Glucose-assisted polyol synthesis of silver nanoplates and nanoprisms in the presence of oxyethylated carboxylic acid published by Ural Federal University eISSN 2411-1414; chimicatechnoacta.ru LETTER 2022, vol. 9(3), No. 20229309 DOI: 10.15826/chimtech.2022.9.3.09 1 of 4 Glucose-assisted polyol synthesis of silver nanoplates and nanoprisms in the presence of oxyethylated carboxylic acid Alexander A. Titkov , Tatiana A. Borisenko, Olga A. Logutenko * Institute of Solid State Chemistry and Mechanochemistry SB RAS, Novosibirsk 630128, Russia * Corresponding author: ologutenko@solid.nsc.ru This paper belongs to the CTFM'22 Special Issue: https://www.kaznu.kz/en/25415/page. Guest Editors: Prof. N. Uvarov and Prof. E. Aubakirov. © 2022, the Authors. This article is published in open access under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/). Abstract This work reports a simple route to synthesizing silver nanoplates and nanoprisms through a polyol approach in the presence of oxy- ethylated carboxylic acid and glucose. The resulting particles were characterized by electron microscopy and X-ray diffraction (XRD). The introduction of glucose and NaOH into the system substantially increases the yield of nanoplates and reduces their thickness. The op- timized reaction conditions can be used to produce, in a one-pot syn- thesis, silver nanoplates and nanoprisms which may have applica- tions as metallic fillers in ink and paste formulations for 2D and 3D printing to fabricate functional components and devices. Keywords silver nanoprisms ethylene glycol glucose reduction Received: 24.06.22 Revised: 21.07.22 Accepted: 21.07.22 Available online: 03.08.22 Key findings ● Glucose promotes the formation of silver nanoplates and nanoprisms at room temperature and in- creases their yield. ● The silver nanoplates change the shape to nanoprisms with increasing temperature. ● In the presence of NaOH, the yield of plate-like structures and their aspect ratios increase. 1. Introduction Over the last few decades, due to the increasing number of applications, conductive inks, pastes and adhesives for flexible printed electronics have received much attention [1, 2]. The metals most commonly used in the ink formula- tions are silver, copper, nickel, gold, aluminum and zinc. However, silver is the best choice for electrically conduc- tive inks, pastes and adhesives because of its high electri- cal and thermal conductivity, chemical stability and the ability of its oxide form to show good conductivity [3]. Silver nanoplates and nanoprisms, a new class of nanostructures with two-dimensional anisotropy, have been of special interest for the applications in sensors and diagnostics because of their structure, optical, electronic, and catalytic properties that are generally superior to those of spherical nanoparticles of a comparable size [4, 5]. It was also shown that, after printing the inks based on non-spherical silver particles onto plastic substrates and subsequent annealing, the resultant Ag patterns are more uniform and show a lower resistivity and improved me- chanical properties as compared to those of similar pat- terns prepared from spherical particles [6]. Different chemical and physical techniques are used to prepare silver particles, including chemical reduction of the silver ions in various media, various types of irradia- tion and electrochemical processes as well as solvothermal and polyol methods, etc. [7]. One of the most common so- lution-phase approaches to producing micrometer- and nanometer-scale silver particles is the polyol process in which the polyol acts both as the solvent and reducing agent. The advantages of the polyol process are that it is low-cost, easy to use, and scalable. It also allows control of the particles size and shape by varying reaction conditions, such as temperature, reduction time, the reagent concentra- tions, and type of stabilizer, resulting in the formation of different morphologies [4, 8]. Among other Ag anisotropic nanoparticles, triangular prisms and plate-like nanostructures are being extensively investigated [9]. The formation of anisotropic shapes is not thermodynamically