–7.93 (d, j = 4.4hz, 1h, ar–h), 8.10–8.08 (d, j = 8 hz, 1h, ar–h) 8.27–8.25(d, j = 8 hz, 2h, ar–h), 8.56 (s, 1h, ar–h), 8.59 (s, 1h, ar–ch), 9.510 (s, 1h, nh); 13c-nmr (100 mhz, dmso-d6, δ ppm): 107.90 (c–ch), 116.91, 122.48, 125.69, 126.99, 129.22, 129.56, 130.51, 132.67, 133.92, 137.69, 140.54 148.19 (c=c), 154.69, 154.19, (c=o); lcms: m/z 470.00 [m+h]+. anal. calcd. for c25h12cln3o5: c 63.91%; h 2.57%; n 8.94%. found: c 62.90%; h 1.58%; n 9.87%. 2.2.4. 4-(4-cyanophenyl)-1,2-dihydro-2-oxo-6-(2-oxo2h-benzo[g]chromen-3-yl)pyridine-3-carbonitrile (4d) orange red solid, yield-76%, m.p. > 300 °c; ftir (kbr, υ cm–1): 3416 (nh), 2029 (c≡n), 1717 (c=o), 1570 (c=c), 1307(c–c);1h-nmr (400 mhz, dmso-d6, δ ppm): 7.18 (s, 1h, ar–ch), 7.59–7.57 (d, j = 8 hz, 1h, ar–h), 7.63–7.61 (d, j = 8 hz, 2h, ar–h) 7.74–7.70 (d, j = 8 hz, 3h, ar–h), 7.96–7.94 (d, j = 8 hz, 2h, ar–h) 8.05–8.03 (d, j = 8 hz, 1h, ar–h) , 8.21–8.19 (d, j = 8 hz, 1h, ar–h), 8.53–8.51 (d, j = 8 hz, 1h, ar–h), 9.49 (s, 1h, nh) ; 13c nmr (100 mhz, dmso-d6, δ ppm): 82.81 (c–c), 95.03 (c–c), 116.88 (c≡n), 120.27, 127.85, 123.85, 123.12, 123.83, 126.72, 126.77, 128.64, 129.07, 129.51, 129.68, 130.47, 134.11, 136.44, 148.86 (c=c), 153.51 (c–nh), 169 (c=o); lcms: m/z 416.07 [m+h]+. anal. calcd. for c26h13n3o3: c 75.18%; h 3.15%; n 10.12%. found: c 71.90%; h 2.14%; n 9.87%. 2.2.5. 4-(hydroxy-3-methylphenyl)-1,2-dihydro-4-2oxo-6-(2-oxo-2h-benzo[g]chromen-3-yl)pyridine3-carbonitrile (4e) pale yellow solid, yield-71%, m.p. > 300 °c; ftir (kbr, υ cm–1); 3414 (nh), 2924 (och3), 2202 (c≡n), 1635 (c=o), 1386(c=c); 1h-nmr (400 mhz, dmso-d6, δ ppm): 3.92 (s, 3h, och3), 6.92 (s, 1h, ar–ch), 7.40–7.38 (d, j = 8 hz, 2h, ar–h), 7.66–7.65 (d, j = 4 hz, 2h, ar–h), 7.82–7.80 (d, j = 8 hz, 2h, ar–h) 7.89–7.83 (s, 1h, ar–h), 8.10–8.08 (d, j = 8 hz, 2h, ar–h) 8.35–8.28 (s, 1h, ar–h), 9.503 (s, 1h, nh), 9.753 (s, 1h, oh) ;13c-nmr (100 mhz, dmso-d6, δ ppm): 63.33 (och3), 110.54, 113.46 (c–c), 116.86 (c≡n), 117.5, 118.45, 123.30, 126.71, 129.52, 130.47, 131.04, 135.24, 135.38, 143.79, 148.06, 148.33 (c=c), 167.14 (c=o); lcms: m/z 449.13 [m+h]+. anal. calcd. for c26h13n3o3: c 72.32%; h 3.60%; n 6.25%. found: c, 71.90%; h 2.14%; n 5.87%. 2.2.6. 3-(nitrophenyl)-1,2-dihydro-4-2-oxo-6-(2-oxo2h-benzo[g]chromen-3-yl)pyridine-3carbonitrile(4f) pale orange solid, yield-74%, m.p. > 300 °c; ftir (kbr, υ cm–1): 3415 (nh), 2202 (c≡n), 1732 (c=o), 1347 (c–c), 1621 (c=c); 1h-nmr (400 mhz, dmso-d6, δ ppm): 7.45 (s, 1h, ar–h), 7.67–7.65 (dd, j = 8 hz, 3h, ar–h), 7.70–7.68 (d, j = 8 hz, 2h, ar–h), 7.80 (s, 1h, ar–h), 7.83–7.81 (d, j = 8 hz, 1h, ar–h) 8.12–8.10 (d, j = 8 hz, 1h, ar–h), 8.35–8.32 (d, j = 8 hz, 1h, ar–h), 8.70–8.68 (d, j = 8 hz, 2h, ar–h), 9.21 (s, 1h, ar–h), 9.47 (s, 1h, nh) ; 13c-nmr (100 mhz, dmso-d6, δ ppm): 95.72 (c–c), 107.50 (c–c), 113.56 (c=c), 116.87 (c–c≡n), 122.87, 123.87, 123.12, 12.49, 126.80, 129.12, 129.52, 130.46, 130.94, 134.87, 135.21, 139.56, 139.56, 139.83, 148.31 (c=c), 159.53(c=o); lcms: m/z 436.04 [m+h]+. anal. calcd. for c26h13n3o3: c 68.97%; h 3.01%; n 9.65%. found: c 65.90%; h 2.14%; n 5.87%. 2.3. pharmacological activities 2.3.1. antibacterial activity the four bacterial strains bacillus subtilis, staphylococcus aureus (gram-positive bacteria) and escherichia coli, pseudomonas aeruginosa (gram-negative bacteria) were used to investigate the antibacterial activity of the synthesized compounds (4a–j) by the disk diffusion method [22]. briefly, all the compounds were dissolved in dmso in two different concentrations (25 and 50 mg/ml), and to this test solution, the previously cultured mueller hinton agar sabouraud’s dextrose agar medium was added and autoclaved at ±37 °c for about 24 h. streptomycin was used as chimica techno acta 2022, vol. 9(4), no. 20229419 article 4 of 13 a standard drug and 10% dmso used as a negative control. the antimicrobial assay of the title compounds was measured by the formed zone of inhibition against pathogenic strains. the test was performed in triplicate and the average was taken as a final reading. the minimum inhibitory concentration (mic) was determined by the serial broth-dilution method [23]. 2.3.2. antioxidant activity the synthesized compounds (4a–j) were screened for dpph scavenging activity [24], and dpph methods were carried out according to the reported procedure [25, 26]. the compounds at different concentrations (5 μg/ml, 10 μg/ml, 20 μg/ml, 40 μg/ml, 80 μg/ml) were used for the analysis. ascorbic acid was choosing for comparison as a standard drug and radical scavenging activities were calculated using the formula [27]: % inhibition = [(acontrol – atest)/acontrol]·100, (1) where acontrol is the absorbance of the control reaction and atest is the absorbance of the synthesized compound. ic50 value was calculated using the formula: ic50 = [(c/ʃi)·50], where ʃc is the sum of synthesized compound concentrations used to test and ʃi is the sum of % of inhibition at different concentration. each value is expressed as a mean ±sd of three replicates. 2.3.3. cytotoxicity the in vitro cytotoxicity was assessed by mtt assay by following the procedure of kumbar et al. [28], against the mcf-7 (breast cancer) cell line. the cells were seeded in a 96-well flat-bottom microplate and maintained at 37 °c in 95% humidity and 5% co2 overnight. different concentrations (200, 100, 50, 25, 12.5 and 6.25 μg/ml) of the samples were treated. the cells were incubated for another 48 h, and the wells were washed twice with pbs. 20 μl of the mtt staining solution was added to each well, and the plate was incubated at 37 °c. after 4 h, 100 μl of dmso was added to each well to dissolve the formazan crystals, and absorbance was recorded at 570 nm using a microplate reader. the percentage of cell survival was calculated by using the following formula [29, 30]. % of cell survial = mean od of test compound mean od of negative control · 100 (2) 2.3.4. in silico molecular docking study the molecular interactions of the synthesized compounds at the binding pocket of human peroxiredoxin 5 protein and p38 map kinase proteins were studied using automated docking by employing the autodock vina program [31]. the co-crystallized structure of human peroxiredoxin 5 protein (pdb id: 1hd2) and p38 map kinase (pdb id: 1ouk) were retrieved from the protein databank, and their substrate binding sites were identified using the pdb sum server [32]. a grid box of dimensions 20x20x20 å with x, y and z coordinates at 7.654, 40.848 and 34.184 for human peroxiredoxin 5 and 20x20x20 å with x, y and z coordinates at 44.438, 32.882 and 32.692 for p38 map kinase were created, respectively. the grid box was set around the residues forming the active pocket. the binding interactions were visualized using biovia discovery studio visualizer v.20.1. 2.3.5. in silico oral bioavailability assessment and adme various physicochemical features and pharmacokinetic descriptors were calculated through the online web tool swiss adme [33]. the oral bioavailability of the synthesized compounds (4a–j) was predicted using the lipinski rule-of-five (ro5) filter [34] to derive the candidate drug pharmacokinetic (pk). the structural properties used in the ro5 filter are derived using osiris data warrior v.4.4.3 software [35]. the bioavailability scores were predicted using the molinspiration server [36]. 3. results and discussions 3.1. chemistry in the present study, we developed a simple, convenient and environmentally safe method for the synthesis of some new 4-(substitutedphenyl)-1,2-dihydro-2-oxo-6-(2oxo-2h-benzo[g]chromen-3-yl)pyridine-3-carbonitrile derivatives (4a–j) via the one-pot reaction of 3-acetyl benzocoumarin (1), substituted aromatic aldehydes (2) and ethyl cyanoacetate (3) in ethanol using ammonium acetate as a catalyst (scheme 1). 3.2. biological activity 3.2.1. antibacterial activity the in vitro antibacterial activity of the synthesized compounds was screened against four pathogenic strains and the results are tabulated in table 2. the result revealed that all the test compounds exerted a varied degree of antibacterial activity against the tested strains. further, to quantify the lowest concentration at which the growth of the organism was prevented, we determined the minimum inhibitory concentration (mic). the results are given in table 3. compounds 4a, 4c, 4h and 4i exhibited equipotent activity against e. coli, pseudomonas aeruginosa and s. aureus with mic 2.1–2.3 mg/ml. scheme 1 synthesis of 4-(substitutedphenyl)-1,2-dihydro-2-oxo-6(2-oxo-2h-benzo[g]chromen-3-yl) pyridine-3-carbonitrile derivatives (4a–j). chimica techno acta 2022, vol. 9(4), no. 20229419 article 5 of 13 from the structure activity relationship studies, it was observed that compounds 4e and 4j, having methoxy groups on the aromatic ring, showed excellent activity among the series when compared to the standard drug. compounds 4a, 4c, 4f and 4g, having –no2 and –cl groups, respectively, displayed promising activity against b. subtilis. the rest of the synthesized compounds showed moderate activity against selected bacterial strains. 3.2.2. antioxidant activity the synthesized compounds (4a–j) were screened for their free radical scavenging activity by the dpph method as shown in figure 1. all the compounds showed varied free radial scavenging capacity in assessment with the standard ascorbic acid. among all the compounds, compound 4b exhibited most effective antioxidant efficacy with ic50 value 34.66±2.43 μg/ml as compared to the reference standard drug (ic50 8.88±1.19 μg/ml). compounds 4a, 4c, 4f and 4j with ic50 in the range of 41.54–44.11 μg/ml showed promising antioxidant activity, and the rest of the compounds showed moderate scavenging activity by the dpph method. therefore, the synthesized compounds exhibited more effective antioxidant efficacy due to the presence of the electron donating group (oh) at para position of the phenyl ring [37]. the results are shown in table 4. 3.2.3. cytotoxicity study the in vitro cytotoxicity of the synthesized compounds (4a–f) was evaluated against the mcf-7 (breast cancer) cell line and shown in figure 2. a graph detailing the concentration versus survival fraction of the compounds was plotted in figures 3 and 4, and the results were expressed as the half-maximal inhibitory concentrations (ic50) (table 5) with doxorubicin as a standard drug. the cytotoxicity results suggested that the test compounds have a very good selectivity against the mcf-7 cell line. the cytotoxicity data revealed that compound 4d possessed significant ic50 values of 22.60±0.30 μg/ml as compare to the standard drug. the remaining compounds displayed considerable selectivity with ic50 values in the range of 37.10±0.36 to 193.97±3.71 μg/ml. figure 1 antioxidant activity of synthesized compounds (c). table 2 bacterial studies of synthesized compounds (4a–j). compound b. subtilis s. aureus e. coli p. aeruginosa 25 mg/ml 50 mg/ml 25 mg/ml 50 mg/ml 25 mg/ml 50 mg/ml 25 mg/ml 50 mg/ml 4a 1.5±0.3 1.9±0.5 1.3±0.12 1.5±0.24 1.2±0.6 1.7±0.8 1.2±0.15 1.6±0.24 4b 2.0±0.12 2.4±0.12 1.8±0.12 2.0±0.21 1.6±0.2 1.8±0.5 2.1±0.25 2.4±0.21 4c 2.0±0.1 2.1±0.4 1.7±0.2 2.1±0.21 1.5±0.22 1.8±0.23 1.8±0.12 1.9±0.26 4d 1.4±0.24 1.7±0.29 1.9±0.23 1.8±0.22 1.8±0.1 2.2±0.30 1.8±0.15 2.1±0.28 4e 1.0±0.21 1.7±0.24 1.0±0.21 2.4±0.25 1.0±0.15 1.4±0.21 1.7±0.2 1.8±0.23 4f 2.0±0.12 2.3±0.21 2.0±0.12 2.3±0.21 1.8±0.23 2.1±0.24 1.6±0.18 2.1±0.23 4g 2.5±0.3 1.9±0.26 2.4±0.25 1.7±0.8 1.6±0.18 2.4±0.12 1.6±0.18 1.7±0.8 4h 1.8±0.12 2.4±0.12 2.1±0.24 1.9±0.26 1.7±0.24 2.2±0.30 1.5±0.22 2.4±0.12 4i 1.5±0.3 1.7±0.2 1.8±0.15 2.2±0.30 1.5±0.22 1.7±0.24 1.9±0.5 1.4±0.21 4j 2.1±0.25 2.2±0.30 1.6±0.2 1.7±0.24 1.8±0.12 2.1±0.24 1.8±0.23 1.6±0.18 streptomycin 2.3±0.32 3.0±0.35 2.5±0.31 2.9±0.35 2.1±0.25 2.5±0.28 2.3±0.27 2.5±0.30 table 3 mic values of the synthesized compounds (4a–j). compound bacillus subtilis s. aureus e. coli p. aeruginosa 4a 2.3±0.26 2.4±0.25 2.1±0.25 2.2±0.26 4b 2.4±0.32 2.1±0.29 2.3±0.25 2.2±0.25 4c 2.4±0.25 2.3±0.26 2.1±0.23 2.3±0.24 4d 2.5±0.26 2.3±0.26 2.3±0.26 2.5±0.29 4e 2.4±0.21 2.1±0.22 2.4±0.26 2.3±0.25 4f 2.5±0.21 2.4±0.23 2.1±0.25 2.3±0.26 4g 2.1±0.25 2.3±0.26 2.3±0.26 2.1±0.25 4h 2.3±0.26 2.2±0.26 2.3±0.26 2.3±0.26 4i 2.3±0.26 2.1±0.25 2.1±0.25 2.3±0.26 4j 2.5±0.26 2.4±0.23 2.3±0.26 2.3±0.26 streptomycin 2.5±0.30 2.5±0.30 2.2±0.26 2.3±0.28 chimica techno acta 2022, vol. 9(4), no. 20229419 article 6 of 13 table 4 dpph radical scavenging activity of the synthesized compounds (4a–j). compound dpph radical scavenging activity % of inhibition concentration, µg/ml 5 10 20 40 80 ic50 4a 3.054±2.71 14.47±1.00 25.63±1.61 50.59±1.05 65.20±0.60 44.11±0.50 4b 10.88±2.19 26.23±2.04 39.70±1.79 54.44±0.92 66.00±1.61 34.66±2.43 4c 2.523±2.65 16.60±2.99 26.95±0.23 47.80±1.38 66.79±1.00 44.02±0.77 4d 11.68±0.66 18.59±1.28 33.46±0.68 38.77±1.60 46.87±1.84 86.36±5.02 4e 4.913±3.22 15.93±1.37 25.75±2.00 38.64±0.04 52.05±1.61 69.33±3.37 4f 4.648±2.71 18.99±0.60 34.39±0.60 50.33±1.00 62.94±0.79 42.30±0.52 4g 2.125±1.28 9.296±1.65 15.53±0.39 23.37±2.79 32.40±2.30 194.10±12.5 4h 12.88±1.50 17.66±1.28 22.84±1.00 25.76±1.00 32.66±0.39 495.40±15.8 4i 17.66±0.22 22.17±0.82 29.48±3.32 35.06±0.79 39.57±0.46 204.37±3.85 4j 25.76±0.46 31.34±0.46 42.09±1.96 47.80±1.59 59.23±0.60 41.54±0.34 standard 42.76±1.15 55.64±1.61 55.51±1.61 59.36±1.73 64.01±0.22 8.88±1.19 table 5 percentage of cell viability against mcf-7 cell line of the synthesized compounds (4a–j). compound mean cell viability of mcf-7 nc 3.125 6.25 12.5 25 50 100 ic50, µg/ml 4a 100 96.69±0.94 61.69±0.31 57.41±0.77 48.07±0.42 38.86±0.76 14.32±0.08 56.13±0.82 4b 68.15±0.53 62.48±0.85 57.13±0.94 39.05±0.84 37.52±0.14 18.87±1.95 37.10±0.36 4c 99.02±0.37 95.44±0.42 93.16±0.27 90.28±0.44 53.18±0.56 12.13±0.48 195.10±1.90 4d 99.35±0.69 95.54±0.42 91.63±0.37 90.38±0.14 88.56±0.50 33.19±0.77 22.60±0.30 4e 92.05±0.91 87.40±0.58 72.61±0.44 56.58±0.42 51.51±0.69 44.91±0.50 193.97±3.71 4f 99.58±0.28 98.14±0.32 95.56±0.65 94.09±0.66 70.01±0.14 32.82±1.08 191.03±4.94 standard 33.80±0.67 30.57±0.42 27.53±0.37 28.56±0.43 26.15±0.17 23.69±0.53 3.16±0.10 std – doxorubicin, nc – negative control values are mean±se, n = 3, *p<0.01 vs. control. figure 2 images of cytotoxicity of the synthesized compounds (4a–f) and negative control. figure 3 graph of % of surviving cells of compounds (4a–f) at different concentration against mcf-7 cell line. figure 4 graph of ic50 value of compounds (4a–f) against mcf-7 cell line. chimica techno acta 2022, vol. 9(4), no. 20229419 article 7 of 13 3.2.4. in silico molecular docking studies the study of intermolecular interactions between the synthesized compounds (4a–j) and enzymes is necessary for the development of novel therapeutic drugs [38]. therefore, we screened the synthesized compounds for in silico molecular docking, which helps to predict the binding modes of the compounds with enzymes. from the results of the docking study, the synthesized compounds established good binding modes with docking receptors of human peroxiredoxin 5 (figures 5, 6) and p38 map kinase (figures 7, 8), respectively. the docking of anti-oxidant and cytotoxicity investigations revealed that the synthesized compounds (4a–j) had significant docking scores in the range of –7.3 to –8.5 kcal/mol with respect to standards ascorbic acid (–6.5 kcal/mol) and –9.8 to –11.0 kcal/mol with respect to standard doxorubicin (–8.4 kcal/mol), respectively. the docked structures with human peroxiredoxin 5 results suggested that compound 4h established the lowest binding energy of –8.5 kcal/mol. the remaining compounds also established good binding modes and one or more hydrogen bonds with amino acid residues thr147, arg127, asn76, arg124, gly46, cys47, thr44 (table s1). the docked structures with p38 map kinase protein results revealed that compound 4d demonstrated the lowest binding energy of –11.0 kcal/mol, forming one or more hydrogen bonds with three amino acid residues lys53, val38, tyr35, val30, ala40, leu108. the remaining compounds also established encouraging binding energies and formed two or more hydrogen bonds with amino acid residues in their active pockets. the results are given in table s2. 3.2.5. adme studies physiochemical descriptors can be evaluated through the parameters such as molecular weight, number of heavy atoms, hydrogen bond acceptors, hydrogen bond donors, rotatable bonds, molar refractivity and topological polar surface area (tpsa). these parameters were evaluated for the synthesized compounds (4a–j), and the results are shown in table 6. the drug-likeness profiles were calculated based on lipinski’s (mw ≤ 500; hba ≤ 10 and hbd ≤ 5) [39], ghose (mw between 160 and 480; log p between –0.4 and 5.6; molar refractivity between 40 and 130, and the total number of atoms between 20 and 70), veber (rotatable bonds ≤ 10 and tpsa ≤ 140), egan (tpsa ≤ 131.6 å²) and muegge (mw between 200 and 600; log p between –2 and 5; tpsa ≤ 150; number of aromatic rings ≤ 7; number of rotatable bonds ≤ 15; hba ≤ 10 and hbd ≤ 5) [40]. all the synthesized compounds obeyed lipinski, ghose, veber, egan and muegge rules. the rule-based score divides the compounds into four probability score classes, i.e., 11%, 17%, 55% and 85%. the acceptable probability score is 55%, which indicates that it passed the rule of five [41, 42]. the synthesized compounds (4a–e) showed a score of 55%, indicating that they all the five rules without any violations with good bioavailability. further, synthetic accessibility of the compounds was assessed to quantify the complexity of the molecular structure. the results showed that the synthetic accessibility score was in the range of 3.44 to 3.67. it shows that no compound has a complex synthetic route (table s3). the predicted lipophilicity parameters were evaluated to study the solubility of the compounds either in aqueous or in non-aqueous medium, and they were calculated by considering the consensus logpo/w. according to this, if the logpo/w values are more negative, then the molecules are more soluble in nature [43]. the results showed that all the compounds have positive logpo/w values. hence, they are less soluble in non-aqueous medium. the values of logs are related to the solubility as follows if logs are between –10 to –6 – poorly soluble, –6 to –4 – moderately soluble, –4 to –2 – soluble, –2 to 0 – very soluble and less than 0 – highly soluble. for our synthesized compounds (4a–j), the logs value is in the range of –5.21 to –6.33; this shows that the compounds are soluble in aqueous media. the results are presented in table s4. the pharmacokinetic parameters such as absorption, skin permeation, distribution, metabolism and excretion were predicted. the predicted absorption and distribution parameters of the compounds are in table s5, indicating that, all the synthesized compounds (4a–j) have high gastrointestinal absorption (except for 4a and 4f) with no blood-brain barrier crossing. table 6 physicochemical properties of synthesized compounds (4a–j). code formula molecular weight no. heavy atoms hba hbd rotatable bonds fraction csp3 molar refractivity tpsa 4a c25h13n3o5 435.39 g/mol 33 6 1 3 0.00 125.02 132.68 å² 4b c26h15brn2o2 467.31 g/mol 31 2 1 2 0.04 125.65 73.72 å² 4c c25h12cln3o5 469.83 g/mol 34 6 1 3 0.00 130.03 132.68 å² 4d c26h13n3o3 415.40 g/mol 32 5 1 2 0.00 120.91 110.65 å² 4e c27h16n2o5 448.43 g/mol 34 6 1 4 0.04 128.08 113.16 å² 4f c25h13n3o5 435.39 g/mol 33 6 1 3 0.00 125.02 132.68 å² 4g c25h13cln2o3 424.84 g/mol 31 4 1 2 0.00 121.21 86.86 å² 4h c27h15n3o3 429.43 g/mol 33 4 2 2 0.00 128.05 102.65 å² 4i c26h17brn2o2 469.33 g/mol 31 3 2 2 0.08 128.28 73.12 å² 4j c26h16n2o4 420.42 g/mol 32 5 1 3 0.04 122.69 96.09 å² chimica techno acta 2022, vol. 9(4), no. 20229419 article 8 of 13 figure 5 three-dimensional and two-dimensional representations of molecular interactions between human peroxiredoxin 5 protein and synthesized compounds (4a–f). 4a 4b 4c 4d 4e 4f chimica techno acta 2022, vol. 9(4), no. 20229419 article 9 of 13 figure 6 three-dimensional and two-dimensional representations of molecular interactions between human peroxiredoxin 5 protein and synthesized compounds (4g–j) and reference drug ascorbic acid. hence, there was no possibility of causing harmful toxicants to appear in the brain and blood stream. if the molecules have more negative logkp value, it means that they possess lower skin permeation [44]. this is true for our synthesized compounds, which have more negative logkp values in the range of –5.41 to –6.46 cm/s (table s5). metabolism plays an important role in the bioavailability of drugs as well as drug-drug interactions [45]. metabolism parameters are important to understanding whether the compounds act as a substrate or a non-substrate of the certain proteins. hence, all the synthesized compounds were evaluated for the metabolism parameters, and the results showed that the compounds (4a–j) are nonsubstrates of permeability glycoprotein (p-gp), cyp1a2, cyp2c19, cyp2d6 and cyp3a4 inhibitors. the p-gp is an efflux membrane transporter, which is widely distributed throughout the body and is responsible for limiting cellular uptake and the distribution of xenobiotic and toxic substances [46]. the compounds (except for 4c and 4e) were found to be non-substrates of cyp1a2 inhibitors. compounds 4b, 4d, 4f, 4g and 4i were found to be substrates of cyp2c19 inhibitors, and the remaining compounds were non-substrates of cyp2c19 inhibitors. 4g 4h 4j 4i chimica techno acta 2022, vol. 9(4), no. 20229419 article 10 of 13 figure 7 three-dimensional and two-dimensional representations of molecular interactions between p38 map kinase protein and synthesized compounds (4a–f). 4f 4e 4d 4c 4b 4a chimica techno acta 2022, vol. 9(4), no. 20229419 article 11 of 13 figure 8 three-dimensional and two-dimensional representations of molecular interactions between p38 map kinase protein and synthesized compounds (4g–j) and reference drug doxorubicin. all the compounds were found to be substrates of cyp2c9 inhibitors. the compounds (except for 4a, 4c, 4f, 4g, 4h) are non-substrates to cyp2d6 inhibitors. all the compounds are non-substrates of cyp3a4 inhibitors. the data are listed in table s6. 4. conclusions in this present work, we synthesized some novel 4(substitutedphenyl)-1,2-dihydro-2-oxo-6-(2-oxo-2hbenzo[g]chromen-3-yl) pyridine-3-carbonitrile derivatives 4(a–j) through the one-pot reaction. the antibacterial activity results show good efficacy against four bacterial strains. the antioxidant activity results suggested that compound 4d exhibited the lowest ic50 value of 22.60±0.30. compound 4b displayed significant cytotoxic effect with an ic50 value of 34.66±2.43 as compared to the other compounds. the in silico docking studies suggested that the synthesized compounds interacted effectively with human peroxiredoxin 5 and p38 map kinase proteins with good binding energy. in that, compounds 4h and 4d show the lowest binding energy values of –8.5 kcal/mol and –11.0 kcal/mol, respectively. doxorubicin 4j 4i 4h 4g chimica techno acta 2022, vol. 9(4), no. 20229419 article 12 of 13 adme studies explained that our synthesized compounds obeyed all the five rules with good bioavailability. pharmacokinetic parameters suggested that the compounds have gi absorption, do not cross the blood-brain barrier, possess low skin permeation, and that there is no possibility of creating harmful toxicants. based on the obtained results, the synthesized compounds are promising materials in the pharmacological fields. supplementary materials supplementary materials are available. funding none. acknowledgments the authors are grateful to the chairman, department of chemistry, kuvempu university, shankaraghatta, for providing the laboratory facilities. one of the authors, muthipeedikanibin joy is grateful to russian science foundation (grants no. 22-23-20189 and 21-13-00304). the authors are also grateful to saif, karnataka university, dharwad for providing the spectra and to maratha mandal, belagavi for biological studies. author contributions conceptualization: m.g.v, y.d.b. data curation: m.g.v, y.d.b. formal analysis: m.g.v, y.d.b. investigation: m.g.v, y.d.b. methodology: m.g.v, y.d.b. project administration: y.d.b., m.n.j. software: s.h. supervision: y.d.b. validation: m.g.v., y.d.b., m.n.j. visualization: m.g.v, y.d.b. writing – original draft: m.g.v, y.d.b. writing – review & editing: m.g.v, y.d.b. conflict of interest the authors declare no conflict of interest. additional information author ids: yadav d. bodke, scopus id 6504415850; muthipeedika nibin joy, scopus id 56072237200. websites: kuvempu university, http://www.kuvempu.ac.in/eng; jain university, https://www.jainuniversity.ac.in; ural federal university, https://urfu.ru/en. references 1. kontogiorgis c, anastasia d, hadjipavlou-litina d. coumarinbased drugs: a patent review (2008-present). expert opin ther patents.2012;22:437–454. doi:10.1517/13543776.2012.678835 2. narale vs. synthesis of coumarin and their 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исследований и получила широкое распространение во многих практических приложениях. сегодня большие усилия направлены на создание фотовольтаических приборов из малотоксичных материалов низкой стоимости с простой технологией получения. в этом отношении весьма перспективными оказались полупроводниковые соединения группы a4b6. в частности, сульфид олова sns благодаря высокому значению коэффициента оптического поглощения, составляющему е. а. федорова1, е. а. базанова1, л. н. маскаева1,2, в. ф. марков1 1уральский федеральный университет,кафедра физической и коллоидной химии, 620002, екатеринбург, ул. мира, 19. e-mail: ka_fed-ra@mail.ru 2уральский институт гпс мчс россии, кафедра химии и процессов горения, 620002, екатеринбург, ул. мира, 22. e-mail: mln@ural.ru механизм формирования пленок sns химическим осаждением из водных растворов* в работе представлены результаты исследования механизма роста пленок сульфида олова при химическом осаждении из водных растворов с использованием сканирующей зондовой микроскопии. по результатам сравнительного анализа морфологии слоев на различных этапах роста и использования фрактального формализма предложена модель роста пленок sns путем кластер-кластерной агрегации с элементами самоорганизации. показано, что формируется сплошной слой, на котором снова осаждаются микрочастицы из раствора. процесс имеет выраженный периодический самоорганизующийся характер. проведенное исследование показало, что предложенная модель роста пленок sns при гидрохимическом осаждении хорошо согласуется с экспериментами и доказывает сложный агрегативный механизм формирования твердой фазы из пересыщенного водного раствора. * исследование проведено при финансовой поддержке молодых ученых урфу в рамках реализации программы развития урфу. у д к 6 61 .8 81 .3 21 .9 © федорова е. а., базанова е. а., маскаева л. н., марков в. ф., 2014 77 2014 | № 2 | cta 104–105 см–1, и оптической ширине запрещенной зоны, равной 1,1–1,5 эв [1], используется в качестве поглощающего слоя в тонкопленочных преобразователях солнечной энергии [1], а также в качестве фотопроводников, полупроводниковых датчиков, микробатарей. большинство существующих методов получения сульфида олова (пульверизация водных растворов с пиролизом на нагретой подложке, физическое осаждение из газовой фазы, метод горячей стенки, молекулярно-лучевая эпитаксия, термическое испарение поликристаллического материала, электрохимическое осаждение) обладают рядом недостатков, к числу которых можно отнести высокотемпературные процессы, лежащие в их основе, создание глубокого вакуума, использование достаточно сложного аппаратурного оформления. вместе с тем значительный интерес представляет метод гидрохимического осаждения тонкопленочных материалов из водных сред [2], отличающийся простотой и минимальным энергопотреблением с широкими возможностями варьирования состава и функциональных свойств. однако интерес в первую очередь направлен на исследование электрофизических свойств получаемых слоев. в то же время практически отсутствуют работы по изучению процессов зарождения и роста твердой фазы, оказывающих первостепенное влияние на структуру и свойства пленок. в раскрытии механизма формирования пленок халькогенидов металлов перспективным является использование фрактального формализма в связи с изложенным, целью настоящей работы являлось исследование механизма формирования пленок сульфида олова при химическом осаждении из водных растворов путем анализа морфологии слоев на различных этапах роста с использованием фрактального формализма. экспериментальная часть гидрохимическое осаждение sns осуществляли на предварительно обезжиренные ситалловые пластины марки ст-150-1 размером 30×24 мм из гидроксо-цитратной системы, содержащей хлорид олова sncl2, трехзамещенный цитрат натрия na3 c6h5o7, гидроксид натрия naoh и тиокарбамид csn2h4 в качестве халькогенизатора. синтез пленок осуществляли при температуре 353 k в течение 5, 60 и 120 минут в герметичных стеклянных реакторах, в которые помещали подложки, закрепленные в специально изготовленные фторопластовые держатели. реактор устанавливали в термостат марки u-10, точность поддержания температуры в котором составляла ±0.1 k. во всех опытах обеспечивали строго определенный порядок сливания реагентов. для изучения механизма роста пленок sns проводили исследование поверхности пленки сканирующим зондовым микроскопом explorer (thermomicroscopes) в режиме контактной атомно-силовой микроскопии (асм). для сканирования поверхности использовали кантилеверы из нитрида кремния (si3n4) с резонансной частотой 17 кгц. механизм формирования пленок sns химическим осаждением из водных растворов 78 cta | № 2 | 2014 результаты и обсуждение образование пленок и их рост при гидрохимическом осаждении сульфидов металлов тиоамидами рассматриваются исследователями в рамках двух основных механизмов: ионно-молекулярного и адсорбционно-агрегативного [3]. их противопоставление, вероятно, связано с большим разнообразием факторов, оказывающих влияние на процесс гидрохимического осаждения. на наш взгляд, при зарождении и росте пленок не исключено проявление каждого из указанных механизмов, и речь может идти лишь о доминирующей роли одного из них в тех или иных создаваемых условиях. при гидрохимическом синтезе пленок халькогенидов металлов создаются сильно неравновесные условия, которые не исключают проявления других механизмов роста. важно представлять, что процесс роста пленок при этом необходимо относить не к поверхностному, а к объемному явлению, так как он реализуется с активным участием объема реакционной смеси. ранее было установлено [4], что при гидрохимическом синтезе образование фазы халькогенида металла в объеме раствора сопровождается накоплением в реакционной ванне их коллоидной фракции. исходя из физико-химического содержания процесса, можно предположить их активную роль и в дальнейшем формировании пленок. в последнее время значительные перспективы в раскрытии механизма формирования новой фазы в условиях, далеких от термодинамического равновесия, открываются на основе использования фрактального формализма [5]. с позиций последнего можно предположить, что определяющую роль в процессах гидрохимического осаждения пленок играют образующиеся в системе первичные структурные единицы – фрактальные кластеры, в качестве которых могут выступать структурированные и уплотнившиеся коллоидные частицы раствора. они являются основой формирующейся новой фазы. в связи с этим наноразмерные коллоидные частицы следует рассматривать в качест ве главного первичного звена в процессе гидрохимического синтеза сульфидов металлов. их агрегация и реорганизация формируют разветвленную структуру, полностью соответствующую принципам фрактальности. стоит учесть также то, что сами коллоидные частицы отвечают всем свойствам фрактальных элементов. для исследования механизма роста пленок sns при гидрохимическом осаждении нами были проведены сравнительные исследования с помощью сканирующего зондового микроскопа поверхности слоя. на рис. 1 а–в показана эволюция морфологии поверхности пленки sns, осажденной тиокарбамидом из гидроксо-цитратной системы во временном интервале от 5 до 120 мин. видно, что если к пятой минуте на ситалловой подложке наблюдаются глобулы размером ~9,1−11,3 нм, то через 60 минут их размер увеличивается до 16,9−23,7 нм. однако интенсивного роста пленки не наблюдается, она имеет островковый характер. можно обратить внимание на образование на подложке наностержней диаметром 28−30 нм. можно предположить, что е. а. федорова, е. а. базанова, л. н. маскаева, в. ф. марков 79 2014 | № 2 | cta механизм формирования пленок sns химическим осаждением из водных растворов эти образования являются гидроксидом или гидроксохлоридом олова, в то время как низкая скорость роста связана с переходом процесса в гетерогенную стадию, суть которой − сульфидизация гидроксида. к 120 минуте размер частиц увеличивается до 37,1−40,7 нм. в то же время на фотографии можно наблюдать упорядочение их формы, что говорит о начале кристаллизации фазы сульфида олова. известно, что с позиций фрактально-кластерного подхода к формированию пленок сульфидов и селенидов металлов важным инструментом, характеризующим механизм роста слоя при гидрохимическом осаждении, является их фрактальная размерность d [2]. этот параметр характеризует степень заполнения поверхности подложки материалом пленки. c целью определения фрактальной размерности пленок была проведена компьютерная обработка микрофотографий слоев sns в период активного роста с использованием программы fractalyse-2.4. расчет фрактальной размерности проводился путем разбиения поля фотографии на клетки различных размеров со стороной a и подсчета их числа, занятых кластерами n. само значение d находили как угловой коэффициент зависимости lgn от lga [6]. полученные значения фрактальной размерности для всех указанных пленок <2 и находятся в пределах dс = 1.17 − 1.30. эти значения для процесса образования пленок, согласно [5], соответствуют механизму кластер-кластерной агрегации (cca) при броуновском движении с вероятностью слипания, близкой к 1. предлагаемая модель предполагает масштабную иерархию образования пленок: образование относительно мелких фрактальных кластеров на первой стадии с их объединением в более крупные агрегаты на следующей стадии. стоит отметить, что фрактальная размерность поверхности больше, составляя ds = 2.17 − 2.36. по общепринятым моделям это является следствием агрегации по механизму кластер-частица (dla), что косвенно подтверждает одновременное протекание процессов адсорбции гидроксида олова и реакционного тиомочевинного комплекса с последующим образованием сульфида, в том числе в мицеллярной форме. с учетом полученных результатов, а также работы [4] может быть предложен следующий механизм роста плерис. 1. асм-изображения поверхности пленки sns. температура процесса – 353 k. продолжительность осаждения: а – 5 мин; б – 60; в – 120 мин размер сканов – 2×2 мкм а б в 80 cta | № 2 | 2014 нок при гидрохимическом осаждении сульфида олова. первичные кластеры, сформированные в объеме реакционной смеси, закрепляются на неоднородной поверхности подложки, постепенно покрывая всю ее поверхность. далее идет процесс их укрупнения за счет объединения адсорбированных частиц и присоединения новых кластерных частиц из раствора. в результате поверхность подложки полностью покрывается кластерными образованиями более высокой масштабной иерархии. причем можно сделать вывод о том, что лимитирующей стадией при формировании пленок сульфида олова является процесс, определяемый взаимодействием халькогенизатора с гидроксидом металла. таким образом, формируется сплошной слой, на котором снова осаждаются микрочастицы из раствора. процесс имеет выраженный периодический самоорганизующийся характер. проведенное исследование показало, что предложенная модель роста пленок sns при гидрохимическом осаждении хорошо согласуется с экспериментами и доказывает сложный агрегативный механизм формирования твердой фазы из пересыщенного водного раствора. 1. bashkirov s. a., gremenok v. f., ivanov v. a. semiconductors, 2011, 45, 749. 2. markov v. f., maskaeva l.i., ivanov p.n. chemical deposition of films sulfides of metals: simulation and experiment. uro ran, ekaterinburg, 2006, 218 p. [марков в. ф., маскаева л. н., иванов п. н. гидрохимическое осаждение пленок сульфидов металлов: моделирование и эксперимент. екатеринбург: уро ран, 2006. 218 с.]. 3. makurin yu. n., pletnev r. n., kleshev d. g., zhelonkin n. a. intermediate complex in chemical reactions. uro, sverdlovsk, 1990, 78 p. [макурин ю. н., плетнев р. н., клещев д. г., желонкин н. а. промежуточный комплекс в химических реакциях. свердловск: уро ан ссср, 1990. 78 с.]. 4. markov v. f., maskaeva l. i. butlerov commun. 2011, 24 (2), 33. 5. smirnov b. m. physics of fractal clusters. nauka, moscow, 1991, 134 p. [смирнов б. м. физика фрактальных кластеров. м.: наука, 1991. 134 с.]. 6. feder e. fractals. mir, moscow, 1991, 254 p [федер е. фракталы. м.: мир, 1991. 254 с.]. е. а. федорова, е. а. базанова, л. н. маскаева, в. ф. марков 81 2014 | № 2 | cta механизм формирования пленок sns химическим осаждением из водных растворов e. a. fedorova1, e. a. bazanova1, l. n. maskaeva1,2, v. f. markov1 1ural federal university, 19, mira street, 620002, ekaterinburg. e-mail: ka_fed-ra@mail.ru 2ural institute of state fire service of emercom of russia, 22 mira street, 620002, ekaterinburg. e-mail: mln@ural.ru formation mechanism of sns films by chemical bath deposition from aqueous solutions the results of investigation of the growth mechanism of sns thin films prepared by hydrochemical deposition by means of a scanning probe microscopy are presented. according to the results of a comparative analysis of layers morphology at different growth stages and the use of fractal formalism growth model of sns films by clustercluster aggregation with elements of self-organization is proposed. it is shown that there is a solid layer, which again are deposited particles of the solution. the process has expressed periodic self-organizing nature. the study showed that the proposed model of film growth sns when hydrochemical deposition agrees well with ex-periments and proves difficult coagulation mechanism of the formation of hard phase of the satu-rated aqueous solution. страница 1 membrane techniques for removal detergents and petroleum products from carwash effluents: a review published by ural federal university eissn 2411-1414 chimicatechnoacta.ru review 2023, vol. 10(1), no. 202310107 doi: 10.15826/chimtech.2023.10.1.07 1 of 12 membrane techniques for removal of detergents and petroleum products from carwash effluents: a review eman s. awad ab* , siraj m. abdulla c, t.m. sabirova a , qusay f. alsalhy d* a: department of chemical technology of fuel and industrial ecology, institute of chemical technology, ural federal university, ekaterinburg 620002, russia b: environmental research center, university of technology-iraq, baghdad 10066, iraq c: department of environmental science and health, college of science, salahaddin university, erbil 44001, iraq d: membrane technology research unit, department of chemical engineering, university of technology-iraq, baghdad 10066, iraq * corresponding author: eman.s.awad@yandex.com (e.s.a.); qusay.f.abdulhameed@uotechnology.edu.iq (q.f.a). this paper belongs to a regular issue. abstract one of the most significant urban services is the carwash, which generates large amounts of wastewater containing a variety of pollutants, including sand, gravel, suspended solids, surfactants, oil products, diesel cleaners, etc., that may cause environmental pollution when transferred to the sewage system without any treatment. the effective treatment is crucial to prevent environmental pollution as well as to recycle the water source. contaminants are removed from carwash effluent using a variety of treatment technologies. this review focuses on identifying and comparing efficiency of using advanced commercial and modified membrane filtration techniques, meeting discharge standard regulations, to treat carwash impurities, especially detergents/surfactants (anionic surfactant) and petroleum products (oil/grease). the results of this review indicate that ultrafiltration membrane (uf) is the most common membrane filtration technology for carwash wastewater treatment. additionally, the adoption of traditional pre-treatment processes may be advantageous before utilization of membrane process for treating carwash wastewater; although conventional treatment processes can produce a high quality of effluent, they are less effective than membrane systems. keywords: anionic surfactant carwash membrane filtration modified membranes water consumption wastewater received: 04.12.22 revised: 25.12.22 accepted: 27.12.22 available online: 11.01.23 key findings ● pollutant removal efficiency of surfactants, oil products and tss from carwash wastewater depends on the pre-treatment method and the type of membranes used. ● the main method for obtaining new modified membrane structures is the combination of various polymers with other materials to improve the membrane performance. © 2022, the authors. this article is published in open access under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). 1. introduction one of the activities that consumes huge amount of water is washing cars. the amount of water consumed depends on both the geographical area and the carwash type, and 150– 600 l of water are often used to wash a car [1]. the discharge of the car wash station without treatment resulted in different harmful impacts on the environment because it includes various types of impurities like oils, hydrocarbons, fats, petroleum fractions, road surface pollutants, small exhaust particles and water-soluble cleansing agent [2]. the composition of carwash wastewater varies greatly depending on the washing technique, type and size of the car that is being washed [3, 4]. the proper treatment and purification of carwash wastewater is considered as a new source of water. in international practices, great attention is paid to the quality of carwash wastewater and the selection of the optimal methods for cleaning it. recently, membrane separation processes have been effectively used to remove carwash contaminants. the manufacturing materials for the membranes are either organic (polymers) or inorganic http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2023.10.1.07 mailto:eman.s.awad@yandex.com mailto:qusay.f.abdulhameed@uotechnology.edu.iq http://creativecommons.org/licenses/by/4.0/ https://orcid.org/0000-0001-6961-8587 https://orcid.org/0000-0001-5449-9909 https://orcid.org/0000-0002-0495-1300 https://crossmark.crossref.org/dialog/?doi=https://doi.org/10.15826/chimtech.2023.10.1.05&domain=pdf&date_stamp=2022-12-22 chimica techno acta 2023, vol. 10(1), no. 202310107 review 2 of 12 doi: 10.15826/chimtech.2023.10.1.07 (ceramic, steel, aluminum, and glass). the membrane processes are able to carry out an effective treatment to decrease the oil content, detergent and other pollutants in carwash wastewater to an acceptable level [5–10]. by conducting a literature survey, it no information was found about the use of modified membranes technologies for treating the contaminants present in carwash wastewater, which is one of the relevant areas of research. in this regard, the purpose of this literature review was to evaluate the efficiency of commercial and modified membrane filtration techniques and hybrid membrane methods for removing surfactants, oily products and other contaminants of carwash units with the possibility of ensuring their compliance with the regulations for reuse or discharge into the centralized sewer network. 2. carwash units’ specifications the carwash wastewater (cww) composition depends on the number of washed cars, the season, the type of carwash, and the parameters like detergent types and concentrations, and the amount of water used. the contaminants of carwash wastewater originate from detergents used in the washing process, oils and greases of the engine, organic materials, metals, residual petroleum, and particles, like carbon, dust, and salt [11, 12]. the international car wash association listed the main parameters of interest to carwash operators, which include: total dissolved solids (tds), total suspended solids (tss), biochemical oxygen demand (bod), chemical oxygen demand (cod), oil and grease, detergent, zinc, lead, and trace quantities of other metals [13]. of these constituents, the carwash operator uses the detergent only to wash off the other parameters from the car surfaces. the parameters characteristic of carwash wastewater mentioned in the literature are listed in table 1. the concentrations of cod, oil and grease, and turbidity have a large range, as indicated in table 1, although some parameters, such as ph, have fewer variation in the studies. according to table 1, several studies revealed the ph of cww were between 6.3–8.7, with the higher value recorded by [1]. also, the electrical conductivity (ec) values were within 138.8–1570 μs/cm. other cww constituents are present in solids that enter the vehicle from dust, mud, and silts, which also increase the turbidity of the wastewater. van bruggen et al. recorded the maximum value of total suspended solids (tss) within 2458 mg/l [14], while shete and n.p. shinkar, recorded the high value of total dissolved solids (tds) within 7920 mg/l [2], and the maximum value of turbidity recorded by mirshahghassemi et al. was within 1400 ntu [15]. the chemical oxidation demand (cod) in cww was ranged between 59–1810 mg/l. the countries such as brazil recorded 59–85 mg/l of cod [16]; indonesia 700 mg/l [17]; malaysia 75.0–738 mg/l [1]; turkey recorded 314 mg/l [18]; and india 460 mg/l [19]. the higher cod observed in belgium was 1810 mg/l [14]. in carwash stations, emulsified oil obtained from washing engine and detergents utilized for vehicles washes contribute to increased bod levels. based on the literature review, the biochemical oxygen demand (bod5) values were 70–320 mg/l in belgium [14] and 27–650 mg/l in south africa [20]. lau et al. recorded the bod5 values in malaysia (10.5–11.9 mg/l that are lower than the others [1]. the oil and grease which are among the cww's most significant pollutants were stated from less than 0.1 mg/l [16] up to more than 1750 mg/l [21]. also, van bruggen et al. found high level of anionic surfactant in cww, about 15.5 mg/l [14]. many studies in the field of treatment carwash wastewater determined, total dissolved solids, total suspended solids, turbidity, and chemical oxygen demand (cod), but they did not measure detergents and oil products despite their great impact on the environment [22]. the two important parameters in carwash wastewater (detergents, and oil products) are described in the following paragraphs. 2.1. structure characteristics and properties of the detergents in carwash technologies in car wash stations, detergents used as cleaning agents contain different types of surfactants. surfactants are surface-active chemicals that reduced the surface tension and are concentrated at the interfaces between bodies or droplets of water or oil to act as foaming or emulsifying agents. their chemical structure has a direct bearing on this mode of action [28]. they are long-chain molecules containing a head group that is hydrophilic (soluble in water) and a tail group that is hydrophobic (oil soluble). table 1 the characteristics of carwash wastewater. parameter units range references ph – 6.3–8.7 [1, 2, 16, 18, 19, 23, 24] conductivity (ec) μs/cm 138.8–1570 [1, 16, 18, 19, 23] turbidity ntu 7.7–1400 [1, 2, 15–17, 23–25] total suspended solids (tss) mg/l 60–2458 [2, 14, 16, 18, 19, 26] total dissolved solids (tds) mg/l 120–7920 [1, 2, 16, 23, 25] chemical oxygen demand (cod) mg/l 59–1810 [1, 2, 14, 16–19, 23–27] biochemical oxygen demand (bod5) mg/l 10.5–650 [1, 14, 20] oil and grease (o&g) mg/l 0.1–1750 [16, 17, 21, 24] anionic surfactant mg/l 0.7–51 [24, 26, 27] https://doi.org/10.15826/chimtech.2023.10.1.07 chimica techno acta 2023, vol. 10(1), no. 202310107 review 3 of 12 doi: 10.15826/chimtech.2023.10.1.07 the major classification of surfactants into classes is based on the characteristics of the hydrophilic head group: anionic with a negative charge, cationic with a positive charge, non-ionic without charge, and zwitterionic with negative and positive charges. the hydrophobic tail group may be long chain hydrocarbons, fluorocarbons, siloxane chains, and short polymer chains [29, 30]. among the numerous surfactant types, anionic surfactants are particularly important because they account for 60% of all soap production worldwide [31]. anionic surfactants are most commonly used in car washing technologies. among the most widespread are those which have a lengthy hydrophobic alkyl chain and a hydrophilic end group that is charged with sulfonate (e.g., linear alkylbenzene sulfonate (las), secondary alkane sulfonate (sas), a-olefin sulfonate (aos), and methylester sulfonate (mes)) or a sulfate charged hydrophilic end group (e.g., alkyl sulfate (fas or as) and alkylether sulfate (aes)) (figure 1), as well as sodium, potassium, or ammonium counterions. sodium dialkylsulfosuccinate, sodium dodecylsulfonate, and sodium odecylbenzenesulfonate are common surfactants. anionic surfactants play a significant part in technical applications owing to their excellent properties like superior water solubility, great cleaning efficiency, and low cost [32]. the methylene blue active substances method (mbas) is used to determine the anionic surfactant content for water and wastewater. anionic surfactants are the most notable of the materials exhibiting methylene blue activity, which is usually utilized in formulations of detergent which are strongly responsive to this approach [33]. mbas with a high concentration of linear alkylbenzene sulfonates (las) may coat the oil and grease with mbas molecules to make these droplets soluble in water. thus, the effluent did not have lower values [34]. the anionic surfactants contained in carwash wastewater and its treatment methods are listed in table 2. 2.2. structure characteristics of the petroleum products in carwash wastewater carwash wastewater can carry petroleum hydrocarbon residues, hydraulic fluids, and lubricating oils. lubricating oils are formed from a basic stock of heavier petroleum hydrocarbons, which are generated from crude oil, together with a variety of additives to enhance their specific qualities. they are mixed using base oils made of petroleum hydrocarbon, polyalphaolefins (pao) or their mixtures in varying ratios [37]. oil and grease that originate from different types of petroleum products in car washes may be released from the vehicle surface, tires, or may be leaked out from the braking system, engine parts, and connections [38]. oil composition is complex, typically containing aliphatic hydrocarbons (73–80%), monoaromatic hydrocarbons (11–15%), diaromatic hydrocarbons (2–5%) and polyaromatic hydrocarbons (4–8%). also, it consists approximately of 20% of the lubrication additives, which include zinc diaryl, zinc dithiophosphate, molybdenum disulfide, metal soaps and other organometallic composites. oil products in carwash wastewater are considered a serious environmental problem because they contain toxic materials (e.g. polyaromatic hydrocarbon, phenol, etc.) affecting the environment [39]. table 3 shows oil and grease content in carwash wastewater and its treatment methods. figure 1 structural formula of common anionic surfactants. table 2 anionic surfactants in various carwash wastewater and the treatment methods. anionic surfactants initial concentration (mg/l) final concentration (mg/l) treatment method references sodium dodecyl sulfate (sds) 100 9.9–51.7 membrane separation [14] sodium dodecylbenzene sulfonate (sdbs) 0.7–2.5 not available membrane separation [26] sodium dodecyl benzene sulfonate (sdbs) 0.8 0.1–0.4 membrane separation [27] linear alkylbenzene sulphonates (las) not declared <0.06 coagulation; membrane separation; granular activated carbon [35] linear alkylbenzene sulphonates (las) 2–5 not available coagulation; membrane separation [24] alkylbenzene surfactant (abs) 3–20 <0.05 sedimentation; surface degreasing; sand filtration; ozonation; uv irradiation, membrane separation [21] dodecyl benzene sulfonate (dbs) 21 12 flocculation column; flotation; sand filtration; chlorination [36] https://doi.org/10.15826/chimtech.2023.10.1.07 chimica techno acta 2023, vol. 10(1), no. 202310107 review 4 of 12 doi: 10.15826/chimtech.2023.10.1.07 table 3 oil and grease in various carwash wastewater and treatment techniques. 3. legislation standards for carwash wastewater to conserve natural resources and give a high-quality wash, a new carwash technique must be used, involving water reusing. some countries have achieved considerable advancements in the reuse of wastewater by establishing laws and regulations, whereas the other ones still lack sufficient planning and restrictions [40]. environmental legislation and regulations have been published for wastewater disposal into the public sewage system. though many countries have their own legislations on environmental quality, the carwash sector rarely enforces application of these laws [41]. greywater standard on carwash wastewater was created in countries like united states, australia, and europe. some countries in europe restricted consumption of fresh water for carwash, or imposed a reclamation (recycling and reuse) percentage of approximately 70–80% to meet the water quality standard [36]. the standards for the carwash wastewater discharge were included in the standard of sewage and effluent discharge. wastewater composition standards (the standards of permissible discharges of substances into water bodies) were established in city of yekaterinburg, sverdlovsk region, russia by the regulation no. 2329 of 2021. furthermore, iraq established iraqi national standards set by the regulation 25 of 1967 for wastewater drained to the water source or into public sewers. malaysia also uses standard a and standard b regulations 2012 based on malaysia sewage and industrial effluent discharge for the effluent discharges of carwash wastewater. these legislations are applied to the carwash wastewater and are focused on suspended solids (ss), oil and grease, and chemical oxygen demand (cod), yet less attention is paid to the surfactant concentration. the legislation standards for wastewater are summarized in table 4. 4. membrane techniques 4.1. commercial membrane techniques a summary of numerous studies on membrane techniques used for the treatment of wastewater from car washes is provided in table 5. the uf membranes were widely used in a variety of industrial applications because of the great efficacy in removing contaminants from wastewater with higher permeation flux than that of the other membrane filtration processes [42–44]. the utilization of uf membranes are the main focus of membrane research in the carwash sector [45, 46]. different commercial and experimental membranes were applied to the carwash effluents that have a various contaminant like detergents/surfactants, oil/grease and others. bruggen et al. investigated seven types of commercial uf membranes with carwash effluents. because of surfactants having a major role in the membrane performance, synthetic detergent solutions present in carwash effluents were employed. three types of surfactants were utilized: sodium dodecyl sulfate (sds) as an anionic surfactant, cetrimide as a cationic surfactant, and triton x-100® as a nonionic surfactant. the results showed that c100f and ultrafilic uf possessed best performance in term of surfactant rejection due to molecular weight cutoff (mwco) of these membranes [14]. in another study, boussu et al. showed that the desirable quality and the intended use (recycling or discharge) of the purified wastewater determine whether to use uf or nf membranes. four typical membranes were used; two uf membranes and two nf membranes for analyzing cod and anionic, cationic and nonionic surfactants of carwash wastewater. the authors concluded that with the proper membrane type (least membrane fouling) and process format (a hybrid process combining uf and/or a biological treatment with nf), membrane processes can be effective. uf membrane is the best option if the purified wastewater is used for recycling and the surfactants presence does not cause a problem [27]. in a related study, boussu et al. investigated the application of nf membrane in the carwash sector using two different nf membranes. they revealed that the removal efficiency of nf membrane was 100% in terms of removing cod and surfactants. the membrane with the shortest mwco, nf270, had the highest retentions, which is consistent with the results. anionic surfactants (sodium dodecylbenzene sulfonate (sdbs)) are better retained than other surfactants because the negative charges of surfactant and the membrane surface are electrostatically attracted to one another [26]. oil and grease initial concentration (mg/l) final concentration (mg/l) treatment method references oil not declared 0.95 coagulation; membrane separation; granular activated carbon [35] oil 5–25 not available coagulation; membrane separation [24] oil 36 2–8 membrane separation [17] fossil oil and grease 500–3000 4–20 sedimentation; surface degreasing; sand filtration; ozonation; uv irradiation; membrane separation [21] https://doi.org/10.15826/chimtech.2023.10.1.07 chimica techno acta 2023, vol. 10(1), no. 202310107 review 5 of 12 doi: 10.15826/chimtech.2023.10.1.07 table 4 the legislation standards for the carwash wastewater. parameters standard in yekaterinburg, sverdlovsk region (regulation no. 2329 of 2021) wastewater composition, mg/l iraqi national standards (regulation no. 25 of 1967) wastewater composition, mg/l malaysia (industrial effluents) regulations 2012 wastewater composition, mg/l north canalization basin southern canalizat ion basin sewerage basin water source public sewers standard a standard b suspended solids 300 96.80 31.48 – – 50 100 bod5 169.40 40.10 30.90 <5 <40 2 40 cod 500.00 176.90 – – <100 80 200 petroleum products 2.21 0.60 1.30 – 10, if water drained/source water is 1:1000; 5, if water drained/source water is 1:500; 3, if water drained/source water is 1:300 1 10 sulphates 80.10 69.00 90.44 200 <400, if the water drained/source water is 1:1000 0.5 0.5 chlorides 53.54 72.00 139.0 200 <600, if the water drained/source water is 1:1000 – – ammonium 25.40 3.30 8.54 1 – – – anionic surfactant 0.80 1.60 2.17 – – – – phosphates–p 0.24 0.24 2.45 0.13 0.98 – – phenol 0.008 0.023 – 0.005 0.01–0.05 0,001 1 chromium (6+) 0.0128 0.01 – 0.05 0.1 0.05 0.05 chromium (3+) 0.0107 0.01 – 0.05 0.1 0.2 0.1 iron 0.50 1.032 – 0.3 2 1 5 zinc 0.05 0.051 – 0.5 2 2 2 copper 0.0312 0.0221 – 0.05 0.2 – – nickel 0.0099 0.0094 – 0.1 0.2 0.2 1 aluminium 0.17 0.22 – 0.1 5 10 15 manganese 0.20 0.10 – 0.1 0.5 0.2 1 in general, the solute rejection of membranes increases with decreasing membrane pore size and porosity. istirokhatun et al. studied the applicability of four different commercial uf membranes with various molecular weight cut-off through filtration in a cross-flow set up [17]. in their study, pes10 had the highest rejection for all pollutants, which is evident in the fact that this membrane has the smallest mwco. the uf membranes have within 90–95%, 78–100%, and 100% rejection for cod, oil and grease, and turbidity, respectively [17]. the concentration of cod can indicate contaminants outside of the vehicle such as various composting dust, bird droppings, or fallen fruit. detergents, too, can contribute to increased levels of cod in effluents and were identified as cod in many studies [1], [18]. lau et al. examined the treatment of carwash effluents by using three various types of commercial polymeric membranes uf and nf; their characteristics summarized in table 5. during filtration in a lab-scale cross-flow unit, it was determined that the cod removal depend on the membrane characteristics and the best removal (91.5%) was gained by the nf270 [1]. in a similar study, uçar [18] filtered carwash wastewater by four uf membranes of varying mwco and one nf membrane. the cod measurements were made to specify the detergent in this study. the results showed the cod removal efficiency corresponding to 97% for nf membrane, which is more than that for the uf membrane. furthermore, these studies emphasize the importance of pre-treatment when using membranes for treatment of carwash wastewater. 4.2. modified membrane techniques membranes are generally prepared from ceramic and polymeric materials. although the cost of manufacturing ceramic membrane is high, it can be minimized by using locally sourced precursors like pore-formers, clay, and plasticizer. zrelli et al. prepared a ceramic membrane from clay and 22% oasis waste by using semidry-pressing process; the membrane was sintered at 800 °c and molded at 8 bars. this ceramic membrane was used to treat carwash wastewater which was collected from five car washing units located in tunisia. the characteristics of the used carwash wastewater in this study were total solid (1115 mg/l), oil content (137 mg/l), ph = 7.5, and conductivity (915 μs/cm). https://doi.org/10.15826/chimtech.2023.10.1.07 chimica techno acta 2023, vol. 10(1), no. 202310107 review 6 of 12 doi: 10.15826/chimtech.2023.10.1.07 table 5 carwash wastewater treatment techniques with various commercial membranes. membrane characteristics influent characteristics effluent characteristics references mwco (kda) material uf c100f 100 cellulose synthetic solutions: nonionic surfactant 100 mg/l; anionic surfactant 100 mg/l; cationic surfactant 100 mg/l; nonionic surfactant 55.9– 94.6 mg/l; anionic surfactant 48.3– 90.1 mg/l; cationic surfactant 5.2–83.3 mg/l [14] p150f 150 polyethersulfone pes 20 polyethersulfone pes 10 10 polyethersulfone hfm 116 100 pvdf hfm 180 250 pvdf ultrafilic uf 100 polyacrylonitrile uf uf p150f 150 polyethersulfone cod 208–316 mg/l; nonionic surfactant 26–39 mg/l; anionic surfactant 0–0.8 mg/l; cationic surfactant 4.3–7.9 mg/l cod 192 mg/l; nonionic surfactant 23 mg/l; anionic surfactant 0; cationic surfactant 7.3 mg/l [27] ultrafilic 100 polyacrylonitrile cod nd; nonionic surfactant 24 mg/l; anionic surfactant 0 mg/l; cationic surfactant 3.9 mg/l nf nfpes10 1.2 polyethersulfone cod 106 mg/l; nonionic surfactant 21 mg/l; anionic surfactant 0.4 mg/l; cationic surfactant 0.9 mg/l nf270 0.17 polyamide cod 10 mg/l; nonionic surfactant 1 mg/l; anionic surfactant 0.1 mg/l; cationic surfactant 0.2 mg/l nf nf270 0.17 polyamide ss 60–140 mg/l; cod 208–382 mg/l; nonionic surfactant 32–51 mg/l; anionic surfactant 0.7–2.5 mg/l; cationic surfactant 1.7–3.7 mg/l cod 33–100 mg/l [26] nfpes10 1.2 polyethersulfone uf pes10 10 poly (ether) sulfone cod 700 mg/l; o&g 36 mg/l; turbidity 186.6 ntu cod 33.3–40 mg/l; turbidity 0.22–0.25 ntu; o&g 0–2 mg/l [17] ps25 25 polysulfone cod 40–70 mg/l; turbidity 0.24–0.57 ntu; o&g 2–8 mg/l ps50 50 polysulfone ps100 100 polysulfone uf ge 1 composite polyamide ph 7.3; cod 314 mg /l; ec 729 μs/cm; po43–p 9.05 mg/l ph 7.34–7.59 cod 64.5–85.5 mg/l; ec 523–629 μs/cm; po43–p < 1 mg/l [18] pt 5 polyethersulfone pw 10 polyethersulfone mw 50 pan/ultrafilic nf nf270 0.2–0.4 ph 7.61; cod 8.1 mg/l; ec 391 μs/cm; po43–p < 0.05 mg/l uf pvdf100 100 polyvinylidene difluoride cod 75.0– 738.0 mg/l; turbidity 34.7– 86.0 ntu; tds 89.2–151.8 mg/l; ec 138.8–260.7 μs/m cod 56.11–82.41 mg/l; turbidity 92.37– 96.85 ntu; tds 13.59–16.56 mg/l; ec 16.9–19.6 μs/m [1] pes30 30 polyethersulfone cod 54.85–83.89 mg/l; turbidity 97.27–97.34 ntu; tds 17.61–31.45 mg/l; ec 23.57–35.44 μs/m nf nf270 0.3 polyamide cod 70.9–91.49 mg/l; turbidity 94.42–98.75 ntu; tds 59.99–61.53 mg/l; ec 61.92–63.62 μs/m https://doi.org/10.15826/chimtech.2023.10.1.07 chimica techno acta 2023, vol. 10(1), no. 202310107 review 7 of 12 doi: 10.15826/chimtech.2023.10.1.07 to reduce the fouling and increase the treatment efficiency, the authors used sedimentation for 1 hour and filtration as a pretreatment of the carwash wastewater samples, and then treated them with a dead-end filtration unit. the authors examined the effect of percentage of oasis waste on open and closed porosity at a molding pressure (8 bars) and sintering temperature (800 °c), as shown in figure 2. the concepts of open and closed porosity are used to describe different types of porous materials. the volume of fluid that the continuous fluid phase occupies in relation to the entire volume of porous material is referred to as the open porosity. in contrast, closed porosity is the percentage of the total volume in which fluids are present but cannot flow effectively [47]. the membranes had stronger hydrophilic characteristics with increased concentration of oasis waste. when the concentration of oasis waste was between 8–15% for the fabricated ceramic membrane, a sharp increase of the open porosity 26.12–40.05% and a slight variation of the closed porosity were detected, and above this concentration, no effect was observed on the open porosity, while the closed porosity increased. furthermore, the evolution of permeate flux and oil rejection were compared for oily wastewater with 125 mg/l oil concentration and carwash wastewater for the prepared ceramic membrane, as shown in figure 3. the authors concluded that the permeate flux decreases with the time increase, and the flux evolution of the carwash wastewater was about 5% lower than that of the oily wastewater. also, the oil rejection of carwash wastewater was about 93% which complies with the tunisian standard of wastewater. these outcomes are a result of using detergents composed of surfactants in the carwash units, which interact with the membrane surface to give reduced. these detergents flux reduction and improved the oil rejection [47]. polymeric modified membranes have been employed for solving issues relating to water treatment or water reuse due to their exceptional efficiency, cost-effectiveness, clean technology, and environmental friendliness by efficiently eliminating oil and grease, detergents, and highly hazardous surfactants from carwash effluents [46, 48]. figure 2 open and closed porosity evolution with percentage of oasis waste [47]. there are few studies on the use of modified membranes for the treatment of carwash wastewater. kamelian et al. prepared 10 types of acrylonitrile-butadienestyrene (abs) membranes with thickness ranged between 82.4–113.9 µm. the impact of solvent-nonsolvent types, abs and additive concentrations (polyethylene glycol (peg)) on the structures and wastewater treatment of carwash was assessed. the 1-methyl-2-pyrrolidone (nmp) and dimethyl acetamide (dmac) were utilized as solvents, and water and heptane (c7) were used as antisolvents. the authors clarified through the crosssectional images that the membranes made by using the nmp/c7 pair (e.g. m2) have a denser structure in comparison with the membranes prepared using the nmp/water pair (e.g. m9) which have a fingerlike structure as shown in figure 4, because nmp has low solubility in heptane (c7); meanwhile, nmp has a large crossaffinity with water. also, the membranes prepared by using 20 wt.% abs have denser and thinner structures in comparison with the membranes prepared by using lower concentration, 17 wt.%, of abs because the high concentration of abs increase the casting solution viscosity, cause slow demixing in the coagulation bath, and thus reduce the nuclei growth rate in the structure through phase inversion. the surface sem images (figure 5) of m1, m2 and m3 proves the porosity reduction with 0, 6, 10 wt.% peg addition, respectively. also, the authors concluded that the membrane structure, which was prepared using nmp/water pair, was negatively impacted by the an migration to the water coagulation bath through the precipitation process. furthermore, similar performance of the membranes prepared with nmp and dmac as solvent results in similar impact on the membrane structure. the authors revealed that the porous membranes fabricated with similar concentrations in the water coagulation bath have lower rejection percentages of cod, tds, and turbidity, and more stable flux. additionally, it was shown through the study of the effectiveness of membranes prepared with various abs concentrations that increasing the abs concentration raises rejection rates while lowering stable flux. figure 3 the permeate flux and oil rejection with time [47]. https://doi.org/10.15826/chimtech.2023.10.1.07 chimica techno acta 2023, vol. 10(1), no. 202310107 review 8 of 12 doi: 10.15826/chimtech.2023.10.1.07 figure 4 the cross-sectional sem images of prepared membranes. figure 5 the surface sem images of some prepared membranes. also, increasing the peg concentration caused an increase in rejection rates and a decrease in stable flux at a constant abs concentration. all these results are consistent with the cross sectional and surface sem images of the membranes. moreover, to study the migration effect from abs to water, the authors used the fourier transform infrared (ftir) spectra, which focused on the characteristic peak of an. the intensity changes as the coagulation bath changes, which means the an migration from abs to water occurred [25]. kiran et al. fabricated two membranes, cellulose acetate (ca) and polyethersulfone (pes), by using hydrophilic polymer sulfonated polyether ether ketone (speek) and nanoclay bentonite, and compared their performance with the commercial polyethersulfone (pes) membrane in the removal of carwash effluent. the authors concluded based on the surface sem images that the membranes ca/speek/bentonite and pes/ speek/bentonite have loose porous structures with clear bigger pores, owing to the incompatibility between inorganic bentonite and an organic polymer; thus, demixing the casting dope solution improves the pore formation. additionally, the bigger surface area and the smaller size of nanoclay bentonite cause it to disperse in both the top and bottom layers of the membrane surface. the membranes' cross-sectional images revealed a thin skin layer and finely interconnected porous structure that were responsible for the improved permeation rate brought on by the addition of both bentonite and speek to the casting dope solution. a higher flux was observed for ca/speek/bentonite membrane (52.3 l/m2h) compared with that of the commercial pes membrane (41.5 l/m2h); this might be caused by more solutes being absorbed onto the membrane surface. also, the higher rejection, 60% cod and 82% turbidity, was gained for the ca/speek/bentonite membrane. in this study, fourier transform infrared (ftir) spectra (figure 6) revealed that the wavenumbers 1030–1060 cm–1 and 550 cm–1 in membranes correspond to alcohols (ch2oh) and disulfide, respectively, which showed that the pollutant was adsorbed on the surface of the membrane. yet, the commercial pes membrane displayed a higher adsorption intensity with carwash effluent, which may be related to its hydrophobic properties [23]. 5. hybrid-membrane techniques numerous studies were published on using integrated membrane techniques either alone or in combination with conventional methods such us mechanical separation, flotation, chemical coagulation, etc. figure 6 fourier transform infrared (ftir) spectra of membranes. reproduced from ref. [23] © 2015 elsevier inc. https://doi.org/10.15826/chimtech.2023.10.1.07 chimica techno acta 2023, vol. 10(1), no. 202310107 review 9 of 12 doi: 10.15826/chimtech.2023.10.1.07 establishing an effective pre-treatment is crucial to ensuring that the membranes operate consistently and to improving the wastewater quality based on its nature and the discharge standard regulation. in the study of nagamani et al. the authors used a combined pre-treatment consisting of utilizing a coarse filter (20 μm pp cartridge), an mf ceramic membrane (3 μm kaolin), and ultimately an nf membrane (500 da polyamide membrane) to ensure that the filtrate is of sufficient quality to be recycled and used again. detergents, oil, grease, and other contaminants may be indicated by the cod concentration. they found that the concentrations of cod post 20 μm cartridge filtration has a minimum change <2%, which means that the particle sizes were less than 20 μm, and the removal efficiency of cod was 99% after filtration by course filter, mf and nf membrane [19]. in another study, moazzem et al. achieved high removal efficiency of turbidity 99.9%, suspended solids 100%, and cod 96% from carwash wastewater by using two types of membranes, including ceramic uf membrane and reverse osmosis (ro) with pretreatment as coagulation flocculation process and sand filtration [22]. also, tan and tang clarified that it is preferable to utilize pretreatment before uf membrane to prevent more contaminants from adsorbing in pores. it was shown that using chemical coagulation as pretreatment by adding kmno4 to the coagulant pac can improve efficiency of the coagulation and help to reduce the blockage of the two types of ps uf membranes with mwco (6 and 20 kda) which were used [24]. in a similar study, tang et al. separated carwash wastewater by using two sorts of ps hollow fiber uf membranes (6 and 20 kda) with enhanced coagulation and granular activated carbon (gac), resulting in good removal levels of oil, cod, bod, and las. the gac tank following the uf membrane can efficiently adsorb las, odor, and color. a schematic diagram of the apparatus is presented in figure 7. afm analysis was conducted on the membrane (figure 8), and it was concluded that the las existence in carwash wastewater might loosen the gel layer and improve the membrane flux [35]. moreover, shete et al. checked the feasibility for obtaining refuse-free water by using sedimentation and induced air flotation as a pretreatment, and then cross-flow uf and reverse osmosis. the removal efficiency values for the total dissolved solids (tds), total suspended solids (tss), oil and grease, and cod by uf were 81%, 82%, 74%, and 67%, respectively (the effluent poses can be safely discharged into any local water bodies, including rivers), and by ro these values were 91%, 82%, 90%, and 81%, respectively (it is safe to reuse the effluent for any productive activity, such as car washing or landscape gardening). it was possible to obtain a sufficient quantity of water with high purity from carwash effluent using these procedures [2]. table 6 provides a summary of several studies on hybrid-membrane techniques that were conducted for the treatment of wastewater from car washes. in the study by jiku et al., coagulation-flotation was utilized as a pre-treatment before hollow fiber ultrafiltration membrane for oil removing from car washing wastewater. the oil content in car washing effluents ranged from 5.2 to 13.47 mg/l. according to the their results, the combined processes may remove more than 40% of the oil content, more than doubling the oil removal rate of the traditional coagulation and flotation method [49]. 6. limitations this review studied the membrane filtration techniques and their effectiveness in eliminating various contaminants from carwash wastewater, including surfactants, oil products, dissolved and suspended particles. the major restriction of membrane filtration for the treatment of carwash is the rapid membrane flux reduction during the operation; therefore, the selection of the suitable membrane or modification of the structure of membrane might be necessary. figure 7 schematic diagram of system setup. figure 8 afm analysis on uf membrane: (a) new uf membrane, (b) membrane contaminated with oil and (c) membrane contaminated with oil and las. reproduced from ref. [35] © iwa publishing 2007. https://doi.org/10.15826/chimtech.2023.10.1.07 chimica techno acta 2023, vol. 10(1), no. 202310107 review 10 of 12 doi: 10.15826/chimtech.2023.10.1.07 table 6 carwash wastewater treatment methods based on hybrid-membrane techniques. pretreatment membrane characteristics influent characteristics effluent characteristics ref. mwco (kda) pore size, μm material coarse filter pp ceramic-mf – 3 kaolin ph 6.4; ec 680 μs/cm; cod 460 mg/l; ts 1280 mg /l after mf+nf ph 7.73; ec 226 μs/cm; cod 4 mg/l [19] nf 0.5 – polyamide coagulationflocculation, sand filtration ceramic-uf – 0.02 zirconia oxide ph 4.66–6.42; ec 404–509 μs/cm; turbidity 522–763 ntu uf ph 5.32; ec 273–298 μs/cm; turbidity 1.84–0.86 ntu [22] ro – – – after uf+ro ph 5.32; ec 7.6–14.6 μs/cm; turbidity 0.86–0.16 ntu enhanced coagulation uf 6 20 – polysulfone ph 6.5–8; turbidity 70 ntu; cod 100–160 mg/l; oil 5–25 mg/l; las 2–5 mg/l not declared [24] enhanced coagulation uf 6 20 – polysulfone not declared cod 33.4 mg/l, bod 4.8 mg/l, turbidity 0.42 ntu, las 0.06 mg/l, oil 0.95 mg/l, ss 1 mg/l ds 115 mg/l [35] granular activated carbon (gac) sedimentation & induced air flotation uf – – – ph 8.5; turbidity 7.7 ntu; tds 7920 mg/l; tss 1134 mg/l; cod 288 mg/l; o&g 34.19 mg/l uf ph 7.26; turbidity 1.20 ntu; tds 791.5 mg/l; tss 124 mg/l; cod 83 mg/l; o&g 3.11 mg/l [2] ro – – – after uf+ro ph 6.38; turbidity 0.0 ntu; tds 140 mg/l; tss 10 mg/l; cod 12.8 mg/l; o&g 0.31mg/l coagulation flotation hollow fiber uf – – – ph 6.9–7.6; oil and grease 5– 13.4 mg/l; turbidity 362–450 ntu oil and grease >2.1– 5.4 mg/l [49] 7. conclusion and future prospects according to the reviewed studies into the membrane filtration systems and hybrid membrane technologies, traditional filtration methods such as mechanical separation, coagulation-flocculation process, air flotation, etc., are the most interesting choices for treating carwash wastewater and getting rid of various contaminants that pose a serious threat to the environment. moreover, these methods cost effective and can produce high-quality filtering. the concentrations of surfactants and oily products were also found to be reduced based on the treatment type and the membrane technology employed. the main approach to obtaining new modified membrane structures is a combination of various polymers and other materials in the manufacturing technology, which allows to improve the removal efficiency and other performance properties of membranes. this study allows giving some suggestions for the future works in the carwash sector. firstly, it is necessary to conduct more studies on using the modified membranes to treat wastewater for car washes, to consider the cost and the main characteristics, and then to apply the membranes on field-scale to obtain an efficient wastewater treatment. also, developing good and costefficient membrane filtration techniques and using them in the car washing will reduce the cost of using municipal water through recycling. ● supplementary materials no supplementary materials are available. ● funding this research had no external funding. https://doi.org/10.15826/chimtech.2023.10.1.07 chimica techno acta 2023, vol. 10(1), no. 202310107 review 11 of 12 doi: 10.15826/chimtech.2023.10.1.07 ● acknowledgments none. ● author contributions conceptualization: e.s.a., s.m.a., t.m.s., q.f.a. data curation: e.s.a., q.f.a. formal analysis: e.s.a., s.m.a., t.m.s., q.f.a. funding acquisition: e.s.a., t.m.s., q.f.a. investigation: e.s.a., s.m.a. methodology: e.s.a. project administration: t.m.s., q.f.a. resources: e.s.a., s.m.a., t.m.s., q.f.a. software: e.s.a., s.m.a. supervision: t.m.s., q.f.a. validation: e.s.a., s.m.a., t.m.s., q.f.a. visualization: e.s.a. writing – original draft: e.s.a. writing – review & editing: t.m.s., q.f.a. ● conflict of interest the authors declare no conflict of interest. ● additional information author ids: eman s. awad, scopus id 56921998200; t.m. sabirova, scopus id 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kinetic region: integrated approach using the math calculations and catalytic experiments published by ural federal university eissn 2411-1414 chimicatechnoacta.ru article 2023, vol. 10(2), no. 202310208 doi: 10.15826/chimtech.2023.10.2.08 1 of 9 testing conditions for como hds catalyst in the kinetic region: integrated approach using the math calculations and catalytic experiments polina p. mukhacheva , yuliya v. vatutina, ivan a. mik * , ksenia a. nadeina, maksim o. kazakov , oleg p. klenov, oleg v. klimov , aleksandr s. noskov boreskov institute of catalysis sb ras, novosibirsk 630090, russia * corresponding author: mikluha.ia@gmail.com this paper belongs to a regular issue. abstract the main idea of the investigation was to define testing parameters with the lowest influence of internal and external diffusion on catalytic activity in hydrodesulfurization of dibenzothiophene. traditional experimental methods were used to determine the conditions for the influence of internal and external diffusion. simultaneous change of a linear feedstock rate and a catalyst loading at constant weight hour space velocity were used to determine the process temperature (240–260 °c) at which the impact of external diffusion is minimal. catalytic tests, including the variation of the catalyst fraction size, were carried out to define the conditions with the lowest influence of internal diffusion. it was found that when the catalyst with the fraction size of 0.1–0.25 mm was used, the fluctuation of sulfur conversion was the smallest. besides, to validate experimental results, the calculations were performed with mass balance equations and expressions used for hds modeling. the resulting data and catalytic experiments demonstrated that the lowest influence of internal and external diffusion is achieved at a temperature process less than 260 °c and a catalyst fraction of 0.1–0.25 mm. keywords diffusion limitation kinetic region hydrodesulfurization dibenzothiophene como hds catalysts received: 15.03.23 revised: 12.04.23 accepted: 15.04.23 available online: 24.04.23 key findings ● testing conditions were consistent with the requirements of the ideal plug flow. ● conditions with the lowest influence of internal and external diffusion were defined. ● experimental results are in good agreement with the calculations. © 2023, the authors. this article is published in open access under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). 1. introduction typical hydrotreating catalysts of diesel fraction are como/al2o3 catalysts with trilobe or quadrilobe granular shape [1–5]. nowadays, most of the solutions for improving the hydrotreating catalysts are aimed at tuning active component properties, namely, at the selective formation of the active phase [6–9]. to directly estimate the effect of changes in properties of the active component on catalytic activity, catalytic tests should exclude most of the process interference parameters. when the liquid feedstock contacts with a solid catalyst during hydrotreating, the following processes occur in the reactor: mass transferring of reagents from the liquid volume to the external surface of a catalyst granule (external diffusion), and diffusion of reagents from external catalyst surface into pores and then to active sites that carry out the reaction (internal diffusion). internal diffusion has the greatest influence on hydrotreating reactions, since these reactions proceed over solid catalysts via contact of feedstock molecules and active sites in pores of a catalyst [10, 11]. it is obvious that the influence of diffusion limitations greatly depends on textural properties of a catalyst, size of granules, reaction conditions and feedstock. so, it is necessary to carry out catalytic tests with low influence of internal and external diffusion on catalytic activity for reliable evaluation of the impact of active component properties on catalytic activity. there is a good theoretical background [10–13] for describing approaches for testing heterogeneous catalysts in http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2023.10.2.08 mailto:mikluha.ia@gmail.com http://creativecommons.org/licenses/by/4.0/ https://orcid.org/0000-0002-5005-0781 https://orcid.org/0000-0002-8336-1797 https://orcid.org/0000-0001-6401-0011 https://orcid.org/0000-0002-8089-2357 https://orcid.org/0000-0002-7038-2070 https://crossmark.crossref.org/dialog/?doi=https://doi.org/10.15826/chimtech.2023.10.2.08&domain=pdf&date_stamp=2023-04-24 https://journals.urfu.ru/index.php/chimtech/rt/suppfiles/6670/0 chimica techno acta 2023, vol. 10(2), no. 202310208 article 2 of 9 doi: 10.15826/chimtech.2023.10.2.08 a flow tube reactor to determine the influence of diffusion limitations on catalyst activity. catalytic experiments, including proportional changes of a linear feedstock velocity and volume of a catalyst at constant liquid hour space velocity (lhsv), are usually carried out. the influence of external diffusion is considered to be minimal, when the variation of a linear feedstock velocity and catalyst volume does not cause a change in the conversion of the addressed reagent. the influence of diffusion can be indirectly estimated by calculating liquid–solid mass transfer coefficient (ks, cm s–1) [11, 14]. when the impact of internal diffusion is the lowest, ks can be determined by mass balance equations of liquid and solid phases. these equations include effective diffusivity and the mass transfer coefficient. the higher ks, the greater impact of external diffusion [14, 15]. after that, catalytic tests are performed to define the influence of internal diffusion on catalytic activity. the tests include the decrease of catalyst’s granular size and activity measurements. when the reduction in granular size does not affect the conversion, the influence of internal diffusion is minimal. [12]. the indirect characteristic used for defining the internal diffusion impact is the catalyst effectiveness factor (ƞ) [11, 14]. when the effectiveness factor is much less than 1, there is an influence of internal diffusion. for example, the effectiveness factor for hydrotreating catalysts with trilobe shape is about 0.3–0.8 for processing model sulfur-containing molecules [14]. when catalysts are tested in hydrotreatment of the real feedstock, the effectiveness factor is usually less than 0.6 [16]. the effectiveness factor should be close to 1 to conduct a correct investigation in the development of hydrotreating catalysts, for example, for the determination of the reaction rate constant, activation energy, etc. this report presents the testing conditions for como/al2o3 hydrotreating catalysts in hydrodesulfurization (hds) of dibenzothiophene (dbt) at the lowest influence of internal and external diffusion. catalytic experiments were carried out in conditions of ideal plug flow. therefore, the obtained results can be used by the researchers working in the field of hydrotreating catalysts and can be adapted to their catalysts test conditions. the mass transfer coefficient and the effectiveness factor of the catalyst were defined using the results of catalytic experiments. they were calculated using the mass balance equations and mathematical expressions. these parameters were calculated with known mathematical expressions previously used in hds modeling [2, 17–27]. 