favored; that is why, in order to promote anisotropic growth of silver nanocrystals, the use of structure-directing agents, which can selectively adsorb on different crystal facets, is required. In most of the re- ported methods, citrate and poly(vinylpyrrolidone) (PVP) http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2022.9.3.09 https://orcid.org/0000-0003-0835-9985 https://orcid.org/0000-0003-1523-5446 mailto:ologutenko@solid.nsc.ru http://creativecommons.org/licenses/by/4.0/ https://crossmark.crossref.org/dialog/?doi=https://doi.org/10.15826/chimtech.2022.9.3.09&domain=pdf&date_stamp=2022-8-3 Chimica Techno Acta 2022, vol. 9(3), No. 20229309 LETTER 2 of 4 have been widely used as capping agents to induce the formation of silver anisotropic particles [10]. Xue et al. reported [11] that citrate ions both reduced silver ions and helped the formation of plate-structured Ag nanoparticles. Zhang et al. found that the list of ligands with selective adhesion to Ag (111) facets can be expanded from citrate to many other di- and tricarboxylate compounds [12]. In con- trast to citrate, PVP binds more strongly to the (100) than (111) facet [13] and this selectively leads to the formation of Ag nanocubes. In addition to citrate and PVP, several other capping agents used to obtain anisotropic structures of sil- ver have also been reported in the literature. Thus, in the presence of Br− ions, the formation of silver nanocubes, rectangular nanobars, and octagonal nanorods is induced [14]. Silver microplates, with average edge length of about 1.5 µm and a thickness of 100 nm, were synthesized in the presence of n-octanol playing an important role in the for- mation of the plate-like structure [15]. Xiong et al. prepared silver nanoplates with a triangular or hexagonal shape by introducing polyacrylamide (PAM) when reducing silver nitrate with ethylene glycol [16]. However, it is worth not- ing that the number of facet-selective capping agents which could be successfully used to prepare silver structures with different shapes is very limited. Herein, we report the results of the study on the reduc- tion of silver ions with ethylene glycol in the presence of 2-[2-(2-methoxyethoxy)ethoxy]acetic acid (MEEAA) and glucose aiming to develop a simple method to prepare sil- ver nanoplates. The proposed method has advantages in terms of both cost and ease of implementation; it does not require unique and expensive equipment and can be used for large-scale production of silver powders. 2. Experimental 2.1. Reagents Silver nitrate (AgNO3), 99.9% purity grade, SoyuzKhimProm, Russia), 2-[2-(2-methoxyethoxy)ethoxy] acetic acid (C7H14O5, MEEAA) of 95% purity grade (Sigma Aldrich, USA), ethylene glycol (HO(CH2)2OH, EG) of 99.9% purity grade, 95% pure ethanol supplied by Khimmed (Russia), and sodium hydrox- ide (NaOH, 50% aqueous solution) were used as received without further purification. 2.2. Synthesis of silver particles The reduction of of silver nitrate was carried out as fol- lows. An appropriate amount of MEEAA was dissolved in 25 ml of ethylene glycol, and then a stoichiometric amount of sodium hydroxide was added to the solution under stir- ring. Silver nitrate was dissolved in ethylene glycol and added to a solution of the sodium salt of MEEAA in eth- ylene glycol under constant stirring. After stirring for 5 min, the mixture was heated to the required tempera- ture, followed by the addition of a solution of glucose in ethylene glycol. After the reaction was complete, the mix- ture was air-cooled and the supernate was decanted. The resulting precipitate was washed three times with ethanol to remove the impurities and then it was dried in air at room temperature. 2.3. Characterization X-ray diffraction (XRD) patterns were recorded on a D8 Advance powder X-ray diffractometer equipped with a 1D Lynx-Eye detector and Ni-filtered Сu Kα radiation (0.02° 2θ step size and an accumulated time per step of 35.4 s). Phase identification was carried out using Powder Diffrac- tion File (PDF) databases (ICDD, Release 2001). Analysis of the samples by transmission electron microscopy (TEM) was performed using a JEM 2010 electron microscope (JEOL, Japan) operating at 200 kV and having a resolution of 0.14 nm. Study of the samples by high-resolution scan- ning electron microscopy (SEM) was performed using a Tescan scanning electron microscope (Czech Republic). 