2. experimental 2.1. catalyst preparation and characterization the como/al2o3 catalyst has been prepared by the following procedure. to prepare impregnating solution, the reagents were sequentially added into the water under stirring in the following order: cobalt hydroxide (baltic enterprise, ltd., russia, pure), molybdenum oxide (alfa aesar, usa, pure) and phosphoric acid (ojsc “tk spectr-khim”, russia, 98%). the reagents were dissolved at 70 °c. after complete dissolution of the reagents, the obtained solution was used for vacuum impregnation of γ-al2o3 support (produced by ooo «npk «synthesis», russia). then, the catalyst was dried at 120 °с during 4 h in air flow. investigation of the catalyst by nitrogen adsorption-desorption was made according to the procedure described in [28]. the catalyst was calcined at 550 °c before analysis. high-resolution transmission electron microscopy (hrtem) and x-ray photoelectron spectroscopy (xps) studies were performed for the catalyst sulfided in h2s flow. the description of the sulfidation procedure is given in [28, 29]. 2.2. catalytic experiment the como/al2o3 hydrotreating catalyst was used to define the testing conditions with the lowest influence of internal and external diffusion. preparation of the catalyst for testing. before testing, the catalyst fraction (dc1 = 0.1–0.25 mm, dc2 = 0.25–0.5 mm and dc3 = 0.5–1.0 mm) was sulfided in a flow-through quartz reactor in h2s flow at atmospheric pressure and a temperature of 220 °c for 2 h and 400 °c for 2 h. the catalyst’s fraction was cooled in helium flow. reactor description. testing of catalysts was carried out in the fixed-bed flow microreactor in all cases. the reactor had the following characteristics: the diameter (dr) – 8 mm, the bed length (lb) – 40 mm, dr/dc1 = 80–32, dr/dc2 = 32–16 and dr/dc3 = 16–8, lb/dc1 = 400–160, lb/dc2 = 160–80 and lb/dc3 = 80–40. to decrease the temperature gradient and to improve hydrodynamics of the reactor in the catalyst’s bed, the sulfide catalyst fraction was uniformly mixed with silicon carbide (the fraction of sic is 0.1–0.25 mm). total volume of the mixture of sic and the catalyst was 4 ml in all cases. it should be noted that conditions of catalytic experiments complied with the ideal plug flow regime: dr/dc>10 and lb/dc>50 [13]. model feed description. the mixture of dbt and undecane was used as the model feedstock. dbt was used as a sulfur-containing compound. dbt content was 14500 ppm (sulfur content is 2500 ppm). undecane (ρ = 0.74 g/cm3) was used as a solvent. reaction conditions. the influence of external diffusion was considered to be minimal, when the conversion of the reacting component does not change at variation of a linear feedstock velocity and a catalyst volume and constant lhsv during catalytic tests [12]. in our case, the catalyst fraction loaded to the reactor was less than 1 g, and it was difficult to correctly measure the volume. therefore, the present catalytic experiments include variation of a linear feedstock velocity (ϑfeed) and catalyst loading (mс) along with the constant weight hour space velocity (whsv, h–1) (ϑfeed·ρfeed/mc). the experiments were performed using the catalyst fraction of 0.1–0.25 mm. the catalyst loadings mс = 0.5 g, 0.4 g and 0.3 g, and the linear feedstock velocities ϑfeed = 54.0 ml h–1, 43.2 ml h–1 and 32.4 ml h–1 were chosen, https://doi.org/10.15826/chimtech.2023.10.2.08 https://doi.org/10.15826/chimtech.2023.10.2.08 chimica techno acta 2023, vol. 10(2), no. 202310208 article 3 of 9 doi: 10.15826/chimtech.2023.10.2.08 while whsv was 80 h–1. the testing conditions were as follows: p = 4 mpa, h2/feedstock ratio = 300 nm3/m3, t = 240 °c, 260 °c and 280 °c. the additional experiment was performed to check the influence of internal diffusion limitations. the catalyst fraction (mс = 0.4 g) with the particle sizes of 0.1–0.25 mm, which was chosen after previous experiments, was used. the following conditions were used: p = 4 mpa, h2/feedstock ratio = 300 nm3/m3, whsv = 80 h–1, t = 225–280 °c. the results of the experiment were used to construct a plot of the ln(k) vs 1000/t dependence. the rate constants of hydrodesulfurization of dibenzothiophene were determined based on the assumption of the pseudo-first order of reaction; equation (1) was used for calculation [3]. this plot allows calculating the activation energy (ea) with the arrhenius equation (2): 𝑘 = −𝐹(𝐷𝐵𝑇) 𝑊 · ln (1 − xdbt 100 ), (1) where k – rate constant, mol/(g·h), f(dbt) – molar flow rate of the feedstock, mol/h, w – catalyst loadings, g, xdbt – conversion of dbt, %. k = k0·exp(–ea/rt). (2) one of the methods of defining the influence of internal diffusion on catalytic activity consists in carrying out a set of experiments with different size of granules/fraction particles of a catalyst [10, 11, 13]. to determine effect of internal diffusion in hds of dbt, the experiments were performed. the sizes of the catalyst fraction were dc1 = 0.1– 0.25 mm, dc2 = 0.25–0.5 mm and dc3 = 0.5–1.0 mm. the testing conditions were as follows: p = 4 mpa, t1 = 240 °с, t2 = 260 °с, ratio h2/feedstock = 300 nm3/m3, whsv = 80 h–1. the catalyst loadings mс = 0.5 g was chosen. in all cases, the time to achieve steady-state of the catalyst was about 12 h. then, 4 liquid reaction products were sampled at each process temperature. the liquid samples were analyzed using te instruments xplorer for the determination of the residual sulfur content. liquid products were analyzed on a perkinelmer gas chromatograph clarus 580 to defined residual dbt content. the resulting dbt content was similar for the samples obtained at one temperature regime (the inaccuracy of the method is 5%) that indicates the absence of catalysts deactivation during the catalytic tests. the conversion of dbt (xdbt) was used as a characteristic of catalytic activity. xdbt was calculated according to equation (3): 𝑋dbt = 𝐶dbt0 − 𝐶dbt 𝐶dbt0 · 100, (3) where cdbt0 is the initial dbt content in the model mixture and cdbt is the content of dbt in the hydrotreated product. 2.3. the estimation of the hdt reactor parameters to make the qualitative estimations of the hdt reactor parameters, one must consider the phenomena that can change the reactor performance. some effects such as axial mass dispersion, catalyst wetting, and wall flow have a macroscopic effect on the mass and heat transfer. thereby their effect must be analyzed to determine whether they should be considered or not in mass balance equations and mathematical expressions [31]. 1. isothermal operation. the temperature of the experimental reactor was controlled within ±1 °c during the collection of the experimental data. for this reason, the reactor was considered isothermal (only the mass balance was taken into account in the calculations. 2. ideal plug behavior. it was determined by chen criterion (2) [31] that the experimental setup does not present plug-flow deviation, since the ratio of catalytic bed length to particle diameter is high enough to avoid back mixing effects. the right-hand side in expression of inequality (4) was 87 , and the lefthand side – 69 (87>69). 𝐿b 𝑑e > √20𝑛 boa.m 𝑓 ln ( 1 1 − 𝑋 100⁄ ) , (4) where lb – reactor-bed length, cm, de – equivalent size of a catalyst particle, cm, bofa.m – axial mass bodenstein number for f phase, n – order of reaction. 3. incomplete wetting. complete irrigation of the catalytic bed was ensured by gierman and harmsen criterion (w, equation (5)), since the wetting number equal to 2·10–1 was obtained. 𝑊 = µl ρl𝑑e 2𝑔 > 5 · 10−6 (5) where μl – viscosity of the liquid phase, mpa s, ρl – liquid density at process conditions, lb ft–3, g – gravitational constant, cm s–2 4. wall flow effect. the experimental reactor presents the ratio of the reactor diameter to equivalent diameter of particles equal to 64. it meets the sie criterion ( 𝐷𝑅 𝑑𝑒 , equation (6)) [31], decreasing the hydrodynamic problems associated with liquid distribution and wall flow. 𝐷r 𝑑e > 25. (6) 3. description of the mathematical calculations 3.1. characteristics of the catalyst bed and physical properties of the feed no effect of internal and external diffusion was confirmed through dependences of estimated hds parameters (𝑘s and η) for some of the conditions presented in the work. estimations below were obtained from isothermal small reactor (in this study, dr = 8 mm) [2, 15, 24, 25, 32, 33]. https://doi.org/10.15826/chimtech.2023.10.2.08 https://doi.org/10.15826/chimtech.2023.10.2.08 chimica techno acta 2023, vol. 10(2), no. 202310208 article 4 of 9 doi: 10.15826/chimtech.2023.10.2.08 mathematical calculations in these works are based on kinetic experimental data, characteristics of the catalyst bed, mass balance equations and other proven chemical engineering expressions. a set of assumptions is assumed in calculating the estimations. the hds reactor is considered isothermal and steady state operated. catalyst deactivation was thought to be insignificant. the reaction is assumed to occur only in the porous solid catalyst, which is uniformly wetted by the liquid. gas and liquid velocities are constant across the reactor. gas–liquid mass transfer was neglected. the particle diameter of the catalyst was taken as the equivalent diameter of the sphere with the same volume and surface area as those of our catalyst. the diffusion effects for different conditions can be estimated from the values of the sulfur content in the product and the catalyst effectiveness factor. therefore, below are the equations for simulation of an isothermal hds reactor that include the conditions for testing and the other ones. the bed porosities (εb) of the catalyst were calculated from the weights of loadings, particles densities and the height of bed in the graduated cylinder (inner diameter 8 mm) [34]. the expressions (7)–(9) can be used to calculate the physical properties of oil and gas at process conditions. the oil density (ρl) as a function of temperature and pressure can be estimated by the standing–katz equation as published in [25, 35]: ρl = ρ0 + ∆ρp − ∆ρt, (7) ∆ρp = [0.167 + 16.181 ∙ 10 −0.0425ρ0 ] ∙ [ 𝑃 1000 ] − 0.01 ∙ ∙ [0.299 + 263 ∙ 10−0.0603ρ0 ] ∙ [ 𝑃 1000 ] 2 , (8) ∆ρt = [0.0133 + 152.4 ∙ (ρ0 + ∆ρp) −2.45] ∙ (𝑇r − 520) − −[8.1 ∙ 10−6 − 0.0622 ∙ 10−0.764(ρ0+∆ρp)] ∙ (𝑇r − 520) 2, (9) where ρ0 – density of oil at 15.6 °c and 101.3 kpa, lb ft–3, δρp – pressure dependence of liquid density, lb ft–3, δρt – temperature correction of liquid density, lb ft–3, 𝑃 – the pressure, 𝑇r is the temperature, °r. glaso’s equation, as presented in [18, 19, 35], was used as a generalized mathematical equation for oil viscosity. equations (10)–(12) are the following: μl = 3.141 ∙ 10 10(𝑇 − 460)−3.444[log10(api)] 𝑎 , (10) 𝑎 = 10.313[log10(𝑇 − 460)] − 36.447, (11) api = 141.5 d15.6 − 131.5, (12) where a – dimensionless number, api – american petroleum institute, t is the temperature (°c), 𝑑15.6 is the specific gravity of oil at 15.6 °c. strictly speaking, equations (7)–(12) for calculating liquid characteristics are valid for petroleum distillates, especially for the ones containing dbt. considering all arguments, the given expressions were used for calculating properties of liquid phase. it should be emphasized that these calculations are approximate. 3.2. mass balance equations hds of oil fractions can be considered as a bimolecular irreversible reaction between the oil (a) and hydrogen (b) reactants [25, 36]: νaa + νbb → νpprod, (13) where νa,νb,νp are stoichiometric coefficients of a, b and product, respectively. this simplified equation of the reaction is assumed to be valid for the case presented with dbt. mass balance equations for the liquid and solid phases are given below. equation for the liquid phase (14): ul d𝐶sull d𝑧 + 𝑘s𝑎𝑡 (𝐶sull − 𝐶suls) = 0 (14) where 𝑘s – the liquid–solid mass transfer coefficient, ul – the superficial velocity of the liquid in the reactor, cm s–1, at – surface area of the particles per unit volume of the bed, cm–1, 𝐶sull – concentration of sulfur compound in the liquid phase, mol cm–3, 𝐶suls – molar liquid phase of sulfur inside the solid, mol cm–3, z – coordinate of reactor bed length. equation for the solid phase (15): 𝑘s𝑎t(𝐶sull − 𝐶suls) νa + (εb − 1)ρpη𝑘𝐶suls 𝑛 = 0, (15) where η is the effectiveness factor, εb – void fraction of the catalyst bed, k – reaction rate coefficient. the value n = 1 was used in the presented work. according to the literature data [3], hds of dbt follows pseudo first reaction order. hds kinetic constant (k) was estimated only by the original approaches described in [18, 37–39]. the procedure of estimation of the kinetic parameters (k0 and ea) is presented in supplementary materials. the inhibiting effect of h2s was not taken into account, since its concentration is not high enough. therefore, the influence of h2s on the hds reaction rate is not significant. since the catalyst particles had a complex shape, the equivalent diameter of the catalyst particle was used to calculate the parameters below. an equivalent size 𝑑e of a catalyst particle can be calculated as (16): 𝑑e = 2𝑉p 𝑆p , (16) where 𝑉p – volume of the catalyst particle, cm 3, 𝑆p – area of the catalyst particle, cm2. the surface area (𝑎t) of the particles per unit volume of the bed was calculated by equation (17): 𝑎t = 6(1 − εb) 𝑑e , (17) the molecular diffusivity of sulfur in the liquid (dlsul, cm2 s–1) is calculated by equation (18) [40]: https://doi.org/10.15826/chimtech.2023.10.2.08 https://doi.org/10.15826/chimtech.2023.10.2.08 chimica techno acta 2023, vol. 10(2), no. 202310208 article 5 of 9 doi: 10.15826/chimtech.2023.10.2.08 𝐷sul 𝐿 = 8.93 ∙ 10−8 νl 0.267𝑇 νsul 0.433μl , (18) where νland νsul are molar volume of solute and liquid solvent, respectively, which are estimated with the following equations (19)–(20) [18]: νi = 0.285(νci 𝑚 )1.048 (19) νc m = 7.5214 ∙ 10−3 𝑇meabp 0.2896 𝑑15.6 −0.7666 (20) where νi – molar volume, cm3 mol–1, νmc – critical specific volume, ft3 mol–1, νmci – critical specific volume of the liquid or gas, ft3 mol–1, 𝑇meabp – the mean average boiling point (°r). internal diffusion limitations are usually expressed in terms of the catalyst effectiveness factor [41]. the effectiveness factor reported in [42, 43] has to be in the range of 0.0057–1. because the particle size of the catalyst is small, the effectiveness factor can be estimated as function of thiele modulus (ϕ) [16, 44]. for the different catalyst shapes (sphere, cylinder, 2-lobe, 4-lobe, etc.), the effectiveness factor can be calculated using expressions which has been proposed for other authors [42, 45, 46]. the generalized modulus (ϕsul) for nth-order irreversible reaction is calculated according to (21) [44]. effective diffusivity of sulfur in the pores of the catalyst (desul, cm 2 s–1) was determined with the equation (20) [44]. ϕsul = 𝑉p 𝑆p [( 𝑛 + 1 2 ) ( 𝑘сsuls 𝑛−1 ρp desul )] 0.5 , (21) desul = θ τ ( 1 1 𝐷sul l⁄ + 1 𝐷k ⁄ ), (22) where ρp – catalyst particle density, g cm–3, θ – particle porosity, τ – tortuosity factor, dk – knudsen diffusivity, cm2 s–1. the tortuosity factor (τ) generally has a value of 2–7 [41]. usually, tortuosity factor is assumed to be 4 [16, 25, 41]. knudsen diffusivity factor (𝐷k) is evaluated as follows (23)–(25) [44, 47]: 𝐷k = 9700rg( 𝑇 𝑀w )0.5, (23) 𝑟g = 2θ 𝑆gρp , (24) θ = ρp𝑉g, (25) where 𝑀w – the molecular weight, 𝑟g – the pore radius, cm, 𝑆g – specific surface area of a catalyst particle, cm 2 g–1, 𝑉g – pore volume per unit mass of catalyst, cm 3 g–1. in present report, the following equation is employed for determining the values of η (26) [40, 44, 45]: η = 3(ϕsulcoth(ϕsul) − 1) ϕsul 2 . (26) since the shape of the catalyst fractions mostly resembles a spherical shape, we used the effectiveness factor formula for spherical particles in the present calculation. 4. results and discussion 4.1. description of the catalyst according to atomic emission spectroscopy data, the como/al2o3 catalyst used for catalytic tests contains 12.4 wt.% mo, 2.7 wt.% co and 1.4 wt.% p. the industrial γal2o3 (produced by “npk “syntez”) was used as the support. textural characteristics of the support and the catalyst are given in table 1. the support has the specific surface area of 223 m2/g, the pore volume of 0.5 cm3/g and the average pore diameter of 9 nm. according to the classification described in [48], the shape of nitrogen adsorption-desorption isotherm of the support corresponds to iv(a) type, while the type of hysteresis loop relates to h2(a) (figure s2). such characteristics are typical for mesoporous materials with cylindrical shape of pores [48]. the shapes of nitrogen adsorption-desorption isotherm and hysteresis loop of the catalyst are the same as those of the support, confirming that no plugging of significant pore volume by active metals during impregnation occurs. pore size distribution curves of the catalyst and the support have similar shape, also indicating no plugging of the pores in the catalyst (figure s2). after supporting of active metals, the specific surface area of the catalyst decreased to 147 m2/g, while pore volume and average pore diameter were similar to those of the support (table 1). the catalyst sulfided in h2s flow was studied by x-ray photoelectron spectroscopy (xps) method. the resulting mo3d and co2p xps spectra were deconvoluted into several mo and co states (figure 1). it was established that active metals are preferentially presented in the catalysts in the sulfur surrounding (more than 55%). the portion of mo in the 4+ state (mo in the mos2 composition [49]) is about 72%. the rest of molybdenum is associated to 5+ (13%) and 6+ (13%) which is characteristic of mo in oxysulfide and oxide states [49]. the fraction of cobalt in the composition of comos phase [50] is about 58%. cobalt in the catalyst is also present in the composition of individual sulfide – coxsy (12%) and co2+ (29%) [49]. the obtained values of the comos phase content in the catalyst are typical for highly active como/al2o3 catalysts [51]. table 1 textural characteristics of γ-al2o3 support and como/al2o3 catalyst. parameter specific surface area, m2/g pore volume, cm3/g average pore diameter, nm average slab length, nm stacking number al2o3 223 0.5 9 – – como/al2o3 147 0.4 10 3.7 2.2 https://doi.org/10.15826/chimtech.2023.10.2.08 https://doi.org/10.15826/chimtech.2023.10.2.08 chimica techno acta 2023, vol. 10(2), no. 202310208 article 6 of 9 doi: 10.15826/chimtech.2023.10.2.08 the sulfide catalyst was also studied by hrtem method. the examples of hrtem images are given in figure s3. the average slab length and stacking number of active component particles, which were calculated by analysing of several images with more than 500 particles, are 3.7 nm and 2.2, respectively (table 1). the resulting values are typical of como/al2o3 hydrotreating catalysts [51]. 4.2. experimental data on the effect of external and internal diffusion the data obtained in the hds experiments to determine the impact of external diffusion are given in table 2. the conditions of catalytic experiments are described in section 2. these experiments allowed us to determine the temperature, at which the dbt conversion or residual sulfur content remained unchanged while the linear feedstock velocity and the catalyst’s loading changed simultaneously at constant whsv. the residual sulfur content and dbt conversion are similar at 240 °c and at 260 °c for ϑfeed = 54.0 and 43.2 ml h–1 and mc = 0.5 g and 0.4 g, respectively (table 2). dbt conversion is changing in the range of 59–69% at 280 °c. the residual sulfur content at the highest process temperature (280 °c) varies significantly for all catalyst loadings. the greatest difference in residual sulfur content at 280 °c is 252 ppm (table 2). so, we cannot draw an unequivocal conclusion about the effect of external diffusion at 280 °c from the data obtained. however, we can conclude that the influence of external diffusion is the lowest at 240 °c and at 260 °c (ϑfeed = 54.0 and 43.2 ml h–1). the next step was to define conditions when the impact of internal diffusion was the smallest. the hydrotreating process was carried out at 240 °c and 260 °c. these temperatures were chosen because of the earlier established minimal influence of external diffusion. table 3 shows the data of the hds experiments to determine the impact of internal diffusion. experimental conditions are given in section 2. it was found that the influence of internal diffusion is more pronounced for the catalyst fractions 0.25–0.5 mm and 0.5–1.0 mm for both temperatures, since the dbt conversion changed in these cases. thus, to decrease the contribution of internal diffusion, it is preferable to use the catalyst fraction of 0.1–0.25 mm. also, we calculated the value of ea from the plot of ln(k) from 1000/t. we used this approach for additional confirmation. for the catalytic experiment, we used the catalyst fraction of 0.1–0.25 mm, according to the results given above (table 3). the testing temperature varied from 225 to 280 °c. detailed experimental conditions are given in section 2. the plot is shown in figure 2. the ea value was 128.0 kj/mol. this value is close to that given in [52] for the kinetic region of reaction. so, we can conclude that diffusion influence is minimal in this region. these results partially agree with the results obtained for 240 and 260 °c (table 2). figure 1 mo3d and co2p xps spectra. table 3 dbt conversion for catalyst fractions 0.1–0.25 mm, 0.25–0.5 mm and 0.5–1.0 mm at 240 °c and 260 °c. catalyst fraction, mm 0.1–0.25 0.25–0.5 0.5–1.0 temperature process, °c xdbt, % 240 11 10 7 260 37 35 27 table 2 influence of temperature on the residual sulfur content and dbt conversion for the catalyst fraction 0.1–0.25 mm. mc, g ϑfeed, ml h–1 temperature process, °c 240 260 280 residual s content, ppm* dbt conversion, %** residual s content, ppm* dbt conversion, %** residual s content, ppm* dbt conversion, %** 0.5 54.0 2224 11 1745 30 923 63 0.4 43.2 2225 11 1751 30 773 69 0.3 32.4 2251 10 1850 26 1025 59 *inaccuracy of the method for determination of residual sulfur content on te instruments xplorer is 5%. ** according to perkinelmer gas chromatograph clarus 580 analysis. https://doi.org/10.15826/chimtech.2023.10.2.08 https://doi.org/10.15826/chimtech.2023.10.2.08 chimica techno acta 2023, vol. 10(2), no. 202310208 article 7 of 9 doi: 10.15826/chimtech.2023.10.2.08 figure 2 arrhenius plots of hds of dbt. it can be concluded that to minimize the effects of internal and external diffusion it is necessary to test the como/al2o3 catalyst in hds of dbt at a temperature less than 260 °c using the catalyst fraction 0.1–0.25 mm. 4.3. calculated data related to the impact of external and of internal diffusion indirect influence of the external diffusion can be estimated by the mass transfer coefficient ks. it should be noted that calculation of this coefficient does not allow us to define the effect of external diffusion. however, effective diffusion in equation (3.16) is used in mass balance equations (3.8) and (3.9). therefore, it is possible to find the dependence of mass balance coefficient from external diffusion at the negligible effect of internal diffusion. in the present report, small catalyst fractions (0.1–0.25 and 0.25–0.5 mm) were used. therefore, the generally accepted equations for calculating ks cannot be applied [32]. in addition, well-known expressions for ks cannot be used because some of the parameters, such as phase velocities, do not satisfy the range of acceptable values. therefore, we used experimental data given in tables 2 and 3 in the calculations (3.8–3.9). the data in table 4 shows that the ks value for the catalyst fraction 0.1–0.25 mm is lower than that for the catalyst fraction 0.25–0.5 mm at all temperatures. so, the effect of external diffusion will be greater for the larger catalyst (0.25–0.5 mm). the lowest ks value was obtained at 240 °c. given the above, the 0.1–0.25 mm catalyst fraction will be less affected by external diffusion at 240 °c. then, the effectiveness factor η will be proportional to the impact of internal diffusion because it relates to the ratio of the diffusion reaction rate to the total reaction rate. therefore, the lower η, the greater the influence of internal diffusion. it allows us to calculate the η value from the equation (3.20). the data in table 5 demonstrate the effect of the particle size on the effectiveness factor. it should be noted that the value of the effectiveness factor is much closer to 1 for the catalyst fraction 0.1–0.25 mm. in addition, the performed calculations are used in present work to confirm the behavior of diffusion effects in hds experiments. the hydrogen flow is in large excess at the reactor inlet in present experimental conditions. because of the hydrogen-rich atmosphere, the residence time distribution of the gas phase is negligible. therefore, only the liquid phase hydrodynamic aspects and the mass transport phenomena were analyzed in this report. the results of the calculations confirm the impact of internal diffusion. the effectiveness factor for the lowest catalyst fraction 0.1–0.25 mm (table 5) is lower than that for the catalyst fraction 0.25–0.5 mm. thus, it follows from the observed correlation of the experimental and the calculation data that the influence of internal diffusion is greater, when a larger catalyst fraction was used. 5. limitations during the improvement and research of hydrotreating catalysts, it is desirable to test catalysts under conditions under which the influence of internal and external diffusion on catalyst activity is minimal. in this case it is possible to establish more reliable correlations between properties of active component particles and catalyst activity. the purpose of this study is to determine such test conditions for hydrotreating catalysts in plug flow regime, under which the influence of internal and external diffusion is minimal. table 5 effectiveness factor for catalyst fractions 0.1–0.25 mm and 0.25–0.5 mm under different temperature process. catalyst fraction, mm 0.1–0.25 0.25–0.5 temperature process, °c ƞ 240 0.9423 0.8933 260 0.9476 0.9025 280 0.9523 0.9106 table 4 mass transfer coefficient factor for catalyst fractions 0.1–0.25 mm and 0.25–0.5 mm under different temperature process. mc, g ϑfeed, ml h–1 temperature process, °c 240 260 280 catalyst fraction, mmd 0.1–0.25 0.25–0.5 0.1–0.25 0.25–0.5 0.1–0.25 0.25–0.5 𝒌𝐬 ∙ 𝟏𝟎 −𝟐, cm s–1 0.5 54.0 0.7329 1.4215 0.8530 1.6743 0.9820 1.9475 0.4 43.2 0.9113 1.7690 1.0605 2.0822 1.2553 2.4910 0.3 32.4 1.1997 2.3258 1.3853 2.7165 1.6078 3.1839 https://doi.org/10.15826/chimtech.2023.10.2.08 https://doi.org/10.15826/chimtech.2023.10.2.08 chimica techno acta 2023, vol. 10(2), no. 202310208 article 8 of 9 doi: 10.15826/chimtech.2023.10.2.08 6. conclusions the conditions for carrying out catalytic tests of the fraction of como/al2o3 hydrotreating catalyst in the fixed-bed flow microreactor were established. the chosen testing conditions complied with the requirements of ideal plug flow. simultaneous variation of a linear feedstock velocity (54.0 ml h–1, 43.2 ml h–1 and 32.4 ml h–1) and a catalyst weight (0.5 g, 0.4 g and 0.3 g) at constant whsv (80 h–1) showed that the influence of external diffusion was the lowest at 240–260 °c. the testing of catalysts fractions with the sizes of 0.1–0.25 mm, 0.25–0.5 mm and 0.5–1.0 mm at 240°с and at 260°с allowed us to establish that the influence of internal diffusion was minimal for the catalyst fraction of 0.1–0.25 mm. when the catalyst fraction size increased to 0.25–0.5 mm and 0.5–1.0 mm, the effect of the mass transfer of feedstock molecules in catalysts pores to active sites on catalytic activity was observed. the obtained results are in good agreement with the mass transfer coefficient and the effectiveness factor, which were calculated by the mass balance equations and mathematical expressions adapted to the size of the catalyst fraction. ● supplementary materials this manuscript contains supplementary materials, which are available on the corresponding online page. ● funding this work was carried out within the framework of the budget projects of ministry of education and science of russian federation aaaa-a21-121011390010-7 and аааа-а21121011890074-4 for boreskov institute of catalysis. ● acknowledgments none. ● author contributions conceptualization: y.v.v., p.p.m., i.a.m. data curation: y.v.v., p.p.m., k.a.n. formal analysis: p.p.m., i.a.m., o.p.k. funding acquisition: o.v.k., a.s.n. investigation: p.p.m., y.v.v., i.a.m., o.p.k. methodology: p.p.m., i.a.m., o.p.k. project administration: o.v.k., a.s.n. supervision: k.a.n., o.v.k., a.s.n. validation: m.o.k, o.v.k., a.s.n. visualization: p.p.m., y.v.v., i.a.m. writing – original draft: p.p.m., y.v.v., i.a.m. writing – review & editing: p.p.m., y.v.v., i.a.m., k.a.n. ● conflict of interest the authors declare no conflict of interest. ● additional information author ids: polina p. mukhacheva, scopus id 57226795240; yuliya v. vatutina, scopus id 57189731746; ivan a. mik, scopus id 55375424900; ksenia a. nadeina, scopus id 57218590135; maksim o. kazakov, scopus id 23485283300; oleg p. klenov, scopus id 6506012360; oleg v. klimov, scopus id 7003783535; aleksandr s. noskov, scopus id 7005685096. website: boreskov institute of catalysis sb ras, https://catalysis.ru. references 1. wang te, yang f, song m, han d. recent advances in the unsupported catalysts for the hydrodesulfurization of fuel. fuel proc technol.2022:235. 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https://doi.org/10.1021/ie00042a024 https://doi.org/10.1016/s0920-5861(98)00152-7 https://doi.org/10.1515/pac-2014-1117 https://doi.org/10.1016/s0257-8972(96)03186-6 https://doi.org/10.1002/sia.2249 https://doi.org/10.1016/j.cattod.2019.01.005 https://doi.org/10.1016/0021-9517(81)90303-1 7 е. а. иванова, т. в. глухарева, ю. ю. моржерин уральский федеральный университет, 620002, ул. мира, 19, екатеринбург. e-mail: kate1809@mail.ru синтез и алкилирование п-тетракисхлоркаликс[4]аренов работа посвящена разработке технологии хлорирования каликсаренов и отработке методик их получения, для исследования биологической активности полученных соединений. были разработаны удобные новые, неописанные в литературе способы получения хлорзамещенных каликсаренов с использованием хлористого сульфурила и гипохлорита натрия. при использовании в качестве исходного вещества детретбутилированного каликс[4] арена, замещенного по нижнему ободу остатками хлоруксусной кислоты или эфира, было показано, что образуется неразделимая смесь продуктов. в отличие от замещенных каликсаренов, неалкилированный по нижнему ободу каликсарен хлорируется с хорошим выходом (до 95 %) с образованием тетракисхлоркаликсарена. при использовании в качестве хлорирующего реагента гипохлорита натрия протекает также омыление сложноэфирных групп под действием гидроксида натрия, выделяющегося в ходе реакции, и реакция хлорирования приводит к образованию хлорированной тетракислоты. у д к 6 61 .7 41 +6 61 .7 23 -1 3 © иванова е. а., глухарева т. в., моржерин ю. ю., 2014 введение пара-галогензамещенные каликсарены – перспективные синтоны [1–3] для функционализации: по верхнему ободу в реакциях соногашира, сузуки, хека, негиши. в основном в литературе описаны методы йодирования [3] и бромирования [1] каликсаренов в пара-положение бензольного кольца. при этом реакции протекают длительное время и требуют достаточно дорогих реагентов или катализаторов. гораздо меньше описаны в литературе пара-хлорпроизводные каликсарена, в основном их получают многостадийным синтезом из хлорфенола. имеются только два примера хлорирования [4, 5] непосредственно самого каликсарена хлорсукцинимидом или соляной кислотой, но эти реакции проходят с низким выходом. 8 е. а. иванова, т. в. глухарева, ю. ю. моржеринcta | № 1 | 2014 кроме того, хлоркаликсарен, замещенный по нижнему ободу остатком уксусной кислоты, является циклическим олигомером феноксиуксусной кислоты, хлорпроизводные которой известны как гербициды и регуляторы роста растений, т. е. хлорпроизводные каликсаренов обладают потенциальной биологической активностью. целью нашей работы явилась разработка новых методов синтеза и отработка методик получения хлорзамещенных производных каликс[4]аренов для последующего исследования реакционной способности и биологической активности. результаты и обсуждение для хлорирования каликсаренов нами был применен хлористый сульфурил. однако при использовании в качестве исходного вещества детретбутилированного каликс[4]арена, замещенного по нижнему ободу остатками хлоруксусной кислоты 1 и эфира 2, было показано, что образуется неразделимая смесь продуктов. вероятно, в данном случае может протекать хлорирование в параи мета-положения фенольных колец. в отличие от соединений 1, 2, неалкилированный по нижнему ободу каликсарен 3 хлорируется с хорошим выходом (до 95 %) с образованием хлоркаликсарена 4. строение полученного соединения было подтверждено данными ямр 1h спектроскопии и масс-спектрометрии. в спектре ямр 1h (рис. 1) наблюдается синглет при 7,23 м.д., который соответствует сигналу ароматических протонов, и уширенный синглет в области 3,8 м.д., характерный для мостиковых протонов сн2 групп. в масс-спектре соотношение пиков м+2, м+4, м+6 свидетельствует о наличии четырех атомов хлора в молекуле. рис. 1. спектр ямр 1н п-хлоркаликсарена 4 в dmso-d6 интенсивность молекулярного пика в масс-спектре соединения 4: m/z, в процентах лит. данные, в процентах 560 (м) 100 100 562 (м+2) 133 131 564 (м+4) 67,5 63,9 566 (м+6) 15,5 14,0 таким образом, нами было показано, что метод хлорирования хлористым сульфурилом непригоден для получе9 2014 | № 1 | ctaсинтез и алкилирование п-тетракисхлоркаликс[4]аренов ния хлорпроизводных каликсаренов, алкилированных по нижнему ободу остатками уксусной кислоты или ее эфира. однако реакция с незамещенным каликсареном протекает в легких условиях и с хорошим выходом. поэтому нами были исследованы реакции модификации пара-хлоркаликсарена 4 по нижнему ободу. при проведении алкилирования этилхлорацетатом с использованием в качестве темплата и основания карбоната натрия было неожиданно обнаружено, что данная реакция приводит к образованию неразделимой смеси конформеров 5 (конформация конус) и 6 (конформация частичный конус), что было установлено на основании спектра ямр 1h. в спектре ямр 1н наблюдали несколько групп сигналов в областях ароматических, мостиковых и протонов заместителей по нижнему ободу, что доказывает наличие изомерных структур. если сигналы протонов каликсарена в конформации конус для всех четырех фенольных колец являются одинаковыми, то для конформации частичный конус наблюдается три набора сигналов. например, в области ароматических протонов присутствует двухпротонные синглет при 7,53 м.д., синглет при 7,07 м.д. и четырехпротонный дублет при 7,13 м.д. соответственное разделение можно наблюдать и на остальных участках спектра. таким образом, нами показано, что при алкилировании п-хлоркаликсарена в стандартных условиях получается смесь конформеров. по-видимому, это связано с тем, что атом хлора в параположении также может участвовать в координации с катионом натрия. в отличие от реакции с этилхлорацетатом, алкилирование йодистым бутилом в аналогичных условиях приводит к одному продукту 7. реакция идет с образованием тетразамещенного продукта в конформации конус, с хорошим выходом. строение соединения было подтверждено данными ямр 1н-спектроскопии. следующим этапом мы использовали в качестве хлорирующего агента раствор гипохлорита натрия. данную методику применили для хлорирования каликсарена 2, замещенного по нижнему ободу этилхлорацетатом. было установлено, что при 10 е. а. иванова, т. в. глухарева, ю. ю. моржеринcta | № 1 | 2014 проведении реакции протекает также омыление сложноэфирных групп под действием гидроксида натрия, выделяющегося в ходе реакции. таким образом, реакция хлорирования приводит к образованию хлорированной тетракислоты 8. на спектре ямр 1н мы наблюдали исчезновение сигналов этоксигрупп, регистрировали сигналы ароматических протонов, которые регистрируются в виде синглета, а также изменение химических сдвигов остальных сигналов, что может свидетельствовать о замещении одного ароматического протона в каждом кольце на атом хлора. кроме того, мы наблюдали появление сигнала карбоксильного протона, что подтверждает протекание реакции гидролиза. также нами было установлено, что при взаимодействии гипохлорита натрия с незамещенным каликсареном 3 получается неразделимая смесь продуктов. по-видимому, в данном случае протекает частичное замещение хлора на гидроксид анион. кроме того, следует отметить, что полученная кислота 8 является циклическим олигомером феноксиуксусной кислоты, хлорпроизводные которой известны как гербициды и регуляторы роста растений, то есть обладает потенциальной биологической активностью. экспериментальная часть спектры ямр 1h получены на спектрометре bruker (400 мгц для 1н) в cdcl3 и dmso-d6, внутренний стандарт – тмс. масс-спектры зарегистрированы на масс-спектрометре серии microtof-q ii фирмы bruker daltonics. контроль за ходом реакций и чистой синтезированных соединений осуществляли с помощью тсх на пластинках silufol uv-254 в системах хлороформ, хлористый метилен-этанол 15:1; 2:1. каликс[4]арен (3) к раствору 22,1 г (34,2 ммоль) п-трет-бутилкаликс[4]арена в 100 мл толуола добавляют 24,9 г (187 ммоль) безводного хлорида алюминия и 12,8 г (136 ммоль) фенола. реакционную массу перемешивают при комнатной температуре в течение 2 часов. затем полученную смесь подкисляют 50 мл 0,2 н соляной кислоты. затем добавляют 50 мл хлороформа и дистиллированную воду (3×100 мл). органический слой отделяют, упаривают, кристаллизуют из этанола, отфильтровывают, сушат. полученный продукт представляет собой твердое белое вещество. выход 8,88 г (61,5 %). спектр ямр 1н (dccl3, δ, м.д., кссв (j), гц): 10.20 (4h, с, 4×oh), 7.05 (8н, д, j = 7.6, 2×4arh), 6.72 (4н, т, j = 7.6, 1×м4arh), 4.26 (4h, с, 1×4arch2), 3.54 (4h, с, 1×4arch2). 25,26,27,28-тетра(этоксикар-бонилметокси)каликс[4]арен (2) к суспензии 4,15 г (9,8 ммоль) каликс[4]арена 5 в сухом ацетонитриле добавляют 8,1 г (58,5 ммоль) карбоната калия. через 15 минут, когда пузырьки газа перестают выделяться, добавляют 6,5 мл (58,5 ммоль) этил11 2014 | № 1 | ctaсинтез и алкилирование п-тетракисхлоркаликс[4]аренов хлорацетата и 9,7 г (58,5 ммоль) йодида натрия. смесь перемешивают при температуре кипения 24 часа. неорганику отфильтровывают. фильтрат упаривают. кристаллизуют из этанола, охлаждают, отфильтровывают и сушат. полученный продукт представляет собой твердое вещество светложелтого цвета. выход 4,75 г (63 %). спектр ямр 1н (dccl3, δ, м.д., кссв (j), гц): 6.64 (12н, м, 3×4arh), 4.88 (4н, д, j = 13.7, 1×4arch2) 4.73 (8н, с, 4aroch2-), 4.21 (8н, к, j = 7.1, 4-och2ch3), 3.24 (4н, д, j = 13.7, 1×4arch2), 1.29 (12н, т, j = 7.1, 4-och2ch3). 5,11,17,23-тетра(хлор)каликс[4]арен (4) к раствору 1,26 г (2,9 ммоль) каликс[4]арена 5 в сухом хлористом метилене добавляют 1,2 мл (14,8 ммоль) хлористого сульфурила. смесь перемешивают при температуре кипения 24 часа. раствор упаривают. кристаллизуют из этанола, отфильтровывают и сушат. полученный продукт представляет собой твердое вещество кремового цвета. выход 1,50 г (90 %). спектр ямр 1н (dmso-d6, δ, м.д., кссв (j), гц): 7.19 (8н, с, 2×4arh), 3,85 (8н, с, 4arch2). м/z: 560 (m, 100 %), 562 (m+2; 133 %), 564 (m+4, 67,5 %), 566 (m+6; 15,5 %). 5,11,17,23-тетра(хлор)(бутокси)каликс[4]арен (7) к суспензии 1,145 г (2,0 ммоль) хлоркаликс[4]арена 27 в сухом дмфа добавляют 0,29 г (12,2 ммоль) гидрида натрия. через 15 минут, когда пузырьки газа перестают выделяться, добавляют 1,9 мл (16,3 ммоль) йодистого бутила. смесь перемешивают при температуре кипения 24 часа. затем полученную смесь подкисляют небольшим количеством 0,5 н соляной кислоты. затем добавляют 25 мл хлороформа и дистиллированную воду (3×50 мл). органический слой отделяют, упаривают, кристаллизуют из этанола, отфильтровывают, сушат. полученный продукт представляет собой твердое белое вещество. выход 0,88 г (56 %). спектр ямр 1н (dccl3, δ, м.д., кссв (j), гц): 6.65 (8н, с, 2×4arh), 4.36 (4н, д, j = 13.5, 1×4arch2), 3.84 (8н, т, j = 2,0, 4aroch2-), 3.08 (4н, д, j = 13.5, 1×4arch2), 1.89…1.80 (8н, м, 2×4ch2 bu), 1.45…1.39 (8н, м, 2×4ch2 bu), 0.98 (12н, т, j = 7.4, 4ch3 bu). общая методика получения каликсаренов 5 и 6 к суспензии 1,01 г (1,8 ммоль) хлоркаликс[4]арена 27 в сухом ацетонитриле добавляют 1,23 г (8,9 ммоль) карбоната калия. через 15 минут, когда пузырьки газа перестают выделяться, добавляют 1,2 мл (8,9 ммоль) этилхлорацетата и 1,48 г (8,9 ммоль) йодида натрия. смесь перемешивают при температуре кипения 72 часа. неорганику отфильтровывают. фильтрат упаривают. соединения 5 и 6 разделяют дробной кристаллизацией из этанола, отфильтровывают и сушат. полученные продукты представляет собой твердые вещества светло-желтого цвета. 12 е. а. иванова, т. в. глухарева, ю. ю. моржеринcta | № 1 | 2014 5,11,17,23-тетра(хлор)(этоксикарбонил-метокси)каликс[4]арен (конус) (5) выход 0,47 г (29 %). спектр ямр 1н (dccl3, δ, м.д., кссв (j), гц): 6.68 (8н, с, 2×4arh), 4.84 (4н, д, j = 13.8, 1×4arch2) 4.66 (8н, с, 4aroch2-), 4.20 (8н, к, j = 6.4, 4-och2ch3), 3.16 (4н, д, j = 13.8, 1×4arch2), 1.28 (12н, т, j = 7.1, 4-och2ch3). 5,11,17,23-тетра(хлор)(этоксикарбонил-метокси)каликс[4]арен (частичный конус) (6) выход 1,03 г (63 %). спектр ямр 1н (dccl3, δ, м.д., кссв (j), гц): 7.53 (2н, с, 2×1arh), 7.13 (2н, д, j = 2.5, 2×1arh), 7.07 (2н, с, 2×1arh), 6.30 (2н, д, j = 2.4, 2×1arh), 4.47 (2н, д, j = 12.9, 2×1arch2), 4.44 (4н, с, 2×2aroch2-), 4.41 (2н, к, j = 7.1, 2×1och2ch3), 4.32 (4н, к, j = 7.4, 2×2och2ch3), 4.27 (2н, д, j = 15.6, 2×1arch2), 4.06 (2н, к, j = 7.2, 2×1och2ch3), 4.02 (2н, с, 2×1aroch2-), 3.87 (2н, д, j = 12.9, 2×1arch2), 3.68 (2н, с, 2×1aroch2-), 3.12 (2н, д, j = 14.2, 2×1arch2), 1.45 (3н, т, j = 7.1, 3×1-och2ch3), 1.36 (6н, т, j = 7.1, 3×2-och2ch3), 1.22 (3н, т, j = 7.1, 3×1-och2ch3). 5,11,17,23-тетра(хлор)(карбокси-метокси)каликс[4]арен (8) к раствору 0,180 г (4,5 ммоль) гидроксида натрия в 10 мл дистиллированной воды добавляют 12 мл тгф и 0,709 г (0,9 ммоль) каликсарена 20. смесь перемешивают до растворения каликс[4]арена. затем медленно, постоянно соблюдая ph = 8,5, при необходимости подкисляя соляной кислотой, прикапывают 16,8 мл (7,6 ммоль) гипохлорита натрия. смесь перемешивают при комнатной температуре 1 час. после этого полученный раствор подкисляют небольшим количеством 0,5 н соляной кислоты до ph = 2–3. затем добавляют 25 мл хлороформа и дистиллированную воду (3×50 мл). органический слой отделяют, упаривают, кристаллизуют из этанола, отфильтровывают, сушат. полученный продукт представляет собой твердое белое вещество. выход 0,46 г (63 %). спектр ямр 1н (dmso-d6, δ, м.д., кссв (j), гц): 12.23 (4н, с, 4он), 6.89…6.63 (8н, м, 2×4arh), 4.90 (4н, д, j = 13.2, 1×4arch2), 4.63 (8н, с, 4aroch2-), 3.22 (4н, д, j = 13.1, 1×4arch2). 1. kumar s., chawla h. m., varadarajan r. tetrahedron lett., 2002, 43, 703. 2. hapiot f., lyskawa j., bricout h., tilloy s., monflier e. adv. synth. catal., 2004, 346, 83. 3. gunji a., takahashi k. synth. commun., 1998, 28, 3933. 4. carroll l. t., hill p. a., ngo c. q., klatt k. p., fantini j. l. tetrahedron, 2013, 69, 5002. 5. peles-lemli b., peles-lemli j., bitter i., kollár l., nagy g., kunsági-máté s. j. incl. phen. macrocycl. chem. 2007, 59, 25. 