3. Results and Discussion Our earlier study showed [17] that the reduction of silver ions with ethylene glycol in the presence of the sodium salt of MEEAA proceeds extremely slowly and leads to the formation of silver nanoparticles of 2–5 nm in size with a very low yield. An increase in the temperature up to 40 °C resulted in the formation of triangular and hexagonal sil- ver nanoplates with edge lengths ranging from 100 to 200 nm and with a thickness of approximately 30 nm, but their yield was too low. A further increase in the tempera- ture to 60–100 °C produced a sample containing irregular- ly shaped polyhedrons and a very small fraction of plates. In the present study, we attempted to produce Ag nano- plates with controlled shapes in high yields by adding glu- cose in the polyol synthesis. As shown in this study, the addition of glucose (Glu) in the synthesis of silver nanoparticles in a mixture of eth- ylene glycol and sodium salt of MEEAA (NaR) affects the yield of silver nanoplates. Thus, at an Ag+:NaR:Glu molar ratio of 1:3:2 at a temperature of 30 °C and a synthesis time of 72 h, the yield of plates was 57%, and their size and thickness were 240 and 40 nm, respectively (Figure 1a). It should be noted that, under similar conditions but at a low- er Ag+ to Glu molar ratio of 1:1, the final product contained 40% of the plates, with mean sizes of 170 nm in edge length and 25 nm in thickness, while the remaining 60% were polyhedral shaped silver nanoparticles. Therefore, a de- crease in the glucose content in the system decreases the yield of nanoplates, their length and thickness. At a molar ratio of glucose to silver of 1:4, under the same conditions, the final product contained 60% of plates with an edge length of 130 nm and a thickness of 40 nm, while the re- maining 40% of silver nanoparticles were polyhedra (Fig- ure 1b). A further increase in the ratio of Ag+:Glu to 1:6 led to a decrease in the nanoplate yield to 50%. The average thickness of these nanoplates was found to be approximate- ly 30 nm, while their edge length was around 200 nm. Chimica Techno Acta 2022, vol. 9(3), No. 20229309 LETTER 3 of 4 It is known [18] that, as pH increases, the value of the redox potential of glucose decreasese, which means that, in an alkaline solution, its ability to donate electrons in- creases. As Raveendran et al. reported [19], the reason for this is that the base facilitates the opening of the glucose ring by the abstraction of the α-proton of the sugar ring oxygen and thereby speeds up both the oxidation of glu- cose to gluconic acid and the reduction of silver ions to silver atoms. Gluconic acid, the glucose derivative result- ing from its oxidation, was reported to form a dense coat- ing on the surface of nanoparticles, thereby stabilizing them [20]. In the presence of NaOH, the reduction reac- tion can proceed according to equation (1): CH2OH(CHOH)4CHO + 2Ag+ + 2OH− → CH2OH(CHOH)4COOH + 2Ag↓ + H2O (1) In order to promote the formation of plate-like struc- tures, it was of interest to investigate the effect of alkali on the reduction of silver ions in ethylene glycol in the presence of glucose. In the synthesis, which was conduct- ed at 30 °C and at an Ag+:NaR:Glu of 1:3:2, with the molar ratio of Ag to NaOH equal to 1:0.1 in the reaction mixture, an increase in the nanoplate yield to 70% was observed. The average edge length of the nanoplates and their thick- ness were 159.7±68.2 and 25 nm, respectively (Figure 2a). Therefore, in the presence of NaOH, the yield of plate-like structures and their aspect ratios were higher than that obtained from the reduction in the absence of NaOH. It should be noted that an increase in the glucose concentra- tion in the reaction system did not lead to any further in- crease in the nanoplate yield, and it remained at 60%. The effect of temperature on the morphology of silver particles formed in the presence of glucose wasstudied. It was shown