13 2014 | № 1 | ctaсинтез и алкилирование п-тетракисхлоркаликс[4]аренов e. a. ivanova, t. v. glukhareva, yu. yu. morzherin ural federal university, 620002, 19 mira street, yekaterinburg. e-mail: kate1809@mail.ru the synthesis and alkylation of p-tetrakischloro-calix[4]arene this work is devoted to the development of a chlorination of a calixarenes and a testing of the methods for their preparation to investigate the biological activity of the obtained compounds. new convinient undescribed in the literature methods of the chlorination using sulphuryl chloride or sodium hypochlorite were designed. by the using de-tert-butyl calix[4]arene, containing lower rin the ethoxy(hydroxy)carbonyl metoxy groups, as the starting compounds in the same reactin l aed to mixture of the produts. the reaction of the calix[4]arene and the sulfuryl chloride led to the tetra-kis-chlorocalix[4]arene with good yield (95 %). страница 1 complexes of polyvinylpyrrolidone and polyethylene glycol with palladium(ii) ions: characterization and catalytic activity published by ural federal university eissn 2411-1414 chimicatechnoacta.ru article 2023, vol. 10(3), no. 202310301 doi: 10.15826/chimtech.2023.10.3.01 1 of 6 complexes of polyvinylpyrrolidone and polyethylene glycol with palladium(ii) ions: characterization and catalytic activity dina n. akbayeva , indira a. smagulova , azhar timurkyzy, botagoz s. bakirova al-farabi kazakh national university, almaty 050040, kazakhstan * corresponding author: dina.akbayeva@bk.ru this paper belongs to the rkfm'23 special issue: https://chem.conf.nstu.ru/. guest editors: prof. n. uvarov and prof. e. aubakirov. abstract in this work, we obtained complexes by mixing aqueous solution of palladium(ii) chloride with polyvinylpyrrolidone and polyethylene glycol. the composition of the complex compounds was determined by potentiometric and conductometric titration. ir spectroscopy and scanning electron microscopy (sem) confirmed the coordination of polymeric ligand to palladium and allowed evaluating the morphology and features of the complex surface. the catalytic activity of the synthesized compounds in the oxidation of octene-1 by inorganic oxidizers (nabro3, k2s2o8) in aqueous-organic media in dimethyl sulfoxide (dmso) under mild conditions was calculated. the reaction product was octanone-2, obtained in good yield (62–98%). quantitative analysis of octanone-2 was made by the gas-chromatographic method. mass spectrometry confirms the formation of octanone-2. the complexes are able to participate in five consecutive catalytic cycles without significant loss of catalytic efficiency. oxidation of octene-1 proceeds by the oxidation-reduction mechanism and consists of two key stages. keywords palladium(ii) ions polyvinylpyrrolidone polyethylene glycol catalysis oxidation octene-1 received: 21.06.23 revised: 13.07.23 accepted: 19.07.23 available online: 24.07.23 key findings ● the composition of the complex compounds was determined by potentiometric and conductometric methods. ● ir spectroscopy and sem confirmed the coordination of polymeric ligand to palladium and allowed evaluating the morphology of the complex surface. ● the catalytic activity of the complexes in the oxidation of octene-1 by inorganic oxidizers under mild conditions was evaluated. © 2023, the authors. this article is published in open access under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). 1. introduction the oxidation of unsaturated hydrocarbons with different oxidants leads to the formation of different oxygencontaining compounds, which are key materials for then synthesis of fine chemicals, pharmaceuticals, and important intermediates in petroleum industrial chemistry [1]. the pd(ii)-catalyzed oxidation of alkenes to carbonyl compounds is one of the most well-known reactions mediated by palladium and has extensive synthetic applications, usually referred to as the wacker reactions [2–4]. the use of cucl2, even in catalytic amount, resulted in the production of noxious copper waste, which is potentially very toxic to aquatic life. it leads to the formation of substantial amounts of ecologically hazardous chlorinated by-products. elimination of cucl2 as co-catalyst would render the wacker oxidation a completely green process [5]. the introduction of functional groups into the polymer during the development of new types of catalytic systems based on metal-polymer complexes plays an important role. nowadays the palladium complexes with peg and pvp ligands are widely used as catalysts for cross-coupling reactions and direct synthesis of hydrogen peroxide from hydrogen and oxygen [6–8]. both sodium bromate (nabro3) and potassium peroxydisulfate (k2s2o8) are inexpensive, commercially available strong oxidizing agents. they have been used with different catalysts in various organic reactions as co-oxidants in stoichiometric quantities [9]. http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2023.10.3.01 mailto:dina.akbayeva@bk.ru http://creativecommons.org/licenses/by/4.0/ https://orcid.org/0000-0001-9101-2418 http://orcid.org/0000-0002-8879-3134 https://crossmark.crossref.org/dialog/?doi=https://doi.org/10.15826/chimtech.2023.10.3.01&domain=pdf&date_stamp=2023-07-24 chimica techno acta 2023, vol. 10(3), no. 202310301 article 2 of 6 doi: 10.15826/chimtech.2023.10.3.01 sodium bromate has been used for selective oxidation of vicinal diols to -hydroxy ketones, oxidation of alcohols and alkyl arenes to the corresponding carbonyl compounds, and selective oxidation of sulfides to sulfoxides [10–13]. the peroxydisulfate ion is one of the strongest known oxidizing agents in aqueous solution. potassium peroxydisulfate has been used for the oxidation of 1,4dihydropyridines to the pyridine derivatives, selective oxidation of alcohols to aldehydes and ketones, c–se bond formation to construct -phenylseleno carbonyl compounds and ,-unsaturated carbonyl compounds [14–16]. this article describes the synthesis and characterization of complexes between palladium(ii) chloride and hydrophilic polymers (polyvinylpyrrolidone (pvp) and polyethylene glycol (peg)). the complexes were characterized by conductometric and potentiometric titration. the obtained polymer-metal complexes pd(ii)–pvp and pd(ii)– peg were tested as catalysts in the oxidation of octene-1 by inorganic oxidants (sodium bromate (nabro3) and potassium peroxydisulfate (k2s2o8)) in dimethyl sulfoxide (dmso) under mild conditions (70 °c, pn2 = 1 atm). 2. experimental palladium chloride (content of metal 59.32%), polyvinylpyrrolidone (molecular mass 40000, applichem, germany), polyethylene glycol (molecular weight 10,000, sigma aldrich, usa), hydrochloric acid (36%), dimethyl sulfoxide, dmso (applichem, germany), distilled water, inorganic salts nabro3, k2s2o8 (sigma aldrich, usa) were used without purification. 2.1. synthesis of h2[pdcl4] the complex h2[pdcl4] was synthesized according to the literature [17]. palladium(ii) chloride (1.0 g, 5.6 mmol) was added to a solution of 30 ml water and 1.0 ml concentrated hcl (36%) contained in a 100-ml round-bottom flask. the resulting mixture was heated under reflux until all the palladium(ii) chloride had been dissolved. the dark-brown solution of h2[pdcl4] was then allowed to cool to room temperature. 2.2. synthesis of pdcl2 – pvp 20 ml of h2[pdcl4] solution (0.5 mmol) was placed in a glass dish and mixed with 20 ml of an aqueous solution of pvp (0.167 g, 1.5 mmol). the mixture was stirred for 10– 20 minutes at ambient temperature in order to allow for complete linking of the pd(ii) ions to the polymer. all volatile components were removed in aspirator vacuum, and the complex was dried and stored in air at ambient temperature. yield: 0.25 g (97%). 2.3. synthesis of pdcl2 – peg 20 ml of h2[pdcl4] solution (0.5 mmol) was placed in a glass dish and mixed with 20 ml of an aqueous solution of peg (0.124 g, 2.0 mmol). the mixture was stirred for 10– 20 minutes at ambient temperature in order to allow for complete linking of the pd(ii) ions to the polymer. all volatile components were removed in aspirator vacuum, and the complex was dried and stored in air at ambient temperature. yield: 0.17 g (95%). the process of complexation between palladium(ii) ion and polymers was investigated by potentiometric and conductometric methods with several ionic strengths and temperatures. potentiometric studies were carried out in a commercial device (phywe, germany) under thermostatically controlled conditions. conductometric studies were performed on a conductivitymeter 13701/93 (phywe, germany) under thermostated conditions. all experiments were carried out under temperature control with an accuracy of ±0.2 °c. ir spectra were recorded on a ft ir-4100 type a jasco instrument (usa) in the range of 4000–450 cm−1. sem images were taken on a jsm-6490la jeol instrument equipped with an x-ray dispersive energy detector (edx) for elemental analysis (japan). samples for the gс and mass spectroscopy were prepared according to the literature procedure [18] by extraction with ethyl acetate. the gc analysis was carried out on shimadzu gc-17a (japan) and varian 3900 (canada) devices in the programmed mode from 70 to 280 °c with 5 °c/min heat rate using a capillary column cschromatography service of type fs-ov-1-cb-0.25. mass spectra were recorded on a varian saturn 2100t device (canada). ir spectra, sem images and mass spectra were obtained in analytical laboratories at the rheinland-pfalz technical university of kaiserslautern-landau (rptu, germany). 2.4. typical reaction procedure oxidation of octene-1 by inorganic oxidizers was carried out in a temperature-controlled laboratory setup with intensive stirring in a glass temperature-controlled reactor under negligible temperature gradient (”a catalytic duck”), equipped by the potentiometric device and connected to the gas burette filled with nitrogen. shaking the reactor with frequency of about 250–300 swingings/min minimizes both the mass transport and mass transfer resistance. the laboratory experiments were performed as follows. the reactor with an entire volume of 150 ml was charged with the catalyst (0.057 mmol) under nitrogen atmosphere. the reactor and the gas burette were preheated to 70 °c. the temperature was maintained by the water circulating between the glass reactor and the heating devices. then, in nitrogen flow, an oxidizer (3 mmol) and aqueous solvent (8 ml, 4:1 by volume) were placed. finally, octene-1 (1 mmol) was added, and an electric stirrer was switched on. the temperature was maintained with an accuracy of ±0.5 °c by means of the thermostat. after the experimental runs the reaction solutions were merged and analyzed on a gas chromatograph. https://doi.org/10.15826/chimtech.2023.10.3.01 chimica techno acta 2023, vol. 10(3), no. 202310301 article 3 of 6 doi: 10.15826/chimtech.2023.10.3.01 3. results and discussion 3.1. potentiometric titration figure 1 shows the potentiometric titration curves of pdcl2–pvp and pdcl2–peg complexes. the mixing of solutions of polymer with salt is accompanied by a ph decrease, which is explained by the deprotonation of initially protonated pvp and peg during the complexation. from the titration curve (figure 1a), the optimal molar ratio of the reacting components k (k=[pd2+]/[pvp]=0.35) was found. it means that one central metal atom bonds with three mono-links of polymer ligands. from the titration curve (figure 1b), the optimal molar ratio of the reacting components k (k=[pd2+]/[peg]=0.25) was found. it means that one central metal atom bonds with four mono-links of polymer ligands. 3.2. conductometric titration in order to confirm the composition of the formed pvp– pd2+ and peg–pd2+ complexes, the dependence of the conductivity corrected for the viscosity on the ratio of the initial component of the system was studied (figure 2). the increase in electrical conductivity is due to the released h+ ions during the reaction between pvp or peg and palladium(ii) ions. figure 1 potentiometriс titration curves of polymer (10−2 m) with palladium salt h2[pdcl4] (10 −2 m) (where v – titrant volume in ml, ph – ph of solution). pvp (a); peg (b). as can be seen from figure 2, the electrical conductivity of the solution passes through the inflection point with an increase in the molar content of metal ions. based on the data obtained as a result of conducted conductometric studies, it can be argued that the complexation process is accompanied by an increase in the electrical conductivity of the system at the ratios pvp–pd2+=3:1 and peg–pd2+=4:1. the complexation process of pvp with pd2+ ions is characterized by negative values of gibbs energy that indicates the spontaneous process of polymer-metal complex formation. for the pd2+–pvp complex in the temperature range 298–318 k the positive value of enthalpy change (δrη0) indicates the endothermic character of complex formation. therefore, the stability of the latter increases with increasing temperature in this range. and in the temperature range of 318–343 k the process of complexation is accompanied by the release of heat (exothermic process). as a result, the strength of the polymer-metal complex decreases with increasing temperature. figure 2 potentiometriс titration curves of polymer (10−2 m) with palladium salt h2[pdcl4] (10 −2 m) (where v – titrant volume in ml, ph – ph of solution,  – specific electrical conductivity of solution in s cm−1). pvp(a); peg (b). https://doi.org/10.15826/chimtech.2023.10.3.01 chimica techno acta 2023, vol. 10(3), no. 202310301 article 4 of 6 doi: 10.15826/chimtech.2023.10.3.01 this ambiguous influence of temperature on the process of complexation is probably caused by conformational changes in the structure of pvp polymer, investigated by liu et al. in [19]. it was found that conformational changes of pvp in aqueous medium are accompanied by exo effects that depend on temperature and molecular weight of the polymer. 3.3. oxidation of octene-1 catalysed by pd(pvp)3 cl2 and pd(peg)4cl2 complexes the synthesized complexes were used as catalysts in the process of oxidation of octene-1 by inorganic oxidizers (nabro3, k2s2o8) in aqueous-organic media in dimethyl sulfoxide under mild conditions (equation 1). reaction conditions and conversion rates of liquidphase oxidation of octene-1 by oxidizers in water-organic solutions are given in table 1. the yield of octanone-1 (or n-hexyl methyl ketone) in the experiments in the presence of pd(ii)–peg complex was determined by gaschromatographic analysis and was 62–81%, that is lower than the product yield in the presence of pd(ii)–pvp complex. according to gc analysis and mass spectrometry of reaction solutions, when the yield was less than 100%, the formation of products other than octanone-2 was not observed. the yield of octanone-2 did not exceed 5% after experiments in the presence of inorganic oxidizers (nabro3, k2s2o8). (1) the high catalytic activity of the monometallic polymeric palladium complexes relates to their solubility in the water-organic reaction solution. as a polarity index of dmso is equal to 7.2, the components of the reaction solution would be expected to dissolve completely in dmso [20]. the mass spectra of octanone-2 obtained from the reaction solution contain identical intensive peaks with m/z: 41, 43, 58, 85, 129, which confirms formation of octanone-2 (figure 3). the catalysts could be recycled as shown in figure 4. the catalytic activity of the pdcl2 declines strongly, while it is demonstrated that pd(pvp)3cl2 and pd(peg)4cl2 can be cycled for at least five times. table 1 wacker process of octene-1 oxidation in the presence of pd(pvp)3cl2 and pd(peg)4cl2 complexes [a]. entry oxidizer conversion, % octanone-2 yield, %b cat pd(pvp)3cl2 1 nabro3 97 97 2 k2s2o8 98 98 cat pd(peg)4cl2 3 nabro3 81 81 4 k2s2o8 62 62 а reaction conditions: octene-1 (1 mmol), cat (0.057 mmol), oxidizer (3 mmol), solvent/water (4:1, 10 ml), 120 min, 70 °c, pn2 = 1 atm. b yields were determined by gc analysis of samples. the activity of the catalyst in dmso correlates best with the level of pd(ii) immobilized on the pvp, and this pd(ii) complex, therefore, seems to be the primary catalytic species. thus, when a solution of the yellow complex was heated at 70 °c it became brown-black, indicative of cluster or colloidal palladium formation. the yield of the product reached 12–30% in dmso after the fifth cycle. a noticeable problem in homogeneous pd-mediated oxidation is catalyst deactivation by aggregation into inactive metallic pd. the selectivity does not change, and octanone-2 was observed as the only product, as in the previous experiments. according to the known values of redox potentials, nabro3 and k2s2o8 were chosen as oxidizing agents. the oxidation of pd(0) and reduction of bro3−, s2o82− are thermodynamically resolved, they proceed quite easily and are characterized by negative values of gо for these processes (–88 and –197 kj, respectively). considering the transitions bro3− + 6h+ + 6e → br− + 3h2o and s2o82− + 2e → 2so42−, it should be noted that the oxidation-reduction potential is higher for k2s2o8 (2.010 v) than for nabro3 (1.440 v) [21, 22]. figure 3 mass spectra of the reaction solution. reaction conditions: pd(pvp)3cl2 (0.057 mmol) – c8h16 (1 mmol) – kio4 (3 mmol) – dmso/h2o (4:1, 10 ml) at 70 °c and pn2 = 1 atm. figure 4 reusing the catalysts: pd(pvp)3cl2 (а) and pd(peg)4cl2 (b). https://doi.org/10.15826/chimtech.2023.10.3.01 chimica techno acta 2023, vol. 10(3), no. 202310301 article 5 of 6 doi: 10.15826/chimtech.2023.10.3.01 the ir spectra of green pvp–pdcl2 complex and the used one are given in figure 5. both ir spectra contain bands at 3402 cm−1 characteristic of pvp. the carbonyl group in pvp–pdcl2 complex is characterized by the peak at 1646 сm−1. it is slightly shifted to 1652 cm−1 in the pvp– pdcl2 complex after the experiment. to evaluate the structure and morphology of the catalysts after the experiment and to identify the arrangement and nature of the phases present on the catalyst surface, sem and edx techniques were employed. figure 6 shows the sem micrograph of a selected region of the pd catalyst used for the octene-1 oxidation. as shown in figure 6b, the sem images of the pd(pvp)3cl2 after the fifth recycling experiment did not show any significant morphological change compared to those of the original sample. one of the reasons in decrease of the catalytic reaction rate is an excess of surface species such as the bromine-, oxygen-, and carbon-containing surface compounds, which could block the pd active sites [23]. the oxidation-reduction mechanism consists of two key stages [24]: reduction of pd(ii)(pol) by octene-1 to pd(0)(pol) with formation of octanone-2 and oxidation of pd(0)(pol) to pd(ii)(pol) by oxidizer. in the hypothetical oxidation reaction equations (equations 2–4), the pvp or peg mono link denotes one polymer ligand bound to the polymer coordinated with palladium. activation [pd(ii)(pol)3–4cl]+ + c8h16 + h2o → [pd(0)(pol)3–4] + c8h16o + 2h+ + cl− (2) bromate oxidation, protonation: [pd(0)(pol)3–4] + nabro3 + 6h+ → [hopd(ii)(pol)3–4]+ + nabr + 3h+ + 2oh− (3) dissociation of one polymer ligand: [hopd(ii)(pol)3–4]+ ⇌ [hopd(ii)(pol)3–4]+ + (pol)dangling (4) 4. limitations the main problem that appeared during this research is the high hygroscopicity of pd(ii)–peg complex in comparison with pd(ii)–pvp one. a possible solution of this problem is the further immobilization of the complex on the supports. 5. conclusions palladium–polymer complexes [pd(pvp)3cl]+ and [pd(peg)4cl]+ were obtained from palladium(ii) chloride, polyvinylpyrrolidone (pvp) and polyethylene glycol (peg). using potentiometric and conductometric titration as well as ir spectroscopy, the structure of the polymeric complexes was established. the polymer complexes were tested for catalytic activity in octene-1 oxidation by the inorganic oxidizers nabro3 and k2s2o8 in dimethyl sulfoxide under mild conditions (70 °c, pn2 = 1 atm). conversion of octene-1 was achieved in 62–98% yield. the final reaction product was octanone-2 (or n-hexyl methyl ketone). the catalysts can be reused at least up to five times. the sem and edx techniques were employed for evaluating the structure and morphology of the catalysts after experiment, and for the identification of the arrangement and nature of the phases present on the catalyst surface. the oxidation-reduction mechanism consisting of two key stages was proposed. ● supplementary materials no supplementary materials are available. figure 5 ir spectra of green pvp–pdcl2 and the used catalyst. figure 6 electronic microphotographs of the pd(pvp)3cl2 complex before (a) and after (b) experiment. https://doi.org/10.15826/chimtech.2023.10.3.01 chimica techno acta 2023, vol. 10(3), no. 202310301 article 6 of 6 doi: 10.15826/chimtech.2023.10.3.01 ● funding this research had no external funding. ● acknowledgments none. ● author contributions conceptualization: d.n.a. data curation: b.s.b., i.a.s. investigation: i.a.s., a.t. methodology: d.n.a., b.s.b. supervision: d.n.a. writing – original draft: d.n.a., b.s.b. writing – review & editing: d.n.a. ● conflict of interest the authors declare no conflict of interest. ● additional information author ids: dina n. akbayeva, scopus id 6505789588; botagoz s. bakirova, scopus id 57204585748; indira a. smagulova, scopus id57220043414. website: al-farabi kazakh national university, https://www.kaznu.kz/en. references 1. weissermel k, arpe hj. industrial organic chemistry. 4th ed. weinheim: wiley-vch; 2003. 491 p. 2. tsuji j. synthetic applications of the palladium-catalyzed oxidation of olefins to ketones. synth. 1984;369–384. doi:10.1055/s-1984-30848 3. takacs jm, jiang xt. the wacker reaction and related alkene oxidation reaction. curr org chem. 2003;7(4):369–396. doi:10.2174/1385272033372851 4. sharma 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palladium-polyvinylpyrrolidone complex in oxidation of octene-1. bull chem react eng catal. 2018;13(3):560–572. doi:10.9767/bcrec.13.3.1980.560-572 https://doi.org/10.15826/chimtech.2023.10.3.01 https://www.scopus.com/authid/detail.uri?authorid=6505789588 https://www.scopus.com/authid/detail.uri?authorid=57204585748 https://www.scopus.com/authid/detail.uri?authorid=57220043414 https://www.kaznu.kz/en https://doi.org/10.1055/s-1984-30848 https://doi.org/10.2174/1385272033372851 https://doi.org/10.2174/1385272043370096 https://doi.org/10.1016/j.tetlet.2013.01.082 https://doi.org/10.1055/s-0036-1589498 https://doi.org/10.1021/acs.organomet.8b00607 https://doi.org/10.1039/2046-2069/2011 https://doi.org/10.1039/d0ra03148h https://doi.org/10.1055/s-0030-1259755 https://doi.org/10.1016/j.tet.2005.03.056 https://doi.org/10.3184/030823402103172464 https://doi.org/10.1007/s00706-007-0840-x https://doi.org/10.1016/j.tetlet.2006.09.065 https://doi.org/10.5267/j.ccl.2015.4.001 https://doi.org/10.1039/d0ra05927g https://doi.org/10.1021/jo200462a https://doi.org/10.1016/s1381-5148(99)00077-2 https://doi.org/10.1021/bp9700263 https://doi.org/10.3390/ma9050318 https://doi.org/10.9767/bcrec.13.3.1980.560-572 98 введение известно, что твердые растворы системы cds-pbs могут применяться в качестве тонкопленочных солнечных элементов с p-n-переходом [1]. кроме того, введение в состав узкозонного сульфида свинца в структуру широкозонного полупроводника cds способствует увеличению дегн. а. форостяная1, а. о. полепишина1, в. ф. марков1, 2, л. н. маскаева1, 2 1уральский федеральный университет, 620002, екатеринбург, ул. мира, 19. e-mail: natal-ku8@yandex.ru 2уральский институт гпс мчс россии, екатеринбург, ул. мира, 22. e-mail: mln@ural.ru получение пленок твердых растворов системы cds-pbs путем модификации поверхности пленки сульфида кадмия при выдержке в водном растворе соли свинца* изучены состав, структура и морфология многофазных полупроводниковых пленок свежеосажденного сульфида кадмия и пленок cds, выдержанных в растворе ацетата свинца pbac 2 . композиции на основе сульфида кадмия, образовавшиеся на межфазной границе cds тв /pb2+ (aqua) , исследовали методами электронной микроскопии, а также с помощью спектров комбинационного рассеяния. впервые показана возможность получения твердых растворов замещения в халькогенидных системах путем ионного обмена на межфазной границе «пленка халькогенида металла – водный раствор». обобщая полученные результаты, можно заключить, что выдержка химически осажденных пленок сульфида кадмия в водном растворе соли свинца обеспечивает включение pbs в состав пленки с образованием тонкопленочных композиций cds-pbs, в том числе твердых растворов замещения pb 1–x cd x s. при этом последующая термообработка слоев при 423 k повышает содержание сульфида свинца в твердом растворе. * исследование проведено при финансовой поддержке молодых ученых урфу в рамках реализации программы развития урфу. у д к 5 46 .8 51 :5 46 .8 12 © форостяная н. а., полепишина а. о., марков в. ф., маскаева л. н., 2014 99 2014 | № 3 | cta радационной, в частности радиационной стойкости тонких пленок [2]. преимуществом твердых растворов pbxcd1−xs также является возможность плавного регулирования ширины запрещенной зоны путем изменения состава, а следовательно, оптических и электрофизических свойств. в связи с этим актуальной становится разработка методов синтеза твердых растворов системы cds-pbs, позволяющих расширить диапазон их составов. известно, что для получения указанных соединений используют, например, термическое испарение в вакууме спеченной шихты, состоящей из cds и pbs [2], гидрохимическое осаждение [3–7], синтез с применением технологий ленгмюра – блоджетт [8], метод спрей-пиролиза [9]. в настоящей работе для получения твердого раствора в системе cds-pbs был использован простой, экономичный технологический прием − химическое осаждение их водных сред с применением модификации поверхности тонкой пленки халькогенида металла путем выдержки ее в растворе соли другого металла. целью настоящей работы являлось исследование состава, структуры и морфологии пленок твердых растворов системы cds-pbs, полученных методом ионообменного замещения на межфазной границе «пленка cds – водный раствор соли свинца». экспериментальная часть в качестве исходного материала были использованы тонкие пленки сульфида кадмия толщиной 250–300 нм, полученные методом гидрохимического осаждения из реакционной системы, содержащей хлорид кадмия cdcl2, лимоннокислый натрий na3c6h5o7, водный раствор аммиака nh4oh и тиокарбамид n2h4cs. осаждение вели в течение 90 минут при температуре 353 k на предварительно обезжиренные ситалловые подложки марки ст-50-1. модификация поверхности тонких пленок сульфида кадмия заключалась в выдерживании гидрохимически осажденной пленки cds в растворе соли свинца (ii), в качестве которой использовали ацетат свинца pb(ch3coo)2. продолжительность выдержки синтезированных слоев cds в водном растворе pb(ch3coo)2 при температурах 353–368 k варьировалось от 1 до 9 часов. предполагалось, что при этом на границе раздела фаз «тонкая пленка – водный раствор соли кадмия (ii)» будет протекать гетерогенная топохимическая ионообменная реакция, характеризующаяся стехиометрическим замещением ионов кадмия cd2+ из твердой фазы тонкой пленки cds на ионы свинца pb2+ из раствора. измерения толщины образцов пленок были выполнены на интерферометре мии-4. термическую обработку пленок проводили в электропечи «пм–1.0–7» с использованием следующего режима: образцы помещали в печь и медленно нагревали от комнатной температуры до 573 k и отключали нагрев. пленки подвергались нагреву со скоростью 3,5 град/мин. получение пленок твердых растворов системы cds-pbs путем модификации поверхности пленки сульфида кадмия при выдержке в водном растворе соли свинца 100 cta | № 3 | 2014 для исследования морфологии поверхности и элементного состава пленок сульфида олова использовали метод растровый электронной микроскоп mira3lmv с рентгеноспектральным электронным микрозондовым анализом (edx). при проведении элементного анализа глубина анализируемого слоя составляла ~1 мкм при напряжении первичного пучка 20 кв. поскольку толщина исследуемых пленок изменялась в пределах от 0,3 до 1,0 мкм, для уменьшения фонового сигнала от ситалловой или стеклянной подложек в ряде случаев напряжение пучка снижали до 10 кв с целью уменьшения глубины анализа. точность определения элементного состава в атомных долях составляла ~10 %. для структурных исследований пленок привлечена лазерная кр-спектроскопия. исследования выполнены на спектрометре renishaw ramascope. спектры регистрировали на микроанализаторе «микрозонд mole» (аргоновый лазер мощностью до 600 мвт, λ = 514.5 нм). результаты и обсуждение для уменьшения объема экспериментальных исследований весьма актуальна возможность прогнозирования состава и структуры пленок. с точки зрения химической термодинамики, возможность обменной реакции на межфазной границе cdsтв/p b 2 + р р определяется разностями значений произведений растворимости исходного вещества (cds) и продукта реакции (pbs), составляющих соответственно 1.6·10−28 и 7,9·10−27, концентрацией ионов металлов, участвующих в процессе, температурой и значением ph раствора, поэтому для установления условий протекания ионообменной реакции был проведен расчет энергии гиббса в зависимости от температуры и рн обменного процесса (рис. 1). расчеты показали, что в условиях проведения синтеза от 298 до 368 k вероятность протекания ионообменной реакции возрастает с уменьшением рн от 8 до 0, а, значит, существует высокая вероятность образования твердого раствора pb1–xcdxs путем ионнообменного замещения кадмия на свинец (ii). результаты расчетов были использованы для выбора оптимальных условий при организации ионообменного процесса в системе cdsтв/pb(ii)aq. толщина пленок cds и модифицированного сульфида кадмия путем ее выдержки в водном растворе ацетат свинца составила 300 нм. рис. 1. температурная зависимость энергии гиббса процесса ионообменного замещения в системе cds-pbs н. а. форостяная, а. о. полепишина, в. ф. марков, л. н. маскаева 101 2014 | № 3 | cta получение пленок твердых растворов системы cds-pbs путем модификации поверхности пленки сульфида кадмия при выдержке в водном растворе соли свинца на рис. 2 показаны электронно-микроскопические изображения поверхности пленок cds (а), pbs (б) и cds, выдержанных в водном растворе ацетата свинца pb(ch3coo)2 при максимальной из используемых температур − 368 k. продолжительность выдержки пленки сульфида кадмия в растворе ацетата свинца составила 60 минут (в) и 540 минут (г). по результатам растровой электронной микроскопии в структуре поверхности модифицированных образцов были отмечены значительные изменения по сравнению с исходными пленками. с увеличением продолжительности и температуры ионообменного процесса наблюдается образование глобул, диаметр которых достигает 1 мкм, которые в свою очередь состоят из нанокристаллитов размером 10–50 нм. данные элементного анализа пленки в различных точках поверх-ности свидетельствуют о том, что пленка состоит в основном из свинца, серы и кадмия. следовательно, можно говорить о вхождении свинца в пленку. также был сделан вывод о том, что увеличение температуры и продолжительности ионного обмена приводит к росту содержания свинца и уменьшению содержания кадмия в пленке, содержание серы при этом меняется незначительно, в пределах ошибки анализа. так, максимально достигнутое количество свинца в составе тонкой пленки составило 42,6 ат. %. это значение было достигнуто выдерживанием пленки сульфида кадмия в водном растворе ацетата свинца в течение 540 минут при температуре процесса 368 k. количество свинца в образце, соответствующем 60-минутному ионообменному процессу при той же температуре, составило 8,27 ат. %, т. е. при увеличении времени контакта тонкой пленки cds с раствором соли свинца, содержание свинца в составе пленки возросло более, чем в пять раз. для аттестации пленок сульфида кадмия, модифицированных в растворе ацетата свинца, использовали спектры комбинационного рассеяния, представленные на рис. 3. на спектрах комбинационного рассеяния, представленных на рис. 3, в спектре сульфида кадмия присут-ствует интенсивный пик 322 см–1, характерный для cds [10]. характеристический пик сульфида свинца [11] 138 см–1 последовательно смещарис. 2. электронно-микроскопические изображения пленок cds (а), pbs (б) и cds, выдержанных в растворе соли свинца при температуре 363 k в течение 1 (в) и 9 (г) часов а в б г 102 cta | № 3 | 2014 ется в высокочастотную область до 143 см–1 как для свежеосажденных, так и для термообработанных пленок. это, вероятно, обусловлено замещением атомов свинца на более легкие атомы кадмия, т. е. из этого мы можем сделать вывод об образовании твердого раствора pb1–xcdxs со стороны свинца. причем термический отжиг обеспечивает более высокое содержание кадмия в структуре сульфида свинца (143 против 140 см–1). обобщая полученные результаты, можно заключить, что выдержка химически осажденных пленок сульфида кадмия в водном растворе соли свинца обеспечивает включение pbs в состав пленки с образованием тонкопленочных композиций cds-pbs, в том числе твердых растворов замещения pb1–xcdxs. при этом последующая термообработка слоев при 423 k повышает содержание сульфида свинца в твердом растворе. 1. obaid a. s., mahdi m. a., hasson z., bououdina m. superlatties and microstructures, 2012, 52, 816. 2. malyar i. v., stetsyura s. v. semiconductors, 2011, 45, 888. 3. mohammed m. a., mousa a. m., ponpon j. p. j. semiconductor technol. science, 2009, 9, 117. 4. bhushan s., chandra t. turk. j. phys., 2008, 32, 21. 5. ezenwa i. a., ekpunobi a. j. pacif. j. scienc. technol., 2010, 11, 404 . 6. bhushan s., mukher m., bose p. j. mater. science: materials in electron.,. 2002, 13, 581. 7. snodh s., mulyankan. intern. res. j., 2009, ii., 9. 8. stetsyura s. v., malyar i. v., serdobintsev a. a., klimova s. a. semiconductors, 2009, 43, 1064. 9. kamruzzaman m., dutta r., podder j. semiconductors, 2012, 46, 957. 10. prabhu rajeev r. bull. mater. sci., 2008, 31, 511. 11. gutiérrez p. r. j. mater. scienc. engineering, 2013, a 3, 1. рис. 3. спектры комбинационного рассеяния пленок cds, pbs и термообработанной и свежеосажденной cds-pbs н. а. форостяная, а. о. полепишина, в. ф. марков, л. н. маскаева 103 2014 | № 3 | cta получение пленок твердых растворов системы cds-pbs путем модификации поверхности пленки сульфида кадмия при выдержке в водном растворе соли свинца n. a. forostyanaya1, a. o. polepishina1, v. f. markov1, 2, l. n. maskaeva1, 2 1ural federal university, 19, mira street, 620002, ekaterinburg. e-mail: natal-ku8@yandex.ru 2ural institute of state fire service of emercom of russia, 22, mira street, 620002, ekaterinburg. e-mail: mln@ural.ru preparation of cds-pbs solid solutions thin films by modifying of the cadmium sulfide film surface when it exposed to an aqueous solution of lead salt the composition, structure, and morphology of multiphase semiconductor as-deposited cds films and cds incubated in a lead acetate solution were studied. compositions examined by electron microscopy and by the raman scattering. for the first time it was present the formation of a solution at the interface «metal chalcogenide thin film water solution». summarizing the results, we can conclude that exposure precipitated films of cadmium sulfide in aqueous salt solution of lead ensures pbs part of the film with the formation of thin-film songs cds-pbs, including solid solutions substitution pb1xcdxs. with subsequent heat treatment of layers when 423 k increases the content of lead sulfide in the solid solution. study on methylene blue adsorption using cashew nut shell-based activated carbon published by ural federal university eissn 2411-1414 chimicatechnoacta.ru article 2023, vol. 10(4), no. 202310401 doi: 10.15826/chimtech.2023.10.4.01 1 of 8 study on methylene blue adsorption using cashew nut shell-based activated carbon hai d. tran a , dinh quan nguyen bc * a: faculty of environment, ho chi minh university of natural resources and environment, ho chi minh city 700.000, vietnam b: laboratory of biofuel and biomass research, faculty of chemical engineering, ho chi minh city university of technology (hcmut), 268 ly thuong kiet, district 10, ho chi minh city 700.000, vietnam c: vietnam national university ho chi minh city, linh trung ward, thu duc district, ho chi minh city 700.000, vietnam * corresponding author: ndquan@hcmut.edu.vn this paper belongs to a regular issue. abstract adsorption is a widely used technique for the treatment of wastewater containing dyes, which are pollutants that can have serious impacts on the aquatic ecosystems. in this work, activated carbon (ac) was prepared from cashew nut shell (cns) and used to adsorb methylene blue (mb) from solution. the cns ac was characterized by scanning electron microscopy, fourier transform infrared spectroscopy, and nitrogen adsorption-desorption isotherms. the adsorption behavior of mb on cns ac was investigated by varying the initial solution ph, adsorbent dosage, and initial mb concentration. the results showed that the cns ac was effective for mb removal, with an adsorption capacity of 24.8 mg/g. the adsorption nature of mb onto the cns ac surface was explored by analyzing the experimental data using isotherm and kinetic models. the freundlich and dubininradushkevich (d-r) isotherm models showed good agreement with the experimental adsorption equilibrium results. the mean adsorption energy was found to be 22.4 kj/mol, indicating chemical adsorption. the adsorption of mb on the cns ac followed pseudo-second-order kinetics. this study demonstrates the potential application of cns ac for mb removal. keywords dye removal adsorption activated carbon isotherm kinetics bio-adsorbent received: 07.07.23 revised: 31.07.23 accepted: 31.07.23 available online: 07.08.23 key findings ● the porous and rough surface of the cns ac is rich in functional groups containing electron donors. ● the equilibrium of mb adsorption onto the cns ac is in good agreement with the freundlich and d-k isotherms. ● the adsorption kinetics correspond to the pseudo-second-order. © 2023, the authors. this article is published in open access under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). 1. introduction due to the hazardous nature of common dyes, such as their poor biodegradability, toxicity, stability, and coloration, the presence of dye pollutants in water has caused major environmental problems [1, 2]. various techniques have been developed for dye removal, including biological treatment, chemical oxidation treatment, advanced oxidation processes, catalytic degradation, physical processes, or hybrid systems [3–6]. as a prominent method among physical processes, adsorption is considered economically feasible because of its highly removal-effective, operating-costeffective, versatile, and available properties [7–9]. a large amount of cns is being discharged in vietnam, which poses a challenge for its management [10]. the high content of organic compounds in the cns suggests that it should be considered as a raw material for the preparation of ac. the cns ac exhibited a potential adsorbent for a variety of pollutants, including methylene blue (mb) [11– 14], brilliant green dye [15], and congo red dye [16]. the cns ac can be prepared by chemical activation using zncl2 [13], koh [11, 14, 15], or h3po4 [17]. acid impregnation can be applied in the protocol of ac preparation to improve the adsorption capacity of ac via the formation of functional groups on the ac surface [18–21]. however, to the best of our knowledge, the cns ac prepared after the http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2023.10.4.01 mailto:ndquan@hcmut.edu.vn https://www.sciencedirect.com/topics/earth-and-planetary-sciences/electron-microscope https://www.sciencedirect.com/topics/engineering/fourier-transform https://www.sciencedirect.com/topics/engineering/fourier-transform http://creativecommons.org/licenses/by/4.0/ https://orcid.org/0000-0002-0103-8866 https://orcid.org/0000-0001-8906-9773 https://crossmark.crossref.org/dialog/?doi=https://doi.org/10.15826/chimtech.2023.10.4.01&domain=pdf&date_stamp=2023-08-07 chimica techno acta 2023, vol. 10(4), no. 202310401 article 2 of 8 doi: 10.15826/chimtech.2023.10.4.01 acid impregnation has not been fully investigated for its dye adsorption performance. this study aims to fill this gap by investigating the adsorption of mb on cns ac that was prepared by hno3 activation. the influence of experimental parameters on mb removal was explored. the analysis of isotherm and kinetic results revealed the nature of mb adsorption on the cns ac. 2. materials and methods 2.1. preparation and characterization of cns ac the cns ac was prepared in two steps. first, the raw cns, which had been mechanically squeezed to separate oil, was carbonized at 500 °c for 2 h to produce cns charcoal. this charcoal was then crushed in a ball mill for 20 min. second, the obtained charcoal was dispersed in an abundant amount of 0.5 m nitric acid (hno3) under ultrasonication for 15 minutes and then kept overnight. solid particles were collected and neutralized by washing and filtrating through an 11-m filter paper (whatmann no. 1) with distillated water. the collected solid was dried at 100 °c for 1 h. the activation process was carried out at 800 °c for 30 min in an electric furnace, which was purged with nitrogen gas to create an inert atmosphere. the functional groups and morphological structure of cns ac were explored by fourier transform infrared spectroscopy (ftir) and scanning electron microscopy (sem) using a prisma e sem system and an is5 nicolet ftir spectrometer, respectively. nitrogen adsorptiondesorption isotherms were performed with a nova 2200e® system (quantachrome instruments, usa) to determine the pore structure. 2.2. preparation of mb solutions a stock mb solution of 1000 ppm was prepared by dissolving 1.0 g of mb (merck) in 1 l of distilled water. the mb solutions at the desired concentrations were obtained by diluting an appropriate volume of the stock solution. a solution of 0.1 m naoh or 0.1 m hcl was used to adjust the ph of the mb solution. 2.3. adsorption experiments batch adsorption experiments were conducted in a 500-ml erlenmeyer flask, which was tightly attached with a silicone rubber stopper. the flask contained 350 ml of mb solution. a small glass tube (with an outer diameter of 4 mm) for sampling was inserted through this stopper. a magnetic stirrer was used to agitate the solution at 150 rpm. the effects of solution ph, cns ac dosage, and initial mb concentration on adsorption performance were investigated at a temperature of 300 k. to reach equilibrium adsorption, the experiment runs were carried out for 3 h. then, samples were collected and filtered through a 0.45 m membrane to determine the equilibrium concentration of mb. for the kinetic study, mb adsorption was performed using the same procedures. the mb concentrations after different contact periods were measured by uv-vis spectroscopy at wavelength of 664 nm using an evolutiontm 350 uv-vis spectrophotometer. equation 1 was used to calculate the amount of adsorbed mb at time t, qt (mg/g). ( )0 t t c c v q m − = (1) where, c0 and ct are the concentrations of mb at initial and at any time t (mg/l), v is the volume of the solution (l), and m is the weight of cns ac employed (g). the adsorption experiment was triplicated to evaluate the accuracy of the results. 