that an increase in temperature from 30 °C to 40 °C led to an increase in the thickness of the silver plates (Figure 2b). Thus, at an Ag+:NaR:Glu molar ratio of 1:3:2, uniform nanoprisms are formed with an edge size of about 150 nm and a thickness of about 70 nm. The reaction yield of the silver nanoprisms was 90%. Under similar conditions but at a lower Ag+ to Glu molar ratio of 1:1, the yield of the silver nanoplates and their thickness also tend to increase as compared to those formed at 30 °C. Thus, as the temper- ature is increased, the Ag nanoplates become thicker and are finally transformed into nanoprisms. The same trend was observed to take place when reducing silver ions with ethylene glycol in the presence of the sodium salt of MEEAA alone [22]. The X-ray diffraction (XRD) pattern of the sample pre- pared under these conditions is shown in Figure 3. As seen, it has four diffraction peaks at 2θ = 38.08°, 44.26°, 64.36°, and 77.52° attributed, respectively, to the diffrac- tion from the {111}, {200}, {220}, and {311} planes of the face-centered cubic (FCC) lattice of silver (JCPDS, card no. 01-071-4613). 4. Conclusions Triangular and hexagonal silver nanoplates were synthe- sized by reduction of silver ions with ethylene glycol in the presence of 2-[2-(2-methoxyethoxy)ethoxy]acetic acid (MEEAA) and glucose. Compared with MEEAA alone, add- ing glucose promotes the synthesis of silver nanoplates and nanoprisms at room temperature and increases their yield. When the temperature is increased, the silver nano- plates were found to undergo a shape transformation to nanoprisms. The addition of NaOH to the reaction mix- tures increases the yield of plate-like structures and their aspect ratios. The proposed method does not require unique and expensive equipment; it is low-cost and can be used for large-scale production of silver powders. Figure 1 Micrographs of the silver nanoparticles prepared in the presence of glucose. Ag+:NaR = 1:3, Т = 30 °С, τ = 72 h; Ag+:Glu = 1:2 (a) and 1:4 (b). Figure 2 Micrographs of the silver nanoparticles prepared in the presence of glucose. Effect of pH (a) and temperature (b) on the size of silver nanoplates. Ag+:NaR:Glu = 1:3:2, T = 30 °C (a) and 40 °C (b), τ = 72 h; Ag:NaOH = 1:0.1 (a) and 1:0 (b). Figure 3 X-ray diffraction pattern of the silver nanoparticles pre- pared in the presence of glucose. Ag+:NaR:Glu = 1:3:2, Т = 30 °С, τ = 72; Ag+:NaOH = 1:0.1. Chimica Techno Acta 2022, vol. 9(3), No. 20229309 LETTER 4 of 4 Supplementary materials No supplementary materials are available. Funding The research was funded within the state assignment to ISSCM SB RAS (Project No. 122032900069-8). Acknowledgments None. Author contributions Conceptualization: A.I.T. Data curation: A.I.T., T.A.B., O.A.L. Formal Analysis: A.I.T., T.A.B., O.A.L. Funding acquisition: A.I.T. Investigation: T.A.B. Methodology: A.I.T., T.A.B., O.A.L. Project administration: A.I.T. Resources: A.I.T Software: A.I.T. Supervision: A.I.T., O.A.L. Validation: A.I.T., O.A.L Visualization: O.A.L. Writing – original draft: O.A.L. Writing – review & editing: A.I.T. Conflict of interest The authors declare no conflict of interest. Additional information Author IDs: Alexander A. Titkov, Scopus ID 11941014000; Tatiana A. Borisenko, Scopus ID 57217250657; Olga A. Logutenko, Scopus ID 6506250321. Website: Institute of Solid State Chemistry and Mechanochemis- try SB RAS, http://www.solid.nsc.ru. References 1. Singh M, Haverinen HM, Dhagat P, Jabbour GE. Inkjet print- ing-process and its applications. Adv Mater. 2010;22:673–685. doi:10.1002/adma.200901141 2. Tekin E, Smith PJ, Schubert US. Inkjet printing as a deposition and patterning tool for polymers and inorganic particles. Soft Matter. 2008;4:703–713. doi:10.1039/B711984D 3. Zhang R, Moon KS, Lin W, Wong CP. Preparation of highly conductive polymer nanocomposites by low temperature sin- tering of silver nanoparticles. J Mater Chem. 2010;20:2018−2023. doi:10.1039/B921072E 4. Loiseau A, Asila V, Boitel-Aullen G, Lam M, Salmain M, Bouj- day S. Silver-based plasmonic nanoparticles for and their use in biosensing. Biosensors. 