3. results and discussion 3.1. morphology of cns ac the cns ac surface has a porous and rough morphology, as shown in figure 1. this morphology is characterized by large and interconnected open channels, which were formed by the decomposition and evaporation of volatile matter during thermal treatment [22]. this structure is proposed to facilitate the transfer of mb molecules from solution to adsorption sites [23], resulting in a fast adsorption rate. 3.2. analysis of porous structure nitrogen adsorption and desorption measurements were used to characterize the porous structure of cns ac. the hysteresis loop in the relative pressure range of 0.3–1.0 (figure 2) is a sign of type iv isotherm according to the iupac classification, indicating the presence of mesopores in the cns ac structure [24, 25]. this is further supported by the bjh pore size distribution (inset in figure 2), which shows that the pore diameters are less than 4 nm, with micropores (< 2 nm) being the dominant pore type. the specific surface area was calculated to be 472 m2/g using the brunauer-emmett-teller method. figure 1 sem image of the cns ac. https://doi.org/10.15826/chimtech.2023.10.4.01 chimica techno acta 2023, vol. 10(4), no. 202310401 article 3 of 8 doi: 10.15826/chimtech.2023.10.4.01 3.3. characterization of the surface chemistry the ftir spectrum (figure 3) displayed characteristic peaks, which provide information on the functional groups on the surface of cns ac. the band at 3400 cm−1 indicates the o−h stretching vibration in water molecules. the c−h sp3 stretching bond of alkane was assigned as the cause of the appearance of the peak at 2921 cm−1 [26, 27]. the sign of c−h aliphatic stretching was illustrated by a band at 2787 cm−1 [28]. the vibration of cc stretching in alkyne groups was reflected by a band at 2285 cm−1. the bands at 1632 and 731 cm−1 correspond to c=o and c−o stretching in aromatic carboxyl, phenolic ester, and conjugated ketonic structures [26]. c−o vibration in alcohol groups is related to a band at 1158 cm−1. the peak at 1050 cm−1 identified c−c bending in the aromatic ring [29]. the presence of the groups containing  bonds (cc, c=o) and the lewis base groups (c=o, c−o) is proposed to promote the interaction of cationic mb molecules with the cns ac surface [30–32]. 4. batch adsorption studies 4.1. effect of solution ph the ph of the solution plays an important role in the adsorption of dyes [32]. as shown in figure 4, the mb removal and qe increased with increasing solution ph from 1 to 5. this is because (1) the functional groups on the cns ac surface become more negatively charged as the ph value increases [33], and (2) mb is deprotonated to form a positively charged species if the solution ph is higher than the pka of mb (5.85) [34]. as a result, the electrostatic attraction between the mb molecules and the cns ac surface is enhanced with increasing solution ph, leading to improved mb adsorption. however, at solution ph values above 5, the competitive adsorption of hydroxide ions (oh–) with mb molecules begins to occur, leading to a gradual decrease in mb removal [35]. therefore, the subsequent adsorption experiments were performed at ph 5, where the maximum mb removal and qe were achieved. 4.2. effect of cns ac dosage the adsorption of mb onto cns ac was investigated at different adsorbent dosages (0.5, 1.0, 1.5, and 2.0 g). as shown in figure 5, mb removal increased with increasing adsorbent dosage, reaching a plateau at 1.5 g. this is because the higher adsorbent dosage provides more adsorptive sites for mb molecules to bind to [36]. at 2.0 g of the cns ac dosage, the mb removal was not significantly higher than at 1.5 g. the adsorption capacity decreased from 42.6 to 14.1 mg/g as the cns ac dosage increased from 0.5 to 2.0 g. the excess of adsorptive sites at higher dosages led to an unsaturated adsorption surface, resulting in a decrease in adsorption capacity [37]. this trend was previously reported for mb adsorption on various biomass-based adsorbents [38–40]. 4.3. effect of initial mb concentration the initial dye concentration affects the dye adsorption performance, which is related to the interfacial process [41]. as shown in figure 6, when the initial mb concentration was increased from 20 to 90 mg/l, the mb removal decreased from 95.7 to 41.3%, while the adsorption capacity increased from 12.8 to 24.8 mg/g. figure 2 nitrogen adsorption-desorption isotherms (the inset: pore-size distribution). figure 3 ftir spectrum of the cns ac. figure 4 effect of initial ph (conditions: c0 = 30 mg/l, m = 1 g, t = 3 hours). https://doi.org/10.15826/chimtech.2023.10.4.01 chimica techno acta 2023, vol. 10(4), no. 202310401 article 4 of 8 doi: 10.15826/chimtech.2023.10.4.01 the higher the mb concentration, the greater the driving force and collision probability between mb cations and adsorptive sites [38, 41]. however, increasing the initial mb concentration causes a denser mb accumulation on the cns ac surface, which leads to faster saturation of adsorptive sites [42]. therefore, the adsorption capacity increased with increasing initial mb concentration, while the mb removal changed in the opposite direction. this behavior is consistent with previous reports [43, 44]. 4.4. adsorption isotherms the nature and mechanism of the interaction between mb molecules and the cns ac surface can be explored by an adsorption isotherm study [45]. in this study, the equilibrium data were analyzed according to the langmuir, freundlich, and dubinin-radushkevich (d-r) isotherms, which were mathematically expressed as equation 2−4 [46]. = + max 1 l e e l e q k c q k c (2) = 1/n e f e q k c (3) − = 2 max dr k e q q e (4)    = +     1 1 e rt c (5) where ce and qe are the mb concentration (mg/l) and adsorption capacity (mg/g) at equilibrium, respectively, qmax is the theoretical maximum adsorption capacity (mg/g), kl is the langmuir isotherm constant (l/mg), kf is the freundlich isotherm constant (mg/g (mg/l)n), n represents the adsorption intensity, kdr is the activity coefficient related to the mean sorption energy (mol2/j2),  is the polyani potential (j2/mol2), r = 8.314 (j/mol/k) is the gas constant, and t = 300 k is the solution temperature. the constant parameters for the selected isotherm models were determined by nonlinear fitting to the experimental data and are presented in table 1. figure 7 shows the relationship between the qe and the ce from the experiment (desired points) and regression (solid plots). the closeness between the isotherm model and experimental results was evaluated using the correlation coefficient, r2. the langmuir isotherm model assumes a monolayer coverage of adsorbate onto a homogenous adsorbent surface [47]. the r2 value of 0.8980 (table 1) for the langmuir model indicates that it is unsatisfactory for describing the equilibrium data obtained. this suggests that the adsorption of mb onto the cns ac surface occurs in multilayers. this may be due to the presence of electron donors via functional groups. the freundlich and d-r isotherm models provide better fits with the experimental data compared to the langmuir isotherm model, as indicated by higher r2 values in table 1. equilibrium data following freundlich implies a multilayer adsorption of the adsorbate onto a heterogeneous adsorbent surface where there is a nonuniform distribution of the adsorption energy and affinities [45, 48]. the freundlich isotherm model yielded a kf value of 14.7 mg/g (mg/l)n, which is higher than previous report [49]. the high kf value reflects a high adsorption capacity. the n value was determined to be 7.3 according to the freundlich isotherm model. for n > 1, the greater the n value, the greater the adsorption intensity [45]. this resulted in a favorable adsorption for increasing the adsorption capacity. the kf and n values are consistent in explaining the mechanism of mb adsorption onto the cns ac. figure 5 effect of cns ac dosage (conditions: c0 = 30 mg/l, ph 5, t = 3 hours). figure 6 effect of initial concentration of mb (conditions: m = 1.5 g, ph 5, t = 3 h). table 1 the calculated parameters for the selected isotherm models. isotherm model r2 calculated parameter langmuir 0.8980 qmax = 23.28 kl = 1.32 freundlich 0.9295 kf = 14.14 n = 7.27 dubinin-radushkevich 0.9316 qmax = 39.52 kdr = 10.3910 −10 https://doi.org/10.15826/chimtech.2023.10.4.01 chimica techno acta 2023, vol. 10(4), no. 202310401 article 5 of 8 doi: 10.15826/chimtech.2023.10.4.01 the d-r isotherm considers micropores filled with adsorbate molecules and sorption energy at the adsorbent surface according to a gaussian distribution [49]. as shown in the inset of figure 2, the range of pore-size diameters in cns ac is less than 4 nm, which is close to the effective diameter of the mb molecule (length of 1.45 nm, width of 0.95 nm) [50]. this allows mb molecules to transfer into the porous matrix and fill micropores. the good fit of the experimental data to the d-r isotherm (r2 = 0.932) supports this hypothesis. according to equation 6, the mean adsorption energy (e) can be calculated to be 22.4 kj/mol, which is higher than the threshold for chemical adsorption of 20 kj/mol, implying the chemical adsorption of mb onto cns ac [51, 52]. = 1 2 dr e k . (6) 4.5. kinetic studies the dynamics of mb adsorption on cns ac were investigated by nonlinear fitting of the experimental kinetic data with three common kinetic models: the pseudo-first-order (pfo), pseudo-second-order (pso), and intra-particle diffusion (w-m) models. these models were expressed by equations 7−9 [53]. ( )−= − 11 k tt eq q e (7) = + 2 2 2 1 e t e q k t q k q t (8) − = + 0.5 t w m q k t c (9) where qt (mg/g) is the amount adsorbed of mb at contact time t, qe (mg/g) is the predicted adsorption capacity at equilibrium; k1 (1/min), k2 (g/mg/min), and kw−m (g/mg/min0.5) are rate constants of pfo, pso, and w-m, respectively; and c (mg/g) represents the contribution of molecular diffusion through the boundary layer. the dependence of the adsorbed mb amount on the contact time is shown in figure 8. the experimental results (desired points) indicate that the mb was rapidly adsorbed onto the cns ac in the first 60 min. this is due to the large bm concentration gradient between the bulk solution and the cns ac surface. the obtained kinetic parameters are presented in table 2. a comparison of the r2 values from the simulation of the three kinetic models suggests that the pso model is the best fitting model to describe the kinetic behavior of mb adsorption on cns ac. this indicates that the adsorption rate is controlled by the chemical interaction between mb and the adsorptive sites on the cns ac surface [42, 54]. the calculated adsorption capacity for mb (18.74 mg/g) according to the pso model was in good agreement with the experiment result (18.65 mg/g). the adsorption mechanism of mb onto cns ac was investigated in a consensus of kinetic and isothermal analyses. 5. limitations experiments on competitive adsorption and applicability for real textile wastewater have not been conducted. 6. conclusion in this work, vietnamese cns was activated with nitric acid to synthesize cns ac. figure 7 isotherm plots for mb adsorption onto the cns ac (conditions: m = 1.5 g, ph 5, t = 3 h). figure 8 adsorption kinetics of mb on cns ac (c0 = 30 mg/l, m = 1.5 g, ph 5). table 2 the calculated parameters for the selected kinetic models. kinetic model r2 calculated parameter pfo 0.9014 qe = 17.29 k1 = 0.11 pso 0.9636 qe = 18.74 k2 = 9.1010 −3 w-m 0.8023 c = 6.07 kw−m = 1.19 https://doi.org/10.15826/chimtech.2023.10.4.01 chimica techno acta 2023, vol. 10(4), no. 202310401 article 6 of 8 doi: 10.15826/chimtech.2023.10.4.01 the obtained cns ac exhibited a porous structure with functional groups containing oxygen or -bonds, which were advantageous for the interaction with cationic molecules. the adsorption of mb on the cns ac was performed at different solution ph values, adsorbent dosages, and initial mb concentrations. the experimental equilibrium data was consistent with freundlich and d-r models, suggesting that the adsorption of mb onto cns ac is a favorable process that occurs in multilayers on a heterogeneous surface. the mean adsorption energy was found to be 22.4 kj/mol, confirming the chemisorption process. the kinetic results followed the pseudo-second-order kinetic model. the results provide valuable insights into the adsorption mechanism of mb on cns ac, which can be used to optimize the adsorption process and improve the removal efficiency. ● supplementary materials no supplementary materials are available. ● funding this research had no external funding. ● acknowledgments we acknowledge ho chi minh city university of technology (hcmut), vnu-hcm for supporting this study. ● author contributions conceptualization: d.q.n. data curation: h.d.t. investigation: h.d.t. methodology: d.q.n., h.d.t. validation: d.q.n. writing – original draft: h.d.t. writing – review & editing: d.q.n. ● conflict of interest the authors declare no conflict of interest. ● additional information author ids: hai d. tran, scopus id 56226812800; dinh quan nguyen, scopus id 15123160800; websites: ho chi minh university of natural resources and environment, http://www.hcmunre.edu.vn/; ho chi minh city university of technology, http://www.hcmut.edu.vn/; vietnam national university ho chi minh city, https://vnuhcm.edu.vn/. references 1. khan i, saeed k, zekker i, zhang b, hendi ah, ahmad a, ahmad s, zada n, ahmad h, shah la. review on methylene blue: its 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new possibilities farit kh. urakaev ab * , natalya v. khan b , almagul i. niyazbayeva b , dinar n. zharlykasimova b, mukhambetkali m. burkitbayev b a: sobolev institute of geology and mineralogy, sb ras, novosibirsk 630090, russia b: faculty of chemistry, al-farabi kazakh national university, almaty 050040, kazakhstan * corresponding author: urakaev@igm.nsc.ru this paper belongs to a regular issue. abstract the task of this article is to update, develop and introduce into scientific practice the method of "mechanochemical recrystallization" in solid-phase systems with small additives of the liquid phase of the solvent and solid-phase precursors to stabilize the formed nanoparticles. the essence of this method is shown using the example of mechanical activation of the s–agno3–nh4x system, where x = cl, br, i, with the addition of dimethyl sulfoxide (dmso), and the resulting mechanochemical synthesis of sulfur-containing nanocomposites s/agx with the controlled content of sulfur nanoparticles (nanosulfur). the predetermined content of nanosulfur in nanocomposites is ensured by a continuous process of dissolution-crystallization (recrystallization) of starting sulfur in the dmso medium in a mechanochemical reactor. the proposed technical solution made it possible to obtain s/agx nanocomposites by a single mechanical treatment of powder precursors – agno3, nh4х, nh4no3 (diluent), commercial sulfur and dmso in planetary ball mills with various milling tools. the method also includes washing the water-soluble components of mechanosynthesis. keywords mechanical activation sulfur silver halides dimethyl sulfoxide recrystallization nanocomposites received: 27.03.23 revised: 16.05.23 accepted: 25.05.23 available online: 05.06.23 key findings ● a method for synthesis of nanocomposites based on silver halides and sulfur with controlled sulfur content in the dmso medium is proposed. ● the synthesis is carried out by mechanical activation of powder precursors – sulfur, silver nitrate, ammonium halides and nitrate. ● nanocomposite formation occurs as a result of reaction process of dissolution-crystallization (recrystallization) of precursors in the dmso medium. © 2023, the authors. this article is published in open access under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). 1. introduction the literature describes many examples of mechanochemical transformations that occur upon the addition of small amounts of liquid, and even introduces a special term, liquid assisted grinding (lag) [1–6]. typically, the liquid provides the very possibility of the transformation, or affects its rate, or the composition of the products. it is more difficult to find examples where the addition of a liquid was used to control the particle size and composition of the mechanosynthesis product. at the same time, the mechanisms of the influence of liquid on mechanochemical transformations remain debatable, and in many works they are not discussed at all [7–10]. the topic of the article is not related to the well-known phenomenon of "recrystallization" in the process of mechanical activation of solid-phase systems [7–18]. here it focuses on the possibility of obtaining nanoparticles and nanocomposites by reactive recrystallization of the initial solid precursors from a solution during their processing in a planetary ball mill with the addition of small amounts of liquid dmso – the precursor solvent [19]. for example, the following ways and results of the implementation of this area of research are known: – the method of mechanical activation of zinc oxide (zno) during its wet grinding with an increase in the solubility of zno to a certain level, subsequent http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2023.10.2.13 mailto:urakaev@igm.nsc.ru http://creativecommons.org/licenses/by/4.0/ https://orcid.org/0000-0001-9992-311x https://orcid.org/0000-0003-1794-0018 https://orcid.org/0000-0003-3180-7969 https://orcid.org/0000-0002-1472-1293 https://crossmark.crossref.org/dialog/?doi=https://doi.org/10.15826/chimtech.2023.10.2.13&domain=pdf&date_stamp=2023-06-05 https://journals.urfu.ru/index.php/chimtech/rt/suppfiles/6705/0 chimica techno acta 2023, vol. 10(2), no. 202310213 article 2 of 8 doi: 10.15826/chimtech.2023.10.2.13 recrystallization and the formation of defects in zno crystallites [20]; – the method for the preparation of nanoparticles of calcium carbonate (caco3) by high-energy grinding in sodium hypochlorite solutions of waste shells of molluscs tapes japonica with the formation of different phases caco3 is associated with mechanical activation of aragonite and dissolution-recrystallization of calcite [21, 22]; – the mechanochemical method for the preparation of nanoparticles of mordenite (18sio2:12naoh:780h2o) from zeolites, following a strategy of recrystallization with recovery after recrystallization of the crushed sample in a solution of hydrothermal basic silicate of high crystallinity of nano-mordenite with a decrease in the content of phase impurities [23]; – a mechanochemical approach is known for obtaining new solid forms of raloxifene hydrochloride (rhc), which is a benzothiophene derivative with low bioavailability for the treatment of osteoporosis due to its poor solubility in water, based both on its individual grinding and grinding with the addition of liquids [24]; – the effects of adding solvents and grinding times on the formation of a ternary salt were systematically studied, and the formation of a nylon 524t ternary salt under solvent-assisted grinding was found to follow a mechanically driven dissolution-recrystallization mechanism [25]; – the authors of this article described the mechanism of crystalline hydrate mechanosynthesis of nanosulfur [26] and copper sulfide nanocrystals [27, 28] from such precursors as copper acetate, sodium sulfide crystalline hydrate, citric acid, and sodium thiosulfate pentahydrate using wear-resistant milling tools. the present work is concerned with mechanochemical synthesis, in particular, with the preparation of sulfur-containing nanocomposites of silver halides s/agx, where x = cl, br, i [29, 30] with a controlled content of sulfur. the objective of the article is a systematic study into the method of "mechanochemical recrystallization" in the agno3– nh4x–s solid-phase system with small additions of the solvent phase – dmso, widely used to dissolve the components of this system [19]. in this case, the controlled content of sulfur in s/agx and the stabilization of the size of the resulting nanoparticles depend on the initial weight of powdered sulfur and the significant additions to this system of a water-soluble powder diluent – an inert additive or a byproduct of the reaction [31], respectively. the closest in technical essence to the proposed method of "mechanochemical recrystallization" are the solution methods for obtaining nanosulfur [32, 33] and sulfur-containing nanocomposites s / agx [29, 30, 34] using dmso. the disadvantage of this method is the impossibility of s / agx synthesis with a controlled sulfur content. the predetermined content of nanosulfur in nanocomposites is ensured by the process of dissolution-crystallization (recrystallization) of starting sulfur in a universal aprotic solvent dmso [19] in a mechanochemical reactor [35]. 2. experimental 2.1. materials and methods dmso, (ch3)2so, was purchased from dimethylsulfoxid biochemica, ≥99.5%, applichem gmbh, darmstadt, germany. silver and ammonium nitrates (agno3, nh4no3), ammonia halides (nh4cl, nh4br, nh4i) and sulfur (s) were purchased from sigma aldrich, germany. for washing, water purified by the purification system smart2pure (thermo scientific, usa) was used. the prepared samples were characterized by different techniques. phase composition of the powders was analyzed by x-ray diffraction (xrd) with a rigaku miniflex 600 xray diffractometer using copper radiation (λ = 0.15405 nm). for processing of x-ray diffraction patterns, the iccd-pdf2 release 2016 database was used. raman spectra of the samples were recorded on a solver spectrum (nt mdt instruments, russia) spectrometer using an 1800/500 diffraction grating, which provides a spectral resolution of 1 cm−1. the raman spectra were excited by a he-ne laser with a wavelength of 633 nm and processed with help of origin lab program. size, morphology and elemental composition of the samples were studied by a scanning electron microscope (sem) quanta 200i 3d (fei, netherlands) equipped by the energy dispersive x-ray analysis (edax) sensor. for the analysis, a mixture of 1 g of a sample and 40 ml of water was treated in an ultrasonic bath for 30 minutes. the sample of the resulting suspension was applied to a silicon microscope substrate. the images of the sulfur nanoparticles (nanosulfur) were produced with a jeol jem-1400 transmission electron microscope (tem; jeol; japan) with 80 kv accelerating voltage. the shape and sizes of the nanosulfur were determined by tem directly at the microscope location by dissolving-washing the mechanosynthesis product with water. the resulting sulfur slurry-colloid was immediately pipetted onto a collodion-coated copper grid for tem, and nanosulfur images were acquired as soon as possible. 2.2. mechanochemical preparation the milling process was realized in the planetary ball mills pulverisette 6 and 5 (fritsch, germany) in a tungsten carbide milling chamber with a volume of 250 ml (1-drum pulverisette 6) and stainless steel milling chambers with a volume of 1 l (4-drum pulverisette 5). the milling was performed in air, using tungsten carbide or stainless steel milling balls with a diameter of 10 mm, ball (600 g)-to-powder (10 g) ratio of 60, rotation speed of the planet carrier of 350 min−1, and a milling time of up to 30 minutes. synthesis of nanosulfur and nanocomposites ys*/agx, where x = cl, br, or i, by "mechanochemical recrystallization" was carried out according to the reactions (s – commercial sulfur; s* – sulfur recrystallized from dmso): https://doi.org/10.15826/chimtech.2023.10.2.13 https://doi.org/10.15826/chimtech.2023.10.2.13 chimica techno acta 2023, vol. 10(2), no. 202310213 article 3 of 8 doi: 10.15826/chimtech.2023.10.2.13 nh4i (diluent, 9 g) + s (1 g) + dmso (1–5 ml) = nh4i + s* + dmso (1–5 ml) (1) agno3 + nh4i + znh4no3 + ys + xdmso = agi + ys* + (z+1) nh4no3 (diluent)+ xdmso (2) agno3 + nh4x + znh4no3 + ys + xdmso = agx + ys* + (z+1)nh4no3 (diluent)+ xdmso (3) using pulverisette 6 for reaction (1), (2), and pulverisette 5 for (3) with ys* content 50 wt.% in s*/agx. advantages of the reactions chosen for the study include: solubility of precursors in dmso; the absence of water (for example, there are no crystalline hydrates) both in the initial precursors and in the products, except for their slight moistening due to the hygroscopicity of dmso [36– 38]; ease, simplicity and high speed of implementation. the essence of this approach is shown in scheme 1 (see also figures s1−s5 in the supplementary materials). it gives examples of the production of nanosulfur in a pulverisette 6 mill (scheme 1a, figure s1a), and nanocomposites s* / agi (scheme 1b, figures s3a, b) and s*/agx (scheme 1b, c) by realizing reactions (2) and (3) in the pulverisette 6 and 5 mills. the addition of the universal solvent, dmso, and neutral diluents (nh4i and nh4no3) makes it possible to stabilize the size of the formed sulfur and silver halide nanoparticles in the dmso medium. 3. results and discussion essentially, we are studying three processes in dmso: (i) preparation of nanosulfur (s*) by mechanochemical recrystallization of the initial sulfur; (ii) mechanosynthesis of nanocomposites based on it with an emphasis on obtaining s*/agi; and (iii) the effect of mechanical activation conditions on the synthesis of s*/agx nanocomposites. 3.1. recrystallization of sulfur in dmso first, according to reaction (1) and/or scheme 1a, we carried out the process of mechanochemical recrystallization in dmso of sulfur with an inert diluent nh4i to prove the transition of sulfur to a nanoscale state. the tem image of sulfur particles are shown in figure 1, and their sizes are in the range of 20–160 nm (average size is about 100 nm) and weakly depend on the amount of added dmso. 3.1.1. xrd, raman spectroscopy and sem-edax data figure s1a shows that the xrd peaks of the sulfur sample obtained by washing and drying the product of mechanical activation of the system sulfur (1 g) – ammonium iodide (9 g) – dmso (2 ml) completely correspond to its standard in the iccd-pdf2 database, pdf card no. 01-083-2283, in the orthorhombic structure (α−s8). the xrd software allowed to determine the size of coherent scattering blocks (crystallite size, d ≈ 70 nm) and lattice microdistortions (ε ≈ 0.2%), see figure s1b and [39–41]. the review article [42] shows that the α−s8 vibrational modes at 153 cm−1 and 220 cm−1 represent, respectively, asymmetric and symmetric bending of the s−s bond. the peak at 473 cm−1 is associated with s−s stretching in the s8 ring. a broad feature at ≈440 cm−1 is present in all solid sulfur allotropes, and corresponds to s−s stretching modes. a small but distinct peak at 248 cm−1 characterizes intramolecular α−s8 vibrations. external α−s8 vibrations in the low frequency range are due to a peak at 88 cm−1. these data are almost identical to the raman spectroscopy of our sulfur sample shown in figure 2. figure 1 tem images of aqueous suspension in the experiment on "mechanochemical recrystallization" of sulfur (weight 1 g), diluent ammonium iodide (nh4i; 9 g) in the pulverisette 6 mill with the addition of dmso (a – 1 ml; b – 5 ml) after dissolution and washing of the diluent and dmso with water. scheme 1 schematic representation of the target product synthesis in reactions (1)–(3) by mechanochemical recrystallization in dmso using planetary mills. pulverisette 6: nanosulfur with the choice of ammonium iodide as a diluent (a). pulverisette 6 and pulverisette 5: s*/agx or s*/agi nanocomposites when the by product of reactions (2) and (3), ammonium nitrate is chosen as a diluent (b). pulverisette 5: preparation of s*/agx nanocomposites with ultrasonic washing of water-soluble products of mechanosynthesis with water and drying of the target product (c). https://doi.org/10.15826/chimtech.2023.10.2.13 https://doi.org/10.15826/chimtech.2023.10.2.13 chimica techno acta 2023, vol. 10(2), no. 202310213 article 4 of 8 doi: 10.15826/chimtech.2023.10.2.13 according to the sem images, for example, the sulfur sample on the tab of figures s2, obtained by washing and drying the product of mechanical activation of the system sulfur (1 g) – ammonium iodide (9 g) – dmso (3 ml), in the enlarged scale is heterogeneous in size and shape of the particles. we can see the presence of both large and small fractions of spherical, flat and other differently shaped particles, mostly, in the form of submicron agglomerates. the presence of a thin layer on top of large particles is also noticeable. the elemental and 100% content of sulfur composition of the sample on the tab is as expected, since the device could not determine the content of other minor impurities due to technical capabilities. 3.2. nanocomposites s*/agi in pulverisette 6 mill similarly, according to reaction (2) and/or scheme 1b, from precursor powders agno3 (≈1.7 g), nh4i (≈1.5 g), nh4no3 (diluent, ≈4.5 g), commercial sulfur (≈2.3 g) and dmso (1÷5 ml) agi/s* nanocomposites were obtained in the pulverisette 6 mill. samples of agi/s* (after 3-fold washing of the water-soluble mechanosynthesis components with water using a centrifuge and drying of the resulting target product for 24 hours at 70 °c) were studied by xrd, raman and sem-edax methods. let us comment on the xrd data shown in figure s3 for the agi/s* nanocomposites. first, in figure s3a, the green pointers indicate the agi lines, which refer to the stable hexagonal phase β−agi and the metastable cubic phase γ−agi. figure s3a is dominated by β−agi lines, and figure s3b is dominated by γ−agi lines. the main sulfur lines, indicated by yellow pointers in figure s3a, refer to the most stable orthorhombic sulfur phase (s8), as in figure s3b. the results of the processing of xrd data using the williamson-hall construction program [39–41] is shown in figure s4. the data of the figures s4 (a–d) make it possible to find the values in crystallite sizes d along the indicated segments of the y-axis, and microdistortions of the lattices ε from the tangent of the slope angle of the straight line. the calculated mean values of d = 23 nm show the existence of nanosized blocks of coherent scattering of sulfur and silver iodide particles, and, in terms of ε = 0.22%, also the presence of their defective structure due to mechanical action on crystallites. the phase composition and component ratio of the agi/s* nanocomposites was also confirmed by raman spectroscopy, as shown in figure s5. it can be seen that there is no significant difference in the spectra of samples 1 (a) and 2 (b). according to the analysis, the sample is represented by silver iodide lines [43]: a peak with a small shoulder at a wave number of ≈106 cm–1; a clear peak at 83 cm–1 is due to the superposition of the lines of silver iodide at ≈74 cm–1 and sulfur at 88 cm–1 (figure 2). other wave numbers, equal to 154, 219, and 473 cm–1, correspond to sulfur in the s8 modification. an insignificant but noticeable peak at ≈246 cm–1 indicates intramolecular s8 vibrations, and a peak at ≈437 cm–1 can be attributed to both intermolecular s8 vibrations and the beginning of the s8 polymerization process [42]. the morphology and particle size were measured by sem (figures 3, 4a). the clear sem image in figure 3 shows that the agi/s* composite particles differ in shapes and sizes. a more detailed and enlarged examination of this image can establish that there are agglomerates of smaller particles and, moreover, nanosulfur sediments are found on their surface. the elemental composition of agi/s* were measured by sem equipped with an edax attachment (figure 4b, c) from which it can be seen that both the sulfur atomic content and the intensity of the sulfur line are close to those for ag and i. similar sem images are also available for agcl/s* and agbr/s*. figure 2 raman spectroscopy of the sulfur sample obtained by washing and drying the product of mechanical activation according to reaction (1) and/or scheme 1a with the addition of 2 ml of dmso (the numbers indicate the correspondence to the data of [42]). figure 3 sem image of agi/s* with the addition of 1 ml of dmso. https://doi.org/10.15826/chimtech.2023.10.2.13 https://doi.org/10.15826/chimtech.2023.10.2.13 chimica techno acta 2023, vol. 10(2), no. 202310213 article 5 of 8 doi: 10.15826/chimtech.2023.10.2.13 3.3. nanocomposites s*/agx in pulverisette 5 mill above, we discussed the results of studying agi/s* nanocomposites synthesized by reaction (2) in the 1-drum pulverisette 6 mill with tungsten carbide milling tools. below are the processed results of xrd (figure 5) and raman spectroscopy (figure 6) of agx/s* nanocomposites declared for completeness of the syntheses according to reactions (3) and/or scheme 1c in the 4-drum pulverisette 5 mill with stainless steel milling tools. xrd patterns of the s*/agcl, s*/agbr and s*/agi synthesized in the dmso medium (1–5 ml), pure sulfur (α−form) and corresponding cubic agx phases are given in figures 5 (a,b,c). it can be seen that they agree, complement and confirm the data in figures s1, s3 for the presence of phases in s*/agi and in figures s4(a,b,c,d) for d ~ 20 nm and ε~0.2%. discussing the data in figures s5 (a,b), we have already noted that s*/agi show a combination of s [42] and agi [43] peaks with an unchanged position; their strong superposition takes place, and these effects are even more typical for s*/agx nanocomposites obtained in the pulverisette 5 mill, as shown in figures 6 (a, b, c). according to the analysis of samples s*/agcl (figures 6a), there are three raman modes at 75, 86 and 240 cm−1 for pure agcl. the peaks at 75 and 240 cm−1 wavenumbers are related to agcl, while the peak at 86 cm−1 is characteristic of elemental ag, which can be formed under influence of the laser, because of the photosensitivity of agcl and its decomposition [22]. raman spectra for pure agbr (figures 6b) are represented by three characteristic peaks at about 70, 130 and 180 cm−1. the peaks at 70 and 130 cm−1 can be attributed to ag lattice vibrations. the peak at 180 cm–1 is conditioned by stretching of the ag−br bond, which is in agreement with the results for agcl considering the difference in mass. for pure agi (figures 6с) two peaks at 74 and 109 cm−1 are seen. the four peaks at 89, 158, 223 and 477 cm−1 are attributed to sulfur, and, as compared to figures s5, they shift to 83, 152, 219 and 474 cm−1. from figures 5, 6 it can also be established that the amount of dmso and the mill used have little effect on the results of xrd and raman spectroscopy. figure 4 sem image of the agi/s* sample with the addition of 5 ml of dmso: the studied field of edax application is given by a cross (a); the result of determining the elemental composition and it table form are given in (b) and in insertion (c). figure 5 results of xrd analysis of samples of mechanosynthesis of nanocomposites s*/agx, x = cl (a); br (b); i (c) with the addition of 5, 3, 2 and 1 ml of dmso in the pulverisette 5 mill. figure 6 raman spectra of samples of mechanosynthesis of nanocomposites s*/agx, x = cl (a); br (b); i (c) with the addition of 5, 3, 2 and 1 ml of dmso in the pulverisette 5 mill. https://doi.org/10.15826/chimtech.2023.10.2.13 https://doi.org/10.15826/chimtech.2023.10.2.13 chimica techno acta 2023, vol. 10(2), no. 202310213 article 6 of 8 doi: 10.15826/chimtech.2023.10.2.13 the proposed technical solution makes it possible to obtain, by single mechanical activation in a planetary ball mill with stainless steel fittings, sulfur-containing nanocomposites agx/s* (x = cl, br, i) of powder precursors – agno3, nh4x, nh4no3 (diluent [31]), commercial sulfur, and liquid phase – universal aprotic solvent dimethyl sulfoxide [19]. the predetermined content of nanosulfur in nanocomposites is provided by the process of dissolutioncrystallization (recrystallization) of sulfur in dimethyl sulfoxide in the mechanochemical reactor [35]. 4. limitations the most important problem for the proposed line of research is the correct assessment of the quantitative ratio of solid (powder precursors): liquid (solvent precursors). this is not the case, and, for example, in this work, for 10 grams of powder precursors, we took 1–5 ml of the liquid dmso solvent. it is intuitively clear that more than 5 ml of dmso seems unacceptable, but decreasing the amounts to less than 1 ml of dmso seems to be the prospect for further work. the second limitation is the choice of a solid-liquid system. in fact, there is no reason to believe that the sulfursilver-halides-dmso system considered here can claim exceptional scientific and applied significance. but the important thing is that there are many such systems, and there is always a chance of success. the last issue concerns the choice of a mechanochemical reactor. in this study, we used, one might say, the highestenergy devices for mechanical activation – planetary ball mills. however, when working with semi-liquid (or semisolid) systems, this is hardly necessary, and it seems that continuous mechanochemical reactors would be better suited here. 5. conclusions for the first time, the method of "mechanochemical recrystallization" in solid-phase systems with small additions of the liquid phase of the precursor solvent – dimethyl sulfoxide – was systematically studied and introduced into scientific practice. the essence of this method is demonstrated by the example of mechanical activation of 10 g of the agno3–nh4i–nh4no3 (diluent)-s system with variable additions of dmso (1–5 ml), which results in the mechanochemical synthesis of sulfur-containing agi/s nanocomposites with a controlled content of nanosulfur. the specified content of nanosulfur in nanocomposites during their synthesis in mechanochemical reactors is taken equal to 50% by weight and is provided by the reaction process of dissolution-crystallization (recrystallization) of the initial sulfur and precursors in dmso. the proposed method made it possible to obtain separately both nanosulfur and agi/s nanocomposites by a single mechanical treatment of powdered precursors agno3, nh4i, nh4no3, technical sulfur and dmso – in planetary ball mills pulverisette 6 (single-drum; accessories – tungsten carbide) and pulverisette 5 (fourdrum; accessories – stainless steel). the method also includes ultrasonic washing of water-soluble components of mechanosynthesis with distilled water using a centrifuge and drying the obtained target product for 24 hours at a temperature of 70 °c. ● supplementary materials this manuscript contains supplementary materials, which are available on the corresponding online page. ● funding this work is done on state assignment of igm sb ras (n0. 122041400031-2) and was supported by the ministry of science and higher education of the republic of kazakhstan (grant no. ap08855868). ● acknowledgments none. ● author contributions conceptualization: f.k.u. data curation: m.m.b. formal analysis: m.m.b., n.v.k., a.i.n. funding acquisition: f.k.u., n.n.k. investigation: f.k.u., n.n.k., a.i.n., d.n.z. methodology: f.k.u., m.m.b., n.v.k. project administration: m.m.b., a.i.n. resources: m.m.b., a.i.n., d.n.z. software: f.k.u., n.n.k. supervision: m.m.b., a.i.n. validation: m.m.b., n.v.k. visualization: f.k.u., m.m.b., n.n.k. writing – original draft: f.k.u., n.n.k. writing – review & editing: f.k.u. ● conflict of interest the authors declare no conflict of interest. ● additional information author ids: farit kh. urakaev, scopus id 35619573400; natalya v. khan, scopus id 57214114418; almagul i. niyazbayeva, scopus id 6505546558; dinar n. zharlykasimova, scopus id 56912424400; mukhambetkali m. burkitbayev, scopus id 8513885600. websites: sobolev institute of geology and mineralogy, https://www.igm.nsc.ru/index.php/en; https://doi.org/10.15826/chimtech.2023.10.2.13 https://doi.org/10.15826/chimtech.2023.10.2.13 http://www.scopus.com/inward/authordetails.url?authorid=35619573400 http://www.scopus.com/inward/authordetails.url?authorid=57214114418&partnerid=mn8toars http://www.scopus.com/inward/authordetails.url?authorid=6505546558 http://www.scopus.com/inward/authordetails.url?authorid=56912424400 http://www.scopus.com/inward/authordetails.url?authorid=8513885600&partnerid=mn8toars https://www.igm.nsc.ru/index.php/en chimica techno acta 2023, vol. 10(2), no. 202310213 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https://doi.org/10.21203/rs.3.rs-1586320/v1 https://doi.org/10.1038/s41598-019-44353-6 https://doi.org/10.1002/slct.202000502 synthesis and properties of polymer electrolytes based on polyurethane elastomer and lithium salts published by ural federal university eissn 2411-1414 chimicatechnoacta.ru letter 2023, vol. 10(3), no. 202310311 doi: 10.15826/chimtech.2023.10.3.11 1 of 5 synthesis and properties of polymer electrolytes based on polyurethane elastomer and lithium salts nikita fedorov * , artem ulihin , nikolai uvarov institute of solid state chemistry and mechanochemistry sb ras, novosibirsk 630090, russia * corresponding author: f-nikita08@mail.ru this paper belongs to the rkfm'23 special issue: https://chem.conf.nstu.ru/. guest editors: prof. n. uvarov and prof. e. aubakirov. abstract polymer solid electrolytes were obtained by swelling the polyurethane elastomer with solutions of lithium salts libf4 and liclo4 in dmso at different concentration of lithium salt. the swelling effect was found to decrease with the increase in the salt concentration, whereas the ionic conductivity has a maximum of 6–8·10–4 s/cm at 5 wt.% lithium salt. the salt solutions incorporated into the polymer pores have melting points ranging from –10 to 2 °c and deswelling takes place at low temperatures. the obtained polyurethane elastomer materials have a high conductivity and may be promising for use in flexible lithium polymer batteries. keywords polymer solid electrolytes polyurethane elastomer swelling effect ionic conductivity effect of the salt concentration on swelling and conductivity received: 12.07.23 revised: 13.08.23 accepted: 22.08.23 available online: 24.08.23 © 2023, the authors. this article is published in open access under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). 