2019;9(2):78. doi:10.3390/bios9020078 5. Kelly KL, Coronado E, Zhao LL, Schatz GC. The optical proper- ties of metal nanoparticles: the influence of size, shape and dielectric environment. J Phys Chem B. 2003;107(3):668–677. doi:10.1021/jp026731y 6. Lee YI, Kim S, Jung SB, Myung NV, Choa YH. Enhanced electri- cal and mechanical properties of silver nanoplatelet-based conductive features direct printed on a flexible substrate. ACS Appl Mater Interfaces. 2013;5(13):5908−5913. doi:10.1021/am401757y 7. Zhao T, Sun R, Yu Sh, Zhang Zh, Zhou L, Huang H, Du R. Size- controlled preparation of silver nanoparticles by a modified polyol method. Colloids Surf A Physicochem Eng Asp. 2010:336:197–202. doi:10.1016/j.colsurfa.2010.06.005 8. Park KH, Im SH, Park OO. The size control of silver nanocrys- tals with different polyols and its application to low-reflection coating materials. Nanotechnol. 2011;22(4):045602. doi:10.1088/0957-4484/22/4/045602 9. Millstone JE, Hurst SJ, Metraux GS, Cutler JI, Mirkin CA. Col- loidal gold and silver triangular nanoprisms. Small. 2009;5(6):646–664. doi:10.1002/smll.200801480 10. Ren HM, Guo Y, Huang SY, Zhang K, Yuen MMF, Fu XZ, Yu S, Sun R, Wong CP. One-Step preparation of silver hexagonal mi- crosheets as electrically conductive adhesive fillers for print- ed electronics. ACS Appl Mater Interfaces. 2015;7:13685– 13692. doi:10.1021/acsami.5b03571 11. Xue C, Mirkin CA. pH-switchable silver nanoprism growth pathways. Angew Chem Int Ed. 2007;46(12):2036–2038. doi:10.1002/anie.200604637 12. Zhang Q, Li N, Goebl J, Lu Z, Yin Y. A systematic study of the synthesis of silver nanoplates: is citrate a “magic” reagent? J Am Chem Soc. 2011;133(46):18931–18939. doi:10.1021/ja2080345 13. Sun YG, Mayers B, Herricks T, Xia YN. Polyol synthesis of uniform silver nanowires: a plausible growth mechanism and the supporting evidence. Nano Lett. 2003;3(7):955–960. doi:10.1021/nl034312m 14. Xia X, Zeng J, Zhang Q, Moran CH, Xia Y. Recent developments in shape-controlled synthesis of silver nanocrystals. J Phys Chem C. 2012;116(41):21647–21656. doi:10.1021/jp306063p 15. You T, Sun S, Song X, Xu S. Simple extraction-solvothermal synthesis of single-crystalline silver microplates. Cryst Res Technol. 2009;44(8):857–860. doi:10.1002/crat.200900332 16. Xiong Y, Siekkinen AR, Wang J, Yin Y, Kim MJ. Xia Y. Synthesis of silver nanoplates at high yields by slowing down the polyol reduction of silver nitrate with polyacrylamide. J Mater Chem. 2007;17:2600–2602. doi:10.1039/B705253G 17. Titkov AI, Borisenko TA, Logutenko OA. Polyol synthesis of silver nano- and microplates in the presence of an ethoxylated carboxylic acid. Chem Sustain Dev. 2020;28:66–72. doi:10.15372/KhUR2020204 18. Shenoy US, Shetty AN. Simple glucose reduction route for one- step synthesis of copper nanodluids. Appl Nanosci. 2014;4:47– 54. doi:10.1007/s13204-012-0169-6 19. Raveendran P, Fu J, Wallen SL. A simple and „green“ method for the synthesis of Au, Ag, and Au-Ag alloy nanoparticles. Green Chem. 2006;8:34–38. doi:10.1039/B512540E 20. Giersig M, Ung T, Liz-Marzan LM, Mulvaney P. Direct observa- tion of chemical reactions in silica-coated gold and silver na- noparticles. Adv Mater Commun. 1997;9(7):570–575. doi:10.1002/adma.19970090712 http://www.scopus.com/inward/authorDetails.url?authorID=11941014000 http://www.scopus.com/inward/authorDetails.url?authorID=57217250657 http://www.scopus.com/inward/authorDetails.url?authorID=6506250321 http://www.solid.nsc.ru/ https://doi.org/10.1002/adma.200901141 https://doi.org/10.1039/B711984D https://doi.org/10.1039/B921072E https://doi.org/10.3390/bios9020078 https://doi.org/10.1021/jp026731y https://doi.org/10.1021/am401757y https://doi.org/10.1016/j.colsurfa.2010.06.005 https://doi.org/10.1088/0957-4484/22/4/045602 https://doi.org/10.1002/smll.200801480 https://doi.org/10.1021/acsami.5b03571 https://doi.org/10.1002/anie.200604637 https://doi.org/10.1021/ja2080345 https://doi.org/10.1021/nl034312m https://doi.org/10.1021/jp306063p https://doi.org/10.1002/crat.200900332 https://doi.org/10.1039/B705253G https://doi.org/10.15372/KhUR2020204 https://doi.org/10.1007/s13204-012-0169-6 https://doi.org/10.1039/B512540E https://doi.org/10.1002/adma.19970090712