1. introduction lithium batteries have gained high importance at present. they are widely used in portable electronic devices, electric vehicles, various energy storage applications and other fields due to their high energy density and excellent service life [1–3]. however, safety concerns because of the growth of lithium dendrites and the resulting short circuit when using liquid electrolytes significantly complicate further development and limit their use. an alternative solution could be to replace the liquid electrolyte with a solid polymer electrolyte (spe). in addition, this would help to solve the problems of fire and explosion in liquid electrolytes using organic solvents [4–7]. ionic conductivity of polymer solid electrolytes occurs via flexible fragments that form an amorphous subsystem (so-called gel phase), whereas hard fragments form crystalline regions of the polymer [3–7]. there are several approaches to increasing the concentration of the amorphous phase: the variation of the concentration or chemical composition of linking functional groups, and the introduction of heterogeneous additives, such as carbon nanotubes or oxide fillers. swelling of electrolyte solutions may also result in a considerable increase in the concentration of gel phase and the increase in the conductivity [12]. in this case the swelling should not lead to the loss of the mechanical stability of the polymer. polyurethane is a promising material as a matrix for creating solid polymer electrolytes. this material has flexible structural designs, can be easily modified (with polymers or fillers), and possesses specific functions (selfhealing, protective layer or high adhesion). owing to these characteristics, it is possible to obtain a higher energy density and use a metal lithium anode in batteries. to date, to our knowledge, most polyurethane-based solid polymer electrolytes have been synthesized using chain extenders, catalysts, and organic solvents, followed by a complex polymerization process. genier et al. [9] synthesized a polymer based on polytetrahydrofuran (pthf) and epoxy resin using a cationic initiator and a photo-initiator. the resulting polymer was impregnated in a libf4 salt solution in acetonitrile, followed by drying to constant weight. despite the long and complicated manufacturing process, the authors managed to obtain a material with ionic conductivity from 8.9·10–6 to 7.8·10–4 s/cm, stability over a wide temperature range, and mechanical strength. another promising approach to the preparation of solid polymer electrolytes was demonstrated by zhao et al. [10], who synthesized a pre-polymer by mixing toluene diisocyanate with polypropylene glycol with the addition of the litfsi salt dissolved in dimethyl http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2023.10.3.11 mailto:xx@yy.zz http://creativecommons.org/licenses/by/4.0/ https://orcid.org/0009-0000-9192-2075 https://orcid.org/0000-0002-6795-0006 https://orcid.org/0000-0002-8209-7533 https://crossmark.crossref.org/dialog/?doi=https://doi.org/10.15826/chimtech.2023.10.3.11domain=pdf&date_stamp=2023-08-24 chimica techno acta 2023, vol. 10(3), no. 202310311 letter 2 of 5 doi: 10.15826/chimtech.2023.10.3.11 carbonate to the resulting mixture. a chain extender and a catalyst were added to the obtained pre-polymers, after which they were poured into moulds for 7 days until complete polymerization. they managed to achieve the maximum ionic conductivity of 9.6·10–5 s/cm at 55 °c. in addition, the polymer electrolyte had good chain flexibility and thermal stability. in this work, polyurethane-based ion-conducting polymer electrolytes were prepared using a commercially available pre-polymer based on p-phenylene diisocyanate (p-pdi) and polyether, 3,3'-dichloro-4,4'-diaminodiphenylmethane (moca) curing agent, and lithium salts, libf4 and liclo4, dissolved in dimethyl sulfoxide (ch3)2so (dmso) by elastomer swelling in solutions with different concentrations of lithium salts. the ionic conductivity of the obtained polymer electrolytes was investigated. 2. experimental a quantity of the adiprene® lfp 1950a, a ppdi terminated polyester prepolymer (crompton corporation), heated to 50 °c was mixed with a given amount of the moca hardener (3,3'-dichloro-4,4'-diaminodiphenylmethane c12h12n2cl2, chemically pure, manufactured by jiangsu xingyuan chemical co ltd) heated to 110 °c using a dispermat cn dissolver at 2000 rpm for 30 s for degassing. next, the resulting liquid mixture was poured into a metal mould and heated for 1 h at 110 °c. then the mould was cooled to room temperature, and the sample was removed and condensed for 7 days before experiments. the synthesis scheme is presented in figure 1. before preparing electrolytes, lithium salts were dried under low vacuum at 150 °c for 24 h. next, electrolytes were prepared in dmso with a given concentration of lithium salts. swelling of polymers with solutions of lithium salts was carried out in a hermetically sealed vessel for 48 h. conductivity measurements were carried out in an argon atmosphere using a two-electrode scheme in the frequency range 25 hz – 1 mhz using an mnipi e-25 immittance meter. conductivity values were determined from the analysis of nyquist plots. differential scanning calorimetry (dsc) was performed on a dsc 204 f1 phoenix netzsch instrument (germany). aluminum (al) crucibles for analysis were pre-calcined at 100 °c. the samples were cooled from 25 °c to –40 °c at a rate of 10 °c/min, kept at –40 °c for 10 min to balance the calorimeter system, then heated to 60 °c at a rate of 10 °c/min. the analysis was carried out under the argon (ar) flow at a rate of 100 ml/min. 3. results and discussion at first, the attempts were made to introduce the lithium salt libf4 and liclo4 directly into the elastomer matrix on heating of the polymer-salt mixtures. as pure salt turned to be insoluble in the polymer, the experiments were performed on swelling the polymer matrix with the solutions of libf4 and liclo4 in dmso. the swelling effect was estimated by the relative change in the polymer mass after the storage of the polymer in the solutions libf4 or liclo4 with different concentrations of the salt. the mass of the samples was measured every hour until the constant mass achieved. results of the swelling experiments are shown in figure 2. as can be seen, the weight gain monotonically decreases by about 10 times with the increase in the salt concentration in the solutions of libf4 or liclo4 in dmso from 1 to 15%. this effect was observed earlier for polyelectrolyte hydrogels [10, 11] and can be explained in terms of the modified flory and rehner theory [14–16] by the interplay between the entropy contribution, osmotic pressure of the solvent and the salt, and the mechanical strain of the polymeric network caused by the incorporation of the salt solution [14–16]. therefore, to achieve the highest lithium content in the polymer, solutions with a moderately high concentration of lithium salts should be used. figure 1 the scheme of the synthesis of polyurethane elastomer, used for the preparation of the polymer solid electrolytes. https://doi.org/10.15826/chimtech.2023.10.3.11 https://doi.org/10.15826/chimtech.2023.10.3.11 chimica techno acta 2023, vol. 10(3), no. 202310311 letter 3 of 5 doi: 10.15826/chimtech.2023.10.3.11 ionic conductivity data for polymer electrolytes obtained after the swelling are presented in figure 3. the dependences of the conductivity on the salt concentration in the libf4 or liclo4 solutions used for swelling have a pronounced maximum at 5 wt.% of the salt, both for the lithium tetrafluoroborate and lithium perchlorate. the presence of the maximum can be explained by the competition between two factors: an increase in the total content of lithium in the solution introduced into the bulk of the polymer during swelling, and a decrease in the total amount of the solution entering the polymer with an increase in the salt concentration. the maximum conductivity of polymers obtained by swelling in solutions of lithium salts was 8.6·10–4 s/cm and 9.1·10–4 s/cm at 25 °c for libf4 and liclo4 salts, respectively. a change in temperature from 25 to 75 °c does not have a significant effect on the ionic conductivity of solid polymer electrolytes, which is associated with a low value of the activation energy of conductivity of 0.13±0.03 ev. low values of the activation energy suggest that the conductivity of the polymers under study is caused by a liquidlike gel phase formed in the pores of the polymer as a result of the swelling of salt solutions in dmso. in order to investigate thermodynamic properties of the electrolyte phase in polymers, thermal analysis studies were carried out. figure 4 shows thermal analysis curves obtained for pure dmso, initial libf4 solutions in dmso, and the polymers after swelling with libf4-dmso solutions of different concentrations. the heat effect observed on the heating relates to the melting of dmso or libf4-dmso solutions, as the pure polymer melts at temperatures above 150 °c with partial decomposition. as seen from figure 5, the intensity of the peak related to the melting process monotonically decreases with the libf4 concentration. comparison of these data with those presented in figure 2 suggests that the peak intensity changes proportionally to the total amount of the libf4-dmso solution absorbed by the polymer matrix as a result of the swelling. the fraction of the amorphous gel phase also decreases with the libf4 concentration, leading to the decrease in the ionic conductivity. figure 2 the dependence of the relative change of the elastomer mass on the concentration of libf4 in the source solution. figure 3 the dependences of the conductivity of polymer electrolytes on the salt concentration in solutions of libf4 (a) or liclo4 (b) used for swelling the polymer. figure 4 thermal analysis curves obtained for (a) pure dmso (curve 1) and libf4-dmso solutions containing 5 and 10 wt.% libf4 (curves 2 and 3, respectively); (b) pure dmso (curve 1) and polymers after swelling with pure dmso (curve 2) and libf4-dmso solutions containing 5, 7, 10 and 15 wt.% libf4 (curves 3, 4, 5 and 6, respectively). https://doi.org/10.15826/chimtech.2023.10.3.11 https://doi.org/10.15826/chimtech.2023.10.3.11 chimica techno acta 2023, vol. 10(3), no. 202310311 letter 4 of 5 doi: 10.15826/chimtech.2023.10.3.11 figure 5 the dependence of the relative change h/h0 of the melting enthalpy of libf4-dmso solutions included into the polymer matrix (h0 is the melting enthalpy of pure dmso in the polymer) on the concentration of libf4 in the source solution. the melting temperatures of libf4 solutions are lower than that of pure dmso, which is typical for solvent-salt systems. the incorporation of pure dmso into the polymer pores during swelling leads to a noticeable decrease in its melting temperature: the peak temperature of the heat effect related to the melting shifts from 16.7 to 5.6 °c. such decrease may be explained by a size effect, as an effective “particle” size of dmso is limited by the volume of pores occupied by dmso in the polymer matrix. in contrast to pure dmso, melting temperatures of the salt solutions located in the polymer are close to those for the initial solutions. moreover, the melting peak splits into two components. it is known that swelling effect increases with temperature [12, 15–17], hence on cooling the effect should vanish. therefore, experimentally observed thermal analysis data suggest that partial or complete deswelling of the solutions takes place at low temperatures. 4. limitations the present study is an initial stage of a complex investigation of polymer solid electrolytes based on polyurethane elastomers. these investigations should include: – optimization of the polymer structure by variation of the concentration of the cross-linking agent. it will allow one to control the internal free volume, elastic properties of the polymer and its ionic conductivity; – study of the swelling of other salts with different cations or anions. in particular, it would be of interest to study a series of lithium salts with cosmotropic and chaotropic anions [18] and their influence upon the swelling behaviour and ionic conductivity of the polymer solid electrolytes containing these salts; – investigation of ionic conductivity of polymer electrolytes in a wide temperature range, especially at low temperatures. such experiments would give information on the glass transitions of amorphous states of ionic salts in polymers, on deswelling processes, and could also enable estimating the possibilities of the practical applications of the polymer solid electrolytes in flexible lithium batteries. 5. conclusions in this work polymer solid electrolytes were obtained by swelling the polyurethane elastomer with solutions of lithium salts libf4 and liclo4 in dmso at different concentration of lithium salt. the swelling effect was observed for pure dmso and was found to decrease with the increase in the salt concentration, whereas the ionic conductivity has a maximum at 5 wt.% lithium salt. the salt incorporated into the polymer pores has a melting temperature ranging from –10 to 2 °c. at low temperatures the deswelling effect seems to be present. nevertheless, the polymer electrolytes obtained in this work have a high ionic conductivity of nearly 10–3 s/cm that is comparable with the best polyurethane elastomer analogues [19, 20]. thus, the obtained polyurethane elastomer membranes showed a high ionic conductivity at room temperature and may be promising for use in flexible lithium polymer batteries. ● supplementary materials no supplementary materials are available. ● funding the work is supported by the ministry of science and higher education of the russian federation, the state assignment no. 121032500065-5. ● acknowledgments the authors thank kristina marchenko for carrying out the thermal analysis experiments. ● author contributions conceptualization: n.u. data curation: a.u. formal analysis: n.u, a.u investigation: n.f. methodology: a.u. project administration: n.u. supervision: n.u. validation: n.u., a.u. writing – original draft: n.f. writing – review & editing: n.u. ● conflict of interest the authors declare no conflict of interest. ● additional information author ids: artem ulihin, scopus id 15046088200; https://doi.org/10.15826/chimtech.2023.10.3.11 https://doi.org/10.15826/chimtech.2023.10.3.11 https://www.scopus.com/authid/detail.uri?authorid=15046088200 chimica techno acta 2023, vol. 10(3), no. 202310311 letter 5 of 5 doi: 10.15826/chimtech.2023.10.3.11 nikolai uvarov, scopus id 7006949152. website: institute of solid state chemistry and mechanochemistry sb ras, http://www.solid.nsc.ru/. references 1. armand m, tarascon jm. building better batteries. nat. 2008;451(7179):652–657. doi:10.1038/451652a 2. dunn b, kamath h, tarascon jm. electrical energy storage for the grid a battery of choices. sci. 2011;334(6058):928–935. doi:10.1126/science1212741 3. zhou q, ma j, dong s, li x, cui g. intermolecular chemistry in solid polymer electrolytes for high-energy-density lithium batteries. adv mater. 2019;31(50):1902029. doi:10.1002/adma.201902029 4. zhang d, meng x, hou w, hu w, mo j, yang t, zhang w, fan q, liu l, jiang b, chu l, li m. solid polymer electrolytes ion conduction mechanisms and enhancement strategies. nano res energy. 2023;2:e9120050. doi:10.26599/nre.2023.9120050 5. agrawal rc, pandey gp. solid polymer electrolytes: materials designing and all-solid-state battery applications an overview. phys. 2008;41(22):223001. doi:10.1088/00223727/41/22/223001 6. quartarone e, mustarelli p. electrolytes for solid-state lithium rechargeable batteries: recent advances and perspectives. chem soc rev. 2011;40:2525–2540. doi:10.1039/c0cs00081g 7. rosero d, meneses j, uribe-kaffure r. composite polymer electrolytes based on (peo)4cf3cooli and multi-walled carbon nanotube (mwcnt). polym. 2023;15(1):49. doi:10.3390/polym15010049 8. sun c, liu j, gong y, wilkinson d, zhang j. recent advances in all-solid-state rechargeable lithium batteries. nano energy. 2017;33:363–386. 10.1016/j.nanoen.2017.01.028 9. francielli s, barna j, wang j, biria s, ian d. solid polymer electrolyte from photo-crosslinked polytetrahydrofuran and a cycloaliphatic epoxide for lithium-ion conduction. mrs advances. 2020;5:2467–2476. doi:10.1557/adv.2020.274 10. zhao h, zhang w, yin x, wu y, du c, zhao w, zhaoab l, liu c. conductive polyurethane elastomer 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electrolytes synthesized from hdi and peo of different molecular weight. electroanal chem.2021;893:115305. doi:10.1016/j.jelechem.2021.115305 https://doi.org/10.15826/chimtech.2023.10.3.11 https://doi.org/10.15826/chimtech.2023.10.3.11 https://www.scopus.com/authid/detail.uri?authorid=7006949152 http://www.solid.nsc.ru/ https://doi.org/10.1038/451652a https://doi.org/10.1126/science1212741 https://doi.org/10.1002/adma.201902029 https://doi.org/10.26599/nre.2023.9120050 https://doi.org/10.1088/0022-3727/41/22/223001 https://doi.org/10.1088/0022-3727/41/22/223001 https://doi.org/10.1039/c0cs00081g https://doi.org/10.3390/polym15010049 https://doi.org/10.1016/j.nanoen.2017.01.028 https://doi.org/10.1557/adv.2020.274 https://doi.org/10.1039/c9ra10944g https://doi.org/10.22037/ijpr.2012.1097 https://doi.org/10.1039/b512748c https://doi.org/10.3390/ma12091464 https://doi.org/10.1088/2399-1984/ab45d5 https://doi.org/10.1063/5.0048152 https://doi.org/10.1016/j.ijmecsci.2018.06.011 https://doi.org/10.1115/1.4036113 https://doi.org/10.1021/acs.langmuir.5b02698 https://doi.org/10.1149/1945-7111/ab8ed2 https://doi.org/10.1016/j.jelechem.2021.115305 the effect of ammonia activation on the desalination potential of natural zeolite published by ural federal university eissn 2411-1414 chimicatechnoacta.ru letter 2023, vol. 10(4), no. 202310305 doi: 10.15826/chimtech.2023.10.3.05 1 of 5 the effect of ammonia activation on the desalination potential of natural zeolite aruzhan k. kenessova ab * , akmaral b. rakhym ab , bagashar b. zhaksybay ab , gulziya a. seilkhanova ab a: department of physical chemistry, catalysis and petrochemistry, al-farabi kazakh national university, almaty 050040, kazakhstan b: center of physicochemical methods of research and analysis, almaty 050012, kazakhstan * corresponding author: kenessova.aruzhan@gmail.com this paper belongs to the rkfm'23 special issue: https://chem.conf.nstu.ru/. guest editors: prof. n. uvarov and prof. e. aubakirov. abstract despite the abundance of water bodies on earth, there is a limited amount of potable water. therefore, the desalination process is of great interest. adsorption of the main contaminants of saline water (na+, k+, cl– ions) is an alternative process of desalination. in the present work, a sorbent based on natural zeolite (nz) modified with ammonium chloride (nh4cl) is obtained and the effect of modification on the removal of na+ and k+ ions from saline water is studied. according to the brunauer-emmett-teller (bet) analysis, the modification of zeolite with nh4cl leads to an increase in its surface area (7.85 to 8.09 m2/g). according to the results of the cation exchange capacity (cec) determination, the modification leads to a decrease in total cec of zeolite (431.67±29.01 to 300.88±31.86 meq/100 g). according to the obtained results, ammonia modification enhances the adsorption ability of nz to extract na+ and k+ ions from saline water. the extraction degree (e) of na+ ions by nh4-z increases from 7.93±1.63 to 10.44±1.52%, while for k+ ions it increases about 2 times (27.69±2.45 to 56.46±3.71%). these results indicate that the ammonia-modified nz can potentially be used as a desalination agent for the removal of na+ and k+ ions from saline water. keywords natural zeolite ammonia activation desalination sodium adsorption potassium adsorption received: 30.06.23 revised: 30.07.23 accepted: 02.08.23 available online: 04.08.23 key findings ● modification of zeolite with nh4cl leads to an increase in its surface area, enhancing its adsorption capabilities. ● the modified zeolite, nh4-z, shows higher selectivity for na+ and k+ ions, resulting in increased extraction percentages. ● nh4cl modification alters zeolite's cation-exchange capacity, favoring enhanced na+ and k+ ion adsorption for desalination. © 2023, the authors. this article is published in open access under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). 1. introduction water is one of the main vital human needs. it is one of the most abundant substances on earth. but despite its abundance, there is only a limited amount of potable water available for human use. the scarcity of fresh water affects people’s daily lifes as well as agriculture, food processing, the economy, and other aspects of life [1]. as the population grows, the need for water becomes an urgent problem. according to recent investigations, 40% population of the earth is already facing water shortages. these data are estimated to grow up to 60% by 2025 [2]. various methods, such as disinfection, aeration, distillation, coagulation, etc., have been used to obtain fresh water [3]. these methods are aimed at removing contaminants from wastewater, such as inorganic and organic impurities, microbes, heavy metal ions, and radiological contaminants. despite the availability of different wastewater purification techniques, they work better in combination by creating multi-stage purification. however, this method tends to be time and energy consuming. saline water desalination is an alternative solution to the problem of freshwater scarcity. desalination is the process of reducing the salinity of saline water [4, 5]. achttp://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2023.10.3.05 https://orcid.org/0000-0001-5452-7543 http://creativecommons.org/licenses/by/4.0/ https://orcid.org/0000-0001-9532-4072 https://orcid.org/0009-0007-1654-5784 https://orcid.org/0000-0002-9939-8316 https://crossmark.crossref.org/dialog/?doi=https://doi.org/10.15826/chimtech.2023.10.3.05&domain=pdf&date_stamp=2023-08-04 chimica techno acta 2023, vol. 10(4), no. 202310402 letter 2 of 5 doi: 10.15826/chimtech.2023.10.3.05 cording to the world health organization (who), the salinity limit for drinking water is 500 ppm [5]. currently, many countries provide fresh water to their the population by by desalting saline water reserves [6, 7]. the desalination process was invented in the 18th century. since then, different desalination methods have been developed. they are reverse osmosis (ro), thermal desalination, multistage flash desalination (msf), multi-effect distillation (med), electrodialysis, and nanofiltration (nf) [8–12]. however, the commercialized desalination methods have several drawbacks, such as the high cost of desalination plants for developing countries that are currently experiencing drinking water storage and high energy consumption [13]. therefore, the existing methods still need to be improved. adsorption is an alternative approach to solving the problem of freshwater scarcity. it is of interest due to its simplicity and effectiveness. adsorption does not require energy consumption [14, 15]. the main contaminants of saline water are na+, k+, and cl– ions, which determine the salinity level of the water. the adsorption of these ions by adsorbent enables freshwater production. however, the use of the adsorption process by any adsorbent for desalination is a relatively new approach. the main challenge here is to develop an effective adsorbent that provides a high adsorption value for the removal of na+, k+, cl– ions. aluminosilicate raw materials (zeolites, clays, etc.) are quite effective and widespread materials, with high sorption activity towards various substances and relatively low cost [14]. zeolites are well-known for their adsorption and ion exchange properties, especially towards various heavy metals and organic compounds [15, 16]. various investigations regarding saline water desalination by zeolites have been carried out. zeolites, especially clinoptilolite, have high cation selectivity and cation exchange capacity (cec), as well as they are non-toxic and low-cost. all these properties make zeolites suitable for the adsorption of na+, k+, cl– ions, thus desalinating saline water [17, 18]. the use of zeolites in the desalination process is one of the promising ways to solve freshwater scarcity. various works have been done to further enhance the adsorption properties of aluminosilicate and other raw materials for desalination purposes. ahmed s. alsaman et al. used hcl acid pretreatment in the preparation of composite silica-gel [19]. in another study, alsaman et al. used acid pretreatment to enhance the adsorption properties of bentonite [20]. moreover, guo et al. investigated the use of zeolite modified with nacl to remove k+ ions from seawater and brackish water [21]. acid treatment was also found to be effective for the use of natural zeolite in adsorption processes [22, 23]. this study is aimed at describing the physicochemical characteristics of the natural zeolite (nz) and modified nz of the shankanai deposit (almaty region, kazakhstan). the key novelty of this study is the modification of nz using nh4cl to enhance its effectiveness in removing na+ and k+ ions from saline water. 2. experimental the following materials and reagents were used for the experiments: zeolite of shankanai deposit (almaty origin), nh4cl, agno3, nacl, kcl. 2.1. natural zeolite modification modified zeolite was obtained by treating dried and ground nz with 1 m nh4cl solution at a ratio of 1:5 for 24 hours and rinsing it with distilled water until the excess cl– ions were removed. the presence of cl– ions was checked by qualitative analysis with 0.1 m agno3 solution. 2.2. sample characterization the morphology of nz and nh4-z was studied, and the elemental analysis was performed using a scanning electron microscope (sem) (quanta 3d 200i dual system, fei, usa) equipped with energy dispersive x-ray spectroscopy (edx). the specific surface area of the zeolite samples was determined by the brunauer-emmett-teller (bet) method. fourier-transform infrared spectroscopy (ftir) analysis was performed to identify the chemical bonds present in the zeolite samples. 2.3. cation-exchange capacity determination for the determination of the cation-exchange capacity (cec) of the samples, the standard method with nh4cl was applied [24]. zeolite samples were mixed with a 1 m nh4cl solution in a ratio of 1:100 and stirred for 24 h on a laboratory shaker (lauda, germany). the suspensions were then centrifuged using a z 306 hermle universal centrifuge (labnet, usa). the cec was calculated as the sum of the concentrations of released na+, k+, mg2+, and ca2+ ions which were calculated using the following formula: 𝑀𝑚𝑒𝑞/100 𝑔 = 𝐶𝑝𝑝𝑚 (𝑒𝑞. 𝑤𝑡 · 10), (1) where mmeq/100 g is the concentration of released cation expressed in meq/100 g; cppm is the concentration of released cation expressed in ppm; eq.wt. is the equivalent weight of the released cation. 2.4. adsorption study the ability of the obtained sorbents to absorb na+ and k+ ions was studied at room temperature. for this purpose, the separate solutions containing na+ and k+ ions with a concentration of 100 mg/l were prepared. 0.1 g of the sorbent was placed in a measuring beaker, filled with 10 ml of the solution, and stirred on the laboratory shaker at room temperature (25±5) °c for 24 hours. then the solution was filtered, and the adsorption value and extraction degree were calculated. the adsorption value was calculated using the following formula: 𝐴 = 𝑐0 − 𝑐𝑒𝑞 𝑚 · 𝑉, (2) where c0 and ceq are initial and equilibrium concentrations of the sorbate, mcg/cm3; v is a volume of the sorbate solu https://doi.org/10.15826/chimtech.2023.10.3.05 chimica techno acta 2023, vol. 10(4), no. 202310402 letter 3 of 5 doi: 10.15826/chimtech.2023.10.3.05 tion, l; m is a sample mass, g. extraction degree of the ions was calculated as follows: 𝐸 = 𝑐0 − 𝑐𝑒𝑞 𝑐0 ∗ 100 %. (3) the initial and equilibrium concentrations of ions were determined by laboratory ionometer “i-160mi” (measuring equipment, russia). 3. results and discussion 3.1. sem the sem images of zeolite samples are presented in figure 1. it can be seen from the sem micrographs that after modifying nz with nh4cl the material becomes looser and a slight increase in the porosity of the surface of the particles is observed. 3.2. elemental analysis the results of the elemental analysis of the zeolite samples are presented in table 1. all the samples contain mainly o, si, and al followed by minor amounts of na, mg, k, ca, and fe. treatment of natural zeolite with 1 m nh4cl leads to a slight increase in the amount of sodium, magnesium, potassium and iron. the changes in the content of elements after modification could be because ammonium ions have a higher affinity for the zeolite’s framework compared to sodium and potassium ions. the selectivity of ammonium ions for those ions could possibly enable the nh4-z to remove these ions from saline water by ion exchange. 3.3. bet bet analysis allows us to define the specific surface area of the studied materials. table 2 represents the the specific surface area values of the initial and modified zeolite. treatment with 1 m nh4cl slightly increases the surface area of nz from 7.85 to 8.09 m2/g, making it favorable for adsorption processes. 3.4. ftir spectroscopy the spectra of nz and nh4-z are shown in figure 2. the ftir spectrum of nz shows prominent peaks at 1025.40 cm–1, 1633.35 cm–1, and 3444.88 cm–1. in the ir spectrum of nz, a strong band at 1025.40 cm–1 corresponds to the stretching vibrations of si–o–si and si–o–al bonds. the peak at 1633.35 cm–1 and 3444.88 cm–1 indicates the vibrations of present water and oh-groups in the structure of nz, suggesting the presence of moisture in the zeolite structure. after the modification, a peak at 761.19 cm–1 appears on the spectrum. the peak at 761.19 cm–1 in the spectrum of nh4-z may be related to the potential change in the tetrahedral structure of zeolite. 3.5. cec the adsorption capacity of zeolites is usually explained by their ion-exchange properties. therefore, an investigation of the cec of zeolite samples is done. the results of cec are presented in table 3. from the cec results of nz, it can be seen that the zeolite contains more calcium ions than the other exchange cations. the second abundant element is sodium. this could be explained by the fact that sodium ions react more easily than magnesium in the ionexchange processes. in the case of nh4cl modification, the release of magnesium and calcium ions decreased significantly, while the sodium and potassium content only slightly decreased, making the total cec to decrease. figure 1 sem images of nz (a) and nh4-z (b). table 1 results of the elemental analysis of the samples. sample c, wt.% o, wt.% na, wt.% mg, wt.% al, wt.% si, wt.% k, wt.% ca, wt.% fe, wt.% nz 3.13 44.97 2.53 2.23 10.18 27.51 1.02 2.99 4.78 nh4-z 3.16 39.83 3.63 2.44 10.22 25.89 1.66 1.66 10.73 https://doi.org/10.15826/chimtech.2023.10.3.05 chimica techno acta 2023, vol. 10(4), no. 202310402 letter 4 of 5 doi: 10.15826/chimtech.2023.10.3.05 figure 2 ftir spectra of (a) nz and (b) nh4-z. table 2 specific surface area of sorbents. sorbent surface area, m2/g nz 7.85 nh4-z 8.09 3.6. adsorption of na+ and k+ ions the absorption capacity of the zeolite samples towards na+ and k+ ions were investigated. the results of the study are presented in table 4 below. from the data in the table, it can be concluded that the modification of nz with nh4cl enhances its adsorption capacities, increasing the extraction degree of na+ ions from 7.93 to 10.44 % and increasing the removal of k+ 2 times. clearly, the modified zeolite has demonstrated a higher affinity for k+ ions compared to na+ ions. this finding is significant and suggests that the obtained adsorbents could be promising materials for application in the desalination of potash brine-impacted groundwater. table 4 adsorption of na+ and k+ ions by zeolite samples. sample e(na+), % e(k+), % nz 7.93±1.63 27.69±2.45 nh4-z 10.44±1.52 56.46±3.71 4. limitations the modified zeolite shows a significant change in the extraction of potassium ions. however, there is no notable change in the extraction of sodium ions. using the twostep modification (ammonia and acid activation) of nz could possibly solve this problem. 5. conclusions in the present work, the physicochemical properties of natural and modified zeolites were studied. the modification of zeolite leads to an increase in its surface area, making it favorable for adsorption processes, but decreases its cec. the removal of na+ and k+ ions by nz and nh4-z shows that the modification of zeolite enables more high extraction of ions to be achieved. from the study results it can be concluded that zeolite modified with nh4cl can be used as potential sorbents for na+ and k+ ions from saline water. ● supplementary materials no supplementary materials are available. ● funding this work has been funded by the science committee of the ministry of education and science of the republic of kazakhstan (grant no. ap09260116). ● acknowledgments none. ● author contributions conceptualization: a.b.r. data curation: a.k.k., b.b.zh. investigation: b.b.zh., a.k.k. methodology: a.b.r., a.k.k., g.a.s. supervision: g.a.s. writing – original draft: a.k.k. writing – review & editing: a.b.r. ● conflict of interest the authors declare no conflict of interest. table 3 cec of zeolite samples (meq/100 g). sample na+ k+ mg2+ ca2+ total nz 152.94±9.34 15.19±1.57 32.91±3.61 230.62±14.49 431.67±29.01 nh4-z 152.09±21.71 13.85±0.85 7.74±0.59 127.20±8.72 300.88±31.86 https://doi.org/10.15826/chimtech.2023.10.3.05 chimica techno acta 2023, vol. 10(4), no. 202310402 letter 5 of 5 doi: 10.15826/chimtech.2023.10.3.05 ● additional information author ids: aruzhan k. kenessova, scopus id 57220024671; akmaral b. rakhym, scopus id 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doi:10.3390/min8010011 https://doi.org/10.15826/chimtech.2023.10.3.05 https://www.scopus.com/authid/detail.uri?authorid=57220024671 https://www.scopus.com/authid/detail.uri?authorid=57208575069 https://www.scopus.com/authid/detail.uri?authorid=56652160000 https://www.kaznu.kz/en https://cfhma.kz/cfhma/ https://doi.org/10.1016/j.desal.2015.01.041 https://doi.org/10.1016/j.scitotenv.2018.12.076 https://doi.org/10.1007/s13201-016-0455-7 https://doi.org/10.1007/s40726-018-0085-9 https://doi.org/10.1016/j.scitotenv.2020.141528 https://doi.org/10.3390/w6051134 https://doi.org/10.3390/app11020670 https://doi.org/10.1016/j.desal.2014.12.020 https://doi.org/10.1016/j.desal.2022.115827 https://doi.org/10.3390/pr8080901 https://doi.org/10.1016/j.joule.2020.06.020 https://doi.org/10.1007/s10311-018-0750-7 https://doi.org/10.1080/19443994.2014.892837 https://doi.org/10.1016/j.jenvman.2018.03.040 https://doi.org/10.1016/j.desal.2012.07.030 https://doi.org/10.1039/c8an01194j https://doi.org/10.1016/j.desal.2017.01.026 https://doi.org/10.1016/j.desal.2017.06.009 https://doi.org/10.1016/j.jclepro.2022.134614 https://doi.org/10.1016/j.cherd.2022.09.017 https://doi.org/10.1080/19443994.2015.1010590 https://doi.org/10.1016/j.desal.2017.06.009 https://doi.org/10.1016/j.scitotenv.2017.03.139 https://doi.org/10.3390/min8010011 a dft-d4 investigation of the complexation phenomenon between pentachlorophenol and β-cyclodextrin published by ural federal university eissn 2411-1414 chimicatechnoacta.ru article 2023, vol. 10(2), no. 202310209 doi: 10.15826/chimtech.2023.10.2.09 1 of 7 a dft-d4 investigation of the complexation phenomenon between pentachlorophenol and β-cyclodextrin zoubir kabouche a, youghourta belhocine b * , tahar benlecheb a, ibtissem meriem assaba bc, abdelkarim litim a, rabab lalalou b, asma mechhoud b a: laboratory of sensors, instrumentations and process (lcip), university of abbes laghrour, khenchela 40000, algeria b: laboratory of catalysis, bioprocess and environment, department of process engineering, faculty of technology, university of 20 august 1955, skikda 21000, algeria c: lrpcsi-laboratoire de recherche sur la physico-chimie des surfaces et interfaces, university of 20 august 1955, skikda 21000, algeria * corresponding author: y.belhocine@univ-skikda.dz this paper belongs to a regular issue. abstract density functional theory (dft) calculations based on the blyp-d4 and pbeh-3c composite methods were performed for investigating the encapsulation mode of pentachlorophenol (pcp) inside the cavity of β-cyclodextrin (β-cd). different quantum chemical parameters such as homo, lumo, and homo–lumo gap were calculated. complexation energies were computed at the molecular level to provide insight into the inclusion of pcp inside the β-cd cavity. the independent gradient model (igm) approach was applied to characterize the non-covalent interactions that occurred during the complex (pcp@β-cd) formation. two modes of inclusion were considered in this work (modes a and b). calculated complexation energies as well as the changes in enthalpy, entropy, and free gibbs energy exhibit negative values for both modes a and b, indicating a thermodynamically favorable process. weak van der waals interactions and one strong intermolecular hydrogen bond act as the main driving forces behind the stabilization of the formed most stable complex. this study was carried out to explore the potential use of the β-cd as a host macrocycle for sensing and capturing pentachlorophenol. keywords β-cyclodextrin pentachlorophenol inclusion complex non-covalent interactions environmental pollution received: 25.02.23 revised: 15.04.23 accepted: 21.04.23 available online: 28.04.23 key findings ● the complexation process between β-cyclodextrin and pentachlorophenol is spontaneous, exothermic and enthalpydriven. ● pentachlorophenol is partially included in the β-cyclodextrin cavity. ● stabilization of pentachlorophenol@β-cyclodextrin complex is due to hydrogen bonding and van der waals interactions. ● the sensing potential of β-cyclodextrin towards pentachlorophenol could be used for environmental monitoring. © 2023, the authors. this article is published in open access under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). 1. introduction the host-guest chemistry has paved the way for the development of supramolecular nanoarchitectures [1] with practical applications such as molecular recognition, drug delivery and electrochemical biosensing [2–4]. host–guest assemblies consist of guest molecules bound to the host molecules through non-covalent interactions (van der waals forces, hydrogen bonding, hydrophobic effect, π···π stacking interactions, etc.). among the different classes of macrocyclic systems, calixarenes [5], pillararenes [6], cucurbiturils [7], and, in particular, cyclodextrins [8–10] are the widely used host molecules in host-guest chemistry. the usefulness of these host molecules lies in their ability to enhance the solubility, stability and bioavailability of poorly water-soluble guests through the complexation process [11, 12]. cyclodextrins (cds) represent a family of cyclic oligosaccharides with unique properties that belong to the cage molecules family; they are usually used as host systems able to be complexed with a wide variety of guests. on the http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2023.10.2.09 http://creativecommons.org/licenses/by/4.0/ https://orcid.org/0000-0003-3876-8683 https://crossmark.crossref.org/dialog/?doi=https://doi.org/10.15826/chimtech.2023.10.2.09&domain=pdf&date_stamp=2023-04-28 chimica techno acta 2023, vol. 10(2), no. 202310209 article 2 of 7 doi: 10.15826/chimtech.2023.10.2.09 other hand, cds are inexpensive and eco-friendly, which makes them suitable for use in several industries [13]. cds are considered as semi-natural products synthesized by simple enzymatic conversion of starch and containing six to twelve glucopyranose units [14–16]; they possess a hydrophilic peripheral surface and hydrophobic interior cavity with an overall truncated cone shape [17, 18]. α-, β-, and γcyclodextrins, composed, respectively, of six, seven, and eight glucopyranose units, represent the three mains common cyclodextrins [19]. pentachlorophenol (pcp) is an industrial prevalent wood preservative used since 1936, particularly, in utility poles and railway ties [20]. its widespread use has caused environment pollution. indeed, the pcp was listed among the 126 priority pollutants by the european community as well as the united states environmental protection agency (usepa) [21] and was classified as a potentially carcinogenic compound by usepa and international agency for research on cancer (iarc) [22]. its use has been, therefore, severely regulated in many countries since 1987, except for the preservation of wood that is limited to industrial uses [23]. consequently, the biodegradation of this toxic substance has attracted growing interest among scientists and researchers with the aim of developing experimental methods for the removal of pcp. an alternative method for the capture of pcp molecules through the supramolecular chemistry concept consists in the encapsulation of pcp by host macrocyclic systems such as cyclodextrins, cucurbiturils, calixarenes, etc. the complexation of guest molecules in the cavity of host systems, particularly, β-cyclodextrin, induces modifications in the physicochemical properties of the guests [24, 25]. theoretical investigations of the host-guest interactions were the subject of several studies with the aim of understanding the complexation behavior at molecular level by determining the forces involved in the stabilization of guest molecules inside the cavities of the macrocyclic hosts. for this purpose, different quantum chemical methods ranging from semi-empirical ones such as am1, pm3, pm6 and pm7 [26–28] to density functional theory based approaches [29– 31] were employed. in this paper, we performed a theoretical study based on the density functional theory (dft) method, aiming at investigating the inclusion phenomenon between the β-cyclodextrin (β-cd) host system and the pentachlorophenol (pcp) guest molecule. the formation of a 1:1 stoichiometry complex was the subject of a previous experimental study [32], while the present work constitutes a complementary approach to rationalizing the inclusion phenomenon. 2. computational procedure orca code (version 4.2.1) [33, 34] was utilized to perform dft calculations. the whole complexation process consists of full geometry optimization of the initial generated complexes formed between pentachlorophenol (pcp) and βcyclodextrin (β-cd) in vacuum using blyp-d4 functional [35–39] associated with the def2-svp basis set. a geometrical counterpoise correction scheme (gcp) [40] was applied to account for the basis set superposition error (bsse). based on the approach proposed by liu and guo [41], the center of pcp (guest) and β-cd (host) was set as the center of the coordinate system (0 å). the guest molecule, pcp, was translated with a step of 1 å from –8 to +8 å along the z-axis, resulting thus in two possible inclusion modes on the side of the wider rim of the β-cd, denoted a or b. these modes correspond to the inclusion orientation of the pcp through β-cd cavity by its terminal chloro group or its hydroxy group (oh), respectively, as represented in figure 1 (a and b) using the visualization application jmol [42]. for a more precise inspection of the lowest energy conformations, we explored and included more initial conformations in the vicinity of the most stable configurations. thus, a step of 0.5 å was considered for a and b modes along the z-axis in the ranges [0–8 å] and [2–8 å], respectively. a total of 48 possible conformations were obtained and fully optimized in vacuum at blyp-d4/def2-svp-gcp level of theory, without any symmetry constraints. the complexation energies were calculated using equation (1): δecomplexation = ecomplex(pcp@β–cd)–(epcp + eβ–cd), (1) where δecomplexation, ecomplexpcp@β–cd, epcp, and eβ–cd represent, respectively, the complexation energy, the optimized energies of the complex, the free pcp, and the free β-cd. figure 1 schematic illustration of the inclusion complexation conformations (mode a) (a) and mode b (b). atomic color code: carbon (grey), hydrogen (white), oxygen (red), chlorine (green). https://doi.org/10.15826/chimtech.2023.10.2.09 https://doi.org/10.15826/chimtech.2023.10.2.09 chimica techno acta 2023, vol. 10(2), no. 202310209 article 3 of 7 doi: 10.15826/chimtech.2023.10.2.09 the most stable configurations correspond to the structures with the lowest complexation energies. the obtained most stable structures calculated at blyp-d4/def2-svp-gcp level of theory for a and b modes were subsequently reoptimized with the more accurate global hybrid pbeh-3c [43] functional in both vacuum and aqueous phase. calculations in water solvent were performed with the smd solvation model [44]. then, the most stable geometry associated with the lowest energy structure was subjected to further analyses, such as non-covalent interactions (ncis) characterization with independent gradient model based on the hirshfeld partitioning scheme (igmh) [45, 46] using multiwfn code [47] and vmd program for visualization [48]. 3. results and discussion 3.1. dft-calculations of complexation energies the most stable configuration corresponds to the lowest energy of all the optimized conformations calculated at dft/blyp-d4/def2-svp-gcp level of theory. figure 2 reports the values of the computed complexation energy for the a and b modes for each optimized conformation. the energy profiles obtained for all configurations in both modes (a and b) exhibit negative complexation energy values, pointing out a thermodynamically favorable process. full geometry optimization was followed by frequency calculations to verify that the obtained structures are true minima. overall, the complexation energies are globally less negative for the a and b configurations located at the negative positions of z-axis (from –8 å to –1 å), whereas more negative values of the complexation energies are observed in the interval of positive values of z axis points. the most stable configurations for a and b modes are located at z = 7.5 and 6.5 å, with the respective complexation energies of –121.39 and –123.79 kj/mol. the re-optimization at pbeh-3c level yielded complexation energies of –69.00 and –70.66 kj/mol in vacuum and –21.02 and –29.53 kj/mol in water solvent for 7.5 a and 6.5 b configurations, respectively, with the complex pcp@β-cd of b mode being more stable than that of a mode. figure 2 energy profile of the complexation between pcp and βcd (a and b modes). the complexation process is thermodynamically more favorable in vacuum than in the water solvent. the structural analysis of the most stable pcp@β-cd complex configuration (mode b at 6.5 å) calculated with pbeh-3c in vacuum shows the partial pentachlorophenol encapsulation inside the β-cd cavity, as illustrated in figure 3. it is worth mentioning that the least stable structure located at z = –1 å for a mode with a complexation energy of –4.05 kj/mol corresponds structurally to the inclusion of the pcp into the β-cd cavity, as shown in figure 4. indeed, the β-cd cavity is not sufficiently large to encapsulate completely the pcp guest within; the total inclusion of pcp involves strong elongation and flattening of β-cd. the obtained results suggest that the stability of the molecular association between pcp and β-cd is enhanced by the partial encapsulation of the pcp guest. the inclusion of pcp depends mainly on the cavity size of β-cd. 3.2. quantum electronic parameters the energies of the frontier molecular orbitals (homo and lumo), and the molecular homo–lumo gap of the most stable inclusion complex were computed at dft/pbeh-3c level in vacuum, and the obtained results are shown in table 1. figure 3 side view of the most stable configuration of the complex pcp@β-cd showing the partial encapsulation of pcp inside β-cd cavity. figure 4 front view of the least stable configuration of the complex pcp@β-cd. https://doi.org/10.15826/chimtech.2023.10.2.09 https://doi.org/10.15826/chimtech.2023.10.2.09 chimica techno acta 2023, vol. 10(2), no. 202310209 article 4 of 7 doi: 10.15826/chimtech.2023.10.2.09 the homo–lumo energy gap is reduced from 9.915 ev for the host molecule β-cd to 6.883 ev after complexation by a percentage variation of about 30.58%, indicating, thus, the potential use of β-cd as a host for pcp detection. the homo and lumo of the most stable pcp@β-cd complex was visualized with iboview program [49, 50] and represented in figure 5. both homo and lumo are almost entirely delocalized over the fused pcp molecule. the homo–lumo energy gap can be used as an indicator of kinetic stability. a large energy separation is associated with a low chemical reactivity and high kinetic stability. upon the complexation, the decrease in the homo– lumo gap of the pcp@β-cd complex (6.88 ev) in comparison with β-cd alone (9.92 ev) indicates that pcp@β-cd complex is more reactive and less stable than β-cd. 3.3. characterization of the intermolecular noncovalent interactions the igmh analysis was performed to provide insights into the nature of the intermolecular non-covalent interactions involved in the stabilization of the pcp@β-cd complex. the igmh plots are colored according to the occurring intermolecular interactions. green and blue colors denote, respectively, weak van der waals and hydrogen-bond interactions. the igmh isosurface of the most stable pcp@β-cd complex (figure 6) was calculated using multiwfn and visualized with the vmd program. the topological analysis shows that green areas associated with van der waals interactions dominated the calculated isosurface; the presence of a one hydrogen bond is revealed by the blue disc, as represented in figure 6, indicating that both weak van der waals interactions and the single intermolecular hydrogen bond act as attractive forces for the stabilization of pcp@β-cd complex. 3.4. statistical thermodynamic calculations the thermodynamic parameters were calculated at pbeh3c level of theory in vacuum using frequency calculation analysis for the most stable configuration. table 1 frontier orbitals and homo–lumo gap for β-cd, pcp, and pcp@β-cd system. parameters β-cd pcp pcp@β-cd ehomo –8.107 –7.841 –7.762 elumo 1.808 –0.854 –0.879 δegap 9.915 6.988 6.883 figure 5 homo and lumo orbitals of pcp@β-cd complex. the enthalpy, entropy, and gibbs free energy changes [51, 52] of the complexation process of pcp with β-cd at standard temperature and pressure values (298.15 k and 1 atm) are reported in table 2. the calculated δg° value is negative, showing that the complexation process is spontaneous. in addition, the negative values of enthalpy and entropy changes (δh° and δs°) indicated that the process is enthalpy-controlled and exothermic in nature. 3.5. natural orbital bond (nbo) analysis of intermolecular interactions the nbo approach [53] provides useful insights for describing and determining the nature of the different donor-acceptor interactions that occur in the molecular systems. the nbo analysis was carried out on the relaxed geometry of the most stable complex at m06-2x/def2-tzvpp [54–56] level of theory in vacuum using gaussian 09 program [57]. the structural analysis (figure 7) shows the presence of one strong hydrogen bond having a stabilization energy of 139.03 kj/mol, formed between hydrogen atom h (160) of terminal cho group of β-cd as the donor and oxygen atom o (121) of the pcp as the acceptor with a short distance of 1.62 å. figure 6 the igmh isosurface (isovalue 0.005 a.u.) of the pcp@βcd complex. figure 7 the significant intermolecular hydrogen bonds for the pcp@β-cd complex. https://doi.org/10.15826/chimtech.2023.10.2.09 https://doi.org/10.15826/chimtech.2023.10.2.09 chimica techno acta 2023, vol. 10(2), no. 202310209 article 5 of 7 doi: 10.15826/chimtech.2023.10.2.09 table 2 energetic and thermodynamic parameters of the complexation process calculated at pbeh-3c levels of theory in vacuum. thermodynamic parameters energetic values δh° (kj/mol) –66.85 δg° (kj/mol) –1.25 δs° (kj/mol) –65.61 4. limitations performing dft calculations using several functionals and several basis sets is useful for comparison purposes; however, the high computational and time cost of such calculations are the limiting factors. 5. conclusion the energetic and electronic properties of the complexation process between pentachlorophenol (pcp) and β-cyclodextrin were computationally studied using dft approach. the main conclusions of the present investigation can be stated as follows: ‒ calculated thermodynamic parameters exhibit negative enthalpy, entropy and gibbs energy changes, indicating that the complexation process is spontaneous, exothermic and enthalpy-driven. ‒ the configuration located at z = 6.5 å for b mode represents the most stable configuration with a complexation energy of –70.66 kj/mol as calculated with pbeh-3c in vacuum. ‒ the structural analysis showed that pcp penetrates partially the β-cyclodextrin cavity. ‒ hydrogen bonding and van der waals interactions were found by igmh analysis to be the main driving forces for the formation and stabilization of the pcp@β-cd complex. ‒ upon complexation, a significant hydrogen bond was formed at a short distance of 1.62 å with a stabilization energy of 139.03 kj/mol. ‒ after complexation, the homo–lumo energy gap decreased by a percentage of 30.58%, suggesting the potential application of the β-cd host system for the encapsulation of pcp. the results of this study revealed the sensing potential of β-cyclodextrin as a suitable host in electronic devices based on biosensors for the detection, capture and encapsulation of pentachlorophenol. this work could serve as a starting point for more deep experimental studies for developing effective biosensors for environmental concerns. ● supplementary materials no supplementary materials are available. ● funding this research had no external funding. ● acknowledgments none. ● author contributions conceptualization: y.b, t.b. data curation: z.k, r.l, a.m. formal analysis: i.m.a, z.k, a.l. funding acquisition: y.b. investigation: r.l. a.m. methodology: y.b., t.b. project administration: y.b. resources: i.m.a., z.k., a.l. software: y.b., z.k, a.l. supervision: y.b., t.b. validation: y.b. visualization: r.l., a.m., z.k., a.l. writing – original draft: y.b., i.m.a., z.k. writing – review & editing: y.b. ● conflict of interest the authors declare no conflict of interest. ● additional information author id: y. belhocine, scopus id 54917426000. websites: university of khenchela, https://univ-khenchela.com; 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https://chem.conf.nstu.ru/. guest editors: prof. n. uvarov and prof. e. aubakirov. abstract hydrophilic molecularly imprinted resins (mir), which are produced using hydrophilic monomers such as phenols, aldehydes, melamine or urea, have recently attracted increasing attention for use in separation and preconcentration. among their obvious advantages are good sorption capacity, high recovery and selectivity, as well as their reusability in aqueous solutions. in this work we applied the bulk molecular imprinting method to produce quercetin-imprinted phenol-amino-formaldehyde resin. for this purpose, phloroglucinol and melamine solutions were mixed with formaldehyde and then polyethylene glycol and quercetin (qu) were added to the obtained solution as a porogen and a template, respectively. the mixture was stirred under heating, then left in the thermostat for a continuous time. the optimum ratio of phloroglucinol to melamine was 3:1. the average molecular mass of porogen (mw) varied between 4000–10000 da. the obtained mir were eluted with ethanol-water mixture (4:1, v/v) in the soxhlet extractor for 36 h to remove the template. the mir were characterized by ftir-spectroscopy, laser diffraction spectroscopy and differential thermal analysis. the maximum recovery and sorption capacity of mir synthesized in the presence of a porogen with mw 10000 were 47% and 4.7 μmol qu/g, respectively. the maximum imprinting factor was 1.41. the sorption kinetics of quercetin by a non-imprinted resin (nir) is best described by a pseudo-second-order model, while mir has a mixed pseudofirst-second-order mechanism. keywords molecular imprinting hydrophilic resins sorption rebinding quercetin received: 04.07.23 revised: 26.07.23 accepted: 16.08.23 available online: 23.08.23 key findings ● we obtained a molecularly imprinted hydrophilic phloroglucinol-melamine-formaldehyde resin for the sorption concentration of quercetin. ● the sorption capacity for quercetin by the molecularly-imprinted sample was ~5 µmol/g, and the imprinting factor was 1.41. ● the quercetin rebinding process was in compliance with the pseudo-second-order model and the freundlich model. © 2023, the authors. this article is published in open access under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). 1. introduction molecularly imprinted polymers (mip) are widely used in analytical chemistry and other fields for selective extraction, separation and preconcentration of target molecules. one of the significant disadvantages of traditional organic solvent synthesized mip is the insufficiently selective binding of organic analytes from aqueous matrices. this is caused by the structural changes of the mip and, consequently, its binding sites due to the swelling of the polymer in polar solvents. hydrophilic molecularly imprinted resins (mir), which are produced using hydrophilic monomers such as phenols, aldehydes, melamine or urea, have recently attracted increasing attention of researchers [1–16]. the high density of hydrophilic functional groups in mir http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2023.10.3.10 mailto:petrova_juju@surgu.ru http://creativecommons.org/licenses/by/4.0/ https://orcid.org/0000-0003-3702-2249 https://orcid.org/0000-0003-3514-3872 https://orcid.org/0009-0007-6153-8380 https://orcid.org/0000-0002-1880-7182 https://crossmark.crossref.org/dialog/?doi=https://doi.org/10.15826/chimtech.2023.10.3.10&domain=pdf&date_stamp=2023-08-23 chimica techno acta 2023, vol. 10(3), no. 202310310 article 2 of 7 doi: 10.15826/chimtech.2023.10.3.10 (hydroxyl, amino and imino groups, as well as ether bonds) promotes the formation of complexes with template molecules through multiple hydrogen bonds, π–π– and electrostatic interactions, which makes molecular imprinting more effective. mir have been widely used in separation and preconcentration [17, 18]. resorcinol-formaldehyde resins were used to extract sulfonamide antibiotics [19] and aminophenol-formaldehyde resins were used to determine perphluorocarboxylic acids, chlorophenols, benzoic acids, dyes, plant growth regulators and for selective absorption of tetramethylpyrazine (ligustrazine) in traditional chinese herb [20–23], etc. among the obvious advantages of mir are good adsorption capacity, high recovery and selectivity, as well as their reusability in aqueous solutions. in this work, the molecular imprinting method was used to produce quercetin-imprinted phloroglucinol-melamineformaldehyde resins [24]. polyethylene glycol of varied average molecular mass was used as a porogen to increase adsorption capacity of mir. quercetin has numerous biological and pharmacological activities, including antiviral, anti-inflammatory, antiallergic and antitumor properties [25]. quercetin is introduced into the composition of some pharmaceutical drugs and dietary supplements; however, its recovery from plant extracts is extremely difficult. so, it is important to develop selective, fast and simple methods for separation and determination of quercetin in plant extracts. 2. materials and methods 2.1. chemicals and materials we used phloroglucinol (≥99.0%, sigma-aldrich, china); melamine (99%, acros organics, united kingdom); formaldehyde (37.6%, merck, germany); polyethylene glycol (average molecular mass, mw: 4000, 6000, and 10000 da, panreac); quercetin (99.3%, sigma-aldrich); acetic acid (99.9%, ecros, russia); acetonitrile for hplc (>99.9%, cryochrome, russia); ethanol (95%, rfc, russia), etc. a standard solution of 5.00∙10–4 mol/l of quercetin was prepared by dissolving it in 95% ethanol; calibration solutions of 1.00∙10–6–7.50∙10–5 mol/l were prepared by diluting the standard solution with ultrapure water (18 mω∙cm, aqualab uvoi-"mf"-1812 water purification system, mediana-filter, russia). 2.2. instrumentation the resin particle size distribution was studied by laser diffraction (sald-2300 particle size analyzer with a saldbc23 batch cell unit, shimadzu, japan). a spectrum 100 ftir spectrometer (perkin elmer, usa) with a quest atr accessory (specac, uk) was used to record ir spectra in the attenuated total reflection (atr) mode. the differential thermal analysis (tga/dsc) was performed with a mettler toledo tga/dsc 3+ star system at a heating rate of 10 °c/min under nitrogen atmosphere with a flow rate of 50 ml/min. the total specific surface area was determined by thermal desorption of gas-adsorbate (bet) using an analyzer of specific surface area of dispersed and porous materials thermosorb tpd 1200 (catakon, russia). the concentration of quercetin in solutions was measured by uvvis spectroscopy (uv-2600, shimadzu, japan). 2.3. synthesis of phloroglucinol-melamine-formaldehyde resins (pmfr) molecularly imprinted resins (mir) were prepared by polycondensation of monomers in an ethanol-water mixture (ethanol:water ratio 5:4, v/v) [24]. for this purpose, phloroglucinol (3 mmol) and formaldehyde (12 mmol) were dissolved in 4.5 ml of ethanol-water mixture at room temperature under ultrasound and magnetically stirred for 30 min (solution a). melamine (1 mmol) and formaldehyde (2 mmol) were dissolved in 1.5 ml of ethanol-water mixture under heating to 80 °c and stirred continuously until complete dissolution (solution b). after cooling solution b to room temperature, it was mixed with solution a. polyethylene glycol (0.025 mmol) as a porogen and quercetin (0.16 mmol) as a template were added to the obtained prepolymerization mixture. the mixture was stirred under heat (40 °c) for 30 min and incubated in an air thermostat at 60 °c for 2 h, then at 80 °c for 24 h. quercetin was not added to the non-imprinted resin (nir) sample. after drying, the pmfr samples were ground for 1 min either in a laboratory ball mill ml-1 (econ, russia) or in an agate mortar. to remove the template after synthesis, the samples were eluted with an ethanol:water mixture (9:1, v/v) by soxhlet extraction (500 mg, 125 ml, 36 h) and then dried at 60 °c. the concentration of quercetin was monitored by spectrophotometry (λ 373.6 nm), and the apparent degree of template removal was calculated as the proportion of quercetin eluted from the pmfr mir samples relative to the amount added during the mir synthesis. 2.4. adsorption experiments the kinetics of quercetin (template) rebinding were studied under static adsorption conditions using 10 μmol/l aqueous solution of quercetin. 50 mg of mir or nir sample was placed in the studied quercetin solution (~50 ml), then aliquots (3.0 ml) of this solution were taken every 5–15 min to determine quercetin by spectrophotometry at 367.6 nm wavelength. to study rebinding isotherms, an adsorption experiment was carried out with 5–70 μmol/l quercetin solutions at 27 °c (ts-1/80 spu dry-air thermostat, russia): 10 mg of mir or nir sample was placed in 10 ml of quercetin solution and incubated for 1 day with periodic stirring until equilibrium was reached. the adsorption properties of mir and nir and the efficiency of molecular imprinting were characterized by calculating the recovery (r, %), sorption capacity (q, μmol/g) and imprinting factor (if) as the ratio of the mir sorption capacity to the nir sorption capacity at the current time t. https://doi.org/10.15826/chimtech.2023.10.3.10 https://doi.org/10.15826/chimtech.2023.10.3.10 chimica techno acta 2023, vol. 10(3), no. 202310310 article 3 of 7 doi: 10.15826/chimtech.2023.10.3.10 the kinetics of quercetin rebinding by mir and nir samples was studied using pseudo-first and pseudo-second order models [6, 21, 26]. the langmuir and freundlich models [9, 21, 26–28] were applied to describe the mechanism of the rebinding. linearized equations were used to test model compliance: the scatchard equation and the logarithmic form of the freundlich equation. in the first case, the adsorption process was characterized by calculating the effective binding constant ka and the maximum sorption capacity qmax. in the second case, the adsorption coefficient β and the empirical constant n were used as a measure of heterogeneity of binding sites. 3. results and discussion in this work, three samples of quercetin-imprinted phenolamino-formaldehyde resins (mir) were obtained by polycondensation of melamine and phloroglucinol (phloroglucinol:melamine ratio 3:1) in the presence of formaldehyde, varying the average molecular mass of polyethylene glycol (porogen) 4000, 6000 and 10000 da: pmf 3-1-4k, pmf 31-6k and pmf 3-1-10k respectively. non-imprinted samples (nir) were obtained in the absence of quercetin. extraction with an ethanol-water mixture (ethanol:water ratio 4:1, v/v) by the soxhlet method for 36 h was chosen to remove the template from the obtained mir samples as a method providing the maximum apparent degree of template removal (table 1). laser diffraction, ftir-spectroscopy, and differential thermal analysis were used to characterize the obtained pmfr samples. it was shown (figure 1) that the median particle diameter of pmf mir increases with the average molecular mass of the porogen from 21.8 (mw 4000) to 67.9 μm (mw 10000). in the ftir spectra (figure 2) out-of-plane deformation bands (δoop) of n–h bonds in the region 811–814 cm–1, c–o–c stretching region 1000–1111 cm–1, nh deformation vibrations in aromatic amines 1272–1370 cm–1, stretch vibrations (ν) of c=c of aromatic ring (1614, 1450 cm–1) and c=n of triazine (1550, 1350 cm–1) and stretching region 3200–3400 cm–1 of o–h and n–h groups were identified. the results of the differential thermal analysis in an inert medium (n2) showed that the resins are thermally stable up to 200 °c, and in the temperature range 250–450 °c (figure 3, tga and dta-curves of thermogravimetric and differential thermal analysis, respectively) they are thermally decomposed, accompanied by an exothermic effect (figure 3, dsc-curve of differential scanning calorimetry). the recovery and sorption capacity of pmfr during the rebinding of quercetin increase with increasing the average molecular mass of polyethylene glycol (table 2). thus, the maximum recovery and sorption capacity of pmf 3-1-10k mir synthesized in the presence of a porogen with an average molecular mass of 10000 da reached ~43% and 4.71 μmol/g of quercetin, respectively. the maximum if was 1.41 (in 90 min). the mir obtained in this work are stable after removal of the template in a soxhlet apparatus using various elution solvents (table 2) and subsequent drying at 60 °c. using 31-6k mir as an example, it was shown that they can be reused after 2–3 elutions with ethanol-water mixture (2–3 cycles). in this case, the decrease in the sorption capacity during the rebinding of quercetin was no more than 8%. the kinetics of quercetin rebinding under static sorption conditions are better described by the pseudo-second-order model for most mir samples (table 3, figure 4a), while for pmf 3-1-10k mir a mixed mechanism was observed (table 4, figure 4b). it should be noted that kinetic models of rebinding for the samples with the highest mw of the porogen (pmf 3-1-10k mir) confirmed (tables 3, 4) the efficiency of molecular imprinting, as qe(mir) > qe(nir). table 1 optimization of elution solvent. pmfr eluent k (%)a pmf 3-1-6k etoh:h2о (4:1, v/v) 22 меoh:h2о (4:1, v/v) 18 etoh:hаcb (9:1, v/v) 17 меoh:hаc (9:1, v/v) 16 acn:h2o (1:1, v/v) 10 a apparent degree of template removal; b hac – acetic acid. figure 1 median diameter (d50) of pmfr (white bars – nir, gray bars – mir). figure 2 atr ftir-spectra of pmfr: pmf 3-1-4k mir (1) and pmf 3-1-4k nir (2), pmf 3-1-6k mir (3) and pmf 3-1-6k nir (4), pmf 3-1-10k mir (5) и pmf 3-1-10k nir (6). https://doi.org/10.15826/chimtech.2023.10.3.10 https://doi.org/10.15826/chimtech.2023.10.3.10 chimica techno acta 2023, vol. 10(3), no. 202310310 article 4 of 7 doi: 10.15826/chimtech.2023.10.3.10 figure 3 tga (black), dsc (red) and dta (blue) curves of pmf 31-10k mir (n2, 10 °c/min). the isotherms of quercetin rebinding by pmfr samples are better described by the freundlich model (table 5), which confirms the heterogeneity of the surface and different types of binding centers (the empirical coefficient n is 0.5–0.6). at the same time, the empirical coefficient β, which characterizes the adsorption of quercetin, is 1.5– 3.0 times higher for mir samples than for nir samples. this can be explained by the formation of molecular imprints that are complementary to the template molecules. the compliance with the freundlich model correlates well with the results of the specific surface area obtained by bet (table 6). the relevant task of this work is to apply the advantages of the prepared mir for selective adsorption of target biomolecules from biological matrix (plant extract). in this experiment, it takes quercetin (template) and rutin as the target flavonols, their diluted solutions as a sample matrix to simulate the selective adsorption of flavonols from the biological matrix (ethanol:water extract). the effect of concentration was studied by adding quercetin or rutin in the range of 7.5∙10–6–7.0∙10–5 mol/l (table 7). no significant change in the imprinting factor of quercetine was observed as the concentration further increased from 7.5∙10–6 to 7.0∙10–5 mol/l. so, it can be concluded that mir can selectively adsorb target flavonol quercetin in diluted ethanol:water extract without the matrix interference of the biological matrix. it was noted (table 7) that pmf 3-1-4k mir selectively adsorbs quercetin, but pmf 3-1-10k mir adsorbs rutin more selectively than quercetin as a template. thus, quercetin can be considered as a dummy template for the selective recovery of rutin. the results proved the specific selectivity of obtained pmf mir, and are expected to be further applied to the imprinting and selective recognition of more flavonoids so as to play an important role in plant analysis. 4. limitations in this work, samples of quercetin-imprinted phloroglucinol-melamine-formaldehyde resins with an insufficiently high recovery (~43%) were obtained, which is probably due to the small pore size and low permeability. therefore, the following studies will be aimed at increasing the sorption capacity of mir samples by optimizing the amount of porogen. at the same time, it is important to control the efficiency of molecular imprinting (if at least 1.5). table 2 sorption parameters of pmfr (50 ml of 10 μmol∙l–1 quercetin solution, 50 mg of pmfr). pmfr rmax (%) qmax (μmol/g) ifmax mir nir mir nir pmf 3-1-4k 21.6 21.7 2.50 2.58 1.13a pmf 3-1-6k 41.4 48.1 4.63 5.42 1.13b pmf 3-1-10k 42.6 41.1 4.71 4.69 1.41c a 15 min; b 35 min; c 90 min. table 3 pseudo-second-order kinetics parameters of pmfr. pmfr q24h (μmol/g) k2 (g∙μmol –1∙min–1) qe (μmol/g) r 2 pmf 3-1-4k mir 2.50 7.9∙104 1.47 0.9290 nir 2.58 4.2∙105 1.60 0.9616 pmf 3-1-6k mir 4.63 2.2∙104 1.92 0.8664 nir 5.42 6.3∙103 3.87 0.8167 pmf 3-1-10k mir 4.71 4.1∙103 3.15 0.7729 nir 4.69 2.2∙104 1.72 0.8604 table 4 pseudo-first-order kinetics parameters of pmfr. pmfr q24h (μmol/g) k1 (min –1) qe (μmol/g) r 2 pmf 3-1-6k mir 4.63 3.2∙10–3 4.17 0.9406 nir 5.42 6.7∙10–3 4.86 0.5760 pmf 3-1-10k mir 4.71 5.5∙10–3 4.62 0.9432 nir 4.69 2.5∙10–3 4.16 0.7472 https://doi.org/10.15826/chimtech.2023.10.3.10 https://doi.org/10.15826/chimtech.2023.10.3.10 chimica techno acta 2023, vol. 10(3), no. 202310310 article 5 of 7 doi: 10.15826/chimtech.2023.10.3.10 5. conclusions therefore, the molecular imprinting methodology allowed obtaining a hydrophilic phloroglucinol-melamine-formaldehyde resin for the sorption concentration of quercetin. it was shown that in the presence of polyethylene glycol (porogen) with an average molecular mass of 10000 da, the sorption capacity of quercetin by the molecularly-imprinted sample was ~5 µmol/g, the specific surface area was 288.1 m2/g, and the imprinting factor was 1.41. it was shown that recovery of quercetin (21–43%) is slightly lower, but the imprinting factor (1.4) is not inferior to that of the similar methods for extracting phenolic compounds [26] and dyes [29] with resorcinol-melamine-formaldehyde and phenol-formaldehyde resins, as well as quercetin with surface-imprinted polymers [30, 31]. modeling of the kinetics and isotherms of quercetin rebinding by the samples, obtained in the presence of polyethylene glycol of different average molecular mass, showed compliance with the pseudo-second-order model and the freundlich model describing an inhomogeneous surface. figure 4 kinetic adsorption curves of pmf 3-1-6k mir (a) and pmf 3-1-10k mir (b) for quercetin rebinding: experimental curve (1), pseudo-first-order model (2), pseudo-second-order model (3). table 5 modeling of quercetin sorption isotherms by freundlich. pmfr β n r2 pmf 3-1-6k mir 4.5∙10–3 0.5 0.9462 nir 2.7∙10–3 0.5 0.9759 pmf 3-1-10k mir 1.1∙10–2 0.6 0.9179 nir 3.7∙10–3 0.5 0.9008 table 6 surface characteristics of the pmfr. pmfr sbet (m 2/g) v (cm3/g) pore size (nm) mir nir mir nir mir nir pmf 3-1-6k 288.1 285.9 0.17 0.15 2.44 2.08 table 7 effect of the сoncentration of quercetin (qu) and rutin (rut) at the range of 7.5∙10–6–7.0∙10–5 mol/l on the imprinting factor (if). mir if (n = 8, p = 0.95a) qu rut pmf 3-1-4k 1.160.06 0.780.09 pmf 3-1-6k 1.180.08 1.200.04 pmf 3-1-10k 1.420.05 1.680.05 a confidence interval ● supplementary materials no supplementary materials are available. ● funding the work was carried out within the framework of the state task of the isscm sb ras (project №121032500065-5). ● acknowledgments the authors are grateful to d.a. lazarev, an expert of the center for collective use of surgut state university, and d.r. mukhutdinov, m.m. gasanova, and u.v. novokshanova for assistance in conducting the experiments. ● author contributions conceptualization: yu.yu.p. formal analysis: e.v.b., yu.g.m. funding acquisition: yu.g.m., yu.yu.p. investigation: e.v.b., d.o.z., yu.g.m. methodology: yu.yu.p., e.v.b., yu.g.m. project administration: yu.yu.p. resources: yu.yu.p., yu.g.m. supervision: yu.yu.p. validation: e.v.b., yu.yu.p. visualization: e.v.b., d.o.z. writing – original draft: yu.yu.p., e.v.b. writing – review & editing: d.o.z., yu.yu.p. ● conflict of interest the authors declare no conflict of interest. ● additional information author ids: yuliya yu. petrova, scopus id 6603754153; elena v. bulatova, scopus id 57193926543; yuliya g. mateyshina, scopus id 6506782050. websites: surgut state university, https://int.surgu.ru/; https://doi.org/10.15826/chimtech.2023.10.3.10 https://doi.org/10.15826/chimtech.2023.10.3.10 https://www.scopus.com/authid/detail.uri?authorid=6603754153 https://www.scopus.com/authid/detail.uri?authorid=57193926543 https://www.scopus.com/authid/detail.uri?authorid=6506782050 https://int.surgu.ru/ chimica techno acta 2023, vol. 10(3), no. 202310310 article 6 of 7 doi: 10.15826/chimtech.2023.10.3.10 institute of solid state chemistry 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chimica techno acta 2023, vol. 10(3), no. 202310310 article 7 of 7 doi: 10.15826/chimtech.2023.10.3.10 environ manage. 2021;300:113707. doi:10.1016/j.jenvman.2021.113707. 30. petrova yy, bulatova ev, sevast'yanova ev, mateyshina yg. quercetin-imprinted monolithic polymer. mater today proc. 2020;31(3):555–557. doi:10.1016/j.matpr.2020.06.213 31. zhi k, li z, luo h, ding y, chen f, tan y, liu h. selective adsorption of quercetin by the sol-gel surface molecularly imprinted polymer. polymers. 2023;15(4):905. doi:10.3390/polym15040905 https://doi.org/10.15826/chimtech.2023.10.3.10 https://doi.org/10.15826/chimtech.2023.10.3.10 https://doi.org/10.1016/j.jenvman.2021.113707. https://doi.org/10.1016/j.matpr.2020.06.213 https://doi.org/10.3390/polym15040905 improvement of protective oxide layers formed by high-frequency plasma electrolytic oxidation on mg-re alloy with lpso-phase published by ural federal university eissn 2411-1414 chimicatechnoacta.ru article 2023, vol. 10(2), no. 202310212 doi: 10.15826/chimtech.2023.10.2.12 1 of 15 improvement of protective oxide layers formed by highfrequency plasma electrolytic oxidation on mg-re alloy with lpso-phase alisa o. cheretaeva a * , pavel a. glukhov a , marat r. shafeev a , alyona g. denisova a , eugeny d. borgardt a , anton v. polunin a , alexander v. katsman ab , mikhail m. krishtal a a: institute of advanced technologies, togliatti state university, togliatti 445020, russia b: department of materials science and engineering, technion – israel institute of technology, haifa 32000, israel * corresponding author: a.cheretaeva@tltsu.ru this paper belongs to a regular issue. abstract oxide layers on mg97y2zn1 magnesium alloy with strengthening lpso-phase were formed by plasma electrolytic oxidation (peo) in bipolar mode with frequency variation of forming current pulses (50 and 500 hz) and addition of sodium aluminate or sodium silicate to alkali phosphate fluoride electrolyte. microstructure, chemical and phase composition, corrosion and mechanical properties of the oxide layers formed were investigated. with increasing current frequency for both electrolytes, an increase in homogeneity of the oxide layers structure and a decrease in their porosity and fracturing at constant thickness were recorded. the oxide layers formed at 500 hz even with some decrease in hardness have better adhesive strength and 2 orders of magnitude higher short-term corrosion resistance values. peo of mg-alloy with lpso-phase in the electrolyte with addition of sodium aluminate in combination with increased pulse frequency (500 hz) allows forming the best-quality uniform oxide layer with high hardness, adhesive strength and corrosion resistance properties. the use of electrolyte with addition of sodium silicate reduced the adhesive strength by 1.5 times and brought down the long-term corrosion resistance of oxide layers by an order of magnitude, as compared with the electrolyte with sodium aluminate. the reason for a significant improvement in the complex of protective properties of the oxide layers with an increase in the current pulse frequency is supposed to be a decrease in the power and duration of individual microarc discharges with simultaneous increase in their number per unit oxidized area. keywords plasma electrolytic oxidation magnesium alloys lpso phase electrolyte system frequency dependence corrosion resistance microhardness adhesive strength received: 17.04.23 revised: 17.05.23 accepted: 23.05.23 available online: 29.05.23 key findings ● peo of mg-re (lpso) alloy allows improving its corrosion behaviour and surface mechanical properties. ● increase of pulse frequency under peo allows decreasing the porosity and heterogeneity of the oxide layers. ● the best corrosion resistance and adhesive strength demonstrate the oxide layer obtained in aluminate electrolyte under high-frequency peo. © 2023, the authors. this article is published in open access under the terms and conditions of the creative commons attribution (cc by) license (http://creativecommons.org/licenses/by/4.0/). 1. introduction magnesium alloys have great potential for different industrial applications due to their high specific strength, damping ability and good workability [1–4]. main disadvantages that prevent wide application of mg alloys in aviation and aerospace industry are low ignition temperature and high fire hazard, absolute mechanical strength deficiency and insufficient corrosion resistance [5–8]. in the past decade, considerable progress has been made in the development of zinc-containing magnesium alloys with rare earth elements (mg–re), which, at a certain zn ratio, can form alloys with a long-period stacking-ordered structure (lpso-phase) [9–12]. compared to conventional mg alloys with dispersion strengthening, the eutectic structures of these alloys after thermal treatment are transhttp://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2023.10.2.12 mailto:a.cheretaeva@tltsu.ru http://creativecommons.org/licenses/by/4.0/ https://orcid.org/0000-0002-3952-9556 https://orcid.org/0009-0001-4600-3608 https://orcid.org/0000-0002-4490-6547 https://orcid.org/0000-0002-1213-2532 https://orcid.org/0000-0002-1080-6548 https://orcid.org/0000-0001-8484-2456 https://orcid.org/0000-0003-0987-8904 https://orcid.org/0000-0001-7189-0002 https://crossmark.crossref.org/dialog/?doi=https://doi.org/10.15826/chimtech.2023.10.2.12&domain=pdf&date_stamp=2023-05-29 chimica techno acta 2023, vol. 10(2), no. 202310212 article 2 of 15 doi: 10.15826/chimtech.2023.10.2.12 formed into lpso-phases shaped as thin plates with 1.5 to 25 nm thickness [13]. they significantly increase the static and fatigue strength, ductility and thermal stability of the alloy. lpso-phase formed from various combinations of mg, zn, y, etc., prevents the movement of dislocations and reduces the anisotropy of the material properties, whereby high mechanical performance is achieved [14, 15]. due to control of the strengthening lpso-phase composition, its orientation, size and volume distribution, the ultimate strength of mg-re alloys in the order of 600 mpa can be achieved, which is comparable with structural steel characteristics; the plasticity of 30% and more is achieved, and also their ignition temperature (flame resistance) could be raised significantly [10, 14]. yet, low corrosion resistance issue remains unresolved [16]. mg is an electrochemically active metal with a low standard electrode potential of –2.37 v [17, 18]. potential difference between the matrix (α-mg) and the lpsophase can reach ~60–250 mv, which further lowers the alloy corrosion resistance due to the occurrence of micro-galvanic couples [5, 16, 19, 20]. therefore, for mg– re (lpso)-alloys to be implemented in unit and aggregate designs, additional solutions that neutralize this effect should be provided, for example, the application of protective coatings. formation of multifunctional oxide ceramic layers on the alloy surface by plasmaelectrolytic oxidation (peo) appears most attractive technology [21, 22]. the peo method is actively used for valve metals (mg, al, ti, zr) and is based on the oxidation of metals under high-energy electrical action in electrolyte solutions of various compositions [23–25]. the peo method advantages are high adhesion of the oxide layer, single-stage treatment, relatively low cost, ease of layer application control and the environmental friendliness. primary surface passivation occurs at the initial treatment stage, and, when certain critical voltage is reached, the dielectric «barrier» layer is broken down and plasma electric microarc discharges are formed across the treated surface [26]. intense mass transfer due to high electric field strength and temperature gradients, combined with solution thermolysis, allows electrolyte components to be embedded into the oxide layers. the necessary oxide layer properties can be achieved by regulating the oxidation mode (the process electrical parameters), main components of the electrolyte and post-treatment processes [27, 28]. such treatment makes it possible to obtain composite ceramic layers with the highest protective characteristics. despite plenty of studies on peo of mg alloys, we are aware of only 2 works in which this technology was applied to mg alloys with lpso-phase [11, 20]. however, the combined effect of electrolyte composition and technological process mode was not investigated in those studies. peo in combination with sealing post-treatment in a ce-containing solution was used in paper [20] to increase the corrosion resistance of mg–y–zn alloy with lpsophase. peo was carried out in an alkaline-silicate-fluoride electrolyte at a forming pulse frequency of 500 hz in the potentiostatic mode at a maximum initial current density of 400 ma·cm–2. peo allowed reducing the icorr of the alloy by 1.5 orders of magnitude. subsequent holding in cecontaining electrolyte made it possible to significantly reduce the surface porosity and the corrosion current to 2.0·10−9 a·cm–2. the effect of the electrolyte composition on the oxidability of the mg–gd–y–zn alloy with lpso-phase and the properties of oxide layers formed was investigated in [11]. the basic electrolyte components were sodium hydroxide and sodium fluoride, to which aluminate, phosphate and sodium silicate were added one at a time; the component combinations were also varied, and the effect of electrolyte composition on the anticorrosive properties of oxide layers was evaluated. the authors [11] found that the oxide layer formed in the electrolyte containing all these components at a concentration of 4 g·l–1 has the best anticorrosive properties – when tested in 3.5 wt.% nacl, the authors managed to reduce the icorr of the alloy by almost 3 orders of magnitude and increase the resistance of the barrier layer by more than 3 orders of magnitude compared to the resistance of charge transfer through the natural oxide film on the mg(lpso)-alloy. among monoadditives, sodium silicate had the greatest effect on anticorrosive properties of the oxide layers, while the best combination of two additives was shown to be the sodium aluminate and sodium phosphate. along with the composition of electrolyte, the peo technological mode has an important effect on increasing the anticorrosion and mechanical properties of the oxide layers [3, 26, 29–32]. in particular, an increase in the current frequency from 50 to 400 hz during peo demonstrated a greater effect on the anticorrosive performance than the use of preliminary anodic passivation [29]. the oxide layers obtained at a relatively high frequency (800 hz) had smaller pore size and were much denser than the coatings obtained at 100 hz [30]. however, the authors of [31] came to the opposite conclusion when studying the peo of the am50 magnesium alloy in the alkalinephosphate electrolyte at three frequencies (10, 100 and 1000 hz). they found that low-frequency peo promotes sintering of the coating, making it denser and improving corrosion resistance. thus, there is no consensus on the peo frequency effect on the properties of the oxide layers formed. however, most authors believe that the intensity of the spark discharge is the most critical factor affecting the quality of coatings [33]. this work is aimed to study the combined effect of peo electrolyte component composition and frequency of forming current pulses on the structure, mechanical and anticorrosive properties of oxide layers formed on the lpsophase magnesium alloy of the mg–6.7y–2.3zn–1.1zr (wt.%) system. https://doi.org/10.15826/chimtech.2023.10.2.12 chimica techno acta 2023, vol. 10(2), no. 202310212 article 3 of 15 doi: 10.15826/chimtech.2023.10.2.12 2. materials and methods oxide layers were obtained on the cast and heat treated mg97y2zn1 magnesium alloy with a strengthening lpsophase (somz, solikamsk, russia). chemical composition of the alloy (wt.%) was determined on the thermo fisher scientific arl 4460 oes optical emission spectrometer: 6.68 y; 2.27 zn; 1.07 zr; 0.056 nd; mn < 0.005; al, fe < 0.002; si, ni, cu < 0.001, the rest is mg. the following phases were detected in the alloy: α-mg, mg12yzn (lpso-phase) and mg3zn3y2 (w-phase) [34]. before peo, the samples were subjected to heat treatment according to the t61 mode: homogenizing annealing at a temperature of 525±5 °c, 24 hours, quenching in water heated to t >80 °c and aging at 200±5 °c, 100 hours. such mode of heat treatment allows obtaining the maximum mechanical properties of this alloy. specimens for peo were cut in the form of rectangular bars with dimensions (60×20×6) mm3, which were sanded before processing using sic-based sanding paper with abrasive 600–1200–2500–5000 grit and isopropyl alcohol as a cutting compound. peo was carried out with alternating current from an original power source for 10 minutes at a constant current density of 10.0±0.5 a·dm–2, the ratio of cathode and anode operating currents of half-cycles k/a = 0.50±0.02 and the electrolyte temperature of 286±2 k. pulse-duty factor was 50%, the proportion of anode/cathode pulses in the total pulse duration was 50%/50% with a symmetrical pause between half–cycles. the frequency of trapezoidal forming pulses (50 hz and 500 hz) and the main electrolyte component, naalo2 or na2sio3 (15 g·l–1), which was added to the aqueous solution of koh (1 g·l–1), na2hpo4·12h2o (10 g·l–1) and naf (10 g·l–1) were varied. the specimens obtained in the electrolyte with addition of sodium aluminate will be hereinafter referred to as peo-a-50/500, and those with addition of sodium metasilicate – peo-s-50/500. structural investigations of oxide layers were carried out on transverse metallographic sections using carl zeiss sigma autoemission scanning electron microscope (sem) with thermionic schottky cathode (germany) in the backscattered electrons (bse) mode. elemental (chemical) composition of oxide layers was studied integrally from the surface (s ≈ 160 mm2) by x-ray fluorescence energy dispersive analysis (xrf) using the shimadzu edx-8000 energy dispersive x-ray fluorescence spectrometer (rhanode tube, u = 15–50 kv, i = 30–310 µa) and on transverse sections by energy dispersive x-ray microanalysis (edxma) using an x-ray spectral microanalysis unit based on the edax team eds energy spectrometer (sdd based edax “apollo x” analyzer) of sigma sem. to remove polarization artifacts during sem investigations, a thin conductive platinum layer was applied to the specimens by the “cold” magnetron (ion) sputtering method. the thickness t, µm and porosity p, % of oxide layers were evaluated from three panoramic cross-sectional images (≈500 µm long) using imagej software. x-ray diffraction analysis of oxide layers was performed on the shimadzu maxima xrd–7000s diffractometer (cu kα radiation, x–ray tube with a long fine focus – lff, braggbrentano geometry) at a tube current of 40 ma, a voltage of 40 kv, a scanning speed of 0.25° min–1 in the range of angles of 15–85° by 2θ in increments of 0.01°. the crystalline phases were identified using the shimadzu pdf2 database. the quantitative phase composition of oxide layers was calculated by the rietveld method. the proportion of x-ray amorphous phase in the oxide layer was also evaluated. hardness measurements according to vickers hv0.01 were performed on transverse specimens on the shimadzu duh-211s dynamic microhardness meter in accordance with iso 14577-1:2015 recommendations under load of 98.1 mn (10 g) at least 10 times for each specimen. the adhesive strength of oxide layers was measured using the nanovea p-macro scratch tester according to the linearly increasing load scheme as per the recommendations of astm c1624-05: a conical rockwell indenter with a vertex angle of 120° and a radius at the apex of 100 nm was used; the scratch length – 15 mm; initial touch load – 0.1 n; final load – 30 n; indenter movement speed – 10 mm/min. at least 5 tests were performed on each specimen. after the scratches were applied, their panoramic shooting was carried out at x20 magnification using the nanovea stiks software, and the coordinate of oxide layer lc massive fracture (tear) initiation was determined. specific critical load of layer failure (fc, n·µm–1) was calculated from the relation of the oxide layer tearing load f to its thickness. electrochemical tests were carried out by methods of potentiodynamic polarization and impedance spectroscopy using the elins p-45x potentiostat-galvanostat with an electrochemical impedance measurement module fra24m (electrochemical instruments) in 3.5 wt.% nacl solution at room temperature (295±2 k). the tests were carried out in a three-electrode electrochemical hold-down cell cs936 (corrtest, china) with a contact area of 1 cm2. platinum mesh (20×20 mm2) was used as an auxiliary electrode, and silver chloride electrode (ag/agcl) filled with saturated solution of potassium chloride was used as a reference electrode. electrode potential of no-polarization specimens (ocp) was stabilized for 60 minutes. specimen potentiodynamic polarization (pdp) was carried out in the range from –150 mv to +1000 mv relative to ocp with a potential sweep rate of 1 mv/s. polarization resistance rp was determined based on astm g102-89(2015)e1 recommendations using the stern-geary constant according to the formula [35]: 𝑅𝑃 = 𝛽𝑎 𝛽c 2.303𝑖corr(𝛽𝑎 + 𝛽c) , (1) where 𝛽𝑎 is the slope of the anode process tafel curve, v/dec, and 𝛽с is the slope of the cathode process tafel curve, v/dec. https://doi.org/10.15826/chimtech.2023.10.2.12 chimica techno acta 2023, vol. 10(2), no. 202310212 article 4 of 15 doi: 10.15826/chimtech.2023.10.2.12 an important factor affecting the corrosion rate of the substrate is the effective interconnected porosity of oxide layers, which was evaluated by the electrochemical method according to the equation [21]: 𝑃eff = ( 𝑅pb 𝑅p ) · 10 −| ∆𝐸corr 𝛽𝑎𝑏 | (2) where peff is the dimensionless value showing the electrochemical porosity of the oxide layer, rpb and βab are the polarization resistance and the anode tafelian slope of the bare alloy (substrate) with no oxide layer, rp is the polarization resistance of the specimen with oxide layer, δecorr is the difference in the corrosion potential between uncoated and coated specimens. the investigation by electrochemical impedance spectroscopy (eis) was carried out at a sinusoidal dither signal with 10 mv amplitude. the tests were run at electrode potential stabilized value in the frequency range from 10 mhz to 300 khz. the analysis of experimental data and the calculation of equivalent circuit parameters were performed using the zview software (scribner associates, usa). the manufactured specimens were held for 14 days in a corrosive environment – 3.5 wt.% nacl at 295±2 k. during this time, a periodic renewal of the corrosive medium was provided to maintain value ph = 7±0.5. following the tests, the external control of the oxide layer state was carried out and the areas of corrosion damage were assessed. 3. results 3.1. voltage-time curves during peo figure 1 shows the characteristic voltage-time curves during peo in both electrolytes at 50 and 500 hz current frequencies. the fast increase of the formation voltage observed in the first 60–70 seconds corresponds to the anodic passivation of the metal substrate. after initial time ~80 sec of the peo process and under voltages about 230– 250 v, the visual sparking on the alloy surface in the electrolyte starts, and then the brightness of the sparks and their number on the surface increase. in addition, the sparks on the anode in the silicate electrolyte seemed to be brighter and pointier, which indicates their greater power compared to the sparks during peo in the aluminate electrolyte. as can be seen, the formation voltages in the silicate electrolyte are higher than those in the aluminate electrolyte for both peo frequencies, and the difference between them during the entire process of sparking is about 6–7%. it should be noted that the amplitude values of the anodic voltage increase with the increase in the frequency of the forming pulses from 50 hz to 500 hz for both electrolytes. a similar effect was observed by kaseem et al. [36]. 3.2. structure, thickness and porosity of oxide layers figure 2 shows panoramic images of the oxide layers formed. the thickness of the oxide layers is approximately 40–50 μm and is virtually in dependent on the variable peo parameters. the oxide layers formed at a pulse frequency of 50 hz in both electrolytes have a very defective structure – there are delaminations and large (up to 10– 15 μm) pores, transverse and main cracks, as well as local oxide layer discontinuities (figure 2). increasing the forming pulse frequency to 500 hz results in lower thickness heterogeneity and defectiveness (porosity, fracturing) of the layer; at the same time, there are no “uncoated” alloy zones or voids in the oxide layers, especially at the point where the lpso-phase breaks the surface. the oxide layers formed in the electrolyte with sodium metasilicate addition have a pronounced two-layer structure. figure 1 voltage-time characteristic curves during peo of the mg97y2zn1 alloy in the aluminate and silicate electrolytes at 50 and 500 hz current frequencies. figure 2 transverse structure of the investigated oxide layers (sem, bse). https://doi.org/10.15826/chimtech.2023.10.2.12 chimica techno acta 2023, vol. 10(2), no. 202310212 article 5 of 15 doi: 10.15826/chimtech.2023.10.2.12 the main and largest defects are located in the inner zone of the oxide layers, directly at the substrate. the transverse structure of the peo-s-50 specimen is characterized by high defectiveness, porosity (more than 13%), presence of multiple discontinuities and delaminations of the oxide layer. the use of sodium aluminate as an electrolyte component in combination with increased frequency during peo allowed obtaining the most homogeneous and low-defect layer among the specimens under consideration. table 1 lists the average thicknesses of the investigated oxide layers and their internal porosity based on the results of sem image processing. as can be seen from table 1, the oxide layers obtained in the electrolyte with sodium aluminate have lower thickness and microhardness, but, at the same time, they are characterized by the least porosity, a smaller spread in the hardness values and the best adhesive strength. 3.3. chemical (elemental) and phase composition of oxide layers the main oxide layer elements are mg, o, p, f, as well as al or si, depending on the electrolyte. these elements make up ≈90–96 wt.% of the oxide layer. na, k and ca, which are introduced into the oxide layer from the electrolyte, and alloy elements (zn, zr, fe, cu and y) with a total content of 1.5–4.0 wt.% were also found. according to the edxma data, higher concentrations of o, p and f and lower contents of al and si were obtained, since this analysis was made across the entire cross-section of the oxide layer, and not from its surface (table 2). distribution of magnesium, oxygen and phosphorus for all oxide layers is equal and uniform (figure 3). table 1 characteristics of oxide layers produced. specimen t (µm) p (%) hv0.01 (mpa) fc (n·µm –1) peo-a-50 41.4±6.1 9.9±0.7 686±138 0.60±0.11 peo-a-500 43.6±9.4 5.9±0.6 661±76 0.67±0.14 peo-s-50 48.6±12.3 13.1±1.0 716±219 0.36±0.09 peo-s-500 46.0±10.1 9.2±2.7 535±171 0.44±0.10 * table 1 shows ±2σ as errors; t is the thickness, µm; p is the porosity, %; hv0.01 is the microhardness, mpa; fc is the specific critical tearing load, n·µm–1 of oxide layers. for the layers obtained at industrial frequency (50 hz), the highest concentration of the element introduced from the main electrolyte component (al or si) is observed in the surface layer. an increase in the pulse frequency during peo results in a drop in the content of this element in the layer, but its distribution becomes more uniform. it should be noted that naalo2 is more actively involved in the oxide layer formation. the al content in the oxide layers under equal technological conditions is ≈22–23 wt.%, which is ≈ 2–3 times higher than the si content. there are differences in the content and distribution of fluorine in the oxide layers: its highest content and the most uniform distribution are characteristic of specimen peo-s-500. for the other specimens, there is a predominant concentration of fluorine in a thin barrier layer at the alloy interface. figure 4 demonstrates xrd patterns of the mg97y2zn1 alloy and the investigated oxide layers, showing that the main phase in all specimens except peo-s-50 is magnesium oxide (mgo, periclase, fm3m), which is formed during the substrate oxidation assisted by micro-arc discharges in the process of peo. the mg2po4f phase (wagnerite phosphoric acid mineral, monoclinic syngony) is also formed in the peo-a-50 oxide layer. for peo-s-50 specimen, the main phase is magnesium silicate, which is the product of interaction of molten magnesium metal and magnesium oxide with silicate ions from the electrolyte. in peo-s-500 specimen, magnesium oxide becomes the main phase again (table 3). the second phase in the oxide layer by weight percentage is determined by the dominant electrolyte component: magnesium aluminate phase mgal2o4 (cubic syngony, fd-3m) is formed in the oxide layer in the aluminate electrolyte, and magnesium silicate mg2sio4 (forsterite, orthorhombic syngony, pmnb) is formed in the silicate electrolyte. there is also some layer amorphization, as evidenced by amorphous halo in the region of 30–45 degrees along 2θ for peo-a specimens, and in the region of 25–40 degrees for peo-s series specimens. calculation of the degree of oxide layers crystallinity (table 3) showed that the amorphous phase content in the oxide layers obtained in the aluminate and silicate electrolytes at industrial frequency is ≈18 and 13.6 vol.%, respectively. table 2 chemical (elemental) composition of oxide layers. specimen method element content (wt.%) mg o al si p f peo-a-50 xrf 34.82±0.08 23.10±0.30 22.63±0.06 – 4.16±0.01 2.33±0.16 edxma 31.52±0.67 30.60±0.71 17.69±1.43 – 12.47±0.36 7.71±1.50 peo-a-500 xrf 38.10±0.08 23.09±0.28 22.08±0.05 – 4.68±0.02 2.89±0.15 edxma 33.27±1.41 30.46±0.76 15.59±0.89 – 12.13±0.65 8.57±1.22 peo-s-50 xrf 43.73±0.09 25.70±0.33 – 12.32±0.01 5.03±0.01 3.50±0.19 edxma 35.78±1.05 31.12±0.93 – 12.02±1.29 11.67±0.30 9.42±1.33 peo-s-500 xrf 48.64±0.10 21.77±0.27 – 6.82±0.02 4.70±0.01 8.68±0.13 edxma 37.66±0.76 28.04±0.60 – 9.25±0.41 11.68±0.38 13.38±0.56 * ± 3σ is listed as error in measurement. https://doi.org/10.15826/chimtech.2023.10.2.12 chimica techno acta 2023, vol. 10(2), no. 202310212 article 6 of 15 doi: 10.15826/chimtech.2023.10.2.12 peo-a-50 peo-a-500 peo-s-50 peo-s-500 figure 3 the bse micrographs of the oxide layer (top row) and the distribution maps of the main elements in it (mg, o, al or si, f and p). table 3 quantitative phase composition of oxide layers. specimen phase content in the oxide layer (wt.%) amorphous phase (vol.%) mgo mgal2o4 mg2sio4 mg2po4f peo-a-50 46.6 40.3 – 13.1 17.94 peo-a-500 69.4 30.6 – – 27.32 peo-s-50 15.4 – 84.6 – 13.57 peo-s-500 92.4 – 7.6 – 37.35 * the degree of reliability of r2 approximation of model empirical diffractogram in jana 2006 software from profile analysis by the rietveld method with account for the statistical weight of each point (wrp) is 95–96% for all specimen. an increase in the frequency of forming pulses to 500 hz results in a higher content of the amorphous phase in the oxide layer composition, which is especially evident for the peo-s-500 specimen – the amorphous phase proportion increased by 2.8 times. also, the composition of x–ray amorphous phase probably includes phosphorus crystalline nuclei and fluorinecontaining phases, since crystalline phases containing p and f were detected only for the peo-a-50 specimen, and the elemental analysis showed total content of these elements in the oxide layer ≈7–13 wt.% (table 2). https://doi.org/10.15826/chimtech.2023.10.2.12 chimica techno acta 2023, vol. 10(2), no. 202310212 article 7 of 15 doi: 10.15826/chimtech.2023.10.2.12 figure 4 xrd patterns of the mg97y2zn1 alloy (as cast and heat treated before peo) (a) and oxide layers obtained in aluminate (peo-a) (b) and silicate (peo-s) (c) electrolyte at forming pulse frequencies of 50 and 500 hz. for the oxide layers formed in the aluminate electrolyte, the magnesium oxide content increases with an increase in the pulse frequency of the forming current by about 1.5 times (to ≈69.4 wt.%), and the fraction of the second phase (mgal2o4) drops by ≈30% (to 30.6 wt.%). when silicate electrolyte is used, a significant activation of substrate oxidation is noted with increasing frequency of peo pulses from 50 to 500 hz: the mgo phase content increases by 6 times (to 92.4 wt.%) and the forsterite content drops by ≈11 times (to ≈7.6 wt.%). 3.4. hardness and adhesive strength the oxide layers obtained in peo at industrial frequency have the highest average microhardness (≈690–720 mpa) (table 1). simultaneously, they are characterized by the greatest heterogeneity and porosity – hv variation coefficients reach 30%. with an increase in the forming pulse operating frequencies there is a certain decrease in hardness, which, however, is not critical, given the spread in measurement statistics. the peo-a-500 specimen, with a slight decrease in hardness (less than 4%), is characterized by its greater uniformity – 661±76 mpa. figure 5 presents the traces of oxide layer scratches, for which the fracture coordinate (lс) is as close as possible to the average value. all specimens are characterized by occurrence of obvious destruction of the oxide layer and exposure of the substrate. the average indenter travel to the substrate exposure for the oxide layer samples formed in the aluminate electrolyte is ≈35% higher than the coordinate lс of the specimens of the peo-s series. a visible effect of using higher frequencies in peo is also noteworthy – the tearing load lс increased by ≈20–25%, depending on the composition of the electrolyte. for the peo-a-500 specimen, the best adhesive strength was recorded in 2 out of 5 tests, no massive fracture of the oxide layer with entire substrate exposure occurred, and other scratches are characterized by the average travel lс ≈ 14.3 mm with a total path length of 15 mm until the metal was completely exposed. similar trends persist when proceeding to specific indicators of adhesive strength assuming different thickness of specimens (table 1): the peo-a-500 specimen has maximum average value fc ≈ 0.67 n/μm. thus, the best oxide layer adhesion-cohesive characteristics are achieved by using the electrolyte with addition of sodium aluminate at a forming pulse frequency of 500 hz. it should be noted that an increase in the adhesive strength of oxide layers is accompanied by a drop in their hardness (table 1), which suggests the mechanism of layer brittle fracture in scratch testing. 3.5. corrosion resistance figure 6 shows the tafel curves of the investigated specimens in a corrosive environment of 3.5% (wt.) nacl. the formation of a protective ceramic layer on the specimens’ surface allowed reducing the corrosion current density of mg97y2zn1 alloy by 1 to 3 orders of magnitude (table 4). the least effect is achieved with peo at industrial current frequency: for specimens obtained at a frequency of 50 hz in the electrolyte with addition of naalo2 and na2sio3, slowdown of the alloy corrosion rate (drop in the corrosion current icorr density) was ≈11 and 19 times, respectively. despite the lower icorr value of the peo-s-50 specimen, its polarization resistance is lower than rp of the peo-a-50 specimen by about 7 times. with similar parameters of cathodic branches of hydrogen reduction for both specimens, anodic branch of the peo-s-50 specimen has a steeper rise, which indicates a more rapid increase in the rate of mg dissolution under anodic polarization. the use of electrolyte with addition of sodium metasilicate in combination with the industrial frequency of forming pulses results in the formation of the most porous oxide layers according to pdp data (≈14%). https://doi.org/10.15826/chimtech.2023.10.2.12 chimica techno acta 2023, vol. 10(2), no. 202310212 article 8 of 15 doi: 10.15826/chimtech.2023.10.2.12 figure 5 images of scratches in the investigated oxide layers (x20, optical light microscopy). figure 6 polarization (tafel) curves of the initial (bare) mg97y2zn1 alloy and after peo. an increase in the current frequency to 500 hz made it possible to further reduce icorr of peo-a-500 and peo-s500 specimens by more than 2 orders of magnitude – to ≈14 and 23 na·cm–2, respectively. the shift of ecorr of the peo-a-500 specimen towards positive direction relative to other samples may be due to a decrease in the number of cl– adsorption centers because of the formation of densest peo layer. a higher value rp ≈ 2.8 mω·cm2 should be noted in the specimen with the oxide layer obtained in aluminate electrolyte, for which the slope of anodic branch is more gentle. the peo-s-500 specimen, despite the low icorr value, is characterized by a “breakdown” of oxide layer under only a slight anode polarization (≈ +0.15 v) and a sharp increase in the current density (by more than an order of magnitude). the results of potentiodynamic polarization are in good agreement with the impedance spectroscopy data. figure 6 shows the results of alternating current (eis) measurements of the investigated samples in nyquist and bode coordinates. the impedance hodographs of the investigated samples are semicircles with different radii. peo conducted at industrial current frequency allows increasing the charge transfer resistance of the surface layer by ≈7–10 times compared to the natural oxide film on the mg-re (lpso) alloy (figure 6, insets). an increase in the frequency of forming pulses to 500 hz in both electrolytes results in a significant gain (by ≈2 orders of magnitude) in the radius of circle and scalar impedance, indicating high protective properties of such oxide layers. modeling using equivalent electrical circuits was carried out to detail the electrochemical processes at the alloy/electrolyte interface. the impedance spectrum of bare alloy was modeled using a simple equivalent diagram with a single r–c(cpe)-circuit (figure 7), and it is limited to the high and medium frequency regions. the capacitive component depends on the capacitance of the double electric layer, and the resistance of charge transfer across the interface. for best description of experimental data, a constant phase element (cpe) was used instead of the ideal capacitance, taking into account the heterogeneity of the natural oxide film on the mg alloy: 𝑍cpe = 1 𝑄(𝑗𝜔)𝑛 , (3) where q is the frequency-independent parameter, j is the imaginary unit (𝑗 = √−1), ω is the cyclic frequency (ω=2πf), n is the exponential factor (n ≤ 1). the spectra of samples with oxide layers have two characteristic “extrema” on the graph of the bode diagram phase angle; therefore, a double loop r–c (cpe)-circuit was used for their detailing, to which two time constants correspond. two inflections indicate a double zone coating structure; they are caused by the presence of an external porous peo layer (cpeout–rout) and an internal dense barrier (cpein–rin) layer. table 4 results of pdp tests of mg97y2zn1 alloy in the initial state and after peo, holding in a corrosive environment of 3.5 wt.% nacl for 1 hour. specimen ocp (v) icorr (µa·cm –2) ecorr (v) rp (mω·cm 2) peff (%) bare alloy –1.609±0.001 31.2±1.90 –1.582±0.006 (1.01±0.56)·10–3 – peo-a-50 –1.603±0.001 2.75±1.36 –1.544±0.077 0.083±0.034 3.42 peo-a-500 –1.544±0.005 0.014±0.002 –1.541±0.013 2.757±0.603 0.11 peo-s-50 –1.615±0.053 1.65±1.09 –1.585±0.062 0.012±0.008 13.9 peo-s-500 –1.610±0.050 0.023±0.008 –1.610±0.050 1.411±0.389 0.07 * ±σ is given as the measurement error. https://doi.org/10.15826/chimtech.2023.10.2.12 chimica techno acta 2023, vol. 10(2), no. 202310212 article 9 of 15 doi: 10.15826/chimtech.2023.10.2.12 figure 7 nyquist and bode curves of the initial mg97y2zn1 alloy and specimens with oxide layers after holding in corrosive environment: 1 hour (left) and 14 days (right) and equivalent circuits used to describe the eis data. markers are experimental points, lines are fitting. the simulation results for the impedance spectra of specimens after 1 hour of holding in a corrosive environment are presented in table 5. it is seen that the oxide layers formed during peo in the silicate electrolyte have the greatest resistance of the coating outer part: rout of the peo-s-500 specimen is more than an order of magnitude higher than the values for the other specimens, which is in good agreement with its structure (figure 1). however, the main contribution to the anticorrosive properties of coatings is made by a thin barrier layer at the alloy interface [37, 38]. peo at a frequency of 50 hz results in an increase in the resistance of charge transfer across the alloy/electrolyte interface by about an order of magnitude (table 5). increasing the frequency of forming pulses from 50 hz to 500 hz during peo further increases rin by more than 2 orders of magnitude – to 1.5–2 mω·cm2. https://doi.org/10.15826/chimtech.2023.10.2.12 chimica techno acta 2023, vol. 10(2), no. 202310212 article 10 of 15 doi: 10.15826/chimtech.2023.10.2.12 table 5 results of processing of eis data for non-oxidized mg97y2zn1 alloy and alloy with oxide layer after 1 hour and 14 days of holding in corrosive environment. specimen rout (kω·cm 2) cpeout rin * (кω·cm2) cpein * |z|f=0.01hz (kω·cm2) qout (ω–1·cm–2·cn) nout qin (ω –1·cm–2·cn) nin 1 hour of holding in 3.5% nacl bare alloy – – – 0.9±0.3 (1.6±0.1)·10–5 0.94±0.01 1.9±0.6 peo-a-50 1.87±0.65 (7.2±1.1)·10–7 0.70±0.01 6.3±2.1 (2.5±1.8)·10–6 0.81±0.09 7.3±2.7 peo-a-500 2.20±0.44 (1.5±0.4)·10–7 0.83±0.02 (2.1±0.7)·103 (7.6±1.7)·10–8 0.83±0.02 (2.2±0.7)·103 peo-s-50 2.72±1.96 (5.3±0.2)·10–7 0.74±0.01 9.1±4.0 (2.4±0.3)·10–6 0.70±0.07 9.3±5.2 peo-s-500 36.6±12.9 (1.8±0.8)·10–8 0.81±0.03 (1.5±0.2)·103 (8.7±4.7)·10–8 0.81±0.01 (1.5±0.2)·103 14 days of holding in 3.5% nacl peo-a-50 0.035±0.007 (2.2±0.7)·10–5 0.55±0.03 4.3±1.2 (8.4±3.1)·10–6 0.86±0.02 5.7±2.8 peo-a-500 0.072±0.006 (1.8±0.3)·10–5 0.58±0.02 13.4±7.1 (2.6±0.6)·10–6 0.93±0.02 14.6±6.9 peo-s-50 0.003±0.003 (2.1±0.3)·10–5 0.80±0.13 0.6±0.2 (4.2±4.2)·10–5 0.92±0.03 0.6±0.3 peo-s-500 0.002±0.001 (3.4±0.3)·10–5 0.65±0.03 1.3±0.5 (2.8±1.3)·10–5 0.91±0.04 1.4±0.8 *cpe and r for the initial alloy are shown in columns rin and cpein. the frequency-independent parameter of the constant phase element (q) corresponds to the interfacial capacitance, the value of which is inversely proportional to the thickness of the oxide layer (double electric layer) and is directly related to its surface area [23]. the specimens formed at 500 hz have the least qin value. thus, reducing the pulse duration triggers the formation of the densest barrier layer with fewer pores. the best anticorrosive characteristics were obtained for the peo-a-500 specimen (tables 4 and 5). holding of specimens in a corrosive environment for 14 days results in a sharp decrease in the scalar impedance values (figure 7) and a change in phase shifts in the high and medium frequency regions. thus, the outer zones of oxide layers almost cease to perform a protective function. the greatest degradation is demonstrated by specimens formed in the silicate electrolyte, which is also clearly seen in the surface images of specimens after corrosion tests (figure 8). two inflections of the phase angle of peo-s-500 specimen in its initial state merge into one extremum during prolonged holding, and |z|f=0.01hz drops by more than 2.5 orders compared to the initial holding stage (1 hour) (figure 6 and 7). specimens formed in the aluminate electrolyte display less tendency to degradation during prolonged holding. despite the drop in the resistance of the outer part of the layer, rin of the peo-a-50 specimen decreased by less than 1.5 times (to ≈4.3 kω·cm2). the peo-a-500 specimen shows highest values of scalar impedance after long holding. despite rin dropping to ≈13 kω·cm2, the oxide layer continues to perform its protective function. before immersion, the surface of all specimens was homogeneous with no visible defects. after long exposure to corrosive environment, the specimens obtained in the electrolyte with addition of sodium metasilicate suffered general corrosion. the deepest corrosion pits are displayed by the peo-s-50 specimen. the specimens formed in the aluminate electrolyte showed only a slight local corrosion on rectangular edges or near the side faces, which indicates their good corrosion resistance and confirms the pdp and eis test data. the peo-a-500 oxide layer is characterized by the best anticorrosive properties, according to the results of eis data and surface images. 4. discussion as can be seen from the results obtained, the oxide layers formed in two electrolytes, at high and low forming current pulse frequencies, have different structures, chemical and phase composition, and also significantly differ in anticorrosive and mechanical characteristics, which is indicative of dissimilarity in the processes of oxidation, mass transfer and generation of reaction products during the oxide layer formation. as can be seen in figure 2, a number of pores are observed in the places where the lpso-phase reaches the magnesium alloy–oxide layer interface for samples peo-a-50 and peo-s-50, and the integrity of the barrier layer is broken. figure 8 macroscopic images (optical light microscopy) of specimens with oxide layers before (upper row) and after (lower row) immersion in 3.5 wt.% nacl for 14 days. https://doi.org/10.15826/chimtech.2023.10.2.12 chimica techno acta 2023, vol. 10(2), no. 202310212 article 11 of 15 doi: 10.15826/chimtech.2023.10.2.12 this suggests that the lpso phase has a negative effect on the process of ignition and combustion of a microarc discharge, and its effect is similar to the effect of silicon in silumins during peo [39, 40]. at the same time, this effect is leveled by an increase in the frequency of forming pulses in both electrolytes, which indicates the possibility of controlling the process of peo of magnesium alloys with an lpso phase. the role of the lpso phase in the formation of the fine structure of the oxide layer and, specifically, the barrier layer at the magnesium alloy–oxide layer interface will be the subject of our further research. a substantial difference in the chemical (elemental) composition of the obtained oxide layers is noteworthy – with the same concentration of sodium aluminate or sodium metasilicate in the electrolyte, the amount of aluminum in the layer is about 1.5–3 times greater than that of silicon (based on two methods data). apparently, this is due to the higher reaction rate of spinel formation mgo + al2o3 = mgal2o4 [41] compared with the reaction of magnesium silicate formation mgo + sio2 = mgsio3 [42]. it is also known that the molar mass of sodium silicate (122 g·mol–1) is about 1.5 times greater than that of sodium aluminate (82 g·mol–1). for each of these electrolyte components, the amount of substance and, consequently, the amount and concentration of aluminate or silicate ions that are present in the electrolyte and can potentially participate in the oxide layer formation during peo can be calculated. for a mass concentration of 15 g·l–1 of each of the components, the molar concentrations of aluminate and sodium silicate in the electrolyte are 0.18 mol·l–1 and 0.12 mol·l–1, respectively. with complete dissociation of substances into ions and with their molar concentrations factored in, с[alo2–] in the electrolyte will be 10.6 g·l–1, while с[sio32–] = 9.12 g·l–1. thus, with an equal mass concentration of sodium aluminate or sodium silicate in the electrolyte, the concentration of aluminate ions capable of reacting during layer formation is about 16% greater than silicate ions, which can further increase the amount of aluminum in the layer compared to the amount of silicon. the increase of the fluorine content in the oxide layers formed in the silicate electrolyte should be noted. it can be assumed that silicate ions accumulate around the anode and form around it a «silicate film» which hinders the microarc breakdown. as a result, the forming voltages increase for the initiation of the microarc discharge (mad) which leads to occurrence of the b-type discharges [43] that penetrate the whole thickness of the oxide layer and reach the interface between the substrate and the coating. in this case, a larger volume of molten metal is formed, and a stronger splash of it to the micropore channel occurs, which leads to a more active capture of the electrolyte components by the melt. in addition, it can be seen that the highest content of al is observed in the outer zone of the coating (figure 3), which indicates the incorporation of aluminum into the oxide layer by a and c discharges [43, 44]. it is worth noting that with an increase in the frequency of the forming current pulses, the proportion of aluminum or silicon in the oxide layer slightly decreases, while porosity and crystallinity of oxide layers are significantly reduced (tables 1, 3 and 4, and figure 2); at the same time, the achieved thickness of oxide layers is maintained (table 1). apparently, this is a consequence of significant differences in the characteristics of micro-arc discharges (mad) that occur at different frequencies of forming pulses in the course of peo. it is well known that the formation of oxide layer is a cyclic electrochemical process; its three main stages are repeated throughout the treatment [45, 46] correspond to: 1) electrical breakdown of the barrier layer at the metal/oxide layer interface and formation of a vapor-gas phase in the discharge (micropore) channel; 2) micro-arc breakdown of the vapor-gas bubble and beginning of the rapid melting of the substrate material due to a very high temperature in the micro-arc [47, 48] accompanied by simultaneous oxidation of alloy elements and reactions with electrolyte components; 3) spew of melt and reaction products to the surface their its rapid cooling, followed by solidification and formation of crystallites of different compounds [49]. all this is accompanied by intense mass transfer and gas formation processes, which determine the composition and structure of the layer and depends mainly on the characteristics of mad during peo. duration of one mad burning in the anode half-cycle ranges from several to tens of microseconds at the initial stages of the oxide layer formation to 100–200 µs when thicknesses in the region of 50–100 µm are reached. at the same time, the “incubation period” (pause between mad occurrence) reaches several tens to hundreds of microseconds [46, 50]. with industrial peo frequency of 50 hz in a “symmetrical” anode-cathode cycle and a pulse-duty factor of 50%, the anode pulse duration is 5000 µs, which is 1– 2 orders longer than the duration of mad. as a result, several mad “waves” and their cascades can occur in one anode pulse that have strong thermal effect and contribute to heating the sections of oxide layer adjacent to the mad breakdown region. at peo pulse frequency of 500 hz, the experimental duration of anode pulse is 500 µs, which, nevertheless, is significantly longer than the burning time of individual mads. it indicates that the microarc discharges at both frequencies belong to the same b-type, when the dielectric breakdown of oxide layer occurs through the vapor-gas bubble in the micropore channel up to the metal substrate, and the molten metal is ejected from the substrate into the micropore channel and onto the surface of the coating, where it rapidly oxidizes and solidifies [3, 51]. it can be assumed, however, that the main reason for the observed changes in the structure and phase composition of the oxide layers is not the reduced duration of https://doi.org/10.15826/chimtech.2023.10.2.12 chimica techno acta 2023, vol. 10(2), no. 202310212 article 12 of 15 doi: 10.15826/chimtech.2023.10.2.12 forming pulse itself, but a decrease in the power and duration of “life” (burning) of a single mad at a shorter anode pulse, which results in a lesser thermal effect of a single mad on the substrate. since the current density is kept constant during peo, the number of mads should increase proportionally with a decrease in their duration (or power) to ensure a given current value. at the same time, the total thermal effect does not change, but the maximum temperatures, reached in the substrate under a single mad, fall. as demonstrated in paper [38], the volume of melting metal is approximately proportional to the duration of micro-arc burning; therefore, a decrease in the mad duration with a proportional increase in their number will not affect the total volume of melted metal, i.e., it will not affect the thickness of oxide layer, which was observed in our experiments (figure 2 and table 1). however, a decrease in the maximum temperatures during melting of the substrate can trigger significant changes in the structure of the oxide layer being formed. the decrease in the temperatures during formation of oxide layer at higher current pulse frequency is evidenced by a change in the phase composition – no mg2po4f phase, characteristic of the peo-a-50 layer and formed as a result of high-temperature sintering, was detected in the peo-a500 oxide layer [53]. we assume that the probable mechanism of the mg2po4f (wagnerite) formation is the hightemperature sintering of mgf2 and mg3(po4)3 according to the reaction equation: mg3(po4)2 + mgf2 → 2mg2po4f. (4) it is worth noting that the wagnerite phase was found only in the peo-a-50 oxide layer and was not observed in other specimens in which phosphorus and fluorine are included only in the amorphous phase. the reasons for this phenomenon are not entirely clear, and it will be the subject of our further research. a decrease in the maximum temperatures during melting should lead to a decrease in the melted volume under a single mad, which increases the cooling rate during solidification. this, in turn, leads to an increase in the fraction of the amorphous phase in the layer, i.e., to a decrease in its crystallinity, which is observed experimentally (table 3). the overall reduction in the porosity and the size of individual pores in the structure of the oxide layer (figure 1) is also likely the result of a decrease in the maximum temperatures reached. shorter mad “lifetime” (or smaller mad power) results in a drop not only in the volume of melted substrate under a single mad, but also in a reduced boiling of liquid metal (magnesium). it is the boiling of metal melt that is mainly responsible for pore formation: bubbles with metal vapor formed during boiling then turn into pores at rapid melt cooling and formation of metal oxide. a decrease in the temperature of molten substrate (magnesium) caused by lower mad duration or power, and, consequently, a decrease in the fraction of boiling and evaporating part of the melt results in a decrease in porosity caused by metal vapor bubbles. furthermore, this leads to a decreased speed of movement of the melt inside the micropore channel during the spew and, consequently, to a less turbulent flow of liquid and capture of a lesser part of vapor-gas phase by the moving melt. taken together, all this leads to the formation of a more homogeneous and less porous structure of oxide layer, with an increased fraction of amorphous phase. it was found that the short-term corrosion resistance of oxide layers formed at 500 hz is distinctly better than that of the one formed at 50 hz (tables 4 and 5). this is probably due to a decrease in porosity as well as compaction of the barrier layer (rin increase by about 3 orders of magnitude – table 5) due to less thermal cracking and gas formation during solidification. pitting corrosion is known to be the main corrosion type in magnesium alloys in chloride-containing environments [54]. consequently, micropores and pore channels of oxide layers negatively affect the corrosion characteristics. larger pores and microcracks of the peo-a-50 and peo-s-50 specimens increase the actual area exposed to the corrosive solution, i.e., they contribute to the magnesium substrate contacting it, which leads to higher values of the corrosion current density (table 4). it can be argued that degradation of oxide layers in a corrosive environment is most affected by the composition of peo electrolyte. in particular, the peo-s-50 specimen with higher short-term anticorrosive characteristics (vs peo-a–50) after 14 days of holding showed most extensive (more than 50% of the specimen area – figure 8) and deep corrosion lesions. similar trends were observed for oxide layers formed at 500 hz. peo-s-500 specimen demonstrates the highest degree of degradation relative to the initial state: |z|f=0.01hz decreases by 3 orders of magnitude – from 1.5 mω·cm2 to 1.4 kω·cm2 (table 5). probably, this fact is associated with the lack of a fluorine-enriched barrier layer (thickness <500–1000 nm, figure 2, distribution f), which has a passivating effect on the surface of the magnesium substrate and gives the barrier layer higher anticorrosive properties [20, 55–57]. it is also likely that the high content of mgo in this oxide layer (92.4%), which tends to dissolve if contacting moisture for long, has an additional effect on the higher degree of degradation. 5. limitations the main problem appeared during this research is stabilization of the open circuit potential (ocp) of the samples. due to the strong fluctuation of ocp on mg-re (lpso) alloy with oxide layer formed by peo, the exposure time in a corrosive environment before electrochemical measurements https://doi.org/10.15826/chimtech.2023.10.2.12 chimica techno acta 2023, vol. 10(2), no. 202310212 article 13 of 15 doi: 10.15826/chimtech.2023.10.2.12 and especially eis tests had to be increased to 2 hours or more. 6. conclusions the effects of current pulse frequency and electrolyte composition during peo of mg97y2zn1 magnesium alloy with strengthening lpso-phase were studied. the peo of the alloy under study at higher frequency of forming current pulses (500 hz) enables forming higher-quality and more uniform oxide layer with enhanced hardness, adhesive strength and anticorrosive properties, the latter exceeding by more than 2 orders of magnitude the parameters obtained using the standard industrial frequency of 50 hz. for both alkaline-phosphate-fluoride electrolytes used, with the addition of sodium aluminate or sodium silicate, at increased frequencies of forming pulses, a continuous oxide layer can be formed with no pronounced delaminations from the substrate or internal pores. the best results were obtained when using electrolyte with addition of sodium aluminate. the use of silicate electrolyte increases the porosity, especially at the frequency of 50 hz. the use of aluminate electrolyte in combination with higher pulse frequency during peo allows achieving the best long–duration corrosion resistance – an order of magnitude higher than when using silicate electrolyte, and also providing the highest and uniform hardness (hv0.01 650–700 mpa) and adhesive strength (0.7–0.8 n·µm–1) of oxide layers on mg-re alloy with strengthening lpsophase. the revealed changes in the structure, composition and properties of oxide layers at the increase in the forming pulse frequency are associated with a drop in the maximum temperatures reached during mad-assisted substrate melting and are probably due to a decrease in the burning duration and power of individual micro-arc discharges. ● supplementary materials no supplementary materials are available. ● funding financial support is provided by the russian science foundation (grant no. 20-79-10262), https://rscf.ru/project/20-79-10262/. ● acknowledgments none. ● author contributions conceptualization: a.o.c., a.v.p., a.v.k, m.m.k. data curation: p.a.g., a.v.k., a.o.c., a.v.p. formal analysis: a.o.c., p.a.g. funding acquisition: a.v.p. investigation: a.o.c., p.a.g., a.g.d., e.d.b., m.r.s., a.v.p. methodology: a.o.c., a.g.d., m.r.s., e.d.b., a.v.p., a.v.k., m.m.k. project administration: a.v.p. resources: a.v.p., m.m.k. supervision: m.m.k. validation: a.v.p., a.v.k., m.m.k. visualization: a.o.c., p.a.g., a.g.d., e.d.b., m.r.s., a.v.p. writing – original draft: a.o.c., p.a.g., a.g.d., e.d.b., m.r.s., a.v.p. writing – review & editing: a.o.c., a.v.p., a.v.k., m.m.k. ● conflict of interest the authors declare no conflict of interest. ● 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